bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in the morphometrics of diplostomid metacercariae (Digenea: Trematoda) infecting the catfish, Clarias gariepinus in Tanzania
Authors: Chibwana F.D. , Nkwengulila G.
Published: July 2009

Diplostomum species are economically important worldwide due to their metacercariae which parasitize the eyes of fish, in both natural and aquaculture systems. However, their striking morphological similarity, especially at the metacercarial stage, makes species separation difficult. Three closely related diplostomid metacercariae, namely Diplostomum mashonense (type 3), Tylodelphys sp. 1 and 2 (type 1 and 2, respectively), coexist in the cranial cavity of the catfish, Clarias gariepinus from Mindu dam, Lake Victoria, Msimbazi, Ruvu and Kilombero rivers. The morphometrics of these three species were analysed by discriminant function analysis to investigate the degree of variation among the populations from the five localities sampled. The first canonical functions for all visual examination plots accounted for over 50% of the between-group variability. The observed differences were mainly from measurements associated with length, indicating that these measurements are important in the description of population characteristics. Visual examination of the samples along the canonical functions showed a clear between-population differentiation. The overall random assignment of individuals into their original groups was high (97%). These extensive morphometric variations introduce doubt about the reliability of measurements in the determination of species in these trematodes, as they may lead to misidentifications.
Stress level in wild harbour porpoises (Phocoena phocoena) during satellite tagging measured by respiration, heart rate and cortisol
Authors: Eskesen I.G. , Teilmann J. , Geertsen B.M. , Desportes G. , Riget F. , Dietz R. , Larsen F. , Siebert U.
Published: July 2009

During satellite tagging of harbour porpoises (Phocoena phocoena), heart rate, respiration rate and cortisol value were measured to evaluate stress effects during handling and tagging. Respiration rates were obtained using video recordings, heart rates were recorded and serum cortisol levels were analysed from blood samples. Differences in heart rates, respiration rates and cortisol levels before and during the tagging events were investigated. An overall significant decrease of 31.5% in respiration rate was found during the tagging event period, while mature porpoises respired significantly more often than immature individuals. Though significant differences in heart rates were found for some individuals, no general significant change for all animals was detected. We found no correlation between cortisol concentration and either heart rate or respiration rate, nor did we find any relationships between cortisol and month of year, sex and body length. As high individual variations occurred in response to tagging of harbour porpoises, it is not possible to give general advice based on the factors investigated, on how to reduce stress during handling. However, pouring water over the animal and lowering it into the water seem to stabilize a stressed animal. Therefore, general precaution and individual judgement based on experience is essential when handling wild harbour porpoises.
Monitoring important coastal sites for bottlenose dolphin in Cardigan Bay, UK
Authors: Pierpoint Chris , Allan Liz , Arnold Holly , Evans Peter , Perry Sarah , Wilberforce Lizzie , Baxter Janet
Published: July 2009

From 1994–2007 Ceredigion County Council and a network of shore-based, volunteer observers monitored levels of boat traffic and the occurrence of bottlenose dolphins Tursiops truncatus at seven sites on the coast of Cardigan Bay, Wales. We report high rates of site use and site occupancy by this species during the summer: at Mwnt for example, dolphins were recorded in >80% of 2 hours' observation periods; and at New Quay Harbour dolphins were present in >30% of all 15-minute intervals. At Mwnt and Aberporth there was a significant annual trend for increasing sighting rates; at Ynys Lochtyn a positive trend was only marginally non-significant; at New Quay Bird's Rock the trend was ambiguous but appeared stable over the seven most recent years. Although trends in site use may not reflect population trends in the wider region, these data were consistent with recent abundance estimates that indicate that the number of bottlenose dolphins using Cardigan Bay is stable or slightly increasing. Average group size at our study sites was small (<3 animals), which contrasts with observations of larger schools of the same population elsewhere in their range. The predominant behaviour in coastal Cardigan Bay is demersal foraging, often by solitary animals in shallow near-shore habitats. There was evidence that boat traffic suppressed site use by dolphins at New Quay Harbour, the busiest monitoring site: sighting rates fell when high numbers of boats were present and sighting rates were higher in 2007 than in previous years, when boat use was reduced due to poor weather during the main tourist season. This study demonstrates that networks of volunteer observers can provide a cost-effective, non-invasive means of gathering data on marine mammals for the purposes of coastal zone management.
Interspecific cetacean interactions during the breeding season of humpback whale (Megaptera novaeangliae) on the north coast of Bahia State, Brazil
Authors: Rossi-Santos Marcos R. , Santos-Neto Elitieri , Baracho Clarêncio G.
Published: July 2009

