bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of fetal urine production to differentiate causes of increased amniotic fluid volume
Authors: Lee S. M. , Jun J. K. , Lee E. J. , Lee J. H. , Park C.‐W. , Park J. S. , Syn H. C.
Published: December 2009

Objectives

In polyhydramnios, amniotic fluid (AF) volume can be increased not only as a result of increased fetal urine production, but also due to several other factors, including impairment of both fetal swallowing and gastrointestinal (GI) absorption of AF. Our aim was to evaluate whether measurement of the fetal urine production rate (UPR) can be used to differentiate the causes of increased AF volume.

Methods

This cross‐sectional study included 54 pregnant women with an increased amniotic fluid index (AFI), defined as AFI ≥ 18 cm, divided into two groups according to the presence of fetal anomalies that are associated with impairment of fetal swallowing or decreased GI absorption of AF (Group 1, n = 14) or the absence of fetal anomalies (Group 2, n = 40). The control group included 96 normal pregnancies with normal AFI (8 ≤ AFI < 18 cm) (Group 3). Fetal UPR was obtained by serial bladder volume measurements (two to four times, with a median interval of 5 min between each) using the rotational method of Virtual Organ Computer‐aided AnaLysis (VOCAL™) with three‐dimensional ultrasound. To adjust for fetal weight (Wt) and gestational age (GA), UPR_Wt and UPR_SD were calculated using the following formulae: UPR_Wt = measured UPR/estimated fetal weight and UPR_SD = (measured UPR − mean UPR for each GA)/SD of UPR for each GA.

Results

The AFI was increased significantly in Groups 1 and 2 compared with Group 3. However, the median fetal UPR in Group 1 did not differ from that of Group 3, in contrast to the higher median fetal UPR in Group 2 compared with Groups 1 and 3; this difference remained significant after adjusting for GA and estimated fetal weight in terms of UPR_SD and UPR_Wt. In Groups 2 and 3, AFI and UPR had a positive correlation in terms of UPR, UPR_SD and UPR_Wt.

Conclusions

Our findings that fetal UPR is significantly increased in cases with increased AFI without fetal anomalies, but not in those with increased AFI and fetal anomalies involving decreased GI absorption of AF, might be used to differentiate causes of increased AF volume. In the absence of fetal anomalies, AFI and fetal UPR correlate positively. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.
Risks and Adequacy of an Optimized Surgical Approach to the Primary Surgical Management of Papillary Thyroid Carcinoma Treated During 1999–2006
Authors: Grant Clive S. , Stulak John M. , Thompson Geoffrey B. , Richards Melanie L. , Reading Carl C. , Hay Ian D.
Published: December 2009

Background

Intense disease surveillance and frequent lymph node metastases (LNMs) in papillary thyroid cancer (PTC) have resulted in increased locoregional recurrences. We examined the safety and efficacy of an optimized surgical approach including preoperative ultrasonograpy (US), bilateral thyroidectomy, routine compartment VI dissection, and lateral neck dissection for LNM.

Methods

During 1999–2006, a total of 420 patients underwent optimized primary surgery; 291(69%) females, median age 46 years; follow‐up 98%, median 4.4 years. Patients were reviewed for tumor characteristics, pattern of LNM, staging, and outcomes.

Results

Total or near‐total thyroidectomy was performed in 212 (51%) and 208 (49%) patients, respectively. Tumors were multicentric, 40% (average 1.7 cm); were bilateral, 30%; and showed extrathyroidal extension, 17%. Overall, 223 (53%) patients had LNMs: 213 (51%) were central and 85 (20%) were lateral jugular. pTNM staging: I, 258 (61%); II, 35 (8%); III, 88 (21%); IV, 39 (9%). AGES (age, grade, extension, and size—thyroid tumor; and MACIS (metastasis, age, completeness of resection, invasion, and size) prognostic scores were low risk in 362 (86%) and 352 (84%), respectively. Relapse developed in 57 (14%) patients: LNM in 44, soft tissue local recurrence (LR) in 5, distant metastases (DM) in 8. Hypoparathyroidism occurred in 5 (1.2%) patients and 1 had unintentional laryngeal nerve damage. Relapse with LNM occurred in previously operated fields in 19 (5%) patients, 11(3%) from disease virulence (LR or DM), preoperative false‐negative (FN) US in 12 (3%), and combination of FN‐US and recurrence in the operated field in 5 (1%) patients.

Conclusions

Recurrence was limited to 5% of patients when the extent of disease was accurately defined and potentially curable. This optimized surgical strategy is relatively safe.
Mortality‐Related Factors in 1056 Radioiodine‐Treated Patients with Well‐Differentiated Thyroid Cancer in Southern Thailand
Authors: Yipintsoi Tada , Premprabha Teerapon , Geater Alan , Thientunyakij Tanyaluck , Thongmak Suchitra
Published: December 2009

Background

Reported risk factors for death related to well differentiated thyroid cancer vary, possibly depending on the methods and geographical site of data collection.

