The nonlinear properties of zinc germanium diphosphide (ZGP) crystals enable their applications in powerful mid-IR optical parametric oscillators and second-harmonic generators. This paper summarizes ...the mechanisms of the laser-induced damage (LID) of high-purity ZGP crystals under periodically pulsed nanosecond irradiation by a Ho3+:YAG laser at 2.1 μm. The ZGP samples were manufactured by “LOC” Ent., Tomsk, Russia, or the Harbin Institute of Technology, China. The impact of processing techniques and the post-growing methods for polishing and anti-reflective coatings on the LID threshold are discussed. The importance of the defect structure of the crystal lattice and the parameters of transparent coatings for increasing the LID threshold are also discussed. The impact of the test laser parameters on the LID threshold and the transient area near the LID threshold obtained using digital holography are analyzed. The influence of the pre-damage processes on the optical parametric oscillations is reported. Lastly, the prospects for improving ZGP crystals to further increase the LID threshold are discussed.
Effects of the addition of resins on aggregation and stability of petroleum asphaltenes in hydrocarbon solutions are studied by dynamic light scattering. The average aggregate size was monitored in ...real time as a function of the concentration of the precipitant (heptane) and resins. It is shown that resins serve as inhibitors for asphaltene aggregation, shifting the onset of aggregation. However, the dependence of the onset on the concentration of resins has a tendency to saturate. The characteristic time of aggregation decreases exponentially upon increase of the precipitant concentration, while it grows linearly upon increase of the concentration of resins. A definition of the onset of asphaltene aggregation based on the time dependence of the aggregate-size growth is suggested. It is also shown for all the samples studied (with and without resins) that the aggregation is controlled by diffusion-limited kinetics. The size of the aggregates as a function of time follows a diffusion-limited-kinetics power law with an exponent α = 0.36 ± 0.04, which is related to the fractal dimension d f of asphaltene clusters as α = 1/(1 + d f).
The electrophysical process in the discharge circuit of a copper vapor laser (CVL) with an LT-10Cu industrial gas discharge tube is studied. It is shown that the pumping of the active medium of the ...CVL is carried out in two stages. During the first (preparatory) stage, the capacitive components of the laser discharge circuit are charged from the storage capacitor; during the second stage, the active medium is pumped. The first stage is changed to the second one as a result of a “breakdown.” Under these conditions, the practical efficiency of a CVL can attain ∼1% in pump circuits with magnetic compression units, and ∼2.5–3% in the case when the energy input is cutoff after a lasing pulse. The conditions for implementing the mode of energy input cutoff after a lasing pulse are considered.
Domain walls in ferroic materials have attracted significant interest in recent years, in particular because of the unique properties that can be found in their vicinity. However, to fully harness ...their potential as nanoscale functional entities, it is essential to achieve reliable and precise control of their nucleation, location, number and velocity. Here, using piezoresponse force microscopy, we show the control and manipulation of domain walls in ferroelectric thin films of Pb(Zr,Ti)O₃ with Pt top electrodes. This high-level control presents an excellent opportunity to demonstrate the versatility and flexibility of ferroelectric domain walls. Their position can be controlled by the tuning of voltage pulses, and multiple domain walls can be nucleated and handled in a reproducible fashion. The system is accurately described by analogy to the classical Stefan problem, which has been used previously to describe many diverse systems and is here applied to electric circuits. This study is a step towards the realization of domain wall nanoelectronics utilizing ferroelectric thin films.
Once considered as mere curiosities, acyl metalloids are now recognized for their utility in enabling chemical synthesis. This perspective considers the reactivity displayed by acylboron, -silicon, ...-germanium, and tellurium species. By highlighting the role of these species in various transformations, we demonstrate how differences between the comprising elements result in varied reaction outcomes. While acylboron compounds are primarily used in polar transformations, germanium and tellurium species have found utility as radical precursors. Applications of acylsilanes are comparatively more diverse, owing to the possibility to access both radical and polar chemistry.
Originally considered as fundamental curiosities, acyl metalloids have proven to be useful tools in synthesis. This perspective aims to highlight the modes of reactivity accessible to boron, silicon, germanium and tellurium species.
