Free Glasses Research Articles

Chaotic Mixing Experiments: Unravelling Contamination Processes on Dacitic Melts

Magmas are the ultimate source of volcanism on Earth. At high-temperatures these complex silicate melts may easily chaotically mix, on their way towards the surface of the planet.The Paraná-Etendeka Magmatic Province (PEMP), one of the largest volcanic provinces of our planet, serves as the focus of this experimental study. The investigation simulates the contamination of high-Ti dacites passing through the continental crust. Our final aim is to contribute to the origin of the high-Ti Chapecó dacites from PEMP, with particular attention to the genesis of Chapecó-Ourinhos dacites (COD).The experimental apparatus is based on the Journal Bearing System. All experimental runs have been operated at atmospheric pressure and a temperature of 1500 °C. A dacitic magma chamber under the assimilation of crustal material has been simulated. The resulting experimental products (dry/bubble free glasses) exhibit concentric folded and stretched filaments of contrasting compositions. The calculated fractal dimension for a representative section is Dbox = 1.60(3), confirming the achievement of chaotic dynamics. Electron Microprobe Analysis (EMPA) from the experimental glasses clearly shows SiO2-contamination, while Al2O3-data indicate lower contamination levels. As a consequence, different elements depict dissimilar curves in chemical transects. We used the parameter σn2 (normalized variance) to quantify the mixing efficiency and differential elemental mobilities. In addition, our data reproduced the chemical behaviour of some elements in COD- dacites, especially the network formers such as Fe, Al, Ti and Si. EMPA reveals clear deviations from the linear mixing model. Our experiments and data replicate a selective contamination process. Differential elemental mobilities could be calculated. Comparisons with natural data depict how the mixing involving Chapecó-Guarapuava (CGD) and Chapecó-Ourinhos (COD) dacitic end-members may have contributed to the generation of more evolved COD from the interaction of CGD pre-existing melts with crustal rocks from the PEMP basement via chaotic dynamics.

Manhattan Vision Screening and Follow-up Study (NYC-SIGHT): Vision and refractive error results

ABSTRACT Clinical relevance Optometrists can play a key role in providing access to eye care in underserved populations by organising community-based eye health screenings that include optometric exams to detect vision impairment and uncorrected refractive error. Background Community-based eye health screenings and optometric exams were conducted in the NYC-SIGHT Study. Methods A sub-analysis of vision impairment and refractive error results within a 5-year prospective, cluster-randomised clinical trial. Eligible individuals (age ≥40 years) were recruited from 10 affordable housing developments in Upper Manhattan. Developments were randomised into usual care (received glasses prescription only) and intervention (free glasses) groups. Participants with 6/12 visual acuity or worse, intraocular pressure 23–29 mmHg, or an unreadable fundus image were scheduled with the study optometrist for refraction and a non-dilated exam. Visual improvement data were obtained by comparing the presenting acuity at screening compared to the best corrected acuity after refraction by the optometrist. Chi-square, two-sample t-tests, and a stepwise multivariate logistic regression model were used to determined factors associated with improvable visual impairment. Results Seven hundred and eight participants completed screening, 308 received an optometric exam. Those with improvable vision impairment (n = 251), mean age: 69.8 years, 70.5% female, 53% African American, 39.8% Hispanic, >95% had health insurance. Refractive error diagnosed in 87.8% of the participants; lines of improvement: 2 lines (n = 59), 3 to 5 lines (n = 120), and ≥6 lines (n = 72). Stepwise multivariate logistic regression analysis showed that participants with visual acuity 6/12 or worse (odds ratio 16.041, 95% confidence interval 6.009 to 42.822, p = 0.000) or a normal fundus image (odds ratio 2.783, 95% confidence interval 1.001 to 7.740, p = 0.05) had significantly higher odds of improvable vision impairment. Conclusion This innovative, targeted community-based study included an optometrist who detected high rates of refractive error and improvable vision impairment in an underserved population living in New York City.

