System and method for detecting cells or components thereof

A system and method for detecting a detectably labeled cell or componentthereof in a sample comprising one or more cells or components thereof, at least one cell or component thereof of which is detectably labeled with at least two detectable labels. In one embodiment, the method comprises: (i) introducing the sample into one or more flow cells of a flow cytometer, (ii) irradiating the sample with one or more light sources that are absorbed by the at least two detectable labels, the absorption of which is to be detected, and (iii) detectingsimultaneously the absorption of light by the at least two detectable labels on the detectably labeled cell or component thereof with an array of photomultiplier tubes, which are operably linked to two or more filters that selectively transmit detectable emissions from the at least two detectable labels

Lake Whitney Comprehensive Water Quality Assessment, Phase 1B- Physical and Biological Assessment (USDOE)

Baylor University Center for Reservoir and Aquatic Systems Research (CRASR) has conducted a phased, comprehensive evaluation of Lake Whitney to determine its suitability for use as a regional water supply reservoir. The area along the Interstate 35 corridor between Dallas / Fort Worth Metroplex and the Waco / Temple Centroplex represents one of the fastest growth areas in the State of Texas and reliable water supplies are critical to sustainable growth. Lake Whitney is situated midway between these two metropolitan areas. Currently, the City of Whitney as well as all of Bosque and Hill counties obtain their potable water from the Trinity Sands aquifer. Additionally, parts of the adjoining McLennan and Burleson counties utilize the Trinity sands aquifer system as a supplement to their surface water supplies. Population growth coupled with increasing demands on this aquifer system in both the Metroplex and Centroplex have resulted in a rapid depletion of groundwater in these rural areas. The Lake Whitney reservoir represents both a potentially local and regional solution for an area experiencing high levels of growth. Because of the large scope of this project as well as the local, regional and national implications, we have designed a multifaceted approach that will lead to the solution of numerous issues related to the feasibility of using Lake Whitney as a water resource to the region. Phase IA (USEPA, QAPP Study Elements 1-4) of this research focused on the physical limnology of the reservoir (bathymetry and fine scale salinity determination) and develops hydrodynamic watershed and reservoir models to evaluate how salinity would be expected to change with varying hydrologic and climatic factors. To this end, we implemented a basic water quality modeling program in collaboration with the Texas Parks and Wildlife Department and the Texas Commission on Environmental Quality to add to the developing long-term database on Lake Whitney. Finally, we conducted an initial assessment of knowledge of watershed and water quality related issues by local residents and stakeholders of Lake Whitney and design an intervention educational program to address any deficiencies discovered. Phase IA was funded primarily from EPA Cooperative Agreement X7-9769 8901-0. Phase IC (USEPA, QAPP Study Element 5) of this research focused on the ambient toxicity of the reservoir with respect to periodic blooms of golden algae. Phase IC was funded primarily from Cooperative Agreement EM-96638001. Phase 1B (USDOE, Study Elements 6-11) complemented work being done via EPA funding on study elements 1-5 and added five new study elements: 6) Salinity Transport in the Brazos Watershed to Lake Whitney; 7) Bacterial Assessment; 8) Organic Contaminant Analysis on Lake Whitney; 9) Plankton Photosynthesis; 10) Lake Whitney Resident Knowledge Assessment; and 11) Engineering Scoping Perspective: Recommendations for Use

Observation of two-dimensional Fermi surface and Dirac dispersion in YbMnSb2_2

We present the crystal structure, electronic structure, and transport properties of the material YbMnSb$_2$, a candidate system for the investigation of Dirac physics in the presence of magnetic order. Our measurements reveal that this system is a low-carrier-density semimetal with a 2D Fermi surface arising from a Dirac dispersion, consistent with the predictions of density functional theory calculations of the antiferromagnetic system. The low temperature resistivity is very large, suggesting scattering in this system is highly efficient at dissipating momentum despite its Dirac-like nature.Comment: 8 pages, 6 figure

Zeeman spectroscopy of CaH molecules in a magnetic trap

In a recent experiment [Weinstein et al., Nature 395, 148 (1998)] we magnetically trapped 108108ground-statecalcium monohydride molecules, CaH(X2Σ,v″=0,J″=0).CaH(X 2Σ,v″=0, J″=0). The molecules were prepared by laser ablation of a solid sample of CaH2CaH2 and loaded via thermalization with a cold (<1(<1 K) 3He3He buffer gas. The magnetic trap was formed by superconducting coils arranged in the anti-Helmholtz configuration. The detection was done by laser fluorescence spectroscopy excited at 635635 nm (in the B2Σ,v′=0−X2Σ,v″=0B 2Σ,v′=0−X 2Σ,v″=0 band) and detected at 692692 nm (within the B,v′=0−X,v″=1B,v′=0−X,v″=1 band). Both a photomultiplier tube and a CCD camera were used. Due to the thermalization of molecular rotation, only a transition from the lowest rotational state could be detected at zero field, N′=1,J′=3/2←N″=0,J″=1/2.N′=1, J′=3/2←N″=0, J″=1/2. In the magnetic field this rotational transition splits into two features, one shifted towards lower and one towards higher frequencies. The measured shifts are linear in field strength and indicate a small difference (0.02 μB)μB) in the magnetic moments between the ground and excited states. Here we present a theoretical analysis of the observed magnetic shifts. These are identified as arising from a rotational perturbation of the B2Σ,v′=0B 2Σ,v′=0 state by a close-lying A2Π,v′=1A 2Π,v′=1 state that lends the B state some of its A character. We find that the Hamiltonian can be well approximated by a 3×33×3 matrix built out of elements that connect states from within the Σ-doublet and the 2Π3/22Π3/2 manifolds. The interaction parameter describing the Σ−Π coupling in the Zeeman Hamiltonian is determined from the observed shifts and the field-free molecular parameters of CaH given by Berg and Klyning [Phys. Scr. 10, 331 (1974)] and by Martin [J. Mol. Spectrosc 108, 66 (1984)].Physic

