bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent advances in capillary electrophoresis and capillary electrochromatography of peptides
Authors: Kašička Václav
Published: December 2003

An overview of the recent developments in the applications of high‐performance capillary electromigration methods, namely zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography, to analysis, preparation, and physicochemical characterization of peptides is presented. New approaches to the theoretical description and experimental verification of the electromigration behavior of peptides and the methodological aspects of capillary electroseparations of peptides, such as rational selection of separation conditions, sample treatment, and suppression of adsorption, are discussed, and new developments in individual separation modes and new designs of detection systems applied to peptide separations are shown. Several types of applications of capillary electromigration methods to peptide analysis are presented: quality control and purity tests, determination in biomatrices, monitoring of physical and chemical changes and enzymatic conversions, amino acid and sequence analysis, and peptide mapping. The examples of micropreparative peptide separations are given and capabilities of capillary electromigration techniques to provide important physicochemical characteristics of peptides are demonstrated.
Recent progress in high‐performance capillary bioseparations
Authors: Huck Christian W. , Stecher Günther , Bakry Rania , Bonn Günther K.
Published: December 2003

Bioanalysis is a fast growing domain with new technological developments in the field of mass spectrometry, separation science, and bioinformatics. The central role of separation prior to detection and evaluation of analytes is indisputable. In fact, since the decipherment of the human genome via multichannel capillary electrophoresis in combination with laser‐induced fluorescence [1], the analysis of the proteome, i.e., the type and amount of all proteins expressed at a certain time by the genome in a cell or tissue [2] became of central interest. Therefore, new fast and sensitive capillary liquid chromatographic, electrophoretic, and electrochromatographic separation techniques, suitable for high‐throughput analysis of proteins, peptides and nucleic acids, are required.
Early hominid hunting and scavenging: A zooarcheological review
Authors: Domínguez‐Rodrigo Manuel , Pickering Travis Rayne
Published: December 2003

Before the early 1980s, the prevailing orthodoxy in paleoanthropology considered Early Stone Age archeological sites in East Africa to represent a primitive form of hominid campsites. The faunal evidence preserved in these sites was viewed as the refuse of carcass meals provided by hominid males in a social system presumptively characterized by sexual division of labor. This interpretation of early hominid life ways, commonly known as the “Home Base” or “Food Sharing” model, was developed most fully by Glynn Isaac.1–4 As Bunn and Stanford5 emphasized, this model was greatly influenced by a paradigm that coalesced between 1966 and 1968, referred to as “Man the Hunter.”6
The gasification recycling technology of plastics WEEE containing brominated flame retardants
Authors: Yamawaki Takashi
Published: December 2003

The recycling of WEEE (waste electrical and electronic equipment) became a requirement in April 2001 in Japan under the Home Appliance Recycling Law. By 2008 the criterion for the recycling ratio will be raised to 80%–90%, and at that time plastic must also be recycled. For this work, gasification processes (feedstock recycling technology) were selected for plastics WEEE recycling. After high temperature treatment, at over 1200°C, shock cooling of the gases to a temperature of roughly under 200°C was done by this process. The generated ‘thin’ gas could then be used as raw materials for chemical industries or for electric power generation. The effect of the high temperature treatment and the shock cooling suppresses the emission of brominated dioxins to a very low level, just as for chlorinated dioxins. Copyright © 2003 John Wiley & Sons, Ltd.
Using heat of combustion data to estimate or assess some threshold flammability properties of materials
Authors: Hshieh Fu‐Yu , B. Hirsch David , D. Beeson Harold
Published: December 2003

This paper gives a brief summary of recent studies using heat of combustion data to estimate or assess some threshold flammability properties of materials. Heat of combustion data can be used to estimate the lower flammability limit, upper flammability limit and minimum oxygen concentration for flame propagation of organic and organosilicon compounds. The data can also be used to assess the threshold oxygen pressure for the combustion of metal alloys in high‐pressure oxygen environments. Copyright © 2003 John Wiley & Sons, Ltd.
Non‐linear time‐domain models for irregular wave diffraction about offshore structures
Authors: Ferrant Pierre , Touzé David Le , Pelletier Karine
Published: December 2003

This paper is devoted to the numerical simulation of non‐linear wave diffraction by three‐dimensional (3D) surface‐piercing structures in the time domain. Two different methods are presented. First a second‐order diffraction model is described, in which a boundary‐element method combined with a time‐stepping procedure are used to solve the first‐ and second‐order diffraction problems in the time domain. The Stokes expansion approach of the free surface non‐linearities results in relatively moderate simulation times, so that long simulations in irregular incident waves become feasible. The model has previously been systematically validated by comparison with available semi‐analytical frequency domain results on regular wave diffraction about simplified geometries. In the present paper, the flexibility and stability of the time‐domain approach to second‐order wave diffraction are further demonstrated by the simulation of bichromatic wave diffraction over a large number of incident wave periods. The second part of the paper addresses the problem of fully non‐linear wave diffraction. Again, the solution procedure is based on a boundary element method (BEM) solution of the boundary‐value problem in the time domain, but the non‐linear boundary conditions are accounted for without any approximation this time. In this fully non‐linear diffraction model, an explicit description of the incident wave is exploited to solve the problem for the diffracted flow only. This approach has a number of practical advantages in terms of accuracy and computational efficiency. In previous publications related to this approach stream‐function theory was utilized to model non‐linear regular incident waves. In this paper, irregular two‐dimensional (2D) incident waves are modelled by means of a recently developed fully non‐linear time‐domain pseudospectral formulation. An original coupling of this 2D pseudospectral model with the 3D non‐linear BEM model is proposed, and its effectiveness is shown on the case of 2D wave packets interacting with a vertical bottom‐mounted cylinder. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical aspects of an algorithm for the Eulerian simulation of two‐phase flows
Authors: Oliveira Paulo J. , Issa Raad I.
Published: December 2003

