bluuebunny/crossref_metadata_2025 huggingface dataset:
A new panlectal medium in Nigeria
Authors: Ajiboye Tunde
Published: November 2005

This paper seeks to draw attention to a phenomenon in language development in Nigeria which tends to support the possibility of language barriers breaking down, not through English or any other exogenous medium, but through the resources provided by our own languages. The index towards the panlectal evolution of our languages is provided by a research recently undertaken by the writer.

On the basis of about 70 lexical cum para-lexical items, it was discovered that speakers of languages as far apart as Hausa, Yoruba and Igbo could still 'communicate' common realities of the society without recourse to their known primary linguistic loyalty. It is being suggested that with words like 'tòkunbò', 'kòbòkóbò', 'ògá' and 'apeteshi' being in use not only in the source language(s), but outside it (them), the way seems open to the possible eventual neutralization of linguistic cleavages. This trend, if sustained, will contribute to the view that communicative efficiency in a multilingual setting may not be the exclusive preserve of the 'colonial' medium. Thirdly, the unifying language of tomorrow (e.g. 'pinglish') may well see evidence from this research as ready data for exploitation.
Negative Evidence in Language Classroom Activities
Authors: Pica Teresa , Washburn Gay N.
Published: November 2005

This study sought to identify and describe how negative evidence was made available and accessible in responses to learners during two classroom activities: a teacher-led discussion, which emphasized communication of subject matter content, and a teacher-led sentence construction exercise, which focused on application of grammatical rules.

Data came from adult, pre-academic English language learners during six discussions of American film and literature, and six sets of sentence construction exercises. Findings revealed little availability of negative evidence in the discussions, as students' fluent, multi-error contributions drew responses that were primarily back-channels and continuation moves. Greater availability and accessibility of negative evidence were found in the sentence construction exercises, as students were given feedback following their completion of individual sentences.

Results from the study suggested several pedagogical implications and applications.
Control and Regulatory Mechanisms Associated with Thermogenesis in Flying Insects and Birds
Authors: Loli Denise , Bicudo José Eduardo P. W.
Published: November 2005

Most insects and birds are able to fly. The chitin made exoskeleton of insects poses them several constraints, and this is one the reasons they are in general small sized animals. On the other hand, because birds possess an endoskeleton made of bones they may grow much larger when compared to insects. The two taxa are quite different with regards to their general “design” platform, in particular with respect to their respiratory and circulatory systems. However, because they fly, they may share in common several traits, namely those associated with the control and regulatory mechanisms governing thermogenesis. High core temperatures are essential for animal flight irrespective of the taxa they belong to. Birds and insects have thus evolved mechanisms which allowed them to control and regulate high rates of heat fluxes. This article discusses possible convergent thermogenic control and regulatory mechanisms associated with flight in insects and birds.
Role of Sarco/Endoplasmic Reticulum Ca2+-ATPase in Thermogenesis
Authors: de Meis Leopoldo , Arruda Ana Paula , Carvalho Denise P.
Published: November 2005

Enzymes are able to handle the energy derived from the hydrolysis of phosphate compounds in such a way as to determine the parcel that is used for work and the fraction that is converted into heat. The sarco/endoplasmic reticulum Ca2+-ATPases (SERCA) is a family of membrane-bound ATPases that are able to transport Ca2+ ion across the membrane using the chemical energy derived from ATP hydrolysis. The heat released during ATP hydrolysis by SERCA may vary from 10 up to 30 kcal/mol depending on the SERCA isoform used and on whether or not a Ca2+ gradient is formed across the membrane. Drugs such as heparin, dimethyl sulfoxide and the platelet-activating factor (PAF) are able to modify the fraction of the chemical energy released during ATP hydrolysis that is used for Ca2+ transport and the fraction that is dissipated in the surrounding medium as heat. The thyroid hormone 3,5,3′-triiodo l-thyronine (T3) regulates the expression and function of the thermogenic SERCA isoforms. Modulation of heat production by SERCA might be one of the mechanisms involved in the increased thermogenesis found in hyperthyroidism.
Genomic Structure and Regulation of Mitochondrial Uncoupling Protein Genes in Mammals and Plants
Authors: Nogueira Fábio T. S. , Borecký Jiri , Vercesi Aníbal E. , Arruda Paulo
Published: November 2005

Uncoupling mitochondrial proteins (UCPs) belong to a discrete family within the mitochondrial anion carrier superfamily. Several uncoupling protein types have been found in mitochondria from mammals and plants, as well as in fishes, fungi, and protozoa. Mammalian UCPs and plant uncoupling proteins (PUMPs) form five distinct subfamilies. Only subfamily III contains both plant and animal uncoupling proteins, as well as UCPs from primitive eukaryotic organisms, which suggest that this group may represent an ancestral cluster from which other UCPs/PUMPs may have evolved. Genetic data indicate that UCPs/PUMPs are regulated at the transcriptional, post-transcriptional, and translational levels. Tissue/organ- and stress-specific gene expression suggests that UCPs/PUMPs are involved in the general balance of basic energy expenditure, protection against reactive oxygen species, and thermogenesis. Finally, the simultaneous occurrence of PUMP and alternative oxidase, another energy-dissipating system in plant mitochondria, raises the question of their response to biotic and abiotic stress at the transcriptional and functional levels.
Neonatal Programming of Body Weight Regulation and Energetic Metabolism
Authors: de Moura Egberto Gaspar , Cottini Magna Cottini F
Published: November 2005

