bluuebunny/crossref_metadata_2025 huggingface dataset:
Glacier retreat on South Georgia and implications for the spread of rats
Authors: Cook A.J. , Poncet S. , Cooper A.P.R. , Herbert D.J. , Christie D.
Published: February 2010

Using archival photography and satellite imagery, we have analysed the rates of advance or retreat of 103 coastal glaciers on South Georgia from the 1950s to the present. Ninety-seven percent of these glaciers have retreated over the period for which observations are available. The average rate of retreat has increased from 8 Ma-1 in the 1950s to 35 Ma-1 at present. The largest retreats have all taken place along the north-east coast, where retreat rates have increased to an average of 60 Ma-1 at present, but those on the south-west coast have also been steadily retreating since the 1950s. These data, along with environmental information about South Georgia, are included in a new Geographic Information System (GIS) of the island. By combining glacier change data with the present distribution of both endemic and invasive species we have identified areas where there is an increased risk of rat invasion to unoccupied coastal regions that are currently protected by glacial barriers. This risk has significant implications for the surrounding ecosystem, in particular depletion in numbers of important breeding populations of ground-nesting birds on the island.
Delirium in care homes
Authors: Siddiqi Najma , Clegg Andrew , Young John
Published: February 2010

Delirium is a distressing but preventable condition associated with increased morbidity and mortality, and significant financial costs. Most research on delirium has focused on high-risk patients in hospitals. Another group also at high risk are residents in care homes for older people. This report reviews the literature on the occurrence, aetiology, outcomes, prevention and treatment of delirium in long-term care. Delirium appears to be common in this setting, with a median point prevalence estimate of 14.2% in studies comparable to the UK. However, there is a paucity of high-quality studies, likely to reflect the difficulty in conducting research in this population and the particular challenges of investigating delirium. Addressing delirium successfully in care homes presents an opportunity to improve care standards and to reduce inequalities in health and social care. Well-designed prospective cohort studies and robust evaluations of interventions to prevent and treat delirium are needed.
On Percolation and the Bunkbed Conjecture
Authors: LINUSSON SVANTE
Published: February 2010

We study a problem on edge percolation on product graphsG×K2. HereGis any finite graph andK2consists of two vertices {0, 1} connected by an edge. Every edge inG×K2is present with probabilitypindependent of other edges. The bunkbed conjecture states that for allGandp, the probability that (u, 0) is in the same component as (v, 0) is greater than or equal to the probability that (u, 0) is in the same component as (v, 1) for every pair of verticesu,v∈G.

We generalize this conjecture and formulate and prove similar statements for randomly directed graphs. The methods lead to a proof of the original conjecture for special classes of graphsG, in particular outerplanar graphs.
Going public in interwar Britain
Authors: Chambers David
Published: February 2010

Utilising a new sample of interwar initial public offerings (IPOs), I consider the effectiveness of the interwar stock market for firms going public. Consistent with the pecking order theory, IPO proceeds contributed only modestly to domestic industry's capital expenditure needs. IPOs of capital-hungry new manufacturing industries raised no more finance than did the rest of manufacturing. This was in part attributable to the detrimental effect of weak financial regulation on investor appetite for newer, riskier enterprises. In terms of the quality of firms allowed onto the market, IPO survival rates of the early and late 1920s were shockingly low, just as earlier research has shown. However, survival rates rebounded strongly in the following decade due not only to the economic recovery but also to tougher scrutiny of listing applications by the London Stock Exchange.
The Influence of Cognitive and Affective Reactions to Feedback on Subsequent Goals
Authors: Ilies Remus , Judge Timothy A. , Wagner David T.
Published: February 2010

This paper focuses on explaining how individuals set goals on multiple performance episodes, in the context of performance feedback comparing their performance on each episode with their respective goal. The proposed model was tested through a longitudinal study of 493 university students’ actual goals and performance on business school exams. Results of a structural equation model supported the proposed conceptual model in which self-efficacy and emotional reactions to feedback mediate the relationship between feedback and subsequent goals. In addition, as expected, participants’ standing on a dispositional measure of behavioral inhibition influenced the strength of their emotional reactions to negative feedback.
Job Burnout, Health-Related Quality of Life, and Sickness Absence in Greek Health Professionals
Authors: Anagnostopoulos Fotios , Niakas Dimitris
Published: February 2010

This study examined how job burnout was associated with sick-leave absence and quality of life in a sample of 487 nurses working in the National Health Care System. Burnout was measured with the Maslach Burnout Inventory, while quality of life was measured with Short-Form Health Survey (SF-36). Data on sick leaves were collected from hospital personnel records. Logistic regression indicated that levels of burnout (emotional exhaustion) were significant predictors of short-term (but not long-term) sickness absence. Long-term sickness absence could be predicted by poor physical health. The findings indicate that burnout not only may negatively impact on quality of life of health-care providers, but also may influence short sick leaves. Implications for the implementation of absence reduction programs are discussed.
Violence and Sex as Advertising Strategies in Television Commercials
Authors: Ferguson Christopher J. , Cruz Amanda M. , Martinez Daniel , Rueda Stephanie M. , Ferguson Diana E.
Published: February 2010

