A camera that powers itself

Wed, 04/15/2015 - 10:03am Holy Evarts, Columbia Univ. School of Engineering and Applied Science A video camera based on a self-powered image sensor can run indefinitely without an external power supply. Image: Computer Vision Laboratory, Columbia EngineeringA research team led by Shree K. Nayar, T.C. Chang Professor of Computer Science at Columbia Engineering, has invented a prototype video camera that is the first to be fully self-powered—it can produce an image each second, indefinitely, of a well-lit indoor scene. They designed a pixel that can not only measure incident light but also convert the incident light into electric power. "We are in the middle of a digital imaging revolution," says Nayar, who directs the Computer Vision Laboratory at Columbia Engineering. He notes that in the last year alone, approximately two billion cameras of various types were sold worldwide. "I think we have just seen the tip of the iceberg. Digital imaging is expected to enable many emerging fields including wearable devices, sensor networks, smart environments, personalized medicine, and the Internet of Things. A camera that can function as an untethered device forever—without any external power supply—would be incredibly useful." A leading researcher in computational imaging, Nayar realized that although digital cameras and solar panels have different purposes—one measures light while the other converts light to power—both are constructed from essentially the same components. At the heart of any digital camera is an image sensor, a chip with millions of pixels. The key enabling device in a pixel is the photodiode, which produces an electric current when exposed to light. This mechanism enables each pixel to measure the intensity of light falling on it. The same photodiode is also used in solar panels to convert incident light to electric power. The photodiode in a camera pixel is used in the photoconductive mode, while in a solar cell it is used in the photovoltaic model. Nayar, working with research engineer Daniel Sims BS'14 and consultant Mikhail Fridberg of ADSP Consulting, used off-the-shelf components to fabricate an image sensor with 30x40 pixels. In his prototype camera, which is housed in a 3D-printed body, each pixel's photodiode is always operated in the photovoltaic mode. The pixel design is very simple, and uses just two transistors. During each image capture cycle, the pixels are used first to record and read out the image and then to harvest energy and charge the sensor's power supply—the image sensor continuously toggles between image capture and power harvesting modes. When the camera is not used to capture images, it can be used to generate power for other devices, such as a phone or a watch. Nayar notes that the image sensor could use a rechargeable battery and charge it via its harvesting capability: "But we took an extreme approach to demonstrate that the sensor is indeed truly self-powered and used just a capacitor to store the harvested energy." "A few different designs for image sensors that can harvest energy have been proposed in the past. However, our prototype is the first demonstration of a fully self-powered video camera," he continues. "And, even though we've used off-the-shelf components to demonstrate our design, our sensor architecture easily lends itself to a compact solid-state imaging chip. We believe our results are a significant step forward in developing an entirely new generation of cameras that can function for a very long duration—ideally, forever—without being externally powered." Source: Columbia Univ.

Statins: Are these cholesterol-lowering drugs right for you?

