bluuebunny/crossref_metadata_2025 huggingface dataset:
Vital effects in coccolith calcite: Cenozoic climate‐pCO2 drove the diversity of carbon acquisition strategies in coccolithophores?
Authors: Bolton Clara T. , Stoll Heather M. , Mendez‐Vicente Ana
Published: September 2012

Coccoliths, calcite plates produced by the marine phytoplankton coccolithophores, have previously shown a large array of carbon and oxygen stable isotope fractionations (termed “vital effects”), correlated to cell size and hypothesized to reflect the varying importance of active carbon acquisition strategies. Culture studies show a reduced range of vital effects between large and small coccolithophores under high CO2, consistent with previous observations of a smaller range of interspecific vital effects in Paleocene coccoliths. We present new fossil data examining coccolithophore vital effects over three key Cenozoic intervals reflecting changing climate and atmospheric partial pressure of CO2 (pCO2). Oxygen and carbon stable isotopes of size‐separated coccolith fractions dominated by different species from well preserved Paleocene‐Eocene thermal maximum (PETM, ∼56 Ma) samples show reduced interspecific differences within the greenhouse boundary conditions of the PETM. Conversely, isotope data from the Plio‐Pleistocene transition (PPT; 3.5–2 Ma) and the last glacial maximum (LGM; ∼22 ka) show persistent vital effects of ∼2‰. PPT and LGM data show a clear positive trend between coccolith (cell) size and isotopic enrichment in coccolith carbonate, as seen in laboratory cultures. On geological timescales, the degree of expression of vital effects in coccoliths appears to be insensitive topCO2 changes over the range ∼350 ppm (Pliocene) to ∼180 ppm (LGM). The modern array of coccolith vital effects arose after the PETM but before the late Pliocene and may reflect the operation of more diverse carbon acquisition strategies in coccolithophores in response to decreasing Cenozoic pCO2.
The sub‐Himalayan fold‐thrust belt in the 1905 Kangra earthquake zone: A critical taper model perspective for seismic hazard analysis
Authors: Singh T. , Awasthi A. K. , Caputo R.
Published: September 2012

We investigate the broader epicentral area of the M = 7.8, 1905 Kangra earthquake(s), north India, affecting the sub‐Himalayan hills. The tectonics of the area is characterized by two major rentrants (Kangra and Dehradun) interposed by the Nahan Salient. The first‐order topography between the Himalayan Frontal Thrust and the Main Boundary Thrust shows a marked lateral variation along strike of the mean gradient, characterized by a very small mean slope angle (∼1°) in correspondence with the reentrants and higher values (∼3°) in the salient. These tectonic and topographic features also show a good correspondence with the peculiar macroseismic field of the 1905 event(s), which is characterized by two distinct intensity maxima, separated by a distance of ∼150 km, clearly overlapping the two major tectonic reentrants. In this paper, based on available geological and geophysical information and a critical analysis of the general mechanical constraints, the seismogenic volume of the external sector of the chain is investigated in terms of critical taper model attempting to clarify the possible correlations between tectonics, topography and seismicity in the sub‐Himalayan belt. Based on different assumptions, three possible seismotectonic scenarios are explored in order to constrain their likelihood and therefore to suggest a potential seismic gap in the area corresponding to the Nahan Salient, which may experience an event of significant magnitude in the future.
The role of solar wind reconnection in driving the Neptune radio emission
Authors: Desch M. D. , Farrell W. M. , Kaiser M. L. , Lepping R. P. , Steinberg J. T. , Villanueva L. A.
Published: September 2012

The only remote diagnostic of conditions within the outer planets' magnetospheres is the highly variable flux of low‐frequency radio waves. As at the other radio planets, Neptune radio emission also manifests, on a time scale of days, major intensity fluctuations that are indicative of a solar wind energy‐coupling process of some kind. We find that the merging of interplanetary magnetic field lines with Neptune's magnetosphere is the best predictor of emitted radio energy. By contrast, viscouslike energy coupling processes, such as might be caused by solar wind density or bulk speed fluctuations, are apparently ineffective in driving the radio emission.
Micron‐sized particles detected near Neptune by the Voyager 2 plasma wave instrument
Authors: Gurnett D. A. , Kurth W. S. , Granroth L. J. , Allendorf S. C. , Poynter R. L.
Published: September 2012

During the Voyager 2 flyby of Neptune the plasma wave and radio astronomy instruments detected numerous impulsive signals that were interpreted as micron‐sized particles striking the spacecraft. This paper presents an analysis of the particle impacts observed by the plasma wave instrument. From analysis of wideband antenna voltage waveforms a peak impact rate of 443 s−1 was observed near the inbound equator crossing, which occurred at a radial distance of 3.45 RN, and a peak impact rate of 151 s−1 was observed near the outbound ring plane crossing, which occurred at a radial distance of 4.20 RN. The inbound peak is offset by 146 ± 4 km north of the equatorial plane, and the outbound peak is offset by 948 ± 65 km south of the equatorial plane. A Gaussian fit of the impact rate profile has a width (to the e−l points) of 537 ± 22 km for the inbound “core” component and 2,073 ± 392 km for the outbound component. These impact rates correspond to maximum number densities of a few times 10−3 m−3. Analysis of the voltage amplitudes induced on the antenna indicates that the particles have masses ranging from 10−10 g to a few times 10−9 g, with an uncertainty of up to a factor of 10. Assuming a mass density of 1 g/cm3, these particles would have radii in the range 5‐10 μm, with an uncertainty of about a factor of 2 to 3. In addition to the high impact rates observed near the two equator crossings, an impact rate of at least 0.6 s−1 was observed over the entire region inside about 8 RN, including the northern polar region. Likely sources for these particles include (1) several of the small satellites (1989N1, 1989N2, 1989N3, and 1989N4) discovered near Neptune by Voyager and (2) the rings. Electromagnetic forces may play an important role in diffusing the particles away from the equatorial plane.
Triton's surface properties: A preliminary analysis from ground‐based, Voyager photopolarimeter subsystem, and laboratory measurements
Authors: Buratti B. J. , Lane A. L. , Gibson J. , Burrows H. , Nelson R. M. , Bliss D. , Smythe W. , Garkanian V. , Wallis B.
Published: September 2012

