Copper‐Catalyzed Enantio‐ and Diastereoselective Addition of Silicon Nucleophiles to 3,3‐Disubstituted Cyclopropenes

A highly stereocontrolled syn‐addition of silicon nucleophiles across cyclopropenes with two different geminal substituents at C3 is reported. Diastereomeric ratios are excellent throughout (d.r.≥98:2) and enantiomeric excesses usually higher than 90 %, even reaching 99 %. This copper‐catalyzed C−Si bond formation closes the gap of the direct synthesis of α‐chiral cyclopropylsilanes.TU Berlin, Open-Access-Mittel - 201

Shape, Thermal and Surface Properties determination of a Candidate Spacecraft Target Asteroid (175706) 1996 FG3

In this paper, a 3D convex shape model of (175706) 1996 FG3, which consists of 2040 triangle facets and 1022 vertices, is derived from the known lightcurves. The best-fit orientation of the asteroid's spin axis is determined to be $\lambda =237.7^\circ$ and $\beta=-83.8^{\circ}$ considering the observation uncertainties, and its rotation period is $\sim$ 3.5935 h . Using the derived shape model, we adopt the so-called advanced thermophysical model (ATPM) to fit three published sets of mid-infrared observations of 1996 FG3 \citep{Wolters2011,Walsh2012}, so as to evaluate its surface properties. Assuming the primary and the secondary bear identical shape, albedo, thermal inertia and surface roughness, the best-fit parameters are obtained from the observations. The geometric albedo and effective diameter of the asteroid are reckoned to be $p_{\rm v}=0.045\pm0.002$, $D_{\rm eff}=1.69^{+0.05}_{-0.02}$ km. The diameters of the primary and secondary are determined to be $D_{1}=1.63^{+0.04}_{-0.03}$ km and $D_{2}=0.45^{+0.04}_{-0.03}$ km, respectively. The surface thermal inertia $\Gamma$ is derived to be a low value of $80\pm40\rm Jm^{-2}s^{-0.5}K^{-1}$ with a roughness fraction $f_{\rm R}$ of $0.8^{+0.2}_{-0.4}$. This indicates that the primary possibly has a regolith layer on its surface, which is likely to be covered by a mixture of dust, fragmentary rocky debris and sand. The minimum regolith depth is estimated to be $5\sim20\rm mm$ from the simulations of subsurface temperature distribution, indicating that 1996 FG3 could be a very suitable target for a sample return mission.Comment: 15 pages, 11 figures, 9 tables, accepted to MNRA

Banking reforms, performance and risk in China

We investigate the impact of the banking reform started from 2005 on ownership structures in China on commercial banks’ profitability, efficiency and risk over the period 2000–2012, providing comprehensive evidence on the impact of banking reform in China. We find that banks on average tend to have higher profitability, lower risk and lower efficiency after the reforms, and the results are robust with our difference-in-difference approach. Our results also show that the Big 5 state-owned banks (SOCB) underperform banks with other types of ownership when risk is measured by non-performing loans (NPLs) over the entire study period but tend to have fewer NPLs than other banks during the post-reform period. Our results provide some supporting evidence on the ongoing banking reforms in China, suggesting that attracting strategic foreign investors and listing SOCBs on stock exchanges appear to be effective ways to help SOCBs deal with the problem of NPLs and manage their risk

Video2GIF: Automatic Generation of Animated GIFs from Video

We introduce the novel problem of automatically generating animated GIFs from video. GIFs are short looping video with no sound, and a perfect combination between image and video that really capture our attention. GIFs tell a story, express emotion, turn events into humorous moments, and are the new wave of photojournalism. We pose the question: Can we automate the entirely manual and elaborate process of GIF creation by leveraging the plethora of user generated GIF content? We propose a Robust Deep RankNet that, given a video, generates a ranked list of its segments according to their suitability as GIF. We train our model to learn what visual content is often selected for GIFs by using over 100K user generated GIFs and their corresponding video sources. We effectively deal with the noisy web data by proposing a novel adaptive Huber loss in the ranking formulation. We show that our approach is robust to outliers and picks up several patterns that are frequently present in popular animated GIFs. On our new large-scale benchmark dataset, we show the advantage of our approach over several state-of-the-art methods.Comment: Accepted to CVPR 201

What mechanisms dominate the activity of Geminid Parent (3200) Phaethon?

A long-term sublimation model to explain how Phaethon could provide the Geminid stream is proposed. We find that it would take $\sim6$ Myr or more for Phaethon to lose all of its internal ice (if ever there was) in its present orbit. Thus, if the asteroid moved from the region of a 5:2 or 8:3 mean motion resonance with Jupiter to its present orbit less than $1$ Myr ago, it may have retained much of its primordial ice. The dust mantle on the sublimating body should have a thickness of at least $15$ m but the mantle could have been less than $1$ m thick $1000$ years ago. We find that the total gas production rate could have been as large as $10^{27}\rm~s^{-1}$ then, and the gas flow could have been capable of lifting dust particles of up to a few centimeters in size. Therefore, gas production during the past millennium could have been sufficient to blow away enough dust particles to explain the entire Geminid stream. For present-day Phaethon, the gas production is comparatively weak. But strong transient gas release with a rate of $\sim4.5\times10^{19}\rm~m^{-2}s^{-1}$ is expected for its south polar region when Phaethon moves from $0^\circ$ to $2^\circ$ mean anomaly near perihelion. Consequently, dust particles with radii of $<\sim260~\mu m$ can be blown away to form a dust tail. In addition, we find that the large surface temperature variation of $>600$ K near perihelion can generate sufficiently large thermal stress to cause fracture of rocks or boulders and provide an efficient mechanism to produce dust particles on the surface. The time scale for this process should be several times longer than the seasonal thermal cycle, thereby dominating the cycle of appearance of the dust tail.Comment: 10 pages, 5 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