Universal cover-time distributions of random motion in bounded granular gases.

The exhaustive random exploration of a complex domain is a fundamental issue in many natural, social, and engineering systems. The key characterizing quantity is the cover time, which is the time to visit every site in the system. One prototypical experimental platform is the confined granular gas, where the random motion of granular particles mimics the wandering of random walkers in a confined region. Here, we investigate the cover-time distribution of the random motion of tracer particles in granular gases confined in four containers to account for different boundary and angle effects and examine whether the cover time of the heterogeneous random motion of the granular gases can be rescaled into the universal Gumbel distribution according to a recent theory [Dong et al., arXiv:2210.05122 (2022)]. It is found that for long cover times, the experimental results are in full accord, while for short cover times, the agreement is reasonable, with noticeable deviations that can be attributed to spatial correlations of the sites in the covering process. Our results, thus, call for further theoretical investigations in order to take into full account these nonideal issues.

Universal cover-time distribution of heterogeneous random walks.

The cover-time problem, i.e., the time to visit every site in a system, is one of the key issues of random walks with wide applications in natural, social, and engineered systems. Addressing the full distribution of cover times for random walk on complex structures has been a long-standing challenge and has attracted persistent efforts. Usually it is assumed that the random walk is noncompact, to facilitate theoretical treatments by neglecting the correlations between visits. The known results are essentially limited to noncompact and homogeneous systems, where different sites are on an equal footing and have identical or close mean first-passage times, such as random walks on a torus. In contrast, realistic random walks are prevailingly heterogeneous with diversified mean first-passage times. Does a universal distribution still exist? Here, by considering the most general situations of noncompact random walks, we uncover a generalized rescaling relation for the cover time, exploiting the diversified mean first-passage times that have not been accounted for before. This allows us to concretely establish a universal distribution of the rescaled cover times for heterogeneous noncompact random walks, which turns out to be the Gumbel universality class that is ubiquitous for a large family of extreme value statistics. Our analysis is based on the transfer matrix framework, which is generic in that, besides heterogeneity, it is also robust against biased protocols, directed links, and self-connecting loops. The finding is corroborated with extensive numerical simulations of diverse heterogeneous noncompact random walks on both model and realistic topological structures. Our technical ingredient may be exploited for other extreme value or ergodicity problems with nonidentical distributions.

Overt and occult hepatitis B infection after neonatal vaccination: mother-to-infant transmission and HBV vaccine effectiveness.

OBJECTIVES: Overt and occult hepatitis B infection (HBI) among mothers and infants were investigated, and the effectiveness of vaccination against HBI was evaluated based on transmission types. METHODS: A hospital-based cohort was built with 2,734 mothers and 330 mother-infant pairs. Their demographic data were collected. Serological HBV markers, nested-PCR for HBV genes, viral load detection, and phylogenetic analysis were done. RESULTS: The overall prevalence of HBI among mothers was 12.1% (330/2,734), with 10.4% for the overt type and 1.8% for the occult type. In 330 out of 1,650 (20%) mother-infant pairs, the overall, type-I (from overt mother to overt infant), type-II (from overt mother to occult infant), and type-Ⅲ (from occult mother to occult infant) transmissions were 1.9% (1/54), 5.6% (3/54) and 0.0% (0/7). The refinement of HBI classification improved the estimate of vaccine effectiveness against HBI from 74.4%-80.9% to 94.4%, which was more prominent for type-II. One mother-infant pair with type-II transmission shared nearly identical complete sequences. However, the high rate of lost-to-follow-up could not be ignored. CONCLUSIONS: During the transition period, HBV is mainly transmitted from the overt type of HBI mother to infant. Intensive prenatal screening for mothers is vital.

Infima statistics of entropy production in an underdamped Brownian motor.

