bluuebunny/crossref_metadata_2025 huggingface dataset:
Paleoclimate Deduced from a Multidisciplinary Study of a Half-Million-Year-Old Stalagmite from Rana, Northern Norway
Authors: Lauritzen Stein-Erik , Løvlie Reidar , Moe Dagfinn , Østbye Eivind
Published: July 2006

A 7-cm-thick flowstone sequence has been dated by extended Uranium series techniques to less than 1.25 myr, with a probable growth interval of ≥350,000–≤730,000 yr B.P. The time span is in accordance with paleomagnetic results revealing normal polarity for the whole sequence, i.e., a depositional age of <730,000 yr B.P. Oxygen isotope variations suggest deposition during three warm periods, interrupted by two isotopically cold hiatuses characterized by bulk resolution and detrital laminae. Calculations suggest that climatic transitions may have involved a shift of 1.1–2.4°C in mean annual temperatures. Contemporary flooding of the cave due to adjacent glacier expansion provides evidence for the widely held view that speleothem deposition is halted by glacier proximity. The flowstone matrix contained appreciable amounts of pollen (pine, birch) as well as larger amounts of charcoal dust. The pollen assemblage suggests a climate comparable with the present, implying that Norway has experienced at least three glacial/interglacial transitions during the growth interval of the speleothem. The warmer periods were characterized by a forest environment, with ample evidence of fire.
Peat Accumulation in Northern Wetlands
Authors: Ovenden Lynn
Published: July 2006

Mean long-term rates of peat accumulation are higher in boreal and temperate peat deposits than in subarctic regions of Canada, although peatlands are extensive in the subarctic. Climatic change probably accounts for the development of southern peatlands during the middle to late Holocene and for the late Holocene decline in growth of many subarctic peat deposits. In northwestern peat deposits, peat of wetSphagnumlawns and treed wetlands tended to accumulate more rapidly than peat ofSphagnumhummocks and sedge fens. Long-term net rates of carbon accumulation in Canadian peatlands typically range from 10 to 35 g C/m2/yr.
A 14,000-Year Pollen Record from Sithylemenkat Lake, North-Central Alaska
Authors: Anderson Patricia M. , Reanier Richard E. , Brubaker Linda B.
Published: July 2006

Pollen analysis of a 14,000-yr-old sediment core from Sithylemenkat Lake provides the first Holocene vegetational history for the Kanuti Flats of north-central Alaska. Basal samples contain a curious and unusual combination of tundra and boreal taxa. Pollen assemblages dating from 13,500 to 9000 yr B.P. are more typical of southern Brooks Range sites and indicate the presence ofBetulashrub tundra with increasedPopulusca. 10,000 to 9000 yr B.P.Picea glaucaappeared ca. 9000 yr B.P. andAlnusca. 8000 yr B.P.P. glaucapopulations declined between 7800 and 5000 yr B.P. with a subsequent reforestation byP. marianaandP. glauca. This pattern is seen at other sites in northeastern Alaska and suggests that the Holocene history of boreal forest is more complex than thought previously.
Atmospheric summer circulation and coastal upwelling in the Arabian Sea during the Holocene and the last glaciation
Authors: Sirocko Frank , Sarnthein Michael , Lange Heinz , Erlenkeuser Helmut
Published: July 2006

Accumulation rates of biogenic and lithogenic components were studied in 39 turbidite-free, well-dated sediment cores from the northern Indian Ocean to define the proportions of fluvial and eolian input and to reconstruct Quaternary patterns of coastal upwelling. The majority of dust deposited in the western Arabian Sea during the Holocene (about 100 × 106t yr−1) is advected from Arabia by northwesterly winds, which overlie the low-level southwest monsoon. The glacial increase in dust flux to 160 × 106t yr−1 culminated in the northern Arabian Sea, most probably due to (i) entrainment of dust, rich in chlorite, dolomite, and lithogenic carbonate in the then-dry Persian Gulf, and (ii) a southward shift of the mean position of the southwest monsoon during glacial summer. This shift is recorded in reduced accumulation rates of biogenic opal and increased rates of marine carbonate off Somalia and Oman. Both the terrigenous and biogenic sediment records show that the northwesterly winds and the southwest monsoon persisted over the last 27,000 yr, as well as the Asian continental summer heat low. However, the glacial seasonal time span of the southwest monsoon season was much reduced, most likely because of a delay in the seasonal onset of the southwest monsoon.
Absolute Dating of the Late-Glacial Period in Switzerland Using Annually Laminated Sediments
Authors: Lotter André F.
Published: July 2006

Results of a high-resolution late-glacial AMS14C chronology from Rotsee, central Switzerland, have given evidence that the atmospheric radiocarbon concentration was not constant between 13,000 and 9500 yr B.P. This resulted in three marked phases of constant radiocarbon age: at 12,700, at 10,000, and at 9500 yr B.P. New results of a late-glacial varve chronology from Soppensee, central Switzerland, suggest that the younger two phases of constant14C age each had a duration of ca. 400 calendar years. The length of the late-glacial chronozones has been calculated on the basis of these replicate varve counts and a comparison with their estimated duration in radiocarbon years shows that the estimated duration of the chronozones Bölling (ca. 800 calendar yr vs 100014C yr) and Younger Dryas (ca. 900 calendar yr vs 100014C yr) agree with the expected time span, whereas the estimated duration of the Alleröd chronozone (ca. 400 calendar yr vs 100014C yr) is substantially shorter than expected. Furthermore, a tentative comparison of varve ages and14C ages suggests that the varve chronology is more than 1000 yr offset toward older ages from the radiocarbon chronology during the late-glacial period.
Geoarchaeological and Paleohydrological Evidence for a Clovis-Age Drought in North America and Its Bearing on Extinction
Authors: Haynes C. Vance
Published: July 2006

