bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and characterization of cellulose fiber/chitosan composites
Authors: Wang Zhengke , Hu Qiaoling , Dai Xiaoguang , Wu Hao , Wang Youxiang , Shen Jiacong
Published: October 2008

Cellulose fiber/chitosan biodegradable rod (CF/CS rod) with layer‐by‐layer structure, good mechanical properties, and excellent X‐ray developing capability was successfully constructed via in‐situ precipitated method. As the ratio of CF to CS was 0.2/20 (wt/wt), the bending strength and bending modulus arrived at 124.1 MPa and 4.3 GPa, respectively, were significantly improved compared with pure CS rod. TGA indicated that the thermal stability of CS rod could be enhanced by mixing with CF, but fiber and matrix are partially compatible. SEM made clear that fibers were randomly dispersed in the CS matrix to connect layers of CS rod that can endure stress. FTIR spectra illuminated that small amount of Schiff base was formed due to the chemical reaction between fibers and CS matrix, which could enhance the mechanical combining stress of the interface. Thus, CF/CS rod has great potential to be used as internal fixation of bone fracture. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Poly(1,3‐butylene adipate) plasticized poly(lactic acid)/carbon black as electrical conductive polymer composites
Authors: Zhijun Qiao , Xingxiang Zhang , Ning Wang , Jianming Fang
Published: October 2008

Poly(1,3‐butylene adipate) (PBA) as the plasticizer for poly(lactic acid) (PLA) and carbon black (CB) as conductive filler, electrically conductive polymer composites (CPC) with different CB and PBA contents were prepared. Fourier transform infrared revealed that the interaction existed between PLA/PBA matrix and CB filler, and PBA could improve this interaction. The rheology showed that CB could obviously improve the apparent viscosity and decrease the fluidity of the composites, but just the reverse for PBA. PLA/PBA/CB composites exhibited the low electrical percolation thresholds of 0.516, 1.20, 2.46, and 2.74 vol% CB at 30, 20, 10, and 0 wt% PBA. The conductivity of the composite containing 3.98 vol% CB and 30 wt% PBA reached 1.67 S/cm. Scanning electron microscopy revealed that the addition of PBA facilitated the dispersion of PLA/CB composites. PBA could dramatically increase the elongation at break of plasticized PLA. But high‐PBA content caused the lowering of tensile strength. With the increasing of CB contents, the enforcement effect on the plasticized PLA became more obvious. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Profiling humoral immune responses to P. falciparum infection with protein microarrays
Authors: Doolan Denise L. , Mu Yunxiang , Unal Berkay , Sundaresh Suman , Hirst Siddiqua , Valdez Conrad , Randall Arlo , Molina Douglas , Liang Xiaowu , Freilich Daniel A. , Oloo J. Aggrey , Blair Peter L. , Aguiar Joao C. , Baldi Pierre , Davies D. Huw , Felgner Philip L.
Published: October 2008

A complete description of the serological response following exposure of humans to complex pathogens is lacking and approaches suitable for accomplishing this are limited. Here we report, using malaria as a model, a method which elucidates the profile of antibodies that develop after natural or experimental infection or after vaccination with attenuated organisms, and which identifies immunoreactive antigens of interest for vaccine development or other applications. Expression vectors encoding 250 Plasmodium falciparum (Pf) proteins were generated by PCR/recombination cloning; the proteins were individually expressed with >90% efficiency in Escherichia coli cell‐free in vitro transcription and translation reactions, and printed directly without purification onto microarray slides. The protein microarrays were probed with human sera from one of four groups which differed in immune status: sterile immunity or no immunity against experimental challenge following vaccination with radiation‐attenuated Pf sporozoites, partial immunity acquired by natural exposure, and no previous exposure to Pf. Overall, 72 highly reactive Pf antigens were identified. Proteomic features associated with immunoreactivity were identified. Importantly, antibody profiles were distinct for each donor group. Information obtained from such analyses will facilitate identifying antigens for vaccine development, dissecting the molecular basis of immunity, monitoring the outcome of whole‐organism vaccine trials, and identifying immune correlates of protection.
A novel solid phase‐ and chemical crosslinking‐based technology for determining protein localization in biological supramolecules
Authors: Horng Wei‐Cheng , Yen Yuan‐Hun , Chang Yen‐Chung
Published: October 2008

A solid phase‐ and chemical crosslinking‐based technology was developed for determining the depths at which various protein constituents reside in a supramolecule. The usefulness of this technology was verified by trials using a synthetic three‐protein complex on glass coverslips. This technology was further applied to investigate the localization of seven major protein components in the postsynaptic density, a landmark supramolecule of the excitatory synapses in mammalian brains. The technology reported here will supplement the already powerful proteomic methodologies in studying the structure/function relationships of supramolecules.
Proteins modulation in human skeletal muscle in the early phase of adaptation to hypobaric hypoxia
Authors: Viganò Agnese , Ripamonti Marilena , De Palma Sara , Capitanio Daniele , Vasso Michele , Wait Robin , Lundby Carsten , Cerretelli Paolo , Gelfi Cecilia
Published: October 2008

