bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal Scale and Qualitative Social Transformation at Chaco Canyon
Authors: Van Dyke Ruth M.
Published: February 2008

One of the strengths of the archaeological discipline is our ability to examine social transformations over the course of centuries or millennia. However, we rarely think about the ways in which temporal scale affects our interpretations of these processes. Transformative social changes look different when seen from the perspective of the longue durée, a human lifespan, or a single day. Although they clearly result from human actions, long-term, major social changes cannot be understood simply as additive concatenations of short-term shifts.
The Colour of Time: Head Pots and Temporal Convergences
Authors: Cobb Charles R. , Drake Eric
Published: February 2008

Colour symbolism permeated the world of indigenous North America. This symbolism was often tied to the cosmos where the earth was viewed as a quadrilateral disk and each of the four cardinal directions was linked with a colour array such as red, white, black, and blue. We suggest that the recurring use of certain colours and colour contrasts comprised a suite of long-term historical practices that were essential for reproducing certain views about the world and about being in the world. Further, the rendering of colour had a plasticity that allowed it to enter a discourse about daily life that was intertwined with notions of the long-term. As a case study, we focus on well-known ceramic head effigies in the central Mississippi Valley to argue that their veneers of contrasting red and white were imbued with a notion of time immemorial that converged with other conceptions of temporality, most importantly, a pressing concern with regional violence, personal safety, and spiritual integrity.
Time Reckoning and Memorials in Mesoamerica
Authors: Clark John E. , Colman Arlene
Published: February 2008

Mesoamerica was the time-place in the New World where the memory arts of writing and calendrical notation achieved their highest forms. Both had long histories going back at least to the first millennium bc and were part of an even longer and wider history of memorials and commemorations dating millennia earlier. In this essay we consider time and memorials as social constructs and forms of practice and provide data for sequential changes in both. As commonly deployed and materialized, history and memorials are about the evolving ‘now’ and future aspirations rather than a fixed past — but they are communicated by re-presenting supposed pasts. In Mesoamerica, the things remembered, the manner of remembering them, and the reasons for doing so evolved with changing social and political institutions and circumstances.
Neogene evolution of the mixed carbonate‐siliciclastic system in the Gulf of Papua, Papua New Guinea
Authors: Tcherepanov Evgueni N. , Droxler André W. , Lapointe Philippe , Dickens Gerald R. , Bentley Sam J. , Beaufort Luc , Peterson Larry C. , Daniell James , Opdyke Bradley N.
Published: February 2008

This paper outlines the evolution of the late Cenozoic mixed carbonate‐siliciclastic depositional system in the Gulf of Papua (GoP), using seismic, gravity, multibeam bathymetry, well data sets, and Landsat imagery. The deposition of the mixed sedimentary sequences was influenced by dynamic interplay of tectonics, eustasy, in situ carbonate production, and siliciclastic sediment supply. The roles of these major factors are estimated during different periods of the GoP margin evolution. The Cenozoic mixed system in the GoP formed in distinct phases. The first phase (Late Cretaceous–Paleocene) was mostly driven by tectonics. Rifting created grabens and uplifted structural blocks which served later as pedestals for carbonate edifices. Active neritic carbonate accumulation characterized the second phase (Eocene–middle Miocene). During this phase, mostly eustatic fluctuations controlled the large‐scale sedimentary geometries of the carbonate system. The third phase (late Miocene–early Pliocene) was characterized by extensive demise of the carbonate platforms in the central part of the study area, which can be triggered by one or combination of several factors, such as eustatic sea level fluctuations, increased tectonic subsidence, uplift, sudden influx of siliciclastics, or dramatic changes in environmental conditions and climate. The fourth phase (late Pliocene‐Holocene) was dominated by siliciclastics, which resulted in the burial of drowned and/or active carbonate platforms, although some platforms still remain alive until present‐day.
CO2 forcing induces semi‐direct effects with consequences for climate feedback interpretations
Authors: Andrews Timothy , Forster Piers M.
Published: February 2008

Climate forcing and feedbacks are diagnosed from seven slab‐ocean GCMs for 2 × CO2 using a regression method. Results are compared to those using conventional methodologies to derive a semi‐direct forcing due to tropospheric adjustment, analogous to the semi‐direct effect of absorbing aerosols. All models show a cloud semi‐direct effect, indicating a rapid cloud response to CO2; cloud typically decreases, enhancing the warming. Similarly there is evidence of semi‐direct effects from water‐vapour, lapse‐rate, ice and snow. Previous estimates of climate feedbacks are unlikely to have taken these semi‐direct effects into account and so misinterpret processes as feedbacks that depend only on the forcing, but not the global surface temperature. We show that the actual cloud feedback is smaller than what previous methods suggest and that a significant part of the cloud response and the large spread between previous model estimates of cloud feedback is due to the semi‐direct forcing.
Seasonal variations in hydrogen deposition to boreal forest soil in southern Finland
Authors: Lallo M. , Aalto T. , Laurila T. , Hatakka J.
Published: February 2008

