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Morphological Study (morphological + study)

Distribution by Scientific Domains

Medical Sciences	28%
Life Sciences	28%
Polymers and Materials Science	23%
Chemistry	10%
Physics and Astronomy	5%
2 Other Domains	6%

Selected Abstracts

Phase Reversion-Induced Nanograined/Ultrafine-Grained Structures in Austenitic Stainless Steel and their Significance in Modulating Cellular Response: Biochemical and Morphological Study with Fibroblasts,

ADVANCED ENGINEERING MATERIALS, Issue 12 2009
R. Devesh Kumar Misra
Materials science, engineering, and biological sciences have been combined to improve the tissue compatibility of medical devices. In this regard, nano/ultrafine structuring of austenitic stainless steel obtained using an innovative approach of "phase-reversion" has been evaluated for modulation of cellular activity. The biochemical and morphology study with fibroblasts point toward the improvement of tissue compatibility on comparison with coarse-grained structures, strengthening the foundation of nanostructured materials for bio-medical applications. [source]

Gas-Phase Polymerization with Transition Metal Catalysts Supported on Montmorillonite , A Particle Morphological Study

MACROMOLECULAR SYMPOSIA, Issue 1 2009
Sang-Young A. Shin
Abstract This investigation focuses on the mechanism of particle fragmentation and growth when clay-supported metallocene catalysts are used to polymerize ethylene in gas-phase reactors. We supported bis(cyclopentadienyl)-zirconium dichloride (Cp2ZrCl2) on montmorillonite (MMT) pretreated with triisobutylaluminum and 10-undecence-1-ol to produce in-situ polyethylene-clay nanocomposites. During gas phase polymerization, the MMT layers were exfoliated by the growing polymer chains, starting from the openings of the clay galleries. After microtoming, the cross-section of the fragmented MMT particles showed bundles of distorted silicate layer stacks, proving that exfoliation took place during polymerization, producing an in-situ polyethylene-clay nanocomposite. Calculations of d-spacing by transmission electron microscopy (TEM) matched those measured by X-ray diffraction (XRD) analysis. [source]

A Morphological Study of Age Changes in Adult Human Auricular Cartilage With Special Emphasis on Elastic Fibers

THE LARYNGOSCOPE, Issue 5 2001
Isamu Ito MD
Abstract Objective It is well known that the size of the human auricle increases after it has finished development. The reason why the size of the human auricle continues to enlarge until advanced age after reaching adulthood was investigated by observation of the ultrastructure of elastic fibers in human auricular cartilage. Methods A total of 1958 subjects (966 males and 992 females) were classified into 18 age groups from 0 to 5 years up to 85 years and above by 5-year intervals. Ear length, ear width, and length of ear attachment were measured with calipers. Human auricular cartilage was obtained from 26 subjects (16 males and 10 females) aged 14 to 79 years, stained by orcein, and examined by light and electron microscopy. Results Each item of measurement of human auricular size increased significantly with age in both males and females. On morphological examination by light and electron microscopy after orcein staining, elastic fibers in the cartilage were almost homogeneous in diameter and surrounded the cartilage lacuna in bundle-like fashion in young persons, whereas those in elderly persons were heterogeneous in thickness and had many fragments surrounding the territorial matrix. In elderly persons, collagen-like fibers and small vesicles with heterogeneous electron density were frequently observed near elastic bundles around the territorial matrix. Conclusion Structural changes of auricular cartilage associated with morphological age changes of elastic fibers may be one of the causes of expansion of the auricle after reaching adulthood. [source]

A Morphological Study of Skeletal Development in Turkey during the Pre-Hatching Stage

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2009
S. H. Atalgin
Summary Skeletal chondrofication, ossification and growth of turkey embryos were investigated and analysed to enable assessment of the developmental status and evaluation of the experimental effects on skeletal development, skeletal mutations and development of cultured embryos. Ten embryos were prepared every 24 h from 8 to 28 days of incubation. The fixed embryos were cleared and stained in toto with Alcian blue & Alizarin red for cartilage and ossified components, respectively. Observation of the skeleton was performed under a stereoscopic microscopy, with special attention to the timing of chondrofication and ossification of the bones. The first occurrence of the primary ossification centres was observed in the femur, tibiotarsus, and the dentary and supra-angular of the mandible on the 12th day, followed immediately by the other long bones. Skeletal features of the skull were determined to show the latest appearance of cartilage and ossification. Hence, all elements of the hyolingual apparatus remained cartilaginous until hatching took place except for the ceratobranchial. Even though the vertebral column chondrified earlier as compared with the ribs and sternum, they ossified later. While chondrofication was present in all the regions of the vertebral column at the same time, ossification progressed from the cervical through caudal regions. The growth rate of the femur was eminently higher than that of the humerus with increase in time, particularly after the 20th day of incubation. This seems to be obviously natural because the eggs used in the study are from the broiler turkey, which gains giant muscle mass at a very short period; precocity is probably at the expense of the bones of the leg rather than those of the wing. [source]

