10 Nov
Public

Bridges and the routes they connect

Bridges carry routes across obstacles such as rivers, valleys, roads, or railway lines. Their forms differ because the distance to be crossed, the ground, the expected use, and the available materials are not the same in every setting. A small footbridge and a long crossing for heavy traffic solve related problems at very different scales. Both must connect their route with reliable support on either side.

Every bridge transfers loads through a structure and into its supports. Different designs arrange this transfer in different ways. Beams, arches, trusses, and suspended systems are familiar examples of broad structural approaches. Their visible shapes are not simply decorative choices. The arrangement of members, joints, and supports is connected with how forces move through the bridge when it carries its own weight and the traffic using it.

The site influences the design as much as the crossing itself. River flow, the shape of a valley, the condition of the ground, and the need for space below the bridge all matter. Foundations connect the visible structure with material beneath the surface. A bridge that appears to stand lightly above the landscape may depend on substantial work that is hidden under water or ground.

Materials bring different properties and practical requirements. Stone, timber, steel, and concrete have all been used in bridge construction. The selection depends on the intended design and the circumstances of building and maintaining it. Temperature changes, water, and repeated use can affect a structure over time. Inspection and maintenance are therefore part of the life of a bridge rather than activities unrelated to its original design.

Looking at a bridge can reveal how it responds to its location. The height of the deck, the position of supports, and the routes approaching it show how a crossing fits into a larger transport network. The experience also differs between walking beneath a bridge and travelling across it. These views connect the structure’s engineering purpose with its everyday role in allowing people and goods to move through a landscape.

06 Aug
Public

Coronavirus disease 2019

COVID-19 is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic.

The symptoms of COVID‑19 can vary but often include fever,[7] fatigue, cough, breathing difficulties, loss of smell, and loss of taste.[8][9][10] Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms.[11][12] Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction).[13] Older people have a higher risk of developing severe symptoms. Some complications result in death. Some people continue to experience a range of effects (long COVID) for months or years after infection, and damage to organs has been observed.[14] Multi-year studies on the long-term effects are ongoing.[15]

COVID‑19 transmission occurs when infectious particles are breathed in or come into contact with the eyes, nose, or mouth. The risk is highest when people are in close proximity, but small airborne particles containing the virus can remain suspended in the air and travel over longer distances, particularly indoors. Transmission can also occur when people touch their eyes, nose, or mouth after touching surfaces or objects that have been contaminated by the virus. People remain contagious for up to 20 days and can spread the virus even if they do not develop symptoms.[16]

Testing methods for COVID-19 to detect the virus’s nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR),[17][18] transcription-mediated amplification,[17][18][19] and reverse transcription loop-mediated isothermal amplification (RT‑LAMP)[17][18] from a nasopharyngeal swab.[20]

Several COVID-19 vaccines have been approved and distributed in various countries, many of which have initiated mass vaccination campaigns. Other preventive measures include physical or social distancing, quarantining, ventilation of indoor spaces, use of face masks or coverings in public, covering coughs and sneezes, hand washing, and keeping unwashed hands away from the face. While drugs have been developed to inhibit the virus, the primary treatment is still symptomatic, managing the disease through supportive care, isolation, and experimental measures.