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With PET (with + pet)
Selected AbstractsDrawing in high pressure CO2,a new route to high performance fibers in memory of late Roger PorterPOLYMER ENGINEERING & SCIENCE, Issue 2 2001Terry Hobbs In this paper, we introduce a new draw technique for polymer orientation and apply it to different polymer fibers: poly(ethylene terephthalate) or PET, nylon 6,6, and ultra-high molecular polyethylene (UHMWPE). In this technique, a polymer is drawn uniaxially in supercritical CO2 using a custom high-pressure apparatus. This technique can be used in replacement of a traditional drawing process or as a post-treatment process. With PET, the technique is not effective at temperatures at or below 130°. In contrast, the process is highly effective for nylon 6,6 where CO2 drawn fibers show significantly higher crystallinity and orientation along with improved mechanical properties. While the fibers are plasticized, the drawability of the fibers is only slightly dependent on temperature. High pressure CO2 drawing of ultrahigh molecular weight polyethylene (UHMWPE) fibers is equally effective. Commercial high performance fibers can be drawn up to a ratio of 1.9 in asecond stage, resulting in large increases in tensile modulus and small improvements in tensile strength. [source] Assessment of Residual Viability by Enoximone Echocardiography in Patients with Previous Myocardial Infarction Correlation with Positron Emission Tomographic Studies and Functional Follow-UpECHOCARDIOGRAPHY, Issue 5 2010Fei Lu M.D. Background: The aim of this study was to evaluate enoximone echocardiography (EE) for the identification of residual myocardial viability in postinfarction patients. Findings obtained during EE were compared with those acquired by myocardial uptake of fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and functional follow-up results. Methods: Twenty-five patients underwent EE and PET 18F-FDG studies. An asynergic segment was considered as having contractile enhancement when the wall motion score decreased by ,1 grade during EE and was defined as viable if 18F-FDG uptake score was ,2 grade on PET. Results: Of 293 dysfunctional segments at baseline, 139 (47%) were viable by PET criteria; 117 (40%) had contractile enhancement induced by enoximone (P = 0.07). Agreement between EE and PET was found in 75% of involved segments (K = 0.46, P < 0.001). The majority of discrepancies (65%, P < 0.01) were mainly due to discordant segments in which PET revealed evidence of 18F-FDG uptake but EE showed no change in wall motion. In 179 revascularized segments, negative predictive value for functional recovery of both tests reached the same value (89% for both), whereas positive predictive value was 82% for EE and 68% for PET, respectively (P < 0.05). Sensitivity was 85% for EE and 88% for PET (P = ns); specificity was 87% and 70%, respectively (P < 0.01). Conclusions: EE yields a fair concordance with PET study. Compared with PET, despite a similar negative accuracy, EE shows a greater specificity for prediction of function recovery after revascularization. (Echocardiography 2010;27:544-551) [source] Functional neuroanatomy of the human near/far response to blur cues: eye-lens accommodation/vergence to point targets varying in depthEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004Hans O. Richter Abstract The purpose of this study was to identify the networks involved in the regulation of visual accommodation/vergence by contrasting the cortical functions subservient to eye-lens accommodation with those evoked by foveal fixation. Neural activity was assessed in normal volunteers by changes in rCBF measured with PET. Thirteen right-handed subjects participated in three monocular tasks: (i) resting with eyes closed; (ii) sustained foveal fixation upon a LED at 1.2 m (0.83 D); and (iii) accommodating alternately on a near (24 cm, 4.16 D) vs. a far (3.0 m, 0.33 D) LED alternately illuminated in sequential 2 s epochs. The contrast between the conditions of near/far accommodation and of constant foveal fixation revealed activation in cerebellar hemispheres and vermis; middle and inferior temporal cortex (BA 20, 21, 37); striate cortex and associative visual areas (BA 17/18). Comparison of the condition of constant fixation with the condition of resting with closed eyes indicated activation of cerebellar hemispheres and vermis; visual cortices (BA 17/18); a right hemisphere dominant network