High altitude hypoxia is a paraphysiological condition triggering redox status disturbances of cell organization leading, via oxidative stress, to proteins, lipids, and DNA damage. In man, skeletal muscle, after prolonged exposure to hypoxia, undergoes mass reduction and alterations at the cellular level featuring a reduction of mitochondrial volume density, accumulation of lipofuscin, a product of lipid peroxidation, and dysregulation of enzymes whose time course is unknown. The effects of 7–9 days exposure to 4559 m (Margherita Hut, Monte Rosa, Italy) on the muscle proteins pattern were investigated, pre‐ and post‐exposure, in ten young subjects, by 2‐D DIGE and MS. Ten milligram biopsies were obtained from the mid part of the vastus lateralis muscle at sea level (control) and at altitude, after 7–9 days hypoxia. Differential analysis indicates that proteins involved in iron transport, tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and oxidative stress responses were significantly (p<0.05) decreased in hypoxia. Parenthetically, hypoxia markers such as hypoxia inducible factor 1 α (HIF‐1α) and pyruvate dehydrogenase kinase 1 (PDK1) were still at the pre‐hypoxia levels, whereas the mammalian target of rapamycin (mTOR), a marker of protein synthesis, was reduced.
Riboproteomic analysis of polypeptides interacting with the internal ribosome‐entry site element of foot‐and‐mouth disease viral RNA
Authors: Pacheco Almudena , Reigadas Sandrine , Martínez‐Salas Encarnación
Published: October 2008

Initiation of translation driven by internal ribosome entry site (IRES) elements depends upon the structural organization of this mRNA region. Besides translation initiation factors (eIFs), auxiliary proteins can also affect IRES activity. With the aim to identify proteins interacting with two unrelated IRESs present in the genome of foot‐and‐mouth disease virus (FMDV) and hepatitis C virus (HCV) we have used a proteomic approach. This procedure allowed the identification of 21 RNA‐binding proteins interacting with discrete regions of the FMDV IRES, domains 3 and 5, and 16 interacting with domain III of the HCV IRES. In support of the binding specificity, the factors interacting with domain 3 differed from those interacting with domain 5, and included three poly(rC)‐binding protein (PCBP) members, besides proliferation‐associated 2G4 (PA2G4) and deleted‐azoospermia 1 (DAZ1) protein. Around 71% of the identified factors associated with the FMDV IRES differ from those interacting with the HCV IRES. The group of proteins interacting with the FMDV or the HCV IRES includes eIF4B and 5 subunits of eIF3, respectively, known to interact with each of these RNAs, validating the results of this approach. According to the function of the identified proteins, 55% are involved in translation control, whereas 35% play a role in different aspects of RNA lifespan. Compilation of factors preferentially associated with FMDV or HCV IRES provides a basis for examining the strategies used by IRESs to recruit the translation machinery.
Lethal and sublethal effects of chlorantraniliprole on three species of Rhagoletis fruit flies (Diptera: Tephritidae)
Authors: Teixeira Luís AF , Gut Larry J , Wise John C , Isaacs Rufus
Published: October 2008

BACKGROUND: Chlorantraniliprole formulated as a 350 g kg−1 WG (Altacor 35WG) for management of apple maggot Rhagoletis pomonella (Walsh), blueberry maggot R. mendax Curran and cherry fruit fly R. cingulata (Loew) (Diptera: Tephritidae) was evaluated in laboratory assays and field trials.

RESULTS: A tarsal contact toxicity bioassay showed that a surface residue of 500 mg L−1 of chlorantraniliprole caused significantly higher mortality of male and female flies of all species compared with a control. Male apple maggot and blueberry maggot mortality was significantly higher than that for females, but there was similar mortality of male and female cherry fruit flies. An ingestion toxicity bioassay showed that 500 mg L−1 of chlorantraniliprole in diet caused significantly higher mortality of male and female flies of all species than the control, but there were no significant differences among the sexes. Delayed egglaying by females that had ingested chlorantraniliprole was found, but there were no significant sublethal effects on either the number of eggs laid or the egg hatch. Field trials with apple maggot and cherry fruit fly showed that protection of fruit by chlorantraniliprole was comparable with that of standard broad‐spectrum insecticides.

CONCLUSIONS: The present data indicate that chlorantraniliprole has suppressant activity against Rhagoletis fruit flies, preventing fruit infestation primarily through direct lethal effects. Copyright © 2008 Society of Chemical Industry
Mild oxide‐hydrothermal synthesis of different aspect ratios of monoclinic BiVO4 nanorods tuned by temperature
Authors: Dong Fengqiang , Wu Qingsheng , Ma Jie , Chen Yijun
Published: October 2008

The monoclinic scheelite BiVO4 nanocrystals were easily prepared via an oxide‐hydrothermal synthesis (OHS) method directly utilizing bulk‐phase materials of V2O5 and Bi2O3 as precursor. In the presence of PEG 4000, the reactions were performed in the mild temperature range from 130 °C to 200 °C. The products were characterized with FTIR, XRD, TEM and UV–vis DRS. These data clearly demonstrated that monoclinic scheelite structure BiVO4 could be synthesized by the feasible OHS route. The aspect ratios of nanorods were increased with the synthesized temperature. The as‐prepared BiVO4 showed high photocatalytic activity, which was demonstrated by degradation of methylene blue (MB) solution under visible‐light irradiation (λ > 420 nm). A growth mechanism of bismuth vanadate was proposed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adjustment of the selenium amount provided during formation of CuInSe2 thin films from the metallic precursors
Authors: López‐García J. , Guillén C.
Published: October 2008

