The influence of a certain volume of fluid in the lower tear meniscus on intraocular pressure measurements using the non-contact tonometer

Background: Intraocular pressure (IOP) is the pressure inside the eye that helps to maintain the integrity and the suitable form of the ocular globe. Precise and accurate measures of IOP are needed for the diagnosis as well as follow-up of glaucoma. In daily clinical practice, Goldmann applanation tonometer (GAT) and Non-contact tonometer (NCT) are the most common devices for measuring IOP. A close agreement between these methods has been showed, particularly in normotensive patients and a poor agreement, especially when IOP levels are above the normal range. Ophthalmologists have noticed a poor agreement between NCT and GAT, observing that by using NCT and after comparing with GAT, there is an overestimation of IOP readings, and particularly it occurs when the eyes are tearful. Previous studies investigate the effect of tears in Non-contact tonometer readings by the instillation of artificial tears, concluding in one of the studies that the variation was less than 1mmHg and not clinically significant, in contrast with another study which the increases were sadistically significant. Tear menisci are a thin strip of tear fluid located between the bulbar conjunctiva and the eyelid margins. We think that the overestimation of IOP readings using NCT could be due to the presence of a higher volume of tear in the lower tear meniscus which might cause an optical interference in the optoelectronic applanation monitoring system of this deviceObjectives: To research the influence of a certain volume of fluid in the lower tear meniscus on IOP measurements using the NCT in healthy eyes. Moreover, to investigate the agreement between IOP readings obtained by NCT and GAT in the presence and absence of this volume of fluidMethods: The study design will be transversal for diagnostic tests of repeated measures. We will study patients with no ocular pathology and IOP<21mmHg. It will consist in the measurement of IOP using NCT before and after the instillation of COLIRCUSÍ FLUOTEST, used as a volume of fluid in the lower tear meniscus, to observe if there will be differences using the paired t-test. Moreover, we will take IOP measures by GAT in order to know the agreement between these methods after and before the application of these eyedrops, using the ICC (intraclass correlation coefficient) and the Bland-Altmann method

Kinetic measurements during transient film growth on zinc

The electrochemical behaviour of zinc has been extensively studied in alkaline and acid media, but only a few studies have been reported in neutral solutions, particularly in deaerated media. Zinc passivation in neutral medium and the effect of the ClO4- ion on the nucleation and growth of the passive layer is studied in this paper by a transient technique at different electrolyte concentrations and applied potentials. ZnO growth rate was shown to decrease with increasing electrolyte concentration. Moreover, passive layer growth occurred followed by pitting nucleation and growth. Film growth and pit nucleation are explained by means of the Macdonald and Engell-Stolica models.

Temperature measurements by oh lif and chemiluminescence kinetic modeling for ethanol flames

OH LIF-thermometry was applied to premixed ethanol flames at atmospheric pressure in a burner for three flame conditions. Flame temperatures were simulated from energy equation with PREMIX code of CHEMKIN software package for comparison. A kinetic modeling based on a model validated through chemiluminescence measurements and on a set of reactions for nitrogen chemistry was evaluated. Marinov's mechanism was also tested. Sensitivity analysis was performed for fuel-rich flame condition with Φ = 1.34. Simulated temperatures from both reaction mechanisms evaluated were higher than experimental values. However, the proposed kinetic modeling resulted in temperature profiles qualitatively very close to the experimental.

Structural and reactivity analyses of 2-benzylamino-1,4-naphthoquinone by X-ray characterization, electrochemical measurements, and dft single-molecule calculations

This study represents an integrated approach towards understanding the electronic and structural aspects of 2-benzylamino-1,4-naphthalenedione, a representative 2-amino-napfthoquinone. To this end, theoretical calculations performed at the B3PW91/6-31+G(d) level of density functional theory, electrochemical and X-ray structural investigation were employed. Two intramolecular H-bonds and other two intermolecular H-bonds were observed, including non-classical interactions. Cyclic voltammogram (CV) and differential pulse voltammetry (DPV) show two pairs of peaks, being each one a monoelectronic process.

