29 research outputs found
Catalytic Steam Gasification of Glucose for Hydrogen Production Using Stable Based Ni on a ÎłâAlumina Fluidizable Catalyst
Six different Ni-based fluidizable catalysts were synthesized using both incipient impregnation and co-
impregnation. Ni-based catalysts were also promoted with 2.0 wt% La or alternatively with 2 wt% Ce. The
preparation procedure included catalysts treated at high temperatures and under free of oxygen conditions.
Catalysts were characterized using BET, XRD, AA, PSD, TPR, TPD, H2-chemisorption. TPR and H2 chemisorp-tion showed good metal dispersion with 10 nm- 40 nm metal crystallites.
Glucose catalytic gasification runs were performed in a CREC Riser Simulator to evaluate the following cata-
lysts: (a) 5 %Ni/Îł-Al2O3, (b) 5 %Ni-2 %La/Îł-Al2O3 and (c) 5 %Ni-2 %Ce/Îł-Al2O3. In all cases, the preparation
steps involved acid solutions with pHs of 1 and 4. In between consecutive runs, different approaches were
considered: (a) A catalyst was regenerated by air, (b) A catalyst was regenerated by air followed by hydrogen
pretreatment, (c) A catalyst was reused directly without any regeneration or hydrogen pretreatment. It was
observed that Ni-based catalysts, which were subjected after every run, to both, air regeneration and hydro-
gen pretreatment, displayed the best yields in close agreement with thermodynamic equilibrium. On the other
hand, Ni-based catalysts regenerated with air only, showed the worst hydrogen yields. In between these two-
hydrogen yield limits, where catalysts not contacted with air nor hydrogen, with these yields being moderately
below chemical equilibrium.
This shows that Ni-based fluidizable catalysts can perform on stream for extended periods, requiring limited
reactivation with air and H2. This makes of gasification using the catalysts of the present study, a viable process alternative that could be implemented at industrial scale
3-AminoÂpyridin-1-ium 3-carbÂoxyÂbenzoÂate
In the title organic salt, C5H7N2
+·C8H5O4
â, the carbÂoxyÂlic group is nearly coplanar with the benzene ring [dihedral angle 1.9â
(4)°] whereas the carboxylÂate group is twisted relative to the benzene ring by 13.6â
(4)°. In the crystal, N-HâŻO and OâHâŻO hydrogen bonds connect the components into a three-dimensional framework consisting of stacks of alternating pairs of anions and cations exhibiting ÏâÏ stacking interÂactions with centroidâcentroid distances in the range 3.676â
(2)â3.711â
(1)â
Ă
. The ÏâÏ stacks extend along [110] and [-110]
Influence of size reduction of fly ash particles by grinding on the chemical properties of geopolymers
Chemical properties of geopolymers were evaluated from the reduction of fly ash particle size by grinding. X-ray diffraction determined that at early curing ages new crystalline phases appear in the matrix of the geopolymer and they remain for 28 days, with increases in intensities up to 60%. In Fourier transform infrared spectroscopy, displacements were identified in the main band of the geopolymers at higher wavenumbers, attributed to the greater rigidity in the structures of the aluminosilicate gel due to the increase of the reaction products in the geopolymers obtained through fly ashsubjected to previous grinding, which is observable in the geopolymers matrix. Results indicate that the reduction of fly ash particle size by grinding has an influence on the chemical properties of geopolymers.Peer ReviewedPostprint (published version
EvaluaciĂłn y comparaciĂłn de geopolimeros obtenidos de dos cenizas volantes mexicanas
