Subnormalized states and trace-nonincreasing maps

We investigate the set of completely positive, trace-nonincreasing linear maps acting on the set M_N of mixed quantum states of size N. Extremal point of this set of maps are characterized and its volume with respect to the Hilbert-Schmidt (Euclidean) measure is computed explicitly for an arbitrary N. The spectra of partially reduced rescaled dynamical matrices associated with trace-nonincreasing completely positive maps belong to the N-cube inscribed in the set of subnormalized states of size N. As a by-product we derive the measure in M_N induced by partial trace of mixed quantum states distributed uniformly with respect to HS-measure in $M_{N^2}$.Comment: LaTeX, 21 pages, 4 Encapsuled PostScript figures, 1 tabl

Si-atoms substitutions effects on the electronic and optical properties of coronene and ovalene

We report a computational comparative study of the ground and excited states properties of graphene nanoribbons, analyzing the case of coronene (C24H12) and ovalene (C32H14) and their silicon-atoms substituted counterparts with single, double and triple atomic insertions. We used density functional theory (DFT) and time-dependent DFT to quantify the effects on the electronic and optical properties as a result of the chemical modifications. In particular, we compared ground-state total energies, electron affinities, ionization energies, fundamental gaps and optical absorption spectra, between the original systems and each substituted one. For both the molecules, we observed a general reduction of the fundamental gap after chemical modification. Concerning the optical properties, therefore, we observed a redshift of the optical onset in all the cases; in particular, we have found that, in one ovalene and coronene trimer-substituted configuration, the absorption edge takes place in the IR

Polyphenolic C-glucosidic ellagitannins present in oak-aged wine inhibit HIV-1 nucleocapsid protein

HIV-1 nucleocapsid protein (NC) is a nucleic acid chaperone implicated in several steps of the virus replication cycle and an attractive new target for drug development. In reverse transcription, NC destabilizes nucleic acid secondary structures and catalyzes the annealing of HIV-1 TAR RNA to its DNA copy (cTAR) to form the heteroduplex TAR/cTAR. A screening program led to the identification of the plant polyphenols acutissimins A and B as potent inhibitors of NC in different assays. These two flavano-ellagitannins, which are found in wine aged in oak barrels, exhibited different mechanisms of protein inhibition and higher potency relatively to their epimers, epiacutissimins A and B, and to simpler structures notably representing hydrolytic fragments and metabolites therefrom

Huge excitonic effects in layered hexagonal boron nitride

The calculated quasiparticle band structure of bulk hexagonal boron nitride using the all-electron GW approximation shows that this compound is an indirect-band-gap semiconductor. The solution of the Bethe-Salpeter equation for the electron-hole two-particle Green function has been used to compute its optical spectra and the results are found in excellent agreement with available experimental data. A detailed analysis is made for the excitonic structures within the band gap and found that the excitons belong to the Frenkel class and are tightly confined within the layers. The calculated exciton binding energy is much larger than that obtained by Watanabe {\it et al} using a Wannier model to interpret their experimental results and assuming that h-BN is a direct-band-gap semiconductor.Comment: 4 pages, 3 figure

Locomotor-like leg movements evoked by rhythmic arm movements in humans

Motion of the upper limbs is often coupled to that of the lower limbs in human bipedal locomotion. It is unclear, however, whether the functional coupling between upper and lower limbs is bi-directional, i.e. whether arm movements can affect the lumbosacral locomotor circuitry. Here we tested the effects of voluntary rhythmic arm movements on the lower limbs. Participants lay horizontally on their side with each leg suspended in an unloading exoskeleton. They moved their arms on an overhead treadmill as if they walked on their hands. Hand-walking in the antero-posterior direction resulted in significant locomotor-like movements of the legs in 58% of the participants. We further investigated quantitatively the responses in a subset of the responsive subjects. We found that the electromyographic (EMG) activity of proximal leg muscles was modulated over each cycle with a timing similar to that of normal locomotion. The frequency of kinematic and EMG oscillations in the legs typically differed from that of arm oscillations. The effect of hand-walking was direction specific since medio-lateral arm movements did not evoke appreciably leg air-stepping. Using externally imposed trunk movements and biomechanical modelling, we ruled out that the leg movements associated with hand-walking were mainly due to the mechanical transmission of trunk oscillations. EMG activity in hamstring muscles associated with hand-walking often continued when the leg movements were transiently blocked by the experimenter or following the termination of arm movements. The present results reinforce the idea that there exists a functional neural coupling between arm and legs

Care of patients with hemoglobin disorders during the COVID-19 pandemic: An overview of recommendations.

The outbreak of Coronavirus Disease 2019 (COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to a global health emergency.1 Compared to the general population, patients with hemoglobin disorders such as sickle cell disease (SCD) or thalassemia are expected to be more severely affected by COVID-19 due to their preexisting chronic morbidities.2 The Centers for Disease Control and Prevention does not report any specific indications for patients with hemoglobinopathies. However, it can be hypothesized that the rapid spread of the virus may render these patients fragile when fighting the infection. SCD, a hematological condition with functional asplenia, puts patients at a greater risk to develop acute pulmonary complications, including viral infections.2 A study by Hussain et al reported four SCD cases that tested positive for COVID-19.3 These cases initially presented to the emergency department for a typical vaso-occlusive crisis (VOC), and the clinical course of their SARS-CoV-2 infection was rather mild. Patients had a history of respiratory complications, such as acute chest syndrome (ACS), asthma, or pulmonary embolism, which may be potential risk factors for progressive COVID-19 pulmonary disease in patients with SCD.3 A series of isolated cases of ACS in SCD patients positive for COVID-19 has been recently reported.4,5 Therefore, very little clinical experience of infected patients with SCD currently exists. For this reason, we believe that certain recommendations must be followed by healthcare professionals treating any SCD patient infected with SARS-CoV-2