The Speaker News Journal

How small are Dr. Pedro A. Quinto-Su’s steam engines? Smaller than red blood cells and most bacteria–between one and three millionths of a meter. The significantly strong pistons are powered by a combined process of optical manipulation which bypasses microfabrication and draws strength from simplicity, taking scientists one step closer to the “lab on a chip” miniaturization of everything.

“The piston–a microsphere–is powered by light, which also heats the sphere inducing the vapor microexplosions. Similar to an internal piston combustion engine,” Dr. Pedro Quinto-Su, physics professor at the Universidad Nacional in Mexico, told The Speaker.

“This is the first time that a steam engine has been miniaturized to a length scale of a micrometer,” Quinto-Su told us. “Also, the engine works in an environment dominated by fluctuations (Brownian), since it is immersed in liquid. In the context of optical micromanipulation the report shows that it is possible to have impulsive forces in an optical tweezer, which could extend even more the wide array of applications that use that technique.”

Quinto-Su placed the microscopic piston in historical context.

“In the past, the improved steam engine design of Watt started the industrial revolution and understanding the mechanism initiated modern thermodynamics. Steam engines were the foundation for all the engines that we have today.

“Now steam engines are mainly used for energy conversion in power plants, where steam turbines convert mechanical energy into electricity.”

There has been much interest in miniaturizing heat engines, Quinto-Su explained.

“In the last few decades there has been a trend in trying to miniaturize everything. In science this concept has been called “lab on a chip” and the idea is to have everything that is needed to make an experiment in a small chip. The interest in miniaturized versions of heat engines is that they could be used to do work in very localized volumes. For example, periodically displacing small objects including nanomaterials.”

Quinto-Su explained the challenges to miniaturization past the 1mm scale–the lower limit until the recent invention–and how his steam engine bypassed the previous obstacles.

“The main problem with tiny heat engines is that the efficiency is very poor. A few heat engines have been demonstrated at the micrometer scale with different working mechanisms. However, traditional heat engines that work with the expansion and compression of gas had not reached scales below 1mm, perhaps because most designs involved the assembly of microfabricated moving parts which made it more challenging–in addition to the expected poor efficiency.

“The implementation of the reported micrometer-sized piston steam engine is very simple and there is no need for microfabrication, only optical access is required. It needs an optical tweezer setup which is a widely available tool.”

Quinto-Su explained how the project began–as an attempt to combine two methods of microscopic manipulation to create the micro-piston.

“The project started by trying to combine two techniques of optical manipulation of microscopic objects immersed in liquids: optical tweezers and microscopic explosions (cavitation bubbles).”

Quinto-Su explained how small the steam engines were, and put in layman’s’ terms  how the various elements of the engines work.

“In the reported engine a spherical microparticle (1 or 3 micrometers in diameter, the largest dimension of a human red blood cell is about 10 micrometers) is periodically displaced by light and microscopic explosions.

“Optical tweezers use a focused laser beam that attracts transparent microscopic objects towards the focused spot. The objects are usually immersed in liquid and they are called colloids, usually these objects are microscopic spheres. Once the microparticles reach the focus of the laser beam they stay trapped in there. This technique exerts very small controlled forces (pico Newtons) in the microscopic objects.

“In contrast, microscopic vapor explosions in liquids exert large impulsive forces in the vicinity where the explosions are created. A vapor explosion creates a rapidly expanding bubble that later collapses (cavitation bubble). The bubble displaces the liquid at a very fast speed which also displaces the objects in the vicinity, exerting impulsive forces several orders of magnitude larger than those of optical tweezers.

“In the reported work, a spherical microparticle that is not completely transparent to the laser beam is placed in an optical tweezer. In this way the sphere is attracted towards the focus of the beam, but at the same time it is heated because it is not transparent to the light. Once the sphere is close to the focus it is heated at a very fast rate and the liquid in contact with the microsphere explodes, pushing the sphere close to the starting position. Then the light forces take over and start attracting the sphere towards the focus repeating the cycle.

“Hence the combination of optical tweezers and vapor explosions resulted in a microparticle (piston) that is periodically attracted towards the focused laser and then is pushed away at a fast speed by microscopic vapor explosions. In a sense it is similar to an internal piston combustion engine.”

