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The history of uranium isotopic reference materials from JRC-Geel during the last 50 years is reviewed by presenting certification methods and relevant applications. The certified isotope ratios are traceable to the SI via gravimetrical preparation, either directly through gravimetrical mixing of highly enriched materials, or indirectly using existing gravimetrically prepared reference materials for calibration of mass spectrometers used for certification measurements. Due to developments of mass spectrometers and analytical methods, certification measurements have improved regarding precision, uncertainties and accuracy. This has led to a comprehensive set of uranium isotopic reference materials available for nuclear safety, security and the scientific community. [ABSTRACT FROM AUTHOR]

Modern public libraries strive for inclusivity. Part of this effort involves enhancing staff capacity for engaging with socially vulnerable populations. This paper presents the outcomes of a study on library use by homeless adults, one of the most vulnerable of populations. The study employed a mix of methods. Part one was quantitative: a survey of library patrons. A second, qualitative phase involved focus groups – two of which were comprised of homeless patrons. Several areas of concern and need emerged, including physical space, safety, library services, and interactions with the library staff. [ABSTRACT FROM AUTHOR]

Individualized social niches arise in social groups, resulting in divergent social behavior profiles among group members. During sensitive life phases, the individualized social niche can profoundly impact the development of social behavior and associated phenotypes such as hormone (e.g. cortisol) concentrations. Focusing on adolescence, we investigated the relationship between the individualized social niche, social behavior, and cortisol concentrations (baseline and responsiveness) in female guinea pigs. Females were pair-housed in early adolescence (initial social pair formation), and a social niche transition was induced after six weeks by replacing the partner with either a larger or smaller female. Regarding social behavior, dominance status was associated with aggression in both the initial social pairs and after the social niche transition, and the results suggest that aggression was rapidly and completely reshaped after the social niche transition. Meanwhile, submissive behavior was rapidly reshaped after the social niche transition, but this was incomplete. The dominance status attained in the initial social pair affected the extent of submissive behavior after the social niche transition, and this effect was still detected three weeks after the social niche transition. Regarding cortisol concentrations, higher baseline cortisol concentrations were measured in dominant females in the initial social pairs. After the social niche transition, cortisol responsiveness significantly increased for the females paired with a larger, older female relative to those paired with a smaller, younger female. These findings demonstrate that the social niche during adolescence plays a significant role in shaping behavior and hormone concentrations in females. • We manipulated the social niche of adolescent female guinea pigs. • Aggressive behavior was immediately adjusted to a new social niche. • Cortisol responsiveness changed over time after a social niche transition. • Past social interactions affected dominance interactions with a different individual. • The social niche during adolescence shaped behavior and cortisol responsiveness. [ABSTRACT FROM AUTHOR]

Permutation tests based on previously developed statistics are proposed for the case of mixed paired and two-sample designs. Different weighting schemes of previous tests are explored to understand the strengths and weaknesses of each test. A simulation study compares the power and Type I error rates of the new tests with those previously developed. Rank-based statistics generally performed as well as or better than parametric statistics, particularly for nonnormal distributions. [ABSTRACT FROM AUTHOR]

Flows of suspensions can be blocked when the suspended particles are densely packed. This makes their formulation and their transport challenging in the industry. In this paper, we study the impact of vibrations on the behavior of dense granular suspensions prepared at a volume fraction above their jamming volume fraction but below the particle assembly random close packing. Vibrations are shown to have a strong effect on their rheological properties and to tune their transition from solidlike to liquidlike behavior. We study suspensions of rough silica particles in a Newtonian fluid. In the absence of vibrations, they have a solidlike behavior: they flow only above a yield stress. Particles are confined by the liquid interface, and the yield stress is of the frictional origin. When vibrations are applied, the yield stress vanishes to give rise to a liquidlike pseudo-Newtonian behavior at a low shear rate. Using shear-reversal experiments, we show that these liquidlike vibrated suspensions of frictional particles behave like nonvibrated suspensions of frictionless particles. As the shear rate is increased, we observe a shear thickening of the vibrated suspensions, eventually leading to shear-jamming. The yield stress behavior is recovered, and vibrations have no more impact. We show that this shear thickening can be tuned by changing the vibration energy injected into the system. We, finally, propose a physical picture based on the competition between contact opening by vibration and contact formation by shear to account for these behaviors. In the framework of the Wyart and Cates [Phys. Rev. Lett. 112, 098302 (2014)] model, vibrations can be seen as introducing a thermal-like repulsive force, yielding a critical stress proportional to the vibration stress introduced by Hanotin et al. [J. Rheol. 59, 253–273 (2015)]. [ABSTRACT FROM AUTHOR]

Architectural designs involving Al- and/or Si-containing top coatings present an effective approach to protect oxidation-sensitive materials such as binary transition metal (TM) diborides against high-temperature oxidation. Using reactive arc evaporation, Al-Si-N, Al-Si-O, and Si-O top coatings were applied on sputter-deposited WB 1.9 , TiB 2.7 , and HfB 2.4 thin films, respectively. A pure Si adhesion layer was introduced prior to the deposition of both oxide-based top coatings (Al-Si-O & Si-O) to prevent in-situ oxidation of the diboride base layers. During thermal annealing up to 1200 °C, Al-Si-O and Si-O provided outstanding oxidation resistance on top of TiB 2.7 and HfB 2.4 , while limited adhesion was observed on WB 1.9 at elevated temperatures. Contrary, Al-Si-N protected architectures suffered from accelerated oxidation beyond 800 to 1000 °C. Isothermal annealing in ambient air at 1200 °C for 30 h confirmed the long-term stability of the oxide-based top coatings, revealing no decohesion or oxygen inward diffusion beyond the Si interlayer. Complementary TEM analysis showed that the Si-O top coating forms a dense SiO 2 scale above the columnar HfB 2.4 , while the formation of a mullite scale (3Al 2 O 3 ·2SiO 2) and pronounced recrystallization is recorded for the Al-Si-O protected HfB 2.4. In summary, the Al-Si-O- and Si-O-based top coatings demonstrated exceptional high-temperature oxidation resistance, fully protecting the TM-diborides from oxidative attack. • Reactively arc evaporated protective top coatings (i.e. , Al-Si-N, Al-Si-O, Si-O). • Top coatings provide oxidation resistance up to 1400 °C. • No oxygen diffusion beyond the top coatings [ABSTRACT FROM AUTHOR]

