Damage Characterization of Polypropylene Honeycomb Sandwich Panels Subjected to Low-Velocity Impact

The post-test deformation and failures of sandwich composites may involve complex interactions between various failure mechanisms. In this study, the extent of impact damages and response of the thermoplastic honeycomb sandwich are analysed through energy profile diagrams and associated load history curves. The degree of the postimpact damages of the sandwich is further characterized using an optical surfaces metrology analysis. The thickness of the honeycomb was found to influence the extent of the damage which occurred following the low-velocity impact. Thicker core was able to sustain a higher load as well as the energy absorption before total failure occurred

DYNAMIC BEHAVIOUR OF PAPER HONEYCOMB SANDWICH PANELS

Low velocity impact tests have been conducted on paper honeycomb sandwich panels. Two panel thicknesses with span length of 100 mm are used; these are 35 mm and 41 mm, respectively. The dynamic behavior of each paper honeycomb thickness is investigated using two types of indentors: hemispherical and bar. The effect of indentor, and specimen length are studied. This includes the pattern of loaddisplacement curve collapse load and energy absorbed. It concludes that the dynamic collapse load on 41 mm thickness for hemispherical indentor increases by 5% compared with 35 mm. The impact energy absorbed for hemispherical indentor increases by 36%

Activated carbon from various agricultural wastes by chemical activation with KOH : preparation and characterization

Activated carbons (AC) were prepared by pyrolysis from oil palm empty fruit bunch (EFB), bamboo stem (BS), and coconut shells (CNS) at 800 °C by using potassium hydroxide under nitrogen atmosphere. The influence of temperature and type of agricultural biomass on surface area and morphological properties investigated. Activated carbon produced from BS have a higher specific surface area (1212 m2 g−1) and microporosity percentage than those produced from oil palm EFB, and CNS lies in the range of commercial activated carbons. The morphological analysis of the samples was determined by scanning electron microscopy. The external surfaces are full of cavities and quite irregular as a result of activation. X-ray diffraction analysis showed degree of crystallinity 13.25% in case of AC-BS sample while AC-EFB and AC-CNS showed a crystallinity of 1.68% and 8.19%, respectivel

Gene Expression Changes in the Prefrontal Cortex, Anterior Cingulate Cortex and Nucleus Accumbens of Mood Disorders Subjects That Committed Suicide

Suicidal behaviors are frequent in mood disorders patients but only a subset of them ever complete suicide. Understanding predisposing factors for suicidal behaviors in high risk populations is of major importance for the prevention and treatment of suicidal behaviors. The objective of this project was to investigate gene expression changes associated with suicide in brains of mood disorder patients by microarrays (Affymetrix HG-U133 Plus2.0) in the dorsolateral prefrontal cortex (DLPFC: 6 Non-suicides, 15 suicides), the anterior cingulate cortex (ACC: 6NS, 9S) and the nucleus accumbens (NAcc: 8NS, 13S). ANCOVA was used to control for age, gender, pH and RNA degradation, with P≤0.01 and fold change±1.25 as criteria for significance. Pathway analysis revealed serotonergic signaling alterations in the DLPFC and glucocorticoid signaling alterations in the ACC and NAcc. The gene with the lowest p-value in the DLPFC was the 5-HT2A gene, previously associated both with suicide and mood disorders. In the ACC 6 metallothionein genes were down-regulated in suicide (MT1E, MT1F, MT1G, MT1H, MT1X, MT2A) and three were down-regulated in the NAcc (MT1F, MT1G, MT1H). Differential expression of selected genes was confirmed by qPCR, we confirmed the 5-HT2A alterations and the global down-regulation of members of the metallothionein subfamilies MT 1 and 2 in suicide completers. MTs 1 and 2 are neuro-protective following stress and glucocorticoid stimulations, suggesting that in suicide victims neuroprotective response to stress and cortisol may be diminished. Our results thus suggest that suicide-specific expression changes in mood disorders involve both glucocorticoids regulated metallothioneins and serotonergic signaling in different regions of the brain

Gene Therapy Restores Auditory and Vestibular Function in a Mouse Model of Usher Syndrome Type 1c

