Surface Disorder Research Articles

Localization and delocationzation of surface disordering in surface mediated melting

Melting of solids usually starts with a thin liquid layer forming on the surface at temperatures below their bulk melting point. While the liquid phase formation in the so-called premelting is understood to be governed by the interface energies among the coexisting solid, liquid, and vapor phases, the influence of the underlying crystal structures on its kinetics, and atomistic mechanisms are unknown, and consequently, ignored in the theory of melting. Here we report the first observation of a strong influence of the underlying crystal structure on melting kinetics with the resulting localization and delocalization behavior of the surface disordering and the liquid layers. With increasing temperature, the surface disordering remains in the localized state with a constant thickness in fcc crystals, whereas it becomes delocalized by growing steadily into the bulk in bcc crystals. In both cases, the surface melting is found to occur with highly correlated atomic motion in the form of extended atomic chains and loops that emit from the disordered surface and transmit to the bulk. This newly discovered mechanism in surface melting is behind the surface melting kinetics: The close packed fcc crystal can effectively impede the correlated atomic motion and limit the surface disordering to only the localized region on surface, while the more openly packed bcc crystal allows for its proliferation by tunneling from the surface into the bulk of the crystals. These findings provide valuable insights for future development of new theories of crystal melting.

Modification of SiO2, ZnO, Fe2O3 and TiN Films by Electronic Excitation under High Energy Ion Impact

It has been known that the modification of non-metallic solid materials (oxides, nitrides, etc.), e.g., the formation of tracks, sputtering representing atomic displacement near the surface and lattice disordering are induced by electronic excitation under high-energy ion impact. We have investigated lattice disordering by the X-ray diffraction (XRD) of SiO2, ZnO, Fe2O3 and TiN films and have also measured the sputtering yields of TiN for a comparison of lattice disordering with sputtering. We find that both the degradation of the XRD intensity per unit ion fluence and the sputtering yields follow the power-law of the electronic stopping power and that these exponents are larger than unity. The exponents for the XRD degradation and sputtering are found to be comparable. These results imply that similar mechanisms are responsible for the lattice disordering and electronic sputtering. A mechanism of electron–lattice coupling, i.e., the energy transfer from the electronic system into the lattice, is discussed based on a crude estimation of atomic displacement due to Coulomb repulsion during the short neutralization time (~fs) in the ionized region. The bandgap scheme or exciton model is examined.

Association of tear matrix metalloproteinase 9 immunoassay with signs and symptoms of dry eye disease: A cross-sectional study using qualitative, semiquantitative, and quantitative strategies

PurposeThis study aimed to analyze the association of tear matrix metalloproteinase 9 (MMP-9) immunoassay with the severity of dry eye (DE) signs and symptoms through qualitative, semiquantitative, and quantitative evaluations of immunoassay band.Materials and methodsThis cross-sectional study enrolled 320 eyes of 320 patients. The clinical signs of DE were assessed using the Ocular Surface Disorder Index (OSDI) score, visual analogue scale (VAS), tear breakup time (tBUT), tear volume evaluation by tear meniscometry, and staining scores of the cornea and conjunctiva by the Oxford grading scheme. The tear MMP-9 immunoassay results were interpreted using qualitative (positive or negative), semi-quantitative (reagent band density on a four-point scale: 0 = negative; 1 = weakly positive; 2 = moderately positive; 3 = strongly positive), and quantitative (ratio of reagent band density to control band density) indicators.ResultsPositive MMP-9 immunoassay results were significantly related to shorter tBUT, tBUT ≤3 seconds, higher corneal staining score, corneal staining score ≥2, and conjunctival staining score ≥2. The semi-quantitative results of the MMP-9 immunoassay were positively correlated with higher corneal staining score (r = 0.122, p = 0.029) and negatively correlated with tBUT (r = -0.125, p = 0.025). However, in the quantitative analysis, none of the DE signs or symptoms were correlated to the band density of the MMP-9 immunoassay.ConclusionsThe positive MMP-9 immunoassay results were related to the severity of ocular signs of DE. However, using quantitative measures of the MMP-9 immunoassay to assess the clinical severity of DE requires further investigation.

Control of the Surface Disorder by Ion-Exchange to Achieve High Open-Circuit Voltage in HC(NH2 )2 PbI3 Perovskite Solar Cell.

