Structural Evolution of GaOx-Shell and Intermetallic Phases in Ga-Pt Supported Catalytically Active Liquid Metal Solutions

We present a comprehensive scale-bridging characterization approach for supported catalytically active liquid metal solutions (SCALMS) which combines lab-based X-ray microscopy, nano X-ray computed tomography (nano-CT), and correlative analytical transmission electron microscopy. SCALMS catalysts consist of low-melting alloy particles and have demonstrated high catalytic activity, selectivity, and long-term stability in propane dehydrogenation (PDH). We established an identical-location nano-CT workflow which allows us to reveal site-specific changes of Ga-Pt SCALMS before and after PDH. These observations are complemented by analytical transmission electron microscopy investigations providing information on the structure, chemical composition, and phase distribution of individual SCALMS particles. Key findings of this combined microscopic approach include (i) structural evolution of the SCALMS particles' GaOx shell, (ii) Pt segregation toward the oxide shell leading to the formation of Ga-Pt intermetallic phases, and (iii) cracking of the oxide shell accompanied by the release of liquid Ga-Pt toward the porous support.

The H-D-isotope effect of heavy water affecting ligand-mediated nanoparticle formation in SANS and NMR experiments

An isotopic effect of normal (H2O) vs. heavy water (D2O) is well known to fundamentally affect the structure and chemical properties of proteins, for instance. Here, we correlate the results from small angle X-ray and neutron scattering (SAXS, SANS) with high-resolution scanning transmission electron microscopy to track the evolution of CdS nanoparticle size and crystallinity from aqueous solution in the presence of the organic ligand ethylenediaminetetraacetate (EDTA) at room temperature in both H2O and D2O. We provide evidence via SANS experiments that exchanging H2O with D2O impacts nanoparticle formation by changing the equilibria and dynamics of EDTA clusters in solution as investigated by nuclear magnetic resonance analysis. The colloidal stability of the CdS nanoparticles, covered by a layer of [Cd(EDTA)]2- complexes, is significantly reduced in D2O despite the strong stabilizing effect of EDTA in suspensions of normal water. Hence, conclusions about nanoparticle formation mechanisms from D2O solutions reveal limited transferability to reactions in normal water due to isotopic effects, which thus need to be discussed for contrast match experiments.

Light-Induced Agglomeration of Single-Atom Platinum in Photocatalysis

With recent advances in the field of single-atoms (SAs) used in photocatalysis, an unprecedented performance of atomically dispersed co-catalysts has been achieved. However, the stability and agglomeration of SA co-catalysts on the semiconductor surface may represent a critical issue in potential applications. Here, the photoinduced destabilization of Pt SAs on the benchmark photocatalyst, TiO₂ , is described. In aqueous solutions within illumination timescales ranging from few minutes to several hours, light-induced agglomeration of Pt SAs to ensembles (dimers, multimers) and finally nanoparticles takes place. The kinetics critically depends on the presence of sacrificial hole scavengers and the used light intensity. Density-functional theory calculations attribute the light induced destabilization of the SA Pt species to binding of surface-coordinated Pt with solution-hydrogen (adsorbed H atoms), which consequently weakens the Pt SA bonding to the TiO₂ surface. Despite the gradual aggregation of Pt SAs into surface clusters and their overall reduction to metallic state, which involves >90% of Pt SAs, the overall photocatalytic H₂ evolution remains virtually unaffected.

Maternal and perinatal obesity induce bronchial obstruction and pulmonary hypertension via IL-6-FoxO1-axis in later life

Obesity is a pre-disposing condition for chronic obstructive pulmonary disease, asthma, and pulmonary arterial hypertension. Accumulating evidence suggests that metabolic influences during development can determine chronic lung diseases (CLD). We demonstrate that maternal obesity causes early metabolic disorder in the offspring. Here, interleukin-6 induced bronchial and microvascular smooth muscle cell (SMC) hyperproliferation and increased airway and pulmonary vascular resistance. The key anti-proliferative transcription factor FoxO1 was inactivated via nuclear exclusion. These findings were confirmed using primary SMC treated with interleukin-6 and pharmacological FoxO1 inhibition as well as genetic FoxO1 ablation and constitutive activation. In vivo, we reproduced the structural and functional alterations in offspring of obese dams via the SMC-specific ablation of FoxO1. The reconstitution of FoxO1 using IL-6-deficient mice and pharmacological treatment did not protect against metabolic disorder but prevented SMC hyperproliferation. In human observational studies, childhood obesity was associated with reduced forced expiratory volume in 1 s/forced vital capacity ratio Z-score (used as proxy for lung function) and asthma. We conclude that the interleukin-6-FoxO1 pathway in SMC is a molecular mechanism by which perinatal obesity programs the bronchial and vascular structure and function, thereby driving CLD development. Thus, FoxO1 reconstitution provides a potential therapeutic option for preventing this metabolic programming of CLD.