Organic and total mercury determination in sediments by cold vapor atomic absorption spectrometry: methodology validation and uncertainty measurements

The purpose of the present study was to validate a method for organic Hg determination in sediment. The procedure for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. Total Hg was performed according to 3051A USEPA methodology. Mercury quantification for both methodologies was then performed by CVAAS. Methodology validation was verified by analyzing certified reference materials for total Hg and methylmercury. The uncertainties for both methodologies were calculated. The quantification limit of 3.3 µg kg-1 was found for organic Hg by CVAAS.

Screening of sweet sorghum accessions for inhibition of secondary sporulation and saccharide measurements in honeydew of Claviceps africana

Certain sweet sorghums (Sorghum bicolor) inhibit the secondary sporulation of Claviceps africana, which occurs on exuded ergot honeydew when the parasite is supplied with excess sucrose, which is then transformed to unique free oligosaccharides fructosyl - mannitol and difructosyl - mannitol with spore germination inhibiting properties. Five accessions (BRA-035726-SUGAR DRIP, BRA-035696-THEIS, BRA-036013-MN-4578, BRA-035947-MN-4418 and CMSXS-633) of sweet sorghum were selected among 50 evaluated. These five accessions failed to support secondary sporulation on the "honeydew" exuded from infected florets. There was a higher concentration (%w/v) of the free oligosaccharides on the honeydew of these accessions when compared to a hybrid male-sterile grain sorghum. Therefore, a possible strategy would be seek to incorporate a sweet character into "A" lines for hybrid seed production in order to restrict secondary disease spread.

Design of Installation for Transport Measurements

In the present work the aim was to prepare an automatic installation for studies of galvanomagnetic effects in solids and to test it by calibration measurements. As a result required automatic installation was created in this work and test measurements were performed. Created setup automatically provides measurements of the magnetoresistance of the Hall effect with an accuracy of ± 2 µV in the temperature range 2 – 300 K and steady magnetic fields up to 6 T. The test measurements of the glassy carbon samples showed that the setup is reliable, has high sensitivity and is easy to use. The results obtained in the research process are pioneer and will be separately analyzed.

Electric field measurements using scanning electron microscope

The main idea of this diploma work is to study electric field distribution on the micro level. For this purpose a silicon edgeless detector was chosen as the object of investigation and scanning electron microscope as an investigation tool. Silicon edgeless detector is an important part of installation for studying proton-proton interactions in TOTEM experiment at Large Hadron Collider. For measurement of electric field distribution inside scanning electron microscope a voltage contrast method was applied.

Harmonical oscillator and electro-mechanical analogy: an interdiscinary experiment to high precision mass variation measurements

In general, the traditional Physics courses needs examples of the aplications of the Physics concepts in other areas such as Chemistry and Biology. This lacks tend to demotivate Chemistry and Biology students regarding to deal with Physical concepts developed in classroom. In this work, the analogy among mechanic and electric oscillators is investigated to be applied in Chemistry and Biology areas, showing to be valuable due to its aplication in techniques that aims to measure mass variation with high precision. This measure could be made in a direct or indirect way. These techniques are known as electrogravimetric techniques and they are important in biosensor aplications. Thus, this paper explores the electromechanic analogy in an interdisciplinary way involving areas like Physics, Chemistry and Biology. Based on this analogy, it is proposed an experiment that can be applied in different ways, i.e. by an basic approach or more deeper, depending on the students specific formation, in other words, Physics, Chemistry or Biology.

