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The effect of collective phonon excitations on the properties of cold atoms in optical lattices is investigated. These phonon excitations are collective excitations, whose appearance is caused by intersite atomic interactions correlating the atoms, and they do not arise without such interactions. These collective excitations should not be confused with lattice vibrations produced by an external force. No such force is assumed. But the considered phonons are purely self-organized collective excitations, characterizing atomic oscillations around lattice sites, due to intersite atomic interactions. It is shown that these excitations can essentially influence the possibility of atoms' being localized. The states that would be insulating in the absence of phonon excitations can become delocalized when these excitations are taken into account. This concerns long-range as well as local atomic interactions. To characterize the region of stability, the Lindemann criterion is used. [ABSTRACT FROM AUTHOR]

In this feasibility study, we tested whether prehospital diagnostic stroke workup enables rational decision-making regarding treatment and the target hospital in persons with suspected stroke.

A strongly interacting Bose gas in an optical lattice is studied using a hardcore interaction. Two different approaches are introduced, one is based on a spin12 Fermi gas with attractive interaction, the other one on a functional integral with an additional constraint slaveboson approach. The relation between fermions and hardcore bosons is briefly discussed for the case of a onedimensional Bose gas. For a threedimensional gas we identify the order parameter of the BoseEinstein condensate through a HubbardStratonovich transformation and treat the corresponding theories within a meanfield approximation and with Gaussian fluctuations. This allows us to evaluate the phase diagram, including the BoseEinstein condensate and the Mott insulator, the densitydensity correlation function, the static structure factor, and the quasiparticle excitation spectrum. The role of quantum and thermal fluctuations are studied in detail for both approaches, where we find good agreement with the GrossPitaevskii equation and with the Bogoliubov approach in the dilute regime. In the dense regime, which is characterized by the phase transition between the BoseEinstein condensate and the Mott insulator, we discuss a renormalized GrossPitaevskii equation. This equation can describe the macroscopic wave function of the BoseEinstein condensate in the dilute regime as well as close to the transition to the Mott insulator. Finally, we compare the results of the attractive spin12 Fermi gas and those of the slaveboson approach and find good agreement for all physical quantities.

In this paper we investigate the use of supercritical carbon dioxide (sc-CO2) for synthesizing calcined mesoporous silicas with tunable pore sizes, wall thickness, and d spacings. Small angle neutron scattering was used to probe the controlled swelling of the triblock copolymer surfactant templating agents, P123 (PEO20PPO69PEO20), P85 (PEO26PPO39PEO26), and F127 (PEO106PPO70PEO106), as a function of CO2 pressure. The transition from the liquid crystal phase to the calcined mesoporous silicas, formed upon condensation and drying, was also studied in detail. Powder X-ray diffraction, transmission electron microscopy, and nitrogen adsorption techniques were used to establish pore diameters, silica wall widths, and the hexagonal packing of the pores within the calcined silicas. Using a direct templating method, the diameters of mesopores and the spacing between the pores could be tuned with a high level of precision. The swelling process was observed to have no detrimental effects on the quality of silica formed, a distinct advantage over conventional swelling techniques, and all of the silicas synthesized in this study were highly ordered over distances of at least 2000 Å.

The paper describes the use of an in-situ microscopy technique, which combines transmission electron microscopy (TEM) with scanning probe microscopy (SPM), to investigate the electrical and mechanical properties of individual silicon and germanium nanowires. Additionally, the formation of ordered arrays of size-monodisperse silicon and germanium nanowires within mesoporous silica powders and thin films using a supercritical fluid inclusion phase technique is described. In particular, we demonstrate ultra high-density arrays of germanium nanowires, up to 2 x 1012 wires per square centimetre. These matric embedded nano-composite materials display unique optical properties such as intense room temperature ultraviolet and visible photoluminescence.

