Automated monosegmented flow analyser. Determination of glucose, creatinine and urea

An automated monosegmented flow analyser containing a sampling valve and a reagent addition module and employing a laboratory-made photodiode array spectrophotometer as detection system is described, The instrument was controlled by a 386SX IBM compatible microcomputer through an IC8255 parallel port that communicates with the interface which controls the sampling valve and reagent addition module, The spectrophotometer was controlled by the same microcomputer through an RS232 serial standard interface, The software for the instrument was written in QuickBasic 4.5. Opto-switches were employed to detect the air bubbles limiting the monosegment, allowing precise sample localisation for reagent addition and signal reading. The main characteristics of the analyser are low reagent consumption and high sensitivity which is independent of the sample volume, The instrument was designed to determine glucose, creatinine or urea in blood plasma and serum without hardware modification, The results were compared against those obtained by the Clinical Hospital of UNICAMP using commercial analysers, Correlation coefficients among the methods were 0.997, 0.982 and 0.996 for glucose, creatinine and urea, respectively.122101039104

THERMODYNAMIC AND KINETIC IMPLICATIONS INVOLVED IN THE TITRATION OF POLYFUNCTIONAL ACIDS BY CATALYTIC THERMOMETRIC TITRIMETRY

The influence of the concentration of reactants on the results of titrations of salicylic acid in acetone with potassium and tetramethylammonium hydroxides in propan-2-ol were investigated. The titrations were performed by catalytic thermometric titrimetry using acetone as the end-point indicator and by potentiometric titrimetry. These and other results are discussed in terms of the equilibrium and kinetic aspects involved in the titrations of polyfunctional acids capable of forming intramolecular hydrogen bonds.116994794

Mass-dependent evolution of the relation between supermassive black hole mass and host spheroid mass since z ~ 1

We investigate the evolution of supermassive black hole mass (M_BH) and the host spheroid mass (M_sph) in order to track the history of the M_BH-M_sph relationship. The typical mass increase of M_BH is calculated by a continuity equation and accretion history, which is estimated from the active galactic nucleus (AGN) luminosity function. The increase in M_sph is also calculated by using a continuity equation and a star formation model, which uses observational data for the formation rate and stellar mass function. We find that the black hole to spheroid mass ratio is expected to be substantially unchanged since z~1.2 for high mass objects (M_BH>10^8.5M_SUN and M_sph>10^11.3M_SUN). In the same redshift range, the spheroid mass is found to increase more rapidly than the black hole mass if M_sph>10^11M_SUN. The proposed mass-dependent model is consistent with the current available observational data in the M_BH-M_sph diagram.Comment: 15 pages, 8 figures, accepted to MNRA

Transcranial Direct Current Stimulation (tDCS): A Beginner's Guide for Design and Implementation

Transcranial direct current stimulation (tDCS) is a popular brain stimulation method that is used to modulate cortical excitability, producing facilitatory or inhibitory effects upon a variety of behaviors. There is, however, a current lack of consensus between studies, with many results suggesting that polarity-specific effects are difficult to obtain. This article explores some of these differences and highlights the experimental parameters that may underlie their occurrence. We provide a general, practical snapshot of tDCS methodology, including what it is used for, how to use it, and considerations for designing an effective and safe experiment. Our aim is to equip researchers who are new to tDCS with the essential knowledge so that they can make informed and well-rounded decisions when designing and running successful experiments. By summarizing the varied approaches, stimulation parameters, and outcomes, this article should help inform future tDCS research in a variety of fields

Mammalian BTBD12 (SLX4) Protects against Genomic Instability during Mammalian Spermatogenesis

The mammalian ortholog of yeast Slx4, BTBD12, is an ATM substrate that functions as a scaffold for various DNA repair activities. Mutations of human BTBD12 have been reported in a new sub-type of Fanconi anemia patients. Recent studies have implicated the fly and worm orthologs, MUS312 and HIM-18, in the regulation of meiotic crossovers arising from double-strand break (DSB) initiating events and also in genome stability prior to meiosis. Using a Btbd12 mutant mouse, we analyzed the role of BTBD12 in mammalian gametogenesis. BTBD12 localizes to pre-meiotic spermatogonia and to meiotic spermatocytes in wildtype males. Btbd12 mutant mice have less than 15% normal spermatozoa and are subfertile. Loss of BTBD12 during embryogenesis results in impaired primordial germ cell proliferation and increased apoptosis, which reduces the spermatogonial pool in the early postnatal testis. During prophase I, DSBs initiate normally in Btbd12 mutant animals. However, DSB repair is delayed or impeded, resulting in persistent γH2AX and RAD51, and the choice of repair pathway may be altered, resulting in elevated MLH1/MLH3 focus numbers at pachynema. The result is an increase in apoptosis through prophase I and beyond. Unlike yeast Slx4, therefore, BTBD12 appears to function in meiotic prophase I, possibly during the recombination events that lead to the production of crossovers. In line with its expected regulation by ATM kinase, BTBD12 protein is reduced in the testis of Atm−/− males, and Btbd12 mutant mice exhibit increased genomic instability in the form of elevated blood cell micronucleus formation similar to that seen in Atm−/− males. Taken together, these data indicate that BTBD12 functions throughout gametogenesis to maintain genome stability, possibly by co-ordinating repair processes and/or by linking DNA repair events to the cell cycle via ATM

ANCA-associated vasculitis.

The anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of disorders involving severe, systemic, small-vessel vasculitis and are characterized by the development of autoantibodies to the neutrophil proteins leukocyte proteinase 3 (PR3-ANCA) or myeloperoxidase (MPO-ANCA). The three AAV subgroups, namely granulomatosis with polyangiitis (GPA), microscopic polyangiitis and eosinophilic GPA (EGPA), are defined according to clinical features. However, genetic and other clinical findings suggest that these clinical syndromes may be better classified as PR3-positive AAV (PR3-AAV), MPO-positive AAV (MPO-AAV) and, for EGPA, by the presence or absence of ANCA (ANCA+ or ANCA-, respectively). Although any tissue can be involved in AAV, the upper and lower respiratory tract and kidneys are most commonly and severely affected. AAVs have a complex and unique pathogenesis, with evidence for a loss of tolerance to neutrophil proteins, which leads to ANCA-mediated neutrophil activation, recruitment and injury, with effector T cells also involved. Without therapy, prognosis is poor but treatments, typically immunosuppressants, have improved survival, albeit with considerable morbidity from glucocorticoids and other immunosuppressive medications. Current challenges include improving the measures of disease activity and risk of relapse, uncertainty about optimal therapy duration and a need for targeted therapies with fewer adverse effects. Meeting these challenges requires a more detailed knowledge of the fundamental biology of AAV as well as cooperative international research and clinical trials with meaningful input from patients

A multichannel photometer based on an array of light emitting diodes for use in multivariate calibration

The development of a multichannel photometer based on an array of eight light emitting diodes (LED) as light sources is described. Optical fibre bundles were employed to guide the light radiation of the LED to the measuring cell and from the cell to the photodiode detector. The instrument was controlled by a microcomputer and was designed to perform absorbance measurements in a single wavelength continuously as well as in all wavelengths (470, 500, 562, 590, 612, 636 and 654 nm) sequentially, allowing its application in multivariate analysis methods. The photometer presented a drift lower than 2 muV h(-1), allowing absorbance measurements with a precision better than 0.003 units. The instrument was applied for the simultaneous determination of Zn(II) and Cu(II) in pharmaceutical and metallic alloy samples, whose pH adjustment followed by the addition of xylenol orange complexing agent were accomplished by employing a monosegmented flow system. Solutions containing both metal ions in the concentration range from 1.0 to 4.0 mg L-1 were employed to constructed the calibration model based on multiple linear regression (MLR), providing root mean square errors of prediction of 0.06 and 0.12 mg L-1 for Zn(II) and Cu(II), respectively. The results obtained by employing the photometer were compared with those obtained by flame atomic absorption spectrometry, showing no significant differences at the 95% confidence level. (C) 2004 Elsevier B.V. All rights reserved.522222322

Use of Nafion (R) membranes for the construction of optical sensors for pH measurements

The behaviour of Nafion (R) polymeric membranes containing acid-base dyes, bromothymol blue (BB) and methyl violet (MV), were studied aiming at constructing an optical sensor for pH measurement. BB revealed to be inadequate for developing sensing phases due to the electrostatic repulsion between negative groups of their molecules and the negative charge of the sulfonate group of the Nation (R), which causes leaching of the dye from the membrane. On the other hand, MV showed to be suitable due to the presence of positive groups in its structure. The membrane prepared from a methanolic solution whose Nafion (R)/dye molar ratio was 20 presented the best analytical properties, changing its color from green to violet in the pH range from 0.6 to 3.0. The membrane can be prepared with good reproducibility, presenting durability of ca. 6 months and response time of 22 s, making possible its use for pH determination in flow analysis systems.28593293

An optical sensor for measurement of gaseous ammonia

A simple optical fibre chemical sensor based on a nafion - crystal violet film for the determination of gaseous ammonia in air is described. The film was prepared from a methanolic solution mixture containing 1.0 x 10(-3) mol L-1 crystal violet and 1.0 x 10(-3) mol L-1 nafion (in sulphonate groups) and determinations of ammonia concentration in air were achieved using reflectance measurements at 580 nm. Ammonia seems to react irreversibly with the film, since it cannot be released by flushing the film with dry air. However, a short pulse of humid air, followed by a stream of dry air can reverse the response of the film, providing a signal recovery greater than 90% at 580 nm. The film did not respond to carbon dioxide even at concentrations higher than 350 ppm, but it responds on exposure to 5 ppm of hydrogen hydrochloride and nitrogen dioxide. The influence of the relative humidity to the sensor response is also presented and response mechanism to ammonia in dry and humid air is suggested. A repeatability of 3.5%, expressed as the rsd of 6 measurements with a 20 ppm NH3 standard, was achieved. The sensitivity of the sensor is tuneable by altering the exposure time to ammonia gas. Detection limits of 1.40 ppm and 0.46 ppm and linear responses up to 50 and 10 ppm in dry air were achieved with exposure times of 30s and 5 min, respectively.19112713