bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling anomalous cosmic ray oxygen gradients over successive solar cycles
Authors: Strauss R. D. , Potgieter M. S.
Published: December 2010

Cosmic ray drift directions depend both on the charge of the particle population under consideration, as well as the heliospheric magnetic field polarity which oscillates within a ∼22 year cycle. The differences in the cosmic ray drift patterns between successive solar cycles manifest themselves in the sign of the latitudinal cosmic ray gradient. For positively charged particles, a positive latitudinal gradient is expected in the qA > 0 polarity cycle, while a negative value is expected in the qA < 0 cycle. For the first time observed radial and latitudinal values for anomalous cosmic ray oxygen are available in both of these cycles. In the present qA < 0 cycle, the observations seem, however, inconsistent with the drift‐dominated considerations discussed above, as the latitudinal gradient is smaller than expected and perhaps even positive. This issue is addressed by using a comprehensive numerical model for anomalous cosmic ray acceleration and transport, based on new diffusion coefficients, to simulate these gradients over the previous two magnetic polarity cycles. Computed gradients and energy spectra (at Earth and at Ulysses) are compared to observations, with good agreement achieved between observations and model predictions. For the qA > 0 cycle, the model predicts a positive latitudinal gradient but for the qA < 0 cycle a latitudinal gradient that is smaller and that can be either positive or negative. It is concluded that drifts and poleward diffusion set up competing latitudinal gradients in the qA < 0 cycle, with the resulting sign of the gradient determined by the most effective of the two processes.
Estimation of radial gradients of phase space density from POLAR observations during a quiet period prior to a sudden solar wind dynamic pressure enhancement
Authors: Kim H.‐J. , Zesta E. , Kim K.‐C. , Shprits Y. , Shi Y. , Lyons L. R.
Published: December 2010

We have analyzed POLAR electron flux data to estimate the radial gradients of electron phase space density (PSD) immediately prior to a sudden solar wind dynamic pressure enhancement at ∼1135 UT on 12 August 2001. In this event, the instantaneous flux changes from the magnetospheric compression at L ∼ 7.6 in the postmidnight magnetic local time sector are observed to be both energy and pitch angle (PA) dependent: a substantial flux increase for lower energies (<∼200 keV) particularly at smaller local PA (<∼50°) and a large flux decrease for relativistic energies that is more pronounced for a larger PA. For this event, because of the extremely steady and quiet solar wind conditions prior to the pressure impact, we can reasonably assume that the temporal variation is negligible and so deduce the spatial and pitch angle distribution of initial electron fluxes to construct the event‐specific electron flux model for a localized region of the nightside outer radiation belt. PSD radial profiles are then estimated for 6.5 < L < 8.5 using the constructed electron flux model and Tsyganenko magnetospheric model for quiet times. The estimates show a positive PSD gradient for low energies (<∼a few 100 s keV at the POLAR location right after the pressure impact) and a negative gradient for relativistic energies. In addition, a rather gradual transition of the radial gradient from highly positive to more negative is found with increasing energy. The expected immediate flux responses using these estimated PSD radial gradients are qualitatively consistent with those observed, partially validating the veracity of the estimated profiles.
Structure and paleoearthquake records of active submarine faults, Cook Strait, New Zealand: Implications for fault interactions, stress loading, and seismic hazard
Authors: Pondard Nicolas , Barnes Philip M.
Published: December 2010

A new interpretation of active faulting in central Cook Strait, New Zealand, reveals tectonic structures associated with the spatial transition from subduction to continental transform faulting. Marine seismic reflection profiles and multibeam bathymetric data indicate that there are no throughgoing crustal faults connecting the North Island Dextral Fault Belt and the Marlborough Fault System in South Island. The major faults terminate offshore, associated with 5–20 km wide step‐overs and a change in regional fault strike. This structure implies that propagation of strike‐slip earthquake ruptures across the strait is not probable. Faulted sedimentary sequences in the Wairau Basin (Marlborough shelf), correlated to glacioeustatic sea level cycles, provide a stratigraphic framework for fault analysis. A high‐resolution study of the postglacial (<20 ka) vertical displacement history of the Cloudy and Vernon faults reveals up to six and five paleoearthquakes since 18 ka, respectively. These long‐timescale records indicate variable recurrence intervals and possibly variable stress drop, thus conforming to the variable slip model of earthquake behavior. Integration of these data with other submarine and terrestrial paleoearthquake records indicates the presence of clustered earthquake sequences involving multiple faults. Different sequences do not always involve the same faults. It appears that earthquake clustering is driven by fault interactions that lead to specific loading conditions favoring the triggering of earthquakes on major faults in relatively short time intervals. Present‐day regional Coulomb stress distribution has been calculated in two scenarios considered to represent minimum and maximum loading conditions. The models, incorporating secular tectonic loading and stress changes associated with major crustal earthquakes, indicate high stress loading in a large part of central Cook Strait. These conditions may favor the triggering of future damaging earthquakes in this region.
Optical and physical characteristics of Bay of Bengal aerosols during W‐ICARB: Spatial and vertical heterogeneities in the marine atmospheric boundary layer and in the vertical column
Authors: Moorthy K. Krishna , Beegum S. Naseema , Babu S. Suresh , Smirnov Alexander , John Sherine Rachel , Kumar K. Raghavendra , Narasimhulu K. , Dutt C. B. S. , Nair Vijayakumar S.
Published: December 2010

