bluuebunny/crossref_metadata_2025 huggingface dataset:
Site‐specific pseudophosphorylation modulates the rate of tau filament dissociation
Authors: Necula Mihaela , Kuret Jeff
Published: February 2005

Hyperphosphorylation of tau is of fundamental importance for neurofibrillary lesion development in Alzheimer's disease, but the mechanisms through which it acts are not clear. Experiments with pseudophosphorylation mutants of full‐length tau protein indicate that incorporation of negative charge into specific sites can modulate the aggregation reaction, and that this occurs by altering the critical concentration of assembly. Here, the kinetic origin of this effect was determined using quantitative electron microscopy methods and pseudophosphorylation mutant T212E in a full‐length four‐repeat tau background. On the basis of disaggregation rates, decreases in critical concentration resulted primarily from decreases in the dissociation rate constant. The results suggest a mechanism through which site‐specific posttranslational modifications can modulate filament accumulation at low free intracellular tau concentrations.
An ecosystem element added to the assessment of Norwegian spring-spawning herring: implementing predation by minke whales
Authors: Tjelmeland Sigurd , Lindstrøm Ulf
Published: February 2005

Predation by minke whales is incorporated in the assessment model of the Norwegian spring-spawning herring stock (SeaStar) used by the ICES Working Group. Three assessment scenarios are performed and evaluated: (1) Default historic assessment where the natural mortality (M) is fixed, (2) assessment where natural mortality is estimated both for adult and juvenile herring, (3) assessment where consumption by minke whales is modelled and the predation and residual natural mortalities are estimated. The annual consumption of juvenile herring in the Barents Sea is estimated exogenously using diet data and a bioenergetic model. The estimated consumption is included in the objective function and the parameters determining the modelled consumption are estimated together with other free parameters of the model in a single operation. The estimated total natural mortality of juvenile herring is lower than the value assumed by the working group (M = 0.9) when either minke whales are included in the model (M = 0.49) or the parameter is estimated directly (M = 0.48). Assessment 3 generates 19% and 34% lower adult and juvenile stock sizes, respectively, than assessment 1, whereas assessments 2 and 3 generate relatively similar stock size estimates. The predation mortality constituted 45% and 10% of the total natural mortality of adult (M = 0.15) and juvenile herring (M = 0.49), respectively.
The Architecture of Control: a Chinese Strategy for e-Governance
Authors: KLUVER RANDOLPH
Published: February 2005

The rapid development of the Peoples' Republic of China has put increasing strains on an overwhelmed administrative and bureaucratic structure that was already hobbled by persistent inefficiency and corruption. In addition to anti-corruption and professionalization campaigns, the government has devised a system of e-governance with the goal of adding stability and order to a chaotic governing process. This includes re-establishing the control of the governing authorities, including improving the quality of surveillance and data gathering and hence policy-making; the elimination of corruption; and ultimately, the re-legitimation of the Communist Party of China. This paper discusses the critical administrative and political problems facing the government, demonstrates ways in which e-government has been designed to meet these, and discusses the problems presented by a reliance on e-government in a developing country.
Models of Improving e-Governance by Back Office Re-Organisation and Integration
Authors: WESTHOLM HILMAR
Published: February 2005

Good service delivery for the users and efficient provision of the services in the back offices is a crucial objective of public administration. The article examines how governance among the different entities in the back offices of service production affects their interoperability and what the main conditions are to improve their integration and service delivery to citizens and companies as users. In a comparative study of back offices in public administrations in 17 European States three innovative strategies or ‘models’ were explored which can lead to improved integration of back offices jointly involved in the production of a specific service. This approach understands different solutions in different countries as functional equivalents. It takes into account that governance structures between entities of the different sectors of the governance triangle are historically grown and therefore cannot simply be copied from one state to another. It also provides leeway for political actors to look for the strategy that fits best their specific socio-political environment.
Shaping the Web of Civic Participation: Civil Society Websites in Eastern Europe
Authors: BRUSZT LÁSZLÓ , VEDRES BALÁZS , STARK DAVID
Published: February 2005

To study technologies of political participation in the era of internet we examine how civic associations in Eastern Europe create socio-technical platforms of civic participation. The creation of socio-technical platforms combines specific technological features with actors and types of acts. Based on data we collected on 1,585 East European civil society websites we identify five emergent genres of online platforms of civic participation: newsletters, interactive platforms, multilingual solicitations, directories, and brochures. In contrast to the utopistic image of a de-territorialized, participatory global civil society shaped by the new technology, our examination of civil society websites finds that the transnational are not inclined to be participatory and the participatory are less likely to be transnational.
A Global Diffusion Model of e-Governance
Authors: ROSE RICHARD
Published: February 2005

