bluuebunny/crossref_metadata_2025 huggingface dataset:
Fundamental importance of the Coulomb hole sum rule to the understanding of the Colle-Salvetti wave function functional
Authors: Pan Xiao-Yin , Sahni Viraht , Massa Lou
Published: July 2006

In this paper we consider the general form of the correlated-determinantal wave function functional of Colle and Salvetti (CS) for the He atom. The specific form employed by CS is the basis for the widely used CS correlation energy formula and the Lee-Yang-Parr correlation energy density functional of Kohn-Sham density functional theory. We show the following: (i) The key assumption of CS for the determination of this wave function functional, viz., that the resulting single-particle density matrix and the Hartree-Fock theory Dirac density matrix are the same, is equivalent to the satisfaction of the Coulomb hole sum rule for each electron position. The specific wave function functional derived by CS does not satisfy this sum rule for any electron position. (ii) Application of the theorem on the one-to-one correspondence between the Coulomb hole sum rule for each electron position and the constraint of normalization for approximate wave functions then proves that the wave function derived by CS violates charge conservation. (iii) Finally, employing the general form of the CS wave function functional, the exact satisfaction of the Coulomb hole sum rule at each electron position then leads to a wave function that is normalized. The structure of the resulting approximate Coulomb holes is reasonably accurate, reproducing both the short- and the long-range behavior of the hole for this atom. Thus, the satisfaction of the Coulomb hole sum rule by an approximate wave function is a necessary condition for constructing wave functions in which electron-electron repulsion is represented reasonably accurately.
Heralding of telecommunication photon pairs with a superconducting single photon detector
Authors: Jaspan Martin A. , Habif Jonathan L. , Hadfield Robert H. , Nam Sae Woo
Published: July 2006

Experiments involving entangled photon pairs created via spontaneous parametric down conversion typically use wavelengths in the visible regime. The extension of a photonic quantum information link to a fiber optical network requires that entangled pairs be created at telecommunication wavelengths (1550nm), for which photon counting detector technology is inferior to visible detection, in particular, low coincidence detection rates of correlated-photon pairs. We demonstrate a correlated-photon pair measurement using the superconducting single photon detector in a heralding scheme that can be used to substantially improve the correlated-photon detection rate.
AND/R: Advanced neutron diffractometer/reflectometer for investigation of thin films and multilayers for the life sciences
Authors: Dura Joseph A. , Pierce Donald J. , Majkrzak Charles F. , Maliszewskyj Nicholas C. , McGillivray Duncan J. , Lösche Mathias , O’Donovan Kevin V. , Mihailescu Mihaela , Perez-Salas Ursula , Worcester David L. , White Stephen H.
Published: July 2006

An elastic neutron scattering instrument, the advanced neutron diffractometer/reflectometer (AND/R), has recently been commissioned at the National Institute of Standards and Technology Center for Neutron Research. The AND/R is the centerpiece of the Cold Neutrons for Biology and Technology partnership, which is dedicated to the structural characterization of thin films and multilayers of biological interest. The instrument is capable of measuring both specular and nonspecular reflectivity, as well as crystalline or semicrystalline diffraction at wave-vector transfers up to approximately 2.20Å−1. A detailed description of this flexible instrument and its performance characteristics in various operating modes are given.
Ca test of Al2O3 gas diffusion barriers grown by atomic layer deposition on polymers
Authors: Carcia P. F. , McLean R. S. , Reilly M. H. , Groner M. D. , George S. M.
Published: July 2006

Quantitative Ca tests were used to determine the water vapor transmission rate (WVTR) through 25nm thick Al2O3 gas diffusion barriers grown on plastic by atomic layer deposition (ALD). The measured WVTRs were 1.7×10−5g∕m2day at 38°C and 6.5×10−5g∕m2day at 60°C. Based on the apparent activation energy, the WVTR at 23°C is estimated to be only 6×10−6g∕m2day. The WVTR values for the Al2O3 ALD film are very similar to the WVTR value for the glass control. These Ca tests indicate that Al2O3 ALD gas diffusion barriers should enable display and lighting applications of highly moisture sensitive organic light-emitting diodes on plastic.
Discrete magnetic microfluidics
Authors: Egatz-Gómez Ana , Melle Sonia , García Antonio A. , Lindsay S. A. , Márquez M. , Domínguez-García P. , Rubio Miguel A. , Picraux S. T. , Taraci J. L. , Clement T. , Yang D. , Hayes Mark A. , Gust Devens
Published: July 2006

We present a method to move and control drops of water on superhydrophobic surfaces using magnetic fields. Small water drops (volume of 5–35μl) that contain fractions of paramagnetic particles as low as 0.1% in weight can be moved at relatively high speed (7cm∕s) by displacing a permanent magnet placed below the surface. Coalescence of two drops has been demonstrated by moving a drop that contains paramagnetic particles towards an aqueous drop that was previously pinned to a surface defect. This approach to microfluidics has the advantages of faster and more flexible control over drop movement.
Potential of discharge-based lithium plasma as an extreme ultraviolet source
Authors: Masnavi Majid , Nakajima Mitsuo , Sasaki Akira , Hotta Eiki , Horioka Kazuhiko
Published: July 2006

Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the spectrum band of 13.5±0.135nm. A model was developed to investigate the wavelength-integrated Lyman-α lines light outputs in hydrogen-like lithium ion. The analysis reveals that the commonly observed low conversion efficiency is largely due to a transient nature of Z discharge-based plasma and that a magnetically confined lithium plasma is an efficient EUV source even at low electron temperature. Calculation shows necessary confinement time that raises the conversion efficiency up to half the spectral efficiency.
Coexisting depinning effect of domain walls during the fatigue in ferroelectric thin films
Authors: Jiang A. Q. , Lin Y. Y. , Tang T. A.
Published: July 2006

Appropriate time relaxation before a driving pulse of domain switching can improve fatigue endurance in Pb(Zr,Ti)O3 thin films. The effect is more evident under a relaxation voltage close to a coercive voltage (Vc) in the same voltage polarity to the driving pulse, in contradiction with previous investigations of domain-wall pinning more effectively under driving voltages close to Vc. Pinning and depinning of domain walls are identified to coexist during bipolar voltage stressing of the films and both modeled per cycle on the basis of charge injection at high frequencies and mobile charge separation at low frequencies.
Inhomogeneous effect of particle size on core-level and valence-band electrons: Size-dependent electronic structure of Cu3N nanoparticles
Authors: Balamurugan B. , Maruyama Toshiro
Published: July 2006

The present study reports a clear evidence and physical significance of an inhomogeneous effect of particle size on electrons originating from various electronic levels of copper nitride nanoparticles. X-ray photoelectron and optical absorption spectroscopy studies reveal that a direct modification of the valence band due to size effects explained by the more appropriate surface bond contraction model results in a strong increase in the binding energy of valence-band electrons as compared to core-level electrons.
Effect of the initial structure of silicon surface on the generation of multiple structural phases by cyclic microindentation
Authors: Pizani P. S. , Jasinevicius R. G. , Zanatta A. R.
Published: July 2006

Raman scattering technique was used to investigate the structural phase transformations and multiple phase generation of silicon induced by cyclic microindentations. Indentation cycles were performed on three different samples: monocrystalline, amorphous film, and on partially amorphous silicon generated by single point diamond turning. The results indicated that the formation of some pressure induced structural phases may be dependent upon the initial structural state of the materials surface: Several different structural phases were only observed in crystalline and partially amorphous Si after microindentation cycles. For completely amorphous Si, no phase formation was evidenced even after several cyclic indentations.
Visual Object Categorisation at Distinct Levels of Abstraction: A New Stimulus Set
Authors: de Beeck Hans Op , Wagemans Johan
Published: July 2006

We designed a new stimulus set with 269 line drawings of everyday artifacts and animals. The stimulus set contains several typical exemplars from a sample of 25 basic-level categories. We determined to what extent these stimuli were named at the basic level and at a more subordinate level. An additional experiment showed the validity of this calibration: typicality ratings were correlated significantly with the level of naming. In a final experiment we found that this effect depends largely on the global configuration of a stimulus as it was still apparent with degraded images obtained by locally shifting small fragments of the drawings.
The Importance of Being Convex: An Advantage for Convexity when Judging Position
Authors: Bertamini Marco
Published: July 2006

Perception of contour polarity was investigated in five experiments in which observers had to judge the vertical position of a vertex. When the vertex was perceived as convex, the level of performance as measured by reaction time and errors was higher than when the same vertex was perceived as concave. I conclude that contour polarity affects how observers perceive shape, and in particular part structure, and that the position of a part is more readily available than the position of a boundary between parts.
Rapid, Object-Based Learning in the Deployment of Transient Attention
Authors: Kristjánsson Árni , Mackeben Manfred , Nakayama Ken
Published: July 2006

We show that transient attention summoned by an exogenous cue shows rapid learning of the relationship between the cue and a subsequent target in a discrimination task. In experiment 1, performance was unaffected when a target always appeared in the same position on a large cue, but was degraded when the target could appear anywhere within the extent of the larger cue. Experiment 2 shows that it was not the predictability of where the target appeared within the cue that aided performance, but rather a consistent location mapping of cue and target, since predictably alternating the target location relative to the cue led to worse performance than when the target was presented in the same location relative to the cue from trial to trial. Further analysis of the results of experiment 2 shows that the learning is rapid, evident after one trial, and has a cumulative influence over four consecutive trials. Possible neural correlates of this form of learning are discussed, with a focus on the supplementary eye fields in the prefrontal cortex. The reported experiments show that transient attention is not a simple reflexive mechanism but can show rapid visuospatial learning, in object-based coordinates.
A Purely Temporal Transparency Mechanism in the Visual System
Authors: Holcombe Alex O
Published: July 2006

