Plant Sensory Systems and Responses

Plant Sensory Systems and Responses tài liệu, giáo án, bài giảng , luận văn, luận án, đồ án, bài tập lớn về tất cả các l...

Trường Đại Học Công Nghệ Thông Tin – ĐHQG Tp.HCMKhoa Mạng Máy Tính và Truyền thông-----o-o-----Lớp MMT03, Nhóm 2:- NGUYỄN THÀNH MSSV:08520347-NGUYỄN THÀNH VINH MSSV:08520618-NGUYỄN HỮU RU MSSV:08520582-TRƯƠNG VĂN VĨ MSSV:08520470Sau đây là bài dịch chương II trong sách “Principles of Digital Communication Systems and Computer Networks” của nhóm em.Phần I – Các hệ thống truyền thông số(Digital Communation System)Chương 2: Lý Thuyết Thông Tin(Information Theory)Claude Shannon đặt nền móng về lý thuyết thông tin năm 1948. Cuốn sách của ông “A Maththemathical Theroy of Communication ” (Một lý thuyết toán học của sự truyền thông tin) được xuất bản trong Tạp chí Bell System Technical là cơ sở cho sự phát triển toàn bộ viễn thông đã diễn ra trong suốt năm thập kỷ qua. Một sự hiểu biết tốt về các khái niệm được đề xuất bởi Shannon là phải bắt đầu những hiểu biết chuyên về viễn thông. Chúng ta nghiên cứu đóng góp của Shannon trong lĩnh vực thông tin liên lạc hiện đại trong chương này.2.1 Yêu cầu của hệ thống truyền tin (communication system): Trong bất kỳ hệ thống truyền tin, sẽ có một nguồn phát hay nguồn tin(information source) mà nguồn phát này phát ra thông tin dưới một vài hình thức, và một nguồn thu hay nguồn nhận (information sink) thu về thông tin. Sự truyền thông tin là kết nối trung gian giữa nguồn thu và nguồn phát.Mục đích của một hệ thống truyền tin là để truyền tin từ nguồn đến đích mà không có lỗi. Tuy nhiên, sự truyền thông tin luôn luôn có một vài lỗi vì nhiễu. Các yêu cầu cơ bản của hệ thống truyền tin là để truyền thông tin không có lỗi mặc dù có nhiễu.Yêu cầu của hệ thống truyền tin là truyền thông tin từ nguồn đến đích mà không có lỗi, mặc dù thực tế là nhiễu luôn luôn có trong các môi trường truyền thông.2.1.1 Hệ thống truyền tinMột sơ đồ chung cho một hệ thống truyền tin được thể hiện trong hình 2.1. Một nguồn tin có thể phát ra các dạng (chẳng hạn như chữ cái tiếng Anh, ngôn ngữ, video, v.v…) được gửi qua các phương tiện truyền dẫn của máy phát. Các phương tiện truyền thông luôn bị nhiễu, và do đó lỗi phát sinh trong quá trình truyền dữ liệu. Ở đầu tiếp nhận, máy nhận giải mã dữ liệu và đưa nó tới nguồn thu.Hình 2.1: sơ đồ chung của hệ thống truyền tinVí dụ, hãy xem xét một nguồn phát mà nó phát đi hai ký tự A và B. Máy phát mã hóa dữ liệu thành một luồng bít. Ví dụ, A có thể mã hóa thành bít 1 và B mã hóa thành bít 0. Luồng của bit 1 và 0 được truyền qua môi trường. Bởi vì có nhiễu, nên bít 1 có thể trở thành 0 hoặc bít 0 có thể trở thành bít 1 ở ngẫu nhiên bất kỳ chỗ nào, như minh họa dưới đây:Ký tự phát ra: A B B A A A B A B ALuồng bít phát ra: 1 0 0 1 1 1 0 1 0 1Luồng bít nhận: 1 0 0 1 1 1 1 1 0 1Nguồn phát Máy phát Máy thu Nguồn thuNhiễu Tại máy thu, một bít nhận được bị lỗi. Làm thế nào để đảm bảo rằng các dữ liệu nhận được có thể được tự sửa lỗi? Shannon có câu trả lời. Hệ thống truyền tin được đưa ra trong hình 2.1 có thể được mở rộng, như thể hiện trong hình 2.2.Hình 2.2: Sơ đồ chung của hệ thống truyền tin được xuất bởi Shannon.Trong một hệ thống truyền thông kỹ thuật số, do ảnh hưởng của nhiễu, lỗi được phát sinh. Kết quả là,bít 1 có thể trở thành bít 0 và bít 0 có thể trở thành bít 1.Trong sơ đồ khối trên, nguồn phát phát ra các ký hiệu được mã hóa bằng 2 loại mã - mã hóa nguồn và kênh mã hóa – và sau đó biến điệu lên và gửi qua phương tiện truyền thông. Tại nơi nhận, bộ điều chế làm nhiệm vụ giải điều chế, và các hoạt động ngược của mã hóa kênh và mã hóa nguồn (kênh giải mã và giải mã nguồn) được thực hiện. Sau đó thông tin được đưa đến nguồn thu. Mỗi khối được giải thích dưới đây.Theo đề xuất của Shannon, hệ thống truyền tin bao gồm bộ mã hoá nguồn, kênh mã hóa và bộ điều biến vào cuối nơi truyền, và bộ giải điều chế, kênh giải mã và bộ giải mã nguồn vào Plant Sensory Systems and Responses Plant Sensory Systems and Responses Bởi: OpenStaxCollege Animals can respond to environmental factors by moving to a new location Plants, however, are rooted in place and must respond to the surrounding environmental factors Plants have sophisticated systems to detect and respond to light, gravity, temperature, and physical touch Receptors sense environmental factors and relay the information to effector systems—often through intermediate chemical