At the Murray Springs Clovis site in southeastern Arizona, stratigraphic and geomorphic evidence indicates that an abnormally low water table 10,900 yr B.P. was followed soon thereafter by a water-table rise accompanied by the deposition of an algal mat (the “black mat”) that buried mammoth tracks, Clovis artifacts, and a well. This water-table fluctuation correlates with pluvial lake fluctuations in the Great Basin during and immediately following Clovis occupation of that region. Many elements of Pleistocene megafauna in North America became extinct during the dry period. Oxygen isotope records show a marked decrease in δ18O correlated with the Younger Dryas cold-dry event of northern Europe which ended 10,750 yr B.P., essentially the same time as the water table began to rise in southeastern Arizona. Clovis hunters may have found large game animals easier prey when concentrated at water holes and under stress. If so, both climate and human predation contributed to Pleistocene extinction in America.
Relative Dating of Moraines Based on Landform Degradation, Lee Vining Canyon, California
Authors: Bursik Marcus
Published: July 2006

Cross-sectional topographic profiles of lateral moraines formed during different glaciations were measured at Lee Vining Canyon, California, to determine whether the degree of moraine degradation could be quantified and used for relative dating. Logarithmic plots of the value of a slope parameter against cross-sectional area show distinct linear trends for moraines of different relative ages. The slopes of these trends suggest that the degradation processes are not among those that can be modeled with the linear diffusion equation.
Pleistocene Paleoclimate of the Arid Region of Israel as Recorded in Calcite Deposits Along Regional Transverse Faults and in Veins
Authors: Avigour A. , Magaritz M. , Issar A.
Published: July 2006

The δ18O and δ13C values of the calcites associated with E-W and NE-SW transverse faults in the Negev, Israel, indicate that calcite was deposited from meteoric water. A regional change in the δ18O and δ13C values was observed. The 18O content in the calcite increases, from the southwestern (δ18O = −17.8‰) to the northeastern (δ18O = −2.9‰) part of the region. The δ13C values show the opposite trend of the 13C content decrease: from +2‰ in the south to −10‰ in the northeast. These trends had to reflect changes in regional paleoclimate, suggesting a change in the isotopic composition of the solution from which the calcite was deposited in different periods. The variations in the δ18O values reflect shifts in the δ18O values of precipitation and are associated with a change in the source of moist air masses which came from the equatorial Atlantic in the early Pleistocene and from the Mediterranean during a later period. Variations in δ13C values reflect changes from humid to arid conditions. Two modes of calcite deposition are suggested: (1) precipitation of calcite minerals in the unsaturated zone following the dissolution in the soil or (2) calcite deposition that occurred as CO2 was lost during emergence of paleogroundwater from Lower Cretaceous and Jurassic aquifers.
Sea Level, Surface Salinity of the Japan Sea, and the Younger Dryas Event in the Northwestern Pacific Ocean
Authors: Keigwin L.D. , Gorbarenko S.A.
Published: July 2006

The Japan Sea was profoundly different during glacial times than today. Available δ18O evidence indicates that sea surface salinity was lower by several per mil. This probably increased the stability of the water column and caused anoxic sedimentary conditions in the deep sea, as shown by the absence of benthic microfossils and the presence of laminated sediment. These changes are likely related to the effects of late Quaternary sea-level change on the shallow sills (ca. 130 m) across which the Japan Sea exchanges with the open ocean. The Hwang He (Yellow River) has previously been implicated as the source of fresh water to the Japan Sea during glaciation, but the possible roles of the Amur River and excess precipitation over evaporation must also be considered. Ambiguous radiocarbon chronologies for the latest Quaternary of Japan Sea cores do not adequately constrain the timing of salinity lowering. Previous studies have suggested that lowest sea surface salinity was achieved 27,000 to 20,000 14C yr B.P. However, if global sea-level fall restricted exchange with the open ocean circulation, then lowest salinity in the Japan Sea may have occurred as recently as 15,000 to 20,000 yr ago when sea level was lowest. If this alternative is correct, then as sea level abruptly rose about 12,000 yr ago, relatively fresh water must have been discharged to the open Pacific. This might have affected the dynamics of outflow, local faunal and floral expression of the polar front, and stable isotope ratios in foraminifera. These environmental changes could be misinterpreted as evidence for the cooling of Younger Dryas age, which has not been identified in nearby terrestrial records.
Patterns of Holocene Environmental Change in the Midwestern United States
Authors: Baker Richard G. , Maher Louis J. , Chumbley Craig A. , Van Zant Kent L.
Published: July 2006

