Scientists have managed to slow down the atoms almost to a complete stop in the largest macro-scale object yet. The research has been published in the journal Science. New Atlas reports: The temperature of a given object is directly tied to the motion of its atoms -- basically, the hotter something is, the more its atoms jiggle around. By extension, there's a point where the object is so cold that its atoms come to a complete standstill, a temperature known as absolute zero (-273.15 C, -459.67 F). Scientists have been able to chill atoms and groups of atoms to a fraction above absolute zero for decades now, inducing what's called the motional ground state. This is a great starting point to then create exotic states of matter, such as supersolids, or fluids that seem to have negative mass. Understandably, it's much harder to do with larger objects, because they're made up of more atoms which are all interacting with their surroundings. But now, a large international team of scientists has broken the record for largest object to be induced into a motional ground state (or extremely closely to one, anyway). Most of the time, these experiments are done with clouds of millions of atoms, but the new test was performed on a 10-kg (22-lb) object that contains almost an octillion atoms. Strangely enough, that "object" isn't just one thing itself but the combined motion of four different objects, with a mass of 40 kg (88 lb) each. The researchers conducted the experiment at LIGO, a huge facility famous for detecting gravitational waves as they wash over Earth. It does this by beaming lasers down two 4-km (2.5-mile) tunnels, and bouncing them back with mirrors -- and those mirrors were the objects that the new study cooled to a motional ground state. The photons of light in LIGO's lasers exert tiny bumps on the mirrors as they bounce off, and these disturbances can be measured in later photons. Since the beams are constant, the scientists have plenty of data about the motions of the atoms in the mirrors -- meaning they can then design the perfect counteracting forces. To do so, the researchers attached electromagnets to the back of each mirror, which reduced their collective motion almost to the motional ground state. The mirrors moved less than one-thousandth the width of a proton, essentially cooling down to a crisp 77 nanokelvins -- a hair above absolute zero. The team says that this breakthrough could enable new quantum experiments on the macro scale.

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An anonymous reader quotes a report from Scientific American: Few harbingers of old age are clearer than the sight of gray hair. As we grow older, black, brown, blonde or red strands lose their youthful hue. Although this may seem like a permanent change, new research reveals that the graying process can be undone -- at least temporarily. In a study published today in eLife, a group of researchers provide the most robust evidence of this phenomenon to date in hair from around a dozen people of various ages, ethnicities and sexes. It also aligns patterns of graying and reversal to periods of stress, which implies that this aging-related process is closely associated with our psychological well-being. The researchers [...] developed a technique to digitize and quantify the subtle changes in color, which they dubbed hair pigmentation patterns, along each strand. These patterns revealed something surprising: In 10 of [the 14 participants], who were between age nine and 39, some graying hairs regained color. The team also found that this occurred not just on the head but in other bodily regions as well. "When we saw this in pubic hair, we thought, 'Okay, this is real,'" [Martin Picard, a mitochondrial psychobiologist at Columbia University] says. "This happens not just in one person or on the head but across the whole body." He adds that because the reversibility only appeared in some hair follicles, however, it is likely limited to specific periods when changes are still able to occur. Most people start noticing their first gray hairs in their 30s -- although some may find them in their late 20s. This period, when graying has just begun, is probably when the process is most reversible, according to [study co-author Ralf Paus, a dermatologist at the University of Miami]. In those with a full head of gray hair, most of the strands have presumably reached a "point of no return," but the possibility remains that some hair follicles may still be malleable to change, he says. In a small subset of participants, the researchers pinpointed segments in single hairs where color changes occurred in the pigmentation patterns. Then they calculated the times when the change happened using the known average growth rate of human hair: approximately one centimeter per month. These participants also provided a history of the most stressful events they had experienced over the course of a year. This analysis revealed that the times when graying or reversal occurred corresponded to periods of significant stress or relaxation. In one individual, a 35-year-old man with auburn hair, five strands of hair underwent graying reversal during the same time span, which coincided with a two-week vacation. Another subject, a 30-year-old woman with black hair, had one strand that contained a white segment that corresponded to two months during which she underwent marital separation and relocation -- her highest-stress period in the year.

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For some time, a collaboration of biologists, chemists and physicists centered at the Universities of Oldenburg (Germany) and Oxford (UK) have been gathering evidence suggesting that the magnetic sense of migratory birds such as European robins is based on a specific light-sensitive protein in the eye. In the current edition of the journal Nature, this team demonstrate that the protein cryptochrome 4, found in birds' retinas, is sensitive to magnetic fields and could well be the long-sought magnetic sensor. Phys.Org reports: First author Jingjing Xu, a doctoral student in Henrik Mouritsen's research group in Oldenburg, took a decisive step toward this success. After extracting the genetic code for the potentially magnetically sensitive cryptochrome 4 in night-migratory European robins, she was able, for the first time, to produce this photoactive molecule in large quantities using bacterial cell cultures. Christiane Timmel's and Stuart Mackenzie's groups in Oxford then used a wide range of magnetic resonance and novel optical spectroscopy techniques to study the protein and demonstrate its pronounced sensitivity to magnetic fields. The team also deciphered the mechanism by which this sensitivity arises -- another important advance. "Electrons that can move within the molecule after blue-light activation play a crucial role," explains Mouritsen. Proteins like cryptochrome consist of chains of amino acids: robin cryptochrome 4 has 527 of them. Oxford's Peter Hore and Oldenburg physicist Ilia Solov'yov performed quantum mechanical calculations supporting the idea that four of the 527 -- known as tryptophans -- are essential for the magnetic properties of the molecule. According to their calculations, electrons hop from one tryptophan to the next generating so-called radical pairs which are magnetically sensitive. To prove this experimentally, the team from Oldenburg produced slightly modified versions of the robin cryptochrome, in which each of the tryptophans in turn was replaced by a different amino acid to block the movement of electrons. Using these modified proteins, the Oxford chemistry groups were able to demonstrate experimentally that electrons move within the cryptochrome as predicted in the calculations -- and that the generated radical pairs are essential to explain the observed magnetic field effects. Hore says "if we can prove that cryptochrome 4 is the magnetic sensor we will have demonstrated a fundamentally quantum mechanism that makes animals sensitive to environmental stimuli a million times weaker than previously thought possible."

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