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State Transitions (state + transition)

Distribution by Scientific Domains

Physics and Astronomy	41%
Life Sciences	34%
Information Science and Computing	6%
Engineering	6%
Chemistry	6%

Distribution within Physics and Astronomy

Solid State Physics	65%
Astronomy & Astrophysics	31%

Kinds of State Transitions

ground state transition

Selected Abstracts

ACCLIMATION TO VARYING LIGHT QUALITIES: TOWARD THE FUNCTIONAL RELATIONSHIP OF STATE TRANSITIONS AND ADJUSTMENT OF PHOTOSYSTEM STOICHIOMETRY

JOURNAL OF PHYCOLOGY, Issue 4 2005
Thomas PfannschmidtArticle first published online: 31 AUG 200
No abstract is available for this article. [source]

State transitions of Vibrio parahaemolyticus VBNC cells evaluated by flow cytometry,

CYTOMETRY, Issue 5 2008
Tania Falcioni
Abstract Background Vibrio parahaemolyticus, in response to environmental conditions, may be present in a viable but nonculturable state (VBNC), which can still be responsible for cases of infectious diseases in humans. Methods The characterization of the cellular states of V. parahaemolyticus during entry into, persistence in, and resuscitation from the VBNC state, was assessed through plate culture method and epifluorescence microscope evaluation of actively respiring cells. Flow cytometry (FCM) in combination with SYBR Green I (SG) and propidium iodide allowed us to distinguish between viable, dead, and damaged-cells. Immunofluorescence labeling detected by FCM was used to study changes in antibody affinity. Results Two groups of bacteria, one with High Nucleic Acid (HNA) and one having Low Nucleic Acid (LNA) content, were differentiated using SG and FCM and each was correlated with cell viability. With the aging of the microcosm, the LNA bacteria population increased while the HNA population gradually disappeared. Cytofluorimetric immunofluorescence analyses showed that the bacterial cell levels dropped from 95% at day 0 to 40% at day 26 and by day 29, antibody affinity was virtually lost. FCM analyses of light scatter signals expressed by cell population highlighted morphological changes indicating a reduction in cell size, as also shown by scanning electron microscopy images and variations in cell structure. Conclusions The methodology used has provided useful data in relation to the state transitions of V. parahaemolyticus regarding cell viability, antigenic surface components, and the quantification of morphological variations during its entry into the VBNC state. © 2008 Clinical Cytometry Society [source]

State transitions and physicochemical aspects of cryoprotection and stabilization in freeze-drying of Lactobacillus rhamnosus GG (LGG)

JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008
K.S. Pehkonen
Abstract Aims:, The frozen and dehydrated state transitions of lactose and trehalose were determined and studied as factors affecting the stability of probiotic bacteria to understand physicochemical aspects of protection against freezing and dehydration of probiotic cultures. Methods and Results:,Lactobacillus rhamnosus GG was frozen (,22 or ,43°C), freeze-dried and stored under controlled water vapour pressure (0%, 11%, 23% and 33% relative vapour pressure) conditions. Lactose, trehalose and their mixture (1 : 1) were used as protective media. These systems were confirmed to exhibit relatively similar state transition and water plasticization behaviour in freeze-concentrated and dehydrated states as determined by differential scanning calorimetry. Ice formation and dehydrated materials were studied using cold-stage microscopy and scanning electron microscopy. Trehalose and lactose,trehalose gave the most effective protection of cell viability as observed from colony forming units after freezing, dehydration and storage. Enhanced cell viability was observed when the freezing temperature was ,43°C. Conclusions:, State transitions of protective media affect ice formation and cell viability in freeze-drying and storage. Formation of a maximally freeze-concentrated matrix with entrapped microbial cells is essential in freezing prior to freeze-drying. Freeze-drying must retain a solid amorphous state of protectant matrices. Freeze-dried matrices contain cells entrapped in the protective matrices in the freezing process. The retention of viability during storage seems to be controlled by water plasticization of the protectant matrix and possibly interactions of water with the dehydrated cells. Highest cell viability was obtained in glassy protective media. Significance and Impact of the Study:, This study shows that physicochemical properties of protective media affect the stability of dehydrated cultures. Trehalose and lactose may be used in combination, which is particularly important for the stabilization of probiotic bacteria in dairy systems. [source]

