Showing papers by "Max Planck Society published in 1987"

Plasma Physics and Controlled Nuclear Fusion Research

Abstract: FIRST EXPERIMENTS IN JET. Results obtained from JET since June 1983 are described which show that this large tokamak behaves in a similar manner to smaller tokamaks, but with correspondingly improved plasma parameters. Long-duration hydrogen and deuterium plasmas (>10 s) have been obtained with electron temperatures reaching > 4 keV for power dissipations < 3 MW and with * Euratom-IPP Association, Institut fur Plasmaphysik, Garching, Federal Republic of Germany. ** Euratom-ENEA Association, Centro di Frascati, Italy. *** Euratom-UKAEA Association, Culham Laboratory, Abingdon, Oxfordshire, United Kingdom. **** University of Dusseldorf, Dusseldorf, Federal Republic of Germany. + Euratom-Ris0 Association, Ris National Laboratory, Roskilde, Denmark. ++ Euratom-CNR Association, Istituto di Física del Plasma, Milan, Italy. +++ Imperial College of Science and Technology, University of London, London, United Kingdom. ++++ Euratom-FOM Association, FOM Instituut voor Plasmafysica,. Nieuwegein, Netherlands. ® Euratom-Suisse Association, Centre de Recherches en Physique des Plasmas, Lausanne, Switzerland.

The foreign antigen binding site and T cell recognition regions of class I histocompatibility antigens

Abstract: Most of the polymorphic amino acids of the class I histocompatibility antigen, HLA-A2, are clustered on top of the molecule in a large groove identified as the recognition site for processed foreign antigens. Many residues critical for T-cell recognition of HLA are located in this site, in positions allowing them to serve as ligands to processed antigens. These findings have implications for how the products of the major histocompatibility complex (MHC) recognize foreign antigens.

Theoretical propositions of life-span developmental psychology : On the dynamics between growth and decline

Abstract: Life-span developmental psychology involves the study of constancy and change in behavior throughout the life course. One aspect of life-span research has been the advancement of a more general, metatheoretical view on the nature of development. The family of theoretical perspectives associated with this metatheoretical view of life-span developmental psychology includes the recognition of multidirectionality in ontogenetic change, consideration of both age-connected and disconnected developmental factors, a focus on the dynamic and continuous interplay between growth (gain) and decline (loss), emphasis on historical embeddedness and other structural contextual factors, and the study of the range of plasticity in development. Application of the family of perspectives associated with life-span developmental psychology is illustrated for the domain of intellectual development. Two recently emerging perspectives of the family of beliefs are given particular attention. The first proposition is methodological and suggests that plasticity can best be studied with a research strategy called testing-the-limits. The second proposition is theoretical and proffers that any developmental change includes the joint occurrence of gain (growth) and loss (decline) in adaptive capacity. To assess the pattern of positive (gains) and negative (losses) consequences resulting from development, it is necessary to know the criterion demands posed by the individual and the environment during the lifelong process of adaptation. The study of life-span development is not a homogeneous field. It comes in two major interrelated modes. The first mode is the extension of developmental studies across the life course without a major effort at the construction of metatheory that emanates from life-span work. The second mode includes the endeavor to explore whether life-span research has specific implications for the general nature of developmental theory. The second approach represents the topic of this article. Specifically, the purpose of this article is twofold. First, after a brief introduction to the field of life-span developmental psychology, some "prototypical" features of the life-span approach in developmental psychology are presented. Second, these features are illustrated by work in one domain: intellectual development. Although the focus of this paper is on life-span developmental psychology and its theoretical thrust, it is important to recognize at the outset that similar perspectives on developmental theory have been advanced in other quarters of developmental scholarship as well (Hetherington & Baltes, in press; Scan; 1986). There is, however, a major difference in the "gestalt" in which the features of the theoretical perspective of life-span psychology are organized.

Mechanism of anion permeation through channels gated by glycine and gamma-aminobutyric acid in mouse cultured spinal neurones.

