Preparation of multiphase block copolymers by redox polymerization process

Redox polymerization of methylmethacrylate (MMA) using Ce(IV) with poly(oxyethylene) having azo and hydroxy functions was carried out to yield methylmethacrylate-ethylene glycol block copolymers with labile azo linkages in the main chain. These prepolymers were used to initiate the radical polymerization of styrene through the thermal decomposition of the azo group, resulting in the formation of multiblock copolymers. Successful blocking has been confirmed by fractional precipitation, a strong change in the molecular weight distribution and spectral measurements.     

Mycobacterial sulfolipids: Spontaneous desulfation

A glycolipid sulfate elaborated in abundance by surface-grown cultures ofMycobacterium tuberculosis has been characterized in earlier studies as a complex 2,3,6,6′-tetraacyl α, α′ trehalose 2′-sulfate. The purified ammonium salt undergoes rapid quantitative desulfation on mere dissolution in reagent grade anhydrous ether. The same reaction is observed in sulfolipids recovered from a number of human strains and one bovine strain. Experimental observations on the normal and acid-catalyzed rates of the reaction and on the influence of other solvents and other cationic forms support a proposed mechanism, which is detailed. Structural criteria which may influence the proclivity for spontaneous desulfation are discussed.     

Investigation of the saturation properties of gyroamplifiers

The saturation properties of a TE_0n gyroamplifier are investigated using a particle-in-cell numerical code. The effect of beam velocity spread is analyzed. It is found that for velocity spread of up to 5%, the reduction in efficiency can be compensated by extending the interaction length. A numerical optimization of efficiency enhancement using a tapered magnetic field was demonstrated. A change in the saturation mechanism from phase trapping to thermalization using the suggested tapering was observed     

Cryptographic Hash Functions from Expander Graphs

We propose constructing provable collision resistant hash functions from expander graphs in which finding cycles is hard. As examples, we investigate two specific families of optimal expander graphs for provable collision resistant hash function constructions: the families of Ramanujan graphs constructed by Lubotzky-Phillips-Sarnak and Pizer respectively. When the hash function is constructed from one of Pizer’s Ramanujan graphs, (the set of supersingular elliptic curves over with ℓ-isogenies, ℓ a prime different from p), then collision resistance follows from hardness of computing isogenies between supersingular elliptic curves. For the LPS graphs, the underlying hard problem is a representation problem in group theory. Constructing our hash functions from optimal expander graphs implies that the outputs closely approximate the uniform distribution. This property is useful for arguing that the output is indistinguishable from random sequences of bits. We estimate the cost per bit to compute these hash functions, and we implement our hash function for several members of the Pizer and LPS graph families and give actual timings.     

Fe-BEA Zeolite Catalysts for NH3-SCR of NOx

Iron-containing zeolites are known to be promising catalysts for the NH₃-SCR reaction. Here, we will investigate the catalytic activity of iron-based BEA catalysts, which was found to exhibit improved activities compared to previously described iron-containing zeolite catalysts, such as ZSM-5 and ZSM-12. Series of Fe-BEA zeolite catalysts were prepared using a range of different preparation methods. Furthermore, we found that an iron concentration around 3 wt% on BEA showed a small optimum in SCR activity compared to the other iron loadings studied.     

Flocculation of fine particles in ceramic wastewater using new types of polymeric flocculants

It appears to be quite a few national and international studies were reported regarding flocculation and settling properties of ceramic industry wastewater containing various mineral matters. Cleaning of ceramic industry wastewaters with ever increasing environmental standards needs effective and economical solid–liquid separation processes. In this study, quantity and type of optimum flocculant concentration were investigated for solid–liquid separation of Umpac ceramic plant (located at Usak, Turkey) wastewaters. A new generation of flocculants namely unique molecular architecture (UMA) are used to obtain high settling velocity along with high solid content waste and circulation water with low turbidity values. Zeta potential of the tailings including quartz, feldspar, clorite, and mica was also measured at different pH values. The flocculation tests were performed in the presence of different types of polymers at different polymer dosages. It seems that Magnafloc 5250 shows higher performance than the anionic flocculant SPK 508 and other anionic UMA flocculants Magnafloc 6260 and Magnafloc 3230. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Individual time-dependent spectral boundaries for improved accuracy in time-frequency analysis of heart rate variability

