the dna extraction protocol

Plant DNA extraction mainly involved the following processes: 1. ** Treatment of samples ** - Taking bananas as an example, the crushing method could be used. The banana was placed in a sealed bag and mashed to destroy the cell wall. You can also weigh 10g of tender plant tissue and cut it into a mortar. Add 10ml of pre-cooled grinding buffer and add about 0.1 g of SSS, and grind it into a paste on an ice bath. 2. ** Add extract ** - For the mashed banana, add 10ml of extract. The extract is a mixture of a surfacing agent and salt. The surfacing agent can clean the cell membrane, and the salt can fully dissolve the DNA into the solution. - For the young plant tissues that were ground into paste, add an equal volume of a mixture of chloride-isopentool (a mixture of 24ml of chloride-isopentool and 1ml of isopentool), add a stopper, shake it vigorously for 30 seconds, transfer it to a centrifugal tube, and let it stand for a moment to remove the tissue protein. Then, spin it at 4000 revolutions per minute for 5 minutes and divide it into three layers. Carefully suck the upper layer of the clear liquid into a graduated test tube, and discard the cell debris, denature protein in the middle layer, and the chloride-like in the lower layer. 3. ** Follow-up treatment ** - For example, place the test tube in a water bath at 72 ° C for 3 minutes (no more than 4 minutes) to inactivate the tissue's DNA. Then quickly take out the test tube, place it in an ice-water bath to cool it to room temperature, and add a 5-mole/L solution (extract: solution = 4:1(V/V)) to make the final concentration of the solution 1-mole/L. - Then, an equal volume of the chloride-Isopentyl alcohol mixture was added into the large test tube again, and the mixture was shaken for 1 minute. After standing still, the mixture was spun at room temperature for 5 minutes at 4000 revolutions per minute, and the supernate was taken and placed into a small beaker. - Use a burette to suck 95% pre-cooled alcohol and slowly add it to the surface of the beaker's supernate until the volume of alcohol is twice that of the supernate. Gently stir it with a glass rod. At this time, the nuclear acid quickly wraps around the glass rod in the form of a fiber. Then, add about 0.5ml of 10ssc (weigh 87.66g of NaCl2 and 44.12g of trisodic citrates, dissolve them separately, and make them 1000ml together) to make the final concentration of 1ssc. - The crude DNA product could be obtained by repeating the steps of alcohol and 10ssc treatment. After that, the processed RNase-like reagent solution (25-milligram/milliliter of the reagent solution was prepared with 0.14-milligram/milliliter of NaCl-like reagent solution, 1-milligram/milliliter of HCl-like reagent solution was added, and the reagent was treated in a water bath at 80 ° C for 5 minutes before use) was added, so that the final concentration of the reagent was 50 - 70? g/milliliter. The reagent was then incubated in a water bath at 37 ° C for 30 minutes to remove the RNase-like reagent. - Add an equal volume of a mixture of chlouroform-isopentanol, shake it in a triangular flask for 1 minute, remove the residual protein and the added RNase-protein, and then incubate it at 4000pm for 5 minutes at room temperature to collect the upper layer of the water solution. After that, the purified DNA solution was obtained by the steps of alcohol and 10ssc. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

