bluuebunny/crossref_metadata_2025 huggingface dataset:
A TiO2 dielectric filled toroidal radio frequency cavity resonator for high‐field NMR
Authors: Butterworth Edward J. , Walsh Edward G. , Hugg James W.
Published: August 2002

RF performance in high‐field MRI applications is improved by filling the resonator with material of relative dielectric constant approximating that of human soft tissue. We demonstrate this by filling a toroidal cavity resonator operating in TEM00 (cyclotron) mode with titanium dioxide (TiO2) in powdered rutile form, and acquiring phantom, human lower leg and human breast images of good quality at 4.1 T. Images made with this resonator had unusually high SNR, while the level of Rf power required to produce a 90° flip angle pulse was about a quartes as high for the filled resonator as for the same resonator before filling. Phantom images obtained with the filled resonator had an SNR of nearly 300 at a resolution of 256 × 256 voxels, nearly three times that of images of the same phantom obtained using a standard volume Rf coil in frequent use at this laboratory. Breast images made at 256 × 256 voxels resolution had an SNR of 174, also unusually high for a volume coil. High‐resolution (512 × 512 voxels) were also obtained, with SNR = 60. Preliminary phantom and in vivo human images are presented in this article. Acquiring the phantom and leg images required significantly less Rf power than did comparable imaging using a conventional coil. In addition, the field lines were focused as they penetrated into the sample, and this resulted in a more homogeneous B1‐field. We believe that these improvements occurred because the dielectric presence minimizes the large dielectric mismatch between air and sample. Copyright © 2001 John Wiley & Sons, Ltd.

Abbreviations used:

EM

electromagnetic

FOV

field‐of‐view, Rf, radio frequency

SNR

signal‐to‐noise ratio.
An approach to modeling performance evaluation on the ethernet with QoS parameters
Authors: Yang Shin‐Jer
Published: August 2002

This paper proposes an empirical approach to model the performance of Ethernet with QoS (Quality of Services) parameters. Hence, how to model the performance of Ethernet becomes a critical issue for the LAN implementation and operation. In the QoS approach, however, Ethernet network performance can be dynamically tuned by existing and enhanced operation parameters based on the current information status of the Ethernet LAN system. Consequently, Ethernet performance can be predicted and maintained through using the proposed methodology, and then to promote the system throughput. Copyright © 2001 John Wiley & Sons, Ltd.
Weighted proportional window control of TCP traffic
Authors: Aweya James , Ouellette Michel , Montuno Delfin Y.
Published: August 2002

This article describes a technique for weighted proportional window control of elastic traffic such as that generated by TCP. This is achieved through the modification of the receiver's advertised window of TCP connections sharing the bottleneck link while taking into account the price that each user of a connection has paid for the service and the total number of active connections sharing the bottleneck link. Copyright © 2001 John Wiley & Sons, Ltd.
Comparison of the effects of HGF, BDNF, CT‐1, CNTF, and the branchial arches on the growth of embryonic cranial motor neurons
Authors: Naeem Arifa , Abbas Leila , Guthrie Sarah
Published: August 2002

In the developing embryo, axon growth and guidance depend on cues that include diffusible molecules. We have shown previously that the branchial arches and hepatocyte growth factor (HGF) are growth‐promoting and chemoattractant for young embryonic cranial motor axons. HGF is produced in the branchial arches of the embryo, but a number of lines of evidence suggest that HGF is unlikely to be the only factor involved in the growth and guidance of these axons. Here we investigate whether other neurotrophic factors could be involved in the growth of young cranial motor neurons in explant cultures. We find that brain‐derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF) and cardiotrophin‐1 (CT‐1) all promote the outgrowth of embryonic cranial motor neurons, while glial cell line‐derived neurotrophic factor (GDNF) and neurotrophin‐3 (NT‐3) fail to affect outgrowth. We next examined whether HGF and the branchial arches had similar effects on motor neuron subpopulations at different axial levels. Our results show that HGF acts as a generalized rather than a specific neurotrophic factor and guidance cue for cranial motor neurons. Although the branchial arches also had general growth‐promoting effects on all motor neuron subpopulations, they chemoattracted different axial levels differentially, with motor neurons from the caudal hindbrain showing the most striking response. © 2002 Wiley Periodicals, Inc. J Neurobiol 51: 101–114, 2002
GABA exerts opposite influence on warm and cold sensitive neurons in medial preoptic area in rats
Authors: Jha Sushil K. , Islam Fakhrul , Mallick Birendra N.
Published: August 2002

The preoptic area regulates body temperature. GABA‐ergic terminals and receptors are present in this area. Local microinjection studies have shown that GABA, its agonist, and its antagonist in this area may modulate body temperature. However, there are warm and cold sensitive neurons, and they are known to be affected by local and peripheral temperatures. In order to understand the mechanism of action of GABA in temperature regulation at the cellular level it was necessary to study the effect of GABA on individual thermosensitive neurons in in vivo preparations. Hence, in this study the responses of preoptic area thermosensitive and insensitive neurons to microiontophoretic application of picrotoxin, a GABA‐A antagonist, were studied in anaesthetized rats. It was observed that a majority of both the thermosensitive and insensitive neurons were affected by microiontophoretic application of picrotoxin. Although almost an equal number of cold and warm sensitive neurons were affected, a majority of the cold sensitive neurons were excited, while a majority of the warm sensitive neurons were inhibited by picrotoxin. The results suggested that in normal conditions GABA acts through GABA‐A receptor in modulating the spontaneous activity of thermosensitive neurons in the preoptic area. Furthermore, the results of the present study taken together with other reports suggest that normally GABA exerts a direct inhibitory action on the cold sensitive neurons, while it acts on presynaptic heteroreceptors, possibly on norepinephrinergic afferent input terminals on the warm sensitive neurons, for mediating its action. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 291–300, 2001
Descending influences on escape behavior and motor pattern in the cockroach
Authors: Schaefer Paul L. , Ritzmann Roy E.
Published: August 2002

