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

Nonlocal de Sitter gravity and its exact cosmological solutions

This paper is devoted to a simple nonlocal de Sitter gravity model and its exact vacuum cosmological solutions. In the Einstein-Hilbert action with $\Lambda$ term, we introduce nonlocality by the following way: $R - 2 \Lambda = \sqrt{R-2\Lambda}\ \sqrt{R-2\Lambda} \to \sqrt{R-2\Lambda}\ F(\Box)\ \sqrt{R-2\Lambda} ,$where${F} (\Box) = 1 + \sum_{n= 1}^{+\infty} \big( f_n \Box^n + f_{-n} \Box^{-n} \big) $is an analytic function of the d'Alembert-Beltrami operator$\Box$and its inverse$\Box^{-1}$. By this way,$R$and$\Lambda$enter with the same form into nonlocal version as they are in the local one, and nonlocal operator$F(\Box)$is dimensionless. The corresponding equations of motion for gravitational field$g_{\mu\nu}$are presented. The first step in finding some exact cosmological solutions is solving the equation$\Box \sqrt{R-2\Lambda} = q \sqrt{R-2\Lambda} , $where$ q =\zeta \Lambda \quad (\zeta \in \mathbb{R})$is an eigenvalue and$\sqrt{R-2\Lambda}$is an eigenfunction of the operator$\Box .$ We presented and discussed several exact cosmological solutions for homogeneous and isotropic universe. One of these solutions mimics effects that are usually assigned to dark matter and dark energy. Some other solutions are examples of the nonsingular bounce ones in flat, closed and open universe. There are also singular and cyclic solutions. All these cosmological solutions are a result of nonlocality and do not exist in the local de Sitter case.Comment: 27 pages, 5 figures. Comments welcom

A Possible Bifurcation in Atmospheres of Strongly Irradiated Stars and Planets

We show that under certain circumstances the differences between the absorption mean and Planck mean opacities can lead to multiple solutions for an LTE atmospheric structure. Since the absorption and Planck mean opacities are not expected to differ significantly in the usual case of radiative equilibrium, non-irradiated atmospheres, the most interesting situations where the effect may play a role are strongly irradiated stars and planets, and also possibly structures where there is a significant deposition of mechanical energy, such as stellar chromospheres and accretion disks. We have presented an illustrative example of a strongly irradiated giant planet where the bifurcation effect is predicted to occur for a certain range of distances from the star.Comment: 22 pages, 6 figures, submitted to Ap

О нелокальной модифицированной гравитации

In the last hundred years many significant gravitational phenomena have been predicted anddiscovered by General Relativity (GR), which is still the best theory of gravity. Nevertheless,due to the great observational discoveries of 20th century some (quantum) theoretical and(astrophysical and cosmological) phenomenological difficulties of modern gravity have beenmotivation to search more general theory of gravity than GR. As a result, many modificationsof GR have been considered. One of promising recent investigations is Nonlocal ModifiedGravity. In this article we present a review of some nonlocal gravity models with theirexact cosmological solutions, in which nonlocality is expressed by an analytic function of thed’Alembert–Beltrami operator. Some of obtained solutions contain effects which are usuallyassigned to the dark matter and dark energy.За последние сто лет многие существенные гравитационные явления были предсказаны и обнаружены Общей теорией относительности (GR), которая до сих пор остается лучшей теорией гравитации. Тем не менее, из-за великих наблюдательных открытий 20-го века некоторые (квантовые) теоретические и (астрофизические и космологические) феноменологические трудности современной гравитации были мотивацией для поиска болееобщей теории гравитации, чем ОТО. В результате были рассмотрены многие модификации ТО. Одним из многообещающих недавних исследований является нелокальная модифицированная гравитация. В этой статье мы представляем обзор некоторых нелокальных гравитационных моделей с их точными космологическими решениями, в которых нелокальность выражается аналитической функцией от оператора Даламбера — Бельтрами. Некоторые из полученных решений содержат эффекты, которые обычно присваиваютсятемной материи и темной энергии

Dizajn, klasifikacija, perspektiva i moguća aplikacija dronova u poljoprivredu Srbije

