364 research outputs found
Trump holds more positive views toward Vladimir Putin than both his predecessor and his own foreign policy team
Content analysis of public statements by Stephen Benedict Dyson and Matthew J. Parent shows that President Trump has described a more positive approach to Russia than that of President Obama, and President Putin has responded in kind. Data shows that foreign policy officials of the Trump administration hold significantly more hostile views toward Russia than the president, providing further insight into the nature of the Putin-Trump relationship
Exercise, Shear Stress, and Flow-Mediated Dilation of Human Conduit Arteries
Flow-mediated dilation (FMD) refers to the relaxation of vascular smooth muscle and the subsequent dilation of the vessel in response to increases in shear stress on the endothelial lining accompanying increases in blood flow. The phenomenon has been shown to be endothelium dependent and as such is used clinically and experimentally as an index of endothelial health. FMD can be assessed by imaging a conduit artery with ultrasound during a period of reactive hyperaemia, typically following a period of prior blood flow occlusion achieved by the inflation of a pneumatic cuff around the limb distal to the imaging site. Previous studies have shown that the health of the endothelium is predictive of the health of the cardiovascular system as a whole. This thesis set out to scrutinize the FMD test as a marker for endothelial health by testing the following five hypotheses:
1. A short burst of high shear is not adequate to elicit the FMD response.
2. Brachial artery dilation following 15 minutes of occlusion is a clearer indicator of endothelium dependent FMD than 5 minutes of occlusion with exercise.
3. Oscillating the post occlusion shear stress will decrease FMD compared to unidirectional shear).
4. Heavy dynamic hand grip exercise 6 minutes before an occlusion-only FMD protocol will result in an enhanced FMD response.
5. Long term bed-rest inactivity will attenuate the FMD response and an exercise program will preserve endothelial function.
The experiments documented in Chapter 2 found that a 20-s shear stress stimulus following 15 min of forearm circulatory occlusion was not adequate to induce an FMD response compared to longer durations of shear and there was a progressive reduction in FMD when the magnitude of the initial peak shear was reduced by limiting the duration of prior occlusion. Also, the FMD response was correlated with the total shear to time of peak diameter for all shear durations and peaks that were studied while the same was not true of peak shear. In Chapter 3 it was revealed that an uncoupling of the shear-to-dilation ratio occurred when dynamic exercise was added to the FMD test as both 15 min of occlusion (15OC) and 5 min of occlusion with 1 min of exercise (1EXin5OC) yielded similar FMD responses, even though the shear stimulus was increased with the addition of exercise. Increased plasma nitrite during hyperaemia was observed only in the 15OC protocol, suggesting that the exercise in the 1EXin5OC protocol initiates dilatory mechanisms that are not as heavily reliant on the shear sensitive nitric oxide pathway . In Chapter 4 it was shown that 5 min of intense dynamic hand grip exercise (5EX) produced a greater dilation than either continuous (15OC) or intermittent (IO) shear following 15OC. Total shear to the time of peak diameter (AUCshear) and peak shear were both correlated to %dilation following 15OC; however this relationship was lost during 5EX and IO. The results of this study echoed the suggestion in Chapter 3 that there was an uncoupling of the intensity of the shear stimulus and the magnitude of vasodilatation when exercise was introduced, and adds that it may be in part due to the oscillatory nature of the shear profile during exercise. The acute effects of local exercise on the FMD response following 15OC were examined in Chapter 5. FMD in the brachial artery was blunted following dynamic hand grip exercise, even though the shear stimulus was greater during PostEX. Nitrite was significantly elevated in CON at 15s while PostEX nitrite was significantly elevated at 30s post cuff release but not different from CON at 15s. The results of this study suggested that prior exercise had a negative effect on FMD which may be related to exercise blunting post occlusion endothelial N ̇O production. Chapter 6 examined the effect of 56 days of head-down tilt bed rest (HDBR) and an exercise countermeasure on conduit artery FMD following release of distal limb ischemia and NMD following sublingual administration of 0.3 mg of nitroglycerin. HDBR without EX decreased the resting diameter of the popliteal artery while EX increased the diameter. HDBR had no effect on the resting diameter of the brachial artery. FMD was elevated in all groups for the brachial but only in the non-exercisers for the popliteal. When change in resting diameter was taken into account the preserved FMD in EX was removed. NMD was not altered by HDBR in any group. There was enhanced endothelial function relative to intrinsic dilatory capacity in both the brachial and popliteal arteries post HDBR.
