Inadequacy of the spectator model in deuteron break-up induced by high-energy hadrons

We discuss the experimental features of the spectator distribution in high-energy reactions on deuterons and we compare them with the quantitative and qualitative predictions of various theoretical models. We find that only a particular type of meson exchange can explain the relative channel dependence. Extending our analysis to the case of a hyperon and a nucleon in the final state, we find it more practical to look at this effect from a different point of view, namely introducing isobars in the final scattering state.     

A method for the evaluation of hail suppression

Zusammenfassung Ein Sequenztest-Verfahren wurde für die Prüfung der Annahme entwickelt, dass Hagelverhinderungsversuche die Frequenz der Hageltage verkleinern. Das Verfahren ist auf die Angaben über den Grossversuch II zur Unterdrückung des Hagels in der Magadinoebene (Schweiz) angewandt worden. Funktionen für die Versuchskenngrössen und Stichproben-Mittelwerte sind ebenfalls entwickelt und am selben Beispiel zur Anwendung gebracht worden. Schliesslich werden die Folgerungen, die sich hinsichtlich der Versuchsverfahren und Testergebnisse abzeichnen, erörtert.

---

---

Advisory Committee on Weather Control, Technical Report No. 4.     

Elliptic difference equations and interior regularity

Summary Letu be a solution of an elliptic differential equation and letu _h be a solution of a corresponding elliptic difference equation. It is proved that ifu _h converges tou at a certain rate as the mesh-widthh tends to zero, then the appropriate difference quotient ofu h converges to the corresponding derivative ofu at the same rate whenh tends to zero.     

Coumarins via the wittig reaction. Synthesis of methoxsalen-5-14C

A new and improved synthesis of methoxsalen ( 3 ) has been developed for the preparation of specifically carbon-14 labelled 3 . Introduction of the label by a Gattermann reaction on 6-hydroxy-7-methoxycoumaran ( 1 ) followed by dehydrogenation provides an intermediate 6 which, on reaction with carbethoxymethylenetriphenylphosphorane ( 8 ) and heat inversion, provides the title compound in overall yields of up to 50%. By these procedures, 3 has been prepared ¹⁴C labelled at C-5. Alternatively, 3 may be prepared from 6 and ethyl cyanoacetate in lower overall chemical yield but in potentially higher radiochemical yield if labelling at C-6 or C-7 is required since the Wittig process utilizes an excess of phosphorane.     

On the rate of convergence of some difference schemes for second order elliptic equations

The purpose of this paper is to estimate the rate of convergence for some natural difference analogues of Dirichlet's problem for uniformly elliptic differential equations, $$\begin{gathered} \sum\limits_{j,k = 1}^N {\frac{\partial }{{\partial x_j }}} \left( {a_{jk} \frac{{\partial u}}{{\partial x_k }}} \right) = F in R, \hfill \\ u = f on B, \hfill \\ \end{gathered}$$ in aN-dimensional domainR with boundaryB. These schemes will in general not be of positive type, and the analysis will therefore be carried out in discreteL ²-norms rather than in the maximum norm. Since our approximation of the boundary condition is rather crude, we will only arrive at a rate of convergence of first order for smoothF andf. Special emphasis will be put on appraising the dependence of the rate of convergence on the regularity ofF andf.     

Shock wave amplification by fabric materials

It has been shown that, when exposed to air shock waves, soft materials such as fabrics can lead to amplification of the peak pressure measured on a reflecting surface behind the fabric. This occurs for a wide range of fabric configurations, including those used in soft-ballistic protection. The goal of this study was to validate a numerical model to develop an improved understanding of this phenomenon and investigate different fabric parameters, including density, permeability and standoff, and their influence on blast amplification. The investigation of fabric parameters was carried out using numerical simulations in an explicit finite element code with coupled fluid–structure interaction. The benefit of this method was the ability to isolate individual parameters. The model predicted similar trends to existing experimental data, though the numerically predicted peak pressures were consistently higher than the experimental values. The parametric study showed that low permeability fabrics result in the highest pressure amplifications. At areal densities on the order 100 g/m², typical of single layer fabrics, amplification also increased with areal density for low permeability materials.      

Field-programmable gate arrays and quantum Monte Carlo: Power efficient coprocessing for scalable high-performance computing

Massively parallel architectures offer the potential to significantly accelerate an application relative to their serial counterparts. However, not all applications exhibit an adequate level of data and/or task parallelism to exploit such platforms. Furthermore, the power consumption associated with these forms of computation renders “scaling out” for exascale levels of performance incompatible with modern sustainable energy policies. In this work, we investigate the potential for field-programmable gate arrays (FPGAs) to feature in future exascale platforms, and their capacity to improve performance per unit power measurements for the purposes of scientific computing. We have focused our efforts on variational Monte Carlo, and report on the benefits of coprocessing with a FPGA relative to a purely multicore system.     

Long-Term Colloidally Stable Aqueous Dispersions of ≤5 nm Spinel Ferrite Nanoparticles

Applications in biomedicine and ferrofluids, for instance, require long-term colloidally stable, concentrated aqueous dispersions of magnetic, biocompatible nanoparticles. Iron oxide and related spinel ferrite nanoparticles stabilized with organic molecules allow fine-tuning of magnetic properties via cation substitution and water-dispersibility. Here, we synthesize≤5 nm iron oxide and spinel ferrite nanoparticles, capped with citrate, betaine and phosphocholine, in a one-pot strategy. We present a robust approach combining elemental (CHN) and thermal gravimetric analysis (TGA) to quantify the ratio of residual solvent molecules and organic stabilizers on the particle surface, being of particular accuracy for ligands with heteroatoms compared to the solvent. SAXS experiments demonstrate the long-term colloidal stability of our aqueous iron oxide and spinel ferrite nanoparticle dispersions for at least 3 months. By the use of SAXS we approved directly the colloidal stability of the nanoparticle dispersions for high concentrations up to 100 g L⁻¹.     

Why edge inversion? Theoretical characterization of the bonding in the transition states for inversion in F n NH(3−n) and FnPH(3−n) (n = 0–3)

As first noted by Dixon et al. (J Am Chem Soc 108:2461–2462, 1986), heavily fluorinated pyramidal phosphorus compounds, e.g., F _n PH_(3?n) with n > 1, invert through a T-shaped transition state (edge inversion) rather than the D_3h-like transition states (vertex inversion) found in the corresponding nitrogen compounds and less fluorinated phosphorus compounds. Subsequent studies by Dixon and coworkers established that this is a general phenomenon and has important chemical consequences. But what is the reason for the change in the structure of the transition state? Recent theoretical investigations have resulted in the discovery of a new type of chemical bond, the recoupled pair bond. In particular, it was found that recoupled pair bond dyads account for the hypervalency of the elements beyond the first row. In this paper, we show that recoupled pair bond dyads also account for the existence of the edge inversion pathway in heavily fluorinated phosphorus compounds and likely account for the presence of the lower energy inversion pathways in pyramidal compounds of other elements beyond the first row.