Zone drawn NEW-TPI thermoplastic polyimide and its blends with Xydar liquid crystalline polymer

In this work we report the effects of single stage zone drawing on the properties of NEW-TPI thermoplastic polyimide homopolymer, and its blends with Amoco's Xydar liquid crystalline polymer. Zone drawing was performed first on homopolymer NEW-TPI films to determine the effect of load weight, heater speed, and drawing temperature on the attainable draw ratio. Degree of crystallinity and chain orientation increase as the draw ratio increases for NEW-TPI. Blends of NEW-TPI/Xydar compositions 90/10 and 70/30 were studied next. In blends, the Xydar component is not molecularly dispersed, and is initially preferentially oriented along the machine direction during the film processing stage. Xydar acts as a nucleation site and lowers the temperature for crystallization of the NEW-TPI from the rubbery amorphous state. Zone drawing was performed either parallel or perpendicular to Xydar's initial preferred orientation direction. Blends with lower Xydar fraction could be zone-drawn to higher ratios. Zone drawing perpendicular to Xydar's initial orientation direction also resulted in increased draw ratio. Dynamic mechanical properties of the zone drawn materials were studied. In homopolymer NEW-TPI, dynamic modulus increased by a factor of two to 4.0 GPa in zone drawn films, largely as a result of the formation of oriented crystallites. In the blends, the modulus parallel to Xydar's initial orientation direction was greater than that in the transverse direction. Depending upon composition and test direction, zone drawing increased the dynamic moduli of the blends from 1.5 up to 2.7 times, in the temperature range from 150°C to 300°C.     

Piecewise affine systems modelling for optimizing hormone therapy of prostate cancer

Prostate cancer is one of the most common malignant neoplasms in men with an overall incidence of approximately 15 per cent during the normal life span. Androgen-deprivation therapy (hormone therapy) is an effective treatment of this disease when progressed to an advanced stage. Despite impressive responses, such treatment when applied on a continuous basis is not curative and eventually culminates in androgen-independent disease. On the other hand, intermittent androgen suppression (IAS) was first conceived as a potential way of delaying progression to androgen-independence, in addition offering the possibility of reducing adverse effects and improving the quality of life. Although the validity of this approach has been confirmed in several clinical studies, the optimal scheduling of the cycles of on- and off-treatment remains to be explored. In the present article, we show that IAS lends itself to mathematical modelling with hybrid dynamical systems and that the model we have developed can be used to select the best strategy for keeping prostate cancer in an androgen-dependent state as long as possible. Our results also suggest that the current way of using IAS exceeds what is necessary for optimal control; in fact, we have found that to achieve optimal control, the amount of therapy (dose and duration of drugs) can be reduced by a factor of one half.     

Gene transfer into muscle by electroporation in vivo

Among the nonviral techniques for gene transfer in vivo, the direct injection of plasmid DNA into muscle is simple, inexpensive, and safe. Applications of this method have been limited by the relatively low expression levels of the transferred gene. We investigated the applicability of in vivo electroporation for gene transfer into muscle, using plasmid DNA expressing interleukin-5 (IL-5) as the vector. The tibialis anterior muscles of mice were injected with the plasmid DNA, and then a pair of electrode needles were inserted into the DNA injection site to deliver electric pulses. Five days later, the serum IL-5 levels were assayed. Mice that did not receive electroporation had serum levels of 0.2 ng/ml. Electroporation enhanced the levels to over 20 ng/ml. Histochemical analysis of muscles injected with a lacZ expression plasmid showed that in vivo electroporation increased both the number of muscle fibers taking up plasmid DNA and the copy number of plasmids introduced into the cells. These results demonstrate that gene transfer into muscle by electroporation in vivo is more efficient than simple intramuscular DNA injection.     

Arrhythmogenic right ventricular cardiomyopathy underlies syndrome of right bundle branch block, ST-segment elevation, and sudden death

In all experimental mammals tested (rats, dogs, primates), intramuscular injections of the oil-soluble antimalarial artemisinin derivatives artemether and arteether have produced an unusual pattern of selective damage to brain stem centers predominantly involved in auditory processing and vestibular reflexes. Artesunate, the most widely used of these compounds, is a water soluble hemisuccinate derivative given parenterally either by intravenous or intramuscular injection. The neurotoxic potential of parenteral artesunate and artemether was compared in a murine model. Adult Swiss albino mice were assigned randomly to 28-day regimens of intramuscular artemether or artesunate in doses ranging from 30 to 100 mg/kg/day. At 30 mg/kg/day, no abnormalities were detected with either drug. At 50 mg/kg/day, abnormalities were observed in six of 12 artemether recipients and two of 12 artesunate recipients. These were reversible in all but one (artemether) mouse. At 100 mg/kg/day, eight of 36 artemether recipients, two of 36 artesunate recipients, and one of 18 control mice died. All but four surviving mice in the artemether group (86%) showed obvious and usually irreversible abnormalities of balance and equilibrium, whereas only four artesunate recipients (11%) exhibited abnormalities, and these were reversible in each case (P < 0.001). At this dose the relative risk (95% confidence interval) for death or disability was 5.3 (2.6-11.2) for artemether recipients. Intramuscular artemether is significantly more neurotoxic than intramuscular artesunate in this murine model.     

