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Time Changes (time + change)
Selected AbstractsTime Changes for Lévy ProcessesMATHEMATICAL FINANCE, Issue 1 2001Hélyette Geman The goal of this paper is to consider pure jump Lévy processes of finite variation with an infinite arrival rate of jumps as models for the logarithm of asset prices. These processes may be written as time-changed Brownian motion. We exhibit the explicit time change for each of a wide class of Lévy processes and show that the time change is a weighted price move measure of time. Additionally, we present a number of Lévy processes that are analytically tractable, in their characteristic functions and Lévy densities, and hence are relevant for option pricing. [source] Placebo-controlled, double-blind dose-finding study of entacapone in fluctuating parkinsonian patients,MOVEMENT DISORDERS, Issue 1 2007Yoshikuni Mizuno MD Abstract We conducted a multicenter randomized, placebo-controlled double-blind parallel-group study in Japanese Parkinson's disease (PD) patients with wearing-off motor fluctuations to determine the clinical efficacy and safety of entacapone as an adjunct to concomitant treatment with levodopa and a dopa decarboxylase inhibitor (DCI). We randomized 341 patients to receive entacapone 100 or 200 mg or placebo per dose of levodopa/DCI for 8 weeks. The primary efficacy variable was on time change while awake, determined by patients' diaries. Mean baseline on time in each group was approximately 8 hours. Mean on time change at final assessment was 1.4 hours each for entacapone 100-mg and 200-mg groups and by 0.5 hours for the placebo group (P < 0.05). The two entacapone doses were equally efficacious. Adverse events occurred in 79 patients (69.9%) in placebo, 82 (72.6%) in 100 mg, and 98 (86.0%) in 200 mg. The most common adverse event with entacapone was an increase in dyskinesias. The overall safety profile was satisfactory in both entacapone groups. In conclusion, both entacapone 100 and 200 mg were equally effective in increasing on time of PD patients with wearing-off fluctuations, although the safety and tolerability profile appeared more favorable for the 100-mg dose. © 2006 Movement Disorder Society [source] Real time monitoring of drug metabolic enzyme response inside human hepatoma GS-3A4-HepG2 cells by means of electrochemical impedance measurementPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2004Masaaki Kobayashi Abstract Cytochrome P-450s (CYPs) are important biopolymers for the maintenance of cellular function. If metabolic activity of the CYP in the cells can be estimated, so can the function of metabolism, which is closer to the organism. In this research, the method of measuring the drug metabolic activity inside the cell by making use of an electrochemical technique was examined. Human hepatoma GS-3A4-HepG2 cells of which the cytochrome P-4503A4 (CYP3A4) drug metabolic activity is found to be the same as that of primary hepatocytes were used in the experiment. The GS-3A4-HepG2 cells were cultured on an indium-tin oxide (ITO) electrode until they became confluent. Substrate testosterone and inhibitor ketoconazole of CYP3A4 were exposed to cells cultured on an ITO electrode, and the reaction was observed by noting the electrochemical impedance measurement. Impedance was decomposed into the resistance component and the reactance component, and each was examined in detail. As a result, according to testosterone concentration change, there was a remarkable time change in the reactance component. A similar impedance measurement was done by using human hepatoma HepG2 cells in which the drug metabolic activity had extremely decreased. Nevertheless, no time change in the reactance component that was noticed in GS-3A4-HepG2 cells was observed. Next, the amount of metabolite in the solution after impedance measurement was measured by means of liquid chromatography-tandem mass spectroscopy (LC-MS/MS). In the experiment with GS-3A4-HepG2 cells, a testosterone concentration-dependent correlation was observed between the reactance component change and the amount of metabolite. But, in the impedance measurement by ketoconazole, the change in reactance components was not observed in either the GS-3A4-HepG2 cells or the HepG2 cells. Ketoconazole and the heme iron in CYP3A4 effect the coordination bond, but ketoconazole was not metabolized by CYP3A4. It was confirmed that the time change in the reactance component which was caused by the testosterone was detected neither in the cells that take up the substrate, nor in the coordination bond between the CYP enzyme and the drug. Therefore, the time change in the remarkable reactance component observed by this electrochemical impedance measurement is dependent on drug metabolic activity. An electrochemical drug metabolic activity measuring method with the human hepatoma GS-3A4-HepG2 cells was able to be established. Copyright © 2004 John Wiley & Sons, Ltd. [source] Precipitation trends over the Russian permafrost-free zone: removing the artifacts of pre-processingINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2001Pavel Ya. Abstract Rain gauge changes, changes in the number of observations per day, and inconsistent corrections to observed precipitation data during the 20th century of the meteorological network of the former Soviet Union make it difficult to address the issue