The illuminating results of their survey received careful analysis and are detailed in the article, “North American Specialty Cut Flower Production and Postharvest Survey,” as found open access journal HortTechnology.

Cut flower production in the United States and Canada has increased in recent years. Due to this resurgence, more information is needed regarding current production and postharvest issues. This research effort and resulting article determined the nature of those issues and provides a guide for how to best address them using 31 major crop species as a template.

The article also listed an additional 99 cut flowers species and categories grown by enterprising local farmers.

Dole adds, “Local is in with consumers, and cut flower growers have responded by producing hundreds of different types of lush, gorgeous flowers. Our research showed that growers and cut flower handlers face a host of challenges in getting those flowers to their customers.”

Of the 1098 surveys sent out, the authors received 210 responses, resulting in a 19% response rate. From that, cross -section data was extrapolated.

Analysis showed that the main perceived production problem was insect management. Crop timing proved to be the second-most important problem, and disease management was ranked third.

Crop timing encompasses a range of related issues, such as determining the correct harvest stage, harvest windows that are too short, flowering all at once, or lack of control when the crop is ready to harvest.

The main postharvest problems were temperature management, hydration, and flower food management. Regarding on-farm postharvest handling, hydration and vase life were the two most mentioned issues.

For postharvest during storage and transport, damage and hydration were the most commonly reported issues.

Customer complaints were also charted, with gauging vase life and petal shattering as the most-mentioned issues.

The survey proved revelatory in that it will allow researchers and businesses to focus on the major cut flower production and postharvest issues and on crops that are most in need of improvement in North America.

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“Scientists had previously noticed that if the AMOC is stronger in a given season or year, sea levels in the northeast U.S. go down. If the AMOC weakens, average sea levels rise considerably,” says Chris Piecuch, a physical oceanographer at WHOI and lead author on the paper. “During the winter of 2009-2010, for example, we saw the AMOC weaken by 30 percent. At the same time, sea level in our region rose by six inches. That doesn’t sound like a lot, but a half-foot of sea level rise, held for months, can have serious coastal impacts.”

“But, it’s been unclear whether those two things — coastal sea level and the AMOC — are linked by cause and effect,” adds Piecuch. Although the study confirmed that AMOC intensity and sea level seem to change at the same time, it found that neither directly causes changes in the behavior of the other. Instead, both seem to be controlled simultaneously by variability in major weather patterns over the North Atlantic, such as the North Atlantic Oscillation (NAO).

“Changes in the NAO alter both AMOC and sea level separately,” says Piecuch. “As the NAO changes, it affects the trade winds, which blow from the east across the tropical Atlantic. When the NAO is high, the trade winds are stronger than normal, which in turn strengthens AMOC. But at the same time, the westerly winds over New England are also stronger than usual. Together with unusually high air pressure on the northeast coast, this lowers the average sea level. It’s wind and pressure that are driving both phenomena.”

According to Piecuch, a study like this was not even possible until recently. For the past few decades, satellite imagery has given scientists a record of movement at the ocean’s surface, but has been unable to detect currents below the surface. Starting in 2004, however, an international team of scientists began maintaining a chain of instruments that stretch across the Atlantic between Florida and Morocco. The instruments, which are collectively called the RAPID array, hold a variety of sensors that measure currents, salinity, and temperature. “RAPID doesn’t resolve the details of every individual current along the way, but it does give us the sum total of the ocean’s behavior, which is what the AMOC represents,” Piecuch notes.

These findings are particularly important for residents along the northeast coast of the U.S., he adds. Existing climate models suggest sea levels will rise globally in the next century due to climate change, but that sea level rise on the New England coast will be greater than the global average. Scientists have traditionally assumed that the heighted future sea level rise in the northeast U.S. is inextricably tied to a weakening of the AMOC, which the climate models also predict. But, given the study’s findings, that assumption might need to be revisited, Piecuch says. “The problem right now is that we only have about 13 years of AMOC data to work with. To get a better sense of how these two things relate to one another in the long term, we’ll need to wait for a longer stretch of observational records to become available,” he says.

Also collaborating on the study were Glen G. Gawarkiewicz and Jiayan Yang of WHOI; Sönke Dangendorf of Universität Siegen in Germany; and Christopher M. Little and Rui M. Ponte of Atmospheric and Environmental Research, Inc.

