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Search Results: 1 - 10 of 175 matches for " Efstratios Tsatis "
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Flow by mean curvature inside a moving ambient space
Annibale Magni,Carlo Mantegazza,Efstratios Tsatis
Mathematics , 2009, DOI: 10.1007/s00028-013-0190-6
Abstract: We show some computations related to the motion by mean curvature flow of a submanifold inside an ambient Riemannian manifold evolving by Ricci or backward Ricci flow. Special emphasis is given to the possible generalization of Huisken's monotonicity formula and its connection with the validity of some Li--Yau--Hamilton differential Harnack--type inequalities in a moving Riemannian manifold.
Sutureless prepuceplasty with wound healing by second intention: An alternative surgical approach in children's phimosis treatment
Efstratios Christianakis
BMC Urology , 2008, DOI: 10.1186/1471-2490-8-6
Abstract: Eightyseven children with phimosis were treated with this new developed technique, between 2003 and 2005. Sutureless prepuceplasty creates a permanent surgical extension of the close prepuce. Stretching and retraction of phimotic foreskin reveals a tight prepuce ring that is cutting in its dorsal surface longitudinally. Rarely triple symmetric incisions in the preputial outlet are necessary. The foreskin is loose and moves absolutely free in bilateral courses. The wounds are healing by second intention. Antisepsis, steroids and Elicina cream, (which contains allantoin, collagen, elastin, glycolic acid and vitamins A, D, and E) should apply daily, for twenty to thirty days.The foreskin is moving in centripetal or efferent courses absolutely loosely, painlessly and bloodlessly. The mean time of follow-up was 27 months (one to four years). No complications were observed.Sutureless prepuceplasty may present an acceptable alternative in children's phimosis reconstruction.Circumcision is probably the oldest and one of the most common elective procedures all over the world. It was initially performed for ritual, religious or family traditional reasons [1]. Simultaneously, circumcision was probably performed for phimosis treatment. Another ancient surgical method for phimosis treatment was the dorsal slit operation, which is a super incision, with no tissue removed [2]. The value of foreskin properties as well as aesthetic reasons determined to other operations preserving the foreskin. The most interesting was the report of prepuceplasty suggested by Homlund DE in 1973. It is a limited dorsal incision of the phimotic prepuce with transverse skin closure with absorbable sutures [3]. Although it is a good operation, it is not without complications or re-operations [4-6]. Sutureless prepuceplasty (SLP) is a faster, easier, painless and without complications technique, which has excellent cosmetic results.Between 2003 and 2005, eightyseven boys (87) with tight phimotic rings, m
Mathematical knowledge and drug dosage calculation: Necessary clinical skills for the nurse
Athanasakis Efstratios
To Vima tou Asklipiou , 2013,
Abstract: When nurses perform their tasks, they manage situations where maths knowledge is required. Such a situation is the calculation of medication dosage. Aim: The literature review of papers relevant with the mathematical knowledge and drug calculation skills of nurses and nursing students. Material-Method: A search of published research and review articles from January 1989 until March 2012, has been conducted in Pubmed database. The search terms used were: nurses, mathematics skills, numeracy skills and medication dosology calculation skills. Results: Literature review showed that many studies focus in the mathematical knowledge and drug dosage calculation competency of nursing students. Results from these studies revealed that nursing students had poor mathematical knowledge and drug dosage calculation skills. In contrast with students, professional nurses are more likely to have sufficient skills in drug calculations. Apart from the papers analyzing calculation skills' assessment, several studies examined educational interventions in the context of calculation skills enhancement. Accuracy and proficiency in the dosage calculation of medications is a preventive factor of errors made at medication preparation and administration. Conclusion: Mathematical knowledge and drug dosage calculation abilities are interrelated concepts and essential clinical skills for the nurse. The fact that nursing students do not have adequate skills for calculating medications' dosage, might be an issue that schools of nursing education should focus in. Further research of the drug dosage calculation skills is considered essential.
