Structure and drug release of superabsorbent sponge prepared by polyelectrolyte complexation and freezing‐induced phase separation

Superabsorbent sponge with uniform porous structure was prepared by polyelectrolyte complex (PEC) of polyacrylic acid (PAA) with inorganic polymers, high polymer state polyaluminum chloride (HPSPAC), in combination with freezing‐induced phase separation (FIPS). The above superabsorbent sponge was prepared under mild conditions, without strong heat, oxidation, or corrosion, which is an ideal superabsorbent material for drug embedding. Structure analysis and swelling kinetics of the superabsorbent sponge as well as kinetics of the release of the model drug, 4‐acetaminophen (AMP), from the sponge were investigated. In addition, effects of the crosslinker HPSPAC, the pH of the solution, and the concentration of NaCl solution on the structure and the swelling property of the sponge and sustained‐release kinetics were explored. Further, the relationship between the structure of the superabsorbent sponge and its swelling property as well as sustained drug‐release characteristics was investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Amoxycillin resistance is one reason for failure of amoxycillin-omeprazole treatment of Helicobacter pylori infection

BACKGROUND: The efficacy of omeprazole and amoxycillin dual therapy to treat Helicobacter pylori infection has been inconsistent, suggesting the presence of host or bacterial factors influencing treatment success. The aim of this study was to assess the role of pre-treatment amoxycillin resistance in the efficacy of omeprazole and amoxycillin dual therapy. METHODS: We studied 43 consecutive dyspeptic patients with H. pylori infection. Pre-treatment H. pylori infection was established by the combination of positive rapid urease test, culture and histology. Amoxycillin susceptibility testing was performed by an Epsilometer test (E-test) method and amoxycillin resistance was defined as minimum inhibitory concentration greater than 8 microg/mL. Patients received 20 mg omeprazole twice daily for 28 days and amoxycillin 1000 mg twice daily for 2 weeks. Adverse effects were documented using a questionnaire. H. pylori status was reassessed 6-8 weeks after the end of treatment by rapid urease testing and histological examination of gastric biopsies. RESULTS: Forty-two dyspeptic patients completed the study, and one patient dropped out. H. pylori infection was cured in 2 3 of 42 patients (55%). The cure rate was higher in patients harbouring amoxycillin-sensitive organisms than in those with resistant strains: 66% (19/29) vs. 31% (4/13), respectively (P = 0.049). No significant differences in cure rates were evident in relation to age, sex, smoking habits or compliance. CONCLUSIONS: The effectiveness of amoxycillin-omeprazole dual therapy was greatly reduced in the presence of pre-treatment amoxycillin-resistant H. pylori. The success rate in patients with amoxycillin-sensitive H. pylori was only 66%, suggesting the presence of additional factors affecting the efficacy of this therapy.     

EXAFS studies on MFI‐type gallosilicate molecular sieves

EXAFS spectroscopy shows that gallium atoms incorporated into the framework of MFI‐type ZSM‐5 gallosilicates have a typical Ga–O bond length of 1.82 ± 0.01 Å corresponding to a tetrahedral coordination. Accordingly, the coordination number, N, was found to take the value N = 4.2 ± 0.3. Template burning (at 773 K) causes little disturbance to the zeolite framework, and most of the gallium remains tetrahedrally coordinated. However, after a heat treatment at 923 K the apparent coordination number was found to decrease, as well as the corresponding Ga–O bond length. These results were interpreted in terms of formation of extra‐framework gallium oxide species which appear to be EXAFS silent. The thermal stability of the gallosilicate framework was found to increase with increasing Si/Ga ratio.     

Issues and recommendations for the recruitment and retention of older ethnic minority adults into clinical research.

A burgeoning literature indicates that treatment of mental disorders offsets mortality, morbidity, and poor quality of life in senior citizens. Unfortunately, ethnic minority senior citizens, who are in most need of mental health services, have not been well represented in psychosocial research. This lack of attention is due, in large part, to difficulties that may arise in recruitment and retention of older ethnic minority adults in research studies. The purpose of this article is to discuss successful methods for recruiting older ethnic minority adults into psychosocial research and to offer specific suggestions for keeping this population involved in longitudinal studies. Also included is a discussion of past research and present data from treatment studies that used the methods discussed in this article. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simplified models of a single-phase power electronic inverter for railway power system stability analysis—Development and evaluation

Use of power electronic equipment has increased and introduced new dynamical phenomena in power systems. For example, new electric rail vehicles (locomotives) equipped with modern power electronic traction chains have caused situations of low-frequency power oscillations and instability in single-phase railway power supply systems. This paper presents the development and implementation of an instantaneous value model and simplified fundamental frequency (RMS) models of such an advanced electric rail vehicle in order to investigate their representation of low-frequency dynamics. The dynamical behaviour is studied by use of both time-domain simulations and linear analysis (eigenvalues) and the degree of simplifications regarding controller dynamics and power system dynamics are presented and discussed. An enhanced RMS model is tested in order to account for the impact of fast current dynamics on the low-frequency behaviour. The results show that this enhanced model is corresponding more closely to the instantaneous value model than what can be obtained by the traditional RMS simplifications and indicate that current dynamics should be included in stability studies involving power electronic inverters.     

