Intrinsic properties of osteomalacia bone evaluated by nanoindentation and FTIRM analysis.

Osteomalacia is a pathological bone condition consisting in a deficient primary mineralization of the matrix, leading to an accumulation of osteoid tissue and reduced bone mechanical strength. The amounts, properties and organization of bone constituents at tissue level, are known to influence its mechanical properties. It is then important to investigate the relationship between mechanical behavior and tissue composition at this scale in order to provide a better understanding of bone fragility mechanisms associates with this pathology. Our purpose was to analyze the links between ultra-structural properties and the mechanical behavior of this pathological bone tissue (osteomalacia) at tissue level (mineral and osteoid separately, or global). Four bone biopsies were taken from patients with osteomalacia, and subsequently embedded, sectioned, and polished. Then nanoindentation tests were performed to determine local elastic modulus E, contact hardness Hc and true hardness H for both mineralized and organic bone phases and for the global bone. The creep of the bone was also studied using a special indentation procedure in order to assess visco-elasto-plastic (creep) bone behavior. This allowed a detailed study of the rheological models adapted to the bone and to calculate the parameters associated to a Burgers model. Ultra-structural parameters were measured by Fourier Transform InfraRed Microspectroscopy (FTIRM) on the same position as the indents. The use of rheological models confirmed a significant contribution from the organic phase on the viscous character of bone tissue. The elastic E and the elasto-plastic Hc deformation were correlated to both collagen maturity and Mineral/Matrix. The pure plastic deformation H was only correlated to the mineral phase. Our data show that mineral phase greatly affects mechanical variables (moduli and viscosities) and that organic phase (as illustrated in osteoid tissue) may play an important role in the creep behavior of bone. In conclusion, this study brings mechanical and physicochemical values for osteoid and mineral phases.

Congener specific determination of polychlorinated naphthalenes in sediment and biota by gas chromatography high resolution mass spectrometry.

An isotope dilution congener-specific method for the determination of the most abundant and most toxic polychlorinated naphthalenes (PCNs) was developed using gas chromatography with high resolution mass spectrometry (GC-HRMS). The method was used to determine the concentration of 24 target congeners and total PCN concentrations in fish and sediment samples. Tissue samples were extracted using pressurized liquid extraction (PLE) and sediment samples were extracted using Soxhlet extraction. Sample extracts were cleaned up using either a manual two-stage open column procedure or an automated FMS Power Prep System with multi-analyte and multi-sample capability using a three-column cleanup procedure. Sediment extracts were cleaned up with a dual open column cleanup technique involving the use of both a multi-layered silica (silver nitrate/acid/base/neutral silica) column followed by column containing carbon-activated silica. Fish tissue extracts were cleaned up on the automated system involving the use of a high capacity ABN (acid/base/neutral column), carbon celite column, and a basic alumina column. The method is capable of producing instrument detection limits (IDLs) between 0.06 and 0.13pg for each PCN (on column), with method detection limits (MDLs) for the fish extracts ranging from 1.3 to 3.4pg/g (wet weight) and 0.46 to 1.2pg/g (dry weight) for sediments. The average accuracy of 34 spiked fish samples analysed over a period of several months was 100% with a precision (%RSD) of 12%. Similarly, the average accuracy for 28 spiked sediment samples was 104% with a precision (%RSD) of 12%. The application of the method to environmental samples was demonstrated through the analysis of sediment and fish samples obtained from Lake Ontario, Canada. The method is used both for the determination of 24 PCNs and to perform non-targeted screening for the remaining 51 PCN congeners, which are included in the total PCN quantification result. It is currently one of the most comprehensive and accurate congener-specific methods available and was developed from the existing techniques used for the determination of polychlorinated dioxins and furans to produce high quality data with only minor modifications in the clean-up procedure. It can therefore be readily adopted by other laboratories performing dioxin and POP analyses.

Coupling of strain, stress, and oxygen non-stoichiometry in thin film Pr0.1Ce0.9O2-δ.