Abstract: 1 The ion-selective and ion transport properties of glycine receptor (GlyR) and gamma-aminobutyric acid receptor (GABAR) channels in the soma membrane of mouse spinal cord neurones were investigated using the whole-cell, cell-attached and outside-out patch versions of the patch-clamp technique 2 Current-voltage (I-V) relations of transmitter-activated currents obtained from whole-cell measurements with 145 mM-Cl- intracellularly and extracellularly, showed outward rectification In voltage-jump experiments, the instantaneous I-V relations were linear, and the steady-state I-V relations were rectifying outwardly indicating that the gating of GlyR and GABAR channels is voltage sensitive 3 The reversal potential of whole-cell currents shifted 56 mV per tenfold change in internal Cl- activity indicating activation of Cl(-)-selective channels The permeability ratio of K+ to Cl- (PK/PCl) was smaller than 005 for both channels 4 The permeability sequence for large polyatomic anions was formate greater than bicarbonate greater than acetate greater than phosphate greater than propionate for GABAR channels; phosphate and propionate were not measurably permeant in GlyR channels This indicates that open GlyR and GABAR channels have effective pore diameters of 52 and 56 A, respectively The sequence of relative permeabilities for small anions was SCN- greater than I- greater than Br- greater than Cl- greater than F- for both channels 5 GlyR and GABAR channels are multi-conductance-state channels In cell-attached patches the single-channel slope conductances close to 0 mV membrane potential were 29, 18 and 10 pS for glycine, and 28, 17 and 10 pS for GABA-activated channels The most frequently observed (main) conductance states were 29 and 17 pS for the GlyR and GABAR channel, respectively 6 In outside-out patches with equal extracellular and intracellular concentrations of 145 mM-Cl-, the conductance states were 46, 30, 20 and 12 pS for GlyR channels and 44, 30, 19 and 12 pS for GABAR channels The most frequently occurring main state was 46 pS for the GlyR and 30 pS for the GABAR channel 7 Single-channel conductances measured in equal 140 mM concentrations of small anions on both membrane faces revealed a conductance sequence of Cl- greater than Br- greater than I- greater than SCN- greater than F- for both channels This is nearly the inverse sequence of that found for the permeability of these ions indicating the presence of binding sites for ions in the channel(ABSTRACT TRUNCATED AT 400 WORDS)

Observation of quantum collapse and revival in a one-atom maser.

Abstract: The dynamics of the interaction of a single Rydberg atom with a single mode of an electromagnetic field in a superconducting cavity was investigated. Velocity-selected atoms were used and the evolution of the atomic inversion as atom and field exchange energy was observed. The quantum collapse and revival predicted by the Jaynes-Cummings model were demonstrated experimentally for the first time. The evaluation of the dynamic behavior of the atoms allows us to determine the statistics of the few photons in the cavity.

Thought contents and cognitive functioning in motivational versus volitional states of mind

Abstract: Do people who are about to make a decision differ from people who are about to enact a decision just made with respect to (1) the contents of their spontaneous stream of thought, and (2) aspects of cognitive functioning reflective of short-term memory? Subjects either made a choice between, or were assigned to, two available test materials allegedly designed to measure creativity and differentially suited to promote an individual's full creative potential. Subjects were, however, interrupted prior to or shortly after making this choice: In Study 1, they were asked to report on the thoughts they experienced during the time period just before the interruption; in Study 2, subjects were interrupted either before or after making a choice and were asked to recall lists of words designed to test memory span. The results of Study 1 confirmed our assumption that predecisional versus postdecisional streams of spontaneous thought reflectmotivational versusvolitional states of mind. That is, predecisional thought was preoccupied with incentive values of goal options, expectancy of performance outcomes, and metamotivational directives, whereas postdecisional thought was concerned with questions of how to implement the pursued goal. In Study 2, subjects in a motivational state of mind exhibited a greater memory span than subjects in a volitional state of mind. Since, in a further study, performance on arithmetic tasks did not improve for subjects in a motivational as opposed to a volitional state of mind, the results of Study 2 are understood as a state-dependent increase in receptivity with respect to incoming information. In interpreting the present findings, the characteristic features of motivational and volitional states are explicated. Furthermore, it is suggested that the dominating research tradition focusing on motivational problems (i.e., expectancy-value models) and the abandoned research tradition concerned with volitional problems (i.e., formation and implementation of an intent) should be integrated into a functional unit.

Interleukin-1 regulates synthesis of nerve growth factor in non-neuronal cells of rat sciatic nerve.

Abstract: The Schwann cells and fibroblast-like cells of the intact sciatic nerve of adult rats synthesize very little nerve growth factor (NGF) (ref. 1). After lesion, however, there is a dramatic increase in the amounts of both NGF-mRNA and NGF protein synthesized by the sciatic non-neuronal cells1,2. This local increase in NGF synthesis partially replaces the interrupted NGF supply from the periphery to the NGF-responsive sensory and sympathetic neurons, whose axons run within the sciatic nerve1. Macrophages, known to invade the site of nerve lesion during wallerian degeneration3,4, are important in the regulation of NGF synthesis5. Here we demonstrate that the effect of macrophages on NGF-mRNA levels in cultured explants of sciatic nerve can be mimicked by conditioned media of activated macrophages, and that interleukin-1 is the responsible agent.