Quinto-Su noted that the the microexplosions are not initiated by a spark, but by a sudden temperature increase, similar to a diesel engine.

The power created by the pistons is significant, Quinto-Su explained.

“The average power is about 0.3 pico Watts and the power density is about two orders of magnitude less than that typical of car engines. However the effects at the microscopic scale are significant and could be used to pump small volumes of liquid or exert impulsive forces in nearby objects.”

The micro-pistons can be compared with the effect of transducers when driven at acoustic and ultrasound frequencies.

“Because transducers can be used to induce oscillations in liquid-gas boundaries which produce flow. In this case, the operation of the engine is periodic displacements of the piston and periodic explosions which also produce flow, similar to the effect of transducers.”

The report, “A microscopic steam engine implemented in an optical tweezer,” was authored by Pedro A. Quinto-Su and was published in Nature Communications

Three videos from Dr Pedro A. Quinto-Su’s research – 1-3 μm particle engines.

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Does the entire library of memories stored throughout our lifetime remain dormant within our minds, and can these memories be restored? New research has led UCLA neurobiologists to conclude that the storage mechanism for memories is actually independent of synaptic change–the mechanism that mediates the expression of memories. Rather, memories are stored in persistent epigenetic changes within the nuclei of neurons, and therefore memories are extremely stable over time and could be restored.

“The idea, long believed by most neuroscientists, that memories are stored in synapses may be incorrect. This implies that the apparent loss of a memory due to synaptic elimination might be reversible. Memories that appear to be lost forever may, in fact, be able to be fully restored,” Dr. David Glanzman, professor of integrative biology, physiology and neurobiology at UCLA and lead author of the study, told The Speaker.

So if the memories remain stored intact, why can’t we access them? The synapses that complete the circuit to the memories are destroyed or eliminated, Glanzman suspects. Glanzman qualified that the problem of memory storage was extremely complex and that he did not possess a complete answer, but he explained how his conception of memory formation was changed by the research.

“At present I believe that memories are formed in the brain by a combination of posttranslational changes—protein phosphorylation, protein dephosphorylation, etc.—gene transcription, protein synthesis and structural changes in neurons.  Pretty much everyone in the field of learning and memory also believes this.

“Where I differ is that I now believe that the storage mechanism for long-term memories is independent from the mechanism that mediates the expression of the memories, which is synaptic change,” Glanzman continued. “The storage mechanism, I believe, is persistent epigenetic changes within the nuclei of neurons.  Given this, I think that long-term memories are actually extremely stable; as long as the cell bodies of the neuronal circuit that contains the memory are intact, the memory will persist.  The memory can appear to be disrupted, however, by destroying or eliminating the synapses among the neurons in the neuronal circuit that retains the memory.  But the apparent elimination of a memory due to synaptic elimination can be reversed and the memory restored.  The data in our eLife study support this idea, although they do not explain how this is actually accomplished.”

In their research, the UCLA team studied Aplysia, a marine snail–particularly the way Aplysia learns to fear a memorable source of harm.

The team trained the snail to defend itself by withdrawing to protect its gills from the harm of mild electric shocks. The snail retained the withdrawal response for several days, indicating long term memory of the stimulus.

The team found that the shock caused serotonin to be released in Aplysia’s central nervous system. New synaptic connections grow as a result of the serotonin, according to the team. The formation of memories can be disrupted by interfering with the synthesis of the proteins that contribute to the new synapses.

When a snail was trained on a task but its ability to immediately produce the proteins was inhibited, the animal would not remember the training 24 hours later, the researchers found, but if an animal was trained and protein synthesis was inhibited later–after 24 hours–the animal would retain the memory. Memories once formed last in long-term memory, the team found.

They also performed experiments with neurons in a Petri dish, and found the same results.

Then the team tested memory loss. Again in a Petri dish, they manipulated synaptic growth with a protein synthesis inhibitor and with serotonin. They found that when they stimulated synaptic growth some time after creating a memory, new synapses grew–not the old ones that would have been stimulated if prevailing theories of memory formation were accurate.

The researchers found that the nervous system appears to be able to regenerate lost synaptic connections–reconnecting memories with new synapses.

