Recent trends related to the use of formal methods in software engineering

An account is given of some recent developments and trends related to the development and use of formal methods in software engineering. Ongoing activities in Europe are focussed on, since there seems to be a notable difference in attitude towards industrial usage of formal methods in Europe and in the U.S. A more detailed account is given of the currently most widespread formal method in Europe: the Vienna Development Method. Finally, the use of Ada is discussed in relation to the application of formal methods, and the potential for constructing Ada-specific tools based on that method is considered

ESTIMATION ISSUES IN SINGLE COMMODITY GRAVITY TRADE MODELS

Recently gravity trade models are applied to disaggregated trade data. Here many zeros are characteristic. In the presence of excess zeros usual Poisson Pseudo Maximum Likelihood (PPML) is still consistent, the variance covariance matrix however is invalid. Correct economic interpretation however requires also the last. So alternative estimators are looked for. STAUB &WINKELMANN (2010) argue that zero-inflated count data models (i.e. zero-inflated Poisson / Negative Binomial Pseudo Maximum Likelihood (ZIPPML / ZINBPML)) are no alternative since under model misspecification these estimators are inconsistent. Yet zeroinflated Poisson Quasi-Likelihood (PQL) is a reliable alternative. It is consistent even under model misspecifications and beyond that robust against unobserved heterogeneity. Another alternative is a log-skew-normal Two-Part Model (G2PM) which generalises the standard lognormal Two-Part Model (2PM). It is insofar advantageous as it adjusts for (negative) skewness and regression coefficients retain usual interpretations as in log-normal models. PQL is useful for multiplicative gravity model estimation and G2PM for log-linear gravity model estimation. Exemplarily the estimators are applied to intra-European piglet trade to assess their empirical performance and applicability for single commodity trade flow analysis. The empirical part favours PQL but G2PM is a reliable alternative for other trade flow analyses. PQL and G2PM should become standard tools for single commodity trade flow analysis.Gravity Model, Excess Zeros, Poisson Quasi Likelihood, Generalised Two Part Model, Gravitationsmodell, Exzess an Nullen, Poisson Quasi Likelihood, Generalisiertes Zwei-Teile Modell, Agribusiness, Agricultural and Food Policy, Agricultural Finance, Demand and Price Analysis, Financial Economics,

Site-specific Photocross-linking Reveals That SecGlp and TRAM Contact Different Regions of a Membrane-inserted Signal Sequence

A chemically charged amber suppressor tRNA was used to introduce the photoactivatable amino acid (Tmd)Phe at a selected position within the signal sequence of the secretory protein preprolactin. This allowed the interactions of the NH -terminal, the central, and the COOH-terminal regions of the signal sequence to be investigated during insertion into the membrane of the endoplasmic reticulum (ER). We found that different regions of the nascent chains were photocross-linked to different ER proteins. The TRAM protein (translocating chain-associating membrane protein) contacts the NHz-terminal region of the signal sequence while the mammalian Sec6lp contacts the hydrophobic core of the signal sequence and regions COOH-terminal of this. These results suggest that the ER translocation complex is composed of heterologous protein subunits which contadcti stinct regions of nascent polypeptides during their membrane insertion

Whole blood co-expression modules associate with metabolic traits and type 2 diabetes : an IMI-DIRECT study

Background The rising prevalence of type 2 diabetes (T2D) poses a major global challenge. It remains unresolved to what extent transcriptomic signatures of metabolic dysregulation and T2D can be observed in easily accessible tissues such as blood. Additionally, large-scale human studies are required to further our understanding of the putative inflammatory component of insulin resistance and T2D. Here we used transcriptomics data from individuals with (n = 789) and without (n = 2127) T2D from the IMI-DIRECT cohorts to describe the co-expression structure of whole blood that mainly reflects processes and cell types of the immune system, and how it relates to metabolically relevant clinical traits and T2D. Methods Clusters of co-expressed genes were identified in the non-diabetic IMI-DIRECT cohort and evaluated with regard to stability, as well as preservation and rewiring in the cohort of individuals with T2D. We performed functional and immune cell signature enrichment analyses, and a genome-wide association study to describe the genetic regulation of the modules. Phenotypic and trans-omics associations of the transcriptomic modules were investigated across both IMI-DIRECT cohorts. Results We identified 55 whole blood co-expression modules, some of which clustered in larger super-modules. We identified a large number of associations between these transcriptomic modules and measures of insulin action and glucose tolerance. Some of the metabolically linked modules reflect neutrophil-lymphocyte ratio in blood while others are independent of white blood cell estimates, including a module of genes encoding neutrophil granule proteins with antibacterial properties for which the strongest associations with clinical traits and T2D status were observed. Through the integration of genetic and multi-omics data, we provide a holistic view of the regulation and molecular context of whole blood transcriptomic modules. We furthermore identified an overlap between genetic signals for T2D and co-expression modules involved in type II interferon signaling. Conclusions Our results offer a large-scale map of whole blood transcriptomic modules in the context of metabolic disease and point to novel biological candidates for future studies related to T2D.Peer reviewe

Why Grain Merchants Will Never Be So Naïve to Use Minimum Variance Hedging in Daily Business: a Critical Discussion