New Hamiltonian formulation of general relativity

Abstract: The phase space of general relativity is first extended in a standard manner to incorporate spinors. New coordinates are then introduced on this enlarged phase space to simplify the structure of constraint equations. Now, the basic variables, satisfying the canonical Poisson-brackets relations, are the (density-valued) soldering forms \ensuremath{\sigma}\ifmmode \tilde{}\else \~{}\fi{} $^{a}$${\mathrm{}}_{A}$${\mathrm{}}^{B}$ and certain spin-connection one-forms ${A}_{\mathrm{aA}}$${\mathrm{}}^{B}$. Constraints of Einstein's theory simply state that \ensuremath{\sigma}\ifmmode \tilde{}\else \~{}\fi{} $^{a}$ satisfies the Gauss law constraint with respect to ${A}_{a}$ and that the curvature tensor ${F}_{\mathrm{abA}}$${\mathrm{}}^{B}$ and ${A}_{a}$ satisfies certain purely algebraic conditions (involving \ensuremath{\sigma}\ifmmode \tilde{}\else \~{}\fi{} $^{a}$). In particular, the constraints are at worst quadratic in the new variables \ensuremath{\sigma}\ifmmode \tilde{}\else \~{}\fi{} $^{a}$ and ${A}_{a}$. This is in striking contrast with the situation with traditional variables, where constraints contain nonpolynomial functions of the three-metric. Simplification occurs because ${A}_{a}$ has information about both the three-metric and its conjugate momentum. In the four-dimensional space-time picture, ${A}_{a}$ turns out to be a potential for the self-dual part of Weyl curvature. An important feature of the new form of constraints is that it provides a natural embedding of the constraint surface of the Einstein phase space into that of Yang-Mills phase space. This embedding provides new tools to analyze a number of issues in both classical and quantum gravity. Some illustrative applications are discussed. Finally, the (Poisson-bracket) algebra of new constraints is computed. The framework sets the stage for another approach to canonical quantum gravity, discussed in forthcoming papers also by Jacobson, Lee, Renteln, and Smolin.

The regulatory c1 locus of Zea mays encodes a protein with homology to myb proto-oncogene products and with structural similarities to transcriptional activators.

Abstract: The structure of the wild-type c1 locus of Zea mays was determined by sequence analysis of one genomic and two cDNA clones. The coding region is composed of three exons (150 bp, 129 bp and one, at least 720 bp) and two small introns (88 bp and 145 bp). Transcription of the mRNAs corresponding to the two cDNA clones cLC6 (1.1 kb) and cLC28 (2.1 kb) starts from the same promoter. Both cDNAs are identical except that cLC28 extends further at its 3' end. A putative protein, 273 amino acids in length was deduced from the sequence of both transcripts. It contains two domains, one basic and the other acidic and might function as a transcriptional activator. The basic domain of this c1-encoded protein shows 40% sequence homology to the protein products of animal myb proto-oncogenes.

Long-term potentiation and NMDA receptors in rat visual cortex

Abstract: In the hippocampus, which is phylogenetically older than the cerebral neocortex, high frequency stimulation of afferent pathways leads to long-term potentiation (LTP) of synaptic transmission1–5. This use-dependent malleability is of considerable interest because it may serve as a substrate for memory processes. However, in the neocortex, whose involvement in learning is undisputed, attempts to demonstrate LTP have remained inconclusive6–8. Here we use intracellular recording techniques to show that LTP can be induced by high frequency stimulation of the optic radiation in slices of the visual cortex of adult rats. We identify as a necessary prerequisite for the induction of LTP the activation of the membrane channel that is associated with the NMDA (N-methyl-D-aspartate) receptor. Selective blockade of this receptor system with DL-2-amino-5-phosphonovalerate consistently prevents LTP as in most hippocampal pathways9–11. In most cortical neurons the activation of the NMDA mechanism and hence the induction of LTP in these experiments requires a concomitant reduction of GABAergic inhibition by low doses of the GABAA antagonist bicuculline. This indicates that in the neocortex the activation threshold of the NMDA-mechanism and consequently the susceptibility to LTP, are strongly influenced by inhibitory processes.