Early Maternal Changes Contributing to the Formation of the Chorioallantoic and Yolk Sac Placentas in Rat: a Morphological Study

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2003
C. Kalo
Summary In order to determine the maternal changes contributing to the formation of the chorioallantoic and yolk-sac placentas, rat gestation sites were examined by light and electron microscopy on days 7 through 10 of pregnancy. On day 7, the implantation chamber showed different compartments and contained the blastocyst in the antimesometrial chamber. The epithelial lining of the implantation chamber disappeared at the antimesometrial chamber, transformed into disintegrated cells in the mesometrial chamber, and showed signs of the programmed cell death in the decidual crypt. On day 8, the mesometrial chamber lumen contained red blood cells and it was continuous with subepithelial sinusoids. The endothelial cells lining the mesometrial sinusoids also showed some characteristics of the sprouting type angiogenesis such as hypertrophy and cell proliferation. While the yolk-sac placental circulation was more obvious with participation of the giant trophoblasts at the antimesometrial pole of the conceptus on day 9, the antimesometrial cells showed autophagic degeneration after the formation of the chorioallantoic placenta on day 10. The contribution of the regional cell death and angiogenesis to form both of the two placentas are discussed. [source]

Morphological study of the lingual papillae of the giant panda (Ailuropoda melanoleuca) by scanning electron microscopy

JOURNAL OF ANATOMY, Issue 2 2008
J. F. Pastor
Abstract Due to the scarcity of giant pandas, there are few descriptions of their morphology and even fewer of their microscopic anatomy and the ultrastructure of their organs. In this study of the complete tongue of an adult male giant panda, we describe the morphology of its lingual surface, the different types of papillae, their characteristics and topographic distribution. It was seen that there are four main types of lingual papillae: filiform, conical, fungiform and vallate. There was no sign of foliate papillae, tuberculum intermolare or sublingua. Papilla distribution was not limited to the dorsum of the tongue, but was also seen on the anterior and ventral surfaces of the tongue. In the anterior third of the midline there is a smooth area with no papillae at all. Morphology of the microgrooves and pores is similar to that observed in other mammals. The papillae share characteristics encountered in Carnivora and herbivorous species of mammals. A narrow bamboo-based diet and specialized manner of eating have together resulted in modification of the tongue of a carnivoran, giving it some characteristics typical of an herbivore. [source]

Morphological study of Czochralski-grown lanthanide orthovanadate single crystals and implications on the mechanism of bulk spiral formation

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010
Hengjiang Cong
Single crystals of monoclinic Nd:LaVO4 with dimensions up to Ø28 × 21,mm have been grown from the near-stoichiometric melt by the Czochralski method, making use of various seed orientations that are perpendicular to the (010), (10), (001) and (00) crystal planes. A sample was also prepared with the seed orientation in an arbitrary direction relative to the crystal. The anisotropic properties of the crystal are manifested in the growth morphology of the as-grown crystals, where different degrees of bulk spiral growth were observed. It was also found that employing the (001) or (00) seed faces severely suppressed the bulk spiral growth, and thus high quality and large-scale Nd:LaVO4 crystals were obtained. The constituent segregation coefficients and high-temperature stability, including the melting point, were determined and evaluated. Based on the attachment energy model of Hartman,Perdok theory, morphology predictions were made for monoclinic LaVO4 and tetragonal YVO4 orthovanadate single crystals. Correlating with the as-grown morphology of both crystals developed along different seed orientations, a theoretical explanation is provided for the influences of seed crystals on bulk spiral formation, crystal quality and utilization ratio. It suggests that breaking the axial symmetry of the ideal atomic level interface between crystal and melt plays a crucial triggering role in bulk spiral formation in the Czochralski growth of lanthanide orthovanadate single crystals. Selecting a proper seed orientation that yields such a highly axially symmetric surface structure consisting of a series of large-area facets with similar growth velocities can greatly reduce bulk spiral formation and thus is preferable in the Czochralski growth of large-sized low-symmetry oxide crystals. [source]

Structures and properties of ternary blends of recycled poly(ethylene terephthalate)/bisphenol-A polycarbonate/(E/nBA/GMA)

