The mass of X-Ray Nova Scorpii 1994 (=GRO J1655--40)]

We have obtained high and intermediate resolution optical spectra of the black-hole candidate Nova Sco 1994 in May/June 1998, when the source was in complete (X-ray) quiescence. We measure the radial velocity curve of the secondary star and obtain a semi-amplitude of K_2=215.5+/-2.4 km/s, which is 6 per cent lower than the only previously determined value. This new value for K_2 thus reduces the binary mass function to f(M) = 2.73+/-0.09 Mo. Using only the high resolution spectra we constrain the rotational broadening of the secondary star, vsini, to lie in the range 82.9-94.9 km/s (95 per cent confidence) and thus constrain the binary mass ratio to lie in the range 0.337--0.436 (95 per cent confidence). We can also combine our results with published limits for the binary inclination to constrain the mass of the compact object and secondary star to the ranges 5.5 -- 7.9 and 1.7 -- 3.3 Mo respectively (95 per cent confidence). Finally, we report on the detection of the Lithium resonance line at 6707.8 A, with an equivalent width of 55+/-8 mA.Comment: 5 pages, 5 figures, accepted by MNRA

Probing spacetime foam with extragalactic sources

Due to quantum fluctuations, spacetime is probably ``foamy'' on very small scales. We propose to detect this texture of spacetime foam by looking for core-halo structures in the images of distant quasars. We find that the Very Large Telescope interferometer will be on the verge of being able to probe the fabric of spacetime when it reaches its design performance. Our method also allows us to use spacetime foam physics and physics of computation to infer the existence of dark energy/matter, independent of the evidence from recent cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several references added; very useful comments and suggestions by Eric Perlman incorporate

Observation of Goos-H\"{a}nchen shifts in metallic reflection

We report the first observation of the Goos-H$\rm \ddot{\textbf{a}}$nchen shift of a light beam incident on a metal surface. This phenomenon is particularly interesting because the Goos-H$\rm \ddot{\textbf{a}}$nchen shift for $p$ polarized light in metals is negative and much bigger than the positive shift for $s$ polarized light. The experimental result for the measured shifts as a function of the angle of incidence is in excellent agreement with theoretical predictions. In an energy-flux interpretation, our measurement shows the existence of a backward energy flow at the bare metal surface when this is excited by a $p$ polarized beam of light.Comment: The parer was published on Optics Express. The new version is modified according to the reviewers suggestion

Behind the wheel: What drives the effects of error handling?

Existing research comparing error management (a strategy focusing on increasing the positive and decreasing the negative consequences of errors) to error prevention (a strategy focusing on working faultlessly), has identified error management as beneficial for multiple outcomes. Yet, due to various methodological limitations, it is unclear whether the effects previously found are due to error prevention, error management, or both. We examine this in an experimental study with a 2 (error prevention: yes vs. no)× 2 (error management: yes vs. no) factorial design. Error prevention had negative effects on cognition and adaptive transfer performance. Error management alleviated worry and boosted one’s perceived self-efficacy. Overall, the results show that error prevention and error management have unique outcomes on negative affect, self-efficacy, cognition, and performance

Hard X-ray lags in GRO J1719-24

We have used the Fourier cross spectra of GRO J1719-24, as obtained with BATSE, to estimate the phase lags between the X-ray flux variations in the 20--50 and 50--100 keV energy bands as a function of Fourier frequency in the interval 0.002--0.488 Hz. Our analysis covers the entire ~80 day X-ray outburst of this black-hole candidate, following the first X-ray detection on 1993 September 25. The X-ray variations in the 50--100 keV band lag those in the 20--50 keV energy band by an approximately constant phase difference of 0.072 +/- 0.010 rad in the frequency interval 0.02--0.20 Hz. The peak phase lags in the interval 0.02--0.20 Hz are about twice those of Cyg X-1 and GRO J0422+32.These results are consistent with models for Comptonization regions composed of extended non-uniform clouds around the central source.Comment: 10 pages, including 4 postscript figures, AASTEX. Accepted for publication by Ap

