bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and properties of thio‐containing poly(ether ether ketone)s
Authors: Wang Yen‐Zen , Lin Chih‐Hung , Chan Bor‐Wen , Hsieh Kuo‐Huang 
Published: February 2004

AbstractA series of thio‐containing poly(ether ether ketone) (PEESK) polymers was synthesized by the introduction of thio groups from 4,4′ thiodiphenol (TDP) into the poly(ether ether ketone) (PEEK) structure via reaction between the phenol and aromatic fluoride groups. The effect of the thio groups on the properties of the PEESK materials was investigated. Differential scanning calorimetry (DSC) analysis and X‐ray diffraction (XRD) patterns show a depression in the crystallinity of the PEESKs with incorporation of the content of thio groups in the backbones. The crystalline structure was identified as an orthorhombic structure with lattice constants of a = 7.52 Å, b = 5.86 Å and c = 10.24 Å for all crystallizable PEESKs. The crystalline structures of the thio‐containing PEEK polymers were the same as that of the neat PEEK, which means the thio‐containing block in the whole thio‐containing PEEK molecule is almost excluded from the crystalline structure and the crystals are completely formed by ‘non‐thio’ blocks only. Due to the glass transition temperature (Tg) and melting temperature (Tm) depression with increase in the TDP content in the reaction system, the processability of the resultant thio‐containing PEEKs could be effectively improved. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of ABA‐type block copolymers of trimethylene carbonate and ϵ‐caprolactone
Authors: Jia Yong Tang , Kim Hak Yong , Gong Jian , Lee Duok Rae , Ding Bin , Bhattarai Narayan 
Published: February 2004

AbstractThis paper describes the synthesis of a series of ABA‐type triblock copolymers of trimethylene carbonate and ϵ‐caprolactone with various molar ratios and analyses the thermal and mechanical properties of the resulting copolymers. The structures of the triblock copolymers were characterized by 1H and 13C nuclear magnetic resonance spectroscopy, FT‐IR spectroscopy and gel permeation chromatography. Results obtained from the various characterization methods proves the successful synthesis of block copolymers of trimethylene carbonate and ϵ‐caprolactone. The thermal properties of the block copolymers were investigated by differential scanning calorimetry. The Tm and ΔHm values of the copolymers decrease with increasing content of trimethylene carbonate units.Two Tgs were found in the copolymers. Furthermore, both of the Tg values increased with increasing content of trimethylene carbonate units. The mechanical properties of the resulting copolymers were studied by using a tensile tester. The results indicated that the mechanical properties of the block copolymers are related to the molar ratio of trimethylene carbonate and ϵ‐caprolactone in the copolymers, as well as the molecular weights of the resulting copolymers. The block copolymer with a molar composition of 50/50 possessed the highest tensile stress at maximum and modulus of elasticity. Block copolymers possessing different properties could be obtained by adjusting the copolymer compositions. Copyright © 2004 Society of Chemical Industry
Grafting of vinyl acetate onto low density polyethylene—starch biodegradable films for printing and packaging applications
Authors: Ghosh RN , Jana T , Ray BC , Adhikari Basudam 
Published: February 2004

AbstractStarch‐based biodegradable low‐density polyethylene (LDPE) films were used for graft copolymerization of vinyl acetate with ceric ammonium nitrate (CAN) in aqueous acidic medium as redox initiator with nitric acid. The extent of grafting was examined by Fourier‐transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR) spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The objective behind the grafting of vinyl acetate onto the LDPE–starch biodegradable films is to make these suitable for printing and packaging applications without affecting the biodegradability of the original films. Copyright © 2004 Society of Chemical Industry
Structure and mechanical properties of polysulfone‐based in situ composites
Authors: García M , Eguiazábal JI , Nazábal J 
Published: February 2004

AbstractComposites based on the polysulfone of bisfenol A (PSF) and a liquid‐crystalline copolyester (Rodrun 5000) were obtained by two processing methods, (1) direct injection moulding (DI) and (2) extrusion followed by injection moulding (PI), across the whole composition range. The blends were immiscible and showed two pure amorphous phases. The inferior mechanical properties of PI blends, and their more difficult processing, meant that the PI procedure is not suitable in these blends. The generally linear relationship of the Young's modulus of the DI blends is due to the counteracting effects of the large orientation of the skin and its low thickness. The improvement in notched impact strength of PSF on the addition of small amounts of LCP indicated an important reduction in its notch sensibility. The tensile strength behaviour was close to linearity, with the exception of the 20/80 blend in which it was synergistic. This had been seen in previous thermoplastic/LCP blends, and depicts a behaviour reminiscent of rubber‐toughened blends. Copyright © 2004 Society of Chemical Industry
Use of temperature‐modulated DSC in kinetic analysis of a catalysed epoxy–anhydride system
Authors: Montserrat S , Pla X 
Published: February 2004

