Temporal Spacing Research Articles

Substantive and operational issues of response bias across levels of analysis: an example of climate-satisfaction relationships.

Two studies tested whether method variance is present at multiple levels of analysis and whether methodological procedures can minimize its impact. In Study 1, 8,052 employees from 71 hotels completed measures of climate, work environment characteristics, and satisfaction. A comparison of correlations at the individual level, cross-level, cross-level split, aggregate level, and aggregate-split level of analysis revealed that response bias was present across multiple levels. Results suggest that samples should be split in half when cross-level and aggregate correlations are computed to ameliorate response bias problems that arise from individual-level method variance. In Study 2, results indicated that the temporal spacing of measures of climate and satisfaction influenced response bias. Implications and recommendations for future research are discussed.

Global versus domain-specific statuses in identity research: a comparison of two self-report measures

The present study explored the potential usefulness of global identity statuses (ideological identity) as opposed to domain-specific statuses (occupation, religion, politics) using self-report measures rather than identity interviews. A total of 339 college students from two colleges in Belgium (Europe) completed both the Extended Objective Measure of Ego-Identity Status (EOM-EIS) and the Dellas Identity Status Inventory — Occupation, Religious Beliefs, Political Ideology (DISI-ORP). Four types of evidence argued in favour of domain-specific statuses (i.e. low convergence in identity status across domains, moderate convergence between global and domain-specific identity statuses, significant gender differences in domain-specific but not in global identity statuses, and significant associations between identity process and identity content in congruent but not in incongruent domains). In line with earlier research using identity status interviews, it was concluded that adolescent identity is not to be considered a unitary construct and the use of domain-specific identity statuses is recommended whenever possible. Theoretical implications of the findings are discussed in terms of adolescents' temporal spacing of identity concerns. Finally, the limitations of identity questionnaires (additive approach to global identity statuses) are pointed out. Identity interviews (indicative approach to global statuses) can yield a very different picture of identity.

Numerical study ofO(a)improved Wilson quark action on an anisotropic lattice

The $O(a)$ improved Wilson quark action on the anisotropic lattice is investigated. We carry out numerical simulations in the quenched approximation at three values of lattice spacing ($a_{\sigma}^{-1}=1$--2 GeV) with the anisotropy $\xi=a_{\sigma}/a_{\tau}=4$, where $a_{\sigma}$ and $a_{\tau}$ are the spatial and the temporal lattice spacings, respectively. The bare anisotropy $\gamma_F$ in the quark field action is numerically tuned by the dispersion relation of mesons so that the renormalized fermionic anisotropy coincides with that of gauge field. This calibration of bare anisotropy is performed to the level of 1 % statistical accuracy in the quark mass region below the charm quark mass. The systematic uncertainty in the calibration is estimated by comparing the results from different types of dispersion relations, which results in 3 % on our coarsest lattice and tends to vanish in the continuum limit. In the chiral limit, there is an additional systematic uncertainty of 1 % from the chiral extrapolation. Taking the central value $\gamma_F=\gamma_F^*$ from the result of the calibration, we compute the light hadron spectrum. Our hadron spectrum is consistent with the result by UKQCD Collaboration on the isotropic lattice. We also study the response of the hadron spectrum to the change of anisotropic parameter, $\gamma_F \to \gamma_F^* + \delta\gamma_F$. We find that the change of $\gamma_F$ by 2 % induces a change of 1 % in the spectrum for physical quark masses. Thus the systematic uncertainty on the anisotropic lattice, as well as the statistical one, is under control.

O(a)-improved quark action on anisotropic lattices and perturbative renormalization of heavy-light currents

We investigate the Symanzik improvement of the Wilson quark action on anisotropic lattices. Taking first a general action with nearest-neighbor and clover interactions, we study the mass dependence of the ratio of the hopping parameters, the clover coefficients, and an improvement coefficient for heavy-light vector and axial vector currents. We show how tree-level improvement can be achieved. For a particular choice of the spatial Wilson coupling, the results simplify, and $O(m_0a_\tau)$ improvement is possible. (Here $m_0$ is the bare quark mass and $a_\tau$ the temporal lattice spacing.) With this choice we calculate the renormalization factors of heavy-light bilinear operators at one-loop order of perturbation theory employing the standard plaquette gauge action.

