A symmetric safety valve

How to set policy in the presence of uncertainty has been central in debates over climate policy. Concern about costs has motivated the proposal for a cap-and-trade program for carbon dioxide, with a “safety valve” that would mitigate against spikes in the cost of emission reductions by introducing additional emission allowances into the market when marginal costs rise above the specified allowance price level. We find two significant problems, both stemming from the asymmetry of an instrument that mitigates only against a price increase. One is that most important examples of price volatility in cap-and-trade programs have occurred not when prices spiked, but instead when allowance prices collapsed. Second, a single-sided safety valve may have unintended consequences for investment. We illustrate that a symmetric safety valve provides environmental and welfare improvements relative to the conventional one-sided approach.     

DS/CDMAM-ary orthogonal signalling in a shadowed Rayleigh channel for mobile communications

In this paper a modified RAKE receiver is studied for a frequency selective mobile radio channel. The reverse link (Mobile to base station) is analysed, assuming lognormal shadowing and Rayleigh fading andK asynchronous users, withM orthogonal sequences per user. The analysis is based on the consideration of the quadrature components of the signal and noise, taking advantage of the multipath effects. The performance evaluation is carried out in terms of both the bit error rate and outage probability in order to qualify completely the proposed receiver. The positive results assure the possibility of applying this system in a microcellular mobile radio environment.     

Efficiency analysis of the Solarflow – An innovative solar-powered desalination unit for treating brackish water

The Solarflow was invented at The Environmental Technology Centre, Murdoch University (the Murdoch ETC) in Perth, Western Australia as part of a doctoral thesis in the early 1990s researching suitable water treatment systems for remote indigenous communities. The design has been modified since this time by its original manufacturer but full commercialisation was not achieved. The current owner Solco Pty Ltd was keen to further improve the efficiency and lower the purchase cost of the unit and engaged the Murdoch ETC to undertake further testing.The Solarflow is a self-contained solar-powered unit capable of producing 400 L/day of high quality drinking water from brackish water via reverse osmosis and requires only 120 W of photovoltaic power. This is achievable due to its innovative energy recovery system. In order to assess the unit's efficiency more accurately the latest high-rate data logging technology from the ResLab laboratory at Murdoch University was employed. This enabled quantification of the Solarflow's unique and complex waveforms of the four key parameters: voltage, current, pressure and flow. The results of this testing are presented in this paper.     

Enteral glutamine supplementation for very-low-birth-weight infants decreases hospital costs

Vertebrate Pax-6 and its Drosophila homolog eyeless play central roles in eye specification, although it is not clear if this represents the ancestral role of this gene class. As the most "primitive" animals with true nervous systems, the Cnidaria may be informative in terms of the evolution of the Pax gene family. For this reason we surveyed the Pax gene complement of a representative of the basal cnidarian class (the Anthozoa), the coral Acropora millepora. cDNAs encoding two coral Pax proteins were isolated. Pax-Aam encoded a protein containing only a paired domain, whereas Pax-Cam also contained a homeodomain clearly related to those in the Pax-6 family. The paired domains in both proteins most resembled the vertebrate Pax-2/5/8 class, but shared several distinctive substitutions. As in most Pax-6 homologs and orthologs, an intron was present in the Pax-Cam locus at a position corresponding to residues 46/47 in the homeodomain. We propose a model for evolution of the Pax family, in which the ancestor of all of the vertebrate Pax genes most resembled Pax-6, and arose via fusion of a Pax-Aam-like gene (encoding only a paired domain) with an anteriorly-expressed homeobox gene resembling the paired-like class.     

In Situ Characterization of Induced Stiction in a MEMS

Stiction remains a limiting factor in the performance and lifetime of MEMS devices. We have developed experimental tools for inducing and quantifying changes in stiction on a large array of MEMS actuators. Thousands of elements were subjected to aggressive wear in order to produce shearing forces that contributed to the degradation of contacting surfaces. Custom electronics were developed to accomplish nonstandard actuation of the MEMS array. Optical techniques were used to characterize the induction of and progression of stiction. A model incorporating experimental and geometrical values was used to determine stiction force as a function of actuation duration and packaging. For a depackaged array, an increase in stiction force of ~230nN (per element) was induced through three days of high-speed actuation     

STOKES FLOW THROUGH A SYSTEM OF PARALLEL INFINITE CYLINDERS WITH AXES ORIENTED AT AN ANGLE TO THE DIRECTION Of MEAN FLOW

Theoretical models based on Stokes flow of air through a fibrous filter predict a significantly higher pressure drop than experimentally measured values. This discrepancy persists even when the interaction of the flow between) neighboring fibers is accounted for. Various authors have attributed this discrepancy to the inhomogeneity of the fiber distribution within the filter and to the possibility that some fibers are partially orientation in the directon of mean flow. It has been shown that fiber density inhomogeneity does indeed contribute to this discrepancy

