1,172 research outputs found
Balmer-Like Series for Baryon Resonances
The pole positions of various baryon resonances have been found to reveal a
well pronounced clustering, the so-called H"ohler cluster. In a previous work,
the H"ohler clusters have been shown to be identical to Lorentz multiplets of
the type (1/2+l', 1/2+l')*[(1/2,0)+(0,1/2)] with l' integer. Here we show that
the cluster positions are well described by means of a Balmer-series like
recursive mass formula.Comment: 5 pages LaTex, World Scientific style, two tables. A missing additive
factor of +1 on the rhs of Eq. (2) has been inserted and thereby a misprint,
not an error, correcte
Classifying Reported and "Missing" Resonances According to Their P and C Properties
The Hilbert space H^3q of the three quarks with one excited quark is
decomposed into Lorentz group representations. It is shown that the quantum
numbers of the reported and ``missing'' resonances fall apart and populate
distinct representations that differ by their parity or/and charge conjugation
properties. In this way, reported and ``missing'' resonances become
distinguishable. For example, resonances from the full listing reported by the
Particle Data Group are accommodated by Rarita-Schwinger (RS) type
representations (k/2,k/2)*[(1/2,0)+(0,1/2)] with k=1,3, and 5, the highest spin
states being J=3/2^-, 7/2^+, and 11/2^+, respectively. In contrast to this,
most of the ``missing'' resonances fall into the opposite parity RS fields of
highest-spins 5/2^-, 5/2^+, and 9/2^+, respectively. Rarita-Schwinger fields
with physical resonances as lower-spin components can be treated as a whole
without imposing auxiliary conditions on them. Such fields do not suffer the
Velo-Zwanziger problem but propagate causally in the presence of
electromagnetic fields. The pathologies associated with RS fields arise
basically because of the attempt to use them to describe isolated spin-J=k+1/ 2
states, rather than multispin-parity clusters. The positions of the observed RS
clusters and their spacing are well explained trough the interplay between the
rotational-like (k/2)(k/2 +1)-rule and a Balmer-like -(k+1)^{-2}-behavior
Lorentz Multiplet Structure of Baryon Spectra and Relativistic Description
The pole positions of the various baryon resonances are known to reveal
well-pronounced clustering, so-called Hoehler clusters. For nonstrange baryons
the Hoehler clusters are shown to be identical to Lorentz multiplets of the
type (j,j)*[(1/2,0)+(0,1/2)] with j being a half-integer. For the Lambda
hyperons below 1800 MeV these clusters are shown to be of the type [(1,0)+
(0,1)]*[(1/2,0)+(0,1/2)] while above 1800 MeV they are parity duplicated
(J,0)+(0,J) (Weinberg-Ahluwalia) states. Therefore, for Lambda hyperons the
restoration of chiral symmetry takes place above 1800 MeV. Finally, it is
demonstrated that the description of spin-3/2 particles in terms of a 2nd rank
antisymmetric Lorentz tensor with Dirac spinor components does not contain any
off-shell parameters and avoids the main difficulties of the Rarita-Schwinger
description based upon a 4-vector with Dirac spinor components.Comment: 12 pages, LaTex, submitted to Mod. Phys. Lett.
Bethe-Salpeter equation with cross-ladder kernel in Minkowski and Euclidean spaces
Some results obtained by a new method for solving the Bethe-Salpeter equation
are presented. The method is valid for any kernel given by irreducible Feynman
graphs. The Bethe-Salpeter amplitude, both in Minkowski and in Euclidean
spaces, and the binding energy for ladder + cross-ladder kernel are found. We
calculate also the corresponding electromagnetic form factor.Comment: 4 pages, 3 figures. Contribution to the proceedings of the 18th
International IUPAP Conference on Few-Body Problems in Physics (FB18),
Santos, Brasil, August 21-26, 2006. To be published in Nucl. Phys.
DNA-viivakoodaus elintarvikkeiden aitoustutkimuksissa
Opinnäytetyön tarkoituksena oli ottaa käyttöön ja validoida DNA-viivakoodaus-menetelmä Elintarviketurvallisuusvirasto Eviralle. DNA-viivakoodaus oli alun perin ekologisiin tutkimuksiin kehitelty menetelmä, mutta pian siitä huomattiin olevan hyötyä myös muilla tutkimusalueilla, kuten elintarvikkeiden aitoustutkimuksissa. Elintarvikepetoksia ja etenkin mereneläviin kohdistuvia väärennöksiä paljastuu yhä enemmän maailmalla. Suomessa näitä väärennöksiä ei ole kovinkaan paljoa tutkittu aikaisemmin.
