What is Pointer?

What is Pointer?

In computer science, a pointer is a programming language object, whose value refers to (or “points to”) another value stored elsewhere in the computer memory using its address. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer.

As an analogy, a page number in a book’s index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number.

The term “Pointer” can also be defined as

  1. A variable does not store a value but store the address of the memory space which contains the value.
  2. A variable that contains the address of a location in memory. The location is the starting point of an allocated object, such as an object or value type, or the element of an array.
  3. A value that designates the address (i.e., the location in memory), of some value.
  4. Variables that hold a memory location.
  5. A memory address.

In general, Pointer is a long thin piece of metal on a scale or dial that moves to indicate a figure or position.

Artificial Skin Lets Person Feel Pressure

Human finger touches robotic finger. The transparent plastic and black device on the golden "fingertip" is the skin-like sensor developed by Stanford engineers. This sensor can detect pressure and transmit that touch sensation to a nerve cell. The goal is to create artificial skin, studded with many such miniaturized sensors, to give prosthetic appendages some of the sensory capabilities of human skin. Credit: Bao Lab
Human finger touches robotic finger. The transparent plastic and black device on the golden “fingertip” is the skin-like sensor developed by Stanford engineers. This sensor can detect pressure and transmit that touch sensation to a nerve cell. The goal is to create artificial skin, studded with many such miniaturized sensors, to give prosthetic appendages some of the sensory capabilities of human skin.
Credit: Bao Lab

Stanford engineers have created a plastic “skin” that can detect how hard it is being pressed and generate an electric signal to deliver this sensory input directly to a living brain cell.

Zhenan Bao, a professor of chemical engineering at Stanford, has spent a decade trying to develop a material that mimics skin’s ability to flex and heal, while also serving as the sensor net that sends touch, temperature and pain signals to the brain. Ultimately she wants to create a flexible electronic fabric embedded with sensors that could cover a prosthetic limb and replicate some of skin’s sensory functions.

Bao’s work, reported today in Science, takes another step toward her goal by replicating one aspect of touch, the sensory mechanism that enables us to distinguish the pressure difference between a limp handshake and a firm grip.

“This is the first time a flexible, skin-like material has been able to detect pressure and also transmit a signal to a component of the nervous system,” said Bao, who led the 17-person research team responsible for the achievement.

Benjamin Tee, a recent doctoral graduate in electrical engineering; Alex Chortos, a doctoral candidate in materials science and engineering; and Andre Berndt, a postdoctoral scholar in bioengineering, were the lead authors on the Science paper.

Digitizing touch

The heart of the technique is a two-ply plastic construct: the top layer creates a sensing mechanism and the bottom layer acts as the circuit to transport electrical signals and translate them into biochemical stimuli compatible with nerve cells. The top layer in the new work featured a sensor that can detect pressure over the same range as human skin, from a light finger tap to a firm handshake.

Five years ago, Bao’s team members first described how to use plastics and rubbers as pressure sensors by measuring the natural springiness of their molecular structures. They then increased this natural pressure sensitivity by indenting a waffle pattern into the thin plastic, which further compresses the plastic’s molecular springs.

To exploit this pressure-sensing capability electronically, the team scattered billions of carbon nanotubes through the waffled plastic. Putting pressure on the plastic squeezes the nanotubes closer together and enables them to conduct electricity.

This allowed the plastic sensor to mimic human skin, which transmits pressure information as short pulses of electricity, similar to Morse code, to the brain. Increasing pressure on the waffled nanotubes squeezes them even closer together, allowing more electricity to flow through the sensor, and those varied impulses are sent as short pulses to the sensing mechanism. Remove pressure, and the flow of pulses relaxes, indicating light touch. Remove all pressure and the pulses cease entirely.

The team then hooked this pressure-sensing mechanism to the second ply of their artificial skin, a flexible electronic circuit that could carry pulses of electricity to nerve cells.

Importing the signal

Bao’s team has been developing flexible electronics that can bend without breaking. For this project, team members worked with researchers from PARC, a Xerox company, which has a technology that uses an inkjet printer to deposit flexible circuits onto plastic. Covering a large surface is important to making artificial skin practical, and the PARC collaboration offered that prospect.

