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J Gomez

Publications and source records attributed to J Gomez.

At least 37 records · Page 2Linked to original sources
PubMed2004

Settleability and kinetics of a nitrifying sludge in a sequencing batch reactor.

A physiological study of a nitrifying sludge was carried out in a sequencing batch reactor (SBR). Pseudo steady-state nitrification conditions were obtained with an ammonium removal efficiency of 99% +/- 1% and 98% +/- 2% conversion of NH4+-N to NO3 - -N. The rate of biomass production was negligible (1.3 +/- 0.1 mg microbial protein-N.L(-1).d(-1)). The sludge presented good settling properties with sludge volume index values lower than 20 mL.g(-1) and an exopolymeric protein/carbohydrate ratio of 0.53 +/- 0.34. Kinetic results indicated that the nitrifying behavior of the sludge changed with the number of cycles. After 22 cycles, a decrease in the specific rate of NO3- -N production coupled with an increase in the NO2- -N accumulation were observed. These results showed that the activity of the nitrite oxidizing bacteria decreased at a longer operation time. Ammonia oxidizing bacteria were found to exhibit the best stability. After 4 months of operation, the specific rates of NH4+-N consumption and NO3- -N production were 1.72 NH4+-N per microbial protein-N per hour (g.g(-1).h(-1)) and 0.54 NO3- -N per microbial protein-N per hour (g.g(-1).h(-1)), respectively.

Bacteria↗
PubMed2004

Increasing hCG concentrations during storage at (+)4 degrees C with the Bayer Centaur Total hCG method.

BACKGROUND: The interpretation of changes in serum human chorionic gonadotropin (hCG) concentrations in early pregnancy requires a knowledge of the day-to-day imprecision of the method at the concentrations measured. We therefore attempted to determine the analytical imprecision of our total hCG method over a 4-week period at concentrations up to 20,000 IU/L. METHODS: Serum specimens with hCG concentrations between 100 and 20,000 IU/L were collected during early pregnancy and analysed using the Bayer Centaur Total hCG method at weekly intervals after storage at (+)4 degrees C and (-)20 degrees C. RESULTS: The reproducibility of hCG results over a 4-week period in refrigerated specimens with an initial hCG concentration below 1000 IU/L was poor (mean coefficient of variation = 17.4%) and there was an apparent increase in serum hCG concentrations of up to 68%. Similar changes occurred in some specimens stored at (-)20 degrees C. Further experiments confirmed that significant increases can occur during the first week following specimen collection. CONCLUSIONS: Total hCG concentrations in serum specimens collected during early pregnancy increase significantly during storage when measured by the Bayer Centaur Total hCG method, possibly due to a conformational change in hyperglycosylated hCG. When this method is used for monitoring early pregnancy, specimens should ideally be analysed on the day of collection.

Chorionic Gonadotropin, beta Subunit, Human↗
PubMed2004

Effect of anaesthesia of the palmar digital nerves on proximal interphalangeal joint pain in the horse.

REASONS FOR PERFORMING STUDY: Anaesthesia of the palmar digital nerves is claimed to attenuate lameness in some horses that are lame because of pain in the proximal interphalangeal (PIP) joint. OBJECTIVE: To determine the response of horses with pain in the PIP joint to anaesthesia of the palmar digital nerves. METHODS: Horses were video recorded trotting before and after induction of pain in the PIP joint and 10 mins after anaesthesia of the palmar digital nerves. The palmar digital nerves were anaesthetised 3 times at different sites, and the video recorded gaits were scored subjectively. RESULTS: The median lameness score of gaits after administration of 2% mepivacaine 1 cm proximal to the cartilages of the foot was not significantly different from the median lameness score before anaesthesia of the palmar digital nerves (P > or = 0.05), although that of 1 of 6 horses improved markedly. The median lameness score was significantly (P < or = 0.05) improved after mepivacaine was administered 2 and 3 cm proximal to the cartilages of the foot. CONCLUSIONS: The PIP joint is unlikely to be anaesthetised when the palmar digital nerves are anaesthetised at the proximal margin of the cartilages of the foot. POTENTIAL RELEVANCE: Pain within the PIP joint cannot be excluded as a cause of lameness when lameness is attenuated by anaesthesia of the palmar digital nerves at any site proximal to the proximal margin of the cartilages of the foot.

