Nickel hydride complexes, defined herein as any molecules bearing a nickel hydrogen bond, are crucial intermediates in numerous nickel-catalyzed reactions. Some of them are also synthetic models of ...nickel-containing enzymes such as NiFe-hydrogenase. The overall objective of this review is to provide a comprehensive overview of this specific type of hydride complexes, which has been studied extensively in recent years. This review begins with the significance and a very brief history of nickel hydride complexes, followed by various methods and spectroscopic or crystallographic tools used to synthesize and characterize these complexes. Also discussed are stoichiometric reactions involving nickel hydride complexes and how some of these reactions are developed into catalytic processes.
The effect of a very short aging treatment (360
s at 873
K) on the superelastic properties has been investigated on the ternary Ti–20Nb–6Zr (at.%) titanium-based alloy. Such short thermal treatment ...is shown to be an efficient way to obtain a recrystallized microstructure with ultrafine β grains of about 1–2
μm. In addition, the associated mechanical properties display an outstanding improvement in superelastic properties, with 3.2% of elastic recovery combined with high tensile strength of around 750
MPa.
Titanium alloys dedicated to biomedical applications may display both clinical and mechanical biocompatibility. Based on nontoxic elements such as Ti, Zr, Nb, Ta, they should combine high mechanical ...resistance with a low elastic modulus close to the bone elasticity (E=20 GPa) to significantly improve bone remodelling and osseointegration processes. These elastic properties can be reached using both lowering of the intrinsic modulus by specific chemical alloying and superelasticity effects associated with a stress-induced phase transformation from the BCC metastable beta phase to the orthorhombic
α
″
martensite. It is shown that the stability of the beta phase can be triggered using a chemical formulation strategy based on the electronic design method initially developed by Morinaga. This method is based on the calculation of two electronic parameters respectively called the bond order (
B
o
) and the d orbital level (
M
d
) for each alloy. By this method, two titanium alloys with various tantalum contents, Ti–29Nb–11Ta–5Zr and Ti–29Nb–6Ta–5Zr (wt%) were prepared. In this paper, the effect of the tantalum content on the elastic modulus/yield strength balance has been investigated and discussed regarding the deformation modes. The martensitic transformation
β
→
α
″
has been observed on Ti–29Nb–6Ta–5Zr in contrast to Ti–29Nb–11Ta–5Zr highlighting the chemical influence of the Ta element on the initial beta phase stability. A formulation strategy is discussed regarding the as-mentioned electronic parameters. Respective influence of cold rolling and flash thermal treatments (in the isothermal omega phase precipitation domain) on the tensile properties has been investigated.
•Combination of gasochromic dye with highly porous silica supraparticles.•Fully integrated sensor system: from the particle synthesis over electronics and a 3D printed diffusion chamber.•Sensitive ...detection of small and slowly rising CO concentrations (<< 20 ppm CO).•Reliable detection of smoldering and open fires , with wood as well as plastic compositions.•Competitive to commercially available smoke detectors.
For early fire detection, the measurement of low and small rising concentrations of the fire typical gas carbon monoxide (CO) is essential. The approach presented herein integrates a highly sensitive colorimetric material into a low cost gas sensor system. The gas sensitive color dye is hosted by silica nanoparticle based supraparticles and then processed to a so-called gas sensor stripe. Changes in the CO concentration enable a change of the sensor stripes color, which is easily detectable as a change of the light that is reflected by the stripe. A diffusion chamber protects the gas sensitive film against harmful environmental influences and interfering light. The capability of the gas sensor system is demonstrated in lab as well as real fire tests. In case of the latter, standardized real fire tests are conducted, as well as realistic mixtures of plastics and wood are smoldered. The developed sensors react in real time to the slowly rising CO concentration during the test fires. Even small amounts of CO (<20 ppm) are reliably detectable.
NASA’s OSIRIS-REx asteroid sample return mission spacecraft includes the Touch And Go Camera System (TAGCAMS) three camera-head instrument. The purpose of TAGCAMS is to provide imagery during the ...mission to facilitate navigation to the target asteroid, confirm acquisition of the asteroid sample, and document asteroid sample stowage. The cameras were designed and constructed by Malin Space Science Systems (MSSS) based on requirements developed by Lockheed Martin and NASA. All three of the cameras are mounted to the spacecraft nadir deck and provide images in the visible part of the spectrum, 400–700 nm. Two of the TAGCAMS cameras, NavCam 1 and NavCam 2, serve as fully redundant navigation cameras to support optical navigation and natural feature tracking. Their boresights are aligned in the nadir direction with small angular offsets for operational convenience. The third TAGCAMS camera, StowCam, provides imagery to assist with and confirm proper stowage of the asteroid sample. Its boresight is pointed at the OSIRIS-REx sample return capsule located on the spacecraft deck. All three cameras have at their heart a
2592
×
1944
pixel
complementary metal oxide semiconductor (CMOS) detector array that provides up to 12-bit pixel depth. All cameras also share the same lens design and a camera field of view of roughly
44
∘
×
32
∘
with a pixel scale of 0.28 mrad/pixel. The StowCam lens is focused to image features on the spacecraft deck, while both NavCam lens focus positions are optimized for imaging at infinity. A brief description of the TAGCAMS instrument and how it is used to support critical OSIRIS-REx operations is provided.
