bluuebunny/crossref_metadata_2025 huggingface dataset:
Carrier compensation by deep levels in Zn1−xMgxO/sapphire
Authors: Hierro A. , Tabares G. , Ulloa J. M. , Muñoz E. , Nakamura A. , Hayashi T. , Temmyo J.
Published: June 2009

A systematic analysis of the deep level spectrum in the lower half of the bandgap of Au–Zn1−xMgxO (0.056<x<0.18) Schottky diodes is presented. Two deep levels are observed at Ev+580 and Ev+280 meV regardless of the bandgap energy with trap concentrations linearly increasing with the Mg content. The Ev+280 meV trap concentration becomes as high as 1.01×1018 cm−3 at 18% Mg, partially compensating the films and causing a decrease from 8.02×1016 to 1.27×1016 cm−3 in the net electron concentration and an increase by three orders of magnitude in the diode series resistance due to electron trapping.
The effective quality factor at low temperatures in dynamic force microscopes with Fabry–Pérot interferometer detection
Authors: Hölscher Hendrik , Milde Peter , Zerweck Ulrich , Eng Lukas M. , Hoffmann Regina
Published: June 2009

The oscillation of a cantilever in ultrahigh vacuum dynamic force microscopy is sometimes measured with the help of a Fabry–Pérot interferometer. We show that the photoinduced forces present in such an interferometer can artificially increase or decrease the effective quality factor of the cantilever. We examine this effect on the basis of a PtIr-coated rectangular silicon cantilever at temperatures between 7.7 and 30 K. By measuring resonance curves we demonstrate that the magnitude of the effective quality factor changes with cantilever-fiber distance, laser power, and temperature.
Enhanced broadband photoresponse of Ge/CdS nanowire radial heterostructures
Authors: Mondal S. P. , Ray S. K.
Published: June 2009

CdS/Ge nanowire heterojunction has been grown by chemical deposition of CdS on Ge nanowire templates. Transmission electron micrographs show the growth of core-shell Ge/CdS nanowire radial heterostructures. Raman spectra reveal the confinement of phonons in nanocrystalline CdS shell grown on Ge nanowires. A diodelike behavior in I-V characteristics of Ge/CdS heterojunction is observed due to the formation of rectifying junction between CdS shells and Ge nanowire cores. An improved photocurrent spectrum of Ge/CdS heterojunction nanowires with broadband response from visible to near-IR region is demonstrated.
OD stretch vibrational relaxation of HOD in liquid to supercritical H2O
Authors: Schäfer Tim , Lindner Jörg , Vöhringer Peter , Schwarzer Dirk
Published: June 2009

The population relaxation of the OD stretching vibration of HOD diluted in H2O is studied by time-resolved infrared pump-probe spectroscopy for temperatures between 278 and 663 K in the density range 0.28≤ρ≤1.01 g/cm3. Transient spectra recorded after exciting the v=0→1 OD stretching transition at low temperatures show a delay between excited state decay and formation of the thermalized spectrum pointing to an intermediately populated state. Above 400 K, the rates of excited state decay and ground state recovery become equivalent and the intermediate state is not detectable anymore. Over the entire thermodynamic range, the derived OD stretch relaxation rate constant kr depends linearly on the static dielectric constant ε of water, indicating a correlation of kr with the average hydrogen bond connectivity of HOD within the H2O network. However, in contrast to the OH stretch relaxation rate constant of the complementary system of HOD in D2O, the low density data of kr(ε) extrapolate to a nonzero intercept for ε→1. Our analysis suggests that at ambient conditions the OD excited state is mainly depopulated by a direct v=1→0 transition, avoiding the excited v=1 HOD bending state. Therefore, at room temperature the detected intermediate is assigned to a nonthermalized state with respect to nuclear degrees of freedom of the solvent molecules, and subsequent formation of the final product spectrum is related to a rearrangement of the hydrogen bond network. Passing over to the gas phase the excited OD stretch state shifts into close resonance with the HOD bend overtone, thereby opening up an additional relaxation channel.
Non-Born–Oppenheimer electronic and nuclear wavepacket dynamics
Authors: Yonehara Takehiro , Takahashi Satoshi , Takatsuka Kazuo
Published: June 2009

A practical quantum theory for unifying electronic and nuclear dynamics, which were separated by the Born–Oppenheimer approximation, is proposed. The theory consists of two processes. Nonadiabatic (quantum) electron wavepacket dynamics on branching (non-Born–Oppenheimer) nuclear paths are first constructed. Since these paths are not the classical trajectories, most of the existing semiclassical theories to generate quantum wavepacket do not work. Therefore, we apply our own developed semiclassical wavepacket theory to these generated non-Born–Oppenheimer paths. This wavepacket is generated based on what we call the action decomposed function, which does not require the information of the so-called stability matrix. Thus, the motion of nuclei is also quantized, and consequently the total wave function is represented as a series of entanglement between the electronic and nuclear wavepackets. In the last half of the article, we show the practice to demonstrate how these independent theories can be unified to give electron-nuclear wavepackets in a two-state model. The wavepackets up to the phases and resultant transition probabilities are compared to the full quantum-mechanical counterparts. It turns out that the lowest level approximation to the wavepacket approach already shows a good agreement with the full quantum quantities. Thus, the present theoretical framework gives a basic method with which to study non-Born–Oppenheimer electronic and nuclear wavepacket states relevant to ultrafast chemical events.
Visualization of a ferroelectric domain structure in the X cut of a LiNbO3 crystal using x-ray diffraction and topography
Authors: Roshchupkin D. V. , Irzhak D. V. , Antipov V. V.
Published: June 2009