Life sciences are currently facing a reproducibility crisis. Originally, the crisis was born out of single alarming failures to reproduce findings at different times and locations. Nowadays, systematic studies indicate that the prevalence of irreproducible research does in fact exceed 50%. Viewed from a rather cynical perspective, Fett's law of the lab "Never replicate a successful experiment" has thus taken on a completely new meaning. In this respect, animal research has come under particular scrutiny, as the stakes are high in terms of both research ethics and societal impact. To counteract this, it is essential to identify sources of poor reproducibility as well as to iron out these failures. We here review the current debate, briefly discuss potential reasons, and summarize steps that have already been undertaken to improve reproducibility in animal research. By the example of classical behavioural phenotyping studies, we particularly highlight the role strict standardization plays in exacerbating the crisis, and review the concept of systematic heterogenization as an alternative strategy to deal with variation in animal studies. Briefly, we argue that systematic variation rather than strict homogenization of experimental conditions benefits the robustness of research findings, and hence their reproducibility. To this end, we will present concrete examples for systematically heterogenized experiments and provide a practical guide on how to apply systematic heterogenization in experimental practice. • Animal research is currently facing a reproducibility crisis. • Systematic heterogenization has been proposed as tool to improve reproducibility. • We here review the concept and give examples for heterogenization strategies. • Lastly, we provide a practical guide on how to introduce the concept in practice. [ABSTRACT FROM AUTHOR]

The IRMM-2019-2029 series of uranium nitrate solutions was certified for the isotopic composition. The solutions were originally prepared for the certification of the IRMM-019-029 series of uranium hexafluoride (UF6) materials in 2014, for which certification measurements were performed by thermal ionization mass spectrometry after conversion of UF6 into uranyl nitrate solutions. Analyses were performed using the modified total evaporation method and for some materials with low 236U abundances, the n(235U)/n(238U) ratio was measured using a n(233U)/n(236U) double spike. The integrity of the certified values after dilution and ampouling of the original solutions was checked through process control measurements. [ABSTRACT FROM AUTHOR]

Provides information on a study investigating the output characteristics and the optical efficiency of SrS:Ce and ZnS:Mn thin-film electroluminescent devices. Methodology used to conduct the study; Theory focusing on the analysis of radiation patterns; Indepth look at algorithm for determining the optical efficiency; Results of study.

Adolescence is a sensitive phase when cues from the social environment can shape consistent individual differences in behavioral and hormonal profiles, but the effect of the social partner on these phenotypes is not well‐understood, especially for females. We therefore aimed to investigate whether the age class and sex of the housing partner affect social behavior and cortisol concentrations in female guinea pigs during adolescence and estimate the repeatability of cortisol concentrations in this life stage. Female guinea pigs were housed upon weaning for 4 weeks with either an adult female, adolescent female, or adolescent male. Social behavior was observed in the home enclosure and a preference test and social interaction test were carried out at the end of the experiment. Cortisol concentrations (baseline and response to a challenge) were measured prior to the start of the experiment and 2 and 4 weeks after pair formation. We hypothesized that the social partner would affect behavior and cortisol concentrations. We found that females housed with an adult female were less aggressive and more consistently displaced by their housing partner than females housed with an adolescent female. Sex of the housing partner did not affect focal female behavior. Regarding hormones, baseline cortisol concentration was neither significantly repeatable nor significantly affected by the housing partner. However, cortisol responsiveness was highly repeatable both 1 h and 2 h after the onset of a challenge. The age class of the housing partner affected cortisol responsiveness, with higher cortisol concentrations measured at 1 h in females housed with an adult female. These results indicate that adolescent female guinea pigs exhibit consistent individual differences in cortisol responsiveness while retaining plasticity to adjust to cues from the social environment. Taken together, we show in a female rodent that the social environment can significantly shape behavioral and endocrine parameters during adolescence. [ABSTRACT FROM AUTHOR]

Recent reports of possible correlations between high energy neutrinos observed by IceCube and Active Galactic Nuclei (AGN) activity sparked a burst of publications that attempt to predict the neutrino flux of these sources. However, often rather crude estimates are used to derive the neutrino rate from the observed photon spectra. In this work neutrino fluxes were computed in a wide parameter space. The starting point of the model was a representation of the full spectral energy density (SED) of 3C 279 . The time-dependent hybrid model that was used for this study takes into account the full pγ reaction chain as well as proton synchrotron, electron-positron-pair cascades and the full SSC scheme. We compare our results to estimates frequently used in the literature. This allows to identify regions in the parameter space for which such estimates are still valid and those in which they can produce significant errors. Furthermore, if estimates for the Doppler factor, magnetic field, proton and electron densities of a source exist, the expected IceCube detection rate is readily available. [ABSTRACT FROM AUTHOR]

The recently reported coincidences between high‐energy neutrino events and major blazar outbursts reinforce the relevance of lepto‐hadronic emission models for blazars. We study the influence of physical parameters on the neutrino output by modeling blazar spectral energy distributions self‐consistently assuming a relativistically propagating acceleration zone surrounded by a larger cooling zone. We find that the gross features of the spectral energy distribution can readily be explained with the model. A rigorous test requires time‐resolved measurements of blazar spectral energy distributions during an outburst and high‐statistics neutrino measurements to discriminate the leptonic and hadronic emission components. [ABSTRACT FROM AUTHOR]

Transition-metal disilicides (TMSi 2) based thin films are suggested as promising, novel protective coating materials used in various high-temperature applications. In this study, we investigate the phase formation, microstructure, and mechanical properties (i.e. H, E, and K IC) of sputter-deposited TMSi x films (TM = Mo, Ta, Nb) in correlation with the varied bias potential. The as-deposited TaSi x and MoSi x coatings show Si sub-stoichiometries with Si/Me (x)< 2, while all the NbSi x coatings are overstoichiometric in Si. All TaSi x and NbSi x coatings are stabilized in their preferred hexagonal structure, whereas the MoSi x coatings exhibit small fractions of T 1 -Mo 5 Si 3 next to the dominant metastable hexagonal β-phase. The oxidation behaviour of the coatings was examined up to 1400 °C. MoSi x based films are distinguished by an outstanding oxidation resistance, forming dense and protective silica scales of only 650 nm after 100 h at 1200 °C – also obtaining an extremely high interfacial stability. In contrast, TaSi x suffers accelerated oxidation at 1200 °C due to the formation of mixed, non-protective scales consisting of Ta 2 O 5 and SiO 2. Moreover, NbSi x coatings show retarded oxidation kinetics up to 60 h at 1200 °C, forming a dense and uniform SiO 2 scale of only 533 ± 131 nm. Micro-cantilever bending experiments reveal that TaSi 1.7 coating exhibit the highest fracture toughness, K IC , of 2.7 ± 0.2 MPa∙m1/2 compared to 2.3 ± 0.1 and 1.7 ± 0.1 MPa∙m1/2 for NbSi 2 . 4 and MoSi 1.9 , respectively. • Mechanical properties of TaSi x and NbSi x exhibit dependency on varied bias potential. • TaSi 1.7 shows the highest K IC of 2.7 ± 0.2 MPa∙m1/2. • Thin Si-based Oxide scale of only 650 nm after 100 h at 1200 °C for MoSi 2. • Retarded oxidation kinetics of NbSi 2 at 1200 °C up to 60 h. • Accelerated oxidation for TaSi 2 over 850 °C by forming mixed oxides. [ABSTRACT FROM AUTHOR]

