Southern blotting application Assignment Example | Topics and Well Written Essays - 750 words

Southern blotting application - Assignment Example A labeled DNA sequence is usually an RFLP probe that hybridizes with either a single or multiple fragments of the digested DNA sample after separation by gel electrophoresis resulting to showing a unique blotting pattern attributed to a genotype that is specific to a locus. RFLP probes are usually short, single or low copy genomic DNA or cDNA clones. Application of RFLP probes are usually used in variation analysis such as in paternity tests, ping and diagnosis of hereditary diseases. RFLP probes are also used in genome mapping. RFLPs are detected by using restriction enzyme that can recognize and fragment a sample of DNA where there is a specific short sequence. This step is known as restriction enzyme digestion. Single nucleotide polymorphisms can either create or destroy restriction endonuclease recognition sites therefore affecting the length and the quantity of DNA fragments resulting from restriction enzyme digestion. Agarose gel electrophoresis separates the resulting DNA fragments and transferred to a membrane through a Southern blot procedure. The membrane is a paper like matrix made up of nitrocellulose and usually has a slight positive charge. The fragment lengths that are complementary to the RFLP probes and are considered as alleles in genetic analysis is determined by the hybridization of the membrane to the labeled DNA probe (National Center for Biotechnology Information ). In developing RFLP probes, a methylation sensitive enzyme digests the total DNA thus enriching the library for sequences that are single or low copy expressed. The digested DNA is size fractionated on preparative agarose gel and excision, elusion and cloning into plasmid vector of is done. The digested plasmids are consequently screened for inserts. Total sheared DNA can be used to probe southern blots of the inserts to select clones that can hybridise to single and low copy sequences. Genomic DNA of different genotypes

Pay Structures, Pay & Merit Assignment Example | Topics and Well Written Essays - 500 words

Pay Structures, Pay & Merit - Assignment Example Executive compensation differs from sales or human resource personnel on the ground that executive compensation involves negotiation between the executive and the employer (Peter, 2002). Thus, it is negotiated and agreed on unlike other employees whose compensations are spelt out in advance. Executive offer letter is more detailed comprising a variety of options such as housing agreements, bonuses, incentives, guaranteed service pack in case of termination of employment, and income protection guarantees in the event of sale or other liquidity event resulting to change in the company administration. All these benefits and variety of options are not available to other employees. Offering of more lucrative salary to executives is made in a bid to attract, motivate, and retain executive officers who have the capability of leading and managing business successfully, link an organization cash incentives with measurable performance align their interests with the company’s’ interests to achieve long-term goals. This has contradicting effects on low paid employees. In some instances, it motivates them to work hard and acquire the executives in order to receive such compensation in future. In other situations, low paid employees are demotivated, arguing that they are the ones who do most of the work, but executives ends up receiving more compensation than them (Worldatwork, 2007). During survival mode, reduction of staff compensation strategy may be preventing layoffs, but an organization may end up losing its top talent. As a human resource manager, I would adopt a pay-for-performance strategy. In implementing this strategy, I would let them be aware that each of them will be compensated with the same amount of monetary value he or she will create for the company, with little basic salary as benchmark. For top management, I will make them realize that their success is counted on how the organization successfully attains its goals (Peter, 2002).

Global Warming Outline Essay Example for Free

Global Warming Outline Essay Pierre de Fermat was born in Beaumont-de-Lomagne, France in August of 1601 and died in 1665. He is considered to be one of the greatest mathematicians of the seventeenth century. Fermat is considered to be one of the fathers of analytic geometry. Fermat along with Blaise Pascal is also considered to be one of the founders of probability theory. Fermat also made contributions in the field of optics and provided a law on light travel and made wrote a few papers about calculus well before Isaac Newton and Gottfried Leibniz were actually born. Fermats most important work was done in the development of modern number theory which was one of his favorite areas in math. He is best remembered for his number theory, in particular for Fermats Last Theorem. This theorem states that: xn + yn = zn has no non-zero integer solutions for x, y and z when n is greater than 2. Fermat almost certainly wrote the marginal note around 1630, when he first studied Diophantuss Arithmetic. It may well be that Fermat realized that his prove was wrong, however, since all his other theorems were stated and restated in challenge problems that Fermat sent to other mathematicians. Although the special cases of n = 3 and n = 4 were issued as challenges the general theorem was never mentioned again by Fermat. In fact in all the mathematical work left by Fermat there is only one proof. Fermat proves that the area of a right trangle cannot be a square. See more: what is essay format Meaning that a rational triangle cannot be a rational square. In symbols, there do not exist integers x, y, z with x2 + y2 = z2 such that xy/2 is a square. From this it is easy to deduce the n = 4 case of Fermats theorem. The proof of Fermats Last Theorem marks the end of a mathematical era. Since all of the tools which were brought to bear on the problem still had to be invented in the time of Fermat. Judging by the tenacity with which the problem wa for so long, Fermats alleged proof seems likely to have been illusionary. This conclusion is further supported by the fact that Fermat searched for proofs for the cases and , which would have been superfluous had he actually been in possession of a general proof.