Combinative aspects of leadership style: The ordering and temporal spacing of leadership behaviors

This article introduces the concept of combinative aspects of leadership style, which addresses elements of leadership style such as the ordering and temporal spacing of leadership behaviors. The major purpose is to show that perceptions of leadership are influenced by the manner in which leadership behaviors are combined. Different combinations of task-oriented leadership statements and socioemotionally oriented leadership statements were examined. All of the participants were full-time employees. In all three of the studies, combinative aspects of leadership style clearly influenced perceptions of leadership statements. The findings indicate that task-oriented leadership should not be provided without socioemotional leadership and that socioemotionally oriented leadership should generally be provided immediately before task-oriented leadership. Further work is needed to investigate the applicability of combinative aspects of leadership style to components of transactional and transformational leadership.

Heavy quarks on anisotropic lattices: The charmonium spectrum

We present results for the mass spectrum of $c{\bar c}$ mesons simulated on anisotropic lattices where the temporal spacing $a_t$ is only half of the spatial spacing $a_s$. The lattice QCD action is the Wilson gauge action plus the clover-improved Wilson fermion action. The two clover coefficients on an anisotropic lattice are estimated using mean links in Landau gauge. The bare velocity of light $\nu_t$ has been tuned to keep the anisotropic, heavy-quark Wilson action relativistic. Local meson operators and three box sources are used in obtaining clear statistics for the lowest lying and first excited charmonium states of $^1S_0$, $^3S_1$, $^1P_1$, $^3P_0$ and $^3P_1$. The continuum limit is discussed by extrapolating from quenched simulations at four lattice spacings in the range 0.1 - 0.3 fm. Results are compared with the observed values in nature and other lattice approaches. Finite volume effects and dispersion relations are checked.

Spatial Organization of Bobcats (Lynx rufus) in Southern Illinois

Abstract Many aspects of spatial organization in solitary carnivores remain unknown due to prohibitively low sample sizes and reliance on only annual home range and overlap data. We estimated size, overlap and fidelity of annual and seasonal home ranges and core areas of 52 (22 male, 30 female) adult bobcats (Lynx rufus) in southern Illinois during 1995–1999 and quantified temporal spacing. We report an unusual pattern of spatial organization for bobcats such that, although male and female annual home-range sizes were similar to other regional populations, we found relatively high levels of intrasexual home-range overlap for males and females. Although intrasexual home-range overlap was extensive, core areas were nearly exclusive, implying that core areas confer benefits to bobcats by reducing competition for resources and may represent areas of more aggressive territoriality within the home range. Only 4 of 52 (8%) bobcats shifted annual home ranges, indicating stable spatial organization in the absence ...

Massed and spaced learning in honeybees: the role of CS, US, the intertrial interval, and the test interval.

Conditioning the proboscis extension reflex of harnessed honeybees (Apis mellifera) is used to study the effect temporal spacing between successive conditioning trials has on memory. Retention is monitored at two long-term intervals corresponding to early (1 and 2 d after conditioning) and late long-term memory (3 and 4 d). The acquisition level is varied by using different conditioned stimuli (odors, mechanical stimulation, and temperature increase at the antenna), varying strengths of the unconditioned stimulus (sucrose), and various numbers of conditioning trials. How learning trials are spaced is the dominant factor both for acquisition and retention, and although longer intertrial intervals lead to better acquisition and higher retention, the level of acquisition per se does not determine the spacing effect on retention. Rather, spaced conditioning leads to higher memory consolidation both during acquisition and later, between the early and long-term memory phases. These consolidation processes can be selectively inhibited by blocking protein synthesis during acquisition.

