The Rare Decay B→K∗γB\to K^{\ast}\gamma: A More Precise Calculation

Efforts to predict the rare exclusive decay $B\to K^{\ast}\gamma$ from the well known inclusive decay $b\to s\gamma$ are frustrated by the effect of the large recoil momentum. We show how to reduce the large uncertainty in calculating this decay by relating $B\to K^{\ast}\gamma$ to the semileptonic process $B\to\rho e\bar{\nu}$ using the heavy-quark symmetry in B decays and SU(3) flavor symmetry. A direct measurement of the $q^{2}$-spectrum for the semileptonic decay can provide accurate information for the exclusive rare decay.Comment: 15 pages, UTPT-93-02, in REVTEX with one figure in ep

New insights into the genetic etiology of Alzheimer's disease and related dementias.

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Numerical modeling of harmonic imaging and pulse inversion fields

Tissue Harmonic Imaging (THI) and Pulse Inversion (PI) Harmonic Imaging exploit the harmonics generated as a result of nonlinear propagation through tissue to improve the performance of imaging systems. A 3D finite difference model, that solves the KZK equation in the frequency domain, is used to investigate the finite amplitude fields produced by rectangular transducers driven with short pulses and their inverses, in water and homogeneous tissue. This enables the characteristic of the fields and the effective PI field to be calculated. The suppression of the fundamental field in PI is monitored, and the suppression of side lobes and a reduction in the effective beamwidth for each field are calculated. In addition, the differences between the pulse and inverse pulse spectra resulting from the use of very short pulses are noted, and the differences in the location of the fundamental and second harmonic spectral peaks observed

The peak rarefactional pressure generated by medical ultrasound systems in water and tissue: a numerical study

Current estimates of in-situ exposure are based on de-rating field measurements made in waterto allow for the attenuation of tissue, using a specific attenuation coefficient of 0.3 dB cm-1 MHz-1. This process assumes that the propagation process is linear. However for medical ultrasound systems nonlinear propagation effects can be significant. In order to explore improved methods of characterising finite amplitude fields an extensive programme of modelling has been performed with the aim of investigating the relationship between finite amplitude fields in tissue and water. This utilised a finite difference solution to the KZK equation to model 35 fields using starting conditions typical of medical ultrasound arrays. In each case the field was modelled in water and then in homogeneous tissue, assuming the specific attenuation coefficient of 0.3 dB cm-1 MHz-1. This enabled the de-rated peak rarefactional acoustic pressure (pr,α) at specific locations, derived from water predictions, to be compared with the corresponding predictions for the peak rarefactional pressure pr in tissue. The results show that a nonlinear propagation parameter and measurement range can be used to give a reasonably good indication of the extent to which pr,α underestimates pr in tissue. Corresponding results for the pulse intensity integral do not demonstrate such a simple relationship. (Work supportedby EPSRC under grant GR/R43747.

Measurement of the phase response of a membrane hydrophone and its application to ultrasonic field characterisation

The accurate measurement of acoustic waveforms containing multiple frequencies is complicated by the need to know the frequency dependent phase response of the measurement system. This is particularly relevant for high amplitude ultrasound propagation resulting in non-linear distortion. However, if the phase response of the system is known then the true acoustic waveform can be recovered. This work describes a means of obtaining the required phase response of a hydrophone and receiver system over a wide frequency range, its application, and impact on measurements

Numerical indicators of nonlinear propagation in acoustic fields

Measurements of acoustic exposure made in water and then derated to account for the attenuation of tissue can be distorted by nonlinear effects. We have evaluated numerical indicators of such distortion in diagnostic ultrasound fields.We evaluate the indicators of the degree of nonlinearity in diagnostic ultrasound fields that could be used to guarantee 'quasi-linearity' or to correct measurements made under nonlinear conditions. A new indicator, σi, is introduced which can be calculated using measurements currently being made in ultrasound test labs