Marvels of Engineering—Roman Aqueducts

OF ALL the feats of ancient engineering, Roman aqueducts are among the most remarkable. “With such an array of indispensable structures carrying so many waters, compare, if you will, the idle Pyramids or the useless, though famous, works of the Greeks!” wrote Sextus Julius Frontinus (35–c. 103 C.E.), Roman governor and water commissioner. *

Why the Need for Aqueducts?

Ancient cities were usually built near an abundant water supply, and Rome was no exception. Originally, the Tiber River and nearby springs and wells provided sufficient water. From the fourth century B.C.E. on, however, Rome grew rapidly, as did its need for water.

Since few people had running water in their homes, the Romans built hundreds of private and public baths. The first public bath in the city of Rome was fed by the Aqua Virgo, dedicated in 19 B.C.E. The builder of this aqueduct, Marcus Agrippa, a close friend of Caesar Augustus, poured much of his vast fortune into overhauling and extending Rome’s water-supply system.

Baths also became social venues, larger ones even having gardens and libraries. After leaving the baths, aqueduct water, which could not be shut off, flowed into the sewers, constantly flushing them of refuse, including waste from the latrines attached to the baths.

Construction and Maintenance

When you hear the words “Roman aqueduct,” do you think of lofty arches running to distant horizons? In fact, arches formed less than 20 percent of those conduits, the larger portion of which lay underground. This more economical design not only protected aqueducts against erosion but also minimized their impact on fields and neighborhoods. For example, the Aqua Marcia, completed  in 140 B.C.E., was about 57 miles (92 km) long but comprised just 7 miles or so (11 km) of arches.

Before building an aqueduct, engineers assessed the quality of a potential water source by examining the clarity, rate of flow, and taste of the water. They also took note of the physical condition of the locals who drank it. Once a site was approved, surveyors calculated the right path and gradient for the conduit, as well as its channel size and length. Slaves evidently provided manpower. Aqueducts could take years to complete, making them costly—especially if arches were needed.

Moreover, aqueducts had to be maintained and protected. To care for them, the city of Rome at one time employed about 700 people. Provisions for maintenance were also incorporated into the design. For instance, underground sections of the aqueducts were made accessible by means of manholes and shafts. When major repairs were needed, engineers could temporarily divert the water away from a damaged section.

Rome’s Urban Aqueducts

By the early third century C.E., 11 major aqueducts served the city of Rome. The first, the Aqua Appia, built in 312 B.C.E. and just over ten miles (16 km) long, ran almost entirely underground. Still preserved in part is the Aqua Claudia, which was some 43 miles (69 km) long with about 6 miles (10 km) of arches, a number of which stood 90 feet (27 m) high!

How much water did the city’s aqueducts carry? A lot! The Aqua Marcia, mentioned earlier, daily channeled about 6.7 million cubic feet (190,000 cu m) of water into Rome. Once the water reached urban areas—gravity being the driving force—it flowed into distribution tanks and then into branches, which channeled the water to other distribution tanks or to locations for water use. Some estimate that Rome’s water distribution system grew to the point that it could have daily supplied more than 265 gallons (1,000 L) of water for each inhabitant.

As the Roman Empire grew, “the aqueducts went wherever Rome went,” says the bookRoman Aqueducts & Water Supply. Travelers in Asia Minor, France, Spain, and North Africa can still gaze in awe at these ancient marvels of engineering.

Invisible shield found thousands of miles above Earth blocks 'killer electrons'

A The barrier to the particle motion was discovered in the Van Allen radiation belts, two doughnut-shaped rings above Earth that are filled with high-energy electrons and protons, said Distinguished Professor Daniel Baker, director of CU-Boulder's Laboratory for Atmospheric and Space Physics (LASP). Held in place by Earth's magnetic field, the Van Allen radiation belts periodically swell and shrink in response to incoming energy disturbances from the sun.

team led by the University of Colorado Boulder has discovered an invisible shield some 7,200 miles above Earth that blocks so-called "killer electrons," which whip around the planet at near-light speed and have been known to threaten astronauts, fry satellites and degrade space systems during intense solar storms.

