Surface Konusu
Kenneth Calimlim
The swelteringly hot lava caused this ice to melt and become unstable; as a result, the rocky rim of Olympus Mons broke off and partially slid away. This collapse came in the form of huge rockfalls and landslides, which slipped downwards and spread widely across the surrounding plains.
Following its formation, Lycus Sulci became even more prominent over time as wind whipped across the martian surface, eroding its material. This wind also picked up dust and carried it far and wide across Mars, later scattering this fine sand over nearby hills and ridges.
Single landslides of the kind experienced by Olympus Mons can be hundreds of metres thick. However, for this behemoth, which saw multiple colossal and overlapping collapses, they can be up to two kilometres thick.
Adam Gordon, O.D., clinical associate professor at the University of Alabama at Birmingham School of Optometry, believes overuse and exposure to blue light may lead to eyestrain and focusing problems, but does not appear to cause long-term harm, eye disease or damage to the retina.
Blue light is normally transmitted through the eye to the retina, because it is visible light that our eyes are designed to receive. Light is visible to the eye and triggers the visual process that leads to vision and sight.
A large body of experimental and clinical evidence over 20-30 years shows that UV light can be harmful to the eye and contribute to diseases such as cataracts, pterygia or growths on the front of the eye, and perhaps macular degeneration. Most eyeglass and sunglass lenses and many contact lenses have been developed to block out UV light.
Digital eyestrain refers to blurred vision and other symptoms such as burning, stinging or tearing of the eyes associated with prolonged use of digital devices. Digital eyestrain leads to dry eyes and puts strain on the muscles that help the eye focus. When staring at a digital device, the eye does not blink as frequently, and this causes faster disruption and evaporation of the tear film that protects the ocular surface. When the surface of the eye begins to dry, irritation is felt, such as burning and stinging.
When viewing digital devices, the eyes are looking at a pixelated image that is rapidly alternating or flickering multiple times per second. It is much harder for the visual system to maintain a sharp or consistent focus on an electronic image compared to a hard image.
To further maintain comfortable vision while using digital devices, it is important to use the 20/20/20 rule. For every 20 minutes of digital device use, look away for 20 seconds focusing on something 20 feet away. Using artificial tear or lubricant drops may also relieve some symptoms of dryness.
There is some early laboratory research using animal models that suggests excessive blue light exposure can damage some sensitive cell layers of the retina. There is no clinical evidence at the present time that links blue light exposure from digital devices to any pathology or disease of the eye.
Macular degeneration and other eye diseases in relation to blue light is the great unknown. The main risk factors for these eye diseases are age, genetic factors, UV light, smoking and poor nutrition more than digital device use.
One of the physiological benefits of visual light, specifically blue light, is the relationship with our internal circadian clock. As part of the sleep/wake cycle, blue light triggers the suppression of melatonin in the brain, keeping us awake. This tells us when we are tired or should be awake.
NASA will acquire the LTV as a service from industry. The indefinite-delivery/indefinite-quantity, milestone-based Lunar Terrain Vehicle Services contract with firm-fixed-price task orders has a combined maximum potential value of $4.6 billion for all awards.
NASA provided technical requirements, capabilities, and safety standards needed for LTV development and operations, and the selected companies have agreed to meet the key agency requirements. The contract request for proposal required each provider to propose a solution to provide end-to-end services, including LTV development, delivery to the Moon, and execution of operations on the lunar surface.
A geographic coordinate system (GCS) is used to define locations on a model of the surface of the earth. The GCS uses a network of imaginary lines (longitude and latitude) to define locations. This network is called a graticule.
The GCS is what ties your coordinate values to real locations on the earth. The coordinates 134.577E, 24.006S only tell you where a location is within a geographic coordinate system. You still need to know which GCS it is in before you know where it is on Earth.
Your data must have a GCS before it knows where it is on earth. Projecting your data is optional, but projecting your map is not. Maps are flat, so your map must have a PCS in order to know how to draw.
