Modelling transverse dunes

Transverse dunes appear in regions of mainly unidirectional wind and high sand availability. A dune model is extended to two dimensional calculation of the shear stress. It is applied to simulate dynamics and morphology of transverse dunes which seem to reach translational invariance and do not stop growing. Hence, simulations of two dimensional dune fields have been performed. Characteristic laws were found for the time evolution of transverse dunes. Bagnold's law of the dune velocity is modified and reproduced. The interaction between transverse dunes led to interesting results which conclude that small dunes can pass through bigger ones.Comment: Submitted to Earth Surface Processes and Landform

Hepatitis induced by noni juice from Morinda citrifolia: A rare cause of hepatotoxicity or the tip of the iceberg?

A 24-year-old female patient presented to her community hospital with mild elevations of serum transaminase and bilirubin levels. Because of multiple sclerosis, she was treated with interferon beta-la for 6 weeks. After exclusion of viral hepatitis due to hepatitis A-E, interferon beta-la was withdrawn under the suspicion of drug-induced hepatitis. One week later, she was admitted again to her community hospital with severe icterus. The transaminase and bilirubin levels were highly elevated, and a beginning impairment of the liver synthesis was expressed by a reduced prothrombin time. The confinement to our department occurred with a fulminant hepatitis and the suspicion of beginning acute liver failure. There was no evidence for hepatitis due to potentially hepatotoxic viruses, alcoholic hepatitis, Budd-Chiari syndrome, hemochromatosis, and Wilson's disease. In her serum there were high titers of liver-kidney microsomal type 1 autoantibody; the serum gamma globulin levels were in the normal range. Fine-needle aspiration biopsy of the liver ruled out an autoimmune hepatitis but showed signs of drug-induced toxicity. During the interview, she admitted that for `general immune system stimulation' she had been drinking Noni juice, a Polynesian herbal remedy made from a tropical fruit (Morinda citrifolia), during the past 4 weeks. After cessation of the Noni juice ingestion, her transaminase levels normalized quickly and were in the normal range within 1 month. Copyright (c) 2006 S. Karger AG, Basel

Dynamics of immersed molecules in superfluids

The dynamics of a molecule immersed in a superfluid medium are considered. Results are derived using a classical hydrodynamic approach followed by canonical quantization. The classical model, a rigid body immersed in incompressible fluid, permits a thorough analysis; its effective Hamiltonian generalizes the usual rigid-rotor Hamiltonian. In contrast to the free rigid rotor, the immersed body is shown to have chaotic dynamics. Quantization of the classical model leads to new and experimentally verifiable features. It is shown, for instance, that chiral molecules can behave as "quantum propellers": the rotational-translational coupling induced by the superfluid leads to a nonzero linear momentum in the ground state. Hydrogen peroxide is a strong candidate for experimental detection of this effect. The signature is a characteristic splitting of rotational absorption lines. The 1_{01} --> 1_{10} line in hydrogen peroxide, for example, is predicted to split into three lines separated by as much as 0.01 cm^{-1}, which is about the experimental linewidth.Comment: 10 pages, 3 figure

The dune size distribution and scaling relations of barchan dune fields

Barchan dunes emerge as a collective phenomena involving the generation of thousands of them in so called barchan dune fields. By measuring the size and position of dunes in Moroccan barchan dune fields, we find that these dunes tend to distribute uniformly in space and follow an unique size distribution function. We introduce an analyticalmean-field approach to show that this empirical size distribution emerges from the interplay of dune collisions and sand flux balance, the two simplest mechanisms for size selection. The analytical model also predicts a scaling relation between the fundamental macroscopic properties characterizing a dune field, namely the inter-dune spacing and the first and second moments of the dune size distribution.Comment: 6 pages, 4 figures. Submitted for publicatio