Impaired Social Behavior in 5-HT3A Receptor Knockout Mice

The 5-HT3 receptor is a ligand-gated ion channel expressed on interneurons throughout the brain. So far, analysis of the 5-HT3A knockout mouse revealed changes in nociceptive processing and a reduction in anxiety related behavior. Recently, it was shown that the 5-HT3 receptor is also expressed on Cajal-Retzius cells which play a key role in cortical development and that knockout mice lacking this receptor showed aberrant growth of the dendritic tree of cortical layer II/III pyramidal neurons. Other mouse models in which serotonergic signaling was disrupted during development showed similar morphological changes in the cortex, and in addition, also deficits in social behavior. Here, we subjected male and female 5-HT3A knockout mice and their non-transgenic littermates to several tests of social behavior. We found that 5-HT3A knockout mice display impaired social communication in the social transmission of food preference task. Interestingly, we showed that in the social interaction test only female 5-HT3A knockout mice spent less time in reciprocal social interaction starting after 5 min of testing. Moreover, we observed differences in preference for social novelty for male and female 5-HT3A knockout mice during the social approach test. However, no changes in olfaction, exploratory activity and anxiety were detected. These results indicate that the 5-HT3A knockout mouse displays impaired social behavior with specific changes in males and females, reminiscent to other mouse models in which serotonergic signaling is disturbed in the developing brain

Alterations in Apical Dendrite Bundling in the Somatosensory Cortex of 5-HT3A Receptor Knockout Mice

In various species and areas of the cerebral cortex, apical dendrites of pyramidal neurons form clusters which extend through several layers of the cortex also known as dendritic bundles. Previously, it has been shown that 5-HT3A receptor knockout mice show hypercomplex apical dendrites of cortical layer 2/3 pyramidal neurons, together with a reduction in reelin levels, a glycoprotein involved in cortical development. Other studies showed that in the mouse presubicular cortex, reelin is involved in the formation of modular structures. Here, we compare apical dendrite bundling in the somatosensory cortex of wildtype and 5-HT3A receptor knockout mice. Using a microtubule associated protein-2 immunostaining to visualize apical dendrites of pyramidal neurons, we compared dendritic bundle properties of wildtype and 5-HT3A receptor knockout mice in tangential sections of the somatosensory cortex. A Voronoi tessellation was performed on immunostained tangential sections to determine the spatial organization of dendrites and to define dendritic bundles. In 5-HT3A receptor knockout mice, dendritic bundle surface was larger compared to wildtype mice, while the number and distribution of reelin-secreting Cajal–Retzius cells was similar for both groups. Together with previously observed differences in dendritic complexity of cortical layer 2/3 pyramidal neurons and cortical reelin levels, these results suggest an important role for the 5-HT3 receptor in determining the spatial organization of cortical connectivity in the mouse somatosensory cortex

Moving beyond job search quantity: Towards a conceptualization and self-regulatory framework of job search quality

