Cellular Automata Simulating Experimental Properties of Traffic Flows

A model for 1D traffic flow is developed, which is discrete in space and time. Like the cellular automaton model by Nagel and Schreckenberg [J. Phys. I France 2, 2221 (1992)], it is simple, fast, and can describe stop-and-go traffic. Due to its relation to the optimal velocity model by Bando et al. [Phys. Rev. E 51, 1035 (1995)], its instability mechanism is of deterministic nature. The model can be easily calibrated to empirical data and displays the experimental features of traffic data recently reported by Kerner and Rehborn [Phys. Rev. E 53, R1297 (1996)].Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.html and http://traffic.comphys.uni-duisburg.de/member/home_schreck.htm

Geometry of integrable dynamical systems on 2-dimensional surfaces

This paper is devoted to the problem of classification, up to smooth isomorphisms or up to orbital equivalence, of smooth integrable vector fields on 2-dimensional surfaces, under some nondegeneracy conditions. The main continuous invariants involved in this classification are the left equivalence classes of period or monodromy functions, and the cohomology classes of period cocycles, which can be expressed in terms of Puiseux series. We also study the problem of Hamiltonianization of these integrable vector fields by a compatible symplectic or Poisson structure.Comment: 31 pages, 12 figures, submitted to a special issue of Acta Mathematica Vietnamic

Microscopic Structure of the Calcium Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Mechanical design for TMX injector system

The injector system for the Tandem Mirror Experiment (TMX) contains the components required to create and maintain a high-temperature, high-density plasma. These components include a streaming-plasma gun in each of the plug tanks to form the target-plasma, 24 neutral-beam source modules for injecting neutral deuterium atoms to heat and replace losses from the plasma, and a gas box system that applies a streaming cold gas to the plasma to stabilize it. This paper discusses the mechanical design problems and solutions for this injector system

An Overview of the Field of Semiotics

AbstractThe quantitative increase in recent years of research into semiotics, among other methods of reading works of art, is notable. Since semiotics is the act of reading as based on a meta-language that is constructed and grounded in logic, understanding the methods applied by the field requires time and experience. In addition, the application of models that differ in relation to each other under different schools of thought and under different names makes its yet more difficult to comprehend the field of semiotics. Despite the different models that are available, approaches display certain commonalities as they are born of the same foundations and objectives. This study will aim to pinpoint the common aspects of the intellectual foundations, methods, objectives and research limitations of the different schools of thought and the models that are involved in the study of semiotics

Surface Adsorption Properties of Peptides Produced by Non-optimum pH Pepsinolysis of Proteins: A Combined Experimental and Self-Consistent-Field Calculation Study

Hypothesis Partial hydrolysis of large molecular weight (Mw), highly aggregated plant proteins is frequently used to improve their solubility. However, if this hydrolysis is extensive, random or nonselective, it is unlikely to improve functional properties such as surface activity, emulsion, or foam-stabilising capacity. Experiments and simulation Soy protein isolate (SPI) was hydrolysed by pepsin under optimal (pH 2.1) and non-optimal (pH 4.7) conditions. The surface activity and emulsion stabilising capacity of the resultant peptides were measured and compared. The colloidal interactions between a pair of emulsion droplets were modelled via Self-Consistent-Field Calculations (SCFC). Findings Hydrolysis at pH 2.1 and 4.7 resulted in a considerable increase in measured surface activity compared to the native (non-hydrolysed) SPI, but the hydrolysate from pH 2.1 was not as good an emulsion stabiliser as the hydrolysate (particularly the fraction Mw > 10 kDa) at pH 4.7. Furthermore, peptide analysis of the latter suggested it was dominated by a fragment of one of the major soy proteins β-conglycinin, with Mw ≈ 25 kDa. SCFC calculations confirmed that interactions mediated by adsorbed layers of this peptide point to it being an excellent emulsion stabiliser

Weak Transitions in A=6 and 7 Nuclei

The $^6$He beta decay and $^7$Be electron capture processes are studied using variational Monte Carlo wave functions, derived from a realistic Hamiltonian consisting of the Argonne $v_{18}$ two-nucleon and Urbana-IX three-nucleon interactions. The model for the nuclear weak axial current includes one- and two-body operators with the strength of the leading two-body term--associated with $\Delta$-isobar excitation of the nucleon--adjusted to reproduce the Gamow-Teller matrix element in tritium $\beta$-decay. The measured half-life of $^6$. He is under-predicted by theory by $\simeq$ 8%, while that of $^7$Be for decay into the ground and first excited states of $^7$Li is over-predicted by $\simeq$ 9%. However, the experimentally known branching ratio for these latter processes is in good agreement with the calculated value. Two-body axial current contributions lead to a $\simeq$ 1.7% (4.4%) increase in the value of the Gamow-Teller matrix element of $^6$He ($^7$Be), obtained with one-body currents only, and slightly worsen (appreciably improve) the agreement between the calculated and measured half-life. Corrections due to retardation effects associated with the finite lepton momentum transfers involved in the decays, as well as contributions of suppressed transitions induced by the weak vector charge and axial current operators, have also been calculated and found to be negligible.Comment: 23 pages 8 tables. submitted to Phys. Rev.

Strangeness in the proton and N*(1535)

The newest progress on the study of the strangeness in the proton and in the lowest negative parity nucleon excited state $N^*(1535)$ is reviewed. Implications on the internal quark structure of the proton, $N^*(1535)$ and other baryons are discussed. The diquark cluster picture for the 5-quark components in baryons gives a natural explanation not only to the empirical indications for a positive strangeness magnetic moment $\mu_s$ and positive strangeness radius of the proton but also the longstanding mass-reverse problem of $N^*(1535)$, $N^*(1440)$ and $\Lambda^*(1405)$ resonances as well as the unusual decay pattern of the $N^*(1535)$ resonance. Evidence for possible existence of $N^*(1535)$'s ${1/2}^-$ SU(3) nonet partners in this picture is pointed out, and suggestion is made to search for these $1/2^-$ hyperon excited states under the well known $\Sigma^*(1385)$, $\Lambda^*(1520)$ and $\Xi^*(1530)$ peaks in various reactions.Comment: 6 pages, 2 figures, Plenary talk at 18th International IUPAP Conference on Few-Body Problems in Physics August 21-26. 2006 Santos SP Brazil; to be published in Nuclear Physics