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1.
Eat Weight Disord ; 27(5): 1585-1591, 2022 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-35178680

RESUMEN

PURPOSE: The concept of time perspective (TP) implies that a mental focus on past, present, or future affect a person makes decisions and take action. Inability to plan their life for a sufficiently long time perspective due to the COVID-19 pandemic appeared to have a pronounced impact on a human's lifestyle influencing their thoughts, feelings, and behaviors, including eating behavior. This study tested two hypotheses: (a) that during COVID-19 isolation, the incidence rate of food addiction is increased, and (b) people with present TP are more likely exhibited signs of food addiction (FA). METHODS: The final study sample included 949 people, mean age 21.8 ± 7.8 years (range: 17-71 years, women: 78.3%). Each participant indicated their personal data and completed Yale Food Addiction Scale and the Zimbardo Time Perspective Inventory. RESULTS: There was an increased incidence rate of FA (OR = 1.678, 95% CI = 1.324, 2.148, p = 0.000) during COVID-19 isolation. Individuals with balanced, future, and past positive TP were less likely to exhibit symptoms of FA. Persons with past negative, and present hedonistic TP were more likely to exhibit signs of FA. CONCLUSION: There was an increased incidence rate of FA during COVID-19 isolation. Persons with shortened time horizon are more likely to exhibit symptoms of FA. LEVEL OF EVIDENCE: Level V, cross-sectional descriptive study.


Asunto(s)
COVID-19 , Adicción a la Comida , Adolescente , Adulto , Estudios Transversales , Conducta Alimentaria , Femenino , Adicción a la Comida/diagnóstico , Adicción a la Comida/epidemiología , Humanos , Pandemias , Encuestas y Cuestionarios , Adulto Joven
2.
Entropy (Basel) ; 25(1)2022 Dec 23.
Artículo en Inglés | MEDLINE | ID: mdl-36673171

RESUMEN

We develop a new approach for asymmetric LDPC-based information reconciliation in order to adapt to the current channel state and achieve better performance and scalability in practical resource-constrained QKD systems. The new scheme combines the advantages of LDPC codes, a priori error rate estimation, rate-adaptive and blind information reconciliation techniques. We compare the performance of several asymmetric and symmetric error correction schemes using a real industrial QKD setup. The proposed asymmetric algorithm achieves significantly higher throughput, providing a secret key rate that is close to the symmetric one in a wide range of error rates. Thus, our approach is found to be particularly efficient for applications with high key rates, limited classical channel capacity and asymmetric computational resource allocation.

3.
Int J Mol Sci ; 21(5)2020 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-32111026

RESUMEN

Inter-patient molecular heterogeneity is the major declared driver of an expanding variety of anticancer drugs and personalizing their prescriptions. Here, we compared interpatient molecular heterogeneities of tumors and repertoires of drugs or their molecular targets currently in use in clinical oncology. We estimated molecular heterogeneity using genomic (whole exome sequencing) and transcriptomic (RNA sequencing) data for 4890 tumors taken from The Cancer Genome Atlas database. For thirteen major cancer types, we compared heterogeneities at the levels of mutations and gene expression with the repertoires of targeted therapeutics and their molecular targets accepted by the current guidelines in oncology. Totally, 85 drugs were investigated, collectively covering 82 individual molecular targets. For the first time, we showed that the repertoires of molecular targets of accepted drugs did not correlate with molecular heterogeneities of different cancer types. On the other hand, we found that the clinical recommendations for the available cancer drugs were strongly congruent with the gene expression but not gene mutation patterns. We detected the best match among the drugs usage recommendations and molecular patterns for the kidney, stomach, bladder, ovarian and endometrial cancers. In contrast, brain tumors, prostate and colorectal cancers showed the lowest match. These findings provide a theoretical basis for reconsidering usage of targeted therapeutics and intensifying drug repurposing efforts.


