Transport coefficients of a mesoscopic fluid dynamics model

We investigate the properties of stochastic rotation dynamics (Malevanets-Kapral method), a mesoscopic model used for simulating fluctuating hydrodynamics. Analytical results are given for the transport coefficients. We discuss the most efficient way of measuring the transport properties and obtain excellent agreement between the theoretical and numerical calculations.Comment: 12 pages, 9 figures, submitted to J. Chem. Phy

Gauge invariance and non-constant gauge couplings

It is shown that space-time dependent gauge couplings do not completely break gauge invariance. We demonstrate this in various gauge theories.Comment: 18 page

Quantum gravitational optics: the induced phase

The geometrical approximation of the extended Maxwell equation in curved spacetime incorporating interactions induced by the vacuum polarization effects is considered. Taking into account these QED interactions and employing the analogy between eikonal equation in geometrical optics and Hamilton-Jacobi equation for the particle motion, we study the phase structure of the modified theory. There is a complicated, local induced phase which is believed to be responsible for the modification of the classical picture of light ray. The main features of QGO could be obtained through the study of this induced phase. We discuss initial principles in conventional and modified geometrical optics and compare the results.Comment: 10 pages, REVTex forma

Assessing with e-Ase

The Educational Development Unit have produced a guide to assist academic staff in transforming assessment practices underpinned by technology. 'Assessing with e-Ase' highlights how technology combined with sound pedagogy has the potential to enhance the student experience of learning, teaching and assessment. Drawing on the experiences, knowledge and understanding of the e-assessment project at Middlesex University, it offers a consideration of contextual, procedural and logistical factors that may impact when using e-assessment practices. Key issues for consideration when developing and implementing e-assessment are included along with the part played by policy and strategy. Examples of departmental case studies, an outline of the support available to staff and links to resources that may provide useful additional information are also included

The Engagement Model of Person-Environment Interaction

This article focuses on growth-promoting aspects in the environment, and the authors propose a strength-based, dynamic model of person-environment interaction. The authors begin by briefly discussing the typical recognition of contextual variables in models that rely on the concept of person-environment fit. This is followed by a review of recent approaches to incorporating positive environmental factors in conceptualizations of human functioning. These approaches lead to an alternative model of person-environment interaction in which the engagement construct (i.e., the quality of a person-environment relationship determined by the extent to which negotiation, participation, and evaluation processes occur during the interaction) replaces the static notion of fit. Finally, the authors outline recommendations for overcoming environmental neglect in research, practice, and training

Labels for non-individuals

Quasi-set theory is a first order theory without identity, which allows us to cope with non-individuals in a sense. A weaker equivalence relation called ``indistinguishability'' is an extension of identity in the sense that if $x$ is identical to $y$ then $x$ and $y$ are indistinguishable, although the reciprocal is not always valid. The interesting point is that quasi-set theory provides us a useful mathematical background for dealing with collections of indistinguishable elementary quantum particles. In the present paper, however, we show that even in quasi-set theory it is possible to label objects that are considered as non-individuals. We intend to prove that individuality has nothing to do with any labelling process at all, as suggested by some authors. We discuss the physical interpretation of our results.Comment: 11 pages, no figure

Measurement of the Spin-forbidden Decay rate (3s3d)1^{1}D2_{2} →\to (3s3p)3^{3}P2,1_{2,1} in 24^{24}Mg

We have measured the spin-forbidden decay rate from (3s3d)$^{1}$D$_{2}$ $\to$ (3s3p)$^{3}$P$_{2,1}$ in $^{24}$Mg atoms trapped in a magneto-optical trap. The total decay rate, summing up both exit channels (3s3p)$^{3}$P$_{1}$ and (3s3p)$^{3}$P$_{2}$, yields (196 $\pm$ 10) s$^{-1}$ in excellent agreement with resent relativistic many-body calculations of [S.G. Porsev et al., Phys. Rev. A. \textbf{64}, 012508 (2001)]. The characterization of this decay channel is important as it may limit the performance of quantum optics experiments carried out with this ladder system as well as two-photon cooling experiments currently explored in several groups.Comment: 9 pages, 4 figure

The early summertime Saharan heat low: sensitivity of the radiation budget and atmospheric heating to water vapour and dust aerosol

The Saharan heat low (SHL) is a key component of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variabil- ity in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quan- tify the independent effects of variability in dust and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Al- geria (21.4◦ N, 0.9◦ E), close to the SHL core for June 2011. Overall, we find dust aerosol and water vapour to be of simi- lar importance in driving variability in the top-of-atmosphere (TOA) radiation budget and therefore the column-integrated heating over the SHL (∼ 7 W m−2 per standard deviation of dust aerosol optical depth – AOD). As such, we infer that SHL intensity is likely to be similarly enhanced by the ef- fects of dust and water vapour surge events. However, the details of the processes differ. Dust generates substantial ra- diative cooling at the surface (∼ 11 W m−2 per standard devi- ation of dust AOD), presumably leading to reduced sensible heat flux in the boundary layer, which is more than com- pensated by direct radiative heating from shortwave (SW) absorption by dust in the dusty boundary layer. In contrast, water vapour invokes a radiative warming at the surface of ∼ 6 W m−2 per standard deviation of column-integrated wa- ter vapour in kg m−2 . Net effects involve a pronounced net atmospheric radiative convergence with heating rates on av- erage of 0.5 K day−1 and up to 6 K day−1 during synop- tic/mesoscale dust events from monsoon surges and convec- tive cold-pool outflows (“haboobs”). On this basis, we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. De- pending on the synoptic context over the region, processes driving variability involve both independent effects of water vapour and dust and compensating events in which dust and water vapour are co-varying. Forecast models typically have biases of up to 2 kg m−2 in column-integrated water vapour (equivalent to a change in 2.6 W m−2 TOA net flux) and typically lack variability in dust and thus are expected to poorly represent these couplings. An improved representa- tion of dust and water vapour and quantification of associ- ated radiative impact in models is thus imperative to further understand the SHL and related climate processes