Low-Frequency Radio Transients in the Galactic Center

We report the detection of a new radio transient source, GCRT J1746-2757, located only 1.1 degrees north of the Galactic center. Consistent with other radio transients toward the Galactic center, this source brightened and faded on a time scale of a few months. No X-ray counterpart was detected. We also report new 0.33 GHz measurements of the radio counterpart to the X-ray transient source, XTE J1748-288, previously detected and monitored at higher radio frequencies. We show that the spectrum of XTE J1748-288 steepened considerably during a period of a few months after its peak. We also discuss the need for a more efficient means of finding additional radio transients

A powerful bursting radio source towards the Galactic Centre

Transient astronomical sources are typically powered by compact objects and usually signify highly explosive or dynamic events. While radio astronomy has an impressive record of obtaining high time resolution observations, usually it is achieved in quite narrow fields-of-view. Consequently, the dynamic radio sky is poorly sampled, in contrast to the situation in the X- and gamma-ray bands in which wide-field instruments routinely detect transient sources. Here we report a new transient source, GCRT J1745-3009, detected in 2002 during a moderately wide-field radio transient monitoring program of the Galactic center (GC) region at 0.33 GHz. The characteristics of its bursts are unlike those known for any other class of radio transient. If located in or near the GC, its brightness temperature (~10^16 K) and the implied energy density within GCRT J1745-3009 vastly exceeds that observed in most other classes of radio astronomical sources, and is consistent with coherent emission processes rarely observed. We conclude that GCRT J1745-3009 is the first member of a new class of radio transient sources, the first of possibly many new classes to be identified through current and upcoming radio surveys.Comment: 16 pages including 3 figures. Appears in Nature, 3 March 200

Pain location and widespread pain in youth with orthopaedic conditions: Exploration of the reliability and validity of a body map

BackgroundPain location and widespread pain are important but underexamined dimensions of paediatric pain. Body map tools to assess pain location in youth have been used for several decades, but few studies have established reliability and validity of these measures. The purpose of this study was to explore the reliability and validity of a pain body map among youth with orthopaedic conditions before surgery.MethodYouth ages 10â 17 years completed the body map and other selfâ reported outcomes at their preoperative clinic visit and at their day of surgery.ResultsMost (91.7%) youth had small discrepancy between body map scores at preoperative clinic visit (baseline) and day of surgery (second assessment), and siteâ toâ site agreement ranged from 78% to 98%. Those with back and lower extremity diagnoses had high correspondence between body map sites and diagnostic sites. Body map scores and widespread pain were associated with other dimensions of pain, as well as other patientâ reported outcomes. Higher pain intensity and widespread pain predicted greater discrepancy between body map scores.ConclusionsThese results support the use of body map tools in further research examining widespread pain among youth by demonstrating adequate reliability, descriptive validity and associative validity.SignificanceThese results contribute to the limited information regarding psychometric properties of paediatric pain body maps, provide novel information about widespread pain among youth undergoing orthopaedic surgeries, and pave the way for improved assessment and treatment of paediatric pain.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147159/1/ejp1282.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147159/2/ejp1282_am.pd

Missed Visits Associated With Future Preexposure Prophylaxis (PrEP) Discontinuation Among PrEP Users in a Municipal Primary Care Health Network

BackgroundMaintaining retention in preexposure prophylaxis (PrEP) care among diverse patient populations will be needed to support PrEP's efficacy. We characterized patterns of PrEP care retention in a US municipal primary care health network and examined whether missed visits, a metric of care retention that is easy to evaluate in clinic, are associated with subsequent discontinuation.MethodsWe included individuals on PrEP from July 2012 until August 2017 in the San Francisco Primary Care Clinics, a 15-clinic municipal health network. We categorized PrEP usage patterns as follows: early discontinuation (<90 days), later discontinuation (after ≥90 days), and continuing use at the end of follow-up. We first examined early discontinuation using adjusted Poisson regression. In patients who continued PrEP for ≥90 days, we examined factors associated with late discontinuation.ResultsOf the 364 individuals who started PrEP, 16% discontinued PrEP before 90 days, 46% discontinued later, and 38% were retained in care over a median 12 months of observation. Transgender women were more likely to discontinue PrEP early (adjusted risk ratio; 2.16; 95% confidence interval, 1.36-3.49), and younger users were more likely to discontinue late (0.82 per 10-year increase in age; .70-.96), as were persons who use illicit drugs (1.59; 1.02-2.47). Missed visits during use of PrEP were associated with future discontinuation (adjusted risk ratio, 1.52; 95% confidence interval, 1.14-2.03). Later year of current PrEP use was associated with both early and late discontinuation.ConclusionDiverse populations may require differentiated care to continue PrEP. Missed visits should trigger tailored interventions to maximize the impact of PrEP

