bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of 60 elements in 616 ocean floor basaltic glasses
Authors: Jenner Frances E. , O'Neill Hugh St. C.
Published: January 2012

The abundances of 60 elements in 616 Ocean Floor Basaltic (OFB) glasses from the Abyssal Volcanic Glass Data File (AVGDF) of the Smithsonian Institution have been determined by laser‐ablation (LA)‐ICP‐MS and electron microprobe analysis (EMPA). The elements analyzed include all 28 of the refractory lithophile elements, which provide the framework for establishing the geochemical behavior and source abundances of volatile, chalcophile and siderophile elements. In addition to the traditionally analyzed elements (rare earth elements (REE), high field strength elements (HFSE), large ion lithophile elements (LILE) and first row transition elements (FRTE)), we report analyses for lesser‐analyzed elements (Li, Be, Ga, Ge, As, Se, Mo, Ag, Cd, In, Sn, Sb, W, Tl and Bi). The precision of the method for most elements is between 2 and 4%, one standard deviation, although ratios of elements determined simultaneously are more precise (e.g., REE, Zr/Hf). Subsets of 329 glasses were analyzed by electron microprobe for S and 154 glasses for Cl. The results define a representative trace element geochemistry of OFB, against which local variations resulting from differences in basalt petrogenesis in a range of tectonic settings or different styles of magmatic differentiation may be compared.
Constraining long‐term denudation and faulting history in intraplate regions by multisystem thermochronology: An example of the Sudetic Marginal Fault (Bohemian Massif, central Europe)
Authors: Danišík Martin , Štěpančíková Petra , Evans Noreen J.
Published: January 2012

The Rychlebské hory Mountain region in the Sudetes (NE Bohemian Massif) provides a natural laboratory for studies of postorogenic landscape evolution. This work reveals both the exhumation history of the region and the paleoactivity along the Sudetic Marginal Fault (SMF) using zircon (U‐Th)/He (ZHe), apatite fission track (AFT), and apatite (U‐Th)/He (AHe) dating of crystalline basement and postorogenic sedimentary samples. Most significantly, and in direct contradiction of traditional paleogeographic reconstructions, this work has found evidence of a large Cretaceous sea and regional burial (to >6.5 km) of the Carboniferous‐Permian basement in the Late Cretaceous (∼95–80 Ma). During the burial by sediments of the Bohemian Cretaceous Basin System, the SMF acted as a normal fault as documented by offset ZHe ages across the fault. At 85–70 Ma, the basin was inverted, Cretaceous strata eroded, and basement blocks were exhumed to the near surface at a rate of ∼300 m/Ma as evidenced by Late Cretaceous–Paleocene AFT ages and thermal modeling results. There is no appreciable difference in AFT and AHe ages across the fault, suggesting that the SMF acted as a reverse fault during exhumation. In the late Eocene–Oligocene, the basement was locally heated to <70°C by magmatic activity related to opening of the Eger rift system. Neogene or younger thermal activity was not recorded in the thermochronological data, confirming that late Cenozoic uplift and erosion of the basement blocks was limited to less than ∼1.5 km in the study area.
Phenotype and functions of conventional dendritic cells are not compromised in aged mice
Authors: Tan Sioh‐Yang , Cavanagh Lois L , d'Advigor William , Shackel Nick , de St Groth Barbara Fazekas , Weninger Wolfgang
Published: January 2012

Aging has profound effects on the immune system, including thymic involution, reduced diversity of the T cell receptor repertoire, reduced effector T cell and B cell function and chronic increase of proinflammatory cytokine production by innate immune cells. The precise effects of aging on conventional dendritic cells (cDC), the main antigen presenting cells of the immune system, however, are not well understood. We found that in aged mice the number of cDC in the spleen and lymph nodes remained stable, whereas the number of cDC in the lungs increased with age. Whereas cDC in mice showed similar cycling kinetics in all organs tested, cDC reconstitution by aged bone marrow precursors was relatively higher than that of their young counterparts. With the exception of CD86, young and aged cDC did not differ in their expression of co‐stimulatory molecules at steady state. Most toll‐like receptor (TLR) ligands induced comparable upregulation of co‐stimulatory molecules CD40, CD86 and B7H1 on young and aged cDC, whereas TLR2 and TLR5 stimulation resulted in reduced upregulation of CD80 and CD86 on aged cDC in vitro. In vivo, influenza infection‐induced upregulation of CD86, but not other co‐stimulatory molecules, was lower in aged DC. Young and aged DC were equally capable of direct and cross presentation of antigens in vitro. Transcriptome analysis did not reveal any significant difference between young and aged cDC. These data show that unlike T and B cells, the maintenance of cDC throughout the life of a healthy animal is relatively robust during the aging process.
Shared-Reading Dynamics: Mothers' Question Use and the Verbal Participation of Children With Specific Language Impairment
Authors: McGinty Anita S. , Justice Laura M. , Zucker Tricia A. , Gosse Carolyn , Skibbe Lori E.
Published: January 2012

Purpose

In this study, the authors used sequential analysis to explore bidirectional and dynamic dependencies between mothers' question use and children’s verbal participation during shared reading.

