bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the peptide and vitamin composition of casein hydrolysates on the β‐galactosidase activity of Kluyveromyces bulgaricus cells
Authors: Decleire M. , DeCat W. , Motte J. C. , Van huynh N. , Callebaut A.
Published: December 2004

Instead of yeast extracts, casein hydrolysates from several suppliers were added to culture media and analyzed with respect to their ability to stimulate β‐galactosidase activity in Kluyveromyces bulgaricus cells. Four enzymatic casein hydrolysates caused a significantly higher stimulation of enzyme activity, while acid casein hydrolysates clearly reduced the enzyme activity. Enzymatic casein hydrolysates, inducing high and low lactase activity, were analyzed with respect to average peptide length (APL), vitamins (niacin, pathothenate) as well as free and bound amino acids. The molecular weights of these casein hydrolysates were estimated by gel filtration. No correlation was found between the degree of enzyme stimulation and the vitamin contents, the APL values and the free amino acid contents of the casein hydrolysates. Casein hydrolysates stimulating the lactase activity were less soluble in water and, in a gel filtration column, they showed three peaks with slightly lower molecular weights than the three peaks seen in hydrolysates which had no effect on activity. APL values of alcoholic precipitates of casein hydrolysates showed an inverse correlation to lactase activity. The molecular weights of alcoholic precipitates of lactase stimulating digests were also lower compared to non‐stimulating ones. Alcoholic precipitates with lactase‐stimulating activity were more hydrophilic, as was shown by a smaller proportion absorbed in a C18 column and by amino acid analysis. Our results sugest that alcoholic precipitates could probably be important in the lactase stimulation and their composition should be further investigated. The mechanism is nevertheless complex and may be caused by various simultaneous factors.
Analyzing nitrogen and sulphide elimination from leachate by coulometric continuous flow titration
Authors: Becker M. , Martienssen M. , Fuhrmann B. , Spohn U.
Published: December 2004

The process of leachate denitrification by populations of nitrifying and denitrifying bacteria was investigated. Leachate, derived from a local municipal landfill site, was nitrified in a continuously operating packed‐bed biofilm reactor and thereafter denitrified in an activated sludge bioreactor. To follow the progress of nitrogen elimination, ammonium, nitrite and nitrate concentrations were determined at all stages of the process. While the nitrite and nitrate concentrations were measured by conventional colorimetric methods, computer controlled coulometric titration with in situ generated hypobromite was used for ammonium determination, which had previously been selectively separated from the sample matrix by gas dialysis. The detection range of the method was from 1 × 10−6 to 1 × 10−3 M ammonium (relative standard deviation (RSD) = 2%, n = 6). No interference of the complex sample matrix was found in ammonium determination. The average ammonium concentration in the leachate was 409 mg/l (standard deviation (SD) = 142 mg/l, n = 55). The ammonium concentrations decreased to 1–5 mg/l during nitrification under continuous operating conditions. Increased ammonium concentrations after nitrification correlated with a decrease in the efficiency of nitrogen elimination by up to 45% due to the build‐up of high concentrations of nitrite. The concentration of sulphides, another source of pollution of the leachate, was also determined by triangle programmed coulometric titration. The average concentration of sulphides in the leachate was 221 mg/l (SD = 374 mg/l; n = 55). The sulphide concentrations decreased to concentrations below the detection limit of the coulometric titration (2 × 10−6M) during nitrification.
Kinetics of olive oil hydrolysis in an enzyme membrane reactor. Bond graph network model of reactor performance (part 1)
Authors: Ceynowa J. , Adamczak P. , Staniszewski M.
Published: December 2004

Hydrolyses of olive oil were performed in a reactor with lipase immobilized on a laboratory ultrafiltration poliamide‐6 membrane. The reactor consisted of two circulating phases of olive oil and buffer solution. For the characterization of the reactor performance, a model of the hydrolysis process was developed. It was created by means of thermodynamic network representation of both the chemical processes and the transport of the reactants. According to an estimated bond graph network, the model is represented quantatively by a set of thirty‐three differential equations representing the time derivatives of the particular species concentration. The parameters of the model were estimated based on experimental data and/or literature notations. Close agreement of numerical estimations of the product concentrations with experimental data was gained. The model enabled an extended analysis of the influence of different reaction parameters, enzyme inhibition and concentration of the reactants on reactor performance.
Urease immobilized on an aminated polysulphone membrane – inhibition by boric acid
Authors: Krajewska B. , Zaborska W. , Leszko M. , Olech A.
Published: December 2004

An enzymatic membrane for application in the processes of decomposition and removal of urea from aqueous solutions was prepared: jack bean urease was immobilized on an aminated polysulphone membrane by adsorption. The inhibition of the system by boric acid was studied using procedures based on the MICHAELIS‐MENTEN integrated equation (non‐linear regression, and the linear transformations of WALKER and SCHMIDT, JENNINGS and NIEMANN, and BOOMAN and NIEMANN). The reaction was carried out in a 100 mM phosphate buffer of pH 7.0, containing 2 mM EDTA, obtained by neutralization of orthophosphoric acid with NaOH, at an initial urea concentration of 10 mM, and a temperature of 25 °C. The reaction was initiated by the addition of the enzyme to the urea solution, and was monitored by removing samples of the reaction mixture for NH3 determinations by the phenol‐hypochlorite method until the urea was exhausted. The results were compared with those obtained earlier under the same reaction conditions for free urease and urease covalently immobilized on chitosan. The inhibition was found to be competitive, similar to that of the free enzyme and urease immobilized on chitosan, with inhibition constants Ki equal to 0.36, 0.19 and 0.60 mM. The results show that adsorption of the enzyme on a polysulphone membrane changed the enzyme to a lesser degree than covalent immobilization of the enzyme on a chitosan membrane.
Growth patterns of yeast colonies depending on nutrient supply
Authors: Boschke E. , Bley Th.
Published: December 2004

Common theories of microbial growth and physiology are formulated exclusively in terms of the isolated microorganisms – especially bacteria. This is, however, an inadmissible simplification because it is obvious that the organization of microbial populations and colonies follows certain general rules.

