The Large Hadron Collider (LHC) is best known for the 2012 discovery of the Higgs boson, which was made by smashing together high-energy protons (see Collection: The History of Observations of the Higgs Boson). But protons are not the only particles accelerated by the collider, and some studies call for colliding much heavier objects. Now a team working on the LHC’s ALICE experiment has collided lead nuclei to study an exotic particle called a hypertriton [1]. The result could help researchers reduce errors in models of the structure of neutron stars.
A hypertriton is a tritium nucleus in which one neutron has been replaced with a lambda hyperon, a heavier particle with a quark configuration of up-down-strange rather than up-down-down. Researchers have long known the energy it takes to bind tritium’s proton and two neutrons. But it was unclear how that energy changed with the neutron–lambda hyperon switch.
The ALICE Collaboration turned to lead–lead collisions to answer this question because these collisions produce hypertritons in much greater numbers than proton–proton ones do. A hypertriton quickly decays into a helium-3 nucleus and a pion, with the decay time and the energy of the decay products depending on the binding energy between the lambda hyperon and the hypertriton core.
Active particles can form two-dimensional solids that are different from those formed by nonmotile particles, showing long-range crystalline order accompanied by giant spontaneous deformations.
If you compress a liquid slowly enough at low temperatures, it will freeze into an ordered solid: a crystal. Or at least that’s what we’re used to seeing in three dimensions. If you instead consider particles confined to a two-dimensional (2D) plane, the outcome is quite different. For equilibrium systems, a 2D solid stabilizes into a structure that lacks long-range order—it becomes less ordered further away from a central lattice site. The behavior of systems far from equilibrium, such as self-propelled particles, remains, however, an open question. In a numerical study of bacteria-like particles, Xia-qing Shi of Soochow University in China and his colleagues now show that active crystals follow a slightly different set of rules than their nonmotile counterparts [1]. Like 2D equilibrium crystals, 2D active systems stabilize into an ordered solid-like phase but with extremely large particle fluctuations around the configuration of a perfect crystal lattice.
Since the 1960s there has been plenty of evidence to support the existence of dark matter through astrophysical and cosmological observations, and at this point we’re very confident that it exists. The question remains, though: what is dark matter actually made of?
Throughout the decades there have been many candidates for dark matter, such as weakly interacting massive particles (WIMPs), neutrinos, and primordial black holes. Candidates like WIMPs were originally theorized because they have properties that address issues in other parts of physics. Another candidate that could answer some thorny physics questions is called the axion.
Axions were originally theorized as a solution to a particle physics question known as the Strong CP Problem, but physicists also realized that axions could be produced in a way that would satisfy requirements for them to be dark matter. These are the particles that the DMRadio experiments search for.
Inside our bodies at every moment, our cells are orchestrating a complex dance of atoms and molecules that uses energy to create, distribute and deploy the substances on which our lives depend.
And it’s not just in our bodies: all animals carry out this dance of metabolism, and it turns out none of them do it quite the same way.
In new research published in Science Advances, we analysed specific carbon atoms in amino acids – the building blocks of proteins – to discover distinctive fingerprints of the metabolism of different species.
Physicists at CERN’s Large Hadron Collider (LHC) have made the first ever direct observation of neutrinos in a particle accelerator.
Neutrinos are tiny, near massless and chargeless particles. They are among the elementary particles that make up the Standard Model of particle physics. Of all the particles in the Standard Model, neutrinos are among the least understood.
Even seeing a neutrino is extremely difficult, despite the fact they are among the most numerous particles in the universe. An estimated 100 trillion (100 million million) neutrinos pass through your body every second!
A combined team of physicists from the University of Sussex and the National Physical Laboratory, both in the U.K., has been designing experiments to identify ultra-light dark matter particles. In their paper published in the open-access New Journal of Physics, the group describes how they are attempting to use the high precision of atomic clocks to detect ultra-light dark matter particle “kicks” that would lead to time variations and, in so doing, would show evidence of dark matter.
Currently, dark matter is not something that has been shown to exist—instead it is more of a placeholder that has been created to explain observations of deviations from the Standard Model of physics—like certain gravitational effects on galaxies. Since its development as a theory back in the early 1930s, physicists around the world have been developing theories and experiments to prove that it exists.
Sadly, despite a lot of time and effort, no such proof has been found. In this new effort, the team in the U.K. is working on a novel way to add credence to dark matter theories—using atomic clocks to detect ultra-light dark matter particles.
Scientists have been able to observe a common interaction in quantum chemistry for the first time, by using a quantum computer to shadow the process at a speed 100 billion times slower than normal.
Known as a conical intersection, the interactions have long been known about, but are usually over in mere femtoseconds – quadrillionths of a second – making direct observations impossible to carry out.