In mammals, weaning constitutes an important phase in the progression to adulthood. It comprises the termination of suckling and is characterized by several changes in the behaviour of both mother and offspring. Furthermore, numerous studies in rodents have shown that the time point of weaning shapes the behavioural profile of the young. Most of these studies, however, have focused on ‘early weaning’, while relatively little work has been done to study ‘late weaning’ effects. The aim of the present study was therefore to explore behavioural effects of ‘late weaning’, and furthermore to gain insights into modulating effects of weaning age on the consistency of behavioural expressions over time. In total, 25 male and 20 female C57BL/6J mice, weaned after three (W3) or four (W4) weeks of age, were subjected to a series of behavioural paradigms widely used to assess anxiety-like behaviour, exploratory locomotion, and nest building performance. Behavioural testing took place with the mice reaching an age of 20 weeks and was repeated eight weeks later to investigate the stability of behavioural expressions over time. At the group level, W4 mice behaved less anxious and more explorative than W3 animals in the Open Field and Novel Cage, while anxiety-like behaviour on the Elevated Plus Maze was modulated by a weaning-age-by-sex interaction. Furthermore, weaning age shaped the degree of behavioural stability over time in a sex-specific way. While W3 females and W4 males displayed a remarkable degree of behavioural stability over time, no such patterns were observed in W3 males and W4 females. Adding to the existing literature, we could thus confirm that effects of weaning age do indeed exist when prolonging this phase, and were furthermore able to provide first evidence for the impact of weaning age and sex on the consistency of behavioural expressions over time. [ABSTRACT FROM AUTHOR]

The Environmental Sample Laboratory (ESL) of the International Atomic Energy Agency (IAEA) routinely analyses environmental swipe samples for their bulk U and Pu isotope amounts and ratios using a Neptune Plus™ (Thermo Fisher Scientific) multi collector-inductively coupled plasma mass spectrometer (MC-ICP-MS). The instrument is equipped with the so-called “L5 ion counter package”, which comprises ten Faraday cups, three classical discrete dynode secondary electron multipliers (SEM), and two compact discrete dynode (CDD) electron multipliers. In contrast to classical SEMs, CDDs only have about twice the width of a Faraday cup and are mounted in-line with the Faraday cups within the multi collector array. The Institute of Reference Materials (IRMM) of the European Commission's Joint Research Centre (JRC) has developed several dedicated uranium isotope reference material series for the investigation of non-linearity and dead time effects of ion counting systems. For instance, a new series of gravimetrically prepared uranium isotope reference materials, the so-called IRMM-074 series, with the 235U/238U isotope ratio held constant at unity and the 233U/235U isotope ratios varying from 1.0 to 10−6 has been prepared and certified. This series is suited for calibration of secondary electron multipliers used widely in isotope mass spectrometry, in particular for thermal ionization mass spectrometry (TIMS), ICP-MS and accelerator mass spectrometry (AMS). The new IRMM-074 series was prepared as a replacement for the already exhausted IRMM-072 predecessor series, which is still on stock at the IAEA. In collaboration between the IAEA and the IRMM, dedicated new procedures have been developed for taking advantage of the IRMM reference materials for linearity testing and dead time determination for the various ion counting detectors of two Neptune Plus™ MC-ICP-MS instruments at the IAEA. Only statically measured ratios were used, and dynamic (peak-jumping) ratios were avoided, which makes these procedures independent on plasma instabilities and therefore ideal for MC-ICP-MS instruments. The dead times of the ion counting systems were found to depend not on the detectors themselves but only on the pulse amplifiers, which allowed to easier investigate them by connecting each pulse amplifier to any detector of the same type within the detector configuration. The new procedures might well be applicable for similarly designed MC-ICP-MS instruments which have already been installed at other laboratories working in the nuclear safeguards and environmental fields. [ABSTRACT FROM AUTHOR]

Besides being recognized as a potential welfare indicator, play behaviour has long been considered to have immediate and/or long-term benefits. In particular, it has been suggested that in play animals learn to cope physically and emotionally with unexpected events. Given that the propensity to play varies greatly between conspecific individuals, such interindividual variability in playfulness may be associated with differences in the animals' future behaviour, a prediction that has rarely been tested. To investigate whether different levels of playfulness in juvenility indeed coincide with behavioural differences in later life, 30 female C57BL/6J mice were subjected to the following series of behavioural observations and tests: (1) quantification of juvenile play behaviour; (2) behavioural testing in paradigms that assess anxiety-like behaviour and exploratory locomotion in an unfamiliar environment; and (3) observation of spontaneous behaviour in the familiar home cage environment. Surprisingly, a high level of juvenile playfulness was predictive of high levels of state anxiety and low levels of exploratory locomotion in later life. While this relationship existed already in adolescence, it became even more prominent in adulthood. By contrast, no substantial differences between playful and less playful mice were found with respect to home cage behaviour. While these findings may reflect better coping abilities in novel and dangerous environments in those mice that played the most during juvenility, they may also argue for the existence of different types of mice. Thus, despite genetic homogeneity and identical housing environments, preferences for either local or global use of space were observed that indicate the emergence of individuality. Concerning animal welfare, our findings suggest that play may constitute a plausible welfare indicator at the population level, but is probably less meaningful for the individual. [ABSTRACT FROM AUTHOR]

We determined the bond interface strength of ultrashort pulse laser-welded fused silica for different processing parameters. To this end, we used a high repetition rate ultrashort pulse laser system to inscribe parallel welding lines with a specific V-shaped design into optically contacted fused silica samples. Afterward, we applied a micro-chevron test to measure the fracture toughness and surface energy of the laser-inscribed welding seams. We analyzed the influence of different processing parameters such as laser repetition rate and line separation on the fracture toughness and fracture surface energy. Welding the entire surface a fracture toughness of $$0.71\,\hbox {MPa}\,\hbox {m}^{1/2}$$ , about 90 % of the pristine bulk material $$({\approx } 0.8\,\hbox {MPa}\,\hbox {m}^{1/2})$$ , is obtained. [ABSTRACT FROM AUTHOR]