In this study deposition velocity (vd) of atmospheric hydrogen to mineral and peat soils was measured in boreal forest environments in southern Finland using soil chamber measurement technique. vd was largest during the snow‐free season (0.04–0.07 cm/s) and smallest during winter (0–0.04 cm/s). Velocities decreased when soil temperature fell below 5°C, but deposition was observed also in near‐zero temperatures. Deposition velocities to organic soil forest floor were larger than to mineral soil, but it was unclear whether this was due to the effect of carbon or the effect on soil porosity. Fluxes to both mineral and peat soils had similar temperature and soil moisture responses. In very dry and moist conditions vd decreased rapidly. Optimum soil moisture ranged from about 6 to 50 % of water by volume. The magnitude of vd was similar at urban Helsinki and at rural Loppi sites.
Climatic and anthropogenic controls of topsoil features in the semi‐arid East Asian steppe
Authors: Liu Hongyan , Yin Yi , Tian Yuhong , Ren Ji , Wang Hongya
Published: February 2008

Topsoil characteristics and their determinants in the steppe on the central Inner Mongolian Plateau were investigated. Percentages of different grain size fractions of topsoil samples from 236 plots and corresponding standardized data of four environmental/human‐activity factors, namely mean annual temperature (MAT), mean annual precipitation (MAP), human disturbance index (HDI) and land use/land cover (LULC) types were used to perform canonical correspondence analysis (CCA). The roles of both human land uses and climatic factors on topsoil grain size distribution are highlighted. Climatic factors seem to have played a significant role in determining the coarse sand (0.2–1 mm in size) percentages in the steppe and meadow by affecting the vegetation cover, while human disturbance indicated by species composition appears to have significantly influenced the percentages of clay (<0.002 mm in size) and fine‐medium silt (0.002–0.016 mm in size) in the typical steppe (P < 0.01). Soil Organic Carbon (SOC) content is negatively correlated with coarse sand percentages (P < 0.01), implying that reduction of soil fertility is linked to soil coarsening. Percentages of fine‐medium silts (0.002–0.016 mm in size) are still more abundant in the area where artificial vegetation are planted and remains as the major source of dust storms. This study implies that afforestation in the steppe region has not improved soil conditions and thus reduced dust storms as earlier expected.
Reply to comment by Yannick Garcin on “Abrupt change in tropical African climate linked to the bipolar seesaw over the past 55,000 years”
Authors: Brown E. T. , Johnson T. C. , Scholz C. A. , Cohen A. S. , King J. W.
Published: February 2008

We welcome this opportunity for additional discussion of the Lake Malawi Drill Core record. We recognized early in this project that the Zr:Ti record shows a striking qualitative resemblance to records of interstadial DO events as preserved in Greenland [Brown et al., 2006]. However, additional radiocarbon constraints on the core's chronology, and the need for a mechanistically realistic interpretation of the record throughout MIS 2 and MIS 3 led us to the conclusion that peaks in the Malawi record (interpreted as southward ITCZ excursions) coincide with Greenland stadials [Brown et al., 2007]. Garcin [2008] has raised several concerns regarding our interpretation of Lake Malawi results from MIS 2 and MIS 3; these fall into five general categories:
The role of the tongue‐of‐ionization in the formation of the poleward wall of the main trough in the European post‐midnight sector
Authors: Middleton H. R. , Pryse S. E. , Wood A. G. , Balthazor R.
Published: February 2008

A series of radio tomography reconstructions from the University of Wales Aberystwyth receiver chains in Scandinavia and the UK, imaging the midnight‐dawn sector on 13 December 2001, reveal a persistent large‐scale electron density enhancement, which forms the poleward wall of the main ionization trough. Measurements by the European Incoherent Scatter radar (EISCAT) rule out in situ soft‐particle precipitation as the main source of the higher densities. SuperDARN plasma drift observations and electric potential patterns place the feature in the dawn cell of the high‐latitude convection, leading to the conclusion that the higher density is likely to have originated as photoionization and was convected over the polar cap to the nightside and around toward dawn in a tongue‐of‐ionization (TOI). Suitable runs of the Coupled Thermosphere‐Ionosphere‐Plasmasphere (CTIP) model support this interpretation and also reveal that the formation of the TOI is heavily UT dependent, which would lead to it being most prominent at nighttime in the European sector.
Antarctic sea ice parameters from AMSR‐E data using two techniques and comparisons with sea ice from SSM/I
Authors: Parkinson Claire L. , Comiso Josefino C.
Published: February 2008

Antarctic sea ice concentrations and extents, derived from the satellite passive microwave data of the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) are close but not identical depending on which of two major algorithms is used in the calculations. Overall, ice extents tend to be higher and ice concentrations lower when determined from the AMSR‐E bootstrap algorithm (ABA) than when determined from the enhanced NASA team (NT2) algorithm, although the differences are within the algorithm error bars. Both algorithms obtain similar negative slopes for the lines of linear least squares fit through the short (4.5‐year) AMSR‐E data record available so far. When the ABA results are compared with results from the bootstrap algorithm applied over the same time period to data from the Special Sensor Microwave Imager (SSM/I), the two bootstrap results, from different satellites and different instruments, match even more closely than the ABA versus NT2 results from the same AMSR‐E instrument. This is encouraging and is likely due to considerable effort to minimize the AMSR‐E versus SSM/I bootstrap differences, in consideration of extending the SSM/I record (which goes back to 1987) with the AMSR‐E results.
Deposition of CO2and erosion of the Martian south perennial cap between 1972 and 2004: Implications for current climate change
Authors: Piqueux Sylvain , Christensen Philip R.
Published: February 2008

