Lubrication and Refrigeration in aeroplanes (Spanish) essays

Lubrication and Refrigeration in aeroplanes (Spanish) essays Lubricacin y refrigeracin Es la operacin de engrase continuo entre las piezas en contacto y con movimientos relativos, que evita el calentamiento y disminuye el desgaste de las piezas. El engrase depende de la cantidad de aceite suministrado, de la fijacin y mantenimiento de la pelà ­cula de aceite entre las superficies en frotamiento, de la evacuacin del aceite y de la evacuacin del calor. Cuando el gasto o caudal de aceite que circula entre las piezas del motor es pequen de la temperatura puede ser tan grande que llegue a hacerse peligroso por ser insuficiente para la evacuacin del calor. Para evitar que la temperatura del aceite alcance valores por encima de los là ­mites permisibles normalmente 120C, lo que significarà ­a una prdida de las cualidades de lubricacin, se dispone de refrigeracin del aceite, por medio de la instalacin de radiadores con un medio refrigerante que en el caso del avin es normalmente el aire que pasa a travs de dicho radiador. En los motores de aviacin la cantidad de calor evacuado por el aceite varà ­a entre 0.3 y 1 calorà ­a por minuto siendo normalmente la diferencia de temperatura de salida y entrada de aceite en el motor entre 10C y 30C. La T ª de entrada en el motor es aprx. 70C y la de salida es de 100C. El sistema de aceite para lubricacin de un motor puede considerarse dividido en dos partes fundamentales: la parte interior al motor llamada zona de lubricacin principal y segundo la parte exterior o circuito auxiliar para almacenamiento central de temperatura y recuperacin de aceite. En los motores de aviacin la presin de aceite a la entrada del motor est regulada normalmente a cinco kg/cm2, y el caudal de aceite proporcionado es aprx. de 0.02 a 0.1 l...

Peri Prefix Meaning in Biology

Peri Prefix Meaning in Biology The prefix (peri-) means around, near, surrounding, covering, or enclosing. It is derived from the Greek peri for about, near, or around. Words That Begin With Peri Perianth (peri-anth): The outer part of a flower that encloses its reproductive parts is called the perianth. The perianth of a flower includes the sepals and petals in angiosperms. Pericardium (peri-cardium): The pericardium is the membranous sac that surrounds and protects the heart. This three-layered membrane serves to keep the heart in place in the chest cavity and prevents over-expansion of the heart. Pericardial fluid, which is located between the middle pericardial layer (parietal pericardium) and the innermost pericardial layer (visceral pericardium), helps to reduce friction between pericardial layers. Perichondrium (peri-chondrium): The layer of fibrous connective tissue that surrounds cartilage, excluding cartilage at the end of joints, is called perichondrium. This tissue covers cartilage in structures of the respiratory system (trachea, larynx, nose, and epiglottis), as well as cartilage of the ribs, outer ear, and auditory tubes. Pericranium (peri-cranium): The pericranium is a membrane that covers the outer surface of the skull. Also called the periosteum, it is the innermost layer of the scalp that covers bone surfaces except at the joints. Pericycle (peri-cycle): Pericycle is plant tissue that surrounds vascular tissue in roots. It initiates the development of lateral roots and is also involved in secondary root growth. Periderm (peri-derm): The outer protective plant tissue layer that surrounds roots and stems is the periderm or bark. The periderm replaces the epidermis in plants that undergo secondary growth. Layers composing the periderm include cork, cork cambium, and phelloderm. Peridium (peri-dium): The outer layer that covers the spore-bearing structure in many fungi is called the peridium. Depending on the fungal species, the peridium may be thin or thick with between one and two layers. Perigee (peri-gee): The perigee is the point in the orbit of a body (moon or satellite) around the Earth where it is nearest to the center of the Earth. The orbiting body travels faster at perigee than at any other point in its orbit. Perikaryon (peri-karyon): Also known as cytoplasm, the perikaryon is all of the contents of a cell surrounding but excluding the nucleus. This term also refers to the cell body of a neuron, excluding the axons and dendrites. Perihelion (peri-helion): The point in the orbit of a body (planet or comet) around the sun where it comes closest to the sun is called the perihelion. Perilymph (peri-lymph): Perilymph is the fluid between the membranous labyrinth and bony labyrinth of the inner ear. Perimysium (peri-mysium): The layer of connective tissue that wraps skeletal muscle fibers into bundles is called perimysium. Perinatal (peri-natal): Perinatal refers to the time period occurring around the time of birth. This period spans from about five months before birth to one month after birth. Perineum (peri-neum): The perineum is the area of the body located between the anus and genital organs. This region spans from the pubic arch to the tail bone. Periodontal (peri-odontal): This term literally means around the tooth and is used to denote tissues that surround and support teeth. Periodontal disease, for example, is a disease of the gums that can range from minor gum inflammation to serious tissue damage and tooth loss. Periosteum (peri-osteum): The periosteum is a dual-layered membrane that covers the outer surface of bones. The outer layer of the periosteum is dense connective tissue formed from collagen. The inner layer contains bone-producing cells called osteoblasts. Peristalsis (peri-stalsis): Peristalsis is the coordinated contraction of smooth muscle around substances within a tube that moves the contents along the tube. Peristalsis occurs in the digestive tract and in tubular structures such as the ureters. Peristome (peri-stome): In zoology, the peristome is a membrane or structure that surrounds the mouth in some invertebrates. In botany, peristome refers to small appendages (resembling teeth) that surround the opening of a capsule in mosses. Peritoneum (peri-toneum): The dual-layered membrane lining of the abdomen that encases abdominal organs is known as the peritoneum. The parietal peritoneum lines the abdominal wall and the visceral peritoneum covers the abdominal organs. Peritubular (peri-tubular): This term describes a position that is adjacent to or surrounds a tubule. For example, the peritubular capillaries are tiny blood vessels that are positioned around nephrons in the kidneys.