Phase Constitution and Dynamic Properties of Spark Plasma‐Sintered Alumina–Titanium Composites

Al₂O₃/Ti composites of various metal to ceramic ratios were fabricated by the spark plasma sintering (SPS) technique. The effects of titanium concentration in the initial mixture on phase composition, and on the static and dynamic (planar impact testing) mechanical properties of the SPS‐processed composites were investigated. It was observed that the significant alumina dissolution in titanium takes place during SPS treatment. The composites fabricated from starting alumina/titanium powder mixtures with a mass fraction of titanium less than 0.8 consisted of two phases, alumina and a solid solution of oxygen and aluminum in titanium. For starting mixtures with higher titanium content, the presence of a Ti₃Al intermetallic phase with a relatively low fraction of dissolved oxygen was detected. Changes in phase composition could explain the effect of titanium content in the starting mixture on physical and mechanical properties of the composites. Mechanisms governing the dynamic response of the composites under loading of different intensities are discussed.     

Influence of flow conditions and system geometry on nitrate use by benthic biofilms: implications for nutrient mitigation

The effects of substratum geometry and overlying velocity on nitrate use by periphyton were assessed. Periphyton was cultivated at an average current velocity of 0.5 cm s(-1) in laboratory mesocosms (120 cm long, 60 cm wide) on polyethylene nets of three different geometries, "1-lay er", "3-layer", and "bedform" structures, overlaying a thin bed of sand. Bulk nitrate use was then measured as the reduction of nitrate concentration in the overlying water under average velocities of 0.005, 0.05, and 0.5 cm s(-1). Periphyton structural characteristics were quantified as algal/bacterial biomass, algal species composition, and bacterial densities. Accrual of microbial biomass increased monotonically with increasing benthic net surface area, with upper sections of structures supporting the highest biomass. Maximum rates of nitrate removal were measured in the bedform geometry at intermediate velocity (173 mg NO3-N m(-2) d(-1)), and the lowest was measured with 1-layer geometry at the fastest velocity (11 mg NO3-N m(-2) d(-1)). Oxygen microprofiles within biofilms demonstrated that hydrodynamic conditions and benthic structure both play a key role in the regulation of microbial processing of nitrate delivered from the water column by promotion of denitrification in downstream sections of bedform substrata. Interactions between hydrodynamic conditions and substratum geometry are expected to regulate microbial activity in all surficial natural and engineered environments and must be parameterized to forecast long-term average biochemical transformation rates in rivers and other dynamic aquatic systems.     

Effects of pre‐emulsifying fat/oil on meat batter stability,texture and microstructure

The effects of pre‐emulsified beef fat and canola oil (CO) (25%) with Tween 80 (T‐80) or sodium caseinate (SC) were studied in beef meat batters prepared at three protein levels (9%, 12% and 15%). Raising meat protein level to 15% resulted in low emulsion stability of products prepared with CO. Using pre‐emulsified beef fat with Tween 80 (BF‐T80) showed significantly higher fat and water losses at all protein levels. There were no differences in fat and water losses between pre‐emulsified beef fat and CO when SC was used at the 9% and 12% protein levels compared to the controls (non pre‐emulsification). Light microscopy revealed fat globule coalescence in the CO meat batters prepared with 15% protein and BF‐T8 treatments, as well as formation of fat channels and more protein aggregation; both resulted in lower emulsion stability. Using SC to emulsify fat/oil produced a finer dispersion of fat globules compared to all the other treatments.     

Asymmetries in a unilateral flanker task depend on the direction of the response: The role of attentional shift and perceptual grouping.

Four experiments were conducted using a flanker task with 1 distractor appearing either on the left or right side of a central target. Responses were made on a keyboard aligned parallel to the displays. A larger flanker effect was obtained when the distractor was on the same side as the response. Two factors account for this asymmetry. First, when the flanker and target are identical, the 2 form a group that is assigned a spatial tag, creating a form of the Simon effect on the basis of the compatibility between the response keys and the group. Second, preparation of a lateralized response appears to entail a shift of visual attention in the corresponding direction, thus enhancing processing of the flanker on the response side. Consistent with the 2nd hypothesis, participants were more likely to correctly recognize letters that were briefly presented at the distractor position on the same side as the response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Constructing predictive models of human running

Running is an essential mode of human locomotion, during which ballistic aerial phases alternate with phases when a single foot contacts the ground. The spring-loaded inverted pendulum (SLIP) provides a starting point for modelling running, and generates ground reaction forces that resemble those of the centre of mass (CoM) of a human runner. Here, we show that while SLIP reproduces within-step kinematics of the CoM in three dimensions, it fails to reproduce stability and predict future motions. We construct SLIP control models using data-driven Floquet analysis, and show how these models may be used to obtain predictive models of human running with six additional states comprising the position and velocity of the swing-leg ankle. Our methods are general, and may be applied to any rhythmic physical system. We provide an approach for identifying an event-driven linear controller that approximates an observed stabilization strategy, and for producing a reduced-state model which closely recovers the observed dynamics.     

