Kinetic Modeling,Thermodynamic Approach and Molecular Dynamics Simulation of Thermal Inactivation of Lipases from Burkholderia cepacia and Rhizomucor miehei

The behavior against temperature and thermal stability of enzymes is a topic of importance for industrial biocatalysis. This study focuses on the kinetics and thermodynamics of the thermal inactivation of Lipase PS from B. cepacia and Palatase from R. miehei. Thermal inactivation was investigated using eight inactivation models at a temperature range of 40–70 °C. Kinetic modeling showed that the first-order model and Weibull distribution were the best equations to describe the residual activity of Lipase PS and Palatase, respectively. The results obtained from the kinetic parameters, decimal reduction time (D and t_R), and temperature required (z and z’) indicated a higher thermal stability of Lipase PS compared to Palatase. The activation energy values (Ea) also indicated that higher energy was required to denature bacterial (34.8 kJ mol⁻¹) than fungal (23.3 kJ mol⁻¹) lipase. The thermodynamic inactivation parameters, Gibbs free energy (ΔG^#), entropy (ΔS^#), and enthalpy (ΔH^#) were also determined. The results showed a ΔG^# for Palatase (86.0–92.1 kJ mol⁻¹) lower than for Lipase PS (98.6–104.9 kJ mol⁻¹), and a negative entropic and positive enthalpic contribution for both lipases. A comparative molecular dynamics simulation and structural analysis at 40 °C and 70 °C were also performed.     

A novel optical waveguide microcantilever sensor for the detection of nanomechanical forces

This study presents a novel generic multipurpose probe based on an array of 20 waveguide channels with microcantilevers acting as optical waveguides operated in the visible range. The principle of operation is based on the sensitivity of energy transfer between two butt-coupled waveguides to their misalignment with respect to each other. The technique can be considered an alternative to the known methods used for the readout of the nanomechanical response of microcantilevers to the external force exerted on them. The cantilever displacement can be detected with a resolution of 18 fm//spl radic/Hz. The limit is generally defined by the shot noise of a conventional photodetector used for the readout of the output signal. Real-time parallel monitoring of several channels can be realized. In contrast to devices based on the atomic force microscope detection principle, no preliminary alignment or adjustment, except for light coupling, is required. The detection of the cantilever deflection at subnanometer range was demonstrated experimentally.     

Pulsus paradoxus in childhood asthma--its prognostic value

One hundred asthmatic children were examined for pulsus paradoxus, a palpable diminution or obliteration of the peripheral pulse during inspiration, while in bronchospasm. Pulsus was measured with a sphygmomanometer and the difference in systolic pressure between inspiration and expiration was noted. Seventy-five children with mild asthma had no palpable pulsus and responded with complete subsidence of symptoms with one or two injections of aqueous epinephrine, 1-1000. Twenty-five children had palpable pulsus ranging from 10 mm to 30 mm. Five patients with pulsus between 10 and 15 mm were admitted to the hospital with status asthmaticus and pneumonia; eight other patients responded to parenteral epinephrine. Twelve children had pulsus of 20 mm or greater and all were hospitalized for uncomplicated status asthmaticus. Pulsus paradoxus may be found in acute exacerbation of childhood asthma and its degree correlates with both the severity and response to bronchodilating agents.     

FPGA based failure monitoring system for machining processes

To be adapted in an easy and economical manner to several machining processes is a desired characteristic in any proposed tool condition monitoring system so as to detect or avoid failures in machine tools. Many modern rotating machines have a servodriver which may, without sensors, acquire a current signal which is directly related to the cutting forces and then be correlated to the cutting tool conditions. Most of the reported systems are designed to work only in one machining process; yet the novelty of this paper is the fact of presenting a hardware signal processing unit implemented in a single field-programmable gate array (FPGA) for acquisition, conditioning, and basic signal monitoring in several machining processes. The system has been proven in industrial processes as well as in laboratories with satisfactory results in both cases. This model is reconfigurable and scalable so that it may be adapted to diverse conditions as an economical stand-alone unit since it does not require either computers nor microprocessors.     

Inhibitory Effect of Termite Fecal Pellets on Fungal Spore Germination

The dampwood termite Zootermopsis angusticollis lines nest chambers and galleries with fecal pellets. The antifungal properties of feces were tested by recording germination rates of spores of the fungus Metarhizium anisopliae that had been incubated with various concentrations of fecal material. The presence of fecal pellet material significantly decreased the germination rates of spores relative to those of control spore solutions lacking fecal material. Spore germination rates were inversely proportional to the amount of fecal matter present in the spore–feces suspensions but were independent of incubation time. The fungistatic effect of the fecal material is virtually immediate and does not require prolonged contact with spores to inhibit germination. This mechanism of biochemical protection may reduce risks of fungal infection in termite nests.     

