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Introduction: Asthma is one of the most common chronic diseases in childhood and is generally characterized by exercise induced bronchoconstriction (EIB). Assessing EIB is time consuming and expensive as it requires a fully equipped pulmonary function laboratory. Analysis of volatile organic compounds (VOCs) in breath is a novel technique for examining biomarkers which may associate with asthma features. The aim of this pilot study was to identify potential markers in the relationship between EIB and VOCs. Methods: Children between four and 14 years old were asked to provide a breath sample prior to undergoing an exercise challenge test to assess for EIB. Results: Breath samples were collected and analyzed in 46 asthmatic children, 21 with EIB and 25 without EIB (NO-EIB). Molecular features (MFs) were not significantly different between EIB and NO-EIB controls. 29 of the 46 children were corticosteroid naïve, 10 with EIB and 13 without. In the corticosteroid naïve group EIB was associated with increased MF23 and MF14 in the lower breath sample (p-value < 0.05). Conclusion: This pilot study shows that EIB was related to an increased MF14 and MF23 in corticosteroid naïve children. The tentative identities of these compounds are octanal and dodecane/tetradecane respectively. These candidate biomarkers have a potential to enable non-invasive diagnosis of EIB in steroid-naïve children. Trial registration This study is registered in the Netherlands trial register (trial no. NL6087) at 14 February 2017. [ABSTRACT FROM AUTHOR]

Background: Asthma is one of the most common chronic diseases in childhood. Regular follow-up of physiological parameters in the home setting, in relation to asthma symptoms, can provide complementary quantitative insights into the dynamics of the asthma status. Despite considerable interest in asthma home-monitoring in children, there is a paucity of scientific evidence, especially on multi-parameter monitoring approaches. Therefore, the aim of this study is to investigate whether asthma control can be accurately assessed in the home situation by combining parameters from respiratory physiology sensors. Methods: Sixty asthmatic and thirty non-asthmatic children were enrolled in the observational WEARCON-study. Asthma control was assessed according to GINA guidelines by the paediatrician. All children were also evaluated during a 2-week home-monitoring period with wearable devices; a physical activity tracker, a handheld spirometer, smart inhalers, and an ambulatory electrocardiography device to monitor heart and respiratory rate. Multiple logistic regression analysis was used to determine which diagnostic measures were associated with asthma control. Results: 24 of the 27 uncontrolled asthmatic children and 29 of the 32 controlled asthmatic children could be accurately identified with this model. The final model showed that a larger variation in pre-exercise lung function (OR = 1.34 95%-CI 1.07-1.68), an earlier wake-up-time (OR = 1.05 95%-CI 1.01-1.10), more reliever use (OR = 1.11 95%-CI 1.03-1.19) and a longer respiratory rate recovery time (OR = 1.12 95%-CI 1.05-1.20) were significant contributors to the probability of having uncontrolled asthma. Conclusions: Home-monitoring of physiological parameters correlates with paediatrician assessed asthma control. The constructed multivariate model identifies 88.9% of all uncontrolled asthmatic children, indicating a high potential for monitoring of asthma control. This may allow healthcare professionals to assess asthma control at home. Trial registration: Netherlands Trail Register, NL6087. Registered 14 February 2017. [ABSTRACT FROM AUTHOR]

An often-overlooked property of transition metal oxide thin films is their microscopic surface structure and its effect on the electronic properties in the ultrathin limit. Contrary to the expected conservation of the perovskite stacking order in the (001) direction, heteroepitaxially grown SrIrO3 films on TiO2-terminated SrTiO3 are found to exhibit a terminating SrO surface layer. The proposed mechanism for the self-organized conversion involves the adsorption of excess oxygen ions at the apical sites of the IrO2-terminated surface and the subsequent decomposition of the IrO6 octahedra into gaseous molecular IrO3 and the remaining SrO-terminated surface. Whereas the ab initio calculated electronic structure of SrO-terminated SrIrO3 in the monolayer limit exhibits a striking similarity to bulk Sr 2 IrO 4 , the broken octahedral symmetry at the IrO2-terminated surface would mix the otherwise crystal field split eg and t 2 g states, resulting in distinctly different low-energy electronic states. [ABSTRACT FROM AUTHOR]

Presents information on a study which used low-temperature photoluminiscence (PL) in analyzing the carbon concentration in metalorganic molecular-beam epitaxy p-gallium arsenide. Correlation between PL characteristics and hole concentration; Determination of the hole concentration by luminescence; Calibration of carbon content with respect to hole concentrations.

Focuses on a study which analyzed the performance of gaseous precursor diethyl-tellurium (DETe) for n-type doping of gallium arsenide. Advantages of using tellurium as a dopant compared to silicon; Properties of the molecular source of DETe; Information on the suitability of tellurium as a dopant.

