bluuebunny/crossref_metadata_2025 huggingface dataset:
The lower Proterozoic Fern Creek Formation, northern Michigan: mineral and bulk geochemical evidence for its glaciogenic origin
Authors: Argast Anne
Published: July 2002

Bulk chemical data indicate the Fern Creek Formation (Early Proterozoic, Marquette Range Supergroup, Lower Chocolay Group) originated as a glacial till, resolving an old argument about the correct interpretation for diamictite-containing units within the formation. There are poor correlations among SiO2,Al2O3,and K2O, and the chemical index of alteration averages 55. These are qualities characteristic of tills and other sediments accumulated in the absence of chemical weathering and transport-induced sorting and inconsistent with an origin as a fluvial deposit (the principal alternate hypothesis). The Archean Carney Lake Gneiss might be the source for at least the lower portions of the Fern Creek Formation. Compositions are similar, and rare earth element trends in the Fern Creek Formation are consistent with derivation from an Archean high-grade terrane. Pegmatites in the gneiss could be the source for monazite, huttonite, and an unnamed fluor-hydroxy-rare earth mineral that occurs in the midsection of the Fern Creek Formation. In addition, mineral and bulk chemical trends are consistent with models involving deep erosion of a complex Archean source, similar to models previously developed for Gowganda tills in the Huronian Supergroup. Samples of the Sturgeon River Quartzite occurring above the Fern Creek Formation were also analyzed. The bulk chemistry is consistent with a well-sorted, supermature quartz arenite.
Evolution of 3.1 and 3.0 Ga volcanic belts and a new thermotectonic model for the Hopedale Block, North Atlantic craton (Canada)
Authors: James D T , Kamo S , Krogh T
Published: July 2002

A new model for evolution of the Archean Hopedale Block, based on mapping and supporting UPb geochronological and geochemical studies, is highlighted by (i) ca. 3.25 Ga emplacement of igneous precursors of Maggo Gneiss; (ii) >3.1 Ga, high-grade Hopedalian metamorphism and attendant deformation; (iii) emplacement of the Hopedale mafic dykes; (iv) 3.1 Ga deposition of Hunt River volcanic rocks; (v) ca. 3.0 Ga deposition of Florence Lake volcanic rocks; (vi) 2.882.96 Ga, greenschist- to amphibolite-facies Fiordian metamorphism and formation of penetrative, northeast-striking Fiordian structures; and (vii) emplacement of a suite of 2.892.83 Ga tonalite to granite intrusions, which partially overlap and locally postdate Fiordian metamorphism and deformation. The Hunt River and Florence Lake volcanic sequences are different in age but similar in most other respects. The former consists mainly of amphibolite-facies mafic metavolcanic rocks and lesser amounts of komatiite flows and metasedimentary and 3105 ± 3 Ma felsic volcanic rocks. The Florence Lake volcanic belt consists mainly of greenschist- to amphibolite-facies mafic metavolcanic rocks, lesser amounts of felsic metavolcanic rocks, dated at 2979 ± 1 and 2990 ± 2 Ma, komatiite flows, and rare metasedimentary rocks. The similarity of rock types, field relationships between different rock types, such as the common association of ultramafic and felsic metavolcanic rocks, and the chemistry of volcanic rocks in both belts suggest a common tectonic setting for each belt. A model involving episodic volcanism, separated by 100 Ma, in ensialic basins is consistent with the dominance of tholeiitic basalt and an abundance of pre-volcanic basement.
Dextral strike-slip faulting in the Cariboo Mountains, British Columbia: a natural example of wrench tectonics in relation to Cordilleran tectonics
Authors: Reid L F , Simony P S , Ross G M
Published: July 2002

The Cariboo Mountains, British Columbia, contain an intracontinental dextral strike-slip fault system that crosscuts the regional fold structures. This fault system accounts for a minimum of 120 km and a maximum of 200 km of dextral strike-slip displacement. This probably accommodates some of the motion associated with the southern termination of the Northern Rocky Mountain Trench Fault and is part of a step-over zone between the Northern Rocky Mountain Trench Fault and the Fraser River  Straight Creek fault systems. The Isaac Lake Synclinorium is a kilometre-scale Jurassic fold structure that is bounded by the dextral oblique Isaac Lake and Winder strike-slip faults. These faults are part of the regional strike-slip fault system that is found throughout the Cariboo Mountains. Deformation associated with the strike-slip faults is complex and is partitioned into motion along the faults and into the formation of kilometre-scale folds that are found in areas between the faults. The angular relationship between the strike-slip faults and folds conforms to models developed for dextral strike-slip fault systems with drag on high-friction faults. We interpreted these structures to have formed during a continuous deformation event. Timing constraints indicate that faulting started by the Late Cretaceous and may have had a long and protracted history into the Tertiary.
The Ketilidian orogen of South Greenland: geochronology, tectonics, magmatism, and fore-arc accretion during Palaeoproterozoic oblique convergence
Authors: Garde A A , Hamilton M A , Chadwick B , Grocott J , McCaffrey K JW
Published: July 2002

