Indraratna B.,University of Wollongong |
Kianfar K.,Coffey |
Rujikiatkamjorn C.,University of Wollongong |
Perera D.,University of Wollongong
Australian Geomechanics Journal | Year: 2014
Application of vacuum pressure with prefabricated vertical drains in soft clays is a popular and effective ground improvement method. Application of vacuum pressure via vertical drains generates a negative excess pore water pressure (PWP) resulting in an immediate increase in effective stress. This paper summarises the recent advancements in vacuum preloading based on laboratory studies, using the conventional and modified Rowe cells. Location and the magnitude of the average PWP and degree of consolidation during vacuum preloading are investigated. Based on the laboratory experiments a new radial consolidation model is proposed for vacuum preloading incorporating non-Darcian flow. Source
Discussions of lab vapor management in the context of sustainability tend to focus on energy conservation without compromising personnel safety. Fume hoods use a lot of energy to protect users from noxious vapors, so we look for safe ways to reduce that energy burden. What we don’t talk about is where all the exhausted vapors go, though we know they don’t just disappear. Thoughtful observers of pollution-control strategies have long-since dismissed the notion that “the solution to pollution is dilution.” Yet, isn’t this what we are doing with our labs, relying on powerful roof fans to pump these noxious vapors into the air, to disperse them away from our work areas? Aren’t we just ignoring the fact they eventually fall back on our neighbors? We propose giving more attention to the emissions from lab facilities that strive for sustainability. It’s easy to dismiss lab building emissions as small compared with industrial discharges, and so not worth attention. And it’s true waste vapor streams vary greatly in amount and character, making them difficult to characterize for control. It’s also true we dilute them with lots of fresh air, so the emitted concentrations are low. Yet, these observations simply evade the question, even as there are indications the problem may be bigger than we assume. As an example, while the EPA defines “de minimis” releases as up to a ton per year of any one hazardous air pollutant, there are many different chemicals, and many labs. Published studies estimate that 10 to 30% of all solvents used in labs are lost as emissions, which isn’t surprising, since the goal of many lab processes is to evaporate solvents and exhaust them through fume hoods. The problem is we don’t have good information about total volume of waste vapors emitted from labs, or even mass balance data on individual labs, much less the health effects of the persistent releases of small quantities of pollutants. These releases are the “second-hand smoke” of lab operations. The toxicity of the solvents used in labs gives us good reason to pump them out of our workspaces, but don’t we have a responsibility to evaluate the risks to our neighbors by doing so? We contend the goal should be to collect as many of these waste vapors and prevent their release. Let’s briefly touch on two technologies that can help. Filtered fume hoods are one such technology; condensers on vacuum pumps are another. Filtered fume hoods don’t have exhaust ducts. Instead, they use carbon-based chemical filtration to trap chemicals used in the hood (and the lab). In many cases, there’s no incremental investment in filtered hoods compared with standard ducted hoods, despite the higher unit costs; reduced volumes of exhausted air yield savings on HVAC infrastructure. As for operating costs, building energy savings offset the costs of periodic filter replacement. Meanwhile, replaced filters and their contaminants are destroyed by high-temperature incineration with 99.99% efficiency. Filtered fume hoods aren’t an appropriate replacement for ducted hoods in all circumstances, but used where appropriate they can dramatically reduce total building emissions at no incremental cost. A second way to reduce releases of waste solvent vapors is to equip vacuum pumps with condensers. Many lab operations are vacuum-driven evaporative processes: drying, concentration, distillation. Even a well-managed rotary evaporator, however, will capture only about 85 to 90% of the vapors passing through its condenser; 10 to 15% of waste vapors are exhausted through fume hoods and roof fans. Alternatively, an oil-free pump equipped with an exhaust condenser can capture 90% of the residual vapors. In combination with the rotary evaporator’s condenser, that amounts to 98% solvent recovery. Use a similarly equipped pump on a local vacuum network supporting multiple vacuum workstations, and you can collect most of the vacuum process vapors in the lab, before they are exhausted. Neither technology cited gets us to 100% recovery, but we can remove a large fraction of solvent vapors before sending them out the top of lab buildings. We contend a sustainable lab building can’t ignore its “second-hand smoke” problem. Click here for more information on lab vacuum technology. Peter Coffey joined VACUUBRAND in 2009 with the mission of bringing to North America energy- and water-saving lab vacuum technology developed by VACUUBRAND of Germany. Earlier, Coffey served as VP of Marketing for BrandTech Scientific Inc. and has held various sales and marketing positions in companies supplying to the scientific markets.
