Scalability and performance of an agent‐based network management middleware

Rapid growth of computer network sizes and uses necessitate analysis of network application middleware in terms of its scalability as well as performance. In this paper we analyze a distributed network management middleware based on agents that can be dispatched to locations where they can execute close to the managed nodes. The described middleware operates between the network protocol layer and the application layer and uses standard TCP protocol and SNMP probes to interface the network. By aggregating requests from many users into a single agent, our system allows multiple managers to probe problem areas with minimal management traffic overhead. We discuss and quantify the benefits of the described middleware by implementing real‐time network managers using our system. The main result of this paper is a comparison of scalability and efficiency of our agent‐based management middleware and traditional SNMP‐based data collection. To this end, we measured traffic in both real and simulated networks. In the latter case, we designed, used and described here a method of separating simulated application flow into separate subflows to simplify design of simulations. Copyright © 2004 John Wiley & Sons, Ltd.     

Management gaps analysis: a case study of groundwater resource management in New Zealand

The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps.     

Dual command travel times and miniload system throughput with turnover-based storage

We analyze travel times for automated storage/retrieval systems. In particular, we apply our travel time model to turnover-based storage systems and determine the mean and variance of dual command travel times. We present detailed numerical results for selected rack shape factors and ABC inventory profiles. We then investigate the effect of alternative rack configurations on travel time performance measures. We also show how to determine the throughput of miniload systems with turnover-based storage and exponentially distributed pick times.     

Similarities in normal and binocularly rivalrous viewing

We report here a series of observations-most of which the reader can experience directly-showing that distinct components of patterned visual stimuli (orthogonal lines of a different hue) vary in perception as sets. Although less frequent and often less complete, these perceptual fluctuations in normal viewing are otherwise similar to the binocular rivalry experienced when incompatible scenes are presented dichoptically.     

Temporary leukocyte depletion reduces ventricular dysfunction during prolonged postischemic reperfusion

Leukocyte depletion improves early postischemic ventricular performance in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subsequent impact on myocardial function is not known. This laboratory study examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old piglets (eight control and seven leukocyte depleted animals) were instrumented by placement of left ventricular short-axis sonomicrometry crystals and an intraventricular micromanometer catheter. Mechanical leukocyte depletion was achieved with Pall RC100 filters (Pall Biomedical, Inc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neonatal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals died after the operation and were excluded from data analysis. Leukocyte filtration reduced the granulocyte count during initial myocardial reperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postoperative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukocyte depletion had significantly better preservation of left ventricular performance (measured by preload recruitable stroke work, p < or = 0.02), left ventricular systolic function (measured by end-systolic pressure-volume relationship, p < or = 0.05), and ventricular compliance (p < or = 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p < or = 0.02) and tissue myeloperoxidase activity (p < or = 0.005) in control animals compared with leukocyte depleted animals. This study demonstrates that leukocyte depletion during initial reperfusion results in sustained improvement in postischemic left ventricular function despite the rapid return of granulocytes to the circulation.     

A DNA-binding element for a steroid receptor-binding factor is flanked by dual nuclear matrix DNA attachment sites in the c-myc gene promoter

The receptor-binding factor (RBF) for the avian oviduct progesterone (Pg) receptor (PR) has previously been shown to be a unique 10-kDa nuclear matrix protein that generates high affinity PR-binding sites on avian DNA. This paper describes the use of Southwestern blot and DNA gel shift analyses with RBF protein to identify a minimal 54-base pair RBF-binding element in the matrix-associated region (MAR) of the Pg-regulated c-myc gene promoter. This element contains a 5'-GC-rich domain and a 3'-AT-rich domain, the latter of which has a homopurine/homopyrimidine structure. The gel shift assays required the generation of an RBF-maltose fusion protein (RBF-MBP), which specifically binds this element and is supershifted when the anti-RBF polyclonal antibody is added. Computer analysis of the full-length amino acid sequence for RBF predicts a DNA-binding motif involving a beta-sheet structure at the N-terminal domain. Southern blot analyses using nuclear matrix DNA suggests that there are dual MAR sites in the c-myc promoter, which flank an intervening domain containing the RBF element. The co-transfection of this MAR sequence, containing the RBF element and cloned into a luciferase reporter vector, together with an RBF expression vector construct, into steroid treated human MCF-7 cells, results in a decrease of the c-myc promoter activity relative to control transfections containing only the parent vector of the RBF expression construct. These data suggest that a unique chromatin/nuclear matrix structure, composed of the RBF-DNA element complex which is flanked by nuclear matrix attachment sites, serves to bind the PR and repress the c-myc promoter.     