CuInSe2 (CIS) thin films were grown by selenization of sequentially evaporated Cu and In metallic precursors. The adjustment of the Selenium amount provided during the selenization process within a partially closed graphite box for film thicknesses between 0.5–2.5 μm was performed. We obtained CuInSe2 films with chalcopyrite structure and preferential orientation along the (112) direction plane. XRD patterns showed intense and narrow peaks that indicate high crystallinity corresponding to a Se amount between 120–180 mg. Direct band gap energy between 0.90–0.97 eV, depending on the Se amount and film thickness, and a high absorption coefficient (∼105 cm–1) were found. A slight improvement in the surface morphology for the optimum Se amount aforementioned was observed. The measured film resistivities varied from 0.1 Ω cm to 40 Ω cm. Thus, the structural, optical and morphological characteristics were dependent of the Se amount provided during the selenization process and after fitting of this selenium, an optimization of the CIS thin films properties and a saving of the Se consumption were achieved. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gelatin nanoparticle fabrication and optimization of the particle size
Authors: Jahanshahi M. , Sanati M. H. , Hajizadeh S. , Babaei Z.
Published: October 2008

The biotechnology industry has recently been demanding second generation of nanoparticle bioproducts such as viruses, plasmids, virus‐like particles and drug‐delivery assemblies (20–300 nm). The possibility of preparing uniform nanoparticles consisting of proteins such as gelatin followed by covalent linkage of avidin was investigated. Gelatin nanoparticles were prepared by two‐step desolvation. As a colloidal drug‐delivery system, the essential parameters in fabrication were optimized by the Taguchi design method. However, for characterizing the nanoparticles AFM and SEM were employed. By introducing 4 factors (temperature, gelatin concentration, agitation speed and the amount of acetone) in 4 levels to the software 16 experiments were carried out and the optimum condition was gained in 50 °C, 45 mg/ml gelatin concentration, 80 ml of acetone based on reduction of the size. The produced nanoparticles size was under 174 nm. The mechanistic of the optimum conditions for preparing protein nanoparticles as well as their characterization are discussed in detail. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnO nanowire field‐effect transistor as a UV photodetector; optimization for maximum sensitivity
Authors: Kim Woong , Chu Kyo Seon
Published: October 2008

We demonstrate that drain–source (Vds) and gate–source voltages (Vgs) of a zinc oxide nanowire (ZnO NW) field‐effect transistor (FET) can be optimized to increase UV photodetection sensitivity. Investigation of the relationship between the sensitivity and the applied voltages reveals that the photodetector is most sensitive when it operates (1) with highest on/off current ratio and (2) at the “bottom” of the subthreshold swing region. Our results can be broadly applied to maximize sensitivity of other FET‐based sensors and detectors. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoinduced dissociation of donor–acceptor pairs in non‐magnetic phase of organic charge‐transfer crystal of tetrathiafulvalene–tetrabromo‐1,4‐benzoquinone
Authors: Itoh Chihiro , Nakata Yasuharu
Published: October 2008

We have studied 532 nm laser‐induced changes in the infrared reflection of a charge‐transfer (CT) crystal of tetrathiafulvalene (TTF) and tetrabromo‐1,4‐benzoquinone (BA) at 4 K. The spectra of the fractional change (ΔR /R) were characterized by dips situated in proximity to the structures ascribed to the ag‐mode vibrations of TTF+ and BA– at low excitation intensity. However, the excitation above 0.2 W cm–2 gave structures characterized by the inverted shape of the ag‐mode structures, indicating that the laser excitation reduced the intensity of the ag‐mode structures. The appearance of the ag‐mode structures is associated with loss of the inversion centre of the crystal due to the dimerization of TTF+ and BA–; hence, the intensity reduction of the ag‐mode structures is ascribed to dissociation of TTF+‐BA– pairs. We found that ΔR /R increased super‐linearly with enhancing excitation intensity. The result suggests that the dissociation involves a multi‐quantum process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton Mott transition and quantum condensation in electron‐hole systems
Authors: Ogawa Tetsuo
Published: October 2008

This paper reviews recent progress of theoretical studies on the metal‐insulator transition and the quantum condensation in photoexcited states, the electron‐hole (eh) systems, which are modeled by the e‐h (two‐band) Hubbard model with both repulsive U and attractive U ′ on‐site interactions. We confine ourselves to a quasithermal‐equilibrium situation. First, we introduce the dynamical mean‐field theory (DMFT) applied to the metalinsulator transition (called the “exciton Mott transition”) of the high‐dimensional e‐h systems at zero and finite temperatures T.We determined the phase diagram of the e‐h Hubbard model and the first‐order exciton Mott transition line in the plane of the (U ′;U) or (U = U ′ T).

