Juan Gilberto Ceballos Maldonado - Academia.edu (original) (raw)

Papers by Juan Gilberto Ceballos Maldonado

Research paper thumbnail of Extendibility of x-ray lithography to ≤130 nm ground rules in complex integrated circuit patterns

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1996

Previous experimental and theoretical evidence indicates that x-ray lithography can be used to pa... more Previous experimental and theoretical evidence indicates that x-ray lithography can be used to pattern 180 nm features. In order to be used in manufacturing, x-ray lithography of complex integrated circuit patterns ie, dense two-dimensional patterns needs to be demonstrated ...

Research paper thumbnail of Wavelength Dependence of Exposure Window and Resist Profile in X-Ray-Lithography

Journal of Vacuum Science & Technology B, 1994

In proximity x-ray lithography, wavelengths in the range of 4-20 A are used. The choice of wavele... more In proximity x-ray lithography, wavelengths in the range of 4-20 A are used. The choice of wavelength is a complicated system issue, which depends on many lithographic aspects. Shorter wavelength x rays offer aerial image diffraction advantages. However, they may also give rise to spurious photoelectron effects. Longer wavelength x rays make mask patterning easier since the absorber can have a smaller aspect ratio for the required contrast, but a thinner, less robust memhrane is needed to give the same x-ray transmission. Softer x rays are also better absorbed in resist. reducing the exposure time, but higher absorption can have an adverse effect on the resist sidewall profile. A study is conducted to address the wavelength issue in x-ray lithography using the exposure window, resist profiles, power efficiency, and the mask contrast as merit/cost functions. Results show that a compromise among these factors is needed to achieve best performance.

Research paper thumbnail of Sequestration and in vivo effect of lead on DE2009 microalga, using high-resolution microscopic techniques

Journal of Hazardous Materials, 2010

Algae are primary producers in a wide variety of natural ecosystems, and these microorganisms hav... more Algae are primary producers in a wide variety of natural ecosystems, and these microorganisms have been used in bioremediation studies. Nevertheless, very little is known about the in vivo effect of heavy metals on individual living cells. In this paper, we have applied a method based on confocal laser scanning microscopy and lambda scan function (CLSM-λscan) to determine the effect of lead (Pb), at different concentrations, on the DE2009 microalga. At the same time, we have optimized a method based on CLSM and image-analysis software (CLSM-IA) to determine in vivo biomass of this microorganism. The results obtained by lambda scan function indicated that the pigment peak decreases while the concentration of metal increases at pH 7. On the other hand at pH 4 there is no good correlation between the concentration of metal and the intensity of the emission of fluorescence of the pigment. Also, in some cases a displacement of the Chl a peak towards 680 nm is produced. Total and individual biomass determined by CLSM-IA shows statistically significant differences between unpolluted and 10 mM polluted cultures. Complementary studies using electron microscopy techniques coupled to energy dispersive X-ray microanalysis (EDX) demonstrate that the microalga can sequestrate Pb extra- and intracellularly.

Research paper thumbnail of Immunological characterization of a unique focus of endemic pemphigus foliaceus in the rural area of El Bagre, Colombia

Journal of Dermatological Science, 1998

Basic Sciencs Caporetion, "nivers~ d A,&qua.-,,i", Color&a A case-control siudy was designed to c... more Basic Sciencs Caporetion, "nivers~ d A,&qua.-,,i", Color&a A case-control siudy was designed to characterize some lmmunologtcal aspects in one locus of endemic pemphigus foliaceous (EPF) I" El Bagre ColomMa Previously we demonstrafed that this focus differs in son~e clInical. epidemiological and environmental risk factors from others EPF foci. Forty-two patients and 27 controls were studied whom matched by age, sex and work condition. The presence of autoantibodies In the seem and sktn of EPF patients were analyzed by direct and indirect immunofluorescence @IF. IIF). immunoblotting, immurwprecipitatton (IP) and ELISA Dy IIF. lgG4 was the commonest IgG subclass producing intercellular staining between keratinocytes. Using anti-lgG3 subclass, an intracelkrlar imnlunofluorescence was detected in 62 2% of the cases and in 6.6% of the controls (~~005) In skin lesions from 18 EPF patient., DIF showed an intercellular keratinocyte staining with predominating IgGl and lgG4 subclasses and C3. In 62.7% of EPF patients. IIF revealed a basal membrane zone staining with IgM. C3 a IgG In a linear or granular pattern. By immunoblottlng. using ncfmal human skin as a substtak?. 33% of EPF sara showed reactivity with a 160 kDa band Moreover, 40% of EPF and 37% of control sera from El Bagre showed reactivity against two bands of approxmv&4y 210 and 195 kDa These bands were "ot detected I" othar controls

