bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise analysis of oil-lubricated journal bearings
Authors: Rho B-H , Kim D-G , Kim K-W
Published: February 2003

The objective of the paper is to provide a procedure for calculating the noise of oil-lubricated journal bearings. In order to obtain acoustical properties of the bearing, a non-linear analysis including rotor imbalance is performed for a rotor-bearing system. Sound pressure levels of the bearing are obtained through frequency analysis of pressure fluctuations calculated from the non-linear analysis using a transmission theory of plane waves. Results show that the sound pressure level of the bearing increases with the rotational speed of the rotor, although the whirl amplitude of the rotor is decreased at high speed. The noise-estimating procedure presented in the paper could be an aid in the evaluation and understanding of acoustical properties of oil-lubricated journal bearings.
Microstructure Control by Solidfication Processing—Outcome from a European Thematic Network
Authors: Lacaze J. , Geer A.L. , Howe A.A. , Ludwig A. , Fredriksson H.
Published: February 2003

MEBSP is the acronym for a pan‐European research effort undertaken to develop means of microstructure control by solidification processing. The mega‐project gathered together eight industries, six research centers, and six universities for four years in a network spanning Europe from Finland to Spain. The article summarizes the results from MEBSP’s four sub‐topics: “nucleation and grain refinement”, “solidification and microsegregation”, “thermophysical data”, and “thermal stresses and strains during solidification”.
Microsegregation and Microstructural Features of Directionally Solidified AlSi and AlSiMg Alloys
Authors: Ahrweiler S. , Ratke L. , Lacaze J.
Published: February 2003

A challenge to current growth theories arises from the comparison of binary and ternary AlSi alloys processed under the same solidification conditions: to explain the phenomena, new concepts on primary spacing, mush evolution, and connective mass transport are needed. The Figure shows an optical micrograph of an AlSiMg alloy, where α‐Al dendrites, silicon lamellae and Mg2Si precipitates can be differentiated.
On the Crystallization Process of Hypoeutectic Al‐6 % Cu,Unmodified and Sr‐Modified Al‐2 % Si Solidification Alloys
Authors: Fjellstedt J. , Fredriksson H.
Published: February 2003

The solidification process of some hypoeutectic aluminum alloys was studied over a wide range of cooling rates. Microsegregation effects were characterized by the minimum concentration of solute found in primary dendrite trunks (see Figure for a typical example), using microprobe analysis, and the fraction of eutectic phases evaluated as a function of the cooling rate. Finally, a non‐equilibrium thermodynamic model of the process, which is able to explain some of the experimental observations, was developed.
Effect of Different Heat Treatments on Microstructure and Segregation of a Nickel base Alloy
Authors: Hermann W. , Lacaze J. , Oquab D.
Published: February 2003

The evolution of microstructure and phase segregation of high chromium single grain nickel base superalloys, which combine outstanding high termperature strength with superior environmental resistance, are investigated. Changes were revealed between the different heat treatments regarding dendritic segregation, morphology and the size of the γ′‐precipitates. The Figure shows a typical micrograph of γ–γ′‐microstructures in an intradendritic area.
Some Issues Concerning Experiments and Models for Alloy Microsegregation
Authors: Lacaze J. , Benigni P. , Howe A.
Published: February 2003

Comparing microsegregation predictions to experimental results is not straightforward. Firstly, modeling needs simplifications to be practicable. Secondly, both sides import their typical errors: on the model side, hypotheses and refinements are often secondary to input data quality, especially thermodynamics. On the experimental side, quenching rates (see Figure for silicon maps of steel samples quenched from different temperatures). This article discusses in detail the problems and pitfalls encounterd in such comparisons.
Thermophysical Properties Benchmark Tests on a Monocrystalline Ni‐base Alloy
Authors: Hermann W. , Neuer G. , Leitner G. , Poeßnecker W. , Quested P. , Richter F. , Sockel H.‐G.
Published: February 2003

Benchmark tests for measuring thermophysical properties of monocrystalline Ni‐base alloys have been conducted. Samples of the same batch of alloys were tested in six different laboratories using a variety of techniques to measure e.g., density, linear thermal expansion, specific heat capacity, thermal diffusivity, and thermal conductivity as a function of temperature. The results of these direct measurements and the derived properties are compared and discussed.
Measurement of the Electric Resistivity of Metals up to and Above the Melting Temperature
Authors: Brandt R. , Neuer G.
Published: February 2003

A device for high‐accuracy measurements of electric resistivity is introduced by the authors. Also, a layout for its use in high‐temperature experiments presented to record resistivity changes around the melting temperature. A demonstration of the apparatus’ precision (performed on steel samples at low temperature, with a deviation of merely 0.5 % from reference date) is given and first high‐temperature results are discussed.
Thermophysical Properties of Mold Materials
Authors: Wolff H. , Engler S. , Schrey A. , Wolf G.
Published: February 2003

The input of experimentally determined thermophysical data and heat transfer coefficients of mold materials increases the quality of simulation calculations. The methods used should provide moderate‐budget support of new developments of mold materials. The phenomenon that the thermophysical characteristics of mold material are not only dependent on the temperature but also on the phase after casting (heating and cooling) indicates a possible direction for further optimization of simulation programs.
How High‐Pressure Die‐Cast Component (HPDC) Foundries Benefit from Numerical Simulation
Authors: Pellikka E.A. , Wendt J.
Published: February 2003

The value of simulating the high pressure die‐casting process is demonstrated by showing and discussing the abilities of state‐of‐the‐art modeling of a typical component of the electronics industry. Process parameters, which can be optimized by simulation as well as process improvements, are identified. An evaluation of HPDC‐modeling in terms of process improvement, quality, and efforts is carried out and prospects for future developments are given.
Influence of Phase‐Transport Phenomena on Macrosegregation and Structure Formation During Solidification
Authors: Wu M. , Ludwig A.
Published: February 2003

