Measuring the configurational temperature of a binary disc packing

Jammed packings of granular materials differ from systems normally described by statistical mechanics in that they are athermal. In recent years a statistical mechanics of static granular media has emerged where the thermodynamic temperature is replaced by a configurational temperature X which describes how the number of mechanically stable configurations depends on the volume. Four different methods have been suggested to measure X. Three of them are computed from properties of the Voronoi volume distribution, the fourth takes into account the contact number and the global volume fraction. This paper answers two questions using experimental binary disc packings: First we test if the four methods to measure compactivity provide identical results when applied to the same dataset. We find that only two of the methods agree quantitatively. Secondly, we test if X is indeed an intensive variable; this becomes true only for samples larger than roughly 200 particles. This result is shown to be due to recently found correlations between the particle volumes [Zhao et al., Europhys. Lett., 2012, 97, 34004].Comment: Open access under Creative Commons Attribution-NonCommercial 3.0 licens

Crater formation during raindrop impact on sand

After a raindrop impacts on a granular bed, a crater is formed as both drop and target deform. After an initial, transient, phase in which the maximum crater depth is reached, the crater broadens outwards until a final steady shape is attained. By varying the impact velocity of the drop and the packing density of the bed, we find that avalanches of grains are important in the second phase and hence, affect the final crater shape. In a previous paper, we introduced an estimate of the impact energy going solely into sand deformation and here we show that both the transient and final crater diameter collapse with this quantity for various packing densities. The aspect ratio of the transient crater is however altered by changes in the packing fraction.Comment: 9 pages, 9 figure

Liquid-grain mixing suppresses droplet spreading and splashing during impact

Would a raindrop impacting on a coarse beach behave differently from that impacting on a desert of fine sand? We study this question by a series of model experiments, where the packing density of the granular target, the wettability of individual grains, the grain size, the impacting liquid, and the impact speed are varied. We find that by increasing the grain size and/or the wettability of individual grains the maximum droplet spreading undergoes a transition from a capillary regime towards a viscous regime, and splashing is suppressed. The liquid-grain mixing is discovered to be the underlying mechanism. An effective viscosity is defined accordingly to quantitatively explain the observations

Correlation between Voronoi volumes in disc packings

We measure the two-point correlation of free Voronoi volumes in binary disc packings, where the packing fraction $\phi_{\rm avg}$ ranges from 0.8175 to 0.8380. We observe short-ranged correlations over the whole range of $\phi_{\rm avg}$ and anti-correlations for $\phi_{\rm avg}>0.8277$. The spatial extent of the anti-correlation increases with $\phi_{\rm avg}$ while the position of the maximum of the anti-correlation and the extent of the positive correlation shrink with $\phi_{\rm avg}$. We conjecture that the onset of anti-correlation corresponds to dilatancy onset in this system

In Vitro and In Vivo Study

Nanofibers have attracted increasing attention in drug delivery and other biomedical applications due to their some special properties. The present study aims to prepare a fiber-based nanosolid dispersion system to enhance the bioavailability of curcumin (CUR). CUR-loaded polyvinyl pyrrolidone (CUR@PVP) nanofibers were successfully prepared via electrospinning. Scanning electron microscopy (SEM) was employed to observe the morphology of the nanofibers, and the SEM image showed that the drug-loaded nanofibers were smooth, and no CUR clusters were found on the surface of the nanofibers. The results of X-ray diffraction (XRD) demonstrated that the CUR was evenly distributed in the nanofibers in an amorphous state. Fourier transform infrared (FTIR) spectroscopy analysis indicated that intermolecular hydrogen bonding occurred between the CUR and the polymer matrix. In vitro dissolution profiles showed that CUR@PVP nanofiber could be quickly dissolved in phosphate-buffered saline (PBS) solution, while negligible dissolution was observed in pure CUR sample. Importantly, in vitro cell viability assays and in vivo animal tests revealed that the nanosolid dispersion system dramatically enhanced the bioavailability and showed effective anticancer effect of the CUR

Metabolic characterization of different-aged Monascus vinegars via HS-SPME-GC-MS and CIL LC-MS approach

Yongchun Monascus vinegar is one of famous Chinese vinegar types because of its unique flavor and special bioactivity. Aging process has been regarded as crucial for enhancing the flavor and quality of vinegar. However, changes in the metabolites along the aging of the vinegar are still poorly understood. In this study, a combination of headspace solid-phase micro-extraction gas chromatography-mass spectrometry and chemical isotope labeling liquid chromatography-mass spectrometry methods was used for investigating the metabolomes of one-year-old, five-year-old and thirty-year-old YMVs. DPPH radical-scavenging activity, total phenolics content, and total flavonoids content correlated positively with the aging time. The metabolite compositions in the different-aged vinegars were clearly separated in the PCA analysis. A total of 1133 volatile and non-volatile metabolites changed along the aging; 392 metabolites were in common whereas 126, 84, and 54 changed metabolites were unique to one-to-five year, one-to-thirty year, and five-to-thirty year-old vinegar comparisons, respectively. Organic acids and dipeptides, exhibiting taste characteristics, with constant increase or decrease with aging time and correlated with antioxidant capacities could be used as biomarkers for differentiating the different-aged vinegars. The results revealed aging time related changes in volatile and non-volatile metabolites in YMVs, providing useful knowledge for improving their quality.Peer reviewe

Characteristics and management of Enterobacteriaceae harboring IMP-4 or IMP-8 carbapenemase in a tertiary hospital

Background: The emergence of Enterobacteriaceae harboring IMP-4 or IMP-8 carbapenemases is rare. We report an occurrence of Enterobacteriaceae harboring IMP-4 or IMP-8 carbapenemases in a Chinese tertiary care hospital from November 2010 to December 2012.Methods: The clinical characteristics of 30 patients were described. The genetic relationship of isolates was determined by pulsed-field gel electrophoresis (PFGE). Carbapenemases were detected by modified Hodge test (MHT) and polymerase chain reactions (PCRs). Amplicons were sequenced and blasted to determine the genotype.Results: Most infected patients were from intensive care unit and had complex and serious underlying illnesses requiring mechanical ventilation. PFGE revealed that Klebsiella pneumoniae showed two major PFGE types. Two Klebsiella oxytoca had an indistinguishable PFGE pattern, while four Enterobacter cloacae were different strains. The sequencing studies showed Enterobacteriaceae harboring IMP-4 or IMP-8 carbapenemase in the 23 infected patients. The majority of patients had infections with the carbapenemase-producing Enterobacteriaceae (CPE) strain, most were successfully treated with a range of antibiotics and discharged.Conclusion: It is important to maintain a high index of suspicion to screen for carbapenemase-producing Enterobacteriaceae strains. Rapid identification of these strains and implementation of stringent procedures are the key to prevent major outbreaks in a hospital setting.Keywords: Carbapenemase, Enterobacteriaceae, IMP-4, IMP-8, clinical outcom