Invasive pulmonary aspergillosis (IPA) is a life-threatening infection predominantly affecting immunocompromised patients, e.g. with acute leukemia. This case report demonstrates that IPA can also occur in non-neutropenic critically ill surgical patients. The case of a 63-year-old woman is reported, who developed IPA of the respiratory tract in the course of diffuse purulent peritonitis. First-line therapy with voriconazol failed to be effective. However, application of caspofungin, intensive kinetic therapy (including prone position) and airway management by interventional bronchoscopy enabled successful treatment of this severe complication. [ABSTRACT FROM AUTHOR]

Travelling Ionospheric Disturbances (TIDs), which are caused by Atmospheric Gravity Waves (AGWs), are detected and characterised by a joint analysis of the results of two measurement techniques: incoherent scatter radar and multiple-receiver GPS measurements. Both techniques to measure TIDs are already well known, but are developed further in this study, and the strengths of the two are combined, in order to obtain semi-automatic tools for objective TID detection. The incoherent scatter radar provides a good vertical range and resolution and the GPS measurements provide a good horizontal range and resolution, while both have a good temporal resolution. Using the combination of the methods, the following parameters of the TID can be determined: the time of day when the TID occurs at one location, the period length (or frequency), the vertical phase velocity, the amplitude spectral density, the vertical wavelength, the azimuth angle of horizontal orientation, the horizontal wavelength, and the horizontal phase velocity. This technique will allow a systematic characterisation of AGWTIDs, which can be useful, among other things, for statistical analyses. The presented technique is demonstrated on data of 20 January 2010 using data from the EISCAT incoherent scatter radar in Tromsø and from the SWEPOS GPS network in Sweden. On this day around 07:00-12:00UT, a mediumscale TID was observed from both data sets simultaneously. The TID had a period length of around 2 h, and its wave propagated southeastward with a horizontal phase velocity of about 67ms-1 and a wavelength of about 500 km. The TID had its maximum amplitude in Tromsø at 10:00 UT. The period length detected from the GPS results was twice the main period length detected from the radar, indicating a different harmonic of the same wave. The horizontal wavelength and phase velocity are also estimated from the radar results using Hines' theory, using the WKB approximation to account for inhomogeneity of the atmosphere. The results of this estimate are higher than those detected from the GPS data. The most likely explanation for this is that Hines' theory overestimated the values, because the atmosphere was too inhomogeneous even for the WKB approximation to be valid. [ABSTRACT FROM AUTHOR]

This paper presents a novel method to determine a baseline for magnetometer data. This baseline consists of all magnetic field components not related to ionospheric and magnetospheric disturbances, i.e. all field components due to solar quiet variations and other background variations, as well as equipment effects. Extraction of this baseline is useful when the disturbance magnetic field is analysed. The full baseline is composed of two main constituents: the diurnal baseline and the long-term baseline. For the diurnal baseline, first "templates" are derived, based on the lowest few harmonics of the daily curves from the quietest days. The diurnal variation of the baseline is obtained by interpolating between these templates. This method ensures a smooth baseline at all times, avoiding any discontinuities at transitions between days. The long-term baseline is obtained by interpolating between the daily median values. This way, the baseline is ensured to follow long-term trends, such as seasonal and tidal variations, as well as equipment drift. The daily median values are calculated for all days except the most disturbed ones; a procedure is included to ensure that the median values used are unaffected by disturbances. This procedure avoids many problems associated with other existing baseline procedures, and makes magnetometer data suitable, for instance, for the calculation of ionospheric equivalent currents related to geomagnetic storms. Even data from remote unmanned magnetometers, which exhibit significant equipment effects, can be made suitable this way, which can give valuable contributions to the equivalent current database. [ABSTRACT FROM AUTHOR]

The ionosphere above Scandinavia in December 2006 is successfully imaged by 4-dimensional tomography using the software package MIDAS from the University of Bath. The method concentrates on medium-scale structures: between 100 km and 2000 km in horizontal size. The input consists of TEC measurements from the dense GPS network Geotrim in Finland. In order to ensure sufficient vertical resolution of the result, EISCAT incoherent scatter radar data from Tromsø are used as additional input to provide the vertical profile information. The TEC offset of the measurements is unknown, but the inversion procedure is able to determine this automatically. This auto-calibration is shown to work well. Comparisons with EISCAT radar results and with occultation results show that the inversion using EISCAT data for profile information is much better able to resolve vertical profiles of irregular structures than the inversion using built-in profiles. Still, with either method the intensities of irregular structures of sizes near the resolution (about 100 km horizontal size) can be underestimated. Also, the accuracy of the inversion worsens above areas where no receivers are available. The ionosphere over Scandinavia in December 2006 often showed a dense E-layer in early morning hours, which generally disappeared during midday when a dense F-layer was present. On 14 December, a strong coronal mass ejection occurred, and many intense irregularities appeared in the ionosphere, which extended to high altitudes. [ABSTRACT FROM AUTHOR]

Background: The impact of brain shift on deep brain stimulation surgery is considerable. In DBS surgery, brain shift is mainly caused by CSF loss. CSF loss can be estimated by post-surgical intracranial air. Different approaches and techniques exist to minimize CSF loss and hence brain shift. The aim of this survey was to investigate the extent and dynamics of CSF loss during DBS surgery, analyze its impact on final electrode position, and describe a simple and inexpensive method of burr hole closure. Methods: Sixty-six patients being treated with deep brain stimulation were retrospectively analyzed for this treatise. During surgery, CSF loss was minimized using bone wax as a burr hole closure. Intracranial air volume was calculated based on early post-surgery stereotactic 3D CT and correlated with duration of surgery and electrode deviations derived from post-surgery image fusion. Results: Median early post-surgery intracranial air was 2.1 cm (range 0-35.7 cm, SD 8.53 cm). No correlation was found between duration of surgery and CSF-loss ( R = 0.078, p = 0.534), indicating that CSF loss mainly occurs early during surgery. Linear regression analysis revealed no significant correlations regarding volume of intracranial air and electrode displacement in any of the three principal axes. No significant difference regarding electrode deviations between first and second side of surgery were observed. Conclusions: CSF loss mainly occurs during the early phase of DBS surgery. CSF loss during a later phase of surgery can be effectively averted by burr hole closure. Postoperative intracranial air volumes up to 35 cm did not result in significant electrode displacement in our series. Comparing our results to studies previously published on this subject, burr hole closure using bone wax is highly effective. [ABSTRACT FROM AUTHOR]