Method

To evaluate variables related to death in well‐differentiated thyroid cancer (WDTC) in a population of southern Thailand, we retrospectively reviewed medical records of all those treated with radioactive iodine (I‐131) at the Division of Nuclear Medicine from 1983 to 2002. We found 1056 subjects. Variables examined included present status of subjects (transfer, lost, died), cause of death (related and not related to WDTC), duration of follow‐up since surgery, largest size of tumor (when available), gender, histology (follicular or papillary, with mixed included in papillary), age of surgery, and site of spread when treated. Survival from WDTC death utilized Kaplan‐Meier and Cox regression analysis.

Results

The median follow‐up was 7 years, while only 4 years elapsed from surgery for those who died. We did not know the status of 16% of the subjects despite attempts to contact them. Survival was not affected by age, gender, or maximum size of tumor. Age at surgery was significant only for the group older than 55 years, with a 10‐year survival of 76%. The spread of the disease that affected survival can be localized to the aerodigestive tract (10‐year survival of 65%) and metastases associated with bone fracture (10‐year survival 34%), while other metastases (including asymptomatic bone metastases) exhibited a 10‐year survival of 93%. Neither lymph node spread nor elevated Tg at maximum stimulation predicted survival.

Conclusions

To better predict survival of WDTC, site of spread and degree of spread has to be specific.
Genetic correlation between behavioural traits in relation to death‐feigning behaviour
Authors: Nakayama Satoshi , Nishi Yusuke , Miyatake Takahisa
Published: December 2009

Individuals frequently behave in a consistent manner across time or in different situations. We examined the repeatability of duration of death‐feigning anti‐predator behaviour when attacked, and then carried out artificial selection for duration to calculate its heritability and examine correlated responses to selection in activity levels, in the confused flour beetle, Tribolium confusum. Three replicates of two strains were established by artificial selection for more than 17 generations: S strains exhibited shorter duration and lower frequency of death feigning while L strains exhibited longer duration and higher frequency of death feigning. Duration of death feigning clearly responded to selection, and significant value of realized heritability was detected in all replicates of the two strains. Examination of locomotor activity levels over a constant period showed that S strains had higher locomotor activity levels than L strains. No significant differences between the sexes were observed. Our study thus demonstrates heritability of death feigning and the existence of a negative genetic correlation between intensity of death feigning and activity level.
Dietary patterns and risk of asthma: results from three countries in European Community Respiratory Health Survey-II
Authors: Hooper Richard , Heinrich Joachim , Omenaas Ernst , Sausenthaler Stefanie , Garcia-Larsen Vanessa , Bakolis Ioannis , Burney Peter
Published: December 2009

Dietary patterns offer an alternative to the analysis of individual foods or nutrients in nutritional epidemiological studies. The aim of the present study was to identify dietary patterns common to different European countries and examine their associations with asthma. In five study centres (two in Germany, two in the UK and one in Norway), 1174 adults aged 29–55 years completed a FFQ and respiratory symptoms questionnaire. A meta-analytic approach was used to identify the dietary patterns and analyse them in relation to current asthma, asthma symptoms and bronchial responsiveness (BHR). Two patterns emerged, generally correlating with the same foods at different centres: one associated with intake of meats and potatoes; the other with fish, fruits and vegetables. There was no evidence that the fish, fruits and vegetables pattern was associated with asthma (OR 1·11 (95 % CI 0·93, 1·33)), symptom score (ratio of means 1·07 (0·98, 1·17)) or BHR (regression coefficient − 0·01 ( − 0·12, 0·10)), though these CI appeared to rule out large protective effects of consuming these foods. There was no overall evidence that the meat and potato pattern was associated with asthma (OR 1·02 (0·79, 1·31)), symptom score (ratio of means 1·07 (0·84, 1·36)) or BHR (regression coefficient − 0·08 ( − 0·27, 0·10)), but there was heterogeneity between centres in the association with symptom score: a negative association at the two German centres; a positive association at the others. Heterogeneity in a multi-centre observational study of diet could suggest alternative explanations for apparent effects of diet, such as uncontrolled confounding.
Variations in compliance with starchy food recommendations and consumption of types of starchy foods according to sociodemographic and socioeconomic characteristics
Authors: Touvier Mathilde , Méjean Caroline , Kesse-Guyot Emmanuelle , Vergnaud Anne-Claire , Péneau Sandrine , Hercberg Serge , Castetbon Katia
Published: December 2009

Nutritional recommendations call for balanced, diversified consumption of starchy foods and increased whole-grain food intake. Their efficiency may depend on sociodemographic and socioeconomic factors, for which little information is available. The aim of the present study was to investigate the relationship between sociodemographic and socioeconomic characteristics and starchy food consumption in a large general population of French adults. Dietary intake was assessed using at least six 24-h dietary records collected, during a 2-year period, from 4574 men and women aged 45–60 years who participated in the Supplémentation en VItamines Minéraux et AntioXydants cohort study in 1995–7. Compliance with the recommendation ( ≥ 3 and < 6 servings/d), non-consumption of whole-grain products, variety and daily cost were compared across sociodemographic and socioeconomic categories using logistic regression and covariance analyses. About 55 % of subjects complied with the starchy food recommendation, with little variation across sociodemographic characteristics. Consumption of whole-grain products was less likely in men (P = 0·001), in subjects with a lower education level (P-trend = 0·01) and in those belonging to intermediate occupational categories (P = 0·02). The variety of starchy food intake increased with education level (P-trend = 0·0002) and was lowest for manual workers (P = 0·03). The proportion of daily food cost spent on starchy foods decreased with occupational category (P < 0·0001), and was higher in rural areas (P = 0·0004). The starchy food budget spent on potatoes decreased with the educational level (P-trend = 0·007), whereas it increased for rice and unsweetened breakfast cereals (P-trend = 0·001 for both). Public recommendations concerning starchy food variety and whole-grain intake should specifically target subjects with a lower education level and/or occupational category.
Predator–prey interactions between a population of Nucella lapillus (Gastropoda: Muricidae) recovering from imposex and Mytilus galloprovincialis (Bivalvia: Mytilidae) on the south-east coast of England
Authors: Morton Brian
Published: December 2009

