Friction Stir-Welded Dissimilar Aluminum Alloys: Microstructure, Mechanical Properties, and Physical State

A356 and 6061 aluminum alloys were joined by friction stir welding at constant tool rotational rate with different tool-traversing speeds. Thermomechanical data of welding showed that increment in tool speed reduced the pseudo heat index and temperature at weld nugget (WN). On the other hand, volume of material within extrusion zone, strain rate, and Zenner Hollomon parameter were reduced with decrease in tool speed. Optical microstructure of WN exhibited nearly uniform dispersion of Si-rich particles, fine grain size of 6061 Al alloy, and disappearance of second phase within 6061 Al alloy. With enhancement in welding speed, matrix grain size became finer, yet size of Si-rich particles did not reduce incessantly. Size of Si-rich particles was governed by interaction time between tool and substrate. Mechanical property of WN was evaluated. It has been found that the maximum joint efficiency of 116% with respect to that of 6061 alloy was obtained at an intermediate tool-traversing speed, where matrix grain size was significantly fine and those of Si-rich particles were substantially small.     

Mathematical modeling of axial crushing of cylindrical tubes

Different aspects of mathematical modeling for the axial crushing of cylindrical tubes with straight fold have been discussed. The variation of circumferential strain during the formation of a fold has been taken into account. The present paper tries to answer questions such as (a) how great is the inside and outside folding, and (b) how the crushing load varies. In the present paper, the influence of the consideration of the conservation of mass on the mathematical formulation has been studied. The results of average and varying circumferential strain have also been compared.     

A wavelet approach for the identification of axonal synaptic varicosities from microscope images.

Direct visualization of synapses is a prerequisite to the analysis of the spatial distribution patterns of synaptic systems. Such an analysis is essential to the understanding of synaptic circuitry. In order to facilitate the visualization of individual synapses at the subcellular level from microscope images, we have introduced a wavelet-based approach for the semiautomated recognition of axonal synaptic varicosities. The proposed approach to image analysis employs a family of redundant wavelet representations. They are specifically designed for the recognition of signal peaks, which correspond to the presence of axonal synaptic varicosities. In this paper, the two-dimensional image of an axon together with its synaptic varicosities is first transformed into a one-dimensional (1-D) profile in which the axonal varicosities are represented by peaks in the signal. Next, by decomposing the 1-D profile in the differential wavelet domain, we employ the multi-scale point-wise product to distinguish between peaks and noises. The ability to separate the true signals (due to synaptic varicosities) from noise makes possible a reliable and accurate recognition of axonal synaptic varicosities. The proposed algorithms are also designed with a variable threshold that effectively allows variable sensitivities in varicosity detection. The algorithm has been systematically validated using images containing varicosities (< or =30) that have been consistently identified by seven human observers. The proposed algorithm can give high sensitivity and specificity with appropriate threshold. The results have indicated that the semiautomatic approach is satisfactory for processing a variety of microscopic images of axons under different conditions.     

Synthesis and Investigation of Surface Active Properties of Counterion Coupled Gemini Surfactants

Three counterion coupled gemini (cocogem) surfactants in the series 1,6‐bis(N,N‐alkyldimethylammonium) adipate, referred as n‐6‐n (n = 12, 14, 16), were synthesized, purified and characterized by ¹H NMR and ¹³C NMR. Their physicochemical properties were investigated by electrical conductivity and surface tension measurements. The degree of ionization, critical micelle concentration (CMC), surface excess at the air/solution interface (Γ_max), minimum area per surfactant molecule at the air/solution interface (A_min), surface tension at the CMC (γ_CMC), and pC₂₀ (negative log of the surfactant molar concentration, required to reduce the surface tension of water by 20 mN m^?1) were calculated. Increase in tail length of the surfactants increases the efficiency of surfactants to decrease the surface tension of water. Thermodynamic parameters, viz. molar free energy at the maximum adsorption attained at CMC (G_min), standard Gibb's energy of micellization (), and standard Gibbs energy of adsorption (), were also calculated. The and values show that the monomers were preferred to be adsorbed at the air/water interface and then in the micellar formation in the bulk. Additionally, fluorescence measurements were used to find the aggregation number. Other relevant surface properties (Krafft point, emulsion stability, foaming ability, micellar stability and dye solubilization ability) were also evaluated. These results suggest that with respect to emulsion formation, micellar stability and dye solubilization, the cocogem with a 16‐carbon chain gives better results, producing 89 % more stable foams and shows better aggregational behavior.     

