bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein dynamics modulated electron transfer kinetics in early stage photosynthesis
Authors: Kundu Prasanta , Dua Arti
Published: February 2013

A recent experiment has probed the electron transfer kinetics in the early stage of photosynthesis in Rhodobacter sphaeroides for the reaction center of wild type and different mutants [Science 316, 747 (2007)]. By monitoring the changes in the transient absorption of the donor-acceptor pair at 280 and 930 nm, both of which show non-exponential temporal decay, the experiment has provided a strong evidence that the initial electron transfer kinetics is modulated by the dynamics of protein backbone. In this work, we present a model where the electron transfer kinetics of the donor-acceptor pair is described along the reaction coordinate associated with the distance fluctuations in a protein backbone. The stochastic evolution of the reaction coordinate is described in terms of a non-Markovian generalized Langevin equation with a memory kernel and Gaussian colored noise, both of which are completely described in terms of the microscopics of the protein normal modes. This model provides excellent fits to the transient absorption signals at 280 and 930 nm associated with protein distance fluctuations and protein dynamics modulated electron transfer reaction, respectively. In contrast to previous models, the present work explains the microscopic origins of the non-exponential decay of the transient absorption curve at 280 nm in terms of multiple time scales of relaxation of the protein normal modes. Dynamic disorder in the reaction pathway due to protein conformational fluctuations which occur on time scales slower than or comparable to the electron transfer kinetics explains the microscopic origin of the non-exponential nature of the transient absorption decay at 930 nm. The theoretical estimates for the relative driving force for five different mutants are in close agreement with the experimental estimates obtained using electrochemical measurements.
Direct shape control of photoreduced nanostructures on proton exchanged ferroelectric templates
Authors: Balobaid Laila , Craig Carville N. , Manzo Michele , Gallo Katia , Rodriguez Brian J.
Published: February 2013

Photoreduction on a periodically proton exchanged ferroelectric crystal leads to the formation of periodic metallic nanostructures on the surface. By varying the depth of the proton exchange (PE) from 0.59 to 3.10 μm in congruent lithium niobate crystals, the width of the lateral diffusion region formed by protons diffusing under the mask layer can be controlled. The resulting deposition occurs in the PE region with the shallowest PE depth and preferentially in the lateral diffusion region for greater PE depths. PE depth-control provides a route for the fabrication of complex metallic nanostructures with controlled dimensions on chemically patterned ferroelectric templates.
Highly correlated ab initio study of the far infrared spectra of methyl acetate
Authors: Senent M. L. , Domínguez-Gómez R. , Carvajal M. , Kleiner I.
Published: February 2013

Highly correlated ab initio calculations (CCSD(T)) are used to compute gas phase spectroscopic parameters of three isotopologues of the methyl acetate (CH3COOCH3, CD3COOCH3, and CH3COOCD3), searching to help experimental assignments and astrophysical detections. The molecule shows two conformers cis and trans separated by a barrier of 4457 cm−1. The potential energy surface presents 18 minima that intertransform through three internal rotation motions. To analyze the far infrared spectrum at low temperatures, a three-dimensional Hamiltonian is solved variationally. The two methyl torsion barriers are calculated to be 99.2 cm−1 (C–CH3) and 413.1 cm−1 (O–CH3), for the cis-conformer. The three fundamental torsional band centers of CH3COOCH3 are predicted to lie at 63.7 cm−1 (C–CH3), 136.1 cm−1 (O–CH3), and 175.8 cm−1 (C–O torsion) providing torsional state separations. For the 27 vibrational modes, anharmonic fundamentals and rovibrational parameters are provided. Computed parameters are compared with those fitted using experimental data.
Semilocal and hybrid meta-generalized gradient approximations based on the understanding of the kinetic-energy-density dependence
Authors: Sun Jianwei , Haunschild Robin , Xiao Bing , Bulik Ireneusz W. , Scuseria Gustavo E. , Perdew John P.
Published: February 2013

We present a global hybrid meta-generalized gradient approximation (meta-GGA) with three empirical parameters, as well as its underlying semilocal meta-GGA and a meta-GGA with only one empirical parameter. All of them are based on the new meta-GGA resulting from the understanding of kinetic-energy-density dependence [J. Sun, B. Xiao, and A. Ruzsinszky, J. Chem. Phys. 137, 051101 (2012)]10.1063/1.4742312. The obtained functionals show robust performances on the considered molecular systems for the properties of heats of formation, barrier heights, and noncovalent interactions. The pair-wise additive dispersion corrections to the functionals are also presented.
Improvement in carrier transport properties by mild thermal annealing of PbS quantum dot solar cells
Authors: Gao Jianbo , Jeong Sohee , Lin Feng , Erslev Peter T. , Semonin Octavi E. , Luther Joseph M. , Beard Matthew C.
Published: February 2013