Over a 52-month period beginning in May 2004 and concluding in August/September 2008, and coinciding with the period over which tributyltin was banned as a ship anti-foulant globally, a population of the dogwhelk, Nucella lapillus on the south-eastern coast of England, was studied for changes in population size and structure, reproduction and feeding behaviour. During the study period, the size of the N. lapillus population grew from ~25 individuals to >500, i.e. a 20-fold increase, and recovery from imposex was total. Significant changes in feeding behaviour were also reported. For example, peaks in N. lapillus predation were recorded over the winter months, but as population size increased, this temporal seasonality was masked due to the growing numbers of juveniles feeding on smaller and smaller individuals of Mytilus galloprovincialis (as opposed to barnacles) as the study progressed. Similarly, with freedom from imposex, the numbers of failed drilling attempts declined and numbers of prey with more than one drill hole increased as the incidence of kleptoparasitism increased. Predated M. galloprovincialis were also increasingly attacked in the antero- and postero-dorsal quadrants of their shells as the study progressed. Contrary to expectations, only a slightly positive relationship between predator and prey sizes was recorded overall however, suggesting that beyond a shell height of ~13 mm, when the transition from barnacle to mussel feeding occurs, M. galloprovincialis individuals of virtually any size are preyed upon by N. lapillus.
Gametogenic cycle of the tropical vermetids Eualetes tulipa and Dendropoma corrodens (Mollusca: Caenogastropoda: Vermetidae)
Authors: Miloslavich Patricia , Klein Eduardo , Penchaszadeh Pablo
Published: December 2009

The population density, annual gametogenic cycle, and size at sexual maturity of two vermetid species, Eualetes tulipa (invasive) and Dendropoma corrodens was studied in the southern Caribbean at the Planta Centro power plant intake channel and at Punta Mayorquina, Morrocoy National Park, respectively. Minimal size of mature females of E. tulipa and D. corrodens was 5.0 and 0.7 cm in body length respectively. The gonad represented between 44 to 47% of total body length, while it represented between 15 to 18% of total body volume (for both males and females). Gonad volume was significantly related to total body volume. A significant quadratic relationship between the number of capsules and female body volume was obtained for E. tulipa, indicating that females measuring 6–10 cm in body length are those that have the highest number of egg capsules. Females larger than 11 cm have a lower fecundity in terms of brooded capsules. Gonad sections of males and females of both species showed that several gametogenesis stages are simultaneous within the same individual. In the female, germ cells, oogoniums and primary oocytes with yolk granules were observed simultaneously. In the male, the spermatogonium, primary and secondary spermatocytes, spermatids and sperm cells were also observed within one gonad. The same pattern was observed throughout the year, showing no maturation/resting period or annual cycle. The area covered by D. corrodens was about 700 m2 with a mean density of 13,000 ind/m2. The area covered by the invasive E. tulipa was at least about 1000 m2, with a density of 27,000 to 29,000 ind/m2 in the first 3 m of depth. A follow up of the E. tulipa population showed that its density is increasing in time and has doubled in 20 years. This population increment could be related to an increase in organic suspended matter as evidenced in the region.
Emerging legal concerns in the Arctic: sovereignty, navigation and land claim disputes
Authors: Parker Richard D. , Madjd-Sadjadi Zagros
Published: December 2009

With global warming, the clearance of the Northwest Passage and the rising demands for new energy resources, the sovereignty of Canadian and other national land claims in the Arctic north is coming into question by those wishing to control access to this region. The present paper examines issues involving emerging landmasses, maritime rights, strategic control and navigation, perhaps the most important variable, and the consequences in terms of commercial economies and geopolitical impacts. We consider many variables such as the 1982 Falkland Islands war as a demonstrative example that may have translatable impact in future years. Our purpose in this paper is to raise awareness of impending geopolitical activities that are inevitable during the 21st century as the Arctic pack ice retreats.
Indigenous peoples as international political actors: a summary
Authors: Tennberg Monica
Published: December 2009

