Enzyme activity in terrestrial soil in relation to exploration of the Martian surface

Urease activity in soil is persistent for long periods under low water, low temperature, and sterile regimes, and it was suggested that some form of enzyme-protective mechanism exists in soil. Dublin soil was extracted by sonication in water followed by adding a mixture of salts. Urease activity is associated with the organo-mineral complex thus obtained and is resistant to the activities of proteolytic enzymes. Clay free soil organic matter prepared subsequently by filtration also exhibits urease activity which is resistant to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis. A model system is presented which suggests both the origin and location of soil ureases and a reason for their persistence in nature

Prevalence of iron deficiency in 62,685 women of seven race/ethnicity groups: The HEIRS Study.

BackgroundFew cross-sectional studies report iron deficiency (ID) prevalence in women of different race/ethnicity and ages in US or Canada.Materials and methodsWe evaluated screening observations on women who participated between 2001-2003 in a cross-sectional, primary care-based sample of adults ages ≥25 y whose observations were complete: race/ethnicity; age; transferrin saturation; serum ferritin; and HFE p.C282Y and p.H63D alleles. We defined ID using a stringent criterion: combined transferrin saturation <10% and serum ferritin <33.7 pmol/L (<15 μg/L). We compared ID prevalence in women of different race/ethnicity subgrouped by age and determined associations of p.C282Y and p.H63D to ID overall, and to ID in women ages 25-44 y with or without self-reported pregnancy.ResultsThese 62,685 women included 27,079 whites, 17,272 blacks, 8,566 Hispanics, 7,615 Asians, 449 Pacific Islanders, 441 Native Americans, and 1,263 participants of other race/ethnicity. Proportions of women with ID were higher in Hispanics and blacks than whites and Asians. Prevalence of ID was significantly greater in women ages 25-54 y of all race/ethnicity groups than women ages ≥55 y of corresponding race/ethnicity. In women ages ≥55 y, ID prevalence did not differ significantly across race/ethnicity. p.C282Y and p.H63D prevalence did not differ significantly in women with or without ID, regardless of race/ethnicity, age subgroup, or pregnancy.ConclusionsID prevalence was greater in Hispanic and black than white and Asian women ages 25-54 y. p.C282Y and p.H63D prevalence did not differ significantly in women with or without ID, regardless of race/ethnicity, age subgroup, or pregnancy

The effect of tDCS on recognition depends on stimulus generalization: Neuro-stimulation can predictably enhance or reduce the face inversion effect

This is the author accepted manuscript. The final version is available from the American Psychological Association via the DOI in this recordThis paper reports results from three experiments that investigate how a particular neurostimulation procedure is able, in certain circumstances, to selectively increase the face inversion effect by enhancing recognition for upright faces, and argues that these effects can be understood in terms of the MKM theory of stimulus representation. We demonstrate how a specific transcranial Direct Current Stimulation (tDCS) methodology can improve performance in circumstances where error-based salience modulation is making face recognition harder. The three experiments used an old/new recognition task involving sets of normal vs Thatcherised faces. The main characteristic of Thatcherised faces is that the eyes and the mouth are upside down, thus emphasizing features that tend to be common to other Thatcherised faces and so leading to stronger generalization making recognition worse. Experiment 1 combined a behavioural and ERP study looking at the N170 peak component, which helped us to calibrate the set of face stimuli needed for subsequent experiments. In Experiment 2 we used our tDCS procedure (between-subjects and double-blind) in an attempt to reduce the negative effects induced by error-based modulation of salience on recognition of upright Thatcherised faces. Results largely confirmed our predictions. In addition, they showed a significant improvement on recognition performance for upright normal faces. Experiment 3 provides the first direct evidence in a single study that the same tDCS procedure is able to both enhance performance when normal faces are presented with Thatcherised faces, and to reduce performance when normal faces are presented with other normal faces (i.e. male vs female faces). We interpret our results by analyzing how salience modulation influences generalization between similar categories of stimuli.European Union Horizon 2020Economic and Social Research Council (ESRC