As a single atom Pd outperforms Pt as the most active co-catalyst for photocatalytic H2 evolution

Here, we evaluate three different noble metal co-catalysts (Pd, Pt, and Au) that are present as single atoms (SAs) on the classic benchmark photocatalyst, TiO₂. To trap the single atoms on the surface, we introduced controlled surface vacancies (Ti³⁺-O_v) on anatase TiO₂ nanosheets by a thermal reduction treatment. After anchoring identical loadings of single atoms of Pd, Pt, and Au, we measure the photocatalytic H₂ generation rate and compare it to the classic nanoparticle co-catalysts on the nanosheets. While nanoparticles yield the well-established the hydrogen evolution reaction activity sequence (Pt > Pd > Au), for the single atom form, Pd radically outperforms Pt and Au. Based on density functional theory (DFT), we ascribe this unusual photocatalytic co-catalyst sequence to the nature of the charge localization on the noble metal SAs embedded in the TiO₂ surface.

Oligothiophene Phosphonic Acids for Self-Assembled Monolayer Field-Effect Transistors

Semiconducting self-assembled monolayers (SAMs) represent highly relevant components for the fabrication of organic thin-film electronics because they enable the precise formation of active π-conjugates in terms of orientation and layer thickness. In this work, we demonstrate self-assembled monolayer field-effect transistors (SAMFETs) composed of phosphonic acid oligomers of 3-hexylthiophene (oligothiophenes-OT) with systematic variations of thiophene repeating units (5, 10, and 20). The devices exhibit stable lateral charge transport with increased mobility as a function of thiophene unit counts. Importantly, our work reveals the packing and intermolecular order of varied-chain-length SAMs at the molecular scale via X-ray reflectivity (XRR) and quantitative X-ray photoelectron spectroscopy (XPS). Short oligomers (OT5-PA and OT10-PA) arrange almost perpendicular to the substrate, forming highly ordered SAMs, whereas the long-chain OT20-PA exhibits a folded structure. By tuning the molecular order in the monolayers via the SAM substitution reaction, the OT20-PA devices show a tripling in mobility.

LPE growth of Tb3Al5O12:Ce single crystalline film converters for WLED application

Efficient phosphor converters for white LEDs based on TbAG:Ce single crystalline films, LPE grown onto YAG substrates, is developed. The film-substrate interface of TbAG:Ce SCF/YAG epitaxial structures was studied using high-resolution STEM images.

Simulation of XXZ Spin Models Using Sideband Transitions in Trapped Bosonic Gases

We theoretically propose and experimentally demonstrate the use of motional sidebands in a trapped ensemble of ^{87}Rb atoms to engineer tunable long-range XXZ spin models. We benchmark our simulator by probing a ferromagnetic to paramagnetic dynamical phase transition in the Lipkin-Meshkov-Glick model, a collective XXZ model plus additional transverse and longitudinal fields, via Rabi spectroscopy. We experimentally reconstruct the boundary between the dynamical phases, which is in good agreement with mean-field theoretical predictions. Our work introduces new possibilities in quantum simulation of anisotropic spin-spin interactions and quantum metrology enhanced by many-body entanglement.

