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G Ball

Publications and source records attributed to G Ball.

At least 19 recordsLinked to original sources
PubMed2005

Scalar interaction limits from the beta-nu correlation of trapped radioactive atoms.

We have set limits on contributions of scalar interactions to nuclear beta decay. A magneto-optical trap provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the measurement of the beta-nu correlation, in a more direct fashion than previously possible. The beta-nu correlation parameter of the 0(+)-->0(+) pure Fermi decay of (38)K(m) is a =0.9981+/-0.0030+0.0032 / -0.0037, consistent with the standard model prediction a =1.

Journal Article↗
PubMed2005

Classification of bacterial species from proteomic data using combinatorial approaches incorporating artificial neural networks, cluster analysis and principal components analysis.

MOTIVATION: Robust computer algorithms are required to interpret the vast amounts of proteomic data currently being produced and to generate generalized models which are applicable to 'real world' scenarios. One such scenario is the classification of bacterial species. These vary immensely, some remaining remarkably stable whereas others are extremely labile showing rapid mutation and change. Such variation makes clinical diagnosis difficult and pathogens may be easily misidentified. RESULTS: We applied artificial neural networks (Neuroshell 2) in parallel with cluster analysis and principal components analysis to surface enhanced laser desorption/ionization (SELDI)-TOF mass spectrometry data with the aim of accurately identifying the bacterium Neisseria meningitidis from species within this genus and other closely related taxa. A subset of ions were identified that allowed for the consistent identification of species, classifying >97% of a separate validation subset of samples into their respective groups. AVAILABILITY: Neuroshell 2 is commercially available from Ward Systems.

Algorithms↗
PubMed2005

Effect of Gaviscon Infant on gastro-oesophageal reflux in infants assessed by combined intraluminal impedance/pH.

BACKGROUND: Gaviscon Infant (GI) has been recommended for gastro-oesophageal reflux (GOR) in infants. Its efficacy has not been examined with a physiologically appropriate denominator to define the degree of GOR. AIM: To investigate the influence of Gaviscon Infant on GOR in infants using combined pH and intraluminal impedance measurement. METHODS: Twenty infants (mean age 163.5 days, range 34-319 days) exclusively bottle fed, with symptoms clinically suggestive of GOR, underwent 24 hour studies of intra-oesophageal 6 channel impedance and dual channel pH monitoring, during which six random administrations (3+3) of Gaviscon Infant (625 mg in 225 ml milk) or placebo (mannitol and Solvito N, 625 mg in 225 ml milk) were given in a double blind fashion. Impedance/pH reflux data were recorded and analysed blind by one observer. RESULTS: The median number of reflux events/hour (1.58 v 1.68), acid reflux events/hour (0.26 v 0.43), minimum distal or proximal pH, total acid clearance time per hour (time with pH below pH 4), and total reflux duration per hour were not significantly different after GI than after placebo. Reflux height was marginally lower after GI (median 66.6% v 77.3% oesophageal length) compared with placebo. CONCLUSIONS: Results showed a marginal but significant difference between Gaviscon Infant and placebo in average reflux height, and raises questions regarding any perceived clinical benefit of its use.

Alginates↗
PubMed2002

An integrated approach utilizing artificial neural networks and SELDI mass spectrometry for the classification of human tumours and rapid identification of potential biomarkers.

