Synthesis and chemistry of highly distorted polycyclic aromatic hydrocarbons

A significant feature of smaller cyclophanes and buckminsterfullerenes is the presence of nonplanar aromatic rings. Such compounds are of considerable interest due to both the synthetic challenge they pose and to their unusual conformational, spectroscopic, and chemical behavior. A great deal of work has focussed on determining the extent to which an aromatic ring can be distorted from planarity while remaining isolable under ambient conditions. Although this question has been examined in detail for isolated benzene rings (for example, through investigations of [n]paracyclophanes), analogous studies of polycyclic aromatic hydrocarbon (PAH) frameworks have never been pursued. -- Here the first systematic examination of the distortion from planarity of a PAH moiety is reported. The synthesis of a number of [n](2,7)pyrenophanes from [3.3]dithiacyclophane precursors is described. Some physical, spectroscopic, and chemical properties of these molecules are also described, and a number of X-ray structures of markedly nonplanar aromatic moieties are reported. From this data, it is concluded that the end-to-end bend of the most strained pyrenophane prepared is greater than the average end-to-end bend of the pyrene moiety. However, POAV analysis of the pyramidalization of pyrenophane sp² carbon atoms reveals markedly lower pyramidalizations than are observed in D₅h C₇₀. Attempts at the functionalization of [n](2,7)pyrenophanes in the hope of using them as precursors for larger nonplanar PAHs were made. However, suitable conditions for functionalization of pyrenophanes were not found. A synthetic approach to a C₂-chiral 1,6-[n]pyrenophane is also described. -- An attempted synthesis of a derivative of the buckybowl pinakene using a tandem Bergman cycloaromatization/free radical conjugate addition is presented. -- The experimental work is preceded by reviews of the literature concerning the concept of aromaticity, nonplanar aromatic molecules (especially [n]paracyclophanes) and fullerene fragments

A polarimetric study of the reflection nebulae NGC 2068 and NGC 2023 in the Orion R1 association

Polarimetry studies of two reflection nebulae in the Orion R1 association are used to determine the nature of the dust in which recently formed stars are embedded in, and show the geometry of the surrounding dust cloud. The data reductions presented are on NGC 2068 and NGC 2023, which are centres of recent low-mass star formation and are embedded on the nearside of LI 630. In the case of NGC 2068, it appears that there is a single illuminating star which illuminates a foreground tilted slab of varying dust density from the rear. A simple tilted slab model assuming single Mie scattering from homogeneous spherical grains was used to fit visual data of traces of polarization, polarized intensity and total intensity through HD 38563N in a north-south direction. The model favoured metallic grains; the best fit being for iron grains and a slab 0.5 parsecs in front of HD 38563N tilted at an angle 55 degrees to the line-of-sight. In the case of NGC 2023, multicolour polarimetry is presented in B,V,R,I and Z. The star HD 37903 was found to be the sole illuminating star. A model to fit the spectral dependence of polarization gave low refractive index grains assuming a power law size distribution. Associated with NGC 2023 are Herbig-Haro objects HH-1, 4, which were found not to be polarized

Teaching, learning, and play in the outdoors: a survey of school and pre-school provision in Scotland

First paragraph: In Scottish pre-schools and schools, through the implementation of Curriculum for Excellence and other policies, it has become an expectation that pupils will receive opportunities to learn outdoors within subject areas and in interdisciplinary studies. This expectation needs empirical investigation. To what extent, in what ways, and with what impacts are schools and pre-schools utilising the school grounds, local areas, and other places beyond as settings for the delivery of Curriculum for Excellence

Factors associated with perceived quality influencing beef consumption behaviour in Ireland