The work was supported by National Science Foundation awards OCE-1558966, OCE-1834739, and OCE-1805029; NASA contract NNH16CT01C; and the J. Lamar Worzel Assistant Scientist Fund and the Penzance Endowed Fund in Support of Assistant Scientists at the Woods Hole Oceanographic Institution.

In fact, they now understand these neurons well enough to be able to make a mouse sing on command or to silence it so that it can’t sing, even when it wants to impress a mate.

This level of understanding and control is a key advancement in the ongoing search for the mechanisms that allow humans to form speech and other communication sounds. The researchers are broadly interested in the brain’s production of speech and have worked with songbirds and mice as models for humans.

“We were interested in understanding how mice produce these ‘love songs,’ as we call them in the lab,” said Katherine Tschida, who led the research as a post-doctoral fellow in both the Richard Mooney and Fan Wang labs at Duke neurobiology.

For this study, Tschida and her colleagues focused on a part of the midbrain called the periaqueductal gray, or PAG for short, because they knew from previous work by others that it would be a key player in the vocalization circuit, she said.

With technology developed by Wang’s lab, they were able to locate and isolate the specific neurons involved in the PAG’s circuitry and then experiment on them.

By turning the neurons on selectively with a light-based method called optogenetics, the researchers found they could make a mouse immediately begin singing, even though it was alone.

On the other hand, silencing the activity of the PAG neurons rendered courting male mice incapable of singing, even while they persisted in all of their other courtship behaviors.

The females turned out to be less interested in the silent types, which also shows that the singing behavior is key to mouse survival.

Both experiments firmly establish that this “stable and distinct population of neurons” is the key conduit between behavior and vocal communication, Tschida said. The work will appear in the Aug. 7 edition of Neuron, but was published early online in mid-June.

“These neurons are acting as a base for vocalization. But they don’t determine the individual parts of the song,” Tschida said. “It’s a ‘gate’ for vocalization.”

Tschida, who will join the Cornell University faculty next year, said the research will now trace PAG’s connections to neurons downstream that communicate with the voicebox, lungs and mouth, for example. And they’ll work toward the behavioral centers upstream that tell the mouse there is a female present and he should start singing.

The researchers hope to form a more complete picture of why mice produce different syllables in different contexts. “We know they do it, but don’t know yet what parts of the brain drive the behavior,” Tschida said.

This research was supported by the National Institutes of Health (MH103908, DC13826, MH117778).

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These migratory elk rely primarily on environmental cues, including a retreating snowline and the greening grasses of spring, to decide when to make these yearly journeys, shows a new study led by University of California, Berkeley, researchers. The study combined GPS tracking data from more than 400 animals in nine major Yellowstone elk populations with satellite imagery to create a comprehensive model of what drives these animals to move.

“We found that the immediate environment is a very effective predictor of when migration occurs,” said Gregory Rickbeil, who conducted the analysis as a postdoctoral researcher in Arthur Middleton’s lab at UC Berkeley. This is in contrast with some other species, such as migratory birds, which rely on changing day length to decide when to move, Rickbeil pointed out.

The results, published in the current issue of the journal Global Change Biology, suggest that, as climate change reshapes the weather and environment of the park, elk should have the means to adjust their migratory patterns to match the new conditions.

While this adaptability may benefit the survival of the elk, it may also have unknown ripple effects in local economies and throughout the Greater Yellowstone Ecosystem — one of the last remaining large, nearly intact ecosystems in Earth’s northern temperate zone, which encompasses about 18 million acres of land managed by more than 25 public entities and hundreds of private landowners. Another recent UC Berkeley-led study suggests that climate change is likely to hit National Parks harder than other areas of the country.

“The decisions that these animals make about when to migrate are absolutely dependent on changes in the landscape, changes that are ultimately governed by the climate,” said Middleton, an assistant professor of environmental science, policy and management at UC Berkeley and senior author on the study. “And in the future, with climate change, we should expect the timing of these mass movements to be altered, which will affect the other wildlife and the people who depend on them, including predators, scavengers and hunters across the ecosystem.”

