UN Thread Types. UN (Unified) is a specification of the shape and dimensions of the thread for a given size (diameter) of fastener and number of threads per inch of fastener length. UN bolts and machine screws are the type of fastener in everyday use in the US, UK, and Canada. UN, UNR, and UNJ thread dimensions are measured in Imperial units.
Causes The airway can become narrowed or blocked due to many causes, including: Allergic reactions in which the trachea or throat swell closed, including allergic reactions to a bee sting, peanuts, antibiotics (such as penicillin), and blood pressure medicines (such as ACE inhibitors) Chemical burns and reactions. Epiglottitis (infection of the structure separating the trachea from the esophagus)
What Is Chronic Bronchitis? Bronchitis is an inflammation of the bronchial tubes (airways), which bring air to and from your lungs. When the bronchial tubes are inflamed, the lining, or mucous membrane, of the airways swells and grows thicker. It also produces an excess amount of mucus. The narrowing and increased blockage of the bronchial tubes from the mucus causes airflow to decrease and a phlegmy cough to develop.