Rheological characteristics of solid,fluid transition in dry granular dense flows: A thermodynamically consistent constitutive model with a pressure-ratio order parameter

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2010
Chung Fang
Abstract Dry granular flows are characterized as quasi-static, dense and collisional states by the interactions among the grains, which is indexed macroscopically by an internal variable, called the order parameter defined as the square root of the static pressure to the total pressure. The solid,fluid state transition is regarded as a second-order phase transition process, and is described by a kinematic evolution of the order parameter. The thermodynamic analysis, based on the Müller,Liu entropy principle, is employed to deduce the equilibrium responses of the constitutive equations, while the dynamic responses are postulated on the basis of a quasi-linear and the second-order Ginzburg,Landau phase transition theories. The obtained model is applied to study the rheological characteristics of a dry granular dense flow between two infinite parallel plates, of which the results are compared with those from DEM simulations to estimate the model validity. The present study provides a general framework for the theoretical justifications on the thermodynamic consistencies of order-parameter-based constitutive models, and can be extended to flows in quasi-static or collisional states. Copyright © 2009 John Wiley & Sons, Ltd. [source]

State transitions and physicochemical aspects of cryoprotection and stabilization in freeze-drying of Lactobacillus rhamnosus GG (LGG)

Investigation of freezing- and thawing-induced biological, chemical, and physical changes to enoxaparin solution

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009
Rahul P. Patel
Abstract This study investigated the effect of freezing and thawing on the biological, physical, and chemical properties of enoxaparin solution. Solutions were frozen and thawed under different conditions, in the presence or absence of dimethyl sulfoxide (DMSO) or 1,2-propanediol (1,2-PD), and the antifactor Xa (AFXa) activity was determined. Enoxaparin solution lost more than 60% of its AFXa activity when thawed rapidly after freezing at ,196°C. The loss of AFXa activity was less with higher freezing temperatures and increased with the number of freeze/thaw cycles, but was independent of the duration of freezing. Slow freezing to ,196°C with rapid thawing, or rapid freezing with slow thawing, resulted in negligible loss of AFXa activity. The loss of AFXa activity did not involve the loss of N -sulfate groups, the breakdown of glycosidic bonds or the glassy state transition. Controlling the freezing or thawing conditions, dilution with water or addition of a small percentage of DMSO ameliorated the loss of enoxaparin AFXa activity. The loss in AFXa activity was found by size exclusion chromatography to be primarily due to aggregation and was reversed by sonication in the presence of DMSO. These results may provide insight into solutions for the long-term storage of concentrated or diluted enoxaparin. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1118,1128, 2009 [source]

Jets from black hole X-ray binaries: testing, refining and extending empirical models for the coupling to X-rays

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009
R. P. Fender
ABSTRACT In this paper we study the relation of radio emission to X-ray spectral and variability properties for a large sample of black hole X-ray binary systems. This is done to test, refine and extend , notably into the timing properties , the previously published ,unified model' for the coupling of accretion and ejection in such sources. In 14 outbursts from 11 different sources we find that in every case the peak radio flux, on occasion directly resolved into discrete relativistic ejections, is associated with the bright hard to soft state transition near the peak of the outburst. We also note the association of the radio flaring with periods of X-ray flaring during this transition in most, but not all, of the systems. In the soft state, radio emission is in nearly all cases either undetectable or optically thin, consistent with the suppression of the core jet in these states and ,relic' radio emission from interactions of previously ejected material and the ambient medium. However, these data cannot rule out an intermittent, optically thin, jet in the soft state. In attempting to associate X-ray timing properties with the ejection events we find a close, but not exact, correspondence between phases of very low integrated X-ray variability and such ejections. In fact the data suggest that there is not a perfect one-to-one correspondence between the radio, X-ray spectral or X-ray timing properties, suggesting that they may be linked simply as symptoms of the underlying state change and not causally to one another. We further study the sparse data on the reactivation of the jet during the transition back to the hard state in decay phase of outbursts, and find marginal evidence for this in one case only. In summary we find no strong evidence against the originally proposed model, confirming and extending some aspects of it with a much larger sample, but note that several aspects remain poorly tested. [source]

