bluuebunny/crossref_metadata_2025 huggingface dataset:
Cognitive, biochemical, and imaging profile of patients suffering from idiopathic normal pressure hydrocephalus
Authors: Tarnaris Andrew , Toma Ahmed K. , Pullen Emily , Chapman Miles D. , Petzold Axel , Cipolotti Lisa , Kitchen Neil D. , Keir Geoff , Lemieux Louis , Watkins Laurence D.
Published: July 2011

Introduction

It has still not been clearly established whether the cognitive deficits of idiopathic normal pressure hydrocephalus (iNPH) are caused by a disturbance in cerebrospinal fluid (CSF) dynamics or an underlying metabolic disturbance.

Objective

To identify the possible associations between biochemical markers, the neuroimaging characteristics, and cognitive deficits of patients undergoing investigations for possible iNPH.

Methods

A CSF sample obtained during a lumbar puncture from 10 patients with iNPH was analyzed for several biochemical markers (lactate, 8‐isoprostane, vascular endothelial growth factor [VEGF], neurofilament heavy protein, glial fibrillary acidic protein, amyloid beta 1‐42, and total tau). All patients underwent a battery of neuropsychological testing and imaging as part of their selection process for their suitability for CSF diversion surgical procedure. Volumetric analysis of imaging was carried out measuring the ventricular volume (VV), intracranial volume (ICV), periventricular lucencies, deep white matter hyperintensities, and white matter (WM) volume, as well as their ratios.

Results

A significant negative correlation of preoperative symptom duration and total tau levels (R = −0.841, P = .002) was found. There was a significant positive correlation (R = 0.648, P = .043) between the levels of VEGF and the VV/ICV ratio. There was a significant positive correlation of the levels of glial fibrillary acidic protein and the VV/deep white matter hyperintensities ratio (R = 0.828, P = .006). A significant negative correlation was observed between the levels of neurofilament heavy protein and the VV/ICV ratio (R = −0.657, P = .039) and the WM volume (R = −0.778, P = .023). Lactate levels were lower for patients performing in the normal range on the Recognition Memory Test for faces. Patients who performed better in the Recognition Memory Test words test had higher ICV volumes. All the patients in this study showed below normal performance when the subcortical function was assessed.

Conclusion

The positive correlation of VEGF with the severity of ventriculomegaly may indicate that this is because of the transmantle pressure gradient; this response may not be because of hypoxia but represents an attempt at neuroregeneration. The degree of reactive gliosis correlates inversely with the severity of WM lesions. Neuronal degeneration is negatively correlated with the volume of the WM in these patients. The small association of volumetry and the cognitive profile of these patients may be consistent with a direct biochemical disturbance being responsible for the cognitive deficit observed. Ongoing studies with set protocols for neuropsychological assessment and volumetric analysis are warranted to further elucidate on the preliminary results of the current study.
DEVELOPMENT AND ADMINISTRATIVE NORMS: THE OFFICE DU NIGER AND DECENTRALIZATION IN FRENCH SUDAN AND MALI
Authors: Diawara Mamadou
Published: July 2011

This article analyses the historical roots of decentralization, a policy which is presented in the development world as the miracle cure to Third World evils. The text is based on the current literature on the topic as well as field research carried out in Mali in the Office du Niger region, which, already in the colonial period, represented a particular decentralization challenge. It offers a critical perspective on the concept of decentralization, which some trace back to the Middle Ages, and examines colonial experiences. How can the Malian state, inherited from the colonial state, decentralize everything whilst adopting the policy according to which the lands of the central delta of the Niger have been state-owned property since 1935? The aim is to show the analogy between problems encountered by the French colonial state and those that plague the Malian post-colonial state, whilst guarding against the sirens of a false authenticity reeking of neo-traditionalism.
‘INSTEAD OF BEGGING, I FARM TO FEED MY CHILDREN’: URBAN AGRICULTURE – AN ALTERNATIVE TO COPPER AND COBALT IN LUBUMBASHI
Authors: Tambwe Nyumbaiza , Rudolph Michael , Greenstein Ran
Published: July 2011

The collapse of the mining company La Générale des Carrières et des Mines (GECAMINES) in the 1990s forced many unemployed workers in Lubumbashi to look at alternative means of survival. The post-GECAMINES era was characterized by acute economic crisis at a time of rapid population growth and increasing urban poverty. The object of this article is threefold: to demonstrate how Lubumbashi residents resorted to agricultural activities within and around the city; to identify reasons for success and failure from three case studies; and to categorize the types of agriculture that emerge. Data were collected by means of semi-structured interviews, in-depth questions and observation. One hundred farming households were selected and interviewed between November 2004 and March 2005. Data were analysed using thematic content analysis for qualitative aspects and SPSS for the quantitative information. Though the living conditions of 75 per cent of urban farmers declined despite the practice of urban agriculture, these conditions might have worsened without it. However, 20 per cent of the households in the sample succeeded in stabilizing their living conditions, even though they were unable to alleviate poverty completely. A few farmers (5 per cent) became food-secure through the practice of urban agriculture.
Repeated cycles of immersion and emersion amplify the crawling rhythm of the intertidal gastropod Hydrobia ulvae
Authors: Vieira Sónia , Coelho Helena , Nolasco Rita , Serôdio João , Barnes Richard S.K. , Queiroga Henrique
Published: July 2011