Four pollen sequences along a transect from north-central Iowa to southeast Wisconsin reveal the distribution of prairie and forest during the Holocene and test the use of pollen isopolls in locating the Holocene prairie-forest border. Prairie was dominant in central Iowa and climate was drier than present from about 8000 to 3000 yr B.P. During the driest part of this period in central Iowa (6500-5500 yr B.P.), mesic forest prevailed in eastern Iowa and Wisconsin, suggesting conditions wetter than at present. Prairie replaced the mesic forest about 5400 yr B.P. in eastern Iowa but did not extend much farther east; mesic forests were replaced in southern Wisconsin and northern Illinois about 5400 yr B.P. by xeric oak forests. This change from mesic to xeric conditions at 5400 yr B.P. was widespread and suggests that the intrusion of drier Pacific air was blocked by maritime tropical air from the Gulf of Mexico until the late Holocene in this area.
HIV/AIDS KNOWLEDGE, WOMEN’S EDUCATION, EPIDEMIC SEVERITY AND PROTECTIVE SEXUAL BEHAVIOUR IN LOW- AND MIDDLE-INCOME COUNTRIES
Authors: SNELLING DANA , RASUGU OMARIBA D. WALTER , HONG SUNGJIN , GEORGIADES KATHOLIKI , RACINE YVONNE , BOYLE MICHAEL H.
Published: July 2006

A fundamental public health strategy to reduce the risk of HIV/AIDS is to increase levels of awareness and knowledge about the disease. Although knowledge about HIV/AIDS and protective sexual behaviour are linked theoretically, relatively little is known about their empirical relationship. Using Demographic and Health Survey data from 23 low- and middle-income countries, this study used multilevel logistic regression models: to examine cross-national variability in the relationship between HIV/AIDS knowledge and protective behaviour (condom use and restricted sex); to investigate the moderating influences of women’s educational attainment on this relationship; and to test the extent to which severity of the HIV/AIDS epidemic accounts for cross-national variability in the association between HIV/AIDS knowledge and protective behaviour. There was an association between increased knowledge of HIV/AIDS and condom use that varied in strength and form cross-nationally. This cross-national variation was accounted for partially by the socioeconomic characteristics of women resident in the study countries and between-country differences in the severity of the HIV epidemic. While education modified the association between HIV/AIDS knowledge and protective behaviour – stronger associations at lower levels of education – epidemic severity exerted a stronger influence on behaviour than any other characteristic. Finally, this study indicates that protective sexual practices are disturbingly low. In eight of 23 countries, overall levels of condom use to prevent STDs and HIV/AIDS were less than 5·0%. Waiting for the spread of HIV/AIDS infection to change sexual practices in low- and middle-income countries will result in dramatic unnecessary suffering.
Coping with depression in later life: a qualitative study of help-seeking in three ethnic groups
Authors: LAWRENCE VANESSA , BANERJEE SUBE , BHUGRA DINESH , SANGHA KULJEET , TURNER SARA , MURRAY JOANNA
Published: July 2006

Background. Research suggests high levels of depression and low levels of service use among older adults from UK minority ethnic groups. This study aimed to explore older adults' attitudes and beliefs regarding what would help someone with depression, and to consider how these may facilitate or deter older people from accessing treatment.

Method. In-depth individual qualitative interviews were conducted with older adults with depression (treated and untreated) and the non-depressed older population. A multi-cultural approach was used that incorporated the perspectives of 32 black Caribbean, 33 South Asian and 45 white British older adults.

Results. Participants felt that the responsibility for combating depression was an internal and individual task with support considered secondary. However, the majority expressed a willingness and desire to discuss psychosocial problems. Within the black Caribbean group, conversing with God through prayer was seen as an effective means of overcoming depression, while a large proportion of South Asian and white British participants identified families as an important source of help. There was wide variation in how older adults construed the role of the general practitioner (GP) and many expressed acute awareness of the demands on GPs' time.

Conclusions. Efforts to socialize and remain active may provide a useful and acceptable adjunct to clinical interventions. However, there is a need to communicate that depression often necessitates formal help, and that it is acceptable to voice concerns regarding emotional states in a GP consultation. The findings suggest that older adults would welcome the opportunity to discuss their feelings with health-care professionals.
Cannabis use disorders in the USA: prevalence, correlates and co-morbidity
Authors: STINSON FREDERICK S. , RUAN W. JUNE , PICKERING ROGER , GRANT BRIDGET F.
Published: July 2006

Background. The purpose of this study was to present 12-month and lifetime estimates of the prevalence, sociodemographic and clinical correlates, and psychiatric co-morbidity of DSM-IV cannabis abuse and dependence.

Method. Data were derived from a large nationally representative survey (n=43093) of US adults.

Results. The prevalence of 12-month and lifetime DSM-IV cannabis abuse (1·1% and 7·2%) exceeded the corresponding rates of cannabis dependence (0·3% and 1·3%). Being male, Native American, widowed/separated/divorced, and residing in the West increased the odds whereas being Black, Asian or Hispanic decreased the odds of cannabis abuse and dependence. Cannabis dependence was significantly associated with low income. Ages of onset for both cannabis use disorders occurred in adolescence and the majority of individuals with these disorders remained untreated. Co-morbidity was high between cannabis use disorders and other Axis I and II disorders.