Nurses’ Research Behavior and Barriers to Research Utilization Into Clinical Nursing Practice: a Closer Look
Efstratios Athanasakis
International Journal of Caring Sciences , 2013,
Abstract: Background: It is widely accepted that utilization of the best-known research evidence in nursing practice entails improvement of nursing care received by patients and strengthening of nursing profession.Aim: The aim of this paper was the review of nurses’ research behavior and the barriers that nurses meet in order to utilize research evidence into clinical nursing practice.Methodology: There has been conducted a literature search in Pubmed and Science Direct libraries, using specific search terms. An important inclusion criterion for the studies was the use of barriers to research utilization scale (BRUS), along or combined with another instrument.Results: A total of 37 original papers included in the present article. A table of the top five barriers to research utilization scale has been conducted. Data from the table indicate that the existence of barriers to incorporation of evidence into practice comes mainly from clinical settings characteristics. In addition, issues about nursing education, nurses’ research and reading habits, facilitators of research utilization and their relevance for nursing staff and clinical practice are also discussed.Conclusions: Since the barriers to research utilization are well identified in the nursing literature and there is a wealth of information on this subject, the next step is to find ways to overcome them and value the impact of the relevant interventions towards research utilization behavior.
Photovoltaic effect for narrow-gap Mott insulators
Efstratios Manousakis
Physics , 2009, DOI: 10.1103/PhysRevB.82.125109
Abstract: We discuss the photovoltaic effect at a p-n heterojunction, in which the illuminated side is a doped Mott insulator, using the simplest description of a Mott insulator within the Hubbard model. We find that the internal quantum efficiency of such a device, if we choose an appropriate narrow-gap Mott insulator, can be significantly enhanced due to impact ionization caused by the photoexcited ``hot'' electron/hole pairs. Namely, the photoexcited electron and/or hole can convert its excess energy beyond the Mott-Hubbard gap to additional electrical energy by creating multiple electron/hole pairs in a time scale which can be shorter than the time characterizing other relaxation processes.
String excitations of a hole in a quantum antiferromagnet and photoelectron spectrospopy
Efstratios Manousakis
Physics , 2007, DOI: 10.1103/PhysRevB.75.035106
Abstract: The aim of the present paper is twofold. The first goal is to show that high resolution angle-resolved photoelectron spectra from cuprates indicate the presence of string-like excitations of the quasihole excitation in a quantum antiferromagnet. In order to compare with the experimental intensity plots, we calculate the spectral function of the t-J and the t-t'-t"-J models within the self-consistent Born approximation for widely accepted values of the parameters of these models. The main features of the high resolution photoelectron spectra are in general agreement with the results based on the above models and can be understood by considering not only the lowest energy quasiparticle peak but, also, the higher energy string-like excitations of the hole. The second goal of the present paper is to make the case that a proper analysis of both the numerical results obtained from these models and of the experimental results, suggests a theoretical picture for the internal structure of the hole-quasiparticle and a string-exchange pairing mechanism due to strong antiferromagnetic correlations among the background spins. We find that, using a simple model in which the Hilbert space is restricted to states of only unbroken strings attached to the holes and in which the holes are connected with unbroken strings, we can provide a good quantitative description of the most accurate numerical results. We find that the holes experience an effective interaction due to a string-exchange mechanism which is characterized by a rather large string tension and this can provide pairing energy scales much larger that those suggested by spin-fluctuation mediated pairing models. In addition, it is argued that such string-exchange interaction tends to bind holes in a bound state with the $d_{x^2-y^2}$ symmetry.
