bluuebunny/crossref_metadata_2025 huggingface dataset:
Prospective assessment of the reliability, validity, and sensitivity to change of the functional assessment of cancer Therapy‐Melanoma questionnaire
Authors: Cormier Janice N. , Ross Merrick I. , Gershenwald Jeffrey E. , Lee Jeffrey E. , Mansfield Paul F. , Camacho Luis H. , Kim Kevin , Webster Kimberly , Cella David , Palmer J. Lynn
Published: March 2008

BACKGROUND.

The authors previously developed a melanoma‐specific module for the Functional Assessment of Cancer Therapy (FACT‐Melanoma), a tool for the assessment of quality of life (QOL) in patients with melanoma. The reliability and validity of the FACT‐Melanoma was examined in this study.

METHODS.

Patients with melanoma (N = 273; stages I‐IV) completed a battery of questionnaires at the time of enrollment. The validity of the instrument was examined by comparing FACT‐Melanoma scores with performance status, disease stage, treatment status, and other scales, including the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Melanoma Module, the Profile of Mood States, and the Marlowe‐Crowne Social Desirability Scale. Patients were assessed after 1 week to assess test‐retest reliability and at 3 months to determine the sensitivity of the instrument to change in performance status.

RESULTS.

The internal consistency and test‐retest reliability (r) of the melanoma subscale (Cronbach α = .85; r = .81) and the total FACT‐Melanoma (α = .95; r = .90) were excellent. Overall, the scales were correlated with other measures, as anticipated. Total FACT‐Melanoma scores, along with scores for physical well‐being, emotional well‐being, functional well‐being, and melanoma‐specific scales, were lower for patients with advanced (stage III/IV) melanoma, poor performance status, and patients who were receiving active treatment. The FACT‐Melanoma total score and the score for physical well‐being were sensitive to changes in performance status (P = .0012 and P = .004, respectively).

CONCLUSIONS.

The results of the current study indicated that the FACT‐Melanoma questionnaire is a reliable and valid instrument for patients with melanoma that can be used for the assessment of QOL in clinical trials. Cancer 2008. © 2008 American Cancer Society.
The modifying effect of C‐reactive protein gene polymorphisms on the association between central obesity and endometrial cancer risk
Authors: Wen Wanqing , Cai Qiuyin , Xiang Yong‐Bing , Xu Wang‐Hong , Ruan Zhi Xian , Cheng Jiarong , Zheng Wei , Shu Xiao‐Ou
Published: March 2008

BACKGROUND.

Obesity is a major risk factor for endometrial cancer. Obesity, particularly central obesity, is considered as a systemic inflammatory condition and is related strongly to insulin resistance. C‐reactive protein (CRP) is the most recognized biologic marker of chronic systematic inflammation, and it is conceivable that the CRP gene may work together with obesity in the development of endometrial cancer.

METHODS.

On the basis of a population‐based case–control study in a Chinese population, the authors obtained obesity measurements and data on 6 CRP single‐nucleotide polymorphisms (SNPs) from 1046 patients with newly diagnosed endometrial cancer (cases) and from 1035 age frequency‐matched controls. The association of the CRP SNPs with endometrial cancer risk and their modification on the association between obesity and endometrial cancer risk were evaluated.

RESULTS.

Although CRP SNPs alone were not associated with endometrial cancer, the associations of endometrial cancer with central obesity, measured as the waist‐to‐hip ratio (WHR) and the waist circumference, seemed to be stronger in women who were homozygous for the major allele of reference SNP (rs)1130864 (cytidine [C]/C) than in women who had the C/thymidine (T) and T/T genotypes (interaction test: P = .013 for WHR; P = .083 for waist circumference). When the women were stratified further by menopausal status, the observed interactions persisted mainly in premenopausal women (interaction test: P < .001 for WHR; P = .002 for waist circumference).

CONCLUSIONS.

The current results suggested that, in the Chinese population that was studied, obesity‐related insulin resistance and proinflammatory effects may play an important role in endometrial cancer risk, and these effects were modified significantly by the CRP SNP rs1130864. Cancer 2008. © 2008 American Cancer Society.
Exponential growth for the wave equation with compact time‐periodic positive potential
Authors: Colombini Ferruccio , Rauch Jeffrey , Petkov Vesselin
Published: March 2008

We prove the existence of smooth positive potentials V(t, x), periodic in time and with compact support in x, for which the Cauchy problem for the wave equation utt − Δxu + V(t, x)u = 0 has solutions with exponentially growing global and local energy. Moreover, we show that there are resonances, z ∈ ℂ, |z| > 1, associated to V(t, x). © 2008 Wiley Periodicals, Inc.
On the Hausdorff dimension of the mather quotient
Authors: Fathi Albert , Rifford Ludovic , Figalli Alessio
Published: March 2008

Under appropriate assumptions on the dimension of the ambient manifold and the regularity of the Hamiltonian, we show that the Mather quotient is small in term of the Hausdorff dimension. Then we present applications in dynamics. © 2008 Wiley Periodicals, Inc.
MR imaging methods for assessing fetal brain development
Authors: Rutherford Mary , Jiang Shuzhou , Allsop Joanna , Perkins Lucinda , Srinivasan Latha , Hayat Tayyib , Kumar Sailesh , Hajnal Jo
Published: March 2008