The volume‐averaging model of solidification during casting is state‐of‐the‐art for describing the various processes involved, e.g., nucleation, phase transport and macroseggregation. Here, simulation results are presented that support the theory by numerical data. Good agreement between calculations and experimental values is demonstrated for an Al‐4 wt.‐% Cu plate casting system, and the crucial influences during the different stages of the process are outlined.
On the Behavior of Hot Crack Formation During Solidification in Fe–Ni Alloys
Authors: Hansson K. , Fredriksson H.
Published: February 2003

The behavior of hot crack (tearing) mechanism during solidification in two Fe–Ni alloys. The mechanical properties during solidification, with focus on their hot crack (tearing) behavior, were investigated by tests on “in‐situ” solidified samples. Hot cracking susceptibility was determined by using the transition temperature for area reduction (hot ductility), e.g., the transition temperature between brittle and ductile fractures. The results of the tensile tests are compared with the liquidus and solidus temperatures, measured by thermal analysis.
Cooperation within MEBSP on the Subject of Air Gap Formation During a Casting Process
Authors: Kron J. , Bellet M. , Ludwig A. , Wendt J. , Pustal B. , Fredriksson H.
Published: February 2003

The goal of quantitatively predicting air gap growth in casting processes is still not reached. Subgroup IV of the international research platform MEBSP is tackling the problem with both an experimental approach (see Figure for a layout currently used at the Royal Institute of Technology) and a variety of simulation programs, being used by different participating institutes.
Grain Refinement of Aluminium Alloys by Inoculation
Authors: Greer A.L. , Cooper P.S. , Meredith M.W. , Schneider W. , Schumacher P. , Spittle J.A. , Tronche A.
Published: February 2003

A review is given of the studies of aluminium inoculation undertaken within the EU Network “Microstructural Engineering by Solidification Processing” (MEBSP). A wide range of studies of industrial practice of grain refining and of the fundamental mechanisms of nucleation and growth have contributed to improved understanding. Particular advances have been made in understanding the relative performance of different grain refiners.
Titelbild: Vesicles and Polymerized Vesicles from Thiophene‐Containing Rod–Coil Block Copolymers (Angew. Chem. 7/2003)
Authors: Vriezema Dennis M. , Hoogboom Johan , Velonia Kelly , Takazawa Ken , Christianen Peter C. M. , Maan Jan. C. , Rowan Alan E. , Nolte Roeland J. M.
Published: February 2003

Enzyme in Vesikeln können die Umsetzung von Substraten katalysieren, die die Vesikelmembran durchdringen. Das Titelbild zeigt eine Vesikel, die aus einem Stab‐Knäuel‐Diblockcopolymer gebildet wird und Lipase B enthält. Die Thiophen‐Einheiten am Polymer lassen sich durch Zugabe eines Metallkomplexes polymerisieren. Dies könnte den Weg zu leitfähigen Vesikelmembranen weisen und neue Möglichkeiten auf dem Gebiet der Nanoreaktoren eröffnen. Lesen Sie mehr hierüber in der Zuschrift von A. E. Rowan und R. J. M. Nolte et al. auf S. 796 ff.
Der Aufbau von Vancomycin: so macht es die Natur
Authors: Hubbard Brian K. , Walsh Christopher T.
Published: February 2003

Antibiotika sind wertvolle Therapeutika im Kampf gegen Infektionen, die durch pathogene Bakterien verursacht werden. Vancomycin ist eine der letzten wirksamen “Waffen” bei lebensbedrohlichen Infektionen durch Gram‐positive Bakterien. Die Regeln, nach denen die Natur die Glycopeptid‐ (Vancomycin) und Lipoglycopeptid‐Antibiotika (Teicoplanin) aufbaut, werden zunehmend geklärt und abgesichert: Zuerst werden Aminosäuren synthetisiert, diese anschließend zusammengebaut und vernetzt. Damit öffnen sich Möglichkeiten, die Synthesestrategien umzuprogrammieren auf der Ebene veränderter Monomere, durch Verschiebungen beim Peptidaufbau und durch verschiedene Enzyme zur Nachbearbeitung des Aglycons.
Titelbild: Structural Color and the Lotus Effect (Angew. Chem. 8/2003)
Authors: Gu Zhong‐Ze , Uetsuka Hiroshi , Takahashi Kazuyuki , Nakajima Rie , Onishi Hiroshi , Fujishima Akira , Sato Osamu
Published: February 2003

Lernen von der Natur um die Materialien der Zukunft zu entwickeln. Das Titelbild zeigt den Morpho‐Schmetterling mit farbgebend strukturierten Flügeln sowie Lotusblätter mit hydrophoben Eigenschaften. Zur Nachahmung dieser natürlichen Stoffe wurden Materialien hergestellt, die die strukturellen Eigenschaften eines inversen Opalfilmes nutzen. Dieser hat eine gleichmäßige farbgebende Struktur und eine Oberfläche mit wohlgeordneten Unebenheiten zur Unterstützung der Hydrophobie. Modifizierung führt zu einer superhydrophoben Oberfläche mit einem großen Wasser‐Kontaktwinkel. Näheres findet sich in der Zuschrift von O. Sato et al. auf S. 922 ff.
NMR‐Techniken zum Screening und zur Identifizierung der Bindung von Liganden an Proteinrezeptoren
Authors: Meyer Bernd , Peters Thomas
Published: February 2003