The large majority of cetacean interspecific studies report only on dolphin interactions, while studies on interactions between odontocete and mysticete are less common. The present work aims to report on sightings of cetacean interactions, during the breeding season of humpback whales(Megaptera novaeangliae), along 370 km of the Bahia State, north-eastern Brazil, addressing aspects of cetacean distribution and behaviour. During 7 seasons (2000–2006), a total of 230 research cruises were performed, in which 38 events of interactions among humpback whales and other cetaceans(Tursiops truncatus, Steno bredanensis, Peponocephala electraandBalaenoptera acutorostrata)were observed, plus another 5 encounters without the whale's presence, includingT. truncatus, S. bredanensis, P. electra, Stenella clymeneandStenella attenuata. Our results confirm the occurrence of multiple cetacean species in the Bahia State, being the first study in the world to report on a large range of interactions involving another 4 cetacean species, grouped with up to 3 mixed species per sighting, with humpback whales in their annual breeding ground.
Subliminal fear priming potentiates negative facial reactions to food pictures in women with anorexia nervosa
Authors: Soussignan R. , Jiang T. , Rigaud D. , Royet J. P. , Schaal B.
Published: July 2009

Background

To investigate hedonic reactivity and the influence of unconscious emotional processes on the low sensitivity to positive reinforcement of food in anorexia nervosa (AN).

Method

AN and healthy women were exposed to palatable food pictures just after a subliminal exposure to facial expressions (happy, disgust, fear and neutral faces), either while fasting or after a standardized meal (hungerversussatiety). Both implicit [facial electromyographic (EMG) activity from zygomatic and corrugator muscles, skin conductance, heart rate, and videotaped facial behavior] and explicit (self-reported pleasure and desire) measures of affective processes were recorded.

Results

In contrast to healthy women, the AN patients did not display objective and subjective indices of pleasure to food pictures when they were in the hunger states. Pleasure to food cues (liking) was more affected than the desire to eat (wanting) in AN patients. Subliminal ‘fear faces’ increased corrugator muscle reactivity to food stimuli in fasting AN patients, as compared to controls.

Conclusions

The results suggest that unconscious fear cues increase the negative appraisal of alimentary stimuli in AN patients and thus contribute to decreased energy intake.
Crossed products by abelian semigroups via transfer operators
Authors: LARSEN NADIA S.
Published: July 2009

We propose a generalization of Exel’s crossed product by a single endomorphism and a transfer operator to the case of actions of abelian semigroups of endomorphisms and associated transfer operators. The motivating example for our definition yields new crossed products, not obviously covered by familiar theory. Our technical machinery builds on Fowler’s theory of Toeplitz and Cuntz–Pimsner algebras of discrete product systems of Hilbert bimodules, which we need to expand to cover a natural notion of relative Cuntz–Pimsner algebras of product systems.
Lattice orbit distribution on ℝ2
Authors: NOGUEIRA ARNALDO
Published: July 2009

We study the distribution on ℝ2of the orbit of a vector under the linear action of SL(2,ℤ). Let Ω⊂ℝ2be a compact set andx∈ℝ2. LetN(k,x) be the number of matricesγ∈SL(2,ℤ) such thatγ(x)∈Ω and ‖γ‖≤k,k=1,2,…. If Ω is a square, we prove the existence of an absolute error term forN(k,x), ask→∞, for almost everyx, which depends on the Diophantine property of the ratio of the coordinates ofx. Our approach translates the question into a Diophantine approximation counting problem which provides the absolute error term. The asymptotical behaviour ofN(k,x) is also obtained using ergodic theory.
Perspectives on the National Institute for Health and Clinical Excellence's recommendations to use health technologies only in research
Authors: Dhalla Irfan A. , Garner Sarah , Chalkidou Kalipso , Littlejohns Peter
Published: July 2009

Background:The concept of using public funds to pay for healthcare interventions only when provided in the context of ongoing research is receiving increasing attention worldwide. Nevertheless, these decisions are often controversial and implementation can be problematic.

Objectives:The aim of this study was to investigate the views of United Kingdom stakeholders on the current arrangements for implementing “only in research” (OIR) decisions and to investigate how improvements might be made.

Methods:After an internal review of previous OIR decisions issued by the National Institute for Health and Clinical Excellence (NICE), deliberations by NICE's Citizens Council, and an international workshop convened by NICE and the United States Agency for Healthcare Research and Quality, thirteen key stakeholders and experts from academia, industry, government, and the National Health Service (NHS) were interviewed using a semistructured interview guide. Interview transcripts were subjected to a framework-based analysis using computer-assisted qualitative data analysis software.

Results:All interviewees endorsed the use of the OIR option. There was a high degree of consensus for several suggestions regarding how the use of the OIR option might be improved. For example, there was universal agreement that a formal process should be established to prioritize research needs arising from OIR decisions and that funds for publicly funded research projects should be channeled in a manner that would better motivate healthcare providers to participate in OIR-related research.

Conclusions:The findings of this study suggest several potential modifications of the OIR pathway in the United Kingdom and may also be helpful to health technology assessment agencies in other countries that already use or are considering using an OIR-like option to reduce the uncertainty inherent in health technology assessment.
Methods, procedures, and contextual characteristics of health technology assessment and health policy decision making: Comparison of health technology assessment agencies in Germany, United Kingdom, France, and Sweden
Authors: Schwarzer Ruth , Siebert Uwe
Published: July 2009

Objectives:The objectives of this study were (i) to develop a systematic framework for describing and comparing different features of health technology assessment (HTA) agencies, (ii) to identify and describe similarities and differences between the agencies, and (iii) to draw conclusions both for producers and users of HTA in research, policy, and practice.

