Probing defects and correlations in the hydrogen-bond network of ab initio water

The hydrogen-bond network of water is characterized by the presence of coordination defects relative to the ideal tetrahedral network of ice, whose fluctuations determine the static and time-dependent properties of the liquid. Because of topological constraints, such defects do not come alone, but are highly correlated coming in a plethora of different pairs. Here we discuss in detail such correlations in the case of ab initio water models and show that they have interesting similarities to regular and defective solid phases of water. Although defect correlations involve deviations from idealized tetrahedrality, they can still be regarded as weaker hydrogen bonds that retain a high degree of directionality. We also investigate how the structure and population of coordination defects is affected by approximations to the inter-atomic potential, finding that in most cases, the qualitative features of the hydrogen bond network are remarkably robust

Periodicity in the Quantity and Ratio of Pheromone Components in Volatile Emissions from Virgin Females of the Spotted Stalk Borer Moth Chilo partellus (Swinhoe)

Volatile sex pheromone was collected from the extruded pheromone gland of females of the spotted stalk borer moth Chilo partellus and trapped on glass wool. The pheromone was collected from females on the night of eclosion, 1st, 2nd, 3rd and 5th scotophases thereafter. The female sex pheromone components, (Z)-11-hexadecenal and (Z)-11-hexadecen-1-ol were identified by gas chromatography co-injection with synthetic authentic compounds and confirmed by GC-mass spectrometry. The quantity of the pheromone components was determined by comparison of GC peak areas with that of (E,Z)-3,13-octadecadienyl acetate as an internal standard. Periodicity in the pheromone emission was uni-modal with a peak about the 7-10 h into the scotophase. During the peak period, (Z)-11-hexadecenal was emitted at a rate of 43.1, 30.9, 21.5 and 16.5 ng/30 min on the day of eclosion, 1st, 3rd and 5th scotophases, respectively. A marked reduction in the release rate of the pheromone components was recorded with progressing age of females. This decrease was faster for (Z)-11-hexadecen-I-ol than for (Z)-11-hexadecenal which resulted in a spectacular shift in the ratio (Z)-11-hexadecen-I-ol ranging from about 1:1 at eclosion to 9:1, 22:1 and 32:1 in the 1st, 3rd and 5th scotophases, respectively. The age-dependent shift in both release rate and ratio of pheromone components corresponds to the change in attractiveness of females to mate-searching males. The periodicity in the quantity and blend ratios of C. partellus pheromone is discussed in light of development of a pheromone-based bait for the management of this pest. Key words: Periodicity, Lepidoptera, Pyralidae, Chilo partellus, sex pheromone, pheromone East and Central African Journal of Pharmaceutical Sciences Vol.6(2) 2003: 36-4

Structure and Dynamics of the Instantaneous Water/Vapor Interface Revisited by Path-Integral and Ab-Initio Molecular Dynamics Simulations

The structure and dynamics of the water/vapor interface is revisited by means of path-integral and second-generation Car-Parrinello ab-initio molecular dynamics simulations in conjunction with an instantaneous surface definition [A. P. Willard and D. Chandler, J. Phys. Chem. B 114, 1954 (2010)]. In agreement with previous studies, we find that one of the OH bonds of the water molecules in the topmost layer is pointing out of the water into the vapor phase, while the orientation of the underlying layer is reversed. Therebetween, an additional water layer is detected, where the molecules are aligned parallel to the instantaneous water surface.Comment: 9 pages, 5 figure

Foreign direct investment (FDI) as a channel of technology diffusion : the case of Saudi Arabia

PhD ThesisCountries' economies should be diversified as much as possible to avoid economic slumps. Saudi Arabia’s economy is highly dependent on oil as a major source of financial resources. However, diversification of economic activities requires improvement in the technological infrastructure of the country. FDI is considered a major source of technology diffusion. When foreign investors move some of their activities to a host country, they create externalities known as Spillovers. Spillovers are created with support of four major channels or effects, which are Demonstration-Imitation, Linkage, Competition and Workers’ Mobility. The aim of this research, hence, is to study the effects of FDI on technology diffusion in Saudi Arabia. It investigates the above mentioned four effects as channels of productivity growth and tries to analyze the spillovers resulting from foreign firms’ operations in the country. Moreover, the study tries to discover the mechanism through which FDI promotes the technology diffusion. This is done by the utilization of the Total Factor Productivity (TFP) analysis. The TFP has been utilized by previous researchers as an indicator of technology flow and separation across cities and countries. The second objective of this research is to study the local investors’ expectation of the future effects of FDI on the technology diffusion in the country. This is done by analyzing interaction between Competition and Linkages. It continues by analyzing the interaction between Training and workers’ Mobility. The third objective of this study is to provide recommendations to the Saudi Arabian General Investment Authority (SAGIA), pertinent to the development of the technology diffusion in Saudi Arabia. To achieve the above mentioned objectives a survey, composed of two parts, was developed. The first part of the survey targeted both foreign and local investors in four major geographical areas of Saudi Arabia. Those areas are the Eastern Province, Riyadh, Qassim and Hail. The second part of the survey targeted the local investors in the same geographical areas. To conduct the data analysis of the first part of the survey, a model is developed based on the Parente and Prescott equation. The data analysis of this portion is conducted using Ordinary Least Square (OLS) regression. The second part of the study is analyzed using the two way Analysis of Variance. In addition, the results of part two analysis were supported by descriptive data analysis. In the first part of study, intra- and inter-industry analyses are performed. In the Inter-Industry level; the study results reveal that there is very limited technology diffusion via the four channels and this result applies without adding control variables related to Size, Age, Location and Type of industry. If those variables are added, our variables of interest lose strength. On the Intra-Industry level, there are two (Chemical and machinery) of seven major business sectors that are not benefiting from FDI existence when it comes to advantages related to technology diffusion. None of the other five sectors, however, is fully benefiting from all the effects. In the analysis, different control variables are added to the analysis to investigate their effects. This includes the Size, Age, Location and the industrial Classification. The results of the second part of the study reveals that interaction between Linkage and Competition is not expected to cause any productivity increase in Saudi Arabia. Moreover, the interaction between Training and workers’ Mobility is not expected to lead to technology diffusion. These results are derived based on local investors’ opinion polls. The result is also supported by extensive descriptive data analysis in which comparison with previous researchers’ results is conducted. In addition, these results are supported by Chi-Square analysis for the sake of accuracy of the hypothesis testing. The research is concluded with recommendations pertinent to the development of the technology diffusion in the country. The actions that are being taken are described, based on the results of this study, Also recommendations for future studies are given at the end of the research