I report evidence for a purely temporal perceptual transparency mechanism. Rapid alternation of two images in the same location can result in the simultaneous experience of both, accompanied by a sense of transparency. This is true even when the sum of the two images does not appear transparent, which suggests that the percept is not mediated by the static transparency processes. At slow rates, alternating gratings were experienced as successive. As the rate was increased, by 8 Hz observers experienced the gratings as simultaneous. The rapidly alternating gratings are apparently processed separately before being combined for awareness by a process that integrates over about 120 ms. A final experiment tested whether the common presentation time of different parts of an image in alternation with another would cause the parts to perceptually bind. Observers did not distinguish between a rapidly alternating intact grating display and one in which halves of the display were exchanged in time. In other words, temporal binding across space did not occur. The temporal transparency phenomenon, in addition to informing theories of transparency and the dynamics of visual processing, may also be useful for the creation of transparent displays for electronic devices.
Active Steering along Corrugated Surfaces
Authors: Kim Nam-Gyoon
Published: July 2006

A study is reported of the effect of dynamic occlusion that arises during locomotion over corrugated surfaces and its facilitating role on the control of locomotion, especially in cluttered environments. Surfaces varied in degree of corrugation and type of texture. Heading accuracy was assessed by having participants perform an active steering task. Results demonstrated the advantage of texture-mapped image surfaces over discrete element surfaces in the corrugated conditions. Observers appear to exploit accretion and deletion of optical texture at the occluding edge to extract and use information about heading direction for the control of movements in cluttered environments.
Spatiotemporal Balance in Competing Apparent Motion is Not Predicted from the Strength of the Single-Motion Percept
Authors: Sakamoto Kazuhiro , Sugiura Takayuki , Kaku Toshihiko , Onizawa Toru , Yano Masafumi
Published: July 2006

Apparent motion is useful for investigating how spatiotemporal cues are integrated to determine the identity of a moving object. To examine its spatiotemporal properties, a competing-motion paradigm has advantages in strict psychophysical evaluation, despite difficulty in object-identity determination, over a non-competing subjective-grading paradigm. The latter has been often used, whereas the former has not been fully investigated. Here, we compared these two paradigms. In the competing-motion experiment, a sample spot was followed by a far and a near test spot with onset asynchrony. We found that the onset asynchrony between the near and far test spots was directly related to the distance ratio between them. This spatial size-invariant relation was not predicted from the strength of the single-apparent-motion percept, estimated from the non-competing subjective-grading experiment in which a sample spot was followed by only one test spot. Moreover, the spatiotemporal balance in competing apparent motion was found not to be valid under negative interstimulus-interval conditions, although a single apparent motion is perceived in those conditions. These clear discrepancies suggest that competing and single apparent motions are processed in a different way according to the difficulty in object identification.
Globalization and the population structure of
Toxoplasma gondii
Authors: Lehmann Tovi , Marcet Paula L. , Graham Doug H. , Dahl Erica R. , Dubey J. P.
Published: July 2006

Toxoplasma gondii
is a protozoan parasite that infects nearly all mammal and bird species worldwide. Usually asymptomatic, toxoplasmosis can be severe and even fatal to many hosts, including people. Elucidating the contribution of genetic variation among parasites to patterns of disease transmission and manifestations has been the goal of many studies. Focusing on the geographic component of this variation, we show that most genotypes are locale-specific, but some are found across continents and are closely related to each other, indicating a recent radiation of a pandemic genotype. Furthermore, we show that the geographic structure of
T. gondii
is extraordinary in having one population that is found in all continents except South America, whereas other populations are generally confined to South America, and yet another population is found worldwide. Our evidence suggests that South American and Eurasian populations have evolved separately until recently, when ships populated by rats, mice, and cats provided
T. gondii
with unprecedented migration opportunities, probably during the transatlantic slave trade. Our results explain several enigmatic features of the population structure of
T. gondii
and demonstrate how pervasive, prompt, and elusive the impact of human globalization is on nature.
Regulation of intracellular free calcium concentration during heterocyst differentiation by HetR and NtcA in
Anabaena
sp. PCC 7120
Authors: Shi Yunming , Zhao Weixing , Zhang Wei , Ye Zi , Zhao Jindong
Published: July 2006

Calcium ions are important to some prokaryotic cellular processes, such as heterocyst differentiation of cyanobacteria. Intracellular free Ca
2+
concentration, [Ca
2+
]
i
, increases several fold in heterocysts and is regulated by CcbP, a Ca
2+
-binding protein found in heterocyst-forming cyanobacteria. We demonstrate here that CcbP is degraded by HetR, a serine-type protease that controls heterocyst differentiation. The degradation depends on Ca
2+
and appears to be specific because HetR did not digest other tested proteins. CcbP was found to bind two Ca
2+
per molecule with
K
D
values of 200 nM and 12.8 μM. Degradation of CcbP releases bound Ca
2+
that contributes significantly to the increase of [Ca
2+
]
i
during the process of heterocyst differentiation in
Anabaena
sp. strain PCC 7120. We suggest that degradation of CcbP is a mechanism of positive autoregulation of HetR. The down-regulation of
ccbP
in differentiating cells and mature heterocysts, which also is critical to the regulation of [Ca
2+
]
i
, depends on NtcA. Coexpression of
ntcA
and a
ccbP
promoter-controlled
gfp
in
Escherichia coli
diminished production of GFP, and the decrease is enhanced by α-ketoglutarate. It was also found that NtcA could bind a fragment of the
ccbP
promoter containing an NtcA-binding sequence in a α-ketoglutarate-dependent fashion. Therefore, [Ca
2+
]
i
is regulated by a collaboration of HetR and NtcA in heterocyst differentiation in
Anabaena
sp. strain PCC 7120.
Antioxidants reduce cone cell death in a model of retinitis pigmentosa
Authors: Komeima Keiichi , Rogers Brian S. , Lu Lili , Campochiaro Peter A.
Published: July 2006

