A rheological study of the order-disorder conformational transition of xanthan gum.

The rheological properties of a moderately concentrated solution of xanthan gum in both the ordered and the disordered state have been studied. Oscillatory shear, steady shear flow, and extensional flow experiments have been performed at different temperatures, covering the order-disorder transition determined by differential scanning calorimetry (DSC). The principle of time/temperature superposition was applied to the xanthan solutions for the different types of flow.

In vivo formation of (+)-anti-benzo[a]pyrene diol-epoxide-plasma albumin adducts in fish.

Benzo[a]pyrene (BaP), a procarcinogenic polycyclic aromatic hydrocarbon (PAH), is bioactivated to BaP diol-epoxides (BPDEs) that can form adducts with DNA and blood proteins. We report here for the first time the in vivo formation of adducts between BPDE and plasma albumin (Alb) from two fish species experimentally exposed to BaP. Brook trout (Salvelinus fontinalis) received either a single i.

Fine-scale tissue distribution of cadmium, inorganic mercury, and methylmercury in nymphs of the burrowing mayfly Hexagenia rigida studied by whole-body autoradiography.

The distribution of inorganic 109Cd(II), inorganic 203Hg(II), and [203Hg] methylmercury (MeHg) in nymphs of the burrowing mayfly Hexagenia rigida after exposure via water and sediments was studied. To better understand the mechanisms underlying the fate of Cd, Hg, and MeHg in this animal and to identify target organs, autoradiography of whole-body cryosections was used to obtain a detailed view of the distribution of the radiolabels. The gut and exoskeleton were the only structures labeled in nymphs exposed to Cd via water or sediments.

A physical map of human chromosome 14.

We report the construction of a tiling path of around 650 clones covering more than 99% of human chromosome 14. Clone overlap information to assemble the map was derived by comparing fully sequenced clones with a database of clone end sequences (sequence tag connector strategy). We selected homogeneously distributed seed points using an auxiliary high-resolution radiation hybrid map comprising 1,895 distinct positions.

Initial sequencing and analysis of the human genome.

The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

Comparative uptake, bioaccumulation, and gill damages of inorganic mercury in tropical and nordic freshwater fish.

This paper reports comparative results on the bioaccumulation of inorganic mercury and resulting gill damages in the tropical fish, Trichomycterus zonatus, and a nordic species, Salvelinus alpinus, using radioisotope 203Hg techniques and scanning electron microscopy. Uptake of inorganic Hg from water was much more important in T. zonatus than in S.

Amniotic fluid concentrations of interleukin-1beta, interleukin-6 and TNF-alpha in chorioamnionitis before 32 weeks of gestation: histological associations and neonatal outcome.

Objectives: To test the association between cytokine levels in the amniotic fluid and (i) the vascular invasion phase of intrauterine infection, (ii) the occurrence of periventricular leukomalacia; to assess the correlation between C-reactive protein levels, a recognised biological marker of inflammation in maternal serum and cytokine levels in the amniotic fluid.

Design: Prospective clinical study.

Setting: Fetal medicine unit and neonatal intensive care unit, Antoine Beclere Hospital, Clamart, France.

Improved screening for breast cancer associated with a telephone-based risk assessment.

Background: Our objective was to develop and field-test a telephone-based breast cancer risk assessment and to assess its efficacy in improving screening behavior. The study was performed at a financial institution and a manufacturing corporation with main offices in Boston, Massachusetts, and branch offices in various regions of the United States.

Methods: A longitudinal study consisting of an initial health risk assessment administered by telephone, with a subsequent follow-up study initiated 8 months later, was performed.

Optical coating without phase dispersion for a Fabry-Perot interferometer.

Phase dispersion induced by coatings can be a critical phenomenon in interferometry. We are interested in special mirrors intended for a Fabry-Perot interferometer with a high reflectance region and a low reflectance region in which phase dispersion on reflection must be avoided. We describe how a classical approach that uses the concepts of admittance and symmetrical multilayers allows the design of simple solutions.

Effects of dispersed and adsorbed crude oil on microalgal and bacterial communities of cold seawater.

: Mesocosm facilities consisting of five 3.5 m(3) stainless steel tanks filled with seawater from the St Lawrence Estuary (Québec, Canada) were used to conduct a 2 month experiment under the natural conditions prevailing at the end of the winter in subarctic environments, with seawater temperatures ranging from-1.5°C (surface ice cover) to 3°C.

Buffer layers for the design of broadband optical filters.

The use of buffer layers is a promising technique in the attempts developed for the design of optical multilayer coatings when two widely separated spectral regions are under consideration. Here we show that the buffer layer, associated with matching layers as in the application mentioned above, can also be exploited in a successive step process to broaden the spectral bandwidth of beam splitters or antireflection coatings.

