Phosphinimine zinc complexes and neutral phosphinimines for ring opening polymerization of lactides.

Achiral arenesulfonates ligands having a (NNN) or (NNO) side arm have been developed (Chapter 2) and their respective zinc ethyl complexes, NNNZnEt 3.2 and NNOZnEt 3.3, have been synthesized and characterized using spectroscopic methods (Chapter 3). NNNZnEt as well as NNOZnEt complexes are stable under nitrogen atmosphere. In the NNOZnEt 3.3 complex the protons associated with the pendant (dimethylamino)ethyl arm are broad indicating that a fluxional process is operative, most likely dissociation of the (dimethylamino)ethyl arm at 25 °C in CD2Cl2. The fluxional behavior present in the 1H NMR spectrum of 3.2 could be arrested by cooling the CD2Cl2 solution to -60 °C. In Chapter 3, the reactivity of 3.2 and 3.3 with alcohols was explored in detail. NNOZnEt was found to be unstable in the presence of alcohols. The NNNZnEt complex does not show any reactivity with weak acids (pKa = 16), such as ethanol, anthrylmethanol or anthrylethanol. Strong acids (pKa = 8-10) like phenols protonate the zinc ethyl bond to produce zinc phenoxide complexes with release of ethane. The rate of the reaction is directly proportional to the acid strength (pKa) of the alcohols. The NNNZnEt complex as well as its corresponding phenoxides show dynamic behavior at 25 °C. The dimethylaminoethyl arms in these complexes are hemilable as indicated by 1H, 13C, 31P and variable temperature NMR, i.e., the dynamic behavior of these complexes was demonstrated. The detail structure of the NNNZnEt was elucidated by examining the single X-crystal structure of analogous air stable NNNZnMe complex. Zinc phenoxides 3.10-3.12 were isolated in good yield by reaction of NNNZnEt complex and one equivalent of the corresponding solid phenols in CH2Cl2 under N2. Zinc phenoxides 3.10- 3.12 were characterized by 1H, 13C, and 31P and multi-dimensional NMR. Fluxional behavior was observed at 25 °C for the pendant (dimethylamino)ethyl arm in complexes 3.10-3.12 as also seen in zinc alkyl complexes 3.7 and 3.13. The dynamic behavior due to association and disassociation of the (dimethylamino) ethyl arm in complexes 3.10- 3.12 could be halted by cooling the CD2Cl2 solutions to -40 °C. Complexes 3.10-3.12 were stable in dry CD2Cl2 for several days at 25 °C and 12 hours at 45 °C. The catalytic activity of zinc phenols with lactide were tested on NMR scale reactions. The discrete zinc phenoxide as well as in situ generated zinc phenoxides 3.10-3.12 show low catalytic activity with dl-lactide. The low reactivity of zinc phenoxides with dl-lactide is probably due to the low electrophilicity of the zinc center. In the second part of this dissertation (Chapter 4), a series of tolyl/phenylethyl phosphinimines 4.1-4.8 were synthesized by Staudinger reaction between azide and various phosphines. These phosphinimines were characterized using 1H, 13C, 31P NMR. In general, the phosphininimine only ring substituted with an electron donating group, such as methoxy or dimethylanino, enhances the basicity of the phosphinimines. The correlation between the basicity of the phosphinimines and the downfield shift of the alcohol hydroxyl group when activated by phosphinimine was studied. The catalytic activity of these phosphinimines towards ring opening polymerization of lactide is correlated by alcohol hydroxyl proton shift when interacted with an alcohol (1:1) in nonhydrogen bonding solvent CDCl3 at 25 °C under N2 atmosphere. The phosphinimines 4.5 to 4.14 were tested for ROP of lactides and their correlation with the basicity estimated with alcohol activation was shown. These phosphinimines represent highly active catalysts for ROP under N2 at ambient temperature. The phosphinimine 4.7 reacts with lactide monomer even in absence of alcohol initiation with reasonable reaction rate. Phosphinimines initiate the ROP of lactide even in the absence of initiating alcohol. However, the addition of alcohol enhances the rate of the reaction. We anticipate that the ease of handling of these catalysts, combined with their high reactivity on the ROP of lactide will make them useful to the synthetic community

