Oxidation of glucose in suspensions of moderately hydrophobized palladium catalysts

In absorption with fast chemical reaction, the reaction occurs only in the liquid-side film at the interface whereas the gas concentration in the bulk of the liquid is about zero. The absorption might be more strongly enhanced if the catalyst concentration in the film was locally increased. For the oxidation of glucose to gluconic acid on suspended Pd/Al₂O₃ particles, particle adhesion at the gas–liquid interface was promoted by moderate hydrophobization with trichloromethylsilane (TCMS). The silanization had no significant effect on the catalyst activity studied under kinetic control. In the mass transfer controlled regime, enhancement of the absorption rate by the hydrophobized Pd/Al₂O₃ catalyst particles occurred at very low catalyst loadings. This can be attributed to locally higher catalyst concentration in the liquid film.     

Cooperating when “you” and “I” are treated fairly: The moderating role of leader prototypicality.

We developed a model predicting that leaders are most effective in stimulating follower cooperation when they consistently treat all group members in a fair manner and are prototypical (i.e., representative of the group's values and norms). In support of this idea, we consistently found that group members cooperated most when prototypical leaders treated themselves as well as their coworkers fairly across a laboratory experiment and 3 cross-sectional field studies. These findings highlight the important role of others' fairness experiences and perceptions in influencing one's own reactions and also the role of leaders as representing the group's values and norms. We discuss implications for fairness theory and the leader prototypicality literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Position dependent velocity profiles in granular avalanches

We present velocity profile measurements in granular avalanches flowing down a flat chute with wide rectangular cross section. The flow is recorded through a transparent side-wall by a high-speed camera, which is able to capture 1,825 pictures in a second. Due to the high frame rate of the camera, several flow features can be observed. Quantitative statements can be made by analysing the images with a pattern matching algorithm. This provides us with flow-normal velocity profiles with a very high temporal and spatial resolution. We find that even on flat surfaces, velocity profiles are strongly changing through the flow and for the range of investigated chute angles (from 26° to 36°) clear trends can be recognised. In the head of the avalanche the velocity is highest, decreasing continuously over the length of the avalanche. Thus, the investigated granular avalanches stretch through the flow. The experimental method allows us to study the evolution of characteristic flow properties such as depth averaged velocity, slip velocity, surface velocity, shear rates or flow depth. Side-wall friction effects are estimated.     

The Role of Reactive Oxygen Species in Microvascular Remodeling

The microcirculation is a portion of the vascular circulatory system that consists of resistance arteries, arterioles, capillaries and venules. It is the place where gases and nutrients are exchanged between blood and tissues. In addition the microcirculation is the major contributor to blood flow resistance and consequently to regulation of blood pressure. Therefore, structural remodeling of this section of the vascular tree has profound implications on cardiovascular pathophysiology. This review is focused on the role that reactive oxygen species (ROS) play on changing the structural characteristics of vessels within the microcirculation. Particular attention is given to the resistance arteries and the functional pathways that are affected by ROS in these vessels and subsequently induce vascular remodeling. The primary sources of ROS in the microcirculation are identified and the effects of ROS on other microcirculatory remodeling phenomena such as rarefaction and collateralization are briefly reviewed.     

Study of prepolymerization complex formation in the synthesis of steroid-based molecularly imprinted polymers

The preparation of steroid-based molecularly imprinted polymers (MIPs) based upon noncovalent interaction is particularly suited for selective capture of steroid hormones in biological and environmental samples. The success of this method lies in the optimization of the interaction between steroids (template) and methacrylic acid (functional monomer) in the prepolymerization mixture. NMR techniques coupled with DFT calculations were used to evaluate the capacity of the methacrylic acid to bind a steroid for future applications. The androstane derivative steroids considered in the present study have two functional groups at C(3) and C(17), which may interact with the methacrylic acid. These can be hydroxyl or ketone groups. Experimental results show that the steroids can be divided in three groups corresponding to the ketone type at C(3), the H-bond strength increasing with the number of double bonds. DFT calculations are in very good agreement with experimental results, showing increasing binding energy from no bonds, a single bond, and two double bond steroids. For steroids holding a hydroxyl group the binding energy obtained in the solvent model is comparable to the binding energy of single bond ketone steroids.     

Bacteriological quality of drinking water from dispensers (coolers) and possible control measures