The surface properties of Triton have been determined from a threefold approach involving analysis of ground‐based and Voyager photopolarimeter subsystem observations of its phase curve, theoretical modeling, and laboratory measurements of the phase functions of a wide variety of materials. The physical parameters derived include the single‐scattering albedo, the single‐particle phase function, the compaction state of the optically active portion of the regolith, and the degree of macroscopic roughness. We find that Triton has a high single‐scattering albedo (0.96 ± 0.01 at 0.75 μm) and an unusually compacted surface possibly similar to that of Europa. Preliminary results suggest that Triton's single‐particle phase function and the macroscopically rough character of its surface are Similar to those of most other icy satellites. Laboratory measurements of the phase curve of a sample of a high‐albedo, compact volatile‐contaminant analogue are in reasonable agreement with Triton's phase curve and provide evidence that the model parameters derived for Triton's surface are physically realistic.
Dust distribution around Neptune: Grain impacts near the ring plane measured by the Voyager Planetary Radio Astronomy Experiment
Authors: Pedersen B. M. , Meyer‐Vernet N. , Aubier M. G. , Zarka P.
Published: September 2012

During the Voyager 2 flyby of Neptune the planetary radio astronomy (PRA) experiment recorded an intense noise near the equatorial plane around 3.4 and 4.2 RN, as already observed during previous Voyager ring plane crossings at Saturn and Uranus. This noise is interpreted as being due to impact ionization of dust grains striking the spacecraft. We deduce a power law index of the grain mass distribution of about 2. The PRA system is sensitive to particles with radii larger than ∼1.6 μm, and the largest particles, detected near the ring plane, are evaluated to have a radius of ∼10 μm. The spatial dust distribution along the spacecraft trajectory around the two equatorial crossings is found not to be symmetrical with respect to the ring plane and spread over wide regions: over ∼2 RN perpendicularly to the equatorial plane with the densest part concentrated within ∼700 km. The vertical optical depth τ of this dense region is found to be 10−6 – 10−8.
Voyager observations of Nereid
Authors: Thomas Peter , Veverka Joseph , Helfenstein Paul
Published: September 2012

We have analyzed observations of Nereid obtained by Voyager 2 over a 12‐day interval at solar phase angles of 25°–96° to determine the satellite's size and basic photometric properties. Nereid's radius is found to be 170 ± 25 km; its geometric albedo (λ = 0.48 μm) exceeds 0.16 and is probably close to 0.2. There is no evidence of a rotation light curve in the Voyager observations, any light curve amplitude being definitely less than 0.15 magnitude (mag) (total amplitude). Hapke's photometric model, applied to a combination of the Voyager and Earth‐based data taken at opposition, yields a geometric albedo of about 0.2, a phase integral of 0.5, and a Bond albedo of 0.1. In terms of albedo, color, and photometric properties, Nereid is similar to some of the icy satellites of Uranus but is quite distinct from the group of six small inner satellites of Neptune discovered by Voyager. Although these satellites share Nereid's neutral color, they are much darker (albedos 6% versus 20%) and have much higher phase coefficients (0.035 versus 0.024 mag/deg). We conclude that Nereid is unlike these “carbonaceous” objects and is probably a “dirty” icy body. The satellite's spin state (period and spin axis direction) cannot be determined from the Voyager data.
CH4 and haze in Triton's lower atmosphere
Authors: Herbert Floyd , Sandel B. R.
Published: September 2012

Voyager 2 ultraviolet spectrometer occultation observations at Triton have revealed two constituents of the troposphere: CH4 and another absorber visible between 1400 and 1600 Å below about 20 km altitude. The CH4appears to be saturated at the surface at both entrance and exit occultation sites. The density scale height and wavelength dependence of the long‐wavelength absorber are consistent with Rayleigh scattering in N2. However, the inferred N2 column abundance is inconsistent with the Voyager radio science (RSS) occultation measurement, and so the N2hypothesis is discarded. The most attractive alternative hypothesis for the identity of the long‐wavelength opacity is Rayleigh scattering by an aerosol haze, because the optical depth is noticeably wavelength dependent, both within the EUV range of measurement and over the range between the EUV and visual wavelengths. EUV Rayleigh scattering requires that the haze particles be very small (≤ 0.03 μm) and abundant. These characteristics suggest formation as photochemical smog or condensing N2 with a great abundance of nucleation centers. Condensation onto ions allows rapid formation of very small particles, so possibly ions created by penetrating magnetospheric charged particles (0.1 to several MeV) are nucleating the haze. Small particle size also promotes long residence times against settling, essential for accumulation to significant abundance and suggesting that eddy transport dominates settling. If this is the case, the haze scale height likely approximates the gas scale height, and the implied temperature is around 38 K. This is lower than the 50 K estimated by the RSS and is also too low for the dust devil hypothesis for the visible atmospheric plumes.
The Voyager encounter with Neptune
Authors: Stone E. C. , Miner E. D.
Published: September 2012

