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In this paper, we investigated the impact of the linewidth of a QCW pulsed sodium laser on the brightness performance of a generating sodium laser guide star by using the numerical simulation tool PRS. We compared the field test results with the simulation results for two TIPC’s 30W class sodium guide star lasers and found the results are in good agreement which proves the tool can be used for prediction. Then, we used the tool to study the influence of D2b repumping and different linewidths from 10MHz to 1GHz on the coupling efficiency and the photon return flux. For the TIPC’s QCW pulsed solid-state laser, when the on-sky power density is 1 W/m2, the coupling efficiency is 79.6 (photons/s/W/(atoms/m2)) without D2b repumping, however, the value is up to 213.3 (photons/s/W/(atoms/m2)) with 15% D2b enabled and is increased by 168% than the value without D2b; when the power density reaches 10 W/m2, the coupling efficiencies without D2b and with 15% D2b are 66.6 and 233.6 (photons/s/W/(atoms/m2)), respectively. The results show that for the QCW pulsed laser, D2b repumping is necessary. With D2b enabled, if the spectral linewidth is too wide or too narrow, the photon return flux will be adversely affected. The return flux of 60MHz is 52.5% higher than that of 1GHz, while the return flux of 300MHz is 37.8% higher than that of 10 MHz when the laser power is 100W.

In the past few years, Chinese astronomical community is actively testing astronomical sites for several new optical/infrared ground-based telescopes. These site testing campaigns conducted were mainly focused on fundamental performances of the site, such as cloud coverage, seeing, temperature, etc. With increasing interests in sodium laser guide star adaptive optics for these new telescopes in the Chinese astronomical community, it is interesting to investigate the performance of the laser guide star at these sites, especially considering that the sodium laser guide star's on-sky performance is significantly influenced by sites' local performances, such as geomagnetic field, sodium layer dynamics, density of air molecule, etc. In this paper, we studied sodium laser guide star's performance of a 20W class Quasi-CW pulsed laser developed by TIPC with numerical simulation for five selected sites in China.

As one crucial component for the latest generation of adaptive optics, tremendous efforts have been put into the development of high performance 20 W class sodium laser guide star laser system. Two such systems, the continuous wave laser by Toptica, and the quasi-continuous pulse laser by TIPC were extensively studied with simulation and field tests. A new type of 20 W class sodium laser, macro–micro pulse laser, is currently being developed by CIOMP. In this paper, we will study its on-sky performance with simulation based on Monte Carlo rate equation method. The predicted coupling efficiency for this laser in the zenith direction in Changchun is 179.73 photons s−1 W−1/(atoms m−2). The variation of coupling efficiency of this type of laser with pointing direction and the effect of D2b repumping are also studied and reported in this paper.

Vertical profile of turbulence strength ( C n 2 ) is one of the most important attributes for evaluating a site’s astronomical performances. Although seeing is commonly used for describing turbulence strength, it can only represent the integral of all layers of the turbulence above the observer. Other techniques which can be applied to produce C n 2 , such as DIMM-MASS, SCIDAR, etc., all rely on rather complex systems to do the measurements. In this paper, we present an idea to evaluate the relative strength of turbulence with entropies of short exposure images taken at different conjugated heights of the turbulence. Initial experimental results are also presented in the paper.

Based on previous site testing and satellite cloud data, Ali, Daocheng and Muztagh-ata have been selected as candidate sites for the Large Optical/Infrared Telescope (LOT) in China. We present the data collection, processing, management and quality analysis for our site testing based on using similar hardware. We analyze meteorological data, seeing, background light, cloud and precipitable water vapor data from 2017 March 10 to 2019 March 10. We also investigated the relative usefulness of our all-sky camera data in comparison to that from the meteorological TERRA satellite data based on a night-by-night comparison of the correlation and consistency between them.We find a 6% discrepancy arising from a wide range of factors.

The Large Optical/infrared Telescope (LOT) is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade. Based on satellite remote sensing data, along with geographical, logistical and political considerations, three candidate sites were chosen for ground-based astronomical performance monitoring. These sites include: Ali in Tibet, Daocheng in Sichuan and Muztagh-ata in Xinjiang. Up until now, all three sites have continuously collected data for two years. In this paper, we will introduce this site testing campaign, and present its monitoring results obtained during the period between March 2017 and March 2019.

A large ground-based optical/infrared telescope is being planned for a world-class astronomical site in China. The cloud-free night percentage is the primary meteorological consideration for evaluating candidate sites. The data from GMS and NOAA satellites and the MODIS instrument were utilized in this research, covering the period from 1996 to 2015. Our data analysis benefits from overlapping results from different independent teams as well as a uniform analysis of selected sites using GMS+NOAA data. Although significant ground-based monitoring is needed to validate these findings, we identify three different geographical regions with a high percentage of cloud-free conditions (∼83% on average), which is slightly lower than at Mauna Kea and Cerro Armazones (∼85% on average) and were chosen for the large international projects TMT and ELT respectively. Our study finds evidence that cloud distributions and the seasonal changes affected by the prevailing westerly winds and summer monsoons reduce the cloud cover in areas influenced by the westerlies. This is consistent with the expectations from climate change models and is suggestive that most of the identified sites will have reduced cloud cover in the future.

