Site Selectivity for CO Adsorption and Stripping on Stepped and Kinked Platinum Surfaces in Alkaline Medium

This work reports experimental evidence that the adsorption of CO on Pt surfaces composed by (111) terraces and steps and/or kinks in alkaline media occurs faster on sites with (100) symmetry, followed by (110) sites. On the other hand, the (111) terrace has the lowest adsorption rate. CO electrooxidation demonstrates the existence of a close relationship between the preferential site CO occupancy and the peak multiplicity observed in CO stripping voltammetry. For the stepped Pt(554) and Pt(544) and kinked Pt(875) single crystal surfaces, the CO stripping process takes place at high potentials (0.80 V vs RHE) when only the (110) or (100) step sites are blocked by CO. However, when the terrace sites with (111) symmetry are fully occupied, new CO stripping peaks appear at lower potentials (<0.68 V vs RHE). For all surfaces, it is observed that the first released sites after partial CO oxidation are (111) terrace sites, followed by the step (110) sites and sites with (100) symmetry. The results of partial CO oxidation suggest that the diffusion of adsorbed CO from sites with (110) or (100) symmetry toward unoccupied (111) terrace sites is negligible. However, CO diffusion from terrace sites to step or kink sites cannot be discarded during the growth of the adsorbed CO adlayer, because of the preferential site occupancy for these latter sites. Due to the fact that the CO oxidation process on stepped Pt surfaces in alkaline media occurs at different potentials on different sites, the activation energies for CO oxidation on the different sites have been estimated. The results for full CO coverage and CO decorated stepped surfaces are in good agreement, indicating that the oxidation of CO on the different sites is not coupled. In the absence of CO on terrace sites, in situ FTIR spectroscopy shows that CO molecules on the (110) step sites are essentially linearly bonded, while on the (100) step sites both linearly and bridge bonded CO are observed. The comparison of these spectra with those obtained when a full coverage is attained shows that the band frequencies for CO on step sites are highly coupled with those on the terrace sites.M.J.S.F. would like to thank CNPq, Brazil, for financial support for his postdoctoral stay at Universidad de Alicante. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, -FEDER)

Approximate solutions to the quantum problem of two apposite charges in a constant magnetic field

Física Teórica, Atómica y Óptic

Changes in carbon stocks in Eucalyptus globulus Labill. plantations induced by different water and nutrient availability

Changes in the carbon stocks under different soil water and nutrient conditions were studied in Eucalyptus globulus Labill. stands in a field experiment, at O ´ bidos (central Portugal). The treatments were irrigation plus a complete fertiliser solution to simulate ‘near optimal’ nutrition (IF), irrigation only (I), and fertilisers added to rain-fed plots (F). The control (C) received neither water nor fertilisers (except a small amount at planting). The production of biomass (aboveground), the litterfall and the soil chemical composition were evaluated regularly during the experiment. Root biomass was estimated at the end of the experiment. Carbon in biomass, litterfall and soil, increased significantly when water and/or nutrients were supplied, in comparison to the control. The amount of carbon accumulated in the system, 6 years after planting, was 8.22, 10.22, 11.23 and 13.76 kg C m 2 in the control, F, I and IF treatments, respectively. The increase of carbon in the system during the same period was 5.86, 7.86, 8.87 and 11.40 kg C m 2 in the control, F, I and IF treatments, respectively. This rise in carbon resulted from the accumulation of long-lived woody biomass, which represented between 77.7 (in IF) and 82.9% (in the control) of the total rise in carbon. Although water was the main limiting factor for biomass accumulation, the allocation of carbon to the soil was mainly related to nutrient supply, irrespective of water availability. The amount of carbon stored belowground, i.e. soil and forest floor, plus stumps and roots, reached 4.2, 4.7, 4.8 and 6.3 kg C m 2 in the control, F, I and IF treatments, respectively. The increase in C in the mineral soil regarding the initial state was, in the same order as above, 0.21, 0.75, 0.58 and 1.21 kg C m 2. These values were 3.6, 9.6, 6.6 and 10.6% of the C accumulated in the whole system, during the experimental period

Disentangling Catalytic Activity at Terrace and Step Sites on Selectively Ru-Modified Well-Ordered Pt Surfaces Probed by CO Electro-oxidation

In heterogeneous (electro)catalysis, the overall catalytic output results from responses of surface sites with different catalytic activities, and their discrimination in terms of what specific site is responsible for a given activity is not an easy task. Here, we use the electro-oxidation of CO as a probe reaction to access the catalytic activity of different sites on high-Miller index stepped Pt surfaces with their {110} steps selectively modified by Ru at different coverages. Data from in situ Fourier transform infrared spectroscopy and cyclic voltammetry evidence that Ru deposited on {110} steps modifies the surface in a nontrivial way, favoring only the electrocatalytic oxidation of CO over {111} terraces. Moreover, these {111} terraces become catalytically active throughout a large potential window. On the other hand, after the deposition of Ru on {110} steps, the partial oxidation of a CO adlayer (by stripping voltammetry and in situ FTIR potential steps) shows that those {110} steps that remain free of Ru seem not to be influenced by the presence of this metal. As a result, the remaining CO adlayer is oxidized on these Ru-free {110} steps at potentials identical to those observed in steps of pure stepped Pt surfaces (in the absence of Ru). First, these findings suggest that COads behaves as a motionless species during its oxidation. Second, they evidence that the impact caused by the presence of Ru in the catalytic activity of Pt(s)-[(n–1)(111)×(110)] stepped surfaces depends on the crystallographic orientation of Pt sites. These results help us to shed new light on the role of Ru in the mechanism of oxidation of CO and allow a deeper understanding regarding the CO tolerance in Pt–Ru catalysts.M.J.S.F. acknowledges financial support from the CNPq (Brazil) (Grants 200390/2011-2 and 313402/2013-2). G.A.C. acknowledges financial assistance from CNPq (Grants 305494/2012-0, 309176/2015-8, and 405695/2013-6) and FUNDECT (Grant 23/200.583/2012). J.M.F. thanks the MINECO (Spain) (Project CTQ2013-44083-P)