Asunto(s)
Sistemas de Liberación de Medicamentos , Heterogeneidad Genética , Oncología Médica/métodos , Terapia Molecular Dirigida/métodos , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Antineoplásicos/uso terapéutico , Análisis por Conglomerados , Quimioterapia , Genómica , Humanos , Mutación , Patología Molecular , Medicina de Precisión/métodos , Transcriptoma , Secuenciación del Exoma
4.
J Transl Med ; 17(1): 100, 2019 03 27.
Artículo en Inglés | MEDLINE | ID: mdl-30917829

RESUMEN

BACKGROUND: Previous studies have identified IFNγ as an important early barrier to oncolytic viruses including vaccinia. The existing innate and adaptive immune barriers restricting oncolytic virotherapy, however, can be overcome using autologous or allogeneic mesenchymal stem cells as carrier cells with unique immunosuppressive properties. METHODS: To test the ability of mesenchymal stem cells to overcome innate and adaptive immune barriers and to successfully deliver oncolytic vaccinia virus to tumor cells, we performed flow cytometry and virus plaque assay analysis of ex vivo co-cultures of stem cells infected with vaccinia virus in the presence of peripheral blood mononuclear cells from healthy donors. Comparative analysis was performed to establish statistically significant correlations and to evaluate the effect of stem cells on the activity of key immune cell populations. RESULTS: Here, we demonstrate that adipose-derived stem cells (ADSCs) have the potential to eradicate resistant tumor cells through a combination of potent virus amplification and sensitization of the tumor cells to virus infection. Moreover, the ADSCs demonstrate ability to function as a virus-amplifying Trojan horse in the presence of both autologous and allogeneic human PBMCs, which can be linked to the intrinsic immunosuppressive properties of stem cells and their unique potential to overcome innate and adaptive immune barriers. The clinical application of ready-to-use ex vivo expanded allogeneic stem cell lines, however, appears significantly restricted by patient-specific allogeneic differences associated with the induction of potent anti-stem cell cytotoxic and IFNγ responses. These allogeneic responses originate from both innate (NK)- and adaptive (T)- immune cells and might compromise therapeutic efficacy through direct elimination of the stem cells or the induction of an anti-viral state, which can block the potential of the Trojan horse to amplify and deliver vaccinia virus to the tumor. CONCLUSIONS: Overall, our findings and data indicate the feasibility to establish simple and informative assays that capture critically important patient-specific differences in the immune responses to the virus and stem cells, which allows for proper patient-stem cell matching and enables the effective use of off-the-shelf allogeneic cell-based delivery platforms, thus providing a more practical and commercially viable alternative to the autologous stem cell approach.


Asunto(s)
Tejido Adiposo/citología , Células Madre Adultas/trasplante , Células Alogénicas/inmunología , Tolerancia Inmunológica , Viroterapia Oncolítica/métodos , Virus Oncolíticos , Virus Vaccinia/fisiología , Células A549 , Inmunidad Adaptativa/fisiología , Tejido Adiposo/inmunología , Células Madre Adultas/inmunología , Células Madre Adultas/virología , Células Alogénicas/citología , Animales , Vacunas contra el Cáncer/administración & dosificación , Vacunas contra el Cáncer/inmunología , Células Cultivadas , Chlorocebus aethiops , Humanos , Inmunidad Innata/fisiología , Inmunomodulación/fisiología , Inmunoterapia Adoptiva/métodos , Células K562 , Ratones , Virus Oncolíticos/inmunología , Trasplante Homólogo/métodos , Virus Vaccinia/inmunología
5.
Molecules ; 23(7)2018 06 26.
Artículo en Inglés | MEDLINE | ID: mdl-29949868

RESUMEN

Dichroism in angle-resolved spectra of circularly polarized fluorescence from freely-rotating CO molecules was studied experimentally and theoretically. For this purpose, carbon monoxide in the gas phase was exposed to circularly polarized soft X-ray synchrotron radiation. The photon energy was tuned across the C 1s→π* resonant excitation, which decayed via the participator Auger transition into the CO⁺ A ²Π state. The dichroic parameter ß1 of the subsequent CO⁺ (A ²Π → X ²Σ⁺) visible fluorescence was measured by photon-induced fluorescence spectroscopy. Present experimental results are explained with the ab initio electronic structure and dynamics calculations performed by the single center method. Our results confirm the possibility to perform partial wave analysis of the emitted photoelectrons in closed-shell molecules.