The escape behavior of the cockroach is a ballistic behavior with well characterized kinematics. The circuitry known to control the behavior lies in the thoracic ganglia, abdominal ganglia, and abdominal nerve cord. Some evidence suggests inputs may occur from the brain or suboesophageal ganglion. We tested this notion by decapitating cockroaches, removing all descending inputs, and evoking escape responses. The decapitated cockroaches exhibited directionally appropriate escape turns. However, there was a front‐to‐back gradient of change: the front legs moved little if at all, the middle legs moved in the proper direction but with reduced excursion, and the rear legs moved normally. The same pattern was seen when only inputs from the brain were removed, the suboesophageal ganglion remaining intact and connected to the thoracic ganglia. Electromyogram (EMG) analysis showed that the loss of or reduction in excursion was accompanied by a loss of or reduction in fast motor neuron activity. The loss of fast motor neuron activity was also observed in a reduced preparation in which descending neural signals were reversibly blocked via an isotonic sucrose solution superfusing the neck connectives, indicating that the changes seen were not due to trauma. Our data demonstrate that while the thoracic circuitry is sufficient to produce directional escape, lesion or blockage of the connective affects the excitability of components of the escape circuitry. Because of the rapidity of the escape response, such effects are likely due to the elimination of tonic descending inputs. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 9–28, 2001
A multilevel Newton–Krylov interface solver for multiphysics couplings of flow in porous media
Authors: Yotov Ivan
Published: August 2002

A multiblock approach to modelling flow in porous media allows for coupling different physical and numerical models in a single simulation through the use of mortar finite elements. The resulting non‐linear algebraic system is reduced to a non‐linear interface problem which is solved by a full approximation scheme (FAS) multigrid with a Newton‐GMRES smoother. Copyright © 2001 John Wiley & Sons, Ltd.
An optimal control problem in estimating the optimal control force for the force vibration system
Authors: Huang Cheng‐Hung
Published: August 2002

An optimal control problem for the force vibration system based on the iterative regularization method, i.e. the conjugate gradient method (CGM), is examined to estimate the optimal control force in a damped system having time‐dependent system parameters such that the desire (or design) system displacements can be satisfied.

It is assumed that no prior information is available on the functional form of the unknown control function in the present study, thus, it is classified as the function estimation.

Numerical simulations are performed to test the validity of the present algorithm by using different types of the desire system displacements. Results show that an excellent estimation on the optimal control force can be obtained with arbitrary initial guesses within a couple of second's CPU time at Pentium III‐500 MHz PC. Copyright © 2001 John Wiley & Sons, Ltd.
Changes in mRNA for ryanodine receptors after transient cerebral ischemia and tolerance induction
Authors: Dahl Christina , Diemer Nils Henrik
Published: August 2002

Disturbance of Ca2+ homeostasis is assumed to precede ischemia‐induced neuronal death. Using the 4‐vessel occlusion model of cerebral ischemia and induction of ischemic tolerance in the rat, we studied the intracellular Ca2+ activated Ca2+ channel, the ryanodine receptor (RyR), by means of in situ hybridisation and immunohistochemistry. We found the level of RyR2 mRNA increased in CA1 and CA3 of the ischemic vulnerable hippocampus following 3 minutes of tolerance inducing ischemia, whereas 9 minutes of ischemia lead to an increased mRNA level in CA1 in contrast to a decrease in CA3. In ischemic tolerant animals (3 + 8.5 minutes of ischemia) the mRNA level was decreased in CA3. In all experimental groups, RyR1 mRNA remained unaltered, whereas RyR3 mRNA decreased in DG. Immunohistochemistry revealed no alterations of the RyR protein level in all the ischemic groups compared to sham‐operated animals. Taken together, these changes do not clarify if the RyR is involved in tolerance induction or in the degenerative process leading to ischemic delayed neuronal death.
Development of the practice environment scale of the nursing work index†‡
Authors: Lake Eileen T.
Published: August 2002

Five subscales were derived from the Nursing Work Index (NWI) to measure the hospital nursing practice environment, using 1985–1986 nurse data from 16 magnet hospitals. The NWI comprises organizational characteristics of the original magnet hospitals. The psychometric properties of the subscales and a composite measure were established. All measures were highly reliable at the nurse and hospital levels. Construct validity was supported by higher scores of nurses in magnet versus nonmagnet hospitals. Confirmatory analyses of contemporary data from 11,636 Pennsylvania nurses supported the subscales. The soundness of the new measures is supported by their theoretical and empirical foundations, conceptual integrity, psychometric strength, and generalizability. The measures could be used to study how the practice environment influences nurse and patient outcomes. © 2002 Wiley Periodicals, Inc. Res Nurs Health 25:176–188, 2002
The great auk and the gannet: a prehistoric perspective on the extinction of the great auk
Authors: Serjeantson Dale
Published: August 2002