Requirement of initial long-range substrate structure in unusual CO pre-oxidation on Pt(111) electrodes

The activation pathway of CO electro-oxidation at low potentials is frequently favored on a catalyst with surface defects. Here, we report a discovery in which an initial long-range substrate structure is required for the activation of an unusual CO pre-oxidation reaction pathway on Pt(111) surfaces which have been flame annealed and then cooled in a CO atmosphere. Different to current understanding about the oxidation of CO on Pt, the activation of this reaction pathway is inhibited as the (111) planes become defect-rich.M.J.S.F and A.A.T. thanks the CAPES (Brazil) Finance Code 001. J.M.F. thanks the MINECO (Spain) CTQ2013-44083-P project

Towards an integrated continuous manufacturing process of adeno- associated virus (AAVs)

Please click Additional Files below to see the full abstract

Infections after chimeric antigen receptor (CAR)-T-cell therapy for hematologic malignancies.

Chimeric antigen receptor (CAR)-T-cell therapies have revolutionized the management of acute lymphoblastic leukemia, non-Hodgkin lymphoma, and multiple myeloma but come at the price of unique toxicities, including cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and long-term "on-target off-tumor" effects. All of these factors increase infection risk in an already highly immunocompromised patient population. Indeed, infectious complications represent the key determinant of non-relapse mortality after CAR-T cells. The temporal distribution of these risk factors shapes different infection patterns early versus late post-CAR-T-cell infusion. Furthermore, due to the expression of their targets on B lineage cells at different stages of differentiation, CD19, and B-cell maturation antigen (BCMA) CAR-T cells induce distinct immune deficits that could require different prevention strategies. Infection incidence is the highest during the first month post-infusion and subsequently decreases thereafter. However, infections remain relatively common even a year after infusion. Bacterial infections predominate early after CD19, while a more equal distribution between bacterial and viral causes is seen after BCMA CAR-T-cell therapy, and fungal infections are universally rare. Cytomegalovirus (CMV) and other herpesviruses are increasingly breported, but whether routine monitoring is warranted for all, or a subgroup of patients, remains to be determined. Clinical practices vary substantially between centers, and many areas of uncertainty remain, including CMV monitoring, antibacterial and antifungal prophylaxis and duration, use of immunoglobulin replacement therapy, and timing of vaccination. Risk stratification tools are available and may help distinguish between infectious and non-infectious causes of fever post-infusion and predict severe infections. These tools need prospective validation, and their integration in clinical practice needs to be systematically studied

Influence of the CO Adsorption Environment on Its Reactivity with (111) Terrace Sites in Stepped Pt Electrodes under Alkaline Media

The effect of the electrode potential in the reactivity of platinum stepped single crystal electrodes with (111) terraces toward CO oxidation has been studied. It is found that the CO adlayer is significantly affected by the potential at which the adlayer is formed. The electrochemical and FTIR experiments show that the adsorbed CO layer formed in acidic solution at 0.03 V vs SHE is different from that formed at −0.67 V vs SHE in alkaline solutions. The major effect of the electrode potential is a change in the long-range structure of CO adlayer. The adlayer formed in alkaline media presents a higher number of defects. These differences affect the onset and peak potential for CO stripping experiments. The stripping voltammogram for the adlayer formed at −0.67 V vs SHE always shows a prewave and the peak potential is more negative than that observed for the adlayer formed at 0.03 V vs SHE. This means that the apparent higher activity for CO oxidation observed in alkaline media is a consequence of the different CO adlayer structure on the (111) terrace, and not a true catalytic effect. The different behavior is discussed in terms of the different mobility of CO observed depending on the electrode potential. Also, the FTIR frequencies are used to estimate the pzc (potential of zero charge) for the Pt(111) electrode covered with a CO adlayer.M.J.S.F would like to thanks CNPq, Brazil, for financial support for his stay at Universidad de Alicante. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)

On the behavior of CO oxidation on shape-controlled Pt nanoparticles in alkaline medium

In this work, the behavior of the CO electro-oxidation reaction on shape-controlled Pt nanoparticles in alkaline medium was examined in order to understand the effect of the surface structure on this reaction. A series of experiments using Pt nanoparticles of different surface structures/shapes was used and the results obtained were compared with the previous knowledge gained from stepped platinum single crystal electrodes. Independently of the preferential orientation of the nanoparticles, the CO oxidation voltammetry exhibits two main peaks: one at ca. 0.56–0.59 V and the second one at 0.66–0.67 V, being the intensity of the peaks dependent on the shape of the nanoparticle. These two peaks have been assigned to the oxidation of CO on the (1 1 1) terraces and on the rest of the sites, respectively. The appearance of two differentiated peaks reveals that these (1 1 1) terraces and the rest of the sites on the nanoparticle surface behave independently of the presence of the other type of sites, that is, they are not connected. The results are discussed considering the effects of the surface mobility of CO and of the OH adsorption properties on the different sites in the oxidation peaks.Farias, M.J.S. would like to thanks CNPq, Brazil, for financial support for his postdoctoral stay at Universidad de Alicante. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)