Growth Mechanism of Helicoidal Nickel Whiskers

NICKEL whiskers obtained by reduction of the iodide of the metal can be classified into two categories : (i) rectilinear whiskers (ii) helicoidal whiskers In general, these whiskers are formed by a stacking of small idiomorphic crystals. The law governing such stackings was determined theoretically in a previous investigation .1,2 It was shown that they were formed from nickel iodide in fusion and that the theory of dendritic growth was quite true for rectilinear whiskers ; the axes of growth are of low indices ( , ---100> ) and the conditions required for dendritic growth as described by Papapetrou3 are fulfilled. Rectilinear whiskers without branches are obtained, because one of the directions of dendritic growth is favoured and the development takes place only in that direction. This paper presents a study of the growth mechanisms of helicoidal whiskers

Growth Mechanism of Helicoidal Nickel Whiskers

Nickel whiskers obtained by reduction of the iodide of the metal can be classified into two categories:- - Rectilinear whiskers - Spiral whiskers Rectilinear whiskers without branches are obtained because one of the directions of dendritic growth is favoured and the development takes place only in that direction

Development du systeme racinaire chez le palmier a huile selon l'origine genetique et le regime hydropotassique du sol

Rootsystem architecture is important in drought resistance, because of its role in water and nutrient mobilizations. The variability of root system architecture of 3 oil palm crosses B, C and E was studied. The3 crosses were different for their sensitivity to drought. The plants were potted into plastic PVC tubes (95 cm in depth x 10 cm in diameter). Each PVC tube was constructed with 6 small tubes assembled together. Two soil moistures regimes and two levels of potassium (K) were tested. For root length, surface area and dry matter, effects of crosses and "cross x K levels x water regime" interactions were significant. The results suggest that breeders could make more progress in selection of root system adapted to drought, if they consider simultaneously both drought and K deficiency parameters. L'architecture du système racinaire du palmier à huile joue un rôle important dans la résistance à la sécheresse, grâce à la mobilisation de l'eau et des sels minéraux. Le système racinaire des plants issusde 3 croisements de palmier à huile B, C et E a été étudiée. Les plants ont été transférés dans des tubes PVC (95 cm de profondeur x 10 cm de diamètre). Chaque tube PVC a consisté en un assemblage de 6 petitstubes. Deux régimes hydriques et deux niveaux de potassium (K) ont été testés. Les effets des croisements et de l'interaction "croisement x niveau de K x régime hydrique" ont été significatifs pour les paramètres tellesla longueur totale, la surface totale et la matière sèche des racines. Ces résultats montrent que pour plus de progrès dans la sélection du système racinaire adapté à la sécheresse, les sélectionneurs gagneraientà prendre en compte à la fois la sécheresse la déficience potassique

Measurement of kinematic and nuclear dependence of R = σ_L/σ_T in deep inelastic electron scattering

We report results on a precision measurement of the ratio R=σ_L/σ_T in deep inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q^2≤10 (GeV/c)^2. Our results show, for the first time, a clear falloff of R with increasing Q^2. Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences R_A-R_D and the cross section ratio σ^A/σ^D between Fe and Au nuclei and the deuteron. Our results for R_A-R_D are consistent with zero for all x, Q^2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios σ^A/σ^D from all recent experiments, at all x, Q^2 values, are now in agreement

Intercalibration of the Hb3gr 40Ar/39Ar dating standard.

The 40Ar/39Ar dating technique is based on the knowledge of the age of neutron fluence monitors (standards). Recent investigations have improved the accuracy and precision of the ages of most of the Phanerozoic-aged standards (e.g. Fish Canyon Tuff sanidine (FCs), Alder Creek sanidine, GA1550 biotite and LP-6 biotite); however, no specific study has been undertaken on the older standards (i.e. Hb3gr hornblende and NL-25 hornblende) generally used to date Precambrian, high Ca/K, and/or meteoritic rocks.In this study, we show that Hb3gr hornblende is relatively homogenous in age, composition (Ca/K) and atmospheric contamination at the single grain level. The mean standard deviation of the 40Ar/39ArK (F-value) derived from this study is 0.49%, comparable to the most homogeneous standards. The intercalibration factor (which allows direct comparison between standards) between Hb3gr and FCs is RFCsHb3gr = 51.945 0.167. Using an age of 28.02 Ma for FCs, the age of Hb3gr derived from the R-value is 1073.6 5.3 Ma (1σ, internal error only) and 8.8 Ma (including all sources of error). This age is indistinguishable within uncertainty from the K/Ar age previously reported at 1072 11 Ma [Turner G., Huneke, J.C., Podosek, F.A., Wasserburg, G.J., 1971. 40Ar-39Ar ages and cosmic ray exposure ages of Apollo 14 samples. Earth Planet. Sci. Lett. 12, 19-35]. The R-value determined in this study can also be used to intercalibrate FCs if we consider the K/Ar date of 1072 Ma as a reference age for Hb3gr. We derive an age of 27.95 0.19 Ma (1σ, internal error only) for FCs which is in agreement with the previous determinations. Altogether, this shows that Hb3gr is a suitable standard for 40Ar/39Ar geochronology

Measurement of the Difference in R=σ_L/σ_T and of σ^A/σ^D in Deep-Inelastic e-D, e-Fe, and e-Au Scattering

We measured the differences in R=σ_L/σ_T and the cross-section ratio σA/σD in deep-inelastic electron scattering from D, Fe, and Au nuclei in the kinematic range 0.2≤x≤0.5 and 1≤Q^2≤5 (Gev/c)^2. Our results for R^A-R^D are consistent with zero for all x and Q^2, indicating that possible contributions to R from nuclear higher-twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The European Muon Collaboration effect is reconfirmed, and the low-x data from all recent experiments, at all Q^2, are now in agreement

Longitudinal and Transverse Response Functions in ^(56)Fe(e,e') at Momentum Transfer near 1 GeV/c

Inclusive electron-scattering cross sections have been measured for ^(56)Fe in the quasielastic region at electron energies between 0.9 and 4.3 GeV, at scattering angles of 15° and 85°. Longitudinal and transverse response functions at a q of 1.14 GeV/c have been extracted using a Rosenbluth separation. The experimental Coulomb sum has been obtained with aid of an extrapolation. The longitudinal response function, after correction for Coulomb distortion, is lower than quasifree-scattering-model predictions at the quasielastic peak and on the high-ω side