Distributed situation awareness in dynamic systems: theoretical development and application of an ergonomics methodology

The purpose of this paper is to propose foundations for a theory of situation awareness based on the analysis of interactions between agents (i.e. both human and non-human) in subsystems. This approach may help to promote a better understanding of technology-mediated interaction in systems, as well as helping in the formulation of hypotheses and predictions concerning distributed situation awareness. It is proposed that agents within a system each hold their own situation awareness, which may be very different from (although compatible with) that of other agents. It is argued that we should not always hope for, or indeed want, sharing of this awareness, as different system agents have different purposes. This view marks situation awareness as a dynamic and collaborative process binding agents together on tasks on a moment-by-moment basis. Implications of this viewpoint for the development of a new theory of, and accompanying methodology for, distributed situation awareness are offered.

Migrant status, age, gender and social isolation in very late-onset schizophrenia-like psychosis

BACKGROUND

Data from two retrospective first contact studies suggest that the risk of developing very-late onset schizophrenia-like psychosis (SLP) may be raised in older migrant than British-born populations resident in the UK.

OBJECTIVE

To investigate whether the relative excess of SLP observed amongst younger and male migrants in the above studies might have been explained by differences in the age-gender structures of migrant and British-born denominator populations. A secondary aim was to examine the associations of migrant group status and gender with markers of social isolation.

METHOD

Eighty-six new referrals of SLP to the Mile End (1997-2003) and Maudsley (1995-2000) hospitals were identified from two retrospective case note studies. Local census data were used to estimate the denominator populations and to calculate rate ratios for migrant and British-born cases of SLP. Case notes were re-examined, to assess markers of social isolation in migrant and British-born patients.

RESULTS

Migrant patients were more likely to be male (odds ratio = 4.8; CI(odds) = 1.8-13.2) than British-born patients. The ratio of first contact rates for migrant compared to British-born populations were highest amongst men. There was a lower mean age of onset of SLP in migrant than British-born patients (t = 4.30, 95% CI = 3.78-10.27), which was largely explained by a higher mean age of illness onset in British-born women. There were no differences between migrant and British-born patients with respect to markers of social isolation. Male patients were more likely to have never married than women (odds ratio = 0.28; 95% CI odds = 0.09-0.89).

CONCLUSIONS

The age-gender structure of the background population is not sufficient to explain the socio-demographic differences between migrant and British-born patients with SLP. Male patients may be more socially isolated.

Proposed Sheffield quantitative criteria in cervical cytology to assist the diagnosis and grading of squamous intra-epithelial lesions, as some Bethesda system definitions require amendment

OBJECTIVE

This study assesses the accuracy of published quantitative and qualitative criteria in the Bethesda System (TBS) for squamous intra-epithelial lesions.

METHODS

Quantitative image analysis was undertaken on illustrations from TBS publications and also from slides in Cytology Training Centre teaching sets. Comparisons were also made with the British Society for Clinical Cytology (BSCC) terminology in cervical cytology, using the illustrations in their terminology publication and amalgamating the results into their proposed new two-tier model.