The article discusses the results of a three year research project studying international indigenous political activism using case studies from the Arctic. Drawing on two different disciplinary starting points, international relations and international law, the project addressed two interrelated questions. The first of these was how relations between states, international organisations and indigenous peoples have been and are currently constructed as legal and political practices; the second was how indigenous peoples construct their political agency through different strategies to further their political interests. These questions are addressed from the point of view of power relations. The power to act is the basic form of political agency. However, this power may take different forms of political action, for example, self-identification, participation, influence, and representation. The main conclusions of the article are: 1) indigenous political agency is based on multiple forms of power; 2) practices of power that enable and constrain indigenous political agency change over time; 3) power circulates and produces multiple sites of encounters for states, international organisations and indigenous people; 4) indigenous political agency is a question of acting; and 5) there are new challenges ahead for indigenous peoples in claiming a political voice, in particular in global climate politics.
Tree community change in a tropical dry forest: the role of roads and exotic plant invasion
Authors: PRASAD AYESHA E.
Published: December 2009

Among the most endangered tropical ecosystems, tropical dry forests are threatened by degradation that includes edge effects arising from perturbations such as the creation and maintenance of roads and other clearings. While much is known about these adverse effects on tree communities in tropical moist forests, similar effects in tropical dry forests are little understood. This paper examines the relationship between roads, road-related exotic plant invasion and tree community change in a tropical dry forest in southern India. Forty pairs of roadside and interior plots across four factorial combinations of road width (wide and narrow) and understorey type (native and exotic) were sampled. Tree death and extant tree community composition were compared using generalized linear models and similarity analyses. Tree death near roads was more than double that away from them, suggesting that roads may increase tree death in these forests. The interactive effect of understorey type (exotic or native) and road width on tree death was significant, with highest tree death near wide roads bordered by exotic understorey. Conversely, tree community composition was influenced by road width and understorey type, but not by proximity to roads. Creation and maintenance of roads for forest management may have serious implications for tree communities in tropical dry forests and should thus be minimized. Exotic plants may also be important contributors to increasing tree death, and further research on their impacts, particularly into underlying mechanisms, is critical to the long-term conservation of tropical dry forest communities.
KS and Tell: Harnessing Web 2.0 at the College of Law
Authors: Simmonds Tony
Published: December 2009

Tony Simmonds describes the various initiatives undertaken, and the lessons learned by the information staff at the College of Law's multiple sites, in relation to social networking including blogging, wikis, and social bookmarking.
Innovative Involvement not Embarrassing Intervention: Using Technology to Connect with Students without Treading on Virtual Toes
Authors: Allbon Emily
Published: December 2009

Emily Allbon recounts her experiences in integrating social networking tools into her work with law students and, in particular, how she has integrated them with her prize-winning portal – Lawbore. She also documents her use of personal response systems in her teaching sessions.
The 8th Nordic Law Library Meeting – Some Information on the Finnish National Digital Library
Authors: Gerrard Craig
Published: December 2009

This article by Craig Gerrard, Librarian, Weightmans LLP reports on plans being drawn up by the Finnish library authorities to implement a huge digital library.
Marketing Your Skills – Winning that Promotion
Authors: Franklin Nicola
Published: December 2009

This practical checklist by Nicola Franklin, Head of Recruitment at Sue Hill Recruitment, gives useful tips on how to market your skills in preparation for internal promotion or a new job.
A conceptual framework for the developmental origins of health and disease
Authors: Gluckman P. D. , Hanson M. A. , Buklijas T.
Published: December 2009

In the last decades, the developmental origins of health and disease (DOHaD) have emerged as a vigorous field combining experimental, clinical, epidemiological and public health research. Its goal is to understand how events in early life shape later morbidity risk, especially of non-communicable chronic diseases. As these diseases become the major cause of morbidity and mortality worldwide, research arising from DOHaD is likely to gain significance to public health and economic development. But action may be hindered by the lack of a firm mechanistic explanation and of a conceptual basis, especially regarding the evolutionary significance of the DOHaD phenomenon. In this article, we provide a succinct historical review of the research into the relationship between development and later disease, consider the evolutionary and developmental significance and discuss the underlying mechanisms of the DOHaD phenomenon. DOHaD should be viewed as a part of a broader biological mechanism ofplasticityby which organisms, in response to cues such as nutrition or hormones, adapt their phenotype to environment. These responses may be divided into those for immediate benefit and those aimed at prediction of a future environment: disease occurs in the mismatch between predicted and realized future. The likely mechanisms that enable plasticity involve epigenetic processes, affecting the expression of genes associated with regulatory pathways. There is now evidence that epigenetic marks may be inherited and so contribute to non-genomic heritable disease risk. We end by discussing the global significance of the DOHaD phenomenon and its potential applications for public health purposes.
Attribution of anthropogenic influence on seasonal sea level pressure
Authors: Gillett N. P. , Stott P. A.
Published: December 2009

Previous analyses of sea level pressure (SLP) trends have often focused on boreal winter trends. Here we demonstrate that externally‐forced SLP trends are observed in all four seasons, with simulated and observed decreases in SLP at high latitudes and increases elsewhere. We find that the observed pattern of seasonal mean zonal mean SLP changes is inconsistent with simulated internal variability, and we detect anthropogenic influence independently of natural influence on SLP. When we divide the globe into the mid‐ and high‐latitude regions of both hemispheres and the tropics and subtropics, we find that external influence is only detectable in the low‐latitude region, where models and observations show increasing trends in SLP, and where internal variability is low, and not in the mid‐ and high‐latitude regions of either hemisphere. Low‐latitude increases in SLP, which are significant compared to internal variability, but which have previously received little attention, could have important regional climate impacts.
Northern Monterey Bay upwelling shadow front: Observations of a coastally and surface‐trapped buoyant plume
Authors: Woodson C. B. , Washburn L. , Barth J. A. , Hoover D. J. , Kirincich A. R. , McManus M. A. , Ryan J. P. , Tyburczy J.
Published: December 2009

