Optical and transport properties of polyaniline films

This thesis presents the results of a comprehensive study on the transport and optical properties of polyaniline (PANI) films. The films are derived by protonation (doping) of the emeraldine base form of polyaniline, as synthesized in Durham, with either 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPSA) or 10- camphorsulfonic acid. Thus, two distinct PANI systems are obtained: PANI-CSA and PANI-AMPSA. The variation of the doping level can affect the metallic properties of the final system, so that samples close to the boundary as well as samples at either side of a disorder induced metal-insulator can be obtained. The relation between the doping level and the degree of disorder, along with the existence of an inherently metallic behaviour in PANI, are investigated through a series of experiments. Temperature dependent dc conductivity measurements ranging from 10-295 K are performed using a closed loop helium cryostat under dynamic vacuum (~10(^-5) mbar). From the conductivity data curves, typical fingerprints of the metallic behaviour are detected for certain samples and an initial estimate of the degree of disorder is implicitly attained. More specific information regarding the microscopic contributions to the transport mechanisms is obtained via low temperature (down to 1.5 K) magnetocon- ductance measurements on selected samples. The magnetic field dependence of conductivity for fields up to 14 T is measured and the suitability of the localization- interaction model for the understanding of the transport mechanism in PANI is examined. Infrared reflectivity (20-9000 cm(^-1)) measurements on samples of both PANI systems are performed. The experimental configuration permits the determination of the sample’s absolute reflectivity. The optical constants are deduced from Kramers- Kronig analysis of the reflectivity data. Typical features of metallic behaviour are examined and analysed in the context of the localization modified Drude model. The results are shown to be consistent with the transport measurements, indicating that PANI is a disordered metal close to the boundary of a disorder induced metal- insulator transition

Doping-dependent studies of the Anderson-Mott localization in polyaniline at the metal-insulator boundary

Temperature-dependent dc conductivity measurements and infrared reflectivity measurements (20–9000 cm−1) were performed on a series of polyaniline samples with two different dopant acids at various doping levels. The typical fingerprints of a disordered metal such as a positive temperature coefficient of resistivity at high temperatures, a very high reflectivity in the far infrared, and a plasma resonance have been observed. The results were analyzed in the framework of the Anderson-Mott localization model and considerable consistency between transport studies and optical measurements was obtained. Various parameters enabling a comparative classification of the materials are also reported

What is the Real Cost of Intraoperative Floppy Iris Syndrome in Cataract Surgery?

This is a Letter and does not have an abstract. Please download the PDF or view the article in HTML

Influence of Intraocular Lens Asphericity and Blue Light Filtering on Visual Outcome, Contrast Sensitivity, and Aberrometry after Uneventful Cataract Extraction

Purpose: To evaluate the effect of asphericity and blue light filter (BLF) of three different intraocular lenses (IOLs) on the visual performance, second- and third-order aberrations (defocus, coma, trefoil), and contrast sensitivity after uneventful cataract surgery. Methods: One hundred and twenty eyes of 60 patients with clinically significant cataract were randomly assigned to receive one of the three IOL types: Bioline Yellow Accurate (aspheric, with BLF, i-medical, Germany), BioAcryl 60125 (spherical, without BLF, Biotech, France), and H65C/N (aspheric, without BLF, PhysIOL, Belgium). Each IOL was implanted in 40 eyes. Complete ophthalmologic examination, functional acuity contrast testing and wavefront analysis were performed 60 days postoperatively. Results: The mean postoperative best-corrected visual acuity (BCVA) was 0.95 ± 0.08, not differing statistically among the IOL groups (P = 0.83). Mean defocus and coma values did not yield any statistically significant difference through the IOL groups varying from –0.784 to –0.614 μm and 0.129 to 0.198 μm (P = 0.79 and 0.34, respectively). Bioline Yellow Accurate IOL presented less trefoil aberrations, 0.108 ± 0.05 μm, compared to the other two IOL types (BioAcryl [0.206 ± 0.19 μm] and Physiol [0.193 ± 0.17 μm], P < 0.05). Contrast sensitivity values did not differ among the groups under all lighting conditions. Bioline Yellow IOL showed a statistically higher loss of contrast sensitivity (between mesopic and mesopic with glare conditions) compared to the BioAcryl and PhysIOL in 12 and 3 cpd spatial frequencies, respectively (P < 0.05). Conclusion: Bioline Yellow IOL indicated lower contrast sensitivity under mesopic conditions when glare was applied but resulted in less trefoil aberrations after uneventful cataract surgery. No further differences were noted in postoperative visual performance among three IOL groups

Peripapillary Neovascular Membrane in a Young Pregnant Woman and Prompt Response to Ranibizumab Injections following Uneventful Delivery