Not all of the material around us is stable. Some materials may undergo radioactive decay to form more stable isotopes. Scientists have now observed a new decay mode for the first time. In this decay, a lighter form of oxygen, oxygen-13 (with eight protons and five neutrons), decays by breaking into three helium nuclei (an atom without the surrounding electrons), a proton, and a positron (the antimatter version of an electron).
Scientists observed this decay by watching a single nucleus break apart and measuring the breakup products. The study is published in the journal Physical Review Letters.
Scientists have previously observed interesting modes of radioactive decay following the process called beta-plus decay. This is where a proton turns into a neutron and emits some of the produced energy by emitting a positron and an antineutrino. After this initial beta-decay, the resulting nucleus can have enough energy to boil off extra particles and make itself more stable.
These all-purpose, desktop machines can reproduce a seemingly infinite variety of items. In fact, they are like miniature factories. In appearance, they resemble a combined washing machine/microwave oven. Raw materials are purchased separately and can be loaded in solid, liquid or powder form. An interior compartment is accessed via a small hatch, where objects are constructed atom-by-atom. The process takes a matter of minutes and the assembled items can be used immediately. New schematics can be accessed from the web and programmed into the machine.
I did not create this animation video and i do not gain any profit from it. This is for educational purposes only.
A molecular assembler, as defined by K. Eric Drexler, is a “proposed device able to guide chemical reactions by positioning reactive molecules with atomic precision”. A molecular assembler is a kind of molecular machine. Some biological molecules such as ribosomes fit this definition. This is because they receive instructions from messenger RNA and then assemble specific sequences of amino acids to construct protein molecules. However, the term “molecular assembler” usually refers to theoretical human-made devices.
Beginning in 2007, the British Engineering and Physical Sciences Research Council has funded development of ribosome-like molecular assemblers. Clearly, molecular assemblers are possible in this limited sense. A technology roadmap project, led by the Battelle Memorial Institute and hosted by several U.S. National Laboratories has explored a range of atomically precise fabrication technologies, including both early-generation and longer-term prospects for programmable molecular assembly; the report was released in December, 2007. In 2008 the Engineering and Physical Sciences Research Council provided funding of 1.5 million pounds over six years for research working towards mechanized mechanosynthesis, in partnership with the Institute for Molecular Manufacturing, amongst others. Likewise, the term “molecular assembler” has been used in science fiction and popular culture to refer to a wide range of fantastic atom-manipulating nanomachines, many of which may be physically impossible in reality. Much of the controversy regarding “molecular assemblers” results from the confusion in the use of the name for both technical concepts and popular fantasies. In 1992, Drexler introduced the related but better-understood term “molecular manufacturing”, which he defined as the programmed “chemical synthesis of complex structures by mechanically positioning reactive molecules, not by manipulating individual atoms”.This article mostly discusses “molecular assemblers” in the popular sense. These include hypothetical machines that manipulate individual atoms and machines with organism-like self-replicating abilities, mobility, ability to consume food, and so forth. These are quite different from devices that merely (as defined above) “guide chemical reactions by positioning reactive molecules with atomic precision”. Because synthetic molecular assemblers have never been constructed and because of the confusion regarding the meaning of the term, there has been much controversy as to whether “molecular assemblers” are possible or simply science fiction. Confusion and controversy also stem from their classification as nanotechnology, which is an active area of laboratory research which has already been applied to the production of real products; however, there had been, until recently, no research efforts into the actual construction of “molecular assemblers”. Nonetheless, a 2013 paper by David Leigh’s group, published in the journal Science, details a new method of synthesizing a peptide in a sequence-specific manner by using an artificial molecular machine that is guided by a molecular strand. This functions in the same way as a ribosome building proteins by assembling amino acids according to a messenger RNA blueprint. The structure of the machine is based on a rotaxane, which is a molecular ring sliding along a molecular axle. The ring carries a thiolate group which removes amino acids in sequence from the axle, transferring them to a peptide assembly site. In 2018, the same group published a more advanced version of this concept in which the molecular ring shuttles along a polymeric track to assemble an oligopeptide that can fold into a α-helix that can perform the enantioselective epoxidation of a chalcone derivative (in a way reminiscent to the ribosome assembling an enzyme). In another paper published in Science in March 2015, chemists at the University of Illinois report a platform that automates the synthesis of 14 classes of small molecules, with thousands of compatible building blocks. In 2017 David Leigh’s group reported a molecular robot that could be programmed to construct any one of four different stereoisomers of a molecular product by using a nanomechanical robotic arm to move a molecular substrate between different reactive sites of an artificial molecular machine. An accompanying News and Views article, titled ‘A molecular assembler’, outlined the operation of the molecular robot as effectively a prototypical molecular assembler.
