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At least 469 records · Page 26Linked to original sources

PubMed1991

Natural foods and their ecological implications for Macaca thibetana at Mount Emei, China.

Natural food plants of partly provisioned groups of Macaca thibetana included about 196 species belonging to 135 genera and 72 families. The macaques consumed mainly bamboo shoots and fruits for about 2 months in autumn, whereas they relied on active or passive provisions from visitors, a variety of structural parts of plants and a small amount of invertebrates in late spring and summer and ate mainly mature leaves and bark for the rest of the year. About half of the species eaten came from the dense herb and shrub layers. This forest-dwelling species shows a distinctive feeding and foraging pattern in comparison with other macaques, explaining why M. thibetana has the largest body weight of all macaques.

Animal Feed↗

PubMed1994

Magnetic resonance imaging study of intracranial vertebrobasilar artery dissections.

BACKGROUND AND PURPOSE: The purpose of this study is to demonstrate the magnetic resonance features of intracranial vertebrobasilar artery dissections and to determine the potential and limitations of magnetic resonance imaging in their diagnosis. METHODS: We studied five consecutive patients with angiographically verified intracranial vertebrobasilar artery dissection with magnetic resonance imaging (0.5 T) in regard to the shapes of the intramural hematoma and the chronological change of its signal intensity. We also estimated the sensitivity of magnetic resonance imaging for diagnosing dissection. RESULTS: We observed intramural hematoma in four patients on the first magnetic resonance scan and in all five patients during the course of the study. The shapes of the intramural hematomas were curvilinear, crescentic, "bamboo-cut," "band-like," and spotty. The intensity of the intramural hematoma varied according to its age. On the T1-weighted and the proton images, the intramural hematomas appeared isointense to slightly hyperintense in the first few days and became hyperintense thereafter. The intramural hematomas became isointense or unrecognizable 2 months after onset. The T1-weighted image and the proton images were superior to the T2-weighted image in demonstrating the intramural hematomas. CONCLUSIONS: Magnetic resonance imaging is a sensitive tool for diagnosing intracranial vertebrobasilar artery dissection, particularly in the subacute to early chronic stage. Magnetic resonance imaging is complementary to angiography in that it can directly visualize intramural hematomas.

Adult↗

PubMedDate not supplied

Low-temperature synthesis of large-area CNx nanotube arrays.

Well-aligned nitrogen-doped multiwall carbon nanotube arrays have been successfully grown over large areas on quartz and silicon wafers by floating-catalyst chemical vapor deposition at low temperatures (600 degrees C). These nitrogen-including nanotubes, derived from pyridine-ferrocene mixtures, have smaller outer diameters but larger inner diameters compared with carbon nanotubes grown from a xylene-ferrocene mixture under similar conditions. The N-doped nanotubes exhibit bamboo-like structures in the core. Elemental analysis and electron energy loss spectroscopy analysis show that the as-prepared nanotubes contain as much as 2.62 wt.% N, with most of the N concentrated in the inner few shells of the nanotube. Such large-scale arrays of well-aligned N-doped nanotubes on silicon wafers have a current density as high as 23.8 mA/cm2 at an applied electric field of 17 V/micron, which can be further improved by patterning the tubes and coating the silicon substrate with a conductive thin metal film for the fabrication of flat panel displays.

Crystallization↗

PubMedDate not supplied

Synthesis and thermoelectric power of nitrogen-doped carbon nanotubes.

