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Selected AbstractsTourism demand modelling: some issues regarding unit roots, co-integration and diagnostic testsINTERNATIONAL JOURNAL OF TOURISM RESEARCH, Issue 5 2003Paresh Kumar Narayan Abstract This paper investigates the all important issue of diagnostic tests, including unit roots and cointegration, in the tourism demand modelling literature. The origins of this study lie in the apparent lack in the tourism economics literature of detail concerning the diagnostic test aspect. Study of this deficiency has suggested that previous literature on tourism demand modelling may be divided into two categories: the pre-1995 and post-1995 studies. It was found that the pre-1995 and some post-1995 studies have ignored unit root tests and co-integration and, hence, are vulnerable to the so-called ,spurious regression' problem. In highlighting the key diagnostic tests reported by post-1995 studies, this paper contends that there is no need to report the autoregressive conditional heteroskedasticity (ARCH) test, which is applicable only to financial market analysis where the dependent variable is return on an asset. More generally, heteroskedasticity is not seen as a problem in time-series data. However, the reporting of a greater than necessary range of diagnostic tests,,,some of which do not have any theoretical justification with regard to tourism demand analysis,,,does not diminish the precision of the results or the model. This paper should appeal to scholars involved in tourism demand modelling. Copyright © 2003 John Wiley & Sons, Ltd. [source] Robustness of time-scale learning of robot motions to uncertainty in acquired knowledgeJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 10 2001C.C. Cheah A disadvantage of present iterative learning control algorithms is that they are generally applicable only in cases where a certain task is performed over and over again. Consequently, if knowledge or control inputs acquired from learning a task can be used on similar tasks, learning will be more efficient. Recently, several methods for constructing the control input of a new motion based on the control inputs acquired from previous learning of similar tasks have been proposed. However, these methods assumed that the perfect control inputs could be obtained from the previous learning. In practice, the control inputs could never be obtained exactly from learning in the presence of certain uncertainties such as disturbance and measurement noises. In addition, it is also not known for sure how the basic motion patterns should be chosen for learning. In this article, the robustness problem of the time-scale learning control to uncertainty in the acquired learning control inputs is formulated and solved. From the analysis, certain new insights such as its implication to choices of basic motion patterns for time-scale learning will be discussed. Simulation results of a 3-link robot are presented to illustrate the analysis. © 2001 John Wiley & Sons, Inc. [source] Copper nitrate trihydrate catalyzed efficient synthesis of bis(indolyl)methanes in acetonitrile at room temperatureJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2007Aayesha Nasreen A catalytic amount of easily available and inexpensive Cu(NO3)3.3H2O (10 mol%) enables electrophilic substitution reaction of indole with structurally divergent aldehydes in acetonitrile to afford the corresponding bis(indolyl)methanes in moderate to excellent yields (65-98%) at ambient temperature. The reaction is highly chemoselective and applicable only to aldehydes and not to ketones. [source] Volume of distribution at steady state for a linear pharmacokinetic system with peripheral eliminationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2004Leonid M. Berezhkovskiy Abstract The problem of finding the steady-state volume of distribution Vss for a linear pharmacokinetic system with peripheral drug elimination is considered. A commonly used equation Vss,=,(D/AUC)*MRT is applicable only for the systems with central (plasma) drug elimination. The following equation, Vss,=,(D/AUC)*MRTint, was obtained, where AUC is the commonly calculated area under the time curve of the total drug concentration in plasma after intravenous (iv) administration of bolus drug dose, D, and MRTint is the intrinsic mean residence time, which is the average time the drug spends in the body (system) after entering the systemic circulation (plasma). The value of MRTint cannot be found from a drug plasma concentration profile after an iv bolus drug input if a peripheral drug exit occurs. The obtained equation does not contain the assumption of an immediate equilibrium of protein and tissue binding in plasma and organs, and thus incorporates the rates of all possible reactions. If drug exits the system only through central compartment (plasma) and there is an instant