Discovery of quasars

The term quasar derives from how these objects were originally discovered in the earliest radio surveys of the sky in the 1950s. Away from the plane of the Milky Way Galaxy, most radio sources were identified with otherwise normal-looking galaxies. Some radio sources, however, coincided with objects that appeared to be unusually blue stars, although photographs of some of these objects showed them to be embedded in faint, fuzzy halos. Because of their almost starlike appearance, they were dubbed “quasi-stellar radio sources,” which by 1964 had been shortened to “quasar.”

The optical spectra of the quasars presented a new mystery. Photographs taken of their spectra showed locations for emission lines at wavelengths that were at odds with all celestial sources then familiar to astronomers. The puzzle was solved by the Dutch American astronomer Maarten Schmidt, who in 1963 recognized that the pattern of emission lines in 3C 273, the brightest known quasar, could be understood as coming from hydrogen atoms that had a redshift (i.e., had their emission lines shifted toward longer, redder wavelengths by the expansion of the universe) of 0.158. In other words, the wavelength of each line was 1.158 times longer than the wavelength measured in the laboratory, where the source is at rest with respect to the observer. At a redshift of this magnitude, 3C 273 was placed by Hubble’s law at a distance of slightly more than two billion light-years. This was a large, though not unprecedented, distance (bright clusters of galaxies had been identified at similar distances), but 3C 273 is about 100 times more luminous than the brightest individual galaxies in those clusters, and nothing so bright had been seen so far away.

An even bigger surprise was that continuing observations of quasars revealed that their brightness can vary significantly on timescales as short as a few days, meaning that the total size of the quasar cannot be more than a few light-days across. Since the quasar is so compact and so luminous, the radiation pressure inside the quasar must be huge; indeed, the only way a quasar can keep from blowing itself up with its own radiation is if it is very massive, at least a million solar masses if it is not to exceed the Eddington limit—the minimum mass at which the outward radiation pressure is balanced by the inward pull of gravity (named after English astronomer Arthur Eddington). Astronomers were faced with a conundrum: how could an object about the size of the solar system have a mass of about a million stars and outshine by 100 times a galaxy of a hundred billion stars?

The right answer—accretion by gravity onto supermassive black holes—was proposed shortly after Schmidt’s discovery independently by Russian astronomersYakov Zel’dovich and Igor Novikov and Austrian American astronomer Edwin Salpeter. The combination of high luminosities and small sizes was sufficiently unpalatable to some astronomers that alternative explanations were posited that did not require the quasars to be at the large distances implied by their redshifts. These alternative interpretations have been discredited, although a few adherents remain. For most astronomers, the redshift controversy was settled definitively in the early 1980s when American astronomer Todd Boroson and Canadian American astronomer John Beverly Oke showed that the fuzzy halos surrounding some quasars are actually starlight from the galaxy hosting the quasar and that these galaxies are at high redshifts.

By 1965 it was recognized that quasars are part of a much larger population of unusually blue sources and that most of these are much weaker radio sources too faint to have been detected in the early radio surveys. This larger population, sharing all quasar properties except extreme radio luminosity, became known as “quasi-stellar objects” or simply QSOs. Since the early 1980s most astronomers have regarded QSOs as the high-luminosity variety of an even larger population of “active galactic nuclei,” or AGNs. (The lower-luminosity AGNs are known as “Seyfert galaxies,” named after the American astronomer Carl K. Seyfert, who first identified them in 1943.)

Font: http://www.britannica.com/EBchecked/topic/486494/quasar/288728/Discovery-of-quasars

Aussie researchers slow down light with very small quantum photon device

A NEW breakthrough led by University of Sydney researchers will see a massive acceleration in information transfer and processing, and secure quantum computing.

Researchers at the Centre of Excellence for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS) nodes at the University of Sydney and Macquarie University have managed to slow light down using silicon photonic crystals.

The research was a collaboration between the Australian universities and the University of Bristol and the University of St Andrews (UK), and the Ecole Centrale de Lyon in France.