As the first significant discovery of the space age, the Van Allen radiation belts were detected in 1958 by Professor James Van Allen and his team at the University of Iowa and were found to be composed of an inner and outer belt extending up to 25,000 miles above Earth's surface. In 2013, Baker -- who received his doctorate under Van Allen -- led a team that used the twin Van Allen Probes launched by NASA in 2012 to discover a third, transient "storage ring" between the inner and outer Van Allen radiation belts that seems to come and go with the intensity of space weather.

The latest mystery revolves around an "extremely sharp" boundary at the inner edge of the outer belt at roughly 7,200 miles in altitude that appears to block the ultrafast electrons from breeching the shield and moving deeper towards Earth's atmosphere.

"It's almost like theses electrons are running into a glass wall in space," said Baker, the study's lead author. "Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons. It's an extremely puzzling phenomenon."

A paper on the subject was published in the Nov. 27 issue of Nature.

The team originally thought the highly charged electrons, which are looping around Earth at more than 100,000 miles per second, would slowly drift downward into the upper atmosphere and gradually be wiped out by interactions with air molecules. But the impenetrable barrier seen by the twin Van Allen belt spacecraft stops the electrons before they get that far, said Baker.

The group looked at a number of scenarios that could create and maintain such a barrier. The team wondered if it might have to do with Earth's magnetic field lines, which trap and control protons and electrons, bouncing them between Earth's poles like beads on a string. The also looked at whether radio signals from human transmitters on Earth could be scattering the charged electrons at the barrier, preventing their downward motion. Neither explanation held scientific water, Baker said.

"Nature abhors strong gradients and generally finds ways to smooth them out, so we would expect some of the relativistic electrons to move inward and some outward," said Baker. "It's not obvious how the slow, gradual processes that should be involved in motion of these particles can conspire to create such a sharp, persistent boundary at this location in space."

Another scenario is that the giant cloud of cold, electrically charged gas called the plasmasphere, which begins about 600 miles above Earth and stretches thousands of miles into the outer Van Allen belt, is scattering the electrons at the boundary with low frequency, electromagnetic waves that create a plasmapheric "hiss," said Baker. The hiss sounds like white noise when played over a speaker, he said.

While Baker said plasmaspheric hiss may play a role in the puzzling space barrier, he believes there is more to the story. "I think the key here is to keep observing the region in exquisite detail, which we can do because of the powerful instruments on the Van Allen probes. If the sun really blasts Earth's magnetosphere with a coronal mass ejection (CME), I suspect it will breach the shield for a period of time," said Baker, also a faculty member in the astrophysical and planetary sciences department.

"It's like looking at the phenomenon with new eyes, with a new set of instrumentation, which give us the detail to say, 'Yes, there is this hard, fast boundary,'" said John Foster, associate director of MIT's Haystack Observatory and a study co-author.

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The above story is based on materials provided by University of Colorado at Bould.

Gravity may have saved the universe after the Big Bang, say researchers

New research by a team of European physicists could explain why the universe did not collapse immediately after the Big Bang.

Studies of the Higgs particle -- discovered at CERN in 2012 and responsible for giving mass to all particles -- have suggested that the production of Higgs particles during the accelerating expansion of the very early universe (inflation) should have led to instability and collapse.

Scientists have been trying to find out why this didn't happen, leading to theories that there must be some new physics that will help explain the origins of the universe that has not yet been discovered. Physicists from Imperial College London, and the Universities of Copenhagen and Helsinki, however, believe there is a simpler explanation.

In a new study in Physical Review Letters, the team describe how the spacetime curvature -- in effect, gravity -- provided the stability needed for the universe to survive expansion in that early period. The team investigated the interaction between the Higgs particles and gravity, taking into account how it would vary with energy.