The welding of transparent materials with ultrashort laser pulse at high repetition rates has attracted much attention due to its potential applications in fields such as optics, microfluidics, optofluidics and precision machinery. One demanding issue is the stable and reliable welding of different materials without the utilization of an intermediate layer or an optical contact. In this work, we maximized the size of the molten volume in order to generate a large pool of molten material which is able to fill an existing gap between the samples. To this end, we used bursts of ultrashort laser pulses with an individual pulse energy of up to $$10\,\upmu \hbox {J}$$ . The laser-induced welding seams exhibit a base area with a size of up to $$450\,\upmu \hbox {m}\,\times 160\,\upmu \hbox {m}$$ . Using these large modifications, we are able to overcome the requirement of an optical contact and weld even gaps with a height of about $$3\,\upmu \hbox {m}$$ . Bulging of the sample surface and ejection of molten material in the gap between the two samples allow to bridge the gap and enable successful welding. We also determined the breaking strength of laser-welded fused silica samples without an optical contact by a three-point bending test. The determined value of up to 73 MPa is equivalent to 85 % of stability of the pristine bulk material. [ABSTRACT FROM AUTHOR]

We investigate the compaction dynamics of vibrated granular suspensions using both digital imaging technique and MRI measurements. Starting from initialy loose packings, our experimental data suggest the existence of two stages in the compaction dynamics: a fast stage at short times where a rising compaction front propagates through the granular suspension and a slow stage at large times where the packing compacts slowly and homogeneously. The compaction dynamics in each stage can be well fitted to usual stretched exponential laws with stretching exponents equal to 2 and 0.45, respectively. The transition time between these two stages, τ , depends on the fluid viscosity, vibration intensity and grain diameter. We show that τ and the velocity of the front decrease roughly linearly with the lubrication Peclet number, Pe related to the competition between the lubrication stress induced by vibrations and the granular pressure. Graphical abstract: [ABSTRACT FROM AUTHOR]

The IRMM-019 to IRMM-029 series of uranium hexafluoride materials is certified for the isotopic composition. After conversion into uranyl nitrate solution, certification and homogeneity measurements were performed by thermal ionization mass spectrometry. Analyses were performed by Modified Total Evaporation and for some materials the major isotope amount ratio n(U)/ n(U) was measured using a n(U)/ n(U) double spike. Measurements were confirmed by UF gas source mass spectrometry. Major isotope amount ratios were certified with relative expanded uncertainties ( k = 2) of 0.015-0.030 % and the minor isotope amount ratios n(U)/ n(U) and n(U)/ n(U) were certified with relative expanded uncertainties of 0.02-3 %. [ABSTRACT FROM AUTHOR]

Distribution patterns of stream biota are the result of complex interactions between individuals and their surrounding environment. Determining the spatial scale by which an organism is most influenced is paramount to understanding distribution patterns. Using a multi-scale approach, we investigated factors influencing habitat associations of larval Ambystoma barbouri (streamside salamander) and Eurycea cirrigera (southern two-lined salamander) in three Kentucky headwater streams. We used likelihood ratio G tests to identify associations between species and mesohabitat (i.e., runs, riffles, and pools), and we used microhabitat variables to predict the presence and abundance of salamanders via a priori multiple regression modeling. Ambystoma barbouri presence and abundance were influenced by conditions at micro-scales, which in turn dictated mesohabitat associations. Eurycea cirrigera were also influenced by microhabitat variables, but displayed associations to A. barbouri presence in late spring. Associations of larval salamanders to mesohabitat and microhabitat parameters shifted from early to late spring, likely in response to changes in developmental stage. The multi-scale approach of our study improved our understanding of complex relationships between larval salamanders and their surrounding environment in headwaters, and underscored the importance of (1) research investigating multiple spatial and temporal scales and (2) heterogeneous in-stream habitat to headwater biota. [ABSTRACT FROM AUTHOR]

Complementary MOSFET and Tunnel-FET inverters based on tri-gated strained Si nanowire arrays are demonstrated. The voltage transfer characteristics as well as the inverter supply currents of both inverter types are analyzed and compared. A degradation of the inverter output voltage is observed due to the ambipolar transfer characteristics of the symmetric homostructure TFET devices. Emulated TFET inverters based on the measured transfer characteristics of SiGe/Si heterostructure nanowire array n-channel TFETs with reduced ambipolarity demonstrate improved inverter switching for supply voltages down to V DD = 0.2 V. [ABSTRACT FROM AUTHOR]

In this work the determination of Cd, Cu, Cr, Fe and Sb as organic and inorganic additives in in-house plastic materials (ABS, LDPE) using electrothermal vaporization combined with inductively coupled plasma optical emission spectroscopy is described. The influence of CCl2F2 as gaseous halogenation modifier was investigated. Especially for the carbide forming elements the sensitivity was improved and the memory effects were significantly reduced. Calibration was performed by external calibration and standard addition with aqueous standard solutions added directly into the sample boats. Absolute limits of detection (3s-criterion) range between 0.1 ng (Cd) and 9 ng (Fe) which corresponds to relative values of 0.1 mg kg−1 and 1.6 mg kg−1, respectively, taking 5 mg as typical sample mass. The detection limits are sufficient to monitor the element contents of plastic materials according to European directives such as European directive on the safety of toys. The developed ETV-ICP-OES method allows a fast analysis with a high sample throughput (3 minutes per analysis), low sample consumption and good trueness and precision for the analyzed elements. Sample preparation is reduced to ashing the samples in a muffle furnace. Furthermore, measurements are possible regardless of the chemical form in the additives. For verification the results obtained with the developed method were compared with measurement results of independent methods ICP-MS/OES after digestion. In addition Cd, Cr and Pb were determined in a solid plastic reference material BAM-H010 to confirm the applicability and accuracy of the method. [ABSTRACT FROM AUTHOR]

Over the past years, certain “vulnerability genes” have been identified that play a key role in the development of mood and anxiety disorders. In particular, a low-expressing variant of the human serotonin transporter (5-HTT) gene has been described that renders individuals more susceptible to adverse experience and hence to the development of psychiatric diseases. However, some authors have recently argued that lower 5-HTT expression not only increases vulnerability to adverse experiences, but also enhances susceptibility to beneficial experiences, thus promoting phenotypic plasticity. The aim of the present study was to assess the effects of 5-HTT expression on susceptibility to beneficial experience in a hypothesis-driven experimental approach. Using a well-established rodent model for the human polymorphism, male heterozygous 5-HTT knockout (HET) and 5-HTT wildtype (WT) mice were either provided with the beneficial experience of cohabitation with a female (mating experience) or kept as naïve controls in single-housing conditions. Following the experimental treatment, they were tested for their anxiety-like behaviour and exploratory locomotion in three widely used behavioural tests. Interestingly, while cohabitation reduced anxiety-like behaviour and increased exploratory locomotion in the open field test in HET mice, it did not affect WT mice, pointing to a genotype-dependent susceptibility to the beneficial experience. Thus, our results might support the view of the low expressing version of the 5-HTT gene as a “plasticity” rather than a “vulnerability” variant. [ABSTRACT FROM AUTHOR]

