bluuebunny/crossref_metadata_2025 huggingface dataset:
Meal conditions affect the absorption of supplemental vitamin D3 but not the plasma 25-hydroxyvitamin D response to supplementation
Authors: Dawson-Hughes Bess , Harris Susan S , Palermo Nancy J , Ceglia Lisa , Rasmussen Helen
Published: February 2013

It is sometimes assumed that dietary fat is required for vitamin D absorption, although the impact of different amounts of dietary fat on vitamin D absorption is not established. This study was conducted to determine whether the presence of a meal and the fat content of the meal influences vitamin D absorption or the 25-hydroxyvitamin D [25(OH)D] response to supplemental vitamin D3. Based on earlier studies in rats we postulated that absorption would be greatest in the low-fat meal group. Sixty-two healthy older men and women were randomly assigned to one of three meal groups: no meal, high-fat meal, or low-fat meal; each was given a monthly 50,000 IU vitamin D3 supplement with the test breakfast meal (or after a fast for the no-meal group) and followed for 90 days. Plasma vitamin D3 was measured by liquid chromatography–mass spectroscopy (LC/MS) before and 12 hours after the first dose; plasma 25(OH)D was measured by radioimmunoassay at baseline and after 30 and 90 days. The mean 12-hour increments in vitamin D3, after adjusting for age and sex, were 200.9 nmol/L in the no-meal group, 207.4 nmol/L in the high-fat meal group, and 241.1 nmol/L in the low-fat meal group (p = 0.038), with the increase in the low-fat group being significantly greater than the increases in the other two groups. However, increments in 25(OH)D levels at 30 and 90 days did not differ significantly in the three groups. We conclude that absorption was increased when a 50,000 IU dose of vitamin D was taken with a low-fat meal, compared with a high-fat meal and no meal, but that the greater absorption did not result in higher plasma 25(OH)D levels in the low-fat meal group.
CYP2C8*3 Polymorphism and Donor Age are Associated With Allograft Dysfunction in Kidney Transplant Recipients Treated With Calcineurin Inhibitors
Authors: Gervasini Guillermo , Garcia Montserrat , Macias Rosa María , Benitez Julio , Caravaca Francisco , Cubero Juan Jose
Published: February 2013

Epoxieicosatrienoic acids (EETs) play a protective role against damaging processes in the kidney. We have assessed the effect of polymorphisms in EETs‐producing enzymes (CYP2C8 and CYP2J2) and other proteins involved in calcineurin inhibitors (CNIs) disposition (CYP3A4, CYP3A5, and ABCB1) on graft function and clinical outcome in 166 renal transplant recipients treated with CNIs. Both CYP2C8*3 and donor age greater than 48 years were associated to a higher incidence of delayed graft function (DGF) [OR = 2.01 (1.1–4.1), P = .04 and 5.14 (2.4–10.9), P < .0001; respectively] and worse creatinine clearance 1 year after grafting (P < .05 and P < .001, respectively). In addition, carrying 4–6 variants in the 3 ABCB1 loci and older donor age were individually associated to higher incidence of calcineurin‐inhibitor‐induced nephrotoxicity [OR = 2.38 (1.1–5.4), P = .03 and OR = 1.03 (1.01–1.06), P = .038]. Regression analyses confirmed the relevant effect of both CYP2C8*3 and donor age on graft dysfunction. Carrying the 2C8*3 allele and having a donor older than 48 years was defined as a high‐risk status and observed to be highly related to DGF [OR = 3.91 (1.46–10.48), P < .01] and worse creatinine clearance (P = .033). Our results show that genetic and clinical parameters can be combined to identify risk factors for allograft dysfunction in renal transplant recipients.
The Effect of Multiple Doses of Ketoconazole or Rifampin on the Single‐ and Multiple‐Dose Pharmacokinetics of Vorapaxar
Authors: Kosoglou Teddy , Statkevich Paul , Kumar Bharath , Xuan Fengjuan , Schiller James E. , Johnson‐Levonas Amy O. , Young Sophia , Cutler David L.
Published: February 2013

This randomized, open‐label, parallel‐group study evaluated the effects of multiple‐dose ketoconazole or rifampin on the single‐ and multiple‐dose pharmacokinetics of vorapaxar. Healthy subjects randomly received one of the following three treatments (N = 12/group): (1) ketoconazole 400 mg once daily (QD) for 28 days (Days 1–28) and single‐dose vorapaxar 20 mg on Day 7 followed by vorapaxar 2.5 mg QD for 21 days (Days 8–28); (2) rifampin 600 mg QD for 28 days (Days 1–28) and single‐dose vorapaxar 20 mg on Day 7 followed by vorapaxar 2.5 mg QD for 21 days (Days 8–28); and (3) placebo QD for 28 days (Days 1–28) and single‐dose vorapaxar 20 mg on Day 7 followed by vorapaxar 2.5 mg QD for 21 days (Days 8–28). Ketoconazole increased the steady‐state vorapaxar AUC0–24 h and Cmax by approximately twofold (GMR [90% CI]: 196% [173,222]; 193% [166,223], respectively), while rifampin decreased vorapaxar AUC0–24 h and Cmax by approximately 50% (GMR [90% CI]: 45.5% [40,52]; 61.4% [52,72], respectively) versus vorapaxar alone. Potent CYP3A4 inhibitors or inducers may cause moderate increases or decreases in vorapaxar exposure, respectively, which may have safety and/or efficacy implications; therefore, their concomitant use with vorapaxar is not recommended.
Population Pharmacodynamics of IPX066: An Oral Extended‐Release Capsule Formulation of Carbidopa–Levodopa, and Immediate‐Release Carbidopa–Levodopa in Patients With Advanced Parkinson's Disease
Authors: Mao Zhongping , Hsu Ann , Gupta Suneel , Modi Nishit B.
Published: February 2013