To determine genetic relationships among representative popcorns (Zea maysL.) of the New World, 56 maize populations from the USA and nine Latin American countries were characterized for 29 morphological traits, 18 isozyme loci, and 31 SSR loci. Cluster and principal component analyses were performed upon standardized morphological data and allelic frequencies from isozyme and SSR loci to elucidate relationships among populations within a geographical and historical context. Three groups of popcorn, with distinctive morphological characteristics and genetic profiles, were identified in the North American populations. The first group includes the North American Yellow Pearl Popcorns, which are currently the most important for U.S. commercial production. This group could be derived from introductions of the race Curagua from Chile into New England in the 19th Century. The second group includes the North American Pointed Rice Popcorns, which probably originated from the complex of traditional races of pointed popcorns from Latin America, such as Palomero Toluqueño, Confite Puntiagudo, Canguil, and Pisankalla, which diffused from the highlands of central Mexico into northern Mexico and then into southwestern USA. The third group includes the North American Early Popcorns, which show a marked influence of Northern Flint maize, from which they probably acquired the trait of early maturity. This third group also shows genetic influences of maize from northwestern Mexico and even from early European varieties of popcorn introduced late in the 19th Century. We propose that the three groups of North American popcorn identified in this study be recognized taxonomically as distinct races, and we provide characteristic traits as well as isozyme and SSR alleles to define the new races.

Water-in-CO2 (W/C) emulsions formed using a nickel Triton X-100 surfactant complex (Ni-surfactant) were used as microreactors for the carbon−carbon coupling reaction between hex-3-yne and CO2 to produce tetra-ethyl pyrone (TEP). The structure of the product, which was isolated in the CO2 phase, was determined using gas chromatography mass spectrometry (GC−MS) and infrared spectroscopy. The Ni-surfactant acted as both an emulsion forming agent and a water soluble catalyst for this carbon−carbon coupling reaction. The optimum yield of TEP was determined to be 69% after 72 h, at a temperature of 70 °C and a pressure of 206 bar. The ease with which the emulsion could be collapsed allowed the facile separation of products from the catalyst and any unreacted starting material. Product selectivity in the W/C emulsions was found to be greater than that obtained using conventional organic methodologies.

Metallic nanowires of cobalt, copper, and iron oxide magnetite (Fe3O4) have been synthesized within the pores of mesoporous silica using a supercritical fluid inclusion technique. The mesoporous matrix provides a means of producing a high density of stable, hexagonally ordered arrays of highly crystalline nanowires. The formation of the metal and metal oxide nanowires within the silica mesopores was confirmed by transmission electron microscopy (TEM), N2 adsorption experiments, and powder X-ray diffraction (PXRD). The mechanism of nanowire formation within the mesopores appears to occur through the initial binding and coating of the pore walls with the metal atoms to form tubelike structures within the mesoporous template. The thickness of these tubes subsequently increases with further metal deposition until nanowires are formed. Additionally, the crystal structure of the cobalt nanowires formed within the mesoporous template can be readily changed by manipulating the density of the supercritical fluid phase.

Here we describe a unique extraction process utilizing pH switches for the selective removal of metal ions into supercritical CO2 using reversed micelles. Supercritical fluid extraction from an aqueous matrix has traditionally been limited by the inherent low pH of the aqueous phase of the system and the use of costly fluorinated chelating agents. The unique extraction process described herein utilizes a cheap, commercially available hydrocarbon surfactant as a complexing agent that forms reversed micelles in CO2. Subsequently, the pH of the biphasic system is controlled by the addition of buffers allowing facile manipulation of metal ion speciation. The control of the metal ion speciation is shown to have a quantitative effect on the efficiency at which metal ions are extracted from the aqueous phase. Furthermore, we demonstrate that pressure-induced pH switches of the aqueous phase can be utilized for the selective separation of chromium(III), cobalt(II), and gold(III) ions from an aqueous metallic broth.

Abstract:: A floating Wigner crystal differs from the standard one by a spatial averaging over positions of the Wigner-crystal lattice. It has the same internal structure as the fixed crystal, but contrary to it, takes into account rotational and/or translational symmetry of the underlying jellium background. We study properties of a floating Wigner molecule in few-electron spin-polarized quantum dots, and show that the floating solid has the lower energy than the standard Wigner crystal with fixed lattice points. We also argue that internal rotational symmetry of individual dots can be broken in arrays of quantum dots, due to degenerate ground states and inter-dot Coulomb coupling.