Fetal magnetic resonance imaging provides an ideal tool for investigating growth and development of the brain in vivo. Current imaging methods have been hampered by fetal motion but recent advances in image acquisition can produce high signal to noise, high resolution 3‐dimensional datasets suitable for objective quantification by state of the art post acquisition computer programs. Continuing development of imaging techniques will allow a unique insight into the developing brain, more specifically process of cell migration, axonal pathway formation, and cortical maturation. Accurate quantification of these developmental processes in the normal fetus will allow us to identify subtle deviations from normal during the second and third trimester of pregnancy either in the compromised fetus or in infants born prematurely. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008
Optical imaging of infants' neurocognitive development: Recent advances and perspectives
Authors: Minagawa‐Kawai Yasuyo , Mori Koichi , Hebden Jeremy C. , Dupoux Emmanuel
Published: March 2008

Near‐infrared spectroscopy (NIRS) provides a unique method of monitoring infant brain function by measuring the changes in the concentrations of oxygenated and deoxygenated hemoglobin. During the past 10 years, NIRS measurement of the developing brain has rapidly expanded. In this article, a brief discussion of the general principles of NIRS, including its technical advantages and limitations, is followed by a detailed review of the role played so far by NIRS in the study of infant perception and cognition, including language, and visual and auditory functions. Results have highlighted, in particular, the developmental changes of cerebral asymmetry associated with speech acquisition. Finally, suggestions for future studies of neurocognitive development using NIRS are presented. Although NIRS studies of the infant brain have yet to fulfill their potential, a review of the work done so far indicates that NIRS is likely to provide many unique insights in the field of developmental neuroscience. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008
Using voltage‐sensitive dye recording to image the functional development of neuronal circuits in vertebrate embryos
Authors: Glover Joel C. , Sato Katsushige , Sato Yoko‐Momose
Published: March 2008

Recent developments in the design of voltage‐sensitive dyes and of recording apparatuses for detecting voltage‐dependent changes in the optical properties of such dyes have established voltage‐sensitive dye recording as an important technique for assessing the functional development of neuronal circuits in the brain and spinal cord. Here we discuss general technical issues regarding the recording of voltage‐sensitive dye signals and describe studies that have utilized this approach to follow the development of sensory and sensorimotor circuits in the embryonic brain stem. Functional imaging through voltage‐sensitive dye recording permits a noninvasive analysis of synaptic development and function at submillisecond temporal resolution in widely distributed circuits. These advantages are particularly valuable in assessing sensorimotor circuit development at early stages when neurons are small and synapses are fragile. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008
Two‐photon imaging of dendritic spine development in the mouse cortex
Authors: Pan Feng , Gan Wen‐Biao
Published: March 2008

Dendritic spines are the postsynaptic sites of most excitatory synapses in the mammalian brain. With the advent of two‐photon microscopy and transgenic mice expressing fluorescent proteins, dendritic spines can now be imaged in the living cerebral cortex over time scales ranging from seconds to years. Recent studies with this in vivo imaging approach have begun to provide important insights into the development and plasticity of dendritic spines in the intact brain. Here, we review these studies and discuss technical requirements for image acquisition. We envision that intravital two‐photon imaging at the level of individual synapses will greatly expand our current understandings of how neuronal networks are assembled and modified throughout life. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008
Cystic lymph node metastasis in patients with head and neck cancer: An HPV‐associated phenomenon
Authors: Goldenberg David , Begum Shahnaz , Westra William H. , Khan Zubair , Sciubba James , Pai Sara I. , Califano Joseph A. , Tufano Ralph P. , Koch Wayne M.
Published: March 2008

Background.

Cystic lymph node metastases have been associated with tonsil cancer. A subset of oropharyngeal cancers contain human papillomavirus (HPV) DNA. The clinical and virologic associations of cystic nodal metastasis in head and neck cancer (HNSCC) were investigated.

Methods.

A retrospective review of patients undergoing neck dissection between 2002 and 2004 identified patients with cystic lymph node metastases. Clinical and pathologic information was recorded. The presence of HPV DNA was analyzed using in situ hybridization in a subset of patients.

Results.

One hundred neck dissections were reviewed and 20 had cystic nodes. Seventeen of these patients had primary tumors arising in the palatine or lingual tonsil. Three were “unknown primary.” HPV DNA was present in 11 of 13 patients with cystic metastases with tissue available for analysis (87%). No HPV DNA was identified in tumor from 21 patients with solid nodal metastasis (p <.0001).

Conclusion.

Cystic cervical lymph node metastasis is strongly associated with HPV‐related tonsillar HNSCC. © 2008 Wiley Periodicals, Inc. Head Neck 2008
Osteosarcoma of the head and neck region: Lessons learned from a single‐institution experience of 50 patients
Authors: Laskar Siddhartha , Basu Ayan , Muckaden Mary Ann , D'Cruz Anil , Pai Suresh , Jambhekar Nirmala , Tike Pramod , Shrivastava Shyam K.
Published: March 2008

Background.

Osteosarcoma of the head and neck region is a rare tumor and is a therapeutic challenge because of its aggressive nature and complex anatomical location. Standard management guidelines are lacking due to paucity of published data.

Methods.

Fifty patients with head and neck osteosarcoma treated at our institute from 1995 to 2004 were reviewed.

Results.

There were 32 men and 18 women (median, 30 years). Mandible (56%) was the most common site. Chondroblastic (46%) was the most common histopathological variant. Treatment comprised multimodality approach using surgery (100%), radiotherapy (36%), and chemotherapy (58%). After a median follow‐up of 16.6 months, 46% were alive and disease free. Median overall survival was 45.7 months, and progression‐free survival was 13.7 months. Mandible and maxilla were favorable sites. Postoperative adjuvant radiotherapy improved local control in patients with adverse prognostic factors.

