Theoretical studies of the phase transition in the anisotropic 2-D square spin lattice

The phase transition occurring in a square 2-D spin lattice governed by an anisotropic Heisenberg Hamiltonian has been studied according to two recently proposed methods. The first one, the Dressed Cluster Method, provides excellent evaluations of the cohesive energy, the discontinuity of its derivative around the critical (isotropic) value of the anisotropy parameter confirms the first-order character of the phase transition. Nevertheless the method introduces two distinct reference functions (either N\'eel or XY) which may in principle force the discontinuity. The Real Space Renormalization Group with Effective Interactions does not reach the same numerical accuracy but it does not introduce a reference function and the phase transition appears qualitatively as due to the existence of two domains, with specific fixed points. The method confirms the dependence of the spin gap on the anisotropy parameter occurring in the Heisenberg-Ising domain

Equivalent Sensor Radiance Generation and Remote Sensing from Model Parameters

In this paper we describe a general procedure for calculating equivalent sensor radiances from variables output from a global atmospheric forecast model. In order to take proper account of the discrepancies between model resolution and sensor footprint the algorithm takes explicit account of the model subgrid variability, in particular its description of the probably density function of total water (vapor and cloud condensate.) The equivalent sensor radiances are then substituted into an operational remote sensing algorithm processing chain to produce a variety of remote sensing products that would normally be produced from actual sensor output. This output can then be used for a wide variety of purposes such as model parameter verification, remote sensing algorithm validation, testing of new retrieval methods and future sensor studies. We show a specific implementation using the GEOS-5 model, the MODIS instrument and the MODIS Adaptive Processing System (MODAPS) Data Collection 5.1 operational remote sensing cloud algorithm processing chain (including the cloud mask, cloud top properties and cloud optical and microphysical properties products.) We focus on clouds and cloud/aerosol interactions, because they are very important to model development and improvement

Checks and Balances in Autoimmune Vasculitis

Age-associated changes in the immune system including alterations in surface protein expression are thought to contribute to an increased susceptibility for autoimmune diseases. The balance between the expression of coinhibitory and costimulatory surface protein molecules, also known as immune checkpoint molecules, is crucial in fine-tuning the immune response and preventing autoimmunity. The activation of specific inhibitory signaling pathways allows cancer cells to evade recognition and destruction by the host immune system. The use of immune checkpoint inhibitors (ICIs) to treat cancer has proven to be effective producing durable antitumor responses in multiple cancer types. However, one of the disadvantages derived from the use of these agents is the appearance of inflammatory manifestations termed immune-related adverse events (irAEs). These irAEs are often relatively mild, but more severe irAEs have been reported as well including several forms of vasculitis. In this article, we argue that age-related changes in expression and function of immune checkpoint molecules lead to an unstable immune system, which is prone to tolerance failure and autoimmune vasculitis development. The topic is introduced by a case report from our hospital describing a melanoma patient treated with ICIs and who subsequently developed biopsy-proven giant cell arteritis. Following this case report, we present an in-depth review on the role of immune checkpoint pathways in the development and progression of autoimmune vasculitis and its relation with an aging immune system

Computational Characterization of a Cholesterol-Based Molecular Rotor in Lipid Membranes

Biophysical properties of cellular membranes critically depend on their content of cholesterol and its interaction with various other lipid species. Cholesterol-dependent friction at the nanoscale can be studied with molecular rotors, whose quantum yield depends on rotational dynamics of functional groups during their excited state lifetime. Here, we present a detailed computational analysis of a phenyl-BODIPY-linked cholesterol based molecular rotor in direct comparison with the well-known TopFluor-cholesterol. We describe a new parametrization strategy of force field parameters for the BODIPY moiety and carry out extensive molecular dynamics simulations of the probe in membranes in the absence or presence of cholesterol. Our study quantifies the extent of membrane perturbation by these probes, analyzes their tilting resistance in the bilayer and derives dynamic properties directly related to the rotor propensity. We show that phenyl-BODIPY-cholesterol bears potential as a cholesterol-dependent molecular rotor to report about microviscosity of sterol-containing model and cell membranes.</p

Nystr\"om methods for high-order CQ solutions of the wave equation in two dimensions

We investigate high-order Convolution Quadratures methods for the solution of the wave equation in unbounded domains in two dimensions that rely on Nystr\"om discretizations for the solution of the ensemble of associated Laplace domain modified Helmholtz problems. We consider two classes of CQ discretizations, one based on linear multistep methods and the other based on Runge-Kutta methods, in conjunction with Nystr\"om discretizations based on Alpert and QBX quadratures of Boundary Integral Equation (BIE) formulations of the Laplace domain Helmholtz problems with complex wavenumbers. We present a variety of accuracy tests that showcase the high-order in time convergence (up to and including fifth order) that the Nystr\"om CQ discretizations are capable of delivering for a variety of two dimensional scatterers and types of boundary conditions

Optimisation of Car Park Designs

The problem presented by ARUP to the UK Study Group 2014 was to investigate methods for maximising the number of car parking spaces that can be placed within a car park. This is particularly important for basement car parks in residential apartment blocks or offices where parking spaces command a high value. Currently the job of allocating spaces is done manually and is very time intensive. The Study Group working on this problem split into teams examining different aspects of the car park design process There were three approaches taken. These approaches include a so-called "tile-and-trim" method in which an optimal layout of cars from an `infinite car park' are overlaid onto the actual car park domain; adjustments are then made to accommodate access from one lane to the next. A second approach seeks to develop an algorithm for optimising the road within a car park on the assumption that car parking spaces should fill the space and that any space needs to be adjacent to the network. A third similar approach focused on schemes for assessing the potential capacity of a small selection of specified road networks within the car park to assist the architect in selecting the optimal road network(s). The problem is a variant of the "bin packing" problem, well known in computer science. It is further complicated by the fact that two different classes of item need to be packed (roads and cars), with both local (immediate access to a road) and global (connectivity of the road network) constraints. Bin-packing is known to be NP-hard, and hence the problem at hand has at least this level of computational complexity. None of the approaches produced a complete solution to the problem posed. Indeed, it was quickly determined by the group that this was a very hard problem (a view reinforced by the many different possible approaches considered) requiring far longer than a week to really make significant progress. All approaches rely to differing degrees on optimisation algorithms which are inherently unreliable unless designed specifically for the intended purpose. It is also not clear whether a relatively simple automated computer algorithm will be able to "beat the eye of the architect"; additional sophistication may be required due to subtle constraints. Apart from determining that the problem is hard, positive outcomes have included: Determining that parking perpendicular to the road in long aisles provides the most efficient packing of cars. Provision of code which "tiles and trims" from an infinite car park onto the given car park with interactive feedback on the number of cars in the packing. Provision of code for optimal packing in a parallel-walled car park. Methods for optimising a road within a given domain based on developing cost functions ensuring that cars fill the car park and have access to the road. Provision of code for optimising a single road in a given (square) space. Description of methods for assessing the capacity of a car park for a set of given road network in order to select optimal road networks. Some ideas for developing possible solutions further

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