bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of additive packages for processing and long‐term thermal stabilization of film grade high‐density polyethelene
Authors: Parrondo Aitor , Allen Norman S. , Edge Michele , Liauw Christopher M. , Fontán Eusebio 
Published: April 2004

AbstractAnalysis and optimization of the simultaneous effects within different additive packages for stabilization during melt processing and long‐term thermal stabilization of high‐density polyethylene were carried out by using a carefully constructed statistical experimental design involving response surface methodology (RSM). The packages consisted of blends of phenolic antioxidants, phosphites, and zinc stearate. The degree of melt processing stabilization was assessed by using melt flow rate (MFR) and yellowness index (YI) measurements conducted on samples that had varying degrees of processing history imposed by varying the number of passes through a twin‐screw extruder. The long‐term thermal stabilization was assessed by YI measurement after oven aging at 110°C. The RSM approach utilized in this study enabled the contribtion of each additive to the stabilization and interactions between the additives to be observed. Furthermore, the concentration and ratio of each additive could be optimized.
Evaluation of surface concentration of erucamide in LLDPE films
Authors: Rawls Amy S. , Hirt Douglas E. , Havens Marvin R. , Roberts William P. 
Published: April 2004

AbstractAdditives are often blended into polymers to improve specific performance features of the finished film. Erucamide is a common slip agent used to reduce a film's coefficient of friction (COF), which is a good attribute for high speed packaging operations. Because such additives must migrate to the surface to be effective, this study focuses on erucamide blooming to the surface of linear low‐density polyethylene (LLDPE) films. Both the surface and bulk concentrations of erucamide were measured over time to determine the equilibrium additive partitioning. The surface concentration was determined by surface washing for different time intervals and extrapolated back to a “zero” time to offset the solvent extraction of additive from the bulk film. The bulk concentration was determined by a deep microwave extraction. Initial experiments with forced aging at 60°C showed significant evaporative losses of erucamide. The final work focused on room temperature, at whcih additive evaporation was negligible. The room temperature blooming results showed that the erucamide surface and bulk concentrations reached equilibrium within 24 hours. The data also showed that erucamide surface concentration increased with initial additive loading for a fixed film thickness and with increased film thickness for a fixed additive concentration.
Mechanical properties and rheological behavior of PVC blended with terpolymers containing N‐phenylmaleimide
Authors: Yang Liting , Liu Guodong , Sun Donghai , Wang Weina , Gao Jungang , Zhang Liucheng , Jin Riguang 
Published: April 2004

AbstractThree kinds of terpolymers containing N‐phenylmaleimide (PhMI) were synthesized by emulsion polymerization. The terpolymers were used as heat‐resistant modifiers, and acrylic‐core/shell (ACR) was used as an impact modifier in blends with PVC. The mechanical properties and rheological behavior of the blended systems were determined. The results showed that the mechanical properties of the blends improved with increasing terpolymer content and that the apparent melt viscosity of the blends decreased with increasing terpolymer content. When 8 phr of ACR was added to the blended system, the mechanical properties and the apparent melt viscosity were greatly improved.
Rheological and mechanical performance of ethyl‐vinyl acetate/poly(vinyl chloride) formulations
Authors: McConnell D. C. , McNally G. M. , Murphy W. R. 
Published: April 2004

AbstractA range of powdered ethyl‐vinyl acetate (EVA) copolymers and poly(vinyl chloride) (PVC) formulations were compounded at PVC:EVA ratios of 100:0, 60:40, 50:50, 40:60, and 0:100. Two grades of EVA with 20% and 27% of vinyl acetate (VAc) (EVA I and EVA II) and two grades of PVC with K values of 56 and 71 (PVC I and PVC II) were used in the investigation. Mechanical analysis was performed on injection molded samples of these blends, and the results showed that the tensile and flexural moduli decreased significantly with increasing EVA concentration. Rheological analysis was performed by using dual capillary rheometry, and the results showed only slight changes in shear viscosity with increasing EVA content, even at lower shear rates. Dynamic mechanical thermal analysis showed partial miscib lity of the PVC and EVA over the range of concentrations studied.
Review of specialty PVC resins
Authors: Shah Ashok C. , Poledna David J. 
Published: April 2004

AbstractWorld consumption of PVC was around 25 MM MT (55 billion pounds) in year 2001, second only to that of low density polyethylene. Only 10% of the PVC produced is classified as specialty PVC resins, while the other 90% is referred to as general purpose (GP) commodity resins. This paper tries to define what specialty PVC resins are, how they are produced, and their markets, applications, fabrication processes, and compounding as compared to those of GP resins.
Chlorinated poly(vinyl chloride) and plasticized chlorinated poly(vinyl chloride)—thermal decomposition studies
Authors: Carty Peter , Price Dennis , John Milnes G. 
Published: April 2004

