bluuebunny/crossref_metadata_2025 huggingface dataset:
Single‐molecule detection of phosphorylation‐induced plasticity changes during ezrin activation
Authors: Liu Dan , Ge Ling , Wang Fengsong , Takahashi Hirohide , Wang Dongmei , Guo Zhen , Yoshimura Shige H. , Ward Tarsha , Ding Xia , Takeyasu Kunio , Yao Xuebiao
Published: July 2007

Ezrin–radixin–moesin protein family provides a regulated link between the cortical actin cytoskeleton and the plasma membrane. Phosphorylation of ezrin has been functionally linked to membrane dynamics and plasticity. Our recent study demonstrated that phosphorylation of the conserved T567 residue of ezrin alters the physiology of gastric parietal cells. However, the molecular mechanism of phosphorylation‐induced ezrin activation has remained elusive. Here we use atomic force microscopy (AFM) to probe phosphorylation‐mediated activation of ezrin in single molecules. The phospho‐mimicking and non‐phosphorylatable mutant ezrin proteins were generated and purified to homogeneity. Comparative analyses of two ezrin mutants by AFM demonstrate the unfolding of the N‐ and C‐terminal domains upon the phospho‐activation. To measure the physical force underlying the inter‐domain contact during mechanical unfolding, we probed the defined region of ezrin using the N‐terminal ezrin coated onto the AFM tip. Comparative force measurements indicate that T567 phosphorylation‐induced unfolding of ezrin favors the inter‐molecular association. Taken together, these results provide molecular illustration of phosphorylation elicited functional activation of ERM proteins and indicate that stimulus‐induced protein conformational change can be used as a signaling mechanism orchestrating cellular dynamics.
From the Curse of Ham to the curse of nature: the influence of natural selection on the debate on human unity before the publication of The Descent of Man
Authors: KENNY ROBERT
Published: July 2007

This paper examines the debate engendered in ethnological and anthropological circles by Darwin's Origin of Species and its effects. The debate was more about the nature of human diversity than about transmutation. By 1859 many polygenists thought monogenism had been clearly shown to be an antiquated and essentially religious concept. Yet the doctrine of natural selection gave rise to a ‘new monogenism’. Proponents of polygenism such as James Hunt claimed natural selection had finally excluded monogenism, but Thomas Huxley, the most prominent exponent of the new monogenism, claimed it amalgamated the ‘best’ of both polygenism and monogenism. What it did provide was an explanation for the irreversible inequality of races, while it maintained that all humans were of one species. This bolstered belief in the innate superiority of the Caucasians over other peoples. The effect was finally to sever British ethnology from its evangelical monogenist roots. More subtly and surprisingly, it provided support in Church circles for a move away from the ideal of the ‘Native Church’.
Compressional magnetoacoustic waves in a quantum dusty magnetoplasma
Authors: SHUKLA P. K.
Published: July 2007

The linear dispersion relation for compressional magnetoacoustic waves in a quantum magnetoplasma is derived, taking into account the quantum Bohm potential and the magnetization of electrons due to the electron-1/2 spin effect. It is found that the quantum forces produce the wave dispersion at quantum scales, which depend on the external magnetic field strength.
Oleic acid is indispensable for intraerythrocytic proliferation of Plasmodium falciparum
Authors: MI-ICHI F. , KANO S. , MITAMURA T.
Published: July 2007

Serum-derived fatty acids are essential for the intraerythrocytic proliferation of Plasmodium falciparum in humans. We previously reported that only limited combinations of fatty acids can support long-term parasite culture, and palmitic acid (C16:0)/oleic acid (C18:1, n-9), palmitic acid (C16:0)/vaccenic acid (C18:1, n-7), or stearic acid (C18:0) are required in these combinations, implying that these fatty acids are key molecules for intraerythrocytic parasite growth (Mi-Ichi et al.2006). Here, we analysed profiles of parasitaemia changes as well as morphologies during the erythrocytic cycle and confirmed the importance of C16:0 and C18:1, n-9. We also provide evidence that C18:1, n-9 but not other C18 monoenoic or dienoic acids maintain the synchronicity of parasite development in serum-free medium when paired with C16:0, resulting in maintained exponential growth. Thus, C18:1, n-9 is indispensable for the intraerythrocytic proliferation of P. falciparum.
Increased levels of thiols protect antimony unresponsiveLeishmania donovanifield isolates against reactive oxygen species generated by trivalent antimony
Authors: MANDAL G. , WYLLIE S. , SINGH N. , SUNDAR S. , FAIRLAMB A. H. , CHATTERJEE M.
Published: July 2007

The current trend of antimony (Sb) unresponsiveness in the Indian subcontinent is a major impediment to effective chemotherapy of visceral leishmaniasis (VL). Although contributory mechanisms studied in laboratory-raised Sb-R parasites include an up-regulation of drug efflux pumps and increased thiols, their role in clinical isolates is not yet substantiated. Accordingly, our objectives were to study the contributory role of thiols in the generation of Sb unresponsiveness in clinical isolates. Promastigotes were isolated from VL patients who were either Sb responsive (n=2) or unresponsive (n=3). Levels of thiols as measured by HPLC and flow cytometry showed higher basal levels of thiols and a faster rate of thiol regeneration in Sb unresponsive strains as compared with sensitive strains. The effects of antimony on generation of reactive oxygen species (ROS) in normal and thiol-depleted conditions as also their H2O2scavenging activity indicated that in unresponsive parasites, Sb-mediated ROS generation was curtailed, which could be reversed by depletion of thiols and was accompanied by a higher H2O2scavenging activity. Higher levels of thiols in Sb-unresponsive field isolates from patients with VL protect parasites from Sb-mediated oxidative stress, thereby contributing to the antimony resistance phenotype.
The cognitive neuropsychology of depression in the elderly
Authors: HERRMANN LUCIE L. , GOODWIN GUY M. , EBMEIER KLAUS P.
Published: July 2007

