A Comparison of Bayesian and Sampling Theory Inferences in a Probit Model

HE PROBIT MODEL IS A POPULAR DEVICE for explaining binary choice decisions in econometrics. It has been used to describe choices such as labor force participation, travel mode, home ownership, and type of education. These and many more examples can be found in papers by Amemiya (1981) and Maddala (1983). Given the contribution of economics towards explaining such choices, and given the nature of data that are collected, prior information on the relationship between a choice probability and several explanatory variables frequently exists. Bayesian inference is a convenient vehicle for including such prior information. Given the increasing popularity of Bayesian inference it is useful to ask whether inferences from a probit model are sensitive to a choice between Bayesian and sampling theory techniques. Of interest is the sensitivity of inference on coefficients, probabilities, and elasticities. We consider these issues in a model designed to explain choice between fixed and variable interest rate mortgages. Two Bayesian priors are employed: a uniform prior on the coefficients, designed to be noninformative for the coefficients, and an inequality restricted prior on the signs of the coefficients. We often know, a priori, whether increasing the value of a particular explanatory variable will have a positive or negative effect on a choice probability. This knowledge can be captured by using a prior probability density function (pdf) that is truncated to be positive or negative. Thus, three sets of results are compared:those from maximum likelihood (ML) estimation, those from Bayesian estimation with an unrestricted uniform prior on the coefficients, and those from Bayesian estimation with a uniform prior truncated to accommodate inequality restrictions on the coefficients.

Evaluation of short dietary questions from the 1995 National Nutrition Survey

Six of the short dietary questions used in the 1995 National Nutrition Survey (see box below) were evaluated for relative validity both directly and indirectly and for consistency, by documenting the differences in mean intakes of foods and nutrients as measured on the 24-hour recall, between groups with different responses to the short questions. 1. Including snacks, how many times do you usually have something to eat in a day including evenings? 2. How many days per week do you usually have something to eat for breakfast? 3. In the last 12 months, were there any times that you ran out of food and couldn’t afford to buy more? 4. What type of milk do you usually consume? 5. How many serves of vegetables do you usually eat each day? (a serve = 1/2 cup cooked vegetables or 1 cup of salad vegetables) 6. How many serves of fruit do you usually eat each day? (a serve = 1 medium piece or 2 small pieces of fruit or 1 cup of diced pieces) These comparisons were made for males and females overall and for population sub-groups of interest including: age, socio-economic disadvantage, region of residence, country of birth, and BMI category. Several limitations to this evaluation of the short questions, as discussed in the report, need to be kept in mind including: · The method for comparison available (24-hour recall) was not ideal (gold standard); as it measures yesterday’s intake. This limitation was overcome by examining only mean differences between groups of respondents, since mean intake for a group can provide a reasonable approximation for ‘usual’ intake. · The need to define and identify, post-hoc, from the 24-hour recall the number of eating occasions, and occasions identified by the respondents as breakfast. · Predetermined response categories for some of the questions effectively limited the number of categories available for evaluation. · Other foods and nutrients, not selected for this evaluation, may have an indirect relationship with the question, and might have shown stronger and more consistent responses. · The number of responses in some categories of the short questions eg for food security may have been too small to detect significant differences between population sub-groups. · No information was available to examine the validity of these questions for detecting differences over time (establishing trends) in food habits and indicators of selected nutrient intakes. By contrast, the strength of this evaluation was its very large sample size, (atypical of most validation studies of dietary assessment) and thus, the opportunity to investigate question performance in a range of broad population sub-groups compared with a well-conducted, quantified survey of intakes. The results of the evaluation are summarised below for each of the questions and specific recommendations for future testing, modifications and use provided for each question. The report concludes with some general recommendations for the further development and evaluation of short dietary questions.

Notes on market failure and the Paretian (Kaldor-Hicks) relevance and irrelevance of unfavourable externalities

The following are notes that have been distributed by me over the last few years to students in Environmental Economics at The University of Queensland. They give particular attention to whether externalities are Pareto or Kaldor-Hicks relevant from a policy point of view. Externalities are Kaldor-Hicks or Pareto irrelevant if no change is possible for which gainers could compensate losers. Both absolute and marginal externalities may be Kaldor-Hicks relevant. Infra-marginal negative externalities are often, but not always, Kaldor-Hicks irrelevant. There are at least two cases where such externalities can be relevant. First, the absolute impact of the negative externality may be so great that the source of the externality should be eliminated. Secondly, if the externality arises from production, its nature may depend on the type of production technique adopted. Although for the technique adopted, an infra-marginal negative externality occurs. That is Paretian irrelevant given that choice of this technique is the only available possibility, alternative techniques may actually be available in practice. Some of these may generate even smaller total external effects and be socially preferable. Both cases are outlined and illustrated in these notes. The analysis reveals the dangers of relying on marginalism for deciding on environmental policy. Total (external) effects are often of great social and economic importance and appropriate social choices cannot be made on the basis of marginalism alone.

