Implications for space radiation environment models from CREAM & CREDO measurements over half a solar cycle.

Flight data obtained between 1990 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSAT-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) provide coverage over half a solar cycle. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor of three increase at high latitudes and the latter a general increase accompanied by a north-westward drift. Comparison of particle fluxes and linear energy transfer (LET) spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatment of locally produced secondary particles. Solar-particle events during this time period have LET spectra significantly below the October 1989 event which has been proposed as a worst case model.     

Effect of Swirling Desolvation Gas Flow in an Atmospheric Pressure Ion Source

A numerical study is performed to examine the effect of introducing a swirling desolvation gas flow on the flow transport characteristics in an electrospray and an atmospheric pressure chemical ionization (APCI) system. An ion source having three coaxial tubes is considered: (1) an inner capillary tube to inject the liquid sample, (2) a center coaxial tube to provide a room temperature gas flow to nebulize the liquid, referred to as the nebulizing gas flow, and (3) an outer coaxial tube having a converging exit to supply a high temperature gas for droplet desolvation, referred to as the desolvation gas flow. The results show that a swirling desolvation gas flow reduces the dispersion of the nebulizing gas and suppresses turbulent diffusion. The effect of swirling desolvation flow on the trajectory of a range of droplet sizes emitted from a source is also considered. Figure

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Sorption of inorganic nanoparticles in woven cellulose fabrics

Titanium dioxide was deposited from aqueous suspension onto cellulosic surfaces.Titania was sourced from Degussa (P25TM,70:30 anatase:rutile).Dry uptake of particles was shown to be rapid and dominant with one-third of the deposition occurring in less than 30 s and over one-half in the first minute.Isotherms were recorded to compare the rate of titanium deposition on dry and pre-wetted cotton.In the dry case uptake reached a maximum in 30 min whereas in the pre-wetted case the uptake was seen to continue beyond 180 min.A broad trend of higher deposition occurring at lower pH was seen,corresponding to the region where surface charges were opposite and thus attractive.Dry pickup was less significant at high pH.The response to varying ionic strength was complex and was attributed to the combined effect of charge screening,particle aggregation and consequent particle entrapment or occlusion.Titania deposition into the interstices of woven cotton sheets resulted in the formation of inorganic,nanoparticulate skeletons which could be isolated by controlled combustion of the cellulose and thus cotton was suggested to have potential for the templated synthesis of high surface area semiconductor materials.     

Analysis of bit error rate and power penalty for a birefringent wavelength division multiplexer

The power penalty and bit error rate degradation encountered when using wavelength division multiplexing devices is analyzed. Analysis is applied to the birefringent wavelength division multiplexer (BWDM) with a sinusoidal transfer function.¹ The degradation in bit error rate is attributed to laser mode partition noise and crosstalk noise.     

Embedded Picard–Vessiot extensions

We prove that if T is a theory of large, bounded, fields of characteristic 0 with almost quantifier elimination, and T_D is the model companion of T∪{“? is a derivation”}, then for any model (𝒰,?) of T_D, differential subfield K of 𝒰 such that C_K?T, and linear differential equation ?Y = AY over K, there is a Picard-Vessiot extension L of K for the equation with K≤L≤𝒰, i.e. L can be embedded in 𝒰 over K, as a differential field. Moreover such L is unique to isomorphism over K as a differential field. Likewise for the analogue for strongly normal extensions for logarithmic differential equations in the sense of Kolchin.     

Second-order inner displacement in the hexagonal close-packed structure

Expressions given recently by Ramanand et al. for second-order sublattice displacements in the hexagonal close-packed structure are shown to be in error. The use of inner elasticity theory leads to expressions that conform fully to the requirements of thermodynamics and crystal symmetry.     

Electrospray ionisation Fourier-transform ion cyclotron resonance mass spectrometry of dynamic combinatorial libraries

The use of electrospray ionisation Fourier-transform ion cyclotron resonance tandem mass spectrometry (ESI-FTICR-MS/MS) for the analysis of dynamic combinatorial libraries (DCLs) of pseudo-peptide macrocyclic hydrazone oligomers is presented. The design of library building blocks results in mixtures of compounds with greater diversity than libraries generated by conventional combinatorial chemistry and so presents increased demands for analysis. The extended capabilities of the FTICR technique, specifically selective ion trapping, sensitivity, high resolution and mass accuracy over a broad mass range, are compatible with these increased demands and, most importantly, without the need for chromatography. Preliminary studies on the sequencing of cyclic oligomers and confirmation of the presence of sequence isomers are presented. These studies highlight the potential of FTICR-MS as a superior technique for the analysis of combinatorially generated compounds.