Structural profile of ultra-high molecular weight polyethylene in acetabular cups worn on hip simulators characterized by confocal Raman spectroscopy

We applied a Raman confocal spectroscopic technique to quantitatively assess the structural features of two kinds of acetabular cups made of ultra-high molecular weight polyethylene. We wanted to know whether polyethylene cups belonging to different generations, and thus manufactured by different procedures, possess different molecular structures and how those differences affected their wear resistance. Emphasis was placed on oxidation profiles developed along the cross-sectional depth of the cups in the main wear zone developed during testing in a hip simulator. The micrometric lateral resolution of the laser beam, focused at surface or sub-surface sectional planes, enabled the visualization of highly resolved microstructural property profiles, including crystalline and amorphous phase fractions. Oxidation profiles retrieved from polyethylene cups belonging to different generations greatly differed after wear testing. The highly cross-linked polyethylene showed a lower degree of crystallinity and oxidation at an appreciably slower rate as compared to that belonging to an earlier generation. (C) 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:893-899, 201

In-depth oxidation and strain profiles in UHMWPE acetabular cups non-destructively studied by confocal Raman microprobe spectroscopy

Raman spectroscopy is used for the characterization of the two main mechanisms responsible for the degradation of acetabular cups in hip joints: creep deformation and oxidation. The term creep refers to the permanent deformation that occurs under the effect of body weight and does not completely recover after load release. This mechanism involves no mass loss from the sample, but packing and adjustment of the polyethylene molecules in their reciprocal positions under pressure. Conversely, oxidation triggers wear, which is accompanied by irreversible mass loss from the material: surface molecules of the polyethylene body oxidize, delaminate and are progressively peeled off, involving volumetric changes and resulting in debris formation. Both degradation mechanisms negatively interact and converge toward cup loosening, which requires revision surgery. In this paper, we show that confocal Raman spectroscopy can be used to separate the contributions to the dimensional change observed in acetabular cups arising from creep and from wear. Raman measurements are completely non-destructive and contactless, and can guide surgeons and materials technologists to optimize surface treatments and molecular structure of polyethylene cups, thus maximizing their in vivo lifetime. (C) Koninklijke Brill NV, Leiden, 200

Confocal Raman spectroscopic analysis of cross-linked ultra-high molecular weight polyethylene for application in artificial hip joints

Confocal spectroscopic techniques are applied to selected Raman bands to study the microscopic features of acetabular cups made of ultra-high molecular weight polyethylene (UHMWPE) before and after implantation in vivo. The micrometric lateral resolution of a laser beam focused on the polymeric surface (or subsurface) enables a highly resolved visualization of 2-D conformational population patterns, including crystalline, amorphous, orthorhombic phase fractions, and oxidation index. An optimized confocal probe configuration, aided by a computational deconvolution of the optical probe, allows minimization of the probe size along the in-depth direction and a nondestructive evaluation of microstructural properties along the material subsurface. Computational deconvolution is also attempted, based on an experimental assessment of the probe response function of the polyethylene Raman spectrum, according to a defocusing technique. A statistical set of high-resolution microstructural data are collected on a fully 3-D level on gamma-ray irradiated UHMWPE acetabular cups both as-received from the maker and after retrieval from a human body. Microstructural properties reveal significant gradients along the immediate material subsurface and distinct differences are found due to the loading history in vivo, which cannot be revealed by conventional optical spectroscopy. The applicability of the confocal spectroscopic technique is valid beyond the particular retrieval cases examined in this study, and can be easily extended to evaluate in-vitro tested components or to quality control of new polyethylene brands. Confocal Raman spectroscopy may also contribute to rationalize the complex effects of gamma-ray irradiation on the surface of medical grade UHMWPE for total joint replacement and, ultimately, to predict their actual lifetime in vivo. (c) 2007 Society of Photo-Optical Instrumentation Engineers

Psychiatric intervention and repeated admission to emergency centres due to drug overdose

