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Sample records for mojca doupona topi

  1. The Top...is it There? A Survey of the CDF and D0 Experiments

    DOE R&D Accomplishments Database

    Tollestrup, A. V.

    1994-12-01

    This paper describes: (1) features that the top quark must have if it exists, and how those features are inferred from various experiments; (2) how top quarks may be produced; (3) what must be accomplished to directly establish that the top quark has been produced in an experiment. Relevant features of the CDF and D0 detectors are described, as are methods useful in a top-quark search for identifying and detecting various kinds of particles. The author reviews data found by both CDF and D0, and discusses differences between the detectors and the data found with each.

  2. Synthesis and biological evaluation of indeno[1,5]naphthyridines as topoisomerase I (TopI) inhibitors with antiproliferative activity.

    PubMed

    Alonso, Concepción; Fuertes, María; González, María; Rubiales, Gloria; Tesauro, Cinzia; Knudsen, Birgitta R; Palacios, Francisco

    2016-06-10

    In an effort to establish new candidates with improved anticancer activity, we report here the synthesis of various series of 7H-indeno[2,1-c][1,5]-naphthyridines and novel 7H-indeno[2,1-c][1,5]-naphthyridine-7-ones and 7H-indeno[2,1-c][1,5]-naphthyridine-7-ols. Most of the products which were synthesized were able to inhibit Topoisomerase I activity. Moreover, in vitro testing demonstrated that a subset of the products exhibited a cytotoxic effect on cell lines derived from human breast cancer (BT 20), human lung adenocarcinoma (A 549), or human ovarian carcinoma (SKOV3). PMID:27017547

  3. Inhibition of Leishmania donovani promastigote DNA topoisomerase I and human monocyte DNA topoisomerases I and II by antimonial drugs and classical antitopoisomerase agents.

    PubMed

    Walker, John; Saravia, Nancy G

    2004-10-01

    We have compared the inhibitor sensitivities of DNA topoisomerase I (TOPI) from Leishmania donovani promastigotes and TOPs I and II of human monocytes using pentavalent and trivalent antimonials (SbV, SbIII) and classical TOP inhibitors. Bis-benzimidazoles (Hoechst-33258 and -33342) were potent inhibitors of both parasite and human TOPI, but Hoechst-33342 was markedly less cytotoxic to promastigotes than to monocytes in vitro. Leishmania donovani was also considerably less sensitive than monocytes to camptothecin, both at enzyme and cellular levels. Sodium stibogluconate (SSG) was the only antimonial to inhibit TOPI, exhibiting a significant (P < 0.05) 3-fold greater potency against the L. donovani enzyme but showed low cytotoxicities against intact promastigotes. The SbV meglumine antimoniate failed to inhibit TOPI and showed negligible cytotoxicities, whereas SbIII drugs were lethal to parasites and monocytes yet poor inhibitors of TOPI. Monocyte TOPII was inhibited by bis-benzimidazoles and insensitive to antimonials and camptothecin. The disparity between the high leishmanicidal activity and low anti-TOPI potency of SbIII indicates that in vivo targeting of L. donovani TOPI by the reductive pathway of antimonial activation is improbable. Nevertheless, the potent direct inhibition of TOPI by SSG and the differential interactions of camptothecin with L. donovani and human TOPI support the possibility of developing parasite-specific derivatives. PMID:15562618

  4. People

    NASA Astrophysics Data System (ADS)

    2005-01-01

    WORLD YEAR OF PHYSICS Around the world with physics Stuart Farmer; Leopold Mathelitsch; Rita Wodzinski and Michael Vollmer; Finn Ingebretsen; Mojca Cepic, Gorazd Planinsic and Mirko Cvahte; Ann-Marie Pendrill; Rajka Jurdana-Sepic INTERVIEW Close encounters of the cosmic kind David Smith talks to Frank Close BIOGRAPHIES Meet Physics Education’s family Steven Chapman and Andrea Pomroy

  5. Protest, Performance and Politics: The Use of "Nano-Media" in Social Movement Activism in South Africa

    ERIC Educational Resources Information Center

    Dawson, Marcelle C.

