bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutational Analysis of a Bifunctional Ferrisiderophore Receptor and Signal-Transducing Protein fromPseudomonas aeruginosa
Authors: James H. Ellen , Beare Paul A. , Martin Lois W. , Lamont Iain L.
Published: June 2005

The FpvA protein ofPseudomonas aeruginosastrain PAO1 mediates uptake of a siderophore, ferripyoverdine. It is also a component of a signal transduction pathway that controls production of an exotoxin, a protease, pyoverdine, and FpvA itself. The purpose of the research described here was to dissect these different functions of FpvA. Signaling involves an N-terminal domain of FpvA, and it was shown that this domain is probably located in the periplasm, as expected. Short peptides were inserted at 36 sites within FpvA by linker insertion mutagenesis. The effects of these mutations on the presence of FpvA in the outer membrane, on FpvA-mediated uptake of ferripyoverdine, and on pyoverdine synthesis and gene expression were determined. Five of the mutations resulted in the absence of FpvA from the outer membrane of the bacteria. All of the remaining mutations eliminated either the transport or signaling function of FpvA and most affected both functions. Three mutations prevented transport of ferripyoverdine but had no effect on the signal transduction pathway showing that transport of ferripyoverdine is not required for the trans-membrane signaling process. Conversely, eight mutations affected pyoverdine-mediated signaling but had no effect on transport of ferripyoverdine. These data show that insertions throughout FpvA resulted in loss of function and that signaling and transport are separate and discrete functions of FpvA.
Llama Antibodies against a Lactococcal Protein Located at the Tip of the Phage Tail Prevent Phage Infection
Authors: De Haard Hans J. W. , Bezemer Sandra , Ledeboer Aat M. , Müller Wally H. , Boender Piet J. , Moineau Sylvain , Coppelmans Marie-Cecile , Verkleij Arie J. , Frenken Leon G. J. , Verrips C. Theo
Published: June 2005

Bacteriophage p2 belongs to the most prevalent lactococcal phage group (936) responsible for considerable losses in industrial production of cheese. Immunization of a llama with bacteriophage p2 led to higher titers of neutralizing heavy-chain antibodies (i.e., devoid of light chains) than of the classical type of immunoglobulins. A panel of p2-specific single-domain antibody fragments was obtained using phage display technology, from which a group of potent neutralizing antibodies were identified. The antigen bound by these antibodies was identified as a protein with a molecular mass of 30 kDa, homologous to open reading frame 18 (ORF18) of phage sk1, another 936-like phage for which the complete genomic sequence is available. By the use of immunoelectron microscopy, the protein is located at the tip of the tail of the phage particle. The addition of purified ORF18 protein to a bacterial culture suppressed phage infection. This result and the inhibition of cell lysis by anti-ORF18 protein antibodies support the conclusion that the ORF18 protein plays a crucial role in the interaction of bacteriophage p2 with the surface receptors of
Lactococcus lactis
.
Genetic Evidence that GTP Is Required for Transposition of IS
903
and Tn
552
in
Escherichia coli
Authors: Coros Abbie M. , Twiss Erin , Tavakoli Norma P. , Derbyshire Keith M.
Published: June 2005

Surprisingly little is known about the role of host factors in regulating transposition, despite the potentially deleterious rearrangements caused by the movement of transposons. An extensive mutant screen was therefore conducted to identify
Escherichia coli
host factors that regulate transposition. An
E. coli
mutant library was screened using a papillation assay that allows detection of IS
903
transposition events by the formation of blue papillae on a colony. Several host mutants were identified that exhibited a unique papillation pattern: a predominant ring of papillae just inside the edge of the colony, implying that transposition was triggered within these cells based on their spatial location within the colony. These mutants were found to be in
pur
genes, whose products are involved in the purine biosynthetic pathway. The transposition ring phenotype was also observed with Tn
552
, but not Tn
10
, establishing that this was not unique to IS
903
and that it was not an artifact of the assay. Further genetic analyses of purine biosynthetic mutants indicated that the ring of transposition was consistent with a GTP requirement for IS
903
and Tn
552
transposition. Together, our observations suggest that transposition occurs during late stages of colony growth and that transposition occurs inside the colony edge in response to both a gradient of exogenous purines across the colony and the developmental stage of the cells.
Bacillus anthracis
Sortase A (SrtA) Anchors LPXTG Motif-Containing Surface Proteins to the Cell Wall Envelope
Authors: Gaspar Andrew H. , Marraffini Luciano A. , Glass Elizabeth M. , DeBord Kristin L. , Ton-That Hung , Schneewind Olaf
Published: June 2005

