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KINSHIP AND HISTORY: TRIBES, GENEALOGIES, AND SOCIAL CHANGE AMONG THE BEDOUIN OF THE EASTERN ARAB WORLD
Most scholars of tribal organization among the Bedouin of the eastern Arab world utilize a two-dimensional, hierarchical model of Bedouin kinship that represents only relations of descent and affinity. This model resembles a genealogy and shows how small descent units are enclosed by larger ones. It implies that tribes grow in size only through biological reproduction. Such a representation of the Bedouin tribe fails to distinguish politically central lineages from politically peripheral lineages and also ignores the processes through which foreign lineages become “attached” as clients to politically powerful, central lineages. To correct and supplement this genealogical model, the author presents a concentric model of Bedouin tribes that adds a “central/peripheral” distinction. This model also includes relations of political “attachment” that can affect the internal morphology and growth of Bedouin tribes in ways that are comparable to the effects of affinal and suckling kinship relations on internal organization. The proposed concentric model thus allows us to represent historical change more accurately and also brings us closer to Bedouin concepts of tribal organization
The Nusselt numbers of horizontal convection
We consider the problem of horizontal convection in which non-uniform
buoyancy, , is imposed on the top surface of a container and
all other surfaces are insulating. Horizontal convection produces a net
horizontal flux of buoyancy, , defined by vertically and temporally
averaging the interior horizontal flux of buoyancy. We show that
; overbar denotes a
space-time average over the top surface, angle brackets denote a volume-time
average and is the molecular diffusivity of buoyancy . This
connection between and
justifies the definition of the
horizontal-convective Nusselt number, , as the ratio of to the corresponding quantity produced
by molecular diffusion alone. We discuss the advantages of this definition of
over other definitions of horizontal-convective Nusselt number currently
in use. We investigate transient effects and show that equilibrates more rapidly than other
global averages, such as the domain averaged kinetic energy and bottom
buoyancy. We show that is
essentially the volume-averaged rate of Boussinesq entropy production within
the enclosure. In statistical steady state, the interior entropy production is
balanced by a flux of entropy through the top surface. This leads to an
equivalent "surface Nusselt number", defined as the surface average of vertical
buoyancy flux through the top surface times the imposed surface buoyancy
. In experiments it is likely easier to evaluate the surface
entropy flux, rather than the volume integral of
demanded by .Comment: 16 pages, 7 figure
Human mitochondrial DNA replication machinery and disease.
The human mitochondrial genome is replicated by DNA polymerase γ in concert with key components of the mitochondrial DNA (mtDNA) replication machinery. Defects in mtDNA replication or nucleotide metabolism cause deletions, point mutations, or depletion of mtDNA. The resulting loss of cellular respiration ultimately induces mitochondrial genetic diseases, including mtDNA depletion syndromes (MDS) such as Alpers or early infantile hepatocerebral syndromes, and mtDNA deletion disorders such as progressive external ophthalmoplegia, ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy. Here we review the current literature regarding human mtDNA replication and heritable disorders caused by genetic changes of the POLG, POLG2, Twinkle, RNASEH1, DNA2, and MGME1 genes
The Orbital Light Curve of Aquila X-1
We obtained R- and I-band CCD photometry of the soft X-ray transient/neutron-
star binary Aql X-1 in 1998 June while it was at quiescence. We find that its
light curve is dominated by ellipsoidal variations, although the ellipsoidal
variations are severely distorted and have unequal maxima. After we correct for
the contaminating flux from a field star located only 0.46" away, the
peak-to-peak amplitude of the modulation is ~0.25 mag in the R band, which
requires the orbital inclination to be greater than 36 degrees. The orbital
period we measure is consistent with the 18.95 h period measured by Chevalier &
Ilovaisky (1998). During its outbursts the light curve of Aql X-1 becomes
single humped. The outburst light curve observed by Garcia et al. (1999) agrees
in phase with our quiescent light curve. We show that the single humped
variation is caused by a ``reflection effect,'' that is, by heating of the side
of the secondary star facing towards the neutron star.Comment: 18 manuscript pages, 7 figures; accepted by A
Comparison of numerical simulation and experimental data for steam-in-place sterilization
A complex problem involving convective flow of a binary mixture containing a condensable vapor and noncondensable gas in a partially enclosed chamber was modelled and results compared to transient experimental values. The finite element model successfully predicted transport processes in dead-ended tubes with inside diameters of 0.4 to 1.0 cm. When buoyancy driven convective flow was dominant, temperature and mixture compositions agreed with experimental data. Data from 0.4 cm tubes indicate diffusion to be the primary air removal method in small diameter tubes and the diffusivity value in the model to be too large
Distributional Impact of U.S. Farm Commodity Programs: Accounting for Alternative Farm Household Typologies
Agricultural households adjust to policy changes through market mechanisms by altering: their production mix, labor input, and on- and off-farm investments. Because of the significant heterogeneity among farms in the US agricultural sector, various types of farm households respond to the same policy change in significantly different ways. The parameters used to classify farm households into different typologies may also play a significant role in the interpretation of observed effects of policy changes. This paper, using a highly disaggregated U.S. Computable General Equilibrium (CGE) model, analyzes the distributional impacts of policy changes involving price-contingent government payments on alternative U.S. farm household typologies. We find that farm households do vary their responses to an elimination of price-contingent support based on location, production specialty, and farm categorization.Agricultural and Food Policy,
Paper Session III-B - Mars Transportation System Synthesis
President George Bush\u27s 1989 challenge to America to support the Space Exploration Initiative (SEI) of Back to the Moon and Manned Mission to Mars gives the space industry an opportunity to achieve effective and efficient space transportation systems (STS\u27s). This paper presents performance and requirements synthesized to support the manned Mars mission of the SEI. The information presented focuses primarily on the Mars transportation system (MTS), which uses nuclear thermal rocket (NTR) propulsion technology associated with accomplishing the manned Mars mission. Data are also shown for a propulsion system options comparison of chemical/ aerobrake and nuclear electric propulsion (NEP) systems
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