    2012-01-01

    Considering the lack of coverage in the mass media of certain kinds of social movement activity, many movements make use of smaller scale, independent media to publicise their struggles. From the vantage point of social movements in South Africa, this paper addresses what Mojca Pajnik and John Downing call "nano-media". Based on interviews with…

  6. Transorbital Orbitocranial Penetrating Injury with an Iron Rod.

    PubMed

    Agrawal, Amit; Reddy, V Umamaheswara; Kumar, S Satish; Hegde, Kishor V; Rao, G Malleswara

    2016-06-01

    Transorbital orbitocranial penetrating injuries (TOPIs) are relatively rare, can be caused by high-speed projectile foreign bodies to low-energy trauma (which is rarer), and account for 24% of penetrating head injuries in adults and approximately 45% in children. We report an uncommon nonfatal case of TOPI where a 16-year-old male child sustained injury due to accidental penetration of metal bar into the forehead. A bicoronal flap was raised to remove the metal bar. The patient recovered well, had normal vision, and doing well at follow-up. PMID:27162571

  7. Green Tea and Bone Metabolism

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Osteoporosis is a major health problem in elderly men and women. Epidemiological evidence has shown association between tea consumption and age-related bone loss in elderly men and women. The aim of this review is to provide a systemic review of green tea and bone health to cover the following topi...

  8. Letter to The Editor: Setting the record straight: a rebuttal to an erroneous analysis on transgenic insecticidal crops and natural enemies.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A letter to the editor was submitted in reply to an article published in Environmental Entomology by Lovei, Andow and Arpaia entitled “ Transgenic Insecticidal Crops and Natural Enemies: A Detailed Review of Laboratory Studies”. The non-target effects of transgenic insecticidal crops has been a topi...

  9. National Plant Diagnostic Network, Taxonomic training videos: Introduction to Aphids - Part 2

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Training is a critical part of aphid (Hemiptera: Aphididae) identification. This video provides visual instruction on important subject areas for aphid regulatory issues. Here the subject of aphids as they relate to disease transmission, biology, identification, and pathways is addressed. Aphid topi...

  10. a Study of Positron Electron Going to Positive Pion Negative Pion Neutral Pion Neutral Pion at 3.090 GEV Center of Mass Energy

    NASA Astrophysics Data System (ADS)

    McGowan, John Francis, III

    The process e^+e^-to pi^+pi^-pi^0pi ^0 is studied at a center of mass energy of 3.090 GeV, the J/psi center of mass energy, by the Mark III detector at SPEAR. The branching ratios for psitopi^+pi ^-pi^0pi^0 and several background processes are measured: psi topi^+pi^-pi^0 pi^0pi^0, psi to K^+/- K^mppi^0 pi^0, and psito K^+/-pi^mppi^0 pi^0. Upper limits on e^+e ^-torho^+rho^- are derived. Evidence is presented that the isobar model of low-energy hadronic interactions may not apply to e ^+e^-topi^+pi^ -pi^0pi^0. Suggestions for further research are made.

  11. A transient overpower experiment in EBR-II

    SciTech Connect

    Herzog, J.P.; Tsai, H.; Dean, E.M.; Aoyama, T.; Yamamoto, K.

    1994-03-01

    The TOPI-IE test was a transient overpower test on irradiate mixed-oxide fuel pins in the Experimental Breeder Reactor-II (EBR-II). The test, the fifth in a series, was part of a cooperative program between the US Department of Energy and the Power Reactor and Nuclear Fuel Development Corporation of Japan to conduct operational transient testing on mixed-oxide fuel pins in the metal-fueled EBR-II. The principle objective of the TOPI-1E test was to assess breaching margins for irradiated mixed-oxide fuel pins over the Plant Protection System (PPS) thresholds during a slow, extended overpower transient. This paper describes the effect of the TOPI-1E experiment on reactor components and the impact of the experiment on the long-term operability of the reactor. The paper discusses the role that SASSYS played in the pre-test safety analysis of the experiment. The ability of SASSYS to model transient overpower events is detailed by comparisons of data from the experiment with computed reactor variables from a SASSYS post-test simulation of the experiment.