Hydrobia ulvae displays an endogenous rhythm of crawling behaviour of circatidal periodicity, with higher levels of activity during high water. In the present study we address the effect of repeated cycles of immersion and emersion at tidal periodicity on the level and synchronism of the behaviour, by contrasting these with the effects of continuous immersion and continuous emersion. Snails were recorded in dark conditions under the different immersion regimes for 3 days. The results show that continuously emersed snails displayed very low levels of activity. Average activity levels of continuously immersed snails and of those subjected to tidal cycles of immersion and emersion were similar, had identical periods related to the period of the tidal cycle, and had similar phase relationships to the expected tidal cycle. However, form-estimates for these two categories of snails differed, the snails subjected to cyclic conditions showing a larger amplitude and greater synchronism of activity. Therefore, it is concluded that recurrent cycles of immersion and emersion should contribute to well defined cycles of activity in the intertidal environment, with greater activity levels during high water.
Acanthaster planci impact on coral communities at permanent transect sites on Bruneian reefs, with a regional overview and a critique on outbreak causes
Authors: Lane David J.W.
Published: July 2011

The submerged coral reefs of Brunei, little-impacted by human activity and characterized by high live coral cover, have no recorded history in recent decades of the presence of the crown-of-thorns (COT), Acanthaster planci. This sea star, first recorded on Brunei reefs in 2008, attained outbreak densities in 2010. At Littledale Shoal its impact on corals at permanent transect sites has been quantified; mean live coral cover reduced by half from 2006 to 2010 due predominantly to predation. Line intersect transect data confirm a predisposition for tabular Acropora species, a prominent feature at this site, although other scleractinian taxa were also predated. Other regional outbreaks are reviewed, including episodes, and their timing, within the neighbouring Coral Triangle (CT). Mounting evidence implicates nutrient-enhanced increases in primary production as a primary cause of COT outbreaks. However, this stands in contrast with a report of global oceanic phytoplankton decline in the past century, and there is little evidence of such a link in the CT, even though this region is characterized by high precipitation, erosional plumes and seasonal upwelling-associated phytoplankton blooms. Furthermore, until survivorship and competency for a wider spectrum of mass-spawned invertebrate planktotrophs in relation to elevated phytoplankton densities is better understood, such evidence, suggesting release from food limitation as the principal cause of enhanced COT recruitment, should be interpreted with caution.
Light intensity, photoperiod duration, daily light flux and coral growth ofGalaxea fascicularisin an aquarium setting: a matter of photons?
Authors: Schutter Miriam , van der Ven Rosa M. , Janse Max , Verreth Johan A.J. , Wijffels René H. , Osinga Ronald
Published: July 2011

Light is one of the most important abiotic factors influencing the (skeletal) growth of scleractinian corals. Light stimulates coral growth by the process of light-enhanced calcification, which is mediated by zooxanthellar photosynthesis. However, the quantity of light that is available for daily coral growth is not only determined by light intensity (i.e. irradiance), but also by photoperiod (i.e. the light duration time). Understanding and optimizing conditions for coral growth is essential for sustainable coral aquaculture. Therefore, in this study, the question was explored whether more light (i.e. more photons), presented either as irradiance or as light duration, would result in more growth. A series of nine genetically identical coral colonies ofGalaxea fascicularisL. were cultured for a period of 18 weeks at different light duration times (8 hours 150 μE m−2s−1:16 hours dark, 12 hours 150 μE m−2s−1:12 hours dark, 16 hours 150 μE m−2s−1:8 hours dark, 24 hours 150 μE m−2s−1:0 hours dark) and different irradiance levels (8 hours 150 μE m−2s−1:16 hours dark, 8 hours 225 μE m−2s−1:16 hours dark and 8 hours 300 μE m−2s−1:16 hours dark). Growth was determined every two weeks by measuring buoyant weight. Temperature, salinity and feeding levels were kept constant during the experiment. To detect possible acclimation of the corals to an increased light duration, rates of net photosynthesis and dark respiration were measured, hereby comparing coral colonies grown under an 8:16 hours light (150 μE m−2s−1):dark cycle with corals grown under a 16:8 hours light (150 μE m−2s−1):dark cycle. No increase in growth was detected with either increasing photoperiod or irradiance. Continuous lighting (24 hours 150 μE m−2s−1:0 hours dark) resulted in immediate bleaching and the corals died after 14 weeks. Hourly photosynthetic rates were significantly reduced in the 16 hour light treatment compared to the 8 hour light treatment. As a result, daily net photosynthetic rates were not significantly different, which may explain the observed specific growth rates. Acclimation to photoperiod duration appeared neither to be mediated by changes in chlorophyll-aconcentration nor zooxanthellae density. Based on the results of this study, we can conclude that the enhancing effect of light on coral growth is not only a matter of photons. Obviously, the availability of light was not limiting growth in these experiments and was probably in excess (i.e. stressful amounts). Other factors are discussed that play a role in determining growth rates and might explain our results.
Seasonal dynamics of subtidal macrophyte assemblages in Sobol Bay (Peter the Great Bay, Sea of Japan) in relation to depth
Authors: Skriptsova Anna V. , Levenets Irina R.
Published: July 2011