The tempo and mode of SIV quasispecies development in vivo calls for massive viral replication and clearance.

Simian immunodeficiency virus (SIV) quasispecies development was followed in four monkeys (Macacca fascicularis) infected by intramuscular inoculation of phage lambda-SIVmac239 DNA. Rooted phylogenetic trees were reconstructed and used to interpret the data. The rate of fixation of base substitutions varied within and between animals reaching 3.

Clonal expansion of T cells and HIV genotypes in microdissected splenic white pulps indicates viral replication in situ and infiltration of HIV-specific cytotoxic T lymphocytes.

Human immunodeficiency virus (HIV) replication and T cell proliferation was investigated in situ by a PCR based analysis of individual microdissected splenic white pulps. Founder effects, revealed by an exquisite compartmentalization of HIV genotypes and T cells, indicated the recruitment of latently infected CD4+ T cells through highly localized antigen presentation, rather than the infection of CD4+ T lymphoblasts by blood borne virus or immune complexes. HIV infected white pulps could be infiltrated by HIV specific cytotoxic T lymphocytes, so implicating them in CD4+ T cell destruction in vivo.

HIV and T cell expansion in splenic white pulps is accompanied by infiltration of HIV-specific cytotoxic T lymphocytes.

Human immunodeficiency virus (HIV) replication and T cell proliferation were investigated in situ by a PCR-based analysis of individual microdissected splenic white pulps. Founder effects, revealed by an exquisite compartmentalization of HIV genotypes and T cells, indicated the recruitment of latently infected CD4+ T cells through highly localized antigen presentation rather than the infection of CD4+ T lymphoblasts by blood-borne virus or immune complexes. HIV-infected white pulps could be infiltrated by HIV-specific cytotoxic T lymphocytes, thereby implicating them in CD4+ T cell destruction in vivo.

Effects of some chelating agents on the uptake and distribution of 54Mn(II) in the brown trout (Salmo trutta).

The effects of humic acids, which are natural metal-complexing compounds, and potassium ethylxanthate, sodium diethyldithiophosphate, sodium dimethyldithiocarbamate, and sodium diethyldithiocarbamate, which are sulphur-containing man-made chelating agents, on the uptake and tissue distribution of 54Mn(II) were studied in brown trout (Salmo trutta). Fish were exposed for 7 days to 0.1 microgram Mn(II).

Anisotropy in thin films: modeling and measurement of guided and nonguided optical properties: application to TiO(2) films.

The main purpose of this research is to study the anisotropic behavior of dielectric material in thin-film form. First we present a theory based on a 4 × 4 transfer matrix linking tangential components of the electromagnetic field on one interface to the tangential components of the electromagnetic field on the other interface of an anisotropic thin film. A biaxial model is associated with the columnar structure of the layer.

Synthesis and research of the optimum conditions for the optical monitoring of non-quarter-wave multilayers.

Many optical filtering problems require the use of assemblies of layers with thicknesses that bear no obvious relationship to each other. Here we present the results obtained for a number of examples in which optical monitoring is performed with a change of control wavelengths for each layer of the stack. For this, it is necessary to determine for each layer the different wavelengths that provide an extremum of transmittance when the required thickness is achieved.

Single-mode couplers through end coatings on optical fibers.

For designing coatings on fiber ends, one should take into consideration the particular illumination conditions that are due to the propagation of light in the fibers. In a single-mode fiber, the guided wave is strongly polarized and the state of polarization greatly depends on the constraints applied to the fiber. In this research, we use Thelen's formalism to search for a law of index alternation of a layer stack to reduce the polarization rate for a given incidence.

Role of interface correlation in light scattering by a multilayer.

Four industries prepared optical coatings with a common design that permits an easy determination of cross-correlation laws between the rough interfaces in the stack. Different pairs of materials and deposition processes were used. After clarifying the differences between scalar and vector theories of light scattering caused by rough interfaces in optical multilayers, we compare the experimental values with both theories.

Measurements of absorption losses in TiO(2) films by a collinear photothermal deflection technique.

We review the principle of photothermal deflection for measuring absorption losses in TiO(2)films. A collinear arrangement gives the best sensitivity for the detection of losses in a low absorbing film deposited on a transparent substrate. The nineteen TiO(2) films produced by six different processes (electron beam evaporation, ion assisted deposition, ion beam sputtering, ion plating, .

Nd:MgO:LiNbO(3) waveguide laser and amplifier.

We report efficient operation of a channel waveguide laser and a channel waveguide amplifier in Nd:MgO:LiNbO(3). For the laser a cw output power of 2.9 mW was obtained for 23.