The paper analyzes the possibility and the needs for the use of specific types of robots (mini unmanned aircraft with different designs and the designation of UAVs) and the possibility of using in agriculture (agrodrone). The year 2015 was proclaimed (Fortune Magazine, 2016) as the year of increasing and widespread use of UAVs in various areas of human activity, especially in agriculture and forestry (75% of use). This is important for large farm areas, where UAV has many useful functions and a very cost-effective commercial application. Today, the needs for UAVs have increased sharply with various opportunities for both civilian and military needs. There is also a significant interest in the development of new drones that can autonomously fly in different environments and locations and can perform various missions and tasks. Over the past decade, a wide range of applications for drones has gained the significance that led to the discovery of various types of unmanned UAVs of different sizes and weights. In this review, the classification of UAVs ranging based on a detailed overview of the development of the drone industry in recent years, this paper demonstrates the evolution of drones and differents application technologies. Of course, this development is very advanced and revolutionary, as well as the development of mobile and smart phones and the Internet, which will open the way for many users to participate in defining the future of UAV implementation. LIVONA Company, Belgrade, Serbia (and Institute of Agricultural Engineering, Faculty of Agriculture in Belgrade, in tehnical cooperation) has a study and plans on the implementation of the model micro drone EBee SQ Livona RTK in the future general plans for inspection of protection Soils of territory Minicipality of Stara Pazova (351 km2), and agricultural company Napredak , and exspecially plans for soils of agriculture of R. Serbia. VEKOM GeoCompany from Belgrade, (in cooperation with Institute of Agricultural Engineering, Faculty of Agriculture in Belgrade), has a study and plans on the implementation of the model of the drone Aibot KX6 model, in the future of application of agricultural soils of region Open pit Kolubara for area from app. 600 km2 and the other soils of Region). Institute of Agricultural Engineering, Faculty of Agriculture in Belgrade, in cooperation with Municipality of Ub, has a study and plans on the implementation of the model micro drone Hubsan H109S X4 PRO in the future plans general inspection of protection Soils and Waters of territory of Municipality Ub (456 km2).U radu su analizirane mogućnosti i potrebe upotrebe specifičnih vrsta robota (mini bespilotnih letelica sa različitim dizajnom, označane kao UAV) i način korištenja u poljoprivredi (agrodron). Časopis Fortune je 2015.godinu proglasio kao godinu sve većeg i široko rasprostranjene upotrbe UAV letelica, u različitim oblastima ljudske delatnosti, posebno u poljoprivredi i šumarstvu (75% upotrebe). Ovo je naročito važno za velike farme i oblasti pod šumama, gde UAV ima mnogo korisnih funkcija i veoma isplative komercijalne aplikacije. Danas, potrebe za UAV imaju nagli porast sa različitim mogućnostima kako za civilne tako i za vojne potrebe. Takođe postoji značajan interes za razvoj novih bespilotnih letelica koji mogu autonomno leteti u različitim okruženjima i lokacijama i obaviti različite misije i zadatke. Tokom protekle decenije XXI veka, širok spektar aplikacija za bespilotne letelice je dobio značaj koji je doveo do konstrukcija različitih tipova bespilotnih UAV, različitih veličina i težina i svakako namene. Naravno, tehnološki razvoj kod dron sistema je veoma tehničko-tehnološki napredan i revolucionaran, uz razvoj mobilnih i pametnih (android) telefona i interneta, brzo otvora puteve i mogućnosti za mnoge korisnike u definisanju nove budućnosti implementacije UAV u različitim oblastima primene . Kompanija Livona d.o.o., Beograd i Institut za poljoprivrednu tehniku, Poljoprivredni fakultet u Beogradu, u tehničkoj saradnji imaju planove o implementaciji modela mikro drona EBee SK Livona RTK u narednim generalnim planovima za inspekciju, zaštitu i korišćenje poljoprivrednih zemljišta Republike Srbije, i posebno teritorije Opštine Stara Pazova (351 km2), gde je posebno mesto poljoprivrednog preduzeća Napredak a.d. VekomGeo d.o.o, Beograd u saradnji sa Institutom za poljoprivrednu tehniku Poljoprivrednog fakulteta u Beogradu ima planove o budućoj upotrebi drona model Aibot X6, za nadzor na površinama od 600 km2 (i poljoprivredna zemljišta) otvorenog kopa R.B. Kolubara ili drugih objekata. Institut za poljoprivrednu tehniku, Poljoprivredni fakultet u Beogradu, ima planove o saradnji sa opštinom Ub, zbog upotrebe modela mikro drona Hubsan H109S Ks4 PRO u inspekciji oko zaštite i načina korišćenja zemljišta i voda na ovoj teritoriji (456 km2)

Increased expression of vascular endothelin type B and angiotensin type 1 receptors in patients with ischemic heart disease

<p>Abstract</p> <p>Background</p> <p>Endothelin-1 and angiotensin II are strong vasoconstrictors. Patients with ischemic heart disease have elevated plasma levels of endothelin-1 and angiotensin II and show increased vascular tone. The aim of the present study was to examine the endothelin and angiotensin II receptor expression in subcutaneous arteries from patients with different degrees of ischemic heart disease.</p> <p>Methods</p> <p>Subcutaneous arteries were obtained, by biopsy from the abdomen, from patients undergoing coronary artery bypass graft (CABG) surgery because of ischemic heart disease (n = 15), patients with angina pectoris without established myocardial infarction (n = 15) and matched cardiovascular healthy controls (n = 15). Endothelin type A (ET_A) and type B (ET_B), and angiotensin type 1 (AT₁) and type 2 (AT₂) receptors expression and function were examined using immunohistochemistry, Western blot and <it>in vitro </it>pharmacology.</p> <p>Results</p> <p>ET_Aand, to a lesser extent, ET_Breceptor staining was observed in the healthy vascular smooth muscle cells. The level of ET_Breceptor expression was higher in patients undergoing CABG surgery (250% ± 23%; P < 0.05) and in the patients with angina pectoris (199% ± 6%; P < 0.05), than in the healthy controls (100% ± 28%). The data was confirmed by Western blotting. Arteries from CABG patients showed increased vasoconstriction upon administration of the selective ET_Breceptor agonist sarafotoxin S6c, compared to healthy controls (P < 0.05). No such difference was found for the ET_Areceptors. AT₁and, to a lesser extent, AT₂receptor immunostaining was seen in the vascular smooth muscle cells. The level of AT₁receptor expression was higher in both the angina pectoris (128% ± 25%; P < 0.05) and in the CABG patients (203% ± 41%; P < 0.05), as compared to the healthy controls (100% ± 25%). The increased AT₁receptor expression was confirmed by Western blotting. Myograph experiment did however not show any change in vasoconstriction to angiotensin II in CABG patients compared to healthy controls (P = n.s).</p> <p>Conclusion</p> <p>The results demonstrate, for the first time, upregulation of ET_Band AT₁receptors in vascular smooth muscle cells in ischemic heart disease. These receptors may play a role in the pathophysiology of ischemic heart disease and could provide important targets for pharmaceutical interventions.</p