We find two types of insulating phases: exciton‐like and biexciton‐like. At the Mott critical temperature such first‐order Mott transition disappears, and the crossover is observed above the critical temperature. Comparison with results by the slave‐boson mean‐field treatment is also made. Role of the inter‐site interaction is also discussed with the use of the extended DMFT. Second, we discuss the crossover between the exciton Bose‐Einstein condensation and the e‐h BCStype condensed state at low temperature using the selfconsistent t ‐matrix and local approximations within the framework of DMFT. We evaluate the transition temperature as a function of the interaction strength. Effects of repulsive on‐site interaction are analyzed. Third, for a one‐dimensional e‐h system, the bosonization and renormalization‐group techniques clarify that the most probable ground state is the insulating biexciton crystal, reflecting the e‐h backward scattering and the long‐range Coulomb interaction. The exciton Mott transition never occurs at zero temperature in one dimension. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton polaritons in bulk CuCl microcavities grown by vacuum deposition
Authors: Oohata Goro , Nishioka Takashi , Kim DaeGwi , Ishihara Hajime , Nakayama Masaaki
Published: October 2008

We demonstrate the realization of cavity polariton states in bulk CuCl microcavities. The CuCl microcavities made from a bulk CuCl layer and distributed Bragg reflectors consisting of PbF2 and PbBr2 layers prepared by vacuum deposition. Angle‐resolved reflectance spectra show the strong coupling characteristics of the excitons and photon mode; namely, the energies of reflectance structures exhibit incident‐angle dependence accompanying with an anticrossing behaviour peculiar to the cavity polaritons. From the phenomenological analysis with a 3×3 Hamiltonian of the cavity‐polariton modes originating from the Z3 exciton, Z1,2 exciton, and cavity photon, it has been revealed that the vacuum Rabi splitting energies in the λ‐thick CuCl active layer are 97 meV and 162 meV for the Z3 and Z1,2 excitons, respectively. We also indicate the potential to control the Rabi‐splitting energy by changing the active layer thickness. Furthermore, the spectral profile of reflectance is reasonably explained by calculations based on a theory of non‐local linear optical response. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Femtosecond time‐resolved reflection spectroscopy in Pr1–xCax MnO3 (x =0.37)
Authors: Peng Xianzhou , Okimoto Yoichi , Endo Masato , Sato Ken , Aizawa Takeshi , Onda Ken , Ishikawa Tadahiko , Koshihara Shin‐ya , Arima Taka‐hisa
Published: October 2008

The ultrafast dynamics of photoinduced phase transition (PIPT) in a crystal of Pr1–x Cax MnO3 (x = 0.37) has been studied by means of femtosecond time‐resolved spectroscopy. Just after photoirradiation of 1.58 eV light at 100 K, ultrafast change of reflectivity (ΔR/R) was observed within ∼1 ps utilizing the probe light of 0.5 eV due to the ferromagnetic metallic phase transition. While the fast component of ΔR/R gradually increases with increasing the excitation intensity, the slow component observed at the delay time of ∼1 ps shows unusual dependence on the excitation intensity. The signature of ΔR/R changes from negative to positive with the excitaiton power, which cannot be explained by the photo‐thermal heating effect. In addition, we investigated the temperature dependence of the ΔR/R at 0.5 eV and observed the sudden change of ΔR/R around TN, which indicates that the efficiency of PIPT is closely correlated with the ordering of spin and extra electron in Mn4+. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonadiabatic theory of excitons in wurtzite AlGaN/GaN quantum‐well heterostructures
Authors: Pokatilov Evghenii P. , Nika Denis L. , Fomin Vladimir M. , Devreese Jozef T.
Published: October 2008

We have theoretically studied exciton states and photoluminescence spectra of the strained wurtzite AlxGa1–xN/GaN quantum‐well heterostructures. The electron energy spectrum is found through numerical solving of the one‐band Schrödinger equation, while the hole and exciton energy spectra are determined from the Schrödinger equation with the non‐symmetrical 6‐band Hamiltonian, including deformational and spin‐orbit interaction. The oscillator forces are calculated and the exciton states are determined, which are active in the process of the optical absorption. Three quantitative conclusions are made in a good agreement with experiments for different values of x as concerns: (i) the red shift of the zero‐phonon photoluminescence (PL) peaks with increase of the quantum‐well width, (ii) the relative intensities of the zero‐phonon and one‐phonon PL peaks, found within the non‐adiabatic approach, and (iii) the values of the PL decay time as a function of the quantum‐well width. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatially indirect photoluminescence of ZnSe/BeTe type II quantum wells in pulsed high magnetic fields
Authors: Takeyama Shojiro , Shen Rui , Enya Yohei , Kojima Eiji , Mino Hirofumi , Akimoto Ryoichi
Published: October 2008

Spatially separated indirect photoemission in a non‐doped ZnSe/BeTe type II quantum structure is investigated by applying pulse magnetic field up to 50 T. The magnetic field dependences of the dichroic photoluminescence (PL) are well explained by an optical transition model associated with a positively charged exciton composed by an electron and two light holes. The PL is suppressed by magnetic field and also by temperature. Weak PL probably arising from localized excitons at interfaces is observed up to the highest magnetic field, and in high temperatures above 20 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman spectroscopy of charge‐ordered states in Magnéli titanium oxides
Authors: Watanabe Masayuki
Published: October 2008

