LONG-TERM MACRO ECONOMIC MODELLING OF THE BULGARIAN ECONOMY TO ANALYSE THE EFFECTS OF ANTICIPATED CHANGES IN THE ENERGY SECTOR

The middle and long-term forecasts of the economy for transition countries is an important challenge in order to understand better the effects of anticipated changes. During the accession negotiation between Bulgaria and the EU the continuation of the Kozloduy Nuclear Power Plant was a major stake both for Bulgaria and for the EU, such that various different options have been intensively discussed. In order to establish a transparent and factual basis different aspects have been analysed among which the consequences of the energy sector, in the local and over-regional economy, in social and environmental aspects. During the process of analysis it appeared appropriate and useful to analyse in-depth also the complex effects on the macro-economy of Bulgaria. In particular, negative and positive effects triggered in sectors others than the energy sector was to be evaluated. For this purpose a macroeconometric model INFORBG of the Bulgarian economy was developed. The model is disaggregated into 14 economic sectors. It represents the system of national accounts and describes the interdependent developments of some 250 macroeconomic variables. Thus it permits to set up consistent quantitative scenarios. In order to assess the macroeconomic consequences of an early closure two scenarios – one describing a deferred closure and the other one describing an early closure - were compared with each other. The model and its calculation results demonstrated a good example for practical use of macro-economic models in analysing anticipated changes in the economy of transition countries.Macro Economic, Bulgarian Economy, Energy

How Knowledge Stock Exchanges can increase student success in Massive Open Online Courses

Massive Open Online Courses (MOOCs) allow lecturers to overcome spatiotemporal boundaries and reach large numbers of participants. However, the completion rates of MOOCs are relatively low, a critical obstacle to their ultimate success. Existing literature suggests that strengthening student interaction has the potential to increase student commitment. The goal of this study is to develop a novel, market-based knowledge-sharing method that fosters student engagement and interaction in MOOCs, addressing the problem of low completion rates and demonstrating how MOOC engagement can lead to greater student success. The proposed method, "Knowledge Stock Exchange" (KSX), is derived from the concept of crowd-based intelligence mechanisms for incentive-compatible information aggregation. Using a popular MOOC as the focus of our empirical study, we show that the KSX method increases student interaction as well as MOOC completion rates. Moreover, we find that KSX participation has a significant positive effect on participants' exam grades

Investigations on Stokes polarization parameters of Vertical-Cavity Surface-Emitting Lasers: spatially, spectrally and time-resolved

Their unique geometrical structure first suggested by Prof. Kenichi Iga in 1977, makes vertical-cavity surface-emitting lasers (VCSELs) compact, versatile, robust and reliable optoelectronic devices, which have already outperformed edge-emitting lasers (EELs) in terms of low threshold current and high wall-plug efficiency. Most relevantly, regarding application field entering and mass production, is their low cost manufacturing due to their property of enabling wafer-level testing. In addition to these benefits provided by their vertical design, VCSELs exhibit complex polarization behavior resulting from the circular symmetry of their resonator and from the isotropic gain of their active medium, mostly based on quantum well (QW) or quantum dots (QD). In principle, the polarization of the light emitted by these optoelectronic devices should reflect the selection rules of the quantum well (QW) optical transition symmetry and thus should exhibit a circularly polarized state of light. However, various symmetry breaking mechanisms, such as strain, thermal effects, electro-optically induced birefringence, dichroism or an applied magnetic field convert this circular polarization to an elliptically polarized emission, often with a large amount of linearly polarized light. Therefore, at a first glance, polarization resolved investigations, using a linear polarizer only, on intensity noise, wave chaos, transverse mode behavior and time-resolved measurements are legitimized, although being restricted to a projection on two orthogonal linear polarization components. But clearly these kinds of measurements do not reveal the entire knowledge of the polarization state, due to the conversion of an eventual circular component into a linear component. In contrast to this rather simple, straightforward projection method the full information about the state of polarization is accessible only by determining the four Stokes polarization parameters (SPPs) S0, S1, S2 and S3. The remarkable fact about these four parameters is that they are directly measurable quantities, thus enabling the complete description of any state of polarization in mathematical terms, including unpolarized light as well as partially polarized light. Noteworthy about the Stokes formalism is the fact, that it has been invented already in 1852 by Sir George Gabriel Stokes. During this time, a crisis in optics appeared due to fundamental different approaches namely the wave- as well as the corpuscular-ansatz. The formulation of the SPPs supports the wave theory essentially, providing explanation of the famous Fresnel-Arago interference laws on the basis of the wave approach for the first time. These SPPs formulated in 1852, are even nowadays the appropriate formalism to describe the complex polarization behavior of VCSELs. The aim of this work is to conduct comprehensive experimental investigations on spatially, spectrally and time-resolved SPPs of transverse single-mode and transverse multi-mode VCSELs. Furthermore, combined measurements such as spatio-spectrally as well as spectro-temporally resolved measurements will be also performed and compared among each other, demonstrating the consistency and reliability of these quantitative results. Moreover, a detailed analysis of each particular transverse mode will be performed, uncovering the physical mechanisms responsible for the state of polarization of the total emission of transverse single-mode as well as multi-mode VCSELs. In addition the time dependence of polarization states of the total emission on a microsecond timescale will be investigated. These overall results in combination with investigations on time-resolved SPPs measurements for each particular transverse mode will be a point of origin for future numerical simulations