We studied the effect of post-deposition thermal annealing in the preparation of PbS quantum dot (QD) solar cells. We find an optimal annealing temperature that improves the power conversion efficiency by a factor of 1.5 for different sized QDs with bandgaps of 1.65 and 1.27 eV. We examined the onset of the photocurrent response and correlated that with domain grain growth and find that annealing the PbS QD array at 120 °C causes little change in the PbS QD size, bandgap, and open-circuit voltage and yet leads to an increase in the carrier transport as realized by an improved current response. We also find a decrease in the activation energy of a shallow trap, which also likely contributes to the improvement in the solar cell efficiency.
Elimination of ghosting artifacts from wavelength-shifting fiber neutron detectors
Authors: Wang C. L. , Clonts L. G. , Diawara Y. , Hannan B. W. , Hodges J. P.
Published: February 2013

Misassignment of neutron position (ghosting) produces artifacts which have been observed in wavelength-shifting (WLS) fiber detectors developed for time-of-flight (TOF) neutron powder diffraction. In position-sensitive detectors (PSDs) with WLS fiber encoding, thermal and cold neutrons interact with a monolithic 6LiF/ZnS:Ag scintillator screen, and scintillation photons are generated and transported through the crossed fibers to photomultipliers (PMTs). The neutron position is determined by photon counts in the PMTs within a preset time window. Ghosting occurs when neutrons hit the group boundaries of two neighboring PMTs for x-position multiplexing, which is modeled as resulting from a long travel length (about 3–5 mm) of a small number of scintillation photons. This model is supported by the change observed in aperture images when the threshold number for photon-pulses was adjusted for neutron event determination. When the threshold number of photon-pulses was set above 10 for each PMT, the ghost peaks in the aperture images and TOF spectra of powder diffraction were strongly suppressed or completely eliminated, and the intrinsic background levels of the WLS detectors were significantly reduced. Our result indicates that WLS fiber detector is a promising alternative for 3He PSDs for neutron scattering.
Stress reconfigurable tunable magnetoelectric resonators as magnetic sensors
Authors: Kiser Jillian , Finkel Peter , Gao Junqi , Dolabdjian Christophe , Li Jiefang , Viehland D.
Published: February 2013

We report a magnetoelastic effect in doubly clamped ferromagnetic magnetostrictive Metglas resonators with electrically and magnetically reconfigurable frequency response. The field-induced resonance frequency shift is due to magnetostrictive strain, which is shown to have a strong dependence on uniaxial stress. Here, we demonstrate that this magnetic field induced behavior can be used as the basis for a simple, tunable, magnetoelectric magnetic field sensor. The effect of tension on the field dependent magnetostrictive constant and the sensor sensitivity is examined, and the equivalent magnetic noise floor of such a sensor is estimated.
Metal-oxide-semiconductor diodes containing C60 fullerenes for non-volatile memory applications
Authors: Beckmeier Daniel , Baumgärtner Hermann
Published: February 2013

For non-volatile memories, silicon-oxide-nitride-oxide-silicon or floating gate structures are used to store information by charging and discharging electronic states reversibly. In this article, we propose to replace the floating gate by C60 molecules. This would allow more defined programming voltages because of the discrete molecular energy levels and a higher resistance to tunneling oxide defects because of the weak electrical connection between the single molecules. Such C60 MOS diode structures are produced and their electrical properties are analyzed regarding current transport and charging mechanism of the molecules. To create the MOS structures, C60 molecules (5% of a monolayer) are evaporated onto a part of a clean silicon wafer and covered by amorphous silicon in situ in an ultra high vacuum system. Then the wafer is oxidized in wet atmosphere at just 710 °C through the C60 layer. The goal is to produce a clean oxide above and under the molecules without destroying them. Aluminum gate contacts are defined on top of these layers to perform complementary capacitance voltage (CV) and current voltage (IV) measurements. First, the gate voltage is swept to analyze the injection current, then CV measurements are performed after each sweep to analyze the charge state of the C60 layer and the oxide quality. Reference diodes without C60 on the same wafer show an identical Fowler-Nordheim (FN) tunneling behavior for currents injected from silicon or from aluminum, respectively. In the CV curves, no pronounced flatband voltage shift is observable. In diodes with C60, for negative gate voltages, a classical FN tunneling is observed and compared to theory. The electron injection from silicon shows a different tunneling current behavior. It starts at a lower electric field and has a smaller slope then a FN current would have. It is identified as a trap-assisted tunneling (TAT) current caused by oxidation-induced traps under the C60 layer. It is modeled by an established analytic TAT model which reproduces the data with a trap energy of 1.8 eV below the oxide conduction band. In the CV measurements the negative voltage IV sweeps result in a shift of the flatband voltages to more negative values. Positive voltage IV sweeps shift the CV curves back onto the starting curves. This proves positive charge trapping in the oxide which results in a non-volatile memory behavior for the diodes with C60.
Maskless implants of 20 keV Ga+ in thin crystalline silicon on insulator
Authors: Mio A. M. , D'Arrigo G. , Milazzo R. G. , Rimini E. , Spinella C. , Peto L. , Nadzeyka A. , Bauerdick S.
Published: February 2013

