Microwave absorption studies of iron encapsulating carbon-polymer nanocomposite films

Iron encapsulated carbon nanoparticle polyvinyl chloride composite films have been prepared by solvent mixing and drying method. The films were characterized by scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). A 5 nm thin graphitic carbon coating is observed on cubic Fe nanoparticles. The microwave absorption studies by wave guide technique in the Ka band range showed highest electromagnetic interference shielding efficiency of 18dB on a 300 micron thick film. The shielding efficiency depends on weight % of the filler in the composite. The data obtained for different films indicate that these lightweight materials are good candidates for potential electromagnetic interference shielding applications.

Growth inhibition of human promonocytic leukaemic U937 cells by interferon gamma is irreversible and not cell cycle phase-specific.

Growth of human promonocytic leukaemic U937 cells was found arrested within 24 h upon exposure to interferon gamma (IFN-gamma). Removal of the interferon did not result in the resumption of growth, as is evident from the absence of doubling of viable cell count and(3)H-thymidine incorporation. 5-Bromo-2'-deoxyuridine-based flow cytometric analysis of the growth-arrested cells, 24 h subsequent to the removal of IFN-gamma, showed absence of DNA synthesis, confirming the irreversible nature of the growth inhibition. Propidium iodide-based flow cytometric analysis of the growth-arrested cells showed a distribution which is typical of a growth inhibition without resulting in the accumulation of cells in any specific phase of the cell cycle. These results indicated that IFN-gamma arrested growth of U937 cells in an irreversible and cell cycle phase-independent manner. These observations were in contrast to our earlier report on the reversible and cell cycle phase-specific growth inhibition of human amniotic (fetal epithelial) WISH cells by the interferon. Copyright 1999 Academic Press.

Design and analysis of rate aware ad hoc 802.11 networks

802.11 WLANs are characterized by high bit error rate and frequent changes in network topology. The key feature that distinguishes WLANs from wired networks is the multi-rate transmission capability, which helps to accommodate a wide range of channel conditions. This has a significant impact on higher layers such as routing and transport levels. While many WLAN products provide rate control at the hardware level to adapt to the channel conditions, some chipsets like Atheros do not have support for automatic rate control. We first present a design and implementation of an FER-based automatic rate control state machine, which utilizes the statistics available at the device driver to find the optimal rate. The results show that the proposed rate switching mechanism adapts quite fast to the channel conditions. The hop count metric used by current routing protocols has proven itself for single rate networks. But it fails to take into account other important factors in a multi-rate network environment. We propose transmission time as a better path quality metric to guide routing decisions. It incorporates the effects of contention for the channel, the air time to send the data and the asymmetry of links. In this paper, we present a new design for a multi-rate mechanism as well as a new routing metric that is responsive to the rate. We address the issues involved in using transmission time as a metric and presents a comparison of the performance of different metrics for dynamic routing.

Chloroquine Inhibits Heme-Dependent Protein Synthesis in Plasmodium falciparum

A cell-free protein-synthesizing system has been reconstituted using the S-30 fraction or ribosomes and the S-100 fraction from Plasmodium falciparum. Addition of heme in vitro stimulates cell-free protein synthesis strikingly. Chloroquine inhibits the heme-dependent protein synthesis in the parasite lysate. The drug has also been found to inhibit parasite protein synthesis in situ at therapeutic concentrations soon after addition to parasite cultures. Ribosomes as well as the S-100 fraction isolated from such chloroquine-treated cultures are defective in protein synthesis. Addition of hemin plus glucose 6-phosphate or high concentrations of GTP, cAMP, and an active preparation of eIF-2 to the parasite cell-free system restores protein synthesis to a significant extent in chloroquine-treated cultures. Under conditions of inhibition of protein synthesis in situ by chloroquine in the culture, the parasite eukaryotic initiation factor 2-alpha- (eIF-2-alpha) is phosphorylated in the parasite lysate to a greater extent than that observed in the control culture. Addition of hemin in vitro suppresses this phosphorylation. eIF-2-alpha kinase activity is present in the parasite lysate and is not a contaminant derived from the human erythrocytes used to culture the parasite. The heme-chloroquine interactive effects can also be demonstrated with purified eIF-2-alpha kinase from rabbit reticulocyte lysate. It is proposed that chloroquine inhibits heme-dependent protein synthesis in the parasite and this is an early event mediating the growth-inhibitory effects of the drug.