The extent to which e-governance develops in a country is a function of the collective national and local capital supplying IT services and of informal social and human capital creating a demand for e-governance. Supply requires public officials and citizens to have access to the Internet and access varies enormously according to a country's modern resources and political openness. But the characterization of these differences as a digital divide is misleadingly static. A diffusion model of Internet access shows that it is more realistic to think of cross-national differences in terms of leading and lagging countries; in this model laggards have the potential to catch up with leaders. Differences in the capacity of countries to supply standard e-government services are a consequence of its degree of modern resources and to supply e-participation facilities reflects its political openness and extent of corruption. In countries with a high degree of modern resources and a majority of adults on line, digital choice creates limits as well as opportunities for e-governance, since most non-users of the Internet are older people who see no need for going on line. Among those on line a majority prefer to contact local and central government by traditional means, such as telephone or writing a letter. In the most modern and open societies the diffusion of the Internet is most likely to promote government efficiency and the virtual linkage of disparate public agencies serving the same client. In developing countries it will be one more pressure to reduce corruption and increase bureaucratization and in relatively closed regimes it can threaten destabilization by strengthening dissident mobilization within and across national borders. Globally, the diffusion process will promote openness in ‘intermestic’ public policies that involve both national and trans-national politics. It will also reduce the proportion of native English-speakers and increase bilingual and bicultural Internet users.
Styles of coping and social support in a cohort of adults with congenital heart disease
Authors: van Rijen Elisabeth H. M. , Utens Elisabeth M. W. J. , Roos-Hesselink Jolien W. , Meijboom Folkert J. , van Domburg Ron T. , Roelandt Jos R. T. C. , Bogers Ad J. J. C. , Verhulst Frank C.
Published: February 2005

Objective:To determine styles of coping, that is personal ways of dealing with problems, and social support, or support from the social environment, in a cohort of adults with congenital heart disease.Methods:We subjected 362 patients with congenital heart disease, aged from 20 to 46 years, belonging to five diagnostic groups, to extensive medical and psychological examination from 20 to 33 years after their first open heart surgical procedure. During psychological examination, 342 patients filled in questionnaires concerning styles of coping, specifically the Utrecht Coping List, and social support, using the Social Support List.Results:Overall, styles of coping in the total sample are comparable to those of peers in the general population, except for lower active problem solving, which can be attributed to female patients. Males with congenital heart disease showed more favourable styles of coping compared to their peers, such as higher seeking of social support, lower passive reaction patterns, and lower expression of negative emotions. Compared to the reference group, the total cohort of patients reported to receive less social support, but also to experience less discrepancies between desired and received social support, indicating feelings of independence in these adults. Females with congenital heart disease were found to seek and receive more social support compared to their male counterparts.Conclusion:Overall, few differences in styles of coping were found between the patients and their reference groups. Perceived social support in the sample of patients was favourable.
Psychological functioning in parents of children undergoing elective cardiac surgery
Authors: Wray Jo , Sensky Tom
Published: February 2005

Purpose: To assess levels of distress, the marital relationship, and styles of coping of parents of children with congenital heart disease, to evaluate any change in these parameters following elective cardiac surgery for their child, and to compare these parents with parents of children undergoing another form of hospital treatment, and with parents of healthy children.Design:A prospective study in which parents were assessed the day before the surgical procedure being undergone by their child, and 12 months afterwards.Participants:We assessed three groups of parents of 75 children, aged from birth to 16.9 years. The first was a group whose children were undergoing surgery because of congenital heart disease, the second was a group whose children were undergoing transplantation of bone marrow, and the third was a group whose children were healthy. Measures used for assessment included the General Health Questionnaire, the Dyadic adjustment scale, and the Utrecht coping list.Results:Parents in both groups of children undergoing surgery had significantly higher rates of distress prior to the surgical procedures than did the parents of the healthy children, but within those whose children were undergoing cardiac surgery, there were no differences between parents of children with cyanotic and acyanotic lesions. Following treatment, there was a significant reduction in the levels of distress in both groups whose children had undergone surgery. There were few differences between any of the groups on the other parameters, and the evaluated indexes showed stability over time.Conclusion:Despite elevated levels of psychological distress prior to surgical procedures, which had fallen after one year, the stability of other parameters of parental functioning over time suggests that the surgical interventions are of less significance than either factors attributable to the presence of chronic illness, or the individual characteristics of the parents.
Childhood angina due to congenital atresia of the coronary sinus
Authors: Suarez William A. , Sundararaghavan Sreekanthan , Bove Edward
Published: February 2005

A young child with exertional chest pain, and an electrocardiographic pattern suggesting reversible ischaemia of the anterior ventricular wall documented by Cardiolyte stress-testing, underwent cardiac catheterization and selective coronary angiography. Although the coronary arteries were entirely normal, the recirculation phase demonstrated marked dilation of the coronary sinus, with atresia of its mouth. At surgery, the patient was confirmed to have muscular atresia at the mouth of the coronary sinus, and underwent unroofing of the coronary sinus to the left atrium, with ligation of a persistent left superior caval vein. Post-operatively, the patient continued to have persistent chest pain, albeit without inducible ischaemia on stress-testing.
PHACES: a neurocutaneous syndrome with anomalies of the aorta and supraaortic vessels
Authors: Wendelin Gerald , Kitzmüller Erwin , Salzer-Muhar Ulrike
Published: February 2005