Methods:We performed a systematic literature search, added information from HTA agencies, and developed a conceptual framework comprising eight main domains: organization, scope, processes, methods, dissemination, decision, implementation, and impact. We grouped relevant items of these domains in an evidence table and chose five HTA agencies to test our framework:DAHTA@DIMDI, HAS, IQWiG, NICE, and SBU. Item and domain similarity was assessed using the percentage of identical characteristics in pairwise comparisons across agencies. Results were interpreted across agencies by demonstrating similarities and differences.

Results:Based on 306 included documents, we identified 90 characteristics of eight main domains appropriate for our framework. After applying the framework to the five agencies, we were able to show 40 percent similarities in “dissemination,” 38 percent in “scope,” 35 percent in “organization,” 29 percent in “methods,” 26 percent in “processes,” 23 percent in “impact,” 19 percent in “decision,” and 17 percent in “implementation.”

Conclusion:We found considerably more differences than similarities of HTA features across agencies and countries. Our framework and comparison provides insights and clarification into the need for harmonization. Our findings could serve as descriptive database facilitating communication between producers and users.
Wireless capsule endoscopy in Italy: Adding context-specific data to the review of the evidence from literature
Authors: Lo Scalzo Alessandra , Ratti Marco , Jefferson Tom , Bernardini Fabio , Cerbo Marina
Published: July 2009

Objectives:The aim of this study was to assess the evidence of diagnostic accuracy of the wireless capsule for endoscopy (WCE) for the diagnosis of obscure gastrointestinal bleeding (OGIB) and small bowel disease in adults and translate it to the context of the Italian National Health Service.

Methods:We performed a systematic review of secondary and primary literature. We reviewed WCE diagnostic accuracy, safety, economic evaluations for OGIB. Context-specific data about WCE diffusion, costs, appropriateness of WCE use were collected by means of a national survey involving all Italian gastroenterological departments.

Results:We updated the systematic review of the most recent health technology assessment report (2006). Our review shows lack of robust comparative evidence of diagnostic accuracy of WCE. The studies' design do not allow collection of reliable evidence due to the uncertainty surrounding morphological variability of bleeding vascular gut lesions. The national survey reported widespread WCE use and data on appropriateness and costs.

Conclusions:Evidence of WCE diagnostic accuracy is of low quality, and there is a requirement for randomized comparisons. Our findings raise the issue of technology governance and show the importance of an assessment before the technology being widely commercialized.
Inadequate reporting of trials compromises the applicability of systematic reviews
Authors: Gartlehner Gerald , Thieda Patricia , Hansen Richard A. , Morgan Laura C. , Shumate Janelle A. , Nissman Daniel B.
Published: July 2009

Background:Uncertainty about the applicability of controlled trial findings is an increasing concern for clinicians and policy decision makers. This study aimed to determine whether information reported in studies included in systematic reviews was adequate enough to assess their applicability.

Methods:We used the databases of four recently conducted systematic reviews on the comparative efficacy and safety of second-generation antidepressants, inhaled corticosteroids, Alzheimer's drugs, and targeted immune modulators. We developed and pilot-tested a questionnaire to assess the adequacy of reporting with respect to seven previously validated criteria of study design that distinguish explanatory from pragmatic studies. For each of the 137 included studies, two reviewers independently assessed the adequacy of reporting.

Results:Overall, only 12 percent of the included studies provided sufficient information to reliably distinguish explanatory from pragmatic studies. The areas with the greatest lack of reporting were the setting of the study, methods of adverse event assessment, and sample size considerations to determine a minimally important difference from a patient perspective.

Conclusions:Substantial shortcomings in reporting exist in aspects of study design important to determine whether a study is applicable to specific populations of interest.
Economic evaluation of continuous renal replacement therapy in acute renal failure
Authors: Klarenbach Scott , Manns Braden , Pannu Neesh , Clement Fiona M. , Wiebe Natasha , Tonelli Marcello ,   For the Alberta Kidney Disease Network
Published: July 2009

Objectives:Controversy exists regarding the optimal method of providing dialysis in critically ill patients with acute renal failure. We sought to determine the cost-effectiveness of treatment strategies.

Methods:Adult subjects requiring renal replacement therapy in a critical care setting who are candidates for intermittent hemodialysis (IHD) or continuous renal replacement therapy (CRRT) were considered within a Markov model. Alternative strategies including IHD, and standard or high dose CRRT were compared. The model considered relevant clinical and economic outcomes, and incorporated data on clinical effectiveness from a recent systematic review and high quality micro-costing data.

Results:In the base-case analysis, CRRT was associated with similar health outcomes but higher costs by ($3,679 more than IHD per patient). In scenarios considering alternate cost sources, and higher intensity of IHD (including daily and longer duration IHD), CRRT remained more costly. Sensitivity analysis indicated that even small differences in the risk of mortality or need for long-term chronic dialysis therapy among surviving patients benefits led to dramatic changes in the cost-effectiveness of the modalities considered.