We present a comparison of Mariner 9, Viking, Mars Orbiter Camera, and Mars Odyssey Thermal Emission Imaging System visible and infrared images of the south perennial cap taken during the summer between 1972 and 1977 and between 1999 and 2004. Between 1972 and 1977, the lateral expansion and the reduction of the patchiness of the cap indicate that CO2ice was deposited. During subsequent years, the distribution of the CO2ice has been modified by the erosion and deposition of CO2on the cap at the kilometer scale. Because vertical deposition of CO2on the cap is only detected when the patchiness decreases as observed between 1972 and 1977, present deposition on the cap would not be detectable and cannot be ruled out. Therefore the current lateral erosion of the walls of the CO2cap at the meter scale is not a sufficient observation to conclude that the climate is changing on Mars. The present mass balance of the cap cannot be estimated from available south polar cap images, and it is not possible to determine with the existing data if the climate of Mars is changing.
Coupled modelling of glacier and streamflow response to future climate scenarios
Authors: Stahl K. , Moore R. D. , Shea J. M. , Hutchinson D. , Cannon A. J.
Published: February 2008

This study investigated the sensitivity of streamflow to changes in climate and glacier cover for the Bridge River basin, British Columbia, using a semi‐distributed conceptual hydrological model coupled with a glacier response model. Mass balance data were used to constrain model parameters. Climate scenarios included a continuation of the current climate and two transient GCM scenarios with greenhouse gas forcing. Modelled glacier mass balance was used to re‐scale the glacier every decade using a volume‐area scaling relation. Glacier area and summer streamflow declined strongly even under the steady‐climate scenario, with the glacier retreating to a new equilibrium within 100 years. For the warming scenarios, glacier retreat continued with no evidence of reaching a new equilibrium. Uncertainty in parameters governing glacier melt produced uncertainty in future glacier retreat and streamflow response. Where mass balance information is not available to assist with calibration, model‐generated future scenarios will be subject to significant uncertainty.
Ribosomal proteins are targets for the NEDD8 pathway
Authors: Xirodimas Dimitris P , Sundqvist Anders , Nakamura Akihiro , Shen Linnan , Botting Catherine , Hay Ronald T
Published: February 2008

Identification of the molecular targets for post‐translational modifications is an important step for explaining the regulated pathways. The ubiquitin‐like molecule NEDD8 is implicated in the regulation of cell proliferation, viability and development. By combining proteomics and in vivo NEDDylation assays, we identified a subset of ribosomal proteins as novel targets for the NEDD8 pathway. We further show that the lack of NEDDylation in cells causes ribosomal protein instability. Our studies identify a novel and specific role of the NEDD8 pathway in protecting a subset of ribosomal proteins from destabilization.
Loss of intestinal crypt progenitor cells owing to inactivation of both Notch1 and Notch2 is accompanied by derepression of CDK inhibitors p27Kip1 and p57Kip2
Authors: Riccio Orbicia , van Gijn Marielle E , Bezdek April C , Pellegrinet Luca , van Es Johan H , Zimber‐Strobl Ursula , Strobl Lothar J , Honjo Tasuku , Clevers Hans , Radtke Freddy
Published: February 2008

The crucial role of individual Notch receptors and the mechanism by which they maintain intestinal crypt progenitor cells were assessed by using a series of inducible gut‐specific Notch mutant mice. We found that Notch1 and Notch2 receptors function redundantly in the gut, as only simultaneous loss of both receptors results in complete conversion of proliferating crypt progenitors into post‐mitotic goblet cells. This conversion correlates with the loss of Hes1 expression and derepression of the cyclin‐dependent kinase (CDK) inhibitors p27Kip1 and p57Kip2. We also found that the promoter of both CDK inhibitor genes is occupied by the Notch effector Hes1 in wild‐type crypt progenitor cells. Thus, our results indicate that Notch‐mediated Hes1 expression contributes to the maintenance of the proliferative crypt compartment of the small intestine by transcriptionally repressing two CDK inhibitors.
A high-current electron beam ion trap as a charge breeder for the reacceleration of rare isotopes at the NSCL (invited)
Authors: Schwarz S. , Bollen G. , Kostin M. , Marti F. , Zavodszky P. , Crespo López-Urrutia J. R. , Dilling J. , Kester O.
Published: February 2008

Reacceleration of low-energy rare isotope beams available from gas stopping of fast-fragment beams or from an ISOL target station to energies in the range of 0.3–12MeV/nucleon is needed for experiments such as low-energy Coulomb excitation and transfer reaction studies and for the precise study of astrophysical reactions. The implementation of charge breeding as a first step in a reaccelerator is a key to obtaining a compact and cost-efficient reacceleration scheme. For highest efficiency it is essential that single charge states are obtained in a short breeding time. A low-emittance beam must be delivered. An electron beam ion trap (EBIT) has the potential to meet these requirements. An EBIT-based charge breeder is presently under design and construction at the NSCL as part of the construction of a reaccelerator for stopped beams from projectile fragmentation. This new facility will have the potential to provide low-energy rare isotope beams not yet available elsewhere.
Beam characteristics of the new DESY H− source and investigations of the plasma load
Authors: Peters J. , Sahling H.-H. , Hansen I.
Published: February 2008