Does that meant that the entire library of a life’s memories could be dormant and could be restored? Possibly, but not in all cases, according to the study. Glanzman used an example to explain what his research had suggested.

“That is a fascinating question,” said Glanzman.”For example, what about the phenomenon of infantile amnesia, that is, the inability of adults to retrieve episodic memories before the age of 2–4 years?  Can those episodic memories from our earliest years be restored?  I frankly don’t know, but I suspect that they can be.  It is possible that the explanation for infantile amnesia is similar to that of the phenomenon we examined in our study, reconsolidation blockade.  There, we found that the apparent elimination of the memory was the result of the reversal of the synaptic growth and, perhaps, of some of the epigenetic changes, such as histone acetylation, that mediated the expression of the memory.

“Notice that some epigenetic changes are intrinsically more stable than others.

“What if infantile amnesia is also a consequence of synaptic loss and reversible epigenetic changes, but that the memory persists as persistent epigenetic changes?  Then, just as we were able to restore memory in the snail following its disappearance due to reconsolidation blockade, we might be able to reverse infantile amnesia.  Similarly, some memories lost in the early stages of Alzheimer’s disease due to the synaptic destruction might be restorable.  However, once the cell bodies of the neurons that make up the memory circuit die, I believe the memory is lost forever.”

Before the recent research, memory was believed to be stored in synapses. Glanzman explained the traditional belief and the remaining challenges to the new theory.

“First, until my work is confirmed by others, it is not fair to say that neuroscientists are mistaken in their belief that long-term memory is stored at synapses.  The idea that memory is not stored at synapses is going to be met with a great deal of skepticism, as any radical new scientific idea should be.

“Having said that, the idea that memory is stored at synapses grew out of the pioneering work of the Spanish neuroanatomist Ramon y Cajal (who was awarded the Nobel Prize in 1906).  Cajal was one of the first to propose that learning and memory involves the growth of new synaptic connections among neurons in the brain.  This idea is now overwhelmingly accepted by neuroscientists.  I certainly believe—and scientific research on Aplysia and other animals confirms—that when an animal learns, synapses in its brain (or nervous system, in the case of the snail) physically change; in some instances the result is synaptic growth, whereas in others it is synaptic retraction.  (The specific pattern of synaptic change depends on the specific type of learning and the particular part of the brain that mediates the learning.)

“Given this, it is natural to think that new memories will be stored, at least in part, as persistent molecular or structural changes in the synapses that grew as the memories formed. It is this part of the synaptic hypothesis of long-term memory that I disagree with.”

The research is expected to hold new hope for sufferers of Alzheimers. Because in the early stages of the disease, synapses are destroyed–not neurons–those memories still exist and could be regained, Glanzman suspects.

The report, “Reinstatement of long-term memory following erasure of its behavioral and synaptic expression in Aplysia,” was completed by Shanping Chen, Diancai Cai, Kaycey Pearce, Philip Y W Sun, Adam C Roberts, and David L Glanzman, and was publied in eLife.

Photos: Christelle Nahas/UCLA

How do cells control their size? What causes them to divide? Contrary to what many biologists have expected, evidence supporting an answer to one of the most fundamental and longstanding problems of biology has been accomplished by UC San Diego researchers. The study surprised even the researchers: a simple quantitative principle explains the phenomena without regard for either of the currently prevailing theories.

“Life is very robust and ‘plastic,’ much more than what biology textbooks tell us. Bacteria probably do not care when they should start replicating their genomes or dividing,” Dr. Suckjoon Jun, assistant professor of physics and molecular biology at the University of California, San Diego and one of the lead authors of the study, told The Speaker.

“Simple mathematical principles help us understand fundamental biology, just like in physics.”

How do cells control their size? What causes them to divide?

Biologists had previously posited two possible solutions: either a cell reaches a certain size, at which it divides into two smaller cells; or after a certain time has passed, the cell divides. The two theories have been known as “sizer” and “timer.”

The results surprised the researchers as well: “adder.”

“The results were completely unexpected,” Jun told us.

Rather than either sizer or timer paradigms, cells were found to add a constant volume each generation, regardless of their newborn size.

