Role of structure of the Pp/magnetite nanocomposites on their thermal properties

The thermal degradation behaviour of polypropylene and its magnetite composites have been investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Distribution of magnetite nanoparticles in a polymer matrix has been studied by scanning and transmission electron microscopy and also atomic force microscopy. The thermal and mechanical properties of nanocomposites based on polypropylene and magnetite nanoparticles have also been investigated. It has shown that, the introduction of Fe3O4 nanoparticles in polypropylene increases its thermal stability of about 1000C. The maximum increase in the thermal stability of PP was observed in the case of a 20% weight content of Fe3O4 nanoparticles in polypropylene

Targeted Drug Delivery using Peptoid Based Nanospheres

While medicine has improved greatly in the last couple of decades, there are negative side effects that accompany many drugs. Undesirable side effects could be greatly reduced if non-systemic drug delivery systems were used because the medicine would harm diseased cells at a much higher rate than it does healthy cells. One possible non-systemic drug delivery system is peptoid nanospheres. These nanospheres will then be linked to another peptoid that is engineered to attach almost exclusively to diseased cells. This research project is focused on designing peptoids that will form nanospheres in solution. Four specific peptoids were synthesized and tested based on previous research conducted in the Servoss lab. These peptoids were synthesized then purified using high pressure liquid chromatography. After purification was complete, circular dichroism was used to determine the relative helicity of the peptoids. The peptoids were then dried on silicon chips and scanning electron microscopy was used to test for nanosphere formation. Next, dynamic light scattering (DLS) was used to determine if the peptoids formed structures in a 4 to 1 methanol and water solution. The two peptoids that DLS indicated might be forming spheres in solution were tested using transmission electron microscopy (TEM). Circular dichroism showed that all the peptoids were helicial while scanning electron microscopy showed that one of the four peptoids formed nanospheres. This indicates that helicity is not the main factor in nanospheres formation. DLS paired with TEM indicated that one of the peptoids formed nanospheres in the 500 – 600 nm size range

Freeze-Thaw Durability and Long-Term Performance Evaluation of Shotcrete in Cold Regions

This study’s aim was to evaluate the freeze-thaw durability of shotcrete in cold regions and predict its long-term performance. One benchmark mix design from the WSDOT was chosen to prepare samples for performance evaluation. Shotcrete specimens were conditioned in accordance with ASTM C666. The long-term freeze-thaw performance after certain cycles was evaluated using the dynamic modulus of elasticity test (ASTM C215), fracture energy test (RILEM 50-FMC), and X-ray CT microstructure imaging analysis. Probabilistic damage analysis was conducted to establish the relation between the durability life and the damage parameter for different probabilities of reliability using the three-parameter Weibull distribution model. The fracture energy test was found to be a more sensitive test method than the dynamic modulus of elasticity for screening material deterioration over time and for capturing accumulative material damage caused by rapid freeze-thaw action, because of smaller durability factors (degradation ratios) obtained from the fracture energy test. X-ray CT imaging analysis is capable of detecting microcracks that form and pore evolution in the aggregate and interface transition zone of conditioned samples. Moreover, the continuum damage mechanic-based model shows potential in predicting long-term material degradation and the service life of shotcrete

An investigation of the facsimile camera response to object motion

A general analytical model of the facsimile camera response to object motion is derived as an initial step toward characterizing the resulting image degradation. This model expresses the spatial convolution of a time-varying object radiance distribution and camera point-spread function for each picture element in the image. Time variations and these two functions during each convolution account for blurring of small image detail, and variations between, as well as during, successive convolutions account for geometric image distortions. If the object moves beyond the angular extent of several picture elements while it is being imaged, then geometric distortion tends to dominate blurring as the primary cause of image degradation. The extent of distortion depends not only on object size and velocity but also on the direction of object motion, and is therefore difficult to classify in a general sense