Conclusions:Given the higher costs of providing CRRT and absence of demonstrated benefit, IHD is the preferred modality in critically ill patients who are candidates for either IHD or CRRT, although this conclusion should be revisited if future clinical trials establish differences in clinical effectiveness between modalities. Future interventions that are proven to improve renal recovery after acute renal failure are likely to be cost-effective, even if very resource intensive.
Using EQ-5D in children with asthma, rheumatic disorders, diabetes, and speech/language and/or hearing disorders
Authors: Willems Daniëlle C. M. , Joore Manuela A. , Nieman Fred H. M. , Severens Johan L. , Wouters Emiel F. M. , Hendriks Johannes J. E.
Published: July 2009

Objectives:This study explores several variables of the EQ-5D child version, a multi-attribute utility instrument, in children with chronic conditions.

Methods:A convenience sample was selected from hospital outpatient records and school records. The sample included children aged 7–18 years with the following chronic conditions: asthma, rheumatic disorders, diabetes, and speech/language and/or hearing disorders. The practicality, convergent validity, and discriminant power were compared with a generic quality of life questionnaire for children (TACQOL) and the 2-week test–retest reliability was assessed.

Results:A total of 182 children or their parents completed the first questionnaire and 161 children/parents completed both questionnaires. The practicality of the EQ-5D was good. Low to moderate correlations were found between the utilities and VAS scores and the TACQOL scales. The discriminant power of the EQ-5D items was low overall and was greater for children with a rheumatic disorder than for children with the other conditions. In the subset of children who experienced no health change between the test and the retest, the reliability of the EQ-5D was moderate to high.

Conclusions:The EQ-5D seems suitable for children, although the use of an additional disease-specific questionnaire is still recommended. The EQ-5D seems the most suitable for children with a chronic physical condition and appears to be reliable for children with a stable health status.
The effects of technological developments on nuclear medicine technologist productivity: A systematic review
Authors: Adams Edwina , Cox Jennifer , Schofield Deborah , Adamson Barbara
Published: July 2009

Objectives:Nuclear medicine has changed rapidly as a result of technological developments. Very little is reported on the effects these developments may have on technologist productivity. This study aims to determine whether advances have created a workplace where more patient studies can be performed with fewer technologists. The level of change in automation or time taken to perform a routine task by the nuclear medicine technologist as a result of technological development over the past decade is reported.

Methods:A systematic review was conducted using Embase.com, Medline, INSPEC, and Cinahl. Two authors reviewed each article for eligibility. Technological developments in routine areas over the past decade were reviewed. The resultant automation or time effects on data acquisition, data processing, and image processing were summarized.

Results:Sixteen articles were included in the areas of myocardial perfusion, information technology, and positron emission tomography (PET). Gamma camera design has halved the acquisition time for myocardial perfusion studies, automated analysis requires little manual intervention and information technologies and filmless departments are more efficient. Developments in PET have reduced acquisition to almost one-fifth of the time.

Conclusions:Substantial efficiencies have occurred over the decade thereby increasing productivity, but whether staffing levels are appropriate for safe, high quality practice is unclear. Future staffing adequacy is of concern given the anticipated increasing service needs.
A 7-year surveillance for ESBL-producingEscherichia coliandKlebsiella pneumoniaeat a university hospital in Taiwan: the increase of CTX-M-15 in the ICU
Authors: SHU J. C. , CHIA J. H. , KUO A. J. , SU L. H. , WU T. L.
Published: July 2009

To monitor the changing trend of extended-spectrum β-lactamase (ESBL)-producing bacteria, a 7-year continuous study was launched in 2001 at the largest tertiary hospital in Taiwan. A significant increase over the study period was evident for ESBL-producing isolates ofEscherichia coli(4·8–10·0%) andKlebsiella pneumoniae(15·0–23·4%). Molecular investigation conducted in three separate periods revealed the prevalent ESBL types and their genetic relatedness. CTX-M-producing isolates (73·8%) were more prevalent than SHV-type ESBLs (37·0%), the most frequent being CTX-M-14 (34·3%), CTX-M-3 (25·9%), and SHV-12 (25·7%). However, a marked increase of CTX-M-15-producing isolates from 2·1% in 2002 to 29·6% in 2007 was also noted. The increase of ESBL-producing isolates in both species may be mainly due to the horizontal transmission of resistance plasmids, while clonal expansion of some epidemic strains further added to the dispersion of ESBL-producingK. pneumoniae.
ZoonoticDirofilaria immitisinfections in a province of Northern Spain
Authors: MORCHÓN R. , MOYA I. , GONZÁLEZ-MIGUEL J. , MONTOYA M. N. , SIMÓN F.
Published: July 2009