Though the migration study’s period was too short to say whether or not climate change is already affecting migratory timing, the tracking data did reveal a surprising trend: Elk on average arrived on their winter ranges 50 days later in 2001 than in 2015. This change had been noted by wildlife managers in the area, but had yet to be quantified on the ecosystem scale until now.

“This [study] provides great insight into the adaptation strategies of elk to climate change in the Greater Yellowstone Ecosystem,” said Jonathan Jarvis, former director of the National Park Service, who now serves as executive director of the Institute for Parks, People, and Biodiversity at UC Berkeley.

Jarvis noted that more broadly, the new picture of the Yellowstone elk migrations provided by the study’s comprehensive mapping effort “clearly demonstrate the need to think and operate at the landscape scale.” He added, “For the park managers, this kind of research gives them options and incentives, such as protection of migration corridors and seasonal habitats, for ensuring elk and other keystone species in the Greater Yellowstone Ecosystem will persist.”

Eating and being eaten

Yellowstone’s approximately 20,000 migratory elk are among the most important large mammals in the ecosystem, comprising about 10 million or so pounds of animal biomass pulsing in and out of the parks and adjacent wilderness areas each year — so where they can be found at any given time matters to both animals and humans alike.

“These elk eat a lot of things, and they are eaten by a lot of things, so wherever these masses of hundreds or thousands of elk are on the landscape determines who gets to eat and who doesn’t,” Middleton said. “In some cases, this could be sensitive populations of carnivores, like grizzly bears or wolves, and on the human side, it could be hunters, some of whom are making their income as outfitters and guides.”

Recent studies have shown that threatened grizzly bears depend heavily on newborn elk calves as a food source in spring — right when the migration is happening — and that a Yellowstone wolf kills, on average, 16 elk per year. Meanwhile, each fall, thousands of hunters from around the country pay guides for the chance to harvest an elk in the wilderness near Yellowstone.

While a smattering of studies has investigated the migration of individual herds in the park, none before this study had investigated the phenomenon on an ecosystem scale. To get a more complete picture of migration, Middleton partnered with state and federal wildlife managers in the Yellowstone region to pool information on 414 elk across nine herds that had been fitted with GPS collars between 2001 and 2017.

Rickbeil then analyzed the data to pinpoint when each elk made its trek from winter range to summer range and back again and used satellite images to infer the conditions on the ground during journeys.

He found that elk tended to leave their winter ranges and set out to their summer ranges as soon as the snow had melted and during the “green-up,” when fresh, nutritious plant growth began to sprout. Likewise, encroaching snowfall and hunting pressure cued them to make the return journey.

The team was surprised by the extent of the elks’ flexibility: One year, a female elk might migrate in early May, but the next year in late July, depending on the timing of snowmelt and green-up.

“They’ve got a big brain and big eyes, and they can look around and, to a large degree, see changes on the landscape and react to them,” Middleton said.

However, Rickbeil notes, the snow cover and vegetation couldn’t fully explain why the elk are now arriving so much later at their winter ranges. Variations in snow depth, which cannot be inferred from satellite data, might explain part of the dramatic change, Rickbeil said.

Alyson Courtemanch, who manages the Greater Yellowstone Ecosystem’s Jackson elk herd as part of her job as a wildlife biologist with the Wyoming Game and Fish Department, says knowing the whereabouts of the elk is critical to her job setting hunting seasons and managing the spread of diseases among wild elk and domestic cattle.

“We’ve been observing a lot of really interesting changes over the past decade about the way that elk are moving across the landscape, specifically of the timing of the migrations,” said Courtemanch, who supplied GPS data on the Jackson herd for the study. “This analysis helped confirm a lot of things that people on the ground had suspected were happening, but that weren’t really quantified.”

“It seems like these animals can adapt to changing climates, which is likely a good thing,” Rickbeil said. “But there will be a lot of consequences to these changes.”

Study co-authors include Jerod A. Merkle of the University of Wyoming; Greg Anderson, Douglas E. McWhirter and Tony Mong of the Wyoming Game and Fish Department; M. Paul Atwood of the Idaho Department of Fish and Game; Jon P. Beckmann of the Wildlife Conservation Society; Eric K. Cole of the U.S. Fish and Wildlife Service; Sarah Dewey and David D. Gustine of the National Park Service; Matthew J. Kauffman of the U.S. Geological Survey and Kelly Proffitt of Montana Fish, Wildlife and Parks.