of century time-scale precipitation changes. In this paper, we use daily and sub-daily synoptic data to account for the effects of these changes on the instrumental homogeneity of precipitation measurements over the Russian permafrost-free zone (RPF, most populous western and central parts of the country). Re-adjustments that were developed during this assessment allow us to (a) develop a system of scale corrections that remove the inhomogeneity owing to wetting/observation time changes over most of the former Soviet Union during the past century, and (b) to estimate precipitation trends over the RPF, reconciling previously contradictory results. The trend that emerges is an increase of about 5% per century. This estimate can be further refined after a more comprehensive set of supplementary data (precipitation type and wind) and metadata (information about the exposure of meteorological sites) is employed. Copyright © 2001 Royal Meteorological Society [source] Writing the reflexive self: an autoethnography of alcoholism and the impact of psychotherapy cultureJOURNAL OF PSYCHIATRIC & MENTAL HEALTH NURSING, Issue 7 2010A. GRANT ba (hons) ma phd cert res meth pgctlhe, enb 650 cert Accessible summary ,,Experimental ethnography allows for the use of fiction in writing. Fiction both enables the preservation of anonymity in accounts based on real people and events and breaks down the barrier between art and science in ethnographic work. The use of fiction, which should not be regarded as synonymous with falsehood, arguably facilitates telling tales in a dramatic and enjoyable way. It is also a useful way of ,writing the self', so that the researcher and the researched become one and the same. Writing the self means using fiction and other literary tools to both construct and clarify the person being written about. In the case of autoethnography, this person is both the researcher and the researched. ,,The short story, which forms the heart of this paper, is based on the author's battle with alcoholism over two decades. It utilizes literary devices, including poetry, time changes, and moves from describing the main protagonist in the story in first to third person. The story describes the author's experiences of feeling increasingly stigmatized and treated as ,other' by members of the humanistic counselling and therapy fraternity. ,,The paper draws to an end with a theoretical discussion of the development of selfhood in society, including the ways in which alcoholic selves can become stigmatized and ,othered'. The author invites readers to contribute towards ending ,us,them' divisions. Abstract Experimental ethnography enables the use of fictionalized accounts that celebrate partial truths and challenge realist and positivist ethnographic authority. Literary devices drawn from fiction arguably allow social researchers to better portray real events. Fiction, which should not be regarded as synonymous with falsehood, enables the telling of tales in dramatic and enjoyable ways. In this account , an autoethnography of alcoholism and the impact of therapy culture , the author's intention is not to make claims for a final word or closure on the topics raised, and juxtaposed with appropriate social theory. It is rather hoped that the text will trigger further meaning creation on the part of the reader and, in terms of praxis, contribute towards creating a kinder and more humane mental health nursing and therapy practice and in the ,off duty' world. [source] Estrogen-Dependent Enhancement of NO Production in the Nucleus Tractus Solitarius Contributes to Ethanol-Induced Hypotension in Conscious Female RatsALCOHOLISM, Issue 2 2009Guichu Li Background:, Our previous pharmacological and cellular studies showed that peripheral (cardiac and vascular) nitric oxide synthase (NOS)-derived NO is implicated in the estrogen (E2)-dependent hypotensive action of ethanol in female rats. The objective of this study was to test the hypothesis that enhanced NO production in the nucleus tractus solitarius (NTS) is implicated in the E2 -dependent hypotensive action of ethanol. Methods:, To achieve this goal, we utilized in vivo electrochemistry to measure real time changes in neuronal NO to investigate the acute effects of intragastric ethanol (0, 0.5, or 1 g/kg) on NO in NTS neurons, blood pressure (BP), and heart rate (HR) in conscious female rats in the absence (ovariectomized, OVX, rats) or presence of E2. Results:, In sham operated (SO) rats, ethanol elicited dose-related increase in NTS NO and reduction in BP. These neurochemical and BP effects of ethanol were absent in OVX rats. Whether the neurochemical effect of ethanol and the associated hypotension are dependent on rapid E2 signaling was investigated. In OVX rats pretreated, 30 minutes earlier, with E2 (1 ,g/kg), intragastric ethanol (1 g/kg) increased NTS NO and reduced BP and these responses were comparable to those obtained in SO rats. Conclusions:, The present findings suggest that increased production of NO in NTS neurons contributes to ethanol-evoked hypotension in female rats. Further, ethanol enhancement of neuronal NO production in the brainstem is dependent on rapid E2 signaling. [source] Nuclear magnetic resonance water relaxation time changes in bananas during ripening: a new mechanismJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2010Fayene Zeferino Ribeiro Abstract