Research paper thumbnail of Description of an unusual focus of endemic pemphigus foliaceus in a rural area of the municipality of El Bagre, Colombia, South America

Journal of Dermatological Science, 1998

A casecontrol study of an endemic focus of pemphigus foliaceus (EPF) m the rural area of El Eagre... more A casecontrol study of an endemic focus of pemphigus foliaceus (EPF) m the rural area of El Eagre, Cdombia was canfed out. Forty-two EPF patients diagnosed by clinical, histopathological and immunological crftwta. and 27 controls from the same area were tested. According to our data, the prevalence of EPF in El Bagre, in the risk group (men among 30 to 70 Mng in rural area) was 1.4 %. All subiects were lvtno in the n&-al area and oerfotmed outdoor ackvlties as rnlnin~ and fan&. Senior m& were the mostly afF&ted (93.3%) with mean age of 50);ears, which are&v differs from the Brazilian foao selvaae fFS) and the Tunisia EPF foci. Fimilia;cases were detected in t9%ot the EFF 'pattents. The predominant dnical form @I%) simulate a &near Usher-like syndrome. Sun expo& was the most imoortant environmental factor assodated unth lW% of the EPF oatfents. The El Bagre area has been subjected to forest destructkm with'consequent increases in the average temperature of the area. The heavy metal mercury. is rouknelly used in large cuantities. in El Bagre for gold extraction. We tested for mercury levels in hair by mass spectrcecopy in the subjects of this study and we found htgher levels in EPF patients compared with co&ok (~~0.05). Higher IgE levels were found In the EPF pattents compared with the controls (vO.05) and no association with atopy or parasNc diseases wis detected by clinical and familiar Nstoty and by several coprology test. Based on these results and in the occupational exposure of PF patients (sun and mercury), we suggest that the combination of these factors couid bigger PF in people that is genetically predsposed.

Research paper thumbnail of The effect of copper on different phototrophic microorganisms determined in vivo and at cellular level by confocal laser microscopy

Ecotoxicology, 2012

Microbial mats are coastal ecosystems that consist mainly of cyanobacteria, primary producers in ... more Microbial mats are coastal ecosystems that consist mainly of cyanobacteria, primary producers in these habitats that play an important role in stabilising delta sediments. However, these ecosystems are subject to various kinds of pollution, including metal contamination, placing their survival at risk. Among heavy metals, copper is an essential metal at low doses and toxic at high doses. This metal is present in different pesticides used in rice production, a thriving agro-industry in the Ebro Delta (Spain). For several years, our group has been studying the Ebro Delta microbial mats and has developed a method for determining the effect that metals cause on cyanobacteria populations. This method is based on confocal laser microscopy coupled to a spectrofluorometer, which rapidly provides simultaneous three-dimensional information on photosynthetic microorganisms and their fluorescence spectra profiles. The current study determines the copper effect on different photosynthetic microorganisms from culture collection (Chroococcus sp. PCC 9106 and Spirulina sp. PCC 6313) and isolated from the environment (Microcoleus-like and the microalga DE2009). Comparing all results obtained it can be observed that the minimum dose of Cu that is capable of significantly altering chlorophyll a (chl a) fluorescence intensity were 1 × 10(-7) M in Chroococcus sp. PCC 9106; 1 × 10(-7) M in Spirulina sp. PCC 6313; 3 × 10(-7) M in Microcoleus and 5 × 10(-6) M in the microalga DE2009. Moreover, the sensitivity of the technique used was 1 × 10(-7) M.

Research paper thumbnail of Viability and Biomass of Micrococcus luteus DE2008 at Different Salinity Concentrations Determined by Specific Fluorochromes and CLSM-Image Analysis