Resistivity phase diagram of cuprates revisited

The phase diagram of the cuprate superconductors has posed a formidable scientific challenge for more than three decades. This challenge is perhaps best exemplified by the need to understand the normal-state charge transport as the system evolves from Mott insulator to Fermi-liquid metal with doping. Here we report a detailed analysis of the temperature (T) and doping (p) dependence of the planar resistivity of simple-tetragonal HgBa$_2$CuO$_{4+\delta}$ (Hg1201), the single-CuO$_2$-layer cuprate with the highest optimal $T_c$. The data allow us to test a recently proposed phenomenological model for the cuprate phase diagram that combines a universal transport scattering rate with spatially inhomogeneous (de)localization of the Mott-localized hole. We find that the model provides an excellent description of the data. We then extend this analysis to prior transport results for several other cuprates, including the Hall number in the overdoped part of the phase diagram, and find little compound-to-compound variation in (de)localization gap scale. The results point to a robust, universal structural origin of the inherent gap inhomogeneity that is unrelated to doping-related disorder. They are inconsistent with the notion that much of the phase diagram is controlled by a quantum critical point, and instead indicate that the unusual electronic properties exhibited by the cuprates are fundamentally related to strong nonlinearities associated with subtle nanoscale inhomogeneity.Comment: 22 pages, 5 figure

Dense packing crystal structures of physical tetrahedra

We present a method for discovering dense packings of general convex hard particles and apply it to study the dense packing behavior of a one-parameter family of particles with tetrahedral symmetry representing a deformation of the ideal mathematical tetrahedron into a less ideal, physical, tetrahedron and all the way to the sphere. Thus, we also connect the two well studied problems of sphere packing and tetrahedron packing on a single axis. Our numerical results uncover a rich optimal-packing behavior, compared to that of other continuous families of particles previously studied. We present four structures as candidates for the optimal packing at different values of the parameter, providing an atlas of crystal structures which might be observed in systems of nano-particles with tetrahedral symmetry

Which Processes Do Users Not Want Online? - Extending Process Virtualization Theory

Following the advent of the Internet more and more processes are provided virtually, i.e., without physical interactions between involved people and objects. For instance, E-Commerce has virtualized shopping processes since products are bought without physical inspection and interaction with sales staff. This study is founded on the key idea of process virtualization theory (PVT) that from the users’ perspective not all processes are equally amenable for virtualization. We investigate characteristics of processes, which are causing users’ resistance toward the virtualized process. Surveying 501 individuals regarding 10 processes, this study constitutes the first quantitative test evaluating the prediction capabilities of PVT by analysis of varying processes. Moreover, it introduces and successfully tests the extended PVT (EPVT), which integrates PVT with multiple, related constructs from extant literature in a unified model with multi-order causal relations. Thereby, it clearly enhances our understanding of human behavior with regard to the frequent phenomenon process virtualization

How Digital Divide affects Public E-Services: The Role of Migration Background

After the private sector the public sector also tries to benefit from the advantages of electronic service delivery, in particular from lower costs and higher service quality. While more and more services are available electronically, resident behind. But high usage rates and therefore a maximized potential target group, covering major parts of society, are essential prerequisite for successful public e-services. If the residents are not using the newly created electronic services, neither they benefit from better service quality nor do the public service provider save money. Digital divide research can be leveraged to maximize the potential target group of public e-service. For this purpose a focus on public e-services as level of analysis is required, since Internet access or regular Internet usage are necessary but no sufficient conditions for being able to use public e-services. This study employs qualitative research methods in an exploratory case study design to analyze the influence of migration background on the capability to use public e-services. It provides two testable propositions for further confirmatory research: Due to limited language skills and different cultural experiences, for residents with migration background Internet experience does not directly translate into confidence in their own public e-service skills

Patriots, Tories, Inebriates, and hussies: The Historical Archaeology of the Abraham Staats House, as a Case Study in Microhistory

To modern suburbanites, life on a farm may seem hopelessly boring or, alternatively, charming and idyllic. Excavations at the Abraham Staats House in New Jersey’s Raritan Valley, just upriver from New Brunswick, provide a revealing glimpse of the dynamic and contentious lives of 18th- and 19th-century farmers. The Staats family, part of the early 18th-century Dutch migration to the Raritan Valley, saw their lives transformed by the Revolutionary War, the arrival of turnpike roads, the construction of the Delaware and Raritan Canal, the emancipation of slaves, the growth of the temperance movement, and family squabbles of Shakespearean proportions. Excavations at the Staats House undertaken by volunteers from the Friends of the Abraham Staats House, the Archaeological Society of New Jersey, and Monmouth University, combined with the rediscovery of long-forgotten diaries, deeds, wills, and court records, provide a richer glimpse into the complex realities of rural life in early New Jersey. Through the detailed intensive study, or microhistory, of this single household, local, regional, and national historical trends are revealed