Structure-property relationships in glass-reinforced polyamide, part 1: The effects of fiber content

We present the results of an extensive study of the performance of injection-molded glass-fiber reinforced polyamide 66 with glass content between 0 and 40% and based on two chopped glass products both sized with polyamide compatible sizing. Mechanical properties generally improved with increasing glass content, modulus linearly, strength with a maximum at 40-50% glass content, and impact showing an initial decrease from the resin value with a minimum at 4% glass content before increasing at higher glass contents. Residual fiber length decreased linearly with increasing glass content. Interfacial strength was found to be in the range of 30-36 MPa, and no significant differences in dry as molded performance was found between the 123D and 173X sizings. Conditioning these composites in either boiling water or water/glycol mixtures leads to a dramatic drop in both tensile modulus and tensile strength. This is most likely due to the high level of matrix plasticization. After conditioning, the 173X sized glass delivered a significantly higher level of tensile elongation at all fiber contents. Excellent agreement was obtained between the experimental data and the theoretical predictions of the rule of mixtures model for modulus and the Kelly-Tyson model for strength over the range of fiber concentrations studied

MutY-Homolog (MYH) inhibition reduces pancreatic cancer cell growth and increases chemosensitivity

Patients with pancreatic ductal adenocarcinoma (PC) have a poor prognosis due to metastases and chemoresistance. PC is characterized by extensive fibrosis, which creates a hypoxic microenvironment, and leads to increased chemoresistance and intracellular oxidative stress. Thus, proteins that protect against oxidative stress are potential therapeutic targets for PC. A key protein that maintains genomic integrity against oxidative damage is MutY-Homolog (MYH). No prior studies have investigated the function of MYH in PC cells. Using siRNA, we showed that knockdown of MYH in PC cells 1) reduced PC cell proliferation and increased apoptosis; 2) further decreased PC cell growth in the presence of oxidative stress and chemotherapy agents (gemcitabine, paclitaxel and vincristine); 3) reduced PC cell metastatic potential; and 4) decreased PC tumor growth in a subcutaneous mouse model in vivo. The results from this study suggest MYH may be a novel therapeutic target for PC that could potentially improve patient outcome by reducing PC cell survival, increasing the efficacy of existing drugs and reducing metastatic spread

ACC Synthase Genes Related to Cold-dependent Ripening in Pear Fruit

The differential regulation of ACC synthase genes has been studied in pear cultivars that either require a long chilling treatment before they are capable of ripening (‘Passe-Crassane’, PC) or not (‘Old-Home’, OH) and in OH x PC hybrids having no (A16) or intermediate (A50) cold requirement. Among the seven Pc-ACS cDNAs isolated, four of them (Pc-ACS1a/b and Pc-ACS2a/b) showed differential expression in relation with cold requirement. Pc-ACS1a transcripts accumulated specifically during chilling and ripening of cold-dependent cultivars while Pc-ACS1b transcripts were detected only during ripening of cold-independent genotypes. Pc- ACS2a mRNA was expressed specifically in cold-dependent genotypes and negatively regulated by ethylene while Pc-ACS2b transcripts accumulated only in cold-independent genotypes and positively regulated by ethylene. Pc-ACS3, 4 and 5 transcripts accumulation was similar in all genotypes, independently of coldrequirements

Posterior cricoid region fluoroscopic findings: the posterior cricoid plication.

