The effects of periodic and continuous market environments on the performance of trading agents

Simulation experiments are conducted on simple continuous double auction (CDA) markets based on the experimental economics work of Vernon Smith. CDA models within experimental economics usually consist of a sequence of discrete trading periods or “days”, with allocations of stock and currency replenished at the start of each day, a situation we call “periodic” replenishment. In our experiments we look at both periodic and continuous-replenishment versions of the CDA. In this we build on the work of Cliff and Preist (2001) with human subjects, but we replace human traders with Zero Intelligence Plus (ZIP) trading agents, a minimal algorithm that can produce equilibrating market behaviour in CDA models. Our results indicate that continuous-replenishment (CR) CDA markets are similar to conventional periodic CDA markets in their ability to show equilibration dynamics. Secondly we show that although both models produce the same behaviour of price formation, they are different playing fields, as periodic markets are more efficient over time than their continuous counterparts. We also find, however, that the volume of trade in periodic CDA markets is concentrated in the early period of each trading day, and the market is in this sense inefficient. We look at whether ZIP agents require different parameters for optimal behaviour in each market type, and find that this is indeed the case. Overall, our conclusions mirror earlier findings on the robustness of the CDA, but we stress that a CR-CDA marketplace equilibrates in a different way to a periodic one

The management of posterior vitreous detachment by an optometrist

Acute posterior vitreous detachment (PVD) is the most common cause of retinal detachment. The management of this condition can be variable and often undue reliance is placed upon associated signs and symptoms which can be a poor indicator of pathology. Optometrists undertake a number of extended roles, however involvement in vitreo-retinal sub-specialities appears to be limited. One objective was to directly compare an optometrist and ophthalmologist in the assessment of patients with PVD, for this a high level of agreement was found (95% sensitivity, 99% specificity, 0.94 kappa). A review of 1107 patients diagnosed with acute PVD that were re-evaluated in a PVD clinic a few weeks later was undertaken to determine whether such reviews are necessary. One-fifth of patients were found to have conditions undiagnosed at the initial assessment, overall 4% of patients had retinal breaks when examined in the PVD clinic and a total of 7% required further intervention. The sensitivity of fundus examination with +90D and 3-mirror lenses was 85-88% for detecting retinal breaks and 7-85% for pigment in the anterior vitreous for the presence of retinal breaks. Therefore patients with acute PVD should be examined by indirect ophthalmoscopy with indentation at the onset of PVD and 4-6 weeks later. The treatment of retinal breaks with laser retinopexy is performed by ophthalmologists with a primary success rate 54-85%. In a pioneering development, an optometrist undertaking this role achieved a comparable primary success rate (79%). Mid-vitreous opacities associated with PVD are described, and noted in 100% of eyes with PVD. The recognition of this sign is important in the diagnosis of PVD and retinal breaks. The importance of diagnostic imaging is also demonstrated, however the timing in relation to onset may be vital

The violence of capitalist development and underdevelopment: The impact on poor women\u27s lives in India.

The deterioration in the life conditions of poor women in India, particularly in rural areas, is often dismissed as the lack of \u27modernity\u27, their experiences being subsumed under \u27modernization/integrationist\u27 perspectives. The view taken in this thesis is that the destruction of self-sufficient and self-sustaining means of production under British colonial rule and the post-colonial State has impoverished small-scale peasant households. Under such conditions poor women are bearing the brunt of poverty because they must often undertake various types of work and services in order to ensure the day-to-day survival of their families. The intensification in their workburden, inadequate nutrition, and the burden of bearing many children because of economic necessity as well as the persistence of sexist attitudes is taking a significant toll on the health of poor females. The mortality rates for women are higher during early childhood and childbearing years, and presently India is one of few countries where the female population has decreased significantly in comparison to males. In this thesis it is argued that the brutality of capitalist development and underdevelopment on the lives of women in India is a form of violence; the destruction of the very self upon which capital accumulation is dependent. It is suggested here that in order to develop and/or recover alternative approaches to existing relations of production and reproduction, feminists at the privileged end of the global economic hierarchy can begin by exploring the nature of their own detachment. This can be an important step towards empowerment and the foundation for a sisterhood that is based on co-operation and reciprocity. (Abstract shortened by UMI.)Dept. of Sociology and Anthropology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .C432. Source: Masters Abstracts International, Volume: 32-02, page: 0507. Adviser: Lynne Phillips. Thesis (M.A.)--University of Windsor (Canada), 1993

The Encapsulation and Release of Flutamide Using Poly (ε-Caprolactone) Microspheres

