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[1] While the Mars upper atmosphere is continuously bombarded by charged particles of solar and planetary origins, the energy flux carried is often not sufficient to significantly affect the neutral atmosphere. However, we show that this is not the case during major space weather events. By applying two Mars global models-a Monte Carlo model for simulating pickup O + precipitation at the exobase and a thermosphere-ionosphere model for assessing its global impact, we find that the thermospheric effects of reentering ions can change from negligible to very important when upstream solar wind conditions vary from normal to extreme. The atmospheric response under the most extreme conditions includes dramatic neutral temperature enhancement, significant neutral composition and wind changes, and increased importance of sputtering loss and possibly even thermal escape of heavy species. Citation: Fang, X.,

Sputtering of the Martian atmosphere by O+pickup ions has been proposed as a potentially important process in the early evolution of the Martian atmosphere. In preparation for the Mars Atmosphere and Volatile Evolution (MAVEN) mission, we performed a study using a Monte Carlo model coupled to a molecular dynamic calculation to investigate the cascade sputtering effects in the region of the Martian exobase. Pickup ion fluxes based on test particle simulations in an MHD model for three different solar wind conditions are used to examine the local and global sputtering efficiencies. The resultant sputtering escape rate is 2×1024 s−1 at nominal solar wind condition and can be enhanced about 50 times when both the interplanetary magnetic field (IMF) strength and the solar wind pressure increase. It is found that when the IMF strength becomes stronger, both the pickup ion precipitation energies and the resultant sputtering efficiencies increase. The related escape flux, hot component, and atmospheric energy deposition deduced from the MAVEN measurements may reveal clues about the prominent enhanced sputtering effects. Significant hemispheric asymmetries can be observed related to the solar wind electric fields. The shielding by the crustal fields and the recycling onto the nightside due to different magnetic field draping features can also lead to regional variations of sputtering efficiencies. The results suggest that disturbed or enhanced solar wind conditions provide the best prospects for detecting sputtering effects for MAVEN mission.

Herein, we report a new series of bifunctional chelators (BFCs) with a high affinity for amyloid aggregates, a strong binding affinity toward Cu­(II), and favorable lipophilicity for potential blood–brain barrier penetration. The alkyl carboxylate ester pendant arms offer up to 3 orders of magnitude higher binding affinity toward Cu­(II) and enable the BFCs to form stable 64Cu-radiolabeled complexes. Among the five compounds tested, the 64Cu-YW-7 and 64Cu-YW-10 complexes exhibit strong and specific staining of amyloid plaques in ex vivo autoradiography studies. Importantly, these BFCs have promising partition coefficient (log D oct) values of 0.91–1.26 and show some brain uptake in biodistribution studies using CD-1 mice. Overall, these BFCs could serve as lead compounds for the development of positron emission tomography imaging agents for AD diagnosis.

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