Constraints on jet X-ray emission in low/hard-state X-ray binaries

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2005
Thomas J. Maccarone
ABSTRACT We show that the similarities between the X-ray properties of low-luminosity accreting black holes and accreting neutron stars, combined with the differences in their radio properties, argue that the X-rays from these systems are unlikely to be formed in the relativistic jets. Specifically, the spectra of extreme island-state neutron stars and low/hard-state black holes are known to be quite similar, while the power spectra from these systems are known to show only minor differences beyond what would be expected from scaling the characteristic variability frequencies by the mass of the compact object. The spectral and temporal similarities thus imply a common emission mechanism that has only minor deviations from having all key parameters scaling linearly with the mass of the compact object, while we show that this is inconsistent with the observations that the radio powers of neutron stars are typically about 30 times lower than those of black holes at the same X-ray luminosity. We also show that an abrupt luminosity change would be expected when a system makes a spectral state transition from a radiatively inefficient jet-dominated accretion flow to a thin disc-dominated flow, but that such a change is not seen. [source]

Temperature dependent high resolution resonant spectroscopy on a charged quantum dot

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2009
M. Kroner
Abstract We present temperature dependent high resolution resonant optical spectroscopy on a single, negatively charged InGaAs quantum dot. We performed laser transmission measurements yielding the natural linewidth of the excitonic ground state transition of a quantum dot in a temperature range from 4.2 K up to 25 K. Here, we describe the linewidth evolution and the temperature induced red shift of the resonance energy with simple models based on the exciton,phonon coupling in the quantum dot. The resonant spectroscopy measurements are complemented with results from non-resonant PL measurements on the very same quantum dot. Here we observe a simple linear behavior of the linewidth according to an effect of a fluctuating environment. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Coherent control of ground state excitons in the nonlinear regime within an ensemble of self-assembled InAs quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009
Thomas Moldaschl
Abstract In this work femtosecond spectral hole burning spectroscopy is used to resonantly excite ground state excitons in an ensemble of self-assembled InAs/GaAs quantum dots with a strong pump pulse. Two fundamental coherent nonlinear effects are observed with the aid of the intrinsic time- and frequency resolution of the setup: The low temperature Rabi oscillation of the two-level system associated with the excitonic ground state transition and the observation of two-photon absorption in the surrounding GaAs crystal matrix. The emergence of the latter effect also infers the existence of charged excitons in the nominally undoped QD sample, backed up by the observation of additional spectral holes next to the excitonic transitions. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Photoreflectance investigations of energy level structure of InAs quantum dashes embedded in InGaAs/InGaAlAs quantum well grown on InP substrate