Analysis of the continuous and collocated measurements of columnar spectral aerosol optical depths (AODs) and mass size distributions in the marine atmospheric boundary layer (MABL) over the Bay of Bengal (BoB), carried out from 27 December 2008 to 29 January 2009 during the Winter Integrated Campaign for Aerosols, Gases and Radiation Budget (W‐ICARB), revealed distinct regional features in the spatial variations of the aerosol properties in the MABL and column. In general, AODs were high over the northern and northwestern parts of the BoB, with pockets of very high values, within which the AODs were as high as ∼0.8 while the smallest values (∼0.1) were observed over the northeastern BoB, off the Myanmar and Bangladesh coasts. Interestingly, though, this region had the highest Angstrom wavelength exponent α (∼1.5), notwithstanding the generally high values that prevailed over the eastern as well as northern coastal regions of India. Back trajectory analyses revealed the significant role of the advected aerosols in the observed spatial pattern. Within the MABL, high accumulation mode mass concentrations (MA) prevailed over the entire BoB with the accumulation fraction ranging from 0.6 to 0.95, whereas very high fine‐mode (r < 0.1 μm) aerosol mass fractions (∼0.8) were observed over the northeastern and western coastal BoB adjoining the Indian mainland (where α was high to very high). The vertical distributions, inferred from the columnar and MABL properties as well as from the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations data, revealed better homogeneity in the northeastern and eastern BoB, whereas significant heterogeneity was seen over other regions.
Constraints on the geologic history of “Home Plate” materials provided by clast morphology and texture
Authors: Yingst R. A. , Crumpler L. , Farrand W. H. , Li R. , de Souza P.
Published: December 2010

We quantified and classified the size, shape, roundness, and texture of 333 loose surface particles (clasts) along the Spirit rover traverse from Martian solar days 750 to 1889. These data provided clues to origin, transport mechanisms, association with geologic units, and other alteration processes. Clasts average 15 mm in size and 0.73 sphericity, and display a low degree of roundness; textures include vesicular, smooth and rough flat‐faceted, and granular, platy clasts. Characteristics are comparable to those for clasts outside the “Home Plate” region. Mapped geologic units around “Home Plate” are characterized by distinctive clast morphologic parameters and only minor adjustments were made to unit boundaries and definitions mapped by others; no new units are suggested by the data. Consistent roundness values seen from unit to unit, coupled with the correlation between unit boundaries and clast characteristics in and outside “Home Plate,” indicate that no appreciable transport has occurred subsequent to fragmentation from outcrop and emplacement. Rather, clasts have been emplaced through volcanic activity and/or impact and have been subjected to weathering processes since that time. We interpret vesicular and flat‐faceted clasts (texture types 1–3) to be derived from Mitcheltree ridge basalts and the presence of these clasts to provide a general outline of the original extent of this unit. Platy, granular‐textured clasts (texture type 5) are derived from the upper Home Plate unit.
Evaluating vaccinia virus cytokine co‐expression in TLR GKO mice
Authors: Sutherland Duncan B , Ranasinghe Charani , Regner Matthias , Phipps Simon , Matthaei Klaus I , Day Stephanie L , Ramshaw Ian A
Published: December 2010

Using Toll‐like receptor (TLR) and MyD88 gene knock‐out (GKO) mice the effect of TLRs and MyD88 on virus replication, interferon (IFN)‐β production, natural killer (NK) cell and CD8T cell responses were assessed following ectromelia virus (ECTV) and recombinant vaccinia virus (rVV) infection. The capacity for rVVs encoding cytokines to restore immune function in MyD88−/− mice was clearly demonstrated. Results showed that TLR2−/−, TLR4−/−and TLR7−/− mice survived ECTV infection whereas MyD88−/− and TLR9−/−mice, in contrast, were highly susceptible. Next, following infection with rVV, MyD88−/− mice elicited reduced serum IFN‐β, NK cell and CD8T cell responses compared with wild‐type mice, whereas TLR9−/− mice showed elevated CD8T cell responses. When MyD88−/−mice were infected with rVV co‐expressing IFN‐β these mice were able to restore IFN‐β levels and CD8T cell responses but not NK cell activation. Interestingly, even though rVV co‐expressing interleukin (IL)‐2 enhanced NK cell activation in MyD88−/− mice, this was not associated with an antiviral effect, as observed in normal mice. Surprisingly, co‐infection with rVV IL‐2/rVV IL‐12, but not rVV IL‐2/rVV IFN‐β, restored the attenuated phenotype of rVV IL‐2 in MyD88−/− mice indicating that the IL‐2/IL‐12 combination promotes antiviral responses. Our results clearly show that the CD8T cell defect observed in MyD88−/− mice to vaccinia virus infection can be restored by rVV‐encoding IFN‐β demonstrating the critical role of this cytokine in T cell mediated immunity and illustrates that the model can provide an effective platform for the elucidation of cytokine immunobiology.
Nonsense‐mediated decay targets have multiple sequence‐related features that can inhibit translation
Authors: Zhang Zhenguo , Zhou Li , Hu Landian , Zhu Yufei , Xu Heng , Liu Yang , Chen Xianfen , Yi Xianfu , Kong Xiangyin , Hurst Laurence D
Published: December 2010