The unexplored role of alkali and alkaline earth elements (ALAEs) on the structure, processing, and biological effects of bioactive glasses.

Bioactive glass has been employed in several medical applications since its inception in 1969. The compositions of these materials have been investigated extensively with emphasis on glass network formers, therapeutic transition metals, and glass network modifiers. Through these experiments, several commercial and experimental compositions have been developed with varying chemical durability, induced physiological responses, and hydroxyapatite forming abilities. In many of these studies, the concentrations of each alkali and alkaline earth element have been altered to monitor changes in structure and biological response. This review aims to discuss the impact of each alkali and alkaline earth element on the structure, processing, and biological effects of bioactive glass. We explore critical questions regarding these elements from both a glass science and biological perspective. Should elements with little biological impact be included? Are alkali free bioactive glasses more promising for greater biological responses? Does this mixed alkali effect show increased degradation rates and should it be employed for optimized dissolution? Each of these questions along with others are evaluated comprehensively and discussed in the final section where guidance for compositional design is provided.

Amplification of blue emission of Tm3+ ions in Li2 O-HfO2 -SiO2 glass system by means of Au0 metallic particles.

Li2 O-HfO2 -SiO2 -Tm2 O3 :Au2 O3 glass samples (containing fixed content of Tm2 O3 and different concentration of Au2 O3 ) were prepared and characterized. Bearing of Au0 metallic particles (MPs) on improving blue emission of thulium ions (Tm3+ ) ions was explored. Optical absorption (OA) spectra exhibited multiple bands excited from 3 H6 of Tm3+ . Additionally, a broad peak in the wavelength range 500-600 nm due to surface plasmon resonance (SPR) of Au0 MPs was noticed in the spectra. Photoluminescence (PL) spectra (of thulium free glasses) indicated a peak in the visible range due to sp → d electronic transition of Au0 MPs. Luminescence spectra of Tm3+ and Au2 O3 co-doped glasses exhibited intense blue emission with substantial increase of intensity with increase of Au2 O3 content. Bearing of Au0 MPs on the reinforcement of blue emission of Tm3+ was discussed in detail with kinetic rate equations.

Evaluation of a combined school-based vision screening and mobile clinic program

Effective vision screening programs for children require follow-up with eye care providers, but studies demonstrate poor follow-up rates after failed screenings. Programs have attempted to address this issue by providing free examinations and glasses after failed screenings. This study presents data from a mobile clinic program that provides instrument-based vision screening, eye examinations, and free glasses directly to children at school. Between 2018 and 2021, a nonprofit organization provided in-school instrument-based screening and noncycloplegic examinations and refractions in elementary, middle, and high schools. Deidentified screening and clinic data were reviewed retrospectively. Information about each school regarding total student enrollment, enrollment based on race, and number of economically disadvantaged students was obtained from the Virginia Department of Education. In the 2019-2020 school year, 14,006 students from 58 schools were screened, and 4,238 (30.3%) were referred. The percentage of economically disadvantaged students was positively correlated to referral rate (R2 = 0.406). Between 2019 and 2020, the mobile clinic examined 3,095 students from the same 58 schools. Of these, 72.9% were prescribed glasses, and 16.3% were referred for a more comprehensive eye examination and treatment. Students were also diagnosed with cataracts, nystagmus, amblyopia, and strabismus. A combined screening program and mobile clinic traveling directly to schools can provide a pipeline for delivering eye care to vulnerable populations.

