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Search Results: 1 - 10 of 217340 matches for " LUIS G. ROA "
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BEHAVIOR OF HERBICIDE BENSULFURON-METHYL IN MICROWAVE-ASSISTED SOLVENT EXTRACTION (MASE) FROM SOILS WITH DIFFERENT PHYSICOCHEMICAL CHARACTERISTICS
ROA,LUIS G.; BáEZ,MARíA E.;
Journal of the Chilean Chemical Society , 2003, DOI: 10.4067/S0717-97072003000300008
Abstract: the feasibility of mase application in the determination of bensulfuron-methyl (bsm) in soils with different organic matter content, consequently with a different capability to adsorb this herbicide is studied. hydrolysis experiments were performed to check the significance of degradation under various temperature and time conditions in aqueous-acetonitrile solutions at various ph. results are shown of the application of the method developed in the determination of bsm in two characteristic chilean soils (organic matter content 1.4 and 11.4 % and ph 7.2 and 5.1, respectively). the maximum temperature that can be used during the heating program is 60c, where the two main degradation products were undetected and recovery percentages reached 95%.
BEHAVIOR OF HERBICIDE BENSULFURON-METHYL IN MICROWAVE-ASSISTED SOLVENT EXTRACTION (MASE) FROM SOILS WITH DIFFERENT PHYSICOCHEMICAL CHARACTERISTICS
LUIS G. ROA,MARíA E. BáEZ
Journal of the Chilean Chemical Society , 2003,
Abstract: The feasibility of MASE application in the determination of Bensulfuron-methyl (BSM) in soils with different organic matter content, consequently with a different capability to adsorb this herbicide is studied. Hydrolysis experiments were performed to check the significance of degradation under various temperature and time conditions in aqueous-acetonitrile solutions at various pH. Results are shown of the application of the method developed in the determination of BSM in two characteristic Chilean soils (organic matter content 1.4 and 11.4 % and pH 7.2 and 5.1, respectively). The maximum temperature that can be used during the heating program is 60C, where the two main degradation products were undetected and recovery percentages reached 95%.
Concealed Quantum Information
Luis Roa
Physics , 2007,
Abstract: We study the teleportation scheme performed by means of a partially entangled pure state. We found that the information belonging to the quantum channel can be distributed into both the system of the transmitter and the system of the receiver. Thus, in order to complete the teleportation process it is required to perform an "unambiguous non-orthogonal quantum states discrimination" and an "extraction of the quantum information" processes. This general scheme allows one to design a strategy for concealing the unknown information of the teleported state. Besides, we showed that the teleportation and the "concealing the quantum information" process, can be probabilistically performed even though the bipartite quantum channel is maximally entangled.
Hallazgos en reintervenciones quirúrgicas por cáncer de la vesícula biliar en pacientes con y sin quimio-radiación preoperatoria
Roa E,ván; de Aretxabala U,Xabier; Araya O,Juan C; Villaseca H,Miguel; Roa S,Juan; Burgos S,Luis; Guzmán G,Pablo;
Revista médica de Chile , 2001, DOI: 10.4067/S0034-98872001000900006
Abstract: background: the usefulness of surgery in the treatment of gallbladder cancer has not been clearly established. the benefits of chemo and radiotherapy are similarly dubious. aim: to report the pathological findings in patients subjected to surgical reinterventions for gallbladder cancer. patients and methods: we report 54 patients with gallbladder cancer that were subjected to a second surgical intervention for resection of liver segments ivb and v and lymph nodes corresponding to the liver hilar, portal, peripancreatic, celiac artery and periaortic territories. thirteen of these patients were subjected to preoperative chemo-radiotherapy (4500 gy and 5-fluouracil 500 mg/m2). results: lymph node metastases were found in 25 and 38%, and liver metastases in 25 and 28% of patients with or without chemo-radiotherapy respectively. the most frequent pathological findings attributed to radiation in the liver were fatty infiltration in 75% of cases, vascular transformation in 83% of cases and minimal periportal lymphocyte infiltration in 40% of cases. lymph nodes were atrophic in 67% of cases and had foci of cortical necrosis in 46% of cases. three cases had regional lymph node and liver metastases. most tumor cells were viable. conclusions: no differences in the number of lymph node or liver metastases were observed between patients with and without chemo-radiotherapy. no effect of the treatment on residual tumor was observed either (rev méd chile 2001; 129: 1013-20
?Es el cáncer de la vesícula biliar una enfermedad de mal pronóstico en Chile?
