Re-ordering chaotic carbon: origins and application of textured carbon.

Formation of nanocrystals with preferred orientation within the amorphous carbon matrix has attracted lots of theoretical and experimental attentions recently. Interesting properties of this films, easy fabrication methods and practical problems associated with the growth of other carbon nanomaterials such as carbon nanotubes (CNTs) and graphene gives this new class of carbon nanostructure a potential to be considered as a replacement for some applications such as thermal management at nanoscale and interconnects. In this short review paper, the fabrication techniques and associated formation mechanisms of these nanostructured films have been discussed. Besides, electrical and thermal properties of these nanostructured films have been compared with CNTs and graphene.

Factors that influence the choice of seeking treatment at polyclinics.

INTRODUCTION: Patients in Singapore can choose their primary care provider on a per-episode basis and pay out-of-pocket for services rendered. The infrastructure of subsidised and private primary care sector facilities differs. Onsite ancillary services are available in subsidised facilities, allowing for convenience of routine investigations, while private clinics are usually standalone practices. This study sought to examine the factors influencing patients' choice of polyclinic. METHODS: This was a cross-sectional survey of a convenient sample of 484 random patients who sought treatment at a polyclinic located in a new housing estate from 24-27 June 2008. RESULTS: The response rate was 85.4% (n = 409). 38.1% of the patients were male. Mean age was 36.2 years. Only 13.8% had a regular private family physician, while 37.3% were followed up at polyclinics. Patients on regular polyclinic follow-up were more likely to be older (p < 0.001), unemployed, retirees or housewives (p < 0.001) and were seeking treatment for chronic diseases (p < 0.001). Geographical convenience (p = 0.002), low cost of consultation (p = 0.024), and onsite laboratory (p = 0.001) and imaging services (p = 0.018) significantly influenced those on regular polyclinic follow-up to attend the polyclinic. CONCLUSION: Affordability, convenience of travel and onsite laboratory facilities influence patients' choice of seeking treatment at polyclinics. Further research examining whether the overall convenience of onsite ancillary services influences patients' choice of primary care provider would be useful in redesigning private primary care infrastructure to enhance patient convenience and encourage more patients to have a regular private family physician.

Noradrenaline-induced changes in intracellular Ca(2+) and tension in mesenteric arteries from diabetic rats.

1. The purpose of this investigation was to determine whether enhanced contractile responses to noradrenaline (NA) of mesenteric arteries from rats with chronic streptozotocin-induced diabetes are associated with increases in mean cytosolic [Ca(2+)]i. 2. [Ca(2+)]i was measured with fura 2-AM, and was monitored simultaneously with tension in perfused endothelium-denuded mesenteric arterial rings from 12 - 14 week diabetic rats and age- and gender-matched control rats. 3. Basal [Ca(2+)]i (expressed as R(n), the normalized fura 2 ratio) was not significantly different in arteries from control and diabetic rats. Similarly, no differences between control and diabetic arteries in the tension or [Ca(2+)]i responses to 80 mM KCl in the presence of phentolamine were detected. 4. The rate of tension development, peak tension and integrated tension in response to 30 microM NA were all significantly greater in diabetic than control arteries. However, this was not associated with enhancement of the corresponding [Ca(2+)]i responses in the diabetic arteries. 5. Peak contractile responses to perfusion with both 0.3 and 3 microM NA, but peak [Ca(2+)]i only in response to 0.3 microM NA, were significantly greater in diabetic than control arteries. 6. NA (30 microM) produced a greater increase in both peak tension and [Ca(2+)]i in diabetic than control arteries perfused with Ca(2+)-free solution containing 1 mM EGTA. Neither the rate nor the magnitude of NA-induced Ca(2+) influx appeared to be altered in the diabetic arteries. 7. The enhanced sustained contractile response of diabetic arteries to NA appears to be dissociated from increases in [Ca(2+)]i, and may be due to other factors, such as an increase in the Ca(2+) sensitivity of the contractile proteins.