Abstract Job seeking is an important aspect throughout people's careers. Extant theory and research has focused on one particular dimension of job search, that is, intensity/effort (i.e., job search quantity), posing that intensity/effort importantly affects employment success. The present conceptual paper extends job search theory by arguing for the importance of job search quality in explaining job search and employment success. We conceptualize job search quality as consisting of process quality and product/behavior quality, and propose that high-quality job search products/behaviors are more likely with a high-quality job search process. A four-phased cyclical self-regulatory model is presented, specifying the components of job search process quality. We build theory regarding the interrelations between quality components, the antecedents and outcomes of job search quality, and the moderators of these relations. This theory offers new and more detailed explanations for previous findings, directions for future research, and practical guidelines regarding (re)employment success and services. At any point, many individuals engage in job seeking, including unemployed people searching for reemployment, employed people looking for a new job, school-leavers or graduating students seeking their first job, and nonworking people (re)entering the labor force In addition to these explanations, one may question whether effort/intensity and number of job search sources/activities are the only important components of people's job search behavior. Although various scholars have coined the notion of job search quality (i.e., Organizational Psychology Review 3(1) quality and the conditions that impact those relations. The purpose of this conceptual paper is threefold. First, it aims to identify and delineate the components of job search quality, as well as conceptualize the relations among those components. In doing so, we synthesize relevant research into a conceptual framework of job search quality. Second, we build theory regarding the antecedents and outcomes of job search quality, and the moderators of these relations. Third, this paper aims to push job seeking research into new directions, by challenging the field to develop, study, and incorporate assessments of job search quality in addition to just job search quantity. We argue that a better understanding of job search quality is essential to advance both research and practice regarding reemployment success and services. We begin with a brief overview of extant job search theory, portraying that previous research has defined job search as a multistage process, albeit without specific attention to quality. We then draw upon the marketing and total quality management literature to argue for a distinction between job search product quality and job search process quality, and for conceptualizing job search process quality as a highly selfregulated job search. Extending previous job search theory and models, we use extant selfregulatory theory and recent advancements in the self-regulation literature to develop the components of our multistage job search quality process framework (see Extant job search theory Previous research describes job search as involving specific behaviors to identify labor market alternatives, acquire information about these alternatives, and actively pursue job opportunities Job search is often conceptualized as a multiphased process, consisting of several sequential stages. In his job search model, Soelberg (1967) described a deliberation phase of evaluation and occupational choice, followed by an implementation phase during which people allocate time, money, and effort to the job search. Building on this idea, Blau (1994) identified a preparatory and an active job search phase. Also broader theories on human behavior and decision-making have been used to suggest different stages in the job search process. For example, In addition to the conceptualization of job search as a multiphased process, recent theorizing has emphasized the self-regulatory Van Hooft et al. 5 Although some of these theories and models (implicitly) recognize the importance of job search quality (i.e., Conceptualizing job search quality The underpinnings of our multicomponent model of job search quality originate from previous work on product/service quality in the marketing literature. Below we describe this research as related to the conceptualization of quality, and argue for distinguishing between job search product quality and job search process quality. Quality as a product versus process The concept of quality in general has multiple and often very broad or muddled definitions. Reeves and Bednar (1994) identified several types of definitions of product/ service quality, and reviewed each definition's strengths and weaknesses. Based on this review, job search quality can be conceptualized as performing one's job search activities in such a way that those meet/exceed the expectations of the demanding parties of the labor market (e.g., selecting organizations, recruiters, assessors, hiring managers, counselors). A strength of this conceptualization is its external, organizationoriented focus, since what is high quality ultimately depends on the evaluations of the demanding parties of the labor market. However, although the demanding parties' expectations include some universals, these are to a large extent idiosyncratic (e.g., in each industry different ideas prevail about what constitutes a high-quality résumé or interview). A remaining question thus is how job seekers should perform their job search activities in order to increase the chances to meet those (idiosyncratic) expectations. Therefore, this external perspective to quality should be complemented by an internal or job seeker perspective, which holds that a high-quality job search refers to a job search that conforms to certain set and established standards and specifications. This definition implies a focus on the job search process. That is, in order to develop the specific quality standards and specifications, the job search should be disaggregated in its composing elements, and quality standards should be developed for each element. These quality standards can then offer prescriptive guidelines for job seekers and their counselors as to how to conduct a high-quality job search, which should ultimately lead to job search products that likely meet/exceed the demanding parties' expectations. Thus, we argue for a distinction between an external, organization-oriented perspective towards quality, and an internal, job seeker perspective towards quality. The