  12. Rainfall influences on ungulate population abundance in the Mara-Serengeti ecosystem.

    PubMed

    Ogutu, J O; Piepho, H-P; Dublin, H T; Bhola, N; Reid, R S

    2008-07-01

    1. Rainfall is the prime climatic factor underpinning the dynamics of African savanna ungulates, but no study has analysed its influence on the abundance of these ungulates at monthly to multiannual time scales. 2. We report relationships between rainfall and changes in age- and sex-structured abundances of seven ungulate species monitored monthly for 15 years using vehicle ground counts in the Maasai Mara National Reserve, Kenya. 3. Abundance showed strong and curvilinear relationships with current and cumulative rainfall, with older topi, Damaliscus korrigum (Ogilby); warthog, Phacochoerus aethiopicus (Pallas); waterbuck, Kobus ellipsyprimnus (Ogilby); and impala, Aepyceros melampus (Lichtenstein) responding to longer lags than younger animals, portraying carryover effects of prior habitat conditions. 4. The abundances of newborn calves were best correlated with monthly rainfall averaged over the preceding 5-6 months for topi, waterbuck, warthog, and 2 months for the migratory zebra Equus burchelli (Gray), but with seasonal rainfall averaged over 2-5 years for giraffe, Giraffa camelopardalis (L.); impala; and kongoni, Alcelaphus busephalus (Pallas). The cumulative late wet-season rainfall was the best predictor of abundance for quarter- to full-grown animals for most species. Monthly rainfall exerted both negative and positive effects on the abundances of zebra, impala and waterbuck. Ignoring age, both sexes responded similarly to rainfall. 5. Births were strongly seasonal only for warthog and topi, but peaked between August and December for most species. Hence abundance was strongly seasonal for young topi and warthog and the migratory zebra. Pronounced seasonality in births for warthog and topi obliterated otherwise strong relationships between abundance and rainfall when both month and rainfall were included in the same model. Aggregated density produced relationships with rainfall similar to those for fully grown animals, emphasizing the necessity of

  13. Geothermal power development in Hawaii. Volume I. Review and analysis

    SciTech Connect

    Not Available

    1982-06-01

    The history of geothermal exploration in Hawaii is reviewed briefly. The nature and occurrences of geothermal resources are presented island by island. An overview of geothermal markets is presented. Other topies covered are: potential markets of the identified geothermal areas, well drilling technology, hydrothermal fluid transport, overland and submarine electrical transmission, community aspects of geothermal development, legal and policy issues associated with mineral and land ownership, logistics and infrastructure, legislation and permitting, land use controls, Regulation 8, Public Utilities Commission, political climate and environment, state plans, county plans, geothermal development risks, and business planning guidelines.

  14. A novel secondary structure based on fused five-membered rings motif

    PubMed Central

    Dhar, Jesmita; Kishore, Raghuvansh; Chakrabarti, Pinak

    2016-01-01

    An analysis of protein structures indicates the existence of a novel, fused five-membered rings motif, comprising of two residues (i and i + 1), stabilized by interresidue Ni+1–H∙∙∙Ni and intraresidue Ni+1–H∙∙∙O=Ci+1 hydrogen bonds. Fused-rings geometry is the common thread running through many commonly occurring motifs, such as β-turn, β-bulge, Asx-turn, Ser/Thr-turn, Schellman motif, and points to its structural robustness. A location close to the beginning of a β-strand is rather common for the motif. Devoid of side chain, Gly seems to be a key player in this motif, occurring at i, for which the backbone torsion angles cluster at ~(−90°, −10°) and (70°, 20°). The fused-rings structures, distant from each other in sequence, can hydrogen bond with each other, and the two segments aligned to each other in a parallel fashion, give rise to a novel secondary structure, topi, which is quite common in proteins, distinct from two major secondary structures, α-helix and β-sheet. Majority of the peptide segments making topi are identified as aggregation-prone and the residues tend to be conserved among homologous proteins. PMID:27511362

