Tag Archives: wireless

New approach creates power out of thin WiFi

Researchers at the National University of Singapore (NUS) and the Tohoku University (TU), Japan, are working to make a device near you powered by the WiFi signals that are commonplace in the modern world.

Image via Pixabay.

Wireless networks are everywhere in towns and cities today. They connect a million devices to the Internet, day in, day out. Needless to say, that’s a lot of energy — over the 2.4GHz radio frequency that such networks use — being beamed all around us all the time. New research is working to harness this energy for a useful purpose, such as charging (for now, tiny) devices.

Airdropping charge

“We are surrounded by WiFi signals, but when we are not using them to access the Internet, they are inactive, and this is a huge waste. Our latest result is a step towards turning readily-available 2.4GHz radio waves into a green source of energy, hence reducing the need for batteries to power electronics that we use regularly.”

“In this way, small electric gadgets and sensors can be powered wirelessly by using radio frequency waves as part of the Internet of Things. With the advent of smart homes and cities, our work could give rise to energy-efficient applications in communication, computing, and neuromorphic systems,” said Professor Yang Hyunsoo from the NUS Department of Electrical and Computer Engineering, who led the research.

The team developed a new technology that uses tiny smart devices known as spin-torque oscillators (STOs), which can harvest and convert wireless radio waves into power for devices. They showed that these devices can successfully harvest energy from WiFi signals and that they could generate enough energy to power a light-emitting diode (LED) wirelessly, without using a battery.

STOs are devices that can receive radio signals and transform them into microwaves. Although that sounds amazing, they’re still an emerging technology, and are still quite inefficient at their job. Currently, STOs are only able to output low levels of power.

One workaround we’re using right now is to stack several STOs together, but this isn’t always viable: many devices have spatial constraints because nobody likes chunky items. Individual STOs are also limited in the range of frequencies they can react to, generally limited to only a few hundred MHz, which further complicates their use.

The team’s solution was to use an array of eight STOs connected in a series. This was then used to convert the 2.4 GHz electromagnetic radio waves used by WiFi into a direct voltage signal (electrical current), fed to a capacitor, and used to light a 1.6-volt LED. Five seconds of charging time on the capacitor was enough to keep the LED lit for one minute with the wireless power switched off.

As part of the research, they also performed a comparison between the STOs series design they used and a parallel design. The latter, they explain, has better time-domain stability, spectral noise behavior, and control over impedance mismatch — or, more to the point for us laymen, it’s better for wireless transmission. The series layout is more efficient at harvesting energy.

“Aside from coming up with an STO array for wireless transmission and energy harvesting, our work also demonstrated control over the synchronising state of coupled STOs using injection locking from an external radio-frequency source,” explains Dr Raghav Sharma, the first author of the paper.

“These results are important for prospective applications of synchronised STOs, such as fast-speed neuromorphic computing.”

In the future, the team plans to increase the number of STOs in their array, and test it for wirelessly charging other devices and sensors. They also hope to get interest from industry in developing on-chip STOs for self-sustained smart systems.

The paper “Electrically connected spin-torque oscillators array for 2.4 GHz WiFi band transmission and energy harvesting” has been published in the journal Nature Communications.

Bio-compatible wireless sensors developed to monitor brain injury

An international research team has developed miniaturized devices to monitor living brain tissue. When no longer needed the devices can be deactivated to dissolve and be reabsorbed into the soft tissue. The wireless sensors were implanted into mice brains and successfully took intracranial pressure and temperature readings.

Dissolvable brain implant consisting of pressure and temperature sensors (bottom right) connected to a wireless transmitter. Image via theguardian

Dissolvable brain implant consisting of pressure and temperature sensors (bottom right) connected to a wireless transmitter. Kang et al, 2017

Electronic implants have long been used in the treatment of medical conditions. Ranging from the humble pacemakers and defibrillators given to cardiac patients all the way to futuristic brain-computer interfaces or injectable meshes that fuse with your brain, it’s hard to imagine today’s medical field without these devices.

Whether implanted permanently or only for short periods of time, the procedure always carries some risk — the devices can hurt surrounding tissues during implantation and their metallic components are prime real estate for bacteria, possibly leading to infections in the area. Not to mention the added risk and distress involved in removing these devices.

