Ivan Velazquez | Universidad del Valle de Mexico (original) (raw)

Papers by Ivan Velazquez

Fish & Shellfish Immunology, 2009

Fish resistance to microorganisms depends basically on the immune response. Although there are se... more Fish resistance to microorganisms depends basically on the immune response. Although there are several studies on the diazinon mammalian immunotoxicity, in the case of fish there are only few. The aim of present study was to evaluate the effect of diazinon on immunological parameters (relative spleen weight, splenocytes count, lysozyme activity, respiratory burst and IgM concentration) in Nile tilapia. Diazinon at sublethal concentrations (0.39 and 0.78 mg/L) did not alter RSW, splenocytes count or lysozyme activity. However, at the highest concentration tested (1.96 mg/L) diazinon significantly increased respiratory burst and IgM concentration. In summary, diazinon (and perhaps other pesticides) could alter immunological response and induce oxidative stress.

Journal of Hazardous Materials, 2011

Endosulfan is a hazardous organochlorine pesticide banned or restricted in several countries. How... more Endosulfan is a hazardous organochlorine pesticide banned or restricted in several countries. However, it has been found in the environment and in animal samples. To study a potential way to bioremediate soils contaminated with this pesticide, two plant species of the genus Ocimum were studied: Ocimum basilicum L. and Ocimum minimum L., since they are economically feasible and well adapted to the climatic conditions of the Nayarit zone (Mexican pacific coast). Young plants were transplanted into soil experimentally polluted with endosulfan. Growth of both species was not affected by endosulfan, the plants grew, flourished, and produced seeds; 30 days later, endosulfan concentration was lower in the soil with O. basilicum than in the soil without plants. On day 90, no differences in endosulfan concentrations were found between soil with or without O. minimum. At day 1, plants in the polluted soil showed lipoperoxidation, as measured by thiobarbituric acid-reactive species (TBARS). Interestingly, a higher TBARS value was observed at day 3 in transplanted plants as compared to non-transplanted plants. In conclusion, both species can endure endosulfan pollution (as high as 1 g kg −1 ) in soils. O. basilicum seems to be an adequate candidate for bioremediation of soils polluted with endosulfan.

European Physical Journal C, 2010

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), tw... more On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|N ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN ch/dη=3.51±0.15(stat.)±0.25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton–antiproton interactions at the same centre-of-mass energy at the CERN Sp \(\overline{\mathrm{p}}\) S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.

Para realizar el control de la calidad del dextrometorfano jarabe, se aplicó la técnica descrita ... more Para realizar el control de la calidad del dextrometorfano jarabe, se aplicó la técnica descrita en la USP 23, y se comprobó la fiabilidad de esta mediante la evaluación de la precisión, exactitud, linealidad y especificidad. Se incluyen además, la determinación de las características organolépticas, pH y contenido por frasco como ensayos propios de medicamentos líquidos de administración oral o de uso externo. DeCS: DEXTROMETORFANO/análisis; DEXTROMETORFANO/farmacología; CONTROL DE CALIDAD; CROMATOGRAFIA LIQUIDA DE ALTA PRESION; CALIDAD DE LOS MEDICAMENTOS; TOS/quimioterapia; QUIMICA FARMACEUTICA. 1 Master en Ciencias. Licenciado en Química. Investigador Auxiliar. 2 Licenciada en Ciencias Farmacéuticas. Hospital Clinicoquirúrgico " Enrique Cabrera. " 3 Licenciado en Ciencias Farmacéuticas. Investigador Agregado. 4 Técnica en Tecnología Farmacéutica.

Revista de Biología Marina y Oceanografía 45(1): 71-76, abril de 2010 Fecundidad y proporción de ... more Revista de Biología Marina y Oceanografía 45(1): 71-76, abril de 2010 Fecundidad y proporción de sexos de Panulirus inflatus en la costa occidental del Golfo de California, México Fecundity and sex ratio of Panulirus inflatus in the west coast of the Gulf of California, México Abstract.-The fecundity and sex ratio of P. inflatus were studied in the western coast of the Gulf of California, Mexico. From February 2004 to January 2005, 567 lobsters were captured, 302 males (M) and 265 females (F). The sex ratio was 1H:1.13 M which did not differ significantly from 1:1. Fecundity varied between 94,837 and 830,149 eggs (384,314

