Heterogeneity assumptions in the specification of bargaining models: a study of household level trade-offs between commuting time and salary

With many real world decisions being made in conjunction with other decision makers, or single agent decisions having an influence on other members of the decision maker's immediate entourage, there is strong interest in studying the relative weight assigned to different agents in such contexts. In the present paper, we focus on the case of one member of a two person household being asked to make choices affecting the travel time and salary of both members. We highlight the presence of significant heterogeneity across individuals not just in their underlying sensitivities, but also in the relative weight they assign to their partner, and show how this weight varies across attributes. This is in contrast to existing work which uses weights assigned to individual agents at the level of the overall utility rather than for individual attributes. We also show clear evidence of a risk of confounding between heterogeneity in marginal sensitivities and heterogeneity in the weights assigned to each member. We show how this can lead to misleading model results, and argue that this may also explain past results showing bargaining or weight parameters outside the usual [0,1] range in more traditional joint decision making contexts. In terms of substantive results, we find that male respondents place more weight on their partner's travel time, while female respondents place more weight on their partner's salary.

Model selection for prognostic time-to-event gene signature discovery with applications in early breast cancer data

Model selection between competing models is a key consideration in the discovery of prognostic multigene signatures. The use of appropriate statistical performance measures as well as verification of biological significance of the signatures is imperative to maximise the chance of external validation of the generated signatures. Current approaches in time-to-event studies often use only a single measure of performance in model selection, such as logrank test p-values, or dichotomise the follow-up times at some phase of the study to facilitate signature discovery. In this study we improve the prognostic signature discovery process through the application of the multivariate partial Cox model combined with the concordance index, hazard ratio of predictions, independence from available clinical covariates and biological enrichment as measures of signature performance. The proposed framework was applied to discover prognostic multigene signatures from early breast cancer data. The partial Cox model combined with the multiple performance measures were used in both guiding the selection of the optimal panel of prognostic genes and prediction of risk within cross validation without dichotomising the follow-up times at any stage. The signatures were successfully externally cross validated in independent breast cancer datasets, yielding a hazard ratio of 2.55 [1.44, 4.51] for the top ranking signature.

Updating Credal Networks is Approximable in Polynomial Time

Credal networks relax the precise probability requirement of Bayesian networks, enabling a richer representation of uncertainty in the form of closed convex sets of probability measures. The increase in expressiveness comes at the expense of higher computational costs. In this paper, we present a new variable elimination algorithm for exactly computing posterior inferences in extensively specified credal networks, which is empirically shown to outperform a state-of-the-art algorithm. The algorithm is then turned into a provably good approximation scheme, that is, a procedure that for any input is guaranteed to return a solution not worse than the optimum by a given factor. Remarkably, we show that when the networks have bounded treewidth and bounded number of states per variable the approximation algorithm runs in time polynomial in the input size and in the inverse of the error factor, thus being the first known fully polynomial-time approximation scheme for inference in credal networks.

Multicenter Randomized Controlled Trial of Withdrawal of Inhaled Corticosteroids in Cystic Fibrosis

Rationale: Lung inflammation and injury is critical in cystic fibrosis. An ideal antiinflammatory agent has not been identified but inhaled corticosteroids are widely used despite lack of evidence.

Objectives: To test the safety of withdrawal of inhaled corticosteroids with the hypothesis this would not be associated with an earlier onset of acute chest exacerbations.

Methods: Multicenter randomized double-blind placebo-controlled trial in 18 pediatric and adult UK centers. Eligibility criteria included age > 6.0 yr, FEV1 ? 40% predicted, and corticosteroid use > 3 mo. During the 2-mo run-in period, all patients received fluticasone; they then took either fluticasone or placebo for 6 mo.

Measurements and Main Results: Fluticasone group: n = 84, median age 14.6 yr, mean (SD) FEV1 76% (18); placebo group: n = 87, median age 15.8 yr, mean (SD) FEV1 76% (18). There was no difference in time to first exacerbation (primary outcome) with hazard ratio (95% confidence interval) of 1.07 (0.68 to 1.70) for fluticasone versus placebo. There was no effect of age, atopy, corticosteroid dose, FEV1, or Pseudomonas aeruginosa status. There was no change in lung function or differences in antibiotic or rescue bronchodilator use. Fewer patients in the fluticasone group withdrew from the study due to lung-related adverse events (9 vs. 15%); with a relative risk (95% confidence interval) of 0.59 (0.23–1.48) fluticasone versus placebo.

Conclusions: In this study population (applicable to 40% of patients with cystic fibrosis in the UK), it appears safe to consider stopping inhaled corticosteroids. Potential advantages will be to reduce the drug burden on patients, reduce adverse effects, and make financial savings.

