Stability Analysis Of Film Research Articles

Diagnosis of dry eye disease and emerging technologies

Dry eye is one of the most commonly encountered problems in ophthalmology. Signs can include punctate epithelial erosions, hyperemia, low tear lakes, rapid tear break-up time, and meibomian gland disease. Current methods of diagnosis include a slit-lamp examination with and without different stains, including fluorescein, rose bengal, and lissamine green. Other methods are the Schirmer test, tear function index, tear break-up time, and functional visual acuity. Emerging technologies include meniscometry, optical coherence tomography, tear film stability analysis, interferometry, tear osmolarity, the tear film normalization test, ocular surface thermography, and tear biomarkers. Patient-specific considerations involve relevant history of autoimmune disease, refractive surgery or use of oral medications, and allergies or rosacea. Other patient considerations include clinical examination for lid margin disease and presence of lagophthalmos or blink abnormalities. Given a complex presentation and a variety of signs and symptoms, it would be beneficial if there was an inexpensive, readily available, and reproducible diagnostic test for dry eye.

Stability analysis of non-isothermal film blowing process for non-Newtonian fluids using variational principles

In this study, a numerical stability analysis of the film blowing process is performed. The numerical scheme used is based on a variational principle model of the film blowing operation. This model employs non-isothermal processing conditions, non-Newtonian behavior of the polymer and physically limiting criteria (maximum tensile and/or hoop stress) to investigate the complex relationship between processing conditions (internal bubble pressure, heat transfer coefficient, mass flow rate, cooling air temperature, melt/die temperature), material parameters (rupture stress, Newtonian viscosity, flow activation energy, power law index) and film blowing stability. It has been shown that the melt/die temperature has the highest impact on the film blowing stability window size as well as on the maximum and minimum achievable film thickness. In more detail, it has been found that processing parameters together with flow activation energy have much higher effect on the film blowing stability and maximum achievable film thickness than the basic rheological characteristics of the polymer melt. On the other hand, the effect of basic rheological parameters of the polymer melt become much more important than processing parameters (except of melt/die temperature) in order to reach minimum film thickness.

Evaluation of Tear Stability After Surgery for Conjunctivochalasis

To evaluate the efficacy of surgical treatment for conjunctivochalasis using the Tear Film Stability Analysis System. Fifteen eyes of 15 patients (74.5 ± 4.8 years; 14 females and 1 male) who had surgical reconstruction of the tear meniscus for conjunctivochalasis underwent evaluation with a symptom questionnaire, Schirmer I test, fluorescein tear film break-up time (FBUT), and break-up time index (BUI) measurement by Tear Film Stability Analysis System examinations that were performed preoperatively and 3 months after the surgery. Changes of these tear parameters were statistically analyzed using the paired t test. After the surgery, the mean FBUT and BUI values significantly improved from 5.7 ± 3.2 s and 42.8 ± 18.7, respectively, to 8.4 ± 2.5 s and 60.7 ± 16.5, respectively (FBUT, p = 0.0438; BUI, p = 0.0036). The mean Schirmer test value showed no significant changes before and after surgery (p = 0.9064). Fourteen eyes (93.3%) had improvement of ocular symptoms after surgery. One eye (6.7%) with no improvement of ocular symptoms, FBUT, and BUI after surgery appeared to have aqueous tear deficiency. Surgical treatment for conjunctivochalasis was associated with improvement of tear stability and clinical dry eye symptoms.

Surface Activity of Surfactant Protein SP-B and SP-C in Different Lipid Environments

Pulmonary surfactant is a mixture of lipids and proteins, essential to reduce the surface tension at the air-liquid interface in the alveoli of mammalian lungs and so stabilizing the respiratory surface. Lack of an operative surfactant is associated with severe respiratory pathologies and supplementation with exogenous surfactants has been widely approached as a potential therapeutic intervention. However, the optimal lipid and protein composition of exogenous surfactants has not been properly established, and clinical surfactants currently in use differ substantially in terms of their lipid and protein moieties. In the present study we have compared the surface activity of native SP-B and /or SP-C, purified from porcine lungs, in the Captive Bubble Surfactometer (CBS), once reconstituted into two different synthetic lipid mixtures: DPPC/POPC/POPG/Chol (50:25:15:10) (lipidS), a mixture mimicking lipid composition in natural surfactant, and DPPC/POPG/Palmitic Acid (68:22:9) (lipidTA), a system widely used as a basis for clinical surfactants. We found similar equilibrium surface tensions after 5 min of adsorption of all the samples, regardless the protein and lipid system, although SP-B exhibited somehow slower initial adsorption in lipidTA. Significant differences were found in SP-B activity under quasi static compression-expansion cycling for the two lipid systems tested. In lipidTA, SP-B allowed reaching tensions near 2mN/m, whereas in lipidS surface tension did not fall below 20mN/m. However, SP-B-containing samples produced similarly low tensions, within the two lipid compositions, once cycled dynamically at physiologically relevant compression-expansion rates. Analysis of film stability under mechanical perturbations showed that SP-B introduces a significant resistance of the films to relaxation, which is particularly remarkable in lipidS samples. This stability was maximal in the simultaneous presence of SP-B and SP-C.

