95 results on '"Haas, Christian"'
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2. VR-control for teleoperation of mobile machines – a review on the practical implementation
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Gerdes, Simon, Sprink, Johannes, Haas, Christian, Opgenoorth, Andreas, and Schmitz, Katharina
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Teleoperation of mobile machines can have benefits on numerous aspects, including improved safety, enhanced efficiency, and reduced environmental impact. However, effects like increased latency, lack of machine feeling and limited field of view result in challenges for operators. The use of VR-systems with operator head motion tracking could improve its application. This paper presents the investigation of a tele-remote control system, using a VR-visual feedback system including a stereo camera that mimics the operator’s head motion. An operator study was conducted to evaluate the influence of the tele-remote control system. It is shown that the investigated system is able to increase the achieved immersion and thus improve the operability of teleoperated mobile machines.
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- 2023
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3. SEA ICE GEOPHYSICS AND REMOTE SENSING.
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Haas, Christian, Spreen, Gunnar, Neudert, Mara, Buth, Lena, Niehaus, Hannah, Lion, Victor, and Hoppmann, Mario
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- 2023
4. PHYSICAL OCEANOGRAPHY.
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von Appen, Wilken-Jon, Kanzow, Torsten, Hoppmann, Mario, McPherson, Rebecca, Hofmann, Zerlina, Mathieu, Laura, Reifenberg, Simon, Becker, Hauke, Monsess, Matthias, Graupner, Rainer, Lochthofen, Normen, Allerholt, Jacob, Fer, Ilker, Ellliot, Fiona, Haas, Christian, and Neudert, Mara
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- 2023
5. Identification of Multimorbidity Patterns in Rheumatoid Arthritis Through Machine Learning
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England, Bryant R., Yang, Yangyuna, Roul, Punyasha, Haas, Christian, Najjar, Lotfollah, Sayles, Harlan, Yu, Fang, Sauer, Brian C., Baker, Joshua F., Xie, Fenglong, Michaud, Kaleb, Curtis, Jeffrey R., and Mikuls, Ted R.
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Recognizing that the interrelationships between chronic conditions that complicate rheumatoid arthritis (RA) are poorly understood, we aimed to identify patterns of multimorbidity and to define their prevalence in RA through machine learning. We constructed RA and age‐ and sex‐matched (1:1) non‐RA cohorts within a large commercial insurance database (MarketScan) and the Veterans Health Administration (VHA). Chronic conditions (n = 44) were identified from diagnosis codes from outpatient and inpatient encounters. Exploratory factor analysis was performed separately in both databases, stratified by RA diagnosis and sex, to identify multimorbidity patterns. The association of RA with different multimorbidity patterns was determined using conditional logistic regression. We studied 226,850 patients in MarketScan (76% female) and 120,780 patients in the VHA (89% male). The primary multimorbidity patterns identified were characterized by the presence of cardiopulmonary, cardiometabolic, and mental health and chronic pain disorders. Multimorbidity patterns were similar between RA and non‐RA patients, female and male patients, and patients in MarketScan and the VHA. RA patients had higher odds of each multimorbidity pattern (odds ratios [ORs] 1.17–2.96), with mental health and chronic pain disorders being the multimorbidity pattern most strongly associated with RA (ORs 2.07–2.96). Cardiopulmonary, cardiometabolic, and mental health and chronic pain disorders represent predominant multimorbidity patterns, each of which is overrepresented in RA. The identification of multimorbidity patterns occurring more frequently in RA is an important first step in progressing toward a holistic approach to RA management and warrants assessment of their clinical and predictive utility.
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- 2023
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6. Pre-existing chronic kidney disease, aetiology of acute kidney injury and infection do not affect renal outcome and mortality
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Buckenmayer, Anna, Siebler, Nadja, and Haas, Christian S.
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Background: We aimed to study the role of aetiology, pre-existing chronic kidney disease (CKD) and infections in acute kidney injury (AKI) on renal outcome and mortality. Methods: This retrospective study analysed patients with AKI admitted to a university nephrology department from January 1st, 2020 through December 31st, 2020. Aetiology of AKI, underlying renal disease in case of pre-existing CKD and presence of infections were assessed. Development of renal function and risk of death were studied with follow-up until January 31st, 2023. Results: Of 1402 patients screened, 432 patients (30.8%, 67.9 ± 15.4 years) fulfilled the inclusion criteria, half of the population presented with advanced CKD. Even though CKD patients were more often in need of chronic dialysis at time of discharge (6.9% vs 4.5%, p< .001), duration of hospital stay was shorter and in-hospital mortality tended to be lower when compared to AKI without prior renal disease. Neither aetiology of AKI nor pre-existing CKD had an impact on the combined endpoint of end-stage kidney disease and mortality (log rank 0.433 and 0.909). Overall, septic patients showed the highest in-hospital mortality (23.5%) and longest hospital stay (30.0 ± 22.8 days, p< .001), while patients with urosepsis had the shortest hospitalisation time (9.7 days) with lowest risk for dialysis (4.4%). Of note, outcome did not differ in patients with AKI when considering the infectious status. Conclusions: Overall renal outcome and mortality in AKI patients were not affected by the cause of AKI, pre-existent CKD or infectious status. Only severity of AKI had a negative impact on outcome. Graphical abstract:
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- 2023
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7. Cybersecurity for industrial automation and control systems
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Haas, Christian, Bretthauer, Georg, and Beyerer, Jürgen
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- 2023
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8. 6: SEA ICE GEOPHYSICS AND BIOCHEMISTRY.
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Haas, Christian, Arndt, Stefanie, Peeken, Ilka, Eggers, Sarah L., Neudert, Mara, Müller, Juliane, Wollenburg, Jutta, Laukert, Georgi, and Schweder, Thomas
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- 2021
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9. Ru(II) Complexes with a Chemical and Redox-Active S2N2Ligand: Structures, Electrochemistry, and Metal–Ligand Cooperativity
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Durgaprasad, Gummadi, Luna, Javier A., Spielvogel, Kyle D., Haas, Christian, Shaw, Scott K., and Daly, Scott R.
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Here we describe the synthesis, structures, and reactivity of Ru complexes containing a triaryl, redox-active S2N2ligand derived from o-phenylenediamine and thioanisole subunits. The coordination chemistry of N,N′-bis[2-(methylthio)phenyl]-1,2-diaminobenzene [H2(MeSNNSMe)] was established by treating RuCl2(PPh3)3with H2(MeSNNSMe) to yield {Ru[H2(MeSNNSMe)]Cl(PPh3)}Cl (1). Coordinated H2(MeSNNSMe) was sequentially deprotonated to form Ru[H(MeSNNSMe)]Cl(PPh3) (2) followed by the five-coordinate, square pyramidal complex Ru(MeSNNSMe)(PPh3) (3). Single-crystal X-ray diffraction (XRD) studies revealed that the ligand structurally rearranged around the metal at each deprotonation step to conjugate the adjacent aryl groups with the o-phenylenediamine backbone. Deprotonation of 2with NaBH4or treatment of 3with BH3·tetrahydrofuran (THF) yielded Ru[(μ-H)BH2](MeSNNSMe)(PPh3) (5) with BH3bound across a Ru–N bond in a metal–ligand cooperative fashion. The cyclic voltammogram of 3in THF revealed three redox events consistent with one-electron oxidations and reductions of the o-phenylenediamine backbone and the metal (Ru3+/Ru2+). Reactions of 3with CO, HBF4, and benzoic acid yielded the new complexes Ru(MeSNNSMe)(CO)(PPh3), {Ru[H(MeSNNSMe)](PPh3)(THF)}BF4, and Ru[H(MeSNNSMe)](PPh3)(PhCO2), indicating broader suitability for small molecule binding and reactivity studies. Subsequent nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry data are reported in addition to molecular structures obtained from single-crystal XRD studies.