Finally the team had to prove that the electronic signal could be recognized by a biological neuron. It did this by adapting a technique developed by Karl Deisseroth, a fellow professor of bioengineering at Stanford who pioneered a field that combines genetics and optics, called optogenetics. Researchers bioengineer cells to make them sensitive to specific frequencies of light, then use light pulses to switch cells, or the processes being carried on inside them, on and off.

For this experiment the team members engineered a line of neurons to simulate a portion of the human nervous system. They translated the electronic pressure signals from the artificial skin into light pulses, which activated the neurons, proving that the artificial skin could generate a sensory output compatible with nerve cells.

Optogenetics was only used as an experimental proof of concept, Bao said, and other methods of stimulating nerves are likely to be used in real prosthetic devices. Bao’s team has already worked with Bianxiao Cui, an associate professor of chemistry at Stanford, to show that direct stimulation of neurons with electrical pulses is possible.

Bao’s team envisions developing different sensors to replicate, for instance, the ability to distinguish corduroy versus silk, or a cold glass of water from a hot cup of coffee. This will take time. There are six types of biological sensing mechanisms in the human hand, and the experiment described in Science reports success in just one of them.

But the current two-ply approach means the team can add sensations as it develops new mechanisms. And the inkjet printing fabrication process suggests how a network of sensors could be deposited over a flexible layer and folded over a prosthetic hand.

“We have a lot of work to take this from experimental to practical applications,” Bao said. “But after spending many years in this work, I now see a clear path where we can take our artificial skin.”


Story Source:

The above post is reprinted from materials provided by Stanford University. The original item was written by Tom Abate. Note: Materials may be edited for content and length.


Journal Reference:

  1. B.C.K. Tee et al. A skin-inspired organic digital mechanoreceptor. Science, 2015 DOI: 10.1126/science.aaa9306

World’s Lightest Material

the-strongest-material-in-the-world

Boeing says it’s created the lightest metal ever, a microlattice material which it describes as 99.99% air.

The microlattice is a “3D open-cellular polymer structure” and is made up of interconnecting hollow tubes, each one measuring 1000 times thinner than a human hair.

The material is 100 times lighter than styrofoam, making it the lightest and also one of the strongest materials known to science.

Sophia Yang, a research scientist at HRL laboratories who worked with Boeing on the creation of the material says that the metal is 99.99% air. She compares the material to bone, whereby the outside of the bone is rigid while the inside is mostly hollow, creating an open-cellular structure which means it’s remarkably strong as well as extremely lightweight.

The material has been made primarily for use in in aerospace engineering. Engineers intend to use the microlattice for plane interiors in places such as side-panels, overhead cabins, or walkway areas. This would drastically reduce the overall weight of the aircraft, making it more fuel-efficient and cheaper to run.

Yang also highlights the material’s ability to absorb high levels of impact. Using the “egg challenge” as an example, she explains: “You need to drop an egg from 25 stories and protect that egg… What we can do is design the microlattice to absorb the force that the egg feels. So instead of having an egg that’s wrapped in three feet of bubble wrap, now you have a much smaller package that your egg can sit in.”

The microlattice was originally unveiled in November 2011 and was named one of 10 world-changing innovations by Popular Mechanics.

What is Logical Block Addressing (LBA)?

Logical Block Address (LBA)

Logical block addressing is a technique that allows a computer to address a hard disk larger than 528 megabytes. A Logical Block Address (LBA) is a 28-bit value that maps to a specific cylinder-head-sector address on the disk. 28 bits allows sufficient variation to specify addresses on a hard disk up to 8.4 gigabytes in data storage capacity.

The term “Logical block addressing” can also be defined as

  1. An address that defines where data is stored on the hard drive.
  2. A common scheme used for specifying the location of blocks of data stored on computer storage devices.
  3. A run-time function of the system BIOS. The BIOS uses LBA for the following commands: read (with and without retries), read verify, read long, write (with and without retries), write verify, write long, read multiple, write multiple, read DMA, write DMA, seek, and format track.