It is often the case that the numerical simulation of two phase flows leads to a number of difficulties associated with the solution algorithms utilized. Those difficulties manifest themselves as an impossibility to converge the iterative solution process, typical of the finite‐volume pressure‐correction methods, and are particularly persistent in cases with phase segregation (complete, or almost complete, separation of one phase from the other) and with fine meshes. A number of effective measures to overcome such problems are here proposed and tested, encompassing: (1) modification of the momentum equations formulation in a way that avoids singularity as volume fractions (α) tend to zero; (2) bounding of the volume fractions during the iterative algorithm in a way that enforces the physical limits, α0 and 1; (3) symmetric treatment of some terms in the equations, and consistent formulation of cell‐face fluxes in order to prevent numerical‐induced oscillations. Copyright © 2003 John Wiley & Sons, Ltd.
Fluid dynamic numerical simulation of a gas phase polymerization reactor
Authors: Gobin Anne , Neau Hervé , Simonin Olivier , Llinas Jean‐Richard , Reiling Vince , Sélo Jean‐Lof̈c
Published: December 2003

This article presents preliminary fluid dynamic simulation results of ethylene polymerization dense fluidized bed using the two‐phase flow numerical code ESTET‐ASTRID developed by Electricité de France for CFB boilers and based on the two‐fluid modelling approach. The continuous phase consists of gas and the dispersed phase consists of catalyst particles. The particle fluctuating motion is modelled using two‐separate transport equations, on the particle kinetic energy and the fluid–particle covariance, developed in the frame of kinetic theory of granular medium accounting for particle–particle and fluid–particle interactions. Time‐dependent 2D and 3D simulations have been performed for industrial and pilot reactor operating conditions. The numerical predictions are in good qualitative agreement with the observed behaviour in terms of bed height, pressure drop and mean flow organization, such as the down falling of the PE particle layer along the walls. Moreover, these simulations help to provide information about instantaneous and time‐averaged solid concentration and velocity fields. Characteristic mechanisms and influence of model closure assumptions on flow predictions are also investigated. Finally, such numerical simulations look very powerful, when validated on exhaustive data collection, to improve design and performance of industrial facilities and to provide insight into the complex physical mechanisms involved. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical simulations of non‐linear wave radiation in inviscid fluid with a free surface
Authors: Markiewicz M. , Ben‐Nasr K. , Mahrenholtz O.
Published: December 2003

The paper deals with the numerical simulation of non‐linear wave radiation by vertical free‐surface piercing structures moving horizontally in water of finite constant depth. A time‐stepping approach combined with the finite element method is used to simulate the potential flows due to high‐frequency oscillations of the structure. The evolution equations for the wave elevation and velocity potential at the free surface, exact up to second order, are derived using Stokes perturbation expansion. The boundary value problems up to second order at each time‐step are solved using the Eulerian description and a fixed mesh of finite elements. The results of simulations are presented for vertical cylinders of circular cross section, and for sloshing waves in annular tanks. Copyright © 2003 John Wiley & Sons, Ltd.
Modification of functional properties of egg‐white proteins
Authors: Campbell Lydia , Raikos Vassilios , Euston Stephen R.
Published: December 2003

Egg‐white proteins are extensively utilised as food ingredients due to their unique functional properties. Several attempts have been made in order to improve the functional properties of egg‐white proteins and to identify the optimal formulations for unique food products. Experimental data proves that controlled denaturation of egg‐white proteins can have a beneficial impact on various functional applications in the food industry such as emulsifying ability, heat stability, gelation. This review describes the effect of heat‐induced denaturation on protein structure and functionality. Studies on the impact of Maillard reaction, which aim to elucidate the structure‐function relationship of egg‐white proteins, are presented. A novel approach which could be the basis for the development of new methods aiming to improve the functional properties of egg‐white proteins is also discussed.
Incidence of aflatoxin B1 in the Egyptain cured meat basterma and control by γ‐irradiation
Authors: Refai Mohamed K. , Niazi Zienab M. , Aziz Nagy H. , Khafaga Nagwa Ebraheem M.
Published: December 2003

In the present studies trials have been carried out to investigate the occurrence of aflatoxin B1 in the Egyptian cured meat basterma and to control such contamination by γ‐rays. Basterma was prepared from fresh salted meat coated with spice paste and stored at room temperature. The total mould counts of basterma samples varied from 103 to 106 cfu/g in summer months and from 102 to 105 cfu/g in winter months. Aspergillus, Penicillium, Mucor, Rhizopus, Fusarium and Cladosporium were the most common fungal genera isolated from basterma samples and its components. Basterma samples contained total aflatoxins at levels from 2.8 to 47 μg·kg–1. Aflatoxins were determined in the spice paste at levels from 9.6 to 120 μg·kg–1 and in pepper (285.6 μg·kg–1), garlic (224.4 μg·kg–1), fenugreek (194.2 μg·kg–1), coriander (166.4 μg·kg–1) and capsicum (42.4 μg·kg–1). At an irradiation dose level of 3 kGy, only one sample each of pepper, fenugreek, and spice paste were contaminated with aflatoxins and all basterma samples and its components were free from aflatoxins at an irradiation dose level of 5 kGy.
Fractionation, solubility and functional properties of wheat bran proteins as influenced by pH and/or salt concentration
Authors: Idris Wisal H. , Babiker Elfadil E. , El Tinay Abdullahi H.
Published: December 2003