Cell wall-anchored surface proteins of gram-positive pathogens play important roles during the establishment of many infectious diseases, but the contributions of surface proteins to the pathogenesis of anthrax have not yet been revealed. Cell wall anchoring in
Staphylococcus aureus
occurs by a transpeptidation mechanism requiring surface proteins with C-terminal sorting signals as well as sortase enzymes. The genome sequence of
Bacillus anthracis
encodes three sortase genes and eleven surface proteins with different types of cell wall sorting signals. Purified
B. anthracis
sortase A cleaved peptides encompassing LPXTG motif-type sorting signals between the threonine (T) and the glycine (G) residues in vitro. Sortase A activity could be inhibited by thiol-reactive reagents, similar to staphylococcal sortases.
B. anthracis
parent strain Sterne 34F
2
, but not variants lacking the
srtA
gene, anchored the collagen-binding MSCRAMM (microbial surface components recognizing adhesive matrix molecules) BasC (BA5258/BAS4884) to the bacterial cell wall. These results suggest that
B. anthracis
SrtA anchors surface proteins bearing LPXTG motif sorting signals to the cell wall envelope of vegetative bacilli.
Spectrum of one-dimensional anharmonic oscillators
Authors: Alhendi H A , Lashin E I
Published: June 2005

We use a power-series expansion to calculate the eigenvalues of anharmonic oscillators bounded by two infinite walls. We show that for large finite values of the separation of the walls, the calculated eigenvalues are of the same high accuracy as the values recently obtained for the unbounded case by the inner-product quantization method. We also apply our method to the Morse potential. The eigenvalues obtained in this case are in excellent agreement with the exact values for the unbounded Morse potential. PACS Nos.: 03.65.Ge, 02.30.Hq
Stability of mixed-convection boundary-layer flow on a porous wedge
Authors: Watanabe T , Taniguchi H , Minato S
Published: June 2005

A theoretical analysis is presented of the stability characteristics of laminar forcedfree mixed-convection boundary-layer flow past an isothermal wedge with uniform suction or injection. The nonsimilar boundary-layer equations for the basic steady flow are solved numerically with a difference-differential scheme in combination with an iterative method for solving the resulting ordinary differential equations. The disturbance equations are then solved numerically on the basis of linear stability theory. The neutral stability curves and the disturbance amplitude of the velocity component and of the temperature are presented graphically for values of the buoyancy parameter ζ, the pressure-gradient parameter m, and the suction/injection parameter X. The results indicate the important role of the suction/injection parameter on the characteristics of both basic flow and disturbance flow. PACS No.: 47.20.k
Viscous fingering with a single fluid
Authors: Holloway Kristi E , de Bruyn John R
Published: June 2005

We study fingering that occurs when hot glycerine displaces cooler, more viscous glycerine in a radial Hele-Shaw cell. We find that fingering occurs for a sufficiently large initial viscosity contrast and for sufficiently high flow rates of the displacing fluid. The wavelength of the fingering instability is proportional to the cell width for thin cells, but the ratio of wavelength to cell width decreases for our thickest cell. Similar fingering is seen in numerical simulations of this system.PACS Nos.: 47.54.+r, 68.15.+e, 47.20.k
Plot size related measurement error bias in tree growth models
Authors: Lappi Juha
Published: June 2005

Local tree density around a tree affects tree growth because neighboring trees compete for the same resources. In forestry trees are often sampled by measuring all the trees in sample plots. The total number of the trees in a sample plot or in a larger plot that also encompasses a border zone is often used as the density measurement for all trees in the plot. When the plot density is used as the measurement of local density around a sample tree, the measurement error is correlated both with the measured value and with the true value. Thus none of the standard measurement error assumptions hold. The bias in the estimated density effect is related to the plot size. Assuming random tree locations and a simple linear model including both overall stand density and local density as predictor variables, the bias is analyzed analytically using weighted distributions. The plot size producing the highest coefficient of determination is rather close to the size of the influence zone, but much larger plot sizes are needed for unbiased estimation. It is safe to measure density from a larger plot than that used for sample tree selection. The analysis may give insight for other cases in multilevel modeling where group variables are used to explain individual responses.
Genetic subpopulation structuring and its implications in a mature eastern white pine stand
Authors: Nijensohn Samuel E , Schaberg Paul G , Hawley Gary J , DeHayes Donald H
Published: June 2005

We examined patterns of genetic structuring within a mature eastern white pine (Pinus strobus L.) forest, using geographic information system (GIS)-based data and maps that combined genetic (isozyme analysis of 46 loci) and other tree-specific information (e.g., size, growth, age, and location) for 220 trees in Jericho, Vermont. Interconnections between genotypic information with other tree characteristics revealed several patterns of genetic structuring. Average observed heterozygosity generally increased with tree age-class, and trees with a high number of rare alleles were disproportionally represented in suppressed crown classes. Spatial structuring was also evident: trees within 5 m of one another were highly related, and levels of relatedness generally decreased with increasing distance between trees. In general, a 35-m-radius circle around any tree circumscribed its zone of genetic similarity. Hierarchical cluster analysis indicated the stand consisted of five family groups that exhibited greater genetic similarity within than among clusters. Temporal structuring (a generation gap) was also evident: trees of similar age showed significant positive relatedness, as did trees 3040 years apart. Patterns of genetic structuring likely resulted from the combined influences of natural selection, isolation by distance, and functional generation times. Genetic structuring may also have biological and management implications. Computer-based simulated harvests suggested that the stand could experience genetic alteration when tree removal criteria disrupted existing structural patterns.
The application of digital photogrammetry and image analysis techniques to derive tree and stand characteristics
Authors: Zagalikis G , Cameron A D , Miller D R
Published: June 2005