Retinitis pigmentosa (RP) is a label for a group of diseases caused by a large number of mutations that result in rod photoreceptor cell death followed by gradual death of cones. The mechanism of cone cell death is uncertain. Rods are a major source of oxygen utilization in the retina and, after rods die, the level of oxygen in the outer retina is increased. In this study, we used the
rd1
mouse model of RP to test the hypothesis that cones die from oxidative damage. A mixture of antioxidants was selected to try to maximize protection against oxidative damage achievable by exogenous supplements; α-tocopherol (200 mg/kg), ascorbic acid (250 mg/kg), Mn(III)tetrakis (4-benzoic acid) porphyrin (10 mg/kg), and α-lipoic acid (100 mg/kg). Mice were treated with daily injections of the mixture or each component alone between postnatal day (P)18 and P35. Between P18 and P35, there was an increase in two biomarkers of oxidative damage, carbonyl adducts measured by ELISA and immunohistochemical staining for acrolein, in the retinas of
rd1
mice. The staining for acrolein in remaining cones at P35 was eliminated in antioxidant-treated
rd1
mice, confirming that the treatment markedly reduced oxidative damage in cones; this was accompanied by a 2-fold increase in cone cell density and a 50% increase in medium-wavelength cone opsin mRNA. Antioxidants also caused some preservation of cone function based upon photopic electroretinograms. These data support the hypothesis that gradual cone cell death after rod cell death in RP is due to oxidative damage, and that antioxidant therapy may provide benefit.
The influence of meaning on the perception of speech sounds
Authors: Kazanina Nina , Phillips Colin , Idsardi William
Published: July 2006

As part of knowledge of language, an adult speaker possesses information on which sounds are used in the language and on the distribution of these sounds in a multidimensional acoustic space. However, a speaker must know not only the sound categories of his language but also the functional significance of these categories, in particular, which sound contrasts are relevant for storing words in memory and which sound contrasts are not. Using magnetoencephalographic brain recordings with speakers of Russian and Korean, we demonstrate that a speaker’s perceptual space, as reflected in early auditory brain responses, is shaped not only by bottom-up analysis of the distribution of sounds in his language but also by more abstract analysis of the functional significance of those sounds.
Topoisomerase IIIα and Bloom’s helicase can resolve a mobile double Holliday junction substrate through convergent branch migration
Authors: Plank Jody L. , Wu Jianhong , Hsieh Tao-shih
Published: July 2006

It has long been suspected that a double Holliday junction (dHJ) could be resolved by a topoisomerase partnered with a helicase by convergent branch migration of the HJs. Genetic analysis of yeast TOP3 and SGS1 has lent considerable evidence to the notion that the protein products of these genes are involved in just such a process, although biochemical analysis of the metabolism of a dHJ has been hindered by the lack of a substrate that adequately replicates the endogenous structure. We have synthesized a dHJ substrate that recapitulates many of the features of an endogenous dHJ and represents a much earlier intermediate in the resolution pathway. Here, we show that
Drosophila
topoisomerase IIIα (Topo IIIα) and Blm (a homolog of Sgs1) are capable of resolving this substrate to non-cross-over products and that this activity is stimulated by replication protein A (RPA). We investigated the ability of other
Drosophila
topoisomerases to perform this reaction in concert with Blm and RPA and discovered that this resolution activity is unique to Topo IIIα. Examination of the mechanism of resolution reveals that Topo IIIα, Blm, and RPA resolve this substrate by convergent migration of the two HJs toward each other, collapsing the dHJ. This mechanism stands in contrast to classic resolvase activities that use a structure-specific endonuclease to cleave the HJs.
Smoking and its correlates in an Australian prisoner population
Authors: BELCHER JOSEPHINE M. , BUTLER TONY , RICHMOND ROBYN L. , WODAK ALEX D. , WILHELM KAY
Published: July 2006

Despite evidence of high rates of smoking among prisoners, there has been limited research that describes smoking patterns and risk factors associated with smoking in this group. This study describes inmate smokers and identifies factors associated with smoking in prison, using a survey comprising a cross‐sectional random sample of inmates stratified by sex, age and Aboriginality. A total of 914 adult inmates (747 men, 167 women) were recruited from 29 New South Wales (Australia) correctional centres. Information on the prevalence of smoking, smoking history, smoking behaviours and other risk factors were collected. Of the participants, 79% were current smokers (78% men, 83% women). Younger inmates were more likely than older inmates to smoke (86% vs. 64%). Most individuals smoked between 11 and 20 cigarettes a day and a median of 50 grams per week. In the previous year, over half (52%) of current smokers had attempted to quit or reduce the amount they smoked. At the time of the survey, 58% of smokers had plans to quit; 21% within 3 months. Independent predictors of current smoking in the multivariate analysis were past use of cannabis and a history of illicit drug use. The prevalence of smoking in prison is extraordinarily high and exceeds that of the general community. Despite this, the majority of prisoners report plans to quit. Readily available smoking cessation advice, support and treatment are needed to assist those wanting to quit in this stressful environment. As the prevalence of smoking within the general community declines, assisting cessation in groups containing a disproportionate number of smokers will become increasingly important. Despite high levels of tobacco dependence, many prisoners intend to quit and health planners and custodial authorities need to encourage and support inmates who do attempt to quit.
How the quality of peer relationships influences college alcohol use
Authors: BORSARI BRIAN , CAREY KATE B.
Published: July 2006

