Bosonization approach to the edge reconstruction of two dimentional electron systems in a quantum dot

We consider the edge reconstruction of electrons in a two dimensional harmonic trap under a strong magnetic field. In this system the edge reconstruction occurs as a result of competition between electron-electron interaction and confining potential. To describe it, we develop a bosonization scheme for two dimensional electron systems. With this method we obtain the excitation spectrum and demonstrate that the edge reconstruction occurs when the value of the magnetic field reaches a critical value. We also show that the edge reconstruction depends on the number of electrons. Additionally, we calculate the third order terms of bosons in Hamiltonian and examine the effect of those terms with a perturbation theory.Comment: 5pages, 6figure

保育者の困り感と研修内容の要望について Ⅲ －幼稚園免許状更新講習受講者へのアンケート調査の分析－

The loss of biodiversity following fragmentation and degradation of habitat is a major issue in conservation biology. As competition for resources increases following habitat loss and fragmentation, severe population declines may occur even in common, highly mobile species; such demographic decline may cause changes within the population structure of the species. The regent honeyeater, Anthochaera phrygia, is a highly nomadic woodland bird once common in its native southeast Australia. It has experienced a sharp decline in abundance since the late 1970s, following clearing of large areas of its preferred habitat, box-ironbark woodland, within the last 200 years. A captive breeding program has been established as part of efforts to restore this species. This study used genetic data to examine the range-wide population structure of regent honeyeaters, including spatial structure, its change through time, sex differences in philopatry and mobility, and genetic differences between the captive and wild populations. There was low genetic differentiation between birds captured in different geographic areas. Despite the recent demographic decline, low spatial structure appears to have some temporal consistency. Both sexes appear to be highly mobile, and there does not seem to be significant genetic differentiation between the captive and wild populations. We conclude that management efforts for survival of this species, including habitat protection, restoration, and release of captive-bred birds into the wild, can treat the species as effectively a single genetic population

In Vitro Assessment of Factors Affecting the Apparent Diffusion Coefficient of Jurkat Cells Using Bio-phantoms

It is well known that many tumor tissues show lower apparent diffusion coefficient (ADC) values, and that several factors are involved in the reduction of ADC values. The aim of this study was to clarify how much each factor contributes to decreases in ADC values. We investigate the roles of cell density, extracellular space, intracellular factors, apoptosis and necrosis in ADC values using bio-phantoms. The ADC values of bio-phantoms, in which Jurkat cells were encapsulated by gellan gum, were measured by a 1.5-Tesla magnetic resonance imaging device with constant diffusion time of 30sec. Heating at 42℃ was used to induce apoptosis while heating at 48℃ was used to induce necrosis. Cell death after heating was evaluated by flow cytometric analysis and electron microscopy. The ADC values of bio-phantoms including non-heated cells decreased linearly with increases in cell density, and showed a steep decline when the distance between cells became less than 3μm. The analysis of ADC values of cells after destruction of cellular structures by sonication suggested that approximately two-thirds of the ADC values of cells originate from their cellular structures. The ADC values of bio-phantoms including necrotic cells increased while those including apoptotic cells decreased. This study quantitatively clarified the role of the cellular factors and the extracellular space in determining the ADC values produced by tumor cells. The intermediate diffusion time of 30msec might be optimal to distinguish between apoptosis and necrosis