A pharmacodynamic model is presented to describe the motor effects (tapping rate, Unified Parkinson's Disease Rating Scale [UPDRS] Part III, and investigator‐rating of ON/OFF, including dyskinesia) of levodopa (LD) in patients with advanced idiopathic Parkinson's disease (PD) treated with immediate‐release (IR) carbidopa–levodopa (CD–LD) or an extended‐release (ER) formulation of CD–LD (IPX066). Twenty‐seven patients participated in this open‐label, randomized, single‐ and multiple‐dose, crossover study. The pharmacodynamic models included a biophase effect site with a sigmoid Emax transduction for tapping and UPDRS and an ordered categorical model for dyskinesia. The pharmacodynamics of LD was characterized by a conduction function with a half‐life of 0.59 hours for tapping rate, and 0.4 hours for UPDRS Part III and dyskinesia. The LD concentration for half‐maximal effect was 1530 ng/mL, 810 ng/mL, and 600 ng/mL for tapping rate, UPDRS Part III, and dyskinesia, respectively. The sigmoidicity of the transduction was 1.53, 2.5, and 2.1 for tapping rate, UPDRS Part III, and dyskinesia, respectively. External validation of the pharmacodynamic model using tapping rate indicated good performance of the model.
The Influence of Bypass Procedures and Other Anatomical Changes in the Gastrointestinal Tract on the Oral Bioavailability of Drugs
Authors: De Smet Julie , Van Bocxlaer Jan , Boussery Koen
Published: February 2013

The gastrointestinal (GI) tract plays an important role in the absorption of orally administered drugs. However, in some cases the anatomy of the GI tract is changed due to GI surgery, which has the potential of influencing drug bioavailability. In this review, we aim to compile, review, and comment the existing but sometimes fragmented scientific data regarding the impact of GI surgery on the oral bioavailability of drugs. Relevant reports were gathered through the PubMed database from database inception through January 2012. Drugs for which at least one trial or case report suggested a change in oral bioavailability or absorption caused by GI surgery are discussed in detail. Major methodological differences, such as study design, number of subjects and choice of reference group, were observed in the reported studies. Predicting the impact of GI surgery on the oral bioavailability was therefore difficult to perform, even the most sophisticated classification systems could not be used for predicting purposes.
Alluvial sediment or playas: What is the dominant source of sand and silt in desert soil vesicular A horizons, southwest USA
Authors: Sweeney Mark R. , McDonald Eric V. , Markley Christopher E.
Published: February 2013

Vesicular A (Av) soil horizons form beneath desert pavements from the accretion of aeolian sediment (dust) commonly thought to be derived primarily from desiccating pluvial lakes and playas, with contributions from ephemeral washes and alluvial fans. Particle size distributions of Av horizons are typically bimodal with primary modes of very fine silt and fine sand, suggesting that the horizon matrix is derived from multiple sources. Here we conduct detailed chemical and physical analysis of both Av horizon soil samples and potential sources of aeolian sediment to better constrain the relative contributions of dust associated with the development of Av horizons. Geochemical data from both sand (125–250 µm) and silt (2–32 µm) fractions in Av horizons and potential dust sources in the eastern Mojave Desert and western Sonora Desert, USA, point to large contributions from nearby sources including distal alluvial fans and washes, and comparably lower contributions from regional sources such as playas. The silt mode is derived from suspension transport of dust, and the fine sand mode is derived from saltating sand. The desiccation of pluvial lakes in the Mojave Desert is commonly believed to have driven episodes of aeolian activity, contributing to sand dunes and Av horizon formation. We propose that alluvial fans and washes are underappreciated as desert dust sources and that pulses of dust from late Pleistocene and Holocene alluvial fans dwarfed pulses of dust from desiccating pluvial lakes in the eastern Mojave Desert.
Response of soil nitrogen retention to the interactive effects of soil texture, hydrology, and organic matter
Authors: Castellano Michael J. , Lewis David Bruce , Kaye Jason P.
Published: February 2013

Advances in nitrogen (N) saturation and retention theories have focused on soil organic matter (SOM) biogeochemistry in the absence of dynamic soil hydrology. Here we exploit two soil types with contrasting textures that span a hillslope gradient to test hypotheses that suggest N saturation symptoms are regulated by the interactive effects of soil texture, OM, and hydrology on N retention capacity (maximum pool size) and N retention kinetics (N retention rate). Down the hillslope gradient, soil solution nitrate (NO3) concentrations sampled with lysimeters increased, while 15NO3‐N retention decreased. Landscape location (upland, hillslope, and toeslope) and soil type interacted to affect soil solution NO3 concentrations so that the downslope increase in NO3 was greater in sandy versus silty soils. These patterns manifest despite a downslope increase in soil organic carbon (SOC) and C/N ratios. A positive correlation between saturated hydraulic conductivity and soil solution NO3 sampled in zero‐tension lysimeters during precipitation events suggested that high hydraulic conductivity promotes periodic rapid NO3 transport at rates that exceed retention kinetics. The downslope increase in soil solution NO3 in spite of a concomitant increase in SOC and C/N ratios provides an important contrast with previous N saturation research that highlights negative correlations between SOM C/N ratios and NO3 concentrations and suggests NO3 transport along connected hillslope flow paths may overwhelm stoichiometric sinks for inorganic N retention in SOM. Our results reveal important gaps in N retention theory based on SOM biogeochemistry alone and demonstrate how coupled biogeochemical and hydrological models can improve predictions of N saturation, particularly when considering periodic advective NO3 transport in the vadose zone. We show that in coarse‐textured soils, low capacity for protection of SOM N by association with fine mineral particles interacts with rapid hydrological flushing of NO3 to enhance the expression of ecosystem N saturation symptoms.
K‐Pg extinction: Reevaluation of the heat‐fire hypothesis
Authors: Robertson Douglas S. , Lewis William M. , Sheehan Peter M. , Toon Owen B.
Published: February 2013

