Aspects of Defect Topology in Smectic Liquid Crystals

We study the topology of smectic defects in two and three dimensions. We give a topological classification of smectic point defects and disclination lines in three dimensions. In addition we describe the combination rules for smectic point defects in two and three dimensions, showing how the broken translational symmetry of the smectic confers a path dependence on the result of defect addition.Comment: 19 pages, 13 figure

Erasure Correction for Noisy Radio Networks

The radio network model is a well-studied model of wireless, multi-hop networks. However, radio networks make the strong assumption that messages are delivered deterministically. The recently introduced noisy radio network model relaxes this assumption by dropping messages independently at random. In this work we quantify the relative computational power of noisy radio networks and classic radio networks. In particular, given a non-adaptive protocol for a fixed radio network we show how to reliably simulate this protocol if noise is introduced with a multiplicative cost of poly(log Delta, log log n) rounds where n is the number nodes in the network and Delta is the max degree. Moreover, we demonstrate that, even if the simulated protocol is not non-adaptive, it can be simulated with a multiplicative O(Delta log ^2 Delta) cost in the number of rounds. Lastly, we argue that simulations with a multiplicative overhead of o(log Delta) are unlikely to exist by proving that an Omega(log Delta) multiplicative round overhead is necessary under certain natural assumptions

Egyptian Agriculture in the 21st Century

In order to perform a proper, integrated assessment of potential climate change impacts on Egypt it was necessary to accurately identify important and impending issues and problems which are and will be facing the Egyptian agriculture sector into the next century. To this aim, two experts in the fields of Agronomy and Irrigated Agriculture in the Middle East were asked to travel to Egypt in order to assess the current state of Egyptian agriculture and pose possible questions and scenarios that will face Egypt in light of its current agricultural practices and management strategies. The paper examines two possible future scenarios for Egypt, one from a non-climate change perspective and the other from a climate change outlook. These scenarios are derived from the authors perspective of the current state of Egyptian agriculture. One viewpoint is that of the pessimist, where Egypt continues to practice poor agriculture management; the other is that of the optimist, with Egypt adopting sound management practices - adapting its cropping pattern and water use practices. Also addressed are the potential impacts of climate change on crop yields and recommendations for agronomic research to mitigate its potential impact

A Chebychev propagator with iterative time ordering for explicitly time-dependent Hamiltonians

A propagation method for time-dependent Schr\"odinger equations with an explicitly time-dependent Hamiltonian is developed where time ordering is achieved iteratively. The explicit time-dependence of the time-dependent Schr\"odinger equation is rewritten as an inhomogeneous term. At each step of the iteration, the resulting inhomogeneous Schr\"odinger equation is solved with the Chebychev propagation scheme presented in J. Chem. Phys. 130, 124108 (2009). The iteratively time-ordering Chebychev propagator is shown to be robust, efficient and accurate and compares very favorably to all other available propagation schemes

Stable Fermion Bag Solitons in the Massive Gross-Neveu Model: Inverse Scattering Analysis

Formation of fermion bag solitons is an important paradigm in the theory of hadron structure. We study this phenomenon non-perturbatively in the 1+1 dimensional Massive Gross-Neveu model, in the large $N$ limit. We find, applying inverse scattering techniques, that the extremal static bag configurations are reflectionless, as in the massless Gross-Neveu model. This adds to existing results of variational calculations, which used reflectionless bag profiles as trial configurations. Only reflectionless trial configurations which support a single pair of charge-conjugate bound states of the associated Dirac equation were used in those calculations, whereas the results in the present paper hold for bag configurations which support an arbitrary number of such pairs. We compute the masses of these multi-bound state solitons, and prove that only bag configurations which bear a single pair of bound states are stable. Each one of these configurations gives rise to an O(2N) antisymmetric tensor multiplet of soliton states, as in the massless Gross-Neveu model.Comment: 10 pages, revtex, no figures; v2: typos corrected, references added; v3: version accepted for publication in the PRD. referencess added. Some minor clarifications added at the beginning of section

