Desktop 3-axis parallel kinematic milling machine

Parallel kinematic machines (PKM) are still a research-and-development topic in many laboratories although many of them, unfortunately, have no PKM at all. Therefore, the use of a desktop educational 3-axis parallel kinematic milling machine is suggested as a help in the process of acquiring basic experiences in the field of PKM. The developed desktop educational 3-axis parallel kinematic milling machine is based on a newly developed 3-DOF spatial parallel mechanism. This paper describes the structure of the machine, modeling approach, and control and programming system based on PC Linux platform with real-time extension and EMC2 (the Enhanced Machine Controller) software system.     

Atorvastatin Modulates Bile Acid Homeostasis in Mice with Diet-Induced Nonalcoholic Steatohepatitis

Bile acids (BA) play a significant role in the pathophysiology of nonalcoholic steatohepatitis (NASH). The present study evaluates the modulation of bile acid metabolomics by atorvastatin, a cholesterol-lowering agent commonly used to treat cardiovascular complications accompanying NASH. NASH was induced in mice by 24 weeks of consuming a high–saturated fat, high-fructose, and high-cholesterol diet (F), with atorvastatin administered orally (20 mg/kg/day) during the last three weeks. Biochemical and histological analyses confirmed the effectiveness of the F diet in inducing NASH. Untreated NASH animals had significantly reduced biliary secretion of BA and increased fecal excretion of BA via decreased apical sodium-dependent bile salt transporter (Asbt)-mediated reabsorption. Atorvastatin decreased liver steatosis and inflammation in NASH animals consistently with a reduction in crucial lipogenic enzyme stearoyl–coenzyme A (CoA) desaturase-1 and nuclear factor kappa light chain enhancer of activated B-cell pro-inflammatory signaling, respectively. In this group, atorvastatin also uniformly enhanced plasma concentration, biliary secretion and fecal excretion of the secondary BA, deoxycholic acid (DCA). However, in the chow diet–fed animals, atorvastatin decreased plasma concentrations of BA, and reduced BA biliary secretions. These changes stemmed primarily from the increased fecal excretion of BA resulting from the reduced Asbt-mediated BA reabsorption in the ileum and suppression of synthesis in the liver. In conclusion, our results reveal that atorvastatin significantly modulates BA metabolomics by altering their intestinal processing and liver synthesis in control and NASH mice.     

Testing environmentally assisted cracking of reactor materials using pneumatic servo-controlled fracture mechanics device

The degradation mechanism, known as stress corrosion cracking or environmentally assisted cracking (EAC) has long been recognized as a major cause of failure of components and structures but the basic mechanisms of this process are not still fully understood and the development of standardized and practicable methods of testing is a key element in a strategy to understand the kinetics of failure and to provide for mitigation measures. At the JRC-IE, Institute for Energy, a new laboratory for EAC testing of nuclear power engineering materials, in particular core internals materials, has been recently commissioned. The main part of the facility consists of a pneumatic servo-controlled fracture mechanics loading system for 3-point-bending tests of fatigue pre-cracked SEN(B) specimens of different sizes, in a high temperature and pressure autoclave.     

Conventional and on-line arithmetic designs for high-speed recursive digital filters

Designs using conventional and on-line arithmetic for performing the recursive computations of Second-Order Direct-Form IIR filters are implemented in a 0.7μ HCMOS gate array technology. The new conventional (bit-parallel) design using two levels of scattered lookahead achieves a rate of 104 Msamples/second. The design eliminates carry propagate addition from the recursive loop and uses radix-4 recoding to reduce the number of partial products. The on-line design is an improved radix-4 multiply-add (MA) module. Two arrays based on the on-line MA module are developed to achieve rates of 128 Msamples/second with two levels of scattered lookahead. Performance and cost comparisons of the designs provide insights into the most appropriate designs to be used for a given word length.     