Individuals suffering from mood and anxiety disorders often show significant disturbances in sleep and circadian rhythms. Animal studies indicate that circadian rhythm disruption can cause increased ...depressive- and anxiety-like behavior, but the underlying mechanisms are unclear. One potential mechanism to explain how circadian rhythms are contributing to mood and anxiety disorders is through dysregulation of the suprachiasmatic nucleus (SCN) of the hypothalamus, known as the "central pacemaker." To investigate the role of the SCN in regulating depressive- and anxiety-like behavior in mice, we chronically manipulated the neural activity of the SCN using two optogenetic stimulation paradigms. As expected, chronic stimulation of the SCN late in the active phase (circadian time 21, CT21) resulted in a shortened period and dampened amplitude of homecage activity rhythms. We also repeatedly stimulated the SCN at unpredictable times during the active phase of mice when SCN firing rates are normally low. This resulted in dampened, fragmented, and unstable homecage activity rhythms. In both chronic SCN optogenetic stimulation paradigms, dampened homecage activity rhythms (decreased amplitude) were directly correlated with increased measures of anxiety-like behavior. In contrast, we only observed a correlation between behavioral despair and homecage activity amplitude in mice stimulated at CT21. Surprisingly, the change in period of homecage activity rhythms was not directly associated with anxiety- or depressive-like behavior. Finally, to determine if anxiety-like behavior is affected during a single SCN stimulation session, we acutely stimulated the SCN in the active phase (zeitgeber time 14-16, ZT14-16) during behavioral testing. Unexpectedly this also resulted in increased anxiety-like behavior. Taken together, these results indicate that SCN-mediated dampening of rhythms is directly correlated with increased anxiety-like behavior. This work is an important step in understanding how specific SCN neural activity disruptions affect depressive- and anxiety-related behavior.
A recently-developed technique for stopping hydration without altering the microstructure by invasive methods is studied. This technique is based on the replacement at the mixing stage of ...cement/binder grains that would otherwise remain unhydrated in real systems at defined hydration stages with inert quartz particles. This technique allows studying hydration-dependent properties in a static equivalent system, where these processes can be decoupled from hydration.
A comprehensive comparison between real and equivalent systems, in terms of mechanical properties as well as physico-chemical ones is presented. Results of mechanical properties support the validity of the approach. Microstructural characterization by means of mercury intrusion porosimetry shows comparable results in terms of total porosity and breakthrough radii. Thermogravimetric analysis shows comparable amounts of hydration products formed. These results suggest that the method can constitute a useful tool for studying the behavior of cementitious materials at early ages, in particular transport phenomena and shrinkage.
Evidence linking common mental disorders (CMD) in pregnant women to adverse birth outcomes is inconsistent, and studies often failed to control for pregnancy complications. This study aimed to ...explore the association between antenatal depression and anxiety symptoms and birth outcomes in a low-obstetric risk sample of mother/child dyads in Ghana and Côte d'Ivoire.
In 2010-2011, a prospective cohort of 1030 women in their third trimester in Ghana and Côte d'Ivoire was enrolled. Depression and anxiety were assessed in the third trimester using the Patient Health Questionnaire depression module and the 7-item Generalized Anxiety Disorder scale. 719 mother/child dyads were included in the analysis. We constructed multivariate regression models to estimate the association between CMD and low birth weight (LBW), and preterm birth (PTB) to control for potential confounders.
The prevalence of depression and anxiety symptoms were 28.9% and 14.2% respectively. The mean birth weight was 3172.1g (SD 440.6) and the prevalence of LBW was 1.7%. The mean gestational age was 39.6 weeks and the proportion of PTB was 4%. Multivariate linear regression revealed no significant association between maternal depression (B=52.2, 95% CI -18.2 122.6, p=0.15) or anxiety (B=17.1, 95% CI -74.6 108.7, p=0.72) and birth weight. Yet, low socio-economic status, female sex of the child, and younger maternal age were associated with lower birth weight. Multivariate logistic regression suggested no significant association between maternal depression (OR: 2.1, 95% CI 0.8 5.6, p=0.15) or anxiety (OR: 1.8, 95% CI 0.6 5.5, p=0.29) with PTB.
Our data suggests that depression and/or anxiety in the 3(rd) trimester of pregnancy are not independent predictors of adverse birth outcomes in low obstetric risk women. The role of pregnancy complications as confounders or effect modifiers in studies of maternal CMD and their impact on birth outcomes should be investigated.
Investigation of bird strike events on composite wing panels Diamantakos, I.; Fotopoulos, K.; Jamin, M. ...
Fatigue & fracture of engineering materials & structures,
October 2017, 2017-10-00, 20171001, Letnik:
40, Številka:
10
Journal Article
Recenzirano
One of the most important events during an aircraft's service life is the impact of a bird (ie, bird strike), which could possibly lead to catastrophic failure. According to airworthiness ...authorities, compliance of an aircraft structure to bird‐strike certification specifications can potentially be proved by simulation. In the present work, combined experimental and numerical investigations are performed, aiming to provide a validated numerical simulation tool for the certification of a composite leading edge structure. To increase the numerical simulation efficiency, the stacked shell approach in the frame of the finite element method is adopted. Comparison of numerical and experimental results shows that the proposed methodology is very promising for the simulation of impact events on complex composite structures. The proposed methodology has been applied for the development of a numerical tool for the simulation of bird strike on a composite leading edge structure.
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