This research was supported by the National Geographic Society, Grant WW-100C-17; the Knobloch Family Foundation; the George B. Storer Foundation and the Rocky Mountain Elk Foundation.

University of Groningen professor Patrick Onck, together with colleagues from Eindhoven University of Technology, have shown that this is possible by using a technique called mechanowetting. “We have come up with a way of transporting droplets by using transverse surface waves. This even works on inclined or vertical surfaces.”

The research was published in Science Advances on 14 June.

The idea of mechanowetting is basically very simple: put a droplet on a transverse surface wave, and the droplet will move with the wave. “One of the properties of water droplets is that they always try to stay on top of a wave. If that top runs ahead, the droplet will run with it,” Onck explains. It is possible to move the droplets by using mechanical deformation to create surface waves. “The remarkable thing about this is that it also works on inclined or vertical surfaces: drops can even move upwards against gravity.”

Theory and practice

Edwin de Jong, PhD candidate in Onck’s group and first author of the paper, tested the concept of mechanowetting by means of a computer model. “When it seemed to work in theory, our colleagues from Eindhoven University of Technology devised an experiment to test it. Our model turned out to be right: in practice, the drops moved exactly as we had imagined.”

Lab-on-a-chip

One of the applications of mechanowetting is in lab-on-a-chip systems, complete laboratories the size of a credit card, which are used to analyze biological fluids such as blood or saliva. This allows the samples to be tested outside the lab, e.g. directly at the bedside, with a much faster response rate. “If we are able to direct each drop separately, it is possible to perform a lot of different tests at high speed with a very small volume of fluid,” says Onck. Transporting droplets separately was already possible by means of electrowetting. “Electrowetting is able to transport droplets by applying electric fields. However, these fields can change the biochemical properties of the sample, and that is something you don’t want when doing blood tests.”

Light waves

In the meantime, Onck’s group is exploring new possibilities. “We have performed computer simulations that show that mechanowetting also works by using light-responsive materials to create waves. Light is especially interesting because of its precision and its ability to control the movement of drops remotely.” In addition to lab-on-a-chip systems, mechanowetting has several other interesting applications, such as self-cleaning surfaces, where water droplets actively absorb and remove the dirt. It also offers opportunities for harvesting moisture from the air, by collecting dew drops for use as drinking water.

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“This work provides circumstantial evidence that the stripe-ordered arrangement of charges and magnetism is good for forming the charge-carrier pairs required for superconductivity to emerge,” said John Tranquada, a physicist at the U.S. Department of Energy’s Brookhaven National Laboratory.

Tranquada and his co-authors from Brookhaven Lab and the National High Magnetic Field Laboratory at Florida State University, where some of the work was done, describe their findings in a paper just published in Science Advances. A related paper in the Proceedings of the National Academy of Sciences by co-author Alexei Tsvelik, a theorist at Brookhaven Lab, provides insight into the theoretical underpinnings for the observations.

The scientists were studying a particular formulation of lanthanum barium copper oxide (LBCO) that exhibits an unusual form of superconductivity at a temperature of 40 Kelvin (-233 degrees Celsius). That’s relatively warm in the realm of superconductors. Conventional superconductors must be cooled with liquid helium to temperatures near -273°C (0 Kelvin or absolute zero) to carry current without energy loss. Understanding the mechanism behind such “high-temperature” superconductivity might guide the discovery or strategic design of superconductors that operate at higher temperatures.

“In principle, such superconductors could improve the electrical power infrastructure with zero-energy-loss power transmission lines,” Tranquada said, “or be used in powerful electromagnets for applications like magnetic resonance imaging (MRI) without the need for costly cooling.”

The mystery of high-Tc

LBCO was the first high-temperature (high-Tc) superconductor discovered, some 33 years ago. It consists of layers of copper-oxide separated by layers composed of lanthanum and barium. Barium contributes fewer electrons than lanthanum to the copper-oxide layers, so at a particular ratio, the imbalance leaves vacancies of electrons, known as holes, in the cuprate planes. Those holes can act as charge carriers and pair up, just like electrons, and at temperatures below 30K, current can move through the material with no resistance in three dimensions — both within and between the layers.

