bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin dynamics in dilute nitride semiconductors at room temperature
Authors: Lombez L. , Braun P.-F. , Carrère H. , Urbaszek B. , Renucci P. , Amand T. , Marie X. , Harmand J. C. , Kalevich V. K.
Published: December 2005

We report optical studies in undoped GaAsN epilayers and InGaAsN quantum wells, which show that a strong electron spin polarization can persist at room temperature. This is a direct consequence of the long spin relaxation time of electrons in dilute nitride materials. Introducing less than 1% of nitrogen in the binary (GaAs) or ternary (InGaAs) alloy increases the electron spin relaxation time at T=300K by a factor greater than 20 in as-grown material before annealing. A drastic drop in the electron spin relaxation time is observed for annealed samples.
Phonon-induced breakdown of negative bend resistance in an asymmetric Si∕SiGe cross junction
Authors: Wieser U. , Poenariu S. A. , Kunze U. , Hackbarth T.
Published: December 2005

An asymmetric nanoscale cross junction is fabricated from a high-mobility Si∕SiGe heterostructure. At T=4.2K, the four-terminal current-voltage characteristics reveal a polarity-dependent breakdown of the negative bend resistance. The breakdown is accompanied by negative differential conductance found in the two-terminal current-voltage characteristics of the orthogonal current leads. We attribute this behavior to phonon emission by hot electrons. From gate-voltage-dependent measurements, we determine a phonon threshold of 19meV.
The Meyer-Neldel compensation law for electrical conductivity in olivine
Authors: Wu Xiaoping , Zheng Yong-Fei
Published: December 2005

The electrical conductivity in olivine is found to obey the compensation law or the Meyer-Neldel rule; that is, a linear correlation exists between the logarithm of prefactor and activation energy. It is shown that the electrical conductivities due to different conduction mechanisms or conducting species converge to a constant at a characteristic temperature, resulting in the Meyer-Neldel rule. A number of experimental diffusion data in olivine also test the validity of the suggestion through the Nernst-Einstein equation.
InAs
∕
InP
(
001
)
quantum dots emitting at 1.55μm grown by low-pressure metalorganic vapor-phase epitaxy
Authors: Michon A. , Saint-Girons G. , Beaudoin G. , Sagnes I. , Largeau L. , Patriarche G.
Published: December 2005

In this letter, we report on the structural and optical properties of self-assembled InAs quantum dots (QDs) directly grown on InP(001) by low-pressure metalorganic vapor-phase epitaxy. Transmission electron microscopy reveals defect-free diamond-shaped QDs with a density as high as 2.5×1010cm−2. The QD photoluminescence exhibits an intense peak centered around 1.58μm (785 meV) at room temperature. Changing the growth rate allows one to control the QD density, while maintaining an intense emission centered at this wavelength. These promising results open the way for the realization of efficient InAs∕InP(001) QD-based devices, such as lasers or single-photon sources.
Fabrication of PbLa0.05TiO3∕Pb1.20(Zr0.52Ti0.48)O3∕PbLa0.05TiO3 ferroelectric structure on platinum electrodes by a sol-gel process
Authors: Ezhilvalavan S. , Samper Victor D , Ying Jackie Y.
Published: December 2005

Ferroelectric PbLa0.05TiO3∕Pb1.20(Zr0.52Ti0.48)O3∕PbLa0.05TiO3 (PLT/PZT/PLT) thin films were fabricated on platinum-coated silicon wafers using a sol-gel process. The PbLa0.05TiO3 layers between the PZT and Pt electrode are used as seeding layers to improve the crystallization and can greatly enhance the ferroelectric properties of the PZT film. Compared with PZT and PbTiO3∕Pb1.20(Zr0.52Ti0.48)O3∕PbTiO3 (PT/PZT/PT) films, the PLT/PZT/PLT capacitors of thickness ∼250nm showed excellent ferroelectric properties in terms of larger remnant polarization (Pr) of ∼19μC∕cm2 (Ec∼60kV∕cm), higher saturation polarization (Ps) of about 45μC∕cm2 for an applied field of 600kV∕cm, fatigue-free characteristics of up to ⩾1010 switching cycles, and a low leakage current density of 10−8A∕cm2 at 200kV∕cm. A possible reason for the beneficial effect of PLT is the improved interfacial characteristics that may lead to the absorption of oxygen vacancies or other point defects from the PZT layer and result in better fatigue properties.
Temperature-dependent exciton dynamics in a ZnO thin film
Authors: Jen Fang-Yi , Lu Yen-Cheng , Chen Cheng-Yen , Wang Hsiang-Chen , Yang C. C. , Zhang Bao-ping , Segawa Yusaburo
Published: December 2005

We measured the temperature-dependent photoluminescence (PL) decay time of the mixed system of free exciton (FX) and donor-bound exciton (DX0) in a ZnO thin film. From the measured cw PL spectra, we also calibrated the individual spectral widths and integrated PL intensities of FX and DX0 by fitting the spectra with four Lorentzian functions. The radiative lifetime of the mixed system was then calibrated based on the thermal quenching rate of the total integrated PL intensity of the system. With the system radiative lifetime data, FX radiative lifetimes were estimated by using a theoretical relation between the lifetime and the spectral width. From the results of FX radiative lifetime, we calibrated the DX0 radiative lifetimes by considering the emission intensity ratio between FX and DX0. The results support our model that the DX0 radiative behavior is similar to that of FX when the thermal energy is smaller than the donor binding energy.
Electrical activation of the Fe2+∕3+ trap in Fe-implanted InP
Authors: Fraboni B. , Gasparotto A. , Cesca T. , Verna A. , Impellizzeri G. , Priolo F.
Published: December 2005

