Шляхи посилення захисних властивостей і стійкості лісів Скибових Горган

In the complex of polyfunctional role of the Carpathian mountain forests the prominent place belongs to their stability and protective properties. In particular, this applies to the Gorgany landscape with fairly complex forest-related and geomorphological natural conditions that contribute to the most serious development of the Carpathian region for harmful natural phenomena. Distribution of forests and natural phenomena in the Gorgany region is characterized by high-altitude changes. The share of spruce stands is quite rapidly increasing from 600 m above the sea level, becoming continuously spreading with a height of 1150 m. At the same time, in this direction, the proportion of fir and beech plantings decreases, which respectively disappear at gipsometric levels of 1000 and 1200 m. The greatest number of harmful processes is inherent in anthropogenically altered landscapes of low mountains with beech and fir forests, somewhat smaller – for the buckwheat, fir-spruce and spruce forests. Distribution of forests and natural phenomena in Gorgany region is characterized by high-altitude changes. The forest cover of the catchments here grows from 45–50 % at the foot of the mountains to 90–95 % in the upper spruce belt. The share of spruce stands is quite rapidly increasing from 600 m above the sea level, becoming continuously spreading with a height of 1150 m. At the same time, in this direction, the proportion of fir and beech plantings decreases, which respectively disappear at gipsometric levels of 1000 and 1200 m. The greatest number of harmful processes is inherent in anthropogenically altered landscapes of low mountains with beech and fir forests, somewhat smaller – for the buckwheat, fir-spruce and spruce forests. The main ways of preventing harmful events are the optimization of forests and the creation of protective stands in the lowlands, the restoration of indigenous forest plantations in all zones, the ecologization of the main felling sites and their technologies. The auxiliary measures include the treatment of watercourses from deforestation, recultivation of drafts and water retention of surface drainage on logs, raising the upper boundary of the forest and preventing snow avalanches, as well as afforestation of rocky debris and sedentary areas. For all six basins of the main Gorgany rivers, the planning and implementation of inter-sectoral environmental measures is very topical.Охарактеризовано природні умови, лісистість водозборів і породний склад лісів гірського ландшафту Скибових Горган в Українських Карпатах. Наведено емпіричні залежності лісових площ, відсотка лісистості та часток ялинових, ялицевих і букових насаджень від гіпсометричних рівнів гірських водозборів. Висвітлено динаміку лісового покриву за останні 40 років. Проаналізовано поширення шкідливих стихійних явищ – снігових лавин, паводкового стоку, ерозійно-селевих, осипних і зсувних процесів, а також вітровалів і сніголомів лісу та всихання ялинників для різних висотних поясів і смуг рослинності –ялинових, буково-ялицево-ялинових і буково-ялицевих лісів. Рекомендовано систему лісівничо-технічних, лісівничо-фітомеліоративних, лісогосподарських і комплексних природоохоронних заходів щодо запобігання шкідливим процесам для різних висотних рівнів гірських схилів. Запропоновано шляхи застосування основних і допоміжних заходів протидії стихії. Відзначено актуальність оптимізації лісистості водозборів, відтворення корінних лісостанів, природоощадного вдосконалення рубок головного користування і ведення лісового господарства на водозбірному принципі. Наведено сучасні й оптимальні для водоохоронно-захисної ролі та стійкості лісів показники лісистості водозборів і частки ялинових насаджень у межах висотних смуг і поясів рослинності. Висвітлено основні напрями міжгалузевої природоохоронної діяльності на головних річкових басейнах Горган

Raman spectrum and lattice parameters of MgB2 as a function of pressure

We report Raman spectra and synchrotron x-ray diffraction measurements of lattice parameters of polycrystalline MgB2 under hydrostatic pressure conditions up to 15 GPa. An anomalously broadened Raman band at 620 cm-1 is observed that exhibits a large linear pressure shift of its frequency. The large mode damping and Gruneisen parameter indicate a highly anharmonic nature of the mode, broadly consistent with theoretical predictions for the E2g in-plane boron stretching mode. The results obtained may provide additional constraints on the electron-phonon coupling in the system.Comment: 3 pages, 3 figure