Remember that it is impossible to draw the round earth on a flat surface without a projection. So when you tell ArcGIS to make a flat map with a GCS, it is forced to choose a projection! So it draws using a pseudo Plate Carre projection. This is just latitude and longitude represented as a simple grid of squares. It is called pseudo because it is measured in angular units (degrees) rather than linear units (meters). This projection is easy to understand and easy to compute, but it also distorts all areas, angles, and distances, so it is senseless to use it for analysis and measurement. You should choose a different PCS.
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Antidiabetic drugs that activate the protein PPARγ had a bright start but soon lost their appeal because of undesirable side effects. Subtle modifications may once again make them suitable for treating diabetes.
An innovative way of mapping the large-scale structure in the Universe sidesteps the need to observe millions of galaxies individually. The approach holds promise for both astrophysical and cosmological studies.
By putting the pieces of a chemical puzzle into the right order, a thorny problem in catalysis has been solved. This opens the door to syntheses of molecules that contain the useful trifluoromethyl group.
The organization of behaviour as sequences of actions requires proper initiation and termination of each action sequence. The neural circuit that signals instructions to start and stop is now revealed.
PPARγ ligands are used to control diabetes, but their anti-diabetic actions are puzzling. Here the authors show that phosphorylation of PPARγ by cyclin-dependent kinase 5 (Cdk5) in mice is linked to obesity induced by high-fat feeding, and that inhibition of the effect in humans by the drug rosiglitazone is closely associated with its anti-diabetic effects. Several anti-diabetic PPARγ ligands directly inhibit the effect, and thus support a more normal non-diabetic pattern of gene expression.
The appropriate initiation and termination of behavioural action sequences is imperative, but the neural mechanisms underlying the learning and execution of fixed behavioural patterns are poorly understood. Here the authors reveal start/stop neuronal activity in basal ganglia circuits that emerge during task training in mice. Genetically altering these circuits disrupted the activity and impaired performance, providing evidence for a causal relationship between the specific neuronal activity and task learning.
These authors report the concentrations of hydrogen, chlorine and sulphur in the mineral apatite from a lunar basalt, and show that the concentrations are indistinguishable from apatites in common terrestrial igneous rocks. They conclude that both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable materials within the Earth.
Graphene nanoribbons (GNRs) have structure-dependent electronic properties that make them attractive for the fabrication of nanoscale electronic devices, but exploiting this potential has been hindered by the lack of precise production methods. Here the authors demonstrate how to reliably produce different GNRs, using precursor monomers that encode the structure of the targeted nanoribbon and are converted into GNRs by means of surface-assisted coupling.
The annual burial of organic carbon in lakes and reservoirs exceeds that of ocean sediments, but inland waters are components of the global carbon cycle that receive only limited attention. Here the authors find that the mineralization of organic carbon in lake sediments exhibits a strong positive relationship with temperature, suggesting that warmer water temperatures lead to more mineralization and less organic carbon burial.
Climate change can affect the phenology, population dynamics and morphology of species, but it is difficult to study all these factors and their interactions at once. Using long-term data for individual yellow-bellied marmots, these authors show that climate change has increased the length of the marmot growing season, leading to a gradual increase in individual size. It has simultaneously increased the fitness of large individuals, leading to a rapid increase in population size.
The European corn borer consists of two sex pheromone races, leading to strong reproductive isolation which could represent a first step in speciation. Female sex pheromone production and male behavioural response are under the control of different genes, but the identity of these genes is unknown. These authors show that allelic variation in a gene essential for pheromone biosynthesis accounts for the phenotypic variation in female pheromone production, leading to race-specific signals.
Transcriptional enhancers are segments of regulatory DNA located some distance from the coding region of a gene, and several of them may sometimes serve apparently redundant functions. These authors demonstrate in Drosophila that such 'redundant' enhancers, by contributing higher overall levels of transcription, ensure robustness of phenotypes against both genetic and environmental perturbations, for example mutations in other genes or temperature changes that would otherwise lead to aberrant development.
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