We have studied the electrical activation of the Fe2+∕3+ trap in Fe-implanted InP by means of capacitance-voltage and deep level transient spectroscopy analyses. Five deep traps have been identified and we have characterized the concentration and depth distribution of the Fe2+∕3+ deep trap, located at EC–0.66eV. The InP substrate background doping, i.e., the Fermi-level position, plays a crucial role in the Fe activation process by setting an upper limit to the amount of Fe centers electrically activated as deep acceptor traps.
Design for a triply resonant vertical-emitting micro-optical parametric oscillator
Authors: Diederichs C. , Tignon J.
Published: December 2005

An approach is proposed for the realization of a vertical-cavity surface-emitting semiconductor micro-optical parametric oscillator that relies on the use of third-order excitonic nonlinearity in isotropic semiconductors. We demonstrate that a planar triple microcavity structure can be designed to provide triple resonance for the parametric frequencies together with built-in cavity phase-matching for all waves at normal incidence. An example is given of a monolithic structure consisting of three strongly coupled AlGaAs∕GaAs lambda microcavities including single InGaAs quantum wells. Applications to the generation of twin photons or entangled photon pairs are discussed.
“EL2” revisited: Observation of metastable and stable energy levels of EL2 in semi-insulating GaAs
Authors: Kabiraj D. , Ghosh Subhasis
Published: December 2005

By using a combination of detailed experimental studies, we identify the metastable and stable energy levels of EL2 in semi-insulating GaAs. These results are discussed in light of the recently proposed models for EL2 in GaAs.
Deployment of titanium thermal barrier for low-temperature carbon nanotube growth
Authors: Chen G. Y. , Poa C. H. P. , Henley S. J. , Stolojan V. , Silva S. R. P. , Haq Sajad
Published: December 2005

Chemical vapor-synthesized carbon nanotubes are typically grown at temperatures around 600°C. We report on the deployment of a titanium layer to help elevate the constraints on the substrate temperature during plasma-assisted growth. The growth is possible through the lowering of the hydrocarbon content used in the deposition, with the only source of heat provided by the plasma. The nanotubes synthesized have a small diameter distribution, which deviates from the usual trend that the diameter is determined by the thickness of the catalyst film. Simple thermodynamic simulations also show that the quantity of heat, that can be distributed, is determined by the thickness of the titanium layer. Despite the lower synthesis temperature, it is shown that this technique allows for high growth rates as well as better quality nanotubes.
Impact of N on the lasing characteristics of GaInNAs∕GaAs quantum well lasers emitting from 1.29 to 1.52μm
Authors: Ulloa J. M. , Hierro A. , Montes M. , Damilano B. , Hugues M. , Barjon J. , Duboz J.-Y. , Massies J.
Published: December 2005

The origin of the degradation with N of the threshold current density (Jth) and external differential quantum efficiency (ηd) of 1.29 to 1.52μmGaInNAs∕GaAs laser diodes is analyzed. Adding N to InGaAs leads to a ∼25% reduction of the carrier injection efficiency and thus to an increase of Jth and a decrease of ηd. This effect is likely related to carrier recombination losses in the barriers and is independent of the N content. The optical absorption losses and the internal transparency current density are found to increase with N content, accounting for the rest of the degradation in Jth. Modeling of the transparency carrier and radiative current densities identifies the increase of the defect-related recombination coefficient in GaInNAs as the dominant effect leading to the N dependence of Jtr.
Cadmium telluride bulk crystal as an ultrafast nonlinear optical switch
Authors: Tatsuura Satoshi , Matsubara Takashi , Mitsu Hiroyuki , Sato Yasuhiro , Iwasa Izumi , Tian Minquan , Furuki Makoto
Published: December 2005

A semiconductor bulk crystal has several advantages as a nonlinear optical material, such as low processing cost, long interaction length, and alleviation of the free-carrier absorption caused by two-photon absorption (TPA). We examine optical properties of semiconductor bulk crystals with different orientations at 1.55μm and find that CdTe[111] has favorable capabilities, such as nonlinear refractive index of 5.23×10−17(m2W), TPA coefficient of 18.3(mmGW), and consequent figure of merit of 0.54. Optical three-dimensional measurements of reflective material are carried out using CdTe[111] as ultrafast optical Kerr shutter and clear images corresponding to surface steps are obtained.
Excellent frequency dispersion of thin gadolinium oxide high-k gate dielectrics
Authors: Pan Tung-Ming , Liao Chao-Sung , Hsu Hui-Hsin , Chen Chun-Lin , Lee Jian-Der , Wang Kuan-Ti , Wang Jer-Chyi
Published: December 2005

In this letter, we reported a high-k gadolinium oxide (Gd2O3) gate dielectric formed by reactive rf sputtering. It is found that the Gd2O3 gate dielectric film exhibits excellent electrical properties such as low leakage current density, high breakdown voltage, and almost no hysteresis and frequency dispersion in C-V curves comparable to that of HfO2 film. This indicates that postprocessing treatments can reduce a large amount of interface trap and can passivate a large amount of trapped charge at defect sites.
Photoluminescence characterization of strained Si-SiGe-on-insulator wafers with different Ge fractions
Authors: Wang Dong , Nakashima Hiroshi , Matsumoto Koji , Nakamae Masahiko
Published: December 2005