BACKGROUND: Nuclear magnetic resonance studies of banana fragments during ripening show an increase on the water transverse relaxation time (T2) and a decrease in water self-diffusion coefficient (D). As T2 and D are normally directly correlated, we studied these two properties in intact bananas during ripening, in an attempt to rule out the effect of injury on the apparent discrepancies in the behavior of T2 and D. RESULTS: The results show that injury in bananas causes a decrease in T2 of the water in vacuoles (T2vac). They also show that T2vac increased and D decreased during ripening, ruling out the injury effect. To explain the apparent discrepancies, we propose a new hypothesis for the increase in T2 values, based on the reduction of Fe3+ ions to Fe2+ by galacturonic acid, produced by the hydrolysis of pectin and a decrease in internal oxygen concentration during ripening. CONCLUSION: As injury alters T2 values it is necessary to use intact bananas to study relaxation times during ripening. The novel interpretation for the increase in T2vac based on reduction of Fe+3 and O2 concentration is an alternative mechanism to that based on the hydrolysis of starch in amyloplasts. Copyright © 2010 Society of Chemical Industry [source] Delayed changes in T1 -weighted signal intensity in a rat model of 15-minute transient focal ischemia studied by magnetic resonance imaging/spectroscopy and synchrotron radiation X-ray fluorescenceMAGNETIC RESONANCE IN MEDICINE, Issue 3 2006Xuxia Wang Abstract Previous studies have found that rats subjected to 15-min transient middle cerebral artery occlusion (MCAO) show neurodegeneration in the dorsolateral striatum only, and the resulting striatal lesion is associated with increased T1 -weighted (T1W) signal intensity (SI) and decreased T2 -weighted (T2W) SI at 2,8 weeks after the initial ischemia. It has been shown that the delayed increase in T1W SI in the ischemic region is associated with deposition of paramagnetic manganese ions. However, it has been suggested that other mechanisms, such as tissue calcification and lipid accumulation, also contribute to the relaxation time changes. To clarify this issue, we measured changes in relaxation times, lipid accumulation, and elemental distributions in the brain of rats subjected to 15-min MCAO using MRI, in vivo 1H MR spectroscopy (MRS), and synchrotron radiation X-ray fluorescence (SRXRF). The results show that a delayed (2 weeks after ischemia) increase in T1W SI in the ischemic striatum is associated with significant increases in manganese, calcium, and iron, but without evident accumulation of MRS-visible lipids or hydroxyapatite precipitation. It was also found that 15-min MCAO results in acutely reduced N-acetylaspartate (NAA)/creatine (Cr) ratio in the ipsilateral striatum, which recovers to the control level at 2 weeks after ischemia. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Opposite Effects of Myocardial Stretch and Verapamil on the Complexity of the Ventricular Fibrillatory Pattern: An Experimental StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2000FRANCISCO J. CHORRO CHORRO, F.J., et al.: Opposite Effects of Myocardial Stretch And Verapamil on The Complexity of The Ventricular Fibrillatory Pattern: An Experimental Study. An experimental model is used to analyze the effects of ventricular stretching and verapamil on the activation patterns during VF. Ten Langendorff-perfused rabbit hearts were used to record VF activity with an epicardial multiple electrode before, during, and after stretching with an intraventricular balloon, under both control conditions and during verapamil (Vp) infusion (0.4,0.8 ,mol). The analyzed parameters were dominant frequency (FrD) spectral analysis, the median (MN) of the VF intervals, and the type of activation maps during VF (I = one wavelet without block lines, II = two simultaneous wavelets with block lines, III = three or more wavelets with block lines). Stretch accelerates VF (FrD: 22.8 ± 6.4 vs 15.2 ± 1.0 Hz, P < 0.01; MN: 48 ± 13 vs 68 ± 6 ms, P < 0.01). On fitting the FrD time changes to an exponential model after applying and suppressing stretch, the time constants (stretch: 101.2 ± 19.6 s; stretch suppression: 97.8 ± 33.2 s) do not differ significantly. Stretching induces a significant variation in the complexity of the VF activation maps with type III increments and type I and II decrements (control: I = 17.5%, II = 50.5%, III = 32%; stretch: I = 7%, II = 36.5%, III = 56.5%, P < 0.001). Vp accelerates VF (FrD: 20.9 ± 1.9 Hz, P < 0.001 vs control; MN: 50 ± 5 ms, P < 0.001 vs control) and diminishes activation maps complexity (I = 25.5%, II = 60.5%, III = 14%, P < 0.001 vs control). On applying stretch during Vp perfusion, the fibrillatory process is not accelerated to any greater degree. However, type I and II map decrements and type III increments are recorded, though reaching percentages similar to control (I = 16.5%, II = 53%, III = 30.5%, NS vs control). The following conclusions were found: (1) myocardial stretching accelerates VF and increases the complexity of the VF activation pattern; (2) time changes in the FrD of VF during and upon suppressing stretch fit an exponential model with similar time constants; and (3) although stretching and verapamil accelerate the VF process, they exert opposite effects upon the complexity of the fibrillatory pattern. [source] | ||||||||||