Peer relationships are consistently linked to alcohol use in college students. However, this disparate literature often reveals contradictory findings regarding the precise mechanisms of peer influence. In this review, we use an organisational framework based on social learning theory (SLT) to demonstrate how the quality of peer relationships may influence personal alcohol use. We propose that the quality of peer relationships enhance the influence of social reinforcement, modelling and cognitive processes on personal alcohol use. Research indicates that the quality of peer relationships influences drinking via three pathways: the lack or breakdown of quality peer relationships, alcohol use being an integral part of peer interactions, and if peers disapprove of alcohol use or do not drink. This conceptualisation of peer influence informs the consistent finding of gender differences in college student drinking. Limitations of the reviewed research include reliance on cross‐sectional surveys, self‐report and homogeneous populations. Future directions for research on quality peer relationships involve detailed longitudinal assessment and the application of advanced statistical methods.
Diversion and criminal justice drug treatment: mechanism of emancipation or social control?
Authors: CLANCEY GARNER , HOWARD JOHN
Published: July 2006

In Australia, as elsewhere, there has been a rapid growth in programs to divert drug‐using offenders from the criminal justice system to assessment and treatment. In this Harm Reduction Digest, which builds on papers presented at the APSAD Conference in Melbourne, November 2005, Clancey and Howard take a reflexive look at the Australian experience since the launch of the National Illicit Drug Diversion Initiative in 1999. In putting diversion within a broader criminological and societal context, they suggest that we may have criminalised drug policy and may ultimately be doing more harm than good.
Inhibition of return impairs episodic memory access
Authors: Massen Cristina , Stegt Stephan J.
Published: July 2006

The term inhibition of return (IOR) refers to a bias against returning attention to a location or object that has recently been attended. The effect has been shown to occur in various perceptual tasks including stimulus detection, localization, and discrimination, but also to affect higher cognitive processes like lexical access. The present experiments examined whether inhibition of return would impair the high-level processing that is required in accessing item representations in episodic memory. The results show that reaction times for recognition memory decisions are increased under IOR. Furthermore, IOR affects the accuracy of recognition memory, and this effect interacts with the ease of memory access, manipulated, for example, by encoding depth in the learning phase. These results suggest that IOR impairs attentional processing up to the highest cognitive levels, including the access of prior item encounters in episodic memory.
Order information and free recall: Evaluating the item-order hypothesis
Authors: Mulligan Neil W. , Lozito Jeffrey P.
Published: July 2006

The item-order hypothesis proposes that order information plays an important role in recall from long-term memory, and it is commonly used to account for the moderating effects of experimental design in memory research. Recent research (Engelkamp, Jahn, & Seiler, 2003; McDaniel, DeLosh, & Merritt, 2000) raises questions about the assumptions underlying the item-order hypothesis. Four experiments tested these assumptions by examining the relationship between free recall and order memory for lists of varying length (8, 16, or 24 unrelated words or pictures). Some groups were given standard free-recall instructions, other groups were explicitly instructed to use order information in free recall, and other groups were given free-recall tests intermixed with tests of order memory (order reconstruction). The results for short lists were consistent with the assumptions of the item-order account. For intermediate-length lists, explicit order instructions and intermixed order tests made recall more reliant on order information, but under standard conditions, order information played little role in recall. For long lists, there was little evidence that order information contributed to recall. In sum, the assumptions of the item-order account held for short lists, received mixed support with intermediate lists, and received no support for longer lists.
Searching for Shereshevskii: What is superior about the memory of synaesthetes?
Authors: Yaro Caroline , Ward Jamie
Published: July 2006

Some individuals with superior memory, such as the mnemonist Shereshevskii (Luria, 1968), are known to have synaesthesia. However, the extent to which superior memory is a general characteristic of synaesthesia is unknown, as is the precise cognitive mechanism by which synaesthesia affects memory. This study demonstrates that synaesthetes tend to report subjectively better than average memory and that these reports are borne out with objective testing. Synaesthetes experiencing colours for words show better memory than matched controls for stimuli that induce synaesthesia (word lists) relative to stimuli that do not (an abstract figure). However, memory advantages are not limited to material that elicits synaesthesia because synaesthetes demonstrate enhanced memory for colour per se (which does not induce a synaesthetic response). Our results suggest that the memory enhancement found in synaesthetes is related to an enhanced retention of colour in both synaesthetic and nonsynaesthetic situations. Furthermore, this may account for the fact that synaesthetic associations, once formed, remain highly consistent.
AGGLOMERATION AND REGIONAL COSTS OF LIVING*
Authors: Suedekum Jens
Published: July 2006