The new DESY H− source with a completely insulated plasma has been thoroughly investigated with emittance and beam profile measurements. The beam profile was measured with a multi-Faraday cup, and for the emittance measurements a slit and grid device was used. More than 200 beam profile and emittance measurements for x as well as y were done. Their dependences on rf power, filter field strength, and gas pressure were measured. The plasma load was investigated with a substitution method. It was possible to determine the real and imaginary parts which is seen by the rf antenna.
First experimental results from 2MeV proton tandem accelerator for neutron production
Authors: Kudryavtsev A. , Belchenko Yu. , Burdakov A. , Davydenko V. , Ivanov A. , Khilchenko A. , Konstantinov S. , Krivenko A. , Kuznetsov A. , Mekler K. , Sanin A. , Shirokov V. , Sorokin I. , Sulyaev Yu. , Tiunov M.
Published: February 2008

A 2MeV proton tandem accelerator with vacuum insulation was developed and first experiments are carried out in the Budker Institute of Nuclear Physics (Novosibirsk). The accelerator is designed for neutron production via reaction Li7(p,n)Be7 for the boron neutron-capture therapy of the brain tumors, and for explosive detection based on 9.1724MeV resonance gamma, which are produced via reaction C13(p,γ)N14, absorption in nitrogen.
Hydrophilic property by contact angle change of ion implanted polycarbonate
Authors: Lee Chan Young , Kil Jae Keun
Published: February 2008

In this study, ion implantation was performed onto a polymer, polycarbonate (PC), in order to investigate surface hydrophilic property through contact angle measurement. PC was irradiated with N, Ar, and Xe ions at the irradiation energy of 20–50keV and the dose range of 5×1015, 1×1016, 7×1016ions∕cm2. The contact angle of water was estimated by means of the sessile drop method and was reduced with increasing fluence and ion mass but increased with increasing implanted energy. The changes of chemical and structural properties are discussed in view of Furier transform infrared and x-ray photoelectron spectroscopy, which shows increasing CO bonding and CC bonding. The surface roughness examined by atomic force microscopy measurement changed smoothly from 3.59to2.22Å as the fluence increased. It is concluded that the change in wettability may be caused by surface carbonization and oxidation as well as surface roughness.
Simulation and beamline experiments for the superconducting electron cyclotron resonance ion source VENUS
Authors: Todd Damon S. , Leitner Daniela , Lyneis Claude M. , Grote David P.
Published: February 2008

The particle-in-cell code WARP has been enhanced to incorporate both two- and three-dimensional sheath extraction models giving WARP the capability of simulating entire ion beam transport systems including the extraction of beams from plasma sources. In this article, we describe a method of producing initial ion distributions for plasma extraction simulations in electron cyclotron resonance (ECR) ion sources based on experimentally measured sputtering on the source biased disk. Using this initialization method, we present preliminary results for extraction and transport simulations of an oxygen beam and compare them with experimental beam imaging on a quartz viewing plate for the superconducting ECR ion source VENUS.
Electron cyclotron resonance ion sources in use for heavy ion cancer therapy
Authors: Tinschert K. , Iannucci R. , Lang R.
Published: February 2008

The use of electron cyclotron resonance (ECR) ion sources for producing ion beams for heavy ion cancer therapy has been established for more than ten years. After the Heavy Ion Medical Accelerator (HIMAC) at Chiba, Japan started therapy of patients with carbon ions in 1994 the first carbon ion beam for patient treatment at the accelerator facility of GSI was delivered in 1997. ECR ion sources are the perfect tool for providing the required ion beams with good stability, high reliability, and easy maintenance after long operating periods. Various investigations were performed at GSI with different combinations of working gas and auxiliary gas to define the optimal beam conditions for an extended use of further ion species for the dedicated Heidelberg Ion Beam Therapy (HIT) facility installed at the Radiological University Hospital Heidelberg, Germany. Commercially available compact all permanent magnet ECR ion sources operated at 14.5GHz were chosen for this facility. Besides for C4+12 these ion sources are used to provide beams of H31+1, He1+3, and O6+16. The final commissioning at the HIT facility could be finished at the end of 2006.
Negative-ion source applications (invited)
Authors: Ishikawa J.
Published: February 2008

In this paper heavy negative-ion sources which we developed and their applications for materials science are reviewed. Heavy negative ions can be effectively produced by the ejection of a sputtered atom through the optimally cesiated surface of target with a low work function. Then, enough continuous negative-ion currents for materials-science applications can be obtained. We developed several kinds of sputter-type heavy negative-ion sources such as neutral- and ionized-alkaline metal bombardment-type heavy negative-ion source and rf-plasma sputter type. In the case where a negative ion is irradiated on a material surface, surface charging seldom takes place because incoming negative charge of the negative ion is well balanced with outgoing negative charge of the released secondary electron. In the negative-ion implantation into an insulator or insulated conductive material, high precision implantation processing with charge-up free properties can be achieved. Negative-ion implantation technique, therefore, can be applied to the following novel material processing systems: the surface modification of micrometer-sized powders, the nanoparticle formation in an insulator for the quantum devices, and the nerve cell growth manipulation by precise control of the biocompatibility of polymer surface. When a negative ion with low kinetic energy approaches the solid surface, the kinetic energy causes the interatomic bonding (kinetic bonding), and formation of a metastable material is promoted. Carbon films with high constituent of sp3 bonding, therefore, can be formed by carbon negative-ion beam deposition.
Compact 2.45GHz microwave ion/atom source
Authors: Sakamoto Y. , Kasuya T. , Wada M. , Maeno S.
Published: February 2008