Using discrete Darboux polynomials to detect and determine preserved measures and integrals of rational maps

In this Letter we propose a systematic approach for detecting and calculating preserved measures and integrals of a rational map. The approach is based on the use of cofactors and Discrete Darboux Polynomials and relies on the use of symbolic algebra tools. Given sufficient computing power, all rational preserved integrals can be found. We show, in two examples, how to use this method to detect and determine preserved measures and integrals of the considered rational maps.Comment: 8 pages, 1 Figur

A study of the distribution of Salmonella serovars in an integrated pig company

A total of 3220 faecal samples from 161 pig farms (rearing and finishing units) belonging to an integrated pig enterprise were collected over a period of 18 months. Salmonella was found in 630 (19.5%) of the samples. At the farm level, 111 of 161 premises (69%) had at least one Salmonella- positive sample. 72.8% of rearing units and 66.6% of finishing units were positive for Salmonella; 61.4% of isolates were S. Typhimurium (387/630 isolates), and 25% of isolates were S. Derby (157/630). S. Panama, which was the third most common serovar (4.9% of isolates), is rarely found in pigs or other animals in the UK and appeared to be largely specific to this company, being found in the multiplier herd as well

Trees and superintegrable Lotka-Volterra families

To any tree on $n$ vertices we associate an $n$-dimensional Lotka-Volterra system with $3n-2$ parameters and prove it is superintegrable, i.e. it admits $n-1$ functionally independent integrals. We also show how these systems can be reduced to an ($n-1$)-dimensional system which is superintegrable and solvable by quadratures.Comment: 13 pages, 2 figure

Exploring cashless fare collection in the context of urban public transport reform in South Africa

As in many developing countries, in South Africa unscheduled paratransit services dominate urban public transport. Despite the resulting scale of fare revenue, the majority of the country’s minibus-taxis operate as cash-only businesses. Drivers typically keep the balance of fare revenue after vehicle rental and fuel consumption payments, while owners seldom include vehicle depreciation as a daily operating expense. There are a number of common consequences. Drivers behave recklessly as they seek to achieve as many peak period trips as possible to maximise income. Capital reserves or affordable finance are not available to renew vehicle fleets. Business owners find it difficult to make operating decisions based on an income-expenditure ledger and principles of profit and loss. Paratransit services are poorly integrated into multi-modal systems when passengers pay fares through different structures and media. Moreover, in contexts where crime and corruption are widespread, on-board cash holding makes public transport vehicles particularly vulnerable. The aim of this paper is to explore the potential of various cashless fare collection (CFC) systems to mitigate these problems, and to review the technology alternatives that are available. The paper presents the results of a review of alternative approaches to CFC, and a qualitative multi-criteria evaluation of these technological alternatives. The criteria include: user and operator acceptability; payment and physical infrastructure; information technology requirements; financial and human resources; and transaction and technology complexity. The three CFC systems that achieved the highest scores in the multi-criteria evaluation were all mobile phone-/mobile network-based systems. Of the three lowest scoring CFC systems, two relied on the passenger having a bank account and one on creating a free-standing fare management and payment system. A key recommendation is that CFC systems are implemented collaboratively and incrementally in order to achieve the requisite stakeholder support.Papers presented at the 36th Southern African Transport Conference, CSIR International Convention Centre, Pretoria, South Africa on 10-13 July 2017.Transportation research board of the national academie

Linear Darboux polynomials for Lotka-Volterra systems, trees and superintegrable families

We present a method to construct superintegrable $n$-component Lotka-Volterra systems with $3n-2$ parameters. We apply the method to Lotka-Volterra systems with $n$ components for $1 < n < 6$, and present several $n$-dimensional superintegrable families. The Lotka-Volterra systems are in one-to-one correspondence with trees on $n$ vertices.Comment: 14 pages, 4 figure