Challenges Faced by Managers in the Public Sector

Challenges Faced by Managers in the Public Sector There are different levels of management in the three different sectors of the economy. There are non-managerial employees, first-line managers, middle managers and the top managers. Robbins et al ;( 2009). This essay will critically evaluate the challenges faced by managers in the public sector organisations. The essay will assess the roles of the manager in this sector and the difficulties managers encounter whilst carrying out their duties. The challenges posed by organisational structure and design with an example from the Northampton Borough Council, the issues due to the organisational culture, privatisation of some of the public sector services, the strategic management of the public sector and the complexities due to the constant changing environment in which these organisations operate, and the challenges to managers of the most recent comprehensive budget cuts, will be evaluated in this essay. The typical roles of a manager in any organisation is to organise, lead, plan and control the activities of the people and other resources within it towards achieving the objectives of that organisation; Naylor (2004). The role a manager plays is dependent on the level of management position although each level has its challenges. At the senior level, the managers role is much broader and in depth and it requires creativity and innovativeness; Robbins et al (2009). The senior manager is involved in decision making, strategic management planning and control, the manager, at this level of management is expected to have an understanding of all areas of the organisation to enable sensible handling of any given situation Hanagan;(2008). The role of the manager did not change in the 21st century rather the method of carrying out the above mentioned roles are different, for instance the manager has to organise work differently, communication is more sophisticated such as, the use of internet, mobile telephones and e-mail. In recent times, the management of change is considered as the most important skill of management due to the pace of change in the 21st century Hanagan, (2008).The rapid changes in technology, enormous improvements in communication, the increase in focus on global economy, and the environment are issues to the modern day manager. In addition to the above, the role of the manager in the public sector is challenged by the constant changes in legislation and political policies subject to government in power Hanagan (2008). An organisation is an arrangement which has been set up for a particular purpose. Robbins et al (2009). Different organisations belong to different sectors of the economy. There are three sectors; the public, the private and the third sector such as social enterprises. This three sectors have some common characteristics which are: they all have distinct purpose, each organisation is made up of people, and all create a structure within which the people could carry out their duties Robbins et al(2009). Organisations are grouped as public sector depending on certain factors such as; how much the organisation competes with similar organisations, goods and services are charged indirectly and how much it allows itself to be influenced by demand and supply of goods and services. The less such organisations are influenced by the above factors the more the organisations are considered as public sector organisations Hanagan (2008). Instances of these organisations are; Local Government council, Libraries, the National Police Force, the Defence Ministry, Colleges and Universities. The common features of these organisations are; they are set up to fulfil specific purposes, they are service motivated, they are accountable to many stakeholders and the public, they carry out their duties for the good of the people and they are funded through the use of taxpayers money. Avery important challenge to a manager whether in the public sector or in the private sector is to be aware of their relevant s takeholders and operate the organisation in ways which will yield maximum returns to each stakeholder group Bloisi et al (2007). The public sector organisation has a centralised organisational structure whereby authority and decision making is made at the senior managerial level. Organisational structure is a connected arrangement of positions and work units through which the important tasks of an organisation are subdivided and categorised to form decision centres from where the strategic plans of the organisation are carried out Bloisi et al (2007). Most of these organisations have a Matrix design structure which enables double responsibility and reporting roles with particular projects. Bloisi et al (2007). The managers in the matrix organisation are challenged by the constant need to resolve conflicts due to differences in perspectives and priority Bloisi et al (2007). For instance, the organisational structure of the Northampton Borough Council has over five managerial levels of management. According to Nicole Macdonald, a HR Manager Strategy with the council, one of the challenges they have is getting approval to carry out plans as quickly as possible. The council has about forty-seven councillors through whom decisions are made. These councillors represent different political fronts. Sometimes it is difficult to reach a consensus on certain issues and therefore arriving at a decision is elongated said, Cassie Triggs, a Democratic Chief Executive Services Manager at the Northampton Borough Council. The manager in the private sector will in relation to their organisational structure which is much flatter be able to arrive at a decision much quicker. Private sector organisational structures are designed to embrace the pace of changes in technology and also to survive. Flatter structure allows for incorporation of ideas from almost every employee in the organisation Bloisi et al (2007). The manager in the private sector will be challenged by how to control an employee wh o is working from home and coming to the place of work only one day in a working week Naylor (2004). Included in the challenges encountered by managers in the public sector are challenges due to the cultural beliefs of the organisation. Organisational culture is the way we do things around here Robbins et al (2009). According to Meek (1988), organisational culture could be used as a means to find out how people behave in a complex setting Hanagan, (2008). Organisational culture can be something abstract or peoples perception and experience within an organised setting. According to Stacey, the culture of any group of people