A grand canonical system of hard-core bosons in an optical lattice is considered. The bosons can occupy randomly N equivalent states at each lattice site. The limit N→∞ is solved exactly in terms of a saddle-point integration, representing a weakly-interacting Bose gas. In the limit N→∞ there is only a condensate if the fugacity of the Bose gas is larger than 1. Corrections in 1/N increase the total density of bosons but suppress the condensate. This indicates a depletion of the condensate due to increasing interaction at finite values of N.

Carbon dioxide produces an anomalous maximum in the swelling of poly(methyl methacrylate) (PMMA) thin films that is not present in bulk films, as shown with in-situ spectroscopic ellipsometry. This maximum and a corresponding minimum in refractive index are observed in regions of pressure where CO2 is highly compressible near the critical point. An effective excess thickness, determined from the height of the anomalous swelling maxima, increases proportionally with increasing initial film thickness, h0, in the range studied of 85 nm < h0 < 325 nm. Therefore, the anomalous swelling maxima suggest concentration inhomogeneities in the thin film, i.e., the onset of polymer/CO2 phase separation, that are influenced by the compressibility of the system and the confinement of the film. The PMMA swelling isotherms are insensitive to changing the substrate from silicon to gallium arsenide.

The formation of water-in-carbon dioxide microemulsions with a cationic perfluoropolyether trimethylammonium acetate surfactant, PFPE−C(O)−NH−CH2−N⁺(CH3)3 CH3COO^-, is reported over a range of temperatures (25−90 °C) and pressures (87.3−415 bar). Spherical droplets are observed by SANS with radii ranging from 16 to 36 Å for water-to-surfactant molar ratios (Wo) from 9.5 to 28. Porod analysis of the SANS data indicates an area of approximately 60 Ų/surfactant molecule at the water−CO2 interface, in reasonable agreement with the value of 72 Ų determined from the change in the droplet radius with Wo. The CO2-phobic functionality between the surfactant headgroup and perfluoropolyether tail reduces CO2 penetration of the tails, resulting in a smaller area/surfactant than in the case of an anionic perfluoropolyether surfactant [Langmuir 1997, 13, 3934]. A relatively rigid film, with a mean film rigidity (2K + &Kmacr;) of approximately 1 kBT, along with the strong partitioning of the surfactant toward CO2 versus water, lead to the small, rigid, spherical water droplets in CO2.

The density of states of Dirac fermions with a random mass on a two-dimensional lattice is considered. We give the explicit asymptotic form of the single-electron density of states as a function of both energy and (average) Dirac mass, in the regime where all states are localized. We make use of a weak-disorder expansion in the parameter g/m², where g is the strength of disorder and m the average Dirac mass for the case in which the evaluation of the (supersymmetric) integrals corresponds to non-uniform solutions of the saddle point equation. The resulting density of states has tails which deviate from the typical pure Gaussian form by an analytic prefactor.

The addition of organic and inorganic buffers to nanometer size water-in-CO2 microemulsion droplets stabilized by ammonium perfluoropolyether (PFPE-NH4) results in an increase in pH from 3 to values of 5−7. The effects of temperature, pressure, buffer type, buffer concentration, ionic strength, and CO2 solubility on the pH inside water-in-CO2 microemulsions and on biphasic water−CO2 systems were measured by the hydrophilic indicator 4-nitrophenyl-2-sulfonate and were predicted accurately with thermodynamic models. In both systems, modest buffer loadings result in a steep pH “jump” from 2.5 pH units. Further increases in pH require large amounts of base to overcome buffering due to the carbonic acid−bicarbonate equilibrium. A pH approaching neutrality was obtained in w/c microemulsions with approximately 1.5 mol kg^-1 NaOH. At high buffer loadings, the effects of temperature and pressure on pH values are negligible.

