Carbazole functionalized isocyanide brushes in heterojunction photovoltaic devices

In this work, carbazole-containing polyisocyanide (PIACz) brushes were used for photovoltaic devices. A photovoltaic device was fabricated on top of the brushes by spin-coating a suitable acceptor and evaporating an Al cathode. Devices with a poly(N-vinylcarbazole) (PVK) bulk polymer were also prepared for comparison. Interestingly, the brushes showed better photovoltaic characteristics as compared to the blended PVK system. This is attributed to the specific morphologies of the polyisocyanide brushes, which provide a large interfacial area between the donor and acceptor for efficient photogeneration. It was found that the device performance varied according to the molecular size of the incorporated acceptors.     

Increase in the coefficient of friction of the rolling stock disc brake via fluid cooling of its friction elements

The paper presents the results of theoretical and experimental investigations in the effect of a partial heat energy removal in the friction contact zone upon the disc brake coefficient of friction during braking. A fluid cooling system for the disc brake friction elements has been proposed based on a recuperative liquidpneumatic heat-exchange apparatus.     

Wavelength calibration of spectra measured by the Global Ozone Monitoring Experiment by use of a high-resolution reference spectrum

Earthshine spectra measured by the nadir-viewing Global Ozone Monitoring Experiment (GOME) spectrometer aboard the second European Remote Sensing (ERS-2) Satellite in the range of 240-790 nm are widely used for the retrieval of concentrations and vertical profiles of atmospheric trace gases. For the near-real-time delivery of ozone columns and profiles at the Royal Netherlands Meterological Institute, a tailor-made wavelength calibration method was developed. The method use a high-resolution (0.01-nm) solar spectrum as the reference spectrum and applies both a shift and a squeeze to the wavelengths in selected windows to find the optimal wavelength grid per window. This method provides a calibration accuracy of 0.002 nm below and 0.001 nm above 290 nm. The new wavelength calibration method can be used on any wavelength window, for example, to improve the calibration of spectra from the GOME Data Processor. A software package, GomeCal, which performs this recalibration, along with an improved polarization and radiometric correction, has been made and has been released via the World Wide Web. The method can be used for any high-resolution (ir)radiance spectrometer, such as the satellite instruments SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Cartography), Ozone Monitoring Instrument, and GOME-2.     

Supramolecular porphyrin polymers in solution and at the solid-liquid interface

We have investigated in detail the self-assembly of a chiral porphyrin trimer in different solvents and correlated this behavior to the aggregation of the molecule at a solid-liquid interface. In n-hexane and cyclohexane, CD spectroscopy and dynamic and static light scattering studies showed that the porphyrin trimer self-assembles already at micromolar concentrations into long, chiral supramolecular polymers, which precipitate as fibers when the solution is drop-cast onto a mica surface. In contrast, in chloroform, the compound is molecularly dissolved up to concentrations of 0.2 mM and when micromolar solutions are drop-cast onto mica, no precipitation of large assemblies occurs. Instead, at the moment that the chloroform film becomes subject to spinodal dewetting and the porphyrin trimers within this film start to self-assemble, extended patterns of equidistant lines of single molecule thick columnar stacks are formed.     

Synergy of cell–cell repulsion and vacuolation in a computational model of lumen formation

A key step in blood vessel development (angiogenesis) is lumen formation: the hollowing of vessels for blood perfusion. Two alternative lumen formation mechanisms are suggested to function in different types of blood vessels. The vacuolation mechanism is suggested for lumen formation in small vessels by coalescence of intracellular vacuoles, a view that was extended to extracellular lumen formation by exocytosis of vacuoles. The cell–cell repulsion mechanism is suggested to initiate extracellular lumen formation in large vessels by active repulsion of adjacent cells, and active cell shape changes extend the lumen. We used an agent-based computer model, based on the cellular Potts model, to compare and study both mechanisms separately and combined. An extensive sensitivity analysis shows that each of the mechanisms on its own can produce lumens in a narrow region of parameter space. However, combining both mechanisms makes lumen formation much more robust to the values of the parameters, suggesting that the mechanisms may work synergistically and operate in parallel, rather than in different vessel types.     

Augmenting solute clearance in peritoneal dialysis

BACKGROUND: The removal of low molecular weight solutes by peritoneal dialysis is less than by hemodialysis. The targets for Kt/Vurea and creatinine clearance formulated in the Dialysis Outcome Quality Initiative are unlikely to be achieved in a substantial portion of peritoneal dialysis patients. Possibilities to increase small solute clearances have therefore been subject to many investigations. METHODS: A review of the literature and of recent new data on determinants of solute removal, such as residual renal function, the role of drained dialysate volume and manipulation of the diffusive capacity of the peritoneum are presented. RESULTS: The contribution of residual GFR is more important for the clearance of creatinine than for Kt/Vurea. It is even more important for the removal of organic acids that are removed from the body by tubular secretion. High dosages of furosemide increase the urinary volume and the fractional Na+ excretion, but have no effect on the magnitude of residual GFR, renal creatinine clearance, renal urea clearance, and peritoneal transport characteristics. The drained dialysate volume per day is the main determinant of the peritoneal removal of urea. Its effect decreases the higher the molecular weight of a solute. It can be augmented by using large instillation volumes, by the application of more exchanges, and by increasing peritoneal ultrafiltration. A large exchange volume is especially effective in patients with an average transport state, but in those with high solute transport rates, Kt/Vurea is especially influenced by the number of exchanges. Possibilities to increase ultrafiltration are discussed. The diffusive capacity of the peritoneum can be augmented by using low dosages of intraperitoneally administered nitroprusside. This increases solute transport most markedly when it is applied in combination with icodextrin as osmotic agent. CONCLUSIONS: Small solutes clearances cannot be increased by furosemide. Increasing the instilled volume of dialysis fluid and the number of exchanges both affect solute clearance. Studies are necessary on long-term effects of manipulation of the peritoneal membrane with nitroprusside.     

