Fingerprinting dark energy

Dark energy perturbations are normally either neglected or else included in a purely numerical way, obscuring their dependence on underlying parameters like the equation of state or the sound speed. However, while many different explanations for the dark energy can have the same equation of state, they usually differ in their perturbations so that these provide a fingerprint for distinguishing between different models with the same equation of state. In this paper we derive simple yet accurate approximations that are able to characterize a specific class of models (encompassing most scalar-field models) which is often generically called "dark energy". We then use the approximate solutions to look at the impact of the dark energy perturbations on the dark matter power spectrum and on the integrated Sachs-Wolfe effect in the cosmic microwave background radiation.Comment: 11 pages, 5 figures, minor changes to match published versio

On the detectability of non-trivial topologies

We explore the main physical processes which potentially affect the topological signal in the Cosmic Microwave Background (CMB) for a range of toroidal universes. We consider specifically reionisation, the integrated Sachs-Wolfe (ISW) effect, the size of the causal horizon, topological defects and primordial gravitational waves. We use three estimators: the information content, the S/N statistic and the Bayesian evidence. While reionisation has nearly no effect on the estimators, we show that taking into account the ISW strongly decreases our ability to detect the topological signal. We also study the impact of varying the relevant cosmological parameters within the 2 sigma ranges allowed by present data. We find that only Omega_Lambda, which influences both ISW and the size of the causal horizon, significantly alters the detection for all three estimators considered here.Comment: 11 pages, 9 figure

Consideraciones críticas de las posibilidades de empleo y rendimiento del intercambiador de calor por suspensión en gases

El intercambiador de calor por suspensión en gases, de cuatro etapas, está destinado a someter el crudo de cemento a un tratamiento primario antes de su entrada al horno rotatorio. Se ofrece ya sólo en Europa por lo menos por cuatro fabricantes de renombre. La primera planta de este tipo operada a escala industrial se instaló en la República Federal Alemana en el año 1950

Intra- and extra-axonal axial diffusivities in the white matter: which one is faster?

A two-compartment model of diffusion in white matter, which accounts for intra- and extra-axonal spaces, is associated with two plausible mathematical scenarios: either the intra-axonal axial diffusivity is higher than the extra-axonal (Branch 1), or the opposite (Branch 2). This duality calls for an independent validation of compartment axial diffusivities, to determine which of the two cases holds. The aim of the present study was to use an intracerebroventricular injection of a gadolinium-based contrast agent to selectively reduce the extracellular water signal in the rat brain, and compare diffusion metrics in the genu of the corpus callosum before and after gadolinium infusion. The diffusion metrics considered were diffusion and kurtosis tensor metrics, as well as compartment-specific estimates of the WMTI-Watson two-compartment model. A strong decrease in genu T1 and T2 relaxation times post-Gd was observed (p < 0.001), as well as an increase of 48% in radial kurtosis (p < 0.05), which implies that the relative fraction of extracellular water signal was selectively decreased. This was further supported by a significant increase in intra-axonal water fraction as estimated from the two-compartment model, for both branches (p < 0.01 for Branch 1, p < 0.05 for Branch 2). However, pre-Gd estimates of axon dispersion in Branch 1 agreed better with literature than those of Branch 2. Furthermore, comparison of post-Gd changes in diffusivity and dispersion between data and simulations further supported Branch 1 as the biologically plausible solution, i.e. the intra-axonal axial diffusivity is higher than the extra-axonal one. This result is fully consistent with other recent measurements of compartment axial diffusivities that used entirely different approaches, such as diffusion tensor encoding

Examining the Impact of Gender, Caretaking on Faculty Research Productivity, Tenure and Promotion Progress During the COVID-19 Pandemic

The COVID-19 pandemic has profoundly impacted the working and home lives of faculty. The largest impact was felt by women and caregivers, who suffered a staggering setback to their research productivity throughout the pandemic, and declines in research productivity have negative downstream consequences for tenure and promotion. The current research sought to examine gender and caregiving differences in research productivity throughout the COVID-19 pandemic among University of Dayton faculty. In two primary studies, research-active faculty were surveyed (Study 1) and interviewed (Study 2) to better understand the impact of gender and caregiving on research productivity during the pandemic. Study 1 also examined research productivity before the pandemic (2019) through the end of 2022 in order to examine change in productivity over time. Due to a small sample of data collected for Study 1, we were unable to examine differences in gender and caregiving, but we did find that multiple indicators of research productivity, ability to conduct research, difficulty with conducting research, and job satisfaction declined during the early pandemic but trended toward 2019 levels by 2022; although the quadratic pattern of the data suggests that these outcomes are beginning to improve over time, the majority of these outcomes have not reached their pre-pandemic values. Study 1 also examined correlations between job stress, burnout, workload, and multiple barriers to being research productive during the pandemic. Study 2 interviewed 19 faculty members and found that the predominantly female sample of faculty felt a lack of separation between their home life and work life during the pandemic, which was particularly pronounced for caregivers. They also reported declines in well-being and health, needing to put a hold on research due to caregiving, and finding it challenging to reset and restart their research. A consistent finding from both studies was that many faculty reported feeling undervalued and unappreciated by the university administration, and reported a lack of trust in the university. We conclude our report with a set of data-driven, equity-focused recommendations to improve faculty research productivity that focus on directing support to faculty research, teaching, and family. We also include additional recommendations that seek to address feelings of being underappreciated and undervalued, and increasing faculty job satisfaction

Conserved Endonuclease Function of Hantavirus L Polymerase.