Stress and strain in thin films of Pr0.1Ce0.9O2-δ, supported on yttria stabilized zirconia (YSZ) and sapphire substrates, induced by large deviations from oxygen stoichiometry (δ = 0) were investigated by in situ high temperature X-ray diffraction and wafer curvature studies. The measured stresses and strains were correlated with change in δ, measured in situ using optical transmission spectroscopy of defect centers in the films and compared with prior chemical capacitance studies. The coefficient of chemical expansion and elastic modulus values for the films were found to be 18% less than, and 16% greater than in the bulk, respectively. Irreproducible stress and strain during cycling on YSZ substrates was observed and related to microstructural changes as observed by TEM. The enthalpy of defect formation was found to be similar for films supported on sapphire and YSZ, and appeared to decrease with tensile stress, and increase with compressive stress. Larger stresses observed for YSZ supported films as compared to sapphire supported films were found and accounted for by the difference in film orientations.

Current status and future directions for in situ transmission electron microscopy.

This review article discusses the current and future possibilities for the application of in situ transmission electron microscopy to reveal synthesis pathways and functional mechanisms in complex and nanoscale materials. The findings of a group of scientists, representing academia, government labs and private sector entities (predominantly commercial vendors) during a workshop, held at the Center for Nanoscale Science and Technology- National Institute of Science and Technology (CNST-NIST), are discussed. We provide a comprehensive review of the scientific needs and future instrument and technique developments required to meet them.

Measuring bandgap states in individual non-stoichiometric oxide nanoparticles using monochromated STEM EELS: The Praseodymium-ceria case.

We describe a method to perform high spatial resolution measurement of the position and density of inter-band impurity states in non-stoichiometric oxides using ultra-high energy resolution electron energy-loss spectroscopy (EELS). This can be employed to study optical and electronic properties of atomic and nanoscale defects in electrically-conducting and optically-active oxides. We employ a monochromated scanning transmission electron microscope with subnanometer diameter electron probe, making this technique suitable for correlating spectroscopic information with high spatial resolution images from small objects such as nanoparticles, surfaces or interfaces. The specific experimental approach outlined here provides direct measurement of the Pr inter-band impurity states in Pr0.1Ce0.9O2-δ via valence-loss EELS, which is interpreted with valence-loss spectral simulation based on density of states data to determine the energy level and character of the inter-band state. Additionally, observation of optical color change upon chemically-induced oxygen non-stoichiometry indicates that the population of the inter-band state is accompanied by an energy level shift within the bandgap.

Growth behavior near the ultimate resolution of nanometer-scale focused electron beam-induced deposition.

An attempt has been made to reach the ultimate spatial resolution for electron beam-induced deposition (EBID) using W(CO)(6) as a precursor. The smallest dots that have been written have an average diameter of 0.72 nm at full width at half maximum (FWHM). A study of the nucleation stage revealed that the growth is different for each dot, despite identical growth conditions. The center of mass of each dot is not exactly on the position irradiated by the e-beam but on a random spot close to the irradiated spot. Also, the growth rate is not constant during deposition and the final deposited volume varies from dot to dot. The annular dark field signal was recorded during growth in the hope to find discrete steps in the signal which would be evidence of the one-by-one deposition of single molecules. Discrete steps were not observed, but by combining atomic force microscope measurements and a statistical analysis of the deposited volumes, it was possible to estimate the average volume of the units of which the deposits consist. It is concluded that the volume per unit is as small as 0.4 nm(3), less than twice the volume of a single W(CO)(6) molecule in the solid phase.

Diffraction patterns of artificial two-dimensional crystals synthesized in situ in an environmental scanning transmission electron microscope.

In this study, we demonstrated the use of electron-beam-induced deposition for synthesis of artificial two-dimensional crystals with an in situ scanning transmission electron microscope. The structures were deposited from W(CO)6 in an environmental scanning transmission electron microscope on a 30-nm-thick Si3N4 substrate. We present clear electron beam diffraction patterns taken from those structures. The distance between the diffraction peaks corresponded to the dot spacing in the self-made surface crystal. We propose using these arrays of dots as anchor points for making artificial crystals for diffraction analysis of weakly scattering or beam-sensitive molecules such as proteins.

Syndrome-based discrimination of single nucleotide polymorphism.

The ability to discriminate nucleic acid sequences is necessary for a wide variety of applications: high throughput screening, distinguishing genetically modified organisms (GMOs), molecular computing, differentiating biological markers, fingerprinting a specific sensor response for complex systems, etc. Hybridization-based target recognition and discrimination is central to the operation of nucleic acid sensor systems. Therefore developing a quantitative correlation between mishybridization events and sensor out put is critical to the accurate interpretation of results. In this work, using experimental data produced by introducing single mutations (single nucleotide polymorphisms, SNPs) in the probe sequence of computational catalytic molecular beacons (deoxyribozyme gates) [1], we investigate coding theory algorithms for uniquely categorizing SNPs based on the calculation of syndromes.