Photoluminescence (PL) was observed for three strained Si-SiGe-on-insulator wafers with different Ge fractions. The PL signals of wafers with 13% and 18% Ge fractions are deep-level free, implying high wafer qualities. A defect-related broad PL signal could be observed for a wafer with 25% Ge fraction. The dependences of the PL signals as well as the wafer’s qualities on Ge fractions were discussed in detail.
Avalanche breakdown and breakdown luminescence of AlGaN multiquantum wells
Authors: Zhang S. K. , Wang W. B. , Dabiran A. M. , Osinsky A. , Wowchak A. M. , Hertog B. , Plaut C. , Chow P. P. , Gundry S. , Troudt E. O. , Alfano R. R.
Published: December 2005

AlGaN p-i-n diodes were fabricated on 6H-SiC substrate using Al0.1Ga0.9N∕Al0.15Ga0.85N multiquantum wells (MQWs) for the active region. Avalanche breakdown and breakdown luminescence of these AlGaN MQW diodes were experimentally investigated. Breakdown electroluminescence from the MQW active layers was observed for unusually low bias values of 9 V. A continuous red shift of the interband luminescence resulting from the Stark effect was observed with increasing reverse bias. The breakdown threshold was found to be as low as 9 V. Polarization-induced electric fields in the Al0.1Ga0.9N well layers were found to have the same direction as the applied field. These polarization fields greatly enhance the ionization coefficient of electrons and help lower the threshold for avalanche breakdown. Substantial enhancement of the ionization coefficient produced by the polarization fields is quantitatively demonstrated with GaN∕AlGaN quantum wells by considering a polarization field with the same direction as the applied field within the GaN well layers.
Mechanical properties of a bulk Cu0.5NiAlCoCrFeSi glassy alloy in 288°C high-purity water
Authors: Chen Y. Y. , Hong U. T. , Yeh J. W. , Shih H. C.
Published: December 2005

The tensile properties and fatigue lives of a bulk Cu0.5NiAlCoCrFeSi glassy alloy were measured in 288°C water and compared with those obtained in air at ∼25°C. The bulk glassy alloy retained good tensile properties in 288°C water, i.e., tensile fracture strength and tensile fracture elongation were, respectively, 2660MPa and 2.01% in air and a little lower, 2000MPa and 1.49%, in 288°C water. The results of fatigue tests confirmed the significant decrease in fatigue life in high-temperature water. A decrease in strain rate from 0.5to0.001%s−1 decreased fatigue life by a factor of ∼5.
Thermal stability of low dielectric constant porous silica films
Authors: Esposito L. , Ottaviani G. , Carollo E. , Bacchetta M.
Published: December 2005

Thermal stability of porous-silica-based low dielectric constant, k, material deposited by chemical vapor deposition has been investigated in a wide temperature range. The films as-deposited and after heat treatments up to 600°C have Si1O1.6C1.4H2.3 composition, permittivity k≈2.8, and porosity h≈0.25. A skeleton of silicon dioxide and empty pores justifies the permittivity and porosity values. Permeation experiments with deuterated water vapor indicate that pores are interconnected. At 700°C, the film has Si1O1.6C1.4H1.4 composition, k≈2.4, and h≈0.21. Bonds with lower polarizability could be responsible for the decrease of k. Above 800°C, carbon segregation and nanoclusters formation occur.
Time-resolved dynamics of resonant and nonresonant broadband picosecond coherent anti-Stokes Raman scattering signals
Authors: Roy Sukesh , Meyer Terrence R. , Gord James R.
Published: December 2005

The time-resolved dynamics of resonant and nonresonant broadband picosecond coherent anti-Stokes Raman scattering (CARS) signals in gas-phase media are investigated. For ∼135ps pump and probe beams and ∼106ps Stokes beams, the magnitude of the nonresonant signals are decreased by more than three orders of magnitude when the probe beam is delayed by ∼110ps, whereas the resonant nitrogen CARS signal is reduced only by a factor of 3. Investigation of these time dynamics is important for understanding the optimal time delay for nonresonant background suppression as well as for understanding the collisional and Doppler dependence of the resonant CARS signals.
Fabrication of vertically aligned Si nanowires and their application in a gated field emission device
Authors: She J. C. , Deng S. Z. , Xu N. S. , Yao R. H. , Chen J.
Published: January 2006

A technique involving a combination of using self-assembled nanomask and anisotropic plasma etching is developed for fabricating vertically aligned single-crystalline Si nanowires (SiNWs). The SiNWs are shown to have excellent field emission performance with the turn-on field as low as 0.8MV∕m and the threshold field being 5.0MV∕m. In addition, an emission current density of 442mA∕cm2 can be obtained at an applied field of ∼14MV∕m. The technique is easily employed to fabricate arrays of SiNW-based field emission microtriodes. Mechanisms are proposed to explain the formation of the SiNWs and the observed field emission properties.
Changes in susceptibility of bovine sperm to in situ DNA denaturation during prolonged incubation at ambient temperature under conditions of exposure to reactive oxygen species and nuclease inhibitor
Authors: Krzyzosiak Jacek , Evenson Donald , Pitt Colin , Jost Lorna , Molan Peter , Vishwanath Ramakrishnan
Published: January 2006