This paper describes the species composition, vertical distribution, and the seasonal changes in the biomass of subtidal macrophytes in Sobol Bay (Peter the Great Bay, Sea of Japan). The samples were collected in the depth-range from 0.5 to 4 m. A total of 65 macrophyte species were identified, among which were 10 species of Chlorophyta, 17 of Phaeophyceae, 37 of Rhodophyta and 1 of Magnoliophyta. Multivariate analyses were performed to detect spatial and temporal variations. Maximum species richness was registered in June, with a particularly dramatic biomass increase of brown algae. Both the number of species and the biomass of macrophytes decreased with increasing depth. Depth clearly affected the patterns of seasonal fluctuations of the species composition and biomass. In the study area, the species composition of the shallow-water algal assemblages was more stable throughout the year compared to that of the algal assemblages found in deeper waters. In total, four macrophyte assemblages were identified in the bay. A Phyllospadix iwatensis and Coccophora langsdorfii dominated assemblage occupied muddy-gravel bottoms in depths from 0.5 to 2 m throughout the year. An assemblage, co-dominated by annual brown algae Desmarestia viridis and Costaria costata, occurred at depths more than 3 m at late spring. Two other assemblages occurred on the rock and boulder bottom at 0.5–2 m depths, but they were temporally separated. An assemblage co-dominated by annual laminarian algae (Undaria pinnatifida and Costaria costata) developed at late spring and was succeeded in the autumn and winter by a Tichocarpus crinitus, Ulva lactuca, Sargassum pallidum and Codium fragile co-dominated assemblage. A comparison between the data obtained in the present study and the results of a previous study conducted in 1927 shows that the macrophytes assemblages in Sobol Bay underwent little change.
Meristic variation in males of the hydrothermal vent octopus,Muusoctopus hydrothermalis(Cephalopoda: Octopodidae)
Authors: Voight Janet R.
Published: July 2011

Intraspecific variation in characters such as arm sucker and gill lamellae counts in octopodids is yet to be thoroughly investigated, potentially hampering our ability to recognize species. In this study, data from 13 specimens ofMuusoctopus hydrothermaliscollected at four hydrothermal vents on the East Pacific Rise between 8°38′N and 12°48′N are considered. Although the northern and southern octopuses differ minimally in size, mean sucker count by arm in the northern group is 11.7 to 22.8% higher than it is in the southern group; in addition these octopuses typically have an additional gill lamella and bulkier funnel organs. The arms of each individual carry a different number of suckers. The difference is significant on nonadjacent arms, a pattern that merits examination in a broader taxonomic context. Why these differences exist among conspecifics remains unknown, the incidence of parasitic copepods is not different between the groups and the between-group variation in arm suckers seen here compares well with a previous report of variation among 18 specimens from the type locality. Increases in meristic characters (counts) in fish are attributed to lower temperatures during embryonic development following Jordan's rule. Northern and southern vents offer the octopuses a wide temperature range, but vent fluid chemistry differs. Northern vent fluids may be more toxic; if so, developing octopus embryos may survive only minimal vent fluid exposure and therefore develop at low temperatures. At the less toxic southern vents, eggs may survive greater exposure to vent fluids and thus develop at higher temperatures.
The potential role of epigenetic responses to diet in ageing
Authors: Ford Dianne , Ions Laura J. , Alatawi Fatema , Wakeling Luisa A.
Published: July 2011

Epigenetic changes may be causal in the ageing process and may be influenced by diet, providing opportunities to improve health in later life. The aim of this review is to provide an overview of several areas of research relevant to this topic and to explore a hypothesis relating to a possible role of epigenetic effects, mediated by sirtuin 1, in the beneficial effects of dietary restriction, including increased lifespan. Epigenetic features of ageing include changes in DNA methylation, both globally and at specific loci, which differ between individuals. A major focus of research on dietary influences on epigenetic status has been on nutrition in utero, because the epigenome is probably particularly malleable during this life-course window and because epigenetic marking by early exposures is a compelling mechanism underlying effects on lifelong health. We explore the potential of diet during adulthood, including the practice of dietary restriction, to affect the epigenetic architecture. We report progress with respect to deriving data to support our hypothesis that sirtuin 1 may mediate some of the effects of dietary restriction through effects on DNA methylation and note observations that resveratrol affects DNA methylation and other epigenetic features. Disentangling cause and effect in the context of epigenetic change and ageing is a challenge and requires better understanding of the underlying mechanisms and also the development of more refined experimental tools to manipulate the epigenetic architecture, to facilitate hypothesis-driven research to elucidate these links and thus to exploit them to improve health across the full life-course through dietary measures.
Soil fertility and crop yields in long-term organic and conventional cropping systems in Eastern Nebraska
Authors: Wortman Sam E. , Galusha Tomie D. , Mason Stephen C. , Francis Charles A.
Published: July 2011