They show that even a small interaction would have been enough to stabilise the universe against decay.

"The Standard Model of particle physics, which scientists use to explain elementary particles and their interactions, has so far not provided an answer to why the universe did not collapse following the Big Bang," explains Professor Arttu Rajantie, from the Department of Physics at Imperial College London.

"Our research investigates the last unknown parameter in the Standard Model -- the interaction between the Higgs particle and gravity. This parameter cannot be measured in particle accelerator experiments, but it has a big effect on the Higgs instability during inflation. Even a relatively small value is enough to explain the survival of the universe without any new physics!"

The team plan to continue their research using cosmological observations to look at this interaction in more detail and explain what effect it would have had on the development of the early universe. In particular, they will use data from current and future European Space Agency missions measuring cosmic microwave background radiation and gravitational waves.

"Our aim is to measure the interaction between gravity and the Higgs field using cosmological data," says Professor Rajantie. "If we are able to do that, we will have supplied the last unknown number in the Standard Model of particle physics and be closer to answering fundamental questions about how we are all here."

The research is funded by the Science and Technology Facilities Council, along with the Villum Foundation, in Denmark, and the Academy of Finland.

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The above story is based on materials provided by Imperial College London. 

Why lizards have bird breath

Whether birds are breathing in or out, air flows in a one-directional loop through their lungs. This pattern was unexpected and for decades biologists assumed it was unique to birds, a special adaptation driven by the intense energy demands of flight.

But that view is wrong, according to University of Utah scientists who now have shown that bird-like breathing also developed in green iguanas -- reptiles not known for high-capacity aerobic fitness. The finding bolsters the case that unidirectional bird-like flow evolved long before the first birds, arising nearly 300 million years ago in a common ancestor of lizards, snakes, crocodiles and dinosaurs including birds.

"We thought we understood how these lungs work, but in fact most of us were completely wrong," says Colleen Farmer, an associate professor of biology at the U and lead author of the new study published today in Proceedings of the National Academy of Sciences. "People have made a lot of assumptions about how lungs work in animals such as reptiles and crocodiles but they never actually measured flow," she says.

In humans and other mammals, lungs have airways with a tree-like branching structure. A main trunk in each lung splits into branches and twigs. Air flows in and out in a tidal fashion. Oxygen and carbon dioxide pass to and from blood in tiny air sacs, called alveoli, at the tips of the smallest airway branches.

In bird lungs, air loops in one direction through a series of tubes lined with blood vessels for gas exchange. Aerodynamic forces act like valves to sustain the one-way flow through cycles of inhalation and exhalation.

"For years, people thought that the design evolved to meet the energetic demands of flight," Farmer says. "That's all wrong. Iguanas don't fly."

Alligators also have a bird-like pattern of airflow. Farmer and Kent Sanders, a radiologist at the U, revealed that in a 2010 study. It was the first evidence that one-directional lung ventilation might be an innovation pre-dating the origin of birds. Earlier this year, Farmer along with Emma Schachner and Robert Cieri at the U, and James Butler of Harvard University reported that monitor lizards have one-directional airflow through their lungs, too.

Those discoveries left open the possibility that crocs and monitor lizards evolved their bird-like lungs independently, that is, their evolution converged on a design similar to birds. The finding of bird-like lungs in yet another group of reptiles builds a stronger case for an origin in the remote past in a common ancestor.

To make the discovery, Farmer and co-authors Cieri, Schachner and Brent Craven of Pennsylvania State University had to find a way to visualize air moving through iguana lungs. In one set of experiments, they used a surgical scope to look inside the lungs of live iguanas as the lizards inhaled harmless smoke from a theatrical fog machine. They also used probes that measure air speed and volume in dissected lungs. Working from 3-D X-ray imaging of the contours of iguana lungs, Craven made a computer model simulating airflow. The model's predictions closely matched the patterns observed in real lungs. "It was dead-on with the directions of flow we observed," Farmer says.