Recent fieldwork, geochemistry, and UPb geochronology in the Palaeoproterozoic Ketilidian orogen provide substantial insights into the timing and mechanisms of its magmatic, sedimentary, and tectonic accretion. From north to south the orogen comprises an Archaean foreland and Border Zone, a calc-alkaline arc, and a migmatized fore arc. Contrasting the marginally older Nagssugtoqidian orogen of central West Greenland, the Ketilidian orogen is juvenile, lacks evidence of continentcontinent collision, and probably evolved during northward subduction of an oceanic plate under the Archaean craton, with a suture south of the present orogen. Palaeoproterozoic dolerite dyke emplacement into the cratonic margin was followed by deposition of Ketilidian cover rocks. Thrusting and dextral transpression before 1848 Ma in the northwest may correlate with 18951870 Ma dextral transpression in the Makkovik orogen, Labrador. Sinistral transpression and I-type granite emplacement followed at 18481805 Ma. In the northeast, limited geochronology indicates deformation and metamorphism at ca. 1800 Ma. The calc-alkaline Julianehåb batholith was largely emplaced between 18541795 Ma during sinistral transpression, giving rise to steep magmatic fabrics and northeast-trending shear zones. Until 1790 Ma, the proximal fore-arc basin (Psammite Zone) received coarse detritus from the batholith, and turbidity currents swept sands and muds into distal parts. Fore-arc sedimentation, pervasive deformation, high temperature  low pressure (HTLP) metamorphism and anatexis occurred at 17951785 Ma: flat-lying planar fabrics with top-to-northeast transport were due to tectonic decoupling at the outboard batholith margin during continued transpression. Rapakivi granite sheets were emplaced at 17551732 Ma and folded into broad arches and narrow synclinal cusps compatible with late-stage sinistral transpression.
Landscape characteristics, land use, and coho salmon (Oncorhynchus kisutch) abundance, Snohomish River, Wash., U.S.A.
Authors: Pess George R , Montgomery David R , Steel E Ashley , Bilby Robert E , Feist Blake E , Greenberg Harvey M
Published: July 2002

We used temporally consistent patterns in the spatial distribution of returning adult coho salmon (Oncorhynchus kisutch) to explore relationships between salmon abundance, landscape characteristics, and land use patterns in the Snohomish River watershed, Wash. The proportion of total adult coho salmon abundance supported by a specific stream reach was consistent among years, even though interannual adult coho salmon abundance varied substantially. Wetland occurrence, local geology, stream gradient, and land use were significantly correlated with adult coho salmon abundance. Median adult coho salmon densities in forest-dominated areas were 1.53.5 times the densities in rural, urban, and agricultural areas. Relationships between these habitat characteristics and adult coho salmon abundance were consistent over time. Spatially explicit statistical models that included these habitat variables explained almost half of the variation in the annual distribution of adult coho salmon. Our analysis indicates that such models can be used to identify and prioritize freshwater areas for protection and restoration.
Estimating riverine fish population size from single- and multiple-pass removal sampling using a hierarchical model
Authors: Wyatt Robin J
Published: July 2002

A hierarchical model is described for estimating population size from single- and multiple-pass removal sampling. The model is appropriate for two-stage sampling schemes, typified by surveys of riverine fish populations, in which multiple sites are surveyed, but a low number of passes are undertaken at each site. The model estimates the average population size within the target area from the raw catch data, and thus allows for differences in the sampling procedure at each site, such as including single-pass sampling. The model also uses the data from all sites to estimate the population size at each individual site. This results in generally improved precision for multiple-pass sites and provides comparable estimates from single-pass sites. A Bayesian approach is described for estimating the parameters of the hierarchical model using sampling importance resampling (SIR). An empirical Bayesian approach, which ignores prior uncertainty but is simpler to implement, is also described. Application of the hierarchical model is illustrated with electrofishing data for 0+ trout (Salmo trutta) in the River Inny, U.K.
Estimating and testing non-additivity in fishing mortality: implications for detecting a fisheries collapse
Authors: Myers Ransom A , Quinn II Terrance J
Published: July 2002

Common in many fisheries collapses is a disproportionate increase in fishing mortality at younger ages. One mechanism by which this increase could occur is sufficient depletion of the population at older ages due to strong overfishing, which leads to targeting of younger fish. Thus, it is essential for assessments to estimate and test for a change in selectivity in the fishery. We introduce a simple and powerful approach based upon Tukey's one degree of freedom test for non-additivity. This approach can be applied within any statistical age-structured population model that estimates selectivity. We illustrate the approach with data from Atlantic cod (Gadus morhua) from St. Pierre Bank, Canada. The results show significant non-additivity in fishing mortality that translates into an increase in selectivity on younger ages when fishing mortality is high. This approach also can be applied to the output of an age-structured model that assumes catch-at-age is known without error or to any survey or catch-per-unit-effort data for which estimates of abundance are made by year and age. We believe that this approach should be routinely applied in assessments, particularly when overfishing has led to depletion of the overall population or to truncation of the age structure.
Production of negatively charged particles in nucleusnucleus collisions at 200A GeV
Authors: Liu F -H
Published: July 2002

Three isotropic emission fireballs are used to describe the rapidity (or pseudorapidity) and transverse momentum distributions of negatively charged particles produced in nucleusnucleus collisions at high energy. The calculated results are compared and shown to be in agreement with the experimental data of 16OAu, 32SS, and 32SAg collisions at 200A GeV.

