Scaling of the specific heat in superfluid films

We study the specific heat of the $x-y$ model on lattices $L \times L \times H$ with $L \gg H$ (i.e. on lattices representing a film geometry) using the Cluster Monte--Carlo method. In the $H$--direction we apply Dirichlet boundary conditions so that the order parameter in the top and bottom layers is zero. We find that our results for the specific heat of various thickness size $H$ collapse on the same universal scaling function. The extracted scaling function of the specific heat is in good agreement with the experimentally determined universal scaling function using no free parameters.Comment: 4 pages, uuencoded compressed PostScrip

The specific heat of superfluids near the transition temperature

The specific heat of the $x-y$ model is studied on cubic lattices of sizes $L \times L \times L$ and on lattices $L \times L \times H$ with $L \gg H$ (i.e. on lattices representing a film geometry) using the Cluster Monte Carlo method. Periodic boundary conditions were applied in all directions. In the cubic case we obtained the ratio of the critical exponents $\alpha/\nu$ from the size dependence of the energy density at the critical temperature $T_{\lambda}$. Using finite--size scaling theory, we find that while for both geometries our results scale to universal functions, these functions differ for the different geometries. We compare our findings to experimental results and results of renormalization group calculations.Comment: self-unpacking uuencoded PostScript file (for instructions see the beginning of the file), 18 pages

State-building, war and violence : evidence from Latin America

In European history, war has played a major role in state‐building and the state monopoly on violence. But war is a very specific form of organized political violence, and it is decreasing on a global scale. Other patterns of armed violence now dominate, ones that seem to undermine state‐building, thus preventing the replication of European experiences. As a consequence, the main focus of the current state‐building debate is on fragility and a lack of violence control inside these states. Evidence from Latin American history shows that the specific patterns of the termination of both war and violence are more important than the specific patterns of their organization. Hence these patterns can be conceptualized as a critical juncture for state‐building. While military victories in war, the subordination of competing armed actors and the prosecution of perpetrators are conducive for state‐building, negotiated settlements, coexistence, and impunity produce instability due to competing patterns of authority, legitimacy, and social cohesion

Alpha-Thioalkylation of Zinc Enolates to Alpha,Alpha-Disubstituted Ketones

An α-alkylation of the 2-methylcycloalkanones 1 and 4 at the higher substituted carbon can be achieved by thioalkylation of the corresponding zinc enolates with the α-chlorosulfides 3. The desulfurization can be carried out with either Raney nickel or lithium in diethylamine for compounds which contain double or triple bonds

A Useful Application of Benzyl Trichloroacetimidate for the Benzylation of Alcohols

Primary, secondary and tertiary alcohols, which are sensitive under basic or acidic reaction conditions, can be 0-benxylated under mild acidic reaction conditions using benxyl 2,2,2-trichloroacetimidate as the benxylation agent. Chiral substrates, which have a tendency towards racemixation under basic reaction conditions, can be benxylated without any loss of chirality

Heat flow profile HF1625 across Hikurangi Margin, New Zealand during SONNE cruise SO247 (SlamZ)

A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the pinchout of the base of gas hydrate stability. We attribute these anomalously high thermal gradients to a fluid pulse leading to advective heat flow while endothermic cooling from gas hydrate dissociation may arrest temperature gradients in the hydrate stability field. Double-bottom simulating reflections in the study area are likely to be caused by uplift based on gas hydrate phase boundary considerations. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. We suggest this seamount may also cause the inferred uplift. Transient expulsion of warm fluids may lead to gas hydrate dissociation with potential implications for seafloor stability