Kirchhoff's Rule for Quantum Wires

In this article we formulate and discuss one particle quantum scattering theory on an arbitrary finite graph with $n$ open ends and where we define the Hamiltonian to be (minus) the Laplace operator with general boundary conditions at the vertices. This results in a scattering theory with $n$ channels. The corresponding on-shell S-matrix formed by the reflection and transmission amplitudes for incoming plane waves of energy $E>0$ is explicitly given in terms of the boundary conditions and the lengths of the internal lines. It is shown to be unitary, which may be viewed as the quantum version of Kirchhoff's law. We exhibit covariance and symmetry properties. It is symmetric if the boundary conditions are real. Also there is a duality transformation on the set of boundary conditions and the lengths of the internal lines such that the low energy behaviour of one theory gives the high energy behaviour of the transformed theory. Finally we provide a composition rule by which the on-shell S-matrix of a graph is factorizable in terms of the S-matrices of its subgraphs. All proofs only use known facts from the theory of self-adjoint extensions, standard linear algebra, complex function theory and elementary arguments from the theory of Hermitean symplectic forms.Comment: 40 page

A Visual History of Tadeusz Kantor's Theatre

A Visual History of Tadeusz Kantor's Theatr

Barriers to Work Place Advancement: the Experience of the White Female Work Force

Glass Ceiling ReportGlassCeilingBackground17WhiteFemaleWorkForce.pdf: 8903 downloads, before Oct. 1, 2020

International Trade and the Natural Resource 'Curse' in Southeast Asia: Does China's Growth Threaten Regional Development

China's growth, along with its increasing integration with world markets through WTO accession, abolition of Multifiber Arrangement (MFA) quotas, and reduced trade barriers with ASEAN, is expected to have significant effects on the structure of regional production and trade. Through bilateral trade growth as well as through competition with China in global markets, Southeast Asia's resource-abundant economies will become more intensive in natural resource-based exports and much less so in low-end, labor-intensive manufacturing such as garments. Both these effects will tend to increase demand for natural resources, one through a direct product market effect, the other by driving down the price of a complementary input, low-skill labor. A question that then arises is how these trends will interact with the other major phenomenon currently sweeping through Southeast Asia, namely decentralization. With reduced national government power and little or no accountability at the local level, the potential for disastrous rates of resource exploitation is high. If sufficiently severe, the combination of increased demand for natural resources and diminished constraints on their could expose the region to reduced rates of economic growth, a variant of the "natural resource curse" argument, which maintains that resource-abundant economies grow more slowly than others.

The promoter and transcribed regions of the Leishmania tarentolae spliced leader RNA gene array are devoid of nucleosomes

<p>Abstract</p> <p>Background</p> <p>The spliced leader (SL) RNA provides the 5' m⁷G cap and first 39 nt for all nuclear mRNAs in kinetoplastids. This small nuclear RNA is transcribed by RNA polymerase II from individual promoters. In <it>Leishmania tarentolae </it>the SL RNA genes reside in two multi-copy tandem arrays designated <it>MINA </it>and <it>MINB</it>. The transcript accumulation from the SL promoter on the drug-selected, episomal SL RNA gene cassette pX-tSL is ~10% that of the genomic array in uncloned <it>L. tarentolae </it>transfectants. This disparity is neither sequence- nor copy-number related, and thus may be due to interference of SL promoter function by epigenetic factors. To explore these possibilities we examined the nucleoplasmic localization of the SL RNA genes as well as their nucleosomal architecture.</p> <p>Results</p> <p>The genomic SL RNA genes and the episome did not co-localize within the nucleus. Each genomic repeat contains one nucleosome regularly positioned within the non-transcribed intergenic region. The 363-bp <it>MINA </it>array was resistant to micrococcal nuclease digestion between the -258 and -72 positions relative to the transcription start point due to nucleosome association, leaving the promoter elements and the entire transcribed region exposed for protein interactions. A pattern of ~164-bp protected segments was observed, corresponding to the amount of DNA typically bound by a nucleosome. By contrast, nucleosomes on the pX-tSL episome were randomly distributed over the episomal SL cassette, reducing transcription factor access to the episomal promoter by approximately 74%. Cloning of the episome transfectants revealed a range of transcriptional activities, implicating a mechanism of epigenetic heredity.</p> <p>Conclusion</p> <p>The disorganized nucleosomes on the pX episome are in a permissive conformation for transcription of the SL RNA cassette approximately 25% of the time within a given parasite. Nucleosome interference is likely the major factor in the apparent transcriptional repression of the SL RNA gene cassette. Coupled with the requirement for run-around transcription that drives expression of the selectable drug marker, transcription of the episomal SL may be reduced even further due to sub-optimal nucleoplasmic localization and initiation complex disruption.</p

News of the Blues: November, 1959

A newsletter for Blue Cross of Florida employees with announcements and special events pertinent to their company