PACS Nos.: 25.75-q, 24.10Pa
The optimal length of a rifle barrel
Authors: Mohazzabi P , Shefchik B M
Published: July 2002

A simple thermodynamic model for projectile propulsion inside a rifle barrel results in a functional relationship between the muzzle speed of the rifle and its barrel length. This relationship is in excellent agreement with the existing experimental data over a wide range of barrel lengths.

PACS No.: 45.40.Gj, 89.00
Studies for the Odin sub-millimetre radiometer. II. Retrieval methodology
Authors: Baron Ph. , Ricaud Ph. , Noë J de la , Eriksson J EP , Merino F , Ridal M , Murtagh D P
Published: July 2002

This paper presents the first algorithm developed to retrieve atmospheric vertical profiles of trace gases from calibrated spectra measured by the sub-millimetre radiometer (SMR) onboard the Odin satellite. An estimation of atmospheric profiles is obtained by means of an inversion of the spectra using the Optimal Estimation Method. Great attention is paid to the study of the simultaneous retrieval of several species and nonlinearity effects. The measurement response is defined to give the altitude domain of a good retrieval. Main sources of measurement and forward model errors are characterized and separated into two categories: the fixed errors and the variable errors. We define a standard retrieval strategy that can be applied to theoretically investigate any frequency band of any observing Odin mode. For each frequency band, two categories of species are defined: the target species, i.e., the main species to be retrieved, and the interfering species, i.e., molecules emitting an interfering radiance in the observed band. The standard code is based upon an inversion of spectra using a linearized forward model and simultaneously estimates target species and interfering species. As an example, inversions of synthetic noise-free spectra of ozone and chlorine monoxide within an autocorrelator band ranging from 501.18 to 501.58 GHz are shown to behave as expected in the middle stratosphere and in the lower mesosphere. The error analysis shows retrieval limitations in the lower stratosphere that are mainly induced by the high sensitivity of the retrieval to parameters such as tangent height, accuracy in the vertical profile of the interfering species, and spectral parameters of both target lines and interfering lines.

PACS Nos.: 42.68Ay, 07.07Df, 07.57Kp
A method for recovering stratospheric minor species densities from the Odin/OSIRIS scattered-sunlight measurements
Authors: McDade I C , Strong K , Haley C S , Stegman J , Murtagh D P , Llewellyn E J
Published: July 2002

A method for recovering minor species density profiles in the stratosphere from observations made with the OSIRIS (optical spectrograph and infrared imager system) instrument on the Odin satellite is described. The OSIRIS instrument measures limb radiances of scattered sunlight over the spectral range 2800 to 8000 Å, for tangent heights ranging from 10 to 100 km. We describe how the limb spectra may be processed using the DOAS (differential optical absorption spectroscopy) technique to derive apparent column densities for the minor atmospheric constituents O3, NO2, OClO, and BrO. We also show how these column densities, measured over a range of tangent heights, may be inverted using an iterative least-squares technique to determine the local density profiles. The procedures are illustrated using simulated limb radiances generated with a realistic OSIRIS instrument model.

PACS Nos.: 42.68Mj, 94.10Dy
Microwave temperature and pressure measurements with the Odin satellite: I. Observational method
Authors: Pardo J R , Ridal M , Murtagh D , Cernicharo J
Published: July 2002

The Odin satellite is equipped with millimetre and sub-millimetre receivers for observations of several molecular lines in the middle and upper atmosphere of our planet (~25100 km, the particular altitude range depending on the species) for studies in dynamics, chemistry, and energy transfer in these regions. The same receivers are also used to observe molecules in outer space, this being the astrophysical share of the project. Among the atmospheric lines that can be observed, we find two corresponding to molecular oxygen (118.75 GHz and 487.25 GHz). These lines can be used for retrievals of the atmospheric temperature vertical profile. In this paper, we describe the radiative-transfer modeling for O2 in the middle and upper atmosphere that we will use as a basis for the retrieval algorithms. Two different observation modes have been planned for Odin, the three-channel operational mode and a high-resolution mode. The first one will determine the temperature and pressure on an operational basis using the oxygen line at 118.75 GHz, while the latter can be used for measurements of both O2 lines, during a small fraction of the total available time for aeronomy, aimed at checking the particular details of the radiative transfer near O2 lines at very high altitudes (>70 km). The Odin temperature measurements are expected to cover the altitude range ~3090 km.

PACS Nos.: 07.57Mj, 94.10Dy, 95.75Rs
Vertical polarization for transient plane waves obliquely incident on a conductive half-space
Authors: Abo-Seida O M
Published: July 2002

The vertical polarization for transient plane waves obliquely incident on a conductive half-space is analytically evaluated. It is assumed that the dispersive half-space is homogenous. Starting with the transmitted waves in the frequency domain, the corresponding time-domain expressions are first represented as inverse Laplace transforms. The integrals of the fields are numerically solved and the results are represented graphically.

