Reversible Pressure-Induced Amorphization in Solid C70 : Raman and Photoluminescence Study

We have studied single crystals of $C_{70}$ by Raman scattering and photoluminescence in the pressure range from 0 to 31.1 GPa. The Raman spectrum at 31.1 GPa shows only a broad band similar to that of the amorphous carbon without any trace of the Raman lines of $C_{70}$. After releasing the pressure from 31.1 GPa, the Raman and the photoluminescence spectra of the recovered sample are that of the starting $C_{70}$ crystal. These results indicate that the $C_{70}$ molecules are stable upto 31.1 GPa and the amorphous carbon high pressure phase is reversible, in sharp contrast to the results on solid $C_{60}$. A qualitative explaination is suggested in terms of inter- versus intra-molecular interactions.Comment: To appear in Phys. Rev. Lett., 12 pages, RevTeX (preprint format), 3 figures available upon reques

Global WEIRDing: Transitions in Wild Plant Knowledge and Treatment Preferences in Congo Hunter-Gatherers

Cultures around the world are converging as populations become more connected. On the one hand this increased connectedness can promote the recombination of existing cultural practices to generate new ones, but on the other it may lead to the replacement of traditional practices and global WEIRDing. Here we examine the process and causes of changes in cultural traits concerning wild plant knowledge in Mbendjele BaYaka hunter–gatherers from Congo. Our results show that the BaYaka who were born in town reported knowing and using fewer plants than the BaYaka who were born in forest camps. Plant uses lost in the town-born BaYaka related to medicine. Unlike the forest-born participants, the town-born BaYaka preferred Western medicine over traditional practices, suggesting that the observed decline of plant knowledge and use is the result of replacement of cultural practices with the new products of cumulative culture

Pressure effects on single wall carbon nanotube bundles

We report high pressure Raman studies on single wall carbon nanotube bundles under hydrostatic conditions using two different pressure transmitting media, alcohol mixture and pure water. The radial and tangential modes show a blue shift when SWNT bundle is immersed in the liquids at ambient pressures. The pressure dependence of the radial modes is the same in both liquids. However, the pressure derivatives dω/dP of the tangential modes are slightly higher for the water medium. Raman results are compared with studies under non-hydrostatic conditions and with recent high-pressure X-ray studies. It is seen that the mode frequencies of the recovered sample after pressure cycling from 26 GPa are downshifted by ~7-10 cm−1 as compared to the starting sample

Pressure-induced phase transformation and structural resilience of single-wall carbon nanotube bundles

We report here an in situ X-ray diffraction investigation of the structural changes in carbon single-wall nanotube bundles under quasihydrostatic pressures up to 13 GPa. In contrast with a recent study [Phys. Rev. Lett. 85, 1887 (2000)] our results show that the triangular lattice of the carbon nanotube bundles continues to persist up to ~10 GPa. The lattice is seen to relax just before the phase transformation that is observed at ~10 GPa. Further, our results display the reversibility of the two-dimensional lattice symmetry even after compression up to 13 GPa well beyond the 5 GPa value observed recently. These experimental results explicitly validate the predicted remarkable mechanical resilience of the nanotubes

High precision temperature controlling AGPase in wheat affecting yield and quality traits

Adenosine diphosphate glucose pyrophosphorylase (AGPase) is the rate limiting enzyme of starch biosynthesis that directly affects the wheat productivity. AGPase and grain growth rate (GGR) discerned to be following strict temperature regimen in wheat disomic chromosome substitution (DCS) lines. The first half of grain filling period had chromosome 1B and 2D as prominent players, whereas second half was mainly controlled by chromosomes 6A and 5B. Chromosome 2D had major contribution towards yield in a specific temperature range of 23 ± 1.5 °C during initial stages of grain filling which can serve as an effective early screening tool for terminal heat tolerance in wheat. Chromosome 2D with highest amylose content can also be utilized to produce low digestibility flour. Grain yield was found to be significantly associated with spikes/plant, grains/spike, grain weight/spike and plant biomass. Further, path analysis indicated that though grains/spike had less direct effect on grain yield but its indirect impact on grain yield via AGPase-21 activity was high

Differential and temperature dependent regulation of ADP-glucose pyrophosphorylase by specific chromosome in wheat grains

A stock of disomic chromosome substitution (DCS) lines having specific chromosome of wheat variety C591 substituted in the background of rest of Chinese spring chromosomes, were used to analyze grain yield components as a function of enzyme activity of ADP–glucose pyrophosphorylase (AGPase), a starch biosynthesis enzyme in wheat grains. Associations between yield characteristics, grain growth rate (GGR) and AGPase enzyme activity of DCS lines suggested a major involvement of chromosome 3A, 4B, 7D and 2D in a temperature dependent manner. Assessment of AGPase assay at different developmental stages such as 14, 21, 28 days post anthesis (DPA) embodied that gene(s) for this enzyme are present on specific chromosomes and operate at different stages of grain development. The DCS line with 7D chromosome has a major contribution in determining the grain starch content. In this line, AGPase enzyme activity was highest at 21 DPA and was the most crucial determinant in its high GGR. Line 4B performed well at only early stage (14 DPA) suggesting that line 4B AGPase requires a lower temperature range for activation as compared to 7D line. Line 3A had substantially reduced (40%) test weights revealing the presence of few down-regulatory elements on chromosome 3A to reduce the activity of AGPase. The DCS line 2D showed higher test weights and grain number than all other lines ascribed to a consistent AGPase activity along with an efficient mechanism for translocation of photosynthates from source to sink. The chromosome 2D shows positive relation with yield attributes therefore, it can be employed to improve wheat productivity via analytical breeding programme

Thermal Stabilization of the HCP Phase in Titanium

We have used a tight-binding model that is fit to first-principles electronic-structure calculations for titanium to calculate quasi-harmonic phonons and the Gibbs free energy of the hexagonal close-packed (hcp) and omega crystal structures. We show that the true zero-temperature ground-state is the omega structure, although this has never been observed experimentally at normal pressure, and that it is the entropy from the thermal population of phonon states which stabilizes the hcp structure at room temperature. We present the first completely theoretical prediction of the temperature- and pressure-dependence of the hcp-omega phase transformation and show that it is in good agreement with experiment. The quasi-harmonic approximation fails to adequately treat the bcc phase because the zero-temperature phonons of this structure are not all stable

“I know my body better than anyone else” Perspectives of people who inject drugs on antimicrobial treatment decision making for serious infections

Introduction: • Few studies have examined the perspectives of patients with lived experience regarding outpatient treatment options for injection drug use (IDU) associated infections. • We sought to better understand the perspectives of both community partners with lived experience who work with people who inject drugs (PWID) and hospitalized patients with IDU-associated infections on shared treatment decision making.https://knowledgeconnection.mainehealth.org/lambrew-retreat-2023/1009/thumbnail.jp