Quantum gas goes below absolute zero .

It may sound less likely than hell freezing over, but physicists have created an atomic gas with a sub-absolute-zero temperature for the first time1. Their technique opens the door to generating negative-Kelvin materials and new quantum devices, and it could even help to solve a cosmological mystery.

Lord Kelvin defined the absolute temperature scale in the mid-1800s in such a way that nothing could be colder than absolute zero. Physicists later realized that the absolute temperature of a gas is related to the average energy of its particles. Absolute zero corresponds to the theoretical state in which particles have no energy at all, and higher temperatures correspond to higher average energies.

However, by the 1950s, physicists working with more exotic systems began to realise that this isn’t always true: Technically, you read off the temperature of a system from a graph that plots the probabilities of its particles being found with certain energies. Normally, most particles have average or near-average energies, with only a few particles zipping around at higher energies. In theory, if the situation is reversed, with more particles having higher, rather than lower, energies, the plot would flip over and the sign of the temperature would change from a positive to a negative absolute temperature, explains Ulrich Schneider, a physicist at the Ludwig Maximilian University in Munich, Germany.

Schneider and his colleagues reached such sub-absolute-zero temperatures with an ultracold quantum gas made up of potassium atoms. Using lasers and magnetic fields, they kept the individual atoms in a lattice arrangement. At positive temperatures, the atoms repel, making the configuration stable. The team then quickly adjusted the magnetic fields, causing the atoms to attract rather than repel each other. “This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react,” says Schneider. “It’s like walking through a valley, then instantly finding yourself on the mountain peak.”

At positive temperatures, such a reversal would be unstable and the atoms would collapse inwards. But the team also adjusted the trapping laser field to make it more energetically favourable for the atoms to stick in their positions. This result, described today in Science1, marks the gas’s transition from just above absolute zero to a few billionths of a Kelvin below absolute zero.

Wolfgang Ketterle, a physicist and Nobel laureate at the Massachusetts Institute of Technology in Cambridge, who has previously demonstrated negative absolute temperatures in a magnetic system2, calls the latest work an “experimental tour de force”. Exotic high-energy states that are hard to generate in the laboratory at positive temperatures become stable at negative absolute temperatures — “as though you can stand a pyramid on its head and not worry about it toppling over,” he notes — and so such techniques can allow these states to be studied in detail. “This may be a way to create new forms of matter in the laboratory,” Ketterle adds.

If built, such systems would behave in strange ways, says Achim Rosch, a theoretical physicist at the University of Cologne in Germany, who proposed the technique used by Schneider and his team3. For instance, Rosch and his colleagues have calculated that whereas clouds of atoms would normally be pulled downwards by gravity, if part of the cloud is at a negative absolute temperature, some atoms will move upwards, apparently defying gravity4.

Another peculiarity of the sub-absolute-zero gas is that it mimics ‘dark energy’, the mysterious force that pushes the Universe to expand at an ever-faster rate against the inward pull of gravity. Schneider notes that the attractive atoms in the gas produced by the team also want to collapse inwards, but do not because the negative absolute temperature stabilises them. “It’s interesting that this weird feature pops up in the Universe and also in the lab,” he says. “This may be something that cosmologists should look at more closely.”

Respiratory infections may increase infants’ risk for diabetes.

Respiratory infections in early childhood, especially in the first year of life, may be a risk factor for the development of type 1 diabetes, according to data.

In a prospective cohort study conducted in Munich, researchers examined data for 148 children at high risk for developing type 1 diabetes with documentation of 1,245 infectious events in 90,750 person-days during their first 3 years of life. Documentation was collected from the ongoing BABYDIET study, a German dietaryintervention study that tests the effects of delayed gluten exposure on the development of islet autoimmunity in children at increased risk for diabetes, researchers wrote.

The HR for islet autoantibody seroconversion associated with respiratory infections was increased during the first 6 months of life (HR=2.27; 95% CI, 1.32-3.91) and for those aged 6 to 11.9 months (HR=1.32; 95% CI, 1.08-1.61).

According to data, a higher number of respiratory infections were reported in the 6 months before islet autoantibody seroconversion and also were associated with an increased HR (HR=1.42; 95% CI, 1.12-1.80), the researchers wrote.

“While there were no islet autoantibody seroconversion events observed in the first 6 months of life, the incidence rates of seroconversion per 100 person-years were 8.51 in the second-half year, 4.07 in the second year, and 3.67 in the third year of life. The mean incidences of the three infection categories also increased considerably after the first 6 months of life and remained relatively constant thereafter, with a slight decline in the third year of life,” researchers wrote.

Besides these findings, there is some evidence connecting short-term effects of infectious events and the development of autoimmunity, they wrote.

Source: Endocrine Today



Clinical features and virological analysis of a case of Middle East respiratory syndrome coronavirus infection.


The Middle East respiratory syndrome coronavirus (MERS-CoV) is an emerging virus involved in cases and case clusters of severe acute respiratory infection in the Arabian Peninsula, Tunisia, Morocco, France, Italy, Germany, and the UK. We provide a full description of a fatal case of MERS-CoV infection and associated phylogenetic analyses.


We report data for a patient who was admitted to the Klinikum Schwabing (Munich, Germany) for severe acute respiratory infection. We did diagnostic RT-PCR and indirect immunofluorescence. From time of diagnosis, respiratory, faecal, and urine samples were obtained for virus quantification. We constructed a maximum likelihood tree of the five available complete MERS-CoV genomes.


A 73-year-old man from Abu Dhabi, United Arab Emirates, was transferred to Klinikum Schwabing on March 19, 2013, on day 11 of illness. He had been diagnosed with multiple myeloma in 2008, and had received several lines of treatment. The patient died on day 18, due to septic shock. MERS-CoV was detected in two samples of bronchoalveolar fluid. Viral loads were highest in samples from the lower respiratory tract (up to 1·2 × 106 copies per mL). Maximum virus concentration in urine samples was 2691 RNA copies per mL on day 13; the virus was not present in the urine after renal failure on day 14. Stool samples obtained on days 12 and 16 contained the virus, with up to 1031 RNA copies per g (close to the lowest detection limit of the assay). One of two oronasal swabs obtained on day 16 were positive, but yielded little viral RNA (5370 copies per mL). No virus was detected in blood. The full virus genome was combined with four other available full genome sequences in a maximum likelihood phylogeny, correlating branch lengths with dates of isolation. The time of the common ancestor was halfway through 2011. Addition of novel genome data from an unlinked case treated 6 months previously in Essen, Germany, showed a clustering of viruses derived from Qatar and the United Arab Emirates.


We have provided the first complete viral load profile in a case of MERS-CoV infection. MERS-CoV might have shedding patterns that are different from those of severe acute respiratory syndrome and so might need alternative diagnostic approaches.

Source: lancet