bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption modes of cysteine on Au(111): Thiolate, amino-thiolate, disulfide
Authors: Di Felice Rosa , Selloni Annabella
Published: February 2004

The adsorption of cysteine on the (111) surface of gold has been studied by means of periodic supercell density-functional theory calculations. A number of different adsorption modes are examined, including adsorption through the thiol group in either thiolate or disulfide form, and adsorption through both the thiol and amino functional groups. We find that at intermediate coverage densities the latter mode of adsorption is favored, followed by thiolate adsorption at the bridge (slightly displace toward fcc) site. The N–Au and S–Au bond strengths in the amino-thiolate adsorption are estimated to be of the order of 6 and 47 kcal/mol, respectively. The electronic structure of the different systems is analyzed, with focus on the total and projected density of states, as well as on the detailed character of the electronic states at the interface. States near the Fermi energy are found to have a metal–molecule antibonding character, whereas metal–molecule bonding states mostly occur near the lower edge of the Au-d band.
Semi-analytical model of self-amplified spontaneous-emission free-electron lasers, including diffraction and pulse-propagation effects
Authors: Dattoli G. , Giannessi L. , Ottaviani P. L. , Ronsivalle C.
Published: February 2004

We use the high-gain free-electron laser logistic equation to describe the field evolution from spontaneous emission to saturation in the self-amplified spontaneous-emission regime. The model we present is capable of including the effects of diffraction, beam qualities, and pulse propagation.
Macroparticle rotation in the vacuum arc plasma jet
Authors: Gidalevich E. , Goldsmith S. , Boxman R. L.
Published: February 2004

The motion of macroparticles (MPs) emitted from the cathode into the vacuum arc plasma jet is considered taking into account asymmetric ion bombardment of the MP surface. The MP velocity is increased up to 0.17 of the plasma jet velocity for an initial MP radius R0=0.1 μm and up to 0.3 of the plasma jet velocity for R0=0.02 μm. The electric current density distribution within the MP caused by the asymmetric plasma bombardment was calculated assuming homogeneous internal conductivity. The electric potential difference between the apex and antiapex points is ≈10−8 V for an MP radius of R0=0.1 μm, while the average MP electric potential relative to the surrounding plasma is V≈−11.27 V. Interaction between the internal electric current and the magnetic field used to collimate the plasma jet rotates the MPs with a frequency of ≈105 s−1.
Estimation of excess solvation numbers of water and cosolvents from preferential interaction and volumetric experiments
Authors: Shimizu Seishi
Published: February 2004

To elucidate, at a molecular level, how cosolvents influence protein stability, it is indispensable to understand the distribution of water and cosolvent molecules around proteins. Calculation of excess solvation numbers of water and cosolvents serves this purpose, and I show that they can be extracted from preferential interaction parameter and volumeric data via the Kirkwood–Buff theory. This scheme was applied to trehalose and glycerol (stabilizers) and urea (denaturant). Important insights from the application include stabilizer-induced enhancement of protein hydration, which, together with the stabilizer’s exclusion from protein surfaces, may contribute to protein stabilization at high osmolyte concentrations.
Effects of wetting and anchoring on capillary phenomena in a confined liquid crystal
Authors: de las Heras D. , Velasco E. , Mederos L.
Published: February 2004

A fluid of hard spherocylinders of length-to-breadth ratio L/D=5 confined between two identical planar, parallel walls—forming a pore of slit geometry—has been studied using a version of the Onsager density-functional theory. The walls impose an exclusion boundary condition over the particle’s centers of mass, while at the same time favoring a particular anchoring at the walls, either parallel or perpendicular to the substrate. We observe the occurrence of a capillary transition, i.e., a phase transition associated with the formation of a nematic film inside the pore at a chemical potential different from μb—the chemical potential at the bulk isotropic–nematic transition. This transition terminates at an Ising-type surface critical point. In line with previous studies based on the macroscopic Kelvin equation and the mesoscopic Landau–de Gennes approach, our microscopic model indicates that the capillary transition is greatly affected by the wetting and anchoring properties of the semi-infinite system, i.e., when the fluid is in contact with a single wall or, equivalently, the walls are at a very large distance. Specifically, in a situation where the walls are preferentially wetted by the nematic phase in the semi-infinite system, one has the standard scenario with the capillary transition taking place at chemical potentials less than μb (capillary nematization transition or capillary ordering transition). By contrast, if the walls tend to orientationally disorder the fluid, the capillary transition may occur at chemical potentials larger than μb, in what may be called a capillary isotropization transition or capillary disordering transition. Moreover, the anchoring transition that occurs in the semi-infinite system may affect very decisively the confinement properties of the liquid crystal and the capillary transitions may become considerably more complicated.
Growth mechanism and properties of ZnO nanorods synthesized by plasma-enhanced chemical vapor deposition
Authors: Liu Xiang , Wu Xiaohua , Cao Hui , Chang R. P. H.
Published: February 2004