Conclusions. Cannabis use disorders continue to present a widespread and serious personal and public health problem. Native Americans were found to have high rates of cannabis use disorders, warranting closer attention to the mental health needs of this subgroup. Associations between cannabis abuse and dependence and Axis I and II disorders were strong, signaling the need for more comprehensive assessment of individuals with cannabis use disorders. Further controlled treatment studies are needed, especially among co-morbid individuals, in view of growing evidence of the adverse personal, medical and societal impacts of cannabis use disorders in the USA.
Styles of Reform: Differences in quango creation between policy sectors in the Netherlands
Authors: VAN THIEL SANDRA
Published: July 2006

National governments follow country-specific reform trajectories, which imply uniform preferences for specific types of quasi-autonomous organisations (quangos). However, at micro level there is little uniformity; similar tasks are charged to different types of quangos. This contradiction could be explained by the existence of styles of quango creation at the level of policy sectors. Do such styles exist? Using the literature on policy styles and administrative culture, four styles of quango creation are deduced: traditional, bureaucratic, professional and managerial. The analysis shows that the majority of Dutch policy sectors indeed have a dominant style of quango-creation. The bureaucratic style is found in ten out of eighteen sectors. Replication of this study may help to improve the explanation of quango creation in western countries.
The USA's international trade in fish leather, from a conservation perspective
Authors: GREY MELISSA , BLAIS ANNE-MARIE , HUNT BOB , VINCENT AMANDA C.J.
Published: July 2006

This paper provides the first analysis of imports and exports of fish leather by the USA. Estimates of minimum levels of trade were obtained from the records of the United States Fish and Wildlife Service for 1997–2001, and possible conservation consequences were considered. Data show that imported leather items used the skins of at least 51 types of fish. Of the 41 identified to species level, six were freshwater fish, eight diadromous and 27 were fully marine. Eels and hagfishes (marketed as ‘eelskin’; eight named species), stingrays (10 named species) and sharks (15 named species) dominated the trade. An average of 725 000 fish-leather products, worth over US$ 6 million, was imported each year to the USA. A significant decline in fish leather imports over the five-year period studied derived largely from changes in ‘eelskin’ imports. Fish leather in the USA was reportedly sourced primarily from the Republic of Korea, mainland China and Thailand, although the records were flawed. About 93% of leather products were obtained from wild fish. Exports from the USA totalled approximately 5% of imports by volume. Many of the fish species comprising the largest imports for leather were characterized by low resilience to exploitation, with one-third of known species considered threatened or near threatened by the World Conservation Union (IUCN). This pilot assessment indicates the need for better record keeping if sustainability of fish exploitation for leather is to be evaluated.
Evidence of trends in daily climate extremes over southern and west Africa
Authors: New Mark , Hewitson Bruce , Stephenson David B. , Tsiga Alois , Kruger Andries , Manhique Atanasio , Gomez Bernard , Coelho Caio A. S. , Masisi Dorcas Ntiki , Kululanga Elina , Mbambalala Ernest , Adesina Francis , Saleh Hemed , Kanyanga Joseph , Adosi Juliana , Bulane Lebohang , Fortunata Lubega , Mdoka Marshall L. , Lajoie Robert
Published: July 2006

There has been a paucity of information on trends in daily climate and climate extremes, especially from developing countries. We report the results of the analysis of daily temperature (maximum and minimum) and precipitation data from 14 south and west African countries over the period 1961–2000. Data were subject to quality control and processing into indices of climate extremes for release to the global community. Temperature extremes show patterns consistent with warming over most of the regions analyzed, with a large proportion of stations showing statistically significant trends for all temperature indices. Over 1961 to 2000, the regionally averaged occurrence of extreme cold (fifth percentile) days and nights has decreased by −3.7 and −6.0 days/decade, respectively. Over the same period, the occurrence of extreme hot (95th percentile) days and nights has increased by 8.2 and 8.6 days/decade, respectively. The average duration of warm (cold) has increased (decreased) by 2.4 (0.5) days/decade and warm spells. Overall, it appears that the hot tails of the distributions of daily maximum temperature have changed more than the cold tails; for minimum temperatures, hot tails show greater changes in the NW of the region, while cold tails have changed more in the SE and east. The diurnal temperature range (DTR) does not exhibit a consistent trend across the region, with many neighboring stations showing opposite trends. However, the DTR shows consistent increases in a zone across Namibia, Botswana, Zambia, and Mozambique, coinciding with more rapid increases in maximum temperature than minimum temperature extremes. Most precipitation indices do not exhibit consistent or statistically significant trends across the region. Regionally averaged total precipitation has decreased but is not statistically significant. At the same time, there has been a statistically significant increase in regionally averaged daily rainfall intensity and dry spell duration. While the majority of stations also show increasing trends for these two indices, only a few of these are statistically significant. There are increasing trends in regionally averaged rainfall on extreme precipitation days and in maximum annual 5‐day and 1‐day rainfall, but only trends for the latter are statistically significant.
Global energy cycle between land and ocean in the simulated 20th century climate systems
Authors: Shin Ho‐Jeong , Chung Il‐Ung , Kim Hyung‐Jin , Kim Jeong‐Woo
Published: July 2006