A thesis submitted to The University of Wolverhampton for the degree of MASTERS OF PHILOSOPHY Research in PharmacyIn 2012 prostate cancer contributed towards 8% (1.1 million cases) of all cancer incidences around the world. This type of cancer is prevalent in men between the ages of 65-79 years old, with 25% of all cases occurring in men younger than 65 years old. Treatments that are currently available for prostate cancer include surgery, hormone therapy, radiation therapy and chemotherapy. These treatment methods are either very invasive or have harsh side effects including diarrhoea, nausea, alter liver function, anaemia and fatigue. A wide range of anti-cancer drugs in use today have very poor physiochemical properties. New knowledge in this area is required to develop an advanced drug delivery system that improves the properties of these drugs. An example is anti-androgenic drugs such as flutamide (FLT) used in hormonal therapy. The disadvantages to FLT are that it has low bioavailability in oral formulations, low aqueous solubility, compliance issues and rapid first pass metabolism. Recent advances in novel drug delivery have led to the formation of controlled release delivery systems using non-toxic polymeric microspheres. These polymeric microspheres encapsulate the active agent improving its bioavailability and compliance, reducing drug toxicity and side effects. The aim of this investigation was to develop a controlled release FLT delivery system in the form of poly (ε-caprolactone) (PCL) microspheres. The study was set out to evaluate the microspheres aesthetics, physicochemical properties and drug release behaviour. A central composite experimental design was employed to evaluate the effect of two process variables, (1) the polymer PCL at three different molecular weights (MW) 80kDa, 65kDa and 10kDa, (2) the surfactant (poly(vinyl alcohol) (PVA) at two molecular weight ranges 13-23kDa and 30-70kDa. Preparing the organic phase consisted of 500mg of PCL and 50mg of FLT being completed dissolved in 10mL chloroform. The inorganic phase was formed by dissolving PVA in deionised water at a 0.5% weight/volume solution. The organic phase was added drop wise into the inorganic phase to create a 1.30 oil/water ratio. The emulsion was homogenised at 5000rpm for 1 minute. The chloroform was rotary evaporated off, followed by centrifugation and being frozen for 24 hours. The scanning electron microscopy (SEM) analysis was carried out with a freeze dried sample of the microspheres. The percentage yield was calculated to see how the sample amount changed with two process variables. Using laser diffraction, the average diameter of microspheres was determined. The percentage encapsulation efficiency (%EE) was carried out by dissolving PCL-FLT microspheres in Sanjit S. Chaggar 1004138 Masters of Philosophy v | P a g e chloroform and ethanol. The solution was centrifuged and the UV-absorbance was recorded at 300nm. The in-vitro drug release was analysed via dissolution, PCL-FLT microspheres were suspended in a dialysis bag and stirred at 100rpm, in a phosphate buffer saline (PBS) solution. The SEM data suggested the PCL 80kDa/ PVA 30-70kDa formulation produced the smoothest and most uniform microspheres with the highest mean percentage encapsulation efficiency at 90.92% ±1.08%. The micrographs showed that as the PCL MW increased from 10kDa to 80kDa the particle size increased from 5.5μm to 8.4μm. Regarding percentage yield the 80kDa/ PVA 13-23kDa FLT loaded formulations produced the most amount of product, averaging at 72.95% ±1.28%. However, after statistical analysis of %EE and product yield there was no significant difference in data between the two MW ranges of PVA (P>0.05). Dissolution results showed PCL 80kDa/ PVA 30-70kDa microspheres to have a maximal release of 80.23% over 16 days with an intial burst release of 15.38% within the first 4 hours of dissolution. This suggested that encapsulted FLT microspheres can be administered less frequently (once every 2 weeks) at a lower dose (50mg), as the release rate (80.23%/ 16 days) of encapsulted FLT is slower than the half life of free FLT (8 hours). Overall the formulation that produced the most ideal microspheres regarding aesthetics, size, yield, encapsulation efficiency and dissolution was the PCL 80kDa/ PVA 30-70kDa formulation. Further studies that can be conducted include transition electron microscopy (TEM) analysis to evaluate the internal components of the PCL-FLT microsphere complex. A co-polymer such as poly(lactic-co-glycolic acid) (PLGA) can be incorparated along side PCL in order to further improve the encapsulation efficiency. Toxicity studies can also be carried out involving prostate cancer cell lines (MTT Assay)