Machines have nothing on mom when it comes to listening

Credit: University of Montreal
Credit: University of Montreal

More than 99% of the time, two words are enough for people with normal hearing to distinguish the voice of a close friend or relative amongst other voices, says the University of Montreal’s Julien Plante-Hébert. His study, presented at the 18th International Congress of Phonetic Sciences, involved playing recordings to Canadian French speakers, who were asked to recognize on multiple trials which of the ten male voices they heard was familiar to them. “Merci beaucoup” turned out to be all they needed to hear.

Plante-Hébert is a voice recognition doctoral student at the university’s Department of Linguistics and Translation. “The auditory capacities of humans are exceptional in terms of identifying familiar voices. At birth, babies can already recognize the voice of their mothers and distinguish the sounds of foreign languages,” Plante-Hébert said. To evaluate these auditory capacities, he created a series of voice “lineups,” a technique inspired by the well-known visual identification procedure used by police, in which a group of individuals sharing similar physical traits are placed before a witness. “A voice lineup is an analogous procedure in which several voices with similar acoustic aspects are presented. In my study, each voice lineup contained different lengths of utterances varying from one to eighteen syllables. Familiarity between the target voice and the identifier was defined by the degree of contact between the interlocutors.” Forty-four people aged 18-65 participated.

Plante-Hébert found that the participants were unable to identify short utterances regardless of their familiarity with the person speaking. However, with utterances of four or more syllables, such as “merci beaucoup,” the success rate was nearly total for very familiar voices. “Identification rates exceed those currently obtained with automatic systems,” he said. Indeed, in his opinion, the best speech recognition systems are much less efficient than auditory system at best, there is a 92% success rate compared to over 99.9% for humans.

Moreover, in a noisy environment, humans can exceed machine-based recognition because of our brain’s ability to filter out ambient noise. “Automatic speaker recognition is in fact the least accurate biometric factor compared to fingerprints or face or iris recognition,” Plante-Hébert said. “While advanced technologies are able to capture a large amount of speech information, only humans so far are able to recognize familiar voices with almost total accuracy,” he concluded.


Story Source:

The above post is reprinted from materials provided by University of Montreal. Note: Materials may be edited for content and length.

What is Storage?

storage-device-computer

 

In a computer, storage is the place where data is held in an electromagnetic or optical form for access by a computer processor. There are two general usages.

  1. Storage is frequently used to mean the devices and data connected to the computer through input/output operations – that is, hard disk and tape systems and other forms of storage that don’t include computer memory and other in-computer storage. For the enterprise, the options for this kind of storage are of much greater variety and expense than that related to memory. This meaning is probably more common in the IT industry than meaning 2 (the following).
  2. In a more formal usage, storage has been divided into:
    1. Primary storage, which holds data in memory (sometimes called random access memory or RAM) and other “built-in” devices such as the processor’s L1 cache, and
    2. Ssecondary storage, which holds data on hard disks, tapes, and other devices requiring input/output operations.

Primary storage is much faster to access than secondary storage because of the proximity of the storage to the processor or because of the nature of the storage devices. On the other hand, secondary storage can hold much more data than primary storage.

In addition to RAM, primary storage includes read-only memory (ROM) and L1 and L2 cache memory. In addition to hard disks, secondary storage includes a range of device types and technologies, including diskettes, Zip drives, redundant array of independent disks (RAID) systems, and holographic storage. Devices that hold storage are collectively known as storage media.

A somewhat antiquated term for primary storage is main storage and a somewhat antiquated term for secondary storage is auxiliary storage. Note that, to add to the confusion, there is an additional meaning for primary storage that distinguishes actively used storage from backup storage.

Nobel Prize in Physics for 2015

Illustration of the Sudbury Neutrino Observatory. Credit: Copyright Johan Jarnestad/The Royal Swedish Academy of Sciences
Illustration of the Sudbury Neutrino Observatory.
Credit: Copyright Johan Jarnestad/The Royal Swedish Academy of Sciences

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2015 to Takaaki Kajita Super-Kamiokande Collaboration University of Tokyo, Kashiwa, Japan and Arthur B. McDonald Sudbury Neutrino Observatory Collaboration Queen’s University, Kingston, Canada “for the discovery of neutrino oscillations, which shows that neutrinos have mass.”

