A pinned-pinned beam with and without a distributed foundation: A simple exact relationship between their eigenvalues

The body of this paper considers a pinned-pinned Bernoulli-Euler beam, from which the core natural frequencies and critical buckling loads corresponding to in-plane flexure, can be determined easily. The theory is then developed to yield an exact relationship between the static axial load in the beam and the frequency of vibration. This enables the core eigenvalues to be related exactly to their counterparts when the beam is additionally supported on a two parameter elastic foundation.The relationship is simple, exact and obviates the complex problems involved in solving the foundation problem using more traditional techniques. A number of illustrative problems are solved to confirm the accuracy and efficacy of the approach

The discovery of 2.78 hour periodic modulation of the X-ray flux from globular cluster source Bo 158 in M31

We report the discovery of periodic intensity dips in the X-ray source XMMU J004314.1+410724, in the globular cluster Bo158 in M31. The X-ray flux was modulated by ~83% at a period of 2.78 hr (10017 s) in an XMM-Newton observation taken 2002 Jan 6-7. The X-ray intensity dips show no energy dependence. We detected weaker dips with the same period in observations taken 2000 June 25 (XMM-Newton) and 1991 June 26 (ROSAT/PSPC). The amplitude of the modulation has been found to be anticorrelated with source X-ray flux: it becomes lower when the source intensity rises. The energy spectrum of Bo158 was stable from observation to observation, with a characteristic cutoff at ~4-6 keV. The photo-electric absorption was consistent with the Galactic foreground value. No significant spectral changes were seen in the course of the dips. If the 2.78 hr cycle is the binary period of Bo158 the system is highly compact, with a binary separation of ~10e11 cm. The association of the source with a globular cluster, together with spectral parameters consistent with Galactic neutron star sources, suggests that X-rays are emitted by an accreting neutron star. The properties of Bo 158 are somewhat reminiscent of the Galactic X-ray sources exhibiting a dip-like modulations. We discuss two possible mechanisms explaining the energy-independent modulation observed in Bo 158: i) the obscuration of the central source by highly ionized material that scatters X-rays out of the line of sight; ii) partial covering of an extended source by an opaque absorber which occults varying fractions of the source.Comment: 10 pages, 4 figures, ApJ, submitted, uses emulateapj styl

Genomic organization of duplicated short wave-sensitive and long wave-sensitive opsin genes in the green swordtail, Xiphophorus helleri

<p>Abstract</p> <p>Background</p> <p>Long wave-sensitive (<it>LWS</it>) opsin genes have undergone multiple lineage-specific duplication events throughout the evolution of teleost fishes. <it>LWS </it>repertoire expansions in live-bearing fishes (family Poeciliidae) have equipped multiple species in this family with up to four <it>LWS </it>genes. Given that color vision, especially attraction to orange male coloration, is important to mate choice within poeciliids, <it>LWS </it>opsins have been proposed as candidate genes driving sexual selection in this family. To date the genomic organization of these genes has not been described in the family Poeciliidae, and little is known about the mechanisms regulating the expression of <it>LWS </it>opsins in any teleost.</p> <p>Results</p> <p>Two BAC clones containing the complete genomic repertoire of <it>LWS </it>opsin genes in the green swordtail fish, <it>Xiphophorus helleri</it>, were identified and sequenced. Three of the four <it>LWS </it>loci identified here were linked in a tandem array downstream of two tightly linked short wave-sensitive 2 (<it>SWS2</it>) opsin genes. The fourth <it>LWS </it>opsin gene, containing only a single intron, was not linked to the other three and is the product of a retrotransposition event. Genomic and phylogenetic results demonstrate that the <it>LWS </it>genes described here share a common evolutionary origin with those previously characterized in other poeciliids. Using qualitative RT-PCR and MSP we showed that each of the <it>LWS </it>and <it>SWS2 </it>opsins, as well as three other cone opsin genes and a single rod opsin gene, were expressed in the eyes of adult female and male <it>X. helleri</it>, contributing to six separate classes of adult retinal cone and rod cells with average λ_maxvalues of 365 nm, 405 nm, 459 nm, 499 nm, 534 nm and 568 nm. Comparative genomic analysis identified two candidate teleost opsin regulatory regions containing putative CRX binding sites and hormone response elements in upstream sequences of <it>LWS </it>gene regions of seven teleost species, including <it>X. helleri</it>.</p> <p>Conclusions</p> <p>We report the first complete genomic description of <it>LWS </it>and <it>SWS2 </it>genes in poeciliids. These data will serve as a reference for future work seeking to understand the relationship between <it>LWS </it>opsin genomic organization, gene expression, gene family evolution, sexual selection and speciation in this fish family.</p