Isolation and Characterization of the aeneas Gene in Drosophila melanogaster

Zur Identifizierung von Faktoren, die bei Drosophila melanogaster zur Kontrolle von gerichteten Zellmigrations- bzw. Wachstumsprozessen beitragen, wurde ein Gal4-vermittelter Fehlexpressions-"Screen" durchgeführt. Es wurden ca. 4000 sogenannte P{EP}-Insertionen untersucht, bei denen endogene Gene mithilfe von Gal4-Treiberlinien in der Epidermis exprimiert wurden. So konnten Genaktivitäten ermittelt werden, deren Fehlexpression das gerichtete Auswachsen der Muskelvorläuferzellen im Drosophila-Embryo beeinflusst und zu einer Veränderung des normalerweise stereotypen Muskelmusters führt. Bei 50 (1,25%) der insgesamt 4000 durchmusterten Linien verursachte die Fehlexpression eine Störung des Musters der Körperwandmuskulatur in Verbindung mit embryonaler Letalität. Die identifizierten Genprodukte umfassen Rezeptoren, Transmembranproteine, Transkriptionsfaktoren und Enzyme. Ferner wurden Faktoren gefunden, die normalerweise nicht am Auswachsen der Muskeln beteiligt sind. Ein Beispiel hierfür ist das näher charakterisierte Kandidatengen, welches aeneas genannt wurde. Die Ergebnisse zeigen, dass die Aktivität des aeneas-Gens Migrationsprozesse beeinflussen kann. Normalerweise ist aeneas-Aktivität an der Migration der Keimzellen zum Entstehungsort der Gonade beteiligt. Das aeneas-Genprodukt ist Mitglied einer neuen, funktionell uncharakterisierten Proteinklasse, welche in so verschiedenen Spezies wie A. thaliana und H. sapiens konserviert ist. Das Protein weist eine Domäne auf, die Ähnlichkeit zur Konsensussequenz der Enzymklasse der 5-Formyltetrahydrofolat Cyclo-Ligasen zeigt. Die Integration eines P{lacW}-Elements in das aeneas-Gen führt bei 25% der homozygoten Embryonen zu einer Störung der Keimzellwanderung. Im Gegensatz zur Wildtypsituation und zu bekannten Migrationsmutanten setzt die Wanderung der Keimzellen deutlich verfrüht ein. Der Phänotyp der aeneas-Mutante deutet auf eine Funktion des Proteins bei Zelladhäsionsvorgängen zwischen Keimzellen und somatischen Zellen hin. Durch die Remobilisierung des P-Elements, verbunden mit einer ungenauen Exzision des P-Elements wurde eine 1,4 kb große Deletion im aeneas-Lokus erzeugt. Diese Deletion führt zum Verlust eines großen Teils des offenen Leserahmens und stellt somit wahrscheinlich eine Nullmutation dar. Bei dieser Mutation sind sowohl die Penetranz, als auch der Migrationsdefekt verstärkt. Dennoch ist die Deletions-Linie lebensfähig und fertil. Die unvollständige Penetranz des aeneas-Phänotyps deutet auf eine redundante Absicherung der Anaeas-Funktion durch andere Genaktivitäten hin.In order to identify factors involved in the control of directed cell migration or growth processes, a Gal4 induced misexpression screen in Drosophila melanogaster was performed. Approximately 4000 P{EP} insertions have been screened, which allow the expression of endogenous genes in the epidermis via Gal4 driver lines. The misexpression of several genes did affect the directed outgrowth of muscle progenitor cells in the Drosophila embryo and caused a rearrangement of the stereotypically arranged muscles. In 50 (1.25%) of 4000 screened lines the misexpression lead to body wall muscle pattern defects associated with embryonic lethality. The identified genes code for receptors, transmembrane proteins, transcription factors and enzyms. In addition genes have been identified that are not involved in the outgrowth of muscles in the wildtype. One example is the candidate gene termed aeneas, which was characterised in detail. Nevertheless our results support, that aeneas gene activity can affect other migration processes. The aeneas gene is for example involved in the migration of the premature germ cells on their way to the origin of the gonades. Aeneas shows homology to a functional uncharacterised protein family, that is conserved in differend species from A. thaliana to H. sapiens. One Aeneas protein domain shows similarity to a consensus sequence of 5-formyltetrahydrofolate cyclo ligase enzyms. The integration of a P{lacW} element in the aeneas gene leads in 25% of the homozygous embryos to a defective migration of the germ cells. In contrast to the wildtype situation or known mutants an untimely initiation of germ cell migration is observed. The aeneas mutant phenotype points to a protein function in cell adhesion between germ cells and somatic cells. The unprecise excision of the P element was caused by remobilisation of the transposon. Thereby a 1.4 kb deletion in the aeneas locus was generated. The deletion covers a large part of the open reading frame and represents presumably a null mutation. The penetrance and the migration defect is increased in this mutation. However this deletion line is still viable and fertile. The low penetrance of the aeneas phenotype points to redundant acting gene functions

