849 research outputs found
The protective effect of resistant starch in type 1 diabetic rats
Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by abnormal carbohydrate metabolism, insulin deficiency and subsequent hyperglycemia. Complications arise with poor glycemic control leading to the onset of microvascular and macrovascular diseases. Advanced glycation end products (AGEs) associated with hyperglycemia infiltrate microvascular tissues, ultimately leading to vascular disease of the nervous system, eyes and kidneys.1 Diabetic nephropathy is the leading cause of chronic kidney disease.2 The severity of this autoimmune disease is therefore independently and dependently associated with numerous pathologies such as cardiovascular disease, vitamin D deficiency and impaired one-carbon metabolism.
CKD is characterized by structural and functional changes of the glomerulus and renal tubules, which results in impaired filtration and reabsorption of various proteins and nutrients involved in methyl group metabolism and vitamin D metabolism. Declining glomerular filtration associated with renal disease is associated with hyperfiltration of vitamin D binding protein (DBP) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), disrupting vitamin D status and decreased homocysteine clearance and subsequent plasma homocysteine elevation.3-5 Understanding the mechanisms that mediate methyl group supply and homocysteine regulation is imperative in the prevention and treatment of these interrelated chronic diseases.
Alterations in key regulatory proteins within one-carbon metabolism have been observed in type 1 diabetes as compensatory mechanisms for disturbed homocysteine levels and methyl group supply. Previous research has demonstrated normalization of glycine N-methyltransferase (GNMT) and other regulatory proteins associated with administration of insulin, glucocorticoids and retinoic acid (RA). These results indicate the potential role of hormonal modulation in regulating one-carbon pathways.6 In addition, we have implemented the use of resistant starch (RS) in our laboratory as a therapeutic dietary agent for glycemic control in diabetes. In these studies, we have demonstrated the ability of RS to prevent and/or alleviate many DM-related complications including weight loss, hyperglycemia and diabetic nephropathy. In addition, RS-treatment normalized gene expression of proteins involved in vitamin D metabolism.
These results have illustrated the protective effect of RS in diabetes, specifically related to diabetic nephropathy and associated perturbations in vitamin D metabolism. The goal of this study was to investigate the effect of dietary RS in preventing/attenuating abnormalities related to diabetes perturbed methyl group metabolism. Furthermore, this study aimed to explore the possibility of RS and glucose as potential hormonal and nutritional modulators in methyl group metabolism using a streptozotocin (STZ)-induced model of T1DM
Path Integral Quantization of Cosmological Perturbations
We derive the first order canonical formulation of cosmological perturbation
theory in a Universe filled by a few scalar fields. This theory is quantized
via well-defined Hamiltonian path integral. The propagator which describes the
evolution of the initial (for instance, vacuum) state, is calculated.Comment: 16 pages, ETH-TH/94-0
Parallel quantized charge pumping
Two quantized charge pumps are operated in parallel. The total current
generated is shown to be far more accurate than the current produced with just
one pump operating at a higher frequency. With the application of a
perpendicular magnetic field the accuracy of quantization is shown to be 20
ppm for a current of pA. The scheme for parallel pumping presented in
this work has applications in quantum information processing, the generation of
single photons in pairs and bunches, neural networking and the development of a
quantum standard for electrical current. All these applications will benefit
greatly from the increase in output current without the characteristic decrease
in accuracy as a result of high-frequency operation
Surface Studies of Oxidation of a Single-Grain Quasicrystal
We have used Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) to characterize the surface properties of a single-grain Al70Pd21Mn9 (APM) quasicrystal (QC) upon oxidation. When oxygen is adsorbed on this surface, a disordered layer is formed at low coverages. This chemisorbed oxygen destroys the five-fold quasiperiodicity completely. Further adsorption of oxygen leads to a thin layer (less than 20 A) of AI oxide which passivates the surface. At elevated temperatures (870 K), adsorption of oxygen induces an enrichment of AI on the surface. This is explained by the exothermicity of its oxide and the possibility of increased mobility of AI at higher temperatures. Al is the only element in this QC which can be oxidized. No evidence of oxidization for Pd and Mn is observed
Evaluation of a portable image overlay projector for the visualisation of surgical navigation data: phantom studies