Blood tests in primary care:a qualitative study of communication and decision making between doctors and patients

OBJECTIVE: Blood tests are commonly used in primary care as a tool to aid diagnosis, and to offer reassurance and validation for patients. If doctors and patients do not have a shared understanding of the reasons for testing and the meaning of results, these aims may not be fulfilled. Shared decision‐making is widely advocated; yet, most research focusses on treatment decisions rather than diagnostic decisions. The aim of this study was to explore communication and decision‐making around diagnostic blood tests in primary care. METHODS: Qualitative interviews were undertaken with patients and clinicians in UK primary care. Patients were interviewed at the time of blood testing, with a follow‐up interview after they received test results. Interviews with clinicians who requested the tests provided paired data to compare clinicians' and patients' expectations, experiences and understandings of tests. Interviews were analysed thematically using inductive and deductive coding. RESULTS: A total of 80 interviews with 28 patients and 19 doctors were completed. We identified a mismatch in expectations and understanding of tests, which led to downstream consequences including frustration, anxiety and uncertainty for patients. There was no evidence of shared decision‐making in consultations preceding the decision to test. Doctors adopted a paternalistic approach, believing that they were protecting patients from anxiety. CONCLUSION: Patients were not able to develop informed preferences and did not perceive that choice is possible in decisions about testing, because they did not have sufficient information and a shared understanding of tests. A lack of shared understanding at the point of decision‐making led to downstream consequences when test results did not fulfil patients' expectations. Although shared decision‐making is recommended as best practice, it does not reflect the reality of doctors' and patients' accounts of testing; a broader model of shared understanding seems to be more relevant to the complexity of primary care diagnosis. PATIENT OR PUBLIC CONTRIBUTION: A patient and public involvement group comprising five participants with lived experience of blood testing in primary care met regularly during the study. They contributed to the development of the research objectives, planning recruitment methods, reviewing patient information leaflets and topic guides and also contributed to discussion of emerging themes at an early stage in the analysis process

Integrin α2β1 mediates outside-in regulation of platelet spreading on collagen through activation of Src kinases and PLCγ2

Collagen plays a critical role in hemostasis by promoting adhesion and activation of platelets at sites of vessel injury. In the present model of platelet–collagen interaction, adhesion is mediated via the inside-out regulation of integrin α2β1 and activation through the glycoprotein VI (GPVI)–Fc receptor (FcR) γ-chain complex. The present study extends this model by demonstrating that engagement of α2β1 by an integrin-specific sequence from within collagen or by collagen itself generates tyrosine kinase–based intracellular signals that lead to formation of filopodia and lamellipodia in the absence of the GPVI–FcR γ-chain complex. The same events do not occur in platelet suspensions. α2β1 activation of adherent platelets stimulates tyrosine phosphorylation of many of the proteins in the GPVI–FcR γ-chain cascade, including Src, Syk, SLP-76, and PLCγ2 as well as plasma membrane calcium ATPase and focal adhesion kinase. α2β1-mediated spreading is dramatically inhibited in the presence of the Src kinase inhibitor PP2 and in PLCγ2-deficient platelets. Spreading is abolished by chelation of intracellular Ca2+. Demonstration that adhesion of platelets to collagen via α2β1 generates intracellular signals provides a new insight into the mechanisms that control thrombus formation and may explain the unstable nature of β1-deficient thrombi and why loss of the GPVI–FcR γ-chain complex has a relatively minor effect on bleeding

