Electrosynthetic and other studies of sulfur imides and aromatic thiazenes

This thesis describes the work carried out by the author between September 1970 and September 1973. The electrolysis products of sulfur and S(_4)N(_4) in liquid ammonia, and (_4)N(_4) in organic solvents were studied with a view to devising improved routes to S(_7)NH, S(_4)(NH)(_4) and other imides. The reactions of these two compounds as model sulfur imides were also investigated. Addition reactions of (NSCl)(_3) were studied because it is the cheapest source of SN and NSCl fragments, and because it was hoped to convert the imides into SN compounds with exocyclic S-Cl bonds. It was found that (NSCl)(_3)/metal chloride adducts behaved as a source of NS(^+) ions in thionyl chloride solution, which reacted with SCl(_2) and S(_4)N(_4) to form the cations S(_2)NCl(_2)(^+) and S(_5)N(_5)(^+) respectively. The structures of these two cations were discussed, in particular the structure and reactions of S(_5)N(_5)(^+) as a member of the "electron rich" aromatic series of sulfur-nitrogen compounds. Other as yet unknown species were predicted as also being members of this series, and their possible stability and preparative routes discussed. A study was also carried out on the little investigated compound "S(_3)N(_2)Cl". The chlorodisulfate derivative:- S(_6)N(_4)(^2+) (ClS(_2)0(_6-))(_2) - was prepared, and the structure (obtained from x-ray crystallographic studied) discussed with reference to the unusual bonding observed in this compound. Finally, a summary of the work carried out at Staveley Chemicals Limited is included

Levamisole augments the natural cytotoxicity in mice

سیتوتوکسیسیته طبیعی (Natural cytotoxicity) یکی از بخش های عمده سیستم ایمنی ذاتی برعلیه سرطان می باشد، که توسط گیرنده های +NC-1.1 و +NC-2 انجام می شود. موش هایی که تحت تاثیر آنتی بادی های ضد NC-2 و NC-1.1 قرار گرفته اند به علت حذف رسپتورهای موجود بر این سلول ها رشد بعضی از تومورها تشدید می گردد. لذا عواملی که سیتوتوکسیسیته طبیعی را توسط این گونه سلول ها تقویت کنند می توانند به عنوان داروهای ضد سرطان مورد استفاده قرار گیرند. در این تحقیق اثر داروی لوامیزول بر تقویت سیتوتوکسیسیته طبیعی سلول های +NC-2 برعلیه فیبروسارکومای WEHI-164 در موش های نژاد BALB/c مورد بررسی قرار گرفت. تزریق لوامیزول به موش ها بطور معنی داری سیتوتوکسیسیته طبیعی سلول های طحال را در کشتن سلول های توموری رادیواکتیو شده با کرومیوم 51 در محیط آزمایشگاه (In vitro) افزایش داد و این اثر 48 ساعت پس از تزریق 10 میلی گرم اثر لوامیزول بر هر کیلوگرم وزن بدن موش بطور معنی داری رشد تومور WEHI-164 را کاهش داد. این اثر با تزریق آنتی بادی ضد NC-2 به موش ها متوقف گردید. این نتیج نشانگر این واقعیت است که اثر ضد توموری لوامیزول (یا حداقل بخشی از آن) توسط سلول های +NC-2 سازماندهی می شود

Visual motion-evoked potentials in man

Visual motion-evoked potentials were recorded from the human scalp. The stimulus chosen for most detailed study was sudden reversal of the motion of a patterned field, on the hypothesis that this was likely to activate only mechanisms selectively sensitive to the direction of stimulus motion. A large proportion of the experiments were designed to test this hypothesis; and in fact they supported it. In addition to motion-reversal VEPs, VEPs to the onset and the offset of pattern motion, and to the appearance and disappearance of patterns were recorded and analysed. The relationships between these different types of VEP were investigated. Also, the dependence of the motion-onset, -offset end -reversal VEPs on certain stimulus parameters was studied. Are motion-reversal VEPs produced by direction-selective mechanisms? That direction-selective mechanisms were at least partly responsible for the motion-reversal VEPs was confirmed, since an adapting stimulus moving in the same direction as the motion before reversal produced an effect on the VEP different to that produced by en adapting stimulus moving in the opposite direction. Further investigation indicated that direction-selective mechanisms were probably the sole contributors to the motion-reversal VEPs, since control experiments failed to support any of the most likely alternative ways in which direction-insensitive mechanisms might theoretically have contributed to the motion-reversal VEPs. In particular, considerable attention was devoted to the possibility that mechanisms sensitive to contrast but insensitive to direction of motion might have been activated by a brief increase in the effective contrast of the stimulus pattern at the moment of reversal, and thereby have contributed to the VEP. Such an increase in the effective contrast could in theory have been caused by the brief slowing down which inevitably occurred at the moment of reversal, but several experiments refuted this interpretation. In particular, the VEPs were virtually independent of the time taken for reversal, but were very dependent on the velocity before and after reversal, reducing almost to zero at very high or very low velocities. A sudden step-displacement or change of the pattern at the moment of reversal suppressed the VEP. This effect was not caused by interference with the time-course of slow movement at reversal, since suppression occurred even when the step-displacement took place outside the period of slow movement. A psychophysical effect has been observed which may be connected with this phenomenon. Involuntary eye movements ere apparent~ not implicated in the production of the VEPs, since periodic and aperiodic stimulation yield similar results. Certain other ways in which VEP components might have arisen, even in the absence of eye movements or imperfections in the stimulus motion, have been investigated; but there has been no indication of the occurrence of such components. So the motion-reversal VEPs probably arose almost entirely from direction-selective mechanisms. Component analysis of VEPs The VEPs to the reversal and to the offset of motion apparently comprised three separate component peaks. In this respect they were similar to pattern-appearance VEPs, and the distribution over the scalp of any one of the components was the same for all three kinds of VEP (e.g. the first peak of the motion-reversal VEP had the some scalp-distribution as the first peak of the motion-offset VEP and the first peak of the pattern-appearance VEP). This implied that the corresponding components originated in the same cortical areas, and a correlation analysis of the amplitudes of the various components of motion-reversal VEPs and pattern-appearance VEPs for different subjects supported this conclusion. Now there is convincing evidence (Jeffreys, 1971) that the first component of pattern-appearance VEPs originates in striate cortex end the later components in extrastriate cortex. It is therefore concluded that the first peaks of motion-reversal and. motion-offset VEPs are likewise probably from striate cortex, and the later peaks from extrastriate. The VEP to motion-onset was very different from the above VEPs, however, and appeared to be more closely related to the pattern-disappearance VEP. It is possible that the same mechanisms underlie these two kinds of VEP. Although motion-reversal VEPs appear to be the product of direction-selective mechanisms alone, it is far from certain that this is true of motion-onset and -offset VEPs. Nevertheless, there is evidence that the latter kinds of VEP may share generating mechanisms with the former; since the motion-reversal VEP was, under many conditions though not all, a good approximation to the sum of the motion-onset and -offset VEPs recorded under similar stimulus conditions. The effects of varying stimulus parameters Motion-reversal VEPs were found to be largely independent of brightness except at the lowest levels, but the latency did tend to increase slightly as the brightness was reduced. Despite the discovery (MaCKay & Rietveld, 1968) that the proximity of a stationary reference line enhances the VEP to the onset of motion of a stimulus line,' it appears that the sharp contours comprising the edge of the visual field did not influence the VEPs to the onset, offset or reversal of pattern motion, since replacing the sharp contours by blurred ones did not affect the VEPs. The onset, offset and reversal VEPs did not depend greatly on the direction of motion. Superimposing a steady motion did, however, markedly modify the VEPs. The effects of using patterns other than visual noise were investigated. Checkerboards and visual noise produced similar results, but line rasters produced very different VEPs