Ground-based forest inventory surveys can provide highly accurate measurements of tree and stand characteristics, but these are expensive to carry out. Aerial photography has been used for several decades as a tool in forest management and inventory. However, conventional methods of interpretation are both time-consuming and costly, with results varying among interpreters. With continuing development of personal computer technology, aerial photographs have become more accessible for digital analysis. This paper presents the potential operational use of digitized aerial photographs for the estimation of tree and stand characteristics of two forest plantations of Sitka spruce (Picea sitchensis (Bong.) Carrière) in Scotland. The digitized aerial photographs were processed using softcopy photogrammetry, and image analysis techniques were used for individual tree crown delineation. For the first site the estimations of stand top height, basal area, volume, biomass, and density (23.7%) were similar to the ground-measured stand characteristics (±10%), whereas for the second site the estimations were less accurate mainly because of the nonoptimal illumination conditions during the acquisition of the aerial photographs.
Quantitative reflectance spectroscopy as an alternative to traditional wet lab analysis of foliar chemistry: near-infrared and mid-infrared calibrations compared
Authors: Richardson Andrew D , Reeves III James B
Published: June 2005

Quantitative reflectance spectroscopy offers an alternative to traditional analytical methods for the determination of the chemical composition of a sample. The objective of this study was to develop a set of spectroscopic calibrations to determine the chemical composition (nutrients, carbon, and fiber constituents, determined using standard wet lab methods) of dried conifer foliage samples (N = 72), and to compare the predictive ability of calibrations based on three different spectral regions: visible and shortwave near infrared (VISsNIR, 400- to 1100-nm wavelengths), near infrared (NIR, 1100- to 2500-nm wavelengths), and mid infrared (MIR, 2500- to 25 000-nm wavelengths). To date, most quantitative reflectance spectroscopy has been based on the VISsNIRNIR, and the ability of MIR calibrations to predict the composition of tree foliage has not been tested. VISsNIR calibrations were clearly inferior to those based on longer wavelengths. For 8 of 11 analytes, the MIR calibrations had the lowest standard error of cross-validation, but in most cases the difference in accuracy between NIR and MIR calibrations was small, and against an independent validation set, there was no clear evidence that either spectral region was superior. Although quantitative MIR spectroscopy is at a more primitive state of development than NIR spectroscopy, these results demonstrate that the mid infrared has considerable promise for quantitative analytical work.
Genetic effects of rooting loblolly pine stem cuttings from a partial diallel mating design
Authors: Baltunis Brian S. , Huber Dudley A. , White Timothy L. , Goldfarb Barry , Stelzer Henry E
Published: June 2005

More than 239 000 stem cuttings from nearly 2200 clones of loblolly pine (Pinus taeda L.) were set in five rooting trials to estimate genetic parameters associated with rooting. Overall rooting success across the five trials was 43%, and significant seasonal effects were observed. Differences among clones within full-sib families accounted for approximately 10%17% of the total variation. On the binary scale, individual-tree narrow-sense heritability (ĥ20.1) ranged from 0.075 to 0.089 for rooting across the five separate settings, while broad-sense heritability (Ĥ20.1) ranged from 0.15 to 0.22. Narrow- and broad-sense heritability estimates on the observed binary scale were transformed to their underlying normal scale (ĥ2N, Ĥ2N). When all of the data from the five trials were analyzed together, ĥ2N(±SE) was 0.081 (0.027), Ĥ2Nwas 0.16 (0.013), the type B additive correlation was 0.68 (0.23), and the type B dominance correlation was 0.61 (0.27). Narrow-sense family mean heritability was 0.83 (0.24), while broad-sense clonal mean heritability was 0.82 (0.074). These moderate to high family and clonal mean heritabilities, moderate type B correlations, and substantial among-family and among-clone genetic variation indicate the potential for increasing rooting efficiency by selecting good rooting families and clones or culling poor rooters.
Wind tunnel measurements of crown streamlining and drag relationships for several hardwood species
Authors: Vollsinger Stephan , Mitchell Stephen J , Byrne Kenneth E , Novak Michael D , Rudnicki Mark
Published: June 2005