Erkenntnisse über Bindungsvorgänge zwischen Liganden und Rezeptoren sind der Schlüssel zu einem Verständnis biologischer Prozesse. Seit kurzem ist es möglich, durch neue NMR‐spektroskopische Techniken Protein‐Protein‐ und Protein‐Ligand‐Wechselwirkungen auf atomarer Ebene zu verstehen. Diese Experimente charakterisieren die Bindungsvorgänge entweder von der Seite des Liganden oder von der des Proteins. Idealerweise werden beide Techniken gemeinsam angewendet und liefern dann ein komplettes Bild der Ligandenbindung an einen Rezeptor. Die in diesem Aufsatz vorgestellten Ansätze erlauben das Screening von Verbindungsbibliotheken genauso wie eine detaillierte Charakterisierung von Bindungsepitopen und einzelnen funktionellen Gruppen, die in die Bindungsvorgänge involviert sind. Die Bestimmung der Bindungsstärke und der Bindungskinetik ist ebenso möglich wie die Untersuchung kompetitiver Bindung, allosterischer Effekte oder der Bindung von Liganden an intakte Viren und membranständige Proteine.
Cover Picture: Vesicles and Polymerized Vesicles from Thiophene‐Containing Rod–Coil Block Copolymers (Angew. Chem. Int. Ed. 7/2003)
Authors: Vriezema Dennis M. , Hoogboom Johan , Velonia Kelly , Takazawa Ken , Christianen Peter C. M. , Maan Jan. C. , Rowan Alan E. , Nolte Roeland J. M.
Published: February 2003

Enzymes in vesicles are able to catalyze the reaction with substrates that permeate the vesicle membrane. The cover picture shows a vesicle built up from a rigid‐rod diblock copolymer that is filled with Candida antarctica lipase B enzymes. The thiophene groups in the polymer can be polymerized by the addition of a metal complex, which may result in conducting vesicle membranes thus creating new possibilities in the area of nanoreactors. Further information can be found in the Communication by A. Rowan, R. Nolte et al. on page 772 ff.
Vancomycin Assembly: Nature's Way
Authors: Hubbard Brian K. , Walsh Christopher T.
Published: February 2003

Antibiotics are precious resources in the fight to combat bacterial infections caused by pathogenic organisms. Vancomycin is one of the antibiotics of last resort in the treatment of life‐threatening infections by gram‐positive bacteria. The rules by which nature assembles the glycopeptide (vancomycin) and lipoglycopeptide (teicoplanin) antibiotics are becoming elucidated and verified: first amino acids are synthesized, then joined together and cross‐linked. This knowledge opens up approaches for reprogramming strategies at the level of altered monomers, swapped assembly lines, and different post‐assembly tailoring enzymes.
Cover Picture: Structural Color and the Lotus Effect (Angew. Chem. Int. Ed. 8/2003)
Authors: Gu Zhong‐Ze , Uetsuka Hiroshi , Takahashi Kazuyuki , Nakajima Rie , Onishi Hiroshi , Fujishima Akira , Sato Osamu
Published: February 2003

Learning from nature to design the materials of the future. The cover picture shows the Morpho butterfly, whose wings displays structural color, and lotus leaves, which exhibit hydrophobicity. To mimic these natural products, materials were prepared that utilize the unique structural properties of an inverse opal film, which displays uniform structural colors and a surface with well‐ordered bumps that aid hydrophobicity. Modification leads to a superhydrophobic surface with a large water‐contact angle. For more information see the Communication by O. Sato et al. on page 894 ff.
NMR Spectroscopy Techniques for Screening and Identifying Ligand Binding to Protein Receptors
Authors: Meyer Bernd , Peters Thomas
Published: February 2003

Binding events of ligands to receptors are the key for an understanding of biological processes. Gaining insight into protein–protein and protein–ligand interactions in solution has recently become possible on an atomic level by new NMR spectroscopic techniques. These experiments identify binding events either by looking at the resonance signals of the ligand or the protein. Ideally, both techniques together deliver a complete picture of ligand binding to a receptor. The approaches discussed in this review allow screening of compound libraries as well as a detailed identification of the groups involved in the binding events. Also, characterization of the binding strength and kinetics is possible, competitive binding as well as allosteric effects can be identified, and it has even been possible to identify ligand binding to intact viruses and membrane‐bound proteins.
Antitubercular Isoniazid and Drug Resistance of Mycobacterium tuberculosis — A Review
Authors: Scior Thomas , Meneses Morales Iván , Garcés Eisele Solón Javier , Domeyer David , Laufer Stefan
Published: February 2003

Isoniazid is one of the most potent drugs available for tuberculosis treatment. As a pro‐drug it requires activation, which is performed by catalase/peroxidase. The active principle, whose identity has not yet been determined unambiguously, then acts on at least one target molecule, the enoyl‐acyl carrier protein, required for the synthesis of the vital mycolic acids present in the cell wall of the bacterium. Some other targets have been proposed in order to explain the unusual potency of isoniazid; however, the supporting data are still controversial. We thoroughly discuss the action of isoniazid, resistance mechanisms, and the possible active product, which includes an isonicotinic acid‐NADH adduct as well as a meta‐isomer of NADH. Both structures have been probed positively in a 3D modeling analysis.
C16 and C17 Substituted Derivatives of Pregnenolone and Progesterone as Inhibitors of 17α‐Hydroxylase‐C17, 20‐lyase: Synthesis and Biological Evaluation
Authors: Haidar Samer , Hartmann Rolf W.
Published: February 2003

17α‐Hydroxylase‐C17, 20‐lyase (P450 17, CYP 17) is a key enzyme in androgen biosynthesis and a target for the treatment of prostate cancer. In order to find novel inhibitors for this enzyme, several compounds bearing different moieties able to complex with the heme iron located in the active site of the enzyme were synthesized. The moieties were introduced into the 16‐position of pregnenolone and progesterone. Their inhibitory activities toward human and rat CYP 17 were determined and compared to the activities of the corresponding 17‐substituted compounds. It became apparent that the 16‐substituted compounds were less active than the parent compounds: they were either moderate or poor inhibitors of the target enzyme. Tested for inhibition of human 5α‐reductase 1 and 2 — a target for the treatment of benign prostatic hyperplasia (BPH) — the title compounds showed some inhibitory activity.
Novel High Energy Intermediate Analogues with Triazasterol‐Related Structures as Inhibitors of Ergosterol Biosynthesis Part I: Synthesis and Antifungal Activity of N‐alkyl‐N′‐(phenethyl‐ and cyclohexenylethyl)guanidines and N2‐Substituted 2‐Imidazolinamines
Authors: Gößnitzer Edith , Malli Roland , Schuster Silvia , Favre Bertrand , Ryder Neil S.
Published: February 2003

