The Future of Aztec Law

This article models a methodology for recovering the substance and nature of the Aztec legal tradition by interrogating reports of precontact indigenous behavior in the works of early colonial ethnographers, as well as in pictorial manuscripts and their accompanying oral performances. It calls for a new, richly recontextualized approach to the study of a medieval civilization whose sophisticated legal and jurisprudential practices have been fundamentally obscured by a long process of decontextualization and the anachronistic applications of modern Western paradigms

An Infrared Camera for Leuschner Observatory and the Berkeley Undergraduate Astronomy Lab

We describe the design, fabrication, and operation of an infrared camera which is in use at the 30-inch telescope of the Leuschner Observatory. The camera is based on a Rockwell PICNIC 256 x 256 pixel HgCdTe array, which is sensitive from 0.9-2.5 micron. The primary purpose of this telescope is for undergraduate instruction. The cost of the camera has been minimized by using commercial parts whereever practical. The camera optics are based on a modified Offner relay which forms a cold pupil where stray thermal radiation from the telescope is baffled. A cold, six-position filter wheel is driven by a cryogenic stepper motor, thus avoiding any mechanical feed throughs. The array control and readout electronics are based on standard PC cards; the only custom component is a simple interface card which buffers the clocks and amplifies the analog signals from the array.Comment: 13 pages, 17 figures. Submitted to Publications of the Astronomical Society of the Pacific: 2001 Jan 10, Accepted 2001 Jan 1

An Alternative Accurate Tracer of Molecular Clouds: The "XCIX_{\rm CI}-Factor"

We explore the utility of CI as an alternative high-fidelity gas mass tracer for Galactic molecular clouds. We evaluate the X$_{\rm CI}$-factor for the 609 $\mu$m carbon line, the analog of the CO X-factor, which is the ratio of the H$_2$ column density to the integrated $^{12}$CO(1-0) line intensity. We use 3D-PDR to post-process hydrodynamic simulations of turbulent, star-forming clouds. We compare the emission of CI and CO for model clouds irradiated by 1 and 10 times the average background and demonstrate that CI is a comparable or superior tracer of the molecular gas distribution for column densities up to $6 \times 10^{23}$ cm$^{-2}$. Our results hold for both reduced and full chemical networks. For our fiducial Galactic cloud we derive an average $X_{\rm CO}$ of $3.0\times 10^{20}$ cm$^{-2}$K$^{-1}$km$^{-1}$s and $X_{\rm CI}$ of $1.1\times 10^{21}$ cm$^{-2}$K$^{-1}$km$^{-1}$s.Comment: 5 pages, 4 figures, 1 table, accepted to MNRAS Letter

The importance of episodic accretion for low-mass star formation

A star acquires much of its mass by accreting material from a disc. Accretion is probably not continuous but episodic. We have developed a method to include the effects of episodic accretion in simulations of star formation. Episodic accretion results in bursts of radiative feedback, during which a protostar is very luminous, and its surrounding disc is heated and stabilised. These bursts typically last only a few hundred years. In contrast, the lulls between bursts may last a few thousand years; during these lulls the luminosity of the protostar is very low, and its disc cools and fragments. Thus, episodic accretion enables the formation of low-mass stars, brown dwarfs and planetary-mass objects by disc fragmentation. If episodic accretion is a common phenomenon among young protostars, then the frequency and duration of accretion bursts may be critical in determining the low-mass end of the stellar initial mass function.Comment: To appear in the Astrophysical Journal. Press release available at: http://www.astro.cf.ac.uk/pub/Dimitrios.Stamatellos/News/News.html Full resolution paper available at http://stacks.iop.org/0004-637X/730/3

Turbocharger Dynamic Analysis: Advanced Design Simulation in Time Domain Using CFD Predicted Thermal Boundary Conditions