The global energy cycle between the land and the ocean has been studied with simulations of the 20th century performed with coupled ocean‐atmosphere climate models. The energy cycle consists of the net energy fluxes at the top‐of‐the‐atmosphere (TOA) and the surface, the atmospheric energy storage rates over the global land and ocean, and the atmospheric energy transport between the land and ocean. The energy cycle was investigated using a multi‐model ensemble for its centennial mean, climatological annual variation and long‐term trend. Some distinctive features of the cycle were revealed: (1) the ocean‐to‐land atmospheric energy transport plays a key role in partitioning the global net TOA flux between the ocean and land, (2) the annual variation of the global net TOA flux is primarily attributed by the ocean surface flux, and (3) it is ascertained that the planetary energy imbalance on the long‐term period is induced by the ocean's heat uptake.
Law Dome CO2, CH4 and N2O ice core records extended to 2000 years BP
Authors: MacFarling Meure C. , Etheridge D. , Trudinger C. , Steele P. , Langenfelds R. , van Ommen T. , Smith A. , Elkins J.
Published: July 2006

New measurements of atmospheric greenhouse gas concentrations in ice from Law Dome, Antarctica reproduce published Law Dome CO2 and CH4 records, extend them back to 2000 years BP, and include N2O. They have very high air age resolution, data density and measurement precision. Firn air measurements span the past 65 years and overlap with the ice core and direct atmospheric observations. Major increases in CO2, CH4 and N2O concentrations during the past 200 years followed a period of relative stability beforehand. Decadal variations during the industrial period include the stabilization of CO2 and slowing of CH4 and N2O growth in the 1940s and 1950s. Variations of up to 10 ppm CO2, 40 ppb CH4 and 10 ppb N2O occurred throughout the preindustrial period. Methane concentrations grew by 100 ppb from AD 0 to 1800, possibly due to early anthropogenic emissions.
Real space pseudopotential calculations for copper clusters
Authors: Li Shen , Alemany M. M. G. , Chelikowsky James R.
Published: July 2006

Neutral and anion clusters of copper, Cun (n=3–11), are examined using real space pseudopotentials constructed within the local spin density approximation. We predict the ground state structure for each cluster, the binding energy, and the corresponding photoelectron spectra, which we compare to experiment. We find strong final state effects in the photoelectron spectra, especially for the smaller clusters. The binding energy as a function of cluster size tracks well with the measured values, although the magnitude of the binding energy exceeds the experimental values by ∼20%, as expected for the local spin density approximation.
Crucial importance of translational entropy of water in pressure denaturation of proteins
Authors: Harano Yuichi , Kinoshita Masahiro
Published: July 2006

We present statistical thermodynamics of pressure denaturation of proteins, in which the three-dimensional integral equation theory is employed. It is applied to a simple model system focusing on the translational entropy of the solvent. The partial molar volume governing the pressure dependence of the structural stability of a protein is expressed for each structure in terms of the excluded volume for the solvent molecules, the solvent-accessible surface area (ASA), and a parameter related to the solvent-density profile formed near the protein surface. It is argued that the entropic effect originating from the translational movement of water molecules plays critical roles in the pressure-induced denaturation. We also show that the exceptionally small size of water molecules among dense liquids in nature is crucial for pressure denaturation. An unfolded structure, which is only moderately less compact than the native structure but has much larger ASA, is shown to turn more stable than the native one at an elevated pressure. The water entropy for the native structure is higher than that for the unfolded structure in the low-pressure region, whereas the opposite is true in the high-pressure region. Such a structure is characterized by the cleft and/or swelling and the water penetration into the interior. In another solvent whose molecular size is 1.5 times larger than that of water, however, the inversion of the stability does not occur any longer. The random coil becomes relatively more destabilized with rising pressure, irrespective of the molecular size of the solvent. These theoretical predictions are in qualitatively good agreement with the experimental observations.
On the effects of ion-wall chemical association on the electric double layer: A density functional approach for the restricted primitive model at a charged wall
Authors: Pizio O. , Sokołowski S.
Published: July 2006

We describe a density functional theory for the restricted primitive model of ionic fluid at a charged wall with active sites to which ions can bond. The theory is an extension of our recent approach [Pizio et al., J. Chem. Phys. 121, 11957 (2004)] and is focused in the effects of specific adsorption of ions on the wall, besides the electrostatic phenomena. In order to solve the problem, we use the first-order thermodynamic perturbation theory of chemical association developed by Wertheim [J. Chem. Phys. 87, 7323 (1987)]. The microscopic structure of the electric double layer and the amount of adsorbed charge are investigated. Also, the temperature dependence of capacitance is analyzed. The capacitance depends on the kind of ions that form associative bonds with the surface sites and is determined by a net charge acting on the diffuse layer. The shape of the temperature dependence of capacitance essentially depends on the association energy and the density of bonding sites.
Conformational identification of tryptamine embedded in superfluid helium droplets using electronic polarization spectroscopy
Authors: Pei Linsen , Zhang Jie , Wu Chengyin , Kong Wei
Published: July 2006