Archaeological finds of the great auk, Alca impennis, and the northern gannet, Sula bassana, from prehistoric and historic coastal sites around the British Isles show the earlier distribution of these birds. They suggest that the great auk bred more widely in the eastern Atlantic than on the few breeding sites which are attested historically. Comparison between the two species suggests that the method of exploitation as well as the biology and behaviour of each contributed to the extinction of the former and the survival of the latter. Copyright © 2001 John Wiley & Sons, Ltd.
On the discontinuity of the costates for optimal control problems with Coulomb friction
Authors: Driessen Brian J. , Sadegh Nader
Published: August 2002

This work points out that the costates are actually discontinuous functions of time for optimal control problems with Coulomb friction. In particular these discontinuities occur at the time points where the velocity of the system changes sign. To our knowledge, this has not been noted before. This phenomenon is demonstrated on a minimum‐time problem with Coulomb friction and the consistency of discontinuous costates and switching functions with respect to the input switches is shown. Copyright © 2001 John Wiley & Sons, Ltd.
Phospholipid coated poly(lactic acid) microspheres for the delivery of LHRH analogues
Authors: Rasiel Aliza , Sheskin Tzviel , Bergelson Lev , Domb Abraham J.
Published: August 2002

The aim of this work was to develop alternative peptide‐loaded microspheres using liposphere formulation—a lipid based microdispersion system. This formulation represents a new type of lipid or polymer‐based encapsulation system developed for parenteral and topical drug delivery of bioactive compounds. Our strategy was to utilize the liposphere formulation to improve the entrapment efficiency and release profile of triptorelin and leuprolide [luteinizing hormone–releasing hormone (LHRH) analogues] in vitro. Peptides (2% w/w) were loaded into lipospheres contained of polylactic acid (PLA) or poly(lactic‐co‐glycolic acid) (PLGA) with several types of phospholipids. The effects of polymer and phospholipid type and concentration, method of preparation and solvents on the liposphere characteristics, particle size, surface and bulk structure, drug diffusion rate, and erosion rate of the polymeric matrix were studied. The use of L‐PLA (Mw = 2000) and hydrogenated soybean phosphatidylcholine (HSPC) with phospholipid–polymer ratio of 1 : 6 w/w, was the most efficient composition that formed lipospheres of particle size in the range of 10 µm with most of the phospholipid embedded on the particles surface. In a typical procedure, peptides were dissolved in N‐methyl‐2‐pyrrolidone (NMP), and dispersed in a solution of polymer and phospholipids in a mixture of NMP and chloroform with the use of 0.1% poly(vinyl alcohol) (PVA) as the emulsified aqueous medium. Uniform microspheres were prepared after solution was mixed at 2000 rpm at room temperature for 30 min. Using this formulation, the entrapment efficiency of LHRH analogues in lipospheres was up to 80%, and the peptides were released for more than 30 days. Copyright © 2002 John Wiley & Sons, Ltd.
Asymmetric hydrogenation ofo‐Cresol andm‐Cresol catalyzed by silica‐supported methylcellulose–L‐alanine–Pd complex
Authors: Huang Kai , Hu Jie , Huang Mei‐Yu , Jiang Ying‐Yan
Published: August 2002

Silica‐supported methylcellulose–L‐alanine–palladium complex (SiO2‐MC–LA–Pd) has been prepared and found to be a high optically active catalyst for asymmetric hydrogenation of o‐cresol and m‐cresol to give (S)‐2‐methylcyclohexanone and (R)‐3‐methylcyclohexanone, respectively, at 25 °C and under an atmospheric hydrogen pressure. The optical yields of (S)‐2‐methylcyclohexanone and (R)‐3‐methylcyclohexanone amounted to 91.5 and 68.5%, respectively, when optimum Pd content in SiO2‐MC–LA–Pd complex, reaction temperature and solvent were selected. SiO2‐MC–LA–Pd catalyst also has shown high stability. The optical yields for (S)‐2‐methylcyclohexanone and (R)‐3‐methylcyclohexanone were kept over 90 and 60%, respectively, when the catalyst was reused several times. Moreover, SiO2‐MC–LA–Pd complex is an economical catalyst. The methylcellulose is an abundant natural biopolymer and the procedure for preparation of the complex is very simple. Copyright © 2001 John Wiley & Sons, Ltd.
Microstaging in cutaneous melanoma
Authors: Ruiter D. J. , Spatz A. , van den Oord J. J. , Cook M. G.
Published: August 2002

Recent papers have addressed critical issues regarding the microstaging of cutaneous melanoma. They concern the new staging proposal by the American Joint Committee on Cancer (AJCC), the presentation of new prognostic models than seem applicable in daily practice, and new immunohistochemical findings than demonstrate prognostic information independently of the conventional major factors. These issues are commented on by the Pathology Committee of the EORTC Melanoma Group. Copyright © 2001 John Wiley & Sons, Ltd.
Ki‐ras mutation type and the survival benefit from adjuvant chemotherapy in Dukes' C colorectal cancer
Authors: Gnanasampanthan G. , Elsaleh H. , McCaul K. , Iacopetta B.
Published: August 2002

Ki‐ras mutations are associated with an increased risk of relapse and death in colorectal cancer (CRC) patients, with some mutations being more aggressive than others. The present study examined the predictive value of different Ki‐ras mutation types in a retrospective series of 430 Dukes' C stage CRC patients, of whom 208 (48%) had received adjuvant chemotherapy with 5‐fluorouracil/levamisole or 5‐fluorouracil/leucovorin. A total of 140 mutations were detected, the majority (58%, 81/140) being glycine to aspartate mutations in codons 12 and 13. Glycine to valine mutations in codon 12 (14%, 20/140) and other less frequent, non‐specified mutation types (28%, 39/140) accounted for the remaining mutations. Kaplan–Meier survival analysis revealed that both Ki‐ras wild‐type and mutant patient groups derived significant survival benefit from chemotherapy. However, when patients were stratified according to the type of mutation, those with non‐aspartate mutations appeared to gain more benefit from this treatment than those with aspartate mutations. Multivariate analysis that included other possible predictive factors in Dukes' C CRC (tumour site, patient sex, TP53 mutation) demonstrated that non‐aspartate mutations in particular were associated with a significant survival benefit from chemotherapy (HR=0.11, 95% CI: 0.04–0.30, p<0.001). These results suggest that the type of Ki‐ras mutation could be a clinically useful molecular marker for the identification of CRC subgroups that are likely to benefit from 5‐fluorouracil‐based adjuvant chemotherapy. Copyright © 2001 John Wiley & Sons, Ltd.
Liquid chromatography–mass spectrometry analysis of propolis
Authors: Midorikawa Kiyoshi , Banskota Arjun H. , Tezuka Yasuhiro , Nagaoka Takema , Matsushige Katsumichi , Message Dejair , Huertas Alfredo A. G. , Kadota Shigetoshi
Published: August 2002

The composition of propolis, a resinous hive product collected by honeybees from various plant sources, depends on various factors such as season and vegetation of the area. Based on standards (either isolated from Brazilian propolis or reported from propolis) including chromane, diterpenes and phenolic compounds, different Brazilian propolis were analysed by LC‐MS in order to determine their chemical constituents. Dicaffeoylquinic acids were detected in almost all water extracts of Brazilian propolis, whereas diterpenes, flavonoids and prenylated phenolic compounds were found in their methanol extracts. Based on the identified chemical constituents and their biological activities, it was determined that the quality of Brazilian propolis could be directly related to the phenolic constituents. Moreover, Baccharis dracunculifolia was concluded to be an important source of Brazilian propolis. Propolis samples from Peru, China and the Netherlands were also studied. Copyright © 2001 John Wiley & Sons, Ltd.
Interval between insulin injection and meal in relation to glycated haemoglobin
Authors: Baker E. Ahmed Abu , Badgandi Mohan , Home Philip D.
Published: August 2002

People who use an insulin regimen with pre‐meal short‐acting human insulin are usually recommended to inject insulin 20–40 min before the meal. It is a widespread impression, however, that most insulin‐treated diabetic patients do not follow such recommendations and inject their pre‐meal insulin preparation with an interval shorter than advised. The aim of the present study was to evaluate the timing of pre‐meal insulin injections, and to assess any relationship of the timing of pre‐meal insulin to overall blood glucose control, together with effects of age, sex, type and duration of diabetes. We studied 179 insulin‐treated diabetic patients, advised in accordance with local protocols to take their pre‐meal insulin injections 20 min or more before meals, using a short exploratory questionnaire. Patients answered one question about the timing of their pre‐meal insulin injection in relation to each main meal. In addition, physicians provided information on the patient's medical and diabetes history and blood glucose control from the medical records. Twenty‐seven per cent of patients reported having their pre‐meal insulin injection 0–5 min before meals, and 31% 6–10 min before meals. Twenty‐four per cent reported an 11–20 min interval, and 18% reported following the recommendations and taking their insulin 20 min or more before meals. HbA1c did not differ with pre‐meal injection interval. Age, sex, body mass index (BMI) and duration of diabetes had no effect on the injection–meal interval reported. In conclusion these results show that only a minority of insulin‐treated patients follow the recommendations regarding the timing of pre‐meal insulin injections. Blood glucose control as assessed by HbA1c is not obviously affected by the timing of pre‐meal insulin injection in relation to meals. Copyright © 2001 John Wiley & Sons, Ltd.
Improving the early management of blood glucose in emergency admissions with chest pain
Authors: Rutter Martin K , Wilcox Emily , Easton Joan , Skinner Jane , Taylor Roy
Published: August 2002

Hyperglycaemia is associated with a worse prognosis after myocardial infarction and good blood glucose control in the peri‐infarct period has been shown to improve outcome. Our primary study was undertaken with the aims of assessing the prevalence and management of hyperglycaemia in patients admitted with acute chest pain. Ninety‐three patients admitted to either Coronary Care (CCU) or Emergency Medical Admission Units (EMAU) with chest pain were studied and of these 14 (15%) had severe hyperglycaemia (>11.0 mmol/L). Blood glucose was not measured in seven (8%) patients and in only 1/14 (7%) patient were established guidelines for the management of hyperglycaemia applied. A revision of management protocol was undertaken and after 18 months we repeated the review of management of hyperglycaemia. Of 114 patients 22 (21%) had severe hyperglycaemia, blood glucose was not measured in ten (9%) and management guidelines were followed in 13 (65%).