The revelations make clear that scientists have much to learn about the physiology of lungs in species other than mammals. Textbooks generally assert that air moving in and out of lungs flows down a pressure gradient from a point of higher pressure to one of lower pressure, but Farmer says her group's findings show that in iguana lungs "that's not what's going on at all." The shapes and angles of the lung airways point jets of air that create one-directional flow.

The mechanics aren't fully known yet, but Farmer says a better understanding could inspire new ways to design devices that circulate or filter blood or other fluids without using mechanical valves. "The geometry of these lungs, it is so weird," Farmer says, "I don't think any engineer would dream that up."

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The above story is based on materials provided by University of Utah.

Scientists Discover Why Mosquitos Love Human Blood

A chemical vapour exuded from human skin became the key reason why mosquitoes turned from feeding on animals to sucking the blood of people, a study has found.

Sulcatone is an important ingredient in the distinctive human odour, and mosquitoes learnt to recognise it many thousands of years ago as a sign that they were near a source of food, scientists have discovered.

Researchers found that the present-day black-bodied mosquitoes that feed on the furry skin of forest animals do not show any preference for sulcatone, but the brown mosquitoes living in and around villages in Africa are highly attracted to the scent.

“We knew that these mosquitoes had evolved to love the way we smell,” said Leslie Vosshall of Rockefeller University in New York, who led the study published in the journal Nature.

“It was a really good evolutionary move. We provide the ideal lifestyle for mosquitoes. We always have water around for them to breed in, we are hairless and we live in large groups,” Professor Vosshall said.

The scientists identified a group of 14 genes in the mosquito genome that are strongly linked to their love of humans and one odour receptor in particular – called Or4 – stood out as being highly active in the human-preferring mosquitoes.

They linked the Or4 receptor with one of many compounds collected from human skin that form part of the natural scent of people. This was the key that locked the mosquito to the smell of its new human host.

Controlling genes with your thoughts

It sounds like something from the scene in Star Wars where Master Yoda instructs the young Luke Skywalker to use the force to release his stricken X-Wing from the swamp: Marc Folcher and other researchers from the group led by Martin Fussenegger, Professor of Biotechnology and Bioengineering at the Department of Biosystems (D-BSSE) in Basel, have developed a novel gene regulation method that enables thought-specific brainwaves to control the conversion of genes into proteins – called gene expression in technical terms.

“For the first time, we have been able to tap into human brainwaves, transfer them wirelessly to a gene network and regulate the expression of a gene depending on the type of thought. Being able to control gene expression via the power of thought is a dream that we’ve been chasing for over a decade,” says Fussenegger.

A source of inspiration for the new thought-controlled gene regulation system was the game Mindflex, where the player wears a special headset with a sensor on the forehead that records brainwaves. The registered electroencephalogram (EEG) is then transferred into the playing environment. The EEG controls a fan that enables a small ball to be thought-guided through an obstacle course.

Wireless transmission to implant

The system, which the Basel-based bioengineers recently presented in the journal Nature Communications, also makes use of an EEG headset. The recorded brainwaves are analysed and wirelessly transmitted via Bluetooth to a controller, which in turn controls a field generator that generates an electromagnetic field; this supplies an implant with an induction current.

 

This diagram shows how the implant takes thoughts, interprets them, and transforms them into electricity to light up a near-infrared LED. (Illustration: Folcher M et al. Nature Communications 2014)

A light then literally goes on in the implant: an integrated LED lamp that emits light in the near-infrared range turns on and illuminates a culture chamber containing genetically modified cells. When the near-infrared light illuminates the cells, they start to produce the desired protein.

Thoughts control protein quantity

The implant was initially tested in cell cultures and mice, and controlled by the thoughts of various test subjects. The researchers used SEAP for the tests, an easy-to-detect human model protein which diffuses from the culture chamber of the implant into the mouse’s bloodstream.

