An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta)

Direct comparisons between photosynthetic O-2 evolution rate and electron transport rate (ETR) were made in situ over 24 h using the benthic macroalga Ulva lactuca (Chlorophyta), growing and measured at a depth of 1.8 m, where the midday irradiance rose to 400-600 mumol photons m(-2) s(-1). O-2 exchange was measured with a 5-chamber data-logging apparatus and ETR with a submersible pulse amplitude modulated (PAM) fluorometer (Diving-PAM). Steady-state quantum yield ((Fm'-Ft)/Fm') decreased from 0.7 during the morning to 0.45 at midday, followed by some recovery in the late afternoon. At low to medium irradiances (0-300 mumol photons m(-2) s(-1)), there was a significant correlation between O-2 evolution and ETR, but at higher irradiances, ETR continued to increase steadily, while O-2 evolution tended towards an asymptote. However at high irradiance levels (600-1200 mumol photons m-(2) s(-1)) ETR was significantly lowered. Two methods of measuring ETR, based on either diel ambient light levels and fluorescence yields or rapid light curves, gave similar results at low to moderate irradiance levels. Nutrient enrichment (increases in [NO3-], [NH4+] and [HPO42-] of 5- to 15-fold over ambient concentrations) resulted in an increase, within hours, in photosynthetic rates measured by both ETR and O-2 evolution techniques. At low irradiances, approximately 6.5 to 8.2 electrons passed through PS II during the evolution of one molecule of O-2, i.e., up to twice the theoretical minimum number of four. However, in nutrient-enriched treatments this ratio dropped to 5.1. The results indicate that PAM fluorescence can be used as a good indication of the photosynthetic rate only at low to medium irradiances.

Effect of manual hyperinflation on hemodynamics, gas exchange, and respiratory mechanics in ventilated patients

The authors investigated the effect of manual hyperinflation (MHI) with set parameters applied to patients on mechanical ventilation on hemodynamics, respiratory mechanics, and gas exchange. Sixteen critically ill patients post-septic shock, with acute lung injury, were studied. Heart rate, arterial pressure, and mean pulmonary artery pressure were recorded every minute. pulmonary artery occlusion pressure, cardiac output, arterial blood gases, and dynamic compliance (C-dyn) were recorded pre- and post-MHI. From this, systemic vascular resistance index (SVRI), cardiac index, oxygen delivery, and partial pressure of oxygen:fraction of inspired oxygen (PaO2:FiO(2)) ratio were calculated. There were significant increases in SVRI (P < 0.05) post-MHI and diastolic arterial pressure (P < 0.01)during MHI. C-dyn increased post-MHI (P < 0.01) and was sustained at 20 minutes post-MHI (P < 0.01). Subjects with an intrapulmonary cause of lung disease had a significant decrease (P = 0.02) in PaO2:FiO(2), and those with extrapulmonary causes of lung disease had a significant increase (P < 0.001) in PaO2:FiO(2) post-MHI. In critically ill patients, MHI resulted in an improvement in lung mechanics and an improvement in gas exchange in patients with lung disease due to extrapulmonary events and did not result in impairment of the cardiovascular system.

Exchange rate sensitivity of Australian international equity funds

This paper analyses the exchange rate exposure displayed by a sample of Australian international equity trusts (IET). Exchange rate exposure is also examined in the context of differing economic climates with particular emphasis on the Asian crisis in mid-1997. It is found that there is evidence of exchange rate exposure particularly in the context of a multiple exchange rate model. Exposure varies substantially between three alternative time periods with different exposure apparent subsequent to the Asian crisis than prior to this event.

Electron exchange coupling for single-donor solid-state spin qubits

Intervalley interference between degenerate conduction band minima has been shown to lead to oscillations in the exchange energy between neighboring phosphorus donor electron states in silicon [B. Koiller, X. Hu, and S. Das Sarma, Phys. Rev. Lett. 88, 027903 (2002); Phys. Rev. B 66, 115201 (2002)]. These same effects lead to an extreme sensitivity of the exchange energy on the relative orientation of the donor atoms, an issue of crucial importance in the construction of silicon-based spin quantum computers. In this article we calculate the donor electron exchange coupling as a function of donor position incorporating the full Bloch structure of the Kohn-Luttinger electron wave functions. It is found that due to the rapidly oscillating nature of the terms they produce, the periodic part of the Bloch functions can be safely ignored in the Heitler-London integrals as was done by Koiller, Hu, and Das Sarma, significantly reducing the complexity of calculations. We address issues of fabrication and calculate the expected exchange coupling between neighboring donors that have been implanted into the silicon substrate using an 15 keV ion beam in the so-called top down fabrication scheme for a Kane solid-state quantum computer. In addition, we calculate the exchange coupling as a function of the voltage bias on control gates used to manipulate the electron wave functions and implement quantum logic operations in the Kane proposal, and find that these gate biases can be used to both increase and decrease the magnitude of the exchange coupling between neighboring donor electrons. The zero-bias results reconfirm those previously obtained by Koiller, Hu, and Das Sarma.

Broadening conceptions of curriculum for young people: Reports from three student-teachers on exchange

Research reports prepared by three Australian preservice teachers--Paula Shaw, Chris Sharp and Scott McDonald--undertaking their teacher education practicum in Canada, form the basis of this paper. The reports provide critical insights into three aspects of education for young people in both Canada and Australia. They also provide critical insight into the ways in which a practicum research project, along with the opportunities afforded through an international experience, enabled the preservice teachers to broaden their understanding of the curriculum for young people, of issues relevant to the diverse needs of young people, and of themselves and their priorities as teachers. The preservice teachers investigated three topics: attempts to reduce homophobia in schools; the presence or absence of Aboriginal content in the school curricula in British Columbia and Queensland; and "schools-within-schools" as a means to meet the needs of diverse student populations. Linda Farr Darling from the University of British Columbia provides a response to the three reports.