AbstractThe curing kinetics of a catalysed epoxy‐anhydride system was studied by temperature‐modulated differential scanning calorimetry. The chemical‐controlled regime was analysed by empirical kinetic equations. The diffusion‐controlled regime was detected by the diffusion factor, DF(α,T), which was calculated from the ratio of the experimental rate to the chemical reaction rate. DF(α,T) was compared with a mobility factor, MF(α,T), which was obtained by measuring the modulus of the complex heat capacity |Cp*|. The equivalence of the two factors allowed the diffusion‐controlled regime to be studied using the |Cp*| signal. However, the results obtained in the epoxy–anhydride system showed a limitation to the method, and this is discussed in terms of the modulation period necessary for the variation in MF(α,T) to occur in the same conversion interval as does DF(α,T). Copyright © 2004 Society of Chemical Industry
Polyaniline prepared in the presence of various acids: a conductivity study
Authors: Stejskal Jaroslav , Hlavatá Drahomíra , Holler Petr , Trchová Miroslava , Prokeš Jan , Sapurina Irina 
Published: February 2004

AbstractPolyaniline (PANI) was prepared by the oxidation of aniline in the presence of various inorganic and organic acids at 20 °C and −50 °C. When strong acids were used, the conductivity of the protonated PANI was typically 1–10 S cm−1. The results indicate that the protonation of PANI in media containing carboxylic acids was achieved with the help of sulfuric acid produced during the reaction with ammonium peroxydisulfate. The conductivity of PANI prepared under such conditions was reduced. Partial benzene‐ring sulfonation has been proposed to explain the wide range in conductivity of PANI bases, 10−11–10−7 S cm−1. The densities of the samples reflect the nature of the acid used. The densities of the corresponding PANI bases exhibit much less variation. Molecular weight and degree of crystallinity of PANI are higher when the polymerization is carried out at −50 °C. The conductivity of the PANI is determined mainly by way of protonation. The effects of molecular weight and of crystallinity on PANI conductivity are marginal. Copyright © 2004 Society of Chemical Industry
Morphological and thermal characterization of interpolymer complexes and blends based on poly(acrylic acid) and hydroxypropylcellulose
Authors: Khutoryanskiy Vitaliy V , Cascone Maria Grazia , Lazzeri Luigi , Barbani Niccoletta , Nurkeeva Zauresh S , Mun Grigoriy A , Dubolazov Artem V 
Published: February 2004

AbstractInterpolymer complexes and blends were prepared based on poly(acrylic acid) and hydroxypropylcellulose. The structural features of polycomplexes and blends were evaluated by scanning electron microscopy and thermal analysis. It was found that the interpolymer complex obtained as a result of co‐precipitation of the polymeric components is characterized by an uniform structure which indicates the complete miscibility between the components. Films were prepared based on blends of neutralized poly(acrylic acid) and hydroxypropylcellulose. In this case the two components resulted immiscible because of the lack of intermolecular hydrogen bonding. Copyright © 2004 Society of Chemical Industry
Mathematical Modeling and Experimental Identification of an Unmanned Helicopter Robot with Flybar Dynamics
Authors: Kim S. K. , Tilbury D. M. 
Published: February 2004

AbstractThis paper presents a mathematical model for a model‐scale unmanned helicopter robot, with emphasis on the dynamics of the flybar. The interaction between the flybar and the main rotor blade is explained in detail; it is shown how the flapping of the flybar increases the stability of the helicopter robot as well as assists in its actuation. The model helicopter has a fast time‐domain response due to its small size, and is inherently unstable. Therefore, most commercially available model helicopters use the flybar to augment stability and make it easier for a pilot to fly. Working from first principles and basic aerodynamics, the equations of motion for full six degree‐of‐freedom with flybar‐degree of freedom are derived. System identification experiments and results are presented to verify the mathematical model structure and to identify model parameters such as inertias and aerodynamic constants. © 2004 Wiley Periodicals, Inc.
Inferior vena cava thrombosis presenting as non‐immune hydrops in the fetus of a woman with diabetes
Authors: Weissmann‐Brenner A. , Ferber A. , O'Reilly‐Green C. , Avila C. , Grassi A. , Divon M. Y. 
Published: February 2004

