Hybrid InGaAsP-InP Mach-Zehnder racetrack resonator for thermooptic switching and coupling control

An InGaAsP-InP optical switch geometry based on electrical control of waveguide-resonator coupling is demonstrated. Thermooptic tuning of a Mach-Zehnder interferometer integrated with a racetrack resonator is shown to result in switching with ON-OFF contrast up to 18.5 dB. The optical characteristics of this unique design enable a substantial reduction of the switching power, to a value of 26 mW in comparison with 40 mW for a conventional Mach-Zehnder interferometer switch. Modulation response measurements reveal a 3 dB bandwidth of 400 kHz and a rise time of 1.8 µs, comparing favorably with current state-of-the-art thermooptic switches

Scanning Electron Microscopy of Vascular Smooth Muscle Cells from Rat Muscular Arteries

The use of scanning electron microscopy (SEM) for the examination of medial smooth muscle cells (SMC) is limited by the presence of connective tissue mass in the adventitia obscuring the detailed structure of the SMC. This study deals with the description of a method which selectively removes the connective tissue, allowing three dimensional observation of SMC using SEM. A number of methods were tried. One method involving post fixation with 2% Os04 used in conjunction with HCl proved most successful in removing the extracellular matrix of large mesenteric arteries from spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto normotensive rats (WKY). In both SHR and WKY, the spindle-shaped cells are circumferentially oriented, and ran parallel to one another and formed a continuous compact medial layer with a number of intercellular junctions being evident. Surface morphology of SMC changed between relaxed and contracted states. Relaxed SMC had a smooth regular surface with very fine longitudinal grooves or striations running parallel to the cell long axis. Contracted SMC possessed regular transverse folds on its surface giving a corrugated appearance. The nerve network possessed a fishnet appearance with many triangular bulges at nerve branch points. The internal elastic laminae showed longitudinal furrows and fenestrations, the number of which varied from vessel to vessel. In the superior mesenteric artery, the SMC were circular and helically arranged. Longitudinally and diagonally arranged SMC were evident at bifurcations. Mesenteric veins consisted of one layer of flattened circular SMC that ran parallel to one another and formed a compact and complete medial layer

Scanning Electron Microscopy of Vascular Smooth Muscle Cells from Spontaneously Hypertensive Rats

The fine structure of vascular smooth muscle cells from large mesenteric arteries of adult (28 weeks) spontaneously hypertensive rats and Wistar-Kyoto rats was studied using scanning electron microscopy (SEM). The effect of the digestion method for SEM on tissue size and smooth muscle cell size was also studied using morphometric analysis. A significant reduction in cell size (42-43%) was present after critical point drying, based on the reduction in volume to surface ratio of smooth muscle cells. However, percent change of volume density and volume to surface ratio of smooth muscle cells after digestion and after critical point drying, was similar between the hypertensives and normotensives. Most of the tissue shrinkage occurred during the digestion process to remove the connective tissue. Overall tissue shrinkage due to the digestion method involving OsO4/HCl and subsequent processing for SEM, based on changes in the thickness of the medial wall, was similar between arteries from hypertensive (34.7%) and normotensive (31.4%). After compensating for the shrinkage, vascular smooth muscle cells from hypertensive animals were found to have a wider soma! region (5.94 μm) than those from the normotensives (5.46 μm), suggesting cellular hypertrophy. We conclude that a significant reduction in size of tissue and smooth muscle cells took place when arteries were processed for SEM. For comparative study of vascular changes in hypertension involving SEM, cellular shrinkage due to processing should be included in the calculations in order to provide a reasonable estimate of the alterations

現代化中家庭結構和功能的改變 : 對北京、香港和雲南家庭的研究 = Are impacts of modernization on family in structure and function universal? A study among Beijing, Hong Kong and Yunnan families

框架 --背景介绍 --“现代化”的定义 --现代化对家庭的影响 --结论和讨论 Contents --Background --Definition of Modernization --Modernization and Its Impacts on Family --Conclusion and Discussio

Service-learning model at Lingnan University : development strategies and outcome assessment