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- 2024
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10. Tunneled central venous catheters for hemodialysis—unfairly condemned? Catheter-related complications in a university hospital setting
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Buckenmayer, Anna, Möller, Bianca, Ostermaier, Claudia, Hoyer, Joachim, and Haas, Christian S
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Background: Central venous catheters (CVCs) provide an immediate hemodialysis access but are considered to be of elevated risk for complications. It remains unclear, if CVCs per sehave relevant impact on clinical outcome. We provide an assessment of CVC-associated complications and their impact on mortality.Methods: In a single center retrospective study, CVC patients between JAN2015-JUN2021 were included. Data on duration of CVC use, complications and comorbidities was collected. Estimated 6-month mortality was compared to actual death rate.Results: About 478 CVCs were analyzed. Initiation of dialysis was the main reason for CVC implantation. Death was predominant for termination of CVC use. Infections were rare (0.6/1000 catheter days), complications were associated with certain comorbidities. Actual 6-month mortality was lower than predicted (14.3% vs 19.6%).Conclusion: (1) CVCs are predominantly implanted for initiation of hemodialysis; (2) serious complications are rare; (3) complications are associated with certain comorbidities; and (4) CVC patients survive longer than predicted.
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- 2024
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11. Contrasting Ice Algae and Snow‐Dependent Irradiance Relationships Between First‐Year and Multiyear Sea Ice
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Lange, Benjamin A., Haas, Christian, Charette, Joannie, Katlein, Christian, Campbell, Karley, Duerksen, Steve, Coupel, Pierre, Anhaus, Philipp, Jutila, Arttu, Tremblay, Pascal O. G., Carlyle, Cody G., and Michel, Christine
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During the 2018 Multidisciplinary Arctic Program‐Last Ice in the Lincoln Sea, we sampled 45 multiyear ice (MYI) and 34 first‐year ice (FYI) cores, combined with snow depth, ice thickness, and transmittance surveys from adjacent level FYI and undeformed MYI. FYI sites show a decoupling between bottom‐ice chlorophyll a(chl a)and snow depth; however, MYI showed a significant correlation between ice‐algal chl abiomass and snow depth. Topographic control of the snow cover resulted in greater spatiotemporal variability of the snow over the level FYI, and consequently transmittance, compared to MYI with an undulating surface. The coupled patterns of snow depth, transmittance, and chl aindicate that MYI provides an environment with more stable light conditions for ice algal growth. The importance of sea ice surface topography for ice algal habitat underpins the potential ecological changes associated with projected increased ice dynamics and deformation. This study presents first results from the 2018 Multidisciplinary Arctic Program‐Last Ice, the most intensive ecologically focused research project ever conducted within the so‐called “Last Ice Area.” This region is of key importance because it is the only place in the Arctic expected to retain summer sea ice by the year 2050. Continued changes to the sea ice environment will have ecological consequences because sea ice is an important habitat for many animals from microscopic ice algae, the base of the food chain, to seals and polar bears. Since the older ice is being replaced by younger ice, we compared older ice to younger ice in order to provide a glimpse into the future. We found that the older ice has a more stable light environment for ice algae due to snow depth patterns associated with surface topography. This can mean that as the older ice is replaced by newer ice, the availability of ice algae as a food source may become more unpredictable. The importance of surface topography for ice algae indicates that the projected acceleration in sea ice drift and increased ridging due to thinner ice will likely have an impact on key sea ice habitat properties. Spatiotemporal changes in snow cover and transmittance were observed for FYI but remained stable for MYI due to differences in topographyThe spatial distribution of bottom‐ice chl abiomass was coupled to snow depth and transmittance in MYI but decoupled in FYIA projected shift to a more dynamic and deformed sea ice cover is likely to be a key driver of ice‐algal habitat variability in the future
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- 2019
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12. SEA ICE PHYSICS.
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Arndt, Stefanie, Stoll, Nicolas Angelo, Winkelmann, Ricarda, Reese, Ronja, Huntemann, Marcus, Haas, Christian, Notz, Dirk, Nicolaus, Marcel, Hoppmann, Mario, Rigor, Ignatius, and Heil, Petra
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- 2018
13. Ru(II) Complexes with a Chemical and Redox-Active S2N2 Ligand: Structures, Electrochemistry, and Metal-Ligand Cooperativity.
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Durgaprasad, Gummadi, Luna, Javier A., Spielvogel, Kyle D., Haas, Christian, Shaw, Scott K., and Daly, Scott R.
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- 2017
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14. Gesundheit und Gesundheitsförderung am Arbeitsplatz aus Mitarbeiterperspektive
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Hammer, Sabine, Deitermann, Martina, Bradaran, Giulia, Siedler, Simone, Bugge, Kristina, and Haas, Christian T.
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Die krankheitsbedingten Fehlzeiten in Deutschland sind in den vergangenen zehn Jahren um rund 30 Prozentpunkte gestiegen. Besonders hoch sind die Fehlzeiten in Berufen mit hoher körperlicher Arbeitslast. Mit dem Ziel, Ursachen steigender Fehlzeiten und mögliche Gegenmaßnahmen aus Sicht von Mitarbeitern zu identifizieren, wurden qualitative Interviews mit 178 Beschäftigten in Handwerk, Transport, Reinigung und Service aus sechs Großunternehmen in Deutschland geführt.
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- 2019
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15. Gesundheit und Gesundheitsförderung am Arbeitsplatz aus Mitarbeiterperspektive.
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Hammer, Sabine, Deitermann, Martina, Bradaran, Giulia, Siedler, Simone, Bugge, Kristina, and Haas, Christian T.