Characteristics of a microwave driven 3.4cm diameter compact ion/atom source equipped with permanent magnets were tested. The source can be mounted to a standard copper gasket flange, and microwave power is supplied through an N-type microwave connector. The ion source plasma was observed through an ion extraction hole with an optical emission spectrometer. Peak height of an optical line spectrum emission corresponding to atomic nitrogen increased in proportion to the microwave input power. Quadrupole mass spectrometer showed that N+ and N2+ were the dominant species in the extracted ion beam. Nitrogen ion current density of 0.23mA∕cm2 was obtained with only 10W discharge power and 6×10−3Pa source surrounding pressure.
Deduction of edge electron density with multiply charged ions in ORNL volume-type electron cyclotron resonance ion source
Authors: You H.-J. , Woo H.-J. , Chung K.-S. , Liu Y. , Meyer F. W. , Lho T. , Lee M.-J.
Published: February 2008

The electron densities in the argon plasmas of the ORNL 6GHz electron cyclotron resonance (ECR) ion source with a flat central magnetic field have been deduced from the ion branches of the electric probe current-voltage curves measured in the edge region of the plasmas. To overcome the difficulties due to unknown velocities of multiply charged ions at the sheath edge, a modified generalized Bohm criterion for the ion sheath velocity is introduced and the mean velocity of all ionic charge states at the sheath edge is assumed to be equal to the sound velocity of the system of particles. The calculated electron densities and temperatures for different plasmas optimized for four charge state distributions are discussed.
Performance optimization of H− multicusp ion source for KIRAMS-30 cyclotron
Authors: Kang Kun Uk , An Dong Hyun , Chang Hong Suk , Chai Jong Seo
Published: February 2008

KIRAMS-30 cyclotron has been developed and implemented for radio isotope production. For the purpose of producing negative hydrogen ions and low energy beam injection to the central region of KIRAMS-30, 10mA H− multicusp ion source with beam kinetic energies in the 20–30keV range and the normalized 4rms emittance less than 1mm mrad was installed. The optimized ion source operating condition is presented and the correlation between the extracted beam current and ion source parameters is described for the performance enhancement of the ion source.
Ion source development at KVI
Authors: Beijers J. P. M. , Kremers H. R. , Mironov V. , Mulder J. , Saminathan S. , Brandenburg S.
Published: February 2008

Ion source development at KVI is focused on increasing the beam intensity from the electron cyclotron resonance ion source injector and optimizing the beam transport and injection into the superconducting AGOR cyclotron. We describe several modifications that have resulted in a significant performance increase of the ion source. We also present the first results of ion transport simulations that have been performed to better understand beam losses in the extraction region and in the low-energy beam transport system. Finally, a new emittance meter based on a combination of the pepperpot and scanning techniques will be described, which will be used to benchmark the simulation studies of ion extraction and transport in detail.
Development of a 1+∕N+ setup for the production of multicharged radioactive alkali ions in SPIRAL
Authors: Eléon C. , Gaubert G. , Jardin P. , Saint-Laurent M.-G. , Alcantara J. , Alvès Condé R. , Barué C. , Boilley D. , Cornell J. C. , Delahaye P. , Dubois M. , Jacquot B. , Leherissier P. , Leroy R. , Lhersonneau G. , Marie-Jeanne M. , Maunoury L. , Pacquet J.-Y. , Pellemoine F. , Pierret C. , Thomas J. C. , Villari A. C. C.
Published: February 2008

In the framework of the production of radioactive ion beams by the isotope separator online method, a new system has been developed at GANIL/SPIRAL I to produce multicharged alkali ions. The principle, referred to as the “direct 1+∕N+ method,” consists of a surface ionization source associated with a multicharged electron-cyclotron-resonance ion source without an intermediate mass separator. This new system has been tested online using a Ca48 primary beam at 60.3AMeV. The experimental evidence of the direct 1+∕N+ process has been obtained for a potential difference between the two sources of 11V and with a 1+∕N+ charge breeding efficiency of 0.04% for K5+47. This value is significantly lower than the value of 6% obtained for stable K ions with the standard 1+∕N+ method. A possible explanation is given in the text.
Understanding extraction and beam transport in the ISIS H− Penning surface plasma ion source
Authors: Faircloth D. C. , Letchford A. P. , Gabor C. , Whitehead M. O. , Wood T. , Jolly S. , Pozimski J. , Savage P. , Woods M.
Published: February 2008

The ISIS H− Penning surface plasma source has been developed to produce beam currents up to 70mA and pulse lengths up to 1.5ms at 50Hz. This paper details the investigation into beam extraction and beam transport in an attempt to understand the beam emittance and to try to improve the emittance. A scintillator profile measurement technique has been developed to assess the performance of different plasma electrode apertures, extraction electrode geometries, and postextraction acceleration configurations. This work shows that the present extraction, beam transport, and postacceleration system are suboptimal and further work is required to improve it.
Linear ion source with closed drift and extended acceleration region
Authors: Park Dong-Hee , Kim Ji-Hwan , Ermakov Yury , Choi Won-Kook
Published: February 2008

Ion source with closed drift, which is caused by E×B field, and extended acceleration region is discussed. Though conventional circular-type closed drift ion source has advantages of high efficiency of gas ionization and low ion beam energy, there is a limitation in enlarging the beam size. Linear ion source with horse-track shape with 270mm ceramic channel width is newly designed and tested. Inert gas (Ar) and reactive gas (O2) are discharged. Discharge is ignited with voltage of 90V. Discharge current is proportional to discharge voltage and increases up to 16.3A in argon and 15.6A in oxygen at discharge voltage of 320V. Extracted ion beam current is also proportional to discharge voltage and is saturated after 280V for both gases. It is measured up to 0.78mA∕cm2 in argon beam and 0.73mA∕cm2 in oxygen beam at a distance of 100mm from the ion source. Argon ion beam shows better space uniformity than oxygen across the beam extraction region.
ITER neutralizer modeling (abstract)
Authors: Minea T. , Lifschitz A. , Maynard G. , Katsonis K. , Bretagne J. , Simonin A.
Published: February 2008