The acronym PHACES summarizes the most important manifestations of a rare neurocutaneous syndrome. Specifically, “P” accounts for malformation of the brain in the region of the posterior fossa, “H” stands for haemangiomas, “A” is for arterial anomalies, and “C” is for coarctation of the aorta along with cardiac defects, “E” is for abnormalities of the eye, and “S” for clefting of the sternum, and/or a supraumbilical abdominal raphe. Our objective is to introduce the syndrome to paediatric cardiologists. Our patient has stenosis of the aortic arch, multiple malformations of the great vessels arising from the aortic arch, intracranial vascular abnormalities, a sternal malformation with a supraumbilical raphe, and facial haemangiomas. We stress that it is important always to consider the existence of this syndrome in all patients with facial haemangiomas.
Restenosis after aortic stenting
Authors: Mookerjee Joydeep , Roebuck Derek , Derrick Graham
Published: February 2005

Aortic coarctation is a recognized arteriopathy in patients with Williams’ syndrome. We present an adolescent with Williams’ syndrome who developed rapid restenosis after primary stenting of coarctation of the aorta. We believe such restenosis within the stent is due to a proliferative response of the abnormal aortic wall. Attention should be paid to the potential for restenosis during follow-up after stenting of aortic coarctation in patients with Williams’ syndrome.
Surgical treatment of an unusual atrial septal defect: the vestibular defect
Authors: Fukuda Toyoki , Kashima Ichiro , Yoshiba Shigeki
Published: February 2005

A 14-year-old female patient underwent surgical treatment of multiple atrial septal defects associated with unroofed coronary sinus and pulmonary valvar stenosis. One of the defects was that of the superior oval fossa and the other a large ellipsoidal defect positioned inferior to the inferior rim of the oval fossa. The patient underwent primary closure of the defects with a favorable result. To the best of our knowledge, this is the first surgical experience of an unusual atrial septal defect or the vestibular defect.
Black shale deposition on the northwest African Shelf during the Cenomanian/Turonian oceanic anoxic event: Climate coupling and global organic carbon burial
Authors: Kolonic Sadat , Wagner Thomas , Forster Astrid , Sinninghe Damsté Jaap S. , Walsworth‐Bell Ben , Erba Elisabetta , Turgeon Steven , Brumsack Hans‐Jürgen , Chellai El Hassane , Tsikos Harilaos , Kuhnt Wolfgang , Kuypers Marcel M. M.
Published: February 2005

High‐resolution geochemical records from a depth transect through the Cenomanian/Turonian (C/T) Tarfaya Basin (northwest African Shelf) reveal high‐amplitude fluctuations in accumulation rates of organic carbon (OC), redox‐sensitive and sulphide‐forming trace metals, and biomarkers indicative of photic zone euxinia. These fluctuations are in general coeval and thus imply a strong relationship of OC burial and water column redox conditions. The pacing and regularity of the records and the absence of a prominent continental signature suggest a dynamic depositional setting linked to orbital and higher‐frequency forcing. Determining the dominant frequency depends on the definition of the most pronounced oceanic anoxic event (OAE2) and its duration. We propose that eccentricity is the main forcing factor at Tarfaya and controlled fluctuations in wind‐driven upwelling of nutrient‐rich, oxygen‐depleted intermediate waters from the adjacent Atlantic and the periodic development of photic zone and bottom water euxinia on the mid‐Cretaceous northwest African shelf. Accumulation records clearly identify the basin center as the primary site of sediment deposition with highest temporal variability and an up to six‐fold increase in OC burial from ∼2 g/m2 · yr prior to the OAE2 to ∼12 g/m2 · yr during the OAE2. Photic zone and bottom water euxinia alternated with periods of greater oxygenation of the water column in response to climate forcing. Mass balance calculations imply that ∼2% of the overall global excess OC burial associated with the OAE2 was deposited in the Tarfaya Basin, an area that represented only ∼0.05% of the total global C/T ocean floor. In fact, the lateral extent of similar black shales along the African continental margin indicates that this part of the ocean contributed significantly to the global increase in organic carbon burial during the OAE2.
Generalized Ohm's law in a 3‐D reconnection experiment
Authors: Cothran C. D. , Landreman M. , Brown M. R. , Matthaeus W. H.
Published: February 2005

We report the measurement of non‐ideal terms of the generalized Ohm's law at a reconnection site of a weakly collisional laboratory magnetohydrodynamic plasma. Results show that the Hall term dominates the measured terms; resistive and electron inertia terms are small. We suggest that electron pressure (not measured) supports the observed quasistatic reconnection rate, and that anomalous resistivity, while not ruled out, is not required to account for the results.
Dynamics of the Jovian magnetosphere for northward interplanetary magnetic field (IMF)
Authors: Fukazawa Keiichiro , Ogino Tatsuki , Walker Raymond J.
Published: February 2005