Interface between Water-Solvent Mixtures and a Hydrophobic Surface

The mechanism behind the stability of organic nanoparticles prepared by liquid antisolvent (LAS) precipitation without a specific stabilizing agent is poorly understood. In this work, we propose that the organic solvent used in the LAS process rapidly forms a molecular stabilizing layer at the interface of the nanoparticles with the aqueous dispersion medium. To confirm this hypothesis, n-octadecyltrichlorosilane (OTS)-functionalized silicon wafers in contact with water-solvent mixtures were used as a flat model system mimicking the solid-liquid interface of the organic nanoparticles. We studied the equilibrium structure of the interface by X-ray reflectometry (XRR) for water-solvent mixtures (methanol, ethanol, 1-propanol, 2-propanol, acetone, and tetrahydrofuran). The formation of an organic solvent-rich layer at the solid-liquid interface was observed. The layer thickness increases with the organic solvent concentration and correlates with the polar and hydrogen bond fraction of Hansen solubility parameters. We developed a self-consistent adsorption model via complementing adsorption isotherms obtained from XRR data with molecular dynamics simulations.

Crystal-structure of active layers of small molecule organic photovoltaics before and after solvent vapor annealing

It is demonstrated by a detailed structural analysis that the crystallinity and the efficiency of small molecule based organic photovoltaics can be tuned by solvent vapor annealing (SVA). Blends made of the small molecule donor 2,2′-[(3,3′″,3″″,4′-tetraoctyl[2,2′:5′,2″:5″,2′″:5′″,2″″-quinquethiophene]-5,5″″-diyl)bis[(Z)-methylidyne(3-ethyl-4-oxo-5,2-thiazolidinediylidene)]]bis-propanedinitrile (DRCN5T) and the acceptor [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) were annealed using solvent vapors with either a high solubility for the donor (tetrahydrofuran), the acceptor (carbon disulfide) or both (chloroform). The samples were analyzed by grazing-incidence wide-angle X-ray scattering (GIWAXS), electron diffraction, X-ray pole figures, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). A phase separation of DRCN5T and PC71BM is induced by SVA leading to a crystallization of DRCN5T and the formation of a DRCN5T enriched layer. The DRCN5T crystallites possess the two dimensional oblique crystal system with the lattice parameters a = 19.2 Å, c = 27.1 Å, and β = 111.1° for the chloroform case. No major differences in the crystal structure for the other solvent vapors were observed. However, the solvent choice strongly influences the size of the DRCN5T enriched layer. Missing periodicity in the [010]-direction leads to the extinction of all Bragg reflections with k ≠ 0. The annealed samples are randomly orientated with respect to the normal of the substrate (fiber texture).

Mixed Organic Ligand Shells: Controlling the Nanoparticle Surface Morphology toward Tuning the Optoelectronic Properties

Precise control over the ratio of perylene bisimide (PBI) monomers and aggregates, immobilized on alumina nanoparticle (NP) surfaces, is demonstrated. Towards this goal, phosphonic acid functionalized PBI derivatives (PA-PBI) are shown to self-assemble into stoichiometrically mixed monolayers featuring aliphatic, glycolic, or fluorinated phosphonic acid ligands, serving as imbedding matrix (PA-M) to afford core-shell NPs. Different but, nevertheless, defined PBI monomer/aggregate composition is achieved by either the variation in the PA-PBI to PA-M ratios, or the utilization of different PA-Ms. Various steady-state as well as time-resolved spectroscopy techniques are applied to probe the core-shell NPs with respect to changes in their optical properties upon variations in the shell composition. To this end, the ratio between monomer and excimer-like emission assists in deriving information on the self-assembled monolayer composition, local ordering, and corresponding aggregate content. With the help of X-ray reflectivity measurements, accompanied by molecular dynamics simulations, the built-up of the particle shells, in general, and the PBI aggregation behavior, in particular, are explored in depth.

Flexible sample cell for real-time GISAXS, GIWAXS and XRR: design and construction

Since the properties of functional materials are highly dependent on their specific structure, and since the structural changes, for example during crystallization, induced by coating and annealing processes are significant, the study of structure and its formation is of interest for fundamental and applied science. However, structure analysis is often limited to ex situ determination of final states due to the lack of specialized sample cells that enable real-time investigations. The lack of such cells is mainly due to their fairly complex design and geometrical restrictions defined by the beamline setups. To overcome this obstacle, an advanced sample cell has been designed and constructed; it combines automated doctor blading, solvent vapor annealing and sample hydration with real-time grazing-incidence wide- and small-angle scattering (GIWAXS/GISAXS) and X-ray reflectivity (XRR). The sample cell has limited spatial requirements and is therefore widely usable at beamlines and laboratory-scale instruments. The cell is fully automatized and remains portable, including the necessary electronics. In addition, the cell can be used by interested scientists in cooperation with the Institute for Crystallography and Structural Physics and is expandable with regard to optical secondary probes. Exemplary research studies are presented, in the form of coating of P3HT:PC₆₁PM thin films, solvent vapor annealing of DRCN5T:PC₇₁BM thin films, and hydration of supported phospholipid multilayers, to demonstrate the capabilities of the in situ cell.