The ionic nature of organic trihalide perovskite leads to structural irregularity and energy disorder at the perovskite surface, which seriously affects the photovoltaic performance of perovskite solar cells. Here, the origin of the perovskite surface disorder is analyzed, and a facial ion-exchange strategy is designed to regulate the surface chemical environment. By the reconstruction of terminal irregular Pb-I bonds and random cations, the repaired surface is characteristic of the reduced band tail states, consequent to the suppression of the uplift of quasi-Fermi level splitting and photocarrier scattering. The optimized device gets a high open-circuit voltage and operational stability. These findings fully elaborate the underlying mechanism concerning perovskite surface problem, giving guidance on tailoring the energy disorder.

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism.

The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe3O4 nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10−4 S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.

Prevalence of Ocular Surface Disorder and Dry Eye in Patients with Glaucoma using Topical Antiglaucoma Medications

Background: The main aim of the study is to establish the prevalence of ocular surface disorders in glaucoma patients treated with topical antiglaucoma medications. Methods: Investigation of 50 eyes of 25 patients has been performed using two or more antiglaucoma medications for six months, and compared with 50 eyes of 25 normal subjects without any ocular problem. After one year each patient was evaluated by Schirmer’s (SCH) test-I Tear break-up time (TBUT), Corneal staining score. Results: The mean values in the glaucoma cases and control groups respectively were as follows: Schirmer’s test-1 (7.63 ± 2.64mm / 12.86 ± 1.93mm; p= 0.001), Tear breakup time (9.44 2 ±.76 sec / 11.8 ± 1.88 sec; p=0.001), Corneal staining score (5.7 ± 2.33 /1.1 ± 0.58; p=0.001). Conclusion: Patients on antiglaucoma therapy have a greater prevalence of ocular surface disease and dry eye. The causative factors were medications with preservatives and longer treatment duration. Keywords: Antiglaucoma medication, dry eye, ocular surface diseases (OSD), Schirmer’s (SCH) test, Tear breakup time, Corneal staining score.

Finite-size effects on the evolution of magnetic correlations and magnetocaloric properties of Pr0.4Bi0.2Sr0.4MnO3

The effect of particle size reduction on the magnetic correlations of Pr0.4Bi0.2Sr0.4MnO3 nanoparticles prepared by top-down approach has been studied in detail. It was observed that as the milling time increases from 0 to 240 min, particle size decreases from 160 to 12 nm. Correspondingly it was observed that the ferromagnetic transition temperature (TC) drops (264 to 213 K) and saturation magnetization (MS) decreases (2.12–0.41 {upmu }_{mathrm{B}}/mathrm{f}.mathrm{u}.) while coercivity (HC) shows a monotonous increase (0.18–1.5 kOe) as the particle size decreases due to increase in milling. The magnetic entropy change (ΔS) also decreases (2.41–0.24 J/kg-K) as particle size decreases indicating a strong correlation between magnetism and particle size. The metamagnetic M–H response of the bulk sample, which signifies the magnetic phase coexistence, is suppressed, and the nature of magnetic interactions demonstrates a transition from long range to short range. The observed characteristics emphasizes that with particle size reduction there is an increase in the surface disorder which can be explained by considering the core–shell model for the nanoparticles.Graphic abstract

Water Soaking Disorder in Strawberries: Triggers, Factors, and Mechanisms.

Water soaking is an important surface disorder of strawberries that limits unprotected field production. The objective was to identify the mechanism(s) of water soaking. Symptomatic fruit show pale, deliquescent patches of skin. This damage extends into the flesh. Numerous cuticular microcracks occurred in water-soaked areas. Water soaking occurred only if the skin was exposed to liquid water. Water soaking was more rapid when the cuticle had been abraded. Water soaking, anthocyanin leakage, and water uptake all increased with incubation time. There was a lag phase for water soaking and anthocyanin leakage, but not for water uptake. Susceptibility to water soaking increased with fruit ripening and mass. Incubation in isotonic PEG 6000 increased cuticular microcracking but decreased water soaking and water uptake. Incubation in hypotonic fruit juice (natural and artificial) increased water soaking incidence and severity but reduced water uptake. Incubation in dilute citric and malic acids increased plasma membrane permeability as indexed by anthocyanin leakage and increased water soaking. Thus, water soaking involves cuticular microcracking, localized water uptake, bursting of cells, and the release of organic acids into the apoplast. The damage propagates from cell to cell.

Non-Linear Thermoelectric Devices with Surface-Disordered Nanowires

We reviewed some recent ideas to improve the efficiency and power output of thermoelectric nano-devices. We focused on two essentially independent aspects: (i) increasing the charge current by taking advantage of an interplay between the material and the thermodynamic parameters, which is only available in the non-linear regime; and (ii) decreasing the heat current by using nanowires with surface disorder, which helps excite localized phonons at random positions that can strongly scatter the propagating phonons carrying the thermal current.