A nano-sized ion beam apparatus has been used as maskless lithography to implant 20 keV Ga+ ions into a 26 nm thick silicon crystalline film on insulator. The ion beam, with about 5 nm standard deviation, delivered few hundred ions during a single shot. Circular areas with nominal diameter of 20 or 50 nm were irradiated to a fluence of 5 × 1014/cm2. Transmission electron microscopy evidenced that the damaged regions are characterized by an irregular contour with many disordered filaments. Damage extends across the layer thickness and fast Fourier transform analysis indicates that implantation causes the amorphization of a region which extends beyond the nominal diameter. In situ annealing experiments demonstrated that the disordered filamentary regions disappear in the 250–450 °C temperature range and the interfaces with the surrounding crystalline regions sharpen. A temperature as high as 600 °C is required to fully re-crystallize the amorphous core of the implanted dots. Reordering occurs by multi-orientation lateral solid-phase epitaxial growth and the breaking of (111) and (101) interfaces, due to the formation of twins, triggers a fast crystallization kinetics. Rapid thermal annealing (890 °C-10 s) completely crystallizes the amorphous regions, twins are absent and small cluster of defects remains instead. Preliminary scanning capacitance measurements indicate that the implanted atoms, after crystallization, are electrically active. The implant method is then a viable processing step for the doping of non-bulk fully depleted ultra-thin-body MOSFET.
Chip in a lab: Microfluidics for next generation life science research
Authors: Streets Aaron M. , Huang Yanyi
Published: February 2013

Microfluidic circuits are characterized by fluidic channels and chambers with a linear dimension on the order of tens to hundreds of micrometers. Components of this size enable lab-on-a-chip technology that has much promise, for example, in the development of point-of-care diagnostics. Micro-scale fluidic circuits also yield practical, physical, and technological advantages for studying biological systems, enhancing the ability of researchers to make more precise quantitative measurements. Microfluidic technology has thus become a powerful tool in the life science research laboratory over the past decade. Here we focus on chip-in-a-lab applications of microfluidics and survey some examples of how small fluidic components have provided researchers with new tools for life science research.
Influence of noise on the threshold for detection of elastic nonlinearity
Authors: Bentahar M. , El Guerjouma R. , Idijmarene S. , Scalerandi M.
Published: February 2013

Nonlinear effects on the propagation of elastic waves in hysteretic media are of great importance, with applications in imaging and monitoring evolution of damage/phase transitions/biological features. However, excitation amplitudes are an issue in order to improve performances of the techniques. Noise effects in the signals can be stronger than the generated nonlinear effects, thus rendering difficult the nonlinear analysis. Here, we analyze the link between the amplitude threshold for detection of nonlinear effects and different kinds of noises, which might be present in experiments. We also discuss the implications in the intrpretation of experiments.
Enhancing crystallinity of C60 layer by thickness-control of underneath pentacene layer for high mobility C60/pentacene ambipolar transistors
Authors: Ahn Kwangseok , Beom Kim Jong , Park Hyunjun , Kim Hyunjung , Hyung Lee Moo , Joon Kim Beom , Ho Cho Jeong , Sung Kang Moon , Ryeol Lee Dong
Published: February 2013

We present systematic control of the crystallinity and electrical transport properties of C60 films that are deposited onto pentacene layers, based on simple tuning of the underneath pentacene layer thickness. With increasing the pentacene layer thickness from 0 to 2 monolayers, we observed improvement in crystallinity and grain size of the C60 layer, which led to dramatic enhancement in electron conduction. Also, hole transport in this bilayer structure could be generated when the thickness of the pentacene layer was above one monolayer. The resulting ambipolar transport thin-film transistors yielded electron and hole mobilities as high as 2.8 and 0.3 cm2 V−1 s−1, respectively, and complementary inverters with gain value above 20.
Manipulation of the magnetron orbit of a positron cloud in a Penning trap
Authors: Mortensen T. , Deller A. , Isaac C. A. , van der Werf D. P. , Charlton M. , Machacek J. R.
Published: February 2013

We describe a simple and versatile method to manipulate the amplitude of the magnetron orbit of ions stored in a Penning trap, applied here to a cloud of low energy positrons. By applying a pulsed voltage to a split electrode in the trap, which is normally used for rotating wall compression of the particles, the size of the magnetron orbit can be changed at will. The modified orbit has been shown to be stable for many magnetron periods. The technique could find use in applications which require off-axis ejection of particles, for instance in the filling of arrays of traps for multicell positron storage.
Simultaneous positive and negative photocurrent response in asymmetric quantum dot infrared photodetectors
Authors: Alvarenga D. , Parra-Murillo C. A. , Penello G. M. , Kawabata R. , Rodrigues W. N. , Miquita D. R. , Schmidt W. , Guimarães P. S. S. , Pires M. P. , Unterrainer K. , Souza P. L.
Published: February 2013

We study the influence on the photocurrent of the final state in bound-to-quasibound transitions in self-assembled quantum dot infrared photodetectors. We investigate two structures designed to explore different mechanisms of carrier extraction and therefore achieve a better insight on these processes. We observe photocurrent in opposite directions, with positive and negative sign, for different incident frequencies at the same applied external electric field. This phenomenon is attributed to the asymmetry of the potential barriers surrounding the quantum dots.
Low attenuation of GHz Rayleigh-like surface acoustic waves in ZnO/GaAs systems immersed in liquid helium
Authors: Pedrós J. , García-Gancedo L. , Ford C. J. B. , Griffiths J. P. , Jones G. A. C. , Flewitt A. J.
Published: February 2013

