SYNOPSISTwo switching phenomena of poly(viny1idene fluoride) (PVDF) containing carbon black (CB) with different crystallization histories are studied. Both the percolation threshold (apt) and the critical concentration of the positive temperature coefficient (PTC) materials (@c) increase as the crystallization temperature declines. PTC and the negative temperature coefficient (NTC) effect become obvious when the cooling speed is reduced. The morphologies of PVDF crystals play a n important role in modifying the shape of the resistivitytemperature ( p -T ) curves. The PTC and NTC intensities of these systems, whose CB contents lie between @pc and @c, increase with increasing crystallinity, which are realized by altering the crystallization histories of the matrices. 0 1996 John Wiley & Sons, Inc. I NTRO DU CTI 0 NThere are two switching phenomena in crystalline polymers filled with conductive particles. The first one is called the percolation transition. The conductivity of the composite increases slowly as the content of the filler increases, and then there is a sudden increase of some 10 orders of magnitude or even more in the conductivity when the filler content reaches a certain level (percolation threshold [@pc]), after which the conductivity increases slightly and monotonically as the filler is added further.The first switching phenomenon is regarded as a geometric phase transition.'-6 Experimental'*6 as well as theoreticaP6 studies of the percolation phenomenon have been reported.The second switching phenomenon is also called the positive temperature coefficient (PTC) effect, i.e., the resistivity of the composite increases remarkably as the elevated temperature reaches the vicinity of the melting point of the polymer matrix, and is then followed by the negative temperature coefficient (NTC) effect by which the resistivity declines quickly beyond the critical temperature ( Tc), which is determined by the melting point of the crystalline p~l y m e r .~-l~ It has been found that the maximum PTC intensity appears at the critical carbon black (CB) concentration * To whom correspondence should be addressed.Journal of Applied Polymer Science, Vol. 62, 743-747 (1996) 0 1996 John Wiley & Sons, Inc.CCC 0021-8995/96/050743-05 (named @c), which is slightly larger than the percolation threshold ( that is determined by the conductivity of CB and the polymer specie^.'^^'^ Narkis et al? and Sircar and WellsI7 showed that any CB parameter which increases conductivity (loading, surface area, structure, porosity) decreases @pc, @c, the PTC effect, and the width of PTC intensity-@ curve. In early works, there are many studies on the PTC/NTC effects of PE/CB composite^^^^'-'^ and several theories about PTC/NTC effects on the basis of the ~y s t e m~. '~. '~ have been established. In this article, the effects of the crystallization histories on @pc and @c, p-Tplots, and PTC and NTC intensities are reported. Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) are used to illustrate the effects o...

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Background. Although the level of serum vascular endothelial growth factor (VEGF) is elevated in coronary artery disease (CAD) patients, its potential role in acute coronary syndrome (ACS) or stable angina pectoris (SAP) patients remains unclear. Objectives. To evaluate diagnostic accuracy of serum VEGF in determining ACS patients from SAP and analyze the association of serum VEGF with coronary artery lesions in SAP or the GRACE score in ACS, which is involved in the poor prognosis of low serum VEGF. Methods. 248 CAD patients and 48 healthy subjects were enrolled in this study. Serum VEGF levels were detected by using ELISA. The Gensini score or GRACE score was calculated among SAP or ACS patients. All the patients were followed up for a period of 12 months (mean: 10.77 months). Results. VEGF serum concentrations were higher in the ACS subgroup than in the SAP subgroup (P<0.001) with diagnostic accuracy of ACS from SAP (AUC: 0.667, sensitivity: 68.5%, specificity: 60.1%, P<0.001). Patients with high risk of Gensini score showed reduced VEGF levels (P<0.001) accompanied by a negative correlation (r = −0.396, P<0.001). Patients with a higher GRACE score indicated lower VEGF levels (P<0.001). Low serum VEGF was one of the potential risk factors with adjusted HR of 0.531 (P=0.048). Conclusion. Serum VEGF exhibits efficient diagnostic value for detection of ACS from SAP with a cutoff value of 648.75 pg/mL. Low serum VEGF indicates severe coronary artery lesions and a higher GRACE score, which suggests poor clinical outcomes.

We design, fabricate and analyze plasmon-enhanced LEDs with the tapered Ag structure that significantly increases plasmonic coupling efficiency at a coupling distance far beyond the penetration depth. The electroluminescence intensity showed a 16-fold increase compared with planar LEDs with a coupling distance of 100 nm. The enhanced coupling efficiency with large distance is originated from the accumulated SP energy at the metal conical tip and the missing momentum provided by the corrugated surface. Therefore, the SP-enhanced LED with tapered Ag structure can maintain a high luminous efficiency and a stable working state even with thick p-GaN layer, which also guarantees a high electrical performance. Our study paves the way for a practical implementation of SP-enhanced LEDs with excellent optical and electrical properties.

Background. Non-high-density lipoprotein cholesterol (non-HDL-c) predicts the severity of coronary artery lesions in patients not treated with statin. The association between non-HDL-c and severity of coronary artery lesions in patients treated with lipid-lowering therapy has been unknown. Hypothesis. We hypothesize a novel marker of non-HDL-c/TC predicts the severity of coronary artery lesions and clinical outcomes in 12 months in the patients treated with statin. Method. 473 subjects who met inclusion criteria were eligible for inclusion. Coronary artery angiography (CAG) was performed, and the Gensini score (GS) was calculated in all the subjects divided into three subgroups of low risk, medium risk, and high risk by the tertiles of GS. The non-HDL-c value was calculated as TC minus HDL-c, while non-HDL-c/TC was the ratio of non-HDL-c and TC. Results. The concentration of non-LDL-c differed between non-obstructive-CAD group and obstructive-CAD group (P<0.05), and non-HDL-c/TC was elevated in the obstructive-CAD group (P<0.05). Increased GS was associated with increasing non-HDL-c/TC (P<0.05). Non-HDL-c/TC (OR: 108.50, 95% CI: 1.57–7520.28; P=0.030) remained as an independent predicting factor of high risk under GS stratification. In unadjusted Cox model, high non-HDL-c/TC (RR: 1.976, 95% CI: 1.155–3.382; P=0.013) predicted the occurrence of adverse events. After multivariate adjustment, high non-HDL-c/TC (RR: 1.921, 95% CI: 1.105–3.339; P=0.021) was an independent predictor of poor outcomes. Conclusion. High level of non-HDL-c/TC presented an excellent prognostic value compared with other lipid-related markers in CAD patients treated with statin.