RESULTS

TBS quantitatively defines low-grade squamous intra-epithelial lesions (LSIL) in both conventional and liquid-based cytology (LBC) preparations as showing nuclear enlargement more than x3 the area of a normal intermediate squamous cell nucleus. This study found that the increase in mean nuclear area was limited to only x2 in conventional preparations. In LBC (SurePath preparations, there was only a statistically non-significant x1.2 increase. This study identified a progressive and statistically significant reduction in mean cytoplasmic area from normal intermediate cells to LSIL and then to high-grade squamous intra-epithelial lesions (HSIL) in both conventional and LBC preparations. Furthermore, the most consistent quantitative finding in both conventional and LBC preparations was a statistically significant increase in the mean area and diameter ratios from normal intermediate cells to LSIL and then to HSIL. In all instances this varied from x2 to just below x3. This is in agreement with TBS, which states that the cytoplasmic area in HSIL is decreased leading to a marked increase in nuclear to cytoplasmic (NC) ratio. With the exception of an increase in mean nuclear area in conventional preparations from normal intermediate cells to LSIL, the predominant cause for this increase in NC ratios was a reduction in mean cytoplasmic area. The numerical increase in NC ratio for LSIL identified in this study was greater than implied by the 'slightly increased' statement in TBS. TBS comments that some HSIL cells can have the same degree of nuclear enlargement as in LSIL and that other HSIL cells may have much smaller nuclei than in LSIL. Both of these qualitative comments were supported in this study. The mean diameter NC ratios of 33% and 50% could provide useful diagnostic assistance in the distinction of normal intermediate cells and LSIL and between LSIL and HSIL, respectively. Because of overlapping individual ranges, however, additional diagnostic features such as nuclear morphology must be used in the distinction of normal intermediate cells, LSIL and HSIL. No statistical difference was identified in the mean diameter NC ratios between ASC-US and LSIL in TBS publications. In addition, the proposed new BSCC low and high grades of squamous abnormality were not statistically different from ASC-US/LSIL and HSIL, respectively. This provides support that the proposed BSCC two-tier system of squamous abnormalities is comparable to TBS. This study shows that LBC has variable but major and significant effects on nuclear and cytoplasmic morphology and that quantitative definitions in conventional preparations cannot be automatically extrapolated to LBC methodology.

CONCLUSIONS

The study shows that some TBS quantitative and qualitative criteria require amendment and that an alternative quantitative approach, such as diameter NC ratio has a more valid scientific evidence base. Furthermore, use of NC ratios avoids the problems associated with the variable changes in nuclear and cytoplasmic areas, occurring between conventional and different commercial LBC preparations. By contrast, classifications based on area comparisons must be tailored to the specific conventional or commercial LBC preparation.

Proposed Sheffield quantitative criteria in cervical cytology to assist the grading of squamous cell dyskaryosis, as the British Society for Clinical Cytology definitions require amendment

OBJECTIVE

In 1986, the British Society for Clinical Cytology (BSCC) published quantitative criteria to assist diagnosis in a three-tier grading system of squamous cell dyskaryosis. In dyskaryotic cells, area nuclear to cytoplasmic (NC) ratios below 50%, between 50% and 66% and over 66% were defined as equating with mild, moderate and severe grades respectively. Following the Terminology Conference in 2002, however, the BSCC recommended on their website that the three-tier model should be replaced by a new two-tier system of low- and high-grade squamous abnormalities. The latter broadly equate with the two-grade Bethesda System (TBS) for reporting squamous intraepithelial lesions. The purpose of this study was to assess the accuracy and reproducibility of the BSCC three-tier quantitative definitions, to investigate if they were applicable to liquid-based cytology (LBC) and to see how they related to the proposed new two-tier BSCC system.

METHODS

Quantitative image analysis was undertaken on illustrations from the 1986 BSCC terminology publication and on microscope slides from external quality assessment and Cytology Training Centre teaching sets.