PACS Nos.: 41.20Jb, 42.25Bs, 42.25Gy, 44.05+e
Low-temperature electrical conductivity of ternary chalcogenide glasses in the system SeS
Authors: El-Shazly O , Ramadan T , El-Hawary M , El-Anany N , Motaweh H A , El-Wahidy E F
Published: July 2002

Ternary chalcogenide glasses in the system SeS were prepared by quenching from the melt. Measurements of the temperature dependence of direct current (dc) electrical conductivity have been made in the temperature interval from room temperature down to 30 K. Two types of conduction mechanisms were found to dominate in the measured temperature range, namely band conduction through extended states (which dominates at the high-temperature region) and hopping around the Fermi level (which dominates at the low-temperature region). The dc conductivity activation energy and pre-exponential factor were calculated for the two types of conduction. It was found that the activation energy and the pre-exponential factor are composition dependent. PACS Nos.: 72.20-i, 73.61.Jc, and 81.05.Gc
Anharmonic coherent states and E ε JahnTeller coupling
Authors: Avram N M , Draganescu Gh. E , Avram C N
Published: July 2002

The octahedral JahnTeller system with E [Formula: see text] ε coupling is studied in the frame of the anharmonic vibrations described by a Morse potential using anharmonic coherent states. The energy levels have been established.

PACS Nos.: 31.30Gs, 71.70Ej, 42.50Ar, 42.50Ct, 33.20Wr
Laser spectroscopic measurements of hyperfine structure in Pr II
Authors: Rivest R C , Izawa M R , Rosner S D , Scholl T J , Wu G , Holt R A
Published: July 2002

We have used fast-ion-beam laser spectroscopy to measure the hyperfine structure of 36 transitions in Pr II in the wavelength range 420460 nm, obtaining the hyperfine constants of 8 odd-parity levels in the range 05079 cm1 and 32 even-parity levels in the range 22 04028 578 cm1 with a typical accuracy of 0.2%. These will find useful application in stellar elemental abundance studies.

PACS Nos.: 32.30-r, 32.10-f
Microwave temperature and pressure measurements with the Odin satellite: II. Retrieval method
Authors: Ridal M , Murtagh D P , Merino F , Pardo J R , Pagani L
Published: July 2002

The millimetre receiver on the Swedish satellite Odin, will be used for detection of the 118.750 GHz oxygen line. The temperature and pressure will be determined from the output of a three-channel filter bank measurement. One frequency bin is centred over the emission-line frequency while the other two cover parts of the line wing, where the opacity is less, providing a useful signal at lower altitudes. The bandwidth of each channel is 40 MHz. The signal in the frequency bin covering the line centre is modeled by a high-resolution model including the Zeeman effect, developed by the Observatoire de ParisMeudon. The other two 40 MHz bins are modeled using the much faster standard Odin forward model, developed at the Department of Meteorology at Stockholm University together with Chalmers University of Technology. The operational retrievals employ an iterative method that uses simulated signals from a reference atmosphere as a lookup table for the pressure. The temperature is then calculated from the equation of hydrostatic equilibrium, and a new lookup table computed. This process is repeated until a convergence criterion is reached. Simulations, including known error sources, show that the temperature can be retrieved with a root mean square (rms) around 3 K, in the altitude range ~ 2590 km using the operational temperature retrieval method (the filter bank method). A sub-millimetre receiver on board Odin will also be used to observe the oxygen line at 487.249 GHz. Both this line and the 118.750 GHz line can be observed in high resolution (150 kHz) for detailed studies of the Zeeman splitting. Retrievals from the high-resolution measurements are expected to give a precision of ± 2 K rms at that resolution. However, this kind of observation will occupy an entire spectrometer and will not be made on a regular basis.

PACS Nos.: 07.57Yb, 94.10Dy, 95.75Rs
Mesospheric ozone: Determination from orbit with the OSIRIS instrument on Odin
Authors: Khabibrakhmanov I K , Degenstein D A , Llewellyn E J
Published: July 2002

The analysis of the data from the optical spectrograph and infrared imager system (OSIRIS) that will fly on the Odin satellite requires special attention as many of the measurements will be made in regions of the atmosphere that are relatively close to terminator. Under these conditions the photochemical processes in the upper atmosphere that are responsible for much of the oxygen infrared atmospheric band airglow emission are nonstationary. It is this latter aspect that complicates the retrieval of the mesospheric ozone profile from the OSIRIS observations. However, a tomographic analysis technique that has been developed specifically for the Odin project allows accurate recovery of local volume emission rates in the orbit plane. It is shown that the tomographic analysis technique can be combined with nonstationary atmospheric photochemistry models to recover the mesospheric ozone profile near the terminator.

PACS Nos.: 94.10Fa, 94.10Rk
Numerical investigations into static and quasistatic problems of two-dimensional dry elastic frictional contact
Authors: Schlesinger M , McAven L F , Yao Y
Published: July 2002

A numerical-modelling method is developed to investigate the stress of the static-equilibrium state of the two-dimensional frictional contact problem achieved through a quasistatic process of increasing loading. The problem of relative tangential displacement between particles on the two contact surfaces is addressed. This scheme relies on solving each of the two contact solids in turn and iterating back and forth. The solutions for the two elastic bodies are connected through the surface traction and surface deformation. The contact surface is approximated by a cubic spline, and friction is modelled using the classical Coulomb friction law. Variational inequalities and finite-element methods are used to implement this scheme and are solved by an optimization method. In addition, the distinction between Cauchy stress and PiolaKirchoff stress is taken into account and discussed. A numerical investigation is conducted into the stress dependence on the loading conditions and geometries of the solids. The results from the numerical examples deviate from Hertz theory and previous reports. Stress is shown to be sensitive to the loading distribution and geometry of contact solids. Therefore, it suggests that an accurate analysis of the dry frictional contact problem requires a refined knowledge of the loading conditions and the total geometry of both solids.