Surface disorder engineering in ZnCdS for cocatalyst free visible light driven hydrogen production

Surface disorder engineering in ZnCdS for cocatalyst free visible light driven hydrogen production

Tear film measurements in four different ethnic groups: Malay, Chinese, Indian and Nigerian

AIM: To compare the non-invasive tear film break-up time (NIBUT), tear break up time (TBUT), basal tear secretion (BTS) and blink rate in four ethnic groups: Malay, Chinese, Indian and Nigerian. METHODS: Totally 120 healthy (61 males and 59 females) subjects (without dry eye symptoms and ocular surface disorder) with the age 20 to 39 years were recruited; 30 were Malays, 30 were Chinese, 31 were Indians and 29 were Nigerians. Based on McMonnies questionnaire and clinical examination, normal subjects were selected. NIBUT, TBUT, BTS were assessed in only one eye (right) of each subject and blink rate was also assessed. RESULTS: There was significant difference in the NIBUT, TBUT, BTS and blink rate among 4 different ethnic groups (P=0.018, 0.001, 0.011, and 0.004 respectively). No statistically significant difference of NIBUT, TBUT, BTS and blink rate was found between the genders among different ethnic groups. Indian had higher median for NIBUT (10±6s), TBUT (7±5s) and BTS (20±20 mm) than other races. Chinese had lower median for NIBUT (7.5±4s) and TBUT (4±2s) while Malay had for BTS (9.5±16 mm) among the groups. There was no significant correlation of blink rate with NIBUT (r=-0.119, P=0.195), TBUT (r=-0.086, P=0.352), and BTS (r=-0.123, P=0.180) respectively. CONCLUSION: The tear-film measurement values are variability in four ethnic groups.

Association among pterygium, cataracts, and cumulative ocular ultraviolet exposure: A cross-sectional study in Han people in China and Taiwan.

PurposePterygium is an ocular surface disorder mainly caused by ultraviolet (UV) light exposure. This study explored the relationships between six cataract types with pterygium and UV exposure.MethodsWe have previously studied cataracts in residents of three regions in China and Taiwan with different UV intensities. From that study, we identified 1,547 subjects with information on the presence or absence of pterygium. Pterygium severity was graded by corneal progress rate. Cataracts were graded by classification systems as three main types (cortical, nuclear, posterior subcapsular) and three subtypes (retrodots, waterclefts, fiber folds) with high prevalence in middle-aged and elderly people. We calculated the cumulative ocular UV exposure (COUV) based on subject data and National Aeronautics and Space Administration data on UV intensities and used logistic regression to calculate odds ratios for the associations of COUV, cataract, and pterygium.ResultsWe found an overall pterygium prevalence of 23.3%, with significant variation among the three regions. Four cataract types (cortical, nuclear, posterior subcapsular, and retrodots) were significantly associated with the presence of pterygium.ConclusionsThere was a significant association between COUV and pterygium, indicating that COUV is associated with the risk of pterygium development and that pterygium is useful as an index of UV exposure. Furthermore, the type of cataract in eyes with pterygium may indicate the level of UV exposure.

(Allen J. Bard Award) Electrochemistry of Platinum: New Views on an Old Problem

Platinum is the most used electrocatalyst in electrochemical energy conversion devices such as fuel cells and electrolysers. In this talk I will highlight the recent work of my group on understanding the surface chemistry of platinum in an aqueous electrolyte, by combining single-crystal electrochemistry, density functional theory calculations, ultra-high-vacuum modeling, in situ spectroscopy and in situ electrochemical scanning tunneling microscopy. I will challenge some existing explanations and interpretations of platinum electrochemistry, and show the sometimes surprising surface disordering of platinum that happens at both positive (anodic) and negative (cathodic) potentials.

XANES reflects coordination change and underlying surface disorder of zinc adsorbed to silica

