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速度：
How A Texas Town Became Water Smart
速度1：
Faced with a booming population and a disappearing water supply, the city of San Antonio responded by dramatically cutting consumption, pioneering new storage techniques and investing in water recycling and desalination projects. It now boasts that it is "Water's Most Resourceful City."
There are so many programs and projects that Chuck Ahrens of Water Resources and Conservation with the San Antonio Water System can hardly keep track.
"I made myself a list and I thought, 'Wow, I don't even know all of our programs.' But then I thought it would be asking a lot to remember all of our programs because we have a lot of them," saysAhrens. His list includes big money projects like desalination. But the city's greatest success is found in simple conservation.
"We have an ordinance that doesn't allow you to water after 10 in the morning and before 8," Ahrens says.
That's to curb evaporation. He says the city has also given out more than a quarter-million water-efficient toilets. The city also offers free audits to show homeowners where they can save water. And if they can't afford new pipes, Ahrens says the city has a program called Plumbers to People.
"Where they know they have a leak, we go ahead and take care of that for them," he says.
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速度2：
These are the things that have allowed San Antonio to be one of the fastest-growing cities in the country while not increasing water consumption. In fact, the city still uses about the same amount of water it did in the early '90s even though it has added more than 300,000 residents.
"Other cities have the advantage that they can see that San Antonio has managed water conservation and we are still growing," says Calvin Finch of Texas A&M's Water Conservation and Technology Center.
But exporting that expertise can be dicey. A few years ago, Water System Director Robert Puente went to Atlanta when it was facing serious drought.
"And so, I and our chief financial officer went out there and gave some talks and made some presentations. They were, I would say, well-received but they did leave scratching their heads. They didn't necessarily understand or agree with what we were doing here in Texas," Puente says.
Puente says his entire business model — to persuade customers to buy less of his product — seems backward in parts of the country where drought is uncommon. In San Antonio the more water you use, the more you pay per gallon. Currently only about half of water utilities across the country do that.
"There's a number of communities that still reward extra water use. Just like if you buy in volume you get a discount," Finch says.
San Antonio also funds conservation programs. But, Puente points out, all that investment pays off when water shortages hit.
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A Clear And Present Danger: How Glass Kills Birds
Modern architecture loves glass. Glass makes interiors brighter and adds sparkle to cityscapes. But glass also kills millions of birds every year when they collide with windows. Biologists say as more glass buildings go up, more birds are dying.
So a group of biologists and architects is trying to do something about that. You'll find some of them at the Powdermill Avian Research Center in western Pennsylvania. They're catching birds.
Biologist Luke DeGroote patrols a mist net that runs for hundreds of yards through a dense, wet forest. It's mid-morning, the sun is just above the tree line, and it's easy to walk right into it. "It's a very fine mesh," he says, "and that's why the birds run into it. They essentially will fly towards the net and fall into these pockets." The pockets at the bottom of the net catch the birds and entangle them.
Biologists normally retrieve the birds — unharmed — and mark them with metal bands to follow their migrations. But today the catch is for Christine Sheppard, an ornithologist with the American Bird Conservancy. Her mission is to stop birds from flying into glass.
A lot of them do, and die.
"Our best estimate is 100 million to a billion" birds in North America die this way every year, she says. It's an incredible number, and she acknowledges it's an estimate. But it's based on reasonable assumptions.
"Almost anybody you talk to has seen a bird hit a building or heard a bird hit," Sheppard says. She's wearing the muddy boots of a field biologist, and she speaks with the passion that many birders hold for the creatures they study. "The fact that so many people are seeing this means it's happening all the time."
Sheppard says birds don't see the way we do. "Reflection is definitely a problem," she explains. Most birds don't have good depth perception beyond their beaks — they have to get relatively close to an object to see much detail or distinguish it from background. Reflections in glass can make it seem as if there's no building there — just more sky, clouds and trees.
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Testing Special Glass
Even when there's no reflection, glass confuses birds. "The other thing that happens," Sheppard says, "is that birds will try to fly through glass to something that's on the other side. This can be a planted atrium. It can be a potted plant."
So Sheppard has set up an experiment at Powdermill. She's putting birds in a tunnel that sits in a grassy part of the reserve. It looks like a house trailer. Two panes of glass enclose one end — there's regular plate glass on one side; next to it is a pane of specially coated glass.
Sheppard is testing various coatings on and in glass that are visible to birds, but not to people. A fine mesh net just in front of the glass keeps the birds from actually hitting it.
Luke DeGroote comes to the tunnel with the morning's catch: catbirds. They screech, though not like any other bird you've heard. "They get their name from that catlike sound that they make," says DeGroote.
