The boson peak and the first sharp diffraction peak in (As2S3)x(GeS2)1–x glasses

The parameters of the boson peak (BP) and the first sharp diffraction peak (FSDP) in (As2S3)x(GeS2)1x glasses measured using high-resolution Raman spectroscopy and high-energy synchrotron X-ray diffraction measurements are examined as a function of x. It has been found that there is no correlation between the positions of BP and FSDP. The BP position shows a nonlinear composition behavior with a maximum at about x = 0.4, whereas the FSDP position changes virtually linearly with x. The intensities of both BP and FSDP show nonlinear composition dependences with the slope changes at x = 0.4, although there is no direct proportionality. Analysis of the partial structure factors for the glasses with x = 0.2, 0.4 and 0.6 obtained in another study has shown that the cation-cation atomic pairs of Ge–Ge, Ge–As and As–As make the largest contribution to FSDP, where the Ge–Ge and Ge–As pairs are dominant

Efecto de Tres Dosis de N,P Y K En la Produccion de Maracuya Amarillo (Passiflora Edulis Sims F. Flavicarpa Deg).

El objetivo de este trabajo fue evaluar el efecto de tres dosis de nitrógeno, fósforo y potasio durante tres años de producción del maracuyá amarillo. El experimento fue conducido en el municipio de Guaíba, Rio Grande del Sur, Brasil, en un suelo de la unidad de mapeamiento São Jerônimo (Laterítico Bruno Rojizo distrófico). El rendimiento médio anual osciló entre 13,7 y 16,7 t/ha en función de los tratamientos. El análisis estadístico no acusó diferencia entre las producciones de los diferentes tratamientos. Los tenores de macronutrientes en las hojas, mostraron valores considerados normales para el cultivo.Made available in DSpace on 2011-04-09T12:18:31Z (GMT). No. of bitstreams: 1 pab03mar91.pdf: 241422 bytes, checksum: 479b54144c239e206e19c9b9d8a03273 (MD5) Previous issue date: 2001-09-17199

ЛАЗЕРНА УСТАНОВКА ДЛЯ ВИМІРЮВАННЯ ПАРАМЕТРІВ АКУСТИЧНОГО ПОЛЯ НА ПОВЕРХНІ АКУСТОПРОВОДІВ

For the first time the possibility of the development and fabrication of the design nondetuned functional optical scheme of the laser heterodyne installation intended for the investigation of the amplitude and phase fields of surface acoustic waves (SAW). The design is characterized not by separate optical elements but the presence of the two units — probe unit and photo-sensor with minimal number of optical elements. This enabled to reduce errors during amplitude and phase measurements, because the installation setup provides high sensitivity to the small amplitude of SAW and good reproducibility of the results. The optical scheme of the device is presented operation principle is described as well as the results of some investigations.Впервые показана возможность разработки и создания устойчивой относительно дестабилизирующих факторов функциональной оптической схемы лазерной гетеродинной установки для исследования амплитудных и фазовых полей поверхностных акустических волн (ПАВ). Установка выполнена не отдельными оптическими элементами а собрана из двух узлов — узла зонда и узла фотоприемника с минимальным количеством элементов. Это дало возможность уменьшить ошибку при проведении амплитудных и фазовых измерений, поскольку установка обеспечивает высокую чувствительность к малым амплитудам ПАВ и хорошую воспроизводимость результатов. Приводится оптическая схема, изложен принцип действия установки, представлены результаты некоторых исследований.Вперше показана можливість розробки та створення стійкої відносно дії дестаб ілізуючих факторів функціональної оптичної схеми лазерної гетеродинної установки, призначеної для дослідження амплітудних і фазових полів поверхневих акустичних хвиль (ПАХ). Вона виконана не окремими оптичними елементами, а зібрана з двох узлів — вузол зонда і вузол фотоприймача з мінімальним числом оптичних елементів. Це дало змогу зменшити похибку при проведенні амплітудних та фазових вимірів, оскільки установка забезпечу є високу чутливість до малих амлітуд ПАХ і хорошу відтворюванність результатів. Наводиться оптична схема, викладено принцип дії установки, надаються результати деяких досліджень

Structural order in (As2_{2}S3_{3})x(GeS2_{2})1−x_{1-x} glasses

Structural order in the chalcogenide glasses of (As$_2$S$_3$)$_x$(GeS$_2$)$_{1−x}$ (x = 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0) system is examined in terms of the parameters of local atomic structure as a function of composition x, obtained using high-resolution Raman spectroscopy, high-energy synchrotron X-ray diffraction, extended X-ray absorption fine structure spectroscopy and reverse Monte-Carlo modeling of diffraction data. As a result of the research carried out it is revealed that the structural order of As-rich (x > 0.4) and Ge-rich (x < 0.4) glasses is organized by the main As−S and Ge−S structural motifs based on pyramidal AsS$_3$ and tetrahedral GeS$_4$ units linked by =As−S−As= and triple bondGe−S−Getriple bond structural configurations, respectively; while for the intermediate compound with x = 0.4 the structural network seems to be better homogeneous on the nanoscale due to appearance of triple bondGe−S−As= mixed structural configurations resulting in misbalance between corner-shared and edge-shared tetrahedral units in comparison with their predicted ratio for binary GeS$_2$ glass and the structure of this alloy is similar to the structure of the stoichiometric glass Ge$_{18.2}$As$_{18.2}$S$_{63.6}$ (i.e., x = 0.455) consisting of a coner-shared network of homogeneously mixed GeS$_4$ tetrahedra and AsS$_3$ pyramids. Based on the structural studies, it is also established that the balance between corner-shared and edge-shared GeS$_4$ tetrahedra in the glass backbone of the investigated GeS$_2$-based glasses seems to be responsible for the interconnectivity between two speculative Raman modes at 370 and 430 cm$^{−1}$. Compositional changes in studied glasses result in the evolution of the observed Raman bands. Such dependences of characteristic constituent Raman bands’ intensities showed that (As$_2$S$_3$)$_x$(GeS$_2$)$_{1−x}$ samples contain different nanophases whose concentration is changing along chosen compositional cross-section

Microstructural study of phase separation in (GeS3)100-xAgx and (GeS2)100-xAgx chalcogenide glasses

Microstructure of (GeS$_3$)$_{100-x}$Agx (x = 0, 5, 10, 15, 20, 25) and (GeS$_2$)$_{100-x}$Agx (x = 0, 5, 10, 15, 20) has been studied by scanning electron microscopy. It is found that the glasses of both systems are phase separated: (GeS$_3$)$_{100-x}$ for 5 ≤ x ≤ 20 at.% and (GeS$_2$)$_{100-x}$Agx for 10 ≤ x ≤ 15 at.%. Morphology of coexisting phases is essentially dependent on the glass composition. The phase-separation is very pronounced in (GeS$_3$)$_{100-x}$Agx glasses and is diminished in (GeS$_2$)$_{100-x}$Agx as indicated by the size and spatial distribution of majority and minority phases