Spatially Varying Steady State Longitudinal Magnetization in Distant Dipolar Field-based Sequences

Sequences based on the Distant Dipolar Field (DDF) have shown great promise for novel spectroscopy and imaging. Unless spatial variation in the longitudinal magnetization, M_{z}(s), is eliminated by relaxation, diffusion, or spoiling techniques by the end of a single repetition, unexpected results can be obtained due to spatial harmonics in the steady state M_{z}^{SS}(s) profile. This is true even in a homogeneous single-component sample. We have developed an analytical expression for the M_{z}^{SS}(s) profile that occurs in DDF sequences when smearing by diffusion is negligible in the TR period. The expression has been verified by directly imaging the M_{z}^{SS}(s) profile after establishing the steady state. more keywords: magnetic resonance, intermolecular multiple quantum coherence, mesoscale structure, iMQC, DDFComment: 7 pages, 4 figures, submitted to Journal of Magnetic Resonanc

Is There a Need for Preoperative Imaging of the Internal Mammary Recipient Site for Autologous Breast Reconstruction?

Preoperative imaging of recipient-site vasculatur in autologous breast reconstruction may potentiate improved outcomes through the identification of individual variations in vascular architecture. There are a range of both normal and pathologic states which can substantially affect the internal mammary vessels in particular, and the identification of these preoperatively may significantly affect operative approach. There are a range of imaging modalities available, with ultrasound particularly useful, and computed tomography angiography (CTA) evolving as a useful option, albeit with radiation exposure. The benefits of CTA must be balanced against its risks, which include contrast nephrotoxicity and allergic reactions, and radiation exposure. The radiation risk with thoracic imaging is substantially higher than that for donor sites, such as the abdominal wall, with reasons including exposure of the contralateral breast to radiation (with a risk of contralateral breast cancer in this population 2 to 6 times higher than that of primary breast cancer, reaching a 20-year incidence of 15%), as well as proximity to the thyroid gland. Current evidence suggests that although many cases may not warrant such imaging because of risk, the benefits of preoperative CTA in selected patients may outweigh the risks of exposure, prompting an individualized approach

Solvent-switchable continuous-breathing behaviour in a diamondoid metal–organic framework and its influence on CO2 versus CH4 selectivity

Understanding the behaviour of flexible metal–organic frameworks (MOFs)—porous crystalline materials that undergo a structural change upon exposure to an external stimulus—underpins their design as responsive materials for specific applications, such as gas separation, molecular sensing, catalysis and drug delivery. Reversible transformations of a MOF between open- and closed-pore forms—a behaviour known as ‘breathing’—typically occur through well-defined crystallographic transitions. By contrast, continuous breathing is rare, and detailed characterization has remained very limited. Here we report a continuous-breathing mechanism that was studied by single-crystal diffraction in a MOF with a diamondoid network, (Me2NH2)[In(ABDC)2] (ABDC, 2-aminobenzene-1,4-dicarboxylate). Desolvation of the MOF in two different solvents leads to two polymorphic activated forms with very different pore openings, markedly different gas-adsorption capacities and different CO2 versus CH4 selectivities. Partial desolvation introduces a gating pressure associated with CO2 adsorption, which shows that the framework can also undergo a combination of stepped and continuous breathing

Humanizing Student–Teacher Relationships for Black Children: Implications for Teachers’ Social–Emotional Training

A growing number of scholars in the field of urban education compellingly demonstrate the myriad ways U.S. schooling for Black youth is dehumanizing. Social and emotional learning (SEL), particularly, transformative social emotional learning (TSEL) has come to the fore as a promising intervention to promote positive inclusive school cultures and relationships while recognizing and accounting for the realities of racial oppression. Here, we discuss teachers’ capacity to develop and negotiate student–teacher relationships that acknowledge and actively confront the dehumanization of Black youth in schools. We provide recommendations for teachers’ social emotional training that can effectively humanize learning environments for Black youth

A multi-layer extension of the stochastic heat equation

Motivated by recent developments on solvable directed polymer models, we define a 'multi-layer' extension of the stochastic heat equation involving non-intersecting Brownian motions.Comment: v4: substantially extended and revised versio

Threshold bounce — occupancy-dependent modulation of the discriminating threshold in silicon detectors

The front-end electronics of silicon detectors are typically designed to ensure optimal noise performance for the expected input charge. A combination of preamplifiers and shaper circuits result in a nontrivial response of the front-end to injected charge, and the magnitude of the response may be sizeable in readout windows subsequent to that in which the charge was initially injected. The modulation of the discriminator threshold due to the superposition of the front-end response across multiple readout windows is coined “threshold bounce”. In this paper, we report a measurement of threshold bounce using silicon modules built for the Phase-II Upgrade of the ATLAS detector at the Large Hadron Collider. These modules utilize ATLAS Binary Chips for their hit readout. The measurement was performed using a micro-focused 15 keV photon beam at the Diamond Light Source synchrotron. The effect of the choice of photon flux and discriminator threshold on the magnitude of the threshold bounce is studied. A Monte Carlo simulation which accounts for the front-end behaviour of the silicon modules is developed, and its predicted hit efficiency is found to be in good agreement with the measured hit efficiency

Non-intersecting squared Bessel paths: critical time and double scaling limit

We consider the double scaling limit for a model of $n$ non-intersecting squared Bessel processes in the confluent case: all paths start at time $t=0$ at the same positive value $x=a$, remain positive, and are conditioned to end at time $t=1$ at $x=0$. After appropriate rescaling, the paths fill a region in the $tx$--plane as $n\to \infty$ that intersects the hard edge at $x=0$ at a critical time $t=t^{*}$. In a previous paper (arXiv:0712.1333), the scaling limits for the positions of the paths at time $t\neq t^{*}$ were shown to be the usual scaling limits from random matrix theory. Here, we describe the limit as $n\to \infty$ of the correlation kernel at critical time $t^{*}$ and in the double scaling regime. We derive an integral representation for the limit kernel which bears some connections with the Pearcey kernel. The analysis is based on the study of a $3\times 3$ matrix valued Riemann-Hilbert problem by the Deift-Zhou steepest descent method. The main ingredient is the construction of a local parametrix at the origin, out of the solutions of a particular third-order linear differential equation, and its matching with a global parametrix.Comment: 53 pages, 15 figure

High anti-cryptosporidium parvum igg seroprevalence in hiv-infected adults in limpopo, south africa

A seroepidemiological study was performed to determine the seroprevalence of Cryptosporidium in human immunodeficiency virus (HIV)-infected adults and local university students in the Limpopo Province, South Africa. Using a custom anti-C. parvum immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA), the seroprevalence of Cryptosporidium was found to be significantly higher (75.3%; 146 of 193) in HIV-infected individuals compared with student volunteers (32.8%; 19 of 58) (P < 0.001). A more recent diagnosis of HIV was associated with anti-C. parvum IgG seropositivity, as was lower weight among HIV-infected women. This is the first seroepidemiologic study of Cryptosporidium in rural South Africa, and it shows high endemicity among the HIV-infected population. In addition to raising the possibility of significant Cryptosporidium-related morbidities, this finding reveals that in Limpopo and perhaps in other low-income, rural populations, interrupting waterborne pathogen transmission will require strategies effective against environmentally hardy parasites such as Cryptosporidium