is that set of beliefs, customs, practices and ways of thinking that they have come to share with each other through being and working together. Hanagan (2008). According to Handy, there are four major types of organisational cultures; the power culture in which the power and authority is from one person in a central position, the role culture which is labelled as a bureaucracy where the role of the individual specialists are more important than position and power , the task culture is about the activity which is being carried out and lastly the person culture which focuses more on what individuals do in a particular setting Mullins (2005). The challenge of managing cultural change in a public sector organisation will depend on how strong the existing culture is and the weight of the proposed change Hanagan (2008).The difficulty is in bringing about the change. For instance the Further and Higher Education Act which made colleges and higher education in England to become Corporate Bodies Limited by Guarantee indicates that organisational culture can be overtaken by accountability to more prominent stakeholders as the organisation would want to survive Hanagan (2008). The challenge is even more where there is existence of subcultures within the organisation. For decades, Public organisations have been managed by people who have been raised into managerial positions through years of service to the organisation, for instance; football clubs were managed by ex-footballers, and schools were managed by former teachers, local government council by people who were promoted through long years of service Hanagan (2008). There are difficulties faced by managers moving from the private sector to the public sector. The manager from the private sector is more focused on profits and accounting to shareholders, decision making is simplified, there is much flexibility and autonomy, there is power and authority attached therefore, the challenge to the private sector manager moving into the public sector will be changing the profit making, quick decision making mindset, there is less power and authority, no flexibility and autonomy Hanagan (2008). These challenges are not without approaches with which the managers could use to minimise them. For instance, the managers could use the recruitment process to recruit people who will fit into the existing culture, by the method of questioning they are made aware of what is important in the organisation, the induction process, promotion policy, training and development Hanagan (2008). Following the challenges posed by organisational structure, design and culture, are the challenges which managers face with the move of the UK government in the 1980s to privatise some of the services of the public sector when they realised that the costs of providing services were becoming too much, costs were weighing much on National budgets and the motive to make public sector organisations to work more effectively and efficiently Hanagan (2008). The move gave rise to such contractual arrangements as the Public Private Partnership (PPP) and the London underground contractual arrangement which came from a simpler Private Finance Initiative (PFI) which was set up to establish contracts between the local authority controlled London Underground and Tubelines and Metronet Hanagan (2008). Privatisation as defined by Bryan Hurl (1992), is the sale of government owned equity in nationalised industries or other commercial enterprises, to private investors with or without the loss of government control of the organisation. There are three methods which have been used by the government, these are; denationalisation which is the sale of public sector assets, deregulation which is removal of barriers to entry to a previously protected market to allow private enterprises to compete and franchising whereby the public sector provides the finance and the private sector provide the services Hurl (1992). One of the key principles of managing resources to deliver better services is by setting up strong partnerships which means that various departments of the public sector are relying on other public, private and third sector to deliver public services, these organisations, most of the time may have better expertise and better understanding of the needs of the citizens Bourn (2003, p26). The increasing difficulty with which public services are delivered is a challenge. According to the National Audit Office, delivery of public services are no longer the duty of a single department for instance, different organisations are involved in provision of criminal justice such as the police, the crown prosecution service, the forensic Science service and the courts. Changes in economic conditions and unforeseen circumstances could place much demand for public services, for instance, the sudden rise in unemployment during the most recent inflationary period. The volume and value of benefits payment made by the job centre plus or the unexpected foot and mouth disease and its effect to the public requires a good resource management Bourn (2003 p18). Some of the services provided by the public sector organisations are; Defence by the Army, Public Health by the NHS, Direct service delivery agencies which handle payments of benefits, issuing of prescriptions and National insurance numbers, processing of student loans, access to heritage, museums and galleries, developing frameworks for other service providers such as regulation of educational standards, teacher training and social housing, promotion of business opportunities abroad, transport integration, purchasing information technology systems and professional services and others. The challenge to the manager is the ability to coordinate and monitor the different service chains involved in the delivery of public services and also the difficulty in ensuring that resources are channelled appropriately to the provision of the most required service Bourn (2003 p.20) . Strategic thinking, planning and continuous are important in every organisation Bloisi et al (2007). Strategic thinking means being able as a manager to device ways to balance both the human, technical and the limited resources of the organisation and the environmental forces Bloisi et al (2007). The public sector manager has no power and authority, no autonomy and flexibility and therefore may not have as much influence in the decision making as their counterpart in the private sector Hanagan (2008). Strategic management is used in the public sector to find out schedules of activities in the sector which fit into the political agendas taking into consideration the politicians who might be looking for quick