A ferroelectric domain structure formed in the X cut of a LiNbO3 crystal by aftergrowth thermoelectrical treatment was studied by x-ray diffraction and topography methods. An external electric field applied along the X axis to the crystal causes shift deformations due to the reverse piezoelectric effect, which permits visualization of domain structures in the X cut of a LiNbO3 crystal. Oppositely directed inclinations of reflecting planes in adjacent domains, caused by the reverse piezoelectric effect, give rise to different diffraction angles in neighboring domains and make visualization of domain structure possible.
InN nanocolumns grown by plasma-assisted molecular beam epitaxy on A-plane GaN templates
Authors: Grandal J. , Sánchez-García M. A. , Calleja E. , Gallardo E. , Calleja J. M. , Luna E. , Trampert A. , Jahn A.
Published: June 2009

This work reports on the growth of wurtzite InN nanocolumns on A-plane GaN templates and on their structural and optical characterization by scanning and transmission electron microscopy, photoluminescence, and Raman spectroscopy. InN nanocolumns grown on A-plane substrates show sharp and pyramidal-like top surfaces that could be attributed to A-plane and M-plane facets, instead of the hexagonal top surfaces observed in nanocolumns grown on C-plane surfaces. The results of these characterization techniques show that the nanocolumns preserve the nonpolar growth orientation of the GaN templates. Good crystal quality is expected from the low temperature (13K) photoluminescence dominant peak at 0.69eV.
Effect of indium composition ratio on solution-processed nanocrystalline InGaZnO thin film transistors
Authors: Kim Gun Hee , Du Ahn Byung , Shin Hyun Soo , Jeong Woong Hee , Kim Hee Jin , Kim Hyun Jae
Published: June 2009

The effects of the indium content on characteristics of nanocrystalline InGaZnO (IGZO) films grown by a sol-gel method and their thin film transistors (TFTs) have been investigated. Excess indium incorporation into IGZO enhances the field effect mobilities of the TFTs due to the increase in conducting path ways and decreases the grain size and the surface roughness of the films because more InO2− ions induce cubic stacking faults with IGZO. These structural variations result in a decrease in density of interfacial trap sites at the semiconductor-gate insulator interface, leading to an improvement of the subthreshold gate swing of the TFTs.
Variation of magnetization reversal in pseudo-spin-valve elliptical rings
Authors: Yu C. , Chiang T. W. , Chen Y. S. , Cheng K. W. , Chen D. C. , Lee S. F. , Liou Y. , Hsu J. H. , Yao Y. D.
Published: June 2009

We studied nanoscale elliptical ring shaped NiFe/Cu/NiFe trilayer pseudo-spin-valve structures. The magnetization reversal processes showed simultaneous-reversal single-step transition or double-step transition involving flux closure states. For various aspect ratios (short axis to long axis) and linewidths, transition between single-step and double-step magnetization reversals was measured to form a phase diagram. When the linewidth was reduced, edge roughness became important. Simulations of the magnetization reversal behavior agreed qualitatively with our results.
Comparative study of electrical instabilities in top-gate InGaZnO thin film transistors with Al2O3 and Al2O3/SiNx gate dielectrics
Authors: Lee Jeong-Min , Cho In-Tak , Lee Jong-Ho , Cheong Woo-Seok , Hwang Chi-Sun , Kwon Hyuck-In
Published: June 2009

A comparative study was made of the performance and electrical instabilities in amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors with Al2O3 and Al2O3/SiNx gate dielectrics. Steeper subthreshold slope is observed in Al2O3 devices, which shows that the density of trap states at the interface of a-IGZO/Al2O3 is lower than that of a-IGZO/SiNx. Under high bias-stresses, a larger degradation is observed in Al2O3/SiNx devices. The device degradation for both devices are mainly attributed to the charge trapping phenomenon, but the different time dependence of threshold voltage shift shows that trapped electrons are more easily redistributed inside the Al2O3 dielectrics.
Impact of field-enhanced band-traps-band tunneling on the dark current generation in germanium p-i-n photodetector
Authors: Ang Kah-Wee , Ng Joseph Weisheng , Lo Guo-Qiang , Kwong Dim-Lee
Published: June 2009

This letter investigates the impact of field-enhanced band-traps-band tunneling on the dark current generation in germanium (Ge) p-i-n photodetector. We show that the existence of defect-induced traps within the forbidden gap forms the underlying leakage mechanism. Enhancing the electric field intensity is found to reduce the activation energy that governs the leakage generation rates. In the presence of enlarged band-bending, the dark current generation is further aggravated by the enhancement in electrons and holes tunneling from the resulting deep levels into the conduction and valence bands, respectively. Such field-enhanced band tunneling effect becomes increasingly prominent with a downsizing of the detector’s depletion width, which imposes a design trade-off between leakage generation and bandwidth enhancement.
Proximity gettering of Cu at a (110)/(001) grain boundary interface formed by direct silicon bonding
Authors: Yu X. , Lu J. , Youssef K. , Rozgonyi G.
Published: June 2009

We have demonstrated that a direct silicon bonded (110)/(001) interface, fabricated using hybrid orientation technology (HOT), acts as a proximity gettering center for Cu during quench annealing. The Cu gettering efficiency, which increases with annealing temperature, can reach more than 99%. Gettered Cu impurities tend to form colonylike precipitates at the (110)/(001) grain boundary (GB) interface when quenched from an elevated temperature. It is believed that interfacial GB imperfections initiate the Cu precipitation, and then, due to the release of a large number of self-interstitials, dislocation loops form and become new gettering centers which enhance the Cu gettering efficiency. These results are of interest for the defect engineering of the HOT wafer in advanced microelectronics and for enhancing our understanding of GBs in multicrystalline photovoltaic silicon.
Nanoenabled microelectromechanical sensor for volatile organic chemical detection
Authors: Zuniga Chiara , Rinaldi Matteo , Khamis Samuel M. , Johnson A. T. , Piazza Gianluca
Published: June 2009