Bacterial colonies are able to generate complex interfacial growth patterns similar to those observed during diffusion‐limited growth processes in non‐living systems. One reason for these patterns is assumed to be the ability of many bacteria to swarm in an active manner on a substrate surface. Therefore the models of bacterial colony growth incorporate “random walkers”, which move actively in response to a gradient in the concentration of nutrients and communicate with each other by means of a chemotactic feedback.

A selected number of yeasts were tested with regard to their colony growth patterns depending on the medium parameters such as nutrient concentration. Growth patterns similar to those which were described in literature for bacteria were also found in these experiments. It concerns in particular growth types like compact growth, fractal growth and dense‐branching growth.

This result allows a hypothesis to be formulated, that – especially in the case of fractal growth patterns – wandering of cells on a substrate surface may be induced by uncontrolled “swimming” on a thin water film caused by the metabolic activity (e.g. respiration) of the cells on the surface of the agar.

Furthermore it was found that an interplay between changes in the individual morphology of yeast cells and the morphology transitions takes place. Such growth patterns are known for Candida sp. which are able to form pseudomycel and blastospores.
Production of extracellular enzymes by two Pleurotus species using banana pseudostem biomass
Authors: Ghosh M. , Mukherjee R. , Nandi B.
Published: December 2004

The degradation of lignocellulosic biomass of banana pseudoste was investigated during solid state fermentation (SSF) by P. ostreatus and P. sajor‐caju. Both organisms proved to be efficient degraders of banana pseudostem biomass. P.ostreatus degraded hemicellulose (40% of dry weight, d.w.) better than cellulose (17.5% of d.w.) and lignin (10% of d.w.). P. sajor‐caju also degraded hemicellulose (31% of d.w.) better than cellulose (12.4% of d.w.) and lignin (6% of d.w.). In both cases, a preferential removal of hemicellulose during the initial growth period and a delayed degradation of lignin were observed. The kinetics of cellulolytic, hemicellulolytic and lignolytic enzyme production in liquid culture were also examined. The activities of CMCase and β‐glucosidase were highest at 16 days of growth and avicelase activity was at its maximum after 24 days (CMCase ‐ 1.1 IU/ml, β‐glucosidase ‐ 0.09 IU/ml in the case of P. ostreatus; CMCase ‐ 1.0 IU/ml, β‐glucosidase ‐ 0.087 ‐ IU/ml in the case of P. sajor‐caju.). Xylanase and laccase activity reached their maximum after day 16 and day 24 of incubation, respectively. (Xylanase ‐ 1.1 IU/ml and laccase 3.0 IU/ml in the case of P. ostreatus; xylanase ‐ 1.0 IU/ml and laccase ‐ 3.6 IU/ml in the case of P. sajor‐caju.). The efficient degrading capacity of test fungi demonstrated their potential use in the conversion of banana pseudostem biomass into mycelial protein‐rich fermented animal feed.
Fusion of yeast protoplasts and isolated nuclei of Fusarium moniliforme
Authors: Heluane H. , Defigueroa L. I. C. , Vázquez F.
Published: December 2004

Protoplasts of a xylose‐fermenting yeast strain (a fusion product of Pachysolen tannophilus and Saccharomyces cerevisiae) were fused with isolated nuclei of the xylan degrading filamentous fungus Fusarium moniliforme. Polyethyleneglycol 4000 was used as the fusogenic agent. Fourteen stable hybrids showing xylanase activity were obtained. It can be assumed that this ability was acquired from the nuclear genome of the fungus, since the parental yeast strain did not show any xylanase activity. The enzymatic activity was determined quantitatively. The parental strain of the fungus reached its maximum xylanase activity of 796 nkat/ml at 96 h of growth. Four of the hybrids had a xylanase activity of between 211 and 297 nkat/l at 24 h of growth. Zymograms of these hybrids showed the presence of xylanases when grown on xylan as the sole carbon source. Using pulse field electrophoresis gels, no difference between the chromosome pattern of the fusion products and the parental yeast strain was observed.
Microbial degradation of poly‐β‐hydroxybutyrate using landfill soils
Authors: Tansengco M. , Dogma I.
Published: December 2004