An odd characteristic of this material is that, in the copper-oxide layers, at the particular barium concentration, the holes segregate into “stripes” that alternate with areas of magnetic alignment. Since this discovery, in 1995, there has been much debate about the role these stripes play in inducing or inhibiting superconductivity.

In 2007, Tranquada and his team discovered the most unusual form of superconductivity in this material at the higher temperature of 40K. If they altered the amount of barium to be just under the amount that allowed 3-D superconductivity, they observed 2-D superconductivity — meaning just within the copper-oxide layers but not between them.

“The superconducting layers seem to decouple from one another,” Tsvelik, the theorist, said. The current can still flow without loss in any direction within the layers, but there is resistivity in the direction perpendicular to the layers. This observation was interpreted as a sign that charge-carrier pairs were forming “pair density waves” with orientations perpendicular to one another in neighboring layers. “That’s why the pairs can’t jump from layer to another. It would be like trying to merge into traffic moving in a perpendicular direction. They can’t merge,” Tsvelik said.

Superconducting stripes are hard to kill

In the new experiment, the scientists dove deeper into exploring the origins of the unusual superconductivity in the special formulation of LBCO by trying to destroy it. “Often times we test things by pushing them to failure,” Tranquada said. Their method of destruction was exposing the material to powerful magnetic fields generated at Florida State.

“As the external field gets bigger, the current in the superconductor grows larger and larger to try to cancel out the magnetic field,” Tranquada explained. “But there’s a limit to the current that can flow without resistance. Finding that limit should tell us something about how strong the superconductor is.”

For example, if the stripes of charge order and magnetism in LBCO are bad for superconductivity, a modest magnetic field should destroy it. “We thought maybe the charge would get frozen in the stripes so that the material would become an insulator,” Tranquada said.

But the superconductivity turned out to be a lot more robust.

Using perfect crystals of LBCO grown by Brookhaven physicist Genda Gu, Yangmu Li, a postdoctoral fellow who works in Tranquada’s lab, took measurements of the material’s resistance and conductivity under various conditions at the National High Magnetic Field Laboratory. At a temperature just above absolute zero with no magnetic field present, the material exhibited full, 3-D superconductivity. Keeping the temperature constant, the scientists had to ramp up the external magnetic field significantly to make the 3-D superconductivity disappear. Even more surprising, when they increased the field strength further, the resistance within the copper-oxide planes went down to zero again!

“We saw the same 2-D superconductivity we’d discovered at 40K,” Tranquada said.

Ramping up the field further destroyed the 2-D superconductivity, but it never completely destroyed the material’s ability to carry ordinary current.

“The resistance grew but then leveled off,” Tranquada noted.

Signs of persistent pairs?

Additional measurements made under the highest-magnetic-field indicated that the charge-carriers in the material, though no longer superconducting, may still exist as pairs, Tranquada said.

“The material becomes a metal that no longer deflects the flow of current,” Tsvelik said. “Whenever you have a current in a magnetic field, you would expect some deflection of the charges — electrons or holes — in the direction perpendicular to the current [what scientists call the Hall effect]. But that’s not what happens. There is no deflection.”

In other words, even after the superconductivity is destroyed, the material keeps one of the key signatures of the “pair density wave” that is characteristic of the superconducting state.

“My theory relates the presence of the charge-rich stripes with the existence of magnetic moments between them to the formation of the pair density wave state,” Tsvelik said. “The observation of no charge deflection at high field shows that the magnetic field can destroy the coherence needed for superconductivity without necessarily destroying the pair density wave.”

“Together these observations provide additional evidence that the stripes are good for pairing,” Tranquada said. “We see the 2-D superconductivity reappear at high field and then, at an even higher field, when we lose the 2-D superconductivity, the material doesn’t just become an insulator. There’s still some current flowing. We may have lost coherent motion of pairs between the stripes, but we may still have pairs within the stripes that can move incoherently and give us an unusual metallic behavior.”

This work was funded by the DOE Office of Science. The National High Magnetic Field Laboratory at Florida State University is supported by the National Science Foundation.