Organic agriculture aims to build soil quality and provide long-term benefits to people and the environment; however, organic practices may reduce crop yields. This long-term study near Mead, NE was conducted to determine differences in soil fertility and crop yields among conventional and organic cropping systems between 1996 and 2007. The conventional system (CR) consisted of corn (Zea maysL.) or sorghum (Sorghum bicolor(L.) Moench)–soybean (Glycine max(L.) Merr.)–sorghum or corn–soybean, whereas the diversified conventional system (DIR) consisted of corn or sorghum–sorghum or corn–soybean–winter wheat (wheat,Triticum aestivumL.). The animal manure-based organic system (OAM) consisted of soybean–corn or sorghum–soybean–wheat, while the forage-based organic system (OFG) consisted of alfalfa (Medicago sativaL.)–alfalfa–corn or sorghum–wheat. Averaged across sampling years, soil organic matter content (OMC), P, pH, Ca, K, Mg and Zn in the top 15 cm of soil were greatest in the OAM system. However, by 2008 OMC was not different between the two organic systems despite almost two times greater carbon inputs in the OAM system. Corn, sorghum and soybean average annual yields were greatest in either of the two conventional systems (7.65, 6.36 and 2.60 Mg ha−1, respectively), whereas wheat yields were greatest in the OAM system (3.07 Mg ha−1). Relative to the mean of the conventional systems, corn yields were reduced by 13 and 33% in the OAM and OFG systems, respectively. Similarly, sorghum yields in the OAM and OFG systems were reduced by 16 and 27%, respectively. Soybean yields were 20% greater in the conventional systems compared with the OAM system. However, wheat yields were 10% greater in the OAM system compared with the conventional DIR system and 23% greater than yield in the OFG system. Alfalfa in the OFG system yielded an average of 7.41 Mg ha−1annually. Competitive yields of organic wheat and alfalfa along with the soil fertility benefits associated with animal manure and perennial forage suggest that aspects of the two organic systems be combined to maximize the productivity and sustainability of organic cropping systems.
A parameterization of the ice‐ocean drag coefficient
Authors: Lu Peng , Li Zhijun , Cheng Bin , Leppäranta Matti
Published: July 2011

A parameterization of the ice‐ocean drag coefficient (Cw) was developed through partitioning the oceanic drag force into three components: (1) form drag on the floe edge, (2) form drag on the ridge keel, and (3) skin friction on the ice bottom. Through these quantities, Cw was expressed as a function of observable sea ice geometric parameters. Sensitivity studies were carried out to investigate the influence of varying sea ice conditions on Cw. The results revealed that Cw increases first and then decreases with increasing ice concentration (A), similar to the observations of the air‐ice drag coefficient, and which is mainly attributed to the nonmonotonic variation of the form drag on the floe edge with ice concentration. Moreover, the form drag on the floe edge is always the dominant component, having a proportion of more than 60% in sea ice with a large aspect ratio (draft/length ≥ 1/100), indicating the necessity of including this term in sea ice dynamic models, particularly for the marginal ice zone (MIZ). The form drag on the ridge keel becomes dominant only when the ridging intensity is extremely high (depth/spacing ≥ 1/20). Additionally, a large value of Cw cannot be caused only by the inclusion of form drag terms but also by large skin friction over rough ice bottoms. Finally, for typical situations in the MIZ with moderate ridging intensity, the parameterization will underestimate Cw by approximately 30% for a rough ice bottom and by over 80% for a smooth ice bottom if no form drags are considered.
Exact analytical solutions for a diffusion problem coupled with a precipitation‐dissolution reaction and feedback of porosity change
Authors: Hayek Mohamed , Kosakowski Georg , Churakov Sergey
Published: July 2011

We present exact analytical solutions for a one‐dimensional diffusion problem coupled with the precipitation‐dissolution reaction and feedback of porosity change. The solutions are obtained in the form of traveling waves and describe spatial and temporal evolutions of solute concentration, porosity, and mineral distribution for a set of initial and boundary conditions. The form of the solutions limits the choice of admissible boundary conditions, which might be difficult to adapt in natural systems, and thus, the solutions are of limited use for such a system. The main application of the derived solutions is therefore the benchmarking of numerical reactive transport codes for systems with strong porosity change. To test the performance of numerical codes, numerical solutions obtained by using a global implicit finite volume technique are compared to the analytical solutions. Good agreement is obtained between the analytical solutions and the numerical solutions when a sufficient spatial discretization resolves the spatial concentration gradients at any time. In the limit of fast kinetics (local equilibrium), steep concentration fronts cannot be resolved in a numerical discretization schema.
Spatial and temporal coherence between Amazon River discharge, salinity, and light absorption by colored organic carbon in western tropical Atlantic surface waters
Authors: Salisbury J. , Vandemark D. , Campbell J. , Hunt C. , Wisser D. , Reul N. , Chapron B.
Published: July 2011

The temporal evolution and spatial distribution of surface salinity and colored detrital matter (cdm) were evaluated within and adjacent to the Amazon River Plume. Study objectives were as follows: first, to document the spatial coherence between Amazon discharge, salinity, cdm, and the nature of the salinity‐cdm relationship; second, to document the temporal and spatial variability of cdm along the trajectory of the low‐salinity Amazon Plume, and third, to explore the departure of cdm from conservative mixing behavior along the plume trajectory into the open ocean. Time series (2003–2007) of surface salinity estimated using the Advanced Microwave Scanning Radiometer–Earth Observing System and corresponding satellite cdm absorption (acdm) data documented a plume of freshened, colored water emanating from the Amazon. Salinity and acdm were generally coherent, but there were regions in which spatial patterns of salinity and acdm did not coincide. Salinity was oppositely phased with discharge, whereas acdm was in phase but lagged discharge and typically remained high after maximum discharge. Along the river plume trajectory, acdm was inversely correlated with salinity, yet there was considerable deviation from conservative mixing behavior during all seasons. Positive anomalies in a linear relationship between salinity and acdm corresponded to areas of enhanced satellite‐retrieved net primary productivity, suggesting the importance of phytoplankton biomass or its subsequent remineralization as a source of cdm. Negative anomalies tended to predominate at the distal sections of the plume trajectories, an observation consistent with the process of photo‐oxidation of cdm over observed time scales of days to weeks.
Signal-transduction protein PII from Synechococcus elongatus PCC 7942 senses low adenylate energy charge in vitro
Authors: Fokina Oleksandra , Herrmann Christina , Forchhammer Karl
Published: July 2011

