The structural dynamics of a molecule are determined by the underlying potential energy landscape. Conical intersections are funnels connecting otherwise separate potential energy surfaces. Posited ...almost a century ago
, conical intersections remain the subject of intense scientific interest
. In biology, they have a pivotal role in vision, photosynthesis and DNA stability
. Accurate theoretical methods for examining conical intersections are at present limited to small molecules. Experimental investigations are challenged by the required time resolution and sensitivity. Current structure-dynamical understanding of conical intersections is thus limited to simple molecules with around ten atoms, on timescales of about 100 fs or longer
. Spectroscopy can achieve better time resolutions
, but provides indirect structural information. Here we present few-femtosecond, atomic-resolution videos of photoactive yellow protein, a 2,000-atom protein, passing through a conical intersection. These videos, extracted from experimental data by machine learning, reveal the dynamical trajectories of de-excitation via a conical intersection, yield the key parameters of the conical intersection controlling the de-excitation process and elucidate the topography of the electronic potential energy surfaces involved.
We describe a new generation of algorithms capable of mapping the structure and conformations of macromolecules and their complexes from large ensembles of heterogeneous snapshots, and demonstrate ...the feasibility of determining both discrete and continuous macromolecular conformational spectra. These algorithms naturally incorporate conformational heterogeneity without resort to sorting and classification, or prior knowledge of the type of heterogeneity present. They are applicable to single-particle diffraction and image datasets produced by X-ray lasers and cryo-electron microscopy, respectively, and particularly suitable for systems not easily amenable to purification or crystallization.
The advent of the X-ray free-electron laser (XFEL) has made it possible to record diffraction snapshots of biological entities injected into the X-ray beam before the onset of radiation damage. ...Algorithmic means must then be used to determine the snapshot orientations and thence the three-dimensional structure of the object. Existing Bayesian approaches are limited in reconstruction resolution typically to 1/10 of the object diameter, with the computational expense increasing as the eighth power of the ratio of diameter to resolution. We present an approach capable of exploiting object symmetries to recover three-dimensional structure to high resolution, and thus reconstruct the structure of the satellite tobacco necrosis virus to atomic level. Our approach offers the highest reconstruction resolution for XFEL snapshots to date and provides a potentially powerful alternative route for analysis of data from crystalline and nano-crystalline objects.
The paper reviews the World Trade Organization's analysis of developments in China's trade policy during 2012–14. The review overlaps with the continuing Great Recession and with China's ...determination to foster a sustainable rate of economic growth. Developments in the country's trade policy include the launching of the Shanghai pilot free trade zone. China faces a series of trade policy‐related challenges including the complex process necessary to internationalise the renminbi.
Imperfect knowledge of the times at which 'snapshots' of a system are recorded degrades our ability to recover dynamical information, and can scramble the sequence of events. In X-ray free-electron ...lasers, for example, the uncertainty--the so-called timing jitter--between the arrival of an optical trigger ('pump') pulse and a probing X-ray pulse can exceed the length of the X-ray pulse by up to two orders of magnitude, marring the otherwise precise time-resolution capabilities of this class of instruments. The widespread notion that little dynamical information is available on timescales shorter than the timing uncertainty has led to various hardware schemes to reduce timing uncertainty. These schemes are expensive, tend to be specific to one experimental approach and cannot be used when the record was created under ill-defined or uncontrolled conditions such as during geological events. Here we present a data-analytical approach, based on singular-value decomposition and nonlinear Laplacian spectral analysis, that can recover the history and dynamics of a system from a dense collection of noisy snapshots spanning a sufficiently large multiple of the timing uncertainty. The power of the algorithm is demonstrated by extracting the underlying dynamics on the few-femtosecond timescale from noisy experimental X-ray free-electron laser data recorded with 300-femtosecond timing uncertainty. Using a noisy dataset from a pump-probe experiment on the Coulomb explosion of nitrogen molecules, our analysis reveals vibrational wave-packets consisting of components with periods as short as 15 femtoseconds, as well as more rapid changes, which have yet to be fully explored. Our approach can potentially be applied whenever dynamical or historical information is tainted by timing uncertainty.