Esta investigaciĂłn se realizĂł con el fin de determinar las diferencias existentes en los geopolimeros obtenidos de dos tipos de cenizas volantes, las cuales fueron caracterizadas mediante FRX, DRX, FT-IT, del mismo modo se determinaron sus propiedades fĂsicas por picnometrĂa, adsorciĂłn de gases (mĂ©todo BET), DTP y MEB. El proceso de activaciĂłn se llevĂł a cabo con NaOH 8M a 80°C por 3, 7, 14, 21, 28 y 90 dĂas, realizando ensayos de compresiĂłn y mĂłdulo dinĂĄmico a los mismos, obteniendo una mejora en los resultados conforme aumenta el tiempo de curado, ademĂĄs se demostrĂł que la variaciĂłn de los contenidos Ăłxidos y las propiedades fĂsicas de las cenizas de partida, juegan uno de los factores mĂĄs importantes en el desarrollo de los geles producto de reacciĂłn (determinado por TGA, FT-IR, DRX y MEB) y por ello la obtenciĂłn de mejores propiedades mecĂĄnicas. (ANGLĂS) This research was conducted in order to determine the differences in the geopolymer obtained from two types of fly ash, which were characterized by XRF, XRD, FT-IR, just as its physical properties were determined by pycnometry, gas adsorption (BET method), PSD and SEM. The activation process was conducted with NaOH 8M at 80°C for 3, 7, 14, 21, 28 and 90 days, to performing compression tests and dynamic module, obtaining a improved results with increasing cure time, also it showed that the variation of oxide content and the physical properties of the starting ash, play one of the most important factors in the development of the reaction product gels (determined by TGA, FT-IR, XRD and SEM) and thus obtaining better mechanical properties.Postprint (published version
Mechanical Properties and Antibacterial Effect on Mono-Strain of Streptococcus mutans of Orthodontic Cements Reinforced with Chlorhexidine-Modified Nanotubes
Recently, several studies have introduced nanotechnology into the area of dental materials with the aim of improving their properties. The objective of this study is to determine the antibacterial and mechanical properties of type I glass ionomers reinforced with halloysite nanotubes modified with 2% chlorhexidine at concentrations of 5% and 10% relative to the total weight of the powder used to construct each sample. Regarding antibacterial effect, 200 samples were established and distributed into four experimental groups and six control groups (4 +ve and 2 âve), with 20 samples each. The mechanical properties were evaluated in 270 samples, assessing microhardness (30 samples), compressive strength (120 samples), and setting time (120 samples). The groups were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, and the antibacterial activity of the ionomers was evaluated on Streptococcus mutans for 24 h. The control and positive control groups showed no antibacterial effect, while the experimental group with 5% concentration showed a zone of growth inhibition between 11.35 mm and 11.45 mm, and the group with 10% concentration showed a zone of growth inhibition between 12.50 mm and 13.20 mm. Statistical differences were observed between the experimental groups with 5% and 10% nanotubes. Regarding
the mechanical properties, microhardness, and setting time, no statistical difference was found when compared with control groups, while compressive strength showed higher significant values, with ionomers modified with 10% concentration of nanotubes resulting in better compressive strength values. The incorporation of nanotubes at concentrations of 5% and 10% effectively inhibited the presence of S. mutans, particularly when the doseâresponse relationship was taken into account, with the advantage of maintaining and improving their mechanical properties
Clinical consequences of BRCA2 hypomorphism