An electron microscopic study of nickel sulfide inclusions in toughened glass

It has been known since the early sixties that nickel sulfide inclusions cause spontaneous fracture of toughened (thermally tempered) glass, but despite the considerable amount of work done on this problem in the last four decades, failures still occur in the field with regularity. In this study we have classified (by viewing through a 60x optical microscope) inclusions into two groups, which are classic and atypical nickel sulfides. The classics look like the nickel sulfide inclusions found at the initiation-of-fracture of windows that have broken spontaneously. We have compared the structure and composition of the atypical inclusions with the structure and composition of the classics. All of the classic and atypical nickel sulfide inclusions studied in this work were found to have a composition in the range of Ni52S48 to Ni48S52. Inclusions on the nickel rich side of stoichiometric NiS were found to be two-phase assemblies, and inclusions on the sulphur rich side of NiS were single phase. It had been proposed that the atypicals were passive, and of a different composition to the classics. However, we found that the difference between passive and dangerous nickel sulfide inclusions was not a difference in composition but rather a difference in the type of material in the internal pore space. The passive's had carbon char in their internal pore space, whereas the pore space of dangerous inclusions contained Na2O. The presence of Na2O and carbon char with the inclusions indicates that the formation of the inclusions results from a reaction of a nickel-rich phase with sodium sulphate and carbon. (C) 2001 Kluwer Academic Publishers.

Localization of neurotransmitters and calcium binding proteins to neurons of salamander and mudpuppy retinas

We wished to identify the different types of retinal neurons on the basis of their content of neuroactive substances in both larval tiger salamander and mudpuppy retinas, favored species for electrophysiological investigation. Sections and wholemounts of retinas were labeled by immunocytochemical methods to demonstrate three calcium binding protein species and the common neurotransmitters, glycine, GABA and acetylcholine. Double immunostained sections and single labeled wholemount retinas were examined by confocal microscopy. Immunostaining patterns appeared to be the same in salamander and mudpuppy. Double and single cones, horizontal cells, some amacrine cells and ganglion cells were strongly calbindin-immunoreactive (IR). Calbindin-IR horizontal cells colocalized GABA. Many bipolar cells, horizontal cells, some amacrine cells and ganglion cells were strongly calretinin-IR. One type of horizontal cell and an infrequently occurring amacrine cell were parvalbumin-IR. Acetylcholine as visualized by ChAT-immunoreactivity was seen in a mirror-symmetric pair of amacrine cells that colocalized GABA and glycine. Glycine and GABA colocalized with calretinin, calbindin and occasionally with parvalbumin in amacrine cells. (C) 2001 Elsevier Science Ltd. All rights reserved.

Cloning and function of the rat colonic epithelial K+ channel K(V)LQT1

K(V)LQT1 (K(V)LQ1) is a voltage-gated K+ channel essential for repolarization of the heart action potential that is defective in cardiac arrhythmia. The channel is inhibited by the chromanol 293B, a compound that blocks cAMP-dependent electrolyte secretion in rat and human colon, therefore suggesting expression of a similar type of K+ channel in the colonic epithelium. We now report cloning and expression of K(V)LQT1 from rat colon. Overlapping clones identified by cDNA-library screening were combined to a full length cDNA that shares high sequence homology to K(V)LQT1 cloned from other species. RT-PCR analysis of rat colonic musoca demonstrated expression of K(V)LQT1 in crypt cells and surface epithelium. Expression of rK(V)LQT1 in Xenopus oocytes induced a typical delayed activated K+ current. that was further activated by increase of intracellular cAMP but not Ca2+ and that was blocked by the chromanol 293B. The same compound blocked a basolateral cAMP-activated K+ conductance in the colonic mucosal epithelium and inhibited whole cell K+ currents in patch-clamp experiments on isolated colonic crypts. We conclude that K(V)QT1 is forming an important component of the basolateral cAMP-activated K+ conductance in the colonic epithelium and plays a crucial role in diseases like secretory diarrhea and cystic fibrosis.

Syndromes with salivary dysfunction predispose to tooth wear: case reports of congenital dysfunction of major salivary glands, Prader-Willi, congenital rubella, and Sjogren's syndromes.

