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Excitons, plasmons and phonons are some of the better known quasiparticles � exotic entities that act in some respects like ordinary particles. New types do not come along all that often but here is one � a fundamentally new many-body particle named the dropleton�. Mackillo Kira and colleagues have identified this new quantum entity, a quantum droplet created when four or more electrons and holes (electronic vacancies) form a tiny correlation bubble via the Coulomb attraction, in direct-gap semiconductors such as gallium arsenide. The cover illustrates the pair-correlation function g(r) of quantum droplets � the central peak of the correlation function shows that electrons and holes are likely to be co-located and the ripples show that otherwise they form regularly spaced shells. (Cover art: Brad Baxley.)
The UK floods show the need to address the risks of climate change, but news teams still insist on pitching experts against sceptics, says Simon L. Lewis.
The week in science: US bolsters patent system; $25-billion pharma deal the biggest in 5 years; and Europe picks exoplanet-hunting mission for 2024 launch.
A powerful method for deducing microbial relationships has been edging its way into civil and criminal investigations. But courts should proceed with caution.
London-based music psychologist John Sloboda explores the subconscious connections and disjunctions between musicians and their audiences. He discusses his experiments on the 'emotional hotspots' experienced by listeners and the surprising power of improvisation.
In a study that showcases the potential of semisynthetic drug design, structural modification of an existing antibiotic with little activity against Mycobacterium tuberculosis has generated a new class of effective antitubercular lead.
Might it be possible to create mirrors for space telescopes, using nothing but microscopic particles held in place by light? A study that exploits a technique called optical binding provides a step towards this goal.
Analyses of ependymoma brain tumours reveal a gene rearrangement in one subtype, but no DNA mutations in two others, suggesting that mechanisms for cancer initiation are broader than is typically thought. See Articles p.445 & p.451
A new value for the atomic mass of the electron is a link in a chain of measurements that will enable a test of the standard model of particle physics with better than part-per-trillion precision. See Letter p.467
A common variant of the autophagy protein ATG16L1 is a risk factor for Crohn's disease. But the genetic alteration is revealed only when the protein is cleaved by the enzyme caspase 3 during cellular stress. See Article p.456
How tiny aerosol particles form and grow from vapours produced by vegetation has been a mystery. The finding that highly oxygenated products form directly from volatile organic compounds may offer the solution. See Letter p.476
Although genetically bland, the posterior fossa group A subgroup of ependymomas, found often in infants and associated with poor prognosis, exhibit widespread epigenetic alterations, namely a CpG island methylator phenotype; these tumours are shown to be susceptible both in vitro and in vivo to various compounds that target epigenetic modifications, such as DNA methylation and H3K27 tri-methylation.
At least two-thirds of supratentorial ependymomas contain oncogenic fusions between RELA, the principal effector of nuclear factor-κB (NF-κB) signalling, and uncharacterized gene C11orf95; C11orf95–RELA fusion proteins translocate spontaneously to the nucleus to activate NF-κB target genes, and rapidly transform neural stem cells to form tumours in mice
The Crohn’s disease risk-conferring T300A variant in the autophagy protein ATG16L1 increases its sensitivity to caspase-3-mediated cleavage; this decreases the induction of autophagy in response to metabolic stress or pathogen infection, leading to increased secretion of inflammatory cytokines.
The optical spectrum of the star SMSS J031300.36−670839.3 shows no evidence of iron; this, together with comparisons of the star’s observed element abundance pattern with those of models, means that SMSS J031300.36−670839.3 must have been seeded with material from a single supernova with an original mass about 60 times that of the Sun.
A very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus, combined with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics, gives a new value of the atomic mass of the electron that is more precise than the currently accepted one by a factor of 13.
Fast optical pulses create a plasma of electrons and holes in a semiconductor in which excitons (pairs of holes and electrons) and combinations of two excitons emerge; now a stable liquid-like droplet of electrons and holes has been detected and called a ‘dropleton’.
The link between biogenic volatile organic compounds in the atmosphere and their conversion to aerosol particles is unclear, but a direct reaction pathway is now described by which volatile organic compounds lead to low-volatility vapours that can then condense onto aerosol surfaces, producing secondary organic aerosol.
We lack thermal histories for magma reservoirs, but here the magma under Mount Hood (Oregon, USA) is shown to have been too cold to mobilize for most of the time it has been stored, which implies that magma mobilizes (at which point it can be imaged geophysically) very quickly prior to eruption.
Dark melanin pigment was detected in the fossilized skin of three distantly related marine reptiles (a leatherback turtle, mosasaur and ichthyosaur); benefits of thermoregulation and/or crypsis may have contributed to this melanisation, which therefore has implications for our understanding of how these animals may have lived.
A new method for identifying genetic loci that influence protein expression in budding yeast reveals considerable complexity in how genetic variation shapes the proteome.
A genetic locus from the gut symbiont Bacteroides ovatus is identified and described that encodes a cohort of enzymes and carbohydrate-binding proteins necessary for the metabolism of xyloglucans—a predominant component of dietary fibre.
Tissue-resident macrophages are shown to stop lipopolysaccharide-induced inflammation by spreading an anti-inflammatory calcium signal to alveolar epithelial cells through connexin-43-positive gap junction channels.
Peptidoglycan is an essential structural component of the cell wall in the majority of bacteria, but the obligate intracellular human pathogen Chlamydia trachomatis was thought to be one of the few exceptions; here a click chemistry approach is used to label peptidoglycan in replicating C. trachomatis with novel d-amino acid dipeptide probes.
A study investigating the mechanisms underlying lateral inhibition and lineage plasticity in the mouse small intestine crypts in vivo finds that crypt cells maintain a permissive chromatin state upon which a transcription factor acts to determine lineage specification, and this is the basis of lateral inhibition.