Background

The cognitive impairment of older depressed patients with late- as opposed to early-onset illness may show important differences, in that patients with early onset may suffer predominantly from impaired episodic memory, and those with late onset mainly from reductions of executive function and processing speed.

Method

We searched Medline and EMBASE as well as individual papers' reference lists for relevant publications, recording comparisons in neuropsychological test results between early-onset depression (EOD), late-onset depression (LOD) and healthy volunteers. Effect sizes are presented for cognitive domains, such as executive function, processing speed, episodic memory, semantic memory and mental state examination.

Results

Patients with LOD showed greater reductions in processing speed and executive function than patients with EOD and controls. Both patient groups showed reduced function in all domains, except mental state, compared with controls.

Conclusion

Pronounced executive deficits are typical of the late-onset patients described in published studies, while episodic memory impairment is not specific to early-onset illness. Possible reasons and confounders are discussed.
Nonlocal electron heat flow in high-Z laser-plasmas with radiation transport
Authors: Keskinen M.J. , Schmitt A.
Published: July 2007

The effects of radiation transport on nonlocal electron heat flow in high Z laser-produced plasmas is studied. Using a Fokker-Planck model for the electron heat flow, which is coupled to a radiation transport model, it is found that radiation transport strongly modifies electron heat transport at the critical surface and in the overdense regions for an aluminum plasma. It is concluded that, without radiation transport effects, the plasma temperature, as computed from Fokker-Planck models, is overestimated in the critical region and underestimated in the overdense region, for high-Z plasmas.
Design aspects and development of humanoid robot THBIP-2
Authors: Xia Zeyang , Liu Li , Xiong Jing , Yi Qiang , Chen Ken
Published: July 2007

This is the first publication presenting the minihumanoid robot THBIP-2, the second-generation biped of Tsinghua University. It is 70 cm in height and 18 kg in weight with 24 degrees of freedom. This paper mainly addresses its mechatronics system realization, including the conceptual design, actuation system, sensing system, and control system. In addition, a walking stability controller based on zero moment point criterion and the walking simulation are presented. Finally, experiments validate and confirm the efficiency of the design.
PLTOOL: A knowledge engineering tool for planning and learning
Authors: Fernández Susana , Borrajo Daniel , Fuentetaja Raquel , Arias Juan D. , Veloso Manuela
Published: July 2007

Absract

Artificial intelligence (AI) planning solves the problem of generating a correct and efficient ordered set of instantiated activities, from a knowledge base of generic actions, which when executed will transform some initial state into some desirable end-state. There is a long tradition of work in AI for developing planners that make use of heuristics that are shown to improve their performance in many real world and artificial domains. The developers of planners have chosen between two extremes when defining those heuristics. The domain-independent planners use domain-independent heuristics, which exploit information only from the ‘syntactic’ structure of the problem space and of the search tree. Therefore, they do not need any ‘semantic’ information from a given domain in order to guide the search. From a knowledge engineering (KE) perspective, the planners that use this type of heuristics have the advantage that the users of this technology need only focus on defining the domain theory and not on defining how to make the planner efficient (how to obtain ‘good’ solutions with the minimal computational resources). However, the domain-dependent planners require users to manually represent knowledge not only about the domain theory, but also about how to make the planner efficient. This approach has the advantage of using either better domain-theory formulations or using domain knowledge for defining the heuristics, thus potentially making them more efficient. However, the efficiency of these domain-dependent planners strongly relies on the KE and planning expertise of the user. When the user is an expert on these two types of knowledge, domain-dependent planners clearly outperform domain-independent planners in terms of number of solved problems and quality of solutions. Machine-learning (ML) techniques applied to solve the planning problems have focused on providing middle-ground solutions as compared to the aforementioned two extremes. Here, the user first defines a domain theory, and then executes the ML techniques that automatically modify or generate new knowledge with respect to both the domain theory and the heuristics. In this paper, we present our work on building a tool, PLTOOL (planning and learning tool), to help users interact with a set of ML techniques and planners. The goal is to provide a KE framework for mixed-initiative generation of efficient and good planning knowledge.
Bayesian spatiotemporal analysis of foot-and-mouth disease data from the Republic of Turkey
Authors: BRANSCUM A. J. , PEREZ A. M. , JOHNSON W. O. , THURMOND M. C.
Published: July 2007

