bluuebunny/crossref_metadata_2025 huggingface dataset:
On thermal diffusion and convection in multicomponent mixtures with application to the thermogravitational column
Authors: Ryzhkov Ilya I. , Shevtsova Valentina M.
Published: February 2007

The theoretical framework for describing the multicomponent mixtures with the Soret effect is revised and extended. The separation ratio, a fundamental parameter characterizing the influence of thermal diffusion on convective phenomena, is generalized to the multicomponent case. It is shown how to define this parameter for a particular component of the mixture. To characterize multicomponent system as a whole, the net separation ratio Ψ, which does not depend on the choice of solvent, is introduced. Based on these results, the dimensionless equations for convection in multicomponent mixture are derived. The proposed formulation is applied to analyzing the steady state separation in the thermogravitational column (TGC). The approximation neglecting vertical diffusion in the column is employed and conditions for its validity are analyzed. The distributions of velocity, temperature, and composition in a multicomponent system are found. The relevant parameters here are the solutal Rayleigh numbers, which characterize the vertical separation of species, and the net solutal Rayleigh number R, which quantifies the overall effect of this separation on the system behavior. It is shown that the key relation of TGC theory, which relates the vertical compositional gradients to the thermal diffusion coefficients, reduces to the dependence of Ψ on R. A detailed study of this dependence is performed. The evolution of vertical velocity and density profiles with changing the net separation ratio is investigated. It is shown that the solution is unique for Ψ≳−1, nonunique for −5≲Ψ≲−1, and does not exist for Ψ≲−5. A particular ternary mixture is considered and its behavior in the column is analyzed.
Weak quantum Borcherds superalgebras and their representations
Authors: Ye Lixia , Li Fang
Published: February 2007

We define a weak quantum Borcherds superalgebra nqd(G), which is a weak Hopf superalgebra. We also discuss the basis and the highest weight modules of nqd(G). Then we study the weak A-form and the classical limit of nqd(G).
Comprehensive study of time-lapsed peak shift in InGaN quantum well structures: Discrimination of localization effect from internal field effect
Authors: Son J. K. , Sakong T. , Lee S. N. , Paek H. S. , Ryu H. , Ha K. H. , Nam O. , Park Y. , Hwang J. S. , Cho Y. H.
Published: February 2007

Time-lapsed emission peak shift behaviors in blue-light-emitting InGaN multiple quantum well (MQW) laser diodes with different well widths are systematically investigated by means of excitation power-dependent, time-resolved optical analysis. By investigating the main emission peak shift as a function of both time evolution and excitation power density, the amount of time-lapsed emission peak shift can be differentiated by two contributions: the excitation power dependent and independent ones. The authors conclude that the power-dependent (power-independent) time-lapsed peak shift can be attributed to the internal electric-field (carrier localization) effect present in vertical growth (lateral in-plane) direction of InGaN MQW laser diode structures.
Off-axis directional beaming of optical field diffracted by a single subwavelength metal slit with asymmetric dielectric surface gratings
Authors: Kim Seyoon , Kim Hwi , Lim Yongjun , Lee Byoungho
Published: February 2007

The authors propose a method for the off-axis directional beaming of optical field diffracted by a single subwavelength metal slit with dielectric surface gratings. In the proposed method, dielectric gratings are optimally designed to directionally couple the surface plasmon polariton modes induced by the metal slit into surrounding medium along a specific off-axis direction. Design of the gratings and the analysis are conducted based on the rigorous coupled wave analysis method. Their simulation shows the off-axis directional beaming of the oblique angle, 20.2°, with respect to the on axis by the proposed method. The beaming angle can be changed by adjusting the grating periods.
Double-flip transfer of indium phosphide layers via adhesive wafer bonding and ion-cutting process
Authors: Chen Wayne , Chen Peng , Jing Yi , Lau S. S. , Kuech T. F. , Liu Jiariu , Wang Xeimei , Chu Wei-Kan
Published: February 2007

A twice-transferred layer of indium phosphide (InP) onto a host substrate by means of ion cutting and adhesive wafer bonding was demonstrated to be suitable for device integration. A thin layer was first transferred onto a glass handle through the ion-cutting process by hydrogen implantation and adhesive bonding. The InP/adhesive/glass structure was then bonded to a host substrate using benzocyclobutene, followed by thermal separation of the temporary bond. The surface of the resulting InP layer is that of the original substrate, demonstrating the feasibility of prefabricated device layer transfer without etching sacrificial donors. The electrical properties of the transferred layer are also presented.
Electron density in low density capillary plasma channel
Authors: Palchan T. , Kaganovich D. , Sasorov P. , Sprangle P. , Ting C. , Zigler A.
Published: February 2007

A low density plasma channel of 1017cm−3 is created in a capillary discharge. The plasma channel is characterized through the hydrogen plasma spectra in the Balmer Hα line. The measured plasma density profiles were found to be in qualitative agreement with the hydrodynamic simulations. Guiding over many vacuum diffraction length using a plasma channel operating in the low density regime is demonstrated.
High Frequency Dielectric Response of the Ionic Liquid N-Methyl-N-ethylpyrrolidinium Dicyanamide
Authors: Schrödle Simon , Annat Gary , MacFarlane Douglas R. , Forsyth Maria , Buchner Richard , Hefter Glenn
Published: January 2007

