Nerve Stimulation May Prevent Migraines

Photograph of the Cefaly anti-migraine device, courtesy of STX-Medssprl via Creative Commons licensing
Photograph of Cefaly anti-migraine device, courtesy of STX-Med via Creative Commons license

While shopping for groceries at Trader Joes, suddenly your peripheral vision disappears. This could be frightening, but you know what is coming — a one-sided pulsating pain, sensitivity to light and noise, nausea, vomiting and seeing flashing lights. You quickly drive home and cancel your plans, because you have a migraine coming. You need to lie still in a dark quiet room for the next 24 hours.

Migraines affect about 30 million Americans. This means that one in four households in the US have at least one member impaired by migraines. Women are three times more likely to be migraine sufferers than men.

Unfortunately, there is currently no cure for migraines. A migraine diary can help identify the headache triggers to avoid. Medications can also help reduce the number of attacks or ease the symptoms, but these medications are often ineffective or cause unpleasant side effects.

Instead migraine sufferers might find relief from a new non-medicinal alternative, a device called a supraorbital transcutaneous stimulator (STS) that stimulates the nerves around the eyes and forehead. A study recently published in Neurology tested the safety and effectiveness of this STS device designed to prevent migraines.

Conducted by researchers in five specialized headache clinics in Belgium, this study was a randomized controlled trial that compared the STS device with an identical-looking sham device. Study participants were aged 18 to 65 who routinely experienced a minimum of two migraine attacks per month. None of the 67 participants had taken anti-migraine medications in the three months leading up to the study.

Both the STS and sham devices used a self-adhesive electrode placed on the forehead that buzzed identically during treatment. Only the STS devices delivered electrical impulses. The participants wore one of the devices for 20 minutes per day for 90 days.

The participants’ migraine diaries indicated that the number of migraine attacks dropped by at least half for 38% of the participants using the STS device, compared with 12% for those using the sham device. Although the severity of the migraines was not reduced, people using the STS device had fewer days with headache, fewer total migraine attacks, and used fewer pain relief medications each month. Most importantly, there were no adverse effects seen in either group.

The study concluded that treatment with a STS device is “effective and safe as a preventive therapy for migraine.” However, only 67 migraine sufferers have been studied and the use of this device was only examined for three months. Larger studies with longer-term treatment are needed to confirm that this STS device is safe and effective.

For more information about migraines and the STS device, check out my KQED Quest blog.

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Curiosity and Nervousness over the Mars Landing

Artist's concept animation depicting the moment that NASA's Curiosity rover touches down onto Mars.
Artist’s animation depicting the moment that NASA’s Curiosity rover touches down onto Mars. (NASA/JPL-Caltech image)

When I tried to make lunch plans with a friend for next week, he didn’t know yet whether he could meet me. That’s because his plans depend on how smoothly the Curiosity rover lands on Mars tonight. His research team put together the Radiation Assessment Detector that is mounted on the top deck of the Curiosity rover.

NASA’s Mars Science Laboratory spacecraft with the Curiosity rover are approaching Mars at this moment. It’s expected to land tonight at 10:31 p.m. PDT (Pacific Daylight Time). The technical challenges involved in the Curiosity’s landing are daunting. The final minutes to landing are described beautifully in the NASA Jet Propulsion Laboratory’s popular video dubbed “The Seven Minutes of Terror.”

We still aren’t sure if life ever existed on Mars. From past missions, researchers know that there used to be water there. Now they want to determine if Mars once had the kind of environment that could be habitable or conducive for the formation of microbial life.

The Curiosity rover is a car-like rover that will search Mars for past or present conditions favorable for life on the planet. It is basically a science lab on wheels, including 10 complex scientific instruments. These instruments are designed to study the chemistry of rocks, soil and atmosphere — searching for signs of past life on Mars.

One of those scientific instruments is the Radiation Assessment Detector, which is designed to characterize the energetic particle spectrum at the surface of Mars. This will allow researchers to determine the radiation dose for humans at the planet surface, as well as provide input on the effects of particles on the surface and atmosphere. The surface is thought to have much higher radiation than Earth, since Mars has a thinner atmosphere and no global magnetic shield to divert charged particles.

Although all research requires patience, hurling your research instrument at a far away planet requires both patience and guts. The landing may cause 7 minutes of terror, but the days of waiting must include its own nail-biting nervousness. When I get together with my friend for lunch, I’ll check his nails. Hopefully the landing will be a success, so he’ll be at the Jet Propulsion Laboratory for the next couple weeks though. I can wait.