Thiol-gelatin-norbornene bioink for laser‐based high‐definition bioprinting

Two-photon polymerization (2PP) is a lithography-based 3D printing method allowing the fabrication of 3D structures with sub-micrometer resolution. This work focuses on the characterization of gelatin-norbornene (Gel-NB) bioinks which enables the embedding of cells via 2PP. The high reactivity of the thiol-ene system allows 2PP processing of cell-containing materials at remarkably high scanning speeds (1000 mm s(-1)) placing this technology in the domain of bioprinting. Atomic force microscopy results demonstrate that the indentation moduli of the produced hydrogel constructs can be adjusted in the 0.2-0.7 kPa range by controlling the 2PP processing parameters. Using this approach gradient 3D constructs are produced and the morphology of the embedded cells is observed in the course of 3 weeks. Furthermore, it is possible to tune the enzymatic degradation of the crosslinked bioink by varying the applied laser power. The 3D printed Gel-NB hydrogel constructs show exceptional biocompatibility, supported cell adhesion, and migration. Furthermore, cells maintain their proliferation capacity demonstrated by Ki-67 immunostaining. Moreover, the results demonstrate that direct embedding of cells provides uniform distribution and high cell loading independently of the pore size of the scaffold. The investigated photosensitive bioink enables high-definition bioprinting of well-defined constructs for long-term cell culture studies

Assessment of mortar evolution in pig slurry by mechanical and ultrasonic measurements

This work presents the results obtained in a long-term experiment focused on the study of the evolution of cementitious materials immersed in pig slurry at real conditions. Cement mortars were made with four different cement types and immersed in pig slurry for 48 months. Furthermore, to separate pure hydration process from pig slurry effect, mortar samples were immersed in water for 12 months at laboratory conditions. Compressive strength, X-ray diffraction and ultrasonic measurements were made in all samples. Ultrasonic measurements were made from ultrasonic images obtained from automatic ultrasonic inspections. Use of ultrasonic images has allowed the extraction of information about the state of the studied materials. An empirical relationship between ultrasonic velocity and compressive strength has been obtained and the long-term effect of pig slurry on cementitious materials has been determined

Multimodal optical characterisation of collagen photodegradation by femtosecond infrared laser ablation.

Collagen is a structural component of the human body, as a connective tissue it can become altered as a result of pathophysiological conditions. Although the collagen degradation mechanism is not fully understood, it plays an important role in ageing, disease progression and applications in therapeutic laser treatments. To fully understand the mechanism of collagen alteration, in our study photo-disruptive effects were induced in collagen I matrix by point-irradiation with a femtosecond Ti-sapphire laser under controlled laser ablation settings. This was followed by multi-modal imaging of the irradiated and surrounding areas to analyse the degradation mechanism. Our multi-modal methodology was based on second harmonic generation (SHG), scanning electron microscope (SEM), autofluorescence (AF) average intensities and the average fluorescence lifetime. This allowed us to quantitatively characterise the degraded area into four distinct zones: (1) depolymerised zone in the laser focal spot as indicated by the loss of SHG signal, (2) enhanced crosslinking zone in the inner boundary of the laser induced cavity as represented by the high fluorescence ring, (3) reduced crosslinking zone formed the outer boundary of the cavity as marked by the increased SHG signal and (4) native collagen. These identified distinct zones were in good agreement with the expected photochemical changes shown using Raman spectroscopy. In addition, imaging using polarisation-resolved SHG (p-SHG) revealed both a high degree of fibre re-orientation and a SHG change in tensor ratios around the irradiation spot. Our multi-modal optical imaging approach can provide a new methodology for defining distinct zones that can be used in a clinical setting to determine suitable thresholds for applying safe laser treatments without affecting the surrounding tissues. Furthermore this technique can be extended to address challenges observed in collagen based tissue engineering and used as a minimally invasive diagnostic tool to characterise diseased and non-diseased collagen rich tissues

Looking at pore scale processes in geomaterials using time-resolved 3D imaging and multi-scale imaging

C

Reliability Testing of AlGaN/GaN HEMTs Under Multiple Stressors

We performed an experiment on AlGaN/GaN HEMTs with high voltage and high power as stressors. We found that devices tested under high power generally degraded more than those tested under high voltage. In particular, the high-voltage-tested devices did not degrade significantly as suggested by some papers in the literature. The same papers in the literature also suggest that high voltages cause cracks and pits. However, the high-voltage-tested devices in this study do not exhibit cracks or pits in TEM images, while the high-power-tested devices exhibit pits