ABSTRACT Standard models of the new economic geography predict that costs of living are lower in the core than in the periphery. But in reality they tend to be higher in agglomeration areas, mainly because of regional differences in housing costs. In this paper, we add a home goods sector to the seminal NEG model of Krugman (1991). We show that a core–periphery structure can endogenously emerge in which the core is the more expensive area. This result has an important normative implication. Since higher costs of living imply falling real wages if there is no nominal wage premium, it is not desirable for everybody to live in the core region.
THE EFFICIENCY OF THE HIGH‐TECH ECONOMY: CONVENTIONAL DEVELOPMENT INDEXES VERSUS A PERFORMANCE INDEX*
Authors: Raab Raymond A. , Kotamraju Pradeep
Published: July 2006

ABSTRACT Data Envelopment Analysis (DEA) is employed to construct an index of relative efficiencies by maximizing two proxies of high‐tech output subject to minimizing five specific resources often associated with high‐tech infrastructure. This approach ranks the 50 U.S. states from the most robustly efficient to the most robustly inefficient. The DEA approach avoids using equal or subjective weights employed in the New State Economy Index rankings. The ranking of the 50 states yields some interesting differences between some states' dominance in high‐tech industries and their economic performance.
Employment, Family Union and Childbearing Decisions in Great Britain
Authors: Aassve Arnstein , Burgess Simon , Propper Carol , Dickson Matt
Published: July 2006

The paper investigates the life-cycle relationship of work and family life in Britain based on the British Household Panel Survey. Using hazard regression techniques we estimate a five-equation model, which includes birth events, union formation, union dissolution, employment and non-employment events. We find that transitions in and out of employment for men are relatively independent of other transitions. In contrast, there are strong links between employment of females, having children and union formation. By undertaking a detailed microsimulations analysis, we show that different levels of labour force participation by females do not necessarily lead to large changes in fertility events. Changes in union formation and fertility events, in contrast, have larger effects on employment.
Neutral Umpires and Leg Before Wicket Decisions in Test Cricket
Authors: Ringrose Trevor J.
Published: July 2006

The proportions of dismissals which were leg before wicket in test cricket matches during 1978–2004 are analysed by using generalized linear and mixed models to assess the effect of location, team and the presence or otherwise of neutral umpires. The location and the team batting are clearly significant. There is also clear evidence of an interaction showing that some teams’ players are out leg before wicket less often at home but there is no further interaction with neutral umpires, suggesting that this is not caused simply by home umpires favouring the home team.
On the Analysis of Long-Term Experiments
Authors: Loughin Thomas M. , Roediger Mollie Poehlman , Milliken George A. , Schmidt John P.
Published: July 2006

Long-term experiments are commonly used tools in agronomy, soil science and other disciplines for comparing the effects of different treatment regimes over an extended length of time. Periodic measurements, typically annual, are taken on experimental units and are often analysed by using customary tools and models for repeated measures. These models contain nothing that accounts for the random environmental variations that typically affect all experimental units simultaneously and can alter treatment effects. This added variability can dominate that from all other sources and can adversely influence the results of a statistical analysis and interfere with its interpretation. The effect that this has on the standard repeated measures analysis is quantified by using an alternative model that allows for random variations over time. This model, however, is not useful for analysis because the random effects are confounded with fixed effects that are already in the repeated measures model. Possible solutions are reviewed and recommendations are made for improving statistical analysis and interpretation in the presence of these extra random variations.
Multiple Randomizations
Authors: Brien C. J. , Bailey R. A.
Published: July 2006

Multitiered experiments are characterized by involving multiple randomizations, in a sense that we make explicit. We compare and contrast six types of multiple randomizations, using a wide range of examples, and discuss their use in designing experiments. We outline a system of describing the randomizations in terms of sets of objects, their associated tiers and the factor nesting, using randomization diagrams, which give a convenient and readily assimilated summary of an experiment's randomization. We also indicate how to formulate a randomization-based mixed model for the analysis of data from such experiments.
Free-Knot Spline Smoothing for Functional Data
Authors: Gervini Daniel
Published: July 2006

The paper introduces free-knot regression spline estimators for the mean and the variance components of a sample of curves. The asymptotic distribution of the mean estimator is derived, and asymptotic confidence bands are constructed. A comparative simulation study shows that free-knot splines estimate salient features of the functions (such as sharp peaks) more accurately than smoothing splines. This adaptive behaviour is also illustrated by an analysis of weather data.
Flexible Modelling of Neuron Firing Rates Across Different Experimental Conditions: An Application to Neural Activity in the Prefrontal Cortex During a Discrimination Task
Authors: Cadarso-Suárez Carmen , Roca-Pardiñas Javier , Molenberghs Geert , Faes Christel , Nácher Verónica , Ojeda Sabiela , Acuña Carlos
Published: July 2006