A series of N‐alkyl‐N′—(phenethyl‐ and cyclohexenylethyl) guanidines and N2‐ and N2, 4‐substituted imidazolin‐2‐amine hydrochlorides with triazasterol‐related structures was designed and synthesized as stable analogues to mimic high energy intermediates of ergosterol biosynthesis. The in vitro antifungal susceptibility tests with a standard panel of pathogenic fungi revealed moderate to strong antimycotic effects of the sixteen prepared compounds, in some cases comparable with the activity observed for itraconazole.
Structure‐Activity Relationship Studies of 1‐Substituted 3‐Dodecanoylindole‐2‐carboxylic Acids as Inhibitors of Cytosolic Phospholipase A2‐Mediated Arachidonic Acid Release in Intact Platelets
Authors: Griessbach Klaus , Klimt Monika , Schulze Elfringhoff Alwine , Lehr Matthias
Published: February 2003

A series of 3‐dodecanoylindole‐2‐carboxylic acid derivatives with varied carboxylic acid substituents at the indole 1‐position were synthesized and evaluated for their ability to inhibit arachidonic acid release in human platelets mediated by the cytosolic phospholipase A2. Structure‐activity relationship studies revealed that increasing the polarity of these substituents by the introduction of additional polar groups in the proximity of the carboxylic acid moiety reduced activity. Conformational restriction of the indole‐1‐carboxylic acid substituents in distinct positions as well as extending the length of these residues led to compounds which did not substantially differ in their potencies.
Synthesis and Antiinflammatory Screening of Some Quinazoline and Quinazolyl‐4‐oxoquinazoline Derivatives
Authors: Gineinah Magdy M. , El‐Sherbeny Magda A. , Nasr Magda N. , Maarouf Azza R.
Published: February 2003

Synthesis of some new derivatives of 2‐aryl‐4‐oxo‐1‐(4‐quinazolyl)quinazolines is described. Methyl N‐(4‐quinazolyl)anthranilate was allowed to react with phenyl iso(thio)cyanate to give 3‐phenyl‐1‐(4‐quinazolyl)‐1, 2, 3, 4‐tetrahydro‐2, 4‐dioxo‐ and 4‐oxo‐2‐thioxoquinazolines (3a and 3b respectively) Alternatively, anthranilic acid amide derivatives were subjected to cyclization with aromatic aldehydes to give 2‐aryl‐4‐oxo‐1‐(4‐quinazolyl)‐1, 2, 3, 4‐tetrahydroquinazolines 5. On the other hand, 2‐chloro‐4‐(4‐substituted 1‐piperazinyl)quinazoline derivatives were subjected to the same type of reactions at the 2‐position to afford the corresponding quinazoline derivatives 8 and 10 respectively. Furthermore, the acid amide 4b cyclized with acid chlorides to give the corresponding 2‐aryl‐1‐(2‐chloro‐4‐quinazolyl)‐4‐oxo‐1, 4‐dihydroquinazolines 11 from which the triazoloquinazoline derivatives 13 and 15 were synthesized through the intermediate hydrazine derivatives 112Mostof the newly synthesized compounds were tested for their antiinflammatory activities. However, some of the novel compounds were found to exhibit good antiinflammatory potencies.
Novel 3‐Arylamino‐ and 3‐Cycloalkylamino‐5, 6‐diphenyl‐pyridazines Active as ACAT Inhibitors
Authors: Toma Lucio , Giovannoni Maria Paola , Vergelli Claudia , Dal Piaz Vittorio , Kwon Byoung‐Mog , Kim Young‐Kook , Gelain Arianna , Barlocco Daniela
Published: February 2003

A new series of pyridazine derivatives, structurally related to the previously reported ACAT inhibitors 3‐(cyclo)alkylamino‐5, 6‐diphenyl‐pyridazines, were synthesized and tested for their inhibitory properties. Substitution of the 3‐alkylamino chain with a phenylamino group maintains activity. In contrast, the presence of either substituents on the phenylamino group or aliphatic rings having more or less than six carbon atoms lowers it.
Statistical bioinformatic methods in microbial genome analysis
Authors: Liò Pietro
Published: February 2003

It is probable that, increasingly, genome investigations are going to be based on statistical formalization. This review summarizes the state of art and potentiality of using statistics in microbial genome analysis. First, I focus on recent advances in functional genomics, such as finding genes and operons, identifying gene conversion events, detecting DNA replication origins and analysing regulatory sites. Then I describe how to use phylogenetic methods in genome analysis and methods for genome‐wide scanning for positively selected amino acids. I conclude with speculations on the future course of genome statistical modeling. BioEssays 25:266–273, 2003. © 2003 Wiley Periodicals, Inc.
Cytogenetics in reproductive medicine: The contribution of comparative genomic hybridization (CGH)
Authors: Wells Dagan , Levy Brynn
Published: February 2003

Cytogenetic research has had a major impact on the field of reproductive medicine, providing an insight into the frequency of chromosomal abnormalities that occur during gametogenesis, embryonic development and pregnancy. In humans, aneuploidy has been found to be relatively common during fetal life, necessitating prenatal screening of high‐risk pregnancies. Aneuploidy rates are higher still during the preimplantation stage of development. An increasing number of IVF laboratories have attempted to improve pregnancy rates by using preimplantation genetic diagnosis (PGD) to ensure that the embryos transferred to the mother are chromosomally normal. This paper reviews some of the techniques that are key to the detection of aneuploidy in reproductive samples including comparative genomic hybridization (CGH). CGH has provided an unparalleled insight into the nature of chromosome imbalance in human embryos and polar bodies. The clinical application of CGH for the purposes of PGD and the future extensions of the methodology, including DNA microarrays, are discussed. BioEssays 25:289–300, 2003. © 2003 Wiley Periodicals, Inc.
Nonculturable bacteria: programmed survival forms or cells at death's door?
Authors: Nyström Thomas
Published: February 2003