AbstractThe thermal decomposition of chlorinated poly(vinyl chloride) and three plasticized chlorinated poly(vinyl chloride) systems has been investigated. The routes of decomposition of these systems have been elucidated by investigating char formation and by using a combination of thermogravimetric analysis (TGA) and prolysis/gas chromatography/mass spectroscopy methods (Py/GC/MS). The effects of the charforming/smoke‐suppressing iron(III) compound FeOOH in these polymer systems has also been investigated. The structure of both CPVC polymer and plasticzer determine the path of thermal decomposition and also the quantity and nature of the decomposition compunds formed. Changes in oxygen index and the formation of smoke during burning in these systems have been related to the char that is formed and also to the chemical nature of the decomposition products.
Fusion mechanism in rigid PVC
Authors: Berard Mark T. 
Published: April 2004

AbstractA classic approach for studying network effects in carbon‐black‐containing rubber was applied to PVC with stabilizer. This approach involves measuring the shear modulus with increasing strain. In carbon‐black‐containing rubber, the modulus drops dramatically at a critical strain level. This is known as the Payne effect and is associated with the breakup of the carbon black network. Rigid PVC that is fused to different levels in a bowl mixer shows exactly the same behavior, and the drop point correlates very well with the fusion peak in the mixing bowl. The relationship between network effects and fusion in PVC is discussed.
Conservative vs. surgical management of septic abortion with renal failure
Authors: Singhal Pravin C. , Kher Vijay K. , Dhall Gian I. , Mehta Ravindera L. , Visweswaran R. Kasi , Nampoory M.R. Narayanan , Chugh Kirpal S. 
Published: April 2004

AbstractThe role of surgery in the management of postabortum renal failure complicated with extensive uterine sepsis, perforation or peritonitis is controversial. This study compares the course and final outcome of 14 patients (66.6%) conservatively managed with appropriate antibiotics, fluid or blood replacement and dialysis, with seven patients (33.3%) for whom hysterectomy or laparotomy was undertaken in addition. Whereas all 14 patients treated conservatively died as the result of uncontrolled septicemia, three of the seven surgical patients recovered completely. Extensive necrosis with perforation of the uterine wall was confirmed either at laparotomy or at autopsy in all 21 women. To reduce mortality, the authors recommend early surgical intervention for patients suffering from post‐abortum renal failure complicated with uterine sepsis or perforation.
Outcome of labor following previous cesarean section
Authors: Wadhawan S. , Narone J.N. 
Published: April 2004

AbstractFour hundred fifty‐one patients who had had previous lower segment cesarean section were studied for subsequent pregnancy outcome at the University Teaching Hospital, Lusaka, Zambia. Of 319 who were allowed to go into labor, 63% succeeded in delivering vaginally, while 37% had to undergo repeat intrapartum cesarean delivery. No maternal death occurred. Scar dehiscence occurred in one case only. Parturition in otherwise obstetrically normal patients seems to be safe, and the trial of labor approach is desirable as it results in a lower number of repeat cesarean deliveries.
Ovarian pregnancy in association with an intrauterine device
Authors: de Vries K. , Shapiro I. , Degani S. , Levitan Z. , Mitrani A. , Sharf M. 
Published: April 2004

AbstractWithin a 1‐year period, two cases of primary ovarian pregnancy associated with an intrauterine device (IUD) occurred in our institution. The clinical signs and symptoms were similar to those in any other ectopic pregnancy. Both cases satisfied the criteria of Spiegelberg. The final diagnosis was based on the histopathological findings. A review of the literature is presented summarizing the 53 cases reported until now. The association between IUD, ectopic pregnancy in general, and ovarian pregnancy in particular is discussed.
Mortality in relation to method of delivery in breech infants
Authors: Petitti Diana B. , Golditch Ira M. 
Published: April 2004

AbstractTo study the relation of method of delivery to perinatal mortality, we examined information from the deliveries of 1593 breech infants weighing 1000 g or more born in 1976 and 1977. In none of the birthweight groups 1000 g or more was neonatal mortality significantly different between infants delivered vaginally compared with those delivered by cesarean section, although the number of deaths was small. In all the birthweight groups, perinatal mortality was higher in breeches delivered vaginally, but the differences were because all of the infants who died before labor were delivered vaginally. Total mortality (intrapartum plus neonatal deaths) in infants who survived to labor was not significantly different in breech infants delivered by one or the other method at any birthweight. These data suggest that routine cesarean delivery for infants 1000 g or more who are in the breech presentation may not be justified from the standpoint of mortality.
Prevention of postoperative infection in cesarean section after rupture of the membranes
Authors: Schedvins K. , Moberg P.J. 
Published: April 2004

