Proof Pearl: Mechanizing the Textbook Proof of Huffman’s Algorithm

Huffman’s algorithm is a procedure for constructing a binary tree with minimum weighted path length. Our Isabelle/HOL proof closely follows the sketches found in standard algorithms textbooks, uncovering a few snags in the process. Another distinguishing feature of our formalization is the use of custom induction rules to help Isabelle’s automatic tactics, leading to very short proofs for most of the lemmas. This work was supported by the DFG grant NI 491/11-1.     

Semi-intelligible Isar Proofs from Machine-Generated Proofs

Sledgehammer is a component of the Isabelle/HOL proof assistant that integrates external automatic theorem provers (ATPs) to discharge interactive proof obligations. As a safeguard against bugs, the proofs found by the external provers are reconstructed in Isabelle. Reconstructing complex arguments involves translating them to Isabelle’s Isar format, supplying suitable justifications for each step. Sledgehammer transforms the proofs by contradiction into direct proofs; it iteratively tests and compresses the output, resulting in simpler and faster proofs; and it supports a wide range of ATPs, including E, LEO-II, Satallax, SPASS, Vampire, veriT, Waldmeister, and Z3.     

Single subject image analysis using the complex general linear model--an application to functional magnetic resonance imaging with multiple inputs

A linear time invariant model is applied to functional fMRI blood flow data. Based on traditional time series analysis, this model assumes that the fMRI stochastic output sequence can be determined by a constant plus a linear filter (hemodynamic response function) of several fixed deterministic inputs and an error term assumed stationary with zero mean. The input function consists of multiple exponential distributed (time delay between images) visual stimuli consisting of negative and erotic images. No a priori assumptions are made about the hemodynamic response function that, in essence, is calculated at each spatial position from the data. The sampling rate for the experiment is 400 ms in order to allow for filtering out higher frequencies associated with the cardiac rate. Since the statistical analysis is carried out in the Fourier domain, temporal correlation problems associated with inference in the time domain are avoided. This formal model easily lends itself to further development based on previously developed statistical techniques.     

Monitoring the Polymorphic Transformation of a Palm Kernel-Based Emulsion Using Ultrasound

Ultrasonic spectrometry was used to monitor the changes in polymorphism of palm kernel fat present in two tempered non-dairy emulsions with different globule sizes. Laser diffraction and differential scanning calorimetry (DSC) were performed to characterize the emulsions. X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) were used to determine the polymorphic state and solid fat content (SFC) of fully hydrogenated palm kernel oil during tempering of the emulsions. The ultrasonic instrument generated a “chirp” signal, which is characterized by its bandwidth. The ultrasonic measurements were carried out using two different pairs of transducers with different center frequencies, 2.25 and 0.5 MHz, and bandwidths. 3D plots were generated disputing time, frequency, and signal strength. The whole tempering process, from start to finish, was better characterized with the 2.25-MHz center frequency transducers. The ultrasonic velocity through the emulsions was always higher for the more stable β′ polymorph than for the α polymorph (p?<?0.05) regardless of the pair of transducers used. The 2.25-MHz transducer revealed no significant difference (p?>?0.05) on the ultrasound velocities obtained for the two globule sizes. Monitoring of polymorphic changes in emulsions using ultrasonic spectrometry could be used for an online measurement system for industrial manufacturing.     

Transient Hyperglycemia and Hypoxia Induce Memory Effects in AngiomiR Expression Profiles of Feto-Placental Endothelial Cells