Despite several studies investigating the impact of sex and violence in television on consumer behavior and memory for products in commercials, results remain inconsistent and debated. The purpose of the current study was to examine the effects of television violence and sex on memory for commercials and willingness to buy products. Two hundred twelve young adults were assigned to watch either a sexual, violent, combined sexual and violent or neutral television show. Within each show were embedded 12 commercials, four violent, four sexual, and four neutral. Results indicated that violent or sexual content of the television show did not impair memory for commercials or willingness to buy products, and that sexual or violent content in the commercials themselves increased memory for those commercials. Implications for the current study are that violent or sexual shows may adequately function in attracting viewers’ attention, with sexual and violent content in the commercials themselves improving viewers memory for products. Use of violent or sexual content in commercials may thus be useful in advertising for brand recall.
“The Unconscious” in Current Psychology
Authors: Norman Elisabeth
Published: February 2010

A series of vignette examples taken from psychological research on motivation, emotion, decision making, and attitudes illustrates how the influence of unconscious processes is often measured in a range of different behaviors. However, the selected studies share an apparent lack of explicit operational definition of what is meant by consciousness, and there seems to be substantial disagreement about the properties of conscious versus unconscious processing: Consciousness is sometimes equated with attention, sometimes with verbal report ability, and sometimes operationalized in terms of behavioral dissociations between different performance measures. Moreover, the examples all seem to share a dichotomous view of conscious and unconscious processes as being qualitatively different. It is suggested that cognitive research on consciousness can help resolve the apparent disagreement about how to define and measure unconscious processing, as is illustrated by a selection of operational definitions and empirical findings from modern cognitive psychology. These empirical findings also point to the existence of intermediate states of conscious awareness, not easily classifiable as either purely conscious or purely unconscious. Recent hypotheses from cognitive psychology, supplemented with models from social, developmental, and clinical psychology, are then presented all of which are compatible with the view of consciousness as a graded rather than an all-or-none phenomenon. Such a view of consciousness would open up for explorations of intermediate states of awareness in addition to more purely conscious or purely unconscious states and thereby increase our understanding of the seemingly “unconscious” aspects of mental life.
Probability distributions of land surface wind speeds over North America
Authors: He Yanping , Monahan Adam Hugh , Jones Colin G. , Dai Aiguo , Biner Sebastien , Caya Daniel , Winger Katja
Published: February 2010

Knowledge of the probability distributions of surface wind speeds (SWS) is essential for surface flux estimation, wind power estimation, and wind risk assessments. The two‐parameter Weibull distribution is the most widely used empirical distribution for SWS. This study considers the probability density function (PDF) of 3‐hourly observations from 720 weather stations over North America for the period 1979–1999. The PDF of SWS is classified by season, time of day, and land surface type. The Weibull PDF is characterized by a particular relationship between the mean, standard deviation, and skewness. While the moments of the observed daytime SWS PDF are found to collapse around this Weibull relationship, the observed nighttime PDF has a broader range of values and is significantly more skewed than the Weibull PDF over rough surfaces. An idealized model shows that SWS skewness has a much greater rate of change with both the mean and standard deviation of surface buoyancy flux under conditions of stable stratification than that of unstable stratification. This result suggests that surface buoyancy flux plays an important role in generating diurnal variation of SWS PDF. Two global reanalyses products (ERA‐40 and NCEP‐NCAR) and three regional climate models (RCMs) (Rossby Centre Atmospheric Model version 3 (RCA3), limited area version of Global Environmental Multiscale Model (GEM‐LAM), and Canadian Regional Climate Model, version 4 (CRCM4)) all have a less skewed nighttime PDF and a more narrow range of the normal wind speed during day and night. Among them, two of the RCMs capture the observed SWS differences across different land cover types, and only one of the RCMs produces the observed seasonal peak of SWS PDF.
Interindividual Variations of Cerebral Blood Flow, Oxygen Delivery, and Metabolism in Relation to Hemoglobin Concentration Measured by Positron Emission Tomography in Humans
Authors: Ibaraki Masanobu , Shinohara Yuki , Nakamura Kazuhiro , Miura Shuichi , Kinoshita Fumiko , Kinoshita Toshibumi
Published: February 2010

Regional cerebral blood flow (CBF) and oxygen metabolism can be measured by positron emission tomography (PET) with 15O-labeled compounds. Hemoglobin (Hb) concentration of blood, a primary determinant of arterial oxygen content (CaO2), influences cerebral circulation. We investigated interindividual variations of CBF, cerebral blood volume (CBV), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) in relation to Hb concentration in healthy human volunteers ( n=17) and in patients with unilateral steno-occlusive disease ( n=44). For the patients, data obtained only from the contralateral hemisphere (normal side) were analyzed. The CBF and OEF were inversely correlated with Hb concentration, but CMRO2 was independent of Hb concentration. Oxygen delivery defined as a product of CaO2 and CBF (CaO2 CBF) increased with a rise of Hb concentration. The analysis with a simple oxygen model showed that oxygen diffusion parameter ( L) was constant over the range of Hb concentration, indicating that a homeostatic mechanism controlling CBF is necessary to maintain CMRO2. The current findings provide important knowledge to understand the control mechanism of cerebral circulation and to interpret the 15O PET data in clinical practice.
Design of a versatile multiaperture negative ion source
Authors: Cavenago M. , Kulevoy T. , Petrenko S. , Antoni V. , Bigi M. , Gazza E. , Recchia M. , Serianni G. , Veltri P.
Published: February 2010

