In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium is a large syncline with superimposed smaller folds. Synclines are a downward fold, termed a synformal syncline, but synclines that point upwards can be found when strata have been overturned and folded. On a geologic map, synclines are recognized as a sequence of rock layers, with the youngest at the fold's center or hinge and with a reverse sequence of the same rock layers on the opposite side of the hinge. If the fold pattern is circular or elongate, the structure is a basin. Folds form during crustal deformation as the result of compression that accompanies orogenic mountain building. Powder River Basin, Wyoming, US Sideling Hill roadcut along Interstate 68 in western Maryland, US, where the Rockwell Formation and overlying Purslane Sandstone are exposed Saou, a commune in the Drôme department in southeastern France The Southland Syncline in the southeastern corner of the South Island of New Zealand, including The Catlins and the Hokonui Hills Strathmore Syncline, Scotland Anticline Homocline Monocline Ridge-and-Valley Appalachians


A Nanolattice is a synthetic porous material consisting of nanometer-size members which are patterned into an ordered lattice structure, like a space frame. Driven by the evolution of 3D printing techniques, nanolattices aiming to exploit beneficial material size effects through miniaturized lattice designs were first developed in the mid-2010s. Nanolattices are the smallest man-made lattice truss structures and a class of metamaterials which derive their properties from both their geometry and the small size of their elements. Therefore, they can possess effective properties which are not found in nature and may not be achieved with larger-scale lattices of the same geometry. To produce nanolattice materials, polymer templates are manufactured by high-resolution 3D printing processes, such as multiphoton lithography, or by self-assembly techniques. Ceramic, metal or composite material nanolattices are formed by post-treatment of the polymer templates with techniques including pyrolysis, atomic layer deposition and electroless plating.

Pyrolysis, which additionally shrinks the lattices by up to 90%, creates the smallest-size structures, whereby the polymeric template material transforms into carbon, or other ceramics and metals, through thermal decomposition in inert atmosphere or vacuum. Nanolattices are the strongest existing cellular materials, they are light-weight, consisting of 50%-99% air, but can be as strong as steel; the small volume of their individual members thereby statistically nearly eliminates the material flaw population and the base material of nanolattices can reach mechanical strengths on the order of the theoretical strength of an ideal, perfect crystal. While such effects are limited to individual, geometrically primitive structures like nanowires, the specific architecture allows nanolattices to exploit them in complex, three-dimensional structures of notably larger overall size. Nanolattices can be designed deformable and recoverable with ceramic base materials, can possess mechanical metamaterial properties like auxetic or meta-fluidic behavior.

Nanolattices can combine mechanical resilience and ultra-low thermal conductivity and can have electromagnetic metamaterial characteristics like optical cloaking. Metamaterials Nanomaterials Microlattice

Air navigation

The basic principles of air navigation are identical to general navigation, which includes the process of planning and controlling the movement of a craft from one place to another. Successful air navigation involves piloting an aircraft from place to place without getting lost, not breaking the laws applying to aircraft, or endangering the safety of those on board or on the ground. Air navigation differs from the navigation of surface craft in several ways. Aircraft cannot stop in mid-air to ascertain their position at leisure. Aircraft are safety-limited by the amount of fuel. There is no in-flight rescue for most aircraft. Additionally, collisions with obstructions are fatal. Therefore, constant awareness of position is critical for aircraft pilots; the techniques used for navigation in the air will depend on whether the aircraft is flying under visual flight rules or instrument flight rules. In the latter case, the pilot will navigate using instruments and radio navigation aids such as beacons, or as directed under radar control by air traffic control.

In the VFR case, a pilot will navigate using "dead reckoning" combined with visual observations, with reference to appropriate maps. This may be supplemented using radio navigation aids or satellite based positioning systems; the first step in navigation is deciding. A private pilot planning a flight under VFR will use an aeronautical chart of the area, published for the use of pilots; this map will depict controlled airspace, radio navigation aids and airfields prominently, as well as hazards to flying such as mountains, tall radio masts, etc. It includes sufficient ground detail – towns, wooded areas – to aid visual navigation. In the UK, the CAA publishes a series of maps covering the whole of the UK at various scales, updated annually; the information is updated in the notices to airmen, or NOTAMs. The pilot will choose a route, taking care to avoid controlled airspace, not permitted for the flight, restricted areas, danger areas and so on; the chosen route is plotted on the map, the lines drawn are called the track.

The aim of all subsequent navigation is to follow the chosen track as as possible. The pilot may elect on one leg to follow a visible feature on the ground such as a railway track, highway, or coast; when an aircraft is in flight, it is moving relative to the body of air. The pilot must adjust heading to compensate for the wind; the pilot will calculate headings to fly for each leg of the trip prior to departure, using the forecast wind directions and speeds supplied by the meteorological authorities for the purpose. These figures are accurate and updated several times per day, but the unpredictable nature of the weather means that the pilot must be prepared to make further adjustments in flight. A general aviation pilot will make use of either a flight computer – a type of slide rule – or a purpose-designed electronic navigational computer to calculate initial headings; the primary instrument of navigation is the magnetic compass. The needle or card aligns itself to magnetic north, which does not coincide with true north, so the pilot must allow for this, called the magnetic variation.

The variation that applies locally is shown on the flight map. Once the pilot has calculated the actual headings required, the next step is to calculate the flight times for each leg; this is necessary to perform accurate dead reckoning. The pilot needs to take into account the slower initial airspeed during climb to calculate the time to top of climb, it is helpful to calculate the top of descent, or the point at which the pilot would plan to commence the descent for landing. The flight time will depend on both the desired cruising speed of the aircraft, the wind – a tailwind will shorten flight times, a headwind will increase them; the flight computer has scales to help pilots compute these easily. The point of no return, sometimes referred to as the PNR, is the point on a flight at which a plane has just enough fuel, plus any mandatory reserve, to return to the airfield from which it departed. Beyond this point that option is closed, the plane must proceed to some other destination. Alternatively, with respect to a large region without airfields, e.g. an ocean, it can mean the point before which it is closer to turn around and after which it is closer to continue.

The Equal time point, referred to as the ETP, is the point in the flight where it would take the same time to continue flying straight, or track back to the departure aerodrome. The ETP is not dependent on fuel, but wind, giving a change in ground speed out from, back to the departure aerodrome. In Nil wind conditions, the ETP is located halfway between the two aerodromes, but in reality it is shifted depending on the windspeed and direction; the aircraft, flying across the Ocean for example, would be required to calculate ETPs for one engine inoperative, a normal ETP. For example, in one engine inoperative and depressurization situations the aircraft would be forced to lower operational altitudes, which would affect its fuel consumption, cruise speed and ground speed; each situation