The MIDAS project at ASU: John Cowley's vision and practical results.

An overview of the conception and development of the MIDAS system at Arizona State University is given: a Microscope for Imaging, Diffraction and Analysis of Surfaces. John Cowley's vision in the early 1980s was ambitious and far-reaching, and it was because of him the authors came to ASU. We were centrally involved in the design and implementation of MIDAS from the mid 1980s onwards; the novel design features are briefly reviewed. Practical results obtained using this instrument are listed, and the scope for future development and applications are indicated. While it is clear that many new results have been demonstrated, even more possibilities still remain to be explored. Some comments are made about the feasibility of such developments in the light of competing instrumentation.

Natural materno-fetal transfer of antibodies to PspA and to PsaA.

UNLABELLED: PspA and PsaA are Streptococcus pneumoniae surface proteins and potential pneumococcal vaccine antigens. The aim of this study was to characterize the transplacental transfer of antibodies to PspA and to PsaA. Paired mother and cord blood sera were obtained at delivery from 28 women. Concentrations of antibodies against PspA, PsaA, tetanus toxoid (vaccine-induced antibodies) and P6-outer membrane protein (OMP) of nontypeable Haemophilus influenzae were determined by ELISA. Antibodies to PspA of the IgG, IgG1 and IgG2 antibodies were also determined. The geometric mean percentage (GM%) of the paired infant:mother antibody were calculated. RESULTS: The GM% of the infant:mother antibody concentrations against PspA, PsaA and P6-OMP antibodies were 64.7% (3.3 micro g/ml in infants vs. 5.1 micro g/ml in mothers), 50.4% (6.8 micro g/ml vs. 13.5 micro g/ml) and 66.7% (5.6 micro g/ml vs. 8.4 micro g/ml), respectively; the GM% of antibodies against tetanus toxoid was 104.5% (4.6 micro g/ml vs. 4.4 micro g/ml). Transplacental transfer of IgG1 was more efficient than that of IgG2 (approximately 120%vs. 65%). A transplacental transfer of antibodies to PspA and to PsaA exist. Moreover, these data suggest an active placental transfer of IgG1 antibodies to PspA since the concentration of these antibodies were consistently higher in cord sera than in the mother's sera.

Lattice measurement and alloy compositions in metal and bimetallic nanoparticles.

A new reliable method for determining the lattice spacings of metallic and bimetallic nanoparticles in phase contrast high resolution electron microscopy (HREM) images was developed. In this study, we discuss problems in applying HREM techniques to single metal (Pt and Au) and bimetallic (AuPd) nanoparticles of unknown shapes and random orientations. Errors arising from particle tilt and edge effects are discussed and analysis criteria are presented to reduce these errors in measuring the lattice parameters of nanoparticles. The accuracy of an individual particle lattice measurement is limited by an effective standard deviation which depends on the size of the individual nanoparticle. For example, the standard deviation for 20-30 A Pt or Au nanoparticles is about 1.5%. To increase the accuracy in determining the lattice spacings of nanoparticles, statistical methods have to be used to obtain the average lattice spacing of an ensemble of nanoparticles. We measured approximately 100 nanoparticles with sizes in the range of 20-30 A and found that the mean lattice spacing can be determined to within 0.2%. By applying Vegard's law to the AuPd bimetallic systems we successfully detected the presence of alloying. For 30 A nanoparticles, the estimated ultimate error in determining the composition of the AuPd alloy is about 3% provided that at least 100 particles are measured. Finally, the challenges in determining the presence of more than one alloy phases in bimetallic nanoparticle systems were also discussed.

New magnetic order in buried native iron oxide layers.

The properties of a magnetically ordered buried Fe oxide layer are presented. This oxide has a room-temperature magnetization exceeding that of Fe3O4 by 42% and of gamma-Fe2O3 by 89%. The oxide consists of a component (70%) with a net moment of 2.0 micro(B)/Fe ion, while the remaining spins yield no net moment. The oxide magnetization is stabilized in part by the proximate Fe metal.

Low-temperature epitaxial growth of the quaternary wide band gap semiconductor SiCAlN.