Despite the importance of beef to the national economy, its importance is not, however, reflected in the national diet. B eefs share of the overall market for fresh meat in Ireland has nearly halved in the past ten years (1986 - 1996). As yet no empirical work has been carried out in Ireland to examine the factors influencing this trend. This study explored the link between how Irish consumers perceived the quality of beef and how this perception affected past purchase behaviour of those who had decreased their consumption levels and those who had maintained them. The rationale for approaching the study of beef consumption from this perspective is supported by research which revealed that market share and profits are correlated with quality as perceived by the consumer. A review of the literature indeed found that many of the factors which have influenced consumers to reduce their red meat consumption were quality related. The methodology used by many of these studies was to directly ask respondents why they had reduced their consumption. The limitation of this technique is that respondents will attempt to rationalise their behaviour. In an attempt to overcome this limitation and uncover the underlying quality factors influencing consumption, a framework for analysing beef quality perception was choosen. The research used was part of a wider international multi-disciplinary EU funded project entitled ‘Meat Quality Policy and Consumer Behaviour’ involving six countries. Telephone interviews were carried out among 500 respondents who carried out most of the food purchases in the household. Questions of particular interest for the dissertation were related to perceptions of beef quality at: 1) the point of consumption; 2) the point of purchase; 3) prior to purchase. Multivariate data analysis techniques were used on the data to address the research question. Results revealed that the discriminating quality factors of safety and meat status explained only a small proportion of the difference between both groups. Explanations and suggestions for further research include the general re-examination of how quality concepts such health, safety and meat status are operationalised. In addition the social aspects of meat eating should be examined. In particular, the link between consumption patterns and the symbolic notions associated with meat

Umbilical hernia repair and recurrence: need for a clinical trial?

Abstract Introduction Umbilical hernia repair, despite its perceived simplicity, is associated with recurrence between 2.7 and 27%, in mesh repair and non mesh repair respectively. Many factors are recognized contributors to recurrence however multiple defects in the linea alba, known to occur in up to 30% of patients, appear to have been overlooked by surgeons. Aims This systematic review assessed reporting of second or multiple linea alba defects in patients undergoing umbilical hernia repair to establish if these anatomical variations could contribute to recurrence along with other potential factors. Methods A systematic review of all published English language articles was undertaken using databases PubMed, Embase, Web of Science and Cochrane Library from January 2014 to 2019. The search terms ‘Umbilical hernia’ AND ‘repair’ AND ‘recurrence’ were used across all databases. Analysis was specified in advance to avoid selection bias, was registered with PROSPERO (154173) and adhered to PRISMA statement. Results Six hundred and forty-six initial papers were refined to 10 following article review and grading. The presence of multiple linea alba defects as a contributor to recurrence was not reported in the literature. One paper mentioned the exclusion of six participants from their study due multiple defects. In all 11 factors were significantly associated with umbilical hernia recurrence. These included: large defect, primary closure without mesh, high BMI in 5/10 publications; smoking, diabetes mellitus, surgical site Infection (SSI) and concurrent hernia in 3/10. In addition, the type of mesh, advanced age, liver disease and non-closure of the defect were identified in individual papers. Conclusion This study identified many factors already known to contribute to umbilical hernia recurrence in adults, but the existence of multiple defects in the linea, despite it prevalence, has evaded investigators. Surgeons need to be consider documentation of this potential confounder which may contribute to recurrence

Influence of Supplemental Feed Choice for Pasture-Based Cows on the Fatty Acid and Volatile Profile of Milk

peer-reviewedThe purpose of this study was to examine the impact of a variety of supplemental feeds on the composition and quality of milk in a pasture-based dairy system. Four pasture-supplemented feeding systems were compared: Group 1 supplementation with 16% crude protein parlour concentrate (CONC); Group 2 supplementation with palm kernel expeller plus parlour concentrate (PKE); Group 3 supplemented with soya hulls plus parlour concentrate (SOYA); Group 4 was supplemented with molassed beet pulp plus parlour concentrate (BEET). Supplemental feeding system was demonstrated to have a significant effect on the size of native casein micelles and the gelation properties of milks. While CONC feeding produced significantly higher casein micelle size, gel strength (Young’s Modulus) was significantly negatively correlated with casein micelle size. Supplemental feeding system had a significant effect on a number of fatty acids (FA) and indices derived therefrom, including total saturated and unsaturated fatty acids, de novo produced FA, omega 3, and omega 6 FA. The volatile profile of milks was also affected by supplemental feed choice, whereby multivariate analysis demonstrated that the CONC diet was distinctly different to that of the PALM, SOYA, and BEET milks. Multivariate analysis demonstrated that it is possible to distinguish milks from different pasture-supplemented feeding systems by their FA profile

The effect of basic fibroblast growth factor on the blood flow and morphologic features of a latissimus dorsi cardiomyoplasty

