Electron glass signatures up to room temperature in disordered insulators

This paper describes the observation of non-equilibrium field effects at room temperature in four disordered insulating systems: granular Al, discontinuous Au, amorphous NbSi and amorphous indium oxide thin films. The use of wide enough gate voltage ranges and a cautious analysis of the data allow us to uncover memory dips (MDs), the advocated hallmark of the electron glass, in the four systems. These MDs are found to relax slowly over days of measurements under gate voltage changes, reflecting the impossibility for the systems to reach an equilibrium state within experimentally accessible times. Our findings demonstrate that these electrical glassy effects, so far essentially reported at cryogenic temperatures, actually extend up to room temperature.

[Dexamethasone intravitreal implant (Ozurdex) in patients with diabetic macular edema: Real life safety and efficacy]

PURPOSE

The goal of this study was to investigate the safety and efficacy of the intravitreal dexamethasone implant (DI) for patients with diabetic macular edema (DME) in real life.

METHODS

We conducted a monocentric retrospective analysis of the change in visual acuity and central macular thickness (CMT) after intravitreal injection of the DI at peak efficacy (2 months after injection) as well as the timing of reinjections and complications in patients with a loss of vision due to DME.

RESULTS

Forty eyes of 33 patients were included, with a mean follow-up of 12.6 months. Thirty percent of the eyes experienced an increase in best corrected visual acuity (BCVA)>15 letters at peak efficacy (P<0.05) after each ID injection. Treatment-naive patients had a sustained response after Ozurdex injection, with better visual acuity at 3 months (P=0.02) and 4 months (P=0.04) than non-naïve patients and better visual acuity at 6 months despite identical baseline visual acuity (P<0.05). Anatomical efficacy was good, with approximately 60% of patients with CMT<300 microns at peak efficacy after each injection of ID. Thirty percent of eyes demonstrated ocular hypertension (OHT)>25mmHg at peak efficacy, and 12.5% of eyes required cataract surgery during follow-up.

CONCLUSION

The DI has good functional and anatomic efficacy in these patients, with a good safety profile. Treatment-naïve patients with more recent DME had a more sustained increase in visual acuity after the injections and better visual recovery at 6 months. This encourages us to initiate DI therapy early if there is no response to anti-vascular endothelial growth factor (anti-VEGF) treatment.

Evidence for thermal activation in the glassy dynamics of insulating granular aluminum conductance

Insulating granular aluminum is one of the proto-typical disordered insulators whose low temperature electrical conductance exhibits ubiquitous non-equilibrium phenomena. These include slow responses to temperature or gate voltage changes, characteristic field effect anomalies and ageing phenomena typical of a glass. In this system the influence of temperature on the glassy dynamics has remained elusive. A similar situation was met in insulating indium oxide and it was concluded that in high carrier density Anderson insulators, electronic slow relaxations essentially proceed via activationless processes. In this work we experimentally demonstrate that thermal effects do play a role and that the slow dynamics in granular aluminum is subject to thermal activation. We show how its signatures can be revealed and activation energy distributions can be extracted, providing a promising grasp on the nature of the microscopic mechanism at work in glassy Anderson insulators. We explain why some of the experimental protocols previously used in the literature fail to reveal thermal activation in these systems. Our results and analyses call for a reassessment of the emblematic case of indium oxide, and question the existence of purely activationless dynamics in any of the systems studied so far.

[Management of wet AMD in France in 2015]

PURPOSE AND CONTEXT

Intravitreal administration of anti-VEGF agents, available in France since 2007, allows stabilization and improvement in visual acuity in wet age-related macular degeneration (AMD). In the past few years, the management of this disease has evolved in terms of both diagnostic methods and treatment schedules, which have been adapted to the pathophysiology of AMD. The goal of this survey, performed in a representative sample of French ophthalmologists, was to describe the evolution of medical practices one year after a similar survey (Massé et al., J Fr Ophtalmol 2016; 39: 40-7).

METHOD

The survey was performed from December, 2014 to March, 2015 in 191 ophthalmologists (53 general ophthalmologists and 98 retina specialists) with an on-line questionnaire. This questionnaire was designed by a committee of ophthalmologists to describe practices concerning screening, diagnosis, treatment and follow-up of wet AMD.

RESULTS

An initial intravitreal injection of an anti-VEGF agent was usually performed within 10 days after the diagnosis of wet AMD by 98% of ophthalmologists and within 5 days by 63%. The treatment protocols favored by retina specialists were pro re nata (PRN) for 58%, Observe and Plan for 25% and Treat and Extend for 17%. Bilateral intravitreal injections were performed on the same day by 46% of retina specialists, mostly for the convenience of the patient and because of the low infectious risk. The initial protocol was maintained by one third of retina specialists throughout the course of treatment, while two thirds of them reported that they reassessed the protocol on average after 5 months.

CONCLUSION

This survey on the practices of the ophthalmologists in wet AMD highlights an improvement in the time course of patient management and an evolution of treatment schedules toward individualized protocols.

Publisher's Note: Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects [Phys. Rev. Lett. 117, 116601 (2016)]

This corrects the article DOI: 10.1103/PhysRevLett.117.116601.

Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects

Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state.

