636 research outputs found
Oil price instability, hedging, and an oil stabilization fund : the case of Venezuela
Full text linkThe Venezuelan government and PDVSA (Venezuela's state oil companies) are both exposed to oil price instability. Given the existing tax structure, PDVSA has a higher exposure than the government, especially when prices drop below $18-20 a barrel. The authors show that the volatility of prices for crude oil is higher (but not significant) than the volatility of prices for refined oil products. And both prices are highly correlated. So, there is not much strength to the argument that Venezuela, being now mainly an exporter of refined products, faces less volatility than when it was exporting mainly crude oil. The basis risk for hedging Venezuelan crude oil was founded to be higher than for other crudes of comparable quality in the region. One explanation could be the pricing policies Venezuela follows, which leads Venezuelan crude oil prices to deviate for long periods from international prices. The basis risk in Venezuelan refined products is much lower and at acceptable levels for risk management. The issue of liquidity is concentrated in contracts for periods of less than a year. For products, the liquidity is concentrated in the nearest 4-5 months. So, for short-term hedges (6-9 months ahead), there is sufficient liquidity for Venezuela to hedge a substantial part of its exports. For longer-term hedges, the over-the-counter market is the more appropriate vehicle. In either case, it will not usually be the case that all production or exports should be hedged. The authors also examined the issue of an oil stabilization fund. For an oil stabilization fund to be effective several preconditions must be met. Most notably: oil prices should not follow a random walk; financial markets are incomplete; and there are large adjustment costs. These conditions do likely apply in Venezuela. Venezuela's best strategy would be to remove as much short-term oil price risk as possible by using short-dated hedging instruments (such as futures, options, or short-dated swaps) and to also do some longer term hedging (using mainly over-the-counter options and long-dated swaps). They also find that an oil stabilization fund should be complemented by using market-based risk management tools. The oil stabilization fund could then be used to manage any remaining interperiod oil price risk to the extent considered necessary.Markets and Market Access,Environmental Economics&Policies,Oil Refining&Gas Industry,Energy and Environment,Energy Demand
Ontogeny of the Complex Sperm in the Macrostomid Flatworm Macrostomum lignano (Macrostomorpha, Rhabditophora)
No full textSpermiogenesis in Macrostomum lignano
(Macrostomorpha, Rhabditophora) is described using
light- and electron microscopy of the successive stages in
sperm development. Ovoid spermatids develop to highly
complex, elongated sperm possessing an undulating distal
(anterior) process (or ‘‘feeler’’), bristles, and a proximal
(posterior) brush. In particular, we present a
detailed account of the morphology and ontogeny of the
bristles, describing for the first time the formation of a
highly specialized bristle complex consisting of several
parts. This complex is ultimately reduced when sperm
are mature. The implications of the development of this
bristle complex on both sperm maturation and the evolution
and function of the bristles are discussed. The
assumed homology between bristles and flagellae questioned
Embryonic origins of hull cells in the flatworm <i>Macrostomum lignano</i> through cell lineage analysis: developmental and phylogenetic implications
No full textThe development of macrostomid flatworms is of interest for evolutionary developmental biology research because these taxa combine characteristics of the canonical spiral cleavage pattern with significant deviations from this pattern. One such deviation is the formation of hull cells, which surround the remaining embryonic primordium during early development. Using live observations with a 4D microscope system, histology, and 3D reconstructions, we analyzed the ontogeny of these hull cells in the macrostomid model organism Macrostomum lignano. Our cell lineage analysis allowed us to find the precursors of the hull cells in this species. We discuss the relation between macrostomid development and the development of other spiralians and the question of whether hull cells are homologous within rhabditophoran flatworms
Corrigendum: CT Angiography or Cardiac MRI for Detection of Coronary Artery Aneurysms in Kawasaki Disease (Frontiers in Pediatrics, (2021), 9, (630462), 10.3389/fped.2021.630462)