Stability of conducting viscous film flowing down an inclined plane with linear temperature variation in the presence of a uniform normal electric field

Weakly nonlinear stability analysis of a thin liquid film falling down a heated inclined plane with linear temperature variation in the presence of a uniform normal electric field has been investigated within the finite amplitude regime. A generalized kinematic equation for the development of free surface is derived by using long wave expansion method. A normal mode approach and the method of multiple scales are used to investigate the linear and weakly nonlinear stability analysis of film flow, respectively. It is found that both Marangoni and electric Weber numbers have destabilizing effect on the film flow. The study reveals that both supercritical stability and subcritical instability are possible for this type of film flow. It is interesting to note that both the Marangoni and electric Weber numbers have qualitatively same influence on the stability characteristics but the effect of Marangoni number is much stronger compare to the electric Weber number. Scrutinizing the effect of Marangoni and electric Weber numbers on the amplitude and speed of waves it is found that, in the supercritical region amplitude and speed of the nonlinear waves increases with the increase in Marangoni and electric Weber numbers, while in the subcritical region the threshold amplitude decreases with the increase in Marangoni and electric Weber numbers. Finally, we obtain that spatially uniform solution is side-band stable in the supercritical region for our considered parameter range.

Análise do filme lacrimal e sua relação com a largura da fenda palpebral e a exoftalmia na oftalmopatia de Graves

To evaluate tear film quality by rose bengal staining and its stability by breakup time, relating with palpebral fissure height and exophthalmos in patients with Graves' ophthalmopathy. We studied 54 eyes of 27 patients with Graves' ophthalmopathy, either in the inflammatory or in the chronic phase of the disease. The evaluation consisted of tear film qualitative analysis by rose bengal staining using the van Bijsterveld grading scale, tear film stability analysis by breakup time, measurement of palpebral fissure height and exophthalmometry. Qui square test was used to perform statistical analysis. Among 27 studied patients, 77.8% were females and 22.2% males. Mean age was 44.26 years (SD 12.67). Mean disease time was 5.85 years (SD 4.47) and mean ophthalmopathy time was 5.81 years (SD 5.37). Among 54 studied eyes, 37% had positive test by van Bijsterveld's grading scale, 33.3% tear film breakup time lower than 5 seconds, 57.4% palpebral fissure height greater than 11 mm and 55.6% exophthalmometry greater than 19 mm. When relating tear film breakup time lower than 5 seconds with palpebral fissure height greater than 11 mm we found an odds ratio of 11.2 (p=0.0008). The remaining relationships did not show statistical significance. Dry eye diagnosed by rose bengal staining and tear film breakup time occurs frequently in Graves' ophthalmopathy. Palpebral fissure height correlates with tear film breakup time in Graves' ophthalmopathy. Its increase may lead to tear film instability.

Effect of the microscale wall topography on the thermocapillary convection within a heated liquid film

Thin films, which are frequently used for cooling of electronic devices and other components, can be ruptured by thermocapillarity leading to appearance of uncontrolled dry patches that significantly reduce the heat and mass transfer characteristics. Microstructured wall surfaces often improve the performance of such devices. However, the effect of the wall microstructure on the heated film dynamics has not been studied to date. When the temperature of the wall differs from that of ambient gas, the presence of a wall microstructure leads to a temperature gradient along the liquid–gas interface. This is a result of the film thickness inhomogeneity resulting from the microstructure. Thus, a thermocapillary convection develops even in the undisturbed state. In the present paper, the thermocapillary film flow on a horizontal microstructured wall is studied in the framework of the long-wave theory and numerically using the volume of fluid method. The predictions of the liquid velocity fields from the above two methods are compared. It is found that the flow is characterized by a steady roll motion. The gas–liquid interface is found to deform in such a way, that the liquid tends to accumulate within the groove. A film stability analysis is also performed. It is found that the wall microstructure destabilizes the film.

Tear film stability analysis system: introducing a new application for videokeratography.

To review our previous studies regarding the development of a tear stability analysis system (TSAS) using videokeratography and the clinical application of TSAS for evaluation of tear film stability in patients subject to laser in situ keratomileusis (LASIK). New software, namely TSAS, was developed for the videokeratography system TMS-2N (topographic modeling system). TSAS automatically captures consecutive corneal surface images every second for 10 seconds. Corneal topographs were analyzed for tear breakup time (TMS-BUT) and tear breakup area (TMS-BUA, the ratio of breakup area to entire color-code area). First, we recruited volunteers to test the sensitivity and specificity of this new system in comparison with the routine method for tear stability analysis, tear film breakup time evaluation by slit-lamp microscope (SLE-BUT), with fluorescence staining. Second, we investigated the practicability of TSAS in dynamic evaluation of tear film stability before and after LASIK. TMS-BUT had a positive correlation with SLE-BUT, whereas TMS-BUA showed a negative correlation. Although they showed similar rates of specificity as SLE-BUT, the sensitivity rates of TMS-BUT and TMS-BUA were 97.5% and 95%, respectively, significantly higher than that of SLE-BUT (75%). The study on patients subject to LASIK showed that tear film stability significantly decreased during the early time period following LASIK and resolved at 6 months after surgery. Eyes that had abnormal TSAS evaluation tended to have higher risk of developing superficial punctuate keratitis and dry eye symptoms after LASIK, and their responses to treatment were slow. TSAS is a noninvasive and objective method with higher sensitivity for tear film stability analysis than SLE-BUT.

