Volatile organic compound detection using nanostructured copolymers

Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.     

Solubility and dissolution rate of progesterone-cyclodextrin-polymer systems

This contribution focused on the solubility improvement of the poorly water-soluble steroid hormone progesterone which, in its natural state, presents a reduced oral bioavailability. In the first part of this study, two simple, reproducible methods that were candidates for use in the preparation of inclusion complexes with cyclodextrins were investigated. Solubility capacities of the progesterone complex with hydroxypropyl-β-CD (HPβ-CD), hydoxypropyl-γ-CD (HPγ-CD), permethyl-β-CD (PMβ-CD), and sulfobutylether-β-CD (SBEβ-CD), prepared by the freeze-drying and precipitation methods, were evaluated by Higuchi phase solubility studies. The results showed that HPβ-CD and PMβ-CD were the most efficient among the four cyclodextrins for the solubilization of progesterone, with the highest apparent stability constants. Therefore, dissolution studies were conducted on these latest progesterone/cyclodextrin complexes and physical mixtures. Two additional natural cyclodextrins, β-CD and γ-CD, were taken as references. Hence, the influence of more highly soluble derivatives of β-CD (HPβ-CD, PMβ-CD) on the progesterone dissolution rate, in comparison to pristine β-CD, alongside an increase in the cavity width for γ-CD versus β-CD, were investigated. The dissolution kinetics of progesterone dissolved from HPβ-CD, PMβ-CD, and γ-CD revealed higher constant rates in comparison to β-CD. Therefore, the aim of the second part of this study was to investigate the possibility of improving the dissolution rate of progesterone/β-CD binary systems upon formation of ternary complexes with the hydrophilic polymer, PEG 6000, as β-CD had the smallest progesterone solubility and dissolution capacity among the four cyclodextrins studied (β-CD, HPβ-CD, HPγ-CD and PMβ-CD). The results indicated that dissolution constant rates were considerably enhanced for the 5% and 10% progesterone/β-CD complexes in PEG 6000.

The interaction of progesterone with the cyclodextrins of interest on the form of the binary physical mixtures, complexes, or ternary complexes were investigated by differential scanning calorimetry (DSC) and Fourier transformed-infrared spectroscopy (FT-IR). The results proved that progesterone was diffused into the cyclodextrin cavity, replacing the water molecules and, in case of ternary systems, that the progesterone β-cyclodextrin was well dispersed into PEG, thus improving progesterone bioavailability for subsequent oral delivery in the same way as derivatized cyclodextrins. The present work proves that ternary complexes are promising systems for drug encapsulation.     

Development and numerical validation of a new model for walls with phase change materials implemented in TRNSYS

This paper presents a model of a wall with variable properties dedicated to modelling phase change materials (PCMs) in building envelopes. The model is implemented in the TRNSYS simulation tool and referred to as Type 3258. The 1-D conduction heat transfer equation is solved using an explicit finite-difference method coupled with an enthalpy method to consider the variable PCM thermal capacity. This model includes temperature-dependent thermal conductivity and PCM-specific effects like hysteresis and supercooling. The stability conditions are discussed and the algorithm implemented in TRNSYS is described. A numerical validation performed on wall test cases proposed by the International Energy Agency is presented, showing that the developed model is in agreement with reference models. The paper also discusses the impact of temporal and spatial discretization on the model performance. Modelling problems encountered when using an effective heat capacity method (compared to an enthalpy method) and when representing supercooling are also discussed.     

Establishing stability: exploring the meaning of ‘home’ for women who have experienced intimate partner violence

There is evidence that involuntary housing instability may undermine health and well-being. For women who have experienced intimate partner violence (IPV), achieving stability is likely as important for other groups, but can be challenging. Through our analysis of 41 interviews with women who have experienced low income and IPV, we argue that definitions of housing stability are multifaceted and for many centred on a shared understanding of the importance of creating an environment of “home”. We found that obtaining housing that satisfied material needs was important to women. However, in asking women to define what housing stability meant to them, we found that other factors related to ontological security and the home, such as safety, community, and comfort, contributed to women’s experiences of stability. Through our discussion of the importance these women placed on establishing stable homes, we argue that future research on women’s experiences with housing stability and IPV should include definitions of stability that capture both material security and women’s experiences with building emotionally stable homes.     

Characterization and Modeling of Precipitation Kinetics in a Fe-Si-Ti Alloy

In this article, we present a systematic study of precipitation kinetics in a Fe-Si-Ti alloy in the temperature range 723?K to 853?K (450?°C to 580?°C), combining complementary tools (transmission electron microscopy (TEM), atom probe tomography (APT), and small-angle neutron scattering (SANS)). We show that the Heusler phase Fe₂SiTi dominates the precipitation process in the investigated time and temperature range, regardless of the details of the initial temperature history. A numerical model based on the evolution of precipitate size classes gives very good agreement with the experimental results, and its application to different alloy compositions provides directions for future alloy optimization.     