The content, fractionation, solubility and functional properties of wheat bran proteins as well as the effects of pH and/or NaCl concentration on some of these functional properties were investigated. The protein content of the bran was found to be 16.80%. Albumin and glutelin are the major fractions of wheat bran proteins. The minimal protein solubility was observed at pH 5.5, the maximum at pH 11.5. The emulsifying capacity, activity and emulsion stability as well as foaming capacity and foam stability were greatly affected by pH and salt concentrations. Lower values were observed at acidic pH and high salt concentration. The least gelation concentration of wheat bran proteins was found to be 16% when the proteins were dissolved in 1.0 M NaCl. The total protein was highly viscous and dispersable with water‐holding capacity of 4.20 mL H2O/g protein, oil‐holding capacity of 1.70 mL oil/g protein and bulk density of 0.29 g/mL while dispensability was found to be 77.30%.
2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH∗︁) test demonstrates antiradical activity of Dorstenia psilurus and Dorstenia ciliata plant extracts
Authors: Kansci Germain , Dongo Etienne , Genot Claude
Published: December 2003

Plants of the Dorstenia genus, used in traditional medicine and as food ingredient in Africa, are rich in polyphenolic compounds which can be involved in prevention of disease and food spoilage through their antioxidant activity. The antiradical activities of extracts of Dorstenia psilurus, D. ciliata and a phenolic compound (6‐prenylapigenin) from D. ciliata were evaluated with the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH∗︁) test. D. psilurus chloroform and D. ciliata ethyl acetate extracts were shown to exhibit antiradical activities, with slow kinetic action. The efficient concentrations at different kinetic times “EC50, t” for the D. ciliata extract: 699, 479, 311 and 251 g/kg after 30, 60, 120 and 180 min, respectively, were always much lower than for the D. psilurus extract: 2341, 2312, 1672 and 1281 g/kg at the same times. The antiradical activity of 6‐prenylapigenin was weak compared to the extracts. These results suggest the antioxidant activities of Dorstenia extracts and might help to understand their traditional use. We propose “EC50, t”, calculated on the curves obtained with DPPH∗︁ test, as a parameter to screen and compare antiradical activities of plant extracts with slow kinetic behaviour.
Forecasting some low‐predictability time series using diffusion indices
Authors: Brisson Marc , Campbell Bryan , Galbraith John W.
Published: December 2003

The growth rates of real output and real investment are two macroeconomic time series which are particularly difficult to forecast. This paper considers the application of diffusion index forecasting models to this problem. We begin by characterizing the performance of standard forecasts, via recently‐introduced measures of predictability and the forecast content, noting the maximum horizon at which the forecasts have value. We then compare diffusion index forecasts with a variety of alternatives, including the forecasts made by the OECD. We find gains in forecast accuracy at short horizons from the diffusion index models, but do not find evidence that the maximum horizon for forecasts can be extended in this way. Copyright © 2003 John Wiley & Sons, Ltd.
Hydrogen peroxide increases gap junctional communication and induces astrocyte toxicity: Regulation by brain macrophages
Authors: Rouach Nathalie , Calvo Charles‐Felix , Duquennoy Helene , Glowinski Jacques , Giaume Christian
Published: December 2003

Cultured astrocytes are highly coupled by gap junction channels mainly constituted by connexin 43. We have previously shown that gap junctional communication (GJC) represents a functional property of astrocytes that is a target for their interaction with other brain cell types, including neurons and brain macrophages. In pathological situations, neurons as well as brain macrophages produce superoxide ions leading to the formation of hydrogen peroxide (H2O2) that can be cytotoxic. We report here that 10‐min exposure to 100 μM H2O2 increases GJC in astrocytes. Moreover, 30‐min exposure to 100 μM H2O2 induces, 24 h later, an astrocyte cell death by both apoptosis and necrosis. This H2O2‐induced astrocyte cell death is not affected when gap junctions are inhibited by several uncoupling agents, including 18α‐glycyrrhetinic acid, halothane, heptanol, and endothelin‐1, indicating that the proportion of cell death is not related to the level of GJC. The effect of H2O2 on gap junction channels does not result from the production of free radicals but is rather linked to modification of the redox equilibrium in astrocytes. Indeed, an oxidative agent reproduces the H2O2‐evoked response while reducing agents prevent the effect of H2O2. Finally, when astrocytes are cocultured with brain macrophages, the effects of H2O2 on both GJC and toxicity are not observed, revealing a new protective role of brain macrophages during oxidative stress. © 2003 Wiley‐Liss, Inc.
Antioxidants are necessary for myelination of dorsal root ganglion neurons, in vitro
Authors: Podratz Jewel L. , Rodriguez Esther H. , Windebank Anthony J.
Published: December 2003