GGN (N-step Backward Agreement): - The sender's theory: - The sender uses the pipeline technology to allow multiple packets to be sent without waiting for acknowledgment, but it is limited by the number of unacknowledged packets in the pipeline cannot exceed the maximum number N. When the upper layer calls the send function (rdt_send ()), the sender first checks whether the send window is full (i.e., whether there are N sent but unacknowledged packets). If the window is not full, a packet is generated and sent, and the relevant variables are updated at the same time. If the window is full, the sender can choose to return the data to the upper layer (in reality, it is more likely to buffer the data or use a synchronization mechanism. The upper layer is only allowed to call the send function when the window is full). - The receiver acknowledges the packet with the sequence number n in a cumulative manner, indicating that the receiver has correctly received all the packets before and including the sequence number n. - If there is a time out (the timer is used to detect the loss of data or acknowledgment packets), the sender will resend all the packets that have been sent but not acknowledged. - Principle of the receiver: The receiver receives the packets and uses the cumulative confirmation method to feedback the situation of the correctly received packets to the sender. PR (select the replay protocol): - The sender and receiver had their own windows. The sender sends the packet without knowing the position of the receiver's window, and the receiver receives the packet without knowing the position of the sender's window. The two windows are not synchronized. - The problem was that if the size of the sequence number space and the window size did not meet a certain condition (for example, a scenario where the size of the sequence number space was 4 and the window size was 6 would be problematic), the receiver might not be able to distinguish between different situations. For example, the receiver might mistake the retransmitted packet as a new packet and receive it incorrectly. Different from the GGN protocol, the ACK (n) and TimeOut (n) in the GGN protocol would cause a lot of resources to be retransmitted, resulting in a waste of resources. The SSR protocol was more selective in dealing with situations such as retransmissions. "Choose" was equally exciting. Everyone was welcome to read it!

In the continuous ARQ protocol, the sender maintained a sending window of a certain size, and the packets within the window could be sent continuously without waiting for the other party's acknowledgment. The sender would slide the sending window forward by one packet every time it received an acknowledgment. The receiver usually uses the method of accumulating acknowledgement, that is, after receiving several packets, it sends an acknowledgement to the last packet that arrives in order, indicating that all the packets up to this packet have been received correctly. However, this method has shortcomings. For example, when the middle packet is lost, the sender cannot know the situation of the subsequent packets, and may need to re-transmit more packets. The sliding window protocol involves a sending window and a receiving window. The transmit window is the range of sequence numbers of the frames that have been sent but have not been acknowledged, and the receive window is the range of sequence numbers of the frames that are expected to be received. When the default window size is 1, you can operate according to the specific sending process. The sliding window protocol could improve the channel utilization and was a reliable transmission mechanism for data communication. The continuous ARQ protocol can be seen as a specific application form of the sliding window protocol under certain conditions (such as the cumulative acknowledgment method). They are all protocol mechanisms that exist to achieve effective and reliable data transmission in the network. "Choose" was equally exciting. Everyone was welcome to read it!

Yes, the selective replay protocol was based on the sliding window flow control technology. It was a sliding window protocol. " Choose " was equally exciting. Everyone was welcome to read it!

Both GGN (Fallback N-frame protocol) and SSR (Random Repeat protocol) were sliding window protocol under the reliable data transmission protocol in computer networks. There were the following differences between the two: 1. ** Receiving window size ** - ** GGN protocol **: Receiving window <br>(W = 1 <br>), which means that the receiver can only receive the data packets that arrive correctly in order. If an error occurs in a data packet, it will cause the subsequent packets to be discarded because they cannot be received in order by the receiver, even if these packets are not error-free and out of order. - ** PR protocol **: If the receiving window size is greater than 1, the receiver can receive packets out of order. 2. ** Confirm Method ** - ** GGN protocol **: uses cumulative acknowledgment. The receiver acknowledges the last frame of a group of frames that arrive in order, indicating that all the frames before this frame have been received. For example, if the sender sends four frames 1, 2, 3, and 4, and the receiver acknowledges frame 4, it means that the four frames 1, 2, 3, and 4 have been received. The previous frames 1, 2, and 3 are no longer separately acknowledged. - ** PR protocol **: Each packet has a separate confirmation mechanism. The receiver can confirm each correctly received packet separately, and the sender can selectively re-transmit the incorrectly received packet according to the confirmation information of the receiver. 3. ** Retransmission mechanism ** - ** GGN protocol **: When the sender receives an acknowledgment for a frame, the sending window will be moved forward. If there is a packet loss or a long delay (such as a timer exceeding), the sender needs to resend all the packets that have been sent but have not been acknowledged. For example, if the sender sends six frames, frame 1, 2, 3, 4, 5, and 6, the receiver will confirm frame 3, and the sender will think that frame 1, 2, and 3 have been sent correctly. If there is a problem later, frame 4, 5, and 6 will need to be retransmitted. - ** PR protocol **: The sender only re-sends the packet that the receiver did not receive correctly, instead of re-transmitting all the sent frames after the acknowledgment frame like the GGN protocol. 4. ** Resource utilization and wastage ** - ** GGN protocol **: Due to the method of accumulating acknowledgement and returning N frames of retransmissions, the error of one packet may lead to the retransmissions of multiple packets, even if these packets themselves are error-free. This causes a waste of resources to a certain extent, especially when the window is large and the bit error rate is high. A large number of unnecessary packets may be frequently retransmitted. - ** SP protocol **: Compared to the GGN protocol, it is more resource-saving because it only reforwards the packets that the receiver did not receive correctly, avoiding unnecessary packet retransmissions and thus improving the channel utilization. However, there were some problems with the SSR protocol. For example, the receiver and sender windows were not synchronized, which could cause errors. "Choose" was equally exciting. Everyone was welcome to read it!

