bluuebunny/crossref_metadata_2025_split huggingface dataset:
Choice of the primary analysis in longitudinal clinical trials
Authors: Mallinckrodt Craig H. , Watkin John G. , Molenberghs Geert , Carroll Raymond J. 
Published: September 2004

AbstractMissing data, and the bias they can cause, are an almost ever‐present concern in clinical trials. The last observation carried forward (LOCF) approach has been frequently utilized to handle missing data in clinical trials, and is often specified in conjunction with analysis of variance (LOCF ANOVA) for the primary analysis. Considerable advances in statistical methodology, and in our ability to implement these methods, have been made in recent years. Likelihood‐based, mixed‐effects model approaches implemented under the missing at random (MAR) framework are now easy to implement, and are commonly used to analyse clinical trial data. Furthermore, such approaches are more robust to the biases from missing data, and provide better control of Type I and Type II errors than LOCF ANOVA. Empirical research and analytic proof have demonstrated that the behaviour of LOCF is uncertain, and in many situations it has not been conservative. Using LOCF as a composite measure of safety, tolerability and efficacy can lead to erroneous conclusions regarding the effectiveness of a drug. This approach also violates the fundamental basis of statistics as it involves testing an outcome that is not a physical parameter of the population, but rather a quantity that can be influenced by investigator behaviour, trial design, etc. Practice should shift away from using LOCF ANOVA as the primary analysis and focus on likelihood‐based, mixed‐effects model approaches developed under the MAR framework, with missing not at random methods used to assess robustness of the primary analysis. Copyright © 2004 John Wiley & Sons, Ltd.
Type I error rates from likelihood‐based repeated measures analyses of incomplete longitudinal data
Authors: Mallinckrodt Craig H. , Kaiser Christopher J. , Watkin John G. , Detke Michael J. , Molenberghs Geert , Carroll Raymond J. 
Published: September 2004

AbstractThe last observation carried forward (LOCF) approach is commonly utilized to handle missing values in the primary analysis of clinical trials. However, recent evidence suggests that likelihood‐based analyses developed under the missing at random (MAR) framework are sensible alternatives. The objective of this study was to assess the Type I error rates from a likelihood‐based MAR approach – mixed‐model repeated measures (MMRM) – compared with LOCF when estimating treatment contrasts for mean change from baseline to endpoint (Δ). Data emulating neuropsychiatric clinical trials were simulated in a 4 × 4 factorial arrangement of scenarios, using four patterns of mean changes over time and four strategies for deleting data to generate subject dropout via an MAR mechanism. In data with no dropout, estimates of Δ and SEΔ from MMRM and LOCF were identical. In data with dropout, the Type I error rates (averaged across all scenarios) for MMRM and LOCF were 5.49% and 16.76%, respectively. In 11 of the 16 scenarios, the Type I error rate from MMRM was at least 1.00% closer to the expected rate of 5.00% than the corresponding rate from LOCF. In no scenario did LOCF yield a Type I error rate that was at least 1.00% closer to the expected rate than the corresponding rate from MMRM. The average estimate of SEΔ from MMRM was greater in data with dropout than in complete data, whereas the average estimate of SEΔ from LOCF was smaller in data with dropout than in complete data, suggesting that standard errors from MMRM better reflected the uncertainty in the data. The results from this investigation support those from previous studies, which found that MMRM provided reasonable control of Type I error even in the presence of MNAR missingness. No universally best approach to analysis of longitudinal data exists. However, likelihood‐based MAR approaches have been shown to perform well in a variety of situations and are a sensible alternative to the LOCF approach. MNAR methods can be used within a sensitivity analysis framework to test the potential presence and impact of MNAR data, thereby assessing robustness of results from an MAR method. Copyright © 2004 John Wiley & Sons, Ltd.
High‐performance liquid chromatography/electrospray ionization ion‐trap tandem mass spectrometric analysis and quantification of phosphatidylcholine molecular species in the serum of cystic fibrosis subjects supplemented with docosahexaenoic acid
Authors: Pacetti Deborah , Malavolta Marco , Bocci Fabio , Boselli Emanuele , Frega Natale G. 
Published: September 2004