encompassing prefrontal (BA 6, 9, 47), superior parietal (BA 7), and superior temporal (BA 40) cortices; and bilateral thalamus. The contrast between the conditions of near/far accommodation with closed-eye rest reflected an incremental summation of the activations found in the previous comparisons (i.e. activations associated with constant fixation). Neural circuits activated selectively during the near/far response to blur cues over those during constant visual fixation, occupy posterior structures that include occipital visual regions, cerebellar hemispheres and vermis, and temporal cortex. [source] The Contribution of Chemoreflex Drives to Resting Breathing in ManEXPERIMENTAL PHYSIOLOGY, Issue 1 2001Safraaz Mahamed The contribution of automatic drives to breathing at rest, relative to behavioural drives such as ,wakefulness', has been a subject of debate. We measured the combined central and peripheral chemoreflex contribution to resting ventilation using a modified rebreathing method that included a prior hyperventilation and addition of oxygen to maintain isoxia at a PET,O2 (end-tidal partial pressure of oxygen) of 100 mmHg. During rebreathing, ventilation was unrelated to PET,CO2 (end-tidal partial pressure of carbon dioxide) in the hypocapnic range, but after a threshold PET,CO2 was exceeded, ventilation increased linearly with PET,CO2. We considered the sub-threshold ventilation to be an estimate of the behavioural drives to breathe (mean ± S.E.M. = 3.1 ± 0.5 l min,1), and compared it to ventilation at rest (mean ± S.E.M. = 9.1 ± 0.7 l min,1). The difference was significant (Student's paired t test, P < 0.001). We also considered the threshold PCO2 observed during rebreathing to be an estimate of the chemoreflex threshold at rest (mean ± S.E.M. = 42.0 ± 0.5 mmHg). However, PET,CO2 during rebreathing estimates mixed venous or tissue PCO2, whereas the resting PET,CO2 during resting breathing estimates Pa,CO2 (arterial partial pressure of carbon dioxide). The chemoreflex threshold measured during rebreathing was therefore reduced by the difference in PET,CO2 at rest and at the start of rebreathing (the plateau estimates the mixed venous PCO2 at rest) in order to make comparisons. The corrected chemoreflex thresholds (mean ± S.E.M. = 26.0 ± 0.9 mmHg) were significantly less (paired Student's t test, P < 0.001) than the resting PET,CO2 values (mean ± S.E.M. = 34.3 ± 0.5 mmHg). We conclude that both the behavioural and chemoreflex drives contribute to resting ventilation. [source] Sentinel node biopsy in oral cavity cancer: Correlation with PET scan and immunohistochemistryHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 1 2003Francisco J. Civantos MD Abstract Background. Lymphoscintigraphy and sentinel node biopsy (LS/SNB) is a minimally invasive technique that samples first-echelon lymph nodes to predict the need for more extensive neck dissection. Methods. We evaluated this technique in 18 oral cavity cancers, stages T1,T3, N0. Patients underwent CT and positron emission tomography (PET) of the neck, followed by LS/SNB, frozen section, immediate selective neck dissection, definitive histology, and immunoperoxidase staining for cytokeratin. Histopathology of the sentinel node was correlated with that of the neck specimen. Results. There were 10 true positives: 6 identified on frozen section; 2 on permanent histology; and 2 only on immunoperoxidase staining. In six, the sentinel node was the only positive node. There were seven true negatives and one false negative. Conclusions. Gross tumor replacement of lymph node architecture may obstruct and redirect lymphatic flow. Overall LS/SNB holds promise for oral cancer. © 2002 Wiley Periodicals, Inc. Head Neck 25: 000,000, 2003 [source] Effects of smoking marijuana on focal attention and brain blood flowHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 3 2007Daniel S. O'Leary Abstract Using an attention task to control cognitive state, we previously found that smoking marijuana changes regional cerebral blood flow (rCBF). The present study measured rCBF during tasks requiring attention to left and right ears in different conditions. Twelve occasional marijuana users (mean age 23.5 years) were imaged with PET using [15O]water after smoking marijuana or placebo cigarettes as they performed a reaction time (RT) baseline task, and a dichotic listening task with attend-right- and attend-left-ear instructions. Smoking marijuana, but not placebo, resulted