Zinc K-edge X-ray absorption near-edge structure (XANES) spectroscopy of Zn adsorbed to silica and Zn-bearing minerals, salts and solutions was conducted to explore how XANES spectra reflect coordination environment and disorder in the surface to which a metal ion is sorbed. Specifically, XANES spectra for five distinct Zn adsorption complexes (Znads) on quartz and amorphous silica [SiO2(am)] are presented from the Zn-water-silica surface system: outer-sphere octahedral Znads on quartz, inner-sphere octahedral Znads on quartz, inner-sphere tetrahedral Znads on quartz, inner-sphere octahedral Znads on SiO2(am) and inner-sphere tetrahedral Znads on SiO2(am). XANES spectral analysis of these complexes on quartz versus SiO2(am) reveals that normalized peak absorbance and K-edge energy position generally decrease with increasing surface disorder and decreasing Zn-O coordination. On quartz, the absorption-edge energy of Znads ranges from 9663.0 to 9664.1 eV for samples dominated by tetrahedrally versus octahedrally coordinated species, respectively. On SiO2(am), the absorption-edge energy of Znads ranges from 9662.3 to9663.4 eV for samples dominated by tetrahedrally versus octahedrally coordinated species, respectively. On both silica substrates, octahedral Znads presents a single K-edge peak feature, whereas tetrahedral Znads presents two absorbance features. The energy space between the two absorbance peak features of the XANES K-edge of tetrahedral Znads is 2.4 eV for Zn on quartz and 3.2 eV for Zn on SiO2(am). Linear combination fitting of samples with a mixture of Znads complex types demonstrates that the XANES spectra of octahedral and tetrahedral Znads on silica are distinct enough for quantitative identification. These results suggest caution when deciphering Zn speciation in natural samples via linear combination approaches using a single Znads standard to represent sorption on a particular mineral surface. Correlation between XANES spectral features and prior extended X-ray absorption fine structure (EXAFS) derived coordination environments for these Znads on silica samples provides insight into Zn speciation in natural systems with XANES compatible Zn concentrations too low for EXAFS analysis.

Tuning magnetic and magnetocaloric properties of Pr0.6Sr0.4MnO3 through size modifications

Particle size as an effective tool for controlling the magnetic and magnetocaloric properties of Pr0.6Sr0.4MnO3 samples has been studied. In the present work, a direct influence of particle size on the magnitude of magnetization and magnetic transition temperature, TC, can be seen. The TC drops from 309 to 242 K, while the saturation magnetization (MS) decreases from 3.6 to 0.5 μB/f.u. as the particle changes from 120 to 9 nm. Concurrently, coercivity (HC) exhibits a drastic rise emphasizing the enhanced surface disorder in the nanoparticles. Another interesting observation is in the magnetic entropy change, ΔS, which though decreases in magnitude from 5.51 to 3.90 J/Kg-K as particle size decreases from 120 to 30 nm, but the temperature range of ΔS (i.e., relative cooling power, RCP) increases from 184.33 to 228.85 J/Kg. Such interplay between magnitude and wider temperature range of ΔS, which can be fine-tuned by particle size, provides an interesting tool for using surface spin disorder, as a control mechanism in modifying physical properties.

Effects on the Ocular Surface from Reading on Different Smartphone Screens: A Prospective Randomized Controlled Study.

The purpose of this study was to investigate the influence of smartphone reading on the ocular surface and to compare the various effects of different screens and light conditions on the ocular surface. One hundred nineteen volunteers were randomly divided into: light + organic light‐emitting diode (OLED), light + electronic ink (eINK), dark + OLED, and dark + eINK. Ocular surface examinations, including noninvasive break‐up time (NIBUT), noninvasive keratograph tear meniscus height (NIKTMH), ocular redness, fluorescein break‐up time (FBUT), corneal fluorescein staining, meibomian gland assessment, Schirmer I Test, and blinking frequency, were performed before and after a reading task. Symptoms were evaluated using the Ocular Surface Disease Index (OSDI) and Computer Vision Syndrome Questionnaire (CVS‐Q). NIBUT and FBUT were decreased statistically significantly after participants read on an OLED screen for 2 hours compared with the baseline in light and dark environments, whereas no statistically significant decrease was observed on an eINK screen. NIKTMH was statistically significantly decreased after reading on an OLED screen in light and dark settings, and the eINK screen had a lesser effect on NIKTMH. An obvious increase in the ocular redness, OSDI and CVS‐Q scores was observed after reading on an OLED screen, whereas the eINK screen had a lesser effect on these indicators. Blink rate increased gradually in OLED subgroups during the reading task, whereas no statistically significant difference was observed in the eINK subgroups. Our research suggested that reading on an OLED screen can cause ocular surface disorder and obvious subjective discomfort, whereas reading on an eINK screen can minimize ocular surface disorder in both dark and light environments.