We have previously shown that high-purity multiwalled carbon nanotubes (pristine MWNTs) can be prepared from a mixture of xylene-ferrocene (99 at% C:1 at% Fe) inside a quartz tube reactor operating at approximately 700 degrees C. In a similar process, approximately 3 g of melamine (C3H6N6) was introduced during the growth of MWNTs to prepare nitrogen-doped nanotubes. The structural and electronic properties of nitrogen-doped MWNTs were determined by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and thermopower measurements. The individual nitrogen-doped nanotube exhibits a bamboo-like structure and comprises 6-16 tube walls, as evidenced by HRTEM studies. The EELS measurements yielded an average nitrogen content of approximately 5 at% in the doped tubes. The thermoelectric power data of nitrogen-doped MWNTs remained negative even after exposure to oxygen for an extended period of time, suggesting that nitrogen doping of MWNTs renders them n-type, consistent with scanning tunneling spectroscopic studies on similar nanotubes.

Crystallization↗

PubMed2005

Vibrational characteristics of carbon nanotubes as nanomechanical resonators.

Using eigenvalue analysis of mass and stiffness matrices directly computed from atomistic simulations, natural frequencies and mode shapes of various carbon nanotubes are studied. The stiffness matrix was developed from the Tersoff-Brenner potential for carbon-carbon interactions. The computed frequencies of the radial breathing modes of a variety of armchair (n, n) nanotubes agree well with results obtained by others using different techniques. In addition, the study reveals diverse mode shapes such as accordion-like axial modes, lateral bending modes, torsional modes, axial shear modes, and radial breathing modes for a variety of single-wall, multi-wall, and bamboo-type carbon nanotubes. The effects of different constraints on the carbon nanotube ends on the computed frequencies and mode shapes have been investigated for possible applications in vibration sensors or electromechanical resonators.

Computer Simulation↗

PubMed2005

Nitrogen doping in carbon nanotubes.

Nitrogen doping of single and multi-walled carbon nanotubes is of great interest both fundamentally, to explore the effect of dopants on quasi-1D electrical conductors, and for applications such as field emission tips, lithium storage, composites and nanoelectronic devices. We present an extensive review of the current state of the art in nitrogen doping of carbon nanotubes, including synthesis techniques, and comparison with nitrogen doped carbon thin films and azofullerenes. Nitrogen doping significantly alters nanotube morphology, leading to compartmentalised 'bamboo' nanotube structures. We review spectroscopic studies of nitrogen dopants using techniques such as X-ray photoemission spectroscopy, electron energy loss spectroscopy and Raman studies, and associated theoretical models. We discuss the role of nanotube curvature and chirality (notably whether the nanotubes are metallic or semiconducting), and the effect of doping on nanotube surface chemistry. Finally we review the effect of nitrogen on the transport properties of carbon nanotubes, notably its ability to induce negative differential resistance in semiconducting tubes.

Crystallization↗

PubMed2005

Synthesis of carbon nanotubes.

Carbon nanotubes play a fundamental role in the rapidly developing field of nanoscience and nanotechnology because of their unique properties and high potential for applications. In this article, the different synthesis methods of carbon nanotubes (both multi-walled and single-walled) are reviewed. From the industrial point of view, the chemical vapor deposition method has shown advantages over laser vaporization and electric arc discharge methods. This article also presents recent work in the controlled synthesis of carbon nanotubes with ordered architectures. Special carbon nanotube configurations, such as nanocoils, nanohorns, bamboo-shaped and carbon cylinder made up from carbon nanotubes are also discussed.

Crystallization↗

PubMed1991

Complications of methods of fracture treatment used by traditional healers: a report of three cases necessitating amputation at Ihiala, Nigeria.

Three fracture cases treated by immobilization with bamboo sticks by traditional bone setters ended up with amputation in a rural hospital, two for gangrene and the third for diaphyseal sequestration. Venous occlusion, followed by interruption of arterial blood supply and immobilization in a dependent position are responsible for the gangrene. Overwhelming sepsis accounted for diaphyseal sequestration in the third patient. These cases illustrate the need for more emphasis to be placed on primary surgical care, centred on rural hospitals, in the developing world.

Adult↗

PubMed1993

Post-embedding in situ hybridization for localization of viral nucleic acid in ultra-thin sections.