A study of the room-temperature ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide by dielectric relaxation spectroscopy over the frequency range 0.2 GHz ≤ ν ≤ 89 GHz has revealed that, in addition to the already known lower frequency processes, there is a broad featureless dielectric loss at higher frequencies. The latter is probably due to the translational (oscillatory) motions of the dipolar ions of the IL relative to each other, with additional contributions from their fast rotation.
Prospects for the Application of Scanning Electrochemical Microscopy in Ionic Liquids
Authors: Carano Maurizio , Bond Alan M.
Published: January 2007

Prospects have been assessed for the application of the technique of scanning electrochemical microscopy (SECM) in viscous ionic liquids. Use of the Fc0/+ redox couple (Fc = ferrocene) to obtain microelectrode approach curves revealed that the required steady state behaviour needed for analysis of data relevant to conducting platinum and insulating glass substrates is moderately easy to achieve in a 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid. However, in the more highly viscous 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid, where significantly lower diffusion coefficients are encountered, approach-curve data that conform to steady state theory are only found with very small microelectrodes (e.g., ≤2 μm diameter), very slow electrode–substrate approach rates (e.g., ≤0.05 μm s–1), and long equilibration times (e.g., 50 s). A comparison is provided with SECM approach curves acquired in aqueous media. SECM images of an Ag substrate in contact with [BMIM][BF4] also are presented and are of only slightly inferior quality to images obtained in water.
Synthesis of Aromatic Cycloketones via Intramolecular Friedel - Crafts Acylation Catalyzed by Heteropoly Acids
Authors: Lan Kun , Fen Shao , Shan Zixing
Published: January 2007

Under liquid-phase conditions, the intramolecular Friedel–Crafts acylation of aryl benzoic acids catalyzed by heteropoly acids were investigated for the first time. Several aryl benzoic acids were refluxed and dehydrated in chlorobenzene in the presence of 0.2 equivalents of a heteropoly acid, and anthraquinone, anthrone, and xanthone were obtained in good yield. At the same time, an intermolecular Friedel–Crafts acylation and decarboxylation reaction were observed in this experiment.
Molecularly Imprinted Polymers and Room Temperature Ionic Liquids: Impact of Template on Polymer Morphology
Authors: Booker Katherine , Bowyer Michael C. , Lennard Chris J. , Holdsworth Clovia I. , McCluskey Adam
Published: January 2007

Molecularly imprinted polymers (MIPs) were generated for trans-aconitic acid 1 and cocaine 2 in a variety of porogens (CH3CN, CHCl3, [bmim][BF4], and [bmim][PF6]). MIP synthesis in either [bmim][BF4] or [bmim][PF6] resulted in significant acceleration of polymerization rates and, in the case of low temperature polymerizations, reactions were complete in less than 2 h, while no product was observed in the corresponding volatile organic carbon (VOC) porogen. In all instances, MIPs generated in [bmim][BF4] or [bmim][PF6] returned imprinting selectivities (I values) on par with or better than the corresponding MIP generated in VOCs. Imprinting values ranged between I = 1 and 2.9, with rebinding limited to 1 h. MIP synthesis conducted at low temperature (5°C) afforded the highest I values.
Scanning electron microscopy examination of MIP morphology highlighted an unexpected template effect with MIP structure varying between discrete nanoparticles and robust monoliths. This template–monomer interaction was also observed in the rates of polymerizations with differences noted in reaction times for 1 and 2 MIPs, thus providing indirect conformation of our previously proposed use of molecular modelling–nuclear magnetic resonance titrations (the MM-NMR method) in the design phase of MIP generation. In addition, considerable batch-to-batch rebinding selectivities were observed.
Investigation of the Electrochemical Properties of Polymer–LiX–Ionic Liquid Ternary Systems
Authors: Tizzani Cosimo , Appetecchi Giovanni B. , Carewska Maria , Kim Guk-Tae , Passerini Stefano
Published: January 2007

The electrochemical properties of ternary systems that consist of a polymer, a lithium salt, and an ionic liquid that shares the same anion (TFSI, bis(trifluoromethansulfonyl)imide) are reported and compared. The investigation involved two different polymers (PVdF-HFP and PTFE) that were selected because of their common use in lithium-based electrochemical devices. It was found that PVdF-HFP swelled by the ionic liquid used in the work while porous PTFE remained inert. The ternary electrolytes showed interesting ionic conductivities. However, the presence of fluorinated polymers resulted in poor interfacial properties with lithium metal electrodes.
N-Methyl-N-Alkylpyrrolidinium Bis(perfluoroethylsulfonyl)amide ([NPf2]–) and Tris(trifluoromethanesulfonyl)methide ([CTf3]–) Salts: Synthesis and Characterization
Authors: Johansson Katarina M. , Adebahr Josefina , Howlett Patrick C. , Forsyth Maria , MacFarlane Douglas R.
Published: January 2007

Novel salts based the pyrrolidinium cation [Cnmpyr]+ (where n denote the number of carbons in the straight alkyl chain) and either the [NPf2]– or [CTf3]– anions have been synthesized and characterized to determine their thermal behaviour, stability, and conductivity. [C1mpyr][NPf2], [C2mpyr][NPf2], and [C1mpyr][CTf3] exhibit behaviour indicative of a plastic crystal phase. Both [C3mpyr][NPf2] and [C4mpyr][NPf2] are RTILs, while all of the [CTf3]– salts, have melting points above 60°C. [C3mpyr][NPf2] exhibited the widest electrochemical window of 5.5 V. The [NPf2]– salt exhibited similar reductive limits to the [NTf2]– anion, –3.2 V versus Fc+|Fc, while [CTf3]– had lower reductive stability. The [CTf3]– salts were more stable towards oxidation, +2.5 V versus Fc+|Fc, compared to the [NPf2]– and [NTf2]– salts.
The Structure of Imidazolium-Based Ionic Liquids: Insights From Ion-Pair Interactions
Authors: Hunt Patricia A. , Gould Ian R. , Kirchner Barbara
Published: January 2007