The population of poly‐β‐hydroxybutyrate‐degrading microorganisms and the biodegradation of PHB in local landfill soils were examined in vitro and in vivo. Forty‐two PHB‐degraders consisting of 12 bacteria, 25 actinomycetes and 5 moulds were isolated. The total PHB‐degraders averaged 4.7 × 107 and 20 × 104 colony forming units (cfu)/g for San Mateo wet and dry soils, respectively, and 2.3 × 107 and 8.5 × 104 cfu/g for Carmona wet and dry samples, respectively. The PHB‐degraders formed 0–59% of the total microbial population in San Mateo and 8–42% in Carmona. Complete (100%) degradation of PHB powder was observed for Chryseomonas‐27 and Aspergillus‐39 on day 5 in shake flask culture and for Streptomyces‐4 on day 7. Burial test in landfill soils showed a 90–91% weight loss of PHB film strips within four weeks; the weight loss of polypropylene film strips was up to 0.12% only. Scanning electron micrographs of degraded films revealed the attachment of microbial cells and fungal mycelium and spores on the surfaces. Holes and cavities were also noted due to the microbial degradation processes.
Isolation of the crude oil degrading marine Acinetobacter sp. E11
Authors: Razak C. N. A. , Wang W. F. , Rahman S. H. S. A. , Basri M. , Salleh A. B.
Published: December 2004

The Acinetobacter sp. E11, isolated from Port Dickson Beach, Malaysia, was able to grow in media containing crude oil as the sole carbon and energy source. Substrate specificity studies showed that the bacterium exhibited substrate preference as growth was observed only in media containing aliphatic hydrocarbons, while aromatic and cyclic hydrocarbons inhibited growth. With the aliphatic hydrocarbons, growth was seen only in the long‐chain alkanes tested (pentadecane, dodecane and hexadecane). No growth was recorded in the short‐chain alkanes (pentane, hexane and heptane) tested. With complex hydrocarbons, only crude oil and 4T SHELL engine oil supported growth. No growth was observed in kerosene and PETRONAS gasoline. The isolate could grow in up to 10% and 20% [v/v] of the crude oil and alkanes tested, respectively. Among the long‐chain alkanes tested, hexadecane was the most preferred, followed by pentadecane and dodecane. Nitrogen and phosphorous supplements were essential for growth and the best growth was achieved with 3% nitrogen/phosphorous additions. Microscopic observation revealed that the bacterium adhered to the hexadecane and crude oil droplets. GC analysis showed that the bacterium was able to degrade more than 60% of the hydrocarbons in the crude oil in 15 days at 37°C compared to the uninoculated media.
Bioremediation of oil contaminated beach sediments using indigenous microorganisms in singapore
Authors: Mathew M. , Obbard J. P. , Ting Y. P. , Gin Y. H. , Tan H. M.
Published: December 2004

The potential of using indigenous microorganisms in beach sediments to degrade petroleum hydrocarbons emanating from marine oil spillages in the Straits of Singapore was investigated. A field trial was conducted using oil contaminated beach sediments from Pulau Semakau – a small island 15 km south of Singapore. The results clearly show that the addition of inorganic nutrients to beach sediments significantly enhanced the activity of indigenous microorganisms (measured using the dehydrogenase enzyme assay and viable cell count techniques), as well as the removal of total recoverable petroleum hydrocarbons (TRPH) over a 50‐day study period (with up to 44% in the case of nutrient addition). The potential of exploiting in‐situ bioremediation techniques for oil spill clean‐up operations in tropical marine environments is discussed.
Studies on α‐amylase production by Bacillus licheniformis MIR‐61
Authors: Castro G. R. , Baigorí M. D. , Sin̄teriz F.
Published: December 2004

An acid α‐amylase hyperproducing strain, designated as MIR‐61, was isolated in a screening procedure from South American soil samples. MIR‐61, a 60°C thermoresistant strain, was identified using 98 biochemical and morphological tests and characterized as Bacillus licheniformis by numerical taxonomy. Batch cultures of B. licheniformis MIR‐61 showed extracellular α‐amylase and α‐glucosidase activities during the exponential growth phase.

The production of α‐amylase was studied at free and constant pH values at 37 and 45°C. Maximum α‐amylase activity (4,767 kU/dm3 in a liquid medium) was detected at 45°C at a constant pH (7.0) in the late exponential phase. The α‐amylase production by B. licheniformis MIR‐61 is 10 to 300 times higher than the enzyme production reported in strains of the same species.

Optimum α‐amylase activity was found at 50 to 67°C in an acid pH range from 5.5 to 6.0. These properties would allow its use in starch industry processes.
In vivo decolourization of the polymeric dye poly R‐478 by corncob cultures of Phanerochaete chrysosporium
Authors: Couto S. Rodríguez , Rivela I. , Sanromán A.
Published: December 2004

In this paper, the in vivo decolourization of the polymeric dye Poly R‐478 by semi‐solid‐state cultures of Phanerochaete chrysosporium BKM‐F‐1767 (ATCC 24725) was investigated, employing corncob as a support. In order to stimulate the ligninolytic system of the fungus, the cultures were supplemented with veratryl alcohol (2 mM) or manganese (IV) oxide (1 g/l).

Maximum manganese‐dependent peroxidase (MnP) and lignin peroxidase (LiP) activities of around 2,000 U/l and 400 U/l were attained by the former, whereas the activities reached by the latter were of about 1,500 U/l and 200 U/l, respectively. Furthermore, laccase activity (around 150 U/l) was only detected in manganese (IV) oxide supplemented cultures.