Anesthesia↗
PubMed2003

Polarization transfer in the 4He(e-->,e'p-->)3H reaction up to Q2=2.6 (GeV/c)2.

We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.

Journal Article↗
PubMed2003

Cross-section measurement of charged-pion photoproduction from hydrogen and deuterium.

We have measured the differential cross section for the gamman-->pi(-)p and gammap-->pi(+)n reactions at theta(c.m.)=90 degrees in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E(gamma) greater, similar 3.3 GeV exhibit a global scaling behavior for both pi(-) and pi(+) photoproduction, consistent with the constituent counting rule and the existing pi(+) photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi(-) to pi(+) photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.

Journal Article↗
PubMed2003

Phase I and pharmacokinetic study of Yondelis (Ecteinascidin-743; ET-743) administered as an infusion over 1 h or 3 h every 21 days in patients with solid tumours.

Yondelis (ET-743) is a novel anticancer agent isolated from the marine ascidian Ecteinascidia turbinata. ET-743 possesses potent antitumour activity and a novel mechanism of action at the level of gene transcription. We conducted two sequential phase I dose escalation and pharmacokinetic studies of ET-743 given as a 1- or a 3-h intravenous (i.v.) infusion. Seventy-two adults with metastatic or advanced solid tumours received ET-743 in escalating doses between 50 and 1100 microg/m(2), initially as a 1-h infusion, and later at doses between 1000 and 1800 microg/m(2) as a 3-h infusion every 3 weeks. The maximum tolerated dose (MTD) of ET-743 was 1100 microg/m(2) for the 1-h infusion schedule and 1800 microg/m(2) when given as a 3-h infusion. Dose-limiting toxicities (DLTs) were fatigue, neutropenia and thrombocytopenia. Transient non-cumulatives grade 3-4 increase in transaminases (not considered DLT) and grades 3-4 nausea and vomiting were frequently observed. Other toxicities (maximum grade 3) included anaemia, increased lactate dehydrogenase (LDH), bilirubin and alkaline phosphatase serum levels, and phlebitis; there were no toxic deaths. One pCR (melanoma), CR (uterine leiomyosarcoma), one PR (colon stromal sarcoma) and a MR (37% tumour shrinkage, gastric stromal sarcoma) were observed. A further 9 patients with colorectal, mesothelioma, bile duct carcinoma and bladder cancer had SD which lasted for six or more treatment cycles. ET-743 pharmacokinetics were linear with the 3-h infusion schedule. The haematological and hepatic toxicities of ET-743 were dose-dependent and not cumulative. Based on the current trial, the recommended dose of ET-743 for phase II studies is 1650 microg/m(2) given as a 3-h infusion.

Adult↗
PubMed2003

Effects of microflora status, dietary bile salts and guar gum on lipid digestibility, intestinal bile salts, and histomorphology in broiler chickens.

The aim of the present study was to reexamine the effects of intestinal viscosity, microflora, and bile salts, and their interactions in order to clarify the mechanisms that explain the effect of intestinal viscosity on lipid digestibility, especially those that could involve microflora. Effects of intestinal viscosity, microflora status, and dietary bile salts on lipid digestibility, intestinal bile salts, and intestinal histomorphology were tested in a 2 x 2 x 2 factorial experiment. The effect of microflora status was examined by comparing conventional chickens to chickens with limited microflora obtained by rearing birds in sterilized conditions. Viscosity and dietary bile salts were tested with guar gum (0 or 0.5% in diets) and sodium taurocholate (0 or 0.3% in diets), respectively. Guar gum was autoclaved and added to the gamma-irradiated diets by mixing inside the sterile isolators. The intestinal concentration of lactic acid and cecal concentration of short-chain fatty acids were both very low in birds with limited microflora compared to conventional birds (P = 0.0001). Chickens with limited microflora had higher gain:feed ratios (P = 0.002), higher fecal lipid digestibility (P = 0.0001), more intestinal conjugated bile salts (P = 0.0001), less intestinal unconjugated bile salts (P = 0.0001), and their gastrointestinal compartments were smaller (P < 0.05) than those of conventional chickens. Addition of bile salts in diets increased the lipid digestibility (P = 0.0001) with a more pronounced effect in conventional birds (P = 0.0001) and in birds fed on guar gum diets (P = 0.002). Feeding the guar gum diets increased the intestinal supernatant viscosity (P = 0.0001) for both microflora status. Guar gum addition increased (P < 0.05) the lactic acid concentration in the small intestine of conventional chickens. Guar gum decreased the fecal lipid digestibility (P = 0.0001) and the intestinal conjugated bile salts (P = 0.0001) for both microflora status. However, the magnitude of lipid digestibility decrease due to guar gum was lower (P = 0.05) in birds with limited microflora than in conventional birds, and the negative effect of guar gum on intestinal conjugated bile salts was more pronounced (P = 0.02) in birds with limited microflora. Bile salt addition reduced the negative effect of guar gum on lipid digestibility (P = 0.02) for both microflora status. The mean lipid digestibilities were negatively correlated (P = 0.0001) with the ratio [Ln(viscosity)/total bile salt] measured in intestinal digesta. Except for gizzard, size of digestive compartments and villus heights increased (P < 0.05) with feed efficiency and digestibility decreased. In conclusion, the results provided evidences that the negative effect of guar gum on lipid digestibility was mainly mediated by its direct effect on intestinal bile salt concentration and efficiency. The small interaction between guar gum and microflora status effects on lipid digestibility had to be accounted for by the low basal level of intestinal bile salts in conventional chickens.