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006
W. Rudno-Rudzi
Abstract Photoreflectance (PR) and photoluminescence measurements have been performed on molecular beam epitaxy grown InAs quantum dashes (QDash) of various sizes, embedded in In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum well (QW), grown on InP substrate. PR response from all relevant parts of the structure, i.e InAs/In0.53Ga0.47As QDashes, InAs/In0.53Ga0.47As/In0.53Ga0.23Al0.24As QW, and In0.53Ga0.23Al0.24As barriers, has been obtained. The lowest energy transition related to the ground state transition in QDashes shifts towards red with the increase in QDash sizes (amount of deposited InAs material) reaching wavelengths longer than for structures without the intermediate QW. The experimental data on the energies of optical transitions combined with the numerical calculation within the effective mass approximation has allowed determining the energy level structure of the entire system, including the values of conduction band offset between InGaAs and InGaAlAs layers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Photocurrent spectroscopy of single InAs/GaAs quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2005
G. Fasching
Abstract In this work, we present a carrier escape study from InAs/GaAs self assembled QD's by the use of photocurrent measurements. As a function of the applied field, we detect a shift of the exciton ground state transition due to the quantum-confined Stark shift. ¿From the measured Stark shift S = 4:3 meV we deduce a exciton dipole moment of p = (4.3 ± 0.2) × 10,29 Cm. The tunneling time, which is directly related to the observed photocurrent linewidth due to , , ,/(2,), changes by a factor of five in the photocurrent regime. The measured linewidth dependency on the electric field is modelled by a simple 1D WKB approximation for the tunneling process, which shows that the energetic position of the wetting layer is important for the measured tunneling time out of the dot. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Polarization controlled edge emission from columnar InAs/GaAs self-assembled quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003
T. Kita
Abstract Polarization anisotropy of photoluminescence (PL) from the cleaved edge surface of columnar InAs/GaAs self-assembled quantum dots (QDs) has been investigated. The columnar QDs were fabricated by closely stacking the Stranski-Krastanov-mode InAs-island layers. PL peak energy and anisotropy of the PL polarization sensitively depends on the stacking layer number. Whereas the single-island-layer sample shows strong transverse-electric (TE)-mode PL, the PL-intensity ratio of TE-mode PL to transverse-magnetic (TM)-mode PL decreases with increasing stacking layer number. The polarization inversion of TE/TM-mode PL-intensity ratio has been accomplished beyond the stacking layer number of 9. The polarization spectra of the columnar QDs with >9 stacking layers indicate that TM-mode becomes dominant near the ground state transition. [source]

MINIMAL VALID AUTOMATA OF SAMPLE SEQUENCES FOR DISCRETE EVENT SYSTEMS

ASIAN JOURNAL OF CONTROL, Issue 2 2004
Sheng-Luen Chung
ABSTRACT Minimal valid automata (MVA) refer to valid automata models that fit a given input-output sequence sample from a Mealy machine model. They are minimal in the sense that the number of states in these automata is minimal. Critical to system identification problems of discrete event systems, MVA can be considered as a special case of the minimization problem for incompletely specified sequential machine (ISSM). While the minimization of ISSM in general is an NP-complete problem, various approaches have been proposed to alleviate computational requirement by taking special structural properties of the ISSM at hand. In essence, MVA is to find the minimal realization of an ISSM where each state only has one subsequent state transition defined. This paper presents an algorithm that divides the minimization process into two phases: first to give a reduced machine for the equivalent sequential machine, and then to minimize the reduced machine into minimal realization solutions. An example with comprehensive coverage on how the associated minimal valid automata are derived is also included. [source]

State transitions of Vibrio parahaemolyticus VBNC cells evaluated by flow cytometry,

Dynamics of human neocortex that optimizes its stability and flexibility

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 9 2006
Walter J. Freeman
The electroencephalogram (EEG) in states of awake, sleep, and seizure in a patient with intractable partial complex seizures was recorded through a 1- × 1-cm microgrid of 64 electrodes on the right inferior temporal gyrus during a week-long neurosurgical evaluation. Comparisons with a normal intracranial EEG were perforce from animals. Analytic phase and amplitude from the Hilbert transform gave the temporal resolution needed to resolve EEG spatiotemporal structure. The rest state revealed multiple overlapping patterns of high-frequency coherent oscillations resembling bubbles in boiling water. Bubble diameters gave estimates of the distances across the cortex over which the cortical oscillations were synchronized. Superimposed on these bubbles were large-sized epochs of phase locking with briefly constant frequency and high amplitude. These coordinated analytic phase differences occurred between short periods of high phase variance. The variance gave evidence for state transitions between transiently stable states with constant phase gradients. In sleep these phase patterns persisted with reduced amplitude, occasionally interrupted by long-lasting (,1 s) epochs with no spatial textures in phase and amplitude despite a large increase in amplitude. Seizures had high amplitude 3/s spikes with steep spatial gradients. Onset occurred after pre-ictal reduction in bubble diameters as evidence for large-scale cortical disintegration preceding loss of stability. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 881,901, 2006. [source]