Background: The Service-Learning and Research Scheme (SLRS) is the showcase of Lingnan’s Service-Learning model, which is the manifestation of Lingnan University’s Liberal Arts education and mission “Education for Service”. The scheme was a pilot project, from 2004 to 2005, which led to the development of a Universitywide protocol for Service-Learning at Lingnan University. Aims: This paper highlights the processes and the strategies of incorporating Service-Learning into courses, based on the experiences in Lingnan University. Implementation and evaluation models are suggested to provide a framework for other interested parties to apply Service-Learning in their learning and teaching. Results: This is a descriptive analysis, associating outcome measurement (three outcomes: “ABC” quality– Adaptability, Brainpower and Creativity) through the process of Service-Learning. Evaluation contents and guidelines for doing Service-Learning are developed based on the past experience in doing Service-Learning at Lingnan. The research element procedures offer instructors with guidance as well as a well-defined protocol and evaluation for Service-Learning programs in Lingnan. Conclusion: In consolidating the above experience and in detailing the validity of the Lingnan Model of Service-Learning, a manual is produced documenting our efforts. This is the first manual which can be the protocol of applying Service-Learning in higher education for students’ whole-person development

Quantification of the Impact of Photon Distinguishability on Measurement-Device- Independent Quantum Key Distribution

Measurement-Device-Independent Quantum Key Distribution (MDI-QKD) is a two-photon protocol devised to eliminate eavesdropping attacks that interrogate or control the detector in realized quantum key distribution systems. In MDI-QKD, the measurements are carried out by an untrusted third party, and the measurement results are announced openly. Knowledge or control of the measurement results gives the third party no information about the secret key. Error-free implementation of the MDI-QKD protocol requires the crypto-communicating parties, Alice and Bob, to independently prepare and transmit single photons that are physically indistinguishable, with the possible exception of their polarization states. In this paper, we apply the formalism of quantum optics and Monte Carlo simulations to quantify the impact of small errors in wavelength, bandwidth, polarization and timing between Alice’s photons and Bob’s photons on the MDI-QKD quantum bit error rate (QBER). Using published single-photon source characteristics from two-photon interference experiments as a test case, our simulations predict that the finite tolerances of these sources contribute (4.04±20/√Nsifted )% to the QBER in an MDI-QKD implementation generating an Nsifted-bit sifted key

Observational Evidence of EHP Effects on the Melting of Snowpack over the Tibetan Plateau

Observational evidences are presented showing that the Indo-Gangetic Plain (IGP) regions, bounded by the high altitude Himalayan mountains, are subject to heavy loading of absorbing aerosols, i.e., black carbon and dust, which can lead to widespread enhancement warming over the Tibetan Plateau and accelerated snowmelt in the western Tibetan Plateau (WTP) and Himalayas. The two pre-monsoon seasons of 2004 and 2005 were strikingly contrasting in terms of the aerosol loading over IGP. The warming of the TP in 2004 relative to 2005 was widespread, covering most of the WTP and Himalayas. This warming is closely linked to patterns of the snow melt. Consistent with the Elevated Heat Pump hypothesis, we find that increased loading of absorbing aerosols over IGP in the pre-monsoon season is associated with increased heating of the upper troposphere by dynamical feedback induced by aerosol heating, and enhances the rate of snowmelt over Himalayas and the WTP in April-May. Composite analysis with more contrasting years also shows that the heating of the troposphere by elevated dust and black carbon aerosols in the boreal spring can lead to widespread enhanced land-atmosphere warming, and accelerated snow melt in the Himalayas and Tibetan Plateau

Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf

We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosphere reddened by normal extinction. Instead, the slope is consistent with scattered light, indicating that circumstellar material is occulting the brown dwarf. By combining the SpeX data with mid-IR photometry and spectroscopy from the Spitzer Space Telescope and previously published millimeter data from Scholz and coworkers, we construct the spectral energy distribution for 2MASS J04381486+2611399 and model it in terms of a young brown dwarf surrounded by an irradiated accretion disk. The presence of both silicate absorption at 10 um and silicate emission at 11 um constrains the inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional evidence of the high inclination of this disk is provided by our detection of asymmetric bipolar extended emission surrounding 2MASS J04381486+2611399 in high-resolution optical images obtained with the Hubble Space Telescope. According to our modeling for the SED and images of this system, the disk contains a large inner hole that is indicative of a transition disk (R_in~58 R_star~0.275 AU) and is somewhat larger than expected from embryo ejection models (R_out=20-40 AU vs. R_out<10-20 AU).Comment: The Astrophysical Journal, in pres