Low attenuation of Sezawa modes operating at GHz frequencies in ZnO/GaAs systems immersed in liquid helium has been observed. This unexpected behaviour for Rayleigh-like surface acoustic waves (SAWs) is explained in terms of the calculated depth profiles of their acoustic Poynting vectors. This analysis allows reproduction of the experimental dispersion of the attenuation coefficient. In addition, the high attenuation of the Rayleigh mode is compensated by the strengthening provided by the ZnO layer. The introduction of the ZnO film will enable the operation of SAW-driven single-photon sources in GaAs-based systems with the best thermal stability provided by the liquid helium bath.
The role height plays in the spreading of liquid droplets over sharp edges
Authors: Mueller Jochen , Haghparastmojaveri Negin , Alan Tuncay , Neild Adrian
Published: February 2013

We show that the volume which can be held on the top of a pillar is dependent on the elevation of the pillar. When a spreading fluid encounters an edge between two inclined surfaces, the angle between them determines the hysteresis at the edge. To examine the changes in the hysteresis as a function of pillar height, circular pillars of various heights ranging from 31.8 μm down to 200 nm were fabricated in silicon. It was found that as the height is reduced below 7.2 μm there is a marked and almost linear decline in the hysteresis offered by the pillar edge.
Comparison of post-detonation combustion in explosives incorporating aluminum nanoparticles: Influence of the passivation layer
Authors: Lewis W. K. , Rumchik C. G. , Smith M. J. , Fernando K. A. S. , Crouse C. A. , Spowart J. E. , Guliants E. A. , Bunker C. E.
Published: February 2013

Aluminum nanoparticles and explosive formulations that incorporate them have been a subject of ongoing interest due to the potential of aluminum particles to dramatically increase energy content relative to conventional organic explosives. We have used time-resolved atomic and molecular emission spectroscopy to monitor the combustion of aluminum nanoparticles within the overall chemical dynamics of post-detonation fireballs. We have studied the energy release dynamics of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) charges incorporating three types of aluminum nanoparticles: commercial oxide-passivated nanoparticles, oleic acid-capped aluminum nanoparticles (AlOA), and nanoparticles in which the oxide shell of the particle has been functionalized with an acrylic monomer and copolymerized into a fluorinated acrylic matrix (AlFA). The results indicate that the commercial nanoparticles and the AlFA nanoparticles are oxidized at a similar rate, while the AlOA nanoparticles combust more quickly. This is most likely due to the fact that the commercial nano-Al and the AlFA particles are both oxide-passivated, while the AlOA particles are protected by an organic shell that is more easily compromised than an oxide layer. The peak fireball temperatures for RDX charges containing 20 wt. % of commercial nano-Al, AlFA, or AlOA were ∼3900 K, ∼3400 K, and ∼4500 K, respectively.
Surface waves on floating liquids induced by ultrasound field
Authors: Geng D. L. , Xie W. J. , Yan N. , Wei B.
Published: February 2013

We demonstrate a kind of wave pattern on the surface of floating liquids in a modulated ultrasound field. The waves are related to the liquid/solid phase transformation process. The nucleation sites of the eutectics locate at the center of these waves, and the eutectic growth direction is parallel to the propagation direction of the waves. It is revealed that such wave phenomenon can be ascribed to the interaction between ultrasound and eutectic growth at the liquid/solid interface. This result may provide a potential method for fabricating wave patterned surfaces on eutectic alloys.
The Effects of Vertical Gradient of Disparity and Combination Mode of Features on the Occurrence of Double Fusion in Panum's Limiting Case
Authors: Li Huayun , Xie Ying , Li Shengming , Xie Shuiqing , Gao Chuang , Yang Zhongle
Published: February 2013

Panum's limiting case generally refers to the phenomenon that two features presented to one eye and a single feature presented to the other are combined and then perceived as two features at different depths. It is still not clear why experimental results derived from the Panum-type configuration (all lines parallel) support a double fusion viewpoint, but they do not for the Wheatstone-type configuration (one line not parallel to the others). Some experimental results support the double fusion theory, while others do not, even under a small disparity. Here we report that, under a small disparity, when the vertical gradients of the horizontal disparity of dichoptic feature pairs in previous Wheatstone-type configurations were increased or decreased, the evidence which was considered to be very convincing in previous studies, either supporting or against the double fusion viewpoint, was challenged, and even turned to support the opposite view. Moreover, it was discovered that changes in the way features were arranged altered the results. Together, these results indicate that double fusion is the common basis for all kinds of Panum-type configurations. But for the Wheatstone-type configurations double fusion is also constrained by the vertical gradient of disparity of the configurations in addition to disparity and influenced by the degree of similarity/conflict between binocular cues and monocular cues resulting from different arrangements of features.
Extending the Mental Number Line—How Do Negative Numbers Contribute?
Authors: Zhang Y u , You Xuqun
Published: February 2013