Brief Report

BackgroundTimely pre-exposure prophylaxis (PrEP) initiation is critical in at-risk populations, given that HIV acquisition risk persists during delays. Time to treatment initiation, a key metric in HIV care, has not been explored among PrEP users. Interventions that reduce time to PrEP initiation could prevent HIV infections.SettingIndividuals initiating PrEP in a large primary care health network of 15 clinics, the San Francisco Primary Care Clinics (SFPCC), from July 2012 to July 2017 (N = 411).MethodsWe examined factors associated with time from first PrEP discussion with a provider to PrEP initiation date using an adjusted Cox proportional-hazards model, with hazard ratios (HRs) >1 indicating earlier initiation. We also examined the relationship between delayed PrEP initiation and PrEP persistence (staying on PrEP) in an adjusted Cox proportional-hazards model.ResultsPrEP users initiated PrEP after a median of only 7 days. However, there were notable outliers, with 29% waiting >30 days and 12% waiting >90 days. In an adjusted proportional-hazards model, a panel management and patient navigation intervention was associated with earlier PrEP initiation [HR: 1.5; 95% confidence interval (CI): 1.1 to 2.0], whereas only other race/ethnicity compared with white race was associated with delayed PrEP initiation (HR: 0.7; 95% CI: 0.5 to 1.0). Delayed PrEP initiation >30 days was associated with shorter PrEP persistence in an adjusted proportional-hazards model (HR: 1.3; 95% CI: 1.0 to 1.7).ConclusionsPrEP initiation within a week is feasible in a primary care safety-net health system. Setting a goal of rapid PrEP initiation, with the support of panel management and patient navigation, could address delays in at-risk groups

Racial/ethnic and HIV risk category disparities in preexposure prophylaxis discontinuation among patients in publicly funded primary care clinics.

ObjectiveDissemination of preexposure prophylaxis (PrEP) is a priority for reducing new HIV infections, especially among vulnerable populations. However, there are limited data available on PrEP discontinuation following initiation, an important component of the PrEP cascade.DesignPatients receiving PrEP within the San Francisco Department of Public Health Primary Care Clinics (SFPCC) are included in a PrEP registry if they received a PrEP prescription, were not receiving postexposure prophylaxis, and not known to be HIV-positive.MethodsWe calculated PrEP discontinuation for patients initiating PrEP at any time from January 2012 to July 2017 and evaluated their association with demographic and risk variables using Cox regression analysis.ResultsOverall, 348 patients received PrEP over the evaluation period. The majority (84%) were men, and the cohort was racially/ethnically diverse. The median duration of PrEP use was 8.3 months. In adjusted analysis, PrEP discontinuation was lower among older patients (aHR 0.89; 95% CI 0.80-0.99; P = 0.03); but higher among black patients (compared with white patients; aHR 1.87; 95% CI 1.27-2.74; P = 0.001), patients who inject drugs (aHR 4.80; 95% CI 2.66-8.67; P < 0.001), and transgender women who have sex with men (compared with MSM; aHR 1.94; 95% CI 1.36-2.77; P < 0.001).ConclusionAge, racial/ethnic, and risk category disparities in PrEP discontinuation were identified among patients in a public health-funded primary care setting. Further efforts are needed to understand and address PrEP discontinuation among priority populations to maximize the preventive impact of PrEP, and reverse HIV-related disparities at a population level

Authorsâ reply to the letter to the editor by Sabour

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147224/1/ejp1345.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147224/2/ejp1345_am.pd

Time evolution of models described by one-dimensional discrete nonlinear Schr\"odinger equation

The dynamics of models described by a one-dimensional discrete nonlinear Schr\"odinger equation is studied. The nonlinearity in these models appears due to the coupling of the electronic motion to optical oscillators which are treated in adiabatic approximation. First, various sizes of nonlinear cluster embedded in an infinite linear chain are considered. The initial excitation is applied either at the end-site or at the middle-site of the cluster. In both the cases we obtain two kinds of transition: (i) a cluster-trapping transition and (ii) a self-trapping transition. The dynamics of the quasiparticle with the end-site initial excitation are found to exhibit, (i) a sharp self-trapping transition, (ii) an amplitude-transition in the site-probabilities and (iii) propagating soliton-like waves in large clusters. Ballistic propagation is observed in random nonlinear systems. The effect of nonlinear impurities on the superdiffusive behavior of random-dimer model is also studied.Comment: 16 pages, REVTEX, 9 figures available upon request, To appear in Physical Review

A Study of The Formation of Stationary Localized States Due to Nonlinear Impurities Using The Discrete Nonlinear Schr\"odinger Equation

The Discrete Nonlinear Schr$\ddot{o}$dinger Equation is used to study the formation of stationary localized states due to a single nonlinear impurity in a Caley tree and a dimeric nonlinear impurity in the one dimensional system. The rotational nonlinear impurity and the impurity of the form $-\chi \mid C \mid^{\sigma}$ where $\sigma$ is arbitrary and $\chi$ is the nonlinearity parameter are considered. Furthermore, $\mid C \mid$ represents the absolute value of the amplitude. Altogether four cases are studies. The usual Greens function approach and the ansatz approach are coherently blended to obtain phase diagrams showing regions of different number of states in the parameter space. Equations of critical lines separating various regions in phase diagrams are derived analytically. For the dimeric problem with the impurity $-\chi \mid C \mid^{\sigma}$, three values of $\mid \chi_{cr} \mid$, namely, $\mid \chi_{cr} \mid = 2$, at $\sigma = 0$ and $\mid \chi_{cr} \mid = 1$ and $\frac{8}{3}$ for $\sigma = 2$ are obtained. Last two values are lower than the existing values. Energy of the states as a function of parameters is also obtained. A model derivation for the impurities is presented. The implication of our results in relation to disordered systems comprising of nonlinear impurities and perfect sites is discussed.Comment: 10 figures available on reques