Notes: As a result of combined magnetization, specific heat, electrical resistivity, and neutron-scattering studies on single crystals, we present a complex magnetic phase diagram of UNiGa that exhibits several antiferromagnetic (AF) phases below TN=39 K. A relatively low magnetic field (∼1–1.5 T) applied along the c-axis induces metamagnetic transitions from the zero-field AF structures to an uncompensated AF and/or to a ferromagnetic (F) phase. All the magnetic structures are collinear (uranium magnetic moments parallel to the c-axis of the hexagonal structure). They consist of F basal-plane sheets which are coupled along c in various ways. The strongly anisotropic magnetism in UNiGa causes anisotropy of the electrical resistivity. The magnetic phase transitions are reflected in pronounced resistivity anomalies especially for current along the c-axis. The metamagnetic transitions are accompanied by giant magnetoresistance (GMR) effects which can be correlated with respective changes of the magnetic periodicity. This implies an important feature of the mechanism responsible for GMR phenomena in UNiGa. The strong resistance enhancement in the paramagnetic range when approaching TN is connected with AF short-range ordering with propagation along the c-axis. © 1996 American Institute of Physics.

Notes: Background/aims: Measurement of cutaneous surface topography can be made by three-dimensional (3-D) profilometry. Different equipment is used for this measurement. The magnitude of the vertical scale required, which can vary from several tens of micrometers (microrelief) to several millimeters (skin pathologies), depends also on the precision required and the duration of acquisition time. Over the last few years, different apparatuses have been produced, with a vertical range that is most frequently used for classical industrial applications, i.e., 0-1000 μm.Methods: The system developed here has a wide range of about 7 mm and is accurate enough to analyse each of the different skin surfaces that fall in this range without changing magnification. An optical principle, operating without any contact with a skin replica, allows a precise measurement with a high scanning speed.Results: The profilometer has a vertical sensitivity of 4 μm within a vertical range of 7 mm. This sensitivity is lower than that of a mechanical or focusing profilometer, but the vertical range is wider.Conclusions: The system has several advantages: because of its verticale range, it can measure large surfaces with great roughness variations; the initial position of the replica beneath the profilometer must be within the 7 mm vertical range; and skin topography can be quantified, without contact, in a short time.

Notes: Background/aims: Usually, skin topography is quantified by means of 2D profilometry using negative- or positive-replicas. To allow a direct in vivo measurement, a new profilometer is built, based on an optical triangulation principle.Conclusion: High speed of measurement can be reached using a non contact profilometer. The ability of a position sensing detector to read the center of gravity of the spot reflected by the skin surface, allows one to reduce the effects of the enlargement due to the skin absorption of the laser beam.

Notes: Background/Aims Skin relief is a matter of interest for dermatologists and surgeons. One of the methods available for surface topography measurement is based on 3D profilometry using skin surface replicas. and most studies use statistical results obtained from a large number of skin replica samples.The advent of optical profilometers (without contact) made it possible to remove the solid positive replica and to reduce the duration of the profilometric data acquisition. Nevertheless this saving of time, to be really interesting, needs to automate the data acquisition on a series of negative replicas.Methods/Results By adding a video camera to the optical profilometer and then by processing the resulting images, we have conceived a system able to carry out topographic measurements on a series of replicas loosely organized on a sample holder, without any human intervention. The silicon replicas in use have a very light colour: nearly white, sometimes slightly blue or green. The laser spot of the profilometer is so luminous that its red colour looks white through the camera. When choosing a replica holder with a matt dark colour and marking the left upper corner of the study area on the replica in black ink, the colours to be differentiated on the image are then close to the black one and the white one.We accordingly change the colour camera image into a black and white image (with 256 grey levels) and then carry out thresholdings to separate the different objects or information included in this image. With the use of a perfectly circular replica, of an accurately known size, laid on the sample holder at the center of the area filmed by the camera, we adjust the threshold level, which allows separation of the replica from its holder. We then move this calibrated replica in order to find the relationship between the size in pixels and the real size on the sample holder, in various positions of the video image.The software has four main built-in stages:〈list style="plain"〉Moving the sample holder beneath the sensor until a part of a replica is detected in the field of view of the camera;Moving the sample holder until this replica lies just in the middle of the image given by the camera;Recognition of the mark of the upper left corner of the surface area to be measured out inside this replica; andMoving the sample holder until the laser spot of the profilometer coincides with the origin of the surface area to be measured out, then carrying out this measurement.From the upper left corner of the sample holder, a scanning, line-by-line or column-by-column (according to the selected priority direction), is carried out until the successive replicas are found, and is stopped as soon as the number of replicas entered by the operator is reached.Conclusion The simplicity of the algorithms used makes it possible to distinguish the next measurement area from the preceding one in a few seconds.

