Negative refraction with tunable absorption in an active dense gas of atoms

Applications of negative index materials (NIM) presently are severely limited by absorption. Next to improvements of metamaterial designs, it has been suggested that dense gases of atoms could form a NIM with negligible losses. In such gases, the low absorption is facilitated by quantum interference. Here, we show that additional gain mechanisms can be used to tune and effectively remove absorption in a dense gas NIM. In our setup, the atoms are coherently prepared by control laser fields, and further driven by a weak incoherent pump field to induce gain. We employ nonlinear optical Bloch equations to analyze the optical response. Metastable Neon is identified as a suitable experimental candidate at infrared frequencies to implement a lossless active negative index material.Comment: 10 pages, 9 figure

Time resolution below 100 ps for the SciTil detector of PANDA employing SiPM

The barrel time-of-flight (TOF) detector for the PANDA experiment at FAIR in Darmstadt is planned as a scintillator tile hodoscope (SciTil) using 8000 small scintillator tiles. It will provide fast event timing for a software trigger in the otherwise trigger-less data acquisition scheme of PANDA, relative timing in a multiple track event topology as well as additional particle identification in the low momentum region. The goal is to achieve a time resolution of sigma ~ 100 ps. We have conducted measurements using organic scintillators coupled to Silicon Photomultipliers (SiPM). The results are encouraging such that we are confident to reach the required time resolution.Comment: 10 pages, 7 figure

Remote sensing of submerged aquatic vegetation in the Lower Chesapeake Bay : final report to National Aeronautical and Space Administration Langley Research Center

Kodak\u27s experimental water penetration film and black and white near infrared film were used to study the distribution of submerged aquatic vegetation in the lower Chesapeake Bay. The water penetration film was very useful in this study compared to the black and white N1R. Optimal results from this film were obtained with the camera aperture closed 1/2 stop from suggested settings. Detailed description of the grass beds were obtained by flying at an altitude of 5,000 feet, at low tide when wind conditions were minimal. There was a 36% reduction in the amount of submerged aquatic vegetation in the lower Chesapeake Bay from 1971 to 1974. The greatest losses occurred in the York, Piankatank and Rappahannock rivers. Recovery of some grass beds occurred primarily through seedling recruitment and subsequent vegetative growth. Cownose rays were suspected as a main factor for the decimation of some of the grass beds.

Time for a culture change? Suboptimal compliance with blood culture standards at a district hospital in Cape Town

Background. The benchmark for contaminated blood cultures (BCs) is 3%. The South African (SA)  guideline aims to optimise BC yield and reduce contamination. Data on BC collection practices in SA  since the publication of the 2010 SA guideline are lacking.Objective. To evaluate compliance with the national guideline for the optimal use of BCs and determine  the BC contamination rate at a local district hospital.Method. An audit of compliance with 22 BC standards was conducted at a district hospital in Cape Town, SA. Standards were evaluated by reviewing clinical and laboratory data and by a clinician questionnaire.Results. Of the 425 BCs reviewed, 12.5% had positive growth, and 4.5% grew contaminants. Only 33% of BC bottles contained the recommended fill volume of 8 - 10 mL, and 96.9% of patients had a single BC within a 24-hour period. Of all the BCs, only 7.8% had a combined blood volume of at least 20 mL. The yield of pathogens in BCs collected after antibiotic exposure was 4.9% compared with 7.5% for those cultures with no prior antibiotic exposure (p=0.3). The overall median needle-to-incubator transport time was 11 hours 25 minutes.Conclusion. The BC contamination rate was high and compliance with most standards was variable or not met. The findings may not be generalisable to other hospitals, and we recommend that each institution reviews its own BC practices. Recommendations made to hospital staff included a re-audit following  implementation of these recommendations

Remote sensing of submerged aquatic vegetation in the lower Chesapeake Bay

An experimental water penetration film and black and white near infrared film were used to study the distribution of submerged aquatic vegetation in the lower Chesapeake Bay. Detailed description of the grass beds was obtained by flying at an altitude of 5,000 feet, at low tide when wind conditions were minimal. Results show that there was a 36% reduction in the amount of submerged aquatic vegetation in the lower Chesapeake Bay from 1971 to 1974, the greatest losses occurring in the York, Piankatank and Rappahannock rivers (tabulated data is given). Recovery of some grass beds occurs primarily through seedling recruitment and subsequent vegetative growth. Cownose rays are suspected as a main factor for the decimation of some of the grass beds. Maps and photographs of the areas studied are given

Pasteurella multocida Toxin Activates Various Heterotrimeric G Proteins by Deamidation

Pasteurella multocida produces a 146-kDa protein toxin (Pasteurella multocida toxin, PMT), which stimulates diverse cellular signal transduction pathways by activating heterotrimeric G proteins. PMT deamidates a conserved glutamine residue of the α-subunit of heterotrimeric G proteins that is essential for GTP-hydrolysis, thereby arresting the G protein in the active state. The toxin substrates are Gαq Gα13 and the Gαi-family proteins. Activation of these α-subunits causes stimulation of phospholipase Cβ, Rho-guanine nucleotide exchange factors or inhibition of adenylyl cyclase. This article provides the current knowledge on PMT concerning the structure-function analysis based on the crystal structure and recently elucidated molecular mode of action. Furthermore, the impact of PMT on cellular signaling is discussed

Distribution and abundance of submerged aquatic vegetation in the lower Chesapeake Bay, Virginia

The distribution and abundance of submerged aquatic vegetation (SAV) in the lower Chesapeake Bay and its tributaries were delineated with color aerial photography and surface information. Over 8500 hectares of SAV were identified on 31 topographic quadrangles. To enable computer retrieval of the aerial resource information, all information from the 1978 mapping effort was entered into a data base based on the Universal Transverse Mercator coordinate system. The greatest concentrations of SAV were found at the mouths of the largest tidal rivers and creeks along the Chesapeake Bay shoreline, and to the east of Tangier and Great Fox Islands. Freshwater and low salinity portions of Virginia\u27s tidal rivers were generally found lacking in large areas of SAV, although numerous small fringing beds and pocket areas associated with adjacent tidal marshes were identified

Flavour singlet pseudoscalar masses in N_f = 2 QCD

We perform a lattice mass analysis in the flavour singlet pseudoscalar channel on the SESAM and TXL full QCD vacuum configurations, with 2 active flavours of dynamical Wilson fermions at beta = 5.6. At our inverse lattice spacing, a^-1 = 2.3 GeV, we retrieve by a chiral extrapolation to the physical light quark masses the value m_eta' = 3.7(+8)(-4) m_pi. A crude extrapolation from (N_f = 3) phenomenology would suggest m_eta' \approx 5.1 m_pi for N_f = 2 QCD. we verify that the mass gap between the singlet state eta' and the pi flavour triplt state is due to gauge configurations with non-trivial topology.Comment: 8 pages, 10 figure