returns which they can point to as their successes and achievements Hanagan (2008). This means that the strategic planning has to be short term. There is lack of clarity in relation to what the manager is trying to achieve. There is the constant challenge to the manager in the public sector as to whether you are trying to fulfil your statutory obligation, please the politicians, follow the directions of the board or the people for whom the services were meant for. The manager in the public sector is challenged as he cannot change or alter the system. There are too many stakeholders, interest groups to satisfy in the public sector therefore the manager in this sector has to device different kinds of ways to deliver information to the different groups in the public who believes they have a stake in the public sector, such methods are through, governing bodies, advisory committees, taskforces, public meetings and public announcements Hanagan (2008). The manager in the private sector uses strategic management to review actions, slow down processes and hence make changes where necessary, the manager in the private sector has a profit making mindset and therefore considers product viability, the private secto r manager has power and authority, flexibility and autonomy and therefore decision making is quicker. The private sector manager is accountable to shareholders Bloisi et al (2007). The public sector is funded by the government and the managers are accountable to whichever ruling political party at any given time. According to the National Audit Office, before the 1998 public service agreements, different departments were funded annually with some exception such as the Department of Health, so there was uncertainty as to whether funding will be the same as the previous year or reduced or increased. This was a challenge to managers as there was no certainty with the flow of funds to make long term plans as the private sector with assurance of long term financing. The agreement was set out with the awareness of the aims, ideals and targets of the various departments Bourn (2003 p.20). Assessed so far are internal factors which challenge managers in the public sector however there are certain external factors which managers have to contend with as well. Some of these are; the speed of technology which has affected every process in organisations irrespective of sector, the force of competing interests who are not ordinary rivals to gain customers but those seeking for resources and those trying to make their points to be heard and the fluctuations in social behaviour which starts with movements in peoples expectations and values Bloisi et al (2007). Finally, managers are currently facing challenges due to the recent comprehensive budget cut. There is greater demand for services however there are fewer resources to meet demand. It is morally challenging to managers to prioritize who to help and who not to In conclusion, Suggested approaches from management science which could alleviate some of the challenges are; the systems approach and contingency approach. With systems approach, managers could discuss their departmental needs in terms of the general organisational requirement. The use of this approach requires open communication and the removal of barriers between the individual departments, also the approach shows management consideration of all the systems involved, synergy that is the whole is greater than the sum of its parts, open and closed systems, limits, movements of information, materials and feedback through which the manager could monitor and evaluate progress reports Hanagan (2008). The second recommended approach is the contingency approach. This approach says that different problems requires different ways of solving them it all depends on how much experience the manager has because what might work well in one situation may not work well in another situation Hanagan (2008). Applica tion of this approach requires that the manager recognises several view points, one of which is the pragmatic view point. Pragmatic viewpoint says that no approach is generally acceptable which means that the manager has to check the motives for every action taken for instance, the services being delivered, the availability of equipment required and also the internal and external environment Hanagan (2008).

It’s Time to Tell the True History of Texas :: Personal Narrative

It’s Time to Tell the True History of Texas When the Bob Bullock Texas State History museum opened in March 2001, it advertised itself as â€Å"The Story of Texas.† It still calls itself the story of Texas in letters chiseled into the top of the building, on its Web site, on signs directing visitors to the museum, and even on the refrigerator magnets you can buy in the gift shop. When I first saw the slogan, I wondered how there could be â€Å"the† story of Texas, since Texas has been culturally diverse throughout its history as a part of Mexico that became a separate nation and later a state. Shortly Texas will have no one group as a majority. I grew up in the Rio Grande Valley, where the great majority of the population, like me, is Mexican American. How was this new museum going to present my story? I had to go and find out.   Ã‚  Ã‚  Ã‚  Ã‚  When I first walked into the lobby, I noticed the large mosaic on the floor but I couldn’t figure out what it depicted. I just saw a campfire and a bunch of wiggly figures. Someone next to me told their kids that they’d be able to see the entire mosaic from the third floor. I decided to wait and do the same.   Ã‚  Ã‚  Ã‚  Ã‚     Ã‚  Ã‚  Ã‚  Ã‚  The first exhibit I saw was the â€Å"It Ain’t Braggin’ if it’s True† (one of my friends told me I had to see the shrine to Lance Armstrong and the rhinestone car). The name of the exhibit didn’t make much sense to me though; aren’t all museum exhibits, especially ones about history, supposed to be true? The big banner in the middle of the room didn’t help much either. It simply said â€Å"Vision† and had a quote about how only those with great vision can see opportunity where others see empty space. Maybe those who have this type of vision get the braggin’ rights?   Ã‚  Ã‚  Ã‚  Ã‚  Texas was never a big empty space. The Spaniards and later the French who came here discovered cultures that were centuries old. But history, and the museum itself, begins with European colonization. The history of Texas, one of the signs says, was shaped by the way the different groups of people who came to Texas responded to the land and to each other. So land, and interaction between different groups of people, would be used a lot in the telling of this story of Texas, I assumed.