PII proteins belong to a family of highly conserved signal-transduction proteins that occurs widely in bacteria, archaea and plants. They respond to the central metabolites ATP, ADP and 2-OG (2-oxoglutarate), and control enzymes, transcription factors and transport proteins involved in nitrogen metabolism. In the present study, we examined the effect of ADP on in vitro PII-signalling properties for the cyanobacterium Synechococcus elongatus, a model for oxygenic phototrophic organisms. Different ADP/ATP ratios strongly affected the properties of PII signalling. Increasing ADP antagonized the binding of 2-OG and directly affected the interactions of PII with its target proteins. The resulting PII-signalling properties indicate that, in mixtures of ADP and ATP, PII trimers are occupied by mixtures of adenylate nucleotides. Binding and kinetic activation of NAGK (N-acetyl-L-glutamate kinase), the controlling enzyme of arginine biosynthesis, by PII was weakened by ADP, but relief from arginine inhibition remained unaffected. On the other hand, ADP enhanced the binding of PII to PipX, a co-activator of the transcription factor NtcA and, furthermore, antagonized the inhibitory effect of 2-OG on PII–PipX interaction. These results indicate that S. elongatus PII directly senses the adenylate energy charge, resulting in target-dependent differential modification of the PII-signalling properties.
Measurement of electron density with the phase-resolved cut-off probe method
Authors: Kwon J. H. , You S. J. , Kim D. W. , Na B. K. , Kim J. H. , Shin Y. H.
Published: July 2011

The phase resolved cut-off probe method, a precise measurement method for the electron density, was recently proposed [J. H. Kwon et al., Appl. Phys. Lett. 96, 081502 (2010)]. This paper presents the measurements of electron density using the method under various experimental conditions (different pressures, powers, chamber volumes, and discharge sources). The result shows that the method is not only in good agreement with the previous method using wave transmittance under various experimental conditions but it is also able to find the cut-off point clearly even under difficult conditions such as high pressure (∼ 1 Torr), high discharge power, and small plasma volume. The details of the experimental setup, the operating mechanism of the probe method, and the data processing procedure (algorithm) are also addressed. Furthermore, the reliability of the measurement method is investigated by using an electromagnetic field simulation with cold plasma model (CST-Drude model, Computer Simulation Technology).
Suppression of multipactor discharge on a dielectric surface by an external magnetic field
Authors: Cai Libing , Wang Jianguo , Zhu Xiangqin , Wang Yue , Xuan Chun , Xia Hongfu
Published: July 2011

The multipactor discharge on a dielectric surface in an external magnetic field is simulated by using the particle-in-cell method, and the electron number, energy, the velocity of the yield of secondary electrons, and the power deposited on dielectric surface in the process of multipactor discharge are investigated. The effects of the strength of the external magnetic field on multipactor are studied. The results show that when the external magnetic field reaches a certain value, the multipactor is weaker than that in the case of no external magnetic field and becomes much lighter versus the strength of the external magnetic field in the half microwave period in which the E×B drift pulls the electrons back to dielectric surface. And in the other half microwave period in which the E×B drift pushes the electrons away from the dielectric surface, the multipactor is cut off. So the power capability can be increased to the fourfold by the suppression of multipactor by applying an external magnetic field.
Piezoelectricity in wurtzite polar semiconductor nanowires: A theoretical study
Authors: Sen Banani , Stroscio Michael , Dutta Mitra
Published: July 2011

By considering acoustic phonon mode displacements in nanowires, the piezoelectrically induced electric polarization vector and the associated potential are calculated. For the case of charge-free semiconductor nanowires, the piezo energies generated by strains applied in different directions are compared. For the directions considered, it is found that the maximum piezo energy in these nanowires is generated for strain applied in the vertical direction (i.e., along z-axis). Moreover, for these nanowires, energy generation in AlN and ZnO are found to be superior to GaN, just as expected based on past treatments of nanowires using phonons of bulk structures.
Large deviations for disordered bosons and multiple orthogonal polynomial ensembles
Authors: Eichelsbacher Peter , Sommerauer Jens , Stolz Michael
Published: July 2011

We prove a large deviations principle for the empirical measures of a class of biorthogonal and multiple orthogonal polynomial ensembles that includes biorthogonal Laguerre, Jacobi, and Hermite ensembles, the matrix model of Lueck, Sommers, and Zirnbauer for disordered bosons, the Stieltjes-Wigert matrix model of Chern-Simons theory, and Angelesco ensembles.
Forced instability of core-annular flow in capillary constrictions
Authors: Beresnev Igor , Gaul William , Vigil R. Dennis
Published: July 2011

