103 research outputs found
The sticky resting box, a new tool for studying resting behaviour of Afrotropical malaria vectors
No full textBackground:
Monitoring densities of adult mosquito populations is a major challenge in efforts to evaluate the epidemiology of mosquito-borne diseases, and their response to vector control interventions. In the case of malaria, collection of outdoor-resting Anophelines is rarely incorporated into surveillance and control, partially due to the lack of standardized collection tools. Such an approach, however, is increasingly important to investigate possible changes in mosquito behaviour in response to the scale up of Insecticide Treated Nets and Indoor Residual Spraying. In this study we evaluated the Sticky Resting Box (SRB) - i.e. a sticky variant of previously investigated mosquito Resting Box, which allows passive collection of mosquitoes entering the box – and compared its performance against traditional methods for indoor and outdoor resting mosquito sampling.<p></p>
Methods:
Daily collections were carried out in two neighbouring villages of Burkina Faso during rainy season 2011 and dry season 2012 by SRB located indoors and outdoors, and by Back-Pack aspiration inside houses (BP) and in ad hoc built outdoor pit-shelters (PIT).<p></p>
Results:
Overall, almost 20,000 Culicidae specimens belonging to 16 species were collected and morphologically identified. Malaria vectors included Anopheles coluzzii (53%), An. arabiensis (12%), An. gambiae s.s. (2.0%) and An. funestus (4.5%). The diversity of species collected in the two villages was similar for SRB and PIT collections outdoors, and significantly higher for SRB than for BP indoors. The population dynamics of An. gambiae s.l. mosquitoes, as obtained by SRB-collections was significantly correlated with those obtained by the traditional methods. The predicted mean estimates of An. gambiae s.l. specimens/sampling-unit/night-of-collections was 6- and 5-times lower for SRB than for BP indoors and PIT outdoors, respectively.<p></p>
Conclusions:
Overall, the daily performance of SRB in terms of number of malaria vectors/trap was lower than that of traditionally used approaches for in- and outdoor collections. However, unlike these methods, SRB could be set up to collect mosquitoes passively over at least a week. This makes SRB a promising tool for passively monitoring anopheline resting populations, with data presented here providing guidance for how to set up SRB-based collections to acquire information comparable to those obtained with other methods.<p></p>
Continuous Authentication using Stylometry
No full textStatic authentication, where user identity is checked once at login time, can be circumvented no matter how strong the authentication mechanism is. Through attacks such as man-in-the-middle and its variants, an authenticated session can be hijacked later after the initial login process has been completed. In the last decade, continuous authentication (CA) using biometrics has emerged as a possible remedy against session hijacking. CA consists of testing the authenticity of the user repeatedly throughout the authenticated session as data becomes available. CA is expected to be carried out unobtrusively, due to its repetitive nature, which means that the authentication information must be collectible without any active involvement of the user and without using any special purpose hardware devices (e.g. biometric readers). Stylometry analysis, which consists of checking whether a target document was written or not by a specific individual, could potentially be used for CA. Although stylometric techniques can achieve high accuracy rates for long documents, it is still challenging to identify an author for short documents, in particular when dealing with large author populations.