Conclusions.

Surgery remains the mainstay of the treatment of head and neck osteosarcoma. Adjuvant radiotherapy improves outcome in patients with adverse factors. © 2008 Wiley Periodicals, Inc. Head Neck 2008
Antineuronal antibodies in Parkinson's disease
Authors: van de Warrenburg Bart P.C. , Church Andrew J. , Martino Davide , Candler Paul M. , Bhatia Kailash P. , Giovannoni Gavin , Quinn Niall P.
Published: March 2008

Antineuronal antibodies (ANAs) have been implicated in the pathophysiology of postinfectious movement disorders, such as Sydenham's chorea. However, their relevance in other movement disorders—in the absence of infectious triggers—remains much disputed. We sought to assess the frequency of ANAs in idiopathic Parkinson's disease (IPD) and to explore whether a specific phenotype is associated with the presence of ANAs. For this purpose, we recruited 76 IPD patients, 9 patients with genetic parkinsonism, and 10 with one of the parkinson‐plus syndromes. They were all subjected to a comprehensive clinical review. In addition, 50 patients with non‐extrapyramidal neurological disease and 30 healthy blood donors served as control populations. Blood samples were tested for the presence of ANAs with Western blotting, using recombinant proteins of the three putative antigens (aldolase C, neuron‐specific enolase, and pyruvate kinase M1). We found these antibodies in 11.8% of the 76 IPD patients, which differed significantly from healthy controls (0%, P = 0.043), but nonsignificantly from patients with genetic parkinsonism (11.1%), with a parkinson‐plus syndrome (10%), or from neurological disease controls (4%). With respect to relevant disease characteristics, IPD patients with or without ANAs were indistinguishable, except for atypical disease features (mainly early falls or freezing and marked Pisa syndrome), which were more frequent in the ANA‐positive IPD group. We conclude that ANAs do not play a role in the majority of patients with IPD, but might be relevant in the pathogenesis of IPD with atypical features. © 2008 Movement Disorder Society
Evidence of increased odds of essential tremor in Parkinson's disease
Authors: Tan Eng‐King , Lee Seng‐Swim , S. Fook‐Chong , Lum Sau‐Ying
Published: March 2008

In a case control study using a standardized protocol, 600 subjects were evaluated for essential tremor (ET). We demonstrated that ET was significantly more frequent in patients with Parkinson's disease (PD) (12/204, 5.9%) compared to diseased controls (2/206, 1%) and healthy controls (1/190, 0.5%). A regression analysis with ET as outcome and group (either PD or healthy controls or diseased controls) as independent variable (adjusting for age and sex) revealed that PD had higher odds of having ET than diseased controls (OR = 5.43, 95% CI = 1.16, 25.39, P < 0.001) and healthy controls (OR = 10.87, 95% CI = 1.39, 85.15, P < 0.001). The low frequency of ET in our controls was further confirmed in a follow‐up study in a group of age and gender matched general medical patients who attended an outpatient clinic (0% frequency). Eight of 204 PD (3.9%) compared to none of diseased (0%) (P = 0.004) and healthy controls (0%) (P = 0.008) had a prior diagnosis of ET. The duration of ET symptoms in patients with PD was 25.1 ± 19.6 (range 3–60) years. A multivariate analysis demonstrated that a lower dose of levodopa (OR = 0.993, 95%CI for OR = 0.988, 0.997, P < 0.001) and a higher age of onset of disease (OR = 1.108, 95%CI for OR = 1.035, 1.187, P < 0.001) were associated with increased odds of PD with ET, compared to patients with PD without ET. In our Asian population, patients with PD were 5 to 10 times more likely to have ET compared to diseased and healthy controls, suggesting that the association of ET and PD is unlikely to be ethnicity‐specific. © 2008 Movement Disorder Society
Provocation of Parkinsonian tremor
Authors: Raethjen Jan , Austermann Kristina , Witt Karsten , Zeuner Kirsten E. , Papengut Frank , Deuschl Günther
Published: March 2008

Classical Parkinsonian rest tremor typically fluctuates over time and can be provoked by stressful situations. We quantified and compared the influence of different provocation methods on classical rest tremor severity. The effect of counting backwards from 100, tapping of the contralateral foot and a Stroop test on the Unified Parkinson's Disease Rating Scale (UPDRS) III rest tremor scores and the accelerometrically measured tremor amplitudes (total power) were analyzed in 18 patients with Parkinson's disease and a Type I tremor. Each of the three provocation methods increased the UPDRS III rest tremor score by 1–2 and the total power by 1–2 orders of magnitude compared with baseline (P < 0.001). The maximal effect was reached on average after 2–3 minutes of provocation. The effects were not significantly different. Provocations clearly influence the result of clinical rest tremor ratings, with the kind of provocation being of minor importance. We therefore suggest that each assessment of Parkinsonian rest tremor should include a systematic provocation and this should be formally included in future versions of the UPDRS. © 2008 Movement Disorder Society
Atypical Parkinsonism in distal myopathy with rimmed vacuoles
Authors: Ishihara Tomohiko , Ozawa Tetsutaro , Igarashi Shuichi , Kitsukawa Yuko , Takagi Masahito , Hirose Masaki , Tokutake Takayoshi , Tanaka Keiko , Nishizawa Masatoyo
Published: March 2008