The polymeric dye Poly R‐478 (0.02 w/v) was added to three‐day‐old cultures. A percentage of biological decolourization of about 85% was achieved using cultures supplemented with veratryl alcohol, whereas MnO2 cultures showed a rather lower percentage of around 58% after nine days of dye incubation. Moreover, a correlation between MnP activity and Poly R‐478 decolourization could be observed, indicating that this enzyme is mainly responsible for dye degradation.

In the present work, the in vivo decolourizing capability of the ligninolytic complex secreted by P. chrysosporium was investigated under the above‐mentioned cultivation conditions, employing a model compound, such as the polymeric dye Poly R‐478.
Socio‐ecological strategies for future sustainability a review of an internet conference
Authors: Doelle H. W. , Foo E.‐L.
Published: December 2004

The recent upsurge in information technology has provided the international community with an easy access to professional journals (e.g. Electronic Journal of Biotechnology at http://www.ejb.org; etc.), discussion groups (e.g. bioenergy@cret.org; digestion@crest.org; etc.) and recently to electronic international conferences (e.g. ICIBS; http://www.cid.harvard.edu/cidbiotech, etc.) as well as a series of biotechnological information material (e.g. http://www.psrast.org, etc.) to stay in contact and receive up‐to‐date information in biotechnology. There is no doubt that this new technology will be more cost effective in future and reach more people in communities around the globe.

This review reports on one such an electronic conference aiming at bridging the communication gap between developed and developing countries. This conference dealt with integrated biosystems and has provided an excellent forum for more than 100 active participants from all regions of the world. As has been demonstrated in this review, the conference was able to show the very different approaches towards the use of biotechnology in developed and developing countries, cold and tropical climate regions owing to their different ecological, economical and societal problems. It also demonstrated very clearly that the field of molecular genetics and/or genetic engineering is not a priority issue in developing countries, but rather the need for clean technologies, multiproduct formation through socio‐economic integrated biosystems, e.g. incorporating microbial waste management into agro‐industries, in human activities and their roles in creating better health conditions, a better environment and sustain development.

It is hoped that this review will lead to a greater use of the electronic facilities available to inform and educate both the northern and the southern communities more readily of their needs and requirements to improve understanding and efforts for a sustainable future.
Biotechnological applications in the oil industry
Authors: Hamer G. , Al‐Awadhi N.
Published: December 2004

During the 20th century, important relationships developed between the oil industry and both microbiological and biotechnological research. Basic microbiological research has played an important role in both the exploration and production sectors of the oil industry, but as the maturity of the industry has progressed, such contributions have been relegated with respect to their importance. With respect to refining and petrochemicals manufacture, process routes have been extensively researched, but only rarely have the biotechnological solutions developed satisfied the economic criteria that resulted in major investment. In fact, situations exist where investment has occurred, but project life was unrealistically short, suggesting a need for extreme caution when evaluating biotechnological processes for the oil industry. However, as far as engineered processes for both biotreatment and bioremediation are concerned, the fundamental research that has underpinned other areas of hydrocarbon microbiology will finally prove to be of both technical and economic value, in ensuring that the essential needs of treatment, rather than disposal, and restoration, rather than environmental destruction, can be satisfied by the oil and other industries involved in both geochemical manipulation and natural resource exploitation.
The influence of growth rate and growth‐limiting factors on the production of ice nuclei in Pseudomonas syringae CCM 4073 in continuous culture
Authors: Sikyta B. , Spilková J. , Dušek J.
Published: December 2004

The influence of different growth‐limiting factors – namely the sources of carbon, nitrogen and phosphorus and the dilution (growth) rate – on the ice‐nucleation activity of Pseudomonas syringe CCM 4073 was studied. A higher ice‐nucleation activity was observed at a lower dilution (growth) rate (D = 0.1 h−1) than at a higher dilution (growth) rate (D = 0.3 h−1). Remarkable differences in ice‐nucleation activity were found in its dependence on the growth‐limiting factor. The highest ice‐nucleation activity was observed under carbon limitation (T90 = −2.7°C), a medium activity under nitrogen limitation (T90 = −5°C) and lowest activity under phosphorus limitation (T90 = −12.3°C). After the addition of excess nitrogen or phosphorus to steady‐state cultures, the ice‐nucleation activity was restored.
Materials Processing—a Key Factor
Authors: Michaeli Walter
Published: December 2004

Critical changes in the properties of materials due to varying processing conditions are the driving force behind the attempt to understand and control processing effects. Walter Michaeli uses the processing of polymers to emphasize the factors important in directing the design and processing of materials and the advantages of the integration of computers into development systems.
Polymers and composites
Authors: Mark Hermann
Published: December 2004

Significant advancement in science and technology may come from various sources, but mainly from two:

the accidental and unexpected discovery of new phenomena e.g. electricity, radioactivity, superconductivity, disintegration (splitting) of the atomic nucleus

the formulation and development of new principles which guide us to the synthesis and application of new and particularly useful polymeric systems.

Along the lines of the second source, interesting and significant progress has been made during the last two decades. This brief introduction attempts to sketch the origin and development of this progress.
Superconductivity—then and now
Authors: Jaeger Herbert
Published: December 2004

The discovery of high‐Tc superconductors in 1986 resulted in a massive research effort which continues today. Superconducting materials have been known, however, since 1911. In this article, the historical background to superconductivity is traced, conventional and high‐Tc materials are described and the theories which are applied to rationalize this phenomenon discussed, always with an eye on current and future applications, for example SQUIDs and levitating trains.
The transduction of host‐guest interactions into electronic signals by molecular systems
Authors: Reinhoudt David N. , Sudhölter Ernst J. R.
Published: December 2004

Synthetic receptor molecules that selectively bind charged guests can store chemical information. The transduction of this information into electronic signals connects the chemical and electronic domains. Field effect transistors (FETs) are attractive transducing elements because these microdevices are able to register and amplify chemical changes at the gate oxide surface of the semiconductor chip.

