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Sustainable agriculture requires balancing crop yields with the effects of pesticides on non-target organisms, such as bees and other crop pollinators. Field studies demonstrated that agricultural use of neonicotinoid insecticides can negatively affect wild bee species1,2, leading to restrictions on these compounds3. However, besides neonicotinoids, field-based evidence of the effects of landscape pesticide exposure on wild bees is lacking. Bees encounter many pesticides in agricultural landscapes4–9and the effects of this landscape exposure on colony growth and development of any bee species remains unknown. Here we show that the many pesticides found in bumble bee-collected pollen are associated with reduced colony performance during crop bloom, especially in simplified landscapes with intensive agricultural practices. Our results from 316 Bombus terrestriscolonies at 106 agricultural sites across eight European countries confirm that the regulatory system fails to sufficiently prevent pesticide-related impacts on non-target organisms, even for a eusocial pollinator species in which colony size may buffer against such impacts10,11. These findings support the need for postapproval monitoring of both pesticide exposure and effects to confirm that the regulatory process is sufficiently protective in limiting the collateral environmental damage of agricultural pesticide use.

The early evolution of a supernova (SN) can reveal information about the environment and the progenitor star. When a star explodes in vacuum, the first photons to escape from its surface appear as a brief, hours-long shock-breakout flare1,2, followed by a cooling phase of emission. However, for stars exploding within a distribution of dense, optically thick circumstellar material (CSM), the first photons escape from the material beyond the stellar edge and the duration of the initial flare can extend to several days, during which the escaping emission indicates photospheric heating3. Early serendipitous observations2,4that lacked ultraviolet (UV) data were unable to determine whether the early emission is heating or cooling and hence the nature of the early explosion event. Here we report UV spectra of the nearby SN 2023ixf in the galaxy Messier 101 (M101). Using the UV data as well as a comprehensive set of further multiwavelength observations, we temporally resolve the emergence of the explosion shock from a thick medium heated by the SN emission. We derive a reliable bolometric light curve that indicates that the shock breaks out from a dense layer with a radius substantially larger than typical supergiants.

To run large-scale algorithms on a quantum computer, error-correcting codes must be able to perform a fundamental set of operations, called logic gates, while isolating the encoded information from noise1–8. We can complete a universal set of logic gates by producing special resources called magic states9–11. It is therefore important to produce high-fidelity magic states to conduct algorithms while introducing a minimal amount of noise to the computation. Here we propose and implement a scheme to prepare a magic state on a superconducting qubit array using error correction. We find that our scheme produces better magic states than those that can be prepared using the individual qubits of the device. This demonstrates a fundamental principle of fault-tolerant quantum computing12, namely, that we can use error correction to improve the quality of logic gates with noisy qubits. Moreover, we show that the yield of magic states can be increased using adaptive circuits, in which the circuit elements are changed depending on the outcome of mid-circuit measurements. This demonstrates an essential capability needed for many error-correction subroutines. We believe that our prototype will be invaluable in the future as it can reduce the number of physical qubits needed to produce high-fidelity magic states in large-scale quantum-computing architectures.

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs)1, sources of high-frequency gravitational waves (GWs)2and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process)3. Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers4–6and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. 7–12). We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A= 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe.

Around 60% of individuals with neurodevelopmental disorders (NDD) remain undiagnosed after comprehensive genetic testing, primarily of protein-coding genes1. Large genome-sequenced cohorts are improving our ability to discover new diagnoses in the non-coding genome. Here we identify the non-coding RNA RNU4-2as a syndromic NDD gene. RNU4-2encodes the U4 small nuclear RNA (snRNA), which is a critical component of the U4/U6.U5 tri-snRNP complex of the major spliceosome2. We identify an 18 base pair region of RNU4-2mapping to two structural elements in the U4/U6 snRNA duplex (the T-loop and stem III) that is severely depleted of variation in the general population, but in which we identify heterozygous variants in 115 individuals with NDD. Most individuals (77.4%) have the same highly recurrent single base insertion (n.64_65insT). In 54 individuals in whom it could be determined, the de novo variants were all on the maternal allele. We demonstrate that RNU4-2is highly expressed in the developing human brain, in contrast to RNU4-1and other U4 homologues. Using RNA sequencing, we show how 5′ splice-site use is systematically disrupted in individuals with RNU4-2variants, consistent with the known role of this region during spliceosome activation. Finally, we estimate that variants in this 18 base pair region explain 0.4% of individuals with NDD. This work underscores the importance of non-coding genes in rare disorders and will provide a diagnosis to thousands of individuals with NDD worldwide.

