On contact numbers in random rod packings

Random packings of non-spherical granular particles are simulated by combining mechanical contraction and molecular dynamics, to determine contact numbers as a function of density. Particle shapes are varied from spheres to thin rods. The observed contact numbers (and packing densities) agree well with experiments on granular packings. Contact numbers are also compared to caging numbers calculated for sphero-cylinders with arbitrary aspect-ratio. The caging number for rods arrested by uncorrelated point contacts asymptotes towards <γ> = 9 at high aspect ratio, strikingly close to the experimental contact number <C> ≈ 9.8 for thin rods. These and other findings confirm that thin-rod packings are dominated by local arrest in the form of truly random neighbor cages. The ideal packing law derived for random rod–rod contacts, supplemented with a calculation for the average contact number, explains both absolute value and aspect-ratio dependence of the packing density of randomly oriented thin rods

Non-affine response: jammed packings versus spring networks

We compare the elastic response of spring networks whose contact geometry is derived from real packings of frictionless discs, to networks obtained by randomly cutting bonds in a highly connected network derived from a well-compressed packing. We find that the shear response of packing-derived networks, and both the shear and compression response of randomly cut networks, are all similar: the elastic moduli vanish linearly near jamming, and distributions characterizing the local geometry of the response scale with distance to jamming. Compression of packing-derived networks is exceptional: the elastic modulus remains constant and the geometrical distributions do not exhibit simple scaling. We conclude that the compression response of jammed packings is anomalous, rather than the shear response.Comment: 6 pages, 6 figures, submitted to ep

The risk protection and redistribution effects of long‐term care co‐payments

Co‐payments for long‐term care (LTC) can impose a substantial financial burden on the elderly. How this burden is distributed across income groups depends on the design of the co‐payment. We estimate the lifecycle dynamics of LTC using Dutch administrative data. These estimates are inputs in a stochastic lifecycle decision model. Using the model, we analyze the welfare effects of the Dutch income‐ and wealth‐ dependent co‐payment system and compare it to alternative systems. We find that the Dutch co‐payment system redistributes income to low‐income groups, who use the most care over their life but contribute the least co‐payments, from high‐income groups, who pay the most. Moreover, the Dutch system protects the middle‐income groups relatively well against financial risk: although alternative co‐payment systems hardly affect these groups average payments, they induce welfare losses of 2% to 4% due to an increased risk of very high co‐paymen

Betere risicospreiding van eigen bijdragen bij verpleeghuiszorg

Ouderen betalen een eigen bijdrage voor het gebruik van verpleeghuiszorg. De hoogte van de eigen bijdrage hangt af van iemands financiële middelen, maar inkomen en vermogen worden verschillend belast. Voor ouderen vormt de eigen bijdrage een aanzienlijk financieel risico. Zo kunnen de jaarlijkse kosten voor langdurige verpleeghuiszorg voor ouderen met een middeninkomen oplopen tot ruim 70% van het netto-inkomen en vele jaren duren

Better off at home? Effects of a nursing home admission on costs, hospitalizations and survival.

Aging-in-place policies substitute home care for nursing home admissions (NHA). They appear to be a win-win by keeping public spending in check and being in line with personal preferences, but have hitherto not been evaluated. We study the impact of NHA eligibility using Dutch administrative data and exploiting variation between randomly assigned assessors in their tendency to grant admission. The impact on mortality is zero, but with considerable effect heterogeneity. Moreover, aging-in-place policies come at the cost of increased curative care, especially hospital admissions, and do not reduce total healthcare spending, suggesting they may not be a win-win after all

Excitations of Ellipsoid Packings near Jamming

We study the vibrational modes of three-dimensional jammed packings of soft ellipsoids of revolution as a function of particle aspect ratio $\epsilon$ and packing fraction. At the jamming transition for ellipsoids, as distinct from the idealized case using spheres where $\epsilon = 1$, there are many unconstrained and non-trivial rotational degrees of freedom. These constitute a set of zero-frequency modes that are gradually mobilized into a new rotational band as $|\epsilon - 1|$ increases. Quite surprisingly, as this new band is separated from zero frequency by a gap, and lies below the onset frequency for translational vibrations, $\omega^*$, the presence of these new degrees of freedom leaves unaltered the basic scenario that the translational spectrum is determined only by the average contact number. Indeed, $\omega^*$ depends solely on coordination as it does for compressed packings of spheres. We also discuss the regime of large $|\epsilon - 1|$, where the two bands merge.Comment: 6 pages, 4 figure

Rural-to-Urban Labor Migration, Household Livelihoods, and the Rural Environment in Chongqing Municipality, Southwest China

Rural migration and its relationship to the rural environment have attracted increasing research interest in recent decades. Rural migration constitutes a key component of human population movement, while rural areas contain most of the world’s natural resources such as land and forests. This study empirically evaluates a conceptual framework incorporating rural household livelihoods as an integrative mediating factor between rural migration and the rural environment in the context of rural-to-urban labor migration in Chongqing Municipality, Southwest China. The analysis draws on data collected through household surveys and key informant interviews from four villages. Results confirm the hypothesis that labor-migrant and non-labor-migrant households differ significantly in livelihood activities including agricultural production, agricultural technology use, income and consumption, and resource use and management. Implications for the subsequent environmental outcomes of rural labor out-migration and corresponding natural resource management and policy in rural origin areas are discussed