Thesis ... of the University of Pennsylvania ... by Luther Ferree Witmer.

Thesis (Ph. D.)--University of Hong Kong, 2005.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 147-152).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 147-149).

The compounds formed by SbCl₃ and the 1-halonaphthalene in the crystalline state may provide information on some of the factors involved in molecular complex formation. The gradation in both the size and the electronegativity of the naphthalene substituent permits comparisons internally and externally with the parent 2SbCl₃.naphthalene complex. Other molecular complexes are briefly surveyed. (l:l) SbCl₃ l-bromonaphthalene forms triclinic crystals, PT. with a=9.08, b=11.98, c=12.72 Å, ∝=113.1, β=93.6, γ 91.5° V=1268 ų, z=4. Photographic Mo data refined to R=0.14 for 591 reflections. The crystal structure is built up of double lawyers of SbCl₃ molecules alternating in the "c" direction with double layers of 1-bromonaphthalene molecules, tilted 25° to [010] . The SbCl₃ molecules form dimers, further bridged into infinite chains. The Sb atoms are in a distorted pentagonal bipyramid environment, with Å bonded chlorine atom and the aromatic π-system in axial positions at 2.38 and 3.32 Å. The lone pair of electrons is stereochemically inactive. (2:l)SbCl₃.l-chloronaphthalene forms monoclinic crystals, Cc, with a=16.059, b=9.525, c=11.674 Å, β=98-63°, V=1765 ų, z=4 , Diffractometer Mo data refined to R=0.l25 for 1035 reflections. The structure is built up of double layers of SbCl₃ molecules alternating in the "a" direction with single layers of l-chloronaphthalene molecules, tilted 25° to [00l] . SbCl₃ molecules form dimers, further bridged into infinite chains. Two non-equivalent SbCl₃ molecules are situated near to the l-chloronaphthalene molecule (?3.32 Å) - Sb(l) is close to the ring carrying the chlorine atom whereas ,Sb(2) is close to the other ring on the opposite side. The Sb atom is in-a distorted, pentagonal bipyramid environment, with a bonded chlorine atom and the aromatic π-system in axial positions at 2.32 and 3.32 Å respectively. Again the lone pair of electrons is stereochemically inactive. ,(l:l)SbCl₃.1-iodonaphthalene forms triclinic crystals, PI, with a=l3.15, b=7.65, C=15-01 Å, ∝ -104.7°, β =102.2°, γ =108-5°, V=1312 ų,Z-4. Photographic Mo data refined to R=0.20 for 678 reflections having l even. With l odd serious streaks appear suggesting a partly disordered structure. The crystal structure is built up of double layers of SbCl₃ molecules alternating in the "a" direction with double layers, of l-iodonaphthalene molecules, tilted ~ 25° to [010] . The two SbCl₃ molecules are linked to one another by Sb...Cl bridging, which are Part of an infinite chain. Plane-to-plane molecular stacking of l-C₁₀H₇I is observed. The Sb environment is similar to that in the l-bromonaphthalene compound. It seems that the SbCl₃:l-halonaphthalene complexes may be linked by an electron-donor-acceptor interaction where an electron donation occurs from the π-system to the antimony atom.

A thin-lens beta-ray spectrometer is described and a brief analysis of its operation is given. A coincidence Geiger-Mueller counter to be used with this instrument is also described. The spectrometer has been calibrated with a line of the thorium B spectrum, and used to obtain beta-ray spectra of radium E and antimony 124. The experimental spectra have been found to agree well with those previously published. Several methods of plotting beta-ray spectra are described and applied to radium E and antimony 124. From the Fermi plot the endpoint of the radium E spectrum appears to be at 1.18 Mev, from the van der Held plot at 1.16 Mev. For antimony 124 four endpoints have been determined from the Fermi plot at .50, .65, .90 and 2.43 Mev. It is shown that the van der Held plot reduces to the Fermi plot for this spectrum. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

