The packing of granular polymer chains

Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here we study the disordered packing of chains constructed out of flexibly-connected hard spheres. Using X-ray tomography, we find long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly-oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally we uncover close similarities between the packing of chains and the glass transition in polymers.Comment: 11 pages, 4 figure

Potential Influences of Volcanic Eruptions on Future Global Land Monsoon Precipitation Changes

The global monsoon system is of exceptional socioeconomic importance owing to its impacts on two-thirds of the globe’s population. Major volcanic eruptions strongly influence global land monsoon (GLM) precipitation change. By using 60 plausible eruption scenarios sampled from reconstructed volcanic proxies over the past 2,500 years, 21st century volcanic influences on GLM precipitation projections are examined with an Earth system model under a moderate emission scenario. The decadal-scale ensemble spread with realistic eruptions (VOLC) increases by 17.5% and 20.1% compared to no-volcanic (NO-VOLC) and constant background-volcanic (VOLC-CONST) scenarios, respectively. Compared with NO-VOLC, the centennial mean VOLC GLM precipitation shows a 10% overall reduction and regionally, Asia is the most impacted. Changes in atmospheric circulation in the aftermath of large volcanic eruptions match the global warming response patterns well with opposite sign, with the North American monsoon precipitation enhanced following large volcanic eruptions, which is in sharp contrast to the robust decrease in Asian monsoon rainfall. Volcanic activity could delay the time of emergence of anthropogenic influence by five years on average over about 60% of the GLM area. Our results demonstrate the importance of statistical representation of potential volcanism for the projections of future monsoon variability. Quantifying volcanic impacts on regional climate projections and their socioeconomic influences on infrastructure planning, food security, and disaster management should be a priority of future work.publishedVersio

Increased Numbers of NK Cells, NKT-Like Cells, and NK Inhibitory Receptors in Peripheral Blood of Patients with Chronic Obstructive Pulmonary Disease

T cells and B cells participate in the pathogenesis of COPD. Currently, NK cells and NKT cells have gained increasing attention. In the present study, 19 COPD patients and 12 healthy nonsmokers (HNS) were recruited, and their pulmonary function was assessed. The frequencies of CD3+ T, CD4+ T, CD8+ T, B, NK, and NKT-like cells were determined using flow cytometry. The frequencies of spontaneous and inducible IFN-γ+ or CD107a+ NK and NKT-like cells as well as activating or inhibitory receptors were also detected. The potential association of lymphocyte subsets with disease severity was further analyzed. Significantly decreased numbers of CD3+ and CD4+ T cells, and the CD4+/CD8+ ratio, but increased numbers of CD3−CD56+ NK and CD3+CD56+ NKT-like cells were observed in COPD patients compared to HNS. The frequencies of inducible IFN-γ-secreting NK and NKT-like cells were less in COPD patients. The frequencies of CD158a and CD158b on NK cells and CD158b on NKT-like cells were greater. The frequency of CD158b+ NK cells was negatively correlated with FEV1% prediction and FEV1/FVC. Our data indicate that COPD patients have immune dysfunction, and higher frequencies of inhibitory NK cells and NKT-like cells may participate in the pathogenesis of COPD

Evolution characteristics of overburden structure and stress in strong mining of the deep coal seam: a case study

As coal resources are gradually being extracted at depth, the overlying strata movement behavior and stress environment become complex and violent, leading to the frequent triggering of strong dynamic hazards. To promote the productivity and effectiveness of mining activities, this paper investigated the evolution characteristics of overburden structure and stress in deep mining by using theoretical analysis, on-site monitoring, and numerical simulation. Based on key strata theory, key layers were determined, and how their movement states have a controlling effect on surface subsidence was analyzed. The evolution process of the overburden spatial structure in deep mining was revealed, which was consistent with the “O-X” type structure. The surrounding rock stress at the working face has gone through three stages, violent change, slow increase, and fluctuant increase, and strong strata behaviors appear because of the fracture and collapse of key layers. The goaf will have a significant effect on the structure, stress, and deformation of the overlying rock, which results in a larger deformation of the surrounding rock within the vicinity. The narrow coal pillar fails to maintain the stability of the overburden structure when the stress exceeds the bearing capacity. The deformation law of the surrounding rock at the roadway was studied, concluding that the existence of the goaf leads to a further increase in deformation