Preparation and characterization of the Pyrrones as thermal structural materials

Development of technique for preparing foam materials to be used as thermal structural components in spacecraft constructio

DIRECT ELECTRON-BEAM PATTERNING OF TEFLON-AF AND ITS APPLICATION TO OPTICAL WAVEGUIDING

Thin films of Teflon AF have been directly patterned by electron-beam lithography without the need for post exposure chemical development. The relationship between pattern depth and exposure dose was found to be linear over a wide range of doses. Pattern depth was also observed to be dependent on initial film thickness. Teflon AF can be directly patterned at doses similar to typical e-beam resists. High resolution features as small as ~200 nm have been resolved. FTIR measurements revealed that CF3 and fluorinated dioxole groups play a significant role in the patterning mechanism. Teflon AF films also exhibited an increase in refractive index upon exposure to the electron-beam. This property has been exploited in waveguiding applications. Waveguides in Teflon AF were patterned using direct electron beam lithography technique. Waveguides were clearly visible to the naked eye. Characterization in the visible region showed evidences of light guiding through the waveguides. However light could not cross the entire chip. Characterization in the infrared region revealed the slab mode even though individual waveguides were not detected

Addition of Zeolite ZSM-5 to an Iron-based Fischer-Tropsch Catalyst supported on Activated Carbon: Effect of Reactor Conditions

An iron-based catalyst containing 6 wt% Mo, 16 wt% Fe, 0.8 wt% Cu, and 0.9 wt% K supported on Norit SX Ultra activated carbon is used as a FTS catalyst. Zeolite ZSM-5 (of medium acidity and Si/Al = 50) is used to check its effect on FT base catalyst to form aromatic compounds and to reduce the size of long-chain hydrocarbons. The influence of ZSM-5 amounts, bed arrangements, and the temperature on the product distribution were investigated.;The performance of ZSM-5 along with the base catalyst was analyzed in two catalyst bed configurations: separate-bed and mixed-bed. Both separate-bed and mixed-bed catalyst arrangements show conversion of alcohols to hydrocarbons and water. The separate-bed arrangement gives higher conversions of CO and H2, and higher yields of liquid hydrocarbons. The decline in FT activity in the mixed bed is probably due to lowering of the alkali content of the iron catalyst because of alkali migration from FT catalyst to ZSM-5, as confirmed by energy-dispersive X-ray spectroscopy of the spent ZSM-5.;Product profiles were analyzed for changing ZSM-5 weight from 50 to 200% of the FTS amount in the separate bed and the mixed bed catalyst arrangements. Oligomerization, aromatization, isomerization, and cracking reactions are enhanced with increasing ZSM-5 weight in both the catalyst arrangements. The base catalyst shows no selectivity towards aromatic compounds, but addition of ZSM-5 in both arrangements forms C7-10 aromatic compounds. Long-chain hydrocarbon molecules (C13+) formed by the base catalyst are effectively cracked, and isomerized on the ZSM-5 catalyst surface in both type of catalyst arrangements.;Product profiles were analyzed for change in the temperature from 280 to 320°C in the base catalyst as well as in the separate-bed catalyst arrangement. Amounts of small-chain hydrocarbons (C1-5) increase with increase in temperature because of higher FTS rates. Liquid hydrocarbon production rate (in both the base catalyst and the separate bed) is increased at 300°C due to increase in FTS rate. Further increase in the temperature causes these rates to drop to give small-chain hydrocarbon (C1-4) species. Aromatic yields are found to reach a maximum at 300°C in the separate bed. The alcohol rate for the base catalyst increases with increase in temperatures probably because of higher FTS rates. 280°C is sufficient to convert all the alcohols formed by the base catalyst in the separate bed.;The base catalyst and ZSM-5 together were tested for 240 h time on stream (TOS) to check the stability of the combination of the catalysts in the separate-bed arrangement. The base catalyst shows stability up to 120 h and slow decline in activity up to 240 h. A progressive loss of the ZSM-5 activity occurred with TOS. Coke deposition on ZSM-5, confirmed by energy-dispersive X-ray spectroscopy, decreases aromatic compound yield, and increases olefin selectivity with time on stream due to reduction in oligomerization reactions