Upon starvation and growth arrest, Escherichia coli cells gradually lose their ability to reproduce. These apparently sterile/nonculturable cells initially remain intact and metabolically active and the underlying molecular mechanism behind this sterility is something of an enigma in bacteriology. Three different models have been proposed to explain this phenomenon. The first theory suggests that starving cells become nonculturable due to cellular deterioration, are moribund, and show some of the same signs of senescence as aging organisms. The two other theories suggest that genetically programmed pathways, rather than stochastic deterioration, trigger nonculturability. One “program” theory suggests that nonculturability is the culmination of an adaptive pathway generating dormant survival forms, similar to spore formation in differentiating bacteria. The other “program” theory states that starved cells lose viability due to activation of genetic modules mediating programmed cell death. The different models will be reviewed and evaluated in light of recent data on the physiology and molecular biology of growth‐arrested E. coli cells. BioEssays 25:204–211, 2003. © 2003 Wiley Periodicals, Inc.
On the mechanism ofWolbachia‐induced cytoplasmic incompatibility: Confronting the models with the facts
Authors: Poinsot Denis , Charlat Sylvain , Merçot Hervé
Published: February 2003

The endocellular bacteriumWolbachiamanipulates the reproduction of its arthropod hosts for its own benefit by various means, the most widespread being cytoplasmic incompatibility (CI). To date, the molecular mechanism involved in CI has not been elucidated. We examine here three different CI models described in previous literature, namely, the “lock‐and‐key”, “titration–restitution” and “slow‐motion” models. We confront them with the full range of CI patterns discovered so far, including the most complex ones such as multiple infections, asymmetrical and partial compatibility relationships and the existence ofWolbachiavariants that can rescue the host from CI but not induce it. We conclude that the lock‐and‐key model is the most parsimonious of the models and fits the observations best. The two other models cannot be categorically invalidated, but they encounter some difficulties that make additional hypotheses necessary. BioEssays 25:259–265, 2003. © 2003 Wiley Periodicals, Inc.
Alzheimer vaccine: amyloid‐β on trial
Authors: Robinson Stephen R. , Bishop Glenda M. , Münch Gerald
Published: February 2003

A new therapeutic approach is being developed for the treatment of Alzheimer's disease (AD). This approach involves the deliberate induction of an autoimmune response to amyloid‐β (Aβ) peptide, the constituent of neuritic plaques that is thought to cause the neurodegeneration and dementia in AD. If this approach is to be effective, antibodies must be produced that can selectively target the toxic forms of Aβ, while leaving the functionally‐relevant forms of Aβ and its precursor protein untouched. Furthermore, an approach needs to be found that avoids provoking an acute neuroinflammatory response. The situation is made even more challenging by uncertainty regarding which isoforms of Aβ contribute to the pathogenesis of AD. BioEssays 25:283–288, 2003. © 2003 Wiley Periodicals, Inc.
AraC protein: A love–hate relationship
Authors: Schleif Robert
Published: February 2003

In the bacterium Escherichia coli, the AraC protein positively and negatively regulates expression of the proteins required for the uptake and catabolism of the sugar L‐arabinose. This essay describes how work from my laboratory on this system spanning more than thirty years has aided our understanding of positive regulation, revealed DNA looping (a mechanism that explains many action‐at‐a‐distance phenomena) and, more recently, has uncovered the mechanism by which arabinose shifts AraC from a state where it prefers to bind to two well‐separated DNA half‐sites and form a DNA loop to a state where it binds to two adjacent half‐sites and activates transcription. This work required learning how to assay, purify, and work with a protein possessing highly uncooperative biochemical properties. Present work is focussed on understanding arabinose‐responsive mechanism in atomic detail and is also directed towards understanding protein structure and function well enough to be able to engineer the allosteric mechanism seen in AraC onto other proteins. BioEssays 25:274–282, 2003. © 2003 Wiley Periodicals, Inc.
Sex‐determination gene and pathway evolution in nematodes
Authors: Stothard Paul , Pilgrim Dave
Published: February 2003

The pathway that controls sexual fate in the nematode Caenorhabditis elegans has been well characterized at the molecular level. By identifying differences between the sex‐determination mechanisms in C. elegans and other nematode species, it should be possible to understand how complex sex‐determining pathways evolve. Towards this goal, orthologues of many of the C. elegans sex regulators have been isolated from other members of the genus Caenorhabditis. Rapid sequence evolution is observed in every case, but several of the orthologues appear to have conserved sex‐determining roles. Thus extensive sequence divergence does not necessarily coincide with changes in pathway structure, although the same forces may contribute to both. This review summarizes recent findings and, with reference to results from other animals, offers explanations for why sex‐determining genes and pathways appear to be evolving rapidly. Experimental strategies that hold promise for illuminating pathway differences between nematodes are also discussed. BioEssays 25: 221–231, 2003. © 2003 Wiley Periodicals, Inc.
Kidney development and the fetal programming of adult disease
Authors: Moritz Karen M. , Dodic Miodrag , Wintour E. Marelyn
Published: February 2003

Recent evidence, from both epidemiological and animal experimental studies, suggest that the very first environment, the intrauterine, is extremely important in determining the future health of the individual. Genetic and ‘lifestyle’ factors impinge on, and can exacerbate, a ‘programming’ effect of an adverse fetal environment. In this review, we present compelling evidence to suggest that one of the major organs affected by an unfavourable prenatal environment is the kidney. Many of the factors that can affect fetal renal development (i.e. exposure to excess glucocorticoids, insufficient vitamin A, protein/calorie malnutrition (in rats) and alterations in the intrarenal renin angiotensinogen system), also produce hypertension in the adult animal. When nephron number is compromised during kidney development, maladaptive functional changes occur and can lead, eventually, to hypertension and/or renal disease. Surprisingly, it is during the very earliest stages of kidney development that the vulnerability to these effects occurs. BioEssays 25:212–220, 2003. © 2003 Wiley Periodicals, Inc.
Does cholesterol use the mitochondrial contact site as a conduit to the steroidogenic pathway?
Authors: Thomson Murray
Published: February 2003

