Nitric oxide and nitrous oxide production and cycling during dissimulatory nitrite reduction by Pseudomonas perfectomarina

The denitrifier Pseudomonas perfectomarina reduced nitrite under conditions of kinetic competition between cells and gas sparging for extracellular dissolved nitric and nitrous oxides, NOaq and N2Oaq, in a chemically defined marine medium. Time courses of nitrite reduction and NOg and N2Og removal were integrated to give NOg , and N2Og yields. At high sparging rates, the NOg yield was >50% of nitrite-N reduced, and the yield of NOg + N2Og was ~75%. Hence interrupted denitrification yields NOaq and N2Oaq as major products. The yields varied with sparging rates in agreement with a quantitative model of denitrification (Betlach, M. P., and Tiedje, J. M. (1981) Appl. Environ. Microbiol. 42, 1074-1084) that applies simplified Michaelis-Menten kinetics to NO2 > NOaq > N2Oaq > N2. The fit gave an estimate of the maximum scavengeable NOaq yield of 73 ± 8% of nitrite-N. Thus a minor path independent of NOaq is also required. The fit of the model to data at lower sparging rates, where normal denitrification products predominate, implies that the extracellular NOaq pool yield is independent of gas sparging rate. Thus in P. perfectomarina NOaq and N2Oaq are intermediates, or facilely equilibrate with true intermediates, during complete denitrification. The recovery of most nitrite-N as NO and/or N20 under perturbed conditions is not an artifact of irreversible product removal, but an attribute of denitrification in this species, and most probably it is characteristic of denitrification in other species as well

Rural to Urban Population Density Scaling of Crime and Property Transactions in English and Welsh Parliamentary Constituencies

Urban population scaling of resource use, creativity metrics, and human behaviors has been widely studied. These studies have not looked in detail at the full range of human environments which represent a continuum from the most rural to heavily urban. We examined monthly police crime reports and property transaction values across all 573 Parliamentary Constituencies in England and Wales, finding that scaling models based on population density provided a far superior framework to traditional population scaling. We found four types of scaling: i ) non-urban scaling in which a single power law explained the relationship between the metrics and population density from the most rural to heavily urban environments, ii ) accelerated scaling in which high population density was associated with an increase in the power-law exponent, iii ) inhibited scaling where the urban environment resulted in a reduction in the power-law exponent but remained positive, and iv ) collapsed scaling where transition to the high density environment resulted in a negative scaling exponent. Urban scaling transitions, when observed, took place universally between 10 and 70 people per hectare. This study significantly refines our understanding of urban scaling, making clear that some of what has been previously ascribed to urban environments may simply be the high density portion of non-urban scaling. It also makes clear that some metrics undergo specific transitions in urban environments and these transitions can include negative scaling exponents indicative of collapse. This study gives promise of far more sophisticated scale adjusted metrics and indicates that studies of urban scaling represent a high density subsection of overall scaling relationships which continue into rural environments

Fluctuation Scaling, Taylor’s Law, and Crime

Fluctuation scaling relationships have been observed in a wide range of processes ranging from internet router traffic to measles cases. Taylor’s law is one such scaling relationship and has been widely applied in ecology to understand communities including trees, birds, human populations, and insects. We show that monthly crime reports in the UK show complex fluctuation scaling which can be approximated by Taylor’s law relationships corresponding to local policing neighborhoods and larger regional and countrywide scales. Regression models applied to local scale data from Derbyshire and Nottinghamshire found that different categories of crime exhibited different scaling exponents with no significant difference between the two regions. On this scale, violence reports were close to a Poisson distribution (α = 1.057±0.026) while burglary exhibited a greater exponent (α = 1.292±0.029) indicative of temporal clustering. These two regions exhibited significantly different pre-exponential factors for the categories of anti-social behavior and burglary indicating that local variations in crime reports can be assessed using fluctuation scaling methods. At regional and countrywide scales, all categories exhibited scaling behavior indicative of temporal clustering evidenced by Taylor’s law exponents from 1.43±0.12 (Drugs) to 2.094±0081 (Other Crimes). Investigating crime behavior via fluctuation scaling gives insight beyond that of raw numbers and is unique in reporting on all processes contributing to the observed variance and is either robust to or exhibits signs of many types of data manipulation

Fermi surface evolution in the antiferromagnetic state for the electron-doped t-t(')-t('')-J model