Background Traumatic brain injury (TBI) is probably as old as human beings. The Edwin Smith Papyrus is the first treatise describing the treatment of patients with TBI and allows insights into themedical examination and treatment of head-injured patients in ancient Egypt. Method Clinical, diagnostic, and therapeutic principles in the treatment of TBI in ancient Egypt were analyzed. Results Methodically, cases and the presentation of each case are neatly classified within the papyrus. The papyrus contains the first description of the brain, pulsations, contusions as the result of TBI, the dura, and cerebrospinal fluid, revealing a more or less sophisticated knowledge of cerebral anatomy. Furthermore, ancient physicians examined wounds, fractures, signs of basal skull fractures, and associated neurological or infectious symptoms, and classified the injury pattern according to their prognosis. Therapeutic options at this time seemed to have been limited. Conclusions The Edwin Smith Papyrus reveals asthonishing observation skill when considering the methods and limits of acient times. These physicians were able to recognize many symptoms of TBI and assign them a prognostic value. [ABSTRACT FROM AUTHOR]

Invasive pulmonary aspergillosis (IPA) is a life-threatening infection predominantly affecting immunocompromised patients, e.g. with acute leukemia. This case report demonstrates that IPA can also occur in non-neutropenic critically ill surgical patients. The case of a 63-year-old woman is reported, who developed IPA of the respiratory tract in the course of diffuse purulent peritonitis. First-line therapy with voriconazol failed to be effective. However, application of caspofungin, intensive kinetic therapy (including prone position) and airway management by interventional bronchoscopy enabled successful treatment of this severe complication. [ABSTRACT FROM AUTHOR]

Ca2+ influx into excitable cells is a prerequisite for neurotransmitter release and regulated exocytosis. Within the group of ten cloned voltage-gated Ca2+ channels, the Cav2.3-containing E-type Ca2+ channels are involved in various physiological processes, such as neurotransmitter release and exocytosis together with other voltage-gated Ca2+ channels of the Cav1, Cav2 and Cav3 subfamily. However, E-type Ca2+ channels also exhibit several subunit-specific features, most of which still remain poorly understood. Cav2.3-containing R-type channels (here called‘E-type channels’) are also located in presynaptic terminals and interact with some synaptic vesicle proteins, the so-called SNARE proteins, although lacking the classical synprint interaction site. E-type channels trigger exocytosis and are also involved in long-term potentiation. Recently, it was shown that the interaction of Cav2.3 with the EF-hand motif containing protein EFHC1 is involved in the aetiology and pathogenesis of juvenile myoclonic epilepsy. [ABSTRACT FROM AUTHOR]

We report the tuning characteristics of a widely tunable photonic crystal coupled-cavity laser and find good agreement with simulations based on a transfer matrix algorithm. The device consists of two photonic crystal channel waveguides that are longitudinally coupled through a photonic crystal section. The cavity modes exhibit slightly different mode spacing and allow a wavelength switching by utilizing the Vernier effect. The supermodes of the integrated structure exhibit an anti-crossing behavior as a result of the contra-directional coupling between the two resonant cavities. [Copyright &y& Elsevier]

We present a number of designs for the integration of photonic crystals (PC) with active semiconductor devices. As a first step, the use of PC blocks as laser mirrors is demonstrated. Ridge-waveguide lasers with a length of 100 μm and two PC mirrors achieve threshold currents below 8 mA. In order to obtain single-mode operation, an intracavity PC mirror can be used, which effectively separates the laser into two coupled cavities. Lasing occurs where two modes of the cavities coincide, leading to single-mode operation with a side-mode suppression ratio (SMSR) of over 35 dB. We also present two full PC devices: a single-mode laser with a coupled resonant cavity waveguide (CROW) and a tunable laser. The CROW device consists of a chain of 40 hexagonal cavities formed in a block of PC, with a total length of 140 μm. Low threshold, single-mode operation with over 40 dB SMSR is demonstrated. Coupled cavities are used for the tunable PC laser, which covers a tuning range of over 30 nm. [Copyright &y& Elsevier]

Waveguide directional couplers, formed by two closely spaced linear defect waveguides in a two-dimensional photonic crystal of air holes in a semiconductor matrix, are numerically studied using plane wave expansion and finite difference time domain methods. The coupling lengths are on a wavelength scale and show a strong wavelength dependence, allowing for the design of compact wavelength selective optical filters. Applications as a channel interleaver for the 1.55 μm wavelength range and as a micrometer sized 1.31/1.55 μm wavelength demultiplexer are presented. [Copyright &y& Elsevier]

