3,477 research outputs found
Path-integral virial estimator for reaction rate calculation based on the quantum instanton approximation
The quantum instanton approximation is a type of quantum transition state
theory that calculates the chemical reaction rate using the reactive flux
correlation function and its low order derivatives at time zero. Here we
present several path-integral estimators for the latter quantities, which
characterize the initial decay profile of the flux correlation function. As
with the internal energy or heat capacity calculation, different estimators
yield different variances (and therefore different convergence properties) in a
Monte Carlo calculation. Here we obtain a virial-type estimator by using a
coordinate scaling procedure rather than integration by parts, which allows
more computational benefits. We also consider two different methods for
treating the flux operator, i.e., local-path and global-path approaches, in
which the latter achieves a smaller variance at the cost of using second-order
potential derivatives. Numerical tests are performed for a one-dimensional
Eckart barrier and a model proton transfer reaction in a polar solvent, which
illustrates the reduced variance of the virial estimator over the corresponding
thermodynamic estimator.Comment: 23 pages, 5 figures, 1 tabl
Src as the link between inflammation and cancer.
Although a causal link between chronic inflammation and cancer has been established, the exact molecular mechanism linking inflammation to cancer remains largely unknown. It was previously postulated that molecular switches responsible for cancer cell development, and for infiltration of inflammatory cells into cancer, were divided into a distinct set of intracellular proteins and signaling pathways. However, recent evidence suggests that both tumor cells and tumor-infiltrating immune cells utilize the same kinases, mostly that of Src family, to facilitate cancer development and progression. In the past few years several groups have found that Src activation both in cancer and inflammatory cells is mainly driven by pro-inflammatory cytokines within the tumor microenvironment. Here we evaluate the cross talks between Src kinase pathways in immune cells and cancer cells. We conclude that Src might serve as a critical mechanistic link between inflammation and cancer, mediating and propagating a cycle between immune and tissue cells that can ultimately lead to the development and progression of cancer
Second-harmonic phonon spectroscopy of -quartz
We demonstrate midinfrared second-harmonic generation as a highly sensitive
phonon spectroscopy technique that we exemplify using -quartz (SiO)
as a model system. A midinfrared free-electron laser provides direct access to
optical phonon resonances ranging from to $1400\
\mathrm{cm}^{-1}T_c=846\ \mathrm{K}\alpha\beta$-quartz,
demonstrating the technique's potential for studies of phase transitions
The effectiveness of faecal removal methods of pasture management to control the cyathostomin burden of donkeys
Background:
The level of anthelmintic resistance within some cyathostomin parasite populations has increased to the level where sole reliance on anthelmintic-based control protocols is not possible. Management-based nematode control methods, including removal of faeces from pasture, are widely recommended for use in association with a reduction in anthelmintic use to reduce selection pressure for drug resistance; however, very little work has been performed to quantitatively assess the effectiveness of such methods.<p></p>
Methods:
We analysed data obtained from 345 donkeys at The Donkey Sanctuary (Devon, UK), managed under three different pasture management techniques, to investigate the effectiveness of faeces removal in strongyle control in equids. The management groups were as follows: no removal of faeces from pasture, manual, twice-weekly removal of faeces from pasture and automatic, twice-weekly removal of faeces from pasture (using a mechanical pasture sweeper). From turn-out onto pasture in May, monthly faecal egg counts were obtained for each donkey and the dataset subjected to an auto regressive moving average model.<p></p>
Results:
There was little to no difference in faecal egg counts between the two methods of faecal removal; both resulted in significantly improved cyathostomin control compared to the results obtained from the donkeys that grazed pasture from which there was no faecal removal.<p></p>
Conclusions:
This study represents a valuable and unique assessment of the effectiveness of the removal of equine faeces from pasture, and provides an evidence base from which to advocate twice-weekly removal of faeces from pasture as an adjunct for equid nematode control. Widespread adoption of this practice could substantially reduce anthelmintic usage, and hence reduce selection pressure for nematode resistance to the currently effective anthelmintic products.<p></p>
Scattering of shock waves in QCD
The cross section of heavy-ion collisions is represented as a double
functional integral with the saddle point being the classical solution of the
Yang-Mills equations with boundary conditions/sources in the form of two shock
waves corresponding to the two colliding ions. I develop the expansion of this
classical solution in powers of the commutator of the Wilson lines describing
the colliding particles and calculate the first two terms of the expansion.Comment: 23 pages, 13 figure
An Investigation of Information Systems Topic Coverage in IS versus Functional Area Business Journals
The purpose of this study is to explore the extent to which IS topics have been published in non-IS business journals (i.e., Accounting, Marketing, Operations, and Organizational Behavior), and to assess whether the IS research in these disciplines lags or leads the comparable coverage in the IS journals. Over 500,000 citations and abstracts have been collected from on-line sources and stored in a database, and analyses are underway
- …