We developed an in situ hybridization technique for localization of plant virus RNA in ultra-thin sections of virus-infected, Lowicryl HM20- or osmium-fixed, Araldite-embedded plant leaf tissues. A digoxigenin-labeled in vitro transcript corresponding to 173 nucleotides at the 3' end of bamboo mosaic virus (BaMV) RNA was used as a riboprobe and the hybrids were detected by incubation with sheep antidigoxigenin antibody followed by gold-labeled rabbit anti-sheep IgG. Pre-treatment of ultra-thin sections with an etching agent was the critical step in enhancing hybridization signals on Lowicryl-embedded thin sections. Etching combined with K-metaperiodate treatment increased the accessibility of nucleic acids to riboprobes in osmicated Araldite-embedded sections. BaMV RNA was specifically detected within chloroplasts, mitochondria, and nuclei of infected cells. BaMV virions and BaMV-specific electron-dense crystalline bodies were also labeled. The labeling intensity on Lowicryl-embedded samples, in general, was much higher than that on osmicated Araldite-embedded samples. However, our procedure offers the advantage that it permits labeling of viral nucleic acids in tissues already processed for routine EM and should be applicable for in situ labeling of any cellular nucleic acids.

Blotting, Northern↗

PubMed1992

Severe deprivation in childhood: a case report from Thailand.

A 3 1/2-year-old girl was incarcerated in a bamboo cage after it was feared she had contracted rabies. Six years later, when she was released, she had lost almost all motor control, displayed a number of stereotypies, was incontinent of both faeces and urine, and was diagnosed as having grand mal epilepsy. After four years of treatment (aged 13) she had shown considerable improvement and her mental age was seven years.

Child↗

PubMed1984

Asymptomatic leptomeningeal dissemination of tumor to the spinal cord: report of three cases.

Three children with a history of malignant tumor (cerebellar medulloblastoma in two cases and adrenal neuroblastoma in one case) are discussed. All three had diffuse leptomeningeal dissemination, which was confirmed at autopsy. Computed tomography (CT) revealed diffuse enhancement of the intracranial subarachnoid spaces after the administration of contrast material. Despite the absence of spinal cord signs and symptoms, autopsy showed severe diffuse seeding of neoplastic cells in the spinal subarachnoid space giving the spinal cord the appearance of a "bamboo stick." Myelography is necessary to disclose clinically silent spinal cord lesions when CT or cerebrospinal fluid cytological examination reveals evidence of subarachnoid dissemination of tumor.

Brain Neoplasms↗

PubMed2007

Dipole hearing measurements in elasmobranch fishes.

The hearing thresholds of the horn shark Heterodontus francisci and the white-spotted bamboo shark Chiloscyllium plagiosum were measured using auditory evoked potentials (AEP) in response to a dipole sound stimulus. The audiograms were similar between the two species with lower frequencies yielding lower particle acceleration thresholds. The particle acceleration audiograms showed more sensitive hearing at low frequencies than previous elasmobranch audiograms, except for the lemon shark Negaprion brevirsotris. Auditory evoked potential signals were also recorded while the dipole stimulus was moved to different locations above the head and body. The strongest AEP signals were recorded from the area around the parietal fossa, supporting previous experiments that suggested this region is important for elasmobranch hearing. This is the first time that hearing experiments have been conducted using a dipole stimulus with elasmobranchs, which more closely mimics the natural sounds of swimming prey.

Animal Communication↗

PubMed2005

Vasodilatation produced by orientin and its mechanism study.