Observations of nonlinear internal waves on the outer New England continental shelf during the summer Shelfbreak Primer study

Observations are presented of nonlinear internal waves on the outer New England continental shelf during the summer Shelfbreak Primer study conducted between July 26 and August 5, 1996. Current and temperature measurements were made with an upward looking acoustic Doppler current profiler (ADCP) located on the 147 m isobath near the shelfbreak and three vertical thermistor moorings located upshelf. Data from the ADCP and two nearby thermistor chains show energetic internal tides propagating at roughly 0.9 m s−1 to the north‐northwest, nearly perpendicular to the local topography with 10–15 cm s−1 horizontal currents and 15–30 m vertical displacements. These waves evolve rapidly within a 5.8 km range into an undular internal tidal bore. Cross‐isobath barotropic tidal currents, responsible for generating the internal tides are in the 5–12 cm s−1 range. The bore formation is highly variable. There is evidence of a correlation between internal tide steepening and a shelfbreak front jet orientation that is oppositely directed to the internal tide propagation. There is no correlation between steepening and the jet's vertical shear. Statistics of the undular bores show rms travel time fluctuations from 0.8 to 1.7 hours and average tidal bore durations from 12 to 9 hours. The average undular bore speed is 0.9 m s−1, with an rms fluctuation of 0.4 m s−1. The number of high‐frequency waves in the bore varies from 0 to 8 near the shelfbreak and increases to 30 waves 26.7 km upshelf. The observed distribution function of temporal spacing between high‐frequency internal waves is spread between 4 and 20 min.

Classification of signal-time curves from dynamic MR mammography by neural networks

The aim of this study was to test the performance of artificial neural networks for the classification of signal-time curves obtained from breast masses by dynamic MRI. Signal-time courses from 105 parenchyma, 162 malignant, and 102 benign tissue regions were examined. The latter two groups were histopathologically verified. Four neural networks corresponding to different temporal resolutions of the signal-time curves were tested. The resolution ranges from 28 measurements with a temporal spacing of 23s to just 3 measurements taken 1.8, 3, and 10 minutes after contrast medium administration. Discrimination between malignant and benign lesions is best if 28 measurement points are used (sensitivity: 84%, specificity: 81%). The use of three measurement points results in 78% sensitivity and 76% specificity. These results correspond to values obtained by human experts who visually evaluated signal-time curves without considering additional morphologic information. All examined networks yielded poor results for the subclassification of the benign lesions into fibroadenomas and benign proliferative changes. Neural networks can computationally fast distinguish between malignant and benign lesions even when only a few post-contrast measurements are made. More precise specification of the type of the benign lesion will require incorporation of additional morphological or pharmacokinetic information.

Performance of the microwave reflectometry diagnostic for density profile measurements on ASDEX Upgrade

The broadband reflectometry system on ASDEX Upgrade is now routinely providing electron density profiles with a minimum temporal spacing of 30 μs. The plasma is probed from zero density to ne=6.64×1019 m−3 at the low field side with combined O and X modes, and from ne=0.318×1019 to ne=6.64×1019 m−3 at the high field side using O mode. Here we analyze the performance of the diagnostic for profile measurements taking into account its design options and the experimental results obtained in a wide range of plasma regimes. We address several questions, in particular the measuring range of the antennas and the range of density gradients. It is shown that it is possible to obtain a detailed evolution of the density profile and density gradient even in the presence of turbulence, providing that sufficient data can be extracted from the plasma. The radial movements of the plasma can be measured with great accuracy, which is especially important for the use of reflectometry for plasma position control, as is proposed for the International Thermonuclear Experimental Reactor. The experimental results demonstrate that the frequency modulation of a continuous wave reflectometry system on ASDEX Upgrade can provide reliable and accurate density profile measurements at both sides of the plasma with automatic analysis.

Genetic and pharmacological demonstration of differential recruitment of cAMP-dependent protein kinases by synaptic activity.