A nanoenabled gravimetric chemical sensor prototype based on the large scale integration of single-stranded DNA (ss-DNA) decorated single-walled carbon nanotubes (SWNTs) as nanofunctionalization layer for aluminum nitride contour-mode resonant microelectromechanical (MEM) gravimetric sensors has been demonstrated. The capability of two distinct single strands of DNA bound to SWNTs to enhance differently the adsorption of volatile organic compounds such as dinitroluene (simulant for explosive vapor) and dymethyl-methylphosphonate (simulant for nerve agent sarin) has been verified experimentally. Different levels of sensitivity (17.3 and 28 KHz μm2/fg) due to separate frequencies of operation (287 and 450 MHz) on the same die have also been shown to prove the large dynamic range of sensitivity attainable with the sensor. The adsorption process in the ss-DNA decorated SWNTs does not occur in the bulk of the material, but solely involves the surface, which permits to achieve 50% recovery in less than 29 s.
Measuring the orbital angular momentum of optical vortices using a multipinhole plate
Authors: Guo Cheng-Shan , Yue Shu-Juan , Wei Gong-Xing
Published: June 2009

We present a method for measuring the orbital angular momentum (OAM) of optical vortices through extracting the phase values sampled by a multipinhole plate. We demonstrate that the phase of an optical vortex passing through a multipinhole plate can be directly extracted from the Fourier transform of a single diffraction intensity pattern according to a simple algorithm and thus the l state or the OAM of the photons can be measured quantitatively.
Synthesis and characterization of N-rich single crystalline SiOxNy nanowires with three-dimensional branches
Authors: Gu Lin , Yu Yan , Penmatsa Varun , Wang Chunlei , Maier Joachim , van Aken Peter A.
Published: June 2009

N-rich single crystalline SiOxNy nanowires with three-dimensional (3D) branches have been synthesized and characterized. In contrast to the reported SiOxNy nanowires, our products exhibit a predominant N concentration and a single crystalline phase throughout the 3D branched structure. These properties are highly favorable for applications on which high dielectric constant and high refractive index are required. Valence electron energy-loss spectroscopy utilizing monochromated electrons reveals that the band gap of the materials is 4.4±0.2 eV. Energy-loss near edge structures of Si L2,3, N K, and O K edges display a strong orbital hybridization.
Determination of wurtzite InN/cubic In2O3 heterojunction band offset by x-ray photoelectron spectroscopy
Authors: Song H. P. , Yang A. L. , Wei H. Y. , Guo Y. , Zhang B. , Zheng G. L. , Yang S. Y. , Liu X. L. , Zhu Q. S. , Wang Z. G. , Yang T. Y. , Wang H. H.
Published: June 2009

In 2 O 3 is a promising partner of InN to form InN/In2O3 heterosystems. The valence band offset (VBO) of wurtzite InN/cubic In2O3 heterojunction is determined by x-ray photoemission spectroscopy. The valence band of In2O3 is found to be 1.47±0.11 eV below that of InN, and a type-I heterojunction with a conduction band offset (CBO) of 0.49–0.99 eV is found. The accurate determination of the VBO and CBO is important for use of InN/In2O3 based electronic devices.
Change in the resistivity of Ge-doped Sb phase change thin films grown by chemical vapor deposition according to their microstructures
Authors: Kim Jin-Hyock , Lee Keun , Chae Su-Jin , Han Il-Keoun , Roh Jae-Sung , Park Sung-Ki , Choi Byung Joon , Hwang Cheol Seong , Cho Eunae , Han Seungwu
Published: June 2009

This study examined the effects of the composition and microstructure on the electric resistivity of Ge-doped Sb phase change thin films grown by cyclic plasma enhanced chemical vapor deposition. Ge and Sb layers were deposited sequentially to form either a GexSby mixture or Ge/Sb nanolaminated films. While the resistivity of the nanolaminated films was higher, the GexSby mixture showed a lower resistivity than the pure Sb film. This can be explained by the increase in carrier density of the alloy, as confirmed by first-principles calculations. An abrupt change in resistance accompanying a phase change was observed at ∼210 °C.
The confirmation of the critical point-Zeno-line similarity set from the numerical modeling data for different interatomic potentials
Authors: Apfelbaum E. M. , Vorob'ev V. S.
Published: June 2009

We use numerical simulation data for several model interatomic potentials to confirm the critical point-Zeno-line relations of similarity (CZS) for the liquid branch of the coexistence curve suggested earlier [E. M. Apfelbaum and V. S. Vorob’ev, J. Phys. Chem. B 112, 13064 (2008)]. These relations have been based on the analysis of experimental values for the critical point parameters and liquid-gas coexistence curves for a large number of real substances and two model systems. We show that the numerical modeling data as a whole confirm the CZS in the domain of the existence of liquid state. The deviations from CZS relations take place for two cases: (a) the numerically calculated coexistence curve gets into domain corresponding to solidification; (b) the liquid-vapor transition becomes metastable with respect to freezing.
Dislocation density reduction in GaN by dislocation filtering through a self-assembled monolayer of silica microspheres
Authors: Li Qiming , Figiel Jeffrey J. , Wang George T.
Published: June 2009

