220 research outputs found
Contribution for the phytochemical studies of Ageratum fastigiatum
Organic extracts from leaves plus branches plus inflorescences of Ageratum fastigiatum (Gardner) R. M. King & H. Rob., Asteraceae, were fractionated through classic chromatography. The steroids stigmasterol, chondrillasterol and campesterol were isolated from hexane extract. The triterpenes lupeol, taraxasterol, α-amyrin, β-amyrin, pseudotaraxasterol, lupeol acetate and α-amyrin acetate were isolated from ethyl acetate extract. Steroids and triterpenes were identified by GC-MS. The coumarin ayapin was isolated from ethanol extract and identified by NMR. Essential oils of the fresh leaves and fresh inflorescences were obtained by hydrodistillation and analyzed for GC-MS. The main components in both essential oils were α-pinene, limonene and germacrene D.FAPEMI
Fracture toughness determination of adhesive and co-cured joints in natural fibre composites
Adhesive bonding has become more efficient in the last few decades due to the adhesives developments,
granting higher strength and ductility. On the other hand, natural fibre composites have recently gained
interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints
between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the
tensile fracture toughness (Gc
n) of adhesive joints between natural fibre composites is studied, by bonding
with a ductile adhesive and co-curing. Conventional methods to obtain Gc
n are used for the co-cured specimens,
while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation,
an optical measurement method is developed for the evaluation of the crack tip opening and
adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated
extraction of these quantities. As output of this work, an optical method that allows an easier and quicker
extraction of the parameters to obtain Gc
n than the available methods is proposed (by the J-integral technique),
and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural
fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively-
bonded joints, the tensile cohesive law of the adhesive is derived by the direct method
Clinic-epidemiological evaluation of ulcers in patients with leprosy sequelae and the effect of low level laser therapy on wound healing: a randomized clinical trial
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Chlamydia trachomatis infection in young pregnant women in Southern Brazil: a cross-sectional study
Frequency of Infection of Lutzomyia Phlebotomines with Leishmania braziliensis in a Brazilian Endemic Area as Assessed by Pinpoint Capture and Polymerase Chain Reaction
Erythropoietin Couples Hematopoiesis with Bone Formation
It is well established that bleeding activates the hematopoietic system to regenerate the loss of mature blood elements. We have shown that hematopoietic stem cells (HSCs) isolated from animals challenged with an acute bleed regulate osteoblast differentiation from marrow stromal cells. This suggests that HSCs participate in bone formation where the molecular basis for this activity is the production of BMP2 and BMP6 by HSCs. Yet, what stimulates HSCs to produce BMPs is unclear.In this study, we demonstrate that erythropoietin (Epo) activates Jak-Stat signaling pathways in HSCs which leads to the production of BMPs. Critically, Epo also directly activates mesenchymal cells to form osteoblasts in vitro, which in vivo leads to bone formation. Importantly, Epo first activates osteoclastogenesis which is later followed by osteoblastogenesis that is induced by either Epo directly or the expression of BMPs by HSCs to form bone.These data for the first time demonstrate that Epo regulates the formation of bone by both direct and indirect pathways, and further demonstrates the exquisite coupling between hematopoiesis and osteopoiesis in the marrow
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