Negative ion sources are a key component of the neutral beam injector to be installed in the International Thermonuclear Experimental Reactor. At present research and development activities address several important issues related to beam extraction, optics, and optimization. Together with the design of real size devices and the accumulation of atomic cross section databases, a relatively small negative ion source [130 mA of H− at 60 kV, named Negative Ion Optimization phase 1 (NIO1)] is under construction at Consorzio RFX to contribute to benchmark numerical simulation tools and to test components, such as emittance scanners, beam dumps, and cesium ovens. NIO1 design, magnet configuration, and rf coupling simulations are described.
Controlled current matching in small molecule organic tandem solar cells using doped spacer layers
Authors: Schueppel Rico , Timmreck Ronny , Allinger Nikola , Mueller Toni , Furno Mauro , Uhrich Christian , Leo Karl , Riede Moritz
Published: February 2010

Current matching of the subcells is crucial to optimize the performance of tandem solar cells. Due to the thin film optics of organic solar cells, the position of the two subcells relative to the reflecting electrode becomes a very important issue. This is demonstrated for an indium tin oxide (ITO)/pin/pii/Al structure with thin intrinsic absorbing layers consisting of zinc-phthalocyanine and fullerene C60 and a metal-free lossless recombination contact between the subcells. By keeping the thickness of the absorbing layers constant and changing only the thickness of the inner p-doped transparent layer in 16 steps from 0to186nm, the distance of the ITO-sided subcell from the reflecting electrode (Al) is systematically varied. Thus, the p-doped layer works as an optical spacer between both subcells. The influence of its thickness on the thin film optics is shown in optical simulations and confirmed with current-voltage measurements. If both subcells are separated only by the recombination contact, they are positioned in the first interference maximum of the incident light and the currents of the individual subcells nearly matches. By increasing the spacer layer thickness, the ITO-sided subcell is moved to the first interference minimum, limiting the measured short circuit current density jsc of the tandem solar cell to about 1∕2 of its initial value without spacer. At a spacer thickness of about 140nm, jsc recovers in the second interference maximum to nearly its original value. Within this series, an almost constant high fill factor of about 59% as well as a constant open circuit voltage of 1.06V is observed, showing that the Ohmic losses in the spacer are negligible. The power conversion efficiency of these devices reaches nearly 4% in the first and approximately 3.6% in the second interference maximum, respectively, in an outdoor test at 1sun. Furthermore, it is shown that for thicker absorber layers, an optimized current density cannot be reached in the first, but only in the second optical interference maximum, making the presented optical spacer an essential component for efficient organic tandem devices.
Observation of reduced radiative recombination in low-well-number strain-balanced quantum well solar cells
Authors: Bessière A. , Connolly J. P. , Barnham K. W. J. , Führer M. F. , Lynch M. , Ballard I. M. , Mazzer M. , Johnson D. C. , Hill G. , Roberts J. S.
Published: February 2010

Absolute electroluminescence and photoluminescence measurements were carried out on strain-balanced quantum well solar cells. Over a range of bias, a reduced radiative recombination in the wells was observed compared to a model assuming a constant quasi-Fermi level separation (QFLS) over the device thickness. This was interpreted as a QFLS suppression in the wells relative to the bulk of 18 and 5 meV, respectively, for the single and five well strain-balanced quantum well solar cells, consistent with previous results on strained single quantum well and double quantum well devices. The photoluminescence spectra at open-circuit voltage under illumination in the well agreed with the electroluminescence spectra in the light in contrast to some theoretical predictions. Generation of hot carriers in the wells could be the thermodynamically compensating phenomenon for the QFLS reduction.
High-frequency magnetic properties of Zn ferrite films deposited by magnetron sputtering
Authors: Guo Dangwei , Zhu Jingyi , Yang Yuancai , Fan Xiaolong , Chai Guozhi , Sui Wenbo , Zhang Zhengmei , Xue Desheng
Published: February 2010

The effect of thermal annealing on structural and magnetic properties has been investigated for Zn ferrite films deposited on Si (111) substrates using radio frequency magnetron sputtering. The saturation magnetization at room temperature was enhanced upto 303 emu/cm3 by annealing at relatively low temperature of 200 °C and decreased at higher temperatures. The complex permeability μ=μ′-iμ″ values of the ferrite films as-deposited and annealed at 200 and 400 °C were measured at frequency upto 5 GHz. These films exhibited better high-frequency properties, especially, the film annealed at 200 °C had a large μ′ of 19.5 and high resonance frequency fr of 1.61 GHz. And the reason was investigated preliminarily based on the bianisotropy model.
Quasi-phase-matched probe-energy electro-optic sampling as a method of narrowband terahertz detection
Authors: Kitaeva G. Kh. , Kovalev S. P. , Naumova I. I. , Akhmedzhanov R. A. , Ilyakov I. E. , Shishkin B. V. , Suvorov E. V.
Published: February 2010

