Resource Type

Correspondence of the Gardner and van Genuchten/Mualem relativepermeability function parameters (open access)

Correspondence of the Gardner and van Genuchten/Mualem relativepermeability function parameters

The Gardner and van Genuchten models of relativepermeability are widely used in analytical and numerical solutions toflow problems. However, the applicab ility of the Gardner model to realproblems is usually limited, because empirical relative permeability datato calibrate the model are not routinely available. In contrast, vanGenuchten parameters can be estimated using more routinely availablematric potential and saturation data. However, the van Genuchten model isnot amenable to analytical solutions. In this paper, we introducegeneralized conversion formulae that reconcile these two models. Ingeneral, we find that the Gardner parameter alpha G is related to the vanGenuchten parameters alpha vG and n by alpha G=alpha vG ~; 1:3 n. Thisconversion rule will allow direct recasting of Gardner-based analyticalsolutions in the van Genuchten parameter space. The validity of theproposed formulae was tested by comparing the predicted relativepermeability of various porous media with measured values.
Date: January 3, 2007
Creator: Ghezzehei, Teamrat A.; Kneafsey, Timothy J. & Su, Grace W.
System: The UNT Digital Library
Setup and Performance of the Rhic Injector Accelerators for the 2007 Run With Gold Ions (open access)

Setup and Performance of the Rhic Injector Accelerators for the 2007 Run With Gold Ions

Gold ions for the 2007 run of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) are accelerated in the Tandem, Booster and AGS prior to injection into RHIC. The setup and performance of this chain of accelerators is reviewed with a focus on improvements in the quality of beam delivered to RHIC. In particular, more uniform stripping foils between Booster and AGS7 and a new bunch merging scheme in AGS have provided beam bunches with reduced longitudinal emittance for RHIC.
Date: June 25, 2007
Creator: Gardner, C.; Ahrens, L.; Alessi, J.; Benjamin, J.; Blaskiewicz, M. & Al., Et
System: The UNT Digital Library
Uniform Beam Distributions at the Target of the NSRL Beam Transfer Line (open access)

Uniform Beam Distributions at the Target of the NSRL Beam Transfer Line

Uniform irradiation of biological or material samples with charged particle beams is desired by experimenters because it reduces radiation dose errors. In this paper we present results of uniform beams produced in the NASA SPACE RADIATION LABORATORY (NSRL) at the Brookhaven National Laboratory (BNL) by a method which was developed theoretically and was proven experimentally at BNL. A similar method which requires collimation of the beam, and also lacks the flexibility of the present method to produce beam various beam sizes at the target, was patented in the year 1988. The present method of producing uniform beam distributions on a plane transverse to the direction of the beam, is based on purely magnetic focusing of the beam and requires no collimation of the beam or any other type of beam interaction with materials. It can also generate uniform beam distributions of various sizes. The method is favorably compared with alternative methods of producing uniform beam distributions and can be applied to the whole energy spectrum of the charged particle beams that are delivered by the BNL Booster synchrotron.
Date: June 25, 2007
Creator: Tsoupas, N.; Ahrens, L.; Brown, K. Chiang, I-Hung, Gardner, C. J.; MacKay, W. W.; Pile, P. & Rusek, A.
System: The UNT Digital Library
Overcoming Depolarizing Resonances in the AGS With Two Helical Partial Snakes (open access)

Overcoming Depolarizing Resonances in the AGS With Two Helical Partial Snakes

Dual partial snake scheme has provided polarized proton beams with 1.5 x 10{sup 11} intensity and 65% polarization for the Relativistic Heavy Ion Collider (RHIC) spin program. To overcome the residual polarization loss due to horizontal resonances in the Brookhaven Alternating Gradient Synchrotron (AGS), a new string of quadrupoles have been added. The horizontal tune can then be set in the spin tune gap generated by the two partial snakes, such that horizontal resonances can also be avoided. This paper presents the accelerator setup and preliminary results.
Date: June 25, 2007
Creator: Huang, H.; Ahrens, L.; Bai, M.; Brown, K. A.; Gardner, C. J.; Glenn, J. W. et al.
System: The UNT Digital Library
Performance of the RADPHI Detector and Trigger in a High Rate Tagged Photon Beam (open access)