Method

The sample was composed of mothers and their preschool-age children with specific language impairment (SLI;
n
= 14). Each mother and child extratextual utterance was transcribed and coded. Mother utterances were coded as “questions” or “other”; in turn, questions were coded for cognitive challenge and topic directiveness. Child utterances were coded as “verbal participation” (related to the book) or “other”; utterances designated as verbal participation were also coded for level of production (minimal, low, high) on the basis of their mean length of utterance.

Results

Descriptive data show variability in mothers' question use and some variability in the level of children’s verbal participation during shared reading. However, mothers' question use did not facilitate higher levels of verbal participation by children. Furthermore, the level of children’s verbal participation did not influence the cognitive challenge and topic directiveness of mothers' question use.

Conclusions

The findings were contrary to hypotheses and collectively suggest potentially unique and challenging verbal dynamics between mothers and their young children with SLI during shared-reading experiences. Future directions for research are discussed.
Developmental Trajectories of Early Communication Skills
Authors: Määttä Sira , Laakso Marja-Leena , Tolvanen Asko , Ahonen Timo , Aro Tuija
Published: January 2012

Purpose

This study focused on developmental trajectories of prelinguistic communication skills and their connections to later parent-reported language difficulties.

Method

The participants represent a subset of a community-based sample of 508 children. Data include parent reports of prelinguistic communication skills at 12, 15, 18, and 21 months and language difficulties at age 4;7 (years;months). The authors used latent profile analysis to identify groups of children with differing developmental trajectories of prelinguistic communication skills (n= 271). The relations among these groups and follow-up data of parent-reported concerns of language development (n= 187), as well as the role of gender, were examined.

Results

Six meaningful prelinguistic communication groups were identified with the latent profile analysis, and these groups showed connections to later parent-reported concerns of language difficulties. Delayed early expressive language and a minor delay of overall performance, together with symbolic difficulties, appeared as predictors of later language difficulties. Nearly 80% of the children whose parents reported language-related concerns at the follow-up stage could already be identified before their 2nd birthday.

Conclusion

The results support the potential of early screening in identifying children at risk of developing language difficulties, particularly when screening includes repeated surveillance of more than one area of communication skills.
Vocal Function in Introverts and Extraverts During a Psychological Stress Reactivity Protocol
Authors: Dietrich Maria , Verdolini Abbott Katherine
Published: January 2012

Purpose

To examine the proposal that introversion predictably influences extralaryngeal and vocal behavior in vocally healthy individuals compared with individuals with extraversion and whether differences are of a nature that may support a risk hypothesis for primary muscle tension dysphonia.

Method

Fifty-four vocally healthy female adults between the ages of 18 and 35 years were divided into 2 groups: introversion (n= 27) and extraversion (n= 27). All participants completed a psychological stress reactivity experiment. Before, during, and after the stressor (public speaking), participants were assessed on extralaryngeal muscle activity (surface electromyography: submental, infrahyoid; control site: tibialis anterior), perceived vocal effort, and vocal acoustics (fundamental frequency and intensity).

Results

Participants in the introversion group exhibited significantly greater infrahyoid muscle activity throughout the protocol and during perceived stress than participants in the extraversion group. For both groups, perceived vocal effort significantly increased during stress, and acoustic measures significantly decreased. Infrahyoid muscle activity during the stress phase was significantly correlated with introversion and Voice Handicap Index scores but not with vocal effort scores.

Conclusions

The data provided evidence of distinct differences in extralaryngeal behavior between introverts and extraverts. The findings are consistent with the trait theory of voice disorders (Roy & Bless, 2000).
Psychometric Evaluation of Children With Auditory Processing Disorder (APD): Comparison With Normal-Hearing and Clinical Non-APD Groups
Authors: Iliadou Vasiliki , Bamiou Doris Eva
Published: January 2012

Purpose

To investigate the clinical utility of the Children's Auditory Processing Performance Scale (CHAPPS; Smoski, Brunt, & Tannahill, 1992) to evaluate listening ability in 12-year-old children referred for auditory processing assessment.

Method

This was a prospective case control study of 97 children (age range = 11;4 [years;months] to 12;7). Auditory processing disorder (APD) was diagnosed based on findings of deficits on at least 1 nonverbal test and on at least 2 tests of an auditory processing test battery. Clinically referred children were grouped as APD (
n
= 38) or non-APD (
n
= 20).

Results

The study found that (a) the APD group performed lower than the non-APD group on the Quiet, Ideal, Memory (
p
< .0001), and Attention (
p
< .05) subscales of the CHAPPS; (b) the non-APD group performed lower than the group with normal hearing on the Noise, Multiple Inputs, and Attention subscales (
p
< .0001); and (c) there were significant moderate-to-strong correlations (Spearman's ρ > .04) between Dichotic Digits, Duration Pattern tests, and the CHAPPS Attention, Memory, and total scores.

Conclusion

The CHAPPS may be a clinically useful tool to evaluate listening ability in 12-year-old children suspected of having APD. Restricting use of the CHAPPS to older children may help address its limitations as reported by other studies.
Perceptual Measures of Speech From Individuals With Parkinson’s Disease and Multiple Sclerosis: Intelligibility and Beyond
Authors: Sussman Joan E. , Tjaden Kris
Published: January 2012

Purpose

The primary purpose of this study was to compare percent correct word and sentence intelligibility scores for individuals with multiple sclerosis (MS) and Parkinson’s disease (PD) with scaled estimates of speech severity obtained for a reading passage.