Two compounds SiC and AlN, normally insoluble in each other below approximately 2000 degrees C, are synthesized as a single-phase solid-solution thin film by molecular beam epitaxy at 750 degrees C. The growth of epitaxial SiCAlN films with hexagonal structure takes place on 6H-SiC(0001) substrates. Two structural models for the hexagonal SiCAlN films are constructed based on first-principles total-energy density functional theory calculations, each showing agreement with the experimental microstructures observed in cross-sectional transmission electron microscopy images. The predicted fundamental band gap is 3.2 eV for the stoichiometric SiCAlN film.

Model channel ion currents in NaCl-extended simple point charge water solution with applied-field molecular dynamics.

Using periodic boundary conditions and a constant applied field, we have simulated current flow through an 8.125-A internal diameter, rigid, atomistic channel with polar walls in a rigid membrane using explicit ions and extended simple point charge water. Channel and bath currents were computed from 10 10-ns trajectories for each of 10 different conditions of concentration and applied voltage. An electric field was applied uniformly throughout the system to all mobile atoms. On average, the resultant net electric field falls primarily across the membrane channel, as expected for two conductive baths separated by a membrane capacitance. The channel is rarely occupied by more than one ion. Current-voltage relations are concentration dependent and superlinear at high concentrations.

Molecular dynamics simulation of continuous current flow through a model biological membrane channel.

The conductance of sodium ions through a simplified channel-membrane system immersed in a reservoir of 1M NaCl in SPC/E water is examined by molecular dynamics simulation. An applied external potential of 1.1 V drives the ions and water through a channel of length 25 A producing a current of 19.6 pA, in reasonable agreement with experimental findings. The stream of ions and water molecules flows continuously because of the constant applied field and periodic boundary conditions. We also examine the potential profile across the simulation cell, the average density distributions of the various species in the reservoir and radially in the channel, and the ion velocity in the channel.

Trace level analysis of polycyclic aromatic hydrocarbons in surface waters by solid phase extraction (SPE) and gas chromatography-ion trap mass spectrometry (GC-ITMS).

Ontario Provincial Water Quality Objectives for polycyclic aromatic hydrocarbons (PAHs) in surface waters require low parts per trillion (ng L(-1))/high parts per quadrillion (pg L(-1)) detection limits. To meet these monitoring requirements, a solid phase extraction-gas chromatography-ion trap mass spectrometry (SPE-GC-ITMS) method was developed. Seventeen priority PAHs commonly monitored in surface and drinking waters were examined using an external ionization ion trap mass spectrometer operated in selected ion monitoring (SIM) mode. Under 70 eV electron ionization (El) conditions, both the quantitative [M]+* ion and confirmatory [M - 2H]+* ion were formed in classical abundance ratios. Each of these ion species was isolated in the ion trap using a specific scan function. However, to overcome poor levels of confirmatory ion abundance which otherwise restrict PAH method detection limits (MDLs), the abundance of [M - 2H]+* ions was augmented during isolation by causing the dissociation of [M]+* with the broad-band waveform used for high mass ion ejection. Augmenting the [M - 2H]+* signal intensity facilitated the achievement of MDLs of approximately 1 ng L(-1). PAHs in surface water samples that were not detected by current Ontario Ministry of the Environment high-performance liquid chromatography (HPLC)-fluorescence and GC-single-stage quadrupole mass spectrometry methods were detected and quantified using the ion trap mass spectrometry SIM method. The data produced by all three methods on natural water samples fortified at sub-parts per billion (ppb) levels were comparable. When applied to Standards Council of Canada/Canadian Association for Environmental Analytical Laboratories (SCC/CAEAL, www.CAEAL.ca) accreditation audit samples, the SPE-GC-ITMS method results met all performance evaluation criteria.

Characterization of nonyl phenol ethoxylates in sewage treatment plants by combined precursor ion scanning and multiple reaction monitoring.

A novel rapid screening technique for the profiling of nonyl phenol ethoxylates (NPEs) in sewage treatment plant (STP) influent/effluent was developed using flow injection with atmospheric pressure ionization coupled to mass spectrometric analysis by combined precursor ion scanning and multiple reaction monitoring. The technique allows for total NPE concentrations as low as 50 parts-per-trillion to be detected in STP samples.

Determination of diquat and paraquat in water by liquid chromatography-(electrospray ionization) mass spectrometry.

