851 research outputs found
Thermally induced behavior of the K-exchanged erionite. A further step in understanding the structural modifications of the erionite group upon heating
Fibrous erionite is a naturally occurring zeolite considered to be highly carcinogenic upon inhalation, even more than crocidolite. Since no iron is typically present in erionite, its toxicity has been attributed to ion-exchanged Fe participating in Fenton chemistry. Recently, a study aimed at investigating possible fiber inactivation routes surprisingly showed that, despite having completely occluded all available pores with K ions, the erionite-Na sample preserved the property to upload Fe (II) within the structure. In this work, the thermal behavior of the K-exchanged erionite-Na was investigated by TG/ DSC and in situ XRPD analyses in order to provide relevant information for modeling the thermally induced behavior of the erionite group. Rietveld refinement results evidenced a general trend of cell parameters and volume with temperature similar to that observed for erionite-K from Rome (Oregon, USA). However, the dependence of Tdehydrand Tbreakfrom Si/Si+Al ratio observed in zeolites (high Si content favours a lower Tdehydrand a higher Tbreak) is not observed, possibly due to the effect of the relevant amount of large K ions dispersed within the erionite cage, acting as reinforcing blocks for the framework. Heating produces a progressive emptying of the Ca sites, common effect previously observed in erionite samples showing different chemistry. In addition, K1 s.s. remains unchanged evidencing the absence of any “internal ion exchange” process, whereas s.s. at K2 increases in the range 438-573 K and then slowly decreases in the range 700-1218 K. Both Rietveld and DSC data suggest the motion of K ions from OW sites toward the walls of the erionite cavity during dehydration
Primary cosmic ray spectrum in the 10 to the 12th power - 10 to the 16th power eV energy range from the NUSEX experiment
A primary cosmic ray spectrum was derived which fits both experimental multiple muon rates and the all-nucleon flux derived from the single muon intensities underground. In the frame of the interaction model developed by Gaisser, Elbert and Stanev, it is possible to reproduce NUSEX muon data with a primary composition in which the iron spectrum is only slightly flatter than the proton one. This result rules out the popular idea that the primary composition varies drastically with increasing energy, leading to the dominance of heavier nuclei at energies 10 to the 15th power to 10 to the 16th power eV
Kaon physics with the KLOE detector
In this paper we discuss the recent finalized analyses by the KLOE experiment
at DANE: the CPT and Lorentz invariance test with entangled pairs, and the precision measurement of the branching fraction of
the decay . We also present the
status of an ongoing analysis aiming to precisely measure the mass
Avaliação da fertilidade dos solos do Distrito Federal.
O SNLCS tem procurado ampliar o alcance e a utilização prática, dos dados obtidos através dos levantamentos de solos que realiza. Prosseguindo as pesquisas que objetivam a elaboração do mapa de solos do Brasil a nível de reconhecimento, esta entidade vem complementando seus trabalhos com mapas de aptidão agrícola das terras, em relação com diferentes tipos de manejo e culturas. Dentro dos parâmetros usados para definir a aptidão agrícola dos solos, a fertilidade e o mais facilmente controlável e aquele cuja alteração modifica mais sensivelmente a produtividade das terras. Por outro lado, os mapas de aptidão, pela sua natureza, não mostram claramente as limitações de uso devido unicamente ao nível de fertilidade das terras. Tal informação é de grande importância ao estudo de viabilidade econômica de projetos agropecuários, por permitir estimar a necessidade de fertilizantes e corretivos para determinada área. A análise conjunta dos mapas de classificação e aptidão agrícola e ainda de uma avaliação da fertilidade dos solos, daria aos usuários dos trabalhos de levantamento uma visão mais completa dos recursos disponíveis, facilitando as decisões quanto ao tipo de exploração agrícola e ao sistema de manejo mais adequado em cada caso. O presente projeto propõe a complementação de cada trabalho de levantamento com uma avaliação e quantificação da fertilidade, cuja precisão e confiabilidade serão tanto maiores quanto maior for o nível de detalhe do levantamento de solos em que seja baseado.bitstream/item/62835/1/CNPS-BOL.-TEC.-74-80.pdf; bitstream/item/125962/1/Avaliacao-da-Fertilidade-dos-Solos-do-Distrito-Federal.pdfAcompanha 1 mapa, color. Escala 1:100.000
High-statistics study of the low-energy cosmic-muons angular distribution - Results from MICRO
We present results from MICRO, a muon telescope with good angular resolution, which has collected more than 31·106 cosmic muons. Upper limits are given for the flux coming from point sources and for the periodic component from Cygnus X3
In Vitro Production of Calcified Bone Matrix onto Wool Keratin Scaffolds via Osteogenic Factors and Electromagnetic Stimulus