Previous studies suggest that there is an association between positive numbers and space; however, there is less agreement for negative numbers. The main purpose of the present study was to investigate the nature of the processing and representation of negative numbers, and the association between negative numbers and space. Results of the two experiments show that low-level processing (perception) of negative numbers can induce spatial shifts of attention. Whether this is caused by their numerical value or absolute value depends on the numerical context and task requirements, indicating that there are both components and holistic processing, and representation for negative numbers. The representation is automatically associated with leftward space; the coding and representation of the mental number line is adaptable to the specific numerical context and task requirements. The mental number line, therefore, can extend to the left side of zero, thus supporting the context-dependent view.
The Role of Odour Quality in the Perception of Binary and Higher-Order Mixtures
Authors: Lindqvist Anna , Höglund Anders , Berglund Birgitta
Published: February 2013

Twenty participants scaled similarities in odour quality, odour intensity and pleasantness/unpleasantness of 10 binary and 5 higher-order mixtures of 5 odorous degradation products from the polymer Polyamide 6.6. The perceived odour qualities of all binary mixtures were represented well as intermediary vectors relative to their component-odour vectors in a three-component principal components analysis. The odour qualities of the “floral/fruity” 2-pentylcyclopentan-1-one and the “sharp/cheese-like” pentanoic acid contributed profoundly to their binary mixtures, as did the “minty” cyclopentanone, but in fewer cases. Conversely, the “ether-like” 2-methyl pyridine and “nutty” butanamide did not contribute much. Odour similarity was shown to be caused by odour quality, rather than odour intensity. Three out of five degradation products formed distinct clusters of odours and were therefore interpreted to be profound contributors to the odour quality of the binary mixtures. The higher-order mixtures created new odour qualities which were completely different and untraceable to their various parts as perceived alone. These results demonstrate that it is critical to research the perception of natural mixtures in order to be able to understand the human olfactory code.
Face or Vase? Areal Homogeneity Effect
Authors: Takashima Midori , Fujii Teruo , Shiina Ken
Published: February 2013

To examine the effect of homogeneity of area in figure-ground organization, we made several variations of Rubin's goblet. Observers were required to judge whether they perceived a goblet or profiles (faces). Our results showed that, when both profiles were the same lightness, the percentage of judgments (goblet vs profiles) were almost equal. When the profiles were different in lightness, so that the homogeneity of the profile areas was broken, observers were more likely to perceive the profiles. When both profile areas had horizontal stripes or concentric circles and the homogeneity of the profile areas was strengthened, those areas tended to be perceived as ground. We concluded that (1) a difference in lightness was sufficient to break up the homogeneity of the profile areas; (2) good continuity was an eminent condition for unifying profile areas as ground.
The Role of Amodal Completion in Shape Formation: Some New Shape Phenomena
Authors: Pinna Baingio
Published: February 2013

Amodal completion occurs when a portion of an object is hidden as a result of its occlusion behind another object. Under these conditions, the object perceived as occluded is seen as a unitary shape, whose boundary contours amodally complete behind the overlapping modal object. Kanizsa (1972, Studia Psychologica 14 208–210) and his collaborators demonstrated some effects related to the amodal completion: shrinkage of the whole figure partially occluded; expansion of the modally visible portions of the same figure; shape deformations against the Gestalt principles of regularity, simplicity, symmetry, and past experience; global increasing of colour quantity of the partially occluded figure. The aim of this work is to demonstrate that the amodal completion is not a necessary factor in inducing the previous effects. This was accomplished through phenomenological experiments whose stimuli were crucial instances (counterexamples) disproving the amodal completion hypothesis and proving the role played by the directional symmetry of the element components of each stimulus pattern. Some new phenomena demonstrated the main role of the directional shape organisation, considered as a principle of shape formation.
Listening to White Noise Counteracts Visual and Haptic Pseudoneglect
Authors: Cattaneo Zaira , Lega Carlotta , Vecchi Tomaso , Vallar Giuseppe
Published: February 2013

Neurologically intact individuals usually show a leftward bias in line bisection, a tendency known as “pseudoneglect”, likely reflecting a right-hemisphere dominance in controlling the allocation of spatial attention. Studies in brain-damaged patients with left visuospatial neglect have reported that auditory stimulation may reduce the deficit, both in a spatially dependent and in a spatially independent way. Here we show for the first time that the concurrent binaural presentation of auditory white noise affects healthy individuals' performance in both visual and haptic bisection, reducing their leftward error. We suggest that this effect depends on the noise boosting alertness and restoring the hemispheric activation balance. Our data clearly show that task-irrelevant auditory noise crossmodally affects the allocation of spatial resources in both the haptic and the visual space; future research may clarify whether these effects are specific for the type of auditory stimulation.
Constructing Stable Spatial Maps of the Word
Authors: Burr David C , Morrone Maria Concetta
Published: February 2013

