检索结果-内蒙古大学图书馆

Preparation and Characterization of Polylactide-block-Poly(butylene adipate) Polyurethane Thermoplastic Elastomer

POLYMER ENGINEERING AND SCIENCE 2011年第5期51卷 908-916页

作者： Zhong, Qian Ren, Jie Wang, Qinfeng Tongji Univ Sch Mat Sci & Engn Inst Nano & Biopolymer Mat Shanghai 200092 Peoples R China Tongji Univ Minist Educ Key Lab Adv Civil Engn Mat Shanghai 200092 Peoples R China

Polylactide-block-poly(butylene adipate) poly(ester-urethane) (PLAEU) thermoplastic elastomer was obtained by melt chain extending reaction with polylactide-block-poly(butylene adipate)-block-polylactide (PBLA) and hexamethylene diisocyanate (HDI). PBLA was previously prepared with L-lactide and poly(butylene adipate) diol (PBA diol). Experimental parameters including feed ratio, polymerization temperature, and time were optimized. The weight average molecular weight (M-w) of PLAEU surpassed 10(5) g/mol. In contrast to corresponding PBLA, the crystallinity and melt temperature (T-m) of PLAEU decreased, whereas its glass transition (T-g) shifted to high temperature due to the 'pseudoextension' structure of polylactide (PLA) block. Additionally, the crystallinity and T-m of PLAEU were subject to crystallization method and molecular weight. The tensile strength of PLAEU varied from 6.61 to 24.41 MPa and elongation from 190% to 780%. Therefore, the mechanical properties of PLAEU can be regulated by altering the length ratio of PLA to PBA block. The high elasticity of PLAEU can be explained with phase separation mechanism. POLYM. ENG. SCI., 51:908-916, 2011. (C) 2011 Society of Plastics Engineers

关键词： LenRto Phase separation melting point Thermoplasts programmable logic arrays elastic bodies Adipates private beauty adviser Glycols

来源：评论

学校读者我要写书评

暂无评论

High speed insertion of bone fracture fixation pins: a finite element penetration model with experimental comparisons

引用

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 2011年第12期22卷 2823-2832页

作者： Prygoski, Matthew P. Pasang, Timotius Schmid, Steven R. Lozier, Antony J. Univ Notre Dame Dept Aerosp & Mech Engn Notre Dame IN 46637 USA AUT Univ Dept Mech & Mfg Engn Auckland New Zealand Zimmer Inc Warsaw IN USA

A new method of bone fracture fixation is considered in which small pins/darts are dynamically inserted into bone to prevent translation and rotation at the fracture site. An ABAQUS model was developed to analyze dart penetration in cortical and cancellous bone for varying dart diameter, material, and velocity, and cortical thickness. The method is advocated for bioresorbable darts, so polylactide (PLA) and magnesium are the materials examined in this study. Numerical results showed that magnesium darts can achieve full penetration in bone while suffering little damage. The PLA darts penetrated thin bone well, but substantial deformation was seen as the cortical thickness increased, especially for small diameter darts. As partial validation, prototype PLA fixation darts were fired into cadaveric bone with a custom nailer. As in the model, the PLA darts could penetrate thin cortices but saw gross deformation when impacted against thicker bone.

关键词： Cortex of kidney programmable logic arrays darts Cancellous Bone

来源：评论

学校读者我要写书评

暂无评论

Kinetics of Water Absorption and Thermal Properties of Poly(lactic acid)/Organomontmorillonite/Poly(ethylene glycol) Nanocomposites

引用

JOURNAL OF VINYL & ADDITIVE TECHNOLOGY 2011年第1期17卷 40-47页

作者： Leu, Ying Ying Chow, Wen Shyang Univ Sains Malaysia Sch Mat & Mineral Resources Engn Nibong Tebal 14300 Pulau Pinang Malaysia

