Microvascular Experimentation in the Chick Chorioallantoic Membrane as a Model for Screening Angiogenic Agents including from Gene-Modified Cells

The chick chorioallantoic membrane (CAM) assay model of angiogenesis has been highlighted as a relatively quick, low cost and effective model for the study of pro-angiogenic and anti-angiogenic factors. The chick CAM is a highly vascularised extraembryonic membrane which functions for gas exchange, nutrient exchange and waste removal for the growing chick embryo. It is beneficial as it can function as a treatment screening tool, which bridges the gap between cell based in vitro studies and in vivo animal experimentation. In this review, we explore the benefits and drawbacks of the CAM assay to study microcirculation, by the investigation of each distinct stage of the CAM assay procedure, including cultivation techniques, treatment applications and methods of determining an angiogenic response using this assay. We detail the angiogenic effect of treatments, including drugs, metabolites, genes and cells used in conjunction with the CAM assay, while also highlighting the testing of genetically modified cells. We also present a detailed exploration of the advantages and limitations of different CAM analysis techniques, including visual assessment, histological and molecular analysis along with vascular casting methods and live blood flow observations.     

Exafs study of the local structure of Ni in Ni-MoS2/C hydrodesulfurization catalysts

To study the local structure of the Ni promoter atom, the Ni and Mo K edge EXAFS spectra of Ni-MoS₂/C hydrodesulfurization catalyst were measured in an in-situ EXAFS cell at 77 K. The Ni atom is situated in a square pyramid of five S atoms at a distance of 2.21 Å from the S atoms. In addition an EXAFS contribution due to a Mo atom at 2.82 Å from the Ni atom could be identified. This local structure indicates that the Ni atoms are situated on top of the S₄ squares at the MoS₂ edges in millerite-type Ni sites. The Ni atoms are situated in the planes of the Mo atoms and not in the intercalation plane midway between successive MoS₂ sandwich layers.     

New Methodology for Quantifying Polycyclic Aromatic Hydrocarbons (PAHs) Using High-Resolution Aerosol Mass Spectrometry

This article presents a new methodology to potentially quantify polycyclic aromatic hydrocarbon (PAH) isomers using high-resolution time of flight aerosol mass spectrometer (HR-AMS). The fragmentation of PAHs within the HR-AMS is such that significant signal remains at the molecular ion. After quantifying the molecular ion signal and taking into account potential interferences, the amount of the parent PAH in the aerosol may be inferred once its fragmentation pattern is also known. The potential of this approach was evaluated using mixed gasoline and diesel engine exhaust sampled under varying conditions. This dataset led to the identification and quantification within the aerosol mass spectra of the molecular ions associated with 53 PAH isomers, including both unsubstituted and functionalized species. An evaluation of anticipated interferences shows that interferences from larger molecular weight PAHs (i.e., PAH/PAH interferences) could be constrained based on the fragmentation behavior of PAHs from existing HR-AMS laboratory spectra. Other signal interferences for this data set are typically less than 5% of the total signal or, for ¹³C isotopic interferents, are well constrained by measurements of the dominant isotope. The experimental data reveal that the fractional PAH molecular ion signal remained stable despite dramatic temporal variability of the total particulate organic signal. The fractional contributions of the molecular ions for grouped PAH species and even individual compounds were remarkably consistent across experiments. The distribution of PAHs showed no apparent dependence on engine load or exhaust type. Full application of this approach will require a greater number of standard HR-AMS spectra for PAHs, so that the relationship between compounds and their molecular ions may be understood more precisely.

Copyright 2015 American Association for Aerosol Research     

Optimizing Thermal-Optical Methods for Measuring Atmospheric Elemental (Black) Carbon: A Response Surface Study

The chemical, physical, and morphological complexity of atmospheric aerosol elemental carbon (EC) presents major problems in assuring measurement accuracy. Since EC and black carbon are often considered equivalent, methods based on thermal-optical analysis (TOA) are widely used for EC in ambient air samples because no prior knowledge of the aerosol's absorption coefficient is required. Nevertheless, different TOA thermal desorption protocols result in wide EC-to-total-carbon (TC) variation. We created three response surfaces with the following response variables: EC/TC, maximum laser attenuation in the He phase ( L max ), and laser attenuation at the end of the He phase ( L He4 ). A two-level central-composite factorial design comprised of four factors considered the temperatures and durations of all desorption steps in TOA's inert (He) phase and the initial step in TOA's oxidizing (O 2 -He) phase. L max was used to assess the positive bias caused by nonvolatile unpyrolized organic carbon (OC char) being measured as native EC. A negative bias that the attenuated laser response does not detect is caused by the loss of native EC in the He phase. L He4 was used as a surrogate indicator for the loss of native EC in the He phase. The intersection between the L max and L He4 surfaces revealed TOA conditions where both the production of OC char in the He phase was maximized and the loss of native EC in the He phase was minimized, therefore leading to an optimized thermal desorption protocol. Based on the sample types used in this study, the following are generalized optimal conditions when TOA is operated in the fixed-step-durations, laser-transmission mode (i.e., TOT): step 1 in He, 190°C for 60 s; step 2 in He, 365°C for 60 s; step 3 in He, 610°C for 60 s; step 4 in He, 835°C for 72 s. For steps 1-4 in O 2 -He, the conditions are 550°C for 180 s, 700°C for 60 s, 850°C for 60 s, and 900°C for 90 s to 120 s, respectively.     