Free Essays: Antigone and Ismene in Oedipus at Colonus :: Oedipus at Colonus Essays

Antigone and Ismene in Oedipus at Colonus "Behold this Oedipus, --/ him who knew the famous riddles and was a man most masterful;/ not a citizen who did not look with envy on his lot-- see him now and see the breakers of misfortune swallow him!" (Oedipus the King, 1524-1527). Now that Oedipus has lost everything-- his wife, mother, kingdom, and all power-- his existence rests entirely on the aid of his two daughters. However, that dependence is not evenly distributed between Antigone and Ismene. Even though both daughters provide assistance to Oedipus, the relationship that Oedipus has with Ismene is weaker in comparison to the firm and unwavering relationship that he has with Antigone. Oedipus's incompetence is evident from the very beginning of the play, explaining why he relies on Antigone time and again. When they arrive at the sacred grove at Colonus, Oedipus asks Antigone to leave him and find out if anyone lives nearby, and she says that she can see a man approaching. To which Oedipus follows with more inquiries: "Is he coming this way? Has he started towards us?" (I, 30). Even after the stranger leaves, Oedipus cannot tell that he has exited until Antigone tells him so. Antigone also aids Oedipus by warning him that she sees the Chorus approaching. Oedipus, once a great intellectual, is not even capable of responding to a simple request of his name without the aid of Antigone: "My child, what can I say to them?" (ii, 214). Additionally, Oedipus seems to need help with every little move he makes, even for the mere act of being seated: "Help me sit down; take care of the blind man." (I, 21). Luckily for Oedipus, his relationship with Antigone reach es a point where Antigone no longer needs instructions from her father; it is assured that she will help him: "After so long, you need not tell me father" (I, 22). Even though Antigone helps her father with everything, Oedipus's reliance on Antigone seems to weigh greatly on her ability to see for him, emphasizing Oedipus's blindness and impotence, as well as the strength of Oedipus's relationship with Antigone. Oedipus and Antigone have a mutual commitment to each other, supporting the fact that their rapport is greater than the attachment between Oedipus and Ismene.

Android Essay

|Google Android |November 15 | | |2011 | |An operating system for mobile devices such as smartphones and tablet computers. Developed by the Open |Operating System | |Handset Alliance led by Google. | | Table of Contents Introduction3 About 4 Architecture7 System Threading11 CPU Scheduling 12 Process States14 Memory Management18 Synchronization Techniques19 Event Handling 20 Security21 Networking22 Evaluation23 Bibliography24 Introduction Since its initial launch on the T-Mobile G1 in October of 2008, Google's Android operating system has evolved rapidly, perhaps more rapidly than any other operating system in recent memory, to become one of the most important and prolific smartphone platforms in the market today. The Android OS is the name of the Linux based operating system owned by Google and supported by the Open Handset Alliance. Android is used as an operating system for devices such as cell phones, tablets and netbooks. Google bought the original developer of the software, Android Inc. , in 2005. Android's kernel (core of the OS) was derived from Linux but has been modified by Google developers. Android is also open source, which means developers can customize the OS for different phones and applications. This is why different phones may have different looking graphical interfaces and features even though they are running the same OS. Android OS is completely open source, which means that developers can use the core OS functions to develop applications, unlike iphone OS which is a closed system. About The version history of the Android operating system began with the release of version 1. 0 in September 2008. Android is a mobile operating system developed by Google and the Open Handset Alliance. Android has seen a number of updates since its original release. These updates to the base operating system typically fix bugs and add new features. Generally, each version is developed under a code name based on a dessert item. The code names were released in alphabetic order: Cupcake, Donut, Eclair, Froyo, Gingerbread, Honeycomb, and Ice Cream Sandwich. Like Apple's Appstore, Google opened its Android market, allowing the apps developers to publish their apps without any restrictions. Unlike Apple's Appstore, Google Android market does not have any restrictions for third party development and will not run an apps approval system. Android is an open source platform. The entire stack, from low-level Linux modules all the way to native libraries, and from the application framework to complete applications, is totally open. More so, Android is licensed under business-friendly licenses (Apache/MIT) so that others can freely extend it and use it for variety of purposes. Even some third-party open source libraries that were brought into the Android stack were rewritten under new license terms. Therefore, every developer has access to the entire platform source code. There are several advantages of the Android OS for developers, besides the fact that it’s completely open source, let’s mention a few: Advantages [pic] †¢ The entire Application framework can be reused and replaced by selective components Wi-Fi network applications support (Depends on hardware) †¢ Dalvik[1] virtual machine enhances the power management systems †¢ Supports 2D and 3D graphics †¢ Supports common media file formats †¢ Reliable and enhanced data storage using SQLite framework[2] †¢ Open source Web-Kit Engine-based web-browser †¢ GPS, Navigational compass, Touch-Unlock, and acceleromet er applications support †¢ Androids development environment includes a device emulator, debugger, performance profiling tool, and an Eclipse IDE plug-in [pic] Logo of Android OS