A patient with distal myopathy with rimmed vacuoles (DMRV) exhibited Parkinsonism with a severe writing tremor that responded poorly to levodopa. Molecular genetic analysis revealed that the patient had the D176V/V572L compound heterozygous mutation in the UDP‐N‐acetylglucosamine 2‐epimerase/N‐acetylmannosamine kinase (GNE) gene. Histopathological examination of a biopsied muscle specimen yielded findings compatible with those of DMRV, which is characterized by the presence of rimmed vacuoles without inflammatory cell infiltration in muscle fibers. The finding of normal cardiac meta‐iodobenzylguanide uptake makes the possibility of incidental Parkinson's disease in this patient unlikely. These observations raise the possibility that atypical Parkinsonism is a rare complication of DMRV associated with GNE mutation. © 2008 Movement Disorder Society
Scaling turbulent atmospheric stratification. I: Turbulence and waves
Authors: Lovejoy S. , Schertzer D. , Lilley M. , Strawbridge K. B. , Radkevich A.
Published: March 2008

In this first of a three‐part series, we argue that the dynamics of turbulence in a stratified atmosphere should depend on the buoyancy over a wide range of vertical scales and on energy flux over a wide range of horizontal scales; it should be scaling, but anisotropic, not isotropic. We compare the leading statistical theories of atmospheric stratification which are conveniently distinguished by the elliptical dimension Ds which quantifies their degree of spatial stratification. This includes the mainstream isotropic 2‐D (large scales), isotropic 3‐D (small scales) theory but also the more recent linear gravity wave theories (Ds = 7/3) and the classical fractionally integrated flux (FIF) 23/9‐D unified scaling model. In the latter, the horizontal wind has a k−5/3 spectrum as a function of horizontal wavenumber determined by the energy flux and a k−11/5 energy spectrum as a function of vertical wavenumber determined by the buoyancy force variance flux. In this model, the physically important notion of scale is determined by the turbulent dynamics, it is not given a priori (i.e. the by usual Euclidean distance). The 23/9‐D FIF model is the most physically and empirically satisfying, being based on turbulent (spectral) fluxes. The FIF model as originally proposed by Schertzer and Lovejoy is actually a vast family of scaling models broadly compatible with turbulent phenomenology and with the classical turbulent laws of Kolmogorov, Corrsin and Obukov. However, until now it has mostly been developed on the basis of structures localized in space–time. In this paper, we show how to construct extreme FIF models with wave‐like structures which are localized in space but unlocalized in space–time, as well as a continuous family of intermediate models which are akin to Lumley–Shur models in which some part of the localized turbulent energy ‘leaks’ into unlocalized waves.

The key point is that the FIF requires two propagators (space–time Green's functions) which can be somewhat different. The first determines the space–time structure of the cascade of fluxes; this must be localized in space–time in order to satisfy the usual turbulence phenomenology. In contrast, the second propagator relates the turbulent fluxes to the observables; although the spatial part of the propagator is localized as before, in space–time it can be unlocalized. (It is still localized in space, now in wave packets.) We display numerical simulations which demonstrate the requisite (anisotropic, multifractal) statistical properties as well as wave‐like phenomenologies. In parts II and III we will examine the empirical evidence for the spatial and temporal parts, respectively, of the model using state‐of‐the‐art lidar data of aerosol backscatter ratios (which we use as a surrogate for passive scalar concentration). Copyright © 2008 Royal Meteorological Society
Vegetation‐hydrology dynamics in complex terrain of semiarid areas: 1. A mechanistic approach to modeling dynamic feedbacks
Authors: Ivanov Valeriy Y. , Bras Rafael L. , Vivoni Enrique R.
Published: March 2008

Vegetation, particularly its dynamics, is the often‐ignored linchpin of the land‐surface hydrology. This work emphasizes the coupled nature of vegetation‐water‐energy dynamics by considering linkages at timescales that vary from hourly to interannual. A series of two papers is presented. A dynamic ecohydrological model [tRIBS + VEGGIE] is described in this paper. It reproduces essential water and energy processes over the complex topography of a river basin and links them to the basic plant life regulatory processes. The framework focuses on ecohydrology of semiarid environments exhibiting abundant input of solar energy but limiting soil water that correspondingly affects vegetation structure and organization. The mechanisms through which water limitation influences plant dynamics are related to carbon assimilation via the control of photosynthesis and stomatal behavior, carbon allocation, stress‐induced foliage loss, as well as recruitment and phenology patterns. This first introductory paper demonstrates model performance using observations for a site located in a semiarid environment of central New Mexico.
Vegetation‐hydrology dynamics in complex terrain of semiarid areas: 2. Energy‐water controls of vegetation spatiotemporal dynamics and topographic niches of favorability
Authors: Ivanov Valeriy Y. , Bras Rafael L. , Vivoni Enrique R.
Published: March 2008