Asunto(s)
Monóxido de Carbono/química , Dicroismo Circular , Modelos Teóricos , Espectrometría de Fluorescencia
6.
J Transl Med ; 14(1): 241, 2016 08 18.
Artículo en Inglés | MEDLINE | ID: mdl-27538520

RESUMEN

BACKGROUND: Tumour resistance to a wide range of drugs (multiple drug resistant, MDR) acquired after intensive chemotherapy is considered to be the main obstacle of the curative treatment of cancer patients. Recent work has shown that oncolytic viruses demonstrated prominent potential for effective treatment of diverse cancers. Here, we evaluated whether genetically modified vaccinia virus (LIVP-GFP) may be effective in treatment of cancers displaying MDR phenotype. METHODS: LIVP-GFP replication, transgene expression and cytopathic effects were analysed in human cervical carcinomas KB-3-1 (MDR-), KB-8-5 (MDR+) and in murine melanoma B-16 (MDR-), murine lymphosarcomas RLS and RLS-40 (MDR+). To investigate the efficacy of this therapy in vivo, we treated immunocompetent mice bearing murine lymphosarcoma RLS-40 (MDR+) (6- to 8-week-old female CBA mice; n = 10/group) or melanoma B-16 (MDR-) (6- to 8-week-old female C57Bl mice; n = 6/group) with LIVP-GFP (5 × 10(7) PFU of virus in 0.1 mL of IMDM immediately and 4 days after tumour implantation). RESULTS: We demonstrated that LIVP-GFP replication was effective in human cervical carcinomas KB-3-1 (MDR-) and KB-8-5 (MDR+) and in murine melanoma B-16 (MDR-), whereas active viral production was not detected in murine lymphosarcomas RLS and RLS-40 (MDR+). Additionally, it was found that in tumour models in immunocompetent mice under the optimized regimen intratumoural injections of LIVP-GFP significantly inhibited melanoma B16 (33 % of mice were with complete response after 90 days) and RLS-40 tumour growth (fourfold increase in tumour doubling time) as well as metastasis. CONCLUSION: The anti-tumour activity of LIVP-GFP is a result of direct oncolysis of tumour cells in case of melanoma B-16 because the virus effectively replicates and destroys these cells, and virus-mediated activation of the host immune system followed by immunologically mediated destruction of of tumour cells in case of lymphosarcoma RLS-40. Thus, the recombinant vaccinia virus LIVP-GFP is able to inhibit the growth of malignant cells with the MDR phenotype and tumour metastasis when administered in the early stages of tumour development.


Asunto(s)
Resistencia a Múltiples Medicamentos , Resistencia a Antineoplásicos , Melanoma Experimental/patología , Virus Oncolíticos/fisiología , Animales , Línea Celular Tumoral , Proliferación Celular , Efecto Citopatogénico Viral , Proteínas Fluorescentes Verdes/metabolismo , Humanos , Inmunidad , Inyecciones , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Fenotipo , Virus Vaccinia/genética , Proteínas Virales/metabolismo , Replicación Viral
8.
Iran Biomed J ; 28(2&3): 59-70, 2024 03 01.
Artículo en Inglés | MEDLINE | ID: mdl-38770843