AbstractSince phosphatidylcholine (PC) is the most abundant phospholipid (PL) class in human serum, its concentration represents an important marker for the evaluation of lipid absorption and metabolism. High‐performance liquid chromatography coupled on‐line with electrospray ionization ion‐trap tandem mass spectrometry (HPLC/ESI‐MS/MS) was successfully applied to the quantitative analysis of PC molecular species from serum of cystic fibrosis (CF) subjects before and after supplementation with docosahexaenoic acid (DHA). Seven molecular species of PC (containing C16:0/C20:4, C16:0/C22:6, C18:0/C20:4, C18:0/C22:6, C16:0/C18:1, C16:0/C18:2 and C18:0/C18:2, respectively) were quantified using MS in the negative scan mode with 1,2‐diundecanoyl‐sn‐glycero‐phosphocholine as the internal standard. The molecular species containing DHA, C16:0/C22:6 and C18:0/C22:6, increased from 41.3 ± 31.7 and 33.1 ± 18.2 to 85.4 ± 20.4 and 52.1 ± 20.7 μg/mL serum, respectively, after a 3‐month supplementation. Interestingly, the species containing arachidonic acid (C18:0/C20:4 and C16:0/C20:4) decreased from 115 ± 55 and 139 ± 57 to 58.1 ± 22.5 and 70.5 ± 28.1, respectively. HPLC/ESI‐MS/MS allowed the direct analysis of the lipid extract without previous purification of PLs, thus it is a useful analytical support in CF research in order to understand the extent of lipid dysfunctions typical of CF or other diseases. The present method might also be used for quantitative analysis of each serum phospholipid class molecular species. However, the instrument response was found to be very dependent on the phospholipid class considered, and thus the use of appropriate standards for each class of PLs is recommended. Copyright © 2004 John Wiley & Sons, Ltd.
Mathematical topographical correction of XPS images using multivariate statistical methods
Authors: Artyushkova Kateryna , Fulghum Julia E. 
Published: September 2004

AbstractFor rough heterogeneous samples, the contrast observed in XPS images may result from both changes in elemental or chemical composition and sample topography. Background image acquisition and subtraction are frequently utilized to minimize topographical effects so that images represent concentration variations in the sample. This procedure may significantly increase the data acquisition time. Multivariate statistical methods can assist in resolving topographical and chemical information from multispectral XPS images. Principal component analysis (PCA) is one method for identification of the highest correlation/variation between the images. Topography, which is common to all of the images, will be resolved in the first most significant component. The score of this component contains spatial information about the topography of the surface, whereas the loading is a quantitative representation of the topography contribution to each elemental/chemical image. The simple‐to‐use self‐modelling mixture analysis (Simplisma) method is a pure variable method that searches for the source of most differences in the data and therefore has the potential to distinguish between chemical and topographical phases in images. The mathematical background correction scheme is developed and validated by comparing results to the experimental background correction for samples with differing degrees of topography. Copyright © 2004 John Wiley & Sons, Ltd.
Porosity in ancient glass from Syria (c. 800 AD) using gas adsorption and atomic force microscopy
Authors: Lester E. , Hilal N. , Henderson J. 
Published: September 2004

AbstractGas adsorption and atomic force microscopy have been used to quantify and compare the porosity, surface area and surface characteristics of five samples from Raqqa in northern Syria dating to ca. 8th century AD. High‐quality high‐pressure liquid chromatography (HPLC) glass was also analysed to compare the results with these characteristics of modern glass. All five ancient samples were found to have some porosity across the microporous (up to 2 nm) and the mesoporous (2–50 nm) range. The reasons for this porosity are not entirely clear at present but are likely to be due to the manufacturing methods used, including the raw materials. A correlation was found between glass chemical composition (especially the total alkali) and pore size, inferring that the melting temperature is one of the parameters that affects the development of pores. The work in this paper presents the preliminary findings from the study of porosity in ancient glass. Copyright © 2004 John Wiley & Sons, Ltd.
Refinement in statechart testing
Authors: Bogdanov K. , Holcombe M. 
Published: September 2004