'Monetary policy in low financial development countries' is about a significant and evolving subject. Designing and implementing monetary policy is complex, and considering an economy's stage of ...development adds further problems. Theoretical advances are important alongside empirical analyses incorporating an economy's features. The book shows that the ground remains fertile for research on monetary policy in developing economies -ranging from the international transmission mechanism of monetary policy to central bank behaviour and communication strategies.
In Australia, and internationally, the shortage of organ and tissue donors significantly limits the number of patients with critical organ or tissue failure who are able to receive a transplant each ...year. The rationale for xenotransplantation - the transplantation of living cells, tissues or organs from one species to another - is to meet this shortfall in human donor material. While early clinical trials showed promise, particularly in patients with type I diabetes whose insulin dependence could be temporarily reversed by the transplantation of porcine islet cells, these benefits have been balanced with scientific, clinical and ethical concerns revolving around the risks of immune rejection and the potential transmission of porcine endogenous retroviruses or other infectious agents from porcine grafts to human recipients. However, the advent of CRISPR/Cas9, a revolutionary gene editing technology, has reignited interest in the field with the possibility of genetically engineering porcine organs and tissues that are less immunogenic and have virtually no risk of transmission of porcine endogenous retroviruses. At the same time, CRISPR/Cas9 may also open up a myriad of possibilities for tissue engineering and stem cell research, which may complement xenotransplantation research by providing an additional source of donor cells, tissues and organs for transplantation into patients. The recent international symposium on gene editing, organised by the US National Academy of Sciences, highlights both the enormous therapeutic potential of CRISPR/Cas9 and the raft of ethical and regulatory challenges that may follow its utilisation in transplantation and in medicine more generally.
This paper presents a hybrid-based multi-agent system (MAS) for integrating process planning with scheduling/rescheduling in job shops or similar kinds of flexible manufacturing environments. The ...approach is called Online Hybrid Agent-based Negotiation (oHAN). It employs the affected operations rescheduling approach to reschedule the operations affected directly or indirectly by the disruptions. The proposed MAS architecture comprises local agents, which are the part and machine agents, and a supervisor agent. The local agents detect the production disturbances and reschedule the affected operations via decentralized negotiations. A comprehensive set of process plan flexibilities including flexible routings and alternative machines is considered during rescheduling. The supervisor agent coordinates and monitors the rescheduling process in order to ensure the observance of a global rescheduling objective. An online hybrid contract-net negotiation protocol (oHCNP) has been established to control the interactions and communications among agents. Two types of disturbances, machine breakdown and new part arrival, are investigated in this paper. Extensive experiments have been conducted and the results show that the proposed approach is effective in solving a large-scale rescheduling problem in a reasonable time. With the introduction of the supervisory control into the decentralized negotiations, the hybrid approach is able to provide solutions with a better global performance.
Terrestrial neutron and alpha particle irradiation data for a 7-nm bulk FinFET technology reveal the persisting reliability threat single-event latchup (SEL) poses to advanced technology nodes. SEL ...is characterized over a wide range of supply voltages and temperatures for this technology node. SEL data is analyzed to determine the holding voltage (<inline-formula> <tex-math notation="LaTeX">V_{\mathrm {HOLD}} </tex-math></inline-formula>) required to sustain SEL, which can be as low as 0.85 V at elevated temperatures. Such low SEL holding voltage within 100 mV of nominal supply voltage poses a major reliability threat.
This paper presents an ant colony optimization (ACO) algorithm in an agent-based system to integrate process planning and shopfloor scheduling (IPPS). The search-based algorithm which aims to obtain ...optimal solutions by an autocatalytic process is incorporated into an established multi-agent system (MAS) platform, with advantages of flexible system architectures and responsive fault tolerance. Artificial ants are implemented as software agents. A graph-based solution method is proposed with the objective of minimizing makespan. Simulation studies have been established to evaluate the performance of the ant approach. The experimental results indicate that the ACO algorithm can effectively solve the IPPS problems and the agent-based implementation can provide a distributive computation of the algorithm.
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