249 research outputs found
Pairs of Bloch electrons and magnetic translation groups
A product of irreducible representations of magnetic translation group is
considered. It leads to irreducible representations which were previously
rejected as nonphysical. A very simple example indicates a possible application
of these representations. In particular, they are important in descriptions of
pairs of electrons in a magnetic field and a periodic potential. The
periodicity of some properties with respect to the charge of a particle is
briefly discussed.Comment: 4 pages, RevTex. Latex2.09, amsfont
An extension of Fourier analysis for the n-torus in the magnetic field and its application to spectral analysis of the magnetic Laplacian
We solved the Schr{\"o}dinger equation for a particle in a uniform magnetic
field in the n-dimensional torus. We obtained a complete set of solutions for a
broad class of problems; the torus T^n = R^n / {\Lambda} is defined as a
quotient of the Euclidean space R^n by an arbitrary n-dimensional lattice
{\Lambda}. The lattice is not necessary either cubic or rectangular. The
magnetic field is also arbitrary. However, we restrict ourselves within
potential-free problems; the Schr{\"o}dinger operator is assumed to be the
Laplace operator defined with the covariant derivative. We defined an algebra
that characterizes the symmetry of the Laplacian and named it the magnetic
algebra. We proved that the space of functions on which the Laplacian acts is
an irreducible representation space of the magnetic algebra. In this sense the
magnetic algebra completely characterizes the quantum mechanics in the magnetic
torus. We developed a new method for Fourier analysis for the magnetic torus
and used it to solve the eigenvalue problem of the Laplacian. All the
eigenfunctions are given in explicit forms.Comment: 32 pages, LaTeX, minor corrections are mad
Spatial clustering of interacting bugs: Levy flights versus Gaussian jumps
A biological competition model where the individuals of the same species
perform a two-dimensional Markovian continuous-time random walk and undergo
reproduction and death is studied. The competition is introduced through the
assumption that the reproduction rate depends on the crowding in the
neighborhood. The spatial dynamics corresponds either to normal diffusion
characterized by Gaussian jumps or to superdiffusion characterized by L\'evy
flights. It is observed that in both cases periodic patterns occur for
appropriate parameters of the model, indicating that the general macroscopic
collective behavior of the system is more strongly influenced by the
competition for the resources than by the type of spatial dynamics. However,
some differences arise that are discussed.Comment: This version incorporates in the text the correction published as an
Erratum in Europhysics Letters (EPL) 95, 69902 (2011) [doi:
10.1209/0295-5075/95/69902
Utjecaj uvjeta grijanja na strukturnu jednolikost i lomno naprezanje aluminijske pjene
In this paper, the possibility to create uniform porous structure for non- symmetric precursor heating was investigated together with changes in collapse stress and their reproducibility. The statistic relative standard deviation (RSD) of pore size was used to determine the structural uniformity. It was shown that proper adjustment of the foaming parameters leads to formation of the uniform foam structure. The compression testing showed that standard deviation of collapse stress was higher for uniform structure than those obtained for non- uniform structure.U ovome radu istražena je mogućnost stvaranja jednolike porozne strukture nesimetričnim zagrijavanjem prekursora, te su isto tako istražene promjene lomnog naprezanja i njihova ponovljivost. Statistička relativna standardna devijacija (RSD) veličine pora koristila se za određivanje strukturne jednolikosti. Pokazano je da pravilan odabir parametara upjenjavanja dovodi do nastajanja jednolike strukture. Tlačna proba je pokazala da je vrijednost standardne devijacije lomnog naprezanja veća za jednoličnu strukturu od onih ostvarenih za nejednoliku strukturu
WPŁYW DODATKU KONCENTRATU BIAŁKOWO-KSANTOFILOWEGO (PX) Z LUCERNY DO MIESZANEK O ZMNIEJSZONYM POZIOMIE BIAŁKA OGÓLNEGO NA WYDALANIE AZOTU, EFEKTY PRODUKCYJNE I JAKOŚĆ MIĘSA TUCZNIKÓW
The infl uence of protein-xanthophyll (PX) concentrate of alfalfa supplement to crude protein-reduced diets was examined in relation to nitrogen excretion, performance parameters and pig meat quality. The investigations included 60 growers (PL x PLW) x Duroc crossbreeds assigned to 3 groups. The conclusion is that there is a large potential to decrease nitrogen emission to the environment by 10% lowering of dietary crude protein intake along with reduced
animal growth rate and elevated mixture utilization. Inclusion of a protein-xanthophyll concentrate (PX) of alfalfa to the diet is likely to diminish disadvantageous productive parameters arising from limiting of total crude protein level in relation to the requirements of pigs feeding norms [1993]. At the same time, it improves feed nitrogen utilization and reduces noxious odour emissions from a piggery. The components of a protein-xanthophyll concentrate (PX)
contribute to increased liver and kidney weight.Celem badań było określenie wpływu dodatku koncentratu białkowo-ksantofi lowego (PX) do mieszanek o zmniejszonym poziomie białka ogólnego na wzrost i wykorzystanie paszy, bilans azotu oraz cechy fi zyko-chemiczne mięsa wieprzowego. Badania dokonano na 60 warchlakach mieszańcach (pbz x wpb) x Duroc podzielonych na 3
grupy. W podsumowaniu należy podkreślić możliwość ograniczenia wydalania azotu do środowiska poprzez 10% ograniczenie poziomu białka w diecie tuczników przy jednoczesnym spadku tempa wzrostu zwierząt i zwiększonym zużyciu mieszanki. Dodatek koncentratu białkowo-ksantofi lowego (PX) z lucerny może zniwelować niekorzystne efekty produkcyjne związane z ograniczeniem poziomu białka surowego w stosunku do Norm Żywienia Świń [1993]
przy jednoczesnej poprawie wykorzystania azotu paszy i zmniejszeniu nieprzyjemnych zapachów odorowych w chlewni. Zawarte w koncentracie białkowo-ksantofi lowym (PX) substancje przyczyniają się do zwiększenia masy wątroby i nerek
Microbiological changes in meat and minced meat from beavers (Castor fiber L.) during refrigerated and frozen storage
This study aims to evaluate the microbiological status, pH, and water activity of European beaver meat to establish its shelf-life and microbiological safety. In this study, the microbiological profiles of meat and minced meat obtained from the carcasses of beavers were investigated. Microbial evaluation of the chilled meat was performed within 24 h after hunting, on the 7th day and 14th day, and the evaluation of the frozen meat was made during the 11th week of storage. Meat samples were analysed for total viable count (TVC), psychrotrophic bacteria count (PBC), Enterobacteriaceae count (EBC), Escherichia coli count (EC), total staphylococcal count (TSC), lactic acid bacteria count (LABC) and total yeast and mould counts (TYMC). Tests for the presence of pathogenic bacteria from the genus Salmonella and Listeria were also performed. Additionally, the pH and water activity were determined. The initial amount of TVC was 4.94 log CFU/g in meat samples and 4.80 log CFU/g in minced meat. After 14 days of storage, the TVC increased to 8.33 in meat samples and 8.08 log CFU/g in minced meat. Pathogenic bacteria such as Listeria and Salmonella were not found in the beaver meat tested. The microbiological state of meat stored frozen for 11 weeks was comparable to the state found in meat stored refrigerated for seven days regarding the number of microorganisms
Emerging Concepts Impacting Head and Neck Cancer Surgery Morbidity
All treatment modalities for head and neck cancer carry with them a risk of adverse events. Head and neck surgeons are faced with significant challenges to minimize associated morbidity and manage its sequelae. Recognizing situations in which a surgical complication is an adverse event inherent to the procedure can alleviate the psychologic impact a complication might have on the treatment team and minimize external and internal pressures. Focusing on the complications that can be effectively modified, future complications can be avoided. Also, some surgical morbidities may not be preventable, necessitating the option to reconsider whether the incidents should be labeled toxic reactions rather than a complication. This discussion highlights some of the areas in which additional research is needed to achieve the goal of minimizing the impact of surgical morbidity.Peer reviewe
Magnetic translation groups in an n-dimensional torus
A charged particle in a uniform magnetic field in a two-dimensional torus has
a discrete noncommutative translation symmetry instead of a continuous
commutative translation symmetry. We study topology and symmetry of a particle
in a magnetic field in a torus of arbitrary dimensions. The magnetic
translation group (MTG) is defined as a group of translations that leave the
gauge field invariant. We show that the MTG on an n-dimensional torus is
isomorphic to a central extension of a cyclic group Z_{nu_1} x ... x
Z_{nu_{2l}} x T^m by U(1) with 2l+m=n. We construct and classify irreducible
unitary representations of the MTG on a three-torus and apply the
representation theory to three examples. We shortly describe a representation
theory for a general n-torus. The MTG on an n-torus can be regarded as a
generalization of the so-called noncommutative torus.Comment: 29 pages, LaTeX2e, title changed, re-organized, to be published in
Journal of Mathematical Physic
Impact of Unexpected Events, Shocking News and Rumours on Foreign Exchange Market Dynamics
We analyze the dynamical response of the world's financial community to
various types of unexpected events, including the 9/11 terrorist attacks as
they unfolded on a minute-by-minute basis. We find that there are various
'species' of news, characterized by how quickly the news get absorbed, how much
meaning and importance is assigned to it by the community, and what subsequent
actions are then taken. For example, the response to the unfolding events of
9/11 shows a gradual collective understanding of what was happening, rather
than an immediate realization. For news items which are not simple economic
statements, and hence whose implications are not immediately obvious, we
uncover periods of collective discovery during which collective opinions seem
to oscillate in a remarkably synchronized way. In the case of a rumour, our
findings also provide a concrete example of contagion in inter-connected
communities. Practical applications of this work include the possibility of
producing selective newsfeeds for specific communities, based on their likely
impact
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