“This ‘adder’ principle quantitatively explains experimental data at both the population and single-cell levels, including the origin and the hierarchy of variability in the size-control mechanisms and how cells maintain size homeostasis,” the researchers concluded, whereas in past research based on “sizer” and “timer” theories led to difficult-to-verify assumptions or population-averaged data and varied interpretations.

Time and size, while variable in some organisms, do not even factor into the existence of “perfect adders” in the newly found and “extraordinarily simple” quantitative principle of cell-size control.

“It seems most bacteria we have studied so far, and more data is coming out of other labs, appear to be perfect adder,” said Jun. “Some higher organisms, such as yeast, do care about size more than bacteria do. For example, small-born yeast cells add more mass than large-born cells to reach division. That is, how much mass they add since birth is sensitive to how big the baby cell was. Nevertheless, the way they reach the target size, generation after generation, works exactly same as the perfect adders such as bacteria, which is quite nice and surprising.”

The growth of cells follow the growth law, the researchers found, and grow exponentially at a constant rate.

Jun explained the challenge that had stood in the way of understanding this aspect of cell division in the past: “Two biggest obstacles have been (one) dogmas that cells somehow must actively sense space or time to control cell size, and (two) technology that did not exist until recently, which now allows monitoring the growth and division patterns of tens of thousands of individual cells under tightly controlled environment.”

The research team developed a tiny device that isolates individual genetic materials.

The tool allowed the researchers to observe thousands of individual bacterial cells–Gram-negative E. coli and Gram-positive B. subtilis–over hundreds of generations. The researchers manipulated the conditions in which the cells lived. A wide range of tightly controlled steady-state growth conditions were experimented with.

According to the researchers, the new method allowed them to produce statistical samples about a thousand times better than had previosly been available.

“We looked at the growth patterns of the cells very very carefully, and realized that there is something really special about the way the cells control their size,” explained Jun.

“No one has been able to answer this question,” Jun said in their press release, noting that this was even the case for the E. coli bacterium, possibly the most extensively studied organism to date.

The research holds the promise of better informing the fight against cancer, since one of the most important problems in the fight is the process of runaway cell division.

The reports, “Cell-size maintenance: universal strategy revealed” and “‘Cell-size control and homeostasis in bacteria” were completed by Suckjoon Jun, Massimp Vergassola and Sattar Taheri-Araghi, and were published in the journal Current Biology .

Images: the work of the researchers

The share of farmland tended by small farmers is shrinking. The land is changing hands. Although small farms are more productive than large farms and tend to grow food products–they produce 80 percent of the world’s food–they are being swallowed up by large corporate farms that grow high-profit crops for export markets. The land left to the largely food-producing small farms is currently only 24 percent of fertile land, and that number is declining sharply.

“Over the past decades, small farmers have been losing access to land at an incredible speed,” Henk Hobbelink, coordinator of GRAIN, told The Speaker. “If we don’t reverse this trend we will not only have more hungry farmers in the future, but the world as a whole will lose the capacity to feed itself.”

GRAIN investigated land use data worldwide to understand the global and specific trends currently taking place with regard to farmland.

“What became very clear from our research is that increasingly fertile farmland is being taken over by huge industrial operations that produce commodities for the global market, not food for people,” Hobbelink told us. “Small farmers, who continue to produce most of the food in the world, are being pushed into an ever diminishing share of the world’s farmland.

“This trend has to be reversed if we want to be able to feed a growing population,” he said.

However, many governments and international organizations are offering grossly incorrect or misleading figures, according to GRAIN, such as those announced by representative’s of the UN Food and Agriculture Organization’s (FAO) recent “State of Food and Agriculture“–which was dedicated to family farming.

At this year’s inauguration of the International Year of Family Farming, UN FAO Director General Jose Graziano da Silva stated that 70 percent of the world’s farmland was managed by families, echoing previous conclusions by the UN and other world organizations.

The percentage of farm land currently in the hands of small farms (an average of 2.2 hectares) is, according to GRAIN, actually less than 25 percent. Excluding China and India–where about half of all small farms are located–the ratio is less than one-fifth.

Similar findings were in evidence for every region of the world.

For example, in Belarus small farmers produced over 80 percent of fruits, vegetables, potatoes and vegetables with only 17 percent of the land. In Botswana, small farmers produced at least 90 percent of millet, maize and groundnuts with less than eight percent of the land.