Programming is an epigenetic phenomena by which nutritional, hormonal, physical psychological and other stressful events acting in a critical period of life, such as gestation and lactation, modifies in a prolonged way certain physiological functions. This process was preserved by natural selection as an important adaptive tool for survival of organisms living in nutritional impaired areas. So, malnutrition during gestation and lactation turns on different genes that provide the organism with a thrifty phenotype. In the case of an abundant supply of nutrients after this period, those organisms that were adapted to a low metabolic waste and higher energy utilization will be in a higher risk of developing metabolic diseases, such as obesity, hyperlipidemia, diabetes mellitus and hypertension. The kind of malnutrition, duration and intensity are important for the type of programming obtained. We discuss some of the hormonal and metabolic changes that occur in gestation or lactation, when malnutrition is applied to the mothers and their offspring. Some of these changes, such as an increase of maternal triiodothyronine (T3), leptin and glucocorticoids (GC) and decrease in prolactin are by itself potential programming factors. Most of these hormones can be transfer through the milk that has other important macronutrients composition changes in malnourished dams. We discuss the programming effects of some of these hormones upon body weight and composition, leptin, thyroid and adrenal functions, and their effects on liver, muscle and adipose tissue metabolism and the consequences on thermogenesis.
Plant Uncoupling Mitochondrial Protein and Alternative Oxidase: Energy Metabolism and Stress
Authors: Borecký Jiří , Vercesi Aníbal E.
Published: November 2005

Energy-dissipation in plant mitochondria can be mediated by inner membrane proteins via two processes: redox potential-dissipation or proton electrochemical potential-dissipation. Alternative oxidases (AOx) and the plant uncoupling mitochondrial proteins (PUMP) perform a type of intrinsic and extrinsic regulation of the coupling between respiration and phosphorylation, respectively. Expression analyses and functional studies on AOx and PUMP under normal and stress conditions suggest that the physiological role of both systems lies most likely in tuning up the mitochondrial energy metabolism in response of cells to stress situations. Indeed, the expression and function of these proteins in non-thermogenic tissues suggest that their primary functions are not related to heat production.
Role of oxidative stress in pathophysiology of peripheral neuropathy and modulation by N‐acetyl‐l‐cysteine in rats
Authors: Naik Ajit K. , Tandan Surendra K. , Dudhgaonkar Shailesh P. , Jadhav Sachin H. , Kataria Meena , Prakash V. Ravi , Kumar Dinesh
Published: November 2005

Objectives: The objectives of this study were to examine the role of reactive oxygen species and oxidative stress in peripheral neuropathy and behavioural pain responses in experimentally induced chronic constriction injury (CCI) of sciatic nerve of rat. Effect of N‐acetyl‐l‐cysteine (NAC) administered intraperitoneally, was also investigated on CCI‐induced neuropathic pain in rats.

Methods: Neuropathy was induced by CCI of the right sciatic nerve in ketamine anaesthetized rats. Effect of intraperitoneally administered NAC in rats was also investigated using nociceptive behavioural tests. Malondialdehyde, an index of oxidative stress and antioxidant enzymes was also estimated in ligated sciatic nerve.

Results: Behavioural tests, mechanical, thermal and cold stimuli confirmed the development of neuropathic pain after the CCI. The malondialdehyde levels of ligated sciatic nerves were significantly increased compared to non‐ligated sciatic nerves (sham operated). The antioxidant enzyme reduced, glutathione was inhibited, while superoxide dismutase increased. However, catalase remained unaffected in the injured sciatic nerves. Intraperitoneal administration of NAC resulted in significant reduction of hyperalgesia in CCI‐induced neuropathic rats.

Conclusions: This study identifies antioxidants superoxide dismutase and reduced glutathione, and oxidative stress as important determinants of neuropathological and behavioural consequences of CCI‐induced neuropathy, and NAC may be a potential candidate for alleviation of neuropathic pain.
Prognostic value of umbilical‐middle cerebral artery pulsatility index ratio in fetuses with growth restriction
Authors: Piazze J. , Padula F. , Cerekja A. , Cosmi E.V. , Anceschi M.M.
Published: November 2005

Objective: To study the utility of Doppler velocimetry and computerized cardiotocography in the management of intrauterine growth restriction and prediction of neonatal outcome. Patients and methods: Seventy‐two pregnant women with fetuses showing growth restriction and delivered within 48 h of their last Doppler velocimetry evaluation. The last computerized cardiotocographic trace from these fetuses was used for statistical analysis, and the last trace from the healthy fetuses of 93 consecutive women undergoing cesarean section was used as control. Umbilical artery pulsatility index (UA PI), middle cerebral artery pulsatility index (MCA PI), UA PI / MCA PI ratio, and uterine artery resistance index (Ut RI) were assessed. Results: Among women with growth‐restricted fetuses, all parameters were significantly higher in those who had hypertension; and in those who had diabetes, only the UA PI / MCA ratio was significantly higher. Umbilical artery PI values and the UA PI / MCA ratio were higher in those who had a nonreassuring result to computerized nonstress test immediately before delivery. A multiple logistic analysis showed that the UA PI / MCA ratio was the only Doppler velocimetry parameter predicting cardiotocographic nonreactivity; furthermore, the predictivity of extended newborn hospitalization (longer than 15 days) was verified, with a sensitivity of 56% and a specificity of 92% when the ratio was higher than 1.26. Conclusion: The MCA PI of fetuses with growth restriction should be assessed. The UA PI / MCA ratio is predictive of a nonreactive computerized cardiotocography trace and of prolonged neonatal hospitalization.
Meteorological evaluation of a weather‐chemistry forecasting model using observations from the TEXAS AQS 2000 field experiment
Authors: Bao J.‐W. , Michelson S. A. , McKeen S. A. , Grell G. A.
Published: November 2005