Instability of fluid cylinders and jets, a highly nonlinear hydrodynamic phenomenon, has fascinated researchers for nearly 150 years. A subset of the phenomenon is the core-annular flow, in which a non-wetting core fluid and a surrounding wall-wetting annulus flow through a solid channel. The model, for example, represents the flow of oil in petroleum reservoirs. The flow may be forced to break up when passing through a channel’s constriction. Although it has long been observed that the breakup occurs near the neck of the constriction, the exact conditions for the occurrence of the forced breakup and its dynamic theory have not been understood. Here, we test a simple geometric conjecture that the fluid will always break in the constrictions of all channels with sufficiently long wavelengths, regardless of the fluid properties. We also test a theory of the phenomenon. Four constricted glass tubes were fabricated above and below the critical wavelength required for the fluid disintegration. In a direct laboratory experiment, the breakup occurred according to the conjecture: the fluids were continuous in the shorter tubes but disintegrated in the longer tubes. The evolution of the interface to its pinch-off was recorded using high-speed digital photography. The experimentally observed core-annulus interface profiles agreed well with the theory, although the total durations of the process agreed less satisfactorily. Nonetheless, as the theory predicts, the ratio between the experimental and theoretical times of the breakup process tends to one with decreasing capillary number. The breakup condition and the dynamic theory of fluid disintegration in constricted channels can serve as quantitative models of this important natural and technical phenomenon.
Vibrational properties between silver (4,4) nanotube and nanowire
Authors: Yang Aping , Fa Wei , Li Xiaowei , Dong Jinming
Published: July 2011

The geometrical structures and vibrational spectra of both the (4,4) single-walled silver nanotube and the stretched one-lattice-parameter-wide fcc Ag nanowire, found in a recent experiment [Nature Nanotechnology 4, 149 (2009)], have been investigated by the density-functional theory calculations within the generalized gradient approximation. It is found that there exist main differences between their vibrational spectra and corresponding Raman- and IR-active spectra. For example, 1) the Raman modes of the Ag tube span a wider frequency range than the Ag wire, and there is its characteristic radial breathing mode at 120 cm−1, in contrast to that of the Ag wire at 129 cm-1, showing also specifically different 1st-order resonant Raman spectra for both of them, which may be used for identifying accurately the Ag tube from the Ag wire in future experiment. 2) The IR modes of the (4,4) Ag tube span a narrower frequency range than the Ag wire, and its highest frequency IR mode lies at 168 cm−1, which is less than that of the stretched Ag wire, lying at about 182 cm−1.
Complex networks analysis of obstructive nephropathy data
Authors: Zanin M. , Boccaletti S.
Published: July 2011

Congenital obstructive nephropathy (ON) is one of the most frequent and complex diseases affecting children, characterized by an abnormal flux of the urine, due to a partial or complete obstruction of the urinary tract; as a consequence, urine may accumulate in the kidney and disturb the normal operation of the organ. Despite important advances, pathological mechanisms are not yet fully understood. In this contribution, the topology of complex networks, based on vectors of features of control and ON subjects, is related with the severity of the pathology. Nodes in these networks represent genetic and metabolic profiles, while connections between them indicate an abnormal relation between their expressions. Resulting topologies allow discriminating ON subjects and detecting which genetic or metabolic elements are responsible for the malfunction.
Field-induced alignment of the nematic director: Studies of nuclear magnetic resonance spectral oscillations in the limit of fast director rotation
Authors: Kantola A. M. , Luckhurst G. R. , Sugimura A. , Tanaka T. , Timimi B. A.
Published: July 2011

Time-resolved NMR spectroscopy is a powerful method to investigate field-induced rotation of the director in a nematic liquid crystal. The method requires that the director does not rotate significantly during the acquisition of the free induction decay and hence the NMR spectrum. We have extended the method to systems where this is not the case and the observed NMR spectra are now found to contain novel oscillatory features. To understand these oscillations, we have developed a model combining both director and spin dynamics. In addition to increasing the information content of the time-resolved NMR spectra, it also proves possible to determine the field-induced relaxation time from a single spectrum.
Influence of defects on structural and electrical properties of VO2 thin films
Authors: Chen Changhong , Zhao Yong , Pan Xuan , Kuryatkov V. , Bernussi A. , Holtz M. , Fan Zhaoyang
Published: July 2011

We present the structural and electrical properties of (011) preferred polycrystalline (Poly) and multidomain (020) epitaxial (Epi) VO2 thin films grown at different temperature (Ts) and on different substrates with variable defects. These defects cause variation in strain, metal-insulator transition (MIT) temperature (TMIT), activation energy (ΔEa), and charge carrier type in insulating phase. Both the Poly- and Epi-VO2 behave n-type conductivity when grown at relative low TS. As TS increases, defects related acceptor density increases to alter conductivity from n- to p-type in the Poly-VO2, while in the Epi-VO2 donor density increases to maintain n-type conductivity. Moreover, the strain along monoclinic am axis dramatically reverses from tensile to compressive in both the Poly- (848 K < TS < 873 K) and Epi-VO2 (873 K < TS < 898 K), and eventually approaches to a constant in the Poly-VO2 (TS ≥ 898 K) in particular. TMIT decreases with increasing the carrier density independent of the conductive type in the lightly doped Poly- and Epi-VO2; however, this trend is reversed in heavily doped n-type Epi-VO2 with a higher TMIT due to the formation of large quantity of small polarons related with V4+-V2+ pair. ΔEa is associated with the carrier density and thus the strain or strained interfacial layer thickness in the Poly- or Epi-VO2. The larger tensile strain or thicker strained layer leads to lower carrier density and higher ΔEa, while the constant strain produces saturated ΔEa.
Bilinear forms on skein modules and steps in Dyck paths
Authors: Cai Xuanting , Mansour Toufik
Published: July 2011