equilibrium between bound and unbound drug fractions in plasma, then MRTint becomes equal to MRT,=,AUMC/AUC, which is calculated using the time course of the total drug concentration in plasma after an iv bolus injection. Thus, the obtained equation coincides with the traditional one, Vss,=,(D/AUC)*MRT, if the assumptions for validity of this equation are met. Experimental methods for determining the steady-state volume of distribution and MRTint, as well as the problem of determining whether peripheral drug elimination occurs, are considered. The equation for calculation of the tissue,plasma partition coefficient with the account of peripheral elimination is obtained. The difference between traditionally calculated Vss,=,(D/AUC)*MRT and the true value given by (D/AUC)*MRTint is discussed. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1628,1640, 2004 [source] Rheological Investigation of Shear Induced-Mixing and Shear Induced-Demixing for Polystyrene/Poly(vinyl methyl ether) BlendMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2004Samy A. Madbouly Abstract Full Paper: The phase behavior of polystyrene (PS) and poly(vinyl methyl ether) (PVME) blend has been investigated rheologically as a function of temperature, composition and oscillating shear rate as well as different heating rates. An LCST (lower critical solution temperature)-type phase diagram was detected rheologically from the sudden changes in the slopes of the dynamic temperature ramps of G, at given heating and shear rate values. The rheological cloud points were dependent on the heating rate, , and oscillating shear rate, . The cloud points shifted a few degrees to higher temperatures with increasing and reached an equilibrium value (heating rate independent) at ,°C/min. The phase diagrams of the blends detected at ,=,0.1 and 1 rad/s were located in lower temperature ranges than the quiescent phase diagram, i.e., oscillating shear rate induced-demixing at these two values for the shear rate. On the other hand, at ,=,10 rad/s, the phase diagram shifted to higher temperatures, higher than the corresponding values found under quiescent conditions, i.e., shear induced-mixing took place. Based on these two observations, shear induced-demixing and shear induced-mixing can be detected rheologically within a single composition at low and high shear rate values, respectively, and this is in good agreement with the previous investigation using simple shear flow techniques. In addition, the William, Landel and Ferry (WLF)-superposition principle was found to be applicable only in the single-phase regime; however, the principle broke-down at a temperature higher than or equal to the cloud point. Furthermore, different spinodal phase diagrams were estimated at different oscillating shear rates based on the theoretical approach of Ajji and Choplin. Spinodal phase diagrams at different oscillating shear rates. [source] Prediction of oxygen transmission rate for thermoformed traysPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2004Marit KvalvÅg Pettersen Abstract There is a desire in the food industry to be able to estimate the oxygen transmission rate (OTR) of packages by knowing the permeability data of unconverted sheet/film, instead of measuring the OTR of packages. Due to thermoforming, the permeability of a material changes and therefore it is difficult to estimate the permeability (OTR) of converted trays from the OTR values of unconverted material. This paper evaluates the possibilities and limitations of predicting the OTR of thermoformed trays. Different methods for the calculation of OTR due to thickness measurements were compared. The use of theoretical thickness was satisfactory in the calculation of OTR of trays based on the OTR of unconverted sheet, area and thickness. Both linear and quadratic regression models were evaluated. Validation of the regression models was made by comparing the measured and calculated OTR of trays made of PS/EVOH/PE, A-PET/PE, PS/PE and PP/PE. These trays were manufactured on different thermoforming machines, different processing parameters and different sizes of mould. None of the models (linear and quadratic) were suitable for the calculation of OTR of trays made of PS/PE and PP/PE. Both linear and quadratic models gave satisfactory agreement with measured values for trays made of both PS/EVOH/PE and A-PET/PE. This case study indicates that a general equation for the calculation of OTR for different polymer combinations was not possible to generate. The equations presented in this paper are strictly applicable only for the polymer combinations used in this experiment, and can not be considered as general equations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Are common symptoms in childhood associated with chronic widespread body pain in adulthood?: Results from the 1958 british birth cohort studyARTHRITIS & RHEUMATISM, Issue 5 2007Gareth T. Jones Objective Studies have shown that common symptoms in childhood predict the onset of chronic widespread pain in the short term. However, it is unknown whether this association persists into adulthood. The aim of the current study was to examine, prospectively, whether children with common symptoms experience an increased risk of chronic widespread pain as adults. Methods Information on vomiting/bilious attacks, abdominal pain, and headaches/migraine was collected on 10,453 7-year-old children, by maternal report. Similar data were gathered when the children were ages 11 years and 16 years. Body pain at age 45 years was assessed by postal questionnaire. Poisson regression was used to examine chronic widespread pain in relation to childhood symptom reporting. Results Of the 10,453 subjects on whom data were obtained when they were children, 7,470 participated at age 45 years (71.5%). Children with multiple symptoms at age 7 years experienced a 50% increased risk of chronic widespread pain (relative risk 1.5 [95% confidence interval 1.03, 2.3]). This relationship persisted after adjustment for sex, recent psychological distress, and childhood and current socioeconomic status, and after excluding children with major illnesses that might have explained early symptom reporting. A similar relationship with symptoms at ages 11 and 16 years was observed, although this was not associated with additional risk compared with that found with the presence of symptoms at age 7 years. However, despite a modest increase in risk, the presence of multiple symptoms at early ages was uncommon (<1.5%), and therefore, the associated population attributable risk was low (<1%). Conclusion Multiple common symptoms in childhood are associated with an increased risk of chronic widespread pain in adulthood. However, the magnitude of this increased risk is modest, and reports of multiple symptoms in childhood are uncommon. Thus the "early pain pathway" phenomenon is applicable only to a small proportion of individuals with chronic widespread pain. [source] Vereinfachtes Verfahren zur Vorhersage des Langzeitverhaltens von Holz-Beton-VerbundkonstruktionenBAUTECHNIK, Issue 4 2005Ralf Avak Prof. Dr.-Ing. Für die Bemessung von nachgiebig verbundenen Biegeträgern aus Holz und Beton wird vom praktisch tätigen Ingenieur in der Regel das ,-Verfahren bevorzugt. Das Verfahren ist Bestandteil nationaler, sowie europäischer Holzbauvorschriften [4], [5]. Für die Berechnung des Langzeitverhaltens ist das ,-Verfahren in seiner derzeitigen Form jedoch nur bedingt geeignet, da es z. B. das Schwinden des Betons nicht berücksichtigt. Im folgenden wird aus diesem Grund ein einfaches analytisches Verfahren vorgestellt, bei dem neben dem Kriechverhalten der Materialien Holz und Beton auch deren Schwind- bzw. Quellverformungen sowie das Langzeitverhalten der Schubverbindungsmittel berücksichtigt werden können. Die Anwendung des Verfahrens ist momentan noch auf Innenbauteile beschränkt. Simplified procedure for the description from the long-term behaviour of timber-concrete composite structures. The ,-procedure is favoured to design timber-concrete composite structures. This procedure is component of current national as well as European timber standards [4], [5]. The ,-procedure isn't suitable to describe the long-term behaviour, because it does not consider the shrinkage of concrete for example. A simplified procedure is introduced in the following. This procedure considers creeping of timber and concrete and , for the first time , swelling and shrinkage of these materials, as well as the long-term behaviour of the shear connectors. Currently it is applicable only to inner structures. [source] Pretherapy quantitative measurement of circulating Epstein,Barr virus DNA is predictive of posttherapy distant failure in patients with early-stage nasopharyngeal carcinoma of undifferentiated typeCANCER, Issue 2 2003Sing-fai Leung M.D. Abstract BACKGROUND Patients with International Union Against Cancer (UICC) Stage I,II nasopharyngeal carcinoma (NPC) appear to have a relatively favorable prognosis and generally are excluded from trials of combined modality treatment. More recently, plasma/serum cell-free Epstein-Barr virus (EBV) DNA has been shown to be measurable in the majority of NPC patients at the time of diagnosis, and appears to have prognostic significance. However, within Stage I-II disease, in which failure events are infrequent, the prognostic impact of the pretreatment EBV DNA level has not been addressed to our knowledge. This issue has management implications because different therapeutic strategies currently are employed for patients with good-risk and those with poor-risk NPC. METHODS A cohort of 90 patients with UICC Stage I-II NPC (World Health Organization Grade 2/3 histology) had their pretherapy plasma/serum EBV DNA levels determined by a