315 research outputs found
Propiedades mecánicas de cermets basados en diboruro de titanio
Las propiedades mecánicas de los cermets basados en diboruro de titanio (TiB
2
) dependen críticamente de la composición de
la fase ligante. Se ha comprobado que tanto la tenacidad como la dureza aumentan significativamente si se evita la formación
de boruros secundarios durante la sinterización en fase líquida. Las observaciones fractográficas realizadas en cermets basados en TiB
2
sin boruros secundarios confirman el comportamiento plástico de la fase ligante durante la fractura. La ruta
pulvimetalúrgica aplicada a estos materiales permite la modificación intencionada de la estructura de la fase ligante desde
ferrita a austenita mediante adiciones de aluminio a las mezclas de polvos. Los valores de tenacidad más elevados se han
obtenido para los cermets con matriz austenítica. El análisis mediante difracción de rayos X de la superficie de fractura de
estos materiales confirma que la fase ligante experimenta transformación martensítica durante la fractura, mecanismo de
aumento de tenacidad ya observado en otros sistemas. Esta nueva familia de materiales duros presenta una excelente combinación de dureza y tenacidad, comparable a la obtenida con grados comerciales de carburos cementados (WC-Co).Peer reviewe
Estudio de la densidad mineral ósea mediante osteosonografía en niños y adolescentes sanos: valores de normalidad
Osteoporosis is a frequent health problem in adults. Optimization of
bone mass acquisition during childhood and adolescence may play a major role in
the prevention of this disease. Osteosonography is a recent technique for
measuring bone mineralization without exposing the patient to radiation.
OBJECTIVES: To measure bone mineral density using osteosonography in healthy
Spanish Caucasian children and adolescents in order to determine normal values.
METHODS: We performed a cross sectional study of 829 healthy child and adolescent
volunteers (360 girls and 469 boys) randomly selected from the urban area of
Pamplona in Navarre (Spain). Ages ranged from 6 to 18 years. ADBM Sonic 1200
ultrasound densitometer from IGEA was used. Daily calcium dietary intake and
amount of physical activity were recorded. RESULTS: Cross sectional standards for
Ad-SOS are presented. Ad-SOS did not significantly change between the ages of 6
and 9 years in girls or until the age of 10 years in boys. From the ages of 10 to
14 years, Ad-SOS values were higher in girls than in boys. After the age of 14
years, no significant differences were found. No correlation was found between
calcium dietary intake, amount of physical exercise or bone mineralization
values. CONCLUSIONS: Measurement of Ad-SOS by osteosonography is an easy, fast
and inexpensive method for measuring bone mineral density in children and
adolescents without exposing them to radiation. It can be used in the pediatric
population to detect early alterations in bone mineralization
Approach to anaerobic bio-degradation of natural and synthetic fabrics: Physico-chemical study of the alteration processes
In this paper, the mesophilic Biochemical Methane Potential of several fabrics was assessed at different Total
Solid concentrations (1–4%TS). Physico-chemical techniques were applied to explore the arising structural
changes on fibers during the anaerobic digestion process. Additionally, the modified Gompertz model was used
to assess and compare the AD performance of the fabrics. In cellulose-based fibers the production of biogas was
enhanced thanks to the easy solubilization of acetate, which is generated upon partial breakage of cellulose
bonds. The crystallinity of vegetal fibers decreased significantly from day 19. The highest methane yields were
attained for silk and wool fabrics at the lowest TS concentrations. Conformational changes in fibroin and keratin
were detected. The highest degrees of degradation were observed in solid samples with lower solid concentrations. Accordingly, the maximum methane yields were reported in the reactors operating with lower TS
Generation of a cadmium-binding filamentous phage through cysteine-rich peptide display on PVIII
132-138M13 is a filamentous bacteriophage with a 6 nm thick and 1 µm length tubular structure. Approximately, 3000 subunits of PVIII, the major coat protein form a cylinder that encapsulates the M13 single-stranded DNA genome. Among capsid proteins sequences, PVIII gene is particularly amenable for the expression of recombinant peptides on the phage surface. It has been identified that thiol rich peptides are able to interact with heavy metals. In this work, we incorporated a heavy metal binding peptide to PVIII producing a viral particle capable of interacting with cadmium. For this purpose, we designed a chimeric gene composed of the coding sequence of a cysteine rich peptide linked to PVIII and cloned into a phagemid vector. Then, we established the optimal conditions for phage production by regulating the expression of the chimeric PVIII protein by using an isopropyl β-D-1-thiogalactopyranoside (IPTG) inducible system. The cysteine rich recombinant phage interacted with cadmium in a highly efficient manner. Considering this novel property, the recombinant phage produced in this work could be used as a nanotechnology tool in the development of affinity columns, concentration systems for cadmium analysis or bioremediation