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Yong Peng
Abstract Recycled poly(ethylene terephthalate)/bisphenol-A polycarbonate/PTW (ethylene, butylacrylate (BA), and glycidylmethacrylate (E/nBA/GMA) terpolymer) were blended in different sequence through low temperature solid state extrusion (LTSSE) was studied. R-PET/PC blends were toughened by PTW, resulting in the improvement of impact strengths. In tensile test, the (PC/PTW)/r-PET blends made by mixing r-PET with the preblend of PC/PTW had noticeable strengthening effect on its tensile properties, which was not impaired by the rubber content due to its strain-hardening occurred following its necking at the constant load. Morphological study by scanning electron microscopy (SEM) was in conformity with the mechanical result. For the (PC/PTW)/r-PET blends, the PC particles were well embedded in the PET matrix and the smooth morphology exhibited. The DSC thermographs for heating and cooling run indicated that the crystallinity of PET rich phase was affected by different blending sequence. In the FTIR test, the different absorption intensity of PC aromatic carbonate carbonyl band was clearly illustrated. The results indicated different blending sequence led to different blending effect. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Morphological study of non-polar (11-20) GaN grown on r-plane (1-102) sapphire

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
C. F. Johnston
Abstract In order to grow high quality non-polar GaN-based LED structures it is important to understand the mechanism of GaN growth by MOVPE on r-plane (1-102) sapphire. In this work, (11-20) GaN epilayers have been characterised at three stages of growth using high resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Following nucleation, 3D islands were grown, then the V/III ratio was lowered and the islands coalesced to form a smooth film. A series of symmetric XRD ,-scans obtained at different azimuthal angles revealed an anisotropy in the layers with respect to the [1-100] and [0001] axes. AFM scans show that the islands are elongated along the [0001] axis. TEM has been used to analyse the layers further. A high density of stacking faults (5x105 cm,1) and threading dislocations (4x1010 cm,2) was found in the film with 120 s high V/III growth followed by low V/III growth. Defects were found to run perpendicular and at ,60 degrees to the sapphire interface in uncoalesced "island" samples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Effects of Ureaplasma urealyticum infection on the male reproductive system in experimental rats

ANDROLOGIA, Issue 5 2010
Y. Wang
Summary To study the effects of Ureaplasma urealyticum (Uu) infection on the male reproductive system, the mechanism of infertility induced by Uu infection was investigated in experimental rats. Male Sprague,Dowley rats were infected with Uu4 (serotype 4) through repeated natural sexual intercourse for 8 weeks to establish infection. After 8 weeks, the blood samples of the animals were collected and analysed for cytokine production, and the animals were microdissected for the analysis of the reproductive system. Morphological study showed that spermatozoa exhibited curling and breaks in the rats infected at different dosages. Of the infected rats, 27.5% had both soft and hard calculi in the urinary tract, compared with 12% in the control groups. Uu infection resulted in a decline of sperm quality, eventually leading to the death of the spermatozoa. In the infected animals, the serum interleukin 6 and interleukin 8 levels increased significantly (P < 0.05), while tumour necrosis factor-alpha and interferon-gamma showed only modest changes. Our observations showed that Uu infection has an impact on sperm morphology, leading to the death of the spermatozoa. It is plausible that the morphological alterations of spermatozoa induced by Uu infection are one of the possible factors that contribute to male infertility. [source]

Effect of seeding sludge type and hydrodynamic shear force on the aerobic sludge granulation in sequencing batch airlift reactors

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
K. Y. Koh
Abstract Two sequencing batch airlift reactors (SBARs) were operated simultaneously for two separate runs. In the first run, two different types of seeding sludge were cultivated in two separate reactors under the same superficial air velocity (SAV). In the second run, the same seeding sludge was cultivated in both reactors but under different SAV, i.e. 1.2 and 3.6 cm s,1. Both runs were carried out for a period of about 20 days, during which the chemical oxygen demand (COD) removal efficiency and morphology of sludge were examined. Batch tests using sodium acetate as the main carbon source were conducted to investigate the COD removal efficiency, and the morphologies of sludge were examined under light microscopy. Results showed that the COD removal efficiency improved with cultivation time. Morphological study showed that all cultivated sludge lost their filamentous species after a few days of cultivation, leaving behind communities of loosely packed pellet-like groups. Although the SAV recommended by other researchers was applied to the SBAR, granulation did not take place at the end of both experimental runs. It was suspected that the failure for aerobic sludge to granulate under the selected operating strategies and reactor configuration was partly due to the intrinsic traits of the sludge microbial community. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Morphological study of acute zonal occult outer retinopathy (AZOOR) by multiplanar optical coherence tomography

