112 research outputs found

    Influence of an Angular Hatching Exposure Strategy on the Surface Roughness During Picosecond Laser Ablation of Hard Materials

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    AbstractInnovative chip breakers for cutting tools made of very hard materials require laser ablation and demand a high quality regarding the manufactured surface. When processing materials such as polycrystalline cubic boron-nitride or tungsten carbide the surface roughness by laser ablation reaches Sa = 1,0-2,9 μm compared to Sa = 0,42 μm achieved by grinding. Therefore in the presented research the influence of the hatching exposure strategy on surface roughness during picosecond laser ablation of tungsten carbide is examined. The areal, layerwise ablation process is separated into its elements which are represented by intersection zones between single and multiple laser vectors. Thus two mechanisms of roughness formation are identified and described by model functions. Further the mechanisms are transferred to areal ablation in which surface roughness decreases due to improved hatching angles compared to a commonly used one of φ= 0°/90°. With this approach the roughness is reduced by approximately factor 2,0-3,5 to Sa = 0,82 μm. In conclusion guidelines are derived which present favorable settings for high quality laser ablation processes

    The COCOMO-Models in the Light of the Agile Software Development

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    Aufwandsschätzungen sind wichtig, um ökonomische und strategische Entscheidungen in der Softwareentwicklung treffen zu können. Verschiedene Veröffentlichungen propagieren das Constructive Cost Model (COCOMO) als ein algorithmisches Kostenmodell, basierend auf Formeln mit objektiven Variablen für Schätzungen in der klassischen Softwareentwicklung (KS). Arbeiten aus der agilen Softwareentwicklung (AS) verweisen auf den Einsatz von erfahrungsbasierten Schätzmethoden und von subjektiven Variablen. Aufgrund der schwachen Operationalisierung im agilen Kontext sind Aussagen über konkrete Ursache- und Wirkungszusammenhänge schwer zu treffen. Hinzu kommt der einseitige Fokus der klassischen und agilen Untersuchungen auf den eigene Forschungsbereich, der nach sich zieht, dass eine Verwendung von Variablen aus COCOMO in der AS unklar ist. Wenn hierzu Details bekannt wären, könnten operationalisierte Variablen aus COCOMO auch in der AS eingesetzt werden. Dadurch wird es möglich, in einer wissenschaftlichen Untersuchung eine Konzeptionierung von konkreten kausalen Abhängigkeiten vorzunehmen – diese Erkenntnisse würden wiederum eine Optimierung des Entwicklungsprozesses erlauben. Zur Identifikation von Variablen wird dazu eine qualitative und deskriptive Arbeit mit einer Literaturrecherche und einer Auswertung der Quellen durchgeführt. Erste Ergebnisse zwischen beiden Welten zeigen dabei sowohl Unterschiede als auch Gemeinsamkeiten. Eine Vielzahl von Variablen aus COCOMO kann in der AS verwendet werden. Inwieweit dies möglich ist, ist von den objektiven und subjektiven Anteilen der Variablen abhängig. Vertreter mit erfahrungsbasiertem Hintergrund wie Analyst Capability (ACAP) und Programmer Capability (PCAP) lassen sich aufgrund von Übereinstimmungen mit personenbezogenen Merkmalen gut in die AS übertragen. Parallel dazu sind Variablen aus dem Prozess- und Werkzeugumfeld weniger gut transferierbar, da konkret die AS einen Fokus auf solche Projektmerkmale ablehnt. Eine Weiterverwendung von Variablen ist damit grundsätzlich unter der Berücksichtigung von gegebenen Rahmenbedingungen möglich.Effort estimations are important in order to make economic and strategic decisions in software development. Various publications propagate the Constructive Cost Model (COCOMO) as an algorithmic cost model, based on formulas with objective variables for estimations in classical software development (KS). Papers from agile software development (AS) refers to the use of experience-based estimation methods and subjective variables. Due to the weak operationalization in an agile context, statements about concrete cause and effect relationships are difficult to make. In addition, there is the one-sided focus of classical and agile investigations on their own research field, which suggests that the use of variables from COCOMO in the AS is unclear. If details were available, operational variables from COCOMO could also be used in the AS. This makes it possible to carry out a conceptualization of concrete causal dependencies in a scientific investigation - these findings in turn would allow an optimization of the development process. To identify variables, a qualitative and descriptive work with a literature research and an evaluation of the sources is carried out. First results between the two worlds show both differences and similarities. A large number of variables from COCOMO can be used in the AS. This is possible depending on the objective and subjective proportions of the variables. Variables with an experience-based background, such as Analyst Capability (ACAP) and Programmer Capability (PCAP), can be well transferred to the AS by matching personal characteristics. At the same time, variables from the process and tool environment are less easily transferable, because AS specifically rejects a focus on such project features. A re-use of variables is thus possible under consideration of given conditions