Uniformly distributed ZnO nanorods have been grown by plasma-enhanced chemical vapor deposition using a two-step process. By controlling the oxygen content in the gas mixture during the nucleation and growth steps, no catalyst is required for the formation of ZnO nanorods. High-resolution transmission electron microscopy studies show that ZnO nanorods are single crystals and that they grow along the c axis of the crystal plane. Alignment of these nanorods with respect to the substrates depends on the lattice mismatch between ZnO and the substrate, the surface electric field, and the amount of defects in the starting nuclei. Room-temperature photoluminescence measurements of these ZnO nanorods have shown ultraviolet peaks at 380 nm with a full width at half-maximum of 106 meV, which are comparable to those found in high-quality ZnO films. Photoluminescence measurements of annealed ZnO nanorods in hydrogen and oxygen atmospheres indicate that the origins of green emission are oxygen vacancies and zinc interstitials, while oxygen interstitials are responsible for the orange-red emission. A mechanism for the nanorod growth is proposed.
Temperature dependence of the current conduction mechanisms in ferroelectric Pb(Zr0.53,Ti0.47)O3 thin films
Authors: Juan Trevor Pi-chun , Chen Si-min , Lee Joseph Ya-min
Published: February 2004

The temperature dependence of the current conduction mechanisms in Au/Pb(Zr0.53,Ti0.47)O3/Pt (Au/PZT/Pt) metal–insulator–metal thin-film capacitors was investigated. The dominant current conduction mechanism from 300 to 375 K is space-charge-limited current (SCLC) due to holes and changes to Schottky emission in the temperature range of 400 to 500 K above the electric field of 0.2 MV/cm. It is observed that the transition voltage (Vtr) of SCLC conduction decreases with increasing temperature. Shallow hole trap levels vary from 0.3 to 0.19 eV above the valence-band edge as the temperature varies from 300 to 375 K. The trap-filled-limited voltage (VTFL) increases with increasing temperature. The deep trap level extracted from VTFL is positioned at 0.39 eV above the valence-band edge. The Au/PZT barrier height extracted from Schottky emission is 0.85 eV. An energy band diagram of the Au/PZT/Pt system is proposed to explain the current–voltage characteristics.
Interfacial phase formation in Cu–Mg alloy films on SiO2
Authors: Frederick M. J. , Ramanath G.
Published: February 2004

We report the chemical changes and phase formation at the film-SiO2 interface during vacuum annealing of supersaturated Cu–10 at. % Mg alloy films sputter-deposited on SiO2. High-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and electron energy loss spectroscopy reveal that both Cu and Mg penetrate ∼20–40 nm into silica at ∼400 °C. At higher temperatures Mg reduces SiO2 leading to the crystallization of a 35-nm-thick continuous interfacial layer comprised of equiaxed grains of cubic MgO and small amounts (≲1 vol %) of monoclinic CuMgSi2O6. Manipulating oxide and silicate formation pathways could open up possibilities for the use of Cu alloys to obtain ultra-thin diffusion barriers at Cu-dielectric interfaces for future metallization structures in integrated circuits.
Comment on “The effects of electric field on the electronic structure of a semiconductor quantum dot” [J. Appl. Phys. 84, 1454 (1998)]
Authors: Menéndez-Proupin E.
Published: February 2004

In a recent article Chang and Xia [J. Appl. Phys. 84, 1454 (1998)] studied theoretically the effects of the electric field on the electronic structure of a spherical semiconductor nanocrystal. The computed hole energies versus electric field intensity show a pattern of avoided crossings and nonzero slopes at zero field. It is argued here that these results are physically incorrect and are possibly due to the use of an incomplete basis set.
Chain-induced effects in the Faraday instability on ferrofluids in a horizontal magnetic field
Authors: Mekhonoshin V. V. , Lange Adrian
Published: February 2004

The linear stability analysis of the Faraday instability on a viscous ferrofluid in a horizontal magnetic field is performed. Strong dipole–dipole interactions lead to the formation of chains elongated in the field direction. The formation of chains results in a qualitative new behavior of the ferrofluid. This new behavior is characterized by a neutral stability curve similar to that observed earlier for Maxwell viscoelastic liquids and causes a significant weakening of the energy dissipation at high frequencies. In the case of a ferrofluid with chains in a horizontal magnetic field, the effective viscosity is anisotropic and depends on the field strength as well as on the wave frequency.
Simulating structure and optical response of vacuum evaporated porous rugate filters
Authors: Kaminska Kate , Suzuki Motofumi , Kimura Kenji , Taga Yasunori , Robbie Kevin
Published: February 2004

The drive to develop better thin film devices stimulates great interest in the understanding and control of the properties and morphology of films. In this article we present a study of the optical response of thin film interference filters, utilizing both experimental tools and computer simulation. The filters were deposited onto flat substrates in high vacuum with the technique of glancing angle deposition, which produces complex film structures with nanometer scale pores. A three-dimensional Monte Carlo simulator accurately reproduced this complicated morphology, while also providing information about nucleation, structure evolution, and packing density. Finally, the results of the computer modeling were used to optimize the effects of process parameters to minimize the difference between the design and the observed optical responses, thus providing a powerful tool for improving the performance of optical devices.
Growth of CdS nanowires using Na-4 mica as template
Authors: Mukherjee P. K. , Chakravorty D.
Published: February 2004