A flexible hierarchical Bayesian spatiotemporal regression model for foot-and-mouth disease (FMD) was applied to data on the annual number of reported FMD cases in Turkey from 1996 to 2003. The longitudinal component of the model was specified as a latent province-specific stochastic process. This stochastic process can accommodate various types of FMD temporal profiles. The model accounted for differences in FMD occurrence across provinces and for spatial correlation. Province-level covariate information was incorporated into the analysis. Results pointed to a decreasing trend in the number of FMD cases in western Turkey and an increasing trend in eastern Turkey from 1996 to 2003. The model also identified provinces with high and with low propensities for FMD occurrence. The model's use of flexible structures for temporal trend and of generally applicable methods for spatial correlation has broad application to predicting future spatiotemporal distributions of disease in other regions of the world.
Balls-in-Bins Processes with Feedback and Brownian Motion
Authors: OLIVEIRA ROBERTO
Published: July 2007

In a balls-in-bins process with feedback, balls are sequentially thrown into bins so that the probability that a bin withnballs obtains the next ball is proportional tof(n) for some functionf. A commonly studied case where there are two bins andf(n) =npforp> 0, and our goal is to study the fine behaviour of this process with two bins and a large initial numbertof balls. Perhaps surprisingly, Brownian Motions are an essential part of both our proofs.

Forp> 1/2, it was known that with probability 1 one of the bins will lead the process at all large enough times. We show that if the first bin starts with$t+\lambda\sqrt{t}$balls (for constant λ∈ℝ), the probability that it always or eventually leads has a non-trivial limit depending on λ.

Forp≤ 1/2, it was known that with probability 1 the bins will alternate in leadership. We show, however, that if the initial fraction of balls in one of the bins is > 1/2, the time until it is overtaken by the remaining bin scales like Θ(t1+1/(1-2p)) forp< 1/2 and exp(Θ(t)) forp= 1/2. In fact, the overtaking time has a non-trivial distribution around the scaling factor, which we determine explicitly.

Our proofs use a continuous-time embedding of the balls-in-bins process (due to Rubin) and a non-standard approximation of the process by Brownian Motion. The techniques presented also extend to more general functionsf.
Regions Without Complex Zeros for Chromatic Polynomials on Graphs with Bounded Degree
Authors: FERNÁNDEZ ROBERTO , PROCACCI ALDO
Published: July 2007

We prove that the chromatic polynomial$P_\mathbb{G}(q)$of a finite graph$\mathbb{G}$of maximal degree Δ is free of zeros for |q| ≥C*(Δ) withThis improves results by Sokal and Borgs. Furthermore, we present a strengthening of this condition for graphs with no triangle-free vertices.
Implantation of stents to ensure an adequate interatrial communication in patients with hypoplastic left heart syndrome
Authors: Rupp Stefan , Michel-Behnke Ina , Valeske Klaus , Akintürk Hakan , Schranz Dietmar
Published: July 2007

Aims

To assess the feasibility of interatrial stenting for left atrial decompression in infants with hypoplastic left heart syndrome treated by a “hybrid-approach”, with bilateral surgical banding of the pulmonary arteries and percutaneous stenting of the arterial duct.

Patients and methods

We stented the atrial septum in 5 infants aged from 21 to 77 days, making the intervention as an elective procedure in 4, but as a rescue procedure in the fifth patient, who had a restrictive foramen. The stents, comprising 2 Jo-stents of 17 millimetres hand-crimped on a balloon catheter with dimensions of 10 by 20 millimetres, and 3 premounted Genesis stents with dimensions of 10 by 19 millimetres, were placed using a 6 French long or short sheath by femoral venous access. The stents were expanded under fluoroscopic guidance to create a slightly diabolo-shaped form that fitted the septum.

Results

The percutaneous interventions were successfully performed in all cases, producing significant improvement in clinical condition after placement. The saturations of oxygen increased from an average of 64% plus or minus 18% to 88% plus or minus 7%, (p < 0.05). During a mean follow up of 2.5 months, without any anticoagulant therapy, there were no complications related to the stenting. Surgical removal of the stents was uneventful during reconstruction of the aortic arch and creation of a bidirectional cavopulmonary connection in 4 patients, and during cardiac transplantation in one.

Conclusion

In the context of the hybrid approach, definitive decompression of the left atrium can be achieved by stenting the atrial septum in infants with hypoplastic left heart syndrome. Placement of the stents is safe and effective, with insertion in the form of a diabolo reducing the risk of dislocation, as well as embolisation of the stent.
Hunger and health among undocumented Mexican migrants in a US urban area
Authors: Hadley Craig , Galea Sandro , Nandi Vijay , Nandi Arijit , Lopez Gerald , Strongarone Stacey , Ompad Danielle
Published: July 2007

Objectives

To measure the occurrence and correlates of hunger and to evaluate the association between hunger and three health indicators among undocumented Mexican immigrants.

Design

Non-probability cross-sectional sample.

Setting

Neighbourhoods within New York City.

Subjects

Four hundred and thirty-one undocumented Mexican immigrants living in the USA.

Results

Hunger was indicated by approximately 28% of respondents. In a multivariate model, working as a day labourer was associated with hunger (odds ratio (OR) 3.33, 95% confidence interval (CI) 1.83–6.06) while receiving public assistance protected against hunger (OR 0.23, 95% CI 0.06–0.88). In multivariate models, respondents who reported experiencing hunger also reported poorer overall health (OR 1.69, 95% CI 0.95–3.02) and more days of poor mental (P= 0.045) and physical health (P< 0.0001). Greater amount of time lived in the USA was also associated with worse overall health (P= 0.054) and more days of poor mental and physical health (P< 0.01).