Nonsense‐mediated mRNA decay (NMD) is a surveillance system that eliminates transcripts with premature termination codons. In this study, we show that mRNAs targeted by NMD are also suppressed at the translational level. The low translational efficiency (TE) is a consequence of multiple features acting in concert, including low translation initiation rate, mediated by 5′ secondary structure and by use of weak initiation sites, and low translation elongation speed, mediated by low codon usage bias. Despite low elongation rates, NMD transcripts show low ribosome density in the coding sequence, probably owing to low initiation rates, high abortion rates or rapid transit of the ribosome following initiation failure. The low TE is observed in the absence of NMD and is not explained by low transcript abundance. Translational inefficiency is flexible, such that NMD targets have increased TE upon starvation. We propose that the low TE predisposes to NMD and/or that it is part of a mechanism for regulation of NMD transcripts.
Defining the budding yeast chromatin‐associated interactome
Authors: Lambert Jean‐Philippe , Fillingham Jeffrey , Siahbazi Mojgan , Greenblatt Jack , Baetz Kristin , Figeys Daniel
Published: December 2010

We previously reported a novel affinity purification (AP) method termed modified chromatin immunopurification (mChIP), which permits selective enrichment of DNA‐bound proteins along with their associated protein network. In this study, we report a large‐scale study of the protein network of 102 chromatin‐related proteins from budding yeast that were analyzed by mChIP coupled to mass spectrometry. This effort resulted in the detection of 2966 high confidence protein associations with 724 distinct preys. mChIP resulted in significantly improved interaction coverage as compared with classical AP methodology for ∼75% of the baits tested. Furthermore, mChIP successfully identified novel binding partners for many lower abundance transcription factors that previously failed using conventional AP methodologies. mChIP was also used to perform targeted studies, particularly of Asf1 and its associated proteins, to allow for a understanding of the physical interplay between Asf1 and two other histone chaperones, Rtt106 and the HIR complex, to be gained.
Evolving a robust signal transduction pathway from weak cross‐talk
Authors: Siryaporn Albert , Perchuk Barrett S , Laub Michael T , Goulian Mark
Published: December 2010

We have evolved a robust two‐component signal transduction pathway from a sensor kinase (SK) and non‐partner response regulator (RR) that show weak cross‐talk in vitro and no detectable cross‐talk in vivo in wild‐type strains. The SK, CpxA, is bifunctional, with both kinase and phosphatase activities for its partner RR. We show that by combining a small number of mutations in CpxA that individually increase phosphorylation of the non‐partner RR OmpR, phosphatase activity against phospho‐OmpR emerges. The resulting circuit also becomes responsive to input signal to CpxA. The effects of combining these mutations in CpxA appear to reflect complex intragenic interactions between multiple sites in the protein. However, by analyzing a simple model of two‐component signaling, we show that the behavior can be explained by a monotonic change in a single parameter controlling protein–protein interaction strength. The results suggest one possible mode of evolution for two‐component systems with bifunctional SKs whereby the remarkable properties and competing reactions that characterize these systems can emerge by combining mutations of the same effect.
A comprehensive map of the mTOR signaling network
Authors: Caron Etienne , Ghosh Samik , Matsuoka Yukiko , Ashton‐Beaucage Dariel , Therrien Marc , Lemieux Sébastien , Perreault Claude , Roux Philippe P , Kitano Hiroaki
Published: December 2010

The mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation. mTOR signaling is frequently dysregulated in oncogenic cells, and thus an attractive target for anticancer therapy. Using CellDesigner, a modeling support software for graphical notation, we present herein a comprehensive map of the mTOR signaling network, which includes 964 species connected by 777 reactions. The map complies with both the systems biology markup language (SBML) and graphical notation (SBGN) for computational analysis and graphical representation, respectively. As captured in the mTOR map, we review and discuss our current understanding of the mTOR signaling network and highlight the impact of mTOR feedback and crosstalk regulations on drug‐based cancer therapy. This map is available on the Payao platform, a Web 2.0 based community‐wide interactive process for creating more accurate and information‐rich databases. Thus, this comprehensive map of the mTOR network will serve as a tool to facilitate systems‐level study of up‐to‐date mTOR network components and signaling events toward the discovery of novel regulatory processes and therapeutic strategies for cancer.
Metabonomic, transcriptomic, and genomic variation of a population cohort
Authors: Inouye Michael , Kettunen Johannes , Soininen Pasi , Silander Kaisa , Ripatti Samuli , Kumpula Linda S , Hämäläinen Eija , Jousilahti Pekka , Kangas Antti J , Männistö Satu , Savolainen Markku J , Jula Antti , Leiviskä Jaana , Palotie Aarno , Salomaa Veikko , Perola Markus , Ala‐Korpela Mika , Peltonen Leena
Published: December 2010

