Cavity Clearance: Fill & Download for Free

As it happens, just yesterday I read a research paper on this in the journal Science.During deep, nondreaming, slow-wave sleep (SWS), cerebral blood flow drops by 25%, reducing cerebral blood volume; brain metabolism and oxygen consumption also fall at this time. The reduced cerebral blood volume allows cerebrospinal fluid (CSF) to flow backward (retrograde flow) about every 20 seconds and flood the third and fourth ventricles (internal cavities) of the brain—opposite the direction of flow indicated by arrows in traditional diagrams like my textbook figure here.This retrograde CSF flow, and its oscillations back and forth as we go in and out of SWS, is thought to contribute to the flushing away and disposal of toxic brain metabolites that accumulate while we’re awake.These new findings suggest possible correlation between the disturbances in SWS seen in many people in old age, impaired clearance of wastes from the brain, and cognitive issues of aging such as dementia and depression.ReferencesN.E. Fultz et al. 1 November 2019. Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep. Science 366:628–631.S. Grubb & M. Lauritzen. Deep sleep drives brain fluid oscillations (summary article). Same issue, p. 572–573.

It seems this may be related to turbulence in airflow through the nose during windy conditions.Briefly, breathing involves an increase in size of the thorax or chest cavity by the diaphragm moving downwards, along with chest wall muscle contraction to elevate the ribs. As the size increases, pressure goes down in the thorax and this 'sucks in' air through the nose.This part of the breathing process is unlikely to be affected by windy conditions. Its what happens at the nose, as it enters the respiratory system that makes the difference.In normal breathing, air passes through the nasal cavity and around three protuberances called the turbinates, namely superior, middle and inferior, in an orderly 'streamlined' flow called Laminar flow. However, under certain conditions airflow may become disordered with multiple eddies, called Turbulent flow.A: Laminar flow and B: Turbulent flow in nasal cavity.(Image courtesy:@http://sciencedirect.com)Whether turbulence occurs or not is determined by the Reynold's number(Re). This number increases as the size of the nasal cavity increases or the flow rate across the cavity increases. At values of Re>2000 flow becomes turbulent like in situations of high flow rates.Under windy conditions, the large volume of air entering at high pressure causes flow to become turbulent. Since flow is also related to the air pressure difference across the nose, it has been calculated that a pressure difference of 40-80 Pa causes flow rate to be high enough (30L/min approx.) to cause turbulence.When turbulence is generated, the air clearance is decreased i.e the air we breathe tends to loiter around the nose rather than getting on with it in the lungs. This produces a sensation of obstruction. In spite of the large amount of air entering the nose!

Its definitely the M1911.M1911The M1911, in all aspects, is a cool-looking weapon.Sure, It doesn’t have the brawny size and feel of say a desert eagle.Desert EagleBut the M1911 has the classy old-school look, which some might say makes the M1911 cooler in appearance.M1911 old schoolAnd due to the fact that the M1911 fires a relatively large caliber, the .45ACP, the M1911 certainly does rank high in the intimidation scale..45ACPThis is only helped by the fact that the M1911 looks very large when held.M1911 heldAs for reliability, the M1911 is known for Its ruggedness, working perfectly in tough terrain like the sands of Iraq.M1911 in IraqThis is due to the fact that the original M1911 was constructed using loose clearances, which helps the M1911 to be able to handle environmental debris like dirt more easily at the expense of some accuracy.M1911 disassembledOthers have also attributed this reliability to the M1911’s old, but much simpler design, which means that the M1911 has a better chance at being more reliable than any other modern pistol.Modern pistol dissassembledThen there’s the fact that the M1911 is made out of cold hard steel, which to some seem to indicate that the M1911 can handle more abuse than say a pistol made out of polymer like the Glock.GlockThe fact that the M1911 fires the large .45ACP means that It will have a more reliable chance of stopping an enemy right in Its tracks than compared to say a 9mm pistol.9mm pistolIt's still a debate that is ongoing, but generally speaking, the M1911 outsizes most of Its competitors, which leads to a larger wound cavity, which of course leads to more blood loss and a higher chance the enemy would die..45ACP wound cavityHence, the M1911 is a cool and intimidating pistol that is also extremely reliable.That’s all folks!