The minimal conformal O(N) vector sigma model at d=3

For the minimal O(N) sigma model, which is defined to be generated by the O(N) scalar auxiliary field alone, all n-point functions, till order 1/N included, can be expressed by elementary functions without logarithms. Consequently, the conformal composite fields of m auxiliary fields possess at the same order such dimensions, which are m times the dimension of the auxiliary field plus the order of differentiation.Comment: 15 page

The structure of Green functions in quantum field theory with a general state

In quantum field theory, the Green function is usually calculated as the expectation value of the time-ordered product of fields over the vacuum. In some cases, especially in degenerate systems, expectation values over general states are required. The corresponding Green functions are essentially more complex than in the vacuum, because they cannot be written in terms of standard Feynman diagrams. Here, a method is proposed to determine the structure of these Green functions and to derive nonperturbative equations for them. The main idea is to transform the cumulants describing correlations into interaction terms.Comment: 13 pages, 6 figure

Histamin u ribi dostupnoj na tržištu Srbije u 2018. godini

Histamine is a biogen amin, which is formed by decarboxylation of the histidine amino acid, under the action of the L-histidine-decarboxylase enzyme. High level of free histidine in fish meat, bacterial histidin decarboxylase activity and high temperature of storage elevate the level of histamine. Among the most important factors that can affect the level of histamine in fish meat are the type of fish and the method of its preservation. In order to determine this dependence, 1030 samples of frozen fish (tuna, mackerel, sardines and sprat) and 167 samples of canned fish (tuna, sardines and mackerel) were monitored for histamine content by ELISA method. It was determined a lower concentration of histamine in frozen fish (from 5.71 mg/kg to 18.03 mg/kg) compared to canned fish (from 15.03 mg/kg to 110.6 mg/kg). The highest histamine concentrations were found in the mackerel samples, regardless of the preservation method (110.6 mg/kg in canned mackerel and 18.03 mg/kg in frozen mackerel), which were significantly higher compared to the histamine levels found in cans of tuna and sardines (p ˂0.0001). Of the total number of samples, three samples (two samples of canned sardines and one sample of canned mackerel) were declared unsafe for human health. In most of the analyzed samples, the level of determined histamine was relatively low, which confirms adequate implementation of control protocols and efficant surveillance of products placed on the Serbian market.Histamin je bioaktivni amin, koji nastaje u reakciji dekarboksilacije aminokiseline histidina, pod dejstvom enzima Lhistidin dekarboksilaze. Visok nivo slobodnog histidina u mesu ribe, aktivnost enzim produkujućih bakterija i visoke temperature skladištenja deluju predisponirajuće na sintezu histamina. Među najznačajnije faktore koji utiču na koncentraciju histamina u mesu ribe jesu vrsta ribe i metod njenog konzervisanja. U cilju utvrđivanja ove zavisnosti, uzorci zamrznute ribe (tune, skuše, sardine i papaline) i ribe u konzervi (tune, sardine i skuše) su analizirani ELISA metodom. Utvrđene su niže koncentracije histamina u uzorcima zamrznute ribe (od 5.71 mg/kg do 18.03 mg/kg) u poređenju sa konzervama od ribe (od 15.03 mg/kg do 110.6 mg/kg). Najviše koncentracije histamina su ustanovljene u uzorcima skuše, bez obzira na metod konzervisanja (110.6 mg/kg u konzervama od skuše i 18.03 mg/kg u zamrznutoj skuši), koje su bile i statistički značajno veće u odnosu na konzerve tune i konzerve sardine (p ˂0.0001). Od ukupnog broja uzoraka, samo tri uzorka (dva uzorka sardine u konzervi i jedan uzorak skuše u konzervi) su proglašeni nebezbednim za zdravlje ljudi. U najvećem broju ispitanih uzoraka izmerene su relativno niske koncentracije histamina, što ukazuje na adekvatno sprovođenje kontrole i nadzora nad proizvodima koji se plasiraju u promet na srpskom tržištu

Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.

Our work describes the synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75with Mn4+/Mn5+charge distribution.</p

Field study on plasma haptoglobin concentrations and total milk somatic cell counts in cows with untreated and treated mastitis

The aim of the present study was to determine plasma haptoglobin concentrations in cows in field conditions. Experiments were carried out a total of 106 cows, divided in 5 groups. The 1stgroup comprised 25 cows with low milk somatic cell counts (SCC), without microbiological findings used as controls; the IIndgroup -23 cows with untreated subclinical mastitis with high milk SCC and without microbiological findings; the IIIrdgroup: 13 cows with untreated subclinical mastitis with high milk SCC and with microbiological findings. The IVthgroup consisted of 17 cows with subclinical mastitis, high milk SCC, microbiological findings, treated with tetracycline HCL 200 mg, neomycin 250 mg, bacitracin 2000 IU, prednisolone 10 mg (Mastijet fort\uae, MSD Animal Health), and the Vthgroup - 28 cows with clinical mastitis treated with Mastijet fort\uae, MSD Animal Health. Our results showed that the mean plasma haptoglobin concentrations in the I (control) group was 0.054\ub10.003 g/L. In the IIndgroup (0.288\ub10.04 g/L) Hp was 5.2 times higher that the mean values of controls (P<0.001). Mean Hp concentration of group III was also statistically significantly different (P<0.001) than that of the control group. The value of Hp in group IV (0.215\ub10.04 g/L) was significantly lower (P<0.05) that mean values of IIndgroup but substantially higher (P<0.001) vs controls. The concentration of haptoglobin in cows of the Vthgroup was statistically significantly lower (P<0.001) compared both with control and IIndgroups. In this study, total somatic cell count showed statistically significant differences (P<0.001) between the control and experimental groups

Operator approach to analytical evaluation of Feynman diagrams

The operator approach to analytical evaluation of multi-loop Feynman diagrams is proposed. We show that the known analytical methods of evaluation of massless Feynman integrals, such as the integration by parts method and the method of "uniqueness" (which is based on the star-triangle relation), can be drastically simplified by using this operator approach. To demonstrate the advantages of the operator method of analytical evaluation of multi-loop Feynman diagrams, we calculate ladder diagrams for the massless $\phi^3$ theory (analytical results for these diagrams are expressed in terms of multiple polylogarithms). It is shown how operator formalism can be applied to calculation of certain massive Feynman diagrams and investigation of Lipatov integrable chain model.Comment: 16 pages. To appear in "Physics of Atomic Nuclei" (Proceedings of SYMPHYS-XII, Yerevan, Armenia, July 03-08, 2006

Optical precursors in transparent media

We theoretically study the linear propagation of a stepwise pulse through a dilute dispersive medium when the frequency of the optical carrier coincides with the center of a natural or electromagnetically induced transparency window of the medium (slow-light systems). We obtain fully analytical expressions of the entirety of the step response and show that, for parameters representative of real experiments, Sommerfeld-Brillouin precursors, main field and second precursors "postcursors" can be distinctly observed, all with amplitudes comparable to that of the incident step. This behavior strongly contrasts with that of the systems generally considered up to now