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Copyright of Zeitschrift für Arbeitswissenschaft is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2019
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16. Changes in the Thickness and Circulation of Multiyear Ice in the Beaufort Gyre Determined From Pseudo‐Lagrangian Methods from 2003–2015
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Mahoney, Andrew R., Hutchings, Jennifer K., Eicken, Hajo, and Haas, Christian
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We combine Eulerian ice draft observations from moored ice‐profiling sonars with buoy‐ and satellite‐derived ice drift data to obtain Lagrangian observations of changes in the thickness distribution of sea ice circulating the Beaufort Sea. We examine repeat measurements of ice draft by identifying events where buoys or pseudobuoys made repeat overpasses within 30 km of ice‐profiling sonar‐equipped Beaufort Gyre Exploration Project moorings. Comparison of ice draft distributions from each overpass indicates that summertime melt rates are related to drift track, with more melt occurring in the southern Beaufort Sea than to the north. Additionally, we find that ice surviving summer in the Beaufort Sea since 2007 is similar in thickness to surrounding first‐year sea ice by the end of the following winter. These findings are supported by continuous ice thickness data from ice mass balance buoys. By examining “plumes” of pseudobuoys originating at each mooring location, we identify anomalous northward transport of ice in the southern Beaufort Sea in 2007 that likely contributed to the record‐breaking reduction in sea ice extent that year. We also find that repeat overpasses have been much rarer since 2007, due to reduced summertime sea ice extent in the Beaufort Gyre and possible changes in ice drift patterns. These changes contribute to diminished replenishment of multiyear sea ice volume in the Arctic. Using ice motion data from buoys and satellites, we track sea ice as it circulates in the Beaufort Gyre and measure changes in its thickness as it passes over moored upward looking sonars. Our results show that ice drifting through the southern Beaufort Sea in summer experiences significant thinning and that multiyear ice surviving the summer does not grow much thicker than first‐year ice even after multiple winters. We also find that the northward retreat of the summertime ice edge in Beaufort Sea is leading to a reduced likelihood of ice recirculating and growing older and thicker in the Beaufort Gyre. Together, these changes make any recovery of the Arctic ice pack increasingly unlikely. Sea ice in the Beaufort Gyre is tracked as it drifts over upward looking sonars to derive Lagrangian changes in its thickness distributionSea ice traversing the Beaufort Sea south of ~75°N experiences significantly greater melt since 2007 than ice to the northBy the end of winter, perennial ice surviving summer in the Beaufort Gyre is similar in thickness to first‐year ice grown in just one season
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- 2019
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17. Estimation of Level and Deformed First-Year Sea Ice Surface Roughness in the Canadian Arctic Archipelago from C- and L-Band Synthetic Aperture Radar
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Cafarella, Silvie Marie, Scharien, Randall, Geldsetzer, Torsten, Howell, Stephen, Haas, Christian, Segal, Rebecca, and Nasonova, Sasha
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AbstractUtilizing synthetic aperture radar (SAR) data to understand and map sea ice roughness is an active area of research. An object-based image analysis is here used to quantitatively link the winter first-year sea ice surface roughness to C-band RADARSAT-2 and L-band ALOS-2 PALSAR-2 SAR backscatter measured in the Canadian Arctic. Results indicate: (1) C-band HH-polarization backscatter is correlated with roughness (r = 0.86) at a shallow incidence angle; and (2) L-band HH- and VV-polarization backscatter is correlated with roughness (r = 0.82) at a shallow incidence angle. Retrieval models for surface roughness are developed and applied to the imagery to demonstrate the potential of SAR for mapping deformation with a best case RMSE of 5 mm. Additionally, strong correlations between C- and L-band SAR backscatter acquired during the advanced melt period, and the winter measured surface roughness, are observed. These results are discussed in the context of SAR potentially providing significant sea ice structural information despite the occurrence of melt and presence of surface melt ponds.
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- 2019
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18. Airborne Observations of Summer Thinning of Multiyear Sea Ice Originating From the Lincoln Sea
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Lange, Benjamin A., Beckers, Justin F., Casey, J. Alec, and Haas, Christian
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To better understand recent changes of Arctic sea ice thickness and extent, it is important to distinguish between the contributions of winter growth and summer melt to the sea ice mass balance. In this study we present a Lagrangian approach to quantify summer sea ice melt in which multiyear ice (MYI) floes that were surveyed by airborne electromagnetic thickness sounding within Nares Strait during summer were backtracked, using satellite imagery, to a region in close proximity (3–20 km) to spring ice thickness surveys carried out in the Lincoln Sea. Typical modal total MYI thicknesses, including ~0.4‐m snow, ranged between 3.9 and 4.7 m in the Lincoln Sea during April. Ice‐only modal thicknesses were between 2.2 and 3.0 m in Nares Strait during August. Total thinning including snow and ice was 1.3 ± 0.1 m including 0.4 ± 0.09 m of snow melt and 0.9 ± 0.2 m of ice melt. This translates to a seasonal net heat input of 305 ± 69 MJ/m2(262 ± 60 MJ/m2for ice only) and seasonal net heat flux of 57 ± 13 W/m2(45 ± 10 W/m2for ice only), which is unlikely to be explained by solar radiation fluxes alone. Furthermore, our approach provides an improvement on traditional ice mass balance buoy estimates because it integrates melt over larger spatial scales, where melt can be highly variable due to differential melt experienced between melt ponds, bare ice, hummocks, and ridges. Some of the oldest and thickest sea ice remains in a small region between Canada, Greenland and the North Pole, the so‐called "Last Ice Area", and will retain this ice longest into the future. Thus, continued monitoring of this unique sea ice habitat is crucial in order to document ongoing changes in the physical environment and to better predict the fate of many animals that depend on sea ice for survival (e.g., polar bears and seals). In this study, we compared sea ice thickness measurements from spring and summer to provide a better understanding of how the ice changes from season to season. Ice thickness changes provide important information on the Arctic Ocean's energy budget, a good indicator of the health of the Arctic Ocean. Our measurements are particularly important because they are the first of their kind over old, thick ice during summer in this unique region. We showed that 0.9 m of old sea ice melted from spring to summer. Although this is comparable to previous studies of old ice, it is important to continue these measurements in order document the expected ongoing changes to the sea ice environment and monitor the health of the Arctic Ocean. MYI surveyed in the Lincoln Sea during spring had modal thicknesses of 3.9‐4.7 m, which thinned to 2.2‐3.0 m in summer in Nares StraitBacktracking individual floes with satellite images was used to reconstruct positions of the same ice fields surveyed in spring and summerEstimated sea ice melt was 0.9 +/‐ 0.2 m, slightly higher than observations by ice mass balance buoys for the same region
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- 2019
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19. Perspective—New Perspectives from Classical Transition State Theory: The Hydrogen Evolution Reaction on Metal Electrodes
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Dadallagei, Kasun S. R., Parr IV, Daniel L., Coduto, Joshua R., Lazicki, Andrew, DeBie, Sidney, Haas, Christian D., and Leddy, Johna
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New perspectives derive from classical transition state theory applied to hydrogen evolution reactions (HER). Trasatti found exchange current density j0increases exponentially with metal electrode work function Φ. The elementary electron transfer step M(e)+Hads+⇄M(0)+Hads•specifies the metal in the transition state and derives rate equations where metal specific physiochemical property Φ is explicit. Linearity of log j0with Φ is quantified. Φ raises j0because Φ lowers the activation energy for electrocatalysis. Rate expressions that embed material specific physiochemical properties provide opportunities for a priori electrocatalyst design and fundamental insights on electron transfer kinetics. New perspectives derive from revisit of established HER data with classical transition state theory.