Metamorphosis in the particle world

The Nobel Prize in Physics 2015 recognises Takaaki Kajita in Japan and Arthur B. McDonald in Canada, for their key contributions to the experiments which demonstrated that neutrinos change identities. This metamorphosis requires that neutrinos have mass. The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe.

Around the turn of the millennium, Takaaki Kajita presented the discovery that neutrinos from the atmosphere switch between two identities on their way to the Super-Kamiokande detector in Japan.

Meanwhile, the research group in Canada led by Arthur B. McDonald could demonstrate that the neutrinos from the Sun were not disappearing on their way to Earth. Instead they were captured with a different identity when arriving to the Sudbury Neutrino Observatory.

A neutrino puzzle that physicists had wrestled with for decades had been resolved. Compared to theoretical calculations of the number of neutrinos, up to two thirds of the neutrinos were missing in measurements performed on Earth. Now, the two experiments discovered that the neutrinos had changed identities.

The discovery led to the far-reaching conclusion that neutrinos, which for a long time were considered massless, must have some mass, however small.

For particle physics this was a historic discovery. Its Standard Model of the innermost workings of matter had been incredibly successful, having resisted all experimental challenges for more than twenty years. However, as it requires neutrinos to be massless, the new observations had clearly showed that the Standard Model cannot be the complete theory of the fundamental constituents of the universe.

The discovery rewarded with this year’s Nobel Prize in Physics have yielded crucial insights into the all but hidden world of neutrinos. After photons, the particles of light, neutrinos are the most numerous in the entire cosmos. Earth is constantly bombarded by them.

Many neutrinos are created in reactions between cosmic radiation and Earth’s atmosphere. Others are produced in nuclear reactions inside the Sun. Thousands of billions of neutrinos are streaming through our bodies each second. Hardly anything can stop them passing; neutrinos are nature’s most elusive elementary particles.

Now the experiments continue and intense activity is underway worldwide in order to capture neutrinos and examine their properties. New discoveries about their deepest secrets are expected to change our current understanding of the history, structure and future fate of the universe.

Takaaki Kajita, Japanese citizen. Born 1959 in Higashimatsuyama, Japan. Ph.D. 1986 from University of Tokyo, Japan. Director of Institute for Cosmic Ray Research and Professor at University of Tokyo, Kashiwa, Japan. www.icrr.u-tokyo.ac.jp/about/greeting_eng.html

Arthur B. McDonald, Canadian citizen. Born 1943 in Sydney, Canada. Ph.D. 1969 from Californa Institute of Technology, Pasadena, CA, USA. Professor Emeritus at Queen’s University, Kingston, Canada. www.queensu.ca/physics/arthur-mcdonald

Prize amount: SEK 8 million, to be shared equally between the Laureates.


Story Source:

The above post is reprinted from materials provided by Nobel Foundation. Note: Materials may be edited for content and length.

Interview Question : What is Hard Disk?

what-is-hard-disk-drive-hdd

A hard disk is part of a unit, often called a “disk drive,” “hard drive,” or “hard disk drive (HDD),” that stores and provides relatively quick access to large amounts of data on an electromagnetically charged surface or set of surfaces. Today’s computers typically come with a hard disk that contains several billion bytes (gigabytes) of storage.

A Hard disk can also be defined as:

  1. a rigid (“hard”) non-removable magnetic disk with a large data storage capacity.
  2. a data storage device used for storing and retrieving digital information using one or more rigid (“hard”) rapidly rotating disks (platters) coated with magnetic material.
  3. A magnetic disk on which you can store computer data. The term hard is used to distinguish it from a soft, or floppy disk. Hard disks hold more data and are faster than floppy disks.

Extra Information

A hard disk is really a set of stacked “disks,” each of which, like phonograph records, has data recorded electromagnetically in concentric circles or “tracks” on the disk. A “head” (something like a phonograph arm but in a relatively fixed position) records (writes) or reads the information on the tracks. Two heads, one on each side of a disk, read or write the data as the disk spins. Each read or write operation requires that data be located, which is an operation called a “seek.” (Data already in a disk cache, however, will be located more quickly.)