Sperm were incubated for up to 9 days in the presence or absence of exogenous
hydrogen peroxide, phenylalanine, catalase and aurintricarboxylic acid to
assess the influence of reactive oxygen species and inhibition of
deoxyribonucleases on sperm chromatin stability. The assessment of sperm DNA
susceptibility to in situ acid denaturation by the sperm
chromatin structure assay did not detect any difference in chromatin stability
between sperm incubated for 9 days under aerobic and anaerobic conditions in a
diluent called 14G. Exposure to exogenous hydrogen peroxide under both aerobic
and anaerobic conditions and to phenylalanine under aerobic conditions (which
produces hydrogen peroxide by a reaction catalysed by the aromatic amino acid
oxidase present in sperm) was detrimental to sperm chromatin stability,
increasing its DNA susceptibility to in situ acid
denaturation over the incubation time. This effect was eliminated if catalase
was present in the diluent. Inclusion of the general deoxyribonuclease
inhibitor aurintricarboxylic acid in the diluent severely decreased sperm
chromatin stability under both aerobic and anaerobic conditions.
Aurintricarboxylic acid was mildly cytotoxic, as revealed by viability
assessment, under aerobic, but not under anaerobic, incubation conditions.
Exogenous hydrogen peroxide, either directly added to the diluent or generated
through the enzymatic oxidation of phenylalanine, was detrimental to sperm
motility and the integrity of the plasma membrane.
Maternal nutrient restriction during early to mid gestation alters the relationship between insulin-like growth factor I and bodyweight at term in fetal sheep
Authors: Heasman Lindsay , Brameld John , Mostyn Alison , Budge Helen , Dawson Janet , Buttery Peter , Stephenson Terence , Symonds Michael E.
Published: January 2006

The present study was designed to determine whether altered placental size, as
a consequence of maternal nutrient restriction in sheep between 28 and 77 days
gestation, is associated with a modified relationship between fetal weight or
dimensions and plasma insulin-like growth factor (IGF) I concentration or
abundance of hepatic IGF-I and IGF-II mRNA close to term. Singleton-bearing
ewes consumed either 1.2 (controls, n = 19) or
0.5 (nutrient restricted, n = 28) their
metabolizable energy (ME) requirements from 28 to 77 days gestation, after
which all ewes were fed in order to fully meet their ME requirements for
maintenance and pregnancy. Close to term (145 1 days) plasma IGF-I
concentration in cord blood was similar between groups, but only significantly
correlated with fetal bodyweight, thoracic circumference, crown–rump
length and lean body mass in lambs born to control
(r2 = 0.38, 0.76, 0.33,
0.42; P<0.001), and not to nutrient-restricted
(r2 = 0.01, 0.11, 0.01,
0.02) ewes. There were no differences in fetal hepatic expression of IGF-I and
IGF-II mRNA between groups close to term. In conclusion, maternal nutrient
restriction in early to mid gestation followed by feeding to requirements up
to term alters the relationship between fetal IGF-I, bodyweight and length.
Increasing maternal nutrition in later gestation after a prolonged period of
nutrient restriction may stimulate fetal nutrient supply such that fetal
growth is enhanced without an increase in plasma IGF-I. As a result, there is
a loss of the relationship between fetal weight and plasma IGF-I concentration
observed in fetuses whose mothers are fed adequately throughout gestation.
Revision of Atractocarpus (Rubiaceae: Gardenieae) in Australia and new combinations for some extra-Australian taxa
Authors: Puttock Christopher F.
Published: January 2006

The seven Australian species of Atractocarpus Schltr.& K.Krause are revised and full descriptions and keys provided. Two newsubspecies, A. benthamianus subsp.glaber and A. fitzalanii subsp.tenuipes are described. Shorter descriptions and notesare provided for eleven extra-Australian species transferred toAtractocarpus from NeofranciellaGuillaumin, Randia s.l., Sukunia A.C.Sm.,Sulitia Merr. and Trukia Kaneh.Seventeen new combinations are made:Atractocarpus benthamianus(Randia benthamiana F.Muell.),A. carolinensis(Randia carolinensis Valeton),A. chartaceus (Gardenia chartaceaF.Muell.), A. crosbyi(Randia crosbyi Burkill),A. decorus (Randia decoraValeton), A. fitzalanii(Gardenia fitzalanii F.Muell.),A. hirtus (Gardenia hirtaF.Muell.), A. longipes(Sukunia longipes A.C.Sm.),A. macarthurii (Randia macarthuriiF.Muell.), A. merikin(Gardenia merikin F.M.Bailey),A. obscurinervius(Gardenia obscurinervia Merr.),A. pentagonioides(Gardenia pentagonioides Seem.),A. pterocarpon(Franciella pterocarpon Guillaumin),A. sessilis (Randia sessilisF.Muell.), A. tahitiensis(Randia tahitiensis Nadeaud),A. tenuiflorus (Randia tenuifloraA.C.Sm.) and A. versteegii(Randia versteegii Valeton).
Revision of Leptosema (Fabaceae: Mirbelieae)
Authors: Crisp M.D.
Published: January 2006

