Tests of Inference for Dummy Variables in Regressions with Logarithmic Transformed Dependent Variables

The interpretation of dummy variables in regressions where the dependent variable is subject to a log transformation has been of continuing interest in economics. However, in the main, these earlier papers do not deal with the inferential aspects of the parameters estimated. In this paper we compare the inference implied by the hypotheses tested on the linear parameter estimated in the model and the tests applied to the proportional change that this parameter implies. An important element in this analysis is the asymmetry introduced by the log transformation. Suggestions are made for the appropriate test procedure in this case. Examples are presented from some common econometric applications of this model in the estimation of hedonic price models and wage equations.Hypothesis tests;lognormal distribution; measures of proportional change; wage equation; hedonic price model

Clustering in a Data Envelopment Analysis Using Bootstrapped Efficiency Scores

This paper explores the insight from the application of cluster analysis to the results of a Data Envelopment Analysis of productive behaviour. Cluster analysis involves the identification of groups among a set of different objects (individuals or characteristics). This is done via the definitions of a distance matrix that defines the relationship between the different objects, which then allows the determination of which objects are most similar into clusters. In the case of DEA, cluster analysis methods can be used to determine the degree of sensitivity of the efficiency score for a particular DMU to the presence of the other DMUs in the sample that make up the reference technology to that DMU. Using the bootstrapped values of the efficiency measures we construct two types of distance matrices. One is defined as a function of the variance covariance matrix of the scores with respect to each other. This implies that the covariance of the score of one DMU is used as a measure of the degree to which the efficiency measure for a single DMU is influenced by the efficiency level of another. An alternative distance measure is defined as a function of the ranks of the bootstrapped efficiency. An example is provided using both measures as the clustering distance for both a one input one output case and a two input two output case.

Inferences for the Extremum of Quadratic Regression Models

Quadratic functions are often used in regression to infer the existence of an extremum in a relationship although tests of the location of the extremum are rarely performed. We investigate the construction of the following confidence intervals: Delta, Fieller, estimated first derivative, bootstrapping, Bayesian and likelihood ratio. We propose interpretations for the unbounded intervals that may be generated by some of these methods. The coverage of the confidence intervals is assessed by Monte Carlo; the Delta and studentized bootstrap can perform quite poorly. Of all the methods, the first derivative method is easiest to implement.Inverted U-Shaped, turning point, Fieller method, Delta method, 1st derivative function, Bayesian, Likelihood ratio, Bootstrap.

Biosynthesis of ketocarotenoids in transgenic cyanobacteria expressing the algal gene for β-C-4-oxygenase, crtO

AbstractThe ketocarotenoid astaxanthin is produced by a number of marine bacteria and microalgae. It is synthesized from β-carotene by the addition of two keto groups to carbons C4 and C4′ and two hydroxyl groups to C3 and C3′. The gene, crtO, encoding β-C-4-oxygenase which converts β-carotene to canthaxanthin was cloned from the green alga Haematococcus pluvialis. We transferred crtO to the cyanobacterium Synechococcus PCC7942, which contains a β-carotene hydroxylase gene and normally accumulates β-carotene and zeaxanthin. The genetically engineered cyanobacterium produced astaxanthin as well as other ketocarotenoids. The results confirm that crtO can function in cyanobacteria in conjunction with the intrinsic carotenoid enzymes to produce astaxanthin. Specifically, this finding indicates that β-carotene hydroxylase, which normally converts β-carotene to zeaxanthin, can also function in the biosynthesis of astaxanthin. These results provide the first evidence of genetic manipulation of a plant-type carotenoid biosynthesis pathway toward the production of novel carotenoids.© 1997 Federation of European Biochemical Societies

A Model of Relative Price Elasticities from Second Moments of Demand

The first of two papers delivered at the joint SEEC/BIEE Energy Modelling Group seminar on 6 May 1994 at the University of Surrey

End Use Elasticities

The second of two papers delivered at the joint SEEC/BIEE Energy Modelling Group seminar on 6 May 1994 at the University of Surrey

Palmitate-induced impairment of glucose-stimulated insulin secretion precedes mitochondrial dysfunction in mouse pancreatic islets

It has been well established that excessive levels of glucose and palmitate lower glucose-stimulated insulin secretion (GSIS) by pancreatic beta cells. This beta cell 'glucolipotoxicity' is possibly mediated by mitochondrial dysfunction, but involvement of bioenergetic failure in the pathological mechanism is subject of ongoing debate. We show here that increased palmitate levels impair GSIS before altering mitochondrial function. We demonstrate that GSIS defects arise from increased insulin release under basal conditions in addition to decreased insulin secretion under glucose-stimulatory conditions. Real-time respiratory analysis of intact mouse pancreatic islets reveals that mitochondrial ATP synthesis is not involved in the mechanism by which basal insulin is elevated. Equally, mitochondrial lipid oxidation and production of reactive oxygen species do not contribute to increased basal insulin secretion. Palmitate does not affect KCl-induced insulin release at a basal or stimulatory glucose level, but elevated basal insulin release is attenuated by palmitoleate and associates with increased intracellular calcium. These findings deepen our understanding of beta cell glucolipotoxicity and reveal that palmitate-induced GSIS impairment is disconnected from mitochondrial dysfunction, a notion that is important when targeting beta cells for the treatment of diabetes and when assessing islet function in human transplants