A major improvement in management of blood glucose in emergency admissions with chest pain has been demonstrated. Further staff education, discussion and review of protocol are indicated to improve and maintain performance on CCU and EMAU. Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis and physical properties of sulfonated syndiotactic polystyrene ionomers
Authors: Li Hua‐Ming , Liu Jin‐Cheng , Zhu Fang‐Ming , Lin Shang‐An
Published: August 2002

Sulfonation of highly stereoregular syndiotactic polystyrene has been accomplished in 1,1,2‐trichloroethane and chloroform (60/40 v/v) mixed solvent. FTIR spectroscopy was used to confirm that the sulfonated syndiotactic polystyrene was the product of the sulfonation reactions. Sodium, potassium, zinc (II), manganese (II) and cobalt (II) salts of the sulfonated polymers exhibited behaviour indicative of strong interactions. FTIR spectroscopy and DSC data showed that the roles of the cation–anionic site interactions in alkali form and transition metal form ionomers are somewhat different. The DSC data also showed that the alkali metal cations had more pronounced effect on Tg than did the transition metal cations. In addition, the crystallization behaviour of the ionomers with a low degree of sulfonation also exhibited considerable differences in comparison with the neat syndiotactic polystyrene. The melting points (Tm) and the degree of crystallization (Xc) were significantly lowered by the presence of the sulfonic acid groups or the sulfonate metal groups. Moreover, the ionomers were more thermally stable and more hygroscopic than the unmodified polymer.

© 2001 Society of Chemical Industry
Thermal and mechanical characterization of epoxy resins toughened using preformed particles
Authors: Day R J , Lovell P A , Wazzan A A
Published: August 2002

Preformed, multilayer particles have been used to toughen an epoxy resin. The particles were formed by emulsion polymerization and consist of alternate glassy and rubbery layers, the outer layer having glycidyl groups to give the possibility of chemical bonding of the particles in the cured resin. Two variants of this type of particle were used, termed GM(47/15) and GM(47/37); both types have an overall diameter of 0.5 µm, but the former have a thicker rubbery layer. For comparison, acrylic toughening particles (ATP) with no surface functionality and a liquid carboxyl‐terminated butadiene–acrylonitrile (CTBN) rubber were used as toughening agents. The epoxy resin system consisted of a commercial diglycidyl ether of bisphenol A (Shell Epon 828) with diamino‐3,5‐diethyl toluene as hardener, two commercial sources of which were used, namely Ethacure‐100 (Albemarle SA) and DX6509 (Shell Chemicals). These hardeners contain a mixture of two isomers, namely 2,6‐diamino‐3,5‐diethyltoluene and 2,4‐diamino‐3,5‐diethyltoluene

Thermogravimetry in nitrogen shows that the preformed toughening particles begin to degrade at 230 °C, whereas the cured resin begins to degrade rapidly at 350 °C. Thus, even though the particles are less thermally stable than the cured resin, their degradation temperature is well above the glass transition temperature of the resin, and their use does not affect the thermal stability of the toughened materials at normal use temperatures.

The performance of the toughening agents was compared using Ethacure‐100 as the hardener. The GM(47/15) and GM(47/37) toughening particles gave rise to a greater toughening effect than the ATP and the CTBN. For example, the fracture energies were: 0.26 kJ m−2 for the unmodified resin; 0.60 kJ m−2 for the resin toughened with CTBN; and 0.69 kJ m−2 for the resin toughened with the GM(47/15) particles. The ultimate tensile stress of the unmodified epoxy resin was 43 MPa, which increased to 55 MPa when 20 wt% of GM(47/15) toughening particles were added.

The toughness of resins cured with the DX6509 hardener were superior to those obtained with the Ethacure‐100 hardener, most probably due to DX6509 producing a less‐highly‐crosslinked network. This highlights the sensitivity of the toughening process to the hardener used, even for hardeners of a similar nature.

© 2001 Society of Chemical Industry
In vitro and in vivo degradation study on novel blends composed of polyphosphazene and polyester or polyanhydride
Authors: Qiu L Y
Published: August 2002

Poly[bis(glycine ethyl ester)phosphazene] (PGP) was blended with poly(D,L‐lactide‐co‐glycolide) (80:20 by mole) (PLGA) and poly[sebacic anhydride‐co‐trimellitylimidoglycine)‐block‐poly(ethylene glycol)] (30:50:20 by mole) (PSTP) in various ratios using a solvent‐mixing technique. The in vitro degradation of polymer blends was examined by treatment in distilled water with or without lipase at 37 °C; the degradation rate of the blends could be regulated by adjusting the composition. PGP/PLGA (70:30 by wt) slabs took 120 days to disappear completely, while PGP/PSTP (70:30 by wt) needed only 20 days. Furthermore, Rhizopus delemer lipase showed the strongest acceleration activity on PGP/PLGA blends. The degree of enzymatic degradation was proportional to the percentage of PLGA in the blend. For comparison, the in vivo degradation of polymer blends was investigated by implanting them subcutaneously in the back of mice, some difference in degradation being observed.

© 2002 Society of Chemical Industry
Effect of epoxy functionalized compatibilizer on the mechanical properties of low‐density polyethylene/plasticized tapioca starch blends
Authors: Sailaja R R N , Reddy A Prasad , Chanda Manas
Published: August 2002

A series of low‐density polyethylene (LDPE) blends with varying proportions of plasticized tapioca starch have been used for the study of their mechanical properties. A functionalized epoxy resin, namely, poly(ethylene‐co‐glycidyl methacrylate) has been used as the compatibilizer. The impact and tensile properties have been measured by standard ASTM methods. The mechanical properties are seen to improve significantly with the addition of the epoxy compatibilizer, approaching values close to those of virgin LDPE. The scanning electron micrographs of the compatibilized blends show ductile failure which evidently contribute to improved mechanical properties.