Systems analysis utilising pathway interactions identifies sonic hedgehog pathway as a primary biomarker and oncogenic target in hepatocellular carcinoma

The development and progression of cancer is associated with disruption of biological networks. Historically studies have identified sets of signature genes involved in events ultimately leading to the development of cancer. Identification of such sets does not indicate which biologic processes are oncogenic drivers and makes it difficult to identify key networks to target for interventions. Using a comprehensive, integrated computational approach, the authors identify the sonic hedgehog (SHH) pathway as the gene network that most significantly distinguishes tumour and tumour‐adjacent samples in human hepatocellular carcinoma (HCC). The analysis reveals that the SHH pathway is commonly activated in the tumour samples and its activity most significantly differentiates tumour from the non‐tumour samples. The authors experimentally validate these in silico findings in the same biologic material using Western blot analysis. This analysis reveals that the expression levels of SHH, phosphorylated cyclin B1, and CDK7 levels are much higher in most tumour tissues as compared to normal tissue. It is also shown that siRNA‐mediated silencing of SHH gene expression resulted in a significant reduction of cell proliferation in a liver cancer cell line, SNU449 indicating that SHH plays a major role in promoting cell proliferation in liver cancer. The SHH pathway is a key network underpinning HCC aetiology which may guide the development of interventions for this most common form of human liver cancer.Inspec keywords: bioinformatics, cancer, cellular biophysics, genetics, liver, molecular biophysics, RNA, systems analysis, tumoursOther keywords: biomedical informatics, human liver cancer, network underpinning HCC aetiology, liver cancer cell line, cell proliferation, SHH gene expression, siRNA‐mediated silencing, CDK7 levels, phosphorylated cyclin B1, Western blot analysis, in silico findings, SHH pathway, human hepatocellular carcinoma, tumour‐adjacent samples, gene network, integrated computational approach, oncogenic drivers, biologic processes, cancer development, biological networks, cancer progression, oncogenic target, primary biomarker, sonic hedgehog pathway, pathway interactions, systems analysis     

Hydrodynamic study of the granular flow in the solar dryer

There are a great many drying processes and types of equipment, such as dryers with immersed channels; the main advantage of this type of dryer, and the reason why it is chosen by manufacturers, is the homogeneous distribution of the drying air, made possible by dihedrons. In our work, we have investigated a flow model with a random double dispersion and have finally shown that the dispersion coefficients are not constant but vary depending on the position of the granular material in the column of dihedrons.     

S-parameter performance degradation in power RF N-LDMOS devices due to hot carrier effects

This paper reports comparative study of technology reliability after accelerated ageing tests under various conditions (electrical and/or thermal stress) and RF life-tests reliability with pulsed bench for radar applications in S-band. It is important to understand the effects of the reliability degradation mechanisms on the S-parameters and in turn on static and dynamic parameters.The analysis of the experimental results is presented and the physical processes responsible for the observed degradation at different stress conditions are studied by means of 2D ATLAS–SILVACO simulations.S-parameters degradation of hot-carrier stressed n-MOS transistors can be explained by the transconductance and miller capacitance shifts, which are resulted from the interface state generation (traps), which results in a build up of negative charge at Si/SiO₂ interface. More interface states are created due to a located maximum impact ionization rate at the gate edge. From our experimental results, hot electron induced RF performance degradation should be taken into consideration in the design of the power RF MOS devices.     

Selective determination of ascorbic acid with a novel hybrid material based 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and the Dawson type ion [P2Mo18O62] immobilized on glassy carbon

In this study, we synthesized a new hybrid material using well-Dawson K₆[P₂Mo₁₈O₆₂]·nH₂O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). CHN elemental analysis showed that one mole of [P₂Mo₁₈O₆₂]⁶⁻ reacts with 6 moles of [BMIM]⁺ to form [BMIM]₆P₂Mo₁₈O₆₂. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid material compared to the parent Dawson POM. The new hybrid material [BMIM]₆P₂Mo₁₈O₆₂ was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P₂Mo₁₈O₆₂]⁶⁻, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]₆P₂Mo₁₈O₆₂. The relationship between the peak currents of the deposited [BMIM]₆P₂Mo₁₈O₆₂ film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]₆P₂Mo₁₈O₆₂ modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]₆P₂Mo₁₈O₆₂ modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]₆P₂Mo₁₈O₆₂ modified GC electrode occurs at low potential of ∼0 V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]₆P₂Mo₁₈O₆₂ and [P₂Mo₁₈O₆₂]⁶⁻ modified GC films towards the oxidation of AA suggests that the significant decrease in the overpotentials recorded with [BMIM]₆P₂Mo₁₈O₆₂ film is related to the presence of ionic liquid cation in the hybrid material, which probably plays the role of the redox mediator. The resulting AA sensor [BMIM]₆P₂Mo₁₈O₆₂/GC has a significant sensitivity of ∼63 nA/μM AA, fast response time (<9 s), low detection limit (<0.1 μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and dopamine, a linear range from 0.1 μM to at least 22 mM AA and was stable for at least 2 weeks. In addition, such AA sensors can operate in a pH range from 0 to at least 7.