Altres ajuts: Asociación Española contra el Cåncer (LABAE16020PORTT)Altres ajuts: Asociación Española contra el Cåncer (ERAPERMED2019-215)The tumor suppressor FANCD1/BRCA2 is crucial for DNA homologous recombination repair (HRR). BRCA2 biallelic pathogenic variants result in a severe form of Fanconi anemia (FA) syndrome, whereas monoallelic pathogenic variants cause mainly hereditary breast and ovarian cancer predisposition. For decades, the co-occurrence in trans with a clearly pathogenic variant led to assume that the other allele was benign. However, here we show a patient with biallelic BRCA2 (c.1813dup and c.7796 A > G) diagnosed at age 33 with FA after a hypertoxic reaction to chemotherapy during breast cancer treatment. After DNA damage, patient cells displayed intermediate chromosome fragility, reduced survival, cell cycle defects, and significantly decreased RAD51 foci formation. With a newly developed cell-based flow cytometric assay, we measured single BRCA2 allele contributions to HRR, and found that expression of the missense allele in a BRCA2 KO cellular background partially recovered HRR activity. Our data suggest that a hypomorphic BRCA2 allele retaining 37-54% of normal HRR function can prevent FA clinical phenotype, but not the early onset of breast cancer and severe hypersensitivity to chemotherapy
De Nueva España a México : El universo musical mexicano entre centenarios (1517-1917)
742 pĂĄgs. ImĂĄgenes color y b/n. Partituras musicales.El fenĂłmeno de las conmemoraciones culturales siempre ha sido un terreno abonado para la producciĂłn cultural y artĂstica del que se han valido los Estados para ofrecer interpretaciones legitimadoras e ideologizadas de la historia, articuladas en torno a las ideas de memoria, naciĂłn y progreso. El presente volumen, resultado de una triple conmemoraciĂłn (el centenario de la RevoluciĂłn Mexicana y la publicaciĂłn de la primera historia de la mĂșsica en MĂ©xico de Alba Herrera â1917â, por un lado; y la llegada del militar andaluz Francisco HernĂĄndez de CĂłrdoba a la costa de la penĂnsula del YucatĂĄn â1517â, por otro), presenta una visiĂłn retrospectiva de la historia musical mexicana a lo largo de esas cuatro centurias. Frente a la rĂgida divisiĂłn cronolĂłgica impuesta por ciertas narrativas, se ofrece asĂ una nociĂłn inclusiva, actual e informada del universo musical mexicano en toda su multiplicidad y riqueza de matices, integrando las Ă©pocas colonial e independiente como lo que realmente son: partes constitutivas de la memoria musical, histĂłrica, cultural y polĂtica del paĂs, con las luces y las sombras propias de cualquier otro periodo
Benzene-1,3,5-tricarboxylic acidâpyridinium-2-olate (1/3)
The asymmetric unit of the title compound, C9H6O6·3C5H5NO, contains one benzene-1,3,5-tricarboxylic acid molecule (BTA) and three pyridin-2-ol molecules each present in the zwitterion form. In the crystal, these entities are linked through OâH...Oâ and N+âH...Oâ hydrogen bonds, forming sheets parallel to (10-1). These layers contain macrocyclic rings of composition [BTA]2[pyol]6 and with graph-set notation R68(44), which are stacked along c through ÏâÏ interactions [inter-centroid distances = 3.536â
(2)â3.948â
(3)â
Ă
]. They are interconnected by N+âH...Oâ hydrogen-bonded chains of pyridin-2-ol molecules running parallel to c, forming a three-dimensional network. There are also CâH...O hydrogen bonds present which reinforce the three-dimensional structure
2,6-Dihydroxy-4-oxo-2-(pyridin-1-ium-3-yl)-4H-1,3,2-benzodioxaborinin-2-ide 0.67-hydrate
The asymmetric unit of the title compound, C12H10BNO5·0.67H2O, contains three independent pyridinylboronic acid esters adopting zwitterionic forms and two water molecules. The six-membered heterocyclic rings in the boronic esters have half-chair conformations and the deviations of the B atoms from the boronate mean planes range from 0.456â
(3) to 0.657â
(3)â
Ă
. All of the B atoms have tetrahedral coordination environments, with BâO and BâC bond lengths of 1.446â
(4)â1.539â
(3) and 1.590â
(5)â1.609â
(5)â
Ă
, respectively. In the crystal, the ester and water molecules are linked into a three-dimensional network by a large number of OâH...O, NâH...O and CâH...O hydrogen bonds. The crystal packing is further accomplished by ÏâÏ interactions, with centroidâcentroid distances of 3.621â
(4)â3.787â
(4)â
Ă