In this paper, the effect on the flow and subsequent pressure drop when the fibers are oriented at an angle to the directon of mean flow is studied. The solution of the three dimensional equation for creeping, incompressible flow in a doubly periodic, infinite lattice of infinite circular cylinders when there is a constant mean flow whose direction makes an acute angle with the axes of the cylinders is given. If the volume fraction of fibers is small, the periodic boundary conditions can be replaced by requiring zero vorticity at the outer boundary of an imagined cylindrical cell of fluid surrounding one of the cylinders. The resulting parallel and transverse problems have known solutions and give an approximate solution to the flow through the periodic lattice. The resulting drag is used to compute the dimensionless pressure drop across a filter for several values of the volume fraction of fiber and is compared to the experimentally determined formula of Davies. It is shown that the average drag over a uniform distribution of fiber orientations yields a pressure drop which is significantly closer to the experimental values of Davies than that resulting from strictly transverse flow.     

Fitting three-parameter lognormal models by numerical global optimization — an improved algorithm

The theoretical maximum likelihood point estimates of the parameters of the three-parameter lognormal distribution (LD) for complete, ungrouped samples are infeasible values for which the likelihood function is positively infinite. This has prompted the search for usable point estimates which are called local-maximum likelihood estimates (LMLE's) and which correspond to the largest finite local maximum of the log-likelihood function (LLF). Previously published work has shown that an effective way to obtain LMLE's is to numerically maximize the conditional LLF of the observations using sequential interior penalty and barrier function methods. These methods are robust but necessitate the numerical solution of a sequence of maximization problems.This paper describes an algorithm for computing LMLE's which involves only a single numerical maximization of a suitably transformed conditional LLF. The results of computational tests indicate that the algorithm, when implemented using computationally efficient and reliable univariate global optimization methods, is a computationally robust method for computing LMLE's of LD parameters.     

Sensitivity to change of the Brief Psychiatric Rating Scale-Extended (BPRS-E): An item and subscale analysis.

The Brief Psychiatric Rating Scale (BPRS) is the most commonly used outcome measure for the severely and persistently mentally ill (SPMI) population, possessing good interrater reliability, concurrent validity, and a strong factor structure. However, psychometric study of the extended version of the BPRS (the BPRS-E) is limited when compared with earlier versions (BPRS and BPRS-A). This study examined the item, factor, and diagnosis-specific sensitivity to change of the BPRS-E, the most recent version of this popular scale. Assessments were conducted at 90-day intervals with 201 adult psychiatric inpatients at the Utah State Hospital, yielding 786 symptom ratings. Of note was that ratings were conducted by independent assessors who were unaware of patients' treatment status. All but 2 of the 24 BPRS-E items, all 4 factors, and the total score were found to be sensitive to change when comparing patients' admission and discharge scores. Patient diagnosis was not associated with item, factor, or total score sensitivity to change. These findings extend the psychometric support for the BPRS-E and have implications for assessing outcome with the SPMI population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanism of a Standalone β-Lactone Synthetase: New Continuous Assay for a Widespread ANL Superfamily Enzyme

Enzyme-catalyzed β-lactone formation from β-hydroxy acids is a crucial step in bacterial biosynthesis of β-lactone natural products and membrane hydrocarbons. We developed a novel, continuous assay for β-lactone synthetase activity using synthetic β-hydroxy acid substrates with alkene or alkyne moieties. β-Lactone formation is followed by rapid decarboxylation to form a conjugated triene chromophore for real-time evaluation by UV/Vis spectroscopy. The assay was used to determine steady-state kinetics of a long-chain β-lactone synthetase, OleC, from the plant pathogen Xanthomonas campestris. Site-directed mutagenesis was used to test the involvement of conserved active site residues in Mg²⁺ and ATP binding. A previous report suggested OleC adenylated the substrate hydroxy group. Here we present several lines of evidence, including hydroxylamine trapping of the AMP intermediate, to demonstrate the substrate carboxyl group is adenylated prior to making the β-lactone final product. A panel of nine substrate analogues were used to investigate the substrate specificity of X. campestris OleC by HPLC and GC-MS. Stereoisomers of 2-hexyl-3hydroxyoctanoic acid were synthesized and OleC preferred the (2R,3S) diastereomer consistent with the stereo-preference of upstream and downstream pathway enzymes. This biochemical knowledge was used to guide phylogenetic analysis of the β-lactone synthetases to map their functional diversity within the acyl-CoA synthetase, NRPS adenylation domain, and luciferase superfamily.