Prescription-induced jump distributions in multiplicative Poisson processes

Generalized Langevin equations (GLE) with multiplicative white Poisson noise pose the usual prescription dilemma leading to different evolution equations (master equations) for the probability distribution. Contrary to the case of multiplicative gaussian white noise, the Stratonovich prescription does not correspond to the well known mid-point (or any other intermediate) prescription. By introducing an inertial term in the GLE we show that the Ito and Stratonovich prescriptions naturally arise depending on two time scales, the one induced by the inertial term and the other determined by the jump event. We also show that when the multiplicative noise is linear in the random variable one prescription can be made equivalent to the other by a suitable transformation in the jump probability distribution. We apply these results to a recently proposed stochastic model describing the dynamics of primary soil salinization, in which the salt mass balance within the soil root zone requires the analysis of different prescriptions arising from the resulting stochastic differential equation forced by multiplicative white Poisson noise whose features are tailored to the characters of the daily precipitation. A method is finally suggested to infer the most appropriate prescription from the data

Effects of adenotonsillectomy on plasma inflammatory biomarkers in obese children with obstructive sleep apnea: A community-based study.

BackgroundObesity and obstructive sleep apnea syndrome (OSA) are highly prevalent and frequently overlapping conditions in children that lead to systemic inflammation, the latter being implicated in the various end-organ morbidities associated with these conditions.AimTo examine the effects of adenotonsillectomy (T&A) on plasma levels of inflammatory markers in obese children with polysomnographically diagnosed OSA who were prospectively recruited from the community.MethodsObese children prospectively diagnosed with OSA, underwent T&A and a second overnight polysomnogram (PSG) after surgery. Plasma fasting morning samples obtained after each of the two PSGs were assayed for multiple inflammatory and metabolic markers including interleukin (IL)-6, IL-18, plasminogen activator inhibitor-1 (PAI-1), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9), adiponectin, apelin C, leptin and osteocrin.ResultsOut of 122 potential candidates, 100 obese children with OSA completed the study with only one-third exhibiting normalization of their PSG after T&A (that is, apnea-hypopnea index (AHI) ≤1/hour total sleep time). However, overall significant decreases in MCP-1, PAI-1, MMP-9, IL-18 and IL-6, and increases in adropin and osteocrin plasma concentrations occurred after T&A. Several of the T&A-responsive biomarkers exhibited excellent sensitivity and moderate specificity to predict residual OSA (that is, AHI⩾5/hTST).ConclusionsA defined subset of systemic inflammatory and metabolic biomarkers is reversibly altered in the context of OSA among community-based obese children, further reinforcing the concept on the interactive pro-inflammatory effects of sleep disorders such as OSA and obesity contributing to downstream end-organ morbidities

Society issues, painkiller solutions, dependence and sustainable agriculture

Mahatma Gandhi listed seven blunders of humanity: Wealth without work, Pleasure without conscience, Commerce without morality, Worship without sacrifice, Politics without principles, Knowledge without character, and Science without humanity. Here I tackle three major issues, climate change, financial crisis and nation security, to disclose weak points of current remedies, and to propose sustainable solutions. Global warming and the unexpected financial crisis will undoubtedly impact all nations. Treating those two critical issues solely by painkiller solutions will fail because only adverse consequences are healed, not their causes. Therefore all sources of issues must be treated at the same time by enhancing collaboration between politicians and scientists. Furthermore, the adverse consequences of globalisation of markets for energy, food and other goods have been overlooked, thus deeply weakening the security of society structures in the event of major breakdowns. Therefore dependence among people, organisations and nations must be redesigned and adapted to take into account ecological, social and security impacts. Solving climate, financial and security issues can be done by using tools and principles developed by agronomists because agronomy integrates mechanisms occurring at various space and time levels. Agriculture is also a central driver for solving most society issues because society has been founded by agriculture, and agriculture is the activity that provides food, renewable energies and materials to humans. I present a to-do list summarising the major practices, principles and benefits of sustainable agriculture based on about 100 recently-published review articles. The practices are agroforestry, allelopathy, aquaculture, beneficial microorganisms and insects, biofertilisation, biofuels, biological control, biological nitrogen fixation, breeding, carbon sequestration, conservation agriculture, crop rotation, cover crops, decision support systems, grass strips, integrated pest management, intercropping, irrigation, mechanical weed control, mulching, no tillage, organic amendments, organic farming, phytoremediation, precision agriculture, seed invigoration, sociology, soil restoration, suicidal germination, terracing, transgenic crops, trap crops, and urban agriculture