Notes: SYNOPSIS. An electronmicroscopic study of Cyanophora paradoxa shows that its cuticle, vestibule, flagellar canals, and chondriome differ from those of Cryptomonadina. The flat cortical vesicles, peripheral tubules, as well as flagellar canals, which are surrounded by tubules, the anterior opening into an oblique depression and the posterior into a ventral groove, are more characteristic of Dinoflagellida. It is evident thus that, following Chadefaud, Cyanophora ought to be classified with primitive Dinoflagellida.Certain cytologic characteristics, especially the structure of the transitional zone (of the flagella), lead us to believe that Glaucocystis nostochinearum also belongs in this group.

Notes: A Cu-1,35 at. % Sn alloy is deformed by compression up to a degree of deformation reaching 45%. The X-ray diffraction study of the bulk specimens thus deformed makes it possible to follow the evolution of elements such as the lattice parameter, the residual stresses and r.m.s. strains, the particle size, dislocation density and the stacking-fault probability in terms of the deformation. The different results observed are compared with those obtained when studying pure Cu as well as the above-mentioned alloy deformed by filing at room temperature. When bulk specimens were studied by transmission electron microscopy, the dislocation density was measured. An approximate method of determination of the stacking-fault energy in this alloy, which presents no extended nodes, is also described.

Notes: An expression for the A(L) Fourier coefficients of an X-ray diffraction line is developed assuming a Gaussian function for the distribution of the chords, i.e. A(L) ∼ ( 1 - {{L}\over{D}} + {{L^{2}}\over{2\sigma \radic 2\pi D}} + \dots) exp (- 2π2L2Sb2{\bar \epsilon}^{2}_{L} + π4L4Sb4{\bar \epsilon}^{4}_{L} + \dots) = Ap(L)Aε(L). Various applications are then performed in order to give the relative magnitude of each of the terms appearing in A(L). The L2 quadratic term of the Ap(L) that has been neglected in previous works is numerically obtained in the special case of elastically isotropic W. Moreover, the anharmonic {\bar \epsilon}^{4}_{L} term is shown to be 105 less than the m.s. (mean square) strain {\bar \epsilon}^{2}_{L} for the same metal. Hyperbolic behaviour as a function of L is found for these terms. An approximate law for the expression of A(L) is then deduced from calculation of the relative magnitude of each term in its expansion. Such a law may be used in order to calculate the particle size and m.s. strains from one single line profile: A(L) ∼ ( 1 - {{L}\over{D}}) exp (- 2π2L2Sb2(〈{\epsilon}^{2}_{L}〉 - 〈{\epsilon}_{L}〉2) . The results are then compared, by the polynomial expansion approximate method, with the values previously obtained. This relation allows us to calculate the particle size and m.s. strain values in each crystallographic direction that may be experimentally reached. The influence of the elastic anisotropy on the behaviour of m.s. strains for the Cu-Sn and W-Th alloys is then deduced.

Notes: It may be very useful to know a mathematical expression which helps reconstruct the X-ray diffraction profile. It is in fact easier to work on one relation I(&thgr;) = f(&thgr;) rather than on a series of experimental points. The relation proposed in this paper, I(x) = A \big[cos\pi{(x-x_o-\delta)\over a}\big]^{n} {K^2 \over K^2 + (x-x_{0})^2},gives a good correspondence between experimental values and the values calculated in the case of a monochromatic source. Its use still remains very simple in the case of a doublet, Kα1 Kα2, which can be expressed as follows: I(x) = I_{K\alpha_{1}}(x) + \textstyle{1\over2} I_{K\alpha_{1}}(x - \Delta). IKα1(x) is given by the previous expression, Δ represents the angular separation of the doublet. Different forms of profiles are used in order to verify the validity of the relation proposed and the results are compared with those resulting from the Rachinger classical method.