Performance of the RADPHI Detector and Trigger in a High Rate Tagged Photon Beam

We describe the design and operation of a detector system for measuring all-photon decays of mesons photoproduced in a tagged photon beam with energies between 4.3 and 5.4 GeV and a flux of 5×107 tagged photons per second. Photons from meson decays were detected with a lead-glass calorimeter with an energy resolution of 11% at 1 GeV. Various veto and trigger components were also present. Final states with as many as six photons were successfully detected and reconstructed.
Date: January 1, 2007
Creator: Jones, R. T.; Bogue, T.; Evans, B. E.; Kornicer, M.; Dzierba, A. R.; Gardner, R. et al.
System: The UNT Digital Library
China Spallation Neutron Source Design (open access)

China Spallation Neutron Source Design

The China Spallation Neutron Source (CSNS) is an accelerator-based high-power project currently in preparation under the direction of the Chinese Academy of Sciences (CAS). The complex is based on an H- linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV, a solid tungsten target station, and five initial instruments for spallation neutron applications. The facility will operate at 25 Hz repetition rate with a phase-I beam power of about 120 kW. The major challenge is to build a robust and reliable user's facility with upgrade potential at a fractional of ''world standard'' cost.
Date: January 29, 2007
Creator: Wei, J.
System: The UNT Digital Library
A Split-Function Lattice for Stochastic Cooling (open access)

A Split-Function Lattice for Stochastic Cooling

Lattice for a 3-GeV cooler ring with split functions is presented. The ring consists of two half-rings of different properties: in one half-ring, the phase-slip factor is near-zero; in the other half-ring, the phase-slip factor is large. The near-zero phase slip minimizes the 'bad mixing' between the stochastic-cooling pick-ups and kickers, while the high phase slip maximizes the 'good mixing' between the kickers and the next-turn pick-ups.
Date: September 10, 2007
Creator: Wei, J.
System: The UNT Digital Library
Novel QCD Effects from Initial and Final State Interactions (open access)

Novel QCD Effects from Initial and Final State Interactions

Initial-state and final-state interactions which are conventionally neglected in the parton model, have a profound effect in QCD hard-scattering reactions. The effects, which arise from gluon exchange between the active and spectator quarks, cause leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and the breakdown of the Lam-Tung relation in Drell-Yan reactions. Diffractive deep inelastic scattering also leads to nuclear shadowing and non-universal antishadowing of nuclear structure functions through multiple scattering reactions in the nuclear target. Factorization-breaking effects are particularly important for hard hadron interactions since both initial-state and final-state interactions appear. Related factorization breaking effects can also appear in exclusive electroproduction reactions and in deeply virtual Compton scattering. None of the effects of initial-state and final-state interactions are incorporated in the light-front wavefunctions of the target hadron computed in isolation.
Date: September 12, 2007
Creator: Brodsky, Stanley J.
System: The UNT Digital Library
The Conformal Template and New Perspectives for Quantum Chromodynamics (open access)

The Conformal Template and New Perspectives for Quantum Chromodynamics

Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial- …
Date: March 6, 2007
Creator: Brodsky, Stanley J.
System: The UNT Digital Library
Novel QCD Phenomena (open access)

Novel QCD Phenomena

I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable {zeta} which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. I also discuss a number of novel phenomenological features of QCD. Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize …
Date: July 6, 2007
Creator: Brodsky, Stanley J.
System: The UNT Digital Library
National Ignition Facility Target Design and Fabrication (open access)

National Ignition Facility Target Design and Fabrication

The current capsule target design for the first ignition experiments at the NIF Facility beginning in 2009 will be a copper-doped beryllium capsule, roughly 2 mm in diameter with 160-{micro}m walls. The capsule will have a 75-{micro}m layer of solid DT on the inside surface, and the capsule will driven with x-rays generated from a gold/uranium cocktail hohlraum. The design specifications are extremely rigorous, particularly with respect to interfaces, which must be very smooth to inhibit Rayleigh-Taylor instability growth. This paper outlines the current design, and focuses on the challenges and advances in capsule fabrication and characterization; hohlraum fabrication, and D-T layering and characterization.
Date: December 10, 2007
Creator: Cook, R. C.; Kozioziemski, B. J.; Nikroo, A.; Wilkens, H. L.; Bhandarkar, S.; Forsman, A. C. et al.
System: The UNT Digital Library
Evaluation of Multiplexed Foot-and-Mouth Disease Nonstructural Protein Antibody Assay Against Standardized Bovine Serum Panel (open access)