To regulate the quantity of released protein, the test subjects were categorised according to three states of mind: bio-feedback, meditation and concentration. Test subjects who played Minecraft on the computer, i.e. who were concentrating, induced average SEAP values in the bloodstream of the mice. When completely relaxed (meditation), the researchers recorded very high SEAP values in the test animals. For bio-feedback, the test subjects observed the LED light of the implant in the body of the mouse and were able to consciously switch the LED light on or off via the visual feedback. This in turn was reflected by the varying amounts of SEAP in the bloodstream of the mice.

New light-sensitive gene construct

“Controlling genes in this way is completely new and is unique in its simplicity,” explains Fussenegger. The light-sensitive optogenetic module that reacts to near-infrared light is a particular advancement. The light shines on a modified light-sensitive protein within the gene-modified cells and triggers an artificial signal cascade, resulting in the production of SEAP. Near-infrared light was used because it is generally not harmful to human cells, can penetrate deep into the tissue and enables the function of the implant to be visually tracked.

The system functions efficiently and effectively in the human-cell culture and human-mouse system. Fussenegger hopes that a thought-controlled implant could one day help to combat neurological diseases, such as chronic headaches, back pain and epilepsy, by detecting specific brainwaves at an early stage and triggering and controlling the creation of certain agents in the implant at exactly the right time.

Newly discovered fossil is a clue to early mammalian evolution

 A newly discovered 66–70 million-year-old groundhog-like creature, massive in size compared to other mammals of its era, provides new and important insights into early mammalian evolution. Stony Brook University paleontologist David Krause, PhD, led the research team that unexpectedly discovered a nearly complete cranium of the mammal, which lived alongside Late Cretaceous dinosaurs in Madagascar. The findings, which shake up current views on the mammalian evolutionary tree, will be published in the journal Nature on November 5.

See more about Vintana in this Stony Brook video.

“We know next to nothing about early mammalian evolution on the southern continents,” said Dr. Krause, a SUNY Distinguished Service Professor in the Department of Anatomical Sciences at Stony Brook. “This discovery, from a time and an area of the world that are very poorly sampled, underscores how very little we know. No paleontologist could have come close to predicting the odd mix of anatomical features that this cranium exhibits.”

The new fossil mammal is named Vintana sertichi. Vintana belongs to a group of early mammals known as gondwanatherians, which previously were known only from isolated teeth and a few scrappy jaw fragments. The well-preserved skull allows the first clear insight into the life habits and relationships of gondwanatherians.

“The discovery of Vintana will likely stir up the pot,” added Krause. “Including it in our analyses reshapes some major branches of the ‘family tree’ of early mammals, grouping gondwanatherians with other taxa that have been very difficult to place in the past.”

The skull is huge, measuring almost five inches long, twice the size of the previously largest known mammalian skull from the entire Age of Dinosaurs of the southern supercontinent of Gondwana. At a time when the vast majority of mammals were shrew- or mouse-sized, living in the shadows of dinosaurs, Vintana was a super heavyweight, estimated to have had a body mass of about 20 pounds, twice or even three times the size of an adult groundhog. Adding to the intrigue is the fact that the cranium of Vintana has a peculiar shape, being very deep, with huge eye-sockets, and long, scimitar-shaped flanges for the attachment of massive chewing muscles.

The initial discovery was made in 2010 and, like many in science, came about by chance.

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Vintana means luck and refers to the circumstances that its discoverer, Joseph Sertich, a former graduate student of Dr. Krause’s at Stony Brook University, had in finding the fossil in 2010. Sertich, now a curator at the Denver Museum of Nature & Science, collected a 150 block of sandstone filled with fish fossils. When the block was CT scanned in Stony Brook’s Department of Radiology the images revealed that something exceedingly rare lay inside—a nearly complete cranium of a previously unknown ancient mammal. The specimen represents only the third occurrence of mammalian skulls from the Cretaceous of the entire Southern Hemisphere, the other two being from Argentina.

