Synthesis and photochemical properties of trans‐2‐(2‐aryl‐ or heteroarylvinyl)‐4,5‐dichloropyridazin‐3(2H)‐ones

trans‐2‐(2‐Aryl‐ or heteroarylvinyl)‐4,5‐dichloropyridazin‐3(2H)‐ones 3 were synthesized from 4,5‐dichloropyridazin‐3(2H)‐one via 2 step. The photochemical behavior of 3 in THF, methylene chloride, acetonitrile and methanol is dependent on the kind of aryl or heterocyclic ring and the solvent polarity     

Adaptive-Repetitive Visual-Servo Control of Low-Flying Aerial Robots via Uncalibrated High-Flying Cameras

This paper presents the design and implementation of an adaptive-repetitive visual-servo control system for a moving high-flying vehicle (HFV) with an uncalibrated camera to monitor, track, and precisely control the movements of a low-flying vehicle (LFV) or mobile ground robot. Applications of this control strategy include the use of high-flying unmanned aerial vehicles (UAVs) with computer vision for monitoring, controlling, and coordinating the movements of lower altitude agents in areas, for example, where GPS signals may be unreliable or nonexistent. When deployed, a remote operator of the HFV defines the desired trajectory for the LFV in the HFV’s camera frame. Due to the circular motion of the HFV, the resulting motion trajectory of the LFV in the image frame can be periodic in time, thus an adaptive-repetitive control system is exploited for regulation and/or trajectory tracking. The adaptive control law is able to handle uncertainties in the camera’s intrinsic and extrinsic parameters. The design and stability analysis of the closed-loop control system is presented, where Lyapunov stability is shown. Simulation and experimental results are presented to demonstrate the effectiveness of the method for controlling the movement of a low-flying quadcopter, demonstrating the capabilities of the visual-servo control system for localization (i.e.,, motion capturing) and trajectory tracking control. In fact, results show that the LFV can be commanded to hover in place as well as track a user-defined flower-shaped closed trajectory, while the HFV and camera system circulates above with constant angular velocity. On average, the proposed adaptive-repetitive visual-servo control system reduces the average RMS tracking error by over 77% in the image plane and over 71% in the world frame compared to using just the adaptive visual-servo control law.     

Design of Optical-Imaging Probes by Screening of Diverse Substrate Libraries Directly in Disease-Tissue Extracts

Fluorescently quenched probes that are specifically activated in the cancer microenvironment have great potential application for diagnosis, early detection, and surgical guidance. These probes are often designed to target specific enzymes associated with diseases by direct optimization using single purified enzymes. However, this can result in painstaking chemistry efforts to produce a probe with suboptimal performance when applied in vivo. We describe here an alternate, unbiased activity-profiling approach in which whole tissue extracts are used to directly identify optimal peptide sequences for probe design. Screening of tumor extracts with a hybrid combinatorial substrate library (HyCoSuL) identified a combination of natural and non-natural amino-acid residues that was used to generate highly efficient tumor-specific probes. This new strategy simplifies and enhances the process of probe optimization without any a priori knowledge of enzyme targets and has the potential to be applied to diverse disease states using clinical or animal-model tissue samples.     

Sonolysis of chlorobenzene in Fenton-type aqueous systems

The influence of ultrasounds (200 kHz frequency) on the decomposition of chlorobenzene (CB) in a water solution (around 100 ppm concentration) containing iron or palladium sulfates was investigated. The intermediates of the sonolysis were identified, thus allowing a deeper insight into the degradation mechanism. It was established that CB degradation starts by pyrolysis inside the cavitation bubbles. The initial sonolysis product is benzene, formed in a reaction occurring outside the cavitation from phenyl radicals and the hydrogen atoms sonolytically generated from the water. Polyphenols as products of the CB sonochemical degradation are reported for the first time. The palladium salt was found to be a useful and sensitive indicator for differentiating the sites and mechanisms of the product formation. An alternative mechanism for the CB sonolysis is advanced, explaining the formation of phenols, polyphenols, chlorophenols and benzene.     

Synthesis of caeliferins, elicitors of plant immune responses: accessing lipophilic natural products via cross metathesis

A cross metathesis (CM)-based synthesis of the caeliferins, a family of sulfooxy fatty acids that elicit plant immune responses, is reported. Unexpectedly, detailed NMR spectroscopic and mass spectrometric analyses of CM reaction mixtures revealed extensive isomerization and homologation of starting materials and products. It is shown that the degree of isomerization and homologation in CM strongly correlates with substrate chain length and lipophilicity. Side-product suppression requires appropriate catalyst selection and use of 1,4-benzoquinone as a hydride scavenger.     