The Voyager Neptune/Interstellar Mission is the continuation of the NASA program of exploration of the outer solar system. The prior phases of the Voyager program included encounters with Jupiter, Saturn, and Uranus as summarized in the Journal of Geophysical Research (volume 86, pages 8121–8841, 1981; volume 88, pages 8625–9018, 1983; and volume 92, pages 14,873–15,375, 1987). Following the successes of these prior phases of the Voyager mission, a new phase was undertaken with the objectives of exploring the Neptune system and continuing the investigation of the interplanetary and interstellar media. An additional objective was to preserve the capability to extend the investigations to include a search for the heliopause. Summaries of results from the Neptune and Triton encounters are reported in the following papers.
Modeling Interindividual Variability in Physiologically Based Pharmacokinetics and Its Link to Mechanistic Covariate Modeling
Authors: Huisinga W , Solms A , Fronton L , Pilari S
Published: September 2012

Covariate modeling is a key step in the analysis of clinical data and is essential for establishing dosing recommendations for specific populations, e.g., in obese individuals and children. So far, no systematic approach exists to leverage the knowledge inherent in physiologically based pharmacokinetic (PBPK) models in this context. We introduce (i) a novel approach to model interindividual variability in PBPK models based on lean body weight (LBW); and (ii) a systematic approach to translate interindividual variability into the design of mechanistic covariate models. We derive a new covariate relation for the volume of distribution at steady state (Vss) that seamlessly integrates body weight and LBW as covariates, with a weighting factor depending on the physicochemical properties of the drug. We further show that for children, PBPK‐based extrapolation and allometric scaling result in very similar predictions for Vss and blood clearance.

CPT: Pharmacometrics & Systems Pharmacology (2012) 1, e4; doi:10.1038/psp.2012.3; advance online publication 26 September 2012
Basic Concepts in Population Modeling, Simulation, and Model‐Based Drug Development
Authors: Mould DR , Upton RN
Published: September 2012

Modeling is an important tool in drug development; population modeling is a complex process requiring robust underlying procedures for ensuring clean data, appropriate computing platforms, adequate resources, and effective communication. Although requiring an investment in resources, it can save time and money by providing a platform for integrating all information gathered on new therapeutic agents. This article provides a brief overview of aspects of modeling and simulation as applied to many areas in drug development.

CPT: Pharmacometrics & Systems Pharmacology (2012) 1, e6; doi:10.1038/psp.2012.4; advance online publication 26 September 2012
A Semi‐Mechanistic Metabolism Model of CYP3A Substrates in Pregnancy: Predicting Changes in Midazolam and Nifedipine Pharmacokinetics
Authors: Quinney SK , Mohamed AN , Hebert MF , Haas DM , Clark S , Umans JG , Caritis SN , Li L ,   For the Obstetric‐fetal Pharmacology Research Unit Network
Published: September 2012

Physiological changes in pregnancy, including changes in body composition and metabolic enzyme activity, can alter drug pharmacokinetics. A semi‐mechanistic metabolism model was developed to describe the pharmacokinetics of two cytochrome P450 3A (CYP3A) substrates, midazolam and nifedipine, in obstetrics patients. The model parameters were optimized to fit the data of oral midazolam pharmacokinetics in pregnant women, by increasing CYP3A‐induced hepatic metabolism 1.6‐fold in the model with no change in gut wall metabolism. Fetal metabolism had a negligible effect on maternal plasma drug concentrations. Validation of the model was performed by applying changes in volume of distribution and metabolism, consistent with those observed for midazolam, to the pharmacokinetics parameters of immediate‐release nifedipine in healthy volunteers. The predicted steady‐state areas under the concentration–time curve (AUCs) for nifedipine were within 15% of the data observed in pregnant women undergoing treatment for preterm labor. This model predicts the pharmacokinetics of two CYP3A substrates in pregnancy, and may be applicable to other CYP3A substrates as well.

CPT: Pharmacometrics & Systems Pharmacology (2012) 1, e2; doi:10.1038/psp.2012.5; advance online publication 26 September 2012
Bridging Clinical Outcomes of Canakinumab Treatment in Patients With Rheumatoid Arthritis With a Population Model of IL‐1β Kinetics
Authors: Ait‐Oudhia S , Lowe PJ , Mager DE
Published: September 2012

Canakinumab, an anti‐interleukin‐1β (IL‐1β) monoclonal antibody, is approved for cryopyrin‐associated periodic syndromes and is under investigation for the management of other inflammatory disorders. In this study, population‐based pharmacokinetic–pharmacodynamic models were developed to understand responses to canakinumab in patients with rheumatoid arthritis (RA). Total canakinumab and total IL‐1β concentrations were obtained from four clinical trials (n = 472). In contrast to traditional models, free IL‐1β concentrations were calculated and used to link canakinumab to changes in C‐reactive protein (CRP) concentrations and American College of Rheumatology (ACR) scores of 20, 50, and 70% improvement. Temporal patterns of total canakinumab, total IL‐1β, CRP, and ACR scores were all well described. Simulations confirmed that 150 mg every 4 weeks improved ACR scores in patients with RA, but no additional benefit was provided by higher doses or more frequent administration. Integrating predicted endogenous free ligand concentrations with biomarkers and clinical outcomes could be extended to new therapies of anti‐inflammatory diseases.

CPT: Pharmacometrics & Systems Pharmacology (2012) 1, e5; doi:10.1038/psp.2012.6; advance online publication 26 September 2012
Optimization of triazole-based TGR5 agonists towards orally available agents
Authors: Futatsugi Kentaro , Bahnck Kevin B. , Brenner Martin B. , Buxton Joanne , Chin Janice E. , Coffey Steven B. , Dubins Jeffrey , Flynn Declan , Gautreau Denise , Guzman-Perez Angel , Hadcock John R. , Hepworth David , Herr Michael , Hinchey Terri , Janssen Ann M. , Jennings Sandra M. , Jiao Wenhua , Lavergne Sophie Y. , Li Bryan , Li Mei , Munchhof Michael J. , Orr Suvi T. M. , Piotrowski David W. , Roush Nicole S. , Sammons Matthew , Stevens Benjamin D. , Storer Gregory , Wang Jian , Warmus Joseph S. , Wei Liuqing , Wolford Angela C.
Published: September 2012

With the challenge of striking the balance of TGR5 potency and clearance, the screening strategy as well as medicinal chemistry strategy are discussed in this article.
Adapted Stories: Creating Accessible Stories for Children With Complex Language Problems
Authors: Dodd Janet L.
Published: September 2012

Many children with autism spectrum and other language impairing disorders present with complicated language problems (CLP; Franke & Durbin, 2011). These children exhibit delays across multiple domains of language and often benefit from narrative- and story-based interventions. However, many children’s stories—the vehicle often employed for these types of interventions—are often too complex for them. The purpose of this article is to introduce a strategy for making stories accessible, linguistically and cognitively, for children with CLP.
An Overview of Dementias
Authors: Dalai Venkata Vijaya K. , Childress Jason E. , Schulz Paul E
Published: September 2012

Dementia is a major public health concern that afflicts an estimated 24.3 million people worldwide. Great strides are being made in order to better diagnose, prevent, and treat these disorders. Dementia is associated with multiple complications, some of which can be life-threatening, such as dysphagia. There is great variability between dementias in terms of when dysphagia and other swallowing disorders occur. In order to prepare the reader for the other articles in this publication discussing swallowing issues in depth, the authors of this article will provide a brief overview of the prevalence, risk factors, pathogenesis, clinical presentation, diagnosis, current treatment options, and implications for eating for the common forms of neurodegenerative dementias.
Apraxia in Dementia: Impact on Oral Intake
Authors: Foundas Anne L. , Shields Jessica A.
Published: September 2012

Dementia is defined as a decline from a prior level of cognitive-behavioral function and is commonly associated with deficits in learned skilled movements (i.e., apraxia). Specifically, patients with Alzheimer's disease, the most common form of degenerative dementia, frequently have problems with manipulating and using tools, such as using a fork to eat a meal. With disease progression, these patients can have difficulty with oral intake, including problems with swallowing.
Design and analysis of a radio frequency extractor in an S-band relativistic klystron amplifier
Authors: Zhang Zehai , Zhang Jun , Shu Ting , Qi Zumin
Published: September 2012

A radio frequency (RF) extractor converts the energy of a strongly modulated intense relativistic electron beam (IREB) into the energy of high power microwave in relativistic klystron amplifier (RKA). In the aim of efficiently extracting the energy of the modulated IREB, a RF extractor with all round coupling structure is proposed. Due to the all round structure, the operating transverse magnetic mode can be established easily and its resonant property can be investigated with an approach of group delay time. Furthermore, the external quality factor can be low enough. The design and analysis of the extractor applied in an S-band RKA are carried out, and the performance of the extractor is validated with three-dimensional (3D) particle-in-cell simulations. The extraction efficiency reaches 27% in the simulation with a totally 3D model of the whole RKA. The primary experiments are also carried out and the results show that the RF extractor with the external quality factor of 7.9 extracted 22% of the beam power and transformed it into the high power microwave. Better results are expected after the parasitic mode between the input and middle cavities is suppressed.
Local existence of solutions to the free boundary value problem for the primitive equations of the ocean
Authors: Ignatova Mihaela , Kukavica Igor , Ziane Mohammed
Published: September 2012

Lions, Temam, and Wang in [“Problème à frontière libre pour les modèles couplés de l'océan et de l'atmosphère,” Acad. Sci., Paris, C. R. 318(12), 1165–1171 (1994)] introduced a free surface model for the primitive equations of the ocean. In this paper, we establish the local well-posedness of the model with analytic initial data.
Synchrotron-based coherent scatter x-ray projection imaging using an array of monoenergetic pencil beams
Authors: Landheer Karl , Johns Paul C.
Published: September 2012