German Multicenter Study Analyzing Antimicrobial Activity of Ceftazidime-Avibactam of Clinical Meropenem-Resistant Pseudomonas aeruginosa Isolates Using a Commercially Available Broth Microdilution Assay

Multidrug resistance is an emerging healthcare issue, especially concerning Pseudomonas aeruginosa. In this multicenter study, P. aeruginosa isolates with resistance against meropenem detected by routine methods were collected and tested for carbapenemase production and susceptibility against ceftazidime-avibactam. Meropenem-resistant isolates of P. aeruginosa from various clinical materials were collected at 11 tertiary care hospitals in Germany from 2017–2019. Minimum inhibitory concentrations (MICs) were determined via microdilution plates (MICRONAUT-S) of ceftazidime-avibactam and meropenem at each center. Detection of the presence of carbapenemases was performed by PCR or immunochromatography. For meropenem-resistant isolates (n = 448), the MIC range of ceftazidime-avibactam was 0.25–128 mg/L, MIC90 was 128 mg/L and MIC50 was 16 mg/L. According to EUCAST clinical breakpoints, 213 of all meropenem-resistant P. aeruginosa isolates were categorized as susceptible (47.5%) to ceftazidime-avibactam. Metallo-β-lactamases (MBL) could be detected in 122 isolates (27.3%). The MIC range of ceftazidime-avibactam in MBL-positive isolates was 4–128 mg/L, MIC90 was >128 mg/L and MIC50 was 32 mg/L. There was strong variation in the prevalence of MBL-positive isolates among centers. Our in vitro results support ceftazidimeavibactam as a treatment option against infections caused by meropenem-resistant, MBL-negative P. aeruginosa

Gain-of-function screen for genes that affect Drosophila muscle pattern formation.

