On Nonlocal Modified Gravity and its Cosmological Solutions

During hundred years of General Relativity (GR), many significant gravitational phenomena have been predicted and discovered. General Relativity is still the best theory of gravity. Nevertheless, some (quantum) theoretical and (astrophysical and cosmological) phenomenological difficulties of modern gravity have been motivation to search more general theory of gravity than GR. As a result, many modifications of GR have been considered. One of promising recent investigations is Nonlocal Modified Gravity. In this article we present a brief review of some nonlocal gravity models with their cosmological solutions, in which nonlocality is expressed by an analytic function of the d'Alembert-Beltrami operator $\Box$. Some new results are also presented.Comment: 16 page

Intervencije za lečenje primarne bilijarne ciroze: Kohranova analiza sistematskih pregleda sa meta-analizama i sekvencijalnim analizama randomizovanih kliničkih studija

Primary biliary cirrhosis is a chronic autoimmune-mediated liver disease characterised by progressive destruction of intrahepatic bile ducts, resulting in chronic cholestasis, portal inflammation, and fibrosis that can lead to cirrhosis and, ultimately, liver failure and the need for liver transplantation. The disease primarely affects middle‐aged women and is associated with osteoporosis ‐ either postmenopausal or secondary to the liver disease. Low bone mass is an important cause of morbidity in patients with primary biliary cirrhosis, leading to an increased risk of fractures, pain, and deformity. Treatment of primary biliary cirrhosis and osteoporosis associated with primary biliary cirrhosis is complicated. A number of drugs have been evaluated for patients with primary biliary cirrhosis (glucocorticosteroids, methotrexat, azathioprine, colchicine, cyclosporin, D-penicillamine, and chlorambucil). Ursodeoxycholic acid is the only drug approved for primary biliary cirrhosis by the U.S. Food and Drug Administration. Bezafibrate may be effective for treatment of primary biliary cirrhosis. Bisphosphonates and hormone replacement may be effective treatment options for osteoporosis in primary biliary cirrhosis, but the effects have only had limited assessment in systematic reviews. Therefore, interventions based on evidence are highly warranted. Cochrane reviews with meta-analyses and trial sequential analyses of randomised clinical trials generally provide the best available evidence for health care interventions and clinical practice. Such Cochrane reviews are used to assess and summarise benefits and harms of clinical interventions. Furthermore, Cochrane reviews will also reveal lack of evidence, and define the specific need for future randomised clinical trials. Objectives To summarize the evidence from Cochrane systematic reviews on treatment options for patients with primary biliary cirrhosis and osteoporosis associated with primary biliary cirrhosis...Primarna bilijarna ciroza je hronična autoimuna bolest jetre koju karakteriše progresivna destrukcija intrahepatičnih žučnih puteva sa posledičnom holestazom, portnom inflamacijom, i fibrozom što dovodi do nastanka ciroze jetre, i hepatičke insuficijencije sa transplantacijom jetre kao jedinom uspešnom terapijskom metodom. Više od 90% bolesnika su žene, prosečne starosti oko 50 godina. Najvažnija komplikacija bolesti vezana za holestazu je osteoporoza gde smanjenje koštane gustine dovodi do velikog rizika za nastanak preloma kostiju, bola i deformiteta. Lečenje primarne bilijarne ciroze, kao i osteoporoze u sklopu primarne bilijarne ciroze je veoma komplikovano. Za sada nema zadovoljavajuće specifične medicinske terapije koja se preporučuje za lečenje ove bolesti. Evaluirani su mnogi lekovi u terapiji ove bolesti (kortikosteroidi, metrotreksat, azatioprin, kolhicin, ciklosporin, D-penicilamin, i hlorambucil), ali do sada prikazani trajali su uglavnom bili kratki, mali i slabo kontrolisani. Ursodeoksiholna kiselina jedini je lek odobren za terapiju primarne bilijarne ciroze. U nekim kontrolisanim studijama konstatovano je da bezafibrat ima višestruka pozitivna dejstva kod bolesnika sa primarnom bilijarnom cirozom. Za bisfosfonate i supstitucionu hormonsku terapiju se očekuje da budu efikasni u terapiji osteoporoze u sklopu primarne bilijarne ciroze, ali ne postoje za sada dokazi efikasnoti u sistematskim pregledima. Kohranovi sistematski pregledi sa meta-analizama i sekvencijalnim analizama randomizovanih kliničkih studija sintetišu dokaze u cilju dobijanja pouzdanog, validnog i kompletnog pregleda proverenih dokaza o korisnim i štetnim efektima terapijskih procedura koristeći metodologiju u kojoj nema pristrasnosti u tumačenju rezultata i izvođenju zaključaka. Takođe, oni mogu ukazati na nedostatak dokaza i potrebu za budućim dobro dizajniranim randomizovanim kliničkim studijama..