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be acquired simultaneous to the primary images and provide additional information. In medical applications scatter imaging can improve x-ray contrast or reduce dose using information that is currently discarded in radiological images to augment the transmitted radiation information. Other applications include non-destructive testing and security. A system at the Canadian Light Source synchrotron was configured which utilizes multiple pencil beams (up to five) to create both primary and coherent scatter projection images, simultaneously. The sample was scanned through the beams using an automated step-and-shoot setup. Pixels were acquired in a hexagonal lattice to maximize packing efficiency. The typical pitch was between 1.0 and 1.6 mm. A Maximum Likelihood-Expectation Maximization-based iterative method was used to disentangle the overlapping information from the flat panel digital x-ray detector. The pixel value of the coherent scatter image was generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. Different angular ranges maximize the contrast between different materials of interest. A five-beam primary and scatter image set (which had a pixel beam time of 990 ms and total scan time of 56 min) of a porcine phantom is included. For comparison a single-beam coherent scatter image of the same phantom is included. The muscle-fat contrast was 0.10 ± 0.01 and 1.16 ± 0.03 for the five-beam primary and scatter images, respectively. The air kerma was measured free in air using aluminum oxide optically stimulated luminescent dosimeters. The total area-averaged air kerma for the scan was measured to be 7.2 ± 0.4 cGy although due to difficulties in small-beam dosimetry this number could be inaccurate.
Hydrogenation-induced change of magneto optical Kerr effect in Pd/Fe bilayers
Authors: Lin Wen-Chin , Chi Chiao-Sung , Ho Tsung-Ying , Tsai Cheng-Jui , Lo Fang-Yuh , Chuang Huan-Chia , Chern Ming-Yau
Published: September 2012

The hydrogenation induced change of magneto-optical Kerr effect (MOKE) was studied in n ML Pd/30 ML Fe bilayers on Al2O3(0001). With the increasing of Pd thickness from 3 ML to 60 ML, the MOKE extinction angle was gradually shifted by 0.6° and the enhancement of Kerr intensity reached 35%–40% after exposure to 1 atm hydrogen. The reversibility of this significant change was demonstrated by cyclic desorption and reabsorption of hydrogen. This study reveals the sensitive MO response in the combination of a magnetic Fe thin film with a highly hydrogenated Pd capping layer.
Laser irradiation effects on the CdTe/ZnTe quantum dot structure studied by Raman and AFM spectroscopy
Authors: Zielony E. , Płaczek-Popko E. , Henrykowski A. , Gumienny Z. , Kamyczek P. , Jacak J. , Nowakowski P. , Karczewski G.
Published: September 2012

Micro-Raman spectroscopy has been applied to investigate the impact of laser irradiation on semiconducting CdTe/ZnTe quantum dots (QDs) structures. A reference sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the p-type GaAs substrate. The Raman spectra have been recorded for different time of a laser exposure and for various laser powers. The spectra for both samples exhibit peak related to the localized longitudinal (LO) ZnTe phonon of a wavenumber equal to 210 cm−1. For the QD sample, a broad band corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm−1. With increasing time of a laser beam exposure and laser power, the spectra get dominated by tellurium—related peaks appearing at wavenumbers around 120 cm−1 and 140 cm−1. Simultaneously, the ZnTe surface undergoes rising damage, with the formation of Te aggregates at the pinhole edge as reveal atomic force microscopy observations. Local temperature of irradiated region has been estimated from the anti-Stokes/Stokes ratio of the Te modes intensity and it was found to be close or exceeding ZnTe melting point. Thus, the laser damage can be explained by the ablation process.
Radiative transitions in stacked type-II ZnMgTe quantum dots embedded in ZnSe
Authors: Manna U. , Zhang Q. , Dhomkar S. , Salakhutdinov I. F. , Tamargo M. C. , Noyan I. C. , Neumark G. F. , Kuskovsky I. L.
Published: September 2012

Sub-monolayer quantities of Mg are introduced in multilayer stacked ZnMgTe quantum dots (QDs) embedded in ZnSe barriers in order to reduce the hole confinement energy by controlling the bandgaps and band-offsets of ZnTe/ZnSe system having type-II band alignment. The photoluminescence (PL) emission from such ZnMgTe/ZnSe QD structure is found to be a broad band centered at 2.35 eV. The higher energy side of the PL band shows a larger blue-shift with increasing excitation intensity and a faster life-time decay due to a greater contribution of the emission from the smaller size dots and the isoelectronic bound excitons. It is found that the characteristic decay time of the PL evolves along the band with a value of 129 ns at 2.18 eV to 19 ns at 2.53 eV. The temperature dependent PL emission is controlled by two thermally activated processes: ionization of electrons away from QD state to the barrier (EA1 ∼ 3 meV) by breaking the type-II excitons and thermal escape of the holes from the ground state to the barrier (EA2 ∼ 114-116 meV). We propose a modified band diagram and energy levels for this ZnMgTe/ZnSe multilayer QD system by determining the composition of Mg inside the QDs and solving the 1-D Schrodinger's equation and show that Mg incorporation lowers the hole activation energy via modification of the valence band offset without changing the barrier significantly.
Investigation of magnetic-pole-enhanced inductively coupled nitrogen-argon plasmas
Authors: Jan F. , Khan A. W. , Saeed A. , Zakaullah M.
Published: September 2012

