Nitrogen deficiency: poor plant growth, pale green leaves, small leaves, lower leaves first aging yellowing or even falling off, then gradually moving up, throughout the whole plant; less pods, pod growth and development.
Phosphorus deficiency: the leaves are dark green, hard and dwarf at the seedling stage; the lower leaves are yellowed during the pod-forming period, and the upper leaves are small and slightly upward.
Potassium deficiency: In the early growth of kidney bean, the leaf edge appears slightly yellow, in the order of the leaf edge, then the leaf vein yellowing, the order is obvious; the leaf edge is dead, as the leaf grows, the leaf curls to the outside, the leaf slightly Hardened, the pods are slightly shorter.
Calcium deficiency: plant dwarf, premature aging, slow growth of vegetative end; lateral root tip death, tumor-like protrusion; leaf veins of parietal leaves are light green or yellow, young leaves are curled, leaf margin turns yellow and green leaves The tip and leaf margin die inward; the top bud of the plant is necrotic, but the old leaf is still green.
Magnesium deficiency: During the growth and development of kidney beans, the green color between the leaves of the lower leaves gradually turns yellow and further develops. Except for the green leaves of the veins and leaf margins, the veins are yellow and white.
Zinc deficiency: Fading from the middle lobe, compared with healthy leaves, the veins are clearly visible; as the veins gradually fade, the leaves turn from yellow to brown; the internodes become shorter, the stems are clustered with small leaves, and the branches are clustered. The leaves are slightly curled to the outside without flowering and pods.
Lack of shed: the plant grows atrophy and becomes brown and dry. The newly formed leaf buds and petioles are shallow, hard and easy to fold; the upper leaves are curled to the outside, and the leaf margins are browned. When the upper veins are carefully observed, there is atrophy, and the apple epidermis appears lignified.
Iron deficiency: the leaves of young leaves are chlorotic, yellowish white. In severe cases, the whole leaves turn yellow and white, but they do not show necrotic spots and do not die.
Molybdenum deficiency: The growth potential of the plant is poor, the young leaves are chlorotic, the leaf flesh between the leaf margin and the veins is yellow-like, the leaf margin is curled to the inside, and the tip of the leaf is atrophied, often causing the plant to not bloom.
Disclaimer: Some articles on this website are transferred from the Internet. If legal rights of third parties are involved, please inform this website. phone
Bone screws, also known as fracture fixation screws, are commonly used in clinical practice to fix orthopedic implants.
Bone screws are usually used to fix internal fractures or dislocations by directly screing into two different bone blocks or fixing an internal implant such as a bone plate to achieve fracture fixation, position the bone and promote its healing. Bone screws are used in a wide range of areas, including the shoulder, elbow, hip, knee, spine, etc. For example, pedicle screw systems are used for spinal fusion, and compression bone screws are commonly used for foot and ankle surgery or fixation of other fractures under pressure. Similar to traditional mechanical screws, the main structures of bone screws also include nail cap, nail body, and nail tip. Screws can be used to fix bone plates or bone fragments. When used for the former, they are called plate screws, and when used for the latter (to prevent the collapse of bone fragments), they are called positional screws. The latter can be inserted into the plate holes, and can be placed on the bone alone (also known as compression screws). Compression screws can be used to increase interfragment pressure.
(1) The screw cap
The screw cap has three main functions: the first is to optimize the force. The protruding cap makes the contact area between the screw and bone larger, increases the load area, optimizes the local force at the screw insertion site, and reduces the risk of bone rupture caused by excessive stress. The second is the positioning effect. The prominent cap makes the bone nail can only be screwed into a certain depth to prevent the whole bone nail from being screwed into the bone completely. The third function is to provide the position of force application by rotating the force groove at the cap to move the bone nail forward and drive it into the bone. Now, the force groove is mostly inner hexagonal, which does not require axial force to maintain the actuator in the center position and is suitable for a wider range of fractures.
(2) Screw the body
The size of the nail body determines the strength and fatigue resistance of the bone nail. The larger the diameter of the nail body, the stronger the strength will be, and the corresponding fatigue resistance will be better. In addition to the diameter of the nail body, the pitch and tooth depth of the screw body thread are also the key parameters of the nail body design. Different thread design has an important effect on the pressure and occlusal performance of the screw.
(3) Screw tip
Tapping is the process of phalangeal nail cutting thread in the bone. According to the shape of the nail tip, the bone nail can be divided into self-tapping nail and non-self-tapping nail. The nail tip of the self-tapping nail is sharper and can be directly screwed into the bone without pre-drilling. Usually, self-tapping screws are used for Cancellous bone, and the bone is compressed when the screw is inserted, so as to increase the bone density of the occlusal part locally and enhance the occlusal effect. However, when inserting screws in Cortical bone, the screw channel is generally pre-punched, and then the bone screw is screwed. Usually, the self-tapping screw is not directly used to prevent the bone screw from being stuck or damaged because the cortical bone is too hard.
Bone Screw,Cancellous Screw,screws in bone,Cortical Screw
Jiangsu Aomed Ortho Medical Technology Co.,Ltd , https://www.medthofixation.com