in increased normalized rCBF in orbital frontal cortex, anterior cingulate, temporal pole, insula, and cerebellum. RCBF was reduced in visual and auditory cortices. These changes occurred in all three tasks and replicated our earlier studies. They appear to reflect the direct effects of marijuana on the brain. Smoking marijuana lowered rCBF in auditory cortices compared to placebo but did not alter the normal pattern of attention-related rCBF asymmetry (i.e., greater rCBF in the temporal lobe contralateral to the direction of attention) that was also observed after placebo. These data indicate that marijuana has dramatic direct effects on rCBF, but causes relatively little change in the normal pattern of task-related rCBF on this auditory focused attention task. Copyright © 2007 John Wiley & Sons, Ltd. [source] Regional cerebral blood flow responses to hyperventilation during sevoflurane anaesthesia studied with PETACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2010L. SCHLÜNZEN Background: Arterial carbon dioxide tension (PaCO2) is an important factor controlling cerebral blood flow (CBF) in neurosurgical patients. It is still unclear whether the hypocapnia-induced decrease in CBF is a general effect on the brain or rather linked to specific brain regions. We evaluated the effects of hyperventilation on regional cerebral blood flow (rCBF) in healthy volunteers during sevoflurane anaesthesia measured with positron emission tomography (PET). Methods: Eight human volunteers were anaesthetized with sevoflurane 1 MAC, while exposed to hyperventilation. During 1 MAC sevoflurane at normocapnia and 1 MAC sevoflurane at hypocapnia, one H215O scan was performed. Statistical parametric maps and conventional regions of interest analysis were used for estimating rCBF differences. Results: Cardiovascular parameters were maintained constant over time. During hyperventilation, the mean PaCO2 was decreased from 5.5 ± 0.7 to 3.8 ± 0.9 kPa. Total CBF decreased during the hypocapnic state by 44%. PET revealed wide variations in CBF between regions. The greatest values of vascular responses during hypocapnia were observed in the thalamus, medial occipitotemporal gyrus, cerebellum, precuneus, putamen and insula regions. The lowest values were observed in the superior parietal lobe, middle and inferior frontal gyrus, middle and inferior temporal gyrus and precentral gyrus. No increases in rCBF were observed. Conclusions: This study reports highly localized and specific changes in rCBF during hyperventilation in sevoflurane anaesthesia, with the most pronounced decreases in the sub cortical grey matter. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve during hypocapnia. [source] Imaging the proliferative status of tumors with PET ,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 5-6 2007Robert H. Mach Abstract The development of radiotracers for imaging solid tumors has recently focused on measuring a tumor's proliferative status. Two different strategies have emerged: (1) radiolabeled DNA precursors that measure DNA synthesis; and (2) radiotracers that label the sigma-2 receptor, a putative biomarker of proliferation. This paper provides a brief description of these two different methods of imaging tumor proliferation that are currently being developed in the field of positron emission tomography (PET). Copyright © 2007 John Wiley & Sons, Ltd. [source] Frederick T. Chin, Cheryl L. Morse, H. Umesha Shetty and Victor W. Pike, automated radiosynthesis of [18F]SPA-RQ for imaging human brain NK1 receptors with PET.JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 11 2006J Label Compd Radiopharm 2005; 49: 17-3 [source] Synthesis of [11C- carbonyl]hydroxyureas by a rhodium-mediated carbonylation reaction using [11C]carbon monoxideJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 5 2006Julien Barletta Abstract [11C]Hydroxyurea has been successfully labelled using [11C]carbon monoxide at low concentration. The decay-corrected radiochemical yield was 38±3%, and the trapping efficiency of [11C]carbon monoxide in the order of 90±5%. This synthesis was performed by a rhodium-mediated carbonylation reaction starting with azidotrimethylsilane and the rhodium complex being made in situ by chloro(1,5-cyclooctadiene)rhodium(I) dimer ([Rh(cod)Cl]2) and 1,2- bis(diphenylphosphino)ethane (dppe). (13C)Hydroxyurea was synthesized using this method and the position of the labelling was confirmed by 13C-NMR. In order to perform accurate LC,MS identification, the derivative 1-hydroxy-3-phenyl[11C]urea was synthesized in a 35±4% decay-corrected radiochemical yield. After 13 µA h bombardment and 21 min synthesis, 1.6 GBq of pure 1-hydroxy-3-phenyl[11C]urea was collected starting from 6.75 GBq of [11C]carbon monoxide and the specific radioactivity of this compound was in the order of 686 GBq/µmol (3.47 nmol total mass). [11C]Hydroxyurea could be used in conjunction with PET to evaluate the uptake of this anticancer agent into tumour tissue in individual patients. Copyright © 2006 John Wiley & Sons, Ltd. [source] Automated radiosynthesis of [18F]SPA-RQ for imaging human brain NK1 receptors with PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2006Frederick T. Chin Abstract [18F]SPA-RQ is an effective radioligand for imaging brain neurokinin type-1 (NK1) receptors in clinical research and drug discovery with positron emission tomography. For the automated regular production of [18F]SPA-RQ for clinical use in the USA under an IND we chose to use a modified commercial synthesis module (TRACERlab FXF-N; GE Medical Systems) with an auxiliary custom-made robotic cooling,heating reactor, after evaluating several alternative radiosynthesis conditions. The automated radiosynthesis and its quality control are described here. [18F]SPA-RQ was regularly obtained within 150 min from the start of radiosynthesis in high radiochemical purity (>99%) and chemical purity and with an overall decay-corrected radiochemical yield of 15±2% (mean±S.D.; n=10) from cyclotron-produced [18F]fluoride ion. The specific radioactivity of [18F]SPA-RQ at the end of synthesis ranged from 644 to 2140 mCi/µmol (23.8,79.2 GBq/µmol). Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis of 2-[(2-chloro-2,-[18F]fluoroethyl)amino]-2H-1,3,2-oxazaphosphorinane-2-oxide (18F-fluorocyclophosphamide), a potential tracer for breast tumor prognostic imaging with PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 9 2005Goran Lacan Abstract A fluorine-18 labeled analog of the widely used chemotherapeutic agent cyclophosphamide was synthesized as a tracer for prognostic imaging with positron emission tomography. 2-[(2-Chloro-2,-[18F]fluoroethyl)amino]-2H-1,3,2-oxazaphosphorinane-2-oxide (18F-fluorocyclophosphamide), was prepared by direct halogen exchange reaction from the parent cyclophosphamide. In small-scale syntheses, radiochemical yields of up to 4.9% and specific activities of 960 Ci/mmol were achieved in a total synthesis time of 60,75 min. The [18F]-labeled cyclophosphamide analog with radioactive purity >99% and chemical purity >96% was suitable for in vivo (microPET imaging) and ex vivo studies of a murine model of human breast tumors. Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis of 6-acrylamido-4-(2-[18F]fluoroanilino)quinazoline: a prospective irreversible EGFR binding probeJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2005Neil Vasdev Abstract Acrylamido-quinazolines substituted at the 6-position bind irreversibly to the intracellular ATP binding domain of the epidermal growth factor receptor (EGFR). A general route was developed for preparing 6-substituted-4-anilinoquinazolines from [18F]fluoroanilines for evaluation as EGFR targeting agents with PET. By a cyclization reaction, 2-[18F]fluoroaniline was reacted with N, -(2-cyano-4-nitrophenyl)- N,N -dimethylimidoformamide to produce 6-nitro-4-(2-[18F]fluoroanilino)quinazoline in 27.5% decay-corrected radiochemical yield. Acid mediated tin chloride reduction of the nitro group was achieved in 5 min (80% conversion) and subsequent acylation with acrylic acid gave 6-acrylamido-4-(2-[18F]fluoroanilino)quinazoline in 8.5% decay-corrected radiochemical yield, from starting fluoride, in less than 2 h. Copyright © 2005 John Wiley & Sons, Ltd. [source] The first enzymatic method for C,18F bond formation: the synthesis of 5,-[18F]-fluoro-5,-deoxyadenosine for imaging with PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2003Laurent Martarello Abstract The use of the key enzyme involved in carbon,fluorine bond formation in Streptomyces cattleya catalysing the formation of 5,-fluoro-5,-deoxyadenosine (5,-FDA) from fluoride ion and S -adenosyl-l-methionine (SAM) was explored for its potential application in fluorine-18 labelling of the adenosine derivative. Enzymatic radiolabelling of [18F]-5,-FDA was successfully carried out starting from SAM and [18F]HF when the concentration of the enzyme preparation was increased from sub-mg/ml values to mg/ml values. The purity of the enzyme had no measurable effect on the radiochemical yield of the reaction and the radiochemical purity of [18F]-5,-FDA. Copyright © 2003 John Wiley & Sons, Ltd. [source] Ortho -[18F]Fluoronitrobenzenes by no-carrier-added nucleophilic aromatic substitution with K[18F]F,K222,A comparative studyJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2002M. Karramkam Abstract The scope of the nucleophilic aromatic ortho -fluorinations from the corresponding ortho -halonitrobenzene precursors (halo-to-fluoro substitutions) with no-carrier-added [18F]fluoride ion as its activated K[18F]F,K222 complex has been evaluated via the radiosynthesis of ortho -[18F]fluoronitrobenzene, chosen as a model reaction. The parameters studied include the influence of the leaving group in the ortho position of the phenyl ring (,Cl, ,Br, ,l), the quantity of precursor used, the type of activation (conventional heating or microwave irradiations), the solvent, the temperature and the reaction time. The iodo-precursor was completely unreactive and the bromo-precursor gave only low incorporation (<10%) in the optimal conditions used (conventional heating at 145°C or microwave activation, 100 W for 120 s). Only the chloro-precursor was found reactive in the conditions described above and up to 70% yield was observed for the formation of ortho -[18F]fluoronitrobenzene ([18F]- 1). In all the experiments, the unwanted ortho -[18F]fluoro-halobenzenes, potentially resulting from the nitro-to-fluoro substitution, could not be detected. These results will be applied for the radiosynthesis of 5-[18F]fluoro-6-nitroquipazine, a potent radioligand for the imaging of the serotonin transporter with PET. Copyright © 2002 John Wiley & Sons, Ltd. [source] Efficient synthesis and formulation of (R)-(,)-[11C]Deprenyl, a selective radioligand for the quantification of MAO-B activity using PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2002Frédéric Dolle Abstract Carbon-11 labeled (R)-(,)-Deprenyl is the tracer of reference for the quantification of monoamine oxidase (MAO)-B activity with PET. In this paper, its radiosynthesis is re-investigated and oriented towards the preparation of multi-milliCuries of radiotracer. Typically, using no-carrier-added [11C]methyl triflate as the alkylating agent, 140,190 mCi (5.1,7.0 GBq) of (R)-(,)-[11C]Deprenyl was obtained within 30 min of radiosynthesis (including HPLC purification and formulation) with specific radioactivities ranging from 0.8 to 1.2 Ci/,mol (29.6,44.4 GBq/,mol). The high efficiency of these radiosyntheses allows for multi-injection protocols and kinetic approaches for absolute quantification of the tracer. Copyright © 2002 John Wiley & Sons, Ltd. [source] Highly efficient synthesis of [11C]S12968 and [11C]S12967, for the in vivo imaging of the cardiac calcium channels using PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 7 2001Frédéric Dolle Abstract The dihydrophyridines S12968 ((,)-S11568, absolute configuration S) and S12967 ((+)-S11568, absolute configuration R), 3-ethyl 5-methyl (,/+)-2-[(2-(2-aminoethoxy)ethoxy)methyl]-4-(2,3-dichlorophenyl)-6-methyl-1,4-dihydropyridine-3,5-dicarboxylate, have both an in vitro profile of high potency and of high selectivity for the low-voltage-dependent L-type calcium channel. In this paper, the radiosynthesis of both enantiomers, S12968 and S12967, with carbon-11, a positron-emitting isotope (half-life : 20.4 min) was investigated and oriented towards the preparation of multi milliCuries of radiotracer. Typically, 130,250 mCi (4.81,9.25 GBq) of [11C]S12968 and [11C]S12967 were obtained within 30 min of radiosynthesis (HPLC purification included) with specific radioactivities ranging from 500 to 1000 mCi/,mol (18.5,37.0 GBq/,mol) using no-carrier-added [11C]methyl triflate as the alkylating agent and the appropriate, enantiomerically pure carboxylic acid precursor at 100°C for 1 min. Based on preliminary PET experiments, only the levo enantiomer S12968 ((,)-[11C]-1) appears to be suitable for myocardial PET imaging as demonstrated in vivo in beagle dogs: with S12968, 85% of the uptake of [11C]S12968 could be inhibited in pretreatment experiments and up to 70% of [11C]S12968 could be displaced. Further investigations are currently underway in order to provide an absolute quantification of ventricular calcium channels with PET. Copyright © 2001 John Wiley & Sons, Ltd. [source] Binding