Animal Feed↗
PubMed2002

Q2 evolution of the generalized Gerasimov-Drell-Hearn integral for the neutron using a 3He target.

We present data on the inclusive scattering of polarized electrons from a polarized 3He target at energies from 0.862 to 5.06 GeV, obtained at a scattering angle of 15.5 degrees. Our data include measurements from the quasielastic peak, through the nucleon resonance region, and beyond, and were used to determine the virtual photon cross-section difference sigma(1/2)-sigma(3/2). We extract the extended Gerasimov-Drell-Hearn integral for the neutron in the range of four-momentum transfer squared Q2 of 0.1-0.9 GeV2.

Journal Article↗
PubMed2002

2H(e,e(')p)n reaction at high recoil momenta.

The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations.

Journal Article↗
PubMed2002

Measurement of G(E(p))/G(M(p)) in e(-->)p---> e(-->)p to Q(2) = 5.6 GeV(2).

The ratio of the electric and magnetic form factors of the proton G(E(p))/G(M(p)), which is an image of its charge and magnetization distributions, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic e(-->)p---> e(-->)p reaction. The new data presented span the range 3.5< Q(2)< 5.6 GeV(2) and are well described by a linear Q(2) fit. Also, the ratio sqrt[Q(2)] F(2(p))/F(1(p)) reaches a constant value above Q(2) = 2 GeV(2).

Journal Article↗
PubMed2002

Relationships between digestibilities of food components and characteristics of wheats (Triticum aestivum) introduced as the only cereal source in a broiler chicken diet.

1. The aim of the experiment was to establish relationships between chemical or physical characteristics of wheats (Triticum aestivum) and digestibilities of food components in broiler chickens fed on wheat-based diets. Twenty-two wheat samples, each differing by their cultivar origin, were included at 550 g/kg in diets offered to male Ross broiler chicks. The other main ingredients were soya bean meal (340 g/kg) and rapeseed oil (68.5 g/kg). Diets were given as pellets. 2. In vitro viscosities of wheats measured as potential applied viscosity (PAV) or real applied viscosity (RAV) varied between 1.91 and 6.03, or between 0.95 and 3.81 ml/g (dry matter basis), respectively. Hardness of wheats varied between 17 (soft) and 95 (very hard), and lipase activity of wheats varied from 1 to 13.6 (relative scale). 3. PAV and RAV values were not significantly correlated with hardness. PAV and RAV values were correlated with (80:20) ethanol:water insoluble, water soluble arabinoxylans (r = 0.961, 0.932, respectively), with the amount of water retained by cell walls (r = 0.656, 0.492, respectively), and with lipase activity (r = 0.600, 0.532, respectively. 4. Hardness was correlated with ash (r = -0.484), nitrogen (r = 0.534), mean particle size of wheat flours (r = 0.631), and specific energy of pelleting (r = -0.574). 5. Wheat diets were evaluated in two assays with 3-week-old chicks, with 11 diets per assay. In each assay, a balance experiment was carried out using the total collection method. Growth performance was also measured during the balance experiment. 6. In vitro viscosity parameters were negatively correlated with diet AMEn (P < 0.05), lipid digestibility (P < 0.05) and, to a lesser extent, protein digestibility (P < 0.05). In vitro viscosity data were positively correlated with food:gain ratio (P < 0.05) and water loss parameters (P < 0.05), and were not significantly (P > 0.05) correlated with starch digestibility. 7. Wheat hardness-related parameters were correlated (P < 0.01) with individual starch digestibility (hardness, proportion of coarse particles in wheat flour, specific energy of pelleting: r = -0.273, -0.305, 0.212, respectively). 8. Wheat lipase activity was negatively correlated with individual lipid (r = -0.179; P < 0.05) and starch (r = -0.225; P < 0.01) digestibilities and with individual diet AMEn (r = -0.266; P < 0.001). Individual diet AMEn values were correlated (r = 0.175) with the values calculated by the EU AMEn prediction equation (Fisher and McNab, 1987). Among the correlations observed between the individual measured AMEn:EU predicted AMEn ratio and wheat parameters (P < 0.05), the correlation obtained with wheat lipase was the highest (r = -0.195). The correlations with lipase could be explained in part by strong correlations between lipase and in vitro viscosity parameters.