The results from Chapter 2 support hypothesis 1, showing that a 20 second burst of high shear stimulus was not adequate to elicit the FMD response during reactive hyperaemia. It is not clear whether hypothesis 2 was supported or not given that the results from Chapter 3 showed on the one hand that the %FMD did not change with the addition of exercise in the occlusion but on the other hand the shear to dilation ratio was altered. The finding, in Chapter 4, that FMD was not reduced when the hyperaemia was intermittent does not support hypothesis 3. In opposition to hypothesis 4, Chapter 5 showed that %FMD was reduced following bouts of heavy hand grip exercise; however the absolute magnitude of vessel diameter was similar in both post exercise and control tests. Finally, hypothesis 5 was also contradicted, with Chapter 6 showing that long term bed-rest enhanced rather than attenuated the FMD response in both arm and leg arteries, while an exercise countermeasure preserved pre-bed-rest FMD in the legs only. In addition to the specific hypotheses tested, there was evidence that acute exercise evoked dilatory mechanisms in the conduit arteries that were not shear/endothelium dependent given that the shear to dilation relationship was uncoupled during, following, and in occlusion protocols that include exercise. The precise mechanisms by which this is achieved are still unknown, but it may be partially due to the oscillatory nature of the elevated blood flow during exercise. I conclude that inference of cardiovascular health from endothelial function by the evaluation of %FMD should be approached with caution, especially in the event that physical activity is involved
Phase transition at finite temperature in one dimension: Adsorbate ordering in Ba/Si(111)3x2
We demonstrate that the Ba-induced Si(111)3x2 reconstruction is a physical
realization of a one-dimensional antiferromagnetic Ising model with long-range
Coulomb interactions. Monte Carlo simulations performed on a corresponding
Coulomb-gas model, which we construct based on density-functional calculations,
reveal an adsorbate-ordering phase transition at finite temperature. We show
numerically that this unusual one-dimensional phase transition should be
detectable by low-energy electron diffraction.Comment: 11 pages + 4 figures. Surf. Sci. Lett. (in press
An Efficient, Green Chemical Synthesis of the Malaria\ud Drug, Piperaquine
To provide a robust, efficient synthesis of the malaria drug piperaquine for potential use in resource-poor settings. We used in-process analytical technologies (IPAT; HPLC) and a program of experiments to develop a synthesis of piperaquine that avoids the presence of a toxic impurity in the API and is optimized for overall yield and operational simplicity. A green-chemical synthesis of piperaquine is described that proceeds in 92 – 93 % overall yield. The chemistry is robust and provides very pure piperaquine tetraphosphate salt (> 99.5 %). The overall process utilizes modest amounts (about 8 kg/kg) of 2-propanol and ethyl acetate as the only organic materials not incorporated into the API; roughly 60 % of this waste can be recycled into the production process. This process also completely avoids the formation of a toxic impurity commonly seen in piperaquine that is otherwise difficult to remove. An efficient synthesis of piperaquine is described that may be useful for application in resource-poor settings as a means of expanding access to and reducing the cost of ACTs
Functional magnetic nanoparticles for protein delivery applications : understanding protein-nanoparticle interactions
Iron oxide nanoparticles (IONPs) surface functionalised with thermo-responsive polymers can encapsulate therapeutic proteins and release them upon heating with an alternating magnetic field above the lower critical solution temperature (LCST). In order to make this delivery system clinically-relevant, we prepared IONPs coated with poly-N-isopropylmethacrylamide (PNIPMAM), a polymer with LCST above human body temperature. The optimal polymer chain length and nanoparticle size to achieve LCST of ca. 45 °C were 19 kDa PNIPMAM and 16 nm IONPs. The PNIPMAM-coated IONPs could encapsulate a range of proteins which were released upon heating above LCST in the presence of a competitor protein or serum. A small amount of encapsulated protein leakage was observed below LCST. The efficiency of protein encapsulation and release was correlated with molecular weight and glycosylation state of the proteins. Magnetic heating resulted in a faster protein release as compared to conventional heating without significant temperature increase of the bulk solution
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A support package for parents of excessively crying infants: development and feasibility study.