During the upwelling season in central California, northwesterly winds along the coast produce a strong upwelling jet that originates at Point Año Nuevo and flows southward across the mouth of Monterey Bay. A convergent front with a mean temperature change of 3.77 ± 0.29°C develops between the warm interior waters and the cold offshore upwelling jet. To examine the forcing mechanisms driving the location and movement of the upwelling shadow front and its effects on biological communities in northern Monterey Bay, oceanographic conditions were monitored using cross‐shelf mooring arrays, drifters, and hydrographic surveys along a 20 km stretch of coast extending northwestward from Santa Cruz, California, during the upwelling season of 2007 (May–September). The alongshore location of the upwelling shadow front at the northern edge of the bay was driven by: regional wind forcing, through an alongshore pressure gradient; buoyancy forces due to the temperature change across the front; and local wind forcing (the diurnal sea breeze). The upwelling shadow front behaved as a surface‐trapped buoyant current, which is superimposed on a poleward barotropic current, moving up and down the coast up to several kilometers each day. We surmise that the front is advected poleward by a preexisting northward barotropic current of 0.10 m s−1 that arises due to an alongshore pressure gradient caused by focused upwelling at Point Año Nuevo. The frontal circulation (onshore surface currents) breaks the typical two‐dimensional wind‐driven, cross‐shelf circulation (offshore surface currents) and introduces another way for water, and the material it contains (e.g., pollutants, larvae), to go across the shelf toward shore.
Calling International Rescue: knowledge lost in literature and data landslide!
Authors: Attwood Teresa K. , Kell Douglas B. , McDermott Philip , Marsh James , Pettifer Steve R. , Thorne David
Published: December 2009

We live in interesting times. Portents of impending catastrophe pervade the literature, calling us to action in the face of unmanageable volumes of scientific data. But it isn't so much data generation per se, but the systematic burial of the knowledge embodied in those data that poses the problem: there is so much information available that we simply no longer know what we know, and finding what we want is hard – too hard. The knowledge we seek is often fragmentary and disconnected, spread thinly across thousands of databases and millions of articles in thousands of journals. The intellectual energy required to search this array of data-archives, and the time and money this wastes, has led several researchers to challenge the methods by which we traditionally commit newly acquired facts and knowledge to the scientific record. We present some of these initiatives here – a whirlwind tour of recent projects to transform scholarly publishing paradigms, culminating in Utopia and the Semantic Biochemical Journal experiment. With their promises to provide new ways of interacting with the literature, and new and more powerful tools to access and extract the knowledge sequestered within it, we ask what advances they make and what obstacles to progress still exist? We explore these questions, and, as you read on, we invite you to engage in an experiment with us, a real-time test of a new technology to rescue data from the dormant pages of published documents. We ask you, please, to read the instructions carefully. The time has come: you may turn over your papers…
Absorption and emission spectra of ultraviolet B blocking methoxy substituted cinnamates investigated using the symmetry-adapted cluster configuration interaction method
Authors: Promkatkaew Malinee , Suramitr Songwut , Karpkird Thitinun Monhaphol , Namuangruk Supawadee , Ehara Masahiro , Hannongbua Supa
Published: December 2009

The absorption and emission spectra of ultraviolet B (UVB) blocking cinnamate derivatives with five different substituted positions were investigated using the symmetry-adapted cluster configuration interaction (SAC-CI) method. This series included cis- and trans-isomers of ortho-, meta-, and para-monomethoxy substituted compounds and 2,4,5-(ortho-, meta-, para-) and 2,4,6-(ortho-, para-) trimethoxy substituted compounds. The ground and excited state geometries were obtained at the B3LYP/6-311G(d) and CIS/D95(d) levels of theory. All the compounds were stable as cis- and trans-isomers in the planar structure in both the S0 and S1 states, except the 2,4,6-trimethoxy substituted compound. The SAC-CI/D95(d) calculations reproduced the recently observed absorption and emission spectra satisfactorily. Three low-lying excited states were found to be relevant for the absorption in the UV blocking energy region. The calculated oscillator strengths of the trans-isomers were larger than the respective cis-isomers, which is in good agreement with the experimental data. In the ortho- and meta-monomethoxy compounds, the most intense peak was assigned as the transition from next highest occupied molecular orbital (next HOMO) to lowest unoccupied molecular orbital (LUMO), whereas in the para-monomethoxy compound, it was assigned to the HOMO to LUMO transition. This feature was interpreted as being from the variation of the molecular orbitals (MOs) due to the different substituted positions, and was used to explain the behavior of the excited states of the trimethoxy compounds. The emission from the local minimum in the planar structure was calculated for the cis- and trans-isomers of the five compounds. The relaxation paths which lead to the nonradiative decay were also investigated briefly. Our SAC-CI calculations provide reliable results and a useful insight into the optical properties of these molecules, and therefore, provide a useful tool for developing UVB blocking compounds with regard to the tuning of the photoabsorption.
Rotational effects in complex-forming bimolecular substitution reactions: A quantum-mechanical approach
Authors: Hennig Carsten , Schmatz Stefan
Published: December 2009