Implementation of free-space quasi-phase-matched electro-optic detection is reported, based on measuring the energy variation of a femtosecond laser pulse induced by a terahertz field. Narrowband probe-energy type of detection is demonstrated using wide-aperture periodically poled Mg:Y:LiNbO3 crystals with as-grown domain gratings. Spectra of air plasma generation measured by this method are compared with the spectrum measured by the conventional ZnTe-based probe-phase ellipsometry scheme. Besides, the conventional method was performed for both types of sources, for the air plasma generation, and for the quasi-phase-matched optical rectification in the same periodically poled Mg:Y:LiNbO3 crystals.
Reducing quantum-regime dielectric loss of silicon nitride for superconducting quantum circuits
Authors: Paik Hanhee , Osborn Kevin D.
Published: February 2010

The loss of amorphous hydrogenated silicon nitride (a-SiNx:H) is measured at 30 mK and 5 GHz using a superconducting LC resonator down to energies where a single-photon is stored, and analyzed with an independent two-level system defect model. Each a-SiNx:H film was deposited with different concentrations of hydrogen impurities. We find that quantum-regime dielectric loss tangent tan δ0 in a-SiNx:H is strongly correlated with N–H impurities, including NH2. By slightly reducing x we are able to reduce tan δ0 by approximately a factor of 50, where the best films show tan δ0≃3×10−5.
Removal of a hydrogenated amorphous carbon film from the tip of a micropipette electrode using direct current corona discharge
Authors: Kakuta Naoto , Okuyama Naoki , Yamada Yukio
Published: February 2010

Micropipette electrodes are fabricated by coating glass micropipettes first with metal and then with hydrogenated amorphous carbon (a-C:H) as an electrical insulator. Furthermore, at the tip of the micropipette electrode, the deposited a-C:H film needs to be removed to expose the metal-coated surface and hollow for the purposes of electrical measurement and injection. This paper describes a convenient and reliable method for removing the a-C:H film using direct current corona discharge in atmospheric air. The initial film removal occurred at an applied voltage of 1.5–2.0 kV, accompanied by an abrupt increase in the discharge current. The discharge current then became stable at a microampere level in the glow corona mode, and the removed area gradually extended.
The injection efficiency measurement and analysis for central region model cyclotron
Authors: Yao Hongjuan , Li Zhenguo , Ge Tao , Wu Longcheng , Guan Fengping , Lv Yinlong , Wang Zhenhui , Liu Gengshou , Zhang Tianjue , Cai Hongru
Published: February 2010

At the China Institute of Atomic Energy, a central region model cyclotron has been constructed, which is dedicated for various experimental verifications to study beam properties. The design features of the ion source and injection line have already been described in other papers. We shall report here the results of the initial beam tests. A wire scanner is employed in the injection line to measure beam transverse sizes and these data can be used to fit the phase plane parameters after the ion source. Based on the beam tests results, the ion source built in 2003 has been improved recently. The improvement is mainly due to the repair of the multicusp field. From the ion source to the exit of the inflector, a transmission efficiency of 93% has been obtained for a continuous and low current input beam. It is also described here the experimental arrangement and the results.
The ground state van der Waals potentials of the strontium dimer and strontium rare-gas complexes
Authors: Yin G. P. , Li P. , Tang K. T.
Published: February 2010

The entire ground state potential energy curve of the strontium dimer is accurately described by the Tang–Toennies potential model defined by the three dispersion coefficients and two well parameters. The predicted vibrational frequency, anharmonicity, and vibration-rotation coupling constant are in excellent agreement with experiment. The Sr2 reduced potential is almost identical to that of Ca2 and Hg2, providing further evidence to the conjecture that the van der Waals dimer potentials of group IIA and group IIB elements have the same shape, which is different from that of rare-gas dimers. The potentials of Sr-RG complexes (RG=He,Ne,Ar,Kr,Xe) are generated by the same potential model with its parameters calculated with combining rules. These potentials are shown to have the same shape which is between that of the strontium and rare-gas dimers.
Long term in vitro stability of fully integrated wireless neural interfaces based on Utah slant electrode array
Authors: Sharma Asha , Rieth Loren , Tathireddy Prashant , Harrison Reid , Solzbacher Florian
Published: February 2010

We herein report in vitro functional stability and recording longevity of a fully integrated wireless neural interface (INI). The INI uses biocompatible Parylene-C as an encapsulation layer, and was immersed in phosphate buffered saline (PBS) for a period of over 150 days. The full functionality (wireless radio-frequency power, command, and signal transmission) and the ability of INI to record artificial action potentials even after 150 days of PBS soaking without any change in signal/noise amplitude constitutes a major milestone in long term stability, and evaluate the encapsulation reliability, functional stability, and potential usefulness for future chronic implants.
Surface photovoltage studies of nonstoichiometric rutile titanium dioxide
Authors: Sheppard L. R. , Dittrich T. , Nowotny J. , Bak T.
Published: February 2010