Enhanced contractile responses of arteries from streptozotocin diabetic rats to sodium fluoride.

1. Previous studies from this laboratory have demonstrated that alpha 1-adrenoceptor-mediated increases in tension and phosphoinositide metabolism are enhanced in the aorta and mesenteric arteries from diabetic rats. The purpose of the present investigation was to determine whether contractile responses to sodium fluoride (NaF), which directly stimulates GTP-binding proteins (G-proteins), are also enhanced in diabetic arteries. 2. NaF (1-20 mM) in the presence of 10 microM aluminium chloride produced slowly developing, concentration-dependent contractions in mesenteric arteries from three month streptozotocin-diabetic (60 mg kg-1, i.v.) male Wistar rats and age-matched control rats. The maximum contractile response but not the sensitivity to NaF was significantly greater in mesenteric arteries from diabetic than from control rats, as was the response to noradrenaline (NA). Maximum contractile responses of aorta and caudal artery from diabetic rats to NaF were also significantly enhanced. 3. Removal of the endothelium and denervation with 6-hydroxydopamine did not significantly alter the maximum contractile response of mesenteric arteries from either control or diabetic rats to NaF. Similarly, NaF had no effect on cyclic AMP levels in aorta, and no difference in cyclic AMP levels, either basally or in the presence of NaF, was detected between control and diabetic rat aorta. 4. Contractile responses of mesenteric arteries from both control and diabetic rats to NaF were diminished in calcium-free Krebs solution, but the NaF response remained significantly elevated in mesenteric arteries from diabetic rats compared to control. 5. Ryanodine (30 microM) which depletes intracellular calcium stores, nifedipine (3 microM) which blocks dihydropyridine-sensitive calcium channels and calphostin C (0.5 microM) which selectively inhibits protein kinase C, all significantly inhibited maximum contractile responses of mesenteric arteries from control and diabetic rats to NaF. There were no significant differences between control and diabetic arteries in the relative magnitude of the inhibition produce by the three antagonist. 6. These data suggest that there may be increased activation of the same signalling processes that mediate NA-stimulated vasoconstriction, perhaps contraction-associated G-proteins or the effectors coupled to these G-proteins, in response to NaF in mesenteric arteries from diabetic rats. This may also be responsible for the enhanced contractile responses of these arteries to alpha 1-adrenoceptor stimulation.

Pharmacological investigation of signaling mechanisms contributing to phasic and tonic components of the contractile response of rat arteries to noradrenaline.

The mechanisms contributing to the contractile responses to two different concentrations of noradrenaline (NA) in rat aorta and mesenteric artery were compared using nifedipine, which inhibits calcium influx through dihydropyridine-sensitive channels, ryanodine, which depletes intracellular calcium stores, and calphostin C, which inhibits protein kinase C (PKC). Both submaximal and maximal concentrations of NA induced a biphasic response in aorta and mesenteric artery, with an early fast phase and a later sustained tonic component. Calcium release from intracellular stores contributed to the phasic component of contraction to both concentrations of NA in aorta, although to a greater extent to the submaximal concentration. In aorta, inhibiting both intracellular calcium release and calcium influx through dihydropyridine-sensitive channels simultaneously or inhibiting PKC activity alone significantly reduced the tonic response to a maximal concentration of NA. However, the tonic response to a submaximal concentration of NA in aorta was significantly inhibited only when intracellular calcium stores were depleted with ryanodine. In mesenteric artery, the phasic response to a maximal concentration of NA was significantly depressed only when both calcium influx and intracellular calcium release were inhibited simultaneously. However, the phasic response to a submaximal concentration of NA was significantly inhibited by blocking calcium influx alone, but not by blocking intracellular calcium release alone. The tonic component of the contractile response to both concentrations of NA in mesenteric artery appeared to be mediated in part by calcium from both intracellular and extracellular sources.(ABSTRACT TRUNCATED AT 250 WORDS)