Meteorological forecasts for the period of 25–30 August 2000 from a coupled weather‐chemistry model are evaluated both qualitatively and quantitatively using the observations from different instruments that were deployed in metropolitan Houston during the Texas Air‐Quality Study 2000 field experiment. The qualitative comparison is carried out with respect to the meteorological processes associated with the influence of the large‐scale flow on the sea breeze that are essential to the development of the surface ozone exceedances over Houston, while the quantitative comparison is focused on the errors and uncertainties of the forecasts. The qualitative comparison is performed with respect to a conceptual model for the influence of the large‐scale flow on the sea breeze. The comparison shows that although the overall forecasted influence of the large‐scale flow on the sea breeze compares qualitatively well to the observations, quantitative differences do exist between the forecasted and observed wind speed and direction, as well as with temperature and moisture. It is found that the forecasted low‐level winds have a systematic easterly bias and the forecasted low‐level temperature has a cold bias. The errors in the forecasted low‐level moisture appear relatively small, but with a cold bias they lead to higher relative humidity in the forecast than in reality. There is great sensitivity of the model forecasted low‐level winds to different initial conditions. The quantitative comparison also indicates that the model's effective horizontal resolution corresponding to 1.67‐km grid spacing is actually about 10 km.
Assessment of an ensemble of seven real‐time ozone forecasts over eastern North America during the summer of 2004
Authors: McKeen S. , Wilczak J. , Grell G. , Djalalova I. , Peckham S. , Hsie E.‐Y. , Gong W. , Bouchet V. , Menard S. , Moffet R. , McHenry J. , McQueen J. , Tang Y. , Carmichael G. R. , Pagowski M. , Chan A. , Dye T. , Frost G. , Lee P. , Mathur R.
Published: November 2005

The real‐time forecasts of ozone (O3) from seven air quality forecast models (AQFMs) are statistically evaluated against observations collected during July and August of 2004 (53 days) through the Aerometric Information Retrieval Now (AIRNow) network at roughly 340 monitoring stations throughout the eastern United States and southern Canada. One of the first ever real‐time ensemble O3 forecasts, created by combining the seven separate forecasts with equal weighting, is also evaluated in terms of standard statistical measures, threshold statistics, and variance analysis. The ensemble based on the mean of the seven models and the ensemble based on the median are found to have significantly more temporal correlation to the observed daily maximum 1‐hour average and maximum 8‐hour average O3 concentrations than any individual model. However, root‐mean‐square errors (RMSE) and skill scores show that the usefulness of the uncorrected ensembles is limited by positive O3 biases in all of the AQFMs. The ensembles and AQFM statistical measures are reevaluated using two simple bias correction algorithms for forecasts at each monitor location: subtraction of the mean bias and a multiplicative ratio adjustment, where corrections are based on the full 53 days of available comparisons. The impact the two bias correction techniques have on RMSE, threshold statistics, and temporal variance is presented. For the threshold statistics a preferred bias correction technique is found to be model dependent and related to whether the model overpredicts or underpredicts observed temporal O3 variance. All statistical measures of the ensemble mean forecast, and particularly the bias‐corrected ensemble forecast, are found to be insensitive to the results of any particular model. The higher correlation coefficients, low RMSE, and better threshold statistics for the ensembles compared to any individual model point to their preference as a real‐time O3 forecast.
Aerosol radiative forcing over Bay of Bengal and Chennai: Comparison with maritime, continental, and urban aerosol models
Authors: Ramachandran S.
Published: November 2005

Aerosol radiative forcings are estimated using the measured aerosol optical depths and a radiative transfer model over the Bay of Bengal and Chennai located on the east coast of India during February–March 2001. The monthly mean aerosol radiative forcings obtained during February are found to be the largest over Bay of Bengal when compared to those determined over coastal India, the Arabian Sea, and tropical Indian Ocean. The top of the atmosphere (TOA) forcing over Bay of Bengal is found to be −9 Wm−2 compared to −6 Wm−2 over the Arabian Sea. Atmospheric absorptions are about +22, +13, +6, and +0.3 Wm−2 over Bay of Bengal, coastal India, Arabian Sea, and tropical Indian Ocean, respectively. The high‐atmospheric absorption over Bay of Bengal is attributed to the presence of higher soot content. The radiative forcings estimated over Bay of Bengal and Chennai are contrasted with those of maritime, continental, and urban aerosol models. TOA forcing for urban aerosols is found to change sign from negative to positive when land surface reflectance is used. The forcing sign change is a consequence of higher albedo over land when compared to the ocean surface and presence of larger amount of soot in urban aerosol than maritime aerosol. Thus a higher soot content over land can exert more significant influence in terms of climate change than over the oceans. The forcings over Bay of Bengal and Chennai are an order of magnitude higher compared to the pristine southern Indian Ocean indicative of high anthropogenic influence.
Direct inhibition of the pacemaker (If) current in rabbit sinoatrial node cells by genistein
Authors: Altomare Claudia , Tognati Agnese , Bescond Jocelyn , Ferroni Arnaldo , Baruscotti Mirko
Published: November 2005

Genistein is a tyrosine kinase inhibitor which interferes with the activity of several ionic channels either by altering modulatory phosphorylating processes or by direct binding. In whole‐cell conditions, genistein induces a partial inhibition of the pacemaker (If) current recorded in cardiac sinoatrial and ventricular myocytes.