Architecture [pic] The main components of the Android architecture: 1. Applications: These are applications written in Java. Some of basic applications include a calendar, email client, SMS program, maps, making phone calls, accessing the Web browser, accessing your contacts list and others. [pic] 2. Application Framework: This is the skeleton or framework which all android developers has to follow. The developers can access all framework APIs an manage phone’s basic functions like resource allocation, switching between processes or programs, telephone applications, and keeping track of the phone’s physical location. The architecture is well designed to simplify the reuse of components. Think of the application framework as a set of basic tools with which a developer can build much more complex tools. [pic] 3. Libraries: This layer consists of Android libraries written in C, C++, and used by various systems. These libraries tell the device how to handle different kinds of data and are exposed to Android developers via Android Application framework. Some of these libraries include media , graphics, 3D, SQLite, web browser library etc. The Android runtime layer which includes set of core java libraries and DVM (Dalvik Virtual Machine) is also located in same layer. [pic] 4. Runtime Android: This layer includes set of base libraries that are required for java libraries. Every Android application gets its own instance of Dalvik virtual machine. Dalvik has been written so that a device can run multiple VMs efficiently and it executes files in executable (. Dex) optimized for minimum memory. [pic] 5. Kernel – Linux: This layer includes Android’s memory management programs, security settings, power management software and several drivers for hardware, file system access, networking and inter-process-communication. The kernel also acts as an abstraction layer between hardware and the rest of the software stack. pic] The basics of the Android kernel are just like any other monolithic architecture, all services (file system, VFS, device drivers, etc. ) as well as core functionality (scheduling, memory allocation, etc) are a tight knit group sharing the same space. The kernel of this system is both a hybrid and a monolithic modular design. It is br oken down into five major subsystems: †¢ Process Scheduler: (SCHED) responsible for controlling process access to the CPU. The scheduler enforces a policy that ensures that processes will have fair access to the CPU, while ensuring that necessary hardware actions are performed by the kernel on time. Memory Manager: (MM) permits multiple processes to securely share the machine's main memory system. In addition, the memory manager supports virtual memory that allows Linux to support processes that use more memory than is available in the system. Unused memory is swapped out to persistent storage using the file system then swapped back in when it is needed. †¢ Virtual File System: (VFS) abstracts the details of the variety of hardware devices by presenting a common file interface to all devices. In addition, the VFS supports several file system formats that are compatible with other operating systems. Network Interface: (NET) provides access to several networking standards an d a variety of network hardware. †¢ Inter-Process Communication: (IPC) subsystem supports several mechanisms for process-to-process communication on a single Linux system. System Threading By default, an Android application runs on a single thread[3]. Single-threaded applications run all commands serially, meaning the next command is not completed until the previous one is done. Another way of saying this is that each call is blocking. This single thread is also known as the UI thread because it’s the thread that processes all the user interface commands as well. The UI thread is responsible for drawing all the elements on the screen as well as processing all the user events, such as touches on the screen, clicks of the button, and so on. Threads may suspend themselves or be suspended either by the Garbage Collector (GC), debugger or the signal monitor thread. The VM controls all the threads through the use of a internal structure where all the created threads are mapped. The GC will only run when all the threads referring to a single process are suspended, in order to avoid inconsistent states. CPU Scheduling The Linux kernel uses the Completely Fair Scheduler (CFS), which has the objective of providing balance between tasks assigned to a processor and applies fairness in the way that CPU time is assigned to tasks. This balance guarantees that all the tasks will have the same CPU share and that, each time that unfairness is verified, the algorithm assures that task rebalancing is performed. Although fairness is guaranteed, this algorithm does not provide any temporal guarantees to tasks, and therefore, neither Android does it, as its scheduling operations are delegated to the Linux kernel. Android uses its own VM named Dalvik (see footnote 2), which was specifically developed for mobile devices and considers memory optimization, battery power saving and low frequency CPU. It relies on the Linux kernel for the core operating system features such as memory management and scheduling and, thus, also presents the drawback of not taking any temporal guarantees into consideration. [pic] In terms of execution, the algorithm works as follows: the tasks with lower virtual runtime are placed on the left side of the tree, and the tasks with the higher virtual runtime are placed on the right. This means that the tasks with the highest need for the processor will always be stored on the left side of the tree. Then, the scheduler picks the left-most node of the tree to be scheduled. Each task is responsible for accounting the CPU time taken during execution and adding this value to the previous virtual runtime value. Then, it is inserted back into the tree, if it has not finished yet. With this pattern of execution, it is guaranteed that the tasks