Comprehensive characterization of human tissues promises novel insights into the biological architecture of human diseases and traits. We assessed metabonomic, transcriptomic, and genomic variation for a large population‐based cohort from the capital region of Finland. Network analyses identified a set of highly correlated genes, the lipid–leukocyte (LL) module, as having a prominent role in over 80 serum metabolites (of 134 measures quantified), including lipoprotein subclasses, lipids, and amino acids. Concurrent association with immune response markers suggested the LL module as a possible link between inflammation, metabolism, and adiposity. Further, genomic variation was used to generate a directed network and infer LL module's largely reactive nature to metabolites. Finally, gene co‐expression in circulating leukocytes was shown to be dependent on serum metabolite concentrations, providing evidence for the hypothesis that the coherence of molecular networks themselves is conditional on environmental factors. These findings show the importance and opportunity of systematic molecular investigation of human population samples. To facilitate and encourage this investigation, the metabonomic, transcriptomic, and genomic data used in this study have been made available as a resource for the research community.
A tunable dual‐promoter integrator for targeting of cancer cells
Authors: Nissim Lior , Bar‐Ziv Roy H
Published: December 2010

Precise discrimination between similar cellular states is essential for autonomous decision‐making scenarios, such as in vivo targeting of diseased cells. Discrimination could be achieved by delivering an effector gene expressed under a highly active context‐specific promoter. Yet, a single‐promoter approach has linear response and offers limited control of specificity and efficacy. Here, we constructed a dual‐promoter integrator, which expresses an effector gene only when the combined activity of two internal input promoters is high. A tunable response provides flexibility in choosing promoter inputs and effector gene output. Experiments using one premalignant and four cancer cell lines, over a wide range of promoter activities, revealed a digital‐like response of input amplification following a sharp activation threshold. The response function is cell dependent with its overall magnitude increasing with degree of malignancy. The tunable digital‐like response provides robustness, acts to remove input noise minimizing false‐positive identification of cell states, and improves targeting precision and efficacy.
From diatoms to silica-based biohybrids
Authors: Nassif Nadine , Livage Jacques
Published: December 2010

Diatom inspired bio-hybrids offer new possibilities for the synthesis of nanostructured materials and the development of nanomedicine.
Syllable-Related Breathing in Infants in the Second Year of Life
Authors: Parham Douglas F. , Buder Eugene H. , Oller D. Kimbrough , Boliek Carol A.
Published: December 2010

Purpose

This study explored whether breathing behaviors of infants within the 2nd year of life differ between tidal breathing and breathing supporting single unarticulated syllables and canonical/articulated syllables.

Method

Vocalizations and breathing kinematics of 9 infants between 53 and 90 weeks of age were recorded. A strict selection protocol was used to identify analyzable breath cycles. Syllables were categorized on the basis of consensus coding. Inspiratory and expiratory durations, excursions, and slopes were calculated for the 3 breath cycle types and were normalized using mean tidal breath measures.

Results

Tidal breathing cycles were significantly different from syllable-related cycles
on
all breathing measures. There were no significant differences between unarticulated syllable cycles and canonical syllable cycles, even after controlling for utterance duration and sound pressure level.

Conclusions

Infants in the 2nd year of life exhibit clear differences between tidal breathing and speech-related breathing, but categorically distinct breath support for syllable types with varying articulatory demands was not evident in the present findings. Speech development introduces increasingly complex utterances, so older infants may produce detectable articulation-related adaptations of breathing kinematics. For younger infants, breath support may vary systematically among utterance types, due more to phonatory variations than to articulatory demands.
Development of a Short Form of the Boston Naming Test for Individuals With Aphasia
Authors: del Toro Christina M. , Bislick Lauren P. , Comer Matthew , Velozo Craig , Romero Sergio , Gonzalez Rothi Leslie J. , Kendall Diane L.
Published: December 2010

Purpose

The purpose of this study was to develop a short form of the Boston Naming Test (BNT; Kaplan, Goodglass, & Weintraub, 2001) for individuals with aphasia and compare it with 2 existing short forms originally analyzed with responses from people with dementia and neurologically healthy adults.

Method

Development of the new BNT–Aphasia Short Form and analysis of the other 2 forms were completed with archival data from 100 individuals with aphasia. The authors developed the BNT–Aphasia Short Form using items from the original 60-item instrument based on item response theory. Rasch analysis was computed on the short forms developed by Graves, Bezeau, Fogarty, and Blair (2004) and by Mack, Freed, Williams, and Henderson (1992).

Results

Analysis of the Graves et al. (2004) short form resulted in the smallest range of item difficulty and the largest floor effect compared with the Mack et al. (1992) short form and the BNT–Aphasia short form. The BNT–Aphasia Short Form showed an increase in information in the middle of the scale relative to both the Graves et al. and the Mack et al. forms.

Conclusions

The new short form demonstrates good psychometric properties when used with individuals with aphasia. However, the Mack et al. form proved to be as psychometrically sound as the BNT–Aphasia Short Form and is also appropriate for individuals with aphasia.
Supervised Home Training of Dialogue Skills in Chronic Aphasia: A Randomized Parallel Group Study
Authors: Nobis-Bosch Ruth , Springer Luise , Radermacher Irmgard , Huber Walter
Published: December 2010

Purpose

The aim of this study was to prove the efficacy of supervised self-training for individuals with aphasia. Linguistic and communicative performance in structured dialogues represented the main study parameters.