Method

Speech samples for 78 talkers were judged, including 30 speakers with MS, 16 speakers with PD, and 32 healthy control speakers. Fifty-two naive listeners performed forced-choice word identification, sentence transcription, or visual analog scaling of speech severity for the Grandfather Passage (Duffy, 2005). Three expert listeners also scaled speech severity for the Grandfather Passage.

Results

Percent correct word and sentence intelligibility scores did not cleanly differentiate speakers with MS, PD, or control speakers. In contrast, both naive and expert listener groups judged reading passages produced by speakers with MS and PD to be more severely impaired than reading passages produced by control talkers.

Conclusion

Scaled estimates of speech severity appear to be sensitive to aspects of speech impairment in MS and PD not captured by word or sentence intelligibility scores. One implication is that scaled estimates of speech severity might prove useful for documenting speech changes related to disease progression or even treatment for individuals with MS and PD with minimal reduction in intelligibility.
Functional Brain Activation Differences in School-Age Children With Speech Sound Errors: Speech and Print Processing
Authors: Preston Jonathan L. , Felsenfeld Susan , Frost Stephen J. , Mencl W. Einar , Fulbright Robert K. , Grigorenko Elena L. , Landi Nicole , Seki Ayumi , Pugh Kenneth R.
Published: January 2012

Purpose

To examine neural response to spoken and printed language in children with speech sound errors (SSE).

Method

Functional magnetic resonance imaging was used to compare processing of auditorily and visually presented words and pseudowords in 17 children with SSE, ages 8;6[years;months] through 10;10, with 17 matched controls.

Results

When processing spoken words and pseudowords, the SSE group showed less activation than typically speaking controls in left middle temporal gyrus. They also showed greater activation than controls in several cortical and subcortical regions (e.g., left superior temporal gyrus, globus pallidus, insula, fusiform, and bilateral parietal regions). In response to printed words and pseudowords, children with SSE had greater activation than controls in regions including bilateral fusiform and anterior cingulate. Some differences were found in both speech and print processing that that may be associated with children with SSE failing to show common patterns of task-induced deactivation and/or attentional resource allocation.

Conclusion

Compared with controls, children with SSE appear to rely more on several dorsal speech perception regions and less on ventral speech perception regions. When processing print, numerous regions were observed to be activated more for the SSE group than for controls.
Effect of Speaker Age on Speech Recognition and Perceived Listening Effort in Older Adults With Hearing Loss
Authors: McAuliffe Megan J. , Wilding Phillipa J. , Rickard Natalie A. , O'Beirne Greg A.
Published: January 2012

Purpose

Older adults exhibit difficulty understanding speech that has been experimentally degraded. Age-related changes to the speech mechanism lead to natural degradations in signal quality. We tested the hypothesis that older adults with hearing loss would exhibit declines in speech recognition when listening to the speech of older adults, compared with the speech of younger adults, and would report greater amounts of listening effort in this task.

Method

Nineteen individuals with age-related hearing loss completed speech recognition and listening effort scaling tasks. Both were conducted in quiet, when listening to high- and low-predictability phrases produced by younger and older speakers, respectively.

Results

No significant difference in speech recognition existed when stimuli were derived from younger or older speakers. However, perceived effort was significantly higher when listening to speech from older adults, as compared with younger adults.

Conclusions

For older individuals with hearing loss, natural degradations in signal quality may require greater listening effort. However, they do not interfere with speech recognition—at least in quiet. Follow-up investigation of the effect of speaker age on speech recognition and listening effort under more challenging noise conditions appears warranted.
Use of Telehealth for Research and Clinical Measures in Cochlear Implant Recipients: A Validation Study
Authors: Hughes Michelle L. , Goehring Jenny L. , Baudhuin Jacquelyn L. , Diaz Gina R. , Sanford Todd , Harpster Roger , Valente Daniel L.
Published: January 2012

Purpose

The goal of this study was to compare clinical and research-based cochlear implant (CI) measures using telehealth versus traditional methods.

Method

This prospective study used an ABA design (A = laboratory, B = remote site). All measures were made twice per visit for the purpose of assessing within-session variability. Twenty-nine adult and pediatric CI recipients participated. Measures included electrode impedance, electrically evoked compound action potential thresholds, psychophysical thresholds using an adaptive procedure, map thresholds and upper comfort levels, and speech perception. Subjects completed a questionnaire at the end of the study.

Results

Results for all electrode-specific measures revealed no statistically significant differences between traditional and remote conditions. Speech perception was significantly poorer in the remote condition, which was likely due to the lack of a sound booth. In general, subjects indicated that they would take advantage of telehealth options at least some of the time, if such options were available.