We propose, in this paper, a model for predicting the rheological response of both vibrated and sheared 3D granular suspensions in stationary and nonstationary conditions. The major assumption of this model is the inherent bimodal behavior of chain forces in granular packings. The model is set up from a kinetic equation describing the dynamic exchange between a population of strongly correlated caged particles and a population of slightly correlated free particles. To compare the predictions of the model to experimental results, the kinetic equation is transformed into a differential constitutive equation, relating stress to strain, by including the effect of the interstitial fluid on the suspension. With only four adjustable parameters intrinsic to the system (i.e., independent of the type of rheological test used), the model is in very close agreement with experiments. Despite the fact that our approach remains at a mean-field level, it is able to predict and describe several rheological behaviors, in stationary, nonstationary conditions, linear and nonlinear regimes, including Newtonian and frictional Coulombian regimes, as well as elastic Hookean and viscoelastic Maxwellian behaviors. It then appears that this two-state approach allows capturing both the viscoelastic behavior of dry granular materials and granular suspensions. Vibrated dense suspensions and granular media are thus unified under a common framework. [ABSTRACT FROM AUTHOR]

This article discusses the age dating results of plutonium/uranium chronometers with a focus on the consequences for age plutonium determination when the basic assumptions of the methodology are not fully met: Incomplete removal of the daughter nuclides at the production date and uranium contamination of plutonium samples. In addition to the Pu/U, Pu/U and Pu/U, the Pu/U chronometer is discussed. The Pu/U radiochronometer has only scarcely been used, due to its high sensitivity to residual uranium. However, it can be a very useful indicator for uranium contamination of aged plutonium samples. [ABSTRACT FROM AUTHOR]

Since the early 1930s, deep hypothermia (cryoanaesthesia) has been a useful anaesthetic in several types of surgery on neonatal rodents. Especially against the background of modern techniques in systems neuroscience, the method enjoys again increasing popularity. However, little is known about its effects on the subsequent adult behavioural and physiological profile. To systematically investigate the effects of neonatal cryoanaesthesia on adult basal and emotional behaviour as well as on physiological development, 59 C57BL/6 mouse pups were randomly assigned to one of three treatment groups: Pups of the first group were exposed to the hypothermia treatment (H) on postnatal day 3, while pups of the other two groups served as controls: These pups either remained in the home cage without any intervention (C), or were separated from the mother for 15min (MS) to differentiate between effects of neonatal isolation alone versus hypothermia that inevitably goes along with neonatal isolation. Subsequent behavioural analyses were conducted during adulthood (P 84-P 130), including tests for exploratory, anxiety-like and depression-like behaviour. At the age of about 145 days mice were decapitated to record BDNF levels in the hippocampus and serum corticosterone. Altogether, H mice were found to display slightly increased anxiety levels on the O-Maze, but did not differ from the control animals in any other behavioural test. Subtle alterations in anxiety-like behaviour, however, were not accompanied by physiological changes in serum corticosterone and hippocampal BDNF levels, arguing against an overall long-lasting effect of neonatal hypothermia on the emotional profile of adult mice. [ABSTRACT FROM AUTHOR]

Abstract: Experimental results on tunneling field-effect transistors (TFETs) based on strained SiGe on SOI nanowire arrays are presented. A heterostructure SiGe/Si TFET with a vertical tunnel junction consisting of an in situ doped SiGe source and a Si channel with a minimum inverse subthreshold slope of 90mV/dec is demonstrated. An increase in tunneling area results in higher on-current. The in situ doped heterojunction TFET shows great improvement compared to a homojunction SiGe on SOI nanowire design with implanted junctions. Temperature dependent measurements and device simulations are performed in order to analyze the tunnel transport mechanism in the devices. [Copyright &y& Elsevier]

Abstract: Electrical characteristics of silicon nanowire tunnel field effect transistors (TFETs) are presented and benchmarked versus other concepts. Particular emphasis is placed on the band to band tunneling (BTBT) junctions, the functional core of the device. Dopant segregation from ion implanted ultrathin silicide contacts is proved as a viable method to achieve steep tunneling junctions. This reduces defect generation by direct implantation into the junction and thus minimizes the risk of trap assisted tunneling. The method is applied to strained silicon, specifically to nanowire array transistors, enabling the realization of n-type and p-type TFETs with fairly high currents and complementary TFET inverters with sharp transitions and good static gain, even at very low drain voltages of V DD =0.2V. These achievements suggest a considerable potential of TFETs for ultralow power applications. Gate-all-around Si nanowire array p-type TFETs have been fabricated to demonstrate the impact of electrostatic control on the device performance. A high on-current of 78μA/μm at V D = V G =1.1V is obtained. [Copyright &y& Elsevier]

Compositionally graded channel AlGaN/GaN high electron mobility transistors (HEMTs) offer a promising route to improve device linearity, which is necessary for low-noise radio-frequency amplifiers. In this work, we demonstrate different grading profiles of a 10-nm-thick AlxGa1−xN channel from x = 0 to x = 0.1 using hot-wall metal-organic chemical vapor deposition (MOCVD). The growth process is developed by optimizing the channel grading and the channel-to-barrier transition. For this purpose, the Al-profiles and the interface sharpness, as determined from scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, are correlated with specific MOCVD process parameters. The results are linked to the channel properties (electron density, electron mobility, and sheet resistance) obtained by contactless Hall and terahertz optical Hall effect measurements coupled with simulations from solving self-consistently Poisson and Schrödinger equations. The impact of incorporating a thin AlN interlayer between the graded channel and the barrier layer on the HEMT properties is investigated and discussed. The optimized graded channel HEMT structure is found to have similarly high electron density (∼ 9 × 10 12 cm−2) as the non-graded conventional structure, though the mobility drops from ∼ 2360 cm2/V s in the conventional to ∼ 960 cm2/V s in the graded structure. The transconductance gm of the linearly graded channel HEMTs is shown to be flatter with smaller g m ′ and g m ″ as compared to the conventional non-graded channel HEMT implying improved device linearity. [ABSTRACT FROM AUTHOR]

Abstract: In this work we experimentally demonstrate a novel method to fabricate short channel complementary planar strained Si (sSOI) TFETs with improved tunneling junctions by implantation into silicide method (IIS). For the first time we have successfully fabricated both, n- and p-type TFETs with high on-currents using ultra thin sSOI structures. We demonstrate all Si complementary TFET (C-TFET) inverters with a gain as large as 60 at V DD =2V and sharp transitions down to very low V DD =0.2V. The first transient response analysis of the NW C-TFET inverter showed a propagation delay of t p <20ns for L G =50nm. Nanowire array devices with improved electrostatic control compared to a planar device geometry with 15nm wires were fabricated using Si1 − x Ge x with x =35% and x =50% showing improved I ON with increasing Ge concentration. As compared to SiGe homojunction devices, Si1 − x Ge x /Si heterostructure NW TFETs show improved I ON/I OFF ratio up to 8 orders of magnitude and reduced trap assisted tunnelling (TAT) due to in situ source doping. [Copyright &y& Elsevier]