Online Ultrasound Measurements of Membrane Compaction

There are several filtration applications in the pulp and paper industry where the capacity and cost-effectiveness of processes are of importance. Ultrafiltration is used to clean process water. Ultrafiltration is a membrane process that separates a certain component or compound from a liquid stream. The pressure difference across the membrane sieves macromolecules smaller than 0.001-0.02 μm through the membrane. When optimizing the filtration process capacity, online information about the conditions of the membrane is needed. Fouling and compaction of the membrane both affect the capacity of the filtration process. In fouling a “cake” layer starts to build on the surface of the membrane. This layer blocks the molecules from sieving through the membrane thereby decreasing the yield of the process. In compaction of the membrane the structure is flattened out because of the high pressure applied. The higher pressure increases the capacity but may damage the structure of the membrane permanently. Information about the compaction is needed to effectively operate the filters. The objective of this study was to develop an accurate system for online monitoring of the condition of the membrane using ultrasound reflectometry. Measurements of ultrafiltration membrane compaction were made successfully utilizing ultrasound. The results were confirmed by permeate flux decline, measurements of compaction with a micrometer, mechanical compaction using a hydraulic piston and a scanning electron microscope (SEM). The scientific contribution of this thesis is to introduce a secondary ultrasound transducer to determine the speed of sound in the fluid used. The speed of sound is highly dependent on the temperature and pressure used in the filters. When the exact speed of sound is obtained by the reference transducer, the effect of temperature and pressure is eliminated. This speed is then used to calculate the distances with a higher accuracy. As the accuracy or the resolution of the ultrasound measurement is increased, the method can be applied to a higher amount of applications especially for processes where fouling layers are thinner because of smaller macromolecules. With the help of the transducer, membrane compaction of 13 μm was measured in the pressure of 5 bars. The results were verified with the permeate flux decline, which indicated that compaction had taken place. The measurements of compaction with a micrometer showed compaction of 23–26 μm. The results are in the same range and confirm the compaction. Mechanical compaction measurements were made using a hydraulic piston, and the result was the same 13 μm as obtained by applying the ultrasound time domain reflectometry (UTDR). A scanning electron microscope (SEM) was used to study the structure of the samples before and after the compaction.

Morphometric Study of Cerebral Arterioles in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy(CADASIL) is the most common hereditary small vessel disease (SVD) leading to vascular dementia. The cause of the disease is mutations in NOTCH3 gene located at chromosome 19p13.1. The gene defect results in accumulation of granular osmiophilic material and extracellular domain of NOTCH3 at vascular smooth muscle cells (VSMCs) with subsequent degeneration of VSMCs. This arteriopathy leads to white matter (WM) rarefaction and multiple lacunar infarctions in both WM and deep grey matter (GM) visible in magnetic resonance imaging. This thesis is focused on the quantitative morphometric analysis of the stenosis and fibrosis in arterioles of the frontal cerebral WM, cortical GM and deep GM (lenticular nucleus (LN), i.e. putamen and globus pallidus). It was performed by assessing four indicators of arteriolar stenosis and fibrosis: (1) diameter of arteriolar lumen, (2) thickness of arteriolar wall, (3) external diameter of arterioles and (4) sclerotic index. These parameters were assessed (a) in 5 elderly CADASIL patients with the mean age of onset 47 years and of death 63 years, (b) in a 32-year-old young CADASIL patient with the first ischemic episode at the age of 29 years and (c) a very old CADASIL patient aged 95 years, who suffered the first stroke at the age of 71 years. These measurements were compared with age-matched controls without stroke, dementia, hypertension, and cerebral amyloid angiopathy. Morphometric analyses disclosed that in all age groups of CADASIL patients compared to corresponding controls there was significant narrowing of arteriolar lumen (stenosis) and fibrotic thickening of the walls (fibrosis) in the WM arterioles, although the significance of stenosis in the very old patient was marginal. In the LN arterioles there was only significant fibrosis without stenosis. These results suggest that the ischemic lesions and lacunar infarcts in the cerebral WM are mainly attributable to the stenosis of arterioles, whereas those in the LN are probably mainly due to hemodynamic changes of the cerebral blood flow. In conclusion: The SVD of CADASIL is characterized by narrowing of lumina and fibrotic thickening of walls predominantly in the cerebral WM arterioles. On the other hand, in the LN the ischemic lesions and lacunar infarcts are most probably hemodynamic due to impaired autoregulation caused by the rigidity of fibrotic arterioles. The pathological cerebral arteriolar alterations begin to develop already at a relatively young age but the onset may be delayed to a remarkably old age. This underlines the well known great variability in the clinical picture of CADASIL. The very late onset of CADASIL may cause its underdiagnosis, because the strokes are common in the elderly and are attributed to common risk factors.