cAMP-dependent protein kinase (PKA) is believed to play a critical role in the expression of long-lasting forms of hippocampal long-term potentiation (LTP). Can distinct patterns of synaptic activity induce forms of LTP that require different isoforms of PKA? To address this question, we used transgenic mice that have genetically reduced hippocampal PKA activity, and a specific pharmacological inhibitor of PKA, Rp-cAMPS. Transgenic mice [R(AB) mice] that express an inhibitory form of a particular type of regulatory subunit of PKA (type-Ialpha) showed significantly reduced LTP in area CA1 of hippocampal slices as compared with slices from wild-type mice. This impairment of LTP expression was evident when LTP was induced by applying repeated, temporally spaced stimulation (4 1-s bursts of 100-Hz applied once every 5 min). In contrast, LTP induced by applying just 60 pulses in a theta-burst pattern was normal in slices from R(AB) mice as compared with slices from wild-type mice. We found that Rp-cAMPS blocked the expression of LTP induced by both spaced tetra-burst and compressed theta-burst stimulation in hippocampal slices of wild-type and R(AB) mice, respectively. Since Rp-cAMPS is a PKA inhibitor that is not selective for any particular isoform of PKA and these R(AB) mice show reduced hippocampal PKA activity resulting from genetic manipulation of a single isoform of PKA regulatory subunit, our data support the idea that distinct patterns of synaptic activity can produce different forms of LTP that significantly engage different isoforms of PKA. In particular, theta-burst LTP significantly recruits isoforms of PKA containing regulatory subunits other than the mutant RIalpha subunit, whereas tetra-burst LTP requires PKA isoforms containing the mutant RIalpha subunit. Thus, altering both the total amount of imposed synaptic activity and the temporal spacing between bursts of imposed activity may subtly modulate the PKA dependence of hippocampal LTP by engaging distinct isoforms of PKA. In a broader context, our findings suggest that synaptic plasticity in the mammalian brain might be importantly regulated by activity-dependent recruitment of different isoforms of key signal transduction molecules.

Measuring postglacial rebound with GPS and absolute gravity

We compare vertical rates of deformation derived from continuous Global Positioning System (GPS) observations and episodic measurements of absolute gravity. We concentrate on 4 sites in a region of North America experiencing postglacial rebound. The rates of uplift from gravity and GPS agree within one standard deviation for all sites. The GPS vertical deformation rates are significantly more precise than the gravity rates, primarily because of the denser temporal spacing provided by continuous GPS tracking. We conclude that continuous GPS observations are more cost efficient and provide more precise estimates of vertical deformation rates than campaign style gravity observations where systematic errors are difficult to quantify.

Firing Rate of Nucleus Accumbens Neurons Is Dopamine-Dependent and Reflects the Timing of Cocaine-Seeking Behavior in Rats on a Progressive Ratio Schedule of Reinforcement

The progressive ratio (PR) schedule of reinforcement is used to determine the reinforcing properties of rewards such as drugs of abuse. In this schedule, the animal is required to press a lever a progressively increasing number of times to receive a reward; the highest ratio obtained before the animal ceases responding is termed "breakpoint." We recorded neuronal spike activity from cells in the nucleus accumbens (NAc) of rats responding on a PR schedule for cocaine reinforcement. A common subtype of NAc cells demonstrated firing rates that varied according to the time between cocaine deliveries. The firing rate was inversely related to the NAc cocaine level predicted by a pharmacokinetic model. At higher response-to-reward ratios, inter-reward intervals were increased, resulting in a decrease in modeled cocaine level and a concomitant increase in firing rate over the session. The final increase in firing rate above a threshold value suggests a neural correlate of breakpoint. The effects of preadministration of dopamine D1 or D2 antagonists on the animals' behavior were similar in that both reduced breakpoint; however, each antagonist had markedly different effects on NAc cell firing. The D1 antagonist SCH23390 reduced firing rates, even at low cocaine levels, whereas the D2 antagonist eticlopride induced a rightward shift in the dose dependence of NAc cell firing relative to modeled cocaine level. Our results suggest that the firing of NAc cells reflects changes in cocaine levels and thereby contributes to the temporal spacing of self-administration and to the cessation of responding at breakpoint.

One-loop self-energy and renormalization of the speed of light for some anisotropic improved quark actions

One-loop corrections to the fermion rest mass M_1, wave function renormalization Z_2 and speed of light renormalization C_0 are presented for lattice actions that combine improved glue with clover or D234 quark actions and keep the temporal and spatial lattice spacings, a_t and a_s, distinct. We explore a range of values for the anisotropy parameter \chi = a_s/a_t and treat both massive and massless fermions.