The first and rate‐limiting step of steroidogenesis is the transfer of cholesterol from the outer mitochondrial membrane to the inner membrane where it is converted to pregnenolone by cytochrome P450 side‐chain cleavage (P450scc). This reaction is modulated in the gonads and adrenals by the steroidogenic acute regulatory protein (StAR), however, the mechanism used by StAR is not understood. The outer and inner mitochondrial membranes are joined at contact sites that are thought to be held in place by protein complexes that bridge the two membranes. While it is generally accepted that proteins are imported into the mitochondrion via contact sites, it is not clear whether cholesterol takes the same conduit to the inner membrane. Strategies to combat diseases caused by interrupted cholesterol transfer will rely on a full understanding of the steroidogenic mechanism. The challenge for the future is to determine whether StAR relies on the molecular architecture that spans the mitochondrial intermembrane space to deliver its cargo. BioEssays 25:252–258, 2003. © 2003 Wiley Periodicals, Inc.
Phylogenomics of type II DNA topoisomerases
Authors: Gadelle Danièle , Filée Jonathan , Buhler Cyril , Forterre Patrick
Published: February 2003

Type II DNA topoisomerases (Topo II) are essential enzymes implicated in key nuclear processes. The recent discovery of a novel kind of Topo II (DNA topoisomerase VI) in Archaea led to a division of these enzymes into two non‐homologous families, (Topo IIA and Topo IIB) and to the identification of the eukaryotic protein that initiates meiotic recombination, Spo11. In the present report, we have updated the distribution of all Topo II in the three domains of life by a phylogenomic approach. Both families exhibit an atypical distribution by comparison with other informational proteins, with predominance of Topo IIA in Bacteria, Eukarya and viruses, and Topo IIB in Archaea. However, plants and some Archaea contain Topo II from both families. We confront this atypical distribution with current hypotheses on the evolution of the three domains of life and origin of DNA genomes. BioEssays 25:232–242, 2003. © 2003 Wiley Periodicals, Inc.
Molecular architecture of intermediate filaments
Authors: Strelkov Sergei V. , Herrmann Harald , Aebi Ueli
Published: February 2003

Together with microtubules and actin microfilaments, ∼11 nm wide intermediate filaments (IFs) constitute the integrated, dynamic filament network present in the cytoplasm of metazoan cells. This network is critically involved in division, motility and other cellular processes. While the structures of microtubules and microfilaments are known in atomic detail, IF architecture is presently much less understood. The elementary ‘building block’ of IFs is a highly elongated, rod‐like dimer based on an α‐helical coiled‐coil structure. Assembly of cytoplasmic IF proteins, such as vimentin, begins with a lateral association of dimers into tetramers and gradually into the so‐called unit‐length filaments (ULFs). Subsequently ULFs start to anneal longitudinally, ultimately yielding mature IFs after a compaction step. For nuclear lamins, however, assembly starts with a head‐to‐tail association of dimers. Recently, X‐ray crystallographic data were obtained for several fragments of the vimentin dimer. Based on the dimer structure, molecular models of the tetramer and the entire filament are now a possibility. BioEssays 25:243–251, 2003. © 2003 Wiley Periodicals, Inc.
Sex steroids, ANGELS and osteoporosis
Authors: Moggs Jonathan G. , Deavall Damian G. , Orphanides George
Published: February 2003

Osteoporosis is characterized by reduced bone density and strength. Bone mass peaks between age 30 and 40 and then declines. This can be accelerated by factors including menopause and insufficient dietary calcium. Hormone replacement therapy (HRT) is currently the standard treatment for osteoporosis. However, growing concern over potential side effects of HRT has driven a search for alternative therapies. A recent report1 reveals a potential alternative to HRT: a gender‐neutral synthetic steroid that increases bone mass and strength without affecting reproductive organs. This compound acts via a novel extranuclear sex steroid receptor signaling mechanism that has important implications for nuclear receptor biology and human health. BioEssays 25:195–199, 2003. © 2003 Wiley Periodicals, Inc.
A Hes1‐based oscillator in cultured cells and its potential implications for the segmentation clock
Authors: Dale J. Kim , Maroto Miguel
Published: February 2003

During somitogenesis an oscillatory mechanism termed the “segmentation” clock generates periodic waves of gene expression, which translate into the periodic spatial pattern manifest as somites. The dynamic expression of the clock genes shares the same periodicity as somitogenesis. Notch signaling is believed to play a role in the segmentation clock mechanism. The paper by Hirata et al.(1) identifies a biological clock in cultured cells that is dependent upon the Notch target gene Hes1, and which shows a periodicity similar to that of the segmentation clock. This finding opens the possibility that the same oscillator mechanism might also operate in other tissues or cell types. BioEssays 25:200–203, 2003. © 2003 Wiley Periodicals, Inc.
Ballungszentrum Muschelbank: Biodiversität und nachhaltige Nutzung
Authors: Buschbaum Christian , Saier Bettina
Published: February 2003

Auf den Sedimentflächen des Wattenmeeres verspinnen sich Miesmuscheln (Mytilus edulis) zu großflächigen Muschelbänken. Diese sind im vergleichsweise artenarmen Wattenmeer Inseln hoher Biodiversität. Etwa 100 festsitzende Algen‐ und Tierarten nutzen die Muschelschalen als Hartsubstrat, und viele mobile Organismen finden in den Nischen zwischen den einzelnen Muscheln einen geeigneten Lebensraum. Sowohl die Artenzusammensetzung, die Dichte als auch die Wechselwirkungen zwischen den Organismen hängen von der Position der Muschelbank im Gezeitenbereich ab. Vor allem die Muschelbänke im dauerüberfluteten Bereich des Wattenmeeres weisen eine hohe Artenvielfalt auf. Sie unterliegen einer intensiven fischereilichen Nutzung, so dass einer der vielfältigsten Lebensräume im Wattenmeer gefährdet ist. Um einen weiteren Verlust an Arten zu verhindern, stellen wir ein nachhaltiges Nutzungskonzept für die Muschelfischerei vor.
Das Devon: Quastenflosser und Nacktpflanzen
Authors: Rothe Peter
Published: February 2003