UV−vis spectroscopy was utilized to measure the decomposition of aqueous HNO3 solutions above 300 °C, in some cases with added NaOH, H2O2, and/or NaNO2, to form NO2, HNO2, NO, N2O, and oxygen. Individual bands corresponding to HNO2 and NO2 were deconvoluted from the spectra up to 400 °C. With constrained nonlinear optimization, areas of these bands were used to determine extinction coefficients of NO2 and HNO2 and equilibrium constants for the reactions:  HNO3 &rlhar2; H⁺ + NO3^-; 2HNO3 &rlhar2; H2O + 2NO2 + (1/2)O2; 2NO2 + H2O &rlhar2; HNO3 + HNO2; 2HNO2 &rlhar2; H2O + 2NO + (1/2)O2; 2NO &rlhar2; N2O + (1/2)O2; (Na⁺)(NO3^-) &rlhar2; Na⁺ + NO3^-.

Photosystem (PS) I preparations from spinach and from a cyanobacterium contain two molecules of phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone) per photosystem, only one of which is rapidly destroyed by ultraviolet light. In preparations of the core of PS I, the P700 reaction center, both quinone molecules are rapidly destroyed by UV irradiation. Nearly complete destruction does not alter the shape and size of the EPR spectrum of the electron acceptor A 1, which is believed to be phylloquinone. Photooxidation of P700, the primary electron donor of PS I, is also not affected. The results provide strong evidence against the identity of redox center A 1with the naphthoquinone.

Isolated neurointermediate lobes of the rat pituitary gland were incubated in Krebs-HEPES solution and the spontaneous outflow of endogenous dopamine and its metabolites (DOPAC, HVA and MOPET) was determined by HPLC with electrochemical detection.

Isolated neurointermediate lobes (NILs) or isolated neural lobes (NLs) of the rat pituitary gland were incubated in Krebs-HEPES solution which contained pargyline and the dopamine uptake inhibitor GBR 12921. The release of endogenous dopamine was determined by HPLC with electrochemical detection. Electrical stimulation of the pituitary stalk induced a frequency-dependent release of dopamine.

The mechanism and driving forces for hepatocellular phallotoxin uptake were studied by a rapid-filtration technique using basolateral liver plasma membrane vesicles (blLPM). An inwardly directed Na+ gradient but not K+-gradient transiently stimulated taurocholate uptake into blLPM 1.4–1.7-fold above the equilibrium value (overshoot), demonstrating functionally intact vesicles. In contrast, overshooting phallotoxin uptake (1.15–1.2-fold intravesicular accumulation above equilibrium value) was observed in the presence of a K+ as well as of a Na+ gradient. Na+ could be replaced by K+ or Li+. In the presence of choline chloride a distinct uptake reduction of 57% was seen. Counter-transport phenomena suggest phallotoxin transport rather than binding. Phallotoxin uptake was inhibited significantly by taurocholate, iodipamide and antamanide, but only slightly by a-amanitin. Creation of a negative intravesicular potential by altered accompanying anions or by valinomycin-induced K+ diffusion potential enhanced the initial uptake rate for phallotoxin, demonstrating rheogenic solute uptake.

Several anionic substances used for cholecystography inhibit the development of protrusions in isolated hepatocytes in response to phalloidin. Drugs from the iopodate family were equieffective with those of the iodipamide type.

A series of covalently binding derivatives of bile acids, fusidic acid and of compounds similar to cholecystographic agents were synthesized. Nearly all of them inhibited the development of protrusions on the surface of isolated hepatocytes regularly seen after treatment with phalloidin. The same compounds inhibited the uptake of demethylphalloin and of cholate in a concentration dependent manner. Two kinds of effects could be distinguished: The irreversible part of the inhibition depended on the incubation period and could not be removed by washing procedures. The reversible one was independent on the duration of the preincubation. Final results indicated that the tested derivatives inhibited either both transports, and the phalloidin response of liver cells to the same degree and in the same manner, or were found to be ineffective in all tests. The above parallelism supports the hypothesis that phallotoxins may be translocated by a carrier system normally responsible for the uptake of bile acids from the portal blood.