Method

In a cross-over design for randomized matched pairs, 18 individuals with chronic aphasia were examined during 12 weeks of supervised home training. Intensive language training, assisted by an electronic learning device (B.A.Bar), was compared with nonlinguistic training. Language performance, communicative abilities, and cognitive abilities were controlled before and after each intervention and at follow-up. The language training was designed to facilitate dialogue skills as required in everyday life.

Results

Robust and specific improvements in the participants' linguistic and communicative abilities were obtained using B.A.Bar dialogue training but not with nonlinguistic training. The transfer to general linguistic and communicative performance remained limited when the whole group was considered. For 30%–50% of the participants, individual analysis revealed significant improvements in spontaneous language and general communicative skills. Furthermore, individual participants demonstrated significant improvements regarding standardized aphasia assessment and proxy rating of communicative effectiveness.

Conclusion

Supervised home training works. This study has proven that it is an effective tool for bolstering linguistic and communicative skills of individuals with aphasia.
Changes in Acoustic Characteristics of the Voice Across the Life Span: Measures From Individuals 4–93 Years of Age
Authors: Stathopoulos Elaine T. , Huber Jessica E. , Sussman Joan E.
Published: December 2010

Purpose

The purpose of the present investigation was to examine acoustic voice changes across the life span. Previous voice production investigations used small numbers of participants, had limited age ranges, and produced contradictory results.

Method

Voice recordings were made from 192 male and female participants 4–93 years of age. Acoustic measures of fundamental frequency (F0), sound pressure level (SPL), and signal-to-noise ratio (SNR) were made. Coefficients of variation for F0, SPL, and SNR served as measures of variability. Variables were analyzed separately with stepwise regressions, using age and sex as predictors.

Results

Differences in F0 and SNR across the life span were sex specific. Male and female participants demonstrated significant nonlinear trends for F0, but the trends were stronger for male participants. Female participants demonstrated a similar nonlinear trend for SNR, whereas male participants demonstrated linear increases in SNR with age. Variability of F0, SPL, and SNR followed nonlinear trends, higher at younger and older ages.

Conclusions

Changes in voice production occur throughout the life span, often in a nonlinear way and differently for male and female individuals. Higher variability of acoustic measures of voice in both young and old speakers reflects changes in anatomic structure, physiologic mechanisms, and motor control.
Prosodic Adaptations to Pitch Perturbation in Running Speech
Authors: Patel Rupal , Niziolek Caroline , Reilly Kevin , Guenther Frank H.
Published: December 2010

Purpose

A feedback perturbation paradigm was used to investigate whether prosodic cues are controlled independently or in an integrated fashion during sentence production.

Method

Twenty-one healthy speakers of American English were asked to produce sentences with emphatic stress while receiving real-time auditory feedback of their productions. The fundamental frequency (F0) of the stressed word in each 4-word sentence was selectively shifted in a sensorimotor adaptation protocol. Speakers experienced either an upward or a downward shift of the stressed word, which gradually altered the perceived stress of the sentence.

Results

Participants in the Up and Down groups adapted to F0 shifts by altering the contrast between stressed and unstressed words differentially, such that the two groups deviated from each other in the perturbation phase. Furthermore, selective F0 perturbation in sentences with emphatic stress resulted in compensatory changes in both F0 and intensity.

Conclusions

Present findings suggest that F0 and intensity are controlled in an integrated fashion to maintain the contrast between stressed and unstressed words. When a cue is impaired through perturbation, speakers not only oppose the perturbation but enhance other prosodic cues to achieve emphatic stress.
Excess carbon in silicon carbide
Authors: Shen X. , Oxley M. P. , Puzyrev Y. , Tuttle B. R. , Duscher G. , Pantelides S. T.
Published: December 2010

The application of SiC in electronic devices is currently hindered by low carrier mobility at the SiC/SiO2 interfaces. Recently, it was reported that 4H–SiC/SiO2 interfaces might have a transition layer on the SiC substrate side with C/Si ratio as high as 1.2, suggesting that carbon is injected into the SiC substrate during oxidation or other processing steps. We report finite-temperature quantum molecular dynamics simulations that explore the behavior of excess carbon in SiC. For SiC with 20% excess carbon, we find that, over short time (∼24 ps), carbon atoms bond to each other and form various complexes, while the silicon lattice is largely unperturbed. These results, however, suggest that at macroscopic times scale, C segregation is likely to occur; therefore a transition layer with 20% extra carbon would not be stable. For a dilute distribution of excess carbon, we explore the pairing of carbon interstitials and show that the formation of dicarbon interstitial cluster is kinetically very favorable, which suggests that isolated carbon clusters may exist inside SiC substrate.
Comprehensive photoluminescence study of chlorine activated polycrystalline cadmium telluride layers
Authors: Kraft C. , Metzner H. , Hädrich M. , Reislöhner U. , Schley P. , Gobsch G. , Goldhahn R.
Published: December 2010