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- 2023
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20. Directed Technical Change and Energy Intensity Dynamics: Structural Change vs. Energy Efficiency
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Haas, Christian and Kempa, Karol
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This paper uses a model with Directed Technical Change to theoretically analyse observable heterogeneous energy intensity developments. Based on the empirical evidence, we decompose changes in aggregate energy intensity into structural changes in the economy (structural effect) and within-sector energy efficiency improvements (efficiency effect). The relative importance of these effects is determined by energy price growth and sectoral productivities that drive the direction of technical change. When research is directed to the labour-intensive sector, the structural effect is the main driver of energy intensity dynamics. In contrast, the efficiency effect dominates energy intensity developments, when research is directed to energy-intensive industries. Increasing energy price generally leads to lower energy intensities and temporal energy price shocks might induce a permanent redirection of innovation activities. We calibrate the model to empirical data and simulate energy intensity developments across countries. The results of our very stylised model are largely consistent with empirical evidence.
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- 2018
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21. An Assessment of State‐of‐the‐Art Mean Sea Surface and Geoid Models of the Arctic Ocean: Implications for Sea Ice Freeboard Retrieval
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Skourup, Henriette, Farrell, Sinéad Louise, Hendricks, Stefan, Ricker, Robert, Armitage, Thomas W. K., Ridout, Andy, Andersen, Ole Baltazar, Haas, Christian, and Baker, Steven
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State‐of‐the‐art Arctic Ocean mean sea surface (MSS) models and global geoid models (GGMs) are used to support sea ice freeboard estimation from satellite altimeters, as well as in oceanographic studies such as mapping sea level anomalies and mean dynamic ocean topography. However, errors in a given model in the high‐frequency domain, primarily due to unresolved gravity features, can result in errors in the estimated along‐track freeboard. These errors are exacerbated in areas with a sparse lead distribution in consolidated ice pack conditions. Additionally model errors can impact ocean geostrophic currents, derived from satellite altimeter data, while remaining biases in these models may impact longer‐term, multisensor oceanographic time series of sea level change in the Arctic. This study focuses on an assessment of five state‐of‐the‐art Arctic MSS models (UCL13/04 and DTU15/13/10) and a commonly used GGM (EGM2008). We describe errors due to unresolved gravity features, intersatellite biases, and remaining satellite orbit errors, and their impact on the derivation of sea ice freeboard. The latest MSS models, incorporating CryoSat‐2 sea surface height measurements, show improved definition of gravity features, such as the Gakkel Ridge. The standard deviation between models ranges 0.03–0.25 m. The impact of remaining MSS/GGM errors on freeboard retrieval can reach several decimeters in parts of the Arctic. While the maximum observed freeboard difference found in the central Arctic was 0.59 m (UCL13 MSS minus EGM2008 GGM), the standard deviation in freeboard differences is 0.03–0.06 m. A major advancement in mapping the Arctic Ocean mean sea surface (MSS) is realized through the inclusion of CryoSat‐2 dataSea ice freeboard retrievals from airborne/satellite altimeter measurements are impacted by the choice of MSS/GGM model used in the retrieval algorithmDepending on which MSS/GGM is used, the standard deviation of freeboard differences ranges 0.03–0.06 m, corresponding to an ice thickness uncertainty of 0.24–0.54 m
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- 2017
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22. Snow thickness profiling on Antarctic sea ice with GPR—Rapid and accurate measurements with the potential to upscale needles to a haystack
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Pfaffhuber, Andreas A., Lieser, Jan L., and Haas, Christian
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Snow thickness on sea ice is a largely undersampled parameter yet of importance for the sea ice mass balance and for satellite‐based sea ice thickness estimates and thus our general understanding of global ice volume change. Traditional direct thickness measurements with meter sticks can provide accurate but only spot information, referred to as “needles” due to their pinpoint focus and information, while airborne and satellite remote sensing snow products, referred to as “the haystack,” have large uncertainties due to their scale. We demonstrate the remarkable accuracy and applicability of ground‐penetrating radar (GPR) snow thickness measurements by comparing them with in situ meter stick data from two field campaigns to Antarctica in late winter/early spring. The efficiency and millimeter‐to‐centimeter accuracy of GPR enables practitioners to acquire extensive, semiregional data with the potential to upscale needles to the haystack and to potentially calibrate satellite remote sensing products that we confirm to derive roughly 30% of the in situ thickness. We find the radar wave propagation velocity in snow to be rather constant (± 6%), encouraging regional snow thickness surveys. Snow thinner than 10 cm is under the detection limit with the off‐the‐shelf GPR setup utilized in our study. Snow on sea ice, especially on Antarctic sea ice, plays a significant role in climate analysis due to its contribution to the mass and volume balance of the cryosphere. The thickness of snow on sea ice is not known in full detail as it is hard to derive from satellite data. Based on an extensive data set from two Antarctic winter/spring expeditions, we show the efficiency and accuracy of ground‐penetrating radar to map snow thickness on a semiregional scale. Such surveys could potentially be extended to larger scales and contribute to satellite snow thickness algorithm calibration schemes. In situ data from 17 sites in East and West Antarctica confirm ground‐based GPR snow thickness profiling feasibility on winter/spring sea iceAverage accuracy of GPR‐derived median snow thickness along 100 and 200 m long profiles is better than 1 cmAnalysis of 1450 individual measurements results in a GPR snow thickness accuracy of 0.1 cm and 13.2 cm precision
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- 2017
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23. Atypical hemolytic uremic syndrome in the setting of complement-amplifying conditions: case reports and a review of the evidence for treatment with eculizumab
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Asif, Arif, Nayer, Ali, and Haas, Christian
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Atypical hemolytic uremic syndrome (aHUS) is a rare, genetic, progressive, life-threatening form of thrombotic microangiopathy (TMA) predominantly caused by dysregulation of the alternative pathway of the complement system. Complement-amplifying conditions (CACs), including pregnancy complications [preeclampsia, HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome], malignant hypertension, autoimmune diseases, transplantation, and others, are associated with the onset of TMA in up to 69 % of cases of aHUS. CACs activate the alternative pathway of complement and may be comorbid with aHUS or may unmask a previously undiagnosed case. In this review, three case reports are presented illustrating the onset and diagnosis of aHUS in the setting of different CACs (pregnancy complications, malignant hypertension, renal transplantation). The report also reviews the evidence for a variety of CACs, including those mentioned above as well as infections and drug-induced TMA, and the overlap with aHUS. Finally, we introduce an algorithm for diagnosis and treatment of aHUS in the setting of CACs. If TMA persists despite initial management for the specific CAC, aHUS should be considered. The terminal complement inhibitor eculizumab should be initiated for all patients with confirmed diagnosis of aHUS, with or without a comorbid CAC.
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- 2017
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24. Biomechanical demand analysis of older passengers in a standing position during bus transport
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Schubert, Patric, Liebherr, Magnus, Kersten, Stephanie, and Haas, Christian T.
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Bus driving maneuvers are likely to trigger perturbation forces that may cause postural instability in standing passengers and cause tumble. These noncollision incidents are considered a major cause of injuries and may induce passenger discomfort in public transport.