Blockade of "NMDA" receptors disrupts experience-dependent plasticity of kitten striate cortex

Abstract: Intracortical infusion of the "N-methyl-D-aspartate" (NMDA) receptor blocker D,L-2-amino-5-phosphonovaleric acid (APV) renders kitten striate cortex resistant to the effects of monocular deprivation. In addition, 1 week of continuous APV treatment (50 nanomoles per hour) produces a striking loss of orientation selectivity in area 17. These data support the hypothesis that crucial variables for the expression of activity-dependent synaptic modifications are a critical level of postsynaptic activation and calcium entry through ion channels linked to NMDA receptors.

Origin of the scattering peak in microemulsions

Abstract: From a Landau theory the static scattering intensity distribution I(q) of microemulsions is obtained. As essential ingredient we have included a negative gradient term in the free energy expression. The form of I(q)∼(a2+c1q2+c2q4)−1 yields for a2>0, c1 0 a single broad scattering peak and a q−4 decay at large q, both properties experimentally observed for a variety of microemulsions containing comparable amounts of water and oil. The peak originates from the modulation in the corresponding space correlation function given by γ(r)=(d/2πr)⋅e−r/ξ⋅sin(2πr/d). It is shown that the scattering intensity relation describes experimental literature data remarkably well, using only three fit parameters.

Differential regulation of mRNA encoding nerve growth factor and its receptor in rat sciatic nerve during development, degeneration, and regeneration: role of macrophages.

Abstract: In newborn rats the levels of nerve growth factor (NGF) mRNA (mRNANGF) and NGF receptor mRNA (mRNA(rec)) in the sciatic nerve were 10 and 120 times higher, respectively, than in adult animals. mRNA(rec) levels decreased steadily from birth, approaching adult levels by the third postnatal week, whereas mRNANGF levels decreased only after the first postnatal week, although also reaching adult levels by the third week. Transection of the adult sciatic nerve resulted in a marked biphasic increase in mRNANGF with time. On the proximal side of the cut, this increase was confined to the area immediately adjacent to the cut; peripherally, a similar biphasic increase was present in all segments. mRNA(rec) levels were also markedly elevated distal to the transection site, in agreement with previous results obtained by immunological methods [Taniuchi, M., Clark, H. B. & Johnson, E. M., Jr. (1986) Proc. Natl. Acad. Sci. USA 83, 4094-4098]. Following a crush lesion (allowing regeneration), the mRNA(rec) levels were rapidly down-regulated as the regenerating nerve fibers passed through the distal segments. Down-regulation of mRNANGF also occurred during regeneration but was slower and not as extensive as that of mRNA(rec) over the time period studied. Changes in mRNANGF and mRNA(rec) occurring in vivo after transection were compared with those observed in pieces of sciatic nerve kept in culture. No difference was found for mRNA(rec). Only the initial rapid increase in mRNANGF occurred in culture, but the in vivo situation could be mimicked by the addition of activated macrophages. This reflects the situation in vivo where, after nerve lesion, macrophages infiltrate the area of the Wallerian degeneration. These results suggest that mRNANGF synthesis in sciatic non-neuronal cells is regulated by macrophages, whereas mRNA(rec) synthesis is determined by axonal contact.

A study in developing visual systems with a new method of staining neurones and their processes in fixed tissue.

Abstract: Carbocyanine dyes, fluorescent lipophilic substances used for optical recordings of membrane voltage and for studies of membrane fluidity, have recently been shown to provide intense and long-lasting staining of neurones in vivo and in vitro (Schwartz & Agranoff, 1981; Honig & Hume, 1985, 1986; Catsicas, Thanos & Clarke, 1986; Landmesser & Honig, 1986; Thanos & Bonhoeffer, 1987). We report here that two of these dyes, diI (1,1',dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate) and diO (3,3'-dioctadecyloxacarbocyanine perchlorate), can also label neurones in embryonic mouse and chicken brain tissue that has been previously fixed in aldehyde fixatives. Neuronal processes and perikarya can be labelled along considerable distances in both anterograde and retrograde directions. The staining of processes and cells, including their finest extensions is smooth and clear, rivalling intracellular injections of HRP or Lucifer Yellow. The appearance and time course of progression of the staining along axons suggest that the staining in fixed tissue occurs due to a process of diffusion of dyes along the plasma membranes of cells. This technique has allowed us to study the first stages in the development of optic fibres in mouse embryos, especially at the optic chiasm. The early retinal projection (E13-E13 1/2) is mainly crossed, but some optic fibres grow to the ipsilateral side of the brain at the outset. Retrogradely labelled ganglion cells from the dorsocentral area of the retina participate in the formation of both the ipsilateral and the contralateral projection. Thus, at early stages, crossed and uncrossed projections arise from identical subregions of the retina and the partition of the retina with respect to the laterality of its projection arises later.

