Prediction of the thermal conductivity of polar pure liquids

Abstract

A relatively simple technique for the prediction of the thermal conductivity of polar organic fluids over the temperature range from 0° to 100°C is presented. The proposed model is basically derived via the generalized property correlation model developed by Riazi and Daubert in 1980. The method requires, as input, only normal boiling point, specific gravities and dipole moments or acentric factors for each compound of interest. Predicted thermal conductivities are compared with 93 literature data for 12 polar liquids. Average deviation between prediction and experiment is approximately within 8–12%, depending on the type of third input parameter, as opposed to 17% for the much involved method of Robins and Kingrea previously recommended.     

Short-Time Oxidation Behavior of Low-Carbon, Low-Silicon Steel in Air at 850–1180 °C: II. Linear to Parabolic Transition Determined Using Existing Gas-Phase Transport and Solid-Phase Diffusion Theories

Existing gas-phase transport and solid-phase diffusion theories are used to calculate the oxidation kinetics of low carbon and low silicon steel in flowing air at 850–1180 °C. The linear-to-parabolic transition scale thickness derived is proportional to the parabolic rate constant and inversely proportional to the linear rate constant. Calculated parabolic rate constants are consistent with experimental results, whereas calculated linear rate constants are 40% smaller and calculated linear-to-parabolic transition scale thicknesses are 20–40% greater than the experimental results. Introduction of a correction factor cannot simultaneously resolve the discrepancies. Various sources causing the discrepancies are discussed. One important issue identified is that the conditions for deriving the equation for calculating the linear rate constant are different from those in laboratory furnaces. The linear-to-parabolic transition scale thickness derived is also a function of gas composition, gas velocity and sample length. An intrinsic gas-phase mass-transfer factor, independent of gas velocity and sample size, is recommended to express the gas-phase mass-transfer coefficient for calculating the linear rate constant.     

High-Performance Switched Reluctance Brushless Drives

Switched reluctance (SR) drives offer the advantages of simple and robust motor construction, high speeds, high overall efficiencies over a wide operating range of torque and speed, simple power converter circuits with a reduced number of switches, and excellent controllability. The basis of these claims is explained. The history of the SR system, in particular the extensive research at Nottingham and Leeds Universities, and the basic operating principles and design considerations for motors and power converters are reviewed. Alternative configurations are discussed. The difficulties of establishing a simple mathematical model for the motor and of calculating torque and inverter VA requirements are examined. A comparison of the VA requirements for SR and pulsewidth modulation (PWM) is given for a 7.85-kW system. Measured drive performance is discussed in terms of efficiency over an operating envelope, specific output, controllability, and power converter ratings. Earlier traction drives, incorporating a constant power range and including regeneration, are reported together with the constant torque industrial drives and more recent traction extensions. The long-term potential of the drive is discussed for a wide range of applications. A comprehensive list of references is provided.     

The sizes of peptides generated from protein by mammalian 26 and 20 S proteasomes. Implications for understanding the degradative mechanism and antigen presentation

Knowledge about the sizes of peptides generated by proteasomes during protein degradation is essential to fully understand their degradative mechanisms and the subsequent steps in protein turnover and generation of major histocompatibility complex class I antigenic peptides. We demonstrate here that 26 S and activated 20 S proteasomes from rabbit muscle degrade denatured, nonubiquitinated proteins in a highly processive fashion but generate different patterns of peptides (despite their containing identical proteolytic sites). With both enzymes, products range in length from 3 to 22 residues, and their abundance decreases with increasing length according to a log-normal distribution. Less than 15% of the products are the length of class I presented peptides (8 or 9 residues), and two-thirds are too short to function in antigen presentation. Surprisingly, these mammalian proteasomes, which contain two "chymotryptic," two "tryptic," and two "post-acidic" active sites, generate peptides with a similar size distribution as do archaeal 20 S proteasomes, which have 14 identical sites. Furthermore, inactivation of the "tryptic" sites altered the peptides produced without significantly affecting their size distribution. Therefore, this distribution is not determined by the number, specificity, or arrangement of the active sites (as proposed by the "molecular ruler" model); instead, we propose that proteolysis continues until products are small enough to diffuse out of the proteasomes.     

The integration of the corneal and limbal fibrils in the human eye

The precise orientation of the collagen fibrils in human cornea and sclera and the method by which these two areas fuse together at the limbus have never been determined, despite the importance of this information. From a consideration of the mechanics of the system, fibril orientation in the tissue has the potential to affect the curvature of the cornea so, by inference, refractive problems such as astigmatism involving an incorrect curvature of the cornea may be related to fibril orientation. The high intensity and small beam size of a synchrotron x-ray source has enabled us to study fibril orientation in post-mortem human cornea and sclera. Previously we have revealed two preferred directions of orientation in the cornea (Meek, K. M., T. Blamires, G. F. Elliot, T. Y. Gyi, and C. J. Nave. 1987. Curr. Eye Res. 6:841-846) and a circumcorneal annulus in the limbus (Newton, R. H., and K. M. Meek. 1998. Invest. Ophthalmol. & Visual Sci. 39: 1125-1134). Here we present the results of our investigation into the relationship between these two features. Our measurements indicate that the corneal fibrils oriented in the two preferred directions bend at the limbus to run circumferentially. On the basis of these results we propose a model as to how the human cornea and sclera fuse together.     

