Extraction of paleohydrology and paleoclimate proxies from vadose zones and paleolake records in the southwestern Great Basin

Thick vadose zones in arid regions recorded past climate changes up to 100 ka, so they are unique archives for continental paleoclimate change and groundwater recharge during the late Quaternary. Despite extensive research on flow and transport in arid regions, the transport properties and general response of arid vadose zones to climate regimes are still not well understood. Some of these issues are addressed with four distinct studies in this dissertation. The first study investigates effects of soil texture, vegetation coverage, and macropores on soil moisture variation at Nevada Test Site (NTS). The simulations show that bare soils have higher soil water content than vegetated soils. Effects of macropore flow on soil water content are insignificant; The second study evaluates the impacts of climate change on solute transport in arid vadose zones. Undisturbed soil cores were collected at ground surface, directly below where tension infiltrometer measurements were made. The water fluxes and Br dispersion coefficients at investigated matric heads were very high due to the coarseness of the soils and possibly due to preferential flow pathways. These high water fluxes are more likely to occur in ephemeral washes. However, higher fluxes through the surface soil would be more likely during wetter climates; The third study simulates paleolake extent in Owens Valley in the last 18 ka. A coupled catchment-lake model is developed in this study, and used to reconstruct the observed paleolake levels for Owens Lake and Searles Lake. Finally, a quantitative time-series of paleoclimate information was obtained; The fourth study models the actual measured chloride profile in Amargosa Desert Research Site (ADRS) with the modified version of the HYDRUS-1D computer code by using variable boundary conditions. The paleoinformation estimated from the third study, and chloride concentration in Greenland ice core (GISP2) are used to prepare the atmospheric boundary file. The simulated chloride profile is in agreement with the measured chloride profile, and simulated water flux at ADRS is ∼0.016 mm/year upward at the base of the profile; Transport properties and general response of vadose zones to climate regimes are addressed by these four independent studies

Identification of Genes Directly Involved in Shell Formation and Their Functions in Pearl Oyster, Pinctada fucata

Mollusk shell formation is a fascinating aspect of biomineralization research. Shell matrix proteins play crucial roles in the control of calcium carbonate crystallization during shell formation in the pearl oyster, Pinctada fucata. Characterization of biomineralization-related genes during larval development could enhance our understanding of shell formation. Genes involved in shell biomineralization were isolated by constructing three suppression subtractive hybridization (SSH) libraries that represented genes expressed at key points during larval shell formation. A total of 2,923 ESTs from these libraries were sequenced and gave 990 unigenes. Unigenes coding for secreted proteins and proteins with tandem-arranged repeat units were screened in the three SSH libraries. A set of sequences coding for genes involved in shell formation was obtained. RT-PCR and in situ hybridization assays were carried out on five genes to investigate their spatial expression in several tissues, especially the mantle tissue. They all showed a different expression pattern from known biomineralization-related genes. Inhibition of the five genes by RNA interference resulted in different defects of the nacreous layer, indicating that they all were involved in aragonite crystallization. Intriguingly, one gene (UD_Cluster94.seq.Singlet1) was restricted to the ‘aragonitic line’. The current data has yielded for the first time, to our knowledge, a suite of biomineralization-related genes active during the developmental stages of P.fucata, five of which were responsible for nacreous layer formation. This provides a useful starting point for isolating new genes involved in shell formation. The effects of genes on the formation of the ‘aragonitic line’, and other areas of the nacreous layer, suggests a different control mechanism for aragonite crystallization initiation from that of mature aragonite growth

The strongest t-norm for fuzzy metric spaces

summary:In this paper, we prove that for a given positive continuous t-norm there is a fuzzy metric space in the sense of George and Veeramani, for which the given t-norm is the strongest one. For the opposite problem, we obtain that there is a fuzzy metric space for which there is no strongest t-norm. As an application of the main results, it is shown that there are infinite non-isometric fuzzy metrics on an infinite set

Convexity Invariance of Fuzzy Sets under the Extension Principles

We discuss the convexity invariance of fuzzy sets under the extension principles. Particularly, we give a necessary and sufficient condition for a mapping to be an inverse *-convex transformation, and also obtain some sufficient conditions for a mapping to be an *-convex transformation. Two applications are given to illustrate the obtained results. Finally, we give some applications of the main results to the hyperstructure convexity invariance of type 2 fuzzy sets under hyperalgebra operations, and to the convexity invariance of fuzzy numbers under basic arithmetic operations

