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Search Results: 1 - 10 of 421806 matches for " Francisco Márquez Linares "
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Trihalomethanes in Comerio Drinking Water and Their Reduction by Nanostructured Materials  [PDF]
Jorge Hernández Bourdon, Francisco Márquez Linares
Soft Nanoscience Letters (SNL) , 2014, DOI: 10.4236/snl.2014.42005
Abstract: The formation of disinfection by-products (DBPs) during chlorination of drinking water is an issue which has drawn significant scientific attention due to the possible adverse effects that these compounds have on human health and the formation of another DBPs. Factors that affect the formation of DBPs include: chlorine dose and residue, contact time, temperature, pH and natural organic matter (NOM). The most frequently detected DBPs in drinking water are trihalomethanes (THMs) and haloacetic acids (HAAs). The MCLs are standards established by the United States Environmental Protection Agency (USEPA) for drinking water quality established in Stage 1, Disinfectants and Disinfection Byproducts Rule (DBPR), and they limit the amount of potentially hazardous substances that are allowed in drinking water. The water quality data for THMs were evaluated in the Puerto Rico Aqueduct and Sewer Authority (PRASA). During this evaluation, the THMs exceeded the maximum contamination limit (MCLs) for the Comerio Water Treatment Plant (CWTP). USEPA classified the THMs as Group B2 carcinogens (shown to cause cancer in laboratory animals). This research evaluated the THMs concentrations in the following sampling sites: CWTP, Río Hondo and Pinas Abajo schools, Comerio Health Center (CDT), and the Vázquez Ortiz family, in the municipality of Comerio Puerto Rcio. The results show that the factors affecting the formation of THMs occur in different concentrations across the distribution line. There are not specific ranges to determine the formation of THMs in drinking water when the chemical and physical parameters were evaluated. Three different nanostructured materials (graphene, mordenite (MOR) and multiwalled carbon nanotubes (MWCNTs)) were used in this research, to reduce the THMs formation by adsorption in specific contact times. The results showed that graphene is the best nanomaterial to reduce THMs in drinking water. Graphene can reduce 80 parts per billion (ppb) of THMs in about 2 hours. In addition mordenite can reduce approximately 80 ppb of THMs and MWCNTs adsorbs 71 ppb of THMs in the same period of time respectively. In order to complement the adsorption results previously obtained, total organic carbon (TOC) analyses were measured, after different contact times with the nanomaterials. During the first 30 minutes, graphene C/Co was reduced to c.a. 0.9, in presence of each THMs solution. MWCNTs and MOR show similar adsorptions trends in comparison with graphene.
Nanotechnology: An Urgent Need  [PDF]
Francisco M. Marquez Linares
Soft Nanoscience Letters (SNL) , 2013, DOI: 10.4236/snl.2013.33008

From the first forecasts and expectations of nanotechnology, in the late 90s, there are many things that have changed and too many expectations not fulfilled. By 2050, the population is expected to exceed 9 billion people. At that time, or even before, the situation in the world can be very difficult if we do not put all the means at our disposal.

Nanomaterials for Drugs Delivery  [PDF]
Francisco Márquez, Carmen Morant
Soft Nanoscience Letters (SNL) , 2014, DOI: 10.4236/snl.2014.43007

As expected for years, nanotechnology has revolutionized engineering, biology, chemistry, physics and medicine of today. These disciplines are evolving thanks to the ongoing development of new materials and applications. Nanomedicine, as application of nanotechnology in the field of health care, has undergone unprecedented development. Some of these changes have real applications as, for example, the use of nanoparticles in MRI imaging, in hyperthermia, in immunotherapy, or to improve the bioavailability of drugs, among others [1]-[3].

