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1
artículo
Publicado 2022
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Objectives: To evaluate the bending and topography properties of surface treated fiber posts. Material and Methods: Experimental, In vitro. The samples were divided into two groups, the flexibility of 40 fiberglass posts from 2 commercial houses was evaluated for each conditioning procedure P1: FGM White Post DC; P2: MAQUIRA Fiber Post. The conditioning techniques were: T1: control T2: Hydrofluoric Acid 10% 15 seconds T3: Hydrogen Peroxide 24% 60 seconds T4: aluminum oxide 50 µm and were subjected to the universal testing machine, for the bending test of 3 points. The topographic surface of the fiberglass posts was observed using a scanning electron microscope. Results: The deflection (mm) showed a significant difference comparing the control groups and the conditioned groups with an average maximum value of 0.59mm ±0.04 and a minimum value of 0.51mm ±0.06. In the maximum force (...
2
artículo
Publicado 2018
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Objective: Evaluate the surface roughness, weight and color of a composite resin, submitted to two finish and polish systems, after contact with beer and rum. Materials and methods: 63 BrilliantTM NG (COLTENE, USA) composite resin discs of 10 mm in diameter and 2 mm thick, after 24 hours of permanence in distilled water, randomly divided into three groups (n: 21) for polishing using Sof-flex (3M-USA) discs and fine-grained diamond burs (KG-Sorensen, Brazil) and third group without any procedure, for each sample the initial measurement was made in weight, roughness and color. The samples were subdivided into three subgroups and submerged in rum, beer or artificial saliva for 7 days; performing a new evaluation of weight, color and roughness. The data obtained were collected in Excel tables and statistically analyzed through Kruskal Wallis, Wilcoxon, Anova and Tukey tests. Results: The Tuk...
3
artículo
Publicado 2025
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Introduction. Contemporary resin composites have improved mechanical properties, such as microhardness and flexural strength, to better withstand masticatory loads. Nevertheless, fracture and wear remain common causes of failure in posterior restorations. Objective. To compare the surface microhardness and flexural strength of Filtek™ Z350 XT (3M ESPE), Estelite Posterior (Tokuyama), Beautifil II (Shofu), and Opallis (FGM). Materials and Methods. In vitro study with four resin composites (n = 10 per group). Disc-shaped specimens (5 mm × 2 mm) were used to evaluate Vickers microhardness (VHN), and bar-shaped specimens (25 mm × 2 mm × 2 mm) to perform a three-point bending test using a universal testing machine. Results. For flexural strength, Estelite Posterior showed the highest mean (136.59 ± 9.13 MPa). For surface microhardness, Filtek Z350 XT yielded the highest value (67.99 ± ...
4
artículo
Publicado 2010
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The origin of the mining property, along the history, has been explain through the basis of two theories. The theory of the accession and the theory of the separation. The first part reffers to the unit of the soil and the subsoil; the second one distinguishes and separates the property of the soil from the subsoil. The theory of the accession considers that the surface (soil) and the deposit (subsoil) are a unit as the mineral deposits are incorporated into the superficial property. The mines belong to the holder of the surface for being an accesory to this one, this argument takes root in the natural Law. Therefore, the mines cant be exploited independently of the soil, faculty reserved only to the owner of the surface who can exploit them freely. The theory of the separation is opposed to the accession for considering to the mining property a different foreign good separated from the ...
5
artículo
Publicado 2018
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The organic monolayers of saturated alkyl chains linked to silicon substrates are used for the development of devices with important electronic properties. In this study, thanks to the use of 10-bromine-1-decene and 11-bromine-1-undecene molecules on silicon surfaces, the formation of a system potentially applicable in the modification of the end groups of the carbon chain is achieved in the organic monolayers, that is to say the functionalization of the monolayer allowing a better charge transport through the molecules. The silicon surface (oxide-free) was passivated by hydrogenation. Respect to the formation of the organic monolayer, the hydrogen-terminated silicon surface was subjected to 200°C with each of the mentioned organic molecules. Both the hydrogenated surface and the organic monolayers were characterized by the measurement of the contact angle between water droplets and the...