In this paper we investigated the vascular activity and possible mechanism of Orientin, from bamboo leaves (Phyllostachys nigra), in isolated thoracic aortic rings from New Zealand rabbit. Among the four compounds, studied, only Orientin relaxed phenylephrine-induced contractions with an IC50 value of 2.28 microM in the endothelium intact and with an IC50 value around 7.27 microM in the endothelium removed aortic rings. The vasorelaxant effect of Orientin on endothelium-intact thoracic aortic rings was attenuated by the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester, but not by indomethacin (a cyclooxygenase inhibitor), tetraethylammonium chloride (K+ channels inhibitor) or propranolol (beta-receptor inhibitor). Furthermore, Orientin inhibited norepinephrine (NE), CaCl2 and KCl-induced vasoconstriction concentration dependently in a non-competitive manner, and also reduced both the initial fast release and the sustained phases of phenylephrine-induced contractions. Orientin can stimulate NO production from endothelial cells. Orientin also increased cyclic guanosine 3,5-cyclic monophosphate (cGMP) levels without changes in adenosine-3',5'-cyclic phosphoric acid (cAMP) in rabbit aorta. The results showed that Orientin relaxed thoracic aortic rings by the nitric oxide-cGMP pathway, and in the vascular smooth muscle inhibited the contraction induced by the activation of receptor-operating and voltage-dependent Ca2+ channels. Cyclooxygenase pathway, potassium channels, beta-receptors and cAMP pathway, on the other hand, had no apparent roles. The inhibition of both intracellular Ca2+ release and extracellular Ca2+ influx may be one of the main vasorelaxant mechanisms of Orientin.

Animals↗

PubMed2001

Characterization of a 4-methylbenzoate-degrading methanogenic consortium as determined by small-subunit rDNA sequence analysis.

A methanogenic consortium that degrades 4-methylbenzoate (MBA) as the sole carbon and energy source was successfully enriched in an upflow anaerobic sludge bed bioreactor and studied. Electron microscopic observation showed that long rods with a distinct collar feature resembling Desulfomonile tiedjei rods were the predominant population, and that these rods formed a close spatial orientation with Methanobrevibacter-like bacteria. In addition, thin filaments and bamboo-shaped filaments that highly resembled the acetoclastic Methanosaeta were also frequently observed. A 16S rDNA clone library was constructed for the domain Bacteria, and 20 sequence types or operational taxonomic units (OTUs) were found out of 139 clones screened. Phylogenetic analysis classified these 20 nearly full-length OTUs into the delta (50.3% of total clones) and gamma (4.3%) subdivisions of the division Proteobacteria, the green non-sulfur bacteria subdivision I (7.2%), Cytophagales (7.2%), Planctomycetes (5.7%), gram-positive low G + C group (8.6%), candidate divisions OP8, OP10 and OP11 (9.3%), and a novel candidate division MBA1 (7.2%) that had an interdivisional sequence similarity less than 75%. However, only 3 OTUs had a sequence similarity higher than 90% to known isolates or environmental 16S rDNA clones, suggesting that the microbial community was diversified and largely unidentified. In particular, those 8 OTUs found in the delta-Proteobacteria were either clustered into novel groups or showed a low sequence similarity to closely related bacteria. It is highly possible that the delta-Proteobacteria were the long rods with a distinct collar feature observed microscopically, and together with the methanogens were mainly responsible for the syntrophic degradation of MBA. The unique and novel microbial populations identified explained the requirement of a long start-up period of up to 426 d for the MBA-degrading consortium.

Journal Article↗

PubMed2005

Low effective dispersal of asexual genotypes in heterogeneous landscapes by the endemic pathogen Penicillium marneffei.

Long-distance dispersal in microbial eukaryotes has been shown to result in the establishment of populations on continental and global scales. Such "ubiquitous dispersal" has been claimed to be a general feature of microbial eukaryotes, homogenising populations over large scales. However, the unprecedented sampling of opportunistic infectious pathogens created by the global AIDS pandemic has revealed that a number of important species exhibit geographic endemicity despite long-distance migration via aerially dispersed spores. One mechanism that might tend to drive such endemicity in the face of aerial dispersal is the evolution of niche-adapted genotypes when sexual reproduction is rare. Dispersal of such asexual physiological "species" will be restricted when natural habitats are heterogeneous, as a consequence of reduced adaptive variation. Using the HIV-associated endemic fungus Penicillium marneffei as our model, we measured the distribution of genetic variation over a variety of spatial scales in two host species, humans and bamboo rats. Our results show that, despite widespread aerial dispersal, isolates of P. marneffei show extensive spatial genetic structure in both host species at local and country-wide scales. We show that the evolution of the P. marneffei genome is overwhelmingly clonal, and that this is perhaps the most asexual fungus yet found. We show that clusters of genotypes are specific to discrete ecological zones and argue that asexuality has led to the evolution of niche-adapted genotypes, and is driving endemicity, by reducing this pathogen's potential to diversify in nature.