The global debris layer created by the end‐Cretaceous impact at Chicxulub contained enough soot to indicate that the entire terrestrial biosphere had burned. Preliminary modeling showed that the reentry of ejecta would have caused a global infrared (IR) pulse sufficient to ignite global fires within a few hours of the Chicxulub impact. This heat pulse and subsequent fires explain the terrestrial survival patterns in the earliest Paleocene, because all the surviving species were plausibly able to take shelter from heat and fire underground or in water. However, new models of the global IR heat pulse as well as the absence of charcoal and the presence of noncharred organic matter have been said to be inconsistent with the idea of global fires that could have caused the extinctions. It was suggested that the soot in the debris layer originated from the impact site itself because the morphology of the soot, the chain length of polycyclic aromatic hydrocarbons, and the presence of carbon cenospheres were said to be inconsistent with burning the terrestrial biosphere. These assertions either are incorrect or have alternate explanations that are consistent with global firestorms. We show that the apparent charcoal depletion in the Cretaceous‐Paleogene layer has been misinterpreted due to the failure to correct properly for sediment deposition rates. We also show that the mass of soot potentially released from the impact site is far too low to supply the observed soot. However, global firestorms are consistent with both data and physical modeling.
Effects of repeated fires on ecosystem C and N stocks along a fire induced forest/grassland gradient
Authors: Cheng Chih‐Hsin , Chen Yung‐Sheng , Huang Yu‐Hsuan , Chiou Chyi‐Rong , Lin Chau‐Chih , Menyailo Oleg V.
Published: February 2013

Repeated fires might have different effect on ecosystem carbon storage than a single fire event, but information on repeated fires and their effects on forest ecosystems and carbon storage is scarce. However, changes in climate, vegetation composition, and human activities are expected to make forests more susceptible to fires that recur with relatively high frequency. In this study, the effects of repeated fires on ecosystem carbon and nitrogen stocks were examined along a fire‐induced forest/grassland gradient wherein the fire events varied from an unburned forest to repeatedly burned grassland. Results from the study show repeated fires drastically decreased ecosystem carbon and nitrogen stocks along the forest/grassland gradient. The reduction began with the disappearance of living tree biomass, and followed by the loss of soil carbon and nitrogen. Within 4 years of the onset of repeated fires on the unburned forest, the original ecosystem carbon and nitrogen stocks were reduced by 42% and 21%, respectively. Subsequent fires caused cumulative reductions in ecosystem carbon and nitrogen stocks by 68% and 44% from the original ecosystem carbon and nitrogen stocks, respectively. The analyses of carbon budgets calculated by vegetation composition and stable isotopic δ13C values indicate that 84% of forest‐derived carbon is lost at grassland, whereas the gain of grass‐derived carbon only compensates 18% for this loss. Such significant losses in ecosystem carbon and nitrogen stocks suggest that the effects of repeated fires have substantial impacts on ecosystem and soil carbon and nitrogen cycling.
Modeling burned area in Europe with the Community Land Model
Authors: Migliavacca M. , Dosio A. , Kloster S. , Ward D. S. , Camia A. , Houborg R. , Houston Durrant T. , Khabarov N. , Krasovskii A. A. , San Miguel‐Ayanz J. , Cescatti A.
Published: February 2013

In this study, we present simulations of a burned area at a European scale for the period 1990–2009 conducted with the Community Land Model (CLM). By using statistics on fire counts and mean fire suppression time from the European Fire Database, we refined the parameterization of the functions describing human ignition/suppression, and we modified the description of biomass availability for fires. The results obtained with the modified model show an improvement of the description of the spatial and interannual variability of the burned area: the model bias is reduced by 45%, and the explained variance is increased by about 9% compared to the original parameterization of the model. The observed relationships between burned area, climate (temperature and precipitation), and aboveground biomass are also reproduced more accurately by the modified model. This is particularly relevant for the applicability of the model to simulate future fire regimes under different climate conditions. However, results showed an overestimation of the burned area for some European countries (e.g., Spain and France) and an underestimation in years with an extreme fire season in Mediterranean countries. Our results highlight the need for refining the parameterization of human ignition/suppression and fuel availability for regional application of fire models implemented in land surface models.
Interannual, seasonal, and retrospective analysis of the methane and carbon dioxide budgets of a temperate peatland
Authors: Olson D. M. , Griffis T. J. , Noormets A. , Kolka R. , Chen J.
Published: February 2013

Three years (2009–2011) of near‐continuous methane (CH4) and carbon dioxide (CO2) fluxes were measured with the eddy covariance (EC) technique at a temperate peatland located within the Marcell Experimental Forest, in northern Minnesota, USA. The peatland was a net source of CH4 and a net sink of CO2 in each year with annual carbon budgets of −26.8 (±18.7), −15.5 (±14.8), and −14.6 (±21.5) g C m−2 yr−1 for 2009–2011, respectively. Differences in the seasonal hydrometeorological conditions among the three study years were most pronounced during 2011, which was considerably warmer (+1.3°C) and wetter (+40 mm) than the 30 year average. The annual CH4 budget was +11.8 (±3.1), +12.2 (±3.0), and +24.9 (±5.6) g C m−2 yr−1 for the respective years and accounted for 23%–39% of the annual carbon budget. The larger CH4 emission in 2011 is attributed to significant warming of the peat column coupled with a high water table position throughout the entire growing season. Historical (1991–2011) CH4 emissions were estimated based on long‐term hydrometeorological records and functional relationships derived from our 3 year field study. The predicted historical annual CH4 budget ranged from +7.8 to +15.2 (±2.7) g CH4‐C m−2 yr−1. Recent (2007–2011) increases in temperature, precipitation, and rising water table at this site suggest that CH4 emissions have been increasing, but were generally greater from 1991 to 1999 when average soil temperature and precipitation were higher than in recent years. The global warming potential (considering CO2 and CH4) for this peatland was calculated based on a 100 year time horizon. In all three study years, the peatland had a net positive radiative forcing on climate and was greatest (+187 g C m−2) in 2011. The interannual variability in CH4 exchange at this site suggests high sensitivity to variations in hydrometeorological conditions.
“Dictating the Suitable Way of Life”: Mental Hygiene for Children and Workers in Socialist Mexico, 1934–1940
Authors: Molina Andrés Ríos
Published: February 2013