Integration of molecular receptors and field effect transistors into one chemical system gives a device that can communicate‐changes of substrate activities in aqueous solution. Simulations of a system in which the receptor molecules are directly attached to the FET gate oxide indicate serious limitations with respect to sensitivity, dynamic range and extreme requirements for complex stability. Therefore we have concentrated on the integration of covalently attached thin membranes.

The problem of the thermodynamically ill‐defined oxidemembrane ipterface has been solved by applying a covalently linked hydrophilic polyhydroxyethylmethacrylate (polyHEMA) gel between the sensing membrane and the silylated gate oxide. A buffered aqueous electrolyte solution in the hydrogel renders the surface potential at the gate oxide constant via the dissociation equilibrium of the residual silanol groups. The subsequent attachment of a polysiloxane membrane that has the required dielectric constant, glass transition temperature Tg, and receptor molecule, provides a stable chemical system that transduces the complexation of cationic species into electronic signals (CHEMFET).

The response to changing K⊕ concentrations in a solution of 0.1 M NaCl is fast (<1 sec) and linear in the concentration range of 10−5–1.0 M (55–58 mV /decade). A reference FET (REFET) based on the same technology is obtained when the intrinsic sensitivity to changes in ion concentration is eliminated by the addition of 2.10−5 mol g−1 of didodecyldimethyl ammonium bromide to the ACE membrane. Differential measurements with a REFET/CHEMFET combination showed excellent linear K⊕ response over long periods of time.

All chemical reactions used are compatible with planar IC technology and allow fabrication on wafer scale.
A new effect in second harmonic generation by poled nematic films
Authors: Yitzchaik Shlomo , Berkovic Garry , Krongauz Valeri
Published: December 2004

Poled nematic films, where the asymmetric axis responsible for second harmonic generation (SHG) is not in the poling direction are reported. Liquid crystalline polymers containing dopant chromophores, or side chain groups with high molecular hyperpolarizabilies exhibit this effect which has potential applications in nonlinear optics.
Surface modification with lasers
Authors: Comita Paul B.
Published: December 2004

Laser‐induced processing has been widely exploited in the microelectronics industry, to produce deposits with well‐controlled chemical composition, feature size, and morphology. A brief survey of the most commonly used techniques for laser patterning of materials on surfaces is presented. The issues which are key to continued progress in the field of surface modification with lasers are examined, including laser heating of surfaces, the role of mass transport in the kinetics of deposit growth, the study of the surface reactions involved in laserinduced processes, and some aspects of materials properties which are important in surface modification techniques.
Charting cation migration in a nickel exchanged zeolitic catalyst: An in situ rietveld X‐ray study
Authors: Couves John W. , Jones Richard H. , Thomas John M. , Smith Barnaby J.
Published: December 2004

X‐ray diffractograms of an active zeolite catalyst (see figure) can yield information concerning the distribution of metal cations within the framework of the catalyst. When thse measurements are carried out during catalysis, the migration of the ions can be followed and the occupation of various sites examined.

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The FEMS in Aachen
Authors: Ford Geoffrey
Published: December 2004

Sir Geoffrey Ford and Ford and Peter Gregory report on the Federation of European Materials Societies and their activities at a recent conference in northern Germany, while Josef Friedrich reveals what a shocking time he had at a meeting on optically active materials in San Jose last October.
Metal diffusion in high‐temperature polymers
Authors: Faupel Franz
Published: December 2004

A radiotracer technique has recently been employed to investigate the migration of Cu and Ag atoms in polyimides, an important process in the electronics industry where composite structures are becoming ever smaller and interfacial chemistry ever more important.
Layered Lead Cuprates: Promising high‐ Tc superconductors
Authors: Raveau B. , Michel C. , Hervieu M. , Groult D. , Provost J.
Published: December 2004

Layered lead cuprates belong to the structural family [ACuO3−α]m (A′O)n which are characterized by the intergrowth of oxygen deficient perovskite layers and rock salt type layers. Located in the rock salt type layers, lead sometimes exhibits the divalent state and sometimes the tetravalent state. A feature of some of these oxides is the disproportionation of Cu(II) to Cu(III) and Cu(I), which up to now has only been observed in YBa2Cu3O7−δ. The superconducting properties of these phases are very promising with the Tc ranging from 40 to 100 K, but the materials also show broad resistive transitions due to oxygen inhomogeneity. The dramatic influence of the method of synthesis on these properties is studied. The issue of the incommensurability of several of these structures is discussed.
Superconducting hollow and solid fibers and thin films of YBa2Cu3OX from a polymeric precursor
Authors: Chien James C. W. , Gong Ben Ming , Yang Yingsong , Cabrera Ivan , Effing Jochem , Ringsdorf Helmut
Published: December 2004

Superconducting hollow fibers of YBa2Cu3Ox (see figure) can be prepared via the supramolecular organization of polymer‐metal complexes. Solid fibers and oriented thin films have also been prepared. The ability to form the superconducting material into different shapes can provide a basis for innovative applications, for instance, the hollow fibers may be used as high‐Tc superconducting lenses.