The novel device, developed by a research team with members from America and South Korea, is described in the journal Nature and could potentially overcome these limitations. Each device houses a pressure and a temperature sensor, each one smaller than a grain of rice. They’re housed in a biodegradable silicone chip that rests on the brain and sends data via wireless transmitters attached to the outside of the skull.

The devices were successfully tested on live rats and recorded pressure and temperature changes that occurred as the animals drifted in and out of consciousness under anesthesia. They proved to be at least as or more accurate than other devices currently available.

The team showed that by tweaking the sensors they could take measurements either from the surface of the brain up to about 5mm below it. The researchers say the device can easily be modified to monitor a wide range of other important physiological parameters of brain function, such as acidity and the motion of fluids. It could also be used to deliver drugs to the brain, and, with the incorporation of microelectrodes, to stimulate or record neuronal activity.

However, what truly makes this sensor unique is the materials that go into building them, the so-called “green electronics.” These materials are designed to be stable for a few weeks then dissolve. If immersed in watery fluids (such as cerebrospinal fluid) these fully biodegradable and bio-compatible materials take about a day to fully dissipate. When the team examined the animal’s brains after the tests, they found no indication of inflammation or scarring around the implantation site.

As well as being safer for the patient the fabrication process is also cheaper and more environmentally-friendly than that employed in existing technologies.

The next step in development is to test the devices in human clinical trials, the researchers said.

The full paper describing these devices is available online in the journal Nature.

Wireless implants can block or induce the sensation of pain

Researchers at the Washington University School of Medicine, St. Louis and University of Illinois at Urbana-Champaign have developed implantable devices that can activate — and in theory, block too — pain signals traveling from the body through the spinal cord before they reach the brain.

The devices are controlled through wireless technology and have huge application in the treatment of chronic pain in parts of the body that don’t respond to other types of treatment. The full study has been published in the journal Nature Biotechnology.

Implanted microLED devices light up, activating peripheral nerve cells in mice.
Image via phys

“Our eventual goal is to use this technology to treat pain in very specific locations by providing a kind of ‘switch’ to turn off the pain signals long before they reach the brain,” said co-senior author Robert W. Gereau IV, PhD, the Dr. Seymour and Rose T. Brown Professor of Anesthesiology and director of the Washington University Pain Center.

The devices are soft and stretchable so they can be implanted into any part of the body, Gereau explains. Previously, similar devices had to be anchored to bone tissue and proved problematic with limbs or other movable body parts.

“But when we’re studying neurons in the spinal cord or in other areas outside of the central nervous system, we need stretchable implants that don’t require anchoring,” he said.

The implants are sutured in place, and each boasts a microLED light that can activate specific neurons. The team behind them hopes to use the implants to blunt pain signals in patients who have pain that cannot be managed with standard therapies.

Experiments with genetically engineered mice (that were given light-sensitive proteins in some of their nerve cells) showed great promise for the devices. To demonstrate that the implants could influence the pain pathway in nerve cells, researchers induced a pain response. The mice were placed in a maze and as they walked through a specific area, the devices lit up and caused the little rodents to feel discomfort. When they left the area, the devices turned off, and the animals quickly learned to avoid the pain inducing part of the maze.

The experiment would have been very difficult with older optogenetic devices, which are tethered to a power source and can inhibit the movement of the mice.

As the new devices are smaller than those previously available, flexible and can be sutured in place, they have potential uses bladder, stomach, intestines, heart or other organs.

“They provide unique, biocompatible platforms for wireless delivery of light to virtually any targeted organ in the body,” he said.

Rogers and Gereau designed the implants with an eye toward manufacturing processes that would allow for mass production so the devices could be available to other researchers. Gereau, Rogers and Michael R. Bruchas, PhD, associate professor of anesthesiology at Washington University, have launched a company called NeuroLux to aid in that goal.

Facebook’s Aquila will bring solar-powered internet to regions not yet connected

This giant, solar-powered, internet giving drone is ready to take to the skies.

By far the most awesome router.
Image via foxnews

Facebook recently unveiled the Aquila, a V-wing flying drone with the wingspan of a Boeing 737 ( almost 93 ft/28.35 m ), which the media giant plans to use to connect developing regions around the world to the internet, and gather a huge amount of likes in the meantime. As there are currently an estimated 5 billion people that don’t have any way to access the world wide web, Facebook hopes the Aquila will be its key to tap into a huge and lucrative market.