Gestational diabetes (GDM) and preeclampsia (PE) are associated with fetal hyperglycemia, fetal hypoxia, or both. These adverse conditions may compromise fetal and placental endothelial cells. In fact, GDM and PE affect feto-placental endothelial function and also program endothelial function and cardiovascular disease risk of the offspring in the long-term. MicroRNAs are short, non-coding RNAs that regulate protein translation and fine tune biological processes. A group of microRNAs termed angiomiRs is particularly involved in the regulation of endothelial function. We hypothesized that transient hyperglycemia and hypoxia may alter angiomiR expression in feto-placental endothelial cells (fpEC). Thus, we isolated primary fpEC after normal, uncomplicated pregnancy, and induced hyperglycemia (25 mM) and hypoxia (6.5%) for 72 h, followed by reversal to normal conditions for another 72 h. Current vs. transient effects on angiomiR profiles were analyzed by RT-qPCR and subjected to miRNA pathway analyses using DIANA miRPath, MIENTURNET and miRPathDB. Both current and transient hypoxia affected angiomiR profile stronger than current and transient hyperglycemia. Both stimuli altered more angiomiRs transiently, i.e., followed by 72 h culture at control conditions. Pathway analysis revealed that hypoxia significantly altered the pathway ‘Proteoglycans in cancer’. Transient hypoxia specifically affected miRNAs related to ‘adherens junction’. Our data reveal that hyperglycemia and hypoxia induce memory effects on angiomiR expression in fpEC. Such memory effects may contribute to long-term adaption and maladaption to hyperglycemia and hypoxia.     

Mobile Robot Motion Framework Based on Enhanced Robust Panel Method

International Journal of Control, Automation and Systems - This paper proposes a framework for the mobile robot motion in partially unknown static and dynamic environments. Its main part is a path...     

The use of nickel oxide as a hole transport material in perovskite solar cell configuration: Achieving a high performance and stable device

Solar cells incorporated with organic-inorganic lead or tin halide-based perovskite materials as active light-absorber surfaces are referred to as perovskite solar cells (PSCs). This fast advancing solar technology has recorded an increase in its efficiency from 3.8% in 2009 to above 25% in recent years. The technology creates room for diverse device architectures, which enhances further development of thin-film solar cells and photovoltaics. This article reviews the use of nanocrystalline nickel oxide (NiO) film as a hole transport material in PSCs. The literature on pure nickel oxide and doped nickel oxide films has been discussed. The principle of operation, charge separation of PSCs and the various parameters that affect the efficient hole transport mechanisms, power conversion efficiency, growth mechanism, and stability of PSCs have also been discussed. Possible electron-blocking applications and future perspective of nickel oxide films have also been discussed.     

Synthesis,Radiosynthesis and Biological Evaluation of Buprenorphine-Derived Phenylazocarboxamides as Novel μ-Opioid Receptor Ligands

Targeted structural modifications have led to a novel type of buprenorphine-derived opioid receptor ligand displaying an improved selectivity profile for the μ-OR subtype. On this basis, it is shown that phenylazocarboxamides may serve as useful bioisosteric replacements for the widely occurring cinnamide units, without loss of OR binding affinity or subtype selectivity. This study further includes functional experiments pointing to weak partial agonist properties of the novel μ-OR ligands, as well as docking and metabolism experiments. Finally, the unique bifunctional character of phenylazocarboxylates, herein serving as precursors for the azocarboxamide subunit, was exploited to demonstrate the accessibility of an ¹⁸F-fluorinated analogue.     

Micro‐Phase Separation within Epoxy Resin Yields Ultrathin Mesoporous Membranes with Increased Scalability by Conversion from Spin‐ to Dip‐Coating Process

Ultrathin mesoporous membranes offer highly desirable characteristics for separation tasks regarding selectivity and mass transport of proteins. They have potential applications as separation devices in microfluidics, diagnostics, sensing, and high‐precision separations for pharmaceutical formulation. Especially for large‐scale and mass production, sophisticated production processes represent a barrier for wider application. A method is developed to produce nanomembranes with a thickness of 75 nm and 40 nm pores with an epoxy resin. The novolac resin is cured with branched polyethylenimine to form a covalently crosslinked polymer membrane with perforations spanning the entire thickness. Pore formation relies on micro‐phase separation of the curing agent during casting and the selective dissolution of the emergent nanodomains which thereby serve as pore templates. The resulting membranes are hydrophilic and therefore suitable for applications with biological fluids. Mechanical testing of the flexible but robust thin films reveals an ultimate tensile strength of 15 MPa and a biaxial modulus of 0.8 GPa. Proteins with a diameter of less than 12 nm can diffuse through the pores and permeation rates are pH dependent. The entire fabrication process is transferred to a dip‐coating approach, which is more suitable for a potential large‐scale production.