Conclusions

Results from this study demonstrate that telehealth is a viable option for research and clinical measures. Additional studies are needed to investigate ways to improve speech perception at remote locations that lack sound booths and to validate the use of telehealth for pediatric services (e.g., play audiometry), sound-field threshold testing, and troubleshooting equipment.
Strategies for Transitioning From PECS to SGD. Part I: Overview and Device Selection
Authors: Frost Lori , McGowan Joy Silverman
Published: January 2012

The Picture Exchange Communication System (PECS) is used to systematically teach functional communication through an evidence-based protocol. As a low-tech AAC system, PECS differs from many treatment protocols in that the learner must give a picture or a sequence of pictures to a communicative partner, thus ensuring social approach and interaction. Students who have mastered Phase IV of the PECS protocol and use a large, categorized vocabulary and sentence structure are candidates for transition to a speech generating devise (SGD). When choosing the SGD, the transition team has an ethical responsibility to ensure that the PECS user does not lose current communication abilities, such as independent access, initiation and efficiency of interactions, and sentence structure and length across environments. With careful assessment of SGD features, the clinician can select a device to replicate current PECS skills and allow for language growth. The use of relevant training strategies from the PECS protocol will help the clinician ensure a successful transition to and use of the SGD.
Impact of Computerized “Sounding out” on Spelling Performance of a Child Who Uses AAC: A Preliminary Report
Authors: McCarthy Jillian H. , Beukelman David R. , Hogan Tiffany P.
Published: January 2012

Spelling is a vital skill for people who rely on augmentative and alternative communication (AAC). The ability to spell words provides an opportunity to create novel and spontaneous communication and increases educational, social, and employment opportunities for children and adults. However, many children and youth who rely on AAC struggle to gain functional spelling skills and written language. The purpose of this preliminary investigation was to develop a strategy to provide auditory letter-sounds using commercially available computer equipment and to evaluate how such a computerized “sounding out” strategy influences spelling accuracy for one child who required AAC support. The spelling accuracy of both consonants and vowels increased during intervention sessions when individual sounds associated with target words were provided compared to the baseline session when individual sounds were not provided. Future directions are discussed.
Uncertainty analysis of thermal conductivity measurements in
materials for energy-efficient buildings
Authors: Laghi L. , Pennecchi F. , Raiteri G.
Published: January 2012

The accuracy of thermal conductivity measurements is even more requested for materials
characterization in energy-efficient buildings field. ENEA-UTTMATF and CertiMaC research
group, as national institute and private laboratory respectively, cooperate in development
of new measurement and analysis methods applied to buildings materials and their
performances. For what concerns this kind of measurements, an Heat Flow-meter Transducer
(HFT) is used. In order to give to both customers and other research institutes involved
in the same field (e.g. International Comparison or International Round Robin Tests) the
most exhaustive evaluation of the tested material thermal conductivity, a complete
uncertainty analysis is implemented on the HFT measures. This uncertainty analysis,
developed accordingly to the international standards and with the contribution of INRiM
Institute, is described in this paper.
Proficiency test scheme for histamine analysis in fishery products in Morocco using the fluorometric method and comparison of results with those obtained with the HPLC reference method
Authors: Rachidi A. , Oualit N. , Touti A. , Duflos G. , Noël L. , Caillaud P.
Published: January 2012

A Proficiency Test Scheme (PTS) for histamine analysis in fishery products using the Lerke and Bell (1976) fluorometric method was conducted in 26 different Moroccan laboratories. The goal of this PTS was to assess the abilities of a network of seven government laboratories and 19 laboratories performing auto-controls on fish processing units in Morocco. The samples used in the PTS were prepared from canned ground mackerel flesh, to which was added two significant concentrations (levels 1 and 2) of histamine. The homogeneity of the PTS samples was verified by a repeatability test and their stability by an intermediate fidelity test. The Cochran test was used to eradicate anomalous scattering and the Grubbs test to eradicate the anomalous averages observed in the results of the participating laboratories. The average and the usual deviations determined for levels 1 and 2 were used to calculate the Z-scores. For level 1 therefore, 23 out of 26 laboratories had satisfactory PTS results, and for level 2, 21 out of 26 laboratories had satisfactory PTS results. An analysis of the PTS samples using the HPLC reference method gave similar results for levels 1 and 2.
Expression and Significance of Lipin1 and AMPKα in Hepatic Insulin Resistance in Diet-Induced Insulin Resistance Rats
Authors: Chen S. , Zhuang X. , Liu Y. , Sun A. , Chen C.
Published: January 2012

Lipin1, a lately indentified adipokine, may link obesity with insulin resistance and diabetes. The present study aimed to investigate the changes and significance of lipin1 expression and lipin1-AMPK signaling in diet-induced hepatic insulin resistance.

24 4-week-old Male Wistar rats were randomly divided into 2 groups: (1) control group (CO), (2) high-fat diet group (HF). Insulin sensitivity was evaluated by hyperinsulinemic-euglycemic clamp technique. The mRNA levels of α1 and α2 subunit of AMPKα as well as Lipin1 were measured using Real-time RT-PCR. The activities of AMPKα and Akt were evaluated by detection of p-AMPKα (Thr-172) and p-Akt (ser473) by Western blot.