White dwarfs, the extremely dense remnants left behind by most stars after their death, are characterized by a mass comparable to that of the Sun compressed into the size of an Earth-like planet. In the resulting strong gravity, heavy elements sink towards the centre and the upper layer of the atmosphere contains only the lightest element present, usually hydrogen or helium1,2. Several mechanisms compete with gravitational settling to change a white dwarf’s surface composition as it cools3, and the fraction of white dwarfs with helium atmospheres is known to increase by a factor of about 2.5 below a temperature of about 30,000 kelvin4–8; therefore, some white dwarfs that appear to have hydrogen-dominated atmospheres above 30,000 kelvin are bound to transition to be helium-dominated as they cool below it. Here we report observations of ZTF J203349.8+322901.1, a transitioning white dwarf with two faces: one side of its atmosphere is dominated by hydrogen and the other one by helium. This peculiar nature is probably caused by the presence of a small magnetic field, which creates an inhomogeneity in temperature, pressure or mixing strength over the surface9–11. ZTF J203349.8+322901.1 might be the most extreme member of a class of magnetic, transitioning white dwarfs—together with GD 323 (ref. 12), a white dwarf that shows similar but much more subtle variations. This class of white dwarfs could help shed light on the physical mechanisms behind the spectral evolution of white dwarfs.

Although circumstantial evidence supports enhanced Toll-like receptor 7 (TLR7) signalling as a mechanism of human systemic autoimmune disease1–7, evidence of lupus-causing TLR7gene variants is lacking. Here we describe human systemic lupus erythematosus caused by a TLR7gain-of-function variant. TLR7 is a sensor of viral RNA8,9and binds to guanosine10–12. We identified a de novo, previously undescribed missense TLR7Y264Hvariant in a child with severe lupus and additional variants in other patients with lupus. The TLR7Y264Hvariant selectively increased sensing of guanosine and 2',3'-cGMP10–12, and was sufficient to cause lupus when introduced into mice. We show that enhanced TLR7 signalling drives aberrant survival of B cell receptor (BCR)-activated B cells, and in a cell-intrinsic manner, accumulation of CD11c+age-associated B cells and germinal centre B cells. Follicular and extrafollicular helper T cells were also increased but these phenotypes were cell-extrinsic. Deficiency of MyD88 (an adaptor protein downstream of TLR7) rescued autoimmunity, aberrant B cell survival, and all cellular and serological phenotypes. Despite prominent spontaneous germinal-centre formation in Tlr7Y264Hmice, autoimmunity was not ameliorated by germinal-centre deficiency, suggesting an extrafollicular origin of pathogenic B cells. We establish the importance of TLR7 and guanosine-containing self-ligands for human lupus pathogenesis, which paves the way for therapeutic TLR7 or MyD88 inhibition.

The ability to program new modes of catalysis into proteins would allow the development of enzyme families with functions beyond those found in nature. To this end, genetic code expansion methodology holds particular promise, as it allows the site-selective introduction of new functional elements into proteins as noncanonical amino acid side chains1–4. Here we exploit an expanded genetic code to develop a photoenzyme that operates by means of triplet energy transfer (EnT) catalysis, a versatile mode of reactivity in organic synthesis that is not accessible to biocatalysis at present5–12. Installation of a genetically encoded photosensitizer into the beta-propeller scaffold of DA_20_00 (ref. 13) converts a de novo Diels–Alderase into a photoenzyme for [2+2] cycloadditions (EnT1.0). Subsequent development and implementation of a platform for photoenzyme evolution afforded an efficient and enantioselective enzyme (EnT1.3, up to 99% enantiomeric excess (e.e.)) that can promote intramolecular and bimolecular cycloadditions, including transformations that have proved challenging to achieve selectively with small-molecule catalysts. EnT1.3 performs >300 turnovers and, in contrast to small-molecule photocatalysts, can operate effectively under aerobic conditions and at ambient temperatures. An X-ray crystal structure of an EnT1.3-product complex shows how multiple functional components work in synergy to promote efficient and selective photocatalysis. This study opens up a wealth of new excited-state chemistry in protein active sites and establishes the framework for developing a new generation of enantioselective photocatalysts.