6
artículo
Publicado 2020
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The preparation in the formation of self-assembled monolayers on silicon surfaces has allowed us the technological advancement of new organic semiconductor materials, obtaining devices that stand out for their electrical properties at the nanometric scale1. For this investigation, the reaction between alkenes and hydrogenated surface of Si (100) was considered to form self-assembled organic monolayers2. The organic molecules of alkenes used were 1-dodecene, 1-tetradecene, 1-hexadecene and 1-octadecene, which stand out for the functionalization process of these organic films. For the treatment of the silicon surface, a previous hydrogenation3,4 reaction was considered, obtaining Si-H functional groups on the surface. Regarding, the formation reaction of the organic monolayer, the silicon substrate of the hydrogenated surface reacted with each of the alkenes5 at 220°C for 2 hours. The exp...
7
artículo
Publicado 2022
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This research develops a microbicidal aqueous paint to prevent infections on high-touch surfaces. Based on the experimental tests, two chemical formulations were proposed consisting of an acrylic latex resin, silicone resin, titanium oxide, zinc omazide, copper oxide nanoparticles and additives. Th e results showed that the formulation 2 paint presented good homogenization, gloss and stability, its average drying time is 30 min, it has adequate metal coating thickness (49.2 μm) and viscosity (60 s in Ford No. 4 cup), according to the standards ASTM D 1186 01 and ASTM D 1200, respectively; Based on these characteristics, it is considered to be of acceptable quality. Th e bioassays carried out with bacteria of Staphylococcus aureus Rosenbach, 1884 and Escherichia coli (Escherich, 1885) by the incorporation method, showed that the two formulations have antifungal and antimicrobial properti...
8
artículo
Publicado 2025
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We present algorithms for computing the differential geometry properties of tangential intersection curves of two surfaces in the three-dimensional Lorentz-Minkowski space E31 . We compute the tangent vector of tangential intersection curves of two surfaces parametric, where the surfaces can be: spacelike, timelike, or lightlike. The first method computed the tangent vector using the equality of the projection of the second derivative vector onto the normal vector and second method computes the tangent vector by applying a rotation to a vector projected onto the tangent space, where the axis of rotation is the normal vector of the surface. In Minkowski space, there are three types of rotations, since the normal vectors can be: spacelike, lightlike, or timelike.
9
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A surface Kerr effect magnetometer (MEKS) was built to measure the magnetic properties of Permalloy (Ni81Fe19) thin films of 20 nm thickness. It was found that the coercive field of the samples has values between 2-6 Oe. The films showed in-plane uniaxial anisotropy and axes of easy and difficult magnetization were identified. The Kerr angle was measured for the longitudinal and polar configurations and the magnetic saturation for different angles of incidence of the light beam. The results were satisfactorily compared with those obtained with a Vibrating Sample Magnetometer (VSM).
10
artículo
Publicado 2021
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Gallium antimonide binary semiconductor has had many applications in optoelectronic devices in recent years. The study of their defects in semiconductor materials is of vital interest for this type of application. But, in addition to the routine characterization of the undoped semiconductor, it is necessary to characterize the effects produced by electrically active impurities in the doped samples. In this work, the structural and electronic properties of the vanadium doped gallium antimonide binary semiconductor (GaSb: V) were studied by means of an Atomic Force Microscope. The scan of its surface was carried out in the tapping mode to obtain images of the topography and topographic profiles of the sample, while the electronic properties were determined through the I vs V curves obtained by the contact mode.