Understanding tree susceptibility to wind damage is central to natural disturbance and succession studies. Susceptibility depends on the wind loads experienced by trees and their ability to resist these loads. In this study, we investigated the wind force or "drag" acting on the crowns of juvenile specimens of three hardwood species common to northwestern North America, black cottonwood (Populus trichocarpa Torr. & A. Gray), red alder (Alnus rubra Bong.), and paper birch (Betula papyrifera Marsh.). Ten freshly cut crowns of each species were exposed to wind speeds from 4 to 20 m/s in a wind tunnel. At 20 m/s, streamlining reduced the frontal area to 28% of its initial value for black cottonwood, 37% for red alder, and 20% for paper birch. Crown drag coefficients calculated using frontal area in still air varied with wind speed. At 20 m/s they ranged from 0.15 to 0.22 for these species. Drag was proportional to the product of mass and wind speed, and to the product of wind speed squared and wind-speed-specific frontal area. Removing branches by whole-branch pruning had little effect on drag per unit branch mass. To further investigate the effect of leaf size, we also used smaller samples of bigleaf maple (Acer macrophyllum Pursh) and trembling aspen (Populus tremuloides Michx.). Whole-crown drag coefficients did not vary systematically with leaf size, but drag per unit of crown mass increased with leaf size. Bigleaf maple had a higher drag per unit of crown mass than other species.
Alternative method for estimating aboveground net primary productivity applied to balsam fir stands in eastern Canada
Authors: Lavigne M B , Foster R J , Goodine G , Bernier P Y , Ung C H
Published: June 2005

Aboveground net primary productivity (ANPP) was measured in three balsam fir (Abies balsamea (L.) Mill.) forests on a climatic transect extending from southern New Brunswick ("warm" study area) to central Quebec ("cool" study area). Annual foliar production was estimated with a relationship between cross-sectional area at breast height of the current-year annual xylem ring and the mass of current-year foliage, using data obtained by harvesting trees at the beginning of the study. This relationship differed among study areas. Annual branch production was determined from annual foliar production and the ratio of annual branch production to annual foliar production. The ratio of branch to foliar production was estimated from intensive measurement of a sample of branches collected at the end of the study period; it varied among years but was similar for all study areas. ANPP was 3.36 Mg C·ha1·year1 at the warm study area, 3.73 Mg C·ha1· year1 at the mid-transect study area, and 3.04 Mg C·ha1·year1 at the cool study area. These estimates of ANPP were greater than those estimated using a conventional method of summing up increment and litterfall. On average, the conventional estimate of ANPP was 83% of the estimate using relationships described above. Because net ecosystem productivity is the difference between NPP and heterotrophic respiration, a 17% underestimate of NPP can have a substantial effect on the estimate of carbon-sink activity of a forest.
AGING IN HOSTILE ENVIRONMENT MODELED BY CELLULAR AUTOMATA WITH GENETIC DYNAMICS
Authors: DZWINEL WITOLD , YUEN DAVID A.
Published: June 2005

We model the evolution of a population on a 2D cellular automata (CA) lattice. Every individual holds a binary "genetic code". The code length and the number of "1"s in the chain correspond to the maximal and actual life-time of individual, respectively. The "genetic code" code is divided onto three life-episodes: "youth", "maturity" and "old age". Only "mature" individuals can procreate. We investigate the duration of the life-episodes and their role in protecting the population from extinction in hostile environments. We observe that in the stable environment, which does not influence the life-time of individuals, the "youth" and the "maturity" periods extend extremely long during evolution, while the "old age" remains short. The situation is different for hostile plaque-like conditions. Under these circumstances, the "youth" period vanishes, while the longer "old age" period stabilizes the population growth, increases its average age and thereby increases its chance of survival. We can conclude that the idle life-episodes set up the control mechanisms, which allow for self-adaptation of the population to varying environmental conditions.
SIMULATION AND EXPERIMENT OF EXTINCTION OR ADAPTATION OF BIOLOGICAL SPECIES AFTER TEMPERATURE CHANGES
Authors: STAUFFER D. , ARNDT H.
Published: June 2005

Can unicellular organisms survive a drastic temperature change, and adapt to it after many generations? In simulations of the Penna model of biological aging, both extinction and adaptation were found for asexual and sexual reproduction as well as for parasex. These model investigations are the basis for the design of evolution experiments with heterotrophic flagellates.
MOLECULAR DYNAMICS SIMULATIONS THROUGH SYMBOLIC PROGRAMMING
Authors: DUDEK MIROSŁAW R. , NADZIEJA TADEUSZ
Published: June 2005

We present an algorithm for the Cauchy problem for the ordinary differential equations which is based on symbolic programming. It is complementary to numerical methods, which use the finite differences. The algorithm consists of two steps. First, it yields a set of polynomials of a given degree n in some formal parameter λ. They represent an analytic form of the truncated solution of the system of differential equations under consideration and the larger value of n the larger interval in which this approximation satisfies the chosen accuracy criterion. We put λ = 1 afterall. The second step is purely numerical. Namely, the numerical values of the polynomials in the interval, in which the difference between them and the polynomials of the smaller degree n - j (for certain j) does not exceed a given accuracy ε, become the numerical solution. In the point, where this accuracy criterion fails the new initial values are defined, just at this "disagreement point", and the whole procedure is repeated.
OPTIMIZATION OF 2D LATTICE CELLULAR AUTOMATA FOR PSEUDORANDOM NUMBER GENERATION
Authors: QUIETA MARIE THERESE ROBLES , GUAN SHENG-UEI
Published: June 2005