We have systematically investigated the Raman spectra of the mixed‐valence compounds TinO2n–1 (n = 4,5,6) known as the Magnéli phases to elucidate the nature of the charge‐ordered states in these compounds. It is found that a stable charge‐ordered state exists only for Ti4O7. In the case of Ti5O9, the charge order is almost completely lost, and the charge order in Ti6O11 is incomplete. Thus each compound seems to be have quite individually. This result is unexpected in view of the similarity in the crystal structure. We interpret this seeming lack of the systematic trend as being due to the electron correlation effect which becomes less effective with increasing n. Also it is suggested that the charge order is unstable for the compounds with odd n. Finally the effects of temperature on the charge ordering in Ti5O9 and Ti6O11 are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Collective effects of excitons with prominent retardation in multiple‐layered structures
Authors: Yasuda Hideki , Ishihara Hajime
Published: October 2008

We have investigated the collective excitonic effects in radiatively coupled thin layers by means of the transient pulse response theory. The degenerate four‐wave mixing (DFWM) signals show a strong dependence on the incident condition of the excitation pulses.

Especially, when excitons in different layers are excited with prominent retardations compared to the pulse durations (that is, excitons in different layers are excited like dominoes), a huge variety of optical responses can occur, never seen in a usual simultaneous excitation of excitons. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy transfer to phonons after photoexcitation in one‐dimensional correlated electron‐phonon systems
Authors: Yonemitsu Kenji , Maeshima Nobuya
Published: October 2008

In order to study relaxation rates of photoexcited states in correlated electron systems, we calculate the time evolution of phonons' kinetic energies after photoexcitation of a one‐dimensional half‐filled Hubbard model coupled with different types of phonons, which modulate transfer integrals, site energies, and on‐site repulsion strengths. Without or with weak dimerization, the energy transfer to phonons that modulate on‐site repulsion strengths is the largest. It increases rapidly as a function of the corresponding displacement. This suggests that the rapid relaxation of photoexcited states in one‐dimensional correlated electron systems is allowed without change in symmetry by phonons that modulate Coulomb repulsion strengths. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Infrared transient absorption spectra for excited transition of excitons and biexcitons in CuCl
Authors: Yoshioka Takaaki , Miyajima Kensuke , Ashida Masaaki , Itoh Tadashi
Published: October 2008

Infrared transient absorption (IRTA) spectra for excitons and biexcitons in CuCl bulk crystal have been measured by pump‐probe spectroscopy. The IRTA peak energy of the exciton agrees with the transition energy between Rydberg 1s to 2p states reported in one‐ and two‐photon absorption measurement. On the other hand, the IRTA peak energy of the biexcitons locates in energy higher than that of the excitons, which is reasonable by taking hydrogen molecule model into account. In addition, our results support the enhancement of the transition energy between 1s and 2p states in quantum dots compared to the bulk case. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Terahertz‐induced extreme nonlinear transients in semiconductor quantum wells
Authors: Lee Yun‐Shik , Danielson J. R. , Prineas J. P. , Steiner J. T. , Kira M. , Koch S. W.
Published: October 2008

We demonstrate terahertz‐induced extreme nonlinear transients in GaAs/AlGaAs quantum‐wells via terahertz‐pump and optical‐probe experiments. The light‐hole and heavy‐hole excitonic resonances exhibit strong spectral modulations that fluctuate on a subpicosecond time scale as the pump‐probe time delay varies. Microscopic many‐body calculations reveal that the experimental observations contain pronounced signatures of ponderomotive contributions, the ac‐Stark effect, and terahertz high harmonic generations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degree of entanglement of photon pairs generated from V‐type system in microcavity
Authors: Ajiki Hiroshi , Ishihara Hajime
Published: October 2008

We propose polarization‐entangled photon generation via resonant hyper‐parametric scattering of a V‐type system in microcavity. Although a bare V‐type system cannot generate entangled photon pairs, microcavity makes the generation possible because of the formation of dressed states.

In the strong‐coupling limit, generation of non‐entangled co‐polarized photons is considerably suppressed due to the photon blockade effect. Furthermore, some entangled photons have different frequencies from those of the input fields, and thus, we can utilize spectral filtering in order to extract entangled photons. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of the time dependent photoluminescence of a J‐aggregate microcavity
Authors: Michetti Paolo , La Rocca Giuseppe C.
Published: October 2008

We have built a model for the optical dynamics of a strongly coupled J‐aggregate microcavity. Our model is based on the description of a J‐aggregate film as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. In a strongly coupled microcavity the excitation spectrum is modified due to the formation of the excitonpolaritons, in which the superradiant states of the optically resonant film are mixed with the cavity photons.

