Extending Syncom 3\u27s Orbital Life Over the Pacific

Syncom 3, launched in August 1964, was the first satellite to be maneuvered to a nearstationary orbit. It is presently functioning as an essential communication link between Hawaii and the Far East, As long as the satellite remains within mutual visibility of these areas, this link will continue to exist. Ironically, the by-product of an unwanted process, namely, gas resulting from decomposition of the propellant (hydrogen peroxide) which was originally intended to provide orbital control, is now being used to maintain this link. If the satellite orbit were not controllable, Syncorn 3 would drift out of the mutual visibility longitude band as a result of forces exerted by the earth\u27s triaxiality, The unstable equilibrium longitude in the Pacific, computed to be at 162.4 °E, lies within this band. Near this point, the control velocity requirements are small, so that minimal control capability, such as is available from the gas, could extend Syncom 3\u27s orbital life for as much as 10 years. This is unlikely, however, because of the degraded condition of the batteries which are essential for operation of the control jets. The satellite on its present drift trajectory should remain visible from Hawaii until early 1969. Longitudinal control of Syncom 3 in the vicinity of the Pacific equilibrium longitude has now been accomplished with gas for approximately 1.5 years. The specific impulse observed is approximately 57.1 seconds. The mass flow rates observed have resulted in velocity increments of about 0.005 fps per pulse, Such high resolution is required to maintain the satellite position close to but west of the equilibrium longitude. This constraint is based on the increased, visibility time for westerly drift in case of complete loss or depletion of control capability. Since the batteries are weak and gas leaks are to be expected in a system not originally designed for use of gas, such a constraint is reasonable

Gold in the past, today and future

This paper deals with gold, which is described as a chemical element. Special attention is paid to its physical-chemical properties and, furthermore, where or in what form it can be found in nature. We discuss the role it has played through history and we inform how gold has been developed to the level it has reached today's value. Still more, when gold is broken into nanoparticles, this form could be highly useful for a wide range of processes, including general nanotechnology, electronics manufacturing and the synthesizing of different functional materials. It is important that we know that gold is also used in industry in many engineering applications (contacts in micro-electronics) and medicine (dental alloys, implants)

Experimental realization of a nonlinear acoustic lens with a tunable focus

We realize a nonlinear acoustic lens composed of a two-dimensional array of sphere chains interfaced with water. The chains are able to support solitary waves which, when interfaced with a linear medium, transmit compact pulses with minimal oscillations. When focused, the lens is able to produce compact pressure pulses of high amplitude, the “sound bullets.” We demonstrate that the focal point can be controlled via pre-compression of the individual chains, as this changes the wave speed within them. The experimental results agree well both spatially and temporally with analytical predictions over a range of focus locations

Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2 - (5s4d)3D2 transition

We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms using the (5s5p)3P2 - (5s4d)3D2 transition. Atom number in a magneto-optical trap is enhanced by driving this transition because Sr atoms that have decayed into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state. Spectroscopy of 84Sr, 86Sr, 87Sr, and 88Sr improves the value of the (5s5p)3P2 - (5s4d)3D2 transition frequency for 88Sr and determines the isotope shifts for the transition.Comment: 4 pages, 5 figure

Estimating particulate matter (PM) concentrations from a meteorological index for data-scarce regions : a pilot study

In regions where air quality data are scarce or access thereto is limited, a comprehensive understanding of air pollution is hindered by a lack of emission data and ambient air pollution measurements. Therefore, in this pilot study, we assess the feasibility of estimating particulate matter (PM) mass concentrations from a meteorological index. Measured PM concentrations from air quality monitoring stations (2013–2016) situated in and around South African air pollution priority areas were analysed. Simulated meteorological parameters were used to calculate the newly-developed Air Dispersion Potential (ADP) index, which describes the meteorological potential for pollution dispersion in the atmosphere. For most conditions, there exists weak (r = 0.1–0.29) to moderate (r = 0.30–0.49) correlations between the ADP index and PM classes. At the three stations with adequate data availability, it was found that the ADP index was relatively successful in predicting conditions of high PM concentrations. An investigation of the effect of meteorological conditions on the diurnal variation of PM concentrations led to both the quantification of this effect, and the realization that at these diverse sites, up to 29% of variation in hourly PM concentrations can be explained by variations in meteorology. The application of the index in this way can play an important role in air quality management by quantifying the impacts of meteorological drivers on PM peaks.SASOL through the Laboratory for Atmospheric Studies (LAS) at the University of Pretoria.https://www.elsevier.com/locate/apr2020-09-01hj2019Geography, Geoinformatics and Meteorolog

Simultaneous chronic rupture of quadriceps tendon and contra-lateral patellar tendon in a patient affected by tertiary hyperparatiroidism

Spontaneous ruptures of the extensor mechanism of the knee are very rare. They tend to increase considerably in patients with metabolic diseases such as chronic renal failure, hyperparathyroidism, diabetes, gout, and systemic lupus erythematosus. The reported case regards a 48-year-old man with chronic, spontaneous and simultaneous quadriceps, and contra-lateral patellar tendon rupture. The patient suffered from chronic renal failure and for the past year from tertiary hyperparathyroidism. Ruptured tendons were repaired and both knee were evaluated monthly for the next 12 months. Good functional recovery was achieved on both knees without relapse. This case emphasizes the importance of long-term high parathyroid hormone level in the etiology of tendons ruptures