No full textAn author name was incorrectly spelled as Diana van Stijn-Bringas Dimitriades. The correct spelling is Diana van Stijn. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated
Correction to: Coronary artery assessment in Kawasaki disease with dual-source CT angiography to uncover vascular pathology (European Radiology, (2020), 30, 1, (432-441), 10.1007/s00330-019-06367-6)
No full textThe original version of this article, published on 19 August 2019, unfortunately contained a mistake. The following correction has therefore been made in the original: The author name D. van Stijn–Bringas Dimitriades was changed to D. van Stijn. The corrected author list is given above. The original article has been corrected
Banking reform in transition countries
Full text linkIn reforming the financial sector in transition economies, one important debate is whether governments should try to reform existing state-owned banks (the rehabilitation approach) or whether a new private banking system should be allowed to emerge (a new entry approach). Or should there be a mix of the two approaches, in which the state bank activities are restricted while a parallel private banking system develops? The authors'cross-country comparison of banks'institutional development in 25 transitional economies suggests that progress can be faster under the new entry approach, especiallyrelative to initial conditions. Progress under the rehabilitation approach appears to be inhibited by poor incentives. In most countries, even those with a good banking infrastructure and a large segment of good banks, a two track process has evolved, with differences between weak and strong banks. Weak banks have moved little beyond central planning. Regression estimates suggest that slow progress of weak banks is associated with: cover concentration, government preferential treatment, and limited new banks entry. The causality direction is often unclear. Policies and structural conditions can affect bank quality. The role of banks will remain limited in many transition economies due to weak legal infrastructures, much uncertainty and inside information, and problems associated with highly leveraged financial intermediaries - including fraud, political interference, and implicit guarantees. In the short run, self-finance and intermediation among enterprises and through nonbank financial institutions may prevail.Financial Intermediation,Banks&Banking Reform,Payment Systems&Infrastructure,Financial Crisis Management&Restructuring,Municipal Financial Management,Banks&Banking Reform,Financial Intermediation,Financial Crisis Management&Restructuring,Municipal Financial Management,Settlement of Investment Disputes
Revenue-productive income tax structures and tax reforms in emerging market economies - evidence from Bulgaria
Full text linkUsing a household budget survey for 1992, The author shows the poor revenue performance and distributional impact of Bulgaria's personal income tax system. He explores the implications for revenue and income distribution of two alternative tax systems - a flat tax and a progressive but simpler three-brackets tax system. He demonstrates that simpler tax structures with lower tax rates could achieve at least equal revenue and distributional objectives and are superior in terms of efficiency and equity. (The findings are robust when Bulgaria's significant tax evasion is included). But tax changes since 1992 have, if anything, moved Bulgaria even further from a simple income tax system: the number of rates and brackets increased from 7 to 10, and the levels of exemption remain unchanged. (Complex, higher rates complicate administration and enforcement and provide incentives for tax evasions. And in the alternative systems the author explores, the poor are protected with higher exemptions.) Fortunately, the country's personal income tax structure began to move toward less nominal progressivity after Bulgaria's 1997 tax reform program. The tax rate in thetop income bracket was reduced from 52 percent to 40 percent, the number of tax brackets was halved, and the exemption level was increased 20 percent (reducing tax burdens on the poor).Environmental Economics&Policies,Public Sector Economics&Finance,Regional Governance,Tax Policy and Administration,Economic Theory&Research,Governance Indicators,Economic Theory&Research,Public Sector Economics&Finance,Environmental Economics&Policies,Tax Policy and Administration
The flatworm puzzle: Uncovering the molecular basis of the remarkable resilience and regenerative capacity of Macrostomum lignano
