220 research outputs found

    Theory of monolayers with boundaries: Exact results and Perturbative analysis

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    Domains and bubbles in tilted phases of Langmuir monolayers contain a class of textures knows as boojums. The boundaries of such domains and bubbles may display either cusp-like features or indentations. We derive analytic expressions for the textures within domains and surrounding bubbles, and for the shapes of the boundaries of these regions. The derivation is perturbative in the deviation of the bounding curve from a circle. This method is not expected to be accurate when the boundary suffers large distortions, but it does provide important clues with regard to the influence of various energetic terms on the order-parameter texture and the shape of the domain or bubble bounding curve. We also look into the effects of thermal fluctuations, which include a sample-size-dependent effective line tension.Comment: replaced with published version, 21 pages, 16 figures include

    LPMLE3 : a novel 1-D approach to study water flow in streambeds using heat as a tracer

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    We introduce LPMLE3, a new 1-D approach to quantify vertical water flow components at streambeds using temperature data collected in different depths. LPMLE3 solves the partial differential equation for coupled water flow and heat transport in the frequency domain. Unlike other 1-D approaches it does not assume a semi-infinite halfspace with the location of the lower boundary condition approaching infinity. Instead, it uses local upper and lower boundary conditions. As such, the streambed can be divided into finite subdomains bound at the top and bottom by a temperature-time series. Information from a third temperature sensor within each subdomain is then used for parameter estimation. LPMLE3 applies a low order local polynomial to separate periodic and transient parts (including the noise contributions) of a temperature-time series and calculates the frequency response of each subdomain to a known temperature input at the streambed top. A maximum-likelihood estimator is used to estimate the vertical component of water flow, thermal diffusivity, and their uncertainties for each streambed subdomain and provides information regarding model quality. We tested the method on synthetic temperature data generated with the numerical model STRIVE and demonstrate how the vertical flow component can be quantified for field data collected in a Belgian stream. We show that by using the results in additional analyses, nonvertical flow components could be identified and by making certain assumptions they could be quantified for each subdomain. LPMLE3 performed well on both simulated and field data and can be considered a valuable addition to the existing 1-D methods

    Metabolic profile of children with extrahepatic portal vein obstruction undergoing meso-Rex bypass

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    Background: Extrahepatic portal vein obstruction (EHPVO) in children is often associated with growth restriction, which improves after the restoration of portal venous flow with a meso-Rex bypass, but the physiologic mechanism is unknown. The purpose of this study was to investigate the mechanism of growth delay in children with EHPVO by detailing the metabolic and nutritional profile before and after meso-Rex bypass. / Methods: Twenty consecutive children with EHPVO were prospectively studied before and 1 year after meso-Rex bypass. Caloric balance was determined by investigating caloric intake via a calorie count, total energy expenditure via a doubly labeled water isotope assay and stool caloric loss by bomb calorimetry. Laboratory markers of nutrition and growth hormone resistance were tested. / Results: Fifteen of the 20 children underwent successful meso-Rex bypass at a median age of 4.3 years. Prealbumin level was abnormally low (14.6 Ā± 3.0 mg/dL) at surgery but improved (17.0 Ā± 4.3 mg/dL) 1 year later (P = 0.026). Mean insulin-like growth factor 1 (IGF-1) level at baseline was 1.57 standard deviations below normal. IGF-1 levels increased from 88.3 Ā± 38.9 to 117.3 Ā± 54.5 ng/mL in the year after surgery (P = 0.047). Caloric intake divided by basal metabolic rate (1.90 Ā± 0.61), total energy expenditure (97.2 Ā± 15.0% of expected), and stool caloric losses (3.7 Ā± 1.8% of caloric intake) were all normal at baseline. / Conclusions: Children with EHPVO suffer from malnutrition and growth hormone resistance, which may explain their well-established finding of growth restriction. Prealbumin and IGF-1 levels improve after a successful meso-Rex bypass

    A Soluble Guanylate Cyclaseā€“Dependent Mechanism Is Involved in the Regulation of Net Hepatic Glucose Uptake by Nitric Oxide in Vivo