A hard disk/drive unit comes with a set rotation speed varying from 4500 to 7200 rpm. Disk access time is measured in milliseconds. Although the physical location can be identified with cylinder, track, and sector locations, these are actually mapped to a logical block address (LBA) that works with the larger address range on today’s hard disks.

To know more regarding the terms follow the post about Difference between Disc and Disk click here.

 

Life History of a Dinosaur: Maiasaura

Research published in the journal Paleobiology is showing more about the life history of Maiasaura peeblesorum than any other known dinosaur. Credit: Courtesy Holly Woodward
Research published in the journal Paleobiology is showing more about the life history of Maiasaura peeblesorum than any other known dinosaur.
Credit: Courtesy Holly Woodward

Decades of research on Montana’s state fossil — the “good mother lizard” Maiasaura peeblesorum — has resulted in the most detailed life history of any dinosaur known and created a model to which all other dinosaurs can be compared, according to new research published recently in the journal Paleobiology.

Researchers from Oklahoma State University, Montana State University and Indiana Purdue University used fossils collected from a huge bonebed in western Montana for their study.

“This is one of the most important pieces of paleontology involving MSU in the past 20 years,” said Jack Horner, curator of the Museum of the Rockies at MSU. “This is a dramatic step forward from studying fossilized creatures as single individuals to understanding their life cycle. We are moving away from the novelty of a single instance to looking at a population of dinosaurs in the same way we look at populations of animals today.”

The study was led by Holly Woodward, who did the research as her doctoral thesis in paleontology at MSU. Woodward is now professor of anatomy at Oklahoma State University Center for Health Sciences.

The Paleobiology study examined the fossil bone microstructure, or histology, of 50 Maiasaura tibiae (shin bones). Bone histology reveals aspects of growth that cannot be obtained by simply looking at the shape of the bone, including information about growth rate, metabolism, age at death, sexual maturity, skeletal maturity and how long a species took to reach adult size.

“Histology is the key to understanding the growth dynamics of extinct animals,” Woodward said. “You can only learn so much from a bone by looking at its shape. But the entire growth history of the animal is recorded within the bone.”

A sample of 50 might not sound like much, but for dinosaur paleontologists dealing with an often sparse fossil record, the Maiasaura fossils are a treasure trove.

“No other histological study of a single dinosaur species approaches our sample size,” Woodward said.

With it, the researchers discovered a wealth of new information about how Maiasaura grew up: it had bird-level growth rates throughout most of its life, and its bone tissue most closely resembled that of modern day warm-blooded large mammals such as elk.

Major life events are recorded in the growth of the bones and the rates at which different-aged animals died.

“By studying the clues in the bone histology, and looking at patterns in the death assemblage, we found multiple pieces of evidence all supporting the same timing of sexual and skeletal maturity,” said Elizabeth Freedman Fowler, curator of paleontology at the Great Plains Dinosaur Museum in Malta and adjunct professor at MSU, who performed the mathematical analyses for the study.

Sexual maturity occurred within the third year of life, and Maiasaura reached an average adult mass of 2.3 tonnes in eight years. Life was especially hard for the very young and the old. The average mortality rate for those less than a year of age was 89.9 percent, and 44.4 percent for individuals 8 years and older.

If Maiasaura individuals could survive through their second year, they enjoyed a six-year window of peak physical and reproductive fitness, when the average mortality rate was just 12.7 percent.

“By looking within the bones, and by synthesizing what previous studies revealed, we now know more about the life history of Maiasaura than any other dinosaur and have the sample size to back up our conclusions,” Woodward said. “Our study makes Maiasaura a model organism to which other dinosaur population biology studies will be compared.”

The 50 tibiae also highlighted the extent of individual size variation within a dinosaur species. Previous dinosaur studies histologically examined a small subset of dinosaur bones and assigned ages to the entire sample based on the lengths of the few histologically aged bones.

“Our results suggest you can’t just measure the length of a dinosaur bone and assume it represents an animal of a certain age,” Woodward said. “Within our sample, there is a lot of variability in the length of the tibia in each age group. It would be like trying to assign an age to a person based on their height because you know the height and age of someone else. Histology is the only way to quantify age in dinosaurs.”