N-heterocyclic carbene (NHC) based ligands and related methods

Polydentate macrocyclic NHCs (NHC ligands) and related methods are disclosed. Such ligands advantageously facilitate a variety of ligand coordination modes and stabilize oxidation states of metal complexes with a number of coordination environments and shapes. The NHC ligands described herein comprise pendant groups configured to facilitate a variety of reactions including: cis-trans isomerization, proton shuttling and facilitating changes in coordination environments as a result of redox reactions

Factors determining English test score of high school students in rural Nepal

Due to globalization and internationalization of education, the importance of English language has been growing consistently. Like many other countries around the globe, English is taught as a compulsory subject from the primary level in Nepal. Despite continuous public and private efforts, achievement in English education is not satisfactory, especially in rural areas, due to numerous socio-cultural and other factors. Thus, this article explores some important determinants of English achievement of high school students in Rural Nepal. Through the questionnaire responses of 407 students from the four villages of Sindhupalchok district, which is explored using Cremer’s V analysis, a strong association between students English test score and their socio-cultural, family, school and personal factors was found

Health Effects of Pesticides among Small Scale Farmers in an Urban Municipality of Nepal: A Descriptive Study

Introduction: Pesticides cause short-term as well as long-term health effects. Agriculture workers are at high risk of effect. So, this study aimed to identify the health effects of pesticides among small-scale farmers in the municipality of Bhaktapur, Nepal. Methods: This was a community-based cross-sectional descriptive study conducted in all wards of Changunarayan Municipality, Bhaktapur, Nepal. Farmers of selected households who adopted agriculture as their main occupation were included in this study. The sample size for the study was 132. Proportionate stratified sampling was used to determine the farmer from each ward and simple random sampling was used to reach every respondent. Face-to-face interview technique and semi-structured questionnaire was used for data collection. The data were analyzed using descriptive statistics and the Chi-square test was applied to measure an association between selected variables. Results: All of the farmers used pesticides and about two-thirds 74(64.9%) experienced both immediate as well as delayed symptoms due to the use of pesticides. Majority of them showed general symptoms such as eye irritation 87(76.3%), difficulty in breathing 70(61.4%) and fatigue 55(48.2%).  There was an association between the frequency of exposure and health effects due to pesticide use which was found to be statistically significant at a significance level with p-value 0.042. Conclusion: Health effects such as skin rashes, effects on the eyes, and respiratory system were reported. The most prevalent effects were eye irritation, difficulty in breathing, and itching of the skin. Training on pesticide use and awareness should be conducted by municipalities to reduce the effects

Land evaluation for peri-urban agriculture using analytical hierarchical process and geographic information system techniques: A case study of Hanoi

This paper presents an integrated technique of analytical hierarchical process (AHP) and geographic information system (GIS) to evaluate the land for peri-urban agriculture. Hanoi province, Vietnam was selected for the case study. Transformation of conventional agriculture to modern cash crops is the current trend in peri-urban Hanoi. A field survey with focused group discussions was conducted. Based on field survey data analysis, soil, land use, water resources, road network and market were chosen as major factors affecting the peri-urban agriculture. A map of each factor with different logical criteria was prepared. The AHP method was applied to identify the priority weight of each factor. Five spatial layers with their corresponding weights were linearly combined to prepare the suitability map. The map was further scaled as high suitable, medium suitable, low suitable and unsuitable land for the peri-urban agriculture. This empirical scenario provides a cost effective, rapid land evaluation framework which may help policy makers, urban and regional planners and researchers working in developing countries

