4,826 research outputs found
Three-dimensional finite element analysis of acoustic instability of solid propellant rocket motors
A three dimensional finite element solution of the acoustic vibration problem in a solid propellant rocket motor is presented. The solution yields the natural circular frequencies of vibration and the corresponding acoustic pressure mode shapes, considering the coupled response of the propellant grain to the acoustic oscillations occurring in the motor cavity. The near incompressibility of the solid propellant is taken into account in the formulation. A relatively simple example problem is solved in order to illustrate the applicability of the analysis and the developed computer code
Predicting preferential DNA vector insertion sites: implications for functional genomics and gene therapy
Viral and transposon vectors have been employed in gene therapy as well as functional genomics studies. However, the goals of gene therapy and functional genomics are entirely different; gene therapists hope to avoid altering endogenous gene expression (especially the activation of oncogenes), whereas geneticists do want to alter expression of chromosomal genes. The odds of either outcome depend on a vector's preference to integrate into genes or control regions, and these preferences vary between vectors. Here we discuss the relative strengths of DNA vectors over viral vectors, and review methods to overcome barriers to delivery inherent to DNA vectors. We also review the tendencies of several classes of retroviral and transposon vectors to target DNA sequences, genes, and genetic elements with respect to the balance between insertion preferences and oncogenic selection. Theoretically, knowing the variables that affect integration for various vectors will allow researchers to choose the vector with the most utility for their specific purposes. The three principle benefits from elucidating factors that affect preferences in integration are as follows: in gene therapy, it allows assessment of the overall risks for activating an oncogene or inactivating a tumor suppressor gene that could lead to severe adverse effects years after treatment; in genomic studies, it allows one to discern random from selected integration events; and in gene therapy as well as functional genomics, it facilitates design of vectors that are better targeted to specific sequences, which would be a significant advance in the art of transgenesis
Justifying reimbursement for Alzheimers diagnostics and treatments: Seeking alignment on evidence
pre-printThe increasing cost of health care combined with expensive new drugs and diagnostics is leading to more frequent gaps between regulatory and reimbursement approval decisions. As a result, persons with Alzheimer's disease may have difficulty accessing the benefits of medical advances. In contrast to the long history and established structure for drug approval, payer decision-making is dispersed, not standardized and perspectives on necessary evidence differ and often poorly defined. Particularly challenging is how to demonstrate the value of drugs and diagnostics for patients who do not yet have significant functional decline. While discussions to develop consensus continue, clinical trials should begin to incorporate health system and patient-oriented outcomes. In some situations additional studies designed to demonstrate value and comparative effectiveness will be needed. Such studies should examine outcomes of representative populations in community settings. To assure scientific advances in diagnosis and treatment benefit patients, developing evidence to support reimbursement will become as important as obtaining regulatory approval
Individual, Family and Abuse Characteristics of 700 British Child and Adolescent Sexual Abusers
The individual, family and abuse characteristics of 700 children and young people referred to nine UK services over a nine-year period between 1992 and 2000 as a result of their sexually abusive behaviours were examined. The most common age at referral was 15 years, though a third of all referrals related to children aged 13 or under. Thirty-eight per cent of the sample were identified as learning disabled. Surprisingly high rates of sexual and non-sexual victimisation were present in the backgrounds of the children and young people referred. A wide range of abusive behaviours was perpetrated with just over half of the sample having penetrated or having attempted to penetrate another individual. Victims were usually known to the abuser but in 75 per cent of cases were not related. Fifty-one per cent of the sample abused females only, though 49 per cent had at least one male victim. The implications for policy and practice with children and young people with harmful sexual behaviours are discussed
A model realisation of the Jaffe-Wilczek correlation for pentaquarks
We discuss a realisation of the pentaquark structure proposed by Jaffe and
Wilczek within a simple quark model with colour-spin contact interactions and
coloured harmonic confinement, which accurately describes the
splitting. In this model spatially compact diquarks are formed in the
pentaquark but no such compact object exists in the nucleon. The colour-spin
attraction brings the Jaffe-Wilczek-like state down to a low mass, compatible
with the experimental observation and below that of the naive ground state with
all -waves. We find, however, that although these trends are maintained, the
extreme effects observed do not survive the required ``smearing'' of the delta
function contact interaction. We also demonstrate the weakness of the
``schematic'' approximation when applied to a system containing a -wave. An
estimate of the anti-charmed pentaquark mass is made which is in line with the
Jaffe-Wilczek prediction and significantly less than the value reported by the
H1 collaboration.Comment: 10 pages, uses psfra
Combined training improves the diagnostic measures of sarcopenia and decreases the inflammation in HIVâinfected individuals
Background
HIV-related sarcopenia is an emerging health issue that often remains undiagnosed and can lead to reduced quality of life, independence, and premature death if untreated. This study investigated the effects of a 6 month combined training (resistance plus aerobic exercise) (CT) intervention on diagnostic measures of sarcopenia, including grip strength, appendicular lean mass index (ALMI), and gait speed.