A massive rotating equatorial plasma sheet dominates Jupiter's magnetosphere and the solar wind and the interplanetary magnetic field (IMF) are not thought to be as important as at Earth. We simulated the Jovian magnetosphere for northward IMF starting from a steady state for southward IMF. About 46 hours after the northward IMF reached the dayside magnetopause reconnection started in the Jovian magnetotail and a plasmoid was launched tailward. This was followed by the formation and ejection of three more plasmoids. In each case the reconnection line (X‐line) moved tailward with the plasmoid. Magnetic flux tubes from the X‐line moved toward and around Jupiter ending up back in the plasma sheet where they were available for additional reconnection. A new reconnection line then formed, a plasmoid was ejected and the process repeated. These phenomena occurred with an average period of 34.3 hours.
Forty‐five years of observed soil moisture in the Ukraine: No summer desiccation (yet)
Authors: Robock Alan , Mu Mingquan , Vinnikov Konstantin , Trofimova Iryna V. , Adamenko Tatyjana I.
Published: February 2005

We present the longest data set of observed soil moisture available in the world, 45 yr of gravimetrically‐observed plant available soil moisture for the top 1 m of soil, observed every 10 days for April–October for 141 stations from fields with either winter or spring cereals from the Ukraine for 1958–2002. We averaged the summer observations over the entire region to account for the observed scale of soil moisture variations, to enhance the portion of the variance that is related to meteorological forcing. The observations show a positive soil moisture trend for the entire period of observation, with the trend leveling off in the last two decades. Although models of global warming predict summer desiccation in a greenhouse‐warmed world, there is no evidence for this in the observations yet, even though the region has been warming for the entire period. While the interannual variations of soil moisture simulated by both the European Centre for Medium‐range Weather Prediction and the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalyses are close to the observations, neither reanalysis simulates the observed upward trend. Climate model simulations for the period show the same general shape as the observations, but differ quite a bit from each other and from the observations. An observed downward trend in insolation may have produced a downward trend in evaporation and may have contributed to the upward soil moisture trend.
Vibrational and thermodynamic properties of MgSiO3 postperovskite
Authors: Tsuchiya Jun , Tsuchiya Taku , Wentzcovitch Renata M.
Published: February 2005

Phonon dispersions and vibrational density of states of MgSiO3 postperovskite, the new high‐pressure phase of MgSiO3 perovskite, are calculated as a function of pressure up to 180 GPa using density‐functional perturbation theory. The calculated frequencies are then used to determine the thermal contribution to the Helmholtz free energy within the quasi‐harmonic approximation. The equation of state and several thermodynamic properties of interest are derived and compared with those of perovskite. The overall thermodynamic properties of postperovskite are almost the same as those of perovskite under its stability conditions.
Resolution dependence of cross‐tropopause ozone transport over east Asia
Authors: Büker M. L. , Hitchman Matthew H. , Tripoli Gregory J. , Pierce R. B. , Browell E. V. , Avery M. A.
Published: February 2005

Detailed analysis of mesoscale transport of ozone across the tropopause over east Asia during the spring of 2001 is conducted using regional simulations with the University of Wisconsin Nonhydrostatic Modeling System (UWNMS), in situ flight data, and a new two‐scale approach to diagnosing this ozone flux. From late February to early April, synoptic activity regularly deformed the tropopause, leading to observations of ozone‐rich (concentration exceeding 80 ppbv) stratospheric intrusions and filaments at tropospheric altitudes. Since model resolution is generally not sufficient to capture detailed small‐scale mixing processes, an upper bound on the flux is proposed by assuming that there exists a dynamical division by spatial scale, above which the wind conservatively advects large‐scale structures, while below it the wind leads to irreversible transport through nonconservative random strain. A formulation for this diagnosis is given and applied to ozone flux across the dynamical tropopause. Simulations were chosen to correspond with DC‐8 flight 15 on 26–27 March over east Asia during the Transport and Chemical Evolution Over the Pacific (TRACE‐P) campaign. Local and domain‐averaged flux values using this method agree with other numerical and observational studies in similar synoptic environments. Sensitivity to numerical resolution, prescribed divisional spatial scale, and potential vorticity (PV) level is investigated. Divergent residual flow in regions of high ozone, and PV gradients tended to maximize flux magnitudes. We estimated the domain‐integrated flow of ozone out of the lowermost stratosphere to be about 0.127 Tg/day. Spectral analysis of the wind field lends support for utilization of this dynamical division in this methodology.
New records of Atlantic hurricanes from Spanish documentary sources
Authors: García‐Herrera Ricardo , Gimeno Luis , Ribera Pedro , Hernández Emiliano
Published: February 2005

Spanish historical documents from the Archivo General de Indias (General Archive of the Indies) have been used to identify Caribbean hurricanes and storms from the sixteenth to the nineteenth centuries. These sources provide previously unrecorded information on hurricanes useful to complete preexisting chronologies and cyclone tracks. Our work adds 10 hurricanes not previously identified, which can now be freely accessed through the World Wide Web. The results suggest that the seventeenth century may have been less active than the sixteenth and eighteenth centuries, with the most active period occurring between 1766 and 1780. Additionally, the study is the first compilation of information about storms (different from hurricanes) in the Caribbean basin.
Impact of cirrus crystal shape on solar spectral irradiance: A case study for subtropical cirrus
Authors: Wendisch Manfred , Pilewskie Peter , Pommier John , Howard Steve , Yang Ping , Heymsfield Andrew J. , Schmitt Carl G. , Baumgardner Darrel , Mayer Bernhard
Published: February 2005