The nitric oxide donor nitroprusside intraperitoneally affects peritoneal permeability in CAPD

Nitroprusside is a nitric oxide (NO) donor. To investigate effects of nitroprusside i.p. on peritoneal permeability and perfusion, standard peritoneal permeability analyses were performed. Ten stable CAPD patients were studied twice within one week with glucose based dialysate (1.36% Dianeal) with and without addition of nitroprusside 4.5 mg/liter. Mass transfer area coefficients (MTAC) of CO2 were calculated to estimate peritoneal blood flow. Nitrate, a stable metabolite of NO, and cGMP, a second messenger of NO synthesis, were measured in plasma and dialysate. The MTACs of low molecular weight solutes were greater with nitroprusside (NP) compared to the control dwell (C): creatinine median 14.1 (NP) versus 9.9 ml/min (C), urea 21.7 (NP) versus 18.5 ml/min (C) and urate 10.5 (NP) versus 8.6 ml/min (C) (P < 0.05 for all). This points to an increased effective peritoneal surface area with nitroprusside. Furthermore, the restriction coefficient for the low molecular weight solutes decreased from 1.28 (C) to 1.23 (NP) (P = 0.02), suggesting some effect also on the size selectivity to these solutes. The effect of nitroprusside on the clearances of serum proteins was more pronounced. The increase with nitroprusside was 34% for beta 2-microglobulin, 70% for albumin, 77% for IgG and 143% for alpha 2-macroglobulin. This reduction in size selectivity was reflected in a decrease in the restriction coefficient for macromolecules from 2.29 (C) to 1.86 (NP), P < 0.01. This implies an increase in the intrinsic permeability of the peritoneal membrane. Kinetic modeling, using computer simulations, was done to analyze these effects in terms of the pore theory, using a convection model and a diffusion model for the transport of macromolecules. Nitroprusside led to an increase of both the large pore radius and the small pore radius and of the unrestricted area over diffusion distance. These effects were more pronounced with the diffusion model. The MTAC CO2 was not different: NP 76.9 and C 84.1 ml/min. MTACs of nitrate were not greater than expected on the basis of the molecular weight during both dwells. The dialysate/plasma (D/P) ratio of cGMP was greater after addition of nitroprusside: 0.36, range 0.21 to 0.77 (C) and 0.74, 0.23 to 2.50 (NP), P = 0.02. With nitroprusside the D/P ratio of cGMP was greater than expected on the basis of its molecular weight (P < 0.001). This points to local generation of cGMP after the addition of nitroprusside, induced by NO. No differences were found in the dialysate concentrations of the prostaglandins (PG) PGE2 and 6-keto-PGF1 alpha and thromboxane B2 after addition of nitroprusside. The transcapillary ultrafiltration rate and the net ultrafiltration rate during four hours were not different with nitroprusside. In conclusion, nitroprusside i.p. increased the effective peritoneal surface area and the intrinsic permeability, but the peritoneal blood flow did not change. The greater than expected D/P ratios of cGMP point to local generation of cGMP with nitroprusside, induced by NO.     

Risk of overtreatment with current peak flow criteria in self-management plans. Dutch CNSLD Study Group. Chronic Non-Specific Lung Disease

Home peak expiratory flow (PEF) measurements have become the cornerstone of asthma self-management plans. However, the cut-off values for changing treatment have not been formally tested. This study focusses on the possible overtreatment brought about by the different cut-off values and denominators currently employed. Data from 133 clinically stable asthmatic patients from a 2.5 yr follow-up study were analysed. The results showed that strict adherence to current criteria would lead to severe overtreatment, with up to 30% of clinically stable patients crossing into the lowest (red) zone at least once a year when personal best is the denominator and when it has not been limited to a defined time of day or to defined prior bronchodilator use. As expected, the passage of clinically stable patients into the lower zones became less frequent when cut-off values were sharpened and when time- and treatment-specific PEFs were used as the denominators. Strict adherence to commonly used peak expiratory flow cut-off values would lead to considerable overtreatment. In order to avoid overtreatment, the morning peak expiratory flow before any (bronchodilator) treatment should be related to the personal best peak expiratory flow measured under the same conditions. The choice of the right cut-off value will also depend on studies being performed to test the amount of undertreatment with a given value.