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A conducting thallium salt of 2,5‐dimethyl‐N, N′‐dicyanoquinone‐diimine, [2,5‐DMe‐DCNQI]2Tl: Comparison with other related radical anion salts
Authors: Hünig Siegfried , Meixner Hubert , Metzenthin Tobias , Langohr Uwe , von Schütz Jost Ulrich , Wolf Hans‐Christopf , Tillmanns Ekkehart
Published: December 2004

A radical anion salt based on thallium (see figure, where M = Tl) has been prepared. It is found to be the only such conducting compound, except the copper analogue, which shows a positive NMR knight shift indicating an electronic interaction between the central atom and the ligand.

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Molecular materials for chemical and physical switching IV: Photomodulation of electric current by light‐sensitive electron‐transfer compounds—aryl/dihydroazulene‐conjugates
Authors: Daub Jörg , Fischer Christian , Salbeck Josef , Ulrich Karl
Published: December 2004

Bichromophoric compounds containing the dihydroazulene ⇄ vinyl heptafulvene couple (see figure) with arenoid “R” groups which act as electron‐transfer groups can be triggered by visible light to produce an electric current. They are therefore of use as molecular switches. A number of different arenoid substituent have been employed and the compounds examined.

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Molecular materials II Part A. Molecular electronics?
Authors: Miller Joel S.
Published: December 2004

The quest for the ultimate in miniaturization “molecular electronics” will be the subject of the next three articles in this series. The first of the three sets the scene with a discussion of the reasons for our interest in this “engineering down” process, and the components needed.
Superstructures and band gaps of bismuth tantalum oxide solid solutions
Authors: Zhou Wuzong
Published: December 2004

The search for superconductors, catalysts, and semiconductors can be facilitated by an understanding of the relationship between the structure of a material and its properties. In this study, high‐resolution electron microscopy (HREM) is used to examine the structures of solid solutions of BiTaO materials including Aurivillius phases, and it is shown that the band gaps of the materials depend on the superstructure rather than on composition.
Molecular materials II Part B. Molecular electronics?
Authors: Miller Joel S.
Published: December 2004

In the second part of this three‐part article the problems which have to be overcome in order to make use of molecular electronics e.g. quantum fluctuations, switching errors, heat dissipation and limited input/output possibilities are examined.
Surface analysis V. Scanning probes for surface magnetization
Authors: Rabe Jürgen P.
Published: December 2004

Improving the lateral resolution of an STM by exploiting the interactions of spin‐polarized electrons with the spins at the surface is one way of imaging surface magnetization, important in the development of future read/write schemes in magnetic thin‐film media. Recent progress made with this and other methods is discussed.
Preformed polymers for Langmuir–Blodgett films– molecular concepts
Authors: Embs Frank , Funhoff Dirk , Laschewsky André , Licht Ulrike , Ohst Holger , Prass Werner , Ringsdorf Helmut , Wegner Gerhard , Wehrmann Rolf
Published: December 2004

The use of preformed polymers for the preparation of Langmuir‐Blodgett (LB) multilayers is reviewed. Principles for polymer self‐organization are outlined and the appropriate molecular designs are discussed. Recent developments in the different classes of polymers for LB multilayers are presented, and their outstanding properties highlighted.
Amphiphilic dyes for nonlinear optics: Dependence of second harmonic generation on functional group substitution
Authors: Bubeck Christoph , Laschewsky André , Lupo Donald , Neher Dieter , Ottenbreit Petra , Paulus Wolfgang , Prass Werner , Ringsdorf Helmut , Wegner Gerhard
Published: December 2004

Communication: Orientation of chromophores by using the Langmuir‐Blodgett film‐prepration procedure, to a degree practically impossible to achieve by poling in polymer matrices in an electric field, has held to materials exhibiting the highest values of the second order susceptibility (χ(2)) yet known. The effect of different functional groups in both phenylhydrazone and stryrylpyridinium compounds on both molecular nonlinearity and order in the films the factors which most strongly influence (χ(2)) has been investigated and a thioether substituent is found to increas (χ(2)) significantly.
The Advanced Photon Source
Authors: Durbin Stephen M.
Published: December 2004

Essay: Synchrotron X‐ray sources are opening up new avenues of research in materials science. Applications include X‐ray diffraction of ever‐smaller samples, X‐ray fluorescence microscopy, and X‐ray tomography, a technique which provides detailed information on the internal structure of materials. The potential contribution of the Advanced Photon Soruce (APS) being built at the Argonne National Laboratory in the USA which should be operational in 1995, and modes of access to the facility are described.
Perfluorochemicals: Blood substitutes and beyond
Authors: Lowe Kenneth C.
Published: December 2004

Review: Biomedical applications of perfluorinated compounds, which are either dense white powders or colorless, odorless liquids, are based on their gas transport capabilities and include resuscitation fluids, microcirculatory support in inschaemic tissues, tumor sensitizers, contrast agents, and the preservation of organs or limbs prior to transplantation. The various formulations, which also contain surfactants, are described with reference to their biocompatibility and modes of use.
A novel Langmuir–Blodgett film of a dibenzylideneacetone–Pd(0) complex and its use for preparation of catalytically active substrates
Authors: Tieke Bernd , Zahir Sheik A. , Mathieu Hans‐J.
Published: December 2004

Communication: The precise control of the amount of catalytic palladium deposited on a substrate as an ultrathin film can be achieved if the films are prepared using the Langmuir–Blodgett technique. The high solubility of the dibenzylideneacetone derivative shown in the figure facilitates this approach, producing films stable at room temperature but which decompose depositing metallic palladium at the melting point of the complex, 165°C.