Temperature and power dependent photoluminescence (PL) measurements were employed in order to study defects in close-space-sublimation grown polycrystalline cadmium telluride layers that had been activated with different chlorine containing compounds. The samples were either measured as-grown or after thermal treatment in an oxygen containing ambient with and without the chlorine containing compounds such as cadmium chloride, hydrochloric acid, and sodium chloride. The as-grown sample is discussed in detail, in order to then demonstrate the changes in the PL spectra induced by the postdeposition treatments. A deep level transition at 1.32 eV was observed in the as-grown sample which can be correlated with cadmium vacancies. Due to postdeposition treatments this deep level transition disappears and a broad band correlated with A-centers arises instead at about 1.43 eV. Another transition band at 1.479 eV in the as-grown sample is not influenced by any postdeposition treatment. Furthermore, by processing solar cells out of the respective samples, the PL results can be related to the solar cell parameters.
Photoluminescence and photoreflectance characterization of ZnxCd1−xSe/MgSe multiple quantum wells
Authors: Wu J. D. , Huang Y. S. , Li B. S. , Shen A. , Tamargo M. C. , Tiong K. K.
Published: December 2010

Photoluminescence (PL) and photoreflectance (PR) were used to characterize ZnxCd1−xSe/MgSe multiple quantum well (MQW) structures grown on InP substrates by molecular beam epitaxy for mid-infrared (IR) device applications. The PL spectra yielded information of the fundamental excitonic recombination and ZnxCd1−xSe cap/spacer band edge emission of the samples. The PR spectra revealed multitude of possible interband transitions in MQW structures. The ground state transitions were assigned by comparing with the PL emission signals taken from the same structures. A comprehensive analysis of the PR spectra led to the identification of various interband transitions. The intersubband transitions were then estimated and found to be in a good agreement with the previous report of Fourier-transform IR absorption measurements [Li et al., Appl. Phys. Lett. 92, 261104 (2008)]. The results demonstrate the potential of using PL and PR as nondestructive optical techniques for characterization of ZnxCd1−xSe/MgSe MQWs for mid-IR device applications.
The warped Sasaki–Matsumoto metric and bundlelike condition
Authors: Alipour-Fakhri Y. , Rezaii M. M.
Published: December 2010

Let \documentclass[12pt]{minimal}\begin{document}$\mathbb {F}^n=(M,F)$\end{document}Fn=(M,F) be a Finsler manifold and G be the Sasaki–Matsumoto metric on \documentclass[12pt]{minimal}\begin{document}$TM^\circ$\end{document}TM∘. Bejancu and Farran [“Finsler geometry and natural foliations on the tangent bundle,” Rep. Math. Phys. 58, 131 (2006)] proved that \documentclass[12pt]{minimal}\begin{document}$\mathbb {F}^n=(M,F)$\end{document}Fn=(M,F) is a Riemannian manifold if and only if the Sasaki–Matsumoto metric G on \documentclass[12pt]{minimal}\begin{document}$TM^\circ$\end{document}TM∘ is bundlelike for the vertical foliation. Let \documentclass[12pt]{minimal}\begin{document}$\mathbb {F}^{n_1+n_2}=(M_1\times _fM_2,F)$\end{document}Fn1+n2=(M1×fM2,F) be the warped product Finsler manifold. In this paper the warped Sasaki–Matsumoto metric \documentclass[12pt]{minimal}\begin{document}${}^*\mathbf {G}$\end{document}*G is introduced for the warped product Finsler manifold, and it is shown if the warped function f is not a constant, then \documentclass[12pt]{minimal}\begin{document}${}^*\mathbf {G}$\end{document}*G on \documentclass[12pt]{minimal}\begin{document}$TM^\circ$\end{document}TM∘ is bundlelike for the warped vertical foliation \documentclass[12pt]{minimal}\begin{document}$\mathcal {V}^*(TM^\circ )$\end{document}V*(TM∘) if and only if \documentclass[12pt]{minimal}\begin{document}$\mathbb {F}^{n_1}_1=(M_1,F_1)$\end{document}F1n1=(M1,F1) and \documentclass[12pt]{minimal}\begin{document}$\mathbb {F}^{n_2}_2=(M_2,F_2)$\end{document}F2n2=(M2,F2) are Riemannian manifolds.
Size effects on the Hall constant in thin gold films
Authors: Henriquez Ricardo , Oyarzun Simon , Flores Marcos , Suarez Marco Antonio , Moraga Luis , Kremer German , Gonzalez-Fuentes Claudio A. , Robles Marcelo , Munoz Raul C.
Published: December 2010

We report the Hall constant RH, drift mobility μD, and Hall mobility μH measured at 4 K in thin gold films deposited on mica substrates, where the dominant electron scattering mechanism is electron-surface scattering. RH increases with increasing film thickness and decreases with increasing magnetic field. For high magnetic fields B≥6 T, RH turns out to be approximately independent of magnetic field, and its value is close to that of the free electron model. We use the high magnetic field values of RH to determine film thickness. This nondestructive method leads to a determination of film thickness that agrees to within 10% with the thickness measured by other techniques. The theoretical predictions, based upon the theory of Fuchs–Sondheimer and the theory of Calecki, are at variance with experimental observations.
The fractional Schrödinger equation for delta potentials
Authors: de Oliveira Edmundo Capelas , Costa Felix Silva , Vaz Jayme
Published: December 2010

The fractional Schrödinger equation is solved for the delta potential and the double delta potential for all energies. The solutions are given in terms of Fox's H-function.
Klein–Gordon equation in hydrodynamical form
Authors: Wong C. Y.
Published: December 2010

