Coexistence of pressure-induced structural phases in bulk black phosphorus: a combined x-ray diffraction and Raman study up to 18 GPa

We report a study of the structural phase transitions induced by pressure in bulk black phosphorus by using both synchrotron x-ray diffraction for pressures up to 12.2 GPa and Raman spectroscopy up to 18.2 GPa. Very recently black phosphorus attracted large attention because of the unique properties of fewlayers samples (phosphorene), but some basic questions are still open in the case of the bulk system. As concerning the presence of a Raman spectrum above 10 GPa, which should not be observed in an elemental simple cubic system, we propose a new explanation by attributing a key role to the non-hydrostatic conditions occurring in Raman experiments. Finally, a combined analysis of Raman and XRD data allowed us to obtain quantitative information on presence and extent of coexistences between different structural phases from ~5 up to ~15 GPa. This information can have an important role in theoretical studies on pressure-induced structural and electronic phase transitions in black phosphorus

Aplikasi Sistem Pakar Mendiagnosa Gizi Buruk pada Anak dengan Metode Dempster-Shafer Berbasis Web

Sistem pakar adalah sistem berbasis komputer yang menggunakan pengetahuan, fakta, dan teknik penalaran dalam memecahkan masalah yang biasanya hanya dapat dipecahkan oleh pakar bidang tertentu. Puskesmas Ome Kota Tidore Kepulauan Selama ini, untuk mendata gizi buruk pada anak-anak melakukannya secara manual. Sehingga membutuhkan waktu yang lama. Peniltian ini bertujuan merancang aplikasi sistem pakar untuk menentukan status gizi buruk pada anak dengan menggunakan metode dempster-shafer, dimana ada beberapa jenis gizi buruk yang biasa dialami oleh anak, karena itu dalam kasus ini ada 3 jenis gizi buruk yang dibahas, yaitu marasmus (kekurangan energi), khowarsiorkor (kekurangan protein), dan marasmus-khowarsiorkor (kekurangan protein dan energi), yang digunakan untuk mengkombinasikan potongan informasi yang terpisah (bukti) untuk mengkalkulasi kemungkinan dari suatu peristiwa. Dengan adanya penelitian ini diharapkan dapat memudahkan pihak puskesmas dalam mengelola dan melacak gizi buruk pada anak-anak di Puskesmas Ome Kota Tidore Kepulauan

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste

In this study the first in situ high-pressure single-crystal X-ray diffraction experiments at Xpress, the Indo-Italian beamline of the Elettra synchrotron, Trieste (Italy), are reported. A description of the beamline experimental setup and of the procedures for single-crystal centring, data collection and processing, using diamond anvil cells, are provided. High-pressure experiments on a synthetic crystal of clinoenstatite (MgSiO3), CaCO3 polymorphs and a natural sample of leucophoenicite [Mn7Si3O12(OH)2] validated the suitability of the beamline experimental setup to: (i) locate and characterize pressure-induced phase transitions; (ii) solve ab initio the crystal structure of high-pressure polymorphs; (iii) perform fine structural analyses at the atomic scale as a function of pressure; (iv) disclose complex symmetry and structural features undetected using conventional X-ray sources

Fatigue in laser shock peened open-hole thin aluminium specimens

An experimental study was performed in order to determine the influence of the sequence of operations on the effectiveness of Laser Shock Peening (LSP) treatment in increasing the fatigue performances of open-hole aluminium specimens. Residual stress measurements, fractographic analysis and FEM analysis were performed, indicating the presence of compressive residual stresses on the surface of the treated specimens and tensile residual stresses in the mid-section along the thickness of the specimens. Negative effects on fatigue lives were encountered on the specimens with the hole already present, while positive effect were observed in specimens in which the hole was drilled after LSP treatment. These results indicate that LSP can be a good solution for “in production” application, in which open holes are to be drilled after the LSP treatment. The application in which LSP is used “in service” on structures with pre-existing cut-outs, has proven to be impracticable in the investigated configuration

High-temperature and high-pressure behavior of carbonates in the ternary diagram CaCO3-MgCO3-FeCO3