In vitro expression of belladonna mottle virus genome

In vitro translation of belladonna mottle virus BDMV(I) genomic RNA in a rabbit reticulocyte lysate system produced proteins of Mr 210,000, 150,000 and 78,000 which form the non-structural proteins. The coat protein, on the other hand, was expressed from a subgenomic RNA which was found to be encapsidated in the empty capsids forming the top component viral particles. The implications of subgenomic RNA encapsidation in viral replication and assembly are discussed.

Studies on the biosynthesis of cytochrome P-450 in rat liver—A probe with phenobarbital

Cytochrome P-450 has been purified from phenobarbital-treated rat livers to a specific content of 17 nmol/mg protein. The major species purified has a molecular weight of 48,000. Using the purified antibody for the cytochrome P-450 preparation it has been shown that the major product synthesized in vivo and in the homologous cell-free system in vitro is the 48,000 molecular weight species. Poly(A)-containing RNA isolated from phenobarbital-treated animals codes for the synthesis of the 48,000 molecular weight species in the wheat germ and reticulocyte lysate cell-free systems. It is concluded that cytochrome P-450 synthesis does not involve processing of a polyprotein precursor, although certain minor modifications including glycosylation of the primary translation product are not ruled out. Phenobarbital treatment of the animal results in a significant increase in the cytochrome P-450 messenger activity as measured in the wheat germ cell-free system.

Inhibition of in Vitro Aminoacylation and Translation by RNA Reactive Antibodies

Antibodies were raised against guanosine-BSA, GMP-BSA and tRNA-mBSA conjugates separately in rabbits. Binding characteristics of these antibodies to various RNAs were studied using a sensitive avidin-biotin micro ELISA. These antibodies inhibited in vitro aminoacylation of tRNA in a dose dependent manner. This inhibition was reversed by the addition of the respective homologous haptens thereby showing the specificity of these antibodies. In vitro translation of endogenous mRNAs in rabbit reticulocyte lysate was also inhibited by these antibodies in a dose dependent manner.

Photocatalytic Inactivation of Escherichia coli with LbL Fabricated Immobilized TiO2 Thin Films

Photocatalysis using semiconductor catalyst such as TiO2, in presence of UV light, is a promising technique for the inactivation of various microorganisms present in water. In the current study, the photocatalytic inactivation of Escherichia coli bacteria was studied with commercial Degussa Aeroxide TiO2 P25 (Aeroxide) and combustion synthesized TiO2 (CS TiO2) catalysts immobilized on glass slides in presence of UV irradiation. Thin films of the catalyst and polyelectrolytes, poly(allyl amine hydrochloride) and poly(styrene sulfonate sodium salt), were deposited on glass slides by layer by layer (LbL) deposition method and characterized by SEM and AFM imaging. The effect of various parameters, namely, catalyst concentration, surface area and number of bilayers, on inactivation was studied. Maximum inactivation of 8-log reduction in the viable count was observed with 1.227 mg/cm(2) of catalyst loaded slides. With this loading, complete inactivation was observed within 90 min and 75 min of irradiation, for Aeroxide and CS TiO2, respectively. Further increase in the catalyst concentration or increasing number of bilayers had no significant effect on inactivation. The effect of surface area on the inactivation was studied by increasing the number of slides and the inactivation was observed to increase with increasing surface area. It was also observed that the immobilized catalyst slides can be used for several cycles leading to an economic process. The study shows potential application of TiO2, for the inactivation of bacteria, in its fixed form by a simple immobilization technique.

Free vibration analysis Of stochastic strings

The free vibration of strings with randomly varying mass and stiffness is considered. The joint probability density functions of the eigenvalues and eigenfunctions are characterized in terms of the solution of a pair of stochastic non-linear initial value problems. Analytical solutions of these equations based on the method of stochastic averaging are obtained. The effects of the mean and autocorrelation of the mass process are included in the analysis. Numerical results for the marginal probability density functions of eigenvalues and eigenfunctions are obtained and are found to compare well with Monte Carlo simulation results. The random eigenvalues, when normalized with respect to their corresponding deterministic values, are observed to tend to become first order stochastically stationary with respect to the mode count.