Journal of Applied Geophysics, 2007

Electrical resistivity tomography (ERI) and ground-penetrating radar (GPR) surveys have been comb... more Electrical resistivity tomography (ERI) and ground-penetrating radar (GPR) surveys have been combined to investigate different volcanic materials, their contacts (lava flows, pyroclastic deposits, dykes) and structures (lava tubes, faults) in Tenerife (Canary Islands). The EM waves mean velocities estimated for the different rocks range from 0.075 to 0.1 m ns − 1 . Nonconsolidated materials such as hydromagmatic, pyroclastic and airfall deposits display the lowest EM mean velocities, whereas massive and consolidated materials, mainly lava flows, show the fastest ones. The higher resistivity values (> 800-1000 Ω m) correspond to lava flows, the intermediate resistivity values (∼ 100-800 Ω m) are related to different types of non-consolidated deposits (pyroclastic or explosive deposits), and the lower resistivity values (5-50 Ω m) correspond to fine grained volcanic materials (altered ignimbrite and hydrovolcanic). ERI usually provides a good definition of the boundaries between the volcanic units, shows a better performance than GPR to locate structures such as lava tubes and faults, and also gives a direct estimation of depth. The resistivity models are better defined if two different datasets obtained from dipole-dipole and Wenner arrays are combined prior to the inversion procedure. On the other hand, due to its greater horizontal and vertical resolution, the GPR technique is the most effective to characterize the internal structure of the volcanic deposits. However, a very strong attenuation of the EM waves has been observed in relation to the pyroclastic deposits, which makes the GPR unable to locate internal boundaries at depths as shallow as 2 m. This problem may also derive from the choice of the frequency antennae. If this is correct, then different antenna frequencies would have produced different results.

BMC Health Services Research, 2009

The philosophy of evidence-based medicine (EBM) was introduced in the early 90s as a new approach... more The philosophy of evidence-based medicine (EBM) was introduced in the early 90s as a new approach to the practice of medicine, using the best available evidence to make decisions about health care. Despite ongoing controversy, EBM has developed enormously and physicians' attitude towards it is generally positive. Nevertheless, in Spain little is known about this topic. We will therefore undertake a study to explore perceptions, attitudes and knowledge about EBM among primary care physicians.

Ecotoxicology, 2010

Substantial efforts have been devoted to developing and applying biomarkers for ecological risk a... more Substantial efforts have been devoted to developing and applying biomarkers for ecological risk assessment. Bivalve mollusks, such as mussels and oysters, are commonly used in environmental monitoring programs because of their wide geographical distribution, great sensitivity to environmental pollutants, and ability to accumulate anthropogenically derived chemicals at a high rate. Acetylcholinesterase (AChE) activity and metallothionein (MT’s) content are representative specific biomarkers that indicate the presence of anticholinesterasic compounds (like organophosphorus and carbamate pesticides) and metals, respectively. The aim of this study was to evaluate AChE activity and MT’s content in Crassostrea corteziensis from Boca de Camichín estuary. The results obtained here showed that AChE activity was 65% lower in oysters from Boca de Camichín than in control organisms. In contrast, MT’s content in collected organisms was not statistically different from that in control organisms. AChE activity and MT’s content in oysters could be used as early biomarkers of effects and exposure to pesticides and heavy metals, respectively, in aquatic environments.

World Mycotoxin Journal, 2010

... Cervantes1, MI Girón-Pérez1, ML Robledo-Marenco1, S. Marín2, JB Velázquez-Fernández1, IM Medi... more ... Cervantes1, MI Girón-Pérez1, ML Robledo-Marenco1, S. Marín2, JB Velázquez-Fernández1, IM Medina-Díaz1, AE Rojas-García1 and AJ ... biologically active substances, like antibodies (Hodkinson and Hunter, 1970), lysozyme, complement system (Alexander, 1985) or C ...

Acta Astronautica, 2003

The steady-state temperature distribution in spacecraft mounting plates and components with discr... more The steady-state temperature distribution in spacecraft mounting plates and components with discrete internal heat generation sources in the form of a thin current carrying wire due to conductive heat transfer has been determined. The heat sources are embedded in a circular plate in the form of a thin circular arc or a spiral and in the case of a sphere as a thin wire running along a diameter. An integral technique using Green's function is used. It is shown that in these cases an elegant closed-form analytical solution or an "almost analytical solution" can be obtained. The behavior of the non-dimensional temperature on the source strength, location and the geometry is discussed.

Acta Astronautica, 2003

The steady-state temperature distribution in spacecraft mounting plates and components with discr... more The steady-state temperature distribution in spacecraft mounting plates and components with discrete internal heat generation sources in the form of a thin current carrying wire due to conductive heat transfer has been determined. The heat sources are embedded in a circular plate in the form of a thin circular arc or a spiral and in the case of a sphere as a thin wire running along a diameter. An integral technique using Green's function is used. It is shown that in these cases an elegant closed-form analytical solution or an "almost analytical solution" can be obtained. The behavior of the non-dimensional temperature on the source strength, location and the geometry is discussed.