Isolated small populations typically have reduced genetic variation and are more susceptible to local extinction. Examining the relationship between genetic variability and survival is important for conservation because it provides insight on evolutionary potential and population viability. We studied genetic associations of survival from egg to metamorphosis in the largest population of critically endangered dusky gopher frogs Lithobates sevosus. This approach allowed us to examine whether heterozygosity-fitness correlations ( HFCs) existed in an r-selected species with large effect size, whereas previous research on HFCs has largely focused on k-selected species often with low effect sizes. Our objectives were to determine if genetic-fitness associations exist, if associations are a result of inbreeding and if natural selection against inbreeding has occurred. Specifically, we examined averaged population responses and HFC in relation to (1) mortality within egg clutches and (2) differential survival of offspring through metamorphosis. To do so, we used eight microsatellite DNA markers to compare genotypes across three life-history stages from a single year in the following temporal order: adults, eggs and metamorphs. We discovered a strong genetic association with survival in early life stages. In terms of average population responses, we documented a within-cohort decrease in FIS with life-history stage progression (adults: FIS = 0.067; eggs: FIS = 0.063; metamorphs: FIS = −0.134), high FST between eggs and metamorphs ( FST = 0.113), and a locus that had larger than expected FST. We found positive genetic-fitness associations for survival of egg clutches and for survival to metamorphosis. We believe that inbreeding is the primary cause; however, we also found evidence suggesting existence of purging selection against a deleterious mutant linked to a microsatellite locus. Survival of individuals with greater genetic variability should prolong persistence of this isolated population. Our study underscores the importance of species management focused on preservation of genetic diversity. [ABSTRACT FROM AUTHOR]

This multicenter study evaluated the accuracy of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry identifications from the VITEK MS system (bioMérieux, Marcy l’Etoile, France) for Enterobacteriaceae typically encountered in the clinical laboratory. Enterobacteriaceae isolates ( n = 965) representing 17 genera and 40 species were analyzed on the VITEK MS system (database v2.0), in accordance with the manufacturer’s instructions. Colony growth (≤72 h) was applied directly to the target slide. Matrix solution (α-cyano-4-hydroxycinnamic acid) was added and allowed to dry before mass spectrometry analysis. On the basis of the confidence level, the VITEK MS system provided a species, genus only, or no identification for each isolate. The accuracy of the mass spectrometric identification was compared to 16S rRNA gene sequencing performed at MIDI Labs (Newark, DE). Supplemental phenotypic testing was performed at bioMérieux when necessary. The VITEK MS result agreed with the reference method identification for 96.7 % of the 965 isolates tested, with 83.8 % correct to the species level and 12.8 % limited to a genus-level identification. There was no identification for 1.7 % of the isolates. The VITEK MS system misidentified 7 isolates (0.7 %) as different genera. Three Pantoea agglomerans isolates were misidentified as Enterobacter spp. and single isolates of Enterobacter cancerogenus, Escherichia hermannii, Hafnia alvei, and Raoultella ornithinolytica were misidentified as Klebsiella oxytoca, Citrobacter koseri, Obesumbacterium proteus, and Enterobacter aerogenes, respectively. Eight isolates (0.8 %) were misidentified as a different species in the correct genus. The VITEK MS system provides reliable mass spectrometric identifications for Enterobacteriaceae. [ABSTRACT FROM AUTHOR]

Abstract: Crotoxin, the main neurotoxic component of the venom of South American rattlesnake (Crotalus durissus terrificus), is reported to have potent antinociceptive activity. Several authors have shown mainly in behavioral pain models that crotoxin induces antinociceptive effects, supposed to be mediated by actions on the central nervous system. The antinociceptive effects of crotoxin (45 μg/kg ip) in rats were verified in this study by increased response latencies in a Hargreaves test and tail flick test. In addition, it was demonstrated that crotoxin does not lead to motor impairments during a rotarod test and open field test. The main objective, carried out by blood oxygen level dependent functional Magnetic Resonance Imaging (BOLD fMRI) in anesthetized rats, was to determine which specific brain structures are involved in these antinociceptive effects. Moreover, potential antihyperalgesic effects were investigated by inducing a local hyperalgesia on the left hind paw. Therefore, antinociceptive effects (right paw) and antihyperalgesic effects (left paw) of crotoxin were able to be differentiated. As a result, crotoxin exhibited dominant antihyperalgesic but also antinociceptive effects during pain stimulation. Reductions of BOLD signal already occurred in brain input structures but were most prominent in primary and secondary somatosensory cortices. In conclusion, BOLD fMRI in anesthetized rats proved to be a helpful tool in toxinology, particularly in unraveled mechanisms of modulating nociception in the central nervous system by (potential) analgesics like crotoxin. [Copyright &y& Elsevier]

We investigate the temporal evolution of the hole depth and shape for percussion drilling at different ambient pressure conditions. Deep drilling is performed in silicon as target material by ultrashort laser pulses at 1030 nm and a duration of 8 ps. Simultaneously, the backlit silhouette of the hole is imaged perpendicular to the drilling direction. While typical process phases like depth development and shape evolution are very similar for atmospheric pressure down to vacuum conditions (10 mbar), the ablation rate in the initial process phase is significantly increased for reduced pressure. The number of pulses till the stop of the drilling process also increases by a pressure reduction and exceeds drilling at atmospheric conditions by two orders of magnitude for a pressure of ca. 10 mbar. Accordingly, the maximum achievable hole depth is more than doubled. We attribute this behavior to an enlarged mean free path for ablation products at reduced pressure and therefore lower or no deposition of particles inside the hole capillary under vacuum conditions while debris fills the hole already after a few thousand pulses at atmospheric pressure. This is supported by scanning electron cross section images of the holes. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied enrichment effects on rats selectively bred for learned helplessness. [•] Enrichment reduced learned helplessness in 14 weeks old, but not 28 weeks old cLH rats. [•] Anhedonic-like behavior was not affected by enrichment. [•] Spontaneous behavior in the home cage was only marginally influenced by enrichment. [•] These data suggest differential effects of environmental enrichment on behavior. [ABSTRACT FROM AUTHOR]