MOTIVATION: MALDI mass spectrometry is able to elicit macromolecular expression data from cellular material and when used in conjunction with Ciphergen protein chip technology (also referred to as SELDI-Surface Enhanced Laser Desorption/Ionization), it permits a semi-high throughput approach to be taken with respect to sample processing and data acquisition. Due to the large array of data that is generated from a single analysis (8-10000 variables using a mass range of 2-15 kDa-this paper) it is essential to implement the use of algorithms that can detect expression patterns from such large volumes of data correlating to a given biological/pathological phenotype from multiple samples. If successful, the methodology could be extrapolated to larger data sets to enable the identification of validated biomarkers correlating strongly to disease progression. This would not only serve to enable tumours to be classified according to their molecular expression profile but could also focus attention upon a relatively small number of molecules that might warrant further biochemical/molecular characterization to assess their suitability as potential therapeutic targets. RESULTS: Using a multi-layer perceptron Artificial Neural Network (ANN) (Neuroshell 2) with a back propagation algorithm we have developed a prototype approach that uses a model system (comprising five low and seven high-grade human astrocytomas) to identify mass spectral peaks whose relative intensity values correlate strongly to tumour grade. Analyzing data derived from MALDI mass spectrometry in conjunction with Ciphergen protein chip technology we have used relative importance values, determined from the weights of trained ANNs (Balls et al., Water, Air Soil Pollut., 85, 1467-1472, 1996), to identify masses that accurately predict tumour grade. Implementing a three-stage procedure, we have screened a population of approximately 100000-120000 variables and identified two ions (m/z values of 13454 and 13457) whose relative intensity pattern was significantly reduced in high-grade astrocytoma. The data from this initial study suggests that application of ANN-based approaches can identify molecular ion patterns which strongly associate with disease grade and that its application to larger cohorts of patient material could potentially facilitate the rapid identification of validated biomarkers having significant clinical (i.e. diagnostic/prognostic) potential for the field of cancer biology. AVAILIBILITY: Neuroshell 2 is commercially available from ward systems.

Astrocytoma↗
PubMed2001

Involvement of the twin-arginine translocation system in protein secretion via the type II pathway.

The general secretory pathway (GSP) is a two-step process for the secretion of proteins by Gram-negative bacteria. The translocation across the outer membrane is carried out by the type II system, which involves machinery called the secreton. This step is considered to be an extension of the general export pathway, i.e. the export of proteins across the inner membrane by the Sec machinery. Here, we demonstrate that two substrates for the Pseudomonas aeruginosa secreton, both phospholipases, use the twin-arginine translocation (Tat) system, instead of the Sec system, for the first step of translocation across the inner membrane. These results challenge the previous vision of the GSP and suggest for the first time a mosaic model in which both the Sec and the Tat systems feed substrates into the secreton. Moreover, since P.aeruginosa phospholipases are secreted virulence factors, the Tat system appears to be a novel determinant of bacterial virulence.

Amino Acid Sequence↗
PubMed2001

A new metabolite from the marine bacterium Vibrio angustum S14.

The new metabolite [1-(2'-methylpropoxy)-2-hydroxy-2-methylpropoxy]butane was isolated from the cell-free culture supernatant of the marine bacterium Vibrio angustum S14 as part of studies investigating the role of chemical signals in prokaryote--prokaryote and prokaryote--eukaryote interactions. The structure was elucidated by interpretation of its high-field NMR and mass spectrometric data. [1-(2'-Methylpropoxy)-2-hydroxy-2-methylpropoxy]butane induced the acylated homoserine lactone (AHL) reporter system in Agrobacterium tumefaciens and bioluminescence in Vibrio harveyi.

Butanes↗
PubMed2001

Reliability of power output measurements during repeated treadmill sprinting in rugby players.

The non-motorized treadmill system initially reported by Lakomy in 1984 has been used extensively to assess sprinting performance. However, there has been limited research into the reliability of power output measurement using such systems. The aim of this study was to design a system and protocol capable of measuring treadmill sprinting performance in rugby players and to assess the reliability of this system for measuring power output. Twenty-seven rugby players, all of whom were familiar with treadmill sprinting, performed three maximal 6 s sprints with 2 min recovery between sprints, on two occasions 1 week apart. Both tests were performed on a non-motorized Woodway tramp treadmill, interfaced to a data acquisition system. There were no significant differences (P > 0.05) between power output for repeated trials on the same day (between trials) or for repeated trials on different days (between days). Limits of agreement for maximum average power (the average of 100 readings per second) were 4+/-98 and 30+/-157 W for between trials and between days, respectively. When reported as ratio limits of agreement, these were 1.07 (*/divided 1.12) and 1.03 (*/divided 1.16), respectively. The limits of agreement for maximum instantaneous power (the highest of 100 readings per second) were 51+/-464 and 105+/-588 W for between trials and between days, respectively. When reported as ratio limits of agreement, these were 1.02 (*/divided 1.20) and 1.04 (*/divided 1.21) for between trials and between days, respectively. The coefficients of variation for all measures of power output were less than 9.3%. Hence, the treadmill system and protocol developed in this study provide a reliable measure of power output for rugby players.