In this dissertation, we propose a new framework for continuous authentication using authorship verification based on the writing style. Authorship verification can be checked using stylometric techniques through the analysis of linguistic styles and writing characteristics of the authors. Different from traditional authorship verification that focuses on long texts, we tackle the use of short messages. Shorter authentication delay (i.e. smaller data sample) is essential to reduce the window size of the re-authentication period in CA. We validate our method using different block sizes, including 140, 280, and 500 characters, and investigate shallow and deep learning architectures for machine learning classification. Experimental evaluation of the proposed authorship verification approach based on the Enron emails dataset with 76 authors yields an Equal Error Rate (EER) of 8.21% and Twitter dataset with 100 authors yields an EER of 10.08%. The evaluation of the approach using relatively smaller forgery samples with 10 authors yields an EER of 5.48%.Graduat
The role of Plasmodium falciparum var genes in malaria in pregnancy
No full textSequestration of Plasmodium falciparum-infected erythrocytes in the placenta is responsible for many of the harmful effects of malaria during pregnancy. Sequestration occurs as a result of parasite adhesion molecules expressed on the surface of infected erythrocytes binding to host receptors in the placenta such as chondroitin sulphate A (CSA). Identification of the parasite ligand(s) responsible for placental adhesion could lead to the development of a vaccine to induce antibodies to prevent placental sequestration. Such a vaccine would reduce the maternal anaemia and infant deaths that are associated with malaria in pregnancy. Current research indicates that the parasite ligands mediating placental adhesion may be members of the P. falciparum variant surface antigen family PfEMP1, encoded by var genes. Two relatively well-conserved subfamilies of var genes have been implicated in placental adhesion, however, their role remains controversial. This review examines the evidence for and against the involvement of var genes in placental adhesion, and considers whether the most appropriate vaccine candidates have yet been identified
From the Theory of the African Origin of Humankind to Modern Social, Legal and Technological Innovations: a Brief Analytical Excursion into Anthroposociogenesis
No full textObjective: to trace the evolution of humanity and to identify the role of various social institutions in order to understand the existential role of laws aimed at ensuring the coexistence of society in the context of technological innovations.Methods: the author used general scientific and special methods of cognition, which allowed tracing the dialectical development of humanity, social transformations and technological innovations.Results: looking back at the history of humanity, which originated on the African continent (the theory of African descent), the author notes the most important changes in the human way of life and environment, which led to the need to build organized societies and regulate social behavior with the help of legislative norms. Law is seen as part of the evolutionary process that was to emerge in the course of human evolution. The critical importance of law in overcoming the global challenges and existential questions of humanity’s continued coexistence arising in the course of evolution is emphasized. In this regard, the historical significance of the Kurukan Fuga Charter of the Malian Empire is emphasized as one of the oldest constitutions in the world, recognized internationally as an important source of legal and political norms for modern societies, regulating the structure of state power and social behaviour, although preserved largely in oral form. It is argued that social and technological change often served as the impetus for the development of new laws. Humanity has many times intervened in its own biological evolution with the help of technology; now it is an important moment from the viewpoint of law and ethics when technology may interfere in further human evolution. The greatest concern in this regard is the era of rapid development of artificial intelligence, which makes new demands on a human being.Scientific novelty: the article shows the role of the African continent in the origin and development of humanity and socio-legal institutions in the light of modern transformations and the construction of a new social reality.Practical significance: the conducted research creates prerequisites for further development of the theory of anthroposociogenesis and in-depth conceptual historical and legal study of the role of the African continent in the development of humanity and its social institutions
A well-conserved Plasmodium falciparum var gene shows an unusual stage-specific transcript pattern
