Effect of fire exposure on cracking, spalling and residual strength of fly ash geopolymer concrete

Fly ash based geopolymer is an emerging alternative binder to cement for making concrete. The cracking, spalling and residual strength behaviours of geopolymer concrete were studied in order to understand its fire endurance, which is essential for its use as a building material. Fly ash based geopolymer and ordinary portland cement (OPC) concrete cylinder specimens were exposed to fires at different temperatures up to 1000 °C, with a heating rate of that given in the International Standards Organization (ISO) 834 standard. Compressive strength of the concretes varied in the range of 39–58 MPa. After the fire exposures, the geopolymer concrete specimens were found to suffer less damage in terms of cracking than the OPC concrete specimens. The OPC concrete cylinders suffered severe spalling for 800 and 1000 °C exposures, while there was no spalling in the geopolymer concrete specimens. The geopolymer concrete specimens generally retained higher strength than the OPC concrete specimens. The Scanning Electron Microscope (SEM) images of geopolymer concrete showed continued densification of the microstructure with the increase of fire temperature. The strength loss in the geopolymer concrete specimens was mainly because of the difference between the thermal expansions of geopolymer matrix and the aggregates

The Star Formation Rate - Dense Gas Relation in the Nuclei of Nearby Galaxies

We investigate the relationship between the star formation rate (SFR) and dense molecular gas mass in the nuclei of galaxies. To do this, we utilize the observed 850 micron luminosity as a proxy for the infrared luminosity and SFR, and correlate this with the observed CO (J=3-2) luminosity. We find tentative evidence that the LIR-CO (J=3-2) index is similar to the Kennicutt-Schmidt (KS) index (N ~ 1.5) in the central ~1.7 kpc of galaxies, and flattens to a roughly linear index when including emission from the entire galaxy. This result may imply that the volumetric Schmidt relation is the underlying driver behind the observed SFR-dense gas correlations, and provides tentative confirmation for recent numerical models. While the data exclude the possibility of a constant LIR-CO (J=3-2) index for both galaxy nuclei and global measurements at the ~80% confidence level, the considerable error bars cannot preclude alternative interpretations.Comment: Accepted at ApJ Letter

Thermal conduction of carbon nanotubes using molecular dynamics

The heat flux autocorrelation functions of carbon nanotubes (CNTs) with different radius and lengths is calculated using equilibrium molecular dynamics. The thermal conductance of CNTs is also calculated using the Green-Kubo relation from the linear response theory. By pointing out the ambiguity in the cross section definition of single wall CNTs, we use the thermal conductance instead of conductivity in calculations and discussions. We find that the thermal conductance of CNTs diverges with the CNT length. After the analysis of vibrational density of states, it can be concluded that more low frequency vibration modes exist in longer CNTs, and they effectively contribute to the divergence of thermal conductance.Comment: 15 pages, 6 figures, submitted to Physical Review

Identification, cloning and characterization of sis7 and sis10 sugar-insensitive mutants of Arabidopsis

<p>Abstract</p> <p>Background</p> <p>The levels of soluble sugars, such as glucose and sucrose, help regulate many plant metabolic, physiological and developmental processes. Genetic screens are helping identify some of the loci involved in plant sugar response and reveal extensive cross-talk between sugar and phytohormone response pathways.</p> <p>Results</p> <p>A forward genetic screen was performed to identify mutants with increased resistance to the inhibitory effects of high levels of exogenous sugars on early <it>Arabidopsis </it>seedling development. The positional cloning and characterization of two of these <it>sugar insensitive </it>(<it>sis</it>) mutants, both of which are also involved in abscisic acid (ABA) biosynthesis or response, are reported. Plants carrying mutations in <it>SIS7/NCED3/STO1 </it>or <it>SIS10/ABI3 </it>are resistant to the inhibitory effects of high levels of exogenous Glc and Suc. Quantitative RT-PCR analyses indicate transcriptional upregulation of ABA biosynthesis genes by high concentrations of Glc in wild-type germinating seeds. Gene expression profiling revealed that a significant number of genes that are expressed at lower levels in germinating <it>sis7-1/nced3-4/sto1-4 </it>seeds than in wild-type seeds are implicated in auxin biosynthesis or transport, suggesting cross-talk between ABA and auxin response pathways. The degree of sugar insensitivity of different <it>sis10/abi3 </it>mutant seedlings shows a strong positive correlation with their level of ABA insensitivity during seed germination.</p> <p>Conclusion</p> <p>Mutations in the <it>SIS7/NCED3/STO1 </it>gene, which is primarily required for ABA biosynthesis under drought conditions, confer a sugar-insensitive phenotype, indicating that a constitutive role in ABA biosynthesis is not necessary to confer sugar insensitivity. Findings presented here clearly demonstrate that mutations in <it>ABI3 </it>can confer a sugar-insensitive phenotype and help explain previous, mixed reports on this topic by showing that ABA and sugar insensitivity exhibit a strong positive correlation in different <it>abi3 </it>mutants. Expression profiling revealed a potentially novel regulation of auxin metabolism and transport in an ABA deficient mutant, <it>sis7-1/nced3-4/sto1-4</it>.</p

Unitarity violation in noninteger dimensional Gross-Neveu-Yukawa model

We construct an explicit example of unitarity violation in fermionic quantum field theories in noninteger dimensions. We study the two-point correlation function of four-fermion operators. We compute the one-loop anomalous dimensions of these operators in the Gross-Neveu-Yukawa model. We find that at one-loop order, the four-fermion operators split into three classes with one class having negative norms. This implies that the theory violates unitarity, following the definition in Ref. [1]

Do semantic contextual cues facilitate transfer learning from video in toddlers?