Profiles of in situ measurements of ice crystal size distribution of subtropical cirrus were used to calculate solar spectral irradiances above and below the clouds. Spheres and nonspherical ice crystal habits (columns, hollows, plates, bullets, and aggregates) were assumed in the calculations. The simulation results were compared to irradiance measurements from the NASA Solar Spectral Flux Radiometer. The microphysical and radiation data were collected by three aircraft during CRYSTAL‐FACE. Two cirrus cases (optical thickness of about 1 and 7) from two mission dates (26 and 23 July 2002) were investigated in detail. The measured downwelling and upwelling irradiance spectra above the cirrus could mostly be reproduced by the radiation model to within ±5–10% for most ice crystal habits. Below the cirrus the simulations disagreed with the measured irradiances due to surface albedo variability along the flight track, and nonoptimal colocation between the microphysical and irradiance measurements. The impact of shape characteristics of the crystals was important for the reflected irradiances above the optically thin cirrus, especially for small solar zenith angles, because in this case single‐scattering dominated the solar radiation field. For the cirrus of moderate optical thickness the enhanced multiple scattering tended to diminish particular shape features caused by nonspherical single‐scattering. Within the ice absorption bands the shape‐related differences in the absorption characteristics of the individual nonspherical ice crystals were amplified if multiple scattering prevailed. Furthermore, it was found that below the cloud the shape sensitivity of the downwelling irradiance spectra is larger compared to the nonsphericity effects on reflected irradiances above the cirrus. Finally, it was shown that the calculated cirrus solar radiative forcing could vary by as much as 26% depending on the ice crystal habit.
Vapor Pressures, Critical Parameters, Boiling Points, and Triple Points of Ammonia and Trideuteroammonia
Authors: Xiang H. W.
Published: February 2005

A simple extended corresponding-states principle is used to represent the vapor pressure of ammonia and trideuteroammonia from the triple point to critical point and to describe the available experimental data along with extrapolation beyond their ranges of available experimental data. This work takes advantage of the adoption of the ITS-90 temperature scale and of the new critical parameters obtained from the extended corresponding-states principle. The vapor pressure data are described within their scatter in the entire temperature range. Comparisons with the available data show that the extended corresponding-states principle may calculate the vapor-pressure values within 0.05%–0.1% The substance-dependent characteristic parameters are given, such as critical temperature, critical density, critical pressure, acentric factor, and aspherical factor. The values of the pressures, along with their first and second derivatives as a function of temperature over the entire region from the triple point to the critical point are tabulated and recommended for scientific and practical uses.
Recommended Liquid–Liquid Equilibrium Data. Part 3. Alkylbenzene–Water Systems
Authors: Góral Marian , Wiśniewska-Gocłowska Barbara , Ma̧czyński Andrzej
Published: February 2005

The recommended liquid–liquid equilibrium (LLE) data for 21 binary alkylbenzene–water systems have been obtained after critical evaluation of all data (392 data sets) reported in the open literature up to the middle of 2003. An equation for prediction of the alkylbenzene solubilities was developed. The predicted alkylbenzene solubilities were used for calculation of water solubility in the second liquid phase. The LLE calculations were done with the equation of state appended with a chemical term proposed by Góral. The recommended data were presented in the form of individual pages containing tables, all the references, and optionally figures.
Estimation of the Heat Capacities of Organic Liquids as a Function of Temperature Using Group Additivity: An Amendment
Authors: Zábranský Milan , Růžička Vlastimil
Published: February 2005

An amendment to a second-order group additivity method for the estimation of the heat capacity of pure organic liquids as a function of temperature in the range from the melting temperature to the normal boiling temperature is reported. The temperature dependence of various group contributions and structural corrections is represented by a series of second order polynomial expressions. The group contribution parameters have been developed from an extended database of more than 1800 recommended heat capacity values. The present method should be more versatile and more accurate than the previous one [Růžička and Domalski, J. Phys. Chem. Ref. Data 22, 597, 619 (1993)] due to the use of a larger database and an improved procedure for parameter calculation.
Yang–Mills action from minimally coupled bosons on R4 and on the four-dimensional Moyal plane
Authors: Loikkanen Juha , Paufler Cornelius
Published: February 2005

We consider bosons on (Euclidean) R4 that are minimally coupled to an external Yang–Mills field. We compute the logarithmically divergent part of the cutoff regularized quantum effective action of this system. We confirm the known result that this term is proportional to the Yang–Mills action. We use pseudodifferential operator methods throughout to prepare the ground for a generalization of our calculation to the noncommutative four-dimensional Moyal plane Rθ4. We also include a detailed comparison of our cutoff regularization to heat kernel techniques. In the case of the noncommutative space, we complement the usual technique of asymptotic expansion in the momentum variable with operator theoretic arguments in order to keep separated quantum from noncommutativity effects. We show that the result from the commutative space R4 still holds if one replaces all pointwise products by the noncommutative Moyal product.
Universality of low-energy scattering in 2+1 dimensions: The nonsymmetric case
Authors: Khuri N. N. , Martin André , Sabatier Pierre C. , Wu Tai Tsun
Published: February 2005