MgB2 tunnel junctions and 19 K low-noise dc superconducting quantum interference devices

Point contact junctions made from two pieces of MgB2 can be adjusted to exhibit either superconductor-insulator-superconductor (SIS) or superconductor-normal metal-superconductor (SNS) current-voltage characteristics. The SIS characteristics are in good agreement with the standard tunneling model for s-wave superconductors, and yield an energy gap of (2.02 +/- 0.08) meV. The SNS characteristics are in good agreement with the predictions of the resistively-shunted junction model. DC Superconducting QUantum Interference Devices made from two SNS junctions yield magnetic field noise as low as 35 fT/Hz^{1/2} at 19 K.Comment: 4 pages, 4 figure

Identification of Coulomb blockade and macroscopic quantum tunneling by noise

The effects of Macroscopic Quantum Tunneling (MQT) and Coulomb Blockade (CB) in Josephson junctions are of considerable significance both for the manifestations of quantum mechanics on the macroscopic scale and potential technological applications. These two complementary effects are shown to be clearly distinguishable from the associated noise spectra. The current noise is determined exactly and a rather sharp crossover between flux noise in the MQT and charge noise in the CB regions is found as the applied voltage is changed. Related results hold for the voltage noise in current-biased junctions.Comment: 6 pages, 3 figures, epl.cls include

Assessing reference conditions and ecological status for lakes using subfossil diatoms

This is the final report to the Environment Agency under an extension to the project, ‘Development of a phytobenthos classification tool for lakes and lochs of UK (DALES– Diatom Assessment of lake and loch ecological status)’ (contract no. SC030103), funded by the Environment Agency (EA).This project forms part of the strategy for the implementation of the European Council Water Framework Directive (WFD), which requires reference conditions to be determined for all water body types including lakes

Palaeoecological study of Lochs Arkaig, Huamavat and Shiel

This is the final report to Marine Harvest on the ‘Palaeoecological study of Lochs Arkaig, Huamavat and Shiel’. The primary objective was to examine the diatom assemblages in sediment cores to assess the trophic status of the three lochs over approximately the last 100-150 years, and to determine conditions prior to the installation of fish farms at these sites

Nonlocal First-Order Hamilton-Jacobi Equations Modelling Dislocations Dynamics

We study nonlocal first-order equations arising in the theory of dislocations. We prove the existence and uniqueness of the solutions of these equations in the case of positive and negative velocities, under suitable regularity assumptions on the initial data and the velocity. These results are based on new $L^1$-type estimates on the viscosity solutions of first-order Hamilton-Jacobi Equations appearing in the so-called ``level-sets approach''. Our work is inspired by and simplifies a recent work of Alvarez, Cardaliaguet and Monneau

Budget feasible mechanisms on matroids

Motivated by many practical applications, in this paper we study budget feasible mechanisms where the goal is to procure independent sets from matroids. More specifically, we are given a matroid =(,) where each ground (indivisible) element is a selfish agent. The cost of each element (i.e., for selling the item or performing a service) is only known to the element itself. There is a buyer with a budget having additive valuations over the set of elements E. The goal is to design an incentive compatible (truthful) budget feasible mechanism which procures an independent set of the matroid under the given budget that yields the largest value possible to the buyer. Our result is a deterministic, polynomial-time, individually rational, truthful and budget feasible mechanism with 4-approximation to the optimal independent set. Then, we extend our mechanism to the setting of matroid intersections in which the goal is to procure common independent sets from multiple matroids. We show that, given a polynomial time deterministic blackbox that returns -approximation solutions to the matroid intersection problem, there exists a deterministic, polynomial time, individually rational, truthful and budget feasible mechanism with (3+1) -approximation to the optimal common independent set