We report electronic polarization spectroscopy of tryptamine embedded in superfluid helium droplets. In a dc electric field, dependence of laser induced fluorescence from tryptamine on the polarization direction of the excitation laser is measured. Among the three observed major conformers A, D, and E, conformers D and E display preference for perpendicular excitation relative to the orientation field, while conformer A is insensitive to the polarization direction of the excitation laser. We attribute the behavior of conformer A to the fact that the angle between the permanent dipole and the transition dipole is close to the magic angle. Using a linear variation method, we can reproduce the polarization preference of the three conformers and determine the angle between the transition dipole and the permanent dipole. Since the side chain exerts small effect on the direction of the transition dipole in the frame of the indole chromophore, all three conformers have a common transition dipole more or less in the indole plane at an angle of ∼60° relative to the long axis of the chromophore. The orientation of the side chain, on the other hand, determines the size and direction of the permanent dipole, thereby affecting the angle between the permanent dipole and the transition dipole. For conformer D in the droplet, our results agree with the Anti(ph) structure, rather than the Anti(py) structure. Our work demonstrates that polarization spectroscopy is effective in conformational identification for molecules that contain a known chromophore. Although coupling of the electronic transition with the helium matrix is not negligible, it does not affect the direction of the transition dipole.
MAXIMA: A balloon-borne cosmic microwave background anisotropy experiment
Authors: Rabii B. , Winant C. D. , Collins J. S. , Lee A. T. , Richards P. L. , Abroe M. E. , Hanany S. , Johnson B. R. , Ade P. , Balbi A. , Bock J. J. , Borrill J. , Stompor R. , Boscaleri A. , Pascale E. , de Bernardis P. , Ferreira P. G. , Hristov V. V. , Lange A. E. , Jaffe A. H. , Netterfield C. B. , Smoot G. F. , Wu J. H. P.
Published: July 2006

We describe the Millimeter wave Anisotropy eXperiment IMaging Array (MAXIMA), a balloon-borne experiment which measured the temperature anisotropy of the cosmic microwave background (CMB) on angular scales of 10′ to 5°. MAXIMA mapped the CMB using 16 bolometric detectors in spectral bands centered at 150, 240, and 410GHz, with 10′ resolution at all frequencies. The combined receiver sensitivity to CMB anisotropy was ∼40μKs. The bolometric detectors, which were cooled to 100mK, were a prototype of the detectors which will be used on the Planck Surveyor Satellite of the European Space Agency. Systematic parasitic contributions were controlled by using four uncorrelated spatial modulations, thorough cross-linking, multiple independent CMB observations, heavily baffled optics, and strong spectral discrimination. Pointing reconstruction was accurate to 1′, and absolute calibration was better than 4%. Two MAXIMA flights with more than 8.5h of CMB observations have mapped a total of 300deg2 of the sky in regions of negligible known foreground emission. MAXIMA results have been released in previous publications and shown to be consistent with the Wilkinson Microwave Anisotropy Probe. MAXIMA I maps, power spectra, and correlation matrices are publicly available at http://cosmology.berkeley.edu/maxima.
Phase control in the vibrational qubit
Authors: Zhao Meiyu , Babikov Dmitri
Published: July 2006

In order to use molecular vibrations for quantum information processing one should be able to shape infrared laser pulses so that they can play the role of accurate quantum gates and drive the required vibrational transitions. In this paper we studied theoretically how the relative phase of the optimized transitions affects accuracy of the quantum gates in such a system. Optimal control theory and numerical propagation of laser-driven vibrational wave packets were employed. The dependencies observed for one-qubit gates NOT, π-rotation, and Hadamard transform are qualitatively similar to each other. The results of the numerical tests agree well with the analytical predictions.
Microstructured silicon photodetector
Authors: Huang Zhihong , Carey James E. , Liu Mingguo , Guo Xiangyi , Mazur Eric , Campbell Joe C.
Published: July 2006

Photodetectors fabricated on microstructured silicon are reported. The photodetectors exhibited high photoresponse; at 3V bias, the responsivities were 92A∕W at 850nm and 119A∕W at 960nm. At wavelengths longer than 1.1μm, the photodetectors still showed strong photoresponse. A generation-recombination gain mechanism has been proposed to explain the photoresponse of these photodiodes. From measurements of the noise current density, the calculated gain was approximately 1200 at 3V bias.
Partial-dislocation-mediated processes in nanocrystalline Ni with nonequilibrium grain boundaries
Authors: Wu X. L. , Zhu Y. T
Published: July 2006

The partial-dislocation-mediated processes have so far eluded high-resolution transmission electron microscopy studies in nanocrystalline (nc) Ni with nonequilibrium grain boundaries. It is revealed that the nc Ni deformed largely by twinning instead of extended partials. The underlying mechanisms including dissociated dislocations, high residual stresses, and stress concentrations near stacking faults are demonstrated and discussed.
Electrospun hybrid organic/inorganic semiconductor Schottky nanodiode
Authors: Pinto Nicholas J. , González Rosana , Johnson Alan T. , MacDiarmid Alan G.
Published: July 2006

We report on a simple method to fabricate, under ambient conditions and within seconds, Schottky nanodiodes using electrospun polyaniline nanofibers and an inorganic n-doped semiconductor. In addition to being a rectifier, the advantage of our design is the complete exposure of the rectifying nanojunction to the surrounding environment, making them attractive candidates in the potential fabrication of low power, supersensitive, and rapid response sensors as well. The diode parameters were calculated assuming the standard thermionic emission model of a Schottky junction, and the use of this junction as a gas sensor was examined.
Nanoscale electrical characterization of organic photovoltaic blends by conductive atomic force microscopy
Authors: Douhéret Olivier , Lutsen Laurence , Swinnen Ann , Breselge Martin , Vandewal Koen , Goris Ludwig , Manca Jean
Published: July 2006