No full textThe var multicopy gene family encodes Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variant antigens, which, through their ability to adhere to a variety of host receptors, are thought to be important virulence factors. The predominant expression of a single cytoadherent PfEMP1 type on an infected red blood cell, and the switching between different PfEMP1 types to evade host protective antibody responses, are processes thought to be controlled at the transcriptional level. Contradictory data have been published on the timing of var gene transcription. Reverse transcription-polymerase chain reaction (RT-PCR) data suggested that transcription of the predominant var gene occurs in the later (pigmented trophozoite) stages, whereas Northern blot data indicated such transcripts only in early (ring) stages. We investigated this discrepancy by Northern blot, with probes covering a diverse var gene repertoire. We confirm that almost all var transcript types were detected only in ring stages. However, one type, the well-conserved varCSA transcript, was present constitutively in different laboratory parasites and does not appear to undergo antigenic variation. Although varCSA has been shown to encode a chondroitin sulphate A (CSA)-binding PfEMP1, we find that the presence of full-length varCSA transcripts does not correlate with the CSA-binding phenotype
Heme Adventures: Roles In Catalysis and Structural Insights
No full textThe full text of this item is not available at this time because the author has placed this item under an embargo until May 15, 2030.Heme enzymes represent a vast class of biological catalysts that enable diverse oxidative transformations essential to life. This dissertation explores the roles of heme in catalysis through detailed biochemical, structural, and mechanistic studies of four distinct enzymes. Beginning with a comprehensive analysis of charge maintenance in non-heme iron oxygenases, the work highlights how ligand scaffolds and substrate interactions govern reaction outcomes. This is followed by subsequent investigations into tyrosine hydroxylase which reveal a novel free radical pathway, providing new insight into substrate oxidation. Structural and functional characterization of Mycobacterium tuberculosis catalase-peroxidase (KatG) identifies a unique indole-N-linked hydroperoxyl adduct that modulates enzymatic activity. The study of RufO, a heme enzyme implicated in rufomycin biosynthesis, suggests that tyrosine is not the native substrate, supported by spectroscopic, crystallographic, docking analyses. Finally, structural and spectroscopic studies of the streptococcal heme-binding protein HupZ demonstrate an unusual mode of heme coordination influenced by C-terminal tagging. Together, these studies underscore the diverse catalytic strategies enabled by heme and iron cofactors and offer broader implications for the design of biomimetic catalysts and therapeutic targets.Chemistr
Toponymie et histoire dans l’Ouest du Burkina Faso
No full textDans l’Ouest du Burkina Faso, au moins une vingtaine d’ethnies s’interpénètrent à tel point que certaines localités présentent deux ou trois groupes de populations appartenant à des ethnies différentes. Aujourd’hui, avec l’arrivée de nouveaux immigrants, attirés par la culture du coton et un climat moins rude que chez eux, ce chevauchement atteint jusqu’à dix ethnies différentes dans les gros villages des zones cotonnières. Pourtant, cet arc-en-ciel ethnique contraste avec une certaine homogénéité « julaïsante » de la toponymie. L'auteur tente d'expliquer cette toponymie à la lumière de l’histoire et de montrer les enjeux qu’elle présente aujourd’hui..In Western Burkina-Faso, some twenty ethnic groups intertwine in such a way that in some villages two or three ethnic groups can be found together. Nowadays, with the arrival of new migrants in cotton growing areas, more than ten different ethnic groups can be found in big villages. However, in spite of this ethnic rainbow, toponomy demonstrates a strong jula influence. The author tries to explain this toponymy through historical factors
Promotion effects of alkali metals on iron molybdate catalysts for CO<sub>2</sub> catalytic hydrogenation
No full textCO2 hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes, as well as to produce valuable chemicals from renewable and abundant resources. Iron catalysts are commonly used for the hydrogenation of carbon oxides to hydrocarbons. Iron-molybdenum catalysts have found numerous applications in catalysis, but have been never evaluated in the CO2 hydrogenation. In this work, the structural properties of iron-molybdenum catalysts without and with a promoting alkali metal (Li, Na, K, Rb, or Cs) were characterized using X-ray diffraction, hydrogen temperature-programmed reduction, CO2 temperature-programmed desorption, in-situ 57Fe Mossbauer spectroscopy and operando X-ray adsorption spectroscopy. Their catalytic performance was evaluated in the CO2 hydrogenation. During the reaction conditions, the catalysts undergo the formation of an iron (II) molybdate structure, accompanied by a partial reduction of molybdenum and carbidization of iron. The rate of CO2 conversion and product selectivity strongly depend on the promoting alkali metals, and electronegativity was identified as an important factor affecting the catalytic performance. Higher CO2 conversion rates were observed with the promoters having higher electronegativity, while low electronegativity of alkali metals favors higher light olefin selectivity.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Fundamental Aspects of Materials and EnergyRID/TS/Instrumenten groe
The Importance of the Women Characters and Imagery in Maryse Conde's Segou
No full textThis thesis analyses the women characters and the imagery relating to women in Segou, a three-volume saga by Maryse Conde. It takes a thematic approach to the topic with some linguistic investigation of imagery. The main focus of this study is to examine the strength of the women characters in the novel. This examination of characters begins with the city which can be viewed as a main 'player' in the novel. Segou the city is central to the lives of many of the Traore, the family around which the story is centred.