On Decomposable Measures Induced by Metrics

We prove that for a given normalized compact metric space it can induce a σ-max-superdecomposable measure, by constructing a Hausdorff pseudometric on its power set. We also prove that the restriction of this set function to the algebra of all measurable sets is a σ-max-decomposable measure. Finally we conclude this paper with two open problems

Common Fixed Point Theorems in a New Fuzzy Metric Space

We generalize the Hausdorff fuzzy metric in the sense of Rodríguez-López and Romaguera, and we introduce a new M∞-fuzzy metric, where M∞-fuzzy metric can be thought of as the degree of nearness between two fuzzy sets with respect to any positive real number. Moreover, under ϕ-contraction condition, in the fuzzy metric space, we give some common fixed point theorems for fuzzy mappings

Marine biogeochemistries of Be and Al: a study based on cosmogenic <SUP>10</SUP>Be, Be and Al in marine calcite, aragonite, and opal

The geochemical behaviors of Be and Al in ocean waters have been successfully studied in recent years using natural, cosmogenic, radioactive10Be and26Al as tracers. The present day dissolved concentrations and distribution of the stable and radioactive isotopes of Be and Al in ocean waters have revealed their short residence times and appreciable effects of exchange fluxes at the coastal and ocean-sediment interfaces. It follows that concentrations of these particle-active elements must have varied in the past with temporal changes in climate, biological productivity and aeolian flux of continental detritus to the oceans. We therefore investigated the feasibility of extending the measurements of Be and Al isotope concentrations in marine systems to the 103-106 y BP time scale. We report here the discovery of significant amounts of intrinsic Be and Al in marine foraminiferal calcite and coral aragonite, and of Al in opal (radiolarians) and aragonite (coral), which makes it possible to determine10Be/Be and26Al/Al in oceans in the past. We also report measured10Be/9Be in foraminiferal calcite in Pacific Ocean cores, which reveal that the concentrations and ratios of the stable and cosmogenic isotopes of Be and Al have varied significantly in the past 30 ky. The implications of these results are discussed

Erosion history of the Tibetan Plateau since the last Interglacial: constraints from the first studies of cosmogenic 10Be from Tibetan bedrock

The cosmogenic 10Be exposure histories of in situ bedrock surfaces from the Tibetan Plateau indicate low erosion rates of <30 mm/ka in southern and central Tibet during the last interglacial–glacial cycle that contrast strongly with unusually rapid erosion rates (60–2000 mm/ka) for Kunlun in northern Tibet during the Holocene, comparable with published values from the Himalaya. By comparing apatite fission-track ages with cosmogenic data, erosion rates in southern Tibet appear to be decelerating since the Miocene, whereas in the Kunlun, erosion rates have accelerated over the same timescale. Such secular changes suggest that the southern and central regions of the plateau had formed their present flat relief by the Pleistocene. Unusually high erosion rates along the northern margin of the plateau may reflect intense tectonic activity during the Holocene. These findings indicate that over much of the high plateau erosion rates are exceptionally low, and therefore the sources of detritus carried by the great Asian rivers that rise in Tibet lie overwhelmingly in bedrocks at lower altitudes. This study illustrates the potential of cosmogenic studies for unraveling the most recent phase of the erosion/exhumation history of orogenic belts that cannot be resolved by either Ar-isotope or fission-track thermochronometers. Autho

Genomic Island-Encoded Diguanylate Cyclase from <i>Vibrio alginolyticus</i> Regulates Biofilm Formation and Motility in <i>Pseudoalteromonas</i>

Many bacteria use the second messenger c-di-GMP to regulate exopolysaccharide production, biofilm formation, motility, virulence, and other phenotypes. The c-di-GMP level is controlled by the complex network of diguanylate cyclases (DGCs) and phosphodiesterases (PDEs) that synthesize and degrade c-di-GMP. In addition to chromosomally encoded DGCs, increasing numbers of DGCs were found to be located on mobile genetic elements. Whether these mobile genetic element-encoded DGCs can modulate the physiological phenotypes in recipient bacteria after horizontal gene transfer should be investigated. In our previous study, a genomic island encoding three DGC proteins (Dgc137, Dgc139, and Dgc140) was characterized in Vibrio alginolyticus isolated from the gastric cavity of the coral Galaxea fascicularis. Here, the effect of the three DGCs in four Pseudoalteromonas strains isolated from coral Galaxea fascicularis and other marine environments was explored. The results showed that when dgc137 is present rather than the three DGC genes, it obviously modulates biofilm formation and bacterial motility in these Pseudoalteromonas strains. Our findings implied that mobile genetic element-encoded DGC could regulate the physiological status of neighboring bacteria in a microbial community by modulating the c-di-GMP level after horizontal gene transfer