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Notes: Abstract We study quantum (Shubnikov-de Haas and de Haas-van Alphen) oscillations and angular oscillations of the reluctance in the organic quasi-two-dimensional metal (BO)2Clx(H2O)y. We show that the Fermi surface in this compound consists of a slightly corrugated cylinder with its axis perpendicular to the conducting plane. The cross section of the cylinder in this plane is a perfect circle of radius k F≃3×107 cm−1. The effective carrier mass associated with this cylinder is m*=(1.65–2.0) m 0 in the conducting plane, while the Dingle temperature is T D=3–4 K.

Notes: Abstract Magnetoresistance and magnetic torque have been studied in the single crystals of the mixed complex (ET)2TlHg(S0.45Se0.55CN)4. The quantum oscillations (Shubnikov-de Haas and de Haas-van Alphen) have been observed and investigated in details in this compound. The behavior of these oscillations is close to that in the complex (ET)2TlHg(SeCN)4 but is characterized by a stronger carrier scattering induced by the disordered positions of the S and Se atoms in the anion.

Notes: Abstract Quantum de Haas-van Alphen oscillations and semiclassical angular magnetoresistance oscillations are observed in the quasi-two-dimensional organic metal κ-(BETS)2GaCl4. The behavior of these oscillations attests to the existence of two cylindrical Fermi surface sheets with axes perpendicular to the conducting plane. The cross-sectional areas of these cylinders in the conducting plane are equal to about 20 and 100% of the corresponding cross section of the Brillouin zone. It is shown that the many-particle interaction can be suppressed significantly in this compound.

Notes: A Faraday-type magnetometer is described in which the magnetic force is measured capacitively by monitoring the displacement of a spring-suspended quartz sample holder. A double gradient coil is used in order to compensate the force on the empty sample holder, thus minimizing the background signal. The magnetometer can be used at any temperature down to 1.4 K and has an ultimate sensitivity for magnetic moments of 2×10−6emu (G cm3).© 1997 American Institute of Physics.

Notes: Summary New results as revealed by scanning and transmission electron microscopy have given us further knowledge about the structure of the olfactory region of vertebrates. With comparative studies we are now able to discuss the functional relationship of this region. In all vertebrates the olfactory cell is a primary sensory cell. The apical segment of the olfactory cell with its olfactory vesicle is involved in the formation of the olfactory border. As a rule the receptor possesses cilia or cilia-like processes. These are absent in the olfactory receptor of the shark, the microvillus receptor of the fish and the olfactory cell of Jabonsons organ of amphibians, reptiles and mammals. The odorous substances in the fish are brought to the receptor membrane by the water flow. In air breathing vertebrates a terminal film is present. This film is a product of secretion from the Bowmans glands. Gasous odorous substances must first be dissolved in the terminal film and penetrate it before reaching the receptor membrane. The cilia-like olfactory process of the fish in the proximal segment is not essentially different from the kinocilia of the supporting cell, except that they are shorter. In contrast the olfactory cell of air-breathing vertebrates form cilia-like processes with a short cilia-like proximal segment and a long and very thin distal end piece. In the amphibians and sauropsidians the end pieces can have a lenght of up to 150 μ and up to 80 μ in mammals. The olfactory vesicles with its processes undergo continuous regeneration. The olfactory epithelium of man show the same structural formation as observed in other mammals. Regressive changes in the adult can lead to a reduction in the number of sensory cells and also to a flattening of the epithelium. Morphological criteria for regenerative processes in the sensory cell structures are present. A specialized olfactory cell type has been found in some teleosts. This cell is characterized by a small pit below the olfactory border in which the cilia of the olfactory cell are redrawn. There is some evidence that this olfactory cell type may be compared with the olfactory cells in the parafollicular tubes of lamprey. The so called rod-shaped receptor in the olfactory mucosa of fishes has no axon and is therefore no olfactory cell. The same kind of cell is also present in the olfactory mucosa of airbreathing animals. We classify this cell as brush cell. Comparative electron microscopic studies reveal identical ultrastructural organization of the olfactory bulb in all classes of vertebrates, including cyclostomes and man. The size and structure of synapses in the olfactory bulb are specific for each connection type. The dark endings of the olfactory receptor cells have small axo-dendritic contacts to the bright mitral or tufted cell processes within the glomeruli. Granule cells, periglomerular cells and mitral cells interact by dendro-dendritic, dendro-axonic and somato-dendritic synaptic complexes which often have “reciprocal” arrangements. Presynaptic endings on the granule cell dendrites and somata contain a large number of small synaptic vesicles and have membrane complexes more than 0.5 μm in diameter. In the periventricular or central zone of the olfactory bulb excitatory synapses with interdigitation between the pre- and postsynaptic processes are present. We are able to give schematic representations of postulated nerve circuits with the aid of the different morphological appearances of the different synapses. The cellular composition of the taste buds of different mammals can be described from electron microscopical studies. As a rule 5 cell types which regenerate through mitosis from the basal or marginal cells can be differentiated. Only the active sensory cell forms synaptic membrane complexes. It sends rod-shaped processes into the taste pores. Growing and dying sensory cells do not possess these processes. The supporting cells surround the single sensory cell. The apical pole of the supporting cell enters the taste pore by a bundle of microvilli. Secretory granules accumulate in the apical part of the supporting cell and empty their contents into the taste pore. The terminal processes of the myelinated afferent nerve fibres form a plexus in the lamina propria and penetrate the taste bud with numerous itraepithelial branchings.