The location of an astronomical observatory is a key factor that affects its scientific productivity. The best astronomical sites are generally those found at high altitudes. Several such sites in western China and the Tibetan plateau are presently under development for astronomy. One of these is Ali, which, at over 5000 m, is one of the highest astronomical sites in the world. In order to further investigate the astronomical potential of Ali, we have installed a lunar scintillometer, for the primary purpose of profiling atmospheric turbulence. This paper describes the instrument and technique, and reports results from the first year of observations. We find that ground layer (GL) turbulence at Ali is remarkably weak and relatively thin. The median seeing, from turbulence in the range 11–500 m above ground, is 0.34 arcsec, with seeing better than 0.26 arcsec occurring 25 per cent of the time. Under median conditions, half of the GL turbulence lies below a height of 62 m. These initial results, and the high altitude and relatively low temperatures, suggest that Ali could prove to be an outstanding site for ground-based astronomy.

A large telescope's adaptive optics (AO) system requires one or more bright artificial laser guide stars to improve its sky coverage. The recent advent of a high power sodium laser is perfect for such application. However, besides the output power, other parameters of the laser also have a significant impact on the brightness of the generated sodium laser guide star, mostly in non-linear relationships. When tuning and optimizing these parameters it is necessary to tune based on a laser guide star generation performance metric. Although return photon fluxis widely used, variability of the atmosphere and sodium layer makes it difficult to compare results from different sites or even within a short time period for the same site. A new metric, coupling efficiency, is adopted in our field tests. In this paper, we will introduce our method for measuring the coupling efficiency of a 20W class pulse sodium laser for AO application during field tests that were conducted during 2013–2015.

We present results on the compact steep-spectrum quasar 3C 48 from observations with the VLBA, MERLIN and EVN at multiple radio frequencies. In the 1.5-GHz VLBI images, the radio jet is characterized by a series of bright knots. The active nucleus is embedded in the southernmost VLBI component A, which is further resolved into two sub-components A1 and A2 at 4.8 and 8.3 GHz. A1 shows a flat spectrum and A2 shows a steep spectrum. The most strongly polarized VLBI components are located at component C $\sim$0.25 arcsec north of the core. The polarization angles at C show gradual changes across the jet width at all observed frequencies, indicative of a gradient in the emission-weighted intrinsic polarization angle across the jet and possibly a systematic gradient in the rotation measure; moreover, the percentage of polarization increases near the curvature at C, likely consistent with the presence of a local jet-ISM interaction and/or changing magnetic-field directions. The hot spot B shows a higher rotation measure, and has no detected proper motion. These facts provide some evidence for a stationary shock in the vicinity of B. Comparison of the present VLBI observations with those made 8.43 years ago suggests a proper motion of $\beta_{app}=3.7\pm0.4 c$ for A2 to the north. The apparent superluminal motion suggests that the relativistic jet plasma moves at a velocity of $\gtrsim0.96 c$ if the jet is viewed at an inclination angle less than $20\degr$. A simple precessing jet model and a hydrodynamical isothermal jet model with helical-mode Kelvin-Helmholtz instabilities are used to fit the oscillatory jet trajectory of 3C 48 defined by the bright knots.

To explore the clinical application value of Provider-Initiated HIV Testing and Counseling (PITC) by analyzing the positive rate of HIV tests for people in need of PITC and that of routine HIV tests.We retrospectively analyzed the demographic and epidemiologic data about the patients seeking PITC services or undergoing routine HIV tests in Nanjing Drum Tower Hospital between January and December 2013.The positive rate of initial HIV screening was 1.98% in the PITC group and 0.24% in the routine test group, while that of confirmed HIV was 0. 40% in the former and 0.07% in the latter, both with statistically significant differences between the two groups (P0.01). The positive rate of HIV was markedly higher in males than in females, particularly in the PITC group.PITC has a high clinical value in HIV detection for targeted subjects and therefore deserves general application in dermatology.

Sodium laser guide star is an ideal source for astronomical adaptive optics system correcting wave-front aberration caused by atmospheric turbulence. However, the cost and difficulties to manufacture a compact high quality sodium laser with power higher than 20W is not a guarantee that the laser will provide a bright enough laser guide star due to the physics of sodium atom in the atmosphere. It would be helpful if a prediction tool could provide the estimation of photon generating performance for arbitrary laser output formats, before an actual laser were designed. Based on rate equation, we developed a Monte Carlo simulation software that could be used to predict sodium laser guide star generating performance for arbitrary laser formats. In this paper, we will describe the model of our simulation, its implementation and present comparison results with field test data.

To observe the distribution character of angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in Chinese population and its relationship with essential hypertension.Polymerase chain reaction (PCR) technique was used to detect the angiotensin converting enzyme gene I/D polymorphism in 2966 subjects of Kailuan Coal Mine, and further restriction analysis was performed.The frequencies of ACE II, ID, DD genotypes in total study population were 41.5%, 38.4%, 20.1%, respectively. The DD genotypes in hypertensive group and that in control group were 18.9% and 21.0%, respectively. There was no significant difference between hypertensive group and control group (P0.05). The same result was seen after stratification by age and gender in each group, respectively(P0.05). The DD genotype and D allele showed a tendency to decrease with the increase of age (P0.001).The above results suggested that essential hypertension was not associated with ACE I/D polymorphism. The distributions of ACE genotype and allele varied with age, and the subjects with the character of DD genotype were at higher risk of early death.