Diffusivity dependence of the transition path ensemble

Transition pathways of stochastic dynamical systems are typically approximated by instantons. Here we show, using a dynamical system containing two competing pathways, that at low-to-intermediate temperatures, instantons can fail to capture the most likely transition pathways. We construct an approximation which includes fluctuations around the instanton and, by comparing with the results of an accurate and efficient path-space Monte Carlo sampling method, find this approximation to hold for a wide range of temperatures. Our work delimits the applicability of large deviation theory and provides methods to probe these limits numerically.Comment: 5 pages, 4 figure

Public sector as pioneer: shorter working weeks as the new gold standard

• A shorter working week in the public sector (with no loss in pay) is badly needed: burn out, work-related poor mental health and bad work-life balance plague public sector staff across organisations. • A 32-hour week in the public sector is not just desirable for worker wellbeing and for reducing the costs of burn out and presenteeism; a 32-hour week would also create hundreds of thousands of jobs and establish a new standard for all employment in the UK. ▪ It would create between 300,000 and 500,000 new full-time equivalent jobs in the sector. • Public sector employment takes up a relatively high proportion of employment in Wales, the North of England and Scotland – entailing that a 32-hour working week would benefit regions that have felt the hardship of austerity most. • Such a policy is eminently affordable and achievable: on Autonomy’s conservative calculations a 32-hour week could cost around £9bn, but the true figure could be much lower at around £5.4bn. ▪ This figure is only 6% of the public sector employment salary bill and just over 1% of the total government spending budget. • In addition to the public sector pioneering through its own working practices, we outline how procurement strategies aimed at private sector partners can encourage broader change across the UK labour market

Efficient Bayesian inference of fully stochastic epidemiological models with applications to COVID-19.

Epidemiological forecasts are beset by uncertainties about the underlying epidemiological processes, and the surveillance process through which data are acquired. We present a Bayesian inference methodology that quantifies these uncertainties, for epidemics that are modelled by (possibly) non-stationary, continuous-time, Markov population processes. The efficiency of the method derives from a functional central limit theorem approximation of the likelihood, valid for large populations. We demonstrate the methodology by analysing the early stages of the COVID-19 pandemic in the UK, based on age-structured data for the number of deaths. This includes maximum a posteriori estimates, Markov chain Monte Carlo sampling of the posterior, computation of the model evidence, and the determination of parameter sensitivities via the Fisher information matrix. Our methodology is implemented in PyRoss, an open-source platform for analysis of epidemiological compartment models

Two-Loop Superstrings VI: Non-Renormalization Theorems and the 4-Point Function

The N-point amplitudes for the Type II and Heterotic superstrings at two-loop order and for $N \leq 4$ massless NS bosons are evaluated explicitly from first principles, using the method of projection onto super period matrices introduced and developed in the first five papers of this series. The gauge-dependent corrections to the vertex operators, identified in paper V, are carefully taken into account, and the crucial counterterms which are Dolbeault exact in one insertion point and de Rham closed in the remaining points are constructed explicitly. This procedure maintains gauge slice independence at every stage of the evaluation. Analysis of the resulting amplitudes demonstrates, from first principles, that for $N\leq 3$, no two-loop corrections occur, while for N=4, no two-loop corrections to the low energy effective action occur for $R^4$ terms in the Type II superstrings, and for $F^4$, $F^2F^2$, $F^2R^2$, and $R^4$ terms in the Heterotic strings.Comment: 98 pages, no figur

Making It Stick: The UK Four-Day Week Pilot One Year On

One year on from the results of the world’s biggest ever four-day working week pilot which took place in the UK in 2022, companies that took part have reported significant and lasting success.The report offers new insight into the effects of a four-day week on workers over the longer term, as well as into the strategies used by organisations to fit shorter working hours to their particular circumstances

Ocean preconditioning of Cyclone Nargis in the Bay of Bengal : interaction between Rossby waves, surface fresh waters, and sea surface temperatures

Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 1741–1755, doi:10.1175/2011JPO4437.1.An in-depth data analysis was conducted to understand the occurrence of a strong sea surface temperature (SST) front in the central Bay of Bengal before the formation of Cyclone Nargis in April 2008. Nargis changed its course after encountering the front and tracked along the front until making landfall. One unique feature of this SST front was its coupling with high sea surface height anomalies (SSHAs), which is unusual for a basin where SST is normally uncorrelated with SSHA. The high SSHAs were associated with downwelling Rossby waves, and the interaction between downwelling and surface fresh waters was a key mechanism to account for the observed SST–SSHA coupling. The near-surface salinity field in the bay is characterized by strong stratification and a pronounced horizontal gradient, with low salinity in the northeast. During the passage of downwelling Rossby waves, freshening of the surface layer was observed when surface velocities were southwestward. Horizontal convergence of freshwater associated with downwelling Rossby waves increased the buoyancy of the upper layer and caused the mixed layer to shoal to within a few meters of the surface. Surface heating trapped in the thin mixed layer caused the fresh layer to warm, whereas the increase in buoyancy from low-salinity waters enhanced the high SSHA associated with Rossby waves. Thus, high SST coincided with high SSHA. The dominant role of salinity in controlling high SSHA suggests that caution should be exercised when computing hurricane heat potential in the bay from SSHA. This situation is different from most tropical oceans, where temperature has the dominant effect on SSHA.This work was supported by the NOAA/Office of Climate Observation (OCO) program

A robust cell cycle control mechanism limits E2F-induced proliferation of terminally differentiated cells in vivo

Overexpression of both CycE and E2F is necessary to trigger cell cycle reentry and overproliferation of terminally differentiated wing cells

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder