18 research outputs found
A route to high surface area, porosity and inclusion of large molecules in crystals
One of the outstanding challenges in the field of porous materials is the design and synthesis of chemical structures with exceptionally high surface areas(1). Such materials are of critical importance to many applications involving catalysis, separation and gas storage. The claim for the highest surface area of a disordered structure is for carbon, at 2,030 m(2) g(-1) (ref. 2). Until recently, the largest surface area of an ordered structure was that of zeolite Y, recorded at 904 m(2) g(-1) (ref. 3). But with the introduction of metal-organic framework materials, this has been exceeded, with values up to 3,000 m(2) g(-1) (refs 4-7). Despite this, no method of determining the upper limit in surface area for a material has yet been found. Here we present a general strategy that has allowed us to realize a structure having by far the highest surface area reported to date. We report the design, synthesis and properties of crystalline Zn4O(1,3,5-benzenetribenzoate)(2), a new metal-organic framework with a surface area estimated at 4,500 m(2) g(-1). This framework, which we name MOF-177, combines this exceptional level of surface area with an ordered structure that has extra-large pores capable of binding polycyclic organic guest molecules-attributes not previously combined in one material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62609/1/nature02311.pd
Molecular Simulation of CO2/H2 Mixture Separation in Metal-organic Frameworks: Effect of Catenation and Electrostatic Interactions
Raman spectra of hydrogen and deuterium adsorbed on a metal-organic framework
Abstract The Raman spectra of H 2 and D 2 adsorbed on metal-organic framework-5 at various pressures (H 2 : 12.8 and 30.3 bar; D 2 : 2.2-24.5 bar) and temperatures (H 2 : 298 K; D 2 : 40-300 K) have been recorded. The shifts observed in the vibrational modes of the gases indicate that physisorption is responsible for the attractive interactions between the gas and the framework; these interactions are larger with respect to those detected for carbon materials. Ó 2005 Elsevier B.V. All rights reserved. The lack of a suitable and cost effective means of storing hydrogen Understanding the intermolecular interactions responsible for gas sorption (e.g., hydrogen) in solids (e.g., MOFs, carbon based materials, etc.) is fundamentally important to the development of new materials with improved gas sorption properties and geometries. The perturbation of the intramolecular potential resulting from intermolecular interaction with an adsorbing surface suggests that vibrational spectroscopy in general, and especially Raman spectroscopy, may turn out to be a useful technique to investigate the physical phenomena that take place because of these interactions Let us consider a pure diatomic gas: the intermolecular interactions (attractive and repulsive) with other gas molecules perturb the intramolecular potentia
Seroepidemiological Study of Viral Activity of Foot and Mouth Diseases through the Test 3ABC Elisa in Cattle from Zulia State-Venezuela
Para determinar la prevalencia de anticuerpos contra la Fiebre
Aftosa (FA) mediante prueba inmunoenzimática, fueron muestreados
bovinos de todos los grupos etarios de los 21 Municipios
del estado Zulia. Se recolectaron mil doscientos ochenta y
uno (1281) muestras de suero sanguíneo y se testearon mediante
técnica de ELISA I-3ABC en el laboratorio de Diagnóstico
e Investigación de Enfermedades Infecciosas de la Facultad de
Ciencias Veterinarias de la Universidad del Zulia. El tamaño de
la muestra se determinó mediante muestreo estratificado con fijación
proporcional e intencional (nivel de confianza del 95% y
error del 2,737% para población bovina y 95% de nivel de confianza
con error de 4,778% para las fincas). Para el análisis estadístico
de resultados los datos fueron registrados en hoja de
cálculo Excel Windows y luego analizados con paquete estadístico
SAS (versión 9,2). Los resultados obtenidos: prevalencia de
23,77% de fincas positivas (97/408), los Municipios con mayor
porcentaje de prevalencia fueron; Machiques de Perijá, Catatumbo,
Colon, y la Cañada de Urdaneta, con 57,58; 54,72;
47,62 y 31,58%, respectivamente. La seroprevalencia por estratificación
de acuerdo a la cantidad de bovinos por finca (tamaño
del fundo) para estratos 1; 2; 3 y 4 fue; fincas de menos de 25
animales 7,69%, entre 25 y 63 animales 8,57%, entre 64 y 119
animales 54,31% y más de 120 animales 18,75% . Los resultados
por grupos etarios: grupo vacas obtuvo la mayor prevalencia
con 25,18%, seguido de toros (16,67%), novillas (12,61%),
novillos (10,34%), becerros (8,61%), mautas (7,85%), becerras
(6,67%) y mautes (6,15%) para un total de prevalencia en todos
los grupos de 13,83% de animales positivos. En conclusión, la
actividad viral es alta, sobre todo en Municipios con mayor vocación
pecuaria, en fincas con mayor cantidad de animales y
en vacas en producción.311 - [email protected] from all age groups of 21 Municipalities of the Zulia
State were sampled to determine the seroprevalence of Footand-
Mouth Disease (FMD) using 3ABC ELISA. One thousand
two hundred eighty one (1281) serum samples were collected
and the presence of antibodies against FMD virus was assessed
through 3ABC ELISA at the Infectious Diseases Diagnosis
and Research laboratory of the Faculty of Veterinary
Sciences, University of Zulia. Sample size was determined following
a proportionally and intentionally stratified sampling
technique: a confidence level of 95% and error of 2.737% at
animal level; and a confidence level of 95% and error of
4.778% at herd level. Data were registered in Excel spreadsheets
and then they were analyzed through SAS/STAT software
(version 9.2). Results were as following: general FMD
seroprevalence was 23.77% at herd level (97/408). Counties
with the highest seroprevalence levels were Machiques de
Perijá, Catatumbo, Colon, and la Cañada de Urdaneta (57.58,
54.72, 47.62 and 31.58%, respectively). As for herd size, observed
seroprevalence was 7.69% in herds of < 25 animals,
8.57% in herds of 25-63 animals, 54.31% in herds of 64-119
animals, and 18.75% in herds of > 120 animals. As for age
groups, the highest seroprevalence was observed in cows
(25.18%), followed by bulls (16.67%), heifers (12.61%), steers
(10.34%), male calves (8.61%), female yearlings (7.85%), female
calves (6.67%), and male yearlings (6.15%) for a general
FMD seroprevalence of 13.83% at animal level. In conclusion,
viral circulation is high, especially in some Counties with intense
livestock activities, and in farms with greater amounts of
animals (especially cows)