Poly(lactic acid) (PLA)/organomontmorillonite (OMMT) nanocomposites were prepared by a melt intercalation technique. The effects of OMMT and poly(ethylene glycol) (PEG) on the thermal properties and water absorption behavior of PLA were investigated. The melting temperature and degree of crystallinity were comparable for the PLA and its nanocomposites. The glass transition temperature and crystallization temperature of PLA were decreased by the addition of PEG. X-ray diffraction results revealed the formation of PLA nanocomposites, as the OMMT was partly intercalated and partly exfoliated. The maximum moisture absorption of PLA was increased in the presence of PEG and the diffusivity of the PLA nanocomposites decreased with increasing concentrations of PEG. However, the activation energy of the nanocomposites increased as the loading of PEG increased. These results indicated that the incorporation of OMMT and PEG enhanced the water-barrier properties of the PLA. J. VINYL ADDIT. TECHNOL., 17:40-47, 2011. (C) 2011 Society of Plastics Engineers

关键词： Organo-modified montmorillonite Crystallization temperature programmable logic arrays Nanocomposites BARRIER PROPERTIES Activation energy Kinetics Polyethylene Glycols Thermal properties

来源：评论

学校读者我要写书评

暂无评论

Fabrication of novel PLA/CDHA bionanocomposite fibers for tissue engineering applications via electrospinning

引用

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 2011年第5期22卷 1183-1193页

作者： Zhou, Huan Touny, Ahmed H. Bhaduri, Sarit B. Univ Toledo Dept Bioengn Toledo OH 43606 USA Helwan Univ Dept Chem Cairo Egypt Univ Toledo Dept Mech Ind & Mfg Engn Toledo OH 43606 USA Univ Toledo Dept Surg Dent Toledo OH 43606 USA

The main theme here is to fabricate PLA (poly lactic-acid)/CDHA (carbonated calcium deficient hydroxyapatite) bionanocomposites, where both the constituents are biocompatible and biodegradable with one dimension in nanometer scale. Such materials are important in tissue engineering applications. The bionanocomposite fibers were fabricated via electrospinning. There are two important signatures of this paper. First, CDHA, rather than HA, is added to PLA as the second phase. As opposed to HA, CDHA mimics the bone mineral composition better and is biodegradable. Therefore, PLA/CDHA fibers should have better biodegradability while maintaining a physiological pH during degradation. To the best of our knowledge, this is the first attempt of electrospinning of such a composite. Second, the CDHA nanoparticles were synthesized using the benign low temperature biomimetic technique, the only route available for the retention of carbonate ions in the HA lattice. The structural properties, degradation behavior, bioactivity, cell adhesion, and growth capability of as-fabricated PLA/CDHA bionanocomposites were investigated. The results show that the incorporation of CDHA decreased PLA fiber diameters, accelerated PLA degradation, buffered pH decrease caused by PLA degradation, improved the bioactivity and biocompatibility of the scaffold. These results prove that PLA/CDHA bionanocomposites have the potential in tissue regeneration applications.

关键词： Electrospinning tissue regeneration Biological activity programmable logic arrays tissue repair One Dimension nanoscale Fiber biodegradability fabrication Fibrous materials Tissue Engineering HOUR ANGLE

来源：评论

学校读者我要写书评

暂无评论

Structure and Immunological Characterization of the Capsular Polysaccharide of a Pyrogenic Liver Abscess Caused by Klebsiella pneumoniae ACTIVATION OF MACROPHAGES THROUGH TOLL-LIKE RECEPTOR 4

引用

JOURNAL OF BIOlogicAL CHEMISTRY 2011年第24期286卷 21041-21051页

作者： Yang, Feng-Ling Yang, Yu-Liang Liao, Pei-Chun Chou, Ju-Ching Tsai, Keng-Chang Yang, An-Suei Sheu, Fuu Lin, Tzu-Lung Hsieh, Pei-Fang Wang, Jin-Town Hua, Kuo-Feng Wu, Shih-Hsiung Acad Sinica Inst Biol Chem Taipei 115 Taiwan Natl Ilan Univ Inst Biotechnol Ilan 260 Taiwan Acad Sinica Genom Res Ctr Taipei 115 Taiwan Natl Taiwan Univ Dept Hort Taipei 106 Taiwan Natl Taiwan Univ Dept Microbiol Taipei 100 Taiwan Natl Taiwan Univ Hosp Dept Internal Med Taipei 100 Taiwan