We follow and modify the Feshbach–Villars formalism by separating the Klein–Gordon equation into two coupled time-dependent Schrödinger equations for particle and antiparticle wave function components with positive probability densities. We find that the equation of motion for the probability densities is in the form of relativistic hydrodynamics where various forces have their classical counterparts, with the additional element of the quantum stress tensor that depends on the derivatives of the amplitude of the wave function. We derive the equation of motion for the Wigner function and we find that its approximate classical weak-field limit coincides with the equation of motion for the distribution function in the collisionless kinetic theory.
Transport of Brownian particles confined to a weakly corrugated channel
Authors: Wang Xinli , Drazer German
Published: December 2010

We investigate the average velocity of Brownian particles driven by a constant external force when constrained to move in two-dimensional, weakly corrugated channels. We consider both the geometric confinement of the particles between solid walls as well as the soft confinement induced by a periodic potential. Using perturbation methods we show that the leading order correction to the marginal probability distribution of particles in the case of soft confinement is equal to that obtained in the case of geometric confinement, provided that the (configuration) integral over the cross-section of the confining potential is equal to the width of the solid channel. We then calculate the probability distribution and average velocity in the case of a sinusoidal variation in the width of the channels. The reduction on the average velocity is larger in the case of soft channels at small Péclet numbers and for relatively narrow channels and the opposite is true at large Péclet numbers and for wide channels. In the limit of large Péclet numbers the convergence to bulk velocity is faster in the case of soft channels. The leading order correction to the average velocity and marginal probability distribution agree well with Brownian Dynamics simulations for the two types of confinement and over a wide range of Péclet numbers.
The thickness of the turbulent/nonturbulent interface is equal to the radius of the large vorticity structures near the edge of the shear layer
Authors: da Silva Carlos B. , Taveira Rodrigo R.
Published: December 2010

Direct numerical simulations at Reynolds numbers ranging from Reλ=30 to 160 show that the thickness δω of the turbulent/nonturbulent (T/NT) interface in planar jets is of the order of the Taylor scale δω∼λ, while in shear free, irrotational/isotropic turbulence is of the order of the Kolmogorov microscale δω∼η. It is shown that δω is equal to the radius of the large vorticity structures (LVSs) in this region, δω≈RLVS. Thus, the mean shear and the Reynolds number affect the T/NT interface thickness insofar as they define the radial dimension of the LVS near the T/NT interface.
Enhancement of the spin pumping efficiency by spin wave mode selection
Authors: Sandweg C. W. , Kajiwara Y. , Ando K. , Saitoh E. , Hillebrands B.
Published: December 2010

The spin pumping efficiency of standing spin wave modes in a rectangular Y3Fe5O12/Pt sample has been investigated by means of inverse spin-Hall effect (ISHE). Standing spin waves drive spin pumping, the generation of spin currents from magnetization precession, into the Pt layer which is converted into a detectable voltage due to the ISHE. We discovered that the spin pumping efficiency is significantly higher for standing surface spin waves, hybridized with thickness modes, rather than for volume spin wave modes. The results suggest that the use of higher-mode surface spin waves allows for the fabrication of an efficient spin-current injector.
Head-on collision of ion acoustic solitary waves in an electron-positron-ion plasma with superthermal electrons
Authors: Chatterjee Prasanta , Ghosh Uday narayan , Roy Kaushik , Muniandy S. V. , Wong C. S. , Sahu Biswajit
Published: December 2010

The head-on collision of ion acoustic solitary waves in a three-component unmagnetized plasma with cold ions, Boltzmann distributed positrons, and superthermal electrons is investigated using the extended Poincaré–Lighthill–Kuo method. The effects of the ratio of electron temperature to positron temperature, the spectral index, κ, of the electron kappa distribution, and fractional concentration of positron component (p) on the phase shift are studied. It is found that the presence of superthermal electrons play a significant role on the collision of ion acoustic solitary waves.
Structure and dynamics of sawteeth crashes in ASDEX Upgrade
Authors: Igochine V. , Boom J. , Classen I. , Dumbrajs O. , Günter S. , Lackner K. , Pereverzev G. , Zohm H. ,   ASDEX Upgrade Team
Published: December 2010

The crash phase of the sawteeth in ASDEX Upgrade tokamak [Herrmann et al., Fusion Sci. Technol. 44(3), 569 (2003)] is investigated in detail in this paper by means of soft x-ray (SXR) and electron cyclotron emission (ECE) diagnostics. Analysis of precursor and postcursor (1,1) modes shows that the crash does not affect the position of the resonant surface q=1. Our experimental results suggest that sawtooth crash models should contain two ingredients to be consistent with experimental observations: (1) the (1,1) mode structure should survive the crash and (2) the flux changes should be small to preserve the position of the q=1 surface close to its original location. Detailed structure of the reconnection point was investigated with ECE imaging diagnostic. It is shown that reconnection starts locally. The expelled core is hot which is consistent with SXR tomography results. The observed results can be explained in the framework of a stochastic model.
Metal-organic frameworks as promising candidates for future ultralow-k dielectrics
Authors: Zagorodniy K. , Seifert G. , Hermann H.
Published: December 2010