Current Microbiology, 2011

In previous studies, our group developed a method based on Confocal Laser Scanning Microscopy and... more In previous studies, our group developed a method based on Confocal Laser Scanning Microscopy and Image Analysis (CLSM-IA) to analyze the diversity and biomass of cyanobacteria in microbial mats. However, this method cannot be applied to heterotrophic microorganisms, as these do not have autofluorescence. In this article, we present a method that combines CLSM-IA and Hoechst 33342 and SYTOX Green fluorochromes (FLU-CLSM-IA) to determine the viability and biomass of Micrococcus luteus DE2008, isolated from a saline microbial mat (Ebro Delta, Tarragona, Spain). The method has been applied to assess the effect of salinity on this microorganism. A reduction in viability and biomass (live cells) was observed as the salt concentration increases. The largest effect was at 100‰ NaCl with a cell death of 27.25% and a decrease in total and individual biomass of 39.75 and 0.009 mgC/cm(3), respectively, both with respect to optimal growth (10 ‰ NaCl). On the other hand, another important contribution of this article was that combining the FLU-CLSM-IA results with those achieved by plate counts enabled us to determine, for first time, the viability and the total biomass of the "dormant cells" (66.75% of viability and 40.59 mgC/cm(3) of total biomass at 100‰ NaCl). FLU-CLSM-IA is an efficient, fast, and reliable method for making a total count of cells at pixel level, including the dormant cells, to evaluate the viability and the biomass of a hetetrophic microorganism, M. luteus DE2008.

Research paper thumbnail of Biosorption of lead and copper by heavy-metal tolerant Micrococcus luteus DE2008

Bioresource Technology, 2012

Micrococcus luteus DE2008 has the ability to absorb lead and copper. The effect of these metals o... more Micrococcus luteus DE2008 has the ability to absorb lead and copper. The effect of these metals on biomass and viability of this microorganism were investigated and removal of the metals from culture media was determined. Lead had no effect on the biomass expressed as mg Carbon/cm(3) of M. Iuteus DE2008, but in the case of copper, the minimum metal concentration that affected the biomass was 0.1 mM Cu(II). According to these results this microorganism shows a greater tolerance for lead. The minimum metal concentration that affected viability (expressed as the percentage of live cells) was 0.5 mM for both metals. M. luteus DE2008 exhibited a specific removal capacity of 408 mg/g for copper and 1965 mg/g for lead. This microorganism has a greater ability to absorb Pb(II) than Cu(II). M. luteus DE2008 could be seen as a microorganism capable of restoring environments polluted by lead and copper.

Research paper thumbnail of Selection of bioindicators to detect lead pollution in Ebro delta microbial mats, using high-resolution microscopic techniques

Aquatic Toxicology, 2011

Lead (Pb) is a metal that is non-essential to any metabolic process and, moreover, highly deleter... more Lead (Pb) is a metal that is non-essential to any metabolic process and, moreover, highly deleterious to life. In microbial mats-benthic stratified ecosystems-located in coastal areas, phototrophic microorganisms (algae and oxygenic phototrophic bacteria) are the primary producers and they are exposed to pollution by metals. In this paper we describe the search for bioindicators among phototrophic populations of Ebro delta microbial mats, using high-resolution microscopic techniques that we have optimized in previous studies. Confocal laser scanning microscopy coupled to a spectrofluorometric detector (CLSM-scan) to determine in vivo sensitivity of different cyanobacteria to lead, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM), both coupled to energy dispersive X-ray microanalysis (EDX), to determine the extra-and intracellular sequestration of this metal in cells, were the techniques used for this purpose. Oscillatoria sp. PCC 7515, Chroococcus sp. PCC 9106 and Spirulina sp. PCC 6313 tested in this paper could be considered bioindicators for lead pollution, because all of these microorganisms are indigenous, have high tolerance to high concentrations of lead and are able to accumulate this metal externally in extracellular polymeric substances (EPS) and intracellularly in polyphosphate (PP) inclusions. Experiments made with microcosms demonstrated that Phormidium-like and Lyngbya-like organisms selected themselves at the highest concentrations of lead assayed. In the present study it is shown that all cyanobacteria studied (both in culture and in microcosms) present PP inclusions in their cytoplasm and that these increase in number in lead polluted cultures and microcosms. We believe that the application of these microscopic techniques open up broad prospects for future studies of metal ecotoxicity.

