Quark Number Susceptibility with Finite Chemical Potential in Holographic QCD

We study the quark number susceptibility in holographic QCD with a finite chemical potential or under an external magnetic field at finite temperature. We first consider the quark number susceptibility with the chemical potential. We observe that approaching the critical temperature from high temperature regime, the quark number susceptibility divided by temperature square develops a peak as we increase the chemical potential, which confirms recent lattice QCD results. We discuss this behavior in connection with the existence of the critical end point in the QCD phase diagram. We also consider the quark number susceptibility under the external magnetic field. We predict that the quark number susceptibility exhibits a blow-up behavior at low temperature as we raise the value of the magnetic field. We finally spell out some limitations of our study.Comment: 25 pages, 3 figures, published versio

Movable genetic elements and antibiotic resistance in enterococci

The enterococci possess genetic elements able to move from one strain to another via conjugation. Certain enterococcal plasmids exhibit a broad host range among gram-positive bacteria, but only when matings are performed on solid surfaces. Other plasmids are more specific to enterococci, transfer efficiently in broth, and encode a response to recipient-produced sex phermones. Transmissible non-plasmid elements, the conjugative transposons, are widespread among the enterococci and determine their own fertility properties. Drug resistance, hemolysin, and bacteriocin determinants are commonly found on the various transmissible enterococcal elements. Examples of the different systems are discussed in this review.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47900/1/10096_2005_Article_BF01963632.pd

Stability of plasma analytes after delayed separation of whole blood: implications for epidemiological studies.

BACKGROUND: Large blood-based epidemiological studies require simple, cost-effective sample collection methods. Immediate sample separation or rapid transport of chilled blood samples to a central laboratory may be impractical or prohibitively expensive. To assess the feasibility and reliability of transporting blood samples over several days at ambient temperature (e.g. by mail), we evaluated the stability of various plasma analytes in samples stored at room temperature or chilled. METHODS: Multiple vacutainers of blood, containing EDTA and aprotinin as preservative, were drawn from 12 volunteers and stored at 21 degrees C or 4 degrees C. Immediately after collection and 1, 2, 3, 4, and 7 days later, vacutainers stored at each temperature were centrifuged, and the plasma was aliquoted and stored at -80 degrees C. Subsequently, all aliquots from each individual were analysed in one analytical run for a range of chemistries. RESULTS: In whole blood stored at room temperature for up to 7 days, concentrations of albumin, apolipoproteins A1 and B (apoA1 and apoB), cholesterol, high density lipoprotein (HDL), total protein, and triglycerides changed by less than 4%, and low density lipoprotein (LDL) by less than 7%. Whilst alanine transaminase (ALT), creatine kinase (CK), creatinine, and gamma-glutamyl transferase (GGT) concentrations changed substantially at room temperature, there was less than 4% change during chilled storage up to 7 days. By contrast, aspartate transaminase (AST) concentrations increased markedly under both conditions. CONCLUSIONS: A wide range of important analytes, including lipids, change by only a few per cent in whole blood during storage at room temperature for several days. Mailed transport of whole blood samples may, therefore, be a simple and cost-effective option for large-scale epidemiological studies

Effect of temperature and light on the stability of fat-soluble vitamins in whole blood over several days: implications for epidemiological studies.

BACKGROUND: Biochemical measurement of fat-soluble vitamins would allow direct assessment in epidemiological studies of their association with disease. However, the perceived instability of these compounds and typically high cost of collection and analysis may make their measurement impractical, particularly in large-scale studies. Using a high performance liquid chromatography assay developed in-house, we have investigated the separate effects of temperature and light on the stability of vitamins in whole blood over several days. METHODS: Multiple blood samples from 10 volunteers were stored at 20 degrees C or 4 degrees C and in dark or light conditions. Immediately after collection and 1, 2, 3, 4, and 7 days later, samples stored under each condition were centrifuged, and the plasma was aliquoted and stored at -80 degrees C. Subsequently, all aliquots from each individual were analysed in one analytical run. RESULTS: In whole blood stored under any of the four conditions for up to 7 days, concentrations of alpha-carotene, beta-carotene, lutein, lycopene, retinol, and alpha-tocopherol changed by less than 8%, and cryptoxanthin and gamma-tocopherol by less than 11%. Although significant temperature effects were observed for alpha-carotene, and alpha- and gamma-tocopherol, and a significant effect of light was observed for alpha-carotene, cryptoxanthin, and lycopene, these analytes changed by less than 1% per day under all conditions. CONCLUSIONS: Concentrations of these fat-soluble vitamins change by only a few per cent in whole blood during storage at room temperature for several days. Hence, delayed separation of blood samples (which may be required for practical reasons in large-scale epidemiological studies) does not preclude reliable measurement of fat-soluble vitamins