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Planets with radii between that of the Earth and Neptune (hereafter referred to as ‘sub-Neptunes’) are found in close-in orbits around more than half of all Sun-like stars1,2. However, their composition, formation and evolution remain poorly understood3. The study of multiplanetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94R⊕to 2.85R⊕. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres.

Abstract: Castilleja exigua is described from an ample collection obtained in the Paramó de Guirigay, Monumento Natural Teta de Niquitao, Trujillo, Venezuela. The new species is a member of subg. and sect. Castilleja. This apparently very rare species is known at present from a single, geographically restricted population and should be considered globally endangered.

Castilleja hidalgensisis described from several collections from xeric limestone sites in central Hidalgo, Mexico. The new species belongs to a small complex of poorly known and uncommon species within sect.Euchroma, sharing important characteristics withC. macrostigma, the first-described taxon in this assemblage. The new species appears to be rare and highly restricted both geographically and ecologically. A key to the species of theC. macrostigmagroup is provided.

Castilleja holmgreniiis described from several collections made in the Sierra Madre Occidental in southeast Sinaloa and adjacent southwest Durango, Mexico. The new species is a member of subgenus and sectionCastilleja. This apparently rare species is presently known from two small, geographically restricted populations. Also provided are a list of theCastillejaspecies of this region with notes on their status and distribution, a key for their identification, and nomenclatural and taxonomic notes concerning some of the species.

The aim of the μCap experiment is a 1% measurement of the singlet capture rate ΛSfor the basic electro-weak reaction μ + p→ n+ νμ. This observable is sensitive to the weak form-factors of the nucleon, in particular to the induced pseudoscalar coupling constant gP. It will provide a rigorous test of theoretical predictions based on the Standard Model and effective theories of QCD. The present method is based on high precision lifetime measurements of μ−in hydrogen gas and the comparison with the free μ+lifetime. The μ−experiment will be performed in ultra-clean, deuterium-depleted H2gas at 10 bar. Low density compared to liquid H2is chosen to avoid uncertainties due to ppμ formation. A time projection chamber acts as a pure hydrogen active target. It defines the muon stop position in 3D and detects rare background reactions. Decay electrons are tracked in cylindrical wire-chambers and a scintillator array covering 75% of 4π.

The measurement of the strong-interaction effects in pionic hydrogen gives access to fundamental properties of the pion–nucleon interaction. Methods developed within the framework of Heavy-Baryon Chiral Perturbation Theory allow calculations with an accuracy of a few per cent, which should be tested by experiment. Techniques advanced for recent experiments on the precision spectroscopy of X-rays from antiprotonic and pionic atoms will be used in a new series of measurements for pionic hydrogen. The aim is to achieve finally an accuracy of 0.2% for the hadronic shift ∈1sand most important of about 1% for the broadening Γ1s. An essential part of the experimental program is an improved understanding of the atomic cascade. At first, the value of ∈1shas to be proven not to be influenced by molecular formation. Secondly, a more accurate determination of Γ1srequires a detailed study of Coulomb deexcitation.

A new experiment is under preparation with the aim to improve considerably the present knowledge of the rate Λs, which should be measured on a level of 1% or better, for the basic electroweak capture reaction of a negative muon on the free proton μp1s→ n+ νμ. The capture rate will be determined by measuring the lifetime of μ−stopped in ultra pure hydrogen at 10 bar pressure and comparing it with the lifetime of the unbound μ+. A new experimental method was developed for this project which should allow measuring the μ−lifetime with at least 10 ppm precision. The basic element of the detector is operating in the hydrogen gas time projection chamber (TPC) surrounded by multi-wire proportional chambers (MWPCs) and scintillator counters. The arrival times and trajectories of the incoming muons and the outgoing decay electrons are measured with this device providing effective suppression of background. Using the TPC as an active target, we can monitor on-line the protium contamination by impurities with a sensitivity better than 10−8. This can be done by detecting the charged products of the muon capture reaction on these impurities. It was demonstrated that the TPC and MWPCs can operate in pure hydrogen under 10 bar pressure providing gas gain up to 10 000.

Abstract.: This is the final publication of the ETH Zurich–Neuch�tel–PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3p–1s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3p–1s transition experiments we obtain the strong-interaction energy level shift eV and the total decay width eV of the state. Taking into account the electromagnetic corrections we find the hadronic s-wave scattering amplitude for elastic scattering and for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector scattering lengths (within the framework of isospin symmetry) are found to be and , respectively. Using the GMO sum rule, we obtain from a new value of the coupling constant () from which follows the Goldberger–Treiman discrepancy . The new values of and imply an increase of the nucleon sigma term by at least 9 MeV.