© 2001 Society of Chemical Industry
Teachers' comfort and importance ratings for interventions for preschoolers with AD/HD
Authors: Stormont Melissa , Stebbins Molly S.
Published: August 2002

The main purpose of this study was to explore preschool teachers' ratings of both the perceived importance of and their comfort levels implementing interventions for children with AD/HD. Participants included 138 teachers from licensed child care facilities. Teachers completed a questionnaire that required them to rate, on a 7‐point Likert‐type scale, the importance of 43 interventions and how comfortable they would be executing the strategy if asked to do so in the classroom. Overall, teachers concluded that the majority of the interventions were mostly important and believed they would be comfortable using the strategies. In addition, findings indicated that preschool teachers' importance and comfort ratings were highly correlated. Teacher variables (i.e., years of teaching experience, educational level, and having a student with AD/HD) were not correlated with, or discriminative of, comfort and importance ratings. The implications of these findings are discussed. © 2001 John Wiley & Sons, Inc.
Kinetics and mechanisms of solvolysis of 3‐chloro‐3‐ethylpentane in alcohols as solvents. Application of multiparametric equations and factor analysis to the solvolytic reactions of tert‐alkyl halides
Authors: Albuquerque Lídia M. P. C. , Moita M. Luísa C. J. , Gonçalves Raquel M. C.
Published: August 2002

This paper introduces a new set of rate constants for solvolysis of 3‐chloro‐3‐ethylpentane in eight monoalcohols, from methanol to 2‐methylbutan‐1‐ol, and in 10 dialcohols, from ethane‐1,2‐diol to pentane‐1,5‐diol, and also in diethylene and triethylene glycol. These results together with previous obtained data for several solvolytic reactions of tert‐alkyl halides (2‐iodo‐2‐methylpropane, 2‐bromo‐2‐methylpropane, 2‐chloro‐2‐methylpropane, 2‐bromo‐2‐methylbutane, 2‐chloro‐2‐methylbutane and 3‐chloro‐3‐methylpentane) in the same mono‐ and dialcohols were studied by means of a standard multiparametric approach and by target factor analysis (TFA). TFA provides an open criterion for selecting the quantity and nature of the possible causes of the variation in the rate constants. The results allow one to identify and quantify the dominant solute–solvent interaction mechanisms affecting the reactions. Solvent dipolarity, polarizability and hydrogen bond donor acidity are the main influences on reactivity, although mono‐ and dialcohols behave differently. Copyright © 2001 John Wiley & Sons, Ltd.
Novel functional initiators for oxazoline polymerization
Authors: Einzmann Mirko , Binder Wolfgang H.
Published: August 2002

The initiating behavior of the functional tosylates 1–4 and triflates 5 and 6 for the cationic ring‐opening polymerization of 2‐methyl‐1,3‐oxazoline was investigated. The emphasis was directed at tosylates and triflates with 2,2‐dimethyl‐1,3‐dioxolane‐, 2,3‐epoxypropyl‐, 2,3‐didodecanoyl‐glycerol‐, and cholest‐5‐en‐moieties that allow the construction of amphiphilic polyoxazoline conjugates. The tosylates were prepared by a simple reaction of the corresponding alcohols with p‐toluenesulfonyl chloride, whereas the preparation of the corresponding triflates required low temperature and the use of 2,6‐di‐tert‐butylpyridine as a sterically hindered base. Among the initiators tested, 2,2‐dimethyl‐(4‐trifluoromethanesulfonyloxymethyl)‐1,3‐dioxolane 6 gave the best results in respect to molecular weight and polydispersity. Starting from the corresponding functional oxazoline polymers obtained with 6 as an initiator, amphiphilic lipid‐polyoxazoline conjugates with a diacylglycerol backbone could be prepared. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2821–2831, 2001
Controlled free‐radical polymerization of 2‐vinylpyridine in the presence of nitroxides
Authors: Chalari Ioanna , Pispas Stergios , Hadjichristidis Nikos
Published: August 2002

Bulk free‐radical polymerization of 2‐vinylpyridine (2VP) in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) was studied under different conditions (temperature and presence of additives). Linear poly‐(2‐vinylpyridine) with a narrow molecular weight distribution and controllable molecular weight was prepared in the presence of acetic anhydride at 95 °C up to a conversion of 66%. At higher conversions side reactions became very important (pseudoliving polymerization). By applying this procedure, well‐defined random copolymers of 2VP with styrene or tert‐butylmethacrylate as well as block copolymers of 2VP with styrene were synthesized. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2889–2895, 2001
Poly(ethylene terephthalate) copolyesters derived from (2S,3S)‐2,3‐dimethoxy‐1,4‐butanediol
Authors: Kint Darwin P. R. , Wigström Emilia , de Ilarduya Antxon Martínez , Alla Abdelilah , Muñoz‐Guerra Sebastián
Published: August 2002

