The Khazars as ‘Sons of Abraham’

The accounts of Ibn Sa‘d, Ibn al-Faqîh and al-Tabarî, going back to Hišâm ibn al-Kalbî (late eighth-early ninth century), a contemporary of one of the culminating stages in the conversion of the Khazars to Judaism, are pious legends put forward to claim a link of the Khazars directly to Abraham’s (Arab) descendants in Khurâsân. Although these tales are Arabo-Muslim in origin, it is likely that a connection of the Khazars with Abraham would have found a receptive audience in a Judeo-Khazar milieu The tale also hints at the origins of the qağanal title among the Khazars, giving it a Biblical pedigree and hence sacral authority that would be understandable and acceptable to the Arabo-Muslim world with which the Khazars had developed significant commercial ties.Сообщения Ибн Са‘да, Ибн ал-Факиха и ат-Табари, опиравшиеся на сведения, почерпнутые из трудов Хишам ибн ал-Кальби (ум. ок. 819/820 г.), современника одного из кульминационных этапов принятия хазарами иудаизма, в сущности являются благочестивыми легендами, выдвинутыми для того, чтобы предъявить претензии на непосредственную, родственную связь хазар с (арабскими) потомками библейского Авраама. Несмотря на то, что эти легенды возводятся к мусульманским источникам, выдвинутая ими связь хазар с Авраамом нашла бы восприимчивую публику в иудейско-хазарской среде. Эти легенды также намекают на происхождение каганского титула у хазар, придавая ему библейскую родословную и тем самым сакральный авторитет, приемлемый арабско-мусульманскому миру, с которым Хазария развивала значительные к тому времени торговые связи

Thermal and Evolved Gas Behavior of Calcite Under Mars Phoenix TEGA Operating Conditions

The Mars Phoenix Scout Mission with its diverse instrument suite successfully examined several soils on the Northern plains of Mars. The Thermal and Evolved Gas Analyzer (TEGA) was employed to detect organic and inorganic materials by coupling a differential scanning calorimeter (DSC) with a magnetic-sector mass spectrometer (MS). Martian soil was heated up to 1000 C in the DSC ovens and evolved gases from mineral decomposition products were examined with the MS. TEGA s DSC has the capability to detect endothermic and exothermic reactions during heating that are characteristic of minerals present in the Martian soil. Initial TEGA results indicated the presence of endothermic peaks with onset temperatures that ranged from 675 C to 750 C with corresponding CO2 release. This result suggests the presence of calcite (CaCO3. CaO + CO2). Organic combustion to CO2 is not likely since this mostly occurs at temperatures below 550 C. Fe-carbonate and Mg-carbonate are not likely because their decomposition temperatures are less than 600 C. TEGA enthalpy determinations suggest that calcite, may occur in the Martian soil in concentrations of approx.1 to 5 wt. %. The detection of calcite could be questioned based on previous results that suggest Mars soils are mostly acidic. However, the Phoenix landing site soil pH was measured at pH 8.3 0.5, which is typical of terrestrial soils where pH is controlled by calcite solubility. The range of onset temperatures and calcite concentration as calculated by TEGA is poorly con-strained in part because of limited thermal data of cal-cite at reduced pressures. TEGA operates at <30 mbar while most calcite literature thermal data was obtained at 1000 mbar or higher pressures

Crystal structure of the CRISPR RNA–guided surveillance complex from Escherichia coli

Clustered regularly interspaced short palindromic repeats (CRISPRs) are essential components of RNA-guided adaptive immune systems that protect bacteria and archaea from viruses and plasmids. In Escherichia coli, short CRISPR-derived RNAs (crRNAs) assemble into a 405-kilodalton multisubunit surveillance complex called Cascade (CRISPR-associated complex for antiviral defense). Here we present the 3.24 angstrom resolution x-ray crystal structure of Cascade. Eleven proteins and a 61-nucleotide crRNA assemble into a seahorse-shaped architecture that binds double-stranded DNA targets complementary to the crRNA-guide sequence. Conserved sequences on the 3' and 5' ends of the crRNA are anchored by proteins at opposite ends of the complex, whereas the guide sequence is displayed along a helical assembly of six interwoven subunits that present five-nucleotide segments of the crRNA in pseudo–A-form configuration. The structure of Cascade suggests a mechanism for assembly and provides insights into the mechanisms of target recognition