Hantaviruses are important emerging pathogens belonging to the Bunyaviridae family. Like other segmented negative strand RNA viruses, the RNA-dependent RNA polymerase (RdRp) also known as L protein of hantaviruses lacks an intrinsic "capping activity". Hantaviruses therefore employ a "cap snatching" strategy acquiring short 5' RNA sequences bearing 5'cap structures by endonucleolytic cleavage from host cell transcripts. The viral endonuclease activity implicated in cap snatching of hantaviruses has been mapped to the N-terminal domain of the L protein. Using a combination of molecular modeling and structure-function analysis we confirm and extend these findings providing evidence for high conservation of the L endonuclease between Old and New World hantaviruses. Recombinant hantavirus L endonuclease showed catalytic activity and a defined cation preference shared by other viral endonucleases. Based on the previously reported remarkably high activity of hantavirus L endonuclease, we established a cell-based assay for the hantavirus endonuclase function. The robustness of the assay and its high-throughput compatible format makes it suitable for small molecule drug screens to identify novel inhibitors of hantavirus endonuclease. Based on the high degree of similarity to RdRp endonucleases, some candidate inhibitors may be broadly active against hantaviruses and other emerging human pathogenic Bunyaviruses

Evaluation of available bandwidth as a routing metric for delay-sensitive IEEE 802.15.4-based ad-hoc networks

In this paper, we evaluate available bandwidth as a routing metric for IEEE 802.15.4-based ad-hoc networks. The available bandwidth on a data forwarding path is an approximation of the forwarding path’s residual data relaying capacity. High available bandwidth on a data forwarding path implies low data traffic load on the path, therefore data flows may experience low delay and high packet delivery ratio (PDR). Our aim is to evaluate available bandwidth as a routing metric. We present different available-bandwidth-based routing protocols for IEEE 802.15.40-based networks, namely: end-to-end available-bandwidth-based routing protocol (ABR), available bandwidth and contention-aware routing protocol (ABCR), and shortest hop-count and available-bandwidth-based opportunistic routing protocol (ABOR). Moreover, we also present variants of ABR and ABCR capable of distributing a flow’s data packets on multiple paths by maintaining the top K downstream nodes (the downstream nodes that advertised best data forwarding paths towards a sink node) corresponding to each sink node in a routing table. We focus on both single-sink and multi-sink networks. We performed extensive simulations, and the simulation results demonstrate that the available bandwidth routing metric shows better results when combined with a routing metric that helps to limit a data forwarding path’s length, i.e., shortest hop-count or intra-flow contention count. For multi-path data forwarding towards the same sink node, and at high traffic volumes, the available bandwidth metric demonstrates best performance when combined with the shortest hop-count routing metric

RPL-based routing protocols for multi-sink wireless sensor networks

Recent studies demonstrate that the performance of a wireless sensor network (WSN) can be improved by deploying multiple sinks in the network. Therefore, in this paper we present different routing protocols for multi-sink WSNs based on the routing protocol for low-power and lossy networks (RPL). Our protocols use different routing metrics and objective functions (OFs). We use the available bandwidth, delay, MAC layer queue occupancy, and expected transmission count (ETX) as the tie-breaking metrics in conjunction with the shortest hop-count metric. Our OFs use the tie-breaking metrics on a greedy or end-to-end basis. Our simulation results demonstrate that the protocols based on the delay, buffer occupancy, and ETX metrics demonstrate best performance, increasing the packet delivery ratio by up to 25% and decreasing the number of retransmissions by up to 65%, compared to a version of the RPL protocol that only uses the hop-count metric. Another key insight is that, using the tie-breaking metrics on a greedy basis demonstrates a slight performance improvement compared to using the metrics on an end-to-end basis. Finally, our results also demonstrate that multiple sinks inside a WSN improve the RPL-based protocol performance

Isolation and in-vitro and in-vivo characterisation of a mutant of Pseudomonas aeruginosa PAO1 that exhibited a reduced postantibiotic effect in response to imipenem

The postantibiotic effect (PAE) is the persistent inhibition of bacterial growth after a brief exposure to an antibiotic. Most β-lactams do not induce a PAE for Gram-negative bacteria, but PAEs have been reported for carbapenems and penems. This study investigated the effect of sequential doses of imipenem on the PAE for Pseudomonas aeruginosa and Escherichia coli cultures in a chemostat. The PAE for the bacterial population did not change even after six successive exposures to imipenem. Nevertheless, screening of colonies isolated after repeated drug exposure identified a single P. aeruginosa mutant whose imipenem PAE was shortened, although the MIC was unchanged. The PAEs for the parent and mutant were studied in vitro in batch culture by monitoring: (i) viable counts; (ii) electrical impedance of the culture medium; (iii) incorporation of radiolabelled N-acetyl-D-glucosamine and (iv) cell volume changes. PAEs for the parent and mutant were found to be significantly different by all in-vitro methods used. Moreover, the median cell volume in antibiotic-exposed cultures remained much smaller and less heterogeneous than in the control cultures, even though both cultures were growing at the same rate. The mutant was found to have a reduced expression of a 52 kDa outer membrane protein. These observations suggest that factors in addition to suppression of bacterial growth should be considered when studying the PAE. The PAEs of imipenem for the parent and mutant were studied in a thigh infection model in leucopenic mice. Similar PAEs were observed in vivo for both parent and mutant in one experiment and no PAEs for either organism were found in a second experiment. This study showed that although the PAE is a stable in-vitro phenomenon, the lack of correlation between the in-vitro and in-vivo results warrants caution in attributing clinical significance to the PAE of imipene