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Process Chain for Numerical Simulation of IMLS
Additive layer manufacturing methods imply, among other advantages, extensive flexibility
concerning their ability to realize mass customization. Despite various efforts towards process
enhancement, numerous deficiencies concerning part distortion or residual stresses are still
observable. The present work deals with the definition of an efficient process chain for
numerical simulation of indirect metal laser sintering (IMLS), in order to improve
dimensional accuracy. The underlying method is based on investigations of dilatometric behavior of iron based powder, which is integrated into reaction kinetic models and coupled
with a finite element analysis (FEA). Thus, singular process steps, e. g. solid phase sintering,
phase transformations or infiltration, are numerically modelled with adequate accuracy.
Referring to thermomechanical simulation, possibilities for pre-scaling of part geometries are
presented.Mechanical Engineerin
An Anti-Corruption Bureau’s Inexorable Endeavor: A Study of Malawi’s Cashgate Scandal
The “Cashgate” scandal has had far-reaching consequences for the southern African nation of Malawi and its people. Western donors suspended budgetary aid—circa 45 million over an eighteen-month period. As a precondition to the resumption of aid, the donors required that the government not only implement financial management reforms but also fully prosecute the perpetrators and recover the stolen assets. The donors’ position solidified when audits of Malawian government ledgers from 2009 to 2014 could not account for 1.4 million in cash and property recovered. Yet, as this essay observes, the quest to secure convictions and recover assets in the more complex cases of senior officials will become quixotic unless the government provides the ACB with sufficient independence, authority, and resources. Lacking ACB operational success, donors seem disinclined to resume direct budgetary support to Malawi. And as Western countries retract, China moves in, extending its influence
Oscillatory instabilities during formic acid oxidation on Pt(100), Pt(110) and Pt(111) under potentiostatic control. II. Model calculations
A kinetic model is developed for the electrocatalytic oxidation of formic acid on Pt under potentiostatic control. The model development proceeds stepwise via a simple model of the electrocatalytic CO oxidation. The full model consists of four coupled, nonlinear ordinary differential equations. The scanned and stationary current/outer potential (I/U) behavior, stationary current oscillations, two-parameter bifurcation diagrams and stirring effects are simulated using realistic model parameters. The numerical findings are found to be consistent with the experimental results given by Strasser et al. The model reproduces period-1 as well as mixed-mode oscillations. Furthermore, a mechanistic analysis of the model was performed: two suboscillators are identified whose characteristics allow a plausible interpretation of the observed dynamics. After a classification of the suboscillators into previously described categories, an attempt is made to identify the minimal mechanistic requirements for electrochemical current oscillations
Rfx6 Maintains the Functional Identity of Adult Pancreatic β Cells.
SummaryIncreasing evidence suggests that loss of β cell characteristics may cause insulin secretory deficiency in diabetes, but the underlying mechanisms remain unclear. Here, we show that Rfx6, whose mutation leads to neonatal diabetes in humans, is essential to maintain key features of functionally mature β cells in mice. Rfx6 loss in adult β cells leads to glucose intolerance, impaired β cell glucose sensing, and defective insulin secretion. This is associated with reduced expression of core components of the insulin secretion pathway, including glucokinase, the Abcc8/SUR1 subunit of KATP channels and voltage-gated Ca2+ channels, which are direct targets of Rfx6. Moreover, Rfx6 contributes to the silencing of the vast majority of “disallowed” genes, a group usually specifically repressed in adult β cells, and thus to the maintenance of β cell maturity. These findings raise the possibility that changes in Rfx6 expression or activity may contribute to β cell failure in humans
catena-Poly[copper(I)-bis(μ-trifluoromethanesulfonato-κ2 O:O′)-copper(I)-bis(μ-trimethyl trithiophosphite)-κ2 P:S;κ2 S:P]
The title compound, [Cu2(CF3SO3)2(C3H9PS3)2]n, crystallizes as infinite chains in which two trimethyl trithiophosphite ligands and two trifluoromethanesulfonate anions bridge the essentially tetrahedrally coordinated CuI ions in an alternating fashion. The P and one S atom of each trimethyl trithiophosphite ligand are employed for coordination. The molecular structure exhibits the rare motif of copper(I) bridged by two trifluoromethanesulfonate anions generating eight-membered rings
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