Response of an artificial iris to light like the human eye

An artificial iris manufactured from intelligent, light-controlled polymer material can react to incoming light in the same ways as the human eye. The Iris was developed by the Smart Photonic Materials research group from the TUT, and it was recently published in the Advanced Materials journal.


The human iris does its job of adjusting your pupil size to meter the amount of light hitting the retina behind without you having to actively think about it. And while a camera’s aperture is designed to work the same way as a biological iris, it’s anything but automatic. Even point-and-shoots rely on complicated control mechanisms to keep your shots from becoming overexposed. But a new “artificial iris” developed at the Tampere University of Technology in Finland can autonomously adjust itself based on how bright the scene is.

Scientists from the Smart Photonic Materials research group developed the iris using a light-sensitive liquid crystal elastomer. The team also employed photoalignment techniques, which accurately position the liquid crystal molecules in a predetermined direction within a tolerance of a few picometers. This is similar to the techniques used originally in LCD TVs to improve viewing angle and contrast but has since been adopted to smartphone screens. “The artificial iris looks a little bit like a contact lens,” TUT Associate Professor Arri Priimägi said. “Its center opens and closes according to the amount of light that hits it.”

The team hopes to eventually develop this technology into an implantable biomedical device. However, before that can happen, the TUT researchers need to first improve the iris’ sensitivity so that it can adapt to smaller changes in brightness. They also need to get it to work in an aqueous environment. However, this new iris is therefore still long ways away from being ready.

Optical Deep Learning: Learning with light

Artificial Neural Networks mimic the way the brain learns from an accumulation of examples. A research team at the Massachusetts Institute of Technology (MIT) has come up with a novel approach to deep learning that uses a nanophotonic processor, which they claim can vastly improve the performance and energy efficiency for processing artificial neural networks.


Optical computers have been conceived before, but are usually aimed at more general-purpose processing. In this case, the researchers have narrowed the application domain considerably. Not only have they restricted their approach to deep learning, they have further limited this initial work to inferencing of neural networks, rather than the more computationally demanding process of training.

The optical chip contains multiple waveguides that shoot beams of light at each other simultaneously, creating interference patterns that correspond to mathematical results. “The chip, once you tune it, can carry out matrix multiplication with, in principle, zero energy, instantly,” said Marin Soljacic, an electrical engineering professor at MIT, in a statement. The accuracy leaves something to be desired for making out vowels, but the nanophotonic chip is still work-in-progress.

The new approach uses multiple light beams(as mentioned above) directed in such a way that their waves interact with each other, producing interference patterns that convey the result of the intended operation. The resulting device is something the researchers call a programmable nanophotonic processor.The result is that the optical chips using this architecture could, in principle, carry out calculations performed in typical artificial intelligence algorithms much faster and using less than one-thousandth as much energy per operation as conventional electronic chips.
The team says it will still take a lot more effort and time to make this system useful; however, once the system is scaled up and fully functioning, it can find many user cases, such as data centers or security systems. The system could also be a boon for self-driving cars or drones, says Harris, or “whenever you need to do a lot of computation but you don’t have a lot of power or time.”


What is Blockchain?

Blockchains in Bitcoin.


A blockchain is a public ledger of all Bitcoin transactions that have ever been executed. It is constantly growing as ‘completed’ blocks are added to it with a new set of recordings. The blocks are added to the blockchain in a linear, chronological order. Each node (computer connected to the Bitcoin network using a client that performs the task of validating and relaying transactions) gets a copy of the blockchain, which gets downloaded automatically upon joining the Bitcoin network. The blockchain has complete information about the addresses and their balances right from the genesis block to the most recently completed block.


Blockchain formation.

The blockchain is seen as the main technological innovation of Bitcoin since it stands as proof of all the transactions on the network. A block is the ‘current’ part of a blockchain which records some or all of the recent transactions, and once completed goes into the blockchain as a permanent database. Each time a block gets completed, a new block is generated. There is a countless number of such blocks in the blockchain. So are the blocks randomly placed in a blockchain? No, they are linked to each other (like a chain) in proper linear, chronological order with every block containing a hash of the previous block.

To use conventional banking as an analogy, the blockchain is like a full history of banking transactions. Bitcoin transactions are entered chronologically in a blockchain just the way bank transactions are. Blocks, meanwhile, are like individual bank statements.

Based on the Bitcoin protocol, the blockchain database is shared by all nodes participating in a system. The full copy of the blockchain has records of every Bitcoin transaction ever executed. It can thus provide insight about facts like how much value belonged a particular address at any point in the past.

In the above representation, the main chain (black) consists of the longest series of blocks from the genesis block (green) to the current block. Orphan blocks (purple) exist outside of the main chain.




Working of Bitcoin and Blockchain


 A blockchain – originally block chain– is a distributed database that is used to maintain a continuously growing list of records, called blocks. Each block contains a timestamp and a link to a previous block. A blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for validating new blocks. By design, blockchains are inherently resistant to modification of the data. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks and the collusion of the network. Functionally, a blockchain can serve as “an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way. The ledger itself can also be programmed to trigger transactions automatically.”