Lu Cía | Universidad de Buenos Aires (original) (raw)

Papers by Lu Cía

Research paper thumbnail of Interparticle interactions and surface contribution to the effective anisotropy in biocompatible iron oxide nanoparticles used for contrast agents

We have investigated the dynamic magnetic properties of dextran-coated magnetite ͑Fe 3 O 4 ͒ nano... more We have investigated the dynamic magnetic properties of dextran-coated magnetite ͑Fe 3 O 4 ͒ nanoparticles in the form of ͑a͒ particles suspended in a carrier liquid and ͑b͒ concentrated powder obtained from lyophilization. The blocking temperature was found to increase from T B =42͑2͒ to 52͑2͒ K ͑@ 0 H =10 mT͒ after lyophilization, showing the effects of dipolar interactions in samples with identical size distributions. The temperature dependence of the hyperfine field B hyp ͑T͒ reveals the effects of collective magnetic excitations at low temperature, and allowed us to obtain the magnetic anisotropy energy E a = 3.6ϫ 10 −21 J for noninteracting particles. The obtained values can be understood assuming only magnetocrystalline anisotropy, without any additional contributions from surface, shape, or exchange origin. Moreover, a magnetocrystalline anisotropy constant value K 1 =10 kJ/m 3 was obtained by assuming the cubic phase with easy magnetic direction ͓111͔ of the bulk material above the Verwey transition, supporting the idea that the Verwey transition is absent in nanosized particles. Accordingly, no indication of magnetic transition at T V could be observed in our measurements. From the dynamical parameters of ac susceptibility ͑f , T͒ curves, the contribution of the dipolar interactions to the total anisotropy energy barrier could be estimated to be ⍀ = 4.5ϫ 10 −21 J, larger than the single-particle value.

Research paper thumbnail of Protoplanetary accretion disc in a binary system

Research paper thumbnail of The collision of protoplanetary accretion discs

Research paper thumbnail of Effect of Yangqixue Qufengshi Recipe on rheumatoid arthritis model mice under different genetic backgrounds

Chinese Journal of Integrative Medicine, 2006

Objective: To study the effect of Yangqixue Qufengshi Recipe (YQXQFS) on rheumatoid arthritis (RA... more Objective: To study the effect of Yangqixue Qufengshi Recipe (YQXQFS) on rheumatoid arthritis (RA) model mice under different genetic backgrounds.Methods: Collagen Induced Arthritis (CIA) were established on HLA-DR4 transgenic (TG) mice and non-transgenic (NTG) mice, which partly were raised with YQXQFS, and the onset day of CIA, the level of type II collagen (C II)-reactive antibodies and the pathological scores of CIA were assessed.Results: Under HLA-DR4 TG background (compared with NTG mice), the earlier onset day of CIA (11.22 ± 3.35 days vs 16.56 ± 4.75 days,P<0.05) and higher level of C II-reactive antibodies (0.2274 ± 0. 1390 μg/ml vs 0. 1101 ± 0.0560 μg/ml,P<0.05) were observed, but the pathological scores of CIA remained unchange. YQXQFS could not influence the onset day of CIA and the level of CII -reactive antibodies, but had a certain effect on the total pathological scores (6.56 ± 3.43 scores vs 11.11 ± 5.64 scores) and bone erosion (0.22 ± 0.44 scores vs 1.67 ± 1.50 scores) of CIA on NTG mice (P<0.05), NTG YQXQFS group compared with NTG experimental group.Conclusion: YQXQFS had a certain effect on RA model, but had no significant effect on HLA-DR4 related CIA.

Research paper thumbnail of Different Therapeutic and Bystander Effects by Intranasal Administration of Homologous Type II and Type IX Collagens on the Collagen-Induced Arthritis and Pristane-Induced Arthritis in Rats

Clinical Immunology, 1999

To assess the efficiency of nasally administered cartilage-specific collagens as vaccination agai... more To assess the efficiency of nasally administered cartilage-specific collagens as vaccination against development of arthritis and to ameliorate already established chronic arthritis, experimental models which develop chronic arthritis, pristane-induced arthritis (PIA), and homologous collagen-induced arthritis (CIA) in the rat were selected. Cartilage-specific collagens type IX (CIX) and type II (CII) were used for vaccination intranasally. A single dose of 250 microg CII instilled intranasally in rats with established PIA ameliorated the disease. For the prevention of disease, the same dose given before immunization was found to be most effective. Most importantly, the disease was more severe if this dose was given three times. For treatment of PIA, CIX was found to be more effective than CII, whereas for treatment of CIA only CII was effective. The amelioration of CIA was associated with a marked suppression of delayed type hypersensitivity and the flare reaction to CII and lower levels of IgG2b anti-CII antibodies in serum, i.e., with suppression of the TH1 rather than the TH2 response to CII. These findings, that cartilage proteins, if given intranasally, can both prevent and ameliorate established chronic arthritis in rats, are of significant importance for possible use in rheumatoid arthritis. The identification of two different cartilage-specific proteins (CII and CIX) effective against a disease induced with a well-defined nonimmunogenic adjuvant such as pristane will be of value for enhancing the effectiveness of the treatment.

Research paper thumbnail of Colorimetric determination of iron in infant fortified formulas by sequential injection analysis

Fresenius Journal of Analytical Chemistry, 1997

A procedure is described for the colorimetric determination of iron in infant fortified formulas... more A procedure is described for the colorimetric determination of iron in infant fortified formulas based on sequential injection analysis (SIA). Iron(III) complexation with thiocyanate is used as colour developing reaction. The system enables the determination of iron in the samples (after digestion by dry ashing and treatment with 0.2 mol/L nitric acid in the range of 0.50–20.0 mg/L, consuming 140 μL of the sample and 8 mg thiocyanate per determination. The reactor geometry and the adjustment of the ionic content of the calibration solutions is important for the accuracy of the results. A regression line according to the equation [Fe(III) (mg/L)]SIA=−0.3(±0.4)+1.03(±0.04) [Fe(III) (mg/L)]FAAS was obtained after comparative analysis of a set of 12 samples. The measurement rate was 34 s, thus allowing to analyze 100 samples per hour with a relative standard deviation lower than 2%.

Research paper thumbnail of ISBN: 9788446020646

Research paper thumbnail of Interparticle interactions and surface contribution to the effective anisotropy in biocompatible iron oxide nanoparticles used for contrast agents

We have investigated the dynamic magnetic properties of dextran-coated magnetite ͑Fe 3 O 4 ͒ nano... more We have investigated the dynamic magnetic properties of dextran-coated magnetite ͑Fe 3 O 4 ͒ nanoparticles in the form of ͑a͒ particles suspended in a carrier liquid and ͑b͒ concentrated powder obtained from lyophilization. The blocking temperature was found to increase from T B =42͑2͒ to 52͑2͒ K ͑@ 0 H =10 mT͒ after lyophilization, showing the effects of dipolar interactions in samples with identical size distributions. The temperature dependence of the hyperfine field B hyp ͑T͒ reveals the effects of collective magnetic excitations at low temperature, and allowed us to obtain the magnetic anisotropy energy E a = 3.6ϫ 10 −21 J for noninteracting particles. The obtained values can be understood assuming only magnetocrystalline anisotropy, without any additional contributions from surface, shape, or exchange origin. Moreover, a magnetocrystalline anisotropy constant value K 1 =10 kJ/m 3 was obtained by assuming the cubic phase with easy magnetic direction ͓111͔ of the bulk material above the Verwey transition, supporting the idea that the Verwey transition is absent in nanosized particles. Accordingly, no indication of magnetic transition at T V could be observed in our measurements. From the dynamical parameters of ac susceptibility ͑f , T͒ curves, the contribution of the dipolar interactions to the total anisotropy energy barrier could be estimated to be ⍀ = 4.5ϫ 10 −21 J, larger than the single-particle value.