Evolution of Mass Outflow in Protostars

We have surveyed 84 Class 0, Class I, and flat-spectrum protostars in mid-infrared [Si II], [Fe II] and [S I] line emission, and 11 of these in far-infrared [O I] emission. We use the results to derive their mass outflow rates. Thereby we observe a strong correlation of mass outflow rates with bolometric luminosity, and with the inferred mass accretion rates of the central objects, which continues through the Class 0 range the trend observed in Class II young stellar objects. Along this trend from large to small mass-flow rates, the different classes of young stellar objects lie in the sequence Class 0 -- Class I/flat-spectrum -- Class II, indicating that the trend is an evolutionary sequence in which mass outflow and accretion rates decrease together with increasing age, while maintaining rough proportionality. The survey results include two which are key tests of magnetocentrifugal outflow-acceleration mechanisms: the distribution of the outflow/accretion branching ratio b, and limits on the distribution of outflow speeds. Neither rule out any of the three leading outflow-acceleration, angular-momentum-ejection mechanisms, but they provide some evidence that disk winds and accretion-powered stellar winds (APSWs) operate in many protostars. An upper edge observed in the branching-ratio distribution is consistent with the upper bound of b = 0.6 found in models of APSWs, and a large fraction (0.31) of the sample have branching ratio sufficiently small that only disk winds, launched on scales as large as several AU, have been demonstrated to account for them.Comment: Version submitted to ApJ: 36 pages, 3 tables, 8 figure

Contribution of the Ventral Subiculum to Inhibitory Regulation of the Hypothalamo-Pituitary-Adrenocortical Axis

Anatomical studies indicate that the ventral subiculum is in a prime position to mediate hippocampal inhibition of the hypothalamo-pituitary-adrenocortical (HPA) axis. The present study evaluated this hypothesis by assessing HPA function following ibotenic acid lesion of the ventral subiculum region. Rats with lesions of the ventral subiculum (vSUB) or ventral hippocampus (vHIPPO) did not show changes in basal corticosterone (CORT) secretion at either circadian peak or nadir time points when compared to sham-lesion rats (SHAM) or unoperated controls. However, rats with vSUB lesions exhibited a prolonged glucocorticoid stress response relative to all other groups. Baseline CRH mRNA levels were significantly increased in the medial parvocellular paraventricular nucleus (PVN) of the vSUB group relative to controls. CRH mRNA differences were particularly pronounced at caudal levels of the nucleus, suggesting topographic organization of vSUB interactions with PVN neurons. Notably, the vHIPPO group, which received large lesions of ventral CA1, CA3 and dentate gyrus without significant subicular damage, showed no change in stress-induced CORT secretion, suggesting that the ventral subiculum proper is principally responsible for ventral hippocampal actions on the HPA stress response. No differences in medial parvocellular PVN AVP mRNA expression were seen in either the vSUB or vHIPPO groups. The results indicate a specific inhibitory action of the ventral subiculum on HPA activation. The increase in CRH biosynthesis and stress-induced CORT secretion in the absence of changes in baseline CORT secretion or AVP mRNA expression suggests that the inhibitory actions of ventral subicular neurons affect the response capacity of the HPA axis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74632/1/j.1365-2826.1995.tb00784.x.pd

Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf

We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosphere reddened by normal extinction. Instead, the slope is consistent with scattered light, indicating that circumstellar material is occulting the brown dwarf. By combining the SpeX data with mid-IR photometry and spectroscopy from the Spitzer Space Telescope and previously published millimeter data from Scholz and coworkers, we construct the spectral energy distribution for 2MASS J04381486+2611399 and model it in terms of a young brown dwarf surrounded by an irradiated accretion disk. The presence of both silicate absorption at 10 um and silicate emission at 11 um constrains the inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional evidence of the high inclination of this disk is provided by our detection of asymmetric bipolar extended emission surrounding 2MASS J04381486+2611399 in high-resolution optical images obtained with the Hubble Space Telescope. According to our modeling for the SED and images of this system, the disk contains a large inner hole that is indicative of a transition disk (R_in~58 R_star~0.275 AU) and is somewhat larger than expected from embryo ejection models (R_out=20-40 AU vs. R_out<10-20 AU).Comment: The Astrophysical Journal, in pres