After theMexicanRevolution (1910–1920), an ambitious project of national reconstruction began in which education and health were two priorities in the consolidation of a new nation. In this context of social, cultural, and political transformation, mental hygiene was a field that made it possible to articulate the professional practice of psychiatrists with the project of the nation promoted by postrevolutionary governments. InMexico, the mental hygiene movement was headed by the same doctors who professionalized the practice of psychiatry and made it a specialized field of knowledge. The first generation of psychiatrists managed to integrate mental hygiene into health and education policies during the socialist administration of presidentLázaroCárdenas; a phenomenon that made evident the articulation between mental hygiene, social medicine, and nationalist discourse. Discussion will focus on proposals made from the perspective of mental hygiene as a function of two social sectors regarded as priorities by theCárdenas government: children and workers.
The Reconstitution of Political Theory: David Easton, Behavioralism, and the Long Road to System
Authors: Gunnell John G.
Published: February 2013

During the last half of the twentieth century, the concept of system was arguably the most important concept in the theoretical repertoire of the discipline of American political science. Although systems analysis was broadly employed in the behavioral sciences, David Easton's work was particularly influential in the study of politics. This is in part because he attempted to develop a distinct account of the political system that was not theoretically subservient either to general systems theory or to conceptions of the social system such as that advanced by Talcott Parsons. Although a great deal of attention has been devoted to Easton's theory, the origins and evolution of the system concept in his work have not been carefully reconstructed and analyzed.
Comparison of acid degumming and enzymatic degumming process for Silybum marianum seed oil
Authors: Mei Lin , Wang Liang , Li Qianqian , Yu Jiangnan , Xu Ximing
Published: February 2013

BACKGROUND

In this study the effects of processing conditions of acid degumming and enzymatic degumming on the removal of phospholipids from Silybum marianum seed oil were investigated and the degumming efficiency was compared based on the phospholipid content.

RESULTS

An orthogonal array experimental design was performed to optimise the process of citric acid degumming. Based on range analysis and analysis of variance, the optimal processing conditions were determined to be a citric acid dosage of 3 g kg−1, a degumming temperature of 70 °C, a water addition of 40 mL kg‐1 and a degumming time of 30 min. Under these conditions the phospholipid content of degummed S. marianum seed oil was reduced from 273.0 to 128.1 mg kg−1. In the case of enzymatic degumming, the effects of enzyme reaction time and enzyme dosage were investigated using single‐factor experiments. The optimal processing conditions were found to be an enzyme reaction time of 6 h and an enzyme dosage of 100 mg kg−1 oil. Under these conditions the phospholipid content of degummed S. marianum seed oil was reduced to 17.95 mg kg−1.

CONCLUSION

The results indicated that enzymatic degumming is more effective than acid degumming. © 2013 Society of Chemical Industry
Knowledge Management Practices in the Nigerian Telecommunications Industry
Authors: Suraj Olunifesi Adekunle , Ajiferuke Isola
Published: February 2013

The main objective of the study was to examine how Nigerian telecommunications organizations leverage knowledge in achieving organizational performance and competitive advantage. Forty organizations were selected by using stratified random sampling from the 150 organizations in the Nigerian telecommunications industry. Twenty‐nine of the selected organizations agreed to participate in the study, and questionnaires were then distributed to 14 senior executives in each of these organizations. Four hundred and six questionnaires were returned, but only 329 complete ones were used for analysis. The results from the study showed the following: that there is poor management of human capital in the Nigerian telecommunications industry; that lack of effective communication appears to be the bane of structural capital management in the industry; that most of the telecommunications companies in Nigeria have had a long‐term relationship with their customers; and that Nigerian telecommunications organizations are familiar with knowledge management as a concept. The results also showed slight differences among the six groups of organizations in their management of intellectual capital with the Local Exchange operators and National Carrier as the best and worst performers, respectively. In conclusion, it is suggested that Nigerian telecommunications organizations should strive to provide a conducive and an enabling working environment, where people can share ideas about work without being shut down by bosses and bureaucrats, and that they should try harder to implement their customers' suggestions, especially when such suggestions have to do with meeting the customers' needs. Copyright © 2013 John Wiley & Sons, Ltd.
A Practical Proposal for a “Competence Plan Fulfillment” Key Performance Indicator
Authors: Capece Guendalina , Bazzica Paolo
Published: February 2013

This paper deals with the creation of a framework for competence management research with specific emphasis on firm context. We consider that the traditional approaches to competence assignment planning lack in the development of appropriate tools for the management of the competence. Nowadays there is, indeed, a need for research into competence and the management of competence. In this paper, we develop a framework for competence management. Because no universally accepted framework exists yet, the following article proposes various aspects of competence management and illustrates a new approach to characterize and manage competency.