Research paper thumbnail of Effect of copper and lead on two consortia of phototrophic microorganisms and their capacity to sequester metals

Aquatic Toxicology, 2013

The roles of consortia of phototrophic microorganisms have been investigated in this paper to det... more The roles of consortia of phototrophic microorganisms have been investigated in this paper to determine their potential role to tolerate or resist metals and to capture them from polluted cultures. With this purpose, two consortia of microorganisms: on one hand, Geitlerinema sp. DE2011 (Ge) and Scenedesmus sp. DE2009 (Sc) (both identified in this paper by molecular biology methods) isolated from Ebro Delta microbial mats, and on the other, Spirulina sp. PCC 6313 (Sp) and Chroococcus sp. PCC 9106 (Ch), from Pasteur culture collection were polluted with copper and lead. In order to analyze the ability of these consortia to tolerate and capture metals, copper and lead were selected, because both have been detected in Ebro Delta microbial mats. The tolerance-resistance to copper and lead for both consortia was determined in vivo and at cellular level by Confocal Laser Scanning Microscopy (CLSM-λscan function). The results obtained demonstrate that both consortia are highly tolerant-resistant to lead and that the limits between the copper concentration having cytotoxic effect and that having an essential effect are very close in these microorganisms. The capacity of both consortia to capture extra- and intracellular copper and lead was determined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) respectively, coupled to an Energy Dispersive X-ray detector (EDX). The results showed that all the microorganisms assayed were able to capture copper extracellularly in the extrapolymeric substances, and lead extra- and intracellularly in polyphosphate inclusions. Moreover, the studied micro-organisms did not exert any inhibitory effect on each other's metal binding capacity. From the results obtained in this paper, it can be concluded that consortia of phototrophic microorganisms could play a very important role in biorepairing sediments polluted by metals, as a result of their ability to tolerate or resist high concentrations of metals and to bioaccumulate them, extra- and intracellulary.

Research paper thumbnail of Isolation and identification of a bacterium with high tolerance to lead and copper from a marine microbial mat in Spain

Annals of Microbiology, 2010

A bacterial strain (DE2008) was isolated from a consortium of microorganisms living in the microb... more A bacterial strain (DE2008) was isolated from a consortium of microorganisms living in the microbial mats of the Ebro Delta with the ability to grow under conditions of high concentrations of lead and copper. Strain DE2008 has been characterized by microscopic and metabolic techniques and identified by sequencing of PCR-amplified 16S rRNA gene fragments as Micrococcus luteus. The strain is highly resistant to lead and copper. Micrococcus luteus DE2008 grew optimally until levels of 1 mM of Pb (NO 3) 2 and CuSO 4 , respectively, and was completely inhibited at 3 mM Pb(NO 3) 2 and at 1.5 mM CuSO 4. Elemental analysis determined by energy-dispersive X-ray spectroscopy (EDX) coupled with scanning electron microscopy and transmission electron microscopy from polluted cultures of DE2008 show that this microorganism can biosorpt Pb and Cu in exopolysaccharide envelopes, without accumulating them inside the cells.

Research paper thumbnail of X-ray lithography for ≤100 nm ground rules in complex patterns

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1997

ABSTRACT Complex patterns with 75–125 nm feature sizes exposed with x-ray lithography are shown. ... more ABSTRACT Complex patterns with 75–125 nm feature sizes exposed with x-ray lithography are shown. Lithographic results for 75–125 nm lines with varying pitch are compared to simulations of image formation and resist dissolution, showing good qualitative agreement. Exposure dose latitude, nested-to-isolated print bias, image shortening, linewidth change with gap, and linearity of printed linewidth versus mask linewidth are quantified for 11–22.5 μm gaps. Critical dimension control error budgets for resist linewidth uniformity are determined for logic patterns at 75 and 100 nm ground rules. Image shortening is quantified for 75–125 nm ground rule static random access memory-like patterns, indicating hammerheads added to line ends reduce shortening to acceptable levels for ≥100 nm ground rules at ≤17.5 μm gaps. With tight gap control and tight mask linewidth control, 100 nm ground rule complex patterns can be printed with good latitude using x-ray lithography. © 1997 American Vacuum Society.

Research paper thumbnail of Política y religión en la derecha cristiana de los Estados Unidos de América

Resumen: El presente ensayo es un apretado resumen de un trabajo de investigación bastante más am... more Resumen: El presente ensayo es un apretado resumen de un trabajo de investigación bastante más amplio sobre el pensamiento conservador de Estados Unidos. Las estrechas vinculaciones históricas, culturales y de mentalidad en los Estados Unidos entre religión y política desde los primeros asentamientos coloniales, fueron cristalizando con el tiempo en un trenzado de valores republicanos y religiosos que con la ética calvinista de fondo y las referencias a los clásicos del republicanismo, alcanza una proyección imparable desde la Revolución en adelante. La expresión de este entrelazamiento es el "experimento" republicano-y la noción roussoniana de la "religión civil" como manifestación pública de esos valores-, por una parte; y por la otra, la noción de "destino" asumida ideológicamente a partir del peso que la propia religión cristiana ha representado en ese país.

