400 research outputs found

    Infrastructure and climate change: a study of impacts and adaptations in Malawi, Mozambique, and Zambia

    Get PDF
    The African Development Bank has called for 40BillionUSDperyearoverthecomingdecadestobeprovidedtoAfricancountriestoaddressdevelopmentissuesdirectlyrelatedtoclimatechange.Thecurrentstudyaddressesakeycomponentoftheseissues,theeffectofclimatechangeontheroadinfrastructureofMalawi,Mozambique,andZambia.Thestudyincorporatesastressor−responseapproachtoestimatetheeffectsofprojectedprecipitation,temperature,andfloodingchangesonthepavedandunpavedroadinfrastructureofthesecountries.Thepaperhighlightstheresultofrunning425climatescenariosforeachroadtypeandpolicyoptionfrom2010to2050.Basedonthisbroadanalysis,itisestimatedthatthethreesouthernAfricancountriesarefacingapotential40 Billion USD per year over the coming decades to be provided to African countries to address development issues directly related to climate change. The current study addresses a key component of these issues, the effect of climate change on the road infrastructure of Malawi, Mozambique, and Zambia. The study incorporates a stressor-response approach to estimate the effects of projected precipitation, temperature, and flooding changes on the paved and unpaved road infrastructure of these countries. The paper highlights the result of running 425 climate scenarios for each road type and policy option from 2010 to 2050. Based on this broad analysis, it is estimated that the three southern African countries are facing a potential 596 million price tag based on median climate scenarios to maintain and repair roads as a result of damages directly related to temperature and precipitation changes from potential climate change through 2050. The challenge for policy makers is to determine the potential risk that a country is facing based on the uncertainties associated with the multiple aspects of climate change modeling. This article is part of a Special Issue on “Climate Change and the Zambezi River Valley” edited by Finn Tarp, James Juana, and Philip Ward

    DESORPTION YIELDS USING keV POLYATOMIC PROJECTILES

    No full text
    We have studied the negative secondary ion emission from solid organic targets bombarded by molecular ions and cluster ions. As an example we present here the results obtained with the compound phenylalanine. We have used organic projectiles of mass 73 [Si (CH3)+], 147[Si(CH3)3 OSi(CH3)2+], 300 [molecular ion of coronene C24H12]+, 598 [coronene dimer 2(M-H)]+, and atomic and polyatomic ions of mass 133 [Cs]+, 393 [Cs2I]+, 653 [Cs3I2]+. These primary ions have been produced in the bombardment of targets of coronene and CsI by fission fragment from a 252Cf source. They were accelerated and focussed on the sample target. Sophisticated time of flight measurements of the primary and secondary ions have been performed with a special data acquisition system. All the time of flight mass spectra were recorded at one. The secondary molecular ion yield of the phenilalanine (M-H)- = 164 has been studied as a function of the energy of impact and of the mass of the projectile. A large enhancement of the yield with the mass and the energy is observed

    Spectral Sensitivity in Ray-Finned Fishes: Diversity, Ecology and Shared Descent

    Get PDF
    A major goal of sensory ecology is to identify factors that underlie sensory-trait variation. One open question centers on why fishes show the greatest diversity among vertebrates in their capacity to detect color (i.e. spectral sensitivity). Over the past several decades, λmax values (photoreceptor class peak sensitivity) and chromacy (photoreceptor class number) have been cataloged for hundreds of fish species, yet the ecological basis of this diversity and the functional significance of high chromacy levels (e.g. tetra- and pentachromacy) remain unclear. In this study, we examined phylogenetic, physiological and ecological patterns of spectral sensitivity of ray-finned fishes (Actinoptergyii) via a meta-analysis of data compiled from 213 species. Across the fishes sampled, our results indicate that trichromacy is most common, ultraviolet λmax values are not found in monochromatic or dichromatic species, and increasing chromacy, including from tetra- to pentachromacy, significantly increases spectral sensitivity range. In an ecological analysis, multivariate phylogenetic latent liability modeling was performed to analyze correlations between chromacy and five hypothesized predictors (depth, habitat, diet, body coloration, body size). In a model not accounting for phylogenetic relatedness, each predictor with the exception of habitat significantly correlated with chromacy: a positive relationship in body color and negative relationships with body size, diet and depth. However, after phylogenetic correction, the only remaining correlated predictor was depth. The findings of this study indicate that phyletic heritage and depth are important factors in fish spectral sensitivity and impart caution about excluding phylogenetic comparative methods in studies of sensory trait variation

    Reproducing Kernels of Generalized Sobolev Spaces via a Green Function Approach with Distributional Operators