Low Voltage Ride Through of Wind Farms With Cage Generators: STATCOM Versus SVC

This paper analyzes the extent to which the low voltage ride through (LVRT) capability of wind farms using squirrel cage generators can be enhanced by the use of a STATCOM, compared to the thyristor controlled static var compensator (SVC). The transient stability margin is proposed as the indicator of LVRT capability. A simplified analytical approach based on torque-slip characteristics is first proposed to quantify the effect of the STATCOM and the SVC on the transient stability margin. Results from experiments with a STATCOM and a 7.5 kW induction machine emulating a wind turbine are used to validate the suggested analytical approach. Further verifications based on detailed time-domain simulations are also provided. Calculations, simulations and measurements confirm how the increased STATCOM rating can provide an increased transient stability margin and thus enhanced LVRT capability. Compared to the SVC, the STATCOM gives a larger contribution to the transient margin as indicated by both calculations and simulations. The inaccuracies introduced by neglecting the flux transients in the suggested approach are discussed and found reasonable for an estimation method when considering the simplicity compared to detailed time-domain simulation studies. A method for estimating the required rating of different compensation devices to ensure stability after a fault is suggested based on the same approach.     

Density Functional Study of the β″ Phase in Al-Mg-Si Alloys

The β″ phase is the major hardening precipitate in Al-Mg-Si alloys. It was studied by atomistic calculations based on density functional theory (DFT), using an atomistic model where the precipitate was embedded in an Al matrix. This allowed quantifying and visualizing the coherency strain in the matrix and within the precipitates. The elastic strain was found to decrease exponentially in the matrix as a function of distance from the precipitate interface. The formation enthalpy of several different chemical compositions of β″ was calculated, and the most stable composition was found to be Mg₅Al₂Si₄. A study of the calculated valence charge density and electron localization function showed that the covalency network between Si-atoms in the precipitate structure is broken when the precipitate contains Al.     

Water resources development projects in Nigeria

Conceived essentially on a basis of agro‐technical and economic criteria, and without adequate knowledge of all other relevant socio‐economic and cultural factors, water resources development projects in Northern Nigeria have proved hazardous. There is a great risk of upsetting traditional farming systems rather than improving them. The imposition of various schemes, expropriation of land, massive displacement of the rural population, introduction of capital‐intensive technology, dictation of cropping patterns, and prohibitive and regressive farm charges are some of the hazards and uncertainties the farmers have had to cope with. This paper examines the various coping mechanisms adopted by the farmers. Their responses are discussed in relation to agitation, rebellion tactics, and risk‐aversion strategies.     

VLSI parallel shift sort algorithm and design

A hardware algorithm called the parallel shift sort (PSS) is presented. The PSS is a hardware adaption of sorting by insertion. The function of the PSS is verified using an invariant method. Since the PSS uses an array of identical cells of low complexity, it is well suited for VLSI implementation. Some of the more important details of an NMOS implementation on a 5.4×5.4 mm chip are shown. The chip which contains approximately 8000 transistors is designed with lambda rules using a 4 μm line width process. A microcomputer expansion card with an array of sorting chips is described logically. The card's sorting time is of order O(N), where N is the product of the number of chips in the array and the number of cells in each chip (16 for the described chip implementation). The card is also capable of sorting arbitrarily wide keys in time proportional to N × K where K is the number of words in the sorting key width.     

Energy-efficient cooperative routing in BER constrained multishop networks

Due to the limited energy supplies of nodes, in many applications like wireless sensor networks energy-efficiency is crucial for extending the lifetime of these networks. We study the routing problem for multihop wireless ad hoc networks based on cooperative transmission. The source node wants to transmit messages to a single destination. Other nodes in the network may operate as relay nodes. In this paper, we propose a cooperative multihop routing for the purpose of power savings, constrained on a required bit error rate (BER) at the destination. We derive analytical results for line and grid network topologies. It is shown that energy savings of 100% are achievable in line and grid networks with a large number of nodes for BER = 10⁻⁴ constraint at the destination.