Reconfigurable robotic machining system controlled and programmed in a machine tool manner

Industrial robots represent a promising cost-effective and flexible alternative for some machining applications. This paper describes the concept of reconfigurable robot multi-axis machining systems for machining the complex parts of light materials with lower tolerances having freeform surfaces. For the basic configuration of a five-axis robotic machining system, the robot modeling approach is shown in detail as well as the prototype of developed control system with programming in G-code. The experimental robotic machining system has been verified by successful machining of several test work pieces.     

Role of Testosterone in Stimulating Seasonal Changes in a Potential Avian Chemosignal

Songbird preen oil contains volatile and semivolatile compounds that may contain information about species, sex, individual identity, and season. We examined the relationship between testosterone (T) and the amounts of preen oil volatile and semivolatile compounds in wild and captive dark-eyed juncos (Junco hyemalis). In wild males and females, we observed an increase in volatile compound relative concentration early in the breeding season. This increase mirrored previously described seasonal elevation in T levels in wild males and females, suggesting a positive relationship between hormone levels and preen gland secretions, and a possible role for these secretions in signaling receptivity. In females, the greatest relative concentrations of most compounds were observed close to egg laying, a time when steroid hormones are high and also the only time that females respond to an injection of gonadotropin-releasing hormone with a short-term increase in T. In a study of captive juncos held on short days, we asked whether the seasonal increases observed in the wild could be induced with experimental elevation of T alone. We found that exogenous T stimulated the production of some volatile compounds in non-breeding individuals of both sexes. However, of the 15 compounds known to increase during the breeding season, only four showed an increase in relative concentration in birds that received T implants. Our results suggest that testosterone levels likely interact with other seasonally induced physiological changes to affect volatile compound amounts in preen oil.     

Strain-Induced Modification of the Optical Characteristics of Quantum Emitters in Hexagonal Boron Nitride

Quantum emitters in hexagonal boron nitride (hBN) are promising building blocks for the realization of integrated quantum photonic systems. However, their spectral inhomogeneity currently limits their potential applications. Here, tensile strain is applied to quantum emitters embedded in few-layer hBN films and both red and blue spectral shifts are realized with tuning magnitudes up to 65 meV, a record for any 2D quantum source. Reversible tuning of the emission and related photophysical properties is demonstrated. Rotation of the optical dipole in response to strain is also observed, suggesting the presence of a second excited state. A theoretical model is derived to describe strain-based tuning in hBN, and the rotation of the optical dipole. The study demonstrates the immense potential for strain tuning of quantum emitters in layered materials to enable their employment in scalable quantum photonic networks.     

Birth and Death of Invading Standing Waves in the BZ-AOT Reaction-diffusion System

We report our experimental observation of modulated standing waves that invade bulk oscillations exhibited by the Belousov-Zhabotinsky-Aerosol OT reverse microemulsion system. The modulated standing waves form within domains bounded by a traveling wave. We also observe that the modulated standing waves give way to traveling waves, which we connect to numerical simulations in a simple chemical model.     

Discovery,Biocatalytic Exploration and Structural Analysis of a 4-Ethylphenol Oxidase from Gulosibacter chungangensis

The vanillyl-alcohol oxidase (VAO) family is a rich source of biocatalysts for the oxidative bioconversion of phenolic compounds. Through genome mining and sequence comparisons, we found that several family members lack a generally conserved catalytic aspartate. This finding led us to study a VAO-homolog featuring a glutamate residue in place of the common aspartate. This 4-ethylphenol oxidase from Gulosibacter chungangensis (Gc4EO) shares 42 % sequence identity with VAO from Penicillium simplicissimum, contains the same 8α-N³-histidyl-bound FAD and uses oxygen as electron acceptor. However, Gc4EO features a distinct substrate scope and product specificity as it is primarily effective in the dehydrogenation of para-substituted phenols with little generation of hydroxylated products. The three-dimensional structure shows that the characteristic glutamate side chain creates a closely packed environment that may limit water accessibility and thereby protect from hydroxylation. With its high thermal stability, well defined structural properties and high expression yields, Gc4EO may become a catalyst of choice for the specific dehydrogenation of phenolic compounds bearing small substituents.