7,014 research outputs found

    Assessment of Smallholder Farmers’ Adaptive Strategies on the Effects of Seasonal Rainfall Variability on Maize Yields in Nyeri County

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    Maize is the leading food crop produced in most parts of the world and a staple food crop in Kenya. Majority of the maize farmers are smallholders due to reduced land sizes as a result of land fragmentation. Maize farming is rain-fed making it more vulnerable to rainfall variability. Over the years, the farmers have increased their resilience and adaptive potential through indigenous knowledge so as to cope with the climate related risks. However, the increasing rainfall variability, frequency and more severe shocks likely surpass their current adaptive strategies. The study assessed existing adaptive strategies of the small-holder maize farmers in Kieni East sub-County in Nyeri Couny to the seasonal rainfall variability effects. The research adopted a mixed research design. Data was obtained from primary and secondary sources. Primary data was obtained using household structured questionnaires. Data was analyzed using descriptive methods and presented using charts and tables. SWOT analysis analyzed several underlying aspects affecting maize farmers in the sub-County. The study found that the farmers have several specific adaptive strategies to the effects of seasonal rainfall variability at their disposal which include but not limited to the use of varieties of maize seeds, seeking training, water harvesting, use of manure and fertilizers. Farmers also respond to rainfall variability by planting maize varieties that are early maturing and drought resistant as well as engaging in alternative farming activities and other economic activities

    Temperature and Precipitation Affect Seasonal Patterns of Dispersing Tobacco Thrips, Frankliniella fusca, and Onion Thrips, Thrips tabaci (Thysanoptera: Thripidae) Caught on Sticky Traps

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    Effects of temperature and precipitation on the temporal patterns of dispersing tobacco thrips, Frankliniella fusca, and onion thrips, Thrips tabaci, caught on yellow sticky traps were estimated in central and eastern North Carolina and eastern Virginia from 1997 through 2001. The impact that these environmental factors had on numbers of F. fusca and T. tabaci caught on sticky traps during April and May was determined using stepwise regression analysis of 43 and 38 site-years of aerial trapping data from 21 and 18 different field locations, respectively. The independent variables used in the regression models included degree-days, total precipitation, and the number of days in which precipitation occurred during January through May. Each variable was significant in explaining variation for both thrips species and, in all models, degree-days was the single best explanatory variable. Precipitation had a comparatively greater effect on T. tabaci than F. fusca. The numbers of F. fusca and T. tabaci captured in flight were positively related to degree-days and the number of days with precipitation but negatively related to total precipitation. Combined in a single model, degree-days, total precipitation, and the number of days with precipitation explained 70 and 55% of the total variation in the number of F. fusca captured from 1 April through 10 May and from 1 April through 31 May, respectively. Regarding T. tabaci flights, degree-days, total precipitation, and the number of days with precipitation collectively explained 57 and 63% of the total variation in the number captured from 1 April through 10 May and from 1 April through 31 May, respectivel

    Aminostratigraphy and Oxygen Isotope Stratigraphy of Marine Terrace Deposits Palos Verdes Hills and San Pedro Areas Los Angeles County California

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    Amino acid and oxygen isotope data for fossils from terraces of the Palos Verdes Hills and San Pedro areas in Los Angeles County California shed new light on the ages of terraces sea level history marine paleotemperatures and late Quaternary tectonics in this region Low terraces on the Palos Verdes peninsula correlate with the 80 ka and 125 ka sea level highstands that are also recorded as terraces on other coasts In San Pedro the Palos Verdes sand the deposit on what is mapped as the first terrace by Woodring and others 1946 was previously thought to be a single deposit amino acid oxygen isotope V series and faunal data indicate that deposits of two ages representing the 80 ka and l25 ka high stands occur within this unit Oxygen isotope data show that on open exposed parts of the Palos Verdes peninsula ocean waters during the l25 ka highstand were cooler than present by about 2 3 2 60C similar to what has been reported for other exposed coastal areas in California In contrast in the protected embayment environment around San Pedro water temperatures during the 125 ka highstand were as warm or warmerthan present During the 80 ka highstand water temperatures were significantly cooler than present even in the relatively protected embayment environment of the San Pedro area Late Quaternary tectonic uplift rates can be calculated from terrace ages and elevations Correlation of the lowest terraces around the Point Fermin area shows that the Cabrillo fault has a late Quaternary vertical movement rate of 0 20 m ka based on the difference in uplift rates on the upthrown and downthrown sides of the fault Elsewhere in the Palos Verdes Hills San Pedro area late Quaternary uplift rates vary from 0 32 m ka to possibly as high as 0 72 m ka These rates which reflect vertical movement on the Palos Verdes fault are in broad agreement with estimated Holocene vertical rates of movement determined for offshore portions of the faul