In the neutralizer of the ITER Neutral Beam Injector, a 1MeV-D− beam passes through an structure filled with D2 gas, where negative ions are mainly converted to fast D0 atoms. Once that the beam is neutralized no further optical correction is possible, i.e., transport from the neutralizer to the confinement chamber is ballistic. Because of this, the transport through the neutralizer determines ultimately the geometrical properties of the neutral beams. The ionization of the buffer gas (D2) filling the neutralizer induced by the D beam creates a rarefied and low temperature plasma (ionization degree ≈10−3, electron temperature ≈20eV). This plasma can screen the electrostatic well of the D beam and, consequently, affect the properties of the extracted beam and the energy transport to the neutralizer walls. On the other hand, the plasma will eventually escape from the neutralizer and move back in the accelerator chain, toward the accelerating grids and the source. We present particle-in-cell simulations of the beam propagation and plasma formation through the neutralizer. Particle-particle and particle-wall collisions are treated using a Monte Carlo approach. Simulations show that the secondary plasma effectively screens the beam space charge preventing beam radial expansion due to Coulomb repulsion between beam ions. First results suggest that the current of plasma ions (D2+) into the accelerator would be of the order of I(D−)∕100, with I(D−) the negative ion current.
Positron annihilation spectroscopic studies of solvothermally synthesized ZnO nanobipyramids and nanoparticles
Authors: Ghoshal Tandra , Biswas Subhajit , Kar Soumitra , Chaudhuri Subhadra , Nambissan P. M. G.
Published: February 2008

Zinc oxide (ZnO) samples in the form of hexagonal-based bipyramids and particles of nanometer dimensions were synthesized through solvothermal route and characterized by x-ray diffraction and transmission electron microscopy. Positron annihilation experiments were performed to study the structural defects such as vacancies and surfaces in these nanosystems. From coincidence Doppler broadening measurements, the positron trapping sites were identified as Zn vacancies or Zn–O–Zn trivacancy clusters. The positron lifetimes, their relative intensities, and the Doppler broadened lineshape parameter S all showed characteristic changes across the nanobipyramid size corresponding to the thermal diffusion length of positrons. In large nanobipyramids, vacancies within the crystallites also trapped positrons and the effects of agglomeration of such vacancies due to increased temperatures of synthesis were reflected in the variation of the annihilation parameters with their base diameters. The sizes of the nanoparticles used were all in the limit of thermal diffusion length of positrons and the annihilation characteristics were in accordance with the decreasing contribution from surfaces with increasing particle size.
How the nature of an observation affects single-trajectory entropies
Authors: Li Ying , Zhao Tong , Bhimalapuram Prabhakar , Dinner Aaron R.
Published: February 2008

Projection of a Markov process with constant rates of transition to a small number of observable aggregated states can result in complex kinetics with memory. Here, we define the entropy production along a single sequence of aggregated states and show that it obeys detailed and integral fluctuation theorems. More importantly, we prove that projection shifts the distribution of entropy production over the ensemble of paths for a nonequilibrium process toward one characteristic of a system at equilibrium. This statement represents an analog of the second law of thermodynamics for path-dependent entropies and thus a new form of constraint of irreversible systems. Numeric examples are presented to illustrate these ideas.
Reorganization energy, activation energy, and mechanism of hole transfer process in DNA: A theoretical study
Authors: Khan Arshad
Published: February 2008

The density functional calculations with aug-cc-pVDZ basis sets on cationic guanine-cytosine (GC+) and adenine-thymine (AT+) base pairs suggest that the cationic charge is almost entirely localized on the G and A units with significant changes in the N–H and N⋯O distances around the H-bonded area. While the calculated intramolecular reorganization energy (λv) for a GC base pair (0.75eV) is remarkably larger than that for an isolated G base (0.49eV), for the AT base pairs these values (0.44 and 0.40eV) are almost the same. The gas phase activation energies (Ea) for GC+GC→GCGC+, AT+AT→ATAT+, and GC+AT→GCAT+ hole transfer processes are 0.19, 0.11, and 0.73eV with rate constants of 1.69×1011, 3.15×1011, and 4.61(0.168)s−1, respectively, at 298K. An alternative mechanism of hole transfer has been proposed on the basis of energy barriers.
Magnetic correlations and spin dynamics in CaMn0.96Mo0.04O3 manganite compound: EPR study
Authors: Rozenberg E. , Auslender M. , Shames A. I. , Martin C. , Hébert S.
Published: February 2008

To study magnetic correlations and spin dynamics of CaMn0.96Mo0.04O3 (CMMO) compound at paramagnetic (PM) state and to probe its low temperature magnetic ordering, X-band electron magnetic resonance (EMR) measurements were performed in 5K⩽T⩽600K interval. The model fittings of EPR peak-to-peak linewidth and double integrated intensity reveal an existence of antiferromagnetic (AFM) and ferromagnetic (FM) correlations at PM state. The enhancement of FM correlations upon cooling and its competition with AFM ones result in FM-like magnetic ground state of CMMO below 110K. The results of EMR measurements evidence that the low temperature magnetic ground state of CMMO may be better described by complex canted magnetic structure with net FM component than by the phase separated state.
Quantum Weibel instability
Authors: Haas F.
Published: February 2008