Four cases-of congenital dysfunction of the major salivary glands as well as of Prader-Willi, congenital rubella, and Sjogren's syndromes-were identified in a series of 500 patients referred for excessive tooth wear. Although there was evidence of consumption of highly acidic drinks, some occlusal parafunction, and unacceptable toothbrushing habits, salivary dysfunction was the salient factor predisposing a patient to tooth wear in these syndromal cases. The 500 subjects have been characterized either as having medical conditions and medications that predispose them to xerostomia or lifestyles in which workplace- and sports-related dehydration lead to reduced salivary flow. Normal salivation, by buffering capacity, clearance by swallowing, pellicle formation, and capacity for remineralization of demineralized enamel, protects the teeth from extrinsic and intrinsic acids that initiate dental erosion. Thus, the syndromes, unrelated in many respects, underline the importance of normal salivation in the protection of teeth against tooth wear by erosion, attrition, and abrasion.

Regulation of yeast acetohydroxyacid synthase by valine and ATP

The first step in the common pathway for the biosynthesis of branched-chain amino acids is catalysed by acetohydroxyacid synthase (AHAS; EC 4.1.3.18). The enzyme is found in plants, fungi and bacteria, and is regulated by controls on transcription and translation, and by allosteric modulation of catalytic activity. It has long been known that the bacterial enzyme is composed of two types of subunit, and a similar arrangement has been found recently for the yeast and plant enzymes. One type of subunit contains the catalytic machinery, whereas the other has a regulatory function. Previously, we have shown [Pang and Duggleby (1999) Biochemistry 38, 5222-5231] that yeast AHAS can be reconstituted from its separately purified subunits. The, reconstituted enzyme is inhibited by valine, and ATP reverses this inhibition. In the present work, we further characterize the structure and the regulatory properties of reconstituted yeast AHAS. High phosphate concentrations are required for reconstitution and it is shown that these conditions are necessary for physical association between the catalytic and regulatory subunits. It is demonstrated by CD spectral changes that ATP binds to the regulatory subunit alone, most probably as MgATP. Neither valine nor MgATP causes dissociation of the regulatory subunit from the catalytic subunit. The specificity of valine inhibition and MgATP activation are examined and it is found that the only effective analogue of either regulator of those tested is the non-hydrolysable ATP mimic, adenosine 5 '-[beta,gamma -imido]triphosphate. The kinetics of regulation are studied in detail and it is shown that the activation by MgATP depends on the valine concentration in a complex manner that is consistent with a proposed quantitative model.

Introducing ethnomethodological analysis to the field of music education

In recent years qualitative research methods have been adopted within in the field of music education and have received widespread acceptance. However, the theoretical framework provided by ethnomethodology (Garfinkel, 1974, in R. Turner, Ethnomethodology , Penguin, Middlesex, UK) and the tools of conversational analysis (Sacks, 1992, Lectures on Conversation , edited by Gail Jefferson, Blackwell, Oxford, UK) have, to this point, been overlooked by researchers in the field of music education. In this paper I argue that the application of ethnomethodological and conversation analytical approaches in the field of research in music education can provide fresh insights into the work of music teachers and how this work is accomplished in institutional settings. Here I demonstrate how a conversation analytical perspective drawing on an ethnomethodological framework might be used to investigate transcripts of audio-recorded interview talk. This type of analysis can illuminate aspects of members' roles in relation to, and perceptions about music education in school settings that might be overlooked in other types of analysis. A conversation analytical approach to the examination of talk-in-interaction explicates in fine-grained detail how members orient to matters at hand in the context of research settings, as well as revealing features of the cultural world of music teaching. Further application of the approach to research problems in other school settings, I argue, will inform the field of music education in ways yet to be realised.

Hydraulic Performances of Minimum Energy Loss Culverts in Australia

Culverts are among the most common hydraulic structures. Modern designs do not differ from ancient structures and are often characterised by significant afflux at design flows. A significant advance was the development of the Minimum Energy Loss (MEL) culverts in the late 1950s. The design technique allows a drastic reduction in upstream flooding associated with lower costs. The development and operational performances of this type of structure is presented. The successful operation of MEL culverts for more than 40 years is documented with first-hand records during and after floods. The experiences demonstrate the design soundness while highlighting the importance of the hydraulic expertise of the design engineers.

Post-traumatic amnesia: Consistency-of-recovery and duration-to-recovery following traumatic brain impairment

The aim of this research was to examine the nature and order of recovery of orientation and memory functioning during Post-Traumatic Amnesia (PTA) in relation to injury severity and PTA duration. The Westmead PTA Scale was used across consecutive testing days to assess the recovery of orientation and memory during PTA in 113 patients. Two new indices were examined: a Consistency-of-Recovery and a Duration-to-Recovery index. a predictable order of recovery was observed during PTA: orientation-to-person recovered sooner and more consistently than the following cluster; orientation-to-time, orientation-to-place, and the ability to remember a face and name. However, the type of memory functioning required for the recall face and name task recovered more consistently than that required for memorizing three pictures. An important overall finding was that the order-of-recovery'' of orientation and memory functioning was dependent upon both the elapsed days since injury, and the consistency of recovery. The newly developed indices were shown to be a valuable means of accounting for differences between groups in the elapsed days to recovery of orientation and memory. These indices also clearly increase the clinical utility of the Westmead PTA Scale and supply an objective means of charting (and potentially predicting) patients' recovery on the different components of orientation and memory throughout their period of hospitalization.

