UV resonance Raman detection and quantitation of domoic acid in phytoplankton

Cultures of the phytoplankton diatom, Pseudonitzschia multiseries, have been harvested under controlled growth conditions ranging from late logarithmic to late stationary phase (17-58 days). The amount of domoic acid (DA) present in the growth media and in the homogenized cells has been determined by HPLC. Defined samples of media, homogenized cells, whole cells, and whole cells in media have been laser excited at 251 nm for the purpose of selectively exciting intense UV resonance Raman spectra from DA in the samples. Neither media nor cell component spectra from algae seriously interfere with DA spectra. The spectral cross sections for the dominant 1652-cm-1 mode of DA have been determined for 242-, 251-, and 257-nm excitation. Maximum sensitivities are achieved with 251-nm excitation because cross sections for DA are a maximum, and interference from other algal components becomes very small. DA concentrations that have been determined with 251-nm excitation by resonance Raman methods correlate closely with values determined independently with HPLC, especially at higher DA concentrations. The UV resonance Raman analysis of DA in phytoplankton algae is shown to be very sensitive and quantitative as well as rapid and nonintrusive.     

Magnetism and magnetotransport in sonochemically-prepared amorphous Co(100-x)Pt(x) nanoalloys

Amorphous nanoalloys of Co(100-x)Pt(x) (0 < or = x < or = 50) prepared sonochemically exhibit a negative magnetotransport effect, showing a maximum for platinum volume fraction of 10%. The oscillatory peak maxima observed in x = 30 composition for residual resistivity, rho0 and Tmin corresponds to the peak minima for the negative MR% in the range of compositions studied. We observe that in weakly exchange coupled amorphous alloys, the local magnetic order at Tmin and the disorder effects observed from rho0 become crucial.     

Undrained Bearing Capacity of Two-Strip Footings on Spatially Random Soil

A probabilistic study on the interference of two parallel rough rigid strip footings on a weightless soil with a randomly distributed undrained shear strength performed. The problem is studied using the random finite element method, where nonlinear finite element analysis is merged with random field theory within a Monte Carlo framework. The variability of undrained shear strength is characterized by a lognormal distribution and an exponentially decaying spatial correlation length. The estimated bearing capacity statistics of isolated and two footings cases are compared and the effect of footing interference discussed. Although interference between footings on frictionless materials is not very great, the effect is shown to be increased by soil variability and spatial correlation length.     

Power aware scalable multicast routing protocol for MANETs

Multicasting is an effective way to provide group communication. In mobile ad hoc networks (MANETs), multicasting can support a wide variety of applications that are characterized by a close degree of collaboration. Since MANETs exhibit severe resource constraints such as battery power, limited bandwidth, dynamic network topology and lack of centralized administration, multicasting in MANETs become complex. The existing multicast routing protocols concentrate more on quality of service parameters like end‐to‐end delay, jitter, bandwidth and power. They do not stress on the scalability factor of the multicast. In this paper, we address the problem of multicast scalability and propose an efficient scalable multicast routing protocol called ‘Power Aware Scalable Multicast Routing Protocol (PASMRP)’ for MANETs. PASMRP uses the concept of class of service with three priority levels and local re‐routing to provide scalability. The protocol also ensures fair utilization of the resources among the nodes through re‐routing and hence the lifetime of the network is increased. The protocol has been simulated and the results show that PASMRP has better scalability and enhanced lifetime than the existing multicast routing protocols. Copyright © 2005 John Wiley & Sons, Ltd.     

A micro-mechanical model for crack growth resistance of particulate-reinforced metal-matrix composites

Particulate-reinforced metal-matrix composites are being developed to satisfy the need for high stiffness, high strength materials by combining the beneficial properties of both metals and ceramics. The use of such composites as structural members necessitates an understanding of their damage tolerance. A model relating the crack growth resistance to initiation toughness and tensile properties is developed in this paper. The crack growth toughness has also been related to fundamental microstructural properties of these composites. A critical ratio of Young's modulus to flow stress to enable stable crack growth has been established. Suitable suggestions for tailoring the microstructure to optimize crack growth toughness have been discussed.     

Conjugation of oligonucleotides via an electrophilic tether: N-chloroacetamidohexyl phosphoramidite reagent

A novel method for the preparation of oligonucleotides conjugated with nucleophilic ligands is described. A new phosphoramidite building block derived from N-chloroacetyl-6-aminohexanol is attached at the 5'-terminus on the last step of oligonucleotide synthesis. Postsynthetic treatment of support-bound modified oligonucleotide with a variety of amines and mercaptans affords conjugates in high yield.     

Omental plug closure of large duodenal defects--an experimental study

An explosive epidemic of Q-fever that occurred at Jedl'ové Kostol'any (Nitra District) in April 1993, had an unusual mode of transmission, unprecedented in Slovakia. The submitted case-reports can be very instructive for both health workers and the lay public. The bulk of infection was spread in the local pub through contaminated garments of animal attendants assisting abortions and births of goats in a large capacity breeding centre of Gemersan Co. By their repeated visits to the local pub the infection most probably spread to other guests by aerosol. A total of 113 persons (103 males, 10 females) contracted Q-fever. Out of them 95 were infected by contact with the goat attendants (84%), and 18 were occupational diseases after direct contact with the infected goats. The human epidemic of Q-fever facilitated to trace an ongoing epizootic of coxiellosis in the herd of goats of Gemersan breed. In order to stop further spread of infection among humans and to contain the outbreak of coxiellosis among animals extensive epidemic and epizootic measures were taken.