Sodium flourophlogopite mica of composition Na4Mg6Al4Si4O20F4⋅x H2O (referred to as Na-4 mica) was prepared by a sol–gel technique. CdS nanowires of 1.2 nm thickness were grown by using the nanochannels within the mica structure. Optical absorption spectra showed peaks at 350 and 504 nm, respectively. These are ascribed to the presence of CdS nanoclusters of diameter ∼1.21 nm and CdS wires of length ∼100 nm, respectively. The nanowires exhibited a photoluminescent peak at 2.37 eV arising due to excitons. The dielectric constant of the nanocomposite was found to be much larger (∼95) than that of the base material (∼17). This has been explained on the basis of a simple stacking of nanoscale capacitors within each grain of Na-4 mica.
Growth and charge transfer luminescence of Yb3+-doped YAlO3 single crystals
Authors: Shim J. B. , Yoshikawa A. , Fukuda T. , Pejchal J. , Nikl M. , Sarukura N. , Yoon D. H.
Published: February 2004

Yb 3+ -doped YAlO3 single crystals have been grown by the Czochralski method with a radio-frequency heating system. Starting melt compositions of Y1−xYbxAlO3 were varied with x=0.02, 0.1, 0.2, 0.3, and 0.45. The best Yb3+-doped YAlO3 single crystals were obtained for a growth rate of 1.0 mm/h. The grown crystals were transparent and almost colorless. To investigate the homogeneity, the effective segregation coefficient of the Yb ion was estimated. The absorption, photoluminescence, and luminescence decay kinetics of Yb3+-doped YAlO3 were investigated for the temperature range 4–300 K. Very fast charge transfer luminescence of Yb3+ from the near ultraviolet to visible spectral range and the high density of the Yb-rich YAlO3 makes this material a promising candidate for fast scintillators.
Organic molecules and nanoparticles in inorganic crystals: Vitamin C in CaCO3 as an ultraviolet absorber
Authors: Sato H. , Ikeya M.
Published: February 2004

Organic molecules and nanoparticles embedded in inorganic crystalline lattices have been studied to add different properties and functions to composite materials. Calcium carbonate was precipitated by dropping an aqueous solution of CaCl2 into that of Na2CO3 containing dissolved vitamin C (ascorbic acid). The optical absorption ascribed to divalent ascorbate anions in the lattice was observed in the ultraviolet B (wavelength: 280–315 nm) region, while solid vitamin C exhibited absorption in the ultraviolet C (100–280 nm) region. The divalent ascorbate anion is only stable in CaCO3 due to the absence of oxygen molecules. Doping CaCO3 with nanoparticles of ZnO also enhanced the absorption in the ultraviolet A (315–380 nm) region. These composite materials are suggested for use as UV absorbers.
Resolving distribution of relaxation times in poly(propylene glycol) on the crossover region
Authors: Tuncer Enis , Furlani Maurizio , Mellander Bengt-Erik
Published: February 2004

In this article, a recently developed numerical technique [E. Tuncer and S. M. Gubański, IEEE Trans. Dielectr. Electr. Insul. 8, 310 (2001)] is applied to poly(propylene glycol) (PPG) complex dielectric data to extract more information about the molecular relaxation processes. The method is based on a constrained-least-squares (C–LSQ) data fitting procedure together with the Monte Carlo method. We preselect the number of relaxation times with no a priori physical assumption, and use the Debye single relaxation as “kernel,” then the obtained weighting factors at each MC step from the C–LSQ method builds up a relaxation time spectrum. When the analysis is repeated for data at different temperatures a relaxation image is created. The obtained relaxation are analyzed using the Lorentz (Cauchy) distribution, which is a special form of the Lévy statistics. In the present report the β and α relaxations are resolved for the PPG. A comparison of the relaxations to those earlier reported in the literature indicate that the presented method provides additional information compared to methods based on empirical formulas. The distribution of relaxation times analysis is especially useful to probe the crossover region where the α and β relaxations merge and the results show that the relaxation after the crossover region at higher temperatures is Arrhenius-type as the β relaxation. Moreover, this relaxation is more likely to be the continuation of the β relaxation, but with a different activation energy.
Effect of organic acids or fermentable carbohydrates on digestibility and nitrogen utilisation of urea-treated wheat straw in buffalo bulls
Authors: Sarwar M. , Khan M. Ajmal , Mahr-un-Nisa
Published: February 2004

