Development of polymer composites using modified, high-structural integrity graphene platelets

Previous studies on polymer/graphene composites have mainly utilized either reduced graphene oxide or graphite nanoplatelets of over 10 nm in thickness. In this study we covalently modified 3-nm thick graphene platelets (GnPs) by the reaction between the GnPs’ epoxide groups and the end-amine groups of a commercial long-chain surfactant (Mw = 2000), compounded the modified GnPs (m-GnPs) with a model polymer epoxy, and investigated the structure and properties of both m-GnPs and their epoxy composites. A low Raman ID/IG ratio of 0.13 was found for m-GnPs corresponding to high structural integ-rity. A percolation threshold of electrical conductivity was observed at 0.32 vol% m-GnPs, and the 0.98 vol% m-GnPs improved the Young’s modulus, fracture energy release rate and glass transition tem-perature of epoxy by 14%, 387% and 13%, respectively. These significantly improved properties are cred-ited to: (i) the low Raman ID/IG ratio of GnPs, maximizing the structural integrity and thus conductivity, stiffness and strength inherited from its sister graphene, (ii) the low thickness of GnPs, minimizing the damaging effect of the poor through-plane mechanical properties and electrical conductivity of graphene,(iii) the high-molecular weight surfactant, leading to uniformly dispersed GnPs in the matrix, and (iv) a covalently bonded interface between m-GnPs and matrix, more effectively transferring load/electron across interface

S-nitrosylation of endogenous protein tyrosine phosphatases in endothelial insulin signaling.

Nitric oxide (NO) exerts its biological function through S-nitrosylation of cellular proteins. Due to the labile nature of this modification under physiological condition, identification of S-nitrosylated residue in enzymes involved in signaling regulation remains technically challenging. The present study investigated whether intrinsic NO produced in endothelium-derived MS-1 cells response to insulin stimulation might target endogenous protein tyrosine phosphatases (PTPs). For this, we have developed an approach using a synthetic reagent that introduces a phenylacetamidyl moiety on S-nitrosylated Cys, followed by detection with anti-phenylacetamidyl Cys (PAC) antibody. Coupling with sequential blocking of free thiols with multiple iodoacetyl-based Cys-reactive chemicals, we employed this PAC-switch method to show that endogenous SHP-2 and PTP1B were S-nitrosylated in MS-1 cells exposed to insulin. The mass spectrometry detected a phenylacetamidyl moiety specifically present on the active-site Cys463 of SHP-2. Focusing on the regulatory role of PTP1B, we showed S-nitrosylation to be the principal Cys reversible redox modification in endothelial insulin signaling. The PAC-switch method in an imaging format illustrated that a pool of S-nitrosylated PTP1B was colocalized with activated insulin receptor to the cell periphery, and that such event was endothelial NO synthase (eNOS)-dependent. Moreover, ectopic expression of the C215S mutant of PTP1B that mimics the active-site Cys215 S-nitrosylated form restored insulin responsiveness in eNOS-ablated cells, which was otherwise insensitive to insulin stimulation. This work not only introduces a new method that explores the role of physiological NO in regulating signal transduction, but also highlights a positive NO effect on promoting insulin responsiveness through S-nitrosylation of PTP1B's active-site Cys215

Statefinder diagnostic and stability of modified gravity consistent with holographic and new agegraphic dark energy

Recently one of us derived the action of modified gravity consistent with the holographic and new-agegraphic dark energy. In this paper, we investigate the stability of the Lagrangians of the modified gravity as discussed in [M. R. Setare, Int. J. Mod. Phys. D 17 (2008) 2219; M. R. Setare, Astrophys. Space Sci. 326 (2010) 27]. We also calculate the statefinder parameters which classify our dark energy model.Comment: 12 pages, 2 figures, accepted by Gen. Relativ. Gravi

Role of the supine lateral radiograph of the spine in vertebroplasty for osteoporotic vertebral compression fracture: a prospective study

<p>Abstract</p> <p>Background</p> <p>Severely collapsed vertebral compression fracture (VCF) is usually considered as a contraindication for vertebroplasty because of critically decreased vertebral height (less than one-third the original height). However, osteoporotic VCF can possess dynamic mobility with intravertebral cleft (IVC), which can be demonstrated on supine lateral radiographs (SuLR) and standing lateral radiographs (StLR). The purposes of this study were to: (1) evaluate the efficacy of SuLR to detect IVCs and assess the intravertebral mobility in VCFs, and (2) evaluate the short-term results of vertebroplasty in severely collapsed VCFs with IVCs.</p> <p>Methods</p> <p>We enrolled 37 patients with 40 symptomatic osteoporotic VCFs for vertebroplasty; 11 had severely collapsed VCFs with concurrent IVCs detected on the SuLR, the others had not-severely collapsed VCFs. A preoperative StLR, SuLR, magnetic resonance imaging (MRI), and postoperative StLR were taken from all patients. Radiographs were digitized to calculate vertebral body morphometrics including vertebral height ratio and Cobb's kyphotic angle. The intensity of the patient's pain was assessed by the visual analogue scale (VAS) on the day before operation and 1 day, 1 month, and 4 months after operation. The patient's VAS scores and image measurement results were assessed with the paired <it>t</it>-test and Pearson correlation tests; Mann-Whitney U test was used for VAS subgroup comparison. Significance was defined as <it>p </it>< 0.05.</p> <p>Results</p> <p>IVCs in patients with not-severely collapsed VCFs were detected in 21 vertebrae (72.4%) by MRI, in 15 vertebrae (51.7%) by preoperative SuLR, and in 7 vertebrae (24.1%) by preoperative StLR. Using the MRI as a gold standard to detect IVCs, SuLR exhibit a sensitivity of 0.71 as compared to StLR that yield a sensitivity of 0.33. In patients with VCFs with IVCs detected on SuLR, the average of the postoperative restoration in vertebral height ratio was significantly higher than that in those without IVCs (17.1% vs. 6.4%). There was no statistical difference in the VAS score between severely collapsed VCFs with IVCs detected on SuLR and not-severely collapsed VCFs at any follow-up time point.</p> <p>Conclusions</p> <p>The SuLR efficiently detects an IVC in VCF, which indicates a better vertebral height correction after vertebroplasty compared to VCF without IVC. Before performing a costly MRI, SuLR can identify more IVCs than StLR in patients with severely collapsed VCFs, whom may become the candidates for vertebroplasty.</p

