bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved liquid chromatography/mass spectrometric analysis of low molecular weight carboxylic acids by ion exclusion separation with electrospray ionization
Authors: Gamoh Keiji , Saitoh Hiroki , Wada Hiroo 
Published: March 2003

AbstractAn improved, simple and sensitive analytical method for low molecular weight organic acids has been developed. A mixture of acetic, propionic, butyric, glycolic, lactic, 2‐hydroxybutyric, malonic, succinic, glutaric, tartaric and citric acids was separated on a semi‐rigid styrene‐divinylbenzene copolymer‐based H‐type cation‐exchange resin (ULTRON PS‐80H) based on an ion exclusion chromatographic (IEC) mechanism, with detection using electrospray ionization mass spectrometry (ESI‐MS). Formic or acetic acid was used as a mobile phase to separate the carboxylic acids within 15 min. For liquid chromatography/mass spectrometry (LC/MS), the ESI interface was used in both positive and negative ionization mode. ESI produced reasonable signals from positive ions, [M+NH4]+, of acetic, propionic and butyric acids and from negative ions, [MH]−, of glycolic, lactic, 2‐hydroxybutyric, malonic, succinic, glutaric, tartaric and citric acids. The effects of ionization parameters, source temperature, capillary voltage and cone voltage, on sensitivity and linearity were examined. Linear plots of peak area versus concentration were obtained over the range 0.1–20 ppm for MS detection. The detection limits of the target carboxylic acids calculated at signal‐to‐noise (S/N) ratio of 3 ranged from 9 to 59 ppb. The reproducibility of retention times and peak areas were 0.55–1.25 and 0.85–2.45%, respectively. Copyright © 2003 John Wiley & Sons, Ltd.
Atmospheric pressure chemical ionisation reversed‐phase liquid chromatography/ion trap mass spectrometry of intact bacteriohopanepolyols
Authors: Talbot Helen M. , Squier Angela H. , Keely Brendan J. , Farrimond Paul 
Published: March 2003

AbstractAtmospheric pressure chemical ionisation liquid chromatography/multi‐stage ion trap mass spectrometry (APCI‐LC/MSn) has been applied to the study of intact bacteriohopanepolyols. Spectral characterisation of bacteriohopanepolyols of known structure present in bacterial extracts (Zymomonas mobilis and a fermenter containing methanotrophs including Methylococcus capsulatus) has revealed greater structural detail than previous liquid chromatography/mass spectrometry (LC/MS) methods and identified characteristic fragmentations indicative of numerous biohopanoid structures. Analysis of a Recent sedimentary extract from Lake Druzhby (Antarctica) has demonstrated the power of this technique to detect biohopanoids in complex samples including at least partial characterisation of previously unknown composite structures. Copyright © 2003 John Wiley & Sons, Ltd.
Tandem mass spectra of ammonium ion, metal ion and ligated metal ion adducts of acyclic sugar derivatives
Authors: Madhusudanan K. P. , Kumar B. , Pathak R. , Pant C. S. , Shaw A. K. 
Published: March 2003

AbstractThe tandem mass (MS/MS) spectra of ammonium ion, metal ion and ligated metal ion adducts of chain‐extended acyclic nitro‐containing deoxyglucose and deoxygalactose derivatives have been studied. The ammonium adducts fragment primarily by elimination of ammonia followed by acetic acid, thus not giving much structural information. In contrast, cationization of these compounds by metal ions and ligated metal ions gave structurally informative and useful fragment ions on MS/MS. The metal ions and ligated metal ions play an important role in controlling and directing fragmentation. Retro‐aldol fragmentation is facilitated by metal ions such as Li+, Na+, Ag+ and Cu+, whereas the adducts with higher alkali metal ions such as Rb+ and Cs+ fragment to give only the corresponding metal ions. The divalent metal ions such as Cu2+ and Ba2+ also induce retro‐aldol fragmentation. However, the charge is carried by the aldehyde fragment in the case of Cu2+ adducts, whereas the nitroalkane fragment carries the charge in the case of Ba2+ adducts. Ligated metal ions such as ZnCl+, CuCl+, InCl2+ and BaCl+ also behave similarly and induce retro‐aldol fragmentation in these acyclic sugars. Both the metal ion and ligated metal ion adducts can fragment by elimination of metal‐containing neutral molecules. Copyright © 2003 John Wiley & Sons, Ltd.
Learning environment, motivation, and achievement in high school science
Authors: Nolen Susan Bobbitt 
Published: March 2003