We report the thermal expansion and the compressibility of carbonates in the ternary compositional diagram CaCO3-MgCO3-FeCO3, determined by in situ X-ray powder and single-crystal diffraction. High-temperature experiments were performed by high-resolution X-ray synchrotron powder diffraction from ambient to decarbonation temperatures (25-850 \ub0C). Single-crystal synchrotron X ray diffraction experiments were performed in a variable pressure range (0-100 GPa), depending on the stability field of the rhombohedral structure at ambient temperature, which is a function of the carbonate composition. The thermal expansion increases from calcite, CaCO3, \u3b10 = 4.10(7) 710-5 K-1, to magnesite, MgCO3, \u3b10 = 7.04(2) 710-5 K-1. In the magnesite-siderite (FeCO3) join, the thermal expansion decreases as iron content increases, with an experimental value of \u3b10 = 6.44(4) 710-5 K-1 for siderite. The compressibility in the ternary join is higher (i.e., lower bulk modulus) in calcite and Mg-calcite [K0 = 77(3) GPa for Ca0.91Mg0.06Fe0.03(CO3)] than in magnesite, K0 = 113(1) GPa, and siderite, K0 = 125(1) GPa. The analysis of thermal expansion and compressibility variation in calcite-magnesite and calcite-iron-magnesite joins clearly shows that the structural changes associated to the order-disorder transitions [i.e., R3c calcite-type structure vs. R3 CaMg(CO3)2 dolomite-type structure] do not affect significantly the thermal expansion and compressibility of carbonate. On the contrary, the chemical compositions of carbonates play a major role on their thermo-elastic properties. Finally, we use our P-V-T equation of state data to calculate the unit-cell volume of a natural ternary carbonate, and we compare the calculated volumes to experimental observations, measured in situ at elevated pressure and temperatures, using a multi-anvil device. The experimental and calculated data are in good agreement demonstrating that the equation of state here reported can describe the volume behavior with the accuracy needed, for example, for a direct chemical estimation of carbonates based on experimental unit-cell volume data of carbonates at high pressures and temperatures

The high pressure diffraction beamline "XPRESS" at Elettra

The opening of the Xpress beamline [1] in 2016 has provided the high-pressure diffraction user community of the Elettra synchrotron facility a dedicated experimental set up at their disposal. This new beamline is part of a scientific partnership between India and Italy under a project administered through the Indian Institute of Sciences (IISc) Bangalore, for the development of a macromolecular and a high-pressure x-ray diffraction facilities, respectively XRD2 [2] and Xpress. A multipole superconducting wiggler (SCW) is the source of these two beamlines. A liquid nitrogen cooled silicon single crystal (cut along the (111) direction) hosted in the splitter chamber in the Front-End section intercepts the beam from the source (SCW) and directs it to the focusing mirror of the Xpress at a fixed energy of 25 keV. At this energy, the SCW provides a factor of 14 higher photon flux compared to the permanent magnet wiggler of XRD1, the existing diffraction beamline. The beam is focused using a toroidal mirror of 1.4 m long and 2.9 mrad grazing angle with a Pt coating to achieve 80% reflectivity at 25 keV. The focused beam from the mirror is further optimized by collimators (presently 80 micron diameter) to have intense and well defined monochromatic beam required for the high-pressure x-ray diffraction experiments. On-line pressure monitoring is achieved through a ruby fluorescence microscope connected side-by-side to the final beam collimator stage. The present experimental stage is equipped to host room temperature - high-pressure powder diffraction measurements using various kinds of Diamond Anvil Cells (DAC) in the pressure range 0-50 GPa. An image plate MAR345, with a controllable linear movement along the beam direction at two fixed vertical positions, is available for recording the diffraction pattern from both powder and single crystal samples. A Gas loading system is under commissioning, while variable temperature (300 \u2013 100 K) capillary powder diffraction stage and limited range low-temperature high-pressure measurements using a specialized DAC and liquid nitrogen cryocooler system are also planned to be added in the near future. [1] http://www.elettra.eu/elettra-beamlines/xpress.html [2] http://www.elettra.eu/elettra-beamlines/xrd2.htm