Non-invasive optical method for real-time assessment of intracorneal riboflavin concentration and efficacy of corneal cross-linking.

Keratoconus is the primary cause of corneal transplantation in young adults worldwide. Riboflavin/UV-A corneal cross-linking may effectively halt the progression of keratoconus if an adequate amount of riboflavin enriches the corneal stroma and is photo-oxidated by UV-A light for generating additional cross-linking bonds between stromal proteins and strengthening the biomechanics of the weakened cornea. Here we reported an UV-A theranostic prototype device for performing corneal cross-linking with the ability to assess corneal intrastromal concentration of riboflavin and to estimate treatment efficacy in real time. Seventeen human donor corneas were treated according to the conventional riboflavin/UV-A corneal cross-linking protocol. Ten of these tissues were probed with atomic force microscopy in order to correlate the intrastromal riboflavin concentration recorded during treatment with the increase in elastic modulus of the anterior corneal stroma. The intrastromal riboflavin concentration and its consumption during UV-A irradiation of the cornea were highly significantly correlated (R = 0.79; P = .03) with the treatment-induced stromal stiffening effect. The present study showed an ophthalmic device that provided an innovative, non-invasive, real-time monitoring solution for estimating corneal cross-linking treatment efficacy on a personalized basis.

Assessment of stromal riboflavin concentration-depth profile in nanotechnology-based transepithelial corneal crosslinking.

PURPOSE: To determine the intrastromal concentration of riboflavin in nanotechnology-based transepithelial corneal crosslinking. SETTING: Consiglio Nazionale delle Ricerche, Messina, Italy. DESIGN: Experimental study. METHODS: Six human donor sclerocorneal tissues were used to evaluate penetration of nanotechnology-based riboflavin 0.1% solution in the stroma through the intact epithelium. Three additional tissues were deepithelialized and soaked with dextran 20.0%-enriched riboflavin 0.1% solution for 30 minutes. After corneal soaking with riboflavin, all tissues were irradiated using a 10 mW/cm2 device for 9 minutes. Two-photon emission fluorescence (TPEF) axial scanning measurements were collected in all specimens before treatment and immediately after corneal soaking with riboflavin and ultraviolet-A (UVA) irradiation of the cornea. The absorbance spectra of each tissue were collected at the same time intervals. The TPEF signals and absorbance spectra were used to calculate the concentration-depth profile of riboflavin in the corneal stroma during treatments. RESULTS: The mean stromal riboflavin concentration was 0.008% ± 0.003% (SD) and 0.017% ± 0.001% after transepithelial soaking with the nanotechnology-based solution and standard soaking, respectively (P = .001). After UVA irradiation of the cornea, the mean consumption of riboflavin was 52% ± 13% and 67% ± 2% in the study group and control group, respectively (P < .01). CONCLUSIONS: The nanotechnology-based platform was effective in enriching the anterior stroma with riboflavin through the intact epithelium, although the riboflavin concentration-depth profile rapidly decreased across the mid and posterior stroma. The treatment-induced stiffening effect on the corneal stroma was not assessed in this study.

Double-Wall Nanotubes and Graphene Nanoplatelets for Hybrid Conductive Adhesives with Enhanced Thermal and Electrical Conductivity.

Improving the electrical and thermal properties of conductive adhesives is essential for the fabrication of compact microelectronic and optoelectronic power devices. Here we report on the addition of a commercially available conductive resin with double-wall carbon nanotubes and graphene nanoplatelets that yields simultaneously improved thermal and electrical conductivity. Using isopropanol as a common solvent for the debundling of nanotubes, exfoliation of graphene, and dispersion of the carbon nanostructures in the epoxy resin, we obtain a nanostructured conducting adhesive with thermal conductivity of ∼12 W/mK and resistivity down to 30 µΩ cm at very small loadings (1% w/w for nanotubes and 0.01% w/w for graphene). The low filler content allows one to keep almost unchanged the glass-transition temperature, the viscosity, and the curing parameters. Die shear measurements show that the nanostructured resins fulfill the MIL-STD-883 requirements when bonding gold-metalized SMD components, even after repeated thermal cycling. The same procedure has been validated on a high-conductivity resin characterized by a higher viscosity, on which we have doubled the thermal conductivity and quadrupled the electrical conductivity. Graphene yields better performances with respect to nanotubes in terms of conductivity and filler quantity needed to improve the resin. We have finally applied the nanostructured resins to bond GaN-based high-electron-mobility transistors in power-amplifier circuits. We observe a decrease of the GaN peak and average temperatures of, respectively, ∼30 °C and ∼10 °C, with respect to the pristine resin. The obtained results are important for the fabrication of advanced packaging materials in power electronic and microwave applications and fit the technological roadmap for CNTs, graphene, and hybrid systems.

On the ergodicity of supercooled molecular glass-forming liquids at the dynamical arrest: the o-terphenyl case.

The dynamics of supercooled ortho-terphenyl has been studied using photon-correlation spectroscopy (PCS) in the depolarized scattering geometry. The obtained relaxation curves are analyzed according to the mode-coupling theory (MCT) for supercooled liquids. The main results are: i) the observation of the secondary Johari-Goldstein relaxation (ß) that has its onset just at the dynamical crossover temperature TB (TM > TB > Tg); ii) the confirmation, of the suggestion of a recent statistical mechanical study, that such a molecular system remains ergodic also below the calorimetric glass-transition temperature Tg. Our experimental data give evidence that the time scales of the primary (α) and this secondary relaxations are correlated. Finally a comparison with recent PCS experiments in a colloidal system confirms the primary role of the dynamical crossover in the physics of the dynamical arrest.

