Triple hourglass Weyl phonons

Unconventional Weyl phonons with higher topological charges in crystalline solids have attracted increasing attention. By symmetry analysis and low-energy $k.p$ effective Hamiltonian, we propose the symmetry enforced triple hourglass Weyl phonons (THWPs) with Chern number $\mathcal C$ = $\pm$ 3 protected by $6_3$ screw rotation symmetry in chiral space groups 173 ($P6_3$) and 182 ($P6_322$). We take LiIO$_3$ with space group 173 as a candidate and confirm that it possesses THWP with linear and quadratic dispersions along the $k_z$ direction and in the $k_x$-$k_y$ plane, respectively. Due to the constraints of crystal symmetry and topological charge conservation, six equivalent single Weyl phonons (SWPs) emerge and lie in the $k_z$ = 0 plane. Therefore, the unique phonon surface arcs connect the projections of two THWPs and six SWPs, leading to nontrivial sextuple-helicoid surface arcs on the (001) surface Brillouin zone. Our work proposes a class of topological phonons and realizes it in realistic materials, providing a perfect platform for experimental observation of THWPs. We expect our work to provide a new idea for detection of unconventional quasiparticles.Comment: 11 pages, 7 figure

Structural Repertoire of HIV-1-Neutralizing Antibodies Targeting the CD4 Supersite in 14 Donors

The site on the HIV-1 gp120 glycoprotein that binds the CD4 receptor is recognized by broadly reactive antibodies, several of which neutralize over 90% of HIV-1 strains. To understand how antibodies achieve such neutralization, we isolated CD4-binding-site (CD4bs) antibodies and analyzed 16 co-crystal structures –8 determined here– of CD4bs antibodies from 14 donors. The 16 antibodies segregated by recognition mode and developmental ontogeny into two types: CDR H3-dominated and VH-gene-restricted. Both could achieve greater than 80% neutralization breadth, and both could develop in the same donor. Although paratope chemistries differed, all 16 gp120-CD4bs antibody complexes showed geometric similarity, with antibody-neutralization breadth correlating with antibody-angle of approach relative to the most effective antibody of each type. The repertoire for effective recognition of the CD4 supersite thus comprises antibodies with distinct paratopes arrayed about two optimal geometric orientations, one achieved by CDR H3 ontogenies and the other achieved by VH-gene-restricted ontogenies

Effect of Temperature on Densification Pressure and the Unit Density in Production of Corn Straw Pellet with a Post-Heating Method

In the biomass densification process, a lot of energy is needed to prevent its spring-back and to overcome the friction between the material and the channel surface of the die so as to build up pressure. However, moisture, particle size, temperature, and type of material all influence the densification pressure, pellet quality, and the density. The research was aimed to find out how the densification pressure and density were affected by the die temperature based on an open-end densification method using a self-developed pellet extruder. When the piston fixed in the front of the extruder moved in a reciprocating way, the raw material was pressed into the opening die, which had a heater wrapped up. Crushed corn straw with a particle size under 4 mm and with a given moisture content of 10% was used to be compacted by the extruder. The results showed that with the increase of the die temperature, the value of densification pressure decreased; however, the quality of pellets was not good at temperatures higher than 140 °C. The proper temperature for corn straw densification was 100 °C, and the value of the unit density was above 1.0 g/cm³. Meanwhile, the surface quality of the pellet was comparatively good. The reference values of the friction coefficient at different temperatures were provided

Effect of Temperature on Densification Pressure and the Unit Density in Production of Corn Straw Pellet with a Post-Heating Method

In the biomass densification process, a lot of energy is needed to prevent its spring-back and to overcome the friction between the material and the channel surface of the die so as to build up pressure. However, moisture, particle size, temperature, and type of material all influence the densification pressure, pellet quality, and the density. The research was aimed to find out how the densification pressure and density were affected by the die temperature based on an open-end densification method using a self-developed pellet extruder. When the piston fixed in the front of the extruder moved in a reciprocating way, the raw material was pressed into the opening die, which had a heater wrapped up. Crushed corn straw with a particle size under 4 mm and with a given moisture content of 10% was used to be compacted by the extruder. The results showed that with the increase of the die temperature, the value of densification pressure decreased; however, the quality of pellets was not good at temperatures higher than 140 °C. The proper temperature for corn straw densification was 100 °C, and the value of the unit density was above 1.0 g/cm³. Meanwhile, the surface quality of the pellet was comparatively good. The reference values of the friction coefficient at different temperatures were provided

Influencing Factors of Cutting Force for Apple Tree Branch Pruning

Apple, which occupies the first position in the world with regard to its yield, is an important economic crop in China. Pruning of apple trees is still dominated by manual pruning, resulting in high labor costs and low efficiency. Additionally, there are some limitations with pruning machines. Thus, research regarding the mechanical properties of apple branches is the basis for the designing proper pruning machine. This paper aims to study the effect of the feed rate, cutting line speed, branch diameter, and moisture content on the cutting force. Results revealed that cutting force depended on the feed rate, cutting line speed, and branch diameter. Furthermore, both the cutting line speed and the branch diameter had a significant effect on the cutting force (p p > 0.05). However, the moisture content had no effect on the cutting force, with a difference of cutting force between samples with moisture content of 15% and 50% less than 5%. Based on the experiments performed, an equation relating the feed rate, the cutting line speed, the branch diameter was derived to calculate the cutting force. By verification test, it established that regression equation was valid with error less than 4%. This study explored the mechanical properties of apple branch, and obtained the optimal cutting parameters, which can provide a reference for the design of the pruning machine