Dirofilaria immitisis the causal agent of canine and feline cardiopulmonary dirofilariasis. Moreover, the existence of canine dirofilariasis implies a risk for human populations living in an endemic area in which, the parasite can cause pulmonary dirofilariasis. The Spanish epidemiological situation is not well understood, lacking data from many central and Northern provinces. In our study, epidemiological data on canine and human dirofilariasis for La Rioja (Northern Spain) have been obtained for the first time. The overall prevalence ofD. immitisin dogs was 12% (9% of patent and 3% of occult infections), being 11·6% the seroprevalence of human residents in this province. The geographic distribution of both canine and humanD. immitisinfections in La Rioja is restricted to humid and irrigated areas near the Ebro Valley River, being absent in the rest of the province where hills and mountains predominate.
Inventory changes in anthropogenic carbon from 1997–2003 in the Atlantic Ocean between 20°S and 65°N
Authors: Steinfeldt Reiner , Rhein Monika , Bullister John L. , Tanhua Toste
Published: July 2009

The oceans absorb and store a significant portion of anthropogenic CO2 emissions, but large uncertainties remain in the quantification of this sink. An improved assessment of the present and future oceanic carbon sink is therefore necessary to provide recommendations for long‐term global carbon cycle and climate policies. The formation of North Atlantic Deep Water (NADW) is a unique fast track for transporting anthropogenic CO2 into the ocean's interior, making the deep waters rich in anthropogenic carbon. Thus the Atlantic is presently estimated to hold 38% of the oceanic anthropogenic CO2 inventory, although its volume makes up only 25% of the world ocean. Here we analyze the inventory change of anthropogenic CO2 in the Atlantic between 1997 and 2003 and its relationship to NADW formation. For the whole region between 20°S and 65°N the inventory amounts to 32.5 ± 9.5 Petagram carbon (Pg C) in 1997 and increases up to 36.0 ± 10.5 Pg C in 2003. This result is quite similar to earlier studies. Moreover, the overall increase of anthropogenic carbon is in close agreement with the expected change due to rising atmospheric CO2 levels of 1.69% a−1. On the other hand, when considering the subpolar region only, the results demonstrate that the recent weakening in the formation of Labrador Sea Water, a component of NADW, has already led to a decrease of the anthropogenic carbon inventory in this water mass. As a consequence, the overall inventory for the total water column in the western subpolar North Atlantic increased only by 2% between 1997 and 2003, much less than the 11% that would be expected from the increase in atmospheric CO2 levels.
Monitoring and analysis of ocean swell fields from space: New methods for routine observations
Authors: Collard Fabrice , Ardhuin Fabrice , Chapron Bertrand
Published: July 2009

Satellite synthetic aperture radar (SAR) observations can provide a global view of ocean swell fields when using a specific “wave mode” sampling. A methodology is presented to routinely derive integral properties of the longer‐wavelength (swell) portion of the wave spectrum from SAR level 2 products and both monitor and predict their evolution across ocean basins. SAR‐derived estimates of swell height and energy‐weighted peak period and direction are validated against buoy observations, and the peak directions are used to project the peak periods in one dimension along the corresponding great circle route, both forward and back in time, using the peak period group velocity. The resulting real‐time data set of great circle–projected peak periods produces two‐dimensional maps that can be used to monitor and predict the spatial extent and temporal evolution of individual ocean swell fields as they propagate from their source region to distant coastlines. The result is found to be consistent with the dispersive arrival of peak swell periods at a midocean buoy. The simple great circle propagation method cannot project the swell heights in space like the peak periods, because energy evolution along a great circle is a function of the source storm characteristics and the unknown swell dissipation rate. A more general geometric optics model is thus proposed for the far field of the storms. This model is applied here to determine the attenuation over long distances. For one of the largest recorded storms, observations of 15 s period swells are consistent with a constant dissipation rate that corresponds to a 3300 km e‐folding scale for the energy. In this case, swell dissipation is a significant term in the wave energy balance at global scales.
Chemical and isotopic characterization of size‐fractionated organic matter from cryoturbated tundra soils, northern Alaska
Authors: Xu Chunhao , Guo Laodong , Ping Chien‐Lu , White Daniel M.
Published: July 2009

Recent studies indicate a second layer of organic matter often accumulates in the lower active layer and upper permafrost in arctic tundra soils as a result of cryoturbation. In this study, cryoturbated organic matter was characterized using a combination of physical size fractionation and modern analytical techniques for elemental composition (C and N), stable isotopes (δ13C and δ15N), radiocarbon content (Δ14C), and molecular fingerprinting (pyrolysis‐gas chromatography/mass spectrometry, Py‐GC/MS). The results indicated that cryoturbated organic matter could be highly bioavailable. Soil organic matter (SOM) associated with fine sand particles was considered to be the organic carbon pool most sensitive to the changing climate. More organic matter is stabilized on clay minerals in arctic tundra soils compared to those in temperate and tropical soils. The bioavailable soluble organic matter extracted from cryoturbated soil was found to have significant long‐term effects on carbon cycling. The similar molecular composition between cryoturbated and surface soil organic matter suggests that the vegetation cover has not significantly changed since the early Holocene. Furthermore, the SOM quality in moist acidic tundra was found to be higher than that of wet nonacidic tundra. With thawing permafrost and a deepening of the active layer, cryotrubated organic matter could reenter the biogeochemical cycles in the Arctic, resulting in a positive feedback to climate change.
Forest disturbance and recovery: A general review in the context of spaceborne remote sensing of impacts on aboveground biomass and canopy structure
Authors: Frolking S. , Palace M. W. , Clark D. B. , Chambers J. Q. , Shugart H. H. , Hurtt G. C.
Published: July 2009

