Micromolding Surface‐Initiated Polymerization: A Versatile Route for Fabrication of Coatings with Microscale Surface Features of Tunable Height

This article introduces a process termed micromolding surface‐initiated polymerization (μMSIP) as a versatile route to provide surface‐bound, partially fluorinated polymer coatings with a homogeneous array of microscale surface features. The process employs hard‐polydimethylsiloxane (h‐PDMS) to mold the surface structure of master substrates exhibiting patterned microscale features. Upon filling the mold with the monomer 5‐(perfluorooctyl)norbornene (NBF8) and placing against a surface that is pre‐activated for surface‐initiated ring‐opening metathesis polymerization (SI‐ROMP), a partially fluorinated polymer film propagates from the surface with features that grow into the recesses of the mold to produce the final microtextured coating. The heights of these features can be tuned from 20–100% of the full height of the mold features based on the amount of initiator employed as well as the polymerization time and temperature. Reproduced topographies include pyramidal and inverted pyramidal structures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images show that the final polymer film exhibits a homogeneously microstructured surface that resembles that of its corresponding master.     

Integrins Increase Sarcoplasmic Reticulum Activity for Excitation—Contraction Coupling in Human Stem Cell-Derived Cardiomyocytes

Engagement of the sarcoplasmic reticulum (SR) Ca²⁺ stores for excitation–contraction (EC)-coupling is a fundamental feature of cardiac muscle cells. Extracellular matrix (ECM) proteins that form the extracellular scaffolding supporting cardiac contractile activity are thought to play an integral role in the modulation of EC-coupling. At baseline, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) show poor utilisation of SR Ca²⁺ stores, leading to inefficient EC-coupling, like developing or human CMs in cardiac diseases such as heart failure. We hypothesised that integrin ligand–receptor interactions between ECM proteins and CMs recruit the SR to Ca²⁺ cycling during EC-coupling. hiPSC-CM monolayers were cultured on fibronectin-coated glass before 24 h treatment with fibril-forming peptides containing the integrin-binding tripeptide sequence arginine–glycine–aspartic acid (2 mM). Micropipette application of 40 mM caffeine in standard or Na⁺/Ca²⁺-free Tyrode’s solutions was used to assess the Ca²⁺ removal mechanisms. Microelectrode recordings were conducted to analyse action potentials in current-clamp. Confocal images of labelled hiPSC-CMs were analysed to investigate hiPSC-CM morphology and ultrastructural arrangements in Ca²⁺ release units. This study demonstrates that peptides containing the integrin-binding sequence arginine–glycine–aspartic acid (1) abbreviate hiPSC-CM Ca²⁺ transient and action potential duration, (2) increase co-localisation between L-type Ca²⁺ channels and ryanodine receptors involved in EC-coupling, and (3) increase the rate of SR-mediated Ca²⁺ cycling. We conclude that integrin-binding peptides induce recruitment of the SR for Ca²⁺ cycling in EC-coupling through functional and structural improvements and demonstrate the importance of the ECM in modulating cardiomyocyte function in physiology.     

Practical experiences of on-line partial discharge measurements ona variety of medium-voltage electrical equipment

In recent years, there has been a considerable amount of discussion concerning partial discharge (PD) measurements on medium-voltage motors and generators. If one considers the total plant electrical distribution system and production equipment, motors comprise only a small part of the plant electrical equipment. If a motor should fail, part of production will likely be shut down and there will be lost revenue. However, there is a wide variety of other equipment in a facility, besides a motor, that can fail and can have a much more devastating effect on the plant's production. Additional items to consider for PD monitoring are the plant incoming transformers (they may be owned by the plant if the plant is purchasing primary power), the incoming switchgear, cables, bus duct, other remote substation switchgear, and power center transformers. Methods have been developed to monitor PD in all types of medium-voltage equipment. This paper discusses application of sensors, methods of measurement and data interpretation and present several case studies     

Nonlinear dynamics of a laser diode with optical feedback systemssubject to modulation

The nonlinear dynamic behavior of a direct frequency-modulated diode laser with strong optical feedback is examined and compared to a laser diode subject to electro-optically modulated, strong optical feedback. Direct modulation is achieved by sinusoidal modulation of the diode laser injection current. Electro-optic modulation is achieved by applying a sinusoidal voltage to an intracavity phase modulating element. The output state (characterized by the output power versus time, the intensity noise spectrum and the optical frequency spectrum) for both types of modulation is dependent on the ratio of the modulation frequency to the external cavity resonant frequency, and the modulation power. A number of distinct states are observed: conventional amplitude modulation (with FM spectra); multimode, low-noise amplitude modulation; multimode, high-noise amplitude modulation; periodic limit-cycle operation; quasi-periodicity; chaos; low-frequency fluctuations; and mode-locking. There are significant differences between the direct and electro-optic frequency-modulation cases. The onset of the dynamic instability is characterized as a noisy period-one oscillation for direct modulation and a low-frequency fluctuation for intracavity electro-optic modulation. Phase portraits produced experimentally with the use of a digital phosphor oscilloscope are shown to agree well with those constructed from output power versus time data. This represents an experimental method for examining the dynamics phase portraits in real-time     

