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排序方式: 共有882条查询结果,搜索用时 264 毫秒
41.
42.
Deiweson Souza-Monteiro Mrcia Cristina dos Santos Guerra Leonardo Oliveira Bittencourt Walessa Alana Bragana Arago Aline Dionizio Felipe Martins Silveira Marília Afonso Rebelo Buzalaf Manoela Domingues Martins Maria Elena Crespo-Lopez Rafael Rodrigues Lima 《International journal of molecular sciences》2022,23(4)
Aluminum (Al) is one of the most abundant elements on Earth, and its high extraction rate and industrial use make human exposure very common. As Al may be a human toxicant, it is important to investigate the effects of Al exposure, mainly at low doses and for prolonged periods, by simulating human exposure. This work aimed to study the effects of low-dose exposure to chloride aluminum (AlCl3) on the oxidative biochemistry, proteomic profile, and morphology of the major salivary glands. Wistar male rats were exposed to 8.3 mg/kg/day of AlCl3 via intragastric gavage for 60 days. Then, the parotid and submandibular glands were subjected to biochemical assays, proteomic evaluation, and histological analysis. Al caused oxidative imbalance in both salivary glands. Dysregulation of protein expression, mainly of those related to cytoarchitecture, energy metabolism and glandular function, was detected in both salivary glands. Al also promoted histological alterations, such as acinar atrophy and an increase in parenchymal tissue. Prolonged exposure to Al, even at low doses, was able to modulate molecular alterations associated with morphological impairments in the salivary glands of rats. From this perspective, prolonged Al exposure may be a risk to exposed populations and their oral health. 相似文献
43.
Dayane Mayumi Miyasaki Alexandra Cristina Senegaglia Srgio Adriane Bezerra de Moura Amanda Leitolis Luiz Guilherme Achcar Capriglione Letícia Fracaro Lidiane Maria Boldrini Leite Paulo Henrique Utumi Felipe Yukio Ishikawa Fragoso Fernando Meyer Alejandro Correa Paulo Roberto Slud Brofman 《International journal of molecular sciences》2022,23(5)
Chronic kidney disease (CKD) is characterized by structural abnormalities and the progressive loss of kidney function. Extracellular vesicles (EVs) from human umbilical cord tissue (hUCT)-derived mesenchymal stem cells (MSCs) and expanded human umbilical cord blood (hUCB)-derived CD133+ cells (eCD133+) maintain the characteristics of the parent cells, providing a new form of cell-free treatment. We evaluated the effects of EVs from hUCT-derived MSCs and hUCB-derived CD133+ cells on rats with CDK induced by an adenine-enriched diet. EVs were isolated by ultracentrifugation and characterized by nanoparticle tracking analysis (NTA) and electron microscopy. The animals were randomized and divided into the MSC-EV group, eEPC-EV group and control group. Infusions occurred on the seventh and 14th days after CKD induction. Evaluations of kidney function were carried out by biochemical and histological analyses. Intense labeling of the α-SMA protein was observed when comparing the control with MSC-EVs. In both groups treated with EVs, a significant increase in serum albumin was observed, and the increase in cystatin C was inhibited. The results indicated improvements in renal function in CKD, demonstrating the therapeutic potential of EVs derived from MSCs and eCD133+ cells and suggesting the possibility that in the future, more than one type of EV will be used concurrently. 相似文献
44.