The active components of a primary pyrogenic liver abscess (PLA) Klebsiella pneumoniae in stimulating cytokine expression in macrophages are still unclear. The capsular polysaccharide (CPS) of PLA K. pneumoniae is important in determining clinical manifestations, and we have shown that it consists of repeating units of the trisaccharide (-> 3)-beta-D-Glc-(1 -> 4)-[2,3-(S)-pyruvate]-beta-D-GlcA-(1 -> 4)-alpha-L-Fuc-(1 ->) and has the unusual feature of extensive pyruvation of glucuronic acid and acetylation of C-2-OH or C-3-OH of fucose. We demonstrated that PLAK. pneumoniae CPS induces secretion of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) by macrophages through Toll-like receptor 4 (TLR4) and that this effect was lost when pyruvation and O-acetylation were chemically destroyed. Furthermore, expression of TNF-alpha and IL-6 in PLA K. pneumoniae CPS-stimulated macrophages was shown to be regulated by the TLR4/ROS/PKC-delta/NF-kappa B, TLR4/PI3-kinase/AKT/NF-kappa B, and TLR4/MAPK signaling pathways.

关键词： Interleukin-6 Macrophages THROUGH Liver Abscess Glucuronic Acids Fucose Klebsiella pneumoniae Active Components programmable logic arrays ACETYLATION Toll-Like Receptor 4 Polysaccharides Pneumonia Tumor Necrosis Factor-alpha

来源：评论

学校读者我要写书评

暂无评论

High Molecular Weight Poly (L-lactic Acid) Clay Nanocomposites Via Solid-State Polymerization

引用

POLYMER COMPOSITES 2011年第3期32卷 497-509页

作者： Katiyar, Vimal Nanavati, Hemant Indian Inst Technol Dept Chem Engn Bombay 400076 Maharashtra India

We propose here, a novel technique to synthesize high molecular weight (MW) poly (L-lactic acid)-clay nanocomposite (PLACN), via solid state polymerization (SSP). We synthesize prepolymer of PLACN (pre-PLACN) from both, L-lactic acid and L-lactide, as starting materials. Synthesis of pre-PLACN from L-lactic acid is carried out via in situ melt polycondensation (MP) of L-lactic acid oligomer, followed by SSP, to achieve high MW PLACN (M-w similar to 138,000 Da). In case of L-lactide as the starting material, we prepare L-lactide-clay intercalated mixture which yields moderate MW pre-PLACN during subsequent ring opening polymerization (ROP). Interestingly, ROP is performed by using hydroxyl functionalized ternary catalyst system (L-lactide Sn(II) octoate oligo (L-lactic acid) complex), which provides the terminal hydroxyl end-groups, required for step-growth SSP. Pre-PLACN MW is now increased to M-w similar to 127,000 Da, by the subsequent SSP process. H-1 NMR analyses confirm that these end-groups, are indeed consumed during SSP. During SSP, the PLACN also achieves up to 90% crystallinity, which may be due to the synchronization of the slow step-growth SSP of poly(L-lactic acid) (PLA) with the crystallization kinetics. Optical purity of PLACNs is similar to that of neat PLA, whereas the thermal stability of PLACNs is significantly superior. As evidenced by wide-angle X-ray scattering/small-angle X-ray scattering analyses and in line with the literature, both, intercalated and exfoliated PLACN morphologies, have been synthesized, by suitable selection of clays. We also verify the correlation between the PLA semicrystalline morphology and the PLACN morphology, which is consistent with those of PLACN synthesized by other techniques. POLYM. COMPOS., 32:497-509,2011. (C) 2011 Society of Plastics Engineers

关键词： Retinopathy of Prematurity poly-L-lactic acid programmable logic arrays solid state clays High molecular weight L-Lactic Acid STEP GROWTH