AbstractWe present a rare case of non‐immune hydrops fetalis (NIHF) caused by a thrombus in the inferior vena cava in a neonate with low levels of anti‐thrombin III. The diagnosis of (NIHF) was made in utero in a 43‐year‐old woman with poorly controlled gestational diabetes who subsequently developed pre‐eclampsia. Cesarean section was performed due to fetal compromise and worsening pre‐eclampsia. The thrombus resolved after neonatal treatment with heparin. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Analysis of sonographic features for the differentiation of benign and malignant breast tumors of different sizes
Authors: Chen S.‐C. , Cheung Y.‐C. , Su C.‐H. , Chen M.‐F. , Hwang T.‐L. , Hsueh S. 
Published: February 2004

AbstractObjectiveTo analyze the value of various sonographic features in differentiating benign from malignant breast tumors of different sizes to improve the diagnostic accuracy in small lesions.MethodsThe sonographic features of 1203 histologically confirmed solid breast lesions were prospectively documented with respect to anteroposterior (AP) diameter/width ratio, shape, margin, echogenicity, echotexture, posterior echo and bilateral refraction sign. The sensitivity, specificity and accuracy of breast ultrasound were calculated for lesions grouped according to size (≤ 1, 1.1–2 and > 2 cm). Univariate and multiple logistic regression analyses including calculation of odds ratios for single sonographic features were used to analyze the significance of the different diagnostic features.ResultsThe accuracy of breast sonography in differentiating between benign and malignant tumors ≤ 1, 1.1–2 and > 2 cm in size was 75.6%, 86.4% and 88.4%, respectively. Univariate analysis demonstrated that all sonographic features were significant in tumors ≥ 1.1 cm. Shape, margin, echogenicity and echotexture were the significant factors in those tumors ≤ 1 cm. Multiple logistic regression analysis demonstrated that margin, shape, posterior echo and echogenicity were the significant factors for differential diagnosis in tumors > 2 cm. Echogenicity, margin, shape, bilateral refraction sign and echotexture were the significant factors for tumors 1.1–2 cm. On multiple regression analysis, margin was the only significant factor for tumors ≤ 1 cm.ConclusionTumor margin is the most important sonographic feature in evaluating breast lesions in any size group. With the combination of significant factors and emphasis on specific features according to size of lesion, the diagnostic accuracy of ultrasound for the differential diagnosis of malignant and benign tumors may be improved. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Accuracy of sonographically estimated fetal weight in 840 women with different pregnancy complications prior to induction of labor
Authors: Ben‐Haroush A. , Yogev Y. , Bar J. , Mashiach R. , Kaplan B. , Hod M. , Meizner I. 
Published: February 2004

AbstractObjectivesTo evaluate the accuracy of sonographically estimated fetal weight (EFW) shortly before induction of labor in the presence of different pregnancy complications, and to define possible variables affecting it.MethodsThe study sample consisted of 840 women with singleton pregnancies and cephalic presentation who were admitted to our unit for induction of labor between January 1999 and December 2000. All underwent detailed ultrasound assessment for EFW, amniotic fluid index, biophysical profile and placental location. Indications included previous Cesarean section, postdate pregnancy, pregnancy‐induced hypertension, diabetic pregnancy, suspected large‐for‐gestational age (LGA) infants, suspected fetal growth restriction (FGR), oligohydramnios, decreased fetal movements, premature rupture of membranes at or before term. EFW was calculated after measuring fetal abdominal circumference and femur length. The EFW was compared with the weight at delivery, 1–3 days later.ResultsThere was a high correlation between EFW and birth weight (R2 = 0.775, P < 0.001). The mean birth weight was 3207 ± 561 g, and mean absolute weight difference was 227 ± 197 g; (absolute range, 0–1700 g; actual range, − 986 to + 1700 g). The mean weight difference was significantly different between the patients with LGA infants, FGR infants and preterm premature rupture of membrances (PPROM) (− 110 ± 281 g, + 113 ± 195 g and + 115 ± 307 g, respectively, P < 0.01). Stepwise linear regression analysis of the effects of maternal and pregnancy characteristics on the weight difference yielded lower gestational age, higher birth weight, anterior placenta, higher gravidity, and younger maternal age as independent and significant variables associated with greater actual weight difference inaccuracy (R2 = 0.099, P < 0.001), and higher birth weight as the only independent and significant variable associated with greater absolute weight difference (R2 = 0.09, P = 0.018).ConclusionsThe sonographic EFW is highly correlated with birth weight. However, clinicians should be aware of the risk of overestimation in pregnancies with suspected LGA and underestimation in pregnancies with PPROM and suspected FGR. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Transvaginal ultrasound detection of multifollicular ovaries in non‐hirsute ovulatory women
Authors: Phy J. , Foong S. , Session D. , Thornhill A. , Tummon I. , Dumesic D. 
Published: February 2004