This paper proposes a generalized approach to 2D CA PRNGs — the 2D lattice CA PRNG — by introducing vertical connections to arrays of 1D CA. The structure of a 2D lattice CA PRNG lies in between that of 1D CA and 2D CA grid PRNGs. With the generalized approach, 2D lattice CA PRNG offers more 2D CA PRNG variations. It is found that they can do better than the conventional 2D CA grid PRNGs. In this paper, the structure and properties of 2D lattice CA are explored by varying the number and location of vertical connections, and by searching for different 2D array settings that can give good randomness based on Diehard test. To get the most out of 2D lattice CA PRNGs, genetic algorithm is employed in searching for good neighborhood characteristics. By adopting an evolutionary approach, the randomness quality of 2D lattice CA PRNGs is optimized. In this paper, a new metric, #rn is introduced as a way of finding a 2D lattice CA PRNG with the least number of cells required to pass Diehard test. Following the introduction of the new metric #rn, a cropping technique is presented to further boost the CA PRNG performance. The cost and efficiency of 2D lattice CA PRNG is compared with past works on CA PRNGs.
CONTROLLING THE VEHICLE STATES IN TWO-LANE TRAFFIC
Authors: LI KEPING , GAO ZIYOU
Published: June 2005

In this paper, we propose a new technique to control the vehicle states in two-lane traffic. A type of the control signals has been designated at a given site (i.e., signal point) of the road. Under the effect of control signal, the drivers on the right lane will slow down when their vehicles pass the signal point. We test this technique for the two-lane traffic model that is based on the deterministic NaSch traffic model. The simulation results indicate that the traffic flow states can be changed from disorder to order by the control signal, and these ordered states are safer.
GENOME-WIDE RESPONSES TO DNA-DAMAGING AGENTS
Authors: Fry Rebecca C. , Begley Thomas J. , Samson Leona D.
Published: June 2005

Genome-wide studies of mRNA regulation and phenotypic responses have shown that eukaryotic cells mount a robust and multifaceted response upon exposure to DNA-damaging agents. The integration of theses studies over frameworks provided by protein-protein interactions, protein-DNA interactions, and subcellular localization information have led to the identification of networked responses to damage. Taken together, these studies illustrate that cellular protection from DNA and other macromolecular damage involves an intricate network of proteins involved in many different cellular functions, some of them expected (e.g., DNA repair and cell cycle checkpoints) but many of them unexpected (e.g., protein trafficking and degradation). This review highlights many of the studies that detail genome-wide responses to DNA-damaging agents and examines how these datasets have been used to build a systems view of cellular responses to damage.
Breeding activity patterns, reproductive modes, and habitat use by anurans (Amphibia) in a seasonal environment in the Pantanal, Brazil
Authors: Prado Cynthia , Uetanabaro Masao , Haddad Célio
Published: June 2005

Annual patterns of breeding activity, reproductive modes, and habitat use are described for a frog community in a seasonal environment, in the southern Pantanal, Mato Grosso do Sul, Brazil. Data were collected monthly between January 1995 and December 1998. A total of 24 species from four families; Bufonidae (3 species), Hylidae (10 species), Leptodactylidae (9 species), and Microhylidae (2 species) were registered. Three reproductive activity patterns are recognized among these species: continuous, explosive, and prolonged; 50% of the species were explosive breeders. Seasonal pattern of reproduction was verified for three analyzed years (1995-1997); most species reproduced during the rainy season (Nov-Jan). The reproduction was aseasonal in 1998; unexpected rains in the dry season lead to an unusual breeding activity. Five reproductive modes were noted — 62.5% of the species have the generalized aquatic mode, and 33.3% deposit eggs embedded in foam nests. Many species used the same sites for reproduction, although temporal partitioning and calling site segregation was observed. The occurrence of many species that exhibit explosive breeding early in the rainy season is common in seasonal and open environments with variable and unpredictable rainfall, as is the case in the Pantanal.
Sexual dimorphism in the Neotropical lizard, Tropidurus torquatus (Squamata, Tropiduridae)
Authors: Pinto Adriana C.S. , Wiederhecker Helga C. , Colli Guarino R.
Published: June 2005

We describe the sexual dimorphism in coloration, body shape, and body size in
Tropidurus torquatus, a widely distributed lizard species in central Brazil.
Adult males have colored patches varying from yellow to yellow-and-black,
and black on the abdomen, ventral aspect of the thighs, and pre-cloacal
flap. Adult females lack ventral colored patches. During ontogeny, there is
a gradual darkening of the patches, but no modification either in patch size
or color is associated with the reproductive cycle. Adult males have wider
heads and thinner bodies than females of the same body size. Males and
females grow at the same rate prior to sexual maturity, but males take
longer to reach sexual maturity, maturing at a larger body size than
females.
Food availability induces geographic variation in reproductive timing of an aquatic oviparous snake (Natrix maura)
Authors: Santos X. , Llorente G.A. , Feriche M. , Pleguezuelos J.M. , Casals F. , de Sostoa A.
Published: June 2005