Research paper thumbnail of Extendibility of x-ray lithography to ≤130 nm ground rules in complex integrated circuit patterns

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1996

Previous experimental and theoretical evidence indicates that x-ray lithography can be used to pa... more Previous experimental and theoretical evidence indicates that x-ray lithography can be used to pattern 180 nm features. In order to be used in manufacturing, x-ray lithography of complex integrated circuit patterns ie, dense two-dimensional patterns needs to be demonstrated ...

Research paper thumbnail of Wavelength Dependence of Exposure Window and Resist Profile in X-Ray-Lithography

Journal of Vacuum Science & Technology B, 1994

In proximity x-ray lithography, wavelengths in the range of 4-20 A are used. The choice of wavele... more In proximity x-ray lithography, wavelengths in the range of 4-20 A are used. The choice of wavelength is a complicated system issue, which depends on many lithographic aspects. Shorter wavelength x rays offer aerial image diffraction advantages. However, they may also give rise to spurious photoelectron effects. Longer wavelength x rays make mask patterning easier since the absorber can have a smaller aspect ratio for the required contrast, but a thinner, less robust memhrane is needed to give the same x-ray transmission. Softer x rays are also better absorbed in resist. reducing the exposure time, but higher absorption can have an adverse effect on the resist sidewall profile. A study is conducted to address the wavelength issue in x-ray lithography using the exposure window, resist profiles, power efficiency, and the mask contrast as merit/cost functions. Results show that a compromise among these factors is needed to achieve best performance.

Research paper thumbnail of Sequestration and in vivo effect of lead on DE2009 microalga, using high-resolution microscopic techniques

Journal of Hazardous Materials, 2010

Algae are primary producers in a wide variety of natural ecosystems, and these microorganisms hav... more Algae are primary producers in a wide variety of natural ecosystems, and these microorganisms have been used in bioremediation studies. Nevertheless, very little is known about the in vivo effect of heavy metals on individual living cells. In this paper, we have applied a method based on confocal laser scanning microscopy and lambda scan function (CLSM-λscan) to determine the effect of lead (Pb), at different concentrations, on the DE2009 microalga. At the same time, we have optimized a method based on CLSM and image-analysis software (CLSM-IA) to determine in vivo biomass of this microorganism. The results obtained by lambda scan function indicated that the pigment peak decreases while the concentration of metal increases at pH 7. On the other hand at pH 4 there is no good correlation between the concentration of metal and the intensity of the emission of fluorescence of the pigment. Also, in some cases a displacement of the Chl a peak towards 680 nm is produced. Total and individual biomass determined by CLSM-IA shows statistically significant differences between unpolluted and 10 mM polluted cultures. Complementary studies using electron microscopy techniques coupled to energy dispersive X-ray microanalysis (EDX) demonstrate that the microalga can sequestrate Pb extra- and intracellularly.

Research paper thumbnail of Immunological characterization of a unique focus of endemic pemphigus foliaceus in the rural area of El Bagre, Colombia

Journal of Dermatological Science, 1998

Basic Sciencs Caporetion, "nivers~ d A,&qua.-,,i", Color&a A case-control siudy was designed to c... more Basic Sciencs Caporetion, "nivers~ d A,&qua.-,,i", Color&a A case-control siudy was designed to characterize some lmmunologtcal aspects in one locus of endemic pemphigus foliaceous (EPF) I" El Bagre ColomMa Previously we demonstrafed that this focus differs in son~e clInical. epidemiological and environmental risk factors from others EPF foci. Forty-two patients and 27 controls were studied whom matched by age, sex and work condition. The presence of autoantibodies In the seem and sktn of EPF patients were analyzed by direct and indirect immunofluorescence @IF. IIF). immunoblotting, immurwprecipitatton (IP) and ELISA Dy IIF. lgG4 was the commonest IgG subclass producing intercellular staining between keratinocytes. Using anti-lgG3 subclass, an intracelkrlar imnlunofluorescence was detected in 62 2% of the cases and in 6.6% of the controls (~~005) In skin lesions from 18 EPF patient., DIF showed an intercellular keratinocyte staining with predominating IgGl and lgG4 subclasses and C3. In 62.7% of EPF patients. IIF revealed a basal membrane zone staining with IgM. C3 a IgG In a linear or granular pattern. By immunoblottlng. using ncfmal human skin as a substtak?. 33% of EPF sara showed reactivity with a 160 kDa band Moreover, 40% of EPF and 37% of control sera from El Bagre showed reactivity against two bands of approxmv&4y 210 and 195 kDa These bands were "ot detected I" othar controls