Low-level dissolved organic carbon subsidies drive a trophic upsurge in a boreal stream

1. Energy pathways in stream food webs are often driven by allochthonous basal resources. However, allochthonous dissolved organic carbon (DOC) is generally viewed as a minor if not insignificant basal resource because much of the DOC pool comprises high molecular weight, recalcitrant compounds and is inefficiently incorporated into biomass. Nevertheless, there is increasing evidence that the relatively small, labile fraction of DOC may indeed fuel microbial activity to a level that stimulates productivity across multiple trophic levels, resulting in a trophic upsurge. Here, we tested the trophic upsurge hypothesis by subsidising the labile DOC pool of an Alaskan boreal stream that had relatively high nutrient availability but low levels of naturally occurring DOC. 2. We continuously added ecologically relevant (0.250 mg C/L, c. 10% increase above ambient bulk DOC) concentrations of labile DOC (acetate-C) for 62 days to a treatment reach that was statistically indistinguishable in its channel form and chemistry from an upstream reference reach. We measured responses of pe-riphyton production and biomass, whole reach metabolism and nutrient uptake, benthic invertebrate abundances, and juvenile salmonid (Dolly Varden, Salvelinus malma) abundance and growth. 3. Measurements of basal ecosystem responses collectively indicated increased en-ergy mobilization at the base of the food web in response to labile DOC addition. Periphyton bacterial production in the treatment reach was generally >1.5× refer-ence reach values, and periphyton ash-free dry mass, chlorophyll-a, and chloro-phyll-a:ash-free dry mass were all greater in the treatment reach by the end of the study. Throughout dosing, ecosystem respiration was 1.3× greater in the treat-ment reach and dissolved inorganic nitrogen uptake was greater in the treatment reach on eight out of nine measurements. 4. Benthic invertebrate counts, dominated by Baetis spp. and Chironomidae, were c. 4× greater after 28 dosing days and c. 8× greater after 56 days in the upstream portion of the treatment reach. Abundance generally declined with increasing dis-tance from the dosing station. Dolly Varden fry and parr age classes were nearly 2× more abundant in the upstream portion of the treatment reach than in any section of the reference reach and also declined with increasing distance from the dosing station. Further, Dolly Varden tagged with passive integrated transponders prior to the experiment had significantly higher instantaneous growth rates in the treatment reach than those recaptured in the reference reach. 5. The strong consumer responses to small quantities of labile DOC mirrored sig-nificant treatment reach increases in basal ecosystem function and therefore demonstrated a response consistent with a trophic upsurge. Terrestrial DOC has historically been viewed as contributing little to metazoan consumers, instead modulating the influence of nutrients and being respired out of a disconnected microbial loop. Because we dosed the treatment reach with a relevant concentra-tion of labile DOC, based on measurements in nearby peatland-draining streams, we suggest that terrestrial DOC deserves more attention as a basal resource for whole food webs, akin to nutrients fuelling green (autochthonous) pathways.Alaska Sustainable Salmon Fund, Grant/Award Number: 4470

Nonlinear Dynamics in Ecosystem Response to Climatic Change: Case Studies and Policy Implications

Many biological, hydrological, and geological processes are interactively linked in ecosystems. These ecological phenomena normally vary within bounded ranges, but rapid, nonlinear changes to markedly different conditions can be triggered by even small differences if threshold values are exceeded. Intrinsic and extrinsic ecological thresholds can lead to effects that cascade among systems, precluding accurate modeling and prediction of system response to climate change. Ten case studies from North America illustrate how changes in climate can lead to rapid, threshold-type responses within ecological communities; the case studies also highlight the role of human activities that alter the rate or direction of system response to climate change. Understanding and anticipating nonlinear dynamics are important aspects of adaptation planning since responses of biological resources to changes in the physical climate system are not necessarily proportional and sometimes, as in the case of complex ecological systems, inherently nonlinear

Quantum correlated twin atomic beams via photo-dissociation of a molecular Bose-Einstein condensate

We study the process of photo-dissociation of a molecular Bose-Einstein condensate as a potential source of strongly correlated twin atomic beams. We show that the two beams can possess nearly perfect quantum squeezing in their relative numbers.Comment: Corrected LaTeX file layou