Fish & Shellfish Immunology, 2009

Fish resistance to microorganisms depends basically on the immune response. Although there are se... more Fish resistance to microorganisms depends basically on the immune response. Although there are several studies on the diazinon mammalian immunotoxicity, in the case of fish there are only few. The aim of present study was to evaluate the effect of diazinon on immunological parameters (relative spleen weight, splenocytes count, lysozyme activity, respiratory burst and IgM concentration) in Nile tilapia. Diazinon at sublethal concentrations (0.39 and 0.78 mg/L) did not alter RSW, splenocytes count or lysozyme activity. However, at the highest concentration tested (1.96 mg/L) diazinon significantly increased respiratory burst and IgM concentration. In summary, diazinon (and perhaps other pesticides) could alter immunological response and induce oxidative stress.

Journal of Hazardous Materials, 2011

Endosulfan is a hazardous organochlorine pesticide banned or restricted in several countries. How... more Endosulfan is a hazardous organochlorine pesticide banned or restricted in several countries. However, it has been found in the environment and in animal samples. To study a potential way to bioremediate soils contaminated with this pesticide, two plant species of the genus Ocimum were studied: Ocimum basilicum L. and Ocimum minimum L., since they are economically feasible and well adapted to the climatic conditions of the Nayarit zone (Mexican pacific coast). Young plants were transplanted into soil experimentally polluted with endosulfan. Growth of both species was not affected by endosulfan, the plants grew, flourished, and produced seeds; 30 days later, endosulfan concentration was lower in the soil with O. basilicum than in the soil without plants. On day 90, no differences in endosulfan concentrations were found between soil with or without O. minimum. At day 1, plants in the polluted soil showed lipoperoxidation, as measured by thiobarbituric acid-reactive species (TBARS). Interestingly, a higher TBARS value was observed at day 3 in transplanted plants as compared to non-transplanted plants. In conclusion, both species can endure endosulfan pollution (as high as 1 g kg −1 ) in soils. O. basilicum seems to be an adequate candidate for bioremediation of soils polluted with endosulfan.

European Physical Journal C, 2010

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), tw... more On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|N ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN ch/dη=3.51±0.15(stat.)±0.25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton–antiproton interactions at the same centre-of-mass energy at the CERN Sp \(\overline{\mathrm{p}}\) S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.

Para realizar el control de la calidad del dextrometorfano jarabe, se aplicó la técnica descrita ... more Para realizar el control de la calidad del dextrometorfano jarabe, se aplicó la técnica descrita en la USP 23, y se comprobó la fiabilidad de esta mediante la evaluación de la precisión, exactitud, linealidad y especificidad. Se incluyen además, la determinación de las características organolépticas, pH y contenido por frasco como ensayos propios de medicamentos líquidos de administración oral o de uso externo. DeCS: DEXTROMETORFANO/análisis; DEXTROMETORFANO/farmacología; CONTROL DE CALIDAD; CROMATOGRAFIA LIQUIDA DE ALTA PRESION; CALIDAD DE LOS MEDICAMENTOS; TOS/quimioterapia; QUIMICA FARMACEUTICA. 1 Master en Ciencias. Licenciado en Química. Investigador Auxiliar. 2 Licenciada en Ciencias Farmacéuticas. Hospital Clinicoquirúrgico " Enrique Cabrera. " 3 Licenciado en Ciencias Farmacéuticas. Investigador Agregado. 4 Técnica en Tecnología Farmacéutica.

Revista de Biología Marina y Oceanografía 45(1): 71-76, abril de 2010 Fecundidad y proporción de ... more Revista de Biología Marina y Oceanografía 45(1): 71-76, abril de 2010 Fecundidad y proporción de sexos de Panulirus inflatus en la costa occidental del Golfo de California, México Fecundity and sex ratio of Panulirus inflatus in the west coast of the Gulf of California, México Abstract.-The fecundity and sex ratio of P. inflatus were studied in the western coast of the Gulf of California, Mexico. From February 2004 to January 2005, 567 lobsters were captured, 302 males (M) and 265 females (F). The sex ratio was 1H:1.13 M which did not differ significantly from 1:1. Fecundity varied between 94,837 and 830,149 eggs (384,314