    Resolved Debris Discs Around A Stars in the Herschel DEBRIS Survey

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    The majority of debris discs discovered so far have only been detected through infrared excess emission above stellar photospheres. While disc properties can be inferred from unresolved photometry alone under various assumptions for the physical properties of dust grains, there is a degeneracy between disc radius and dust temperature that depends on the grain size distribution and optical properties. By resolving the disc we can measure the actual location of the dust. The launch of Herschel, with an angular resolution superior to previous far-infrared telescopes, allows us to spatially resolve more discs and locate the dust directly. Here we present the nine resolved discs around A stars between 20 and 40 pc observed by the DEBRIS survey. We use these data to investigate the disc radii by fitting narrow ring models to images at 70, 100 and 160 {\mu}m and by fitting blackbodies to full spectral energy distributions. We do this with the aim of finding an improved way of estimating disc radii for unresolved systems. The ratio between the resolved and blackbody radii varies between 1 and 2.5. This ratio is inversely correlated with luminosity and any remaining discrepancies are most likely explained by differences to the minimum size of grain in the size distribution or differences in composition. We find that three of the systems are well fit by a narrow ring, two systems are borderline cases and the other four likely require wider or multiple rings to fully explain the observations, reflecting the diversity of planetary systems.Comment: 19 pages, 13 figures, 6 tables. Accepted for publication in MNRA

    The incidence of deep vein thrombosis detected by routine surveillance ultrasound in neurosurgery patients receiving dual modality prophylaxis.

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    The optimal method of thromboprophylaxis and the value of screening ultrasonography for detection of deep venous thrombosis (DVT) in neurosurgery patients remains unclear. The goal of this study was to determine the incidence of DVT in neurosurgical patients who, by hospital protocol, receive surveillance ultrasonography of the lower extremities twice weekly, in addition to prophylaxis with unfractionated heparin and external pneumatic compression sleeves. A retrospective review of 7,298 ultrasound studies carried out on 2,593 patients over 4 years at a university neurosurgical hospital was conducted. There was a 7.4% incidence of proximal lower extremity DVT and a 9.7% total incidence including distal DVT. A greater number of distal DVTs were detected with the implementation of whole-leg ultrasonography in the last 2 years of observation. Chart review of 237 patients diagnosed with DVT demonstrated an admitting diagnosis of subarachnoid hemorrhage in nearly half of the patients. The median hospital length of stay for DVT patients was 18 days. Institutional control data demonstrated non-ruptured aneurysm and cerebrovascular anomalies to be the leading reason for admission, followed closely by subarachnoid hemorrhage. The hospital protocol of biweekly screening ultrasound and dual modality prophylaxis for neurosurgery patients resulted in a proximal DVT incidence consistent with that demonstrated by previous studies of standardized dual modality prophylaxis, and higher than that demonstrated in previous studies that employed ultrasound screening protocols

    Reproductive Modes in Onion Thrips (Thysanoptera: Thripidae) Populations from New York Onion Fields

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    Thrips exhibit different reproductive modes including thelytoky (females produced from unfertilized eggs), arrhenotoky (males produced from unfertilized eggs and females produced from fertilized eggs) and deuterotoky (females and males produced from unfertilized eggs). We investigated patterns of reproductive modes in onion thrips, Thrips tabaci Lindeman, populations and potential effects of the bacterium Wolbachia and temperature on these modes. We also examined the possibility that male-producing T. tabaci populations were resistant to the frequently used insecticides, lambda-cyhalothrin and methomyl. In New York during 2002-2004, T. tabaci populations were sampled from 20 onion fields and reproductive mode was determined by identifying sex of progeny from virgins. Half of the populations were thelytokous and half were a mix of thelytokous, arrhenotokous and deuterotokous individuals, which we refer to as a male-producing population. In two of four cases, the reproductive mode of a population from the same onion field changed across years, suggesting that populations either mix or an external factor caused the change. To address the latter, we speculated that Wolbachia or high temperature mediated reproductive modes. Samples of T. tabaci representing each reproductive mode were examined for Wolbachia using diagnostic polymerase chain reaction (PCR), but it was not detected. Cytological examination of ovaries from two additional thelytokous lines also showed no evidence of Wolbachia. Similarly, high temperature did not affect sex allocation ratios in either thelytokous or male-producing populations. Male-producing T. tabaci populations were not positively correlated with resistance to lambda-cyhalothrin, or tolerance to methomyl. The role of the different reproductive modes in T. tabaci populations in onion fields remains unclea

    The debris disk around gamma Doradus resolved with Herschel

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    We present observations of the debris disk around gamma Doradus, an F1V star, from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free Reconnaissance in the Infrared/Submillimetre). The disk is well-resolved at 70, 100 and 160 micron, resolved along its major axis at 250 micron, detected but not resolved at 350 micron, and confused with a background source at 500 micron. It is one of our best resolved targets and we find it to have a radially broad dust distribution. The modelling of the resolved images cannot distinguish between two configurations: an arrangement of a warm inner ring at several AU (best-fit 4 AU) and a cool outer belt extending from ~55 to 400 AU or an arrangement of two cool, narrow rings at ~70 AU and ~190 AU. This suggests that any configuration between these two is also possible. Both models have a total fractional luminosity of ~10^{-5} and are consistent with the disk being aligned with the stellar equator. The inner edge of either possible configuration suggests that the most likely region to find planets in this system would be within ~55 AU of the star. A transient event is not needed to explain the warm dust's fractional luminosity.Comment: 12 pages, 6 figures, accepted for publication in Ap
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