The quantum dynamics of the complex-forming SN2 reaction Cl−+CH3Br→ClCH3+Br− is studied with emphasis on rotational effects. The pseudotriatomic system Cl-Me-Br is treated with a corresponding three-dimensional (3D) potential energy surface as a function of the two scattering coordinates and the enclosed angle where the geometry of the methyl group Me is optimized at each point. The 3D space is divided into three different parts, the interaction region, an intermediate region, and the asymptotic region. In line with simple classical-mechanical arguments and previous classical trajectory calculations, initial rotational motion of CH3Br seemingly decreases the reaction probability. However, the dynamical inclusion of the rotational degree of freedom and the presence of the many rovibrational product states overall lead to a large increase in reactivity compared to our previous collinear study on this reaction. If the reactant is rotationally excited, the higher vibrational product states are depleted in favor of lower-lying levels. Starting the reaction with rotationless reactants may end up in significant rotational excitation in the product molecules (translation-to-rotation energy transfer). On the other hand, initial rotational energy in rotationally highly excited reactants is to a large amount converted into translational and vibrational energy. The average amount of rotational energy in the products shows a twofold vibrational excitation-independent saturation (i.e., memorylessness), with respect to both initial rotational excitation and translational energy. Since only about one-half of all reactant states end in rotationless products, the reaction probability should be increased by a factor of 2; the actually larger reactivity points to other dynamical effects that play an important role in the reaction.
Carrier recombination processes in In-polar n-InN in regions of low residual electron density
Authors: Ishitani Yoshihiro , Kato Kenta , Ogiwara Hitoshi , Che Song-Bek , Yoshikawa Akihiko , Wang Xinqiang
Published: December 2009

Photoluminescence (PL) spectra of In-polar n-type InN films with different dislocation and residual electron densities are investigated in the temperature range 15–300 K. The dependence of PL intensity on temperature is analyzed by using a model function that is based on rate equations for photoexcited hole density. By considering the relation between the dislocation densities estimated from the widths of the peaks of x-ray ω-rocking curves and the parameters obtained from the rate equations, two kinds of nonradiative carrier recombination processes are identified. One process is independent of threading dislocations and is thermally activated, while the other takes place in the vicinity of edge-type dislocations and requires no activation energy.
Electrical characteristics and mechanical limitation of polycrystalline silicon thin film transistor on steel foil under strain
Authors: Kuo Po-Chin , Jamshidi-Roudbari Abbas , Hatalis Miltiadis
Published: December 2009

This work investigates the effect of mechanical strain on the electrical characteristics of polycrystalline silicon thin film transistors (poly-Si TFTs). Poly-Si TFTs were fabricated on steel foil substrate and characterized under the strain ranging from −1.2% to 1.1% induced by bending. The electron mobility increased under tensile and decreased under compressive strain while that of the hole exhibited an opposite trend. For both n-channel and p-channel poly-Si TFTs, the threshold voltage decreased and the subthreshold slope increased under tensile strain, while the subthreshold slope was observed decreased under compressive strain. The off current of both types of TFTs decreased under tensile and increased under compressive strain. Poly-Si TFTs on steel foil failed at the tensile strain of 1.2% due to cracking of the channel material.
Effect of transverse magnetic field on domain wall propagation in magnetically bistable glass-coated amorphous microwires
Authors: Zhukova Valentina , Blanco Juan M. , Ipatov Mihail , Zhukov Arcady
Published: December 2009

We experimentally studied domain wall (DW) propagation in amorphous Fe69Si10B15C6 and Co56Fe8Ni10Si11B16 microwires. We found that, in some cases, application of transverse magnetic field increases DW velocity in studied microwires. This effect is explained considering effect of transverse magnetic anisotropy on DW propagation. Considerable increase of DW velocity has been observed at enhanced longitudinal magnetic field, H. Such abrupt increasing of DW velocity can be related with defects contribution.
Short time transient thermal behavior of solid-state microrefrigerators
Authors: Ezzahri Y. , Christofferson J. , Zeng G. , Shakouri A.
Published: December 2009

We present detailed experimental and theoretical studies of the short time transient thermal behavior of SiGe superlattice microrefrigerators on a chip. Transient temperature profiles of microrefrigerator devices of different sizes are obtained using thermoreflectance technique. Thermal imaging with submicron spatial resolution, 0.1 K temperature resolution, and 100 ns temporal resolution is achieved. The dynamic behavior of the microrefrigerators shows an interplay between Peltier and Joule effects. Peltier cooling appears first with a time constant of about 10–30 μs, then Joule heating in the device starts taking over with a time constant of about 50–150 μs. The experimental results agree very well with the theoretical predictions based on thermal quadruple method. The difference in the two time constants can be explained considering the three-dimensional thermal resistances and capacitances of the microrefrigerator. In addition this shows that the Joule heating at the top metal/semiconductor interface does not dominate the microrefrigerator performance. Experimental results show that under high current pulsed operation, the microrefrigerator device can provide cooling for about 30 μs, even though steady state measurements show heating.
How long are the ends of polyene chains?
Authors: Schmalz T. G. , Griffin L. L.
Published: December 2009