The biophysical properties of neurons are the foundation for computation in the brain. Neuronal size is a key determinant of single neuron input–output features and varies substantially across species1–3. However, it is unknown whether different species adapt neuronal properties to conserve how single neurons process information4–7. Here we characterize layer 5 cortical pyramidal neurons across 10 mammalian species to identify the allometric relationships that govern how neuronal biophysics change with cell size. In 9 of the 10 species, we observe conserved rules that control the conductance of voltage-gated potassium and HCN channels. Species with larger neurons, and therefore a decreased surface-to-volume ratio, exhibit higher membrane ionic conductances. This relationship produces a conserved conductance per unit brain volume. These size-dependent rules result in large but predictable changes in somatic and dendritic integrative properties. Human neurons do not follow these allometric relationships, exhibiting much lower voltage-gated potassium and HCN conductances. Together, our results in layer 5 neurons identify conserved evolutionary principles for neuronal biophysics in mammals as well as notable features of the human cortex.

Global concern over widely documented declines in pollinators1–3has led to the identification of anthropogenic stressors that, individually, are detrimental to bee populations4–7. Synergistic interactions between these stressors could substantially amplify the environmental effect of these stressors and could therefore have important implications for policy decisions that aim to improve the health of pollinators3,8,9. Here, to quantitatively assess the scale of this threat, we conducted a meta-analysis of 356 interaction effect sizes from 90 studies in which bees were exposed to combinations of agrochemicals, nutritional stressors and/or parasites. We found an overall synergistic effect between multiple stressors on bee mortality. Subgroup analysis of bee mortality revealed strong evidence for synergy when bees were exposed to multiple agrochemicals at field-realistic levels, but interactions were not greater than additive expectations when bees were exposed to parasites and/or nutritional stressors. All interactive effects on proxies of fitness, behaviour, parasite load and immune responses were either additive or antagonistic; therefore, the potential mechanisms that drive the observed synergistic interactions for bee mortality remain unclear. Environmental risk assessment schemes that assume additive effects of the risk of agrochemical exposure may underestimate the interactive effect of anthropogenic stressors on bee mortality and will fail to protect the pollinators that provide a key ecosystem service that underpins sustainable agriculture.

Coronaviruses are prone to transmission to new host species, as recently demonstrated by the spread to humans of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic1. Small animal models that recapitulate SARS-CoV-2 disease are needed urgently for rapid evaluation of medical countermeasures2,3. SARS-CoV-2 cannot infect wild-type laboratory mice owing to inefficient interactions between the viral spike protein and the mouse orthologue of the human receptor, angiotensin-converting enzyme 2 (ACE2)4. Here we used reverse genetics5to remodel the interaction between SARS-CoV-2 spike protein and mouse ACE2 and designed mouse-adapted SARS-CoV-2 (SARS-CoV-2 MA), a recombinant virus that can use mouse ACE2 for entry into cells. SARS-CoV-2 MA was able to replicate in the upper and lower airways of both young adult and aged BALB/c mice. SARS-CoV-2 MA caused more severe disease in aged mice, and exhibited more clinically relevant phenotypes than those seen in Hfh4-ACE2transgenic mice, which express human ACE2 under the control of the Hfh4(also known as Foxj1) promoter. We demonstrate the utility of this model using vaccine-challenge studies in immune-competent mice with native expression of mouse ACE2. Finally, we show that the clinical candidate interferon-?1a (IFN-?1a) potently inhibits SARS-CoV-2 replication in primary human airway epithelial cells in vitro—both prophylactic and therapeutic administration of IFN-?1a diminished SARS-CoV-2 replication in mice. In summary, the mouse-adapted SARS-CoV-2 MA model demonstrates age-related disease pathogenesis and supports the clinical use of pegylated IFN-?1a as a treatment for human COVID-196.