Während des Devons wurden die Voraussetzungen für das Variskische Gebirgssystem geschaffen, das heute große Teile Europas geologisch bestimmt. Ein durch Rotsedimente geprägter Festlandsbereich im Norden ging in ein südliches Meer über, dessen wechselvolle Entwicklung Flach‐ und Tiefseeareale kennzeichnen, deren vielfältige Fossilienwelt durch die unterschiedlichen Wassertiefen gesteuert scheint. Riffe wuchsen am Schelfrand und auf untermeerischen Vulkanschwellen und produzierten große Mengen von Kalk. Das entsprechend warme Klima war durch die plattentektonische Konfiguration bedingt, der devonische Äquator verlief durch Europa und Nordamerika. Die fortschreitende Eroberung des Landes durch Pflanzen und Wirbeltiere macht das Devon zu einem der wesentlichsten geologischen Systeme in der Geschichte der Erde.
Völlig losgelöst: Schüler forschen unter Weltraumbedingungen
Authors: Schwertner Jürgen , Wiedemann Meike , Hanke Wolfgang
Published: February 2003

Die Untersuchung der Schwerkraftabhängigkeit biologischer Systeme ist Ausgangsbasis eines gemeinsamen aufwendigen Projektes der Universität Hohenheim und des Wilhelms‐Gymnasiums in Stuttgart, das auf einer Tagung des DLR von Wissenschaftlern unter anderem zur Popularisierung der Raumforschung unter Jugendlichen angeregt wurde. Auch die interessierte Öffentlichkeit soll mit diesem Projekt erreicht werden, und es soll gezeigt werden, dass solche Projekte für alle Beteiligten profitabel sein können.
Naturwunder in Gefahr: Rift‐Valley‐Seen Kenias
Authors: Krienitz Lothar , Ballot Andreas , Kotut Kiplagat , Wiegand Claudia , Codd Geoff. A. , Pflugmacher Stephan
Published: February 2003

An fünf Rift‐Valley‐Seen in Kenia wird gezeigt, welchen Gefahren diese einmaligen Habitate ausgesetzt sind. Als Parameter zur Gewässerbewertung wurde die Biodiversität des Phytoplanktons herangezogen. Besonders die Cyanobakterienpopulationen haben erheblichen Einfluss auf das ökologische Gleichgewicht der Seen und die Nutzbarkeit des Wassers. Die Untersuchungsgewässer repräsentieren hochinteressante Biodiversitäts‐ und Salinitätsgradienten. Der Baringosee ist starken Verlandungs‐ und zunehmend auch Versalzungsproblemen ausgesetzt, darüber hinaus wurden Microcystine nachgewiesen. An den alkalinen Seen Bogoria und Nakuru ist seit zwei Jahrzehnten eine erhöhte Sterberate des Kleinen Flamingos beobachtet worden. Bisherige Befunde weisen auf verschiedene Ursachen hin: Pestizide, Schwermetalle, bakterielle Krankheiten sowie Leber‐ und Nervengifte aus der Gruppe der Cyanotoxine. Der Naivashasee als Süßwasser leidet unter erheblicher Übernutzung und Degradation, was sich auch an seiner ehemaligen Bucht, dem Oloidiensee, durch einen deutlichen Anstieg des Salzgehaltes und einer Verarmung des Phytoplanktons zeigt.
Stephen Jay Gould
Authors: Benedetter‐Herramhof Andrea
Published: February 2003

Wie nur wenige andere verstand es der amerikanische Paläontologe Stephen Jay Gould, seine Leserschaft für die Evolutionsforschung zu begeistern. In Fachkreisen waren seine unkonventionellen Ansätze und Interpretationen nicht unumstritten: Während er für seine Anhänger der maßgebliche Verfechter der modernen Evolutionstheorie war, wurde er für seine Gegner zur Zielscheibe heftiger Kritik. Doch ungeachtet dessen, ob man Goulds neuen Entwürfen der Evolutionstheorie in allem folgen mag oder nicht, werden seine Ideen die Forschung noch für Jahre und Jahrzehnte bereichern.
Maus‐Genom entziffert
Authors: Zimmer Andreas
Published: February 2003

Wie viele Gene braucht eine Maus? Der Beantwortung dieser Frage, ein zentrales Anliegen der molekularen Genetik und der Genomprojekte, sind wir nun mit der gleichzeitigen Sequenzierung des Mausgenoms durch das International Mouse Genome Sequencing Consortium und des Transkriptoms durch das internationale FANTOM (Functional Annotation of the Mouse) Consortium ein ganzes Stück näher gekommen. Zum ersten Mal verfügen wir damit über die genomische Sequenz eines Säugetiers und die experimentell abgesicherte Analyse der darin kodierten Transkripte.
Fossiler Gleitflieger mit vier Flügeln
Authors: Kronberg Inge
Published: February 2003

Es ist unstrittig, dass die Vögel Nachkommen der Dinosaurier sind. Innerhalb der Dinosaurier sind die Dromaeosaurier wohl die engsten Vogelverwandten. Nach wie vor wird aber diskutiert, wie die Vögel den Luftraum erschlossen: Lösten sie sich flatternd vom Boden oder ließen sie sich gleitend von Bäumen fallen? Die Entdeckung eines Dinosaurierfossils mit vier Flügeln und langen Federn erregte daher Aufsehen.
Neue Fledermausarten in Europa
Authors: Kiefer Andreas , Seitz Alfred , Veith Michael
Published: February 2003

Molekulare Methoden haben in den vergangenen Jahren die Biologie verändert. Ob in der Physiologie, Ethologie, Ökologie oder Systematik — überall haben insbesondere die Techniken der Polymerase‐Kettenreaktion (PCR) und die automatisierte DNA‐Sequenzierung zu revolutionären Fortschritten geführt. Als direkte Folge dieser technischen Revolution nimmt die Zahl der bekannten Tier‐ und Pflanzenarten selbst in einem gut untersuchten Raum wie Europa rapide zu.