Heart rate variability (HRV) is a major noninvasive technique for evaluating the autonomic nervous system (ANS). Use of time-frequency approach to analyze HRV allows investigating the ANS behavior from the power integrals, as a function of time, in both steady-state and non steady-state. Power integrals are examined mainly in the low-frequency and the high-frequency bands. Traditionally, constant boundaries are chosen to determine the frequency bands of interest. However, these ranges are individual, and can be strongly affected by physiologic conditions (body position, breathing frequency). In order to determine the dynamic boundaries of the frequency bands more accurately, especially during autonomic challenges, we developed an algorithm for the detection of individual time-dependent spectral boundaries (ITSB). The ITSB was tested on recordings from a series of standard autonomic maneuvers with rest periods between them, and the response to stand was compared to the known physiological response. A major advantage of the ITSB is the ability to reliably define the mid-frequency range, which provides the potential to investigate the physiologic importance of this range.     

Epidemiological monitoring in the vicinity of a coal-fired power plant

An epidemiological monitoring program has been designed and put into operation in response to a health monitoring requirement of a permit to build a coal-fired power plant. It will consist of four 350 megawatt units and is being built on the Mediterranean coast about halfway between Tel-Aviv and Haifa; the first unit became operational in 1981.The resident population within a 10 km. radius consists of about 69,000 persons. The permit to build this power plant required the installation of a comprehensive monitoring network including environmental, health and agricultural monitoring. Four types of studies are included in the epidemiological monitoring program: mortality analyses, monitoring of requests for health services, studies of pulmonary symptoms and lung function in school children, and panel studies of children and adults with chronic pulmonary conditions. Areas of maximal expected exposure risk and two other comparable areas of lesser risk were chosen, based on expected emissions, meteorological and topographical considerations; baseline data were gathered for a year prior to the operation of the first unit of the power plant. Subsequent data are planned to be collected for another 10 years. The program permits detection of short-term effects based on increases in health service requests, medium-term effects by repeat examination of panelists, and long-term effects based on pulmonary conditions among school children. The initial survey, before plant operations showed, among other things, lower flow rates for children in the area expected to have medium levels of exposure.     

Age-related positivity enhancement is not universal: Older Chinese look away from positive stimuli.

Socioemotional selectivity theory postulates that with age, people are motivated to derive emotional meaning from life, leading them to pay more attention to positive relative to negative/neutral stimuli. The authors argue that cultures that differ in what they consider to be emotionally meaningful may show this preference to different extents. Using eye-tracking techniques, the authors compared visual attention toward emotional (happy, fearful, sad, and angry) and neutral facial expressions among 46 younger and 57 older Hong Kong Chinese. In contrast to prior Western findings, older but not younger Chinese looked away from happy facial expressions, suggesting that they do not show attentional preferences toward positive stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determination of optimal EDM machining parameters for machined pure titanium-porcelain adhesion

The objective of this experimental study is to determine electrical discharge machining (EDM) parameters that offer the best adhesion at the interface of a machined titanium–porcelain composite. First of all, with Taguchi method, machining parameters that will be effective in the bonding strength as well as their interactions on each other were determined in the test. Then, multiple level experiments were conducted to determine how the effective parameters varied over a wide area. Slopes of the curves obtained in these tests were studied, and then, final tests were conducted to obtain the best bonding strength possible. In this way, machining parameters that would offer the highest bonding strength of the titanium–porcelain matrix in a stepwise adjustable EDM machine were obtained. By taking into consideration the steps on the EDM machine where the tests were conducted, it is seen that, when a full factorial experiment is undertaken, 5 power?×?2 polarity?×?2 type of dielectric?×?2 sandblasting or non-sandblasting?×?2 kind of electrode?×?10 pulse-on time, it necessitates 800 different tests to be executed, but, with the applied method, 16?+?18?+?3 yields 37 different tests where the results that include all possible alternatives were obtained. As a result, EDM machining parameters that offer the highest adhesion and are relatively higher, 31.5 N/mm², than the acceptable minimum value of 25 N/mm² were specified.