“When we realized what was staring back at us on the computer screen, we were stunned,” said Joe Groenke, Krause’s technician and the first to view the CT images. Groenke spent the next six months extracting the skull from the surrounding rock matrix, one sand grain at a time.

Dr. Krause and his team conducted a comprehensive analysis of the skull, much of it using micro-computed tomography and scanning electron microscopy to reveal minute aspects of its anatomy, including areas like the braincase, nasal cavity, and inner ear that are poorly known in almost all early mammals. They compared the skull to those of hundreds of other fossil and extant mammals.

Various features of its teeth, eye sockets, nasal cavity, braincase, and inner ears revealed that Vintana was likely a large-eyed herbivore that was agile, with keen senses of hearing and smell. These and other features were also used to analyze its relationships to other early mammals. This phylogenetic analysis demonstrated that Vintana and other gondwanatherians were close relatives of multituberculates, the most successful mammalian contemporaries of dinosaurs on the northern continents. Gondwanatherians and multituberculates also grouped with another enigmatic taxon, the Haramiyida. The analysis by Krause’s team is the first to find strong evidence for clustering these three groups together, primarily because the cranial anatomy of gondwanatherians was previously completely unknown.

Dr. Krause emphasizes that a major question remains for scientists: How did such a peculiar creature evolve?

With its long-term isolation from the rest of the world, Madagascar had been an island for over 20 million years prior to the time in which the strata containing Vintana were deposited. Dr. Krause and his team theorize that the very primitive features of the cranium are holdovers from when the ancient lineage that ultimately produced Vintana was marooned on the island. It was this isolation, first from Africa, then Antarctica/Australia, and finally the Indian subcontinent, that allowed for the evolution of unique and bizarre features amidst Vintana’s primitive foundation of characteristics.

The research by Dr. Krause and colleagues on Vintana sertichi is supported by the National Science Foundation and the National Geographic Society.

Peers Hail the Study as Groundbreaking

Dr. Zhe-Xi Luo, a leading expert on early mammalian evolution from the University of Chicago, reviewed the manuscript for Nature. He hailed the Vintana as “the discovery of the decade for understanding the deep history of mammals; it offers the best case of how plate tectonics and biogeography have impacted animal evolution – a lineage of mammals isolated on a part of the ancient Gondwana had evolved some extraordinary features beyond our previous imagination. This new study of Vintana is a giant leap forward toward resolving the long-standing mystery of gondwanatherian mammals, which has puzzled paleontologists for decades.” Luo went on to say,
“Vintana is also a galvanizing discovery for the future decades.  With features so remarkably different from those of other mammals previously known to science, this fossil tells us how little we knew about the early evolution of mammals – it will stimulate paleontologists to conduct more field exploration in order to advance the frontier of deep time history and evolution.”

Dr. Guillermo Rougier from the University of Louisville, another expert who also reviewed the Nature paper, concurred, calling the study “a remarkable achievement” and predicted that the paper “will shake the field upon publication; the specimen is exceptional.”

“This is the first discovery of a cranial fossil from a very enigmatic extinct group of mammals called Gondwanatheria in the Southern Hemisphere,” says Dr. Yusheng (Chris) Liu, Program Director in the National Science Foundation (NSF)’s Division of Earth Sciences, which funded the research.  “This important find will help us better understand the early evolution of gondwanatherians and their relatives.”

“In 1940, National Geographic supported its first paleontological expedition, sending Professor Joseph P. Connolly to the South Dakota Badlands in search of fossils,” said Dr. John Francis, vice president of research, conservation and exploration at the National Geographic Society. “More than six decades later, the Society continues to support scientists and explorers around the world, including Professor Krause’s groundbreaking work in Madagascar. We congratulate Professor Krause on this remarkable discovery and look forward to his next expedition with the National Geographic Society.”

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