Consistent Anisotropic Repulsions for Simple Molecules

We extract atom-atom potentials from the effective spherical potentials that suc cessfully model Hugoniot experiments on molecular fluids, e.g., $O_2$ and $N_2$. In the case of $O_2$ the resulting potentials compare very well with the atom-atom potentials used in studies of solid-state propertie s, while for $N_2$ they are considerably softer at short distances. Ground state (T=0K) and room temperatu re calculations performed with the new $N-N$ potential resolve the previous discrepancy between experimental and theoretical results.Comment: RevTeX, 5 figure

Simple Metals at High Pressure

In this lecture we review high-pressure phase transition sequences exhibited by simple elements, looking at the examples of the main group I, II, IV, V, and VI elements. General trends are established by analyzing the changes in coordination number on compression. Experimentally found phase transitions and crystal structures are discussed with a brief description of the present theoretical picture.Comment: 22 pages, 4 figures, lecture notes for the lecture given at the Erice course on High-Pressure Crystallography in June 2009, Sicily, Ital

Mechanical Deformation Induced in Si and GaN Under Berkovich Nanoindentation

Details of Berkovich nanoindentation-induced mechanical deformation mechanisms of single-crystal Si(100) and the metal-organic chemical-vapor deposition (MOCVD) derived GaN thin films have been systematic investigated by means of micro-Raman spectroscopy and cross-sectional transmission electron microscopy (XTEM) techniques. The XTEM samples were prepared by using focused ion beam (FIB) milling to accurately position the cross-section of the nanoindented area. The behaviors of the discontinuities displayed in the loading and unloading segments of the load-displacement curves of Si and GaN thin films performed with a Berkovich diamond indenter tip were explained by the observed microstructure features obtained from XTEM analyses. According to the observations of micro-Raman and XTEM, the nanoindentation-induced mechanical deformation is due primarily to the generation and propagation of dislocations gliding along the pyramidal and basal planes specific to the hexagonal structure of GaN thin films rather than by indentation-induced phase transformations displayed in Si

Isostructural second-order phase transition of b-Bi2O3 at high pressures: an experimental and theoretical study

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp507826jWe report a joint experimental and theoretical study of the structural and vibrational properties of synthetic sphaerobismoite (beta-Bi2O3) at high pressures in which room-temperature angle-dispersive X-ray diffraction (XRD) and Raman scattering measurements have been complemented with ab initio total energy and lattice dynamics calculations. Striking changes in Raman spectra were observed around 2 GPa, whereas X-ray diffraction measurements evidence no change in the tetragonal symmetry of the compound up to 20 GPa; however, a significant change exists in the compressibility when increasing pressure above 2 GPa. These features have been understood by means of theoretical calculations, which show that beta-Bi2O3 undergoes a pressure-induced isostructural phase transition near 2 GPa. In the new isostructural beta' phase, the Bi3+ and O2- environments become more regular than those in the original beta phase because of the strong decrease in the activity of the lone electron pair of Bi above 2 GPa. Raman measurements and theoretical calculations provide evidence of the second-order nature of the pressure-induced isostructural transition. Above 20 GPa, XRD measurements suggest a partial amorphization of the sample despite Raman measurements still show weak peaks, probably related to a new unknown phase which remains up to 27 GPa. On pressure release, XRD patterns and Raman spectra below 2 GPa correspond to elemental Bi-I, thus evidencing a pressure-induced decomposition of the sample during downstroke.Financial support from the Spanish Consolider Ingenio 2010 Program (MALTA Project CSD2007-00045) is acknowledged. This work was also supported by Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under Project 201050/2012-9, Spanish MICINN under Projects MAT2010-21270-004-01/03/04 and MAT2013-46649-C4-2/3/4-P, Spanish MINECO under Project CTQ2012-36253-C03-02, and from Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia under Projects UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11. Supercomputer time has been provided by the Red Espanola de Supercomputacion (RES) and the MALTA cluster. JAS. acknowledges Juan de la Cierva fellowship program for financial support.Pereira, ALJ.; Sans Tresserras, JÁ.; Vilaplana Cerda, RI.; Gomis, O.; Manjón Herrera, FJ.; Rodriguez-Hernandez, P.; Muñoz, A.... (2014). Isostructural second-order phase transition of b-Bi2O3 at high pressures: an experimental and theoretical study. Journal of Physical Chemistry C. 118(40):23189-23201. https://doi.org/10.1021/jp507826jS23189232011184