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- 2017
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25. Sea‐ice thickness from field measurements in the northwestern Barents Sea
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King, Jennifer, Spreen, Gunnar, Gerland, Sebastian, Haas, Christian, Hendricks, Stefan, Kaleschke, Lars, and Wang, Caixin
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The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter‐time sea‐ice area in the Arctic, at −23±4%decade−1. Sea‐ice thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter‐borne electromagnetic (HEM) ice thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to ice thickness calculated from ice draft measured by ULS deployed between 1994 and 1996. These data show that ice thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long‐range advection. In a year with a large inflow of sea‐ice from the Arctic Basin, the Barents Sea ice cover is dominated by thick multiyear ice; as was the case in 2003 and 1995. In a year with an ice cover that was mainly grown in situ, the ice will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in ice thickness. In 2003 the dominant ice class was more than 2 years old; and modal sea‐ice thickness varied regionally from 0.6 to 1.4 m, with the thinner ice being either first‐year ice, or multiyear ice which had come into contact with warm Atlantic water. In 2014 the ice cover was predominantly locally grown ice less than 1 month old (regional modes of 0.5–0.8 m). These two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere. Sea‐ice thickness in the northwestern Barents Sea is strongly variable, both interannually and regionallySea‐ice thickness depends on the balance between local ice formation and long‐range advection of old iceRelations between ice age and thickness can be complicated by specific environmental factors; e.g., warm Atlantic water
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- 2017
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26. Deep uncertainty and the transition to a low-carbon economy
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Haas, Christian, Jahns, Henriette, Kempa, Karol, and Moslener, Ulf
- Abstract
The transformation of economies towards net zero greenhouse gas (GHG) emissions within very few decades will require substantial investments. However, the transition to a low-carbon economy exhibits a high degree of complexity and path dependency. Consequently, firms and investors systematically face deep uncertainty, a situation with no information about the probabilities of possible outcomes, where even the possible outcomes are not known. In this article, we present concepts and classifications of un-certainty and discuss potential sources of deep uncertainty for firms and investors, such as uncertainty about technology development and innovation, the behaviour of competitors, or climate-related policy development. Standard modelling-based decision support tools typically used by firms and investors are of limited value under deep un-certainty. Thus, deep uncertainty deters decision-making and delays low-carbon in-vestment. This article addresses this issue by providing an overview of approaches for decision-making under deep uncertainty. We analyse their applicability for firms and investors and discuss what challenges they might face. Based on this analysis, we de-rive guidelines for policymakers to reduce deep uncertainty and support firms' decision-making under deep uncertainty.
- Published
- 2023
- Full Text
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27. Open-Source Chromatographic Data Analysis for Reaction Optimization and Screening
- Author
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Haas, Christian P., Lübbesmeyer, Maximilian, Jin, Edward H., McDonald, Matthew A., Koscher, Brent A., Guimond, Nicolas, Di Rocco, Laura, Kayser, Henning, Leweke, Samuel, Niedenführ, Sebastian, Nicholls, Rachel, Greeves, Emily, Barber, David M., Hillenbrand, Julius, Volpin, Giulio, and Jensen, Klavs F.
- Abstract
Automation and digitalization solutions in the field of small molecule synthesis face new challenges for chemical reaction analysis, especially in the field of high-performance liquid chromatography (HPLC). Chromatographic data remains locked in vendors’ hardware and software components, limiting their potential in automated workflows and data science applications. In this work, we present an open-source Python project called MOCCA for the analysis of HPLC–DAD (photodiode array detector) raw data. MOCCA provides a comprehensive set of data analysis features, including an automated peak deconvolution routine of known signals, even if overlapped with signals of unexpected impurities or side products. We highlight the broad applicability of MOCCA in four studies: (i) a simulation study to validate MOCCA’s data analysis features; (ii) a reaction kinetics study on a Knoevenagel condensation reaction demonstrating MOCCA’s peak deconvolution feature; (iii) a closed-loop optimization study for the alkylation of 2-pyridone without human control during data analysis; (iv) a well plate screening of categorical reaction parameters for a novel palladium-catalyzed cyanation of aryl halides employing O-protected cyanohydrins. By publishing MOCCA as a Python package with this work, we envision an open-source community project for chromatographic data analysis with the potential of further advancing its scope and capabilities.
- Published
- 2023
- Full Text
- View/download PDF
28. Bacterial communities from Arctic seasonal sea ice are more compositionally variable than those from multi-year sea ice
- Author
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Hatam, Ido, Lange, Benjamin, Beckers, Justin, Haas, Christian, and Lanoil, Brian
- Abstract
Arctic sea ice can be classified into two types: seasonal ice (first-year ice, FYI) and multi-year ice (MYI). Despite striking differences in the physical and chemical characteristics of FYI and MYI, and the key role sea ice bacteria play in biogeochemical cycles of the Arctic Ocean, there are a limited number of studies comparing the bacterial communities from these two ice types. Here, we compare the membership and composition of bacterial communities from FYI and MYI sampled north of Ellesmere Island, Canada. Our results show that communities from both ice types were dominated by similar class-level phylogenetic groups. However, at the operational taxonomic unit (OTU) level, communities from MYI and FYI differed in both membership and composition. Communities from MYI sites had consistent structure, with similar membership (presence/absence) and composition (OTU abundance) independent of location and year of sample. By contrast, communities from FYI were more variable. Although FYI bacterial communities from different locations and different years shared similar membership, they varied significantly in composition. Should these findings apply to sea ice across the Arctic, we predict increased compositional variability in sea ice bacterial communities resulting from the ongoing transition from predominantly MYI to FYI, which may impact nutrient dynamics in the Arctic Ocean.
- Published
- 2016
- Full Text
- View/download PDF
29. Bacterial communities from Arctic seasonal sea ice are more compositionally variable than those from multi-year sea ice
- Author
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Hatam, Ido, Lange, Benjamin, Beckers, Justin, Haas, Christian, and Lanoil, Brian
- Abstract
Arctic sea ice can be classified into two types: seasonal ice (first-year ice, FYI) and multi-year ice (MYI). Despite striking differences in the physical and chemical characteristics of FYI and MYI, and the key role sea ice bacteria play in biogeochemical cycles of the Arctic Ocean, there are a limited number of studies comparing the bacterial communities from these two ice types. Here, we compare the membership and composition of bacterial communities from FYI and MYI sampled north of Ellesmere Island, Canada. Our results show that communities from both ice types were dominated by similar class-level phylogenetic groups. However, at the operational taxonomic unit (OTU) level, communities from MYI and FYI differed in both membership and composition. Communities from MYI sites had consistent structure, with similar membership (presence/absence) and composition (OTU abundance) independent of location and year of sample. By contrast, communities from FYI were more variable. Although FYI bacterial communities from different locations and different years shared similar membership, they varied significantly in composition. Should these findings apply to sea ice across the Arctic, we predict increased compositional variability in sea ice bacterial communities resulting from the ongoing transition from predominantly MYI to FYI, which may impact nutrient dynamics in the Arctic Ocean.