Field experiments in labor economics

In this thesis I show with three studies how field experiments can enhance our understanding of labor markets. Economists traditionally assume that individuals exclusively respond to monetary incentives. As a consequence, if workers have no prospect of future employment at the firm and pay is not contingent on their performance, a wage change should not affect effort. Some economists, however, have recognized that this narrow view of human motivation may severely limit our progress in understanding incentives. In Chapters 2 and 3, I investigate the role of psychological motives like the desire to reciprocate in the context of a real‐life work environment. The first experiment explores the impact of a wage increase on work performance when there is no economic reason for workers to change their effort. I find that workers reciprocate a generous wage with higher performance, particularly those workers who care about fairness and felt underpaid prior to the wage increase. The second experiment investigates the effects of a wage cut on performance when either all workers in a team or only some of them suffer the cut. I show that a general pay cut reduces performance, while a wage cut for only some of the workers reduces their performance more than twice as much. This finding demonstrates the powerful force of social comparison and the need to build the social nature of humans into economic theory. In Chapter 4, I examine the joint effects of monetary incentives and social interaction on work performance. Many jobs offer wage schemes that create positive or negative externalities on coworkers. Whether or not workers have the possibility to interact socially at work may distort the intended incentives of these schemes. I find that under relative incentives, when own effort imposes a negative externality on the coworker’s income, social interaction works against monetary incentives and leads to low performance due to collusion. However, the more workers differ in skills the less able they are to sustain collusive agreements. In der vorliegenden Dissertation zeige ich anhand von drei Studien wie Feldexperimente unser Verständnis von Arbeitsmärkten verbessern können. Ökonomen gehen traditionell davon aus, dass Individuen ausschliesslich auf materielle Anreize reagieren. Wenn also Arbeitskräfte keine Aussicht auf eine langfristige Anstellung haben und deren Lohn nicht von der Leistung abhängt, dann sollte eine Lohnveränderung keinen Einfluss auf die Arbeitsleistung haben. Manche Ökonomen haben jedoch erkannt, dass diese Sichtweise des menschlichen Verhaltens beschränkt ist und unseren Fortschritt im Verständnis von Anreizen bremsen kann. In den Kapiteln 2 und 3 untersuche ich die Bedeutung von psychologischen Motiven wie Fairness oder Reziprozität in echten Arbeitsumgebungen. Das erste Experiment untersucht den Einfluss einer Lohnerhöhung auf die Arbeitsleistung, wenn Arbeitskräfte keinen ökonomischen Grund haben, ihren Arbeitseinsatz zu ändern. Diese Studie zeigt, dass Arbeitskräfte einen grosszügigen Lohn mit höherer Arbeitsleistung erwidern. Dies gilt besonders für diejenigen, die Fairness als wichtig empfinden und sich vor der Lohnerhöhung unterbezahlt fühlten. Das zweite Experiment untersucht die Wirkung einer Lohnkürzung auf die Arbeitsleistung, wenn entweder das ganze Team oder nur einen Teil davon betroffen ist. Diese Studie zeigt auf, dass eine generelle Lohnkürzung die Arbeitsleistung senkt, wohingegen eine Lohnkürzung nur für einzelne Arbeitskräfte deren Leistung um mehr als das Doppelte reduziert. Diese Erkenntnis unterstreicht die Bedeutung von sozialen Motiven und die Notwendigkeit einer Veränderung des Menschenbilds in der Ökonomie. In Kapitel 4 erforsche ich den gemeinsamen Einfluss von materiellen Anreizen und sozialer Interaktion auf die Arbeitsleistung. Viele Firmen bieten Lohnsysteme an, bei welchen die eigene Leistung vor‐ oder nachteilhafte Nebeneffekte auf das Einkommen der Arbeitskollegen hat. Soziale Interaktion am Arbeitsplatz kann dabei die Anreize dieser Lohnsysteme verzerren. Diese Studie findet heraus, dass bei Entlohnung der Arbeitskräfte durch Turnieranreize, d.h. wenn die eigene Leistung sich nachteilhaft auf das Einkommen der Arbeitskollegen auswirkt, soziale Interaktion die Anreize ausser Kraft setzt und zu geheimen Absprachen führt. Wenn hingegen Arbeitskräfte sehr unterschiedliche Fähigkeiten besitzen, dann sind geheime Absprachen schwieriger aufrecht zu halten

Role of O-6-methylguanine-DNA methyltransferase and effect of O-6-benzylguanine on the anti-tumor activity of cis-diaminedichloroplatinum(II) in oral cancer cell lines

The DNA repair enzyme, O-6-methylguanine-DNA methyltransferase (MGMT) modulates the effectiveness of alkylating agents. However, the relationship between MGMT and the sensitivities to other agents has not been explored. In the present study, the association between MGMT expression and the cellular sensitivity to the platinum agent, CDDP was examined in four human oral cancer cell tines. CDDP depleted MGMT protein and mRNA levels in all four cell tines. Two cell lines with low MGMT expression were sensitive to an alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine and CDDP, whereas two other cell tines with high MGMT expression were resistant to both agents. Furthermore, the addition of the MGMT inhibitor, O-6-benzylguanine (O-6-BG), invariably enhanced CDDP sensitivity. CDDP depleted MGMT expression, and CDDP sensitivity was enhanced by O-6-BG. These results provide valuable information about the relationship between MGMT expression and CDDP sensitivity in oral cancer chemotherapy. (c) 2005 Elsevier Ltd. All rights reserved. </p