The aim of the present investigation was to assess how processing at elevated temperatures impacts upon the room temperature electronic structure of rutile TiO2. Consequently, strongly reduced and oxidized rutile TiO2 pellets were processed under controlled conditions and studied using surface photovoltage spectroscopy. Under illumination with photon energies above the band gap energy, reduced and oxidized rutile, respectively, displayed positive and negative surface photovoltages. This result indicates that undoped TiO2 may be tailored to promote either photoreduction or photo-oxidation reactions. Several transitions involving surface and bulk electronic states within the band gap were observed in oxidized rutile, but in contrast, similar states could not be readily distinguished in reduced rutile. A band diagram of oxidized rutile is proposed.
Surface plasmon enhanced band edge luminescence of ZnO nanorods by capping Au nanoparticles
Authors: Cheng C. W. , Sie E. J. , Liu B. , Huan C. H. A. , Sum T. C. , Sun H. D. , Fan H. J.
Published: February 2010

The author observe sixfold enhancement in the near band gap emission of ZnO nanorods by employing surface plasmon of Au nanoparticles, while the defect-related emission is completely suppressed. Time-resolved photoluminescence indicates that the decay process becomes much faster by Au capping. The remarkable enhancement of the ultraviolet emission intensities and transition rates is ascribed to the charge transfer and efficient coupling between ZnO nanorods and Au surface plasmons. The suppression of the green emission might be due to a combined effect of Au surface plasmon and passivation of the ZnO nanorod surface traps.
Role of negatively charged defects in the lattice contraction of Al–Si–N
Authors: Pignedoli C. A. , Passerone D. , Hug H. J. , Pélisson-Schecker A. , Patscheider J.
Published: February 2010

Experiments reveal that incorporation of substitutional Si in wurtzite AlN up to 6 at. % results in a lattice contraction in the [0001] direction. The contraction is linear and, for higher silicon contents, the lattice parameters remain constant. We investigate the geometric and electronic properties of Al–Si–N compounds with Si content varying from 0 to 9 at. % by means of ab initio simulations based on density functional theory. We demonstrate that charged defects are necessary to support the experimental evidence of a shrinking cell parameter: an ideal Al–Si–N wurtzite structure with delocalized charges would undergo lattice expansion due to Coulomb repulsion upon Si incorporation. Charged defects that act as acceptors and compensate the excess charge coming from Si overcompensate the lattice expansion and therefore promote a lattice contraction.
Cellular in vivo imaging reveals coordinated regulation of pituitary microcirculation and GH cell network function
Authors: Lafont Chrystel , Desarménien Michel G. , Cassou Mathieu , Molino François , Lecoq Jérôme , Hodson David , Lacampagne Alain , Mennessier Gérard , El Yandouzi Taoufik , Carmignac Danielle , Fontanaud Pierre , Christian Helen , Coutry Nathalie , Fernandez-Fuente Marta , Charpak Serge , Le Tissier Paul , Robinson Iain CAF , Mollard Patrice
Published: February 2010

Growth hormone (GH) exerts its actions via coordinated pulsatile secretion from a GH cell network into the bloodstream. Practically nothing is known about how the network receives its inputs in vivo and releases hormones into pituitary capillaries to shape GH pulses. Here we have developed in vivo approaches to measure local blood flow, oxygen partial pressure, and cell activity at single-cell resolution in mouse pituitary glands in situ. When secretagogue (GHRH) distribution was modeled with fluorescent markers injected into either the bloodstream or the nearby intercapillary space, a restricted distribution gradient evolved within the pituitary parenchyma. Injection of GHRH led to stimulation of both GH cell network activities and GH secretion, which was temporally associated with increases in blood flow rates and oxygen supply by capillaries, as well as oxygen consumption. Moreover, we observed a time-limiting step for hormone output at the perivascular level; macromolecules injected into the extracellular parenchyma moved rapidly to the perivascular space, but were then cleared more slowly in a size-dependent manner into capillary blood. Our findings suggest that GH pulse generation is not simply a GH cell network response, but is shaped by a tissue microenvironment context involving a functional association between the GH cell network activity and fluid microcirculation.
RNA looping by PTB: Evidence using FRET and NMR spectroscopy for a role in splicing repression
Authors: Lamichhane Rajan , Daubner Gerrit M. , Thomas-Crusells Judith , Auweter Sigrid D. , Manatschal Cristina , Austin Keyunna S. , Valniuk Oksana , Allain Frédéric H.-T. , Rueda David
Published: February 2010

Alternative splicing plays an important role in generating proteome diversity. The polypyrimidine tract–binding protein (PTB) is a key alternative splicing factor involved in exon repression. It has been proposed that PTB acts by looping out exons flanked by pyrimidine tracts. We present fluorescence, NMR, and in vivo splicing data in support of a role of PTB in inducing RNA loops. We show that the RNA recognition motifs (RRMs) 3 and 4 of PTB can bind two distant pyrimidine tracts and bring their 5′ and 3′ ends in close proximity, thus looping the RNA. Efficient looping requires an intervening sequence of 15 nucleotides or longer between the pyrimidine tracts. RRM3 and RRM4 bind the 5′ and the 3′ pyrimidine tracts, respectively, in a specific directionality and work synergistically for efficient splicing repression in vivo.
The Murray Springs Clovis site, Pleistocene extinction, and the question of extraterrestrial impact
Authors: Haynes C. Vance , Boerner J. , Domanik K. , Lauretta D. , Ballenger J. , Goreva J.
Published: February 2010

