Highly pi-conjugated perylenediimide (PDI) oligomers are promising low band gap organic materials for various applications in optoelectronics. In this work, individual fluorescence dynamics of ethynylene- and butadiynylene-bridged dimeric and trimeric PDIs (PEP, PBP, and PEPEP) were monitored and analyzed by single-molecule fluorescence spectroscopy to gain information on the degree of extension of pi-conjugation through the acetylene bridge in PDI multichromophores. The simultaneous measurements of fluorescence intensity, lifetime, and spectrum indicate a sequential decrease in pi-conjugation upon photobleaching of PDI monomer units. Furthermore, Huang-Rhys (HR) factors, S, are obtained to evaluate the degree of electronic coupling in view of pi-conjugation and overall rigidity between the PDI units in PDI oligomers at the single-molecule level. In addition, butadiynylene-bridged dimeric PDI (PBP) reveals conformational heterogeneity due to the long butadiynylene linker. These results suggest a new way to control the photophysical properties of the PDI multichromophoric system by expansion of pi-conjugation and modification with different linker groups.[GRAPHICS]
A self-terminating gate recess wet etching technique with thermal oxidation of the AlGaN/GaN layer followed by etching in potassium hydroxide (KOH) solution was recently proposed by the present authors for normally-off AlGaN/GaN metal-oxide semiconductor field effect transistors (MOSFETs). In this present reported work, the oxidation process inside the AlGaN/GaN heterostructure involved in this technique was analysed using several material characterisation methods. The measurement results show that the concentration and depth of the O element distribution increase with increased thermal oxidation temperature. It is worth noting that after 650 degrees C oxidation almost no O element could be found in the GaN layer and the O element mainly locates in the AlGaN layer with an obvious correlation between the distribution of Al and O elements, where the Al(Ga)-oxide was detected by X-ray photoelectron spectroscopy, which could be etched by 70 degrees C KOH. Thus, self-terminating wet etching on the AlGaN/GaN material is achieved.
In this letter, we investigated the behaviors of surface-and buffer-induced current collapse in AlGaN/GaN high-electron mobility transistors (HEMTs) using a soft-switched pulsed I-V measurement with different quiescent bias points. It is found that the surface-and buffer-related current collapse have different relationship with the gate and drain biases (V-GS0, V-DS0) during quiescent bias stress. The surface-induced current collapse in devices without passivation monotonically increases with the negative V-GS0, suggesting that an electron injection to the surface from gate leakage is the dominant mechanism and the Si3N4 passivation could effectively eliminate such current collapse. The buffer-induced current collapse in devices with intentionally carbon-doped buffer layer exhibits a different relationship with V-GS0 after surface passivation. The buffer-related current collapse shows a bell-shaped behavior with V-GS0, suggesting that a hot electron trapping in the buffer is the dominant mechanism. The soft-switched pulsed I-V measurement provides an effective method to distinguish between the surface-and buffer-related current collapse in group III-nitride HEMTs.
A three-stage heavy ion acceleration scheme for generation of high-energy quasimonoenergetic heavy ion beams is investigated using two-dimensional particle-in-cell simulation and analytical modeling. The scheme is based on the interaction of an intense linearly polarized laser pulse with a compound two-layer target (a front heavy ion layer + a second light ion layer). We identify that, under appropriate conditions, the heavy ions preaccelerated by a two-stage acceleration process in the front layer can be injected into the light ion shock wave in the second layer for a further third-stage acceleration. These injected heavy ions are not influenced by the screening effect from the light ions, and an isolated high-energy heavy ion beam with relatively low-energy spread is thus formed. Two-dimensional particle-in-cell simulations show that approximately 100MeV/u quasimonoenergetic Fe24+ beams can be obtained by linearly polarized laser pulses at intensities of 1.1x1021W/cm2.