Ecosystems of dry climates are a particularly interesting subject for ecohydrological studies, as water is generally considered to be the key limiting resource. This work focuses on vegetation‐water‐energy dynamics occurring on the complex terrain of a semiarid area characteristic of central New Mexico. The study employs a mechanistic model of coupled interactions to construct a set of numerical experiments carried out for two small‐scale synthetic domains that exhibit particular hillslope curvatures. The linkages between terrain attributes and patterns of C4 grass productivity and water balance components are examined for three generic soil types. It is argued that in conditions of negligible moisture exchange, aspect and slope are the key determinants of both the hydrologic behavior and the degree of site “favorability” to vegetation. Certain topographic locations are more favorable to vegetation, as compared to a flat horizontal surface not influenced by lateral effects. These locations are associated with sites of northerly aspect with surface slopes within a narrow range of magnitudes. Contributions from both rainfall and radiation forcings are discussed to explain the existence of these topographic niches. The sensitivity of results is investigated by modifying the dominant mechanism of lateral water transfer. Two additional controlling topographic features are explored, corresponding to the contiguous and global terrain convergence levels. It is argued that their effects on vegetation‐hydrology dynamics at a given location are characteristically superimposed with the impact of site‐specific terrain attributes. Furthermore, the results lead to a conceptual relationship linking vegetation‐hydrology quantities at different landscape locations.
Accuracy of top soil moisture simulation using a mechanistic model with limited soil characterization
Authors: Chanzy A. , Mumen M. , Richard G.
Published: March 2008

For many applications, soil water flow models require knowledge of soil properties and conditions that is difficult to obtain. In this study, we analyzed the impact of approximations on model prediction of soil water content when only limited soil property data are available. The TEC model of Chanzy and Bruckler (1993), representing soil heat and water flows, was selected since it is based on soil properties that can be estimated with the pedotransfer function, and it is driven by standard climatic data. The impact of the choices made for soil hydraulic properties, initial soil water conditions, and lower boundary conditions for a wide range of soil were studied. In this study, emphasis was placed on estimating moisture in the surface soil layer (0–30 cm) and was limited to wet and moderately dry soil conditions, which can be critical for applications in agriculture to determine trafficable days and in surface hydrology. The results from this study indicate the importance of soil hydraulic properties and moisture profile initialization, which may lead to errors larger than 0.10 m3 m−3 on soil moisture in the surface layer. The pedotransfer function proposed by Wösten (1997) led to the best simulated soil moisture in the top 30 cm, but initialization has a strong impact. Thus a “warming up” period of 70 days is needed to mitigate the initialization error. This duration can be reduced according to the amount of precipitation. We propose starting simulations 48 hours after the last significant rainfall with an initial water potential of −10 kPa. At the bottom of the soil, a gravitational flux at a depth of at least 80 cm is recommended to compute the boundary conditions. These recommendations for implementing a soil water transfer model were evaluated against independent experimental data, and a moisture accuracy (root mean square error) of 0.04 m3 m−3 was obtained.
Passive scalars in stratified turbulence
Authors: Brethouwer G. , Lindborg E.
Published: March 2008

Statistics of a passive scalar (or tracer) with a horizontal mean gradient in randomly forced and strongly stratified turbulence are investigated by numerical simulations. We observe that horizontal isotropy of the passive scalar spectrum is satisfied in the inertial range. The spectrum has the form Eθ(kh) = CθɛθɛK−1/3kh−5/3, where ɛθ, ɛK are the dissipation of scalar variance and kinetic energy respectively, and Cθ ≃ 0.5 is a constant. This spectrum is consistent with atmospheric measurements in the mesoscale range with wavelengths 1–500 km. We also calculate the fourth‐order passive scalar structure function and show that intermittency effects are present in stratified turbulence.
A new hypothesis for the origin and redistribution of sulfates in the equatorial region of western Mars
Authors: Fan Chaojun , Schulze‐Makuch Dirk , Fairén Alberto G. , Wolff John A.
Published: March 2008

The formation of sulfates on Mars has been under debate since they were identified by several Mars missions starting from the 1970s. We propose that sulfates formed as evaporites in enclosed standing bodies of water in the Valles Marineris area following the early alteration of Martian basaltic crust, were then elevated by the Tharsis uplift, and transported together with rock materials to Meridiani Planum by periodic outbursts of water, where they were deposited as sediments. The proposed model comprehensively addresses all forms of sulfate occurrences near the equator in the western Martian hemisphere and relates it to physiographic processes (volcanic, tectonic and sedimentary) affecting the Martian surface.
A statistic‐thermodynamic model for the DOM degradation in the estuary
Authors: Zheng Quanan , Chen Qin , Zhao Haihong , Shi Jiuxin , Cao Yong , Wang Dan
Published: March 2008

This study aims to clarify the role of dissolved salts playing in the degradation process of terrestrial dissolved organic matter (DOM) at a scale of molecular movement. The molecular thermal movement is perpetual motion. In a multi‐molecular system, this random motion also causes collision between the molecules. Seawater is a multi‐molecular system consisting from water, salt, and terrestrial DOM molecules. This study attributes the DOM degradation in the estuary to the inelastic collision of DOM molecule with charged salt ions. From statistic‐thermodynamic theories of molecular collision, the DOM degradation model and the DOM distribution model are derived. The models are validated by the field observations and satellite data. Thus, we conclude that the inelastic collision between the terrestrial DOM molecules and dissolved salt ions in seawater is a decisive dynamic mechanism for rapid loss of terrestrial DOM.
The SAFRAN‐ISBA‐MODCOU hydrometeorological model applied over France
Authors: Habets F. , Boone A. , Champeaux J. L. , Etchevers P. , Franchistéguy L. , Leblois E. , Ledoux E. , Le Moigne P. , Martin E. , Morel S. , Noilhan J. , Quintana Seguí P. , Rousset‐Regimbeau F. , Viennot P.
Published: March 2008

