Global Energetics of Solar Flares: III. Non thermal Energies

This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power law slope and flux, and the thermal/nonthermal cross-over energy $e_{\mathrm{co}}$. From these parameters we calculate the total nonthermal energy $E_{\mathrm{nt}}$ in electrons with two different methods: (i) using the observed cross-over energy $e_{\mathrm{co}}$ as low-energy cutoff, and (ii) using the low-energy cutoff $e_{\mathrm{wt}}$ predicted by the warm thick-target bremsstrahlung model of Kontar et al. {\bf Based on a mean temperature of $T_e=8.6$ MK in active regions we find low-energy cutoff energies of $e_{\mathrm{wt}} =6.2\pm 1.6$ keV for the warm-target model, which is significantly lower than the cross-over energies $e_{\mathrm{co}}=21 \pm 6$ keV. Comparing with the statistics of magnetically dissipated energies $E_{\mathrm{mag}}$ and thermal energies $E_{\mathrm{th}}$ from the two previous studies, we find the following mean (logarithmic) energy ratios with the warm-target model: $E_{\mathrm{nt}} = 0.41 \ E_{\mathrm{mag}}$, $E_{\mathrm{th}} = 0.08 \ E_{\mathrm{mag}}$, and $E_{\mathrm{th}} = 0.15 \ E_{\mathrm{nt}}$. The total dissipated magnetic energy exceeds the thermal energy in 95% and the nonthermal energy in 71% of the flare events, which confirms that magnetic reconnection processes are sufficient to explain flare energies. The nonthermal energy exceeds the thermal energy in 85\% of the events, which largely confirms the warm thick-target model.Comment: 34p, 9 Figs., 1 Tabl

The normalization of sibling violence: Does gender and personal experience of violence influence perceptions of physical assault against siblings?

Despite its pervasive and detrimental nature, sibling violence (SV) remains marginalized as a harmless and inconsequential form of familial aggression. The present study investigates the extent to which perceptions of SV differ from those of other types of interpersonal violence. A total of 605 respondents (197 males, 408 females) read one of four hypothetical physical assault scenarios that varied according to perpetrator–victim relationship type (i.e., sibling vs. dating partner vs. peer vs. stranger) before completing a series of 24 attribution items. Respondents also reported on their own experiences of interpersonal violence during childhood. Exploratory factor analysis reduced 23 attribution items to three internally reliable factors reflecting perceived assault severity, victim culpability, and victim resistance ratings. A 4 × 2 MANCOVA—controlling for respondent age—revealed several significant effects. Overall, males deemed the assault less severe and the victim more culpable than did females. In addition, the sibling assault was deemed less severe compared to assault on either a dating partner or a stranger, with the victim of SV rated just as culpable as the victim of dating, peer, or stranger-perpetrated violence. Finally, respondents with more (frequent) experiences of childhood SV victimization perceived the hypothetical SV assault as being less severe, and victim more culpable, than respondents with no SV victimization. Results are discussed in the context of SV normalization. Methodological limitations and applications for current findings are also outlined

Heterogeneous Reductive Isomerization Reaction Using Catalytic Pd/C and H_2

A highly selective catalytic reductive isomerization reaction is described. The extremely mild and neutral reaction conditions (10% Pd/C, H_2, and MeOH at 0 °C) tolerate a wide range of functional groups and generally result in excellent yields. Mechanistic studies suggest that this reaction does not proceed via a stepwise reduction/elimination sequence or a π-allylpalladium intermediate

The Total Synthesis of (+)-Dragmacidin F

The first total synthesis of (+)-dragmacidin F has been accomplished, establishing the absolute configuration of this biologically important, antiviral marine alkaloid. The convergent route described features a palladium-mediated oxidative pyrrole carbocylization reaction to construct the [3.3.1] bicycle, as well as a highly selective Suzuki coupling to build the carbon skeleton of the natural product. A late-stage Neber rearrangement allows for the facile installation of the aminoimidazole moiety to provide (+)-dragmacidin F