When a drug is administered to a patient, the blood distributes it throughout the body. In the case of very localized diseases (i.e. tumors), only a small fraction of the drug reaches the target. Chemotherapy is one of the most aggressive treatment options used in some types of cancer, and is usually administered intravenously. In this type of therapy, the drug circulates throughout the body, reaching and destroying healthy and cancerous tissues, producing side effects throughout the body, sometimes with serious consequences for the health of the patient (nephrotoxicity, cardiotoxicity, peripheral neuropathy, anemia, etc.). Among the many applications of nanotechnology, the fabrication of nanostructures capable of safely transporting these drugs is seen as a strategy for reducing these side effects. Nanoparticles are able to carry and release the drug in the right place and with the required dose, greatly reducing the problems associated with direct treatment with these drugs.

In recent years, there have been continuous improvements in the design and development of new tailor-made drug delivery systems [4], including hollow magnetic nanoparticles, liposomal structures, dendrimers, nanoporous silicon, etc. These structures can be obtained with different molecular weights (in the case of polymers), structures, shapes, and even with the appropriate functional groups for interaction at the desired positions. However, a great effort is still required to solve many of the current problems [5], including toxicity, aggregation, solubility and stability in the human body, physiological processes of elimination, identification of targets by highly specific receptors, controlled drug release over time, etc.