We investigated the mechanism of action of genistein (50 μM) on theIfcurrent in whole‐cell, cell‐attached, and inside‐out configurations, and the measured fractional inhibitions were similar: 26.6, 27.2, and 33.6%, respectively.

When ATP was removed from the whole‐cell pipette solution no differences were revealed in the effect of the drug when compared to metabolically active cells. Genistein fully maintained its blocking ability even when herbimycin, a tyrosine kinase inhibitor, was added to the whole‐cell ATP‐free pipette solution.

Genistein‐induced block was independent of the gating state of the channel and did not display voltage or current dependence; this independence distinguishes genistein from all other f‐channel blockers.

When inside‐out experiments were performed to test for a direct interaction with the channel, genistein, superfused on the intracellular side of the membrane, decreased the maximalIfconductance, and slightly shifted the current–activation curve to the left. Furthermore, the effect of genistein was independent of cAMP modulation.

We conclude that, in addition to its tyrosine kinase‐inhibitory properties, genistein also blocksIfby directly interacting with the channel, and thus cannot be considered a valuable pharmacological tool to investigate phosphorylation‐dependent modulatory pathways of theIfcurrent and of cardiac rhythm.

British Journal of Pharmacology(2006)147, 36–44. doi:10.1038/sj.bjp.0706433
In vivorelease of non‐neuronal acetylcholine from the human skin as measured by dermal microdialysis: effect of botulinum toxin
Authors: Schlereth Tanja , Birklein Frank , Haack Katrinan , Schiffmann Susanne , Kilbinger Heinz , Kirkpatrick Charles James , Wessler Ignaz
Published: November 2005

Acetylcholine is synthesized in the majority of non‐neuronal cells, for example in human skin. In the present experiments, thein vivorelease of acetylcholine was measured by dermal microdialysis.

Two microdialysis membranes were inserted intradermally at the medial shank of volunteers. Physiological saline containing 1 μMneostigmine was perfused at a constant rate of 4 μl min−1and the effluent was collected in six subsequent 20 min periods. Acetylcholine was measured by high‐pressure liquid chromatography (HPLC) combined with bioreactors and electrochemical detection.

Analysis of the effluent by HPLC showed an acetylcholine peak that disappeared, when the analytical column was packed with acetylcholine‐specific esterase, confirming the presence of acetylcholine.

In the absence of neostigmine, 71±51 pmol acetylcholine (n=4) was found during a 120 min period. The amount increased to 183±43 pmol (n=34), when the perfusion medium contained 1 μMneostigmine.

Injection of 100 MU botulinum toxin subcutaneously blocked sweating completely, but the release of acetylcholine was not affected (botulinum toxin treated skin: 116±70 pmol acetylcholine/120 min; untreated skin: 50±20 pmol;n=4).

Quinine (1 mM), inhibitor of organic cation transporters, and carnitine (0.1 mM), substrate of the Na+‐dependent carnitine transporter OCTN2, tended to reduce acetylcholine release (by 40%, not significant).

Our experiments demonstrate, for the first time, thein vivorelease of non‐neuronal acetylcholine in human skin. Organic cation transporters are not predominantly involved in the release of non‐neuronal acetylcholine from the human skin.

British Journal of Pharmacology(2006)147, 183–187. doi:10.1038/sj.bjp.0706451
The reaction kinetics of Cu with the CdTe(111)-B surface: Formation of metastable CuxTe(x∼2)
Authors: Teeter Glenn
Published: November 2005

In the present study, elemental Cu is deposited on the clean CdTe(111)-B surface and annealed in vacuum. Surface-composition maps generated by scanning Auger microcopy provide evidence that a reaction occurs between Cu and the CdTe(111)-B substrate that results in the formation of a metastable copper telluride phase CuxTe(x∼2) at the surface. In situ thermal-desorption mass spectrometry measurements show that elemental Cd is released during the reaction and desorbs from the surface. Desorption of Te from the substrate is suppressed during the reaction. Analysis of Cd desorption traces demonstrates that the Cu+CdTe(111)-B reaction proceeds via zero-order kinetics, with an activation energy of 180±5kJmol−1.
Weak intermolecular interactions calculated with diffusion Monte Carlo
Authors: Diedrich Christian , Lüchow Arne , Grimme Stefan
Published: November 2005

The performance of fixed node diffusion Monte Carlo (FNDMC) for weakly interacting molecules is investigated. The effect of Gaussian basis sets on the asymptotic description of the molecular orbitals which is crucial for a successful importance sampling is analyzed for the example of the hydrogen atom. We find that accurate reference binding energies of the water, the ammonia, and the T-shaped as well as the parallel-displaced benzene dimer are correctly reproduced by FNDMC. The binding energies for the benzene dimers are −3.00(0.38) and −3.58(0.38)kcal∕mol, respectively. The description of the methane dimer which has the smallest binding energy and a quite large intermolecular distance requires a more flexible basis set of diffuse quadruple-ζ quality in order to prevent sampling errors.
Canonical perturbation theory for complex electron dynamics in gyrotron resonators
Authors: Kominis Y. , Dumbrajs O. , Avramides K. A. , Hizanidis K. , Vomvoridis J. L.
Published: November 2005