contend the CPU time in a fair manner. Another aspect of the fairness of the algorithm is the adjustments that it performs when the tasks are waiting for an I/O device. In this case, the tasks are compensated with the amount of time taken to receive the information they needed to complete its objective. [pic] Since the introduction of the CFS, the concept of scheduling classes was also introduced. Basically, these classes provide the connection between the main generic scheduler functionalities and the specific scheduler classes that implement the scheduling algorithms. This concept allows several tasks to be scheduled differently by using different algorithms for this purpose. Regarding the main scheduler, it is periodic and preemptive. Its periodicity is activated by the frequency of the CPU clock. It allows preemption either when a high priority task needs CPU time or when an interrupt exists. As for task priorities, these can be dynamically modified with the nice command and currently the kernel supports 140 priorities, where the values ranging from 0 to 99 are reserved for real-time processes and the values ranging from 100 to 139 are reserved for normal processes. Process States The order in which processes are killed to reclaim resources is determined by the priority of the hosted applications. An application’s priority is equal to its highest-priority component. Where two applications have the same priority, the process that has been at a lower priority longest will be killed first. Process priority is also affected by interprocess dependencies; if an application has a dependency on a Service or Content Provider supplied by a second application, the secondary application will have at least as high a priority as the application it supports. All Android applications will remain running and in memory until the system needs its resources for other applications. A process has five different states. [pic] †¢ Active Processes Active (foreground) processes are those hosting applications with components currently interacting with the user. These are the processes Android is trying to keep responsive by reclaiming resources. There are generally very few of these processes, and they will be killed only as a last resort. Active processes include: o Activities in an â€Å"active† state; that is, they are in the foreground and responding to user events. You will explore Activity states in greater detail later in this chapter. Activities, Services, or Broadcast Receivers that are currently executing an onReceive event handler. o Services that are executing an onStart, onCreate, or onDestroy event handler. †¢ Visible Processes Visible, but inactive processes are those hosting â€Å"visible† Activities. As the name suggests, visible Activities are visible, but they aren’t in the foreground or responding to user events. Thi s happens when an Activity is only partially obscured (by a non-full-screen or transparent Activity). There are generally very few visible processes, and they’ll only be killed in extreme circumstances to allow active processes to continue. Started Service Processes Processes hosting Services that have been started. Services support ongoing processing that should continue without a visible interface. Because Services don’t interact directly with the user, they receive a slightly lower priority than visible Activities. They are still considered to be foreground processes and won’t be killed unless resources are needed for active or visible processes. †¢ Background Processes Processes hosting Activities that aren’t visible and that don’t have any Services that have been started are considered background processes. There will generally be a large number of background processes that Android will kill using a last-seen-first-killed pat- tern to obtain resources for foreground processes. †¢ Empty Processes To improve overall system performance, Android often retains applications in memory after they have reached the end of their lifetimes. Android maintains this cache to improve the start-up time of applications when they’re re-launched. These processes are routinely killed as required. State Diagram [pic] Memory Management Android’s process and memory management is a little unusual. Like Java and . NET, Android uses its own run time and virtual machine to manage application memory. Unlike either of these frameworks, the Android run time also manages the process lifetimes. Android ensures application responsiveness by stopping and killing processes as necessary to free resources for higher-priority applications. Each Android application runs in a separate process within its own Dalvik instance, relinquishing all responsibility for memory and process management to the Android run time, which stops and kills processes as necessary to manage resources. Dalvik and the Android run time sit on top of a Linux kernel that handles low-level hardware interaction including drivers and memory management, while a set of APIs provides access to all of the under- lying services, features, and hardware. Synchronization Techniques Regarding synchronization, Android uses its own implementation of libc – named bionic. Bionic has its own implementation of the pthread library and it does not support process-shared mutexes and condition variables. However, thread mutexing and thread condition variables are supported in a limited manner. Currently, inter-process communication is handled by Open-Binder. In terms of real-time limitations, the mechanisms provided by the architecture do not solve the old problems related with priority inversion. Therefore, synchronization protocols such as priority ceiling and inheritance are not implemented. Event Handling In terms of interrupt/event handling, these are performed by the kernel via device drivers. Afterwards, the kernel is notified and then is responsible for notifying the application waiting for that specific interrupt/event. None of the parts involved in the handling has a notion of the time restrictions available