Leptosema has 13 species with pea-flowers modified forbird-pollination. It is endemic to Australia, being distributed widely in thewest, centre, north and north-east of the continent. This paper is a monographof the genus. Updated cladistic and biogeographic analyses are presented and,based on the former, a new classification is formalised. Taxa described as neware Leptosema sect. Leptosema, L.ser. Callipetalum, L. cervicorneCrisp, L chapmanii Crisp,L. villosum Crisp, L. sect.Oolobium Crisp and L. ser.Pereostemon Crisp. New combinations or ranks are madefor L. aphyllum (Hook.) Crisp,L. macrocarpum (Benth.) Crisp, L.tomentosum (Benth.) Crisp,L. uniflorum (R.Br. ex Benth.) Crisp, andL. sect. Burgesia (F.Muell.)Crisp. Lectotypes are chosen for the synonymsBrachysema aphyllum Hook.,B. chambersii (F.Muell.) F.Muell. ex Benth.,B. macrocarpum Benth.,B. oxylobioides (F.Muell.) Benth.,B. uniflorum R.Br. ex Benth.,Burgesia homaloclada F.Muell.,Jacksonia anomala Ewart & Morrison,J. petrophiloides W.Fitzg. andTempletonia regina J.L.Drumm.
Involvement of KU80 in T-DNA integration in plant cells
Authors: Li Jianxiong , Vaidya Manjusha , White Charles , Vainstein Alexander , Citovsky Vitaly , Tzfira Tzvi
Published: December 2005

In
Agrobacterium
-mediated genetic transformation of plant cells, the bacterium exports a well defined transferred DNA (T-DNA) fragment and a series of virulence proteins into the host cell. Following its nuclear import, the single-stranded T-DNA is stripped of its escorting proteins, most likely converts to a double-stranded (ds) form, and integrates into the host genome. Little is known about the precise mechanism of T-DNA integration in plants, and no plant proteins specifically associated to T-DNA have been identified. Here we report the direct involvement of KU80, a protein that binds dsT-DNA intermediates. We show that
ku80
-mutant
Arabidopsis
plants are defective in T-DNA integration in somatic cells, whereas KU80-overexpressing plants exhibit increased susceptibility to
Agrobacterium
infection and increased resistance to DNA-damaging agents. The direct interaction between dsT-DNA molecules and KU80
in planta
was confirmed by immunoprecipitation of KU80 dsT-DNA complexes from
Agrobacterium
-infected plants. Transformation of KU80-overexpressing plants with two separate T-DNA molecules resulted in an increased rate of extrachromosomal T-DNA to T-DNA recombination, indicating that KU80 bridges between dsT-DNAs and double-strand breaks. This last result further supports the notion that integration of T-DNA molecules occurs through ds intermediates and requires active participation of the host's nonhomologous end-joining repair machinery.
Enhancer-independent Mu transposition from two topologically distinct synapses
Authors: Yin Zhiqi , Harshey Rasika M.
Published: December 2005

Transposition of Mu is strictly dependent on a specific orientation of the left (L) and right (R) ends of Mu and a distant enhancer site (E) located on supercoiled DNA. Five DNA crossings are trapped in the three-site synapse, two of which are contributed by the interwrapping of L and R. To determine the contribution of E to the interwrapping of Mu ends, we examined the topology of the LR synapse under two different enhancer-independent reaction conditions. One of these conditions, which also alleviates the requirement for a specific orientation of Mu ends, revealed two topologically distinct arrangements of the ends. In their normal relative orientation, L and R were either plectonemically interwrapped or aligned by random collision. Addition of the enhancer to this system channeled synapsis toward the interwrapped pathway. When the ends were in the wrong relative orientation, synapsis occurred exclusively by random collision. In the second enhancer-independent condition, which retains the requirement for a specific orientation of Mu ends, synapsis of L and R was entirely by interwrapping. The two distinct kinds of synapses also were identified by gel electrophoresis. We discuss these results in the context of the “topological filter” model and consider the many contributions the enhancer makes to the biologically relevant interwrapped synapse.
Modeling the spatiotemporal cortical activity associated with the line-motion illusion in primary visual cortex
Authors: Rangan Aaditya V. , Cai David , McLaughlin David W.
Published: December 2005

Our large-scale computational model of the primary visual cortex that incorporates orientation-specific, long-range couplings with slow NMDA conductances operates in a fluctuating dynamic state of intermittent desuppression (IDS), which captures the behavior of coherent spontaneous cortical activity, as revealed by
in vivo
optical imaging based on voltage-sensitive dyes. Here, we address the functional significance of the IDS cortical operating points by investigating our model cortex response to the Hikosaka line-motion illusion (LMI) stimulus—a cue of a quickly flashed stationary square followed a few milliseconds later by a stationary bar. As revealed by voltage-sensitive dye imaging, there is an intriguing similarity between the cortical spatiotemporal activity in response to (
i
) the Hikosaka LMI stimulus and (
ii
) a small moving square. This similarity is believed to be associated with the preattentive illusory motion perception. Our numerical cortex produces similar spatiotemporal patterns in response to the two stimuli above, which are both in very good agreement with experimental results. The essential network mechanisms underpinning the LMI phenomenon in our model are (
i
) the spatiotemporal structure of the LMI input as sculpted by the lateral geniculate nucleus, (
ii
) a priming effect of the long-range NMDA-type cortical coupling, and (
iii
) the NMDA conductance–voltage correlation manifested in the IDS state. This mechanism in our model cortex, in turn, suggests a physiological underpinning for the LMI-associated patterns in the visual cortex of anaesthetized cat.
Simultaneous dopamine and single-unit recordings reveal accumbens GABAergic responses: Implications for intracranial self-stimulation
Authors: Cheer Joseph F. , Heien Michael L. A. V. , Garris Paul A. , Carelli Regina M. , Wightman R. Mark
Published: December 2005