Human melanoma cells express functional endothelin-1 receptors

Current evidence suggests that endothelium-derived factors enhance human melanoma vascular invasion. Therefore, we studied human melanoma cell expression of receptors to the endothelium-derived peptide, endothelin-1 (ET-1), and determined if they respond to ET-1 with proliferation and chemokinesis. Human metastatic melanoma cell lines were found to have specific, saturable, high affinity ET-1 binding. Northern analysis and competitive inhibition studies confirmed that melanoma cells express the ETB receptor isoform. Ten nanomolar ET-1 caused an 8.2 to 25.5-fold increase in intracellular free calcium. ET-1 was found to be a weak mitogen for melanoma cells, however, melanoma cell chemokinesis was significantly increased by ET-1. These data suggest that ET-1 may be involved in providing a chemokinetic and growth factor environment that enhances perivascular proliferation and invasiveness of melanoma cells.     

Iterative solution techniques in boundary element analysis

Iterative techniques for the solution of the algebraic equations associated with the direct boundary element analysis (BEA) method are discussed. Continuum structural response analysis problems are considered, employing single- and multi-zone boundary element models with and without zone condensation. The impact on convergence rate and computer resource requirements associated with the sparse and blocked matrices, resulting in multi-zone BEA, is studied. Both conjugate gradient and generalized minimum residual preconditioned iterative solvers are applied for these problems and the performance of these algorithms is reported. Included is a quantification of the impact of the preconditioning utilized to render the boundary element matrices solvable by the respective iterative methods in a time competitive with direct methods. To characterize the potential of these iterative techniques, we discuss accuracy, storage and timing statistics in comparison with analogous information from direct, sparse blocked matrix factorization procedures. Matrix populations that experience block fill-in during the direct decomposition process are included. With different degrees of preconditioning, iterative equation solving is shown to be competitive with direct methods for the problems considered.     

The relationship of school breakfast to psychosocial and academic functioning: cross-sectional and longitudinal observations in an inner-city school sample

BACKGROUND: Oesophagitis has been shown by standard manometry to be associated with impaired oesophageal motility, but it remains unclear if this abnormality improves with healing of oesophagitis. AIM: To determine if healing of oesophagitis improves oesophageal motility using solid bolus oesophageal transit scintigraphy and combined ambulatory oesophageal motility/pH monitoring. METHODS: Patients with grade II-III oesophagitis underwent ambulatory motility/pH monitoring (using a Konigsberg catheter with four pressure transducers at 5 cm intervals) and solid bolus scintigraphy before and after treatment with omeprazole 20 mg b.d. for 8-14 weeks. RESULTS: Three (11%) of the 28 patients failed to heal. Initial scintigraphy was abnormal in 18 (67%) of 27 patients (one refused scintigraphy). Twenty-three of the 25 healed patients had repeat studies showing no significant change in the number which were abnormal (16 (64%), P = 1.0) or the overall oesophageal transit time (P = 0.65). Due to intolerance of the technique, only 11 patients had ambulatory motility/pH performed both before and after healing, giving the study 90% power to detect a 5 mmHg increase in peristaltic amplitude. No significant improvement was seen in any motility or pH parameter after healing of oesophagitis. CONCLUSION: Analysis of oesophageal motility showed no improvement in peristaltic activity after healing of oesophagitis, suggesting that the abnormal motility is either a primary disorder or an irreversible consequence of mucosal damage.     

Tuning and enhancing enantioselective quenching of calixarene hosts by chiral guest amines.

The synthesis of a propranolol amide derivative of p-allylcalix[4]arene is described, which has been designed to behave as a molecular sensor capable of distinguishing chiral amines on the basis of their shape and chirality. This molecule can discriminate between the enantiomers of phenylalaninol through the quenching of the fluorescence emission in methanol in contrast to an (S)-dinaphthylprolinol calix[4]arene derivative, which can discriminate between the enantiomers of phenylglycinol, but not phenylalaninol. The separation between the naphthyl fluorophores and the hydrogen-bonding sites within the chiral cavity can be tuned to recognize guest amines with similar separation between aryl groups and hydrogen-bonding sites. The formation of metal ion complexes of the p-allylcalix[4]arene propranolol amide derivative is shown to induce a more regular and rigid cone conformation in the calix[4]arene macrocycle, which generates a significant enhancement in the observed enantiomeric discrimination.