Revised cutoff values of serum aminotransferase in detecting viral hepatitis among CAPD patients: experience from Taiwan, an endemic area for hepatitis B

BACKGROUND: To determine the best cutoff values of aspartate aminotransferase (AST) and alanine amino-transferase (ALT) in detecting viral hepatitis C infection among patients of continuous ambulatory peritoneal dialysis (CAPD). METHODS: 90 (44 male and 46 female) CAPD patients and 526 adult controls (266 male, 260 female) were enrolled. Serum AST and ALT were measured by an auto-analyser monthly. Serum HBsAg was examined using a RIA method and anti-HCV by an second-generation EIA method. The best cutoff values of AST and ALT for detecting viral hepatitis were obtained from the ROC (receiver-operating characteristic) curve. RESULTS: The prevalence of anti-HCV(+) was significantly higher in CAPD patients (16.7%) than in normal controls (4.9%), while that of HBsAg(+) was similar in both groups. CAPD patients had significantly lower levels of serum aminotransferases compared to normal controls. Mean AST were 23.8 IU/l in normal control and 18.8 IU/l in the CAPD patients (P < 0.001). Mean ALT were 21.9 IU/l in normal controls and 15.3 IU/l in the CAPD patients (P < 0.001). CAPD patients with HCV infection had higher serum AST and ALT levels than those without. However, HBV infection did not cause significant serum aminotransferase elevation in patients. The conventional cutoff values of AST (40 IU/l) and ALT (40 IU/l) for detecting viral hepatitis yielded only a sensitivity of 27.3 and 18.2% respectively; on the contrary, our revised cutoff values of AST (24 IU/l) and ALT (17 IU/l) had better sensitivities (AST, 72.7%; ALT, 63.6%). For serial aminotransferase values, the sensitivity of AST and ALT for detecting HCV were 36.4 and 27.3% by conventional criteria, and were both 81.8%, by our newly revised criteria. CONCLUSIONS: Serum aminotransferase cutoff values should be modified for screening viral hepatitis in a CAPD population. Our new cutoff criteria had important clinical implications in providing benefits of earlier detection and possible prevention from chronic hepatic deteriorations.     

Pegylated peptides. V. Carboxy-terminal PEGylated analogs of growth hormone-releasing factor (GRF) display enhanced duration of biological activity in vivo

In the present study, human growth hormone-releasing factor (hGRF) and analogs were successfully pegylated at the carboxy-terminus using a novel solid- and solution-phase strategy. Following synthesis, these pegylated hGRF analogs were evaluated for in vitro and in vivo biological activity. Specifically, hGRF (1-29)-NH2, [Ala15]-hGRF (1-29)-NH2, [desNH2Tyr1, D-Ala2, Ala15]-hGRF(1-29)-NH2 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-OH were each C-terminally extended using a Gly-Gly-Cys-NH2 spacer (previously demonstrated not to alter intrinsic biological activity), and then monopegylated via coupling to an activated dithiopyridyl-PEG reagent. PEG moieties of 750, 2000, 5000 or 10,000 molecular weight (MW) were examined to determine the effect of polymer weight on activity. Initial biological evaluations in vitro revealed that all C-terminally pegylated hGRF analogs retained high growth hormone (GH)-releasing potencies, regardless of the MW of PEG polymer employed. Two of these pegylated hGRF analogs, [desNH2Tyr1, D-Ala2, Ala15]-hGRF (1-29)-Gly-Gly-Cys(NH2)-S-Nle-PEG5000 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-Gly-Cys(NH2)-S-Nle-PEG5000, were subsequently evaluated in both pig and mouse models and found to be highly potent (in vivo potency range = 12-55-fold that of native hGRF). Relative to their non-pegylated counterparts, these two pegylated hGRF analogs exhibited enhanced duration of activity.     

Egg handling and storage

The relative importance of fat and lean tissue mass in determining bone mineral mass among postmenopausal women was examined in this 1-year longitudinal study. Fifty postmenopausal Caucasian women entered the study; 45 of them completed a 1-year follow-up. Dual-energy X-ray absorptiometry was employed for measuring total and regional bone mineral density (BMD) and bone mineral content (BMC), fat tissue mass (FTM), lean tissue mass (LTM), and body weight. Results from linear regression analysis using the cross-sectional data (n = 50) of the study indicated that LTM explained a larger percentage of variation in bone mineral mass than did FTM. FTM and LTM were found to be moderately correlated (r = 0.55); when FTM was entered in the same predicting regression models, LTM was a significant predictor (p < 0.05) of the total and regional BMC, but not BMD. The percent FTM (and inversely %LTM) was correlated with BMD and BMC, but significant correlation was primarily found only for total body BMD (or BMC). Weight was the best predictor of total body BMD and BMC. Longitudinally (n = 45), annual changes in both FTM and weight were significantly associated with annual changes in regional BMD after adjustment for initial bone mineral values (p < 0.05). We conclude that bone mineral mass is more closely related to LTM than to FTM, while annual changes in regional BMD are more closely correlated with changes in FTM in healthy postmenopausal women. Meanwhile, increased body weight is significantly associated with increased bone mineral mass.