The viperine snake Natrix maura is a common water snake, which forages on
aquatic prey such as fish and frogs in Western Mediterranean water bodies.
Female viperine snakes collected from three populations at the Iberian
Peninsula during the vitellogenesis period were compared. Mean clutch size
and range, as well as the slope of the regression between body size and
clutch size, did not show differences between populations. In contrast, mean
size of enlarged follicles of females collected in May from the Ebro Delta
proved significantly smaller than those of females from the Matarranya River
(50 km far) and the Granada Depression (500 km far). There were no
differences in climatic conditions between areas. However, seasonal
variation in food availability was significantly different in the Ebro
Delta. In this area, the rice fields are dry in early spring as men control
the water flow, and prey are not available. This energetic constraint
induced female viperine snakes to adjust reproductive timing according to
seasonal availability and to delay vitellogenesis for at least one month. By
contrast, other Mediterranean populations exhibited a rather high prey
availability from early spring (e.g. Matarranya River), females being in
good condition in this season and consequently vitellogenesis starting
earlier than in the Ebro Delta. This study illustrates a new case of
reproductive plasticity in snakes.
Protein polymorphism in populations of Boa constrictor occidentalis (Boidae) from Córdoba province, Argentina
Authors: Rivera Paula C. , Chiaraviglio Margarita , Pérez Gabriela , Gardenal Cristina N.
Published: June 2005

Boa constrictor occidentalis, the only subspecies of the genus Boa present in
Argentina, is endangered because of the strong hunting pressure due to the
skin and pet-shop trade and the destruction and fragmentation of its
habitat. We estimated levels of protein polymorphism and determined the
degree of genetic differentiation between two populations of B. c.
occidentalis in Córdoba province, Argentina. We obtained blood samples from
93 specimens in two sampling sites 200 km apart. A total of 17 proteins
affording information on 25 presumptive loci were studied by gel
electrophoresis techniques. Only four loci were polymorphic: 6-Pgdh-1,
Cat-1, Ldh and Hp. The mean heterozygosity per locus was low (0.06 and
0.07). Life history and ecological traits of this snake may explain the low
levels of polymorphism found. No evidence of inbreeding was detected. The
average genetic differentiation between the two sampled areas was not
significant ( = 0.004). These results would indicate a relatively recent
fragmentation of an original gene pool.
Age, size and growth of the southern crested newt Triturus karelinii (Strauch 1870) in a population from Bozdag (Western Turkey)
Authors: Olgun Kurtulus , Uzum Nazan , Avci Azız , Miaud Claude
Published: June 2005

We studied the characteristics of bone growth assessed by skeletochronology
in a southern crested newt Triturus karelinii (Urodela) population from
Western Turkey. The timing and patterns of bone arrested growth were
observed using the phalanges of juveniles and adults that were caught in
spring at a breeding site. A metamorphosis line was found in the juveniles.
In some adults, a classical succession of single lines of arrested growth
was observed in about 50% of the cross sections. However, the other adults
exhibited a succession of double lines of arrested growth in their
phalanges. Due to the arid summer and cold winter climate in the Bozdag
region (1200 m a.s.l.), we argue that in this last case, the lines of
arrested growth were deposited during both the summer (aestivation) and
winter (wintering). Body length, age and growth were similar in males and
females. The age of maturity was 3 to 4 years old and longevity was 8 and 11
years in males and females respectively. Body length and age among
taxonomically related large bodied newts of the T. cristatus complex were
reported from populations experiencing various environmental conditions.
Body length and age at maturity were similar to that observed in other newt
species. However, longevity seems to be lower than expected in the T.
karelinii studied population. We hypothesized that the arid climate of
Bozdag could cause a higher mortality risk during the terrestrial phase of
the life cycle. Studying more populations exposed to various conditions is
clearly needed to assess interpopulational variation of these life-history
traits in this newt species.
Mixing and Entrainment in the Red Sea Outflow Plume. Part I: Plume Structure
Authors: Peters Hartmut , Johns William E. , Bower Amy S. , Fratantoni David M.
Published: June 2005

When the salty and heavy water of the Red Sea exits from the Strait of Bab el Mandeb, it continues downslope into the Gulf of Aden mainly along two channels. The 130-km-long “Northern Channel” (NC) is topographically confined and is typically only 5 km wide. In it, the Red Sea plume shows unanticipated patterns of vertical structure, turbulent mixing, and entrainment. Above the seafloor a 25–120-m-thick weakly stratified layer shows little dilution along the channel. Hence this bottom layer undergoes only weak entrainment. In contrast, a 35–285-m-thick interfacial layer shows stronger entrainment and is shown in a companion paper to undergo vigorous turbulent mixing. It is thus the interface that exhibits the bulk of entrainment of the Red Sea plume in the NC. The interfacial layer also carries most of the overall plume transport, increasingly so with downstream distance. The “Southern Channel” (SC) is wider than the NC and is accessed from the latter by a sill about 33 m above the floor of the NC. Entrainment into the bottom layer of the SC is diagnosed to be strong near the entry into the SC such that the near-bottom density and salinity are smaller in the SC than in the NC at the same distance from Bab el Mandeb. In comparison with winter conditions, the authors encountered weaker outflow with shallower equilibration depths during the summer cruise. Bulk Froude numbers computed for the whole plume varied within the range 0.2–1. Local maxima occurred in relatively steep channel sections and coincided with locations of significant entrainment.
Fall–Winter Current Reversals on the Texas–Louisiana Continental Shelf
Authors: Chu Peter P. , Ivanov Leonid M. , Melnichenko Oleg V.
Published: June 2005