The calculation of the steady‐state photoluminescence, following a constant non resonant pumping, explains the thermal activation of the upper polariton photoluminescence as a consequence of a bottleneck effect in the relaxation. The results of our calculation of the time dependent photoluminescence pumping following non resonant pulsed pumping are here presented. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface excitonic recombination dynamics in ZnO nanowires
Authors: Richters Jan‐Peter , Wischmeier Lars , Rückmann Ilja , Gutowski Jürgen , Voss Tobias
Published: October 2008

The optical properties of ZnO nanowires are strongly influenced by surface effects. For diameters smaller than 200 nm, a surface exciton recombination band is observed. We report on the recombination dynamics of this emission band using low temperature and time resolved photoluminescence spectroscopy. We find a biexponential decay with different decay constants for different emission wavelengths on the band. We present a model to explain the biexponential decay characteristics and report on possibilities to experimentally enhance the relative intensity of the surface exciton emission by embedding the ZnO nanowires into polymer matrices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ionization equilibrium and Mott transition in an excited semiconductor, phase diagram
Authors: Richter F. , Semkat D. , Kremp D. , Henneberger K.
Published: October 2008

The thermodynamic properties of an electron–hole plasma in a highly excited semiconductor are investigated. Special attention is directed to the influence of many‐particle effects like screening, lowering of the ionization energy, and Mott effect on the ionization equilibrium. In particular, the Mott effect limits the region of existence of excitons and, therefore, of a possible Bose–Einstein condensate at low temperatures. Results for the chemical potential and the degree of ionization are presented for cuprous oxide. A possible window for the occurrence of a BEC of excitons taking into account the Mott effect is shown. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature degradation of the gain transition in terahertz quantum cascade lasers – the role of acoustic phonon scattering
Authors: Nelander Rikard , Wacker Andreas
Published: October 2008

The temperature degradation in terahertz quantum cascade lasers is investigated with the focus on the role of acoustic phonon scattering. A self‐energy describing the electron‐acoustic phonon interaction is derived and used to study the importance in transport and optical properties.

We observe a strong degradation of the gain peak with temperature. Despite the very small coupling to electrons, the exclusion of acoustic phonon scattering alters the current and peak gain in the order of 5%. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical study of phononassisted singlet‐singlet relaxation in two‐electron semiconductor quantum dot molecules
Authors: Grodecka Anna , Machnikowski Paweł , Förstner Jens
Published: October 2008

Phonon‐assisted singlet‐singlet relaxation in semiconductor quantum dot molecules is studied theoretically. Laterally coupled quantum dot structures doped with two electrons are considered. We take into account interaction with acoustic phonon modes via deformation potential and piezoelectric coupling. We show that piezoelectric mechanism for the considered system is of great importance and for some ranges of quantum dot molecule parameters is the dominant contribution to relaxation.

It is shown that the phonon‐assisted tunneling is much faster (down to ∼ 6 ps even at zero temperature) in comparison with other decoherence processes. The influence of Coulomb interaction is discussed and its consequences are indicated. We calculate the relaxation rates for GaAs quantum dot molecules and study the dependence on quantum dot size, distance and offset between the constituent quantum dots. In addition the temperature dependence of the tunneling rates is analyzed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semiconductor excitons in strong terahertz fields
Authors: Steiner J. T. , Kira M. , Koch S. W.
Published: October 2008

A microscopic theory for the nonlinear terahertz response of excited semiconductor systems is presented. It is shown that the measurable quantities in typical terahertz transmission/reflection experiments contain large ponderomotive contributions which mask the signatures from terahertz‐induced many‐body transitions. A scheme is developed to remove the ponderomotive contributions and applied to isolate the signatures of Rabi oscillations of an exciton population. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of strong lightmatter coupling in semiconductor quantum‐dot microcavities
Authors: Schneebeli L. , Kira M. , Koch S. W.
Published: October 2008

Maxwell‐Bloch and luminescence equations are presented which describe vacuum Rabi splitting and the quantum rungs on the Jaynes‐Cummings ladder for strongly‐coupled dot‐cavity systems. Resonance fluorescence conditions are considered where an optical pump is exciting the dot‐cavity system while the re‐emitted light is detected.

An analytical formula for the vacuum Rabi splitting is derived and a pumping mechanism for the direct generation of the second rung is presented and analyzed. An optimum pumping frequency and optimum pumping intensity are identified for the generation of the second rung. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton spin decay in quantum dots: single and double phonon ssisted transitions
Authors: Roszak K. , Machnikowski P. , Axt V. M. , Kuhn T.
Published: October 2008

We study phonon assisted transitions leading to exciton spin decay in quantum dots. We concentrate on couplings specific to the hole (Bir‐Pikus Hamiltonian) and the exciton as a whole (short‐range exchange interaction). A system strongly confined in a self‐assembled quantum dot is considered.

We discuss single‐phonon assisted processes arising from the interplay of these interactions and show the dominating role of transverse phonons. We have also found a new two‐phonon assisted transition, connected with the interplay of different parts of the Bir‐Pikus Hamiltonian in the presence of the singlet‐triplet splitting. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical model for coherent optical manipulation of a single spin state in a charged quantum dot
Authors: Slavcheva Gabriela
Published: October 2008

The optically‐induced coherent spin dynamics of a single spin confined in a charged quantum dot (QD) is theoretically studied employing coupled vector Maxwell‐pseudospin formalism. Generalized pseudospin master equation is derived for description of the time evolution of spin coherences and spin populations including spin population transfer and dissipation in the system through spin relaxation processes. The equation is solved in the time domain self‐consistently with the vector Maxwell equations for the optical wave propagation coupled to it via macroscopic medium polarisation. Using the model the long‐lived electron spin coherence left behind a single resonant ultrashort optical excitation of the electron‐trion transition in a charged QD is simulated in the low‐ and high‐intensity Rabi oscillations regime. Signatures of the polarised photoluminescence (PL), predicted by the model, such as the appearance of a second echo pulse after the excitation and characteristic PL trace shape, are discussed for realization of high‐fidelity schemes for coherent readout of a single spin polarisation state. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four‐wave mixing optical response of an ensemble of quantum dot molecules
Authors: Sitek A. , Machnikowski P.
Published: October 2008

Four‐wave mixing (FWM) optical response from a sample containing a non‐homogeneously broadened ensemble of vertically stacked pairs of quantum dots is studied theoretically. The effects of collective interaction between the dots and their electromagnetic environment are analyzed. It is shown that the shape of the FWM echo is affected by the coupling between the two dots and, to some extent, by the statistics of the ensemble.