In vitro treatment of isolated rat hepatocytes with brominated taurodehydrocholic acid (BTC) reduced their sensitivity against phalloidin and inhibited the uptake of phalloidin as well as of cholate in an irreversible and concentration dependent manner. BTC was taken up itself by liver cells; this process was inhibited by 4,4'-diisothiocyano 2,2'-stilbene disulfonate (DIDS).

A model for disordered superfluids and superconductors is considered in terms of the Bogoliubov-de Gennes equation with a random order parameter field. Two characteristic cases are distinguished: model I with a real order parameter (time reversal invariant system) and model II with a complex order parameter (broken time reversal invariance). The fluctuations of the order parameter close the gap in both models, and we investigate the states at the center of the filled gap. The two models have distinctive properties in terms of the quasiparticle states due to different symmetries. Model II exhibits only localized quasiparticle states at the band center. In contrast, the fluctuations of the real order parameter of model I can be described by a nonlinear sigma model which leads to a transition from localized to extended states for dimensionsd>2.

A liquid of flux lines in a random superconductor is considered. We find spontaneous breaking of a continous internal symmetry from averaging over the random potential. A corresponding Goldstone mode describes diffusion of the flux lines. The diffusion coefficient vanishes if we exceed a critical strength of randomness. This is accompanied by a divergent correlation length. An interpretation of the behavior is a “freezing” transition of the flux liquid into a glass-like state.

A “flux liquid” serves as a model for the Abrikosov phase of a type II superconductor with short coherence length and strong fluctuations. Here we discuss the effect of anisotropy due to the planes in the material and disorder due to impurities in terms of the density-density correlation function. We find that both effects change the qualitative behavior of the correlation lengths.

A method is described for the preparation of isolated hepatocytes from 5 day old rats, based on the procedure of Berry and Friend (1969). In contrast to the original procedure the liver of newborn rats was perfused in the reverse direction from the vena cava caudalis (pars thoracalis) to the vena portae.

For the purification of the bile acid transport proteins from rat hepatocytes high affinity taurocholic acid derivatives were synthesized. One type was designed for coupling to a Sepharose matrix and the other for copolymerization with acrylamide. The resulting matrices were found to be suitable for affinity chromatography and affinity electrophoresis. In both syntheses, 3α, 12α-dihydroxy-7β-amino (tauro) cholic acid derivatives were used as the starting material, since substitution in this position had previously been shown not to alter transport affinity constant.

Isolated hepatocytes, prepared from 5 day old rats, from regenerating livers or from livers after poisoning with carbon tetrachloride, are less sensitive to phalloidin in vitro than hepatocytes from untreated adult controls. The time course of the reduced susceptibility to phalloidin was compared with the ability of hepatocytes to take up bile acids under various conditions. SDS-electrophoresis of cell lysates gave no evidence for decreased levels of actin in cells with reduced sensitivity to phalloidin. In contrast, there was a good relationship between the active uptake of bile acids and the sensitivity of hepatocytes to phalloidin. The decreased response of hepatocytes from baby rats, from regenerating livers or from poisoned livers to phalloidin is more probably related to differences in phalloidin uptake than to a reduced endowment with microfilamentous structures.