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Molecular materials III Molecular materials with increased superconducting and ferromagnetic critical temperatures
Authors: Miller Joel S.
Published: December 2004

Research News/Molecular Materials III: Recent developments in the molecular approach to superconductivity, for example the work of Williams et al. in increasing the Tc to 12.8 K, and new work in the field of molecular ferromagnets, where the Tc has also been significantly increased are described.
Large enhancement of the carrier mobility in semiconducting α‐sexithienylene thin films by pulsed electrochemical inclusion of metal
Authors: Xu Bai , Fichou Denis , Horowitz Gilles , Garnier Francis
Published: December 2004

Communication: The performance of molecular‐based devices canb e improved by increasing the carrier mobility of the organic semiconductor. A method for achieving up to a 700‐fold increase in the carrier mobility, which involves the electrochemical inclusion of metal ions (silver and copper) into the semiconducting organic material, is reported. The effect is thought to be the result of the metal ions acting as bridges between neighboring polymer chains thus increasing the interchain carrier hopping rate.
DCNQIs—new electron acceptors for charge‐transfer complexes and highly conducting radical anion salts
Authors: Hünig Siegfried , Erk Peter
Published: December 2004

Review: Organic conducting materials show potential for applications in, for example, electrostatic shielding or in pressure sensing. In the past, research aimed at the optimization of the properties of these materials e.g. the charge‐transfer (CT) complex tetrathiafulvalene/tetracyanoquinodümine (TTF/TCNQ, see figure) have concentrated mainly on varying the structure of the donor (TTF). Here, in contrast, the recent progress made in the identification, synthesis, and characterization of new acceptors suitable for use in CT complexes, the N,N'‐dicyanoquinonediimines (DCNQIs) is reviewed.

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Mixed semiconductor component quantum supralattices: Silver, sodium chloro, iodo‐sodalites
Authors: Stein Andreas , Meszaros Michele , Macdonald Peter M. , Ozin Geoffrey A. , Stucky Galen D.
Published: December 2004

Communication: Resonant tunneling quantum dot transistors or high‐gain heterojunction multiple quantum dot laser arrays are two potential applications of the title compounds. The new materials are composed of periodic arrays of all‐space filling β‐cages containing atomically precise, organized assemblies of single‐size and shape M4X clusters, (see figure).

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Biomaterials highlights IX. Bioactive ceramics
Authors: Heimke Günther
Published: December 2004

Research News/Biomaterials Highlights IX: Materials with active bone‐bonding ability have found applications in medicine for coatings of, for example, load‐bearing dental or orthopedic implants. These bioactive materials, which are based on calcium‐phosphate‐containing glasses of glass ceramics or Caphosphate‐ceramics, have the problem however that they do not perform well under shear loading. The various materials employed and the factors which affect their performance are discussed.
Chemical interactions in GaAs‐LEC crystal growth
Authors: Lambert Ulrich , Wiese Ulrich
Published: December 2004

Review: Light‐emitting diodes, high‐speed transistors, laser diodes, and solar cells are just a few of the applications of gallium arsenide (GaAs), for which the availability of ultrapure materials or materials with closely controlled impurity profiles is of utmost importance. The development and optimization of one major method of GaAs crystal growth is described with special emphasis on the possibilities of controlling the conductivity characteristics of the material.
Towards a planar, double‐stranded polymer
Authors: Godt Adelheid , Schluter Arnulf‐Dieter
Published: December 2004

Communication: Unsaturated ladder polymers consisting of a perfect sequence of all‐carbon six‐membered rings (polycatafusenes) are predicted to exhibit intrinsic electrical conductivity and high optical nonlinearity. One step towards this goal, the chemically induced unfolding of a coiled ladder polymer (see Figure), where the geometries of the carbons marked “B” regulates the overall structure, is reported.

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‘Sir humphry davy who abominated gravy…’
Authors: Thomas John Meurig.
Published: December 2004

Essay: Humphry Davy made many contributions to basic science, including materials science. In this extended Christmas essay, one of the most recent directors of the Royal Institution in London reviews the and work of one of his most illustrious predecessors from a humble beginning as the son of a Cornish woodcarver to the heights of the Presidency of the Royal Society.
Orientation and dynamics in polymers by infrared dichroism spectroscopy
Authors: Reynolds Nicholas
Published: December 2004

Research News: The oreintation of polymer molecules has a significant effect on the mechanical properties of polymeric materials. Infrared dichroism spectroscopy is a highly sensitive, chemically specific technique for examining the orientation of the electrical dipole moments in molecules ans as such can be applied to the study of the mechanisms of orientational relaxation in entangled polymer melts. The technique and some of its recent applications are presented.
Crystal structure and electrical properties of κ‐((S,S)‐DMBEDT–TTF)2ClO4
Authors: Zambounis John S. , Mayer Carl W. , Hauenstein Kurt , Hilti Bruno , Hofherr Walther , Pfeiffer Jurgen , Bürkle Markus , Rihs Grety
Published: December 2004