ACTA OPHTHALMOLOGICA, Issue 4 2009
Yoshiko Takai
Abstract. Purpose:, We set out to determine whether morphological retinal changes occur in patients with acute zonal occult outer retinopathy (AZOOR). Methods:, Five patients diagnosed with AZOOR were studied. They included two men and three women, with an age range of 23,51 years. Symptoms and findings were retrospectively and prospectively collected. The three-dimensional multiplanar optical coherence tomography (OCT) Ophthalmoscope® was used to examine the morphology of the retina in patients who were examined between April 2000 to December 2004. Standardized full-field electroretinograms (ERGs) and multifocal ERGs (mfERGs) were recorded. Results:, All the patients reported an acute onset of visual disturbances including a decrease of central vision and photopsia. The a- and b-waves of full-field ERGs were decreased, and the mfERGs in the central area were reduced. Ophthalmoscopic examination showed no obvious fundus abnormalities. OCT Ophthalmoscopic® images of a cross-sectional plane revealed hyporeflection at the level of the photoreceptor layer in the macular region in three of five patients, and presence of one or two layers in which the inner/outer segment junction of the photoreceptor layer was absent in the other two patients. En-face, constant depth C-scans, which present the image parallel to the retina, revealed an abnormal, patchy hyper-reflection in the affected eyes of two patients and in the non-affected eye in one of these two patients. Conclusions:, The changes in OCT Ophthalmoscope® B-scan images indicate morphological damage to the photoreceptors, which probably accounts for the functional alterations. The alterations in the C-scan image in the normal fellow eye of one patient suggest that morphological changes may precede symptomatic changes. [source]

Human breast areolae as scent organs: Morphological data and possible involvement in maternal-neonatal coadaptation

DEVELOPMENTAL PSYCHOBIOLOGY, Issue 2 2006
Benoist Schaal
Abstract In humans, areolar skin glands (AG) enlarge during pregnancy and lactation. Their role in mother-infant interactions may pertain to protective, mechanical, and communicative functions. It was questioned here whether more profuse AG could be related to more optimal adaptation to breastfeeding. A morphological study of the areolae was undertaken between birth and day 3 to assess the number, secretory status, and spatial distribution of AG. These data were related to infants' weight variation, mothers' perception of their infant's behavior at breast, and time between delivery and onset of lactation. AG were seen in virtually all women but with great interindividual variations; their areolar distribution was nonrandom, and about 1/5 of the women had AG giving off a secretion. The AG number was positively related with neonatal weight gain between birth and day 3, and with the mother's perception of infant's latching speed and sucking activity. AG numbers were also positively related with the onset of lactation in first-time mothers. In conclusion, the maternal endowment in AG may contribute to the infants' breastfeeding performance, early growth, and the mother's lactation onset. © 2006 Wiley Periodicals, Inc. Dev Psyshobiol 48: 100,110, 2006. [source]

Lucidina kotbandia, a New Species (Coleoptera: Lampyridae) from Korea

ENTOMOLOGICAL RESEARCH, Issue 3 2005
Hae Chul PARK
ABSTRACT We described one new Lampyrid species, Lucidina kotbandia Park et Kang n. sp. from Korea. Based on comparative morphological study and distribution, the new species mainly distributed in Hamgyeongnam-Do, Gangweon-Do, Gyeonggi-Do and Chungcheongbuk-Do of Korea. Also, the descriptions, the illustration of the adult habitus and line drawings of the aedeagus of Lucidina kotbandia Park et Kang n. sp. were provided. [source]

Absence of lymphatic vessels in human dental pulp: a morphological study

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2010
Renato Gerli
Gerli R, Secciani I, Sozio F, Rossi A, Weber E, Lorenzini G. Absence of lymphatic vessels in human dental pulp: a morphological study. Eur J Oral Sci 2010; 118: 110,117. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci Few and controversial data are available in the literature regarding the presence of lymphatic vessels in the human dental pulp. The present study was designed to examine morphologically the existence of a lymph drainage system in human dental pulp. Human dental pulp and skin sections were immunohistochemically stained with specific antibodies for lymphatic endothelium (D2-40, LYVE-1, VEGFR-3 [vascular endothelial growth factor receptor-3], and Prox-1), with the pan-endothelial markers CD31 and von Willebrand factor (vWF), and with the blood-specific marker CD34. Several blood vessels were identified in human pulps and skin. Lymphatic vessels were found in all human skin samples but in none of the pulps examined. Western blotting performed on human dermis and on pulps treated with collagenase (to remove odontoblasts) confirmed these results. Transmission electron microscopy indicated that vessels which, by light microscopy, appeared to be initial lymphatic vessels had no anchoring filaments or discontinuous basement membrane, both of which are typical ultrastructural characteristics of lymphatic vessels. These results suggest that under normal conditions human dental pulp does not contain true lymphatic vessels. The various theories about dental pulp interstitial fluid circulation should be revised accordingly. [source]

