Optimal Foreign Reserves: The Case of Croatia

This paper develops a simple model of precautionary foreign reserves in a dollarized economy subject to a sudden stop shock that occurs concurrently with a bank run. By including specific features of the Croatian economy in our model we extend the framework of Goncalves (2007). An analytical expression of optimal reserves is derived and calibrated for Croatia in order to evaluate the adequacy of the Croatian National Bank foreign reserves. We show that the precautionary demand for reserves is consistent with the trend of the strong accumulation of foreign reserves over the last ten years. Whether this trend has been too strong or whether the actual reserves are lower than the optimal reserves depends on the possible reaction of the parent banks during a crisis. We show that for plausible values of parameters, the Croatian National Bank has enough reserves to fight a possible crisis of the magnitude of the 1998/1999 sudden stop with a banking crisis episode. This result holds regardless of the parent banks’ reaction. We also show how use of the two standard indicators of “optimal” reserves, the Greenspan-Guidotti and the 3-months-of-imports rules, might lead to an unrealistic assessment of foreign reserves optimality in the case of Croatia.sudden stop, banking crisis, dollarized economy, optimal reserves

Tool-supported building of DSLs from OWL ontologies

Domain-specific languages (DSLs) are computer languages intended for problem solving in a specific domain. Ontology is a formal representation of a set of concepts from a particular domain and the relations between them. An ontology may be used to describe a domain and to reason about the entities within the domain. This paper presents an Ontology2DSL framework to build DSLs from OWL ontologies. Ontology2DSL enables the semi-automated construction of a formal grammar and programs from an OWL ontology. The design approach, the functionalities of the framework, and a case study are also addressed in this paper. Special attention is paid to the architecture that encompasses the following components: the transformation pattern builder, the OWL parser, the rule reader, the rule execution component and the transaction logger

TEM and STEM investigations of SrO-doped Sr(Ti,Nb)O3-δ thermoelectrics

Sr(Ti1-xNbx)O3-δ solid solutions are promising materials for n-type high-temperature thermoelectrics1. In our study 10 mol% of SrO excess was added to stoichiometric composition with x=0.2 in order to introduce Ruddlesden-Popper (RP) type-planar faults2,3 into the material, thus minimizing thermal conductivity. TEM and STEM were used to study possible ordering and/or distribution of Nb on Ti sites in the perovskite structure. All results were obtained in a Jeol ARM-200F with a CFEG and Cs probe corrector. HAADF imaging was performed at angles from 70 to 175 mrad, while ABF imaging from 11 to 23 mrad. EDXS spectra were acquired using JEOL Centurio Dry SD100GV SDD Detector. RP planar faults, as viewed along [001] zone axis, are shown in HRTEM micrograph in figure 1. The commonly observed number of perovskite unit cells between the planar faults is >2, which corresponds to various homologous compounds with the formula Srn+1(Ti,Nb)nO3n+1. However, solid solution Sr(Ti,Nb)O3-type grains with no RP faults can also be observed (bottom inset in Fig. 1). A HR HAADF STEM image of ordered RP faults (Fig. 2) shows that while the measured intensities of individual Sr atomic columns along a single fault do not scatter significantly, the (Ti,Nb)O atom columns exhibit quite large differences in measured intensities, thus indicating significant variation in Nb and Ti content within a single atom column. Quantitative analysis of measured intensities is in progress. The comparison between simultaneously acquired HAADF and ABF images of a single RP fault is shown in figure 3. While pure oxygen atomic columns cannot be resolved in the HAADF image, they can be readily observed using ABF imaging. The positions of oxygen atom columns along the planar faults are in full agreement with the structural model of a RP planar fault. Additional information on Nb distribution within perovskite matrix/RP faults was obtained by EDXS. While low magnification EDXS mappings show enrichment of Sr at RP faults accompanied by a corresponding decrease in Ti and Nb content, atom-resolved EDXS mappings confirm that individual mixed (Ti,Nb)O atom columns contain different Nb content (annotated atom column). Additionally, the spot EDXS line analysis (net counts) again shows much larger scatter in accumulated net counts for Ti as compared with Sr. The results being presented clearly show that no Nb is incorporated into the SrO RP faults and that the Nb is inhomogeneously incorporated within (Ti,Nb)O atom columns

The availability of land for perennial energy crops in Great Britain

This paper defines the potentially available land for perennial energy crops across Great Britain as the first component of a broader appraisal undertaken by the ‘Spatial Modelling of Bioenergy in Great Britain to 2050’ project. Combining data on seven primary constraints in a GIS reduced the available area to just over 9 M ha (40% of GB). Adding other restrictions based on land cover naturalness scores to represent landscape considerations resulted in a final area of 8.5 M ha (37% of GB). This distribution was compared with the locations of Miscanthus and SRC willow established under the English Energy Crop Scheme during 2001–2011 and it was found that 83% of the planting fell within the defined available land. Such a correspondence provides confidence that the factors considered in the analysis were broadly consistent with previous planting decisions

