Anisotropy of relaxation time for ∆1 –minimum of conduction band in n-Ge

Обчислено параметр анізотропії часів релаксації для L 1 та ∆ 1-мінімумів зони провідності кристалів n-Ge із різною концентрацією домішки. Показано, що при одновісному деформуванні кристалів n-Ge (Х>2,4 ГПа) уздов ж кристалографічного напряму, унаслідок інверсії типу абсолютного мінімуму, зазнає і кількісних, і якісних змін параметр анізотропії часів релаксації. ; The anisotropy parameter of relaxation time for L 1 and ∆ 1-minimums of the conduction band in n-Ge with different impurity concentrations was calculated. Theory shows that quantitatively and qualitatively changes the anisotropy parameter of relaxation times as a result of the absolute minimum type inversion of the conduction band, about uniaxial stress (X>2,4 GPa) along the crystallographic direction

Mechanisms of electron scattering in uniaxially deformed n\textit{n}-Ge⟨Sb, Au⟩\text{Ge} \langle \text{Sb, Au}\rangle single crystals

Temperature dependencies for concentration and the Hall mobility of electrons for the $\textit{n}$-$\text{Ge} \langle \text{Sb}\rangle$ and \linebreak $\textit{n}$-$\text{Ge} \langle \text{Sb, Au}\rangle$ single crystals uniaxially deformed along the crystallographic directions [100] and [111] are obtained on the basis of piezo-Hall effect measurements. A deformation-induced increase of the Hall mobility of electrons for $\textit{n}$-$\text{Ge} \langle \text{Sb, Au}\rangle$ single crystals at the uniaxial pressure along the crystallographic direction [100] has been revealed. A comparison of the obtained experimental results with the corresponding theoretical calculations of temperature dependencies of the Hall mobility showed that the obtained effect occurs at the expense of the reduction probability of electron scattering on the fluctuational potential. Its amplitude depends on the tempe\-rature and on the value of the uniaxial pressure. It has also been shown that an increase of the Hall mobility for the $\textit{n}$-$\text{Ge} \langle \text{Sb, Au}\rangle$ single crystals uniaxially deformed along the crystallographic direction [111] with an increasing temperature turns out to be insignificant and is observed only for the uniaxial pressures $P<0.28$ GPa. A decrease of the Hall mobility of electrons at the expense of the deformational redistribution of electrons among the valleys of the germanium conduction band with different mobility should be taken into account in the present case. The Hall mobility magnitude for the uniaxially deformed $\textit{n}$-$\text{Ge} \langle \text{Sb}\rangle$ single crystals is determined only by the mechanisms of phonon scattering and we have not observed the effect of the growth of the Hall mobility with an increase of temperature or the magnitude of uniaxial pressure.Comment: 10 pages, 7 figure

Methodology of measurement of electrical properties of n-ge single crystals under high uniaxial pressure

На основі теорії опору матеріалів для різних кристалографічних напрямків розраховано залежність критичної механічної напруги від площі поперечного перерізу зразків n-Ge, що використовуються при дослідженнях деформаційних ефектів при високих одновісних тисках. Визначено оптимальні параметри форми даних зразків. Оцінено вплив геометричних розмірів зразків на точність вимірювання питомої електропровідності монокристалів n-Ge для монокристалів із низьким, середнім та високим рівнем легування.Based on the theory of strength of materials dependence of the critical mechanical stress on the cross-section and shape of samples n-Ge, which used in research of deformation effects under high uniaxial pressures are obtained. The analytical expressions for the first critical mechanical stress for n-Ge samples for measurement of piezoresistance, using the solution of the problem for the Euler for elastically deformed rod, are obtained. The critical stress for the case of rigidly fixed ends of rod is calculated. The dependences of the critical stress on the cross-section of sample for rectangular parallelepiped form and dumbbell form of sample are obtained. We considered the cases of uniaxial pressure in crystallographic directions [100], [110] and [111]. Take into account dependences of critical mechanical stress on the cross-section of samples for different shapes and parameters measurement setup for study deformation effects the optimal size and shape for these samples are determinate. To achieve maximum stability samples, the minimal permissible length of the sample and the maximum value of the cross-section are defined. The minimal length of the investigated samples was determined because of specificity of samples preparation and parameters of measurement setup. So for dumbbell form of sample allowable length is equal to 3 mm, and rectangular parallelepiped form - 4 mm. The maximum allowable dimensions of cross-sectional of the sample is dependent on the maximum pressure force that can develop measuring setup for get some pressure . In this case, defined dimensions of cross-section of samples to achieve a pressure P=2·109 Pa. The question of the influence of low-current electrodes on the measured value of conductivity in the case of a weak magnetic field are discussed. The effect of geometrical dimensions of samples for precision measurement of conductivity of single crystals of n-Ge with low, medium and high levels of doping are estimated

slq(2)sl_q(2) Realizations for Kepler and Oscillator Potentials and q-Canonical Transformations