This article presented the features of the mixed mode and H mode in magnetic pole enhanced, inductively coupled Ar-N2 plasmas using RF-compensated Langmuir probe measurements. To fully characterize plasma parameters and electron energy probability functions (EEPFs), the gas pressure and argon content were varied. It was observed that with increasing the nitrogen content and gas pressure, the critical RF power to sustain H mode increases; this increase was more prominent for pure nitrogen discharge at higher pressure. The electron number density (ne) shows increasing trend with increasing RF power, while at higher gas pressures, the electron number density decreases at fixed RF power. Mostly, the EEPFs show a Maxwellian distribution even at low RF power (for higher argon content in the discharge) and at moderate RF power (for higher or pure nitrogen content in the discharge) for pressures of 15–60 mTorr. With increasing the nitrogen content in the mixture, the low energy part of the EEPF is more Druyvesteyn with a distorted high energy tail at low RF power. At fixed RF power, the slope of EEPF changes sharply with increasing pressure. It was observed that in hybrid mode, the EEPF at higher gas pressure (75 mTorr) in a pure nitrogen discharge shows a flat hole near the average electron energy of 3 eV and changes to Maxwellian distribution in H mode. The skin depth versus RF power shows that the skin depth is smaller than the critical dimension of the chamber, regardless of the gas type and the gas pressure.
Photothermal characterization of the thermal properties of materials using four characteristic modulation frequencies in two-layer systems
Authors: Vales-Pinzon C. , Ordonez-Miranda J. , Alvarado-Gil J. J.
Published: September 2012

A simple photothermal methodology for determining simultaneously and in four different ways the thermal diffusivity and thermal effusivity of the illuminated layer in a two-layer system is presented. The method is based on the analysis of the photothermal signal of the whole system normalized by the corresponding signal of the illuminated one-layer system. Our approach uses the modulation frequencies at which the normalized amplitude (phase) passes through unity (zero) and reaches its maximum (minimum). It is shown that these four characteristic modulation frequencies are independent of the thermal effusivities of the layers, and their values can be used to obtain the thermal diffusivity of the illuminated layer. Then, by using the exact complex expression of the normalized photothermal signal with the experimental data for its amplitude and phase, the thermal effusivity of the same layer can be found. In order to show the usefulness of this approach, the method is applied to a glassy carbon sample in thermal contact with three different types of very thick back layers of air, water, and glycerine. It is shown that the highest (lowest) accuracy on the measurement of the thermal properties corresponds to the frequency at which the zero (minimum) of the normalized phase occurs.
Influencing modulation properties of quantum-dot semiconductor lasers by carrier lifetime engineering
Authors: Lingnau Benjamin , Lüdge Kathy , Chow Weng W. , Schöll Eckehard
Published: September 2012

The relaxation oscillation (RO) parameters and modulation properties of quantum-dot lasers are investigated depending on effective charge carrier scattering lifetimes of the confined quantum-dot states. We find three dynamical regimes of the laser, characterized by the level of synchronization between carrier dynamics in quantum-dots and quantum-well. For scattering rates similar to the RO frequency, a strong damping is found. On either side of this regime, simulations show low RO damping and improved dynamical response. Depending on the regime, the modulation response differs from conventional analytical predictions. Our results suggest the possibility of tailoring quantum-dot laser dynamical behavior via bandstructure engineering.
Edge atoms effects on the perpendicular anisotropy of ultrathin magnetic layers
Authors: Geshev J. , Gündel A. , Zaharieva I. , Schmidt J. E.
Published: September 2012

The present work reports experimental and theoretical results for electrodeposited Co/Au(111) ultrathin layers with very specific magnetic behavior. We show that the observed two peaks in the out-of-plane magnetization versus deposition time variation could be explained by the remarkably high perpendicular anisotropy of the perimeter atoms of low-dimensional islands formed during the layer-by-layer growth, as compared to that of the surface atoms. Our results indicate that it is possible to sustain high anisotropy in very small grains without coming across the superparamagnetic limit, opening excellent opportunities for materials engineering.
A modified Weibull model for tensile strength distribution of carbon nanotube fibers with strain rate and size effects
Authors: Sun Gengzhi , Pang John H. L. , Zhou Jinyuan , Zhang Yani , Zhan Zhaoyao , Zheng Lianxi
Published: September 2012

Fundamental studies on the effects of strain rate and size on the distribution of tensile strength of carbon nanotube (CNT) fibers are reported in this paper. Experimental data show that the mechanical strength of CNT fibers increases from 0.2 to 0.8 GPa as the strain rate increases from 0.00001 to 0.1 (1/s). In addition, the influence of fiber diameter at low and high strain rate conditions was investigated further with statistical analysis. A modified Weibull distribution model for characterizing the tensile strength distribution of CNT fibers taking into account the effect of strain rate and fiber diameter is proposed.
Microstructural and ferromagnetic resonance properties of epitaxial nickel ferrite films grown by chemical vapor deposition
Authors: Li N. , Schäfer S. , Datta R. , Mewes T. , Klein T. M. , Gupta A.
Published: September 2012