[[abstract]]By use of the slave-boson mean-field approach, we have studied the electron-doped t-t'-t''-J model in the antiferromagnetic (AF) state. It is found that at low doping the Fermi surface (FS) pockets appear around (+/-pi,0) and (0,+/-pi), and upon increased doping the other ones will form around (+/-pi/2,+/-pi/2). The evolution of the FS with doping as well as the calculated spectral weight are consistent with the experimental results.[[fileno]]2010128010006[[department]]物理

Criticism and society: The birth of the modern critical subject in China

Focuses on the creation and establishment of critical theory system in China. Application of imported critical approaches and theoretical formulations; Distortion of Euramerican critical theories; Identification of traditional Chinese criticism; Inseparability of criticism and politics.published_or_final_versio

Life Satisfaction among Elderly Households in Public Rental Housing in Singapore

We set out to investigate how satisfied the poor elderly Singaporean households in social housing are with their lives, especially in relation to their housing, in an attempt to find measures to improve, where possible, the life satisfaction of this group of elderly Singaporeans. We use archival and empirical research for our investigation. The results from 403 respondents to our survey are analyzed through logistic regression and factor analysis. We find that the life satisfaction of the elderly residents of social housing is very low. Furthermore we find that home modification that meets the requirements of the respondents will substantially improve their life satisfaction. Given that these elderly households neither have the right nor financial means to modify their housing units and precincts, it is incumbent upon the government, through the relevant authorities such as HDB, Town Councils and BCA to effect the necessary home modifications to create a more elderlyfriendly physical environment to improve the life satisfaction of the elderly households in social housing in Singapore. This arguably is a social imperative which should not be subjugated to economic niceties as social housing is not a luxurious housing choice but the last safety net for basic shelter

When R > 0.8 R0: fluorescence anisotropy, non-additive intensity, and cluster size

Assembly and clustering feature in many biological processes and homo-FRET and fluorescence anisotropy can assist in estimating the aggregation state of a system. The distance dependence of resonance energy transfer is well described and tested. Similarly, assessment of cluster size using steady state anisotropy is well described for non-oriented systems when R 0.8 R0. Fused trimeric DNA clusters labelled with fluorescein were engineered to provide inter-fluorophore distances from 0.7 to 1.6 R/R0 and intensity and anisotropy were measured. These constructs cover a range where anisotropy effects depend on distance. Analytical expressions were derived for fully labelled and fractionally labelled clusters and the experimental results analysed. The experimental results showed that: 1) the system underwent distance dependent quenching; 2) when incompletely labelled both doubly and triply labelled forms could be assessed to obtain distance dependent intensity factors; 3) the anisotropy behaviour of a multiply labelled cluster of a particular size depends on the behaviour of the fluorophores and their distance in a cluster. This work establishes that when emission intensity data are available the analytically useful range for investigating clusters does not have to be restricted to R < 0.8 R0 and is applicable to cases where the anisotropy of a cluster of N fluorophores is not well approximated by r1/N

A Double-threshold GARCH Model for the French Franc/Deutschmark exchange rate

This paper combines and generalizes a number of recent time series models of daily exchange rate series by using a SETAR model which also allows the variance equation of a GARCH specification for the error terms to be drawn from more than one regime. An application of the model to the French Franc/Deutschmark exchange rate demonstrates that out-of-sample forecasts for the exchange rate volatility are also improved when the restriction that the data it is drawn from a single regime is removed. This result highlights the importance of considering both types of regime shift (i.e. thresholds in variance as well as in mean) when analysing financial time series

Statistical models for identifying frequent hitters in high throughput screening

High throughput screening (HTS) interrogates compound libraries to find those that are “active” in an assay. To better understand compound behavior in HTS, we assessed an existing binomial survivor function (BSF) model of “frequent hitters” using 872 publicly available HTS data sets. We found large numbers of “infrequent hitters” using this model leading us to reject the BSF for identifying “frequent hitters.” As alternatives, we investigated generalized logistic, gamma, and negative binomial distributions as models for compound behavior. The gamma model reduced the proportion of both frequent and infrequent hitters relative to the BSF. Within this data set, conclusions about individual compound behavior were limited by the number of times individual compounds were tested (1–1613 times) and disproportionate testing of some compounds. Specifically, most tests (78%) were on a 309,847-compound subset (17.6% of compounds) each tested ≥ 300 times. We concluded that the disproportionate retesting of some compounds represents compound repurposing at scale rather than drug discovery. The approach to drug discovery represented by these 872 data sets characterizes the assays well by challenging them with many compounds while each compound is characterized poorly with a single assay. Aggregating the testing information from each compound across the multiple screens yielded a continuum with no clear boundary between normal and frequent hitting compounds