Crystal structure of solid Oxygen at high pressure and low temperature

Results of X-ray diffraction experiments on solid oxygen at low temperature and at pressures up to 10 GPa are presented.A careful sample preparation and annealing around 240 K allowed to obtain very good diffraction patterns in the orthorhombic delta-phase. This phase is stable at low temperature, in contrast to some recent data [Y. Akahama et al., Phys. Rev. B64, 054105 (2001)], and transforms with decreasing pressure into a monoclinic phase, which is identified as the low pressure alpha-phase. The discontinuous change of the lattice parameters, and the observed metastability of the alpha-phase increasing pressure suggest that the transition is of the first order.Comment: 4 pages with three figure

Hydrogen atom in a spherical well: linear approximation

We discuss the boundary effects on a quantum system by examining the problem of a hydrogen atom in a spherical well. By using an approximation method which is linear in energy we calculate the boundary corrections to the ground-state energy and wave function. We obtain the asymptotic dependence of the ground-state energy on the radius of the well.Comment: Revised version to appear in European Journal of Physic

First principles study of strain/electronic interplay in ZnO; Stress and temperature dependence of the piezoelectric constants

We present a first-principles study of the relationship between stress, temperature and electronic properties in piezoelectric ZnO. Our method is a plane wave pseudopotential implementation of density functional theory and density functional linear response within the local density approximation. We observe marked changes in the piezoelectric and dielectric constants when the material is distorted. This stress dependence is the result of strong, bond length dependent, hybridization between the O $2p$ and Zn $3d$ electrons. Our results indicate that fine tuning of the piezoelectric properties for specific device applications can be achieved by control of the ZnO lattice constant, for example by epitaxial growth on an appropriate substrate.Comment: accepted for publication in Phys. Rev.

Vibrational excitons, resonant energy transfer, and local structure in liquid benzene

The presence of vibrational excitons in liquid benzene has been tested by the method of isotopic dilution. A C6H6/C6D6 concentration study on the infrared and Raman fundamental modes reveals that the umbrella (A2u) vibrational exciton in solid benzene retains its characteristics upon melting and at room temperature. The total liquid exciton bandwidth is about 40 cm−1, practically the same as in the solid. This indicates an instantaneous local liquid structure similar to that of the solid (the Ci crystal site symmetry is also nearly preserved), in general agreement with indications from other methods. The fastest nearest neighbor vibrational resonant transfer takes about 1 psec. The residual linewidth at isotopic dilution is 3–4 cm−1, which is due to inhomogeneous and/or homogeneous broadening. The respective overall reorientational and/or translational relaxation takes about 2 psec or longer. The exciton linewidth is proportional to the square root of the isotopic concentration except for a sudden break at some critical concentration.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70052/2/JCPSA6-66-11-5035-1.pd

Temperature dependence of surface reconstructions of Au on Pd(110)

Surface reconstructions of Au film on Pd(110) substrate are studied using a local Einstein approximation to quasiharmonic theory with the Sutton-Chen interatomic potential. Temperature dependent surface free energies for different coverages and surface structures are calculated. Experimentally observed transformations from $(1\times1)$ to $(1 \times 2)$ and $(1 \times 3)$ structures can be explained in the framework of this model. Also conditions for Stranski-Krastanov growth mode are found to comply with experiments. The domain of validity of the model neglecting mixing entropy is analyzed.Comment: 7 pages, REVTeX two-column format, 3 postscript figures available on request from [email protected] To appear in Phys. Rev. Letter

Erratum: Thermodynamics of solid and liquid EAM metals: A variational study [J. Chem. Phys. 94, 5090 (1991)]

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70785/2/JCPSA6-95-8-6197-1.pd

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

GAMBARAN PENGETAHUAN DAN TINDAKAN MASYARAKAT TENTANG PENGENDALIAN VEKTOR DEMAM BERDARAH DENGUE DI DESA TOUURE KABUPATEN MINAHASA TAHUN 2020