AbstractPrevious studies designed to determine whether latissimus cardiomyoplasty could be used to revascularize ischemic myocardium showed that after operation the latissimus was ischemic and had severely deteriorated. This study was undertaken to determine whether basic fibroblast growth factor, a potent angiogenic peptide, would improve the vascularity of the latissimus and enhance collateral formation between the muscle of the cardiomyoplasty and ischemic myocardium. In goats, myocardial ischemia was induced with an ameroid constrictor and cardiomyoplasty performed. The latissimus was continuously stimulated electrically at 2 Hz for 6 weeks and given four weekly bolus injections of human recombinant basic fibroblast growth factor (80 μg infused into the left subclavian artery). In eight animals, rates of regional blood flow were measured and both the heart and latissimus were evaluated histochemically. The latissimus blood flow rate was 0.114 ± 0.029 ml/gm per minute, which was three times greater than that of historical controls (chronically stimulated latissimus cardiomyoplasty without basic fibroblast growth factor treatment; 0.042 ± 0.007 ml/gm per minute, p < 0.05). Associated with the improved blood flow, there was significantly less evidence of skeletal muscle fiber dropout and muscle fibrosis in the animals treated with basic fibroblast growth factor. Latissimus-derived collateral flow to ischemic myocardium developed in five of the eight goats and averaged 0.288 ± 0.075 ml/gm per minute. This flow was 42.8% ± 15.7% ( n = 5) of the flow required by normal myocardium (which was 0.728 ± 0.095 ml/gm per minute). This value for latissimus-derived collateral blood flow was almost twice that of the historical controls (24.0% ± 3.9%), but the increase did not achieve statistical significance ( p = 0.08). These results hold the promise that basic fibroblast growth factor treatment might enhance the formation of extramyocardial collaterals to the heart and improve skeletal muscle function. (J THORAC CARDIOVASC SURG 1996;111:19-28

Influence of the environment and probes on rapid DNA sequencing via transverse electronic transport

We study theoretically the feasibility of using transverse electronic transport within a nanopore for rapid DNA sequencing. Specifically, we examine the effects of the environment and detection probes on the distinguishability of the DNA bases. We find that the intrinsic measurement bandwidth of the electrodes helps the detection of single bases by averaging over the current distributions of each base. We also find that although the overall magnitude of the current may change dramatically with different detection conditions, the intrinsic distinguishability of the bases is not significantly affected by pore size and transverse field strength. The latter is the result of very effective stabilization of the DNA by the transverse field induced by the probes, so long as that field is much larger than the field that drives DNA through the pore. In addition, the ions and water together effectively screen the charge on the nucleotides, so that the electron states participating in the transport properties of the latter ones resemble those of the uncharged species. Finally, water in the environment has negligible direct influence on the transverse electrical current.Comment: 14 pages, 5 figure

Replicate high-density rat genome oligonucleotide microarrays reveal hundreds of regulated genes in the dorsal root ganglion after peripheral nerve injury.

BACKGROUND: Rat oligonucleotide microarrays were used to detect changes in gene expression in the dorsal root ganglion (DRG) 3 days following sciatic nerve transection (axotomy). Two comparisons were made using two sets of triplicate microarrays, naïve versus naïve and naïve versus axotomy. RESULTS: Microarray variability was assessed using the naïve versus naïve comparison. These results support use of a P < 0.05 significance threshold for detecting regulated genes, despite the large number of hypothesis tests required. For the naïve versus axotomy comparison, a 2-fold cut off alone led to an estimated error rate of 16%; combining a >1.5-fold expression change and P < 0.05 significance reduced the estimated error to 5%. The 2-fold cut off identified 178 genes while the combined >1.5-fold and P < 0.05 criteria generated 240 putatively regulated genes, which we have listed. Many of these have not been described as regulated in the DRG by axotomy. Northern blot, quantitative slot blots and in situ hybridization verified the expression of 24 transcripts. These data showed an 83% concordance rate with the arrays; most mismatches represent genes with low expression levels reflecting limits of array sensitivity. A significant correlation was found between actual mRNA differences and relative changes between microarrays (r(2 )= 0.8567). Temporal patterns of individual genes regulation varied. CONCLUSIONS: We identify parameters for microarray analysis which reduce error while identifying many putatively regulated genes. Functional classification of these genes suggest reorganization of cell structural components, activation of genes expressed by immune and inflammatory cells and down-regulation of genes involved in neurotransmission