We use Jones-Wenzl idempotents to construct bases for the relative Kauffman bracket skein module of a square with n points colored 1 and one point colored h. We consider a natural bilinear form on this skein module. We calculate the determinant of the matrix for this form with respect to the natural basis. We reduce the computation to count some steps in generalized Dyck paths. Moreover, we relate our determinant to a determinant on semi-meanders.
Quasi-degenerate second-order perturbation theory for occupation restricted multiple active space self-consistent field reference functions
Authors: Roskop Luke , Gordon Mark S.
Published: July 2011

A multi-configuration quasi-degenerate second-order perturbation method based on the occupation restricted multiple active space (ORMAS-PT/ORMAS) reference wavefunction is presented. ORMAS gives one the ability to approximate a complete active space self-consistent field (CASSCF) wavefunction using only a subset of the configurations from the CASSCF space. The essential idea behind ORMAS-PT is to use the multi-reference Møller-Plesset formalism to correct the ORMAS reference energy. A computational scheme employing direct CI methodology is presented. Several tests are presented to demonstrate the performance of the ORMAS-PT method.
Polarizations of coupling kinetic Alfvén and slow waves
Authors: Chen L. , Wu D. J.
Published: July 2011

Kinetic Alfvén waves (KAWs) are dispersive Alfvén waves with short perpendicular wavelengths and have been extensively applied to various energization phenomena of plasma particles. KAWs are coupled to slow magnetosonic waves in the case of a finite-β plasma. In this paper, the electromagnetic polarization states of the coupling KAWs and slow waves are investigated. The results show that the polarization states of these waves depend sensitively on the local plasma parameters such as the ion-electron temperature ratio (α=Ti/Te) and the plasma kinetic-magnetic pressure ratio (β=2μ0n(Ti+Te)/B2) as well as their perpendicular wavenumber (k⊥ρi). The polarization states of waves play an important and key role in wave-particle interactions and hence have a great interest of understanding the physics of particle energization phenomena by these waves.
How well do time-integrated Kα images represent hot electron spatial distributions?
Authors: Ovchinnikov V. M. , Kemp G. E. , Schumacher D. W. , Freeman R. R. , Van Woerkom L. D.
Published: July 2011

A computational study is described, which addresses how well spatially resolved time-integrated Kα images recorded in intense laser-plasma experiments correlate with the distribution of “hot” (>1 MeV) electrons as they propagate through the target. The hot electron angular distribution leaving the laser-plasma region is critically important for many applications such as Fast Ignition or laser based x-ray sources; and Kα images are commonly used as a diagnostic. It is found that Kα images can easily mislead due to refluxing and other effects. Using the particle-in-cell code LSP, it is shown that a Kα image is not solely determined by the initial population of forward directed hot electrons, but rather also depends upon “delayed” hot electrons, and in fact continues to evolve long after the end of the laser interaction. Of particular note, there is a population of hot electrons created during the laser-plasma interaction that acquire a velocity direction opposite that of the laser and subsequently reflux off the front surface of the target, deflect when they encounter magnetic fields in the laser-plasma region, and then traverse the target in a wide spatial distribution. These delayed fast electrons create significant features in the Kα time-integrated images. Electrons refluxing from the sides and the back of the target are also found to play a significant role in forming the final Kα image. The relative contribution of these processes is found to vary depending on depth within target. These effects make efforts to find simple correlations between Kα images and, for example, Fast Ignition relevant parameters prone to error. Suggestions for future target design are provided.
Triple-path collector optics for grazing incident x-ray emission spectrometer
Authors: Tokushima T. , Horikawa Y. , Shin S.
Published: July 2011

A new type of collector optics was developed for grazing incident x-ray emission spectrometer. The collector optics used two cylindrical mirrors to add two extra light paths while keeping the center light path that directly illuminates the grating. The design and properties of the spectrometer using the triple-path collector optics were evaluated using ray-tracing simulations, and validity of this design in terms of throughput and energy resolution was confirmed by the experimentally obtained spectra.
Photopyroelectric technique for the measurement of thermal and optical properties of pigments in liquid solution
Authors: Balderas-López J. A.
Published: July 2011

The analytical solution for the one-dimensional heat diffusion problem for a two-layer system, in the Beer-Lambert model for light absorption, is shown to be useful for the implementation of a novel photopyroelectric (PPE) methodology, for the measurement of thermal and optical properties for pigments in liquid solution. The PPE signal, as a function of the sample's thickness, is used for this goal. Exponential decay for the PPE amplitude, followed by a constant PPE phase, for solutions at low dye concentration and an exponential decay for the PPE amplitude but a linear PPE phase behavior for the higher concentrated ones are shown and are, respectively, used for the measurement of the optical absorption coefficient and thermal diffusivity for liquid samples. These PPE phase behaviors also provide a criterion to decide on the corresponding limit for optical and thermal properties measurement. This PPE methodology was tested by measuring the optical absorption coefficient (at 658 nm) and thermal diffusivity for solution of methylene blue and copper sulfate in distilled water at various concentrations. Independent measurements of optical properties, using a commercial spectrometer, were done to compare with the corresponding ones obtained with this PPE methodology, finding very good agreement to each other.
On the general variable-coefficient KP equation with self-consistent sources
Authors: Sun Ye-Peng , Tam Hon-Wah
Published: July 2011

