3,458 research outputs found

    Resource Sharing and Coevolution in Evolving Cellular Automata

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    Evolving one-dimensional cellular automata (CAs) with genetic algorithms has provided insight into how improved performance on a task requiring global coordination emerges when only local interactions are possible. Two approaches that can affect the search efficiency of the genetic algorithm are coevolution, in which a population of problems---in our case, initial configurations of the CA lattice---evolves along with the population of CAs; and resource sharing, in which a greater proportion of a limited fitness resource is assigned to those CAs which correctly solve problems that fewer other CAs in the population can solve. Here we present evidence that, in contrast to what has been suggested elsewhere, the improvements observed when both techniques are used together depend largely on resource sharing alone.Comment: 8 pages, 1 figure; http://www.santafe.edu/~evca/rsc.ps.g

    Probing the structure of entanglement with entanglement moments

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    We introduce and define a set of functions on pure bipartite states called entanglement moments. Usual entanglement measures tell you if two systems are entangled, while entanglement moments tell you both if and how two systems are entangled. They are defined with respect to a measurement basis in one system (e.g., a measuring device), and output numbers describing how a system (e.g., a qubit) is entangled with that measurement basis. The moments utilize different distance measures on the Hilbert space of the measured system, and can be generalized to any N-dimensional Hilbert space. As an application, they can distinguish between projective and non-projective measurements. As a particular example, we take the Rabi model's eigenstates and calculate the entanglement moments as well as the full distribution of entanglement.Comment: 5 pages, 5 figure

    Practical applications of small-angle neutron scattering.

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    Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel. Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below

    Linking ventilation heterogeneity quantified via hyperpolarized He-3 MRI to dynamic lung mechanics and airway hyperresponsiveness

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    Advancements in hyperpolarized helium-3 MRI (HP 3He-MRI) have introduced the ability to render and quantify ventilation patterns throughout the anatomic regions of the lung. The goal of this study was to establish how ventilation heterogeneity relates to the dynamic changes in mechanical lung function and airway hyperresponsiveness in asthmatic subjects. In four healthy and nine mild-to-moderate asthmatic subjects, we measured dynamic lung resistance and lung elastance from 0.1 to 8 Hz via a broadband ventilation waveform technique. We quantified ventilation heterogeneity using a recently developed coefficient of variation method from HP 3He-MRI imaging. Dynamic lung mechanics and imaging were performed at baseline, post-challenge, and after a series of five deep inspirations. AHR was measured via the concentration of agonist that elicits a 20% decrease in the subject’s forced expiratory volume in one second compared to baseline (PC20) dose. The ventilation coefficient of variation was correlated to low-frequency lung resistance (R = 0.647, P < 0.0001), the difference between high and low frequency lung resistance (R = 0.668, P < 0.0001), and low-frequency lung elastance (R = 0.547, P = 0.0003). In asthmatic subjects with PC20 values <25 mg/mL, the coefficient of variation at baseline exhibited a strong negative trend (R = -0.798, P = 0.02) to PC20 dose. Our findings were consistent with the notion of peripheral rather than central involvement of ventilation heterogeneity. Also, the degree of AHR appears to be dependent on the degree to which baseline airway constriction creates baseline ventilation heterogeneity. HP 3He-MRI imaging may be a powerful predictor of the degree of AHR and in tracking the efficacy of therapy.This work was funded by the National Heart, Lung, and Blood Institute Grants R01 HL62269-04 and R01 HL-096797

    IMPLEMENTATION OF TACTICAL OPEN SOURCE 5G MOBILE NETWORKS

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    The implementation of fifth-generation (5G) communications technology is a global effort, with China leading the way. The Department of Defense has initiated efforts on 5G implementation from smart warehouses to virtual combat training; however, focus on the tactical communications level remains minimal. This thesis examines the feasibility of using OpenAirInterface Software Alliance (OSA) software to build a private mobile ad hoc 5G network for various military applications. First, we created a Fourth Generation/Long Term Evolution network utilizing commercial off-the-shelf equipment and software to operate the radio access network (RAN), software-defined radio, and an evolved packet core (EPC). Then we connected the EPC to an 802.11 network for internet access. We successfully configured a subscriber identification module and smartphone and attached it to the network for data services. Although the OSA software is robust and customizable, it is difficult to make changes, is restrictive in which user equipment (UE) can connect to the network, and does not reliably allow the UE to connect. The potential of OSA software for military applications is apparent but does not appear ready for field implementation. Going forward, we recommend researchers use this work to implement new software versions and test scalability to reassess the feasibility of OSA software.NCWDGLieutenant Commander, United States NavyApproved for public release. Distribution is unlimited

    Loans on sale: Credit market seasonality, borrower need, and lender rents

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    The market for corporate credit is characterized by significant seasonal variation, both in interest rates and the volume of new lending. Firms borrowing from banks during seasonal "sales" in late spring and fall issue at 19 basis points cheaper than winter and summer borrowers. Issuers during cheap seasons appear to have less immediate needs, but are enticed by low rates to engage in precautionary borrowing. High interest rate periods capture borrowers with unanticipated, non-deferrable investment needs. Consistent with models of intertemporal price discrimination, seasonality is strongly associated with market concentration among a few large banks with repeated interactions