AbstractIn a study of the relationship between high school students' perceptions of their science learning environments and their motivation, learning strategies, and achievement, 377 students in 22 introductory science classrooms completed surveys in the fall and spring of their ninth‐grade year. Hierarchical linear regression was used to model the effects of variables at both the classroom and individual level simultaneously. High intraclass agreement (indicated by high parameter reliability) on all classroom environment measures indicated that students shared perceptions of the classroom learning environment. Controlling for other factors, shared perceptions that only the most able could succeed in science classrooms and that instruction was fast‐paced and focused on correct answers negatively predicted science achievement, as measured on a districtwide curriculum‐linked test. Shared perceptions that classrooms focused on understanding and independent thinking positively predicted students' self‐reported satisfaction with learning. Implications of these results for both teaching and research into classroom environments are discussed. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 347–368, 2003
High school students' ideas about theories and theory change after a biological inquiry unit
Authors: Sandoval William A. , Morrison Kathryn 
Published: March 2003

AbstractStudents' epistemological beliefs about scientific knowledge and practice are one important influence on their approach to learning. This article explores the effects that students' inquiry during a 4‐week technology‐supported unit on evolution and natural selection had on their beliefs about the nature of science. Before and after the study, 8 students were interviewed using the Nature of Science interview developed by Carey and colleagues. Overall, students held a view of science as a search for right answers about the world. Yet, the inconsistency of individuals' responses undermines the assumption that students have stable, coherent epistemological frameworks. Students' expressed ideas did not change over the course of the intervention, suggesting important differences between students' talk during inquiry and their abilities to talk epistemologically about science. Combined with previous work, our findings emphasize the crucial role of an explicit epistemic discourse in developing students' epistemological understanding. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 369–392, 2003
Intervention program to keep girls in the science pipeline: Outcome differences by ethnic status
Authors: Jayaratne Toby Epstein , Thomas Nancy G. , Trautmann Marcella 
Published: March 2003

AbstractThis study evaluated a 2‐week residential program aimed at enhancing the science interest and persistence of high‐achieving 8th‐grade girls. Questionnaires were administered to 38 program participants (14 of whom were of minority ethnicity) and 173 applicants who did not attend the program, at 3 time points: preprogram, 1 year postprogram, and 4 years postprogram. Outcomes, measured postprogram, included science self‐concept and interest, persistence and aspirations in science, science activities, science course‐taking in high school, and plans for a science college major. There was no main effect of program participation on any of the outcome measures, but a significant Participation × Ethnicity interaction effect occurred for all but one of the outcome variables. At Time 2, and especially Time 3, nonminority participants tended to have the most positive outcomes, whereas minority participants tended to have the most negative outcomes, compared with applicants. Post hoc analyses showed that although nonminority girls overall were more advantaged, this difference did not explain results. Several interpretations for these findings are discussed, the most likely that some global feature of the program, not any intervention component, interacted over time with the girls' postprogram experience. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 393–414, 2003
Cognitive factors affecting student understanding of geologic time
Authors: Dodick Jeff , Orion Nir 
Published: March 2003