The existence of superconductivity in chiral molecular systems is suggested by studies of the title compound. The work, which is an important extension of studies of recently organic superconductors based on unsymmetrical molecules, shows that a sudden, but incomplete loss of resistivity (by a factor of 500) takes place at 3 K and 5 kbar. Both this behavior and the crystal‐packing motif suggest that the transition is of a superconducting nature.
Superconducting electronics in the TlCaBaCuO System
Authors: Martens Jon S. , Ginley David S.
Published: December 2004

The high‐Tc superconductor (HTS) Tl‐Ca‐Ba‐Cu‐O is an attractive material for applications because of its high transition temperature and structural properties. The bassic structural features, methods of film growth, device processing sequences, and some device and microwave circuit applications are discussed, with special attention being paid to active devices based both on Josephson junctions and on controlled flux flow in the non‐Josephson domain.
Materials research strategy at hoechst
Authors: Felcht Utz‐Hellmuth
Published: December 2004

A refocusing of materials research strategy has been necessary for many chemical companies engaged in the materials sector due to increased competition and the ever more international nature of the market. It is aimed at bringing the products of research nearer to the market, and in producing research efforts which are more dynamic, international and interdisciplinary. The historical development of the chemical industry's involvement in materials and anew tri‐regional concept with which Hoechst will approach future challegnes is presented.
Materials harder than diamond?
Authors: Riedel Ralf
Published: December 2004

The hardest known materials, diamond and cubic boron nitride, are thermodynamically stable only at high pressure and temperature. Chemical vapor deposition and sputtering have offered low‐pressure alternatives to the traditional synthetic methods and these techniques have recently been exploited for the production of new super‐hard materials such as boron carbonitride and carbon nitride, which could be harder than diamond.
Chemical vapor deposition of silicon carbide powders using pulsed CO2 Lasers
Authors: Scholz Malte , Fuß Werner , Kompa Karl‐Ludwig
Published: December 2004

A carbosilane polymer which survives temperatures up to 2000°C is reported. It deposits on the surface of SiC particulates which form during the laser pyrolysis of tetramethylsilane, and has possible applications as a sintering aid for SiC or in reducing brittleness in ceramic composites. Powders consisting of 8–10 nm SiC crystallites embedded in the carbosilane polymer are produced in the plasma formed by a focused CO2 laser.
Polymer‐mediated crystallization of inorganic solids: Calcite nucleation on poly(organosiloxane) surfaces
Authors: Brisdon Brian J. , Heywood Brigid R. , Hodson Annabelle G. W. , Mann Stephen , Wong Kim K. W.
Published: December 2004

The controlled deposition of inorganic crystalline solids at polymeric surfaces is of considerable technological and biological interest. Advantages of such inorganic–polymeric metrices are their enhanced thermal and chemical stability, an important factor in the future design of polymer–ceramic composites. The coral‐like growths of calcium silicate shown in the Figure overgrow deposited calcite at high catalyst concentrations.

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A model for the successful growth of polycrystalline films of CuInSe2 by multisource physical vacuum evaporation
Authors: Klenk Reiner , Walter Thomas , Schock Hans‐Werner , Cahen David
Published: December 2004

Solar cells based on CuInSe2 polycrystalline thin films (see Figure) are one of the few realistic alternatives to polycrystalline Si for practical conversion of solar energy into electricity. A model explaining the important role of the secondary copper chalcogenide phases in the deposition of the CuInSe2 films by physical vacuum evaporation is presented.

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Optically transparent nanometal composite membranes
Authors: Foss Colby A. , Hornyak Gabor L. , Stockert Jon A. , Martin Charles R.
Published: December 2004

Small metal particles embedded in an optically transparent matrix result in a composite material which can be transparent in the infrared and into the visible (metals are usually optically opaque). The nanoparticles of the metal are produced by the “template” method, where the material is synthesized within the pores of a nanoporous membrane (see Figure).

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Materials R & D in the electrical and electronics industry
Authors: Weyrich Claus
Published: December 2004

The training of R & D managers is just one of the many topics discussed by one of the senior figures in the research and development activities of Siemens. The planning of future R & D aims in the electronics industry, based on indentifying market requirements and producing materials faster than competitors which perform to the desired level at the desired price, and the various factors which affect this planning are discussed.
Morphological and molecular processes observed using scanning tunneling microscopy on organic conductors
Authors: Magonov Sergei N. , Bar Georg , Gorenberg Arkadij Y. , Yagubskii Eduard B. , Cantow Hans‐Joachim
Published: December 2004

Step‐by‐step surface layer restoration in organic superconducting salts has been observed using STM. The Figure shows a step, approximately 1.8 nm in height, with an uneven boundary. Over a period of time the step edge is seen to “heal” under positive tip bias, where the current flows from the tip to the sample. Under reversed bias the degradation of the surface has been observed.

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3‐D optical data storage by two‐photon excitation
Authors: Strickler James H. , Webb Watt W.
Published: December 2004

Increased data density and media capacity is a constant goal of research into optical storage. These‐dimensional optical storage offers this large increase because the volume density limit is 1/λ3 rather than the 1/λ2 achievable with 2‐D storage. Holographic storage and spectral hole burning have been examined in the past; here an alternative is presented based on two‐photon excitation.