11
artículo
Publicado 2017
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In the present work, two experimental designs were carried out to find the optimal conditions to manufacture nylon nanowires and to synthesize graphene. The results obtained were: 0.68 M (NH4)2SO4 and 11.45 V; and 27 kV, 2.3 mL / h and 11.40 cm as the distance from the needle to the collector, respectively. This way, nylon nanowires and graphene were produced, both of nanometric size. Using these materials, a nanowire/graphene composite was prepared using optimum manufacturing conditions. The materials obtained (nylon nanowires, graphene and composite) were characterized morphologically (SEM) and chemically (FTIR, UV), verifying their nanometric scale, functional groups and their UV blocking properties. This work opens new perspectives for the use of recycled nylon to obtain electrospinned nano‐fibers that can be functionalized, in this case with graphene, and exhibit interesting prope...
12
artículo
Publicado 2017
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In the present work, two experimental designs were carried out to find the optimal conditions to manufacture nylon nanowires and to synthesize graphene. The results obtained were: 0.68 M (NH4)2SO4 and 11.45 V; and 27 kV, 2.3 mL / h and 11.40 cm as the distance from the needle to the collector, respectively. This way, nylon nanowires and graphene were produced, both of nanometric size. Using these materials, a nanowire/graphene composite was prepared using optimum manufacturing conditions. The materials obtained (nylon nanowires, graphene and composite) were characterized morphologically (SEM) and chemically (FTIR, UV), verifying their nanometric scale, functional groups and their UV blocking properties. This work opens new perspectives for the use of recycled nylon to obtain electrospinned nano‐fibers that can be functionalized, in this case with graphene, and exhibit interesting prope...
13
artículo
Publicado 2023
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Este estudio utilizó las propiedades hidrogeoquímicas de las aguas superficiales que rodean un proyecto minero en Perú, para compararlas con los estándares de calidad ambiental establecidos en el Decreto Supremo 004-2017-MINAM, centrándose en la categoría 3 para riego de vegetales y bebida para animales. Se evaluaron parámetros físico-químicos, inorgánicos, microbiológicos y parasitarios en lagunas y manantiales. Los resultados determinaron la presencia de depósitos ligeramente alcalinos con un pH de 9.59 y depósitos ligeramente ácidos con un pH de 5.33, así como depósitos con alto contenido de hierro, manganeso y zinc. Para garantizar la fiabilidad del análisis químico, se realizó un balance iónico de los principales cationes y aniones disueltos. El diagrama de Piper determinó la predominancia de aguas sulfatadas cálcicas, así como la presencia de un depósito de ...
14
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This work was supported by the Cienciactiva -?FONDECYT, Per? [117-2016]. This paper was written in the context of the project: ?Estudio comparativo del potencial de fibras naturales end?micas del Per? para su uso como refuerzo en materiales compuestos laminados? founded by the Consejo Nacional de Ciencia, Tecnolog?a e Innovaci?n Tecnol?gica (CONCYTEC) under the contract number N? 117-2016-FONDECYT. The authors of this paper appreciate the financial support from the Peruvian Government.
15
artículo
Publicado 2018
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Nowadays, micromanipulation has an important role for assembly of micro-electromechanical components, because it enables to assemble very small components with different material properties and geometrical shapes in order to create complex multifunctional systems. Also, micromanipulation has contributed significantly in the field of medicine enabling manipulation of cells, molecules and bio-particles to study their behavior. Thus, a micromanipulation method that could move biological objects and microcomponents in an accurate, fast and multiple manner is needed. The preferred methods in the microscale are non-contact methods because they allow manipulating objects without damage or contamination. In this scope, microflows are very good candidates to drag micro-objects according to the flows direction and velocity, producing a drag force over the objects. In this research work, a study, t...