quantitative polymerase chain reaction assay and correlated with the probability of posttherapy failure. All patients received radiation therapy only, except for three patients who also received concurrent chemotherapy. Kaplan,Meier plots of the probability of locoregional failure, distant failure, and cancer-specific survival were compared with reference to clinical stage and EBV DNA levels. RESULTS With a median follow-up time of 45 months, 12 patients and 7 patients, respectively, had developed locoregional and distant failures, including 2 patients with both local and distant failures. Patients with distant failure had significantly higher pretherapy EBV DNA levels than those without failure (a median of 13,219 copies/mL [interquatile-range, 274,635 copies/mL] vs. a median of 423 copies/mL [interquatile-range, 2753 copies/mL]). The probability of distant failure was significantly higher in patients with high (> 4000 copies/mL plasma) compared with low EBV DNA levels (P = 0.0001, log-rank test) and for Stage IIB disease compared with Stage I and Stage IIA disease combined (P = 0.0149, log-rank test), but was not significantly different between patients with Stage II and those with Stage I disease. The risks of locoregional failure were not significantly different between patients with high and those with low EBV DNA levels, and also was not significantly different between clinical substages. Approximately 35% of patients with Stage IIB disease were in the at-risk group for distant failure, as identified by high EBV DNA levels. CONCLUSIONS Within a group of patients with UICC Stage I-II NPC, the pretherapy plasma EBV DNA level was found to identify a poor-risk group with a probability of distant failure similar to that of patients with advanced stage disease. This group of patients may warrant management considerations currently applicable only to cases of Stage III-IV disease. The prognostic significance of designating Stage IIB disease as per the 1997 UICC staging was confirmed, although the pretherapy EBV DNA level appears to be a more powerful prognostic discriminator in patients with early-stage NPC. Cancer 2003;98:288,91. © 2003 American Cancer Society. DOI 10.1002/cncr.11496 [source] Effectiveness and cost of bisphosphonate therapy in tumor bone diseaseCANCER, Issue S3 2003Jean-Jacques Body M.D., Ph.D. Abstract BACKGROUND Tumor-induced osteolysis due to breast carcinoma and myeloma is responsible for a considerable morbidity that severely impairs patients'quality of life. Osteoclast-mediated bone resorption is reported to be increased markedly in patients with tumor bone disease and can be inhibited by bisphosphonate therapy. METHODS The incidence of skeletal complications and the effectiveness of bisphosphonate therapy in patients with breast carcinoma metastatic to bone or in those with myeloma were derived from large-scale, long-term, placebo-controlled trials with clodronate or pamidronate. To the authors' knowledge, there are few studies published to date evaluating the cost-effectiveness of bisphosphonate therapy, and the majority that do exist often are based on models and are applicable only to a particular health care system. RESULTS From the placebo groups of the above-mentioned trials, one can estimate that approximately 25,40% of the patients with breast carcinoma metastatic to bone will require radiotherapy for bone pain and approximately 17,50% will sustain incident vertebral fractures yearly. The incidence of complications is reported to be lower in myeloma patients. The prolonged administration of bisphosphonates reportedly can reduce the frequency of skeletal-related events by approximately 25,50%. Maximal efficacy appears to have been achieved with the current therapeutic schemes based on monthly intravenous infusions. Beneficial effects appear to be obtained more readily using the intravenous route rather than the oral route. The costs of bisphosphonate therapy appear to be higher than the cost savings from the prevention of skeletal-related events. The costs per quality of life-adjusted year have been estimated to be > $100,000, but more research is needed. Limited data suggest that zoledronic acid will not reduce treatment costs but the short infusion time will lead to substantial time savings for patients and for outpatient oncology facilities. CONCLUSIONS As is the case for many agents used in oncology, bisphosphonates remain a relatively expensive therapy. More studies are needed to evaluate their cost-effectiveness ratio correctly. A ceiling effect has been reached with current therapeutic schemes and tailoring therapy to the individual patient needs to be evaluated correctly to increase therapeutic effectiveness and improve quality of life further without increasing treatment costs. Cancer 2003;97(3 Suppl):859,65. © 2003 American Cancer Society. DOI 10.1002/cncr.11139 [source] | ||||||||||||||||