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    OBJECTIVE We previously showed that elevating hepatic nitric oxide (NO) levels reduced net hepatic glucose uptake (NHGU) in the presence of portal glucose delivery, hyperglycemia, and hyperinsulinemia. The aim of the present study was to determine the role of a downstream signal, soluble guanylate cyclase (sGC), in the regulation of NHGU by NO. RESEARCH DESIGN AND METHODS Studies were performed on 42-hā€“fasted conscious dogs fitted with vascular catheters. At 0 min, somatostatin was given peripherally along with 4Ɨ basal insulin and basal glucagon intraportally. Glucose was delivered at a variable rate via a leg vein to double the blood glucose level and hepatic glucose load throughout the study. From 90 to 270 min, an intraportal infusion of the sGC inhibitor 1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one (ODQ) was given in āˆ’sGC (n = 10) and āˆ’sGC/+NO (n = 6), whereas saline was given in saline infusion (SAL) (n = 10). The āˆ’sGC/+NO group also received intraportal SIN-1 (NO donor) to elevate hepatic NO from 180 to 270 min. RESULTS In the presence of 4Ɨ basal insulin, basal glucagon, and hyperglycemia (2Ɨ basal ), inhibition of sGC in the liver enhanced NHGU (mg/kg/min; 210ā€“270 min) by āˆ¼55% (2.9 Ā± 0.2 in SAL vs. 4.6 Ā± 0.5 in āˆ’sGC). Further elevating hepatic NO failed to reduce NHGU (4.5 Ā± 0.7 in āˆ’sGC/+NO). Net hepatic carbon retention (i.e., glycogen synthesis; mg glucose equivalents/kg/min) increased to 3.8 Ā± 0.2 in āˆ’sGC and 3.8 Ā± 0.4 in āˆ’sGC/+NO vs. 2.4 Ā± 0.2 in SAL (P < 0.05). CONCLUSIONS NO regulates liver glucose uptake through a sGC-dependent pathway. The latter could be a target for pharmacologic intervention to increase meal-associated hepatic glucose uptake in individuals with type 2 diabetes

    Unexpected outcome from Trousseau syndrome

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    <p>Abstract</p> <p>Background</p> <p>Unprovoked superficial thrombophlebitis and subsequent venous thromboembolism are well-described albeit rare presenting features of advanced visceral malignancy that often manifest too late for curative intervention to be beneficial.</p> <p>Case Presentation</p> <p>We present the first reported case of early gastric carcinoma presenting with these paraneoplastic phenomena in an otherwise healthy farmer. The early presentation allowed for a curative partial gastrectomy, which itself was complicated by the presence of a deep vein thrombosis extending into the inferior vena cava. Fortunately, stabilization of the clot allowed for surgery to proceed without the need for a caval filter. The patient was referred for adjuvant chemotherapy and has since made an excellent recovery.</p> <p>Conclusions</p> <p>This case provides new evidence for the presentation of superficial thrombophlebitis in early gastric carcinoma and the potential for curative surgery in such instances. A high index of suspicion and a prompt diagnostic workup are essential for timely planning and execution of surgery in these early albeit rare presentations.</p

    Glacier loss and hydro-social risks in the Peruvian Andes

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    Accelerating glacier recession in tropical highlands and in the Peruvian Andes specifically is a manifestation of global climate change that is influencing the hydrologic cycle and impacting water resources across a range of socio-environmental systems. Despite predictions regarding the negative effects of long-term glacier decline on water availability, many uncertainties remain regarding the timing and variability of hydrologic changes and their impacts. To improve context-specific understandings of the effects of climate change and glacial melt on water resources in the tropical Andes, this article synthesizes results from long-term transdisciplinary research with new findings from two glacierized Peruvian watersheds to develop and apply a multi-level conceptual framework focused on the coupled biophysical and social determinants of water access and hydro-social risks in these contexts. The framework identifies several interacting variablesā€”hydrologic transformation, land cover change, perceptions of water availability, water use and infrastructure in local and regional economies, and water rights and governanceā€”to broadly assess how glacier change is embedded with social risks and vulnerability across diverse water uses and sectors. The primary focus is on the Santa River watershed draining the Cordillera Blanca to the Pacific. Additional analysis of hydrologic change and water access in the geographically distinct Shullcas River watershed draining the Huaytapallana massif towards the city of Huancayo further illuminates the heterogeneous character of hydrologic risk and vulnerability in the Andes