Methods
Forty participants were randomized into either a CT group (n = 20; age = 38.3 ± 4.9 years) or a control group (CON; n = 20; age = 37.9 ± 5.1 years). Participants in the CT group performed three supervised sessions per week for 6 months, consisting of weekly reverse linear periodized resistance training followed by 20 min aerobic training. Participants in the CON group were instructed to continue with their current lifestyle habits. Assessments were completed at baseline and after 6 months. Statistical analyses were performed using a two-way analysis of covariance (ANCOVA) adjusted for sex and preintervention values. Primary outcomes included grip strength, ALMI, and gait speed. Secondary outcomes were changes in levels of pro-inflammatory cytokines (IL-6 and TNF-α), IGF-1, and myostatin. Associations were explored between changes in inflammatory markers (IL-6 and TNF-α), gait speed, and ALMI with grip strength.
Results
A significant increase in ALMI was found for CT compared with CON (0.29 ± 0.13 kg/m2 vs. â0.11 ± 0.14 kg/m2, respectively; P 85%).
Conclusions
Combined training appears to be an effective means to counteract sarcopenia and improve various inflammatory markers and growth hormones in people living with HIV
Positive practices : solution-focused and narrative therapeutic techniques with children with sexually harmful behaviours
This article explores the use of solution-focused and Narrative Therapeutic approaches with a boy who had sexually harmful behaviours. The paper will highlight the practical challenges of working with someone who is 'problem-saturated' through institutionalisation and who is also subjected to powerful discourses claiming the 'truth' about him. The use of solution-focused and Narrative Therapeutic principles and approaches will be demonstrated in the work described, in a way that allows the reader to reflect on how these may differ from modernist understandings and responses to this behaviour
Chiral extrapolation of lattice moments of proton quark distributions
We present the resolution of a long-standing discrepancy between the moments
of parton distributions calculated from lattice QCD and their experimental
values. We propose a simple extrapolation formula for the moments of the
nonsinglet quark distribution u-d, as a function of quark mass, which embodies
the general constraints imposed by the chiral symmetry of QCD. The inclusion of
the leading nonanalytic behavior leads to an excellent description of both the
lattice data and the experimental values of the moments.Comment: 9 pages, 1 figure, to appear in Physical Review Letter
Chiral Behaviour of the Rho Meson in Lattice QCD
In order to guide the extrapolation of the mass of the rho meson calculated
in lattice QCD with dynamical fermions, we study the contributions to its
self-energy which vary most rapidly as the quark mass approaches zero; from the
processes and . It turns out that in
analysing the most recent data from CP-PACS it is crucial to estimate the
self-energy from using the same grid of discrete momenta as
included implicitly in the lattice simulation. The correction associated with
the continuum, infinite volume limit can then be found by calculating the
corresponding integrals exactly. Our error analysis suggests that a factor of
10 improvement in statistics at the lowest quark mass for which data currently
exists would allow one to determine the physical rho mass to within 5%.
Finally, our analysis throws new light on a long-standing problem with the
J-parameter.Comment: 13 pages, 7 figures. Full analytic forms of the self-energies are
included and a correction in the omega-pi self-energ
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