To interact rapidly and effectively with our environment, our brain needs access to a neural representation—or map—of the spatial layout of the external world. However, the construction of such a map poses major challenges to the visual system, given that the images on our retinae depend on where the eyes are looking, and shift each time we move our eyes, head, and body to explore the world. Much research has been devoted to how the stability is achieved, with the debate often polarized between the utility of spatiotopic maps (that remain solid in external coordinates), as opposed to transiently updated retinotopic maps. Our research suggests that the visual system uses both strategies to maintain stability. f MRI, motion-adaptation, and saccade-adaptation studies demonstrate and characterize spatiotopic neural maps within the dorsal visual stream that remain solid in external rather than retinal coordinates. However, the construction of these maps takes time (up to 500 ms) and attentional resources. To solve the immediate problems created by individual saccades, we postulate the existence of a separate system to bridge each saccade with neural units that are ‘transiently craniotopic’. These units prepare for the effects of saccades with a shift of their receptive fields before the saccade starts, then relaxing back into their standard position during the saccade, compensating for its action. Psychophysical studies investigating localization of stimuli flashed briefly around the time of saccades provide strong support for these neural mechanisms, and show quantitatively how they integrate information across saccades. This transient system cooperates with the spatiotopic mechanism to provide a useful map to guide interactions with our environment: one rapid and transitory, bringing into play the high-resolution visual areas; the other slow, long-lasting, and low-resolution, useful for interacting with the world.
Validation of Jarman’s method of calculation of hospital standardised mortality ratios
Authors: Bhat Sunil Kumar , Malla Sangeeta
Published: February 2013

Objective.
To compare Jarman-derived hospital standardised mortality ratios (HSMR) and Linkage-derived cumulative mortality ratios (CMR).

Methods.
HSMR and CMR values for four groups of hospitals were derived from four single-year cohorts of linked patient admissions and deaths, and compared; differences were explored and reasons for non-matching and discordance were suggested.

Results.
For the group of metropolitan teaching hospitals the Jarman-derived HSMR value of 0.95 (95% CI 0.93–0.97) was significantly lower than the Linkage-derived CMR value of 0.99 (95% CI 0.97–1.01). The opposite result was seen for the group of metropolitan non-teaching public hospitals: the Linkage-derived CMR of 0.81 (0.77–0.85) was significantly lower than the Jarman method HSMR of 1.03 (0.98–1.07).
Unmatched deaths in the study resulted from a condition unique to the Jarman method. Besides there being fewer deaths based only on the hospital separation records, 593 of these records suggested wrongly diagnosed deaths, possibly due to erroneous coding. Also, 467 hospital separation records deemed not to have involved transfer in the Jarman method database were detected by the Linkage method. However, excluding these unmatched deaths did not result in total concordance for two-method hospital-related deaths.

Conclusions.
Incorrect deaths in the Jarman method can be overcome by using the Linked method. The Jarman method, unable to adjust for the contiguous transfers related to the death, apportioned excess deaths unfairly to the teaching hospitals group.

What is known about the topic?
HSMR based on hospital separation record information can reflect hospital performance if monitored over a regular period. Despite considerable variability, inter-hospital comparison league tables of hospitals based on such ratios have been published.

What does this paper add?
This study demonstrated that the Linkage-derived CMR, utilising valid details from the state death registry, more accurately ascertains number of deaths than does the Jarman method-derived HSMR.

What are the implications for practitioners?
Where data linkages are possible, dual death derivations by the Jarman method and the Linked method can identify any unmatched or discordant deaths. Detailed exploration may help identify any differing hospital discharge practices.
Misperceptions regarding protective barrier method use for safer sex among African-American women who have sex with women
Authors: Muzny Christina A. , Harbison Hanne S. , Pembleton Elizabeth S. , Hook Edward W. , Austin Erika L.
Published: February 2013

Background
Barrier methods for HIV and sexually transmissible infection (STI) prevention among women who have sex with women (WSW) are available, although their effectiveness has not been systematically investigated. These methods are infrequently used by WSW. As part of a larger study on STI risk perceptions and safer sex among African-American WSW, we discovered several misperceptions regarding barrier methods that may be associated with their limited use. Methods: Participants were recruited from the Jefferson County Health Department STI Clinic and through word of mouth in Birmingham, Alabama, for focus group discussions exploring perceptions of STI risk and safer sex. Results: Seven focus groups with 29 participants were conducted (age range: 19–43 years). Several misperceptions regarding barrier methods were identified, notably the conflation of dental dams and female condoms. Descriptions of the use of barrier methods were qualified with phrases suggesting their hypothetical, rather than actual, use. Additional evidence that barrier methods are not actually used came from beliefs that dental dams and female condoms are available in major grocery stores or department store chains. Conclusions: Those providing sexual health services to WSW should be cautious in assuming that WSW have accurate information regarding barrier methods for safer sex. Sexual health services provided to WSW should include an accurate description of what barrier methods are, how to distinguish them from barrier methods more commonly used during heterosexual sex (female and male condoms), and how to use them correctly. Future studies are needed to address how effectively these measures reduce transmission of STIs among WSW.
The prevalence of sexually transmissible infections among female sex workers from countries with low and high prevalences in Melbourne
Authors: Tang Haiping , Hocking Jane S. , Fehler Glenda , Williams Hennriette , Chen Marcus Y. , Fairley Christopher K.
Published: February 2013