PACS Nos.: 03.40D, 46.30P, 62.20P
Structural effects on chemo- and enantioselectivity ofCandida antarcticalipase B - Resolution of β-amino esters
Authors: Gedey Szilvia , Liljeblad Arto , Lázár László , Fülöp Ferenc , Kanerva Liisa T
Published: July 2002

The Candida antarctica lipase B-catalyzed reactions of five β-amino esters with neat butyl butanoate and with 2,2,2-trifluoroethyl butanoate in diisopropyl ether were studied, as were the reactions of the same β-amino esters and their N-butanamides with neat butanol. The possibility for sequential resolution, where the amino and ester functions of the substrate both react with an achiral butanoate, became less likely with increasing size of the substrate from ethyl 3-aminobutanoate (1a) to pentanoate (1b) or larger. On the other hand, the alcoholyses of N-acylated β-amino esters successfully proceeded in butanol with E > 100. Gram-scale resolution of the N-butanoylated 1a was performed to demonstrate the usefulness of the method. Key words: lipase, interesterification, acylation, alcoholysis, resolution, β-amino esters.
Rationalization of enzyme enantioselectivity by active-site cubic-space models
Authors: Ottolina Gianluca , Carrea Giacomo
Published: July 2002

Active-site models of enzymes are important tools that help researchers in understanding and predicting the stereochemical outcome of enzymatic reactions. In this article, various active-site models for dehydrogenases, hydrolases, oxygenases, and oxynitrilases have been reviewed.
Biomimetic decarboxylative condensation between malonate and acetate units attached to a glycoluril template
Authors: Chen Hao , Harrison Paul H.M.
Published: July 2002

Compound 10 (3,4,7,8-tetramethyl-2,5-dithioglycoluril) was converted in two steps to 12a, which contains a malonate and acetate unit attached to N1 and N6, respectively. These two groups are held in proximity in a manner analogous to the loaded ketosynthase domain of polyketide and fatty acid synthases. After cleavage of the methyl ester by pig liver esterase (PLE), a polar intermediate assigned to acid 15 was separated. This material undergoes conversion to acetoacetylglycoluril 18 upon attempted isolation. The overall conversion thus resembles the decarboxylative condensation catalyzed by ketosynthase. Furthermore, isotope labeling and product studies support a mechanism in which decarboxylation of 15 precedes an intramolecular Claisen-like condensation, as it is believed to occur for the ketosynthase enzymic case. The system thus provides a functional chemical model of the key carboncarbon bond-forming step in fatty acid and polyketide biosynthesis.Key words: biomimetic, decarboxylation, polyketide, esterase, Claisen condensation.
Chemo-enzymatic synthesis of the C15C23unit of Leptomycin B
Authors: Scheck Michael , Waldmann Herbert
Published: July 2002

The asymmetric synthesis of the C15C23unit of Leptomycin B (LMB) is described. All four stereocenters of the C15C23unit were prepared from one building block exhibiting only one stereocenter. This building block was synthesized via either an enzymatic transformation or starting from a chiral reagent.Key words: Leptomycin, natural product synthesis, enzymatic transformation, Aldol reaction, Pseudomonas fluorescence lipase (PFL).
Chemo-enzymatic synthesis of trimeric sialyl Lewisxpentadecasaccharide
Authors: Liu Yeuk Chuen , Li Hong , Otter Albin , Kamath Vivekanand P , Streiff Markus B , Palcic Monica M
Published: July 2002

The enzymatic synthesis of trimeric sialyl Lewisxpentadecasaccharide (6), a 15-mer, from a trimannoside precursor required six different glycosyltransferase enzymes and four nucleotide donor sugars. Three N-acetylglucosaminyl residues were transferred from UDP-N-acetylglucosamine to a trimannoside by N-acetylglucosaminyltransferases I, II, and V, respectively. Galactosylation using β(1[Formula: see text]4) galactosyltransferase and UDP-galactose gave three N-acetyl lactosamine units in nonasaccharide 4. Sialylation of 4 with α(2[Formula: see text]3) sialyltransferase and CMP-N-acetylneuraminic acid was followed by fucosylation with α(1[Formula: see text]3) fucosyltransferase and GDP-fucose giving the 15-mer 6 in mg quantities. Compound 4 was also converted to a trimeric Lewisxdodecasaccharide 12-mer with α(1[Formula: see text]3) fucosyltransferase and GDP-fucose and to a trimeric α-2,6-sialyl N-acetyllactosamine dodecasaccharide 12-mer with α(2[Formula: see text]6) sialyltransferase and CMP-N-acetylneuraminic acid. Key words: glycosyltransferases, pentadecasaccharide, sialyl Lewisx.
Enzymatic synthesis of octyl glucoside catalyzed by almond β-glucosidase in organic media
Authors: Ducret Amélie , Carrière Jean-François , Trani Michael , Lortie Robert
Published: July 2002

The synthesis of n-octyl-β-D-glucopyranoside can be performed by direct condensation of 1-octanol and glucose, catalyzed by immobilized almond beta-glucosidase, using solid glucose suspended in 1-octanol as a reaction media. Both the rate of reaction and the conversion could be enhanced by using acetonitrile and N,N-dimethylformamide (DMF) as co-solvents, the latter giving the best results. The rate of reaction was dependent on the concentration of DMF and on the initial water activity (aw), with higher water activity fostering faster reactions. The rate increased with DMF concentration, up to 20% DMF, but diminished rapidly at higher concentrations. Product concentration could be increased from 40 to 100 mM by going from 0 to 20% DMF; however, it was not sensitive to the initial water activity.Key words: β-glucosidase, alkyl glycosides, reverse hydrolysis, water activity, organic solvent.
Genetic parameters and gains for growth and wood properties in Florida source loblolly pine in the southeastern United States
Authors: Atwood Ryan A , White Timothy L , Huber Dudley A
Published: July 2002