Find out whether your risk factors for heart disease make you a good candidate for statin therapy. By Mayo Clinic Staff Statins are drugs that can lower your cholesterol. They work by blocking a substance your body needs to make cholesterol. Statins may also help your body reabsorb cholesterol that has built up in plaques on your artery walls, preventing further blockage in your blood vessels and heart attacks. Statins include medications such as atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev), pitavastatin (Livalo), pravastatin (Pravachol), rosuvastatin (Crestor) and simvastatin (Zocor). Lower-cost generic versions of many statin medications are available. Already shown to be effective in lowering cholesterol, statins may have other potential benefits. But doctors are far from knowing everything about statins. Are they right for everybody with high cholesterol? What kinds of side effects may occur? Can statins help prevent other diseases? Should you be on a statin? Whether you need to be on a statin depends on your cholesterol level, along with your other risk factors for cardiovascular disease. Most people should try to keep their total cholesterol level below 200 milligrams per deciliter (mg/dL) (6.22 millimoles per liter, or mmol/L). Low-density lipoprotein cholesterol (LDL, or "bad" cholesterol) should be below 100 mg/dL (3.37 mmol/L). But the numbers alone won't tell you or your doctor the whole story. High cholesterol is only one of a number of risk factors for heart attack and stroke. The most important factor to consider is a person's long-term risk of experiencing a heart attack or stroke. If the risk is very low, there is probably no need for statins, unless the LDL is above 190 mg/dL (4.9 mmol/L). If the risk is very high — for example, someone who has had a heart attack in the past — the person may benefit from statins, even if his or her cholesterol is not elevated. Risk assessment tools Your doctor may suggest using an online tool to better understand your long-term risks of developing heart disease. The American College of Cardiology and the American Heart Association have recently developed an online tool to predict a person's chances of having a heart attack in the next 10 years. For people under the age of 50, the Framingham cardiovascular disease risk calculator might be a better option because it provides a 30-year risk prediction. In addition to your cholesterol numbers, these risk calculators also ask about your age, race, sex, blood pressure and whether you have diabetes or smoke cigarettes. New cholesterol guidelines New guidelines from the American College of Cardiology and American Heart Association focus on four main groups of people who may be helped by statins: People who already have cardiovascular disease. This group includes people who have had heart attacks, strokes caused by blockages in a blood vessel, mini-strokes (transient ischemic attacks), peripheral artery disease, or prior surgery to open or replace coronary arteries. People who have very high LDL (bad) cholesterol. This group includes adults who have LDL cholesterol levels of 190 mg/dL (4.9 mmol/L) or higher. People who have diabetes. This group includes adults who have diabetes and an LDL between 70 and 189 mg/dL (1.8 and 4.9 mmol/L), especially if they have evidence of vascular disease. People who have a higher 10-year risk of heart attack. This group includes people who have an LDL above 100 mg/dL (1.8 mmol/L) and whose 10-year risk of a heart attack is 7.5 percent or higher. Lifestyle is still key for preventing heart disease Lifestyle changes are essential for reducing your risk of heart disease, whether you take a statin or not. To reduce your risk: Quit smoking and avoid secondhand smoke Eat a healthy diet that's low in saturated fat, trans fat, refined carbohydrates and salt, and rich in fruits, vegetables, fish, and whole grains. Be physically active, sit less and exercise regularly Maintain a healthy waist girth: less than 40 inches in men and less than 35 inches in women If you're following the recommended lifestyle behaviors but your cholesterol — particularly your LDL (bad) cholesterol — remains high, statins might be an option for you. Risk factors for heart disease and stroke are: Smoking High cholesterol High blood pressure Diabetes Being overweight or obese Family history of heart disease, especially if it was before the age of 55 in male relatives or before 65 in female relatives Not exercising Poor stress and anger management Older age Narrowing of the arteries in your neck, arms or legs (peripheral artery disease) See more In-depth Consider statins a lifelong commitment You may think that once your cholesterol goes down, you can stop taking medication. But if your cholesterol levels have decreased after you take a statin, you'll likely need to stay on it indefinitely. If you stop taking it, your cholesterol levels will probably go back up. The exception may be if you make significant changes to your diet or lose a lot of weight. Substantial lifestyle changes may help you lower your cholesterol without continuing to take the medication, but don't make any changes to your medications without talking to your doctor first. The side effects of statins Although statins are well-tolerated by most people, they do have side effects, some of which may go away as your body adjusts to the medication. Common, less serious side effects Muscle and joint aches (most common) Headache Nausea Rare but potentially serious side effects Muscle problems. Statins may cause muscle pain and tenderness, particularly if you're taking a high dosage. In severe cases, muscle cells can break down (rhabdomyolysis) and release a protein called myoglobin into the bloodstream. Myoglobin can damage your kidneys. Liver damage. Occasionally, statin use causes an increase in liver enzymes. If the increase is only mild, you can continue to take the drug. Contact your doctor immediately if you have unusual fatigue or weakness, loss of appetite, pain in your upper abdomen, dark-colored urine, or yellowing of your skin or eyes. Increased blood sugar or type 2 diabetes. It's possible your blood sugar (blood glucose) level may increase when you take a statin, which may lead to developing type 2 diabetes. Cognitive problems. Some people have experienced memory loss and confusion after using statins. However, scientific studies have failed to prove that statins actually cause cognitive problems. It's important to consider the effects of statins on other organs in your body, especially if you have health problems such as liver or kidney disease. Also, check whether statins interact with any other prescription or over-the-counter drugs or supplements you take. Keep in mind that when you begin to take a statin, you'll most likely be on it for the rest of your life. Side effects are often minor, but if you experience them, you may want to talk to your doctor about decreasing your dose or trying a different statin. Don't stop taking a statin without talking to your doctor first. What other benefits do statins have? Statins may have benefits other than just lowering your cholesterol. One promising benefit of statins appears to be their anti-inflammatory properties, which help stabilize the lining of blood vessels. This has potentially far-reaching effects, from the brain and heart to blood vessels and organs throughout the body. In the heart, stabilizing the blood vessel linings would make plaques less likely to rupture, thereby reducing the chance of a heart attack. Statins also help relax blood vessels, lowering blood pressure. Weighing the risks and benefits of statins When thinking about whether you should take statins for high cholesterol, ask yourself these questions: Do I have other risk factors for cardiovascular disease? Am I willing and able to make lifestyle changes to improve my health? Am I concerned about taking a pill every day, perhaps for the rest of my life? Am I concerned about statins' side effects or interactions with other drugs? It's important to take into account not only your medical reasons for a decision, but also your personal values and concerns. Talk to your doctor about your total risk of cardiovascular disease and discuss how your lifestyle and preferences play a role in your decision about taking medication for high cholesterol.