Abstract An existing statechart testing method developed by the authors allows a tester to show the equivalence of the behaviour of an implementation of some software system to its Harel statechart specification, by testing. This requires a rather large test set and satisfaction of certain requirements for both a specification and an implementation. Introduction of additional constraints permits reduction in a test set size, without weakening of the conclusions obtained by testing. This paper describes how a test set can be derived from a relatively big statechart and investigates the role of a few specific constraints in the reduction of test set size, depending on where in the system structure these constraints are used. The main contribution of the paper is a demonstration that enforcing relatively weak constraints in the right place of a system's structure makes it possible to reduce the size of a test set by many orders of magnitude. The practical use of the contribution is to help developers structure a system under construction in such a way that it is completely testable using the described testing method with few additional constraints. Copyright © 2004 John Wiley & Sons, Ltd.
The hybrid process that combines traditional requirements and use cases
Authors: Daniels Jesse , Bahill Terry 
Published: September 2004

AbstractFor many years systems engineers have produced traditional system requirements specifications containing shall‐statement requirements. The rapid adoption of use case modeling for capturing functional requirements in the software community has caused systems engineers to examine the utility of use case models for capturing system‐level functional requirements. A transition from traditional shall‐statement requirements to use case modeling has raised some issues and questions. This paper advocates a hybrid requirements process in which use case modeling and traditional shall‐statement requirements are applied together to effectively express both functional and nonfunctional requirements for complex, hierarchical systems. This paper also presents a practical method for extracting requirements from the use case text to produce a robust requirements specification. © 2004 Wiley Periodicals, Inc. Syst Eng 7: 303–319, 2004
Life‐history traits of standard and autochthonous cladocerans: II. Acute and chronic effects of acetylsalicylic acid metabolites
Authors: Marques Catarina R. , Abrantes Nelson , Gonçalves Fernando 
Published: September 2004

AbstractMetabolic products are often more toxic than their pharmacological parent compounds. Therefore, the acute and chronic effects of the main metabolites—salicylic acid (SAL), gentisic acid (GEN), and o‐hydroxyhippuric acid (HDP)—of acetylsalicylic acid (ASA), the active ingredient in Aspirin® and many other pharmaceuticals, were assessed using standard (Daphnia magna) and autochthonous (Daphnia longispina) cladocerans. The sequence of decreasing levels of acute and chronic toxicity of ASA metabolites to daphnids was GEN > SAL > HDP. HDP did not present acute toxicity, but chronic exposures enabled the production of abnormal neonates and, in particular, egg abortion. Thus, reproduction was the end point most susceptible to HDP. On the other hand, SAL and GEN induced changes in the normal patterns of reproduction and growth of both species. In general, D. longispina was more sensitive than was D. magna, although the population growth of the autochthonous species was superior under SAL exposures than that of the standard test species. Although the concentrations that were determined to have a toxic effect were above the levels detected in aquatic environmental samples, exposure to low levels of pharmacologically active substances for a duration longer than the test period may induce changes in nontarget organisms. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 527–540, 2004.
Elemental characterization of airborne particles in Khartoum, Sudan
Authors: El‐Tahir H. M. , Selin Lindgren Eva , Habbani F. I. 
Published: September 2004

AbstractThe aim of this study was to investigate the elemental composition of airborne particles in the Khartoum area, particularly small inhalable particles of diameter ≤10 µm. Aerosol particles were collected during the period April–May 2001. The sampling was done using a dichotomous virtual impactor capable of separating airborne particles <2.5 µm in a fine mode and 2.5–10 µm particles in a coarse mode. Energy‐dispersive x‐ray fluorescence analysis was used to determine the elemental concentrations of 14 elements in the samples. Concentrations of black carbon were also measured on the two size fractions. The results obtained were compared with previous data from Khartoum and other African locations. Si, K, Ca, Ti, Mn, Fe, Zn and Sr were found to be dominant in the collected particulates. Day period collections were found to have higher elemental concentrations than those of night periods. This is attributed to higher traffic levels and wind speeds. The results show that dust aerosol transport and resuspension are the main sources that affect the quality of ambient air in the Khartoum area. The elemental concentrations from anthropogenic sources are generally low. Copyright © 2004 John Wiley & Sons, Ltd.
Species discrimination of fish using frequency-dependent acoustic backscatter
Authors: Logerwell Elizabeth A. , Wilson Christopher D. 
Published: September 2004