The design of the MEG II experiment Baldini, A. M.; Baracchini, E.; Bemporad, C. ...
The European physical journal. C, Particles and fields,
05/2018, Volume:
78, Issue:
5
Journal Article
Peer reviewed
Open access
The MEG experiment, designed to search for the
μ
+
→
e
+
γ
decay, completed data-taking in 2013 reaching a sensitivity level of
5.3
×
10
-
13
for the branching ratio. In order to increase the ...sensitivity reach of the experiment by an order of magnitude to the level of
6
×
10
-
14
, a total upgrade, involving substantial changes to the experiment, has been undertaken, known as MEG II. We present both the motivation for the upgrade and a detailed overview of the design of the experiment and of the expected detector performance.
Bronchial asthma (BA) is a disease that still lacks an exhaustive treatment protocol. In this regard, the global medical community pays special attention to the genetic prerequisites for the ...occurrence of this disease. Therefore, the search for the genetic polymorphisms underlying bronchial asthma has expanded considerably. As the present study progressed, a significant amount of scientific medical literature was analyzed and 167 genes reported to be associated with the development of bronchial asthma were identified. A group of participants (n = 7,303) who had voluntarily provided their biomaterial (venous blood) to be used in the research conducted by the Federal Medical Biological Agency of Russia was formed to subsequently perform a bioinformatic verification of known associations and search for new ones. This group of participants was divided into four cohorts, including two sex-distinct cohorts of individuals with a history of asthma and two sex-distinct cohorts of apparently healthy individuals. A search for polymorphisms was made in each cohort among the selected genes, and genetic variants were identified whose difference in occurrence in the different cohorts was statistically significant (significance level less than 0.0001). The study revealed 11 polymorphisms that affect the development of asthma: four genetic variants (rs869106717, rs1461555098, rs189649077, and rs1199362453), which are more common in men with bronchial asthma compared to apparently healthy men; five genetic variants (rs1923038536, rs181066119, rs143247175, rs140597386, and rs762042586), which are more common in women with bronchial asthma compared to apparently healthy women; and two genetic variants (rs1219244986 and rs2291651) that are rare in women with a history of asthma.
Sorption experiments, X-ray structural analysis and NMR relaxation measurements were used in the study of peculiarities of interaction between water and chitosan-based composite films containing from ...0.5 to 30 wt% of chitin nanofibrils. Comparison between dependences of amplitude of free induction decay signal, as well as spin-spin (spin-lattice) relaxation times on moisture content in samples led us to the conclusion that the composite films have more ordered supramolecular structure than pure chitosan films. It was demonstrated that the results of sorption and NMR relaxation experiments correlate well with the data of X-ray structural analysis.
Display omitted
•Introducing of chitin nanofibrils results in decrease in sorption capacity of chitosan-chitin composite films.•Chitosan-chitin composite films are characterized by denser package of macromolecules.•Chitosan macromolecules form ordered structures on the surface of chitin nanofibrils.
Background
Cognitive impairment is an irreversible, aging-associated condition that robs people of their independence. The purpose of this study was to investigate possible causes of this condition ...and propose preventive options.
Methods
We assessed cognitive status in long-living adults aged 90+ (
n
= 2,559) and performed a genome wide association study using two sets of variables: Mini-Mental State Examination scores as a continuous variable (linear regression) and cognitive status as a binary variable (> 24, no cognitive impairment; <10, impairment) (logistic regression).
Results
Both variations yielded the same polymorphisms, including a well-known marker of dementia, rs429358in the APOE gene. Molecular dynamics simulations showed that this polymorphism leads to changes in the structure of alpha helices and the mobility of the lipid-binding domain in the APOE protein.
Conclusion
These changes, along with higher LDL and total cholesterol levels, could be the mechanism underlying the development of cognitive impairment in older adults. However, this polymorphism is not the only determining factor in cognitive impairment. The polygenic risk score model included 45 polymorphisms (ROC AUC 69%), further confirming the multifactorial nature of this condition. Our findings, particularly the results of PRS modeling, could contribute to the development of early detection strategies for predisposition to cognitive impairment in older adults.
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