8,426 research outputs found
Effects of zinc on microalgal biofilms in intertidal and subtidal habitats
Microalgal biofilms are sensitive to environmental conditions. Impacts of contaminants on assemblages of marine biofilm are often investigated in laboratories or in mesocosms. Such experiments are rarely representative of the effects of contaminants on biofilms under natural conditions. Studies in field situations, with enough power to detect impacts, are necessary to develop a better understanding of the effects of contaminants on ecological processes. Metals are a common contaminant of marine systems and can cause disturbances to assemblages. Using a new technique to experimentally deliver contaminants to microalgal assemblages, hypotheses were tested regarding the effects of zinc on microalgal biofilms growing on settlement panels in subtidal and intertidal habitats. PAM fluorometry was used to assess the amount and physiological state of biofilms on panels. Control panels deployed for 1 month in each habitat had significantly greater amounts of biofilm than those exposed to zinc. After deployment for 3 months, the results varied with location. The observed effects on the biofilm did not, however, cause significant changes in the macro-invertebrate assemblages that developed on the panels
Cladding strategies for building-integrated photovoltaics
Photovoltaic cladding on the surfaces of commercial buildings has the potential for considerable reductions in carbon emissions due to embedded renewable power generation displacing conventional power utilization. In this paper, a model is described for the optimization of photovoltaic cladding densities on commercial building surfaces. The model uses a modified form of the ‘fill factor’ method for photovoltaic power supply coupled to new regression-based procedures for power demand estimation. An optimization is included based on a defined ‘mean index of satisfaction’ for matched power supply and demand (i.e., zero power exportation to the grid). The mean index of satisfaction directly translates to the reduction in carbon emission that might be expected over conventional power use. On clear days throughout the year, reductions of conventional power use of at least 60% can be achieved with an optimum cladding pattern targeted to lighting and small power load demands
Fermi-Frenet coordinates for space-like curves
We generalize Fermi coordinates, which correspond to an adapted set of
coordinates describing the vicinity of an observer's worldline, to the
worldsheet of an arbitrary spatial curve in a static spacetime. The spatial
coordinate axes are fixed using a covariant Frenet triad so that the metric can
be expressed using the curvature and torsion of the spatial curve. As an
application of Fermi-Frenet coordinates, we show that they allow covariant
inertial forces to be expressed in a simple and physically intuitive way.Comment: 7 page
Digestion of Protein in Premature and Term Infants.
Premature birth rates and premature infant morbidity remain discouragingly high. Improving nourishment for these infants is the key for accelerating their development and decreasing disease risk. Dietary protein is essential for growth and development of infants. Studies on protein nourishment for premature infants have focused on protein requirements for catch-up growth, nitrogen balance, and digestive protease concentrations and activities. However, little is known about the processes and products of protein digestion in the premature infant. This review briefly summarizes the protein requirements of term and preterm infants, and the protein content of milk from women delivering preterm and at term. An in-depth review is presented of the current knowledge of term and preterm infant dietary protein digestion, including human milk protease and anti-protease concentrations; neonatal intestinal pH, and enzyme activities and concentrations; and protein fermentation by intestinal bacteria. The advantages and disadvantages of incomplete protein digestion as well as factors that increase resistance to proteolysis of particular proteins are discussed. In order to better understand protein digestion in preterm and term infants, future studies should examine protein and peptide fragment products of digestion in saliva, gastric, intestinal and fecal samples, as well as the effects of the gut micro biome on protein degradation. The confluence of new mass spectrometry technology and new bioinformatics programs will now allow thorough identification of the array of peptides produced in the infant as they are digested
Switched wave packets: A route to nonperturbative quantum control
The dynamic Stark effect due to a strong nonresonant but nonionizing laser field provides a route to quantum control via the creation of novel superposition states. We consider the creation of a field-free "switched" wave packet through adiabatic turn-on and sudden turn-off of a strong dynamic Stark interaction. There are two limiting cases for such wave packets. The first is a Raman-type coupling, illustrated by the creation of field-free molecular axis alignment. An experimental demonstration is given. The second case is that of dipole-type coupling, illustrated by the creation of charge localization in an array of quantum wells
Habitability of known exoplanetary systems based on measured stellar properties
At present, because of observational selection effects, we know of no
exoplanetary systems with any planetary masses close to that of the Earth. We
have therefore used computer models to see whether such planets could be
dynamically stable in the presence of the more massive planets known to be
present, and in particular whether planets with roughly an Earth mass could
remain confined to the classical habitable zone (HZ) for long enough for life
to have emerged.
