Surface pump-probe femtosecond-laser mass spectrometry: time-, mass-, and velocity-resolved detection of surface reaction dynamics

A detailed account of the experimental methodology of surface pump-probe femtosecond-laser mass spectrometry is presented. This recently introduced technique enables the direct time-resolved investigation of surface reaction dynamics by monitoring the mass and the relative velocity of intermediates and products of a photoinduced surface reaction via multiphoton ionization. As a model system, the photodissociation dynamics of methyl iodide adsorbed at submonolayer coverage on magnesia ultrathin films is investigated. The magnesia surface preparation and characterization as well as the pulsed deposition of methyl iodide are described. The femtosecond-laser excitation (pump) and, in particular, the resonant multiphoton ionization surface detection (probe) schemas are discussed in detail. Results of pump-probe time-resolved methyl and iodine atom detection experiments are presented and the potential of this method for velocity-resolved photofragment analysis is evaluated.     

Role of Al, Ti, and Zr in Gray Iron Preconditioning/Inoculation

A research was done to investigate the effect of strong deoxidizing elements, such as Al, Zr, and Ti, in gray irons in laboratory experiments. The conclusions drawn were based mainly on thermal analysis, chill (carbides) sensitivity, graphite characteristics, and SEM analysis. Al and Zr have visible beneficial effects in preconditioning of gray irons, by favoring lower undercooling during solidification. Ti has an inconclusive role, with limited influence, but promotes undercooled graphite formation. Complex (Mn,X)S compounds, nucleated on the previously formed small oxide-based sites, were found as the major nucleation sites for graphite in gray irons, with specific distribution of Al, Ti, and Zr. Al,Zr-FeSi preconditioning of electrically melted and Sr-FeSi inoculated gray irons avoided type D graphite and carbides in 3 mm sections castings.     

Formulation‐properties versatility of wood fiber biocomposites based on polylactide and polylactide/thermoplastic starch blends

This article discusses the interrelation between formulation, processing, and properties of biocomposites composed of a bioplastic reinforced with wood fibers. Polylactide (PLA) and polylactide/thermoplastic starch blends (PLA/TPS) were used as polymeric matrices. Two grades of PLA, an amorphous and a semicrystalline one, were studied. TPS content in the PLA/TPS blends was set at 30, 50, and 70 wt%. Two types of wood fiber were selected, a hardwood (HW) and a softwood (SW), to investigate the effect of the fiber type on the biocomposite properties. Finally, the impact of different additives on biocomposite properties was studied with the purpose to enhance the bioplastic/wood fiber adhesion and, therefore, the final mechanical performance. The biocomposites containing 30 wt% of wood fibers were obtained by twin‐screw extrusion. The properties of the biocomposites are described in terms of morphology, thermal, rheological, and mechanical properties. Furthermore, the biocomposites were tested for humidity and water absorption and biodegradability. An almost 100% increase in elastic modulus and 25% in tensile strength were observed for PLA/wood fiber biocomposite with the best compatibilization strategy used. The presence of the TPS in the biocomposites at 30 and 50 wt% maintained the tensile strength higher or at least equal as for the virgin PLA. These superior tensile results were due to the inherent affinity between the matrices and wood fibers improved by the addition of a combination of coupling and a branching agent. In addition to their outstanding mechanical performance, the biocomposites showed high biodegradation within 60 days. POLYM. ENG. SCI., 54:1325–1340, 2014. © Her Majesty the Queen in Right of Canada 2013 ¹      

Obtaining asphalt binder rheological properties from BBR strength test—the effect of loading rate

Mechanics of Time-Dependent Materials - Selecting asphalt binders that have good cracking resistance at low temperatures is the first step in designing asphalt mixtures for durable asphalt...     

New Pyrrole Derivatives as Promising Biological Agents: Design,Synthesis, Characterization,In Silico,and Cytotoxicity Evaluation

The current study describes the synthesis, physicochemical characterization and cytotoxicity evaluation of a new series of pyrrole derivatives in order to identify new bioactive molecules. The new pyrroles were obtained by reaction of benzimidazolium bromide derivatives with asymmetrical acetylenes in 1,2-epoxybutane under reflux through the Huisgen [3 + 2] cycloaddition of several ylide intermediates to the corresponding dipolarophiles. The intermediates salts were obtained from corresponding benzimidazole with bromoacetonitrile. The structures of the newly synthesized compounds were confirmed by elemental analysis, spectral techniques (i.e., IR, ¹H-NMR and ¹³C-NMR) and single-crystal X-ray analysis. The cytotoxicity of the synthesized compounds was evaluated on plant cells (i.e., Triticum aestivum L.) and animal cells using aquatic crustaceans (i.e., Artemia franciscana Kellogg and Daphnia magna Straus). The potential antitumor activity of several of the pyrrole derivatives was studied by performing in vitro cytotoxicity assays on human adenocarcinoma-derived cell lines (i.e., LoVo (colon), MCF-7 (breast), and SK-OV-3 (ovary)) and normal human umbilical vein endothelial cells (HUVECs). The obtained results of the cytotoxicity assessment indicated that the tested compounds had nontoxic activity on Triticum aestivum L., while on Artemia franciscana Kellogg nauplii, only compounds 2c and 4c had moderate toxicity. On Daphnia magna, 4b and 4c showed high toxicity; 2a, 2b, and 2c moderate to high toxicity; only 4a and 4d were nontoxic. The compound-mediated cytotoxicity assays showed that several pyrrole compounds demonstrated dose- and time-dependent cytotoxic activity against all tested tumor cell lines, the highest antitumor properties being achieved by 4a and its homologue 4d, especially against LoVo colon cells.     