Observational Evidence for Mode Coupling in the Chromospheric Network

Oscillations in network bright points (NBPs) are studied at a variety of chromospheric heights. In particular, the three-dimensional variation of NBP oscillations is studied using image segmentation and cross-correlation analysis between images taken in light of Ca II K3, Ha core, Mg I b2, and Mg I b1-0.4 Å. Wavelet analysis is used to isolate wave packets in time and to search for height-dependent time delays that result from upward- or downward-directed traveling waves. In each NBP studied, we find evidence for kink-mode waves (1.3, 1.9 mHz), traveling up through the chromosphere and coupling with sausage-mode waves (2.6, 3.8 mHz). This provides a means for depositing energy in the upper chromosphere. We also find evidence for other upward- and downward-propagating waves in the 1.3-4.6 mHz range. Some oscillations do not correspond to traveling waves, and we attribute these to waves generated in neighboring regions.

Molecular effects in the ionization of N-2, O-2, and F-2 by intense laser fields

In this paper we study the response in time of N2, O2, and F2 to laser pulses having a wavelength of 390 nm. We find single-ionization suppression in O2 and its absence in F2, in accordance with experimental results at lambda= 800 nm. Within our framework of time-dependent density functional theory we are able to explain deviations from the predictions of intense-field many-body S-matrix theory (IMST). We confirm the connection of ionization suppression with destructive interference of outgoing electron waves from the ionized electron orbital. However, the prediction of ionization suppression, justified within the IMST approach through the symmetry of the highest occupied molecular orbital (HOMO), is not reliable since it turns out that—e.g., in the case of F2—the electronic response to the laser pulse is rather complicated and does not lead to dominant depletion of the HOMO. Therefore, the symmetry of the HOMO is not sufficient to predict ionization suppression. However, at least for F2, the symmetry of the dominantly ionized orbital is consistent with the nonsuppression of ionization.

In vitro activity of tea-tree oil against clinical skin isolates of meticillin-resistant and -sensitive Staphylococcus aureus and coagulase-negative staphylococci growing planktonically and as biofilms

The susceptibility of Staphylococcus aureus [meticillin-resistant (MRSA) and meticillin-sensitive (MSSA)] and coagulase-negative staphylococci (CoNS), which respectively form part of the transient and commensal skin flora, to tea-tree oil (TTO) was compared using broth microdilution and quantitative in vitro time-kill test methods. MRSA and MSSA isolates were significantly less susceptible than CoNS isolates, as measured by both MIC and minimum bactericidal concentration. A significant decrease in the mean viable count of all isolates in comparison with the control was seen at each time interval in time-kill assays. However, the only significant difference in the overall mean log(10) reduction in viable count between the groups of isolates was between CoNS and MSSA at 3 h, with CoNS isolates demonstrating a significantly lower mean reduction. To provide a better simulation of in vivo conditions on the skin, where bacteria are reported to grow as microcolonies encased in glycocalyx, the bactericidal activity of TTO against isolates grown as biofilms was also compared. Biofilms formed by MSSA and MRSA isolates were completely eradicated following exposure to 5 % TTO for 1 h. In contrast, of the biofilms formed by the nine CoNS isolates tested, only five were completely killed, although a reduction in viable count was apparent for the other four isolates. These results suggest that TTO exerts a greater bactericidal activity against biofilm-grown MRSA and MSSA isolates than against some biofilm-grown CoNS isolates.

Changes in muscle recruitment patterns during skill acquisition

The control of movement is predicated upon a system of constraints of musculoskeletal and neural origin. The focus of the present study was upon the manner in which such constraints are adapted or superseded during the acquisition of motor skill. Individuals participated in five experimental sessions, ill which they attempted to produce abduction-adduction movements of the index finger in time with an auditory metronome. During each trial, the metronome frequency was increased in eight steps from an individually determined base frequency. Electromyographic (EMC) activity was recorded from first dorsal interosseous (FDI), first volar interosseous (FVI), flexor digitorum superficialis (FDS), and extensor digitorum communis (EDC) muscles. The movements produced on the final day of acquisition more accurately matched the required profile, and exhibited greater spatial and temporal stability, than those generated during initial performance. Tn the early stages of skill acquisition, an alternating pattern of activation in FDI and FVI was maintained, even at the highest frequencies. Tn contrast, as the frequency of movement was increased, activity in FDS and EDC was either tonic or intermittent. As learning proceeded, alterations in recruitment patterns were expressed primarily in the extrinsic muscles (EDC and FDS). These changes took the form of increases in the postural role of these muscles, shifts to phasic patterns of activation, or selective disengagement of these muscles. These findings suggest that there is considerable flexibility in the composition of muscle synergies, which is exploited by individuals during the acquisition of coordination.

Time-dependent R -matrix theory for ultrafast atomic processes

We describe an ab initio nonperturbative time-dependent R-matrix theory for ultrafast atomic processes. This theory enables investigations of the interaction of few-femtosecond and -attosecond pulse lasers with complex multielectron atoms and atomic ions. A derivation and analysis of the basic equations are given, which propagate the atomic wave function in the presence of the laser field forward in time in the internal and external R-matrix regions. To verify the accuracy of the approach, we investigate two-photon ionization of Ne irradiated by an intense laser pulse and compare current results with those obtained using the R-matrix Floquet method and an alternative time-dependent method. We also verify the capability of the current approach by applying it to the study of two-dimensional momentum distributions of electrons ejected from Ne due to irradiation by a sequence of 2 as light pulses in the presence of a 780 nm laser field.