来源：评论

学校读者我要写书评

暂无评论

Continuous fabrication of monodisperse polylactide microspheres by droplet-to-particle technology using microfluidic emulsification and emulsion-solvent diffusion

引用

SOFT MATTER 2011年第21期7卷 9894-9897页

作者： Watanabe, Takaichi Ono, Tsutomu Kimura, Yukitaka Okayama Univ Grad Sch Environm Sci Dept Mat & Energy Sci Kita Ku Okayama 7008530 Japan

Monodisperse polylactide (PLA) microspheres were continuously fabricated by microfluidic emulsification and subsequent dilution in water. The diameter was precisely tuned from 6 to 50 mu m by changing the flow rate of the fluids in microfluidics or the PLA concentration in the dispersed phase. The use of amphiphilic oil-soluble poly(ethylene glycol)-b-polylactide (o-PEG-PLA) as a matrix resulted in a highly porous microsphere morphology, and the porosity was controlled by blending PLA. Therefore, mono-disperse PLA microspheres with the predetermined surface porosity were continuously produced by just enough reagents and energy.

关键词： programmable logic arrays microparticles PORE SURFACE Polylactides emulsifying Microfluidics Microspheres Flow rates

来源：评论

学校读者我要写书评

暂无评论

Transparent bionanocomposites with improved properties prepared from acetylated bacterial cellulose and poly(lactic acid) through a simple approach

引用

GREEN CHEMISTRY 2011年第2期13卷 419-427页

作者： Tome, Liliana C. Pinto, Ricardo J. B. Trovatti, Eliane Freire, Carmen S. R. Silvestre, Armando J. D. Pascoal Neto, Carlos Gandini, Alessandro Univ Aveiro CICECO P-3810193 Aveiro Portugal Univ Aveiro Dept Chem P-3810193 Aveiro Portugal

The preparation and characterization of biocomposite materials with improved properties based on poly(lactic acid) (PLA) and bacterial cellulose, and, for comparative purposes, vegetal cellulose fibers, both in their pristine form or after acetylation, is reported. The composite materials were obtained through the simple and green mechanical compounding of a PLA matrix and bacterial cellulose nanofibrils (or vegetable fibers), and were characterized by TGA, DSC, tensile assays, DMA, SEM and water uptake. The bionanocomposites obtained from PLA and acetylated bacterial cellulose were particularly interesting, given the considerable improvement in thermal and mechanical properties, as evidenced by the significant increase in both elastic and Young moduli, and in the tensile strength (increments of about 100, 40 and 25%, respectively) at very low nanofiller loadings (up to 6%). These nanocomposites also showed low hygroscopicity and considerable transparency, features reported here for the first time.

关键词： Cellulose Composites programmable logic arrays ACETYLATION cellulose microfibrils simplicial approximation Cellulose fibers Vegetable fibers poly(lactic acid)

来源：评论

学校读者我要写书评

暂无评论

Characterization and Prediction of Prolonged Air Leak After Pulmonary Resection: A Nationwide Study Setting Up the Index of Prolonged Air Leak

引用

ANNALS OF THORACIC SURGERY 2011年第3期92卷 1062-1068页

作者： Rivera, Caroline Bernard, Alain Falcoz, Pierre-Emmanuel Thomas, Pascal Schmidt, Aurelie Benard, Steve Vicaut, Eric Dahan, Marcel Haut Leveque Hosp CHU Bordeaux Dept Thorac Surg F-33604 Pessac France Bocage Hosp CHU Dijon Dijon France Civil Hosp CHU Strasbourg Strasbourg France North Hosp CHU Marseille Marseille France Steve Consultants Lyon France Fernand Widal Hosp Paris France Larrey Hosp CHU Toulouse Toulouse France