BACKGROUND: Around 20% of 1- to 4-month-old infants cry for long periods without an apparent reason. Traditionally, this was attributed to gastrointestinal disorder ('colic'), but evidence shows that just 5% of infants cry a lot because of organic disturbances; in most cases, the crying is attributable to normal developmental processes. This has led to a focus on the impact of the crying on parents. Parental vulnerabilities influence how parents evaluate and respond to the crying and predict adverse outcomes. By developing evidence-based services that support parents, this study was designed to take the first steps towards national health services that enhance the coping and well-being of parents whose babies excessively cry. Related aims were to improve these infants' outcomes and how NHS money is spent. OBJECTIVES: To develop a novel intervention package to support parents of excessively crying infants and to examine the feasibility of delivering and evaluating it in the NHS. DESIGN: Stage 1 of this study aimed to (1) complete a literature review to identify example support materials, (2) obtain parents' guidance on the support needed when a baby cries excessively, together with their evaluation of the example materials, and (3) develop a support package based on the results. Stage 2 aimed to (1) recruit 60 parents whose babies were currently excessively crying, (2) assess parents' and NHS professionals' willingness to complete a study of the support package, (3) measure the use and evaluation of the package components, (4) estimate the package component costs and (5) provide evidence on the feasibility and methods for a large-scale trial. SETTING: Primary health care. PARTICIPANTS: Stage 1: 20 parents of previously excessively crying infants and 55 health visitors (HVs) or specialist community public health nurses (SCPHNs). Stage 2: 57 parents of currently excessively crying infants and 124 HVs/SCPHNs. INTERVENTIONS: The support package included a website, a printed booklet and a programme of cognitive-behavioural therapy-based sessions delivered to parents by a qualified practitioner. MAIN OUTCOME MEASURES: (1) Demographic data, (2) figures for parents' use of the package components and continuation in the study, (3) parents' and HVs'/SCPHNs' ratings of the package components and suitability for NHS use, (4) questionnaire measures of parental well-being and infant health and (5) costs. RESULTS: Most parents (95%) accessed the website or printed materials and half (51%) attended the practitioner sessions. All 52 parents and 85% of HVs/SCPHNs providing data would support the inclusion of the package in the NHS. It was associated with reduced parental frustration, anxiety, depression, reported infant crying and contacts with health professionals and increased knowledge about crying. Methods for a full trial and figures for the cost of excessive infant crying for the NHS and each package element were identified. LIMITATIONS: No control group was included. Most of the recruited parents were white, well educated and in stable relationships. CONCLUSIONS: Parents and HVs/SCPHNs recognise the need for NHS provisions that support parents of excessively crying babies and consider the materials developed to meet that need. A full-scale randomised controlled trial is feasible and desirable. TRIAL REGISTRATION: Current Controlled Trials ISRCTN84975637. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 56. See the NIHR Journals Library website for further project information
Feynman's interpretation of quantum theory
A historically important but little known debate regarding the necessity and
meaning of macroscopic superpositions, in particular those containing different
gravitational fields, is discussed from a modern perspective.Comment: Published version for Eur.Phys.J. H. 15 pages pdf. Final version
available at
http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1140/epjh/e2011-10035-
A Race against Time: Reduced Azithromycin Susceptibility in Salmonella enterica Serovar Typhi in Pakistan
Antimicrobial resistance is an ongoing issue in the treatment of typhoid fever. Resistance to first-line antimicrobials and extensively drug resistant (XDR) Salmonella Typhi isolates in Pakistan have left azithromycin as the only remaining effective oral treatment. Here, we report the emergence of organisms with a single point mutation in acrB gene, implicated in azithromycin resistance, in a S. Typhi isolate from Pakistan. The isolation of this organism is worrisome and highlights the significance of the introduction of typhoid conjugate vaccine in South Asia.Importance: The emergence of XDR Salmonella Typhi in Pakistan has left azithromycin as the only viable oral treatment option. Here, we report the detection of an azithromycin resistance-associated mutation in one S. Typhi isolate. This finding is important because any possible spread of azithromycin resistance in S. Typhi isolates would make it nearly impossible to treat in outpatient settings due to the need of injectable antibiotics. Our findings also signify the importance of introduction of typhoid conjugate vaccine in regions of endemicity such as Pakistan