We demonstrate the use of self-assembled monolayers of silica microspheres as selective growth masks for significant threading dislocation density reduction in GaN on sapphire epilayers. During GaN regrowth through the close-packed monolayer, the silica microspheres effectively terminate the propagation of threading dislocations. As a result, the threading dislocation density, measured by large area atomic force microscopy and cathodoluminescence scans, is reduced from 3.3×109 to 4.0×107 cm−2. This nearly two orders of magnitude reduction is attributed to dislocation blocking and bending by the unique interface between GaN and silica microspheres.
Funnel hopping: Searching the cluster potential energy surface over the funnels
Authors: Cheng Longjiu , Feng Yan , Yang Jie , Yang Jinlong
Published: June 2009

We designed a cluster surface smoothing method that can fast locate the minimum of the funnels in the potential energy surface (PES). By inserting the cluster surface smoothing approach into the gradient-based local optimization (LO)-phase and the global optimization (GO)-phase as a second LO-phase, the GO-phase can focus on the global information oWalesf the PES over the various funnels. Following the definition of “basin-hopping” method [D. J. and J. P. K. Doye, J. Phys. Chem. A 101, 5111 (1997)], this method is named as “funnel hopping.” Taking a simple version of the genetic algorithm as the GO-phase, the funnel-hopping method can locate all the known putative global minima of the Lennard-Jones clusters and the extremely short-ranged Morse clusters up to cluster size N=160 with much lower costs compared to the basin-hopping methods. Moreover the funnel-hopping method can locate the minimum of various funnels in the PES in one calculation.
Site preference of Re in NiAl and valence band structure of NiAl containing Re: First-principles study and photoelectron spectrum
Authors: Wei H. , Liang J. J. , Sun B. Z. , Zheng Q. , Sun X. F. , Peng P. , Yao X. , Dargusch M. S.
Published: June 2009

The site preference of Re in NiAl was studied using first-principles calculations. The calculation of formation energies of the NiAl alloys indicated the site preference of Re on the Ni sites. The valence band structures of the NiAl alloys were investigated by photoelectron spectroscopy. The valence band spectra of the NiAl with Re shifted away from the Fermi energy level so that the Ni d-band centroid moved to a higher energy by 0.25 eV as Re was added. Such a shift could be attributed to the Ni-Re interaction, which was supported by the photoelectron spectroscopy measurement.
Microwave-assisted three-dimensional multilayer magnetic recording
Authors: Winkler G. , Suess D. , Lee J. , Fidler J. , Bashir M. A. , Dean J. , Goncharov A. , Hrkac G. , Bance S. , Schrefl T.
Published: June 2009

Layer-selective writing of two layer bit patterned media is demonstrated by performing micromagnetic finite element simulations. Selectivity is achieved by controlling the frequency of an oscillating magnetic field in the gigahertz range, applied in addition to the head field. Generation of the microwave field by means of a wire next to the tip of a single pole head is proposed. The Oersted field from the alternating current induces magnetic oscillations in the pole tip which create a high frequency field that is superimposed to the perpendicular write field. The amplitude of the ac field component is in the order of 0.1 T.
A rapid method for flow-ready cylindrical microchannel fabrication
Authors: Henthorn Kimberly H.
Published: June 2009

Most current methods of microchannel fabrication are expensive and time consuming or result in noncylindrical channels, which is undesirable for many applications. A rapid inexpensive method for the fabrication of flow-ready cylindrical polymer microchannels from polydimethylsiloxane (PDMS) is presented here. In this method, cylindrical needles are used as molds for the channels and also function as flow delivery devices after fabrication. Validation of channel function and smoothness can be accomplished by comparing experimental data to theoretical models. One model was previously developed by the author to predict the incipient motion of a glass sphere in contact with a perfectly smooth PDMS surface and deviations from the model are expected to be a function of channel roughness. The data collected in the present channels show fairly good agreement with the theoretical model, indicating a relatively smooth and consistent surface. In addition, detailed SEM images of the channel showed that the internal surface was qualitatively very smooth.
Optimal electro-optic sensor configuration for phase noise limited, remote field sensing applications
Authors: Garzarella A. , Qadri S. B. , Wu Dong Ho
Published: June 2009

Electro-optic (EO) sensors, used for the nonperturbative detection of electric fields, are typically configured to modulate an optical probe beam along a crystal direction in which the EO tensor coefficient is largest. However in fiber optic EO sensors, such configurations can be strongly limited by phase noise and cumbersome compensation optics. Our results demonstrate that a greater signal to noise ratio can be achieved by modulating along a crystal direction of low static birefringence, even when the active EO tensor coefficient is several times smaller.
Revisiting the origin of open circuit voltage in nanocrystalline-TiO2/polymer heterojunction solar cells
Authors: Al-Dmour H. , Taylor D. M.
Published: June 2009

Recent reports suggest that the open circuit voltage, VOC, in polymeric heterojunction solar cells is determined by the energy difference between the highest occupied molecular orbital of the electron donor and the lowest unoccupied molecular orbital of the electron acceptor. Here we show that in solar cells formed from nanocrystalline titanium dioxide (nc-TiO2) and poly(3-hexylthiophene) (P3HT), VOC may arise from a depletion region at the nc-TiO2/P3HT interface, which only forms in the presence of oxygen. Under illumination in vacuum, photovoltaic behavior is swamped by a significant increase in photoconduction enabled by reduced electron trapping in the absence of oxygen.
Excitation and focusing of terahertz surface plasmons using a grating coupler with elliptically curved grooves
Authors: Gaborit Gwenael , Armand Damien , Coutaz Jean-Louis , Nazarov Maxim , Shkurinov Alexander
Published: June 2009