Research paper thumbnail of Description of an unusual focus of endemic pemphigus foliaceus in a rural area of the municipality of El Bagre, Colombia, South America

Journal of Dermatological Science, 1998

A casecontrol study of an endemic focus of pemphigus foliaceus (EPF) m the rural area of El Eagre... more A casecontrol study of an endemic focus of pemphigus foliaceus (EPF) m the rural area of El Eagre, Cdombia was canfed out. Forty-two EPF patients diagnosed by clinical, histopathological and immunological crftwta. and 27 controls from the same area were tested. According to our data, the prevalence of EPF in El Bagre, in the risk group (men among 30 to 70 Mng in rural area) was 1.4 %. All subiects were lvtno in the n&-al area and oerfotmed outdoor ackvlties as rnlnin~ and fan&. Senior m& were the mostly afF&ted (93.3%) with mean age of 50);ears, which are&v differs from the Brazilian foao selvaae fFS) and the Tunisia EPF foci. Fimilia;cases were detected in t9%ot the EFF 'pattents. The predominant dnical form @I%) simulate a &near Usher-like syndrome. Sun expo& was the most imoortant environmental factor assodated unth lW% of the EPF oatfents. The El Bagre area has been subjected to forest destructkm with'consequent increases in the average temperature of the area. The heavy metal mercury. is rouknelly used in large cuantities. in El Bagre for gold extraction. We tested for mercury levels in hair by mass spectrcecopy in the subjects of this study and we found htgher levels in EPF patients compared with co&ok (~~0.05). Higher IgE levels were found In the EPF pattents compared with the controls (vO.05) and no association with atopy or parasNc diseases wis detected by clinical and familiar Nstoty and by several coprology test. Based on these results and in the occupational exposure of PF patients (sun and mercury), we suggest that the combination of these factors couid bigger PF in people that is genetically predsposed.

Research paper thumbnail of The effect of copper on different phototrophic microorganisms determined in vivo and at cellular level by confocal laser microscopy

Ecotoxicology, 2012

Microbial mats are coastal ecosystems that consist mainly of cyanobacteria, primary producers in ... more Microbial mats are coastal ecosystems that consist mainly of cyanobacteria, primary producers in these habitats that play an important role in stabilising delta sediments. However, these ecosystems are subject to various kinds of pollution, including metal contamination, placing their survival at risk. Among heavy metals, copper is an essential metal at low doses and toxic at high doses. This metal is present in different pesticides used in rice production, a thriving agro-industry in the Ebro Delta (Spain). For several years, our group has been studying the Ebro Delta microbial mats and has developed a method for determining the effect that metals cause on cyanobacteria populations. This method is based on confocal laser microscopy coupled to a spectrofluorometer, which rapidly provides simultaneous three-dimensional information on photosynthetic microorganisms and their fluorescence spectra profiles. The current study determines the copper effect on different photosynthetic microorganisms from culture collection (Chroococcus sp. PCC 9106 and Spirulina sp. PCC 6313) and isolated from the environment (Microcoleus-like and the microalga DE2009). Comparing all results obtained it can be observed that the minimum dose of Cu that is capable of significantly altering chlorophyll a (chl a) fluorescence intensity were 1 × 10(-7) M in Chroococcus sp. PCC 9106; 1 × 10(-7) M in Spirulina sp. PCC 6313; 3 × 10(-7) M in Microcoleus and 5 × 10(-6) M in the microalga DE2009. Moreover, the sensitivity of the technique used was 1 × 10(-7) M.

Research paper thumbnail of Viability and Biomass of Micrococcus luteus DE2008 at Different Salinity Concentrations Determined by Specific Fluorochromes and CLSM-Image Analysis