external perspective refers to job search quality as job search behaviors or products (i.e., networking Van Hooft et al. 7 behavior, résumés, application letters, interview behavior) that meet/exceed the expectations of the demanding parties at the labor market. Operationalization and measurement of job search quality according to this perspective by definition involves (to some extent subjective) ratings of for example recruiters, hiring managers, or employment counselors on the extent to which the job seeker's products (e.g., résumé, application letter) or behaviors (e.g., networking, interview behavior) meet/ exceed their expectations. The internal perspective, in contrast, focuses on job search quality as a job search process that conforms to certain standards and specifications. The conceptualization of quality as composed of process quality and product quality can be further substantiated using the total quality management (TQM) literature. The core idea of TQM is hat high-quality products are impossible without implementing high-quality processes Similarly to TQM, we argue that highquality job search products and behaviors are more likely when the job search process is of high quality, and that a high-quality job search process is characterized by cycles of planning and analysis of the performed activities, enabling continuous improvement and learning. That is, job search is a difficult and complex process, involving a wide array of available methods and channels to use, and multiple behaviors that job seekers are often relatively unfamiliar with. Oftentimes, it is unclear exactly which methods and behaviors are effective and which are not. With conscious and careful attention to planning, analysis of performed job search activities, and adjustment and improvement of one's job search behavior based on such analysis and feedback from the environment, it is more likely that job seekers can learn and enhance their performance in order to improve fit with the labor market demands and meet the recruiting organizations' expectations. Therefore, it is important to further explicate what a high-quality process exactly entails. Given the multiphased nature of the job search process, we pose that job search process quality cannot be conceptualized as a single one-dimensional construct, but is multidimensional in nature, encapsulating all phases of the job search process. The next sections focus on elaborating job search process quality, using self-regulation theory. Job search quality as a self-regulated process Self-regulation refers to ''those processes, internal and/or transactional, that enable an individual to guide his/her goal-directed activities over time and across changing circumstances (contexts)'' (Karoly, 1993, p. 25). Similarly, Zimmerman (2000, p. 14) defines self-regulation as processes of ''self-generated thoughts, feelings, and actions that are planned and cyclically adapted to the attainment of personal goals.'' Self-regulation involves selfcontrol of attention, thoughts, affect, and behavior deliberately or automatically Self-regulation is especially needed in the attainment of distal goals that involve lengthy processes, composed of tasks low on intrinsic (activity-related) motivation and high on extrinsic (outcome-related) motivation Organizational Psychology Review 3(1) needed as those tasks are inherently pleasurable, interesting, and fun. However, for tasks that are difficult, boring, unpleasant, or otherwise aversive (i.e., low intrinsic motivation), but important to attain some valued goal (i.e., high extrinsic motivation), people need selfregulation (e.g., regulation of effort, reminding oneself of the valued outcome, maintenance actions directed at increasing interest) to ensure task persistence and performance. For most individuals, job search is characterized by this combination of low intrinsic and relatively high extrinsic motivation. That is, job search activities are rarely considered to be fun, enjoyable, and entertaining. Rather, the job search process is mostly experienced as difficult and full of negative emotions The cognitive forethought phases are succeeded by a behavioral phase of goal striving, directional maintenance, and volitional control during which self-regulation is needed to initiate and maintain the planned activities. Lastly, we propose that a high-quality job search process requires reflection and revision. That is, without thorough analysis and evaluation of one's job search behavior in the context of the established goals and based on the feedback from the environment, an upward cycle of learning and performance enhancement (which is an essential part of quality; cf. TQM, a process Summary and formal definitions of job search quality In summary, we argued that in conceptualizing job search quality one must distinguish between the quality of job search behaviors/products and the quality of the job search process. We further argued that higher quality behaviors/products are more likely the higher the process quality. Based on an organization-oriented, external perspective towards quality, we defined job search product quality as the extent to which a job seeker's job search behaviors/products meet/exceed the expectations of the demanding parties at the labor market. Furthermore, using a job seeker-oriented, internal perspective towards quality, job search process quality was conceptualized as the extent to which the process conforms to certain standards and specifications. Based on TQM, which focuses on quality cycles, we theorized that those process quality standards and specifications refer to conforming to the ordered sequence of four self-regulatory job search phases. Thus, synthesizing the job seeker-oriented, internal perspective on quality, the TQM principles, and self-regulation theory, we define job search process quality as the extent to which a job search is self-regulated, that is, the extent to which a job search is conducted by cycling through the four sequential self-regulatory phases of goal establishment, planning of the goal pursuit, goal striving, and reflection

Renormalization of gauge fields using Hopf algebras

We describe the Hopf algebraic structure of Feynman graphs for non-abelian gauge theories, and prove compatibility of the so-called Slavnov-Taylor identities with the coproduct. When these identities are taken into account, the coproduct closes on the Green's functions, which thus generate a Hopf subalgebra.Comment: 16 pages, 1 figure; uses feynmp. To appear in "Recent Developments in Quantum Field Theory". Eds. B. Fauser, J. Tolksdorf and E. Zeidler. Birkhauser Verlag, Basel 200