Thermodynamics and Statistical Mechanics of dense granular media

By detailed Molecular Dynamics and Monte Carlo simulations %of a realistic model we show that granular materials at rest can be described as thermodynamics systems. First we show that granular packs can be characterized by few parameters, as much as fluids or solids. Then, in a second independent step, we demonstrate that these states can be described in terms of equilibrium distributions which coincide with the Statistical Mechanics of powders first proposed by Edwards. We also derive the system equation of state as a function of the ``configurational temperature'', its new intensive thermodynamic parameter.Comment: Supplementary Informations adde

Shear instabilities in granular mixtures

Dynamical instabilities in fluid mechanics are responsible of a variety of important common phenomena, such as waves on the sea surface or Taylor vorteces in Couette flow. In granular media dynamical instabilities has just begun to be discovered. Here we show by means of molecular dynamics simulation the existence of a new dynamical instability of a granular mixture under oscillating horizontal shear, which leads to the formation of a striped pattern where the components are segregated. We investigate the properties of such a Kelvin-Helmholtz like instability and show how it is connected to pattern formation in granular flow and segregation.Comment: Phys. Rev. Lett. 94, 18800

Do Transfer Taxes Reduce Intergenerational Transfers?

We estimate the effect of taxes on intergenerational transfers exploiting a sequence of Italian reforms culminating with the abolishment of transfer taxes. We use the 1993-2006 Survey of Household Income and Wealth, which has data on real estate transfers received and information on potential donors as well as recipients. Differences-in-differences estimates indicate that the abolition of transfer taxes increased the probability that high-wealth donors make a transfer by 2 percentage points and square meters transferred by 5.5 meters relative to poorer donors. Since we have data only on real estate transfers, we cannot rule out that the effect of the reform reflects also a change in the composition of transfers.Transfer Taxes, Intergenerational Transfers. Intergenerational Mobility

Jamming phase diagram for frictional particles

The non-equilibrium transition from a fluid-like state to a disordered solid-like state, known as the jamming transition, occurs in a wide variety of physical systems, such as colloidal suspensions and molecular fluids, when the temperature is lowered or the density increased. Shear stress, as temperature, favors the fluid-like state, and must be also considered to define the system 'jamming phase diagram' [1-4]. Frictionless athermal systems [1], for instance, can be described by the zero temperature plane of the jamming diagram in the temperature, density, stress space. Here we consider the jamming of athermal frictional systems [8-13] such as granular materials, which are important to a number of applications from geophysics to industry. At constant volume and applied shear stress[1, 2], we show that while in absence of friction a system is either fluid-like or jammed, in the presence of friction a new region in the density shear-stress plane appears, where new dynamical regimes are found. In this region a system may slip, or even flow with a steady velocity for a long time in response to an applied stress, but then eventually jams. Jamming in non-thermal frictional systems is described here by a phase diagram in the density, shear-stress and friction space

A Single-Center Experience With 1400 Patients

To assess whether the pattern of presentation and the outcome of monoclonal gammopathy of undetermined significance (MGUS) have changed over the last 3 decades, we evaluated 1400 patients, divided into 3 groups: group I (1975-1987), group II (1988-1997), and group III (1998-2007). We observed a significant increase in age (p = 0.001), IgM and biclonal MGUS (p = 0.003), hemoglobin (p < 0.0001), and albumin (p = 0.0001), and a significant reduction of monoclonal (M)-protein concentration (p < 0.0001), percentage of bone marrow plasma cells (p < 0.0001), and beta2-microglobulin (p = 0.0001) over the 3 decades. The proportion of patients with M-protein <1.5 g/dL was significantly higher in group III (66%) than in group II (44%) and group I (26%) (p < 0.0001). By Kaplan-Meier analysis, group III had a significantly lower 5-year probability of transformation (5%) compared to group II (12%) and group I (22%) (p = 0.003). Patients with M-protein <1.5 g/dL had the same life expectancy as the general population (standardized mortality ratio 1.09; p = 0.41). In conclusion, we found that the pattern of presentation of MGUS has changed over time and now includes a higher proportion of patients with more favorable presenting features and probably a better outcome compared to patients presenting in the past. This changing scenario calls for revising the current concepts of the clinical significance of MGUS and the management of patients

Dynamic nuclear polarisation NMR of nanosized zirconium phosphate polymer fillers

International audience; Surface functionalisation with organic modifiers of multi-layered zirconium phosphate (ZrP) nanoparticles used as polymer fillers can be directly probed by dynamic nuclear polarisation NMR, which provides unambiguous evidence of the presence of P-O-C chemical bonds at the surface of the ZrP layers, thereby confirming successful functionalisation

Physiological and ultrastructural effects of acute ozone fumigation in the lichen Xanthoria parietina: the role of parietin and hydration state

The physiological and ultrastructural effects induced by acute exposure to ozone (O3) were investigated in the lichen Xanthoria parietina. Our working hypothesis was that parietin content and hydration of the thalli may play a role in the modulation of the effects of O3 exposure. Four batches of X. parietina samples, dry and wet, with (P+) and without (Pâ\u88\u92) parietin, were fumigated for 1 h with 3 ppm O3. The effects of O3 were assessed immediately after the fumigation and after one week of recovery under controlled conditions. O3 fumigation caused physiological and ultrastructural impairment both to the photobiont and the mycobiont, irrespective if samples were fumigated wet or dry, and P+ or Pâ\u88\u92. However, one week after fumigation, a recovery was observed in P+ samples for the photobiont and in dry samples for the mycobiont. We suggest that the hydration state may play a major role in determining the severity of the damage, while the presence of parietin may promote the recovery. Our results provide physiological and ultrastructural basis to explain the ecological insensitivity of lichens to high environmental levels of ozone occurring during dry Mediterranean summers

Making the most of imperfect data: A critical evaluation of standard information collected in farm household surveys

Household surveys are one of the most commonly used tools for generating insight into rural communities. Despite their prevalence, few studies comprehensively evaluate the quality of data derived from farm household surveys. We critically evaluated a series of standard reported values and indicators that are captured in multiple farm household surveys, and then quantified their credibility, consistency and, thus, their reliability. Surprisingly, even variables which might be considered ‘easy to estimate’ had instances of non-credible observations. In addition, measurements of maize yields and land owned were found to be less reliable than other stationary variables. This lack of reliability has implications for monitoring food security status, poverty status and the land productivity of households. Despite this rather bleak picture, our analysis also shows that if the same farm households are followed over time, the sample sizes needed to detect substantial changes are in the order of hundreds of surveys, and not in the thousands. Our research highlights the value of targeted and systematised household surveys and the importance of ongoing efforts to improve data quality. Improvements must be based on the foundations of robust survey design, transparency of experimental design and effective training. The quality and usability of such data can be further enhanced by improving coordination between agencies, incorporating mixed modes of data collection and continuing systematic validation programmes