Evaluation of the tear film stability after laser in situ keratomileusis using the tear film stability analysis system

Purpose To evaluate the tear film stability of patients before and after laser in situ keratomileusis (LASIK) using the tear film stability analysis system (TSAS). Design Prospective observational case series. Methods New videokeratography software for a topographic modeling system (TMS-2N) was developed that can automatically capture consecutive corneal surface images every second for 10 seconds. Thirty-four subjects (64 eyes) who underwent myopia LASIK were enrolled in this study. All subjects were examined with the new system before LASIK and at 1 week, 1 month, 3 months, and 6 months after the surgery. Corneal topographs were analyzed for tear breakup time (TMS breakup time) and breakup area (TMS breakup area). Based on pre-LASIK TSAS analysis, subjects were separated into normal and abnormal TSAS value groups. The criteria for the normal group were either TMS breakup time more than 5 seconds or TMS breakup area less than 0.2. The percentage of the occurrence of superficial punctuate keratitis was compared between the two groups with regard to subject's dry eye signs and symptoms. Results Tear film stability decreased significantly during the early period after LASIK, as indexed by decreased TMS breakup time and increased TMS breakup area. Tear film instability resolved at 6 months after surgery. Before LASIK, 22 subjects (43 eyes) had normal TSAS evaluation and 12 subjects (21 eyes) were abnormal. After LASIK, among normal TSAS value eyes, 8 of 43 (18.6%) eyes developed superficial punctuate keratitis. In sharp contrast, 14 of 21 (66.7%) eyes in the abnormal group displayed superficial punctuate keratitis, correlating well with the patients' dry eye symptoms. The difference in the presence of superficial punctuate keratitis after LASIK between normal and abnormal TSAS value groups was statistically significant ( P < .001). Subjects with abnormal TSAS evaluation also displayed resistance to dry eye treatment and had extended period of recovery. Conclusions Tear film stability analysis can be a useful means for screening LASIK candidates before surgery and for prognosticating dry eye symptoms thereafter.

A new method for tear film stability analysis using videokeratography

PurposeTo report a new tear film stability analysis system using videokeratography. DesignObservational case series. MethodsNew videokeratography software for TMS-2N (topographic modeling system; TOMEY Corporation, Nagoya, Japan) was developed that can automatically capture consecutive corneal surface images every second for 10 seconds. Forty-eight adult volunteers (80 eyes) were recruited for this study, and all subjects were examined with the new system. Corneal topographs were analyzed for tear breakup time (TMS-BUT) and the ratio of breakup area to entire color-code area (TMS-BUA) was calculated. Routine methods for tear film breakup time evaluation using slit-lamp microscope and fluorescence staining (SLE-BUT) were performed for comparison purposes. Regressive correlations of TMS-BUT or TMS-BUA with SLE-BUT were analyzed. Based on SLE results, subjects were separated into two groups with normal and short BUT, respectively. TMS-BUT and TMS-BUA were compared with SLE-BUT data with regard to the sensitivity and specificity of evaluation of dry eye symptoms. ResultsTopographic modeling system–tear breakup time (TMS–BUT) had a positive correlation with SLE-BUT (R = 0.7219, P < .0001), whereas TMS-BUA showed a negative correlation (R = 0.6317, P < .0001). Among 34 eyes with normal SLE-BUT, 11 eyes (32.35%) displayed abnormal TMS-BUT, 9 (81.82%) of which were associated with dry eye symptoms. The sensitivities of TMS-BUT and TMS-BUA were 97.5% and 95%, respectively, significantly higher than that of SLE-BUT (75%), with P = .008 and 0.01, respectively. Topographic modeling system–BUT and TMS-BUA displayed a similar rate of specificity in comparison with SLE-BUT. ConclusionsThis new videokeratography system is a noninvasive and objective method with increased sensitivity for tear film stability analysis.

Analysis of film stability and column durability in open tubular glass capillary columns

A considerable body of knowledge on the physicochemical relationships between thin films and hard surfaces which has been amassed in other fields can assist our understanding of film stability and column durability in open tubular glass capillary columns. Reasons for the high success ratio of untreated glass columns coated by the heated-inlet-tube modification of the Golay coating technique are discussed.