Evidence of Tailoring the Interfacial Chemical Composition in Normal Structure Hybrid Organohalide Perovskites by a Self-Assembled Monolayer

Current-voltage hysteresis is a major issue for normal architecture organo-halide perovskite solar cells. In this manuscript we reveal a several-angstrom thick methylammonium iodide-rich interface between the perovskite and the metal oxide. Surface functionalization via self-assembled monolayers allowed us to control the composition of the interface monolayer from Pb poor to Pb rich, which, in parallel, suppresses hysteresis in perovskite solar cells. The bulk of the perovskite films is not affected by the interface engineering and remains highly crystalline in the surface-normal direction over the whole film thickness. The subnanometer structural modifications of the buried interface were revealed by X-ray reflectivity, which is most sensitive to monitor changes in the mass density of only several-angstrom thin interfacial layers as a function of substrate functionalization. From Kelvin probe force microscopy study on a solar cell cross section, we further demonstrate local variations of the potential on different electron-transporting layers within a solar cell. On the basis of these findings, we present a unifying model explaining hysteresis in perovskite solar cells, giving an insight into one crucial aspect of hysteresis for the first time and paving way for new strategies in the field of perovskite-based opto-electronic devices.

Self-assembled monolayer field-effect transistors based on oligo-9,9'-dioctylfluorene phosphonic acids

The use of functional oligomers of π-conjugated oligofluorenes led to a region-selective assembly of amorphous monolayers which exhibit robust lateral charge transport pathways in self-assembled monolayer field-effect transistors over long distances and even in mixed monolayers of semiconducting and insulating molecules. This oligomer concept might stimulate a new molecular design of self-assembling semiconducting materials.

Bioactivation of titanium dioxide scaffolds by ALP-functionalization

Three dimensional TiO₂ scaffolds are receiving renewed attention for bone tissue engineering (TE) due to their biocompatibility and attractive mechanical properties. However the bioactivity of these scaffolds is comparatively lower than that of bioactive glass or hydroxyapatite (HA) scaffolds. One strategy to improve bioactivity is to functionalize the surface of the scaffolds using biomolecules. Alkaline phosphatase (ALP) was chosen in this study due to its important role in the bone mineralization process. The current study investigated the ALP functionalization of 3D titanium dioxide scaffolds using self-polymerization of dopamine. Robust titanium scaffolds (compressive strength∼2.7 ± 0.3 MPa) were produced via foam replica method. Enzyme grafting was performed by dip-coating in polydopamine/ALP solution. The presence of ALP was indirectly confirmed by contact angle measurements and enzymatic activity study. The influence of the enzyme on the bioactivity, e.g. hydroxyapatite formation on the scaffold surface, was measured in simulated body fluid (SBF). After 28 days in SBF, 5 mg ALP coated titania scaffolds exhibited increased hydroxyapatite formation. It was thus confirmed that ALP enhances the bioactivity of titania scaffolds, converting an inert bioceramic in an attractive bioactive system for bone TE.