Evaluation of Multiplexed Foot-and-Mouth Disease Nonstructural Protein Antibody Assay Against Standardized Bovine Serum Panel

Liquid array technology has previously been used to show proof-of-principle of a multiplexed non structural protein serological assay to differentiate foot-and-mouth infected and vaccinated animals. The current multiplexed assay consists of synthetically produced peptide signatures 3A, 3B and 3D and recombinant protein signature 3ABC in combination with four controls. To determine diagnostic specificity of each signature in the multiplex, the assay was evaluated against a naive population (n = 104) and a vaccinated population (n = 94). Subsequently, the multiplexed assay was assessed using a panel of bovine sera generated by the World Reference Laboratory for foot-and-mouth disease in Pirbright, UK. This sera panel has been used to assess the performance of other singleplex ELISA-based non-structural protein antibody assays. The 3ABC signature in the multiplexed assay showed comparative performance to a commercially available non-structural protein 3ABC ELISA (Cedi test{reg_sign}) and additional information pertaining to the relative diagnostic sensitivity of each signature in the multiplex is acquired in one experiment. The encouraging results of the evaluation of the multiplexed assay against a panel of diagnostically relevant samples promotes further assay development and optimization to generate an assay for routine use in foot-and-mouth disease surveillance.
Date: May 14, 2007
Creator: Perkins, J; Parida, S & Clavijo, A
System: The UNT Digital Library
Design and testing of a unique active Compton-suppressed LaBr3(Ce) detector system for improved sensitivity assays of TRU in remote-handled TRU wastes (open access)

Design and testing of a unique active Compton-suppressed LaBr3(Ce) detector system for improved sensitivity assays of TRU in remote-handled TRU wastes

The US Department of Energy’s transuranic (TRU) waste inventory includes about 4,500 m3 of remote-handled TRU (RH-TRU) wastes composed of a variety of containerized waste forms having a contact surface dose rate that exceeds 2 mSv/hr (200 mrem/hr) containing waste materials with a total TRU concentration greater than 3700 Bq/g (100 nCi/g). As part of a research project to investigate the use of active Compton-suppressed room-temperature gamma-ray detectors for direct non-destructive quantification of the TRU content of these RH-TRU wastes, we have designed and purchased a unique detector system using a LaBr3(Ce) primary detector and a NaI(Tl) suppression mantle. The LaBr3(Ce) primary detector is a cylindrical unit ~25 mm in diameter by 76 mm long viewed by a 38 mm diameter photomultiplier. The NaI(Tl) suppression mantle (secondary detector) is 175 mm by 175 mm with a center well that accommodates the primary detector. An important feature of this arrangement is the lack of any “can” between the primary and secondary detectors. These primary and secondary detectors are optically isolated by a thin layer (.003") of aluminized kapton, but the hermetic seal and thus the aluminum can surrounds the outer boundary of the detector system envelope. The hermetic seal at the …
Date: October 1, 2007
Creator: Hartwell, J. K.; McIlwain, M. E. & Kulisek, J. A.
System: The UNT Digital Library
New experimental capabilities and theoretical insights of high pressure compression waves (open access)

New experimental capabilities and theoretical insights of high pressure compression waves

Currently there are three platforms that offer quasi-isentropic compression or ramp-wave compression (RWC): light-gas gun, magnetic flux (Z-pinch), and laser. We focus here on the light-gas gun technique and on some current theoretical insights from experimental data. A gradient impedance through the length of the impactor provides the pressure pulse upon impactor to the subject material. Applications and results are given concerning high-pressure strength and liquid to solid, phase transition of water plus its associated phase fraction history. We also introduce the Korteweg-deVries-Burgers equation as a means to understand the evolution these RWC waves that propagate through the thickness of the subject material. This equation has the necessary competition between non-linear, dispersion, and dissipation processes, which is shown through observed structures that are manifested in the experimental particle velocity histories. Such methodology points towards a possible quantifiable dissipation, through which RWC experiments may be analyzed.
Date: July 20, 2007
Creator: Orlikowski, D.; Nguyen, J.; Patterson, J. R.; Minich, R.; Martin, L. P. & Holmes, N.
System: The UNT Digital Library
Accelerating Polarized Protons to 250 GEV (open access)

