A generalized rheological model for shear thinning fluids

A generalized rheological model for shear thinning fluids has been developed. The new model relates shear stress to shear rate for this type of fluids and predicts the behaviour of hyperbolic, parabolic, elliptic, and Newtonian fluids with or without yield stress at one or both extremes of the shear rate. It correlates the shear stress to the shear rate for a variety of drilling fluids better than both the power-law and Hershel-Bulkley model. It can also predict the viscosity of these fluids. The shear stress and viscosity are required for pressure drop calculations of flow in pipes, annuli, and packed beds.     

Monoclonal antibody AE-2 modulates carbamate and organophosphate inhibition of fetal bovine serum acetylcholinesterase

The monoclonal antibody AE-2, raised against the human erythrocyte acetylcholinesterase (AChE) dimer (acetylcholine acetylhydrolase, EC 3.1.1.7), binds to other mammalian AChEs, including the tetramer that occurs in fetal bovine serum (FBS). AE-2 partially inhibited the rate of hydrolysis of the charged substrate acetylthiocholine by FBS AChE, whereas it increased the rate of hydrolysis of the neutral substrate indophenyl acetate. Present results show that AE-2 decreases the rate of inhibition of FBS AChE by the positively charged organophosphate amiton-p-toluene sulfonate and the positively charged carbamates pyridostigmine and neostigmine but accelerates inhibition of FBS AChE by the neutral organophosphates paraoxon and diisopropylfluorophosphate. Results suggest that AE-2 may allosterically modulate an anionic site in the catalytic center of FBS AChE.     

Properties of tetrahedral amorphous carbon prepared by vacuum arc deposition

The structural, optical, electrical and physical properties of amorphous carbon deposited from the filtered plasma stream of a vacuum arc were investigated. The structure was determined by electron diffraction, neutron diffraction and energy loss spectroscopy and the tetrahedral coordination of the material was confirmed. The measurements gave a nearest neighbour distance of 1.53 Å, a bond angle of 110 and a coordination number of four. A model is proposed in which the compressive stress generated in the film by energetic ion impact produces pressure and temperature conditions lying well inside the region of the carbon phase diagram within which diamond is stable. The model is confirmed by measurements of stress and plasmon energy as a function of ion energy. The model also predicts the formation of sp²-rich materials on the surface owing to stress relaxation and this is confirmed by a study of the surface plasmon energy. Some nuclear magnetic resonance, infrared and optical properties are reported and the behaviour of diodes using tetrahedral amorphous carbon is discussed.     

Integrated MR imaging approach to valvular heart disease

With development of cine and velocity encoded magnetic resonance imaging, it is now feasible to detect and quantify aortic and mitral stenosis and regurgitation accurately. In addition, magnetic resonance imaging has the capabilities to assess simultaneously left and right ventricular mass, volumes, and function precisely. The high accuracy and reproducibility of magnetic resonance imaging in quantification of regurgitation and ventricular function has the potential to provide improved monitoring of therapy and optimal timing of surgery in patients with valvular dysfunction. In comparison to echocardiography and angiography, some current limitations of magnetic resonance imaging to an integrated approach of valvular heart disease exist, which may be removed with future refinement of magnetic resonance imaging technology for cardiovascular imaging.     

Polystyrene foams. II. Structure–impact properties relationships

In the first part of this series of articles, the relations between the foaming conditions and the microstructure of expanded polystyrene (EPS) were explored. In this part, the effects of the foaming conditions and the microstructure of EPS on impact properties are discussed. Regression analysis was conducted on the data and expressions were developed to quantify these relationships. Moreover, the importance of the individual structural parameters was determined. Statistical analysis of the data showed that foaming time was the most important factor determining the impact strength, while foaming temperature was the most important factor controlling the specific impact strength. The deformation of cells at the crack tip, as a result of bending and/or buckling of cell walls, can increase the failure strain, which leads to an increase in failure energy. In expanded polymers, the majority of the absorbed energy during impact loading is dissipated as plastic work. The transition of plane stress conditions to plane strain conditions, due to expansion, can be considered as another source of toughening in EPS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1421–1426, 2003     