Objectives
To assess the proportion of female sex workers (FSWs) from low-prevalence (‘other’) and high-prevalence countries (HPCs) for sexually transmissible infections (STIs) in Melbourne. Methods: Retrospective data analysis from the Melbourne Sexual Health Centre database for February 2002–May 2011. Results: Some 1702 HPC FSWs, 2594 other FSWs and 13 644 nonFSW women were included, with 12 891 and 21 611 consultations, respectively, for HPC FSWs and other FSWs. Proportions of HPC FSWs with chlamydia (Chlamydia trachomatis) (4.2% v. 3.3%, P = 0.14), gonorrhoea (Neisseria gonorrhoeae) (0.24% v. 0.31%, P = 0.66) or trichomonas (0.65 v. 0.46, P = 0.42) at first visit were similar to those of other FSWs, but nonFSWs had a higher prevalence of chlamydia and gonorrhoea (P < 0.01). On return visits, chlamydia (1.2% v. 0.92%, P < 0.05) and gonorrhoea (0.29% v. 0.10%, P = <0.05) were more common in HPC FSWs than other FSWs. The presence of any of these STIs among FSWs was predicted by having private nonpaying partners in the last year (adjusted odds ratio (AOR): 1.99 (95% confidence interval (CI): 1.52–2.61)), having private partners from overseas (AOR: 1.69 (95% CI: 1.33–2.16)) and being a HPC FSW (AOR: 1.38 (95% CI: 1.12–1.72)). Injecting drug use was less common in HPC FSWs than in other FSWs (0.82% v. 16.54%, P < 0.0001). Conclusions: STI prevalence was low among FSWs from countries with high and low background STI. Among FSWs having private sex partners and private partners from overseas were the primary predictors for STIs.
Analysis of Prey Selection by Double‐Crested Cormorants: A 15‐Year Diet Study in Oneida Lake, New York
Authors: DeBruyne Robin L. , Coleman Jeremy T. H. , Jackson James R. , Rudstam Lars G. , VanDeValk Anthony J.
Published: February 2013

Piscivorous birds, in particular cormorants Phalacrocorax spp., have been reported to cause declines in some fish populations in both Europe and North America, but not in others. This difference may be due to prey selection by cormorants that is further dependent on the composition of the fish assemblage present. We present 15 years of diet data collected from Oneida Lake, New York, where we have previously documented negative effects of double‐crested cormorants Phalacrocorax auritus on two fish populations valued by anglers: Walleye Sander vitreus and Yellow Perch Perca flavescens. The Oneida Lake fish community changed through the study period and this change was reflected in cormorant diet samples. Diet samples were variable based on season and year with Emerald Shiner Notropis atherinoides, Gizzard Shad Dorosoma cepedianum, Lepomis spp., Logperch Percina caprodes, Walleye, and Yellow Perch having the highest overall relative importance. In years when age‐0 Gizzard Shad were abundant they dominated double‐crested cormorant diets in the fall after the shad reached a length of 45 mm. Consumption of Emerald Shiner and Gizzard Shad was positively related to each species’ abundance, but no significant correlation between availability and consumption was found for Walleye, White Perch Morone americana, or Yellow Perch. Double‐crested cormorants may be displaying prey‐switching behavior and selecting for smaller, soft‐rayed, prey species. We conclude that variation in fish recruitment influences double‐crested cormorant food selection habits and highlight the importance of continued monitoring with changing fish communities to reliably assess potential impacts of cormorants on a fish community over time.
Route Use and Survival of Juvenile Chinook Salmon through the San Joaquin River Delta
Authors: Buchanan Rebecca A. , Skalski John R. , Brandes Patricia L. , Fuller Andrea
Published: February 2013

The survival of juvenile Chinook Salmon through the lower San Joaquin River and Sacramento–San Joaquin River Delta in California was estimated using acoustic tags in the spring of 2009 and 2010. The focus was on route use and survival within two major routes through the Delta: the San Joaquin River, which skirts most of the interior Delta to the east, and the Old River, a distributary of the San Joaquin River leading to federal and state water export facilities that pump water out of the Delta. The estimated probability of using the Old River route was 0.47 in both 2009 and 2010. Survival through the southern (i.e., upstream) portion of the Delta was very low in 2009, estimated at 0.06, and there was no significant difference between the Old River and San Joaquin River routes. Estimated survival through the Southern Delta was considerably higher in 2010 (0.56), being higher in the Old River route than in the San Joaquin route. Total estimated survival through the entire Delta (estimated only in 2010) was low (0.05); again, survival was higher through the Old River. Most fish in the Old River that survived to the end of the Delta had been salvaged from the federal water export facility on the Old River and trucked around the remainder of the Delta. The very low survival estimates reported here are considerably lower than observed salmon survival through comparable reaches of other large West Coast river systems and are unlikely to be sustainable for this salmon population. More research into mortality factors in the Delta and new management actions will be necessary to recover this population.

