University of Nottingham

About: University of Nottingham is a education organization based out in Nottingham, Nottingham, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 54772 authors who have published 119600 publications receiving 4227408 citations. The organization is also known as: The University of Nottingham & University College, Nottingham.

A survey of dynamic scheduling in manufacturing systems

Abstract: In most real-world environments, scheduling is an ongoing reactive process where the presence of a variety of unexpected disruptions is usually inevitable, and continually forces reconsideration and revision of pre-established schedules. Many of the approaches developed to solve the problem of static scheduling are often impractical in real-world environments, and the near-optimal schedules with respect to the estimated data may become obsolete when they are released to the shop floor. This paper outlines the limitations of the static approaches to scheduling in the presence of real-time information and presents a number of issues that have come up in recent years on dynamic scheduling. The paper defines the problem of dynamic scheduling and provides a review of the state-of-the-art of currently developing research on dynamic scheduling. The principles of several dynamic scheduling techniques, namely, heuristics, meta-heuristics, multi-agent systems, and other artificial intelligence techniques are described in detail, followed by a discussion and comparison of their potential.

Mid-infrared supercontinuum covering the 1.4–13.3 μm molecular fingerprint region using ultra-high NA chalcogenide step-index fibre

Abstract: Mid-infrared supercontinuum generation with a record-breaking spectral coverage of 1.4–13.3 µm is demonstrated by launching intense ultra-short pulses into short pieces of ultra-high numerical aperture step-index chalcogenide glass optical fibre consisting of a GaAsSe cladding and an As2Se3 core.

Antisense gene that inhibits synthesis of the hormone ethylene in transgenic plants

Abstract: ETHYLENE controls many physiological and developmental processes in higher plants, including ripening of fruit, abscission, senescence and responses to wounding1. Although the accumulation of messenger RNAs in ripening fruit and senescing leaves has been correlated with ethylene production and perception2–4, the regulatory mechanisms governing ethylene synthesis and the stimulation of gene expression by ethylene are not understood. We have previously shown that the complementary DNA, pTOM13, corresponds to an mRNA whose synthesis is correlated with that of ethylene in ripening fruit and wounded leaves5,6,8. The pTOM13 mRNA encodes a protein of relative molecular mass 35,0006. The cDNA and three related genomic clones have been sequenced, but the function of the protein is unknown7–9. We show here that antisense RNA, which has previously been used only to reduce the expression of genes of known function10–12, when applied to pTOM13, reduces ethylene synthesis in a gene dosage-dependent manner. Analysis of these novel mutants suggests that pTOM13 encodes a polypeptide involved in the conversion of 1-amino-cyclopropane-1-carboxylic acid to ethylene by the ethylene-forming enzyme (ACC-oxidase).

Warm dark matter as a solution to the small scale crisis: New constraints from high redshift Lyman-α forest data

Abstract: We present updated constraints on the free-streaming of warm dark matter (WDM) particles derived from an analysis of the Lyman-$\ensuremath{\alpha}$ flux power spectrum measured from high-resolution spectra of 25 $zg4$ quasars obtained with the Keck High Resolution Echelle Spectrometer and the Magellan Inamori Kyocera Echelle spectrograph. We utilize a new suite of high-resolution hydrodynamical simulations that explore WDM masses of 1, 2 and 4 keV (assuming the WDM consists of thermal relics), along with different physically motivated thermal histories. We carefully address different sources of systematic error that may affect our final results and perform an analysis of the Lyman-$\ensuremath{\alpha}$ flux power with conservative error estimates. By using a method that samples the multidimensional astrophysical and cosmological parameter space, we obtain a lower limit ${m}_{\mathrm{WDM}}\ensuremath{\gtrsim}3.3\text{ }\text{ }\mathrm{keV}$ ($2\ensuremath{\sigma}$) for warm dark matter particles in the form of early decoupled thermal relics. Adding the Sloan Digital Sky Survey Lyman-$\ensuremath{\alpha}$ flux power spectrum does not improve this limit. Thermal relics of masses 1, 2 and 2.5 keV are disfavored by the data at about the $9\ensuremath{\sigma}$, $4\ensuremath{\sigma}$ and $3\ensuremath{\sigma}$ C.L., respectively. Our analysis disfavors WDM models where there is a suppression in the linear matter power spectrum at (nonlinear) scales corresponding to $k=10h/\mathrm{Mpc}$ which deviates more than 10% from a Lambda cold dark matter model. Given this limit, the corresponding ``free-streaming mass'' below which the mass function may be suppressed is $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{8}{h}^{\ensuremath{-}1}{\mathrm{M}}_{\ensuremath{\bigodot}}$. There is thus very little room for a contribution of the free-streaming of WDM to the solution of what has been termed the small scale crisis of cold dark matter.