We report the development of current-controlled widely tunable laser diodes based on InP with photonic crystal reflectors. The lasers consist of two longitudinally coupled and individually contacted segments that are coupled through photonic crystal sections. Two designs are presented, one based on a gain-coupled distributed feedback mechanism, the second based on contra-directional coupling of two photonic crystal waveguides. The emission wavelength can be switched quasi-continuously over a range around 53 nm for the first design. [ABSTRACT FROM AUTHOR]

Background: Asthma is one of the most common chronic diseases in childhood. Regular follow-up of physiological parameters in the home setting, in relation to asthma symptoms, can provide complementary quantitative insights into the dynamics of the asthma status. Despite considerable interest in asthma home-monitoring in children, there is a paucity of scientific evidence, especially on multi-parameter monitoring approaches. Therefore, the aim of this study is to investigate whether asthma control can be accurately assessed in the home situation by combining parameters from respiratory physiology sensors.Methods: Sixty asthmatic and thirty non-asthmatic children were enrolled in the observational WEARCON-study. Asthma control was assessed according to GINA guidelines by the paediatrician. All children were also evaluated during a 2-week home-monitoring period with wearable devices; a physical activity tracker, a handheld spirometer, smart inhalers, and an ambulatory electrocardiography device to monitor heart and respiratory rate. Multiple logistic regression analysis was used to determine which diagnostic measures were associated with asthma control.Results: 24 of the 27 uncontrolled asthmatic children and 29 of the 32 controlled asthmatic children could be accurately identified with this model. The final model showed that a larger variation in pre-exercise lung function (OR = 1.34 95%-CI 1.07-1.68), an earlier wake-up-time (OR = 1.05 95%-CI 1.01-1.10), more reliever use (OR = 1.11 95%-CI 1.03-1.19) and a longer respiratory rate recovery time (OR = 1.12 95%-CI 1.05-1.20) were significant contributors to the probability of having uncontrolled asthma.Conclusions: Home-monitoring of physiological parameters correlates with paediatrician assessed asthma control. The constructed multivariate model identifies 88.9% of all uncontrolled asthmatic children, indicating a high potential for monitoring of asthma control. This may allow healthcare professionals to assess asthma control at home.Trial Registration: Netherlands Trail Register, NL6087 . Registered 14 February 2017. [ABSTRACT FROM AUTHOR]

A new approach for coherent positive index guided distributed feedback lasers array using laterally coupled gratings is demonstrated. The device fabrication requires no regrowth which makes this concept suitable for a variety of material systems. The lasers are based on an InGaAs/GaAs single quantum well structure emitting around 980 nm with high sidemode suppression ratio of more than 50 dB. [ABSTRACT FROM AUTHOR]

We report the development of a tunable laser diode based on InP using photonic crystal mirrors. The laser consists of two longitudinally coupled ridge waveguide segments that are coupled through a photonic crystal mirror segment. A laterally defined binary superimposed grating provides a distributed feedback in each of the cavities. Quasi-continuous tuning is achieved in a 24.5 nm window with 56 channels as typically required by wavelength division multiplexing applications. [ABSTRACT FROM AUTHOR]

We have investigated tunable distributed feedback (DFB) lasers based on InGaAsP quantum wells grown by molecular-beam epitaxy. Two-section tunable DFB lasers were fabricated by patterning laterally gain coupling binary superimposed gratings perpendicular to the ridge waveguide. Side mode suppression ratios of up to 42 dB have been achieved. The tuning range covers 25 nm. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines gain-coupled lasers based on metal gratings patterned laterally to the laser ridge. Determination of emission wavelengths; Wave threshold currents; Output spectrum of a laterally gain coupled laser.

Observes the metalorganic molecular beam epitaxy of gallium arsenide growth rates interactions between the precursors of TMgallium and TE gallium. Proposal on the elementary adsorption and desorption mechanism; Investigation on the separate and common injection of alkyls; Discussion on the species contributing to gallium arsenide growth.

Thin‐films patterned with complex motifs are of fundamental interest because of their advanced optical, mechanical and electronic properties, but fabrication of these materials remains challenging. Self‐organization strategies, such as immersion controlled reaction‐diffusion patterning, have shown great potential for production of patterned thin‐films. However, the autonomous nature of such processes limits controllable pattern customizability and complexity. Here, it is demonstrated that photography inspired manipulation processes can overcome this limitation to create highly‐complex tapestries of micropatterned films (MPF's). Inspired by classical photographic processes, MPF's are developed, bleached, exposed, fixed, and contoured into user‐defined shapes and photographic toning reactions are used to convert the chemical composition MPF's, while preserving the original stripe patterns. By applying principles of composite photography, highly complex tapestries composed of multiple MPF layers are designed, where each layer can be individually manipulated into a specific shape and composition. By overcoming fundamental limitations, this synergistic approach broadens the design possibilities of reaction‐diffusion processes, furthering the potential of self‐organization strategies for the development of complex materials. [ABSTRACT FROM AUTHOR]

Objective: Exercise-induced bronchoconstriction (EIB) is a specific morbidity of childhood asthma and an important sign of uncontrolled asthma. The occurrence of EIB is insufficiently identified by the Childhood Asthma Control Test (C-ACT) and Asthma Control Test (ACT). This study aimed to (1) evaluate the Visual Analog Scale (VAS) for dyspnea as a tool to detect EIB in asthmatic children and (2) assess the value of combining (C-)ACT outcomes with VAS scores. Methods: We measured EIB in 75 asthmatic children (mean age 10.8 years) with a standardized exercise challenge test (ECT) performed in cold and dry air. Children and parents reported VAS dyspnea scores before and after the ECT. Asthma control was assessed by the (C-)ACT. Results: Changes in VAS scores (ΔVAS) of children and parents correlated moderately with fall in forced expiratory volume in 1 second (FEV1), respectively rs=0.57 (p <.001) and rs=0.58 (p <.001). At a ΔVAS cutoff value of ≥3 in children, sensitivity and specificity for EIB were 80% and 79% (AUC 0.82). Out of 38 children diagnosed with EIB, 37 had a (C-)ACT score of ≤19 and/or a ΔVAS of ≥3, corresponding with a sensitivity of 97% and a negative predictive value of 96%. Conclusion: This study shows that the VAS could be an effective additional tool for diagnosing EIB in children. A reported difference in VAS scores of ≥3 after a standardized ECT combined with low (C-)ACT scores was highly effective in detecting and excluding EIB. [ABSTRACT FROM AUTHOR]

GaAs-based singlemode emission at 1.5 µm has been realised for the first time in continuous-wave operation. GaInNAsSb active-layer material and GaAsN strain-compensating barriers have been used in combination with lateral distributed feedback. Laser diodes with a threshold current of 95 mA, an external efficiency of 0.15 W/A and a maximum output power of more than 10 mW could be demonstrated. A sidemode suppression ratio better than 31 dB could be realised at a singlemode emission wavelength of 1496 nm. [ABSTRACT FROM AUTHOR]

The authors report the development of laterally gain-coupled ring lasers that exhibit uni-directional and singlemode operation. Counter-propagating modes in the ring are suppressed such that 83% of the light output comes from only one propagation direction. The mode stability of the ring laser is significantly improved through the introduction of a gain-coupled distributed feedback mechanism. [ABSTRACT FROM AUTHOR]

We have fabricated short cavity lasers with deeply etched Bragg mirrors based on 1.55 μm emitting InGaAsP/InP laser structures. Continuous-wave operation has been obtained for devices with a length of 40 μm, showing threshold currents of 12 mA. The dynamic properties of the lasers were studied by measurements of the relative intensity noise (RIN). A maximum modulation frequency of 8.4 GHz was extracted from the RIN data. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The layered van der Waals compounds ( MnBi 2 Te 4)( Bi 2 Te 3) were recently established as the first intrinsic magnetic topological insulators. We report a study on the epitaxial growth of (MnBi 2 Te 4) m (Bi 2 Te 3) n films based on the co-deposition of MnTe and Bi 2 Te 3 on BaF 2 (111) substrates. X-ray diffraction and scanning transmission electron microscopy evidence the formation of multilayers of stacked MnBi 2 Te 4 septuple layers and Bi 2 Te 3 quintuple layers with a predominance of MnBi 2 Te 4. The elemental composition and morphology of the films is further characterized by x-ray photoemission spectroscopy and atomic force microscopy. X-ray magnetic circular and linear dichroism spectra are comparable to those obtained for MnBi 2 Te 4 single crystals and confirm antiferromagnetic order in the films. [ABSTRACT FROM AUTHOR]

Introduction: Acute subdural hematoma (aSDH) is one of the main causes of high mortality and morbidity in traumatic brain injury. Prognosis is poor due to the rapid volume shift and mass effect. Cerebral perfusion is likely affected in this condition. This study quantifies perfusion changes in aSDH using early ER polytrauma CT with perfusion imaging (CTP). Methods: Data of 54 patients with traumatic aSDH were retrospectively collected. Glasgow Coma scale (GCS), perfusion parameters, therapeutic decisions and imaging data including hematoma thickness, midline shift, and hematoma localization were analyzed. The cortical perfusion parameters of each hemisphere, the area anterior to the hematoma (AAH), area below the hematoma (ABH), area posterior to the hematoma (PAH), and corresponding mirrored contralateral regions were determined. Results: We found a significant difference in Tmax in affected and unaffected whole-hemisphere data (mean 4.0 s vs. 3.3 s, p < 0.05) and a significantly different mean for Tmax in ABH and for the corresponding mirrored area (mABH) (mean 3.8 s vs. 3.1 s, p < 0.05). No significant perfusion changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were found. Conclusion: There was a significant elevation of time to maximum (Tmax) values in the underlying cortical area of aSDH. Possible pathophysiological explanations, the influence on immediate surgical decision-making and further therapeutic consequences have to be evaluated. [ABSTRACT FROM AUTHOR]

The 2017 Faraday Discussion on Surface Enhanced Raman Scattering (SERS) attracted more than a hundred delegates from a broad spectrum of backgrounds and experience levels, bringing together leading scientists involved in the long living field of SERS. The meeting gave an overview of the liveliness of the topic, characterised by open questions and fascinating science still to discover. In the following, we discuss the topics covered during this meeting and briefly highlight the content of each presentation. [ABSTRACT FROM AUTHOR]