Building a tool oriented towards competency allocation allows the development of a dynamic competency database and is a first step to improving the achievement of relevant goals such as competence allocation or project team building (matching of tasks and competencies), and the development and transfer of competencies (e.g., by supporting reflective practice). Copyright © 2013 John Wiley & Sons, Ltd.
Global asymptotic stability of certain third‐order nonlinear differential equations
Authors: Zhang Lijuan , Yu Lixin
Published: February 2013

In this paper, we give some sufficient conditions to guarantee global asymptotic stability of the zero solution of the third‐order nonlinear differential equation: x ′ ′ ′ + g(x,x ′ ,x ′ ′ ) + f(x,x ′ )x ′ + h(x) = 0. Two examples are also given to illustrate our results. Copyright © 2013 John Wiley & Sons, Ltd.
Nutrient leakage from the North Pacific to the Bering Sea (IODP Site U1341) following the onset of Northern Hemispheric Glaciation?
Authors: März C. , Schnetger B. , Brumsack H.‐J.
Published: February 2013

Intergrated Ocean Drilling Program Expedition 323 recovered a sediment record covering the last ~4.3 Ma from the Bering Sea (Integrated Ocean Drilling Program Site U1341, Bowers Ridge, 2177 m water depth). To resolve Pliocene‐Pleistocene paleoenvironmental changes in this marginal basin, ~190 sediment samples were analyzed for their bulk element composition. Aluminium contents in Bowers Ridge sediments are variable but overall higher toward younger sediments, probably related to the intensification of the Northern Hemispheric Glaciation and increasing sea ice transport in the Bering Sea. The gradual increase of terrigenous input is mirrored by decreasing SiO2 and excess Si (Sixs) contents, but the overall Si enrichment of the deposits reflects continuous opal deposition since the Pliocene at Bowers Ridge. Unlike in the North Pacific, the Sixs record at Site U1341 does not support a dramatic decrease in opal export following the onset of the Northern Hemispheric Glaciation around 2.7 Ma, but SiO2xs have higher accumulation rates (up to ~8 g/cm2/ka) between ~2.6 and ~1.8 Ma BP. During this period, the major oceanic opal deposition centers shifted globally from open marine high latitude regions to upwelling areas. We here discuss how the onset of North Pacific stratification at ~2.7 Ma BP may have caused leakage of nutrient‐rich deep/intermediate North Pacific water into the Bering Sea via the deep Kamtchatka Strait, leading to increased opal deposition—and likely reactive organic matter export—at Bowers Ridge. As a result, magnetic and geochemical records were overprinted by intensified diagenesis, significantly affecting their applications as paleoceanographic proxies.
Reconstructing 7000 years of North Atlantic hurricane variability using deep‐sea sediment cores from the western Great Bahama Bank
Authors: Toomey Michael R. , Curry William B. , Donnelly Jeffrey P. , van Hengstum Peter J.
Published: February 2013

Available overwash records from coastal barrier systems document significant variability in North Atlantic hurricane activity during the late Holocene. The same climate forcings that may have controlled cyclone activity over this interval (e.g., the West African Monsoon, El Niño–Southern Oscillation (ENSO)) show abrupt changes around 6000 yrs B.P., but most coastal sedimentary records do not span this time period. Establishing longer records is essential for understanding mid‐Holocene patterns of storminess and their climatic drivers, which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity. Storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep‐sea, and bank‐edge sediments may offer an unexplored archive of long‐term hurricane activity. Here, we develop this new approach, reconstructing more than 7000 years of North Atlantic hurricane variability using coarse‐grained deposits in sediment cores from the leeward margin of the Great Bahama Bank. High energy event layers within the resulting archive are (1) broadly correlated throughout an offbank transect of multi‐cores, (2) closely matched with historic hurricane events, and (3) synchronous with previous intervals of heightened North Atlantic hurricane activity in overwash reconstructions from Puerto Rico and elsewhere in the Bahamas. Lower storm frequency prior to 4400 yrs B.P. in our records suggests that precession and increased NH summer insolation may have greatly limited hurricane potential intensity, outweighing weakened ENSO and a stronger West African Monsoon—factors thought to be favorable for hurricane development.
Nutrient conditions in the subpolar North Atlantic during the last glacial period reconstructed from foraminifera‐bound nitrogen isotopes
Authors: Straub M. , Tremblay M. M. , Sigman D. M. , Studer A. S. , Ren H. , Toggweiler J. R. , Haug G. H.
Published: February 2013

Surface nitrate concentration is a potentially useful diagnostic in reconstructing the past circulation of high‐latitude North Atlantic waters. Moreover, nutrient consumption in the North Atlantic surface impacts the atmospheric concentration of carbon dioxide. To reconstruct nutrient conditions in the subpolar North Atlantic region during the last ice age, a record of foraminifera‐bound δ15N was measured in Neogloboquadrina pachyderma (sin.) from core V28‐73 south of Iceland (57.2°N, 20.9°W). Foraminifera‐bound δ15N is up to 2‰ lower during the last ice age than during the Holocene, suggesting as much as ~25% less complete nitrate consumption during the former. This is consistent with stronger light limitation associated with a deeper summer surface mixed layer, perhaps related to the formation of Glacial North Atlantic Intermediate Water previously suggested to have occurred near the core site. However, three single‐point maxima in δ15N in the glacial section and the sharp deglacial δ15N rise coincide with Heinrich event layers. This suggests that increased water column stratification during Heinrich events, presumably due to surface freshening, reduced the nutrient supply from below and led to nearly complete nitrate consumption in the summertime mixed layer. The Heinrich layers in V28‐73 are not accompanied by δ18O minima in either N. pachyderma (sin.) or Globigerinoides bulloides, which we tentatively attribute to extreme mixed‐layer shoaling. The reconstructed subpolar North Atlantic upper water column changes—both glacial/interglacial and millennial—are inverse to those inferred for the Antarctic.
Coupled and decoupled responses of continental and marine organic‐sedimentary systems through the Paleocene‐Eocene thermal maximum, New Jersey margin, USA
Authors: Schneider‐Mor Aya , Bowen Gabriel J.
Published: February 2013