RESUMEN

Despite the unconditional success achieved in the treatment and prevention of AMI over the past 40 years, mortality in this disease remains high. Hence, it is necessary to develop novel drugs with mechanism of action different from those currently used in clinical practices. Studying the molecular mechanisms involved in the cardioprotective effect of adapting to cold could contribute to the development of drugs that increase cardiac tolerance to the impact of ischemia/reperfusion. An analysis of the published data shows that the long-term human stay in the Far North contributes to the occurrence of cardiovascular diseases. At the same time, chronic and continuous exposure to cold increases tolerance of the rat heart to ischemia/ reperfusion. It has been demonstrated that the cardioprotective effect of cold adaptation depends on the activation of ROS production, stimulation of the ß2-adrenergic receptor and protein kinase C, MPT pore closing, and KATP channel.


Asunto(s)
Adaptación Fisiológica , Frío , Humanos , Animales , Sistema Cardiovascular/fisiopatología , Sistema Cardiovascular/efectos de los fármacos , Daño por Reperfusión Miocárdica/fisiopatología , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/patología , Daño por Reperfusión/fisiopatología , Daño por Reperfusión/metabolismo , Especies Reactivas de Oxígeno/metabolismo
9.
J Phys Chem A ; 117(41): 10692-701, 2013 Oct 17.
Artículo en Inglés | MEDLINE | ID: mdl-24050537

RESUMEN

The interaction between the network of chemical reactions of the compound 4',7-dihydroxyflavylium and ß-cyclodextrin was studied by means of pH jumps, followed by UV-vis absorption, flash photolysis, stopped flow, and NMR. The trans-chalcone is the network species exhibiting the strongest interaction with the host. In moderately acidic medium, 95% of the trans-chalcone, 2.5 × 10(-5) M, in the presence of ß-cyclodextrin, 9 × 10(-3) M, is expected to fill the host cavity (association constant 2.2 × 10(3) M(-1)). In contrast, flavylium cation does not interact (association constant ≈ 0). Irradiation of the trans-chalcone in the presence of ß-cyclodextrin 9 mM leads to the flavylium cation appearance. Light is thus capable of removing the trans-chalcone from the ß-cyclodextrin, leaving the cavity empty. The system is reversible and trans-chalcone goes back to the initial state upon switching off the light due to the thermodynamic favorable conversion of flavylium cation to trans-chalcone in the presence of ß-cyclodextrin.

10.
Biology (Basel) ; 13(1)2023 Dec 30.
Artículo en Inglés | MEDLINE | ID: mdl-38248453

RESUMEN

This study explores the relationship between the light features of the Arctic spring equinox and circadian rhythms, sleep and metabolic health. Residents (N = 62) provided week-long actigraphy measures, including light exposure, which were related to body mass index (BMI), leptin and cortisol. Lower wrist temperature (wT) and higher evening blue light exposure (BLE), expressed as a novel index, the nocturnal excess index (NEIbl), were the most sensitive actigraphy measures associated with BMI. A higher BMI was linked to nocturnal BLE within distinct time windows. These associations were present specifically in carriers of the MTNR1B rs10830963 G-allele. A larger wake-after-sleep onset (WASO), smaller 24 h amplitude and earlier phase of the activity rhythm were associated with higher leptin. Higher cortisol was associated with an earlier M10 onset of BLE and with our other novel index, the Daylight Deficit Index of blue light, DDIbl. We also found sex-, age- and population-dependent differences in the parametric and non-parametric indices of BLE, wT and physical activity, while there were no differences in any sleep characteristics. Overall, this study determined sensitive actigraphy markers of light exposure and wT predictive of metabolic health and showed that these markers are linked to melatonin receptor polymorphism.