Adult↗
PubMed2000

Development of a multi-factor model for predicting the effects of ambient ozone on the biomass of white clover.

Results are presented from the UN/ECE ICP Vegetation (International Cooperative Programme on effects of air pollution on natural vegetation and crops) experiments in which ozone(O(3))-resistant (NC-R) and -sensitive (NC-S) clones of white clover (Trifolium repens cv. Regal) were exposed to ambient O(3) episodes at 14 sites in eight European countries in 1996, 1997 and 1998. The plants were grown according to a standard protocol, and the forage was harvested every 28 days for 4-5 months per year by excision 7 cm above the soil surface. Biomass ratio (NC-S/NC-R) was related to the climatic and pollutant conditions at each site using multiple linear regression (MLR) and artificial neural networks (ANNs). Twenty-one input parameters [e.g. AOT40, 7-h mean O(3) concentration, daylight vapour pressure deficit (VPD), daily maximum temperature] were considered individually and in combination with the aim of developing a model with high r(2) and simple structure that could be used to predict biomass change in white clover. MLR models were generally more complex, and performed less well for unseen data than non-linear ANN models. The ANN model with the best performance had five inputs with an r(2) value of 0.84 for the training data, and 0.71 for previously unseen data. Two inputs to the model described the O(3) conditions (AOT40 and 24-h mean for O(3)), two described temperature (daylight mean and 24-h mean temperature), and the fifth input appeared to be differentiating between semi-urban and rural sites (NO concentration at 17:00). Neither VPD nor harvest interval was an important component of the model. The model predicted that a 5% reduction in biomass ratio was associated with AOT40s in the range 0.9-1.7 ppm x h (microl l(-1) h) accumulated over 28 days, with plants being most sensitive in conditions of low NO(x), medium-range temperature, and high 24-h mean O(3) concentration.

Journal Article↗
PubMed2000

Nicarbazin contamination in feeds as a cause of residues in eggs.

A survey was carried out to investigate the prevalence of nicarbazin residues in eggs in Northern Ireland. Nicarbazin, in the form of 4,4'-dinitrocarbanilide (DNC), was detected in 39 of the 190 eggs analysed. An experiment was designed to establish the relationship between nicarbazin-contaminated feed and nicarbazin residues in eggs. The concentrations of both the DNC and 4,6-dimethyl-2-hydroxypyrimidine (DHP) components of the drug in eggs were proportional to feed levels. The maximum feed nicarbazin concentration of 12.1 mg/kg (8.6 mg/kg DNC and 3.5 mg/kg DHP) gave rise to mean maximum whole egg concentrations of 631 micrograms/kg DNC and 51.8 micrograms/kg DHP. After withdrawal of the experimental diet, DNC was undetectable in eggs after 12 days and DHP after 3 days. Feed contaminated with nicarbazin at concentrations greater than about 2 mg/kg gave rise to egg DNC residues at concentrations greater than the Differential Action Limit (DAL) set by the UK (100 micrograms/kg). DNC was contained almost entirely in the yolk of the egg, whereas DHP was distributed between albumen and yolk in a ratio of approximately 3:1.

Animal Feed↗
PubMed2000

Numerical investigation of the effects of classical phase space structure on a quantum system with decoherence

We present a detailed numerical study of a chaotic classical system and its quantum counterpart. The system is a special case of a kicked rotor and for certain parameter values possesses cantori dividing chaotic regions of the classical phase space. We investigate the diffusion of particles through a cantorus. A quantum analysis confirms that the cantori act as barriers. We numerically estimate the classical phase space flux through the cantorus per kick and relate this quantity to the behavior of the quantum system. We introduce decoherence via environmental interactions with the quantum system and observe the subsequent increase in the transport of quantum particles through the boundary.

Journal Article↗
PubMed2000

Momentum distributions for the quantum delta-kicked rotor with decoherence

We report on the momentum distribution line shapes for the quantum delta-kicked rotor in the presence of environment induced decoherence. Experimental and numerical results are presented. In the experiment ultracold cesium atoms are subjected to a pulsed standing wave of near resonant light. Spontaneous scattering of photons destroys dynamical localization. For the scattering rates used in our experiment the momentum distribution shapes remain essentially exponential.