We have demonstrated that myelination of dorsal root ganglion (DRG) axons occurs in a fully defined, serum‐free medium (B27). This implies that there may be components in B27 medium that support myelination. To determine which of the components in B27 were essential for myelination, we systematically removed components from B27 until myelination was lost. We added these components to a fully defined minimal medium (N2) that supports neuron survival but not myelination. When antioxidants were removed from B27, myelination was lost. However, the individual antioxidants did not induce myelination when added to N2 medium. Addition of ascorbic acid along with the B27 antioxidants was sufficient to induce myelination in N2 medium, which was enhanced by retinyl acetate. Removal of vitamin E from B27 caused a partial loss of myelination, and addition of vitamin E to N2 medium containing ascorbic acid induced partial myelination. Addition of serum to the B27 myelinating medium inhibited myelination completely. These results indicate that antioxidants are important for myelination, in vitro. Vitamin E may play an important role. Use of a serum‐free medium may be beneficial for in vitro myelination studies because serum has unknown inhibitory effects. © 2003 Wiley‐Liss, Inc.
Selective staining by vital dyes of Müller glial cells in retinal wholemounts
Authors: Uckermann Ortrud , Iandiev Ianors , Francke Mike , Franze Kristian , Grosche Jens , Wolf Sebastian , Kohen Leon , Wiedemann Peter , Reichenbach Andreas , Bringmann Andreas
Published: December 2003

Müller glial cells within the retina may respond to different signaling molecules with an elevation of their intracellular free calcium. To prove the localization of the recorded calcium responses in Müller cells within acutely isolated retinal wholemounts, retinal pieces from adult animals and humans were exposed to different vital dyes just after the calcium imaging records were finished. The dyes, Mitotracker Orange, Mitotracker Green, Celltracker Orange, Celltracker Green, and monochlorobimane, are all selectively taken up by Müller glial cells, while neuronal cells remain largely devoid of the dyes. By using this method, it can be demonstrated that the free calcium alterations within the wholemounts indeed occur within Müller cells. Moreover, the cross‐sectional areas of (dye‐filled) Müller glial cell bodies, as well as of (dye‐free) neuronal cell bodies, can be measured in retinal wholemounts, and the spatial densities of both types of cells can be determined. The vital dye loading of Müller cells may facilitate investigations of stimulus‐induced alterations of retinal glial cell physiology and morphology. © 2003 Wiley‐Liss, Inc.
Activation of p38 mitogen‐activated protein kinase in spinal hyperactive microglia contributes to pain hypersensitivity following peripheral nerve injury
Authors: Tsuda Makoto , Mizokoshi Akito , Shigemoto‐Mogami Yukari , Koizumi Schuichi , Inoue Kazuhide
Published: December 2003

Neuropathic pain is an expression of pathological operation of the nervous system, which commonly results from nerve injury and is characterized by pain hypersensitivity to innocuous stimuli, a phenomenon known as tactile allodynia. The mechanisms by which nerve injury creates tactile allodynia have remained largely unknown. We report that the development of tactile allodynia following nerve injury requires activation of p38 mitogen‐activated protein kinase (p38MAPK), a member of the MAPK family, in spinal microglia. We found that immunofluorescence and protein levels of the dually phosphorylated active form of p38MAPK (phospho‐p38MAPK) were increased in the dorsal horn ipsilateral to spinal nerve injury. Interestingly, the phospho‐p38MAPK immunofluorescence in the dorsal horn was found exclusively in microglia, but not in neurons or astrocytes. The level of phospho‐p38MAPK immunofluorescence in individual microglial cells was much higher in the hyperactive phenotype in the ipsilateral dorsal horn than the resting one in the contralateral side. Intrathecal administration of the p38MAPK inhibitor, 4‐(4‐fluorophenyl)‐2‐(4‐methylsulfonylphenyl)‐5‐(4‐pyridyl)‐1H‐imidazole (SB203580), suppresses development of the nerve injury‐induced tactile allodynia. Taken together, our results demonstrate that nerve injury‐induced pain hypersensitivity depends on activation of the p38MAPK signaling pathway in hyperactive microglia in the dorsal horn following peripheral nerve injury. © 2003 Wiley‐Liss, Inc.
Helicoid Shiftamers for the Transport of π‐Clumps and Charges
Authors: Tantillo Dean J. , Hoffmann Roald
Published: December 2003

Hypothetical helical organic polymers with localized electrons, charges, and/or atoms are described, in which these localized substructures can move along the backbones of the polymers via sigmatropic H shifts.
Novel Route to L‐Hexoses from L‐Ascorbic Acid: Asymmetric Synthesis of L‐Galactopyranose and L‐Talopyranose Preliminary Communication
Authors: Ermolenko Ludmila , Sasaki N. André , Potier Pierre
Published: December 2003

A novel route with L‐ascorbic acid as a single common starting material to asymmetric synthesis of all eight diastereomers of L‐hexoses is described. Assessment of this new approach is demonstrated by the expedient synthesis of L‐galactopyranose and L‐talopyranose derivatives. Key steps involve stereoselective preparation of chiral (E)‐ and (Z)‐γ‐hydroxy‐α,β‐unsaturated esters and their stereo‐controlled dihydroxylation by OsO4.
A Model Study towards a Conceptually New Synthetic Entry into the Seco‐ and Heteroyohimbine Alkaloid Families
Authors: Vogelsang Thomas , Borschberg Hans‐Jürg
Published: December 2003

