Association of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) with age of puberty among children living near a chemical plant

Animal studies suggest that perfluorocarbons (PFCs) may alter sexual maturation. Relationships of human PFC exposure with puberty are not clear. We conducted a cross-sectional study to investigate whether perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were associated with indicators of sexual maturation in a 2005-2006 survey of residents with PFOA water contamination from the Mid-Ohio Valley. Participants were 3076 boys and 2931 girls aged 8-18 years. They were classified as having reached puberty based on either hormone levels (total >50 ng/dL and free >5 pg/mL testosterone in boys and estradiol >20 pg/mL in girls) or onset of menarche. We estimated the odds of having reached puberty classified by these criteria and the fitted median age of reaching puberty in relation to serum PFOA and PFOS concentrations measured when puberty status was assigned. For boys, there was a relationship of reduced odds of reached puberty (raised testosterone) with increasing PFOS (delay of 190 days between the highest and lowest quartile). For girls, higher concentrations of PFOA or PFOS were associated with reduced odds of postmenarche (130 and 138 days of delay, respectively). In conclusion, our study showed a later age of puberty in this population correlated with PFC concentrations.     

Glycolaldehyde‐modified β‐lactoglobulin AGEs are unable to stimulate inflammatory signaling pathways in RAGE‐expressing human cell lines

Scope: Advanced glycation endproducts (AGEs) are suspected to stimulate inflammatory signaling pathways in target tissues via activation of the receptor for AGEs. Endotoxins are generally recognized as potential contamination of AGE preparations and stimulate biological actions that are very similar as or identical to those induced by AGEs. Methods and results: In our study, we used glycolaldehyde‐modified β‐lactoglobulin preparations as model AGEs and employed two methods to remove endotoxin using either affinity columns or extraction with Triton X‐114 (TX‐114). Affinity column‐purified AGEs retained their ability to stimulate inflammatory signaling as measured by mRNA expression of inflammatory cytokines in the human lung epithelial cell line Beas2b. However, glycolaldehyde‐modified AGEs purified by extraction with TX‐114 did not show any stimulation of mRNA expression of inflammatory cytokines. The presence of a cell stimulating endotoxin‐like activity was demonstrated in the detergent phase after extraction with TX‐114, thus indicating that not AGEs but a lipophilic contamination was responsible for the stimulation of inflammatory signaling. Conclusion: Our results demonstrate that glycolaldehyde‐modified AGEs are unable to induce inflammatory signaling in receptor for AGE‐expressing cells. The observed cell‐activating activity can be ascribed to an endotoxin‐like lipophilic contamination present in AGE preparations and affinity column purification was insufficient to remove this contamination.     

Attaching of flexible chains to novolacs on the basis of bisphenol A

Networks containing both flexible segments and rigid structures were synthesized on the basis of bisphenol A novolacs and diglycidylether of butanediol using imidazole as an accelerator. A stoichiometric ratio between epoxy groups and phenolic groups of the novolacs leads to networks with methylene bridges as network junctions. In contrast to this, the same reaction with bisphenol A leads to completely soluble products. The glass transition temperature of this soluble material is considerably lower than the glass transition temperature of the networks. Increasing content of methylene bridges in the novolacs leads to an increase of the glass transition temperature of the networks and to a decrease of the δc_p value at the glass transition. Furthermore, epoxy excess leads to networks with rubber-structure of the bisphenol A novolac used in the reaction with the diglycidylether. It was found that conformations with intramolecular hydrogen bondings exist between phenolic hydroxyl groups, which considerably influence the reactivity of the novolac with the epoxy group. © 1996 John Wiley & Sons, Inc.     

An Innovative Submerged Entry Nozzle Design for Billet and Bloom Casting

Fluid flow in the mold has a significant impact on the quality of continuously cast steel products.Since it is strongly influenced by the SEN design,attention h...     

iFlash:80℃活化漂白与新型皂洗

加工技术与设备的发展通常会使加工时间缩短.但是新型助剂的应用也可减少加工时间,大大降低成本.随着iFlash系统的应用,漂白温度可降至80℃,活性染料染色后皂洗的时间也大大缩短.因此,织物间歇式染色得到优化,在不增加额外投资的情况下运行更经济.     

Critical review of models for H2-permeation through polymers with focus on the differential pressure method

To reduce loss of hydrogen in storage vessels with high energy-to-weight-ratio, new materials, especially polymers, have to be developed as barrier materials. Very established methods for characterization of barrier materials with permeation measurements are the time-lag and flow rate method along with the differential pressure method, which resembles the nature of hydrogen vessel systems very well. Long measurement durations are necessary to gain suitable measurement data for these evaluation methods, and often restrictive conditions have to be fullfilled. For these reasons, common models for hydrogen permeation through single-layer and multi-layer membranes, as well as models for hydrogen gas properties were collected and reviewed. Using current computer power together with these models can reduce measurement time for characterization of the barrier properties of materials, while additional information about the quality of the measurement results is obtained.     

Structure–Property Relationships in Aligned Electrospun Barium Titanate Nanofibers

Barium titanate nanofibers were uniaxially aligned by electrospinning onto a rotating copper wire drum and alignment was maintained during calcination of the fibers. Two methods for maintaining alignment during calcination were tested, by either using carbon tape or a peeling off method to remove the aligned fibers from the mandrel followed by calcination. The carbon tape removal method led to the formation of shorter aligned nanowires while the peeling off method resulted in longer nanofibers. Additionally, the effects of calcination temperature and time on crystal structure were also examined. The degree of tetragonality in the barium titanate nanofibers increased at higher calcination temperatures and times. Piezoelectricity was confirmed in the nanofibers calcined using piezoeresponse force microscopy, yielding a d₃₃ value of 15.5 pm/V. Using the methods presented here, large quantities of aligned piezoelectric barium titanate and other ceramic fibers or wires can be produced to fulfill their demand in novel microelectronics.     

Rheology and colloidal structure of silver nanoparticles dispersed in diethylene glycol

Rheological behavior of agglomerated silver nanoparticles (~ 40 nm) suspended in diethylene glycol over a wide range of volumetric solids concentrations (? = 0.11–4.38%) was studied. The nanoparticle suspensions generally exhibited a yield pseudoplastic behavior. Bingham plastic, Herschel–Bulkley and Casson models were used to evaluate the shear stress-shear rate dependency. Analyzing the effect of silver concentrations on the yield stress and viscosity of the suspensions followed an exponential form, revealing an increase in the degree of interparticle interactions with increasing solid concentrations. Fractal dimension (D_f) was estimated from the suspension yield stress and ? dependence, and was determined as D_f = 1.51–1.62 for the flocculated nanoparticle suspensions. This suggested that the suspension structure was probably dominated by the diffusion-limited cluster–cluster aggregation (DLCA) due mostly to the strong attractions involved in the interparticle potentials. Maximum solids concentration of the suspensions was determined to be ?_m = 11%.