AbstractA critical element of the earth sciences is reconstructing geological structures and systems that have developed over time. A survey of the science education literature shows that there has been little attention given to this concept. In this study, we present a model, based on Montagnero's (1996) model of diachronic thinking, which describes how students reconstruct geological transformations over time. For geology, three schemes of diachronic thinking are relevant: 1. Transformation, which is a principle of change; in geology it is understood through actualistic thinking (the idea that present proceeses can be used to model the past). 2. Temporal organization, which defines the sequential order of a transformation; in geology it is based on the three‐dimensional relationship among strata. 3. Interstage linkage, which is the connections between successive stages of a transformation; in geology it is based on both actualism and causal reasoning. Three specialized instruments were designed to determine the factors which influence reconstructive thinking: (a) the GeoTAT which tests diachronic thinking skills, (b) the TST which tests the relationship between spatial thinking and temporal thinking, and (c) the SFT which tests the influence of dimensional factors on temporal awareness. Based on the model constructed in this study we define the critical factors influencing reconstructive thinking: (a) the transformation scheme which influences the other diachronic schemes, (b) knowledge of geological processes, and (c) extracognitive factors. Among the students tested, there was a significant difference between Grade 9–12 students and Grade 7–8 students in their ability to reconstruct geological phenomena using diachronic thinking. This suggests that somewhere between Grades 7 and 8 it is possible to start teaching some of the logical principles used in geology to reconstruct geological structures. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 415–442, 2003
The lung‐to‐head ratio and fetoscopic temporary tracheal occlusion: prediction of survival in severe left congenital diaphragmatic hernia
Authors: Keller R. L. , Glidden D. V. , Paek B. W. , Goldstein R. B. , Feldstein V. A. , Callen P. W. , Filly R. A. , Albanese C. T. 
Published: March 2003

AbstractObjectivesTo evaluate the reliability of sonographic lung‐to‐head ratio (LHR) measurement as a predictor of survival in fetuses with congenital diaphragmatic hernia (CDH) and to compare the probability of survival in those with temporary tracheal occlusion (TO) or standard care with respect to the LHR.MethodsFifty‐six fetuses with left CDH with liver herniated into the thorax at complete prenatal evaluation were included in logistic regression analyses of antenatal predictors of survival to hospital discharge. Sixteen subjects underwent TO and 40 received standard care.ResultsLHR was a significant predictor of survival, with probability of survival increasing with increasing LHR (odds ratio (OR) 8.5, P = 0.04). When subjects with anomalies were excluded, the LHR effect was similar after adjustment for TO (OR 7.1, P = 0.11). Linear spline models suggested a plateau in survival at an LHR of 1.0 and all models suggested increased odds of survival with TO. Minimum LHR measurements had a high degree of inter‐ and intraobserver agreement (intraclass correlation coefficients of 0.70 and 0.80, respectively).ConclusionsCalculation of the LHR in fetuses with CDH is a reliable and powerful predictor of survival to hospital discharge, although improving odds of survival may plateau at an LHR of 1.0. TO may have an independent benefit on survival to hospital discharge. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
The role of fetal nuchal translucency and ductus venosus Doppler at 11–14 weeks of gestation in the detection of major congenital heart defects
Authors: Favre R. , Cherif Y. , Kohler M. , Kohler A. , Hunsinger M.‐C. , Bouffet N. , Tanghe M. , Cancellier M. , Nisand I. 
Published: March 2003

AbstractObjectiveTo determine whether, in a selected high‐risk population, Doppler velocimetry of the ductus venosus can improve the predictive capacity of increased nuchal translucency in the detection of major congenital heart defects in chromosomally normal fetuses at 11–14 weeks of gestation.MethodsDuctus venosus Doppler ultrasound blood velocity waveforms were obtained prospectively at 11–14 weeks of gestation in 1040 consecutive singleton pregnancies. Waveforms were classified either as normal in the presence of a positive A‐wave, or as abnormal if the A‐wave was absent or negative. All cases were screened for chromosomal defects by a combination of maternal age and fetal nuchal translucency thickness. In 484 cases karyotyping was performed. Those fetuses found to be chromosomally normal by prenatal cytogenetic analysis, and which had abnormally increased nuchal translucency and/or abnormal ductus venosus Doppler velocimetry, underwent fetal echocardiography at 14–16 weeks of gestation. Ultrasound examination was repeated at 22–24 weeks of gestation in all women. The sensitivity, specificity and positive and negative predictive values for the detection of major cardiac defects of increased nuchal translucency thickness alone, ductus venosus Doppler alone and increased nuchal translucency thickness in association with abnormal ductus venosus Doppler were determined.ResultsIn 29 of 998 fetuses presumed to be chromosomally normal, reversed or absent flow during atrial contraction was associated with increased (> 95
th
centile for crown–rump length) nuchal translucency. Major cardiac defects were observed in 9 of these 29 fetuses. No other major cardiac abnormalities were found in chromosomally normal fetuses in spite of the presence of either increased nuchal translucency alone or abnormal ductus venosus velocimetry. A total of 25 cardiac malformations were observed in the population. Fifteen were associated with aneuploidy and 10 fetuses had a normal karyotype. Nine of the 10 had major cardiac anomalies and one had a ventricular septal defect. The nine cases with normal karyotype and major cardiac anomalies had both increased nuchal translucency and abnormal ductus venosus flow velocity waveforms.ConclusionIn chromosomally normal fetuses with increased nuchal translucency, assessment of ductus venosus blood flow velocimetry could improve the predictive capacity for an underlying major cardiac defect. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Fetal brain/liver volume ratio and umbilical volume flow parameters relative to normal and abnormal human development
Authors: Boito S. , Struijk P. C. , Ursem N. T. C. , Fedele L. , Wladimiroff J. W. 
Published: March 2003