In this work we study conjugation in all-trans polyene chains H(HCCH)nH with a view to establishing the length scale for the interaction between conjugated double bonds. As a polyene oligomer is made longer, bond length alternation between formal carbon-carbon single and double bonds diminishes toward the middle of the chain, eventually reaching a constant value characteristic of an “infinite” chain. However those bonds near the end of the chain continue to be influenced by the end, even in the long-chain limit. We have determined optimized geometries for polyene oligomers with up to n=11 repeat units at the MP2/cc-pVTZ level. At this length the central-most bonds are almost converged to the long chain limit, for which we estimate RCC=1.3652 Å and RCC=1.4238 Å. In contrast, the endmost double bond has a length of 1.3442 Å and the endmost single bond has a length of 1.4425 Å. We find that a given bond is significantly influenced by conjugation paths through up to six neighboring conjugated double bonds. End effects can also be monitored by examining the energy increment per added monomer as the oligomer length is increased. This analysis also indicates that significant conjugation effects extend out through approximately six neighboring double bonds. From the energy per monomer of the longest chains we extract a value of about 8 kcal/mol for the extra stabilization energy per monomer due to conjugation in long chains.
Quantum algorithm for molecular properties and geometry optimization
Authors: Kassal Ivan , Aspuru-Guzik Alán
Published: December 2009

Quantum computers, if available, could substantially accelerate quantum simulations. We extend this result to show that the computation of molecular properties (energy derivatives) could also be sped up using quantum computers. We provide a quantum algorithm for the numerical evaluation of molecular properties, whose time cost is a constant multiple of the time needed to compute the molecular energy, regardless of the size of the system. Molecular properties computed with the proposed approach could also be used for the optimization of molecular geometries or other properties. For that purpose, we discuss the benefits of quantum techniques for Newton’s method and Householder methods. Finally, global minima for the proposed optimizations can be found using the quantum basin hopper algorithm, which offers an additional quadratic reduction in cost over classical multi-start techniques.
Strain effects on work functions of pristine and potassium-decorated carbon nanotubes
Authors: Cai Yongqing , Zhang Aihua , Ping Feng Yuan , Zhang Chun , Fatt Teoh Hao , Wei Ho Ghim
Published: December 2009

Strain dependence of electronic structures and work functions of both pristine and potassium doped (5,5) (armchair) and (9,0) (zigzag) carbon nanotubes (CNTs) has been thoroughly studied using first-principles calculations based on density functional theory. We found that for pristine cases, the uniaxial strain has strong effects on work functions of CNTs, and the responses of work functions of CNT (5,5) and (9,0) to the strain are distinctly different. When the strain changes from −10% to 10%, the work function of the CNT (5,5) increases monotonically from 3.95 to 4.57 eV, and the work function of the (9,0) varies between 4.27 and 5.24 eV in a complicated manner. When coated with potassium, for both CNTs, work functions can be lowered down by more than 2.0 eV, and the strain dependence of work functions changes drastically. Our studies suggested that the combination of chemical coating and tuning of strain may be a powerful tool for controlling work functions of CNTs, which in turn will be useful in future design of CNT-based electronic and field-emitting devices.
Shape dependent carrier dynamics in InAs/GaAs nanostructures
Authors: Lin C. H. , Ling H. S. , Su S. K. , Lin S. D. , Lee C. P. , Sun K. W.
Published: December 2009

We present systematic experimental studies of the temperature dependence of continuous wave and time-resolved photoluminescence spectroscopy in self-assembled InAs/GaAs nanostructures as the shape of quantum structures evolved from dot to ring. The carrier dynamics show strong dependence on the geometrical shape of the nanostructures under investigation. An increase in photoluminescence decay time of the excited and ground states is observed as the shape of nanostructures changed from dot, volcano, to ring. It is attributed to the carrier thermalization between the dark and ground states. The photoluminescence excitation spectra of the quantum rings reveal resonances related to the dark states. A rate equation model is proposed to interpret the observed carrier dynamics.
Bulk anisotropic Nd2Fe14B/α-Fe nanocomposite magnets prepared by hot-deformation processing of amorphous alloys
Authors: Liu Yanguo , Xu Lei , Guo Defeng , Li Wei , Wang Qingfeng , Zhang Xiangyi
Published: December 2009

We succeeded in producing bulk anisotropic Nd2Fe14B/α-Fe nanocomposite magnets by hot-deformation processing of Nd-lean amorphous Nd9Fe85B6. The bulk Nd2Fe14B/α-Fe nanocomposite magnets yielded at a uniaxial stress of 310 MPa at 700 °C for 2 min show a strong magnetic anisotropy and enhanced magnetic properties, e.g., an increase of ∼51.4% in the maximum energy product along the stress direction as compared with the magnets produced by annealing amorphous Nd9Fe85B6. A large uniaxial stress is favorable for the (00l) texture development of Nd2Fe14B nanocrystals in the amorphous matrix, which may be attributed to a preferential nucleation and growth of Nd2Fe14B crystals at the stress. The present study provides a strategy to induce the texture for R2Fe14B phase in R-lean (R=rare earth) alloys and thus is of wide interest for yielding bulk anisotropic nanocomposite magnets with a high volume fraction of α-Fe phase.
Structure and vibrational spectra of H+(HF)n (n=2–9) clusters: Anab initiostudy
Authors: Sophy K. B. , Kuo Jer-Lai
Published: December 2009