DNA-viivakoodaus-menetelmä perustuu siihen, että genomista on valittu alue, jossa lajin sisällä emäsjärjestys vaihtelee mahdollisimman vähän ja eri lajien välillä suuresti. Lajit voidaan erottaa toisistaan viivakoodialueen sekvenssien perusteella. Eläinlajeilla käytetään usein mitokondriaalisen DNA:n sytokromi c oksidaasi 1 -geeniä (CO1) ja kasveilla kloroplastin maturaasi K (matK)- ja ribuloosi bisfosfaatti karboksylaasi iso alayksikkö (rbcL) -geenejä.
Opinnäytetyön laboratorio-osuus suoritettiin pääosin Yhdysvaltain elintarvike- ja lääkevirasto FDA:n laatiman työohjeen mukaisesti. Kalanäytteestä eristettiin DNA, josta monistettiin PCR:llä tietty nukleotidijakso. PCR-tuote puhdistettiin ja sekvensoitiin. Sekvensoinnin tulokset käsiteltiin bioinformatiikan työkaluin ja saatuja sekvenssejä verrattiin sekvenssitietokantoihin, jolloin saatiin selville näytteen kalalaji.
Menetelmän käyttöönotto onnistui hyvin. DNA-eristys onnistui, mikäli näytemäärä ei ollut liian suuri. Erilaiset matriisit, kuten savustettu tai suolattu kala, eivät aiheuttaneet ongelmia. Poikkeuksena olivat ainoastaan liian prosessoidut tuotteet, kuten öljyyn säilötty purkkikala. Työssä käytetyt alukkeet toimivat usealle lajille, ja lajintunnistus onnistui vähintään sukutasolle asti. Alustavien tutkimusten perusteella samat alukkeet ja menetelmä soveltuvat myös eläinlajien määritykseen.The purpose of this Bachelor’s thesis was to implement and validate a DNA barcoding method for Finnish Food Safety Authority Evira. DNA barcoding method was originally developed for ecological studies, but soon it was found to be useful in other areas of research as well, such as food authenticity studies. Increasing amount of food frauds, especially seafood forgeries have been found around the world. In Finland, these forgeries have not been studied intensively until recently.
DNA barcoding method is based on analysis of a selected area in the genome. The selected genome area should have as little sequence variety as possible within a species and as much as possible between different species. Species can be identified by the sequences of the barcode region. The cytochrome c oxidase subunit 1 gene (CO1) from mitochondrial DNA is often used with animal identification, and maturase K (matK) and ribulose bisphosphate carboxylase large chain (rbcL) genes from the chloroplast are used when researching plants.
The laboratory work in this thesis was carried out mainly in accordance with the standard operating procedure made by the U.S. Food and Drug Administration FDA. The DNA was extracted from the fish sample, and a specific nucleotide sequence was amplified from the DNA. The PCR product was purified and sequenced. The results of the sequencing were processed with bioinformatics tools, and the gained sequences were compared to sequence databases to identify the species of the fish sample.
The implementation of this method was successful. DNA extraction succeeded if the sample was not too large. Different matrices, such as smoked or salted fish, did not cause problems. The only exceptions were too far processed products, such as fish canned in oil. The primers used in this thesis were functional in many species and the identification of the species was successful until the family level at least. On the bases of the preliminary studies, the same primers and method are also suitable for the identification of several animal species
Octet and Decuplet Baryons in a Confining and Covariant Diquark-Quark Model
We treat baryons as bound states of scalar or axialvector diquarks and a
constituent quark which interact through quark exchange. We obtain fully
four-dimensional wave functions for both octet and decuplet baryons as
solutions of the corresponding Bethe-Salpeter equation. Applications currently
under investigation are: electromagnetic and strong form factors and
strangeness production processes.Comment: 4 pages, 1 figure; talk given by R. Alkofer at PANIC 9
Does the effective Lagrangian for low-energy QCD scale?
QCD is not an approximately scale invariant theory. Hence a dilaton field is
not expected to provide a good description of the low-energy dynamics
associated with the gluon condensate. Even if such a field is introduced, it
remains almost unchanged in hadronic matter at normal densities. This is
because the large glueball mass together with the size of the phenomenological
gluon condensate ensure that changes to that condensate are very small at such
densities. Any changes in hadronic masses and decay constants in matter
generated by that condensate will be much smaller that those produced directly
by changes in the quark condensate. Hence masses and decay constants are not
expected to display a universal scaling.Comment: 7 pages (RevTeX), MC/TH 94/0
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