The realizations of the Lie algebra corresponding to the dynamical symmetry group SO(2,1) of the Kepler and oscillator potentials are q-deformed. The q-canonical transformation connecting two realizations is given and a general definition for q-canonical transformation is deduced. q-Schr\"{o}dinger equation for a Kepler like potential is obtained from the q-oscillator Schr\"{o}dinger equation. Energy spectrum and the ground state wave function are calculated.Comment: 12 pages, Latex twice, (Comparison with the other approaches and some refs. added. The version which will appear in J. Phys. A

The global campaign to eliminate HBV and HCV infection: International Viral Hepatitis Elimination Meeting and core indicators for development towards the 2030 elimination goals

Hepatitis B virus (HBV) and hepatitis C virus (HCV) affect more than 320 million people worldwide, which is more than HIV, tuberculosis (TB) and malaria combined. Elimination of HBV and HCV will, therefore, produce substantial public health and economic benefits and, most importantly, the prevention of 1.2 million deaths per year. In 2016, member states of the World Health Assembly unanimously adopted a resolution declaring that viral hepatitis should be eliminated by 2030. Currently, few countries have elimination programmes in place and even though the tools to achieve elimination are available, the right resources, commitments and allocations are lacking. During the fifth International Viral Hepatitis Elimination Meeting (IVHEM), 7–8 December 2018, Amsterdam, the Netherlands, an expert panel of clinicians, virologists and public health specialists discussed the current status of viral hepatitis elimination programmes across multiple countries, challenges in achieving elimination and the core indicators for monitoring progress, approaches that have failed and successful elimination plans

Tree mode of death and mortality risk factors across Amazon forests

The&nbsp;carbon sink capacity of tropical forests&nbsp;is substantially affected by tree mortality. However, the main drivers of tropical&nbsp;tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing &gt; 3800 species from 189 long-term&nbsp;RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single&nbsp;most important predictor of tree death in Amazonia, with faster-growing species being at&nbsp;higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region&nbsp;species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a&nbsp;holistic pan-Amazonian picture of tree death but large-scale&nbsp;evidence for the overarching importance of the growth–survival trade-off in driving tropical&nbsp;tree mortality

An integrative approach to discovering cryptic species within the Bemisia tabaci whitefly species complex

Bemisia tabaci is a cryptic whitefly-species complex that includes some of the most damaging pests and plant-virus vectors of a diverse range of food and fibre crops worldwide. We combine experimental evidence of: (i) differences in reproductive compatibility, (ii) hybrid verification using a specific nuclear DNA marker and hybrid fertility confirmation and (iii) high-throughput sequencing-derived mitogenomes, to show that the “Mediterranean” (MED) B. tabaci comprises at least two distinct biological species; the globally invasive MED from the Mediterranean Basin and the “African silver-leafing” (ASL) from sub-Saharan Africa, which has no associated invasion records. We demonstrate that, contrary to its common name, the “ASL” does not induce squash silver-leafing symptoms and show that species delimitation based on the widely applied 3.5% partial mtCOI gene sequence divergence threshold produces discordant results, depending on the mtCOI region selected. Of the 292 published mtCOI sequences from MED/ASL groups, 158 (54%) are low quality and/or potential pseudogenes. We demonstrate fundamental deficiencies in delimiting cryptic B. tabaci species, based solely on partial sequences of a mitochondrial barcoding gene. We advocate an integrative approach to reveal the true species richness within cryptic species complexes, which is integral to the deployment of effective pest and disease management strategies

Carbon uptake by mature Amazon forests has mitigated Amazon nations' carbon emissions

Background: Several independent lines of evidence suggest that Amazon forests have provided a significant carbon sink service, and also that the Amazon carbon sink in intact, mature forests may now be threatened as a result of different processes. There has however been no work done to quantify non-land-use-change forest carbon fluxes on a national basis within Amazonia, or to place these national fluxes and their possible changes in the context of the major anthropogenic carbon fluxes in the region. Here we present a first attempt to interpret results from groundbased monitoring of mature forest carbon fluxes in a biogeographically, politically, and temporally differentiated way. Specifically, using results from a large long-term network of forest plots, we estimate the Amazon biomass carbon balance over the last three decades for the different regions and nine nations of Amazonia, and evaluate the magnitude and trajectory of these differentiated balances in relation to major national anthropogenic carbon emissions. Results: The sink of carbon into mature forests has been remarkably geographically ubiquitous across Amazonia, being substantial and persistent in each of the five biogeographic regions within Amazonia. Between 1980 and 2010, it has more than mitigated the fossil fuel emissions of every single national economy, except that of Venezuela. For most nations (Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname) the sink has probably additionally mitigated all anthropogenic carbon emissions due to Amazon deforestation and other land use change. While the sink has weakened in some regions since 2000, our analysis suggests that Amazon nations which are able to conserve large areas of natural and semi-natural landscape still contribute globally-significant carbon sequestration. Conclusions: Mature forests across all of Amazonia have contributed significantly to mitigating climate change for decades. Yet Amazon nations have not directly benefited from providing this global scale ecosystem service. We suggest that better monitoring and reporting of the carbon fluxes within mature forests, and understanding the drivers of changes in their balance, must become national, as well as international, priorities