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Activities in an intensive care unit (ICU) at a major teaching hospital are modelled by means of a queue-theoretic approach. Using data supplied by the ICU relating to the admissions process, the bed availability and the length of stay of patients, it was possible to fit theoretical distributions to the observed ‘arrival’ and ‘service’ distributions. Queueing equations relevant to a multi-channel system having random arrivals and hyper-exponential service times for each channel are set up, and solved iteratively. Results obtained match well with observations, and the model is then utilised to investigate several ‘what if? ’ scenarios. Reference is made to a simulation model developed in conjunction with the queueing model.

The metronomic predictability of the environment has elicited strong selection pressures for the evolution of endogenous circadian clocks. Circadian clocks drive molecular and behavioural rhythms that approximate the 24 h periodicity of our environment. Found almost ubiquitously among phyla, circadian clocks allow preadaptation to rhythms concomitant with the natural cycles of the Earth. Cycles in light intensity and temperature for example act as important cues that couple circadian clocks to the environment via a process called entrainment. This review summarizes our current understanding of the general and molecular principles of entrainment in the model organism Neurospora crassa, a simple eukaryote that has one of the best-studied circadian systems and light-signalling pathways.

The intensive care unit (ICU) of a hospital is an essential yet costly resource. Consequently, intensive care modelling has become increasingly prevalent in recent years in attempts to increase efficiency and reduce costs. Previous models have usually assumed that the numbers of beds available are restricted; when all beds are occupied, any additional patients are referred elsewhere or elective surgeries are cancelled. In this study, activities at the ICU at a large teaching hospital were modelled using data relating to all admissions to the ICU during the year 2000—a total of 1084 admissions. The unit is unusual in that the majority of patients referred for intensive care therapy are admitted. Bed numbers are increased when necessary to cope with demand. However, nurses are a restricted resource. In order to maintain the required nurse:patient ratio of at least one:one, supplementary nurses are employed during busy periods. Supplementary nurse costs are substantial and so nurse utilization must be closely monitored. The development of a model that calculates the required number of supplementary nurses per shift, and also encapsulates the time-dependent nature of elective surgery admissions and complex duration-of-stay profiles, is presented in this paper. In particular, the model is used to determine the number of rostered nurses that are required to minimize overall nursing staff costs.

Light is one of the major signals that keep biological clocks in harmony with the outside world. Consequently, if we want to understand how circadian clocks function at the molecular level, a study of the lightinput pathways to the clock is of fundamental importance.

Marine invertebrate taxa that survived the late Permian (latest Changhsingian) mass extinction event are all much smaller than they were prior to the event, an example of the Lilliput effect. New taxa that first appeared in the immediate extinction aftermath are also small compared to their size in younger strata. The Lilliput effect is a temporary phenomenon, with most surviving taxa returning to pre-extinction size in the first two conodont zones of the Triassic. In this study, the growth rates, of some of the Early Triassic Lilliput animals, estimated by growth-line analysis, were compared from different stratigraphic levels to determine how this variable fluctuated as body size returned to pre-extinction values after the event. Specimens were collected from the Mazzin and Siusi members of the Werfen Formation in northern Italy, from facies deposited in a tropical, mixed siliciclastic-carbonate ramp setting. Measurements of the bivalves Unionites and Claraia, the gastropod Bellerophon and the brachiopod '. Lingula' were made in the field, with subsequent growth-line analysis conducted on well-preserved specimens of 'Lingula'. Specimens collected from the basal Triassic Mazzin Member were smaller than those from the younger Siusi Member. Growth-line analysis indicates that the smaller Mazzin Member specimens had a greater number of more closely spaced growth lines than the larger Siusi Member specimens. The small, 'Lilliput' animals living in the immediate aftermath of the Late Permian event therefore suffered more interruptions to growth and had overall slower growth rates than larger individuals living in later recovery times. Frequent interruptions to growth and an overall slower growth rate in specimens from the Hindeodus parvus and Isarcicella isarcica zones of the Mazzin Member (lower Induan) reflects suboptimal environmental conditions, such as the frequency or severity of low-oxygen episodes, temperature extremes, and/or disruptions to primary productivity. © 2010 Elsevier B.V.

In this study we devised an equation that provides a new way of identifying B-cell chronic lymphocytic leukemia (CLL) patients who will require early therapeutic intervention. The equation was developed by studying the biology of the disease with a focus on cell signal transduction. Using statistical analysis, we show that measured tyrosine phosphorylation can be described as a function of VH gene mutation status, and the expression of ZAP-70 and CD38 (r2 = 0.81, n = 49). Furthermore, we show that tyrosine phosphorylation has biological relevance as it sets a threshold for the activation of the transcription factor, NF-kB, resulting in the modulation of cell survival. Using the equation derived from our training dataset we calculated tyrosine phosphorylation in a cohort of 155 unselected CLL patient samples. The patient cohort was then divided into those with calculated tyrosine phosphorylation above or below the threshold required to activate NF-kB. Patients with high calculated tyrosine phosphorylation had a shorter time to first treatment. This method identified more patients at risk of requiring early treatment than VH gene mutation status, ZAP-70 or CD38. Furthermore, calculated tyrosine phosphorylation identifies patients that will require early intervention within the mutated VH gene cohort and even patients that have Stage A disease.

The metronomic predictability of the environment has elicited strong selection pressures for the evolution of endogenous circadian clocks. Circadian clocks drive molecular and behavioural rhythms that approximate the 24 h periodicity of our environment. Found almost ubiquitously among phyla, circadian clocks allow preadaptation to rhythms concomitant with the natural cycles of the Earth. Cycles in light intensity and temperature for example act as important cues that couple circadian clocks to the environment via a process called entrainment. This review summarizes our current understanding of the general and molecular principles of entrainment in the model organism Neurospora crassa , a simple eukaryote that has one of the best-studied circadian systems and light-signalling pathways.