The field of plasmonics, which studies the resonant interactions of electromagnetic waves and free electrons in solid-state materials1, has yet to be put to large-scale commercial application2owing to the large amount of loss that usually occurs in plasmonic materials3. Organic light-emitting devices (OLEDs)4–7have been incorporated into billions of commercial products because of their good colour saturation, versatile form factor8and low power consumption9, but could still be improved in terms of efficiency and stability. Although OLEDs incorporating organic phosphors achieve an internal charge-to-light conversion of unity10, their refractive index contrast reduces the observable fraction of photons outside the device to around 25 per cent11–13. Further, during OLED operation, a localized buildup of slow-decaying14triplet excitons and charges15gradually reduces the brightness of the device in a process called ageing16,17, which can result in ‘burn-in’ effects on the display. Simultaneously improving device efficiency and stability is of paramount importance for OLED technology. Here we demonstrate an OLED that uses the decay rate enhancement18of a plasmonic system to increase device stability, while maintaining efficiency by incorporating a nanoparticle-based out-coupling scheme to extract energy from the plasmon mode. Using an archetypal phosphorescent emitter, we achieve a two-fold increase in operational stability at the same brightness as a reference conventional device while simultaneously extracting 16 per cent of the energy from the plasmon mode as light. Our approach to increasing OLED stability avoids material-specific designs19–22and is applicable to all commercial OLEDs that are currently used for lighting panels, televisions and mobile displays.

The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to large uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary processes provide a route to understanding planetary interiors. Planets found in and near the typically barren hot-Neptune ‘desert’1,2(a region in mass–radius space that contains few planets) have proved to be particularly valuable in this regard. These planets include HD149026b3, which is thought to have an unusually massive core, and recent discoveries such as LTT9779b4and NGTS-4b5, on which photoevaporation has removed a substantial part of their outer atmospheres. Here we report observations of the planet TOI-849b, which has a radius smaller than Neptune’s but an anomalously large mass of 39.1−2.6+2.7Earth masses and a density of 5.2−0.8+0.7grams per cubic centimetre, similar to Earth’s. Interior-structure models suggest that any gaseous envelope of pure hydrogen and helium consists of no more than 3.9−0.9+0.8per cent of the total planetary mass. The planet could have been a gas giant before undergoing extreme mass loss via thermal self-disruption or giant planet collisions, or it could have avoided substantial gas accretion, perhaps through gap opening or late formation6. Although photoevaporation rates cannot account for the mass loss required to reduce a Jupiter-like gas giant, they can remove a small (a few Earth masses) hydrogen and helium envelope on timescales of several billion years, implying that any remaining atmosphere on TOI-849b is likely to be enriched by water or other volatiles from the planetary interior. We conclude that TOI-849b is the remnant core of a giant planet.

Despite considerable efforts over the past decade, only 34 fast radio bursts—intense bursts of radio emission from beyond our Galaxy—have been reported1,2. Attempts to understand the population as a whole have been hindered by the highly heterogeneous nature of the searches, which have been conducted with telescopes of different sensitivities, at a range of radio frequencies, and in environments corrupted by different levels of radio-frequency interference from human activity. Searches have been further complicated by uncertain burst positions and brightnesses—a consequence of the transient nature of the sources and the poor angular resolution of the detecting instruments. The discovery of repeating bursts from one source3, and its subsequent localization4to a dwarf galaxy at a distance of 3.7 billion light years, confirmed that the population of fast radio bursts is located at cosmological distances. However, the nature of the emission remains elusive. Here we report a well controlled, wide-field radio survey for these bursts. We found 20, none of which repeated during follow-up observations between 185–1,097 hours after the initial detections. The sample includes both the nearest and the most energetic bursts detected so far. The survey demonstrates that there is a relationship between burst dispersion and brightness and that the high-fluence bursts are the nearby analogues of the more distant events found in higher-sensitivity, narrower-field surveys5.

Glucagon-like peptide 1 (GLP-1) regulates glucose homeostasis through the control of insulin release from the pancreas. GLP-1 peptide agonists are efficacious drugs for the treatment of diabetes. To gain insight into the molecular mechanism of action of GLP-1 peptides, here we report the crystal structure of the full-length GLP-1 receptor bound to a truncated peptide agonist. The peptide agonist retains an α-helical conformation as it sits deep within the receptor-binding pocket. The arrangement of the transmembrane helices reveals hallmarks of an active conformation similar to that observed in class A receptors. Guided by this structural information, we design peptide agonists with potent in vivo activity in a mouse model of diabetes.