Structural characterization of gel-grown neodymium copper oxalate single crystals

Sparingly soluble neodymium copper oxalate (NCO) single crystals were grown by gel method, by the diffusion of a mixture of neodymium nitrate and cupric nitrate into the set gel containing oxalic acid. Tabular crystal, revealing well-defined dissolution figures has been recorded. X-ray diffraction studies of the powdered sample reveal that NCO is crystalline. Infrared absorption spectrum confirmed the formation of oxalato complex with water of crystallization, while energy dispersive X-ray analysis established the presence of neodymium dominant over copper in the sample. X-ray photoelectron spectroscopic studies established the presence of Nd and Cu in oxide states besides (C2O4)(2-) oxalate group. The intensities of Nd (3d(5/2)) and Cu (2p(3/2)) peaks measured in terms of maximum photoelectron count rates also revealed the presence of Nd in predominance. The inductively coupled plasma analysis supports the EDAX and XPS data by the estimation of neodymium percentage by weight to that of copper present in the NCO sample. On the basis of these findings, an empirical structure for NCO has been proposed. The implications are discussed.

Effect of chronic administration of Tamoxifen on fertility in male bonnet monkeys (Macaca radiata)

Administration of Tamoxifen via the Alzet pump at a rate of 50 mu g hr(-1) for 90 days in the adult male bonnet monkeys Macaca radiata had no effect on the serum testosterone concentration determined at 10 AM and 10 PM as well as total sperm count determined at 15-day intervals over a period of 260 days. However, a significant reduction in sperm motility was observed beyond 90 days up until the 225th day. Breeding studies conducted from day 90 to 260 revealed that these males were infertile.

A polynomial bound on the number of light cycles in an undirected graph

Let G be an undirected graph with a positive real weight on each edge. It is shown that the number of minimum-weight cycles of G is bounded above by a polynomial in the number of edges of G. A similar bound holds if we wish to count the number of cycles with weight at most a constant multiple of the minimum weight of a cycle of G.

Tree structure for efficient data mining using rough sets

In data mining, an important goal is to generate an abstraction of the data. Such an abstraction helps in reducing the space and search time requirements of the overall decision making process. Further, it is important that the abstraction is generated from the data with a small number of disk scans. We propose a novel data structure, pattern count tree (PC-tree), that can be built by scanning the database only once. PC-tree is a minimal size complete representation of the data and it can be used to represent dynamic databases with the help of knowledge that is either static or changing. We show that further compactness can be achieved by constructing the PC-tree on segmented patterns. We exploit the flexibility offered by rough sets to realize a rough PC-tree and use it for efficient and effective rough classification. To be consistent with the sizes of the branches of the PC-tree, we use upper and lower approximations of feature sets in a manner different from the conventional rough set theory. We conducted experiments using the proposed classification scheme on a large-scale hand-written digit data set. We use the experimental results to establish the efficacy of the proposed approach. (C) 2002 Elsevier Science B.V. All rights reserved.

Reliable Routing in Sensor Networks

In sensor networks, routing algorithms should be designed such that packet losses due to wireless links are reduced.In this paper, we present a ”potential”-based routing scheme to find routes with high packet delivery ratios. The basic idea is to define a scalar potential value at each node in the network and forward data to the neighbour with the highest potential.For a simple 2-relay network, we propose a potential function that takes into account wireless channel state. Markov-chain based analysis provides analytical expressions for packet delivery ratio. Considerable improvement can be observed compared to a channel-state-oblivious policy. This motivates us to define a channel-state-dependent potential function in a general network context. Simulations show that for a relatively slowly changing wireless network, our approach can provide up to 20% better performance than the commonly- used shortest-hop-count-based routing.

Inter and intra crystalline ion exchange equilibria in the system Fe Cr Al O

The tie lines delineating ion-exchange equilibria between FeCr2O4FeAl2O4 spinel solid solution and Cr2O3Al2O3 solid solution with corundum structure have been determined at 1373 K by electron microprobe and EDAX point count analysis of oxide phases equilibrated with metallic iron. Activities in the spinel solid solution are derived from the tie lines and the thermodynamic data on Cr2O3Al2O3 solid solution available in the literature. The oxygen potentials corresponding to the tie-line composition of oxide phases in equilibrium with metallic iron were measured using solid oxide galvanic cells with CaOZrO2 and Y2O3ThO2 electrolytes. These electrochemical measurements also yield activities in the spinel solid solution, in good agreement with those obtained from tie lines. The activity-composition relationship in the spinel solid solution is analysed in terms of the intra-crystalline ion exchange between the tetrahedral and octahedral sites of the spinel structures. The ion exchange is governed by site-preference energies of the cations and the entropy of cations mixing on each site.