Three water dispensers (coolers) were bacteriologically monitored over a period of 3 months to evaluate their hygienic status. For this purpose, 174 samples of chilled and unchilled water were analyzed for levels of mesophilic aerobic bacteria and the presence of Escherichia coli and enterococci in 100-ml samples, and the presence of Pseudomonas aeruginosa in 10- and 100-ml samples. Additionally, 12 samples from 20-liter plastic bottles of spring water used to supply the coolers and 36 samples of 12 different brands of noncarbonated bottled mineral water were similarly analyzed. Water from the coolers yielded aerobic plate counts of 3 to 5 log CFU/ml with a geometric mean of 3.86 log CFU/ml, whereas water from the 20-liter bottles had a mean aerobic plate count of 3.3 log CFU/ml. Aerobic plate counts for noncarbonated mineral waters were generally lower (13 samples, < 10 CFU/ml; 6 samples, 10 to 10(2) CFU/ml; 13 samples, 10(2) to 10(3) CFU/ml; 3 samples, 10(3) to 10(4) CFU/ ml; 1 sample, 2 x 10(4) CFU/ml). Although occasional professional cleaning of the coolers did not affect the aerobic plate count, P. aeruginosa was successfully eliminated 2 weeks after cleaning, with only one cooler becoming recolonized. Neither E. coli nor enterococci was found in any of the water samples tested. However, P. aeruginosa was identified in three (25%) of twelve 100-ml samples from 20-liter bottles of spring water; a similar frequency of 24.1% was seen for water samples from coolers. Overall, 35 (21.6%) of 162 water samples (10 ml) from coolers also yielded P. aeruginosa, suggesting potential growth of P. aeruginosa in the dispensers. Pulsed-field gel electrophoresis typing and antibiotic susceptibility testing found 19 P. aeruginosa isolates from the coolers and bottles to be identical, indicating that a single strain originated from the bottled water rather than the surroundings of the coolers. Because P. aeruginosa can cause serious nosocomial infections, its spread should be strictly controlled in institutions caring for vulnerable people such as hospitals and nursing homes. Consequently, in keeping with legal requirement for bottled spring and mineral water in Switzerland, it is also advisable that P. aeruginosa be absent in 100-ml samples of cooler water.     

Programs with lists are counter automata

We address the problem of verifying programs manipulating one-selector linked data structures. We propose and study in detail an application of counter automata as an accurate abstract model for this problem. We let control states of the counter automata correspond to abstract heap graphs where list segments without sharing are collapsed, and use counters to keep track of the number of elements in these segments. As a significant theoretical result, we show that the obtained counter automata are bisimilar to the original programs. Moreover, from a practical point of view, our translation allows one to apply efficient automatic analysis techniques and tools developed for counter automata (integer programs) in order to verify both safety as well as termination of list-manipulating programs. As another theoretical contribution, we prove that if the control of the generated counter automata does not contain nested loops (i.e., these automata are flat), both safety and termination are decidable for the original programs. Subsequently, we generalise our counter-automata-based model to keep track of ordering properties over lists storing ordered data. Finally, we show effectiveness of our approach by verifying automatically safety as well as termination of several sorting programs.     

The time course of perceptual choice: The leaky, competing accumulator model.

The time course of perceptual choice is discussed in a model of gradual, leaky, stochastic, and competitive information accumulation in nonlinear decision units. Special cases of the model match a classical diffusion process, but leakage and competition work together to address several challenges to existing diffusion, random walk, and accumulator models. The model accounts for data from choice tasks using both time-controlled (e.g., response signal) and standard reaction time paradigms and its adequacy compares favorably with other approaches. A new paradigm that controls the time of arrival of information supporting different choice alternatives provides further support. The model captures choice behavior regardless of the number of alternatives, accounting for the log-linear relation between reaction time and number of alternatives (Hick's law) and explains a complex pattern of visual and contextual priming in visual word identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy balances for gravity currents with a jump at the interface produced by lock release

The exchanges of energy for an inviscid Boussinesq gravity current which is released from a lock and then propagates over a horizontal boundary are considered. In this study the depth ratio of ambient to lock, H, is smaller than 2; it is well known that in this case the interface of the current displays a backward-moving jump during the initial stage of the flow. The effects of this discontinuity on the energy balances are investigated using the two-layer shallow-water formulation. This is an extension of the work of Ungarish (Acta Mech 201:63–81, 2008) which covered only the smooth-interface case H ≥ 2. The energies in the current and in the ambient are calculated from numerical solutions of the initial-value shallow-water problem. Corresponding analytical energy balances are presented and the contribution of the backward-moving jump is elucidated. Both the numerical and analytical results indicate that, in general, the increase of kinetic energy of the shallow-water system cannot fully recover the decay of potential energy during the propagation. This imbalance (per unit time) of energy in the present lock-release time-dependent problem is well approximated by the rate of “dissipation” predicted by Benjamin’s (J. Fluid Mech 31:209–248, 1968) classical analysis of the steady-state current. The backward-moving jump enhances the dissipation when H is close to 1; however, for H > 1.4 (approximately) the contribution of this discontinuity to dissipation is insignificant. The general trend is that all shallow-water currents produced by lock-release are dissipative, and the dissipation increases with H. Three Froude-number formulas for the front-speed condition were considered, and it is concluded that Benjamin’s classical function is the most consistent with the motion of the jump, and produces the least dissipative currents.     

A time-efficient and accurate strain estimation concept for ultrasonic elastography using iterative phase zero estimation

In ultrasonic elastography, the exact estimation of temporal displacements between two signals is the key to estimating strain. An algorithm was previously proposed that estimates these displacements using phase differences of the corresponding base-band signals. A major advantage of these algorithms compared with correlation techniques is the computational efficiency. In this paper, an extension of the algorithm is presented that iteratively takes into account the time shifts of the signals to overcome the problems of aliasing and accuracy in the estimation of the phase shift. Thus, it can be proven that the algorithm is equivalent to the search of the maximum of the correlation function. Furthermore, a robust logarithmic compression is proposed that only compresses the envelope of the signal. This compression does not introduce systematic errors and significantly reduces decorrelation noise. The resulting algorithm is a computationally simple and very fast alternative to conventional correlation techniques, and the accuracy of strain images is improved.