Heat transport through diffusive interfaces Flanagan, Jason D.; Lefler, Angela S.; Radko, Timour
Geophysical research letters,
28 May 2013, Letnik:
40, Številka:
10
Journal Article
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Odprti dostop
We perform a series of 3‐D Direct Numerical Simulations (DNS) to assess the vertical heat transport through thermohaline staircases in the Arctic Ocean. The diagnostics of DNS, performed for the ...first time in the realistic parameter range, result in vertical fluxes exceeding those of extant “four‐thirds flux laws” by as much as a factor of 2 and suggest that the 4/3 exponent may require downward revision. Through a series of equivalent 2‐D DNS, we show that they are consistent with their more resource‐intensive 3‐D counterparts for sufficiently large density ratio (Rρ) but underestimate heat transport for low Rρ. Finally, we examine the role of boundary conditions in controlling the vertical heat transport. Rigid boundaries—a necessary ingredient in laboratory‐derived flux‐laws—are shown to reduce the estimates of heat fluxes relative to the corresponding periodic boundary conditions.
Key Points
A new flux law describing vertical heat transport is formulatedHigh resolution 3D DNS relevant to Arctic staircases are performedThe validity of the four‐thirds flux law exponent is testedThe effects of different boundary conditions are examined
This study examines the interaction of diffusive convection and shear through a series of 2D and 3D direct numerical simulations (DNS). The model employed is based on the Boussinesq equations of ...motion with oscillating shear represented by a forcing term in the momentum equation. This study calculates thermal diffusivities for a wide range of Froude numbers and density ratios and compares the results with those from the analysis of observational data gathered during a 2005 expedition to the eastern Weddell Sea. The patterns of layering and the strong dependence of thermal diffusivity on the density ratio described here are in agreement with observations. Additionally, the authors evaluate salinity fluxes that are inaccessible from field data and formulate a parameterization of buoyancy transport. The relative significance of double diffusion and shear is quantified through comparison of density fluxes, efficiency factor, and dissipation ratio for the regimes with/without diffusive convection. This study assesses the accuracy of the thermal production dissipation and turbulent kinetic energy balances, commonly used in microstructure-based observational studies, and quantifies the length of the averaging period required for reliable statistics and the spatial variability of heat flux.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Striated muscle-specific disruption of the dystroglycan
(DAG1) gene results in loss of the dystrophin-glycoprotein complex in differentiated muscle and a remarkably mild muscular dystrophy with ...hypertrophy and without tissue fibrosis. We find that satellite cells, expressing dystroglycan, support continued efficient regeneration of skeletal muscle along with transient expression of dystroglycan in regenerating muscle fibers. We demonstrate a similar phenomenon of reexpression of functional dystroglycan in regenerating muscle fibers in a mild form of human muscular dystrophy caused by disruption of posttranslational dystroglycan processing. Thus, maintenance of regenerative capacity by satellite cells expressing dystroglycan is likely responsible for mild disease progression in mice and possibly humans. Therefore, inadequate repair of skeletal muscle by satellite cells represents an important mechanism affecting the pathogenesis of muscular dystrophy.
INTRODUCTION:The American College of Obstetricians and Gynecologists recommends offering preconception and prenatal screening to all couples for cystic fibrosis, whereas the American College of ...Medical Genetics also recommends screening for spinal muscular atrophy. Both groups suggest specific screening if there is a family or personal history of a genetic disease or if the individual is from a high-risk ethnic group. The purpose of this study was to determine whether availability of a more comprehensive, affordable genetic screening tool increased the number of infertility patients choosing to be screened for cystic fibrosis and other genetic diseases.
METHODS:This was a retrospective chart review of new infertility patients evaluated between May 2010 and May 2013. These couples had a detailed pedigree and were offered the Counsyl expanded carrier screening test.
RESULTS:Sixteen hundred sixty-nine new infertility couples were offered Counsyl expanded carrier screening. The carrier frequency for cystic fibrosis was 6.8% with 0% of the couples concordant heterozygotes. The carrier frequency for spinal muscular atrophy was 2.51% with 0% of the couples concordant heterozygotes. Fragile X premutation was found in 2.78% (2/72).