16
artículo
Publicado 2019
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In this work, graphite powder was used as initial material to obtain graphene oxides (GO). We propose the reduction of graphene oxides, by physical-chemical method, which consists in a thermo and chemical reduction in the presence of NaBH4 to obtain reduced graphene oxides (RGO). Furthermore, the presence of functional groups and the nanocrystal size were determined by Visive, FTIR and Raman spectroscopy in both samples, GO and RGO. Thereby, we observe that the use of physical-chemical method to obtain RGO produces a signicant defects decrease, shown by the D band of the Raman spectrum which practically disappear after this reduction. In addition to this, a morphological study made by AFM have shown relative ats surfaces in the nano-graphene samples obtained by the presented technique.
17
artículo
Publicado 2021
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The biological properties of mesenchymal stem cells (MSCs) from synovial fluid from horse limb joints were analysed. The samples were characterized by their peculiarity of adhering to the plastic of the culture flasks. The electromagnetic field technique (MACS) and the surface biomarker STRO-1 were used to optimize their isolation by enriching mesenchymal precursor cells (MSC-LS). To determine the expression of multipotency genes, total RNA was extracted and M-MLV reverse transcriptase was used for the cDNA, which served as a template for qPCR (quantitative PCR). qPCR was performed using the BioRad system with Sybr Green quantification. The multipotency genes quantified were OCT4 and NANOG. The cells selected using MACS with the surface biomarker STRO-1 (CMM-LS STRO-1) proliferate more rapidly than the CMM-LS obtained without purification. In addition, they showed a greater predispositio...
18
artículo
Publicado 2024
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El objetivo de este estudio es conocer el efecto de los abonos orgánicos sobre el crecimiento y la productividad del maíz amarillo y las propiedades del suelo salino. El experimento se llevó a cabo en la granja de Sayeed Habib Al-Khatib en la ciudad de Numaniyah a 45 km al oeste de la ciudad de Kut durante la temporada agrícola de 2024. Para estudiar 3 tipos de residuos orgánicos: vacas, F1, ovejas F2, y aves de corral F3, a continuación, una mezcla de ellos, (F1 + F2), (F1 + F3), (F2 + F3), para conocer el efecto de estos fertilizantes en el crecimiento y la producción de plantas de maíz y las propiedades del suelo. La tierra se aró, se trituró y se mezcló, después se añadieron los residuos al suelo con la capa superficial 2 t.ha-1, a continuación se plantaron los granos de maíz y se empezó a regar hasta el final del experimento. Las operaciones agrícolas y el servicio ...
19
artículo
Publicado 2025
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La rizósfera es el hábitat de las raíces. Así, se espera que las propiedades del suelo rizosférico estén más estrechamente relacionadas con la producción de plantas. En última instancia, el uso sostenible de recursos naturales, el suministro alimenticio para la sociedad y la ecología de la superficie terrestre son afectados. Esta hipótesis ha sido principalmente evaluada con propiedades individuales de combinaciones suelo-elemento-planta específicas, pero no globalmente. El objetivo de esta investigación fue determinar si las propiedades químicas del suelo rizosférico estaban mas íntimamente asociadas con el crecimiento y nutrición mineral de plantas que aquellas del suelo no rizosférico. Para ello, se compararon relaciones lineales entre variables de suelo y planta para ambos tipos de suelo. Muestras de los 2 tipos de suelo se tomaron en un campo de maíz (Zea mays L.)...
20
artículo
Publicado 2021
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Edible films were elaborated from gelatin solutions (4% w/v) of mahi-mahi skin (Coryphaena hippurus) with 2,5; 5; 7,5 and 10% v/v of oregano extract (OE) and its physicochemical, antimicrobial, structural and surface properties were determined. The control and with 2.5% OE films showed the lowest moisture and opacity values and the highest viscosity values. All films with OE inhibited the growth of Staphylococcus aureus and Proteus vulgaris. Alone films with 10% OE showed antimicrobial activity against all the strains evaluated. Scanning electron microscopy showed that the incorporation of oregano extract in the film-forming solutions, FFS, was related to an increase in the presence of oil droplets in the films, showing the lipid fraction of OE. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyzes showed the interaction between gelatin, pla...
