252 research outputs found

    Evolution of Hemoglobinopathy Prevention in Africa: Results, Problems and Prospect

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    Hemoglobinopathies are a group of inherited hemoglobin disorders. Initially described in the subtropical regions, they are now spread all around the world because of migration. Their high frequency and clinical severity make them a major public health problem mostly in Africa due to the limited resources reserved for the management and prevention of these diseases. Despite considerable advances in the control and management of the hemoglobinopathies, therapeutic approach and follow- up still pose problems because of the major economic and organizational difficulties in the developing countries, particularly in Africa where problems are majored by other factors including social and cultural backgrounds, high consanguinity, as well as the coexistence of infection and malnutrition. Effective prevention programs have been carried out successfully in many European countries concerned by hemoglobinopathies. They should be extended to African regions where hemoglobin disorders account for more than 70% of total hemoglobinopathies in the world. Prevention should remain the major priority of health services to reduce incidence of hemoglobinopathies in Africa. Hereby we present the Tunisian experience that may reflect globally the profile of the prevention evolution of hemoglobinopathies in North Africa

    Is There A Difference Between Domestic And Foreign Risk Premium? The Case Of China Stock Market

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    This article studies the dynamic return and market price of risk for Chinese stocks (A-B shares). A Multivariate DCC-GARCH model is used to capture the feature of time-varying volatility in stock returns. We show evidence of different pricing mechanisms explained by the difference in the expected return and market price of risk between A and B shares. However, the significance of the difference between market prices of risk disappears if GARCH models are used

    The Evolution Of Risk Premiums In Emerging Stock Markets: The Case Of Latin America And Asia Region

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    This paper employs a conditional version of the International Capital Asset Pricing Model (ICAPM) to investigate the determinants of regional integration of stock markets in Latin America and Asia over the period 1996-2008. This model allows for three sources of time-varying risks: common international market risk, exchange rate risk, and regional market risk. At the empirical level, we make use of the asymmetric multivariate BEKK-GARCH of Baba et al.’s (1990) process to simultaneously estimate the ICAPM. Our results show that the currency risk premium is the most important component of the total premium followed by the global market premium. As for the regional risk, our findings show that it is significantly priced for our studied emerging regions but its contribution to the total risk premium is weak

    Kupershmidt operators on Hom-Malcev algebras and their deformation

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    The main feature of Hom-algebras is that the identities defining the structures are twisted by linear maps. The purpose of this paper is to introduce and study a Hom-type generalization of pre-Malcev algebras, called Hom-pre-Malcev algebras. We also introduce the notion of Kupershmidt operators of Hom-Malcev and Hom-pre-Malcev algebras and show the connections between Hom-Malcev and Hom-pre-Malcev algebras using Kupershmidt operators. Hom-pre-Malcev algebras generalize Hom-pre-Lie algebras to the Hom-alternative setting and fit into a bigger framework with a close relationship with Hom-pre-alternative algebras. Finally, we establish a deformation theory of Kupershmidt operators on a Hom-Malcev algebra in consistence with the general principles of deformation theories and introduce the notion of Nijenhuis elements.Comment: arXiv admin note: substantial text overlap with arXiv:2105.00606; text overlap with arXiv:1803.09287 by other author

    Performance of a wastewater treatment plant in south-eastern Algeria

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    The experimental study was carried out on an urban wastewater purification station located in the region of El Oued -Kounine- in south-eastern Algeria. During 6 months, samples were taken every month to study the Physico-chemical parameters of this station. Monthly monitoring of SS, COD, BOD5 was made from September 2017 to February 2018 and the results obtained show that the average elimination rates were 77.76, 74.10 and 80% respectively for BOD5, DCO and SS. The average of the ratio COD/BOD5 during the 6 months of follow-up is equal to 2.9