    Effectiveness of insider trading law in South Africa's equity market: the mergers and acquisitions example

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    Thesis (M.M. (Finance & Investment))--University of the Witwatersrand, Faculty of Commerce, Law and Management, Graduate School of Business Administration, 2015.Shares in takeover target companies listed on the JSE have historically earned abnormal returns in the days preceding the public announcements of planned takeovers. This has not been tested since the enforcement of insider trading law in South Africa. Furthermore, it is unclear whether the existence of such abnormal returns occur as a result of legal market activity or if it infers illegal insider trading. The extent of Average Cumulative Abnormal Returns (“ACAR”) that occur in the 21 days preceding the announcement of a takeover is established for a sample of 57 takeovers that transpired between 2004 and 2014. ACAR establishes the average abnormal return that each takeover target company accumulates during the 21 day event window. 30 Personal Interviews offer insight into the causes of Cumulative Abnormal Returns (“CAR”) preceding each takeover announcement. Results indicate that shares in takeover target companies accumulate significant ACAR (9.03%) during the 21 trading days preceding the first public announcement of a takeover. Interview findings include the existence of plausible legal explanations for instances of CAR, which contradicts the suggestion that ACAR constitutes prima facie evidence of illegal insider trading. However, the study resolved that the occurrences of CAR were as a result of both legal market activity and illegal insider trading occurring after widespread information leaks. The existence of significant ACAR – more so than in previous South African studies – highlights the need for further investigation into the effectiveness of South African insider trading law in preventing illegal insider trading preceding the announcement of planned takeovers

    New ages from Sehonghong rock shelter: Implications for the late Pleistocene occupation of highland Lesotho

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    Sehonghong rock shelter is situated in the eastern Lesotho highlands, a climatically extreme region of southern Africa. The site is one of a handful in southern Africa that preserves human occupations before, during, and after the Last GlacialMaximum(LGM). The site's long and well-preserved sequence makes it relevant to addressing questions of human mobility, subsistence, and technology in relation to broader environmental change. Here we present a Bayesian-modelled radiocarbon chronology for the LGM and terminal Pleistocene occupations at Sehonghong. Our model incorporates previously published radiocarbon dates and new accelerator mass spectrometry ages. We also present archaeological evidence to test the hypothesis that Sehonghong was occupied in a series of punctuated events, and that some of these occupations were more intensive than others. Previous chronological and archaeological data were insufficient for testing these hypotheses. The new dates and archaeological data confirmthat the sitewas occupied intensively in the early LGMand immediately thereafter. The site was otherwise occupied sporadically.We find that greater site occupation density is not always correlated with intensified use of local resources as measured by increased bipolar reduction and fish consumption. The new dates further confirm that Sehonghong contains some of the oldest evidence for systematic freshwater fishing in southern Africa. The availability of fish, a high fat protein source, probably stimulated human occupation, however sporadic, of suchmontane environments during cooler and drier periods. These findings suggest behavioural variability in response to shifting mobility and subsistence strategies. Our brief discussion informs upon huntergatherer occupation of southern Africanmontane environments more broadly and human behavioural variability during the LGM

    Prevalence and risk factors of sarcopenia among adults living in nursing homes

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    Objectives: Sarcopenia is a progressive loss of skeletal muscle and muscle function, with significant healthand disability consequences for older adults. We aimed to evaluate the prevalence and risk factors ofsarcopenia among older residential aged care adults using the European Working Group on Sarcopeniain Older People (EWGSOP) criteria.Study design: A cross-sectional study design that assessed older people (n = 102, mean age 84.5 ± 8.2 years)residing in 11 long-term nursing homes in Australia.Main outcome measurements: Sarcopenia was diagnosed from assessments of skeletal mass index bybioelectrical impedance analysis, muscle strength by handheld dynamometer, and physical performanceby the 2.4 m habitual walking speed test. Secondary variables where collected to inform a risk factoranalysis.Results: Forty one (40.2%) participants were diagnosed as sarcopenic, 38 (95%) of whom were categorizedas having severe sarcopenia. Univariate logistic regression found that body mass index (BMI) (Oddsratio (OR) = 0.86; 95% confidence interval (CI) 0.78–0.94), low physical performance (OR = 0.83; 95% CI0.69–1.00), nutritional status (OR = 0.19; 95% CI 0.05–0.68) and sitting time (OR = 1.18; 95% CI 1.00–1.39)were predictive of sarcopenia. With multivariate logistic regression, only low BMI (OR = 0.80; 95% CI0.65–0.97) remained predictive.Conclusions: The prevalence of sarcopenia among older residential aged care adults is very high. Inaddition, low BMI is a predictive of sarcopenia
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