On the classification of time series and cross wavelet phase variance

The continuous wavelet transform (CWT) is arguably one of the best tools to explore underlying characteristic features of time series data. Its application in large time series classification experiments, however, has been severely limited due to the large amount of redundant associated information. By extending the capabilities of the CWT to perform cross wavelet analysis (CWA), common frequency behaviour between two time series is highlighted, and the potential to extract amplitude modulated (AM) and frequency modulation (FM) characteristics in an automated way is possible. Characterisation of AM is relatively straightforward and can be resolved by any number of Euclidean based techniques in both the time and frequency domains. FM on the other hand, is somewhat more difficult as it transcends multiple wavelet scales. In this study, linear combinations of scales are used to extract both AM similarity (derived from global wavelet power spectra) and FM coherency, using a new method developed called cross wavelet phase variance (CWPV). The methodology is applied to large scale classification problems (using benchmark time series), in which the method clearly outperforms other common distance-based measures. Lastly, the approach provides a powerful framework in which AM and FM characteristics common between time series can be explicitly mapped to their corresponding scales, and with some initial optimisation, can be applied to any classification problem

Dating the stone age at Rose Cottage Cave South Africa - An exercise in optically dating cave sediments

Results and analysis of Optically Stimulated Luminescence (OSL) dating of the Middle Stone Age (MSA) and Later Stone Age (LSA) sediments at Rose Cottage Cave (RCC) are presented. Seventeen luminescence samples taken over the last decade were used in this study. Fourteen of these samples were dated (eight in Pretoria and six in Risø, Denmark by A. S. Murray). The samples were taken from the entire sequence and gave age ranges from the bottom of the sequence up until the Oakhurst LSA industry. The protocol that was used is the conventional single-aliquot regenerative (SAR) protocol, due to its ability to correct for behavioural problems associated with OSL dating. This study is primarily concerned with testing the validity of the conventional SAR protocol applied to South African archaeological sites. RCC presents problematic sediments for OSL dating because of a high feldspar component in the sediments at the site (OSL dating is preferably done on quartz grains due to a better understanding of the mechanisms of OSL production). Assessing the radiation dose samples received during their burial period was problematic due to the large presence of potassium rich feldspars. Assessing the radiation dose was problematic because the measurement of potassium (K) returned different values using several independent techniques. The mode of sediment deposition via different depositional mechanisms such as, fluvial, and clast spalling present difficult challenges in assessing the zero age value of a sample. OSL ages were compared to a well defined radiocarbon chronology from RCC, and any inconsistencies would motivate closer sorting of the different dating techniques. In this study it was found that not all feldspar grains were removed from the quartz extracts during pretreatment procedures. The ability of the SAR protocol to pick out feldspar contamination was therefore not conclusive, and single grain measurements had to be used to differentiate quartz and feldspar grains. The likelihood of age contamination from problematic depositional events was not supported and the results suggest that aeolian deposition was the main mechanism at the site. The vertical separation of depositional events i.e. the varying archaeological events, is very dense at RCC and this introduces the possibility of sample mixing during collection. For a few samples it is shown that sample mixing has occurred as mixing is usually evident in the degree of scatter in the OSL results. After all the inconsistencies in OSL/Radiocarbon age correlations were worked out, a coherent OSL chronology was obtained. Certain issues surrounding dosimetry however, are still not resolved. These issues are beyond the scope of this study and so caution is advised when using OSL dates done with little or no dose-rate analysis. The resulting dates provide a useful dataset for archaeologists who now have added resources to asses the Middle Stone Age (MSA) and better compare synchronous evidence from different sites in order to contribute to the debate surrounding the origins of modern humans and modern human behaviour. These results combined with the well established radiocarbon chronology give age ranges as follows: The Pre-Howiesons Poort (Pre-HP) MSA IIb industry is between 94 and 68 thousand years ago (ka); the Howiesons Poort (HP) industry is between 68 and 55 ka; the Post –HP MSA III dates to between 55 and 48 ka; the ‘almost sterile sands’ (which include the MSA IV industry) are between 48 and >27 ka; the MSA/LSA transition is between 27 and 20 ka; the Robberg LSA industry is between 20 and 10.5 ka; the Oakhurst LSA industry ranges from 10.5 to 8.5 ka; and the Wilton LSA industries are <8.5 ka.Dissertation (M(Archaeology))--University of Pretoria, 2007.Anthropology and Archaeologyunrestricte

Optimization Space Pruning without Regrets

International audienceMany computationally-intensive algorithms benefit from the wide parallelism offered by Graphical Processing Units (GPUs). However , the search for a close-to-optimal implementation remains extremely tedious due to the specialization and complexity of GPU architectures.We present a novel approach to automatically discover the best performing code from a given set of possible implementations. It involves a branch and bound algorithm with two distinctive features: (1) an analytic performance model of a lower bound on the execution time, and (2) the ability to estimate such bounds on a partially-specified implementation.The unique features of this performance model allow to aggressively prune the optimization space without eliminating the best performing implementation. While the space considered in this paper focuses on GPUs, the approach is generic enough to be applied to other architectures.We implemented our algorithm in a tool called Telamon and demonstrate its effectiveness on a huge, architecture-specific and input-sensitive optimization space. The information provided by the performance model also helps to identify ways to enrich the search space to consider better candidates, or to highlight architectural bottlenecks

An update of the tsetse fly (Diptera: Glossinidae) distribution and African animal trypanosomosis prevalence in north-eastern KwaZulu-Natal, South Africa