Fall–winter recurrence of current reversal from westward to eastward is identified on the Texas–Louisiana continental shelf using the current-meter [Texas–Louisiana Shelf Physical Oceanography Program (LATEX-A)] and near-surface drifting buoy [Surface Current and Lagrangian Drift Program (SCULP-1)] observations in 1993 and 1994. Reversal events roughly satisfy the Poisson distribution with one current reversal nearly every 12 days. Synoptic winds seem responsible for the current reversal events. Other processes such as offshore eddies shed from the Loop Current and river runoff are less important to change alongshore flow direction at synoptic scales. A statistical model is established to predict the synoptic current reversal using the surface wind observations.
The Effects of Wind Forcing and Background Mean Currents on the Latitudinal Structure of Equatorial Rossby Waves
Authors: Perez Renellys C. , Chelton Dudley B. , Miller Robert N.
Published: June 2005

The latitudinal structure of annual equatorial Rossby waves in the tropical Pacific Ocean based on sea surface height (SSH) and thermocline depth observations is equatorially asymmetric, which differs from the structure of the linear waves of classical theory that are often presumed to dominate the variability. The nature of this asymmetry is such that the northern SSH maximum (along 5.5°N) is roughly 2 times that of the southern maximum (along 6.5°S). In addition, the observed westward phase speeds are roughly 0.5 times the predicted speed of 90 cm s−1 and are also asymmetric with the northern phase speeds, about 25% faster than the southern phase speeds. One hypothesized mechanism for the observed annual equatorial Rossby wave amplitude asymmetry is modification of the meridional structure by the asymmetric meridional shears associated with the equatorial current system. Another hypothesis is the asymmetry of the annually varying wind forcing, which is stronger north of the equator. A reduced-gravity, nonlinear, β-plane model with rectangular basin geometry forced by idealized Quick Scatterometer (QuikSCAT) wind stress is used to test these two mechanisms. The model with an asymmetric background mean current system perturbed with symmetric annually varying winds consistently produces asymmetric Rossby waves with a northern maximum (4.7°N) that is 1.6 times the southern maximum (5.2°S) and westward phase speeds of approximately 53 ± 13 cm s−1 along both latitudes. Simulations with a symmetric background mean current system perturbed by asymmetric annually varying winds fail to produce the observed Rossby wave structure unless the perturbation winds become strong enough for nonlinear interactions to produce asymmetry in the background mean current system. The observed latitudinal asymmetry of the phase speed is found to be critically dependent on the inclusion of realistic coastline boundaries.
Non-Normal Effects on Salt Finger Growth
Authors: Eisenman Ian
Published: June 2005

Salt fingers, which occur because of the difference in diffusivities of salt and heat in water, may play an important role in ocean mixing and circulation. Previous studies have suggested the long-time dominance of initially fastest growing finger perturbations. Finger growth has been theoretically derived in terms of the normal modes of the idealized system, which include a growing mode and a pair of decaying internal wave modes. Because these normal modes are not orthogonal, however, transient effects can occur related to the interaction between the modes, as explained by the generalized stability theory of non-normal growth. Initial growth of a perturbation that is not along a normal mode can be faster than the leading normal mode. In this study, the effects of non-normal growth on salt finger formation are investigated. It is shown that some salt finger perturbations that are a superposition of the growing mode and the decaying modes initially grow faster than pure growing normal mode perturbations. These non-normal effects are found to be significant for up to 10 or more e-folding times of the growing normal mode. The generalization of the standard idealized salt finger growth dynamics to include non-normal effects is found to lead to fastest-growing fingers that agree less well with observed fully developed salt fingers than the fastest-growing normal mode previously investigated.
Baroclinic Instability of Frontal Geostrophic Currents over a Slope
Authors: Pavec Marc , Carton Xavier , Swaters Gordon
Published: June 2005

The Phillips problem of baroclinic instability is generalized in a frontal geostrophic model. The configuration used here is a two-layer flow (with quasigeostrophic upper-layer current) over a sloping bottom. Baroclinic instability in the frontal model has a single unstable mode, corresponding to isobaths and isopycnals sloping in the same direction, contrary to the quasigeostrophic model, which has two unstable modes. In physical terms, this is explained by the absence of relative vorticity in the lower (frontal) layer. Indeed, the frontal geostrophic model can be related to the quasigeostrophic model in the limit of very small thickness of the lower layer, implying that potential vorticity reduces to vortex stretching in this layer. This stability study is then extended to unsteady flows. In the frontal geostrophic model, a mean flow oscillation can stabilize an unstable steady flow; it can destabilize a stable steady flow only for a discrete spectrum of low frequencies. In this case, the model equations reduce to the Mathieu equation, the properties of which are well known.
An Historical Review of the Mental Health Services in the People’s Republic of China
Authors: Yip Kam-Shing
Published: June 2005

Background: This paper is an attempt to describe the historical development of the mental health services in the PRC.