Determination of Microstructural Changes By Severely Plastically Deformed Copper-Aluminum Alloy: Optical Study

Our work deals with the problem of producing a complex metal-ceramic composite using the processes of internal oxidation (IO) and severe plastic deformation. For this purpose, Cu-Al alloy with 0.4wt.% of Al was used. IO of sample serves in the first step of the processing as a means for attaining a fine dispersion of nanosized oxide particles in the metal matrix. Production technology continues with repeated application of severe plastic deformation (SPD) of the resulting metal-matrix composite to produce the bulk nanoscaled structural material. SPD was carried out with equal channel angular pressing (ECAP), which allowed that the material could be subjected to an intense plastic strain through simple shear. Microstructural characteristics of one phase and multiphase material was studied on internally oxidized Cu with 0.4wt.% of Al sample composed of one phase copper-aluminum solid solution in the core and fine dispersed oxide particles in the same matrix in the mantle region. In this manner AFM, X-ray diffraction and Raman spectroscopy were used. Local structures in plastically deformed samples reflect presence of Cu, CuO, Cu2O, Cu4O3 or Al2O3 structural characteristics, depending on type of sample

The Risk of orofacial cleft lip/palate due to maternal ambient air pollution exposure : a call for further research in South Africa

BACKGROUND: Despite being underreported, orofacial cleft lip/palate (CLP) remains in the top five of South Africa’s most common congenital disorders. Maternal air pollution exposure has been associated with CLP in neonates. South Africa has high air pollution levels due to domestic burning practices, coal-fired power plants, mining, industry, and traffic pollution, among other sources. We investigated air pollutant levels in geographic locations of CLP cases. METHODS: : In a retrospective case series study (2006–2020) from a combined dataset by a Gauteng surgeon and South African Operation Smile, the maternal address at pregnancy was obtained for 2,515 CLP cases. Data from the South African Air Quality Information System was used to calculate annual averages of particulate matter (PM) concentrations of particles < 10 µm (PM10) and < 2.5 µm (PM2.5). Correlation analysis determined the relationship between average PM2.5/PM10 concentrations and CLP birth prevalence. Hotspot analysis was done using the Average Nearest Neighbor tool in ArcGIS. RESULTS: Correlation analysis showed an increasing trend of CLP birth prevalence to PM10 (CC = 0.61, 95% CI = 0.38–0.77, p < 0.001) and PM2.5 (CC = 0.63, 95% CI = 0.42–0.77, p < 0.001). Hot spot analysis revealed that areas with higher concentrations of PM10 and PM2.5 had a higher proclivity for maternal residence (z-score = –68.2, p < 0.001). CLP birth prevalence hotspot clusters were identified in district municipalities in the provinces of Gauteng, Limpopo, North-West, Mpumalanga, and Free State. KwaZulu-Natal and Eastern Cape had lower PM10 and PM2.5 concentrations and were cold spot clusters. CONCLUSIONS: Maternal exposure to air pollution is known to impact the fetal environment and increase CLP risk. We discovered enough evidence of an effect to warrant further investigation. We advocate for a concerted effort by the government, physicians, researchers, non-government organizations working with CLP patients, and others to collect quality data on all maternal information and pollutant levels in all provinces of South Africa. Collaboration and data sharing for additional research will help us better understand the impact of air pollution on CLP in South Africa.https://www.annalsofglobalhealth.orgGeography, Geoinformatics and Meteorolog

The sensitivity of simulated surface-level pollution concentrations to WRF-ARW-model PBL parameterisation schemes over the Highveld of South Africa

An understanding of the sensitivity of pollutant concentrations to planetary boundary layer (PBL) schemes in numerical weather prediction (NWP) models can provide insight into model results, and possibly advance the accuracy of air pollution modelling. Meteorological output from the Advanced Research Weather Research and Forecasting (WRF-ARW) model, with four frequently used PBL schemes, is used as input for an air quality model. The simulations resulting from the different schemes are compared with each other and evaluated making use of observational air pollution concentration data for a spring and a winter month of 2016 in South Africa. Sensitivity exists in surface-level pollution concentrations as simulated by the considered PBL schemes. No single PBL scheme consistently performed best across the five considered pollutants, five sites and two seasons. During analysis of the air quality simulations, it was found that the two local closure schemes – Mellor-Yamada-Janjić (MYJ) and Mellor-Yamada Nakanishi Niino (MYNN) – often performed well, while the non-local closure schemes – Yonsei University (YSU) and Asymmetric Convection Modelling (ACM) – featured as best-performing schemes the least number of times. Sensitivity also exists on a spatial scale between schemes when simulating sulphur dioxide (SO2) plumes from tall stacks, and the MYNN scheme frequently produced the highest concentrations of SO2. The results from this study should be considered when configuring NWP models for the simulation of air quality in the Highveld region.A CSIR Parliamentary Granthttp://www.elsevier.com/locate/atmoshj2022Geography, Geoinformatics and Meteorolog