The strychnine-binding subunit of the glycine receptor shows homology with nicotinic acetylcholine receptors.

Abstract: We have cloned and sequenced cDNAs of the strychnine-binding subunit of the rat glycine receptor, a neurotransmitter-gated chloride channel protein of the CNS. The deduced polypeptide shows significant structural and amino-acid sequence homology with nicotinic acetylcholine receptor proteins, indicating that there is a family of genes encoding neurotransmitter-gated ion channels.

Interband critical points of GaAs and their temperature dependence

Abstract: The complex dielectric function \ensuremath{\epsilon}(\ensuremath{\omega}) of GaAs was measured from 20 to 750 K with a scanning rotating-analyzer ellipsometer. The structures observed in the 1.3\char21{}5.5-eV photon-energy region, attributed to transitions near the \ensuremath{\Gamma} point of the Brillouin zone (${E}_{0}$, ${E}_{0}$+${\ensuremath{\Delta}}_{0}$, ${E}_{0}^{\mathcal{'}}$), along the \ensuremath{\Lambda} direction (${E}_{1}$, ${E}_{1}$+${\ensuremath{\Delta}}_{1}$), and near the X point (${E}_{2}$), are analyzed by fitting the second-derivative spectrum ${d}^{2}$\ensuremath{\epsilon}(\ensuremath{\omega})/d${\ensuremath{\omega}}^{2}$ to analytic critical-point line shapes. The ${E}_{0}^{\mathcal{'}}$ and ${E}_{2}$ critical points are best fitted in the whole temperature region by a two-dimensional line shape, whereas the ${E}_{1}$ and ${E}_{1}$+${\ensuremath{\Delta}}_{1}$ transitions are best fitted up to room temperature by a Lorentzian interacting with a continuum of interband transitions (Fano line shape). The excitonic character of the ${E}_{1}$ and ${E}_{1}$+${\ensuremath{\Delta}}_{1}$ transitions is discussed within several theoretical approaches. The experiments indicate that up to room temperature the localized Lorentzian interacting with the continuum is dominant, whereas at higher temperatures the modification of the two-dimensional Van Hove singularity due to the electron-hole attractive perturbation is a better description of the measurements. For all critical points, the energy decreases with increasing temperature while the broadening increases. This dependence on temperature is analyzed in terms of averaged phonon frequencies which cause a renormalization of the energies and a broadening of the band gaps.

Transport and storage of CO2 in the ocean ——an inorganic ocean-circulation carbon cycle model

Abstract: Inorganic carbon in the ocean is modelled as a passive tracer advected by a three-dimensional current field computed from a dynamical global ocean circulation model. The carbon exchange between the ocean and atmosphere is determined directly from the (temperature-dependent) chemical interaction rates in the mixed layer, using a standard CO2 flux relation at the air-sea interface. The carbon cycle is closed by coupling the ocean to a one-layer, horizontally diffusive atmosphere. Biological sources and sinks are not included. In this form the ocean carbon model contains essentially no free tuning parameters. The model may be regarded as a reference for interpreting numerical experiments with extended versions of the model including biological processes in the ocean (Bacastow R and Maier-Reimer E in prep.) and on land (Esser G et al in prep.). Qualitatively, the model reproduces the principal features of the observed CO2 distribution bution in the surface ocean. However, the amplitudes of surface pCO2 are underestimated in upwelling regions by a factor of the order of 1.5 due to the missing biological pump. The model without biota may, nevertheless, be applied to compute the storage capacity of the ocean to first order for anthropogenic CO2 emissions. In the linear regime, the response of the model may be represented by an impulse response function which can be approximated by a superposition of exponentials with different amplitudes and time constants. This provides a simple reference for comparison with box models. The largest-amplitude (∼0.35) exponential has a time constant of 300 years. The effective storage capacity of the oceans is strongly dependent on the time history of the anthropogenic input, as found also in earlier box model studies.