After treatment of 4 months, HF group showed significantly increased levels of body weight, fasting plasma glucose and insulin levels; Plasma and liver total cholesterol (TC), triglycerides (TG) levels were also markedly elevated; Lipin1 expression at both mRNA and protein levels were significantly deceased. Compared with CO group, the mRNA and protein levels of AMPKα1 and AMPKα2 were not changed, whereas the p-AMPK (Thr-172) and p-AKT (ser473) levels in liver were significantly decreased in HF group.

These findings indicated that the decrease in lipin1 expression and AMPKα activation may contribute to hepatic insulin resistance in diet-induced obese rats.
Availability of Self-Recorded Axillary Temperature for Assessment of Thermic Effects of Food: Relationship between HDL-Cholesterol Level and Postprandial Thermoregulation in Type 2 Diabetic Patients
Authors: Suzuki S. , Nishio S.-i. , Ishii H. , Sato A. , Takeda T. , Komatsu M.
Published: January 2012

The present study was performed to develop a simple procedure for assessment of body temperature and to determine whether postprandial thermoregulation is related to metabolic regulation in diabetic patients.

We examined 101 male and female subjects with diabetes. Axillary temperature was measured prior to and after all meals (3 meals per day) and self-recorded for 1 week. The averages were calculated. Positive postprandial thermoregulation (PPT) was defined as a pattern in which each of 3 average postprandial temperatures was higher than the corresponding 3 preprandial temperatures. Negative postprandial thermoregulation (NPT) was defined as the pattern except for PPT.

A significant increase in postprandial temperature was observed. With the exception of high-density lipoprotein (HDL)-cholesterol levels, there were no relationships between the categorized postprandial thermoregulation and other factors, including age, sex, body mass index, thyroid function, HbA1c, diabetic complications, lipid metabolism, and calorie intake. Logistic analysis indicated an independent positive relation between HDL-cholesterol and PPT.

A simple method for measurement of body temperature indicated that HDL-cholesterol level was predominantly associated with thermic effects of food in diabetic patients, while other metabolic factors showed no such relations. HDL-cholesterol may affect the postprandial regulation of body temperature in diabetic patients.
Energy landscapes of ion clusters in isotropic quadrupolar and octupolar traps
Authors: Calvo F. , Yurtsever E. , Wales D. J.
Published: January 2012

The energy landscapes of ion clouds confined in isotropic quadrupolar and octupolar traps are characterized for several representative cluster sizes. All clusters exhibit stable multishell structures that belong to separate funnels. Quadrupolar confinement leads to more homogeneous clusters and denser distributions of isomers than octupolar confinement. Statistical analysis of the transition states indicates that the barriers associated with intrashell motion are lower but more asymmetric and more cooperative compared to intershell motion. The relaxation between low-energy funnels with different arrangements of shells mostly exhibits Arrhenius kinetics, with a weak variation of the activation energy at higher temperatures.
Elastic and piezoelectric constants of tourmaline single crystals at non-ambient temperatures determined by resonant ultrasound spectroscopy
Authors: Shekhar Pandey Chandra , Schreuer Jürgen
Published: January 2012

The full sets of elastic constants (considering piezoelectric effect, i.e., taking into account piezoelectric coupling effects) and piezoelectric stress constants of five natural tourmaline single crystals of different chemical composition have been determined from room temperature up to ∼900 K employing resonant ultrasound spectroscopy. Further, the coefficients of thermal expansion were studied in a wide temperature range from 100 K to 950 K. Electron microprobe analysis showed that the chemical composition of investigated samples varied over a wide range, which allows to study the compositional dependence of thermal, elastic, and piezoelectric properties of tourmalines. At room temperature, the piezoelectric constants of tourmalines were found at-least 1.5 times higher than that for α-quartz. Importantly, we find that the application of tourmaline at temperatures up to its decomposition temperature is not limited by phase transitionsor any ultrasound dissipation effects.
Molecular dynamics simulation study of the water-mediated interaction between zwitterionic and charged surfaces
Authors: Eun Changsun , Berkowitz Max L.
Published: January 2012

We calculated the potential of mean force (PMF) for the interaction between a model zwitterionic bilayer and a model charged bilayer. To understand the role of water, we separated the PMF into two components: one due to direct interaction and the other due to water-mediated interaction. In our calculations, we observed that water-mediated interaction is attractive at larger distances and repulsive at shorter. The calculation of the entropic and enthalpic contributions to the solvent-mediated components of the PMF showed that attraction is entropically dominant, while repulsion is dominated by the enthalpy.
Stretching semiflexible polymer chains: Evidence for the importance of excluded volume effects from Monte Carlo simulation
Authors: Hsu Hsiao-Ping , Binder Kurt
Published: January 2012