  15. Should anthropology be part of cognitive science?

    PubMed

    Beller, Sieghard; Bender, Andrea; Medin, Douglas L

    2012-07-01

    Anthropology and the other cognitive science (CS) subdisciplines currently maintain a troubled relationship. With a debate in topiCS we aim at exploring the prospects for improving this relationship, and our introduction is intended as a catalyst for this debate. In order to encourage a frank sharing of perspectives, our comments will be deliberately provocative. Several challenges for a successful rapprochement are identified, encompassing the diverging paths that CS and anthropology have taken in the past, the degree of compatibility between (1) CS and (2) anthropology with regard to methodology and (3) research strategies, (4) the importance of anthropology for CS, and (5) the need for disciplinary diversity. Given this set of challenges, a reconciliation seems unlikely to follow on the heels of good intentions alone. PMID:22685087

  16. Trans-orbital orbitocranial penetrating injury by pointed iron rod

    PubMed Central

    Tewari, Vinod Kumar; Dubey, Ram Shringar; Dubey, Gyan Chand

    2015-01-01

    Trans-orbital orbitocranial penetrating injury (TOPI) by a foreign body is an extremely rare compound head injury having a potential to cause major morbidity and mortality. Preoperative radiological imaging by CT scan is very important for operative guidance, but in remote area where CT scan is not available, the patient is generally referred to tertiary level. Here we present a case which was dealt successfully without CT scan, only on the basis of stable clinical status and X-rays. We present a case of a 35-year-old man who had an accidental injury (fall from height) by rod. Immediate X-ray (anteroposterior and lateral views) revealed that the pointed end of the foreign body (rod) was inside the ipsilateral anterior fossa via basifrontal bone up to frontal vertex, not crossing the midline. CT scan was not available and his vitals with GCS were normal (15/15). He was operated with the help of an ophthalmic surgeon by right frontotemporal craniotomy. The patient was discharged on 10th day without any neurological deficit except restricted right eyeball movement to superolateral and ptosis. The restricted eyeball movements recovered after third month of follow up with remnant ptosis for 2 years. This case highlights an unusual case, direct visualization and repair of brain structures with higher antibiotics can save the life even in remote areas where CT scan is still not available only on the basis of stable GCS and X-rays. PMID:25883487

  17. Game over! Wildlife collapse in northern Central African Republic.

    PubMed

    Bouché, Philippe; Nzapa Mbeti Mange, Roland; Tankalet, Floride; Zowoya, Florent; Lejeune, Philippe; Vermeulen, Cédric

    2012-11-01

    The wildlife populations of northern Central African Republic (CAR) have long suffered intense uncontrolled hunting. Socio-political turmoil in northern CAR that started in 2002 resulted in a rebellion in 2006. An aerial sample count was carried out in northern CAR after the ceasefire to assess the impact of this troubled period on wildlife. The survey was flown at the end of the dry season in February-March 2010. It covered a landscape complex of 95,000 km² comprising national parks, hunting reserves and community hunting areas. Comparison with earlier surveys revealed a dramatic decline of wildlife: the numbers of large mammals fell by 94% in 30 years, probably due to poaching, loss of habitat and diseases brought by illegal movements of cattle. Elephant (Loxodonta africana), Reduncinae and topi (Damaliscus lunatus) populations showed the greatest decline (each over 90%). Other species declined by 70-80% during the same period. The future of wildlife in this area is dark without a strong commitment to provide adequate funding and quickly implement of determined field management. Reinforced cooperation with neighbouring Chad and Sudan is required since they are facing similar problems. PMID:22170159

  18. Improving the Care of Patients with Chronic Kidney Disease Using Group Visits: A Pilot Study to Reflect an Emphasis on the Patients Rather Than the Disease.

