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

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 Geography Of Canadian Inventions: An Urban And Regional Analysis Between 1975 And 1989

An analysis of Canadian patent, industrial directory and census data can distinguish and explain inventive patterns in Canada between 1975 and 1989. Such an analysis is needed to update and expand the geography of invention literature, because few studies examine the many varied characteristics of Canadian inventive regions and firms.;An examination of about 90 percent of Canada\u27s patented inventions in 1975, 1981 and 1989 provided a temporal understanding about the relative amount of inventive activity in Canadian regions at the firm and entrepreneurial level. Further, geographic information about the number and types of inventions traded by Canada is analyzed for the three study periods.;Multivariate regression models of Canadian census and patent data provided insight about the socio-economic characteristics of Canadian inventive regions in 1981. Additionally, factor and discriminant models proved useful for detecting those characteristics that typify Canadian inventive enterprises. Data for these latter models are available in Canadian industrial directories and patent sources.;It is shown that the geographic core of Canadian inventive activity collapsed from an area between Quebec City and Sarnia in 1975 to an area between Montreal and Kitchener-Waterloo in 1989. Also, Canada\u27s three largest cities became much less inventive after 1981. This outcome can be attributed to the less inventive nature of recent foreign owned, and large, Canadian enterprises. Most Canadian cities are less inventive today than a decade ago, because: (1) Greater technological know-how is required of Canadian inventors, and; (2) There are international economic forces acting on Canadian inventive activity.;A large population base and skilled labour force are two important variables associated with major inventive Canadian regions. These conditions are absent in the Maritime region, but are abundant in Southern Ontario. It is shown that, as foreign owned enterprises became less inventive in Canada, certain industries, i.e., electronic, had more of their inventions developed by Canadian-owned enterprises. Lastly, the relationship between the size distribution of enterprises and their inventiveness is J-shaped. It is possible that this relationship could soon become U-shaped, because small Canadian enterprises are creating a larger share of Canada\u27s inventions

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 threshold for a q-sorting methodology for computer-adaptive surveys

© 2017 Proceedings of the 25th European Conference on Information Systems, ECIS 2017. All rights reserved. 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 content and construct validity. We have created a new q-sorting technique where the hierarchies that independent raters develop are transformed into a quantitative form, and that quantitative form is tested to determine the inter-rater reliability of the individual branches in the hierarchy. The hierarchies are then successively transformed to test if they branch in the same way. The objective of this paper is to identify suitable measures and a “good enough” threshold for demonstrating the similarity of two CAS trees. To find suitable measures, we perform a set of bootstrap simulations to measure how various statistics change as a hypothetical CAS deviates from a “true” version. We find that the 3 measures of association, Goodman and Kruskal's Lambda, Cohen's Kappa, and Goodman and Kruskal's Gamma together provide information useful for assessing construct validity in CAS. In future work we are interested in both finding a “good enough” threshold(s) for assessing the overall similarity between tree hierarchies and diagnosing causes of disagreements between the tree hierarchies

A test of a computer-adaptive survey using online reviews

© 26th European Conference on Information Systems: Beyond Digitization - Facets of Socio-Technical Change, ECIS 2018. All Rights Reserved. Traditional surveys are excellent instruments for establishing the correlational relationship between two constructs. However, they are unable to identify reasons why such correlations exist. Computer-Adaptive Surveys (CAS) are multi-dimensional instruments where questions asked of respondents depend on the previous questions asked. Assessing the validity of CAS is an underexplored research area as CAS differs from traditional surveys. Therefore, validating a CAS requires different techniques. This study attempts to validate the conclusion validity of a CAS about café customer satisfaction using online customer reviews. For our CAS to have conclusion validity, there should be a high correspondence where most respondents in CAS and online reviewers both agree that certain constructs are the cause of their dissatisfaction. We created a Computer-Adaptive Survey (CAS) of café satisfaction and used online customer reviews to assess its conclusion validity. Our research thus contributes to the measurement literature in two ways, one, we demonstrate that CAS captures the same criticisms of cafes as that in online reviews, and two, CAS captures problems about customer satisfaction at a deeper level than that found in online reviews

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

Examining the Impact of the Great Recession on the Commuting Patterns of Workers in West Virginia

The Great Recession (2007-2009) continues to effect workers in West Virginia. For many people throughout the state it has become increasingly difficult to not only find a job, but to be hired. People can face job searches that can extend for months, with little or no success. It is not well known, however, if an unfavorable economic climate has caused people to travel farther abroad for employment. This paper uses Longitudinal Employer Household Dynamics Origin-Destination Employment Statistics (LODES) for the period 2002-2011 from the U.S. Census to evaluate the impact of the Great Recession on the commuting patterns of workers in West Virginia. The analysis compares job inflows, job outflows, and work commute distances before and after the onset of the recession for the five largest cities in the state: Charleston, Huntington, Parkersburg, Morgantown, and Wheeling. There is strong evidence for each city that the Great Recession has forced people to travel greater distances to work. The number of workers who live outside city limits have doubled for some cities, suggesting that their ability to find work close to home has been affected the most. Whether or not the role of each city as an employment magnet and labor supplier has changed is discussed