Quantum Vibrational Impurity Embedded in a One-dimensional Chain

We perform a fully quantum mechanical numerical calculation for the problem of a single electron (or excitation) propagating in a N-site one-dimensional chain in the presence of a single Holstein impurity. We compute the long-time averaged probability for finding the electron on the impurity site as a function of the nonlinearity parameter, defined in terms of the electron-phonon coupling strength and the oscillator frequency. The results, in the intermediate nonlinearity parameter range, differ substantially from the ones obtained through the use of the discrete nonlinear Schroedinger equation, even in the high-frequency regime.Comment: 8 pages, 4 figure

Aflatoksin M1 u mliječnim međuproduktima nastalim u proizvodnji Manchego sira: razdioba i postojanost

Aflatoxin M1 (AFM1) distribution in curd, whey, Manchego cheese, the traditional Spanish whey cheese Requesón and Requesón whey, and its stability during two different cold treatments, have been studied. Raw ewe’s milk was artificially contaminated with AFM1 in a final concentration of 50 and 100 ng kg-1, and was used to produce Manchego cheese. AFM1 determinations were carried out by HPLC with fluorimetric detection after immunoaffinity clean-up. The mean AFM1 concentrations in the produced curd and Manchego cheese were approximately 2- and 3-fold higher than the initial milk they were made from, and the levels of this toxin remaining in whey were 42.3 % and 51.3 % of the initial concentrations. In the Requesón samples, the mean AFM1 values were 1.7 times higher than those in the corresponding whey, while 33.7 % and 44.4 % of the AFM1 concentration detected in milk also appeared in the Requesón whey. Short refrigeration and freezing periods did not affect the toxin levels in either curd or Requesón samples. When ewe’s milk destined for Manchego cheese-making is AFM1-contaminated at the EU limit level (50 ng kg-1) or double, a concentration of this toxin will appear in the manufactured products, but values will be considerably below the toxic doses (Tolerable Daily Intake = 2 ng kg-1 body weight per day), which poses a human health problem.U istraživanju je utvrđivana razdioba aflatoksina M1 (AFM1) u grušu, sirutki, Manchego siru, tradicionalnom španjolskom Requesón siru načinjenom od sirutke i Requesón sirutki te njegova stabilnost tijekom dva različita tretmana hlađenja. Svježe ovčje mlijeko je “umjetno” kontaminirano s AFM1 u završnoj koncentraciji od 50 i 100 ng kg-1 i korišteno je u proizvodnji Manchego sira. Koncentracije AFM1 mjerene su HPLC fluorometrijskom detekcijom nakon potpunog pročišćavanja imunoafinitetnim postupkom. Srednje vrijednosti koncentracija AFM1 u proizvedenom grušu i Manchego siru bile su oko 2 do 3 puta veće od prvotnog mlijeka od kojeg su načinjeni, a razine toksina zaostale u sirutki bile su 42,3 % i 51,3 % od početne koncentracije. U Requesón uzorcima srednje AFM1 vrijednosti bile su 1,7 puta veće od onih u uzorcima sirutke, dok su AFM1 koncentracije 33,7 % i 44,4 % utvrđene u mlijeku, također utvrđene i u odgovarajućim uzorcima Requesón sirutke. Kratka razdoblja hlađenja i zamrzavanja nisu utjecala na razinu toksina u grušu i Requesón uzorcima. U slučaju kada je ovčje mlijeko namijenjeno za proizvodnju Manchego sira kontaminirano s AFM1 na razini EU-propisa (50 ng kg-1), ili dvostruko većom od te granice, određena koncentracija tog toksina pojavit će se u prerađevinama, ali će vrijednosti biti znatno niže od toksičnih doza (podnošljive dnevne doze = 2 ng kg-1 tjelesne mase dnevno), što predstavlja određeni problem za ljudsko zdravlje

Performance of current microbial tests for screening antibiotics in sheep and goat milk

[EN] The detection capability (CC beta) of some microbial screening tests currently available was calculated for sheep and goat milk in accordance with Commission Decision 657/2002/EC. The CC beta was at or below the maximum residue limit (MRL) for most beta-lactams assessed and other non-beta-lactam drugs such as neomycin, tylosin, sulfadiazine and sulfadimethoxine. However, the tests were less sensitive in the detection of most non-beta-lactam drugs such as quinolones and tetracyclines at safety levels. When individual sheep milk samples free of antibiotics were analysed, an elevated somatic cell count was related to the occurrence of non-compliant results in all the methods assessed. To guarantee the safety of milk and dairy products from small ruminants, the periodical implementation of screening tests more sensitive towards non-beta-lactam drugs would be appropriate. (C) 2014 Elsevier Ltd. All rights reserved.This research forms part of the Project AGL2009-11524 financed by the Ministerio de Ciencia e Innovacion (Madrid, Spain).Beltrán Martínez, MC.; Berruga Fernandez, MI.; Molina Casanova, A.; Lisandro Althaus, R.; Molina Pons, MP. (2015). Performance of current microbial tests for screening antibiotics in sheep and goat milk. International Dairy Journal. 41:13-15. https://doi.org/10.1016/j.idairyj.2014.09.007S13154

Identification of two novel mutations in CDHR1 in consanguineous Spanish families with autosomal recessive retinal dystrophy.

