Factors affecting the temporal stability of semipermanent bilayer coatings in capillary electrophoresis prepared using double-chained surfactants

Surfactants such as didodecyldimethylammonium bromide (DDAB) adsorb onto fused-silica capillaries to form semipermanent bilayer coatings. However, such coatings must be regenerated between runs to maintain efficiency and reproducibility. In this paper, chemical and physical factors affecting the stability of DDAB coatings are investigated. Chemical factors such as ionic strength and the nature of the buffer anion (e.g., from acetate to phosphate), which decrease the critical micelle concentration of DDAB, improve the coating stability. Increasing buffer pH also increases the coating stability. Finally, reducing the capillary diameter and reducing the volume of buffer flushed through the capillary enhance the coating stability. Using 50 mM acetate, pH 5.0, in a 25-microm-i.d. capillary, cationic proteins were separated with efficiencies of 1.05 million plates/m and a run-to-run migration time reproducibility of 0.6-0.8% RSD for 10 successive runs without regeneration of the DDAB coating between runs.     

Effect of composition on DC conductivity of co-evaporated Cu-GeO2 thin cermet films

Thin films containing 0 to 100 vol%Cu was prepared by thermal co-evaporation. The samples were 200 nm thick, deposited at 600 K at a rate of 0.8 nm/s. DC conductivity measurements were carried out using the van der Pauw four probe technique for 0 to 100 vol%Cu films in the temperature range 150 to 600 K. Samples containing 60 vol%Cu exhibited a metallic-like behaviour with positive TCR whereas lower concentrations exhibited an activated conduction mechanism with negative TCR.     

Foreword: Hearsay testimony in trials involving child witnesses.

Allowing hearsay testimony in child abuse cases represents a dramatic and controversial change to the legal system, yet little scholarly and empirical work has been devoted to the topic. This special theme issue contains 12 articles written by psycholegal scholars from the United States, United Kingdom, and Canada. It is organized to address 3 basic issues that should be of interest to psycholegal. researchers, as well as police officers, judges, lawyers, and other members of the legal community. (a) How often is hearsay testimony used? How is it used in comparison to other innovations designed to protect the psychological welfare of the child witness? (b) How accurate is hearsay testimony? Is it as accurate as the child's own account? (c) Do jurors believe hearsay testimony? How much weight do or should jurors give to hearsay testimony? Two critical commentaries, one legal and one psychological, follow these articles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Uptake, retention, and repellency of a potential carrier of active ingredients in crack and crevice treatments for stored-grain beetles

Crack and crevice treatments are important in modern stored-beetle management, because: (1) pests are abundant in such microhabitats, (2) they potentially deliver insecticides to insect pests without contaminating food products, and (3) they can significantly reduce the need for broadcast spray applications and/or fumigations. As part of on-going research into the development of novel insecticide delivery systems to be used in processed and unprocessed food environments, we examined uptake and behavioural responses of Oryzaephilus surinamensis to an electrostatically chargeable powder, Entostat^TM. Entostat is a processed plant wax and has been identified as a potential carrier for active ingredients to be delivered to cracks and crevices in food facilities. Depending upon the initial Entostat concentration in rolled oats, 0.03–0.26 μg powder was extracted from individual beetles 72 h after being transferred from treated to untreated food. SEM images showed that Entostat adhered to all body parts, including joints, between body segments, and at the insertions of body hairs. Choice experiments showed that O. surinamensis individuals were repelled, when rolled oats in cracks contained >5% Entostat. In a three-choice experiment cracks contained: (1) untreated oats, (2) oats mixed with 5% (w/w) Entostat, or (3) oats mixed with 5% (w/w) Entostat and a piece of filter paper containing a beetle attractant which was also inserted into the crack. The beetle attractant did not significantly increase the attractiveness of the crack in which it was applied, but the average powder uptake of beetles from cracks treated with the attractant was significantly higher than from the other cracks. Results presented here suggested that Entostat adhering to insects was retained over several days and that considerable amounts of Entostat were taken up even when beetles were offered a choice between treated and untreated cracks.     

Controlling first service and calving interval by prostaglandin F2 alpha, gonadotropin-releasing hormone, and timed insemination

Our objective was to determine if calving intervals could be shortened and made less variable by using prostaglandin F2 alpha to control the occurrence of first services. Holstein cows (n = 348) were assigned at calving to four treatment groups. Control cows (n = 88) were inseminated at their first observed estrus after 40 d postpartum. Estrous cycles of the remaining cows were synchronized with prostaglandin F2 alpha to allow insemination (first services) 80 h after the second injection (n = 86), insemination at 80 h preceded by gonadotropin-releasing hormone at 72 h (n = 86), or insemination at 72 and 96 h (n = 88) after the second injection (51 to 57 d postpartum). By design, interval to first service was reduced to 57 d for treated cows (63 d for controls) and was less variable (12% of that for controls). Conception rate at first service was lower after timed inseminations than that of controls. Intervals to conception and subsequent calving were similar in all treated cows and controls. Of cows sampled, 23 of 176 (13%) failed to respond with luteolysis when progesterone in serum exceeded 1 ng/ml, and 26 of 176 (15%) had low concentrations of progesterone in serum and could not respond to prostaglandin F2 alpha. Poor response to timed inseminations may have occurred because only 72% of 176 cows sampled responded with luteolysis. When only cows observed in estrus were considered, conception rate approached that of controls (51%).(ABSTRACT TRUNCATED AT 250 WORDS)     