Conductive atomic force microscopy (CAFM) is introduced to perform electrical characterization of organic photovoltaic blends with high spatial resolution. Reference blends used in organic bulk heterojunction solar cells are investigated. The ability of CAFM to electrically evidence phase separated donor and acceptor regions is demonstrated. Furthermore, local spectroscopy is performed to analyze charge transport mechanisms in the blends. Significant modifications of the electrical properties of the semiconducting polymers are shown to occur after blending with fullerene derivatives. Finally, the sensitivity of CAFM to photoelectrical phenomena is revealed. Current variations of few picoamperes are locally observed under illumination of P3HT:PCBM.
In-polar InN grown by plasma-assisted molecular beam epitaxy
Authors: Gallinat Chad S. , Koblmüller Gregor , Brown Jay S. , Bernardis Sarah , Speck James S. , Chern Grace D. , Readinger Eric D. , Shen Hongen , Wraback Michael
Published: July 2006

We study the effect of different deposition conditions on the properties of In-polar InN grown by plasma-assisted molecular beam epitaxy. GaN buffer layers grown in the Ga-droplet regime prior to the InN deposition significantly improved the surface morphology of InN films grown with excess In flux. Using this approach, In-polar InN films have been realized with room temperature electron mobilities as high as 2250cm2∕Vs. We correlate electron concentrations in our InN films with the unintentionally incorporated impurities, oxygen and hydrogen. A surface electron accumulation layer of 5.11×1013cm−2 is measured for In-polar InN. Analysis of optical absorption data provides a band gap energy of ∼0.65eV for the thickest InN films.
Complex quantum ring structures formed by droplet epitaxy
Authors: Huang Shesong , Niu Zhichuan , Fang Zhidan , Ni Haiqiao , Gong Zheng , Xia Jianbai
Published: July 2006

Well-defined complex quantum ring structures formed by droplet epitaxy are demonstrated. By varying the temperature of the crystallizing Ga droplets and changing the As flux, GaAs∕AlGaAs quantum single rings and concentric quantum double rings are fabricated, and double-ring complexes are observed. The growth mechanism of these quantum ring complexes is addressed.
A
Drosophila
model of Barth syndrome
Authors: Xu Yang , Condell Morgan , Plesken Heide , Edelman-Novemsky Irit , Ma Jinping , Ren Mindong , Schlame Michael
Published: July 2006

Barth syndrome is an X-linked disease presenting with cardiomyopathy and skeletal muscle weakness. It is caused by mutations in tafazzin, a putative acyl transferase that has been associated with altered metabolism of the mitochondrial phospholipid cardiolipin. To investigate the molecular basis of Barth syndrome, we created
Drosophila melanogaster
mutants, resulting from imprecise excision of a P element inserted upstream of the coding region of the tafazzin gene. Homozygous flies for that mutation were unable to express the full-length isoform of tafazzin, as documented by RNA and Western blot analysis, but two shorter tafazzin transcripts were still present, although the expression levels of their encoded proteins were too low to be detectable by Western blotting. The tafazzin mutation caused an 80% reduction of cardiolipin and a diversification of its molecular composition, similar to the changes seen in Barth patients. Other phospholipids, like phosphatidylcholine and phosphatidylethanolamine, were not affected. Flies with the tafazzin mutation showed a reduced locomotor activity, measured in flying and climbing assays, and their indirect flight muscles displayed frequent mitochondrial abnormalities, mostly in the cristae membranes. Thus, tafazzin mutations in
Drosophila
generated a Barth-related phenotype, with the triad of abnormal cardiolipin, pathologic mitochondria, and motor weakness, suggesting causal links between these findings. We conclude that a lack of full-length tafazzin is responsible for the cardiolipin deficiency, which is integral to the disease mechanism, leading to mitochondrial myopathy.
The mRNA Export Factor Sus1 Is Involved in Spt/Ada/Gcn5 Acetyltransferase-mediated H2B Deubiquitinylation through Its Interaction with Ubp8 and Sgf11
Authors: Köhler Alwin , Pascual-García Pau , Llopis Ana , Zapater Meritxell , Posas Francesc , Hurt Ed , Rodríguez-Navarro Susana
Published: July 2006

Sus1 acts in nuclear mRNA export via its association with the nuclear pore-associated Sac3–Thp1–Cdc31 complex. In addition, Sus1 plays a role in transcription through its interaction with the Spt/Ada/Gcn5 acetyltransferase (SAGA) complex. Here, we have analyzed function and interaction of Sus1 within the SAGA complex. We demonstrate that Sus1 is involved in the SAGA-dependent histone H2B deubiquitinylation and maintenance of normal H3 methylation levels. By deletion analyses, we show that binding of Sus1 to SAGA depends on the deubiquitinylating enzyme Ubp8 and Sgf11. Moreover, a stable subcomplex between Sus1, Sgf11, and Ubp8 could be dissociated from SAGA under high salt conditions. In vivo recruitment of Sus1 to the activated GAL1 promoter depends on Ubp8 and vice versa. In addition, histones coenrich during SAGA purification in a Sus1–Sgf11–Ubp8-dependent way. Interestingly, sgf11 deletion enhances the mRNA export defect observed in sus1Δ cells. Thus, the Sus1–Sgf11–Ubp8 module could work at the junction between SAGA-dependent transcription and nuclear mRNA export.
Initiation of Attachment and Generation of Mature Focal Adhesions by Integrin-containing Filopodia in Cell Spreading
Authors: Partridge Michael A. , Marcantonio Eugene E.
Published: July 2006