Inherited retinal dystrophies present extensive phenotypic and genetic heterogeneity, posing a challenge for patients' molecular and clinical diagnoses. In this study, we wanted to clinically characterize and investigate the molecular etiology of an atypical form of autosomal recessive retinal dystrophy in two consanguineous Spanish families. Affected members of the respective families exhibited an array of clinical features including reduced visual acuity, photophobia, defective color vision, reduced or absent ERG responses, macular atrophy and pigmentary deposits in the peripheral retina. Genetic investigation included autozygosity mapping coupled with exome sequencing in the first family, whereas autozygome-guided candidate gene screening was performed by means of Sanger DNA sequencing in the second family. Our approach revealed nucleotide changes in CDHR1; a homozygous missense variant (c.1720C > G, p.P574A) and a homozygous single base transition (c.1485 + 2T > C) affecting the canonical 5' splice site of intron 13, respectively. Both changes co-segregated with the disease and were absent among cohorts of unrelated control individuals. To date, only five mutations in CDHR1 have been identified, all resulting in premature stop codons leading to mRNA nonsense mediated decay. Our work reports two previously unidentified homozygous mutations in CDHR1 further expanding the mutational spectrum of this gene

Self-trapping transition for nonlinear impurities embedded in a Cayley tree

The self-trapping transition due to a single and a dimer nonlinear impurity embedded in a Cayley tree is studied. In particular, the effect of a perfectly nonlinear Cayley tree is considered. A sharp self-trapping transition is observed in each case. It is also observed that the transition is much sharper compared to the case of one-dimensional lattices. For each system, the critical values of $\chi$ for the self-trapping transitions are found to obey a power-law behavior as a function of the connectivity $K$ of the Cayley tree.Comment: 6 pages, 7 fig

Evolution of wave packets in quasi-1D and 1D random media: diffusion versus localization

We study numerically the evolution of wavepackets in quasi one-dimensional random systems described by a tight-binding Hamiltonian with long-range random interactions. Results are presented for the scaling properties of the width of packets in three time regimes: ballistic, diffusive and localized. Particular attention is given to the fluctuations of packet widths in both the diffusive and localized regime. Scaling properties of the steady-state distribution are also analyzed and compared with theoretical expression borrowed from one-dimensional Anderson theory. Analogies and differences with the kicked rotator model and the one-dimensional localization are discussed.Comment: 32 pages, LaTex, 11 PostScript figure

Vitamin D and melanoma

La relación entre la vitamina D y diversos tumores ha sido objeto de estudio por varios autores en los últimos años. El papel protector de la vitamina D se ha confirmado en estudios epidemiológicos para tumores como el de colon y se ha sugerido en el melanoma. La vitamina D podría tener un papel antitumoral, de tal manera que una menor actividad de la vitamina D estaría relacionada con un mayor riesgo de melanoma. La mayor parte de la vitamina D se obtiene a través de la radiación ultravioleta. Surge así la controversia entre el beneficio de la vitamina D y su función antitumoral, frente a la radiación ultravioleta, carcinógeno conocido que altera el ADN de las células y aumenta el riesgo de cáncer cutáneo. El objetivo de nuestra revisión es proporcionar un análisis detallado que hace referencia al actual interés en la vitamina D y el melanoma.The relationship between vitamin D and various tumors has been studied by several authors in recent years. The protective role of vitamin D has been confirmed in epidemiological studies for tumors such as colon cancer and melanoma has been suggested. Vitamin D may have an antitumor role, so that a reduced activity of vitamin D be associated with an increased risk of melanoma. Most vitamin D is obtained through ultraviolet radiation. This led to the dispute between the benefit of vitamin D and its antitumor function, compared to ultraviolet radiation, a carcinogen known to alter the DNA of cells and increases the risk of skin cancer. The objective of our review is to provide a detailed analysis refers to the current interest in vitamin D and melanoma

Instabilities and Bifurcations of Nonlinear Impurity Modes

We study the structure and stability of nonlinear impurity modes in the discrete nonlinear Schr{\"o}dinger equation with a single on-site nonlinear impurity emphasizing the effects of interplay between discreteness, nonlinearity and disorder. We show how the interaction of a nonlinear localized mode (a discrete soliton or discrete breather) with a repulsive impurity generates a family of stationary states near the impurity site, as well as examine both theoretical and numerical criteria for the transition between different localized states via a cascade of bifurcations.Comment: 8 pages, 8 figures, Phys. Rev. E in pres

Strong and weak chaos in weakly nonintegrable many-body Hamiltonian systems

We study properties of chaos in generic one-dimensional nonlinear Hamiltonian lattices comprised of weakly coupled nonlinear oscillators, by numerical simulations of continuous-time systems and symplectic maps. For small coupling, the measure of chaos is found to be proportional to the coupling strength and lattice length, with the typical maximal Lyapunov exponent being proportional to the square root of coupling. This strong chaos appears as a result of triplet resonances between nearby modes. In addition to strong chaos we observe a weakly chaotic component having much smaller Lyapunov exponent, the measure of which drops approximately as a square of the coupling strength down to smallest couplings we were able to reach. We argue that this weak chaos is linked to the regime of fast Arnold diffusion discussed by Chirikov and Vecheslavov. In disordered lattices of large size we find a subdiffusive spreading of initially localized wave packets over larger and larger number of modes. The relations between the exponent of this spreading and the exponent in the dependence of the fast Arnold diffusion on coupling strength are analyzed. We also trace parallels between the slow spreading of chaos and deterministic rheology.Comment: 15 pages, 14 figure