Evaluation of Drinking Water Treatment Technology: An Entropy-Based Fuzzy Application

Environmental risk management strategy often encounters conflicting criteria of a subjective and objective nature that are associated with a particular management system concerning multicriteria decision making. In this study, a combination of subjective and objective criteria for risk management has been applied for drinking water treatment technology. Fuzzy set theory has been incorporated in this study. Fuzzy triangular membership functions have been developed to capture uncertainties of the model parameter values. The analytic hierarchy process has been incorporated to construct subjective priority schemes for different hierarchy level attributes. In developing subjective priority schemes, flexible ranges of importance were considered; thus the uncertainties associated with crisp values were incorporated. Using the concept of entropy, subjective importance of the objective attributes have been transformed into integrated importance. The overall ranking was evaluated based on subjective and objective criteria. An example of human health risk management from drinking water disinfection by-products has been presented through several drinking water treatment technologies. Finally, the best treatment technology is outlined.     

Inter- and intra-observer variation in the reporting of cervical smears: specialist cytopathologists versus histopathologists

In modern conception on the mechanisms of a brain edema-swelling formation and a role of various tissue factors in these processes are examined in the issue. Particular attention is paid to analysis of nervous mediator and metabolic changes with a brain edema-swelling. Conceptional models of this reaction development are also presented.     

Complete regression of established human glioblastoma tumor xenograft by interleukin-4 toxin therapy

No curative therapy is available for malignant gliomas. We have discovered that human glioblastoma cells express high affinity interleukin-4 receptor (IL-4R), which is an attractive target for receptor-directed IL-4 toxin therapy. The IL-4 toxin, IL-4(38-37)-PE38KDEL, is a fusion protein containing translocation and enzymatic domains of Pseudomonas exotoxin and a circularly permuted human IL-4. The IL-4 toxin binds specifically to the IL-4R and is highly cytotoxic to glioblastoma cells, as determined by clonogenic and protein synthesis inhibition assays. Intratumoral administration of the IL-4 toxin given on alternate days for 3-4 doses into U251 glioblastoma flank tumors in nude mice, showed a complete remission of small (approximately 13 mm3) and large (approximately 60 mm3) tumors in all animals, without any evidence of toxicity. A significant antitumor activity was also observed when the IL-4 toxin was administered via i.p. and i.v. routes. These results demonstrate that the IL-4 toxin may be a new therapeutic drug for the treatment of human glioblastoma. Therefore, we have begun a Phase I clinical trial with IL-4(38-37)-PE38KDEL for treatment of human glioblastoma.     

Comparison of mixed liquor filterability measured with bench and pilot-scale membrane bioreactors.

Parallel experimental tests to measure mixed liquor filterability for submerged membrane bioreactors were conducted over a six month period using three ZW-500 pilot plants and a ZW-10 lab-scale filterability apparatus. Non-air sparged conditions during the tests yielded operation behaviour that was equivalent to dead-end filtration. The fouling resistance increased linearly with the intercepted mass until a critical point was reached at which point significant cake compression was induced and the resistance began to increase exponentially. Although the point of cake compression appears to be dependent on the membrane module design, similar resistance per unit solid mass intercepted per unit area (R(mass)) values were observed when the same mixed liquor was filtered. Coupled with the established correlation between the R(mass) and the critical flux, it is suggested that the filterability test results from a side-stream, lab-scale module may be used to predict fouling potential in a full scale MBR wastewater treatment system without interrupting the full-scale MBR operation.     

A geometry based simplified analytical model of switched reluctance machines for real-time controller implementation

A geometry based simplified analytical model that decouples the current and position effect on flux and torque in the switched reluctance motor (SRM) drives is presented in this paper. This model gives a direct relation between phase current and torque accounting for the high degree of nonlinearity of the machine. A simple flux model and its inverse relationship have been developed to meet the diverse requirements of controller design. The paper emphasizes and demonstrates the importance of these relationships for real time controller implementation of high performance SRM drives.     

Energy-efficient C-dump converters for switched reluctance motors

Two energy-efficient converter topologies, derived from the conventional C-dump converter, are proposed for switched reluctance motor (SRM) drives. The proposed topologies overcome the limitations of the conventional C-dump converter, and could reduce the overall cost of the SRM drive. The voltage ratings of the dump capacitor and some of the switching devices in the proposed converters are reduced to the supply voltage (V_dc) level compared to twice the supply voltage (2V _dc) in the conventional C-dump converter. Also, the size of the dump inductor is considerably reduced. The converters have simple control requirements, and allow the motor phase current to freewheel during chopping mode. Simulation and experimental results of the converters are presented and discussed