One hundred and thirteen open-pollinated families from Florida source loblolly pine (Pinus taeda L.) were tested in four states in the southeastern United States. Heritabilities and genetic correlations were estimated for volume, specific gravity, and latewood percentage at three different growth stages: juvenile (ages 010 years), mature (1117 years), and total (017 years). Heritabilities of growth traits (0.090.11) were consistently lower than for wood property traits (0.160.33). Growth traits for Florida loblolly exhibited high genotype × environment interaction (rB = 0.44), whereas wood properties did not (rB = 0.90). The higher heritabilities and genetic stability across environments make wood properties amenable to genetic manipulation through breeding programs. In contrast, the high genotype × environment interaction of growth traits for Florida loblolly pine requires more research to understand the possible implication of these effects on breeding programs. Traittrait and ageage genetic correlations were determined for growth and wood properties. Strong positive ageage correlations were present for latewood percentage, volume, and specific gravity. Weak negative traittrait genetic correlations existed between specific gravity and volume across ages (0.13 to 0.43). No genetic correlation existed between latewood percentage and volume, while a moderate favorable genetic correlation existed between latewood percentage and specific gravity (0.47 to 0.59). Genetic gains in volume and specific gravity were compared for various types of selection. In one type, forward selection of the top 20 individuals (of 3484) based on 17-year volume, resulted in a 20.5% genetic gain in volume; however, a concomitant loss of 6.4% also occurred in specific gravity. If a selection index was used to hold specific gravity constant, a gain in total volume of 14% was obtained.
The utility of the two-pass harvesting system: an analysis using the ecosystem simulation model FORECAST
Authors: Welham Clive , Seely Brad , Kimmins Hamish
Published: July 2002

The ecosystem model FORECAST was used to simulate the yield potential in Saskatchewan mixedwoods of the two-pass harvesting system. The simulated two-pass stand consisted of an overstory population of pure trembling aspen (Populus tremuloides Michx.) with a white spruce (Picea glauca (Moench) Voss) understory. The aspen was removed at year 60, and yields of the understory spruce and resprouting aspen were simulated for 80 years thereafter. The two-pass simulations were compared with two simulated conventional harvesting systems. The first system consisted of a single final harvest at year 140. In the second system, a clearcut was conducted at year 60. White spruce was then planted in the subsequent year at 400, 600, or 800 stems/ha, and aspen also permitted to resprout. Growth was then simulated for a further 80 years. FORECAST projections indicated that the two-pass system might be effective for releasing the white spruce understory, achieving at least a twofold gain in spruce volume relative to conventional methods. Furthermore, total volumes exceeded those derived from the unmanaged stand, while second rotation yields of aspen declined with spruce understory density. These simulations suggest the two-pass harvesting system has strong potential as a tool for mixedwood management.
Nonpeptidic endothelin-converting enzyme inhibitors and their potential therapeutic applications
Authors: Jeng Arco Y , Mulder Paul , Kwan Aij-Lie , Battistini Bruno
Published: July 2002

Endothelins (ETs) are potent vasoconstrictors, promitogens, and inflammatory mediators. They have been implicated in the pathogenesis of various cardiovascular, renal, pulmonary, and central nervous system diseases. Since the final step of the biosynthesis of ETs is catalyzed by a family of endothelin-converting enzymes (ECEs), inhibitors of these enzymes may represent novel therapeutic agents. Currently, seven isoforms of these metalloproteases have been identified; they all share a significant amino acid sequence identity with neutral endopeptidase 24.11 (NEP), another metalloprotease. Therefore, it is not surprising that the majority of ECE inhibitors also possess potent NEP inhibitory activity. To date, three classes of ECE inhibitors have been synthesized: dual ECE/NEP inhibitors, triple ECE/NEP/ACE inhibitors, and selective ECE inhibitors. Potential clinical applications of these compounds in hypertension, chronic heart failure, restenosis, renal failure, and cerebral vasospasm deduced from studies with relevant animal models are reviewed.Key words: endothelin-converting enzyme, ECE, inhibitors, phosphoramidon, CGS 26303, CGS 35066, FR 901533, SCH 54470, metalloprotease.
Structural similarity between the bone marrow extracellular matrix protein and neurokinin 1 could be the limiting factor in the hematopoietic effects of substance P
Authors: Rameshwar Pranela , Gascon Pedro , Bandari Persis S , Joshi Deval D , Fernandes Annemarie , Dang Anju
Published: July 2002