    PubMed

    Montoya, Vicki; Sole, Mary Lou; Norris, Anne E

    2016-01-01

    This two-group, repeated-measures experimental study assessed the efficacy of a nurse practitioner-facilitated chronic kidney disease (CKD) group visit (GV) model versus usual nephrology care for patients with Stage 4 CKD. The study enrolled patients from two sites of an outpatient nephrology practice (n = 30) and randomized subjects to usual care (n = 14) or to the GV model (n = 16). Data regarding CKD knowledge, self-efficacy/disease self-management, and physiologic measures were collected at baseline, 6 months, and 9 months. Satisfaction was obtained at 6 months and 9 months. Usual nephrology office visit components were maintained during six monthly GVs, with group discussions of CKD-related topies. Results indicated a statistical improvement in CKD knowledge for both groups (F[1.498, 34.446] = 6.363, p = 0.008). An upward trend in mean scores for self-management subscales and self-efficacy scores was demonstrated in the GV patients, with no improvement found in the usual care group. Twenty-six of 30 patients completed the study, with 92% attendance in the GV group. GV satisfaction was high. PMID:27501629

  19. Antibodies to some pathogenic agents in free-living wild species in Tanzania.

    PubMed

    Hamblin, C; Anderson, E C; Jago, M; Mlengeya, T; Hipji, K

    1990-12-01

    A total of 535 sera from eight species of wildlife were collected from different game areas in Tanzania between 1987 and 1989. These sera were tested for antibodies against foot-and-mouth disease, bovine herpes virus types 1 and 2, lumpy skin disease, bovine viral diarrhoea, Akabane, bovine ephemeral fever, bluetongue, enzootic bovine leucosis, African horse sickness and African swine fever viruses and Brucella abortus based on the expected species susceptibility. Sera from buffalo Syncerus caffer, wildebeest Connochaetes taurinus and topi Damaliscus korrigum contained antibodies against the majority of the pathogens tested. Antibodies to fewer pathogens were detected in sera from the other species. No antibodies to lumpy skin disease virus were detected in any of the sera examined. African horse sickness antibodies were detected in sera from Zebra and African swine fever antibodies were detected in wart hog. The occurrence of antibodies to these agents suggests that wild species act as reservoirs of infection for some of these pathogens. However, until the susceptibility of individual species is proven by isolation of the aetiological agents their role must remain speculative. PMID:2123458

  20. Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

    NASA Astrophysics Data System (ADS)

    Kohn, Matthew J.; Schoeninger, Margaret J.; Valley, John W.

    1996-10-01

    The applicability of rapid and precise laser probe analysis of tooth enamel for δ18O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 μm, and elimination of adsorbed water and organic compounds with BrF 5. Typical analytical reproducibilities for 0.5-2 mg samples are ±0.08‰ (± 1σ). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF 2 with little evidence for residual O 2. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel (>95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel δ18O values (V-SMOW) are approximately: 25‰ (goat), 27‰ (oryx), 28‰ (dikdik and zebra), 29‰ (topi), 30‰ (gerenuk), and 32‰ (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover, and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies.

  1. Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

    SciTech Connect

    Kohn, M.J.; Valley, J.W.; Schoeninger, M.J.

    1996-10-01

    The applicability of rapid and precise laser probe analysis of tooth enamel for {delta}{sup 18}O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 {mu}m, and elimination of adsorbed water and organic compounds with BrF{sub 5}. Typical analytical reproducibilities for 0.5-2 mg samples are {+-}0.08{per_thousand} ({+-} 1{sigma}). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF{sub 2} with little evidence for residual O{sub 2}. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel ( >95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel {delta}{sup 18}O values (V-SMOW) are approximately: 25{per_thousand} (goat). 27{per_thousand} (oryx), 28{per_thousand} (dikdik and zebra), 29{per_thousand} (topi), 30{per_thousand} (gerenuk), and 32{per_thousand} (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover. and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies. 66 refs., 2 figs., 2 tabs.

  2. Hydatid disease in the Turkana District of Kenya. III. The significance of wild animals in the transmission of Echinococcus granulosus, with particular reference to Turkana and Masailand in Kenya.