The Weibel instability is analyzed for quantum plasmas described by the Wigner–Maxwell model. For a suitable class of electromagnetic potentials, the Wigner–Maxwell system is linearized yielding a general dispersion relation for transverse electromagnetic waves. For a double Gaussian equilibrium with temperature anisotropy, the derived dispersion relation generalizes the classical Weibel instability equation. More detailed analytical results are obtained for the cases of extreme temperature anisotropy and for a three-dimensional water bag distribution. In all cases, quantum effects tend to weaken or suppress the instability. Applications are discussed for dense astrophysical objects such as white dwarfs and neutron stars as well as for tunnel-ionized plasmas with controllable perpendicular plasma temperature.
Characterization of a multi-keV x-ray source produced by nanosecond laser irradiation of a solid target: The influence of laser focus spot and target thickness
Authors: Hu Guang-Yue , Zheng Jian , Shen Bai-fei , Lei An-le , Liu Shen-Ye , Zhang Ji-Yan , Yang Jia-Min , Ding Yong-Kun , Hu Xin , Huang Yi-Xiang , Du Hua-Bing , Yi Rong-Qing , Xu Zhi-zhan
Published: February 2008

The influence of focus spot and target thickness on multi-keV x-ray sources generated by 2ns duration laser heated solid targets are investigated on the Shenguang II laser facility. In the case of thick-foil targets, the experimental data and theoretical analysis show that the emission volume of the x-ray sources is sensitive to the laser focus spot and proportional to the 3 power of the focus spot size. The steady x-ray flux is proportional to the 5∕3 power of the focus spot size of the given laser beam in our experimental condition. In the case of thin-foil targets, experimental data show that there is an optimal foil thickness corresponding to the given laser parameters. With the given laser beam, the optimal thin-foil thickness is proportional to the −2∕3 power of the focus spot size, and the optimal x-ray energy of thin foil is independent of focus spot size.
Propagating volume and localized spin wave modes on a lattice of circular magnetic antidots
Authors: Kostylev Mikhail , Gubbiotti Gianluca , Carlotti Giovanni , Socino Giovanni , Tacchi Silvia , Wang Chenchen , Singh Navab , Adeyeye Adekunle O. , Stamps Robert L.
Published: February 2008

The spectrum of spin wave excitations on a nanometric two-dimensional periodical array of circular holes in a magnetic film was measured using the Brillouin light scattering technique. Two modes with positive group velocity in the frequency range between 4 and 7GHz were observed. Our calculations show that these correspond to the two lowest modes propagating along the edges of an effective stripe waveguide, perpendicular to the applied field, whose width is equal to the interhole distance. Moreover, a number of higher-frequency modes has been measured and identified as volume excitations of the same effective stripe.
Apparatus to study crystal channeling and volume reflection phenomena at the SPS H8 beamline
Authors: Scandale Walter , Efthymiopoulos Ilias , Still Dean A. , Carnera Alberto , Della Mea Gianantonio , De Salvador Davide , Milan Riccardo , Vomiero Alberto , Baricordi Stefano , Chiozzi Stefano , Dalpiaz Pietro , Damiani Chiara , Fiorini Massimiliano , Guidi Vincenzo , Martinelli Giuliano , Mazzolari Andrea , Milan Emiliano , Ambrosi Giovanni , Azzarello Philipp , Battiston Roberto , Bertucci Bruna , Burger William J. , Ionica Maria , Zuccon Paolo , Cavoto Gianluca , Santacesaria Roberta , Valente Paolo , Vallazza Erik , Afonin Alexander G. , Baranov Vladimir T. , Chesnokov Yury A. , Kotov Vladilen I. , Maisheev Vladimir A. , Yazynin Igor A. , Afanasiev Sergey V. , Kovalenko Alexander D. , Taratin Alexander M. , Bondar Nikolai F. , Denisov Alexander S. , Gavrikov Yury A. , Ivanov Yuri M. , Ivochkin Vladimir G. , Kosyanenko Sergey V. , Lapina Lyubov P. , Levtchenko Peter M. , Petrunin Anatoli A. , Skorobogatov Vyacheslav V. , Suvorov Vsevolod M. , Bolognini Davide , Foggetta Luca , Hasan Said , Prest Michela
Published: February 2008

A high performance apparatus has been designed and built by the H8-RD22 collaboration for the study of channeling and volume reflection phenomena in the interaction of 400GeV∕c protons with bent silicon crystals, during the 2006 data taking in the external beamline H8 of the CERN SPS. High-quality silicon short crystals were bent by either anticlastic or quasimosaic effects. Alignment with the highly parallel (8μrad divergence) proton beam was guaranteed through a submicroradian goniometric system equipped with both rotational and translational stages. Particle tracking was possible by a series of silicon microstrip detectors with high-resolution and a parallel plate gas chamber, triggered by various scintillating detectors located along the beamline. Experimental observation of volume reflection with 400GeV∕c protons proved true with a deflection angle of (10.4±0.5)μrad with respect to the unperturbed beam, with a silicon crystal whose (111) planes were parallel to the beam.
Collective dynamics and ferromagnetic order in random planar arrays of magnetic granules
Authors: Pogorelov Y. G. , Kakazei G. N. , Costa M. D. , Sousa J. B.
Published: February 2008