Convective condensation in a stator–rotor–stator spinning disc reactor

Centrifugal intensification of condensation heat transfer in the rotor–stator cavities of a stator–rotor–stator spinning disc reactor (srs‐SDR) is studied, as a function of rotational velocity ω, volumetric throughflow rate , and average temperature driving force . For the current range of ω, heat transfer from the vapor bubbles to the condensate liquid is limiting, due to a relatively low gas–liquid interfacial area a_GL. For rad s^?1, a strong increase of a_GL, results in increasing the reactor‐average condensation heat transfer coefficient h_c from 1600 to 5600 W m^?2 K^?1, for condensation of pure dichloromethane vapor. Condensation heat transfer in the srs‐SDR is enhanced by rotation, independent of the vapor velocity. The intensified condensation comes at the cost of relatively high energy dissipation rates, indicating condensation in the srs‐SDR is more suited as a means to supply heat (e.g. in an intensified reactor‐heat exchanger), rather than for bulk cooling purposes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3784–3796, 2016     

Characterization of Pt?CAu and Ni?CAu Clusters on TiO2(110)

The surface composition and properties of Pt?CAu and Ni?CAu clusters on TiO₂(110) have been studied by scanning tunneling microscopy (STM), low energy ion scattering (LEIS) and soft X-ray photoelectron spectroscopy (sXPS). STM studies show that bimetallic clusters are formed during sequential deposition of the two metals, regardless of the order of deposition. At the 2?ML of Au/2?ML of Pt or Ni coverages studied here, the second metal contributes to the growth of existing clusters rather than forming new pure metal clusters. LEIS experiments demonstrate that the surfaces of the bimetallic clusters are almost 100% Au when 2?ML of Au is deposited on top of 2?ML of Pt or Ni. However, a much larger fraction of Pt or Ni (50 and 20%, respectively) remains at the surface when 2?ML of Pt or Ni is deposited on 2?ML of Au, most likely due to limited diffusion of atoms within the clusters at room temperature. According to sXPS investigations, the binding energies of the metals in the bimetallic clusters are shifted from those observed for pure metal clusters; the Pt(4f_7/2) and Ni(3p_3/2) peaks are shifted to lower binding energies while the position of the Au(4f_7/2) peak is dominated by surface core level shifts. Pure Pt clusters as well as 0.4?ML of Au on 2 ML of Pt clusters reduce the titania support upon encapsulation after annealing to 800?K, whereas 2?ML of Au on 2?ML of Pt clusters do not reduce titania, presumably because there is no Pt at the surface of the clusters. Pure Ni clusters are also known to become encapsulated upon heating, but the reduction of titania is much less extensive compared to that of pure Pt clusters.     

Production of antimicrobially active silk proteins by use of metal‐containing dyestuffs

The work presented here discusses a new technique for preparing silk fibers and films with persistent antimicrobial activity through use of metallic dyestuffs during the fiber dyeing process. The length of the silk fibers investigated contracted when the fibers were immersed in concentrated neutral salt solutions, such as calcium or potassium nitrate, at elevated temperature levels. The birefringence and molecular orientation of the silk fibroin molecules became less ordered by the action of the neutral salt solutions, resulting in increased dyestuff absorption. Subsequently, contracted silk fibers were dyed with metallic dyestuffs containing Cr or Cu for the purpose of obtaining silk fibers with antimicrobial activity. Silk fibers dyed with metallic dyestuffs showed significant antimicrobial activity against the plant pathogen Cornebacterium and the human pathogen Coli bacillus. Tensile strength of the silk fibers after the salt shrinking and dyeing processes did not show a significant change, whereas the elongation at break was increased slightly. The techniques described here for preparing significantly active antimicrobial silk fibers are effective and economic ways of providing new materials for industrial and biomedical applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1181–1188, 2002     

A Refinement on the Notion of Type I and II (Co)MoS Phases in Hydrotreating Catalysts

Hydrotalcite-like compounds with boron anions in the interlayer were obtained using a coprecipitation method. The effect of different pH values during the preparation was investigated and the effect on crystallinity and phase distribution studied. The influence of different methods of acidity regulation was also analyzed. The efficiency of synthesis of boron-containing anionic clays was evaluated, and the good thermal stability of the materials was noted. Surface characteristics were determined by X-ray photoelectron spectroscopy and correlated to the bulk properties obtained by X-ray diffraction and ²⁷Al and ¹¹B MAS NMR. The samples tested in gas-phase Beckmann rearrangement showed caprolactam formation, and the results were related to the surface features.     

Development of On-Line High Performance Liquid Chromatography (HPLC)-Biochemical Detection Methods as Tools in the Identification of Bioactives

Biochemical detection (BCD) methods are commonly used to screen plant extracts for specific biological activities in batch assays. Traditionally, bioactives in the most active extracts were identified through time-consuming bio-assay guided fractionation until single active compounds could be isolated. Not only are isolation procedures often tedious, but they could also lead to artifact formation. On-line coupling of BCD assays to high performance liquid chromatography (HPLC) is gaining ground as a high resolution screening technique to overcome problems associated with pre-isolation by measuring the effects of compounds post-column directly after separation. To date, several on-line HPLC-BCD assays, applied to whole plant extracts and mixtures, have been published. In this review the focus will fall on enzyme-based, receptor-based and antioxidant assays.