Huge but light

The Aquila is quite large – huge compared to other drones – it is quite light, only weighing between 880 and 1,100 pounds ( 400 to 500 kilograms ) as the craft is meant to reach extremely high altitudes, above commercial planes and much of the cloud cover.

Beaming down Internet!
Image via alphr

“I’m excited to announce we’ve completed construction of our first full scale aircraft, Aquila, as part of our Internet.org effort,” Zuckerberg wrote. “Aquila is a solar powered unmanned plane that beams down Internet connectivity from the sky. It has the wingspan of a Boeing 737, but weighs less than a car and can stay in the air for months at a time.”

“When deployed, it will be able to circle a remote region for up to 90 days, beaming connectivity down to people from an altitude of 60,000 to 90,000 [feet],” according to Facebook.

In order to conserve energy, the plane will lower its altitude at night when sunlight is not available to power the planes.

And it has lasers

In regions without Internet access, ground-based lasers will pinpoint the location of the nearest Aquila. The craft will move towards the signal, then determine the specific location based on the laser signal. Because the Aquila depends on laser communication via the sky, Internet service can become slow and patchy in bad weather weather.

But Facebook is making great progress with lasers. The company has tested a system that delivers data at the speed of dozens of gigabytes per second, much higher than the current technology in use can deliver.

“We’ve also made a breakthrough in laser communications technology. We’ve successfully tested a new laser that can transmit data at 10 gigabits per second. That’s ten times faster than any previous system, and it can accurately connect with a point the size of a dime from more than 10 miles away.”

The Aquila drones are designed to stay airborne for up to three months, far longer than the current record of two weeks. To enable such a long flight, Facebook has equipped its autonomous plane with solar panels, which cover the top of the plane’s body. The company hopes that this longevity will allow for the creation of a resilient network of Internet-transmitting planes. In partnership with local carriers, the Aquila could play an important role in finally opening the world wide web to the whole wide world.

 

This five-cell metamaterial converts stray microwave energy, as from a WiFi hub, into more than 7 volts of electricity with an efficiency of 36.8 percent—comparable to a solar cell. (c) Duke University

Microwave harvester converts wireless energy into direct current with solar cell-like efficiency

This five-cell metamaterial converts stray microwave energy, as from a WiFi hub, into more than 7 volts of electricity with an efficiency of 36.8 percent—comparable to a solar cell. (c) Duke University

This five-cell metamaterial converts stray microwave energy, as from a WiFi hub, into more than 7 volts of electricity with an efficiency of 36.8 percent—comparable to a solar cell. (c) Duke University

Using a range of cheap materials arranged in a specific manner, researchers at Duke University have demonstrated a device that captures microwave signals, such as those relayed by WiFi or even satellites high up above in Earth’s orbit, an converts this free, lost energy into electrical current. The harvesting and conversion efficiency of the device is on par with currently photo-voltaic solar panels. In the future, such circuits could be used to always wirelessly power your phone when it’s not in use or charge a battery in your home.

It’s enough to open  your notebook just about anywhere downtown in a developed city to spot tens and tens of public WiFi hotspots. There are maybe tens of thousands of WiFi networks in a developed city, and all of these waste energy by constantly relaying microwave signals. The same applies to satellites, sound signals and other sources. What if you could harvest and cut the waste a bit?

This is what the Duke team of engineers, comprised of undergraduate engineering student Allen Hawkes, working with graduate student Alexander Katko and lead investigator Steven Cummer, set out to do. Using simple materials like five fiberglass and copper energy conductors wired together on a circuit board  to form a five-cell metamaterial array. The resulting device harnesses microwave energy and converts it into direct current 7.3V electricity. For reference, your  Universal Serial Bus (USB)  charges small electronic devices with 5V, so a system coupled with the Duke metamaterial circuit could provide free charging for your mobile devices.

“We were aiming for the highest energy efficiency we could achieve,” said Hawkes. “We had been getting energy efficiency around 6 to 10 percent, but with this design we were able to dramatically improve energy conversion to 37 percent, which is comparable to what is achieved in solar cells.”

“It’s possible to use this design for a lot of different frequencies and types of energy, including vibration and sound energy harvesting,” Katko said. “Until now, a lot of work with metamaterials has been theoretical. We are showing that with a little work, these materials can be useful for consumer applications.”