AbstractObjectivesTo characterize ovarian morphology in a group of ovulatory, non‐hirsute women with infertility and normal circulating levels of gonadotropins and sex steroids.MethodsThirty‐three women with normal physical examinations, regular ovulatory menses, and absence of hirsutism (Ferriman–Gallwey score ≤ 7) were studied. No woman had thyroid disease, galactorrhea, polycystic ovary syndrome, 21‐hydroxylase deficiency or diabetes. Two‐dimensional (2D) transvaginal sonography (TVS) was used to measure follicle size and ovarian volume on menstrual cycle day 5. Three‐dimensional (3D) TVS images were stored to determine the number of follicles (measuring 2–10 mm in diameter) in the largest sonographic plane. Fasting blood sampling and oral glucose tolerance testing were performed to assess serum gonadotropin and sex steroid levels as well as glucose tolerance.ResultsThe median ovarian volume by 2D‐TVS imaging was 7.2 (range, 2.3–15.8) cm3 (n = 64 ovaries). No follicles were > 10 mm in diameter. The median number of follicles by 3D‐TVS was 4 (range, 2–8) (n = 63 ovaries) in the largest sonographic plane. Fourteen of 63 ovaries (22%) had six or more small follicles in one plane distributed within normal stroma (multifollicular ovary, MFO). No ovary had 10 or more follicles in one plane located within abundant stroma (polycystic ovary). Of 33 women examined, 20 women (61%) had apparently normal ovaries bilaterally, while 13 (39%) had at least one MFO. There were no significant differences between women with and those without MFO in serum gonadotropin and steroid levels or glucose tolerance.ConclusionsMFO is a common morphological variant in non‐hirsute ovulatory women with normal gonadotropin secretion and ovarian steroidogenesis. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Umbilical venous volume flow and fetal behavioral states in the normally developing fetus
Authors: Boito S. M. E. , Ursem N. T. C. , Struijk P. C. , Stijnen T. , Wladimiroff J. W. 
Published: February 2004

AbstractObjectiveTo determine the relationship between umbilical venous (UV) volume flow and fetal behavioral states 1F (quiet sleep) and 2F (active sleep) in normal pregnancies at 36–40 weeks of gestation.MethodsFetal behavioral states were established in 17 normal pregnancies by means of combined assessment of fetal heart rate patterns (FHRP), and fetal eye and body movements. UV vessel area (mm2) as obtained by tracing the inner vessel area using Labview and Imaq Vision software and UV time‐averaged flow velocity (mm/s Doppler) were multiplied to calculate UV volume flow (mL/min) including flow/kg fetus. The pulsatility index (PI) in the umbilical artery was also determined. In each woman, all parameters were measured between three and five times in each behavioral state. Data are reported as mean ± 1 SD and analyzed by paired t‐test.ResultsNo statistically significant behavioral‐state‐related changes were observed for UV time‐averaged velocity and UV volume flow, resulting in UV volume flow/kg fetus of 69.1 ± 14.9 mL/min*kg at 1F and 71.6 ± 12.1 mL/min*kg at 2F (not significant). A statistically significant increase (P = 0.02) was established for UV cross‐sectional area (46.4 ± 8.6 mm2 vs. 49.0 ± 10.1 mm2) and for fetal heart rate (FHR) from 134.2 ± 10.3 bpm in 1F to 144.2 ± 7 bpm in 2F. Umbilical artery PI was not significantly different between the two behavioral states.ConclusionsOn the basis of high venous vessel wall compliance, the significant increase in UV cross‐sectional area during fetal behavioral state 2F may be determined by a rise in mean venous pressure. The significant rise in FHR may reflect increased fetal cardiac output during state 2F while the resistance at the hepato‐ductal pathway remains relatively constant with the purpose of meeting raised energy demands during the active sleep state. This is further supported by the observed trend towards an increase in UV volume flow. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Relationship between monitoring parameters and perinatal outcome in severe, early intrauterine growth restriction
Authors: Bilardo C. M. , Wolf H. , Stigter R. H. , Ville Y. , Baez E. , Visser G. H. A. , Hecher K. 
Published: February 2004

