Use of inverse gas chromatography to quantify interactions in amine cured epoxy resins

Flory–Huggins interaction parameters, λ, were determined for a series of probes in an amine cured epoxy resin matrix (433–493 K) and its precursors (324–363 K) by inverse gas chromatography (IGC). Hildebrand–Scatchard theory was combined with Flory–Huggins theory in order to estimate infinte dilution solubility parameters (δ₂) for the matrix and its precursors at 298 K. It was shown that the value of the solubility parameter for the cured resin matrix lies between those of its precursors. Compared to the majority of published work, an unusual aspect of this application of IGC is that solubility parameters have been determined when the stationery phases are (i) small molecules and (ii) a highly crosslinked polymer. Moreover, all possible attempts have been made to ensure equilibrium conditions between probe and stationary phase, and compensation for asymmetry of peak profile has been applied in determining δ₂. The solubility parameters estimated by IGC are in good agreement with those calculated by other methods.     

Methane/natural gas storage and delivered capacity for activated carbons in dry and wet conditions

Methane/natural gas storage and delivered capacity for three different activated carbons in dry and wet conditions were measured. In all tests the temperature of the bed was maintained constant at 277.15 K and pressure was increased up to 10 MPa. Natural gas storage capacity was less than methane storage capacity in dry conditions for all the three activated carbons tested, while the gas delivery was almost the same. One of activated carbon tested (NC120) showed the possibility of hydrate forming for pressures higher than 4 MPa but the amount of gas stored still was less than the amount stored in dry conditions over the whole range of pressure. The analysis of the gas delivered at each pressure steps shows that considerable amount of heavy components do not come out from the bed even at very low pressures in both dry and wet condition tests. Repeatability of the sorption/desorption processes - vital for possible commercial/industrial use - has been examined over various cycles.     

Modeling of gold microbeams as strain and pressure sensors for characterizing MEMS packages

This work presents the modeling of gold microbeams for characterizing Micro-electro-mechanical systems (MEMS) packages in terms of both strains induced to the MEMS devices and hermetic sealing capability. The proposed test structures are based on arrays of rectangular-shaped clamped-free and clamped–clamped beams, to be realized with a film of electroplated gold by surface micromachining technology. The resonant frequency of the microbeams is modeled by FEM simulations as a function of substrate deformations, which could be induced by the package. Clamped–clamped bridges show a linear change of the square of the resonant frequency in case of in-plane deformations, in fairly good agreement with an approximate analytical model. Cantilever beams are modeled as variable capacitors to detect out-of-plane deformations. Finally, an analytical model to study cantilever beams as resonators for detecting pressure changes is discussed and compared with preliminary experimental results, showing an impact on the quality factor in a range from 10^?2 mbar to 1?bar.     

One-radius triplets

The one-radius triplet is an optical system that consists of three lenses. Either the radii of curvature of the lenses have the same absolute value or one radius of curvature has an infinitely large value. The advantage of such optical systems is that their production cost is less than that of systems with ordinary triplets. Here a theory of one-radius triplets is described and tables of parameters for their modification are provided. Residual aberrations are given for several selected triplets. One-radius triplets are suitable for use in laser technology and metrology.     

PI3K and AKT: Unfaithful Partners in Cancer

The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway regulates multiple cellular processes. An overactivation of the pathway is frequently present in human malignancies and plays a key role in cancer progression. Hence, its inhibition has become a promising approach in cancer therapy. However, the development of resistances, such as the abrogation of negative feedback mechanisms or the activation of other proliferative signaling pathways, has considerably limited the anticancer efficacy of PI3K/AKT inhibitors. In addition, emerging evidence points out that although AKT is acknowledged as the major downstream effector of PI3K, both PI3K and AKT can operate independently of each other in cancer, revealing another level of complexity in this pathway. Here, we highlight the complex relationship between PI3K and AKT in cancer and further discuss the consequences of this relationship for cancer therapy.     

Graphene substrates promote adherence of human osteoblasts and mesenchymal stromal cells

The biocompatibility of large single layer graphene produced by chemical vapour deposition was investigated using human osteoblasts and mesenchymal stromal cells. The study was focused on cellular adhesion, morphology and the ability to proliferate on graphene substrates. It was found that both of the cell types which were tested adhered and proliferated better when cultured on graphene films than on a SiO₂ substrate.     

TEM investigation on zirconate formation and chromium poisoning in LSM/YSZ cathode

Cell durability is a crucial technological issue for SOFC commercialization, and considerable progress has been made in recent years. A number of degradation pathways have been established, amongst which microstructural changes, poisoning effects and formation of less conductive phases. In this study, transmission electron microscopy was used to observe submicron-scale effects on selected cathode zones of an anode supported cell tested in SOFC stack repeat element configuration. The test has been performed with a dedicated segmented test bench, at 800 °C for 1900 h, which allowed to spatially resolve degradation processes, and therefore to improve their correlation with localized post-test analysis. Evidence is presented of reaction products (mainly SrZrO₃) at the LSM/YSZ interfaces as well as of contaminants, in particular Cr, but also Si. A polarized cell segment is compared to an unpolarized one, to assess any influence of cathode polarization.     

A hierarchical modeling approach for risk assessment in developmental toxicity studies

Within the past decade, there has been an increasing interest in the problem of joint analysis of clustered multiple outcome data, motivated by developmental toxicity applications. Typically, a toxic insult early in gestation may result in a resorbed fetus or a fetal death. If however the fetus survives the entire gestation period, growth reduction such as low birth weight may occur, or can exhibit a malformation. Ideally, a model should take the complete hierarchical structure of the data into account. So far, however, one has tackled the challenges in this setting only partly each time making different restricting assumptions (e.g., restriction to viable fetuses only). In addition, because of genetic similarity and the same treatment conditions, offsprings of the same mother behave more alike than those of another mother. Thus, responses on different fetuses within a cluster are likely to be correlated. The ultimate scientific question requires assessing the full effect of dose administration, not only in the malformation and weight outcome, but also in the death outcome. A hierarchical Bayesian method is proposed to this effect. Such a model can serve as a basis for quantitative risk assessment.