AbstractObjectivesTo estimate fetal brain volume from head circumference and published postmortem data; to determine normal values for the fetal brain/liver volume ratio relative to gestational age; to establish the relationship between the brain/liver volume ratio and fetal circulatory parameters during normal and restricted (SGA) fetal growth.Patients and MethodThis was a cross‐sectional study involving a total of 47 uncomplicated pregnancies appropriate‐for‐gestational age (AGA) and 23 pregnancies resulting in the delivery of a SGA fetus. At enrollment gestational age ranged between 20 and 36 weeks in both groups. Umbilical venous cross‐sectional area and time‐averaged velocity for calculation of volume flow as well as velocity waveforms from the umbilical artery, middle cerebral artery and ductus venosus, were recorded. Fetal liver volume measurements were obtained using three‐dimensional ultrasound. Fetal brain volume was estimated from fetal head volume following comparison with published postmortem data on fetal brain weight.ResultsA significant correlation was observed between prenatally estimated fetal head volume and postmortem fetal brain volume. Fetal brain volume was approximately half that of fetal head volume. The normal fetal brain/liver volume ratio demonstrated a significant reduction with gestational age (R = −0.54; P < 0.001). The normal mean ± standard
deviation (SD) fetal brain/liver volume ratio (3.4 ± 0.7) was significantly different (P < 0.001) from the mean fetal brain/liver volume ratio in the SGA group (n = 23) (5.9 ± 1.9). A significant difference existed for mean umbilical venous volume flow between AGA (104.7 ± 26.9 mL/min/kg) and SGA (59.6 ± 22.7 mL/min/kg) fetuses. In the SGA fetus, there was a significant inverse relationship (P < 0.001) between fetal weight‐related umbilical venous volume flow and fetal brain/liver volume ratio. In a subset of 16 SGA and 16 AGA fetuses matched for gestational age, a significant difference existed for umbilical artery pulsatility index (2.30 ± 1.52 vs. 0.99 ± 0.19), fetal middle cerebral artery pulsatility index (1.3 ± 0.4 vs. 2.1 ± 0.3) and late diastolic flow velocity in the fetal ductus venosus (6.9 ± 14.2 cm/s vs. 23.9 ± 8.8 cm/s), but not for peak systolic, early diastolic and time‐averaged velocity in the ductus venosus.ConclusionSonographic estimates of fetal brain volume can be obtained. The fetal brain/liver volume ratio is a predictor of fetal outcome in the growth‐restricted fetus. An inverse relationship exists in SGA fetuses between brain/liver volume ratio and fetal weight‐related umbilical venous blood flow. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
First‐trimester diagnosis and management of pregnancies implanted into the lower uterine segment Cesarean section scar
Authors: Jurkovic D. , Hillaby K. , Woelfer B. , Lawrence A. , Salim R. , Elson C. J. 
Published: March 2003