Research Methods: An archive of related literature

Findings: The development of the mental health services in the PRC could be divided into several stages: the introduction of mental asylums by western missionaries before 1949; indigenization of the treatment model after the establishment of the PRC (1949-1963). Strong political control governed diagnosis and treatment as well as detention and discharge of mental patients during the Cultural Revolution (1964-1976). Later, because of modernization and reform advocated by Deng Xiao-ping, western models of treatment and rehabilitation were gradually introduced by psychiatrists in the PRC. Nevertheless, dilemmas such as human rights versus political control, community integration versus community control, diversity versus centrality, huge demand but inadequate services seemed to challenge the further development of the mental health service in the PRC.
Social Services Day Care and Health Services Day Care in Mental Health: Do they Differ?
Authors: Catty Jocelyn , Goddard Kim , Burns Tom
Published: June 2005

Background: The difference between the services provided by day hospitals and day centres is far from clear. The supposition that day hospitals would provide an acute service, while day centres would offer social support for a more chronic population has been contentious and there is little evidence of how they are currently used.

Aims: We aimed to ascertain the differences between day hospitals (partial hospitalisation) and social service day centres in functions and roles, as perceived by staff, service users and referrers.

Methods: The views of service users and staff at two day hospitals and four day centres were ascertained through questionnaires and interviews, along with those of staff of eight Community Mental Health Teams, who constitute the sole pathway to the two services.

Results: Day hospitals were perceived by both referrers and clients to offer short-term, more intensive ‘treatment’ to more acutely ill people in need of mental health monitoring. Day centres were perceived to offer longer-term support, particularly social support, to people more likely to have longer-term and psychotic illnesses.

Conclusion: There is currently a clear distinction between day centres and day hospitals, in key features of their services and client groups. It would be unwise to treat them as interchangeable.
Polyurethane Catalysis by Tertiary Amines
Authors: Van Maris Roger , Tamano Yutaka , Yoshimura Hiroyuki , Gay Kenneth M.
Published: June 2005

In the production of polyurethane foam, catalysts play an important role. With a good selection of the catalyst, the desired profile in reaction, foaming, flowability, and foam properties can be obtained. In this article a deeper insight into the molecular catalyst structure-polymer properties relationship will be given. The selection of catalyst is based on its activity as well as performance on physical foam properties. Depending on the molecular structure of the catalyst, the activity will be different. This activity relates to the catalysis of the gel and blow reaction but also the allophonate, biuret, and trimerisation reactions. Via a model system, each of these reactions is studied to understand the reaction mechanism in a better way.
A Study of the Reaction Kinetics of Polyisocyanurate Foam Formulations using Real-time FTIR
Authors: Romero Richard R. , Grigsby Robert A. , Rister Ernest L. , Pratt Jennifer K. , Ridgway Don
Published: June 2005

The use of alternative blowing agents for the production of polyisocyanurate (PIR) rigid foam has created a need to better understand how various catalysts participate in isocyanurate formation. The improvement of isocyanate conversion to isocyanurate is one approach to overcome the greater flammability inherent with the use of hydrocarbons. In situ Fourier Transform Infrared (FTIR) has been used to follow the reaction kinetics of PIR development during foam preparation.

The activity of amine catalysts for isocyanate conversion is characterized through the use of in situ FTIR. Identification of the reaction products formed from the blowing, gelling, and trimerization reactions provides the opportunity to profile the catalytic effects as the reaction proceeds. Several traditional amine catalysts used by PIR foam manufacturers have been evaluated. The design of catalyst blends in PIR formulation can now be based upon the results of the catalytic activity characterization.

In this article, the focus is on understanding the synergies between catalysts used in PIR formulations. Real-time in situ FTIR is the technique of choice for the evaluation of catalysts blends for optimal performance and processing properties.
Experimental Study of FRP Tube-encased Concrete Columns
Authors: Li Guoqiang , Torres Sadi , Alaywan Walid , Abadie Christopher
Published: June 2005

Fiber-reinforced plastic (FRP) tube-encased concrete columns (FRP/ECCs) represent a formwork-free, steel-free, and corrosion-resistant alternative for construction of new infrastructure. In this study, twenty-seven φ101.6 × 304.8 mm2FRP/ECCs are prepared. The composite columns are divided into three equal groups. Each group is prepared using concrete with different 28-d compressive strength. The first group is prepared using 35 MPa concrete, the second group using 50 MPa concrete, and the third one using 80 MPa concrete. FRP tubes with 5-mm wall thickness are used, which are filament-wound E-glass fiber-reinforced vinyl ester tubes with fibers orientated at ±54° from the axial direction. Coaxial compression, four-point bending, and push-out tests are conducted. Strain gages are used to monitor the local strain distributions of the FRP tubes. It has been found that the structural behavior of FRP/ECCs depends on the concrete strength. The confinement efficiency and the interfacial bonding strength are low for very high strength concrete.