On the Impact of Linear Siloxanated Side Chains on the Molecular Self-Assembling and Charge Transport Properties of Conjugated Polymers

Herein reported is the impact of the functionalization of four different semiconducting polymer structures by a linear siloxane-terminated side-chains. The latter is tetrasiloxane (Si₄) or trisiloxane (Si₃) chains, substituted at their extremity to a pentylene linker. The polymer structure is based on 5,6-difluorobenzothiadiazole comonomer (PF2), a diketopyrrolopyrrole unit (PDPP-TT), a naphtalediimide unit (PNDI-T₂), and a poly[bis(thiophen-2-yl)thieno[3,2,b]thiophene (PBTTT). The properties of these siloxane-functionalized polymers are scrutinized and compared with the ones of their alkyl-substituted polymer analogues. The impact of the alkyl-to-siloxane chain substitution clearly depends on the molecular section of the side chains. When a branched 2-octyldodecyl chain (C₂₀) is replaced by a Si₄ chain of same molecular section, the greatest impact is the strong increase of the π-stacking overlap of the polymer backbones. This effect leads to a significative enhancement of the charge mobility values of the polymers. As in-plane and out-of-plane mobility are increased simultaneously, this π-overlap enhancement effect happens to be preponderant over the polymer orientation variations. When a linear tetradecyl chain (C₁₄) is replaced by a linear Si₃ chain of twice larger molecular section, the polymer structure is profoundly affected. While PBTTT-C₁₄ is crystalline and purely edge-on, PBTTT-Si₃ is mesomorphic and shows a mixed face-on/edge-on orientation.     

Optimization of the side-chain density to improve the charge transport and photovoltaic performances of a low band gap copolymer

Poor processability and low molecular weights are often hindering the efficient utilization of novel conjugated polymers in optoelectronic devices. Increasing the alkyl side-chain density generally enhances the polymer solubility but may affect as well its optoelectronic properties. In this work, we use density functional theory to identify ways to increase the side-chain density of donor-acceptor alternate copolymers based on 2,1,3-benzothiadiazole, thiophene and thieno[3,2-b]thiophene units, without modifying there otherwise promising frontier orbital energy levels. Following the theoretical results, a new polymer could be synthesized, exhibiting good processability and improved charge transport. As a consequence, the photovoltaic device performances of this polymer family could be enhanced, reaching a 3.7% power conversion efficiency in a standard device configuration and without any post-deposition treatment.     

Neurodevelopmental outcome after prenatal exposure to opiates

The new population on dialysis today consists mainly of high risk patients (the elderly, diabetics, etc.) with high cardiovascular scores, and such vascular pathology is the most important predisposing factor for the occurrence of a frequent intradialytic clinical complication, vascular instability syndrome, which covers a range of clinical problems. Recently a new dialysis technique, profiled hemodialysis (PHD), has been set up and proposed for routine use. PHD consists of the clinical use of preestablished individual dialysis profiles aimed at antagonizing the changes in intradialytic plasma osmolarity by continuous modulation of dialysate sodium concentration throughout the whole extracorporeal session. In particular, PHD aims at reducing the fall of plasma osmolarity in the first half of the session (when it is higher) by reducing the sodium removal rate through increasing its dialysate concentration while taking into account the desired individual sodium balance to be reached at the end of the session. In this work, we report clinical experience with PHD compared to standard hemodialysis with constant sodium dialysate (SHD) in terms of its efficacy to maintain a more stable intradialytic blood volume (BV) and more stable hemodynamics. The PHD used in this work has been implemented by a mathematical model for computing the individual dialysate sodium profile which we have recently validated (Ursino M, Coli L, La Manna G, Grilli Cicilioni M, Dalmastri V, Guidicissi A, Masotti P, Avanzolini G, Stefani S, Bonomini V. A simple mathematical model of intradialytic sodium kinetics: "in vivo" validation during hemodialysis with constant or variable sodium. Int J Artif Organs 1996;19:393-403.). Eleven uremic patients affected by hypotension at the beginning of dialysis treatment were studied. Each patient first underwent an SHD treatment and 1 week later a PHD treatment. The 2 extracorporeal sessions (one on SHD and the other on PHD) were performed in each individual patient under identical operative conditions including the sodium mass removal by the end of the session and the ultrafiltration rate. The crit line and Doppler echocardiography were used to determine BV, cardiac output (CO), and stroke volume (SV) throughout the sessions. The mean blood pressure (MBP) and heart rate (HR) were simultaneously monitored. PHD was associated with a more stable intradialytic BV and more stable hemodynamics compared to SHD. The higher stability of BV and cardiac function (in terms of SV and CO maintenance) which was obtained above all in the first half of the PHD session was associated with a higher stability of the MBP and the HR. This resulted in an enhancement in cardiovascular tolerance to ultrafiltration throughout the session in all tested patients. In contrast, SHD in the same patients was characterized by early significant changes in BV and cardiovascular parameters resulting in a significant decrease of the MBP and a significant increase of the HR throughout the session and also 1 h after the end of dialysis. Our results indicate that PHD may represent an efficient approach for the treatment of patients suffering from intradialytic vascular instability. If long-term clinical practice confirms the efficacy of PHD in controlling dialysis intolerance symptoms, it will have great scope as a routine procedure.     