AbstractObjectiveTo investigate whether pathological changes in the umbilical artery (UA), ductus venosus (DV) and short‐term fetal heart variation are related to perinatal outcome in severe, early intrauterine growth restriction (IUGR).MethodsThis multicenter, prospective, longitudinal, observational study was carried out in the Departments of Fetal Medicine and Obstetrics in Hamburg, Amsterdam, Utrecht and London. In 70 singleton pregnancies with IUGR fetuses, delivered at 26–33 weeks of gestation because of antepartum fetal distress, short‐term variation (STV) of fetal heart rate, pulsatility index of the fetal UA (UA PI) and DV pulsatility index for veins (DV PIV) were assessed at least weekly. The final measurement was performed within 24 h of delivery. Standard cut‐off levels (2 SD or 3 SD, absent flow or reversed flow) were used and new cut‐off levels were calculated by means of receiver–operating characteristics analysis. Adverse outcome was defined as perinatal death, cerebral hemorrhage (≥ Grade II) or bronchopulmonary dysplasia before discharge. The predictive value for adverse outcome was calculated for different cut‐off levels of the monitoring parameters, adjusted for gestational age (GA), by multivariate logistic regression analysis. Data were analyzed separately for three different time blocks, namely 8–14, 2–7 and 0–1 days before delivery.ResultsAdverse perinatal outcome occurred in 18/70 (26%) infants. During the last 24 h before delivery DV PIV and UA PI were significantly higher and STV lower in the adverse outcome group, while 2–7 days before delivery only DV PIV was significantly higher. Adverse perinatal outcome could be predicted at 0–1 days before delivery by DV PIV at a cut‐off of three multiples of the SD (odds ratio (OR) 11.3; 95% CI 2.3–57) and GA (OR 0.4; 95% CI 0.3–0.8), at 2–7 days by DV PIV at 2 SD (OR 3.0; 95% CI 0.8–12) and GA (OR 0.5; 95% CI 0.3–0.8) and at 8–14 days by DV PIV at 2 SD (OR 3.9; 95% CI 0.8–20) and GA (OR 0.5; 95% CI 0.3–0.8). Other parameters did not contribute to the multivariate model.ConclusionsDV PIV measurement is the best predictor of perinatal outcome. This measurement may be useful in timing the delivery of early IUGR fetuses and in improving perinatal outcome, even when delivery may be indicated at an earlier GA. However, as GA was also an important factor influencing outcome, with poorer outcome at earlier gestation at delivery, this hypothesis needs to be tested in a multicenter, prospective, randomized trial. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Evaluation of femur length during the second and third trimesters in fetuses with myelomeningocele
Authors: Williams G. , Coakley F. V. , Qayyum S. , Glenn O. A. , Breiman R. S. , Callen P. W. 
Published: February 2004

AbstractObjectivesTo determine if the femur length of fetuses with myelomeningocele is shorter in the second and third trimesters compared with that of normal fetuses.MethodsWe retrospectively collected measurements of femur length, head circumference, biparietal diameter and abdominal circumference from detailed obstetric ultrasound studies performed during the second and third trimesters in 31 fetuses with myelomeningocele and 43 fetuses with no detectable anomaly. The gestational age predicted by each parameter (based on Hadlock's tables) was compared with the true gestational age (based on last menstrual period), using the ANCOVA test to determine if there was a statistically significant difference between the two groups of fetuses.ResultsThere was no significant difference in femur length (P = 0.60) or in abdominal circumference (P = 0.85) between fetuses with myelomeningocele and normal fetuses. Fetuses with myelomeningocele did have a significantly lower biparietal diameter and head circumference (P ≤ 0.001).ConclusionsMyelomeningocele is not associated with reduced femur length in the second and third trimesters, suggesting that the known postnatal lower extremity foreshortening in patients with myelomeningocele develops late in gestation or after birth. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.