Dust Explosion Characteristics of Cellulose Acetates with Different Degrees of Acetylation

PresentationIn this work, the relation between various degrees of acetylation (CAs) of Cellulose acetate (CA) to dust explosion characteristics as minimum explosible concentration (MEC) and minimum ignition energy (MIE) have been studied. Also, we attempt to clarify the relative of moisture content and water adsorption to cellulose, cellulose ester as CA and cellulose ether as Methyl cellulose (MC), Ethyl cellulose (EC), Hydroxyethyl cellulose (HEC), Hydroxypropyl cellulose (HPC), and sodium carboxymethyl cellulose (CMC) to MEC and MIE have been studied. We found that the chemical derivatives have significant on thermal behavior of cellulose which Td of CA shifted to higher temperature because of acetate derivative effect. Meanwhile, Td of cellulose ethers as MC, EC, HEC, HEC and CMC were shifted to lower temperature. Moreover, CAs was not evident effect to Td of CA. Moisture content of cellulose powder had not significant on MEC of both air dry and absolute dry powder were 55 g/m3. But, we found MEC was relative to its moisture content of CA which absolute dry was more sensitive on explosion than dry CA powder. However, MEC was consistent with the hydrophilicity index at 75%RH of dry and absolute dry of cellulose, cellulose acetate and cellulose ethers in present work. MIE was not corresponding to moisture content of cellulose ether and cellulose ester but it was relative to cellulose. The results from our experiments, comparing with CAs, chemical derivatives have more significant on moisture adsorption, thermal stability and dust explosion characteristics of cellulose

Thermal Behavior and Dust Explosion Characteristics of Spent Coffee Grounds and Jatropha as Biodiesel Feedstock

PresentationThis work examined the minimum explosion limit (MEL), minimum ignition energy (MIE), cohesion, dispersibility, decomposition temperature (Td) and burning rates of spent coffee ground (SCG), jatropha kernel (JK) and jatropha shell (JS) were studied. The MIE values of oily SCG containing 21.3 wt% and oil-extracted SCG were 35 and 120 g m-3 , respectively. Moreover, cohesion of oily SCG and oil-extracted SCG were high level and low level, respectively. It was found that MIE of oily SCG containing 21.3wt% of oil was low although high cohesion. While oil-extracted jatropha kernels and shells had MEL values of 45 and 110 g m-3 , respectively. However, Oily JK containing 60.7 wt% of oil was not exploded reason for high cohesion and no form dust cloud. The MIE values of untreated SCG, oil-extracted SCG, oil-extracted JK and JS were found to be >3000, >3000, 1515, and >3000 mJ, respectively. These biomasses were needed high energy ignition for explosion. Burning rates of JK and JS were 0.21 and 0.04 mm s-1, respectively, these values were very slow compared with cellulose used as a reference materials was 0.67 mm s-1. Besides SCG were not capable of ignition. The Td of both untreated SCG and oil-extracted SCG were 240 and 241 °C while the Td of untreated JK (60.7wt% oil), oil-extracted JK, and JS were 195, 189, and 233 ̊C indicating that the ignition temperature is influenced by oil content. Consequently, the results demonstrate that oily solid biomasses such as SCG and jatropha are associated with a high risk of fire, dust explosion, and related incident

Intracellular ATP levels in mouse cortical excitatory neurons varies with sleep–wake states.

Whilst the brain is assumed to exert homeostatic functions to keep the cellular energy status constant under physiological conditions, this has not been experimentally proven. Here, we conducted in vivo optical recordings of intracellular concentration of adenosine 5’-triphosphate (ATP), the major cellular energy metabolite, using a genetically encoded sensor in the mouse brain. We demonstrate that intracellular ATP levels in cortical excitatory neurons fluctuate in a cortex-wide manner depending on the sleep-wake states, correlating with arousal. Interestingly, ATP levels profoundly decreased during rapid eye movement sleep, suggesting a negative energy balance in neurons despite a simultaneous increase in cerebral hemodynamics for energy supply. The reduction in intracellular ATP was also observed in response to local electrical stimulation for neuronal activation, whereas the hemodynamics were simultaneously enhanced. These observations indicate that cerebral energy metabolism may not always meet neuronal energy demands, consequently resulting in physiological fluctuations of intracellular ATP levels in neurons

Spatial Frequency-Based Analysis of Mean Red Blood Cell Speed in Single Microvessels: Investigation of Microvascular Perfusion in Rat Cerebral Cortex

