Real time noise and wavelength correlations in octave-spanning supercontinuum generation.

We use dispersive Fourier transformation to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation. We study both the onset phase of supercontinuum generation with distinct dispersive wave generation, as well as a highly-unstable supercontinuum regime spanning an octave in bandwidth. Wavelength correlation maps allow interactions between separated spectral components to be identified, even when such interactions are not apparent in shot-to-shot or average measurements. Experimental results are interpreted using numerical simulations. Our results show the clear advantages of dispersive Fourier transformation for studying spectral noise during supercontinuum generation.

Spectral dynamics of modulation instability described using Akhmediev breather theory.

The Akhmediev breather formalism of modulation instability is extended to describe the spectral dynamics of induced multiple sideband generation from a modulated continuous wave field. Exact theoretical results describing the frequency domain evolution are compared with experiments performed using single mode fiber around 1550 nm. The spectral theory is shown to reproduce the depletion dynamics of an injected modulated continuous wave pump and to describe the Fermi-Pasta-Ulam recurrence and recovery towards the initial state. Realistic simulations including higher-order dispersion, loss, and Raman scattering are used to identify that the primary physical factors that preclude perfect recurrence are related to imperfect initial conditions.

Ultrastructural localization of acid mucosubstances in the mouse colon with iron-containing stains.

Selective ultrastructural staining of acid mucosubstances in sites containing histochemically identifiable sulfo- and sialomucins has been obtained in fixed cryostat sections with both ferric chloride and colloidal iron solutions. The rectosigmoid region of mouse colon was fixed in glutaraldehyde, formalin, or phosphate-buffered osmium tetroxide, and 40 micro cryostat sections of this material were treated with 0.1 to 0.4% ferric chloride or with a solution of dialyzed ferric chloride, ammonia, and glycerin. Specific staining depended upon the pH of the iron-containing solutions, and the optimal value was found to be approximately 2.0. Specific localization of acid mucosubstances has been noted in intracellular sites, including globules within colonic goblet cells and "deep crypt" mucous cells, small vesicles of the superficial nongoblet epithelial cells, and Golgi lamellae within each of these cell types. Extracellular material, presumed to be acid mucosubstance, was found on the surface of the epithelial microvilli and on the lumenal surface of capillary endothelium. Similar material formed a reticular network surrounding stromal cells, collagen bundles, and various colonic connective tissue elements.

Human lymphocytes: similarity of B and T cell surface morphology.

When viewed by scanning electron microscopy human lymphocytes fixed in suspension and processed with minimal cell loss appear uniformly covered with short microvilli. Contrary to previous reports, lymphocytes from subpopulations selectively enriched for T cells are villous and indistinguishable from B lymphocytes. Whereas lymphocyte surface architecture can change rapidly and substantially in response to environmental modifications, such as contact with an underlying surface, these alterations are similar for both B and T cells and do not serve to distinguish these subpopulations.

Ultrastructural concomitants of sodium butyrate-enhanced ectopic production of chorionic gonadotropin and its alpha subunit human bronchogenic carcinoma (ChaGo) cells.

Sodium butyrate treatment of cultures of ChaGo (human lung cancer) cells resulted in increased production of human chorionic gonadotropin (hCG) and its alpha subunit (hCG-alpha) and induced a variety of morphologic changes. Elongation and flattening of cells were seen by light microscopy. Immunocytochemistry with antisera against hCG and against hCG-alpha showed an increase in cells containing stainable hCG-alpha. Scanning electron microscopy demonstrated enhanced adhesion of cells to glass cover slips, with elongation, flattening, and decreased cytoplasmic blebs. Ultrastructural changes were examined by transmission electron microscopy and evaluated quantitatively by an unbiased observer. Significant findings included increases in perinuclear tonofilaments, smooth endoplasmic reticulum vesicles, dense mitochondrial inclusions, and lipid granules, as well as decreases in intercellular desmosomes, free polyribosomes, mitochondrial dense granules, and Golgi complexes. The most notable change, a marked decrease in condensed chromatin clumps, may have reflected a butyrate-induced biochemical modification of chromatin leading to enhanced accessibility of certain genes for transcription.

Topography of nonneoplastic and neoplastic cells of common origin.

The possibility that neoplastic transformation may characteristically alter cell surface morphology prompted a comparison by scanning electron microscopy of nonneoplastic and tumorigenic cell lines from a single clone of mouse embryo cells. Among those studied by scanning electron microscopy, six lines of this clone proved nonneoplastic, and nine others underwent neoplastic transformation in culture, as evidenced by tumor production in vivo. Combined cinephotomicrography and scanning electron microscopy allowed the determination of postmitotic time and topography of individual cells without perturbing the cells or detectably altering their surface morphology; no pattern of morphological change as a function of postmitotic time was evident in either nonneoplastic or neoplastic cell populations. Accordingly, these cell populations could be compared under their usual conditions of attached asynchronous growth despite differences in proliferation rates. Cells of the neoplastic lines were characteristically less spread, and some lines displayed greater morphological variability than was evident among cells of nonneoplastic lines. However, most cells in all nine neoplastic lines and all six nonneoplastic lines were smooth surfaced. Thus, the exaggerated incidence of microvilli, ruffles, or blebs reported for established tumor-derived lines and most morphologically transformed lines did not prove a reliable criterion of neoplastic state for these cell lines of common origin grown under the same culture conditions.

Structure-activity relationships and pharmacological profile of selective tricyclic antimuscarinics.

