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Farinelli S.,Core Dynamics
Journal of Geometric Mechanics | Year: 2015

We have embedded the classical theory of stochastic finance into a differential geometric framework called Geometric Arbitrage Theory and show that it is possible to: Write arbitrage as curvature of a principal fibre bundle. Parameterize arbitrage strategies by its holonomy. Give the Fundamental Theorem of Asset Pricing a differential homotopic characterization. Characterize Geometric Arbitrage Theory by five principles and show they are consistent with the classical theory of stochastic finance. Derive for a closed market the equilibrium solution for market portfolio and dynamics in the cases where: Arbitrage is allowed but minimized. - Arbitrage is not allowed. Prove that the no-free-lunch-with-vanishing-risk condition implies the zero curvature condition. The converse is in general not true and additionally requires the Novikov condition for the instantaneous Sharpe Ratio to be satisfied. © American Institute of Mathematical Sciences. Source

Arav A.,Israel Agricultural Research Organization | Gavish Z.,Israel Agricultural Research Organization | Elami A.,Hadassah University Hospital | Natan Y.,Core Dynamics | And 3 more authors.
Reproductive BioMedicine Online | Year: 2010

Whole ovary cryopreservation and transplantation has been proposed as a method for preserving long-term ovarian function. This work reports ovarian function 6 years post transplantation of frozen-thawed whole sheep ovaries. Three 9-month-old Assaf sheep underwent unilateral oophorectomy to provide organs for the experiments. After perfusing with cold University of Wisconsin solution supplemented with 10% dimethyl sulphoxide, ovaries were cryopreserved using unidirectional solidification freezing technology. After thawing, ovaries were re-perfused and re-transplanted orthotopically by microvascular re-anastomosis, to the contralateral ovarian pedicle after removing the remaining ovary. Six years following transplantation and after inducing superovulation, the sheep were killed and the ovaries analysed. Two ovaries had normal size and shape showing some recent corpora lutea, while the third showed atrophic changes. A total of 36 antral follicles were counted by transillumination and four germinal vesicle oocytes were aspirated and matured in vitro to metaphase II. Serum progesterone concentrations were indicative of ovulatory activity in one of the three sheep. Histological evaluations revealed normal tissue architecture, intact blood vessels and follicles at various stages. Currently, this is the longest recorded ovarian function after cryopreservation and re-transplantation. Cryopreservation of whole ovaries, using directional freezing combined with microvascular anastomosis, is a promising method for preserving long-term reproductive capacity and endocrine function. © 2009, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved. Source

Kim Y.,Pohang University of Science and Technology | Yeom M.,Pohang University of Science and Technology | Kim H.,Pohang University of Science and Technology | Lim J.,Pohang University of Science and Technology | And 6 more authors.
Molecular Plant | Year: 2012

The endogenous circadian clock regulates many physiological processes related to plant survival and adaptability. GIGANTEA (GI), a clock-associated protein, contributes to the maintenance of circadian period length and amplitude, and also regulates flowering time and hypocotyl growth in response to day length. Similarly, EARLY FLOWERING 4 (ELF4), another clock regulator, also contributes to these processes. However, little is known about either the genetic or molecular interactions between GI and ELF4 in Arabidopsis. In this study, we investigated the genetic interactions between GI and ELF4 in the regulation of circadian clock-controlled outputs. Our mutant analysis shows that GI is epistatic to ELF4 in flowering time determination, while ELF4 is epistatic to GI in hypocotyl growth regulation. Moreover, GI and ELF4 have a synergistic or additive effect on endogenous clock regulation. Gene expression profiling of gi, elf4, and gi elf4 mutants further established that GI and ELF4 have differentially dominant influences on circadian physiological outputs at dusk and dawn, respectively. This phasing of GI and ELF4 influences provides a potential means to achieve diversity in the regulation of circadian physiological outputs, including flowering time and hypocotyl growth. © 2012 The Author. Source

Maffei S.,University of Milan | Hanenberg M.,Wageningen University | Pennarossa G.,University of Sassari | Silva J.R.V.,Federal University of Ceara | And 3 more authors.
Fertility and Sterility | Year: 2013