Topological Insulators are in focus of immense research efforts and rapid scientific progress is obtained in that field. Bi2Se3 has proven to be a topological insulator material that provides a large band gap and a band structure with a single Dirac cone at the T-point. This makes Bi2Se3 one of the most promising three dimensional topological insulator materials. While Bi2Se3 nanowires and nanoflakes so far were fabricated with different methods and for different purposes, we here present the first Bi2Se3 nanowires as well as nanoflakes grown by molecular beam epitaxy. The nanostructures were nucleated on pretreated, silicon (100) wafers. Altering the growth conditions nanoflakes could be fabricated instead of nanowires; both with high crystalline quality, confirmed by scanning electron microscopy as well as transmission electron microscopy. These nanostructures have promise for spintronic devices and Majorana fermion observation in contact to superconductor materials. [ABSTRACT FROM AUTHOR]

We study the electroluminescence (EL) emission of purely n-doped resonant tunneling diodes in a wide temperature range. The paper demonstrates that the EL originates from impact ionization and radiative recombination in the extended collector region of the tunneling device. Bistable current-voltage response and EL are detected and their respective high and low states are tuned under varying temperature. The bistability of the EL intensity can be switched from direct to inverted with respect to the tunneling current and the optical on/off ratio can be enhanced with increasing temperature. One order of magnitude amplification of the optical on/off ratio can be attained compared to the electrical one. Our observation can be explained by an interplay of moderate peak-to-valley current ratios, large resonance voltages, and electron energy loss mechanisms, and thus, could be applied as an alternative route towards optoelectronic applications of tunneling devices. [ABSTRACT FROM AUTHOR]

The paper reports on the realization of multilayer (In,Ga)As/GaP quantum dot (QD) lasers grown by gas source molecular beam epitaxy. The QDs have been embedded in (Al,Ga)P/GaP waveguide structures. Laser operation at 710 nm is obtained for broad area laser devices with a threshold current density of 4.4 kA/cm2 at a heat-sink temperature of 80 K. [ABSTRACT FROM AUTHOR]

We present a statistical study of Traveling Ionospheric Disturbances (TIDs) as observed by the EISCAT Svalbard Radar (ESR) during the continuous IPY-run (March 2007-February 2008) with field-aligned measurements. We have developed a semi-automatic routine for searching and extracting Atmospheric Gravity Wave (AGW) activity. The collected data shows that AGW-TID signatures are common in the high-latitude ionosphere especially in the field-aligned ion velocity data (244 cases of AGW-TID signatures in daily records), but they can be observed also in electron density (26 cases), electron temperature (12 cases) and ion temperature (26 cases). During the IPY campaign (in solar minimum conditions) AGW-TID events appear more frequently during summer months than during the winter months. It remains still as a topic for future studies whether the observed seasonal variation is natural or caused by seasonal variation in the performance of the observational method that we use (AGW-TID signature may be more pronounced in a dense ionosphere). In our AGW-TID dataset the distribution of the oscillation periods has two peaks, one around 0.5-0.7 h and the other around 1.1-1.3 h. The diurnal occurrence rate has a deep minimum in the region of magnetic midnight, which might be partly explained by irregular auroral activity obscuring the TID signatures from our detection routines. As both the period and horizontal phase speed estimates (as derived from the classical AGW dispersion relation) show values typical both for large scale TIDs and mesoscale TIDs it is difficult to distinguish whether the generator for highlatitude AGW-TIDs resides typically in the troposphere or in the near-Earth space. The results of our statistical analysis give anyway some valuable reference information for the future efforts to learn more about the dominating TID source mechanisms in polar cap conditions, and to improve AGW simulations. [ABSTRACT FROM AUTHOR]

A GaAs metal–semiconductor field-effect transistor (MESFET) has been realized based on mix-and-match fabrication using optical lithography for the ohmic contacts and imprint lithography for the gate. The gate length and width are 1.2 and 80 μm, respectively, the channel length is 4 μm. For the gate definition a Si-mold is embossed into a thin polymer film located on top of an n-doped GaAs layer. The gate is fabricated by metal evaporation and lift-off. [Copyright &y& Elsevier]

We present the realization of four different learning rules with a quantum dot memristor by tuning the shape, the magnitude, the polarity and the timing of voltage pulses. The memristor displays a large maximum to minimum conductance ratio of about 57 000 at zero bias voltage. The high and low conductances correspond to different amounts of electrons localized in quantum dots, which can be successively raised or lowered by the timing and shapes of incoming voltage pulses. Modifications of the pulse shapes allow altering the conductance change in dependence on the time difference. Hence, we are able to mimic different learning processes in neural networks with a single device. In addition, the device performance under pulsed excitation is emulated combining the Landauer-Büttiker formalism with a dynamic model for the quantum dot charging, which allows explaining the whole spectrum of learning responses in terms of structural parameters that can be adjusted during fabrication, such as gating efficiencies and tunneling rates. The presented memristor may pave the way for future artificial synapses with a stimulus-dependent capability of learning. [ABSTRACT FROM AUTHOR]

Excitonic emission from single InAs/InGaAlAs/InP quantum dashes has been investigated in terms of controlling the polarization anisotropy by altering the shape of the processed sub-micrometer mesa structures. Photoluminescence has been measured from exemplary single quantum dashes emitting around 1.3 and 1.55 µm and placed inside rectangular mesas of various orientation, asymmetry, and sizes. The detected degree of linear polarization of bright exciton emission ranges from -0.1 to ca. 0.55, compared to 0.25 for dashes in unaltered or isotropic in-plane dielectric surrounding. These results are interpreted by numerical simulations using an emitter coupled with a single optical mode in such a mesa and outgoing in the direction normal to the sample surface. [ABSTRACT FROM AUTHOR]

