Thermal analysis comparison between two random glass fibre reinforced thermoplastic matrix composites bonded by adhesives using microwaves: preliminary results

[Abstract]: This paper compares the thermal analysis of two types of random glass fibre reinforced thermoplastic matrix composites joined by adhesives using microwave energy. Fixed frequency, 2.45 GHz, microwave facility is used to join thirty three percent by weight random glass fibre reinforced polystyrene composite [PS/GF (33%)] and thirty three percent by weight random glass fibre reinforced low density polyethylene composite [LDPE/GF (33%)]. The facility used is shown in Figure 1. With a given power level, the composites were exposed to various exposure times to microwave irradiation. The primer or coupling agent used was 5-minute two-part adhesive. The heat distribution of the samples of the two types of composites was analysed and compared. The relationship between the heat distribution and the lap shear strength of the samples was also compared and discussed

Pulsed THz radiation due to phonon-polariton effect in [110] ZnTe crystal

Pulsed terahertz (THz) radiation, generated through optical rectification (OR) by exciting [110] ZnTe crystal with ultrafast optical pulses, typically consists of only a few cycles of electromagnetic field oscillations with a duration about a couple of picoseconds. However, it is possible, under appropriate conditions, to generate a long damped oscillation tail (LDOT) following the main cycles. The LDOT can last tens of picoseconds and its Fourier transform shows a higher and narrower frequency peak than that of the main pulse. We have demonstrated that the generation of the LDOT depends on both the duration of the optical pulse and its central wavelength. Furthermore, we have also performed theoretical calculations based upon the OR effect coupled with the phonon-polariton mode of ZnTe and obtained theoretical THz waveforms in good agreement with our experimental observation.Comment: 9 pages, 5 figure

Temperature dependent d-d excitations in manganites probed by resonant inelastic x-ray scattering

We report the observation of temperature dependent electronic excitations in various manganites utilizing resonant inelastic x-ray scattering (RIXS) at the Mn K-edge. Excitations were observed between 1.5 and 16 eV with temperature dependence found as high as 10 eV. The change in spectral weight between 1.5 and 5 eV was found to be related to the magnetic order and independent of the conductivity. On the basis of LDA+U and Wannier function calculations, this dependence is associated with intersite d-d excitations. Finally, the connection between the RIXS cross-section and the loss function is addressed.Comment: 5 pages, 5 figure

The Associations between Near Visual Activity and Incident Myopia in Children: A Nationwide 4-Year Follow-up Study

OBJECTIVE: This nationwide population-based study aimed to examine the prospective association between near visual activities and incident myopia in Taiwanese children 7 to 12 years old over a 4-year follow-up period. DESIGN: Prospective cohort design. PARTICIPANTS: There were 1958 children aged 7 to 12 years from the Taiwan 2009 National Health Interview Survey who were linked to the 2009 through 2013 claims data from the National Health Insurance system. METHODS: Multivariable Cox proportional hazard models were used to estimate the associations between 3 types of near visual activities in sedentary posture, namely reading (< 0.5, 0.5-0.9, ≥1.0 hours per day [h/d]), use of computer, Internet, and games (<0.5, 0.5-0.9, ≥1.0 h/d), and "cram school" attendance (<0.5, 0.5-1.9, ≥2.0 h/d), and incident myopia. MAIN OUTCOME MEASURES: Prevalent myopia was defined as those who had ≥2 ambulatory care claims (International Classification of Diseases code 367.1) in 2008-2009. Incident myopia was defined by those who had at least 2 ambulatory care claims (International Classification of Diseases code 367.1) during the 4-year follow-up period (2010-2013) after excluding prevalent cases. RESULTS: Overall, 26.8% of children had myopia at baseline, and 27.7% of those without myopia at baseline developed incident myopia between 2010 and 2013. On average, they spent 0.68±0.86 h/d on computer/Internet use, 0.63±0.67 h/d on reading, and 2.78±3.53 h/d on cram school. The results showed that children attending cram schools ≥2 h/d (hazard ratio, 1.31; 95% confidence interval, 1.03-1.68) had a higher risk of incident myopia. The effects of these activities remained similar in sensitivity analyses. CONCLUSIONS: Cram school attendance for ≥2 h/d may increase the risk of children's incident myopia. This effect may be due to increased near visual activity or reduced time outdoors