Background. The objective of this study was to better characterize prolonged air leak (PAL), defined as an air leak longer than 7 days, and to develop and validate a predictive model of this complication after pulmonary resection. Methods. All lung resections entered in Epithor, the French national thoracic database (French Society of Thoracic and Cardiovascular Surgery), were analyzed. Data collected between 2004 and 2008 (n = 24,113) were used to build the model using backward stepwise variable selection, and the 2009 data (n = 6,813) were used for external validation. The primary outcome was PAL. Results of the predictive model were used to propose a score: the index of PAL (IPAL). Results. Prevalence of PAL after pulmonary resection was 6.9% (n = 1,655) in the development data set. In the final model, 9 variables were selected: gender, body mass index, dyspnea score, presence of pleural adhesions, lobectomy or segmentectomy, bilobectomy, bulla resection, pulmonary volume reduction, and location on upper lobe. In the development data set, the C-index was 0.71 (95% confidence interval [CI], 0.70 to 0.72). At external validation, the C-index was 0.69 (95% CI, 0.66 to 0.72) and the calibration slope (ie, the agreement between observed outcomes and predictions) was 0.874 (<1). A score chart based on these analyses has been proposed. The formula to calculate the IPAL is the following: gender (F = 0;M = 4) - (body mass index-24) + 2 x dyspnea score + pleural adhesion (no = 0;yes = 4) + pulmonary resection (wedge = 0;lobectomy or segmentectomy = 7;bilobectomy = 11;bulla resection = 2;volume reduction = 14) + location (lower or middle lobe = 0;upper = 4). Conclusions. Surgeons can easily use the well-validated model to determine intraoperative preventive measures of PAL. (Ann Thorac Surg 2011;92:1062-8) (C) 2011 by The Society of Thoracic Surgeons

关键词： SHCBP1 gene programmable logic arrays Cardiovascular Surgical Procedures upper lobe air leakages LRIT1 gene Pneumonectomy

来源：评论

学校读者我要写书评

暂无评论

Estimating the Risk of Prolonged Air Leak after Pulmonary Resection Using a Simple Scoring System

引用

JOURNAL OF THE AMERICAN COLLEGE OF SURGEONS 2011年第6期212卷 1027-1032页

作者： Lee, Lawrence Hanley, Stephen C. Robineau, Catherine Sirois, Christian Mulder, David S. Ferri, Lorenzo E. McGill Univ Div Thorac Surg Ctr Hlth Dept Surg Montreal PQ H3G 1A4 Canada

BACKGROUND: The high rate of prolonged air leak (PAL) after pulmonary resection has prompted interest in surgical adjuncts designed to prevent this complication. However, these adjuncts are costly and might not be beneficial if used routinely. Identification of patients at highest risk might allow for more effective use of these adjuncts. Therefore, we sought to develop a simple scoring system to predict PAL. STUDY DESIGN: A derivation set of 580 patients was identified from a prospectively entered database of consecutive pulmonary resections at a single institution from 2002 to 2007. Patient and operative characteristics were compared using Student's t-test and chi-square tests. Significant variables on univariate analysis were entered into a stepwise logistic regression to establish a simple predictive model to estimate the risk of PAL. This scoring system was then validated in a consecutive set of 381 patients operated at the same institution from 2007 to 2009. RESULTS: The rate of PAL was 14% in the derivation set and 18% in the validation set. Poor pulmonary function (forced expiratory volume in 1 second and carbon monoxide diffusing capacity, percent predicted) and pleural adhesions were significantly associated with PAL in the derivation set. A weighted scoring system was devised using pleural adhesions (+2 points), forced expiratory volume in 1 second (+1 per 10% below 100%), and carbon monoxide diffusing capacity (+1 per 20% below 100%). Total number of points estimated the probability of PAL. Hosmer-Lemeshow goodness-of-fit test confirmed validity (p > 0.2) of this scoring system in the validation set. CONCLUSIONS: We have devised and validated a simple scoring system to predict the probability of PAL after pulmonary resection. (J Am Coll Surg 2011;212:1027-1032. (C) 2011 by the American College of Surgeons)

关键词： LRIT1 gene Pneumonectomy SHCBP1 gene programmable logic arrays scoring system air leakages pleural adhesion derivation Measurement of carbon monoxide diffusing capacity

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：