Full text linkModelorganismen zijn essentieel voor biomedisch onderzoek. Dikwijls wordt een kleine selectie gevestigde modelorganismen gebruikt, maar in het laatste decennia zijn meerdere nieuwe modelorganismen ontwikkeld. Dit proefschrift is een samenvatting van de ontwikkeling van zo’n nieuw modelorganisme, de vrij-levende platworm Macrostomum lignano. Dit dier staat bekend om haar opzienbarende vermogen tot regeneratie. Geamputeerd hoofden kunnen een nieuw lichaam, inclusief geslachtsorganen, in drie weken laten terug groeien. Dit wordt mogelijk gemaakt door neoblasten: cellen die kunnen delen en nieuwe cellen vormen, nodig om beschadigd of missend weefsel te vervangen. Om te bestuderen hoe dit werkt, is het genoom en transcriptoom van de worm opgesteld. Bovendien zijn de genen verrijkt in neoblasten en cellen van geslachtsorganen gekarakteriseerd. Een deel van deze genen zijn specifiek voor platwormen, maar sommige zijn ook aanwezig in andere dieren en mensen. In dit proefschrift onderzoeken we de functie van een selectie van genen van beide groepen. Het transcriptoom heeft het ook mogelijk gemaakt om andere interessante eigenschappen van M. lignano, zoals de lange levensduur en resistentie tegen ioniserende straling te onderzoeken. Zo is bijvoorbeeld het verouderingsprofiel gekarakteriseerd en onderzocht waarom dit dier meerdere jaren kan leven. Ook hebben wij getest welke dosis ioniserende straling de worm kan overleven en beschreven hoe gen expressie verandert na bestraling. Door het bestuderen van verschillende vragen en het ontwikkelen van technieken hiervoor, hebben we een belangrijke stap gezet in het ontwikkelen van M. lignano als modelorganisme. De verkregen resultaten zijn waardevol voor het onderzoek van M. lignano, andere platwormen en biomedisch onderzoek
A carcinogenic trigger to study the function of tumor suppressor genes in Schmidtea mediterranea
Full text linkPlanarians have been long known for their regenerative ability, which hinges on pluripotency. Recently, however, the planarian model has been successfully established for routine toxicological screens aimed to assess overproliferation, mutagenicity and tumorigenesis. In this study, we focused on planarian tumor suppressor genes (TSGs) and their role during chemically induced carcinogenic stress in Schmidtea mediterranea. Combining in silico and proteomic screens with exposure to human carcinogen type 1A agent cadmium (Cd), we showed that many TSGs have a function in stem cells and that, in general, exposure to Cd accelerated the onset and increased the severity of the observed phenotype. This suggested that the interaction between environmental and genetic factors plays an important role in tumor development in S. mediterranea. Therefore, we further focused on the synergistic effects of Cd exposure and p53 knockdown (KD) at the cellular and molecular levels. Cd also produced a specific proteomic landscape in homeostatic animals, with 172 proteins differentially expressed, 43 of which were downregulated. Several of these proteins have tumor suppressor function in human and other animals, namely Wilms Tumor 1 Associated Protein (WT1), Heat Shock Protein 90 (HSP90), Glioma Pathogenesis-Related Protein 1 (GLIPR1) and Matrix Metalloproteinase B (Smed-MMPB). Both Glipr1 and MmpB KD produced large outgrowths, epidermal lesions and epidermal blisters. The epidermal blisters that formed as a consequence of Smed-MmpB KD were populated by smedwi1+ cells, many of which were actively proliferating, while large outgrowths contained ectopically differentiated structures, such as photoreceptors, nervous tissue and a small pharynx. In conclusion, Smed-MmpB is a planarian TSG that prevents stem cell proliferation and differentiation outside the proper milieu
On the Religious Sources of Autonomy and Self-Expression: Charles Taylor and Marcel Gauchet
No full textSelf-expression is often called upon as a fundamental individual or collective right. In this article, the author explores the anthropological and historical conditions that constitute self-expression. For that purpose, he looks at two contemporary thinkers, Charles Taylor and Marcel Gauchet. The first part reflects their anthropological presuppositions. The second part focuses on the historical implementation of these presuppositions in both thinkers, thereby paying special attention to the way religion is involved in shaping the phenomenon of self-expression. It will turn out that self-expression and its underlying notion of autonomy are not won against forms of religious paternalism, but are rather the result of transformations established by (Christian) religion itself. As to the contemporary role of self-expression, Stijn Latré concludes by pointing out the fundamental divergence between Taylor and Gauchet
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