Influence of urea treated wheat straw (UTWS) ensiled with organic acids and fermentable carbohydrates on ruminal parameters, digestion kinetics, digestibility, and nitrogen (N) balance was studied in Nili-Ravi buffalo bulls fed restricted diets. Four diets having 50% UTWS ensiled with acetic acid (AD), formic acid (FD), acidified molasses (MD), and corn steep liquor (CD) were fed to ruminally cannulated bulls in a 4 × 4 Latin square design. Higher ruminal ammonia N at 3 h post feeding was observed with AD and FD diets; however, at 9 and 12 h post feeding it was higher with MD and CD diets. Ruminal total volatile fatty acids and acetate concentrations were significantly higher with MD and CD diets than AD and FD diets. The ruminal degradability, rate of disappearance, and lag time of dry matter (DM) and neutral detergent fibre (NDF) were statistically higher with MD and CD diets than AD and FD diets. Total bacterial, viable, and cellulolytic ruminal counts were significantly higher in bulls fed CD and MD diets than AD and CD diets. The digestibility of DM, organic matter, NDF, and acid detergent fibre was significantly higher in bulls fed CD and MD diets than AD and FD diets. The N retained out of N intake was higher in bulls fed CD and MD diets than those fed AD and FD diets. This study indicated that the UTWS ensiled with fermentable carbohydrates is of better feeding value for ruminants than UTWS ensiled with organic acids.
The effect of plastic mulch and row covers on the growth and physiology of cucumber
Authors: Ibarra-Jiménez L. , Quezada-Martín M. R. , Rosa-Ibarra M. de la
Published: February 2004

To determine the effectiveness of black plastic mulch alone and in combination with row covers, on growth and physiological changes of cucumber plants, 6 treatments were established in a randomised complete block design with 4 replications: bare soil (control); black polyethylene mulch alone (B); B plus a clear cover of perforated polyethylene (BRCP); B plus a white cover of perforated polyethylene (BRWP); B plus an Agribon cover of polypropylene (BRA); and B plus a Kimberly farm row cover (BRK). For the plants grown with mulch or mulch combined with row covers, the dry weight of leaves 50 days after seeding (DAS), and the dry weight of whole plants (at 50 and 110 DAS) were significantly (P<0.05) different from the control. Early yields of treatments B, BRCP, BRWP, BRA and BRK were 2.1, 1.9, 2.6, 1.9 and 2.4 times higher than the control, which yielded 10 t/ha. Total yields were increased by 9.7, 15.4, 19.8, 14.9 and 20 t/ha, over the control which yielded 104 t/ha. Increases in plant dry weight explained the changes in yield. Stomatal conductance may explain in part, the increase in photosynthetic rate, but may not explain yield increase.
Evaluation of a hand-held burner for the control of woody weeds by flaming
Authors: Vitelli J. S. , Madigan B. A.
Published: February 2004

A hand-held burner (Atarus Ranger) was evaluated as a method for controlling woody weeds by flaming in sensitive or riparian areas where traditional methods, such as chemical or mechanical control, have limited usefulness. The equipment was trialled on 3 North Queensland weed species: bellyache bush (Jatropha gossypiifolia), parkinsonia (Parkinsonia aculeata) and rubber vine (Cryptostegia grandiflora), at 5 different heat durations (0, 10, 30, 60 and 120 s) and on 3 plant size classes based on basal diameter (15–25, >25–50 and >50 mm).No significant difference in percentage mortality was recorded between a 10 s treatment and longer heat treatments for bellyache bush and parkinsonia plants, or between a 60 s treatment and longer heat treatments for rubber vine. A 10 s treatment killed 92% of the treated bellyache bush plants and 83% of the parkinsonia plants, while a 60 s treatment killed 76% of the treated rubber vine plants (values are the means of all size classes combined).Flaming was least effective on rubber vine, which had the thickest bark, but was highly effective on bellyache bush, which had the highest bark moisture content. Weeds with a low capacity for root suckering, thin bark, high bark moisture content and low bark density appear the best candidates for flaming. Flaming is an effective technique for the control of woody weeds with efficacy varying among species. Individual plants are targeted, and the technique is accepted by organic farming groups.
Evaluation of drought resistance-related traits in durum wheat somaclonal lines selected in vitro
Authors: Bajji M. , Bertin P. , Lutts S. , Kinet J-M.
Published: February 2004

Somaclonal variation associated with in vitro selection has been used as a source of variability to improve drought resistance of 3 durum wheat (Triticum durum Desf.) cultivars (Selbera, Sebou, and Kyperounda). In a previous study, R0 plants with improved drought resistance-related characters were regenerated after selection on culture media containing polyethylene glycol (PEG). This improvement was transmitted to the R1 progeny. The present study analysed the behaviour of the selected tissue culture-derived lines in subsequent R2, R3 and R4�generations. Differences in electrolyte leakage, chlorophyll fluorescence (Fv/Fm), stomatal conductance and days to heading were found between the parental cultivars and most of their in vitro-derived lines. The changes may differ from one cultivar to another. Many promising somaclonal lines still presented improvement for at least 3 of the 4�parameters measured comparatively to initial cultivars. Somaclonal variation thus appears to induce a wide range of modifications among individual components of drought-resistance mechanisms. These improved traits could be valuable if shown to be inherited and to give enhanced agronomic performances in future field studies.
A simple method for collecting urine samples from male cattle
Authors: Jeffery M. R.
Published: February 2004

A harness arrangement made from heavy duty plastic, velcro strips and absorbent cloth allowed the collection of spot samples of urine from 36 steers confined in individual feeding pens. Clean samples of up to 50�mL were collected from all steers on each sampling day without operators being present at all times.
Response of canola and Indian mustard to sowing date in the grain belt of north-eastern Australia
Authors: Robertson M. J. , Holland J. F. , Bambach R.
Published: February 2004