    PubMed

    MacPherson, C N; Karstad, L; Stevenson, P; Arundel, J H

    1983-02-01

    The results are given of a study on the role of wildlife in the transmission of Echinococcus granulosus in the Turkana and Narok Districts of Kenya. A total of 76 wild carnivores belonging to three separate species was examined from Turkana District. Echinococcus adults were found in 11 of 38 silver-backed jackals (Canis mesomelas) and in six of 22 golden jackals (Canis aureus). This is the first record of golden jackals being infected with this parasite in Kenya. None of 16 spotted hyaenas (Crocuta crocuta) harboured the parasite. Morphological features of the parasites obtained from the jackals were compared with material obtained from dogs in the same area. No morphological differences were recorded when this material was compared with data reported by others, hence the Turkana material belonged to the single species E. granulosus. Three silver-backed jackals and three puppies (Canis familiaris) were successfully infected with protoscolices obtained from a hydatid cyst surgically removed from a Turkana patient. Three spotted hyaenas fed the same material failed to become infected. None of 152 wild herbivores of five species examined in Turkana harboured hydatid cysts. The natural jackal infections in this District are thought to be incidental and dependent on the continuance of the domestic cycle. The role of the Turkana themselves in the perpetuation of the cycle is discussed. Twenty-six wild herbivores of six species were examined for hydatid cysts, in Narok District; hydatids were found in three wildebeest (Connochaetes taurinus) and a single topi (Damaliscus korrigum). The discovery of fertile cysts in wildebeest and the reported infections in lions (Panthera leo), Cape hunting dogs (Lycaon pictus) and silver-backed jackals, support previous evidence of the existence of a wildlife cycle in the Masailand and Serengeti regions of East Africa. The relationship of this cycle to the domestic cycle operating in the same area is unclear and requires further

  3. How Rainfall Variation Influences Reproductive Patterns of African Savanna Ungulates in an Equatorial Region Where Photoperiod Variation Is Absent.

    PubMed

    Ogutu, Joseph O; Owen-Smith, Norman; Piepho, Hans-Peter; Dublin, Holly T

    2015-01-01

    In high temperate latitudes, ungulates generally give birth within a narrow time window when conditions are optimal for offspring survival in spring or early summer, and use changing photoperiod to time conceptions so as to anticipate these conditions. However, in low tropical latitudes day length variation is minimal, and rainfall variation makes the seasonal cycle less predictable. Nevertheless, several ungulate species retain narrow birth peaks under such conditions, while others show births spread quite widely through the year. We investigated how within-year and between-year variation in rainfall influenced the reproductive timing of four ungulate species showing these contrasting patterns in the Masai Mara region of Kenya. All four species exhibited birth peaks during the putative optimal period in the early wet season. For hartebeest and impala, the birth peak was diffuse and offspring were born throughout the year. In contrast, topi and warthog showed a narrow seasonal concentration of births, with conceptions suppressed once monthly rainfall fell below a threshold level. High rainfall in the previous season and high early rains in the current year enhanced survival into the juvenile stage for all the species except impala. Our findings reveal how rainfall variation affecting grass growth and hence herbivore nutrition can govern the reproductive phenology of ungulates in tropical latitudes where day length variation is minimal. The underlying mechanism seems to be the suppression of conceptions once nutritional gains become insufficient. Through responding proximally to within-year variation in rainfall, tropical savanna ungulates are less likely to be affected adversely by the consequences of global warming for vegetation phenology than northern ungulates showing more rigid photoperiodic control over reproductive timing. PMID:26295154

  4. How Rainfall Variation Influences Reproductive Patterns of African Savanna Ungulates in an Equatorial Region Where Photoperiod Variation Is Absent

    PubMed Central

    Ogutu, Joseph O.; Owen-Smith, Norman; Piepho, Hans-Peter; Dublin, Holly T.