In the time‐integrated signal, oscillations on picosecond delay time scale appear which lead to a reduction of the coherent response for coupled dots. For longer delays, the evolution is dominated by radiative decay, with the decay rate increasing from Γ to 2Γ(superradiance effect) as the coupling becomes stronger. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier‐carrier and carrier‐phonon scattering in the low‐density and low‐temperature regime for resonantly pumped semiconductor quantum dots
Authors: Seebeck J. , Lorke M. , Gartner P. , Jahnke F.
Published: October 2008

We study carrier relaxation due to Coulomb scattering and interaction with LO‐phonons in semiconductor quantum dots at low temperatures. Scattering for different relaxation process are evaluated for various carrier distributions that correspond to stages of the typical relaxation kinetics after optical excitation with a weak pulse, generating on average less than one electron per quantum dot.

Even when the spacing of the quantum dot energy levels does not match the LO‐phonon energy, we.nd that carrier‐LO‐phonon scattering, in addition to electronelectron and electron‐hole interaction, provides efficient carrier relaxation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
THz measurements of the optical response in a two‐dimensional electron gas
Authors: Chatterjee S. , Grunwald T. , Köhler D. , Pierz K. , Golde D. , Kira M. , Koch S.W.
Published: October 2008

We present an experimental study of the THz transmission through a two dimensional electron gas embedded in a high electron‐mobility transistor‐like structure. Similar to previous experiments in a three‐dimensional system, a clear resonance is observed in the imaginary part of the inverse dielectric function ℱ{1/ε (ω)}. A detailed analysis using a Drude‐like response cannot explain all experimental findings. These significant deviations make a more detailed microscopic analysis necessary. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular dynamics simulation on HP1 protein binding by histone H3 tail methylation and phosphorylation
Authors: Jiang Yan‐Ke , Zou Jian‐Wei , Wu Yu‐Qian , Zhang Na , Yu Qing‐Sen , Jiang Yong‐Jun
Published: October 2008

Trimethylation of histone H3 lysine 9 is important for recruiting heterochromatin protein 1 (HP1) to discrete regions of the genome, thereby regulating gene expression, chromatin packaging, and heterochromatin formation. Phosphorylation of histone H3 has been linked with mitotic chromatin condensation. During mitosis in vivo, H3 lysine 9 methylation and serine 10 phosphorylation can occur concomitantly on the same histone tail, whereas the influence of phosphorylation to trimethylation H3 tail recruiting HP1 remains controversial. In this work, molecular dynamics simulation of HP1 complexed with both trimethylated and phosphorylated H3 tail were performed and compared with the results from the previous methylated H3‐HP1 trajectory. It is clear from the 10‐ns dynamics simulation that two adjacent posttranslational modifications directly increase the flexibility of the H3 tail and weaken HP1 binding to chromatin. A combinatorial readout of two adjacent posttranslational modifications—a stable methylation and a dynamic phosphorylation mark—establish a regulatory mechanism of protein–protein interactions. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Ab‐initio studies of magnetic properties of small‐sized and cuboctahedral aluminum nanoclusters
Authors: Phung T. V. B. , Hashimoto T. , Nishikawa K. , Nagao H.
Published: October 2008

Magnetic properties of Aln clusters are investigated using ab initio density functional calculations based on plane‐wave and the all electron projector augmented‐wave (PAW) method. We present stable structures of small‐sized Aln (n = 2–17) clusters obtained from optimization with binding energy, magnetization, and compared our results with experiment data. The size dependence of binding energy and magnetization are clarified. For large clusters, we discuss the stability of cuboctahedral Aln clusters with up to 923 atoms based on the size dependent binding energy. The coefficients corresponding to surface and edge energies for cuboctahedral Aln clusters have been estimated. We have obtained the cohesive energy of the bulk system to be Ec = 3.418 eV, close to the experimental value (3.39 eV) through the fitting function of size dependent binding energy. We discuss the magnetization of cuboctahedral Aln clusters in relation to shell structure. When the size of the cluster is enlarged, the distribution of magnetization shows that the spin density is largest at the outmost shell. From Al309 to Al923 clusters, electron and spin density in the center and innermost shell behave similar to the bulk. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Identification of lysophosphatidylcholine (LPC) and platelet activating factor (PAF) from PC12 cells and mouse cortex using liquid chromatography/multi‐stage mass spectrometry (LC/MS3)
Authors: Smith Jeffrey C. , Hou Weimin , Whitehead Shawn N. , Ethier Martin , Bennett Steffany A. L. , Figeys Daniel
Published: October 2008