Conclusions

The present study shows that food insecurity and hunger may be problems among undocumented migrants living in the USA. Uncertain and unpredictable work schedules and limited access to public assistance may contribute to high levels of hunger, which in turn may also negatively affect mental and physical health. Increasing amount of time lived in the USA is also associated with poorer health indicators. Programmes that provide undocumented migrants with emergency access to resources may reduce food insecurity and lead to improved health outcomes among this vulnerable population.
Performance of a food-frequency questionnaire in the US NIH–AARP (National Institutes of Health–American Association of Retired Persons) Diet and Health Study
Authors: Thompson Frances E , Kipnis Victor , Midthune Douglas , Freedman Laurence S , Carroll Raymond J , Subar Amy F , Brown Charles C , Butcher Matthew S , Mouw Traci , Leitzmann Michael , Schatzkin Arthur
Published: July 2007

Objective

We evaluated the performance of the food-frequency questionnaire (FFQ) administered to participants in the US NIH–AARP (National Institutes of Health–American Association of Retired Persons) Diet and Health Study, a cohort of 566 404 persons living in the USA and aged 50–71 years at baseline in 1995.

Design

The 124-item FFQ was evaluated within a measurement error model using two non-consecutive 24-hour dietary recalls (24HRs) as the reference.

Setting

Participants were from six states (California, Florida, Pennsylvania, New Jersey, North Carolina and Louisiana) and two metropolitan areas (Atlanta, Georgia and Detroit, Michigan).

Subjects

A subgroup of the cohort consisting of 2053 individuals.

Results

For the 26 nutrient constituents examined, estimated correlations with true intake (not energy-adjusted) ranged from 0.22 to 0.67, and attenuation factors ranged from 0.15 to 0.49. When adjusted for reported energy intake, performance improved; estimated correlations with true intake ranged from 0.36 to 0.76, and attenuation factors ranged from 0.24 to 0.68. These results compare favourably with those from other large prospective studies. However, previous biomarker-based studies suggest that, due to correlation of errors in FFQs and self-report reference instruments such as the 24HR, the correlations and attenuation factors observed in most calibration studies, including ours, tend to overestimate FFQ performance.

Conclusion

The performance of the FFQ in the NIH–AARP Diet and Health Study, in conjunction with the study’s large sample size and wide range of dietary intake, is likely to allow detection of moderate (≥1.8) relative risks between many energy-adjusted nutrients and common cancers.
Ethnic differences in 1-year follow-up effect of the Dutch Schoolgruiten Project – promoting fruit and vegetable consumption among primary-school children
Authors: Tak Nannah I , te Velde Saskia J , Brug Johannes
Published: July 2007

Objective

To evaluate the effect of a primary school-based intervention providing free fruit and vegetables (F&V), separately for children of Dutch and of non-Western ethnicity.

Setting

Primary schools in two regions (west and east) in The Netherlands.

Design and methods

Participating schoolchildren and their parents completed questionnaires at baseline and 1 year later, including questions on usual F&V intake, potential determinants and general demographics. Primary outcomes were the usual fruit intake and the usual vegetable intake as assessed by parent- and child self-reported food frequency measures. Secondary outcome measures were child- or parent-reported taste preference, knowledge of daily recommendations, availability, and accessibility for fruit intake. Multilevel regression analyses were used to assess differences at follow-up adjusted for baseline values between the control and intervention group using both child and parent reports.

Subjects

Five hundred and sixty-five children of Dutch ethnicity and 388 children of non-Western ethnicity (mean age 9.9 years at baseline) and their parents.

Results

Children of non-Western ethnicity in the intervention group reported a significantly higher vegetable intake (difference = 20.7 g day–1, 95% confidence interval (CI) = 7.6–33.7). A significant positive intervention effect was also found for fruit intake for children of Dutch ethnicity (difference = 0.23 pieces day–1, 95% CI = 0.07–0.39). No significant effects in intake were observed based on parent reports. Significant positive intervention effects were also found for perceived accessibility among children of non-Western ethnicity, as well as for parent-reported taste preference of their child among children of non-Western ethnicity and boys of Dutch ethnicity.

Conclusion

Providing children with free F&V had some positive effects on child-reported intakes and important correlates of intakes.
Traditional food diversity predicts dietary quality for the Awajún in the Peruvian Amazon
Authors: Roche ML , Creed-Kanashiro HM , Tuesta I , Kuhnlein HV
Published: July 2007

Objective

Our goal was to assess the potential for evaluating strengths of the Awajún traditional food system using dietary assessment, a traditional food diversity score and ranking of local foods.

Design

The method was used for dietary data obtained from mothers and children in the Awajún culture of the Peruvian Amazon where >90% of the dietary energy is derived from local, traditional food. Traditional food diversity scores were calculated from repeat 24-hour recalls. Group mean intakes of energy, fat, protein, iron, vitamin A and vitamin C from each food item were used to rank foods by nutrient contribution.

Setting

The study took place in six remote communities along the lower Cenepa River in the Amazonas District of Peru, South America.

Subjects

Dietary data were collected from 49 Awajún mothers and 34 children aged 3–6 years, representative of the six communities.

