Interlaboratory GC/MS response factor precision

A quality control procedure for Fused Silica Capillary Column Gas Chromatography/Mass Spectroscopy (FSCC GC/MS) was tested and shown to produce similar response factors at five Spectroscopy (FSCC GC/MS) was tested and shown to produce similar response factors at five laboratories. The average relative standard deviation (RSD) of interlaboratory response factors for fifty three compounds of environmental interest determined at each laboratory at nominal injected weights of 20, 100, and 200 ng was found to be 18.9% for four of the five laboratories which participated in this work. These data demonstrate that similar response factors can be attained in routine GC/MS measurements when adequate quality control is maintained.     

Measurement of the structure functionsF 2 andxF 3 and comparison with QCD predictions including kinematical and dynamical higher twist effects

The isoscalar nucleon structure functionsF ₂(x, Q ²) andxF ₃(x, Q ²) are measured in the range 0<Q ²<64 GeV², 1.7<W ²<250 GeV²,x<0.7 using ν and \(\bar v\) interactions on neon in BEBC. The data are used to evaluate possible higher twist contributions and to determine their impact on the evaluation of the QCD parameter Λ. In contrast to previous analyses reaching to such lowW ² values, it is found that a low \(\Lambda _{\overline {MS} } \) value in the neighbourhood of 100 MeV describes the data adequately and that the contribution of dynamical higher twist effects is small and negative.     

Valence instabilities, phase transitions, and abrupt lattice expansion at 5 K in the YbGaGe system

The powder synchrotron X-ray diffraction technique was used to study the thermal expansion behavior of the mixed valence layered compound, YbGa1.05Ge0.95 in the temperature range 3-1123 K. A surprising abrupt isosymmetric phase transition, accompanied by a dramatic volume increase (negative thermal expansion), was found at 5 K induced by a sudden Yb valence transition from +(2 + epsilon) toward +2. At high temperatures, the material undergoes a transformation to a highly disordered structure until it eventually collapses at 1123 K to a structure with isovalent Yb ions and flat Ga/Ge planes (AlB2 type).     

A pulsed proton NMR study on ammonia diffusion in titanium-rich TiS2·NH3

Measurements of the proton spin-lattice relaxation time T₁ on three stoichiometries of titanium-rich Ti_1+xS₂·NH₃ show that the diffusion of intercalated ammonia is not dependent on the presence of titanium interstials although these reduce dramatically the rate of uptake of ammonia.     

Implementation of an analogue model of a memristor based on a light-dependent resistor

In this paper,an analogue model of a memristor using a light-dependent resistor(LDR) is presented.This model can be simplified into two parts:a control circuit and a variable resistor.It can be used to easily verify theoretical presumptions about the switching properties of memristors.This LDR-based memristor model can also be used in both simulations and experiments for future research into memristor applications.The paper includes mathematical models,simulations,and experimental results.     

Production of π0 mesons and charged hadrons in\bar v neon and ν neon charged current interactions

The average multiplicities of charged hadrons and of π⁺, π^? and π⁰ mesons, produced in \(\bar v\) Ne and νNe charged current interactions in the forward and backward hemispheres of theW ^±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (y _Lab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π⁰ multiplicity accurately. The ratio of average π multiplicities \(\frac{{2\left\langle {n_{\pi ^O } } \right\rangle }}{{[\left\langle {n_{\pi ^ + } } \right\rangle + \left\langle {n_{\pi ^ - } } \right\rangle ]}}\) is consistent with 1. In the backward hemisphere \(\left\langle {n_{\pi ^O } } \right\rangle \) is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between \(\mathop v\limits^{( - )} \) and \(\mathop v\limits^{( - )} \) , \(\mathop v\limits^{( - )} \) scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial \(\mathop v\limits^{( - )} \) interaction.     