    The effects of private equity investors on the governance of firms

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    Companies that receive external equity typically experience a separation of ownership and control, where owners who are not involved in the company (principals) have to rely on the management team (agents) for achieving expected goals and target levels. Theoretical literature argues that when ownership and control are separated, principals develop governance structures to reduce agency costs and align agents’ incentives (Berle and Means, 1932; Jensen and Meckling, 1976; Grossman and Hart, 1986; Zingales, 1995). Likewise, optimal financial structure design by financial intermediaries can effectively help to mitigate agency problems by identifying self-enforcing equilibria (Diamond, 1984; Fama and Jensen, 1985; Stiglitz, 1985; Bhattacharya and Thakor, 1993; Barry, 1994). In general terms, governance and financial devices can be thought of as either internal control mechanisms (such as the board) or external control mechanisms (such as the market for corporate control). An increasingly important external control mechanism affecting the governance of young and fast-growing companies worldwide is the emergence of institutional and private equity investors, as equity owners. Institutional investors have the potential to influence management’s activities directly through their ownership, and indirectly by trading their shares (Gillan and Starks, 2003). In this respect private equity investors are differentiated from institutional ones in the longer-term view and in the significantly more hands-on approach that they pursue when investing in a portfolio company. As a result, companies backed by private equity investors represent a fruitful environment to investigate the use and efficiency of a multitude of control mechanisms. The surge over the last 30 years in investment activity by private equity investors at large has given rise to an increased specialization of this class of investors conditional on the risk return profiles associated with different investment and firm life cycle stages. For instance, business angels supporting the archetypical ‘paper company’ start-up face a risk exposure that in terms of both magnitude and characteristics is significantly different from that incurred by a private equity investor acquiring control of a mature company. Yet, investors in this market share common traits such as a value maximization approach, risk‒return informed decisions, and a deep knowledge of governance mechanisms. As such their influence on portfolio company governance mechanisms is largely similar in terms of depth and breadth. In this chapter we aim at presenting an up-to-date review of the main theoretical contributions and empirical results in this active and growing field of research

    Intrinsic Capability of Budding Yeast Cofilin to Promote Turnover of Tropomyosin-Bound Actin Filaments

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    The ability of actin filaments to function in cell morphogenesis and motility is closely coupled to their dynamic properties. Yeast cells contain two prominent actin structures, cables and patches, both of which are rapidly assembled and disassembled. Although genetic studies have shown that rapid actin turnover in patches and cables depends on cofilin, how cofilin might control cable disassembly remains unclear, because tropomyosin, a component of actin cables, is thought to protect actin filaments against the depolymerizing activity of ADF/cofilin. We have identified cofilin as a yeast tropomyosin (Tpm1) binding protein through Tpm1 affinity column and mass spectrometry. Using a variety of assays, we show that yeast cofilin can efficiently depolymerize and sever yeast actin filaments decorated with either Tpm1 or mouse tropomyosins TM1 and TM4. Our results suggest that yeast cofilin has the intrinsic ability to promote actin cable turnover, and that the severing activity may rely on its ability to bind Tpm1

    Arterielle Revaskularisierung der unteren Extremitäten mit konditionierter kleinkalibriger Vena saphena magna