- Published
- 2016
- Full Text
- View/download PDF
30. Varianzbasiertes Gangtraining für Multiple-Sklerose -Patienten.
- Author
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Lutz, Christina, Kersten, Stephanie, Liebherr, Magnus, and Haas, Christian T.
- Published
- 2015
31. ACTIVITIES OF THE SEA ICE PHYSICS GROUP.
- Author
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Bublitz, Anne, Winkler, Maria, Haas, Christian, Nicolaus, Marcel, and Hendricks, Stefan
- Abstract
The article discusses airborne electromagnetic induction (AEM) systems used on a Polarstern cruise to continue the time series of ice thickness measurement in the Arctic Ocean. Topics discussed include survey results being utilized to minimize ship time across the Arctic as well as the use of the AEM Bird from York University in Toronto, Ontario. Also mentioned is the undertaking being a part of the International Arctic Buoy Programme (IABP).
- Published
- 2015
32. Software-based smart factory networking
- Author
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Bauer, Robert, Bless, Roland, Haas, Christian, Jung, Markus, and Zitterbart, Martina
- Abstract
This paper describes a framework for software-based networking in smart factories (SF) that enables them to easily adapt the communication network to changing requirements. Similar to cloud-based systems, such SFs could be seen as production clusters that could be rented and configured as needed. The SF network utilizes software-defined networking (SDN) combined with network functions virtualization (NFV) in order to achieve the required flexibility. This paper presents and discusses our visionof a network architecture for SFs based on SDN and network virtualization in order to support smart services especially for Industrie 4.0. Despite the fact that the technology is nowadays not yet ready for deployment in today's manufacturing networks, we present a framework for software-defined factory networks and discuss possible challenges and benefits.
- Published
- 2016
- Full Text
- View/download PDF
33. Evaluation of Operation IceBridge quick‐look snow depth estimates on sea ice
- Author
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King, Joshua, Howell, Stephen, Derksen, Chris, Rutter, Nick, Toose, Peter, Beckers, Justin F., Haas, Christian, Kurtz, Nathan, and Richter‐Menge, Jacqueline
- Abstract
We evaluate Operation IceBridge (OIB) “quick‐look” snow depth on sea ice retrievals using in situ measurements taken over immobile first‐year ice (FYI) and multiyear ice (MYI) during March of 2014. Good agreement was found over undeformed FYI (−4.5 cm mean bias) with reduced agreement over deformed FYI (−6.6 cm mean bias). Over MYI, the mean bias was −5.7 cm, but 54% of retrievals were discarded by the OIB retrieval process as compared to only 10% over FYI. Footprint scale analysis revealed a root‐mean‐square error (RMSE) of 6.2 cm over undeformed FYI with RMSE of 10.5 cm and 17.5 cm in the more complex deformed FYI and MYI environments. Correlation analysis was used to demonstrate contrasting retrieval uncertainty associated with spatial aggregation and ice surface roughness. OIB QL snow depth on sea ice retrieval performs well in level ice environmentsDeformed first‐year and multiyear ice are difficult retrieval environments for the OIB QL productSurface roughness contributes to diminished correlation between measured and retrieved snow depths
- Published
- 2015
- Full Text
- View/download PDF
34. Ice thickness in the Northwest Passage
- Author
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Haas, Christian and Howell, Stephen E. L.
- Abstract
Recently, the feasibility of commercial shipping in the ice‐prone Northwest Passage (NWP) has attracted a lot of attention. However, very little ice thickness information actually exists. We present results of the first ever airborne electromagnetic ice thickness surveys over the NWP carried out in April and May 2011 and 2015 over first‐year and multiyear ice. These show modal thicknesses between 1.8 and 2.0 m in all regions. Mean thicknesses over 3 m and thick, deformed ice were observed over some multiyear ice regimes shown to originate from the Arctic Ocean. Thick ice features more than 100 m wide and thicker than 4 m occurred frequently. Results indicate that even in today's climate, ice conditions must still be considered severe. These results have important implications for the prediction of ice breakup and summer ice conditions, and the assessment of sea ice hazards during the summer shipping season. Ice is still quite thick in Northwest Passage and potentially hazardous for shippingMean ice thickness depends on age and specific source region of sea ice in previous summersMean ice thickness and deformation decrease with decreasing northern latitude
- Published
- 2015
- Full Text
- View/download PDF
35. No stress after 24‐hour on‐call shifts?
- Author
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Harbeck, Birgit, Suefke, Sven, Haas, Christian S., Lehnert, Hendrik, Kropp, Peter, and Moenig, Heiner
- Abstract
No stress after 24‐hour on‐call shifts? : Birgit Harbeck, et al. Department of Medicine I, University of Luebeck, Germany Irregular sleep patterns can adversely affect physiological functions and have been associated with increased physiological and psychological stress. Nocturnal work of physicians during 24‐hour on‐call shifts (OCS) disrupts the sleep/wake cycle. Chronic exposure to distress has been shown to affect cardiovascular homeostasis and to impair performance in neurocognitive and simulated clinical tasks. In a prospective cohort study, biochemical and physiological stress parameters were assessed in 11 female and 9 male physicians (median age: 32 years, range 26−42 years) before a normal working day and after a 24‐hour OCS in internal medicine. In addition, various tests of attentional performance (TAP) were conducted. The levels of thyroid stimulating hormone (TSH) were significantly higher after a 24‐ hour OCS, while there were no significant changes in cortisol, epinephrine, and norepinephrine levels. Heart rate variability and skin resistance increased following an OCS, although the differences were not statistically significant. Intrinsic alertness was comparable, while phasic alertness was significantly improved following a 24‐hour OCS. Focused attention tended to be better following a night shift. There was no correlation with age or medical working experience; however, men experienced more stress than women. Following a 24‐hour OCS, (i) TSH may be an early and sensitive biochemical predictor of stress; (ii) other classical biochemical stress parameters do not depict the psychological stress perceived by physicians; (iii) there may be a mismatch between experienced and objective stress levels; (iv) neurocognitive functions are not impaired, while performance may even be improved; and (v) men might be more sensitive to distress.
- Published
- 2015
- Full Text
- View/download PDF
36. No stress after 24-hour on-call shifts?
- Author
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Harbeck, Birgit, Suefke, Sven, Haas, Christian S, Lehnert, Hendrik, Kropp, Peter, and Moenig, Heiner
- Published
- 2015
- Full Text
- View/download PDF
37. Acute kidney injury and thrombocytopenic fever--consider the infrequent causes.
- Author
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Haas, Christian S., Lehne, Walter, Muck, Philip, Boehm, Anja, Rupp, Jan, Steinhoff, Juergen, and Lehnert, Hendrik
- Abstract
Acute kidney injury (AKI), fever, hepatosplenomegaly, and thrombocytopenia are characteristics of Hantavirus infections and leptospirosis, both worldwide zoonoses. Although AKI is usually the result of tubulointerstitial nephritis, glomerular damage with significant albuminuria and hematuria may be noted in both entities. Although Hantavirus infections are endemic in Western Europe and the United States, leptospirosis is predominantly seen in parts of South America and Asia. We here report 3 cases of thrombocytopenic fever and AKI presenting within several months in Northern Germany with initially suspected Hantavirus infection. Serologic testing finally unraveled the diagnosis of leptospiral infection. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
38. Computed tomography angiography in patients with suspected pulmonary embolism—too often considered?
- Author
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Haap, Michael M., Gatidis, Sergios, Horger, Marius, Riessen, Reimer, Lehnert, Hendrik, and Haas, Christian S.