A method for the determination of the herbicides diquat and paraquat in water was developed using liquid chromatography-(electrospray ionization) mass spectrometry [LC-(ESI)MS]. The analytes were isolated on an ENVI-8 DSK solid phase extraction (SPE) disk and eluted with 5-M trifluoroacetic acid (TFA). The eluate was evaporated to dryness and the analytes were redissolved in the mobile phase (7% methanol/93% water/25-mM TFA). The extract was analyzed by liquid chromatography (C1 column) with postcolumn addition of propionic acid/methanol followed by (ESI)MS. Diquat was detected using the [M(2+)-H+] ion (M2+ = dication) at m/z 183, whereas paraquat was detected using the mono-trifluoroacetate ion pair [M2 +/- OOCCF3] at m/z 299. Quantitation was done by isotope dilution mass spectrometry using d4-diquat and d8-paraquat and the corresponding ions [M(2+)-D+] and [M2 +/- OOCCF3] at m/z 186 and m/z 307, respectively. Detection limits of 0.1 and 0.2 microgram/L, respectively (based on the dications), were adequate to meet the Ontario Drinking Water Objectives of 70 and 10 micrograms/L, respectively, and the Ontario Provincial Water Quality Objective for diquat of 0.5 microgram/L. Precision and accuracy were 14% and 6% for diquat and 12% and 3% for paraquat.

Effect of dietary cholesterol on low density lipoprotein-receptor, 3-hydroxy-3-methylglutaryl-CoA reductase, and low density lipoprotein receptor-related protein mRNA expression in healthy humans.

We investigated the possibility that dietary cholesterol downregulates the expression of low density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase genes of circulating mononuclear cells in vivo in healthy humans. We also studied the variations of the LDL receptor-related protein (LRP) gene in the same conditions. Dieters (n = 5) were submitted to a 4-d fat restriction (mean cholesterol intake: 6+/-4 mg/d), followed by a 7-d cholesterol (a mean of 791+/-150 mg/d) supplementation. Controls (n = 3) did not change their diet. During fat restriction, serum total and LDL cholesterol decreased significantly (P < 0.05), and LDL receptor and HMG-CoA reductase mRNA copy numbers in mononuclear cells increased by 57 and 147%, respectively (P < 0.05). After reintroducing cholesterol, serum cholesterol was stable whereas LDL receptor and HMG-CoA reductase mRNA decreased by 46 and 72% (P < 0.05) and LRP mRNA increased by 59% (P < 0.005). The changes in LDL receptor and HMG-CoA reductase mRNA abundance were correlated (r = +0.79, P = 0.02) during cholesterol reintroduction as were LDL receptor and LRP mRNA levels, but negatively (r = -0.70, P = 0.05). Also, 70% of the variability in LRP mRNA (P < 0.005) was explained by dietary cholesterol. Thus, the basic mechanisms regulating cellular cholesterol content, the coordinate feedback repression of genes governing the synthesis and uptake of cholesterol, are operating in vivo in humans. However, serum cholesterol did not increase in response to dietary cholesterol, suggesting that these mechanisms may not play as predominant a role as previously believed in the short-term control of serum cholesterol in vivo in humans. A new finding is that LRP gene is also sensitive to dietary cholesterol, suggesting that it may participate in the control of serum cholesterol. Further in vivo studies in humans are warranted to explore the molecular mechanisms of the physiological response to dietary cholesterol in humans.

Exercise-induced changes in plasma vitamin B-6 concentrations do not vary with exercise intensity.

This study examined the effect of high vs moderate exercise intensity on changes in concentration of plasma pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid (4-PA) in human subjects. Eight physically active subjects were tested twice at 60% and 85% maximum oxygen consumption (VO2max) for 30 and 20 min, respectively, on a bicycle ergometer. Blood samples were obtained before and during exercise. Data were adjusted for changes in plasma volume calculated from changes in hematocrit. PLP concentrations significantly increased during exercise (P < 0.0001), with 79% of the rise in PLP concentration occurring within 5 min. 4-PA concentration increased steadily through exercise and was 23% higher at 20 min than at 0 min. Exercise intensity had no effect on the magnitude or rate of either increase for either PLP or 4-PA. PL concentration did not vary with exercise duration, but was significantly higher at 60% compared with 85% VO2max (P = 0.001). No significant differences were observed in glucose concentration. The data do not support hypotheses in the literature that PLP concentration rises during exercise to support exercise-induced shifts in substrate utilization.