High tech start-ups in University Science Park incubators: The relationship between the start-up’s lifecycle progression and use of the incubator’s resources

University Science Park incubators (USIs) have emerged as a means by which Government, academia and business can develop high technology business firms (spin out HTBFs) from initial conception through to becoming established small firms, which are ready to move beyond the Science Park confines. Although there is considerable literature on how USIs can be improved and developed there is a paucity of studies, which explore how lifecycle development within HTBFs in USIs can affect how they use the unique resources and opportunities of the USI. Moreover, there is a focus on single point in time studies, which do not adequately investigate the longitudinal dynamics of HTBF lifecycle development within USIs. Therefore, the aim of this paper is to explore the longitudinal use of the unique resources of the USI by HTBFs at different lifecycle stages. The research methodology involved 18 HTBFs within two separate USIs. A series of longitudinal interviews and focus groups were conducted with HTBFs and USI staff over a 36-month period. NUD*IST software was used in developing the coding and analysis of transcripts. The results show that a HTBF's propensity to make effective use of the USI's resources and support increases as the lifecycle stage of the company increases and the small-firm searches for independence and autonomy. Therefore, further research is required to investigate the following two outstanding questions; firstly, which usage pattern is associated with the HTBF's ultimate success or failure in the marketplace? And secondly, are there any services missing from the observed array that the USI could provide to enhance the HTBF's degree of ultimate success? © 2007 Elsevier Ltd. All rights reserved.

Electromagnetic beam profile dynamics in collisional plasmas

The compression of a finite extent Gaussian laser pulse in collisional plasma is investigated. An analytical model is employed to describe the spatiotemporal evolution of a laser pulse propagating through the plasma medium. The pulse geometry is modeled via an appropriate ansatz which takes into account both beam radius (in space) and pulse width (in time). Compression and self-focusing are taken into account via appropriated group velocity dispersion and nonlinearity terms. The competition among the collisional nonlinearity in the plasma and the effect of divergence due to diffraction is pointed out and investigated numerically. Our results suggest that laser pulse compression and intensity localization is enhanced by plasma collisionality. In specific, a pulse width compression by an order of magnitude approximately is observed, for typical collisional laser plasma parameters, along with a significant increase in the intensity.

Iterative Multiuser Detection and Decoding for DS-CDMA System With Space-Time Linear Dispersion

This paper considers a Q-ary orthogonal direct-sequence code-division multiple-access (DS-CDMA) system with high-rate space-time linear dispersion codes (LDCs) in time-varying Rayleigh fading multiple-input-multiple-output (MIMO) channels. We propose a joint multiuser detection, LDC decoding, Q-ary demodulation, and channel-decoding algorithm and apply the turbo processing principle to improve system performance in an iterative fashion. The proposed iterative scheme demonstrates faster convergence and superior performance compared with the V-BLAST-based DS-CDMA system and is shown to approach the single-user performance bound. We also show that the CDMA system is able to exploit the time diversity offered by the LDCS in rapid-fading channels.

4 ◦C and beyond: what did this mean for biodiversity in the past?

How do the predicted climatic changes (IPCC, 2007) for the next century compare in magnitude and rate to those that Earth has previously encountered? Are there comparable intervals of rapid rates of temperature change, sea-level rise and levels of atmospheric CO2 that can be used as analogues to assess possible biotic responses to future change? Or are we stepping into the great unknown? This perspective article focuses on intervals in time in the fossil record when atmospheric CO2 concentrations increased up to 1200 ppmv, temperatures in mid- to high-latitudes increased by greater than 4 ?C within 60 years, and sea levels rose by up to 3 m higher than present. For these intervals in time, case studies of past biotic responses are presented to demonstrate the scale and impact of the magnitude and rate of such climate changes on biodiversity. We argue that although the underlying mechanisms responsible for these past changes in climate were very different (i.e. natural processes rather than anthropogenic), the rates and magnitude of climate change are similar to those predicted for the future and therefore potentially relevant to understanding future biotic response. What emerges from these past records is evidence for rapid community turnover, migrations, development of novel ecosystems and thresholds from one stable ecosystem state to another, but there is very little evidence for broad-scale extinctions due to a warming world. Based on this evidence from the fossil record, we make four recommendations for future climate-change integrated conservation strategies.

Two-dimensional hygrothermal transfer in porous building materials

A two-dimensional mathematical model for evaluating the simultaneous heat and moisture migration in porous building materials was proposed. Vapor content and temperature were chosen as the principal driving potentials. The numerical solution was based on the control volume finite difference technique with fully implicit scheme in time. Two validation experiments were developed in this study. The evolution of transient moisture distributions in both one-dimensional and two-dimensional cases was measured. A comparison between experimental results and those obtained by the numerical model proves that they are fully consistent with each other. The model can be easily integrated into a whole building heat, air and moisture transfer model. Another main advantage of the present numerical method lies in the fact that the required moisture transport properties are comparatively simple and easy to determine.