Ultrafast Laser Synchronization Breakthrough

AMO experiment schematic
Set-up of a nitrogen pulse-pump experiment that uses pulse arrival time information from a cross-correlator mounted downstream from the experiment. Figure courtesy of SLAC National Accelerator Laboratory.

A journal article, just published in Applied Physics Letters, details a major breakthrough for experiments at SLAC’s Linac Coherent Light Source (LCLS).

LCLS delivers intense ultrashort x-ray pulses that can be used to study the motion of atoms as they respond to external triggers, such as an optical laser. In these “pump-probe” experiments, the optical laser “pump” pulse starts a reaction in the material, while the x-ray “probe” pulse investigates the state of the material after a defined time delay. A sequence of x-ray pulses, with different time delays between the laser and x-ray pulses, is used to “film” the reaction in the material.

LCLS ultrafast x-ray pulses basically act like high-speed flashes of a camera strobe, allowing scientists to capture images with a “shutter speed” of less than 100 femtoseconds – the time it takes light to travel the width of a human hair.

In order to be able to “film” optically-induced ultrafast processes, however, scientists need more than just ultrashort x-ray and laser pulses. They also need to synchronize the x-ray pulses to the optical laser pulses with almost femtosecond accuracy, in order to have snapshots with good time resolution (“sharp focus”). This is a major challenge, since the main laser system for the x-ray free electron laser is a kilometer away from the optical laser and experiment.

State-of-the-art synchronization is performed at LCLS by accurately measuring the arrival times of the electron bunches (and corresponding x-ray pulses) relative to the radiofrequency that drives the accelerator, since the optical laser is locked to this reference radiofrequency. The best time resolution so far achieved with this approach is 280 fs (full width at half maximum, FWHM).

Recently, scientists at the LCLS Atomic, Molecular and Optical Science Instrument (AMO) dramatically improved the time resolution for their pump-probe experiments. Their new synchronization strategy is to directly measure the relative arrival time of both the x-ray and optical laser pulses at the experiment on a shot-by-shot basis. They do this by introducing into the x-ray beam what they call a cross-correlator, which is mounted downstream of the main experiment.

AMO scientists split their laser beam, sending it to both a pump-probe experiment and the cross-correlator (with a time delay). In the cross-correlator, the laser beam is reflected off a Si3N4 thin film. The spot of the laser pulse is then imaged with a long-distance microscope on a CCD camera. X-ray pulses also hit the same surface of the Si3N4 film, quasi-instantaneously changing the surface reflectivity.

The x-ray pulse very briefly changes the surface reflectivity. By imaging and measuring the position of this reflectivity change with the reflected laser, AMO scientists can directly measure the relative arrival time of the x-ray and optical laser pulses at their experiment. The scientists then use this pulse arrival time information from the cross-correlator to correct their corresponding experimental data on a shot-by-shot basis.

The AMO team demonstrated their improved time resolution with a nitrogen pump-probe experiment. With the time information from the cross-correlator, they were able to decrease the time resolution of their nitrogen experiment down to only 50 fs (FWHM). That’s almost down to the theoretical limit, allowing scientists to investigate all sorts of new ultrafast science.

Solar Research Shines

sunshine
Courtesy of Creative Commons

Everyone loves the idea of solar power — heating and cooling your home using the sun as a clean, free source of power. It sounds like the ultimate way to lower your carbon foot print! However, solar cells are expensive and typically only about 15% efficient, as I discussed in an earlier blog.

In order to make solar power more practical on a wide scale, a lot of research is underway to increase solar power efficiency. Stanford researchers have just reported a significant breakthrough in such solar power research, as described in their new paper in Nature Materials. They have developed a novel solar technology that uses both the light and heat of the sun to generate electricity. This new technology could double solar power efficiency and make it more affordable.

When most people think of solar power, they think of rooftop solar panels. These sort of solar panels (or arrays of photovoltaic solar cells) use expensive semiconductor materials to convert photons of light into electricity. The photons from sunlight are absorbed by the semiconductor material, so the energy from the photons is given to the electrons in the semiconductor. The energy given to an electron can “excite” it from the valence band to the conduction band, where it is free to move around within the semiconductor to produce electricity. Solar panels basically convert solar energy into direct current electricity. However, these types of solar panels aren’t very efficient. If an excited photon doesn’t absorb enough energy, then it can’t make it to the conduction band to produce electricity. On the other hand, if an excited photon absorbs more energy than needed (to make it to the conduction band) then the excess energy is lost as heat. In silicon solar panels, half of the solar energy that hits the solar panel is lost due to these two processes. Ideally you would like to somehow harvest the energy that is lost as heat, in order to make solar cells more efficient.