In the adult bone marrow (BM), immune cells are replenished through the process of definitive hematopoiesis, which is regulated by a complex process of cellular and humoral interactions. The latter include substance P (SP), a neurotransmitter that is produced by neural and nonneural cells. Neurokinin-1 (NK-1), the high-affinity SP receptor, shares structural similarity with fibronectin, a component of the BM extracellular matrix proteins. This study examines how such similarity could alter the effects of SP on the proliferation of the immature BM progenitors. In vitro studies show that 1 ng fibronectin/mL enhanced the stimulatory effect of SP on the proliferation of primitive BM progenitors. This finding was studied by computational studies: proteomics and three-dimensional molecular modeling. Use of surface-enhanced laser desorption/ionization ProteinChip®technology showed that despite the induction of neutral endopeptidase, exogenous fibronectin hindered the degradation of SP to SP(14). These findings support a protective role for fibronectin in the digestion of SP. Since SP(14) is a negative regulator of hematopoiesis, this report indicates that the structural similarity between fibronectin and NK-1 could be important for maintaining hematopoietic stimulation. These studies could be extrapolated to hematological disorders that are associated with SPfibronectin complexes.Key words: substance P, fibronectin, stem cell, neuropeptide, bone marrow.
Activation and targeting of mitogen-activated protein kinases by G-protein-coupled receptors
Authors: Luttrell Louis M
Published: July 2002

Over the past decade, it has become apparent that many G-protein-coupled receptors (GPCRs) generate signals that control cellular differentiation and growth, including stimulation of Ras family GTPases and activation of mitogen-activated protein (MAP) kinase pathways. The mechanisms that GPCRs use to control the activity of MAP kinases vary between receptor and cell type but fall broadly into one of three categories: signals initiated by classical G protein effectors, e.g., protein kinase (PK)A and PKC, signals initiated by cross-talk between GPCRs and classical receptor tyrosine kinases, e.g., "transactivation" of epidermal growth factor (EGF) receptors, and signals initiated by direct interaction between β-arrestins and components of the MAP kinase cascade, e.g., β-arrestin "scaffolds". While each of these pathways results in increased cellular MAP kinase activity, emerging data suggest that they are not functionally redundant. MAP kinase activation occurring via PKC-dependent pathways and EGF receptor transactivation leads to nuclear translocation of the kinase and stimulates cell proliferation, while MAP kinase activation via β-arrestin scaffolds primarily increases cytosolic kinase activity. By controlling the spatial and temporal distribution of MAP kinase activity within the cell, the consequences of GPCR-stimulated MAP kinase activation may be determined by the mechanism by which they are activated.Key words: G-protein-coupled receptor, receptor tyrosine kinase, β-arrestin, mitogen-activated protein kinase, extracellular signal-regulated kinase.
Relevant role of Leu265in helix VI of the angiotensin AT1receptor in agonist binding and activity
Authors: Correa Silvana Aparecida Alves , França Lucimar Pereira , Costa-Neto Claudio Miguel , Oliveira Laerte , Paiva Antonio Cechelli Mattos , Shimuta Suma Imura
Published: July 2002

The finding of critical residues for angiotensin II (AII) binding and receptor signalling in helices V and VI led us to assess if, in this region of the receptor, aliphatic side chains might play a role in the agonist-mediated mechanism. Two mutations of the angiotensin AT1receptor were designed to explore a possible role of a leucine at two positions, Leu265and Leu268. Thus two mutants, L265D and L268D, were prepared through single substitutions of Leu265, located in the C-terminal region of transmembrane VI (TM-VI), and Leu268, in the adjoining region of the third extracellular loop (EC-3), for an aspartyl residue, and were stably transfected into Chinese hamster ovary (CHO) cells. Ligand-binding experiments and the functional assays determining inositol phosphate (IP) production were performed in these cells expressing these mutants. No significant changes were found in the binding affinity for the ligands, AII, DuP753, and [Sar1Leu8]AII in the mutant L268D. Moreover, the relative potency and the maximum effect on IP production of this mutant were similar to those of the wild-type receptor. In contrast, L265D mutant AT1receptor, located within the transmembrane domain, markedly decreased binding affinity and ability to stimulate phosphatidylinositol turnover. Our results suggest that the hydrophobic side chain of Leu265, at the C-terminal portion of the AT1's TM-VI, but not Leu268, which belongs to the EC-3 loop, might interact with the AII molecule. On the other side, the aliphatic side chain of Leu265may be involved in the formation of the ligand binding sites through allosteric effects, thus helping to stabilize the receptor structure around the agonist binding site for full activity.Key words: angiotensin II, AT1receptor, site-directed mutagenesis.
Melanin-concentrating hormone and its receptors: state of the art
Authors: Boutin Jean A , Suply Thomas , Audinot Valérie , Rodriguez Marianne , Beauverger Philippe , Nicolas Jean-Paul , Galizzi Jean-Pierre , Fauchère Jean-Luc
Published: July 2002

Melanin-concentrating hormone (MCH) is a cyclic neuropeptide of nineteen amino acids in mammals. Its involvement in the feeding behaviour has been well established during the last few years. A first receptor subtype, now termed MCH1R, was discovered in 1999, following the desorphanisation of the SLC1 orphan receptor, using either reverse pharmacology or systematic screening of agonist candidates. A second MCH receptor, MCH2R, has been discovered recently, by several groups working on data mining of genomic banks. The molecular pharmacology of these two receptors is only described on the basis of the action of peptides derived from MCH. The present review tentatively summarizes the knowledge on these two receptors and presents the first attempts to discover new classes of antagonists that might have major roles in the control of obesity and feeding behaviour.Key words: melanin-concentrating hormone, melanin-concentrating hormone receptor, SLC-1, food intake, obesity.
Adenosine participates in regulation of smooth muscle relaxation in aortas from rats with experimental hypothyroidism
Authors: Baños G , Martínez F , Grimaldo J I , Franco M
Published: July 2002