The hydrometeorological model SIM consists of a meteorological analysis system (SAFRAN), a land surface model (ISBA), and a hydrogeological model (MODCOU). It generates atmospheric forcing at an hourly time step, and it computes water and surface energy budgets, the river flow at more than 900 river‐gauging stations, and the level of several aquifers. SIM was extended over all of France in order to have a homogeneous nationwide monitoring of the water resources: it can therefore be used to forecast flood risk and to monitor drought risk over the entire nation. The hydrometeorological model was applied over a 10‐year period from 1995 to 2005. In this paper the databases used by the SIM model are presented; then the 10‐year simulation is assessed by using the observations of daily streamflow, piezometric head, and snow depth. This assessment shows that SIM is able to reproduce the spatial and temporal variabilities of the water fluxes. The efficiency is above 0.55 (reasonable results) for 66% of the simulated river gauges, and above 0.65 (rather good results) for 36% of them. However, the SIM system produces worse results during the driest years, which is more likely due to the fact that only few aquifers are simulated explicitly. The annual evolution of the snow depth is well reproduced, with a square correlation coefficient around 0.9 over the large altitude range in the domain. The streamflow observations were used to estimate the overall error of the simulated latent heat flux, which was estimated to be less than 4%.
Constraints on the Pleistocene chronology of sediments from the Lomonosov Ridge
Authors: O'Regan Matthew , King John , Backman Jan , Jakobsson Martin , Pälike Heiko , Moran Kathryn , Heil Clifford , Sakamoto Tatsuhiko , Cronin Thomas M. , Jordan Richard W.
Published: March 2008

Despite its importance in the global climate system, age‐calibrated marine geologic records reflecting the evolution of glacial cycles through the Pleistocene are largely absent from the central Arctic Ocean. This is especially true for sediments older than 200 ka. Three sites cored during the Integrated Ocean Drilling Program's Expedition 302, the Arctic Coring Expedition (ACEX), provide a 27 m continuous sedimentary section from the Lomonosov Ridge in the central Arctic Ocean. Two key biostratigraphic datums and constraints from the magnetic inclination data are used to anchor the chronology of these sediments back to the base of the Cobb Mountain subchron (1215 ka). Beyond 1215 ka, two best fitting geomagnetic models are used to investigate the nature of cyclostratigraphic change. Within this chronology we show that bulk and mineral magnetic properties of the sediments vary on predicted Milankovitch frequencies. These cyclic variations record “glacial” and “interglacial” modes of sediment deposition on the Lomonosov Ridge as evident in studies of ice‐rafted debris and stable isotopic and faunal assemblages for the last two glacial cycles and were used to tune the age model. Potential errors, which largely arise from uncertainties in the nature of downhole paleomagnetic variability, and the choice of a tuning target are handled by defining an error envelope that is based on the best fitting cyclostratigraphic and geomagnetic solutions.
A new rainfall model based on the Neyman‐Scott process using cubic copulas
Authors: Evin G. , Favre A.‐C.
Published: March 2008

A classical way to model rainfall is to use a Poisson process. Authors generally employed cluster of rectangular pulses to reproduce the hierarchical structure of rainfall storms. Although independence between cell intensity and duration turned out to be a nonrealistic assumption, only a few models link these variables. In this paper, a Neyman‐Scott cluster process considering dependence between cell depth and duration is developed. We introduce this link with a cubic copula. Copulas are multivariate distributions modeling the dependence structure between variables, preserving the marginal distributions. Thanks to this flexibility, we are able to introduce a global concept of dependence between cell depth and duration. We derive the aggregated moments (first‐, second‐, and third‐order moments) from the new model for several families of polynomial copulas and perform an application on Belgium and American data.
Modes of free convection in fractured low‐permeability media
Authors: Simmons C. T. , Sharp J. M. , Nield D. A.
Published: March 2008

Abundant data indicate significant fluid and solute fluxes across low‐permeability shales in the Gulf of Mexico, the precise mechanisms of which are poorly understood. In this study, we analyze possible modes of intrafracture and interfracture free convection that may occur across fractured low‐permeability layers, such as shales. Fracture spacing, fracture aperture, shale thickness, and the density gradient across the shale unit are shown to play key roles in the governing fluid and solute transport processes. All modes of free convection (parallel to the fracture plane, perpendicular to the fracture plane, and convection between fractures on the larger layer scale) are theoretically possible for reasonable hydrogeologic parameters. Free convection parallel to the fracture plane is shown to be the dominant (and most likely) mode of free convection, requiring only very modest salinity differences for onset to occur. Least likely is convection perpendicular to the fracture plane. The results presented here suggest that free convection may not be uncommon in thick shale sequences, such as in the Gulf of Mexico Basin. An important consequence of these findings is that analyses that do not consider both interfracture and intrafracture convection modes may significantly underestimate the likelihood of the occurrence of free convection. These findings have important implications for the study of free convection and solute transport processes in fractured low‐permeability media and associated numerical modeling analyses.
An ab initio investigation on (CO2)n and CO2(Ar)m clusters: Geometries and IR spectra
Authors: Jovan Jose K. V. , Gadre Shridhar R.
Published: March 2008