Microwave harvester

Another application could be to improve the energy efficiency of appliances by wirelessly recovering power that is now lost during use.

“The properties of metamaterials allow for design flexibility not possible with ordinary devices like antennas,” said Katko. “When traditional antennas are close to each other in space they talk to each other and interfere with each other’s operation. The design process used to create our metamaterial array takes these effects into account, allowing the cells to work together.”

A metamaterial coating could be applied to the ceiling of your living room, for instance, to harvest free energy from microwaves that litter space all around us. A more interesting, and maybe more practical, application might be coating smartphones with a thin layer of mematerial directly, so your phone charges constantly with significant benefits for your battery life. It’s unclear though how much voltage a thin and small surface metamaterial circuit might provide.

“Our work demonstrates a simple and inexpensive approach to electromagnetic power harvesting,” said Cummer.  “The beauty of the design is that the basic building blocks are self-contained and additive. One can simply assemble more blocks to increase the scavenged power.”

In remote locations, like in the desert or the middle of the wilderness, a series of power-harvesting blocks could be assembled to capture the signal from a known set of satellites passing overhead. The generated power would be far from impressive, of course, but it might still be enough to power a small array of sensors, the researchers believe.

Their device and findings were reported in the journal Applied Physics Letters

 

how-ip-camera-works

How IP cameras work: the basics of modern surveillance

In an ever more crowded and complex world, people are more aware of the need for security, both in business settings and at home.  The need for alarm systems, limited access, extra locks, and passwords are all common these days.  Surveillance via a system of digital cameras is also gaining popularity, and such systems can be surprisingly affordable for those on a tight budget.  Such surveillance commonly uses internet protocol cameras, also known as IP cameras, to effectively monitor important locations in a home or office.   While it is standard in many commercial and industrial settings, these cameras can easily be used for home surveillance too.

A Digital Generation of Cameras

Cutting edge digital surveillance cameras have surpassed the old model of closed circuit television, seen frequently in the corner of the room in minimarts and banks.  These new digital cameras use a computer network to both send and receive information.  In this new system, the network manager does not need to be in one place, as these cameras can be accessed over the internet.  If a building has wi-fi capability, then the system can be accessed anywhere.  This can help efficiency.  For example, it allows security team officers to patrol the second floor of a store and still access a live feed of the first floor.  The cameras are smaller, and the visual resolution is better too.   They even offer HD capability.

how-ip-camera-works

Special Features

New digital surveillance cameras function like webcams, but they can do more, too.  For instance, they can be controlled remotely and repositioned for different usage.  This might come into play with different uses of a space.  For example, if a politician is giving a speech in the lobby of a hotel, the camera could be pointed at a podium rather than on the entry doors.  Another great feature is offered on cameras set up to respond to movement, sound, or heat.  When nothing is going on, there is no wasted recording, but as soon as there is action, the camera goes live.  If there is a questionable incident, this makes it much easier to locate the desired footage.  This saves time and thus money.   These cameras can also be used to safely communicate over distance, as when a gas station attendant in a security cage safely communicates with a customer having a problem at the pump.

Home Security Applications

IP cameras can be used at home for personal use, whether it’s monitoring the liquor cabinet or the front porch.  Their uses are nearly endless.  Since some cameras are only a few inches long, they are easy to place in many spots:  on a shelf, beside a computer, on a counter, or even a windowsill.  The latter may be especially appropriate if there has been a rash of thefts in the area.  Parents with young children need to get out on the town once in a while, and they will often hire a nanny or babysitter.  That’s a perfect time to use a small camera for home surveillance.  If anything goes wrong, the parents can watch the footage and quickly get to the root of the problem.  When a teenage girl starts dating a boy the family doesn’t know, her parents may have some concerns.  While they may not want to embarrass either teenager with their presence, they may want to have a hidden camera in the living room or a bedroom– just in case.

Setup for the world record of wireless data transmission at 100 gigabits per second: The receiver unit (left) receives the radio signal that is recorded by the oscilloscope (right). (Photo: KIT)

World record wireless transmission of 100 Gbit/s achieved

German researchers at the Karlsruhe Institute of Technology (KIT) have achieved a new world record for wireless data transmission after they successfully reached  100 gigabits/second over a distance of 20 meters and  at a frequency of 237.5 GHz. This translates into a  transfer rate of 12.5 gigabytes per second – equivalent to exchanging the contents of a blue-ray disk or of five DVDs between two devices by radio within two seconds only! The previous record, achieved by the same KIT researchers, was of 40 Gbps.