Role of tryptophan residues of Erv1: Trp95 and Trp183 are important for its folding and oxidase function

Erv1 is an FAD-dependent sulphydryl oxidase of the ERV/ALR sub-family, and an essential component of the mitochondrial import and assembly pathway. Erv1 contains six tryptophan residues, which are all located in the highly conserved C-terminal FAD-binding domain. Though important structural roles were predicted for the invariable Trp95, no experimental study has been reported. In this study, we investigated the structural and functional roles of individual Trp residues of Erv1. Six single Trp-to-Phe yeast mutant strains were generated and their effects on cell viability were tested at various temperatures. Then, the mutants were purified from E. coli. Their effects on folding, FAD-binding, and Erv1 activity were characterised. Our results showed that Erv1W95F has the strongest effect on the stability and function of Erv1, and followed by Erv1W183F. Erv1W95F results in a decrease of the Tm of Erv1 by 23°C, a significant loss of the oxidase activity, and thus causing cell growth defects at both 30°C and 37°C. Erv1W183F induces changes in the oligomerisation state of Erv1, along with a pronounced effect on the stability of Erv1 and its function at 37°C, whilst the other mutants had no clear effect on the function of Erv1 including the highly conserved Trp157 mutant. Finally, computational analysis indicates that Trp95 plays a key role in stabilising the isoalloxazine ring to interact with Cys133. Taken together, this study provided important insights into the molecular mechanism of how sulfhydryl oxidases use FAD in catalyzing disulfide bond formation

Bindung des C1-Carriers Tetrahydromethanopterin und seiner Derivate an Enzyme des Energiestoffwechselweges methanbildender Archaeen