Current Microbiology, 2011

In previous studies, our group developed a method based on Confocal Laser Scanning Microscopy and... more In previous studies, our group developed a method based on Confocal Laser Scanning Microscopy and Image Analysis (CLSM-IA) to analyze the diversity and biomass of cyanobacteria in microbial mats. However, this method cannot be applied to heterotrophic microorganisms, as these do not have autofluorescence. In this article, we present a method that combines CLSM-IA and Hoechst 33342 and SYTOX Green fluorochromes (FLU-CLSM-IA) to determine the viability and biomass of Micrococcus luteus DE2008, isolated from a saline microbial mat (Ebro Delta, Tarragona, Spain). The method has been applied to assess the effect of salinity on this microorganism. A reduction in viability and biomass (live cells) was observed as the salt concentration increases. The largest effect was at 100‰ NaCl with a cell death of 27.25% and a decrease in total and individual biomass of 39.75 and 0.009 mgC/cm(3), respectively, both with respect to optimal growth (10 ‰ NaCl). On the other hand, another important contribution of this article was that combining the FLU-CLSM-IA results with those achieved by plate counts enabled us to determine, for first time, the viability and the total biomass of the "dormant cells" (66.75% of viability and 40.59 mgC/cm(3) of total biomass at 100‰ NaCl). FLU-CLSM-IA is an efficient, fast, and reliable method for making a total count of cells at pixel level, including the dormant cells, to evaluate the viability and the biomass of a hetetrophic microorganism, M. luteus DE2008.

Research paper thumbnail of Biosorption of lead and copper by heavy-metal tolerant Micrococcus luteus DE2008

Bioresource Technology, 2012

Micrococcus luteus DE2008 has the ability to absorb lead and copper. The effect of these metals o... more Micrococcus luteus DE2008 has the ability to absorb lead and copper. The effect of these metals on biomass and viability of this microorganism were investigated and removal of the metals from culture media was determined. Lead had no effect on the biomass expressed as mg Carbon/cm(3) of M. Iuteus DE2008, but in the case of copper, the minimum metal concentration that affected the biomass was 0.1 mM Cu(II). According to these results this microorganism shows a greater tolerance for lead. The minimum metal concentration that affected viability (expressed as the percentage of live cells) was 0.5 mM for both metals. M. luteus DE2008 exhibited a specific removal capacity of 408 mg/g for copper and 1965 mg/g for lead. This microorganism has a greater ability to absorb Pb(II) than Cu(II). M. luteus DE2008 could be seen as a microorganism capable of restoring environments polluted by lead and copper.

Research paper thumbnail of Selection of bioindicators to detect lead pollution in Ebro delta microbial mats, using high-resolution microscopic techniques

Aquatic Toxicology, 2011

Lead (Pb) is a metal that is non-essential to any metabolic process and, moreover, highly deleter... more Lead (Pb) is a metal that is non-essential to any metabolic process and, moreover, highly deleterious to life. In microbial mats-benthic stratified ecosystems-located in coastal areas, phototrophic microorganisms (algae and oxygenic phototrophic bacteria) are the primary producers and they are exposed to pollution by metals. In this paper we describe the search for bioindicators among phototrophic populations of Ebro delta microbial mats, using high-resolution microscopic techniques that we have optimized in previous studies. Confocal laser scanning microscopy coupled to a spectrofluorometric detector (CLSM-scan) to determine in vivo sensitivity of different cyanobacteria to lead, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM), both coupled to energy dispersive X-ray microanalysis (EDX), to determine the extra-and intracellular sequestration of this metal in cells, were the techniques used for this purpose. Oscillatoria sp. PCC 7515, Chroococcus sp. PCC 9106 and Spirulina sp. PCC 6313 tested in this paper could be considered bioindicators for lead pollution, because all of these microorganisms are indigenous, have high tolerance to high concentrations of lead and are able to accumulate this metal externally in extracellular polymeric substances (EPS) and intracellularly in polyphosphate (PP) inclusions. Experiments made with microcosms demonstrated that Phormidium-like and Lyngbya-like organisms selected themselves at the highest concentrations of lead assayed. In the present study it is shown that all cyanobacteria studied (both in culture and in microcosms) present PP inclusions in their cytoplasm and that these increase in number in lead polluted cultures and microcosms. We believe that the application of these microscopic techniques open up broad prospects for future studies of metal ecotoxicity.

Research paper thumbnail of Effect of copper and lead on two consortia of phototrophic microorganisms and their capacity to sequester metals