A model study is presented that paves the way to a new and flexible synthetic approach towards the seco‐ and heteroyohimbine alkaloid class. The key step involves a highly diastereoselective Cope rearrangement of an (E,E)‐azacyclodeca‐3,7‐diene grafted onto a 3‐ethylindole moiety to furnish a trans‐3,4‐divinylpiperidine derivative in 83% yield.
On the Distance‐Independent Hole Transfer over Long (A⋅T)n‐Sequences in DNA
Authors: Furrer Ernst , Giese Bernd
Published: December 2003

Electron holes can travel through DNA double strands over long distances in a multistep ‘hopping’ process. But the influence of the DNA sequence on this process is still not understood in all details. We have carried out new experiments to understand the recent observation that the efficiency of the hole transport between guanines (G), which are separated from each other by long adenine⋅thymine (A⋅T) sequences, is nearly independent of the length of the (A⋅T)n sequence for n ≥ 4. For this purpose, a new synthesis of the modified adenosine 16 and its incorporation into a DNA double strand was worked out. Subsequent experiments demonstrated that the hole transport between GGG units and the H2O trapping of the guanine radical cation display similar rates. We conclude that the charge must be already partially equilibrated before being trapped by H2O. Thus, the weak distance effect is caused not only by the rate of the hole transport, but also by its equilibration over the (A ⋅ T)n sequence.
ω‐Fluoro Thiafatty Acids: New Mechanistic Probes of Desaturase‐Mediated Reactions
Authors: Hodgson Derek J. , Lao Kim Y. Y. , Dawson Brian , Buist Peter H.
Published: December 2003

A series of 18‐fluoro thiastearates were prepared and incubated with a yeast Δ9‐desaturating system. The relative efficiency of desaturase‐mediated sulfoxidation was monitored via 19F‐NMR analysis of the sulfoxide products, and a strong preference for oxo transfer to the S‐atom occupying the 9‐position was confirmed. The oxidation profile obtained in this manner matched that of analogous experiments with non‐fluorinated substrates. These results form the basis of a versatile 19F‐NMR‐based method for mapping the position of the putative diiron oxidant relative to substrate, and has potential application to the study of membrane‐bound desaturases in vitro.
The Cofactor of Tetrachloroethene Reductive Dehalogenase of Dehalospirillum multivorans Is Norpseudo‐B12, a New Type of a Natural Corrinoid
Authors: Kräutler Bernhard , Fieber Wolfgang , Ostermann Sigrid , Fasching Mario , Ongania Karl‐Hans , Gruber Karl , Kratky Christoph , Mikl Christian , Siebert Anke , Diekert Gabriele
Published: December 2003

The corrinoid cofactor of the tetrachloroethene reductive dehalogenase of Dehalospirillum multivorans was isolated in its Coβ‐cyano form. This cofactor represents the main corrinoid found in D. multivorans cells. Analysis of the isolated cyano‐corrinoid by a combination of HPLC and UV/VIS‐absorbance spectroscopy revealed it to be nonidentical to a variety of known natural B12 derivatives. From high‐resolution mass‐spectrometric analysis, the molecular formula of the corrinoid isolated from D. multivorans could be deduced as C58H81CoN17O14P. The sample of the novel corrinoid from D. multivorans was further analyzed by UV/VIS, CD, and one‐ and two‐dimensional 1H‐, 13C‐, and 15N‐NMR spectroscopy, which indicated its structure to be closely related to that of pseudovitamin B12 (Coβ‐cyano‐7″‐adeninylcobamide). By the same means, the corrinoid could be shown to differ from pseudovitamin B12 only by the lack of the methyl group attached to carbon 176, and, therefore, it was named norpseudovitamin B12 (or, more precisely, 176‐norpseudovitamin B12). Norpseudovitamin B12 represents the first example of a ‘complete’ B12‐cofactor that lacks one of the methyl groups of the cobamide moiety, indicating that the B12‐biosynthetic pathway in D. multivorans differs from that of other organisms. X‐Ray crystal‐structures were determined for norpseudovitamin B12 from D. multivorans and the analogues pseudovitamin B12 and factor A (Coβ‐cyano‐7″‐[2‐methyl]adeninylcobamide). These first accurate crystal structures of complete corrinoids with an adeninyl pseudonucleotide confirmed the expected coordination properties around Co and corroborated the close conformational similarity of the nucleotide moieties of norpseudovitamin B12 and its two homologues.
On Facts and Artefacts: The Difficulty to Evaluate an Artificial Nuclease
Authors: Pitsch Stefan , Scheffer Ute , Hey Markus , Strick Andreas , Göbel Michael W.
Published: December 2003

A number of promising synthetic catalysts for the hydrolytic degradation of RNA have been developed in recent years. Some of them show remarkable selectivity for pyrimidine nucleotides. The general problem of all these studies is to distinguish between real effects and artefacts caused by traces of contaminating natural ribonucleases. We show that methods representing the current state of the art (diethylpyrocarbonate treatment, sterilization, ultrafiltration, etc.) do not sufficiently protect against severe artefacts. However, an incorruptible assay could be found by comparing the cleavage of RNA and its mirror image. Enantiomeric RNA is completely resistant to enzymatic degradation, whereas achiral nonpeptide catalysts, by fundamental laws of symmetry, cannot distinguish between enantiomers and will induce exactly the same cleavage pattern with both substrates.
Crystalline Phase Separation of Racemic and Nonracemic Zwitterionic α‐Amino Acid Amphiphiles in a Phospholipid Environment at the Air/Water Interface: A Grazing‐Incidence X‐Ray Diffraction Study
Authors: Weissbuch Isabelle , Rubinstein Irina , Weygand Markus J. , Kjaer Kristian , Leiserowitz Leslie , Lahav Meir
Published: December 2003