Assessment of metabolic changes in the striatum of a MPTP-intoxicated canine model: in vivo ¹H-MRS study of an animal model for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel ¹H water suppressed magnetic resonance spectroscopy (¹H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm³) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that ¹H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication.     

Dielectric electrorheological fluids: Theory and experiment

Electrorheological (ER) fluids are a class of materials whose rheological properties are controllable by the application of an electric field. A dielectric electrorheological (DER) fluid is the simplest type of ER fluid, in which the material components follow a linear electrostatic response. We review and discuss the progress of the studies on physics of this type of material. A first-principles theory of DER fluids, along with relevant experimental verifications, are presented in some detail. In particular, the properties presented include static equilibrium structure, shear modulus, static yield stress and its variation with applied electric field frequency, and structure-induced dielectric nonlinearity.     

Thermoelectric Properties of Indium-Selenium Nanocomposites Prepared by Mechanical Alloying and Spark Plasma Sintering

Indium-selenium-based compounds have received much attention as thermoelectric materials since a high thermoelectric figure of merit of 1.48 at 705?K was observed in In₄Se_2.35. In this study, four different compositions of indium-selenium compounds, In₂Se₃, InSe, In₄Se₃, and In₄Se_2.35, were prepared by mechanical alloying followed by spark plasma sintering. Their thermoelectric properties such as electrical resistivity, Seebeck coefficient, and thermal conductivity were measured in the temperature range of 300?K to 673?K. All the In-Se compounds comprised nanoscaled structures and exhibited n-type conductivity with Seebeck coefficients ranging from ?159???V?K^?1 to ?568???V?K^?1 at room temperature.     

The effects of functionalized graphene nanosheets on the thermal and mechanical properties of epoxy composites for anisotropic conductive adhesives (ACAs)

Functionalized graphene/epoxy composites were prepared using the epoxy resin diglycidyl ether of bisphenol A. Graphene oxide (GO) and Al(OH)₃-coated graphene (Al-GO) fillers were fabricated using the Hummers method and a simple sol–gel method, with aluminum isopropoxide as the aluminum precursor. X-ray photoelectron spectroscopy verified the successful formation of functional groups onto the GO and Al-GO. The dispersion of functionalized graphene fillers showed an even distribution within the epoxy resins. A dynamic mechanical analysis was used to investigate the changes in the mechanical properties of the epoxy composites, which included neat epoxy and epoxy with various concentrations of graphene-based fillers. The storage modulus and tan δ graphs illustrate the enhancement achieved by increasing the amount of filler. The composite with 3 wt.% GO had the highest storage modulus and glass transition temperature. The thermal conductivities of the composites with graphene-based fillers were enhanced compared to those without fillers. The 3 wt.% GO/epoxy composite had the highest thermal conductivity, which was nearly twice that of the neat epoxy resin.     

Comparative metabolomics reveals biogenesis of ascarosides, a modular library of small-molecule signals in C. elegans

In the model organism Caenorhabditis elegans, a family of endogenous small molecules, the ascarosides function as key regulators of developmental timing and behavior that act upstream of conserved signaling pathways. The ascarosides are based on the dideoxysugar ascarylose, which is linked to fatty-acid-like side chains of varying lengths derived from peroxisomal β-oxidation. Despite the importance of ascarosides for many aspects of C. elegans biology, knowledge of their structures, biosynthesis, and homeostasis remains incomplete. We used an MS/MS-based screen to profile ascarosides in C. elegans wild-type and mutant metabolomes, which revealed a much greater structural diversity of ascaroside derivatives than previously reported. Comparison of the metabolomes from wild-type and a series of peroxisomal β-oxidation mutants showed that the enoyl CoA-hydratase MAOC-1 serves an important role in ascaroside biosynthesis and clarified the functions of two other enzymes, ACOX-1 and DHS-28. We show that, following peroxisomal β-oxidation, the ascarosides are selectively derivatized with moieties of varied biogenetic origin and that such modifications can dramatically affect biological activity, producing signaling molecules active at low femtomolar concentrations. Based on these results, the ascarosides appear as a modular library of small-molecule signals, integrating building blocks from three major metabolic pathways: carbohydrate metabolism, peroxisomal β-oxidation of fatty acids, and amino acid catabolism. Our screen further demonstrates that ascaroside biosynthesis is directly affected by nutritional status and that excretion of the final products is highly selective.