characteristics and sensitivity to endogenous dopamine of [11C]-(+)-PHNO, a new agonist radiotracer for imaging the high-affinity state of D2 receptors in vivo using positron emission tomographyJOURNAL OF NEUROCHEMISTRY, Issue 4 2006Nathalie Ginovart Abstract [11C]-(+)-PHNO (4-propyl-9-hydroxynaphthoxazine) is a new agonist radioligand that provides a unique opportunity to measure the high-affinity states of the D2 receptors (D2 -high) using positron emission tomography (PET). Here we report on the distribution, displaceablity, specificity and modeling of [11C]-(+)-PHNO and compare it with the well characterized antagonist D2 radioligand, [11C]raclopride, in cat. [11C]-(+)-PHNO displayed high uptake in striatum with a mean striatal binding potential (BP) of 3.95 ± 0.85. Pre-treatment with specific D1 (SCH23390), D2 (raclopride, haloperidol) and D3 receptor (SB-277011) antagonists indicated that [11C]-(+)-PHNO binding in striatum is specific to D2 receptors. Within-subject comparisons showed that [11C]-(+)-PHNO BP in striatum was almost 2.5-fold higher than that measured with [11C]-(,)-NPA ([11C]-(,)-N-propyl-norapomorphine). Comparison of the dose-effect of amphetamine (0.1, 0.5 and 2 mg/kg; i.v.) showed that [11C]-(+)-PHNO was more sensitive to the dopamine releasing effect of amphetamine than [11C]raclopride. Amphetamine induced up to 83 ± 4% inhibition of [11C]-(+)-PHNO BP and only up to 56 ± 8% inhibition of [11C]raclopride BP. Scatchard analyses of [11C]-(+)-PHNO and [11C]raclopride bindings in two cats showed that the Bmax obtained with the agonist (29.6 and 32.9 pmol/mL) equalled that obtained with the antagonist (30.6 and 33.4 pmol/mL). The high penetration of [11C]-(+)-PHNO in brain, its high signal-to-noise ratio, its favorable in vivo kinetics and its high sensitivity to amphetamine shows that [11C]-(+)-PHNO has highly suitable characteristics for probing the D2 -high with PET. [source] Poly(ethylene terephthalate) reinforced by N,N,-diphenyl biphenyl-3,3,,4,4,-tetracarboxydiimide moietiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2002Jun Xiao Abstract Starting with 3,3,,4,4,-biphenyltetracarboxylic dianhydride and methyl aminobenzoate, we synthesized a novel rodlike imide-containing monomer, N,N,-bis[p -(methoxy carbonyl) phenyl]-biphenyl-3,3,,4,4,-tetracarboxydiimide (BMBI). The polycondensation of BMBI with dimethyl terephthalate and ethylene glycol yielded a series of copoly(ester imide)s based on the BMBI-modified poly(ethylene terephthalate) (PET) backbone. Compared with PET, these BMBI-modified polyesters had higher glass-transition temperatures and higher stiffness and strength. In particular, the poly(ethylene terephthalate imide) PETI-5, which contained 5 mol % of the imide moieties, had a glass-transition temperature of 89.9 °C (11 °C higher than the glass-transition temperature of PET), a tensile modulus of 869.4 MPa (20.2 % higher than that of PET), and a tensile strength of 80.8 MPa (38.8 % higher than that of PET). Therefore, a significant reinforcing effect was observed in these imide-modified polyesters, and a new approach to higher property polyesters was suggested. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 852,863, 2002; DOI 10.1002/pola.10169 [source] Perfusion in free breast reconstruction flap zones assessed with positron emission tomographyMICROSURGERY, Issue 6 2010Aleksi Schrey M.D. The aim of this pilot study was to determine the postoperative blood perfusion (BFPET) and perfusion heterogeneity (BFPET HG) in free microvascular breast reconstruction flap zones with positron emission tomography (PET). Regional BFPET and BFPET HG of the adipose tissue in medial, central, and lateral parts of 13 free flaps were assessed on the first postoperative morning with PET using oxygen-15-labeled water ([15O]H2O) in 12 patients undergoing breast reconstruction with a deep inferior epigastric perforator (DIEP) or a transverse rectus abdominis muscle (TRAM) flap. The mean BFPET values did not differ between DIEP and TRAM flaps (P = 0.791). The mean BFPET values were higher in zone III compared with zone I (P = 0.024). During follow-up, fat necrosis was identified in three patients in the medial part (zone II) of the flap. However, the adipose tissue BFPET assessed on the first postoperative day from all zones of the flap using PET with radiowater was normal. The BFPET HG was higher in the control side (i.e., in the healthy breast tissue) compared with the flap (P = 0.042). The