CONCLUSIONS:With availability of the Counsyl screening test, the percentage of new infertility patients choosing to have preconception genetic screening increased from 2% to 8%. The largest increase (17.5% of new patients) in screening followed the reduction in out-of-pocket expense in May 2012. Infertility patients are in a unique position to investigate their family history, discuss appropriate preconception genetic screening, and, if discovered to be at high risk of a genetic illness, review their reproductive options.
Reimbursement for genetic counseling services was examined at a single institution. Patient encounters utilizing the 96040 CPT® code from 7/31/2009 through 7/31/2013 were reviewed. Exclusion criteria ...included billing records of patients seen by a physician the same day, self-pay, Medicaid, and Medicare patients. Of the 8,630 encounters with a genetic counselor, 582 encounters were eligible for review. Descriptive statistics (i.e., percentage of encounters receiving some level of reimbursement, average reimbursement rate, number of third party payors providing any level of reimbursement, and number of ICD-9 codes receiving any level of reimbursement) depicted reimbursement of the 96040 CPT® code for the encounters analyzed. Statistical analysis found a significant difference in reimbursement between third party payors that do and do not credential genetic counselors (
p
< .0001). There was no statistically significant difference between reimbursement rates for primary diagnostic ICD-9 codes when compared to primary diagnostic ICD-9 V codes used. Results will provide a useful baseline for local and national comparisons due to the paucity of data regarding CPT® 96040.
Purpose of Review
The understanding of genetic contributions to miscarriage and infertility have benefited from advancements in genetic technologies, such as chromosomal microarray and next ...generation sequencing. Even with these modern tools, there continue to be disparities in management and counseling. This review explores recent genetic advances in reproductive health and provides evidence that genetic counseling by a genetic counselor empowers individuals to make appropriate reproductive decisions based upon their experience and values.
Recent Findings
The standard of care for products of conception testing is now chromosomal microarray. Genetic testing should be considered in cases of low sperm count, premature ovarian failure, and in context of family history. Expanded reproductive options, including preimplantation genetic testing, may increase the chances of live birth in cases of recurrent miscarriage, age-related infertility, and previous failed IVF cycles.
Summary
Modern genetic tools may delineate underlying causes of infertility or miscarriage. In addition to processing the complex emotions related to infertility and miscarriage, patients also value understanding the genetic contributions when making informed decisions about reproductive health.
We review 3 cases where array comparative genomic hybridization made a difference in the medical management of the patient, ended the diagnostic odyssey, predicted prognosis for the patient, and/or ...provided closure to the family. Comparative genomic hybridization is a useful tool for testing individuals with clinical examinations suggestive of a genetic syndrome but in which a specific syndrome may be difficult to pinpoint. The cost is similar to that of a standard karyotype but there is a higher yield in children and adults with clinical signs of a genetic syndrome.
ABSTRACT
Aquaporins are a growing family of transmembrane proteins that transport water and, in some cases, glycerol and urea across cellular membranes. Aquaporin‐4 (AQP4) is enriched at the ...sarcolemma of skeletal muscle and may play a role in accommodating the rapid changes in cell volume and hydrostatic forces that occur during contraction in order to prevent damage to the sarcolemma. Recent evidence has shown that AQP4 is absent in dystrophindeficient mdx mice, suggesting that AQP4 associates with dystrophin and has a role in the dystrophic process. To examine the relationship between aquaporins and muscle disease, and between aquaporins and dystrophin, we have investigated aquaporin expression in various mouse models of muscular dystrophy and cardiomyopathy before and after the onset of pathology. We find that AQP4 is expressed in prenecrotic mdx muscle despite the absence of dystrophin and that AQP4 is lost after the onset of muscle degeneration. Analysis of various dystrophin transgenic mice reveals that AQP4 is lost even when the dystrophin‐glycoprotein complex is present, suggesting that loss of AQP4 is not directly resulting from loss of the DGC. AQP4 was also lost in muscular dystrophies caused by primary mutations in the sarcoglycan genes. Taken together, our data demonstrate that AQP4 loss in skeletal muscle correlates with muscular dystrophy and is a common feature of pathogenesis.—Crosbie, R. H., Dovico, S. A., Flanagan, J. D., Chamberlain, J. S., Ownby, C. L., Campbell, K. P. Characterization of aquaporin‐4 in muscle and muscular dystrophy. FASEB J. 16, 943–949 (2002)
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