Decreased emitter sheet resistivity loss in high-eficiency silicon solar cells

State-of-the-art two-dimensional (2D) numerical semiconductor device simulation tools are applied to bifacially contacted silicon solar cells of practical dimensions in order to investigate the 2D effects arising from ohmic voltage drops in cell emitters due to finite front metal grid line spacings. the 2D simulations show that for typical front finger spacings of high-efficiency silicon solar cells the minority carrier flow in the base deviates strongly from the purely linear flow assumed by one-dimensional (1D) theory. Compared to conventional 1D theory, this 2D effect results in reduced emitter sheet resistivity losses, an increased optimum front finger spacing and a reduced impact of finger spacing on cell efficiency. the 2D effects are of particular importance for concentrator solar cells. The 2D simulations presented in this work considerably improve the general understanding of internal device physics of high-efficiency silicon solar cells and reveal the limits of 1D models for the simulation of these devices.     

Shielding effectiveness of carbon-filled nylon 6,6

Electrically conductive resins can be made by adding electrically conductive fillers to typically insulating polymers. Resins with an electrical resistivity of approximately 10⁰ ohm-cm or less can be used for electromagnetic and radio frequency interference shielding applications. This research focused on performing compounding runs followed by injection molding and shielding effectiveness testing of carbon filled nylon 6,6 based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a surface-treated polyacrylonitrile (PAN)-based carbon fiber. Conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 2³ factorial design and a complete replicate. The objective of this paper was to determine the effects and interactions of each filler on the shielding effectiveness properties of the conductive resins. Carbon fiber caused the largest increase in shielding effectiveness. Also, all the single fillers and combinations of fillers were statistically significant at the 95% confidence level, except the composite containing carbon black and synthetic graphite particles tested at 800 MHz. Polym. Compos. 25:407–416, 2004. © 2004 Society of Plastics Engineers.     

Emissions and encapsulation of cadmium in CdTe PV modules during fires

Fires in residential and commercial properties are not uncommon. If such fires involve the roof, photovoltaic arrays mounted on the roof will be exposed to the flames. The amount of cadmium that can be released in fires involving CdTe PV and the magnitude of associated health risks has been debated. The current study aims in delineating this issue. Previous thermogravimetric studies of CdTe, involved pure CdTe and single‐glass PV modules. The current study is based on glass–glass CdTe PV modules which are the only ones in the market. Pieces of commercial CdTe photovoltaic (PV) modules, sizes 25×3 cm, were heated to temperatures up to 1100°C to simulate exposure to residential and commercial building fires. The temperature rate and duration in these experiments were defined according to standard protocols. Four different types of analysis were performed to investigate emissions and redistribution of elements in the matrix of heated CdTe PV modules: (1) measurements of sample weight loss as a function of temperature; (2) analyses of Cd and Te in the gaseous emissions; (3) Cd distribution in the heated glass using synchrotron X‐ray fluorescence microprobe analysis; and (4) chemical analysis for Cd and Te in the acid‐digested glass. These experiments showed that almost all (i.e., 99·5%) of the cadmium content of CdTe PV modules was encapsulated in the molten glass matrix; a small amount of Cd escaped from the perimeter of the samples before the two sheets of glass melted together. Adjusting for this loss in full‐size modules, results in 99·96% retention of Cd. Multiplying this with the probability of occurrence for residential fires in wood‐frame houses in the US (e.g., 10⁻⁴), results in emissions of 0·06 mg/GWh; the probability of sustained fires and subsequent emissions in adequately designed and maintained utility systems appears to be zero. Published in 2005 by John Wiley & Sons, Ltd.     

Detection of microRNA in cattle serum and their potential use to diagnose severity of Johne's disease

Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's disease in ruminants, which is characterized by chronic progressive granulomatous enteritis. The infection leads to wasting and weight loss in the animals and eventually death, causing considerable production losses to the agricultural industry worldwide. Currently available ELISA- and PCR-based diagnostic tests have limited sensitivity and specificity during early MAP infection in cattle, suggesting that there is an urgent demand for alternative diagnostic tests. Circulating microRNA (miRNA) have recently gained attention as potential biomarkers for several diseases in humans. However, knowledge and use of miRNA as biomarkers in diseases of ruminants, including Johne's disease, are very limited. Here we used NanoString nCounter technology (NanoString, Seattle, WA), a digital platform for amplification-free and hybridization-based quantitative measurement of miRNA in the sera of noninfected and naturally MAP-infected cattle with different severity of infection. Using probes developed against human miRNA, 26 miRNA were detected in cattle serum; 13 of these miRNA were previously uncharacterized for cattle. Canonical discrimination analysis using 20 miRNA grouped animals into 4 distinct clusters based on their disease status, suggesting that the levels of these miRNA can reflect disease severity. A model was developed using a combination of 4 miRNA (miR-1976, miR-873-3p, miR-520f-3p, and miR-126-3p), which distinguished moderate and severely infected animals from noninfected animals. Our study demonstrated the ability of the NanoString nCounter technology to detect differential expression of circulating miRNA in cattle and contributes to widely growing evidence that miRNA can be used as biomarkers in infectious diseases in cattle.