This is the first research breakthrough at CUDOS since its official relaunch in the beginning of April, as reported by Electronics News.

CUDOS researchers generated individual pairs of photons in the smallest device ever by slowing light down using silicon photonic crystals. At 100 microns long CUDOS’s quantum photon device is 100 times smaller than the one-centimetre devices used by other groups.

According to Dr Chunle Xiong of the University of Sydney, a co-author and Project Leader for the CUDOS program in Quantum Integrated Photonics, the scale of the device means potentially hundreds of them can be incorporated into a single chip. 

 

Dr. Chunle Xiong holding the new (small) and old chip (big), Professor Ben Eggleton, CUDOS Director and Dr Christian Grillet.

This could herald practical quantum technologies which will make communications much more secure and computations which are many times faster than currently possible.

“We are able to do this by slowing light down through the use of silicon photonic crystals, which means the ultrashort device behaves as a much longer device, so that the photons are generated in only 100 microns,” explained Dr Xiong.

Information security is ensured due to the nature of quantum computing. Current optical systems use classical light to carry information, and this can be easily tapped into by hackers.

In quantum computing, it is not possible to copy information encoded in quantum states without being noticed by the system. Single photon devices will ensure communication and information systems are secure from hackers.

The experiment and findings have been outlined in a paper to be presented at a prestigious international conference in Baltimore (USA) next week.
Below: a video from the relaunch of CUDOS.
 http://www.youtube.com/watch?feature=player_embedded&v=830YgQ_C9fY

Different Types of Technology and their Educational Applications

Many different types of technology can be used to support and enhance learning. Everything from video content and digital moviemaking to laptop computing and handheld technologies (Marshall, 2002) have been used in classrooms, and new uses of technology such as podcasting are constantly emerging.

Various technologies deliver different kinds of content and serve different purposes in the classroom. For example, word processing and e-mail promote communication skills; database and spreadsheet programs promote organizational skills; and modeling software promotes the understanding of science and math concepts. It is important to consider how these electronic technologies differ and what characteristics make them important as vehicles for education (Becker, 1994).

Technologies available in classrooms today range from simple tool-based applications (such as word processors) to online repositories of scientific data and primary historical documents, to handheld computers, closed-circuit television channels, and two-way distance learning classrooms. Even the cell phones that many students now carry with them can be used to learn (Prensky, 2005).

Each technology is likely to play a different role in students' learning. Rather than trying to describe the impact of all technologies as if they were the same, researchers need to think about what kind of technologies are being used in the classroom and for what purposes. Two general distinctions can be made. Students can learn "from" computers—where technology used essentially as tutors and serves to increase students basic skills and knowledge; and can learn "with" computers—where technology is used a tool that can be applied to a variety of goals in the learning process and can serve as a resource to help develop higher order thinking, creativity and research skills (Reeves, 1998; Ringstaff & Kelley, 2002).

The primary form of student learning "from" computers is what Murphy, Penuel, Means, Korbak and Whaley (2001) describe as discrete educational software (DES) programs, such as integrated learning systems (ILS), computer-assisted instruction (CAI), and computer-based instruction (CBI). These software applications are also among the most widely available applications of educational technology in schools today, along with word-processing software, and have existed in classrooms for more than 20 years (Becker, Ravitz, & Wong, 1999).

According to Murphy et al, teachers use DES not only to supplement instruction, as in the past, but also to introduce topics, provide means for self-study, and offer opportunities to learn concepts otherwise inaccessible to students. The software also manifests two key assumptions about how computers can assist learning. First, the user's ability to interact with the software is narrowly defined in ways designed specifically to promote learning with the tools. Second, computers are viewed as a medium for learning, rather than as tools that could support further learning (Murphy et al, 2001).

While DES remains the most commonly used approach to computer use in student learning, in more recent years, use of computers in schools has grown more diversified as educators recognize the potential of learning "with" technology as a means for enhancing students' reasoning and problem-solving abilities. In part, this shift has been driven by the plethora of new information and communication devices now increasingly available to students in school and at home, each of which offers new affordances to teachers and students alike for improving student achievement and for meeting the demand for 21^st century skills describe earlier. No longer limited to school labs, school hours and specific devices, technology access is increasingly centered on the learner experience.

