The Cyprus Institute

About: The Cyprus Institute is a other organization based out in Nicosia, Cyprus. It is known for research contribution in the topics: Aerosol & Environmental science. The organization has 418 authors who have published 1252 publications receiving 32586 citations.

Neutron electric dipole moment using $N_{f} =2+1+1$ twisted mass fermions

Abstract: We evaluate the neutron electric dipole moment $|{\stackrel{\ensuremath{\rightarrow}}{d}}_{N}|$ using lattice QCD techniques. The gauge configurations analyzed are produced by the European Twisted Mass Collaboration using ${N}_{f}=2+1+1$ twisted mass fermions at one value of the lattice spacing of $a\ensuremath{\simeq}0.082\text{ }\text{ }\mathrm{fm}$ and a light quark mass corresponding to ${m}_{\ensuremath{\pi}}\ensuremath{\simeq}373\text{ }\text{ }\mathrm{MeV}$. Our approach to extract the neutron electric dipole moment is based on the calculation of the $CP$-odd electromagnetic form factor ${F}_{3}({Q}^{2})$ for small values of the vacuum angle $\ensuremath{\theta}$ in the limit of zero Euclidean momentum transfer ${Q}^{2}$. The limit ${Q}^{2}\ensuremath{\rightarrow}0$ is realized either by adopting a parametrization of the momentum dependence of ${F}_{3}({Q}^{2})$ and performing a fit or by employing new position space methods, which involve the elimination of the kinematical momentum factor in front of ${F}_{3}({Q}^{2})$. The computation in the presence of a $CP$-violating term requires the evaluation of the topological charge $\mathcal{Q}$. This is computed by applying the cooling technique and the gradient flow with three different actions, namely the Wilson, the Symanzik tree-level improved and the Iwasaki action. We demonstrate that cooling and gradient flow give equivalent results for the neutron electric dipole moment. Our analysis yields a value of $|{\stackrel{\ensuremath{\rightarrow}}{d}}_{N}|=0.045(6)(1)\overline{\ensuremath{\theta}}e\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{fm}$ for the ensemble with ${m}_{\ensuremath{\pi}}=373\text{ }\text{ }\mathrm{MeV}$ considered.

Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry

Abstract: . The Arabian Peninsula is characterized by high and increasing levels of photochemical air pollution. Strong solar irradiation, high temperatures and large anthropogenic emissions of reactive trace gases result in intense photochemical activity, especially during the summer months. However, air chemistry measurements in the region are scarce. In order to assess regional pollution sources and oxidation rates, the first ship-based direct measurements of total OH reactivity were performed in summer 2017 from a vessel traveling around the peninsula during the AQABA (Air Quality and Climate Change in the Arabian Basin) campaign. Total OH reactivity is the total loss frequency of OH radicals due to all reactive compounds present in air and defines the local lifetime of OH, the most important oxidant in the troposphere. During the AQABA campaign, the total OH reactivity ranged from below the detection limit (5.4 s −1 ) over the northwestern Indian Ocean (Arabian Sea) to a maximum of 32.8±9.6 s −1 over the Arabian Gulf (also known as Persian Gulf) when air originated from large petroleum extraction/processing facilities in Iraq and Kuwait. In the polluted marine regions, OH reactivity was broadly comparable to highly populated urban centers in intensity and composition. The permanent influence of heavy maritime traffic over the seaways of the Red Sea, Gulf of Aden and Gulf of Oman resulted in median OH sinks of 7.9–8.5 s −1 . Due to the rapid oxidation of direct volatile organic compound (VOC) emissions, oxygenated volatile organic compounds (OVOCs) were observed to be the main contributor to OH reactivity around the Arabian Peninsula (9 %–35 % by region). Over the Arabian Gulf, alkanes and alkenes from the petroleum extraction and processing industry were an important OH sink with ∼9 % of total OH reactivity each, whereas NOx and aromatic hydrocarbons ( ∼10 % each) played a larger role in the Suez Canal, which is influenced more by ship traffic and urban emissions. We investigated the number and identity of chemical species necessary to explain the total OH sink. Taking into account ∼100 individually measured chemical species, the observed total OH reactivity can typically be accounted for within the measurement uncertainty (50 %), with 10 dominant trace gases accounting for 20 %–39 % of regional total OH reactivity. The chemical regimes causing the intense ozone pollution around the Arabian Peninsula were investigated using total OH reactivity measurements. Ozone vs. OH reactivity relationships were found to be a useful tool for differentiating between ozone titration in fresh emissions and photochemically aged air masses. Our results show that the ratio of NOx - and VOC-attributed OH reactivity was favorable for ozone formation almost all around the Arabian Peninsula, which is due to NOx and VOCs from ship exhausts and, often, oil/gas production. Therewith, total OH reactivity measurements help to elucidate the chemical processes underlying the extreme tropospheric ozone concentrations observed in summer over the Arabian Basin.

Indirect evidence of the composition of nucleation mode atmospheric particles in the high Arctic

Abstract: Previous long-term observations have shown that nanoparticle formation events are common in the summer-time high Arctic and linked to local photochemical activity. However, current knowledge is limited with respect to the chemical precursors of resulting nanoparticles and the compounds involved in their subsequent growth. Here we report case-study measurements during new particle formation (NPF) events of the particle size distribution (diameter > 7 nm) and for the first time the volatility of monodisperse particles having diameter ≤40 nm, providing indirect information about their composition. Volatility measurements provide indirect evidence that a predominant fraction of the 12 nm particle population is ammoniated sulfates in the summertime high Arctic. Our observations further suggest that the majority of the sub-40 nm particle population during NPF events does not exist in the form of sulfuric acid but rather as partly or fully neutralized ammoniated sulfates.