Abrupt forest disturbances generating gaps >0.001 km2 impact roughly 0.4–0.7 million km2 a−1. Fire, windstorms, logging, and shifting cultivation are dominant disturbances; minor contributors are land conversion, flooding, landslides, and avalanches. All can have substantial impacts on canopy biomass and structure. Quantifying disturbance location, extent, severity, and the fate of disturbed biomass will improve carbon budget estimates and lead to better initialization, parameterization, and/or testing of forest carbon cycle models. Spaceborne remote sensing maps large‐scale forest disturbance occurrence, location, and extent, particularly with moderate‐ and fine‐scale resolution passive optical/near‐infrared (NIR) instruments. High‐resolution remote sensing (e.g., ∼1 m passive optical/NIR, or small footprint lidar) can map crown geometry and gaps, but has rarely been systematically applied to study small‐scale disturbance and natural mortality gap dynamics over large regions. Reducing uncertainty in disturbance and recovery impacts on global forest carbon balance requires quantification of (1) predisturbance forest biomass; (2) disturbance impact on standing biomass and its fate; and (3) rate of biomass accumulation during recovery. Active remote sensing data (e.g., lidar, radar) are more directly indicative of canopy biomass and many structural properties than passive instrument data; a new generation of instruments designed to generate global coverage/sampling of canopy biomass and structure can improve our ability to quantify the carbon balance of Earth's forests. Generating a high‐quality quantitative assessment of disturbance impacts on canopy biomass and structure with spaceborne remote sensing requires comprehensive, well designed, and well coordinated field programs collecting high‐quality ground‐based data and linkages to dynamical models that can use this information.
How universal is the C function in the bulk atmospheric boundary layer similarity approach for estimating surface sensible heat flux?
Authors: Sugita Michiaki , Kato Hidekazu , Kotani Ayumi , Toda Motomu
Published: July 2009

The C function which appears in the formulation for the bulk atmospheric boundary layer similarity (BAS) approach estimating sensible heat flux (H) at the surface under unstable stability conditions was examined to investigate its universality and whether or not it is a function of atmospheric stability alone, using data sets obtained from five large‐scale experiments that took place in diverse geographical locations with different surface covers and climate conditions (ranging from the tropics to the boreal zone). Coefficients in several forms of the C function, first assumed as a function of the stability alone, were calibrated against these data sets to maximize the agreement between H values derived from the BAS and those reference values independently determined. The agreement of H values for this calibration, for all data sets except one, was excellent, with a root‐mean‐square error on the order of 20 W m−2 under the condition that the exact values of surface scalar roughness and atmospheric stability were known. The findings indicate that the C function is a function of stability only and is universal within this accuracy level. Inclusion of another possible parameter, the ratio of the rotational height scale and the actual depth of the mixed layer, did not improve the results. A selection of different scaling for surface layer height did not produce better results, either. Practical limitations of the BAS approach were also investigated by considering one site that did not yield satisfactory results. Using an error propagation analysis, it was determined that this finding was mainly caused by weak surface heating in this area under near neutral conditions and that the difference between the potential temperature at the surface and that in the mixed layer was too small to be used beyond the measurement error limit in the BAS approach. The need for a method to estimate surface scalar roughness was also identified as the largest remaining problem in the BAS approach used for actual flux estimations.
Prepulse minimization in KALI-5000
Authors: Kumar D. Durga Praveen , Mitra S. , Senthil K. , Sharma Vishnu K. , Singh S. K. , Roy A. , Sharma Archana , Nagesh K. V. , Chakravarthy D. P.
Published: July 2009

A pulse power system (1 MV, 50 kA, and 100 ns) based on Marx generator and Blumlein pulse forming line has been built for generating high power microwaves. The Blumlein configuration poses a prepulse problem and hence the diode gap had to be increased to match the diode impedance to the Blumlein impedance during the main pulse. A simple method to eliminate prepulse voltage using a vacuum sparkgap and a resistor is given. Another fundamental approach of increasing the inductance of Marx generator to minimize the prepulse voltage is also presented. Experimental results for both of these configurations are given.
Fluorescence quenching in an organic donor-acceptor dyad: A first principles study
Authors: Körzdörfer T. , Tretiak S. , Kümmel S.
Published: July 2009

Perylene bisimide and triphenyl diamine are prototypical organic dyes frequently used in organic solar cells and light emitting devices. Recent Förster-resonant-energy-transfer experiments on a bridged organic dyad consisting of triphenyl diamine as an energy-donor and perylene bisimide as an energy-acceptor revealed a strong fluorescence quenching on the perylene bisimide. This quenching is absent in a solution of free donors and acceptors and thus attributed to the presence of the saturated CH2O(CH2)12-bridge. We investigate the cause of the fluorescence quenching as well as the special role of the covalently bound bridge by means of time dependent density functional theory and molecular dynamics. The conformational dynamics of the bridged system leads to a charge transfer process between donor and acceptor that causes the acceptor fluorescence quenching.
Relativistic dynamics of quasistable states. II. Differentiable representations of the causal Poincaré semigroup
Authors: Wickramasekara S.
Published: July 2009