Microstructural and ferromagnetic resonance properties of epitaxial nickel ferrite (NiFe2O4) films grown by direct liquid injection chemical vapor deposition are reported. While high-quality epitaxial growth of NiFe2O4 films on (100)-oriented MgAl2O4 substrate is confirmed by high resolution transmission electron microscopy, bright field (diffraction contrast) TEM studies reveal the presence of dislocations and also dark diffused contrast areas, which originate from antiphase domains. Angle and frequency-dependent ferromagnetic resonance (FMR) experiments are conducted to determine the magnetic anisotropy and the magnetic relaxation. A low out-of-plane FMR linewidth of ∼160 Oe has been observed at a frequency of 10 GHz.
Fabrication and photoluminescence of SiC quantum dots stemming from 3C, 6H, and 4H polytypes of bulk SiC
Authors: Fan Jiyang , Li Hongxia , Wang Jing , Xiao Min
Published: September 2012

We report the fabrication and photoluminescence properties of the colloidal SiC quantum dots (QDs) stemming, respectively, from diminishing different polytypes (3C, 6H, and 4H) of bulk SiC crystals using electrochemical method. The three types of obtained SiC QDs show unexpected quite-similar photoluminescence, photoluminescence excitation, and transient photoluminescence properties. This strange phenomenon is explained by using the polytypic transformations of the colloidal SiC QDs driven by ultrasonic waves. Our results will greatly deepen our understanding of the fundamental physics of nanoscale SiC.
Fluorescence, Phosphorescence, and Delayed Fluorescence of Benzil in Imidazolium Ionic Liquids
Authors: Khara Dinesh Chandra , Samanta Anunay
Published: September 2012

Temperature dependence of the emission behaviour of benzil has been studied in three imidazolium ionic liquids differing in their polarity and viscosity. Room temperature absorption and steady-state emission spectra suggest that the ground and excited state conformers of benzil in ionic liquids are similar to those in conventional organic solvents. The non-degassed solutions of benzil in ionic liquids show phosphorescence at room temperature in contrast to conventional solvents where phosphorescence is commonly observed in degassed conditions. This study reveals that a thermally activated reverse intersystem crossing (T1↝S1) process is responsible for the drastic change in phosphorescence intensity with temperature in ionic liquids. The rate constant () of this process is found to be dependent on the polarity of the media and is 5 times higher in most polar ionic liquids. The evidence of the presence of multiple conformers of benzil in frozen conditions is obtained from the excitation wavelength dependence of the phosphorescence spectra.
Unprecedented Mn(II) - Phosphate 3D Coordination Polymer with Novel pkb1 Topological Network Showing Spin-Canted Antiferromagnetism
Authors: Ahmad Musheer , Sharma Manish K. , Singh Ruchi , Mrozinski Jerzy , Bharadwaj Parimal K.
Published: September 2012

A novel Mn(II)phosphate coordination polymer, {Mn2.5(HPO4PO4)H2O)2}n, has been synthesized under solvothermal conditions. This is the first phosphate-based Mn(II) complex, which is obtained in excellent yield without using any external organic amine as a structure directing agent. The complex has a 3D non-interpenetrated unprecedented 5-nodal (5,5,6,6,7)-connected pkb1 topological network. It has been characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis (CHN analyzer and energy-dispersive X-ray spectroscopy), and thermogravimetry. Variable temperature magnetic susceptibility measurements indicate that the complex exhibits spin-canted antiferromagnetic behaviour at low temperature. The electron paramagnetic resonance measurements, at ambient and at low temperature, of the complex are also consistent with magnetic behaviour.
Carbazole-Functionalised Poly(1-phenyl-1-alkyne)s: Synthesis, Light Emission, and Fluorescent Photopatterning
Authors: Lam Jacky W. Y. , Qin Anjun , Dong Yuping , Liu Jianzhao , Jim Cathy K. W. , Hong Yuning , Kwok Hoi Sing , Tang Ben Zhong
Published: September 2012

Carbazole-containing 1-phenyl-1-alkynes with different spacer lengths [C6H5C≡C(CH2)mCar 1(m) (m = 3, 4, 9), Car =9-carbazolyl] were synthesised in high yields by consecutive substitution and coupling reactions of n-chloro-1-alkynes. Polymerisation of the monomers was effected by NbCl5– and WCl6–Ph4Sn catalysts, furnishing soluble polymers P1(m) with high molecular weights in high yields. All the polymers were thermally stable, commencing to lose their weights at high temperatures (≥ 400°C). Photoexcitation of their THF solutions induced strong blue light emissions with high quantum efficiencies up to 92 %. Multilayer electroluminescence devices with configurations of ITO/P1(m)(:PVK)/BCP/Alq3/LiF/Al were constructed, which gave blue light with maximum luminance and external quantum efficiency of 438 cd m–2 and 0.63 %. UV irradiation of a thin film of P1(4) through a mask oxidized and quenched the light emission of the exposed parts, generating a two-dimensional luminescent photopattern.
Conducting Material-incorporated Electrorheological Fluids: Core-shell Structured Spheres
Authors: Liu Ying Dan , Zhang Ke , Zhang Wen Ling , Choi Hyoung Jin
Published: September 2012