A new experiment for a high-precision measurement of the pion mass at a 1 ppm level is presented. It combines an improved cyclotron trap that produces pionic and muonic atoms in a small volume with a doubly focusing crystal spectrometer to measure the corresponding exotic X-ray transitions with high accuracy and a novel type of CCD detector. The muonic X-rays lines serve as highly accurate calibration lines. The measurement has been accomplished recently. A detailed analysis of the data is on the way.

Carbonates that rim the South Wales Coalfield contain a pervasive late Paleozoic CRM residing in magnetite. The CRM in the eastern part of the basin was acquired after deformation, and geochemical results are consistent with a connection between remagnetization and orogenic-type fluids. In the western part of the basin, the CRM is synfolding but the geochemical results do not support a connection with orogenic fluids.

Abstract:  An ocean-atmosphere box model is presented where the polar ocean box is of variable extent and may be covered with ice. Ice thickness and temperature are predicted on the basis of a simple thermodynamic sea-ice model. The stimulation of internal variability by sea-ice is explored. Experiments are conducted with the full model but also with model versions where atmospheric and oceanic transport processes are partly suppressed. Moreover, reduced versions of the sea-ice model are tested. Some of the resulting climate states exhibit little internal variability and a steady growth of ice thickness. However, a wide range of internal fluctuations is generated in other runs. These include quasiperiodic oscillations where ice-free phases alternate with ice-covered states and chaotic behaviour. It is a key result that the choice of the sea-ice model has a profound impact on the fluctuations.

Muon capture on hydrogen gives a unique possibility for a measurement of the pseudo-scalar form factor gp(qc2= -0.88 mμ2) of the nucleonic weak current, thus providing a sensitive test of the QCD chiral symmetry perturbation theory which predicts the value of this form factor with a precision of Δgp/gp≃ 2%. For adequate comparison with theory, the muon capture rate Λcshould be measured with a precision of ΔΛc/Λc≤ 1%, that is an order of magnitude better than the precision of the present world data. We report on the project of an experiment designed to provide the required precision. Also, we present the final result of our previous experiment on a high precision measurement of the μ3He capture rate and compare this result with the PCAC prediction.

In the PS207 experiment at CERN, X-rays from antiprotonic hydrogen and deuterium have been measured at low pressure. The strong interaction shift and the broadening of the Kαtransition in antiprotonic hydrogen were determined. Evidence was found for the individual hyperfine components of the protonium ground state.

We have performed an experiment to investigate various processes induced by muons in hydrogen-deuterium mixtures. Preliminary results are given for cascade X-ray yields, q1s, relative yields of conversion muons and fusion γ-rays, molecular formation and hyperfine transition rates.

The DEAR (DAΦNE Exotic Atom Research) experiment at the new φ-factory DAΦNE of Laboratori Nazionali di Frascati aims for a 1% measurement of the line shift of the K-complex due to strong interaction in kaonic hydrogen. This presentation is meant to prove that the high statistics and good resolution obtainable with DEAR will be able to disentangle the kaonic hydrogen K-complex lines (a cascade unconstrained fit), obtaining in this way constraints for what concerns the cascade parameters and, consequently, information regarding the physical processes involved in the kaonic hydrogen atomic cascade.

Unlike the majority of Michel parameters which are consistent with the Standard Model V-Ainteraction, the experimental value of ξ″(=0.65±0.36) [1] is poorly known. Our experiment will measure the longitudinal polarization, PL, of positrons emitted from the decay of polarized muons. The value of PL, equal to unity in the Standard Model, will decrease for high energy positrons emitted antiparallel to the muon spin if the combination of Michel parameters ξ″/ξξ′ − 1 deviates from the Standard Model value of zero.

We present CCDs (CCD = charge-coupled device) as high performance X-ray detectors. These silicon pixel detectors (whose concept was invented in 1970) are mainly used today for detection of visible light with digital cameras. Generally, X-rays are detected by inserting a phosphorescent screen and collecting the light obtained onto the CCD. However X-rays can also be detected directly with excellent background rejection capabilities, good energy resolution and intrinsic pixel-size position resolution but with mediocre efficiency in a relatively small energy range and little or no timing information. For this application a slow, low noise electronics is needed. We will discuss how these detectors work, their advantages and disadvantages as well as future possibilities and limitations.

