پایگاه خبری تحلیلی انتخاب (Entekhab.ir) : ویروس کرونا نه تنها جنبههای مختلفی از زندگی بشر را در بر گرفته بلکه به دلیل پیچیده بودن ساختار ویروسی هر روز شکل تازهای از خود ارائه میدهد. این مساله کار را به جایی رسانده که هنوز محققان نتوانستهاند واکسن ویروس کرونا را تولید کنند. از سوی دیگر نوع تاثیرگذاری و انتقال ویروس کرونا به هر فرد نیز در پژوهشهای تازه نکات منحصربهفردی مطرح کرده است. یک تحقیق جدید نشان میدهد چطور قطرات تنفسی که در زمان حرف زدن و نفس کشیدن در فضا پخش میشوند میتوانند در انتقال ویروس کرونا به خصوص در فضاهای بسته نقش داشته باشند.
Bats have an efficient circulatory system. They seem to make use of particularly strong venomotion, a rhythmic contraction of venous wall muscles. In most mammals, the walls of the veins provide mainly passive resistance, maintaining their shape as deoxygenated blood flows through them, but in bats they appear to actively support blood flow back to the heart with this pumping action.[62][63] Since their bodies are relatively small and lightweight, bats are not at risk of blood flow rushing to their heads when roosting.[64]
Bats possess a highly adapted respiratory system to cope with the demands of powered flight, an energetically taxing activity that requires a large continuous throughput of oxygen. In bats, the relative alveolar surface area and pulmonary capillary blood volume are larger than in most other small quadrupedal mammals.[65] During flight the respiratory cycle has a one-to-one relationship with the wing-beat cycle.[66] Because of the restraints of the mammalian lungs, bats cannot maintain high-altitude flight.[48]
The wings are highly vascularized membranes, the larger blood vessels visible against the light.[67]
It takes a lot of energy and an efficient circulatory system to work the flight muscles of bats. Energy supply to the muscles engaged in flight require about double the amount compared to the muscles that do not use flight as a means of mammalian locomotion. In parallel to energy consumption, blood oxygen levels of flying animals are twice as much as those of their terrestrially locomoting mammals. As the blood supply controls the amount of oxygen supplied throughout the body, the circulatory system must respond accordingly. Therefore, compared to a terrestrial mammal of the same relative size, the bat's heart can be up to three times larger, and pump more blood.[68] Cardiac output is directly derived from heart rate and stroke volume of the blood;[69] an active microbat can reach a heart rate of 1000 beats per minute.[70]
With its extremely thin membranous tissue, a bat's wing can significantly contribute to the organism's total gas exchange efficiency.[56] Because of the high energy demand of flight, the bat's body meets those demands by exchanging gas through the patagium of the wing. When the bat has its wings spread it allows for an increase in surface area to volume ratio. The surface area of the wings is about 85% of the total body surface area, suggesting the possibility of a useful degree of gas exchange.[56] The subcutaneous vessels in the membrane lie very close to the surface and allow for the diffusion of oxygen and carbon dioxide.[71]
افسوس! که صف در صف، خشکیده و بی باریم!؟ ...