Accelerating Polarized Protons to 250 GEV

The Relativistic Heavy Ion Collider (RHIC) as the first high energy polarized proton collider was designed t o provide polarized proton collisions a t a maximum beam energy of 250 GeV. I t has been providing collisions a t a beam energy of 100 Gel' since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100 GeV with careful control of the betatron tunes and the vertical orbit distortions. However, the intrinsic spin resonances beyond 100 GeV are about a factor of two stronger than those below 100 GeV? making it important t o examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were accelerated t o the record energy of 250 GeV in RHIC with a polarization of 46% measured a t top energy in 2006. The polarization measurement as a function of beam energy also shows some polarization loss around 136 GeV, the first strong intrinsic resonance above 100 GeV. This paper presents the results and discusses the sensitivity of the polarization survival t o orbit distortions.
Date: June 25, 2007
Creator: Bai, M.; Ahrens, L.; Alekseev, I. G.; Alessi, J.; Beebe-Wang, J. & AL., ET
System: The UNT Digital Library
A Survey of Hadron Therapy Accelerator Technologies. (open access)

A Survey of Hadron Therapy Accelerator Technologies.

Hadron therapy has entered a new age [1]. The number of facilities grows steadily, and 'consumer' interest is high. Some groups are working on new accelerator technology, while others optimize existing designs by reducing capital and operating costs, and improving performance. This paper surveys the current requirements and directions in accelerator technology for hadron therapy.
Date: June 25, 2007
Creator: Peggs, S.; Satogata, T. & Flanz, J.
System: The UNT Digital Library
Sensitivity analysis for joint inversion of ground-penetratingradar and thermal-hydrological data from a large-scale underground heatertest (open access)

Sensitivity analysis for joint inversion of ground-penetratingradar and thermal-hydrological data from a large-scale underground heatertest

We describe a joint inversion approach that combinesgeophysical and thermal-hydrological data for the estimation of (1)thermal-hydrological parameters (such as permeability, porosity, thermalconductivity, and parameters of the capillary pressure and relativepermeability functions) that are necessary for predicting the flow offluids and heat in fractured porous media, and (2) parameters of thepetrophysical function that relates water saturation, porosity andtemperature to the dielectric constant. The approach incorporates thecoupled simulation of nonisothermal multiphase fluid flow andground-penetrating radar (GPR) travel times within an optimizationframework. We discuss application of the approach to a large-scale insitu heater test which was conducted at Yucca Mountain, Nevada, to betterunderstand the coupled thermal, hydrological, mechanical, and chemicalprocesses that may occur in the fractured rock mass around a geologicrepository for high-level radioactive waste. We provide a description ofthe time-lapse geophysical data (i.e., cross-borehole ground-penetratingradar) and thermal-hydrological data (i.e., temperature and water contentdata) collected before and during the four-year heating phase of thetest, and analyze the sensitivity of the most relevantthermal-hydrological and petrophysical parameters to the available data.To demonstrate feasibility of the approach, and as a first step towardcomprehensive inversion of the heater test data, we apply the approach toestimate one parameter, the permeability of the rock matrix.
Date: June 25, 2007
Creator: Kowalsky, M. B.; Birkholzer, J.; Peterson, J.; Finsterle, S.; Mukhopadhya, Y. S. & Tsang, Y. T.
System: The UNT Digital Library
Diagnostic evaluation of a multiplexed RT-PCR microsphere array assay for the detection of foot-and-mouth disease virus and look-alike disease viruses (open access)

Diagnostic evaluation of a multiplexed RT-PCR microsphere array assay for the detection of foot-and-mouth disease virus and look-alike disease viruses