Using a diffraction grating with elliptically curved grooves engraved at the top of an aluminum slab, surface plasmons in the terahertz frequency range are efficiently excited with an incoming parallel beam and focused over the metal surface down to the diffraction limit. At 0.5 THz, the lateral confinement of the surface plasmon is 1 mm while its extension in air is 0.74 mm, much smaller than the calculated value for a semi-infinite substrate having the conductivity of bulk aluminum.
A Historical Note on Illusory Contours in Shadow Writing
Authors: Vezzani Stefano , Marino Barbara F M
Published: June 2009

It is widely accepted that illusory contours have been first displayed and discussed by Schumann (1900, Zeitschrift für Psychologie und Physiologie der Sinnesorgane23 1–32). Here we show that, before him, Jastrow (1899, Popular Science Monthly54 299–312) produced illusory contours consisting of a shadow word. A brief history of shadow writing in psychological literature from Jastrow to Brunswik is presented, in which the contributions of Pillsbury, Warren, Koffka, and Benussi are examined.
Sexual and Food Preference in Apotemnophilia and Anorexia: Interactions between ‘Beliefs' and ‘Needs' Regulated by Two-Way Connections between Body Image and Limbic Structures
Authors: Ramachandran Vilayanur S , Brang David , McGeoch Paul D , Rosar William
Published: June 2009

Apotemnophilia straddles the boundary between neurology and psychiatry. It is a condition in which individuals experience the strong and specific desire for amputation of a healthy limb. Research suggests this disorder may be of neurological origin, specifically that the body image centers of the brain lack a cortical representation for a particular limb. A curious aspect of this condition is that sufferers often report an attraction to amputees in addition to desiring their own limb be removed. We postulate that sexual ‘aesthetic preference’ for certain body morphology is dictated in all individuals in part by the cortical representation of one's body image.
A Case of Quasi-Infinite Visual Acuity and Illusory Size
Authors: Harmening Wolf M
Published: June 2009

In certain real-life situations, moiré patterns can enhance the observer's ability to resolve fine spatial detail of solid structures, theoretically to unlimited degrees. An example of such a situation can be seen in traffic signs on the M25 motorway around London. Moreover, owing to the interferential nature of the moiré pattern, its angular physical size is independent of observer distance, and thus creates an apparent size discrepancy: the closer you get, the smaller the size of the pattern appears to be—an illusory situation resembling Michael Ende's tale of the pseudo-giant Mr Tur Tur.
Polyacrylamide-gel Electrophoresis of Enzymes during Morphogenesis of Sclerotia of Sclerotinia sclerotiorum
Authors: Wong A. L. , Willetts H. J.
Published: June 2009

Succinate dehydrogenase (SDH) and glucose-6-phosphate dehydrogenase (Glu-6-PDH) from Sclerotinia sclerotiorum (Lib.) de Bary were moderately active in submerged mycelium while in non-sclerotial aerial mycelium arylesterase and acid phosphatase were very active. In sclerotial initials, glyceraldehyde-3-phosphate dehydrogenase (Gly-3-PDH) and SDH were at their highest level of activity, Glu-6-PDH and phosphogluconate dehydrogenase (PGDH) were moderately active, laccase activity increased markedly, and tyrosinase was detected for the first time, its activity being moderate. In young compacting sclerotia, the activities of Glu-6-PDH and PGDH increased, Gly-3-PDH and SDH showed lowered activities, and laccase activity decreased. Suppression of the glycolytic Krebs-cycle pathway and the stimulation of the pentose phosphate pathway seem important during the compaction and maturation of sclerotia. Tyrosinase may be involved in sclerotial initiation.
A Method of Isolating Anucleated Yeast Protoplasts Unable to Synthesize the Glucan Fibrillar Component of the Wall
Authors: Kopecká Marie , Gabriel M. , Nečas O.
Published: June 2009

A mixture of nucleated and anucleated protoplasts was produced from log-phase Saccharomyces cerevisiae by the use of snail enzymes. The mixture was separated by centrifugation, and anucleated protoplasts were studied by means of light and electron microscopy. Anucleated protoplasts did not synthesize glucan fibrils even though they seemed to contain all other basic structures in their cytoplasm, and the structure of the plasma membrane was unchanged. This was in sharp contrast to ordinary nucleated protoplasts which synthesized glucan fibrils even after inhibition of protein synthesis by cycloheximide. The reason for this behaviour of anucleated protoplasts is not clear. Such anucleated yeast protoplasts represent the first example of uniform anucleated fungi produced by a reproducible method.
The Isolation of Rhapidosomes from the Blue-green Alga, Spirulina
Authors: Chang Helen Y. Y. , Allen Mary M.
Published: June 2009

Rhapidosomes, similar to those found in the flexibacterium Saprospira, have been isolated in the blue-green algal counterpart of Saprospira, Spirulina. They have been partially purified by renografin density gradients and shown to contain protein and a negligible amount of nucleic acid. Mitomycin C induction causes an increase in the number of rhapidosomes as well as an increase in the number of intact rhapidosome particles.
The Action of Bacteriophage Ω8 on Two Strains of Escherichia coli 08
Authors: Wallenfels Barbara , Jann K.
Published: June 2009

Bacteriophage Ω8 is propagated in Escherichia coli E56b (08: K27-:H-), a non-capsulated strain. Another non-capsulated strain, E. coli 2398 (08:K?-:H-), is killed by bacteriophage Ω8 without phage propagation. This strain was formerly believed to be E. coli 093:K?-:H-, cross-reacting with strain E56b. We have established chemical and serological identity of the 08-specific lipopolysaccharides of the two strains.