AbstractPatients having a cesarean section more than 6 h after rupture of the membranes constitute a high risk group for postoperative infections. Two such groups were studied. Patients were given either cefuroxim 1.5 g every 8th hour for 24 h followed by cefadroxil 0.5 g twice daily for 6 days or received no medication. The infection rate was significantly reduced in the treatment group as compared to the control group (15% vs. 48%). Non‐infected patients had a significantly shorter stay in hospital (8 days vs. 12 days).Combined use of these drugs for prevention of postcesarean infection has not previously been reported. No side effects of the antibiotic prophylaxis were reported.
How Chinese clinicians contribute to the improvement of maternity care
Authors: Yan R.Y. 
Published: April 2004

AbstractClinicians in China are deeply involved in efforts to improve maternity care throughout the country. A Women's Health section has been established in the Chinese Society of Obstetrics and Gynecology. Staff of tertiary hospitals participate in perinatal surveillance of cities, including regular maternal and perinatal mortality meetings and comparative inter‐hospital evaluations of service and clinical statistics. Clinicians from larger urban centers visit rural hospitals to provide guidance in management of high risk patients.
Ethnic and other factors affecting birthweight in Singapore
Authors: Viegas O.A.C. , Ratnam S.S. , Cole T.J. 
Published: April 2004

AbstractData on 1800 term babies, 600 from each of the Chinese, Malay and Indian racial groups, were used to identify the factors affecting birthweight in Singapore. After adjustment for gestation, maternal height and other variables, the mean Indian birthweight was 100 g less than for the Chinese (P < 0.001), while the Malays averaged 33 g less than the Chinese. The shortfall in Indian birthweight is thought to be due, at least partly, to environmental factors.
Placental site trophoblastic tumor associated with immature ovarian teratoma
Authors: Stetler‐Stevenson W. , Lurain J.R. , Murad T. 
Published: April 2004

AbstractThis paper describes a woman who developed three malignancies within a very short time. Two of these, immature teratoma and placental site trophoblastic tumor, were rare gynecological neoplasms. The third was a breast carcinoma. This is the first report of an association of placental site trophoblastic tumor with a primary germ cell tumor of the ovary.
Vaginal birth after cesarean section in rural Tanzania
Authors: van Roosmalen J. 
Published: April 2004

AbstractEighty‐seven of 134 women with a history of previous cesarean section in two rural hospitals in Tanzania had a vaginal delivery after a trial of labor. The incidence of scar‐rupture was high; in 9 of 134 cases (6.7%). Maternal death, however, did not occur. It is concluded that a trial of labor is justified, and that the risk of scar‐rupture should be balanced with the risk of repeat operations.
Pregnancy‐associated hypertension in Maputo. A study on maternal characteristics and perinatal outcome in 1275 consecutive cases
Authors: Merz R. , Said A. , Bergström S. , Bugalho A. , Samucidine M. 
Published: April 2004

AbstractA total of 1275 consecutive cases of pregnancy‐associated hypertension were registered in the Maputo Central Hospital (corresponding to 2.9% of a total of 43 794 city parturients). In the hypertensive and in the reference populations the following prevalence figures were registered, respectively: age below 25 years, 52% and 23% (P < 0.0005); nulliparity, 33% and 19% (P < 0.0005); twin pregnancies, 3.9% and 1.7% (P < 0.0005); stillbirths, 5.7% and 2.3% (P < 0.0005); and low birthweight (LBW), 22.9% and 10.7% (P < 0.0005). In the hypertensive population the prevalence of LBW newborns was 20.1% in the liveborn group, while it was 68.4% in the stillborn group (P < 0.0005). In the ongoing perinatal audit it was found useful to review hypertensive women separately, in order to assess current routines in cases of pregnancy hypertension.
The effects of mandatory and optional use on students’ ratings of a computer‐based learning package
Authors: Garland Kate , Noyes Jan 
Published: April 2004

AbstractContinuing developments in educational technology and increasing undergraduate numbers in the UK have facilitated the use of computer‐based learning packages. One of the effects of the increasing use of these packages is the shift in teaching of material from being primarily lecturer‐led to student‐driven. This has a number of implications concerning using the package, since it is quite likely that students will be working in isolation, and the use of the package may be mandatory or optional. In this study we report on the usefulness ratings of a software package for undergraduate use within the context of whether or not students choose to use it. Level 1 students and lecturers in Economics were surveyed at three UK universities. Findings indicate that students whose use was mandatory rated the learning package as more useful than those whose use was optional. Reasons for non‐use centred on lack of instruction and on student apathy. These results have important implications for the use of computer‐based learning packages and for understanding user attitudes.
Automated finger spelling by highly realistic 3D animation
Authors: Adamo‐Villani Nicoletta , Beni Gerardo 
Published: April 2004