The growth of a denitrifying Pseudomonas strain on benzoic acid and 2-aminobenzoic acid (anthranilic acid) has been studied. The organism grew aerobically on benzoate, 2-aminobenzoate, and gentisate, but not on catechol or protocatechuic acid. These and other findings suggest that aerobic degradation of benzoic acid was via gentisic acid. Under completely anaerobic conditions in the presence of nitrate, benzoate and 2-aminobenzoate (5 mM each) were oxidized to CO2 with the concurrent reduction of NO3-to NO2-. Only after complete NO3-consumption was NO2-reduced to N2. Cells contained a NADP-specific 2-oxoglutaate dehydrogenase, in contrast to a NAD-specific pyruvate dehydrogenase. During anaerobic metabolism of [carboxyl-14C]benzoic acid, 16% of the label of metabolized benzoic acid was incorporated into cell material; this excludes intermediary decarboxylation during anaerobic metabolism. Extracts catalysed the activation of benzoic acid and a variety of its derivatives to the respective aryl-coenzyme A thioesters, ATP being cleaved to AMP and PPi; two synthetase activites were present. Extracts from 2-aminobenzoate-grown cells catalyzed a NADH-dependent reduction of 2-aminobenzoyl-CoA (100 nmol·min-1·mg-1 cell protein) to an unidentified CoA thioester, with a stoichiometric release of NH3 and a stoichiometry of ˜ 3 mol NADH oxidized per mol 2-aminobenzyol-CoA reduced when tested under aerobic conditions. The 2-aminobenzoyl-CoA reductase activity was lacking in anaerobic benzoate-grown cells and in aerobic cells. This is taken as evidence that 2-aminobenzoyl-CoA reductase is a key enzyme in a novel reductive pathway of anaerobic 2-aminobenzoic acid metabolism.

Ad-dimensional model of fluctuating flux lines with hard-core interaction is considered. Ford=3 this is a description of the Abrikosov flux phase in superconducting systems with short coherence length. Introducing flux lines with different colors, one can solve the limit of infinitely many colors. This solution, which describes free fermions, is a mean-field approximation in the case of a finite number of colors. Ford?3 this solution agrees with the result of a perturbative treatment of hard-core bosons. Moreover, the entanglement of the flux lines has only an irrelevant effect of the colored flux lines.

The proposed photometric method is based on the reaction of S2- with iodo-nitro-tetrazolium chloride (INT). PO43-, Cl- and SO42- up to concentrations of 5 · 10-2 mol/l, S2O32- up to 10-4 mol/l and S3O62- up to 2 · 10-4 mol/l do not interfere. It is possible to determine S2- down to concentrations of 3.4 · 10-5 mol/l, corresponding to 1 µg of S2-, within 30 min. The relative standard deviation in the case of 3.2 µg of S2- is ±6.4% rel.

SO32- can be determined photometrically with trinitrobenzoic acid within 2 min. SO42-, S2O32-, S2- and SxO62- in concentrations up to 1 mMole/100 ml do not interfere. The limit of determination is 0.22 mg SO32-/100 ml, the standard deviation for the determination of 7 mg SO32- is ± 0.59 Rel.-%.

Summary To exclude an involvement of ligandin in the uptake and storage of phalloidin in hepatocytes equilibriumdialysis studies were made with phalloidin, cholic acid and bromosulfophthalein (BSP). Binding studies with isolated ligandin indicated that the affinity of ligandin for phalloidin is low (KD=0.8×10−3 M). Phalloidin neither displaced BSP (KD=1.3×10−7M) or cholic acid (KD=7.6×10−5 M) from ligandin, when preloaded with these substrates.

The uptake of trace amounts of 3H-demethylphalloin (3H-DMP) by isolated hepatocytes was studied in the presence of various concentrations of unlabeled demethylphalloin (DMP), of phalloin and of phalloidin. The addition of phalloidin (or phalloin) reduces the uptake of 3H-DMP more than the addition of the equivalent concentration of DMP. The error caused by dilution of 3H-DMP with phalloin or phalloidin is not constant and depends on the concentration of the unlabeled compound. The relative differences between the uptake of 3H-DMP in the presence of demethylphalloin and in the presence of either phalloin or phalloidin cannot be explained by a competitive model. Some consequences for the use of 3H-DMP in toxicokinetic experiments are discussed.

Summary 3H-Demethylphalloin (3H-DMP) a cyclopeptide very similar to phalloidin is taken up by isolated hepatocytes in vitro. Hepatocytes prepared from newborn animals are less sensitive to phalloidin. Their uptake of 3H-DMP is about one tenth of that of cells from adult animals. Ascites hepatoma cells, known to be insensitive to phalloidin took up negligible amounts of 3H-DMP. Cells prepared from regenerating livers took up insignificantly lower amounts of the toxin than in hepatocytes from adult animals.