Complex electron dynamics in gyrotron resonators are analyzed in the context of the Hamiltonian formalism. Application of the canonical perturbation theory provides analytical approximate invariants of the electron motion. The latter are used for describing the resonant structure of the electron phase space and the electron rest energies at the output of the cavity. Hysteresis effects are also described through analytic expressions and approximate electron distribution functions are provided. The general case of resonant interaction at an arbitrary harmonic of the electron cyclotron frequency is considered and the effect of a varying frequency mismatch is studied. Also, the case of electron interaction with multiple rf modes is investigated.
Stability and electronic structure of ordered Si0.75Ge0.25C alloy
Authors: Chen Z. W. , Lv M. Y. , Liu R. P.
Published: November 2005

Calculations are performed on the stability and electronic structure of an ordered Si0.75Ge0.25C alloy within the generalized gradient approximation using the first-principles method. The alloy is stable at zero pressure and temperature, with its lattice constant 4.34 Å close to that of cubic SiC and bulk modulus 223 GPa. An analysis of the band structure and density of states shows the cubic alloy to be an indirect semiconductor with a wider band gap compared to SiC and therefore is a candidate material that can function in heterostructure applications. When combined with cubic SiC to form heterostructure bipolar transistors, an enhancement coefficient 2×104 for current gain β would be expected relative to the SiC homojunction bipolar junction transistors at room temperature.
Effect of nitrogen incorporation in ferromagnetic (Ga,Mn)As epilayers
Authors: Oshiyama I. , Kondo T. , Munekata H.
Published: November 2005

Physical properties of ferromagnetic p-type Ga1−xMnxAs1−yNy epitaxial films (x=0.045 and y=0–0.032) grown by molecular-beam epitaxy are described. It is found that the incorporation of nitrogen gradually suppresses the metallic behavior of p-(Ga,Mn)As, especially at low temperatures. The Curie temperature TC decreases accordingly with increasing y value. The reduction in TC is discussed in terms of the suppression of hole-mediated long-range spin-exchange interaction due to the enhancement of carrier localization. Perpendicular magnetic anisotropy appears at the region around y=0.02, reflecting the reduced lattice constant due to substitutionally incorporated nitrogen. No significant change was found in the magnetic circular dichroism spectra in the photon energy region around the band gap of (Ga,Mn)As. Our experimental results show that the theoretical prediction based on the double exchange interaction [V. A. Dinh et al., Jpn. J. Appl. Phys., Part 2 42, L888 (2003)] is hardly materialized in this system.
Titanium fullerenoid oxides
Authors: Ducati C. , Barborini E. , Bongiorno G. , Vinati S. , Milani P. , Midgley P. A.
Published: November 2005

Nanostructured titanium oxide films synthesized by supersonic cluster beam deposition were analyzed by high-resolution transmission electron microscopy. Nanoparticles were produced in a pulsed microplasma cluster source in the presence of He or helium-oxygen mixture as carrier gas. While films grown using He consist only of rutile and anatase TiO2 nanocrystals formed upon exposure to air, films grown with a He∕O mixture also contain isolated TiOx cages that closely resemble carbon fullerenes. The diameter of the cages ranges from about 0.9to2.7nm. A fraction of the cages have irregular shapes, possibly induced by oxygen vacancies. The TiOx fullerenoids grow in the gas phase, in a narrow temperature/pressure range within the cluster source, and are preserved through low-energy deposition.
Emission properties of a-plane GaN grown by metal-organic chemical-vapor deposition
Authors: Paskov P. P. , Schifano R. , Monemar B. , Paskova T. , Figge S. , Hommel D.
Published: November 2005

We report on the emission properties of nonpolar a-plane GaN layers grown on r-plane sapphire. Temperature-, excitation-density-, and polarization-dependent photoluminescences and spatially resolved microphotoluminescence and cathodoluminescence are employed in order to clarify the nature of the different emission bands in the 3.0–3.5eV spectral range. In the near band-edge region the emission lines of the donor-bound excitons (3.472eV) and free excitons (3.478eV) are resolved in the polarized low-temperature spectra, indicating a good quality of the layers. At low energies two other emissions bands with intensity and shape varying with the excited area are observed. The 3.42eV emission commonly attributed to the excitons bound to basal plane stacking faults shows thermal quenching with two activation energies (7 and 30meV) and an S-shaped temperature dependence of the peak position. This behavior is analyzed in terms of hole localization in the vicinity of the stacking faults. The emission band that peaked at 3.29eV is found to blueshift and saturate with increasing excitation intensity. The spatially resolved cathodoluminesence measurements show that the emission is asymmetrically distributed around the triangular-shaped pits occurring at the surface. The 3.29eV emission is suggested to involve impurities, which decorate the partial dislocation terminating the basal stacking faults.
Sample heating in near-field scanning optical microscopy
Authors: Erickson Elizabeth S. , Dunn Robert C.
Published: November 2005

