Structural influences in nature

Not Include

Studies of Ylides and of Two Synthetic Intermediates by X-Ray Analysis

In this thesis the techniques of crystal structure analysis are applied to the study of bonding and molecular conformation. The contents are divided into three parts, and in PART I various theoretical aspects of the methods of structure determination are discussed, with special emphasis being placed on the Direct Methods of structure elucidation which are used extensively in this research. PART II is concerned with the study, by X-ray analysis, of five Ylide-type compounds. In an attempt to rationalise the little-studied bonding systems and conformations exhibited by such molecules, the crystal structures of the three first-row ylides N-trimethylamraonio-benzamidate, N-trimethyl-ammonio-nitramidate and (+)-3-diazocamphor, and of the two second-row ylides N-(p-toluenesulphonyl)-iminodimethyl-sulphur(IV) and N-(p-toluenesulphonyl)-iminotriphenyl-phosphorane have been determined. The results of these analyses allow trends in the stability of this class of compound to be examined in relation to the bonding interactions involved, and in the case of second-row ylides, the possible involvement in the bonding of d-orbitals of the second-row element can be examined. The final section of PART II is devoted to comparisons with the structures of other relevant molecules, in an effort to further investigate bonding and conformational trends in this class of chemical compound. Moreover, an interesting correlation is suggested between the bonding interactions involved in ylides and the conformations adopted by these molecules. Accounts of the structure analyses of two terpenoid synthetic intermediates are contained in PART III. A knowledge of the relative stereochemistries of the diol systems in both 2beta-carbomethoxy-5alpha,6alpha-dihydroxy-7,7-dimethyl-tricyclo[6.2 1.01,6] undecane and also the unsubstituted derivative of 2a-carbomethoxy-5beta-chloroacetoxy-7,7-dimethyl-tricyclo[6.2.1.0 1,6] undecan-6beta-ol is essential to a better understanding, in mechanistic terms, of the novel rearrangements of these compounds. The overall similarity of both systems, but yet differing relative stereochemistries, provide an opportunity to study in detail the changes which may result from alterations in the relative stereochemistries of substituents and ring fusions. Interesting features reproduced in both molecules are the long C(sp3)-C(sp3) bonds (ca. 1.59 A) connecting completely substituted, eclipsed sp3 centres, probably the result of the strain inherent in these bonds. Finally, the thesis contains several published papers by the author, two of which are not otherwise included in the contents. Both describe the crystal structure analysis of 5-methoxycarbonylmethylene-2-piperidino-2-thiazolin-4-one, the addition product of N-thiocarbamoylpiperidine and Dimethylacetylenedicarboxylate, a reaction which has caused considerable speculation

Test Data of Flow Field of Shuttle SRM Nozzle Joint with Bond Defects, Using Unheated Air

The nozzle-to-case joint on the Shuttle SRM (as redesigned after the Challenger accident) features an adhesive sealant filling and bonding the joint, with a wiper O-ring to prevent the adhesive from reaching and disabling the closure O-ring. Flawless implementation of that joint design would ensure that hot, corrosive propellant combustion gases never reach the closure O-ring. However, understanding the flow field related to bonding defects is prudent. A comprehensive test program was conducted to quantify such flow fields and associated heating environments. A two-dimensional, full-scale model represented 65 inches of the nozzle joint, using unheated air as the test medium, in a blowdown mode. Geometry variations modeled RSRM assembly tolerances, and two types of bonding defects: pullaways and blowholes. A range of the magnitude of each type defect was tested. Also a range of operational parameters was tested, representative of the RSRM flow environment, including duplication of RSRM Mach and Reynolds numbers. Extensive instrumentation was provided to quantify pressures, heat rates, and velocities. The resulting data established that larger geometric defects cause larger pressure and larger heating, at the closure O-ring region. Velocity trends were not so straight-forward. Variations in assembly tolerances did not generally affect flow fields or heating. Operational parameters affected flow fields and heating as might be expected, increasing density or velocity increased heating. Complete details of this test effort are presented

Identifying Research Fields within Business and Management: A Journal Cross-Citation Analysis

A discipline such as business and management (B&M) is very broad and has many fields within it, ranging from fairly scientific ones such as management science or economics to softer ones such as information systems. There are at least three reasons why it is important to identify these sub-fields accurately. Firstly, to give insight into the structure of the subject area and identify perhaps unrecognised commonalities; second for the purpose of normalizing citation data as it is well known that citation rates vary significantly between different disciplines. And thirdly, because journal rankings and lists tend to split their classifications into different subjects – for example, the Association of Business Schools (ABS) list, which is a standard in the UK, has 22 different fields. Unfortunately, at the moment these are created in an ad hoc manner with no underlying rigour. The purpose of this paper is to identify possible sub-fields in B&M rigorously based on actual citation patterns. We have examined 450 journals in B&M which are included in the ISI Web of Science (WoS) and analysed the cross-citation rates between them enabling us to generate sets of coherent and consistent sub-fields that minimise the extent to which journals appear in several categories. Implications and limitations of the analysis are discussed

Benefits of an energy storage device for a wind farm

Energy storage has been a long sought after concept that could give several benefits for an intermittent energy source like wind power. The primary objective of the study presented in this paper is to determine the role that energy storage can play in alleviating network constraints and avoid the need for network investment. Two case studies have been considered in which a new wind farm would cause an existing adjacent radial line to be thermally overloaded at times of high wind, unless the generated wind power is curtailed. Important parameters affecting the viability of using energy storage for the purpose of avoiding spillage without reinforcing the network are: line length, ratio of wind farm size to line rating, wind farm energy curtailment, network reinforcement costs, energy storage systems costs, electricity wholesale price, and losses in the store and power conversion

