Automatic discovery of interpretable planning strategies

Machine Learning - When making decisions, people often overlook critical information or are overly swayed by irrelevant information. A common approach to mitigate these biases is to provide...     

The electrodeposition of aluminium from xylene and ether-hydride electrolytes

A comparative study of aluminium electrodeposition from xylene and ether electrolytes is presented. The kinetic parameters of aluminium deposition from the tetrahydrofuran (THF) and xylene electrolytes are presented. In the case of the THF and diethylether solutions investigations of aluminium nucleation were also made. It was found that the rate of aluminium deposition was highest in the THF electrolyte composed of AlCl₃ and LiAlH₄ in a ratio 1:1. This electrolyte is recommended for deposition of aluminium protective coatings of thickness over 20 µm     

On the existence of affine invariant descent directions

This paper begins with a brief review of affine invariance and its significance for iterative algorithms. It then explores the existence of affine invariant descent directions for unconstrained minimization. While there may exist several affine invariant descent directions for smooth functions at a given point, it is shown that for quadratic functions, there exists exactly one invariant descent direction in the strictly convex case and generally none in the case where the Hessian is singular or indefinite. These results can be generalized to smooth nonlinear functions and have implications regarding the initialization of minimization algorithms. They stand in contrast to recent works on constrained convex and nonconvex optimization for which there may exist an affine invariant ‘frame’ that depends on the feasible set and that can be used to define an affine invariant descent direction.     

Gastric Serotonin Biosynthesis and Its Functional Role in L-Arginine-Induced Gastric Proton Secretion

Among mammals, serotonin is predominantly found in the gastrointestinal tract, where it has been shown to participate in pathway-regulating satiation. For the stomach, vascular serotonin release induced by gastric distension is thought to chiefly contribute to satiation after food intake. However, little information is available on the capability of gastric cells to synthesize, release and respond to serotonin by functional changes of mechanisms regulating gastric acid secretion. We investigated whether human gastric cells are capable of serotonin synthesis and release. First, HGT-1 cells, derived from a human adenocarcinoma of the stomach, and human stomach specimens were immunostained positive for serotonin. In HGT-1 cells, incubation with the tryptophan hydroxylase inhibitor p-chlorophenylalanine reduced the mean serotonin-induced fluorescence signal intensity by 27%. Serotonin release of 147 ± 18%, compared to control HGT-1 cells (set to 100%) was demonstrated after treatment with 30 mM of the satiating amino acid L-Arg. Granisetron, a 5-HT3 receptor antagonist, reduced this L-Arg-induced serotonin release, as well as L-Arg-induced proton secretion. Similarly to the in vitro experiment, human antrum samples released serotonin upon incubation with 10 mM L-Arg. Overall, our data suggest that human parietal cells in culture, as well as from the gastric antrum, synthesize serotonin and release it after treatment with L-Arg via an HTR3-related mechanism. Moreover, we suggest not only gastric distension but also gastric acid secretion to result in peripheral serotonin release.     

A solid state amperometric humidity sensor

The behaviour of cells of the form Ag(s) |Ag₇I₄AsO₄(s)|M(s), where Ag₇I₄AsO₄ is a vitreous solid electrolyte with high silver ion conductivity and M is an inert anode such as platinum or stainless steel, has been investigated under different levels of d.c. polarisation. It has been shown that electrolytes of this type are not readily electrolysed, even under applications of large fields (despite the negligible impedance of the cathode). On the other hand, the anode is readily depolarised by water vapour, and the resulting cell current is related to the humidity of the gas in contact with it. The applicability of such cells for quantitative humidity determination by amperometry has been assessed.On leave from the Technical University of Gdansk, Poland     

The solution of euclidean norm trust region SQP subproblems via second-order cone programs: an overview and elementary introduction

It is well known that convex sequential quadratic programming (SQP) subproblems with an Euclidean norm trust region constraint can be reduced to second-order cone programs for which the theory of Euclidean Jordan algebras leads to efficient interior-point algorithms. Here, a brief and self-contained outline of the principles of such an implementation is given and the application to SQP subproblems as well as to cubic regularization problems is discussed. All identities relevant for the implementation are derived from scratch and are compared to interior-point methods for linear programs (LPs). Sparsity of the data of the SQP subproblem can be maintained essentially in the same way as for interior-point methods for LPs. The presentation is intended as an introduction for students and for colleagues who may have heard about Jordan algebras but did not yet find the time to get involved with them. A simple Matlab implementation is made available and the discussion of implementational aspects addresses a scaling property that is critical for SQP subproblems.