Embryo Microinjection and Electroporation in the Chordate Ciona intestinalis

Simple model organisms are instrumental for in vivo studies of developmental and cellular differentiation processes. Currently, the evolutionary distance to man of conventional invertebrate model systems and the complexity of genomes in vertebrates are critical challenges to modeling human normal and pathological conditions. The chordate Ciona intestinalis is an invertebrate chordate that emerged from a common ancestor with the vertebrates and may represent features at the interface between invertebrates and vertebrates. A common body plan with much simpler cellular and genomic composition should unveil gene regulatory network (GRN) links and functional genomics readouts explaining phenomena in the vertebrate condition. The compact genome of Ciona, a fixed embryonic lineage with few divisions and large cells, combined with versatile community tools foster efficient gene functional analyses in this organism. Here, we present several crucial methods for this promising model organism, which belongs to the closest sister group to vertebrates. We present protocols for transient transgenesis by electroporation, along with microinjection-mediated gene knockdown, which together provide the means to study gene function and genomic regulatory elements. We extend our protocols to provide information on how community databases are utilized for in silico design of gene regulatory or gene functional experiments. An example study demonstrates how novel information can be gained on the interplay, and its quantification, of selected neural factors conserved between Ciona and man. Furthermore, we show examples of differential subcellular localization in embryonic cells, following DNA electroporation in Ciona zygotes. Finally, we discuss the potential of these protocols to be adapted for tissue specific gene interference with emerging gene editing methods. The in vivo approaches in Ciona overcome major shortcomings of classical model organisms in the quest of unraveling conserved mechanisms in the chordate developmental program, relevant to stem cell research, drug discovery, and subsequent clinical application.

Structure of n-Alkyltrichlorosilane Monolayers on Si(100)/SiO2

The structure of n-alkyltrichlorosilane self-assembled monolayers (SAMs) of alkyl chain lengths n = 12, 14, 18, and 22 formed on the amorphous native oxide of silicon (100) has been investigated via angstrom-resolution surface X-ray scattering techniques, with particular focus on the proliferation of lateral order along the molecules' long axis. Grazing incidence diffraction shows that the monolayer is composed of hexagonally packed crystalline-like domains for n = 14, 18, and 22 with a lateral size of about 60 Å. However, Bragg rod analysis shows that ∼12 of the CH2 units are not included in the crystalline-like domains. We assign this, and the limited lateral crystallites' size, to strain induced by the size mismatch between the optimal chain-chain and headgroup-headgroup spacings. Analysis of X-ray reflectivity profiles for n = 12, 14, and 22 shows that the density profile used to successfully model n = 18 provides an excellent fit where the analysis-derived parameters provide complementary structural information to the grazing incidence results.

Nanoscale structure of Si/SiO2/organics interfaces

X-ray reflectivity measurements of increasingly more complex interfaces involving silicon (001) substrates reveal the existence of a thin low-density layer intruding between the single-crystalline silicon and the amorphous native SiO2 terminating it. The importance of accounting for this layer in modeling silicon/liquid interfaces and silicon-supported monolayers is demonstrated by comparing fits of the measured reflectivity curves by models including and excluding this layer. The inclusion of this layer, with 6-8 missing electrons per silicon unit cell area, consistent with one missing oxygen atom whose bonds remain hydrogen passivated, is found to be particularly important for an accurate and high-resolution determination of the surface normal density profile from reflectivities spanning extended momentum transfer ranges, now measurable at modern third-generation synchrotron sources.

About precipitates in boron doped Si investigated by dynamical X-ray diffraction

Thickness-dependent Pendellösung oscillations as described in the dynamical theory of diffraction are highly sensitive to strain fields from defects in a host crystal. Based on this, we present a novel approach to determine the precipitation kinetics of oxygen in silicon (Si) at the early stages of clustering at high temperatures. We present in-situ measurements up to 11000C performed with the characteristic Kα1-line at 59.31 keV. The extracted static Debye-Waller factors are evaluated as a function of annealing time within a diffusion limited model of growing spherical precipitates. We investigated moderately p- ([B] ≍ 1015 1/cm3) and highly p+ ([B] ≍ 1018 1/cm3) boron doped Czochralski Si crystals at different nucleation and growth temperatures to determine the nucleation and precipitation kinetics as well as the long time precipitation behavior. At 6500C the diffusion constant found is enhanced compared to the extrapolated value for normal diffusion [1], and it is one order of magnitude lower compared to SIMS data [2]. However, it is close to the value obtained from dislocation unlocking experiments [3]. Moreover, the nucleation rates in p+ material are enhanced at 4500C and 7800C compared to the p- samples. The acceleration at 4500C can be explained with boron enhanced oxygen dimer diffusion, whereas the nucleation rate at 7800C is much too high to be accounted for by the enhanced oxygen dimer diffusivity alone. An analysis of the misfit strain yields a platelet morphology of the precipitates with a higher aspect ratio in the p- than in the p+ case. The long time precipitation behavior at 9000C shows a second growth regime of comparable amplitude in both materials. This can be interpreted as Ostwald ripening and gives access to the surface energy of the precipitates.