Young children typically demonstrate a transfer deficit, learning less from video than live presentations. Semantically meaningful context has been demonstrated to enhance learning in young children. We examined the effect of a semantically meaningful context on toddlers\u27 imitation performance. Two- and 2.5-year-olds participated in a puzzle imitation task to examine learning from either a live or televised model. The model demonstrated how to assemble a three-piece puzzle to make a fish or a boat, with the puzzle demonstration occurring against a semantically meaningful background context (ocean) or a yellow background (no context). Participants in the video condition performed significantly worse than participants in the live condition, demonstrating the typical transfer deficit effect. While the context helped improve overall levels of imitation, especially for the boat puzzle, only individual differences in the ability to self-generate a stimulus label were associated with a reduction in the transfer deficit

Syntaphilin Ubiquitination Regulates Mitochondrial Dynamics and Tumor Cell Movements.

Syntaphilin (SNPH) inhibits the movement of mitochondria in tumor cells, preventing their accumulation at the cortical cytoskeleton and limiting the bioenergetics of cell motility and invasion. Although this may suppress metastasis, the regulation of the SNPH pathway is not well understood. Using a global proteomics screen, we show that SNPH associates with multiple regulators of ubiquitin-dependent responses and is ubiquitinated by the E3 ligase CHIP (or STUB1) on Lys111 and Lys153 in the microtubule-binding domain. SNPH ubiquitination did not result in protein degradation, but instead anchored SNPH on tubulin to inhibit mitochondrial motility and cycles of organelle fusion and fission, that is dynamics. Expression of ubiquitination-defective SNPH mutant Lys111!Arg or Lys153!Arg increased the speed and distance traveled by mitochondria, repositioned mitochondria to the cortical cytoskeleton, and supported heightened tumor chemotaxis, invasion, and metastasis in vivo. Interference with SNPH ubiquitination activated mitochondrial dynamics, resulting in increased recruitment of the fission regulator dynamin-related protein-1 (Drp1) to mitochondria and Drp1-dependent tumor cell motility. These data uncover nondegradative ubiquitination of SNPH as a key regulator of mitochondrial trafficking and tumor cell motility and invasion. In this way, SNPH may function as a unique, ubiquitination-regulated suppressor of metastasis

Unitary Isobar Model - MAID2007

The unitary isobar model MAID2007 has been developed to analyze the world data of pion photo- and electroproduction. The model contains both a common background and several resonance terms. The background is unitarized according to the K-matrix prescription, and the 13 four-star resonances with masses below 2 GeV are described by appropriately unitarized Breit-Wigner forms. The data have been analyzed by both single-energy and global fits, and the transverse and longitudinal helicity amplitudes have been extracted for the four-star resonances below 2 GeV. Because of its inherent simplicity, MAID2007 is well adopted for predictions and analysis of the observables in pion photo- and electroproduction.Comment: 32 pages including 13 tables and 24 figure

Purification, identification and characterisation of the active site of a Seprase-like activity from bovine serum

The study and identification for the first time of a soluble form of a Seprase activity from bovine serum is presented. To date, this activity has only been reported to be an integral membrane protease but has been known to shed from its membrane. The activity was purified 30,197-fold to homogeneity, using a combination of column chromatographies, from bovine serum. Inhibition by DFP, resulting in an IC50 of 100nM confirms classification as a serine protease. The protease after separation and visualisation by native PAGE was subjected to tryptic digestion and the subsequent peptides sequenced. Each peptide sequenced was found to be present in the primary structure of Seprase/Fibroblast Activation Protein (FAP), a serine gelatinase specific for proline-containing peptides and macromolecules. Substrate specificity studies using kinetic, RP-HPLC and LC-MS analysis of synthetic peptides suggest that this peptidase has an extended substrate-binding region in addition to the primary specificity site S1. This analysis revealed at least five subsites to be involved in enzyme-substrate binding, 1 with the smallest peptide cleaved being a tetrapeptide. A proline residue in position P1 was absolutely necessary therefore showing high primary substrate specificity for the Pro-X bond, while a preference for a hydrophobic residue at the C-terminal end of the scissile bond (P1ʹ′) was evident. The enzyme also showed complete insensitivity to the prolyl oligopeptidase specific inhibitors, JTP-4819, Fmoc-Ala-pyrrCN and Z-Phe-Pro-BT. To date, no physiological substrate has clearly been defined for this protease but its ability to effectively degrade gelatin suggests a candidate protein substrate in vivo and a possible role in extracellular matrix protein degradation