Abstract
The difference between mean volume-backscattering strength at 120 and 38 kHz (ΔMVBS) has been used to discriminate acoustically between macrozooplankton species, and between macrozooplankton and fish or small zooplankton. We examined whether ΔMVBS could be used to discriminate between juvenile pollock (Theragra chalcogramma) and capelin (Mallotus villosus). Acoustic data at 38 and 120 kHz were collected in the Gulf of Alaska during August 2000 and 2001. We selected scattering layers of juvenile pollock and capelin that were sampled directly by midwater trawls. Although we found statistically significant differences at minimum integration thresholds ranging from −85 dB to −69 dB, the greatest difference between ΔMVBS of juvenile pollock and capelin was observed at the highest integration threshold (−69 dB). We also found that, although there was substantial overlap between the frequency distributions of juvenile pollock and capelin ΔMVBS at the smallest scale of analysis (0.1 nautical mile × 5 m cells), there was virtually no overlap between the ΔMVBS distributions at the largest scale (∼1 nautical mile × 20 m aggregations). We conclude that acoustic differencing at the scale of fish aggregations and at high integration thresholds can be used to distinguish between juvenile pollock and capelin.
Hearing Loss with Semicircular Canal Transection and Pseudomonas Aeruginosa Otitis Media
Authors: Prevatt Angela R. , Sedwick Jack D. , Gajewski Byron J. , Antonelli Patrick J. 
Published: September 2004

OBJECTIVETo determine if Pseudomonas aeruginosa (PA) otitis media (OM) increases the risk of sensorineural hearing loss (SNHL) with semicircular canal transection in the guinea pig model.METHODSPA was injected transtympanically into both middle ears of pigmented guinea pigs. Saline‐injected animals served as controls. Two to 4 days after injection, one horizontal semicircular canal was transected and sealed. Hearing was tested using electrocochleography before and after transection.RESULTSPA‐OM was induced in all PA‐injected ears. Five days after semicircular canal transection, click‐evoked thresholds were significantly elevated in ears with PA‐OM (P = 0.00009) but not in saline‐injected ears (P = 0.398).CONCLUSIONViolation of the inner ear in the presence of PA‐OM is associated with increased risk of SNHL in the guinea pig.SIGNIFICANCEFactors unique to PA infection may be responsible for SNHL with labyrinthine injury in humans with chronic otitis media.
Experimental Evaluation of Drills for Extended Frontal Sinusotomy
Authors: Hosemann Werner , Herzog Daniela , Beule Achim G. , Kaftan Holger 
Published: September 2004

OBJECTIVEEndonasal extended frontal sinusotomy is needed in rare cases of therapy‐resistant chronic frontal sinusitis. Several types of burs have been invented to ablate strong bone in the frontal sinus access but nevertheless surgical results seem to differ significantly. The benefits and shortcomings of different burs are subjected to a comparative evaluation.STUDY DESIGNFive cadaver specimens were duplicated by means of dental molding and casting techniques to provide identical microanatomy for comparative studies on frontal sinusotomy. Different burs (conventional straight bur, right‐angled bur according to Blokmanis, and curved frontal sinusbur) were applied to create a type IIb frontal sinusotomy according to Draf in microanatomical replicas. The geometry of the frontonasal neoostium was measured and its dimensions were contrasted to the collateral damage. Bone ablation was calculated by repeated weighting and the area of damaged mucosa was quantified using a 3D analyzing system.RESULTSA frontal sinus neoostium measuring 9 × 10 mm on average was created by type IIb frontal sinusotomy according to Draf. The complementary use of an angled bur showed some specific improvements that applied best to spacious anatomic specimens. Those specimens subjected to an extensive use of the straight drill revealed significant collateral damage forming a contrast to minor enlargement of the neoostium. The curved frontal sinus bur showed considerable technical insufficiencies.CONCLUSIONSJudicious use of the straight drill is recommended for those rare cases of therapy‐resistant frontal sinusitis treated by an extended type of frontal sinusotomy. New technical refinements of the curved frontal sinus burs should be subjected to repeated evaluation.
3D Computed Tomographic Analysis of Frontal Recess Anatomy in Patients Without Frontal Sinusitis
Authors: Lee Walter T. , Kuhn Frederick A. , Citardi Martin J. 
Published: September 2004

