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Thesis (M.S.E.C.E.)--University of Massachusetts Amherst, 2008. / Includes bibliographical references (p. 68-73).

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Metallothioneins are ubiquitous sulphur-rich heavy metal binding proteins whose biosynthesis is induced in response to a variety of agents, including heavy metals. A number of isoforms of metallothionein are known to be induced by heavy metals in the common mussel Mytilus edulis, and recently interest has centred on the nature of these proteins and their possible utility as pollution indicator agents. Cadmium-induced metallotheioneins were isolated from mussels by procedures which included gel permeation and anion-exchange chromatography. They were shown to comprise two molecular mass classes of 10 and 20KDa. The 10kDa class was resolved by anion-exchange into four components designated 10-I, 10-II, 1--III and 10-IV. The 20kDa class was similarly resolved into three components designated 20-I, 20-II and 20-III. The amino acid sequences of each of the components in both of the classes were determined. This involved digestion with a variety of proteinases and separation of the resulting peptides. The abundance of crysteines in these mussel metallotheioneins necessitated their derivatisation with methyl-p-nitrobenzenesulphonate to generate the S-methyl derivative of cysteine which has been found to be suitable for peptide mapping by HPLC and sequence analysis by automated methods. The components of the 20kDa class were shown to possess linked peptides consisting of 71 amino acids, which were distinct from the 72 amino acid peptides of the 10kDa class. It is suggested that the two monomers in the 20kDa proteins are linked via S-Cd-S bonding, i.e. a bridging cadmium ion. The various components within both classes exhibited homology, particularly with regard to the location of the cysteine residues, to metallothioneins from other species, including mammals. On the basis of this homology these proteins were classified as class I metallothioneins.

This field study evaluates the impact of replacing existing 17-inch Cathode Ray Tube (CRT) monitors with 19 and 21-inch CRT monitors and 18.1-inch Flat Panel Displays (FPDs) on matrices of productivity, visual comfort, and physical discomfort among 30 employees within a large insurance company (Policy Service and Claims). Metrics were analyzed over a five (5) month period. During Phase One (initial eight weeks) of the study, metrics were gathered weekly on 17-inch CRT monitors to establish a baseline of data on productivity, visual comfort and physical discomfort. During Phase Two (12 weeks), each subject used the 19-inch CRT, 21-inch CRT and 18.1-inch FPD for two weeks, respectively interspersed with other subjects in the study utilizing 17-inch monitors for the same time period. Initially, it appears that the 19-inch monitor enables users to enter more keystrokes per hour ( x19 =1894) than its 17-inch counterpart ( x17=1721) which would be a productivity enhancement. However, this value is not statistically significant (p>0.34). Analysis of additional performance metrics yielded similar results (p>0.2). The users’ level of visual comfort increased with all test display units over their existing 17-inch counterpart (p<0.023), but the data was not meaningful due to the minute difference between their mean values (&#8710;<0.75). Physical discomfort metrics were analyzed among all of the monitor treatments. Most employees were relatively comfortable through the duration of the study. Mean values across all physical discomfort metrics measured were less than one on a Borg scale of zero to ten, but none of the values among treatments were significant (p>0.31). Anecdotally, the users preferred the larger monitors.

In this dissertation I describe the analysis of two types of electronic devices. The first is an image intensifier/photomultiplier combination used in a laser communications receiver. The second type is high resolution display monitors to be used in digital radiology. The analysis of these devices centered on the influence of noise on their performance though I also measured other device characteristics. I present here a method of characterizing noise that can be used for a variety of detector and display devices; however, I concentrated my analysis on an optical communication receiver by ITT and high resolution display monitors by MegaScan, Tektronix and US Pixel. The optical receiver is called a hybrid device because it combines an image intensifier (II) and a photomultiplier tube. The II has a large active area and its specially processed photocathode gives it an extended red response. The photomultiplier tube (PMT) provides a high gain, low noise and low dark current. The hybrid tube had a maximum gain of 8 x 10⁶, a noise factor of 1.64 and an information capacity of 1.3 x 10⁶ bits per second. The high resolution monitors we examined were black and white monitors with a pixel matrix of at least 1024 x 1536 pixels and 256 grey levels. The maximum luminance from the monitors was 88 ft-Lamberts (for the US Pixel monitor) and a maximum information capacity of 8.9 x 10⁶ bits (for the MegaScan monitor). We measured spatial and temporal noise for the monitors. Spatial noise was the dominant noise, except at low grey levels. Veiling glare was evident in all three monitors and dramatically reduced the dynamic ranges of the monitors.

No description available.