    2015-01-01

    In high temperate latitudes, ungulates generally give birth within a narrow time window when conditions are optimal for offspring survival in spring or early summer, and use changing photoperiod to time conceptions so as to anticipate these conditions. However, in low tropical latitudes day length variation is minimal, and rainfall variation makes the seasonal cycle less predictable. Nevertheless, several ungulate species retain narrow birth peaks under such conditions, while others show births spread quite widely through the year. We investigated how within-year and between-year variation in rainfall influenced the reproductive timing of four ungulate species showing these contrasting patterns in the Masai Mara region of Kenya. All four species exhibited birth peaks during the putative optimal period in the early wet season. For hartebeest and impala, the birth peak was diffuse and offspring were born throughout the year. In contrast, topi and warthog showed a narrow seasonal concentration of births, with conceptions suppressed once monthly rainfall fell below a threshold level. High rainfall in the previous season and high early rains in the current year enhanced survival into the juvenile stage for all the species except impala. Our findings reveal how rainfall variation affecting grass growth and hence herbivore nutrition can govern the reproductive phenology of ungulates in tropical latitudes where day length variation is minimal. The underlying mechanism seems to be the suppression of conceptions once nutritional gains become insufficient. Through responding proximally to within-year variation in rainfall, tropical savanna ungulates are less likely to be affected adversely by the consequences of global warming for vegetation phenology than northern ungulates showing more rigid photoperiodic control over reproductive timing. PMID:26295154

  5. Body size and the division of niche space: food and predation differentially shape the distribution of Serengeti grazers.

    PubMed

    Hopcraft, J Grant C; Anderson, T Michael; Pérez-Vila, Saleta; Mayemba, Emilian; Olff, Han

    2012-01-01

    1. Theory predicts that small grazers are regulated by the digestive quality of grass, while large grazers extract sufficient nutrients from low-quality forage and are regulated by its abundance instead. In addition, predation potentially affects populations of small grazers more than large grazers, because predators have difficulty capturing and handling large prey. 2. We analyse the spatial distribution of five grazer species of different body size in relation to gradients of food availability and predation risk. Specifically, we investigate how the quality of grass, the abundance of grass biomass and the associated risks of predation affect the habitat use of small, intermediate and large savanna grazers at a landscape level. 3. Resource selection functions of five mammalian grazer species surveyed over a 21-year period in Serengeti are calculated using logistic regressions. Variables included in the analyses are grass nitrogen, rainfall, topographic wetness index, woody cover, drainage lines, landscape curvature, water and human habitation. Structural equation modelling (SEM) is used to aggregate predictor variables into 'composites' representing food quality, food abundance and predation risk. Subsequently, SEM is used to investigate species' habitat use, defined as their recurrence in 5 × 5 km cells across repeated censuses. 4. The distribution of small grazers is constrained by predation and food quality, whereas the distribution of large grazers is relatively unconstrained. The distribution of the largest grazer (African buffalo) is primarily associated with forage abundance but not predation risk, while the distributions of the smallest grazers (Thomson's gazelle and Grant's gazelle) are associated with high grass quality and negatively with the risk of predation. The distributions of intermediate sized grazers (Coke's hartebeest and topi) suggest they optimize access to grass biomass of sufficient quality in relatively predator-safe areas. 5. The results

  6. Nutritional studies on East African herbivores. 2. Losses of nitrogen in the faeces.

    PubMed

    Arman, P; Hopcraft, D; McDonald, I

    1975-03-01

    taurinus Burchell), to 8-4 for for the other ruminants (sheep, goat, hartebeest, gazelle, duiker, buffalo (Syncerus caffer Sparrman)), kob (Adenota kob thomasi Sclater), reedbuck (Redunca redunca Pallas) and topi (Damalisucs korrigum Ogilby). For ruminants (sheep, hartebeest, duiker and kob), excluding eland, given legumes the value was 8-6, and for sheep and duiker given herbs the value was 14-7. With shrubs, faecal-N losses were variable and sometimes high. 7. With the pelleted diets, true digestibilities of crude protein (N times 6-25) varied from 0-84 to 0-91. 8. The results are discussed in relation to the digestive physiology and feeding habits of the various species, and there is an examination of the feasibility of using linear regressions of crude protein in the diet v. N in the faecal DM for evaluating the quality of the diets selected by free-ranging East African herbivores. PMID:1115763