Results

Higher traditional food diversity was associated with greater protein, fibre, vitamin and mineral intakes when controlling for energy (partial correlations = 0.37 to 0.64). Unique sources for iron, total vitamin A and vitamin C were found in the Awajún traditional food system.

Conclusions

A traditional food diversity score was a useful tool for predicting nutrient adequacy for the Awajún. Promotion of the Awajún traditional food system should focus on dietary diversity and unique nutrient-dense local foods.
Crustal deformation and source models of the Yellowstone volcanic field from geodetic data
Authors: Vasco D. W. , Puskas C. M. , Smith R. B. , Meertens C. M.
Published: July 2007

Geodetic observations, comprising Interferometric Synthetic Aperture Radar (InSAR), Global Positioning System (GPS), and precision leveling measurements, are used to infer volume change in the subsurface associated with the dynamics of the Yellowstone volcanic system. We focus primarily on the Yellowstone Caldera and its related magmatic, hydrothermal, and fault systems. It appears that known faults play a significant role in controlling crustal volume increases and decreases due to the migration of volcanic and hydrothermal fluids. For example, over 5 cm of subsidence from 1992 to 1995 is associated with source volume changes 6–10 km beneath the NW‐trending Elephant Back fault zone and a north‐trending fault cutting across the caldera. Furthermore, we are able to image an episode of fluid intrusion near the northern edge of the caldera. The intrusion is elongated in the north‐south direction and is parallel to the north‐trending volume decrease. The primary intrusion and related hydrothermal activity occurred between 1996 and 2000, though the volume changes appear to have continued, shallowed, and changed shape between 2000 and 2002. There is evidence that the intrusive activity influenced extensional faults to the north of the caldera.
The Hatteras Front: August 2004 velocity and density structure
Authors: Savidge Dana K. , Austin Jay A.
Published: July 2007

The Hatteras Front is a persistent mesoscale cross‐shelf oriented front off Cape Hatteras, North Carolina. It is the boundary between relatively cool, fresh Mid‐Atlantic Bight shelf waters and warmer, saltier shelf waters of the South Atlantic Bight, which both converge along‐shelf upon Cape Hatteras year round. The Frontal Interaction Near Cape Hatteras (FINCH) project was conducted in 2004–2005 to intensively sample the Hatteras Front with shipboard ADCP and undulating towed CTD. This paper documents velocity and density structures associated with the cross‐shelf oriented zone of Hatteras Front during the August 2004 field season. Property gradients across the Hatteras Front are large, with temperature (T) and salinity (S) differences of ∼4–6°C, 2–5 psu, respectively over distances of 1–2 km. The T and S are not completely compensating, and a strong density (ρ) gradient also exists, with Δρ of ∼2 kg/m3 across a gentler 10 km wide front. The density gradient results in a steric sea‐level height gradient of ∼1–2 cm across the Front, which is in approximate geostrophic balance with a surface intensified jet, directed shoreward along the cross‐shelf oriented Front. The velocity is sheared with depth at 3.0 × 10−2 to 5.0 × 10−2 s−1 in the upper 5 m of the jet; a rate consistent with the density gradient according to the thermal wind relationship. Shoreward transport of ∼4.8 × 104 m3/s results from the surface intensified jet. The structure of the velocity field associated with the Hatteras Front resembles that of a slope‐controlled buoyant plume, as described by Lentz and Helfrich (2002). Velocity and density structures are similar during both advancing (southwestward) and retreating (northeastward) motion of the Front.
Airborne dust transport to the eastern Pacific Ocean off southern California: Evidence from San Clemente Island
Authors: Muhs Daniel R. , Budahn James , Reheis Marith , Beann Jossh , Skipp Gary , Fisher Eric
Published: July 2007

Islands are natural dust traps, and San Clemente Island, California, is a good example. Soils on marine terraces cut into Miocene andesite on this island are clay‐rich Vertisols or Alfisols with vertic properties. These soils are overlain by silt‐rich mantles, 5–20 cm thick, that contrast sharply with the underlying clay‐rich subsoils. The silt mantles have a mineralogy that is distinct from the island bedrock. Silt mantles are rich in quartz, which is rare in the island andesite. The clay fraction of the silt mantles is dominated by mica, also absent from local andesite, and contrasts with the subsoils, dominated by smectite. Ternary plots of immobile trace elements (Sc‐Th‐La and Ta‐Nd‐Cr) show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust. In contrast, the silt and, to a lesser extent, clay fractions of the silt mantles have compositions closer to average upper continental crust. The silt mantles have particle size distributions similar to loess and Mojave Desert dust, but are coarser than long‐range‐transported Asian dust. We infer from these observations that the silt mantles are derived from airborne dust from the North American mainland, probably river valleys in the coastal mountains of southern California and/or the Mojave Desert. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when “Santa Ana” conditions prevail, caused by a high‐pressure cell centered over the Great Basin. Examination of satellite imagery shows that easterly Santa Ana winds carry abundant dust to the eastern Pacific Ocean and the California Channel Islands. Airborne dust from mainland North America may be an important component of the offshore sediment budget in the easternmost Pacific Ocean, a finding of potential biogeochemical and climatic significance.
Response of California Current forcing to mid‐Holocene insolation and sea surface temperatures
Authors: Diffenbaugh Noah S. , Ashfaq Moetasim
Published: July 2007