On stability analysis of systems featuring a multiplicative combination of nonlinear and linear time‐invariant feedback

We show that sufficient conditions for the finite‐gain stability of certain systems featuring a multiplicative combination of memoryless nonlinear feedback and linear time‐invariant feedback, as encountered in some systems' biology prototype applications, can be obtained by building on the Rantzer multipliers. These results are obtained by observing that for all finite energy signals x, the time‐truncated inner product 〈x, H(x)N(x)〉_T is positive for all T>0 if N belongs to a subclass of positive memoryless monotone nonlinearities and if, in addition, H is a Rantzer multiplier. Copyright © 2011 John Wiley & Sons, Ltd.     

Hypoglycaemia‐free artificial pancreas project

Driving blood glycaemia from hyperglycaemia to euglycaemia as fast as possible while avoiding hypoglycaemia is a major problem for decades for type‐1 diabetes and is solved in this study. A control algorithm is designed that guaranties hypoglycaemia avoidance for the first time both from the theory of positive systems point of view and from the most pragmatic clinical practice. The solution consists of a state feedback control law that computes the required hyperglycaemia correction bolus in real‐time to safely steer glycaemia to the target. A rigorous proof is given that shows that the control‐law respects the positivity of the control and of the glucose concentration error: as a result, no hypoglycaemic episode occurs. The so‐called hypo‐free strategy control is tested with all the UVA/Padova T1DM simulator patients (i.e. ten adults, ten adolescents, and ten children) during a fasting‐night scenario and in a hybrid closed‐loop scenario including three meals. The theoretical results are assessed by the simulations on a large cohort of virtual patients and encourage clinical trials.Inspec keywords: biochemistry, medical control systems, blood, diseases, medical computing, closed loop systems, biomedical equipment, state feedback, patient treatment, patient monitoring, biomedical measurement, physiological models, sugarOther keywords: fasting‐night scenario, hybrid closed‐loop scenario, hypoglycaemia‐free artificial pancreas project, blood glycaemia, euglycaemia, type‐1 diabetes, control algorithm, guaranties hypoglycaemia avoidance, pragmatic clinical practice, state feedback control law, required hyperglycaemia correction bolus, rigorous proof, control‐law, glucose concentration error, hypo‐free strategy control     

Propranolol Hydrochloride Binding in Calcium Alginate Beads

The interaction of propranolol hydrochloride with alginate molecular chains in calcium alginate beads was investigated. The drug was either incorporated into formed calcium alginate gel beads or incorporated simultaneously with the gelation of alginate beads by Ca²⁺. Bed produced by the former method had a higher drug content and lower Ca²⁺ level compared to those prepared by the latter method. The extent of drug binding to the alginate molecules increased with decreasing Ca²⁺ levels in the beads, indicating that propranolol and Ca²⁺ shared common binding sites in the alginate chains, me appearance of the beads and the molphology of the alginate polymer in the beads were affected by the amounts of both propranolol and Ca²⁺ in the beads. Differential scanning calorimetry (DSC) analyses showed that the formation of the calcium alginate gel structure was impeded in the presence of propranolol molecules.     

Nonminimum phase adaptive inverse control for settle performance applications

Single-track hard disk drive (HDD) seek performance is measured by settle time, $t_s$, defined as the time from the arrival of a seek command until the measured position reaches and stays within an acceptable distance from the target track. Our previous work has shown feedforward dynamic inversion, coupled with an aggressive desired trajectory $y_d$, is capable of achieving high performance settle times when the closed-loop dynamics are time-invariant and accurately modeled. In contrast, we describe an adaptive inversion procedure in this paper which removes the requirement for accurate initial models and tracks the position-variant dynamics present in our Servo Track Writer (STW) experimental apparatus. The proposed indirect adaptive inversion algorithm relies on a recursive least squares (RLS) estimate of the closed-loop dynamics. Pre-filtering of the RLS input signals, covariance resetting, and relative NMP system partitioning are necessary additions to the baseline adaptive algorithm in order to achieve fast settle times. Compared to the nonadaptive solution with accurate system identification, we show the adaptive algorithm achieves a 22% reduction in average settle time and a 53% reduction in settle time standard deviation.     

Reactive transport in porous media: a comparison of model prediction with laboratory visualization

Groundwater transport models that accurately describe spreading of nonreactive solutes in an aquifer can poorly predict concentrations of reactive solutes. The dispersive term in the advection-dispersion equation can overpredict pore-scale mixing, and thereby overpredict homogeneous chemical reaction. We quantified this experimentally by imaging instantaneous colorimetric reactions between solutions of aqueous CuSO4 and EDTA4- within a 30-cm long translucent chamber packed with cryolite sand that closely matched the optical index of refraction of water. A charge-coupled device camera was used to quantify concentrations of blue CuEDTA2- within the chamber as it was produced by mixing of the two reactants at different flow rates. We compared these experimental results with a new analytic solution for instantaneous bimolecular reaction coupled with advection and dispersion of the product and reactants. For all flow rates, the concentrations of CuEDTA2- recorded in the experiments were about 20% less than predicted by the analytic solution, thereby demonstrating that models assuming complete mixing at the pore scale can overpredict reaction during transport.