35 research outputs found
Experimental Study of the Nematic Transition in Granular Spherocylinder Packings under Tapping
Using x-ray tomography, we experimentally investigate the nematic transition
in granular spherocylinder packings induced by tapping. Upon the validation of
the Edwards ensemble framework in spherocylinders, we introduce an empirical
free energy that accounts for the influence of gravity and the mechanical
stability requirements specific to granular systems. This free energy can
predict not only the correct phase transition behavior of the system from a
disordered state to a nematic phase, but also a phase coexistence range and
nucleation energy barriers that agree with experimental observations.Comment: 19 pages, 5 figure
Translational and rotational dynamical heterogeneities in granular systems
We use X-ray tomography to investigate the translational and rotational
dynamical heterogeneities of a three dimensional hard ellipsoids granular
packing driven by oscillatory shear. We find that particles which translate
quickly form clusters with a size distribution given by a power-law with an
exponent that is independent of the strain amplitude. Identical behavior is
found for particles that are translating slowly, rotating quickly, or rotating
slowly. The geometrical properties of these four different types of clusters
are the same as those of random clusters. Different cluster types are
considerably correlated/anticorrelated, indicating a significant coupling
between translational and rotational degrees of freedom. Surprisingly these
clusters are formed already at time scales that are much shorter than the
relaxation time, in stark contrast to the behavior found in
glass-forming systems.Comment: 9 page
Genome-wide characterization of the auxin response factor (ARF) gene family of litchi (Litchi chinensis Sonn.): phylogenetic analysis, miRNA regulation and expression changes during fruit abscission
Auxin response factors (ARFs) play fundamental roles in modulating various biological processes including fruit development and abscission via regulating the expression of auxin response genes. Currently, little is known about roles of ARFs in litchi (Litchi chinensis Sonn.), an economically important subtropical fruit tree whose production is suffering from fruit abscission. In this study, a genome-wide analysis of ARFs was conducted for litchi, 39 ARF genes (LcARFs) were identified. Conserved domain analysis showed that all the LcARFs identified have the signature B3 DNA-binding (B3) and ARF (Aux_rep) domains, with only 23 members having the dimerization domain (Aux_IAA). The number of exons in LcARF genes ranges from 2 to 16, suggesting a large variation for the gene structure of LcARFs. Phylogenetic analysis showed that the 39 LcARFs could be divided into three main groups: class I, II, and III. In total, 23 LcARFs were found to be potential targets of small RNAs, with three conserved and one novel miRNA-ARF (miRN43-ARF9) regulatory pathways discovered in litchi. Expression patterns were used to evaluate candidate LcARFs involved in various developmental processes, especially in flower formation and organ abscission. The results revealed that most ARF genes likely acted as repressors in litchi fruit abscission, that is, ARF2D/2E, 7A/7B, 9A/9B, 16A/16B, while a few LcARFs, such as LcARF5A/B, might be positively involved in this process. These findings provide useful information and resources for further studies on the roles of ARF genes in litchi growth and development, especially in the process of fruit abscission
Origin of Non-cubic Scaling Law in Disordered Granular Packing
Recent diffraction experiments on metallic glasses have unveiled an
unexpected non-cubic scaling law between density and average interatomic
distance, which lead to the speculations on the presence of fractal glass
order. Using X-ray tomography we identify here a similar non-cubic scaling law
in disordered granular packing of spherical particles. We find that the scaling
law is directly related to the contact neighbors within first nearest neighbor
shell, and therefore is closely connected to the phenomenon of jamming. The
seemingly universal scaling exponent around 2.5 arises due to the isostatic
condition with contact number around 6, and we argue that the exponent should
not be universal.Comment: 24 pages, 8 figures,to be published in Phys. Rev. Let
Structural and Topological Nature of Plasticity in Sheared Granular Materials
Upon mechanical loading, granular materials yield and undergo plastic
deformation. The nature of plastic deformation is essential for the development
of the macroscopic constitutive models and the understanding of shear band
formation. However, we still do not fully understand the microscopic nature of
plastic deformation in disordered granular materials. Here we used synchrotron
X-ray tomography technique to track the structural evolutions of
three-dimensional granular materials under shear. We establish that highly
distorted coplanar tetrahedra are the structural defects responsible for
microscopic plasticity in disordered granular packings. The elementary plastic
events occur through flip events which correspond to a neighbor switching
process among these coplanar tetrahedra (or equivalently as the rotation motion
of 4-ring disclinations). These events are discrete in space and possess
specific orientations with the principal stress direction.Comment: 26 pages, 11 figures, 2 tables, to be published in Nature
Communication
Metformin Uniquely Prevents Thrombosis by Inhibiting Platelet Activation and mtDNA Release
Thrombosis and its complications are the leading cause of death in patients with diabetes. Metformin, a first-line therapy for type 2 diabetes, is the only drug demonstrated to reduce cardiovascular complications in diabetic patients. However, whether metformin can effectively prevent thrombosis and its potential mechanism of action is unknown. Here we show, metformin prevents both venous and arterial thrombosis with no significant prolonged bleeding time by inhibiting platelet activation and extracellular mitochondrial DNA (mtDNA) release. Specifically, metformin inhibits mitochondrial complex I and thereby protects mitochondrial function, reduces activated platelet-induced mitochondrial hyperpolarization, reactive oxygen species overload and associated membrane damage. In mitochondrial function assays designed to detect amounts of extracellular mtDNA, we found that metformin prevents mtDNA release. This study also demonstrated that mtDNA induces platelet activation through a DC-SIGN dependent pathway. Metformin exemplifies a promising new class of antiplatelet agents that are highly effective at inhibiting platelet activation by decreasing the release of free mtDNA, which induces platelet activation in a DC-SIGN-dependent manner. This study has established a novel therapeutic strategy and molecular target for thrombotic diseases, especially for thrombotic complications of diabetes mellitus
Development and validation of a nomogram model for predicting unfavorable functional outcomes in ischemic stroke patients after acute phase
IntroductionPrediction of post-stroke functional outcome is important for personalized rehabilitation treatment, we aimed to develop an effective nomogram for predicting long-term unfavorable functional outcomes in ischemic stroke patients after acute phase.MethodsWe retrospectively analyzed clinical data, rehabilitation data, and longitudinal follow-up data from ischemic stroke patients who underwent early rehabilitation at multiple centers in China. An unfavorable functional outcome was defined as a modified Rankin Scale (mRS) score of 3–6 at 90 days after onset. Patients were randomly allocated to either a training or test cohort in a ratio of 4:1. Univariate and multivariate logistic regression analyses were used to identify the predictors for the development of a predictive nomogram. The area under the receiver operating characteristic curve (AUC) was used to evaluate predictive ability in both the training and test cohorts.ResultsA total of 856 patients (training cohort: n = 684; test cohort: n = 172) were included in this study. Among them, 518 patients experienced unfavorable outcomes 90 days after ischemic stroke. Trial of ORG 10172 in Acute Stroke Treatment classification (p = 0.024), antihypertensive agents use [odds ratio (OR) = 1.86; p = 0.041], 15-day Barthel Index score (OR = 0.930; p < 0.001) and 15-day mRS score (OR = 13.494; p < 0.001) were selected as predictors for the unfavorable outcome nomogram. The nomogram model showed good predictive performance in both the training (AUC = 0.950) and test cohorts (AUC = 0.942).ConclusionThe constructed nomogram model could be a practical tool for predicting unfavorable functional outcomes in ischemic stroke patients underwent early rehabilitation after acute phase