Encounters and medication use for ocular surface disorders among patients treated with dupilumab: A cohort study

BackgroundAlthough dupilumab has been associated with the development of conjunctivitis, little is known about other ocular surface disorders such as dry eye and how these side effects are managed.ObjectiveTo evaluate the incidence and management of ocular surface disorders, including dry eye and conjunctivitis, among patients treated with dupilumab.MethodsUsing US claims data, we evaluated the incidence of encounters for ocular surface disorders among patients treated with dupilumab. Secondary outcomes included ophthalmic medication use. A propensity score matched, active-comparator, new-user cohort design was used to compare the incidence of ocular surface disorders between those starting dupilumab versus methotrexate.ResultsAmong those with a history of atopic dermatitis, encounters for ocular surface disorders were more common in the 6 months after starting dupilumab than in the 6 months prior (11.7% versus 8.7%, P < .001); 59.7% of those with a new ocular surface disorder diagnosis filled a prescription for an ophthalmic medication. The incidence of ocular surface disorders was higher among those treated with dupilumab than that in those treated with methotrexate (odds ratio 1.64; 95% confidence interval 1.17-2.30).LimitationsObservational design.ConclusionsDupilumab use for atopic dermatitis was associated with an increased risk of ocular surface disorders. Most patients who developed an ocular surface disorder received a prescription for an ophthalmic medication.

Clinical profile, ocular morbidity and visual loss in psoriasis: Experience in a multispeciality hospital

To analyse various ocular abnormalities and visual morbidity in patients with psoriasis and to detect ocular complications following psoriasis treatment. A prospective observational study was conducted among 120 psoriasis patients. All patients underwent slit lamp examination, indirect ophthalmoscopy, Schirmer’s test, Tear breakup time and Rose Bengal staining and ancillary investigations when required. Among 120 patients, the prevalence of ocular manifestation was 57%, of whom 22% were symptomatic. Ocular features were most common in scalp psoriasis and pustular psoriasis. Disease duration was not found to have any impact on the severity of ocular manifestation. The most common ophthalmic feature was ocular surface disorder (46%), followed by cataract (30%), meibomitis (17%) and blepharitis in 16%. Correlation between tests was calculated using kappa coefficient and statistical significance was found in the pattern of conjunctival staining with a p value of 0.02. Out of 9 patients with psoriatic arthritis, 3% showed signs of chronic uveitis. Steroid induced glaucoma was seen in 27% and ocular hypertension in 21%. Corticosteroid used in systemic management frequently caused visual morbidity. Ocular signs and symptoms in psoriasis may be subtle and overlooked, hence complete ophthalmic examination is recommended for early detection of ocular abnormalities. Early treatment for dry eye is important to prevent irreversible ocular surface changes. Regular monitoring prevents steroid induced cataract and steroid induced glaucoma. As multisystem involvement is seen in psoriasis, a multidisciplinary approach reduces ocular morbidity.

X-ray photoelectron spectroscopy study on effects of ultra-high-pressure annealing on surface of Mg-ion-implanted GaN

The effects of ultra-high-pressure annealing (UHPA) on the surface of Mg-ion-implanted GaN were investigated by X-ray photoelectron spectroscopy (XPS). After Mg ion implantation or Mg–N co-implantation, GaN was annealed at 1400 °C for 5 min under a nitrogen pressure of 1 GPa. No deterioration of the surface stoichiometry occurred after UHPA despite the extremely high annealing temperature. The angle-resolved XPS with calibration showed that the surface Fermi level was pinned at 0.5 eV from the conduction band edge after dehydrogenation subsequent to UHPA. However, the absence of pinning at the charge neutrality level showed that surface disorder was absent after UHPA. The surface photovoltaic effect as evidence of the achievement of p-type conduction even in the near-surface region was more remarkable for Mg–N-ion-implanted samples after dehydrogenation subsequent to UHPA. There is the possibility that the density of N-vacancy-related defects was reduced more by Mg–N co-implantation.

Micro-scale hollow nanosphere as highly efficient ORR electrocatalyst derived from the self-assembly of triblock copolymer (L64)

The micro-scale hollow nanosphere with rich defect was synthesized by pyrolyzing the transparent film composed of the co-polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymer (L64) and Zn (OH)2, which formed in the mixture solution of ethanol and n-hexane. The content increase of n-hexane in the mixture solution would decrease the formation rate during self-assembly of block copolymers, which was beneficial for forming the uniformly distributed nano-carbon spheres obtained. As the ratio of ethanol and n-hexane is 1:1, the as-synthesized product (noted as C (1:1)) has an even pore size (7 nm) and hollow nanosphere morphology, which possessed the highest specific surface area (753 m2 g−1) and disorder (ID/IG, 3.4). In terms of ORR performance, C (1:1) exhibits not only superior cycle stability and methanol-tolerance than 20% Pt/C but also comparable half-wave potential (0.76 V vs. RHE) to that of commercial 20% Pt/C (0.80 V) in 0.1 M KOH solution.