In dieser Arbeit sollte die Bindung von Tetrahydromethanopterinderivaten an zwei Enzyme des methanogenen, CO2-reduzierenden Energiestoffwechselweges strukturell charakterisiert werden. In jenem Stoffwechselweg verläuft die schrittweise Reduktion von CO2 über die Bindung an den C1-Carrier Tetrahydromethanopterin (H4MPT), ein Tetrahydrofolat-Analogon, welches unter anderem in methanogenen Archaeen zu finden ist. Die thermophilen bzw. hyperthermophilen Ursprungsorganismen der untersuchten Enzyme, Methanothermobacter marburgensis, Methanocaldococcus jannaschii und Methanopyrus kandleri, sind aufgrund ihrer Anpassung an extreme Habitate durch spezielle genomische, strukturelle und enzymatische Eigenschaften von strukturbiologischem Interesse. Beim ersten in dieser Arbeit untersuchten Enzym handelte es sich um den aus acht Untereinheiten bestehenden membrangebundenen N5-Methyl-H4MPT:Coenzym M-Methyltransferasekomplex (MtrA-H). Dieser katalysiert in einem zweistufigen Mechanismus den Methyltransfer von H4MPT zum Co(I) der prosthetischen Gruppe 5’-Hydroxybenzimidazolylcobamid (Vitamin B12a), um die Methylgruppe dann auf Coenzym M zu übertragen. Gleichzeitig findet ein der Energiekonservierung dienender vektorieller Natriumtransport über die Membran statt. Für den Mtr-Komplex aus M. marburgensis (670 kDa) lag bereits ein Protokoll zur Reinigung unter anaeroben Bedingungen vor. Dieses wurde im Rahmen dieser Arbeit verbessert, für die Isolierung und Reinigung unter aeroben Bedingungen vereinfacht und für die Erfordernisse der zur Strukturbestimmung verwendeten elektronenmikroskopischen Einzelpartikelmessung optimiert. Neben der Präparation des kompletten Komplexes MtrA-H wurde als Alternative die Präparation des Enzymkomplexes MtrA-G unter möglichst vollständiger Abtrennung der hydrophilsten Untereinheit MtrH gewählt. Mit der zu diesem Zweck entwickelten Methode konnte das Abdissoziieren von MtrH besser als im etablierten Protokoll kontrolliert und somit die Homogenität der Probe deutlich verbessert werden. Dies schafft zum einen die Vorraussetzungen für eine Kristallisation zur Röntgenstrukturanalyse, zum anderen war auch in bei der elektronenmikroskopischen Einzelpartikelmessung erkennbar, dass mit dem Mtr-Komplex ohne MtrH bessere Ergebnisse zu erzielen sind. Parallel zu den Untersuchungen am Gesamtkomplex sollten die den Cobamid-Cofaktor bindende Untereinheit MtrA sowie die H4MPT-bindende Untereinheit MtrH in für die Kristallisation und röntgenkristallographische Untersuchung ausreichender Menge und Qualität gereinigt werden. Hierfür wurden MtrA und MtrH aus oben genannten Organismen für die heterologe Expression in E. coli kloniert, die Expressionsbedingungen optimiert und Reinigungsprotokolle etabliert. Anschließend wurden die Untereinheiten umfangreichen Kristallisationsversuchen unterzogen. Die Untereinheit MtrA aus M. jannaschii konnte ohne die C-terminale Transmembranhelix als lösliches Protein in E. coli produziert und als Holoprotein bis zur Homogenität gereinigt werden. Bei M. kandleri MtrA gelang die Herstellung von geringen Mengen teilweise löslichen StrepII-Fusionsproteins ohne C-terminale Transmembranhelix in E. coli. Eine Produktion der Untereinheit MtrH in E. coli als lösliches Protein war bei keiner der in dieser Arbeit getesteten Varianten möglich. Mit dem in Einschlusskörperchen exprimierten Protein aus M. marburgensis wurde eine Reinigung und Rückfaltung versucht. Auch eine Co-Expression der Untereinheiten MtrA und MtrH, durch welche eine bessere Faltung und Löslichkeit erreicht werden sollte, war nur in Einschlusskörperchen möglich. Das zweite in dieser Arbeit untersuchte Enzym, die F420 abhängige N5,N10 Methylen-H4MPT-Dehydrogenase (Mtd), katalysiert den reversiblen, stereospezifischen Hydrid-Transfer zwischen reduziertem F420 (F420H2) und Methenyl-H4MPT+, welches hierbei zu Methylen-H4MPT reduziert wird. Die Reaktion verläuft über einen ternären Komplex bestehend aus Protein, Substrat (Methylen-H4MPT) und Cosubstrat (F420), welcher strukturell charakterisiert werden sollte. Das gereinigte, rekombinante Enzym aus M. kandleri wurde mit verschiedenen H4MPT- und F420-Derivaten co-kristallisiert, die Struktur des ternären Komplexes röntgenkristallographisch bestimmt und die Bindung von H4MPT und F420 analysiert. Methenyl-H4MPT+ und F420H2 sind in der in dieser Arbeit gelösten Kristallstruktur in katalytisch aktiver Konformation gebunden, jedoch kann bei einer Auflösung von 1,8 Å nicht beurteilt werden, ob Methylen-H4MPT und F420 oder Methenyl-H4MPT+ und F420H2 vorlagen. Ein Vergleich mit der Struktur von M. kandleri-Mtd (KMtd) ohne Substrat und Cosubstrat ergab nur äußerst geringe Abweichungen in der Proteinkonformation, sodass sich KMtd überraschenderweise als Beispiel für ein Enzym mit ungewöhnlich starrer, vorgegebener Bindetasche erwies.The aim of this study was a structural characterization of the binding of tetrahydromethanopterin derivatives to enzymes of the energy conserving CO2-reducing methanogenic pathway. In this pathway the stepwise reduction of CO2 proceeds via binding to the tetrahydrofolate analog tetrahydromethanopterin (H4MPT) which is found i. a. in methanogenic archaea. Due to the adaptation of the thermophilic and hyperthermophilic source organisms (Methanothermobacter marburgensis, Methanocaldococcus jannaschii and Methanopyrus kandleri) to their extreme habitats by genomic, structural and enzymatic features, they are of special interest for structural biology. The first enzyme investigated in this study is the eight subunits containing membrane bound complex of N5-methyl-H4MPT:coenzyme M methyltransferase (MtrA-H). Firstly, it catalyzes the methyl group transfer from H4MPT to the Co(I) of the prosthetic group (5’-hydroxybenzimidazolylcobamide; vitamin B12a). In a second step, it transfers the methyl group to coenzyme M, which is coupled to an energy conserving vectorial sodium ion transport across the membrane. The purification protocol for Mtr complex from M. marburgensis (670 kDa) previously established under anaerobic conditions was enhanced, simplified for isolation and purification under aerobic conditions and optimized for electron microscopic single particle reconstruction. Besides the preparation of the complete complex MtrA-H, the preparation of enzyme complex MtrA-G without the most hydrophilic subunit MtrH was chosen as a second approach. The purification method developed for this purpose improved the control over dissociation of MtrH from complex MtrA-G and enhanced the homogeneity of the sample significantly. Thus, the prerequisites for crystallization and subsequent X-ray studies were created as well as for electron microscopic single particle reconstruction, which was confirmed by experiments with MtrA-G (without MtrH) promising far better results. Concurrently to the studies on the complete Mtr complex, cobamide containing subunit MtrA and H4MPT binding subunit MtrH should be purified to homogeneity in quantities sufficient for crystallization and X-ray analysis. Therefore, MtrA and MtrH from source organisms mentioned above were cloned for heterologous expression in E. coli, expression conditions were optimized and purification protocols were established. The purified proteins were used for extensive crystallization experiments. MtrA from M. jannaschii without its transmembrane helix could be produced in E. coli as a soluble protein. The holoprotein could be purified to homogeneity but crystallization failed presumably due to its exceptionally high solubility. MtrA from M. kandleri was produced in E. coli as a StrepII fusion protein without transmembrane helix only in marginal amounts. The production of subunit MtrH in E. coli as a soluble protein was not possible regardless of the variants tested in this thesis. Attempts to refold and purify to homogeneity the M. marburgensis protein expressed in inclusion bodies were without success. Co-expression of MtrA and MtrH with the objective of improving folding and solubility also led to the production of inclusion bodies which could not be refolded and purified together. The second enzyme analyzed in this thesis, F420-dependent N5,N10-methylene-H4MPT dehydrogenase (Mtd), catalyzes the reversible stereospecific hydride transfer between reduced F420 (F420H2) and methenyl-H4MPT+, the latter being thereby reduced to methylene-H4MPT. The ternary complex involved in this reaction consists of the protein part, substrate (methylene-H4MPT) and co-substrate (F420) and was structurally characterized in this thesis. The purified recombinant enzyme from M. kandleri was co-crystallized with several H4MPT and F420 derivatives, the structure of the ternary complex was determined by X-ray crystallography and the binding of H4MPT and F420 was analyzed. In the structure solved in the thesis methenyl-H4MPT+ and F420H2 are bound in a catalytically active conformation, but a resolution of 1.8 Å precludes a discrimination between either methylene-H4MPT and F420 or methenyl-H4MPT+ and F420H2. Compared to the structure of M. kandleri Mtd (KMtd) without substrate and co-substrate bound, only marginal variations of the protein conformation were visible. Thus KMtd can be considered as a surprising and extreme example of an enzyme with an exceptionally rigid, preformed binding pocket

