323,156 research outputs found
Towards a methodology for measuring the true degree of efficiency in a speculative market
No full textBetting markets have drawn much attention in the economics, finance and operational research literaturebecause they provide a valuable window on the manner in which individuals use information in widerfinancial markets. One question that has received particular attention is to what extent individualsdiscount information in market prices. The predominant approach to explore this issue involvespredictive modeling to forecast market outcomes and examining empirically whether abnormal returnscan be made by employing these forecasts. It is argued here that present practices to assess suchforecasting models, including the use of point estimates and information, which would not be availablein practice (at the forecasting stage) and failing to update forecasting models with information from therecent past, may give rise to misleading conclusions regarding a market’s informational efficiency.Hypotheses are developed to conceptualize these views and are tested by means of extensive empiricalexperimentation using real-world data from the Hong Kong horserace betting market. Our studyidentifies several sources of bias and confirms that current practices may not be relied upon. A moreappropriate modeling procedure for assessing the true degree of market efficiency is then proposed
Unilateral lesion of the pedunculopontine nucleus induces hyperactivity in the subthalamic nucleus and substantia nigra in the rat
No full textRecent data suggest a role for the pedunculopontine nucleus (PPN) in the pathophysiology of Parkinson's disease. Although there is anatomical evidence that the PPN and the basal ganglia are reciprocally connected, the functional importance of these connections is poorly understood. Lesioning of the PPN was shown to induce akinesia in primates, whereas in the 6-hydroxydopamine rat model the PPN was found to be hyperactive. As both nigrostriatal dopamine depletion and lesioning of the PPN were shown to induce akinesia and parkinsonism, the present study was performed in order to investigate the changes in neuronal activity of the subthalamic nucleus (STN) and the substantia nigra pars reticulata (SNr) after unilateral ibotenic acid lesioning of the PPN and after unilateral 6-hydroxydopamine lesioning of the substantia nigra pars compacta (SNc). The firing rate of STN neurones significantly increased from 10.2 +/- 6.2 (mean +/- SD) to 14.6 +/- 11.7 spikes/s after lesion of the PPN and to 18.6 +/- 14.5 spikes/s after lesion of the SNc. The activity of the SNr significantly increased from 19.6 +/- 10.5 to 28.7 +/- 13.4 spikes/s after PPN lesioning and to 23.5 +/- 10.8 spikes/s after SNc lesioning. Furthermore, PPN lesion decreased the number of spontaneously firing dopaminergic SNc cells, while having no effect on their firing rate. The results of our study show that lesion of the PPN leads to hyperactivity of the STN and SNr, similar to the changes induced by lesion of the SNc. Moreover, the decreased activity of SNc cells observed after PPN lesion might be at the origin of activity changes in the STN and SNr
A primer of simple theories
No full textAbstract. We present a self-contained exposition of the basic aspects of simple theories while developing the fundamentals of forking calculus. We expound also the deeper aspects of S. Shelah’s 1980 paper Simple unstable theories. The concept of weak dividing has been replaced with that of forking. The exposition is from a contemporary perspective and takes into account contributions due to S. Buechler, E. Hrushovski, B. Kim, O. Lessmann, S. Shelah and A. Pillay
Allergic contact dermatitis caused by lidocaine and latex gloves?