[Complications associated with inguinal orchiectomy and scrotal orchiectomy]

Inguinal excision of testis is technically an elementary surgical procedure. According to the indication (e.g., malignant tumors, infarction, inflammation), an inguinal or alternatively a transcrotal approach is possible. Despite its straightforwardness, surgery of the scrotum includes remarkable risks and complications such as postoperative hemorrhage, hematoma formation, infections, and disturbances of wound healing followed by insufficient unfavorable cosmetic results. Nerve injury may be accompanied by temporary or persistent paresthesias which have been documented in our patients undergoing orchiectomy.

Extended coherence time on the clock transition of optically trapped rubidium

Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of (87)Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4×10(-11)τ(-1/2), where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

Effect of different gamma-irradiation doses on cytotoxicity and material properties of porous polyether-urethane polymer

Biomaterials respond to sterilization methods differently. Steam sterilization might decrease the performance of thermoplastic polyether-urethane (TPU); however, the effect of different gamma-radiation doses on this polymer is contradictory in present literature. The purpose of this study was to investigate the differences between irradiative doses in comparison with steam sterilization on a porous TPU scaffold produced by a new processing method. No significant differences in the surface chemical structure were found with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis when comparing with the sterilization methods. The molecular weight (M(w)) had a net increase from 11.5 +/- 0.039 to 13.2 +/- 0.072 kDa by gamma-sterilization from 10 to 60 kGy. The samples that were irradiated (>60 kGy) had also an increase in polydispersity index (PDI; 1.45 +/- 0.007) in comparison with the nonsterile ones (1.31 +/- 0.017), which indicate branching. Liquid chromatography/mass spectroscopy (LC/MS) analysis showed that there was a correlation between the concentration of the breakdown product, methyl dianiline, and cytotoxicity. The concentration of this compound was found to be four times higher in steam-sterilized sample (1.3 +/- 0.01 ppb) compared with that of the polymer sample gamma-sterilized at 10 kGy (0.3 +/- 0.01 ppb). The cytotoxicity of TPU was found to decrease with higher radiation doses, and was significantly higher for the steam-sterilized samples. It is recommended that TPU produced with the described foaming method should be sterilized by gamma-irradiation at 25 kGy or higher doses.

A novel processing method for injection-molded polyether–urethane scaffolds. Part 1: Processing

A large-scale scaffold processing method with injection molding has been successfully developed. Water was used as afoaming agent for the new technique. NaCl was used as a porogen to achieve an open-cell structure. Organic solvents, which are common foaming agents for polyurethane, where not used. Toxic remains in the polymer were therefore prevented. Pore size and porosity was adjustable through process parameters. A parameter study showed that an increase in injection pressure, plasticize speed, cylinder, and mold temperature raised the mean pore diameter. The porosity also could be mended by the cylinder and mold temperature, in addition to NaCl concentration. It was possible to produce scaffolds with a porosity of 64 +/- 3%, a pore size distribution from 30-450 microm, and a mean pore diameter of 270 +/- 90 microm. The interconnective pores were found to lie between 5 and 58 microm.

Biostability of polyether-urethane scaffolds: a comparison of two novel processing methods and the effect of higher gamma-irradiation dose

This article deals with enzyme-induced biodegradation behavior of thermoplastic polyether-urethane (TPU). Porous scaffolds were processed by a new foaming method applied in hot pressing and injection molding. The scaffolds were subsequently gamma sterilized. The samples were incubated with cholesterol esterase (CE) for 28 days to simulate an enzymatic degradation order to assess polymer biostability. The main focus of degradation products was the most toxic one: methylene dianiline (MDA). LC/MS was used to separate the breakdown products and to identify possible MDA amounts. The results showed that (a) the hot-pressed sample released an MDA amount almost twice as large (0.26 ng +/- 0.008) as that of the injection-molded samples (0.15 ng +/- 0.003) after incubation with enzyme activity in the physiological range, and (b) a tenfold increase in CE activity revealed considerably higher MDA amounts (7540.0 ng +/- 0.004). This enzyme concentration is physiologically unlikely, however, but may occur for extreme high inflammation behavior. Even for extremely high levels of CE enzyme, the scaffold will not discharge MDA above toxic levels. The injection-molded samples sterilized at 25 kGy seem to represent the most promising processing method. Therefore, the new injection-molding foaming process of polyether-urethane can be considered appropriate for use as a biomaterial.