RESULTS

Analysis of mean NC ratios showed that mild, moderate and severe dyskaryosis exist as statistically different populations. Overlap of NC ratio ranges, however, limits their practical application in the three-tier model, although interestingly no overlap was noted between mild and severe dyskaryosis. No grade of dyskaryosis had a mean area NC ratio over 50%, indicating that the BSCC quantitative definitions are incorrect. The mean diameter NC ratios for mild, moderate and severe dyskaryosis were found to be 40%, 49% and 66% respectively. Accordingly it is possible that those reporting cervical cytology could be interpreting the BSCC NC ratios as meaning diameter rather than area. Amalgamation of the three-tier results into the proposed two-tier model shows that the resulting mean NC area and diameter ratios identify statistically different low- and high-grade populations. The reduced degree of overlap, however, of NC ratio ranges in the two-tier model implies that NC ratios could have a useful practical role in the separation of the low- and high-grade categories. The two categories were reasonably well separated by mean area and diameter NC ratios of 25% and 50% respectively. A two-tier model combining mild with moderate rather than severe dyskaryosis was found to be a statistically valid alternative but gave rise to NC ratios that would be difficult to use in practice. Except for moderate dyskaryosis, no significant differences were identified between the mean NC ratios of either conventional and LBC preparations or LBC preparations using two different commercial methodologies (SurePath and ThinPrep). Differences, however, were noted in area measurements between SurePath and ThinPrep and this has potential implications for classifications (such as TBS) using area comparisons as their basis. In addition, it was found that the increased NC ratio, associated with higher grades of dyskaryosis is more a consequence of progressive cytoplasmic area reduction rather than nuclear area increase. The similar NC ratios of borderline nuclear changes associated with human papilloma virus and mild dyskaryosis support the BSCC proposal that these can be combined to constitute a low-grade category. This study shows that the BSCC area NC ratio criteria of grading squamous cell dyskaryosis require amendment. In addition, this study supports the new BSCC recommendation of low- and high-grade squamous cell categories.

CONCLUSIONS

The study proposes Sheffield quantitative criteria to assist the grading of squamous cell abnormalities. Quantitative diameter NC ratio measurements, however, must always be accompanied by detailed assessment of qualitative morphological features and in particular those relating to nuclear chromatin. This is equally relevant to both two- and three-tier models.

Hydration level monitoring using embedded piezoresistive microcantilever sensors

A new MEMS based sensor technology, embedded piezoresistive microcantilever (EPM) sensors, may be useful in the real-time monitoring of hydration levels in athletes or other individuals whose activities may result in dehydration. In these devices, organic polymers or functionalized polymeric materials respond to osmolality changes in a person's saliva by expanding or contracting volumetrically. These volumetric changes are measured by tiny piezoresistive microcantilevers embedded in the polymeric material. In this report, we have tested a prototype device utilizing UV crosslinked poly(vinyl acetate) as the active sensing material. This device was able to reliably respond to 1% changes in sodium chloride concentration in solution or alternately to 1% changes in relative humidity.

Human embryonal carcinoma stem cells: models of embryonic development in humans

There are few reliable experimental systems available to study the molecular mechanisms that govern human embryonic development. Embryonal carcinoma (EC) cells are pluripotent stem cells derived from teratocarcinomas and are considered the malignant counterparts of human embryonic stem (ES) cells. Several of the existing human EC stem cell lines provide robust and simple culture systems to study certain aspects of cellular differentiation in a manner pertinent to human embryogenesis. Here we review the strategies used to derive and characterize the established and recognized human EC stem cell line TERA2.cl.SP12. Furthermore, we demonstrate the value of human EC stem cells as a model of early development and focus on cell fate determination in the embryonic ectoderm.

Contamination of chicken carcasses in Gauteng, South Africa, by Salmonella, Listeria monocytogenes and Campylobacter

The presence of the foodborne pathogens, Salmonella spp., Listeria monocytogenes and Campylobacter spp., on 99 fresh and frozen chicken carcasses sourced from various retailers in Gauteng, South Africa, was investigated. Using culture methods, 60.6% of the carcasses were found to be contaminated with one or more pathogens, with 19.2%, 19.2% and 32.3% of the carcasses being found to harbour Salmonella, L. monocytogenes and Campylobacter, respectively. The extent of contamination with one or more pathogens was not significantly different (p>0.1) between fresh or frozen samples or between samples from butcheries, supermarkets or street vendors. Significantly more (p<0.1) fresh carcasses from butcheries than from other outlets were contaminated with Salmonella, while more fresh carcasses from supermarkets were contaminated with Campylobacter. The proportion of carcasses with L. monocytogenes from all sources were similar. Polymerase chain reaction (PCR) results indicate an even higher extent of pathogen contamination, but the PCR techniques need to be further refined before they can be used routinely.