An ab initio investigation on CO2 homoclusters is done at MPWB1K∕6-31++G(2d) level of theory. Electrostatic guidelines are found to be useful for generating initial structures of (CO2)n clusters. The ab initio minimum energy geometries of (CO2)n with n=2–8 are T shaped, cyclic, trigonal pyramidal, tetragonal pyramidal, tetragonal bipyramidal, pentagonal bipyramidal, and pentagonal bipyramid with one CO2 molecule attached to it. A test calculation on (CO2)20 cluster is also reported. The geometric parameters of the energetically most favored (CO2)n clusters match quite well their experimental counterparts (wherever available) as well as those derived from molecular dynamics studies. The effect of clustering is quantified through the asymmetric C–O stretching frequency shift relative to the single CO2 molecule. (CO2)n clusters show an increasing blueshift from 1.8to9.6cm−1 on increasing number of CO2 molecules from n=2 to 8. The energetics and geometries of CO2(Ar)m clusters have also been explored at the same level of theory. The geometries for m=1–6 show a predominant T type of the argon-CO2 molecule interaction. Higher clusters with m=7–12 show that the argon atoms cluster around the oxygen atom after the saturation of the central carbon atom. The CO2(Ar)m clusters exhibit an increasing redshift in the C–O asymmetric stretch relative to CO2 molecule of 0.7–5.6cm−1 with increasing number of argon atoms through m=1–8.
CO oxidation on unsupported Au55, Ag55, and Au25Ag30 nanoclusters
Authors: Chang C. M. , Cheng C. , Wei C. M.
Published: March 2008

Using density functional calculations, we demonstrate a catalytic reaction path with activation barriers of less than 0.5eV for CO oxidation on the neutral and unsupported icosahedral nanoclusters of Au55, Ag55, and Au25Ag30. Both CO and O2 adsorb more strongly on these clusters than on the corresponding bulk surfaces. The reaction path consists of an intermediate involving OOCO complex through which the coadsorption energy of CO and O2 on these clusters is expected to play an important role in the reaction. Based on the studies for the Au and Ag nanoclusters, a model alloy nanocluster of Au25Ag30 was designed to provide a larger coadsorption energy for CO and O2 and was anticipated to be a better catalyst for CO oxidation from energetic analysis.
Self-assembly of long chain alkanes and their derivatives on graphite
Authors: Yang Teng , Berber Savas , Liu Jun-Fu , Miller Glen P. , Tománek David
Published: March 2008

We combine scanning tunneling microscopy (STM) measurements with ab initio calculations to study the self-assembly of long chain alkanes and related alcohol and carboxylic acid molecules on graphite. For each system, we identify the optimum adsorption geometry and explain the energetic origin of the domain formation observed in the STM images. Our results for the hierarchy of adsorbate-adsorbate and adsorbate-substrate interactions provide a quantitative basis to understand the ordering of long chain alkanes in self-assembled monolayers and ways to modify it using alcohol and acid functional groups.
Simulating the collapse transition of a two-dimensional semiflexible lattice polymer
Authors: Zhou Jie , Ou-Yang Zhong-Can , Zhou Haijun
Published: March 2008

It has been revealed by mean-field theories and computer simulations that the nature of the collapse transition of a polymer is influenced by its bending stiffness ϵb. In two dimensions, a recent analytical work demonstrated that the collapse transition of a partially directed lattice polymer is always first order as long as ϵb is positive [H. Zhou et al., Phys. Rev. Lett. 97, 158302 (2006)]. Here we employ Monte Carlo simulation to investigate systematically the effect of bending stiffness on the static properties of a two-dimensional lattice polymer. The system’s phase diagram at zero force is obtained. Depending on ϵb and the temperature T, the polymer can be in one of the three phases: crystal, disordered globule, or swollen coil. The crystal-globule transition is discontinuous and the globule-coil transition is continuous. At moderate or high values of ϵb the intermediate globular phase disappears and the polymer has only a discontinuous crystal-coil transition. When an external force is applied, the force-induced collapse transition will either be continuous or discontinuous, depending on whether the polymer is originally in the globular or the crystal phase at zero force. The simulation results also demonstrate an interesting scaling behavior of the polymer at the force-induced globule-coil transition.
Energy confinement and magnetic field generation in the SSPX spheromak
Authors: Hudson B. , Wood R. D. , McLean H. S. , Hooper E. B. , Hill D. N. , Jayakumar J. , Moller J. , Montez D. , Romero-Talamás C. A. , Casper T. A. , Johnson J. A. , LoDestro L. L. , Mezonlin E. , Pearlstein L. D.
Published: March 2008

The Sustained Spheromak Physics Experiment (SSPX) [Hooper et al., Nuclear Fusion 39, 863 (1999)] explores the physics of efficient magnetic field buildup and energy confinement, both essential parts of advancing the spheromak concept. Extending the spheromak formation phase increases the efficiency of magnetic field generation with the maximum edge magnetic field for a given injector current (B∕I) from 0.65T∕MA previously to 0.9T∕MA. We have achieved the highest electron temperatures (Te) recorded for a spheromak with Te>500eV, toroidal magnetic field ∼1T, and toroidal current (∼1MA) [Wood et al., “Improved magnetic field generation efficiency and higher temperature spheromak plasmas,” Phys. Rev. Lett. (submitted)]. Extending the sustainment phase to >8ms extends the period of low magnetic fluctuations (<1%) by 50%. The NIMROD three-dimensional resistive magnetohydrodynamics code [Sovinec et al., Phys. Plasmas 10, 1727 (2003)] reproduces the observed flux amplification ψpol∕ψgun. Successive gun pulses are demonstrated to maintain the magnetic field in a quasisteady state against resistive decay. Initial measurements of neutral particle flux in multipulse operation show charge-exchange power loss <1% of gun input power and dominantly collisional majority ion heating. The evolution of electron temperature shows a distinct and robust feature of spheromak formation: A hollow-to-peaked Te(r) associated with q∼1∕2.
Ion-acoustic shocks in quantum electron-positron-ion plasmas
Authors: Roy K. , Misra A. P. , Chatterjee P.
Published: March 2008