In situ measurements of tropospheric volcanic plumes in Ecuador and Colombia during TC

A NASA DC‐8 research aircraft penetrated tropospheric gas and aerosol plumes sourced from active volcanoes in Ecuador and Colombia during the Tropical Composition, Cloud and Climate Coupling (TC4 ) mission in July–August 2007. The likely source volcanoes were Tungurahua (Ecuador) and Nevado del Huila (Colombia). The TC4 data provide rare insight into the chemistry of volcanic plumes in the tropical troposphere and permit a comparison of SO2 column amounts measured by the Ozone Monitoring Instrument (OMI) on the Aura satellite with in situ SO2 measurements. Elevated concentrations of SO2, sulfate aerosol, and particles were measured by DC‐8 instrumentation in volcanic outflow at altitudes of 3–6 km. Estimated plume ages range from ∼2 h at Huila to ∼22–48 h downwind of Ecuador. The plumes contained sulfate‐rich accumulation mode particles that were variably neutralized and often highly acidic. A significant fraction of supermicron volcanic ash was evident in one plume. In‐plume O3 concentrations were ∼70%–80% of ambient levels downwind of Ecuador, but data are insufficient to ascribe this to O3 depletion via reactive halogen chemistry. The TC4 data record rapid cloud processing of the Huila volcanic plume involving aqueous‐phase oxidation of SO2 by H2O2, but overall the data suggest average in‐plume SO2 to sulfate conversion rates of ∼1%–2% h−1 . SO2 column amounts measured in the Tungurahua plume (∼0.1–0.2 Dobson units) are commensurate with average SO2 columns retrieved from OMI measurements in the volcanic outflow region in July 2007. The TC4 data set provides further evidence of the impact of volcanic emissions on tropospheric acidity and oxidizing capacit

Assessing direct contributions of morphological awareness and prosodic sensitivity to children’s word reading and reading comprehension

We examined the independent contributions of prosodic sensitivity and morphological awareness to word reading, text reading accuracy, and reading comprehension. We did so in a longitudinal study of English-speaking children (N = 70). At 5 to 7 years of age, children completed the metalinguistic measures along with control measures of phonological awareness and vocabulary. Children completed the reading measures two years later. Morphological awareness, but not prosodic sensitivity made a significant independent contribution to word reading, text reading accuracy and reading comprehension. The effects of morphological awareness on reading comprehension remained after controls for word reading. These results suggest that morphological awareness needs to be considered seriously in models of reading development and that prosodic sensitivity might have primarily indirect relations to reading outcomes. Keywords: Morphological Awareness; Prosody; Word Reading; Reading Comprehension

NASA Langley Airborne High Spectral Resolution Lidar Instrument Description

NASA Langley Research Center (LaRC) recently developed the LaRC Airborne High Spectral Resolution Lidar (HSRL) to make measurements of aerosol and cloud distribution and optical properties. The Airborne HSRL has undergone as series of test flights and was successfully deployed on the Megacity Initiative: Local and Global Research Observations (MILAGRO) field mission in March 2006 (see Hair et al. in these proceedings). This paper provides an overview of the design of the Airborne HSRL and descriptions of some key subsystems unique to this instrument

Placebo prescription and empathy of the physician: a cross-sectional study

Background: Empathy in the patient-physician relationship is a major component in an effective placebo treatment, as in every medical treatment. Understanding the role of empathy of the physician in the placebo effect may help dissect some of the context variables responsible for the effectiveness of the placebo. Objectives: To determine the frequency of placebo prescription, doctors' beliefs, motivation, and attitudes to placebos in general practice in northern Portugal and to test the association between placebo prescription and physician empathy. Methods: A cross-sectional study was conducted between November 2014 and January 2015 among general practice specialists and interns from 14 health centres in a northern Portuguese health region. The self-report questionnaire included the Portuguese version of the Jefferson scale of physician empathy (JSPE) and a questionnaire about placebo prescription. Associations between demographic variables, JSPE score, prescription of placebo, and the attitudes to placebo score were tested with the chi-squared statistic, student t-tests for independent samples, and Pearson correlation. Results: The study included 93 general practitioners (GP) (response rate: 74%). Placebos were prescribed by 73% (n = 68) of the respondents. GPs who prescribe placebo are significantly younger (mean age = 38.4 years; SD = 11.1; t (90) = 2.98, P<.05, d = 0.67) than non-prescribers (mean age = 46.5 years; SD = 13.3). Favourable attitudes towards placebo prescription are associated with higher empathy scores (R = 0.310, P<.01). Conclusion: Placebo prescription is frequent and associated with empathy from the prescriber, especially among younger GPs.info:eu-repo/semantics/publishedVersio

Interpreting Lidar Measurements to Better Estimate Surface PM2.S in Study Regions of DISCOVER-AQ

The use of satellite AOD data to estimate surface PM2.5 has been broadly studied in various regions. Some showed good results while some showed relatively poor with the simple relationship between AOD and PM2.5. The key factor is the aerosol vertical distribution. Lidar extinction profiles provide insights into the aerosol mixing not only in the boundary layer but also quantifying residual aerosol abundance above boundary layer with e-folding scale height. The normalizing AOD by hazy layer height is proven better in correlating with PM2.5. In other words, extinction measurements near the surface can be a proxy for surface PM2.5. In this study, we will use NASA airborne HSRL (High Spectral Resolution Lidar) during SJV2007 (San Joaquin Valley, February 2007) and surface MPLNet (Micropulse Lidar Network) at GSFC between 2007 and 2010 to characterize the relationship for the DISCOVER-AQ (Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality) field experiments; the first over Baltimore-Washington was conducted in July 2011