Demam Berdarah Dengue (DBD) adalah salah satu penyakit menular yang dapat dan sering menimbulkan wabah yang tidak jarang menyebabkan kematian. Berdasarkan data kasus DBD di tahun 2017 kasus DBD yang ada di wilayah kerja Puskesmas Tompaso berjumlah 9 kasus, pada tahun 2018 terdapat 8 kasus DBD di wilayah kerja Puskesmas Tompaso, sedangkan di tahun 2019 sebanyak 36 kasus yang berada di wilayah kerja Puskesmas Tompaso dan 18 kasus (50% dari total kasus) berasal dari Desa Touure Kecamatan Tompaso Kabupaten Minahasa. Masih tingginya angka kesakitan dan kematian DBD salah satu faktornya adalah kurangnya pengetahuan masyarakat tentand DBD dan tindakan masyarakat yang kurang baik dalam pengendalian vektor DBD berpotensi menjadi factor risiko penularan penyakit DBD. Tujuan penelitian adalah untuk mengetahui gambaran pengetahuan dan tindakan masyarakat tentang pengendalian vektor DBD di desa Touure kecamatan Tompaso tahun 2020. Jenis penelitian yang digunakan yaitu penelitian survei deskriptif. Sampel penelitian adalah masyarakat desa Touure kecamatan Tompaso sebanyak 70 masyarakat. Analisis data dilakukan secara deskriptif berdasarkan distribusi frekwensi. Instrumen yang digunakan dalam penelitian berupa kuesioner selain itu, penelitian ini menggunakan alat tulis menulis, komputer/ laptop dan kamera. Data yang diperoleh ditampilkan menggunakan tabel. Hasil penelitian menunjukkan bahwa pengetahuan responden paling banyak terdistribusi pada kategori tidak baik (78,6%), menunjukkan bahwa tindakan responden paling banyak terdistribusi pada kategori tidak baik (70%).         Kata Kunci :Demam Berdarah Dengue, Pengetahuan masyarakat, Tindakan masyarakat ABSTRACTDengue Hemorrhagic Fever (DHF) is a contagious disease that can and often causes epidemics that often cause death. Based on data on dengue cases in 2017 there were 9 cases of dengue fever in the Tompaso Puskesmas work area, in 2018 there were 8 cases of dengue in the Tompaso Puskesmas work area, while in 2019 there were 36 cases in the Tompaso Puskesmas work area and 18 cases (50% of the total cases) came from Touure Village, Tompaso District, Minahasa Regency. The high rate of DHF morbidity and mortality is one of the factors is the lack of public knowledge about DHF and poor community action in controlling the DHF vector which is a risk factor for DHF transmission. The research objective was to describe the knowledge and actions of the community about dengue fever in the village of Touure, Tompaso District in 2020. The type of research used was descriptive survey research. The research sample was 70 people in Touure village, Tompaso district. Data analysis was carried out descriptively based on frequency distribution. The instrument used in the research was a questionnaire in addition to that, research using written stationery, computers / laptops and cameras. Data that can be used using tables. The results showed that the respondents' knowledge was mostly distributed in the bad category (78.6%), indicating that the respondent's actions were mostly distributed in the bad category (70%). Keywords : Dengue Hemorrhagic Fever, Community Knowledge, Community Actio

A fully coupled 2D model of equiaxed eutectic solidification

We propose a model of equiaxed eutectic solidification that couples the macroscopic level of heat diffusion with the microscopic level of nucleation and growth of the eutectic grains. The heat equation with the source term corresponding to the latent heat release due to solidification is calculated numerically by means of an implicit finite difference method. In the time stepping scheme, the evolution of solid fraction is deduced from a stochastic model of nucleation and growth which uses the local temperature (interpolated from the FDM mesh) to determine the local grain density and the local growth rate. The solid-liquid interface of each grain is tracked by using a subdivision of each grain perimeter in a large number of sectors. The state of each sector (i.e. whether it is still in contact with the liquid or already captured by an other grain) and the increase of radius of each grain during one time step allows one to compute the increase of solid fraction. As for deterministic models, the results of the model are the evolution of temperature and of solid fraction at any point of the sample. Moreover the model provides a complete picture of the microstructure, thus not limiting the microstructural information to the average grain density but allowing one to compute any stereological value of interest. We apply the model to the solidification of gray cast iron