The interaction of a laser-generated cavity with a solid boundary

In this paper new observations of a laser-generated cavitation bubble interacting with an inertial boundary are presented. Employing schlieren photography techniques and a thin film transducer placed on the surface of the boundary, the pressure stresses induced in the solid boundary and the surrounding fluid by collapsing bubbles, created very close to the solid surface, are experimentally measured. Liquid jet development, shock wave emission, and "splash" phenomena are identified. For different creation sites close to the boundary, the relevance of each of these phenomena with respect to potentially damaging pressure stresses in the boundary is speculated on.     

Observable effects of scalar fields and varying constants

We show by using the method of matched asymptotic expansions that a sufficient condition can be derived which determines when a local experiment will detect the cosmological variation of a scalar field which is driving the spacetime variation of a supposed constant of Nature. We extend our earlier analyses of this problem by including the possibility that the local region is undergoing collapse inside a virialised structure, like a galaxy or galaxy cluster. We show by direct calculation that the sufficient condition is met to high precision in our own local region and we can therefore legitimately use local observations to place constraints upon the variation of “constants” of Nature on cosmological scales.     

Synthesis of photocleavable poly(methyl methacrylate‐block‐d‐lactide) via atom‐transfer radical polymerization and ring‐opening polymerization

The synthesis and characterization of a photocleavable block copolymer containing an ortho‐nitrobenzyl (ONB) linker between poly(methyl methacrylate) and poly(d ‐lactide) blocks is presented here. The block copolymers were synthesized via atom transfer radical polymerization (ATRP) of MMA followed by ring‐opening polymerization (ROP) of d ‐Lactide and ROP of d ‐lactide followed by ATRP of MMA from a difunctional photoresponsive ONB initiator, respectively. The challenges and limitations during synthesis of the photocleavable block copolymers using the difunctional photoresponsive ONB initiator are discussed. The photocleavage of the copolymers occurs under mild conditions by simple irradiation with 302 nm wavelength UV light (Relative intensity at 7.6 cm: 1500 μW/cm²) for several hours. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4309–4316     

Determination of the configuration of histrelin,and LHRH analog,by chiral capillary gas chromatography

Summary Summary The assigned chirality at each center of the synthetic nonapeptide histrelin (L-pyroglutamyl-L-histidyl-L-tryptophyl-L-seryl-L-tyrosyl-D-N^im-benzyl-histidyl-L-leucyl-L-arginyl-L-proline-ethylamide) was verified using chiral gas chromatography. The procedure involved acid hydrolysis of histrelin to the constituent amino acids, derivatization as the N-pentafluoropropionyl/isopropyl esters and the analysis of the mixture using a commercially available 25m chiral capillary column (Chirasil-L-Val). There was no significant difference in the retention time of the amino acids obtained from the hydrolysate mixture when compared to the appropriate standards. Additionally, the hydrolysate was spiked with the D and L amino acids to prove the identity of closely eluting peaks. Luteinizing hormone-releasing hormone     

On-line nuclear orientation and relaxation studies of Cs isotopes

The hyperfine field of CsFe has been measured to be (+)40.8(0.7)T, using the technique of on-line low temperature nuclear orientation. The time dependent relaxation of¹²¹Cs^m Fe has also been investigated using a new technique, giving a Korringa constant C_k of 0.059 (15) sK. From this, an effective relaxation time of 3.0 (0.8)s can be deduced for the short lived¹¹⁸Cs^m(T_1/2=17s). This value has then been used to extract the magnetic moment of¹¹⁸Cs^m to be |μ|=5.4 (1.1) nm.     