    Organic Food Claims in Europe

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    Better regulatory guidelines, improved testing methods, and additional research into product quality criteria are needed to further develop the European organic food market

    Whole transcriptome RNA-Seq analysis reveals extensive cell type-specific compartmentalization in Volvox carteri

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    Klein B, Wibberg D, Hallmann A. Whole transcriptome RNA-Seq analysis reveals extensive cell type-specific compartmentalization in Volvox carteri. BMC Biology. 2017;15(1): 111.Background One of evolution’s most important achievements is the development and radiation of multicellular organisms with different types of cells. Complex multicellularity has evolved several times in eukaryotes; yet, in most lineages, an investigation of its molecular background is considerably challenging since the transition occurred too far in the past and, in addition, these lineages evolved a large number of cell types. However, for volvocine green algae, such as Volvox carteri, multicellularity is a relatively recent innovation. Furthermore, V. carteri shows a complete division of labor between only two cell types – small, flagellated somatic cells and large, immotile reproductive cells. Thus, V. carteri provides a unique opportunity to study multicellularity and cellular differentiation at the molecular level. Results This study provides a whole transcriptome RNA-Seq analysis of separated cell types of the multicellular green alga V. carteri f. nagariensis to reveal cell type-specific components and functions. To this end, 246 million quality filtered reads were mapped to the genome and valid expression data were obtained for 93% of the 14,247 gene loci. In the subsequent search for protein domains with assigned molecular function, we identified 9435 previously classified domains in 44% of all gene loci. Furthermore, in 43% of all gene loci we identified 15,254 domains that are involved in biological processes. All identified domains were investigated regarding cell type-specific expression. Moreover, we provide further insight into the expression pattern of previously described gene families (e.g., pherophorin, extracellular matrix metalloprotease, and VARL families). Our results demonstrate an extensive compartmentalization of the transcriptome between cell types: More than half of all genes show a clear difference in expression between somatic and reproductive cells. Conclusions This study constitutes the first transcriptome-wide RNA-Seq analysis of separated cell types of V. carteri focusing on gene expression. The high degree of differential expression indicates a strong differentiation of cell types despite the fact that V. carteri diverged relatively recently from its unicellular relatives. Our expression dataset and the bioinformatic analyses provide the opportunity to further investigate and understand the mechanisms of cell type-specific expression and its transcriptional regulation

    The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

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    Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

    Topographical expression of class IA and class II phosphoinositide 3-kinase enzymes in normal human tissues is consistent with a role in differentiation

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    BACKGROUND: Growth factor, cytokine and chemokine-induced activation of PI3K enzymes constitutes the start of a complex signalling cascade, which ultimately mediates cellular activities such as proliferation, differentiation, chemotaxis, survival, trafficking, and glucose homeostasis. The PI3K enzyme family is divided into 3 classes; class I (subdivided into IA and IB), class II (PI3K-C2α, PI3K-C2β and PI3K-C2γ) and class III PI3K. Expression of these enzymes in human tissue has not been clearly defined. METHODS: In this study, we analysed the immunohistochemical topographical expression profile of class IA (anti-p85 adaptor) and class II PI3K (PI3K-C2α and PI3K-C2β) enzymes in 104 formalin-fixed, paraffin embedded normal adult human (age 33–71 years, median 44 years) tissue specimens including those from the gastrointestinal, genitourinary, hepatobiliary, endocrine, integument and lymphoid systems. Antibody specificity was verified by Western blotting of cell lysates and peptide blocking studies. Immunohistochemistry intensity was scored from undetectable to strong. RESULTS: PI3K enzymes were expressed in selected cell populations of epithelial or mesenchymal origin. Columnar epithelium and transitional epithelia were reactive but mucous secreting and stratified squamous epithelia were not. Mesenchymal elements (smooth muscle and endothelial cells) and glomerular epithelium were only expressed PI3K-C2α while ganglion cells expressed p85 and PI3K-C2β. All three enzymes were detected in macrophages, which served as an internal positive control. None of the three PI3K isozymes was detected in the stem cell/progenitor compartments or in B lymphocyte aggregates. CONCLUSIONS: Taken together, these data suggest that PI3K enzyme distribution is not ubiquitous but expressed selectively in fully differentiated, non-proliferating cells. Identification of the normal in vivo expression pattern of class IA and class II PI3K paves the way for further analyses which will clarify the role played by these enzymes in inflammatory, neoplastic and other human disease conditions
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