Solar power can also be generated by a thermionic energy convertor, which directly converts heat into electricity. A thermionic converter produces electricity by causing a heat-induced flow of electrons from a hot cathode across a vacuum gap to a cooler anode. However, only a small fraction of the electrons gain sufficient thermal energy to generate this kind of electricity, and very high temperatures are needed for efficient thermionic conversion.

The Stanford researchers have recently developed a new process that exploits the benefits of both solar and thermal cell conversion. The research was led by Nicholas Melosh, as a joint venture of Stanford and SLAC National Accelerator Laboratory. Melosh’s group coated a piece of semiconducting material with a thin layer of metal cesium, demonstrating that this allowed the material to use both light and heat to generate electricity. This new PETE (photon-enhanced thermionic emission) device used the same basic architecture as a thermionic converter except with this special semiconductor as the cathode.

Although the physical process of this PETE device is different than the standard solar cell mechanisms, the new device gives a similar response at very high temperatures. In fact, the PETE device is most efficient at over 200 C. This means that PETE devices won’t replace rooftop solar panels, since they require higher temperatures to be efficient. Instead, they could be used in combination with solar concentrators as part of a large scale solar power plant, for instance in the Mojave Desert.

Melosh’s initial “proof of concept” research was performed with the semiconductor galium nitride to demonstrate that the new energy conversion process works, but galium nitride isn’t suitable for solar applications. They plan to extend their research to other semiconductors, such as gallium arsenide which is commonly used in household electronics. Based on theoretical calculations, they expect to develop PETE devices that operate with a 50 percent efficiency at temperatures exceeding 200 C. They hope to design the new PETE devices so they can be easily incorporated into existing solar power plants, significantly increasing the efficiency of solar power to make it competitive with oil.

Robotic Arm Reaches Out To Knee Surgeons

Orthopedic surgeons have found a helpful hand, or more precisely a robotic arm, that will allow them to perform more accurate knee surgeries. MAKO Surgical has released a Robotic Arm Interactive Orthopedic System that is designed to assist surgeons during knee resurfacing operations. This medical robotic arm has just been selected by R&D Magazine as a winner of the 48th Annual R&D 100 Awards, identifying it as one of the 100 most technologically significant products introduced into the marketplace over the past year.

More than 10 million Americans have knee osteoarthritis, and it is the most common cause of disability in the United States. Osteoarthritis occurs when the cartilage between two bones is worn down and the bones begin to directly rub against each other at the joint. The main problem for knees is the deterioration of the articular cartilage, the smooth lining that covers the ends of the leg bones where they meet to form the knee joint. This cartilage deterioration typically leads to pain, stiffness, limited range in motion of the knee, localized swelling, and the formation of bone spurs (small growths of new bone). The pain is usually worse after activity.

Knee osteoarthritis is diagnosed based on medical history, physical examination, x-ray imaging and possibly MRI (magnetic resonance imaging). Although many people with osteoarthritis don’t need surgery, in some cases surgery is required. Surgery may involve joint replacement in which the rough worn surfaces of the joint are replaced with a smooth artificial material, such as metal or plastic pieces.

Most people affected by osteoarthritis of the knee are older than 45 years. However, some younger active patients have early osteoarthritis. Such patients with arthritis in only one area of the knee can have partial knee resurfacing surgery, which is significantly less invasive than standard total knee replacement surgery. Partial knee resurfacing replaces only the deteriorated section of the knee with a small partial knee implant, without disturbing the knee’s healthy tissue. The benefits of this less invasive surgery can be significant: smaller incision, less bone removed, less discomfort, shorter hospital stay, less physical therapy required, and more rapid healing. Since less bone is removed (about 0.25” instead of 0.5”), future total knee replacement surgery can also be more easily performed, if necessary.

However, partial knee resurfacing can be a difficult operation to perform. Using the MAKO robotic arm system to assist with the surgery will hopefully provide increased stability and precision. It also allows the surgery to be performed for a greater number of patients, since it allows the replacement of the top (patellofemoral) portion of the knee joint instead of just the inner (medial) or outer (lateral) portion. The system provides patient-specific, pre-surgical planning with 3-D modeling based on CT (x-ray computed tomography) images. The system also provides real-time visual, tactile and auditory feedback during the surgery. This should enable the orthopedic surgeons to more precisely position the partial knee implants. Hopefully this new technology will help provide a more natural feeling artificial knee and a healthier active lifestyle to some people that suffer from knee osteoarthritis.