Roa E,Iván; De Aretxabala U,Xabier; Roa S,Juan; Araya O,Juan C; Villaseca H,Miguel; Guzmán G,Pablo; Burgos S,Luis;
Revista médica de Chile , 2002, DOI: 10.4067/S0034-98872002001100014
Abstract: gallbladder cancer is frequent in chile, but it is not uniformly mortal. the diagnosis is usually made after a cholecystectomy. indicated for a symptomatic cholelithiasis. global survival of gallbladder cancer can be as high as 40% at five years. in 69% of women of less than 30 years old, the tumor is detected in early stages. in these cases, cholecystectomy is the curative procedure, with a 90% survival at five years. according to our experience, cholecystectomies should be performed between 40 and 50 years of age in men and between 30 and 40 years in women. the prognostic factors that should be considered are symptoms associated to lithiasis, age, parity, obesity, size of stones and the size of the gallbladder. if the tumor is detected in early stages, the survival is good. the natural history of the disease would change significantly if all women with symptomatic stones were operated (rev méd chile 2002; 130: 1295-1302).
Decoherence assisting a measurement-driven quantum evolution process
L. Roa,G. Olivares
Physics , 2005, DOI: 10.1103/PhysRevA.73.062327
Abstract: We study the problem of driving an unknown initial mixed quantum state onto a known pure state without using unitary transformations. This can be achieved, in an efficient manner, with the help of sequential measurements on at least two unbiased bases. However here we found that, when the system is affected by a decoherence mechanism, only one observable is required in order to achieve the same goal. In this way the decoherence can assist the process. We show that, depending on the sort of decoherence, the process can converge faster or slower than the method implemented by means of two complementary observables.
Qubits entanglement dynamics modified by an effective atomic environment
I. Sainz,A. B. Klimov,Luis Roa
Physics , 2005, DOI: 10.1103/PhysRevA.73.032303
Abstract: We study entanglement dynamics of a couple of two-level atoms resonantly interacting with a cavity mode and embedded in a dispersive atomic environment. We show that in the absence of the environment the entanglement reaches its maximum value when only one exitation is involved. Then, we find that the atomic environment modifies that entanglement dynamics and induces a typical collapse-revival structure even for an initial one photon Fock state of the field.
Quantum phase transitions in an effective Hamiltonian: fast and slow systems
Isabel Sainz,Andrei B. Klimov,Luis Roa
Mathematics , 2008, DOI: 10.1088/1751-8113/41/35/355301
Abstract: An effective Hamiltonian describing interaction between generic "fast" and a "slow" systems is obtained in the strong interaction limit. The result is applied for studying the effect of quantum phase transition as a bifurcation of the ground state of the "slow subsystem" in the thermodynamic limit. Examples as atom-field and atom-atom interactions are analyzed in detail.
Quemaduras por frío: Revisión de 10 A?os
EULUFí M,ALEX; PI?EROS B,JOSé LUIS; CALDERóN O,WILFREDO; CUADRA C,áLVARO; DANILLA E,STEFAN; LéNIZ M,PATRICIO; ROCO M,HéCTOR; ROA G,RICARDO; EULUFí M,CHRISTIAN;
Revista chilena de cirugía , 2006, DOI: 10.4067/S0718-40262006000500005
Abstract: background: cold injuries are usually caused by gases or liquids at very low temperatures or by exposure to extremely cold environments. aim: to review the experience with cold injuries. material and methods: retrospective review of medical records of 10 patients admitted to hospital del trabajador with cold injuries, between 1993 and 2003. results: all patients were male and their ages ranged between 17 and 68 years. nine patients were injured by cold gases or liquids and one patient was exposed to an environmental temperature of -25 oc. three had solely type a burns, one had a/ab burns, three had ab/b burns and one, b burns. the mean injured body surface area was 1.6%. in all, lesions were restricted to the hands and only one had involvement of the forearms. mean hospital stay was 9 days, excluding one patient that was transferred to united states on the first day of admission. four patients required surgery and were subjected to a mean of 3.5 interventions. one patient required finger amputation and two had functional sequelae at the end of treatment. conclusions: the objectives of the treatment of cold injuries should be to prevent sequelae, avoid amputations and obtain a rapid healing of lesions
Balance Equations of Electromagnetic Angular Momentum  [PDF]
Ignacio Campos-Flores, José Luis Jiménez-Ramírez, José Antonio Eduardo Roa-Neri
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2017, DOI: 10.4236/jemaa.2017.912017
Abstract: We give theoretical foundation to torque densities proposed in the past, like the one used by Beth to study experimentally the action of circularly polarized radiation on a birefringent material, or that proposed by Mansuripur to resolve a seeming paradox concerning the Lorentz force law and relativity. Our results provide new insights into electromagnetic theory, since they provide a unified and general treatment of the balance of lineal and angular momentum that permits a better assessment of some torques. Thus in this work we extend the derivations we have made of balance equations for electromagnetic linear momentum to balance equations for electromagnetic angular momentum. These balance equations are derived from the macroscopic Maxwell equations by means of vector and tensor identities and from the different ways in which these equations are written in terms of fields E, D, B, and H, as well as polarizations P, and M. Therefore these balance equations are as sound as the macroscopic Maxwell equations, with the limitations of the constitutive relations.
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