In many electrophysiological experiments the main objectives include estimation of the firing rate of a single neuron, as well as a comparison of its temporal evolution across different experimental conditions. To accomplish these two goals, we propose a flexible approach based on the logistic generalized additive model including condition-by-time interactions. If an interaction of this type is detected in the model, we then establish that the use of the temporal odds ratio curves is very useful in discriminating between the conditions under which the firing probability is higher. Bootstrap techniques are used for testing for interactions and constructing pointwise confidence bands for the true odds ratio curves. Finally, we apply the new methodology to assessing relationships between neural response and decision-making in movement-selective neurons in the prefrontal cortex of behaving monkeys.
High Dimensional Multivariate Mixed Models for Binary Questionnaire Data
Authors: Fieuws Steffen , Verbeke Geert , Boen Filip , Delecluse Christophe
Published: July 2006

Questionnaires that are used to measure the effect of an intervention often consist of different sets of items, each set possibly measuring another concept. Mixed models with set-specific random effects are a flexible tool to model the different sets of items jointly. However, computational problems typically arise as the number of sets increases. This is especially true when the random-effects distribution cannot be integrated out analytically, as with mixed models for binary data. A pairwise modelling strategy, in which all possible bivariate mixed models are fitted and where inference follows from pseudolikelihood theory, has been proposed as a solution. This approach has been applied to assess the effect of physical activity on psychocognitive functioning, the latter measured by a battery of questionnaires.
A Generalized Estimating Equation Method for Fitting Autocorrelated Ordinal Score Data with an Application in Horticultural Research
Authors: Parsons N. R. , Edmondson R. N. , Gilmour S. G.
Published: July 2006

Generalized estimating equations for correlated repeated ordinal score data are developed assuming a proportional odds model and a working correlation structure based on a first-order autoregressive process. Repeated ordinal scores on the same experimental units, not necessarily with equally spaced time intervals, are assumed and a new algorithm for the joint estimation of the model regression parameters and the correlation coefficient is developed. Approximate standard errors for the estimated correlation coefficient are developed and a simulation study is used to compare the new methodology with existing methodology. The work was part of a project on post-harvest quality of pot-plants and the generalized estimating equation model is used to analyse data on poinsettia and begonia pot-plant quality deterioration over time. The relationship between the key attributes of plant quality and the quality and longevity of ornamental pot-plants during shelf and after-sales life is explored.
Ethnic differences in allopregnanolone concentrations in women during rest and following mental stress
Authors: Girdler Susan S. , Beth Mechlin M. , Light Kathleen C. , Leslie Morrow A.
Published: July 2006

The neuroactive steroid allopregnanolone (ALLO) is stress sensitive, negatively modulates the HPA axis, and has been implicated in mood disorders. We examined ethnic differences in plasma ALLO at rest and following mental stress in African American (AA) men (n=21) and women (n=24) and non‐Hispanic White men (n=24) and women (n=25). Overall, AA women had lower ALLO concentrations than non‐Hispanic White women (p<.05), especially following mental stress (p<.01). Only 20% of AA women showed the expected stress‐induced increase in ALLO compared with 59% of non‐Hispanic White women (p<.01). No ethnic differences were seen in men. For both ethnic groups, poststress ALLO was negatively correlated with poststress cortisol (p<.05). Results are interpreted to reflect dysregulation in ALLO mechanisms in AA women and may have implications for ethnic differences in mood disorders.
Responses to the Trier Social Stress Test (TSST) in single versus grouped participants
Authors: Childs Emma , Vicini Lisa Marie , De Wit Harriet
Published: July 2006

Psychological stress plays an important role in psychopathologies. Laboratory methods have been designed to study stress responses in health and disease. The Trier Social Stress Test is a procedure designed to induce psychosocial stress, but the method is costly in terms of time and personnel requirements. We investigated whether conducting the task with multiple participants influenced cortisol, heart rate, and subjective responses and improved efficiency. Healthy male and female volunteers (N=32) performed the task individually or in groups. Salivary cortisol, anxiety, and jitteriness increased and calmness decreased similarly in both conditions. Grouped participants exhibited greater peak increases in heart rate than those who performed individually. The findings suggest that the TSST may be conducted with multiple participants without significantly affecting subjective and cortisol responses to the task.
The impact of emotions on the sensory and affective dimension of perceived dyspnea
Authors: Von Leupoldt Andreas , Mertz Corinna , Kegat Sarah , Burmester Swantje , Dahme Bernhard
Published: July 2006

Dyspnea is an impairing symptom in various diseases. Recent research has shown that the perception of dyspnea, like pain, consists of a sensory (intensity) and an affective (unpleasantness) dimension, but little is known about the specific impact of different emotions on these distinct dimensions. We therefore examined the impact of viewing affective picture series of positive, neutral, and negative valence on perceived dyspnea during resistive load breathing in healthy volunteers. Inspiratory time (Ti), breathing frequency (f), and oscillatory resistance (Ros) remained unchanged across conditions. Ratings for unpleasantness of dyspnea increased from positive to neutral to negative series, but ratings for intensity of dyspnea showed no changes. The results suggest that the affective dimension of the perception of dyspnea is particularly vulnerable to emotional influences, irrespective of objective lung function.
Attentional set mixing: Effects on target selection and selective response activation
Authors: Ruge Hannes , Stoet Gijsbert , Naumann Ewald
Published: July 2006