Luminescence efficiency of Sm3+ ions in hafnia added lithium silicate glass system-the impact of Au0 particles

In this study, Li2O-HfO2-SiO2-Sm2O3-Au2O3 glasses (doped with fixed concentration of Sm2O3 and varied contents of Au2O3) were synthesized and characterized. The role of Au0 particles on improvisation of red emission of Sm3+ ions was investigated. Optical absorption (OA) spectra of these glasses indicated a number of bands excited from 6H5/2 of Sm3+ ions. A broad band in the greenish-yellow spectral region due to surface plasmon resonance (SPR) of Au0 nanoparticles was also detected in these spectra. Photoluminescence (PL) spectra of (Sm free glasses) embedded with Au0 metallic particles (MPs) showed a wide band in the visible region ascribed to the transition of electrons from sp → d energy bands. Luminescence spectra of Sm3+ doped glasses revealed bright orange and red emission bands with substantial increased intensities with increased concentration of Au2O3. Effect of Au0 MPs on the red emission efficiency of Sm3+ ions was emphasized with kinetic rate equations.

Evaluation of a combined school-based vision screening and mobile clinic program

Uncorrected refractive error can lead to lowered academic performance. Many children depend on state-mandated school vision screening programs. Effective screening programs require follow-up with eye care providers, but studies demonstrate poor follow-up rates after failed screenings. Programs have attempted to mediate this issue by providing free examinations and glasses after failed screenings. This study presents data from a mobile clinic program that provides instrument-based vision screening, eye examinations, and free glasses directly to children at school.

Design and development of transparent glasses for radiation shielding applications

In this work, we present the fabrication of free lead glasses for radiation shielding applications by applying the melt-quenching method. The impact of Bi2O3 on the physical, mechanical and radiation shielding properties was investigated. The density of the glasses enhances from 3.833 to 4.283 g/cm3 due to the change of the Bi2O3 content. The Makishima and Mackenzie (MM) were used to calculate the Young's modulus (Y), bulk modulus (B), and longitudinal modulus (L). These parameters have been studies as a function of the mol% of Bi2O3 present in the samples. We evaluated the photon shielding competence of the prepared glasses and the calculations were carried out using Phy-X/PSD software between 0.015 and 15 MeV photon energies. From our results, it is demonstrated that the value of the effective atomic number (Zeff) in the low energy range was obviously enhanced with the growth of Bi2O3 contents. The linear attenuation coefficient (LAC) and Zeff results have similar trends, which enhance by adding Bi2O3 contents, and reduce with increasing the energy. The results indicated that the borate glasses with high concentration of Bi2O3 had higher radiation shielding properties than some commercial glasses. So, these prepared glasses may utilize in some applications such as radiation shielding.

The Immediate and Long-Term Impact of Free Glasses Clinics in the Los Angeles Area

While glasses are essential to proper vision for millions, more than 250,000 Los Angeles residents in need of glasses have failed to obtain them. To combat this issue, three free glasses clinics utilizing donated glasses were implemented at Los Angeles County + University of Southern California Medical Center (LAC+USC) from November 2021 to March 2022. The objective of this study was to determine the impact of free glasses on patients. Patients who received free glasses completed primary surveys, which determined the cause behind the inaccessibility to glasses and the difficulty of life without glasses. Secondary surveys were conducted 90 days (Group 1), 150 days (Group 2), or 210 days (Group 3) after the clinic to determine the longer-term impact of free glasses. Of the 320 respondents, cost prevented 68% of patients from obtaining glasses, and patients’ daily activities without glasses were significantly harder as a result (difficulty of 3.63 out of 5). Upon receiving glasses, patients reported an improvement of 4.51 out of 5 in vision. After the allotted period, 83% of Group 1, 69% of Group 2, and 65% of Group 3 reported continue glasses use. Across all three groups, patients reported an improvement of 4.72 out of 5 in improvement of daily activities. While donated glasses did not always match patients’ prescriptions exactly, they increased ease of basic tasks (reading, walking and driving) for patients. This model could be adopted in hospitals serving patient populations where cost is a barrier.
 