Evaluation of gastric toxicity of indomethacin acid, salt form and complexed forms with hydroxypropyl-,-cyclodextrin on Wistar rats: histopathologic analysis

FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 6 2009
A.C. Ribeiro-Rama
Abstract Indomethacin (IM) is a non-steroidal anti-inflammatory drug which inhibits prostaglandin biosynthesis. It is practically insoluble in water and has the capacity to induce gastric injury. Hydroxypropyl-,-cyclodextrin (HP-,-CD) is an alkylated derivative of ,-CD with the capacity to form inclusion complexes with suitable molecules. IM is considered to form partial inclusion complexes with HP-,-CD by enclosure of the p -chlorobenzoic part of the molecule in the cyclodextrin channel, reducing the adverse effects. The aim of this paper is to evaluate the gastric damage induced by the IM inclusion complex prepared by freeze-drying and spray-drying. A total of 135 Wistar rats weighing 224.4 ± 62.5 g were put into 10 groups. They were allowed free access to water but were maintained fasted for 18 h before the first administration until the end of the experiment. IM acid-form, IM trihydrated-sodium-salt and IM-HP-,-CD spray and freeze-dried, at normal and toxic doses, were administered through gastric cannula once/day for 3 days. Seventy-two hours after the first administration, the animals were sacrificed and the stomachs collected and prepared for morphological study by using the haematoxylin-eosin technique. Lesion indexes (rated 0/4) were developed and the type of injury was scored according to the severity of damage and the incidence of microscopic evidence of harm. Microscopic assessment demonstrated levels of injury with index one on 10,25%. The type of complexation method had different incidence but the same degree. The results show that IM inclusion complexation protects against gastric injury, reducing the incidence and the maximum degree of severity from 4 to 1, with a better performance of the spray-dried complex. [source]

An ecomorphological study of the raptorial digital tendon locking mechanism

IBIS, Issue 3 2006
LUKE EINODER
Extensive adaptive radiation in hindlimb design among raptors is well known. However, the degree of variation in the structure and expression of the digital tendon locking mechanism (TLM) and its adaptive significance have received little attention. This comparative morphological study of 12 raptor and three non-raptor species revealed a distinct raptorial design, characterized by a distally located TLM that is densely packed with locking elements of increased robustness and height. Although the Falconiformes and Strigiformes converged upon this pattern, unique design features were identified among the nocturnal birds of prey. Variation in TLM structure was often consistent with phylogeny, although interfamily similarities were revealed among a number of species with the same dietary habit. The evolutionary factors that may have led to the observed variation, as well as the biomechanical implications of varying designs, are discussed. [source]

The ancient inhabitants of Jebel Moya redux: measures of population affinity based on dental morphology

INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2007
J. D. Irish
Abstract This paper reexamines some of the methods and craniometric findings in the classic volume The Ancient Inhabitants of Jebel Moya (Sudan) (1955) by Mukherjee, Rao & Trevor, in light of recent archaeological data and relative to a new dental morphological study. Archaeological evidence characterises these inhabitants as having been heavily influenced by outside sources; yet they managed to establish and maintain their own distinctive culture as seen in the site features and surviving artefact collections. The dental study, modelled after the original craniometric-based investigation and using the same or similar comparative samples, detected complementary indications of outside biological influence. In the study, up to 36 dental traits were recorded in a total of 19 African samples. The most influential traits in driving inter-sample variation were then identified, and phenetic affinities were calculated using the Mahalanobis D2 statistic for non-metric traits. If phenetic similarity provides an estimate of genetic relatedness, these affinities, like the original craniometric findings, suggest that the Jebel Moyans exhibited a mosaic of features that are reminiscent of, yet distinct from, both sub-Saharan and North African peoples. Together, these different lines of evidence correspond to portray the Jebel Moya populace as a uniform, although distinct, biocultural amalgam. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Structure of nanoporous zirconia-based powders synthesized by different gel-combustion routes

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007
Jorge R. Casanova
Zirconia-based ceramics that retain their metastable tetragonal phase at room temperature are widely studied due to their excellent mechanical and electrical properties. When these materials are prepared from precursor nanopowders with high specific surface areas, this phase is retained in dense ceramic bodies. In this work, we present a morphological study of nanocrystalline ZrO2,2.8 mol% Y2O3 powders synthesized by the gel-combustion method, using different organic fuels , alanine, glycine, lysine and citric acid , and calcined at temperatures ranging from 873 to 1173,K. The nanopore structures were investigated by small-angle X-ray scattering. The experimental results indicate that nanopores in samples prepared with alanine, glycine and lysine have an essentially single-mode volume distribution for calcination temperatures up to 1073,K, while those calcined at 1173,K exhibit a more complex and wider volume distribution. The volume-weighted average of the nanopore radii monotonically increases with increasing calcination temperature. The samples prepared with citric acid exhibit a size distribution much wider than the others. The Brunauer,Emmett,Teller technique was used to determine specific surface area and X-ray diffraction, environmental scanning electron microscopy and transmission electron microscopy were also employed for a complete characterization of the samples. [source]