It has been claimed for more than a century that atmospheric new particle formation is primarily influenced by the presence of sulfuric acid. However, the activation process of sulfuric acid related clusters into detectable particles is still an unresolved topic. In this study we focus on the PARADE campaign measurements conducted during August/September 2011 at Mt Kleiner Feldberg in central Germany. During this campaign a set of radicals, organic and inorganic compounds and oxidants and aerosol properties were measured or calculated. We compared a range of organic and inorganic nucleation theories, evaluating their ability to simulate measured particle formation rates at 3 nm in diameter (J(3)) for a variety of different conditions. Nucleation mechanisms involving only sulfuric acid tentatively captured the observed noon-time daily maximum in J(3), but displayed an increasing difference to J(3) measurements during the rest of the diurnal cycle. Including large organic radicals, i.e. organic peroxy radicals (RO2) deriving from monoterpenes and their oxidation products, in the nucleation mechanism improved the correlation between observed and simulated J(3). This supports a recently proposed empirical relationship for new particle formation that has been used in global models. However, the best match between theory and measurements for the site of interest was found for an activation process based on large organic peroxy radicals and stabilised Criegee intermediates (sCI). This novel laboratory-derived algorithm simulated the daily pattern and intensity of J(3) observed in the ambient data. In this algorithm organic derived radicals are involved in activation and growth and link the formation rate of smallest aerosol particles with OH during daytime and NO3 during night-time. Because the RO2 lifetime is controlled by HO2 and NO we conclude that peroxy radicals and NO seem to play an important role for ambient radical chemistry not only with respect to oxidation capacity but also for the activation process of new particle formation. This is supposed to have significant impact of atmospheric radical species on aerosol chemistry and should be taken into account when studying the impact of new particles in climate feedback cycles.
BACKGROUND: Numerous genetic risk factors of ischemic stroke (IS) have been reported from both candidate gene and genome-wide strategies with inconsistent results. The objective of this study was to confirm the relationship between 10 previously identified single-nucleotide polymorphisms (SNPs) and IS in the Chinese population. METHODS: A family-based study was conducted in a rural area of Beijing, with a total of 227 IS families with 622 participants recruited. Both linkage and association analyses were performed, with all the sibling pairs derived from the 227 families analyzed using the sib-pair test of model-free linkage to assess linkage between SNPs and IS, with association analyses including a family-based association test (FBAT) and generalized estimating equations (GEE). RESULTS: Nonparametric linkage analysis revealed that the rs1800796 polymorphism in the interleukin-6 (IL-6) gene is significantly linked to the small arterial occlusion (SAO) subtype (p=0.022), while the rs7193343 polymorphism in the ZFHX3 gene is linked to IS (p=0.002) under the dominant model. Significant allelic associations were identified between the G allele of rs1800796 and IS (p=0.042) and the SAO subtype (p=0.025) in the FBAT. The GEE method revealed that the G allele of rs1800796 increased IS risk by 1.55-fold (95% 95% confidence interval [CI]: 1.01, 2.37; p=0.043) and 2.43-fold (95% CI: 1.32, 4.45; p=0.004) in the SAO subtype in the dominant model, which correlated with the significant associations detected in the FBAT. CONCLUSIONS: In this study, we confirmed that the SNP of rs1800796 in the IL-6 gene is related to IS and the SAO subtype using different statistical approaches. These findings could contribute to identifying individuals with a high IS risk.
This paper studies how displaced royal families in the Roman principate speak about their royal ancestry. Gaius Julius Antiochus Epiphanes "Philopappos" and his sister Julia Balbilla, who were descendents of the Orontid dynasty of Commagene in northwestern Syria, are objects of this study. The kingdom of Commagene was twice incorporated into the Roman province of Syria, first upon the death of Antiochos III Epiphanes in 17 CE, then during Vespasian's reign in 72 CE. Philopappos and Balbilla were displaced and eventually integrated into the circle of the Roman senatorial élite. The two siblings are examples of displaced royal families "at work," creating their extraordinary status within the Roman principate through monumental and literary works that claim inheritance to their ancestral past.
This paper will first review relevant scholarship – such as David Braund on client kingship (1984), Joel Allen on hostage and hostage taking in the principate (2006), Paul Burton on Roman foreign relations in the Republic (2011) – to clarify the operating terms of amicitia, fides, and foedus that formed the socio-political context within which Philopappos and Balbilla operated. The second part of the paper will discuss how the visual and inscriptional programme of Philopappos' monument at Athens and Babilla's graffitti poetry on the statue of Memnon in Egyptian Thebes negotiate socio-political contexts. This paper argues thatPhilopappos' monument did not only speak to his extraordinary status as humbled royalty under Rome, but also his belonging to Athens, and how Commagenian royalty and Roman citizenship attributed to his sense of belonging. Similarly, Balbilla was a valued member of Hadrian and Sabina's court specifically because of her conscious pronouncement of her family's royal blood and their piety, which qualities were pronounced in her graffiti poetry. Together, Philopappos and Balbilla marks a change in the nature of client kingship from Trajan onwards, as royal members become valued not for their ability to govern kingdoms, but for their extraordinary status as royal Roman citizens.