Sol-Gel Prepared Nanoscopic Metal Fluorides - a New Class of Tunable Acid-Base Catalysts

In this article, the high potential of the fluorolytic sol-gel process to synthesise nanoscopic metal fluorides with different acid-base properties is shown. These nanoscopic materials exhibit high potential to be used as heterogeneous catalysts due to their high surface areas and their tunable surface properties. Thus, for each specific reaction the required surface properties of the catalysts can be ”adjusted” to achieve a high yield and selectivity of the desired product. As a consequence, a greener method of chemical production can be accomplished. Moreover the cheap and easy synthesis of the catalysts using basic chemicals makes them not only interesting for fundamental research but provides an easy transformation to industrial applications

Quantifying the Effects of Hyperthermal Atomic Oxygen and Thermal Fatigue Environments on Carbon Nanotube Sheets for Space-Based Applications

The effects of atomic oxygen and thermal fatigue on two different types of carbon nanotube sheets were studied. One set was treated with nitric acid, while the other set was left untreated. Monotonic tensile tests were performed before and after exposure to determine the effects of either exposure type on the sheets’ mechanical properties. Electrical conductivity and electromagnetic interference measurements were recorded to determine the effects of AO-exposure and thermal cycling on the sheets’ electrical properties. Neither exposure type affected the sheets’ specific strengths. Both exposure types increased the sheets’ specific stiffnesses and decreased the sheets’ strains at failure. The electrical conductivity of both sheets decreased due to the different exposure types, while the EMI shielding effectiveness was unaffected. Scanning electron microscopy was used to observe any changes in the sheets’ surface morphologies, while energy-dispersive X-ray spectroscopy was used to determine the effects of AO on the sheets’ chemical makeup

Effects of Thermal Process Parameters on Mechanical Interlayer Strength for Additively Manufactured Ultem 9085

The effects of the envelope temperature on the microstructure and mechanical strength of Ultem 9085 fused deposition modeling (FDM) components were studied. A customized build chamber was developed for a commercial 3D printer in order to control the envelope temperature during printing. Test specimens were printed in the vertical direction because their mechanical strength exhibited the greatest dependence on inter-layer adhesion and neck development. A delay was introduced between two layers in each specimen in order to create a weak region where the neck was not expected to fully develop. However, none of the specimens failed in this region. Mechanical testing revealed that neck growth was highly dependent on the envelope temperature, and the strength was shown to vary significantly (20%) based on the envelope temperature. The variability of the mechanical strength also decreased as the envelope temperature increased. Thermal imaging revealed that the cooling rate of the specimens was consistent regardless of the envelope temperature. Fracture analysis confirmed that higher envelope temperatures improved the amount of neck growth and inter-layer adhesion in the specimens. This study showed that increasing the envelope temperature created parts with higher strengths and improved consistencies

The Impact of Laser Control on The Porosity And Microstructure of Selective Laser Melted Nickel Superalloy 718

Additively manufacturing high performance metals by laser processing represents an exciting opportunity to exploit localized properties by varying input parameters throughout the process. This work explores the solidification and microstructural properties of selectively laser melted (SLM) Inconel 718 (IN718) using unique processing parameters. By employing traditional pulsed laser physics techniques, samples were manufactured with a continuous wave laser to study a potential ubiquitous approach. While the overall power density was controlled, the power, speed, and hatch spacing were varied. The porosity and grain sizes of the samples were characterized by optical and scanning electron microscopes. The influence of processing parameters showed physical differences in the final samples. Sample degradation was observed in higher power processes with porosity up 10%, likely due to increased temperatures and more intense thermal gradients

What is Wrong with Water Barometers?

Every student who studies atmospheric pressure in physics or chemistry learns the principles behind the construction of barometers. Cistern barometers, such as those found in most laboratories, consist of a long glass tube containing an inverted column of liquid having an open end in a cistern of the liquid. Students learn that the column of liquid is supported by air pressure and is equal in weight to a column of air of the same diameter

Density Functional Study of Cubic to Rhombohedral Transition in α\alpha-AlF3_3

Under heating, $\alpha$-AlF$_3$ undergoes a structural phase transition from rhombohedral to cubic at temperature $T$ around 730 K. The density functional method is used to examine the $T$=0 energy surface in the structural parameter space, and finds the minimum in good agreement with the observed rhombohedral structure. The energy surface and electronic wave-functions at the minimum are then used to calculate properties including density of states, $\Gamma$-point phonon modes, and the dielectric function. The dipole formed at each fluorine ion in the low temperature phase is also calculated, and is used in a classical electrostatic picture to examine possible antiferroelectric aspects of this phase transition.Comment: A 6-page manuscript with 4 figures and 4 table