Intracranial self-stimulation (ICS) is a motivated behavior that results from contingent activation of the brain reward system. ICS with stimulating electrodes placed in the medial forebrain bundle (MFB) is particularly robust. However, the neurons that course through this pathway use a variety of neurotransmitters including dopamine and GABA. For this reason, the neurotransmitters that are central to this behavior, and the specific roles that they subserve, remain unclear. Here, we used extracellular electrophysiology and cyclic voltammetry at the same electrode in awake rats to simultaneously examine cell firing and dopamine release in the nucleus accumbens (NAc) during ICS and noncontingent stimulation of the MFB. ICS elicited dopamine release in the NAc and produced coincident time-locked changes (predominantly inhibitions) in the activity of a subset of NAc neurons. Similar responses were elicited with noncontingent stimulations. The changes in firing rate induced by noncontingent stimulations were reversed by the GABA
A
receptor antagonist bicuculline. Most time-locked unit activity was unaffected by D1 or D2-like dopamine-receptor antagonists, or by inhibition of evoked dopamine release, although, for a minority of units, the D1 dopamine-receptor antagonist SCH23390 attenuated neural activity. Thus, neurons in the NAc are preferentially inhibited by GABA
A
receptors after MFB stimulation, a mechanism that may also be important in ICS.
The evolutionary history of Cys-tRNA
Cys
formation
Authors: O'Donoghue Patrick , Sethi Anurag , Woese Carl R. , Luthey-Schulten Zaida A.
Published: December 2005

The recent discovery of an alternate pathway for indirectly charging tRNA
Cys
has stimulated a re-examination of the evolutionary history of Cys-tRNA
Cys
formation. In the first step of the pathway,
O
-phosphoseryl-tRNA synthetase charges tRNA
Cys
with
O
-phosphoserine (Sep), a precursor of the cognate amino acid. In the following step, Sep-tRNA:Cys-tRNA synthase (SepCysS) converts Sep to Cys in a tRNA-dependent reaction. The existence of such a pathway raises several evolutionary questions, including whether the indirect pathway is a recent evolutionary invention, as might be implied from its localization to the
Euryarchaea
, or, as evidence presented here indicates, whether this pathway is more ancient, perhaps already in existence at the time of the last universal common ancestral state. A comparative phylogenetic approach is used, combining evolutionary information from protein sequences and structures, that takes both the signature of horizontal gene transfer and the recurrence of the full canonical phylogenetic pattern into account, to document the complete evolutionary history of cysteine coding and understand the nature of this process in the last universal common ancestral state. Resulting from the historical study of tRNA
Cys
aminoacylation and the integrative perspective of sequence, structure, and function are 3D models of
O
-phosphoseryl-tRNA synthetase and SepCysS, which provide experimentally testable predictions regarding the identity and function of key active-site residues in these proteins. The model of SepCysS is used to suggest a sulfhydrylation reaction mechanism, which is predicted to occur at the interface of a SepCysS dimer.
CREB-binding protein controls response to cocaine by acetylating histones at the fosB promoter in the mouse striatum
Authors: Levine Amir A. , Guan Zhonghui , Barco Angel , Xu Shiqin , Kandel Eric R. , Schwartz James H.
Published: December 2005

Remodeling chromatin is essential for cAMP-regulated gene expression, necessary not only for development but also for memory storage and other enduring mental states. Histone acetylation and deacetylation mediate long-lasting forms of synaptic plasticity in
Aplysia
as well as cognition in mice. Here, we show that histone acetylation by the cAMP-response element binding protein (CREB)-binding protein (CBP) mediates sensitivity to cocaine by regulating expression of the fosB gene and its splice variant, ΔfosB, a transcription factor previously implicated in addiction. Using the chromatin immunoprecipitation assay with antibodies against histone H4 or CBP, we find that CBP is recruited to the fosB promoter to acetylate histone H4 in response to acute exposure to cocaine. We show that mutant mice that lack one allele of the CBP gene and have normal levels of fosB expression are less sensitive to chronic (10-day) administration of cocaine than are wild-type mice. This decreased sensitivity is correlated with decreased histone acetylation and results in decreased fosB expression and diminished accumulation of ΔfosB. Thus, CBP, which forms part of the promoter complex with CREB, mediates sensitivity to cocaine by acetylating histones.
Increase in TNF-α and inducible nitric oxide synthase-expressing dendritic cells in psoriasis and reduction with efalizumab (anti-CD11a)
Authors: Lowes Michelle A. , Chamian Francesca , Abello Maria Veronica , Fuentes-Duculan Judilyn , Lin Shao-Lee , Nussbaum Rachel , Novitskaya Inna , Carbonaro Henrietta , Cardinale Irma , Kikuchi Toyoko , Gilleaudeau Patricia , Sullivan-Whalen Mary , Wittkowski Knut M. , Papp Kim , Garovoy Marvin , Dummer Wolfgang , Steinman Ralph M. , Krueger James G.
Published: December 2005