Superelasticity and stability of a shape memory alloy hexagonal honeycomb under in-plane compression

Nitinol (NiTi) shape memory alloy honeycombs, fabricated in low densities using a new brazing method [Grummon, D., Shaw, J., Foltz, J., 2006. Fabrication of cellular shape memory alloy materials by reactive eutectic brazing using niobium. Materials Science and Engineering A 438–440, 1113–1118], recently demonstrated enhanced shape memory and superelastic properties [Shaw, J. A., Grummon, D. S., Foltz, J., 2007b. Superelastic NiTi honeycombs: Fabrication and experiments. Smart Materials and Structures 16, S170–S178] by exploiting kinematic amplification of thin-walled deformations. The realization of such adaptive, light-weight cellular structures opens interesting possibilities for design and novel applications. This paper addresses the consequent need for design and simulation tools for engineers to make effective use of such structures by, as a first step, analyzing the multi-scale stability aspects of the superelastic behavior of a particular hexagonal, thin-walled, SMA honeycomb under in-plane compression. An in-depth parameter study is performed of the influence of different material laws on the behavior of honeycombs of finite and infinite extent with perfect and imperfect initial geometries. A finite element-based simulation is presented that credibly captures the behavior seen in experiments.     

A single-mode KrF laser

Single-mode operation of a KrF laser oscillator has been achieved for the first time. The laser medium is pumped by an electron beam which allows excitation for a much longer duration than with discharge pumping. The long excitation time, together with the use of a short oscillator cavity with a low single-pass gain, allows many roundtrips before saturation is reached. This makes line-narrowing easier and single-mode operation has been achieved using only two intracavity etalons.Technical Research Centre of Finland, Helsinki, Finland     

Palladium(II)-catalyzed intramolecular aminoacetoxylation of sugar derived alkenyl tosylsulfonamide: Total synthesis of l-deoxyallonojirimycin

Palladium catalyzed intramolecular aminoacetoxylation of d-ribose derived alkenyl tosylsulfonamide to deliver l-deoxyallonojirimycin in an overall yield of 19%. The preliminary screening of l-deoxyallonojirimycin against carbohydrate processing enzymes showed moderate inhibitory activity against α-glucosidase (yeast) and α-mannosidases.     

Natural convection in a partitioned enclosure heated from below

Cubic spline collection numerical method has been developed to determine two dimensional natural convection in a partitioned enclosure heated from below. The both sides of impermeable partition are considered to have continuity in heat flux and temperatures. The governing equations are solved with aid of the SADI procedure. Parametric studies of the effects of the partition and Rayleigh number on the fluid flow and temperature fields have been performed. Results show that the location of the partition and Rayleigh number have a significant influence on the flow and heat transfer characteristics.

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Freie Konvektion in einem von unten beheizten, unterteiltem Hohlraum

Zusammenfassung Eine numerische dreidimensionale SplineMethode zur Berechnung der zweidimensionalen Naturkonvektion in einem von unten beheizten, unterteiltem Hohlraum wird vorgestellt. Der Wärmestrom und die Temperatur auf beiden Seiten der undurchlässigen Trennwand werden als konstant betrachtet. Mit Hilfe der SADI-Prozedur werden die beschreibenden Gleichungen gelöst. Über den Einfluß der Unterteilung und der Rayleigh-Zahl auf die Strömung des Fluids und das Temperaturfeld wird eine Parameter-Studie durchgeführt. Die Ergebnisse zeigen, daß die Anordnung der Unterteilung und die Rayleigh-Zahl einen entscheidenden Einfluß auf das Wärmeübertragungsverhalten haben.

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Nomenclature A aspect ratio=L/H - g gravitational acceleration - H enclosure height - H₁ distance between the top wall of enclosure and the partition - H₂ distance between the bottom wall of enclosure and the partition - k thermal conductivity of fluid - L enclosure length - m number of vertical grid lines - n number of horizontal grid lines - Nu Nusselt number - P pressure - Pr Prandtl number - Q heat transfer across enclosure - Ra Rayleigh number based onH - t time - T dimensional temperature - T _H temperature of warm horizontal wall - T _L temperature of cold horizontal wall - T ₀ average temperature=T(_H+T_L)/2 - T temperature difference between the hot and cold wall =T _H–T_L - u, U dimensional and dimensionless horizontal velocity - , V dimensional and dimensionless vertical velocity - x, X dimensional and dimensionless horizontal coordinate - y, Y dimensional and dimensionless vertical coordinate - fluid thermal diffusivity - coefficient of thermal expansion - viscosity - kinematic viscosity=/g9 - density - , dimensional and dimensionless stream function - dimensionless temperature - , dimensional and dimensionless vorticity - dimensionless time