messengers—to bring about plant responses Plant Responses to Light Plants have a number of sophisticated uses for light that go far beyond their ability to photosynthesize low-molecular-weight sugars using only carbon dioxide, light, and water Photomorphogenesis is the growth and development of plants in response to light It allows plants to optimize their use of light and space Photoperiodism is the ability to use light to track time Plants can tell the time of day and time of year by sensing and using various wavelengths of sunlight Phototropism is a directional response that allows plants to grow towards, or even away from, light The sensing of light in the environment is important to plants; it can be crucial for competition and survival The response of plants to light is mediated by different photoreceptors, which are comprised of a protein covalently bonded to a light-absorbing pigment called a chromophore Together, the two are called a chromoprotein The red/far-red and violet-blue regions of the visible light spectrum trigger structural development in plants Sensory photoreceptors absorb light in these particular regions of the visible light spectrum because of the quality of light available in the daylight spectrum In terrestrial habitats, light absorption by chlorophylls peaks in the blue and red regions of the spectrum As light filters through the canopy and the blue and red wavelengths are absorbed, the spectrum shifts to the far-red end, shifting the plant community to those plants better adapted to respond to far-red light Blue-light receptors allow plants to gauge the direction and abundance of sunlight, which is rich in 1/14 Plant Sensory Systems and Responses blue–green emissions Water absorbs red light, which makes the detection of blue light essential for algae and aquatic plants The Phytochrome System and the Red/Far-Red Response The phytochromes are a family of chromoproteins with a linear tetrapyrrole chromophore, similar to the ringed tetrapyrrole light-absorbing head group of chlorophyll Phytochromes have two photo-interconvertible forms: Pr and Pfr Pr absorbs red light (~667 nm) and is immediately converted to Pfr Pfr absorbs far-red light (~730 nm) and is quickly converted back to Pr Absorption of red or far-red light causes a massive change to the shape of the chromophore, altering the conformation and activity of the phytochrome protein to which it is bound Pfr is the physiologically active form of the protein; therefore, exposure to red light yields physiological activity Exposure to far-red light inhibits phytochrome activity Together, the two forms represent the phytochrome system ([link]) The phytochrome system acts as a biological light switch It monitors the level, intensity, duration, and color of environmental light The effect of red light is reversible by immediately shining far-red light on the sample, which converts the chromoprotein to the inactive Pr form Additionally, Pfr can slowly revert to Pr in the dark, or break down over time In all instances, the physiological response induced by red light is reversed The active form of phytochrome (Pfr) can directly activate other molecules in the cytoplasm, or it can be trafficked to the nucleus, where it directly activates or represses specific gene expression Once the phytochrome system evolved, plants adapted it to serve a variety of needs Unfiltered, full sunlight contains much more red light than far-red light Because chlorophyll absorbs strongly in the red region of the visible spectrum, but not in the farred region, any plant in the shade of another plant on the forest floor will be exposed to red-depleted, far-red-enriched light The preponderance of far-red light converts phytochrome in the shaded leaves to the Pr (inactive) form, slowing growth The nearest non-shaded (or even less-shaded) areas on the forest floor have more red light; leaves exposed to these areas sense the red light, which activates the Pfr form and induces growth In short, plant shoots use the phytochrome system to grow away from shade and towards light Because competition for light is so fierce in a dense plant community, the evolutionary advantages of the phytochrome system are obvious In seeds, the phytochrome system is not used to determine direction and quality of light (shaded versus unshaded) Instead, is it used merely to determine if there is any