Small changes of surface temperature, clearance and bearing profile can significantly change stiffness and damping characteristics of slider bearings. This may influence dynamics and in case of turbochargers the rotor radial deflection. Noise, Vibration, Harshness (NVH) or durability issues like rotor colliding with housing may be implied as a consequence. This paper presents a new methodology for dynamic turbocharger investigation. It considers multi-body dynamics (MBD) of flexible rotor and housing structures coupled with elasto-hydrodynamics (EHD) of the inner and outer oil film. The energy equation for calculation of oil film temperature is considered in EHD using   hermal boundary condition obtained from 3D computational fluid dynamics (CFD) simulation. Typical targets for CFD simulation within the turbocharger development process are flow and thermal investigation as well as specifically providing accurate thermal boundary condition for thermo-mechanical fatigue analysis. For this purpose CFD analysis considers a fully coupled fluid-structure interaction. However, the same CFD model can be used to provide the required boundary conditions for dynamic analysis as well. The bearing profiles under thermal load are derived from Finite Element (FEM) analysis based on same thermal boundary conditions. The authors demonstrate the application of the methodology for a typical turbocharger design study applied for heavy-duty engines with full floating bushings that have radial bore connections between inner and outer oil films. The rotor operating speed reaches up to 110 krpm. Dynamic simulation results with nominal clearance and temperature are compared with the results obtained when CFD and FEM predicted boundary conditions are used. Based on results for the oil film pressure and flow through each oil film as well as flow between inner and outer oil film a valid conclusion about the rotor dynamic behaviour, bearing mechanical and thermal loads can be made. The presented methodology proves to be a next level approach in prediction of turbocharger simulation in the development process

The influence of the turbulent perturbation scale on prestellar core fragmentation and disk formation

The collapse of weakly turbulent prestellar cores is a critical stage in the process of star formation. Being highly non-linear and stochastic, the outcome of collapse can only be explored theoretically by performing large ensembles of numerical simulations. Standard practice is to quantify the initial turbulent velocity field in a core in terms of the amount of turbulent energy (or some equivalent) and the exponent in the power spectrum (n \equiv -d log Pk /d log k). In this paper, we present a numerical study of the influence of the details of the turbulent velocity field on the collapse of an isolated, weakly turbulent, low-mass prestellar core. We show that, as long as n > 3 (as is usually assumed), a more critical parameter than n is the maximum wavelength in the turbulent velocity field, {\lambda}_MAX. This is because {\lambda}_MAX carries most of the turbulent energy, and thereby influences both the amount and the spatial coherence of the angular momentum in the core. We show that the formation of dense filaments during collapse depends critically on {\lambda}_MAX, and we explain this finding using a force balance analysis. We also show that the core only has a high probability of fragmenting if {\lambda}_MAX > 0.5 R_CORE (where R_CORE is the core radius); that the dominant mode of fragmentation involves the formation and break-up of filaments; and that, although small protostellar disks (with radius R_DISK <= 20 AU) form routinely, more extended disks are rare. In turbulent, low-mass cores of the type we simulate here, the formation of large, fragmenting protostellar disks is suppressed by early fragmentation in the filaments.Comment: 11 pages, 7 figures; accepted for publication by MNRA

Influence of Portosystemic Shunt on Liver Regeneration after Hepatic Resection in Pigs

Objective. The minimal amount of liver mass necessary for regeneration is still a matter of debate. The aim of the study was to analyze liver regeneration factors after extended resection with or without portosystemic shunt. Methods. An extended left hemihepatectomy was performed in 25 domestic pigs, in 15 cases after a portosystemic H-shunt. The expression of Ki-67, VEGF, TGF-α, FGF, and CK-7 was analyzed in paraffin-embedded tissue sections. Results. The volume of the remnant liver increased about 2.5-fold at the end of the first week after resection. With 19 cells/10 Glisson fields versus 4/10, Ki-67-expression was significantly higher in the H-shunt group. VEGF- and CK-7-expressions were significantly higher in the control group. No significant change was found in FGF-expression. The expression of TGF-α was higher, but not significantly, in the control group. Conclusions. The expression of Ki-67, and therefore hepatocyte regeneration, was increased in the shunt group. The expression of CK-7 on biliary epithelium and the expression of VEGF, however, were stronger in the control group