Journal Article↗

PubMed1980

Acute histoplasmosis. Description of an outbreak in northern Louisiana.

An outbreak of acute histoplasmosis occurred in northern Louisiana in September 1977. All six men who cleared a field of bamboo cane known to be a blackbird roosting site were affected. All had clinical and roentgenographic findings of acute pulmonary histoplasmosis, and all recovered. Seroconversion or fourfold rise in antibody to Histoplasma capsulatum yeast--or mycelial-form antigens were demonstrated in five. Immunodiffusion testing showed that all six patients developed H capsulatum M bands, and two developed H bands specific for active infection. The H capsulatum was isolated from the soil in the cane field. This is the first report of an outbreak of histoplasmosis in Louisiana and the first known isolation of H capsulatum from Louisiana soil.

Adult↗

PubMed1992

[Microhabitats of Aedes albopictus (Skuse) in the region of the Paraiba Valley, São Paulo State, Brazil].

The objective of this study was the determination of extent of the spatial distribution of Aedes albopictus in the Paraíba River Valley, State S. Paulo, Brazil. Thus, collections of larvae and pupae mosquitoes were carried out at six sites distributed along a transection with a 10-km extension. The target was the tree-holes but artificial containers were also used in this investigation. Aedes terrens and Ae. albopictus were the only species of genus Aedes present in the tree-holes mentioned. The segregation of seven species of the tree-hole community was undertaken in the light of macrohabitat and microhabitat features. Thus, the distribution of Ae. albopictus was found to cover the rural, rural-urban and urban zones, but the rural-urban held the preference. Ae. albopictus never present in the residual and primary forest. The favorable factor to infestation with Ae. albopictus in the Paraíba Valley seems to have been the large number of natural niches made vacant by human influence. The rain has been important in the production of larvae and pupae, but the rainfall period does not coincide with the maximum production on them. The tree-holes whose volume exceeded 600 ml were the most productive breeding places. The abundance of these two stages occurs in the summer and autumn. However, the highest peak was observed in the months of March and April. These seasonal variations were found to be common in both the bamboo trap and the artificial container. The temperature data suggest a limit of from 17 to 23 degrees C for the best development of larvae. In the light of this, the strain of Ae. albopictus studied seems to have originated in tropical Asia. Just as happened with Ae. aegypti it may become an important epidemiological vector for the dengue fever and provide links for yellow fever transmission in Brazil.

Aedes↗

PubMed1995

Duration of larval and pupal development stages of Aedes albopictus in natural and artificial containers.

Aedes albopictus were reared in different containers: a tree hole, a bamboo stump and an auto tire. The total times from egg hatching to adult emergence were of 19.6, 27.3 and 37.5 days, respectively, according to the container. The first, second and third-instar larvae presented growth periods with highly similar durations. The fourth-instar larvae was longer than the others stages. The pupation time was longer than the fourth-instar larvae growth period. The temperature of the breeding sites studied, which was of 18 degrees C to 22 degrees C on average, was also taken into consideration. The mortality of the immature stages was analysed and compared as between the experimental groups; it was lower in the natural containers than in the discarded tire. The average wing length of adult females emerging from tree hole was significantly larger (p < 0.05) than that of those emerging from the tire.

Aedes↗