We find that CD11c
+
cells with many markers of dendritic cells (DCs) are a major cell type in the skin lesions of psoriasis. These CD11c
+
cells, which are evident in both epidermis and dermis, are the sites for the expression of two mediators of inflammation, inducible nitric oxide synthase (iNOS) and TNF-α in diseased skin. These cells express HLA-DR, CD40, and CD86, lack the Langerin and CD14 markers of Langerhans cells and monocytes, respectively, and to a significant extent express the DC maturation markers DC-LAMP and CD83. Treatment of psoriasis with efalizumab (anti-CD11a, Raptiva) strongly reduces infiltration by these DCs in patients responding to this agent. Disease activity after therapy was more related to DC infiltrates and iNOS mRNA levels than T cell infiltrates, and CD11c
+
cells responded more quickly to therapy than epidermal keratinocytes. Our results suggest that a type of DC, which resembles murine “Tip-DCs” that can accumulate during infection, has proinflammatory effects in psoriasis through nitric oxide and TNF-α production, and can be an important target for suppressive therapies.
Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system
Authors: Xiao Zhongju , Suga Nobuo
Published: December 2005

Focal electric stimulation of the auditory cortex is well suited for exploration of the function of the corticofugal (descending) system and the neural mechanism of plasticity in the central auditory system, because it evokes changes in frequency-tuning, called best frequency (BF) shifts, as does auditory fear conditioning. The Doppler-shifted constant frequency (DSCF) area of the primary auditory cortex of the mustached bat is highly specialized for fine frequency analysis. Focal electric stimulation of the DSCF area evokes the BF shifts of ipsilateral cortical and collicular neurons away from the BF of stimulated neurons, whereas the stimulation evokes the BF shifts of contralateral cortical and collicular neurons either toward or away from the stimulated BF. The direction of contralateral BF shifts shows a flip-flop, depending on the spatial relationship between the stimulated and recorded neurons. This asymmetry in corticofugal modulation is mostly, if not totally, created by two subdivisions of the stimulated DSCF area that transmit signals to the contralateral DSCF area, presumably through the corpus callosum. This intriguing asymmetry in corticofugal modulation presumably functions for equalization of the reorganization of the frequency maps of the DSCF areas and subcortical auditory nuclei on both sides.
Black Musicians in Northern US Cities during the Early 20th Century: A Test of the Critical Mass Hypothesis of Urban Sub-culture Theory
Authors: Boyd Robert L.
Published: December 2005

According to the sub-culture theory of urbanism, a vital social world will emerge in a city when there is a 'critical mass' of members of some unique population. This hypothesis is tested by analysing the entertainment sub-culture that developed around the musical styles of the southern Blacks who moved to northern cities in the US in the early 20th century. The employment rate of Blacks in the musical professions is examined as an indicator of the vitality of this sub-culture, because this rate reflects the extent to which Blacks could make a living as musicians. Regression analyses of census data from 1910 to 1930 show that, as hypothesised, the rate at which Blacks were employed as professional musicians became positively associated with the size of the Black populations of the urban north only after these populations reached critical mass levels. It is concluded that the central notion of sub-culture theory-that group size intensifies sub-cultures and fosters unconventionality-can help to explain the rise of the social world of Black musicians in northern cities in the US during the early 20th century.
An Appraisal of the Use of Airline Data in Assessing the World City Network: A Research Note on Data
Authors: Derudder B. , Witlox F.
Published: December 2005

Information on air passenger flows is potentially a prime data source for assessing spatial patterns in the world city network, but previous analyses of this issue have been hampered by inadequate and/or partial data. The ensuing analytical deficiencies have reduced the overall value of these analyses. Therefore, this paper examines how some of these deficiencies might be rectified. First, it reviews the rationale for using airline data to analyse the world city network. Secondly, it assesses the problems encountered by previous research. The third section elaborates on the construction of a global intercity matrix based on the so-called Marketing Information Data Transfer database and explains how this matrix can circumvent some previously identified problems.
Networks in Cities, Cities in Networks: Territory and Globalisation Intertwined in Telecommunications Infrastructure Development in Europe
Authors: Rutherford Jonathan
Published: December 2005

There appears to be substantial convergence in the type and extent of telecommunications networks being deployed between and in major European cities to serve increasing numbers of corporate clients, thus forming one of the principal material elements in the development of a world city network. Through a broad theoretical discussion and an empirical exploration of the interurban and intraurban network development of one of the major telecommunications providers in Europe, however, it is shown how the planning, construction and expansion of these infrastructures remain crucially shaped by a variety of historical, regulatory, economic, physical and organisational constraints and compulsions which are specific to individual cities. It is argued that the mutually constitutive nature of economic and technological connectivities suggests, therefore, that the development of a world city network continues to have an important dimension of territorial fixity, reflecting the multiscalar entanglement of territory and globalisation that forms the world cities of today.
City Centre Regeneration through Residential Development: Contributing to Sustainability
Authors: Bromley Rosemary D. F. , Tallon Andrew R. , Thomas Colin J.
Published: December 2005

Following a discussion of recent policies for the city centre in Britain, the paper explores the contribution of residential development to aspects of sustainability, drawing on a range of survey evidence in Bristol and Swansea. The residents are frequent shoppers, helping to sustain the local daytime economy. Sustainability goals are also supported because large proportions of residents walk to city centre attractions, and many also to their places of work, showing reduced reliance on the private car. Support for the expanding nighttime economy reflects the age, gender and social class composition of the resident population, with different attractions receiving different levels of support from different social groups, but with younger adults as the mainstay. Sustainability in the city centre context appears best served by a majority of young adult residents, ameliorated by a sizeable proportion of older adults, and an absence of households with children. Grandiose government sustainability aims of creating the truly balanced community which includes many children, should be modified in this local context.
Social Cohesion in Post-war Estates in the Netherlands: Differences between Socioeconomic and Ethnic Groups
Authors: Dekker Karien , Bolt Gideon
Published: December 2005

