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Used First (used + first)
Selected AbstractsItem Selection in Computerized Adaptive Testing: Should More Discriminating Items be Used First?JOURNAL OF EDUCATIONAL MEASUREMENT, Issue 3 2001Kit-Tai Hau During computerized adaptive testing (CAT), items are selected continuously according to the test-taker's estimated ability. The traditional method of attaining the highest efficiency in ability estimation is to select items of maximum Fisher information at the currently estimated ability. Test security has become a problem because high-discrimination items are more likely to be selected and become overexposed. So, there seems to be a tradeoff between high efficiency in ability estimations and balanced usage of items. This series of four studies with simulated data addressed the dilemma by focusing on the notion of whether more or less discriminating items should be used first in CAT. The first study demonstrated that the common maximum information method with Sympson and Hetter (1985) control resulted in the use of more discriminating items first. The remaining studies showed that using items in the reverse order (i.e., less discriminating items first), as described in Chang and Ying's (1999) stratified method had potential advantages: (a) a more balanced item usage and (b) a relatively stable resultant item pool structure with easy and inexpensive management. This stratified method may have ability-estimation efficiency better than or close to that of other methods, particularly for operational item pools when retired items cannot be totally replenished with similar highly discriminating items. It is argued that the judicious selection of items, as in the stratified method, is a more active control of item exposure, which can successfully even out the usage of all items. [source] Continuous glucose monitoring and closed-loop systemsDIABETIC MEDICINE, Issue 1 2006R. Hovorka Abstract Background The last two decades have witnessed unprecedented technological progress in the development of continuous glucose sensors, resulting in the first generation of commercial glucose monitors. This has fuelled the development of prototypes of a closed-loop system based on the combination of a continuous monitor, a control algorithm, and an insulin pump. Method A review of electromechanical closed-loop approaches is presented. This is followed by a review of existing prototypes and associated glucose sensors. A literature review was undertaken from 1960 to 2004. Results Two main approaches exist. The extracorporeal s.c.,s.c. approach employs subcutaneous glucose monitoring and subcutaneous insulin delivery. The implantable i.v.,i.p. approach adopts intravenous sampling and intraperitoneal insulin delivery. Feasibility of both solutions has been demonstrated in small-scale laboratory studies using either the classical proportional,integral,derivative controller or a model predictive controller. Performance in the home setting has yet to be demonstrated. Conclusions The glucose monitor remains the main limiting factor in the development of a commercially viable closed-loop system, as presently available monitors fail to demonstrate satisfactory characteristics in terms of reliability and/or accuracy. Regulatory issues are the second limiting factor. Closed-loop systems are likely to be used first by health-care professionals in controlled environments such as intensive care units. [source] Selectivity and competitive interactions between two benthic invertebrate grazers (Asellus aquaticus and Potamopyrgus antipodarum): an experimental study using 13C- and 15N-labelled diatomsFRESHWATER BIOLOGY, Issue 2 2005N. ABERLE Summary 1. Tracer experiments with two diatoms labelled with 13C (Nitzschia palea) and 15N (Fragilaria crotonensis), were conducted to investigate feeding selectivity and interspecific competition between the grazers Asellus aquaticus (Isopoda, Crustacea) and Potamopyrgus antipodarum (Hydrobiidae, Gastropoda). Conventional methods, such as cell counts and estimated biovolume, were used first to detect feeding preferences within the different grazer treatments. 2. The results revealed a significant decline in algal biovolume in all grazer treatments and no indications of active selectivity were observed. In contrast to conventional methods, measurements based on isotope signatures showed strong differences in tracer uptake, thus indicating different degrees of assimilation and digestion by the two grazers. 3. The selectivity index Q, which provides information on the uptake ratio of 13C to 15N, showed a significant time effect for both grazer species and a significant difference between single- and mixed-grazer treatments for P. antipodarum. Thus, this technique enabled the direct quantification of the uptake by grazers and, therefore, served as an ideal tool for the detection of passive selectivity. 4. Our results indicate a shift in feeding preferences related to between-species competition and a potential divergence of trophic niches when species coexist. [source] Diagnosis of pancreatic cancerHPB, Issue 5 2006Fumihiko Miura Abstract The ability to diagnose pancreatic carcinoma has been rapidly improving with the recent advances in diagnostic techniques such as contrast-enhanced Doppler ultrasound (US), helical computed tomography (CT), enhanced magnetic resonance imaging (MRI), and endoscopic US (EUS). Each technique has advantages and limitations, making the selection of the proper diagnostic technique, in terms of purpose and characteristics, especially important. Abdominal US is the modality often used first to identify a cause of abdominal pain or jaundice, while the accuracy of conventional US for diagnosing pancreatic tumors is only 50,70%. CT is the most widely