A large number of ab-initio (B3LYP/6–31++G(d,p)) computed ion-pair structures have been examined in order to determine if such calculations are capable of offering insight into the physical properties of the liquid state, particularly viscosity and melting point. Ion pairings based around the 1-butyl-3-methylimidazolium (C4C1im) cations and a range of anions (Cl, BF4, and N(Tf)2 where N(Tf)2 is bis(trifluoromethylsulfonly)imide) were chosen because of the range of viscosities exhibited by the corresponding ionic liquids. We have used these results to build up a ‘picture’ of the ionic liquid structure which is consistent with molecular dynamics simulations and experimental evidence. However, further work is required to established if such an analysis could be predictive. Nevertheless, we establish clear relationships relating ion-pair association energy, a derived ‘connectivity index’, and the diversity of structures with viscosity and melting point. Our calculations indicate that ions in C4C1imCl form a strong, highly connected and regular array thus rationalizing the high viscosity and melting point. In contrast the ion-pairs of C4C1imN(Tf)2 form a weakly interacting, highly disordered, and low connectivity network consistent with the low viscosity and melting point. C4C1imBF4 lies midway between these two extremes.
Towards a Better Understanding of 'Delocalized Charge' in Ionic Liquid Anions
Authors: Izgorodina Ekaterina I. , Forsyth Maria , MacFarlane Douglas R.
Published: January 2007

One of the main characteristics that are attributed to ionic liquids (especially those with a low melting point) is that the anions comprising the ionic liquids possess a certain degree of charge delocalization as compared to anions in traditional molten salts. Based on the proton affinity equilibrium we proposed a new energetic criterion that can be used as a measure of charge delocalization. The proposed proton affinity comparison quantifies the extent to which ionic liquid anions are delocalized. Thus it should lead to a better understanding towards the design of task-specific ionic liquids. Therefore, this criterion can be applied to newly designed anions to assure that the extent of charge delocalization falls within the same range of values on the proton affinity scale as other commonly used ionic liquid anions.
AFM-Assisted Investigation of the Corrosion Behaviour of Magnesium and AZ91 Alloys in an Ionic Liquid with Varying Water Content
Authors: Shkurankov Andrey , Zein El Abedin Sherif , Endres Frank
Published: January 2007

Atomic force microscopy (AFM)-assisted corrosion measurements of poly- and microcrystalline magnesium, of AZ91D magnesium alloys, and of AZ91D alloys with defined amounts of metallic impurities (Cu, Ni, and Si) in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethylsulfonate with variable water contents is reported. Whereas both magnesium and the AZ91 alloys show a tremendous corrosion in aqueous solutions, they are practically inert in the water-free ionic liquid. The apparent electrochemical window of the water-free ionic liquid on magnesium and its alloys can reach values of 10 V and more. The low corrosion rate of AZ91 alloys with metallic impurities, in any case, follows the trend in aqueous solutions: in comparison to the base alloy, the addition of nickel and silicon leads to higher corrosion rates. Upon addition of water to the ionic liquid two effects are observed. The higher the water content in the ionic liquid, the lower the corrosion potential and the higher the corrosion rate. Poly- and microcrystalline magnesium shows a surprisingly complicated corrosion behaviour, which gives rise to different processes during electrochemical polarization. As a proof-of-principle, in-situ AFM measurements were performed on the corrosion of AZ91D alloy in the ionic liquid. No corrosion products are observed at the surface in the water-free ionic liquid by in-situ AFM, even after several hours at +3 V versus a saturated calomel electrode (SCE), which indicates surface passivation in the ionic liquid.
Synthesis and Complexes of the New Scorpionate Ligand Tris[3-(4-benzonitrile)-pyrazol-1-yl]borate
Authors: Batten Stuart R. , Duriska Martin B. , Jensen Paul , Lu Jinzhen
Published: January 2007

A new scorpionate ligand, hydro-tris[3-(4-benzonitrile)-pyrazol-1-yl]borate (Tp4bz), was synthesized and the crystal structures of its potassium salt and its MnII, CoII, NiII, and CdII complexes were determined.
Metal Exchange within a Body-Centred Cubic Hydrogen-Bonded Network
Authors: Abrahams Brendan F. , FitzGerald Nicholas J. , Hudson Timothy A. , Robson Richard , Shalders Richard D.
Published: January 2007

A hydrogen bonded network of composition Zn8(C4O7)4(H2O)12·hydrate was shown to undergo a single crystal to single crystal exchange process when crystals are immersed in a concentrated aqueous solution of Ni(ii). In the exchange process, half of the zinc(ii) centres are replaced by nickel(ii) centres. The process of metal ion exchange was monitored using IR spectroscopy. Crystal structures of the transformed crystal and the product generated from a direct synthetic approach are presented.
An Investigation of a Phosphinate-Based Ionic Liquid for Corrosion Protection of Magnesium Alloy AZ31
Authors: Howlett Patrick C. , Zhang Stephen , MacFarlane Douglas R. , Forsyth Maria
Published: January 2007