The Hot Gas Environment of the Radio Galaxy 3C 388: Quenching the Accumulation of Cool Gas in a Cluster Core by a Nuclear Outburst
We present results from a 35 ks {\em Chandra}/ACIS-I observation of the hot
ICM around the FR II radio galaxy 3C 388. 3C 388 resides in a cluster
environment with an ICM temperature of 3.5 keV. We detect cavities in the
ICM coincident with the radio lobes. The enthalpy of these cavities is
ergs. The work done on the gas by the inflation of the
lobes is ergs, or 0.87 keV per particle out to the
radius of the lobes. The radiative timescale for gas at the center of the
cluster at the current temperature is a few Gyrs. The gas in the core was
probably cooler and denser before the outburst, so the cooling time was
considerably shorter. We are therefore likely to be witnessing the quenching of
a cluster cooling flow by a radio galaxy outburst. The mechanical power of the
lobes is at least 20 times larger than the radiative losses out to the cooling
radius. Outbursts of similar power with a 5% duty cycle would be more
than sufficient to continually reheat the cluster core over the Hubble time and
prevent the cooling of any significant amount of gas. The mechanical power of
the outburst is also roughly two orders of magnitude larger than either the
X-ray luminosity of the active nucleus or the radio luminosity of the lobes.
The equipartition pressure of the radio lobes is more than an order of
magnitude lower than that of the ambient medium, indicating that the pressure
of the lobe is dominated by something other than the relativistic electrons
radiating at GHz frequencies.Comment: 28 pages, 10 figures - accepted for publication in the Astrophysical
Journa
Growth, yield and physiology of Verticillium-inoculated pepper plants treated with ATAD and composted sewage sludge
A greenhouse experiment was conducted to investigate the impact of sanitized sewage sludges, ATAD (aerobic thermophilic autothermic digestion) and composted, on Verticillium-induced wilt in pepper plants (Capsicum annuum L. cv. Piquillo). Two doses of ATAD (15 and 30% v/v) and three of composted sludge (15, 30 and 45% v/v) were applied to a peat-based potting mix. Unamended substrate was included as control. Half of the plants were inoculated with V. dahliae, whereas the other half remained non-inoculated. Result showed that ATAD and composted sludge increased growth and yield of non-inoculated plants. V. dahliae reduced net photosynthesis (P n), mainly as a consequence of stomatal closure, 5 weeks after pathogen inoculation. The actual photosystem II efficiency was also reduced and consequently the electron transport rate (ETR). No photoinhibitory damage was observed at this time in diseased plants. At the end of the experiment, diseased plants showed lower plant biomass and fruit yield. ATAD sludge had little effect on the disease. Compost slightly alleviated Verticillium-induced wilt when applied at lower doses (15% v/v), which resulted in increased P n and ETR, and higher plant biomass and fruit yield. By contrast, higher doses of compost (45% v/v) enhanced the effect of the pathogen, which was related to the high substrate salinity in this treatment
Reduced Bone Mineralization in Adolescent Survivors of Malignant Bone Tumors: Comparison of Quantitative Ultrasound and Dual-Energy X-Ray Absorptiometry
To assess bone mineralization in adolescents with bone tumors at
remission using quantitative digital ultrasound (QUS) and dual-energy x-ray
absorptiometry (DEXA), and to compare the bone mineralization values obtained by
both methods. METHODS: Patients studied were 36 adolescents (21 boys, 15 girls)
who had completed treatment of a bone tumor at the University Hospital of the
University of Navarra (Pamplona, Spain). QUS was performed at the distal
metaphysis of the proximal phalanxes of the last four fingers of the nondominant
hand. A DBM Sonic 1200 Ultrasound densitometer was used. DEXA measurements were
made at the lumbar spine (vertebrae L1-L4) using the Hologic QDR 4500 W device.
Calcium and vitamin D daily intake and grade of physical activity were recorded.
RESULTS: Mean age at bone mineralization determination was 19.11 years.
Disease-free survival was 4.97 years. Decreased bone mineralization was observed
by both methods. Bone mineralization absolute values measured by QUS and DEXA
were significantly correlated. The sensitivity, specificity, diagnostic accuracy,
and positive and negative predictive values of QUS for predicting osteopenia were
36.4%, 80.0%, 66.7%, 44.4%, and 74.1%, respectively. Daily vitamin D intake was
below the recommended dietary allowances. CONCLUSIONS: Adolescents in remission
from bone tumors have low bone mineralization determined by DEXA or QUS
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