The flux of sediment and organic carbon from continents to the coastal ocean is an important factor governing organic burial in coastal sediments, and these systems preserve important records of environmental and biogeochemical conditions during past global change events. Burial of organic materials in coastal systems can be promoted by chemical resilience or through protection by association with mineral surfaces, but the role and influence of these processes on organic records from ancient sediments is poorly known. We studied sediment and organic matter burial as particulate organic matter (POM) and mineral‐bound organic matter (MOM) in near‐shore marine sediments from the Wilson Lake core (New Jersey, USA) that span the Paleocene‐Eocene thermal maximum (PETM), a climatic perturbation 55.9 Myr ago. Our results show that distinct POM and MOM fractions can be isolated from sediments. Both fractions appear to be dominated by terrestrial material, but POM consisted primarily of recently synthesized material whereas MOM included a significant fraction of pre‐aged organic matter from soils or ancient sediments. Variation in organic burial through the PETM is associated with changes in inorganic nitrogen burial, clay mineralogy, and clastic grain size that we associate with enhanced continental weathering, erosion and redeposition of ancient kaolinites, and eustatic sea level variation, respectively. These results provide a new perspective on factors governing carbon burial and carbon isotope records in ancient marine margin settings and offer information on rate and phasing of late Paleocene/early Eocene Earth system changes that may constrain interpretations of the cause of the PETM climate change event.
School Vouchers and Student Outcomes: Experimental Evidence from Washington, DC
Authors: Wolf Patrick J. , Kisida Brian , Gutmann Babette , Puma Michael , Eissa Nada , Rizzo Lou
Published: February 2013

School vouchers are the most contentious form of parental school choice. Vouchers provide government funds that parents can use to send their children to private schools of their choice. Here we examine the empirical question of whether or not a school voucher program in Washington, DC, affected achievement or the rate of high school graduation for participating students. The District of Columbia Opportunity Scholarship Program (OSP) has operated in the nation's capital since 2004, funded by a federal government appropriation. Because the program was oversubscribed in its early years of operation, and vouchers were awarded by lottery, we were able to use the “gold standard” evaluation method of a randomized experiment to determine what impacts the OSP had on student outcomes. Our analysis revealed compelling evidence that the DC voucher program had a positive impact on high school graduation rates, suggestive evidence that the program increased reading achievement, and no evidence that it affected math achievement. We discuss the implications of these findings in light of recent policy developments including the reauthorization of the OSP and the enactment or expansion of more than a dozen school voucher or voucher‐type programs throughout the United States in 2011 and 2012.
Kompetenzanmaßung?/„Verschleierte Wirklichkeit”︁ oder Erkennbare Welt?
Authors: Kafka P. , Krueger F. R.
Published: February 2013

P. Kafka
Festansprache des Präsidenten
Authors: Schmidt‐Tiedemann K. J.
Published: February 2013

Nach der Begrüßung der Ehrengäste — beginnend mit der Frau Bundesminister für Bildung und Wissenschaft, Dr. Dorothee Wilms –, der ausländischen Gäste und der Teilnehmer sowie einem Dank an die Gastgeber und die Organisatoren der Tagung folgte der Hauptteil der Ansprache.
Hahn‐Meitner‐Institut für Kernforschung 25 Jahre alt
Authors: Greulich W.
Published: February 2013

Im März dieses Jahres wurde das Hahn‐Meitner‐Institut für Kernforschung (HMI) in Berlin‐Wannsee 25 Jahre alt. Auf dem Programm der zweitägigen Jubiläumsfeier Mitte Juni standen ein wissenschaftliches Kolloquium (14. Juni) mit Vorträgen über den derzeitigen Stand und zukünftige Entwicklungen der Forschung im HMI, ein Festakt in der Berliner Urania (15. Juni), an dern fast 900 eingeladene Gäste teilnahmen, und im Anschluß daran eine Gaudi auf dem Gelände des HMI, zu der auch die Bewohner von Berlin‐Wannsee eingeladen waren.
Physik und Abrüstung: Eindrücke von der „Arms Control and Disarmament”︁‐Diskussion an einer amerikanischen Universität
Authors: Bienlein J. K.
Published: February 2013

Die Vorlesungen des „Arms Control and Disarmament Program”︁ der Stanford University sowie studentische Aktivitäten dort werden beschrieben. Aus der sachlichen Diskussion ist ein Gesichtspunkt herausgegriffen: Die Chance, die Wissenschaft und Technik bieten, um das gegenseitige Mißtrauen in der Welt abzubauen und die Verifizierung von Rüstungskontrollabkommen zu ermöglichen. Die Abkommen über den Teststopp oberirdischer Kernwaffenversuche sowie der SALT‐II‐Vertrag werden als Beispiele erläutert. Zur Erleichterung des Verständnisses des Umfelds der US‐Diskussion sind einige Bemerkungen über Amerika und die Rolle der großen Universitäten vorangestellt.
Mehr Licht!: Neben BESSY und HASYLAB nehmen die Pläne für eine europäische Synchrotronstrahlungsquelle Gestalt an
Authors: Koch E. E.
Published: February 2013

Nach der Entwicklung von Speichermengen, die eigens für die Erzeugung von Synchrotronstrahlung optimiert wurden, bahnt sich jetzt durch den Einsatz spezieller Magnetstrukturen, sogenannter Wiggler und Undulatoren, ein neues Zeitalter in der Nutzung dieser einzigartigen Strahlungsquelle an. Diese Entwicklung wird weitreichende Auswirkungen auf die Spektroskopie und Strukturuntersuchung mit Vakuum‐Ultraviolett und Röntgenstrahlung haben, vergleichbar der ursprünglichen Einführung der Synchrotronstrahlung als spektroskopisches Werkzeug. Ausgehend von einer kurzen Beschreibung der bestehenden Einrichtungen in Deutschland, dem Berliner Speicherring für Synchrotronstrahlung BESSY und dem Hamburger Synchrotronstrahlungslabor HASYLAB, werden die Eigenschaften der geplanten Europäischen Synchrotronstrahlungsquelle (ESRF) beschrieben. Mit ihr wird elektromagnetische Strahlung insbesondere im Röntgenbereich verfügbar, mit Intensitäten an der Grenze des technisch Beherrschbaren.
Experimentelle Tests der Myon‐Leptonenzahl‐Erhaltung
Authors: Engfer R.
Published: February 2013