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    Einführung: Die höchste Offenheitsrate in der arteriellen Bypasschirurgie der unteren Extremitäten wird mit einem Segment der Vena saphena magna (VSM) von ausreichender Länge und Durchmesser erreicht. Dabei ist der Venendurchmesser der einzige signifikant korrelierende Faktor für das Auftreten einer Transplantatsstenose und damit der beste Prädiktor für die primäre und die sekundäre 2-Jahre-Durchgängigkeitsrates. In 20-40% der Patienten fehlt ein bzgl. des Lumens geeignetes Segment der Vena saphena magna zur Herstellung eines Bypasses bei der primären Operation. Daher wurde eine Technik entwickelt, kleinlumige Vena saphena magna Segmente mittels einer Valvulotomie zu erweitern. Ziel: Eine zu kleinlumige Vena saphena magna soll VSM für eine spätere Verwendung als autologes Bypassmaterial der unteren Extremität konditioniert werden. Die häufigsten Indikationen für eine derartige Konditionierung sind die Bypassverwendung bei der operativen Therapie der peripheren arteriellen Verschlusskrankheit (pAVK) und beim Aneurysma der Arteria poplitea (PA). Methoden: Diese prospektive Pilotstudie würde zwischen Juni 2007 und November 2011 durchgeführt. 25 Patienten (26 Fälle) mit einem VSM Durchmesser zwischen 2 und 3mm erhielten eine in situ VSM-Valvulotomie. Die Zerstörung der suffizienten Venenklappen ermöglicht einen retrograden Blutstrom in die Vena saphena magna. Der hierdurch erzeugte Wachstumsreiz soll zu einer Durchmesserzunahme der Vene führen. Nach Erreichen eines Durchmessers von > 3mm für infragenuale Rekonstruktionen und von > 3,5 mm für supragenuale Rekonstruktion wurden die konditionierten Venensegmente als Bypass implantiert. Bei 23 Patienten war die Bypassindikation eine nicht kritische pAVK. Bei 2 Patienten war ein Aneurysma der Arteria poplitea die Indikation. Einschlusskriterium für Teilnahme an der Studie war eine nicht variköse VSM mit einem Querdurchmesser zwischen 2 und 3 mm. Die Venenevaluation erfolgte duplexsonografisch im Stehen durch eine Beurteilung der epifaszialen Vena saphena magna von der Leiste bis zum Innenknöchel. Messpunkte waren: 10 cm unterhalb des Hiatus saphenus, 10 cm oberhalb des Knies, 10 cm unterhalb des Knies und 10 cm oberhalb des Innenknöchels. Um das Venenwachstum zu ermitteln, diente als Messpunkt der kleinste ermittelte Durchmesser über einem Messbereich von 10 mm. Drei Patienten, bei denen ein femoropoplitealer Bypass oberhalb des Kniegelenkes implantiert wurde, hatten bei der Implantation einen Durchmesser der konditionierten VSM > 3.5 mm. Bei 13 Patienten mit Bypassimplantation unterhalb des Kniegelenkes war die konditionierte VSM > 3mm. Eine Wiederholung der Valvulotomie war in keinem der Patienten nötwendig. Die valvulotomierte VSM wurde bei allen Bypassoperationen offen chirurgisch entnommen. Zur postoperativen Kontrolle erfolgten eine Duplexuntersuchung und eine ABI-Messung 1,3,6,12,18 und 24 Monate nach der Implantation. Ergebnisse: Durchschnittlich vergrößerte sich der VSM-Durchmesser von initial 2,5±0,18 mm vor Valvulotomie auf 2,8±0,2 mm, 3,0±0,3mm und 3,2±0,4 mm jeweils 30, 60 und 90 Tage nach Valvolutomie. Bei der Entnahme betrug der durchschnittliche Bypassdurchmesser 3.7±0.6 mm. Die primäre 1-Jahres-Offenheitsrate mit der valvulotomierten VSM war 81±9,8% im Vergleich zu in der Literatur publizierten 58,0%±8,4% für alloplastische Transplantate, 51% für kleinkalibrige VSM und 81,6%±3,6% für Armvenentransplantate. Die sekundäre 1-Jahres-Offenheitsrate mit der Valvulotomietechnik betrug 87%±8,3% verglichen mit 82,6% für in der Literatur angegebene Transplantationen mit kleinkalibriger VSM. Die primäre 2-Jahres-Offenheitsrate mit der Valvulotomietechnik betrug 69%±11,8%, verglichen mit 50% in der Literatur angegebener Transplantationen von kleinkalibrige VSM benutzt wurden und 72%, falls Armvenentransplantate benutzt wurden. Die sekundäre 2-Jahres-Offenheitsrate mit der Valvulotomietechnik lag bei 75%±11%. Fazit: Die Valvulotomie kann zur Zunahme des Venendurchmessers vor Anlage eines femoro-distalen Bypasses verwendet werden, weil sie regelhaft zum Reflux in der valvulotomierten Vene führt