Alternative starting materials for the production of aluminum foam by the powder metallurgical process

In the past it has already been proven that aluminum foam is a construction material appropriate for numerous applications. Especially in domains such as machine tool manufacturing and vehicle construction the combination of lightweight design and vibration damping is of great importance and aluminum foam can unfold its full potential. The widespread use of aluminum foam is still hampered by the high production costs resulting from the expensive production process and starting materials. The present work focuses on studies of alternative, cheaper starting materials. The results of current investigations follow the idea that aluminum chips may be successfully used as base material instead of atomized powders, without negatively influencing the macroscopic foam structure. It could also be proven that good foaming rates can be achieved with calcium carbonate as foaming agent for aluminum. That's why already in the near future, it will be possible to use recycling materials like aluminum chips in the series production of aluminum foams by the powder metallurgical process (PM process). Since sorted aluminum chips cost less than 1 €/kg, and calcium carbonate costs only a fraction of titanium hydride, a distinct price reduction for aluminum foam, and the lowering of the inhibition threshold for its application should be possible. Further studies are required to examine the static and dynamic properties of the foams and to compare them with conventional aluminum foams.     

Changing the regioselectivity of a P450 from C15 to C11 hydroxylation of progesterone

CYP106A2 is known as a 15β‐hydroxylase, but also shows minor 11α‐hydroxylase activity for progesterone. 11α‐Hydroxyprogesterone is an important pharmaceutical compound with anti‐androgenic and blood‐pressure‐regulating activity. This work therefore focused on directing the regioselectivity of the enzyme towards hydroxylation at position 11 in the C ring of the steroid through a combination of saturation mutagenesis and rational site‐directed mutagenesis. With the aid of data from a homology model of CYP106A2 containing docked progesterone, together with site‐directed mutagenesis of active‐site residues (Lisurek et al. ChemBioChem 2008 , 9, 1439–1449), a saturation mutagenesis library at positions A395 and G397 was created. Screening of the library identified the mutants A395I and A395W/G397K as having 11α‐hydroxylase activities 8.9 and 11.5 times higher than that of the wild type (WT). In the next step, additional mutations were integrated by a rational site‐directed mutagenesis approach to increase the catalytic efficiency. Of the 40 candidates analyzed, the mutants A106T/A395I, A106T/A395I/R409L, and T89N/A395I turned out to display increased 11α‐hydroxylase selectivities and activities relative to the WT (14.3‐, 12.6‐, and 11.8‐fold increases in selectivity and 39.3‐, 108‐, and 24.4‐ in k_cat/K_m). In the last step of the study, the best mutants were applied in a whole‐cell biotransformation. In these experiments the production (percentage) of 15β‐hydroxyprogesterone decreased from 50.4 % (wild type) to 4.8 % (mutant T89N/A395I), whereas that of 11α‐hydroxyprogesterone increased from 27.7 to 80.9 %, thus demonstrating an impressive regioselectivity.     

New expression method and characterization of recombinant human granulocyte colony stimulating factor in a stable protein formulation

Human recombinant granulocyte colony stimulating factor (rhG-CSF) is widely used in hematology and oncology for the treatment of neutropenia, for the restoration of neutrophil production after bone marrow transplantation, for myelodysplastic syndromes, and aplastic anemia. The E. coli expression system is commonly used for fast recombinant production of rhG-CSF at a large scale. We have applied a novel autoinduction method for the batch expression of rhG-CSF to study whether this new system would increase cell mass and target-protein yield compared to conventional E. coli cell culture and induction with isopropyl β-D-thiogalactopyranoside (IPTG). We could demonstrate 3-fold higher culture densities and a 5-fold higher protein yield compared to IPTG induction without the need to monitor cell growth in a shortened 24 h expression procedure. rhG-CSF expressed in autoinduction media was successfully extracted from E. coli inclusion bodies and refolded by dialysis. After size exclusion chromatography (SEC) purification, rhG-CSF showed similar conformation, biological activity and aggregation profile compared to the commercially available biosimilar TEVAgrastim(?) (TEVA Pharma AG). Expression by autoinduction is suggested as a cost- and time-effective method for rhG-CSF production.     

Development of a LC-IT-TOF MS Procedure to Quantify Veterinary Drug Residues in Milk Employing a QuEChERS Approach

A sensitive liquid chromatography coupled to high-resolution tandem mass spectrometry (LC-IT-TOF MS) with electrospray ionization method for the identification and quantification of five antibiotic residues in milk has been developed. For sample preparation, a simple modification of the QuEChERS method was used with further sample cleanup using dispersive solid phase extraction according to AOAC official standards 2007.01. The method yielded acceptable accuracy values for each drug at each level, with mean recoveries (n?=?3) ranging from 83 to 92 %. The recovery of antibiotics of the intra-assay ranged from 85 to 95 % (RSD?<?9 %) and the inter-assay from 84 to 95 % (RSD?<?11 %). A total of 31 milk samples, either pasteurized or fresh whole milk, were analyzed following the method. Amoxicillin and oxytetracycline (two of the pasteurized milk samples), ampicillin and amoxicillin (3 of 25 fresh milk samples), and tetracycline and oxytetracycline (two other fresh milk samples out of 25) were detected at levels below the current Brazilian maximum residue levels.     