Ab Initio Quality NMR Parameters in Solid-State Materials Using a High-Dimensional Neural-Network Representation.

Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental tools to probe the local atomic order of a wide range of solid-state compounds. However, due to the complexity of the related spectra, in particular for amorphous materials, their interpretation in terms of structural information is often challenging. These difficulties can be overcome by combining molecular dynamics simulations to generate realistic structural models with an ab initio evaluation of the corresponding chemical shift and quadrupolar coupling tensors. However, due to computational constraints, this approach is limited to relatively small system sizes which, for amorphous materials, prevents an adequate statistical sampling of the distribution of the local environments that is required to quantitatively describe the system. In this work, we present an approach to efficiently and accurately predict the NMR parameters of very large systems. This is achieved by using a high-dimensional neural-network representation of NMR parameters that are calculated using an ab initio formalism. To illustrate the potential of this approach, we applied this neural-network NMR (NN-NMR) method on the (17)O and (29)Si quadrupolar coupling and chemical shift parameters of various crystalline silica polymorphs and silica glasses. This approach is, in principal, general and has the potential to be applied to predict the NMR properties of various materials.This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acs.jctc.5b0100

Effects of exposing adults of Amblyomma variegatum to neem cake extracts in traps baited with semiochemicals under semi–laboratory conditions

The efficacy of a trap baited with an attractant blend comprising of attraction aggregation- attachment pheromone (AAAP), 1-octen-3-ol and CO2 and treated with Neem (Azadirachta indica) cake extracts (0.6% of azadirachtin) to attract and expose the ticks, Amblyomma variegatum (Fabricius) (Acari: Ixodidae) to the active constituents of the cake was evaluated in circular field plots.. Ticks were released at various distances from trap placed at the center of the plots. Ticks that arrived at the trap (and exposed to the extracts) and those in control plots were collected and their mortality was monitored in the laboratory over a three-week period. All concentrations of the neem extracts caused mortality of A. variegatum adults with highest mortality rate (97.8%) recorded in the concentration of 30 % of extracts. The mortality of the ticks was also dependent upon the time ticks were exposed to the extracts. The findings suggest the possibility of using semiochemicals-baited traps in combination with neem extracts for off-host control of these ticks in smallholder farms.Key words: Amblyomma variegatum, traps, Azadirachta indica, semiochemical

Cardiovascular risk factors in school children from low middle income families in Karachi, Pakistan

Serum levels of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C) and trigly cerides (TG) were determined on 239 school children aged 5-19 years belonging to lower middle class families. The mean TC, LDL-C, HDL-C and TG ranged from 3.70-4.37 mmol/L, 2.17- 2.70 mmol/L, 0.94-1.14 mmol/L, 1.07-1.26 mmol/L respectively. In general, girls had higher TC, LDL-C and HDL-C levels. There was no significant difference in the TG levels between boys and girls. Thirty-three percent of the girls and 22% of the boys had TC level _4.4 mmol/L, the level at which dietary intervention is recommended for children. Fifty-three percent of the girls and 37% of the boys bad TG levels _ than the 90th percentile of the levels for children of similar age and sex in North America. The HDL-C levels were low with 37% of the girls and 44% of boys having values _ the lath percentile of levels for North American children. The mean daily intake of cholesterol ranged from 241 mg to 364 mg/day. Except for the 5-9 year olds, boys had a higher cholesterol intake than girls (P\u3c0.005). Twenty-two percent of the boys and 32% of the girls were overweight but weight status was significantly associated with elevated TC levels only in the boys (P \u3c0.05). Activity level was not significantly related to TC levels but girls who were active had significantly higher HDL-C levels than girls who were sedentary (P \u3c0.02). Family history of cardiovascular disease was significantly associated with elevated cholesterol levels in girls (P \u3c0.05). The results show that the prevalence of cardiovascular risk factors in these school children is relatively high even though they belong to lower middle class families in a developing countr