11.
Vaccines (Basel) ; 11(5)2023 May 18.
Artículo en Inglés | MEDLINE | ID: mdl-37243102

RESUMEN

The State Research Center of Virology and Biotechnology "VECTOR" of the Federal Service for the Oversight of Consumer Protection and Welfare (Rospotrebnadzor) has developed the peptide-based EpiVacCorona vaccine, which is the first synthetic peptide-based antiviral vaccine for mass immunization in international vaccinology. An early clinical trial (Phase I-II) demonstrated that the EpiVacCorona vaccine is a safe product. The "Multicenter double-blind, placebo-controlled, comparative, randomized trial to assess the tolerability, safety, immunogenicity and prophylactic efficacy of the EpiVacCorona COVID-19 vaccine based on peptide antigens in 3000 volunteers aged 18 years and older" was performed regarding vaccine safety. The key objectives of the study were to evaluate the safety and prophylactic efficacy of the two-dose EpiVacCorona vaccine administered via the intramuscular route. The results of the clinical study (Phase III) demonstrated the safety of the EpiVacCorona vaccine. Vaccine administration was accompanied by mild local reactions in ≤27% of cases and mild systemic reactions in ≤14% of cases. The prophylactic efficacy of the EpiVacCorona COVID-19 vaccine after the completion of the vaccination series was 82.5% (CI95 = 75.3-87.6%). The high safety and efficacy of the vaccine give grounds for recommending this vaccine for regular seasonal prevention of COVID-19 as a safe and effective medicinal product.

12.
Nanotechnology ; 23(17): 175302, 2012 May 04.
Artículo en Inglés | MEDLINE | ID: mdl-22481483

RESUMEN

It is a well-known fact that a sphere offers less surface area, and thus less surface energy, than any other arrangement of the same volume. From this perspective, all other shapes are metastable objects. In this paper, we present and discuss a manifestation of this metastability: the spontaneous alignment of free-standing amorphous nanowires towards, and ultimately parallel to, a flux of directional ion irradiation. The behavior expected from surface energy reduction is the opposite of that predicted by both theory and experiment regarding defect generation in crystalline nanowires, but is consistent with other observations on non-crystalline materials. We verify our expectations by bending and aligning finely stranded amorphous silica nanowires, noting that such nanostructures are particularly susceptible to bending through ion-induced surface energy reduction. We offer support for this mechanism through bending rate studies, thermal annealing experiments and mathematical modeling. Experimentally, we also demonstrate selective reorientation of nanowires in patterned areas, as well as conformal coating of reoriented arrays with functional materials. These capabilities offer the prospect of exploiting engineered surface anisotropies in optical, fluidic and micromechanical applications.

13.
Cancers (Basel) ; 14(24)2022 Dec 07.
Artículo en Inglés | MEDLINE | ID: mdl-36551519

RESUMEN

In the past, different bacterial species have been tested for cancer therapy in preclinical and clinical studies. The success of bacterial cancer therapy is mainly dependent on the ability of the utilized bacteria to overcome the host immune defense system to colonize the tumors and to initiate tumor-specific immunity. In recent years, several groups have demonstrated that the gut microbiome plays an important role of modulation of the host immune response and has an impact on therapeutic responses in murine models and in cohorts of human cancer patients. Here we analyzed the impact of the gut microbiome on tumor colonization and tumor therapy by the Escherichia coli Nissle 1917 (EcN) strain. This EcN strain is a promising cancer therapy candidate with probiotic properties. In our study, we observed significantly better tumor colonization by EcN after antibiotic-induced temporal depletion of the gut microbiome and after two intranasal applications of the EcN derivate (EcN/pMUT-gfp Knr) in 4T1 tumor-bearing syngeneic BALB/c mice. In addition, we demonstrated significant reduction in tumor growth and extended survival of the EcN-treated mice in contrast to phosphate-buffered saline (PBS)-treated tumor-bearing control animals. Multispectral imaging of immune cells revealed that depletion of the gut microbiome led to significantly lower infiltration of cytotoxic and helper T cells (CD4 and CD8 cells) in PBS tumors of mice pretreated with antibiotics in comparison with antibiotic untreated PBS-or EcN treated mice. These findings may help in the future advancement of cancer treatment strategies using E. coli Nissle 1917.