One of the most notable trends in lab vacuum technology is the movement away from central vacuum supply in new science buildings. This trend is consistent with owners’ objectives to have facilities that are adaptable as science changes, as budgets rise and fall and programs respond. Central vacuum relies on large pumps and ballast tanks, supporting building-wide networks of copper piping. It is often a technology that runs 24/7, that is, including nights and weekends. And as most lab buildings are only occupied about 40 hours a week, this means 70% of the time central vacuum systems are operated without anyone using the vacuum in order for it to be available in the event someone does use the system. And due to its constant operation, central vacuum uses a lot of energy. “Some central vacuum pumps can adapt somewhat to demand, but the pump that responds is a very large pump and it can rarely get below 50% of full capacity,” says Peter Coffey, VP of Marketing, VACUUBRAND, INC. “Because building-wide central vacuum installations are so inflexible, they are usually oversized to ensure vacuum can be made available anywhere in building should the need arise in the future.” The approach consumes a lot of resources to preserve an option of adaptability in the future. Vacuum and plug loads “There are a lot of energy solutions to account for in designing a building, such as the building envelope, the way the HVAC system operates and the engineering of fume hood controls,” says Coffey. “But once a building is in place, then the plug loads are an operational issue.” Plug loads offer an opportunity to reduce energy consumption by choosing the right equipment and managing it properly. Lab vacuum technology can represent 15% of the plug loads in a lab, making vacuum plug loads important to energy efficiency in a lab. Variable-speed vacuum pumps can use 70 to 90% less energy for bench production of vacuum. The technology does this by having a motor turn only as much as needed to create or maintain the vacuum. “A chance to save 70% of 15% of total plug loads means an overall 10% savings opportunity in total plug loads. This and the move from central vacuum to local vacuum can make a big difference in how much energy is used for vacuum in a lab building,” says Coffey. In fact, by using variable-speed pumps as “server” pumps for multi-user local vacuum networks, labs have an efficient, sustainable vacuum system that can reduce energy consumption by 90% or more. The combination can also save lab space and offers the adaptability to accommodate future needs without overbuilding. Vacuum technology evolution Central vacuum can produce a level of vacuum suitable for simple suction. This modest level of vacuum is appropriate for aspiration, cell culture and filtration application. “But it isn’t sufficient for deeper vacuum applications, like those in the chemistry labs” says Coffey. Central vacuum is also a highly variable source of vacuum, meaning the actual pressure conditions can change dramatically over the course of the day. “What happens here is people have central vacuum in their buildings, but when they need stable, deeper vacuum, or vacuum they can control electronically, they have to purchase a pump in addition,” says Coffey. “So they end up paying twice for vacuum—once for a general-purpose vacuum and once for a vacuum that accomplishes a specific purpose.” This is driving lab owners to decide, not only because this idea of duplication, but because of the increasing presence of dry labs, that many labs might not need central vacuum supply. “If you want a flexible space, if there’s a way you can produce vacuum locally, instead of centrally, that’s a good chance to significantly reduce the energy devoted to vacuum,” says Coffey. It should be noted that when people reference dry labs, they are speaking of computers used in order to simulate scientific chemical or biological processes, or for analysis of massive data troves. These dry labs are used to handle the data that’s produced by the wet labs. The wet labs aren’t obsolete. They produce the data the dry labs analyze; they complement the wet labs. “For lab planning, it used to be 100% wet lab, and it’s now moved to a mix of wet and dry lab, and that generally depends on the nature of the science done,” says Coffey. However, when designers are designing a building, they are never sure what the future will bring, both in terms of type of wet lab, but also wet lab versus dry lab space. And if they aren’t certain about what the proportion will be, they will want the flexibility going forward to supply the wet lab when it needs vacuum, “but without putting in all the investment that’s necessary to support wet labs for spaces that may never be built out,” says Coffey. Also driving this move away from central vacuum utilities is the movement toward multidisciplinary science buildings, both for academic institutions and for “problem-focused” research. “Since the vacuum needed by the various scientific disciplines varies greatly, and dry labs are becoming increasingly important, one-size-fits-all vacuum seems less appropriate,” says Coffey. This trend is also evident in other modular utilities like point-of-use ultrapure water systems and ductless fume hoods. The future of lab vacuum One of the oldest options for producing lab vacuum is the water jet aspirator, a device where cold water rushes through a tube attached to a faucet and the rush of water causes suction on a side arm connected to the vacuum application. While these devices are inexpensive to buy and produce a fairly deep vacuum that could be applied in common chemistry labs, they suffer in water efficiency. A single aspirator operating at 2 gpm for 10 hours a week wastes 50,000 to 60,000 gallons of water per year to produce vacuum. This can add up to a million gallons or much more per year in a lab building. Because of this, LEED standards restrict the use of such technology in their certification program. So while central vacuum is “greener” in terms of water use, it fails in terms of energy consumption. “The future of lab vacuum technology is very much towards local supply of vacuum, either an individual pump on the bench or local networks that are built into labs and provided a lab at a time,” says Coffey. The trend toward buildings without central vacuum, for the reasons described above, also serves flexibility goals, and makes a safer environment for researchers and those in the lab. Beyond safety, advances in control and automation of lab vacuum have led to pumping units that automatically respond to demand for vacuum, and systems that can automate evaporative processes without user programming. The automation saves researchers time, protects samples, reduces wear on pumps and reduces energy use. “With budgets tight in both academic and industrial research, process automation in labs frees up the most precious resource in the lab—the attention and creativity of the researcher,” says Coffey. The result: Energy and water efficiency, as well as greater productivity and convenience for the scientist.
