Dr. Karthik  Kumar  Md image

Dr. Karthik Kumar Md

350 W Thomas Rd Attn: Neuroradiology Dept
Phoenix AZ 85013
602 067-7783
Medical School: Other - Unknown
Accepts Medicare: No
Participates In eRX: No
Participates In PQRS: No
Participates In EHR: No
License #: 47583
NPI: 1770746638
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Outcome of 2 cc pure sulfur hexafluoride gas tamponade for macular hole surgery. - BMC ophthalmology
Isoexpansile concentrations of intraocular gases are typically used as tamponading agent in macular hole surgery. Using a small volume of the pure form of these gases may achieve the same result without increasing the incidence of postoperative complications. The purpose of this study was to evaluate the anatomical and visual outcomes following macular hole surgery with 2 cc pure (100 %) sulfur hexafluoride (SF6) gas tamponade.A retrospective study of eyes with idiopathic macular holes that underwent 23-gauge pars plana vitrectomy with 2 cc pure SF6 gas tamponade. Macular hole surgery was performed alone or in combination with phacoemulsification in eyes with cataract. Preoperative and postoperative data including best corrected visual acuity recorded in LogMAR units, slit-lamp biomicroscopy, and optical coherence tomography were analysed. Surgical complications were also recorded.Seventy six eyes of seventy five patients were analysed. A closure rate of 100 % was achieved with reoperation in 4 eyes. There was a significant improvement in best-corrected visual acuity from a mean of 0.65 LogMAR preoperatively to 0.36 at 6 months (p value 0.004). Forty five (59 %) eyes gained at least 2 lines on the Snellen visual acuity chart. Postoperative elevation in intraocular pressure (≥30 mmHg) was documented in 3 eyes (4 %).Macular hole surgery with 2 cc pure SF6 gas tamponade achieved a high success rate with a low incidence of complications. The smaller volume of gas required makes it a cheaper technique.
Transbronchial lung biopsy (TBLB) in diagnosing pulmonary alveolar proteinosis (PAP): forgotten role in Australia? - Respirology case reports
Transbronchial lung biopsy (TBLB) is uncommonly performed in non-malignant conditions because of its low sensitivity and small tissue samples. It is not routinely performed in Australia to investigate idiopathic pulmonary fibrosis, although it can be a useful adjunct in obtaining tissue diagnosis in selected conditions in interstitial lung disease (ILD). A 52-year-old non-smoker received a living unrelated renal transplant in January 2014 but developed insidious onset of dyspnea on exertion 1 year later. Computed tomography of the thorax showed bilateral persistent ground glass opacifications with a characteristic crazy paving pattern, although P neumocystis jirovecii pneumonia was more concerning. He was treated as P neumocystis jirovecii pneumonia but his initial bronchoscopy failed to confirm either diagnoses. He then went on to TBLB that showed the presence of periodic acid-Schiff staining material. We conclude that TBLB is a useful adjunct to obtain histological diagnosis of ILD in carefully selected patients with appropriate radiological indications.
Selective (bio)functionalization of solid-state nanopores. - ACS applied materials & interfaces
We present a method to selectively (bio)functionalize nanoscale features with the same materials chemistry. It was successfully combined with nanosphere lithography to fabricate and functionalize solid-state nanopores with PEG-brushes, supported lipid membranes, and functional proteins over large areas. The method is inexpensive, can be performed without specialized equipment, and can be applied to both topographic and planar surface modification.
Three-dimensional plasmonic stereoscopic prints in full colour. - Nature communications
Metal nanostructures can be designed to scatter different colours depending on the polarization of the incident light. Such spectral control is attractive for applications such as high-density optical storage, but challenges remain in creating microprints with a single-layer architecture that simultaneously enables full-spectral and polarization control of the scattered light. Here we demonstrate independently tunable biaxial colour pixels composed of isolated nanoellipses or nanosquare dimers that can exhibit a full range of colours in reflection mode with linear polarization dependence. Effective polarization-sensitive full-colour prints are realized. With this, we encoded two colour images within the same area and further use this to achieve depth perception by realizing three-dimensional stereoscopic colour microprint. Coupled with the low cost and durability of aluminium as the functional material in our pixel design, such polarization-sensitive encoding can realize a wide spectrum of applications in colour displays, data storage and anti-counterfeiting technologies.
Plasmonic color palettes for photorealistic printing with aluminum nanostructures. - Nano letters
We introduce the first plasmonic palette utilizing color generation strategies for photorealistic printing with aluminum nanostructures. Our work expands the visible color space through spatially mixing and adjusting the nanoscale spacing of discrete nanostructures. With aluminum as the plasmonic material, we achieved enhanced durability and dramatically reduced materials costs with our nanostructures compared to commonly used plasmonic materials such as gold and silver, as well as size regimes scalable to higher-throughput approaches such as photolithography and nanoimprint lithography. These advances could pave the way toward a new generation of low-cost, high-resolution, plasmonic color printing with direct applications in security tagging, cryptography, and information storage.