14.
Cardiovasc Toxicol ; 22(6): 558-578, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-35429258

RESUMEN

Obesity, ethanol, and contaminants are known risk factors of cardiovascular and metabolic diseases (CMD). However, their interplay on clinical profiles of these diseases remains unclear, and thus were investigated in this study. Male lean or obese JCR rats were given water or 10% ethanol and orally treated with or without a contaminant mixture (CM) dissolved in corn oil and loaded on two cookies at 0, 1.6, or 16 mg/kg BW/day dose levels for 4 weeks. The CM consisted 22 environmental contaminants found in human blood or serum of Northern populations. Over 60 parameters related to CMD were examined. The results revealed that obesity in JCR rats resembles the clinical profiles of non-alcoholic fatty liver disease in humans. Obesity was also associated with increased serum and organ retention of mercury, one of the chemical components of CM. Exposure to ethanol lightened hyperlipidemia, increased liver retention of mercury, and increased risk for hypertension in the obese rats. CM lessened hyperlipidemia and hyperenzymemia, worsened systemic inflammation and increased the risk for hypertension in the obese rats. CM markedly increased serum ethanol levels with or without ethanol exposure. Tissue total mercury contents significantly correlated with clinical parameters with altered profiles by both ethanol and obesity. These results suggest that obese individuals may be more prone to contaminant accumulation. Ethanol and CM exposure can alter clinical profiles associated with obesity, which may lead to misdiagnosis of CMD associated with obesity. CM can alter endogenous production and/or metabolism of ethanol, further complicating disease progression, diagnosis, and treatment.


Asunto(s)
Hipertensión , Mercurio , Enfermedades Metabólicas , Animales , Etanol/metabolismo , Etanol/toxicidad , Masculino , Obesidad/complicaciones , Obesidad/diagnóstico , Ratas
16.
Anal Bioanal Chem ; 401(9): 2785-92, 2011 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-21858497

RESUMEN

The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 µg L(-1) depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below µg L(-1) level in natural water. It is based on solid-phase extraction using TiO(2) nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg(-1) (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3-4% k = 2 for a cadmium content of around 100 ng kg(-1)). We applied the developed method to the groundwater and wastewater samples ERM-CA615 and BCR-713, respectively, and results agreed with certificate values within uncertainty statements.

17.
Proc Natl Acad Sci U S A ; 105(21): 7353-8, 2008 May 27.
Artículo en Inglés | MEDLINE | ID: mdl-18508969

RESUMEN

Because of their potential for use in advanced electronic, nanomechanical, and other applications, large two-dimensional, carbon-rich networks have become an important target to the scientific community. Current methods for the synthesis of these materials have many limitations including lack of molecular-level control and poor diversity. Here, we present a method for the synthesis of two-dimensional carbon nanomaterials synthesized by Mo- and Cu-catalyzed cross-linking of alkyne-containing self-assembled monolayers on SiO(2) and Si(3)N(4). When deposited and cross-linked on flat surfaces, spheres, cylinders, or textured substrates, monolayers take the form of these templates and retain their structure on template removal. These nanomaterials can also be transferred from surface to surface and suspended over cavities without tearing. This approach to the synthesis of monolayer carbon networks greatly expands the chemistry, morphology, and size of carbon films accessible for analysis and device applications.

18.
J Org Chem ; 75(4): 1047-60, 2010 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-20073523

RESUMEN

Through the introduction of an aryl chloride substituent, the selectivity of palladium-catalyzed direct arylation may be diverted to provide alternative regioisomeric products in high yields. In cases where low reactivity is typically observed, the presence of the carbon-chlorine bond can serve to enhance reactivity and provide superior outcomes. From a strategic perspective, the C-Cl bond is easily introduced and can be employed in a variety of subsequent transformations to provide a wealth of highly functionalized heterocycles with minimal substrate preactivation. The impact of the C-Cl functional group on direct arylation reactivity has also been evaluated mechanistically, and the observed reactivity profiles correlate very well with that predicted by a concerted metalation-deprotonation pathway.