A grazing‐incidence X‐ray‐diffraction (GIXD) study of the self‐assembly, on water, of nonracemic γ‐stearyl glutamic acid (pure or as a mixture with racemic or (S)‐1,2‐dipalmitoyl‐glycero‐3‐phosphoethanolamine (DPPE)) demonstrated a phase separation of the α‐amino acid amphiphile into racemic and enantiomorphous two‐dimensional crystallites within the phospholipid domains. The packing arrangements of the two α‐amino acid crystalline phases were identical to those found in the absence of DPPE and have been determined, at almost atomic resolution, by X‐ray structure‐factor calculations. By contrast, racemic and nonracemic Nε‐stearoyllysine spontaneously segregated into two‐dimensional enantiomorphous domains within the DPPE environment that induced a change in the tilt direction of the hydrocarbon chains of the α‐amino acid molecules. Phase separation of nonracemic amphiphiles, originating from preferred lateral homochiral or heterochiral intermolecular interactions, is in agreement with the formation of enantiomerically pure or enriched homochiral oligopeptides in overrepresented amounts in the polycondensation of activated nonracemic amphiphilic α‐amino acids on plain water or within phospholipid monolayers.
Invited reaction: Informal learning and the transfer of learning: How managers develop proficiency
Authors: Marsick Victoria J.
Published: December 2003

Enos, Kehrhahn, and Bell have made an important contribution to measuring informal learning and its transfer as
proficiency in a set of company‐identified managerial skills. Measurement of informal learning is at the
crux of research that seeks to link learning outcomes to other indicators of effective performance. The ability to
show how informal learning affects managerial proficiency also would help practitioners build a better business
case for planning and supporting informal learning. A drawback to the research methodology employed in this study
is reliance on self‐report, which the authors note but do not fully discuss. Questions also arise about the
nature of skills measured and the nature of managerial work in what appears to be a period of transition in the
company they examined. I conclude with some thoughts on alternative lenses for considering implications for
practice.
Learning orientation and goal orientation context: Relationships with cognitive and affective learning outcomes
Authors: Martocchio Joseph J. , Hertenstein Edward J.
Published: December 2003

A field experiment of ninety‐six employees tested a model of the relationships among dispositional
learning orientation, self‐efficacy, goal orientation context, and declarative knowledge. Specifically, the
model predicted positive influences of task‐specific self‐efficacy (pre‐ and
mid‐training) and declarative knowledge in the relationship between learning orientation and
posttraining self‐efficacy. In addition, the model included a positive path from goal orientation context
(0 = performance; 1 = learning) to posttraining self‐efficacy. Finally, the
model included the interactive effect of learning orientation and goal orientation context on posttraining
self‐efficacy. The setting was an introductory Microsoft Access 97 software training course. But for three,
the hypotheses were supported, including the hypothesized interaction effect. Tests of three alternative models
showed poorer fits to the data than the hypothesized model.
Perceptions of constructive and destructive conflict within and across family subsystems
Authors: Rinaldi Christina M. , Howe Nina
Published: December 2003

Family members' (mothers, fathers, siblings) perceptions of the frequency and types of constructive and destructive conflict strategies used within and across the three family subsystems (marital, parent–child, sibling) were investigated. Participants included 60 fifth‐ and sixth‐grade, middle‐class white children, their closest‐in‐age sibling, and both parents. Each family member rated their perceptions of conflict resolution strategies employed in marital, parent–child, and sibling relationships. Overall, family members demonstrated agreement on the frequency and types of conflict within the three family subsystems and generally reported employing similar conflict tactics across different subsystems. Additionally, parent–child conflict strategies were partially linked to both constructive and destructive sibling and marital conflict. These results are best understood in light of both the shared family perspective view and the spillover hypothesis of family dynamics (Margolin et al., 1996; Minuchin, 1988). Implications for examining conflict strategies within and across subsystems are discussed within the context of recent theory on family functioning. Copyright © 2003 John Wiley & Sons, Ltd.
When home is in jail: child development in Spanish penitentiary units
Authors: Jiménez Jesús M. , Palacios Jesús
Published: December 2003

The quality of the educational family context of children who live with their mothers in prison (N=127, ageM=16.3 months) as well as how this situation affects their level of development are analysed. The assessment of these contexts was carried out using the HOME scale. The evaluation of the children's development was carried out using the Brunet–Lézine scale. The data shows that the quality of this context is extremely low, with one of the most striking features being the low score obtained in the subscales of provision of play materials and variety of experiences. Moreover, there are significant differences in the scores that are related to the mother's level of education, ethnic origins and the type of prison where they are serving their sentences. As for the scores obtained by the children in the Brunet–Lézine scale, the data shows that their level of development is similar to that of the infant population in general although we also found that the development quotients of the children in the group with the lowest scores in the HOME scale tend to drop significantly after 18 months of age. The results are discussed taking into account the interaction of context and development under the light of the canalization hypothesis, and making some suggestions about possible ways to improve these children's life conditions. Copyright © 2003 John Wiley & Sons, Ltd.
Links between socialization goals and child‐rearing practices in Chinese and Indian mothers
Authors: Rao Nirmala , McHale James P. , Pearson Emma
Published: December 2003

