Surface Whiskerization Of Carbon Fibers With Carbon Nanotubes

Carbon fibers are the main reinforcing fibers used in high performance polymer matrix composites in various applications such as manufacturing of aerospace vehicles and high quality sports gear. Composite performance can be enhanced by applying an optimum level of fiber surface treatment. Surface treatments may be classified into oxidative and non-oxidative treatments. In this study, whiskerization which is a type of non-oxidative treatment was employed. This treatment involved the coating of untreated carbon fibers with carbon nanotubes (CNTs). There are three main objectives in this study. The first objective was to design and fabricate a chemical vapour deposition (CVD) reactor system that enables the growth of CNTs from carbon fiber surface. The second objective was to carry out whiskerization treatment at various conditions and to characterize the CNT-coated fibers at these conditions. Characterization of CNT-coated fibers was conducted at varying regions within the reaction tube; at reaction temperatures between 800-1000oC and carrier gas (hydrogen) flow rates between 100-500ml/min. Characterization of the CNTs formed on the carbon fibers was also conducted. The third objective was to investigate the flexural properties of composites made from untreated and CNT-coated carbon fibers. A CVD reactor system, referred to as CVD rig was successfully designed and fabricated to grow CNTs on untreated carbon fiber. CNTs grew on carbon fiber at region 1 for all treatment conditions. The CNTs grown on the carbon fibers increased in length and distinctness of parallel graphitic sheets alignment as the reaction temperature increased from 800 to 1000oC. As the hydrogen flow rate increased from 100 to 500 ml/min, the CNT coatings on the fibers were relatively more even and the amorphous carbon impurities (indicated by clumps) on the CNT-coated fibers disappeared (only observed at 800oC). “Whisker-like” morphology and bi-directional growth were the two types of CNT conformations produced in this study. The CNTs grown was identified as multi-walled carbon nanotubes (MWCNTs). Whiskerization treatment on carbon fibers increases the flexural strength of composites between 44-122%. Higher reaction temperature and hydrogen flow rate during carbon fiber whiskerization treatment lowers the flexural strength of its composite. Hydrogen flow rate has lesser impact on the flexural strength as compared to the reaction temperature. Observation of carbon fiber-epoxy composite fracture surface indicated CNT-coated carbon fiber bonds better with epoxy matrix compared to untreated carbon fiber

CVD whiskerization treatment process for the enhancement of carbon fiber composite flexural strength

Carbon fiber composite performance can be enhanced by applying an optimum level of fiber surface treatment such as whiskerization. The main objectives of this study were to conduct whiskerization through carbon nanotube (CNT)-coating of carbon fiber via chemical vapour deposition (CVD) at various conditions (temperature and hydrogen flow rate) and to investigate the enhancement in flexural strength of composites fabricated from these CNT-coated carbon fibers. The results indicated that CNTs were able to grow onto the carbon fibres with the highest amount of whiskerization occurring for samples nearest the reactant gas inlet of the CVD Rig. Various whiskerization behaviours were observed at different reaction temperatures and flow rates. From flexural tests, it was found that whiskerization treatment on carbon fibers increases the flexural strength of its composites between 44-122%

New Polychaete Records from Seagrass Beds at Minicoy Island, Lakshadweep, India

Species composition, distribution and taxonomic description of polychaete fauna in the seagrass beds of the Minicoy lagoon, Lakshadweep, India were studied during 1999 - 2001. In 4 stations, 27 species of polychaetes belonging to 14 genera were identified. Of these 27 species, 10 species of polychaetes, belonging to 8 genera under 6 families, comprise new distributional records from Minicoy Island, and the descriptions of these species are provided. Among these, Glycera lancadivae, G. tesselata, and Eurythoe matthaii are found to be the most dominant species

Novel Devices for Studying Acute and Chronic Mechanical Stress in Retinal Pigment Epithelial Cells

Choroidal neovascularization (CNV) is a major cause of blindness in patients with age-related macular degeneration (AMD). Overexpression of vascular endothelial growth factor (VEGF), a potent angiogenic protein, by retinal pigment epithelial (RPE) cells is a key stimulator of CNV. Mechanical stress occurs during different stages of AMD and is a possible inducer of VEGF expression in RPE cells. However, robust and realistic approaches to studying acute and chronic mechanical stress under various AMD stages do not exist.The majority of previous work has studied cyclic stretching of RPE cells grown on flexible substrates, but an ideal model must be able to mimic localized and continuous stretching of the RPE as would occur in AMD in vivo. To bridge this gap, we developed two in vitro devices to model chronic and acute mechanical stress on RPE cells during different stages of AMD. In one device, high levels of continuous mechanical stress were applied to focal regions of the RPE monolayer by stretching the underlying silicon substrate to study the role of chronic mechanical stimulation. In the second device, RPE cells were grown on porous plastic substrates and acute stress was studied by stretching small areas. Using these devices, we studied the effect of mechanical stress on VEGF expression in RPE cells.Our results suggest that mechanical stress in RPE cells inducesVEGF expression and promotes in vitro angiogenesis. These results confirm the hypothesis that mechanical stress is involved in the initiation and progression of CNV

Muscle Atrophy Marker Expression Differs between Rotary Cell Culture System and Animal Studies