Nonlinear propagation of quantum ion-acoustic waves (QIAWs) in a dense quantum plasma whose constituents are electrons, positrons, and positive ions is investigated using a quantum hydrodynamic model. The standard reductive perturbation technique is used to derive the Korteweg–de Vries–Burger (KdVB) equation for QIAWs. It is shown by numerical simulation that the KdVB equation has either oscillatory or monotonic shock wave solutions depending on the system parameters H proportional to quantum diffraction, μi the effect of ion kinematic viscosity, and μ the equilibrium electron to ion density ratio. The results may have relevance in dense astrophysical plasmas (such as neutron stars) as well as in intense laser solid density plasma experiments where the particle density is about 1025−1028m−3.
Wide forbidden band induced by the interference of different transverse acoustic standing-wave modes
Authors: Tao Zhiyong , He Weiyu , Xiao Yumeng , Wang Xinlong
Published: March 2008

A non-Bragg nature forbidden band is experimentally observed in an axially symmetric hard-walled duct with a periodically varying cross section. Unlike the familiar Bragg ones, the observed bandgap is found to result from the interference of sound wave modes having different transverse standing-wave profiles, the so-called non-Bragg resonance. The experiments also show that the non-Bragg band can be comparably wider than the Bragg one; furthermore, the sound transmission loss within the band can be much more effective, exhibiting the great significance of the non-Bragg resonance in wave propagation in periodic waveguides.
Electric field effect on a two-fluid interface instability in channel flow for fast electric times
Authors: Uguz A. Kerem , Ozen O. , Aubry N.
Published: March 2008

The application of an electric field to a two-fluid layer in channel flow has been shown to be an effective way to destabilize microscale interfacial flows. Here, we perform a linear stability analysis of a flat interface between two leaky dielectric liquids flowing in a channel while also subjected to an electric field parallel to the interface. It is shown that the analysis simplifies for fast electric charge relaxation times, in which case conditions for the electric field to be either stabilizing or destabilizing are derived analytically. These results are compared to those previously obtained for a normal electric field.
Fast imaging of edge localized mode structure and dynamics in DIII-D
Authors: Yu J. H. , Boedo J. A. , Hollmann E. M. , Moyer R. A. , Rudakov D. L. , Snyder P. B.
Published: March 2008

Fast-framing images of CIII and Dα emission in the low-field-side plasma boundary of the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] show that edge localized modes (ELMs) rapidly eject multiple field-aligned filaments from the plasma edge. The toroidal and poloidal mode numbers of these filaments depend on normalized plasma density, with measured ELM toroidal mode numbers ranging from ⩽10 to 20 in low-density plasmas and 15 to 35 in high-density plasmas. In high-density plasmas with moderate collisionality νped*=0.50, ELMs originate at the low-field-side midplane region and the ion parallel velocity in the scrape-off layer is faster for ELMs with larger Dα divertor emission, suggesting that large ELMs eject higher-temperature ions from deeper within the plasma compared to small ELMs. In low-density plasmas with collisionality νped*=0.25, the midplane and divertor ELM signals appear simultaneously, indicating that ELM behavior depends on collisionality. At all νped*, ELMs drive parallel fluxes to the divertor; in addition, ELMs drive cross-field propagation of filaments, which results in plasma-wall interactions that are poloidally localized within 15cm of the midplane. Using the wall interactions as signatures of the filaments in the scrape-off layer, the measured poloidal width of the filament ranges from 1to5cm.
Controlling the red luminescence from silicon quantum dots in hydrogenated amorphous silicon nitride films
Authors: Hao H. L. , Wu L. K. , Shen W. Z.
Published: March 2008

We report on a simple way to control the red luminescence from silicon quantum dots (Si QDs) in hydrogenated amorphous silicon nitride. The achievement has been realized through annealing treatments, which effectively modify the dot size, density, and surface chemistry. High resolution transmission electron microscopy, Raman scattering, infrared absorption, and x-ray photoelectron spectroscopy have been employed to reveal the existence, chemical compositions, bonding environment, and evolution of the Si QDs. We have also identified the transition of the dominant luminescence mechanism in the Si QDs from quantum confinement effect to interface state assisted radiative recombination.
Synthesis and ferromagnetism of Co-doped TiO2−δ nanobelts by metallorganic chemical vapor deposition
Authors: Quynh Hoa Nguyen Thi , Lee Zonghoon , Kang Seung-Hee , Radmilovic Velimir , Kim Eui-Tae
Published: March 2008

Ti 1 − x Co x O 2 − δ nanobelts were synthesized without using any metal catalysts by metallorganic chemical vapor deposition. The nanobelts consisted of ∼10–20nm nanocrystallites, which were dominantly rutile structure. The Ti0.986Co0.014O2−δ nanobelt sample showed a magnetic anisotropy with a high coercive field value (∼500Oe) at room temperature, significantly affected by intrinsic effect. In contrast, the Ti0.982Co0.018O2−δ nanobelt sample revealed isotropic magnetic characteristics due to enhanced Co clustering. A few or several Co clusters per nanobelt were typically observed even in the lightly Co-doped Ti0.986Co0.014O2−δ nanobelts because of the very thin thickness (∼20nm) and high specific surface area of nanobelts.