Mothers of preschoolers in China and India reported on the value they accorded to items tapping two socialization goals, Filial Piety and Socioemotional Development and two parenting styles, Authoritative and Authoritarian. In both cultures, maternal valuing of Filial Piety was associated with greater exertion of parental control, whereas greater valuing of Socioemotional Development was related to more frequent use of Authoritative practices. However, patterns in relationships between Filial Piety, Socioemotional Development and Authoritative parenting differed across Chinese and Indian mothers. Positive associations were found among these three variables for Indian mothers, reflecting Hindu beliefs about young children and childhood. Among Chinese mothers, on the other hand, Filial Piety was negatively related with Socioemotional Development and the use of Authoritative practices. Our results suggest that Chinese mothers believe that the use of authoritative practices, which encourage socioemotional development in children, will inhibit achievement of filial behaviour and academic achievement. Contrasts between these two Asian cultures highlight the importance of considering parents' socialization goals and beliefs in cross‐cultural studies of child‐rearing practices. Copyright © 2003 John Wiley & Sons, Ltd.
Photocrosslinkable polysaccharides based on chondroitin sulfate
Authors: Li Qiang , Williams Christopher G. , Sun Danny D. N. , Wang Jun , Leong Kam , Elisseeff Jennifer H.
Published: December 2003

Photopolymerizing hydrogels have demonstrated potential for use as a scaffold in numerous tissue‐engineering applications. The majority of photopolymerizing hydrogels are made from purely synthetic polymers. The purpose of this study was to synthesize and characterize photopolymerizing hydrogels derived from the biopolymer chondroitin sulfate in order to enhance the bioactivity of the scaffold and potentially improve tissue regeneration. Methacrylate groups were added to chondroitin sulfate, a major component of cartilage, using glycidyl methacrylate. The gels exhibited viscoelastic behavior typical of hydrogels. Cogels based on chondroitin sulfate and poly(ethylene glycol) demonstrated increasing pore size with increasing concentration of chondroitin sulfate as determined by water content, mechanical strength, and morphology using scanning electron microscopy. The chondroitin sulfate hydrogels degraded specifically in the presence of the enzyme chondroitinase. Chondrocytes remained viable after photoencapsulation and incubation in the biogels, suggesting their possible use for cartilage tissue engineering. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 28–33, 2004
Design and fabrication of standardized hydroxyapatite scaffolds with a defined macro‐architecture by rapid prototyping for bone‐tissue‐engineering research
Authors: Wilson C. E. , de Bruijn J. D. , van Blitterswijk C. A. , Verbout A. J. , Dhert W. J. A.
Published: December 2003

This investigation describes the production and characterization of calcium phosphate scaffolds with defined and reproducible porous macro‐architectures and their preliminary in vitro and in vivo bone‐tissue‐engineered response. Fugitive wax molds were designed and produced using a rapid prototyping technique. An aqueous hydroxyapatite slurry was cast in these molds. After sintering at 1250°C and then cleaning, dimensional and material characterizations of the scaffolds were performed. The resulting scaffolds represented the design, and their dimensions were remarkably consistent. A texture inherent to the layer‐by‐layer production of the mold was impressed onto the vertical surfaces of the scaffolds. The surface roughness (Ra) of the textured surfaces was significantly greater than that of the nontextured surfaces. Material analyses revealed a β‐TCP phase in addition to hydroxyapatite for the molded ceramics. Non‐molded control ceramics exhibited only hydroxyapatite. Thirty scaffolds were seeded with culture‐expanded goat bone‐marrow stromal cells (BMSCs) and implanted subcutaneously in nude mice for 4 or 6 weeks. Histology revealed mineralized bone formation in all the scaffolds for both implantation periods. After 4 weeks, bone was present primarily as a layer on scaffold surfaces. After 6 weeks, the surface bone formation was accompanied by bone budding from the surface and occasional bridging of pores. This budding and bridging bone formation almost always was associated with textured scaffold surfaces. However, the area percentage of bone in pores was similar for the 4‐ and 6‐week implantation periods. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 123–132, 2004
Recombinant growth/differentiation factor‐5 (GDF‐5) stimulates osteogenic differentiation of marrow mesenchymal stem cells in porous hydroxyapatite ceramic
Authors: Shimaoka Hideki , Dohi Yoshiko , Ohgushi Hajime , Ikeuchi Masako , Okamoto Masanori , Kudo Akira , Kirita Tadaaki , Yonemasu Kunio
Published: December 2003