Water as foaming agent for open cell polyurethane structures

The problem of moisture in polymer processing is known to any polymer engineer, as air bubbles may be formed. Hence granulates are generally dried prior to manufacturing. This study tried to develop a novel processing methods for scaffolds with controlled moisture content in thermoplastic polyurethane. The common foaming agents for polyurethane are organic solvents, whose residues remaining in the scaffold may be harmful to adherent cells, protein growth factors or nearby tissues. Water was used as a foaming agent and NaCl was used as porogens to achieve an open-cell structure. The polyether-polyurethane samples were processed in a heated press, and achieved a porosity of 64%. The pore size ranged between 50 and 500 microm. Human fibroblasts adhered and proliferate in the scaffold. A non-toxic production process was developed to manufacture a porous structure with a thermoplastic polyether-polyurethane. The process enables a mass-production of samples with adjustable pore size and porosity. In contrast to an existing method (solvent casting), the processing of the samples was not limited by its thickness. The process parameters, which attribute mostly to the pore building, were filling volume, temperature, NaCl-concentration and water-uptake rate.

Nutrition and physical activity interventions to reduce cardiovascular disease risk in health care settings: a quantitative review with a focus on women

The authors conducted a quantitative literature review of the impact of 32 diet and physical activity (PA) interventions delivered in health care settings on cardiovascular disease risk factors. Intervention effects were relatively modest but statistically significant for PA, body mass index or weight, dietary fat, blood pressure, and total and low-density lipoprotein serum cholesterol. Intervention effects were generally larger for samples with a mean age >50 years and for studies with <6 months follow-up. Type of comparison group, type of intervention, and use of a behavior theory did not have a consistent impact on intervention effects. Few studies focused on persons of color, although the results from these studies are promising.

Minimal molecular determinants of substrates for recognition by the intestinal peptide transporter

Proton-dependent electrogenic transporters for di- and tripeptides have been identified in bacteria, fungi, plants, and mammalian cells. They all show sequence-independent transport of all possible di- and tripeptides as well as of a variety of peptidomimetics. We used the mammalian intestinal peptide transporter PEPT1 as a model to define the molecular basis for its multisubstrate specificity. By employing computational analysis of possible substrate conformations in combination with transport assays using transgenic yeast cells and Xenopus laevis oocytes expressing PEPT1, the minimal structural requirements for substrate binding and transport were determined. Based on a series of medium chain fatty acids bearing an amino group as a head group (omega-amino fatty acids, omega-AFA), we show that electrogenic transport by PEPT1 requires as a minimum the two ionized head groups separated by at least four methylene groups. Consequently, a > 500 pm < 630 pm distance between the two charged centers (carboxylic carbon and amino nitrogen) is sufficient for substrate recognition and transport. Removal of either the amino group or the carboxyl group in omega-AFA maintained the affinity of the compound for interaction with the transporter but abolished the capability for electrogenic transport. Additional groups in the omega-AFA backbone that provide more hydrogen bonding sites appear to increase substrate affinity but are not essential. The information provided here does (a) explain the capability of the peptide carrier for sequence-independent transport of thousands of different substrates and (b) set the molecular basis for a rational drug design to increase the absorption of peptide-based drugs mediated by PEPT1.

Delta-aminolevulinic acid transport by intestinal and renal peptide transporters and its physiological and clinical implications