Modulated heterodyne light scattering set-up for measuring long relaxation time at small and wide angle.

We present a simple, compact, and versatile experimental setup working in the heterodyne detection mode with modulation of the reference beam. The system is implemented with a collection optics based on a unimodal optical fiber coupler. This choice allows the heterodyne to be used in a wide range of scattering angles, even for very small ones, without losing the optical beating. The apparatus can be successfully used to study translational diffusive dynamics of dispersed particles at scattering angles smaller than 5° and it is suitable for exploring slow relaxation processes in sub-Hertz frequency domain, for example, in glass-forming systems. It is also possible to measure the electrophoretic mobility by applying an electric field into a charged particles solution.

Transport properties of glass-forming liquids suggest that dynamic crossover temperature is as important as the glass transition temperature.

It is becoming common practice to partition glass-forming liquids into two classes based on the dependence of the shear viscosity η on temperature T. In an Arrhenius plot, ln η vs 1/T, a strong liquid shows linear behavior whereas a fragile liquid exhibits an upward curvature [super-Arrhenius (SA) behavior], a situation customarily described by using the Vogel-Fulcher-Tammann law. Here we analyze existing data of the transport coefficients of 84 glass-forming liquids. We show the data are consistent, on decreasing temperature, with the onset of a well-defined dynamical crossover η(×), where η(×) has the same value, η(×) ≈ 10(3) Poise, for all 84 liquids. The crossover temperature, T(×), located well above the calorimetric glass transition temperature T(g), marks significant variations in the system thermodynamics, evidenced by the change of the SA-like T dependence above T(×) to Arrhenius behavior below T(×). We also show that below T(×) the familiar Stokes-Einstein relation D/T ∼ η(-1) breaks down and is replaced by a fractional form D/T ∼ η(-ζ), with ζ ≈ 0.85.

Dynamical crossover and breakdown of the Stokes-Einstein relation in confined water and in methanol-diluted bulk water.

Using nuclear magnetic resonance and quasi-elastic neutron scattering spectroscopic techniques, we obtain experimental evidence of a well-defined dynamic crossover temperature T(L) in supercooled water. We consider three different geometrical environments: (i) water confined in a nanotube (quasi-one-dimensional water), (ii) water in the first hydration layer of the lysozyme protein (quasi-two-dimensional water), and (iii) water in a mixture with methanol at a methanol molar fraction of x = 0.22 (quasi-three-dimensional water). The temperature predicted using a power law approach to analyze the bulk water viscosity in the super-Arrhenius regime defines the fragile-to-strong transition and the Stokes-Einstein relation breakdown recently observed in confined water. Our experiments show that these observed processes are independent of the system dimension d and are instead caused by the onset of an extended hydrogen-bond network that governs the dynamical properties of water as it approaches dynamic arrest.

Clustering dynamics in water/methanol mixtures: a nuclear magnetic resonance study at 205 k

Proton nuclear magnetic resonance (1H NMR) experiments have been performed to measure the spin-lattice, T1, and spin-spin, T2, relaxation times of the three functional groups in water/methanol mixtures at different methanol molar fractions (XMeOH=0, 0.04, 0.1, 0.24, 0.5, 1) as a function of temperature in the range 205 K

Splenic embolization in a Jehovah's Witness: role of recombinant human factor VIIa.

A case of a 50-year-old Jehovah's Witness with cryptogenic cirrhosis, severe portal hypertension and a coagulopathy, who underwent splenic embolization to improve the platelet count after receiving recombinant human Factor VIIa, is reported. Following the infusion of recombinant human Factor VIIa, the coagulopathy was rapidly corrected and it became possible to safely embolize her spleen. The changes in prothrombin time, international normalized ratio and activated partial thromboplastin time as well as thrombomodulin, tissue factor and plasminogen activator inhibitor after the infusion are presented. As a result of the splenic embolization, her platelet count normalized and she has been listed for liver transplantation.

Antiphospholipid antibodies before and after liver transplantation.

OBJECTIVE: The aim of this study was to determine whether liver transplantation of patients with antiphospholipid antibodies (APA) is 1) adversely affected with vascular thrombosis and 2) whether such antibodies persist post transplantation. METHODS: Twelve patients with APA awaiting transplant were identified and characterized biochemically and immunologically. Each had the level of APA determined using commercially available enzyme-linked immunoassay kits before, during, and after liver transplantation. RESULTS: No patient in this series experienced a transplant-related vascular thrombosis. The titer of APA fell to levels at or below those present in normals and remained low in two of 12 or undetectable in 10 of 12 patients 1 yr after liver transplantation. CONCLUSIONS: We reached the following conclusions: 1) Antiphospholipid positivity does not identify patients at high risk for post-transplant vascular thrombosis. 2) The levels of antiphospholipid present in sera pretransplant fell during transplantation and remained low or undetectable 1 month and 1 yr post transplantation.

The role of nursing in managing treatment-associated adverse effects in patients with hepatitis C.

The treatment for chronic hepatitis C with interferon and ribavirin is associated with a large number of untoward side effects ( Cornberg, Wedemeyer &, Manns, 2002). Management of these adverse effects has a great impact on the compliance of affected patients during the course of their treatment. Thus, the influence of the nurse on patient compliance and quality of life improvement during interferon and ribavirin treatment cannot be understated. Anecdotally, from the patient's point of view, the adverse effects of treatment often overshadow the goal of treatment, viral clearance. Nurses, as a result of their role as patient advocates, have the ability to enhance treatment compliance greatly by recognizing and managing treatment-associated side effects.