The X-ray crystal structure of the transmembrane portion of the human glucagon receptor, a class B G-protein-coupled receptor (GPCR), is solved in the presence of the antagonist MK-0893, with potential implications for the development of therapeutics that target other class B GPCRs.

Several species related to Drosophila melanogaster have two loci containing sequences which code for the major heat-shock protein of molecular weight 70,000 (hsp70). These sequences are arranged as two pairs of inverted repeats. The structure of the 87C locus in D. melanogaster seems to have arisen through DNA insertion. Hsp70-coding sequences at the two loci are not evolving independently. Gene conversion between hsp70 genes has apparently occurred both within and between loci.

A Correction to this paper has been published: https://doi.org/10.1038/s41586-020-03107-5

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

One of the most important inhibitory modulators of synaptic transmission in mammalian brain is adenosine. At some cholinergic terminals, adenosine is known to inhibit further release of acetyl-choline. It is unclear whether adenosine is released directly at the synapse or whether ATP is co-released with transmitter and hydro-lysed to adenosine in the synaptic cleft1–4. Methods used in the past for isolating nerve terminals have not yielded homogeneous preparations, making it impossible to determine whether sufficient ATP or adenosine is released at specific synapses for inhibition of transmitter release to occur. Immunoaffinity purification techniques5–8have recently permitted the preparation of homogeneous populations of cholinergic nerve terminals9, which release ATP upon stimulation10. We now report that in immunoisolated cholinergic nerve terminals from the striatum synaptic ectophos-phohydrolases convert this ATP to adenosine, which inhibits further acetylcholine release, but this inhibitory effect is not seen in cortical cholinergic terminals lacking the complete ectophospho-hydrolase pathway. Therefore the differing adenosine-mediated modulation in different brain areas is controlled by the presence and activity of synaptic ectophosphohydrolases.

EXPERIMENTAL allergic neuritis (EAN), an autoimmune demye-linating disease of peripheral nerve, and a model of human inflammatory polyneuritis (Guillain–Barré syndrome), can be produced by immunisation with peripheral nerve tissue in complete Freund's adjuvant (CFA)1,2. EAN, like its central nervous system counterpart, experimental allergic encephalomyelitis (EAE), has been considered as the result of cell-mediated immunity2,3, which can be transferred with lymphoid cells4,5. Sera from animals with EAN or EAE induced by whole nervous tissue antigen are capable of demyelinating myelinated organotypic cultures of peripheral or central nervous system origin, respectively6,7. The demyelinating factor in EAE sera is immunoglobulin8,9. However, little evidence has been presented to suggest that the demyelinating antibodies which can be demonstrated in vitro are involved in the pathogenesis of these diseases in vivo4,10–12. EAN and EAE have not been transferred passively with serum from affected to recipient animals by systemic4,11or intravitreous injection12. We report here the first successful transfer of demyelination with EAN serum. Antiserum was injected directly into nerve parenchyma of recipient animals to circumvent the blood–nerve barrier. The demyelination was associated with macrophages but not with lymphocytic infiltration. The ability of sera to transfer demyelination correlated with their capacity to demyelinate cultured dorsal root ganglia. Organ specificity and complement dependency strongly suggested that the reaction was antibody-dependent and complement-mediated.

GENIC heterozygosity at enzyme loci has been examined for correlation with parameters as diverse as substrate specificity1, physiological function2and quaternary structure3. However, none of these has provided an adequate explanation for allozymic variation in general. One report4suggested a positive relationship for Drosophilaenzymes between heterozygosity and subunit molecular weight (MW), which can be equated to the size of the structural gene element. Various models, both neutral and selective, would predict a correlation between gene size and variability5–7. Recently, a similar correlation has been found within three classes of vertebrates8,31, and between the number of rare alleles and subunit size in human populations9,10. We report here that we have tested the relationship between heterozygosity and subunit size in Drosophilaspecies with a new selection of enzymes. Our results indicate that the correlation is indeed general. The relationship is quasi-linear and does not differ significantly from several models. The results support the hypothesis that there are constraints on the number of sites available to charge substitution within an enzyme molecule.

