4,470 research outputs found
Symmetry, Entropy, Diversity and (why not?) Quantum Statistics in Society
We describe society as a nonequilibrium probabilistic system: N individuals
occupy W resource states in it and produce entropy S over definite time
periods. Resulting thermodynamics is however unusual because a second entropy,
H, measures a typically social feature, inequality or diversity in the
distribution of available resources. A symmetry phase transition takes place at
Gini values 1/3, where realistic distributions become asymmetric. Four
constraints act on S: expectedly, N and W, and new ones, diversity and
interactions between individuals; the latter result from the two coordinates of
a single point in the data, the peak. The occupation number of a job is either
zero or one, suggesting Fermi-Dirac statistics for employment. Contrariwise, an
indefinite nujmber of individuals can occupy a state defined as a quantile of
income or of age, so Bose-Einstein statistics may be required.
Indistinguishability rather than anonymity of individuals and resources is thus
needed. Interactions between individuals define define classes of equivalence
that happen to coincide with acceptable definitions of social classes or
periods in human life. The entropy S is non-extensive and obtainable from data.
Theoretical laws are compared to data in four different cases of economical or
physiological diversity. Acceptable fits are found for all of them.Comment: 13 pages, 2 figure
Electrical Nanoprobing of Semiconducting Carbon Nanotubes using an Atomic Force Microscope
We use an Atomic Force Microscope (AFM) tip to locally probe the electronic
properties of semiconducting carbon nanotube transistors. A gold-coated AFM tip
serves as a voltage or current probe in three-probe measurement setup. Using
the tip as a movable current probe, we investigate the scaling of the device
properties with channel length. Using the tip as a voltage probe, we study the
properties of the contacts. We find that Au makes an excellent contact in the
p-region, with no Schottky barrier. In the n-region large contact resistances
were found which dominate the transport properties.Comment: 4 pages, 5 figure
Isotropic, Nematic and Smectic A Phase Behaviour in a Fictitious Field
Phase behaviours of liquid crystals under external fields, conjugate to the
nematic order and smectic order, are studied within the framework of mean field
approximation developed by McMillan. It is found that phase diagrams, of
temperature vs interaction parameter of smectic A order, show several
topologically different types caused by the external fields. The influences of
the field conjugate to the smectic A phase, which is fictitious field, are
precisely discussed.Comment: To be published in J. Phys. Soc. Jpn. vol.73 No.
State Differentiation by Transient Truncation in Coupled Threshold Dynamics
Dynamics with a threshold input--output relation commonly exist in gene,
signal-transduction, and neural networks. Coupled dynamical systems of such
threshold elements are investigated, in an effort to find differentiation of
elements induced by the interaction. Through global diffusive coupling, novel
states are found to be generated that are not the original attractor of
single-element threshold dynamics, but are sustained through the interaction
with the elements located at the original attractor. This stabilization of the
novel state(s) is not related to symmetry breaking, but is explained as the
truncation of transient trajectories to the original attractor due to the
coupling. Single-element dynamics with winding transient trajectories located
at a low-dimensional manifold and having turning points are shown to be
essential to the generation of such novel state(s) in a coupled system.
Universality of this mechanism for the novel state generation and its relevance
to biological cell differentiation are briefly discussed.Comment: 8 pages. Phys. Rev. E. in pres
Gene identification for the cblD defect of vitamin B12 metabolism
Background Vitamin B12 (cobalamin) is an essential cofactor in several metabolic pathways. Intracellular conversion of cobalamin to its two coenzymes, adenosylcobalamin in mitochondria and methylcobalamin in the cytoplasm, is necessary for the homeostasis of methylmalonic acid and homocysteine. Nine defects of intracellular cobalamin metabolism have been defined by means of somatic complementation analysis. One of these defects, the cblD defect, can cause isolated methylmalonic aciduria, isolated homocystinuria, or both. Affected persons present with multisystem clinical abnormalities, including developmental, hematologic, neurologic, and metabolic findings. The gene responsible for the cblD defect has not been identified.
Methods We studied seven patients with the cblD defect, and skin fibroblasts from each were investigated in cell culture. Microcell-mediated chromosome transfer and refined genetic mapping were used to localize the responsible gene. This gene was transfected into cblD fibroblasts to test for the rescue of adenosylcobalamin and methylcobalamin synthesis.
Results The cblD gene was localized to human chromosome 2q23.2, and a candidate gene, designated MMADHC (methylmalonic aciduria, cblD type, and homocystinuria), was identified in this region. Transfection of wild-type MMADHC rescued the cellular phenotype, and the functional importance of mutant alleles was shown by means of transfection with mutant constructs. The predicted MMADHC protein has sequence homology with a bacterial ATP-binding cassette transporter and contains a putative cobalamin binding motif and a putative mitochondrial targeting sequence.
Conclusions Mutations in a gene we designated MMADHC are responsible for the cblD defect in vitamin B12 metabolism. Various mutations are associated with each of the three biochemical phenotypes of the disorder
Generation of measures on the torus with good sequences of integers
Let be a strictly increasing sequence of positive
integers and denote . We say
is good if for every real the limit exists. By the Riesz representation theorem, a sequence
is good iff for every real the sequence possesses an
asymptotic distribution modulo 1. Another characterization of a good sequence
follows from the spectral theorem: the sequence is good iff in any
probability measure preserving system the limit exists in -norm for .
Of these three characterization of a good set, the one about limit measures
is the most suitable for us, and we are interested in finding out what the
limit measure
on the torus can be. In this first paper on the subject, we investigate the
case of a single irrational . We show that if is a good set then
for every irrational the limit measure must be a
continuous Borel probability measure. Using random methods, we show that the
limit measure can be any measure which is absolutely
continuous with respect to the Haar-Lebesgue probability measure on the torus.
On the other hand, if is the uniform probability measure supported on the
Cantor set, there are some irrational so that for no good sequence
can we have the limit measure equal . We leave open the
question whether for any continuous Borel probability measure on the
torus there is an irrational and a good sequence so that
.Comment: 44 page
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