Some of the evidence for the recent hypothesis of an extraterrestrial impact that caused late Pleistocene megafaunal extinctions [Firestone et al. (2007)
Proc Natl Acad Sci USA
104:16016–16021] was based upon samples collected at Murray Springs, a Clovis archaeological site in southeastern Arizona. Here we describe sampling and analyses of magnetic separates from within, above, and below the lower Younger Dryas boundary (LYDB) black mat at Murray Springs, as well as radiation measurements from the LYDB at Murray Springs and two other well-stratified Clovis sites. The main magnetic fraction at Murray Springs is maghemite. Magnetic microspherules have terrestrial origins but also occur as cosmic dust particles. We failed to find iridium or radiation anomalies. The evidence for massive biomass burning at Murray Springs is addressed and found to be lacking. We could not substantiate some of the claims by Firestone and others, but our findings do not preclude a terminal Pleistocene cosmic event.
Surgery with molecular fluorescence imaging using activatable cell-penetrating peptides decreases residual cancer and improves survival
Authors: Nguyen Quyen T. , Olson Emilia S. , Aguilera Todd A. , Jiang Tao , Scadeng Miriam , Ellies Lesley G. , Tsien Roger Y.
Published: February 2010

The completeness of tumor removal during surgery is dependent on the surgeon’s ability to differentiate tumor from normal tissue using subjective criteria that are not easily quantifiable. A way to objectively assess tumor margins during surgery in patients would be of great value. We have developed a method to visualize tumors during surgery using activatable cell-penetrating peptides (ACPPs), in which the fluorescently labeled, polycationic cell-penetrating peptide (CPP) is coupled via a cleavable linker to a neutralizing peptide. Upon exposure to proteases characteristic of tumor tissue, the linker is cleaved, dissociating the inhibitory peptide and allowing the CPP to bind to and enter tumor cells. In mice, xenografts stably transfected with green fluorescent protein show colocalization with the Cy5-labeled ACPPs. In the same mouse models, Cy5-labeled free ACPPs and ACPPs conjugated to dendrimers (ACPPDs) delineate the margin between tumor and adjacent tissue, resulting in improved precision of tumor resection. Surgery guided by ACPPD resulted in fewer residual cancer cells left in the animal after surgery as measured by Alu PCR. A single injection of ACPPD dually labeled with Cy5 and gadolinium chelates enabled preoperative whole-body tumor detection by MRI, intraoperative guidance by real-time fluorescence, intraoperative histological analysis of margin status by fluorescence, and postoperative MRI tumor quantification. Animals whose tumors were resected with ACPPD guidance had better long-term tumor-free survival and overall survival than animals whose tumors were resected with traditional bright-field illumination only.
Field-effect-tuned lateral organic diodes
Authors: Dhar Bal Mukund , Kini Geetha S. , Xia Guoqiang , Jung Byung Jun , Markovic Nina , Katz Howard E.
Published: February 2010

The operation of organic diodes in solar cells and light-emitting displays strongly depends on the properties of the interfaces between hole- and electron-carrying organic semiconductors. Such interfaces are difficult to characterize, as they are usually buried under the surface or exist as an irregular “bulk heterojunction.” Using a unique fluorinated barrier layer-based lithographic technique, we fabricated a lateral organic p-n junction, allowing the first observation of the potential at an organic p-n interface simultaneously with the charge transport measurements. We find that the diode characteristics of the device (current output and rectification ratio) are consistent with the changes in the surface potentials near the junction, and the current-voltage curves and junction potentials are strongly and self-consistently modulated by a third, gate electrode. The generality of our technique makes this an attractive method to investigate the physics of organic semiconductor junctions. The lithographic technique is applicable to a wide variety of soft material patterns. The observation of built-in potentials makes an important connection between organic junctions and textbook descriptions of inorganic devices. Finally, these kinds of potentials may prove to be controlling factors in charge separation efficiency in organic photovoltaics.
The tolerance–fecundity trade-off and the maintenance of diversity in seed size
Authors: Muller-Landau Helene C.
Published: February 2010