No full textA 65 year old man suffered from edema of his penis and scrotum 30 min after investigation of the bladder using a Tiemann catheter, natural latex gloves, and Instillagel as lubricant. The skin lesions lasted for 2 days. This reaction occurred a second time after catheterization of the bladder. At first the diagnosis of a latex allergy was assumed. To confirm this diagnosis, skin prick tests and intracutaneous tests using natural latex milk extracts were performed. The intracutaneous tests turned out to be positive. The specific IgE for latex was analyzed using the CAP method and showed a positive result (1.42 KU/l,CAP class 2). To prove the clinical relevance of these findings, a provocation test was performed by wearing natural latex gloves for 30 min. Surprisingly, the provocation test caused no symptoms, indicating that, at present, the patient suffers from latex sensitization rather than a clinically relevant natural latex allergy. Further investigation of other suspected agents, such as the catheter and the lubricant, revealed that lidocaine, a component of Instillagel, was the substance most presumably responsible for causing the skin reactions. Additional patch tests with different local anesthetics confirmed these findings. We were also able to demonstrate a skin reaction to cinchocaine. Despite the similarity in the side chains the observed patch test reactions are not to be interpreted as immunological cross-reactions. Hypersensitivity to local anesthetics is a rare phenomenon, whereas natural latex allergy is frequent. Therefore, when the apparent symptoms are more plausibly explained by a more common disease (e.g., latex allergy),the likeliest diagnosis of a bona fide allergy to local anesthetics could easily be missed. However, the correct diagnosis is of particular importance to patients,as contact dermatitis to local anesthetics could sometimes also induce immediate type reactions when applied parenterally. This case demonstrates unequivocally that all suspected substances should be investigated by different diagnostic methods, including provocation tests, in order to make the right diagnosis
Patch testing with p-toluene diamine preparations of different ages
No full textAnalyses of the stability of 1% p-toluene diamine (PTD) in petrolatum used for patch testing showed a rapid decline of the PTD concentration down to 0.1%, possibly due to the generation of dye complexes. To study whether the diagnostic quality of this test preparation is compromised by the chemical reactions taken place, a multicentre study was conducted by the German Contact Dermatitis Research Group (DKG), comparing patch test results in 177 patients with simultaneously tested PTD preparations of different ages. During the 10-month course of this study, the age of the batches ranged from 2 to 11 months for batch A, from 7 to 16 months for batch B and from 11 to 20 months for batch C. There were no statistically significant differences between reactions to batches A and B, A and C, and B and C. Agreement of patch test reactions to the 3 batches was very good and comparable to the general reproducibility of patch test with standard allergens. The chemical reactions mentioned above apparently do not affect the diagnostic quality of PTD patch test preparations because the true allergen probably is not PTD itself, but one or more of the reaction products
IVDK data 2008-2013: Analysis of questionnaire and patch test results with regard to p-phenylenediamine (PPD) sensitization and cross-reactions
No full textIVDK data 2008-2013: Analysis of questionnaire and patch test results with regard to p-phenylenediamine (PPD) sensitization and cross-reactions
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Lesion of the pedunculopontine nucleus reverses hyperactivity of the subthalamic nucleus and substantia nigra pars reticulata in a 6-hydroxydopamine rat model
No full textThe pedunculopontine nucleus (PPN) and the subthalamic nucleus (STN) are reciprocally connected by excitatory projections. In the 6-hydroxydopamine (6-OHDA) rat model the PPN was found to be hyperactive. Similarly, the STN and the substantia nigra pars reticulata (SNr) showed increased activity in Parkinson's disease (PD) animal models. A lesion of the STN was shown to restore increased activity levels in the SNr of 6-OHDA-treated rats. As the STN and the PPN were reciprocally connected by excitatory projections and both structures were shown to be hyperactive in PD animal models, the present study was performed in order to investigate the changes in neuronal activity of the STN and SNr under urethane anesthesia after unilateral ibotenic acid lesioning of the PPN in animals with previous unilateral 6-OHDA lesions of the substantia nigra pars compacta (SNc). The firing rate of STN neurons significantly increased from 10.3 +/- 0.6 spikes/s (mean +/- SEM) to 17.8 +/- 1.8 spikes/s after SNc lesion and returned to normal levels of 10.8 +/- 0.7 spikes/s after additional lesion of the PPN. Similarly, the firing rate of SNr neurons significantly increased from 19.0 +/- 1.1 to 25.9 +/- 1.4 spikes/s after SNc lesion, the hyperactivity being reversed after additional PPN lesion to 16.8 +/- 1.2 spikes/s. The reversal of STN and SNr hyperactivity of 6-OHDA-treated rats by additional PPN lesion suggests an important modulatory influence of the PPN on STN activity. Moreover, these findings could indicate a new therapeutic strategy in PD by interventional modulation of the PPN
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