The birds are in cloth bags; DeGroote wears several tied on a string around his neck. Sheppard's assistant, Cara Menzel, takes one and gives it a number — this one is 49931. Then she gently puts it in the tunnel. A camera mounted in the trailer wall focuses inside and films which glass window it flies toward. "Direct left," she says. The bird flew directly to the left, toward the regular glass.
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The glass on the right has a pattern of lines painted on the inside, and the idea is to see if the bird will avoid it. The pattern is made of a material that reflects ultraviolet light. Birds see well in the ultraviolet range. Presumably, they see the pattern as something solid; the human eye can barely make it out.
But Menzel notes that when the sun sets, it's a whole new problem — "especially during these big migrations," she explains, "where the birds are coming through in larger numbers, and a lot of them fly over at night." Biologists believe birds are attracted to the lights inside buildings at night.
Sheppard has studied birds all her life. She says the real difficulty is trying to think like one — to figure out why they do what they do. There's been some research in Europe on bird-friendly glass, but not much here.
"Not enough people know about it, and it's really important," she says. "Many people believe that birds have an intrinsic right not be killed. Birds are seed dispersers; they eat tons of bugs. So every bird that's killed on a building is an ecological service that we lose."
Several cities in the U.S. and Canada either have or are considering new building codes that require bird-friendly materials. And there are some quick fixes for windows — decals or sheets of patterned plastic that attach to glass.
But ideally, biologists and architects want solutions that people can't see and that will be standard products in buildings — and that won't cost an arm and a leg.
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越障：
Implantable Devices Could Detect and Halt Epileptic Seizures
Electrical stimulation, brain "cooling" and drug-delivery devices are all being developed as antiseizure tools
Epilepsy affects some 2.7 million Americans—more than Parkinson’s disease, multiple sclerosis and amyotrophic lateral sclerosis(Lou Gehrig's disease) combined. More than half of patients can achieve seizure control with treatment, yet almost a third of people with epilepsy have a refractory form of the disease that does not respond well to existing antiepileptic drugs. Nor are these patients typically helped by the one implanted device—Cyberonics' Vagus Nerve Stimulator (VNS)—that has had U.S. Food and Drug Administration approval for treatment of epilepsy since 1997.
Because epilepsy causes repeated, sudden seizures, people with the condition would benefit greatly from a therapy that can detect seizures just as they are starting or, eventually, predict them before they begin and prevent them from happening. A new generation of implantable devices is looking to pick up where medications—and even the VNS—often leave off, at least for people whose seizures routinely begin in one part of the brain (the seizure focus). "Closed-loop" devices are designed to monitor the seizure focus, detect patterns of electrical activity that indicate a seizure is beginning, and quickly respond without external intervention. Such responses could include electrical stimulation, cooling or focused drug delivery—all meant to interrupt the activity and stop the seizure.
Closed-loop devices are considered a new frontier in epilepsy treatment because of their responsiveness. By comparison, the VNS is an open-loop device that stimulates the vagus nerve—a pair of nerves running from the brain stem to the abdomen—to deliver mild electrical pulses (which mitigate the electrical activity of seizures) to the brain on a consistent schedule rather than in response to detected seizure activity. The concept of a closed-loop device for epilepsy comes out of the cardiac world, jumping off from implanted defibrillators that monitor the heart and deliver stimulation in response to an event.
Responsive neurostimulation
So far, only one closed-loop device has reached human trials: NeuroPace's Responsive Neurostimulation System (RNS), an electrical-stimulation implant with two leads, each containing four electrodes, placed in the brain at the seizure focus. The RNS detects electrical activity that denotes the start of a seizure and delivers direct electrical stimulation to interrupt the activity and normalize the area. The device is surgically positioned in a section of the skull, can be accessed via outpatient surgery when the battery has to be changed, and is imperceptible to the patient and others—all strong design advantages for patients and doctors. The implant, which is now seeking FDA approval, also records information on electrical activity in the brain throughout the day for later review. The RNS has a laptop-based wand interface for remote patient monitoring.
Results of the RNS trials, which tested the implant in conjunction with medications, have been mixed: seizure frequency was reduced by about half in approximately 50 percent of patients. "For a patient to go though permanent implanting of the device on the skull, and electrodes over the brain, which is what is needed for RNS, you'd want it to eliminate most or all seizures, which isn't the result in most patients," says John Miller, director of the University of Washington School of Medicine's Regional EpilepsyCenter at Harborview in Seattle. Possible ways to improve the device's effectiveness, Miller says, could include refining patient selection, improving electrode placement or honing the RNS's detection process so that it can pick up seizure activity earlier.