The Address Resolution Protocol was a network layer protocol. It was between the data link layer and the network layer. It played a vital role in network communication, just like the address translator in the network. Its main function was to convert the IP address of the network layer to the data link layer's IP address. This was because in network communication, although the IP address was used to identify the host at the network layer, it was forwarded through the IP address at the data link layer (such as the ether network). The host or the layer 3 network device would maintain an ARP-table to store the IP address and the MAC-address map. The ARP-table entries included dynamic and static ARP-table entries. The working process was as follows: When host A needed to communicate with host B, it first determined the forwarded IP address according to the route table, and then checked the local ARP-buffer. If there was no matching address, it would broadcast an ARP-request frame in the network. All hosts in the same broadcast domain will receive this request. For example, after receiving the request, host C will find that the destination address is not its own, and then it will buffer the address of host A into its own ARP-table, and then discard the packet. After receiving the request, host B will find that the destination address is its own, and then it will buffer the address of host A and give a response. Then it will package its own address in the response ARP-packet and send it to host A. After receiving the response, host A will update its own ARP-buffer. There were two ways to obtain the ARPs: static and dynamic. The static acquisition was equivalent to manually configuration of the address map in the ARP-table. If the physical address changed, it would need to be manually changed, which was more troublesome. The dynamic acquisition was to obtain and update the address map by the host through the protocol, which was relatively convenient. In addition, there was also a free ARP-type message that was used to detect whether there was an IP address conflict. It would send a broadcast message with the same source and destination IP. Under normal circumstances, it was not expected to receive a response. If a response was received, it meant that there was an address conflict. In the Windows system, there were related ARP-commands. For example, ARP-a could check the ARP-buffer table, and ARP-d could delete the ARP-buffer table. However, due to network communication requirements, the buffer table might be regenerated immediately. In November 1982, the Internet Engineering Task Force (IetF) published the Internet Packet Packet Interface Problem (ARPG) 826. It was an indispensable protocol for the Internet Packet Interface Version 4, which was the most widely used version of the Internet protocol.(The Internet Packet Interface Version 6 was still in the early stages of deployment.) The role of the ARP-protocol in the car's ether network was the same as that of the traditional ether network. "Choose" was equally exciting. Everyone was welcome to read it!