A high-throughput multiplexed assay was developed for the differential laboratory diagnosis of foot-and-mouth disease virus (FMDV) from viruses which cause clinically similar diseases of livestock. This assay simultaneously screens for five RNA and two DNA viruses using multiplexed reverse transcription PCR (mRT-PCR) amplification coupled with a microsphere hybridization array and flow-cytometric detection. Two of the seventeen primer-probe sets included in this multiplex assay were adopted from previously characterized real-time RT-PCR (rRT-PCR) assays for FMDV. The diagnostic accuracy of the mRT-PCR was evaluated using 287 field samples, including 248 (true positive n= 213, true negative n=34) from suspect cases of foot-and-mouth disease collected from 65 countries between 1965 and 2006 and 39 true negative samples collected from healthy animals. The mRT-PCR assay results were compared with two singleplex rRT-PCR assays, using virus isolation with antigen-ELISA as the reference method. The diagnostic sensitivity of the mRT-PCR assay for FMDV was 93.9% [95% C.I. 89.8-96.4%], compared to 98.1% [95% C.I. 95.3-99.3%] for the two singleplex rRT-PCR assays used in combination. In addition, the assay could reliably differentiate between FMDV and other vesicular viruses such as swine vesicular disease virus and vesicular exanthema of swine virus. Interestingly, the mRT-PCR detected parapoxvirus (n=2) and bovine …
Date: July 26, 2007
Creator: Hindson, B J; Reid, S M; Baker, B R; Ebert, K; Ferris, N P; Bentley Tammero, L F et al.
System: The UNT Digital Library
Resolving the Formation of Protogalaxies. II.Central Gravitational Collapse (open access)

Resolving the Formation of Protogalaxies. II.Central Gravitational Collapse

Numerous cosmological hydrodynamic studies have addressed the formation of galaxies. Here we choose to study the first stages of galaxy formation, including non-equilibrium atomic primordial gas cooling, gravity and hydrodynamics. Using initial conditions appropriate for the concordance cosmological model of structure formation, we perform two adaptive mesh refinement simulations of {approx} 10{sup 8} M{sub {circle_dot}} galaxies at high redshift. The calculations resolve the Jeans length at all times with more than 16 cells and capture over 14 orders of magnitude in length scales. In both cases, the dense, 10{sup 5} solar mass, one parsec central regions are found to contract rapidly and have turbulent Mach numbers up to 4. Despite the ever decreasing Jeans length of the isothermal gas, we only find one site of fragmentation during the collapse. However, rotational secular bar instabilities transport angular momentum outwards in the central parsec as the gas continues to collapse and lead to multiple nested unstable fragments with decreasing masses down to sub-Jupiter mass scales. Although these numerical experiments neglect star formation and feedback, they clearly highlight the physics of turbulence in gravitationally collapsing gas. The angular momentum segregation seen in our calculations plays an important role in theories that form supermassive …
Date: October 15, 2007
Creator: Wise, John H.; Turk, Matthew J. & Abel, Tom
System: The UNT Digital Library
Dalitz plot analysis of the D+ ---> K- pi+ pi+ decay in the FOCUS experiment (open access)

Dalitz plot analysis of the D+ ---> K- pi+ pi+ decay in the FOCUS experiment

Using data collected by the high energy photoproduction experiment FOCUS at Fermilab we performed a Dalitz plot analysis of the Cabibbo favored decay D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +}. This study uses 53653 Dalitz-plot events with a signal fraction of {approx} 97%, and represents the highest statistics, most complete Dalitz plot analysis for this channel. Results are presented and discussed using two different formalisms. The first is a simple sum of Breit-Wigner functions with freely fitted masses and widths. It is the model traditionally adopted and serves as comparison with the already published analyses. The second uses a K-matrix approach for the dominant S-wave, in which the parameters are fixed by first fitting K{pi} scattering data and continued to threshold by Chiral Perturbation Theory. We show that the Dalitz plot distribution for this decay is consistent with the assumption of two body dominance of the final state interactions and the description of these interactions is in agreement with other data on the K{pi} final state.
Date: May 1, 2007
Creator: Link, J. M.; Yager, P. M.; /UC, Davis; Anjos, J. C.; Bediaga, I.; Castromonte, C. et al.
System: The UNT Digital Library
Study of the D0 ---> pi- pi+ pi- pi+ decay (open access)