Mid-diastolic potential is related to the reentrant circuit in a patient with verapamil-sensitive idiopathic left ventricular tachycardia

We report a case of verapamil-sensitive idiopathic ventricular tachycardia in which a mid-diastolic potential (MDP) 45 msec preceding the Purkinje potential (P potential) was recorded. Pacing during the tachycardia caused concealed entrainment, and the stimulus-QRS interval was equal to the P potential-QRS interval. The interval between the last pacing stimulus and the next P potential (postpacing interval) was longer than the ventricular tachycardia cycle length, but the MDP was orthodromically activated. These findings suggest that the MDP was on the reentrant circuit and the P potential was not on the reentrant circuit, but a bystander.     

Radiofrequency catheter ablation of concealed atrioventricular accessory pathways using a "simultaneous pacing method"

The retrograde atrial potential at a successful ablation site is usually obscured by the wide and large ventricular potential during atrioventricular reentrant tachycardia or ventricular pacing, which makes it difficult to determine the appropriate ablation site for a concealed accessory pathway. A pacing maneuver named the "simultaneous pacing method" is proposed herein to differentiate the retrograde atrial potential from the ventricular potential for a successful ablation of the concealed accessory pathway. Catheter ablation was performed in 12 patients with a single left free-wall concealed accessory pathway. The atrial insertion site was determined by the simultaneous pacing method in six patients (group I) and by ventricular pacing in six patients (group II). In the simultaneous pacing method, electrograms recorded during ventricular pacing in the earliest retrograde atrial activation site are a fusion of the ventricular potential and the following retrograde atrial potential. When atrial and ventricular pacings are performed simultaneously (simultaneous pacing), the end portion of the electrograms recorded at the same site is solely the ventricular component, because atrial is activated earlier. The atrial potential can be confirmed during ventricular pacing in comparison with the electrograms during the "simultaneous pacing." Radiofrequency catheter ablation was successful in eliminating conduction through the accessory pathway in all 12 patients. The radiofrequency applications in group I were significantly fewer than those in group II (1.7 +/- 1.0 in group I, 5.3 +/- 3.2 in group II, P < 0.05). The total procedure time in group I was significantly shorter than in group II (57.8 +/- 15.7 vs 106.7 +/- 41.6 mins in group II, respectively, P < 0.05). The fluoroscopy time in group I was significantly shorter than in group II (54.0 +/- 7.9 vs 81.3 +/- 26.3 mins, respectively, P < 0.05). We were able to determine the atrial insertion site of accessory pathways by the simultaneous pacing method. The simultaneous pacing method was useful in eliminating concealed left free-wall accessory pathways.     

Design effects on the fretting wear behaviour of ball bearings

A change in design of a ball bearing is described based on the results of numerical and experimental analysis to reduce fretting wear. Increasing the radii of curvature of the inner and outer races by a small amount reduces the product of the relative slip δ and the tangential traction τ at the contact region, both of which are caused by Heathcote slip. This results in the consequent reduction in fretting wear because there is a good correlation between the amount of fretting wear and τδ. This prediction is confirmed experimentally by increasing the groove radius of the inner race from 4.02 to 4.21 mm for a ball of radius 3.97 mm.     

Gas Release of SiC Implanted with Deuterium or Helium

Helium (He⁺) or Deuterium (D₂⁺) (20 keV) was implanted into polycrystalline β-SiC with an ion dose of 7.2 × 10²¹ (D or He)/m². The implanted specimens were heated at a heating rate of 10 or 20 K/min from room temperature to 1373 K, and the thermal release spectroscopic data were obtained. A sharp peak appeared at approximately 1270 K in the case of He release, and here the activation energy was estimated to be approximately 4.4 eV. Two overlapped peaks appeared at approximately 900 and 1200 K in the case of D₂ release. The shapes of spectra showed strong dependence on the heating rate.     

Mass Spectrometric Analysis of Sphingomyelin with N-α-Hydroxy Fatty Acyl Residue in Mouse Tissues

Sphingomyelin (SM) with N-α-hydroxy fatty acyl residues (hSM) has been shown to occur in mammalian skin and digestive epithelia. However, the metabolism and physiological relevance of this characteristic SM species have not been fully elucidated yet. Here, we show methods for mass spectrometric characterization and quantification of hSM. The hSM in mouse skin was isolated by TLC. The hydroxy hexadecanoyl residue was confirmed by electron impact ionization-induced fragmentation in gas chromatography–mass spectrometry. Mass shift analysis of acetylated hSM by time of flight mass spectrometry revealed the number of hydroxyl groups in the molecule. After correcting the difference in detection efficacy, hSM in mouse skin and intestinal mucosa were quantified by liquid chromatography–tandem mass spectrometry, and found to be 16.5 ± 2.0 and 0.8 ± 0.4 nmol/μmol phospholipid, respectively. The methods described here are applicable to biological experiments on hSM in epithelia of the body surface and digestive tract.