BFPET HG was lower in zone III than in zone I (P = 0.03) and in zone II (P < 0.001). In this pilot study, PET was used for the first time for studying the adipose tissue perfusion in different zones in free flaps in a clinical setup, finding that the mean BFPET values did not differ between DIEP and TRAM flaps, and that zone II was sometimes not as well perfused as zone III supporting revisited zone division. © 2010 Wiley-Liss, Inc. Microsurgery 30:430,436, 2010. [source] Recycling of poly(ethylene terephthalate) as polymer-polymer composites,POLYMER ENGINEERING & SCIENCE, Issue 4 2002M. Evstatiev Microfibrillar reinforced composites (MFC) comprising an isotropic matrix from a lower melting polymer reinforced by microfibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding. Low density polyethylene (LDPE) (matrix) and recycled poly(ethylene terephthalate) (PET) (reinforcing material) from bottles were melt blended (in 30/70 and 50/50 PET/LDPE wt ratio) and extruded, followed by continuous drawing, pelletizing and injection molding of dogbone samples. Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS), dynamic mechanical thermal analysis (DMTA), and mechanical testing. SEM and WAXS showed that the extruded blend is isotropic but becomes highly oriented after drawing, being converted into a polymer-polymer composite upon injection molding at temperatures below the melting temperature of PET. This MFC is characterized by an isotropic LDPE matrix reinforced by randomly distributed PET microfibrils, as concluded from the WAXS patterns and SEM observations. The MFC dogbone samples show impressive mechanical properties,the elastic modulus is about 10 times higher than that of LDPE and about three times higher than reinforced LDPE with glass spheres, approaching the modulus of LDPE reinforced with 30 wt% short-glass fibers (GF). The tensile strength is at least two times higher than that of LDPE or of reinforced LDPE with glass spheres, approaching that of reinforced LDPE with 30 wt% GF. The impact strength of LDPE increases by 50% after reinforcement with PET. It is concluded that: (i) the MFC approach can be applied in industrially relevant conditions using various blend partners, and (ii) the MFC concept represents an attractive alternative for recycling of PET as well as other polymers. [source] Effect of poly(ethylene glycol) on the solid-state polymerization of poly(ethylene terephthalate)POLYMER INTERNATIONAL, Issue 3 2006E Bhoje Gowd Abstract Poly(ethylene glycol) (PEG) and end-capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol,1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in Tg and similar crystallization behavior. Solid-state polymerization (SSP) was performed on these blend samples using Sb2O3 as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry [source] Cognitive reserve hypothesis: Pittsburgh Compound B and fluorodeoxyglucose positron emission tomography in relation to education in mild Alzheimer's diseaseANNALS OF NEUROLOGY, Issue 1 2008Nina M. Kemppainen MD Objective The reduced risk for Alzheimer's disease (AD) in high-educated individuals has been proposed to reflect brain cognitive reserve, which would provide more efficient compensatory mechanisms against the underlying pathology, and thus delayed clinical expression. Our aim was to find possible differences in brain amyloid ligand 11C-labeled Pittsburgh Compound B ([11C]PIB) uptake and glucose metabolism in high- and low-educated patients with mild AD. Methods Twelve high-educated and 13 low-educated patients with the same degree of cognitive deterioration were studied with PET using [11C]PIB and 18F-fluorodeoxyglucose as ligands. The between-group differences were analyzed with voxel-based statistical method, and quantitative data were obtained with automated region-of-interest analysis. Results High-educated patients showed increased [11C]PIB uptake in the lateral frontal cortex compared with low-educated patients. Moreover, high-educated patients had significantly lower glucose metabolic rate in the temporoparietal cortical regions compared with low-educated patients. Interpretation Our results suggesting more advanced pathological and functional brain changes in high-educated patients with mild AD are in accordance with the brain cognitive reserve hypothesis and point out the importance of development of reliable markers of underlying AD pathology for early AD diagnostics. Ann Neurol 2007 [source] | ||||||||||||||||