Conducting material-based electro-responsive particles have become important as the smart soft matter in electrorheological (ER) fluids. These materials include conducting polymers, such as polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene), and carbon materials, such as carbon nanotubes and graphene oxide. Core-shell structured ER particles containing these materials as either core or shell species have attracted increasing interest owing to their outstanding advantages of an enhanced ER effect or diverse ER mechanism, lighter particulate density and lower cost. This paper summarizes the recent advances in synthesis methods as well as the critical characteristics of the core-shell structured particles, such as shear stress, yield stress and dielectric properties.
CD24 expression is important in male urothelial tumorigenesis and metastasis in mice and is androgen regulated
Authors: Overdevest Jonathan B. , Knubel Kristina H. , Duex Jason E. , Thomas Shibu , Nitz Matthew D. , Harding Michael A. , Smith Steven C. , Frierson Henry F. , Conaway Mark , Theodorescu Dan
Published: September 2012

Overexpression of CD24, a glycosyl phosphatidylinositol-linked sialoglycoprotein, is associated with poor outcome in urothelial carcinoma and contributes to experimental tumor growth and metastasis. However, the requirement for CD24 (Cd24ain mice) in tumorigenesis and spontaneous metastasis from the orthotopic site remains uncharacterized. UsingN-butyl-N-(4-hydroxybutyl) nitrosamine induction of invasive and metastatic bladder cancer, we show thatCd24a-deficient male mice developed fewer bladder tumors than C57BL/6 control male mice. Evaluating only mice with evidence of primary tumors, we observed thatCd24a-deficient male mice also had fewer metastases than wild-type counterparts. In parallel observations, stratification of patients based on CD24 immunohistochemical expression in their tumors revealed that high levels of CD24 are associated with poor prognosis in males. In female patients and mice the above observations were not present. Given the significant role of CD24 in males, we sought to assess the relationship between androgen and CD24 regulation. We discovered that androgen receptor knockdown in UM-UC-3 and TCCSUP human urothelial carcinoma cell lines resulted in suppression of CD24 expression and cell proliferation. Androgen treatment also led to increased CD24 promoter activity, dependent on the presence of androgen receptor. In vivo, androgen deprivation resulted in reduced growth and CD24 expression of UM-UC-3 xenografts, and the latter was rescued by exogenous CD24 overexpression. These findings demonstrate an important role for CD24 in urothelial tumorigenesis and metastasis in male mice and indicate that CD24 is androgen regulated, providing the foundation for urothelial bladder cancer therapy with antiandrogens.
Superstructure of the centromeric complex of TubZR
C
plasmid partitioning systems
Authors: Aylett Christopher H. S. , Löwe Jan
Published: September 2012

Bacterial plasmid partitioning systems segregate plasmids into each daughter cell. In the well-understood ParMR
C
plasmid partitioning system, adapter protein ParR binds to centromere
parC
, forming a helix around which the DNA is externally wrapped. This complex stabilizes the growth of a filament of actin-like ParM protein, which pushes the plasmids to the poles. The TubZR
C
plasmid partitioning system consists of two proteins, tubulin-like TubZ and TubR, and a DNA centromere,
tubC
, which perform analogous roles to those in ParMR
C
, despite being unrelated in sequence and structure. We have dissected in detail the binding sites that comprise
Bacillus thuringiensis tubC
, visualized the TubR
C
complex by electron microscopy, and determined a crystal structure of TubR bound to the
tubC
repeat. We show that the TubR
C
complex takes the form of a flexible DNA–protein filament, formed by lateral coating along the plasmid from
tubC
, the full length of which is required for the successful in vitro stabilization of TubZ filaments. We also show that TubR from
Bacillus megaterium
forms a helical superstructure resembling that of ParR. We suggest that the TubR
C
DNA–protein filament may bind to, and stabilize, the TubZ filament by forming such a ring-like structure around it. The helical superstructure of this TubR
C
may indicate convergent evolution between the actin-containing ParMR
C
and tubulin-containing TubZR
C
systems.
Size-Dependent Effects of Coded Wire Tags on Mortality and Tag Retention in Redtail Culter Culter mongolicus
Authors: Lin Mingli , Xia Yuguo , Murphy Brian R. , Li Zhongjie , Liu Jiashou , Zhang Tanglin , Ye Shaowen
Published: September 2012

Redtail culter Culter mongolicus, a threatened piscivorous fish species in China's inland waters, has exhibited serious population decline. As part of a stock enhancement research project in shallow lakes of the Yangtze River basin, China, we evaluated the performance of coded wire tags (CWTs) for marking juvenile redtail culter. Through a short-term indoor experiment, we marked hatchery-reared juveniles from three size groups (mean ± SE, small: 46.85 ± 0.67 mm, intermediate: 53.76 ± 0.62 mm, large: 63.42 ± 1.05 mm) in the dorsal muscle with CWTs and tested whether marking effects on tag retention and mortality were size-specific. Tag retention was more than 98% in all the three size groups and appeared to be unaffected by fish size. Tag losses were found only within 3 d of marking. Tagging-induced mortality of small marked juveniles (58%) was significantly higher than those of intermediate (5%) and large (1%) marked juveniles and was also significantly higher than small unmarked ones (17%). The relationship of marked mortality and total length was quantitatively described by an exponential decay model. Mortality in small marked juveniles occurred mainly within 24 h after marking, which accounted for 71% of the mortality in this marked size. In order to avoid high posttagging mortality and biases in stocking assessment programs, we suggest it is worth the extra fish-culture costs to use juveniles of at least 57 mm (which displayed 90% survival in our experiment) for stocking assessment programs that utilize CWTs for a handling-sensitive species like redtail culter.

Received December 1, 2011; accepted June 28, 2012