Integrin receptors, and associated cytoplasmic proteins mediate adhesion, cell signaling and connections to the cytoskeleton. Using fluorescent protein chimeras, we analyzed initial integrin adhesion in spreading fibroblasts with Total Internal Reflection Fluorescence (TIRF) microscopy. Surprisingly, sequential radial projection of integrin and actin containing filopodia formed the initial cell-matrix contacts. These Cdc42-dependent, integrin-containing projections recruited cytoplasmic focal adhesion (FA) proteins in a hierarchical manner; initially talin with integrin and subsequently FAK and paxillin. Radial FA structures then anchored cortical actin bridges between them and subsequently cells reorganized their actin, a process promoted by Src, and characterized by lateral FA reorientation to provide anchor points for actin stress fibers. Finally, the nascent adhesions coalesced until they formed mature FAs.
Evidence for an apartheid-like social structure in early Anglo-Saxon England
Authors: Thomas Mark G , Stumpf Michael P.H , Härke Heinrich
Published: July 2006

The role of migration in the Anglo-Saxon transition in England remains controversial. Archaeological and historical evidence is inconclusive, but current estimates of the contribution of migrants to the English population range from less than 10 000 to as many as 200 000. In contrast, recent studies based on Y-chromosome variation posit a considerably higher contribution to the modern English gene pool (50–100%). Historical evidence suggests that following the Anglo-Saxon transition, people of indigenous ethnicity were at an economic and legal disadvantage compared to those having Anglo-Saxon ethnicity. It is likely that such a disadvantage would lead to differential reproductive success. We examine the effect of differential reproductive success, coupled with limited intermarriage between distinct ethnic groups, on the spread of genetic variants. Computer simulations indicate that a social structure limiting intermarriage between indigenous Britons and an initially small Anglo-Saxon immigrant population provide a plausible explanation of the high degree of Continental male-line ancestry in England.
Compartmentalization of intracellular proinflammatory cytokines in bronchial intraepithelial T cells of stable lung transplant patients
Authors: Hodge G , Hodge S , Reynolds P N , Holmes M
Published: July 2006

Allograft rejection remains a major cause of morbidity and mortality following lung transplantation and is associated with an increased expression of T cell proinflammatory cytokines. We have shown that CD4+ T cell proinflammatory cytokine production was significantly reduced in peripheral blood and bronchoalveolar lavage (BAL) of stable lung transplant patients, consistent with immunosuppression therapy. However, analysis of inflammatory cytokine profiles of intraepithelial T cells in bronchial brushing (BB) may be more relevant than peripheral blood or BAL T cells for assessing immune graft status. To investigate the immunomodulatory effects of currently used immunosuppressive regimens on bronchial intraepithelial T cell cytokine production, whole blood, BAL and BB from stable lung transplant patients and control volunteers were stimulated in vitro and cytokine production by CD8+ and CD4+ T cell subsets determined using multi-parameter flow cytometry. In bronchial intraepithelial T cell subsets in control subjects and transplant patients there was compartmentalization of interferon (IFN)-γ and tumour necrosis factor (TNF)-α production, a decrease in interleukin (IL)-2 production by CD4+ T cells and CD4 : CD8 inversion compared with blood and BAL. Although there was a decrease in T cell proinflammatory cytokine production in blood of transplant patients, this was not found in BAL or bronchial intraepithelial CD8 T cell subsets, suggesting that the same level of immunosuppression may not occur in the lung of transplant recipients. Drugs that effectively reduce CD8 T cell proinflammatory cytokine production in the lung compartment may improve current protocols for reducing graft rejection in these patients.
Mannan-binding lectin plasma levels in leprosy: deficiency confers protection against the lepromatous but not the tuberculoid forms
Authors: Dornelles L N , Pereira-Ferrari L , Messias-Reason I
Published: July 2006

Mannan-binding lectin (MBL) is an important component of the first-line defence against infections. Evidence has shown that MBL deficiency, reducing phagocytosis and internalization of intracellular pathogens may protect the host against intracellular infections such as leprosy. In this study, we speculated whether genetically determined low MBL serum levels confer protection against Mycobacterium leprae infection. One hundred and ninety-one patients with leprosy, presenting lepromatous (n = 118), tuberculoid (n = 31), dimorph (n = 30) and indeterminate (n = 12) clinical forms and 110 healthy controls matched with the patients according to sex, age and ethnic background were investigated. MBL concentrations were measured in a double-antibody enzyme immune assay and C-reactive protein (CRP) serum levels by nephelometry. A significant negative association of MBL low values (< 100 ng/ml) was observed with lepromatous patients when comparing with controls and tuberculoid patients [10/118, 8.47%versus 21/110, 19.09%P = 0.03 χ2 with Yates’ correction, odds ratio (OR) 0.39, confidence interval (CI) 0.18–0.88 and 8/31, 25.81%, P = 0.02, OR 0.27, CI 0.09–0.75, respectively]. There was no significant difference in the distribution of MBL levels between patients and controls or among the clinical forms. The concentration of CRP was significantly increased in the patients (P = 0.0002) and in the lepromatous form (P = 0.0001) when compared to controls. A weak positive correlation between MBL and CRP levels was observed in the patients (P = 0.010, R = 0.255). These data suggest a protective role for MBL deficiency against the development of the most severe and multi-bacillary form of leprosy.