225 research outputs found
The multi-scale nature of the solar wind
The solar wind is a magnetized plasma and as such exhibits collective plasma
behavior associated with its characteristic spatial and temporal scales. The
characteristic length scales include the size of the heliosphere, the
collisional mean free paths of all species, their inertial lengths, their
gyration radii, and their Debye lengths. The characteristic timescales include
the expansion time, the collision times, and the periods associated with
gyration, waves, and oscillations. We review the past and present research into
the multi-scale nature of the solar wind based on in-situ spacecraft
measurements and plasma theory. We emphasize that couplings of processes across
scales are important for the global dynamics and thermodynamics of the solar
wind. We describe methods to measure in-situ properties of particles and
fields. We then discuss the role of expansion effects, non-equilibrium
distribution functions, collisions, waves, turbulence, and kinetic
microinstabilities for the multi-scale plasma evolution.Comment: 155 pages, 24 figure
Polytropic Behavior of Solar Wind Protons Observed by Parker Solar Probe
A polytropic process describes the transition of a fluid from one state to
another through a specific relationship between the fluid density and
temperature. The value of the polytropic index that governs this relationship
determines the heat transfer and the effective degrees of freedom during the
process. In this study, we analyze solar wind proton plasma measurements,
obtained by the Faraday cup instrument on-board Parker Solar Probe. We examine
the large-scale variations of the proton plasma density and temperature within
the inner heliosphere explored by the spacecraft. We also address a polytropic
behavior in the density and temperature fluctuations in short-time intervals,
which we analyze in order to derive the effective polytropic index of small
time-scale processes. The large-scale variations of the solar wind proton
density and temperature which are associated with the plasma expansion through
the heliosphere, follow a polytropic model with a polytropic index ~5/3. On the
other hand, the short time-scale fluctuations which may be associated with
turbulence, follow a model with a larger polytropic index. We investigate
possible correlations between the polytropic index of short time-scale
fluctuations and the plasma speed, plasma beta, and the magnetic field
direction. We discuss the scenario of mechanisms including energy transfer or
mechanisms that restrict the particle effective degrees of freedom.Comment: 20 pages, 9 figure
Inside perspective of the synthetic and computational toolbox of JAK inhibitors: Recent updates
The mechanisms of inflammation and cancer are intertwined by complex networks of signaling pathways. Dysregulations in the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway underlie several pathogenic conditions related to chronic inflammatory states, autoimmune diseases and cancer. Historically, the potential application of JAK inhibition has been thoroughly explored, thus triggering an escalation of favorable results in this field. So far, five JAK inhibitors have been approved by the Food and Drug Administration (FDA) for the treatment of different diseases. Considering the complexity of JAK-depending processes and their involvement in multiple disorders, JAK inhibitors are the perfect candidates for drug repurposing and for the assessment of multitarget strategies. Herein we reviewed the recent progress concerning JAK inhibition, including the innovations provided by the release of JAKs crystal structures and the improvement of synthetic strategies aimed to simplify of the industrial scale-up
Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities
We use magnetic helicity to characterise solar wind fluctuations at
proton-kinetic scales from Wind observations. For the first time, we separate
the contributions to helicity from fluctuations propagating at angles
quasi-parallel and oblique to the local mean magnetic field, . We
find that the helicity of quasi-parallel fluctuations is consistent with
Alfv\'en-ion cyclotron and fast magnetosonic-whistler modes driven by proton
temperature anisotropy instabilities and the presence of a relative drift
between -particles and protons. We also find that the helicity of
oblique fluctuations has little dependence on proton temperature anisotropy and
is consistent with fluctuations from the anisotropic turbulent cascade. Our
results show that parallel-propagating fluctuations at proton-kinetic scales in
the solar wind are dominated by proton temperature anisotropy instabilities and
not the turbulent cascade. We also provide evidence that the behaviour of
fluctuations at these scales is independent of the origin and macroscopic
properties of the solar wind.Comment: Accepted for publication in ApJL. 6 Pages, 3 figures, 1 tabl
In silico food-drug interaction: A case study of eluxadoline and fatty meal
Food-drug interaction is an infrequently considered aspect in clinical practice. Usually, drugs are taken together with meals and what follows may adversely affect pharmacokinetic and pharmacodynamic properties, and hence, the therapeutic effects. In this study, a computational protocol was proposed to explain the different assimilations of two µ-receptors agonists, eluxadoline and loperamide, with a peculiar pharmacokinetic profile. Compared to loperamide, eluxadoline is absorbed less after the intake of a fatty meal, and the LogP values do not explain this event. Firstly, keeping in mind the different pH in the intestinal tract, the protonation states of both compounds were calculated. Then, all structures were subjected to a conformational search by using MonteCarlo and Molecular Dynamics methods, with solvation terms mimicking the water and weak polar solvent (octanol). Both computational results showed that eluxadoline has less conformational freedom in octanol, unlike loperamide, which exhibits constant behavior in both solvents. Therefore, we hypothesize that fatty meal causes the “closure” of the eluxadoline molecule to prevent the exposure of the polar groups and their interaction with water, necessary for the drug absorption. Based on our results, this work could be a reasonable “case study”, useful for future investigation of the drug pharmacokinetic profile
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