Nanomaterials for Sensor Applications  [PDF]
Francisco Márquez, Carmen Morant
Soft Nanoscience Letters (SNL) , 2015, DOI: 10.4236/snl.2015.51001
Abstract: Recently, a large part of the advances in nanotechnology have been directed towards the development of high-speed electronics, more efficient catalysts, and sensors. This latter group of applications has great relevance and unprecedented development potential for the coming years.So far, some of the main objectives for the development of sensors have focused on making more sensitive, effective and specific sensing devices.The improvement of these systems and the increase of specificity are clearly associated with a decrease in size of the components, which can lead to obtaining more rapid action, almost in real time. Nanomaterials currently used in sensor development include a long list of nanostructured systems, as for example: metal nanotubes, nanowires, nanofibers, nanocomposites, nanorods, nanoparticles, nanostructured polymers, and different allotropes of carbon as carbon nanotubes, graphene or fullerenes, among others.
Electron Confinement Effect of Laser Dyes within Dendritic Structures  [PDF]
Francisco Márquez, María José Sabater
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2011, DOI: 10.4236/jeas.2011.11001
Abstract: Dendrimers are a novel class of nanometric-size macromolecules with a regular tree-dimensional like array of branch units.1,2 Their synthetic availability in a wide range of sizes combined with their peculiar architecture makes them versatile building blocks for a wide range of potential applications.3 Some years ago, Meijer and co-workers reported that the modification of terminal amine functionalities of a fifth generation poly(propyleneimine) dendrimer (DAB-dendr-(NH2)64) with bulky substituents, (typically N-t-BOC protected phenylalanine), results in the formation of the so-called “dendritic box” (DAB-dendr-(NH-t-BOC-L-Phe)64).4 Within this macromolecular structure it is possible to encapsulate a variety of guest molecules due to the existence of internal cavities in the core. The photophysical properties of the guests can be modulated by the innovative electron confinement effect. In this respect, we wish to report that the emission frequency of organic dyes can be easily modulated by encapsulation in a dendritic box. The emission bands of dye molecules incorporated into a dendrimer can effectively be red shifted with respect to their emission in solution and contrary to other confined spaces of considerable hardness, the magnitude of this shifting can be regulated under appropriate experimental conditions. This peculiar effect could have unprecedented applications in the development of supramolecular devices relating to the frequency tuning of organic laser dyes.
Breijo’s Electrocardiographic Model  [PDF]
Francisco R. Breijo-Márquez
Open Journal of Internal Medicine (OJIM) , 2018, DOI: 10.4236/ojim.2018.81011
Abstract: Breijo’s electrocardiographic model is becoming better known to cardiologists every day. The decrease in the PR interval, together with the decrease of the QTc interval in the same individual, is the main and only feature of the same individual. It can often go unnoticed, but many problems could be avoided if it was previously diagnosed, including sudden death.
Hydrogen from Sunlight Water Splitting: Is It Our Future?  [PDF]
Francisco Márquez, Kleber R Pirota, Carmen Morant
Soft Nanoscience Letters (SNL) , 2013, DOI: 10.4236/snl.2013.34019
Abstract: Environmental pollution and the growing need to find new sources of energy are some of the challenges of our century. The unstoppable growth of population, the increasing energy needs of emerging countries, and the foreseeable shortage of fossil fuels in a few years, make imperative to develop new energy generation processes and, in this regard, nanotechnology and the development of new nanomaterials will play a decisive role for the future of the planet.
Nanomaterials in Biomedicine  [PDF]
Mosaad A. Abdel-Wahhab, Francisco Márquez
Soft Nanoscience Letters (SNL) , 2015, DOI: 10.4236/snl.2015.53006
Abstract: Nowadays, nanomaterials have become an emerging field that has shown great promise in the development of novel diagnostic, imaging and therapeutic agents for a variety of diseases, including cancer, due to their nanoscale size effects and increased surface area. In comparison to their larger counterparts, nanomaterials have unique physicochemical and biological properties including size, shape, chemical composition, surface structure and charge, aggregation and agglomeration, and solubility which can affect their interactions with biomolecules and cells. Nanoparticles (NPs) with size-tunable light emission have demonstrated an impressive potential as high-efficiency delivery transporters for biomolecules into cells, being used to produce exceptional images of tumor sites. Moreover, NPs delivery system has been widely applied in pharmaceutical field to enhance absorption of bioactive compounds since they can interact with several phytochemicals by hydrogen bonds and hydrophobic interactions to encapsulate these phytochemicals in NPs and thus enhance aqueous solubility of the chemicals. Moreover, NPs also can prevent against oxidation/degradation of the phytochemicals encapsulated in the gastrointestinal tract and can be taken directly up by epithelial cells in the small intestine resulting in the increase of absorption and bioavailability of phytochemicals. In general, there are two specific fields of utilization of intrinsically active NPs as pharmacologic agents including oxidative-related pathologies and cancer. On the other hand, Redox active NPs have been shown to ameliorate many clinically relevant pathological disorders that implicate oxidative stress, reducing the oxidative burden and alleviating many important symptoms. Such NPs act either in a catalytic way resembling the action of antioxidant enzymes such as catalase and superoxide dismutase, or as activating surfaces to facilitate reactions between the aqueous environment and the reactive oxygen species present at high level in the pathological tissues.
Influência do avan?o cinemático das rodas dianteiras sobre a eficiência em tra??o de tratores com quatro rodas motrizes n?o isodiamétricas
Schlosser, José Fernando;Linares, Pilar;Márquez, Luis;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000600020
Abstract: the objective of this experiment was to study the effect of cinematic relationship between trator axles on traction efficiency of four-wheel tractor drive system. results indicated that a higher traction efficiency was observed when cinematic relationship was close to one (using the same peripheral wheel speed). considering a hard soil surface the trator absorbed vibrations due to interference between axles. however, on a soft soil surface the trator traction was smooth with a higher front wheel slippage index.
Desenvolvimento de metodologia para previs?o do fen?meno de vibra??es decorrentes da interferência entre eixos de um trator com tra??o dianteira auxiliar (TDA)
Schlosser, José Fernando;Márquez, Luis;Linares, Pilar;
Ciência Rural , 2001, DOI: 10.1590/S0103-84782001000600011
Abstract: a field experiment was carried out to evaluate the conditions for the appeareance of the power hope phenomenon. it consists in low frequency vibrations and great amplitude. this physical phenomenon is very common in fwa tractors, mainly with unequal tires diameter in front and rear axle. to promote power hope, different weight distribution conditions, different tire pressure and different drawbar force were used. power hope occurence conditions were determined using simple methodology, which uses tire radio in the calculations.
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