[Impact of cataract surgery on central macular thickness in diabetic patients without diabetic retinopathy]

PURPOSE

To determine whether cataract surgery increases macular thickness in diabetic patients without preoperative retinopathy or macular edema.

PATIENTS AND METHODS

In a prospective, non-controlled study, we compared preoperative macular thickness as measured by OCT to that measured 3 and 6 months after cataract surgery.

RESULTS

Thirty-six eyes of 21 patients (ten men and 11 women) were included in the study from November 2008 to May 2009. Mean foveolar thickness measured preoperatively was 198 μm (± 18.5 μm) compared with 202 μm (±17.2 μm) 3 months postoperatively and 212 μm (± 18.9 μm) 6 months postoperatively.

DISCUSSION

In our study, we do not show a significant increase in central foveolar thickness 3 months after cataract surgery; however, we do measure a significant increase at 6 months. This increase in thickness is similar to that found in the literature after cataract surgery in a non-diabetic population.

CONCLUSION

Cataract surgery in diabetic patients without preoperative retinopathy does not appear to induce significant macular thickening compared to non-diabetic patients. The period prior to any diabetic retinopathy or maculopathy seems to be the most amenable to cataract surgery when necessary.

[OCT measurement of the impact of Nd:YAG laser capsulotomy on foveal thickness]

INTRODUCTION

Posterior capsular opacification is the commonest complication of cataract surgery. It is treated with Nd:YAG laser capsulotomy. However, after treatment, cases of cystoid macular edema have been reported. The purpose of this study was to measure the foveal thickness change after Nd:YAG capsulotomy using optical coherence tomography (OCT) in order to clarify the physiopathology of this edema.

PATIENTS AND METHODS

A prospective, single-center study was conducted on patients who underwent Nd:YAG laser capsulotomy between May 2008 and November 2009. All patients received the same drug protocol after Nd:YAG capsulotomy (acetazolamide, apraclonidine, and rimexolone). Demographic parameters (age, sex, and medical history), clinical features (visual acuity, intraocular pressure) before and after Nd:YAG laser, and laser complications were analyzed. Central foveal thickness was measured by OCT (Stratus OCT 3, Zeiss). Data were collected before Nd:YAG laser capsulotomy and 1 week, 1 month, and 3 months after capsulotomy. The preoperative and postoperative thicknesses were compared. We used a Student t-test for statistical analysis.

RESULTS

Thirty eyes of 26 patients were analyzed. The mean foveal thickness was 209 ± 26 μm before capsulotomy, 213 ± 23 μm, 204 ± 19 μm, 213 ± 23 μm 1 week, 1 month, and 3 months, respectively, after capsulotomy. The foveal thickness did not significantly change during the first 3 months following laser treatment. No complications occurred.

DISCUSSION AND CONCLUSION

Macular cystoid edema was a classical complication after Nd:YAG capsulotomy. However, there was no significant increase of macular thickness shortly after Nd:YAG capsulotomy in our study.

Slow conductance relaxation in insulating granular Al: evidence for screening effects

It is shown that the conductance relaxations observed in electrical field effect measurements on granular Al films are the sum of two contributions. One is sensitive to gate voltage changes and gives the already reported anomalous electrical field effect. The other one is independent of the gate voltage history and starts when the films are cooled down to low temperature. Their relative amplitude is strongly thickness-dependent which demonstrates the existence of a finite screening length in our insulating films and allows its quantitative estimate (about 10 nm at 4 K). This metalliclike screening should be taken into account in the electron glass models of disordered insulators.

Novel method for the plan-view TEM preparation of thin samples on brittle substrates by mechanical and ion beam thinning

A new preparation method has been developed in order to avoid the breaking of brittle samples for plan-view TEM investigation during and after mechanical and ion beam thinning. The thinning procedure is carried out on a reduced size piece of the sample (about 1.6 x 0.8 mm(2) or about 1-1.6 mm diameter) that is embedded into a 3-mm-diameter Ti disk, which fits the sample holder of the TEM. The small sample size and the supporting metal disk assure the mechanical stability and minimize the possibility of breaking during and after the preparation: The Ti disk is placed on adhesive kapton tape, a cut piece of the sample is put into the slot of the disk, pressed onto the tape and embedded with glue. The tape keeps the parts in place and in the same plane, keeps the sample surface safe from the embedding glue and can be removed easily after the glue solidifies. Subsequently, the embedded sample is thinned from the rear by well-known mechanical and ion beam techniques until electron transparency. This simple solution lowers the risk of failed sample preparation remarkably and makes it possible to reduce the thickness of the sample to about 50 microm by mechanical thinning. As a result, dimpling becomes unnecessary and low angle ion milling gives a large transparent area for TEM. Its efficiency has been proved by successful preparation of numerous thin film samples on Si, sapphire, and glass substrates. The method is compatible with the widespread cross-sectional thinning procedures, and can be easily adopted by TEM laboratories.

Magnetotransverse scattering of surface plasmon polaritons

We show experimentally that the in-plane scattering of surface plasmon polaritons (SPP) is influenced by a perpendicular magnetic field. The average SPP flux is deflected into the direction perpendicular to both its initial propagation direction and the magnetic field direction. From a phenomenological point of view, this is an analogy to the Hall effect for electrons and a 2D equivalent of the photonic Hall effect.