AbstractObjectiveTo describe first‐trimester ultrasound diagnosis and management of pregnancies implanted into uterine Cesarean section scars.MethodsAll women referred for an ultrasound scan because of suspected early pregnancy complications were screened for pregnancies implanted into a previous Cesarean section scar. The management of Cesarean section scar pregnancies included transvaginal surgical evacuation, medical treatment with local injection of 25 mg methotrexate into the exocelomic cavity and expectant management.ResultsEighteen Cesarean section scar pregnancies were diagnosed in a 4‐year period. The prevalence in the local population was 1 : 1800 pregnancies. Surgical treatment was used in eight women and it was successful in all cases. The respective success rates of medical treatment and expectant management were 5/7 (71%) and 1/3 (33%). Five women (28%) required blood transfusion and one woman (6%) had a hysterectomy.ConclusionsCesarean section scar pregnancies are more common than previously thought. When the diagnosis is made in the first trimester the prognosis is good and the risk of hysterectomy is relatively low. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Contraction stress test versus ductus venosus Doppler evaluation for the prediction of adverse perinatal outcome in growth‐restricted fetuses with non‐reassuring non‐stress test
Authors: Figueras F. , Martínez J. M. , Puerto B. , Coll O. , Cararach V. , Vanrell J. A. 
Published: March 2003

AbstractObjectiveTo compare Doppler evaluation of the ductus venosus and contraction stress test (CST) in the prediction of adverse perinatal outcome in growth‐restricted fetuses with evidence of hemodynamic redistribution and a non‐reactive non‐stress test (NST).MethodsData were collected from all singleton pregnancies seen in our Fetal Surveillance Unit who underwent antenatal monitoring for fetal growth restriction, non‐reactive NST and arterial redistribution beyond 26 weeks of pregnancy. Patients were divided into four groups based on their CST and ductus venosus waveform results. Perinatal outcome was evaluated by means of four variables: the need for admission to the neonatal intensive care unit (NICU), need for neonatal intubation, an umbilical artery pH < 7.10 and significant neonatal morbidity. Outcome was compared among fetuses delivered within 3 days of their antenatal test. Logistic regression analysis was used to analyze the relation between predictive and outcome variables.ResultsSixty‐eight women met the inclusion criteria for the study. The positive predictive value of the CST was 45% for admission to the NICU, 13% for significant neonatal morbidity, 26% for need of neonatal intubation and 29% for umbilical artery pH < 7.10. The positive predictive values of abnormal ductus venosus waveform (ADVW) were 81.5%, 26%, 48% and 55%. Groups with ADVW showed significantly poorer neonatal outcome. No significant differences were observed when CST results were compared. Logistic regression analysis showed that both gestational age at delivery and ADVW significantly predict the occurrence of adverse perinatal outcome.ConclusionIn growth‐restricted fetuses with hemodynamic redistribution and a non‐reassuring NST, Doppler assessment of the ductus venosus correlates with adverse perinatal outcome. In this clinical situation there is no benefit of CST in terms of prediction. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
The interobserver reliability and validity of volume calculation from three‐dimensional ultrasound datasets in the in vitro setting
Authors: Raine‐Fenning N. J. , Clewes J. S. , Kendall N. R. , Bunkheila A. K. , Campbell B. K. , Johnson I. R. 
Published: March 2003

AbstractObjectivesThe primary aim of this validation study was to determine the interobserver reliability and validity of measurements of phantom objects of known volume using conventional and rotational techniques of volume calculation according to measurement technique.MethodsTwo observers each acquired a single three‐dimensional ultrasound dataset of three water‐filled objects of different size and shape. The same two observers measured all six datasets using both the conventional technique and the newer rotational technique (Virtual Organ Computer‐aided AnaLysis, VOCAL™) of volume calculation. Reliability was assessed by calculating intraclass correlation coefficients (ICC) and validity by examining the percentage difference from the ‘true’ volume, as determined by a water displacement technique, by the limits of agreement method.ResultsAll of the techniques were highly reliable (ICC: 0.9962–0.9997) and valid to within 4% of the ‘true’ volumes. There were no significant differences in reliability according to measurement plane or between observers. Measurements made with the 6° rotation step were significantly more reliable than those made by all other techniques with the exception of the 9° rotation step (P < 0.05) and significantly more valid than those made with the 30° rotation step or conventional technique (P < 0.05).ConclusionsVolume calculation in the in vitro setting is both reliable and valid but is dependent upon the technique applied, with rotational measurements of volume proving superior to conventional techniques. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.