This study uses clusters formed in a UHV-compatible cluster apparatus, which was built and commissioned during this thesis. The design and operation of the cluster deposition system is described. This system is optimised for high clus- ter fluxes and for the production of cluster assembled nanoscale devices. One key feature of the system is a high degree of flexibility, including interchangeable sputtering and inert gas aggregation sources, and two kinds of mass spectrome- ter, which allow both characterisation of the cluster size distribution and deposi- tion of mass-selected clusters. Another key feature is that clusters are deposited onto electrically contacted lithographically defined devices mounted on an UHV- compatible cryostat cold finger, allowing deposition at room temperature as well as at cryogenic and at elevated temperatures. The electrically contacted nanoscale cluster devices were fabricated using a novel template technique. Hereby, clusters are placed between two electrodes separated only by ∼100 nm. The width of the cluster ensemble is in the order of a few cluster diameters, which means that the assembled clusters form a cluster wire bridging the electrode separation. During this thesis, the design and layout has been optimised to be able to measure electrical properties of the cluster devices and in particular to investigate the interaction between the cluster ensemble and the contact electrodes. In-situ electrical characterisation of cluster assembled nanoscale devices are performed in the temperature range 4.2 K to 375 K. The samples are provided with a backgate, which in principle allows modification of the conduction through the cluster ensemble by applying a gate voltage. However, no change in conduc- tion with changes in gate voltages was seen. The main focus of the electrical measurements is on the current voltage char- acteristics. It was noticed that the nanoscale bismuth (and antimony) cluster devices exhibited non-linear current voltage characteristics, which were in stark contrast to the linear current voltage characteristics measured for cluster films previously. Investigations into the causes of this non-linearity suggests that tun- nelling conduction occurs between the cluster ensemble (wire) and the contact electrodes. The non-linear current voltage characteristics were fitted using three models of tunnelling conduction and appear to be best fitted using a model in- volving fluctuation-assisted tunnelling through barriers of different heights. Further, measurements of the temperature dependent resistance are performed showing an increase of resistance with decreasing temperature for bismuth and antimony assembled cluster devices. The temperature dependence of bismuth as- sembled cluster wires can be explained by the decrease of the carrier concentration in bismuth for decreasing temperature. Annealing of the cluster ensemble and the cluster contact connection resulted in an increase in conduction. This increase of conduction can be explained due to the current flow through the cluster wire. Locally, at the bottlenecks, the current flow causes resistive heating and subsequently coalescence of two (or more) clusters.

In Bihar state, India, the cure rate of antimonial compounds in the treatment of visceral leishmaniasis (VL) has declined from over 85% to less than 50%. This has been attributed to prolonged, widespread misuse of antimonials within the Indian private healthcare system. An alternative resistance hypothesis is that exposure to arsenic in drinking water in this region has resulted in antimony-resistant Leishmania parasites. Leishmania donovani were serially passaged in mice exposed to environmentally-relevant levels of arsenic in drinking water. Arsenic accumulation in organs of these mice was proportional to exposure. After five passages, isolated parasites were refractory to SbV in drug sensitivity assays. Treatment of infected mice with SbV confirmed that these parasites retained resistance in vivo, supporting this hypothesis. A retrospective field study on a cohort of antimony treated VL patients was performed in an arsenic contaminated area of Bihar to evaluate the presence of an increased risk of treatment failure and death in those exposed to arsenic. It demonstrated a significant increased risk of death from VL in arsenic exposed patients but did not indicate a significant relationship between arsenic exposure and antimonial treatment failure. Collectively these data suggest that it is biochemically possible that arsenic contamination may have contributed to the development of antimonial resistance in Bihar although issues of underpower and the retrospective nature of our epidemiological study made it difficult to conclusively demonstrate this. Further research in to the relationships between arsenic exposure and antimonial treatment failure and death in the leishmaniases is warranted.