OBJECTIVEDescribe frontal sinus pneumatization in patients with no history of frontal sinus disease.STUDY DESIGN AND METHODSAll 1‐mm axial sinus CT scans performed from 2001 through 2003 were eligible for review on a CBYON Suite workstation (CBYON, Mountain View, CA). Exclusion criteria included frontal sinusitis, sinonasal polyposis, age < 18 years, sinus malignancy, fibroosseous lesions, maxillofacial trauma, congenital anomaly, and sinus surgery.RESULTSA total of 50 patients met the inclusion criteria. The prevalence of each structure was: agger nasi cell (89%), type 1 frontal cell (37%), type 2 frontal cell (19%), type 3 frontal cell (8%), type 4 frontal cell (0%), supraorbital ethmoid cell (62%), suprabullar cell (15%), frontal bullar cell (9%), interfrontal septal cell (14%), and recessus terminalis (22%).CONCLUSIONSThis study describes frontal pneumatization in patients without a history of conditions that influence frontal pneumatization. The results characterize normal frontal recess/sinus pneumatization patterns.
Evaluation of the Framelock Reference‐Arc Fixation Device for Image‐Guided Surgery
Authors: Strong E. Bradley , Diaz Rodney C. 
Published: September 2004

OBJECTIVESThe FrameLock (FL) is a bone anchored, reference arc fixation device for image guided surgery. This study compares the stability of the FL to the FESS frame (FF), a friction fit device.METHODSThe FL and FF were independently applied to a cadaver. Fifteen sequentially larger impulse forces were applied to each device (0.39–5.8 N*s). Following each impulse, anatomic drift was recorded. A 29 patient prospective clinical trial tested the accuracy of each device before and after surgery.RESULTSThe FL showed significantly less anatomic drift for all weights except 0.39 N*s (P < 0.01). The average clinical displacement of the FL was 0.07 mm, and of the FF was 1.02 mm (P < 0.0009). Linear regression analysis of anatomic drift as a function of the procedure duration revealed a positive correlation for the FF (y = 0.61x), but not for the FL (y = 0.02x).CONCLUSIONSThe bone anchored FL is significantly more stable than the friction fit FF.
Endoscopic and Endoscope‐Assisted Resections of Inverted Sinonasal Papillomas
Authors: Wolfe Stephen G. , Schlosser Rodney J. , Bolger William E. , Lanza Donald C. , Kennedy David W. 
Published: September 2004

OBJECTIVETo evaluate the success of endoscopic and endoscope‐assisted resection of inverted sinonasal papillomas and to assess the indications for adjunctive external procedures.STUDY DESIGNRetrospective chart review.RESULTSFifty patients were treated surgically during the 10‐year study period and had greater than 1 year of follow‐up care. These patients had a recurrence rate of 14% (7/50) with a mean follow‐up of 31.1 months. Of these 7 patients with recurrences, 3 were treated primarily at this institution, and 4 had been treated prior to referral. Recurrence was 11% (3/27) for primary resections and 17% (4/23) for secondary resections. Average time to recurrence was 11.7 months. Of the patients, 38% (19/50) had adjunctive external procedures either during the initial resection or for the management of recurrent disease.CONCLUSIONSEndoscopic and endoscope‐assisted resections of inverted papilloma are effective techniques for managing inverted papilloma. The intraoperative findings, most importantly the site(s) of tumor attachment, dictate whether an endoscopic procedure is sufficient to complete resect the inverted papilloma or whether an adjunctive external procedure is required. Appropriate patient selection and an aggressive surgical approach are necessary for the management of these neoplasms.