to perform its operations. This behavior becomes more serious when considering interrupts. In Linux the interrupts are the highest priority tasks, and therefore, this means that a high priority task can be interrupted by the arrival of an interrupt. This is considered a big drawback, as it is not possible to make the system totally predictable. Security Android has a unique security model, which focuses on putting the user in control of the device. Android devices however, don’t all come from one place, the open nature of the platform allows for proprietary extensions and changes. These extensions can help or could interfere with security, being able to analyze a distribution of Android is therefore an important step in protecting information on that system. Android applications run in a sandbox, an isolated area of the operating system that does not have access to the rest of the system's resources, unless access permissions are granted by the user when the application is installed. Before installing an application, Android Market displays all required permissions. A game may need to enable vibration, for example, but should not need to read messages or access the phonebook. After reviewing these permissions, the user can decide whether to install the application. Networking Android supports connectivity technologies including Global System for Mobile Communications (GSM)[4], Enhanced Data rates for GSM Evolution (EDGE)[5], Integrated Digital Enhanced Network (IDEN)[6], Code division multiple access (CDMA)[7], Evolution-Data Optimized (EV-DO)[8], Universal Mobile Telecommunications System (UMTS)[9], Bluetooth[10], Wi-Fi[11], LTE[12], (Near field communication) NFC[13] and Worldwide Interoperability for Microwave Access (WiMAX)[14]. Evaluation Mobile software development has evolved incredibly over time, giving us the power of not having to carry our laptop everywhere, or waiting to get home to access our networks or documents, 3G and 4G speeds directly on our phones give us that power, making mobile devices the most popular way to stay connected, as speeds are comparable to standard net speeds. Android has emerged as a new mobile development platform, building on past successes and avoiding past failures of other platforms. The android OS is an open source, meaning that is freely available to anyone who wishes to learn it. Google has opened up the software to creativity, because now we all have access to learning the development process. Hackers, coders, and all techy gurus have created a plethora of net-libraries ranging from support groups, forums and websites to further help newbies in the process. Android was designed to empower developers to think creatively by giving them almost absolute power over creating innovative applications. Bibliography Android Developers. Web. 11 Nov. 2011. . Burnette, Ed. Hello, Android: Introducing Google's Mobile Development Platform. Raleigh, NC: Pragmatic helf, 2010. Print. Burns, Jesse. â€Å"DEVELOPING SECURE MOBILE APPLICATIONS FOR ANDROID. † DEVELOPING SECURE MOBILE APPLICATIONS FOR ANDROID (2008). Print. Linux. com | The Source for Linux Information. Web. 11 Nov. 2011. . Maia, Claudio, Luis Nogueira, and Luis Pinho. â€Å"Evaluating Android OS for Embedded Real-Time Systems. † Print. â€Å"Memory Management in Android  « Welcome to Mobile World !!! † Welcome to Mobile World !!! Web. 11 Nov. 2011. . Shevchenko, Aleksey. â€Å"Application Handling of Database Timeouts and Deadlocks – Developer. om. † Developer. com: Your Home for Java and Open Source Development Knowledge. Web. 11 Nov. 2011. . â€Å"White Paper Android by 2012, Android OS, Android SDK. † Upload & Share PowerPoint Presentations and Documents. Web. 11 Nov. 2011. . ———————– [1]A Java interpreter machine, completely optimized for Android platform a nd which is developed to run on low-end memory mobile devices. One of the prominent aspects in Dalvik is its capability to run along an application compilation enhancing the runtime performance of the applications. Dalvik is not exactly, a Java machine, because Dalvik could not read Java code, but consists its own byte code called â€Å"dex† and so the executable files compacted using Dalvik holds the file type name ‘. dex'. Google states that the credit for Androids successful development goes to Dalvik VM, because this type of virtual machine, delivers a good performance over various stages of an application runtime environment, conserving more battery-power during long run of an application. [2] An embedded relational database management system contained in a elatively small (~275 kB) C programming library. The source code for SQLite is in the public domain. [3] Processing of one command at a time [4] A standard set developed by the European Telecommunications Standards Institute (ETSI) to describe technologies for second generation (or â€Å"2G†) digital cellular networks [5] A digital mobile phone technology that allows improved data transmission rates as a backward-com patible extension of GSM. [6] A mobile telecommunications technology, developed by Motorola, which provides its users the benefits of a trunked radio and a cellular telephone 7] A channel access method used by various radio communication technologies [8] A telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access [9] A third generation mobile cellular technology for networks based on the GSM standard [10] Technology standard for exchanging data over short distances (using short wavelength radio transmissions in the ISM band from 2400-2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security 11] A mechanism for wirelessly connecting electronic devices [12] A preliminary mobile communication standard, formally submitted as a candidate 4G system [13] NFC allows for simplified transactions, data exchange, and wireless connections between two devices in proximity to e ach other, usually by no more than a few centimeters [14] A communication technology for wirelessly delivering high-speed Internet service to large geographical areas