Several major rivers, including the Mississippi, were expected to crest at or above record levels as flood waters rushed toward the Gulf of Mexico, the National Weather Service said. Flooding has closed many roads and parts of Interstate 44, a major artery running from west Texas to St. Louis. Water rose to the rooftops of homes and businesses in Missouri, where Governor Jay Nixon called the flooding "historic and dangerous." About 300 people in Valley Park, Missouri, west of St. Louis, were evacuated because a levee that protects the community might be breached by the Meramec River, said Chief Rick Wilken of the Valley Park Fire District. "We have seven people who are going to wait it out," Wilken said. "Some people just want to hang onto their homes." The American Red Cross had seven shelters open in St. Louis on Wednesday, and spokesman Zach Collins said people were trying to help each other. "There was one lady who only had $67 in her bank account but gave 34 of it for cereal and pop tarts and that sort of thing, just to give back," Collins said. Louisiana Governor Bobby Jindal declared a state of emergency as the waters moved south toward his state. Flash flood warnings were issued for parts of the Carolinas and Georgia. At least 24 people have died in Missouri, Illinois, Arkansas and Oklahoma in flooding after days of downpours that brought as much as 12 inches (30 cm) of rain to some areas. Most of the deaths resulted from people driving into flooded areas. In Eureka, Missouri, along the Meramec River, Mayor Kevin Coffey said a man was rescued from atop the cab of his pick-up truck after spending the night in a parking lot to watch over his gun shop business. "This is 4 feet (1.2 meters) above the worst flood we ever had," Coffey said after helping to put sandbags around a school. "The town looks like one huge lake." Historic floods on the Mississippi in 1993, 1995 and 2011 occurred during warm weather, after snow melts in the north. AccuWeather senior meteorologist Alex Sosnowski called it highly unusual to have heavy flooding in winter and said it could presage trouble for the spring. "The gun may be loaded again for another major flooding event," said Sosnowski, who cited the El Nino weather pattern as the source of recent heavy rains. "You're not supposed to get this kind of heavy rainfall during the wintertime." Agriculture experts said that water standing more than a week could kill the soft red winter wheat crop. Export premiums for corn and soybeans were at their highest levels in weeks because of stalled barge traffic on swollen rivers. Livestock also has been hard hit. About 2,500 hogs drowned in an Illinois barn after a creek overflowed its banks, said Jennifer Tirey, a spokeswoman for the state's Pork Producers Association. "There was no electricity and roads were impassable. It was just impossible to get to those pigs,” she said. The U.S. flooding is occurring at the same time as historic El Nino-related flooding across northern England. The El Nino weather phenomenon tends to disturb global weather patterns as ocean water temperatures rise above normal across the central and eastern Pacific, near the equator. Several major rivers, including the Mississippi, and tributaries in Missouri and Illinois were poised to crest at record or above-record levels, the National Weather Service said, but parts of the region were already inundated. Flood warnings were issued from eastern Oklahoma into southeastern Kansas, southern Missouri, central Illinois and parts of Arkansas, Kentucky, Tennessee, and the Florida panhandle. While the rains have stopped for now, freezing weather is setting in, which will make the cleanup a miserable undertaking, Sosnowski said. At the confluence of the Mississippi and Missouri rivers, about 20 miles (32 km) north of St. Louis, residents of the towns West Alton and Arnold were told to evacuate on Tuesday. About 400 residents and businesses in the town of Pacific also have evacuated. The U.S. Coast Guard closed a 5-mile (8 km) stretch of the Mississippi near St. Louis on Tuesday to all vessel traffic due to hazardous conditions. The Mississippi River, the third longest river in North America, is expected to crest over the weekend at Thebes, Illinois, at 47.5 feet, more than a foot and a half (46 cm) above the 1995 record, according to the National Weather Service. The severe weather has stranded tens of thousands of people during one of the busiest travel times of the year. More than 750 flights were canceled and 4,760 delayed as of mid-afternoon on Wednesday, according to FlightAware.com.