Pulsed electromagnetic field (PEMF) has drawn attention as a potential tool to improve the ability of bone biomaterials to integrate into the surrounding tissue. We investigated the effects of PEMF (frequency, 75 Hz; magnetic induction amplitude, 2 mT; pulse duration, 1.3 ms) on human osteoblast-like cells (SAOS-2) seeded onto wool keratin scaffolds in terms of proliferation, differentiation, and production of the calcified bone extracellular matrix. The wool keratin scaffold offered a 3D porous architecture for cell guesting and nutrient diffusion, suggesting its possible use as a filler to repair bone defects. Here, the combined approach of applying a daily PEMF exposure with additional osteogenic factors stimulated the cells to increase both the deposition of bone-related proteins and calcified matrix onto the wool keratin scaffolds. Also, the presence of SAOS-2 cells, or PEMF, or osteogenic factors did not influence the compression behavior or the resilience of keratin scaffolds in wet conditions. Besides, ageing tests revealed that wool keratin scaffolds were very stable and showed a lower degradation rate compared to commercial collagen sponges. It is for these reasons that this tissue engineering strategy, which improves the osteointegration properties of the wool keratin scaffold, may have a promising application for long term support of bone formation in vivo
Suppression of flavor violation in an A4 warped extra dimensional model
In an attempt to simultaneously explain the observed masses and mixing
patterns of both quarks and leptons, we recently proposed a model
(JHEP08(2010)115) based on the non abelian discrete flavor group A4,
implemented in a custodial RS setup with a bulk Higgs. We showed that the
standard model flavor structure can be realized within the zero mode
approximation (ZMA), with nearly tribimaximal (TBM) neutrino mixing and a
realistic CKM matrix with rather mild assumptions. An important advantage of
this framework with respect to flavor anarchic models is the vanishing of the
dangerous tree level KK gluon contribution to \epsilon_K and the suppression of
the new physics one loop contributions to the neutron EDM, \epsilon'/\epsilon,
b->s\gamma and Higgs mediated flavor changing neutral current (FCNC) processes.
These results are obtained beyond the ZMA, in order to account for the the full
flavor structure and mixing of the zero modes and first Kaluza-Klein (KK) modes
of all generations. The resulting constraints on the KK mass scale are shown to
be significantly relaxed compared to the flavor anarchic case, showing
explicitly the role of non abelian discrete flavor symmetries in relaxing
flavor violation bounds within the RS setup. As a byproduct of our analysis we
also obtain the same contributions for the custodial anarchic case with two
SU(2)_R doublets for each fermion generation.Comment: 8 pages, 4 figures; contribution prepared for DISCRETE'10 - Symposium
on Prospects in the Physics of Discrete Symmetrie
Atmospheric pressure non-equilibriumplasma for the production of composite materials
In the evolving field of tissue engineering, continuous advances are required
to improve scaffold design and fabrication to obtain biomimetic supports for
cell adhesion, proliferation, penetration and differentiation. Both electrospun
fibrous scaffolds and hydrogels are used in this field since they well
reproduce the structure of the extracellular matrix (ECM) of many biological
tissues. Limitations of these two types of materials can be overcome
through their combination, by developing composite structures combining
enhanced mechanical properties (provided by the fibrous components) and
improved cell penetration (provided by the gel phase) in a superior ability to
mimic natural ECM that is constituted by both a fibrous protein network and
a hydrogel matrix. Here we develop new composite materials made of
electrospun PLLA scaffolds and poly(amidoamine) hydrogels with different
degrees of crosslinking. To promote compatibilization and good adhesion
between the two materials, surface chemical reactions between hydrogels
and PLLA mats are induced by inserting amino functional groups on
electrospun PLLA mats by means of atmospheric pressure non-thermal
plasma. Results will be presented concerning the exposure of PLLA
substrates to the plasma region generated by a Dielectric Barrier Discharge
at atmospheric pressure, driven by a HV Amplifier connected to a function
generator operating with a microsecond rise time and operated in N2.
Surface and solid-state thermo-mechanical characterizations of plasma
treated substrates and of resulting composite materials at different
crosslinking degrees are presented. Results of mechanical tests show a high
adhesion between hydrogel and plasma treated PLLA electrospun mats,
underlining the opportunity to use atmospheric non-thermal plasmas to
fabricate a composite starting from two materials otherwise physically
incompatible. Potential effects of nanofibrous-hydrogel were evaluated by
investigating pluripotent stem cells response
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