Bruce and Levin (1997), for example, look at ways in which the tools, techniques, and applications of technology can support integrated, inquiry-based learning to "engage children in exploring, thinking, reading, writing, researching, inventing, problem-solving, and experiencing the world." They developed the idea of technology as media with four different focuses: media for inquiry (such as data modeling, spreadsheets, access to online databases, access to online observatories and microscopes, and hypertext), media for communication (such as word processing, e-mail, synchronous conferencing, graphics software, simulations, and tutorials), media for construction (such as robotics, computer-aided design, and control systems), and media for expression (such as interactive video, animation software, and music composition).

In a review of existing evidence of technology's impact on learning, Marshall (2002) found strong evidence that educational technology "complements what a great teacher does naturally," extending their reach and broadening their students' experience beyond the classroom. "With ever-expanding content and technology choices, from video to multimedia to the Internet," Marshall suggests "there's an unprecedented need to understand the recipe for success, which involves the learner, the teacher, the content, and the environment in which technology is used."

Single-electron transistor may be quantum leap for memory/processors

A TEAM led by researchers from the University of Pittsburgh has created a single-electron transistor would could be the basis of quantum computer components.The device is called SketchSET, or sketch-based single-electron transistor.
 It is the first single-electron transistor made entirely of oxide-based materials. Its central component which measures 1.5nm in diameter operates with only one or two electrons, and the number of electrons in residence results in distinct conductive properties. Wires extending from the transistor carry additional electrons across the island. The sheer scale of the transistor means many of them can be fitted into a small space, opening the way for ultradense memories and quantum processors, providing an exponential leap in computing capabilities over current technology.

The researchers say the central island can also be used as an artificial atom for developing new classes of artificial electronic materials, such as exotic superconductors with properties not found in natural materials.

The single-electron transistor is its extremely sensitive to an electric charge. The transistor can also act as a solid-state memory in its ferroelectric state. 

The ferroelectric state can, in the absence of external power, control the number of electrons on the island, which in turn can be used to represent the 1 or 0 state of a memory element. A computer memory based on this property would be able to retain information even when the processor itself is powered down.

More: http://www.electronicsnews.com.au/news/single-electron-transistor-may-be-quantum-leap-for

Word Formation

O estudo da morfologia, ou seja, da formação de palavras, serve para demonstrar a flexibilidade da língua, flexibilidade esta que permite ao falante nativo transferir palavras de uma categoria a outra, através da adição de afixos.

Infelizmente, regras de formação de palavras não se aplicam a todas as palavras, tendo na verdade uma aplicação, ou uma "produtividade" muito limitada. Ou seja, a regra só se aplica àquelas palavras já consagradas pelo uso na língua. Do ponto de vista daquele que aprende inglês, a regra ajuda apenas no reconhecimento das palavras, não na produção. Portanto, de pouco adianta aprender a regra para poder aplicá-la na formação de palavras. O que também, mais uma vez, demonstra a eficácia superior da assimilação natural (acquisition) sobre estudo formal (learning) no processo de aprendizado de línguas.

A utilidade de se conhecer as principais regras de formação de palavras, do ponto de vista daquele que está desenvolvendo familiaridade com inglês, está no fato de que este conhecimento permite a identificação da provável categoria gramatical mesmo quando não se conhece a palavra no seu significado, o que é de grande utilidade na interpretação de textos.

São 3 os processos de formação de palavras:

AFFIXATION: É a adição de prefixos e sufixos.
Ex: pleasant - unpleasant, meaning - meaningful - meaningless.

