Clearance

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Related to mucociliary clearance: mucociliary clearance rate

clearance

1. 
a. the disposal of merchandise at reduced prices
b. (as modifier): a clearance sale
2. the act of clearing an area of land of its inhabitants by mass eviction
3. Dentistry the extraction of all of a person's teeth
4. a less common word for clearing

Clearance

 

the maximum profile of an object. As applied to transport vehicles and the moving parts of stationary machines, clearance is determined on the basis of their safe movement among other machines and structures. Outside the clearance, which permits the movement of machines in different directions, it is possible to erect structures and set up machines, lathes, and the safety zone for people. For example, the clearance of a moving train is the maximum profile in a plane perpendicular to the axis of the railway track beyond which no part of a locomotive or car should project when in working order. A railway clearance gauge is the maximum profile in a plane perpendicular to the axis of the railway track within which no parts of structures and equipment should extend. Meeting these clearances ensures the safe movement of trains in tunnels, on bridges, and under over-bridges. Underbridge clearance is the profile of the clear opening under a bridge between the bottom of its span structure and the estimated navigable level in height and between the supports of the span in width.

REFERENCES

Evgrafov, G. K., and N. N. Bogdanov. Proektirovanie mostov. Moscow, 1966.
Evgrafov, G. K., and N. N. Bogdanov. Zheleznye dorogi. Moscow, 1968.
Evgrafov, G. K., and N. N. Bogdanov. AvtomobiV. Ekspluatatsiia i remont. Entsiklopedicheskii slovar’-spravochnik. Moscow, 1968.

I. A. IVANOV


Clearance

 

the distance from ground level (plane of reference) to the lowest structural member of a motor vehicle, excluding the wheels; one of the parameters that determine the operational trafficability of motor vehicles.

The minimum permissible clearances established in the USSR are 200 mm, 240 mm, 260 mm, and 270 mm for fully loaded trucks with carrying capacities of 1.5 tons, 3 tons, 5 tons, and 8-12 tons, respectively, and 240-270 mm for buses, depending on their length and purpose.

clearance

[′klir·əns]
(engineering)
Unobstructed space required for occasional removal of parts of equipment.
(mechanical engineering)
In a piston-and-cylinder mechanism, the space at the end of the cylinder when the piston is at dead-center position toward the end of the cylinder.
The ratio of the volume of this space to the piston displacement during a stroke.
(mining engineering)
The space between the top or side of a car and the roof or wall.
(navigation)
The clear space between a vessel and an object such as a navigation light, hazard to navigation, or another vessel.
A specific message from air-traffic control to a pilot of an aircraft allowing him to proceed in accordance with the flight plan which the pilot had filed, or with some modification of the original plan.
In the instrument landing system, the difference in the depth of modulation which is required to produce a full-scale deflection of the course deviation indicator needle in any flight sector outside the on-course sectors.
(ordnance)
Elevation of a gun at such an angle that a projectile will not strike an obstacle between the muzzle and the target.
(petroleum engineering)
The annular space between down-hole drill-string equipment, such as bits, core barrels, and casing, and the walls of the borehole with the down-hole equipment centered in the hole.

clearance

1. Open space between two elements of a building to aid in proper placement, to compensate for minor inaccuracies in cutting, or to allow unobstructed movement between parts.
2. The space or distance allowed for anchorage or erection processes or to accommodate dimensional variations in the building structure.

air traffic control clearance

Authorization for an aircraft to proceed under conditions specified by an air traffic control unit (ICAO). This is to prevent collisions between known aircraft. The pilot-in-command of an aircraft must not deviate from the provisions of VFR (visual flight rules) or IFR (instrument flight rules) air traffic clearance except in an emergency or unless an amended clearance has been obtained. Additionally, the pilot may request a different clearance if he or she has information available that makes another course of action more practical or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued. Pilots may also request clarification or amendment, as appropriate, any time a clearance is not fully understood or is considered unacceptable because of safety. Controllers should, in any such instance and to the extent of operational practicality and safety, honor the pilot's request. The pilot is responsible for requesting an amended clearance if ATC issues a clearance that would cause him or her to deviate from a rule or regulation, or, in the pilot's opinion, would place the aircraft in jeopardy. Normally, only the word clearance is used, and it may be prefixed by words such as start-up, taxi, takeoff, departure, approach, or landing to indicate the particular portion of flight to which the ATC clearance relates. Also called an air traffic clearance.
References in periodicals archive ?
These findings suggest an association between VCPT clearance changes and altered airway [NO.sub.x] levels consistent with a role for NO metabolism in the regulation of mucociliary clearance. These findings suggest the need to further study the mechanisms of increased airway clearance during chest physiotherapy to establish the role nitric oxide plays in regulating this response.
The effects of nasal drops and their additives on human nasal mucociliary clearance. Rhinology 20, 127-137.
ADVANTAGES: * May be self-administered by some users * May be used where weak cough function is the sole impediment to normal secretion clearance * May replace oral or nasopharyngeal suctioning in some patients DISADVANTAGES: * Technique-dependent * Requires motivation and cooperation by caregiver * Not a "complete" airway clearance method except where "weak" cough is the only defect of the mucociliary clearance mechanism
Airway mucus is responsible for hydration of the epithelium and acts as an essential protective component of the innate defense system of the airways [38, 39]: inhaled microorganisms, noxious agents, and particles get entrapped in mucus and eliminated by mucociliary clearance (MCC) and/or cough, thus protecting the lung from airway infection and inflammation.
Mucociliary clearance is an important defence mechanism for both upper and lower airways and "its impairment[...] predisposes to chronic infection of the nose, paranasal sinuses and the respiratory tree" [66].
CONCLUSIONS: Alterations in somatic growth, lung development, and the expression of genes involved in mucociliary clearance and innate immunity in the lung are potential mechanisms through which early life arsenic exposure impacts respiratory health.
The effects of topical agents of fluticasone propionate, oxymetazoline, and 3% and 0.9% sodium chloride solutions on mucociliary clearance in Me therapy of acute bacterial rhinosinusitis in vivo.
The mucociliary clearance system, together with good cough function and appropriate immune responses, protects most people from serious threats to lung health.
* Lack of physical activity cause poor mucociliary clearance and decreased epithelial stimulation leading to excessive mucus and oedema.
ENaC and CFTR are closely related to the airway mucociliary clearance. Ion transporters may play a critical role in pathogenesis of asthmatic exacerbations.
(3) Pneumatized structures of the nose and sinuses have a mucosal lining whose mucociliary clearance will be associated with a drainage pathway into the nose.
Chronic alcohol exposure also impairs lung innate host defense by desensitizing effective mucociliary clearance [1], rendering cilia unresponsive to stress.