4,496 research outputs found
Antimicrobial potential of Eucalyptus globulus against biofilms of Staphylococcus aureus isolated from bovine mastitis
Staphylococcus aureus are among the most common species isolated
from bovine mastitis. The pathogenesis of this bacterium is facilitated by a
number of virulence factors, including the ability to adhere to abiotic
surfaces and/or host tissues often leading to biofilms formation. From the
clinical perspective, the most important feature of Staphylococcus
species biofilms is their high tolerance to the conventional antimicrobial
therapy. So, the increasing number of bovine mastitis and the higher
levels of Staphylococcus species resistance to traditional antimicrobial
agents are considered an important alert for the necessity to focus the
future research on identification and development of new strategies to
combat S. aureus mastitis. Recently, the interest in natural alternatives
based on plant extracts has been rising. In addition to their health
benefits, their antimicrobial potential has been increasingly reported.
Taking this into consideration, the evaluation of hydromethanolic extracts
of E. globulus against S. aureus biofilms was tested and compared with
penicillin, one of the antibiotics most often used in the treatment of cattle
infections. All mastitis isolates tested were good-biofilm producers. As
expected penicillin has demonstrated poor activity against S. aureus
biofilms (<1 log reduction). However, E. globulus Labill was bactericidal,
promoting a biofilm cell reduction of 2-3 log. Therefore, the present work
showed the potential antimicrobial activity of E. globulus against S.
aureus from bovine mastitis, namely in biofilm mode of growth and drew
attention to its promising use as an alternative to penicillin
Lipid and glicemic profile of rats fed a semi-purified diet supplemented with agaricus brasiliensis mushroom.
Al-containing MCM-41 type materials prepared by different synthesis methods: hydrothermal stability and catalytic properties
Al-containing MCM-41 type materials were prepared by three different synthesis methods
(aluminum grafting on the calcined MCM-41, pH adjustment during the crystallization period
and crystallization in the presence of zeolite seeds). The samples were characterized by
powder XRD, nitrogen adsorption, 27Al MAS NMR and FTIR with pyridine as probe
molecule. All the samples exhibit a high hydrothermal stability at high temperature just with a
minor structural degradation. N2 adsorption data obtained for the sample prepared from a gel
containing zeolite seeds suggest a higher structural resistance to the hydrothermal treatment in
comparison with the samples prepared by other methods. A different type of pyridine
adsorbed, probably interacting simultaneously with a Brönsted and a Lewis acid site, is
observed upon pyridine adsorption. This type of adsorption is stronger for the sample
prepared in the presence of zeolite seeds and is not observed on Al-grafted MCM-41.
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The catalytic activity towards the isomerization of α-pinene depends mainly on the number of
Brönsted acid sites. The data obtained in this study strongly indicate that for this type of
materials, the Lewis acid sites do not influence the selectivity for the isomerization products
Glycemic behavior of Yellow Peachpalm flour (Bactris gasipaes Kunth. Var. GasipaesHenderson) in diabetic and non-diabetic Wistar rats.
Amino acid and mineral composition of yellow and red peachpalm flour (Bactris gasipaes Kunth. Var. Gasipaes Henderson).
Comparison between ingestion of yellow and red peachpalm flour (Bactris gasipaes Kunth. Var. GasipaesHenderson) over glycemic behavior in diabetic and non-diabetic wistar rats.
Theory of third-order polarizability of interlayer excitons due to intra-excitonic energy level transitions
n this paper, we employ a fully microscopic approach to the study of
interlayer excitons in layered materials. We discuss the utilization of
Fowler's and Karplus' method to access the dynamical polarizability of
non--interacting interlayer excitons in a
--based van der Waals heterostructure.
Following from the calculation of the linear polarizability, we consider
Svendsen's variational method to the dynamic third--order polarizability. With
this variational method, we study both two--photon absorption and
third--harmonic generation processes for interlayer excitons in a
hetero--bilayer, discussing the various
intra--excitonic energy level transitions observed.Comment: 13 page
Microscopic theory of the polarizability of transition metal dichalcogenides excitons: Application to WSe2
In this paper we develop a fully microscopic theory of the polarizability of
excitons in transition metal dichalcogenides. We apply our method to the
description of the excitation p dark states. These states are not observable
in absorption experiments but can be excited in a pump-probe experiment. As an
example we consider p dark states in WSe\textsubscript{2}. We find a good
agreement between recent experimental measurements and our theoretical
calculations.Comment: 10 pages, 4 figures; we welcome comments and requests for adding
relevant references to the topi
Efficient co-templating roles of amines and amides admixed with alkylammonium salts for the stabilisation of new AlPO4-n topologies
Two different aluminophosphate structures were synthesised in aqueous media using as
main template methylamine (MA), directly added, or generated in situ from methylformamide (MF). Both involve novel AlPO4-n topologies that undergo structural transformations upon template removal, yielding above 350°C microporous thermostable materials with interesting
properties. Tetraalkylammonium (TEA) cations were used optionally as co-templates along
with MA. Only non protonated MA was found incorporated into the pore volume of both
structures, in relatively strong interaction with the framework oxygens. TEA appeared to
stabilise one of the phases at defined stages of nucleation and/or growth processes, without playing any specific structure-directing role
Modelling of the IPS buoy wave energy converter including the effect of non-uniform tube cross-section
An important class of floating wave energy converters (that includes the IPS buoy, the Wavebob and the PowerBuoy) comprehends devices in which the energy is converted from the relative (essentially heaving) motion between two bodies oscillating differently. The paper considers the case of the IPS buoy, consisting of a floater rigidly connected to a fully submerged vertical (acceleration) tube open at both ends. The tube contains a piston whose motion relative to the floater-tube system (motion originated by wave action on the floater and by the inertia of the water enclosed in the tube) drives a power take-off mechanism (PTO) (assumed to be a linear damper). To solve the problem of the end-stops, the central part of the tube, along which the piston slides, bells out at either end to limit the stroke of the piston. The use of a hydraulic turbine inside the tube is examined as an alternative to the piston. A frequency domain analysis of the device in regular waves is developed, combined with a one-dimensional unsteady flow model inside the tube (whose cross-section is in general nonuniform). Numerical results are presented for a cylindrical buoy in regular waves, including the optimization of the acceleration tube geometry and PTO damping coefficient for several wave periods
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