Seed size commonly varies by five to six orders of magnitude among coexisting plant species, a pattern ecologists have long sought to explain. Because seed size trades off with seed number, small-seeded species clearly have the advantage in fecundity, but what is the countervailing advantage of large seeds? Higher competitive ability combined with strong competitive asymmetry can in theory allow coexistence through a competition–colonization trade-off, but empirical evidence is inconsistent with this mechanism. Instead, the key advantage of large seeds appears to be their tolerance of stresses such as shade or drought that are present in some but not all regeneration sites. Here I present a simple, analytically tractable model of species coexistence in heterogeneous habitats through a tolerance–fecundity trade-off. Under this mechanism, the more tolerant species win all of the more stressful regeneration sites and some of those that are less stressful, whereas the more fecund species win most but not all of the less stressful sites. The tolerance–fecundity trade-off enables stable coexistence of large numbers of species in models with and without seed limitation. The tolerance–fecundity mechanism provides an excellent explanation for the maintenance of diversity of seed size within plant communities and also suggests new hypotheses for coexistence in animal and microbial communities.
Molecular basis of odor coding in the malaria vector mosquito
Anopheles gambiae
Authors: Wang Guirong , Carey Allison F. , Carlson John R. , Zwiebel Laurence J.
Published: February 2010

A systematic functional analysis across much of the conventional
Anopheles gambiae
odorant receptor (AgOR) repertoire was carried out in
Xenopus
oocytes using two-electrode, voltage-clamp electrophysiology. The resulting data indicate that each AgOR manifests a distinct odor-response profile and tuning breadth. The large diversity of tuning responses ranges from AgORs that are responsive to a single or small number of odorants (specialists) to more broadly tuned receptors (generalists). Several AgORs were identified that respond robustly to a range of human volatiles that may play a critical role in anopheline host selection. AgOR responses were analyzed further by constructing a multidimensional odor space representing the relationships between odorants and AgOR responses. Within this space, the distance between odorants is related to both chemical class and concentration and may correlate with olfactory discrimination. This study provides a comprehensive overview of olfactory coding mechanisms of
An. gambiae
that ultimately may aid in fostering the design and development of olfactory-based strategies for reducing the transmission of malaria and other mosquito-borne diseases.
Three-dimensional structure of tropism-switching
Bordetella
bacteriophage
Authors: Dai Wei , Hodes Asher , Hui Wong H. , Gingery Mari , Miller Jeff F. , Zhou Z. Hong
Published: February 2010

Bacteriophage BPP-1, which infects
Bordetella
species, can switch its specificity by mutations to the ligand-binding surface of its major tropism-determinant protein, Mtd. This targeted mutagenesis results from the activity of a phage-encoded diversity-generating retroelement. Purified Mtd binds its receptor with low affinity, yet BPP-1 binding and infection of
Bordettella
cells are efficient because of high-avidity binding between phage-associated Mtd and its receptor. Here, using an integrative approach of three-dimensional (3D) structural analyses of the entire phage by cryo-electron tomography and single-prticle cryo-electron microscopy, we provide direct localization of Mtd in the phage and the structural basis of the high-avidity binding of the BPP-1 phage. Our structure shows that each BPP-1 particle has a T = 7 icosahedral head and an unusual tail apparatus consisting of a short central tail “hub,” six short tail spikes, and six extended tail fibers. Subtomographic averaging of the tail fiber maps revealed a two-lobed globular structure at the distal end of each long tail fiber. Tomographic reconstructions of immuno-gold-labeled BPP-1 directly localized Mtd to these globular structures. Finally, our icosahedral reconstruction of the BPP-1 head at 7Å resolution reveals an HK97-like major capsid protein stabilized by a smaller cementing protein. Our structure represents a unique bacteriophage reconstruction with its tail fibers and ligand-binding domains shown in relation to its tail apparatus. The localization of Mtd at the distal ends of the six tail fibers explains the high avidity binding of Mtd molecules to cell surfaces for initiation of infection.
Climatic context and ecological implications of summer fog decline in the coast redwood region
Authors: Johnstone James A. , Dawson Todd E.
Published: February 2010

Biogeographical, physiological, and paleoecological evidence suggests that the coast redwood [Sequoia sempervirens(D. Don) Endl.] is closely associated with the presence of summer marine fog along the Pacific coast of California. Here we present a novel record of summer fog frequency in the coast redwood region upon the basis of direct hourly measurements of cloud ceiling heights from 1951 to 2008. Our analysis shows that coastal summer fog frequency is a remarkably integrative measure of United States Pacific coastal climate, with strong statistical connections to the wind-driven upwelling system of the California Current and the broad ocean temperature pattern known as the Pacific Decadal Oscillation. By using a long-term index of daily maximum land temperatures, we infer a 33% reduction in fog frequency since the early 20th century. We present tree physiological data suggesting that coast redwood and other ecosystems along the United States west coast may be increasingly drought stressed under a summer climate of reduced fog frequency and greater evaporative demand.
Abduction and asylum in the lives of transcription factors
Authors: Burger Anat , Walczak Aleksandra M. , Wolynes Peter G.
Published: February 2010