Sowing date is an important determinant of yield in canola. The arrival at an optimum sowing time will depend on trade-offs between lowered frost risk with delayed sowing and lowered yield potential. A comprehensive analysis of response to sowing date has not been conducted for northern environments, a new region for canola production. The aim of this study was to analyse the response of phenology, yield and oil content of current cultivars of canola to sowing date (April–September) in north-eastern Australia, using 17 sowings from Tamworth (31.09°S) to Lawes (27.55°S). Three cultivars were studied: an early and late flowering canola and an advanced breeding line of Indian mustard. For all 3 genotypes, a delay in sowing shortened the time to 50% flowering and to maturity, while differences among the genotypes in time to flowering for sowing dates around 15 May reflected their known differences in phenological development. For sowings at Tamworth beyond 15 May, a 1 day delay in sowing delayed flowering by 0.42, 0.42 and 0.37 days in Indian mustard, Monty and Oscar, respectively. Delay in maturity was 0.58, 0.56 and 0.54 days per day delay in sowing date. Yield and oil content penalties due to delayed sowing were similar to those found previously in other Australian environments. The decline of grain yield with delay in sowing date could be largely explained by the decline in biomass at maturity, while for oil content it could be related positively to harvest index and seed size, and negatively to temperature conditions post-anthesis. Indian mustard had a lower harvest index, grain yield and oil content than both canola cultivars. Oil content exceeded 40% in canola in half of the sowings. Information on the response of oilseed Brassicas to sowing date can be used to quantify the trade-offs between frost risk and crop productivity with sowing date for different cultivar types.
Effect of nitrogen and potassium fertilisation on vegetative growth and flowering of mature carob trees (Ceratonia siliqua): variations in leaf area index and water use indices
Authors: Correia P. J. , Martins-Loução M. A.
Published: February 2004

This work aimed to assess how potassium (K) and nitrogen (N) fertilisation may affect the use of precipitation in terms of vegetative and flowering response of 15-year-old carob trees during a 3-year experiment. A��field trial was conducted in 1997, 1998 and 1999 in Algarve (Southern Portugal) in a calcareous soil. Four fertilisation treatments were tested: no fertiliser (control); 0.8 kg N/tree (N treatment); 1 kg K2O/tree (K treatment) and 0.8 kg N/tree plus 1 kg K2O/tree (NK treatment). No irrigation was applied during the experimental period. Branch length increments were measured every month throughout the growing season and inflorescence number was registered once per year. There was a strong seasonal effect on vegetative growth, since low levels of precipitation (115 mm) during October 1998–March 1999 suppressed the increment in branch length. N supplied to the trees (N and NK treatments) tended to increase water use indices in terms of vegetative growth. No response to K alone was observed in trees fertilised only with K. The number of inflorescences increased throughout the experimental period, particularly for N and NK treatments, and a reduction of the precipitation amount during April, May and June, may also enhance flowering. This knowledge could be important when making decisions concerning fertilisation under dry conditions. The results reported here indicate that tree growth (expressed as the branch growth) and flower production under dry-farming conditions, may be achieved by applying 0.8 kg of N (as ammonium nitrate)�per tree during the growing season. However, N uptake and use depends on soil water availability.
Effects of level of feeding of concentrates during early lactation on the yield and composition of milk from grazing dairy cows with varying body condition score at calving
Authors: Stockdale C. R.
Published: February 2004

An experiment was undertaken to establish the influence of body condition at calving on milk production and composition using diets typical of those currently used in Victoria. Seventy-two cows were fed differently from April 2001 to achieve target body condition scores (BCS) by 1 month before calving of about 4�(3.5–4.5), 5 (4.5–5.5) or 6 (5.5–6.5) units on an 8-point scale. The actual mean BCS at calving for the 3 treatments were 3.8, 5.2 and 5.7 units (P<0.05). After calving, cows grazed at pasture allowances of about 35 kg DM/cow.day and received 1 of 2 levels of supplementation (1 or 6 kg DM of pelleted concentrates per day) for about the first 10�weeks of lactation. The low BCS cows lost less body condition (0.35 v. 1.27 units; P<0.05) for a shorter period (4.8 v. 7.9 weeks; P<0.05) than did the medium and high BCS cows. The low BCS cows also ate more pasture than the other 2 BCS groups, but only when expressed as a percentage of liveweight (2.91 v. 2.73%; P<0.05). Improvements in BCS at calving resulted in higher milk fat percentages in early lactation (3.31% for low BCS cows v. 3.60% for the 2 higher BCS groups; P<0.05), while milk protein and lactose were not affected (P>0.05). At the lower level of feeding in early lactation, milk production increased (P<0.05) linearly as BCS at calving increased, by 1.0 kg milk per unit of body condition per day. However, when energy intake was increased by feeding 6 kg of concentrates, milk production increased as body condition increased (P<0.05) from the low to medium BCS, but there was no significant benefit beyond the medium BCS. Therefore, the hypothesis, that providing that cows are fed well with grazed pasture supplemented with high-energy concentrates in early lactation, BCS at calving will have no effect on subsequent milk production, was at least partially disproved, and it may be that it is never possible for cows at pasture to be sufficiently well fed.
A survey of possible associations between preharvest environment conditions and postharvest rejections of cut freesia flowers
Authors: Darras A. I. , Joyce D. C. , Terry L. A.
Published: February 2004