State transitions and physicochemical aspects of cryoprotection and stabilization in freeze-drying of Lactobacillus rhamnosus GG (LGG)

Vertical excitation energies for ribose and deoxyribose nucleosides

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2007
Remmick So
Abstract Vertical excitation energies for DNA and RNA nucleosides are determined with electron structure calculations using the time-dependent density functional theory (TDDFT) method at the B3LYP/6-311++G(d,p) level for nucleoside structures optimized at the same level of theory. The excitation energies and state assignments are verified using B3LYP/aug-cc-pVDZ level calculations. The nature of the first four excited states of the nucleosides are studied and compared with those of isolated bases. The lowest n,* and ,,* transitions in the nucleoside remain localized on the aromatic rings of the base moiety. New low-energy n,* and ,,* transitions are introduced in the nucleosides as a result of bonding to the ribose and deoxyribose molecules. The effect on the low-lying excited state transitions of the binding to phosphate groups at the 5,- and 3,,5,-hydroxyl sites of the uracil ribose nucleoside are also studied. Some implications of these calculations on the de-excitation dynamics of nucleic acids are discussed. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007. [source]

THE ANTARCTIC PSYCHROPHILE, CHLAMYDOMONAS RAUDENSIS ETTL (UWO241) (CHLOROPHYCEAE, CHLOROPHYTA), EXHIBITS A LIMITED CAPACITY TO PHOTOACCLIMATE TO RED LIGHT,

JOURNAL OF PHYCOLOGY, Issue 4 2005
Rachael M. Morgan-Kiss
The psychrophilic Antarctic alga, Chlamydomonas raudensis Ettl (UWO241), grows under an extreme environment of low temperature and low irradiance of a limited spectral quality (blue-green). We investigated the ability of C. raudensis to acclimate to long-term imbalances in excitation caused by light quality through adjustments in photosystem stoichiometry. Log-phase cultures of C. raudensis and C. reinhardtii grown under white light were shifted to either blue or red light for 12 h. Previously, we reported that C. raudensis lacks the ability to redistribute light energy via the short-term mechanism of state transitions. However, similar to the model of mesophilic alga, C. reinhardtii, the psychrophile retained the capacity for long-term adjustment in energy distribution between PSI and PSII by modulating the levels of PSI reaction center polypeptides, PsaA/PsaB, with minimal changes in the content of the PSII polypeptide, D1, in response to changes in light quality. The functional consequences of the modulation in PSI/PSII stoichiometry in the psychrophile were distinct from those observed in C. reinhardtii. Exposure of C. raudensis to red light caused 1) an inhibition of growth and photosynthetic rates, 2) an increased reduction state of the intersystem plastoquinone pool with concomitant increases in nonphotochemical quenching, 3) an uncoupling of the major light-harvesting complex from the PSII core, and 4) differential thylakoid protein phosphorylation profiles compared with C. reinhardtii. We conclude that the characteristic low levels of PSI relative to PSII set the limit in the capacity of C. raudensis to photoacclimate to an environment enriched in red light. [source]