Inclusion properties of volatile organic compounds in a calixarene-based organic zeolite

The inclusion properties of a calixarene-based porous material have been studied to investigate the adsorption and the desorption of carbon tetrachloride, chloroform, and water in the zeolite-like structure. Uptake and release processes have been studied both by time-resolved powder X-ray diffraction and by thermogravimetric analysis to obtain structural and kinetic information. The selected guests are able to enter the structure with an increase in the host cell volume and with time-dependent diffusivity coefficients. Chloroform molecules act as a permanent porosity switch promoting a phase transition to non-porous triclinic form.     

Nitrate ion-selective sensor based on electrochemically prepared conducting polypyrrole films

Nitrate-doped polypyrrole (PPy) films on a glassy carbon substrate have been prepared electrochemically in aqueous, acetonitrile, and propylene carbonate solutions for use as nitrate sensors. Lithium nitrate, sodium nitrate, nitric acid, tetraethylammonium p-toluene sulfonate (TS), and tetradodecylammonium nitrate (TDN) were employed as electrolytes. The effect of dibutylphthalate (DBP) as a plasticizer on the sensitivity and lifetime of PPy film sensors was also investigated. A Nernstian behavior with a slope of 56.9 m V/decade over 0.1–7.4 × 10⁻⁵ M NO and a detection limit of 4.7 × 10⁻⁵ M were observed for the polymer sensor prepared in acetonitrile solution containing lithium nitrate and 15% plasticizer (DBP). A lifetime of more than 6 months for this PPy film electrode was obtained.     

Extremes of nuclear structure

With the advent of medium and large gamma detector arrays, it is now possible to look at nuclear structure at high rotational forces. The role of pairing correlations and their eventual breakdown, along with the shell effects have showed us the interesting physics for nuclei at high spins — superdeformation, shape co-existence, yrast traps, alignments and their dramatic effects on nuclear structure and so on. Nuclear structure studies have recently become even more exciting, due to efforts and possibilities to reach nuclei far off from the stability valley. Coupling of gamma ray arrays with ‘filters’, like neutron wall, charged particle detector array, gamma ray total energy and multiplicity castles, conversion electron spectrometers etc gives a great handle to study nuclei produced online with ‘low’ cross-sections. Recently we studied, nuclei in mass region 80 using an array of 8 germanium detectors in conjunction with the recoil mass analyser, HIRA at the Nuclear Science Centre and, most unexpectedly came across the phenomenon of identical bands, with two quasi-particle difference. The discovery of magnetic rotation is another highlight. Our study of light In nucleus, 107In brought us face to face with the ‘dipole’ bands. I plan to discuss some of these aspects. There is also an immensely important development — that of the ‘radioactive ion beams’. The availability of RIB, will probably very dramatically influence our ‘conventional’ concept of nuclear structure. The exotic shapes of these exotic nuclei and some of their expected properties will also be touched upon.     

On the structures of X- and Y-type zeolites. Structural changes within the cavities of Na-Y during dehydration and contrasts with Na-X systems

Samples of dehydrated and partially dehydrated Na-Y were examined by X-ray diffraction methods revealing the progressive structural changes which occur as water is removed and the different behaviour compared with Na-X. The differences between Na-Y and Na-X reflect the reduced Al content of Na-Y and the consequential lower average capability of each framework oxygen atom for balancing cation charges. In the small-pore region of Na-Y, the total number of Na atoms remains relatively constant during dehydration (ca. 15 per unit cell compared withca. 18 in Na-X); unlike Na-X, Na-Y, has no site I atoms. Significant dehydration of the small-pore region, and the change from low to high site II occupancy, do not occur until the total water content of the sample is less than that which pertains under atmospheric conditions. In the 12-ring regionn of Na-Y, [Na(H₂O)₂]⁺ units are observed at an intermediate level of dehydration, possibly linked by water molecules astride the site III region to networks in adjacent 12-rings. There is no build-up, as in Na-X, of Na at site III, and site IIB (=III) is (at least partially) occupied by H₂O rather than Na. Further dehydration progressively removes H₂O but there is little rearrangement of Na atom positions, except the build-up in site II which accounts for much of the loss of Na from the mobile phase.