IT has been known, for many years that, following a large haemorrhage, dog plasma develops the ability to stimulate smooth muscle in vitro1,2and to increase the blood pressure when injected into anephric dogs3–6. These experiments suggested that the concentration of renin and angiotensin in the blood might be increased in such circumstances, and this has been confirmed in more recent studies, which have shown, that both the concentration of angiotensin in. the blood7–9and the concentration of plasma renin10are increased after heavy bleeding in the dog.

This corrects the article DOI: 10.1038/nature22800

ATTEMPTS to demonstrate the action of natural selection at enzyme loci have relied mainly on in vitro biochemical techniques to detect differences between allelic forms of the enzymes1–3. It is usually assumed that differences detected in this way will be relevant in vivo. The data on human inborn errors of metabolism do not support this view, however; in the majority of cases these are recessive. Heterozygotes, which usually have about 50% normal enzyme activity, rarely show clinical symptoms4. As any difference in activity between allozymes is likely to be much smaller, it cannot be assumed that such differences will necessarily be physiologically important. The properties of an enzyme molecule can only be biologically significant to the extent to which they affect the concentrations and flow of intermediates in its metabolic pathways. It was recently shown that changes in the concentration of most enzymes in a pathway at steady state will have little effect on flux5,6. Therefore, to demonstrate that differences in fitness between strains possessing different genotypes at an enzyme locus are caused by that gene substitution, it is necessary not only to show that differences in kinetic parameters can be detected in vitro, but also that changes in the activity of the enzyme will affect flux through that pathway. I previously described7significant changes in genotype frequency at a phosphoglucomutase locus in a wild population of field mice (Apodemus sylvaticus) which occurred at a time of food shortage and declining population numbers. I report here the results of some in vivo experiments on glycogen metabolism in animals of different genotypes at this locus, inducing glycogenolysis by fasting. The results parallel survival data from the wild population and suggest that the genotype of an individual at this locus is of physiological significance and may therefore be subject to natural selection.

OUR investigations of synthetic polypeptides, which have been proceeding concurrently with, although independently of, those described by Astbury and Dalgliesh1, were also inspired by the announcement of the discovery of a benzene-soluble co-polymer prepared from anhydro-N-carboxy-DL-β-phenylalanine and L-leucine by Woodward and Schramm2using the Leuchs polymerization3.

IN 1888–92, Grassi and Rovelli1fed onchospheres of Davainea proglottina to the slugs Limax cinereus, Agriolimax agrestis and Limax flavus and were able in less than twenty days to obtain cysticercoids which when fed to hens developed into D. proglottina. In spite of these experiments, the authors did not exclude the possibility of direct infection, since they considered that these intermediate hosts were not present in sufficient numbers to account for the very heavy infection of the poultry in Rovellasca where they worked. Railliet and Lucet2attempted to establish direct infection and failed, but they considered that other slugs, in addition to those used by Grassi and Rovelli, could serve as intermediate hosts.

CONSIDERABLE effort has been devoted recently to the establishment of simple experimental criteria by which the stereochemistry of five-coordinate transition metal species can be recognized. They have been primarily concerned with examination of the electronic spectra and, when paramagnetic, the bulk (powder) susceptibilities. These techniques have long been used successfully to differentiate between octahedral and tetrahedral coordination in complexes. It must be emphasized, however, that this success is dependent on only these two alternative stereochemistries having been previously established. A substantial number of five-coordinate complexes of nickel(II) and cobalt(II) have been prepared and some of these have sufficiently distinctive electronic reflectance spectra to reveal their geometry. The point dipole and point charge calculations of Ciampolini1, of Ciampolini and Bettini (personal communication) and of Wood2have provided bases for their assignment and also for the low temperature polarized single crystal spectra (unpublished work of Kohl, Gerloch and Lewis) of the molecules, M (arsine oxide)4X2(M = Co, Ni; X = ClO4−, NO3−). By contrast the reflectance spectrum of β-Co(paphy)Cl2may be equally well assigned3on the basis of octahedral or tetrahedral stereochemistry although the X-ray data4established this as five-coordinate.