Solar-Powered Drip Irrigation May Save Lives in Africa

Americans spend on average 12.4% of their paycheck on food according to the U.S. Department of Labor’s latest survey. In contrast, sub-Saharan African communities spend 50-80% of their income on food, even though they are engaged in agricultural production as their main livelihood. These communities rely on rain-fed agriculture for crop production, despite having a short annual rainy season of only 3-6 months. Traditionally women and girls are responsible for hauling water by hand from very long distances in order to grow some crops, particularly during the long dry season.

Only 4% of cropland is irrigated in sub-Saharan Africa. Clearly irrigation could help improve quality of life for these food-insecure communities, if a water source is available. The most efficient type of irrigation for such a dry climate is drip (micro) irrigation, which delivers water and fertilizer directly to the roots of a plant. Low-pressure drip irrigation systems require only 1 m of pressure to irrigate plots of up to 1,000 square meters (0.25 acres). However, this irrigation technology requires access to a reliable water source.

One solution is a photovoltaic-powered drip irrigation system that combines the efficiency of the drip irrigation with the reliability of a solar-powered water pump. In such a system, a photovoltaic solar array powers a surface or submersible pump (depending on the water source) that feeds water into a reservoir. The reservoir then gravity-distributes the water to the low-pressure drip irrigation system. Energy is stored via the height of column of water in the reservoir. These systems can be configured so that no batteries are required. The pump only runs during the daytime and the system passively self-regulates. Namely, the volume of water increases on clear hot days when plants need the most water.

This kind of solar-powered drip irrigation system was tested in two rural villages in Northern Benin. The systems were installed and financed by an Non-governmental Organization, Solar Electric Light Fund, with the goal of boosting vegetable production from communal gardens in order to combat high malnutrition and poverty levels. The research was performed in collaboration with Stanford University. This NGO-academic research team scientifically evaluated the impact of the irrigation system on the community through a randomized controlled project that was rigorously studied and analyzed. The study results were recently published by Stanford University in the Proceeding of the National Academy of Sciences.

Three solar-powered drip irrigation systems were installed in two villages. Each irrigation system was used collectively by an agricultural group of 30-35 women, who each farmed her own 120 square meter plot and some additional shared plots used for group expenses. Researchers monitored these communities, as well as two “control” villages in which women’s agricultural groups grew vegetables by hand watering. This allowed a comparison between the solar-powered drip irrigation system to traditional watering method.

Each of the solar-powered irrigation systems supplied on average 1.9 tonnes of produce per month — including high-valued crops such as tomatoes, okra, peppers, eggplants, carrots, and greens — without displacing other agricultural production. The women farmers kept on average 18% by weight of the vegetables and sold the rest at local markets. As a result, vegetable intake across all villages increased by about 1 serving (150 g raw weight) per day during the rainy season. For the villages with irrigation systems, the vegetable intake rose to 3-5 servings per day even during the dry season. Overall the users of the irrigation systems showed remarkable benefits even in the first year, compared with the control households. The article states, “Their standard of living increased relative to the non-beneficiaries (by 80% of the baseline), their consumption of vegetables increased to the Recommended Daily Allowance, and the income generated by production of market vegetables enabled them to purchase staples and protein during the dry season.”

Hardly anyone is going to argue against the potential benefit of irrigation in Africa. However, one question remains — is the expense of a solar-powered system really necessary? The Stanford researchers would argue that it is, despite the expensive up-front costs. They compared their irrigation system with a hypothetical alternative system that used a liquid-fuel (gasoline, kerosene, or diesel) engine-driven pump, instead of the photovoltaic array and pump. This alternate pump can have significant problems, because fuel supplies can be unreliable and fuel prices volatile. According to their analysis, the solar-powered irrigation system is actually more cost effective in the long run, particular when fuel prices are high. It is also better for the environment since it doesn’t cause carbon-emissions.

The solar-powered drip irrigation system in the Benin project cost approximately $18,000 to install ($475 per 120 square meter plot) and requires about $5,750 ($143 per plot) per year to maintain. Based on the projected earnings of the farmers, the system should pay for itself in about 2.3 years. In addition, the cost of the photovoltaic arrays is expected to lower for larger-scale projects.

The project in Benin isn’t the only one underway. Solar-powered drip irrigation systems are also being installed by other groups in different areas of the world. For instance, the Sustainable Agriculture Water Management Project has installed solar-powered drip irrigation systems to 5,000 farmers in Sri Lanka’s dry zones. The hope is that these international efforts can provide substantial economic, nutritional, and environmental benefits to food-insecure impoverished communities.