Recent studies suggest that there are many nonfunctional transcription factor binding sites along a genome. Although these “decoy” sites compete with the promoter region for binding of transcription factors, they may also protect these proteins from degradation. We show that in the limit of perfect protection, where bound transcription factors are never degraded, the competitive effect of nonfunctional binding sites is completely canceled out by the stability gained from reduced degradation. We examine the response of an autoregulated gene to the total number of transcription factors to quantify the consequences of competition for transcription factors. We show that intuition about this system can be gained by mathematically constructing a single gene with effective parameters that reproduce the behavior of a gene with added decoy sites. In analogy to dressed particles in many-body systems we term this description a “quasi gene.” We find that protective decoys buffer against noise by reducing correlations between transcription factors, specifically in the case of production of transcription factors in bursts. We show that the addition of protective decoy sites causes the level of gene expression to approach that predicted from deterministic mass action models. Finally, we show that protective decoy sites decrease the size of the region of parameter space that exhibits bistability.
PD-1 and CTLA-4 combination blockade expands infiltrating T cells and reduces regulatory T and myeloid cells within B16 melanoma tumors
Authors: Curran Michael A. , Montalvo Welby , Yagita Hideo , Allison James P.
Published: February 2010

Vaccination with irradiated B16 melanoma cells expressing either GM-CSF (Gvax) or Flt3-ligand (Fvax) combined with antibody blockade of the negative T-cell costimulatory receptor cytotoxic T-lymphocyte antigen-4 (CTLA-4) promotes rejection of preimplanted tumors. Despite CTLA-4 blockade, T-cell proliferation and cytokine production can be inhibited by the interaction of programmed death-1 (PD-1) with its ligands PD-L1 and PD-L2 or by the interaction of PD-L1 with B7-1. Here, we show that the combination of CTLA-4 and PD-1 blockade is more than twice as effective as either alone in promoting the rejection of B16 melanomas in conjunction with Fvax. Adding αPD-L1 to this regimen results in rejection of 65% of preimplanted tumors vs. 10% with CTLA-4 blockade alone. Combination PD-1 and CTLA-4 blockade increases effector T-cell (Teff) infiltration, resulting in highly advantageous Teff-to-regulatory T-cell ratios with the tumor. The fraction of tumor-infiltrating Teffs expressing CTLA-4 and PD-1 increases, reflecting the proliferation and accumulation of cells that would otherwise be anergized. Combination blockade also synergistically increases Teff-to-myeloid-derived suppressor cell ratios within B16 melanomas. IFN-γ production increases in both the tumor and vaccine draining lymph nodes, as does the frequency of IFN-γ/TNF-α double-producing CD8
+
T cells within the tumor. These results suggest that combination blockade of the PD-1/PD-L1- and CTLA-4-negative costimulatory pathways allows tumor-specific T cells that would otherwise be inactivated to continue to expand and carry out effector functions, thereby shifting the tumor microenvironment from suppressive to inflammatory.
A role for a bacterial ortholog of the Ro autoantigen in starvation-induced rRNA degradation
Authors: Wurtmann Elisabeth J. , Wolin Sandra L.
Published: February 2010

Cellular adaptations to stress often involve changes in RNA metabolism. One RNA-binding protein that has been implicated in RNA handling during environmental stress in both animal cells and prokaryotes is the Ro autoantigen. However, the function of Ro in stress conditions has been unknown. We report that a Ro protein in the radiation-resistant eubacterium
Deinococcus radiodurans
participates in ribosomal RNA (rRNA) degradation during growth in stationary phase, a form of starvation. Levels of the Ro ortholog Rsr increase dramatically during growth in stationary phase and the presence of Rsr confers a growth advantage. Examination of rRNA profiles reveals that Rsr, the 3′ to 5′ exoribonuclease polynucleotide phosphorylase (PNP) and additional nucleases are all involved in the extensive rRNA decay that occurs during starvation of this bacterium. We show that Rsr, PNP, and an Rsr-PNP complex exhibit increased sedimentation with ribosomal subunits during stationary phase. As the fractionation of PNP with ribosomal subunits is strongly enhanced in the presence of Rsr, we propose that Ro proteins function as cofactors to increase the association of exonucleases with certain substrates during stress.
Dendritic cell targeted HIV gag protein vaccine provides help to a DNA vaccine including mobilization of protective CD8
+
T cells
Authors: Nchinda Godwin , Amadu David , Trumpfheller Christine , Mizenina Olga , Überla Klaus , Steinman Ralph M.
Published: February 2010

To improve the efficacy of T cell–based vaccination, we pursued the principle that CD4
+
T cells provide help for functional CD8
+
T cell immunity. To do so, we administered HIV gag to mice successively as protein and DNA vaccines. To achieve strong CD4
+
T cell immunity, the protein vaccine was targeted selectively to DEC-205, a receptor for antigen presentation on dendritic cells. This targeting helped CD8
+
T cell immunity develop to a subsequent DNA vaccine and improved protection to intranasal challenge with recombinant vaccinia gag virus, including more rapid accumulation of CD8
+
T cells in the lung. The helper effect of dendritic cell-targeted protein vaccine was mimicked by immunization with specific MHC II binding HIV gag peptides but not peptides from a disparate
Yersinia pestis
microbe. CD4
+
helper cells upon adoptive transfer allowed wild-type, but not CD40
−/−
, recipient mice to respond better to the DNA vaccine. The transfer also enabled recipients to more rapidly accumulate gag-specific CD8
+
T cells in the lung following challenge with vaccinia gag virus. Thus, complementary prime boost vaccination, in which prime and boost favor distinct types of T cell immunity, improves plasmid DNA immunization, including mobilization of CD8
+
T cells to sites of infection.