Preparation of ultra-high-molecular-weight polyethylene and its morphological study with a heterogeneous Ziegler,Natta catalyst

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
G. H. Zohuri
Abstract Ultra-high-molecular-weight polyethylene (PE) with viscosity-average molecular weight (Mv) of 3.1 × 106 to 5.2 × 106 was prepared with a heterogeneous Ziegler,Natta MgCl2 (ethoxide type)/TiCl4/triethylaluminum catalyst system under controlled conditions. The optimum activity of the catalyst was obtained at a [Al]/[Ti] molar ratio of 61 : 1 and a polymerization temperature of 60°C, whereas the activity of the catalyst increased with monomer pressure and decreased with hydrogen concentration. The titanium content of the catalyst was 2.4 wt %. The rate/time profile of the catalyst was a decay type with a short acceleration period. Mv of the PE obtained decreased with increasing hydrogen concentration and polymerization temperature. The effect of stirrer speeds from 100 to 400 rpm did not so much affect the catalyst activity; however, dramatic effects were observed on the morphology of the polymer particles obtained. A stirrer speed of 200 rpm produced PE with a uniform globulelike morphological growth on the polymer particles. The particle size distributions of the polymer samples were determined and were between 14 and 67 ,m. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Dynamic rheological and morphological study of the compatibility of thermoplastic polyurethane/ethylene,octene copolymer blends

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Jin Yang
Abstract Two grafted ethylene,octene copolymers [POEs; i.e., POE-g-maleic anhydried (MAH) and aminated POE (denoted by POE-g-NH2) were used as compatibilizers in immiscible blends of thermoplastic polyurethane (TPU) and POE. The effects of the compatibilizers on the dynamic rheological properties and morphologies of the TPU/POE blends were investigated. The characteristic rheological behaviors of the blends indicated that the strong interactions between the two phases were due to the compatibilization. Microstructural observation confirmed that the compatibilizers were located at the interface in the blends and formed a stable interfacial layer and smaller dispersed phase particle size. Compared with POE- g -MAH, POE- g -NH2 exhibited a better compatibilization effect in the TPU/POE blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Compatibility study of recycled poly(vinyl chloride)/styrene-acrylonitrile blends

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007
David Garcia
Abstract The aim of the present study is to analyze the compatibility between recycled Poly(vinyl chloride) (PVC) and styrene-acrylonitrile copolymer (SAN). With this objective recycled PVC coming from credit cards have been blended with both virgin and recycled SAN with the aim of increase the benefits of recycled PVC. The compatibility of the components will be crucial for the final properties of the material. Furthermore, the recycled nature of some of the components will determine the compatibilization capability of the blend. The degradation level in the recycled materials was determined using Fourier transform infrared spectroscopy (FTIR). The compatibility between the PVC and the SAN was studied using differential scanning calorimetry and dynamic mechanical analysis. A greater compatibility was observed in mixtures of PVC and virgin SAN than in mixtures of PVC and recycled SAN. Finally, a morphological study of the fracture surface under cryogenic conditions was carried out using scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

External genital morphology of the ring-tailed lemur (Lemur catta): Females are naturally "masculinized"

JOURNAL OF MORPHOLOGY, Issue 4 2008
Christine M. Drea
Abstract The extravagance and diversity of external genitalia have been well characterized in male primates; however, much less is known about sex differences or variation in female form. Our study represents a departure from traditional investigations of primate reproductive anatomy because we 1) focus on external rather than internal genitalia, 2) measure both male and female structures, and 3) examine a strepsirrhine rather than an anthropoid primate. The subjects for morphological study were 21 reproductively intact, adult ring-tailed lemurs (Lemur catta), including 10 females and 11 males, two of which (one per sex) subsequently died of natural causes and also served as specimens for gross anatomical dissection. Male external genitalia presented a typical masculine configuration, with a complex distal penile morphology. In contrast, females were unusual among mammals, presenting an enlarged, pendulous external clitoris, tunneled by the urethra. Females had a shorter anogenital distance and a larger urethral meatus than did males, but organ diameter and circumference showed no sex differences. Dissection confirmed these characterizations. Noteworthy in the male were the presence of a "levator penis" muscle and discontinuity in the corpus spongiosum along the penile shaft; noteworthy in the female were an elongated clitoral shaft and glans clitoridis. The female urethra, while incorporated within the clitoral body, was not surrounded by erectile tissue, as we detected no corpus spongiosum. The os clitoridis was 43% the length and 24% the height of the os penis. On the basis of these first detailed descriptions of strepsirrhine external genitalia (for either sex), we characterize those of the female ring-tailed lemur as moderately "masculinized." Our results highlight certain morphological similarities and differences between ring-tailed lemurs and the most male-like of female mammals, the spotted hyena (Crocuta crocuta), and call attention to a potential hormonal mechanism of "masculinization" in female lemur development. J. Morphol., 2008. © 2007 Wiley-Liss, Inc. [source]