Semiflexible macromolecules in dilute solution under very good solvent conditions are modeled by self-avoiding walks on the simple cubic lattice (d = 3 dimensions) and square lattice (d = 2 dimensions), varying chain stiffness by an energy penalty εb for chain bending. In the absence of excluded volume interactions, the persistence length ℓp of the polymers would then simply be \documentclass[12pt]{minimal}\begin{document}$\ell _p\break=\ell _b(2d-2)^{-1}q_b^{-1}$\end{document}ℓp=ℓb(2d−2)−1qb−1 with qb = exp (−εb/kBT), the bond length ℓb being the lattice spacing, and kBT is the thermal energy. Using Monte Carlo simulations applying the pruned-enriched Rosenbluth method (PERM), both qb and the chain length N are varied over a wide range (0.005 ⩽ qb ⩽ 1, N ⩽ 50 000), and also a stretching force f is applied to one chain end (fixing the other end at the origin). In the absence of this force, in d = 2 a single crossover from rod-like behavior (for contour lengths less than ℓp) to swollen coils occurs, invalidating the Kratky-Porod model, while in d = 3 a double crossover occurs, from rods to Gaussian coils (as implied by the Kratky-Porod model) and then to coils that are swollen due to the excluded volume interaction. If the stretching force is applied, excluded volume interactions matter for the force versus extension relation irrespective of chain stiffness in d = 2, while theories based on the Kratky-Porod model are found to work in d = 3 for stiff chains in an intermediate regime of chain extensions. While for qb ≪ 1 in this model a persistence length can be estimated from the initial decay of bond-orientational correlations, it is argued that this is not possible for more complex wormlike chains (e.g., bottle-brush polymers). Consequences for the proper interpretation of experiments are briefly discussed.
Coarse-grained potential models for structural prediction of carbon dioxide (CO2) in confined environments
Authors: Sanghi T. , Aluru N. R.
Published: January 2012

In this paper, we propose coarse-grained single-site (CGSS), wall-CO2, and CO2-CO2 interaction potential models to study the structure of carbon dioxide under confinement. The CGSS potentials are used in an empirical potential based quasi-continuum theory, EQT, to compute the center-of-mass density and potential profiles of CO2 confined inside different size graphite slit pores. Results obtained from EQT are compared with those obtained from all-atom molecular dynamics (AA-MD) simulations, and are found to be in good agreement with each other. Though these CGSS interaction potentials are primarily developed and parameterized for EQT, they are also used to perform coarse-grained molecular dynamics (CG-MD) simulations. The results obtained from CG-MD simulations are also found to be in reasonable agreement with AA-MD simulation results.
Determination of the electronic structure of ferroelectric surfaces by scanning tunneling microscopy
Authors: Kraya L. Y. , Kraya R.
Published: January 2012

The electronic structures and the origin of the in-gap states of the BaTiO3 (001) (2 × 2), (√5 × √5), and (3 × 1) reconstructions are investigated using scanning tunneling microscopy and low energy electron diffraction. We find a shift of the in-gap states toward the valence band as the order of the reconstructions increase. We argue that Ti adatoms are responsible for the in-gap state, and a decrease in the oxidation state of the Ti adatom as a function of the reconstruction is attributed to the shift of the in-gap state within the local density of states.
Flux pinning properties of correlated pinning at low temperatures in ErBCO films with inclined columnar defects
Authors: Awaji S. , Namba M. , Watanabe K. , Kai H. , Mukaida M. , Okayasu S.
Published: January 2012

The effect of c-axis correlated pinning on the critical current density at low temperatures under high magnetic fields was investigated on the basis of the transport critical current density and irreversibility field properties of an ErBa2Cu3Oy film with inclined columnar defects. We found that the contribution of correlated pinning on Jc decreased drastically with decreasing temperature under high magnetic fields above the matching field, but still retained more than a 60% enhancement at 13 K. These effects of correlated pinning can be described using a cooperative model based on a combination of correlated and random pinning. At low temperatures, the presence of a matching field limited the flux pinning force for correlated pinning in comparison with that of random pinning, while the ratio of the maximum pinning force of the correlated pinning to the random one was proportional to the inverse of the irreversibility field. This suggests that the low efficiency of correlated pinning at low temperatures under a strong magnetic field is a result of a high irreversibility field and a low matching field. In order to improve the critical current properties at low temperatures under high magnetic fields, an increase in the matching field and/or the introduction of strong random pinning are effective.
Ultrahigh dielectric constant of thin films obtained by electrostatic force microscopy and artificial neural networks
Authors: Castellano-Hernández E. , Sacha G. M.
Published: January 2012

A detailed analysis of the electrostatic interaction between an electrostatic force microscope tip and a thin film is presented. By using artificial neural networks, an equivalent semiinfinite sample has been described as an excellent approximation to characterize the whole thin film sample. A useful analytical expression has been also developed. In the case of very small thin film thicknesses (around 1 nm), the electric response of the material differs even for very high dielectric constants. This effect can be very important for thin materials where the finite size effect can be described by an ultrahigh thin film dielectric constant.
Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells
Authors: Northrup J. E. , Chua C. L. , Yang Z. , Wunderer T. , Kneissl M. , Johnson N. M. , Kolbe T.
Published: January 2012

For AlGaN-based multi-quantum-well light emitters grown on c-plane substrates there is a tendency for the polarization of the emitted light to switch from transverse electric (TE) polarization to transverse magnetic (TM) polarization as the wavelength decreases. This transition depends on various factors that include the strain in the quantum well. Experimental results are presented that illustrate the phenomenon for nitride light emitting diodes (LEDs) grown on sapphire and on bulk AlN. Model calculations are presented which quantify the dependence of the TE/TM switch on the quantum well strain and the Al composition in the barriers surrounding the well.
Nanocomposite lanthanum strontium manganite thin films formed by using a chemical solution deposition
Authors: Moreno C. , Abellán P. , Sandiumenge F. , Casanove M.-J. , Obradors X.
Published: January 2012

