The story-line of the activities that have produced the first group of scientists in Mexico working on particle accelerator science and technology is briefly presented.
•For the thiophene hydrogenation, the Ni(0.5)–Pt/HMOR catalyst is the most active.•Ni(X)–Pt/HMOR samples exhibit thio-resistance and thio-tolerance on thiophene HYD.•Ni(X)–Pt/HMOR catalysts show ...hydrogenation activity in the presence of 500ppm S.•Ni(X)–Pt/HMOR catalysts is less prone to deactivation.•Hydrogen spillover plays a key role in keeping HYD activity in the presence of sulfur.
A series of Ni(X)–Pt/HMOR catalysts (X=0, 0.5, 1.0, 1.5 and 2.0wt% of Ni and a fixed quantity of Pt=1wt%) were prepared and tested in the hydrogenation (HYD) of naphthalene with and without thiophene and also in the hydroconversion of thiophene. The catalysts were characterized using N2 physisorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and TEM-EDS elemental analysis. The TPR and TEM results indicate that Pt is mainly located inside the pore system of the mordenite, whereas Ni is located on both the external surface and inside the pore system of the mordenite zeolite. Naphthalene hydrogenation exhibited a high conversion for all the catalysts. In the presence of a sulfur compound and for naphthalene hydrogenation, all the tested catalysts present a fast deactivation. Ni/HMOR catalyst was less active and presents complete deactivation. However, the Ni(0.5)–Pt/HMOR and Pt/HMOR catalysts are able to convert thiophene and produce mainly tetrahydrothiophene. This hydrogenation activity was stable, at least for 12h, showing that the catalytic system can preserve some of the hydrogenating capability. The values of thiophene hydroconversion and the selectivity to tetrahydrothiophene are much higher than the reported for similar systems. The hydrogenation activity is most likely due to the hydrogen spillover.
•Undoped and N-doped ZnTe films were deposited by RF magnetron sputtering.•The presence of hexagonal ZnTe and Te phases were found in coexistence for undoped and N-doped ZnTe films.•The electrical ...characterization showed that doping with nitrogen reduces the resistivity in four orders of magnitude.
Undoped and N-doped ZnTe films were deposited by RF magnetron sputtering. Undoped ZnTe films were grown varying the substrate temperature, while N-doped ZnTe films were obtained at 360 °C with different N nominal concentrations. The XRD and HR-TEM results showed that ZnTe and Te phases coexist in undoped and N-doped ZnTe films. Raman analysis showed the presence of signals associated with tellurium-rich phases as well as the mode of Zn-Te bond. The incorporation of N in the ZnTe films was corroborated through XPS measurements. The optical characterization showed that the increase in N nominal concentration in the ZnTe lattice reduces the bandgap from 2.38 eV (undoped) to 1.48 eV for the highest nominal N content. The electrical characterization showed that doping with nitrogen reduces the resistivity in four orders of magnitude. CdS/CdTe solar cells were fabricated using undoped and N-doped films to evaluate their performance through the J-V curves.
The Importance and Benefits of Species Gascon, Claude; Brooks, Thomas M.; Contreras-MacBeath, Topiltzin ...
CB/Current biology,
05/2015, Letnik:
25, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Humans depend on biodiversity in myriad ways, yet species are being rapidly lost due to human activities. The ecosystem services approach to conservation tries to establish the value that society ...derives from the natural world such that the true cost of proposed development actions becomes apparent to decision makers. Species are an integral component of ecosystems, and the value they provide in terms of services should be a standard part of ecosystem assessments. However, assessing the value of species is difficult and will always remain incomplete. Some of the most difficult species’ benefits to assess are those that accrue unexpectedly or are wholly unanticipated. In this review, we consider recent examples from a wide variety of species and a diverse set of ecosystem services that illustrate this point and support the application of the precautionary principle to decisions affecting the natural world.
Gascon et al. give examples of unexpected benefits species provide to humanity.