We present a characterization of doped InAs layers in interband cascade lasers exploiting the plasmon-enhanced waveguiding. Fast differential reflectance was employed in order to identify the plasma-edge frequency via the Berreman effect and shown as an advantageous method when compared to other types of measurements. The carrier concentration was then derived and compared with the nominal doping densities. The emission properties of the investigated structures were studied by means of photoluminescence (PL). Its full-width at half-maximum and integrated intensity were extracted from PL spectra and analyzed in the function of the doping density (carrier concentration). The PL linewidth was found to be independent of the carrier concentration indicating an insignificant contribution of doping to the structural properties deterioration. The PL intensity decay with the carrier concentration suggests being dominated by Auger recombination losses. [ABSTRACT FROM AUTHOR]

Type II InAs/GaInSb quantum wells (QWs) grown on GaSb or InAs substrates and designed to be integrated in the active region of interband cascade lasers (ICLs) emitting in the mid infrared have been investigated. Optical spectroscopy, combined with band structure calculations, has been used to probe their electronic properties. A design with multiple InAs QWs has been compared with the more common double W-shaped QW and it has been demonstrated that it allows red shifting the emission wavelength and enhancing the transition oscillator strength. This can be beneficial for the improvements of the ICLs performances, especially when considering their long-wavelength operation. [ABSTRACT FROM AUTHOR]

Compared to traditional non-linear optical crystals, like BaB2O4, KTiOPO4 or LiNbO3, semiconductor integrated sources of photon pairs may operate at pump wavelengths much closer to the bandgap of the materials. This is also the case for Bragg-reflection waveguides (BRWs) targeting parametric down-conversion (PDC) to the telecom C-band. The large non-linear coefficient of the AlGaAs alloy and the strong confinement of the light enable extremely bright integrated photon pair sources. However, under certain circumstances, a significant amount of detrimental broadband photoluminescence has been observed in BRWs. We show that this is mainly a result of linear absorption near the core and subsequent radiative recombination of electron–hole pairs at deep impurity levels in the semiconductor. For PDC with BRWs, we conclude that devices operating near the long wavelength end of the S-band or the short C-band require temporal filtering shorter than 1 ns. We predict that shifting the operating wavelengths to the L-band reduces the amount of photoluminescence by 70% and making small adjustments in the material composition results in its total reduction of 90%. Such measures enable us to increase the average pump power and/or the repetition rate, which makes integrated photon pair sources with on-chip multi-gigahertz pair rates feasible for future devices. [ABSTRACT FROM AUTHOR]

Optical properties of molecular beam epitaxially grown type II 'W' shaped GaSb/AlSb/InAs/GaIn(As)Sb/InAs/AlSb/GaSb quantum wells (QWs) designed for the active region of interband cascade lasers have been investigated. Temperature dependence of Fourier-transformed photoluminescence and photoreflectance was employed to probe the effects of addition of arsenic into the original ternary valence band well of GaInSb. It is revealed that adding arsenic provides an additional degree of freedom in terms of band alignment and strain tailoring and allows enhancing the oscillator strength of the active type II transition. On the other hand, however, arsenic incorporation apparently also affects the structural and optical material quality via generating carrier trapping states at the interfaces, which can deteriorate the radiative efficiency. These have been evidenced in several spectroscopic features and are also confirmed by cross-sectional transmission electron microscopy images. While arsenic incorporation into type II QWs is a powerful heterostructure engineering tool for optoelectronic devices, a compromise has to be found between ideal band structure properties and high quality morphological properties. [ABSTRACT FROM AUTHOR]

Optical transitions in GaAs1-xNx/GaAs quantum wells (QWs) have been probed by two complementary techniques, modulation spectroscopy in a form of photoreflectance and surface photovoltage spectroscopy. Transition energies in QWs of various widths and N contents have been compared with the results of band structure calculations based on the 10-band k·p Hamiltonian. Due to the observation of higher order transitions in the measured spectra, the band gap discontinuities at the GaAsN/GaAs interface and the electron effective masses could be determined, both treated as semi-free parameters to get the best matching between the theoretical and experimental energies. We have obtained the chemical conduction band offset values of 86% for x = 1.2% and 83% for x = 2.2%, respectively. For these determined band offsets, the electron effective masses equal to about 0.09 mo in QWs with 1.2% N and 0.15 mo for the case of larger N content of 2.2%. [ABSTRACT FROM AUTHOR]

We have investigated theoretically two kinds of dilute-nitride-based quantum well structures, InGaAsN/GaAs and InGaAsN/GaAsN/GaAs, both able to emit at 1.3 μm. The ground state transition energy and its oscillator strength have been probed as a function of the material composition in the single particle as well as the excitonic approximations. The modification of the bandgap energy due to nitrogen incorporation has been taken into account by using a two-level repulsion model. We have shown that in spite of a decrease of the electron-hole wave functions overlap with the mole fraction of nitrogen, the overall transition intensity of the excitonic transition can increase significantly due to the strongly composition dependent mass of the exciton. The latter makes dilute nitride quantum wells good candidates for the polaritonic physics and Bose-Einstein condensation of exciton polaritons at telecommunication wavelengths. We have also demonstrated that the exact values of the band offsets are necessary to be known as they have a critical impact on the actual transition oscillator strengths in these quantum wells. [ABSTRACT FROM AUTHOR]