Journal of Applied Geophysics, 2007

Electrical resistivity tomography (ERI) and ground-penetrating radar (GPR) surveys have been comb... more Electrical resistivity tomography (ERI) and ground-penetrating radar (GPR) surveys have been combined to investigate different volcanic materials, their contacts (lava flows, pyroclastic deposits, dykes) and structures (lava tubes, faults) in Tenerife (Canary Islands). The EM waves mean velocities estimated for the different rocks range from 0.075 to 0.1 m ns − 1 . Nonconsolidated materials such as hydromagmatic, pyroclastic and airfall deposits display the lowest EM mean velocities, whereas massive and consolidated materials, mainly lava flows, show the fastest ones. The higher resistivity values (> 800-1000 Ω m) correspond to lava flows, the intermediate resistivity values (∼ 100-800 Ω m) are related to different types of non-consolidated deposits (pyroclastic or explosive deposits), and the lower resistivity values (5-50 Ω m) correspond to fine grained volcanic materials (altered ignimbrite and hydrovolcanic). ERI usually provides a good definition of the boundaries between the volcanic units, shows a better performance than GPR to locate structures such as lava tubes and faults, and also gives a direct estimation of depth. The resistivity models are better defined if two different datasets obtained from dipole-dipole and Wenner arrays are combined prior to the inversion procedure. On the other hand, due to its greater horizontal and vertical resolution, the GPR technique is the most effective to characterize the internal structure of the volcanic deposits. However, a very strong attenuation of the EM waves has been observed in relation to the pyroclastic deposits, which makes the GPR unable to locate internal boundaries at depths as shallow as 2 m. This problem may also derive from the choice of the frequency antennae. If this is correct, then different antenna frequencies would have produced different results.

BMC Health Services Research, 2009

The philosophy of evidence-based medicine (EBM) was introduced in the early 90s as a new approach... more The philosophy of evidence-based medicine (EBM) was introduced in the early 90s as a new approach to the practice of medicine, using the best available evidence to make decisions about health care. Despite ongoing controversy, EBM has developed enormously and physicians' attitude towards it is generally positive. Nevertheless, in Spain little is known about this topic. We will therefore undertake a study to explore perceptions, attitudes and knowledge about EBM among primary care physicians.

Ecotoxicology, 2010

Substantial efforts have been devoted to developing and applying biomarkers for ecological risk a... more Substantial efforts have been devoted to developing and applying biomarkers for ecological risk assessment. Bivalve mollusks, such as mussels and oysters, are commonly used in environmental monitoring programs because of their wide geographical distribution, great sensitivity to environmental pollutants, and ability to accumulate anthropogenically derived chemicals at a high rate. Acetylcholinesterase (AChE) activity and metallothionein (MT’s) content are representative specific biomarkers that indicate the presence of anticholinesterasic compounds (like organophosphorus and carbamate pesticides) and metals, respectively. The aim of this study was to evaluate AChE activity and MT’s content in Crassostrea corteziensis from Boca de Camichín estuary. The results obtained here showed that AChE activity was 65% lower in oysters from Boca de Camichín than in control organisms. In contrast, MT’s content in collected organisms was not statistically different from that in control organisms. AChE activity and MT’s content in oysters could be used as early biomarkers of effects and exposure to pesticides and heavy metals, respectively, in aquatic environments.

World Mycotoxin Journal, 2010

... Cervantes1, MI Girón-Pérez1, ML Robledo-Marenco1, S. Marín2, JB Velázquez-Fernández1, IM Medi... more ... Cervantes1, MI Girón-Pérez1, ML Robledo-Marenco1, S. Marín2, JB Velázquez-Fernández1, IM Medina-Díaz1, AE Rojas-García1 and AJ ... biologically active substances, like antibodies (Hodkinson and Hunter, 1970), lysozyme, complement system (Alexander, 1985) or C ...

Acta Astronautica, 2003

The steady-state temperature distribution in spacecraft mounting plates and components with discr... more The steady-state temperature distribution in spacecraft mounting plates and components with discrete internal heat generation sources in the form of a thin current carrying wire due to conductive heat transfer has been determined. The heat sources are embedded in a circular plate in the form of a thin circular arc or a spiral and in the case of a sphere as a thin wire running along a diameter. An integral technique using Green's function is used. It is shown that in these cases an elegant closed-form analytical solution or an "almost analytical solution" can be obtained. The behavior of the non-dimensional temperature on the source strength, location and the geometry is discussed.

Acta Astronautica, 2003

The steady-state temperature distribution in spacecraft mounting plates and components with discr... more The steady-state temperature distribution in spacecraft mounting plates and components with discrete internal heat generation sources in the form of a thin current carrying wire due to conductive heat transfer has been determined. The heat sources are embedded in a circular plate in the form of a thin circular arc or a spiral and in the case of a sphere as a thin wire running along a diameter. An integral technique using Green's function is used. It is shown that in these cases an elegant closed-form analytical solution or an "almost analytical solution" can be obtained. The behavior of the non-dimensional temperature on the source strength, location and the geometry is discussed.