The abundance of an invasive freshwater snail Tarebia granifera (Lamarck, 1822) in the Nseleni River, South Africa

The invasive freshwater snail Tarebia granifera (Lamarck, 1822) was first reported in South Africa in 1999 and it has become widespread across the country, with some evidence to suggest that it reduces benthic macroinvertebrate biodiversity. The current study aimed to identify the primary abiotic drivers behind abundance patterns of T. granifera, by comparing the current abundance of the snail in three different regions, and at three depths, of the highly modified Nseleni River in KwaZulu-Natal, South Africa. Tarebia granifera was well established throughout the Nseleni River system, with an overall preference for shallow waters and seasonal temporal patterns of abundance. Although it is uncertain what the ecological impacts of the snail in this system are, its high abundances suggest that it should be controlled where possible and prevented from invading other systems in the region

PHOTOSYNTHETIC – FERMENTATIVE FUEL CELL USED IN A BIOFUEL PROCESSING FACILITY

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Catch-can performance under a line-source sprinkler

A line-source sprinkler configuration provides a linearly decreasing irrigation application rate perpendicular to the sprinkler line and has been utilized to study crop response to variable irrigation amounts. The effect on measured irrigation application depths from using various types of catch-cans in those studies is not known. Derived relationships between crop yield and applied water is dependent on the accuracy of measured catch-can water volumes. The purpose of this study was to evaluate catch-can characteristic effects on measurement of sprinkler irrigation depths in a line source. This was accomplished by evaluating six types of catch-cans: (1) 83 mm diameter polypropylene separatory funnel (with evaporation-suppressing oil), (2) 82 mm diameter PVC reducer can (with evaporation-suppressing oil), (3) 151 mm diameter metal can, (4)64 x 59 mm wedge rain gauge, (5) 146 mm white plastic bucket, and (6) 100 mm diameter clear plastic funnel rain gauge. The cans were placed at five application rate conditions (2.8, 5.5, 8.7, 12.6, and 14.8 mm/h). Cumulative catch depths differed among the catch-can types. However, only the metal can and white bucket cumulative application depths at the lowest application rate were statistically different from those of the control (separatory funnel). Catch-cans with a larger diameter opening exhibited less variation in catch depths. Measured evaporation of standing water from catch-cans varied from 0.04 mm/h (funnel rain gauge) to 1.81 mm/h (separatory funnel without evaporation-suppressing oil). Water applied to a bucket's sidewall evaporated at a higher rate than standing water. Inaccuracy of application depth measurement may occur at low application rates even when catch-cans meet the ASAE Standard. The relatively good performance of the funnel rain gauge and catch-cans with evaporation-suppressing oil (and subsequently less depth than the ASAE Standard requires) suggests that it may be appropriate to re-evaluate the standard to consider such devices

Field-induced thermal metal-to-insulator transition in underdoped LSCO

The transport of heat and charge in cuprates was measured in undoped and heavily-underdoped single crystal La_{2-x}Sr_xCuO_{4+delta} (LSCO). In underdoped LSCO, the thermal conductivity is found to decrease with increasing magnetic field in the T --> 0 limit, in striking contrast to the increase observed in all superconductors, including cuprates at higher doping. The suppression of superconductivity with magnetic field shows that a novel thermal metal-to-insulator transition occurs upon going from the superconducting state to the field-induced normal state.Comment: 2 pages, 2 figures, submitted to M2S-Rio 2003 Proceeding

Dimethylsulfoniopropionate in corals and its interrelations with bacterial assemblages in coral surface mucus

Corals produce copious amounts of dimethylsulfoniopropionate (DMSP), a sulfur compound thought toplay a role in structuring coral-associated bacterial communities. We tested the hypothesis that a linkage exists betweenDMSP availability in coral tissues and the community dynamics of bacteria in coral surface mucus. We determinedDMSP concentrations in three coral species (Meandrina meandrites, Porites astreoides and Siderastrea siderea) at twosampling depths (5 and 25 m) and times of day (dawn and noon) at Curac¸ao, Southern Caribbean. DMSP concentration(4–409 nmol cm?2 coral surface) varied with host species-specific traits such as Symbiodinium cell abundance, but notwith depth or time of sampling. Exposure of corals to air caused a doubling of their DMSPconcentration. The phylogeneticaffiliation of mucus-associated bacteria was examined by clone libraries targeting three main subclades of the bacterialDMSP demethylase gene (dmdA). dmdA gene abundance was determined by quantitative Polymerase Chain Reaction(qPCR) against a reference housekeeping gene (recA). Overall, a higher availability of DMSP corresponded to a lowerrelative abundance of the dmdA gene, but this pattern was not uniform across all host species or bacterial dmdA subclades,suggesting the existence of distinct DMSP microbial niches or varying dmdA DMSP affinities. This is the first studyquantifying dmdA gene abundance in corals and linking related changes in the community dynamics of DMSP-degradingbacteria to DMSP availability. Our study suggests that DMSP mediates the regulation of microbe