light at all This is especially important in species with very small seeds, such as lettuce Because of their size, ...Abstract of thesis entitled “A Study of Channel Estimation for OFDM Systems and System Capacity for MIMO-OFDM Systems” Submitted by Zhou Wen For the degree of Doctor of Philosophy at the university of Hong Kong in July 2010 This thesis concerns about two issues for the next generation of wireless communications, namely, the channel estimation for orthogonal frequency-division multiplexing (OFDM) systems and the multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system capacity. For channel estimation for OFDM systems over quasi-static fading channels having resolvable mulitipath number L, a novel fast linear minimum mean square error (LMMSE) channel estimation method is proposed and investigated. The proposed algorithm deploys Fourier transform (FFT) and the computational complexity is therefore significantly reduced to O(Nplog2(Np)), as compared to that of O(Np3) for the conventional LMMSE method, where the notation O(·) is the Bachmann–Landau function and Np is the number of pilots for an OFDM symbol. The normalized mean square errors (NMSE) are derived in closed-form expressions. Numerical results show that the NMSE is marginally the same with that of the conventional LMMSE for signal to noise ratio (SNR) ranges from 0 dB to 25 dB. For channel estimation for OFDM systems over fast fading and dispersive channels, a novel channel estimation and data detection method is proposed to reduce the inter-carrier interference (ICI). A new pilot pattern composed of the comb-type and the grouped pilot pattern is proposed. A closed-form expression for channel estimation mean square error (MSE) has been derived. For SNR = 15 dB, normalized Doppler shift of 0.06, and L = 6, both computer simulation and numerical results have consistently shown that the ICI is reduced by 70.6% and 43.2%, respectively for channel estimation MSE and bit error rate (BER). The pilot number per OFDM symbol is also reduced significantly by 92.3%, as compared to the comb-type pilot pattern. A closed-form mathematic expression has been proposed for the capacity of the closed-loop MIMO-OFDM systems with imperfect feedback channel. The lower threshold of feedback SNR is derived. For L = 6, numerical results show that the lower threshold of feedback SNR is proportional to antenna numbers N′ and system SNR. The increasing rate of the feedback SNR threshold increases from 0.82 to 1.01 when N′ increases from 2 to 16. The variance and mean of OFDM system capacity over Rayleigh channels and Ricean channels have been respectively investigated that the closed-form expression for the capacity variance has been proposed. The resultant system capacity variances over the two channels are respectively evaluated by numerical method and also verified by computer simulation. The joint probability density function (PDF) of two arbitrary correlated Ricean random variables has also been derived in an integral form. Numerical results reveal that the variance of OFDM system is proportional to SNR and inversely proportional to L for the two channels respectively. For the same two respective channels, the variance marginally increases with a linear rate of 0.166 bit2/dB and 0.125 bit2/dB, when L = 2 and SNR ranges PLANT SYSTEMS FOR EXPRESSION PLANT SYSTEMS FOR EXPRESSION OF RECOMBINANT PROTEINS OF RECOMBINANT PROTEINS 1 1 Assoc. Prof. Dr. Chu Hoang Ha Plant Cell Biotechnology Department (PCB) Institute of Biotechnology (IBT) A teaching module of “Expression Systems and bioreactions” Unit Hanoi 12/2011 Why plant systems are used ? Why plant systems are used ?  Cheaper than mammalian, insect, or prokaryotic Cheaper than mammalian, insect, or prokaryotic systems systems  Agricultural infrastructure already in place Agricultural infrastructure already in place  Easy to scale-up Easy to scale-up  No human pathogens, endotoxins in plants No human pathogens, endotoxins in plants  Correct folding, modifications Correct folding, modifications  High volume High volume  Direct use Direct use 2 2 4 4 What kind of plants are What kind of plants are used as host? used as host?  