Stochastic modeling of usage patterns in a web-based information system

JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 7 2002
Hui-Min Chen
Users move from one state (or task) to another in an information system's labyrinth as they try to accomplish their work, and the amount of time they spend in each state varies. This article uses continuous-time stochastic models, mainly based on semi-Markov chains, to derive user state transition patterns (both in rates and in probabilities) in a Web-based information system. The methodology was demonstrated with 126,925 search sessions drawn from the transaction logs of the University of California's MELVYL® library catalog system (www.melvyl.ucop.edu). First, user sessions were categorized into six groups based on their similar use of the system. Second, by using a three-layer hierarchical taxonomy of the system Web pages, user sessions in each usage group were transformed into a sequence of states. All the usage groups but one have third-order sequential dependency in state transitions. The sole exception has fourth-order sequential dependency. The transition rates as well as transition probabilities of the semi-Markov model provide a background for interpreting user behavior probabilistically, at various levels of detail. Finally, the differences in derived usage patterns between usage groups were tested statistically. The test results showed that different groups have distinct patterns of system use. Knowledge of the extent of sequential dependency is beneficial because it allows one to predict a user's next move in a search space based on the past moves that have been made. It can also be used to help customize the design of the user interface to the system to facilitate interaction. The group CL6 labeled "knowledgeable and sophisticated usage" and the group CL7 labeled "unsophisticated usage" both had third-order sequential dependency and had the same most-frequently occurring search pattern: screen display, record display, screen display, and record display. The group CL8 called "highly interactive use with good search results" had fourth-order sequential dependency, and its most frequently occurring pattern was the same as CL6 and CL7 with one more screen display action added. The group CL13, called "known-item searching" had third-order sequential dependency, and its most frequently occurring pattern was index access, search with retrievals, screen display, and record display. Group CL14 called "help intensive searching," and CL18 called "relatively unsuccessful" both had third-order sequential dependency, and for both groups the most frequently occurring pattern was index access, search without retrievals, index access, and again, search without retrievals. [source]

Parallel tracks in infrared versus X-ray emission in black hole X-ray transient outbursts: a hysteresis effect?

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
David M. Russell
ABSTRACT We report the discovery of a new hysteresis effect in black hole X-ray binary state transitions, that of the near-infrared (NIR) flux (which most likely originates in the jets) versus X-ray flux. We find, looking at existing data sets, that the IR emission of black hole X-ray transients appears to be weaker in the low/hard state rise of an outburst than the low/hard state decline of an outburst at a given X-ray luminosity. We discuss how this effect may be caused by a shift in the radiative efficiency of the inflowing or outflowing matter, or variations in the disc viscosity or the spectrum/power of the jet. In addition we show that there is a correlation (in slope but not in normalization) between IR and X-ray luminosities on the rise and decline, for all three low-mass black hole X-ray binaries with well-sampled IR and X-ray coverage: LNIR,L0.5,0.7X. In the high/soft state this slope is much shallower; LNIR,L0.1,0.2X, and we find that the NIR emission in this state is most likely dominated by the viscously heated (as opposed to X-ray heated) accretion disc in all three sources. [source]

Influence of the annealing temperature on the optical transitions of InGaAsP-based quantum well structures investigated by photoreflectance spectroscopy

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2005
A. Podhorodecki
Abstract Photoreflectance (PR) and photoluminescence (PL) spectroscopies have been used to study the effect of the rapid thermal annealing (RTA) on InGaAsP-based quantum wells (QWs) which are the active part of a laser structure tailored at 1.5 µm. In the case of PL, it has been observed that the RTA enhances PL intensity and tunes the emission wavelength of the laser structure to blue. In case of PR due to its absorption character, we were able to study QW transitions related to excited states, besides the fundamental transition observed in PL. In addition, optical transitions related to other part of the laser structure have been observed in PR. It has been shown that there exists a "critical" annealing temperature (720 °C) where the energy shift appears. We have observed a blueshift for both the ground and excited state transitions, but in the case of the ground state transitions the blueshift has been found to be bigger. The magnitude of this blueshift has been found to change linearly from 0 to ,15 meV with the rise of temperature from 720 to 780 °C. Below 720 °C no significant change in the energy of the QW transitions is observed. In the case of PR transitions related to the other part of the laser structure, i.e., the quaternary InGaAsP barriers, it has been observed that after annealing PR features associated with these layers rather do not shift, they change only their line-shape. Also, it has been shown that RTA does not destroy the optical quality of the samples. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Photon-assisted tunneling in GaN nanowire white light emitting diodes