The 08-specific lipopolysaccharides of both strains inhibited the infection of Escherichia coli E56b with bacteriophage Ω8 equally well. The adsorption rate constants of Ω8 were identical for the two strains of E. coli 08. Evidence was obtained with 32P-labelled bacteriophage Ω8 for penetration of viral DNA into both bacterial strains. In host strain E56b, phage particle synthesis occurred normally. In strain 2398 the viral DNA was not degraded but its expression was blocked. The killing effect of Ω8 on E. coli strain 2398 is supposed to be due to damage of the cytoplasmic membrane, which could not be reversed under the influence of viral information. This was indicated by a blockage of cellular respiration, β-galactoside transport and RNA as well as protein synthesis.
The Pyruvate Carboxylase of Verticillium albo-atrum
Authors: Hartman R. E. , Keen N. T.
Published: June 2009

The pyruvate carboxylase of Verticillium albo-atrum had a pH optimum of 7·8 and a specific requirement for ATP. At the optimum pH, magnesium ions were required for maximum activity, while at pH 6·8 manganese was more effective than magnesium. Potassium was stimulatory while sodium was ineffective. Avidin and p-chloromercuribenzoate strongly inhibited the enzyme while biotin and dithiothreitol, respectively, reversed the effect of the inhibitors. Aspartate and oxalacetate were inhibitory while acetyl-CoA and CoA reversed the inhibition by aspartate. These cofactors were ineffective in the absence of aspartate. None of the tested metabolic intermediates was stimulatory to pyruvate carboxylase activity while NADP+ and 2,3-diphosphoglycerate were the most effective inhibitors (75%) at a concentration of 6·7 mM. Levels of pyruvate carboxylase in cells grown on glucose, acetate, malate, xylose, glycerol or aspartate differed only slightly. The data indicated that the physiological role of pyruvate carboxylase in V. albo-atrum is the anaplerotic biosynthesis of C4 Krebs-cycle intermediates from pyruvate.
Studies on the α-L-Arabinofuranosidase Complex from Sclerotinia fructigena in Relation to Brown Rot of Apple
Authors: Laborda F. , Archer S. A. , Fielding A. H. , Byrde R. J. W.
Published: June 2009

α-L-Arabinofuranosidase (AF) was detected in apple fruitlets experimentally infected by Sclerotinia fructigena. In extracts of such fruitlets, three AF isoenzymes were separated by preparative isoelectric focusing. When the fungus was grown in shake culture with different carbon sources, AF was detected in each culture filtrate and mycelial homogenate. Although fungus growth and total AF varied with the carbon source, the AF isoenzyme pattern was similar in each instance to that obtained when grown on sodium polypectate.

Each of the partially purified AF isoenzymes behaved differently in substrate specificity and inhibitor studies; however, each showed a specificity for α-L-arabino-furanosides. The two extracellular AF isoenzymes released monomeric arabinose when incubated with araban or apple cell walls. External AF III (pI 6·5) was more active on a substrate of apple cell wall material than external AF I (pI 3·0). The latter form of the enzyme was less susceptible to inhibition by either oxidized or unoxidized apple juice. Two isolates of Sclerotinia fructigena with low growth rate in vivo secreted no AF III in vitro.
The Effects of the Carbon Source on Glutamate Dehydrogenase Activities in Aspergillus nidulans
Authors: Hynes M. J.
Published: June 2009

The NADP-specific glutamate dehydrogenase (NADP-GDH) activity of Aspergillus nidulans was rapidly lost from cultures starved for a carbon source. This loss of NADP-GDH was blocked by protein synthesis inhibitors. Glutamate repressed NADP-GDH but did not cause rapid loss of activity. Since NADP-GDH is involved in the participation of ammonium in the regulation of nitrogen metabolism, the loss of NADP-GDH activity accompanying carbon starvation may be important in the interaction between carbon and nitrogen metabolism. Increased NAD specific glutamate dehydrogenase activity (NAD-GDH) was observed when mycelium was transferred to medium lacking glucose. The increase in NAD-GDH activity was greatest when glutamate was present. Protein synthesis inhibitors did not prevent this increase in activity.

Two mutants, amdT102 and amdT19, which are altered in regulation of nitrogen metabolism, are similar to the wild-type strain with regard to regulation of NADP-GDH and NAD-GDH.
R factors from Providence
Authors: Hedges R. W.
Published: June 2009

Of more than 100 R factors transferred from naturally occurring Providence strains, approximately 60 % belonged to the A-C compatibility complex. Plasmids of groups F1, J, N, P and X, and the prototype of a new group G were also transferred. The Providence R factor set differs from those of Proteus rettgeri and P. morganii most strikingly in the abundance of plasmids of the A-C group and the infrequency of N group plasmids.
The Wall Structure of Schizosaccharomyces pombe
Authors: Bush D. A. , Horisberger M. , Horman I. , Wursch P.
Published: June 2009

The wall structure of the fission yeast Schizosaccharomyces pombe, examined by enzymic techniques, consists of a galactomannan, an α-glucan and β-glucan. The structures of the α-glucan and galactomannan were investigated by methylation. The wall structure is discussed in relation to the taxonomic position of the genus Schizosaccharomyces.
The Phosphoenolpyruvate Carboxykinase of Verticillium albo-atrum
Authors: Hartman R. E. , Keen N. T.
Published: June 2009

Partially purified phosphoenolpyruvate carboxykinase from Verticillium albo-atrum had a pH optimum of 6·2 and required manganese for maximum activity, having lesser activity with iron or cobalt. Sodium and potassium ions were slightly stimulatory. Adenosine-5′-diphosphate increased activity and inosine-5′-diphosphate supported low activity, but other nucleotides were ineffective. Inhibition of the enzyme by p-chloromercuribenzoate was partially reversed by dithiothreitol. Avidin had no effect on enzyme activity. Oxalacetate slightly stimulated the enzyme and NADP+ strongly inhibited, but aspartate and acetyl-CoA showed no effect. Low levels of phosphoenolpyruvate carboxykinase were present in cells grown on glucose, xylose, or glycerol. Aspartate, pyruvate, and acetate as carbon sources resulted in higher levels of activity and malate gave the highest. The data indicate that the enzyme functions physiologically in the gluconeogenic conversion of oxalacetate to phosphoenolpyruvate.
A Study of the Kinetics of Hyphal Extension and Branch Initiation of Fungal Mycelia
Authors: Trinci A. P. J.
Published: June 2009