used imaging examination for the detection and staging of pancreatic carcinoma. Pancreatic adenocarcinoma is generally depicted as a hypoattenuating area on contrast-enhanced CT. The reported sensitivity of helical CT in revealing pancreatic carcinoma is high, ranging between 89% and 97%. Multi-detector-row (MD) CT may offer an improvement in the early detection and accurate staging of pancreatic carcinoma. It should be taken into consideration that some pancreatic adenocarcinomas are depicted as isoattenuating and that pancreatitis accompanied by pancreatic adenocarcinoma might occasionally result in the overestimation of staging. T1-weighted spin-echo images with fat suppression and dynamic gradient-echo MR images enhanced with gadolinium have been reported to be superior to helical CT for detecting small lesions. However, chronic pancreatitis and pancreatic carcinoma are not distinguished on the basis of degree and time of enhancement on dynamic gadolinium-enhanced MRI. EUS is superior to spiral CT and MRI in the detection of small tumors, and can also localize lymph node metastases or vascular tumor infiltration with high sensitivity. EUS-guided fine-needle aspiration biopsy is a safe and highly accurate method for tissue diagnosis of patients with suspected pancreatic carcinoma. 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been suggested as a promising modality for noninvasive differentiation between benign and malignant lesions. Previous studies reported the sensitivity and specificity of FDG-PET for detecting malignant pancreatic tumors as being 71,100% and 64,90%, respectively. FDG-PET does not replace, but is complementary to morphologic imaging, and therefore, in doubtful cases, the method must be combined with other imaging modalities. [source] Item Selection in Computerized Adaptive Testing: Should More Discriminating Items be Used First?JOURNAL OF EDUCATIONAL MEASUREMENT, Issue 3 2001Kit-Tai Hau During computerized adaptive testing (CAT), items are selected continuously according to the test-taker's estimated ability. The traditional method of attaining the highest efficiency in ability estimation is to select items of maximum Fisher information at the currently estimated ability. Test security has become a problem because high-discrimination items are more likely to be selected and become overexposed. So, there seems to be a tradeoff between high efficiency in ability estimations and balanced usage of items. This series of four studies with simulated data addressed the dilemma by focusing on the notion of whether more or less discriminating items should be used first in CAT. The first study demonstrated that the common maximum information method with Sympson and Hetter (1985) control resulted in the use of more discriminating items first. The remaining studies showed that using items in the reverse order (i.e., less discriminating items first), as described in Chang and Ying's (1999) stratified method had potential advantages: (a) a more balanced item usage and (b) a relatively stable resultant item pool structure with easy and inexpensive management. This stratified method may have ability-estimation efficiency better than or close to that of other methods, particularly for operational item pools when retired items cannot be totally replenished with similar highly discriminating items. It is argued that the judicious selection of items, as in the stratified method, is a more active control of item exposure, which can successfully even out the usage of all items. [source] A heuristic design procedure for water-using networks with multiple contaminantsAICHE JOURNAL, Issue 2 2009Zhi-Yong Liu Abstract On the analogy of the water-using networks with single contaminant, we will introduce new methodology concepts: the concentration potentials of the demand streams and those of the source streams in the water-using systems with multiple contaminants, based on the overall allocation possibility of the source streams to the demand streams. In the design procedure, the performing order of the processes is determined by the inlet concentration potentials of the processes. The processes with the lowest inlet concentration potential will be performed first. When satisfying the inlet stream of the process being performed, the source with the largest quasi-allocation amount, which is defined in this article, will be used first. A few literature examples are investigated to show the method proposed. The results show that the method proposed in this work is very simple and the freshwater consumptions of the designs obtained are very close to the minimum freshwater targets. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Review article: strategies to determine whether hypergastrinaemia is due to Zollinger,Ellison syndrome rather than a more common benign causeALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 10 2009S. V. M. MURUGESAN Summary Background, As there is considerable overlap between the fasting serum gastrin concentrations found in Zollinger,Ellison syndrome and various common conditions such as Helicobacter pylori infection and acid suppressing medication use, establishing the cause of hypergastrinaemia in individual cases can sometimes be difficult. Aim, To review the causes of hypergastrinaemia and the role of additional non-invasive investigations in hypergastrinaemic patients. Methods, Review of articles following a Pubmed search. Results, As gastrinomas may cause serious complications and be potentially life threatening, investigation of hypergastrinaemic patients should particularly focus on confirming or refuting the diagnosis of Zollinger,Ellison syndrome. Establishing the cause of hypergastrinaemia may be difficult when there is only a mild-to-moderate elevation of fasting serum