Effect of regular and hydrolysed dairy proteins on texture,microstructure and colour of lean poultry meat batters

The use of 2% milk protein isolate (MPI), and some of its fractions which included caseinate, whey protein isolate (WPI), two whey protein hydrolysates (5.2% and 8.5%; WPH‐I and WPH‐II respectively) and β‐lactoglobulin (β‐lac) was evaluated in lean chicken breast meat batters. Adding caseinate and MPI resulted in the highest fracture force values, and caseinate also provided higher yield compared with the control. Both proteins were observed to form distinct protein islands embedded within the meat protein matrix, which appeared to enhance the gel structure. The two hydrolysates provided the highest yield compared with all other treatments. However, adding WPH‐II also resulted in the lowest fracture force and hardness values, while WPH‐I provided similar values to the control. The low hardness value could be explained by the light micrograph which showed WPH‐II interfering with the binding of the meat proteins. The WPI and β‐lac provided similar yield, fracture and hardness values as the control. The colour of the products was most affected by the WHP‐I and WHP‐II; both resulted in lower lightness, yellowness and overall spectra reflectance curves. A cost analysis revealed that caseinate addition was the most economical in this lean meat system.     

GP-Sumo: Using genetic programming to evolve sumobots

We describe the evolution—via genetic programming—of control systems for real-world, sumo-fighting robots—sumobots, in adherence with the Robothon rules: Two robots face each other within a circular arena, the objective of each being to push the other outside the arena boundaries. Our robots are minimally equipped with sensors and actuators, the intent being to seek out good fighters with this restricted platform, in a limited amount of time. We describe four sets of experiments—of gradually increasing difficulty—which also test a number of evolutionary methods: single-population vs. coevolution, static fitness vs. dynamic fitness, and real vs. dummy opponents.     

Selective cytotoxicity of dermaseptin S3 toward intraerythrocytic Plasmodium falciparum and the underlying molecular basis

The antimicrobial activity of various naturally occurring microbicidal peptides was reported to result from their interaction with microbial membrane. In this study, we investigated the cytotoxicity of the hemolytic peptide dermaseptin S4 (DS4) and the nonhemolytic peptide dermaseptin S3 (DS3) toward human erythrocytes infected by the malaria parasite Plasmodium falciparum. Both DS4 and DS3 inhibited the parasite's ability to incorporate [3H]hypoxanthine. However, while DS4 was toxic toward both the parasite and the host erythrocyte, DS3 was toxic only toward the intraerythrocytic parasite. To gain insight into the mechanism of this selective cytotoxicity, we labeled the peptides with fluorescent probes and investigated their organization in solution and in membranes. In Plasmodium-infected cells, rhodamine-labeled peptides interacted directly with the intracellular parasite, in contrast to noninfected cells, where the peptides remained bound to the erythrocyte plasma membrane. Binding experiments to phospholipid membranes revealed that DS3 and DS4 had similar binding characteristics. Membrane permeation studies indicated that the peptides were equally potent in permeating phosphatidylserine/phosphatidylcholine vesicles, whereas DS4 was more permeative with phosphatidylcholine vesicles. In aqueous solutions, DS4 was found to be in a higher aggregation state. Nevertheless, both DS3 and DS4 spontaneously dissociated to monomers upon interaction with vesicles, albeit with different kinetics. In light of these results, we propose a mechanism by which dermaseptins permeate cells and affect intraerythrocytic parasites.     

The melanocyte-stimulating hormone (MSH) receptor in M2R mouse melanoma tumours: solubilization and properties of the receptor-MSH complex and its covalently crosslinked conjugate

Several properties of the MSH receptor in solid melanotic and amelanotic mouse M2R tumour isografts were studied in C57BL mice. Using cell membrane fractions prepared from such tumours and the superpotent [Nle4,D-Phe7]alpha MSH analogue, the affinity and receptor contents of the two tumour variants were found to be similar. When occupied by MSH, the receptor-MSH complex (R.MSH) was readily soluble in cholate. In the solubilized form, R.MSH was extremely stable and dissociated to an extent of only 30% within 12 days at 4 degrees C. While this high stability can be maintained in the pH range of 7.0-8.5, the solubilized R.MSH complex becomes increasingly unstable below pH 7.0 and totally dissociates at a pH < 6.0. In the membrane-bound form, the R.MSH complex shows a parallel pH stability profile which is shifted down by approximately two pH units. In addition to low pH, the R.MSH complex becomes unstable and totally dissociates in the presence of 10 mM EGTA, suggesting that the calcium-sensitive function of the receptor is still associated with the receptor in the detergent-soluble state. The R.MSH complexes in the soluble and membrane-bound forms are also totally resistant to proteolytic digestion by V8 protease, but were slowly digested by trypsin. Treatment of R.MSH with 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride or bis (sulphosuccinimidyl) suberate led to covalent crosslinking of MSH to the receptor molecule. The electrophoretic mobility on SDS-PAGE of the 43/46 kD doublet of the receptor-MSH conjugate (R*MSH) was identical to the photoaffinity labelled MSH receptor product described earlier in cultured M2R cells. However, the efficiency of production of the crosslinked product was approximately 30%, much higher than that achieved previously by photoaffinity labelling. Using rabbit polyclonal anti-alpha MSH antibodies, the R*MSH conjugate was identifiable on Western immunoblots. These results provide a basis for further development of procedures for purification of the MSH receptor molecule and studying its protein structure.     

Localization vs. Identification of Semi-Algebraic Sets

Machine Learning - How difficult is it to find the position of a known object using random samples? We study this question, which is central to Computer Vision and Robotics, in a formal way. We...