Weak Equivalence Principle Test on a Sounding Rocket

SR-POEM, our principle of equivalence measurement on a sounding rocket, will compare the free fall rate of two substances yielding an uncertainty of E-16 in the estimate of \eta. During the past two years, the design concept has matured and we have been working on the required technology, including a laser gauge that is self aligning and able to reach 0.1 pm per root hertz for periods up to 40 s. We describe the status and plans for this project.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28-July 2, 201

City profile Kathmandu

Kathmandu is the capital of Nepal and forms the core of the nation’s most populous urban region. Thecity has been important economically, administratively, and politically for hundreds of years. With itsancient monuments scattered around, Kathmandu is an emerging city where several plans and conceptshave been implemented for its development. Like many cities of the developing world, it has been facingrapid population expansion and daunting socio-economic problems. There are issues of inadequateurban management of the city’s expansion, including inadequate infrastructure and squatter settlements,with severe environmental consequences including air, water and other forms of pollution. In thisprofile, Kathmandu is defined as comprising the two contiguous and closely interlinked administrativeentities, Kathmandu Metropolitan City and Lalitpur Sub-Metropolitan City. The paper analyzes historicalurban development process, current plans and programmes, land use change and some contemporarysocio-economic indicators for Kathmandu city, traces the major urban problems of the city, andconsiders future direction for its development

General Landscape Connectivity Model (GLCM): a new way to map whole of landscape biodiversity functional connectivity for operational planning and reporting

Graph-theoretic approaches are commonly used to map landscape connectivity networks to inform environmental management priorities. We developed the new General Landscape Connectivity Model (GLCM), as a operationally practical way of evaluating and mapping habitat networks to inform conservation priorities and plans. GLCM is built on two complementary metapopulation ecology-based measures: Neighbourhood habitat area (Ni) and habitat link value (Li). Ni is a measure of the amount of connected habitat to each location considering its cross-scale connectivity to neighbouring habitat. The remaining Ni across a region can be reported as an indicator of Ecological Carrying Capacity for wildlife (plants and animals). Li at any location is its contribution to the landscape connectivity of the study region (i.e. which is reported as summed Ni across a region) by virtue of providing the ‘least-cost’ linkages between concentrations of habitat. Mapped Li provides valuable insights into the pattern of a region’s habitat network, highlighting functioning habitat corridors and stepping-stones, and candidate areas for conservation and restoration. Due to its foundations in ecological theory and its parsimonious design, GLCM addresses a number of criteria we list as important, while addressing criticisms often levelled at graph-theoretical approaches. We present results for three south-east Australian case studies using continuous-value ecological condition surfaces as input. However, a simple habitat/non-habitat binary surface approximating a threshold ecological condition can also be used. GLCM has been designed to specifically address the need for generic landscape connectivity assessment at regional scales, and broader. It incorporates connectivity analyses across a range of spatial scales and granularities relevant to broad ranges of taxa and movement processes (foraging, dispersal and migration). Successively finer spatial scales are more intensively sampled based on a simple scaling-law. This approach allows analysis resoluti ons to be determined by data-driven ecological relevance rather than by processing limitations. The operational advantages of GLCM means that landscape connectivity assessments can be readily updated with refined or changed inputs including time-series remote sensing of land cover, or applied to alternative scenarios of land use, ecological restoration, climate projections or combinations of these

The SAR Handbook: Comprehensive Methodologies for Forest Monitoring and Biomass Estimation

This Synthetic Aperture Radar (SAR) handbook of applied methods for forest monitoring and biomass estimation has been developed by SERVIR in collaboration with SilvaCarbon to address pressing needs in the development of operational forest monitoring services. Despite the existence of SAR technology with all-weather capability for over 30 years, the applied use of this technology for operational purposes has proven difficult. This handbook seeks to provide understandable, easy-to-assimilate technical material to remote sensing specialists that may not have expertise on SAR but are interested in leveraging SAR technology in the forestry sector