Growth of Mucor hiemalis, Geotrichum candidum, Aspergillus nidulans, Neurospora crassa and Penicillium chrysogenum was studied by time lapse photography. The total hyphal length of the mycelium of each species increased at an exponential rate; in M. hiemalis exponential growth continued until the mycelium had a total hyphal length in excess of 10 mm. After spore germination there was an initial phase of discontinuous tip production followed by a phase of ‘continuous’ tip production. The hyphal length and number of tips possessed by a mycelium increased exponentially at approximately the same specific growth rate. The amplitude of the oscillations in the length of the hyphal growth unit of a mycelium decreased progressively during mycelial growth and eventually the growth unit attained a more or less constant value. The results support the hypothesis that mycelial growth involves the duplication of a ‘growth unit’ which consists of a tip and a certain mean length of hypha.
Polyamine, Magnesium and Ribonucleic Acid Levels in Steady-state Cultures of the Mould Aspergillus nidulans
Authors: Bushell M. E. , Bull A. T.
Published: June 2009

Results from experiments in vitro strongly suggest that major roles can be ascribed to polyamines in controlling the stability, activity and synthesis of ribonucleic acids. Furthermore, functional substitution of polyamines for inorganic cations, particularly magnesium ions, in cell-free protein synthesis is well substantiated (see Cohen, 1971). Recently we have been analysing the effects of culture conditions on the chemical composition of Aspergillus nidulans and have found fluctuations in polyamine and magnesium concentrations in response to a changing environment, while biomass and RNA remained constant. This paper describes the influence of steady-state growth rate on hyphal concentrations of spermidine, spermine and Mg2+ ions.
Alteration of Macromolecular Synthesis and Membrane Permeability by a Streptococcus sanguis Bacteriocin
Authors: Schlegel R. , Slade H. D.
Published: June 2009

Although the elaboration of bacteriocins by streptococci has been described previously (Brock & David, 1963; Kuttner, 1966; Kelstrup & Gibbons, 1969; Overturf & Mortimer, 1970; Kramer & Brandis, 1972), few attempts have been made to purify and characterize these bactericidal factors (Kramer & Brandis, 1972). Streptococcus sanguis (strain Challis) produces a streptocin which is lethal for Streptococcus sanguis (strain Wicky) and can be purified by ammonium sulphate fractionation and Sephadex G-100 column chromatography. We exposed sensitive strain Wicky cells to Challis streptocin and observed macromolecular synthesis and membrane permeability.
The Spontaneous Release of Somatic Antigen from Vibrio cholerae
Authors: Pike R. M. , Chandler Cleo H.
Published: June 2009

Culture supernatants of Ogawa and Inaba strains of Vibrio cholerae contained, judging by their ability to inhibit the vibriocidal action of homologus The release of antigen was readily detectable during the exponential phase of growth. The release of antigen was not entirely dependent on cell lysis or death, nor was the decrease in the pH of the medium during the early phase of growth responsible for antigen release. As the concentration of antigen increased, protein, carbohydrate and 260 nm-absorbing material increased in dialysed supernatants but an intracellular enzyme, malate dehydrogenase, was not detectable up to 40 h growth. The antigen demonstrable in supernatants at 40 h accounted for more than a third of the total capacity of the cultures to inhibit vibriocidal antibody. Ethylenediaminetetra-acetate not only increased the release of antigen in suspensions of agar-grown vibrios but also released intracellular substances. Supernatants of Ogawa cultures were distinctly more inhibitory than Inaba supernatants but both were equally effective in gel diffusion precipitation.
Localization of α-L-Arabinofuranosidase and Acid Phosphatase in Mycelium of Sclerotinia fructigena
Authors: Hislop E. C. , Barnaby Vivien M. , Shellis Claire , Laborda F.
Published: June 2009

α-L-Arabinofuranosidase (AF) and acid p-nitrophenyl phosphatase (AP) were secreted by Sclerotinia fructigena grown in a liquid pectin/ammonium tartrate medium. ‘Gentle’ mechanical manipulation of mycelium solubilized most of the AF and much of the AP, while brief acid treatment considerably inactivated both enzymes. Both enzymes were present predominantly in a soluble form in homo-genates prepared for subcellular fractionation, but some particulate activity of both was recovered from a sucrose density gradient in a fraction which also contained mitochondria. Azo-dye techniques with appropriate 1-naphthyl derivatives as substrates and p-(acetoxymercuric) aniline diazotate as capturing agent produced similar staining patterns for both enzymes in the light and electron microscopes, but the distribution of β-glycerophosphatase activity as visualized by the Gomori technique was more variable. A proportion of the activity of the enzymes remaining after fixation was located between the plasmalemma and the hyphal wall, in vacuoles in the cytoplasm, and in spherosome-like bodies. Some evidence was obtained for structure-linked latency of both enzymes and for their secretion by a process of reverse pinocytosis.
Lysis Induced by Sodium Ion and Its Relation to Lytic Enzyme Systems in Clostridium saccharoperbutylacetonicum
Authors: OGATA S. , HONGO M.
Published: June 2009

Summary: Growing Clostridium saccharoperbutylacetonicum was lysed by sodium ion concentrations above o'I M (maximum effect at 0.3 M). The rate of lysis depended on the age of the culture. The most rapid lysis occurred in organisms from logarithmically growing cultures which were incubated for 3 to 5 h; organisms from stationary phase cultures were completely resistant to Na+-induced lysis. Sodium ion-induced lysis was related to autolysis of the organisms and was greatly affected by pH and temperature. The optimum pH was about 6.0, and the optimum temperature 35°C. Various chemical inhibitors, including known enzyme inhibitors (such as Cu2+ and p-chloromercuribenzoate) and fixative agents (such as formalin and glutaraldehyde), inhibited the lysis, while organisms whose growth had been inhibited by antibiotics such as tetracycline, were also resistant to Na+-induced lysis. The lysate produced by Na+-treatment itself had lytic activity on isolated walls, thought to be due to its content of autolysin.