This work reports a preliminary exploration of the potential of the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (P6,6,6,14M3PPh) for use as a conversion coating agent for corrosion protection of magnesium alloy AZ31. Results obtained for the as received IL did not indicate any measureable improvement in protection. However, when the IL was allowed to reach equilibrium/saturation with moisture from the atmosphere, treatment with this ‘wet’ solution resulted in a substantial improvement in corrosion resistance. Preliminary electrochemical, optical, and spectroscopic characterization of the film will be presented along with a possible mechanism for film formation.
Erbium(III) Chloride: a Very Active Acylation Catalyst
Authors: Dalpozzo Renato , De Nino Antonio , Maiuolo Loredana , Oliverio Manuela , Procopio Antonio , Russo Beatrice , Tocci Amedeo
Published: January 2007

Erbium(iii) chloride is a powerful catalyst for the acylation of alcohols and phenols. The reaction works well for a large variety of simple and functionalized substrates by using different kinds of acidic anhydrides (Ac2O, (EtCO)2O, (PriCO)2O, (ButCO)2O, and (CF3CO)2), without isomerization of chiral centres. Moreover, the catalyst can be easily recycled and reused without significant loss of activity.
Protic Ionic Liquids and Ionicity
Authors: Nuthakki Bharathi , Greaves Tamar L. , Krodkiewska Irena , Weerawardena Asoka , Burgar M. Iko , Mulder Roger J. , Drummond Calum J.
Published: January 2007

Protic ionic liquids (PILs) are a subset of ionic liquids formed by the equimolar mixing of a Brønsted acid and a Brønsted base. PILs have been categorized as poor ionic liquids. However, the issue of assessing the ionicity of PILs is still a matter of debate. In this work we studied some physicochemical properties of three chosen PILs, namely, ethanolammonium acetate (EOAA), 2-methylbutylammonium formate (2MBAF), and pentylammonium formate (PeAF), at the initial equimolar (stoichiometric) acid/base ratio and in the presence of excess acid and base. DSC phase-transition studies along with NMR, IR, and Raman spectroscopy were performed on the chosen PILs. The results are discussed in terms of the degree of ionization (extent of proton transfer from the Brønsted acid to Brønsted base), and the possibility of the formation of polar 1:1 complexes and larger aggregates in the neat stoichiometric PILs.
Facile Synthesis of a Chiral Ionic Liquid Derived from 1-Phenylethylamine
Authors: Ashraf Syed A. , Pornputtkul Yingpit , Kane-Maguire Leon A. P. , Wallace Gordon G.
Published: January 2007

A simple route is described to enantiomerically pure ionic liquids derived from (+)- and (–)-1-phenylethylamine. These very low melting point (–42°C) ionic liquids, containing the bis(trifluoromethylsulfonylimide) anion, possess a wide electrochemical potential window between –2.0 and +2.0 V (versus Ag|AgCl). They show chiral discrimination between the enantiomeric forms of Mosher’s salt, suggesting their potential as media for electrochemical asymmetric syntheses or chiral chromatography.
Synthesis of Some Glycosylated Derivatives of 2-Deoxy-2-fluoro-β-laminaribiosyl Fluoride: Another Success for Glycosynthases
Authors: Scaffidi Adrian , Stick Robert V. , Stubbs Keith A.
Published: January 2007

The synthesis of 4,6-di-O-acetyl-2-deoxy-2-fluoro-3-O-(tetra-O-acetyl-β-d-glucopyranosyl)-β-d-glucosyl fluoride is described. Upon deacetylation and treatment with α-d-glucopyranosyl fluoride in the presence of a glycosynthase, three products, all 2-deoxy-2-fluoro-β-glycosyl fluorides, could be isolated: a trisaccharide, a tetrasaccharide, and a pentasaccharide. An attempt to convert a trisaccharide glycal into a related difluoride, employing Selectfluor, is also reported.
Ionic Liquids—Progress on the Fundamental Issues
Authors: MacFarlane Douglas R. , Seddon Kenneth R.
Published: January 2007

Ionic liquids challenge conventional descriptions of fluids in a variety of ways. In the past, it has been common to oversimplify their behaviour and to ignore the complexity that was possible, given the burgeoning range of ionic liquids available. Here we discuss what is meant by the term ‘ionic liquid’ and some of the key fundamental issues in understanding their properties.
Effect of pretreatment with insulin on the response of buffaloes with inactive ovaries to gonadotrophin-releasing hormone agonist treatment in summer
Authors: Ramoun Adel A. , Osman Khalid T. , Darwish Samy A. , Karen Aly M. , Gamal Magdy H.
Published: January 2007