- Abstract
Abstract: Background: Pulmonary embolism (PE) is a major cause of morbidity and mortality associated with surgery and medical illnesses. In recent years, pulmonary computed tomography angiography (CTA) has become the diagnostic method of choice. However, it remains unclear when to perform CTA and how often a decision based on clinical judgment results in positive or negative findings. Methods: In a retrospective study, 261 patients admitted for suspected PE were evaluated with pulmonary CTA. Decisions to order CTA were based on clinical judgment and optionally quantitative d-dimer assays. Clinical, radiologic, and laboratory data were revisited and compared in patients with and without proven PE. Results: The patients'' mean age was 63 ± 1 years; almost 30% of all participants had at least a moderately reduced renal function. Pulmonary CTA demonstrated PE in only 14.9%; both age and sex distribution was comparable in the PE and non-PE group. Proximal deep vein thrombosis or pathologic chest x-rays were significantly more likely in patients with PE (P < .001 and P < .05), whereas echocardiography results were comparable. d-dimer values were noticeably higher in the PE group (P < .001); however, C-reactive protein and troponin T levels were not helpful. Conclusions: Pulmonary CTA confirmed PE in only a minority of patients and may be overused. Clinical judgment in conjunction with d-dimer evaluation was of limited help to predict positive results but surprisingly comparable with previous results using pretest probability scoring systems. Using present and previous data, a simplified enhanced algorithm is proposed to reduce use of CTA. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
39. Computed tomography angiography in patients with suspected pulmonary embolism-too often considered?
- Author
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Haap, Michael M., Gatidis, Sergios, Horger, Marius, Riessen, Reimer, Lehnert, Hendrik, and Haas, Christian S.
- Abstract
Background: Pulmonary embolism (PE) is a major cause of morbidity and mortality associated with surgery and medical illnesses. In recent years, pulmonary computed tomography angiography (CTA) has become the diagnostic method of choice. However, it remains unclear when to perform CTA and how often a decision based on clinical judgment results in positive or negative findings.Methods: In a retrospective study, 261 patients admitted for suspected PE were evaluated with pulmonary CTA. Decisions to order CTA were based on clinical judgment and optionally quantitative d-dimer assays. Clinical, radiologic, and laboratory data were revisited and compared in patients with and without proven PE.Results: The patients' mean age was 63 ± 1 years; almost 30% of all participants had at least a moderately reduced renal function. Pulmonary CTA demonstrated PE in only 14.9%; both age and sex distribution was comparable in the PE and non-PE group. Proximal deep vein thrombosis or pathologic chest x-rays were significantly more likely in patients with PE (P < .001 and P < .05), whereas echocardiography results were comparable. d-dimer values were noticeably higher in the PE group (P < .001); however, C-reactive protein and troponin T levels were not helpful.Conclusions: Pulmonary CTA confirmed PE in only a minority of patients and may be overused. Clinical judgment in conjunction with d-dimer evaluation was of limited help to predict positive results but surprisingly comparable with previous results using pretest probability scoring systems. Using present and previous data, a simplified enhanced algorithm is proposed to reduce use of CTA. [ABSTRACT FROM AUTHOR]- Published
- 2012
- Full Text
- View/download PDF
40. ASSISTENZSYSTEME FÜR DAS PARKEN.
- Author
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NAGLER, ANDREAS, LüBCKE, MICHAEL, and HAAS, CHRISTIAN
- Published
- 2011
41. Asymptomatic Sustained Ventricular Fibrillation in a Patient With Left Ventricular Assist Device.
- Author
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Busch, Mathias C., Haap, Michael, Kristen, Arnt, and Haas, Christian S.
- Abstract
Optimal medical treatment, cardiac resynchronization, and the use of an implantable cardioverter defibrillator are established therapies of severe congestive heart failure. In refractory cases, left ventricular assist devices are more and more used not only as bridging to cardiac transplantation but also as destination therapy. Ventricular arrhythmias may represent a life-threatening condition and often result in clinical deterioration in patients with congestive heart failure. We report a case of asymptomatic sustained ventricular fibrillation with preserved hemodynamics caused by a nonpulsatile left ventricular assist device. Consecutive adequate but unsuccessful discharges of the implantable cardioverter defibrillator were the only sign of the usually fatal arrhythmia, prompting the patient to consult emergency services. Electrolyte supplementation and initiation of therapy with amiodarone followed by external defibrillation resulted in successful restoration of a stable cardiac rhythm after 3.5 hours. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
42. 4. REGIONAL VARIABILITY OF SEA ICE PROPERTIES AND THICKNESS IN THE NORTHWESTERN WEDDELL SEA OBTAINED BY IN-SITU AND SATELLITE MEASUREMENTS.
- Author
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Haas, Christian, Friedrich, Anika, Li, Zijun, Nicolaus, Marcel, Pfaffling, Andreas, and Toyota, Takenobu
- Abstract
The article presents the sea ice investigations performed by the research vessel Polarstern in the north-western Weddell Sea southward of the South Orkney Islands. Among the main objectives of the sea ice geophysical programme were quantification of the regional variability of first- and second-year sea ice and snow thickness in the north-western Weddell Sea and investigation of physical and biological ice properties and processes. A series of measurements have been carried out on the ice in order to address those goals including ice coring and analyses of ice temperature, salinity and texture profiles and snow-pit measurements of snow properties during ice stations.
- Published
- 2009
43. Direct helicopter EM -- Sea-ice thickness inversion assessed with synthetic and field data.
- Author
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Pfaffling, Andreas, Haas, Christian, and Reid, James E.
- Subjects
DEPTH sounding ,INVERSION (Geophysics) ,THICKNESS measurement ,CLIMATE change ,BRACKISH waters - Abstract
Accuracy and precision of helicopter electromagnetic (HEM) sounding are the essential parameters for HEM sea-ice thickness profiling. For sea-ice thickness research, the quality of HEM ice thickness estimates must be better than I0 cm to detect potential climatologic thickness changes. We introduce and assess a direct, ID HEM data inversion algorithm for estimating sea-ice thickness. For synthetic quality assessment, an analytically determined HEM sea-ice thickness sensitivity is used to derive precision and accuracy. Precision is related directly to random, instrumental noise, although accuracy is defined by systematic bias arising from the data processing algorithm. For the in-phase component of the HEM response, sensitivity increases with frequency and coil spacing, but decreases with flying height. For small-scale HEM instruments used in sea-ice thickness surveys, instrumental noise must not exceed 5 ppm to reach ice thickness precision of 10 cm at 15-m nominal flying height. Comparable precision is yielded at 30-m height for conventional exploration HEM systems with bigger coil spacings. Accuracy losses caused by approximations made for the direct inversion are negligible for brackish water and remain better than 10 cm for saline water. Synthetic precision and accuracy estimates are verified with drill-hole validated field data from East Antarctica, where HEM-derived level-ice thickness agrees with drilling results to within 4%, or 2 cm [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
44. Spatially resolved determination of atomic particle densities and line shapes within an arc...
- Author
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Pretzler, Georg and Haas, Christian
- Subjects
ATOMS ,CHROMIUM - Abstract
Presents a study which measured the particle density of ground-state chromium atoms with one cross section of an arc plasma, while determining the spatial distribution of the line shape of the chromium resonance line at 427.48 nm. Scanning of dye laser wavelength; Statistical data supporting the study.