Possible role of 3He impurities in solid 4He
Efstratios Manousakis
Physics , 2006, DOI: 10.1209/0295-5075/78/36002
Abstract: We use a quantum lattice gas model to describe essential aspects of the motion of 4He atoms and of 3He impurities in solid 4He. This study suggests that 3He impurities bind to defects and promote 4He atoms to interstitial sites which can turn the bosonic quantum disordered crystal into a metastable supersolid. It is suggested that defects and interstitial atoms are produced during the solid 4He nucleation process where the role of 3He impurities (in addition to the cooling rate) is known to be important even at very small (1 ppm) impurity concentration. It is also proposed that such defects can form a glass phase during the 4He solid growth by rapid cooling.
A Quantum-Dot Array as Model for Copper-Oxide Superconductors: A Dedicated Quantum Simulator for the Many-Fermion Problem
Efstratios Manousakis
Physics , 2002,
Abstract: Quantum systems with a large number of fermionic degrees of freedom are intractable by quantum simulations. In this paper we introduce the concept of a dedicated quantum simulator(DQS) which is an artificial system of quantum dots whose Hamiltonian maps exactly to the original many fermion problem. While the universal quantum simulator (UQS) introduced by Feynman in 1982 can simulate any quantum mechanical many-body problem, a DQS can only solve a particular many body problem. Our concept of the dedicated quantum simulator is not a quantum computer but rather a quantum "analog" device, dedicated to a particular quantum computation. As an example, we consider the system of the $CuO$ plane in the copper-oxide superconductors and we propose an array of electrostatically confined quantum dots to be used as its dedicated quantum simulator. We show that this dedicated device can be used to image stripe formation as a function of the electron doping using electric force microscopy. We argue that such a dedicated quantum simulator may be easier to realize in the future compared to a general purpose quantum computer.
Hole-pair hopping in arrangements of hole-rich/hole-poor domains in a quantum antiferromagnet
Efstratios Manousakis
Physics , 2002, DOI: 10.1103/PhysRevB.67.195103
Abstract: We study the motion of holes in a doped quantum antiferromagnet in the presence of arrangements of hole-rich and hole-poor domains such as the stripe-phase in high-$T_C$ cuprates. When these structures form, it becomes energetically favorable for single holes, pairs of holes or small bound-hole clusters to hop from one hole-rich domain to another due to quantum fluctuations. However, we find that at temperature of approximately 100 K, the probability for bound hole-pair exchange between neighboring hole-rich regions in the stripe phase, is one or two orders of magnitude larger than single-hole or multi-hole droplet exchange. As a result holes in a given hole-rich domain penetrate further into the antiferromagnetically aligned domains when they do it in pairs. At temperature of about 100 K and below bound pairs of holes hop from one hole-rich domain to another with high probability. Therefore our main finding is that the presence of the antiferromagnetic hole-poor domains act as a filter which selects, from the hole-rich domains (where holes form a self-bound liquid), hole pairs which can be exchanged throughout the system. This fluid of bound hole pairs can undergo a superfluid phase ordering at the above mentioned temperature scale.
Founding quantum theory on the basis of consciousness
Efstratios Manousakis
Physics , 2006, DOI: 10.1007/s10701-006-9049-9
Abstract: In the present work, quantum theory is founded on the framework of consciousness, in contrast to earlier suggestions that consciousness might be understood starting from quantum theory. The notion of streams of consciousness, usually restricted to conscious beings, is extended to the notion of a Universal/Global stream of conscious flow of ordered events. The streams of conscious events which we experience constitute sub-streams of the Universal stream. Our postulated ontological character of consciousness also consists of an operator which acts on a state of potential consciousness to create or modify the likelihoods for later events to occur and become part of the Universal conscious flow. A generalized process of measurement-perception is introduced, where the operation of consciousness brings into existence, from a state of potentiality, the event in consciousness. This is mathematically represented by (a) an operator acting on the state of potential-consciousness before an actual event arises in consciousness and (b) the reflecting of the result of this operation back onto the state of potential-consciousness for comparison in order for the event to arise in consciousness. Beginning from our postulated ontology that consciousness is primary and from the most elementary conscious contents, such as perception of periodic change and motion, quantum theory follows naturally as the description of the conscious experience.
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