    Full text link
    In this paper we introduce a generalized Sobolev space by defining a semi-inner product formulated in terms of a vector distributional operator P\mathbf{P} consisting of finitely or countably many distributional operators PnP_n, which are defined on the dual space of the Schwartz space. The types of operators we consider include not only differential operators, but also more general distributional operators such as pseudo-differential operators. We deduce that a certain appropriate full-space Green function GG with respect to L:=P∗TPL:=\mathbf{P}^{\ast T}\mathbf{P} now becomes a conditionally positive definite function. In order to support this claim we ensure that the distributional adjoint operator P∗\mathbf{P}^{\ast} of P\mathbf{P} is well-defined in the distributional sense. Under sufficient conditions, the native space (reproducing-kernel Hilbert space) associated with the Green function GG can be isometrically embedded into or even be isometrically equivalent to a generalized Sobolev space. As an application, we take linear combinations of translates of the Green function with possibly added polynomial terms and construct a multivariate minimum-norm interpolant sf,Xs_{f,X} to data values sampled from an unknown generalized Sobolev function ff at data sites located in some set X⊂RdX \subset \mathbb{R}^d. We provide several examples, such as Mat\'ern kernels or Gaussian kernels, that illustrate how many reproducing-kernel Hilbert spaces of well-known reproducing kernels are isometrically equivalent to a generalized Sobolev space. These examples further illustrate how we can rescale the Sobolev spaces by the vector distributional operator P\mathbf{P}. Introducing the notion of scale as part of the definition of a generalized Sobolev space may help us to choose the "best" kernel function for kernel-based approximation methods.Comment: Update version of the publish at Num. Math. closed to Qi Ye's Ph.D. thesis (\url{http://mypages.iit.edu/~qye3/PhdThesis-2012-AMS-QiYe-IIT.pdf}

    On the nucleation of ikaite (CaCO3x6H2O) – A comparative study in the presence and absence of mineral surfaces

    Get PDF
    The formation of ikaite (CaCO3x6H2O) was studied in the presence and absence of quartz and mica surfaces using desupersaturation curves from cryo-mixed-batch-reactor experiments. Upon nucleation and growth within the reactor, the solution approached solubility of the precipitating carbonate phase. For ikaite, a solubility constant of log Ksp ikaite = -7.3 ± 0.1 was found (T = 0 °C). At supersaturations Ωikaite < 15, the nucleation of ikaite was significantly promoted by the presence of quartz or mica. This promotion prevented a competing nucleation of anhydrous calcium carbonates. In the presence of quartz or mica, therefore, ikaite forms over a much broader supersaturation range than in the absence. Similarly strong promotors of ikaite nucleation rather than anhydrous carbonate nucleation were previously attributed to calcite-inhibiting substances only. At supersaturations Ωikaite ≄ 8, application of classical nucleation theory on induction periods of ikaite formation yielded an effective interfacial energy of 15 ± 3 mJ/m2. Compared to data of anhydrous CaCO3 phases, this interfacial energy is low and expresses the highly hydrated character of ikaite. At supersaturations Ωikaite ≄ 18, a transient amorphous phase appeared besides ikaite. Our results show that a comprehensive understanding of ikaite formation in natural settings requires consideration not only of supersaturation and presence of calcite-inhibitors but also of the presence or absence of mineral surfaces capable of promoting heterogeneous nucleation of ikaite

    Dynamic light filtering over dermal opsin as a sensory feedback system in fish color change

    Get PDF
    Dynamic color change has evolved multiple times, with a physiological basis that has been repeatedly linked to dermal photoreception via the study of excised skin preparations. Despite the widespread prevalence of dermal photoreception, both its physiology and its function in regulating color change remain poorly understood. By examining the morphology, physiology, and optics of dermal photoreception in hogfish (Lachnolaimus maximus), we describe a cellular mechanism in which chromatophore pigment activity (i.e., dispersion and aggregation) alters the transmitted light striking SWS1 receptors in the skin. When dispersed, chromatophore pigment selectively absorbs the short-wavelength light required to activate the skin’s SWS1 opsin, which we localized to a morphologically specialized population of putative dermal photoreceptors. As SWS1 is nested beneath chromatophores and thus subject to light changes from pigment activity, one possible function of dermal photoreception in hogfish is to monitor chromatophores to detect information about color change performance. This framework of sensory feedback provides insight into the significance of dermal photoreception among color-changing animals

    Androgen receptor abnormalities

    Get PDF
    The human androgen receptor is a member of the superfamily of steroid hormone receptors. Proper functioning of this protein is a prerequisite for normal male sexual differentiation and development. The cloning of the human androgen receptor cDNA and the elucidation of the genomic organization of the corresponding gene has enabled us to study androgen receptors in subjects with the clinical manifestation of androgen insensitivity and in a human prostate carcinoma cell line (LNCaP). Using PCR amplification, subcloning and sequencing of exons 2–8, we identified a G → T mutation in the androgen receptor gene of a subject with the complete form of androgen insensitivity, which inactivates the splice donor site at the exon 4/intron 4 boundary. This mutation causes the inactivation of a cryptic splice donor site in exon 4, which results in the deletion of 41 amino acids from the steroid binding domain. In two other independently arising cases we identified two different nucleotide alterations in codon 686 (GAC; aspartic acid) located in exon 4. One mutation (G → C) results in an aspartic acid → histidine substitution (with negligible androgen binding), whereas the other mutation (G → A) leads to an aspartic acid → asparagine substitution (normal androgen binding, but a rapidly dissociating androgen receptor complex). Sequence analysis of the androgen receptor in human LNCaP-cells (lymph node carcinoma of the prostate) revealed a point mutation (A → G) in codon 868 in exon 8 resulting in the substitution of threonine by alanine. This mutation is the cause of the altered steroid binding specificity of the LNCaP-cell androgen receptor. The functional consequences of the observed mutations with respect to protein expression, specific ligand binding and transcriptional activation, were established after transient expression of the mutant receptors in COS and HeLa cells. These findings illustrate that functional error
    • 

    corecore