Asunto(s)
Cloruros/química , Reactivos de Enlaces Cruzados/química , Compuestos Heterocíclicos/química , Compuestos Heterocíclicos/síntesis química , Paladio/química , Catálisis , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estereoisomerismo
19.
Anal Bioanal Chem ; 396(6): 2349-61, 2010 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-20165837

RESUMEN

This paper describes the application of TiO(2) nano-particles (anatase form) for the solid-phase extraction of iron from coastal seawater samples. We investigated the adsorption processes by infra-red spectroscopy. We compared in batch and on-(mini)column extraction approaches (0.1 and 0.05 g TiO(2) per sample, respectively), combined to external calibration and detection by inductively coupled plasma mass spectrometry at medium mass resolution. Globally, this titania phase was slightly more efficient with seawater than with ultra-pure water, although between pH 2 and pH 7, the Fe retention efficiency progressed more in ultra-pure water than in seawater (6.9 versus 4.8 times improvement). Different reaction schemes are proposed between Fe(III) species and the two main categories of titania sites at pH 2 (adsorption of [FeL(x)]((3-x)+) via possibly the mediation of chlorides) and at pH 7 (adsorption of [Fe(OH)(2)](+) and precipitation of [Fe(OH)(3)](0)). Under optimised conditions, the inlet system was pre-cleaned by pumping 6% HCl for approximately 2 h, and the column was conditioned by aspirating ultra-pure water (1.7 g min(-1)) and 0.05% ammonia (0.6 g min(-1)) for 1 min. Then 3 g seawater sample was loaded at the same flow rate while being mixed on-line with 0.05% ammonia at 0.6 g min(-1) to adjust the pH to 7. The iron retained on the oxide powder was then eluted with 3 g 6% HCl (<0.002% residual salinity in the separated samples). The overall procedural blank was 220 +/- 46 (2 s, n = 16) ng Fe kg(-1) (the titania was renewed in the column every 20 samples, with 2-min rinsing in between samples with 6% HCl at 1.5 g min(-1)). The recovery estimated from the Canadian certified reference material CASS-2 was 69.5 +/- 7.6% (2 s, n = 4). Typically, the relative combined uncertainty (k = 2) estimated for the measurement of approximately 1 microg Fe kg(-1) (0.45 microm filtered and acidified to pH 1.5) of seawater was approximately 12%. We applied our method to a similar sample, from the coastal region of the North Sea. The agreement well within stated uncertainties of our result with the value obtained independently by isotope dilution mass spectrometry further validated our method.


Asunto(s)
Hierro/análisis , Nanopartículas del Metal/química , Agua de Mar/análisis , Extracción en Fase Sólida/métodos , Titanio/química , Adsorción , Extracción en Fase Sólida/instrumentación
20.
Microsc Microanal ; 16(2): 183-93, 2010 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-20187990

RESUMEN

We evaluate the probe forming capability of a JEOL 2200FS transmission electron microscope equipped with a spherical aberration (Cs) probe corrector. The achievement of a real space sub-Angstrom (0.1 nm) probe for scanning transmission electron microscopy (STEM) imaging is demonstrated by acquisition and modeling of high-angle annular dark-field STEM images. We show that by optimizing the illumination system, large probe currents and large collection angles for electron energy loss spectroscopy (EELS) can be combined to yield EELS fine structure data spatially resolved to the atomic scale. We demonstrate the probe forming flexibility provided by the additional lenses in the probe corrector in several ways, including the formation of nanometer-sized parallel beams for nanoarea electron diffraction, and the formation of focused probes for convergent beam electron diffraction with a range of convergence angles. The different probes that can be formed using the probe corrected STEM opens up new applications for electron microscopy and diffraction.

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