Because there are currently no biological treatments for deafness, we sought to advance gene therapy approaches to treat genetic deafness. We reasoned that gene delivery systems that target auditory and vestibular sensory cells with high efficiency would be required to restore complex auditory and balance function. We focused on Usher Syndrome, a devastating genetic disorder that causes blindness, balance disorders and profound deafness, and used a knock-in mouse model, Ush1c c.216G>A, which carries a cryptic splice site mutation found in French-Acadian patients with Usher Syndrome type IC (USH1C). Following delivery of wild-type Ush1c into the inner ears of neonatal Ush1c c.216G>A mice, we find recovery of gene and protein expression, restoration of sensory cell function, rescue of complex auditory function and recovery of hearing and balance behavior to near wild-type levels. The data represent unprecedented recovery of inner ear function and suggest that biological therapies to treat deafness may be suitable for translation to humans with genetic inner ear disorders

Progress in gene therapy for neurological disorders

Diseases of the nervous system have devastating effects and are widely distributed among the population, being especially prevalent in the elderly. These diseases are often caused by inherited genetic mutations that result in abnormal nervous system development, neurodegeneration, or impaired neuronal function. Other causes of neurological diseases include genetic and epigenetic changes induced by environmental insults, injury, disease-related events or inflammatory processes. Standard medical and surgical practice has not proved effective in curing or treating these diseases, and appropriate pharmaceuticals do not exist or are insufficient to slow disease progression. Gene therapy is emerging as a powerful approach with potential to treat and even cure some of the most common diseases of the nervous system. Gene therapy for neurological diseases has been made possible through progress in understanding the underlying disease mechanisms, particularly those involving sensory neurons, and also by improvement of gene vector design, therapeutic gene selection, and methods of delivery. Progress in the field has renewed our optimism for gene therapy as a treatment modality that can be used by neurologists, ophthalmologists and neurosurgeons. In this Review, we describe the promising gene therapy strategies that have the potential to treat patients with neurological diseases and discuss prospects for future development of gene therapy

The Fracture Properties of Environmental-Friendly Fiber Metal Laminates

The tensile and impact properties of environmental-friendly composites and FMLs have been investigated. Of the four composites investigated here, a SRPP composite offered superior properties to basalt-, flax-, and hemp fiber-reinforced PP composites. Adding aluminum layers to the outer surfaces of the composites resulted in a significant enhancement in the tensile and impact properties of the laminates. The tensile strength and modulus properties of the FMLs obey a rule of mixtures approach, suggesting that simple procedures can be used to design these hybrid systems. Under low-velocity impact loading, the SRPP, and its associated FML, offered the highest resistance to perforation, as a result of gross plastic deformation in the composite and metal plies. A semi-empirical model, previously employed to characterize metal plates, was used to characterize the low-velocity impact response of the laminates investigated here. The model was capable of predicting the trends in the experimental data with reasonable success. This evidence suggests that environmental-friendly fiber-based FMLs offer significant potential for use in engineering applications

Effect of compatibiliser on the accelerated weathering performance of polypropylene-silica nanocomposites

The specimens prepared in this study were melt blended of neat polypropylene (PP), PP/nanosilica (2 wt%), and PP/nanosilica with 3 wt% of PP grafted maleic anhydride (PP-g-MA). The nanocomposites were placed in the accelerated weathering test (AWT) chamber for 200 hours composed of alternating 8 hours of ultra violet (UV) exposure and 4 hours of condensation. The mechanical properties and morphology before and after exposure to AWT specimens were determined using a tensile test instrument and field emission scanning electron microscope (FESEM). Results showed that the weathered specimens with PP-g-MA compatibilizer have higher tensile strength and higher modulus of elasticity than the weathered specimens without the compatibilizer. Moreover, FESEM images showed less cracking and deformation on the fractured surface of exposed nanocomposites with PP-g-MA. It was concluded that the addition of PP-g-MA led to an increased compatibility of matrix and nanofiller, and further improved the weather resistance of nanocomposites. © 2014 W. S. Maney & Son Ltd