Manual asymmetries in the preparation and control of goal-directed movements

The primary purpose of this experiment was to determine if left hand reaction time advantages in manual aiming result from a right hemisphere attentional advantage or an early right hemisphere role in movement preparation. Right-handed participants were required to either make rapid goal-directed movements to small targets or simply lift their hand upon target illumination. The amount of advance information about the target for a particular trial was manipulated by precuing a subset of potential targets prior to the reaction time interval. When participants were required to make aiming movements to targets in left space, the left hand enjoyed a reaction advantage that was not present for aiming in right space: or simple finger lifts. This advantage was independent of the amount or type of advance information provided by the precue. This finding supports the movement planning hypothesis. With respect to movement execution, participants completed their aiming movements more quickly when aiming with their right hand, particularly in right space. This right hand advantage in right space was due to the time required to decelerate the movement and to make feedback-based adjustments late in the movement trajectory. (C) 2001 Academic Press.

It's the first bites that count: Survival of first-instar monarchs on milkweeds

Mortality of first instars is generally very high, but variable, and is caused by many factors, including physical and chemical plant characters, weather and natural enemies. Here, a summary of detailed field-based studies of the early-stage survival of a specialist lepidopteran herbivore is presented. First-instar larvae of the monarch butterfly, Danaus plexippus, a milkweed specialist, generally grew faster and survived better on leaves when latex flow was reduced by partial severance of the leaf petiole. The outcome depended on milkweed species, and was related to the amount of latex produced, as well as other plant characters, such as leaf hairs, microclimate and concentration of secondary metabolites. Even for a so-called 'milkweed specialist', larval performance and survival appears to be related to the concentration of cardenolides produced by the plants (a potential chemical defence against herbivory). This case study of monarchs and milkweeds highlights the need for field-based experiments to assess the effect of plant characters on the usually poor survival of early instar phytophagous insects. Few similar studies concerning the performance and survival of first-instar, eucalypt-specific herbivores have been conducted, but this type of study is considered essential based on the findings obtained using D. plexippus.

The ecological basis of life history variation in marsupials

Our understanding of the diversity of mammalian life histories is based almost exclusively on eutherian mammals, in which the slow-fast continuum persists even after controlling for effects of body size and phylogeny. In this paper, we use modern comparative methods to test the extent to which this eutherian-based framework can be extrapolated to metatherian mammals. First, we examine the pattern of covariation among life history traits, and second, we test for correlations between variation in life history and variation in six candidate ecological variables: type of diet, extent of intraspecific competition, risk of juvenile mortality, diurnal pattern of activity, arboreality, and rainfall pattern. Even when controlling for body size and phylogeny, we observe a slow-fast continuum in metatherian mammals. Some parameters involved are different from those identified by studies of eutherians, but the underlying relationships among longevity, fecundity, and age at maturity persist. We also show that overall variation in a key life history variable, reproductive output (measured by annual reproductive rate and litter size), is significantly related to variation in type of diet, with a foliage-rich diet being associated with low fecundity. This is interesting because, although ecological correlations have been found within some eutherian subgroups, modern comparative approaches have failed to reveal robust ecological correlates of overall life history diversity in eutherians. Copyright ESA. All rights reserved.

Valuing ecological functions of biodiversity in changbaishan mountain biosphere reserve in northeast china

Conservation of biodiversity can generate considerable indirect economic value and this is being increasingly recognized in China. For a forest ecosystem type of a nature reserve, the most important of its values are its ecological functions which provide human beings and other living things with beneficial environmental services. These services include water conservancy, soil protection, CO2 fixation and O-2 release, nutrient cycling, pollutant decomposition, and disease and pest control. Based on a case study in Changbaishan Mountain Biosphere Reserve in Northeast China, this paper provides a monetary valuation of these services by using opportunity cost and alternative cost methods. Using such an approach, this reserve is valued at 510.11 million yuan (USD 61.68 mill.) per year, 10 times higher than the opportunity cost (51.78 mill. yuan/ha.a) for regular timber production. While China has heeded United Nations Environmental Program (UNEP)'s call for economic evaluation of ecological functions, the assessment techniques used need to be improved in China and in the West for reasons mentioned.