The changing Canadian inventive spatial economic pattern: An urban and regional analysis between 1881 and 1986

Canadian urban and regional patent and trademark data was analysed between 1881 and 1986 in an attempt to distinguish spatial inventive patterns in Canada over time. Inventive activity, as a pre—condition for economic development, is a viable indicator for predicting future economic growth in an inventive spatial economy. As such, it will be possible to extend the description of spatial inventive patterns in Canada after 1986. The percentage and relative level of inventive activity in urban centers and regions in Canada will help distinguish spatial inventive patterns in Canada over time. This information was based on a 25 percent systematic sample of registered Canadian patents and trademarks between 1881 and 1986. Inventive activity was also compared to population growth and unemployment levels in an attempt to discern the relationship between inventive activity and urban growth. This analysis compared the number of inventions per 10,000 population in 1981 to the percentage of population growth between 1981 and 1986 and unemployment levels in 1986 for twenty-four major Census Metropolitan Areas in Canada. It was found that the Canadian inventive spatial economy is very dynamic. However, an overall pattern of concentration was detected. For example, inventive impulses in the Maritime region was lacking after 1911. In the west, impulses of varying intensity were evident over time and space. Most of Canada\u27s healthy inventive activity was found in Central Canada. Further, the core region lost some of its inventive importance during the post-war years, however, between 1981 and 1986, this region experienced traditionally high levels of inventive activity. Also, there was a noticeable pattern of inventive concentration towards higher ordered places in the Canadian urban hierarchy, and a rationalization of Canada\u27s core region from a Quebec City to Windsor axis to a Toronto to Kitchener—waterloo axis with a trunk line towards Hamilton and two island impulses in Montreal and Ottawa. Lastly, there was a positive and significant relationship between inventive activity and urban growth, lending support to the notion that recent inventive concentration in the core region of Canada can be expected to continue well into the next decade

A Q-sorting methodology for Computer-Adaptive Surveys - Style "Research"

Computer-Adaptive Surveys (CAS) are multi-dimensional instruments where questions asked of respondents depend on the previous questions asked. Due to the complexity of CAS, little work has been done on developing methods for validating their construct validity. This paper describes the process of using a variant of Q-sorting to validate a CAS item bank. The method and preliminary results are presented. In addition, lessons learned from this study are discussed