“Because rural peoples’ access to land is under attack everywhere. From Honduras to Kenya and from Palestine to the Philippines, people are being dislodged from their farms and villages,” GRAIN found. “Those who resist are being jailed or killed. Widespread agrarian strikes in Colombia, protests by community leaders in Madagascar, nationwide marches by landless folk in India, occupations in Andalusia–the list of actions and struggles goes on and on.”

Eighty percent is also the figure given for the percentage of the world’s hungry people who live in rural areas. Many of these people are farmers or farmworkers.

Hobbelink explained this finding to us by saying that it was the result of small farmers simply not having enough land to produce food, and losing access to land at a rapid rate.

There were six general findings GRAIN found to be most compelling.

First, most of the world’s farms are shrinking. Second, the total of these farms account for less than 25 percent of the world’s farmland. Third, big farms are getting bigger, and small farms and farmers are losing to them. Fourth, despite this, small farms continue to be the world’s biggest food producers. Fifth, overall, small farms are more productive than big farms. Sixth, most small farmers are women.

Particularly surprising to the researchers was that land was becoming increasingly concentrated, despite extensive global agrarian reforms.

A “kind of reverse agrarian reform” is taking place in many countries, according to GRAIN. Most of this is happening through corporate land grabbing in Africa and foreign investment and massive farm expansion in Latin America and Asia.

Besides land concentration, among the forces causing small farms to collapse are population pressure and lack of access to land.

Even in India and Asia farms have been shrinking. In India, the size of the average farm is 50 percent of what it was in the 1970s, and in China farm sizes shrunk 25 percent between 1985 and 2000.

In Africa, where no official statistics for farmland concentration were available to GRAIN, researchers based their conclusions on research papers that indicated small farms were shrinking there as well.

Why small farms produce so much, and why they are losing to big corporate farms, was explained by GRAIN in their report: small farms tend to focus on food production, which is then bought from local markets and eaten. Large farms focus on return on investment, and tend to grow more export commodities such as animal feed, biofuels, and wood products. Thus, big farms, with maximized profits, are able to buy more land to produce high-profit commodities.

“Corporate farms a backed by big money, often from the finance industry, investment firms, etc.,” Hobbelink told us. “They are also able to access and influence political decisions at high level, and in this way often get handed over huge swaths of land at incredible low prices or for free. In the meanwhile, small farmers don’t have access to credit, and are up against agricultural policies that discriminate against them.”

Besides that, however, small farms tend to be more productive than large farms anyway, according to GRAIN. This phenomenon, which has been termed “the productivity paradox” because it seems contrary to what many people are told, is evinced in statistics. In nine EU countries, small farms have at least double the productivity of large farms, and the other countries show only slightly higher productivity for large farms. According to their findings, GRAIN calculated that if large farms in some Central American and African nations were as productive as small farms, national agricultural production would double.

In its findings, GRAIN also pointed out that big farms are less productive even with more resource consumption, the best land, most of the irrigation water, and better credit and technical assistance.

Much of the disparity is also due to differences in labor, GRAIN concluded. Big farms cut labor to maximize profits, and this labor is needed for better production.

“There are multiple factors at play,” Hobbelink told us. “In countries with big population growth, farmers without access to more land are forced to divide their land amongst their children. Expansion of urban areas into farmland, the same for mining, tourism, etc. But perhaps the most important factor is the global expansion of industrial plantation farming encroaching upon areas where small farmers and indigenous peoples live.

“The reason why small farmers still produce the majority of the world’s food is twofold. On one hand–as we show in our report–they are simply more efficient, more productive, than the large industrial plantations. And on the other hand they prioritize their land use towards producing food, while industrial plantations mostly produce commodities that no one can eat, or that need a lot of processing before they end up in our food: soybean, oilpalm, sugarcane, rapeseed, etc.”

“The bottom line is that land is becoming more and more concentrated in the hands of the rich and powerful, not that small farmers are doing well,” GRAIN concluded.

“Today, small farmers feed the world and we need them to continue to do so,” said Hobbelink. “If we don’t reverse the current trend of the corporate takeover of the worlds farmland to produce industrial commodities, they will not be able to do so and we will all lose out.”

Photos: all belong to the work of GRAIN