The aim of the present study was to evaluate the effect of a pretreatment with insulin on the response of buffalo cows with inactive ovaries to gonadotrophin-releasing hormone agonist (GnRHa) treatment during hot summer months (July and August). Thirty-six Egyptian buffalo cows with inactive ovaries were randomly allocated into three groups: (1) group treated with GnRHa (G1, n = 16) in which each buffalo received an intramuscular injection of 250 mg of GnRHa (Day 0; gonadorelin, Fertagyl); (2) group treated with insulin before the GnRHa injection (G2, n = 8) in which each buffalo received a subcutaneous injection of biphasic insulin at a dose of 0.25 IU kg–1 bodyweight once daily starting at Day –3 for 3 consecutive days, followed by an intramuscular injection of 250 mg of GnRHa on Day 0; and (3) the control group (G3, n = 12) in which each buffalo cow received an intramuscular injection of 2.5 mL of sterile saline on Day 0. The ovaries of all animals were examined by trans-rectal ultrasonography (5 MHz) on Days –7, –3 and 0 and continued thereafter at 4-day intervals until oestrus or the end of the experiment. On the same days that ultrasound examinations were performed blood samples were collected to measure the progesterone concentrations. Administration of insulin for 3 days before GnRHa injection (G2) significantly (P < 0.05) increased the diameter of the largest follicle from 6.85 ± 0.64 to 12.4 ± 0.88 mm. There was a significant (P < 0.01) increase in the oestrous induction rate in G2 compared with both G1 and G3 during the first 12 days after the treatment interval. It is concluded that pretreatment with insulin for 3 days before GnRHa injection increases the diameter of the dominant follicle and therefore the oestrous induction rate of acyclic buffaloes.
Vascular endothelial growth factor production by rat granulated metrial gland cells and their morphological features in normal and pathological conditions
Authors: Kaloglu Celal , Bulut H. Eray
Published: January 2007

Granulated metrial gland (GMG) cells are pregnancy-specific cells that may have many functions in successful placentation and pregnancy. In the present study, changes in the rat GMG cell structure, distribution and vascular endothelial growth factor (VEGF) expression during early pregnancy were evaluated by light microscopy. Implantation sites taken from females with spontaneous abortion were also investigated. On Day 7 of pregnancy, GMG cells were distributed through the implantation and interimplantation sites. They formed metrial glands in the mesometrial triangle on Day 9, and were observed in the decidua basalis on Day 14 of pregnancy. Avidin–biotin complex immunohistochemistry revealed that GMG cells showed moderate staining for VEGF at the beginning of pregnancy and intense staining on Days 9 and 10 of pregnancy. They were localised mostly near the newly formed blood vessels. The implantation sites from spontaneously aborting females showed numerous leucocytes in the lumen of mesometrial blood vessels. In spontaneously aborting females, GMG cells showed a distinct morphology, increased in number and volume, their granules were denser and degranulation was observed. These results suggest that rat GMG cells might be a guide for placental angiogenesis and they might share a role with leucocytes in pathological conditions.
Sexing of Dorper sheep fetuses derived from natural mating and embryo transfer by ultrasonography
Authors: Santos M. H. B. , Gonzalez C. I. M. , Bezerra F. Q. G. , Neves J. P. , Reichenbach H.-D. , Lima P. F. , Oliveira M. A. L.
Published: January 2007

In order to improve fetal sexing in the Dorper sheep breed, the objective of the present study was to determine, by repeated ultrasonographic examinations, the migration period of the genital tubercle (GT) in sheep fetuses derived from natural mating or embryo transfer and to compare the accuracy of a single examination with repeated examinations at short intervals. For this purpose, transrectal ultrasound was performed, using a double-frequency linear transducer (6.0 and 8.0 MHz) for monitoring 51 sheep fetuses distributed in three experimental groups (EI, EII and EIII). The fetuses in EI (n = 23) and EII (n = 18) derived, respectively, from natural mating and embryo transfer were monitored at 48-h intervals from the 30th to 60th day of gestation and sexed based on the final location of the GT. The fetuses in EIII (n = 10), which originated from embryo transfer, were examined only once on the 65th day of gestation and sexed taking into consideration the final position of the GT and/or by identification of anatomical structures of external genitalia. The accuracy of fetal sexing was 91.3% (21 fetuses sexed/23 quantified) in EI, 88.9% (16 sexed/18 quantified) in EII and 100% (10 sexed/10 quantified) in EIII, without significant difference (P > 0.05) between experiments. Migration of the GT occurred earlier (P < 0.05) in fetuses produced by natural mating (43.0 ± 2.8 days) than in those derived from embryo transfer (46.1 ± 4.7 days). The results show that fetal sexing can be done from the 50th day onward in fetuses produced by natural mating and from the 60th day onward in fetuses derived from frozen embryos. It can also be concluded that repeated ultrasonographic exams in short time intervals do not maximise the accuracy of fetal sexing. In addition, real-time ultrasonography is a reliable tool for fetal sex determination in sheep after Day 50 of gestation, taking into account both the location of the GT and the identification of external genital structures.
Synthetic seminal plasma peptide inhibits testosterone production in frog testis in vitro
Authors: Quassinti Luana , Maccari Ennio , Murri Oretta , Bramucci Massimo
Published: January 2007

The role of synthetic seminal plasma peptide, designed using biochemical and mass spectroscopy analyses of native peptides extracted from seminal plasma, was studied in amphibian (Rana esculenta) testicular steroidogenesis. Production of testosterone and prostaglandin F2α was determined by incubating frog testes with synthetic peptide in vitro. Analysis of the data showed a dose-dependent inhibition of testosterone production (43% at 10−5 m concentration) without prostaglandin F2α synthesis being affected. Determination of the peptide activity during the annual R. esculenta reproductive cycle showed inhibition of testosterone production in post-reproductive and recovery periods, suggesting a possible involvement of peptide in gonad steroidogenesis.
Ejaculate traits in the Namibian cheetah (Acinonyx jubatus): influence of age, season and captivity
Authors: Crosier Adrienne E. , Marker Laurie , Howard JoGayle , Pukazhenthi Budhan S. , Henghali Josephine N. , Wildt David E.
Published: January 2007