An unpredicted outbreak of African animal trypanosomosis or nagana in 1990 in north-eastern KwaZulu-Natal necessitated an emergency control programme, utilising the extensive cattledipping system in the area, as well as a reassessment of the tsetse and trypanosomosis problem in the province. Since 1990, sporadic blood sampling of cattle at the dip tanks in the naganainfested areas were undertaken to identify trypanosome species involved and to determine the infection prevalence in cattle. The distribution and species composition of the tsetse populations in the area were also investigated. From November 2005 to November 2007 selected dip tanks were surveyed for trypanosome infection prevalence. During April 2005 to August 2009 the distribution and abundance of tsetse populations were assessed with odour-baited H traps. The tsetse and trypanosome distribution maps were updated and potential correlations between tsetse apparent densities (ADs) and the prevalence of trypanosomosis were assessed. Glossina brevipalpis Newstead and Glossina austeni Newstead were recorded in locations where they have not previously been collected. No significant correlation between tsetse relative abundance and nagana prevalence was found, which indicated complex interactions between tsetse fly presence and disease prevalence. This was epitomised by data that indicated that despite large differences in the ADs of G. austeni and G. brevipalpis, trypanosome infection prevalence was similar in all three districts in the area. This study clearly indicated that both tsetse species play significant roles in trypanosome transmission and that it will be essential that any control strategy, which aims at sustainable management of the disease, should target both species

Modélisation de la qualité des stations et de la croissance individuelle des arbres dans des peuplements purs et mélangés de Pinus brutia dans le nord-est de la Grèce

International audienc

Risk factors for Coronavirus disease 2019 (Covid-19) death in a population cohort study from the Western Cape province, South Africa

Risk factors for coronavirus disease 2019 (COVID-19) death in sub-Saharan Africa and the effects of human immunodeficiency virus (HIV) and tuberculosis on COVID-19 outcomes are unknown. We conducted a population cohort study using linked data from adults attending public-sector health facilities in the Western Cape, South Africa. We used Cox proportional hazards models, adjusted for age, sex, location, and comorbidities, to examine the associations between HIV, tuberculosis, and COVID-19 death from 1 March to 9 June 2020 among (1) public-sector “active patients” (≥1 visit in the 3 years before March 2020); (2) laboratory-diagnosed COVID-19 cases; and (3) hospitalized COVID-19 cases. We calculated the standardized mortality ratio (SMR) for COVID-19, comparing adults living with and without HIV using modeled population estimates.Among 3 460 932 patients (16% living with HIV), 22 308 were diagnosed with COVID-19, of whom 625 died. COVID19 death was associated with male sex, increasing age, diabetes, hypertension, and chronic kidney disease. HIV was associated with COVID-19 mortality (adjusted hazard ratio [aHR], 2.14; 95% confidence interval [CI], 1.70–2.70), with similar risks across strata of viral loads and immunosuppression. Current and previous diagnoses of tuberculosis were associated with COVID-19 death (aHR, 2.70 [95% CI, 1.81–4.04] and 1.51 [95% CI, 1.18–1.93], respectively). The SMR for COVID-19 death associated with HIV was 2.39 (95% CI, 1.96–2.86); population attributable fraction 8.5% (95% CI, 6.1–11.1)

Competitive intelligence: construct exploration, validation and equivalence

Purpose: – Little empirical research has been conducted on competitive intelligence (CI). This paper aims to contribute to the quantitative strand of the CI literature by exploring and validating the theoretical constructs of the CI process. Design/methodology/approach: – Data from 601 questionnaires filled out by South African and Flemish exporters were subjected to exploratory factor analysis and construct equivalence analysis between the sub‐samples. Findings: – The results showed that the CI process consists of three constructs, while the context in which CI takes place consists of four constructs. This agrees to some extent with the literature. When verifying the constructs for both cultures it was found that all but one CI context construct can be viewed as equivalent in both groups. Bias analysis identified one item in the questionnaire that was biased. Via regression analysis it was also indicated that the context in which CI takes place influences the CI process to a large extent. The research identified size as an important influencing factor in a business' CI process. Practical implications: – Businesses involved in CI should take note that an improvement in their formal infrastructure, employee involvement and internal information processes could enhance their CI capability. Originality/value: – This paper contributes towards the formalising of the constructs of competitive intelligence.http://dx.doi.org/10.1108/0001253081088800

Outcomes of laboratory-confirmed SARS-CoV-2 infection during resurgence driven by Omicron lineages BA.4 and BA.5 compared with previous waves in the Western Cape Province, South Africa

Objectives: We aimed to compare the clinical severity of Omicron BA.4/BA.5 infection with BA.1 and earlier variant infections among laboratory-confirmed SARS-CoV-2 cases in the Western Cape, South Africa, using timing of infection to infer the lineage/variant causing infection. Methods: We included public sector patients aged ≥20 years with laboratory-confirmed COVID-19 between May 01-May 21, 2022 (BA.4/BA.5 wave) and equivalent previous wave periods. We compared the risk between waves of (i) death and (ii) severe hospitalization/death (all within 21 days of diagnosis) using Cox regression adjusted for demographics, comorbidities, admission pressure, vaccination, and previous infection. Results: Among 3793 patients from the BA.4/BA.5 wave and 190,836 patients from previous waves, the risk of severe hospitalization/death was similar in the BA.4/BA.5 and BA.1 waves (adjusted hazard ratio [aHR] 1.12; 95% confidence interval [CI] 0.93; 1.34). Both Omicron waves had a lower risk of severe outcomes than previous waves. Previous infection (aHR 0.29, 95% CI 0.24; 0.36) and vaccination (aHR 0.17; 95% CI 0.07; 0.40 for at least three doses vs no vaccine) were protective. Conclusion: Disease severity was similar among diagnosed COVID-19 cases in the BA.4/BA.5 and BA.1 periods in the context of growing immunity against SARS-CoV-2 due to previous infection and vaccination, both of which were strongly protective