The discovery of the M1-selective receptor antagonist pirenzepine was the impetus for a research project directed towards the development of selective muscarinic antagonists. In the pursuit of this objective, compounds with different selectivity profiles have been found. AF-DX 116 was the first cardioselective antagonist synthesized. Subsequently novel M2 receptor antagonists have been discovered with higher potency and selectivity. Moreover, a pirenzepine-type compound UH-AH 37 has been identified that, in contrast to pirenzepine, shows a higher affinity for ileal than for atrial muscarinic receptors. Among tricyclic muscarinic receptor antagonists three different selectivity profiles have been identified, namely: M1 greater than M3 greater than M2, Msm for pirenzepine; M2 greater than M1 greater than M3, Msm for AF-DX 116, AF-DX 384, AQ-RA 741; and Msm congruent to M1 greater than M2, M3 for UH-AH 37 and its (+) enantiomer.

Effects of retinoic acid on embryonic chick skin.

The influence of vitamin A on differentiating epithelia was examined in explants of skin from 14-day chick embryos exposed to retinoic acid (RA) in low, moderate, and high doses. The changes observed in RA-treated cultures are both dose- and time-dependent and are reversible when explants are transferred to control medium. The periderm sloughs prematurely and horizontal stratification is lost. Keratinization is inhibited and fewer desmosomes and tonofilaments are seen. Surface epidermal cells develop microvilli, bulge upwards, and detach. Golgi elements, rough endoplasmic reticulum, and polyribosomes are unusually prominent. Mucin granules form and gland-like structures develop with intercellular canaliculi characterized by tight junctions, brush borders, and dense secretory contents. On the basis of present evidence there are several possible mechanisms by which RA could alter epidermal differentiation. RA-induced gaps in the basal lamina allow direct contact between epidermal basal cells and fibroblasts and collagen fibers which could result in inappropriate dermal signals reaching the epidermis. In younger embryos the entire epidermis, including the mitotically inactive surface cells, appears to respond to RA, and this could imply an epigenetic modulation of cell phenotype. Finally, after the formation of a stratum corneum in older embryos only the relatively undifferentiated basal layer shows a metaplastic response, indicating that RA could be acting directly on the genome.

Cornifying Darier disease--a unique variant. I. Report of a case.

A unique variant of Darier disease is described in which a patient was disabled by large, painful, cutaneous horns present on all extremities. The cornified lesions were distinguished by the presence of numerous corps ronds in the basal portion of the greatly hyperkeratotic stratum corneum, hypertrophic dermal villi containing enlarged capillaries, vacuolar dilatation of rough endoplasmic reticulum in sublacunar basal cells, unusually numerous Odland bodies in spinous cells adjacent to lacunae, and persistent attachment of tonofilaments to disrupted desmosomes. Complete separation of tonofilaments from intact desmosomes was not observed. Scanning electron microscopy revealed varied surface morphological appearances of corps ronds and of the epidermal cells covering the elongated dermal villi. The surface cells of cutaneous horns showed little tendency to desquamate.

Synthesis and antimicrobial activity of pyrimidinylureidocephalosporins.

The synthesis of a series of 7R-[(R)-2-[3-[5-pyrimidinyl]ureido]-2-(aryl)acetamido]-3-cephem-4- carboxylates is described. Variation of the substituents at the 3-position in the cephem nucleus, at the 2-position of the pyrimidine ring, and of the phenyl residue in the acyl side chain is carried out. Qualitative structure-activity relationships in this series are discussed. VX-VD 2, the most interesting compound, exhibits broad antimicrobial activity against Gram-negative bacteria, including Pseudomonas aeruginosa.

Modification of spectinomycin. 2. Derivatives of 4-dihydro-4-deoxy-4(R)-aminospectinomycin.

Acyl derivatives 5a approximately j and alkyl derivatives 7a approximately r of 4-dihydro-4-deoxy-4(R)-aminospectinomycin (1a) were prepared and tested for antibacterial activity. Only acyl compounds derived from long chain aliphatic acids showed activity in vitro, but were inactive when tested in vivo. All alkyl derivatives were active in vitro. In vivo however only the short chain derivatives 7a approximately c were active. Compound 7b showed higher activity than spectinomycin.

Observation of Kuznetsov-Ma soliton dynamics in optical fibre.

The nonlinear Schrödinger equation (NLSE) is a central model of nonlinear science, applying to hydrodynamics, plasma physics, molecular biology and optics. The NLSE admits only few elementary analytic solutions, but one in particular describing a localized soliton on a finite background is of intense current interest in the context of understanding the physics of extreme waves. However, although the first solution of this type was the Kuznetzov-Ma (KM) soliton derived in 1977, there have in fact been no quantitative experiments confirming its validity. We report here novel experiments in optical fibre that confirm the KM soliton theory, completing an important series of experiments that have now observed a complete family of soliton on background solutions to the NLSE. Our results also show that KM dynamics appear more universally than for the specific conditions originally considered, and can be interpreted as an analytic description of Fermi-Pasta-Ulam recurrence in NLSE propagation.

Real-time full bandwidth measurement of spectral noise in supercontinuum generation.

The ability to measure real-time fluctuations of ultrashort pulses propagating in optical fiber has provided significant insights into fundamental dynamical effects such as modulation instability and the formation of frequency-shifting rogue wave solitons. We report here a detailed study of real-time fluctuations across the full bandwidth of a fiber supercontinuum which directly reveals the significant variation in measured noise statistics across the spectrum, and which allows us to study correlations between widely separated spectral components. For two different propagation distances corresponding to the onset phase of spectral broadening and the fully-developed supercontinuum, we measure real time noise across the supercontinuum bandwidth, and we quantify the supercontinuum noise using statistical higher-order moments and a frequency-dependent intensity correlation map. We identify correlated spectral regions within the supercontinuum associated with simultaneous sideband generation, as well as signatures of pump depletion and soliton-like pump dynamics. Experimental results are in excellent agreement with simulations.