For a very large class of potentials, V(x⃗),x⃗∊R2, we prove the universality of the low-energy scattering amplitude, f(k⃗′,k⃗). The result is f=π∕2(1∕logk)+o(1)∕[log(1∕k)]. The only exceptions occur if V happens to have a zero-energy bound state. Our new result includes as a special subclass the case of rotationally symmetric potentials, V(∣x⃗∣).
Study on boundary–boundary correlation functions of the two-dimensional Ising model using topological interaction method
Authors: Suzuki Masuo , Suzuki Hidenori , Chang Shu-Chiuan
Published: February 2005

The topological interaction method is applied to the evaluation of boundary–boundary correlation functions, which yield the square of the spontaneous magnetization mb at the boundary in the thermodynamic limit. One of the remarkable results is that the boundary–boundary correlation function CM is found to be nonmonotonic with respect to the system size M for T<Tc, because of boundary effects. On the other hand, it is monotonic above Tc, CM≃(A+(T)∕M)exp(−M∕ξ) with the correlation length ξ and with A+(T)∼T−Tc near the critical point Tc. At the critical point, CM∼1∕M, and below Tc, CM≃mb2+(−A−(T)M+B(T)+C(T)∕M)exp(−M∕ξ), where A−(T)∼mb3, B(T)∼mb2, C(T)∼mb∼T−Tc. Fisher’s finite-size scaling is confirmed in this respect.
Coupling or decoupling bed and flow dynamics: Fast and slow sediment waves at high Froude numbers
Authors: Colombini Marco , Stocchino Alessandro
Published: February 2005

The effect of coupling or decoupling bed and flow dynamics is analyzed in the framework of a linear analysis of the stability of a uniform, rotational, two-dimensional flow in an infinitely wide channel with a bed composed by incoherent sediments. It is shown that results obtained with the coupled analysis in term of instability of slow sediment waves of the dune/antidune kind are quite similar to the results obtained making use of the “quasisteady hypothesis,” which forms the basis of most of the existing linear stability analyses of bedforms and formally justifies the decoupling procedure. Small differences can be observed, for Froude numbers of O(1), in the surroundings of the marginal curves that bound the instability regions, mainly due to the removal of the artificial resonance that is introduced in the analysis when the quasisteady hypothesis is enforced. The decoupled approach, however, completely wipes out a mode of instability associated with fast-moving sediment waves, which appear at high Froude numbers in connection with the formation of roll waves on the free surface. This mode of instability, characterized by large wavelengths, is shown to coexist with the slower, shorter antidune mode.
Electron-beam-generated x rays from X pinches
Authors: Shelkovenko T. A. , Pikuz S. A. , Song B. M. , Chandler K. M. , Mitchell M. D. , Hammer D. A. , Ivanenkov G. V. , Mingaleev A. R. , Romanova V. M.
Published: February 2005

X pinches are well known to produce very small, dense plasma pinches (“micropinches”) that emit short bursts of 1.5–8keV radiation [Shelkovenko et al., Phys. Plasmas 9, 2165 (2002)]. X-ray radiation in the 8–100keV range is also emitted, only a small portion of which is associated with the micropinches. Beginning immediately after the soft x-ray burst, higher energy x-ray emission is observed that is attributed to energetic electrons accelerated in the gaps that appear in the X-pinch plasma structure. The temporal, spectral, and spatial properties of this higher energy radiation (8–100keV) have been studied using two ∼0.1μs pulsed power generators, one operating at up to 450kA peak current and the other up to 270kA. This radiation was also used for imaging in a low magnification configuration, and spatial resolution of a few tens of micrometers was demonstrated.
Collapse and merging of cavity regions in a granular material due to viscous flow
Authors: Kaneko Yoshifumi , Sano Osamu
Published: February 2005

Experimental studies are made on the collapse of macroscopic cavity regions placed in an otherwise homogeneous granular material due to viscous flow. First, an initially circular two-dimensional hole is exposed to a uniform flow at infinity and the process of boundary shape deformation due to locally enhanced stress components is clarified. Above a certain critical velocity, particles on the upstream-side boundary lose contact with neighboring ones, and are carried to the other side of the boundary. At the same time the fluidized region develops towards upstream direction in the granular material. A simple scaling law on the reduction of the void area is obtained. Second, attention is paid to the interaction of two circular cavities of equal radii, whose center-to-center distance and angle of attack are varied. In some configuration of cavities, lowering of the critical velocity of collapse is recognized. Successive processes on the collapse of upstream-side and downstream-side cavities are classified depending on the magnitude of velocity and the configuration of cavities. A possible scenario on the growth of global scale patterns in granular material such as water vein formation and landslides is suggested.
Controlling magnetic moment and its fluctuations in individual semimagnetic quantum dots with different exchange interactions
Authors: Dorozhkin P. S. , Kulakovskii V. D. , Chernenko A. V. , Brichkin A. S. , Ivanov S. V. , Toropov A. A.
Published: February 2005