We have investigated the growth mechanism and surface structure of magnetite (Fe3O4) films grown on semiconducting ZnO substrates. Growth proceeds in a wetting layer plus island-mode and a later coalescence of islands, as was verified by electron diffraction, topography measurements of the surface, and the investigation of the microstructure. The typical (111) surface diffraction pattern magnetite is observed already at the early island growth stage. Due to the island-like growth mode, domain boundaries form upon coalescence of the islands. Twin boundaries have been evidenced between neighboring domains. Island growth enables partial relaxation of the misfit strain. [ABSTRACT FROM AUTHOR]

We present passive mode locking of a GaSb-based monolithic diode laser emitting at 2.2 μm with a fundamental repetition rate around 9.57 GHz. A pulse width of ∼2.4 ps is reconstructed by shifted wave intermode beat Fourier transform spectroscopy-measurements, yielding a time-bandwidth product of 1.8. Mode-locking is observed for a range of reverse bias voltages from 1.3 to 3.3 V and driving currents from 110 to 300 mA. The continuous wave output power is ∼17.5 mW with the absorber segment left floating and ∼4.5 mW at a reverse bias of 3.1 V in the mode-locked regime. The full-width-half-maximum of the radio frequency signal is measured for all operation conditions, with a minimum of 8.4 kHz. [ABSTRACT FROM AUTHOR]

A strong ~11‐min‐long surge of the lobe reconnection was observed during a substorm on the tailward side of the near‐Earth neutral line. In the southern lobe near the reconnection separatrix the MMS spacecraft observed short‐duration earthward electron beams providing the local Hall current, tailward propagating Alfven wave (AW) bursts with Poynting flux up to 10−4 W/m2, and large‐amplitude E field spikes (e‐holes) and low hybrid waves. The reconnection surge was accompanied by substorm current wedge formation and fast poleward expansion of auroral bulge‐related westward electrojet in the conjugate ionosphere. During its meridional crossing above the expanding bulge the Metop‐2 spacecraft observed an intense energetic precipitation spike near the expected X line foot point and confirmed the dipolarized character of magnetic field lines inside of the bulge. Globally the observed average reconnection rate ( ~3.3 mV/m) was sufficient to produce the magnetic flux increase in the bulge, associated with observed fast poleward expansion (about 6° latitude in 5 min). Plain Language Summary: Although magnetic reconnection in the magnetotail has been proposed to be the core process for the strong global magnetospheric reconfiguration and for huge particle acceleration during magnetospheric substorms, this association is mostly based on indirect evidence, because reconnection intermittently activates in different parts of the tail current sheet, and it is difficult to monitor its location and intensity variations based on direct spacecraft observations. On 28 July 2017 the MMS spacecraft succeeded in staying in the magnetotail near the active reconnection separatrix for a relatively long time during the surge of reconnection. At the same time the electric currents were enhanced and moved poleward in the magnetically conjugate part of the ionosphere, indicating configurational changes in the magnetotail. At the same minute the Metop‐2 spacecraft in low‐Earth orbit passed above this region and detected precipitating electrons of different energies as well as their distribution in the loss cone, which yielded conclusions about the strength of the equatorial magnetic field in the reconnected flux tubes. This unprecedented combination of conjugate observations allows us to confirm directly the important global consequences of an intense near‐Earth reconnection event, which have been suggested in the near‐Earth neutral line substorm scenario but could not be previously observed together in the same event. Key Points: MMS observed 11‐min‐long lobe reconnection surge near the separatrix during fast poleward electrojet expansion in the conjugate ionosphereIntense hard electron precipitation near the footpoint of the neutral line and dipolarized fieldlines in the interior of auroral bulge are confirmedDirect link and consistence of poleward auroral expansion and reconnection rates are demonstrated [ABSTRACT FROM AUTHOR]

Provides information on an experimental study investigating optical transitions near the band edge in molecular-beam epitaxy grown 6H GaN films on sapphire. Methodology used to conduct the experiment; Information on the photoluminescence results; Conclusion reached on the experiment.

In this work, monolithic mode-locked GaSb-based lasers at 1.7 µm emission wavelength with heterodyne measurement of the frequency comb are presented. Mode-locking operation was confirmed by measuring the optical beatnote at the round-trip frequency of 9.56 GHz and analysing the frequency comb. Mode-locking operation occurred from 0.1 to 3.3 V reverse bias voltages at the absorber section and driving currents from 160 to 400 mA at the laser section with a minimum beatnote width of 6.6 kHz. The frequency comb spans over 13 nm with a mode spacing of 0.10 nm, measured by heterodyne-detection with a distributed feedback laser. [ABSTRACT FROM AUTHOR]

Photon echo from trions and excitons in (In,Ga)As/GaAs quantum dots was studied theoretically and experimentally. Theoretical analysis allowed us to distinguish between photon echo signals from excitons and trions measured in the same range of wavelength using different polarization configurations of laser excitation. The theoretical predictions are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]