Study of the D0 ---> pi- pi+ pi- pi+ decay

Using data from the FOCUS (E831) experiment at Fermilab, they present new measurements for the Cabbibo-suppressed decay mode D{sup 0} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup +}. They measure the branching ratio {Lambda}(D{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -})/{Lambda}(D{sup 0} {yields} K{sup -} {pi}{sup +}{pi}{sup -}{pi}{sup +}) = 0.0914 {+-} 0.0018 {+-} 0.0022. An amplitude analysis has been performed, a first for this channel, in order to determine the resonant substructure of this decay mode. The dominant component is the decay D{sup 0} {yields} a{sub 1}(1260){sup +}{pi}{sup -}, accounting for 60% of the decay rate. The second most dominant contribution comes from the decay D{sup 0} {yields} {rho}(770){sup 0}{rho}(770){sup 0}, with a fraction of 25%. They also study the a{sub 1}(1260) line shape and resonant substructure. Using the helicity formalism for the angular distribution of the decay D{sup 0} {yields} {rho}(770){sup 0}{rho}(770){sup 0}, they measure a longitudinal polarization of P{sub L} = (71 {+-} 4 {+-} 2)%.
Date: January 1, 2007
Creator: Link, J. M.; Yager, P. M.; /UC, Davis; Anjos, J. C.; Bediaga, I.; Castromonte, C. et al.
System: The UNT Digital Library
Modelos de interacción humano-ambiental: el enfoque de la Biocomplejidad (open access)

Modelos de interacción humano-ambiental: el enfoque de la Biocomplejidad

Article discussing models of human-nature interactions and a biocomplexity approach.
Date: September 2007
Creator: Acevedo, Miguel F.; Rosales, Judith; Delgado, Luz A.; Ablan, Magdiel; Dávila, Jacinto; Callicott, J. Baird et al.
System: The UNT Digital Library
Dissecting Biological Dark Matter: Single Cell Genetic Analysis of TM7, a Rare and Uncultivated Microbe from the Human Mouth (open access)

Dissecting Biological Dark Matter: Single Cell Genetic Analysis of TM7, a Rare and Uncultivated Microbe from the Human Mouth

We have developed a microfluidic device that allows the isolation and genome amplification of individual microbial cells, thereby enabling organism-level genomic analysis of complex microbial ecosystems without the need for culture. This device was used to perform a directed survey of the human subgingival crevice and to isolate bacteria having rod-like morphology. Several isolated microbes had a 16S rRNA sequence that placed them in candidate phylum TM7, which has no cultivated or sequenced members. Genome amplification from individual TM7 cells allowed us to sequence and assemble >1,000 genes, providing insight into the physiology of members of this phylum. This approach enables single-cell genetic analysis of any uncultivated minority member of a microbial community.
Date: July 1, 2007
Creator: Fenner, Marsha W; Marcy, Yann; Ouverney, Cleber; Bik, Elisabeth M.; Losekann, Tina; Ivanova, Natalia et al.
System: The UNT Digital Library
Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics (open access)

Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics

We present the discovery of 2MASS J21321145+1341584AB as a closely separated (0.066'') very low-mass field dwarf binary resolved in the near-infrared by the Keck II Telescope using laser guide star adaptive optics. Physical association is deduced from the angular proximity of the components and constraints on their common proper motion. We have obtained a near-infrared spectrum of the binary and find that it is best described by an L5{+-}0.5 primary and an L7.5{+-}0.5 secondary. Model-dependent masses predict that the two components straddle the hydrogen burning limit threshold with the primary likely stellar and the secondary likely substellar. The properties of this sytem - close projected separation (1.8{+-}0.3AU) and near unity mass ratio - are consistent with previous results for very low-mass field binaries. The relatively short estimated orbital period of this system ({approx}7-12 yr) makes it a good target for dynamical mass measurements. Interestingly, the system's angular separation is the tightest yet for any very low-mass binary published from a ground-based telescope and is the tightest binary discovered with laser guide star adaptive optics to date.
Date: February 2, 2007
Creator: Siegler, N; Close, L; Burgasser, A; Cruz, K; Marois, C; Macintosh, B et al.
System: The UNT Digital Library