We construct two rigged Hilbert spaces that furnish differentiable representations of the causal Poincaré semigroup. These rigged Hilbert spaces provide the mathematical foundation for a theory of relativistic quasistable states that synthesizes the S-matrix description of resonance scattering with the Bakamjian–Thomas construction for interacting relativistic quantum systems.
Generalized relative entropies and the capacity of classical-quantum channels
Authors: Mosonyi Milán , Datta Nilanjana
Published: July 2009

We provide lower and upper bounds on the information transmission capacity of one single use of a classical-quantum channel. The lower bound is expressed in terms of the Hoeffding capacity, which we define similarly to the Holevo capacity but replacing the relative entropy with the Hoeffding distance. Similarly, our upper bound is in terms of a quantity obtained by replacing the relative entropy with the recently introduced max-relative entropy in the definition of the divergence radius of a channel.
Low-energy potential scattering in two and three dimensions
Authors: Khuri N. N. , Martin André , Richard J.-M. , Wu Tai Tsun
Published: July 2009

Conditions are established for the existence of a scattering length and an effective range in the low-energy expansion of the S-wave phase shift of a central potential in two and three dimensions. The behavior of the phase shift as a function of the momentum is also derived for longer-range power-law potentials which do not fulfill these conditions.
Longitudinal bulk acoustic mass sensor
Authors: Hales J. H. , Teva J. , Boisen A. , Davis Z. J.
Published: July 2009

A polycrystalline silicon longitudinal bulk acoustic cantilever is fabricated and operated in air at 51 MHz. A mass sensitivity of 100 Hz/fg (1 fg=10−15 g) is obtained from the preliminary experiments where a minute mass is deposited on the device by means of focused ion beam. The total noise in the currently applied measurement system allows for a minimum detectable mass of 0.5 fg in air.
Pitfalls in Kelvin probe measurements
Authors: Ottinger Oliver M. , Melzer Christian , von Seggern Heinz
Published: July 2009

We report on the interpretation of thickness-dependent surface potential profiles in insulators on metal substrates measured by Kelvin probe method. The electrical potentials are calculated within a self-consistent model taking both the conductive substrate and the insulator into account. It is shown that interpreting the Kelvin potentials for different layer thicknesses as the prevailing potential profile of a thick insulator film is generally wrong. Even more controversially, the reconstruction of the potential profile in a thick insulator layer on the basis of layer-thickness-dependent Kelvin measurements alone is per se impossible. This will be demonstrated exemplarily on the basis of doped and undoped organic films on conductive substrates.
Resistance and superconductivity switching caused by carrier injection: Evidences of self-trapping carriers in oxide electronics
Authors: Chen Yuansha , Chen Liping , Lian Guijun , Xiong Guangcheng
Published: July 2009

Carrier injection performed in doped-manganite junction exhibits stable resistance switching effect and variety of interface barrier adjusted by electric fields, which demonstrates roles of the carrier movement across interface and suggests the importance of injected carriers’ staying. All observations suggest that the staying of injected carriers in the functional oxides leads to a carrier self-trapping mechanism to understand resistance switching phenomenon. More results in other oxide junctions and epitaxial doped manganite films support carrier self-trapping model and exhibit the importance of heterointerface on stabilizing the self-trapping carriers. Superconductivity achieved and adjusted by carrier injection can be distinct evidence that the self-trapping carriers as minority played important roles in operating of oxides’ intrinsic property. This phenomenon could relate to a novel area of researches and applications in oxide electronics.
High temperature shear modulus determination using a laser-ultrasonic surface acoustic-wave device
Authors: Nadal M.-H. , Hubert C. , Oltra R.
Published: July 2009

For radioactive thin specimens in high pressure or high temperature environments, the conventional approach for high precision elastic modulus measurements is not easy. Radiation damage to transducer’s bonds or the substantial changes in specimen dimensions induced by temperature, pressure, and phase transitions, reduce the intrinsic accuracy of the time-of-flight acoustic measurements. We describe here an alternative approach in which the surface acoustic-wave (SAW) velocity is measured directly with a fixed propagation distance, independent of specimen dimensions. Then, using the known relationship between SAW and shear velocities, it is possible to obtain the shear modulus with a high accuracy without measuring the bulk shear wave. Laser ultrasonics was used combining a pulsed laser source with a heterodyne interferometer. The proposed technique is validated for Al, Au, Ta, and Pb 0.8% Ca, TA6V4 without phase transitions, and for Sn and Co through the phase transitions.
Characteristics of SiC pillar-shaped nanostructure Schottky diode
Authors: Han Sang Youn , Lee Jong-Lam
Published: July 2009