Reaktionen und Zerfälle, bei denen die Myon‐Leptonenzahl (Lμ) nicht erhalten bleibt, sind in fast allen neueren Elementarteilchen‐Modellen, die über das Standardmodell hinausgehen, erlaubt, und es gibt auch keine ersichtliche Symmetrie, die eine strenge Lμ‐Erhaltung fordert. Solche Prozesse, die im folgenden der Kürze halber als „Lμ‐verletzend”︁ bezeichnet werden, sollten daher auftreten — wenn auch mit einer sehr geringen Wahrscheinlichkeit. Bis heute ist noch kein Lμ‐verletzender Prozeß beobachtet worden. Statt dessen ließen sich experimentell nur obere Grenzen bestimmen, die die Parameter der Teilchenmodelle einschränken, z. B. untere Grenzen der Massen von zusätzlich postulierten Eichbosonen liefern. Sollten künftig Lμ‐verletzende Prozesse beobachtet werden, so sind deren Verzweigungsverhältnisse sehr empfindliche Größen zum Test dieser Modelle und ihrer Parameter. Solche Beobachtungen wären dann eine wesentliche Ergänzung der Experimente mit Hochenergie‐Beschleunigern der neuen Generation und ein wichtiger Beitrag zur Lösung des Rätsels der Teilchenfamilien. Jede Möglichkeit, die oberen Wahrscheinlichkeitsgrenzen von Lμ‐verletzenden Prozessen experimentell zu präzisieren, sollte daher wahrgenommen werden.
Begegnungen mit den Physik‐Nobelpreisträgern des Jahres 1984
Authors: Faissner H. C.
Published: February 2013

„Für ihre entscheidenden Beiträge zu dem großen Projekt, das zur Entdeckung der Feldquanten W und Z, den Vermittlern der Schwachen Wechselwirkung, führte”︁, wurden Carlo Rubbia und Simon van der Meer, beide vom CERN (Genf), mit dem Physik‐Nobelpreis 1984 ausgezeichnet. Über die „entscheidenden Beiträge”︁ haben die Physikalischen Blätter in Heft 5/1983 und 11/1983 [1, 2] ausführlich berichtet. Dies soll hier nicht wiederholt werden. Statt dessen zeichnet Professor Faissner, der mit den beiden Laureaten seit über zwanzig Jahren durch gemeinsame Forschungsprojekte verbunden ist und zu den Autoren der ausgezeichneten Arbeiten gehört, im folgenden ein lebendiges Bild von den Persönlichkeiten Rubbias und van der Meers. Er berichtet über Begegnungen und Gespräche, an die er sich besonders gut erinnert; über einige davon hat er Tagebuch geführt. Er skizziert damit auch den weiten Weg, den CERN von den ersten tastenden Versuchen auf dem Gebiet der schwachen Wechselwirkung bis zur glanzvollen Bestätigung der einheitlichen elektroschwachen Theorie gegangen ist.
Grundlagenforschung — Fluch oder Segen?: Festrede zum 25jährigen Jubiläum von DESY
Authors: Panofsky Wolfgang K. H.
Published: February 2013

„Wir haben uns hier versammelt, um das 25jährige Jubiläum von DESY zu feiern. Es freut mich sehr, daß ich an diesem Fest mitwirken kann, und zwar aus mehreren Gründen. Erstens ist DESY ein Schwesterinstitut des Stanford Linear Accelerator Center, kurz SLAC, das zur Stanford‐Universität in Kalifornien gehört und wo ich seit 34 Jahren arbeite. SLAC und DESY arbeiten auf ähnlichen Gebieten, wir betreiben beide Elektronenbeschleuniger und Elektron‐Positron‐Speicherringe, unsere Institute haben ähnliche Größe, wir haben beide ungefähr die gleiche Zahl von, Mitarbeitern, und wir fangen beide jetzt an, Kollisionsmaschinen neuer Art zu bauen. Zum anderen bin ich sehr gerne hier, um DESY zu den großen Fortschritten der Wissenschaft zu gratulieren, die von hier in Bewegung gesetzt werden. Und schließlich ist dies für mich ein sentimentaler Besuch. Von 1919 bis 1934 lebte ich als Kind in Hamburg; ich wurde an der Gelehrtenschule des Johanneums erzogen, und mein Vater lehrte an der Universität Hamburg.
Fraktale Strukturen, Mandelbrot‐Menge und die Theorie der Phasenübergänge
Authors: Peitgen H. O. , Richter P. H.
Published: February 2013

Zum Titelbild des neuen Jahrgangs
Wissenschaft, Bildung und Politik: Wechselwirkungen
Authors: Maier H.
Published: February 2013

Aus Platzgründen kann das Referat von Kultusminister Maier hier nicht in voller Länge wiedergegeben werden. Im folgenden ist der zweite Teil der Rede abgedruckt, der sich mit einigen aktuellen Problemen der staatlichen Forschungsförderung befaßt, wie Elitebildung, Nachwuchsförderung, Verbesserung der Rahmenbedingungen für wissenschaftliche Arbeit und, abschließend, Transfer wissenschaftlicher Forschungsergebnisse in die allgemeine Bildung. In den hier nicht wiedergegebenen Abschnitten seines Vortrages referierte Professor Maier zunächst über die Bedeutung einer freiheitlichen Gesellschaftsordnung als der zentralen Voraussetzung für ungehinderte Forschung. Sodann beschrieb er die heutige Wissenschaftsförderung im Kontext staatlicher Wirtschaftspolitik. Ein weiterer Abschnitt war der heute so populären Kritik an naturwissenschaftlicher Forschung und technischer Entwicklung gewidmet, die sich aus dem Spannungsfeld Ökonomie — Ökologie nährt.
Ionentriebwerke für Satelliten und Raumsonden
Authors: Löb H.
Published: February 2013

