Self-Assembly of Patchy Particles into Polymer Chains: A Parameter-Free Comparison between Wertheim Theory and Monte Carlo Simulation

We numerically study a simple fluid composed of particles having a hard-core repulsion, complemented by two short-ranged attractive (sticky) spots at the particle poles, which provides a simple model for equilibrium polymerization of linear chains. The simplicity of the model allows for a close comparison, with no fitting parameters, between simulations and theoretical predictions based on the Wertheim perturbation theory, a unique framework for the analytic prediction of the properties of self-assembling particle systems in terms of molecular parameter and liquid state correlation functions. This theory has not been subjected to stringent tests against simulation data for ordering across the polymerization transition. We numerically determine many of the thermodynamic properties governing this basic form of self-assembly (energy per particle, order parameter or average fraction of particles in the associated state, average chain length, chain length distribution, average end-to-end distance of the chains, and the static structure factor) and find that predictions of the Wertheim theory accord remarkably well with the simulation results

Photoluminescence of High Quality Epitaxial p-type InN

Indium nitride (InN) is a group III-V semiconductor that is part of the Al,Ga:N family. It is an infrared bandgap semiconductor with great potential for use in photovoltaic applications. Being an intrinsically n-type material, p-type doping is naturally one of the ongoing hot topics in InN research, which is of interest in the fabrication of pn junctions. Plasma-assisted molecular beam epitaxy (PAMBE) grown Mg doped InN thin film was investigated via systematic optical characterizations. Photoluminescence (PL) measurement has been a key part of the research, exhibiting a wide range of spectral lines between 0.54 and 0.67 eV. In a critical Mg concentration range of 2.6×10¹⁷ and 1.0×10¹⁸ cm⁻³, a strong luminescence line at 0.6 eV has been associated with a Mg-related deep acceptor. Correspondingly, a variable magnetic field Hall (VFH) effect measurement has successfully probed a buried hole-mediated conductivity path underneath a surface electron accumulation layer. This specific doping range also led to a manifestation of a “true” band-to-band transition at 0.67 eV. Such an observation has not previously been reported for InN and in our case this assignment is convincingly supported by the quadratic characteristic of the excitation power law. This established that a rigorous control of Mg flux can sufficiently compensate the background electron concentration of InN via the substitutional incorporation on In sites (Mg_In). However, introduction of donor-like complexes somewhat suppressed this process if too much Mg or even alternative dopants such as Zn and Mn were used. Also distinctively observed was a strongly quenched PL quantum efficiency from heavily doped films, where time-resolved differential transmission (TRDT) measurement showed a biexponential carrier lifetime decay curve owing to the onset of Auger recombination processes. These observations certainly have profound implications for devices and beyond

The distribution of burden of dental caries in schoolchildren: a critique of the high-risk caries prevention strategy for populations

BACKGROUND: The 'high-risk approach' is a commonly adopted strategy recommended for the prevention of dental caries in populations. The scientific basis for the strategy has been questioned. The objective of this study is to assess the contribution that children identified at 'high-risk' made towards the total of new caries lesions over a 4-year period, by analysing the distribution of new lesions per 100 children. METHODS: Data are from the National Preventive Dentistry Demonstration Programme (NPDDP) in the United States. The analyses identified the distribution of new carious lesions over a 4-year period in four groups of 7 year-old children who received differing preventive regimes. RESULTS: The majority of new lesions occurred in those children classified at lowest caries risk at baseline. Irrespective of the preventive regime adopted and the initial caries levels, children classified as 'highest risk' contributed less than 6% of the total number of new lesions developing over 4 years. CONCLUSION: These findings challenge the basis for the adoption of a high-risk strategy

Universal Statistical Behavior of Neural Spike Trains

We construct a model that predicts the statistical properties of spike trains generated by a sensory neuron. The model describes the combined effects of the neuron's intrinsic properties, the noise in the surrounding, and the external driving stimulus. We show that the spike trains exhibit universal statistical behavior over short times, modulated by a strongly stimulus-dependent behavior over long times. These predictions are confirmed in experiments on H1, a motion-sensitive neuron in the fly visual system.Comment: 7 pages, 4 figure

An extremal effective survey about extremal effective cycles in moduli spaces of curves

We survey recent developments and open problems about extremal effective divisors and higher codimension cycles in moduli spaces of curves.Comment: Submitted to the Proceedings of the Abel Symposium 2017. Comments are welcom