The objective was to examine the influence of animal age, season and captivity status on seminal quality in wild-born cheetahs (Acinonyx jubatus) in Namibia, Africa. Animals were divided into three age categories: juvenile (14–24 months; n = 16 males, 23 ejaculates); adult (25–120 months; n = 76 males, 172 ejaculates); and aged (>120 months; n = 5 males, 5 ejaculates). Seasons were categorised into hot–wet (January–April), cold–dry (May–August) and hot–dry (September–December). A comparison between freshly wild-caught (n = 29 males, 41 ejaculates) and captive-held cheetahs (n = 68 males, 159 ejaculates) was also conducted. Raw ejaculates contained 69.0 ± 1.1% motile spermatozoa (mean ± s.e.m.) with 73.6 ± 1.5% of these cells containing an intact acrosome. Overall, 18.4 ± 0.9% of spermatozoa were morphologically normal, with midpiece anomalies being the most prevalent (~39%) defect. Juvenile cheetahs produced ejaculates with poorer sperm motility, forward progressive status, lower seminal volume and fewer total motile spermatozoa than adult and aged animals. Spermatogenesis continued unabated throughout the year and was minimally influenced by season. Proportions of sperm malformations were also not affected by season. Ejaculates from captive cheetahs had increased volume and intact acrosomes, but lower sperm density than wild-caught counterparts. In summary, Namibian cheetahs produce an extraordinarily high proportion of pleiomorphic spermatozoa regardless of age, season or living (captive versus free-ranging) status. Young males less than 2 years of age produce poorer ejaculate quality than adult and aged males. Because (1) all study animals were wild born and (2) there was little difference between freshly caught males and those maintained in captivity for protracted periods, our results affirm that teratospermia in the cheetah is mostly genetically derived. It also appears that an ex situ environment for the Namibian cheetah can ensure sperm quality comparable with that for free-living males.
Somatic cell nuclear transfer in pigs: recent achievements and future possibilities
Authors: Vajta Gábor , Zhang Yunhai , Macháty Zoltán
Published: January 2007

During the past 6 years, considerable advancement has been achieved in experimental embryology of pigs. This process was mainly generated by the rapidly increasing need for transgenic pigs for biomedical research purposes, both for future xenotransplantation to replace damaged human organs or tissues, and for creating authentic animal models for human diseases to study aetiology, pathogenesis and possible therapy. Theoretically, among various possibilities, an established somatic cell nuclear transfer system with genetically engineered donor cells seems to be an efficient and reliable approach to achieve this goal. However, as the result of unfortunate coincidence of known and unknown factors, porcine embryology had been a handicapped branch of reproductive research in domestic animals and a very intensive and focused research was required to eliminate or minimise this handicap. This review summarises recent achievements both in the background technologies (maturation, activation, embryo culture) and the actual performance of the nuclear replacement. Recent simplified methods for in vivo development after embryo transfer are also discussed. Finally, several fields of potential application for human medical purposes are discussed. The authors conclude that although in this early phase of research no direct evidence can be provided about the practical use of transgenic pigs produced by somatic cell nuclear transfer as organ donors or disease models, the future chances even in medium term are good, and at least proportional with the efforts and sums that are invested into this research area worldwide.
Expression of androgen receptor and 3β-hydroxysteroid dehydrogenase in corpora lutea during pregnancy in the rat
Authors: Szołtys M. , Słomczyńska M. , Galas J. , Duda M. , Sakiewicz A.
Published: January 2007

Immunoexpression of androgen receptor (AR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) was investigated in three generations of corpora lutea (CLs), found in the ovaries of rats on Days 1, 2, 5, 9, 14 and 20 of pregnancy. The youngest generation of CLs functioned during the whole pregnancy, whereas the older and the oldest generations underwent earlier regression. The newly formed CLs exhibited weak cytoplasmic 3β-HSD expression. During subsequent days, a gradual increase in 3β-HSD immunolabelling was observed, followed by a decrease on Day 20. In the older and the oldest CLs, surviving luteal cells demonstrated strong, although in the oldest CLs mostly perinuclear, 3β-HSD immunoreaction. The newly formed CLs showed weak nuclear AR immunolabelling, which became stronger during the following days. On Day 20, luteal cells demonstrated a weaker nuclear immunoreaction. The older and oldest generations of CLs exhibited weaker and almost negative AR immunolabelling, respectively. Of special interest was the richly vascularised apical region of young CLs. Here luteal cells with more intensive 3β-HSD staining predominated, whereas cytoplasmic AR immunoreaction was accompanied by positive or negative nuclear AR immunoexpression. The present studies showed differences in AR and 3β-HSD distribution within various generations of CLs and within particular regions of the same young CL.
Effects of vitrification procedures on subsequent development and ultrastructure of in vitro-matured swamp buffalo (Bubalus bubalis) oocytes
Authors: Boonkusol Duangjai , Faisaikarm Tassanee , Dinnyes Andras , Kitiyanant Yindee
Published: January 2007