FDTD analysis of a metal-strip-loaded dielectric leaky-wave antenna

The finite-difference time-domain (FDTD) method is used to analyze a dielectric leaky-wave antenna comprising metal strips etched on a rectangular dielectric rod. The radiation patterns of the leaky-wave antenna with and without the transition are determined by using FDTD. The effects of the launching discontinuity on the performance of the antenna are discussed. In addition, the application of the perfectly matched layer (PML) technique to the three-dimensional (3-D) dielectric waveguide and its performance, compared to those of the Mur's (1981) first-order and super-absorbing Mur's first-order absorbing boundary conditions (ABCs) are described. In addition, the effects caused by perturbation on the wave propagation characteristics of dielectric waveguide are also discussed. The FDTD results are verified by a W-band experiment and found to be in good agreement     

Long-chain derivatives with a hexahydrothioxotetrazine moiety as potential antimicrobial agents

A series of hexahydrothioxotetrazine-containing compounds I–IV were evaluated for their antimicrobial activity. Fungi (Aspergillus sydowii, A. nidulari, A. terreus, Fusarium solanum, Trichoderma viridae, T. lignorum, Rhizopus arrhitus andCandida albicans) and bacteria (Escherichia coli, Salmonella sp.,Pseudomonas aeruginosa, bacillus sp.,Staphylococcus aureus, Klebsella sp.,Shigella sp. andStreptococcus faecalis) were used for this examination. Compounds I–III showed 90% growth inhibition against a large number of fungi. Two compounds (II and III) have shown significant antibacterial activity. The most striking feature of this study is that compound II, which does not carry an ester function, is the most potent antifungal and antibacterial agent. In general, these promising compounds may be of commercial significance in the future and therefore need developmental studies.     

FDTD analysis of dielectric resonators with curved surfaces

In this paper, the finite-difference time-domain (FDTD) method is applied to calculate the resonant frequency of dielectric resonators (DRs) with curved surface. The contour-path integral FDTD (CFDTD) is modified to deal with the curved surface of the dielectric body while the traditional rectangular cells are maintained. Results are compared with theoretical values and staircase approximation, and show that the present method is more accurate than the staircase approximation     

Panic disorder: effective treatment options

Panic disorder is a distressing and debilitating condition with a familial tendency; it may be associated with situational (agoraphobic) avoidance. The diagnosis of panic disorder requires recurrent, unexpected panic attacks and at least one of the following characteristics: persistent concern about having an additional attack (anticipatory anxiety); worry about the implications of an attack or its consequences (e.g., a catastrophic medical or mental consequence) and making a significant change in behavior as a consequence of the attacks. A variety of pharmacologic interventions is available, as are non-pharmacologic cognitive or cognitive-behavioral therapies that have demonstrated safety and efficacy in the treatment of panic disorder. Early detection and thoughtful selection of appropriate first-line interventions can help these patients, who often have been impaired for years, regain their confidence and ability to function in society.     

Sensitivity and specificity of a short questionnaire for food insecurity surveillance in Iran

BACKGROUND: Food insecurity is frequent in both developed and developing countries, affecting from 5% to 25% of the general population. It has considerable health impacts on the physical, social, and psychological status of individuals in communities suffering from food insecurity. OBJECTIVE: The aim of this study was to document the epidemiologic features of food insecurity in the northwest region of Iran and to evaluate the sensitivity and specificity of a short-form (six items) questionnaire for screening of food insecurity in the region. METHODS: This cross-sectional study was conducted on 300 subjects (132 male and 168 female) selected randomly in the Asadabadi area of the northwest of Iran. Information on food consumption was obtained by a 24-hour food-recall questionnaire for 3 days in a week. This information was compared with the data from the Household Food Security Scale (six-item short questionnaire) to assess the applicability of this short scale for the surveillance of food insecurity. Hunger was defined as inadequate intake of energy. Hidden hunger was defined as adequate intake of energy and inadequate intake of one (or more) of four key nutrients (protein, calcium, vitamin A, and vitamin B2). RESULTS: The prevalence of hunger and hidden hunger in the area according to the 24-hour food-recall questionnaire was 26% and 42%, respectively. Only 32% of the study population was secure in terms of having access to all key nutrients. The sensitivity, specificity, and accuracy of the short questionnaire for screening for hunger in the population were 98.7%, 85.5%, and 89%, respectively; and the corresponding values for hidden hunger were 23.5%, 96.9%, and 56.3%. CONCLUSIONS: Our findings indicate that food insecurity is prevalent in the northwest of Iran. The short questionnaire (six items) may be used as a simple, low-cost, rapid, and useful tool for the screening of food insecurity and energy intake in similar areas.