AbstractWe present the design of a new 3D animation tool for self‐teaching (signing and reading) finger spelling—the first basic component in learning any sign language. We have designed a highly realistic hand with natural animation of the finger motions. Smoothness of motion (in real time) is achieved via programmable blending of animation segments. The hand is utilised by a programme that automatically converts text to finger spelling with controllable playback speed and playback views. The programme can be operated in two modes for two basic applications: learning to read (finger spelling) and learning to sign. For both modes, multi‐sided views are provided. In addition, for the signing mode, a mirror view is provided for the common technique of using a mirror for feedback in practising finger spelling. An additional view revealing the joint structure of the hand allows the signer to practise the subjective view without having to guess the position of the fingers. This is the first example of highly realistic 3D animation that can be used practically to teach a basic aspect of sign language. The method is applicable more generally to sign language, and this finger‐spelling application should be regarded as a first step toward the extension of highly realistic 3D animation to sign language in general.
Large predators and their prey in a southern African savanna: a predator's size determines its prey size range
Authors: Radloff Frans G. T. , Du Toit Johan T. 
Published: April 2004

Summary

A long‐term (13‐year) data set, based on > 4000 kills, was used to test whether a sympatric group of large predators adheres to the theoretical predictions that (1) mean prey body size and (2) prey diversity increase as functions of predator body size.
All kills observed by safari guides are documented routinely in Mala Mala Private Game Reserve, South Africa. We analysed these records for lion (Panthera leo, Linnaeus), leopard (Panthera pardus, Linnaeus), cheetah (Acinonyx jubatus, Schreber) and African wild dog (Lycaon pictus, Temminck). Males and females of the sexually dimorphic felid species were treated as functionally distinct predator types. Prey types were classified by species, sex and age class.
Prey profiles were compared among predator types in terms of richness and evenness to consider how both the range of prey types used and the dominance of particular prey types within each range may be influenced by predator size. No significant size‐dependent relationships were found, so factors separate from or additional to body size must explain variation in prey diversity across sympatric predators.
A statistically strong relationship was found between mean prey mass and predator mass (r2 = 0·86, P= 0·002), although pairwise comparisons showed that most predators killed similar prey despite wide differences in predator size. Also, minimum prey mass was independent of predator mass while maximum prey mass was strongly dependent on predator mass (r2 = 0·71, P= 0·017). The ecological significance is that larger predators do not specialize on larger prey, but exploit a wider range of prey sizes.
Predator–prey body size, interaction strength and the stability of a real food web
Authors: Emmerson Mark C. , Raffaelli Dave 
Published: April 2004

SummaryWe examined the empirical relationship between predator–prey body size ratio and interaction strength in the Ythan Estuary food web.We have refined a previously published version of the food web and explored how size‐based predatory effects might affect food web dynamics. To do so, we used four predatory speciesCrangon crangon(Linnaeus),Carcinus maenas(Linnaeus),Pomatoschistus microps(Krøyer) andPlatichthys flesus(Linnaeus) and one common prey speciesCorophium volutator(Pallas) from the food web.All predators and prey were sorted into small, medium and large size classes and placed into mesocosms in all possible pairwise combinations of size and species identity to determine per capita effects of predators on prey (aij).Using Lotka–Volterra dynamics the empirical body size relationships obtained from these experiments and other relationships already available for the Ythan Estuary, we parameterized a food web model for this system. The local stability properties of the resulting food web models were then determined.We found that by choosing interaction strengths using an empirically defined scaling law, the resulting food web models are always dynamically stable, despite the residual uncertainties in the modelling approach. This contrasts with the statistical expectation that random webs with random parameters have a vanishingly improbable chance of stability.The patterning of predator and prey body sizes in real ecosystems affects the arrangement of interaction strengths, which in turn determines food web stability.
Estimating the density of ground‐dwelling arthropods with pitfall traps using a nested‐cross array
Authors: Perner Jörg , Schueler Silvio 
Published: April 2004

SummaryA new procedure for estimating the population densities of ground‐dwelling arthropods with pitfall trapping is described. It couples the fitting of single hyperbolic functions to trap data with the use of a ‘nested‐cross array’, a cross‐shaped trap arrangement with distances between traps doubling with increasing distance from the central trap.We used individual‐based simulation modelling to test the method's reliability given changes in population density, turning rate, trapping period, beetle distribution and intertrap distance.Simulations show that function fits are more likely, and density estimates more accurate, with greater body size and therefore with net displacement, increasing population density, decreasing aggregation and increased turning rate.Simulation indicates that the method is a promising procedure for density estimation that is worth testing in the field. Reliable density estimates are possible if the traps contain a neutral preservative, arrays are established in nearly homogeneous parts of habitat and the arms of the nested‐cross array are distant from habitat edges.