The influence of exchange interaction between exciton and magnetic impurity spins on magnetic moment and its fluctuations in semimagnetic quantum dots has been investigated with the use of individual dot magnetophotoluminescence technique. In quantum dots with strong exchange interaction, both the polarization of magnetic ions and magnetic fluctuations in a dot are highly influenced by the formation of exciton magnetic polaron. In contrast, in the quantum dots with weak interaction, the localized exciton acts as a perfect noninvasive probe: it allows one to analyze the quantum-dot magnetic moment and its fluctuations with negligibly small influence on the dot magnetization. Numerical values of exchange magnetic field and magnetic polaron energy are obtained and analyzed for both types of dots.
Nondestructive characterization of dislocations and micropipes in high-resistivity 6H–SiC wafers by deep-level photoluminescence mapping
Authors: Tajima M. , Higashi E. , Hayashi T. , Kinoshita H. , Shiomi H.
Published: February 2005

We demonstrated the effectiveness of deep-level photoluminescence (PL) mapping for nondestructive detection of dislocations and micropipes in high-resistivity 6H–SiC wafers. PL spectra of the wafers at room temperature were dominated by a broad band with a peak at 1.3eV, which was traceable to the Si vacancy-related V1, V2, and V3 lines at 4.2K. The intensity-mapping pattern agreed closely with the etch-pit pattern both on a wafer scale and on a microscopic scale. Large dark spots with one or two bright cores, small dark spots, and dark lines corresponded to micropipes, threading screw dislocations, and edge dislocations forming small angle grain boundaries, respectively. The intensity reduction around dislocations and micropipes was attributed to a decrease of the radiative centers for the 1.3eV band, which occurred as a result either of the interaction between vacancies and dislocations or of the gettering effect of vacancy-related defects.
Visualization of electrons and holes localized in gate thin film of metal SiO2–Si3N4–SiO2 semiconductor-type flash memory using scanning nonlinear dielectric microscopy after writing-erasing cycling
Authors: Honda Koichiro , Hashimoto Sunao , Cho Yasuo
Published: February 2005

We applied scanning nonlinear dielectric microscopy and succeeded in clarifying the position of the electrons/holes in the gate SiO2–Si3N4–SiO2 (ONO) film of the metal-ONO-semiconductor-type flash memory after the write-erase cycling operation. The electrons were found in the Si3N4 part of the ONO film. The holes, on the other hand, were found in the Si3N4 film as well as at the bottom SiO2 film. We also showed that neither injected electrons nor injected holes accumulate during the write-erase cycling. This indicates that the remaining carrier in the ONO film is space charge and would not be expected to continue to increase infinitely with repeated injections and that most of the injected carriers would recombine with each other. After recombination, they exist separately and are electrically neutralized only.
Stability of fully deuterated amorphous silicon thin-film transistors
Authors: Lin Shufan , Flewitt Andrew J. , Milne William I. , Wehrspohn Ralf B. , Powell Martin J.
Published: February 2005

The threshold voltage stability of fully deuterated (a-Si:D) and hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) is compared. The difference in the kinetic energy of D+ and H+ ions upon impact with the growing surface during radio-frequency plasma-enhanced chemical vapor deposition leads to material having different physical properties for the same nominal deposition conditions. However, a-Si:D and a-Si:H grown at the same growth rate by adjusting the gas pressure have almost identical properties. By using the growth rate as a normalizing parameter for comparing a-Si:H and a-Si:D TFTs, it is shown that there is no difference in the stability of a-Si:D compared with a-Si:H TFTs. This study rules out the possibility of a giant isotopic effect in amorphous silicon TFTs, and supports the model for Si dangling bond defect creation in a-Si:H where the breaking of weak Si–Si bonds is the rate-limiting step.
Reorientation of the H2O cage studied by terahertz time-domain spectroscopy
Authors: Yu B. L. , Yang Y. , Zeng F. , Xin X. , Alfano R. R.
Published: February 2005

The terahertz absorption spectrum of a thin film of liquid H2O of ∼14μm thickness showed a clear absorption mode at 1.56THz(∼53cm−1). This mode is attributed to the bending motion of the intermolecular hydrogen-bond coordinate in a water cage. The dielectric relaxation times of a slow τ1∼9ps and a fast τ2∼0.2ps component (0.4–2.0THz) were determined using a double Debye dielectric model.
Optical and electrical properties of polycrystalline silicon–germanium thin films prepared by aluminum-induced layer exchange
Authors: Gjukic M. , Lechner R. , Buschbeck M. , Stutzmann M.
Published: February 2005

Large-grained polycrystalline silicon–germanium (poly-Si1−xGex) thin films have been obtained by the aluminum-induced layer exchange (ALILE) process. The optical and electrical properties of these layers have been investigated as a function of the alloy composition. Optical reflection spectra and Hall effect mobility measurements indicate a high structural quality of the recrystallized thin films, which is comparable to bulk crystalline silicon–germanium (c-Si1−xGex) samples prepared by more sophisticated methods. Due to the increasing solubility of aluminum as a substitutional shallow acceptor with increasing germanium content, the room temperature carrier density of holes is found to increase from 1.5×1018cm−3 in poly-Si to 5×1020cm−3 in poly-Ge produced by ALILE.
Fabrication and photoluminescence properties of porous CdSe
Authors: Tiginyanu I. M. , Monaico E. , Ursaki V. V. , Tezlevan V. E. , Boyd Robert W.
Published: February 2005