Enhanced defect emission of TiO2-doped transparent glass-ceramics embedding ZnO quantum dots with optimized heat-treatment schedule

This work mainly concentrated on the structural and optical properties of TiO 2 -doped transparent glass-ceramics embedding ZnO quantum dots (QDs). The results show that the concentration of non-bridging oxygen and related defects in the glasses increases and thermal parameters decreases by the introduction of TiO 2 . The surface defect concentration of ZnO QDs is greatly improved and the size of ZnO QDs is reduced by heat treatment below the T g and the introduction of TiO 2 . The green emission of glasses is mainly derived from oxygen vacancy defects and the yellow emission of glass-ceramics primarily originated from oxygen interstitial defects which show a tendency of enhancing first and then reducing with the increase of TiO 2 content. Among them, the optimal content for the strongest emission intensity of TiO 2 -doped glasses and glass-ceramics was determined to be 1.0 mol%, and the relative exceeds 10 times and 5.4 times that of TiO 2 -free glasses and glass-ceramics, respectively. The average size of ZnO QDs (∼2.1 nm) remarkably close to its exciton Bohr radius is successfully prepared by the optimal heat treatment condition (630 °C/8 h, below the T g ). The results show that these glass-ceramics embedding ZnO QDs are good yellow emission materials and have application prospects in WLEDs.

Effect of V2O5 on structural and elastic properties of alkali silicate SiO2–Na2O–NaF glasses

A series of V2O5–doped alkali silicate SiO2–Na2O–NaF glasses were prepared by the melt quenching technique. Amorphousness of the samples was characterized using powder X-Ray diffraction (XRD) analysis; and the structural role of V2O5, Na2O and NaF in the silicate network was explored using Fourier Transform Infrared (FTIR) spectroscopy. Elastic properties, determined by using ultrasonic technique, were correlated with the compositional and structural parameters as well as the excess molar volume. The substitution of SiO2 by Na2O and NaF in the base SiO2–Na2O–NaF glass resulted in the breaking of Si–O–Si linkages and creation of NBOs, whereas the addition of V2O5 resulted in formation of VO5 structural units and weak V–O–V and Si–O–V linkages. Makishima-Mackenzie's theory is valid for pure SiO2 and V2O5–free glasses. The discrepancy between theoretical and observed elastic moduli and micro-hardness of V2O5–doped glasses was discussed in details.

Providing vouchers and value information for already free eye exams increases uptake among a low-income minority population: A randomized trial.

We study whether vouchers without and with value information encourage attendance of already free follow-up appointments among low-income minority individuals referred for evaluation of possible eye disease. Between May 2017 and September 2018, 821 individuals referred from 114 screening events across Baltimore City were offered (1) standard referral for a free follow-up appointment and prescription glasses, (2) a paper voucher described as redeemable for free follow-up and prescription glasses, or (3) an otherwise identical paper voucher which also indicated the monetary value of the appointment ($250). Under all three conditions, all referred individuals received the same patient education, counseling, and appointment reminders. We find that vouchers without and with value information increase follow-up by 12.5 and 20.3 percentage points, respectively, corresponding to a 36% and 58% increase compared to the standard referral for free follow-up (i.e., without a voucher). We conclude that using vouchers is a promising, low-cost approach to increase uptake of already free health services, particularly when the vouchers also provide value information.

Corrosion behavior of new rare-earth free Cu-based metallic glasses in NaCl solution of different molarity