und dadurch ein relevantes Venenwachstum verursacht. Zwischen 60 und 90 Tagen nach Valvulotomie wird ein Venenduchmesser > 3.5 mm erreicht und die valvulotomierte VSM kann als femoropoplitealer Bypass oberhalb des Kniegelenkes implantiert werden. Für eine Anastomose unterhalb des Kniegelenkes genügt ein Wachstum bis > 3 mm. Wenn die valvulotomierte Vene einen entsprechenden Durchmesser erreicht, kann die konditionierte VSM benutzt werden, um einen Bypass mit guter Offenheitsprognose zu konstruieren oder einen nicht funktionierenden Bypass zu ersetzen.Introduction: To achieve the best patency, great saphenous vein (GSV) of adequate length and diameter should be used for arterial bypass surgery. GSV diameter is the only factor significantly correlated with graft-stenosis and is the best predictor of the primary and secondary 2-year patency. At primary surgery 20-40% of patients lack suitably sized GSV. Therefore, a technique was developed to expand small GSV by in situ valvulotomy for later use as lower extremity arterial bypass. Objective: The aim was to condition small diameter great saphenous vein (GSV) for later use as adequately sized autologous lower extremity arterial bypass for the two most common indications for lower limb bypass: peripheral arterial occlusive disease (PAOD) and popliteal artery aneurysm (PA). Methods: This prospective pilot study was conducted in the vascular unit of the Theresienkrankenhaus, Mannheim between June 2007 and November 2011. 25 patients (26 indicated lower extremity bypasses) with GSV diameter between 2-3mm received in situ GSV valvulotomy and after GSV dilation to > 3mm for below-knee revascularization and > 3.5 mm for above-knee revascularization, arterial bypass surgery was performed with the valvulotomised GSV. Bypasses were planned for 23 patients with moderate PAOD and two patients with PA. The inclusion criterion for study participation was a minimal non-varicose GSV with a diameter of 2-3 mm. Duplex ultrasound vein mapping was carried out continuously in an upright position from calf to groin: vein diameters 10 cm below the sapheno-femoral junction, 10 cm above the knee, 10 cm below the knee and 10 cm above the ankle joint were documented. The smallest diameter over a length of 10 mm provided the starting point to determine vein growth. In 3 patients requiring an above-knee bypass valvulotomised GSV >3.5mm ∅ was used. In 13 patients requiring a below-knee bypass valvulotomised GSV >3mm ∅ was used. The valvulotomised GSV was openly harvested, repeated valvulotomy was unnecessary. Followup exams (duplex ultrasound bypass mapping, duplex graft scan and ABI) were planned at discharge, 1, 3, 6, 9 months and one year postoperatively and every 6 months thereafter for a minimum of 2 years. Results: The mean GSV diameter increased from 2.5±0.18 mm pre-valvulotomy to 2.8±0.2 mm and to 3.0±0.3mm and 3.2±0.4 mm at 30, 60 and 90 days post–valvulotomy, respectively. At harvest, bypasses measured on average 3.7±0.6 mm. One-year primary patency of bypasses using GSV after valvulotomy was 81±9.8% compared to 58.0% ± 8.4% reported for prosthetic grafts or 51% when small diameter GSV is used or upper limb vein with 81.6% ± 3.6%. One-year secondary patency with the valvulotomy technique was 87±8.3 % compared to 82.6% when small diameter GSV is used. Two-year primary patency with the valvulotomy technique was 69±11.8 %, compared to 50% when small diameter GSV was used and 72% for upper limb vein. Two-year secondary patency with the valvulotomy technique was 75±11%. Conclusion: Valvulotomy can be used to expand small diameter GSV for lower extremity arterial bypass. Reflux in valvulotomized small diameter GSV causes sufficient dilation to permit its later use as an arterial lower extremity bypass. Between 60-90 days after valvulotomy the vein reaches a diameter ≥ 3 mm for below-knee or ≥ 3.5 mm for aboveknee bypass, at which time the bypass can be constructed. When the valvulotomized vein reaches adequate diameter, or the need for a patent bypass arises later, the conditioned GSV can then be used to construct the bypass
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