Heating near the aperture of aluminum coated, fiber optic near-field scanning optical microscopy probes was studied as a function of input and output powers. Using the shear-force feedback method, near-field probes were positioned nanometers above a thermochromic polymer and spectra were recorded as the input power was varied. Excitation at 405 nm of a thin polymer film incorporating perylene and N-allyl-N-methylaniline leads to dual emission peaks in the spectra. The relative peak intensity is temperature sensitive leading to a ratiometric measurement, which avoids complications based solely on intensity. Using this method, we find that the proximal end of typical near-field probes modestly increase in temperature to 40–45 °C at output powers of a few nanowatts (input power of ∼0.15mW). This increases to 55–65 °C at higher output powers of 50 nW or greater (input power of ∼2–4mW). Thermal heating of the probe at higher powers leads to probe elongation, which limits the heating experienced by the sample.
On the role of dislocation loops in silicon light emitting diodes
Authors: Lourenço M. A. , Milosavljević M. , Gwilliam R. M. , Homewood K. P. , Shao G.
Published: November 2005

The role of boron-induced dislocation loops on the suppression of the luminescence thermal quenching in silicon-based light-emitting diodes is investigated here. Luminescence measurements and cross-sectional transmission-electron-microscopy images from devices fabricated by boron implantation into crystalline silicon, and into a pre-amorphized substrate, to prevent the boron-induced loops formation, were compared. The results show that, in the devices incorporating dislocation loops between the depletion region and sample surface (the boron induced loops), the thermal quenching has been completely eliminated, in contrast with devices fabricated from the pre-amorphized substrate where strong thermal quenching is still observed.
Negative luminescence of long-wavelength InAs∕GaSb superlattice photodiodes
Authors: Hoffman Darin , Hood Andrew , Wei Yajun , Gin Aaron , Fuchs Frank , Razeghi Manijeh
Published: November 2005

The electrically pumped emission behavior of binary type-II InAs∕GaSb superlattice photodiodes has been studied in the spectral range between 8μm and 13μm. With a radiometric calibration of the experimental setup, the internal and external quantum efficiency has been determined in the temperature range between 80K and 300K for both, the negative and positive luminescence. The negative luminescence efficiency approaches values as high as 35% without antireflection coating. The temperature dependence of the internal quantum efficiency near zero-bias voltage allows for the determination of the electron-hole-electron Auger recombination coefficient of Γn=1×1024cm6s−1.
Phonon-hopping thermal conduction in quantum dot superlattices
Authors: Shamsa Manu , Liu Weili , Balandin Alexander A. , Liu Jianlin
Published: November 2005

We investigated the thermal conductivity in Ge∕Si quantum dot superlattices both theoretically and experimentally. It is proposed that thermal conduction through the quantum dot superlattices can be described by the phonon-hopping model with the interface transparency obtained from the experiment. Thermal conductivity has been measured as a function of temperature T from 10K to 400K. We have observed an order of magnitude decrease in thermal conductivity value compared to bulk and shift of its peak position to higher temperatures. The thermal conductivity manifests T0.7-T0.9 dependence for T⩽200K. The phonon-hopping model describes the measured thermal conductivity surprisingly well over the wide range of T from ∼40Kto400K. The model allows one to include the specifics of thermal conduction in quantum dot superlattices, such as the dot size, disorder, and interface quality. Our results suggest that the examined quantum dot superlattices are closer to the disordered or polycrystalline materials in terms of thermal transport.
Solution-processed n-type organic thin-film transistors with high field-effect mobility
Authors: Chikamatsu Masayuki , Nagamatsu Shuichi , Yoshida Yuji , Saito Kazuhiro , Yase Kiyoshi , Kikuchi Koichi
Published: November 2005

We report the performance of solution-processed n-type organic thin-film transistors (OTFTs) based on C60 derivatives. Long-chain alkyl-substituted C60, C60-fused N-methylpyrrolidine-meta-C12 phenyl (C60MC12), was used as a semiconducting layer. The C60MC12-thin-film transistor shows high electron mobility of 0.067cm2∕Vs in saturation regime. From the result of x-ray diffraction analysis, the C60MC12 active layer forms highly ordered crystalline film. We found that self-assemble ability of long alkyl chains plays an important role for fabrication of highly ordered crystalline film, leading to achievement of high electron mobility in solution-processed n-type OTFTs.
Void formation during early stages of passivation: Initial oxidation of iron nanoparticles at room temperature
Authors: Wang C. M. , Baer D. R. , Thomas L. E. , Amonette J. E. , Antony Jiji , Qiang You , Duscher G.
Published: November 2005

The examination of nanoparticles allows study of some processes and mechanisms that are not as easily observed for films or other types of studies in which sample preparation artifacts have been the cause of some uncertainties. Microstructure of iron nanoparticles passivated with iron oxide shell was studied using high-resolution transmission electron microscopy and high-angle annular dark-field imaging in aberration-corrected scanning transmission electron microscopy. Voids were readily observed on both small single-crystal α-Fe nanoparticles formed in a sputtering process and the more complex particles created by reduction of an oxide by hydrogen. Although the formation of hollow spheres of nanoparticles has been engineered for Co at higher temperatures [Y. Yin, R. M. Riou, C. K. Erdonmez, S. Hughes, G. A. Somorjari, and A. P. Alivisatos, Science 304, 711 (2004)], they occur for iron at room temperature and provide insight into the initial oxidation processes of iron. There exists a critical size of ∼8nm for which the iron has been fully oxidized, leading to a hollow iron-oxide nanoparticle. For particles larger than the critical size, an iron/iron-oxide core-shell structure was formed and voids reside at the interface between the oxide shell and the iron core. The present observation provides new insight for tailoring of metal/metal-oxide core-shell structured nanoparticles for applications related to optics, magnetism, and nanoelectronics.
Scaffolds, Stem Cells, and Tissue Engineering: A Potent Combination!
Authors: Cao Yang , Croll Tristan I. , Lees Justin G. , Tuch Bernard E. , Cooper-White Justin J.
Published: November 2005