A FIELD investigation was carried out in April 1961 to determine the distribution of permafrost below a lake in the Mackenzie River delta1–3. This study was of special interest inasmuch as the delta lake is situated in an old river bed and the occurrence of permafrost is considerably affected by the large number of lakes and channels in the immediate vicinity. A similar but more detailed investigation was undertaken by the Division of Building Research of the National Research Council of Canada during April and May 1964 at a small lake about 5 miles north-east of Inuvik, Northwest Territories. This lake was selected because it was completely isolated from other bodies of water which might influence the ground thermal regime.

THIS communication presents the results of a radio-carbon age determination on organic material recently found in fluvioglacial deposits exposed in the workings of the Cardiganshire Sand and Gravel Co. at Banc-y-Warren (Cardiganshire), (SN 202482). This well developed kame-complex was described by Williams in 1927 (ref. 1).

WE have found that a non-steroidal oestrogen antagonist1 will inhibit spontaneous (4 µg/ml.) and electrically induced (20 µg/ml.) contractions of the oestrous rat uterus in vitro1,2. Similar results were obtained in vitro with electrically stimulated uteri (about 30 µg/ml.) removed from rabbits immediately after coitus. This report concerns the effect of CN-55,945-27*on uterine contractility when infused intravenously into unanaesthetized rabbits post partum.

DAVIES1has studied the thermal decomposition of a bituminous coal, and has laid particular emphasis on the heat flux to the coal particles. Individual spheres of coal were suspended from a recording balance in a stream of hot nitrogen. To begin with, the weight record showed a constant rate of loss and in the final part the rate of weight loss decreased with time. The initial constant rate of weight loss was found to be directly proportional to the heat flux and was zero at about 400° C.

THE thawing effect of water in contact with permafrost is of considerable importance to engineers engaged on construction work that may involve flooding areas of perennially frozen ground. There is little information at present available, however, to indicate the magnitude of the effect which might be expected. An investigation of the present level of permafrost under natural bodies of water in the north, such as lakes and streams, is one means of improving our knowledge of this effect and of providing some guidance to engineers. During April 1961 a drilling programme was carried out by the Division of Building Research of the Canadian National Research Council to determine the distribution of permafrost under a lake in the Mackenzie River Delta (68° 18′ N., 133° 50′ W.) at the new town-site of Inuvik, Northwest Territories, near the arctic coast.

THE long-standing problem of how methyl groups migrate from nuclear to extra-nuclear nitrogen atoms in heterocyclic compounds has now been decided experimentally in the pyrimidine series.

IT was shown by Gutowsky, Ray, Rutledge and Unterberger1that crude oils exhibit electron resonance and by Poindexter2that the Overhauser effect is found in crude oils. The existence of the Overhauser effect depends on at least a part of the relaxation of the protons being due to the free electrons. Because the electron resonance and Overhauser effect results vary from sample to sample, it seemed of interest to make proton relaxation measurements on a number of samples of crude oil. The proton relaxation in crude oils is also of interest because of the introduction of proton precession instruments for underground measurements in oil wells3.

POLYMERIZATION products from p-xylene have been shown to contain, inter alia, a hitherto undescribed hydrocarbon, the novel structure of which has been determined solely by X-ray diffraction to be tricyclo [8: 2: 2: 24:7] hexadeca-4: 6: 10: 12 (1): 13: 15-hexaene. We propose as a suitable trivial name ‘di-p-xylylene’.

THE crystal structure of acetanilide has been determined1by classical X-ray diffraction methods, making use of information derived from polarized infra-red radiation technique as a time-saver in the trial-and-error process. The crystals from water or ethanol vary in form from plates {100} to truncated bipyramids {111}, but growth from the molten state results in acicular crystals, elongated along [b] and tabular on (100). The orthorhombic unit cell contains eight molecules and has dimensions: [a] = 19.50, [b] = 9.46 and [c] = 7.96 A.; space group Pbca — D2h15.

MILLIPEDES lay their eggs in hollow capsules of their own construction, within which the emerged young spend the early part of their existence. The capsules are moulded primarily of soil and vegetable debris, and are built with the apparent addition of maternal enteric constituents, both oral and aboral in origin1,2, which suggests that they might be impregnated chemically for defence against microorganisms. Here we present evidence indicating that for at least two species of millipede this hypothesis does not apply, because neither antibacterial nor antifungal substances could be detected in the walls of their capsules.