Poly(ester urethane)s with polycaprolactone soft segments: A morphological study

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002
Juliana Kloss
Abstract Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft-segment/hard-segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide-angle X-ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL-rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117,4130, 2002 [source]

Evidence of innervation following extracellular matrix scaffold-mediated remodelling of muscular tissues

JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 8 2009
Vineet Agrawal
Abstract Naturally occurring porcine-derived extracellular matrix (ECM) has successfully been used as a biological scaffold material for site-specific reconstruction of a wide variety of tissues. The site-specific remodelling process includes rapid degradation of the scaffold, with concomitant recruitment of mononuclear, endothelial and bone marrow-derived cells, and can lead to the formation of functional skeletal and smooth muscle tissue. However, the temporal and spatial patterns of innervation of the remodelling scaffold material in muscular tissues are not well understood. A retrospective study was conducted to investigate the presence of nervous tissue in a rat model of abdominal wall reconstruction and a canine model of oesophageal reconstruction in which ECM scaffolds were used as inductive scaffolds. Evidence of mature nerve, immature nerve and Schwann cells was found within the remodelled ECM at 28 days in the rat body wall model, and at 91 days post surgery in a canine model of oesophageal repair. Additionally, a microscopic and morphological study that investigated the response of primary cultured neurons seeded upon an ECM scaffold showed that neuronal survival and outgrowth were supported by the ECM substrate. Finally, matricryptic peptides resulting from rapid degradation of the ECM scaffold induced migration of terminal Schwann cells in a concentration-dependent fashion in vitro. The findings of this study suggest that the reconstruction of tissues in which innervation is an important functional component is possible with the use of biological scaffolds composed of extracellular matrix. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Sphere-to-Rod Transition of Micelles formed by the Semicrystalline Polybutadiene- block -Poly(ethylene oxide) Block Copolymer in a Selective Solvent

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010
Adriana M. Mihut
Abstract We present a morphological study of the micellization of an asymmetric semicrystalline block copolymer, poly(butadiene)- block -poly(ethylene oxide), in the selective solvent n -heptane. The molecular weights of the poly(butadiene) (PB) and poly(ethylene oxide) (PEO) blocks are 26 and 3.5,kg,·,mol,1, respectively. In this solvent, micellization into a liquid PEO-core and a corona of PB-chains takes place at room temperature. Through a thermally controlled crystallization of the PEO core at ,30,°C, spherical micelles with a crystalline PEO core and a PB corona are obtained. However, crystallization at much lower temperatures (,196,°C; liquid nitrogen) leads to the transition from spherical to rod-like micelles. With time these rod-like micelles aggregate and form long needles. Concomitantly, the degree of crystallinity of the PEO-cores of the rod-like micelles increases. The transition from a spherical to a rod-like morphology can be explained by a decrease of solvent power of the solvent n -heptane for the PB-corona chains: n -Heptane becomes a poor solvent at very low temperatures leading to a shrinking of the coronar chains. This favors the transition from spheres to a morphology with a smaller mean curvature, that is, to a cylindrical morphology. [source]

Phylogeny of the subgenus Culicoides and related species in Italy, inferred from internal transcribed spacer 2 ribosomal DNA sequences

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2006
L. M. Gomulski
Abstract., Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) include vectors for the economically important animal diseases, bluetongue (BT) and African horse sickness (AHS). In the Mediterranean Basin, these diseases are transmitted by four species of Culicoides: the first three belong in the subgenus Avaritia Fox and are Culicoides imicola Kieffer, Culicoides obsoletus (Meigen) and Culicoides scoticus Downes and Kettle; the fourth is Culicoides pulicaris (Linnaeus) in the subgenus Culicoides Latreille. In the Palaearctic Region, this subgenus (usually referred to as the C. pulicaris group) now includes a loose miscellany of some 50 taxa. The lack of clarity surrounding its taxonomy stimulated the present morphological and molecular study of 11 species collected in Italy. Phylogenetic analysis of nuclear ribosomal DNA internal transcribed spacer 2 (ITS2) sequence variation demonstrated a high degree of divergence. These results, combined with those from a parallel morphological study, disclosed: (1) that some previously described taxa should be resurrected from synonymy; (2) that there are new species to be described; (3) that the subgenus Culicoides (as currently employed) is a polyphyletic assemblage of four lineages , the subgenus Culicoides sensu stricto, the subgenus Silvicola Mirzaeva and Isaev, the subgenus Hoffmania Fox and the hitherto unrecognized Fagineus species complex. Each is discussed briefly (but not defined) and its constituent Palaearctic taxa listed. Strong congruence between morphological and molecular data holds promise for resolving many of the difficult taxonomic issues plaguing the accurate identification of vector Culicoides around the world. [source]