Horner, a coauthor on the research and curator of the Museum of the Rockies at MSU where the Maiasaura fossils are reposited, discovered and named Maiasaura in 1979. He made headlines by announcing the world’s first discovery of fossil dinosaur embryos and eggs. Based on the immature development of the baby dinosaur fossils found in nests, Horner hypothesized that they were helpless upon hatching and had to be cared for by parents, so naming the dinosaur Maiasaura, Latin for “good mother lizard.”

Studies that followed revealed aspects of Maiasaura biology including that they were social and nested in colonies; Maiasaura walked on two legs when young and shifted to walking on all four as they got bigger; their preferred foods included rotting wood; and that their environment was warm and semi-arid, with a long dry season prone to drought.

The tibiae included in the Paleobiology study came from a single bonebed in western Montana covering at least two square kilometers. More than 30 years of excavation and thousands of fossils later, the bonebed shows no signs of running dry. Woodward plans to lead annual summer excavations of the Maiasaura bonebed to collect more data.

“Our study kicks off The Maiasaura Life History Project, which seeks to learn as much as possible about Maiasaura and its environment 76 million years ago by continuing to collect and histologically examine fossils from the bonebed, adding statistical strength to the sample,” she said.

“We plan to examine other skeletal elements to make a histological ‘map’ of Maiasaura, seeing if the different bones in its body grew at different rates, which would allow us to study more aspects of its biology and behavior. We also want to better understand the environment in which Maiasaura lived, including the life histories of other animals in the ecosystem,” she added.

The Maiasaura Life History Project will also provide opportunities for college-aged students accompanying Woodward in her excavations to learn about the fields of ecology, biology and geology, thereby encouraging younger generations to pursue careers in science.

In addition to Woodward, Horner and Freedman Fowler, James Farlow, professor emeritus of Geology at Indiana Purdue University, contributed to the Paleobiology paper.


Story Source:

The above post is reprinted from materials provided by Montana State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Holly N. Woodward, Elizabeth A. Freedman Fowler, James O. Farlow, John R. Horner. Maiasaura, a model organism for extinct vertebrate population biology: a large sample statistical assessment of growth dynamics and survivorship. Paleobiology, 2015; 1 DOI: 10.1017/pab.2015.19

Virtual reality for mice teaches scientists about navigation

A mouse is ready to enter a virtual-reality system where its brain can be imaged while it thinks it’s running through a maze.
A mouse is ready to enter a virtual-reality system where its brain can be imaged while it thinks it’s running through a maze.

 

Scientists can now observe the brains of lab animals in microscopic detail as the animals go about some action. A technique called two-photon imaging, in particular, allows neuroscientists to watch thousands of neurons working in concert to encode information.

The trouble is, two-photon imaging requires the animal’s head to stay fixed in place. That would seem to preclude watching the brain as the animal does anything of much interest.

One creative solution is virtual reality—a computer-generated environment experienced through a headset. A few years ago neuroscientists started designing tiny virtual-reality systems to fool mice into thinking they were navigating a maze when they were really running on the top of a large ball, their heads fixed in position.

Until now, however, mice didn’t run on the ball until they’d had weeks of training. Jeremy Freeman, working with colleague Nicholas Sofroniew and others at the HHMI Janelia Research Campus in Virginia, created a virtual maze the mice seem to understand right away: they navigate through virtual corridors without training. It’s designed to exploit the way mice navigate in nature, Freeman says. Instead of relying primarily on their eyes, mice rely heavily on their whiskers to feel their way through the world.

In the whisker-oriented virtual reality, the walls move to give the mouse the illusion that it is running down winding corridors, he says. But the whole time, the rodent’s head is stationary.

This approach doesn’t translate neatly to the human world. Mice rely heavily on their whiskers to get around, and the neural imaging requires genetically altering mice to produce fluorescent proteins. However, this mouse-sized VR could still shed plenty of light on autism and other conditions that affect decisions, learning and the senses.


Story Source:

The above post is reprinted from materials provided by MIT Technology Review. Note: Materials may be edited for content and length.