Animal Feed↗
PubMed2002

Analyses of degradation products from lipid and protein hydrolyses in the small intestine of broiler chickens fed on maize-based diets containing guar gum, or wheat-based diets.

1. Three maize diets containing graded levels (0, 0.1, 0.3%) of guar gum and two wheat diets differing in their in vitro viscosities were fed to male broiler chickens (7 to 23 d) for measurements of growth performance and analyses of degradation products from lipid and protein hydrolyses in the small intestine of broiler chickens. Analyses of degradation products were conducted to define which step (hydrolysis or absorption) was most involved in the negative effects of the digesta viscosity on lipid and protein digestibilities. The experiment was also carried out to examine whether effects of wheats could be explained in terms of intestinal viscosity alone. 2. The intestinal viscosities with wheat diets were within the range of those observed with the three maize diets. The correlations between in vivo and in vitro viscosities were higher with real than with potential applied viscosity of diets, both in jejunum and ileum. 3. The mean gain:food ratio observed with wheat diets was lower (P<0.05) than with maize diets despite lower (P<0.05) mean intestinal viscosities in birds given the wheat than given the maize diets. This shows that factors different from intestinal viscosity were also involved in the negative effects of wheats. 4. Distributions of nitrogen compounds in digesta were characterised by low proportions of compounds with high molecular weight (>12,000). For all classes of nitrogen compounds, the contents measured in digesta dry matter did not differ between chickens fed with or without guar gum. 5. Distributions of lipid classes in both jejunum and ileum were characterised by a large proportion of free fatty acids (FFA) and very few triglycerides (TG). In the ileum, FFA and TG contents were both positively correlated with supernatant viscosity, but the slope for FFA content was 35 times higher than for TG. In these relationships, there was no difference between maize and wheat diets. 6. It is concluded that absorption was the main step involved in the lipid digestibility reduction due to intestinal viscosity. For proteins, the most important step (hydrolysis or absorption) involved in decreased digestibility due to intestinal viscosity was not clearly identified.

Animal Feed↗
PubMed2001

Precision measurement of the spin-dependent asymmetry in the threshold region of 3He(e, e').

We present the first precision measurement of the spin-dependent asymmetry in the threshold region of 3He(e,e') at Q2 values of 0.1 and 0.2 (GeV/c)2. The agreement between the data and nonrelativistic Faddeev calculations which include both final-state interactions and meson-exchange current effects is very good at Q2 = 0.1 (GeV/c)2, while a small discrepancy at Q2 = 0.2 (GeV/c)2 is observed.

Journal Article↗
PubMed2001

Enzyme kinetics determined using calorimetry: a general assay for enzyme activity?

Two techniques for determining enzyme kinetic constants using isothermal titration microcalorimetry are presented. The methods are based on the proportionality between the rate of a reaction and the thermal power (heat/time) generated. (i) An enzyme can be titrated with increasing amounts of substrate, while pseudo-first-order conditions are maintained. (ii) Following a single injection, the change in thermal power as substrate is depleted can be continuously monitored. Both methods allow highly precise kinetic characterization in a single experiment and can be used to measure enzyme inhibition. Applicability is demonstrated using a representative enzyme from each EC classification, including (i) oxidation-reduction activity of DHFR (EC 1.5.1.3); (ii) transferase activity of creatine phosphokinase (EC 2.7.3.2) and hexokinase (EC 2.7.1.1); (iii) hydrolytic activity of Helicobacter pylori urease (EC 3.5.1.5), trypsin (EC 3.4.21.4), and the HIV-1 protease (EC 3.4.21.16); (iv) lyase activity of heparinase (EC 4.1.1.7); and (v) ligase activity of pyruvate carboxylate (EC 6.4.1.1). This nondestructive method is completely general, enabling precise analysis of reactions in spectroscopically opaque solutions, using physiological substrates. Such a universal assay may have wide applicability in functional genomics.

