Core Tip: In 1992, the United States President George W. Bush announced that "genetically modified foods and natural foods are essentially the same." Eighteen years later, genetically modified foods have troubled Americans again. The Institute of Environmental Medicine of the US Academy of Sciences has drawn a sensational conclusion that "the consumption of genetically modified foods has serious health risks, including infertility, immune problems, accelerated aging, insulin regulation, and changes in major organs and gastrointestinal systems." Then, genetically modified foods Is it a disaster or a blessing to humanity? A doctor tips: Avoid eating genetically modified foods The U.S. comprehensive reflection on transgenes began last year and climaxed in recent times. Commentaries and editorials published in the New York Times on June 12th and 20th of this year stated that the development of genetically modified technology products for more than a decade has been largely ineffective and has failed to realize the promised lesson that humans have not fully understood the function of genes. Even if we understand it, we may not be able to develop technological products and processing methods that are conducive to human health and ecological protection. As early as May of 2009, the report launched by the American Academy of Environmental Medicine Science caused a sensation. The report strongly recommends that genetically modified foods pose a serious safety threat to patients, call on members' doctors not to allow their patients to eat genetically modified foods, and educate the community's population to avoid eating genetically modified foods. "Some animal experiments have shown that eating genetically modified foods has serious risks of damaging health, including infertility, immune problems, accelerated aging, insulin regulation and changes in major organs and gastrointestinal system," concluded the Institute of Environmental Medicine, US Academy of Sciences Yes, "The relationship between genetically modified foods and the adverse effects of health is not related to it, but there is a causal relationship." “More and more doctors have already prescribed a prescription for non-GM foods (to patients).†World-renowned biologist Pushpalmi Balgar concluded after reviewing more than 600 scientific journals: GMOs are the United States. A major factor in the rapid deterioration of human health. Regarding the principle of transgene damage, the Institute pointed out that the genes inserted into genetically modified soybeans will be transferred to the DNA of the bacteria that lives in our intestines and continue to function. This means that after eating, although we do not eat genetically modified foods, we continue to produce potentially harmful genetic proteins in our bodies. "To be thorough, eating GM corn will transform our intestinal bacteria into living pesticides. Factory, probably until we die." After the report was released, the U.S. Department of Health published a scientific paper at the end of 2009 that indicated that GM foods can cause harm to the viscera. According to the research report of the National Science Foundation, most people have negative attitudes and doubts about genetic modification. In the United States, genetically modified foods are not labeled, but officially certified non-genetically modified foods, that is, natural and organic foods will be clearly labeled. Data from the U.S. Department of Agriculture showed that the retail sales of organic food in the United States rose from 3.6 billion U.S. dollars in 1997 to 211 billion U.S. dollars in 2008. Despite the economic recession in the United States, the organic market has been booming and has led to periodical organic products. shortage. B "Super Pest": Make pesticide consumption increase substantially In addition to health, the troubles caused by GM crops to agriculture have also attracted the attention of academics and government departments. In April this year, the US National Academy of Sciences released the report “Impact of GM Crops on the Sustainability of U.S. Agricultureâ€, pointing out that the weed issue that has caused peasants' distress points out that the planting of GM crops does not eliminate weeds. Instead, the use of herbicides continues. Rising, threatening environmental security. In addition to super weeds, superbugs have also appeared in GM farmland. In addition to failing to prevent pests, GM crops have caused pests that were originally small pests to become "super pests." The report of the National Academy of Sciences uses 16 years of practical facts and statistical data to make it clear that the long-term cultivation of genetically modified crops will bring unrecoverable side effects to the agricultural economy. The US Department of Agriculture, which has consistently maintained that American farmers have benefited from the cultivation of genetically modified crops, has finally changed its position. The latest statistics from the US Department of Agriculture acknowledge that after planting genetically modified crops, the cost of fuel for agricultural operations has more than doubled and the amount of pesticides used has exceeded natural levels. Crop planting and seed costs have also increased significantly. At present, in the game with the U.S. government departments, the limelight of GM companies that have been at the upper hand has begun to weaken. A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check Valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow. Check Valves, Water Check Valves, Brass Check Valves, Sanitary Check Valves ZHEJIANG KINGSIR VALVE CO., LTD. , https://www.kingsirvalves.com
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with both balls and seats made of artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with Ball Valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
A swing check valve or tilting disc check valve is check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing check valves can come in various sizes, large check valves are often swing check valves. The flapper valve in a flush-toilet mechanism is an example of this type of valve. Tank pressure holding it closed is overcome by manual lift of the flapper. It then remains open until the tank Drains and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve, used in applications such firefighting and fire life safety systems. A hinged gate only remains open in the inflowing direction. The clapper valve often also has a spring that keeps the gate shut when there is no forward pressure. Another example is the backwater valve (for sanitary drainage system) that protects against flooding caused by return flow of sewage waters. Such risk occurs most often in sanitary drainage systems connected to combined sewerage systems and in rainwater drainage systems. It may be caused by intense rainfall, thaw or flood.
A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. In addition to closing in response to backflow or insufficient forward pressure (normal check-valve behavior), it can also be deliberately shut by an external mechanism, thereby preventing any flow regardless of forward pressure.
A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
An in-line check valve is a check valve similar to the lift check valve. However, this valve generally has a spring that will 'lift' when there is pressure on the upstream side of the valve. The pressure needed on the upstream side of the valve to overcome the spring tension is called the 'cracking pressure'. When the pressure going through the valve goes below the cracking pressure, the spring will close the valve to prevent back-flow in the process.
A duckbill valve is a check valve in which flow proceeds through a soft tube that protrudes into the downstream side. Back-pressure collapses this tube, cutting off flow.
A pneumatic non-return valve.
Multiple check valves can be connected in series. For example, a double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines. There are also double ball check valves in which there are two ball/seat combinations sequentially in the same body to ensure positive leak-tight shutoff when blocking reverse flow; and piston check valves, wafer check valves, and ball-and-cone check valves.