Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults

The Facet of Human Impact: Solenopsis invicta Buren, 1972 Spreading around the Atlantic Forest

The present investigation deals with some aspects of the diversity of fire ants (Hymenoptera: Formicidae) in their native range. The Red Imported Fire Ant Solenopsis invicta is native to the tropical and subtropical inland territories of South America. In Brazil, it mainly occurs around the Pantanal region and across the Paraguay river, a region composed of grasslands which are seasonally flooded. Recent studies have evidenced this fire ant species is gradually spreading to other regions of Brazil. In the present investigation, we surveyed the molecular diversity of S. invicta populations across fragments of Atlantic Forest in Sao Paulo, Brazil, using mtDNA COI haplotypes. Fire ant nests were sampled along the highways lining the northern and southern slope sides of the mountain range Serra do Mar, SP, Brazil. Four haplotypes were identified (H1-H4), which were assessed for similarity to deposited records by other authors, revealing that the haplotypes H1 and H2 are likely of foreign origin through recent reintroduction via a marine port to the south of the Serra do Mar mountain range. On the other hand, the haplotypes H3 and H4, predominating among the inland samples from the northern side of the mountain range, were most similar to previous records from more central regions of Brazil. Haplotypes clustered into distinct supergroups, further pointing to the occurrence of two separate expansion waves of S. invicta in the region. We suggest the obtained pattern indicates the mountain range may function as a geographical barrier deferring gene flow

Asymmetric nuclear motion of the F 1s–ionized state in BF3 probed by quadruple-ion-coincidence momentum imaging

Using the quadruple-ion-coincidence momentum imaging technique, we find that the momentum correlation of the four atomic ions departed from one BF34+ parent molecular ion produced via multiple Auger decay after F 1s ionization exhibits asymmetric fragmentation in which the B+ ion is ejected in the direction opposite to one of the F+ ions. This observation provides evidence of symmetry lowering, from D3h to C3v in the F 1s–ionized state

Search for dinucleon decay into pions at Super-Kamiokande

A search for dinucleon decay into pions with the Super-Kamiokande detector has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is a process that violates baryon number by two units. We present the first search for dinucleon decay to pions in a large water Cherenkov detector. The modes $^{16}$O$(pp) \rightarrow$ $^{14}$C$\pi^{+}\pi^{+}$, $^{16}$O$(pn) \rightarrow$ $^{14}$N$\pi^{+}\pi^{0}$, and $^{16}$O$(nn) \rightarrow$ $^{14}$O$\pi^{0}\pi^{0}$ are investigated. No significant excess in the Super-Kamiokande data has been found, so a lower limit on the lifetime of the process per oxygen nucleus is determined. These limits are: $\tau_{pp\rightarrow\pi^{+}\pi^{+}} > 7.22 \times 10^{31}$ years, $\tau_{pn\rightarrow\pi^{+}\pi^{0}} > 1.70 \times 10^{32}$ years, and $\tau_{nn\rightarrow\pi^{0}\pi^{0}} > 4.04 \times 10^{32}$ years. The lower limits on each mode are about two orders of magnitude better than previous limits from searches for dinucleon decay in iron.Comment: 20 pages, 17 figures. Accepted for publication in Physical Review D on March 30, 201

The uronic acid content of coccolith-associated polysaccharides provides insight into coccolithogenesis and past climate

Unicellular phytoplanktonic algae (coccolithophores) are among the most prolific producers of calcium carbonate on the planet, with a production of ∼1026 coccoliths per year. During their lith formation, coccolithophores mainly employ coccolith-associated polysaccharides (CAPs) for the regulation of crystal nucleation and growth. These macromolecules interact with the intracellular calcifying compartment (coccolith vesicle) through the charged carboxyl groups of their uronic acid residues. Here we report the isolation of CAPs from modern day coccolithophores and their prehistoric predecessors and we demonstrate that their uronic acid content (UAC) offers a species-specific signature. We also show that there is a correlation between the UAC of CAPs and the internal saturation state of the coccolith vesicle that, for most geologically abundant species, is inextricably linked to carbon availability. These findings suggest that the UAC of CAPs reports on the adaptation of coccolithogenesis to environmental changes and can be used for the estimation of past CO2 concentrations