Purpose: Occurrence of choroidal neovascularization (CNV) during pregnancy has been reported as a complication of presumed ocular histoplasmosis syndrome or punctuate inner chorioretinopathy. To our knowledge, idiopathic CNV (ICNV) during pregnancy has only been reported once in the relevant literature. Bevacizumab has been used for the treatment of ICNV in small case series. However, there is limited experience regarding the use of ranibizumab for the management of ICNV. Case Report: A 31-year-old woman in the eighth month of her second pregnancy was diagnosed with mild macular and papillary edema. She was followed up using biomicroscopy, fluorescein angiography (FA), and optical coherence tomography (OCT). After 3 months, visual acuity further deteriorated and funduscopy, FA and OCT findings revealed a juxtapapillary choroidal neovascular membrane (CNVM). After two ranibizumab injections, best-corrected visual acuity increased significantly, physiological macular anatomy was restored and no subretinal fluid was observed. Discussion: In this case report, we present a young pregnant patient with peripapillary ICNV and neurosensory detachment involving the macula, and treatment of the eye with intravitreal ranibizumab following uneventful delivery. Increased angiogenic factor levels associated with pregnancy may contribute to the onset of CNV although this relationship has to be investigated experimentally. The rapid response to ranibizumab suggests that this anti-VEGF agent may be an alternative treatment option in the management of peripapillary ICNV

Ablation of Left Atrial Tachycardia following Catheter Ablation of Atrial Fibrillation: 12-Month Success Rates

The treatment of atrial tachycardia following catheter ablation of atrial fibrillation is often challenging. Electrophysiological studies using high-resolution 3D mapping systems have contributed significantly to their understanding, and new ablation approaches have shown high rates of acute terminations with low recurrences for the clinical AT. However, patient populations are very heterogeneous, and long-term data of the freedom from any atrial tachycardia or any arrhythmia are still sparse. To evaluate long-term success, a unified patient population and predefined ablation strategies are preferred. In this study, we present 12-month success and mean 30 month follow-up data of catheter ablation of left atrial tachycardia. All 35 patients had a history of pulmonary vein isolation (PVI), 71% of which had a previous substrate modification. A total of 54 ATs, with a mean cycle length 297 ± 86 ms, 31 macro-reentries, and 4 localized reentries, were targeted. The ablation strategy to be used was given by the study protocol, depending on the type of reentry and the number of critical isthmuses. All available ablation strategies were included: standard (anatomical) lines, individual lines, critical isthmuses, and focal ablation. All ATs were terminated by ablation. A total of 91% terminated upon the first ablation strategy. Freedom from any AT after 12 months was 82%, and from any arrhythmia, it was 77%. The multi-procedure success after 30 months was 65% for any AT and 55% for any arrhythmia. In conclusion, individual ablation strategies based on the reentry mechanism and the number of critical isthmuses seems promising and demonstrates a high long-term clinical success. Tachycardia comprising a single critical isthmus can be ablated by critical isthmus ablation only. These patients present with the highest 12-month and long-term success rates

Bandage contact lens and topical steroids are risk factors for the development of microbial keratitis after epithelium-off CXL

Objective:To investigate the role of bandage contact lenses (BCL) and topical steroids as risk factors for the development of microbial keratitis after epithelium-off corneal collagen cross-linking (CXL). Methods and Analysis:Patients undergoing CXL between February 2011 and July 2017 were included. Patients were divided into two groups: those who were treated postoperatively with a BCL, topical antimicrobial and steroids (group 1) and those who received only a topical antimicrobial until healing of the epithelial defect before introduction of topical steroids (group 2). Results:1273 eyes of 964 patients were included. Group 1 comprised 316 eyes and group 2 comprised 957 eyes. There were no significant differences in the presence of persisting corneal haze or scarring between the two groups (p=0.57). Microbial keratitis occurred in nine eyes (0.71% of eyes) of eight (0.83%) patients (one case was bilateral) out of 1273 eyes. Staphylococcus aureus was cultured from corneal scrapes in seven out of nine (77.8%) cases and from contiguous sites in the two cases. All cases occurred in group 1 (incidence=2.85%) and none in group 2 (p<0.0001). A greater proportion of patients who developed microbial keratitis were atopic (75%, p=0.4). Conclusion:The use of BCL and topical steroids prior to healing of the epithelium is a significant risk factor for microbial keratitis. S. aureus is the most common micro-organism and is likely to originate from an endogenous site. Not using a BCL and delaying the introduction of topical steroids until epithelial healing significantly reduce the risk of developing microbial keratitis without increasing the risk of persistent corneal haze

Optical study on doped polyaniline composite films

Localization driven by disorder has a strong influence on the conducting property of conducting polymer. A class of authors hold the opinion that disorder in the material is homogeneous and conducting polymer is disordered metal close to Anderson-Mott Metal-Insulator transition, while others treat the disorder as inhomogeneous and have the conclusion that conducting polymer is a composite of ordered metallic regions and disordered insulating regions. The morphology of conducting polymers is an important factor that have influence on the type and extent of disorder. Different protonic acids used as dopants and moisture have affection on polymer chain arrangement and interchain interactions. A PANI-CSA film, two PANI-CSA/PANI-DBSA composite films with different dopants ratio, and one of the composite films with different moisture content are studied. Absolute reflectivity measurements are performed on the films. Optical conductivity and the real part of dielectric function are calculated by Kramers-Kronig(KK) relations. $\sigma_1(\omega)$ and $\epsilon_1(\omega)$ derivate from simple Drude model in low frequency range and tendencies of the three sample are different and non-monotonic. The Localization Modified Drude model(LMD) in the framework of Anderson-Mott theory can not give a good fit to the experimental data. By introducing a distribution of relaxation time into LMD, reasonable fits for all three samples are obtained. This result supports the inhomogeneous picture.Comment: 6 figures, 7 page