A new general variable-coefficient KP equation with self-consistent sources and its Grammian solutions is obtained by using the source generation procedure. Moreover, by applying the Pfaffianization procedure, a new coupled variable-coefficient KP equation is constructed. Its Wronski-type Pfaffian solution and Gramm-type Pfaffian solution are given. At last, a new integrable system of the general variable-coefficient KP equation with self-consistent sources is established.
Note: High sensitivity pulsed electron spin resonance spectroscopy with induction detection
Authors: Twig Ygal , Dikarov Ekaterina , Hutchison Wayne D. , Blank Aharon
Published: July 2011

Commercial electron spin resonance spectroscopy and imaging systems make use of the so-called “induction” or “Faraday” detection, which is based on a radio frequency coil or a microwave resonator. The sensitivity of induction detection does not exceed ∼3 × 108 spins/√Hz. Here we show that through the use of a new type of surface loop-gap microresonators (inner size of 20 μm), operating at cryogenic temperatures at a field of 0.5 T, one can improve upon this sensitivity barrier by more than 2 orders of magnitude and reach spin sensitivities of ∼1.5 × 106 spins/√Hz or ∼2.5 × 104 spins for 1 h.
Effect of domain walls on the electrocaloric properties of Pb(Zr1−x,Tix)O3 thin films
Authors: Karthik J. , Martin L. W.
Published: July 2011

The electrocaloric properties of polydomain epitaxial Pb(Zr1-x,Tix)O3 thin films are investigated using a Ginzburg-Landau-Devonshire thermodynamic model as a function of strain, temperature, and composition for 0.65 ≤ x ≤ 1. Polarization transitions driven by epitaxial strain and extrinsic contributions from domain wall displacements are found to dramatically impact the electrocaloric response. Careful choice of epitaxial misfit strain and composition allows one to harness the intrinsic and extrinsic contributions to obtain large adiabatic temperature changes much below the Curie temperature of the material.
Contact resistance in top-gated graphene field-effect transistors
Authors: Huang Bo-Chao , Zhang Ming , Wang Yanjie , Woo Jason
Published: July 2011

The parasitic resistance of different source/drain metals for top-gated graphene field-effect transistors was extracted by fitting the measured ID-VG data with a resistance model and was found to be a significant part of the total resistance of graphene field-effect transistors. The results show that Ti/Au gives relatively large contact resistance, about 7500 Ω·μm. Ni/Au contact shows better result compared to Ti/Au, which is around 2100 Ω·μm. The lowest contact resistance was given by Ti/Pd/Au, which is around 750 Ω·μm. The contact resistivity for Ti/Pd/Au source/drain contact is around 2 × 10−6 Ω·cm2, close to state of the art GaAs technology.
The investigation of depoling mechanism of densified KNbO3 piezoelectric ceramic
Authors: Ge Haiyan , Hou Yudong , Rao Xue , Zhu Mankang , Wang Hao , Yan Hui
Published: July 2011

Thermal depoling phenomena determine the upper temperature limit of the piezoelectric ceramics in application. In this paper, high-densified KNbO3 ceramics derived from single-crystalline nanostructures exhibited favorable piezoelectric constants d33, which varied from 105 to 80 pC/N over a broad temperature range from 25 to 225 °C. In situ x-ray diffraction combined with Raman spectra demonstrate clearly the transition sequence of crystallographic orientations during thermal depoling process. The interaction between defect dipoles D and spontaneous polarization inside domains Ps favored to preserve piezoelectric activity, while the spontaneous rotation of Ps induced by the phase transition resulted in the deliquesce of d33.
On-chip silicon-based active photonic molecules by complete photonic bandgap light confinement
Authors: Qian Bo , Chen Kunji , Chen San , Li Wei , Zhang Xiangao , Xu Jun , Huang Xinfan , Pavesi Lorenzo , Jiang Chunping
Published: July 2011

We demonstrate an on-chip silicon-based active photonic molecule (PM) structures formed by two coupled photonic quantum dots with complete photonic bandgap (PBG) light confinement. The photonic quantum dots are grown by conformal deposition of amorphous silicon nitride multilayers on patterned substrates. A fine structure of the coupled optical modes in PMs has been observed which shows similarity to the electronic bonding (BN) and antibonding (ABN) states in a molecule.
Microwave coupled electron tunneling measurement of Co nanoparticles
Authors: Jiang W. , Birk F. Tijiwa , Davidović D.
Published: July 2011

We study electron tunneling through Co nanoparticles in the presence of repeated microwave pulses at 4.2 K. While individual pulses are too weak to affect the magnetic switching field, repeated microwave pulses start to reduce the magnetic switching field at 10 μs spacing. We use I-V curve as a thermometer to show that the microwave pulses do not heat the sample, showing that magnetization in Co nanoparticles is directly excited by microwave pulses, and the relaxation time of the excitation energy is in the range of microsecond.