Botrytis cinerea is the major pathogen infecting cut freesia flowers. Flecking symptoms on petals caused by this fungus result in postharvest rejections and substantial economic loss to both growers and sellers. In a limited survey for industry, numbers of freesia stems sent from a specialist grower in The Netherlands and rejected at a cut flower wholesaler in the United Kingdom were documented. Relationships between preharvest environment conditions in Holland that may predispose flowers to infection and postharvest freesia rejection levels in the United Kingdom due to B. cinerea flecking symptom expression are reported. Freesia rejections peaked during spring and, to a lesser degree, autumn periods. However, no clear correlations between preharvest growing environment conditions (e.g. 3-day means for temperature preceding harvest) and postharvest rejection frequency (%) could be discerned. Thus, sporadic freesia rejections in the United Kingdom were probably attributable either to other unresolved variables during the pre- (e.g. infection pressure) and/or postharvest (e.g. condensation events) phases or to interactions among predisposing variables.
Which reproductive technologies are most relevant to studying, managing and conserving wildlife?
Authors: Pukazhenthi Budhan S. , Wildt David E.
Published: February 2004

The advent of in vitro fertilisation (IVF) and embryo transfer in the 1970s led to speculation about the potential value of these and other ‘reproductive technologies’ to conserving endangered species. So far, and for the most part, assisted breeding techniques that are routine in domesticated species are not easily adapted to wildlife. Species differences in reproductive form (anatomy/morphology) and function (mechanisms regulating reproductive success) limit the practical applicability for offspring production. Thus, the limiting factor is the lack of basic knowledge about thousands of unstudied species, the foundation that is essential to allowing reproduction to be enhanced and/or controlled. There now is excellent evidence that reproductive technologies are most useful as tools for studying how different species reproduce, especially defining novel and unique mechanisms. The present paper reviews the status and relevance of various reproductive technologies that are useful or have potential for wildlife. Modern examples of progress are provided indicating how these tools are being used to understand ways that wildlife species reproduce and, in some cases, how such knowledge has been used for successful assisted breeding, improved management and conservation.
Gene transcription and regulation of oocyte maturation
Authors: Rodriguez Karina F. , Farin Charlotte E.
Published: February 2004

The developmental potential of an embryo is dependent on the developmental potential of the oocyte from which it originates. The process of oocyte maturation is critical for the efficient application of biotechnologies such as in vitro embryo production and mammalian cloning. However, the overall efficiency of in vitro maturation remains low because oocytes matured in vitro have a lower developmental competence than oocytes matured in vivo. Furthermore, oocytes that have been exposed to gonadotropins have greater developmental competence than oocytes matured in the absence of gonadotropins. By understanding the molecular mechanisms underlying gonadotropin-induced maturation, improvement in oocyte maturation technologies may be expected as procedures to manipulate specific factors involved in signalling for resumption of meiosis are identified. The present review will focus on transcriptional mechanisms underlying the maturation of mammalian oocytes in vitro, as well as on the acquisition of oocyte developmental competence. In addition, a working model for the transcriptional control of mammalian oocyte maturation is proposed.
Oocyte proteomics: localisation of mouse zona pellucida protein 3 to the plasma membrane of ovulated mouse eggs
Authors: Coonrod S. A. , Calvert M. E. , Reddi P. P. , Kasper E. N. , Digilio L. C. , Herr J. C.
Published: February 2004

In order to gain a deeper understanding of the molecular underpinnings of sperm–egg interaction and early development, we have used two-dimensional (2D) electrophoresis, avidin blotting and tandem mass spectrometry to identify, clone and characterise abundant molecules from the mouse egg proteome. Two-dimensional avidin blots of biotinylated zona-free eggs revealed an abundant approximately 75-kDa surface-labelled heterogeneous protein possessing a staining pattern similar to that of the zona pellucida glycoprotein, mouse ZP3 (mZP3). In light of this observation, we investigated whether mZP3 specifically localises to the plasma membrane of mature eggs. Zona pellucidae of immature mouse oocytes and mature eggs were removed using acid Tyrode’s solution, chymotrypsin or mechanical shearing. Indirect immunofluorescence using the mZP3 monoclonal antibody (mAb) IE-10 demonstrated strong continuous staining over the entire surface of immature oocytes and weak microvillar staining on ovulated eggs, regardless of the method of zona removal. Interestingly, in mature eggs, increased fluorescence intensity was observed following artificial activation and fertilisation, whereas little to no fluorescence was observed in degenerated eggs. The surface localisation of ZP3 on mature eggs was supported by the finding that the IE-10 mAb immunoprecipitated an approximate 75-kDa protein from lysates of biotinylated zona-free eggs. To further investigate the specificity of the localisation of mZP3 to the oolemma, indirect immunofluorescence was performed using the IE-10 mAb on both CV-1 and CHO cells transfected with full-length recombinant mZP3 (re-mZP3). Plasma membrane targeting of the expressed re-mZP3 protein was observed in both cell lines. The membrane association of re-mZP3 was confirmed by the finding that biotinylated re-mZP3 (approximately 75 kDa) is immunoprecipitated from the hydrophobic phase of Triton X-114 extracts of transfected cells following phase partitioning. Immunoprecipitation assays also demonstrated that surface re-mZP3 was released from transfected CV-1 in a time-dependent manner. These results demonstrate that ZP3 is specifically associated with the surface of mature eggs and its subsequent release from the cell surface may represent one mechanism by which ZP3 is secreted. Furthermore, the increase in ZP3 surface expression following fertilisation suggests that ZP3 may have a functional role during sperm–oolemma binding and fusion. These results also validate the usefulness of using the 2D proteomic approach to identify and characterise egg-surface proteins.
Embryogenomics of pre-implantation mammalian development: current status
Authors: Ko Minoru S. H.
Published: February 2004