Elektrische Raketentriebwerke stehen heute an der Schwelle ihres praktischen Einsatzes. Als Niederschub‐Systeme mit großen Strahlgeschwindigkeiten werden sie die konventionellen, chemischen Antriebe ergänzen, und zwar bei der Stabilisierung schwerer Satelliten sowie zur Durchführung anspruchsvoller interplanetarer Flüge. Unter mehreren Modellen aus den Triebwerksklassen Ionen‐ und Plasmageräte spielen die deutschen Radiofrequenz‐Ionentriebwerke RIT 10 und RIT 35 international eine wichtige Rolle.
25 Jahre Laser
Authors: Kaiser W.
Published: February 2013

Das Jahr 1960 brachte mit der Entwicklung des ersten Lasers den Auftakt einer beispiellosen Erfolgsgeschichte einer neuen Technologie. Als Lichtquelle extrem monochromatischer Strahlung, extrem hoher Leistung, extremer Schmalbandigkeit und einen weiten Bereich des Spektrums erfassend oder sogar durchstimmbar hat der Laser heute seinen festen Platz in Technik, Medizin, Umweltforschung, Kunst und Unterhaltung und vor allem in der Wissenschaft gefunden. Laser haben dazu beigetragen, das Licht selbst besser zu verstehen (Photonenstatistik) und, als Hilfsmittel der Spektroskopie, die Struktur von Atomen, Molekülen und Festkörpern aufzuklären. Immer neue Anwendungsmöglichkeiten halten den Laser in den Schlagzeilen. 1984 wurden nach Angaben des Magazins Lasers & Applications in den nichtkommunistischen Ländern 1 255 700 Laser verkauft (darunter knapp 1 Million Halbleiterlaser und über 200 000 He‐Ne‐Laser.) Im folgenden zeichnet ein „Mann der ersten Stunde”︁ einen kurzen Abriß der faszinierenden Entwicklung des Lasers und seiner Anwendungen.
Schwerpunkt Biophysik: Strukturfluktuationen in Proteinen
Authors: Parak F.
Published: February 2013

Der dreidimensionale Aufbau von Proteinmolekülen ist nicht beliebig genau definiert. Bei physiologischen Temperaturen verschwimmt die Struktur durch diffusionsartige Bewegungen von Molekülbereichen. Selbst bei tiefen Temperaturen scheint es kein eindeutiges Energieminimum für eine einzige wohldefinierte Struktur zu geben. Mößbauer‐Absorptionsmessungen und Röntgen‐Strukturuntersuchungen an Myoglobin geben ein physikalisches Bild der Dynamik von Proteinen.
Elektronenspektroskopie von Atomen, Molekülen und kondensierter Materie
Authors: Siegbahn K.
Published: February 2013

Die Elektronenspektroskopie hat zu einer unschätzbaren Bereicherung der Physik, der Chemie und insbesondere der Oberflächenforschung geführt und bedeutungsvolle Anwendungen in der modernen Technologie hervorgebracht. Der folgende Artikel gibt einen Überblick über dieses neue Forschungsfeld mit Beispielen aus verschiedenen Bereichen, wobei die kürzlich erzielten Fortschritte auf dem Gebiet der Flüssigkeiten und Lösungen besonders berücksichtigt werden.
Fraktale und die Theorie der Phasenübergänge
Authors: Peitgen H.‐O. , Richter P. H.
Published: February 2013

Fraktale Strukturen erregen derzeit das Interesse von Wissenschaftlern in Naturwissenschaft und Technik. Neuere Untersuchungen an speziellen Spinsystemen scheinen nahezulegen, daß die Phasengrenzen im Sinne von C. N. Yang und T. D. Lee fraktale Eigenschaften haben.
Rückblicke auf die Heidelberger Physik im Jubiläumsjahr der Universität
Authors: Brix P. , Zu Putlitz G.
Published: February 2013

Die Ruperto‐Carola zu Heidelberg, älteste Universität Deutschlands, feiert 1986 ihr 600jähriges Bestehen. Mit aus diesem Grund findet vom 17. bis 21. März 1986 in Heidelberg die 50. Physikertagung der DPG statt. Außerdem ist 1986 ein Gedenkjahr für die Physik. Das ist dreifacher Anlaß zurückzublicken. Georg Quincke richtete 1885 als Prorektor „einen Blick rückwärts auf die Entwicklung der Physik an unserer Hochschule, die im nächsten Jahre ihr 500jähriges Jubiläum feiern soll”︁ [1]. Wir wählen hier aus der nachfolgenden Entwicklung (vgl. [2]) nur weniges aus.
Oberflächen — Grenzen zwischen innen und außen
Authors: Müller K.
Published: February 2013

Oberflächen sind Grenzbereiche des Festkörpers mit anderen physikalischen und chemischen Eigenschaften, als sie vom Kristallvolumen her bekannt sind. Oft werden Oberflächenstrukturen beobachtet, die es im Innern des Festkörpers nicht gibt. Dieser Artikel handelt vom generellen Aufbau der Oberflächen sowie von ihren Strukturen und den Meβmethoden, mit denen man sie bestimmen kann.
SIS und ESR — der Ausbau der GSI: Bei der Gesellschaft für Schwerionenforschung in Darmstadt (GSI) entstehen ein Schwerionensynchrotron (SIS) und ein Experimentierspeicherring (ESR)
Authors: Dreisigacker E.
Published: February 2013

Mit dem Ziel, den Energiebereich der Schwerionenforschung etwa um das Hundertfache zu höheren Energien auszuweiten, wird die Beschleunigeranlage der GSI zur Zeit um ein Schwerionensynchrotron (SIS) und einen Experimentierspeicherring (ESR) erweitert. Zu dem Projekt gehören auch der Bau einer Experimentierhalle (Targethalle) sowie der Umbau des UNI‐LAC zum Injektor für SIS. Alles zusammen soll 275 Millionen DM kosten und bis 1990 verwirklicht sein. Finanziert wird der Ausbau zu etwa 97 % durch den Bund, zu 3 % durch das Land Hessen, das auch das Gelände gestellt hat.