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

We Mean Green Environmental Science Club

Lesson Plans for an Environmental Science Club. This club seeks to promote environmental awareness to elementary students through hands-on activities, videos, and discussion

'Distorted gravity: The intensive and extensive margins of international trade' revisited ; an application to an intermediate Melitz model

With the extension of the standard Melitz Model from Ahn et al. [2011], the important role of intermediaries in facilitating trade is now recognized. In this paper, we are going to expand Chaney's [2008] approach to an Intermediate Melitz Model. By researching if Chaney's results still apply for an Intermediate Melitz Model, main results of Chaney are confirmed for the direct export model, but this is not so for the indirect export mode. Here, the elasticity of substitution still dampens the extensive margins; however, whether the dampening effect on the extensive margin still dominates the magnifying effect on the intensive margin is ambiguous. Also, the elasticities of trade ows are no longer larger, but rather smaller than in the Krugman Model. All results are economically meaningful. --international trade,Intermediate Melitz Model,firm heterogeneity,elasticities of trade flows,extensive and intensive margins

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,

Is an immune reaction required for malignant transformation and cancer growth?

Increasing evidence has shown that probably all malignant mouse cells, even those of spontaneous sporadic cancers, are endowed with tumor-specific antigens. Stimulation of cancer growth, rather than inhibition by the immune reaction, is seemingly the prevalent effect in the animal of origin (the autochthonous animal). Small initial dosages of even strong tumor antigens tend to produce stimulatory immune reactions rather than tumor inhibition in any animal. Thus, an immune response at a low level may be an essential growth-driving feature of nascent cancers, and this may be why all cancers apparently have tumor-specific antigens. Inasmuch as a low level of immunity is stimulatory to tumor growth while larger dosages are inhibitory, immuno-selection via this low response may tend to keep the antitumor immune reaction weak and at a nearly maximal stimulatory level throughout most of a tumor’s existence. These facts suggest that both suppression of tumor immunity and a heightened immune reaction might each be therapeutic although very contrasting modalities

A new kink in an old theory of carcinogenesis

According to Berenblum’s two-stage hypothesis, the first stage in carcinogenesis is the production of benign premalignant lesions. Between this initiation stage and the formation of a malignant tumor there is often a long lag phase. We propose that this lag is caused by the delay in the formation of a new and rare tumor-specific antigen, which induces an immune response that stimulates tumor growth. Such tumor-specific antigens could arise as a result of a mutator-like phenotype, which is supposedly present in the benign initial stage of carcinogenesis. According to this hypothesis, the first stage lesion provides a weakly mutagenic environment conducive to the formation of the new antigen(s). If no such new antigens appear so there is no consequent immune response, it is argued that carcinogenesis would seldom if ever ensue

Fast, precise, and widely tunable frequency control of an optical parametric oscillator referenced to a frequency comb

Optical frequency combs (OFC) provide a convenient reference for the frequency stabilization of continuous-wave lasers. We demonstrate a frequency control method relying on tracking over a wide range and stabilizing the beat note between the laser and the OFC. The approach combines fast frequency ramps on a millisecond timescale in the entire mode-hop free tuning range of the laser and precise stabilization to single frequencies. We apply it to a commercially available optical parametric oscillator (OPO) and demonstrate tuning over more than 60 GHz with a ramping speed up to 3 GHz/ms. Frequency ramps spanning 15 GHz are performed in less than 10 ms, with the OPO instantly relocked to the OFC after the ramp at any desired frequency. The developed control hardware and software is able to stabilize the OPO to sub-MHz precision and to perform sequences of fast frequency ramps automatically.Comment: 8 pages, 7 figures, accepted for publication in Review of Scientific Instrument

Working Photos: Propaganda, Participation, and the Visual Production of Memory in Nazi Germany

This article examines images of Germany's “working world” in the 1930s and 1940s. Analyzing photos from three different genres—factory photography, special-occasion industrial photography, and the work of nonprofessional photographers—it addresses a series of questions: How was the “working world” depicted in photographs from this period? What were the different modes, functions, and effects of visual representations of work and workers in these three genres? In what ways did these photographs contribute to the (visual) production and “shaping” of memory—in terms of worker experiences, as well as with respect to attempts by the National Socialists to promote ideological notions of community-building (Vergemeinschaftung)? The main argument is that photography served as an important tool for the mobilization and self-mobilization of German workers under the Nazi regime.Dieser Aufsatz untersucht Bilder der “Arbeitswelt” Deutschlands aus den 1930er- und 1940er-Jahren. Anhand von aus drei unterschiedlichen Genres stammenden Fotografien—Werksfotografien, zu besonderen Anlässen hergestellte Industriefotografien und Amateurfotografien—werden eine Reihe von Fragen angesprochen: Wie stellte sich die Arbeiterwelt in Fotografien aus dieser Zeit dar? Welches waren die unterschiedlichen Arten, Funktionen und Wirkungen der visuellen Repräsentation von Arbeit und Arbeitern in diesen drei Genres? Wie genau trugen diese Fotografien zur (visuellen) Produktion sowie zur Formung und “Gestaltung” von Erinnerung bei—im Sinne von Arbeitererfahrungen, aber auch im Hinblick auf die Versuche der Nationalsozialisten, ideologische Vorstellungen von Vergemeinschaftung zu fördern? Wie gezeigt wird, hat Fotografie als wichtiges Werkzeug der Mobilisierung wie auch der Selbstmobilisierung deutscher Arbeiter unter dem nationalsozialistischen Regime gedient.Peer Reviewe