Doppler Setting can be specified for each individual baseband in the OPT, removing the burden to do this for each possible observing run by the observer. For more details, refer to the Doppler Correction section within the Spectral Line guide. An antenna is shadowed when its line-of-sight to the source is partially or fully blocked by another antenna in front of it. The shadowed antenna will collect less radiation from the source than if it had not been shadowed, reducing the sensitivity on the baselines to that antenna. Shadowing is more likely to occur when sources are at low elevation and when the antennas are in more compact configurations.
The OPT will report, per scan, the maximum amount of shadowing, if any, will occur according to the location in the sky of the target and the configuration of the observations. D-configuration is affected by shadowing more than the other configurations because the antennas are at their closest proximity to each other. If you select "Any" configuration, the OPT will calculate the worst-case scenario by assuming the D-configuration to calculate shadowing. If any calibration scans will be shadowed for any of the valid LST start times, we recommend increasing the observing time of the calibration source to account for the loss of sensitivity.
Table 2. All shadowed baselines will be similarly affected. Note that the loss of sensitivity is not linear with the fractional shadowing. Avoiding antenna shadowing during the D-configuration relies on the azimuth of the antennas, which is dependent on the location of the source and the LST start time. Shadowing is worst along the azimuths of the arms in both directions , so has a six-fold symmetry. See Figure 2.
Figure 2. In this section there will be an extensive discussion of antenna wraps. Here we define some terminology to avoid confusion. Clockwise CW wrap : also known as the Right or Outer wrap.
South wrap : this term is used for the unambiguous section of the wraps where there is no preference over the use of either CW or CCW wraps. When to request an antenna wrap : Unless the first source i. If the SB starts with either 3C or 3C48, then an antenna wrap should be selected and continue to specify that wrap for the startup sequence of the SB. Select a wrap which takes the antennas in a direction so there is plenty of room for the antennas to move without having to unwrap again; check the LST start range by stepping through at least every hour, making sure that all scans have plenty of on source time no less than 20sec for standard observing and no less than 2min30sec for reference pointing.
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Sometimes the LST start range will need to be adjusted to avoid an unwrap. Antenna Wrap Caveats : When the schedule summary reports a calculated wrap CW or calculated wrap CCW , do not assume that the calculated wrap will be the starting wrap. The calculated wrap is also a good indication that a wrap should be set, and not always in the calculated direction. Do not be alarmed if you request a wrap and it does not appear in the schedule summary report. During the observation of a single source, or by switching from one source to the next, the antennas are continuously changing their pointing toward different directions in the sky.
The cables for power, communication, and data transfer have a limited length and wrap around the rotation azimuth axis of the antenna while the antenna moves. Software directs the antenna movements to prevent them from tightening and snapping when the cables reach the azimuth cable wrap limit, i. At a wrap limit, instead of continuous tracking during a scan or directly moving to the next scan at a scan boundary, the antennas will move the opposite long way while unwrapping the cables. Perhaps experiment with different azimuth and elevation starting positions to investigate the effect and starting slew times for a particular scheduling block.
This happens when a target and calibrator are close to, but on opposite sides of The OPT will show slew times much longer than expected for the angular source separation, and indicate an azimuth wrap CW or CCW, see next paragraph on only one of the sources in the reports of the scan list. So even if a calibrator may be a bit further away or less strong, it may be the better option when it is on the same side of zenith. Experiment with different LST start times to investigate the effect for a particular scheduling block if no suitable calibrator can be found on the same side of zenith.
The most important antenna wrap issue arises at the start of the scheduling block as the wrap chosen determines the wrap for the rest of the observation if not specified in further scans. This wrap should also align the azimuth of antennas combined from previous different subarrays at the start of observing. When the antennas slew toward the first source in the scheduling block, there are two options: clockwise CW, also known as Right or Outer or counterclockwise CCW, also known as Left or Inner ; see Figure 2.baidryckinpebyc.tk
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In dynamic scheduling, the software will choose the shortest slew to the first source unless otherwise specified in the antenna wrap option in the first scan s in the scheduling block. This default software choice may or may not be the optimum case for the observations. That is, observations entirely on the south wrap or entirely on the north wrap should be fine, but if you include any of the common standard flux density scale calibrators 3C48, 3C most likely the observation will include LSTs where these sources are on the other wrap.
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Use this diagram in conjunction with the azimuth column in the scan listing of the scheduling block report for different LST start times to investigate whether any wrap issues may occur. That is, many observers should take note to avoid any problems by adhering to the guidelines below. It should be noted, for completeness, that the online software monitors the azimuth of the antennas constantly i. As this happens at the actual azimuth after the global pointing model and possible additional reference pointing corrections are applied , the time at which a specific the first antenna might unwrap may be different from another antenna the last by a minute or so.
To avoid unwrapping antennas at different times, make sure the scans do not start or stop very close to these azimuth limits for any of the potential LST start times of the scheduling block. Note that for this reasoning, the RA and LST range should be within 12h of each other to properly determine rise or set.
If the difference is larger, add 24h to either the RA or LST range values, whichever has the lower value in the scheduling block. Always make sure to check the wraps in the Reports tab of the scheduling block in the OPT. For more detailed information on setting antenna wraps, see the section How to Proceed below. First, their declination is almost the latitude of the VLA Yet this can seriously compromise a biodiversity which the new species being introduced does not accommodate.
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Similarly, wetlands converted into cultivated land lose the enormous biodiversity which they formerly hosted. In some coastal areas the disappearance of ecosystems sustained by mangrove swamps is a source of serious concern. Selective forms of fishing which discard much of what they collect continue unabated.
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Particularly threatened are marine organisms which we tend to overlook, like some forms of plankton; they represent a significant element in the ocean food chain, and species used for our food ultimately depend on them. In tropical and subtropical seas, we find coral reefs comparable to the great forests on dry land, for they shelter approximately a million species, including fish, crabs, molluscs, sponges and algae. It is aggravated by the rise in temperature of the oceans. All of this helps us to see that every intervention in nature can have consequences which are not immediately evident, and that certain ways of exploiting resources prove costly in terms of degradation which ultimately reaches the ocean bed itself.
Greater investment needs to be made in research aimed at understanding more fully the functioning of ecosystems and adequately analyzing the different variables associated with any significant modification of the environment. Because all creatures are connected, each must be cherished with love and respect, for all of us as living creatures are dependent on one another.
Each area is responsible for the care of this family.
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This will require undertaking a careful inventory of the species which it hosts, with a view to developing programmes and strategies of protection with particular care for safeguarding species heading towards extinction. Human beings too are creatures of this world, enjoying a right to life and happiness, and endowed with unique dignity.
Nowadays, for example, we are conscious of the disproportionate and unruly growth of many cities, which have become unhealthy to live in, not only because of pollution caused by toxic emissions but also as a result of urban chaos, poor transportation, and visual pollution and noise. Many cities are huge, inefficient structures, excessively wasteful of energy and water. Neighbourhoods, even those recently built, are congested, chaotic and lacking in sufficient green space.
We were not meant to be inundated by cement, asphalt, glass and metal, and deprived of physical contact with nature. The social dimensions of global change include the effects of technological innovations on employment, social exclusion, an inequitable distribution and consumption of energy and other services, social breakdown, increased violence and a rise in new forms of social aggression, drug trafficking, growing drug use by young people, and the loss of identity. These are signs that the growth of the past two centuries has not always led to an integral development and an improvement in the quality of life.
Some of these signs are also symptomatic of real social decline, the silent rupture of the bonds of integration and social cohesion.