Spermatological research of the Patagonian blennie was carried, specifically biometric parameters, sperm density, sperm count and motility in different activation mediums (815, 716, 590 and ...0 mOSm kg−1), at different temperatures (5, 10 and 15°C) and pH levels (5, 7 and 9). The results indicate that Patagonian blennie spermatozoa have a primitive form, with a total length of 44.09 ± 3.36 μm, with a head length of 2.15 ± 0.28 μm and head width of 2.5 ± 0.31 μm. The mid‐piece had a length of 0.72 ± 0.12 μm, and its tail measures 41.21 ± 3.21 μm long. The motility pattern indicates that the spermatozoa are found immobile in the seminal plasma and only initiates its movement in a hypertonic medium from 590 to 815 mOsm kg−1. The longest motility time that was registered at 10°C in 716 mOSm kg−1 was of 245 ± 39 s and an optimum pH of 7 was observed.
This work reports the synthesis of LiNbO3 nanocrystals by an aerosol assisted chemical vapor deposition method, onto silicon (001) substrates. Some of the nanocrystals showed a hexagonal morphology ...and characteristic sizes ranging from a few tens to a few hundreds of nanometers. The nanocrystals with hexagonal structure were obtained at 773K using a carrier gas flow of 6L/min and a deposition time of 90min. Structural, morphological, photoluminescence and cathodoluminescence properties were studied by grazing incidence X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, fluorospectrometry, and cathodoluminescence, respectively. An extraordinary violet luminescence at 396nm with excitation in UV region (280nm) was observed in one of the samples. Cathodoluminescence (CL) imaging and spectroscopy studies of the nanocrystals exhibit stimulated emission of light in the near ultraviolet–violet–green spectral region. The emission peaks in CL spectra varied according to the nature of nanoparticles. A red-shift in the CL spectra with a decrease in the particle size was observed. Apparently the size of LiNbO3 typical nanocrystals investigated in this work has tuned the photoluminescence emission. This result encourages the use and integration of LiNbO3 nanocrystals into nanophotonics applications.
•Optimum nucleation conditions to obtain LiNbO3 nanocrystals by AACVD were determined.•The size of LiNbO3 typical nanocrystals investigated has tuned the photoluminescence emission.•A red-shift in the cathodoluminescence spectra with a decrease in the nanocrystal size was observed.
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•An optimal allocation system for scarce resources should simultaneously ensure maximal utility, but also equity.•Large differences exist between centers and countries for ethical and ...legislative reasons.•A future globally applicable strategy should combine donor and recipient factors.•This strategy must predict probability of death on the waiting list, post-transplant survival and morbidity, and costs.
An optimal allocation system for scarce resources should simultaneously ensure maximal utility, but also equity. The most frequent principles for allocation policies in liver transplantation are therefore criteria that rely on pre-transplant survival (sickest first policy), post-transplant survival (utility), or on their combination (benefit). However, large differences exist between centers and countries for ethical and legislative reasons. The aim of this study was to report the current worldwide practice of liver graft allocation and discuss respective advantages and disadvantages.
Countries around the world that perform 95 or more deceased donor liver transplantations per year were analyzed for donation and allocation policies, as well as recipient characteristics.
Most countries use the model for end-stage liver disease (MELD) score, or variations of it, for organ allocation, while some countries opt for center-based allocation systems based on their specific requirements, and some countries combine both a MELD and center-based approach. Both the MELD and center-specific allocation systems have inherent limitations. For example, most countries or allocation systems address the limitations of the MELD system by adding extra points to recipient’s laboratory scores based on clinical information. It is also clear from this study that cancer, as an indication for liver transplantation, requires special attention.
The sickest first policy is the most reasonable basis for the allocation of liver grafts. While MELD is currently the standard for this model, many adjustments were implemented in most countries. A future globally applicable strategy should combine donor and recipient factors, predicting probability of death on the waiting list, post-transplant survival and morbidity, and perhaps costs.
An optimal allocation system for scarce resources should simultaneously ensure maximal utility, but also equity. While the model for end-stage liver disease is currently the standard for this model, many adjustments were implemented in most countries. A future globally applicable strategy should combine donor and recipient factors predicting probability of death on the waiting list, post-transplant survival and morbidity, and perhaps costs.
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