Received March 28, 2012; accepted September 5, 2012
A Probabilistic Model for Assessing Passage Performance of Coastal Cutthroat Trout through Corrugated Metal Culverts
Authors: Peterson N. Phil , Simmons Ryan K. , Cardoso Tamre , Light Jeffrey T.
Published: February 2013

We conducted a series of volitional trials with wild-caught resident Coastal Cutthroat Trout Oncorhynchus clarkii clarkii in a 12.2-m-long, 1.8-m-diameter culvert test facility to develop a probabilistic model for predicting rates of upstream passage over a wide range of average velocities. The results of the passage trials indicated that the percentage of fish attempting passage and the percentage of fish successfully passing decreased as the trial target average velocity increased. At our highest trial average velocity of 2.4 m/s, 31% of test fish that chose to attempt passage passed after two nights of observation. Passage performance was generally better for larger fish, but this pattern was only statistically significant for a single trial (1.9 m/s). Fish ascended through the pipe more quickly as velocity increased. At higher test velocities fish favored the left side of the pipe (looking downstream), which contained a reduced-velocity zone created by the slightly oblique orientation of culvert corrugations. Our data provide the basis for a logistic model describing the probability of passage for Coastal Cutthroat Trout through bare corrugated metal culverts with no outlet drop. Empirical studies testing fish passage, such as this one, can inform culvert assessment protocols currently in use.

Received April 9, 2012; accepted November 7, 2012
Environmental Context Effects on Episodic Memory are Dependent on Retrieval Mode and Modulated by Neuropsychological Status
Authors: Barak Ohr , Vakil Eli , Levy Daniel A.
Published: February 2013

Contextual change or constancy between occasions of memory formation and retrieval are commonly assumed to affect retrieval success, yet such effects may be inconsistent, and the processes leading to the pattern of effects are still not well understood. We conducted a systematic investigation of environmental context effects on memory, using a range of materials (common objects, pictures of familiar and unfamiliar faces, words, and sentences), and four types of retrieval (free recall, cued recall, recognition, and order memory), all assessed within participants. Additionally, we examined the influence of mnemonic challenge on context effects by examining both healthy participants and a group of patients in rehabilitation following traumatic brain injury (TBI). We found no effects of contextual factors on tests of recognition for either group of participants, but effects did emerge for cued and free recall, with the most prominent effects being on memory for objects. Furthermore, while patients’ memory abilities in general were impaired relative to the comparison group, they exhibited greater influences of contextual reinstatement on several recall tasks. These results support suggestions that environmental context effects on memory are dependent on retrieval mode and on the extent to which retrieval is challenging because of neurocognitive status. Additionally, findings of environmental context effects in memory-impaired TBI patients suggest that by harnessing such preserved indirect memory (e.g., using reminder technologies), it may be possible to ameliorate TBI patients’ difficulties in explicit remembering.
The Establishment-Level Behavior of Vacancies and Hiring
*
Authors: Davis Steven J. , Faberman R. Jason , Haltiwanger John C.
Published: February 2013

This paper is the first to study vacancies, hires, and vacancy yields at the establishment level in the Job Openings and Labor Turnover Survey, a large sample of US employers. To interpret the data, we develop a simple model that identifies the flow of new vacancies and the job-filling rate for vacant positions. The fill rate moves counter to aggregate employment but rises steeply with employer growth rates in the cross section. It falls with employer size, rises with worker turnover rates, and varies by a factor of four across major industry groups. We also develop evidence that the employer-level hiring technology exhibits mild increasing returns in vacancies, and that employers rely heavily on other instruments, in addition to vacancies, as they vary hires. Building from our evidence and a generalized matching function, we construct a new index of recruiting intensity (per vacancy). Recruiting intensity partly explains the recent breakdown in the standard matching function, delivers a better-fitting empirical Beveridge curve, and accounts for a large share of fluctuations in aggregate hires. Our evidence and analysis provide useful inputs for assessing, developing, and calibrating theoretical models of search, matching, and hiring in the labor market.
Song type matching is an honest early threat signal in a hierarchical animal communication system
Authors: Akçay Çag˘lar , Tom Mari E. , Campbell S. Elizabeth , Beecher Michael D.
Published: February 2013

Aggressive encounters between animals often involve significant amounts of signalling before or in lieu of physical fights. When, as is often the case, these apparent threat signals are neither inherently costly nor inherently indicative of fighting ability, we should ask whether they are in fact honest signals, i.e. do they predict that escalation is imminent? While signalling theories have indicated that such ‘conventional’ threat signals can honestly predict escalation, attempts to gather supporting empirical evidence have mostly failed. For example, recent studies in songbirds of song type matching (replying to an opponent's song with the same song type he has just sung) have failed to confirm that it predicts an eventual attack by the signaller. In the present study of song sparrows (
Melospiza melodia
), we tested the hypothesis that song type matching is an early threat signal in a hierarchical signalling system. We used an improved model-playback design that simulated an escalating intrusion onto the subject's territory: the simulated opponent first sang in hiding from the boundary before moving to the centre of the territory, where he revealed himself and continued to sing. We found that type matching beginning in the boundary phase and continuing into the escalation phase, or beginning immediately after the escalation, reliably predicted both subsequent escalated signalling (soft songs and wing waves) and subsequent attack on the model, supporting the hypothesis that type matching is a reliable early threat signal.