Stem cells, either from embryonic or adult sources, have demonstrated the potential to differentiate into a wide range of tissues depending on culture conditions. This makes them prime candidates for use in tissue engineering applications. Current technology allows us to process biocompatible and biodegradable polymers into three-dimensional (3D) configurations, either as solid porous scaffolds or hydrogels, with controlled macro and/or micro spatial geometry and surface chemistry. Such control provides us with the ability to present highly controlled microenvironments to a chosen cell type. However, the precise microenvironments required for optimal expansion and/or differentiation of stem cells are only now being elucidated, and hence the controlled use of stem cells in tissue engineering remains a very young field. We present here a brief review of the current literature detailing interactions between stem cells and 3D scaffolds of varying morphology and chemical properties, concluding with remaining challenges for those interested in tissue engineering using tailored scaffolds and stem cells.
MyoD induces myogenic differentiation through cooperation of its NH2- and COOH-terminal regions
Authors: Ishibashi Jeff , Perry Robert L. , Asakura Atsushi , Rudnicki Michael A.
Published: November 2005

MyoD and Myf5 are basic helix-loop-helix transcription factors that play key but redundant roles in specifying myogenic progenitors during embryogenesis. However, there are functional differences between the two transcription factors that impact myoblast proliferation and differentiation. Target gene activation could be one such difference. We have used microarray and polymerase chain reaction approaches to measure the induction of muscle gene expression by MyoD and Myf5 in an in vitro model. In proliferating cells, MyoD and Myf5 function very similarly to activate the expression of likely growth phase target genes such as L-myc, m-cadherin, Mcpt8, Runx1, Spp1, Six1, IGFBP5, and Chrnβ1. MyoD, however, is strikingly more effective than Myf5 at inducing differentiation-phase target genes. This distinction between MyoD and Myf5 results from a novel and unanticipated cooperation between the MyoD NH2- and COOH-terminal regions. Together, these results support the notion that Myf5 functions toward myoblast proliferation, whereas MyoD prepares myoblasts for efficient differentiation.
The matrix protein CCN1 (CYR61) induces apoptosis in fibroblasts
Authors: Todorovicç Viktor , Chen Chih-Chiun , Hay Nissim , Lau Lester F.
Published: November 2005

Integrin-mediated cell adhesion to extracellular matrix proteins is known to promote cell survival, whereas detachment from the matrix can cause rapid apoptotic death in some cell types. Contrary to this paradigm, we show that fibroblast adhesion to the angiogenic matrix protein CCN1 (CYR61) induces apoptosis, whereas endothelial cell adhesion to CCN1 promotes cell survival. CCN1 induces fibroblast apoptosis through its adhesion receptors, integrin α6β1 and the heparan sulfate proteoglycan (HSPG) syndecan-4, triggering the transcription-independent p53 activation of Bax to render cytochrome c release and activation of caspase-9 and -3. Neither caspase-8 activity nor de novo transcription or translation is required for this process. These results show that cellular interaction with a specific matrix protein can either induce or suppress apoptosis in a cell type–specific manner and that integrin α6β1-HSPGs can function as receptors to induce p53-dependent apoptosis.
FAK signaling is critical for ErbB-2/ErbB-3 receptor cooperation for oncogenic transformation and invasion
Authors: Benlimame Naciba , He Qiang , Jie Su , Xiao Dingzhang , Xu Ying Jie , Loignon Martin , Schlaepfer David D. , Alaoui-Jamali Moulay A.
Published: November 2005

The overexpression of members of the ErbB tyrosine kinase receptor family has been associated with cancer progression. We demonstrate that focal adhesion kinase (FAK) is essential for oncogenic transformation and cell invasion that is induced by ErbB-2 and -3 receptor signaling. ErbB-2/3 overexpression in FAK-deficient cells fails to promote cell transformation and rescue chemotaxis deficiency. Restoration of FAK rescues both oncogenic transformation and invasion that is induced by ErbB-2/3 in vitro and in vivo. In contrast, the inhibition of FAK in FAK-proficient invasive cancer cells prevented cell invasion and metastasis formation. The activation of ErbB-2/3 regulates FAK phosphorylation at Tyr-397, -861, and -925. ErbB-induced oncogenic transformation correlates with the ability of FAK to restore ErbB-2/3–induced mitogen-activated protein kinase (MAPK) activation; the inhibition of MAPK prevented oncogenic transformation. In contrast, the inhibition of Src but not MAPK prevented ErbB–FAK-induced chemotaxis. In migratory cells, activated ErbB-2/3 receptors colocalize with activated FAK at cell protrusions. This colocalization requires intact FAK. In summary, distinct FAK signaling has an essential function in ErbB-induced oncogenesis and invasiveness.
IGF-I increases bone marrow contribution to adult skeletal muscle and enhances the fusion of myelomonocytic precursors
Authors: Sacco Alessandra , Doyonnas Regis , LaBarge Mark A. , Hammer Mark M. , Kraft Peggy , Blau Helen M.
Published: November 2005

