Singularly Perturbed Monotone Systems and an Application to Double Phosphorylation Cycles

The theory of monotone dynamical systems has been found very useful in the modeling of some gene, protein, and signaling networks. In monotone systems, every net feedback loop is positive. On the other hand, negative feedback loops are important features of many systems, since they are required for adaptation and precision. This paper shows that, provided that these negative loops act at a comparatively fast time scale, the main dynamical property of (strongly) monotone systems, convergence to steady states, is still valid. An application is worked out to a double-phosphorylation ``futile cycle'' motif which plays a central role in eukaryotic cell signaling.Comment: 21 pages, 3 figures, corrected typos, references remove

The JWST early-release science program for direct observations of exoplanetary systems II: A 1 to 20 μm spectrum of the planetary-mass companion VHS 1256-1257 b

Stars and planetary system

An evaluation of the hydrogen sulphide water screening test and coliform counts for water quality assessment in rural Malaysia

The H2S water screening test and the membrane filtration faecal coliform count were compared with Escherichia coli counts for water samples collected from household water sources and domestic drinking water in rural Malaysia. Water samples were taken from 151 wells, 44 taps supplying water from the treated municipal supply and 192 domestic stored water supplies. E. coli were detected in 20% of the samples (42% of wells, 7% of tap water and 6% of drinking water). Excellent correlation (Spearman's rank correlation rs = 0 · 93) was found between the faecal coliform and E. coli counts for all sample types. The H2S method was poorly correlated whether read at 18 or 30 h. False positive rates were highest for well water, and false negative rates were highest for both well and drinking water samples, with low E. coli counts. The faecal coliform test was an excellent predictor of the presence of E. coli in these water samples, while the H2S test was very inadequate

Energy storage for wind integration: Hydropower and other contributions

The amount of wind power and other timevariable non-dispatchable renewable energy sources (RES) is rapidly increasing in the world. A few power systems are already facing very high penetrations from variable renewables which can surpass the systems’ consumption during no-load periods, requiring the energy excess to be curtailed, exported or stored. The limitations of electric energy storage naturally lead to the selection of the well-known form of storing potential energy in reservoirs of reversible hydropower stations, although other technologies such as heat storage are also being used successfully. This paper reviews the storage technologies that are available and may be used on a power system scale and compares their advantages and disadvantages for the integration of fast-growing renewables, such as wind power, with a special focus on the role of pumped hydro storage

Does obesity compromise survival in women with breast cancer?

Summary Obesity, measured by high body mass index (BMI430 kg/m2) is associated with an increased risk of postmenopausal breast cancer but the effect of obesity on prognosis is not clear. A prospectively accrued and regularly validated database of 1579 patients with breast cancer treated in a district general hospital between 1963 and 1999 was analysed for clinical and pathological tumour characteristics including the family history, grade, tumour type, treatment and outcome. The risk factors and outcome of obese and non-obese patients were compared. Breast cancer in obese women was associated with significantly larger tumour size and worse Nottingham prognostic index. There was no statistically significant difference in overall and disease-free survival between obese and nonobese group. Hazard ratios (95% Cl) were 0.81 (0.62–1.06) and 0.80 (0.63–1.01), respectively. In the present study, obesity is not an indicator of worst prognosis of breast cancer