Journal Article↗
PubMed2000

Alteration of the lipopolysaccharide structure affects the functioning of the Xcp secretory system in Pseudomonas aeruginosa.

Pseudomonas aeruginosa secretes a wide range of hydrolytic enzymes into the external medium by the Xcp secretion machinery. To better understand the role played by envelope constituents in the functioning of this type II secretory system, we have studied the influence of lipopolysaccharide (LPS) on the secretion of two extracellular enzymes, the elastase LasB and the lipase LipA. Strains with defective LPS decreased production of LasB and altered the secretion processes of both LasB and LipA without any apparent effect on the composition of the Xcp machinery. The PAO1algC strain, defective in the outer core of LPS, was leaky, as shown by the extracellular release of the periplasmic beta-lactamase. Generation of an xcpR mutation in this mutant led only to a partial accumulation of LasB within the cells, indicating that in strain PAO1algC with a functional xcpR gene, LasB was released in the extracellular medium partly by leakage and partly by secretion. The pool of LasB released into the medium by leakage was not recovered in an active form, while extracellular LasB was active when secreted via the secretory machinery. Further analysis revealed that the presence of a functional Xcp machinery is strictly required for the activation process of LasB. Our results provide evidence that the Xcp system is not fully functional when the LPS structure of P. aeruginosa is altered.

Aspartic Acid Endopeptidases↗
PubMed1999

Determination of nicarbazin in feeds using liquid chromatography-electrospray mass spectrometry.

A method is presented for the determination of the 4,4'-dinitrocarbanilide component of the coccidiostat nicarbazin in animal feeds. Samples are extracted by shaking with methanol and analysed, without further clean-up, using liquid chromatography-electrospray mass spectrometry. A deuterated form of the analyte is employed as internal standard to improve the repeatability of the method. The method has been validated at levels between 0.1 and 100 mg kg-1 with internal standard corrected recoveries between 88 and 101% and RSD values < 8%.

Animal Feed↗
PubMed1999

Assembly of XcpR in the cytoplasmic membrane is required for extracellular protein secretion in Pseudomonas aeruginosa.

A broad range of extracellular proteins secreted by Pseudomonas aeruginosa use the type II or general secretory pathway (GSP) to reach the medium. This pathway requires the expression of at least 12 xcp gene products. XcpR, a putative nucleotide-binding protein, is essential for the secretion process across the outer membrane even though the protein contains no hydrophobic sequence that could target or anchor it to the bacterial envelope. For a better understanding of the relationship between XcpR and the other Xcp proteins which are located in the envelope, we have studied its subcellular localization. In a wild-type P. aeruginosa strain, XcpR was found associated with the cytoplasmic membrane. This association depends on the presence of the XcpY protein, which also appears to be necessary for XcpR stability. Functional complementation of an xcpY mutant required the XcpY protein to be expressed at a low level. Higher expression precluded the complementing activity of XcpY, although membrane association of XcpR was restored. This behavior suggested that an excess of free XcpY might interfere with the secretion by formation of inactive XcpR-XcpY complexes which cannot properly interact with their natural partners in the secretion machinery. These data show that a precise stoichiometric ratio between several components may be crucial for the functioning of the GSP.

Bacterial Proteins↗
PubMed1997

Failure to find an association between hepatitis C virus and thyroid autoimmunity.

A high frequency of hepatitis C antibodies has been reported from France in patients with autoimmune thyroiditis. Two cases of Hashimoto's thyroiditis in association with chronic active hepatitis and hepatitis C infection have also been reported. We have examined this potential association in 46 patients with autoimmune hypothyroidism and found that 16 apparently had hepatitis C antibodies in one of the two commercially available enzyme-linked immunosorbent assays (ELISA), but all patients were negative in a confirmatory commercially available recombinant immunoblot assay (RIBA-3) indicating that none of the patients were truly positive for hepatitis C antibodies. We also tested sera from 111 patients with proven hepatitis C infection and found no increased prevalence of thyroid autoantibodies. These results suggest that hepatitis C infection is not a risk factor for the development of thyroid autoimmunity in the United Kingdom.

Adult↗