Minimum variance hedging is probably one of the most popular concepts in the literature on agricultural futures markets. It has been applied many times in the literature, and all studies confirmed that minimum variance hedging has the potential to improve the effectiveness of hedging. However, despite this advantage, no grain merchant has ever used minimum variance hedging in daily business. In this paper we show that grain merchants have a good reason for this. Minimum variance hedging prevents them from trading the basis. If grain merchants do not trade the basis, they will not generate the profits that are necessary to cover the costs of grain storage and will go bankrupt sooner or later. In theory, risk avoidance may be a desirable goal, but in reality, it is not affordable. In fact, the only longterm sustainable strategy is basis trading

ESTIMATION ISSUES IN SINGLE COMMODITY GRAVITY TRADE MODELS

Recently gravity trade models are applied to disaggregated trade data. Here many zeros are characteristic. In the presence of excess zeros usual Poisson Pseudo Maximum Likelihood (PPML) is still consistent, the variance covariance matrix however is invalid. Correct economic interpretation however requires also the last. So alternative estimators are looked for. STAUB &WINKELMANN (2010) argue that zero-inflated count data models (i.e. zero-inflated Poisson / Negative Binomial Pseudo Maximum Likelihood (ZIPPML / ZINBPML)) are no alternative since under model misspecification these estimators are inconsistent. Yet zeroinflated Poisson Quasi-Likelihood (PQL) is a reliable alternative. It is consistent even under model misspecifications and beyond that robust against unobserved heterogeneity. Another alternative is a log-skew-normal Two-Part Model (G2PM) which generalises the standard lognormal Two-Part Model (2PM). It is insofar advantageous as it adjusts for (negative) skewness and regression coefficients retain usual interpretations as in log-normal models. PQL is useful for multiplicative gravity model estimation and G2PM for log-linear gravity model estimation. Exemplarily the estimators are applied to intra-European piglet trade to assess their empirical performance and applicability for single commodity trade flow analysis. The empirical part favours PQL but G2PM is a reliable alternative for other trade flow analyses. PQL and G2PM should become standard tools for single commodity trade flow analysis

Estimation Issues in Single Commodity Gravity Trade Models

Recently gravity trade models are applied to disaggregated trade data. Here many zeros are characteristic. In the presence of excess zeros usual Poisson Pseudo Maximum Likelihood (PPML) is still consistent, the variance covariance matrix however is invalid. Correct economic interpretation however requires also the last. So alternative estimators are looked for. Staub & Winkelmann [2010] argue that zeroinflated count data models (i.e. zero-inflated Poisson / Negative Binomial Pseudo Maximum Likelihood (ZIPPML / ZINBPML)) are no alternative since under model misspecification these estimators are inconsistent. Yet zero-inflated Poisson Quasi- Likelihood (PQL) is a reliable alternative. It is consistent even under model misspecifications and beyond that robust against unobserved heterogeneity. Another alternative is a log-skew-normal Two-Part Model (G2PM) which generalizes the standard log-normal Two-Part Model (2PM). It is insofar advantageous as it adjusts for (negative) skewness and regression coefficients retain usual interpretations as in log-normal models. PQL is useful for multiplicative gravity model estimation and G2PM for log-linear gravity model estimation. Exemplarily the estimators are applied to intra-European piglet trade to assess their empirical performance and applicability for single commodity trade flow analysis. The empirical part favours PQL but G2PM is a reliable alternative for other trade flow analyses. PQL and G2PM should become standard tools for single commodity trade flow analysis

Structural Gravity Estimation & Agriculture

Recently, discussion about the appropriate estimation of gravity trade models has started in agriculture. Here, we are going to review recent developments in the literature. It appears that fixed effects Poisson Pseudo Maximum Likelihood is not only the only consistent estimator [Santos Silva and Tenreyro, 2006] but also it already allows for a structural fit [Fally, 2012]. Fixed effects in conjunction with the adding-up property of Poisson Pseudo Maximum Likelihood - which has been so far neglected - can be harnessed to directly deduce multilateral resistance indexes (i.e. general equilibrium effects) from reduced-form estimation. This innovation made by Fally will ease comparative statics and incidence analysis, making Poisson Pseudo Maximum Likelihood even more preferable in practice

Optionshandel Und Maispreisvolatilitat: Does the Tail Wag the Dog?

In dieser Arbeit werden Auswirkungen von Agar-Optionen auf die Volatilität des den Optionen zugrundeliegenden Futuresmarktes analysiert. Bisherige Analysen bezogen sich nahezu ausschließlich auf den Finanzmarkt. Für den Agrarmarkt scheinen noch keine empirischen Erkenntnisse zu existieren. Es besteht die Sichtweise, dass Optionen exzessive Volatilität im zugrundeliegenden Basismarkt hervorrufen könnten. Die vorliegende Arbeit soll einen Teil zur Diskussion um die Agrarpreisspekulation und den damit verbundenen Auswirkungen auf die Preisentwicklung beitragen. Gegenstand ist der Mais-Derivatemarkt der französischen Terminbörse MATIF. Zur Analyse wird auf ein EGARCH-Modell zurückgegriffen. Die auf zwei Untersuchungszeiträume von Dezember 2000 bis Dezember 2007 und Dezember 2007 bis Dezember 2013 geschätzten Ergebnisse lassen keine signifikanten Zusammenhänge der Volatilität des Futuresmarktes und dem Optionshandel erkennen