Gene structure and extracellular secretion of Neisseria gonorrhoeae IgA protease

Abstract: Several human bacterial pathogens, including the Gram-negative diplococcus Neisseria gonorrhoeae, produce extracellular proteases that are specific for human immunoglobulin IgA1, (refs 1, 2). Immunoglobulin A (IgA) proteases have been studied extensively and the genes of some species cloned in Escherichia coli3–7, but their role in pathogenesis remains unclear8. Recently we derived a DNA fragment of 5 kilobases (kb) from N. gonorrhoeae MS 11 directing extracellular active enzyme in E. coli4. Although the mature enzyme of strain MS 11 was shown to have a relative molecular mass of 106,000 (Mr 106K) in gels4, the DNA sequence of this cloned fragment reveals a single gene coding for a 169K precursor of IgA protease. The precursor contains three functional domains, the amino-terminal leader which is assumed to initiate the inner membrane transport of the precursor, the protease, and a carboxyl-terminal 'helper' domain apparently required for extracellular secretion (excretion). Based on the structural features of the precursor, we propose a model in which the helper serves as a pore for excretion of the protease domain through the outer membrane. IgA protease acquires an active conformation as its extracellular transport proceeds and is released as a proform from the membrane-bound helper by autoproteolysis. The soluble proform further matures into the 106 K IgA protease and a small stable α-protein.

Determination of anteroposterior polarity in Drosophila

Abstract: The principles of pattern formation in embryogenesis can be studied in Drosophila by means of a powerful combination of genetic and transplantation experiments. The segmented pattern of the Drosophila embryo is organized by two activities localized at the anterior and posterior egg poles. Both activities exert inducing and polarizing effects on the pattern when transplanted to other egg regions. A small set of maternal genes have been identified that are required for these activities. Mutants in these genes lack either the anterior or posterior part of the segmented pattern. The unsegmented terminal embryonic regions require a third class of genes and form independently of the anterior and posterior centers.

Temperature dependence of the dielectric function and interband critical points in silicon

Abstract: The complex dielectric function \ensuremath{\epsilon}(\ensuremath{\omega}) of Si was measured ellipsometrically in the 1.7--5.7-eV photon-energy range at temperatures between 30 and 820 K. The observed structures are analyzed by fitting the second-derivative spectrum ${d}^{2}$\ensuremath{\epsilon}/d${\ensuremath{\omega}}^{2}$ with analytic critical-point line shapes. Results for the temperature dependence of the parameters of these critical points, labeled ${E}_{0}^{\mathcal{'}}$, ${E}_{1}$, ${E}_{2}$, and ${E}_{1}^{\mathcal{'}}$, are presented. The data show good agreement with microscopic calculations for the energy shift and the broadening of interband transitions with temperature based on the electron-phonon interaction. The character of the ${E}_{1}$ transitions in semiconductors is analyzed. We find that for Si and light III-V or II-VI compounds an excitonic line shape represents best the experimental data, whereas for Ge, \ensuremath{\alpha}-Sn, and heavy III-V or II-VI compounds a two-dimensional critical point yields the best representation.

Complete integrability of relativistic Calogero-Moser systems and elliptic function identities

Abstract: Poincare-invariant generalizations of the Galilei-invariant Calogero-Moser AΓ-particle systems are studied. A quantization of the classical integrals S1?...,SN is presented such that the operators Si9...,SN mutually commute. As a corollary it follows that Si9...9SN Poisson commute. These results hinge on functional equations satisfied by the Weierstrass σ- and 0*- functions. A generalized Cauchy identity involving the σ-function leads to an N x N matrix L whose symmetric functions are proportional to Sl5 ...9SN.

Multiple Light Scattering from Disordered Media. The Effect of Brownian Motion of Scatterers

Abstract: We have measured the time autocorrelation function of the light intensity multiply scattered from turbid aqueous suspensions of submicron size polystyrene spheres in directions near backscattering. It is found strongly non-exponential at short times revealing the very fast decay of coherence in extended scattering loops due to the thermal motion of the many spheres involved; the longest living decay time is found remarkably close to the single particle backscattering relaxation time even under conditions of interparticle interactions. These features are only weakly affected by the particular interference effect between time-reversed pairs of loops giving rise to the coherent backscattering enhancement. A simple argument is presented which accounts for these observations.

Timing and site of nerve growth factor synthesis in developing skin in relation to innervation and expression of the receptor

Abstract: We show that nerve growth factor (NGF) synthesis in developing skin begins with sensory innervation and that sensory neurons do not express NGF receptors until their fibres reach their cutaneous targets. Both cutaneous epithelium and mesenchyme synthesize NGF, the concentration of messenger RNA for NGF being higher in the more densely innervated epithelium.