We find that mid‐Holocene insolation causes systematic changes in wind forcing of the California Current system, suppressing wind stress in the spring and enhancing wind stress in the summer and autumn. Both large‐ and regional‐scale processes play an important role in the insolation enhancement of wind stress, with elevated summer insolation magnifying both large‐scale sea level pressure gradients and regional‐scale land‐sea thermal contrast. We find that prescribed changes in large‐scale sea surface temperatures (SSTs) amplify the response of nearshore wind stress to mid‐Holocene insolation, with SST magnification of changes in large‐scale sea level pressure gradients overcoming SST muting of changes in regional‐scale land‐sea thermal contrast. The climate model simulations are supported by proxy‐inferred cooler‐than‐present sea surface temperatures in the northern California Current system, as well as by high nitrogen isotope values in the southern California Current system. Our results highlight the importance of multiscale dynamical interactions in regulating the response of regional environments to global‐scale changes in radiative forcing.
Nonparametric methods for modeling GCM and scenario uncertainty in drought assessment
Authors: Ghosh Subimal , Mujumdar P. P.
Published: July 2007

Hydrologic implications of global climate change are usually assessed by downscaling appropriate predictors simulated by general circulation models (GCMs). Results from GCM simulations are subjected to a number of uncertainties due to incomplete knowledge about the underlying geophysical processes of global change (GCM uncertainties) and due to uncertain future scenarios (scenario uncertainties). With a relatively small number of GCMs available and a finite number of scenarios simulated by them, uncertainties in the hydrologic impacts at a smaller spatial scale become particularly pronounced. In this paper, a methodology is developed to address such uncertainties for a specific problem of drought impact assessment with results from GCM simulations. Samples of a drought indicator are generated with downscaled precipitation from available GCMs and scenarios. Since it is very unlikely that such small samples resulting from GCM scenarios fit a known parametric distribution, nonparametric methods such as kernel density estimation and orthonormal series methods are used to determine the probability distribution function (PDF) of the drought indicator. Principal component analysis, fuzzy clustering, and statistical regression are used for downscaling the mean sea level pressure (MSLP) output from the GCMs to precipitation at a smaller spatial scale. Reanalysis data from the National Center for Environmental Prediction (NCEP) are used in relating precipitation with MSLP. The information generated through the PDF of the drought indicator in a future year may be used in long‐term planning decisions. The methodology is demonstrated with a case study of the drought‐prone Orissa meteorological subdivision in India.
Revealing land cover change in California with satellite data
Authors: Potter Christopher , Genovese Vanessa , Gross Peggy , Boriah, Shyam , Steinbach Michael , Kumar Vipin
Published: July 2007

The conversion of natural land cover into human‐dominated cover types continues to be a change of global proportions with many unknown environmental consequences. Noteworthy conversions of this type include tree stand harvests in forested regions, urbanization, and agricultural intensification in former woodland and natural grassland areas. Determining where, when, and why natural ecosystem conversions occur is a crucial scientific concern [Foley et al., 2005]. Characteristics of the land cover can have important impacts on local climate, radiation balance, biogeochemistry, hydrology and the diversity and abundance of terrestrial species [Randerson et al., 2006]. Consequently, understanding trends in land cover conversion at local scales is a requirement for making useful numerical predictions about other regional and global changes. It is urgent that accurate, timely, and economical tools be made available to document these conversions and aid in the management of their impacts.
Impact of land cover change on surface climate: Relevance of the radiative forcing concept
Authors: Davin E. L. , de Noblet‐Ducoudré N. , Friedlingstein P.
Published: July 2007

We use the IPSL climate model to investigate biophysical impacts of Anthropogenic Land Cover Change (ALCC) on surface climate. Including both the changes in surface albedo and evapotranspiration, we find that ALCC represents a radiative forcing of −0.29 W/m2 from 1860 to 1992 and of −0.7 W/m2 from 1992 to 2100. The simulated surface temperature response to ALCC indicates a historical cooling of 0.05 K and an additional cooling due to future changes of 0.14 K, which is consistent with the sign of the radiative forcing. However, this cooling is substantially lower than the one we would have obtained if it was caused by a radiatively equivalent change in CO2 concentration. These results thus question the relevance of the radiative forcing framework in the context of land use change, since the radiative forcing due to ALCC may not be comparable to the one exerted by other anthropogenic perturbations.
Relativistic particle acceleration in the process of whistler‐mode chorus wave generation
Authors: Katoh Yuto , Omura Yoshiharu
Published: July 2007

We have found that efficient acceleration of resonant electrons takes place in a self‐consistent particle simulation reproducing whistler‐mode chorus emissions. While the majority of electrons lose energy contributing to the generation of chorus emissions, a fraction of resonant electrons having large pitch angle are simultaneously energized through nonlinear wave trapping by the generated chorus emissions. A small fraction of energetic electrons are energized over 100 keV during 2500 Ωe0−1. We also find that such accelerated electrons show a characteristic behavior turning their motion from equatorward to poleward during the acceleration process, which is explained by the relativistic turning acceleration (RTA) process. The present study clarifies that the role of nonlinear wave trapping is significant in the energization process of relativistic electrons by narrowband whistler‐mode chorus emissions.
Relation between rainfall duration and diurnal variation in the warm season precipitation over central eastern China
Authors: Yu Rucong , Xu Youping , Zhou Tianjun , Li Jian
Published: July 2007