Abstract: Individual housing of social species is a common phenomenon in laboratory animal facilities. Single housing, however, is known to inflict social deprivation with a number of detrimental consequences. Aiming to improve housing conditions of single housed rodents, we investigated the simulation of social housing by mirrors in a series of behavioural experiments and biochemical parameters in mice. We found that chronic mirror-image stimulation increased exploratory behaviours in the holeboard and novel cage tests, but did not alter anxiety, locomotor, or depression-like behaviours. Moreover, no influence on visual recognition memory was observed. Hippocampal brain-derived neurotrophic factor (BDNF) levels, a biomarker for enrichment effects, were unaltered. In line, mirror-image stimulation did not alter home cage behaviour in mice housed with and without mirrors when left undisturbed. Thus, though we found subtle behavioural effects after long-term mirror exposure, we conclude that the simulation of social housing by mirrors is not sufficient to gain the presumably beneficial outcomes induced by social housing. [Copyright &y& Elsevier]

Uranium hexafluoride gas source mass spectrometry at IRMM is based on two foundations, firstly the operation of a UF6 gas source mass spectrometer (GSMS) and secondly the preparation of primary UF6 reference materials, which were converted from gravimetrically prepared mixtures of highly enriched oxides of 235U and 238U. Recently a new GSMS for uranium isotopic measurements using UF6 gas, the “URANUS” from Thermo Fisher, was installed at IRMM, which also allows measurements of the so-called “minor” isotope ratios n(234U)/n(238U) and n(236U)/n(238U). In this paper the design and the implementation of measurement techniques for the new URANUS GSMS are described. This includes the “single standard” and the “double standard” (DS) method as well as the newly developed “memory corrected double standard” method (MCDS). This required a detailed investigation of memory effects within the GSMS instrument, in particular regarding the dependence of memory effects on the isotope ratios of samples and standards. The results of this study led to new recommendations for the selection of the standards for a given sample and for suitable measurement procedures. The measurement performance for the “major” isotope ratio n(235U)/n(238U) as well as the “minor” isotope ratios n(234U)/n(238U) and n(236U)/n(238U) is presented and compared with other mass spectrometric techniques. With the installation and validation of the new URANUS GSMS instrument IRMM has established two new complementary techniques for measuring the full isotopic composition of uranium samples. UF6 GSMS in combination with the MCDS method is considered the preferred technique for samples in the UF6 form and for smaller uncertainties for measurements of the major ratio n(235U)/n(238U), while thermal ionization mass spectrometry (TIMS), in combination with the “modified total evaporation” (MTE) method as well as ion counting and high abundance sensitivity for the detection of 236U, provides a superior measurement performance for the minor isotope ratios n(234U)/n(238U) and n(236U)/n(238U). [ABSTRACT FROM AUTHOR]

We report on the joining of different glass types with dissimilar optical, thermal and mechanical properties by ultrashort laser welding at high repetition rates. Femtosecond laser pulses were focused at the interface of two optically contacted transparent samples. Using nonlinear absorption processes and heat accumulation of successive pulses, we achieved strong bonds between the samples. We used a three-point bending test to determine the breaking strength. With this technique, we achieved for instance for a borosilicate glass a breaking strength of up to 95 % of the bulk material. In addition, we even welded different material combinations. Although the welded glasses exhibit different thermal and mechanical properties, we obtained breaking strengths which are comparable to the utilized bulk materials. Using Raman spectroscopy we mapped the laser-processed material along the welded interface. Thereby, we determined that the welds consist of a mixture of both species, which is formed during the laser induced melting of the materials. [ABSTRACT FROM AUTHOR]

The European Water Framework Directive (WFD) was enacted in the year 2000 with a stepwise approach. After legal implementation in the various member states large efforts were undertaken for the initial characterization of water bodies, risk assessment, to implement extensive monitoring schemes and to develop management plans at different aggregation levels by the year 2010. The initial characterization process and risk assessment had to be finalized by 2004 and delineated water bodies including a typological classification and identified the significant pressures and impacts in a screening procedure. In parallel, monitoring programmes and new biological indicator systems were developed in order to proof and refine the results of the risk assessment with an ecological indicator based assessment in a subsequent step which was finalized in 2009. Although the risk assessment for Germany was based on existing data that were originally collected for other purposes and came from a large variety of environmental or economical sectors, the results differ only slightly from the monitoring and indicator based information with respect to classifications of the 'ecological status' and 'chemical status'. From this result we conclude that a risk assessment based on a careful application and intelligent combination of existing data sources with proven quality allows the recognition of trends and the identification of priorities for action of measures already at an early stage of a management process. However, monitoring schemes and advanced sets of ecological indicators are essential in later management steps both for narrowing uncertainties remaining from the risk assessment and to allow for effect controls of implemented measures. Moreover, these monitoring indicators should differentiate the effects of multiple stressors more factor specific and with respect to ecosystem states and functions. In conclusion, we see risk and indicator based assessments as complementary elements in Integrated Water Resources Management (IWRM), which have to be linked in systematic and phased procedures. [ABSTRACT FROM AUTHOR]

Of 48 available crania dated older than 1104AD, from the archaeological site of Skeljastadir in Thorsardalur, Iceland, 24 (50%) had torus mandibularis. There was no sex difference observed. The prevalence is similar among other populations in the northern hemisphere from the same time period. According to a number of authors, environmental and functional factors, particularly high masticatory activity, play a predominant part in the etiology. People from artic- and subartic areas survived on an animal diet, mostly fish and meat, but people living further south in a more temperate climate had more of an agricultural diet. Higher prevalence was found in the age group above 36 years than in the group 35 years and below. The majority of the tori were small or medium in size. The most frequently occurring variant was the multiple bilateral form, followed by the multiple unilateral form. The prevalence of torus mandibularis in the study was much higher than found in modern Iceland. [ABSTRACT FROM AUTHOR]

The nanoscale structure of femtosecond laser-induced modifications known as 'nanogratings' has been the subject of speculation and intensive debate throughout the decade since their discovery. The aim of this work is to gain dependable information on the three-dimensional (3D) substructure of nanogratings down to the nanometre scale. To this end, non-destructive small angle X-ray scattering (SAXS) was employed to determine the characteristic sizes associated with the smallest features over a wide range of inscription parameters. The characteristic size of these cavities is 30 × 200 × 300 nm3 and largely independent of the exposure parameters, whereas prolonged exposure to laser pulses leads to an increase in their total number. Subsequently, focused ion beam (FIB) milling was used to dissect an extended volume and for the first time directly observe the 3D structure of nanogratings with nanometre resolution. The experiments clearly show that hollow cavities are the primary constituents of nanogratings and that their sheet-like arrangement gives rise to the well-known periodicity. [ABSTRACT FROM AUTHOR]