For their experiment, the scientists used the latest photonic and electronic technologies.  First, the radio signals are generated by means of an optical method, which involves superimposing two laser signals of different frequencies. The resulting electrical signal has a frequency equal to the frequency difference of the two optical signals – 237.5 GHz. Several bits are combined by so-called data symbols and transmitted at the same time. Upon transmission, the radio signals are received by active integrated electronic circuits.

Setup for the world record of wireless data transmission at 100 gigabits per second: The receiver unit (left) receives the radio signal that is recorded by the oscilloscope (right). (Photo: KIT)

Setup for the world record of wireless data transmission at 100 gigabits per second: The receiver unit (left) receives the radio signal that is recorded by the oscilloscope (right). (Photo: KIT)

The radio signals are transmitted using  an ultra-broadband so-called photon mixer made by the Japanese company NTT-NEL.  The millimeter-wave electrical signal is then radiated via an antenna, while a semiconductor chip  that can cope with advanced modulation formats, like these huge working frequencies, translates the signal. As a result, the radio link can be integrated into modern optical fiber networks in a bit-transparent way.

“It is a major advantage of the photonic method that data streams from fiber-optical systems can directly be converted into high-frequency radio signals,” Professor Jürg Leuthold says. He proposed the photonic extension that was realized in this project. The former head of the KIT Institute of Photonics and Quantum Electronics (IPQ) is now affiliated with ETH Zurich. “This advantage makes the integration of radio relay links of high bit rates into optical fiber networks easier and more flexible.“ In contrast to a purely electronic transmitter, no intermediate electronic circuit is needed. “Due to the large bandwidth and the good linearity of the photon mixer, the method is excellently suited for transmission of advanced modulation formats with multiple amplitude and phase states. This will be a necessity in future fiber-optical systems,” Leuthold adds.

In the laboratory experiment, radio relay transmission has covered a distance of up to 20 m already. (Photo: KIT)

In the laboratory experiment, radio relay transmission has covered a distance of up to 20 m already. (Photo: KIT)

The research was part of the “Millilink” project which aims to  bring broadband internet connections to rural and under-connected areas.

“Our project focused on integration of a broadband radio relay link into fiber-optical systems,” Professor Ingmar Kallfass says. He coordinated the “Millilink” project under a shared professorship funded by the Fraunhofer Institute for Applied Solid State Physics (IAF) and the Karlsruhe Institute of Technology (KIT). Since early 2013, he has been conducting research at Stuttgart University. “For rural areas in particular, this technology represents an inexpensive and flexible alternative to optical fiber networks, whose extension can often not be justified from an economic point of view.”

The KIT researchers are confident they can scale their technique and increase data rate even further. They consider a 1 terabit per second transfer to be feasible!

 “By employing optical and electrical multiplexing techniques, i.e., by simultaneously transmitting multiple data streams, and by using multiple transmitting and receiving antennas, the data rate could be multiplied,” says Swen König from the KIT Institute of Photonics and Quantum Electronics (IPQ), who conceived and conducted the recent world-record experiment. “Hence, radio systems having a data rate of 1 terabit per second appear to be feasible.”

Findings were reported in Nature Photonics.

A schematic of the brain-2-brain interface developed by University of Washington researchers.

Brain-to-brain interface allows first telepathic exchange of information between two humans

In a mind-boggling and, frankly, a bit frightening breakthrough, researchers at University of Washington have devised a brain-to-brain interface that for the first time has allowed the remote exchange of information between two human brains. The test that demonstrated the technology, although simple in nature, shows of a powerful display of force. One researcher (human brain #1), connected through a brain signal reading device sends this signal over the internet to a remotely located researcher (human brain #2) who responds. Namely, brain #1 instructs brain#2 to move his hand and press a key on the keyboard just by thinking about it. Powerful stuff!

Now, similar research has been made before, but only with animal subjects on the receiving end (Harvard researchers controlled the actions of a mouse through a brain-to-brain interface). Also, most importantly the technology devised by the University of Washington researchers is completely non-invasive, requiring no kind of implants or surgery what so ever.

