Effective dynamics of strongly dissipative Rydberg gases

We investigate the evolution of interacting Rydberg gases in the limit of strong noise and dissipation. Starting from a description in terms of a Markovian quantum master equation we derive effective equations of motion that govern the dynamics on a "coarse-grained" timescale where fast dissipative degrees of freedom have been adiabatically eliminated. Specifically, we consider two scenarios which are of relevance for current theoretical and experimental studies --- Rydberg atoms in a two-level (spin) approximation subject to strong dephasing noise as well as Rydberg atoms under so-called electromagnetically induced transparency (EIT) conditions and fast radiative decay. In the former case we find that the effective dynamics is described by classical rate equations up to second order in an appropriate perturbative expansion. This drastically reduces the computational complexity of numerical simulations in comparison to the full quantum master equation. When accounting for the fourth order correction in this expansion, however, we find that the resulting equation breaks the preservation of positivity and thus cannot be interpreted as a proper classical master rate equation. In the EIT system we find that the expansion up to second order retains information not only on the "classical" observables, but also on some quantum coherences. Nevertheless, this perturbative treatment still achieves a non-trivial reduction of complexity with respect to the original problem

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

Simultaneous inversion of active and passive source datasets for 3-D seismic structure with application to Tasmania

Refraction, wide-angle reflection and teleseismic arrival time data are combined in a simultaneous inversion for 3-D lithospheric P-wavespeed and Moho geometry beneath Tasmania, southeast Australia. A new iterative non-linear tomography scheme, which incorporates a novel grid-based method of traveltime prediction, is used to obtain the solution model. Synthetic resolution tests demonstrate that the crucial issue of trade-off between interface depth and layer velocity is satisfactorily resolved. In contrast to previous results from separate inversions of the active and passive source datasets, the new images reveal a zone of elevated wavespeed beneath the Cambrian Mt. Read Volcanics, and indicate that both crustal thinning and elevated wavespeeds occur beneath northeast Tasmania, which supports the case for the existence of a prior passive margin. Otherwise, most major inferences from the previous studies, including evidence for remnant subduction and crustal shortening, are supported by the new results

Cover Page 1) Title of the paper: PERCEPTUAL DFT WATERMARKING WITH IMPROVED DETECTION AND ROBUSTNESS TO GEOMETRICAL DISTORTIONS

title = {Perceptual DFT watermarking with improved detection and robustness to geometrical distortions}, journal = {Accepted for publication in IEEE Transactions o

Root Cause Analysis for Long-Lived TCP Connections

While the applications using the Internet have changed over time, TCP is still the dominating transport protocol that carries over 90% of the total traffic. Throughput is the key performance metric for long TCP connections. The achieved throughput results from the aggregate effects of the network path, the parameters of the TCP end points, and the application on top of TCP. Finding out which of these factors is limiting the throughput of a TCP connection -- referred to as TCP root cause analysis -- is important for end users that want to understand the origins of their problems, ISPs that need to troubleshoot their network, and application designers that need to know how to interpret the performance of the application. In this paper, we revisit TCP root cause analysis by first demonstrating the weaknesses of a previously proposed flight-based approach. We next discuss in detail the different possible limitations and highlight the need to account for the application behavior during the analysis process. The main contribution of this paper is a new approach based on the analysis of time series extracted from packet traces. These time series allow for a quantitative assessment of the different causes with respect to the resulting throughput. We demonstrate the interest of our approach on a large BitTorrent dataset

InTraBase: Integrated Traffic Analysis Based on a Database Management System

Internet traffic analysis as a research area has attracted lots of interest over the last decade. The traffic data collected for analysis are usually stored in plain files and the analysis tools consist of customized scripts each tailored for a specific task. As data are often collected over a longer period of time or from different vantage points, it is important to keep metadata that describe the data collected. The use of separate files to store the data, the metadata, and the analysis scripts provides an abstraction that is much too primitive: The information that "glues" these different files together is not made explicit but is solely in the heads of the people involved in the activity. As a consequence, manipulating the data is very cumbersome, does not scale, and severely limits the way these data can be analyzed

On the interaction between internet applications and tcp

Abstract. We focus in this paper on passive traffic measurement techniques that collect traces of TCP packets and analyze them to derive, for example, round-trip times or aggregate metrics such as average throughput. The seminal work of Zhang [1] has shown that for more than 50% of the TCP connections observed, it is not the network bandwidth that limits the throughput but rather the application or mechanisms such as TCP slow start or too small a receiver window. Certain types of analysis of the network characteristics are meaningful only when performed on TCP traffic that experiences minimal interference by the application. To eliminate such interference, we propose a generic method that partitions the packets of a TCP connection in bulk data transfer and in application limited periods: The packets of a bulk data transfer period (BTP) experience minimal interference from the application, while the packets of an application limited period (ALP) experience interference from the application that prevents TCP from fully utilizing the network resources because the application does not produce data fast enough. As a proof of concept, we apply our algorithm to public Internet traffic traces and show that unless the effects of the application are filtered out, studying the end-to-end path and traffic characteristics from a network point of view can produce biased results.

Preoperative metaphyseal cancellous bone density is associated with intraoperative conversion to stemmed total shoulder arthroplasty

Background: Methods to determine whether a stemless humeral component is appropriate for anatomic total shoulder arthroplasty are varied and often subjective. Objective preoperative data regarding metaphyseal bone quality may help guide surgical decision-making. This study sought to evaluate preoperative proximal humeral bone quality and determine whether it is predictive of intraoperative conversion to a stemmed humeral component. Methods: Consecutive patients who underwent primary anatomic total shoulder arthroplasty from a single-surgeon practice were enrolled. All patients received a preoperative computed tomography (CT) scan for surgical templating purposes. The exclusion criteria were lack of a preoperative CT scan, preoperative plan for a stemmed component, and intraoperative conversion to a stem for a reason other than bone quality (ie, fracture). Preoperative CT scans were analyzed with an automated templating software. Cortical index and thickness were calculated, and bone density of the proximal diaphysis, cancellous metaphysis, and cortical metaphysis was obtained by averaging Hounsfield units (HU) across anatomically defined regions using a previously validated technique. The decision to convert to a stemmed humeral component was made intraoperatively based on a lack of stability of the trial stemless component. Bone quality measurements were compared between stemless and stemmed groups. An exact logistic regression was used incorporating gender and age. Results: A total of 79 patients who underwent primary anatomic total shoulder arthroplasty were included in this study. Of these patients, 6 underwent intraoperative conversion to a stemmed humeral component (7.6%). There was no significant difference between cohorts in terms of cortical index and bone density within the proximal diaphysis and cortical metaphysis. On univariate analysis, cortical thickness, metaphyseal cancellous bone density, and gender were significantly different between groups. Patients receiving a stem had significantly lower metaphyseal cancellous bone density than those receiving stemless components (5.5 ± 11.2 HU vs. 47.6 ± 29.4 HU, P<.001). All patients converted to stems were female individuals (P = .01) and had metaphyseal cancellous bone density less than 20 HU (P<.001). Conclusions: Metaphyseal cancellous bone density can be calculated on preoperative CT scans and is associated with intraoperative conversion to a stemmed humeral component in anatomic shoulder arthroplasty. A threshold of 20 HU can be used to predict which patients are more likely to require stemmed components