1,022 research outputs found
Cooling Techniques for Trapped Ions
This book chapter gives an introduction to, and an overview of, methods for
cooling trapped ions. The main addressees are researchers entering the field.
It is not intended as a comprehensive survey and historical account of the
extensive literature on this topic. We present the physical ideas behind
several cooling schemes, outline their mathematical description, and point to
relevant literature useful for a more in-depth study of this topic.Comment: Part of the Proceedings of the Les Houches Winter School on the
Physics with Trapped Charged Particles held in January 2012. References
updated in mid 201
Testing the Hubble Law with the IRAS 1.2 Jy Redshift Survey
We test and reject the claim of Segal et al. (1993) that the correlation of
redshifts and flux densities in a complete sample of IRAS galaxies favors a
quadratic redshift-distance relation over the linear Hubble law. This is done,
in effect, by treating the entire galaxy luminosity function as derived from
the 60 micron 1.2 Jy IRAS redshift survey of Fisher et al. (1995) as a distance
indicator; equivalently, we compare the flux density distribution of galaxies
as a function of redshift with predictions under different redshift-distance
cosmologies, under the assumption of a universal luminosity function. This
method does not assume a uniform distribution of galaxies in space. We find
that this test has rather weak discriminatory power, as argued by Petrosian
(1993), and the differences between models are not as stark as one might expect
a priori. Even so, we find that the Hubble law is indeed more strongly
supported by the analysis than is the quadratic redshift-distance relation. We
identify a bias in the the Segal et al. determination of the luminosity
function, which could lead one to mistakenly favor the quadratic
redshift-distance law. We also present several complementary analyses of the
density field of the sample; the galaxy density field is found to be close to
homogeneous on large scales if the Hubble law is assumed, while this is not the
case with the quadratic redshift-distance relation.Comment: 27 pages Latex (w/figures), ApJ, in press. Uses AAS macros,
postscript also available at
http://www.astro.princeton.edu/~library/preprints/pop682.ps.g
The Uncertainty of Fluxes
In the ordinary quantum Maxwell theory of a free electromagnetic field,
formulated on a curved 3-manifold, we observe that magnetic and electric fluxes
cannot be simultaneously measured. This uncertainty principle reflects torsion:
fluxes modulo torsion can be simultaneously measured. We also develop the
Hamilton theory of self-dual fields, noting that they are quantized by
Pontrjagin self-dual cohomology theories and that the quantum Hilbert space is
Z/2-graded, so typically contains both bosonic and fermionic states.
Significantly, these ideas apply to the Ramond-Ramond field in string theory,
showing that its K-theory class cannot be measured.Comment: 33 pages; minor modifications for publication in Commun. Math. Phy
A Compact Microchip-Based Atomic Clock Based on Ultracold Trapped Rb Atoms
We propose a compact atomic clock based on ultracold Rb atoms that are
magnetically trapped near the surface of an atom microchip. An interrogation
scheme that combines electromagnetically-induced transparency (EIT) with
Ramsey's method of separated oscillatory fields can achieve atomic shot-noise
level performance of 10^{-13}/sqrt(tau) for 10^6 atoms. The EIT signal can be
detected with a heterodyne technique that provides noiseless gain; with this
technique the optical phase shift of a 100 pW probe beam can be detected at the
photon shot-noise level. Numerical calculations of the density matrix equations
are used to identify realistic operating parameters at which AC Stark shifts
are eliminated. By considering fluctuations in these parameters, we estimate
that AC Stark shifts can be canceled to a level better than 2*10^{-14}. An
overview of the apparatus is presented with estimates of duty cycle and power
consumption.Comment: 15 pages, 11 figures, 5 table
Rolul central al prelungirilor citoplasmatice ale podocitelor în condiții de normă și boli glomerulare
Background. Podocytes cells are part of the filtration barrier that prevent loss of proteins into urine. Podocytes injury
that presents in various range of diseases result in proteinuria. The mechanisms of injuries can vary, but all of them
lead to the foot process effacement of podocytes. Objective
of the study. Studying the morphology and normal function
of the podocytes foot process and of associated changes of
them within glomerular diseases. Material and Methods.
The research is based on literary sources that were analyzed using PubMed, NCBI and Medline published within
the period of 2012-2022. Results. The analyzed research showed that the podocyte foot processes are attached
to the glomerular capillaries at the glomerular basement
membrane (GBM) by forming intercellular junctions that
form slit diaphragm of filtration barrier. Morphologically,
the podocytes are atypical polarized epithelial cells that are
divided into 3 separate structural and functional elements:
a large cell body, major extending processes, and minor foot
processes. The apical domain is negatively charged, which
is limiting the passage of albumin into urine. The injured
podocytes undergo effacement, and in result reduction of
filtration barrier function and proteinuria. Conclusion. The
podocyte injury lead to impaired of the filtration barrier
function. The injury to the podocyte result in effacement,
that is part of the pathophysiological processes in variety of
disease process, which injured the podocyte, and result in
nephrotic syndrome.Introducere. Podocitele, parte componentă din bariera de
filtrare, previn pierderea proteinelor în urină. Leziunile podocitelor, prezente într-un șir de boli renale, duc la proteinurie. Mecanismele leziunilor sunt variate și duc la atrofierea prelungirii citoplasmatice a podocitului. Scopul lucrării. Studierea morfologiei și funcției normale a prelungirii
citoplasmatice ale podocitelor și a modificărilor asociate
acestora în cadrul bolilor glomerulare. Material și Metode. Cercetarea se bazează pe surse bibliografice care au fost
analizate folosind PubMed, NCBI și Medline, publicate în
perioada 2012-2022. Rezultate. Lucrările analizate au evidențiat că prelungirile podocitelor sunt atașate de capilarele glomerulare la nivelul membranei bazale (GBM) prin formarea de joncțiuni intercelulare, care realizează fantele barierei de filtrare. Din punct de vedere morfologic, podocitele
sunt celule epiteliale polarizate atipice, care sunt împărțite
în 3 domenii structurale și funcționale diferite: corp celular,
prelungirile primare și prelungirile secundare. Domeniul
apical este încărcat negativ, ceea ce limitează trecerea albuminei în urină. Podocitele lezate sunt supuse atrofierii și, ca
urmare, apare proteinuria și se reduce funcția barierei de
filtrare. Concluzii. Leziunile podocitelor conduc la afectarea funcției barierei de filtrare. Leziunea podocitului rezultă
în atrofierea prelungirilor, urmare proceselor fiziopatologic
în cadrul unui șir de boli renale, care duc la uzarea podocitului și la sindrom nefrotic
The central role of podocyte foot processes in the normal conditions and glomerular diseases
Introduction: Podocytes cells are part of the filtration barrier that prevent loss of proteins into urine. Podocytes injury that present in various range of diseases result in proteinuria. The mechanisms of injuries can vary, but all them lead to the foot process effacement of podocytes.