We report the results of a study of the growth of pores in n-CdSe single crystals using anodic etching techniques. Upon anodization in dark, a nonuniform distribution of pores was produced. However, anodic dissolution of the material under in situ UV illumination proves to result in uniform distribution of pores stretching perpendicularly to the initial surface of the specimen. The porous structures exhibit less luminescence than the bulk samples. These results pave the way for cost-effective manufacturing of CdSe-based semiconductor nanotemplates for nanofabrication.
Spatial and temporal variation in fish-assemblage structure in isolated waterholes during the 2001 dry season of an arid-zone floodplain river, Cooper Creek, Australia
Authors: Arthington Angela H. , Balcombe Stephen R. , Wilson Glenn A. , Thoms Martin C. , Marshall Jon
Published: February 2005

Spatial and temporal variation in fish-assemblage structure within isolated waterholes on the floodplains of Cooper Creek, Australia, was studied during the 2001 dry season, a period of natural drought in this arid-zone river. Spatial variation in fish-assemblage structure and the abundance of five species in disconnected waterholes early in the dry season (April 2001) were related to the extent of floodplain inundation 14 months previously, and to the interconnectedness of waterholes and waterhole habitat structure. As the dry season progressed, waterhole volumes decreased owing to evaporative water loss and structural habitat elements (anabranches, bars, boulders) became exposed. Marked changes in fish assemblage structure between the early (April) and late (September) dry season were related to habitat loss but not to water chemistry. Interactions between flow and habitat across a nested hierarchy of spatial scales (the floodplain, the waterhole and habitat patches within waterholes) were crucial to the persistence of fish assemblages through the 2001 dry season. We conclude that the magnitude, timing and frequency of floodplain inundation and natural variations in waterhole volume must be maintained if we wish to sustain the distinctive habitats and fish assemblages of this arid-zone floodplain river.
A universal plasmid library encoding all permutations of small interfering RNA
Authors: Chen Meihong , Zhang Lishu , Zhang Hong-Yan , Xiong Xiahui , Wang Bo , Du Quan , Lu Bing , Wahlestedt Claes , Liang Zicai
Published: February 2005

Small interfering RNA (siRNA) is normally designed to silence preselected known genes. Such selections are inevitably prone to bias as a result of limited knowledge about the biological process, transcript identity, and functions. A library that contains all permutations of siRNA could avoid such problems. In this paper, it is shown that 5 × 10
7
siRNA-encoding plasmids can be constructed in a single tube by using vectors with two mutated RNA polymerase III promoters arranged in a convergent manner. Such a library was used to carry out genomewide screening of functional genes in a phenotype-driven manner. Multiple siRNAs that induce a significant increase of cell proliferation speed were identified.
Convergent signaling by acidosis and receptor activator of NF-κB ligand (RANKL) on the calcium/calcineurin/NFAT pathway in osteoclasts
Authors: Komarova Svetlana V. , Pereverzev Alexey , Shum Jonathan W. , Sims Stephen M. , Dixon S. Jeffrey
Published: February 2005

Systemic acidosis has detrimental effects on the skeleton, and local acidosis coincides with bone destruction in inflammatory and metastatic diseases. Acidification dramatically enhances osteoclastic resorption, although the underlying mechanism has remained elusive. We investigated the effect of acidosis on the osteoclastogenic transcription factor NFATc1, which upon dephosphorylation translocates from the cytoplasm to nuclei. Lowering extracellular pH dramatically increased accumulation of NFATc1 in nuclei of rat and rabbit osteoclasts to levels comparable with those induced by the proresorptive cytokine receptor activator of NF-κB ligand (RANKL). Activation of NFATc1 by RANKL was mediated by means of prolonged stimulation of the Ca2+/calmodulin-dependent protein phosphatase, calcineurin. In contrast, NFATc1 activation by acidosis involved stimulation of calcineurin and suppression of NFATc1 inactivation. Acidosis, like RANKL, induced transient elevation of cytosolic free Ca2+concentration ([Ca2+]i), which persisted in Ca2+-free media and was abolished by inhibition of phospholipase C or depletion of intracellular Ca2+stores. Real-time-PCR of osteoclast-like cells generated from RAW 264.7 cells revealed high levels of expression of ovarian cancer G protein-coupled receptor 1, which links extracellular acidification to elevation of [Ca2+]i. In addition, the calcineurin inhibitor cyclosporin A suppressed the stimulatory effect of acidification on resorption, implicating NFAT in mediating the actions of acidosis on osteoclast activity. In summary, acidification and RANKL induce signals in osteoclasts that converge on the Ca2+/calcineurin/NFAT pathway. Acidosis acts directly on osteoclasts to activate NFATc1 and stimulate resorption.