Multiband superconductivity in NbSe_2 from heat transport

The thermal conductivity of the layered s-wave superconductor NbSe_2 was measured down to T_c/100 throughout the vortex state. With increasing field, we identify two regimes: one with localized states at fields very near H_c1 and one with highly delocalized quasiparticle excitations at higher fields. The two associated length scales are most naturally explained as multi-band superconductivity, with distinct small and large superconducting gaps on different sheets of the Fermi surface.Comment: 2 pages, 2 figures, submitted to M2S-Rio 2003 Proceeding

No Evidence Supporting Flare Driven High-Frequency Global Oscillations

The underlying physics that generates the excitations in the global low-frequency, < 5.3 mHz, solar acoustic power spectrum is a well known process that is attributed to solar convection; However, a definitive explanation as to what causes excitations in the high-frequency regime, > 5.3 mHz, has yet to be found. Karoff and Kjeldsen (Astrophys. J. 678, 73-76, 2008) concluded that there is a correlation between solar flares and the global high-frequency solar acoustic waves. We have used the Global Oscillations Network Group (GONG) helioseismic data in an attempt to verify Karoff and Kjeldsen (2008) results as well as compare the post-flare acoustic power spectrum to the pre-flare acoustic power spectrum for 31 solar flares. Among the 31 flares analyzed, we observe that a decrease in acoustic power after the solar flare is just as likely as an increase. Furthermore, while we do observe variations in acoustic power that are most likely associated with the usual p-modes associated with solar convection, these variations do not show any significant temporal association with flares. We find no evidence that consistently supports flare driven high-frequency waves.Comment: 20 pages, 9 figures, Accepted for publication in Solar Physic

Doping dependence of superconducting gap in YBa_2Cu_3O_y from universal heat transport

Thermal transport in the T -> 0 limit was measured as a function of doping in high-quality single crystals of the cuprate superconductor YBa_2Cu_3O_y. The residual linear term kappa_0/T is found to decrease as one moves from the overdoped regime towards the Mott insulator region of the phase diagram. The doping dependence of the low-energy quasiparticle gap extracted from kappa_0/T is seen to scale closely with that of the pseudogap, arguing against a non-superconducting origin for the pseudogap. The presence of a linear term for all dopings is evidence against the existence of a quantum phase transition to an order parameter with a complex (ix) component.Comment: 2 pages, 2 figures, submitted to M2S-Rio 2003 Proceeding

Irrigation Management -- Water Requirements and Water Balance

This paper seeks to discuss irrigation water requirement estimates in the light of current practice, important developments during the 1970's, significant research and future research and applications of that research. Each of these are elaborated in more detail in the text of this paper. A major addition to the science and art of estimating irrigation water requirements has been to replace the often ambiguous "potential evapotranspiration" with "reference crop evapotranspiration". In the past decade a series of experiments relating irrigation water applications to crop yield now permit a much better economic analysis of the use of water for irrigation. The estimation of monthly irrigation water requirements was facilitated, particularly for varying climatic conditions with the United Nations publication "Crop Water Requirements" by Doorenbos and Pruitt (1977). Estimation of daily water requirements for purposes of irrigation scheduling has been refined by the development of an albedo model and a wind function for the Penman method, that is variable throughout the season, Wright (1981). Several western states are experiencing lawsuits or other legal deliberations involving seasonal irrigation water requirements because of conflicts between groups of water users or water right transfers from agriculture to industry or municipal use. Irrigation scheduling continues to be refined from the standpoints of predicting ET, verifying yield conditions and other factors like production and peak pumping power reduction. Future research probably will include emphasis on breeding crops that require less water, refinements on the relationships between yields and water consumption, refinements in methods of estimating irrigation water requirements, and the development of irrigation schemes that minimize water and energy requirements. For other methods and more detail the reader is referred to sources such as Doorenbos and Pruitt (1977), Jensen (1974), Barman. et al. (1981)

Field-induced quantum critical point in CeCoIn_5

The resistivity of CeCoIn_5 was measured down to 20 mK in magnetic fields of up to 16 T. With increasing field, we observe a suppression of the non-Fermi liquid behavior, rho~T, and the development of a Fermi liquid state, with its characteristic rho=rho_0+AT^2 dependence. The field dependence of the T^2 coefficient shows critical behavior with an exponent of ~4/3. This is evidence for a new field-induced quantum critical point, occuring in this case at a critical field which coincides with the superconducting upper critical field H_c2.Comment: 2 pages, 2 figures, submitted to M2S-Rio 2003 Proceeding