About 3o to 6o min after mitomycin C treatment (which induced the production of the phage tail-like bacteriocin clostocin O), the organisms were temporarily resistant to Na+-induced lysis. However the organisms reverted to the state of high sensitivity to Na+ when clostocin O-associated endolysin was produced. We suggest that Na+-induced lysis is due to the action of wall lytic enzymes such as autolysin and clostocin O-endolysin.
The Inducible Quinate-Shikimate Catabolic Pathway in Neurospora crassa: Genetic Organization
Authors: CHALEFF R. S.
Published: June 2009

Summary: In Neurospora crassa the conversion of quinate and shikimate to protocatechuate is catalysed by three inducible enzymes. Previous studies have demonstrated that the qa-1 locus encodes a multimeric regulatory protein which is required for the synthesis of the three catabolic enzymes. The qa-2 locus has been shown to encode catabolic dehydroquinase. This work defines two new classes of mutants. The qa-3 locus is the structural gene for a bifunctional enzyme which catalyses the dehydrogenation of quinate and shikimate. Mutants of the qa-4 class specifically lack 5-dehydroshikimate dehydrase. Alleles of the four different qa mutant classes are tightly clustered and are located to the left of me-7 in L.G. VII.
Genetic Control of some Metabolic Modifications during the Sporulation of Saccharomyces cerevisiae Hansen
Authors: VEZINHET FRANCOISE , ROGER M. , PELLECUER MONIQUE , GALZY P.
Published: June 2009

Summary: The biochemical modifications of two yeast strains, a/α and α/α, have been studied during incubation in a sporulation medium. The increases in dry cell weight, protein, carbohydrate and lipid contents, as well as the variation in respiration rate are quite similar for the two strains. Mating type gene control of sporulation is discussed.
Host Specificity of DNA in Haemophilus influenzae: The Restriction and Modification Systems in Strains Rb and Rf
Authors: PIEKAROWICZ A. , KAUC L. , GLOVER S. W.
Published: June 2009

Summary: Haemophilus influenzae Rf possesses two distinct host specificity systems F1 and F2 each of which is able to restrict and modify Haemophilus phage HP1c1, while strain Rb possesses only one system, B. Among restriction-deficient mutants isolated from strain Rf, the r-m+ as well as r-m- phenotypes for these two systems were obtained after either one or two mutational steps. The F1 system was introduced into H. influenzae Rd by genetic transformation to show that the D1 and F1 systems are not allelic.
Host Specificity of DNA in Haemophilus influenzae: Similarity between Host-specificity Types of Haemophilus influenzae Re and Rf
Authors: PIEKAROWICZ A. , KALINOWSKA JULITA
Published: June 2009

Summary: Strain Re of Haemophilus influenzae carries two genetically distinct host-specificity systems E1 and E2 each of which is able to restrict Haemophilus phage HP1c1 and each of which confers a specific modification upon phage grown in strain Re. These two systems are apparently identical to the host-specificity systems of H. influenzae Rf F1 and F2.
Studies on a Bactericidal Substance Produced by Group A Streptococci
Authors: WOLFF L. F. , DUNCAN J. L.
Published: June 2009

Summary: During bacteriophage studies of group A streptococci, some strains produced an inhibitory substance active against other group A strains. The inhibitory material was not found in broth cultures and could only be extracted from cultures grown in semi-solid agar; its activity was assayed by the inhibition of growth and killing of a sensitive group A strain, 12203. Viable counts showed that 2 h exposure to the factor at 37°C produced greater than 90% inhibition and more than 60% killing of the treated culture. Turbidimetric measurements indicated no gross lysis of the sensitive culture and a dose-response curve demonstrated that approximately two bactericidal factor molecules were sufficient to inactivate a colony-forming unit of strain 12203. The inhibitory factor was of low molecular weight as judged by its diffusibility; it was concentrated by lyophilization and partially purified by gel filtration on G-10 Sephadex. The factor was resistant to proteolytic enzymes, nucleases and lipase as well as reducing and oxidizing conditions. Activity was lost at 60°C, but the factor was stable at ---70°C. The bactericidal substance was stable within the pH range 2 to 12. These properties, as well as the wide range of activity of the bactericidal factor on several Gram-positive and -negative organisms, suggest that it is an inhibitory substance other than a bacteriocin.
Genetic Analysis in a Melanin-producing Streptomycete, Streptomyces glaucescens
Authors: BAUMANN R. , HÜTTER R. , HOPWOOD D. A.
Published: June 2009

Summary: Using crossing and analysis procedures similar to those applied to Streptomyces coelicolor
a3(2), several auxotrophic and streptomycin-resistant markers were located on a circular linkage map of the melanin-producing Streptomyces glaucescens, strain eth22794. The linkage map of S. glaucescens is similar to that of S. coelicolor ≪g≫a≪/g≫3(2), in the sequence of markers and in the presence of two long silent regions.