The rationale for limit order trading

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : DO 2335 (16) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Morphology of Porous Hosts Directs Preferred Polymorph Formation and Influences Kinetics of Solid/Solid Transitions of Confined Pharmaceuticals

The pore morphology of a porous host may determine which polymorph a crystallizable guest preferentially forms and may influence the kinetics of solid/solid transitions. Slow cooling of the drug acetaminophen (ACE) inside the straight cylindrical pores of anodic aluminum oxide (AAO, tortuosity = 1) in contact with a bulk ACE surface film preferentially yields uniformly oriented form II and/or form III crystals. The occurring orientations of form II and form III crystals are characterized by high structural registry along the AAO pores. The uniformly oriented form III crystals inside the AAO pores were readily converted into likewise uniformly oriented form II crystals by a solid/solid transition. Thus, we obtained uniformly oriented form II crystals in AAO at high yields. We suggest that sporadic heterogeneous nucleation at bulk crystals formed in the bulk surface film on top of the AAO coupled with kinetic selection of crystal orientations results in fast growth of properly oriented crystals along the 100 μm deep AAO pores. This mechanism is suppressed in controlled porous glass (CPG) having isotropic spongelike pores (tortuosity > 1.5) with free growth paths on the order of 100 nm, where form I formed instead. Moreover, the transition from form III to form II is suppressed in CPG. Possible reasons may include impingement of the propagation front of the solid/solid transition on the CPG pore walls after short propagation paths and inevitable formation of form II grains with different orientations separated by energetically disadvantageous grain boundaries. The results reported here are relevant to mesoscopic crystal engineering aimed at controlled drug release from nanoscale delivery systems. Polymorphs not accessible otherwise in nanoscale containers may be produced at high yields. The principles reported here may be transferred to areas such as nanowire-based organic electronics

Specific Variants in the MLH1 Gene Region May Drive DNA Methylation, Loss of Protein Expression, and MSI-H Colorectal Cancer

Background: We previously identified an association between a mismatch repair gene, MLH1, promoter SNP (rs1800734) and microsatellite unstable (MSI-H) colorectal cancers (CRCs) in two samples. The current study expanded on this finding as we explored the genetic basis of DNA methylation in this region of chromosome 3. We hypothesized that specific polymorphisms in the MLH1 gene region predispose it to DNA methylation, resulting in the loss of MLH1 gene expression, mismatch-repair function, and consequently to genome-wide microsatellite instability. Methodology/Principal Findings: We first tested our hypothesis in one sample from Ontario (901 cases, 1,097 controls) and replicated major findings in two additional samples from Newfoundland and Labrador (479 cases, 336 controls) and from Seattle (591 cases, 629 controls). Logistic regression was used to test for association between SNPs in the region of MLH1 and CRC, MSI-H CRC, MLH1 gene expression in CRC, and DNA methylation in CRC. The association between rs1800734 and MSI-H CRCs, previously reported in Ontario and Newfoundland, was replicated in the Seattle sample. Two additional SNPs, in strong linkage disequilibrium with rs1800734, showed strong associations with MLH1 promoter methylation, loss of MLH1 protein, and MSI-H CRC in all three samples. The logistic regression model of MSI-H CRC that included MLH1-promotermethylation status and MLH1 immunohisotchemistry status fit most parsimoniously in all three samples combined. When rs1800734 was added to this model, its effect was not statistically significant (P-value = 0.72 vs. 2.361024 when the SNP was examined alone). Conclusions/Significance: The observed association of rs1800734 with MSI-H CRC occurs through its effect on the MLH1 promoter methylation, MLH1 IHC deficiency, or both

Q4 Continuité et discontinuité dans les enregistrements quaternaires - Première partie

Organisé par l’AFEQ et le CNF-INQUA dans le cadre de la Réunion des Sciences de la Terre (RST) (Strasbourg 22 - 23 Septembre 2004