The price quoted for contractual translation was usually affected by many factors: 1. ** Language pair **: Common ones such as Chinese-English translation may cost 200 - 400 yuan per 1,000 words; translation between minor languages and Chinese may cost 300 - 500 yuan per 1,000 words. 2. ** The complexity of the agreement **: For general agreements, the terms are relatively common and simple, and the fee is relatively low, about 200 - 300 yuan/1,000 words; for agreements involving complicated legal terms, professional terms, and strict format requirements, the fee may be 350 - 500 yuan/1,000 words. 3. ** Delivery Time **: During the normal delivery period, the above standard charges will be applied. If the customer requests urgent delivery, an additional fee may be added. 4. ** Translator's Quality Requirement **: Standard quality, able to accurately convey the content of the agreement, moderate fee; High quality, accurate language, compliance with legal documents, high fee. In general, the price of the contract translation was about 200 - 500 yuan per thousand words. The specific price still needed to be confirmed in detail. In addition, the word "protocol" has different meanings in different scenarios. In the Internet industry, it has the meaning of "protocol"(for example, the full name of the IP address is Internet Protocol Address). In the political context, it is inclined to reach a political consensus, rule, or speech technique (such as political protocol). In the diplomatic context, it means a set of rules or etiquette (such as diplomatic protocol). When translating the protocol, you need to accurately understand the meaning of these words in different context. "Choose" was equally exciting. Everyone was welcome to read it!

The secure real-time transport protocol (SARFT) was a protocol defined on the basis of the real-time transport protocol. Its main purpose is to provide encryption, message authentication, integrity assurance, and replay protection for the ATM data in unicasting and multicasting applications. In the WebRTong communication scenario, the negotiation of MasterKey and MasterSalt was completed through the negotiation of the NTLS, and then the exchanged keys were used to perform encryption on the Realm Transfer Function (Realm Transfer Function) and the Realm Transfer Function (Realm Transfer Function) to achieve secure transmission. Because the protocol itself does not protect the load data, it may cause the attacker to directly play the audio and video stream after capturing the packet, and the SARFT solved this problem. From a structural point of view, the encrypted portion of the SARFT structure is composed of the following components: the reload, the imprinting, and the pad count (usually only the reload data is encrypted). The verified Portion is composed of the header, the Header extension, and the encrypted Portion. The encrypted portion in the structure of the STCP is the part after the RCP Header. The E-flag explicitly indicates whether the RCP packet is encrypted. The STCP index indicates the serial number of the RCP packet to prevent replay attacks. The part to be verified, the Genuine Portion, is composed of the RCP Header and the encrypted portion. In the protocol, the two-element set < Each stream's Cryptographic Context contains parameters such as SSRC, Cipher, Authentication, and Anti-Replay Data. The Session Key in these parameters is derived by using the Key Derivation Function on the Master Key. Before encryption, both parties need to negotiate the encryption algorithm and the secret key. For example, the negotiation method of sip can be used. In sip, add: a = crypto field to store the encryption type and the secret key, and the secret key also needs to be encrypted. "Choose" was equally exciting. Everyone was welcome to read it!

Go-back- N (GGN): - In the stop-and-wait protocol, the sender can only send one frame at a time, and the channel utilization rate is low. However, the backward N-frame protocol uses a sliding window method, and the sender maintains a set of sending windows, and can send multiple data frames at a time. The receiver uses the method of cumulative confirmation, and the sender moves the sending window forward after receiving the confirmation. When there was a problem (such as frame loss or long delay), the sender used the method of retreating N frames to re-transmit. The timer here was used to recover data frames or confirm the loss of frames, similar to the timer in the pause protocol. Choosing the Repeat protocol: - Different from the N-frame backward protocol, when the receiver receives an out-of-order frame, it will not discard all subsequent frames like the N-frame backward protocol. Instead, it will buffer the correctly received out-of-order frame. When the sender found that a frame was lost, it only retransmitted the lost frame, instead of retransmitting the subsequent N frames from the lost frame like the backward N frames protocol. This could avoid unnecessary data retransmissions and improve transmission efficiency, especially in a poor network environment with a high packet loss rate. Both of these two types of protocol were designed to deal with the loss of frames and the disorder of order during data transmission to improve the reliability and efficiency of data transmission. However, the specific ways in which they dealt with the problem were different. "Choose" was equally exciting. Everyone was welcome to read it!