The effect of geometrical shape on the electrical transport was analyzed in SiC nanostructure Schottky diode. Two different contacts, the pillar-shaped nanostructure contact and nanoscale contact, were fabricated separately from top down method. Compared with nanoscale contact, the nanostructure contact showed the low current level, but similar Schottky barrier property. This is attributed by the fact that pillar-shaped nanostructure has smaller base areas which prevent the electrons from efficient transport into the nanostructure. This led to the decrease in electron mobility, resulting in the higher resistance in the I-V curves. From Fowler–Nordheim plot, it was almost linear for higher voltage region, but the linear behavior disappeared in the lower one. This implied that the electron tunneling was the main transport mechanism at higher electric field in this structure.
Fully voltage-controlled electrohydrodynamic jet printing of conductive silver tracks with a sub-100 μm linewidth
Authors: Wang Ke , Paine Mark D. , Stark John P. W.
Published: July 2009

Silver microtracks with excellent electrical functionality were created by electrohydrodynamic jet (e-jet) printing of commercial metallo-organic ink. Novel e-jet printing was performed in a fully voltage-controlled fashion. By using a 20 μm nozzle and reducing the printing distance to 50 μm, metallic tracks with a sub-100 μm linewidth were successfully achieved on Si substrates. The physical properties of the printed tracks were characterized by means of scanning electron microscopy, atomic force microscopy, energy-dispersive x-ray spectrum analysis, and electrical measurements. A low resistivity in the range (2–4)×10−8 Ω m, 1.7–2.4 times of the theoretical value of silver, was obtained for the printed microtracks. A uniform fine track with a 35 μm feature size was produced by pulsed jet printing operating at low voltage, and a drop-on-demand capability of ∼7 pl/drop was estimated.
Probing hot spots on protein-protein interfaces with all-atom free-energy simulation
Authors: Meliciani Irene , Klenin Konstantin , Strunk Timo , Schmitz Katja , Wenzel Wolfgang
Published: July 2009

Modulation of protein-protein interactions by competitive small-molecule binding emerges as a promising avenue for drug discovery. Hot spots, i.e., amino acids with important contributions to the overall interaction energy, provide useful targets within these interfaces. To avoid time-consuming mutagenesis experiments, computational alanine screening has been developed for the prediction of hot spots based on existing structural information. Here we use the all-atom free-energy force field PFF02 to identify important amino acid residues in the complexes of the chemokine interleukin-8 (CXCL8) and an N-terminal peptide of its cognate receptor CXCR1, and of ERBIN, a molecular marker of the basolateral membrane in epithelial cells, in complex with the ERBIN-binding domain of tyrosin kinase ERBB2. The results of our analysis agree with available experimental functional assays, indicating that this approach is suitable for computational alanine screening and may help to identify competitive peptides as starting points for the development of inhibitors of protein-protein interactions for pharmaceutically relevant targets.
Shock-induced transformations in crystalline RDX: A uniaxial constant-stress Hugoniostat molecular dynamics simulation study
Authors: Bedrov Dmitry , Hooper Justin B. , Smith Grant D. , Sewell Thomas D.
Published: July 2009

Molecular dynamics (MD) simulations of uniaxial shock compression along the [100] and [001] directions in the α polymorph of hexahydro-1,3,5-trinitro-1,3,5-triazine (α-RDX) have been conducted over a wide range of shock pressures using the uniaxial constant stress Hugoniostat method [Ravelo et al., Phys. Rev. B 70, 014103 (2004)]. We demonstrate that the Hugoniostat method is suitable for studying shock compression in atomic-scale models of energetic materials without the necessity to consider the extremely large simulation cells required for an explicit shock wave simulation. Specifically, direct comparison of results obtained using the Hugoniostat approach to those reported by Thompson and co-workers [Phys. Rev. B 78, 014107 (2008)] based on large-scale MD simulations of shocks using the shock front absorbing boundary condition (SFABC) approach indicates that Hugoniostat simulations of systems containing several thousand molecules reproduced the salient features observed in the SFABC simulations involving roughly a quarter-million molecules, namely, nucleation and growth of nanoscale shear bands for shocks propagating along the [100] direction and the polymorphic α-γ phase transition for shocks directed along the [001] direction. The Hugoniostat simulations yielded predictions of the Hugoniot elastic limit for the [100] shock direction consistent with SFABC simulation results.
On the dynamics of axisymmetric turbulent separating/reattaching flows
Authors: Weiss Pierre-Élie , Deck Sébastien , Robinet Jean-Christophe , Sagaut Pierre
Published: July 2009

The present work focuses on the intrinsic properties of an axisymmetric separating/reattaching flow. A numerical simulation of a compressible flow over a cylinder extended by another cylinder of smaller diameter is performed at a Reynolds number based on free stream velocity U∞ and on the diameter of the larger cylinder D of 1.2×106. Statistical and fluctuating properties are scrutinized and compared with the available experimental data. Especially, experimental wall pressure coefficient and rms pressure fluctuations are well-reproduced by the simulation. A large scale coherent motion associated to fD/U∞≈0.2 rules the organization of the flow. Moreover, these properties are linked to a linear stability analysis coupled with a two-point correlation analysis unveiling the major importance of highly coherent antisymmetric modes in the flow behavior. Finally, the axisymmetric body dynamics seems to be led by a significant absolutely unstable area suggesting a global instability mechanism.