This article reports the production of an EP-element insertion library with more than 3,700 unique target sites within the Drosophila melanogaster genome and its use to systematically identify genes that affect embryonic muscle pattern formation. We designed a UAS/GAL4 system to drive GAL4-responsive expression of the EP-targeted genes in developing apodeme cells to which migrating myotubes finally attach and in an intrasegmental pattern of cells that serve myotubes as a migration substrate on their way towards the apodemes. The results suggest that misexpression of more than 1.5% of the Drosophila genes can interfere with proper myotube guidance and/or muscle attachment. In addition to factors already known to participate in these processes, we identified a number of enzymes that participate in the synthesis or modification of protein carbohydrate side chains and in Ubiquitin modifications and/or the Ubiquitin-dependent degradation of proteins, suggesting that these processes are relevant for muscle pattern formation

Investigations on Stokes polarization parameters of Vertical-Cavity Surface-Emitting Lasers: spatially, spectrally and time-resolved

Their unique geometrical structure first suggested by Prof. Kenichi Iga in 1977, makes vertical-cavity surface-emitting lasers (VCSELs) compact, versatile, robust and reliable optoelectronic devices, which have already outperformed edge-emitting lasers (EELs) in terms of low threshold current and high wall-plug efficiency. Most relevantly, regarding application field entering and mass production, is their low cost manufacturing due to their property of enabling wafer-level testing. In addition to these benefits provided by their vertical design, VCSELs exhibit complex polarization behavior resulting from the circular symmetry of their resonator and from the isotropic gain of their active medium, mostly based on quantum well (QW) or quantum dots (QD). In principle, the polarization of the light emitted by these optoelectronic devices should reflect the selection rules of the quantum well (QW) optical transition symmetry and thus should exhibit a circularly polarized state of light. However, various symmetry breaking mechanisms, such as strain, thermal effects, electro-optically induced birefringence, dichroism or an applied magnetic field convert this circular polarization to an elliptically polarized emission, often with a large amount of linearly polarized light. Therefore, at a first glance, polarization resolved investigations, using a linear polarizer only, on intensity noise, wave chaos, transverse mode behavior and time-resolved measurements are legitimized, although being restricted to a projection on two orthogonal linear polarization components. But clearly these kinds of measurements do not reveal the entire knowledge of the polarization state, due to the conversion of an eventual circular component into a linear component. In contrast to this rather simple, straightforward projection method the full information about the state of polarization is accessible only by determining the four Stokes polarization parameters (SPPs) S0, S1, S2 and S3. The remarkable fact about these four parameters is that they are directly measurable quantities, thus enabling the complete description of any state of polarization in mathematical terms, including unpolarized light as well as partially polarized light. Noteworthy about the Stokes formalism is the fact, that it has been invented already in 1852 by Sir George Gabriel Stokes. During this time, a crisis in optics appeared due to fundamental different approaches namely the wave- as well as the corpuscular-ansatz. The formulation of the SPPs supports the wave theory essentially, providing explanation of the famous Fresnel-Arago interference laws on the basis of the wave approach for the first time. These SPPs formulated in 1852, are even nowadays the appropriate formalism to describe the complex polarization behavior of VCSELs. The aim of this work is to conduct comprehensive experimental investigations on spatially, spectrally and time-resolved SPPs of transverse single-mode and transverse multi-mode VCSELs. Furthermore, combined measurements such as spatio-spectrally as well as spectro-temporally resolved measurements will be also performed and compared among each other, demonstrating the consistency and reliability of these quantitative results. Moreover, a detailed analysis of each particular transverse mode will be performed, uncovering the physical mechanisms responsible for the state of polarization of the total emission of transverse single-mode as well as multi-mode VCSELs. In addition the time dependence of polarization states of the total emission on a microsecond timescale will be investigated. These overall results in combination with investigations on time-resolved SPPs measurements for each particular transverse mode will be a point of origin for future numerical simulations