Anna Broto-Ribas Claudia Vignatti Alicia Jimenez-Almarza Javier Luis-Barrera Zahra Dolatkhah Felipe Gandara Inhar Imaz Ruben Mas-Balleste Jose Aleman Daniel Maspoch 《Nano Research》2021,14(2):458-465
A well-established strategy to synthesize heterogeneous,metal-organic framework(MOF)catalysts that exhibit nanoconfinement effects,and specific pores with highly-localized catalytic sites,is to use organic linkers containing organocatalytic centers.Here,we report that by combining this linker approach with reticular chemistry,and exploiting three-dimensioanl(3D)MOF-structural data from the Cambridge Structural Database,we have designed four heterogeneous MOF-based catalysts for standard organic transformations.These programmable MOFs are isoreticular versions of pcu IRMOF-16,feu UiO-68 and pillared-pcu SNU-8X,the three most common topologies of MOFs built from the organic linker p.p'-terphenyldicarboxylic acid(tpdc).To synthesize the four squaramide-based MOFs,we designed and synthesized a linker,4,4’-((3,4-dioxocyclobut-1-ene-1,2-diyl)bis(azanedyil))dibenzoic acid(Sq_tpdc),which is identical in directionality and length to tpdc but which contains organocatalytic squaramide centers.Squaramides were chosen because their immobilization into a framework enhances its reactivity and stability while avoiding any self-quenching phenomena.Therefore,the four MOFs share the same organocatalytic squaramide moiety,but confine it within distinct pore environments.We then evaluated these MOFs as heterogeneous H-bonding catalysts in organic transformations:a Friedel-Crafts alkylation and an epoxide ring-opening.Some of them exhibited good performance in both reactions but all showed distinct catalytic profiles that reflect their structural differences. 相似文献
45.
Karen Lizeth Galindo-Hernández Aída Tapia-Rodríguez Felipe Alatriste-Mondragón Lourdes B. Celis Jorge Arreola-Vargas Elías Razo-Flores 《International Journal of Hydrogen Energy》2018,43(49):22116-22125
Agave tequilana bagasse is a suitable lignocellulosic residue for energy production. However, the presence of lignin and the heterogeneous structure of hemicellulose may hinder the availability of polysaccharides. In this work, the pretreatment of A. tequilana bagasse with alkaline hydrogen peroxide (AHP) followed by enzymatic saccharification with hemicellulases and cellulases was assessed for the removal of lignin and extraction of fermentable sugars, respectively. Results of the AHP pretreatment indicated that it is possible to attain up to 97% delignification and recover 88% of cellulose and hemicellulose after only 1.5 h of treatment. Regarding the saccharification process, the total sugar yield and productivity were both increased by 2-fold using an enzymatic mixture (cellulases + hemicellulases) compared to single enzyme hydrolysis (cellulases), evidencing synergism. Further evaluation of the hydrolyzates as substrate for hydrogen and methane production, resulted in yields 1.5 and 3.6-times (215.14 ± 13 L H2 and 393.4 ± 13 L CH4 per kg bagasse, respectively) superior to those obtained with hydrolyzates of non-pretreated bagasse processed with a single enzyme. Overall, using AHP pretreatment and subsequent hydrolysis with enzymatic mixtures improves the saccharification of A. tequilana bagasse enhancing the production of hydrogen and methane. 相似文献
46.
Victor H. Alcocer-Yamanaka Velitchko G. Tzatchkov Felipe I. Arreguin-Cortes 《Water Resources Management》2012,26(7):1779-1792
Residential water demand is one of the most difficult parameters to determine when modeling drinking water distribution networks.
It has been proven to be a stochastic process that can be characterized as a series of rectangular pulses with a set intensity,
duration and frequency. These parameters can be determined using stochastic models such as the Neyman-Scott Rectangular Pulse
(NSRP) model. The NSRP model is based on the solution of a non-linear optimization problem. This solution involves theoretical
moments that represent the synthetic demand series (equiprobable) and the observed moments (field measurements) that statistically
establish the measured demand series. The NSRP model has been applied for residential demand, and the results have been published.
However, this model has not been validated for a real distribution network or compared with traditional methods. The present
study compared the results of synthetic stochastic demand series, which were calculated using the NSRP model, applied to the
determination of pressures, flow rates and leaks; to the results obtained using traditional simulation methods, which use
the curve of hourly variation in demand, and to actual pressure and flow rate measurements. The Humaya sector of Culiacan,
Sinaloa, Mexico, was used as the study area. 相似文献
47.