Sogar innerhalb der europäischen Säugetiere wurden mittels molekularer Verfahren bislang unerkannt gebliebene, so genannte kryptische Arten entdeckt wie beispielsweise die Langohrfledermäuse Plecotus alpinus und Plecotus sardus.
Partnerwahl mit Schalleffekt
Authors: Wendler Silke
Published: February 2003

Im Flachlandregenwald von Borneo lebt der etwa 2, 5 Zentimeter große Frosch Metaphrynella sundana. Zur Paarungszeit versuchen die Männchen, durch nächtliche Rufe die Weibchen auf sich aufmerksam zu machen — und schrecken dabei auch vor technischen Tricks nicht zurück.
Folgen des Klimawandels
Authors: Irsch Wilhelm
Published: February 2003

Eine Gruppe von US‐amerikanischen Wissenschaftlern hat durch Auswertung von Langzeitstudien ein weiteres Mosaiksteinchen zu dem sich langsam abzeichnenden Bild von den Auswirkungen einer globalen Erderwärmung hinzugefügt.
Transportproteine für Bor identifiziert
Authors: Brennicke Axel
Published: February 2003

Über das Element Bor macht man sich normalerweise keine Gedanken, obwohl es lebensnotwendig ist. Bewussten Kontakt mit Bor haben wir höchstens in Form von „Borwasser”︁ zur Augenspülung. Wenn aber nicht genügend Bor im Boden verfügbar ist, wachsen Pflanzen nicht richtig und kümmern vor sich hin. Jetzt gelang es einer japanischen Arbeitsgruppe zum ersten Mal, die Moleküle in Pflanzen zu identifizieren, die das Element Bor transportieren und seine Konzentration regulieren. Ähnliche Moleküle sind in den menschlichen Nieren am Transport von Carbonat beteiligt.
Das Trauma‐Gedächtnis: Biologie der Angst
Authors: Rüegg Johann Caspar
Published: February 2003

Opfer von schweren Verkehrsunfällen und anderen lebensbedrohlichen Ereignissen bekommen oft noch Wochen oder Monate nach dem Trauma posttraumatische Belastungsstörungen. Sie reagieren dann beispielsweise mit Angst und Panik, wenn sie — etwa beim Quietschen von Autoreifen — wieder an das traumatische Geschehen erinnert werden, das im Traumagedächtnis gespeichert ist. Experimente an furchtkonditionierten Ratten haben jetzt aufgedeckt, welche biochemischen und neurophysiologischen Vorgänge beim Erwerb eines solchen Gedächtnisses für Angst ablaufen können: Konditionierte Reaktionen der Furcht entstehen letztlich dadurch, dass traumatische Erfahrungen (durch Lernprozesse) die Genexpression bestimmter neuronaler Proteine und damit die Struktur neuronaler Netzwerke des Gehirns (vor allem in der Amygdala) krankmachend verändern und damit eine Spur im Traumagedächtnis hinterlassen.
Das Geheimnis der Austrocknungstoleranz: Wiederauferstehungspflanzen
Authors: Hilbricht Tobias , Bartels Dorothea
Published: February 2003

Wiederauferstehungspflanzen wie Craterostigma plantagineum besitzen im vollentwickelten Zustand eine Eigenschaft, die man bei den meisten Embryonen der Samenpflanzen antrifft: sie sind austrocknungstolerant und überdauern einen beinahe vollständigen Entzug des Zellwassers ohne Vitalitätsverlust. Vermutlich sind die Biosynthese von LEA‐Proteinen und die Bildung von Saccharose aus 2‐Octulose an der Ausprägung der Trockentoleranz in C. plantagineum maßgeblich beteiligt. Das Phytohormon ABA als wichtiges Signalmolekül im Zusammenhang mit Trockenstress reguliert unter anderem die Aktivitäten von Transkriptionsfaktoren, die an der Expression von lea‐Genen beteiligt sind. Die Ausprägung der Trockentoleranz bei C. plantagineum wird allerdings durch viele Faktoren und Prozesse bestimmt, die sich in gleicher oder ähnlicher Form auch im Embryo der Samenpflanzen stattfinden.
Auf den Duft kommt es an
Authors: Wendler Silke
Published: February 2003

Pflanzen können auf die Anwesenheit von pflanzenfressenden Insekten mit der Erzeugung von Duftstoffen reagieren, um beispielsweise natürliche Feinde des Insektes anzulocken oder eine Eiablage zu verhindern. Bisher unbekannt war, dass Insekten die Zusammensetzung von pflanzlichen Duftcocktails für eigene Zwecke nutzen können, wie die Gallwespe Antistrophus rufus zeigt.
The HUPO Proteomics Standards Initiative meeting: towards common standards for exchanging proteomics data
Authors: Orchard Sandra , Kersey Paul , Hermjakob Henning , Apweiler Rolf
Published: February 2003

The Proteomics Standards Initiative (PSI) aims to define community standards for data representation in proteomics and to facilitate data comparison, exchange and verification. Initially the fields of protein–protein interactions (PPI) and mass spectroscopy have been targeted and the inaugural meeting of the PSI addressed the questions of data storage and exchange in both of these areas. The PPI group rapidly reached consensus as to the minimum requirements for a data exchange model; an XML draft is now being produced. The mass spectroscopy group have achieved major advances in the definition of a required data model and working groups are currently taking these discussions further. A further meeting is planned in January 2003 to advance both these projects. Copyright © 2003 John Wiley & Sons, Ltd.