Birational geometry of hypersurfaces in products of projective spaces

We study the birational properties of hypersurfaces in products of projective spaces. In the case of hypersurfaces in Pm x Pn, we describe their nef, movable and e ective cones and determine when they are Mori dream spaces. Using this, we give new simple examples of non-Mori dream spaces and analogues of Mumford's example of a strictly nef line bundle which is not ample.This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s00209-015-1415-

Numerical Model of a Variable-Combined-Cycle Engine for Dual Subsonic and Supersonic Cruise

Efficient high speed propulsion requires exploiting the cooling capability of the cryogenic fuel in the propulsion cycle. This paper presents the numerical model of a combined cycle engine while in air turbo-rocket configuration. Specific models of the various heat exchanger modules and the turbomachinery elements were developed to represent the physical behavior at off-design operation. The dynamic nature of the model allows the introduction of the engine control logic that limits the operation of certain subcomponents and extends the overall engine operational envelope. The specific impulse and uninstalled thrust are detailed while flying a determined trajectory between Mach 2.5 and 5 for varying throttling levels throughout the operational envelope

GIS-BASED SUITABILITY MODELLING FOR THE EUROPEAN OYSTER WITHIN THE GERMAN EXCLUSIVE ZONE OF THE NORTH SEA

Oyster reefs are ecologically important habitats that have been suffering from anthropogenic stressors and severe damages over the past century. More than 85 % of the world's oyster reefs have already been destroyed, have disappeared or their existence is under severe and immediate threat. Due to their central ecological importance for benthic and bentho-pelagic systems and processes associated with important ecosystem functions and services, the restoration of oyster reefs is a focus of marine conservation measures worldwide. In the context of marine spatial planning and complex land use conflicts, and aimed at maximising the ecological success of such restoration measures, GIS-based habitat suitability analyses for oyster reintroduction have been conducted. The aim of the present study was to model and identify suitable habitats for the European oyster within the marine protected areas of Borkum Reefground and Sylt Outer Reef in the German Bight for which the restoration of biogenic reefs, namely native oyster reefs is a designated measure. For this purpose, a multi-criteria decision analysis was designed and applied. Based on geodata of the ecological habitat preferences of the European oyster and relevant logistic factors (contraindicated uses), suitable large- scale areas were successfully identified for which a reintroduction of the formerly native species is favourable. Both suitable and unsuitable habitats could therefore successfully be identified for both nature reserves. Due to the large impact of different standardisation procedures for the suitability variables applied, corresponding results may differ quite severely. Hence four different classifications were applied on the most important factor, ground fisheries accounting for a relative weighting of ca. 30% in the derived suitability formula. The results undermine the necessity of well-grounded scientific and practical reasons to decide on a suitable classification procedure in the multicriteria analysis

Intrinsic activity in the fly brain gates visual information during behavioral choices

The small insect brain is often described as an input/output system that executes reflex-like behaviors. It can also initiate neural activity and behaviors intrinsically, seen as spontaneous behaviors, different arousal states and sleep. However, less is known about how intrinsic activity in neural circuits affects sensory information processing in the insect brain and variability in behavior. Here, by simultaneously monitoring Drosophila's behavioral choices and brain activity in a flight simulator system, we identify intrinsic activity that is associated with the act of selecting between visual stimuli. We recorded neural output (multiunit action potentials and local field potentials) in the left and right optic lobes of a tethered flying Drosophila, while its attempts to follow visual motion (yaw torque) were measured by a torque meter. We show that when facing competing motion stimuli on its left and right, Drosophila typically generate large torque responses that flip from side to side. The delayed onset (0.1-1 s) and spontaneous switch-like dynamics of these responses, and the fact that the flies sometimes oppose the stimuli by flying straight, make this behavior different from the classic steering reflexes. Drosophila, thus, seem to choose one stimulus at a time and attempt to rotate toward its direction. With this behavior, the neural output of the optic lobes alternates; being augmented on the side chosen for body rotation and suppressed on the opposite side, even though the visual input to the fly eyes stays the same. Thus, the flow of information from the fly eyes is gated intrinsically. Such modulation can be noise-induced or intentional; with one possibility being that the fly brain highlights chosen information while ignoring the irrelevant, similar to what we know to occur in higher animals