37 research outputs found
Singlet oxygen from cation driven superoxide disproportionation and consequences for aprotic metal-O2 batteries
Aprotic alkali metal-oxygen batteries require reversible formation of metal superoxide or peroxide on cycling. Severe parasitic reactions cause poor rechargeability, efficiency, and cycle life and have been shown to be caused by singlet oxygen (1O2) that forms at all stages of cycling. However, its formation mechanism remains unclear. We show that disproportionation of superoxide, the product or intermediate on discharge and charge, to peroxide and oxygen is responsible for 1O2 formation. While the overall reaction is driven by the stability of peroxide and thus favored by stronger Lewis acidic cations such as Li+, the 1O2 fraction is enhanced by weak Lewis acids such as organic cations. Concurrently, the metal peroxide yield drops with increasing 1O2. The results explain a major parasitic pathway during cell cycling and the growing severity in K-, Na-, and Li-O2 cells based on the growing propensity for disproportionation. High capacities and rates with peroxides are now realized to require solution processes, which form peroxide or release O2via disproportionation. The results therefore establish the central dilemma that disproportionation is required for high capacity but also responsible for irreversible reactions. Highly reversible cell operation requires hence finding reaction routes that avoid disproportionation
Search for elementary particles bearing a magnetic charge: an experimental design in the from of a modified variant
Measurement of neutral current e+/-p cross sections at high Bjorken x with the ZEUS detector
The neutral current e+/-p cross section has been measured up to values of
Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated
luminosity of 187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) =
318GeV. Differential cross sections in x and Q2, the exchanged boson
virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method
and greatly increased amount of data allows a finer binning in the high-x
region of the neutral current cross section and leads to a measurement with
much improved precision compared to a similar earlier analysis. The
measurements are compared to Standard Model expectations based on a variety of
recent parton distribution functions.Comment: 39 pages, 9 figure
Measurement of beauty and charm production in deep inelastic scattering at HERA and measurement of the beauty-quark mass
The ZEUS collaborationThe production of beauty and charm quarks in ep interactions has been studied with
the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q^2 < 1000 GeV^2
using an integrated luminosity of 354 pb^{−1}. The beauty and charm content in events
with at least one jet have been extracted using the invariant mass of charged tracks
associated with secondary vertices and the decay-length significance of these vertices.
Differential cross sections as a function of Q^2, Bjorken x, jet trans- verse energy
and pseudorapidity were measured and compared with next-to-leading-order QCD
calculations. The beauty and charm contributions to the proton structure functions
were extracted from the double-differential cross section as a function of x and Q^2.
The running beauty-quark mass, m_b at the scale m_b , was determined from a QCD fit
at next-to-leading order to HERA data for the first time and found to be
m_b(m_b) = 4.07 ± 0.14(fit)_{−0.07}^{+0.01}(mod.)_{−0.00}^{+0.05}(param.)_{−0.05}^{+0.08}(theo.)GeV.We appreciate the contributions to the construction, maintenance and operation of the
ZEUS detector of many people who are not listed as authors. The HERA machine group
and the DESY computing staff are especially acknowledged for their success in providing
excellent operation of the collider and the data-analysis environment. We thank the DESY
directorate for their strong support and encouragement. It is a pleasure to thank the
ABKM, CTEQ, JR and MSTW groups that provided the predictions for F_2^{b\overline{b}} shown in figure
12. We gratefully acknowledge the advice from S. Alekhin and R. Plačakytė concerning
the appropriate usage of OPENQCDRAD and HERAFitter. Article funded by SCOAP
Photoproduction of isolated photons, inclusively and with a jet, at HERA
ZEUS CollaborationThe photoproduction of isolated photons, both inclusive and together with a jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 374 pb^{−1}. Differential cross sections are presented in the isolated-photon transverse-energy and pseudorapidity ranges 6 < E^γ_T < 15 GeV and
−0.7 < η^γ < 0.9, and for jet transverse-energy and pseudorapidity ranges 4 < E^{jet}_T < 35 GeV and −1.5 <η^{jet} < 1.8, for exchanged-photon virtualities Q^2 < 1 GeV^2. Differential cross sections are also presented
for inclusive isolated-photon production as functions of the transverse energy and pseudorapidity of the photon. Higher-order theoretical calculations are compared to the results.We appreciate the contributions to the construction, maintenance and operation of the ZEUS detector made by many people who are not listed as authors. The HERA machine group and the DESY computing staff are especially acknowledged for their success in providing excellent operation of the collider and the data-analysis environment. We thank the DESY directorate for their strong support and encouragement. We also thank M. Fontannaz, G. Heinrich, A. Lipatov, M. Malyshev and N. Zotov for providing assistance and theoretical results. Funded by SCOAP