Mayra A. D. Saleh Renato C. F. Neves Paula M. Moraes Paula M. Lima Felipe A. dos Santos Fábio A. Silva Pedro M. Padilha 《Sensing and Instrumentation for Food Quality and Safety》2009,3(2):108-113
This paper proposes a method to determine iron in samples of fish feed and feces using ultrasound in the extraction of the
analyte and in subsequent quantification by flame atomic absorption spectrometry. Using HCl 0.10 mol L−1 as the extraction solution, the optimal conditions of extraction were found to be: granulometry of the sample <60 μm; a sonication
time of five cycles of 10 s and sonication power of 136 W. The method was applied in studies of the availability of iron in
four food sources used in the diet of Nile Tilapia. The results obtained with the proposed extraction method allowed us to
calculate the coefficients of apparent digestibility of iron in the food sources, which was not possible when using results
obtained from samples mineralized by acid digestion. 相似文献
48.
João Felipe G. Oliveira Izabelly Larissa Lucena Rosana M. Alves Saboya Marcelo L. Rodrigues Antonio Eurico B. Torres Fabiano A. Narciso Fernandes Célio L. Cavalcante Expedito José S. Parente 《Renewable Energy》2010,35(11):2581-2584
The production of biodiesel by esterification with ethanol using waste oil generated in the refining of coconut oil was investigated in this study. The reaction was performed with and without adsorption of water in order to verify the effect of removing water on the reaction conversion. Methanol was also evaluated as an esterification agent. For both ethanol and methanol, conversions over 99% mol were observed. Simultaneous water adsorption allowed the use of lower alcohol/oil molar ratios thus enabling better economics to a possible industrial process. 相似文献
49.
Three different boundary element methods (BEM) for transient dynamic crack analysis in two-dimensional (2-D), homogeneous,
anisotropic and linear elastic solids are presented. Hypersingular traction boundary integral equations (BIEs) in frequency-
domain, Laplace-domain and time-domain with the corresponding elastodynamic fundamental solutions are applied for this purpose.
In the frequency-domain and the Laplace-domain BEM, numerical solutions are first obtained in the transformed domain for discrete
frequency or Laplace-transform parameters. Time-dependent results are subsequently obtained by means of the inverse Fourier-transform
and the inverse Laplace-transform algorithm of Stehfest. In the time-domain BEM, the quadrature formula of Lubich is adopted
to approximate the arising convolution integrals in the time-domain BIEs. Hypersingular integrals involved in the traction
BIEs are computed through a regularization process that converts the hypersingular integrals to regular integrals, which can
be computed numerically, and singular integrals which can be integrated analytically. Numerical results for the dynamic stress
intensity factors are presented and discussed for a finite crack in an infinite domain subjected to an impact crack-face loading. 相似文献
50.
Jaime Pitarch José M Catalá-Civera Felipe L Pe?aranda-Foix Beatriz García-Ba?os 《The Journal of microwave power and electromagnetic energy》2007,41(4):46-61
Waveguide structures are very popular in the microwave power industry due to their power handling capabilities. Modal expansion of the waveguide fields and application of the circuit theory allow for the division of a complex device into several simpler sections which can be analyzed separately with the best suited method. The modal techniques can be divided into two groups--those which analyze junctions or discontinuities and those which examine propagation characteristics. In this paper, a review of modal techniques for high power applications is given. Modal expansion of the fields in the waveguides is then performed and applied to modeling of k-furcated waveguides. The modal analysis based on the Coupled Mode Method is described for the waveguides partially filled with isotropic materials. A hybrid modal analysis coupled with Finite Element Method suitable for more complex waveguide structures is also described. Computational results obtained for some real-life microwave devices are presented. Excellent agreement was found when comparing the results with those generated with a commercial FDTD simulator demonstrates the validity and reliability of the proposed method. 相似文献