Work in closed-loop electrical stimulation is also happening at Boston’s Center for Integration of Medicine and Innovative Technology, where researchers are effectively attempting to turn the VNS into a closed-loop device by developing a nonimplanted add-on system to detect early seizure activity and automatically fire the VNS in response. The VNS comes with a therapy magnet wristband that allows wearers to stimulate the device if they feel a seizure coming on (a sensation called an aura), but not everyone is physically able to do so once the aura begins. The CIMIT system automates the process, activating the VNS once the start of a seizure is detected through electroencephalogram and electrocardiogram readings.
Cool it
Another key area of closed-loop research is focal cooling. Here, an implant—after detecting the onset of a seizure by sensing a rise in brain temperature at the seizure focus, which may slightly precede the start of abnormal electrical activity—rapidly cools the involved region to halt the event. The warming associated with the seizure focus makes thermal detection and cooling a potentially promising technique. One center of focal cooling research is the University of Kansas Medical Center, whereIvan Osorio, professor of neurology, has collaborated with an international research partnership to design a prototype implant with funding from the U.S. Department of Energy. Work on cooling is also in progress at other sites, including Yale University and the University of Minnesota.
"I think cooling is the most promising approach," says Miller, who collaborates on cooling research led by a University of Washington colleague. "If a particular cooling temperature can be found that prevents seizures, but does not injure the brain or interfere with normal brain function, it would be possible to maintain the region of brain around the seizure focus at that temperature all the time, so that it would not be necessary to detect the seizures to apply the therapy."
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剩余部分：
Targeted drug delivery
The third possible mode of operation for closed-loop devices would use convection-enhanced drug delivery (CED). CED involves feeding seizure-halting medications directly to specific areas of brain tissue through an implanted catheter; the concept of CED is designed to avoid the systemic side effects of giving medications orally and having them suffuse through the bloodstream in order to reach the brain.
Yet CED may ultimately prove more useful on a set infusion schedule, rather than linked to a responsive, automated seizure-detection system. "Our current conception of how CED would be used in epilepsy is that patients would receive periodic infusions of a long-lasting antiseizure agent into the epileptic brain region," says Michael Rogawski, chair of neurology at the University of California, Davis, whose lab is working with British Columbia–based biopharmaceutical company MedGenesis Therapeutix to develop an implantable CED device for epilepsy. "Seizure control might be maintained for months," he says. "This approach greatly simplifies the technical challenges in comparison with a device that must sense and deliver a drug on a moment-to-moment basis."
Deep-brain stimulation
With electrical stimulation, too, some patients will find that an open-loop device that fires consistently works better—like the VNS, or Medtronic's Deep Brain Stimulation(DBS) implant for epilepsy, which the FDA is now reviewing. Similar to the company's widely-used DBS technology for Parkinson’s disease, the DBS for epilepsy is placed within the brain and consistently stimulates a region called the anterior nucleus of the thalamus, which helps control the electrical excitability of the cortex.
Unlike closed-loop devices, which typically require a distinct seizure focus, the DBS can be used to treat patients whose seizures appear to engulf the entire brain, or large portions of it, at once. "If you look at the population of patients who have these very unlocalizable, diffuse seizure disorders, folks who are having many, many seizures a day and are just devastated—if you can control some of those seizures even in some of those patients, you've done a great good for the families and the patients," says Dennis Spencer, chair of neurosurgery and director of the Epilepsy Surgery Program at Yale University School of Medicine. "We think that the DBS will open up a path for therapy."
Closing the loop
Closed-loop technologies for epilepsy face several hurdles. Skeptics note that brain surgery poses significant risks, and that the benefits of implanted devices will not always outweigh those dangers. There are also concerns about the possibility of false positives—detection of electrical activity that turns out not to be a seizure. "If the intervention did cause a transient interruption in brain function, it would be undesirable for the patient," Miller says. "For example, if the area that was being affected mediated language, the person might have a brief interruption in the ability to speak."
Researchers also acknowledge that in a condition as variable as epilepsy, there will never be a single solution, such as cooling, stimulation or drug delivery alone. "We may need to use more than one modality to fully control epilepsy," Osorio says. "But all of that hinges on the ability to detect in real time—and to quantify—seizures."
Although the design of first-generation closed-loop devices is just beginning, theoretical development of the second generation is already underway. Because people with epilepsy never know when and where a seizure will occur, the goal of second-generation closed-loop devices will be finding a way to predict seizures before they begin and intervene to prevent them. "You can detect seizures, but you're still detecting them too late to really have a major therapeutic possibility," Spencer says. " rediction is where we're really looking to put our eggs—in that basket." |
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发表于 2012-8-13 14:05:16
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