Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among dental professionals

Background. MRSA (methicillin-resistant Staphylococcus aureus) is a multi-drug resistant bacterium that is quite prevalent in social environments where close person-to-person contact and crowding are an issue. In dental settings, the likelihood of transmission of MRSA may be higher than among other healthcare practitioners because of the close proximity between a patient's nose (where MRSA colonizes) and the field of procedure (the mouth) to the dental professional. Objective. To estimate the prevalence of MRSA nasal colonization among dental professionals (dentists and dental hygienists) in the Greater Houston Metropolitan Area, Texas, and analyze its associations with demographic, professional and personal protective equipment-related variables. Methods. 800 dental professionals (400 dentists and 400 dental hygienists) were randomly selected in the Greater Houston Metropolitan Area. Multiple waves of nasal swab kits and a self-administered questionnaire were mailed to increase the response rate of the study population. The swabs were cultured on chromagenic agar growth medium and bacterial growth results were evaluated after 18 hours. Positively selected bacterial colonies were confirmed as MRSA by further culturing these isolated bacteria on blood agar plates. Associations between positive nasal swabs and self-reported professional practice patterns, personal protective equipment use and demographics were analyzed using multiple logistic regression. Main Results. Completed questionnaires and nasal swabs were received from 496 study participants (68%). Fourteen cultures were positive for MRSA (4.2% among dentists and 1.6% among dental hygienists, p=0.07). After adjusting for gender, dental hygienists had a significantly lower prevalence of nasal colonization of MRSA as compared to dentists (OR: 0.20, 95% CI: 0.05–0.75). No other significant associations or interactions were found. Conclusion. The prevalence of nasal colonization with MRSA among dentists is similar to that reported for health care workers in general, whereas prevalence among dental hygienists is only slightly above that of the general population (1%). Differences in practice patterns and use of personal protective equipment did not explain this difference in this study, and was possibly due either to residual confounding or unexplored risk factors. Increased prevalence of MRSA among dentists warrants further investigation as to the reason for the increased rate and to allow implementation of measures to avoid transmission and progression to disease. ^

Helium-3 in different carriers from pelagic clays of DSDP Hole 91-596B and Core LR-44-GPC-3

To better understand the composition, characteristics of helium diffusion, and size distribution of interplanetary dust particles (IDPs) responsible for the long-term retention of extraterrestrial 3He, we carried out leaching, stepped heating, and sieving experiments on pelagic clays that varied in age from 0.5 Ma to ~90 Myr. The leaching experiments suggest that the host phase(s) of 3He in geologically old sediments are neither organic matter nor refractory phases, such as diamond, graphite, Al2O3, and SiC, but are consistent with extraterrestrial silicates, Fe-Ni sulfides, and possibly magnetite. Stepped heating experiments demonstrate that the 3He release profiles from the magnetic and non-magnetic components of the pelagic clays are remarkably similar. Because helium diffusion is likely to be controlled by mineral chemistry and structure, the stepped heating results suggest a single carrier that may be magnetite, or more probably a phase associated with magnetite. Furthermore, the stepped outgassing experiments indicate that about 20% of the 3He will be lost through diffusion at seafloor temperatures after 50 Myrs, while sedimentary rocks exposed on the Earth's surface for the same amount of time would lose up to 60%. The absolute magnitude of the 3He loss is, however, likely to depend upon the 3He concentration profile within the IDPs, which is not well known. Contrary to previous suggestions that micrometeorites in the size range of 50-100 µm in diameter are responsible for the extraterrestrial 3He in geologically old sediments [Stuart, F.M., Harrop, P.J., Knott, S., Turner, G., 1999. Laser extraction of helium isotopes from Antarctic micrometeorites: source of He and implications for the flux of extraterrestrial 3He flux to earth. Geochimica et Cosmochimica Acta, 63, 2653-2665, doi:10.1016/S0016-7037(99)00161-1], our sieving experiment demonstrates that at most 20% of the 3He is carried by particles greater than 50 µm in diameter. The size-distribution of the 3He-bearing particles implies that extraterrestrial 3He in sediments record the IDP flux rather than the micrometeorite flux.

Energy consumption and carbon dioxide emissions in rail and road freight transport in Spain: a case study of car carriers and bulk petrochemicals

This article provides a new methodology for estimating fuel consumption and emissions by enabling a correct comparison between freight transportation modes. The approach is developed and integrated as a part of an intelligent transportation system dealing with goods movement. A key issue is related to energy consumption ratios and consequent CO2 emissions. Energy consumption ratios are often used based on transport demand. However, including other ratios based on transport supply can be useful. Furthermore, it is important to indicate which factors are associated with variations in energy consumption and emissions; especially of interest are parameters that have a higher incidence and order of magnitude, in order to fairly compare and understand the difference between transport modes and sub-modes. The study finds that the use of an energy consumption equation can improve the quality of the estimates. The study proposes that coefficients that define the energy consumption equation should be tested to determine market niches and sources of improvement in energy consumption according to the category of vehicles, fuel types used, and classes of products transported.

Preliminary temperature accelerated life test (ALT) on lattice mismatched triple-junction concentrator solar cells-on-carriers

A temperature accelerated life test on concentrator lattice mismatched Ga0.37In0.63P/Ga0.83In0.17As/Ge triple-junction solar cells-on-carrier is being carried out. The solar cells have been tested at three different temperatures: 125, 145 and 165°C and the nominal photo-current condition (500X) is emulated by injecting current in darkness. The final objective of these tests is to evaluate the reliability, warranty period, and failure mechanism of these solar cells in a moderate period of time. Up to now only the test at 165°C has finished. Therefore, we cannot provide complete reliability information, but we have carried out preliminary data and failure analysis with the current results.

Case-control study of risk of cerebral sinus thrombosis in oral contraceptive users who are carriers of hereditary prothrombotic conditions

Objective: To investigate whether users of oral contraceptives who are carriers of a hereditary prothrombotic condition (factor V Leiden mutation, protein C, S, or antithrombin deficiency) have an increased risk of cerebral sinus thrombosis.

Branched co-polymers of histidine and lysine are efficient carriers of plasmids

We previously determined that a linear co-polymer of histidine and lysine (HK) in combination with liposomes enhanced the transfection efficiency of cationic liposomes. In the current study, we designed a series of HK polymers with increased branching and/or histidine/lysine ratio to determine if either variable affects transfection efficiency. In the presence of liposomes, the branched polymer with the highest number of histidines, HHK4b, was the most effective at enhancing gene expression. Furthermore, when serum was added to the medium during transfection, the combination of HHK4b and liposomes as a gene-delivery vehicle increased luciferase expression 400-fold compared to liposomes alone. In contrast to linear HK polymers, the higher branched HHK polymers were effective carriers of plasmids in the absence of liposomes. Without liposomes, the HHK4b carrier enhanced luciferase expression 15-fold in comparison with the lesser branched HHK2b carrier and increased expression by 5-logs in comparison with the HHK or HK carrier. The interplay of several parameters including increased condensation of DNA, buffering of acidic endosomes and differential binding affinities of polymer with DNA have a role in the enhancement of transfection by the HK polymers. In addition to suggesting that branched HK polymers are promising gene-delivery vehicles, this study provides a framework for the development of more efficient peptide-bond-based polymers of histidine and lysine.