Novel poly(ethylene terephthalate) (PET) copolyesters, abbreviated PEDMBT, containing optically active (2S,3S)‐2,3‐dimethoxy‐1,4‐butanediol (DMBD) as the second comonomer were investigated. Copolymers with ethylene glycol to DMBD ratios between 95/5 and 50/50 as well as the two parent homopolymers, PET and PDMBT, were prepared by a two‐step melt polycondensation. The resulting copolymers were found to approximately have the composition of the polymerization reaction feed and a random microstructure. Polymer intrinsic viscosities varied from 0.4 to 0.6 dL g−1 with weight‐average molecular weights ranging from 16,000 to 44,000. PEDMBT copolyesters were distinguished in being much more soluble than PET and showing an increasing affinity for water with the content in dimethoxy groups. According to the asymmetric constitution of DMBD, they displayed optical activity in solution. Both melting and glass‐transition temperatures of the copolyesters were observed to steadily decrease with the content in DMBD. PEDMBTs were found to be crystalline for contents in DMBD up to 30 mol %. Both powder and fiber X‐ray diffraction revealed that the same crystalline structure is shared by PET and the crystalline copolyesters. The homopolyester PDMBT resulted in becoming a polymer with a crystallinity comparable to PET but with a significantly different crystalline structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3250–3262, 2001
Initial step of anthracene‐sensitized photoacid generation from diphenyliodonium hexafluorophosphate in an epoxy matrix studied by steady‐state and laser‐flash photolyses
Authors: Kura Hisatoshi , Fujihara Kan , Kimura Akira , Ohno Teruhisa , Matsumura Michio , Hirata Yoshinori , Okada Tadashi
Published: August 2002

The anthracene‐sensitized photodecomposition of diphenyliodonium hexafluorophosphate was studied in an epoxy matrix. From steady‐state photolysis, the generation of protons, which are considered to be the actual initiators of the polymerization of epoxides, was confirmed. In addition, 9‐phenylanthracene was detected as a main product from anthracene. From time‐resolved laser‐flash photolysis, a broad absorption band with a peak at about 500 nm was observed that was thought to be due to the precursor of 9‐phenylanthracene. On the basis of these results, we propose electron transfer from anthracene in the excited singlet state to the diphenyliodonium cation as the initial step of photoacid generation. This process is followed by fast chemical reactions, which generate 9‐phenylanthracene and protons, and back electron transfer from the diphenyliodine radical to the anthracene cation radical. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2937–2946, 2001
Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) studied with paramagnetic spin probes. I. Electron spin resonance spectra
Authors: Varghese Biji , Schlick Shulamith
Published: August 2002

Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) was studied as a function of the butadiene content and method of preparation with electron spin resonance (ESR) spectra of nitroxide spin probes. Results for the ABS polymers were evaluated by comparison with similar studies of the homopolymers polybutadiene (PB), polystyrene (PS), and polyacrylonitrile (PAN) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Two spin probes were selected for this study: 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD). The probes varied in size and were selected because their hydrocarbon backbone made them compatible with the polymers studied. The ESR spectra were measured in the temperature range 120–420 K and were analyzed in terms of line shapes, line widths, and hyperfine splitting from the 14N nucleus; the appearance of more than one spectral component was taken as an indication of microphase separation. Only one spectral component was detected for 10DND in PB, PS, and PAN and in the copolymers SAN and SB. In contrast, two spectral components differing in their dynamic properties were detected for both probes in the three types of ABS samples studied and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The behavior of the fast component in ABS prepared by mass polymerization suggested that the low‐Tg (glass‐transition‐temperature) phase was almost pure PB. The corresponding phase in ABS prepared by emulsion grafting also contained styrene and acrylonitrile monomers. A redistribution of the spin probes on heating occurred with heating near the Tg of the SAN phase, suggesting that the ABS polymers as prepared were not in thermodynamic equilibrium. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 415–423, 2002; DOI 10.1002/polb.10109
Stress distribution in poly‐p‐phenylenebenzobisoxazole (PBO) fiber estimated from vibrational spectroscopic measurement under tension. II. Analysis of inhomogeneous stress distribution in PBO fiber
Authors: Kitagawa Tooru , Tashiro Kohji , Yabuki Kazuyuki
Published: August 2002

Fourier transform Raman spectra were measured for poly‐p‐phenylenebenzobisoxazole (PBO) fiber subjected to a tensile stress, and the Raman shift factor (the frequency shift caused by 1 GPa tensile stress) depended strongly on the sample‐preparation condition. To clarify the reasons of this dependency, a mechanical series parallel model was adopted that could successfully and quantitatively explain the observed Raman shift factors and gave a concreate heterogeneous stress distribution in the PBO fibers. As a result, a mechanical series model was reasonable for PBO fiber. Broadening of Raman bands, which was observed when the PBO fiber was tensioned, could also be interpreted on the basis of an idea of heterogeneous stress distribution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1281–1287, 2002
Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends
Authors: Ceccorulli Giuseppina , Scandola Mariastella , Adamus Grazyna
Published: August 2002

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002
Respiratory mechanics in very low birth weight infants during continuous versus intermittent gavage feeds
Authors: Brar Gamdur , Geiss Donna , Brion Luc P. , Rios Angel
Published: August 2002

This study was designed to determine whether respiratory mechanics in stable, very low birth weight infants changed after replacing intermittent feeds with continuous feeding. We measured static respiratory system compliance, respiratory system resistance, functional residual capacity (FRC), and tidal volume immediately before feeds and at 20, 60, and 120 min after feeds, and again the next day on continuous feeds. Patients selected for enrollment into the study needed to fulfill the following criteria: 1) birth weight and postnatal weight < 1,500 g, 2) no need for mechanical ventilation, positive airway pressure, or supplemental oxygen, 3) receiving and tolerating at least 100 mL/kg/day of intermittent gavage feeds, and 4) no change in methylxanthine or diuretic dosage for 3 days before the study. Respiratory mechanics were measured using the SensorMedics 2600 Pediatric Pulmonary Cart (Yorba Linda, CA). We studied 16 infants (gestational age 28.3 ± 3.7 weeks, mean ± SD) at a postnatal age of 10–82 days.