Abstract: Uranium and plutonium particulate test materials are becoming increasingly important as the reliability of measurement results has to be demonstrated to regulatory bodies responsible for maintaining effective nuclear safeguards. In order to address this issue, the Institute for Reference Materials and Measurements (IRMM) in collaboration with the Institute for Transuranium Elements (ITU) has initiated a study to investigate the feasibility of preparing and characterizing a uranium particle reference material for nuclear safeguards, which is finally certified for isotopic abundances and for the uranium mass per particle. Such control particles are specifically required to evaluate responses of instruments based on mass spectrometric detection (e.g. SIMS, TIMS, LA-ICPMS) and to help ensuring the reliability and comparability of measurement results worldwide. In this paper, a methodology is described which allows quantifying the uranium mass in single micron particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS). This methodology is characterized by substantial improvements recently achieved at IRMM in terms of sensitivity and measurement accuracy in the field of uranium particle analysis by TIMS. The use of monodisperse uranium oxide particles prepared using an aerosol generation technique developed at ITU, which is capable of producing particles of well-characterized size and isotopic composition was exploited. The evidence of a straightforward correlation between the particle volume and the mass of uranium was demonstrated in this study. Experimental results have shown that the uranium mass per particle can be measured via the ID-TIMS method to a relative expanded uncertainty of about 10% (coverage factor k =2). The availability of reliable and validated methods for the characterization of uranium particles is considered to be essential for the establishment of SI-traceable measurement results. It is therefore expected that the method developed in this study is valuable for the certification of particulate materials in which the isotopic composition and the content of uranium must be accurately known. [Copyright &y& Elsevier]

Abstract: When kept in barren and restrictive cages, animals frequently develop stereotypic behaviour patterns that are characterized by high repetition rates, conspicuous invariance and an apparent lack of function. Although millions of animals are affected, the underlying causes and mechanisms are still unclear. Growing evidence suggests that cage-induced stereotypies may reflect pathological dysfunction within basal ganglia circuitry expressed by perseverative behaviour. In order to assess whether variation in stereotypy performance and variation in perseverative behaviour may have a common cause in ICR CD-1 mice, we assessed the effects of environmental enrichment on both phenomena. We raised 48 female ICR CD-1 mice in standard or enriched cages from three weeks to either 6 or 11 months of age and measured stereotypy level in the home cage and perseveration on an extinction task. We further examined whether enriched rearing conditions (early enrichment) protect mice from the developing stereotypies later in life and whether stereotypies developed in barren cages would persist in an enriched environment (late enrichment) by transferring standard mice to enriched cages and vice versa for 14 weeks after completion of the extinction task. We found no evidence for a causal relation between stereotypy and perseveration in mice. However, transfer to enriched cages reduced stereotypy levels significantly both at 6 and 11 months of age indicating that stereotypies had not become established yet. Finally, we found that removing enrichments at both ages did not induce higher stereotypy levels, thereby confirming earlier reports of a neuroprotective effect of early enrichment. [Copyright &y& Elsevier]

We investigate the mechanical behavior of granular suspensions subjected to coupled vibrations and shear. At high shear stress, whatever the mechanical vibration energy and bead size, the system behaves like a homogeneous suspension of hard spheres. At low shear stress, in addition to a dependence on bead size, vibration energy drastically influences the viscosity of the material that can decrease by more than 2 orders of magnitude. All experiments can be rationalized by introducing a hydrodynamical Peclet number defined as the ratio between the lubrication stress induced by vibrations and granular pressure. The behavior of vibrated wet and dry granular materials can then be unified by assimilating the Hookean stress in dry media to the lubrication stress in suspensions. [ABSTRACT FROM AUTHOR]

We report on the temporal evolution of the percussion drilling process in deep laser drilling. Ultrashort laser pulses at 1030 nm and a duration of 8 ps were used to machine silicon while simultaneously imaging the silhouette of the hole using an illumination wavelength above the band edge. We investigate the influence of the processing parameters fluence and pulse energy on the depth and shape of the hole demonstrating different phases of the drilling process. In the first phase, a tapered hole is formed with highly reproducible shape and depth. In the following, the evolution of the hole shape is irregular and imperfections like bulges, changes of the drilling direction and the formation of multiple hole ends occur. In the final phase, the maximum depth stays constant while the volume still increases due to enlargement of the hole diameter and the possible formation of multiple hole ends. Deviations from the ideal hole shape occur primarily in the lower part of the hole. Their extent can be reduced by increasing the amount of applied pulse energy. Moreover, the pulse energy is chiefly determining the maximum achievable hole depth, which is largely independent of the focusing conditions and corresponding fluence. [ABSTRACT FROM AUTHOR]

Dense TRIP-matrix composites containing 5 vol.% Mg-PSZ as reinforcing phase were produced by employing the spark plasma sintering technique. A continuous and seamless interface between the ceramic particles and the steel matrix was achieved. Compression tests revealed better mechanical properties of the 5 vol.% Mg-PSZ-TRIP steel composites in comparison with both, pure and Al2O3 reinforced TRIP steel. The underlying deformation mechanism within the austenitic matrix entailed a pronounced martensite formation. An additional phase transformation was observed within the ZrO2 particles. The enhanced mechanical properties of the 5 vol.% Mg-PSZ composite are dedicated to the transformation strengthening of the ceramic particles. Finally a model of the reinforcing mechanism is proposed. [ABSTRACT FROM AUTHOR]

We investigate the formation of self-organized nanostructures inside the bulk of fused silica induced by ultrafast laser pulses at high repetition rates. Three distinct stages of the evolution from random nanostructures to periodic nanogratings are identified. In addition, for the first time nanograting formation in fused silica is observed at repetition rates as high as 9.4 MHz, thereby significantly extending the parameter window for nanograting inscription. Throughout the whole parameter range, a strong dependence of the grating period on the number of incident pulses was revealed. [ABSTRACT FROM AUTHOR]

We report on the welding of fused silica with ultrashort laser pulses at high repetition rates. Femtosecond laser pulses were focused at the interface of two optically contacted fused silica samples. Due to the nonlinear absorption in the focal volume and heat accumulation of successive pulses, the laser acts as a localized heat source at the focus position. Here, we analyze the influence of the laser and processing parameters on the amount of molten material. Moreover, we determine the achievable breaking stress by a three point bending test. With optimized parameters up to 75% of the breaking stress of the bulk material have been obtained. [ABSTRACT FROM AUTHOR]

Abstract: A method is described that allows measuring the isotopic composition of small uranium oxide particles (less than 1μm in diameter) for nuclear safeguards purposes. In support to the development of reliable tools for the identification of uranium and plutonium signatures in trace amounts of nuclear materials, improvements in scanning electron microscopy (SEM) and thermal ionization mass spectrometry (TIMS) in combination with filament carburization and multiple ion counting (MIC) detection were investigated. The method that has been set up enables the analysis of single particles by a combination of analytical tools, thus yielding morphological, elemental and isotopic information. Hereby individual particles of certified reference materials (CRMs) containing uranium at femtogram levels were analysed. The results showed that the combination of techniques proposed in this work is suitable for the accurate determination of uranium isotope ratios in single particles with improved capabilities for the minor abundant isotopes. [Copyright &y& Elsevier]