Tunneling injection and recombination of carriers in self-assembled quantum dots

This thesis describes an experimental investigation of the resonant injection of carriers into self-assembled indium arsenide (InAs) quantum dots incorporated in the intrinsic region of gallium arsenide (GaAs) p-i-n resonant tunneling diodes, and of the resulting electroluminescence spectrum associated with carrier recombination in the quantum dots, wetting layer and GaAs matrix. A series of devices of different designs have been measured and it is shown that bipolar resonant injection, i.e. resonant injection of both electrons andholes, into the zero-dimensional states provided by the InAs quantum dots is possible. It is shown that bias-tunable tunneling of carriers into the dots provides a means of controlling injection and light emission from a small number of individual dots within a large ensemble. Magnetotunneling spectroscopy is used to investigate the possibility that fluctuations in the potential profile of the GaAs emitter layer play a significant role in the carrier dynamics of such devices. We also show that the extent of carrier energy relaxation prior to recombination can be controlled by tailoring the morphology of the quantum dot layer. Additionally, a study into the phenomenon of low-temperature up-conversion electroluminescence (UCEL) is presented. Injection of carriers into the quantum dot states at an applied bias well below the GaAs flat-band condition results in near-band-edge GaAs electroluminescence, i.e., emission of photons with energies much larger than that supplied by the applied bias and the thermal energy. The origin of this UCEL is discussed and is attributed to carrier excitation resulting from (non-radiative) Auger recombination of electron-hole pairs in the quantum dot ground states

N terminus is key to the dominant negative suppression of CaV2 calcium channels: implications for episodic ataxia type 2

Expression of the calcium channels CaV2.1 and CaV2.2 is markedly suppressed by co-expression with truncated constructs containing Domain I. This is the basis for the phenomenon of dominant negative suppression observed for many of the episodic ataxia type 2 mutations in CaV2.1 that predict truncated channels. The process of dominant negative suppression has been shown previously to stem from interaction between the full-length and truncated channels and to result in downstream consequences of the unfolded protein response and endoplasmic reticulum-associated protein degradation. We have now identified the specific domain that triggers this effect. For both CaV2.1 and CaV2.2, the minimum construct producing suppression was the cytoplasmic N terminus. Suppression was enhanced by tethering the N terminus to the membrane with a CAAX motif. The 11-amino acid motif (including Arg52 and Arg54) within the N terminus, which we have previously shown to be required for G protein modulation, is also essential for dominant negative suppression. Suppression is prevented by addition of an N-terminal tag (XFP) to the full-length and truncated constructs. We further show that suppression of CaV2.2 currents by the N terminus-CAAX construct is accompanied by a reduction in CaV2.2 protein level, and this is also prevented by mutation of Arg52 and Arg54 to Ala in the truncated construct. Taken together, our evidence indicates that both the extreme N terminus and the Arg52, Arg54 motif are involved in the processes underlying dominant negative suppression

Tunneling injection and recombination of carriers in self-assembled quantum dots

This thesis describes an experimental investigation of the resonant injection of carriers into self-assembled indium arsenide (InAs) quantum dots incorporated in the intrinsic region of gallium arsenide (GaAs) p-i-n resonant tunneling diodes, and of the resulting electroluminescence spectrum associated with carrier recombination in the quantum dots, wetting layer and GaAs matrix. A series of devices of different designs have been measured and it is shown that bipolar resonant injection, i.e. resonant injection of both electrons andholes, into the zero-dimensional states provided by the InAs quantum dots is possible. It is shown that bias-tunable tunneling of carriers into the dots provides a means of controlling injection and light emission from a small number of individual dots within a large ensemble. Magnetotunneling spectroscopy is used to investigate the possibility that fluctuations in the potential profile of the GaAs emitter layer play a significant role in the carrier dynamics of such devices. We also show that the extent of carrier energy relaxation prior to recombination can be controlled by tailoring the morphology of the quantum dot layer. Additionally, a study into the phenomenon of low-temperature up-conversion electroluminescence (UCEL) is presented. Injection of carriers into the quantum dot states at an applied bias well below the GaAs flat-band condition results in near-band-edge GaAs electroluminescence, i.e., emission of photons with energies much larger than that supplied by the applied bias and the thermal energy. The origin of this UCEL is discussed and is attributed to carrier excitation resulting from (non-radiative) Auger recombination of electron-hole pairs in the quantum dot ground states

Sharp electroluminescence lines excited by tunneling injection into a large ensemble of quantum dots

We observe a strong bias-dependence of the electroluminescence spectra of an ensemble of self-assembled InAs quantum dots (QDs) excited by tunnelling injection of carriers from the n- and p-doped GaAs layers of a p-i-n diode. We show that the dot emission evolves from a broad band above flat-band condition to a series of sharp emission lines below a characteristic bias voltage. Also, we present a study of the electroluminescence under resonant bias excitation of the dots and demonstrate up-conversion luminescence. © 2007 American Institute of Physics

Sharp-line electroluminescence from individual quantum dots by resonant tunneling injection of carriers

We report sharp electroluminescence lines from individual self-assembled InAs quantum dots (QDs) excited by resonant tunneling injection of carriers from the n- and p-doped GaAs layers of a p-i-n diode. Bias-tunable tunneling of carriers into the dots provides a means of controlling injection and light emission from a small number of individual dots within a large ensemble. We also show that the extent of carrier energy relaxation prior to recombination can be controlled by tailoring the morphology of the QD layer. © 2006 American Institute of Physics