Using hourly station rain‐gauge data during 1991–2004, we studied the relation between rainfall duration and diurnal variation during the warm season (May to September) over the central eastern China (105–120°E, 26–36°N). Our result shows that more than 60% of the total rainfall in the central eastern China comes from long‐duration rainfall events (an event that lasts longer than 6 hours). The long‐duration rainfall events tend to have their maximum hourly rainfall around early morning, while short‐duration rainfall events (an event of 1–3 hours in duration) have their peak rainfall around late afternoon. This contrast explains the two peaks in the diurnal variation of averaged precipitation over the central eastern China shown in previous studies.
Photodissociation of the δ(0,0) and δ(1,0) bands of nitric oxide in the stratosphere and the mesosphere: A molecular‐adapted quantum defect orbital calculation of photolysis rate constants
Authors: Mayor E. , Velasco A. M. , Martín I.
Published: July 2007

The availability of data concerning the upper atmosphere is essential for an understanding of both the change in solar activity on the Earth and of the different processes that have direct effects on the biosphere, in particular those with harmful environmental consequences. The main goal of the present work is the theoretical analysis of the photodissociation of nitric oxide (NO), which plays an important role in the chemical and energetic balance of the upper atmosphere. Given that the molecular absorption cross section is directly linked to the photodissociation rate of the molecule, we have first determined photoabsorption cross sections and then used the calculated values to obtain the rate constants for the photodissociation processes. The photodissociation of NO at a given wavelength range is triggered by the predissociation of the δ(0,0) and δ(1,0) bands. Through the analysis of the predissociation rate constants, a study of the dissociative behavior of NO by absorption of light within the VUV spectral region has been performed. The dependence on the altitude arises from the temperature changes to the doppler‐broaded halfwidth, in addition to the state population, and the solar zenith angle of the atmospheric photodissociation rate constants of this molecule have been calculated with the molecular‐adapted quantum defect orbital (MQDO) approach. Altitudes ranging from 20 to 90 km, which comprise the stratosphere and mesosphere, have been considered.
Carbon and nitrogen fixation and metabolite exchange in and between individual cells of Anabaena oscillarioides
Authors: Popa Radu , Weber Peter K , Pett-Ridge Jennifer , Finzi Juliette A , Fallon Stewart J , Hutcheon Ian D , Nealson Kenneth H , Capone Douglas G
Published: July 2007

Filamentous nitrogen fixing cyanobacteria are key players in global nutrient cycling, but the relationship between CO2- and N2-fixation and intercellular exchange of these elements remains poorly understood in many genera. Using high-resolution nanometer-scale secondary ion mass spectrometry (NanoSIMS) in conjunction with enriched H13CO3− and 15N2 incubations of Anabaena oscillarioides, we imaged the cellular distributions of C, N and P and 13C and 15N enrichments at multiple time points during a diurnal cycle as proxies for C and N assimilation. The temporal and spatial distributions of the newly fixed C and N were highly heterogeneous at both the intra- and inter-cellular scale, and indicative of regions performing active assimilation and biosynthesis. Subcellular components such as the neck region of heterocycts, cell division septae and putative cyanophycin granules were clearly identifiable by their elemental composition. Newly fixed nitrogen was rapidly exported from heterocysts and was evenly allocated among vegetative cells, with the exception of the most remote vegetative cells between heterocysts, which were N limited based on lower 15N enrichment. Preexisting functional heterocysts had the lowest levels of 13C and 15N enrichment, while heterocysts that were inferred to have differentiated during the experiment had higher levels of enrichment. This innovative approach, combining stable isotope labeling and NanoSIMS elemental and isotopic imaging, allows characterization of cellular development (division, heterocyst differentiation), changes in individual cell composition and cellular roles in metabolite exchange.
Improvements of high-throughput culturing yielded novel SAR11 strains and other abundant marine bacteria from the Oregon coast and the Bermuda Atlantic Time Series study site
Authors: Stingl Ulrich , Tripp Harry James , Giovannoni Stephen J
Published: July 2007

The introduction of high-throughput dilution-to-extinction culturing (HTC) of marine bacterioplankton using sterilized natural sea water as media yielded isolates of many abundant but previously uncultured marine bacterial clades. In early experiments, bacteria from the SAR11 cluster (class Alphaproteobacteria), which are presumed to be the most abundant prokaryotes on earth, were cultured. Although many additional attempts were made, no further strains of the SAR11 clade were obtained. Here, we describe improvements to the HTC technique, which led to the isolation of 17 new SAR11 strains from the Oregon coast and the Sargasso Sea, accounting for 28% and 31% of all isolates in these experiments. Phylogenetic analysis of the internal transcribed spacer (ITS) region showed that the isolates from the Oregon coast represent three different subclusters of SAR11, while isolates from the Sargasso Sea were more uniform and represented a single ITS cluster. A PCR assay proved the presence of proteorhodopsin (PR) in nearly all SAR11 isolates. Analysis of PR amino-acid sequences indicated that isolates from the Oregon coast were tuned to either green or blue light, while PRs from strains obtained from the Sargasso Sea were exclusively tuned to maximum absorbance in the blue. Interestingly, phylogenies based on PR and ITS did not correlate, suggesting lateral gene transfer. In addition to the new SAR11 strains, many novel strains belonging to clusters of previously uncultured or undescribed species of different bacterial phyla, including the first strain of the highly abundant alphaproteobacterial SAR116 clade, were isolated using the modified methods.
Modified Korteweg-deVries soliton evolution at critical density of negative ions in an inhomogeneous magnetized cold plasma
Authors: Singh Dhananjay K. , Malik Hitendra K.
Published: July 2007