Pre-implantation development is marked by many critical molecular events, including the maternal to zygotic transition and the first differentiation of cells. Understanding such events is important, for both basic reproductive biology and practical applications, including regenerative medicine and livestock production. Scarcity of materials has hampered the progress of the field, but systematic genomics approaches are beginning to be applied to the study of pre-implantation development, resulting in unprecedented amounts of data about the pre-implantation process. The first step in embryogenomics is to collect and sequence cDNAs (expressed sequence tags (ESTs)) for genes that are expressed and function in these early embryos. Mouse work is the most advanced, with 140111 ESTs derived from all stages of pre-implantation development currently available in the public sequence database. For other mammals, at present only approximately 1000 ESTs can be found in the public database, but efforts by several groups are generating cDNA libraries and ESTs. In the present review, the current status of the implementation of these investigative tools for mammalian pre-implantation embryos is discussed.
Biosecurity issues associated with current and emerging embryo technologies
Authors: Stringfellow David A. , Givens M. Daniel , Waldrop Julie G.
Published: February 2004

A variety of procedures associated with in vivo and in vitro embryo production, as well as cloning and transgenics, are in current use by both researchers and practitioners. Biohazards associated with these procedures could influence clinical proficiency and the outcome of basic research or result in unusual distribution of pathogens in populations of animals. By their nature, embryo technologies are vulnerable to contamination from numerous sources. Although pathogens can originate in the physical environments in which embryo technologies are applied, they are more likely to be introduced via animals or materials of animal origin. However, it is important to note that both the occurrence and consequences of contamination are heavily influenced by environmental circumstances. This paper represents a philosophical description of biohazards associated with three generations of embryo technologies using the cow as a model species. Emphasis is placed on sources of contamination, current or suggested preventive actions and the issue of environmental changes as they relate to the emergence of biohazards and the implementation of biosecurity measures. Some specific pathogens are discussed for illustration. In addition, details of the risks associated with introducing bovine viral diarrhoea virus in each of three generations of embryo technologies are described.
Biosecurity strategies for conserving valuable livestock genetic resources
Authors: Wrathall Anthony E. , Simmons Hugh A. , Bowles Dianna J. , Jones Sam
Published: February 2004

The foot and mouth disease (FMD) epidemic in the UK in 2001 highlighted the threat of infectious diseases to rare and valuable livestock and stimulated a renewed interest in biosecurity and conservation. However, not all diseases resemble FMD: their transmission routes and pathological effects vary greatly, so biosecurity strategies must take this into account. Realism is also needed as to which diseases to exclude and which will have to be tolerated. The aim should be to minimise disease generally and to exclude those diseases that threaten the existence of livestock or preclude their national or international movement. Achieving this requires a team effort, bearing in mind the livestock species involved, the farming system (‘open’ or ‘closed’) and the premises. Effective biosecurity demands that practically every aspect of farm life is controlled, including movements of people, vehicles, equipment, food, manure, animal carcasses and wildlife. Above all, biosecurity strategies must cover the disease risks associated with moving the livestock themselves and this will require quarantine if adult or juvenile animals are imported into the herd or flock. The present paper emphasises the important role that reproductive technologies, such as artificial insemination and embryo transfer, can have in biosecurity strategies because they offer much safer ways for getting new genetic materials into herds/flocks than bringing in live animals. Embryo transfer is especially safe when the sanitary protocols promoted by the International Embryo Transfer Society and advocated by the Office International des Epizooties (the ‘World Organisation for Animal Health’) are used. Embryo transfer can also allow the full genetic complement to be salvaged from infected animals. Cryobanking of genetic materials, especially embryos, is another valuable biosecurity strategy because it enables their storage for conservation in the face of contingencies, such as epidemic disease and other catastrophes.
1DEVELOPMENT OF BOVINE NUCLEAR TRANSFER EMBRYOS CLONED FROM FOLLICULAR DONOR CELLS IN SEQUENTIAL STAGES OF DIFFERENTIATION
Authors: Batchelder C.A. , Hoffert K.A. , Bertolini M. , Moyer A.L. , Anderson G.B.
Published: February 2004