Multicenter clinical trial of recombinant human insulin-like growth factor I in patients with acute renal failure

Multicenter clinical trial of recombinant human insulin-like growth factor I in patients with acute renal failure.BackgroundPatients with acute renal failure (ARF) have high morbidity and mortality rates, particularly if they have serious comorbid conditions. Several studies indicate that in rats with ARF caused by ischemia or certain nephrotoxins, insulin-like growth factor-I (IGF-I) enhances the recovery of renal function and suppresses protein catabolism.MethodsOur objective was to determine whether injections of recombinant human IGF-I (rhIGF-I) would enhance the recovery of renal function and is safe in patients with ARF. The study was designed as a randomized, double-blind, placebo-controlled trial in intensive care units in 20 teaching hospitals. Seventy-two patients with ARF were randomized to receive rhIGF-I (35 patients) or placebo (37 patients). The most common causes of ARF in the rhIGF-I and placebo groups were, respectively, sepsis (37 and 35% of patients) and hypotension or hemodynamic shock (42 and 27% of patients). At baseline, the mean (± sd) APACHE II scores in the rhIGF-I and placebo-treated groups were 24 ± 5 and 25 ± 8, respectively. In the rhIGF-I and placebo groups, the mean (median) urine volume and urinary iothalamate clearances (glomerular filtration rate) were 1116 ± 1037 (887) and 1402 ± 1183 (1430)ml/24hr and 6.4 ± 5.9 (4.3) and 8.7 ± 7.2 (4.4)ml/min and did not differ between the two groups. Patients were injected subcutaneously every 12hours with rhIGF-I, 100 μg/kg desirable body weight, or placebo for up to 14days. Injections were started within six days of the onset of ARF. The primary end-point was a change in glomerular filtration rate from baseline. Other end points included changes from baseline in urine volume, creatinine clearance and serum urea, creatinine, albumin and transferrin, frequency of hemodialysis or ultrafiltration, and mortality rate.ResultsDuring the treatment period, which averaged 10.7 ± 4.1 and 10.6 ± 4.5days in the rhIGF-I and placebo groups, there were no differences in the changes from baseline values of the glomerular filtration rate, creatinine clearance, daily urine volume, or serum urea nitrogen, creatinine, albumin or transferrin. In patients who did not receive renal replacement therapy, there was also no significant difference in serum creatinine and urea between the two groups. Twenty patients in the rhIGF-I group and 17 placebo-treated patients underwent dialysis or ultrafiltration. Twelve rhIGF-I–treated patients and 12 placebo-treated patients died during the 28days after the onset of treatment.ConclusionsrhIGF-I does not accelerate the recovery of renal function in ARF patients with substantial comorbidity

Patients' views on their decision making during inpatient rehabilitation after newly acquired spinal cord injury - A qualitative interview-based study

Introduction: Involving patients in decision making is a legal requirement in many countries, associated with better rehabilitation outcomes, but not easily accomplished during initial inpatient rehabilitation after severe trauma. Providing medical treatment according to the principles of shared decision making is challenging as a point in case for persons with spinal cord injury (SCI). Objectives: The aim of this study was to retrospectively explore the patients' views on their participation in decision making during their first inpatient rehabilitation after onset of SCI, in order to optimize treatment concepts. Methods: A total of 22 participants with SCI were interviewed in-depth using a semi-structured interview scheme between 6months and 35years post-onset. Interviews were transcribed verbatim and analysed with the Mayring method for qualitative content analysis. Results: Participants experienced a substantially reduced ability to participate in decision making during the early phase after SCI. They perceived physical, psychological and environmental factors to have impacted upon this ability. Patients mentioned regaining their ability to make decisions was an important goal during their first rehabilitation. Receiving adequate information in an understandable and personalized way was a prerequisite to achieve this goal. Other important factors included medical and psychological condition, personal engagement, time and dialogue with peers. Conclusion: During the initial rehabilitation of patients with SCI, professionals need to deal with the discrepancy between the obligation to respect a patient's autonomy and their diminished ability for decision making

New Insights into Metabolic Properties of Marine Bacteria Encoding Proteorhodopsins

Proteorhodopsin phototrophy was recently discovered in oceanic surface waters. In an effort to characterize uncultured proteorhodopsin-exploiting bacteria, large-insert bacterial artificial chromosome (BAC) libraries from the Mediterranean Sea and Red Sea were analyzed. Fifty-five BACs carried diverse proteorhodopsin genes, and we confirmed the function of five. We calculate that proteorhodopsin-exploiting bacteria account for 13% of microorganisms in the photic zone. We further show that some proteorhodopsin-containing bacteria possess a retinal biosynthetic pathway and a reverse sulfite reductase operon, employed by prokaryotes oxidizing sulfur compounds. Thus, these novel phototrophs are an unexpectedly large and metabolically diverse component of the marine microbial surface water