From old wars to new wars and global terrorism

Even before 9/11 there were claims that the nature of war had changed fundamentally. The 9/11 attacks created an urgent need to understand contemporary wars and their relationship to older conventional and terrorist wars, both of which exhibit remarkable regularities. The frequency-intensity distribution of fatalities in "old wars", 1816-1980, is a power-law with exponent 1.80. Global terrorist attacks, 1968-present, also follow a power-law with exponent 1.71 for G7 countries and 2.5 for non-G7 countries. Here we analyze two ongoing, high-profile wars on opposite sides of the globe - Colombia and Iraq. Our analysis uses our own unique dataset for killings and injuries in Colombia, plus publicly available data for civilians killed in Iraq. We show strong evidence for power-law behavior within each war. Despite substantial differences in contexts and data coverage, the power-law coefficients for both wars are tending toward 2.5, which is a value characteristic of non-G7 terrorism as opposed to old wars. We propose a plausible yet analytically-solvable model of modern insurgent warfare, which can explain these observations.Comment: For more information, please contact [email protected] or [email protected]

Negative-energy perturbations in cylindrical equilibria with a radial electric field

The impact of an equilibrium radial electric field $E$ on negative-energy perturbations (NEPs) (which are potentially dangerous because they can lead to either linear or nonlinear explosive instabilities) in cylindrical equilibria of magnetically confined plasmas is investigated within the framework of Maxwell-drift kinetic theory. It turns out that for wave vectors with a non-vanishing component parallel to the magnetic field the conditions for the existence of NEPs in equilibria with E=0 [G. N. Throumoulopoulos and D. Pfirsch, Phys. Rev. E 53, 2767 (1996)] remain valid, while the condition for the existence of perpendicular NEPs, which are found to be the most important perturbations, is modified. For $|e_i\phi|\approx T_i$ ($\phi$ is the electrostatic potential) and $T_i/T_e > \beta_c\approx P/(B^2/8\pi)$ ($P$ is the total plasma pressure), a case which is of operational interest in magnetic confinement systems, the existence of perpendicular NEPs depends on $e_\nu E$, where $e_\nu$ is the charge of the particle species $\nu$. In this case the electric field can reduce the NEPs activity in the edge region of tokamaklike and stellaratorlike equilibria with identical parabolic pressure profiles, the reduction of electron NEPs being more pronounced than that of ion NEPs.Comment: 30 pages, late

Negative-Energy Perturbations in Circularly Cylindrical Equilibria within the Framework of Maxwell-Drift Kinetic Theory

The conditions for the existence of negative-energy perturbations (which could be nonlinearly unstable and cause anomalous transport) are investigated in the framework of linearized collisionless Maxwell-drift kinetic theory for the case of equilibria of magnetically confined, circularly cylindrical plasmas and vanishing initial field perturbations. For wave vectors with a non-vanishing component parallel to the magnetic field, the plane equilibrium conditions (derived by Throumoulopoulos and Pfirsch [Phys Rev. E {\bf 49}, 3290 (1994)]) are shown to remain valid, while the condition for perpendicular perturbations (which are found to be the most important modes) is modified. Consequently, besides the tokamak equilibrium regime in which the existence of negative-energy perturbations is related to the threshold value of 2/3 of the quantity $\eta_\nu = \frac {\partial \ln T_\nu} {\partial \ln N_\nu}$, a new regime appears, not present in plane equilibria, in which negative-energy perturbations exist for {\em any} value of $\eta_\nu$. For various analytic cold-ion tokamak equilibria a substantial fraction of thermal electrons are associated with negative-energy perturbations (active particles). In particular, for linearly stable equilibria of a paramagnetic plasma with flat electron temperature profile ($\eta_e=0$), the entire velocity space is occupied by active electrons. The part of the velocity space occupied by active particles increases from the center to the plasma edge and is larger in a paramagnetic plasma than in a diamagnetic plasma with the same pressure profile. It is also shown that, unlike in plane equilibria, negative-energy perturbations exist in force-free reversed-field pinch equilibria with a substantial fraction of active particles.Comment: 31 pages, late

Phase Transforming Cellular Materials (PXCMs) Design and Assembly

We introduce a new class of phase transforming cellular materials (PXCMs) based on locally bistable or metastable unit cells that form periodic microstructures, where the thermomechanical behavior of each unit cell exhibits snap-through type behavior. We propose to explore the capabilities of these new materials to improve structural resistance to damage caused by natural hazards including PXCM in structural members. The main benefits of this material are that it can absorb energy and is reusable. During the first part of this work, a fabrication method for PXCMs based on the assembly material slotted stripes was explored. The 1D unit cell of the PXCM was dis-assembled into six components. CAD models of these components were designed, 3D printed, and assembled together to allow us to explore the fabrication of PXCMs in different materials without relying on 3D printing. On the second part of this work, we explored the geometric design space of the PXCMs that exhibit phase transformation in two or more preferential directions. For this, 2D and 3D geometric designs where proposed and a parametric study was performed using 3D-printed models to explore the behavior of each individual cell. The 1D assembly design and the 2D models did not demonstrate expected PXCM behavior when subjected to compression. However, most of the 3D geometric models demonstrated the expected PXCM behaviors when subjected to compression — bistability/ metastability, energy absorption, and phase transformation capabilities. More testing needs to be done in the future to further determine the behavioral patterns for the PXCM models

A new hybrid: Artesunate-Tumacona B

In recent years, the emergence of Plasmodium strains resistant to artemisinin derivatives, such as the commercial antimalarial Artesunate, has been detected. For this reason, in the search for new strategies to malaria control, we used the antiplasmodial activity of natural products from plant Solanum nudum, such as Tumacona B (SN2), to synthesize a new hybrid Artesunate-Tumacona B. The antiplasmodial activity and cytotoxicity of this hybrid was evaluated in vitro. We found a potent activity with IC50 = 0.0044μM in the strain 3D7 (chloroquine sensitive) and IC50= 0.0059 μM for the strain FCR3 (chloroquine resistant) and low cytotoxicity in HepG2 human liver cells with a CC50 = 12.6 μM. This makes the hybrid a new and promising compound

FPTAS for Weighted Fibonacci Gates and Its Applications

Fibonacci gate problems have severed as computation primitives to solve other problems by holographic algorithm and play an important role in the dichotomy of exact counting for Holant and CSP frameworks. We generalize them to weighted cases and allow each vertex function to have different parameters, which is a much boarder family and #P-hard for exactly counting. We design a fully polynomial-time approximation scheme (FPTAS) for this generalization by correlation decay technique. This is the first deterministic FPTAS for approximate counting in the general Holant framework without a degree bound. We also formally introduce holographic reduction in the study of approximate counting and these weighted Fibonacci gate problems serve as computation primitives for approximate counting. Under holographic reduction, we obtain FPTAS for other Holant problems and spin problems. One important application is developing an FPTAS for a large range of ferromagnetic two-state spin systems. This is the first deterministic FPTAS in the ferromagnetic range for two-state spin systems without a degree bound. Besides these algorithms, we also develop several new tools and techniques to establish the correlation decay property, which are applicable in other problems