The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
C M B Henderson - One of the best experts on this subject based on the ideXlab platform.
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tetragonal cubic phase transition in kgasi2o6 synthetic leucite analogue and its probable mechanism
Journal of Solid State Chemistry, 2020Co-Authors: Anthony M. T. Bell, C M B HendersonAbstract:Abstract Synthetic leucite KGaSi2O6 at 298K is I41/a tetragonal and is isostructural with natural leucite (KAlSi2O6); with unit cell parameters of a = 13.1099 (4), c = 13.8100 (4) A, V = 2373.50 (12) A3. With increasing temperature it undergoes a reversible, displacive phase transition from I41/a to cubic I a 3 ‾ d ; this well-studied phase transition in KAlSi2O6 occurs at ~930K. However for KGaSi2O6 it is smeared out from 673 to ~970K where it consists of a mixture of the low- and high-temperature polymorphs. The proportion of the cubic phase increases with temperature; the cubic phase volume is ~1% larger than the coexisting tetragonal polymorph. At a fixed temperature within this ‘region of coexistence’ phase proportions do not change. Such features are characteristic of 1st order, diffusionless, strain-meditated, martensitic-type phase transitions. It seems that the phase transition for synthetic KGaSi2O6 is close to being purely ferroelastic in character.
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variable stoichiometry in tectosilicates having the leucite pollucite type structure with particular emphasis on modelling the interframework cavity cation environment
Journal of Solid State Chemistry, 2017Co-Authors: Anthony M. T. Bell, C M B Henderson, K S KnightAbstract:Abstract Unit cell data for synthetic samples of I41/a or Ia-3d AAlSi2O6 (A=K,Rb,Tl,Cs) leucite/pollucites are compared to those for feldspar-stoichiometry leucite analogues (Rb,Tl,Cs)0.75□0.25Al0.75Si2.25O6. I41/a solid solutions between KAlSi2O6 and KAlSi3O8 (orthoclase feldspar, Or) and between K(Al0.85Fe0.15)Si2O6 and Or both show increasing volumes and decreasing c/a with increasing Or. Phase relations are given for KAlSi3O8-RbAlSi3O8; monoclinic feldspars occur at low temperatures and I41/a leucites at higher temperatures; volumes of leucite solid solutions increase with increasing Rb. The cell volume of Rb0.75□0.25Al0.75Si2.25O6 leucite is larger than that of RbAlSi2O6 leucite. Published leucite/pollucite structures belonging to different Space Group symmetries are treated as having the cubic Ia-3d topology with a ‘pseudocell’ edge V1/3 (V = unit cell volume); inequivalent site bond lengths and angles provide mean structural parameters for the cubic ‘pseudocells’. Multivariant linear regression equations using mean A – O distances as the independent variable were obtained using other structural parameters as dependent variables. Only two independent variables (V and mean tetrahedral ionic radius) are required to account for >90% of the variation. These regression equations can be used to predict the sizes of the cavity cation sites in leucite/pollucite-type phases of any stoichiometry.
Kenneth C Anderson - One of the best experts on this subject based on the ideXlab platform.
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blockade of hsp27 overcomes bortezomib proteasome inhibitor ps 341 resistance in lymphoma cells
Cancer Research, 2003Co-Authors: Dharminder Chauhan, Guilan Li, Yasuyuki Ohtake, Reshma Shringarpure, Teru Hideshima, Klaus Podar, Kenneth C AndersonAbstract:Bortezomib (PS-341), a selective inhibitor of proteasome, induces apoptosis in various tumor cells, but its mechanism of action is unclear. Treatment with PS-341 induces apoptosis in SUDHL6 (DHL6), but not SUDHL4 (DHL4), lymphoma cells. Microarray analysis shows high RNA levels of heat shock protein-27 (Hsp27) in DHL4 versus DHL6 cells, which correlates with Hsp27 protein expression. Blocking Hsp27 using an antisense strategy restores the apoptotic response to PS-341 in DHL4 cells; conversely, ectopic expression of wild-type Hsp27 renders PS-341-sensitive DHL6 cells resistant to PS-341. These findings provide the first evidence that Hsp27 confers PS-341 resistance.