Fabrication and characterization of room temperature operating single electron transistors using focused ion beam technologies

The single electron transistor (SET) is a Coulomb blockade device, whose operation is based on the controlled manipulation of individual electrons. Single electron transistors show immense potential to be used in future ultra lowpower devices, high density memory and also in high precision electrometry. Most SET devices operate at cryogenic temperatures, because the charging energy is much smaller than the thermal oscillations. The room temperature operation of these devices is possible with sub- 10nm nano-islands due to the inverse dependance of charging energy on the radius of the conducting nano-island. The fabrication of sub-10nm features with existing lithographic techniques is a technological challenge. Here we present the results for the first room temperature operating SET device fabricated using Focused Ion Beam deposition technology. The SET device, incorporates an array of tungsten nano-islands with an average diameter of 8nm. The SET devices shows clear Coulomb blockade for different gate voltages at room temperature. The charging energy of the device was calculated to be 160.0 meV; the capacitance per junction was found to be 0.94 atto F; and the tunnel resistance per junction was calculated to be 1.26 G Ω. The tunnel resistance is five orders of magnitude larger than the quantum of resistance (26 k Ω) and allows for the localization of electrons on the tungsten nano-island. The lower capacitance of the device combined with the high tunnel resistance, allows for the Coulomb blockade effects observed at room temperature. Different device configurations, minimizing the total capacitance of the device have been explored. The effect of the geometry of the nano electrodes on the device characteristics has been presented. Simulated device characteristics, based on the soliton model have been discussed. The first application of SET device as a gas sensor has been demonstrated

Bad Gurley Feminism: The Myth of Post-War Domesticity

According to feminist history, the 1950s constitute a lapse in feminist literature as women in the post-war era were ushered into the realm of domesticity. In this article I argue that this perceived literary “gap” was both created and perpetuated by feminist historians and scholars who insist that Betty Friedan’s The Feminine Mystique (1963) was the defining feminist text of the time. I offer an alternative discourse to that of Friedan by presenting feminist writers who challenge, rather than adopt, masculine ideology as the means to women’s empowerment. I end by encouraging feminists to allow commonly dismissed feminists from the 1950s, like Cosmopolitan editor Helen Gurley Brown and domestic humor writers Shirley Jackson and Jean Kerr, into the feminist canon

Development and optimization of pyrrone polymers, June 1966 - June 1967

Development and optimization of pyrrone polymer

Room temperature operational single electron transistor fabricated by focused ion beam deposition

We present the fabrication and room temperature operation of single electron transistors using 8nm8nmtungsten islands deposited by focused ion beamdeposition technique. The tunnel junctions are fabricated using oxidation of tungsten in peracetic acid. Clear Coulomb oscillations, showing charging and discharging of the nanoislands, are seen at room temperature. The device consists of an array of tunnel junctions; the tunnel resistance of individual tunnel junction of the device is calculated to be as high as 25.13GΩ25.13GΩ. The effective capacitance of the array of tunnel junctions was found to be 0.499aF0.499aF, giving a charging energy of 160.6meV160.6meV

A comparison of Brittlebush (Encelia farinosa) productivity and health during drought and post rainfall

Encelia farinosa is well adapted for drought tolerance as its leaves transform color based on water availability. We were puzzled by a question that any desert botanist must consider. How does the photosynthetic efficiency of E. farinosa fluctuate as it transitions from a state of drought to a state of soil saturation within a 72 hour period? In this experiment we looked at the effects of irrigation on the health and quantum yield of the brittlebush by looking at photosynthetic rates using the portable photosynthesis system LI-COR 6400 when applied to two leaves on a given plant and water potential (ψ) using a Scholander-type pressure chamber on the stems. We attempted to understand how quickly these processes take place from pre-rainfall conditions to post-rainfall conditions up to 72 hours after. We concluded that E. farinosa does not fluctuate significantly in terms of photosynthetic rate, transpiration, and quantum yield with dry as opposed to irrigated soil. However, transpiration and quantum yield significantly increased for the first 24 hours immediately following rainfall, leading us to speculate whether the plant operates at peak efficiency within this window