Adenosine Triphosphate↗
PubMed2001

Saccharinate as a versatile polyfunctional ligand. Four distinct coordination modes, misdirected valence, and a dominant aggregate structure from a single reaction system.

The reaction system consisting of copper, saccharinate, and the auxiliary ligands H(2)O, PPh(3), and NH(3) produces a sequence of compounds in which saccharinate is coordinated to copper in four distinct manners. The complex trans-[Cu(sacch)(2)(H(2)O)(4)] (2) (produced by thermal dehydration of trans-[Cu(sacch)(2)(H(2)O)(4)].2H(2)O (1)) reacts with triphenylphosphine in CH(2)Cl(2) to produce any or all of three Cu(I) complexes, depending upon conditions. The three Cu(I) compounds are Cu(sacch)(PPh(3))(3) (3), in which saccharinate binds to copper through the carbonyl group of the ligand, Cu(sacch)(PPh(3))(2) (4), in which sacch binds to Cu through its charge-bearing nitrogen atom; and [Cu(sacch)(PPh(3))](2) (5), a dinuclear complex in which saccharinate bridges two Cu centers through its imidate nitrogen and carbonyl oxygen atoms. Complexes 3-5 can be isolated individually, although in solution they exist in a complex equilibrium which has been examined by NMR spectroscopy. Each of the three Cu(I) products reacts with NH(3) in CH(2)Cl(2) solution to produce trans-[Cu(sacch)(2)(NH(3))(4)] (6), an unstable Cu(II) complex that exhibits misdirected valence at the Cu-N(sacch) bond. Complex 6 evolves spontaneously to [Cu(sacch)(NH(3))(4)](sacch).H(2)O (7), which in the solid state is dominated by a supramolecular aggregate of two formula units, linked by hydrogen bonding in which the water molecule plays a central role. Alternative pathways exist to several of the products. The X-ray crystal structure analyses of 3-7 are reported and establish the coordination modes of saccharinate, the misdirected valence in 6, and the supramolecular aggregation in 7. The structure analysis of 7 by single-crystal neutron diffraction is reported and together with the previously reported neutron structure analysis of 1 establishes the substitution of the auxiliary ligand H(2)O by NH(3) in the Cu(II) products.

Journal Article↗
PubMed2001

A new robotic endoscope manipulator. A preliminary trial to evaluate the performance of a voice-operated industrial robot and a human assistant in several simulated and real endoscopic operations.

We report our learning experience in simulated and real surgical tasks with a new voice-controlled robotic endoscope manipulator: an industrial robot with the tool-holder arm modified to support the optic and camera. The manipulator control-card programs have been rewritten to meet the needs of endoscopic surgeons. For this preliminary work, systems engineers with an additional monitor monitored, recorded, and compared the percentage effectiveness and precision of the responses of the robotic and human assistant to successive oral commands during the several different experimental surgical tasks. Simultaneously, to help develop this voice-commanded system for future, more precise robotic manipulation of surgical instruments, they measured the cartesian and spherical coordinates of successive positions of the optic. In unexpectedly difficult experimental conditions, the tireless robot proved more precise and effective than the demonstrably fatigable human: the steadier screen images of the robotic manipulations helped the surgeon tie knots in 7-0 sutures.

Animals↗
PubMed2001

Dynamics of the 16O(e, e'p) reaction at high missing energies.

We measured the cross section and response functions for the quasielastic 16O(e,e'p) reaction for missing energies 25< or =E(m)< or =120 MeV at missing momenta P(m)< or =340 MeV/c. For 25<E(m)<50 MeV and P(m) approximately 60 MeV/c, the reaction is dominated by a single 1s(1/2) proton knockout. At larger P(m), the single-particle aspects are increasingly masked by more complicated processes. Calculations which include pion exchange currents, isobar currents, and short-range correlations account for the shape and the transversity, but for only half of the magnitude of the measured cross section.

Journal Article↗