The present study reports the glass-forming ability, density change on crystallization and corrosion behavior of newly developed rare-earth free Cu-based metallic glasses (CBMGs). The critical casting thickness of these new CBMGs increased from 15 mm at 8 at.% Hf to 22 mm at 12 at.% Hf, reaching a maximum value of 28.5 mm at 13.5 at.% Hf. It dropped to 24 mm and 15 mm thereafter, for 15 and 20 at.% Hf, respectively. The alloys showed a monotonic increase in density going from 8 at.% Hf to 20 at.% Hf, with the density of amorphous samples increasing from 7.83 g/cm3 to 8.84 g/cm3 and crystallized samples increasing from 7.92 g/cm3 to 8.91 g/cm3. Potentiodynamic polarization tests carried out in 0.1, 0.2 and 0.5 M NaCl solution at 25 °C showed a direct correlation between corrosion resistance and Hf content in the order: 8 at.% < 13.5 at.% < 20 at.% Hf. Increase in NaCl concentration also had a significant impact on the corrosion intensity due to the chaotropic effect. Scanning electron microscopy of corroded sample surfaces showed formation and eventual merging of individual micro cracks resulting in a mud-cracking pattern. Energy-dispersive X-ray spectroscopy maps of pitted regions revealed reduction in Zr and Al concentration with increase in Hf and Cu percentage for all compositions. An increase in the O concentration along with the appearance of new peaks in the X-ray photoelectron spectroscopy results, measured post corrosion, confirmed the formation of metal oxides and oxyhydroxides in the passive layer.

A seven-year analysis of the role and impact of a free community eye clinic

BackgroundThe Indiana University Student Outreach Clinic (IUSOC) Eye Clinic is a monthly student-run eye clinic that provides free visual screening to the Near East Side community of Indianapolis, IN, USA. Screening includes assessments of visual acuity, intraocular pressure, peripheral visual fields, refraction, and non-mydriatic fundus photography.MethodsThis is a retrospective chart review of 875 patients seen at the IUSOC Eye Clinic from October 2013 to February 2020. Data on demographics, insurance coverage, ocular history, physical examination, suspected diagnosis, referral status, and glasses provided were collected and analyzed.Results875 patients were seen at the IUSOC Eye Clinic from October 2013 to February 2020. 39.2% of the patients seen at the clinic reported being uninsured. 61.4% of patients were found to have visual acuity of 20/40 or worse, while 51.3% of patients were found to have a near visual acuity of 20/40 or worse. 20.3% of patients were referred to the local county hospital for further evaluation by an ophthalmologist, 14.4% of patients received free glasses prescriptions, and 27.9% of patients received free reading glasses. Common reasons for referral for further ophthalmology evaluation included glaucoma, decreased visual acuity, and diabetic retinopathy. An estimated value of services provided over the seven years of the clinic was 1271 relative value units.ConclusionThe IUSOC Eye Clinic fills an important role in advancing ocular health and preventing irreversible blindness in an underserved Indianapolis community. Additionally, the clinic demonstrates an educational model for involving medical student volunteers.

Review on the synthesis and doping strategies in enhancing the Na ion conductivity of Na3Zr2Si2PO12 (NASICON) based solid electrolytes

Na3Zr2Si2PO12 based solid electrolytes are well known materials because of their potential applications in different solid-state ionic devices. This review article presents the structural and transport results of Na3Zr2Si2PO12 based solid electrolytes prepared by different dry and wet methods known in the literature. The advantages and limitations of different synthesis methodologies to achieve the phase pure, high dense Na3Zr2Si2PO12 based materials are presented. The influence of the valence state, ionic radii of aliovalent dopants on the ionic conductivity of Na3Zr2Si2PO12 have been discussed with respect to their crystal structure. The role of sintering temperature, sintering durations, and sintering agents on the phase purity, density, and conductivity of Na3Zr2Si2PO12 based solid electrolytes are reviewed. Besides Na3Zr2Si2PO12 based polycrystalline solid electrolytes, the transport results of Na3Zr2Si2PO12 based grain boundary free glasses and flexible polymer electrolytes are also discussed. The applications of Na3Zr2Si2PO12 based solid electrolytes in different electrochemical devices are outlined.