The contribution of adenosine receptors was evaluated in vascular relaxation in experimental hypothyroidism. Hypothyroid aortic rings contracted less than normal controls with noradrenaline, phenylephrine, and KCl; the difference was maintained after incubation with 1,3-dipropyl-8-p-sulfophenylxanthine (an A1 and A2 adenosine receptor blocker). The vascular relaxation induced by acetylcholine or carbachol was similar in normal and hypothyroid aortic rings. However, adenosine, N6-cyclopentyladenosine (an A1 adenosine receptor analogue), and 5'-N-ethylcarbox amidoadenosine (an A2 and A3 adenosine analogue) induced vasodilation that was larger in hypothyroid than in normal aortas. Nω-nitro-L-arginine methyl ester shifted the dose-response curves of adenosine, N6-cyclopentyladenosine, or 5'-N-ethylcarboxamidoadenosine to the right in both normal and hypothyroid vessels. The blocker 1,3-dipropyl-8-p-sulfophenylxanthine significantly reduced adenosine-induced relaxation in the hypothyroid but not in the normal aortic vessels. These results suggest that in hypothyroid aortas, a larger adenosine-mediated vasodilation is observed probably due to an increase in receptor number or sensitivity.Key words: adenosine receptors, nitric oxide, hypothyroidism, smooth muscle, rat aorta.
Seasonal reproduction in the highveld mole-rat, Cryptomys hottentotus pretoriae (Rodentia: Bathyergidae)
Authors: Rensburg L Janse van , Bennett N C , Merwe M van der , Schoeman A S
Published: July 2002

The highveld mole-rat, Cryptomys hottentotus pretoriae, is a cooperatively breeding rodent that exhibits seasonal breeding and a reproductive division of labour. Body mass, reproductive-tract morphometrics, ovarian histology, and plasma oestrogen and progesterone concentrations were studied for both reproductive and non-reproductive females from 55 colonies, the main objective being to determine the inclination of this species towards seasonal breeding. Offspring are born from July through to November. However, qualitative analysis of ovarian histology revealed that reproductive females retain the potential for ovulation and subsequent production of corpora lutea during the late-summer nonbreeding period (DecemberMarch). Seasonal differences were found in ovarian morphometrics and hormone concentrations that are associated with enhanced follicular activation in April and May and subsequent conceptions from July through to November during the breeding period. The nonbreeding period coincides with maximal dispersal opportunities in the summer-rainfall areas inhabited by the highveld mole-rat. Body mass, reproductive-tract morphometrics, testicular histology, and plasma testosterone concentrations were determined for reproductive and non-reproductive males from 37 colonies. Available evidence suggests that there is a gradual increase in testicular mass for reproductive males as the breeding season approaches, but after September the testicular parameters fall. Seminiferous-tubule diameter was significantly greater in reproductive males but exhibited no seasonal variation. Testosterone concentrations were higher in reproductive males. Current data support a lack of gonadal regression in males during the nonbreeding season.
Evolution of the Dawson caribou (Rangifer tarandus dawsoni)
Authors: Byun S A , Koop B F , Reimchen T E
Published: July 2002

The Dawson caribou (Rangifer tarandus dawsoni) was a rare subspecies of caribou that inhabited Haida Gwaii, an archipelago located 80 km off the west coast of Canada. It became extinct during the early part of the 20th century and to this day all that remains of Dawson caribou are several pelts, skulls, and antlers. With the exception of a physical description based on these remains, not much is known about the taxonomy of this subspecies of caribou. Using molecular and ancient-DNA techniques, we sequenced 215 base pairs of the mitochondrial gene cytochrome b and compared these sequences with those from conspecifics Rangifer tarandus caribou (woodland caribou) and Rangifer tarandus granti (barren-ground caribou). These analyses suggest that the Dawson caribou was not genetically distinct. The unique morphology characterizing this extinct form of caribou may have been of recent origin, either from local selection pressures or from environmentally induced phenotypic plasticity.
Forest composition around wolf (Canis lupus) dens in eastern Algonquin Provincial Park, Ontario
Authors: Norris D Ryan , Theberge Mary T , Theberge John B
Published: July 2002

Den-site selection is a poorly understood aspect of wolf (Canis lupus) ecology, particularly for populations in forested ecosystems. Using a geographic information system and remote-sensing imagery, we examined patterns of habitat use around wolf dens in Algonquin Provincial Park, Ontario. Sixteen den sites were sampled for eight habitat types in their immediately vicinity, as well as at radii of 500, 1000, 1500, and 2000 m. We used a resource-selection ratio to determine whether specific habitat types were preferred or avoided at different radii relative to the total proportion of habitat types found within the study area. Wolves established dens in areas with significantly high proportions of pine forest up to and including a 1000-m radius and low proportions of tolerant and intolerant hardwoods within 500 m. We conclude that wolves establish den sites based primarily on the presence of pine forest, a habitat that is frequently logged within Park boundaries and subject to problems with regeneration after cutting. Dens sites are likely not limiting in this population, but our results suggest the need to protect current den sites at a relatively large spatial scale. These results also provide unique information to assess the potential for recolonization and reintroduction of wolf populations in other areas.