Assessment of Night Vision Problems in Patients with Congenital Stationary Night Blindness

Congenital Stationary Night Blindness (CSNB) is a retinal disorder caused by a signal transmission defect between photoreceptors and bipolar cells. CSNB can be subdivided in CSNB2 (rod signal transmission reduced) and CSNB1 (rod signal transmission absent). The present study is the first in which night vision problems are assessed in CSNB patients in a systematic way, with the purpose of improving rehabilitation for these patients. We assessed the night vision problems of 13 CSNB2 patients and 9 CSNB1 patients by means of a questionnaire on low luminance situations. We furthermore investigated their dark adapted visual functions by the Goldmann Weekers dark adaptation curve, a dark adapted static visual field, and a two-dimensional version of the ‘‘Light Lab’’. In the latter test, a digital image of a living room with objects was projected on a screen. While increasing the luminance of the image, we asked the patients to report on detection and recognition of objects. The questionnaire showed that the CSNB2 patients hardly experienced any night vision problems, while all CSNB1 patients experienced some problems although they generally did not describe them as severe. The three scotopic tests showed minimally to moderately decreased dark adapted visual functions in the CSNB2 patients, with differences between patients. In contrast, the dark adapted visual functions of the CSNB1 patients were more severely affected, but showed almost no differences between patients. The results from the ‘‘2D Light Lab’’ showed that all CSNB1 patients were blind at low intensities (equal to starlight), but quickly regained vision at higher intensities (full moonlight). Just above their dark adapted thresholds both CSNB1 and CSNB2 patients had normal visual fields. From the results we conclude that night vision problems in CSNB, in contrast to what the name suggests, are not conspicuous and generally not disabling

Carbon Nanotubes: Chemical Vapor Deposition Synthesis and Application in Electrochemical Double Layer Supercapacitors

Carbon nanotubes (CNTs) have become a popular area of materials science research due to their outstanding material properties coupled with their small size. CNTs are expected to be included in a wide variety of applications and devices in the near future. Among these devices which are nearing mass production are electrochemical double layer (ECDL) supercapacitors. The current methods to produce CNTs are numerous, with each synthesis variable resulting in changes in the physical properties of the CNT. A wide array of studies have focused on the effects of specific synthesis conditions. This research expands on earlier work done using bulk nickel catalyst, alumina supported iron catalyst, and standard chemical vapor deposition (CVD) synthesis methods. This work also investigates the effect of an applied voltage to the CVD chamber during synthesis on the physical nature of the CNTs produced. In addition, the work analyzes a novel nickel catalyst system, and the CNTs produced using this catalyst. The results of the effects of synthesis conditions on resultant CNTs are included. Additionally, CNT based ECDL supercapacitors were manufactured and tested. Scanning electron microscope (SEM) analysis reveals that catalyst choice, catalyst thickness, synthesis temperature, and applied voltage have different results on CNT dimensions. Nanotube diameter distribution and average diameter data demonstrate the effect of each synthesis condition. Additionally, the concept of an alignment parameter is introduced in order to quantify the effect of an electric field on CNT alignment. CNT based ECDL supercapacitors testing reveals that CNTs work well as an active material when a higher purity is achieved. The molarity of the electrolyte also has an effect on the performance of CNT based ECDL supercapacitors. On the basis of this research, we conclude that CNT physical dimensions can be moderately controlled based on the choice of synthesis conditions. Also, the novel nickel catalyst system investigated in this research has potential to produce bulk quantities of CNT under specific conditions. Finally, purified CNTs are recommended as a suitable active material for ECDL supercapacitors.M.S.Committee Co-Chair: Carter, Brent; Committee Co-Chair: Ready, Jud; Committee Member: Snyder, Bob; Committee Member: Wang, Zhong Li

A thin film triode type carbon nanotube field emission cathode

The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the Si substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs. Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 μA cm-2 and a gate current density of 1.68 mA cm-2 at 250 V