396 research outputs found

    Conservation Laws in Cellular Automata

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    If X is a discrete abelian group and B a finite set, then a cellular automaton (CA) is a continuous map F:B^X-->B^X that commutes with all X-shifts. If g is a real-valued function on B, then, for any b in B^X, we define G(b) to be the sum over all x in X of g(b_x) (if finite). We say g is `conserved' by F if G is constant under the action of F. We characterize such `conservation laws' in several ways, deriving both theoretical consequences and practical tests, and provide a method for constructing all one-dimensional CA exhibiting a given conservation law.Comment: 19 pages, LaTeX 2E with one (1) Encapsulated PostScript figure. To appear in Nonlinearity. (v2) minor changes/corrections; new references added to bibliograph

    A Novel High Throughput Assay for Anthelmintic Drug Screening and Resistance Diagnosis by Real-Time Monitoring of Parasite Motility

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    Parasitic worms cause untold morbidity and mortality on billions of people and livestock. Drugs are available but resistance is problematic in livestock parasites and is a looming threat for human helminths. Currently, new drug discovery and resistance monitoring is hindered as drug efficacy is assessed by observing motility or development of parasites using laborious, subjective, low-throughput methods evaluated by eye using microscopy. Here we describe a novel application for a cell monitoring device (xCELLigence) that can simply and objectively assess real time anti-parasite efficacy of drugs on eggs, larvae and adults in a fully automated, label-free, high-throughput fashion. This technique overcomes the current low-throughput bottleneck in anthelmintic drug development and resistance detection pipelines. The widespread use of this device to screen for new therapeutics or emerging drug resistance will be an invaluable asset in the fight against human, animal and plant parasitic helminths and other pathogens that plague our planet

    The Genetic Structure and History of Africans and African Americans.

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    Africa is the source of all modern humans, but characterization of genetic variation and of relationships among populations across the continent has been enigmatic. We studied 121 African populations, four African American populations, and 60 non-African populations for patterns of variation at 1327 nuclear microsatellite and insertion/deletion markers. We identified 14 ancestral population clusters in Africa that correlate with self-described ethnicity and shared cultural and/or linguistic properties. We observed high levels of mixed ancestry in most populations, reflecting historical migration events across the continent. Our data also provide evidence for shared ancestry among geographically diverse hunter-gatherer populations (Khoesan speakers and Pygmies). The ancestry of African Americans is predominantly from Niger-Kordofanian (approximately 71%), European (approximately 13%), and other African (approximately 8%) populations, although admixture levels varied considerably among individuals. This study helps tease apart the complex evolutionary history of Africans and African Americans, aiding both anthropological and genetic epidemiologic studies

    Revival of the magnetar PSR J1622-4950: observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

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    New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation.Comment: Published in ApJ (2018 April 5); 13 pages, 4 figure

    Co-creation workshops for work life oriented ICT education

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    ICT Companies in Finland today are facing problems in recruiting the right skilled workforce to meet their needs [1]. There is particular shortage of application developers, application designers, web professionals and coders in the South Ostrobothnia area of Finland [2]. Typical degree courses offered by universities would not work because there is a mismatch between the university degrees offered and the needs of these companies. There is a need to develop a new approach to address this shortage. In response to this, local University of Applied Sciences has developed a new ICT education programme using co-creation methods. The new approach is based on the concepts of co-creation of value from service science. This paper discusses the importance of this new approach in education and how it can be implemented. Empirical data is gathered through observation of and reflection on the development of the ICT programme which follows the principles of co-creation

    An investigation into the correlation of vitamin D status and management outcomes in patients with severe COVID-19 at a South African tertiary hospital

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    Background: Severe coronavirus disease 2019 (COVID-19) has a poor prognosis, and biomarkers may predict disease severity. The aim of this study was to assess the effect of baseline vitamin D (VitD) inadequacy on the outcomes of patients with severe COVID-19 admitted to the intensive care unit (ICU) of a tertiary hospital in South Africa. // Methods: Patients with confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were recruited during wave II of the pandemic in Cape Town. Eighty-six patients were included in the study. They were categorized into three groups: VitD deficient, VitD insufficient, and VitD sufficient. The VitD deficient and VitD insufficient groups were combined to form a ‘VitD inadequate’ group. Cox regression analysis was done to assess the association between VitD status and mortality. Factors with P < 0.05 in the adjusted multivariable Cox regression analysis were considered statistically significant. // Results: The proportion of VitD inadequacy was 64% (55/86); this group had a significantly higher proportion with hypertension (66%; P = 0.012). The Kaplan–Meier curve showed no significant difference in the probability of survival among the COVID-19 patients admitted to the ICU with or without VitD inadequacy. However, patients with elevated serum creatinine were significantly more at risk of dying (adjusted hazard ratio 1.008, 95% confidence interval 1.002–1.030; P = 0.017). // Conclusions: This study found a high prevalence of VitD inadequacy (combined deficiency and insufficiency) in COVID-19 patients admitted to the ICU. This may indicate a possible risk of severe disease. Whilst there was no statistically significant relationship between VitD status and mortality in this cohort, baseline VitD may be an important prognostic biomarker in COVID-19 patients admitted to the ICU, particularly in those with comorbidities that predispose to VitD deficiency

    Characterization of the nearby L/T binary brown dwarf wise J104915.57–531906.1 at 2 pc from the sun

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    WISE J104915.57−-531906.1 is a L/T brown dwarf binary located 2pc from the Sun. The pair contains the closest known brown dwarfs and is the third closest known system, stellar or sub-stellar. We report comprehensive follow-up observations of this newly uncovered system. We have determined the spectral types of both components (L8+/-1, for the primary, agreeing with the discovery paper; T1.5+/-2 for the secondary, which was lacking spectroscopic type determination in the discovery paper) and, for the first time, their radial velocities (V_rad~23.1, 19.5 km/s) using optical spectra obtained at the Southern African Large Telescope (SALT) and other facilities located at the South African Astronomical Observatory (SAAO). The relative radial velocity of the two components is smaller than the range of orbital velocities for theoretically predicted masses, implying that they form a gravitationally bound system. We report resolved near-infrared JHK_S photometry from the IRSF telescope at the SAAO which yields colors consistent with the spectroscopically derived spectral types. The available kinematic and photometric information excludes the possibility that the object belongs to any of the known nearby young moving groups or associations. Simultaneous optical polarimetry observations taken at the SAAO 1.9-m give a non-detection with an upper limit of 0.07%. For the given spectral types and absolute magnitudes, 1Gyr theoretical models predict masses of 0.04--0.05 M_odot for the primary, and 0.03--0.05 M_odot for the secondary

    A quantified triple bottom line for tourism: experimental results

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    The tradition of tourism businesses and regional tourism industries is to measure their value to the host community by jobs, wages and tax revenues even though every member of that community is impacted on a daily basis though a broad variety of impacts. This paper demonstrates a conceptual approach for measuring the relative importance of the major dimensions of community quality of life that can be influenced by the tourism industry in order to calculate an indication of overall impact on the well being of community residents. Furthermore, we have formulated a conjoint model that values this overall performance in monetary units. A conjoint model for estimating importance is successfully implemented using samples of college students and tourism industry professionals in the US and Cyprus. A monetary version of Triple Bottom Line impacts is calculated for the impacts of a specific hypothetical tourism business development
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