Non-Gaussian randomness outside and inside the bat’s brain

Reflector placement in the habitats of bats is pronouncedly random. Furthermore, the impulsive nature of reflection sequences generated by facets found, e.g., in foliage can endow the probability density function of the received echo amplitudes with heavy tails. Two useful features for classification of foliages, which may be utilized by bats as ubiquitous landmarks, are the extent to which the amplitude distribution deviates from Gaussian (its ‘‘peakiness’’) and an eventual nonstationary gain of the propagation channel. The signal processing in the bat’s auditory system does not have direct access to the target’s reflection sequence, however. Even the shortest echolocation pulses seen in bats are chirps with durations, which are nonnegligible compared to the duration of the reflection sequence and the temporal spacing of salient peaks inside of it. On reception, echoes are subjected to bandpass filtering and demodulation. The latter step prohibits recovery of the reflection sequence by means of pulse compression using a matched filter. Consequently, it is investigated how the demodulated filter bank output may be used directly as a substrate for target classification. Specifically, the possible role of encoding the waveforms in sparse spike trains and comparing binaural information is evaluated.

Non-perturbative improvement of the anisotropic Wilson QCD action

We describe the first steps in the extension of the Symanzik O( a) improvement program for Wilson-type quark actions to anisotropic lattices, with a temporal lattice spacing smaller than the spatial one. This provides a fully relativistic and computationally efficient framework for the study of heavy quarks. We illustrate our method with accurate results for the quenched charmonium spectrum.

EEG evidence of stimulus-directed response dynamics in human somatosensory cortex

Dense multichannel recordings of scalp electroencephalogram (EEG) were obtained in the vicinity of primary somatosensory cortex, time-locked to repetitive vibrotactile stimulation of sites on the right index finger of a single human subject. Frequency-domain analysis of cross-trial averages revealed prominent `driving' responses in the EEG at the frequency of stimulation, which under specific stimulus conditions displayed pronounced changes in amplitude and topographic organization over brief (4 s) durations of stimulus exposure. The changes were systematic and physiologically coherent, evolving toward driving-response topographies observed in the same subject in conjunction with periodic microstimulation of single mechanoreceptive afferents whose receptive fields occupied corresponding positions on the digit. This dynamic process was orderly and reproducible, and could be controlled by manipulating factors such as the amplitude, frequency, and temporal spacing of the stimuli. The results are tentatively interpreted in light of a previously proposed neurophysiological model of stimulus-driven response plasticity in mammalian somatosensory cortex.

The anisotropic Wilson gauge action

Anisotropic lattices, with a temporal lattice spacing smaller than the spatial one, allow precision Monte Carlo calculations of problems that are difficult to study otherwise: heavy quarks, glueballs, hybrids, and high temperature thermodynamics, for example. We here perform the first step required for such studies with the (quenched) Wilson gauge action, namely, the determination of the renormalized anisotropy Ξ as a function of the bare anisotropy Ξ 0 and the coupling. By, essentially, comparing the finite-volume heavy quark potential where the quarks are separated along a spatial direction with that where they are separated along the time direction, we determine the relation between Ξ and Ξ 0 to a fraction of 1% for weak and to 1% for strong coupling. We present a simple parameterization of this relation for 1 ⩽ Ξ ⩽ 6 and 5.5 ⩽ β ⩽ ∞, which incorporates the known one-loop result and reproduces our non-perturbative determinations within errors. Besides solving the problem of how to choose the bare anisotropies if one wants to take the continuum limit at fixed renormalized anisotropy, this parameterization also yields accurate estimates of the derivative ∂Ξ 0 ∂Ξ needed in thermodynamic studies.

Propagation factor errors due to the assumption of lateral homogeneity

Propagation conditions are frequently assessed by making a single measurement of the vertical refractivity and injecting this profile into a propagation model from which the two‐dimensional propagation factor field is calculated. Such an assessment tacitly assumes lateral homogeneity of the refractivity environment. That is, the refractive index is assumed to vary only as a function of height above the Earth's surface. Hitherto, the authors, using only case studies, have determined errors in propagation assessment employing the above assumptions. The objective of this paper is to characterize the errors in the propagation factor field using a statistical database of multiple arrays of refractivity profiles covering many days. In this effort, errors in the propagation factor field at 1, 3, and 10 GHz are derived for the case in which single refractive index profile measurements are used to calculate the two‐dimensional propagation factor field. This “error” field is subsequently compared with the “benchmark” or “truth” propagation factor field calculated using an array of refractivity profiles. The errors are statistically deduced by combining measurements from 30 days over defined two‐dimensional areas. The methodology for which the above type of propagation assessment is addressed may also be used to establish temporal and lateral spacing requirements employing similar statistical databases.