TAP free energy, spin glasses and variational inference

We consider the Sherrington–Kirkpatrick model of spin glasses with ferromagnetically biased couplings. For a specific choice of the couplings mean, the resulting Gibbs measure is equivalent to the Bayesian posterior for a high-dimensional estimation problem known as “${\mathbb{Z}}_{2}$ synchronization.” Statistical physics suggests to compute the expectation with respect to this Gibbs measure (the posterior mean in the synchronization problem), by minimizing the so-called Thouless–Anderson–Palmer (TAP) free energy, instead of the mean field (MF) free energy. We prove that this identification is correct, provided the ferromagnetic bias is larger than a constant (i.e., the noise level is small enough in synchronization). Namely, we prove that the scaled $\ell _{2}$ distance between any low energy local minimizers of the TAP free energy and the mean of the Gibbs measure vanishes in the large size limit. Our proof technique is based on upper bounding the expected number of critical points of the TAP free energy using the Kac–Rice formula.

Providing Vouchers and Value Information for Already Free Eye Exams Increases Uptake Among a Low-Income Minority Population: A Randomized Trial

We study whether vouchers with and without value information encourage completion of already free follow-up appointments in a low-income minority population in Baltimore City referred for possible eye disease. Between May 2017 and September 2018, 821 individuals referred for free follow-up from 114 screening events received 1) standard referral, 2) a voucher redeemable for free follow-up and prescription glasses, or 3) a voucher including a statement of monetary value ($250). All referred individuals received patient education, counseling, and appointment reminders. We find that vouchers without and with value information increase follow-up appointments by 12.5 and 20.3 percentage points, respectively, corresponding to a 36%-58% increase compared to the standard referral with no voucher. We conclude that reframing free targeted health service offers by providing vouchers with value information is a promising, low-cost tool to increase uptake.

Impact of spectacles wear on uncorrected visual acuity among urban migrant primary school children in China: a cluster-randomised clinical trial

ObjectiveTo estimate the effect of providing free spectacles on uncorrected visual acuity (VA) among urban migrant Chinese school children.DesignExploratory analysis from a parallel cluster-randomised clinical trial.MethodsAfter baseline survey and VA...

Combination of broad emission bands of Ti3+,4+/ Eu2+,3+ co-doped OH− free low silica calcium aluminosilicate glasses as emitting phosphors for white lighting devices

In this report, Ti3+, 4+/Eu2+, 3+ co-doped OH− free low silica calcium aluminosilicate glasses (LSCAS) were synthesized and their optical properties investigated aiming applications as phosphors for white light generation. This research explores the possibility of combining the broad emission bands in the visible of these glasses co-doped with Ti3+,4+/Eu2+ ions with those in the red emitted by Eu3+, in addition to the high luminescence quantum yield they present. The excitation and emission results show that exciting the samples at 300 nm, a broad emission band is generated, embracing very well the visible region. The emission spectra were analyzed by (x-y) CIE-1931 chromaticity diagram and the color rendering index (CRI) presented Ra values up to 80, with the correlate color temperature (CCT) varying from 4995 to 6609 K. The luminescence quantum yield determined by Thermal Lens Spectroscopy showed values of 38 and 42% for the samples with (in wt%) 0.1Eu2O3-2.0TiO2 and 0.5Eu2O3-2.0TiO2, respectively. Finally, the energy transfer processes between these luminescent ions were discussed, highlighting the potential of the Eu–Ti LSCAS glasses as candidates for the development of devices for white light generation.

Abnormal relaxation kinetics in D-mannitol glass confined by nanoporous alumina

The relaxation kinetics and phase transformations of the confined D-mannitol (DM) in nanoporous alumina are studied in-situ using a high-precision nano-calorimeter. We find that the crystallization behavior can be suppressed when it is confined in nanopores smaller than 50 nm. The confined DM glass has a much smaller fragility (~76) than free DM glass (~125), confirming the enhanced glass-forming ability. It is intriguing that during isothermal annealing both the confined and free DM glasses relaxation kinetics experience two relaxation stages that have distinct activation energies. The relaxation activation energy of the confined glass is about 25%-29% smaller than the free glass, which is attributed to the reduced dimensionality. The abnormal kinetics observed in the confined DM glass open a new avenue for preparing stable glasses.