A dynamical study is done on existence and stability of ferromagnetically ordered ground state in a positionally disordered planar array of magnetic moments coupled only by dipolar forces. Starting from almost aligned ground state under a strong enough applied field, the excitation energy spectrum and related eigenmodes are found, permitting to develop a mean-field analysis of the static magnetization in function of magnetic field and temperature. In the limit of zero applied field, the stability conditions are obtained for the onset of in-plane spontaneous magnetization, manifesting a specific “order from disorder” mechanism.
Role of dopant incorporation on the magnetic properties of Ce1−xNixO2 nanoparticles: An electron paramagnetic resonance study
Authors: Misra S. K. , Andronenko S. I. , Engelhard M. H. , Thurber A. , Reddy K. M. , Punnoose A.
Published: February 2008

Nickel doping has been found to produce weak room-temperature ferromagnetism (FM) in CeO2. The saturation magnetization (Ms) of the chemically synthesized Ce1−xNixO2 samples showed a maximum for x=0.04, above which the magnetization decreased gradually. For Ce1−xNixO2 samples with x⩾0.04, an activation process involving slow annealing of the sample to 500°C increased the Ms by more than two orders of magnitude. However, no such activation effect was observed in samples with x<0.04. Electron paramagnetic resonance (EPR) technique has been exploited to understand (i) the gradual decrease in the FM and subsequent disappearance of FM with increase in x for x>0.04, and (ii) the dramatic increase in Ms in the activated Ce1−xNixO2 samples with x⩾0.04 and the absence of this behavior in samples with x<0.04. Detailed analysis by simulation of the EPR data on several as-prepared Ce1−xNixO2 samples with 0.01⩽x⩽0.10 at 5 and 300K indicates the presence of several paramagnetic species: (i) two magnetically inequivalent Ni2+ ions with the ionic spin S=1, (ii) one Ce3+ ion with spin S=1∕2, and (iii) three O2− defects with S=1∕2. The spectra of the samples with x<0.04 are dominated by a single Ni2+ EPR line ascribed to dopant ions in substitutional sites, whereas in samples with x⩾0.04, there is an additional EPR line attributed to Ni2+ ions occupying interstitial sites. In the activated sample with x=0.08, the EPR line due to the interstitial Ni2+ ions is completely absent, and only the line due to substitutional Ni2+ ions is present, suggesting that the enhanced FM arises from migration of Ni2+ ions from interstitial to substitutional sites.
Pulsed wire magnetic field measurement on the permanent magnet focusing device of millimeter-wave traveling wave tube
Authors: Lei Tao , Wang Xiaoming , Wang Mingyan
Published: February 2008

In our case, the pulsed wire method is applied to the magnetic field measurement of the permanent magnets in focusing device of millimeter-wave traveling wave tube (TWT). The focusing device using permanent magnets is used to help the electron beam keep shape and make it possible go through the slow-wave circuit, effectively interact with the microwave field and well received by collectors, which makes the measurement become a key factor for the development of the millimeter-wave TWT technique. Furthermore, the wire method can be extended used to magnetic field measurement of the magnet with small via hole. The pulsed wire technique is based on the excitation of the harmonics of a wire vibration by Lorenz forces between current in a wire and the surrounding magnetic field. Knowing the amplitude and the phase of the various harmonics of the wire vibration, one can easily reconstruct the surrounding magnetic field. As sensitive the wire system is, ultrastable supporters, high accurate mechanical adjusters, precise light and electric centering device are installed and relevant parameters are properly chosen. In addition, shorter wire is used to reduce the sag, and a simple and effective wire-position detector providing accuracy up to 1μm is designed and tested. Experiment confirms the theoretical conclusions and shows a positive future of application. The prototype system can show several relevant results, e.g., three-dimensional magnetic intensity distribution, maximum, minimum, and medium magnetic inductions, pole pitch error, etc.
Fast ignition relevant study of the flux of high intensity laser-generated electrons via a hollow cone into a laser-imploded plasma
Authors: Key M. H. , Adam J. C. , Akli K. U. , Borghesi M. , Chen M. H. , Evans R. G. , Freeman R. R. , Habara H. , Hatchett S. P. , Hill J. M. , Heron A. , King J. A. , Kodama R. , Lancaster K. L. , MacKinnon A. J. , Patel P. , Phillips T. , Romagnani L. , Snavely R. A. , Stephens R. , Stoeckl C. , Town R. , Toyama Y. , Zhang B. , Zepf M. , Norreys P. A.
Published: February 2008

An integrated experiment relevant to fast ignition . A Cu-doped deuterated polymer spherical shell target with an inserted hollow Au cone is imploded by a six-beam 900-J, 1-ns laser. A 10-ps, 70-J laser pulse is focused into the cone at the time of peak compression. The flux of high-energy electrons through the imploded material is determined from the yield of CuKα fluorescence by comparison with a Monte Carlo model. The electrons are estimated to carry about 15% of the laser energy. Collisional and Ohmic heating are modeled, and Ohmic effects are shown to be relatively unimportant. An electron spectrometer shows significantly greater reduction of the transmitted electron flux than is calculated in the model. Enhanced scattering by instability-induced magnetic fields is suggested. An extension of this fluor-based technique to measurement of coupling efficiency to the ignition hot spot in future larger-scale fast ignition experiments is outlined.