A class of Zn4O(CO2)6-based metal-organic frameworks (MOFs) is theoretically analyzed with respect to suitability as an interlayer dielectric material for applications in semiconducting devices. The static dielectric constant is calculated using the Clausius–Mossotti approach. For 3 of about 30 of the considered MOFs excellent combinations of ultralow dielectric constant, elastic bulk modulus, and gap energy are found favoring these materials as outstanding candidates for future ultralow-k dielectric materials.
Emission of cylindrical and elliptical vector beams from radial Bragg Lasers
Authors: Weiss Ori , Scheuer Jacob
Published: December 2010

Radially and azimuthally polarized beams are shown to be naturally emitted from radial Bragg lasers depending on the supported polarization in the cavity (TE or TM). The impact of structure imperfection and deviation from a circular shape on the lasing properties is investigated, showing a red-shift in the resonance frequency, and a modification of the radial/azimuthal polarization profile forming elliptical vector beams. The comparison of the analysis to the experimental results indicates that the fabricated lasers are not perfectly circular with ellipticity in the order of 1%.
Direct acoustic phonon excitation by intense and ultrashort terahertz pulses
Authors: Manceau J.-M. , Loukakos P. A. , Tzortzakis S.
Published: December 2010

We report on the direct and resonant excitation of acoustic phonons in an AlGaAs intrinsic semiconductor using intense coherent and single cycle terahertz pulses created by two-color femtosecond laser pulse filamentation in air. While the electrons are left unperturbed, we follow the lattice dynamics with time-delayed optical photons tuned to the interband transition.
Highly polarized self-assembled chains of single layer InP/(In,Ga)P quantum dots
Authors: Ugur Asli , Hatami Fariba , Vamivakas A. Nick , Lombez Laurent , Atatüre Mete , Volz Kerstin , Masselink W. Ted
Published: December 2010

Well-ordered chains of InP quantum dots on a self-organized undulating In0.48Ga0.52P surface exhibit optical anisotropy due to their shape and the In0.48Ga0.52P matrix. The structures are investigated by polarization-dependent photoluminescence together with transmission electron microscopy. Luminescence from the In0.48Ga0.52P matrix is polarized in one crystallographic direction due to anisotropic strain arising from a lateral compositional modulation. The photoluminescence measurements show enhanced linear polarization in the alignment direction of quantum dots, [1¯10]. A polarization degree of 66% is observed; this polarization in emission is independent of the polarization of the excitation laser. The optical anisotropy is achieved with a straightforward heterostructure, requiring only a single layer of QDs.
Infants and Toddlers Show Enlarged Visual Sensitivity to Nonaccidental Compared with Metric Shape Changes
Authors: Kayaert Greet , Wagemans Johan
Published: December 2010

Some shape changes are more important for object perception than others. We used a habituation paradigm to measure visual sensitivity to a nonaccidental shape change—that is, the transformation of a trapezium into a triangle and vice versa—and a metric shape change—that is, changing the aspect ratio of the shapes. Our data show that an enhanced perceptual sensitivity to nonaccidental changes is already present in infancy and remains stable into toddlerhood. We have thus established an example of how early visual perception deviates from the null hypothesis of representing similarity as a function of physical overlap between shapes, and does so in agreement with more cognitive, categorical demands.
The Viewing-from-Above Bias and the Silhouette Illusion
Authors: Troje Nikolaus F , McAdam Matthew
Published: December 2010

The silhouette illusion published online a number of years ago by the Japanese Flash designer Nobuyuki Kayahara has received substantial attention from the online community. One feature that seems to make it interesting is an apparent rotational bias: Observers see it spinning more often clockwise than counter-clockwise. Here, we show that this rotational bias is in fact due to the visual system's preference for viewpoints from above rather than from below.
Isoprene emission from phytoplankton monocultures: the relationship with chlorophyll-a, cell volume and carbon content
Authors: Bonsang B. , Gros V. , Peeken I. , Yassaa N. , Bluhm K. , Zoellner E. , Sarda-Esteve R. , Williams J.
Published: December 2010

Environmental context Isoprene, a natural product of both terrestrial vegetation and marine organisms, is rapidly oxidised in the atmosphere, and thereby plays a key role in the regional budget of oxidants. Although isoprene production from terrestrial plants has been extensively investigated, production processes and emission rates from marine species are still poorly understood. We present results from laboratory experiments showing that isoprene is emitted from living phytoplankton cells at variable rates depending on the light intensity, cell volume, and carbon content of the plankton cells. Abstract We report here isoprene emission rates determined from various phytoplankton cultures incubated under PAR light which was varied so as to simulate a natural diel cycle. Phytoplankton species representative of different phytoplankton functional types (PFTs) namely: cyanobacteria, diatoms, coccolithophorides, and chlorophytes have been studied. Biomass normalised isoprene emission rates presented here relative to the chlorophyll-a (Chl-a) content of the cultures showed that the two cyanobacteria (Synechococcus and Trichodesmium) were the strongest emitters with emission rates in the range of 17 to 28 µg C5H8 g–1 Chl-a h–1. Diatoms produced isoprene in a significantly lower emission range: 3 to 7.5 µg C5H8 g–1 Chl-a h–1 and Dunaliella tertiolecta was by far the lowest emitter of our investigated plankton cultures. Despite the group specific differences observed, a high emission rate variance was observed to occur within one phytoplankton group. However, a combination of literature and our own data showed a clear relationship between the actual cell volume and the isoprene emission rates. This relationship could be a valuable tool for future modelling approaches of global isoprene emissions.