Transgenic plants Transgenic plants including including Cereal plants Cereal plants Fruit plants Fruit plants Leguminous plants Leguminous plants Vegetable plants Vegetable plants 6 6 “ “ High level expression is essential High level expression is essential for economic recombinant protein for economic recombinant protein production” production”  Offset costs of production, purification Offset costs of production, purification  Compete with other sources Compete with other sources  Ensure efficacy Ensure efficacy To date… • Few small-scale products have reached market • Not produced economically on large-scale 8 8 Types of plant expression systems Types of plant expression systems  On the basis of compartmentation of recombinant proteins On the basis of compartmentation of recombinant proteins b) By transient expression of genetically engineered viruses 10 10 6 Future Trends: Fourth Generation (4G) Systems and Beyond 6.1 Introduction By looking back to the history of wireless systems, one can reach the conclusion that the industry follows a ten-year cycle. First generation systems were introduced in 1981 followed by the deployment of second generation systems in 1991, ten years later. Moreover, third generation systems are due for deployment in 2001–2002. From the point of view of services, 1G systems offered only voice services, 2G systems also offered support for a primitive type of low-speed data services and 3G systems will enable a vast number of advanced voice and high-speed data services. The trend is towards support for even advanced data services. 3G networks, although having the advantage of support for IP and enhanced mobility, will suffer from a divergence between several standards. This divergence will limit easy roaming between 3G networks based on different standards, thus limiting user mobility. Furthermore, 3G networks will have, in the best case, an upper capacity limit of 2 Mbps. Although more than enough for the application demands of the years to come, 3G networks will most likely need to evolve in order to meet the mobile application demands of the next decades. As in all areas of technology, the quest for better and more efficient systems never ends and as soon as the time for deployment of a system comes, research on the next generation is usually under way. Consequently, the imminent deployment of 3G systems is accompanied by initiation of research on the next generation of systems. If the ten-year cycle continues, it is logical to expect that the next generation of wireless systems, known as Fourth Generation (4G), will reach deployment stage somewhere around 2010. As seen later in the chapter, the vision for 4G and future systems is towards unification of various mobile and wireless networks. However, there is a fundamental difference between wireless cellular and wireless data networks, such as WLANs. The difference is that cellular systems are commonly circuit-switched, meaning that for a certain call, a connection estab- lishment has to take place prior to the call. On the contrary, wireless data networks are packet- switched. It is expected that the evolution of wireless networks towards an integrated system will produce a common packet-switched (possibly IP-based) platform for wireless systems, thus enabling the ‘wireless Internet’. However, in order for such an integration to take place research is needed in order to provide interoperability between wireless cellular networks and wireless data networks. The envisioned unified platform for the next generations of wireless networks will provide transparent integration with the wired networks and enable users to seamlessly access multimedia contents such as voice, data and video, irrespective of the access methods of the various wireless networks involved. The next generations of wireless networks target the market of 2010 and beyond, aiming to offer increased data rates with reports mentioning from 50 Mbps to 155 Mbps. In the course of their development many different types of issues (technical, economical, etc.) must be studied and resolved. Some of them, such as the development of even more efficient modulation techniques, identification of new spectrum, and developments in battery technology/power consumption, are quite straightforward and have been identified during 2G and 3G research and development stages. Other issues are not so clear and are heavily dependent on the evolution of the telecommunications market and society in general. These issues need to be identified and resolved at 2Apr il 2003, 17:00:47 The Complete FreeBSD (filesys.mm), page 181 10 File systems and devices In this chapter: • File permissions • Mandator y Access Control • Links • Director y hierarchy • File system types • Mounting file systems • FreeBSD devices • Vir tual ter minals In this chapter: • File permissions • Mandator y Access Control • Links • Director y hierarchy • File system types • Mounting file systems • FreeBSD devices • Vir tual ter minals One of the most revolutionary concepts of the UNIX operating system was its file system, the way in which it stores data. Although most other operating systems have copied it since then, including Microsoft’splatforms, none have come close to the elegance with which it is implemented. Manyaspects of the file system are not immediately obvious, some of them not eventoseasoned UNIX users. We’v e already looked at file naming conventions on page 125. In the next section, we’ll look at the file system access, structure and hierarchy, and on page 195 we’ll look at how the file system treats hardware devices as files. File permissions AUNIX system may potentially be used by manypeople, so UNIX includes a method of protecting data from access by unauthorized persons. Every file has three items of information associated with it that describe who can access it in what manner: • The file owner,the user ID of the person who owns the file. • The file group,the group ID of the group that ‘‘owns’’the file. • Alist of what the owner,the group and other people can do with the file. The possible actions are reading, writing or executing. filesys.mm,v v4.17 (2003/04/02 06:43:57) 181 File permissions 182 2April 2003, 17:00:47 The Complete FreeBSD ( /tools/tmac.Mn), page 182 Forexample, you might have a program that accesses private data, and you want to be sure that only you can execute it. Youdothis by setting the permissions so that only the owner can execute it. Or you might have a textdocument in development, and you want to be sure that you are the only person who can change it. On the other hand, the people who work with you have a need to be able to refer to the document. Youset the permissions so that only the owner can write it, that the owner and group can read it, and, because it’snot ready for publication yet, you don’tallowanybody else to access it. Traditionally,the permissions are represented by three groups of rwx: r stands for read permission, w stands for write permission, and x stands for execute permission. The three groups represent the permissions for the owner,the group and others respectively.Ifthe permission is not granted, it is represented by a hyphen (-). Thus, the permissions for the program I discussed above would be r-x------ (I can read and execute the program, and nobody else can do anything with it). The permissions for the draft document would be rw-r----- (I can read and write, the group can read, and others can’taccess it). Typical FreeBSD file access permissions are rwxr-xr-x for programs and rw-r--r-- for other system files. In some cases, however, you’ll find that other permissions are required.For example, the file ˜/.rhosts,which is used by some network programs for user validation, may contain the user’spassword in legible form. To help ensure that other people don’tread it, the network programs refuse to read it unless its permissions are rw-------.The vast majority of system problems in UNIX can be traced to incorrect permissions, so you should pay particular attention to them. Apart from these access permissions, executables can also have two bits set to specify the access permissions of the process when it is run. If the setuid (set user ID)bit is set, the process always runs as if it had been started by its owner.Ifthe setgid (set group ID)bit is set, it runs as if it had been started by its group. This is frequently .. .Plant Sensory Systems and Responses blue–green emissions Water absorbs red light, which makes the detection of blue light essential for algae and aquatic plants The Phytochrome System and. .. been studied the longest and is the best understood 4/14 Plant Sensory Systems and Responses In their 1880 treatise The Power of Movements in Plants, Charles Darwin and his son Francis first... response Link to Learning 5/14 Plant Sensory Systems and Responses Use the navigation menu in the left panel of this website to view images of plants in motion Plant Responses to Gravity Whether