The region posterior to the cricoid cartilage is challenging to assess fluoroscopically. The purpose of this investigation is to critically evaluate the posterior cricoid (PC) region on fluoroscopy and describe patterns of common findings. This was a case control study. All fluoroscopic swallowing studies performed between June 16, 2009, and February 9, 2010, were reviewed for features seen in the PC region. These findings were categorized into distinct patterns and compared to fluoroscopic studies performed in a cohort of normal volunteers. Two hundred patient studies and 149 healthy volunteer studies were reviewed. The mean age of the referred patient cohort and the volunteer cohort was 57 years (±19) and 61 years (±16), respectively (p > 0.05). The patient cohort was 53% male and the control cohort was 56% female (p > 0.05). Four groups were identified. Pharyngoesophageal webs were seen in 7% (10/149) of controls and 14% (28/200) of patients (p = 0.03). A PC arch impression was seen in 16% of patients (32/200) and controls (24/149) (p = 1). A PC plication was demonstrated in 23% (34/149) of controls and 30% (60/200) of patients (p = 0.13). No distinctive PC region findings were seen in 54% (81/149) of controls and 42% (84/200) of referred patients (p = 0.02). Four patients (2%) had both a web and a PC plication. Four categories of PC region findings were identified (unremarkable PC region, web, PC arch impression, and PC plication). Both patients referred for swallowing studies and healthy volunteers demonstrated esophageal webs, PC arch impressions, and PC plications. Only webs were more common in patients than in control subjects (p = 0.03). The PC impression and PC plication are likely to represent normal variants that may be identified on fluoroscopic swallow studies

Structure-property relationships in glass-reinforced polyamide, Part 3: Effects of hydrolysis ageing on the dimensional stability and performance of short glass-fiber-reinforced polyamide 66

We present results on an in-depth study of the effects of hydrolysis testing on the mechanical performance, weight change, and dimensional stability of injection moulded glass-fibre reinforced polyamide 66 based on two chopped fibre products with different sizing formulations. Composite and resin samples have been characterised both dry as moulded and after conditioning at either 120°C or 150°C for a range of times up to 1000 hours. The results reveal that hydrothermal ageing in water-glycol mixtures results in significant changes in the mechanical performance, weight, and dimensions of these materials. The negative effects of conditioning could be mitigated to some degree by the appropriate choice of the glass fibre sizing; however the sizing effect diminished with increasing conditioning time. All materials showed a weight increase due to conditioning at 120°C which was typical of a single Fickian diffusion process and there was clear evidence of multiple processes involved when conditioning at 150°C. It was not apparent that the glass fibre sizing affected the dimensional stability of the composites. We show that there is a strong correlation between the swelling of these samples and the level of fluid adsorption. Although the PA66 resin showed reasonably homogeneous swelling, the composites exhibited different levels of swelling depending on direction. These effects were well in line with the known effects of fibres on restriction of the matrix deformation (mechanical, thermal or moisture swelling) in the fibre direction. These differences correlate well with the average fibre orientation with respect to the various direction axes. Composite tensile strength and unnotched impact resistance appeared to scale inversely with the level of swelling of the material

The Origin of OB Clusters: From 10 pc to 0.1 pc

We observe the 1.2 mm continuum emission around the OB cluster forming region G10.6-0.4, using the IRAM 30m telescope MAMBO-2 bolometer array and the Submillimeter array. Comparison of the Spitzer 24 $\mu$m and 8 $\mu$m images with our 1.2 mm continuum maps reveals the ionization front of an HII region, the photon-dominated layer, and several 5 pc scale filaments following the outer edge of the photon-dominated layer. The filaments, which are resolved in the MAMBO-2 observations, show regularly spaced parsec-scale molecular clumps, embedded with a cluster of submillimeter molecular cores as shown in the SMA 0.87 mm observations. Toward the center of the G10.6-0.4 region, the combined SMA+IRAM 30m continuum image reveals several, parsec-scale protrusions. They may continue down to within 0.1 pc of the geometric center of a dense 3 pc size structure, where a 200 M$_{\odot}$ OB cluster resides. The observed filaments may facilitate mass accretion onto the central cluster--forming region in the presence of strong radiative and mechanical stellar feedbacks. Their filamentary geometry may also facilitate fragmentation. We did not detect any significant polarized emission at 0.87 mm in the inner 1 pc region with the SMA.Comment: 32 pages, 10 figures, Accepted by ApJ on 2011.October