Composite Majorana Fermion Wavefunctions in Nanowires

We consider Majorana fermions (MFs) in quasi-one-dimensional nanowire systems containing normal and superconducting sections where the topological phase based on Rashba spin orbit interaction can be tuned by magnetic fields. We derive explicit analytic solutions of the MF wavefunction in the weak and strong spin orbit interaction regimes. We find that the wavefunction for one single MF is a composite object formed by superpositions of different MF wavefunctions which have nearly disjoint supports in momentum space. These contributions are coming from the extrema of the spectrum, one centered around zero momentum and the other around the two Fermi points. As a result, the various MF wavefunctions have different localization lengths in real space and interference among them leads to pronounced oscillations of the MF probability density. For a transparent normal-superconducting junction we find that in the topological phase the MF leaks out from the superconducting into the normal section of the wire and is delocalized over the entire normal section, in agreement with recent numerical results by Chevallier et al. (arXiv:1203.2643)

Entanglement formation and violation of Bell's inequality with a semiconductor single photon source

We report the generation of polarization-entangled photons, using a quantum dot single photon source, linear optics and photodetectors. Two photons created independently are observed to violate Bell's inequality. The density matrix describing the polarization state of the postselected photon pairs is also reconstructed, and agrees well with a simple model predicting the quality of entanglement from the known parameters of the single photon source. Our scheme provides a method to generate no more than one entangled photon pair per cycle, a feature useful to enhance quantum cryptography protocols using entangled photons.Comment: 4 pages, 3 figures, submitted to PR

Formaldehyde in screen printing indoor

The presence of formaldehyde in air samples has been detected in five screen printing facilities in Novi Sad, Serbia. Air samples were sampled continuously during 4 hours, and concentration levels of formaldehyde was determined by UV-VIS spectrometry at 580 nm. The range of formaldehyde concentrations was from 0.413 to 0.836 ppm. Comparison of the detected concentration levels with the permissible exposure limit of 0.75 ppm (the OSHA standard) indicated that the formaldehyde concentration in facility 5 was 1.11 times higher than prescribed value

Small Open Reading Frames, Non-Coding RNAs and Repetitive Elements in Bradyrhizobium japonicum USDA 110

Small open reading frames (sORFs) and genes for non-coding RNAs are poorly investigated components of most genomes. Our analysis of 1391 ORFs recently annotated in the soybean symbiont Bradyrhizobium japonicum USDA 110 revealed that 78% of them contain less than 80 codons. Twenty-one of these sORFs are conserved in or outside Alphaproteobacteria and most of them are similar to genes found in transposable elements, in line with their broad distribution. Stabilizing selection was demonstrated for sORFs with proteomic evidence and bll1319_ISGA which is conserved at the nucleotide level in 16 alphaproteobacterial species, 79 species from other taxa and 49 other Proteobacteria. Further we used Northern blot hybridization to validate ten small RNAs (BjsR1 to BjsR10) belonging to new RNA families. We found that BjsR1 and BjsR3 have homologs outside the genus Bradyrhizobium, and BjsR5, BjsR6, BjsR7, and BjsR10 have up to four imperfect copies in Bradyrhizobium genomes. BjsR8, BjsR9, and BjsR10 are present exclusively in nodules, while the other sRNAs are also expressed in liquid cultures. We also found that the level of BjsR4 decreases after exposure to tellurite and iron, and this down-regulation contributes to survival under high iron conditions. Analysis of additional small RNAs overlapping with 3’-UTRs revealed two new repetitive elements named Br-REP1 and Br-REP2. These REP elements may play roles in the genomic plasticity and gene regulation and could be useful for strain identification by PCR-fingerprinting. Furthermore, we studied two potential toxin genes in the symbiotic island and confirmed toxicity of the yhaV homolog bll1687 but not of the newly annotated higB homolog blr0229_ISGA in E. coli. Finally, we revealed transcription interference resulting in an antisense RNA complementary to blr1853, a gene induced in symbiosis. The presented results expand our knowledge on sORFs, non-coding RNAs and repetitive elements in B. japonicum and related bacteria

Unstable Giants

We find giant graviton solutions in Frolov's three parameter generalization of the Lunin-Maldacena background. The background we study has $\tilde{\gamma}_1=0$ and $\tilde{\gamma}_2=\tilde{\gamma}_3=\tilde{\gamma}$. This class of backgrounds provide a non-superymmetric example of the gauge theory/gravity correspondence that can be tested quantitatively, as recently shown by Frolov, Roiban and Tseytlin. The giant graviton solutions we find have a greater energy than the point gravitons, making them unstable states. Despite this, we find striking quantitative agreement between the gauge theory and gravity descriptions of open strings attached to the giant.Comment: 1+24 pages, 2 figures; v2: coupling to NSNS B field included, refs added and typos corrected; v3 new results on stability of giants included, presentation improved, refs added; v4 final version to appear in Phys. Rev.

ANALYSIS OF THE IMPACT OF SOCIAL NETWORKS ON THE QUALITY OF LIFE AND EDUCATION OF YOUNG PEOPLE

Social networks are a way of creating a virtual identity and entering into relationships with strangers in a series of interactions that were not known to a man before the existence of the Internet. Mobile phones and the virtual world often create a personality of a person that is not the same in the real world. It can be said that technology has changed the course of humanity and human consciousness and contributed to many changes in the mentality of society, especially among the youth. Children are often overwhelmed by materialism and jealousy, which further encourages them to become an unconscious, immoral and unambitious population. One of the negative effects of social networks is the abuse of privacy, which is also becoming a growing problem everywhere in the world and should not be ignored. However, a positive attitude should be maintained when it comes to social networks, because they facilitate communication, access to information and learning, greater availability of services and free advertising of some products or services. High school students use the Internet intensively every day, and the work raises the question of whether they use it constructively or destructively. The research was conducted in 2019, the population of high school students was observed and 100 students were included on the territory of Belgrade, Niš and Vitina