A single-step process to prepare epitaxial nanocomposite La0.7Sr0.3MnO3/La2O3 thin films formed by spontaneous phase separation using a chemical solution deposition is presented. High magnetic field and temperature dependences of magnetic, transport, and magneto-transport properties of the films were investigated. The relationship between the enhanced magnetoresistance and microstructure and chemical inhomogeneities of the films are discussed.
Defect characterization in Mg-doped GaN studied using a monoenergetic positron beam
Authors: Uedono A. , Ishibashi S. , Tenjinbayashi K. , Tsutsui T. , Nakahara K. , Takamizu D. , Chichibu S. F.
Published: January 2012

Vacancy-type defects in Mg-doped GaN grown by metalorganic vapor phase epitaxy were probed using a monoenergetic positron beam. For a sample fabricated with a high H2-flow rate, before post-growth annealing the major defect species detected by positrons was identified as vacancy-clusters. Evidence suggested that other donor-type defects such as nitrogen vacancies also existed. The defects increased the Fermi level position, and enhanced the diffusion of positrons toward the surface. The annihilation of positrons at the top surface was suppressed by Mg-doping. This was attributed to the introduction of a subsurface layer (<6 nm) with a low defect concentration, where the Fermi level position was considered to decrease due to partial activation of Mg. For samples after annealing, the trapping of positrons by residual vacancy-type defects was observed, and the sample crystal quality was found to depend on that before annealing.
Magnetoresistance oscillations arising from edge-localized electrons in low-defect graphene antidot-lattices
Authors: Shimizu T. , Nakamura J. , Tada K. , Yagi Y. , Haruyama J.
Published: January 2012

The so-called zigzag edge of graphenes has localized and strongly spin-polarized electrons. However, magnetoresistance (MR) behavior associated with the edge electrons has not been reported in graphenes. Here, we measure MR of graphene antidot-lattices, honeycomb-like arrays of hexagonal antidots with a large ensemble of hydrogen-terminated and low-defect antidot edges, prepared by a nonlithographic method using nanoporous alumina templates. We find anomalous MR oscillations arising from localized electron spins existing at the antidot edges. These are promising for realization of spintronic devices.
Efficient optical trapping using small arrays of plasmonic nanoblock pairs
Authors: Tanaka Yoshito , Sasaki Keiji
Published: January 2012

We report that a small two-dimensional array of gold nanoblock pairs separated by a nanometric gap significantly improves the performance of optical trapping compared to a single nanoblock pair. The array of 4 × 4 pairs suppresses the Brownian motion of a trapped 1 μm diameter particle by a factor of six compared to the single pair. In addition, the array enables particle trapping for a longer period of time. These results are essential for biological applications where intense optical irradiation is a concern.
Ambient effects on electric-field-induced local charge modification of TiO2
Authors: Kim Haeri , Hong Seungbum , Kim Dong-Wook
Published: January 2012

We investigated the surface potential of TiO2 single crystals using scanning probe microscopy (SPM) under different gas environment. The SPM tip-induced electrical stress resulted in reversal in the surface potential, Vsurf, polarity only in H2/Ar (ΔVsurf = 0.30 eV) and not in Ar and O2. Quantitative measurement of the influence of ambient gas on the surface potential led us to develop a model where the adsorbed oxygen molecules and oxygen vacancies interact to change their relative concentration leading to different surface potential in TiO2. These results will give us insights into ambient-dependent physical phenomena in oxide thin film nanostructures.
Competitive partitioning of rotational energy in gas ensemble equilibration
Authors: McCaffery Anthony J. , Marsh Richard J.
Published: January 2012

A wide-ranging computational study of equilibration in binary mixtures of diatomic gases reveals the existence of competition between the constituent species for the orbital angular momentum and energy available on collision with the bath gas. The ensembles consist of a bath gas AB(v;j), and a highly excited minor component CD(v′;j′), present in the ratio AB:CD = 10:1. Each ensemble contains 8000 molecules. Rotational temperatures (Tr) are found to differ widely at equilibration with TrAB/TrCD varying from 2.74 to 0.92, indicating unequal partitioning of rotational energy and angular momentum between the two species. Unusually, low values of Tr are found generally to be associated with diatomics of low reduced mass. To test effects of the equi-partition theorem on low Tr we undertook calculations on HF(6;4) in N2(0;10) over the range 100–2000 K. No significant change in TrN2/TrHF was found. Two potential sources of rotational inequality are examined in detail. The first is possible asymmetry of −Δj and +Δj probabilities for molecules in mid- to high j states resulting from the quadratic dependence of rotational energy on j. The second is the efficiency of conversion of orbital angular momentum, generated on collision with bath gas molecules, into molecular rotation. Comparison of these two possible effects with computed TrAB/TrCD shows the efficiency factor to be an excellent predictor of partitioning between the two species. Our finding that Tr values for molecules such as HF and OH are considerably lower than other modal temperatures suggests that the determination of gas ensemble temperatures from Boltzmann fits to rotational distributions of diatomics of low reduced mass may require a degree of caution.
Hybrid density functional theory study of band gap tuning in AlN and GaN through equibiaxial strains
Authors: Duan Yifeng , Qin Lixia , Shi Liwei , Tang Gang , Shi Hongliang
Published: January 2012