Introduction: Presenting visual feedback for image-guided surgery on a monitor requires the surgeon to perform time-consuming comparisons and diversion of sight and attention away from the patient. Deficiencies in previously developed augmented reality systems for image-guided surgery have, however, prevented the general acceptance of any one technique as a viable alternative to monitor displays. This work presents an evaluation of the feasibility and versatility of a novel augmented reality approach for the visualisation of surgical planning and navigation data. The approach, which utilises a portable image overlay device, was evaluated during integration into existing surgical navigation systems and during application within simulated navigated surgery scenarios. Methods: A range of anatomical models, surgical planning data and guidance information taken from liver surgery, cranio-maxillofacial surgery, orthopaedic surgery and biopsy were displayed on patient-specific phantoms, directly on to the patient's skin and on to cadaver tissue. The feasibility of employing the proposed augmented reality visualisation approach in each of the four tested clinical applications was qualitatively assessed for usability, visibility, workspace, line of sight and obtrusiveness. Results: The visualisation approach was found to assist in spatial understanding and reduced the need for sight diversion throughout the simulated surgical procedures. The approach enabled structures to be identified and targeted quickly and intuitively. All validated augmented reality scenes were easily visible and were implemented with minimal overhead. The device showed sufficient workspace for each of the presented applications, and the approach was minimally intrusiveness to the surgical scene. Conclusion: The presented visualisation approach proved to be versatile and applicable to a range of image-guided surgery applications, overcoming many of the deficiencies of previously described AR approaches. The approach presents an initial step towards a widely accepted alternative to monitor displays for the visualisation of surgical navigation dat
Photoelectron spectra of an Al70Pd21Mn9 quasicrystal and the cubic alloy Al60Pd25Mn15
Photoelectron spectra of a fivefold quasicrystalline alloy Al70Pd21Mn9 and a related cubic alloy Al60Pd25Mn15 reveal two noteworthy features. The first is that the Pd 3dlines fall at binding energies which are 2.2 eV higher than in pure Pd. A similar shift is observed for Pd in other alloys. The second noteworthy feature is that the Mn 2p3/2 line is very sharp in the quasicrystal. Fitting the experimental peaks with a Doniach-Sunjic line shpae suggests that the position and density of Mn states near EFis very sensitive to the structural and/or chemical environment of Mn in the alloys, and that this accounts for the shape of the 2p3/2 Mn line. The sharpness of the Mn line may be a fingerprint of the quasicrystalline phase within the AlPdMn family
The New White Flight
White charter school enclaves—defined as charter schools located in school districts that are thirty percent or less white, but that enroll a student body that is fifty percent or greater white— are emerging across the country. The emergence of white charter school enclaves is the result of a sobering and ugly truth: when given a choice, white parents as a collective tend to choose racially segregated, predominately white schools. Empirical research supports this claim. Empirical research also demonstrates that white parents as a collective will make that choice even when presented with the option of a more racially diverse school that is of good academic quality.
Despite the connection between collective white parental choice and school segregation, greater choice continues to be injected into the school assignment process. School choice assignment policies, particularly charter schools, are proliferating at a substantial rate. As a result, parental choice rather than systemic design is creating new patterns of racial segregation and inequality in public schools. Yet the Supreme Court’s school desegregation jurisprudence insulates racial segregation in schools ostensibly caused by parental choice rather than systemic design from regulation. Consequently, the new patterns of racial segregation in public schools caused by collective white parental choice largely escapes regulation by courts.
This article argues that the time has come to reconsider the legal and normative viability of regulating racial segregation in public schools caused by collective white parental choice. The article makes two important contributions to the legal literature on school desegregation. First, using white charter school enclaves as an example, it documents the ways in which school choice policies are being used to allow whites as a collective to satisfy their preference for segregated predominately white schools. Second, the article sets forth both constitutional and normative arguments for regulating the private choices that result in stark racial segregation patterns in public schools
Towards single-electron metrology
We review the status of the understanding of single-electron transport (SET)
devices with respect to their applicability in metrology. Their envisioned role
as the basis of a high-precision electrical standard is outlined and is
discussed in the context of other standards. The operation principles of single
electron transistors, turnstiles and pumps are explained and the fundamental
limits of these devices are discussed in detail. We describe the various
physical mechanisms that influence the device uncertainty and review the
analytical and numerical methods needed to calculate the intrinsic uncertainty
and to optimise the fabrication and operation parameters. Recent experimental
results are evaluated and compared with theoretical predictions. Although there
are discrepancies between theory and experiments, the intrinsic uncertainty is
already small enough to start preparing for the first SET-based metrological
applications.Comment: 39 pages, 14 figures. Review paper to be published in International
Journal of Modern Physics
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