The morphological development of the hydrogen bond network in the protonated hydrogen fluoride clusters, H+(HF)n (n=2–9), is investigated in detail by ab initio methods. We find a dominance of the linear morphology, which is energetically well separated from the other minimum energy morphologies of the clusters. The geometry for these clusters shows a pattern due to the cooperativity effect prevalent in the hydrogen bonds, as a result of the difference in electronegativities of hydrogen and fluorine atom in the HF molecule. The variations in the covalent HF and hydrogen bond distances in the clusters are in turn reflected in the vibrational spectra. Distinct HF stretching modes for the linear and ring with tail structures were identified. We have discussed the signature peaks for the two possible ion-core morphologies present in the clusters. The highly corrosive nature of HF makes it difficult to study using experiments. We, thus, believe that our structure and vibrational spectra calculations would be useful in understanding the key features in these systems.
Symmetry group and exact solutions for the 2+1 dimensional Ablowitz–Kaup–Newell–Segur equation
Authors: Ren Bo , Xu Xue-jun , Lin Ji
Published: December 2009

A (2+1) dimensional Ablowitz–Kaup–Newell–Segur (AKNS) system is obtained from the potential Boiti–Leon–Manna–Pempinelli equation by means of an asymptotically exact reduction method based on Fourier expansion and spatiotemporal rescaling. Furthermore, applying the modified direct method to the (2+1) dimensional AKNS system, we get its symmetry and the relationship between the new solution and the old one. Based on the relationship, a new solution can be obtained by using a given solution of the equation.
Dynamic pathways to mediate reactions buried in thermal fluctuations. II. Numerical illustrations using a model system
Authors: Kawai Shinnosuke , Komatsuzaki Tamiki
Published: December 2009

The framework recently developed for the extraction of a dynamic reaction coordinate to mediate reactions buried in thermal fluctuation is examined with a model system. Numerical simulations are carried out for an underdamped Langevin equation with the Müller–Brown potential surface, which contains three wells and two saddles, and are compared to the prediction by the theory. Reaction probabilities for specific initial conditions of the system as well as their average over the Boltzmann distribution are investigated in the position space and in a space spanned by the position coordinates and the velocities of the system. The nonlinear couplings between the reactive and the nonreactive modes are shown to have significant effects on the reactivity in the model system. The magnitude and the direction of the nonlinear effect are different for the two saddles, which is found to be correctly reproduced by our theory. The whole position-velocity space of the model system is found to be divided into the two distinct regions: One is of mainly reactive (with reaction probability more than half) initial conditions and the other, the mainly nonreactive (with reaction probability less than half) ones. Our theory can actually assign their boundaries as the zero of the statistical average of the new reaction coordinate as an analytical functional of both the original position coordinates and velocities of the system (solute), as well as of the random force and the friction constants from the environment (solvent). The result validates the statement in the previous paper that the sign of the reaction coordinate thus extracted determines the fate of the reaction. Physical interpretation of the reactivity under thermal fluctuation that is naturally derived, thanks to the analyticity of the theoretical framework, is also exemplified for the model system.
Methane molecule confined in the small and large cages of structure I clathrate hydrate: Quantum six-dimensional calculations of the coupled translation-rotation eigenstates
Authors: Matanović Ivana , Xu Minzhong , Moskowitz Jules W. , Eckert Juergen , Bačić Zlatko
Published: December 2009

We report fully coupled quantum six-dimensional (6D) calculations of the translation-rotation (T-R) energy levels of CH4 molecule inside the small dodecahedral (512) and large tetracaidecahedral (51262) cages of the structure I clathrate hydrate. The quantum dynamics of the three translational and three rotational degrees of freedom of CH4 are treated rigorously, while the guest molecule and the host cavities are taken to be rigid. The matrix of the full 6D T-R Hamiltonian is diagonalized in the product basis of contracted translational and angular basis functions, generated by solving two reduced-dimension (3D) eigenvalue problems. A pairwise additive CH4-cage 6D potential energy surface (PES) is employed, constructed using the anisotropic CH4H2O pair potential which was utilized previously in the molecular dynamics simulations of methane hydrate. Our calculations elucidate the key features of the T-R energy level structure of the nanoconfined CH4. The rotational levels of methane exhibit an elaborate pattern of splittings caused by the angular anisotropy of the environment; the splitting patterns are identical for both types of cages. Translationally excited T-R states in the small cage are assigned in terms of the quantum numbers n and l of the 3D isotropic harmonic oscillator and those in the large cage using the Cartesian quantum numbers. Extensive comparison is made with the data from the inelastic neutron scattering studies of methane hydrate, allowing an assessment of the accuracy of the 6D PES employed.