Parallel computing and the generation of basic plasma data

Comprehensive simulations of the processing plasmas used in semiconductor fabrication will depend on the availability of basic data for many microscopic processes that occur in the plasma and at the surface. Cross sections for electron collisions, a principal mechanism for producing reactive species in these plasmas, are among the most important such data; however, electron-collision cross sections are difficult to measure, and the available data are, at best, sketchy for the polyatomic feed gases of interest. While computational approaches to obtaining such data are thus potentially of significant value, studies of electron collisions with polyatomic gases at relevant energies are numerically intensive. In this article, we report on the progress we have made in exploiting large-scale distributed-memory parallel computers, consisting of hundreds of interconnected microprocessors, to generate electron-collision cross sections for gases of interest in plasma simulations

Collisions of low-energy electrons with CO_2

We report cross sections for collisions of low-energy electrons with carbon dioxide obtained by the Schwinger multichannel variational method.Elastic cross sections are obtained in the static-exchange-plus-polarization approximation. We pay particular attention to the position of the ^2Π_u resonance and to the strong enhancement in the integral cross section near zero energy, both prominent features whose accurate treatment requires an accounting for polarization effects. To include such effects in the resonant symmetry, we use an objective and physically motivated criterion to construct a set of configurations that accurately accounts for polarization while avoiding overcorrelation. In addition, we study the origin of the nonisotropic behavior of the elastic differential cross section at very low energies and conclude that it is caused by significant contributions from vibrationally excited CO_2. Cross sections from threshold to 50 eV for excitation of the ^3Σ^+_u, ^1Δ_u, ^3Δ_u, ^3Σ^−_u, and ^1Σ^−_u states that arise from the (^1π_g → ^2π_u) transition are presented for the first time

Single and fractionated ionizing radiation induce alterations in endothelial connexin expression and channel function

Radiotherapy is an effective treatment for most tumor types. However, emerging evidence indicates an increased risk for atherosclerosis after ionizing radiation exposure, initiated by endothelial cell dysfunction. Interestingly, endothelial cells express connexin (Cx) proteins that are reported to exert proatherogenic as well as atheroprotective effects. Furthermore, Cxs form channels, gap junctions and hemichannels, that are involved in bystander signaling that leads to indirect radiation effects in non-exposed cells. We here aimed to investigate the consequences of endothelial cell irradiation on Cx expression and channel function. Telomerase immortalized human Coronary Artery/Microvascular Endothelial cells were exposed to single and fractionated X-rays. Several biological endpoints were investigated at different time points after exposure: Cx gene and protein expression, gap junctional dye coupling and hemichannel function. We demonstrate that single and fractionated irradiation induce upregulation of proatherogenic Cx43 and downregulation of atheroprotective Cx40 gene and protein levels in a dose-dependent manner. Single and fractionated irradiation furthermore increased gap junctional communication and induced hemichannel opening. Our findings indicate alterations in Cx expression that are typically observed in endothelial cells covering atherosclerotic plaques. The observed radiation-induced increase in Cx channel function may promote bystander signaling thereby exacerbating endothelial cell damage and atherogenesis

Propose Strategies to Enhance the Biodiversity Status and Traditional Knowledge Systems Relevant for the Conservation of Pan Troglodytes Ellioti in the Kimbi-Fungom National Park and Kom-Wum Forest Reserve

This study entitle propose strategies to enhance the biodiversity status and traditional knowledge systems relevant for the conservation of Pan troglodytes ellioti was undertaken in the Kimbi-Fungom National Park (KWFR) and Kom-Wum Forest Reserve (KWFR) Northwest region of Cameroon. The main objective was to investigate sustainable tactics that will contribute to trim down pressure on Pan troglodytes ellioti and other flagship species around the study areas. Data collections were undertaken with the help of interviewed administered questionnaires, informal interview using interview guide, group discussion and direct observations activities. Following interviewees response, sixty eight (68%) of the respondents were confident that they could take up effective management of the K-FNP and K-WFR. Equally, 92% of respondents agreed to the fact that increasing population, poverty increment, insufficient modern health facilities, influx of new cultural activities due to loss of traditional taboos and totemic beliefs, remains greater threat to chimpanzees in the study areas. Most of the interviewees (74%) agreed that updating of knowledge on the abundance and distribution of chimpanzee, identifying location of all human activities especially huts, farms, shortcuts and illegal market in the park/reserve through regular patrols with eco-guards to reinforce order and ensure a better protection for chimpanzees is vital. Much more, 95% of respondent accepted the fact that old and new traditional knowledge of conservation such as taboos/law, totemic beliefs, sacred forests, royal species, automatic spiritual sanction, harvesting seasons should be revived and encourage through traditional institutions/council to better protect chimpanzees. Furthermore, 85% of interviewees accepted the suggestion that to get rid of poor traditional practices that uses chimpanzee's body parts/meat for medicine and rituals, can be replace with goats, sheep, pig, fouls body parts/meat. To reduce over dependent and conflicts on chimpanzees products and other natural resources, 97% of the respondents were in favour that income generating micro-projects such as fish farming, animal rearing, and market gardening should be promoted. Providing jobs through ecotourism activities such as forest clearance and excursions, construction of adequate and equip infrastructures were highly welcome by 99% of interviewees. To attain all these, regular conservation educational programmes in schools, meeting places and in “ngumba” houses should be promoted to well sensitize population on chimpanzee's conservation