Self-harm, with or without suicidal intent, substantially increases the risk of future suicide and is known to be the strongest predictor of completed suicide. Furthermore, repetition of self-harm is common: 16% of patients who self-harmed were found to repeat a similar episode within 1 year. Repetition of self-harm increases the risk of completed suicide. One study found overdose to be the most prevalent type of suicide attempt that required admission, and approximately 80% of self-harm episodes have been reported to involve overdose. It is therefore necessary to prevent the repetition of self-harm by drug overdose. According to clinical guidelines on the management of self-harm published in 2004, it is recommended that every patient presenting to hospital with self-harm should undergo a psychosocial assessment by specialists before being discharged. Despite this recommendation, some studies have found that many patients, especially those with repeated self-harm did not actually receive such assessments. That would suggest that the guideline has not been widely used – possibly because it was not based on firm evidence. There is a lack of data on the influence of psychosocial assessments on preventing repetition of self-harm. Some studies have suggested that such assessments do have an influence, but they were based on a small sample size or on a small number of highly advanced institutions. The present study focused on patients with drug overdose who were admitted to emergency centres. Using a national in-patient database in Japan, it aimed to investigate whether psychiatric intervention before discharge was associated with reduced patient readmissions with drug overdose.UTokyo Research掲載「過量服薬による入院患者と精神科医による診察の関係」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/psychiatric-intervention-and-repeated-emergency-admission-due-to-drug-overdose.htmlUTokyo Research "Psychiatric intervention and repeated emergency admission due to drug overdose" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/psychiatric-intervention-and-repeated-emergency-admission-due-to-drug-overdose.htm

Low-temperature Synthesis of FeTe0.5Se0.5 Polycrystals with a High Transport Critical Current Density

We have prepared high-quality polycrystalline FeTe0.5Se0.5 at temperature as low as 550{\deg}C. The transport critical current density evaluated by the current-voltage characteristics is over 700 A/cm2 at 4.2 K under zero field, which is several times larger than FeTe0.5Se0.5 superconducting wires. The critical current density estimated from magneto-optical images of flux penetration is also similar to this value. The upper critical field of the polycrystalline FeTe0.5Se0.5 at T = 0 K estimated by Werthamer-Helfand-Hohenberg theory is 585 kOe, which is comparable to that of single crystals. This study gives some insight into how to improve the performance of FeTe0.5Se0.5 superconducting wires.Comment: 12 pages, 6 figure

Effect of Serum Cholesterol on Insulin Secretory Capacity: Shimane CoHRE Study

<div><p>Objectives</p><p>Previous studies indicate that, in addition to the blood glucose level, the lipid level in the blood may affect functions of pancreatic beta cells. In this study, we aimed to examine whether there was a relationship between the serum level of total cholesterol (TC) and the insulin secretory capacity in healthy subjects.</p><p>Subjects and Methods</p><p>In participants of health examinations conducted from 2006 to 2010, we analyzed data from a total of 2,499 subjects (1,057 men and 1,442 women) after exclusion of individuals with dyslipidemia, thyroid dysfunction, diabetes, HbA1c≥6.5%, or fasting blood glucose≥126 mg/dL. Homeostasis model assessment for beta cell function (HOMA-beta) was utilized as a model representing the pancreatic beta cell function.</p><p>Results</p><p>Although the serum TC level had a positive correlation with HOMA-beta in a univariate correlation analysis, after adjustment by confounding factors in a multiple regression analysis, HOMA-beta had a negative correlation with TC. This was further confirmed in a multiple logistic regression analysis, showing that higher TC was an independent risk factor for decreased insulin secretory capacity (defined as HOMA-beta≤30%) together with higher age, lower BMI, lower TG, male sex and regular alcohol intake. After the participants were stratified by BMI into three groups, the effect of TC on HOMA-beta increased along with the increase in BMI, and it was highly significant in the highest tertile.</p><p>Conclusion</p><p>This cross-sectional study indicated that increased serum TC level might be related to the decrease of insulin secretory capacity in aged healthy population and that reduction of TC is more necessary in obese subjects to prevent diabetes.</p></div

Multiple linear regression analysis on HOMA-beta with various parameters.

<p>SE: standard error, std beta: standardized regression coefficient.</p

Multiple linear regression analysis on HOMA-beta in stratified tertile groups by BMI.

<p>SE: standard error, std beta: standardized regression coefficient.</p