To help people who have lost their sense of taste or have difficulty monitoring what they eat, a team of researchers at Virginia Commonwealth University is working on an artificial taste-sensing system. The design will both monitor and manage the user's diet and also potentially help modify eating behaviors. "The first app is something simple," said Richard Costanzo, Ph.D., professor of physiology and biophysics and director of research in the Department of Otolaryngology in the School of Medicine. "Like, why not set up a detection system for something like salt, which is pretty easy to detect and may help people with hypertension." Costanzo is an expert in taste and smell, and first conceived this idea for an artificial taste-sensing system that goes inside the mouth a few years ago. His original design was a tooth with a miniaturized sensor that fits like a filling. Since then, he has brought in collaborators to bring his idea to life, including Woon-Hong Yeo, Ph.D., assistant professor in the Department of Mechanical and Nuclear Engineering in the School of Engineering. Yeo specializes in flexible electronics and low-profile biosensors and has been developing the exact kind of nanotechnology-driven electronics needed for Costanzo's idea. Instead of large electrodes, a tangle of wires and bulky control stations for health monitoring, Yeo works in the miniature. He designs nano-tattoos—small, ultralight, wearable monitoring devices that feel like a second skin and move with the human body. "We miniaturize everything," he said. "Microscopes are our friends." Yeo and Costanzo received funding from the MEDARVA Research Foundation in Richmond to develop a sodium-sensing system in the oral cavity. Instead of the tooth mount of Costanzo's first design, this device is designed to be worn inside the mouth, mounted on an orthodontic retainer created by James Coffey, D.D.S., associate professor of prosthodontics in the VCU School of Dentistry. Think of it as a Fitbit for the mouth. In the case of the Fitbit, the technology measures acceleration and translates that information into data such as distance, steps and calories burned. It also will encourage you to move if you've been idle too long. For the sodium-sensing device, the technology measures the concentration of sodium ions coming in through the mouth and transmits the data to a smartphone or other monitoring system. Once the sodium threshold is reached for the day, the user is alerted. So if an elderly woman with hypertension is eating potato chips (while wearing the taste-sensing retainer), and she reaches her sodium maximum for the day, she will get an alert so she knows to stop eating sodium. "This is a serious problem, hypertension—diabetes is another problem but that's more sugar related—and right now there are no devices out there that are bionically monitoring this information, feeding back this information, or beeping and saying, 'Hey, you've had enough,'" Costanzo said. He believes it could also teach people to modify their eating behavior in the way that other biofeedback apps do, again like the Fitbit. The app with feedback alert system is being developed through a collaboration with Wei Cheng, Ph.D., assistant professor of computer science in the VCU School of Engineering, and the Websmith Group in Richmond. The sodium-sensing system starts with a microcircuit pattern that Yeo designed on the computer with illustration software. There are then more than 50 steps in the microfabrication process that took Yeo a year to devise. The final sensor consists of a copper membrane circuit that's 200 nanometers thick (that's 100 times thinner than a strand of human hair), a data-processing chip that converts the analog data from the sensors into digital data, and a Bluetooth chip that transmits the digital data to a wireless receiver or smartphone. All of it fits onto a thin piece of flexible elastomer slightly thicker than a Band-Aid measuring about 2 by 1 inches. "The advantage is that it can be bendable and stretchable without fracturing the material so we can put it on pretty much any surface," Yeo said. He'll work with the retainer mount for now, but he mentions the possibility of the sensor simply being glued to the roof of the mouth. Yeo will eventually expand the taste sensor to include the other four tastes: sour, sweet, bitter and umami. "I'm working on the sodium sensor and trying to add a pH sensor for sour, and the three other tastes will come later," Yeo said. "Umami is the hardest." Eventually, Costanzo and Yeo want to connect their sensor with the body. Much like a cochlear implant stimulates cochlear nerves to help a deaf person hear again, an internal taste implant would receive data from the food molecules coming in and then stimulate the appropriate nerves to create a perception of that taste. "We're approaching an era in the next couple decades where we will be interfacing with the brain and our perceptions with electronic devices," Costanzo said. "Maybe we can even trick our brains into liking broccoli."