Lianwen Zheng - One of the best experts on this subject based on the ideXlab platform.
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microrna 141 3p targets dapk1 and inhibits apoptosis in rat ovarian granulosa cells
Cell Biochemistry and Function, 2017Co-Authors: Dandan Li, Chunjin Li, Duo Xu, Ying Xu, Lili Zhang, Lu Chen, Lianwen ZhengAbstract:The polycystic ovary syndrome (PCOS) is a complex and heterogeneous endocrine disorder. MicroRNAs negatively regulate the expression of target genes at posttranscriptional level by binding to the 3′ untranslated region of target genes. Our previous study showed that miR-141-3p was dramatically decreased in the ovaries of rat PCOS models. In this study, we aimed to characterize the target of miR-141-3p in rat ovarian granulosa cells. 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay showed that cell viability was dramatically increased when miR-141-3p was overexpressed but was decreased when miR-141-3p was interfered. Flow cytometry showed that cell apoptotic rate was dramatically decreased when miR-141-3p was overexpressed but was increased when miR-141-3p was interfered. Bioinformatics analysis predicted that death-associated protein kinase 1 (DAPK1) might be the target gene of miR-141-3p because the 3′ untranslated region of DAPK1 contains sequences complementary to microRNA-141-3p. Transfection with miR-141-3p mimics and inhibitor into granulosa cells showed that both DAPK1 mRNA and protein levels were negatively correlated with miR-141-3p level. Dual-luciferase reporter assay established that DAPK1 was the target of miR-141-3p. Taken together, our data indicate that miR-141-3p may inhibit ovarian granulosa cell apoptosis via targeting DAPK1 and is involved in the etiology of PCOS.
Masahiro Tanaka - One of the best experts on this subject based on the ideXlab platform.
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jahn teller structural phase transition around 280k in limn2o4
Materials Research Bulletin, 1995Co-Authors: Atsuo Yamada, Masahiro TanakaAbstract:The structural phase transition of spinel LiMn2O4 (Fd3m at room temperature) was investigated using thermal analysis and powder x-ray diffraction. The phase transition was observed around Tt=280K with a temperature hysteresis of about 10K. It was revealed that the low temperature phase (T < Tt) is a mixture of Fd3m (c/a = 1) and I41/amd (c/a = 1.011). The phase transformation from Fd3m to I41/amd proceeds with the decrease in temperature until the volume fraction of the I41/amd phase saturates at 65% at around 260K, just below Tt. The single phase of I41/amd never appeared even at 220K, far below Tt. This phase transition is of a first-order character and is owing to the cooperative Jahn-Teller effect of Mn3+. Cell performance utilizing the LiMn2O4 cathode is also discussed.
Hui Zhao - One of the best experts on this subject based on the ideXlab platform.
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measurement of the vaporization enthalpy of complex mixtures by correlation gas chromatography the vaporization enthalpy of rp 1 jp 7 and jp 8 rocket and jet fuels at t 298 15 k
Energy & Fuels, 2005Co-Authors: James S Chickos, Hui ZhaoAbstract:The use of correlation-gas chromatography to measure the vaporization enthalpy { Hm(298.15 K)} of complex fuels is demonstrated using RP-1, JP-7, and JP-8, which are all rocket and jet fuels. Vaporization enthalpies of 308, 341, and 441 kJ/kg have been obtained assuming average compositions of C12H23.4, C12H25, and C11H21, respectively. The H/C ratio in these fuels has been measured by 1H NMR, and an average molecular weight has been determined using gas chromatography. Some variance in composition with the literature values has been observed. The vaporization enthalpies are compared to those in the literature and to values estimated for these compositions. The estimated values are discussed in terms of the composition of the fuel. The effect of detector bias in evaluating the mole fraction of each hydrocarbon present, as a function of size, is tested and determined to have a relatively small effect on the vaporization enthalpy.