Direct observation of metal-insulator transition in single-crystalline germanium telluride nanowire memory devices prior to amorphization. - Nano letters
Structural defects and their dynamics play an important role in controlling the behavior of phase-change materials (PCM) used in low-power nonvolatile memory devices. However, not much is known about the influence of disorder on the electronic properties of crystalline PCM prior to a structural phase-change. Here, we show that the application of voltage pulses to single-crystalline GeTe nanowire memory devices introduces structural disorder in the form of dislocations and antiphase boundaries (APB). The dynamic evolution and pile-up of APBs increases disorder at a local region of the nanowire, which electronically transforms it from a metal to a dirty metal to an insulator, while still retaining single-crystalline long-range order. We also observe that close to this metal-insulator transition, precise control over the applied voltage is required to create an insulating state; otherwise the system ends up in a more disordered amorphous phase suggesting the role of electronic instabilities during the structural phase-change.
Embedded plasmonic nanomenhirs as location-specific biosensors. - Nano letters
We introduce a novel optical biosensing platform that exploits the asymmetry of nanostructures embedded in nanocavities, termed nanomenhirs. Upon oblique illumination using plane polarized white light, two plasmonic resonances attributable to the bases and the axes of the nanomenhirs emerge; these are used for location-specific sensing of membrane-binding events. Numerical simulations of the near field distributions confirmed the experimental results. As a proof-of-concept, we present a model biosensing experiment that exploits the dual-sensing capability, the size selectivity offered by the sensor geometry, and the possibility to separately biochemically modify the nanomenhirs and the nanocavities for the specific binding of lipid membrane structures to the nanomenhirs.
Printing colour at the optical diffraction limit. - Nature nanotechnology
The highest possible resolution for printed colour images is determined by the diffraction limit of visible light. To achieve this limit, individual colour elements (or pixels) with a pitch of 250 nm are required, translating into printed images at a resolution of ∼100,000 dots per inch (d.p.i.). However, methods for dispensing multiple colourants or fabricating structural colour through plasmonic structures have insufficient resolution and limited scalability. Here, we present a non-colourant method that achieves bright-field colour prints with resolutions up to the optical diffraction limit. Colour information is encoded in the dimensional parameters of metal nanostructures, so that tuning their plasmon resonance determines the colours of the individual pixels. Our colour-mapping strategy produces images with both sharp colour changes and fine tonal variations, is amenable to large-volume colour printing via nanoimprint lithography, and could be useful in making microimages for security, steganography, nanoscale optical filters and high-density spectrally encoded optical data storage.
Monolithic integration of binary-phase Fresnel zone plate objectives on 2-axis scanning micromirrors for compact microscopes. - Optics express
We demonstrated a unique monolithic integration of Fresnel elliptical zone plate (EZP) objective on a 2-axis staggered vertical comb-drive micromirror with 500 μm by 800 μm surface area via direct patterning of reflective binary phase modulation elements on a silicon chip. The need for focusing optics is thus obviated, simplifying the micro-endoscope assembly and improving its form factor. The design of binary phase EZP was guided by simulations based on FFT based Rayleigh-Sommerfeld diffraction model. For dual-axis scanning angles up to 9º by 9º at the image plane, the simulated diffracted Airy disks on a spatial map have been demonstrated to vary from 10.5 μm to 28.6 μm. Micromirrors scanning ±9º (optical) about both axes are patterned with elliptical zones designed for 7 mm focal length and 20þ off-axis 635-nm illumination using 635 nm laser. Videos of samples acquired with ~15 μm lateral resolution over 1mm × 0.35 mm field of view (FOV) at 5.0 frames/second using the device in both transmission and reflectance modes bench-top single-fiber laser scanning confocal microscope confirmed the applicability of the device to micro-endoscopy.
Direct and reliable patterning of plasmonic nanostructures with sub-10-nm gaps. - ACS nano
Nanoscale gaps in metal films enable strong field enhancements in plasmonic structures. However, the reliable fabrication of ultrasmall gaps (<10 nm) for real applications is still challenging. In this work, we report a method to directly and reliably fabricate sub-10-nm gaps in plasmonic structures without restrictions on pattern design. This method is based on a lift-off process using high-resolution electron-beam lithography with a negative-tone hydrogen silsesquioxane (HSQ) resist, where the resulting nanogap size is determined by the width of the patterned HSQ structure, which could be written at less than 10 nm. With this method, we fabricated densely packed gold nanostructures of varying geometries separated by ultrasmall gaps. By controlling structure sizes during lithography with nanometer precision, the plasmon resonances of the resulting patterns could be accurately tuned. Optical and surface-enhanced Raman scattering (SERS) measurements on the patterned structures show that this technique has promising applications in the fabrication of passively tunable plasmonic nanostructures with ultrasmall gaps.© 2011 American Chemical Society

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