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Evaluating the irritant factors of silicone and hydrocolloid skin contact adhesives using trans-epidermal water loss, protein stripping, erythema, and ease of removal
YesA composite silicone skin adhesive material was designed to improve its water vapor permeability to offer advantages to wearer comfort compared to existing skin adhesive dressings available (including perforated silicone and hydrocolloid products). The chemical and mechanical properties of this novel dressing were analyzed to show that it has a high creep compliance, offering anisotropic elasticity that is likely to place less stress on the skin. A participant study was carried out in which 31 participants wore a novel silicone skin adhesive (Sil2) and a hydrocolloid competitor and were monitored for physiological response to the dressings. Trans-epidermal water loss (TEWL) was measured pre- and postwear to determine impairment of skin barrier function. Sil2 exhibited a higher vapor permeability than the hydrocolloid dressings during wear. Peel strength measurements and dye counter staining of the removed dressings showed that the hydrocolloid had a higher adhesion to the participants’ skin, resulting in a greater removal of proteins from the stratum corneum and a higher pain rating from participants on removal. Once the dressings were removed, TEWL of the participants skin beneath the Sil2 was close to normal in comparison to the hydrocolloid dressings that showed an increase in skin TEWL, indicating that the skin had been highly occluded. Analysis of the skin immediately after removal showed a higher incidence of erythema following application of hydrocolloid dressings (>60%) compared to Sil2, (T.S. received partial funding to study skin adhesive materials from a Medical Research Council Confidence in Concept grant obtained by John Bridgeman at the University of Bradford (MC_PC_19030). Initial formulation and characterization work benchmarking the Sil2 material was funded in part by Trio Healthcare Ltd., who have had no role in the analysis or interpretation of the data presented. All data was obtained independently by staff at the University of Bradford. We also wish to thank the Royal Society of Chemistry for funding Edward Dyson’s position as a research technician via a Research Enablement Grant (E21-8346952505)
Whole Genome Sequence Analysis of Salmonella Typhi Isolated in Thailand before and after the Introduction of a National Immunization Program.
Vaccines against Salmonella Typhi, the causative agent of typhoid fever, are commonly used by travellers, however, there are few examples of national immunization programs in endemic areas. There is therefore a paucity of data on the impact of typhoid immunization programs on localised populations of S. Typhi. Here we have used whole genome sequencing (WGS) to characterise 44 historical bacterial isolates collected before and after a national typhoid immunization program that was implemented in Thailand in 1977 in response to a large outbreak; the program was highly effective in reducing typhoid case numbers. Thai isolates were highly diverse, including 10 distinct phylogenetic lineages or genotypes. Novel prophage and plasmids were also detected, including examples that were previously only reported in Shigella sonnei and Escherichia coli. The majority of S. Typhi genotypes observed prior to the immunization program were not observed following it. Post-vaccine era isolates were more closely related to S. Typhi isolated from neighbouring countries than to earlier Thai isolates, providing no evidence for the local persistence of endemic S. Typhi following the national immunization program. Rather, later cases of typhoid appeared to be caused by the occasional importation of common genotypes from neighbouring Vietnam, Laos, and Cambodia. These data show the value of WGS in understanding the impacts of vaccination on pathogen populations and provide support for the proposal that large-scale typhoid immunization programs in endemic areas could result in lasting local disease elimination, although larger prospective studies are needed to test this directly
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