Measured stellar properties have been used to determine for each system the
present location of the HZ. We have also determined the critical distances from
the orbit of each giant planet within which an Earth-mass planet would suffer
large orbital changes. We then evaluated the present habitability of each and
every exoplanetary system by examining the penetration of these critical
distances into the HZ. The critical distances can be obtained by extensive
computer modelling of an exoplanetary system. This is far too time consuming to
apply to all of the 150 or so systems already known, and to keep up with the
latest discoveries. Therefore, in earlier work we studied a few systems in
great detail, and developed a speedier means of obtaining the critical
distances. We summarize this comparatively quick method here. We can then
evaluate comparatively quickly the present habitability of each exoplanetary
system by examining the penetration of the critical distance(s) into the HZ.
The results are encouraging for astrobiology.Comment: Accepted for publication by The Astrophysical Journal. A few
revisions have been made following suggestions by the refere
Universal quantum computation by discontinuous quantum walk
Quantum walks are the quantum-mechanical analog of random walks, in which a
quantum `walker' evolves between initial and final states by traversing the
edges of a graph, either in discrete steps from node to node or via continuous
evolution under the Hamiltonian furnished by the adjacency matrix of the graph.
We present a hybrid scheme for universal quantum computation in which a quantum
walker takes discrete steps of continuous evolution. This `discontinuous'
quantum walk employs perfect quantum state transfer between two nodes of
specific subgraphs chosen to implement a universal gate set, thereby ensuring
unitary evolution without requiring the introduction of an ancillary coin
space. The run time is linear in the number of simulated qubits and gates. The
scheme allows multiple runs of the algorithm to be executed almost
simultaneously by starting walkers one timestep apart.Comment: 7 pages, revte
Risk Culture, Neoclassical Economics, and Enterprise Risk Management
Financial regulators, rating agencies and many commentators have blamed weak Risk Culture for many of the large losses and financial company failures of the past decade. But their exposition regarding a strong Risk Culture only goes as far as describing a few of the risk management practices of an organization and falls far short of describing the beliefs and motivations that are at the heart of any culture. This discussion will present thinking about how the fundamental beliefs of Neo Classical Economics clash with the recommended risk practices and how the beliefs that underpin Enterprise Risk Management are fundamentally consistent with the recommended risk management practices but differ significantly from Neo Classical Economics beliefs
All on the same train, but heading in different directions
Insurance company managers are surveyed to discern their alignment with four risk attitudes predicted by Plural Rationality Theory. Each company management team is shown to contain a mix of beliefs, but not always the same mix. Since each belief is tied to a different expectation for appropriate risk management, there are inherent conflicts with a risk management culture that is tied to a single belief. The paper concludes with descriptions of hybrid risk management cultures that would have some appeal to various pairs of the four beliefs
Designing Secure Ethereum Smart Contracts: A Finite State Machine Based Approach
The adoption of blockchain-based distributed computation platforms is growing
fast. Some of these platforms, such as Ethereum, provide support for
implementing smart contracts, which are envisioned to have novel applications
in a broad range of areas, including finance and Internet-of-Things. However, a
significant number of smart contracts deployed in practice suffer from security
vulnerabilities, which enable malicious users to steal assets from a contract
or to cause damage. Vulnerabilities present a serious issue since contracts may
handle financial assets of considerable value, and contract bugs are
non-fixable by design. To help developers create more secure smart contracts,
we introduce FSolidM, a framework rooted in rigorous semantics for designing
con- tracts as Finite State Machines (FSM). We present a tool for creating FSM
on an easy-to-use graphical interface and for automatically generating Ethereum
contracts. Further, we introduce a set of design patterns, which we implement
as plugins that developers can easily add to their contracts to enhance
security and functionality
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