Muscular atrophy, defined as the loss of muscle tissue, is a serious issue for immobilized patients on Earth and for humans during spaceflight, where microgravity prevents normal muscle loading. In vitro modeling is an important step in understanding atrophy mechanisms and testing countermeasures before animal trials. The most ideal environment for modeling must be empirically determined to best mimic known responses in vivo. To simulate microgravity conditions, murine C2C12 myoblasts were cultured in a rotary cell culture system (RCCS). Alginate encapsulation was compared against polystyrene microcarrier beads as a substrate for culturing these adherent muscle cells. Changes after culture under simulated microgravity were characterized by assessing mRNA expression of MuRF1, MAFbx, Caspase 3, Akt2, mTOR, Ankrd1, and Foxo3. Protein concentration of myosin heavy chain 4 (Myh4) was used as a differentiation marker. Cell morphology and substrate structure were evaluated with brightfield and fluorescent imaging. Differentiated C2C12 cells encapsulated in alginate had a significant increase in MuRF1 only following simulated microgravity culture and were morphologically dissimilar to normal cultured muscle tissue. On the other hand, C2C12 cells cultured on polystyrene microcarriers had significantly increased expression of MuRF1, Caspase 3, and Foxo3 and easily identifiable multinucleated myotubes. The extent of differentiation was higher in simulated microgravity and protein synthesis more active with increased Myh4, Akt2, and mTOR. The in vitro microcarrier model described herein significantly increases expression of several of the same atrophy markers as in vivo models. However, unlike animal models, MAFbx and Ankrd1 were not significantly increased and the fold change in MuRF1 and Foxo3 was lower than expected. Using a standard commercially available RCCS, the substrates and culture methods described only partially model changes in mRNAs associated with atrophy in vivo

Acute Mechanical Stress in Primary Porcine RPE Cells Induces Angiogenic Factor Expression and In Vitro Angiogenesis

Background Choroidal neovascularization (CNV) is a major cause of blindness in patients with age-related macular degeneration. CNV is characterized by new blood vessel growth and subretinal fluid accumulation, which results in mechanical pressure on retinal pigment epithelial (RPE) cells. The overexpression of RPE-derived angiogenic factors plays an important role in inducing CNV. In this work, we investigated the effect of mechanical stress on the expression of angiogenic factors in porcine RPE cells and determined the impact of conditioned medium on in-vitro angiogenesis. Results The goal of this study was to determine whether low levels of acute mechanical stress during early CNV can induce the expression of angiogenic factors in RPE cells and accelerate angiogenesis. Using a novel device, acute mechanical stress was applied to primary porcine RPE cells and the resulting changes in the expression of major angiogenic factors, VEGF, ANG2, HIF-1α, IL6, IL8 and TNF-α, were examined using immunocytochemistry, qRT-PCR, and ELISA. An in vitro tube formation assay was used to determine the effect of secreted angiogenic proteins due to mechanical stress on endothelial tube formation by human umbilical vein endothelial cells (HUVECs). Our results showed an increase in the expression of VEGF, ANG2, IL-6 and IL-8 in response to mechanical stress, resulting in increased in vitro angiogenesis. Abnormal epithelial-mesenchymal transition (EMT) in RPE cells is also associated with CNV and further retinal degeneration. Our qRT-PCR results verified an increase in the expression of EMT genes, CDH2, VIM and FN1, in RPE cells. Conclusions In conclusion, we showed that acute mechanical stress induces the expression of major angiogenic and EMT factors and promotes in vitro angiogenesis, suggesting that mechanical stress plays a role in promoting aberrant angiogenesis in AMD

Characterization of the Effects of Radiation on Skeletal and Smooth Muscle Cells

Muscular atrophy is a serious issue for extended spaceflight. Understanding and preventing the role of ionizing radiation in skeletal muscle loss would preserve the strength and endurance of astronauts and enable longer duration space travel and exploration. Irradiation was performed in the USU material physics group\u27s Space Suvivability Test Chamber. C2C12 and CRL-1999 cells were exposed to dosages ranging from 0.5 - 36.8 Gy. Cell viability and growth rate were measured immediately following irradiation

Macro benthos of Minicoy island, Lakshadweep

The lack of sufficient information on benthic fauna of an Island territory in India paved the way for the present study. This is an attempt to study the macrobenthos at the intertidal zones of seagrass and mangrove ecosystems of Minicoy Island of Lakshadweep. The objectives of the study include the identification of benthic fauna, their distribution and composition, standing stock, qualitative and quantitative nature in relation to hydrography, seasons and sediment texture, community structure analysis and trophic relationships. For this purpose a monthly plan of sample collection and analysis were carried out at six stations in the Minicoy seagrass/mangrove area from September 1999 to August 200 1. The first chapter gives an introduction covering the importance of benthos, inter tidal zones, seagrass beds and mangroves. Review of literature, scope and purpose of study are also included in this chapter. The second chapter 'Materials and Methods' describes the study area, period of study and frequency of sampling. The methods adopted for the study of environmental parameters, macrofauna and benthic abundance, statistical techniques etc. are explained in this chapter. The third, fourth, fi fth and sixth chapters contain the results of the studies on environmental parameters, bottom fauna, regression analysis for correlation and benthic production respectively. The seventh chapter is the discussion based on the results and the eighth is the summary and conclusion