gastrin concentration and concurrent treatment with proton pump inhibitor drugs and the presence of H. pylori infection can both confuse the clinical picture. A variety of provocative tests are therefore useful for establishing whether a hypergastrinaemic patient has a gastrinoma and current evidence suggests that the secretin test should be used first line. Conclusions, We suggest an algorithm for the investigation of patients found to have an elevated fasting serum gastrin concentration and address the roles of gastrin stimulation tests in current clinical practice. [source] A Delphi survey of patients' views of services for borderline personality disorder: A preliminary reportPERSONALITY AND MENTAL HEALTH, Issue 1 2008Daniel Webb Background,Department of Health guidelines stipulate that specialist personality disorder services should gather feedback from service users. Aim,The Gwylfa Therapy Service (GTS) is a new specialist service for people with borderline personality disorder (BPD). The aim of this study was to gather users' views of services sought and/or received before the inception of the GTS and their views of the GTS. Method,A Delphi survey method was used first to elicit patients' views on services, and then to identify levels of consensus on the views generated. Results,The findings presented here identify what service users value in the treatment they receive, namely respect, professionalism, a service that meets their needs and personal support. Opinions regarding non-specialist services indicated that, overall, police, general practitioners, community psychiatric nurses, psychologists and counsellors were viewed positively, and psychiatric hospital staff was viewed positively but with room for improvement. General hospital staff was viewed unfavourably. Users' views of the GTS were favourable. Discussion,This study begins to shed light upon the education, training and supervision needs of staff from services that come into contact with patients with BPD. Furthermore, the way these services may be better integrated with each other and GTS is identified as requiring attention. Care must be taken to avoid distressing, damaging and disaffecting patients as they pass through general services en route to a specialist team. Copyright © 2008 John Wiley & Sons, Ltd. [source] Geminin predicts adverse clinical outcome in breast cancer by reflecting cell-cycle progressionTHE JOURNAL OF PATHOLOGY, Issue 2 2004Michael A Gonzalez Abstract Geminin inhibits DNA replication by preventing Cdt1 from loading minichromosome maintenance (MCM) proteins onto DNA. The present study has investigated whether the frequency of geminin expression predicts clinical outcome in breast cancer. Immunohistochemistry was used first to examine geminin expression in normal and malignant breast tissue (n = 67). Correlations with cell-cycle parameters, pathological features, and clinical outcome were then determined using an invasive breast carcinoma tissue microarray (n = 165). Breast carcinomas were scanned for mutations (n = 61) and copy number imbalances (n = 241) of the geminin gene. Finally, the cell cycle distribution of geminin in breast cancer cells was investigated in vivo and in vitro. Despite a putative tumour suppressor function, it was found that increased geminin expression is a powerful independent indicator of adverse prognosis in invasive breast cancer. Both poor overall survival (p = 0.0002) and the development of distant metastases (p = 0.005) are predicted by high geminin expression, which performs better in this patient cohort than traditional factors currently used to determine prognosis and appropriate therapy. No mutations or deletions of the geminin gene and no evidence that a high frequency of protein expression is related to gene amplification were found. It is shown that geminin is expressed from S to M phase in breast carcinoma tissue and cell lines, disappearing at the metaphase,anaphase transition. While MCM proteins identify all non-quiescent cells, geminin identifies the sub-fraction that have entered S phase, but not exited mitosis, thereby indicating the rate of cell-cycle progression. It is suggested that this explains its unexpected value as a prognostic marker in breast cancer. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] A randomised crossover trial comparing the i-gel supraglottic airway and classic laryngeal mask airway,ANAESTHESIA, Issue 6 2009C. Janakiraman Summary In a randomised cross-over study, we compared the performance of the single use i-gel supraglottic airway and reusable classic laryngeal mask airway (cLMATM) in 50 healthy anaesthetised patients who were breathing spontaneously. Primary outcome was successful insertion at first attempt. Secondary outcomes included overall insertion success rate, ease of insertion, leak pressure and fibreoptic position. Success rate for insertion at the first attempt was significantly different (54% with i-gel vs 86% with cLMA; p = 0.001). Overall success after two attempts (when the anaesthetist was allowed to change the size of the device) improved to 84% with i-gel vs 92% with cLMA; p = 0.22. In 14 patients, the i-gel when used first needed to be replaced with a larger size. Leak pressure was higher for the i-gel (median [IQR] 20 [14,24] cm H2O than the cLMA 17 [12,22] cm H2O; p = 0.023). The fibreoptic view through the device was significantly better with the i-gel than the cLMA, which was statistically significant (p = 0.03). We conclude that, with its current sizing recommendations, the i-gel is not an acceptable alternative to cLMA. However because of the significantly improved success rate after a larger sized i-gel was used, we recommend the manufacturer to review the sizing guidelines to improve the success rate. [source] | ||||||||||