Structural transformation and the variation in the band gap of (0001) AlN and GaN films as a function of equibiaxial in-plane strain are studied using the HSE06 range-separated hybrid functional. Although AlN and GaN under strain share the same structural transition from wurtzite to a graphitelike phase, their electronic properties are significantly different. Both wurtzite and graphitelike AlN under strain can display either direct or indirect band structures, whereas the band gap of wurtzite GaN is always direct and graphitelike GaN always indirect. Furthermore, it is more difficult for AlN than GaN to obtain the graphitelike semi-metallic phase. Our results for GaN support the conclusions obtained from standard density functional theory [Dong et al., Appl. Phys. Lett. 96, 202106 (2010)]
Note: An adhesion measurement setup for bioinspired fibrillar surfaces using flat probes
Authors: Kroner E. , Blau J. , Arzt E.
Published: January 2012

Current adhesion measurement setups designed for experiments on bioinspired fibrillar surfaces, either commercial or constructed in-house, do not allow adhesion measurements with in situ visualization, high resolution, high force range, and controlled alignment at the same time. In this paper a new adhesion tester is presented, which enables contact experiments with controlled tilt angle (accuracy of ±0.02°). This allows the use of flat probes and thus greatly simplifies the determination of experimental parameters such as pull-off strength or Young's modulus. The deflection of a double-clamped glass beam is measured by laser interferometry with an accuracy of ±60 nm, which yields a precise force measurement over three orders of magnitude force range without changing the glass beam. Contact formation and detachment events can be visualized in situ. The current adhesion tester is designed for force measurements in the range of 1 μN to 1 N and fills the gap between macroscopic tests and atomic force microscopy measurements.
Photovoltaic quantum dot quantum cascade infrared photodetector
Authors: Barve A. V. , Krishna S.
Published: January 2012

Design and characterization of a quantum dot quantum cascade detector for photovoltaic midwave infrared photodetection (λpeak = 5.5 μm) is demonstrated. The quantum cascade barrier region provides the internal electric field to transfer photoexcited electrons into quantum dots of the next stack, enabling zero bias operation. Increased carrier relaxation time for intersubband transitions in quantum dots provides a distinct advantage for the carrier transport. Responsivity of 10 mA/W and detectivity of 9 × 109 cm Hz1/2 W−1 at 77 K for f/2 optics has been obtained at zero bias. Dark current density is 6.5 × 10−7A cm−2, at 80 K at zero bias.
A novel and compact nanoindentation device for in situ nanoindentation tests inside the scanning electron microscope
Authors: Huang Hu , Zhao Hongwei , Mi Jie , Yang Jie , Wan Shunguang , Xu Lixia , Ma Zhichao
Published: January 2012

In situ nanomechanical tests provide a unique insight into mechanical behaviors of materials, such as fracture onset and crack propagation, shear band formation and so on. This paper presents a novel in situ nanoindentation device with dimensions of 103mm×74mm×60mm. Integrating the stepper motor, the piezoelectric actuator and the flexure hinge, the device can realize coarse adjustment of the specimen and precision loading and unloading of the indenter automatically. A novel indenter holder was designed to guarantee that the indenter penetrates into and withdraws from the specimen surface vertically. Closed-loop control of the indentation process was established to solve the problem of nonlinearity of the piezoelectric actuator and to enrich the loading modes. The in situ indentation test of Indium Phosphide (InP) inside the scanning electron microscope (SEM) was carried out and the experimental result indicates the feasibility of the developed device.
Can we breed Merino sheep with softer, whiter, more photostable wool?
Authors: Hatcher S. , Hynd P. I. , Thornberry K. J. , Gabb S.
Published: January 2012

Genetic parameters (heritability, phenotypic and genetic correlations) were estimated for a range of visual and measured wool traits recorded from the 2008 shearing of the initial cohort of Merino progeny born into the Sheep CRC’s Information Nucleus Flock. The aim of this initial analysis was to determine the feasibility of selectively breeding Merino sheep for softer, whiter, more photostable wool and to quantify the likely impact on other wool production and quality traits. The estimates of heritability were high for handle and clean colour (0.86 and 0.70, respectively) and moderate for photostability (0.18), with some evidence of maternal effects for both handle and photostability. The phenotypic correlations between handle and clean colour and between handle and photostability were close to zero, indicating that achieving the ‘triple’ objective of softer, whiter, more photostable wool in the current generation through phenotypic selection alone would be difficult. There was evidence of an antagonistic relationship between handle and photostability (–0.36), such that genetic selection for softer wool will produce less photostable wool that will yellow on exposure to UV irradiation. However genetic selection for whiter wool is complementary to photostability and will result in whiter wool that is less likely to yellow. Genetic selection to improve handle, colour and photostability can be achieved with few detrimental effects on other visual and measured wool traits, particularly if they are included in an appropriate selection index.