A conceptual model for project management of exploration and production in the oil and gas industry: The case of a Brazilian company

The objective of this study was to obtain a better understanding of factors that influence Exploration and Production (E&P) project management success and corporate financial performance. The study follows structural equation modeling (SEM) methodology to achieve greater understanding of the intricate network of relationships between variables involved in E&P project management. A comprehensive theoretical framework was needed to formulate the conceptual basis of research. Observation of the real world and practical experiences were also important. To that end, we conducted a case study in a large Brazilian oil company. Field research was essential because of the lack of similar studies in the oil and gas sector. The model developed is a theoretical construct known as a structural and measurement model (set of latent variables, observed variables and hypotheses, depicted in a path diagram). This model contributes significantly to the company because it is a global representation of the main factors for improving E&P project management. However, the findings should be interpreted with caution because adjustment and validation of the theoretical model were not performed.     

Photon emission as a tool for esd failure localization and as a technique for studying ESD phenomena

Photon emission microscopy gives the opportunity for non-destructive localization of failure sites on VLSI chips. Failures that can be detected using photon emission microscopy are gate-oxide breakdown, latch-up, junction breakdown and intermetal oxide failures. This makes it a valuable evaluation technique of failures in ESD protection circuits. Real-time photon emission observations of reverse-biased transistors showed that this technique is also an important tool in the evaluation and development of ESD protection circuits.     

Nanoleakage evaluation of resin luting systems to dental enamel and leucite-reinforced ceramic

Purpose: The aim of this study was to evaluate the nanoleakage patterns between dental enamel and reinforced leucite ceramic, bonded with resin luting systems and a flowable composite resin. Materials and Methods: Twelve crowns of bovine incisors were randomly divided into four groups (n = 3) according to the luting procedure: Excite/Variolink II, Clearfil SE Bond/Panavia F, Scotchbond Multi‐Purpose Plus/RelyX ARC, and Single Bond 2/Filtek Z350 Flow. To evaluate the nanoleakage patterns, IPS Empress Esthetic disks (5 mm Ø and 1.2‐mm thick) were bonded to enamel, and, after 24 h, the specimens were immersed in a 50% (w/v) solution of silver nitrate (24 h), fixed, dehydrated, and processed scanning electron microscopy (SEM). Results: None nanoleakage on interface of the groups that Single Bond 2 followed by the flowable composite were used. The highest percentage of nanoleakage was shown by the Excite/Variolink II protocol. Also, in all conditions tested, none silver nitrate uptake was observed between the leucite‐reinforced ceramic and the resin luting cement. Conclusions: The use of a two‐step etch‐and‐rinse adhesive with flowable composite was able to promote an adequate seal of the bond interface at the enamel. Moreover, the conventional dual‐cured resin cements associated with simplified and dual‐cured adhesives tested are also indicated to bond thin ceramics to enamel, since all presented low silver nitrate uptake. Microsc. Res. Tech., 2012. © 2011 Wiley Periodicals, Inc.     

Der Bazar der Anforderungen

Traditionelles Requirements Engineering ist auf die Ermittlung, Festschreibung und Nachvollziehbarkeit von Anforderungen in den Informationssystemen einer Organisation fokussiert. Die fortschreitende Globalisierung und Vernetzung hat neue Formen der Zusammenarbeit und der informationstechnischen Unterstützung hervorgebracht. Auf Basis von zwei Fallstudien zu offenen Innovationsprozessen haben wir die Anforderungen an ein adaptives Requirements Engineering für emergente Communities ermittelt. Zur informatischen Unterstützung haben wir ein i*-Modell für die Beschreibung der wechselseitigen Abh?ngigkeiten zwischen den Communities und den von ihnen genutzten Informationssystemen aus der Sichtweise des adaptiven RE entwickelt. Wir unterstützen das adaptive RE durch einen Dienstbaukasten, der in die zu entwickelnden Informationssysteme integriert werden kann. Dadurch entsteht im Sinne der Open-Source-Bewegung ein Bazar von Anforderungen. Diesen Vorgang haben wir prototypisch in einen Store für webbasierte Widgets zur Gestaltung von personalisierten Lernumgebungen umgesetzt.