Notes: Abstract We have measured the specific heat capacity of a single crystal of UPt3 in zero magnetic field, in 2 T, and in 4 T (above $$B_{C_2 } $$ )with the adiabatic warm-up method down to a final temperature of 15 mK. The results prove our previous assumption that the normal state of UPt3 exhibits a similar, slightly modified specific heat anomaly around 20 mK as is present in the superconducting state. It is most probably a signature of long range magnetic order. Entropy balance aboveT C is fulfilled if both low-temperature peaks are included. For UBe13 (in the superconducting state) we find no specific heat anomaly down to 24 mK but a deviation from the power law valid at higher temperatures. DC-magnetization measurements on a second single crystal of UPt3 in a SQUID system yield a temperature dependence ∼T 2 between 150 and 20 mK extending the temperature range of earlier measurements by a factor of 4.

Notes: Abstract Measurements of the γ-ray anisotropy of recoil-implanted52Mn ions in pure Au down to 3 mK indicate marked deviations from free-ion behavior in low applied fields. The effective hyperfine field that explains the anisotropy is found to decrease below 10 mK. Although this behavior could be a signature of a “bound” Kondon state with a lower effective hyperfine coupling constant, it is better explained as arising from a combination of Kondo and relaxation effects. The data indicate that the Mn local moment relaxation timeT 1 is comparable to or larger than the Larmor precession time of the Mn nuclei at 3 mK. Other possible reasons for an attenuated γ-ray anisotropy, such as nuclear quadrupole and second-order crystal field effects, are also considered.

Notes: Abstract The specific heat of several CeNiSn single crystals of various purity has been measured in the temperature range from 25 mK to 5 K and in magnetic fields from zero to 7 Tesla. At very low temperatures (below ∼200 mK) the specific heat is found to vary linearly with temperature (C=γT), the coefficient γ decreasing with increasing purity. Above 200 mK, the specific heat is well described as the sum of a linear and a quadratic term. An applied magnetic field affects mostly the linear term, which first slightly decreases, then strongly increases with field. In magnetic fields, a nuclear hyperfine specific heat contribution is superimposed, which is due mostly to the bare Zeeman-splitting of the 115 Sn, 117 Sn, 119 Sn nuclei (all with spin I=1/2 and with abundances of 0.35, 7.61, and 8.58% respectively) in the externally applied field. The results on the specific heat at very low temperatures in applied fields fit into the model of an enhanced (heavy-fermion type) density of states which is modified by coherent antiferromagnetic fluctuations into a V-shaped density of states at the Fermi energy.

Notes: Abstract The temperature dependence of the muon spin relaxation rate \lambda was measured in two samples of CeNiSn with markedly different impurity content and in the quasi‐ternary compounds CePtxNi1-xSn (x=0.12,\ ,0.2) and CeCuxNi1-xSn (x=0.05,\ ,0.1,\ ,0.2) in order to study the development of magnetic correlations. No significant change in \lambda was found for the two samples of CeNiSn although their low temperature specific heat differs strongly. Hence μSR probes the intrinsic magnetic properties of the spin‐liquid state of CeNiSn. Replacing Ni with up to 20% Pt results only in minor changes of \lambda. In contrast, a strong effect is seen when Ni is replaced by Cu. Already at 10% Cu the system forms a spin‐glass‐like state below 0.9 K. At 20% Cu this behavior is strengthened, but antiferromagnetic order of the type seen in CePtSn or CePdSn is not reached. The results show further that the change in 4f hybridization initiated by volume expansion in the alloyed samples is not the dominating mechanism strengthening the magnetic correlations. Decisive is the increase in d electron density when replacing Ni by Cu.

Notes: Abstract We present zero and longitudinal field μ SR measurements of single crystal and polycrystalline specimens of the heavy fermion compound CePt2Sn2. Above 1 K the behaviour of the two samples is indistinguishable; the muon 1/T_1 increases with decreasing temperature until 25 K when it plateaus. The 1/T_1 relaxation rate differs strongly for the two cases below \sim\,0.8\ K. At 0.1 K a rate of about 20 μ s-1 is seen in the polycrystal while in the single crystal it is only about 5 μ s-1. Even more revealing is the fact that longitudinal field decoupling spectra at very low temperatures demonstrate an essentially static spin system to be present in the polycrystalline material while the single crystal shows definite dynamic spin properties. We conclude that, in the presence of the distortion, long range magnetic order occurs below 0.9 K while in tetragonal symmetry long range order is suppressed (probably due to frustration) and spin fluctuations remain for T\rightarrow0.