In the Netherlands, the post-war housing estates are increasingly experiencing problems. Some of these relate to the concentration of households with a low socioeconomic status on these estates. The Big Cities Policy aims to improve liveability in deprived urban areas by increasing the number of high-income households and thereby decreasing the share of problem-causing households in the neighbourhood. The increased differentiation in education, ethnicity, income, home-ownership structure and lifestyle presents a challenge to social cohesion. This paper demonstrates how differences between socioeconomic and ethnic groups relate to different dimensions of social cohesion: social networks, common values and place attachment and identity. The issue is interesting since social cohesion can help enhance liveability and increase the tolerance between groups that is so often lacking in multiethnic neighbourhoods with residents from many different socioeconomic backgrounds. The paper is based on a fieldwork study undertaken on two estates in the cities of Utrecht and The Hague in the Netherlands. As expected, quantitative analyses show clear differences between native Dutch people and members of other ethnic groups. Contrary to expectations, socioeconomic characteristics do not lead on all dimensions of social cohesion to differences in the degree of social cohesion. The conclusion drawn is that increasing the diversity of socioeconomic or ethnic groups in deprived urban areas is likely to lead to less social cohesion.
Shifts along the Decommodification-Commodification Continuum: Housing Delivery and State Accumulation in Hong Kong
Authors: La Grange Adrienne , Pretorius Frederik
Published: December 2005

This paper engages with the discourse about commodification of housing in an Asian context and presents a methodology to explore shifts in the delivery of housing along the decommodification-commodification continuum. It reviews the extent to which the Hong Kong state has articulated an understanding of a continuum through its actions in the public and private housing sectors, and how it has acted developmentally in manipulating shifts along the continuum. It is found that, although Hong Kong had a large squatter population, the state controlled the commodification of squatter housing and also implemented an enormously successful and publically lucrative assisted home-ownership scheme, whose success in large part is explained by state management of the commodified nature of this tenure. The paper also reviews how the state's control of decommodified land through state ownership and leasehold alienation, and commodified housing in the private sector, led to the generation of large revenues to fund developmentalist activities. In all, unlike many other examples, the benefits of commodified housing in Hong Kong seem to have flowed in large measure from the private sector to the public sector; from this perspective, the paper offers another insight into the oft-neglected public management aspects of Hong Kong as a development case study.
Globalisation and the Structure of Urban Social Space: The Lesson from Tel Aviv
Authors: Schnell Izhak , Benjamini Yoav
Published: December 2005

Social area analysis tends to view the city as constituted of a mosaic of socially homogeneous containers. The Chicago model views the mosaic as compactly organised around one centre and as a response to geometrically deduced forces. The Los Angeles model views social areas to be socially constituted in a more dispersed geometry. Our model, verified in this study, shows that globalising cities may produce highly heterogeneous residential spaces, even in highly ethnic societies. We propose to start the analysis from individuals' behaviour, with respect to their actual daily life-spaces and social networks. We argue that, under these conditions, a multilayered spatial model better describes the socio-spatial reality of cities that integrate people in the globalising world. Each layer represents a socially constituted space which integrates participants in a particular social network. Members of the network manage their daily life in these spaces, which are not necessarily continuous, and in many cases expand into wide and sometimes even global horizons, creating thereby interstices with other groups' social spaces. In most cases, there are partly open social networks among layered social areas but, in one-third of the cases, protagonists developed social networks only with colleagues from their own ethnic group, avoiding interlayered networks. This may lead to social segregation even in residentially heterogeneous areas. In such cases, segregation is the result of a lack of social networks among layers. However, segregation may also follow the traditional model, in which a group concentrates in an ethnically homogeneous residential space. This may develop in areas claimed by one social group constituting a segregated territory and having intraethnic networks limited to the specific ethnic territory.
Capital, Crime Control and Statecraft in the Entrepreneurial City
Authors: Coleman Roy , Tombs Steve , Whyte Dave
Published: December 2005

Recent debates have drawn attention to the centrality of crime and disorder discourses within the rationale of contemporary urban entrepreneurial rule and how these have targeted ideological and political resources onto policing 'quality of life' infractions on the streets. In extending these insights, the paper focuses upon the regeneration of urban order in the UK and how this is being increasingly practised through a form of corporatised statecraft that underpins the shaping of discourses and responses to crime, harm and risk in city spaces. Attention is given to the processes by which 'regeneration' and entrepreneurialised governance are not only 'opening-up' but also 'closing-down' urban spaces as objects of surveillance and regulation. It is not only that crimes on the streets and associated hindrances to entrepreneurial rule are selected as the proper objects of power; at the same time, and through a series of integrally linked processes, other urban harms are being marginalised. The trajectory of regenerative discourse and practice, it is argued, is resulting in a stabilisation of opportunity structures for corporate crimes and harms, whilst at the same further exposing the relatively powerless to the punitive gaze of the extended surveillance capacity being developed as part of the entrepreneurial landscape.