Experimental observation of the crystallization of a paired holon state

A new excitation is observed at 201 meV in the doped-hole ladder cuprate Sr$_{14}$Cu$_{24}$O$_{41}$, using ultraviolet resonance Raman scattering with incident light at 3.7 eV polarized along the direction of the rungs. The excitation is found to be of charge nature, with a temperature independent excitation energy, and can be understood via an intra-ladder pair-breaking process. The intensity tracks closely the order parameter of the charge density wave in the ladder (CDW$_L$), but persists above the CDW$_L$ transition temperature ($T_{CDW_L}$), indicating a strong local pairing above $T_{CDW_L}$. The 201 meV excitation vanishes in La$_{6}$Ca$_{8}$Cu$_{24}$O$_{41+\delta}$, and La$_{5}$Ca$_{9}$Cu$_{24}$O$_{41}$ which are samples with no holes in the ladders. Our results suggest that the doped holes in the ladder are composite bosons consisting of paired holons that order below $T_{CDW}$.Comment: Accepted for publication in Physical Review Letters (4 figures

Decoherence of a Josephson qubit due to coupling to two level systems

Noise and decoherence are major obstacles to the implementation of Josephson junction qubits in quantum computing. Recent experiments suggest that two level systems (TLS) in the oxide tunnel barrier are a source of decoherence. We explore two decoherence mechanisms in which these two level systems lead to the decay of Rabi oscillations that result when Josephson junction qubits are subjected to strong microwave driving. (A) We consider a Josephson qubit coupled resonantly to a two level system, i.e., the qubit and TLS have equal energy splittings. As a result of this resonant interaction, the occupation probability of the excited state of the qubit exhibits beating. Decoherence of the qubit results when the two level system decays from its excited state by emitting a phonon. (B) Fluctuations of the two level systems in the oxide barrier produce fluctuations and 1/f noise in the Josephson junction critical current I_o. This in turn leads to fluctuations in the qubit energy splitting that degrades the qubit coherence. We compare our results with experiments on Josephson junction phase qubits.Comment: 23 pages, Latex, 6 encapsulated postscript figure

Can physical activity eliminate the mortality risk associated with poor sleep? A 15-year follow-up of 341,248 MJ Cohort participant

Background: This study examined the joint associations of sleep patterns and physical activity (PA) with all-cause, cardiovascular disease (CVD), and cancer mortality. Methods: A total of 341,248 adults (mean age = 39.7 years; men: 48.3%) were included in the study, with a 15-year follow-up. Participants reported sleep duration and disturbances (difficulty falling asleep, easily awakened, or use of sleeping medication). PA was classified into 4 levels: <7.5, 7.5–14.9, 15–29.9, and ≥30 metabolic equivalent hours per week (MET-h/week). To understand the joint associations of sleep patterns and PA with mortality, Cox proportional hazard models were conducted, with exposure variables combining sleep duration/disturbances and PA. Results: Compared with the reference group (sleeping 6–8 h/day), individuals who slept >8 h/day had higher risk for all-cause mortality (hazard ratios (HR) = 1.31, 95% confidence interval (95%CI): 1.25–1.37), CVD mortality (HR = 1.30, 95%CI: 1.17–1.45), and cancer mortality (HR = 1.13, 95%CI: 1.04–1.22). Short sleep duration was not associated with mortality risk. Increased risk of all-cause and CVD mortality was found in participants who had difficulty falling asleep (HR = 1.12, 95%CI: 1.07–1.18; HR = 1.16, 95%CI: 1.04–1.30, respectively), and used sleeping medication (HR = 1.26, 95%CI: 1.16–1.37; HR = 1.34, 95%CI: 1.10–1.62, respectively) compared with those who slept well. Long sleep duration and sleep disturbances were not associated with risk of all-cause and CVD mortality among individuals achieving a PA level of ≥15 MET-h/week, and in particular among those achieving ≥30 MET-h/week. Conclusions: Long sleep duration, difficulty falling asleep, and use of sleeping medication were related to a higher risk of death. Being physically active at a moderate intensity for 25–65 min/day eliminated these detrimental associations