Ruthenium-106 brachytherapy for peripheral retinal capillary hemangioma

OBJECTIVE: This study aimed to evaluate the efficacy and safety of ruthenium-106 brachytherapy of large peripheral retinal capillary hemangiomas. DESIGN: A retrospective case series. PARTICIPANTS: In 25 eyes of 24 patients, peripheral capillary retinal hemangiomas were treated. INTERVENTION: Brachytherapy using 106-ruthenium/106-rhodium plaques was performed. MAIN OUTCOME MEASURES: Eyes were reviewed for hemangioma regression after brachytherapy, occurrence of retinal detachment, requirement of additional vitreoretinal surgery, final visual outcome, and final retinal status. RESULTS: Preoperative mean visual acuity of all eyes treated was 20/60, mean hemangioma diameter was 3.8 mm, corresponding to approximately 2 disc diameters. In 14 eyes, the retina was attached before surgery, 8 eyes showed an exudative detachment, and 3 eyes showed a traction detachment. Fifteen patients had definite von Hippel-Lindau syndrome. Twenty-three of 25 hemangiomas could be destroyed by single brachytherapy. In 16 eyes, a favorable outcome could be achieved. In nine eyes, outcome was unfavorable, characterized by a severe drop in visual acuity, a persisting exudative retinal detachment, or a recurrent traction detachment. In one eye requiring repeated brachytherapy, irradiation retinopathy occurred. Hemangiomas up to a size of approximately 5.0 mm without preoperative exudative detachment could be treated safely by brachytherapy, whereas a larger hemangioma size or a pre-existing exudative retinal detachment predisposed to an unfavorable outcome. CONCLUSION: Solitary peripheral retinal hemangioma can be ablated effectively by ruthenium-106 brachytherapy. A favorable outcome can be expected if the hemangioma diameter is 5.0 mm or smaller and if there is no preoperative exudative retinal detachment.     

Parental divorce during early adolescence in Caucasian families: The role of family process variables in predicting the long-term consequences for early adult psychosocial adjustment.

The relationship between parental divorce occurring during adolescence and young adult psychosocial adjustment was examined, as was the role of family process variables in clarifying this relationship. Participants were young Caucasian adults from divorced (n?=?119) and married (n?=?123) families. Assessments were conducted during adolescence and 6 years later during early adulthood. Young adults from married families reported more secure romantic attachments than those from divorced families; however, differences were not evident in other domains of psychosocial adjustment after demographic variables were controlled. Three family process variables (parent–adolescent relationship, interparental conflict, and maternal depressive symptoms) were examined as potential mediators and moderators of the association between parental divorce and young adult adjustment. No evidence supporting mediation or moderation was found; however, the parent–adolescent and parent–young adult relationships, particularly when the identified parent was the father, emerged as significant predictors of young adult psychosocial adjustment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Site-specific DNA binding using a variation of the double stranded RNA binding motif

The integrase family of site-specific recombinases catalyze a diverse array of DNA rearrangements in archaebacteria, eubacteria and yeast. The solution structure of the DNA binding domain of the integrase protein from the conjugative transposon Tn916 has been determined using NMR spectroscopy. The structure provides the first insights into distal site DNA binding by a site-specific integrase and reveals that the N-terminal domain is structurally similar to the double stranded RNA binding domain (dsRBD). The results of chemical shift mapping experiments suggest that the integrase protein interacts with DNA using residues located on the face of its three stranded beta-sheet. This surface differs from the proposed RNA binding surface in dsRBDs, suggesting that different surfaces on the same protein fold can be used to bind DNA and RNA.     

Abciximab therapy and unplanned coronary stent deployment: favorable effects on stent use, clinical outcomes, and bleeding complications. EPILOG Trial Investigators

BACKGROUND: Recent studies indicate that eradication of Helicobacter pylori might prevent peptic ulcer formation in patients treated with non-steroidal anti-inflammatory drugs (NSAIDs). On the other hand, gastric adaptation after repeated exposures to aspirin (ASA) is well documented but the influence of H. pylori on this process remains to be elucidated. AIM: To compare gastric damage and adaptation following repeated exposures to ASA in a group of patients with H. pylori infection, before and after eradication of the bacterium, and in H. pylori-negative controls. METHODS: Eight healthy volunteers without H. pylori infection and eight patients with duodenal ulcer (DU) history and H. pylori infection before and after H. pylori eradication were given ASA 2 g/day for a period of 14 days. Mucosal damage was evaluated by endoscopy and histology of biopsy samples. Gastric microbleeding, DNA synthesis in the gastric mucosa and mucosal expression, as well as luminal content of transforming growth factor-alpha (TGFalpha) were determined on days 0, 3, 7 and 14 of the ASA course. RESULTS: In all patients aspirin-induced gastric damage reached a maximum on day 3. In H. pylori-positive patients, this damage was maintained at a similar level up to day 14, whereas in H. pylori-negative controls and H. pylori-eradicated patients this damage significantly lessened on day 14 and was accompanied by elevated DNA synthesis as well as increased mucosal expression and luminal release of TGFalpha.