    Optimization of percutaneous biopsy for diagnosis and pretreatment risk assessment of neuroblastoma

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    BackgroundImage- guided percutaneous core needle biopsy (PCNB) is increasingly utilized to diagnose solid tumors. The objective of this study is to determine whether PCNB is adequate for modern biologic characterization of neuroblastoma.ProcedureA multi- institutional retrospective study was performed by the Pediatric Surgical Oncology Research Collaborative on children with neuroblastoma at 12 institutions over a 3- year period. Data collected included demographics, clinical details, biopsy technique, complications, and adequacy of biopsies for cytogenetic markers utilized by the Childrenā€™s Oncology Group for risk stratification.ResultsA total of 243 children were identified with a diagnosis of neuroblastoma: 79 (32.5%) tumor excision at diagnosis, 94 (38.7%) open incisional biopsy (IB), and 70 (28.8%) PCNB. Compared to IB, there was no significant difference in ability to accurately obtain a primary diagnosis by PCNB (95.7%ƂĀ vs 98.9%, PƂĀ =ƂĀ .314) or determine MYCN copy number (92.4%ƂĀ vs 97.8%, PƂĀ =ƂĀ .111). The yield for loss of heterozygosity and tumor ploidy was lower with PCNB versus IB (56.1%ƂĀ vs 90.9%, PƂĀ <ƂĀ .05; and 58.0%ƂĀ vs. 88.5%, PƂĀ <ƂĀ .05). Complications did not differ between groups (2.9 % vs 3.3%, PƂĀ =ƂĀ 1.000), though the PCNB group had fewer blood transfusions and lower opioid usage. Efficacy of PCNB was improved for loss of heterozygosity when a pediatric pathologist evaluated the fresh specimen for adequacy.ConclusionsPCNB is a less invasive alternative to open biopsy for primary diagnosis and MYCN oncogene status in patients with neuroblastoma. Our data suggest that PCNB could be optimized for complete genetic analysis by standardized protocols and real- time pathology assessment of specimen quality.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154667/1/pbc28153_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154667/2/pbc28153.pd

    Optimization of percutaneous biopsy for diagnosis and pretreatment risk assessment of neuroblastoma

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    Background: Image-guided percutaneous core needle biopsy (PCNB) is increasingly utilized to diagnose solid tumors. The objective of this study is to determine whether PCNB is adequate for modern biologic characterization of neuroblastoma. Procedure: A multi-institutional retrospective study was performed by the Pediatric Surgical Oncology Research Collaborative on children with neuroblastoma at 12 institutions over a 3-year period. Data collected included demographics, clinical details, biopsy technique, complications, and adequacy of biopsies for cytogenetic markers utilized by the Children\u27s Oncology Group for risk stratification. Results: A total of 243 children were identified with a diagnosis of neuroblastoma: 79 (32.5%) tumor excision at diagnosis, 94 (38.7%) open incisional biopsy (IB), and 70 (28.8%) PCNB. Compared to IB, there was no significant difference in ability to accurately obtain a primary diagnosis by PCNB (95.7% vs 98.9%, P =.314) or determine MYCN copy number (92.4% vs 97.8%, P =.111). The yield for loss of heterozygosity and tumor ploidy was lower with PCNB versus IB (56.1% vs 90.9%, P \u3c.05; and 58.0% vs. 88.5%, P \u3c.05). Complications did not differ between groups (2.9 % vs 3.3%, P = 1.000), though the PCNB group had fewer blood transfusions and lower opioid usage. Efficacy of PCNB was improved for loss of heterozygosity when a pediatric pathologist evaluated the fresh specimen for adequacy. Conclusions: PCNB is a less invasive alternative to open biopsy for primary diagnosis and MYCN oncogene status in patients with neuroblastoma. Our data suggest that PCNB could be optimized for complete genetic analysis by standardized protocols and real-time pathology assessment of specimen quality
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