The women in the novel, especially Nya, have a marked influence on the lives of their offspring; the strength of character of one's offspring being determined more by the mother than by the father. ultimately a woman's strength is in the realm of motherhood. An analysis of the myth and imagery in the novel reveals the feminine nature of the cosmos. However this 'power' relates to another world where women once reigned supreme. In the novel men reign supreme, not women. The city and the other characters apart, the author as a 'character' is also significant. The identity quest which consumes so many of the characters in the novel is also Maryse Conde's quest. She too is in search of her past and of a land unknown. Maryse Conde is not only writing a novel for the enjoyment of her readers, she is also 'weaving' a 'past' for herself, a type of cosmogeny. Segou is a narrative work of the Traore clan over five generations, of the spread of Islam, of war and of the destruction of a kingdom. It is also Maryse Conde's story
Cyclodextrin-, UV-, and high pH-induced fluorescence enhancement of the pesticide azinphos-methyl: Applications to its trace analysis
No full textVarious methods for the enhancement of the fluorescence of the pesticide azinphos-methyl are reported. The addition of hydroxypropyl-beta-cyclodextrin was found to moderately enhance the fluorescence by a factor of three, presumably via inclusion of the pesticide into the cyclodextrin cavity. This complexation was found to occur with an association constant of 690 +/- 140 M-1. This enhancement was found to be too low to be useful in a fluorescence-based analytical method for this pesticide. Exposure of azinphos-methyl to UV light was also found to result in enhanced fluorescence, with much larger enhancement than in the case of addition of cyclodextrins. This enhancement was presumed to occur via photolysis of azinphos-methyl to a more fluorescent photoproduct. However, the difficulty of providing a constant UV dosage prevents its useful application as a fluorescence-based analytical method. Finally, it was found that base hydrolysis of azinphos-methyl resulted in a very large fluorescence enhancement. Although this enhancement was previously reported in the literature, it was found that contrary to the published reports, the hydrolysis occurred rapidly at room temperature, with no need for carrying out the reaction at increased temperature. Fluorescence enhancements of a factor of 300 were obtained by simply adding the appropriate amount of an aqueous NaOH solution to the aqueous azinphos-methyl sample. This procedure was used as the basis of a simple fluorescence-based analytical method for azinphos-methyl in water, with excellent linear calibration curves obtained down to concentrations of 5 ppb.PT: J; CR: *DEP AGR FOR, 1999, PEST SAL REP *DEP TECHN ENV, 1999, REL RANK AC PEST RIS AARON JJ, 1993, ANAL PROC, V30, P72 BENESI HA, 1949, J AM CHEM SOC, V71, P2703 COLY A, 1994, ANALYST, V119, P1205 COLY A, 1998, ANAL CHIM ACTA, V360, P129 COLY A, 1998, TALANTA, V46, P815 DELAPENA AM, 1993, J INCLUS PHENOM MOL, V15, P131 HASSALL KA, 1990, BIOCH USE PESTICIDES KAHN AR, 1998, CHEM REV, V98, P1977 LI S, 1992, CHEM REV, V92, P1457 MARQUEZ JC, 1990, ANALYST, V115, P1003 MILES CJ, 1988, ANAL CHEM, V60, P220 PANDERO S, 1993, TALANTA, V40, P225 PATEL BM, 1991, TALANTA, V38, P913 SANCHEZ FG, 1992, ANALYST, V117, P195 SANRAME CN, 1996, J PHYS CHEM-US, V100, P8151 SZELTLI J, 1998, CHEM REV, V98, P1743 TRAORE S, 1987, ANAL LETT, V20, P1995 VILCHEQUERO JL, 1994, FRESEN J ANAL CHEM, V350, P626 WAGNER BD, 1998, J PHOTOCH PHOTOBIO A, V114, P151 WAGNER BD, 2000, J INCL PHENOM MACRO, V38, P467; NR: 22; TC: 3; J9: CAN J CHEM; PG: 7; GA: 607YFSource type: Electronic(1
- …