Purpose: Studying the morphology and normal function of the podocytes foot process and of associated changes of them within glomerular diseases.
Material and methods: The research is based on literary sources that were analyzed using PubMed, NCBI and Medline published within the period of 2012-2022.
Results: The analyzed researches showed that the podocyte foot processes are attached to the glomerular capillaries at the
glomerular basement membrane (GBM) by forming intercellular junctions that form slit diaphragm of filtration barrier.
Morphologically, the podocytes are atypical polarized epithelial cells that are divided into 3 separate structural and functional
elements: a large cell body, major extending processes, and minor foot processes. The apical domain is negatively charged, which is
limiting the passage of albumin into urine. The injured podocytes undergo effacement, and in result reduction of filtration barrier
function and proteinuria.
Conclusions:
The podocyte foot processes are attached to the
glomerular capillaries at the glomerular basement
membrane (GBM) by forming intercellular junctions
that form slit diaphragm of filtration barrier.
The podocytes are divided into 3 separate structural
and functional elements: a large cell body, major
extending processes, minor foot processes.
The apical domain is negatively charged, which is
limiting the passage of albumin into urine. The injured
podocytes undergo effacement, and in result reduction
of filtration barrier function and proteinuria
Nationale Identität durch politische Mythen
Film als politikwissenschaftlichen Forschungsgegenstand zu betrachten, ist der ganz allgemeine Ansatz dieser Diplomarbeit. Das konkrete Forschungsinteresse ist dabei die Darstellung und Vermittlung politischer Mythen und deren Implikationen für die nationale Identität einer Bevölkerung. Die Deutsche Demokratische Republik (DDR) ist dabei ein besonders aufschlussreiches Untersuchungsobjekt, da diese von Anfang an auf einem großen Mythos basierte. Gemeint ist der Antifaschismus-Mythos, der als Gründungslegitimation diente und bis zum Ende der DDR 1990 als der wesentliche Systemstabilisator herangezogen wurde.
Im theoretischen Teil der Arbeit wird erklärt, warum die Existenz und Glaubwürdigkeit politischer Mythen für die Aufrechterhaltung nationaler Gemeinschaften essentiell sind.
Die Diplomarbeit macht schließlich deutlich, inwieweit Film geeignet ist, diese Kohärenz von Mythos, Identität und Nationalstaat aufzuzeigen.
In der qualitativen Inhaltsanalyse von drei Filmen, „…und deine Liebe auch“, „Die Glatzkopfbande“ und die Episode „Phoenix“ des vierteiligen Films „Geschichten jener Nacht“, stellt sich heraus, dass die ZuseherInnen eindeutig beeinflusst werden sollten, dem propagierten Ideal zu gehorchen und für „ihre“ Heimat einzustehen. Die Darstellung des Antifaschismus-Mythos diente dabei als Hilfsmittel
Extrachromosomal circles of satellite repeats and 5S ribosomal DNA in human cells
<p>Abstract</p> <p>Background</p> <p>Extrachomosomal circular DNA (eccDNA) is ubiquitous in eukaryotic organisms and was detected in every organism tested, including in humans. A two-dimensional gel electrophoresis facilitates the detection of eccDNA in preparations of genomic DNA. Using this technique we have previously demonstrated that most of eccDNA consists of exact multiples of chromosomal tandemly repeated DNA, including both coding genes and satellite DNA.</p> <p>Results</p> <p>Here we report the occurrence of eccDNA in every tested human cell line. It has heterogeneous mass ranging from less than 2 kb to over 20 kb. We describe eccDNA homologous to human alpha satellite and the <it>Sst</it>I mega satellite. Moreover, we show, for the first time, circular multimers of the human 5S ribosomal DNA (rDNA), similar to previous findings in <it>Drosophila </it>and plants. We further demonstrate structures that correspond to intermediates of rolling circle replication, which emerge from the circular multimers of 5S rDNA and <it>Sst</it>I satellite.</p> <p>Conclusions</p> <p>These findings, and previous reports, support the general notion that every chromosomal tandem repeat is prone to generate eccDNA in eukryoric organisms including humans. They suggest the possible involvement of eccDNA in the length variability observed in arrays of tandem repeats. The implications of eccDNA on genome biology may include mechanisms of centromere evolution, concerted evolution and homogenization of tandem repeats and genomic plasticity.</p
- …