Non-commutative geometry and irreversibility

A kinetics built upon $q$-calculus, the calculus of discrete dilatations, is shown to describe diffusion on a hierarchical lattice. The only observable on this ultrametric space is the "quasi-position" whose eigenvalues are the levels of the hierarchy, corresponding to the volume ofphase space available to the system at any given time. Motion along the lattice of quasi-positions is irreversible.Comment: 15 pages, 2 figures, Revtex formatte

Statistics of a hydrophobic chain near a hydrophobic boundary

We study the behaviour of a hydrophobic chain near a hydrophobic boundary in two dimensions, using the decorated lattice model of Berkema and Widom [G.T. Barkema and B. Widom, J. Chem. Phys. 113, 2349 (2000)] to obtain effective, temperature dependent intrachain and chain-boundary interactions. We use these interactions to construct two model hamiltonians which can be solved exactly. Our results compare favorably with preliminary Monte Carlo computations, using the same effective interactions. At relatively low temperatures and at high temperatures, we find that the chain is randomly configured in the ambient water, and detached from the wall, whereas at intermediate temperatures it adsorbs onto the wall in a stretched or partially folded state, again depending upon the temperature, and the energy of solvation.Comment: 6 pages text, 11 figure

Spectral Renormalization Group for the Gaussian model and ψ4\psi^4 theory on non-spatial networks

We implement the spectral renormalization group on different deterministic non-spatial networks without translational invariance. We calculate the thermodynamic critical exponents for the Gaussian model on the Cayley tree and the diamond lattice, and find that they are functions of the spectral dimension, $\tilde{d}$. The results are shown to be consistent with those from exact summation and finite size scaling approaches. At $\tilde{d}=2$, the lower critical dimension for the Ising universality class, the Gaussian fixed point is stable with respect to a $\psi^4$ perturbation up to second order. However, on generalized diamond lattices, non-Gaussian fixed points arise for $2<\tilde{d}<4$.Comment: 16 pages, 14 figures, 5 tables. The paper has been extended to include a $\psi^4$ interactions and higher spectral dimension

Random model for RNA interference yields scale free network

We introduce a random bit-string model of post-transcriptional genetic regulation based on sequence matching. The model spontaneously yields a scale free network with power law scaling with $\gamma=-1$ and also exhibits log-periodic behaviour. The in-degree distribution is much narrower, and exhibits a pronounced peak followed by a Gaussian distribution. The network is of the smallest world type, with the average minimum path length independent of the size of the network, as long as the network consists of one giant cluster. The percolation threshold depends on the system size.Comment: 9 pages, 13 figures, submitted to Midterm Conference COSIN on ``Growing Networks and Graphs in Statistical Physics, Finance, Biology and Social Systems'', Rome, 1-5 September 200

Dissipative Dynamics and the Statistics of Energy States of a Hookean Model for Protein Folding

A generic model of a random polypeptide chain, with discrete torsional degrees of freedom and Hookean springs connecting pairs of hydrophobic residues, reproduces the energy probability distribution of real proteins over a very large range of energies. We show that this system with harmonic interactions, under dissipative dynamics driven by random noise, leads to a distribution of energy states obeying a modified one-dimensional Ornstein-Uhlenbeck process and giving rise to the so called Wigner distribution. A tunably fine- or coarse-grained sampling of the energy landscape yields a family of distributions for the energies and energy spacings.Comment: RevTeX, 24 pages, including 8 figure

Tariff valuation bases and trade among developing countries : do developing countries discriminate against their own trade?

In establishing the value of imports for tariff assessment, most countries apply duties either to the cost-insurance-freight (c.i.f.) or the free-on-board (f.o.b.) value of the traded good. One effect of using the far more common c.i.f. base is to place a disproportinate burden on countries that have higher freight and insurance costs. Distant countries often not only pay higher transport costs, but are further penalized by disproportionate tariff costs that worsen their competitive disadvantage. The f.o.b. valuation procedure does not penalize exporters for their location, but applies a nominal tariff rate directly to the export costs of each country. Using cost information for six Latin American countries, this paper examines the influence of the two procedures on the level and incidence of tariff protection. It concludes that transport and insurance costs generally put developing countries at a disadvantage (compared to developed countries) on interregional trade and that the relatively high Latin American tariffs on c.i.f. prices further worsen their competitive position. To correct the bias against trade between developing countries, it is recommended that f.o.b. valuation procedures used by developed countries be adopted. This change would also reduce tariff barriers considerably.Economic Theory&Research,Common Carriers Industry,Transport and Trade Logistics,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies

The restrictiveness of the multi-fibre arrangement on Eastern European trade

Historically, Eastern Europe has not been favorably treated in terms of quota growth in the European Community and U.S. markets - often quite the contrary. But the EC and U.S. treatment of these countries has already changed since their reform and can be expected to become even more favorable. Eastern Europe's exports of textiles and clothing have tended to be more capital-intensive and less specialized than those of other major suppliers, including Asia's newly industrialized economies. Erzan and Holmes argue that Eastern Europe's expansion of relatively labor-intensive products has probably been inhibited byquotas and by the weak adjustment mechanisms inherent in a centrally planned economic system. If so, given market reforms in Eastern Europe, exports of labor-intensive textiles and clothing should expand more than proportionately and the degree of specialization should increase if the Multi-Fibre Arrangement is abolished or its grip on Eastern Europe's exports is relaxed in the EC. Putting aside questions of the composition of exports, textile and clothing exports are to expand considerably because they make up a large part of labor-intensive manufacturers, where Eastern Europe's comparative advantage lies in the near future.Markets and Market Access,Economic Theory&Research,Environmental Economics&Policies,Economic Adjustment and Lending,Access to Markets

Protection facing exports from sub-Saharan Africa in the EC, Japan, and the United States

The authors address two questions in this report : 1) have exporters in sub - Saharan Africa (SSA) faced more or less protection in Japan, the EC, and the United States than other developing countries and 2) to what extent has protection in those markets constrained SSA's export growth. The authors find that on the whole SSA suffered relatively little from either tariff or nontariff protection in the major industrial markets. In part, this is because they often get a better preferential treatment, especially in the EC, and also, it is because their exports are heavy in primary goods which aregenerally subject to less protection. The authors finally point out that there is no compelling evidence that protection in the major industrial markets has constrained export growth in SSA.Economic Theory&Research,Trade Policy,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Export Competitiveness