CONVERSION: É a adoção da palavra em outra categoria gramatical sem qualquer transformação.
Ex: drive (verbo) - drive (substantivo)

COMPOUNDING: Refere-se à junção de duas palavras para formar uma terceira.
Ex: tea + pot = teapot, arm + chair = armchair

AFFIXATION: Dos dois tipos de afixos em inglês - prefixos e sufixos, - sufixos são aqueles que apresentam maior produtividade, isto é, a porcentagem de incidência é mais alta. Sufixos têm a função de transformar a categoria gramatical das palavras a que se aplicam. Isto é, um determinado sufixo será sempre aplicado a uma determinada categoria de palavra e resultará sempre numa outra determinada categoria.

Prefixos, por sua vez, normalmente não alteram a categoria gramatical da palavra-base a que se aplicam. Seu papel é predominantemente semântico, isto é, eles alteram o significado da base.

Understanding Chemical and Physical Reactions

 Did you know that nothing on Earth ever really disappears? It may see like snow disappears in the sun, or that the flames make wood vanish in a fire, but that is not what is happening. Snow melts and becomes gas that rises into the atmosphere, and burned wood turns into ash and smoke.  Matter is never created or destroyed. It just changes form! All matter is made up of tiny molecules, and when these molecules are changed or moved around, the matter changes form. Today you will learn about the two ways matter can change. These changes are called reactions.

Physical Reactions The first way matter can change is through a physical reaction. A physical reaction causes the matter to shift shape or state. For example, if you crush a cardboard box, only the shape changes. It has the same molecules, and is still a cardboard box, even if it is flat. This is a physical reaction. Another kind of physical reaction is an ice cube melting. As it melts, the ice changes from a solid to a liquid state. Even though it is no longer frozen, the matter is still water. That makes it a physical change.

 Physical changes are usually caused by some form of motion or pressure, or a change in temperature. When water boils and turns into steam, it is undergoing a physical change caused by a change in temperature. When wool is spun into thread, the physical change is caused by a motion. A sheet of metal is the result of powerful pressure machines that flatten the steel.

 When trying to determine if a change is a physical reaction or not, as yourself: Is this change reversible?  In other words, can you go backwards or change the matter into its original form. For most physical reactions, the answer is ‘Yes.’ The cardboard box can be straightened out, and water can be frozenonce again into ice. Steam can condense and return to its liquid state of water, and wool thread can be taken apart. However, not all physical reactions are easily reversed. 

Chemical Reactions

The second way matter can change is through a chemical reaction. Chemical changes occur when two or more substances combine and react to each other. In a chemical reaction, matter doesn’t just change form as it does in a physical reaction. Chemical reactions cause the molecules of matter to change. This is more than a change in shape or state. Most of the time, an entirely new kind of matter is created.

 Baking is a perfect example of a chemical reaction. Imagine all of the ingredients needed to make a batch of brownies. Eggs, flour, oil, water, and cocoa are stirred together. After heating the mixture to a high temperature for a set period of time, you have something very different than the parts you put into the bowl. Burning a piece of paper is also a chemical reaction. The basic substance of the paper is changed into something new: smoke and ashes. These new substances have very different molecules than the original piece of paper.

  

When trying to determine if a change is a chemical reaction, it helps to look at what was produced as a result of the change. If the reaction creates energy like light or heat, or if a gas or solid is produced, the change is a chemical reaction. Other signs of a chemical reaction include an odor or change in color. 

Another way to identify a chemical reaction is to examine whether or not the change can be reversed. Unlike physical reactions, chemical reactions can not be performed backwards to produce the original parts. For example, after those brownies come out of the oven, it is impossible to separate the oil, eggs, flour, and other ingredients ever again. They have been chemically changed into a new substance.

Summing Up

 Remember, in a physical reaction, the matter changes form, but keeps the same molecules. Molecules are simply rearranged so the matter has a new shape or state. Physical reactions are often reversible. Chemical reactions cause the molecules of the substances to change, creating a new kind of matter.  Chemical reactions usually produce new colors, energy, gases, odors, solids, or liquids. They are not reversible. 

Chemical and physical changes are going on around us all the time. By studying the natural way these changes occur, scientists have found ways to use chemical and physical changes to create building materials, medicines, and thousands of other helpful tools. Reactions can be as complex as creating a cure for a disease, and as simple as brushing your teeth.