Conditioning information in mutual fund performance evaluation: Portuguese evidence

We estimate and compare the performance of Portuguese-based mutual funds that invest in the domestic market and in the European market using unconditional and conditional models of performance evaluation. Besides applying both partial and full conditional models, we use European information variables, instead of the most common local ones, and consider stochastically detrended conditional variables in order to avoid spurious regressions. The results suggest that mutual fund managers are not able to outperform the market, presenting negative or neutral performance. The incorporation of conditioning information in performance evaluation models is supported by our findings, as it improves the explanatory power of the models and there is evidence of both time-varying betas and alphas related to the public information variables. It is also shown that the number of lags to be used in the stochastic detrending procedure is a critical choice, as it will impact the significance of the conditioning information. In addition, we observe a distance effect, since managers who invest locally seem to outperform those who invest in the European market. However, after controlling for public information, this effect is slightly reduced. Furthermore, the results suggest that survivorship bias has a small impact on performance estimates.

Measuring fund performance using multi-factor models: evidence for the Portuguese market

This paper examines the performance of Portuguese equity funds investing in the domestic and in the European Union market, using several unconditional and conditional multi-factor models. In terms of overall performance, we find that National funds are neutral performers, while European Union funds under-perform the market significantly. These results do not seem to be a consequence of management fees. Overall, our findings are supportive of the robustness of conditional multi-factor models. In fact, Portuguese equity funds seem to be relatively more exposed to smallcaps and more value-oriented. Also, they present strong evidence of time-varying betas and, in the case of the European Union funds, of time-varying alphas too. Finally, in terms of market timing, our tests suggest that mutual fund managers in our sample do not exhibit any market timing abilities. Nevertheless, we find some evidence of timevarying conditional market timing abilities but only at the individual fund level.

STOCK EXCHANGE LISTING INDUCES SOPHISTICATION OF CAPITAL BUDGETING

This article compares capital budgeting techniques employed in listed and unlisted companies in Brazil. We surveyed the Chief Financial Officers (CFOs) of 398 listed companies and 300 large unlisted companies, and based on 91 respondents, the results suggest that the CFOs of listed companies tend to use less simplistic methods more often, for example: NPV and CAPM, and that CFOs of unlisted companies are less likely to estimate the cost of equity, despite being large companies. These findings indicate that stock exchange listing may require greater sophistication of the capital budgeting process.

DISPOSITION EFFECT AMONG BRAZILIAN EQUITY FUND MANAGERS

The disposition effect predicts that investors tend to sell winning stocks too soon and ride losing stocks too long. Despite the wide range of research evidence about this issue, the reasons that lead investors to act this way are still subject to much controversy between rational and behavioral explanations. In this article, the main goal was to test two competing behavioral motivations to justify the disposition effect: prospect theory and mean reversion bias. To achieve it, an analysis of monthly transactions for a sample of 51 Brazilian equity funds from 2002 to 2008 was conducted and regression models with qualitative dependent variables were estimated in order to set the probability of a manager to realize a capital gain or loss as a function of the stock return. The results brought evidence that prospect theory seems to guide the decision-making process of the managers, but the hypothesis that the disposition effect is due to mean reversion bias could not be confirmed.

La social stock exchange au Portugal: un nouvel allié de l'économie sociale

Résumé Cet article vise à contribuer à la connaissance de la Bolsa de Valores Sociais (BVS) — Social Stock Exchange — récemment créé au Portugal, dont le but primatial était de permettre la prise de moyens de financement des entités de l'Économie Sociale engagées dans des projets d'éducation et d'entreprenariat. Il se penchera sur la qualification juridique des divers types d'entités cotées dans la BVS, sur le concept d'investisseur social et sur la protection dont il jouira, vis-à-vis des exigences de transparence et de gouvernance qui incombent à ces entités. Le thème proposé sera examiné en soulignant les virtualités et le potentiel de la BVS, faisant référence à l'un ou à l'autre sujet qui viennent à effet, avec un accent particulier sur l'avantage d'élaborer un code de gouvernance corporative pour les entités de l'Économie Sociale. Abstract This article aims to contribute to the knowledge of the Bolsa de Valores Sociais (BVS) — Social Stock Exchange — recently created in Portugal, whose primatial purpose was to allow the taking of means of financing the Social Economy entities, engaged in projects in education and entrepreneurship. It will reflect on the legal classification of the various types of entities rated in the BVS, on the concept of social investor and on the protection he will enjoy, leading to the consequent demands for transparency and governance that falls upon those entities. The proposed theme will be discussed highlighting the virtues and potential of BVS, playing in one or two topics that comes to purpose, with particular emphasis on the relevance of drawing up a code of corporate governance for entities of the Social Economy. Resumen Este artículo tiene como objetivo contribuir al conocimiento de la Bolsa de Valores Sociales (BVS), recientemente creada en Portugal, cuya finalidad principal es que las entidades de la economía social dedicadas a proyectos en las áreas de educación y de iniciativa empresarial puedan obtener medios financieros. Se abordará la calificación jurídica de los diversos tipos de entidades que cotizan en la BVS, así como el concepto de inversor social y la protección de que éste goza, con las consiguientes exigencias en materia de transparencia y de gobierno que recaen sobre esas entidades. Se analizará la temática propuesta destacando las virtudes y potencialidades de la BVS, sin omitir algún otro tópico adyacente que resulte relevante, en especial la conveniencia de que sea elaborado un código de gobernanza corporativa para las entidades de la economía social.

Futuros: estudo de caso sobre futuros cambiais

Mestrado em Contabilidade