A New Method for the Treatment of Sperm Samples for Ultrastructural Study Based on the Use of Animal Tissues as Biological Containers

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 9 2007
Concepción Junquera
Abstract The study of the ultrastructure of spematozoa by means of transmission electron microscopy often presents with problems of interpretation according to the method employed, depending on whether samples are either centrifuged previously to the fixation or immersed in viscous gels. The major problems of interpretation are: changes in the location of vesicles originated during the maturation process and modifications in the adsorption of seminal plasma proteins to the sperm membrane surface. The aim of our study is to communicate an original new method for the treatment of spermatozoa for ultrastructural study. Our method is based on the use of animal tissues as biological containers, inside which the spermatic suspensions are included. We developed this method using fresh sperm samples taken from mature Rasa aragonesa rams. As biological container, we used 2.5-cm long segments of the intestine of 1-week-old chickens (Gallus gallus) (diameter around 4 mm). To avoid any influence of digestive enzymes of the mucosa on the sperm surface, we put each intestine fragment inside out by means of microdissection forceps under bifocal optical microscope and cold light. One of the edges was tied with thin suture silk. The sperm suspension was injected in the optimal experimental condition and amount. Finally, the still open edge of the intestine segment was tied with silk in the same way as the other segment edge. By using this technique, we can perform a suitable morphological study at an ultrastructural level. In addition, the functional relationship of the ultrastructural components of the target cells is correctly preserved. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source]

Phylogeny of the Neotropical sharpshooter genus Acrobelus Stål (Hemiptera, Cicadellidae, Cicadellinae)

MITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE IN BERLIN-DEUTSCHE ENTOMOLOGISCHE ZEITSCHRIFT, Issue 1 2007
Paula C. Ceotto
Abstract A comparative morphological study of the genus Acrobelus Stål, 1869 yielded 25 characters of the head, thorax, and male and female genitalia. The analysis included the five known Acrobelus species (A. reflexus, A. ecuadorianus, A. colombianus, A. nessimiani, and A. rakitovi), five outgroup taxa (Desamera eliasi, Deselvana excavata, Ichthyobelus bellicosus, Omagua fitchi, and Raphirhinus phosphoreus), and resulted in one most parsimonious tree. The monophyly of the genus is recovered with a single unambiguous apomorphy and relatively low support indices. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Assessment of spinal cord pathology following trauma using early changes in the spinal cord evoked potentials: A pharmacological and morphological study in the rat

MUSCLE AND NERVE, Issue S11 2002
Hari Shanker Sharma PhD
Abstract The possibility that spinal cord pathology following trauma can be assessed with early changes in the spinal cord evoked potentials (SCEPs) was examined in a rat model. Spinal cord injury (SCI) was produced in Equithesin-anesthetized (3 ml/kg, i.p.) rats through a longitudinal incision into the right dorsal horn at the T10,11 segments. The SCEPs were recorded with epidural electrodes placed over the T9 (rostral) segment of the cord. The SCEPs consisted of a small positive amplitude and a broad and high negative amplitude (NA). SCI resulted in an instant depression of the rostral NA that lasted for 1 h. However, the latency of NA continued to increase over time. At 5 h, spinal cord blood flow declined by 30% in the T9 segment, whereas the spinal cord water content and the permeability of the blood,spinal cord barrier (BSCB) were markedly increased. Damage to the nerve cells, glial cells, and myelin was quite common in the spinal cord, as seen by light and electron microscopy. Pretreatment with p -chlorophenylalanine, indomethacin, ibuprofen, and nimodipine attenuated the SCEP changes immediately after trauma and resulted in a marked reduction in edema formation, BSCB permeability, and blood flow changes at 5 h. However, pretreatment with cyproheptadine, dexamethasone, phentolamine, and propranolol failed to attenuate the SCEP changes after SCI and did not reduce the cord pathology. These observations suggest that early changes in SCEP reflect secondary injury-induced alterations in the cord microenvironment. Obviously, these changes are crucial in determining the ultimate magnitude and severity of cord pathology. © 2002 Wiley Periodicals, Inc. Muscle Nerve Supplement 11: S83,S91, 2002 [source]