Objective To compare conventional slow equilibrium cooling and directional freezing for cryopreservation of whole ovaries. Design Experimental animal study. Setting Academic research environment. Animal(s) Adult ewes. Intervention(s) Eighty-one ovaries were randomly assigned to fresh control, conventional freezing (CF), and directional freezing (DF) group. Ovaries of CF and DF groups were perfused via the ovarian artery with Leibovitz L-15 medium, 10% fetal bovine serum, and 1.5 M dimethyl sulfoxide for 5 minutes. Each ovary was inserted into a glass test tube containing 10 mL of the same solution and cooled to -100 C or -70 C, respectively. Ovaries were stored in liquid nitrogen for a minimum of 2 weeks. Main Outcome Measure(s) Structural integrity of cortical and medulla regions, vascular integrity, follicle in vitro development, cell proliferation, and DNA damage and repair. Result(s) All examined parameters indicate that the structure of DF ovaries remains largely intact and comparable to fresh controls, whereas significant damages were observed in CF ovaries. Conclusion(s) Directional freezing allows good preservation of whole ovaries, with most of the parameters taken into consideration almost identical to those recorded in fresh control samples. This encourages a reconsideration of the possible use of whole-ovary cryopreservation as a viable alternative to cortical fragments. Copyright © 2013 American Society for Reproductive Medicine, Published by Elsevier Inc. Source

Maffei S.,University of Milan | Pennarossa G.,University of Sassari | Brevini T.A.L.,University of Milan | Arav A.,Core Dynamics | Gandolfi F.,University of Milan
Human Reproduction | Year: 2014

STUDY QUESTION: Does directional freezing improve the structural and functional integrity of ovarian fragments compared with conventional slow freezing and to whole ovary cryopreservation? SUMMARY ANSWER: Compared with slow freezing, the use of directional freezing significantly improves all structural and functional parameters of ovarian fragments assessed in vitro and, overall, whole ovaries were better preserved than ovarian fragments. WHAT IS KNOWN ALREADY: Directional freezing has been developed to provide an alternative way to cryopreserve large biological samples and it is known to improve the structural and functional integrity of whole ovaries. Conventional slow freezing of ovarian fragments is the procedure more widely used in clinical settings but it causes substantial structural damage that limits the functional period after transfer back into the patient. STUDY DESIGN, SIZE, DURATION: We performed a 2 × 2 factorial design experiment on a total of 40 sheep ovaries, divided into four groups (n = 10 ovaries per group): (i) directional freezing of whole ovary (DFwo); (ii) directional freezing of ovarian fragments (DFof); (iii) conventional freezing of whole ovary (CFwo); (iv) conventional freezing of ovarian fragments (CFof). An additional eight ovaries were used as fresh controls. PARTICIPANTS/ MATERIALS, SETTING, METHODS: Ewe ovaries were randomly assigned to one of the experimental groups and frozen accordingly. Upon thawing, ovarian tissue was examined morphologically and cultured in vitro for 7 days. Samples were analyzed for cell proliferation and apoptosis, for DNA damage and repair activity, and for the presence of a panel of heat shock proteins (HSPs) by immunohistochemistry. MAIN RESULTS AND THE ROLE OF CHANCE: Most studied parameters were significantly improved (P < 0.05) in all samples cryopreserved with directional compared with slow freezing. The proportion of primordial follicles, which developed to the primary stage in whole ovaries (53 ± 1.7%) and in ovarian fragments (44 ± 1.8%) cryopreserved with directional freezing, was greater than with slow frozen whole ovaries (6 ± 0.5%, P = 0.001) or fragments (32 ± 1.5%, P = 0.004). After 7 days of culture, cell proliferation in DFwo (28 ± 0.73%) was the highest of all groups (P < 0.05) followed by DFof (23 ± 0.81%), CFof (20 ± 0.79%) and CFwo (9 ± 0.85%). Directional freezing also resulted in a better preservation of the cell capacity to repair DNA damage compared with slow freezing both in whole ovaries and ovarian fragments. Apoptosis and HSP protein levels were significantly increased only in the CFwo group. Direct comparison demonstrated that, overall, DFwo had better parameters than DFof and was no different from the fresh controls. LIMITATIONS, REASONS FOR CAUTION: The study is limited to an in vitro evaluation and uses sheep ovaries, which are smaller than human ovaries and therefore may withstand the procedures better. WIDER IMPLICATIONS OF THE FINDINGS: Improved integrity of ovarian morphology may translate to improved outcomes after transplantation. Alternatively, the particularly good preservation of whole ovaries suggests they could provide a source of ovarian follicles for in vitro culture in those cases when the presence of malignant cells poses a substantial risk for the patient. STUDY FUNDING/COMPETING INTEREST(S): Supported by: Associazione Italiana per la Ricerca sul Cancro (AIRC) IG 10376, Carraresi Foundation and by Legge 7 Regione Autonoma Sardegna (R.A.S). There are no conflicts of interest. © The Author 2013. Source

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