The average interindividual coefficient of variance was 20 ± 2% for static compliance, 35 ± 6% for resistance, 18 ± 3% for FRC, and 19 ± 3% for tidal volume. Repeated‐measures analysis of variance did not reveal any significant difference in respiratory mechanics with intermittent vs. continuous feeding.

The data suggest that static respiratory mechanics in stable, very low birth weight infants are not affected by changing enteral feeds from intermittent gavage to a continuous schedule. Pediatr Pulmonol. 2001; 32:442–446. © 2001 Wiley‐Liss, Inc.
Management of oxygenation in pediatric acute hypoxemic respiratory failure
Authors: Matthews Benjamin D. , Noviski Natan
Published: August 2002

The prognosis for patients with acute respiratory distress syndrome (ARDS) in adults and children has improved since its formal acceptance as a clinical entity in 1967. Because acute hypoxemic respiratory failure is the hallmark of acute lung injury and ARDS, the management of oxygenation is crucial. Physicians managing pediatric patients with acute lung injury or ARDS are faced with a complex array of options influencing oxygenation. Certain treatment strategies can influence clinical outcomes, such as a lung‐protective ventilation strategy that specifies a low tidal volume (6 mL/kg) and a plateau pressure limit (30 cm H2O) (Acute Respiratory Distress Network, N Engl J Med 2000;342:1301–1308). Other lung‐protective strategies such as different levels of positive end‐expiratory pressure, altered inspiratory:expiratory ratios, recruitment maneuvers, prone positioning, and extraneous gases or drugs may impact clinical outcomes but require further clinical study.

This paper reviews state‐of‐the‐art strategies on the management of oxygenation in acute hypoxemic respiratory failure and attempts to guide pediatric pulmonologists in managing children with respiratory failure. Pediatr Pulmonol. 2001; 32:459–470. © 2001 Wiley‐Liss, Inc.
Airway compression following thymus hyperplasia in an infant with Pierre Robin sequence and congenital diaphragmatic hernia
Authors: Hentschel R. , Willital G. , Hülskamp G. , Rieger C.
Published: August 2002

A female infant with respiratory embarrassment due to external compression of the tracheobronchial tree by the thymus is presented. After successful intrauterine drainage of pleural effusions, she was born with a diaphragmatic hernia and Pierre Robin sequence, which required long‐term mechanical ventilation and several surgical interventions, including tracheostomy, until she breathed spontaneously. At age 7 months, she was rehospitalized in respiratory failure because of pneumonia. At this time, thymus hyperplasia was first diagnosed, which had caused tracheobronchomalacia and displacement of the tracheobronchial tree. Weaning from the ventilator was unsuccesful for 8 weeks. She underwent thymectomy, following which impairment of breathing resolved immediately. Different manifestations of thymus enlargement and their relation to impaired breathing are discussed. Pediatr Pulmonol. 2001; 32:476–479. © 2001 Wiley‐Liss, Inc.
Proliferation of prostate cancer cells in the bone marrow predicts recurrence in patients with localized prostate cancer
Authors: Bianco Fernando J. , Wood David P. , de Oliveira Jose Gomes , Nemeth Jeffrey A. , Beaman Andrew A. , Cher Michael L.
Published: August 2002

Background

Reverse‐transcription polymerase chain reaction (RT‐PCR) amplification of prostate specific antigen (PSA) mRNA has been used to detect the presence of prostate cancer cells in the peripheral blood and bone marrow of patients with clinically localized disease. Some studies have demonstrated a correlation between detection of PSA‐mRNA and disease recurrence. However, many RT‐PCR‐positive patients remain disease‐free. We propose that phenotypic characterization of individual micrometastatic cells may provide more prognostic information than mere detection of such cells.

Methods

We studied 58 patients undergoing radical prostatectomy for clinically localized disease whose bone marrow had been found to contain PSA‐mRNA by RT‐PCR. Immunohistochemical detection and phenotypic characterization of micrometastatic cells was performed using a two‐color technique: cytokeratin antibody for detection and the MIB‐1 antibody for proliferation. The clinical endpoint was disease recurrence.

Results

One or more micrometastatic cells were proliferating in 36.2% of the patients; the disease‐free survival rate was 76.2% in this group. In contrast, in the patients with non‐proliferating cells, 97.3% remained disease‐free (P = 0.025). Multivariate analysis demonstrated that the presence of proliferating cells was the only preoperative variable that correlated with disease‐free survival (P = 0.05).

Conclusions

Determination of the phenotype of individual micrometastatic cells can contribute prognostic information above and beyond the mere determination of their presence or absence. Phenotypic characterization of individual micrometastatic cells may ultimately be used to select patients for systemic therapy given either alone or in combination with local therapy. Prostate 49:235–242, 2001. © 2001 Wiley‐Liss, Inc.