Aquatic Toxicology, 2013

The roles of consortia of phototrophic microorganisms have been investigated in this paper to det... more The roles of consortia of phototrophic microorganisms have been investigated in this paper to determine their potential role to tolerate or resist metals and to capture them from polluted cultures. With this purpose, two consortia of microorganisms: on one hand, Geitlerinema sp. DE2011 (Ge) and Scenedesmus sp. DE2009 (Sc) (both identified in this paper by molecular biology methods) isolated from Ebro Delta microbial mats, and on the other, Spirulina sp. PCC 6313 (Sp) and Chroococcus sp. PCC 9106 (Ch), from Pasteur culture collection were polluted with copper and lead. In order to analyze the ability of these consortia to tolerate and capture metals, copper and lead were selected, because both have been detected in Ebro Delta microbial mats. The tolerance-resistance to copper and lead for both consortia was determined in vivo and at cellular level by Confocal Laser Scanning Microscopy (CLSM-λscan function). The results obtained demonstrate that both consortia are highly tolerant-resistant to lead and that the limits between the copper concentration having cytotoxic effect and that having an essential effect are very close in these microorganisms. The capacity of both consortia to capture extra- and intracellular copper and lead was determined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) respectively, coupled to an Energy Dispersive X-ray detector (EDX). The results showed that all the microorganisms assayed were able to capture copper extracellularly in the extrapolymeric substances, and lead extra- and intracellularly in polyphosphate inclusions. Moreover, the studied micro-organisms did not exert any inhibitory effect on each other's metal binding capacity. From the results obtained in this paper, it can be concluded that consortia of phototrophic microorganisms could play a very important role in biorepairing sediments polluted by metals, as a result of their ability to tolerate or resist high concentrations of metals and to bioaccumulate them, extra- and intracellulary.

Research paper thumbnail of Isolation and identification of a bacterium with high tolerance to lead and copper from a marine microbial mat in Spain

Annals of Microbiology, 2010

A bacterial strain (DE2008) was isolated from a consortium of microorganisms living in the microb... more A bacterial strain (DE2008) was isolated from a consortium of microorganisms living in the microbial mats of the Ebro Delta with the ability to grow under conditions of high concentrations of lead and copper. Strain DE2008 has been characterized by microscopic and metabolic techniques and identified by sequencing of PCR-amplified 16S rRNA gene fragments as Micrococcus luteus. The strain is highly resistant to lead and copper. Micrococcus luteus DE2008 grew optimally until levels of 1 mM of Pb (NO 3) 2 and CuSO 4 , respectively, and was completely inhibited at 3 mM Pb(NO 3) 2 and at 1.5 mM CuSO 4. Elemental analysis determined by energy-dispersive X-ray spectroscopy (EDX) coupled with scanning electron microscopy and transmission electron microscopy from polluted cultures of DE2008 show that this microorganism can biosorpt Pb and Cu in exopolysaccharide envelopes, without accumulating them inside the cells.

Research paper thumbnail of X-ray lithography for ≤100 nm ground rules in complex patterns

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1997

ABSTRACT Complex patterns with 75–125 nm feature sizes exposed with x-ray lithography are shown. ... more ABSTRACT Complex patterns with 75–125 nm feature sizes exposed with x-ray lithography are shown. Lithographic results for 75–125 nm lines with varying pitch are compared to simulations of image formation and resist dissolution, showing good qualitative agreement. Exposure dose latitude, nested-to-isolated print bias, image shortening, linewidth change with gap, and linearity of printed linewidth versus mask linewidth are quantified for 11–22.5 μm gaps. Critical dimension control error budgets for resist linewidth uniformity are determined for logic patterns at 75 and 100 nm ground rules. Image shortening is quantified for 75–125 nm ground rule static random access memory-like patterns, indicating hammerheads added to line ends reduce shortening to acceptable levels for ≥100 nm ground rules at ≤17.5 μm gaps. With tight gap control and tight mask linewidth control, 100 nm ground rule complex patterns can be printed with good latitude using x-ray lithography. © 1997 American Vacuum Society.

Research paper thumbnail of Política y religión en la derecha cristiana de los Estados Unidos de América

Resumen: El presente ensayo es un apretado resumen de un trabajo de investigación bastante más am... more Resumen: El presente ensayo es un apretado resumen de un trabajo de investigación bastante más amplio sobre el pensamiento conservador de Estados Unidos. Las estrechas vinculaciones históricas, culturales y de mentalidad en los Estados Unidos entre religión y política desde los primeros asentamientos coloniales, fueron cristalizando con el tiempo en un trenzado de valores republicanos y religiosos que con la ética calvinista de fondo y las referencias a los clásicos del republicanismo, alcanza una proyección imparable desde la Revolución en adelante. La expresión de este entrelazamiento es el "experimento" republicano-y la noción roussoniana de la "religión civil" como manifestación pública de esos valores-, por una parte; y por la otra, la noción de "destino" asumida ideológicamente a partir del peso que la propia religión cristiana ha representado en ese país.