Soliton propagation at critical density of negative ions is studied for weakly inhomogeneous magnetized cold plasma having positive ions, negative ions, and electrons. A general phase velocity relation is obtained and possible modes are studied for different cases involving different constituents of the plasma. Two types of modes (fast and slow) are found to propagate for the equal mass of the positive and negative ions. However, a limit on the obliqueness of magnetic field is obtained for the propagation of slow mode. For both types of modes, a variable coefficient modified Korteweg-deVries equation with an additional term arisen due to the density gradient is realized, which admits solutions for compressive solitons and rarefactive solitons of the same amplitudes at critical negative ion density. The propagation characteristics of these solitons are studied under the effect of densities of ions, magnetic field, and its obliqueness. The amplitudes of fast and slow wave solitons show their opposite behavior with the negative ion concentration, which is consistent with the variation of phase velocities with the negative ion density.
Quasibound continuum states in SiF4 (D̃A12) photoionization: Photoelectron-vibrational coupling
Authors: Montuoro Raffaele , Lucchese Robert R. , Bozek John D. , Das Aloke , Poliakoff E. D.
Published: July 2007

The authors report a fully vibrationally resolved photoelectron spectroscopy investigation of a nonplanar molecule studied over a range of excitation energies. Experimental results for all four fundamental vibrational modes are presented. In each case significant non-Franck-Condon effects are seen. The vibrational branching ratio for the totally symmetric mode ν1+ is found to be strongly affected by resonant excitation in the SiF4+ (D̃A12) photoionization channel. This is shown to be the result of two distinct shape resonances, which for the first time have been both confirmed by theoretical calculations. Vibrationally resolved Schwinger photoionization calculations are used to understand the vibronic coupling for the photoelectrons, both using ab initio and harmonic vibrational wave functions.
Micro-Hall bar as a sensor to detect the interaction of nanoscale ferromagnetic disks and columns
Authors: Hao Y. L. , Peeters F. M.
Published: July 2007

The response of a ballistic two-dimensional electron gas (2DEG) confined to a Hall cross and subjected to a locally inhomogeneous magnetic field which is created by two parallel or antiparallel magnetized cylindrical dots deposited above the 2DEG is investigated. The Hall and bend resistances are calculated as a function of the magnetization of the magnetic dots for different positions of the dots on the Hall bar. The Hall and bend resistances are different for parallel and antiparallel magnetized dots and depend on the relative position of the magnetic dots on the Hall bar.
Critical behavior of blind spots in sensor networks
Authors: Huang Liang , Lai Ying-Cheng , Park Kwangho , Zhang Junshan , Hu Zhifeng
Published: July 2007

Blind spots in sensor networks, i.e., individual nodes or small groups of nodes isolated from the rest of the network, are of great concern as they may significantly degrade the network’s ability to collect and process information. As the operations of many types of sensors in realistic applications rely on short-lifetime power supplies (e.g., batteries), once they are used up (“off”), replacements become necessary (“on”). This off-and-on process can lead to blind spots. An issue of both theoretical and practical interest concerns the dynamical process and the critical behavior associated with the occurrence of blind spots. In particular, there can be various network topologies, and the off-and-on process can be characterized by the probability that a node functions normally, or the occupying probability of a node in the network. The question to be addressed in this paper concerns how the dynamics of blind spots depend on the network topology and on the occupying probability. For regular, random, and mixed networks, we provide theoretical formulas relating the probability of blind spots to the occupying probability, from which the critical point for the occurrence of blind spots can be determined. For scale-free networks, we present a procedure to estimate the critical point. While our theoretical and numerical analyses are presented in the framework of sensor networks, we expect our results to be generally applicable to network partitioning issues in other networks, such as the wireless cellular network, the Internet, or transportation networks, where the issue of blind spots may be of concern.
Ion induced snowballs as a diagnostic tool to investigate the caging of metal clusters in large helium droplets
Authors: Döppner Tilo , Diederich Thomas , Göde Sebastian , Przystawik Andreas , Tiggesbäumker Josef , Meiwes-Broer Karl-Heinz
Published: July 2007

Metal clusters embedded in ultracold helium nanodroplets are exposed to femtosecond laser pulses with intensities of 1013–1014W∕cm2. The influence of the matrix on the ionization and fragmentation dynamics is studied by pump-probe time-of-flight mass spectrometry. Special attention is paid to the generation of helium snowballs around positive metal ions (Mez+HeN, z=1,2). Closings of the first and second helium shells are found for silver at N1=10,12 and N2=32,44, as well as for magnesium at N1=19–20. The distinct abundance enhancement of helium snowballs in the presence of isolated atoms and small clusters in the droplets is used as a diagnostics to explore the cage effect. For silver, a reaggregation of the clusters is observed at 30ps after femtosecond laser excitation.