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/clay nanocomposites for replacement of mineral oil based materials

Due to the short‐running of mineral oil and the increasing waste problem, biopolymers become more and more important. However, they still suffer from disadvantages, and in many cases, their properties are still insufficient to replace mineral oil based plastics. In this study, the biobased and biodegradable polymer poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) is reinforced by different clay types and their effect on the properties profile is investigated. Natural as well as organomodified montmorillonite and bentonite are dispersed by melt mixing within the PHBV matrix. Thermal stability, crystallization behavior, and dynamic mechanical properties as well as the materials morphology is analyzed. Dispersion state of the nanoclay is found to be crucial for the improvement of the material performance and well dispersed organomodified clays reveal to simultaneously improve different properties of PHBV matrix. POLYM. COMPOS., 34:1033–1040, 2013. © 2013 Society of Plastics Engineers     

Activation of the Constitutive Androstane Receptor Inhibits Leukocyte Adhesiveness to Dysfunctional Endothelium

Leukocyte cell recruitment into the vascular subendothelium constitutes an early event in the atherogenic process. As the effect of the constitutive androstane receptor (CAR) on leukocyte recruitment and endothelial dysfunction is poorly understood, this study investigated whether the role of CAR activation can affect this response and the underlying mechanisms involved. Under physiological flow conditions, TNFα-induced endothelial adhesion of human leukocyte cells was concentration-dependently inhibited by preincubation of human umbilical arterial endothelial cells with the selective human CAR ligand CITCO. CAR agonism also prevented TNFα induced VCAM-1 expression, as well as MCP-1/CCL-2 and RANTES/CCL-5 release in endothelial cells. Suppression of CAR expression with a small interfering RNA abrogated the inhibitory effects of CITCO on these responses. Furthermore, CITCO increased interaction of CAR with Retinoid X Receptor (RXR) and reduced TNFα-induced p38-MAPK/NF-κB activation. In vivo, using intravital microscopy in the mouse cremasteric microcirculation treatment with the selective mouse CAR ligand TCPOBOP inhibited TNFα-induced leukocyte rolling flux, adhesion, and emigration and decreased VCAM-1 in endothelium. These results reveal that CAR agonists can inhibit the initial inflammatory response that precedes the atherogenic process by targeting different steps in the leukocyte recruitment cascade. Therefore, CAR agonists may constitute a new therapeutic tool in controlling cardiovascular disease-associated inflammatory processes.     

Multiresponsive PEDOT–Ionic Liquid Materials for the Design of Surfaces with Switchable Wettability

Among the different types of stimuli‐responsive polymers, conjugated polymers reveal unique multiresponsive behavior. In this work, the synthesis and characterization of new functional poly(3,4‐ethylenedioxythiophenes) (PEDOT) bearing imidazolium ionic‐liquid moieties (PEDOT‐Im) is reported. PEDOT‐Im polymers show multiresponsive properties to a variety of stimuli, such as temperature, pH, oxidative doping, and presence of anions. These stimuli provoke different changes in PEDOT‐Im, such as changes in color, oxidation state, and, wetting behavior. In all cases, a reversible effect is observed, and the polymers reveal responsive properties in solution as well as in the form of thin films. Whereas sensitiveness to pH and oxidative doping are known phenomena for other PEDOT derivatives, responsiveness to temperature and to anions is a unique property of PEDOT‐Im. The anion exchange is further investigated by means of the Quartz Crystal Microbalance with dissipation. Anion exchanges induce fast, adjustable, and reversible contact angle changes between 24° and 107°. As a potential application, surfaces with switchable wettability triggered by anion solutions are prepared by spin‐coating PEDOT‐Im films onto different substrates.     

Self-expanding metallic endoprosthesis in the treatment of recurrent ureteral stenosis

OBJECTIVE: To describe two cases of recurrent fibrotic stricture of the uretero-vesical junction treated with a metallic self-expanding endoprosthesis which has successfully achieved patency of the stenotic area in the medium-term. METHODS: Two cases of difficult ureteral stricture are described. Both cases presented obstruction of the terminal ureter by abundant fibrotic tissue in the bladder wall following radical prostatectomy in one case and TUR in the other for non-infiltrating bladder carcinoma. Several attempts to recover patency by endoscopic resection and placement of a double-J stent in these patients had previously failed. The patients were therefore submitted to resection of the fibrotic area and insertion of a self-expanding endoprosthesis (Wallstent), which was eventually enclosed by fibrous tissue at its vesical portion. Both cases underwent resection again and another endoprosthesis (Memotherm) was inserted to extend the previous prosthesis 1 cm within the bladder lumen. RESULTS/CONCLUSIONS: When the endoprosthesis is placed in the uretero-vesical junction with its tip flush with the bladder wall, it is eventually enclosed by fibrous tissue, which invariably leads to recurrent obstruction. We have found that extending the prosthesis 1 cm within the bladder lumen can overcome the foregoing complication, although the long-term results have as yet to be established.