Lipids play essential roles in cellular structural support, energy storage and signal transduction. Recently, mass spectrometry (MS) has been used to produce three‐dimensional maps that elucidate the lipid composition of complex cellular lysates. The identification of individual lipids within these maps is slow and requires the synthesis and spiking of each candidate lipid. We present a novel MS‐based technique that rapidly elucidates the atomic connectivity of the fatty acid/alcohol substituent on the sn‐1 position of several different families of glycerophosphocholine‐containing lipids within the confines of a chromatographic separation. Sodiated lipid species were fragmented to produce radical cations which lost successive methylene groups upon further collisional activation to reveal the identity of the parent molecule. This approach was demonstrated to be effective on isobaric members of the lysophosphatidylcholine (LPC) and platelet activating factor (PAF) families of glycerophospholipids. We demonstrate the application of this technique to unambiguously identify these species within complex cellular lysates and tissue extracts. Copyright © 2008 John Wiley & Sons, Ltd.
Structure and stability of B5C and C5B clusters
Authors: Liu Chunhui , Liu Lili , Han Peilin , Tang Mingsheng , Fu Huafeng
Published: October 2008

Geometry optimizations and vibrational frequencies of B5C and C5B clusters were calculated with the Becke‐3LYP method using the 6‐311+G(d) basis set and some stable configurations of B5C and C5B clusters have been found. The most stable structure of B5C is a planar six‐membered ring. However, for C5B clusters, the most stable structure is linear with a boron atom in position 3. Various configurations of B5C clusters containing three‐membered boron rings have predominance in energy, whereas various configurations of C5B clusters containing three‐membered carbon rings are disadvantageous in energy. In B5C clusters, isomer2 can be converted into isomer1 by surmounting an energy barrier of 43.83 kJ.mol−1. In C5B clusters, the conversions of isomer5 into isomer2 and isomer7 into isomer2 have energy barriers of 19.66 and 20.57 kJ.mol−1, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Quantitation of glutathione by liquid chromatography/positive electrospray ionization tandem mass spectrometry
Authors: Zhang Fagen , Bartels Michael J. , Geter David R. , Jeong Yo‐Chan , Schisler Melissa R. , Wood Amanda J. , Kan Lynn , Gollapudi B. Bhaskar
Published: October 2008

Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine. It is present in practically all cells and has several important roles, such as preventing the oxidation of the sulfhydryl groups of proteins within a cell. Evidence for GSH deficiency or depletion has been found in a variety of diseases and toxicity‐related studies, including diabetes and induction of oxidative stress to form reactive oxygen species which cause DNA, lipid, and protein oxidations. A simple, selective, and sensitive analytical method for measuring low levels of GSH in biological fluids would therefore be desirable to conduct GSH deficiency or depletion‐related mechanistic toxicity studies. Here a method for both low‐ and high‐level quantitation of GSH from cultured cells and rat liver tissues via liquid chromatography/positive electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) has been developed. The lower limit of quantitation (LOQ) of the method was 5 ng/mL. The method is linear over a wide dynamic concentration range of 5.0 to 5000.0 ng/mL, with a correlation coefficient R2 > 0.99. The intra‐day assay precision relative standard deviation (RSD) values for all quality control (QC) samples were ≤16.31%, with accuracy values ranging from 94.13 to 97.80%. The inter‐day assay precision RSD values for all QC samples were ≤15.94%, with accuracy values ranging from 94.51 to 100.29%. With this method, low levels of GSH from diethyl maleate (DEM)‐treated mouse lymphoma cells, and GSH in rat liver tissues, were quantified. Copyright © 2008 John Wiley & Sons, Ltd.
Stability radii of positive linear systems under fractional perturbations
Authors: Anh Bui The , Son Nguyen Khoa
Published: October 2008

In this paper we study stability radii of positive linear discrete‐time systems under fractional perturbations. It is shown that real and complex stability radii coincide and can be computed by a simple formula. From the obtained results, we apply to derive estimates and computable formulae for the stability radii of positive linear delay systems. Finally, a simple example is given to illustrate the obtained results. Copyright © 2008 John Wiley & Sons, Ltd.
The universal common good: faith‐based partnerships and sustainable development
Authors: Morse Stephen , McNamara Nora
Published: October 2008

Partnership is increasingly espoused as the best relationship between members of the sustainable development aid chain, and implies a respect for the position of all and a desire to avoid a situation where one group dominates another. It also implies a form of relationship that is not just ‘better’ for the sake of it but that is more able to help achieve sustainable development. However, given the inevitable inequalities in power between donors that have the resources and field partners that do not it can be hard to put this ideal into practice. This paper explores the function of partnership within a group of closely related institutions that comprise the Catholic Church development chain. The research focussed on three Catholic Church based donors (one from the USA and two from Europe) and their partners in Abuja Ecclesiastical Province, Nigeria. Relationships between and within various strata of the Church in Nigeria were also examined. Relationships were ‘patchy’ at all levels. One of the donors had a significant operational presence in Nigeria and this was regarded by some respondents as a parallel structure that seriously undermined local bodies. However, while problems existed, there was a sense of inter‐dependence arising from a shared sense of values and Catholic Social Teaching, which allowed partners to work through their stresses and conflicts. It is the innate sustainability of the aid chain itself founded upon a set of shared values that provided the space and time for problems to be addressed. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.