Performance is impaired under set mixing conditions that require frequent readjustments of attentional focus over an extended time period. We compared set repetitions within pure blocks (constant focus of attention) to physically identical repetitions within mixed blocks (changing focus of attention). The aim was to investigate how set mixing affects target selection, indexed by the N2pc component, and selective response activation, indexed by the lateralized readiness potential (LRP). We found that set mixing prolonged the evolution of the N2pc while leaving its onset unaffected. Impaired target selection indicated by the N2pc mixing effect also delayed the start of response planning indexed by an onset delay of the stimulus‐locked LRP, explaining one part of the behavioral mixing cost. A larger part of mixing cost could be attributed to a prolonged response planning phase, indexed by an earlier onset of the response‐locked LRP.
Trimeric Autotransporters Require Trimerization of the Passenger Domain for Stability and Adhesive Activity
Authors: Cotter Shane E. , Surana Neeraj K. , Grass Susan , St. Geme Joseph W.
Published: July 2006

In recent years, structural studies have identified a number of bacterial, viral, and eukaryotic adhesive proteins that have a trimeric architecture. The prototype examples in bacteria are the
Haemophilus influenzae
Hia adhesin and the
Yersinia enterocolitica
YadA adhesin. Both Hia and YadA are members of the trimeric-autotransporter subfamily and are characterized by an internal passenger domain that harbors adhesive activity and a short C-terminal translocator domain that inserts into the outer membrane and facilitates delivery of the passenger domain to the bacterial surface. In this study, we examined the relationship between trimerization of the Hia and YadA passenger domains and the capacity for adhesive activity. We found that subunit-subunit interactions and stable trimerization are essential for native folding and stability and ultimately for full-level adhesive activity. These results raise the possibility that disruption of the trimeric architecture of trimeric autotransporters, and possibly other trimeric adhesins, may be an effective strategy to eliminate adhesive activity.
Control of Acetyl-Coenzyme A Synthetase (AcsA) Activity by Acetylation/Deacetylation without NAD
+
Involvement in
Bacillus subtilis
Authors: Gardner Jeffrey G. , Grundy Frank J. , Henkin Tina M. , Escalante-Semerena Jorge C.
Published: July 2006

Posttranslational modification is an efficient mechanism for controlling the activity of structural proteins, gene expression regulators, and enzymes in response to rapidly changing physiological conditions. Here we report in vitro and in vivo evidence that the
acuABC
operon of the gram-positive soil bacterium
Bacillus subtilis
encodes a protein acetyltransferase (AcuA) and a protein deacetylase (AcuC), which may control the activity of acetyl-coenzyme A (CoA) synthetase (AMP-forming, AcsA) in this bacterium. Results from in vitro experiments using purified proteins show that AcsA is a substrate for the acetyl-CoA-dependent AcuA acetyltransferase. Mass spectrometry analysis of a tryptic digest of acetylated AcsA (AcsA
Ac
) identified residue Lys549 as the sole modification site in the protein. Unlike sirtuins, the AcuC protein did not require NAD
+
as cosubstrate to deacetylate AcsA
Ac
. The function of the putative AcuB protein remains unknown.
Characterization ofBacillus anthracis-Like Bacteria Isolated from Wild Great Apes from Côte d'Ivoire and Cameroon
Authors: Klee Silke R. , Özel Muhsin , Appel Bernd , Boesch Christophe , Ellerbrok Heinz , Jacob Daniela , Holland Gudrun , Leendertz Fabian H. , Pauli Georg , Grunow Roland , Nattermann Herbert
Published: July 2006

We present the microbiological and molecular characterization of bacteria isolated from four chimpanzees and one gorilla thought to have died of an anthrax-like disease in Côte d'Ivoire and Cameroon. These isolates differed significantly from classicBacillus anthracisby the following criteria: motility, resistance to the gamma phage, and, for isolates from Cameroon, resistance to penicillin G. A capsule was expressed not only after induction by CO2and bicarbonate but also under normal growth conditions. Subcultivation resulted in beta-hemolytic activity and gamma phage susceptibility in some subclones, suggesting differences in gene regulation compared to classicB. anthracis. The isolates from Côte d'Ivoire and Cameroon showed slight differences in their biochemical characteristics and MICs of different antibiotics but were identical in all molecular features and sequences analyzed. PCR and Southern blot analyses confirmed the presence of both the toxin and the capsule plasmid, with sizes corresponding to theB. anthracisvirulence plasmids pXO1 and pXO2. Protective antigen was expressed and secreted into the culture supernatant. The isolates possessed variants of the Ba813 marker and the SG-749 fragment differing from that of classicB. anthracisstrains. Multilocus sequence typing revealed a close relationship of our atypical isolates with both classicB. anthracisstrains and two uncommonly virulentBacillus cereusandBacillus thuringiensisisolates. We propose that the newly discovered atypicalB. anthracisstrains share a common ancestor with classicB. anthracisor that they emerged recently by transfer of theB. anthracisplasmids to a strain of theB. cereusgroup.