Parameter estimation of diffusion models from discrete observations

A short review of diffusion parameter estimations methods from discrete observations is presented. The applicability of a new estimation method on inferences about a diffusion growth model is discussed

Parameter estimation of diffusion models

Parameter estimation problems of diffusion models are discussed. The problems of maximum likelihood estimation and model selections from continuous observations are illustrated through diffusion growth model which generalizes some classical ones

In vivo skin regeneration and wound healing using cell micro-transplantation

BACKGROUND: The accumulation of senescent cells in tissues alters tissue homeostasis and affects wound healing. It is also considered to be the main contributing factor to aging. In addition to losing their ability to divide, senescent cells exert detrimental effects on surrounding tissues through their senescence-associated secretory phenotype (SASP). They also affect stem cells and their niche, reducing their capacity to divide which increasingly reduces tissue regenerative capacity over time. The aim of our study was to restore aged skin by increasing the fraction of young cells in vivo using a young cell micro-transplantation technique on Fischer 344 rats. Employing the same technique, we also used wild-type skin fibroblasts and stem cells in order to heal Dominant Dystrophic Epidermolysis Bulosa (DDEB) wounds and skin blistering. RESULTS: We demonstrate that implantation of young fibroblasts restores cell density, revitalizes cell proliferation in the dermis and epidermis, rejuvenates collagen I and III matrices, and boosts epidermal stem cell proliferation in rats with advancing age. We were also able to reduce blistering in DDEB rats by transplantation of skin stem cells but not skin fibroblasts. CONCLUSIONS: Our intervention proves that a local increase of young cells in the dermis changes tissue homeostasis well enough to revitalize the stem cell niche, ensuring overall skin restoration and rejuvenation as well as healing DDEB skin. Our method has great potential for clinical applications in skin aging, as well as for the treatment of various skin diseases

Alternative approach to the optimality of the threshold strategy for spectrally negative Levy processes

Consider the optimal dividend problem for an insurance company whose uncontrolled surplus precess evolves as a spectrally negative Levy process. We assume that dividends are paid to the shareholders according to admissible strategies whose dividend rate is bounded by a constant. The objective is to find a dividend policy so as to maximize the expected discounted value of dividends which are paid to the shareholders until the company is ruined. Kyprianou, Loeffen and Perez [28] have shown that a refraction strategy (also called threshold strategy) forms an optimal strategy under the condition that the Levy measure has a completely monotone density. In this paper, we propose an alternative approach to this optimal problem.Comment: 16 page

СУЧАСНІ ВІДОМОСТІ ПРО РОЗВИТОК ТА СТАНОВЛЕННЯ БУДОВИ КІСТОК КИСТІ

If in anatomy of the foot the leading principle is connection of individual parts, strengthening of their ligaments, then in the hand each component tends to become free, each joint tries to get rid of its connections, and each link – to get an individual perfected form. The article offers a brief review of the basic mechanisms of development and formation of the hand bones. In the process of evolution of the three parts of the arm (shoulder, forearm and hand), its final (distal) part – the hand – is of a particular importance. It becomes not only the performer of the will, but also the creator, educator of the brain. The territory of the projection of the hand and especially the thumb in the anterior and posterior central convolutions of the cerebral cortex is almost as long as the rest of the body. The skeleton of the hand is formed by skeletal tissues, which include cartilage and bone tissue having the only source of development – the mesenchyme. The cartilaginous tissue develops from the mesenchyme. In the embryo in the period of 5-6 weeks, chondrogenic areas are formed in the mesenchyme. They are determined by the greater density of the location of mesenchymal cells, significant mitotic activity and the absence of blood vessels. The function of the hand consists of three elements. Stretched forward hand, open, with straight fingers serves as a shovel,; bent fingers - crochet, tongs; more difficult function – snatching. When it is executed, a person, depending on the purpose of the movement, on the nature of the object (size, weight, shape, texture) forms a new mechanism from the hand each time. In the core of various movements of the hand there are six types of grasping: ragged, interdigital, planar, pinching, cylindrical, and spherical. The processes of osteo- and chondrogenesis are in a certain dependence on carbohydrate and lipid metabolism, in particular on the complete and sequential synthesis of carbohydrate-protein complexes – glycosaminoglycans, proteoglycans, collagen and their interaction with each other. Disorders in these processes lead to bone problems and, consequently, to the formation of cartilage defects and bones. In most cases, there is a certain sequence of appearance of ossification centers: first, the center of ossification of the trapezoid bone, then the navicular bone, and the last on – the trapezoid. At the same time, by the end of this age period, the ossification of the cartilaginous models of the epiphyses of the metacarpal bones and phalanges of the finger ends, and the design of the bone structure of the epimetaphysis of the short tubular bones.Если в анатомии ноги царит принцип соединения отдельных частей, укрепление их связок, то в руке каждая ее составляющая стремится стать свободной, каждый сустав пытается избавиться от своих кандалов, а каждое звено – получить индивидуальную отточенную форму. В статье предлагается краткий обзор основных механизмов развития и становления строения костей кисти. В процессе эволюции из трех звеньев руки (плечо, предплечье и кисть) особое значение приобретала ее конечная (дистальная) часть – кисть. Она становится не только исполнительницей воли, но и создателем, воспитателем мозга. Территория проекции кисти и особенно большого пальца в передней и задней центральных извилинах коры больших полушарий мозга имеет почти такую же длину, как все остальное тело.Якщо в анатомії ноги панує принцип з’єднання окремих частин, зміцнення їх зв’язків, то в руці кожна її складова прагне стати вільною, кожен суглоб намагається позбутися своїх кайданів, а кожна ланка – отримати індивідуальну відточену форму. У статті пропонується короткий огляд основних механізмів розвитку та становлення будови кісток кисті. У процесі еволюції із трьох ланок руки (плече, передпліччя і кисть) особливого значення набувала її кінцева (дистальна) частина – кисть. Вона стає не тільки виконавицею волі, але і творцем, вихователем мозку. Територія проекції кисті і особливо великого пальця в передній і задній центральних звивинах кори великих півкуль мозку має майже таку ж довжину, як усе інше тіло