Muscle damage has been shown to enhance the contribution of bone marrow–derived cells (BMDCs) to regenerating skeletal muscle. One responsible cell type involved in this process is a hematopoietic stem cell derivative, the myelomonocytic precursor (MMC). However, the molecular components responsible for this injury-related response remain largely unknown. In this paper, we show that delivery of insulin-like growth factor I (IGF-I) to adult skeletal muscle by three different methods—plasmid electroporation, injection of genetically engineered myoblasts, and recombinant protein injection—increases the integration of BMDCs up to fourfold. To investigate the underlying mechanism, we developed an in vitro fusion assay in which co-cultures of MMCs and myotubes were exposed to IGF-I. The number of fusion events was substantially augmented by IGF-I, independent of its effect on cell survival. These results provide novel evidence that a single factor, IGF-I, is sufficient to enhance the fusion of bone marrow derivatives with adult skeletal muscle.
Complete maturation of the plastid protein translocation channel requires a type I signal peptidase
Authors: Inoue Kentaro , Baldwin Amy J. , Shipman Rebecca L. , Matsui Kyoko , Theg Steven M. , Ohme-Takagi Masaru
Published: November 2005

The protein translocation channel at the plastid outer envelope membrane, Toc75, is essential for the viability of plants from the embryonic stage. It is encoded in the nucleus and is synthesized with a bipartite transit peptide that is cleaved during maturation. Despite its important function, the molecular mechanism and the biological significance of the full maturation of Toc75 remain unclear. In this study, we show that a type I signal peptidase (SPase I) is responsible for this process. First, we demonstrate that a bacterial SPase I converted Toc75 precursor to its mature form in vitro. Next, we show that disruption of a gene encoding plastidic SPase I (Plsp1) resulted in the accumulation of immature forms of Toc75, severe reduction of plastid internal membrane development, and a seedling lethal phenotype. These phenotypes were rescued by the overexpression of Plsp1 complementary DNA. Plsp1 appeared to be targeted both to the envelope and to the thylakoidal membranes; thus, it may have multiple functions.
The immunogenicity of a viral cytotoxic T cell epitope is controlled by its MHC-bound conformation
Authors: Tynan Fleur E. , Elhassen Diah , Purcell Anthony W. , Burrows Jacqueline M. , Borg Natalie A. , Miles John J. , Williamson Nicholas A. , Green Kate J. , Tellam Judy , Kjer-Nielsen Lars , McCluskey James , Rossjohn Jamie , Burrows Scott R.
Published: November 2005

Thousands of potentially antigenic peptides are encoded by an infecting pathogen; however, only a small proportion induce measurable CD8+ T cell responses. To investigate the factors that control peptide immunogenicity, we have examined the cytotoxic T lymphocyte (CTL) response to a previously undefined epitope (77APQPAPENAY86) from the BZLF1 protein of Epstein-Barr virus (EBV). This peptide binds well to two human histocompatibility leukocyte antigen (HLA) allotypes, HLA-B*3501 and HLA-B*3508, which differ by a single amino acid at position 156 (156Leucine vs. 156Arginine, respectively). Surprisingly, only individuals expressing HLA-B*3508 show evidence of a CTL response to the 77APQPAPENAY86 epitope even though EBV-infected cells expressing HLA-B*3501 process and present similar amounts of peptide for CTL recognition, suggesting that factors other than peptide presentation levels are influencing immunogenicity. Functional and structural analysis revealed marked conformational differences in the peptide, when bound to each HLA-B35 allotype, that are dictated by the polymorphic HLA residue 156 and that directly affected T cell receptor recognition. These data indicate that the immunogenicity of an antigenic peptide is influenced not only by how well the peptide binds to major histocompatibility complex (MHC) molecules but also by its bound conformation. It also illustrates a novel mechanism through which MHC polymorphism can further diversify the immune response to infecting pathogens.
Differential antitumor immunity mediated by NKT cell subsets in vivo
Authors: Crowe Nadine Y. , Coquet Jonathan M. , Berzins Stuart P. , Kyparissoudis Konstantinos , Keating Rachael , Pellicci Daniel G. , Hayakawa Yoshihiro , Godfrey Dale I. , Smyth Mark J.
Published: November 2005

We showed previously that NKT cell–deficient TCR Jα18−/− mice are more susceptible to methylcholanthrene (MCA)-induced sarcomas, and that normal tumor surveillance can be restored by adoptive transfer of WT liver-derived NKT cells. Liver-derived NKT cells were used in these studies because of their relative abundance in this organ, and it was assumed that they were representative of NKT cells from other sites. We compared NKT cells from liver, thymus, and spleen for their ability to mediate rejection of the sarcoma cell line (MCA-1) in vivo, and found that this was a specialized function of liver-derived NKT cells. Furthermore, when CD4+ and CD4− liver-derived NKT cells were administered separately, MCA-1 rejection was mediated primarily by the CD4− fraction. Very similar results were achieved using the B16F10 melanoma metastasis model, which requires NKT cell stimulation with α-galactosylceramide. The impaired ability of thymus-derived NKT cells was due, in part, to their production of IL-4, because tumor immunity was clearly enhanced after transfer of IL-4–deficient thymus-derived NKT cells. This is the first study to demonstrate the existence of functionally distinct NKT cell subsets in vivo and may shed light on the long-appreciated paradox that NKT cells function as immunosuppressive cells in some disease models, whereas they promote cell-mediated immunity in others.