454 research outputs found
Neuronal mechanisms of motor learning and motor memory consolidation in healthy old adults
No full textIt is controversial whether or not old adults are capable of learning new motor skills and consolidate the performance gains into motor memory in the offline period. The underlying neuronal mechanisms are equally unclear. We determined the magnitude of motor learning and motor memory consolidation in healthy old adults and examined if specific metrics of neuronal excitability measured by magnetic brain stimulation mediate the practice and retention effects. Eleven healthy old adults practiced a wrist extension-flexion visuomotor skill for 20 min (MP, 71.3 years), while a second group only watched the templates without movements (attentional control, AC, n = 11, 70.5 years). There was 40 % motor learning in MP but none in AC (interaction, p < 0.001) with the skill retained 24 h later in MP and a 16 % improvement in AC. Corticospinal excitability at rest and during task did not change, but when measured during contraction at 20 % of maximal force, it strongly increased in MP and decreased in AC (interaction, p = 0.002). Intracortical inhibition at rest and during the task decreased and facilitation at rest increased in MP, but these metrics changed in the opposite direction in AC. These neuronal changes were especially profound at retention. Healthy old adults can learn a new motor skill and consolidate the learned skill into motor memory, processes that are most likely mediated by disinhibitory mechanisms. These results are relevant for the increasing number of old adults who need to learn and relearn movements during motor rehabilitation
What Determines Expected International Asset Returns?
No full textThis paper characterizes the forces that determine time-variation in expected international asset returns. We offer a number of innovations. By using the latent factor technique, we do not have to prespecify the sources of risk. We solve for the latent premiums and characterize their time-variation. We find evidence that the first factor premium resembles the expected return on the world market porfolio. However, the inclusion of this premium alone is not sufficient to explain the conditional variation in the returns. We find evidence of a second factor premium which is related to foreign exchange risk. Our sample includes new data on both international industry portfolios and international fixed income portfolios. We find that the two latent factor model performs better in explaining the conditional variation in asset returns than a prespecified two factor model. Finally, we show that differences in the risk loadings are important in accounting for the cross-sectional variation in the international returns.International investment, Asset pricing, Latent variables, Exchange rate risk, Factor models
Imaging of Uveal Melanoma—Current Standard and Methods in Development
No full textUveal melanoma is the most common primary intraocular malignancy in adults, characterized by an insidious onset and poor prognosis strongly associated with tumor size and the presence of distant metastases, most commonly in the liver. Contrary to most tumor identification, a biopsy followed by a pathological exam is used only in certain cases. Therefore, an early and noninvasive diagnosis is essential to enhance patients’ chances for early treatment. We reviewed imaging modalities currently used in the diagnostics of uveal melanoma, including fundus imaging, ultrasonography (US), optical coherence tomography (OCT), single-photon emission computed tomography (SPECT), fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), fundus autofluorescence (FAF), as well as positron emission tomography/computed tomography (PET/CT) or magnetic resonance imaging (MRI). The principle of imaging techniques is briefly explained, along with their role in the diagnostic process and a summary of their advantages and limitations. Further, the experimental data and the advancements in imaging modalities are explained. We describe UM imaging innovations, show their current usage and development, and explain the possibilities of utilizing such modalities to diagnose uveal melanoma in the future
Modelling the Interactions Across International Stock, Bond and Foreign Exchange Markets
No full textThe benefits of investing internationally depend on three conditions, namely cross-country correlations, market volatilities, and future changes in currency risks (see Odier and Solnik (1993)). This paper investigates these conditions for several countries. Many papers have modelled both domestic interactions across asset markets and international interactions in individual asset markets in isolation, but rarely have they examined international interactions across asset markets. The paper fills this gap by modelling the international interactions across stock, bond and foreign exchange markets. Two models that meet these purposes are the VARMA-AGARCH model of McAleer et al. (2009) and the VARMA-GARCH model of Ling and McAleer (2003). The countries that will be modelled in this paper are Australia, Japan, Singapore, New Zealand and USA.