Delta-aminolevulinic acid (ALA) is the precursor of porphyrin synthesis and has been recently used in vitro and in clinical studies as an endogenous photosensitizer for photodynamic therapy in the treatment of various tumors. For this purpose, ALA is given topically, systemically, or orally. When administered by the oral route, it shows excellent intestinal absorption. ALA is also efficiently reabsorbed in the renal proximal tubule after glomerular filtration. However, the pathways and mechanisms for its transmembrane transport into epithelial cells of intestine and kidney are unknown. Here we demonstrate that ALA uses the intestinal and renal apical peptide transporters for entering into epithelial cells. Kinetics and characteristics of ALA transport were determined in Xenopus laevis ooyctes and Pichia pastoris yeast cells expressing either the cloned intestinal peptide transporter PEPT1 or the renal form PEPT2. By using radiolabeled ALA and electrophysiological techniques in these heterologous expression systems, we established that: (a) PEPT1 and PEPT2 translocate 3H-ALA by saturable and pH-dependent transport mechanisms, (b) that ALA and di-/tripeptides, but not GABA or related amino acids, compete at the same substrate-binding site of the carriers, and (c) that ALA transport is electrogenic in nature as a consequence of H+/ALA cotransport. Reverse transcriptase-PCR analysis performed with specific primers for PEPT1 and PEPT2 in rabbit tissues demonstrates that, in particular, the PEPT2 mRNA is expressed in a variety of other tissues including lung, brain, and mammary gland, which have been shown to accumulate ALA. This suggests that these tissues could take up the porphyrin precusor via expressed peptide transporters, providing the endogenous photosensitizers for efficient photodynamic therapy.

Doxacurium and mivacurium do not trigger malignant hyperthermia in susceptible swine

The role of succinylcholine in the precipitation of malignant hyperthermia (MH) necessitates the testing of new neuromuscular relaxants for their ability to trigger MH in MH-susceptible swine before general human use. We tested doxacurium and mivacurium, two new nondepolarizing bis-benzylisoquinolinium neuromuscular relaxants, at ED95 and at four times ED95 doses in swine previously documented to be MH-susceptible. In none of the 16 animals was MH triggered after administration of these relaxants, whereas all animals developed fatal MH after administration of halothane or halothane plus succinylcholine. Muscle biopsy specimens taken before administration of the relaxant confirmed that all animals had increased sensitivity to halothane, caffeine, or both. Thus, we conclude that doxacurium and mivacurium are not triggering agents of malignant hyperthermia in MH-susceptible swine.

Thalamonal, droperidol and fentanyl in induced hypovolaemic shock in the conscious dog

Previous studies had shown that Thalamonal exerts a protective activity against hypovolaemic shock in experimental animals as well as in patients. The purpose of the present study was to make a long-term evaluation of the value of single doses of Thalamonal fentanyl and droperidol as shock-protecting agents in conscious dogs which received no replacement of blood loss. The study was conducted in 20 animals in which devices were implanted for measuring heart rate, arterial and venous blood pressure, left ventricular and left atrial blood pressure. The dogs were divided into 4 groups, receiving 20 ml of an i.v. injection containing either 0.025 mg/kg fentanyl, 0.625 mg/kg droperidol, 0.25 ml/kg Thalamonal (0.625 mg/kg droperidol + 0.0125 mg/kg fentanyl), or saline. Thalamonal allowed a 100 per cent survival of the dogs, one of the 5 animals survived in the droperidol group, whereas fentanyl and saline were completely ineffective. As a possible mechanism of action the interruption of the vicious sequence of blood loss, vasoconstriction and circulatory arrest at a peripheral and/or central level is discussed. The hypothesis of intracorporeal blood volume correction under the influence of Thalamonal as an anti-vasoconstrictor seems to be logical but needs further investigation.

The effect of glucagon on the pulmonary transvascular fluid filtration rate

Administration of glucagon has been shown to decrease pulmonary vascular resistance, but its primary site of action is undetermined. Whether this is on the arterial or venous side of the capillary would be reflected in the microvascular hydrostatic pressure. We used the pulmonary flow of lymph, a sensitive index of the transvascular fluid filtration rate, to monitor the microvascular hydrostatic pressure. Eight unanesthetized sheep with a surgically created long-term fistula for monitoring pulmonary lymph were given a 3-mg bolus of glucagon after a baseline period. We found no change in pulmonary arterial or left atrial pressures but noted a significant increase in cardiac output and a decrease in pulmonary resistance. The flow of pulmonary lymph increased by 50 percent for 30 minutes after administration of glucagon, and the protein content of the lymph decreased by 15 percent, indicating a large increase in the microvascular hydrostatic pressure. From these data, we calculated a decrease in arterial resistance from 60 percent to 30 percent of the total and, subsequently, an increase of 6 cm H2O in the microvascular hydrostatic pressure. Administration of glucagon, therefore, decreases the arterial resistance while increasing microvascular pressure in the process.