The purpose of the present study was to investigate the effects of two vitrification procedures on developmental capacity and ultrastructural changes of matured swamp buffalo oocytes. In vitro-matured oocytes were vitrified by using 35 and 40% ethylene glycol as vitrification solution for solid surface vitrification (SSV) and in-straw vitrification (ISV), respectively. Survival rate of vitrified–warmed oocytes, evaluated on the basis of ooplasm homogeneity, oolemma integrity and zona pellucida intactness, as well as parthenogenetic blastocyst rates of vitrified–warmed oocytes were significantly higher with SSV (89.3 and 13.6%, respectively) than ISV (81.8 and 5.5%, respectively). However, they were still significantly lower than that of control oocytes (100 and 34.2%, respectively). For examining the ultrastructural changes, fresh, VS-exposed (ISV and SSV), and vitrified–warmed (ISV and SSV) oocytes were processed for transmission electron microscopy. In VS-exposed oocytes, reduction of microvilli abundance and damage of mitochondrial membrane were found only in the ISV group. In vitrified–warmed oocytes, however, it was clear that both methods of vitrification induced profound ultrastructural modifications to microvilli, mitochondria, oolemma and cortical granules as well as to the size and position of vesicles. Damaged mitochondria were, however, more abundant in ISV vitrified oocytes than in SSV vitrified oocytes, which correlated with the developmental data, showing the superiority of the SSV method. The present study demonstrated the feasibility of vitrification of in vitro-matured swamp buffalo oocytes.
Characterisation of a human sperm cell subpopulation marked by the presence of the TSH2B histone
Authors: Singleton Stephanie , Mudrak Olga , Morshedi Mahmood , Oehninger Sergio , Zalenskaya Irina , Zalensky Andrei
Published: January 2007

During the process of mammalian spermiogenesis, a significant reorganisation of the chromatin structure occurs involving the sequential substitution of somatic histones with protamines. In the human sperm nucleus, ~15% of the basic nuclear protein complement is maintained as histones. Human testis/sperm-specific histone H2B (hTSH2B) is a variant of the histone H2B expressed exclusively in spermatogenic germline cells and present in some mature sperm cells. Thus, this protein marks a subpopulation of sperm cells in the ejaculate. Using indirect immunofluorescence, we examined the influence of hTSH2B on zona pellucida binding and sperm head decondensation in amphibian egg cell-free extract. As suggested by previous studies, we found that hTSH2B can be localised in only ~30% of sperm cells within a given ejaculate. We established that the presence of hTSH2B does not influence sperm zona pellucida binding capacity. Finally, we found that decondensation occurred more rapidly and to a greater extent in those cells containing hTSH2B. We propose that the presence or absence of hTSH2B within spermatozoa influences pronuclei formation and the activation of paternal genes following fertilisation and during early embryonic development.
Regulation of yeast oscillatory dynamics
Authors: Murray Douglas B. , Beckmann Manfred , Kitano Hiroaki
Published: February 2007

When yeast cells are grown continuously at high cell density, a respiratory oscillation percolates throughout the population. Many essential cellular functions have been shown to be separated temporally during each cycle; however, the regulatory mechanisms involved in oscillatory dynamics remain to be elucidated. Through GC-MS analysis we found that the majority of metabolites show oscillatory dynamics, with 70% of the identified metabolite concentrations peaking in conjunction with NAD(P)H. Through statistical analyses of microarray data, we identified that biosynthetic events have a defined order, and this program is initiated when respiration rates are increasing. We then combined metabolic, transcriptional data and statistical analyses of transcription factor activity, identified the top oscillatory parameters, and filtered a large-scale yeast interaction network according to these parameters. The analyses and controlled experimental perturbation provided evidence that a transcriptional complex formed part of the timing circuit for biosynthetic, reductive, and cell cycle programs in the cell. This circuitry does not act in isolation because both have strong translational, proteomic, and metabolic regulatory mechanisms. Our data lead us to conclude that the regulation of the respiratory oscillation revolves around coupled subgraphs containing large numbers of proteins and metabolites, with a potential to oscillate, and no definable hierarchy, i.e., heterarchical control.
Direct measurement of force generation by actin filament polymerization using an optical trap
Authors: Footer Matthew J. , Kerssemakers Jacob W. J. , Theriot Julie A. , Dogterom Marileen
Published: February 2007

Actin filament polymerization generates force for protrusion of the leading edge in motile cells. In protrusive structures, multiple actin filaments are arranged in cross-linked webs (as in lamellipodia or pseudopodia) or parallel bundles (as in filopodia). We have used an optical trap to directly measure the forces generated by elongation of a few parallel-growing actin filaments brought into apposition with a rigid barrier, mimicking the geometry of filopodial protrusion. We find that the growth of approximately eight actin parallel-growing filaments can be stalled by relatively small applied load forces on the order of 1 pN, consistent with the theoretical load required to stall the elongation of a single filament under our conditions. Indeed, large length fluctuations during the stall phase indicate that only the longest actin filament in the bundle is in contact with the barrier at any given time. These results suggest that force generation by small actin bundles is limited by a dynamic instability of single actin filaments, and therefore living cells must use actin-associated factors to suppress this instability to generate substantial forces by elongation of parallel bundles of actin filaments.
Phase-variable expression of a family of glycoproteins imparts a dynamic surface to a symbiont in its human intestinal ecosystem
Authors: Fletcher C. Mark , Coyne Michael J. , Bentley David L. , Villa Otto F. , Comstock Laurie E.
Published: February 2007