Status of large mammals: case study of gorilla (Gorilla gorilla diehi), chimpanzee (Pan troglodytes ellioti) and buffalo (Syncerus caffer), Menchum South, NW Cameroon

This study entitled status of large mammals: case study of gorilla, chimpanzee and buffalo, was carried out in the Black Bush Area of Waindow (BBAW), Menchum South, NW Cameroon from January-March, 2014. The general objective was to determine the status of large mammal's species and to investigate the presence of gorilla, chimpanzees and buffalo reported by the indigenous people in order to contribute to the conservation of these species in the region. The recce- survey method was used for species inventory whereby direct and indirect observations of bio-indicators of these species and human signs were recorded. From the result, the encounter rates of buffalo and chimpanzee were 0.35 and 0.26 signs per km respectively with no gorilla sign observed. Spatial distribution maps revealed great concentration of these species in the northern zone. Hunting recorded the highest encounter rate of 0.42 signs per km of anthropogenic activities. As such, one could deduce that the pressures exacerbated on these animals due to human activities and encroachment by Nigeria traders, and grazers placed the remaining species under intense threat of disappearing within the study areas. It is therefore necessary to intensify conservation efforts so as to urgently address these species concerns

Molecular dynamics simulations and photoluminescence measurements of annealed ZnO surfaces

The effect of thermal annealing on wurtzite ZnO, terminated by two surfaces, (0 0 0 $\bar 1$) (which is oxygen-terminated) and (0 0 0 1) (which is Zn-terminated), is investigated via molecular dynamics simulation using reactive force field (ReaxFF). As a result of annealing at a threshold temperature range of 700~K < T_{\mbox{\small t}} \leq 800~K, surface oxygen atoms begin to sublimate from the (0 0 0 $\bar 1$) surface, while no atom leaves the (0 0 0 1) surface. The ratio of oxygen leaving the surface increases with temperature $T$ (for T \geq T_{\mbox{\small t}}). The relative luminescence intensity of the secondary peak in the photoluminescence (PL) spectra, interpreted as a measurement of amount of vacancies on the sample surfaces, qualitatively agrees with the threshold behavior as found in the MD simulations. Our simulations have also revealed the formation of oxygen dimers on the surface and evolution of partial charge distribution during the annealing process. Our MD simulation based on the ReaxFF is consistent with experimental observations.Comment: 26 pages, 11 figures. Manuscript submitted to Physica

Status of Blue Duiker (Cephalophus monticola) and Bushbuck (Tragelaphus scriptus) in Kom -Wum Forest Reserve, North West Region, Cameroon

The study titled “Status of Blue duiker (Cephalophus monticola) and Bushbuck (Tragelaphus scriptus) in Kom-Wum Forest Reserve, North West Region-Cameroon, was realized from the 15th of January to March 31st, 2015. The general objective was to contribute to the conservation of Blue duiker and Bushbuck by establishing a baseline data in Kom-Wum Forest Reserve which will serve as guide for management decisions. The methodology used was “reconnaissance walk, questionnaires, semi structured interviews and focused group discussions. Results obtained indicated that twelve species of mammals were recorded through direct and indirect bio-indicators. The family of Cercopithecidae was the most represented (41.7%) (Putty nosed (Cercopithecus nictitans), Vervet (Cercopithecus aethiops), Patas (Erythrobus patas), Mona (Cercopithecus mona) monkeys and Olive Baboon (Papio Anubis). The results equally revealed that Chimpanzees (Pan troglodytes ellioti), Red duiker (Cephalophus dorsalis), Blue duiker and Bushbuck were the most abundant animals with encounter rates of 3.8, 2.91, 2.41 and 1.93signs per km respectively. The GIS distribution maps showed that Blue duikers and Bushbucks were more in the North East and South West potions of the reserve respectively. The mean encounter rate of anthropogenic activities (hunting, agriculture and logging) stood at 0.94 sign per kilometer. Hunting was most preponderant with an E.R of 1.41 sign per km (50%), followed by agriculture 1.0 sign per km (36%) and lastly logging 0.41 sign per km (14%). Encounter rates of anthropogenic activities plotted against those of mammals gave a coefficient of determination (R2) =0.058 hence, mammal distribution is only slightly affected by human activities. Up to 65% of the respondents expressed negative attitudes towards conservation of resources in the reserve for the fact that it is their natural heritage and they should not be restrained from exploiting them. A majority (80%) of the respondents however agreed that the reserve is owned and controlled by the government. Though plagued by human interference, the reserve still harbours some Bushbuck and Blue duiker. We therefore recommend that the council, government, NGOs and the local community to step up conservation efforts

Dynamical mean field theory of optical third harmonic generation

We formulate the third harmonic generation (THG) within the dynamical mean field theory (DMFT) approximation of the Hubbard model. In the limit of large dimensions, where DMFT becomes exact, the vertex corrections to current vertices are identically zero, and hence the calculation of the THG spectrum reduces to a time-ordered convolution, followd by appropriate analytic continuuation. We present the typical THG spectrum of the Hubbard model obtained by this method. Within our DMFT calculation, we observe a nontrivial approximate {\em scaling} function describing the THG spectra in all Mott insulators, independent of the gap magnitude.Comment: 4 eps figure