BACKGROUND: Our previous study has shown that prenatal exposure to X-ray irradiation causes cerebral hypo-perfusion during the postnatal development of central nervous system (CNS). However, the source of the hypo-perfusion and its impact on the CNS development remains unclear. The present study developed an automatic analysis method to determine the mean red blood cell (RBC) speed through single microvessels imaged with two-photon microscopy in the cerebral cortex of rats prenatally exposed to X-ray irradiation (1.5 Gy). METHODOLOGY/PRINCIPAL FINDINGS: We obtained a mean RBC speed (0.9±0.6 mm/sec) that ranged from 0.2 to 4.4 mm/sec from 121 vessels in the radiation-exposed rats, which was about 40% lower than that of normal rats that were not exposed. These results were then compared with the conventional method for monitoring microvascular perfusion using the arteriovenous transit time (AVTT) determined by tracking fluorescent markers. A significant increase in the AVTT was observed in the exposed rats (1.9±0.6 sec) as compared to the age-matched non-exposed rats (1.2±0.3 sec). The results indicate that parenchyma capillary blood velocity in the exposed rats was approximately 37% lower than in non-exposed rats. CONCLUSIONS/SIGNIFICANCE: The algorithm presented is simple and robust relative to monitoring individual RBC speeds, which is superior in terms of noise tolerance and computation time. The demonstrative results show that the method developed in this study for determining the mean RBC speed in the spatial frequency domain was consistent with the conventional transit time method

Functional MRI and Diffusion Tensor Imaging of Brain Reorganization After Experimental Stroke

The potential of the adult brain to reorganize after ischemic injury is critical for functional recovery and provides a significant target for therapeutic strategies to promote brain repair. Despite the accumulating evidence of brain plasticity, the interaction and significance of morphological and physiological modifications in post-stroke brain tissue remain mostly unclear. Neuroimaging techniques such as functional MRI (fMRI) and diffusion tensor imaging (DTI) enable in vivo assessment of the spatial and temporal pattern of functional and structural changes inside and outside ischemic lesion areas. This can contribute to the elucidation of critical aspects in post-stroke brain remodeling. Task/stimulus-related fMRI, resting-state fMRI, or pharmacological MRI enables direct or indirect measurement of neuronal activation, functional connectivity, or neurotransmitter system responses, respectively. DTI allows estimation of the structural integrity and connectivity of white matter tracts. Together, these MRI methods provide an unprecedented means to (a) measure longitudinal changes in tissue structure and function close by and remote from ischemic lesion areas, (b) evaluate the organizational profile of neural networks after stroke, and (c) identify degenerative and restorative processes that affect post-stroke functional outcome. Besides, the availability of MRI in clinical institutions as well as research laboratories provides an optimal basis for translational research on stroke recovery. This review gives an overview of the current status and perspectives of fMRI and DTI applications to study brain reorganization in experimental stroke models

Phylogenetic and Evolutionary Patterns in Microbial Carotenoid Biosynthesis Are Revealed by Comparative Genomics

BACKGROUND: Carotenoids are multifunctional, taxonomically widespread and biotechnologically important pigments. Their biosynthesis serves as a model system for understanding the evolution of secondary metabolism. Microbial carotenoid diversity and evolution has hitherto been analyzed primarily from structural and biosynthetic perspectives, with the few phylogenetic analyses of microbial carotenoid biosynthetic proteins using either used limited datasets or lacking methodological rigor. Given the recent accumulation of microbial genome sequences, a reappraisal of microbial carotenoid biosynthetic diversity and evolution from the perspective of comparative genomics is warranted to validate and complement models of microbial carotenoid diversity and evolution based upon structural and biosynthetic data. METHODOLOGY/PRINCIPAL FINDINGS: Comparative genomics were used to identify and analyze in silico microbial carotenoid biosynthetic pathways. Four major phylogenetic lineages of carotenoid biosynthesis are suggested composed of: (i) Proteobacteria; (ii) Firmicutes; (iii) Chlorobi, Cyanobacteria and photosynthetic eukaryotes; and (iv) Archaea, Bacteroidetes and two separate sub-lineages of Actinobacteria. Using this phylogenetic framework, specific evolutionary mechanisms are proposed for carotenoid desaturase CrtI-family enzymes and carotenoid cyclases. Several phylogenetic lineage-specific evolutionary mechanisms are also suggested, including: (i) horizontal gene transfer; (ii) gene acquisition followed by differential gene loss; (iii) co-evolution with other biochemical structures such as proteorhodopsins; and (iv) positive selection. CONCLUSIONS/SIGNIFICANCE: Comparative genomics analyses of microbial carotenoid biosynthetic proteins indicate a much greater taxonomic diversity then that identified based on structural and biosynthetic data, and divides microbial carotenoid biosynthesis into several, well-supported phylogenetic lineages not evident previously. This phylogenetic framework is applicable to understanding the evolution of specific carotenoid biosynthetic proteins or the unique characteristics of carotenoid biosynthetic evolution in a specific phylogenetic lineage. Together, these analyses suggest a "bramble" model for microbial carotenoid biosynthesis whereby later biosynthetic steps exhibit greater evolutionary plasticity and reticulation compared to those closer to the biosynthetic "root". Structural diversification may be constrained ("trimmed") where selection is strong, but less so where selection is weaker. These analyses also highlight likely productive avenues for future research and bioprospecting by identifying both gaps in current knowledge and taxa which may particularly facilitate carotenoid diversification