To evaluate the growth/differentiation factor‐5 (GDF‐5) in the in vivo osteogenic potential of bone marrow mesenchymal stem cells (MSCs), we subcutaneously implanted five different kinds of hydroxyapatite (HA) ceramic implants: HA alone, GDF‐5/HA composites (GDF/HA), MSCs/HA composites, the MSCs/HA composites supplemented with GDF‐5 (GDF/MSCs/HA), and recombinant bone morphogenetic protein‐2 (BMP/MSCs/HA). Neither the HA alone nor the GDF/HA composites exhibited any bone formation at any time after implantation. At 4 weeks, the MSCs/HA composites exhibited a certain amount of bone formation in some pore areas. In contrast, at 2 weeks, the GDF/MSCs/HA composites exhibited histologically obvious de novo bone formation together with active osteoblasts in many pore areas and additional bone formation at 4 weeks. In the de novo formed bone, neither chondrocytes nor endochondral bone was detected. The GDF/MSCs/HA composites also showed high alkaline phosphatase (ALP) and osteocalcin expression determined at both the protein and gene levels and the high level of expression was well maintained even at 4 weeks. Compared with GDF/MSCs/HA, the BMP/MSCs/HA composites exhibited excellent osteogenesis with relatively early osteoblastic phenotype expression. The results indicate that GDF‐5 synergistically enhances de novo bone formation capability of MSCs/HA composite and suggest that tissue‐engineered GDF/MSCs/HA composites could be used as bone graft substitutes. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 168–176, 2004
Ultrastructural comparison of hydroxyapatite and silicon‐substituted hydroxyapatite for biomedical applications
Authors: Porter Alexandra E. , Best Serena M. , Bonfield William
Published: December 2003

Silicon‐substituted hydroxyapatite (Si‐HA) has been shown to lead to significantly increased rates of bone apposition when compared with phase‐pure hydroxyapatite (HA) bioceramic implants (Patel N, et al. J Mater Sci Mater Med 2002;13:1199–1206). However, uncertainty remains about the mechanism by which Si increases the in vivo bioactivity. In this study, defect structures in Si‐HA were observed and characterized for the first time using high‐resolution transmission electron microscopy. Using tilting experiments and the g · b = 0 criterion for invisibility, the Burgers vectors of dislocations in phase‐pure HA and 0.8 wt % Si‐HA were characterized to be screw and mixed in character. Dislocations were observed in both pure HA and 0.8 wt % Si‐HA with no significant difference in dislocation density between HA and Si‐HA. However, our findings suggest that an increased number of triple junctions in Si‐HA may have a significant role in increasing the solubility of the material and the subsequent rate at which bone apposes Si‐HA ceramics. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 133–141, 2004
Evolution of OTP‐Independent larval skeleton patterning in the direct‐developing sea urchin, Heliocidaris erythrogramma
Authors: ZHOU NA , WILSON KEEN A. , ANDREWS MARY E. , KAUFFMAN JEFFERY S. , RAFF RUDOLF A.
Published: December 2003

Heliocidaris erythrogramma is a direct‐developing sea urchin that has evolved a modified ontogeny, a reduced larval skeleton, and accelerated development of the adult skeleton. The Orthopedia gene (Otp) encodes a homeodomain transcription factor crucial in patterning the larval skeleton of indirect‐developing sea urchins. We compare the role of Otp in larvae of the indirect‐developing sea urchin Heliocidaris tuberculata and its direct‐developing congener H. erythrogramma. Otp is a single‐copy gene with an identical protein sequence in these species. Expression of Otp is initiated by the late gastrula, initially in two cells of the oral ectoderm in H. tuberculata. These cells are restricted to oral ectoderm and exhibit left‐right symmetry. There are about 266 copies of Otp mRNA per Otp‐ expressing cell in H. tuberculata. We tested OTP function in H. tuberculata and H. erythrogramma embryos by microinjection of Otp mRNA. Mis‐expression of Otp mRNA in H. tuberculata radialized the embryos and caused defects during larval skeletogenesis. Mis‐expression of Otp mRNA in H. erythrogramma embryos did not affect skeleton formation. This is consistent with the observation by in situ hybridization of no concentration of Otp transcript in any particular cells or region of the H. erythrogramma larva, and measurement of a level of less than one copy of endogenous Otp mRNA per cell in H. erythrogramma. OTP plays an important role in patterning the larval skeleton of H. tuberculata, but this role apparently has been lost in the evolution of the H. erythrogramma larva, and replaced by a new patterning mechanism. J. Exp. Zool. (Mol. Dev. Evol.) 300B:58–71, 2003. © 2003 Wiley‐Liss, Inc.
Semi‐transitive graphs
Authors: Wilson Steve
Published: December 2003

In this paper, we first consider graphs allowing symmetry groups which act transitively on edges but not on darts (directed edges). We see that there are two ways in which this can happen and we introduce the terms bi‐transitive and semi‐transitive to describe them. We examine the elementary implications of each condition and consider families of examples; primary among these are the semi‐transitive spider‐graphs PS(k,N;r) and MPS(k,N;r). We show how a product operation can be used to produce larger graphs of each type from smaller ones. We introduce the alternet of a directed graph. This links the two conditions, for each alternet of a semi‐transitive graph (if it has more than one) is a bi‐transitive graph. We show how the alternets can be used to understand the structure of a semi‐transitive graph, and that the action of the group on the set of alternets can be an interesting structure in its own right. We use alternets to define the attachment number of the graph, and the important special cases of tightly attached and loosely attached graphs. In the case of tightly attached graphs, we show an addressing scheme to describe the graph with coordinates. Finally, we use the addressing scheme to complete the classification of tightly attached semi‐transitive graphs of degree 4 begun by Marus̆ic̆ and Praeger. This classification shows that nearly all such graphs are spider‐graphs. © 2003 Wiley Periodicals, Inc. J Graph Theory 45: 1–27, 2004