The second law of thermodynamics states that the entropy never decreases for isolated macroscopical systems, which defines the arrow of time. For small systems, although the entropy increases on average, due to strong fluctuation, it may encounter a temporary decrease. The probability of negative entropy production follows the fluctuation theorem. Recently, it has been demonstrated theoretically the infima law that there exists a lower bound for the average values of the minima of the negative entropy production, which is -k_{B}. In this paper, we have constructed a horizontal Brownian motor immersed in a granular gas, whose dynamics is governed by the underdamped stochastic process. By recording the angular motion of the motor and measuring the key parameters of the system, we experimentally demonstrate that, despite the nonideal elements in the experiments and that the complex underlying dynamics, the average value of the minima of the negative entropy production is still bounded by -k_{B}, which may invoke further theoretical investigations of the applicability of the infima law in nonideal realistic small systems.

[Exploration of the early detection of lung parenchyma micronodules, nodule coalescence and emphysema by CT and HRCT in coal miners with and without coal-worker's pneumoconiosis evidence].

OBJECTIVE: To explore the sensitivity and accuracy of CT and HRCT in early detection of coal-worker's pneumoconiosis (CWP) associated micronodules, nodule coalescence and emphysema from coal miners with and without radiographic CWP evidence. METHOD: Continuously Thorax-Vol. CT scanning and High resolution CT scanning were performed on 113 coal miners with or without radiographic CWP evidence and 37 health controls by the use of Multi Spiral Computed Tomography (MSCT). The CT and HRCT images were evaluated for lung parenchyma opacity profusion category, nodule coalescence, emphysema index and mean lung attenuation, and then compared with that on radiographs. RESULT: Good agreement for CWP associated opacity profusion grading was achieved between radiographs and CT scans (Kappa = 0.771). The sensitivity of CT and HRCT were 98.70% for CWP diagnosis when compared with radiographs. 8 (22.22%) cases out of 36 radiographic CWP negative coal miners were categorized as grade 1 opacity profusion in consistent with CWP on CT and HRCT scans, and 26 (35.62%) cases out of 73 radiographic grade 1-2 CWP patients were detected to have at least grade 3 nodular profusion on CT and HRCT scans. Among 113 coal miners, 36 (31.86%) were recognized as emphysema positive on CT; whereas only 7 (6.19%) on radiographs. According to CT opacity profusion grading, mean lung attenuation in coal miners with grade 1-2 opacity profusion classification was significantly increased than that in health control, CWP negative coal miner and grade 4 opacity profusion groups (F1 = -45.73, F2 = -23.00 and F3 = 52.72, P < 0.01 and P < 0.05). CONCLUSION: CT and HRCT acquired from MSCT showed high sensitive and accurate for the early detection of micronodules, nodule coalescence and emphysema in coal miners. It could be used as semi-quantitative and quantitative method in early diagnosis of CWP and its complications.

Changes of tumor necrosis factor, surfactant protein A, and phospholipids in bronchoalveolar lavage fluid in the development and progression of coal workers' pneumoconiosis.

OBJECTIVE: To evaluate the alterations of biomarkers in the development and progression of coal workers' pneumoconiosis (CWP). METHODS: The type and number of cells, and the levels of tumor necrosis factor-alpha (TNF-alpha), pulmonary surfactant protein, phospholipids and fibronectin in bronchoalveolar lavage fluid were assayed in 14 health active coal miners, 21 coal miners without CWP and 13 miners with CWP of 0/1 to 1/1. RESULTS: Compared to active coal miners without CWP (8.23 microg/mL), TNF-alpha concentration was gradually decreased when dust exposure was stopped (5.90 microg/mL). Elevated surfactant protein A (SP-A) level and phosphatidylglycerol (PG) to phosphatidylinositol (PI) ratio were found in miners actively exposed to coal dust (6528 ng/mL for SP-A and 10. for PG/PI), and both parameters decreased when CWP progressed from CWP (0/1) (3419 microg/mL for SP-A and 5.9 for PG/PI) to CWP (1/1) (1654 microg/mL for SP-A and 5.5 for PG/PI). CONCLUSION: Biomarkers in bronchoalveolar lavage fluid can be used to screen coal miners at high risk of developing coal workers' pneumoconiosis.