Exponential ATP amplification through simultaneous regeneration from AMP and pyrophosphate for luminescence detection of bacteria

a b s t r a c t Bacteria monitoring is essential for many industrial manufacturing processes, particularly those involving in food, biopharmaceuticals, and semiconductor production. Firefly luciferase ATP luminescence assay is a rapid and simple bacteria detection method. However, the detection limit of this assay for Escherichia coli is approximately 10 4 colony-forming units (CFU), which is insufficient for many applications. This study aims to improve the assay sensitivity by simultaneous conversion of PP i and AMP, two products of the luciferase reaction, back to ATP to form two chain-reaction loops. Because each consumed ATP continuously produces two new ATP molecules, this approach can achieve exponential amplification of ATP. Two consecutive enzyme reactions were employed to regenerate AMP into ATP: adenylate kinase converting AMP into ADP using UTP as the energy source, and acetate kinase catalyzing acetyl phosphate and ADP into ATP. The PP i -recycling loop was completed using ATP sulfurylase and adenosine 5 0 phosphosulfate. The modification maintains good quantification linearity in the ATP luminescence assay and greatly increases its bacteria detection sensitivity. This improved method can detect bacteria concentrations of fewer than 10 CFU. This exponential ATP amplification assay will benefit bacteria monitoring in public health and manufacturing processes that require high-quality water. Ó 2011 Elsevier Inc. All rights reserved. Bacteria monitoring is essential for many industrial manufacturing processes, and particularly those involving food, semiconductors, and biopharmaceuticals. The presence of bacteria reduces production yield and may cause serious health problems in humans. Researchers have developed several rapid assays for detecting bacteria in water. These methods include polymerase chain reactions, fluorescence in situ hybridization [1], b-D-glucuronidase activity measurement The ATP luminescence assay is a rapid, sensitive, and easy-toperform method based on the detection of ATP, a molecule ubiquitously present in all living cells. The enzyme luciferase catalyzes the oxidation of the substrate luciferin while transforming the energy derived from ATP into light, which can be quantified by a luminometer. This assay has been widely used in bacteria monitoring for food hygiene [4] and surface cleanliness The current detection limit of the ATP luminescence method for Escherichia coli is approximately 10 4 colony-forming units (CFU) 1 [12,13], which is not sensitive enough for many industrial and medical applications. Several approaches have been adopted to improve the assay sensitivity. The first strategy involves the identification of chemical extractants that can effectively disrupt bacterial cells while not interfering with the luminescence assay. Both dimethyl sulfoxide (DMSO) 0003-2697/$ -see front matter

Two Loop Scalar Self-Mass during Inflation

We work in the locally de Sitter background of an inflating universe and consider a massless, minimally coupled scalar with a quartic self-interaction. We use dimensional regularization to compute the fully renormalized scalar self-mass-squared at one and two loop order for a state which is released in Bunch-Davies vacuum at t=0. Although the field strength and coupling constant renormalizations are identical to those of lfat space, the geometry induces a non-zero mass renormalization. The finite part also shows a sort of growing mass that competes with the classical force in eventually turning off this system's super-acceleration.Comment: 31 pages, 5 figures, revtex4, revised for publication with extended list of reference

Overexpression of podocalyxin-like protein is an independent factor of poor prognosis in colorectal cancer

Background:Podocalyxin-like 1 (PODXL) is a cell-adhesion glycoprotein and stem cell marker that has been associated with an aggressive tumour phenotype and poor prognosis in several forms of cancer. In this study, we investigated the prognostic impact of PODXL expression in colorectal cancer (CRC).Methods:Using tissue microarrays and immunohistochemistry, PODXL expression was evaluated in 536 incident CRC cases from a prospective, population-based cohort study. Kaplan-Meier analysis and Cox proportional hazards modelling were used to assess the impact of PODXL expression on cancer-specific survival (CSS) and overall survival (OS).Results:High PODXL expression was significantly associated with unfavourable clinicopathological characteristics, a shorter CSS (hazard ratio (HR)=1.98; 95% confidence interval (CI) 1.38-2.84, P<0.001) and 5-year OS (HR=1.85; 95% CI 1.29-2.64, P=0.001); the latter remaining significant in multivariate analysis (HR=1.52; 95% CI 1.03-2.25, P=0.036). In addition, in curatively resected stage III (T1-4, N1-2, M0) patients (n=122) with tumours with high PODXL expression, a significant benefit from adjuvant chemotherapy was demonstrated (p(interaction) =0.004 for CSS and 0.015 for 5-year OS in multivariate analysis).Conclusion:Podocalyxin-like 1 expression is an independent factor of poor prognosis in CRC. Our results also suggest that PODXL may be a useful marker to stratify patients for adjuvant chemotherapy