ROS-Induced DNA-Damage and Autophagy in Oral Squamous Cell Carcinoma by Usnea barbata Oil Extract—An In Vitro Study

Oxidative stress is associated with aging, cancers, and numerous metabolic and chronic disorders, and phenolic compounds are well known for their health-promoting role due to their free-radical scavenging activity. These phytochemicals could also exhibit pro-oxidant effects. Due to its bioactive phenolic secondary metabolites, Usnea barbata (L.) Weber ex. F.H. Wigg (U. barbata) displays anticancer and antioxidant activities and has been used as a phytomedicine for thousands of years. The present work aims to analyze the properties of U. barbata extract in canola oil (UBO). The UBO cytotoxicity on oral squamous cell carcinoma (OSCC) CLS-354 cell line and blood cell cultures was explored through complex flow cytometry analyses regarding apoptosis, reactive oxygen species (ROS) levels, the enzymatic activity of caspase 3/7, cell cycle, nuclear shrinkage (NS), autophagy (A), and synthesis of deoxyribonucleic acid (DNA). All these studies were concomitantly performed on canola oil (CNO) to evidence the interaction of lichen metabolites with the constituents of this green solvent used for extraction. The obtained data evidenced that UBO inhibited CLS-354 oral cancer cell proliferation through ROS generation (316.67 × 10⁴), determining higher levels of nuclear shrinkage (40.12%), cell cycle arrest in G0/G1 (92.51%; G0 is the differentiation phase, while during G1 phase occurs preparation for cell division), DNA fragmentation (2.97%), and autophagy (62.98%) than in blood cells. At a substantially higher ROS level in blood cells (5250.00 × 10⁴), the processes that lead to cell death—NS (30.05%), cell cycle arrest in G0/G1 (86.30%), DNA fragmentation (0.72%), and autophagy (39.37%)—are considerably lower than in CLS-354 oral cancer cells. Our work reveals the ROS-mediated anticancer potential of UBO through DNA damage and autophagy. Moreover, the present study suggests that UBO pharmacological potential could result from the synergism between lichen secondary metabolites and canola oil phytoconstituents.     

Catalytic enhancement of hydrogen evolution reaction on copper in the presence of benzylamine

Benzylamine catalytic effect on the cathodic hydrogen evolution in acid aqueous solution has been studied on copper electrode. Experimental results obtained by voltammetric techniques emphasize that the presence of benzylamine in 1 M sulfuric acid solution enhances the hydrogen evolution reaction (HER). In such a solution, benzylamine is protonated and exists as benzylammonium cation. Kinetic parameters of HER have been determined, observing a significant increase of the exchange current in the presence of benzylamine. Also, a decrease of the cathodic transfer coefficient has been noticed. Activation energy for HER has been computed on the basis of the Arrhenius plots. In the presence of benzylamine the activation energy was 33.0 kJ mol⁻¹, whereas without benzylamine a greater value was obtained: 94.6 kJ mol⁻¹. The catalytic effect of benzylamine was confirmed by electrochemical impedance spectroscopy. The considerable diminution of the double layer capacity is a valid proof of the strong adsorption of benzylamine at the Cu - sulfuric acid solution interface, while the reduction of the charge transfer resistance is a symptom of the enhancement of HER. Ab initio molecular modeling of benzylammonium ion showed that, due to a high value of the dipole moment, the molecules are oriented in the most favorable position for the charge transfer reaction, i.e., with the protonated amino group facing toward the electrode.     

Picture-Hanging Puzzles

We show how to hang a picture by wrapping rope around n nails, making a polynomial number of twists, such that the picture falls whenever any k out of the n nails get removed, and the picture remains hanging when fewer than k nails get removed. This construction makes for some fun mathematical magic performances. More generally, we characterize the possible Boolean functions characterizing when the picture falls in terms of which nails get removed as all monotone Boolean functions. This construction requires an exponential number of twists in the worst case, but exponential complexity is almost always necessary for general functions.     

Design of Full‐Order Observers for Systems with Unknown Inputs by Using the Eigenstructure Assignment

In this paper a full‐order observer is suggested in order to achieve finite‐time reconstruction of the state vector for a class of linear systems with unknown inputs. The proposed design procedure is a combination of the approaches proposed by Lin & Wang [1] and Trinh & Ha [2]. The resulted observer has been improved, from the robustness point of view, by this paper's authors by using a novel and efficient method; it consists of adding three robustness terms which cancel the negative effect of the uncertainties which can appear in the system. The effectiveness of the suggested design algorithm is illustrated by a numerical example (aircraft lateral motion).