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
P.-C. Yeh
Abstract We reported intensive greenish white light electroluminescence, accompanied with 364 nm bandedge emission from GaN nanowires/p-GaN light emitting diode operated in the high-field forward bias regime. Strong bandedge emission, dominant over visible luminescence from bandgap state transitions, was also observed in the reverse bias regime. These observations were ascribed to a formation of n+ -p tunnel junction in the high-field regime and emission mechanism due to photon-assisted tunneling process. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Effect of external pH on the growth, photosynthesis and photosynthetic electron transport of Chlamydomonas acidophila Negoro, isolated from an extremely acidic lake (pH 2.6)

PLANT CELL & ENVIRONMENT, Issue 10 2005
ANTJE GERLOFF-ELIAS
ABSTRACT In extremely acidic lakes, low primary production rates have been measured. We assumed that proton stress might explain these observations and therefore investigated the photosynthetic behaviour of a Chlamydomonas species, a main primary producer in acidic lakes, over a range of pH values. Identified as C. acidophila using small subunit rDNA analysis, this species is identical to other isolates from acidic environments in Europe and South America, suggesting a worldwide distribution. Laboratory experiments with C. acidophila, revealed a broad pH-tolerance for growth and photosynthesis, the lower pH limit lying at pH 1.5 and the upper limit at pH 7. Growth rates at optimum pH conditions (pH 3 and 5) were equal to those of the mesophilic Chlamydomonas reinhardtii. In contrast, photosynthetic rates were significantly higher, suggesting that higher photosynthetic rates compensated for higher dark respiration rates, as confirmed experimentally. Electron transport capacities of PSI and PSII, P700+ re-reduction times and measurements of PSII fluorescence revealed the induction of alternative electron transport mechanisms, such as chlororespiration, state transitions and cyclic electron transport, only at suboptimal pH values (pH 1.5; 4 and 6,7). The results indicate, that C. acidophila is well adapted to low pH and that the relatively low primary production rates are not a result of pH stress. [source]

On the relation between supersoft X-ray sources and VY Scl stars: The cases of V504 Cen and VY Scl,

ASTRONOMISCHE NACHRICHTEN, Issue 2 2010
J. Greiner
Abstract We summarise our optical monitoring program of VY Scl stars with the SMARTS telescopes, and triggered X-ray as well as optical observations after/during state transitions of V504 Cen and VY Scl (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Monitoring a Complex Medium Fermentation with Sample-Sample Two-Dimensional FT-NIR Correlation Spectroscopy

BIOTECHNOLOGY PROGRESS, Issue 3 2006
Ana P. Ferreira
The possibility of monitoring state transitions during the time course of a fermentation through the analysis of the on-line collected near-infrared (NIR) spectra with sample-sample two-dimensional correlation spectroscopy (SS-2DCoS) was investigated. SS-2DCoS has proved to be useful for extracting process information directly from the spectra collected on-line. The complexity of the system studied prevented the extraction of concentration profiles, but nevertheless, the application of SS-2DCoS enables the identification of fermentation state transitions due to metabolic and morphological changes of the microorganism. [source]

The structural context of recent transitions to democracy

EUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 3 2004
RENSKE DOORENSPLEET
An analysis of the influence of these structural factors is however important, and it has not yet been done in a systematic way in order to explain recent transitions to democracy since 1989. It will be shown that some structural factors indeed play a role in generating transitions to democracy. These results contradict the idea that structural factors can be ignored when explaining recent transitions to democracy. An additional finding in this article is that some structural factors, such as economic development, growth and a country's role in the world-system had an unexpected impact on democratic transitions since the end of the Cold War. These findings set bounds to the strength of the modernization and world-system theories to explain transitions to democracy, but on the other hand, democratic diffusion played a significant role after 1989. In the (structural) context in which a state had a peripheral role, a low level of economic growth and a high proportion of democratic neighbors, the probability of a state's transition to democracy was high. This structural context seemed to be fertile soil for recent transitions to democracy. [source]