The Genetic Origin of Daunians and the Pan-Mediterranean Southern Italian Iron Age Context
No full textThe geographical location and shape of Apulia, a narrow land stretching out in the sea at the South of Italy, made this region a Mediterranean crossroads connecting Western Europe and the Balkans. Such movements culminated at the beginning of the Iron Age with the Iapygian civilization which consisted of three cultures: Peucetians, Messapians, and Daunians. Among them, the Daunians left a peculiar cultural heritage, with one-of-a-kind stelae and pottery, but, despite the extensive archaeological literature, their origin has been lost to time. In order to shed light on this and to provide a genetic picture of Iron Age Southern Italy, we collected and sequenced human remains from three archaeological sites geographically located in Northern Apulia (the area historically inhabited by Daunians) and radiocarbon dated between 1157 and 275 calBCE. We find that Iron Age Apulian samples are still distant from the genetic variability of modern-day Apulians, they show a degree of genetic heterogeneity comparable with the cosmopolitan Republican and Imperial Roman civilization, even though a few kilometers and centuries separate them, and they are well inserted into the Iron Age Pan-Mediterranean genetic landscape. Our study provides for the first time a window on the genetic make-up of pre-Roman Apulia, whose increasing connectivity within the Mediterranean landscape, would have contributed to laying the foundation for modern genetic variability. In this light, the genetic profile of Daunians may be compatible with an at least partial autochthonous origin, with plausible contributions from the Balkan peninsula
International portfolio diversification: analyzing efficient portfolios with various risk measures from a Dutch perspective
No full textThis paper investigates whether there are international portfolio diversification benefits from a Dutch perspective. To accomplish this, several domestic, regional (European) and international portfolio were created. These portfolios were analyzed using the Efficient Frontier Model of Markowitz as altered by Solnik (1974; 1993) in conjunction with several quantitative measures; EF index, Sharpe ratio, Sortino ratio and Treynor ratio. The analysis covers a sample period of 14 year (2002 – 2015) as well as sub-periods before and after the Global Financial Crisis. The results of this study are expected to show there are international diversification benefits for the Dutch investor
The Stability of the Covariances of International Property Share Returns
No full textThis paper looks at the covariance structure of international property share returns. Portfolio models, which are used to generate efficient international asset allocations, require estimates of a covariance structure of asset returns as input. Usually, the realized structure is used as a proxy, but that is only valid if this structure is stable. We test for this stability. We find covariances of international property share returns to be unstable, while correlations are stable between some time-periods, and unstable between others. The results cast some doubts on the use of standard portfolio models for the allocation of international real estate portfolios.
Foreign exchange risk, world diversification and Taiwanese ADRs
No full textThis study tries to answer the following question: Should the US investors purchase American depository receipts (ADRs) issued by Taiwanese multinationals? The conditional international asset pricing model of Dumas and Solnik (Journal of Finance, 50, 445-79, 1995) is applied to price these Taiwanese American depository receipts (ADRs). Empirical results show that foreign exchange risk is priced in Taiwanese ADRs. Moreover, Taiwanese ADRs are shown to help US investors diversify their portfolios globally. These findings suggest that Taiwanese ADRs are valid investment tools for US investors who seek international diversifications
Keep Your Landmarks Close and the Hypogastric Nerve Closer: An Approach to Nerve-sparing Endometriosis Surgery
No full textObjective: Excisional techniques used to surgically treat deep infiltrating endometriosis (DIE) can result in inadvertent damage to the autonomic nervous system of the pelvis, leading to urinary, anorectal, and sexual dysfunction [1–4]. This educational video illustrates the autonomic neuroanatomy of the pelvis, identifying the predictable location of the hypogastric nerve in relation to other pelvic landmarks, and demonstrates a surgical technique for sparing the hypogastric nerve and inferior hypogastric plexus. Design: Using didactic schematics and medical drawings, we discuss and illustrate the autonomic neuroanatomy of the pelvis. With annotated laparoscopic footage, we demonstrate a stepwise approach for identifying, dissecting, and preserving the hypogastric nerve during pelvic surgery. Setting: Tertiary care academic hospitals: Mount Sinai Hospital in Toronto, Ontario, Canada, and S. Orsola Hospital in Bologna, Italy. Interventions: Radical excision of DIE with adequate identification and sparing of the hypogastric nerve and inferior hypogastric plexus bilaterally was performed, following an overview of pelvic neuroanatomy. The superior hypogastric plexus was described and the hypogastric nerve, the most superficial and readily identifiable component of the inferior hypogastric plexus, was identified and used as a landmark to preserve autonomic bundles in the pelvis. The following steps, illustrated with laparoscopic footage, describe a surgical technique developed to identify and preserve the hypogastric nerve and the deeper inferior hypogastric plexus without the need for more extensive pelvic dissection to the level of the sacral nerve roots: (1) transperitoneal identification of the hypogastric nerve, with a pulling maneuver for confirmation; (2) opening of the retroperitoneum at the level of the pelvic brim and retroperitoneal identification of the ureter; (3) medial dissection and identification of the hypogastric nerve; and (4) lateralization of the hypogastric nerve, allowing for safe resection of DIE. Conclusion: The hypogastric nerve follows a predictable course and can be identified, dissected, and spared during pelvic surgery, making it an important landmark for the preservation of pelvic autonomic innervation
Equity portfolio investment in developing countries : a literature survey
No full textThe author surveys the literature on equity portfolio investment to develop a research agenda that could help developing countries interested in attracting equity portfolio flows. He finds that a broad literature exists on equity portfolio flows, but that most empirical tests have focused on industrial countries. Although some of the analytical papers may be applicable to developing countries, the author identifies areas of empirical research of specific interest to developing countries: identifying barriers that prevent a free flow of (equity portfolio) capitalbetween industrial and developing countries; quantifying the opportunity costs of these barriers in higher risk-adjusted cost of capital and lower flow of capital; analyzing the optimal amount of portfolio investment and the degree to which investors in industrial countries are currently (under-) invested in developing countries; and analyzing the efficiency of the various stock markets in developing countries, as inefficient stock markets could be a barrier to foreign flows. This research could help policymakers in developing countries make decisions about liberalizing capital accounts, reforming financial markets, and coping with the potential volatility of equity portfolio flows.Economic Theory&Research,International Terrorism&Counterterrorism,Banks&Banking Reform,Financial Intermediation,Markets and Market Access
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