- Published
- 1997
45. Security in Border Control and Area Monitoring
- Author
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Krüger, Daniela, Haas, Christian, Rothenpieler, Peter, Dudek, Denise, and Pfisterer, Dennis
- Abstract
AbstractArea monitoring is one of the most popular application scenarios for wireless sensor networks. The pure task of distributed object tracking has often been investigated, but little attention has been given to secure object tracking. This article contains a security analysis and an attacker model for the scenario of secure border surveillance and describes security mechanisms and protocols as well as a realization of such a system.
- Published
- 2010
- Full Text
- View/download PDF
46. Simulation of the CryoSat-2 satellite radar altimeter sea ice thickness retrieval uncertainty
- Author
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Tonboe, Rasmus T., Pedersen, Leif Toudal, and Haas, Christian
- Abstract
Although it is well known that radar waves penetrate into snow and sea ice, the exact mechanisms for radar altimeter scattering and its link to the depth of the effective scattering surface from sea ice are not well known. Previously proposed mechanisms linked the snow-ice interface, i.e., the dominating scattering horizon, directly with the depth of the effective scattering surface. However, simulations using a multilayer radar scattering model show that the effective scattering surface is affected by snow-cover and ice properties. With the coming CryoSat-2 (planned launch in 2010) satellite radar altimeter, it is proposed that sea ice thickness can be derived during winter by measuring its freeboard. In this study we evaluate the radar altimeter sea ice thickness retrieval uncertainty in terms of floe buoyancy, radar penetration, and ice type distribution using both a scattering model and Archimedes’ principle. The effect of the snow cover on the floe buoyancy and radar penetration and on the ice cover spatial and temporal variability is assessed from field campaign measurements in the Arctic resulting in ice thickness uncertainties of about 0.3 m for the snow depth variability and 0.3 m for the snow density variability. In addition to these well-known uncertainties, we use high-resolution RADARSAT synthetic aperture radar (SAR) data to simulate errors due to the variability of the effective scattering surface as a result of the subfootprint spatial backscatter and elevation distribution, sometimes called preferential sampling. In particular, in areas where ridges represent a significant part of the ice volume (e.g., the Lincoln Sea), the average simulated altimeter thickness estimate of 2.68 m is lower than the real average footprint thickness of 3.85 m, making preferential sampling the single most important error source. This means that the errors are large and yet manageable if the relevant quantities are known a priori. Radar altimeter ice thickness retrieval uncertainties are discussed.
- Published
- 2010
- Full Text
- View/download PDF
47. Effect of interleukin-15 on the course of myocarditis in Coxsackievirus B3-infected BALB/c mice
- Author
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Bigalke, Boris, Schwimmbeck, Peter L., Haas, Christian S., and Lindemann, Stephan
- Abstract
Cytokines have an important role in both the initiation and perpetuation of viral myocarditis. Because a causative therapy of myocarditis is not yet well established and immunomodulation is a promising approach, the influence of interleukin (IL)-15, a proinflammatory cytokine, on the course of experimental myocarditis in Coxsackievirus B3 (CVB3)-infected mice was examined.
- Published
- 2009
- Full Text
- View/download PDF
48. Angiopoietin 1 and 2 gene and protein expression is differentially regulated in acute anti-Thy1.1 glomerulonephritis
- Author
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Câmpean, Valentina, Karpe, Britta, Haas, Christian, Atalla, Akram, Peters, Harm, Rupprecht, Harald, Liebner, Stefan, Acker, Till, Plate, Karl, and Amann, Kerstin
- Abstract
Capillary neoformation is important in repair of glomerular injury of various origins. VEGF was shown to be crucial for glomerular capillary repair in glomerulonephritis (GN). We reasoned that other angiogenic factors are likewise involved in glomerular capillary remodeling and found angiopoietin 1 and -2 (ANG1 and ANG2) mRNA to be upregulated in cDNA microarrays of microdissected glomeruli of anti-Thy1.1 GN of the rat. We then studied glomerular in situ gene and protein expression of ANG1 and ANG2 and their receptor Tie-2 in the course of anti-Thy1.1 GN, which was induced by injection of OX-7 antibody. Animals were perfusion fixed at days 6and 12after GN induction and compared with nonnephritic controls receiving PBS. Capillary damage and repair were quantitatively analyzed using stereological techniques. Gene and protein expression of ANG1 and ANG2 and their receptor Tie-2 was analyzed using real-time quantitative PCR from microdissected glomeruli, nonradioactive in situ hybridization, double immunofluorescence, and Western blot analysis. Glomerular capillarization assessed as length density was significantly lower at day 6of anti-Thy1.1 GN than in controls; it was back to normal values at day 12. ANG1 and ANG2 gene expression was markedly upregulated at day 6of the disease compared with controls. Protein expression of ANG1 and ANG2 was confined to podocytes and that of Tie-2 to endothelial cells. At day 12of anti-Thy1.1 GN when capillary restoration was nearly completed, ANG1 and ANG2 gene expression returned to basal levels, whereas Tie-2 expression was still high. With the use of a combined molecular and in situ approach, the spatial and temporal gene and protein expression of the angiopoietins and their receptor was analyzed in anti-Thy1.1 GN. The results indicate that glomerular expression of ANG1 and ANG2 and Tie-2 is differentially regulated and may contribute to healing and endothelial cell stabilization in experimental GN.
- Published
- 2008
- Full Text
- View/download PDF
49. Antarctic Sea Ice -- the Odd Down South.
- Author
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Haas, Christian
- Abstract
The article discusses a research on the changes in the Arctic sea-ice cover in comparison with sea-ice trends in the Southern Ocean around Antartica with the goal of understanding the nature and role of Antartic sea ice. It refers to the remoteness of the Southern Ocean and Antarctica as obstacles in studying the larger regions of the Antarctic. It recommends the establishment by Canada of a program of Antarctic research cruises or a long-range aircraft like a Basler BT67 converted DC-3 as tools to make Canada a leader in Antarctic and Arctic research.
- Published
- 2008
50. What you should know about the work-up of a renal biopsy.
- Author
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Amann, Kerstin and Haas, Christian S
- Published
- 2006
- Full Text
- View/download PDF
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