Research paper thumbnail of Protoplanetary accretion disc in a binary system

Research paper thumbnail of The collision of protoplanetary accretion discs

Research paper thumbnail of Effect of Yangqixue Qufengshi Recipe on rheumatoid arthritis model mice under different genetic backgrounds

Chinese Journal of Integrative Medicine, 2006

Objective: To study the effect of Yangqixue Qufengshi Recipe (YQXQFS) on rheumatoid arthritis (RA... more Objective: To study the effect of Yangqixue Qufengshi Recipe (YQXQFS) on rheumatoid arthritis (RA) model mice under different genetic backgrounds.Methods: Collagen Induced Arthritis (CIA) were established on HLA-DR4 transgenic (TG) mice and non-transgenic (NTG) mice, which partly were raised with YQXQFS, and the onset day of CIA, the level of type II collagen (C II)-reactive antibodies and the pathological scores of CIA were assessed.Results: Under HLA-DR4 TG background (compared with NTG mice), the earlier onset day of CIA (11.22 ± 3.35 days vs 16.56 ± 4.75 days,P<0.05) and higher level of C II-reactive antibodies (0.2274 ± 0. 1390 μg/ml vs 0. 1101 ± 0.0560 μg/ml,P<0.05) were observed, but the pathological scores of CIA remained unchange. YQXQFS could not influence the onset day of CIA and the level of CII -reactive antibodies, but had a certain effect on the total pathological scores (6.56 ± 3.43 scores vs 11.11 ± 5.64 scores) and bone erosion (0.22 ± 0.44 scores vs 1.67 ± 1.50 scores) of CIA on NTG mice (P<0.05), NTG YQXQFS group compared with NTG experimental group.Conclusion: YQXQFS had a certain effect on RA model, but had no significant effect on HLA-DR4 related CIA.

Research paper thumbnail of Different Therapeutic and Bystander Effects by Intranasal Administration of Homologous Type II and Type IX Collagens on the Collagen-Induced Arthritis and Pristane-Induced Arthritis in Rats

Clinical Immunology, 1999

To assess the efficiency of nasally administered cartilage-specific collagens as vaccination agai... more To assess the efficiency of nasally administered cartilage-specific collagens as vaccination against development of arthritis and to ameliorate already established chronic arthritis, experimental models which develop chronic arthritis, pristane-induced arthritis (PIA), and homologous collagen-induced arthritis (CIA) in the rat were selected. Cartilage-specific collagens type IX (CIX) and type II (CII) were used for vaccination intranasally. A single dose of 250 microg CII instilled intranasally in rats with established PIA ameliorated the disease. For the prevention of disease, the same dose given before immunization was found to be most effective. Most importantly, the disease was more severe if this dose was given three times. For treatment of PIA, CIX was found to be more effective than CII, whereas for treatment of CIA only CII was effective. The amelioration of CIA was associated with a marked suppression of delayed type hypersensitivity and the flare reaction to CII and lower levels of IgG2b anti-CII antibodies in serum, i.e., with suppression of the TH1 rather than the TH2 response to CII. These findings, that cartilage proteins, if given intranasally, can both prevent and ameliorate established chronic arthritis in rats, are of significant importance for possible use in rheumatoid arthritis. The identification of two different cartilage-specific proteins (CII and CIX) effective against a disease induced with a well-defined nonimmunogenic adjuvant such as pristane will be of value for enhancing the effectiveness of the treatment.

Research paper thumbnail of Colorimetric determination of iron in infant fortified formulas by sequential injection analysis

Fresenius Journal of Analytical Chemistry, 1997

A procedure is described for the colorimetric determination of iron in infant fortified formulas... more A procedure is described for the colorimetric determination of iron in infant fortified formulas based on sequential injection analysis (SIA). Iron(III) complexation with thiocyanate is used as colour developing reaction. The system enables the determination of iron in the samples (after digestion by dry ashing and treatment with 0.2 mol/L nitric acid in the range of 0.50–20.0 mg/L, consuming 140 μL of the sample and 8 mg thiocyanate per determination. The reactor geometry and the adjustment of the ionic content of the calibration solutions is important for the accuracy of the results. A regression line according to the equation [Fe(III) (mg/L)]SIA=−0.3(±0.4)+1.03(±0.04) [Fe(III) (mg/L)]FAAS was obtained after comparative analysis of a set of 12 samples. The measurement rate was 34 s, thus allowing to analyze 100 samples per hour with a relative standard deviation lower than 2%.

Research paper thumbnail of ISBN: 9788446020646