The PPAR-γ agonist pioglitazone modulates inflammation and induces neuroprotection in parkinsonian monkeys

<p>Abstract</p> <p>Background</p> <p>Activation of the peroxisome proliferator-activated receptor gamma (PPAR-γ) has been proposed as a possible neuroprotective strategy to slow down the progression of early Parkinson's disease (PD). Here we report preclinical data on the use of the PPAR-γ agonist pioglitazone (Actos^®; Takeda Pharmaceuticals Ltd.) in a paradigm resembling early PD in nonhuman primates.</p> <p>Methods</p> <p>Rhesus monkeys that were trained to perform a battery of behavioral tests received a single intracarotid arterial injection of 20 ml of saline containing 3 mg of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Twenty-four hours later the monkeys were assessed using a clinical rating scale, matched accordingly to disability, randomly assigned to one of three groups [placebo (n = 5), 2.5 (n = 6) or 5 (n = 5) mg/kg of pioglitazone] and their treatments started. Three months after daily oral dosing, the animals were necropsied.</p> <p>Results</p> <p>We observed significant improvements in clinical rating score (<it>P </it>= 0.02) in the animals treated with 5 mg/kg compared to placebo. Behavioral recovery was associated with preservation of nigrostriatal dopaminergic markers, observed as higher tyrosine hydroxylase (TH) putaminal optical density (<it>P </it>= 0.011), higher stereological cell counts of TH-ir (<it>P </it>= 0.02) and vesicular monoamine transporter-2 (VMAT-2)-ir nigral neurons (<it>P </it>= 0.006). Stereological cell counts of Nissl stained nigral neurons confirmed neuroprotection (<it>P </it>= 0.017). Pioglitazone-treated monkeys also showed a dose-dependent modulation of CD68-ir inflammatory cells, that was significantly decreased for 5 mg/kg treated animals compared to placebo (<it>P </it>= 0.018). A separate experiment to assess CSF penetration of pioglitazone revealed that 5 mg/kg p.o. induced consistently higher levels than 2.5 mg/kg and 7.5 mg/kg. p.o.</p> <p>Conclusions</p> <p>Our results indicate that oral administration of pioglitazone is neuroprotective when administered early after inducing a parkinsonian syndrome in rhesus monkeys and supports the concept that PPAR-γ is a viable target against neurodegeneration.</p

Influence of Nano-Sized SiC on the Laser Powder Bed Fusion of Molybdenum

Consolidation of pure molybdenum through laser powder bed fusion and other additive manufacturing techniques is complicated by a high melting temperature, thermal conductivity and ductile-to-brittle transition temperature. Nano-sized SiC particles (0.1 wt%) were homogeneously mixed with molybdenum powder and the printing characteristics, chemical composition, microstructure, mechanical properties were compared to pure molybdenum for scan speeds of 100, 200, 400, and 800 mm/s. The addition of SiC improved the optically determined density and flexural strength at 400 mm/s by 92% and 80%, respectively. The oxygen content was reduced by an average of 52% over the four scan speeds analyzed. Two mechanisms of oxygen reduction were identified as responsible for the improvements: oxidation of free carbon and the creation of secondary phase nanoparticles. This study illustrates the promising influence of nanoparticle additions to refractory metals in laser powder bed fusion

Mitigation of Anisotropic Fatigue in Nickel Alloy 718 Manufactured via Selective Laser Melting

The tension-tension fatigue behavior of heat treated selective laser melted (SLM) nickel alloy 718 (IN718) tensile specimens was tested and compared to as-built specimens. In addition to the industry standard IN718 heat treatment, a modified heat treatment was developed and tested in order to mitigate the anisotropic mechanical properties inherent to SLM materials. Electron backscatter diffraction verified that the modified heat treatment significantly affected the microstructure in all build planes. Three different print orientations were studied to determine their effect on the fatigue behavior. Both heat treatments improved the fatigue life of the specimens, although neither surpassed the fatigue life of wrought specimens. The modified heat treatment reduced the effect of the print orientation on the fatigue life. Surface roughness estimates made by laser scanning microscopy revealed a threshold between roughness controlled fatigue life behavior and print orientation fatigue life dependence. Fracture surface analysis indicated that the print orientation was the greatest factor that influences crack initiation and propagation