The recent report of the synthesis of glycoproteins by the abundant intestinal symbionts
Bacteroides
showed that these organisms use a novel bacterial enzyme to decorate their surfaces with a sugar residue derived from their environment. As a first step in understanding the importance of these glycoproteins to the bacteria and to the bacterial–host symbiosis, we identified and characterized the abundant glycoproteins of
Bacteroides distasonis
(proposed reclassification as
Parabacteroides distasonis
) [Sakamoto M, Benno Y (2006)
Int J Syst Evol Microbiol
56:1599–1605]. Using lectin-affinity purification followed by tandem mass spectrometry, we identified a family of at least nine glycoproteins, similar only to the S-layer glycoproteins of
Tannerella forsythia
. Analysis of one of these purified glycoproteins demonstrated that the glycan is primarily a polymer of xylose, a monosaccharide rarely found in bacterial glycans. Even more unexpected was the finding that seven of nine of the glycoprotein promoters undergo DNA inversion, a process that we show is active in their endogenous human environment. Using cross-species functional assays, we show that a single serine family site-specific recombinase globally mediates the inversions of these glycoprotein promoters. This regulatory mechanism is similar to that of the
Bacteroides fragilis
capsular polysaccharides and establishes DNA inversion as a general and ancient means of regulation of glycan-containing surface molecules of these important human intestinal symbionts.
Brain shape in human microcephalics and
Homo floresiensis
Authors: Falk Dean , Hildebolt Charles , Smith Kirk , Morwood M. J. , Sutikna Thomas , Jatmiko  , Saptomo E. Wayhu , Imhof Herwig , Seidler Horst , Prior Fred
Published: February 2007

Because the cranial capacity of LB1 (
Homo floresiensis
) is only 417 cm
3
, some workers propose that it represents a microcephalic
Homo sapiens
rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological
H. sapiens
specimen that, like LB1, represents an ≈3-foot-tall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1's with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1's having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.
Interleukin 7 reduces the levels of spontaneous apoptosis in CD4+and CD8+T cells from HIV-1-infected individuals
Authors: Vassena Lia , Proschan Michael , Fauci Anthony S. , Lusso Paolo
Published: February 2007

Apoptosis has been suggested as one of the major mechanisms of CD4+T cell depletion during the course of HIV type 1 (HIV-1) infection. Here, we show that interleukin 7 (IL-7), a nonredundant cytokine that plays essential roles in the generation and homeostasis of the T cell compartment of the immune system, exerts strong antiapoptotic effectsex vivoon both CD4+and CD8+T cells derived from HIV-1-infected subjects. The level of IL-7-mediated reduction of apoptosis was inversely correlated with the number of circulating CD4+T cells, indicating a higher sensitivity to IL-7 effects in patients with more advanced disease. The antiapoptotic effect of IL-7 was uncoupled from the induction of cellular proliferation or endogenous HIV-1 replication. These results provide a further rationale for consideration of IL-7 as an agent of immune reconstitution in HIV-1 infection.
Mast cells contribute to initiation of autoantibody-mediated arthritis via IL-1
Authors: Nigrovic Peter A. , Binstadt Bryce A. , Monach Paul A. , Johnsen Alyssa , Gurish Michael , Iwakura Yoichiro , Benoist Christophe , Mathis Diane , Lee David M.
Published: February 2007

Mast cells are immune sentinels that participate in the defense against bacteria and parasites. Resident within the joint, mast cells become activated in human rheumatoid arthritis and are implicated in the pathogenesis of experimental murine synovitis. However, their arthritogenic role remains undefined. Using a model of autoantibody-induced arthritis, we show that mast cells contribute to the initiation of inflammation within the joint by elaboration of IL-1. Mast cells become activated to produce this cytokine via the IgG immune complex receptor FcγRIII. Interestingly, mast cells become dispensable for the perpetuation of arthritis after delivery of IL-1, highlighting the contribution of this lineage to arthritis induction. These findings illuminate a mechanism by which mast cells can participate in the pathogenesis of autoimmune inflammatory arthritis and provide insights of potential relevance to human rheumatoid arthritis.
Open-cap conformation of intramembrane protease GlpG
Authors: Wang Yongcheng , Ha Ya
Published: February 2007

The active sites of intramembrane proteases are positioned in the lipid bilayer to facilitate peptide bond hydrolysis in the membrane. Previous crystallographic analysis of
Escherichia coli
GlpG, an intramembrane protease of the rhomboid family, has revealed an internal and hydrophilic active site in an apparently closed conformation. Here we describe the crystal structure of GlpG in a more open conformation, where the capping loop L5 has been lifted, exposing the previously buried and catalytically essential Ser-201 to outside aqueous solution. A water molecule now moves into the putative oxyanion hole that is constituted of a main-chain amide (Ser-201) and two conserved side chains (His-150 and Asn-154). The loop movement also destabilizes a hydrophobic side chain (Phe-245) previously buried between transmembrane helices S2 and S5 and creates a side portal from the lipid to protease active site. These results provide insights into the conformational plasticity of GlpG to accommodate substrate binding and catalysis and into the chirality of the reaction intermediate.
On the Pessimistic Induction and Two Fallacies
Authors: Saatsi Juha T.
Published: February 2007

The Pessimistic Induction from falsity of past theories forms a perennial argument against scientific realism. This paper considers and rebuts two recent arguments—due to Lewis (2001) and Lange (2002)—to the conclusion that the Pessimistic Induction (in its best known form) is fallacious. It re-establishes the dignity of the Pessimistic Induction by calling to mind the basic objective of the argument, and hence restores the propriety of the realist program of responding to PMI by undermining one or another of its premises.