In principle, the schematic of brain-to-brain information exchange is rather simple, exploiting work already employed in the field of medicine, particularly in brain-computer interfaces. Brain #1 is connected to a computer which receives electric signals from the brain via a strapped on special type of EEG, typically employed in brain-computer interfaces. This signal is then transmitted through the internet to a second computer, which picks it up and sends it to brain #2 through  a Magstim transcranial magnetic stimulation (TMS) machine – a exciting technology that stimulates specific neurons by  electromagnetic induction. TMS set-ups have been used successfully before in the field of medicine to stimulate the activity of regions of the brain associated with depression, or to reduce the activity of a region, which might help with the treatment of other conditions, such as Parkinson’s.

A schematic of the brain-2-brain interface developed by University of Washington researchers.

A schematic of the brain-2-brain interface developed by University of Washington researchers.

In the experiment, led by Rajesh Rao and Andrea Stocco, a video game is played in which the objective is to hit a target with a canon – both brains are playing the same game in a co-op fashion. Brain#1 doesn’t have any hands-on capabilities and can only watch and think of firing the cannon. Acting as the sender, brain#1 sends the signal over to brain#2 who has his hands over the ‘launch’ key. When stimulated, brain#2 acts and presses the key that launches a cannon ball at the target in the video game. A video presentation is available and can be seen below for a clear picture of how this brain-to-brain technology works.

“It was both exciting and eerie to watch an imagined action from my brain get translated into actual action by another brain,” Rao said. “This was basically a one-way flow of information from my brain to his. The next step is having a more equitable two-way conversation directly between the two brains.”

Now, I know what you’re thinking: mind-control devices; a real life, easy to implement Manchurian candidate. Amazing as the technology may be, claims such as these at this point offer way too much credit to the brain-to-brain interface than its deserves. Chantel Prat, who was also involved in the work, dispels any concerns: There’s no possible way the technology that we have could be used on a person unknowingly or without their willing participation.”

Could you actually send complex information like images, intricate action patterns (collectively twitch your fingers in a desired pattern, move your legs to a certain objective etc.) or verbal thoughts, essentially allowing for a telepathic conversation using this technology? Not yet. We still know very, very little about the human brain. You’d need to know exactly which part of the brain and precisely what neurons to target to relay this kind of information.

“The Internet was a way to connect computers, and now it can be a way to connect brains,” Stocco said. “We want to take the knowledge of a brain and transmit it directly from brain to brain.”

Recently Google unveiled Glass, a pair of high-tech spectacles that offers augmented reality capabilities, allowing the wearer to receive information like brand name, horse power and other technical aspects of a car just by looking at it for instance. In time, such technology might become not only as common as smartphones are today, but even more powerful. It’s not completely insane to image a world in a not so distance future in which people voluntarily have implants that allow the recipient to receive complex information like that relayed by Google Glass directly into the brain. The capabilities then seem endless and, again, terrifying at the same time. Not here to throw gas on conspiracy theorist fires, but I can’t help but entertain the idea.

source

Man sues neighbor for irritating his ‘electromagnetic allergies’

There are weird lawsuits you can understand, and then there are just weird lawsuits. If you find this sort of things interesting, you gotta listen to this: a man from Santa Fe filed a half a million dollars trial against his neighbor for using and iPhone and other wireless devices that trigger his ‘electrocmegnetic allergies’.

Wi Fi - the new yin and yang

Wi Fi - the new yin and yang

Yahoo News reports that Arthur F., the plaintiff has been sleeping at his friends or in his car in order to avoid the electromagnetic waves created by the Wi-Fi devices from the nearby house. He allegedly suffers Electromagnetic Sensitivity, with symptoms that include “nausea, vertigo, diarrhea, ringing in the ears, severe headaches and body aches, crippling joint pains, insomnia, impaired vision, impaired muscular control”, as well as others, even worse.

Even more, he’s not alone in his battle. Apparently there’s a whole group in Santa Fe that intends to remove all Wi-Fi hot spots because people are suffering from this sort of allergy. But wait, it’s not even an allergy; they want to classify it as a disability and are claiming Americans with Disabilities Act. What’s your take on this? If you ask me, it’s just a bunch of people trying to make some fuss and money where they shouldn’t but… I may be wrong.