Efficient production of cloned embryos and live offspring is dependent on the ability of the nuclear-donor cell to be reprogrammed to direct normal conceptus development. Results of comparative studies indicate that embryonic and fetal cells are more successful candidates for nuclear transfer (NT) than terminally differentiated cells. Comparison of donor-cell efficiency is difficult to interpret across laboratories and from donor animals of varying genetic backgrounds and tissues of origin. This study was undertaken to determine the effect of the stage of differentiation of adult somatic donor cells derived from one-cell lineage of an individual donor animal. The follicular cell lineage including preantral follicle (PAFC), cumulus (CC), granulosa (GC), and luteal cells (LC) was chosen as several cell types in the lineage have previously proven successful for NT. Donor cell cultures were established from a 3-year-old Holstein cow. Embryos were reconstructed using confluent, early passage cultures. For each replicate, embryos were produced from two donor cell types in randomized block design (14 trials). Viable embryos were transferred to recipient females after 7 days of in vitro culture. Pregnancy and fetal viability were monitored weekly by ultrasonography from Days 30–100 of gestation and by rectal palpation thereafter. Embryos reconstructed from PAFC were less likely to develop to the blastocyst stage on Day 7 than embryos derived from CC or LC (Table 1, P<0.05). Pregnancy rates at Day 30 were similar across donor cell types. A greater proportion of PAFC embryos were viable at Day 60 of gestation than embryos derived from CC and GC (P<0.05). To date, normal cloned calves have been delivered at term from CC and GC, and two pregnancies (n=3 fetuses) are ongoing from PAFC. The fetus cloned from LC, the terminally differentiated cell type in the lineage, was spontaneously aborted at day 211 with congenital abnormalities. Results from comparative studies of development of mouse embryos cloned from embryonic stem (ES) cells v. somatic donor cells indicate that ES-derived clones are less efficient in blastocyst formation, but survival to term is greater (Humpherys D et al., 2002 PNAS 99, 12889–12894). Likewise, our results in cattle suggest that PAFC, the least differentiated cells in the lineage, result in fewer cloned blastocysts, but blastocysts that do develop are more likely to progress through implantation and into later stages of pregnancy.

Table 1.

Development of NT embryos reconstructed from follicular donor cells at sequential stages of differentiation
10CASA EVALUATION OF SEXED AND NON-SEXED FROZEN BULL SEMEN
Authors: Brogliatti G. , Barreiro G. , Larraburu G. , Laborde A.
Published: February 2004

Flow citometry cell sorting has been proven successfully to separate X and Y sperm; however, the technology is still too stressfull for the viability of the sorted semen. The objective of this study was to evaluate nonsexed and sexed frozen sperm motility characteristics using a CASA technology. Ejaculates from 4 different bulls (3 Holstein and 1 Angus) were collected, and processed as split non-sexed and sexed semen samples using Tris egg yolk extenders. X and Y sperm were separated using a high-speed sorter (SX Moflo). Cryopreservation was done at the same time under appropiate conditions using a programmed cryochamber. Thawing procedure was done at 37°C for 30s and a sample of each straw was placed in the evaluation chamber. The experiment was repeated twice and two chambers with 30 observations each were analyzed each time. Mean and standard deviation of each characteristic were calculated, compared and analyzed statistically. The sperm concentration was determined by means of a burker counting chamber. Sperm quality was determined at 0h after thawing, and later at 1h, 2h and 3h after incubation in a glass tube at 30°C. The following sperm motility parameters were determined with the Hamilton Thorne (HTM-ceros 12.1) on at least 1000 spermatozoa: velocity average path (VAP), velocity straight line (VSL), amplitude lateral head (ALH), beat cross frequency (BCF), straightness (STR), linearity (LIN), and percentage of progressively motile spermatozoa (PMS). Linearity of nonsexed spermatozoa was 53±3.5, 47±0.8, 43±7.8 and 42±4.5 for the 0h and the 3 test incubation times and 49.5±3.7, 51.2±3.7, 43.3±7.8 and 44.5±7.6, respectively, for sexed semen. There were no significant differences (P>0.05) in the progressive velocity, track speed and linearity between sexed and nonsexed semen. The percentage of static cells was 33%, 30%, 47% and 50% for the 0h and the 3 test incubation periods; however, the percentage of static cells for the sexed semen was 53%, 71%, 77% and 82%, respectively. Results from the analysis indicate a significant increase (P<0.01) in the number and the percentage of static cells with time. The lateral amplitude of sperm motility for nonsexed semen was 5.9±0.5, 6.8±0.8, 6.0±0.4 and 5.1±0.7, and for sexed semen 6.6±0.7, 6.8±0.4, 6.4±0.4 and 5.5±1.7, respectively. The percentage of progressively motile sperm was significantly different at 0 time 49.7±4.9 and 23.1±4.9 for nonsexed and sexed semen respectively. After 3 hours of incubation the percentage of progressively motile sperm was 38.7±10.2 and 3.7±3.2 for nonsexed and sexed semen, respectively. In conclusion, sexed frozen semen seems to have characteristics similar to those of normal nonsexed semen. However, a significant decrease in the percentage of progressively motile cells could affect pregnancy rates. More research needs to be done to detect differences between bulls and cryoprotectans.Research supported by Centro Genetico Bovino de EOLIA sa Argentina.