Effects of location, classroom orientation, and air change rate on potential aerosol exposure: an experimental and computational study

This study examined the dispersion of potentially infectious aerosols in classrooms by means of both a CO₂ tracer gas, and multizone contaminant transport modeling. A total of 20 tests were conducted in three different university classrooms at multiple air change rates (4.4-9.7/h), each with two different room orientations: one with the tracer gas released from six student desks toward the air return, and one with the same tracer gas released away from it. Resulting tracer concentrations were measured by 19 different monitors arrayed throughout the room. Steady-state, mean tracer gas concentrations were calculated in six instructor zones (A-F) around the periphery of the room, with the results normalized by the concentration at the return, which was assumed to be representative of the well-mixed volume of the room. Across all classrooms, zones farthest from the return (C, D) had the lowest mean normalized concentrations (0.75), while those closest to the return (A, F) had the highest (0.95). This effect was consistent across room orientations (release both toward and away from the return), and air change rates. In addition, all zones around the periphery of the room had a significantly lower concentration than those adjacent to the sources. Increasing the ventilation rate reduced tracer gas concentrations significantly. Similar trends were observed via a novel approach to CONTAM modeling of the same rooms. These results indicate that informed selection of teaching location within the classroom could reduce instructor exposure.

Attitudes towards HIV testing via home-sampling kits ordered online (RUClear pilots 2011-12)

BACKGROUND

The burden of disease relating to undiagnosed HIV infection is significant in the UK. BHIVA (British HIV Association) recommends population screening in high prevalence areas, expanding outside traditional antenatal/GUM settings.

METHODS

RUClear 2011-12 piloted expanding HIV testing outside traditional settings using home-sampling kits (dry-blood-spot testing) ordered online. Greater Manchester residents (≥age 16) could request testing via an established, online chlamydia testing service (www.ruclear.co.uk). Participant attitudes towards this new service were assessed. Qualitative methods (thematic analysis) were used to analyse free-text data submitted by participants via hard copy questionnaires issued in all testing kits.

RESULTS

79.9% (2447/3062) participants completed questionnaires, of which 30.9% (756/2447) provided free-text data. Participants overwhelmingly supported the service, valuing particularly accessibility and convenience, allowing individuals to order tests any time of day and self-sample comfortably at home; avoiding the invasive nature of venipuncture and avoiding the need for face-to-face interaction with health services. The pilot was also clinically and cost-effective.

CONCLUSION

Testing via home-sampling kits ordered online (dry-blood-spot testing) was felt to be an acceptable and convenient method for accessing a HIV test. Many individuals undertook HIV testing where they would otherwise not have been tested at all. Expansion of similar services may increase the uptake of HIV testing.

Diarrhetic shellfish poisoning toxin esters in Danish blue mussels and surf clams

Until recently, little focus was given to the presence of diarrhetic shellfish poisoning (DSP) toxin esters in seafood products. However, during the last few years, the occurrence of a high percentage of esters of the total amount of DSP toxins present in some seafood products has been observed. Samples of Danish surf clams (Spisola spp.) and blue mussels (Mytilus edulis) from 1999-2004 were analysed by liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) for the presence of DSP toxin esters. The samples contained only okadaic acid and esters of okadaic acid. The level of total okadaic acid equivalents ranged from 224 to 2516 microg kg-1 in surf clams. The percentage of okadaic acid esters of the total okadaic acid equivalents ranged from 83 to 98%, mean 95%. The level of total okadaic acid equivalents ranged from 43 to 1631 microg kg-1 in blue mussels. The percentage of okadaic acid esters of the total okadaic acid equivalents ranged from 21 to 86%, mean 59%. The probability of a high percentage of okadaic acid esters seems to increase with higher amounts of total okadaic acid equivalents in the bivalves. The large prevalence of DSP toxin esters are of particular importance because of the increased use of chemical methods instead of mouse bioassay for the detection of DSP toxicity.

Hepatitis B in a residential population with a mental handicap

Hepatitis serology was used to assess the nature and extent of hepatitis B virus (HBV) infection in the population of a residential centre for people with a mental handicap comprising 56 with Down's Syndrome (DS) and 193 with other mental handicaps (OMH). Markers of HBV were present in 170 cases (68%), of which 25 (10%) were HBsAg positive and potential carriers and 145 IgG anti-HBc positive (58%) indicating exposure to but not necessarily immunity from the virus. Of 25 who were HBsAg positive five were HBeAg positive, 17 were anti-HBe positive, two were HBsAg positive only and one was anti-HBe plus IgM anti-HBc positive. Age and length of residence were significantly associated with HBsAg, IgG anti-HBc and total markers of infection but the degree of mental handicap was not and the DS/OMH ratio only with HBsAg. The results indicated widespread HBV infection, no acute disease cases, relatively few infectious cases and a pre-disposition of DS residents to retain HBsAg in their sera. Vaccination of staff and at risk residents is recommended.

Identification and characterization of the adenosine 3',5'-cyclic monophosphate binding proteins appearing during the development of Dictyostelium discoideum

A photosensitive, radioactive analogue of cyclic adenosine monophosphate, 8-azido-adenosine 3',5'-[32P]monophosphate (8-N3-cyclic AMP), was used to label the cyclic AMP binding proteins of Dictyostelium discoideum. During development cytosolic proteins appear which are specifically labeled by the photoaffinity agent. The proteins are developmentally regulated since they are only found in starved, developing cells. Unlabeled cyclic AMP competes specifically with the labeled analogue for protein binding sites in contrast to unlabeled 5'-AMP which does not compete. A mutant which develops spores but is deficient in stalk cell production produces a different set of cyclic AMP binding proteins from the parent strain.

Probabilistic behavior of DNA segregation in Escherichia coli

The pattern of segregation of DNA in Escherichia coli B/rK was analyzed by using the Methocel technique for forming chains of cells and the membrane binding elution method. Strain B/rK was shown to have a relatively high degree of nonrandom segregation and was used in a critical experiment to test the proposal that only one DNA strand acts nonrandomly during segregation. Thymidine-labeled cells were bound to a nitrocellulose membrane, and newly dividing cells were eluted from the membrane for six generations. The segregation of DNA in the eluted cells as well as in the cells bound to the membrane was examined by the Methocel technique. No difference in segregation was found between the two populations of cells, a result which indicates that the two strands are equivalent in segregation and that the pattern of segregation is not the result of a permanent binding of any strand to a pole of a cell.