The scientific program and the experimental setup of the DEAR (DAΦNE Exotic Atom Research) experiment at the new φ-factory DAΦNE of Laboratori Nazionali di Frascati are described. The objective of DEAR is to perform a 1% measurement of the Kαline shift due to the strong interaction in kaonic hydrogen. A measurement will also be performed on kaonic deuterium for the first time. The aim is to investigate low-energy $$\overline K N$$ physics and to understand SU(3) chiral symmetry breaking. The setup takes advantage of the unique features of the “kaon beam” from the φ decay in DAΦNE; of a low-temperature pressurized gaseous target; and of a detector for soft X-rays – the Charge-Coupled Device (CCD) – characterized by a very good energy (and spatial) resolution and by an unprecedented background rejection capability. The DEAR experiment represents a major effort in the study of low energy $$\overline K N$$ interactions and has the potential to produce a breakthrough in the field.

The energy and time distributions of the decay X-rays of excited, metastable, molecular (dµHe)*-resonances were measured. The comparison of the observed energy spectra with calculated ones suggests that decay from the rotational state J= 1 dominates at the investigated conditions. The muon transfer rates from ground state deuterium to the helium isotopes 3He and 4He at low temperatures were determined from the time distributions of these spectra. Additionally, the temperature dependence of the muon transfer rate was clearly established in deuterium / 4He mixtures.

The transfer reaction of negative muons from muonic protium to 3and 4in binary and triple gas mixtures was studied. In the binary mixtures the transfer rates to the two helium isotopes were determined from the time distribution of the 7-keV X-rays of the intermediate muonic molecule (pµHe)*. The experimental transfer rate to 4is in good agreement with theoretical predictions, whereas the rate to 3is a factor 2 to 3 smaller than the predicted ones. Radiative branching ratios of the (pµHe)8 molecular decay were obtained. Muon transfer from excited states of muonic protium gives the main contribution to the total intensity of the µHe Lyman series in the binary mixtures. Values of q1sHeare determined.

Abstract:  Principal oscillation pattern (POP) analysis fits a first order multivariate autoregressive model to a reduced subset of the variables of a complex system. It has been shown in the past that important modes of complex systems can be detected through the POP technique. In this note two problems with this method will be addressed. Firstly, the POP analysis may face difficulties if the reduced system is of higher order in time than first. An example from linear equatorial wave dynamics is given to illustrate this point. Autoregressive models of higher order (MOP-models) are shown to provide a partial solution in such situations but are not fully satisfactory either. Nonlinearity may cause problems as well. A nonlinear low-order model is used to discuss this point. Both the POP and the MOP scheme are applied without data reduction. The MOP approach is superior to the POP technique in that it detects oscillating patterns which elude the POP analysis. The results suggest that the MOP analysis may be a valuable extension of the POP approach.

93% of 88 children with severe frequent migraine recovered on oligoantigenic diets; the causative foods were identified by sequential reintroduction, and the role of the foods provoking migraine was established by a double-blind controlled trial in 40 of the children. Most patients responded to several foods. Many foods were involved, suggesting an allergic rather than an idiosyncratic (metabolic) pathogenesis. Associated symptoms which improved in addition to headache included abdominal pain, behaviour disorder, fits, asthma, and eczema. In most of the patients in whom migraine was provoked by non-specific factors, such as blows to the head, exercise, and flashing lights, this provocation no longer occurred while they were on the diet.

An attempt is made to understand the channelling effect observed in the Rhine valley by the use of simple models. We consider two-dimensional flow of a homogeneous rotating viscous fluid over a valley. Two different approaches are described: (i) a linear theory of a horizontally averaged flow over a valley of finite depth; (ii) a numerical model. The linear theory gives wind profiles in the valley which compare favorably with the results of the nonlinear numerical model. There is qualitative agreement with observations. An analysis of the linear solution reveals that the channelling effect is a feature of Ekman flow where advection is important above the valley, but not in the valley.

Abstract: Muon transfer from hydrogen isotopes to helium is of importance in muon-catalyzed fusion and serves as a unique tool for the direct observation of the mesomolecular ion (pµHe)*. During two data-taking runs in 1994 and 1995 at PSI, measurements of the transfer from protium to helium were carried out using CCD's and Ge-diodes as independent X-ray detectors to obtain information on the time distribution and intensity of the 7 keV decay X-ray of the mesomolecular ion. Dual1H2 +4 He and triple1H2 + Ne +3,4He gas mixtures at low temperatures were investigated to extract transfer rates. Protium of high purity was available. For the first time a transfer rate from muonic protium to3He was measured. A general survey of our measurements and preliminary analysis is presented.

Abstract: The first direct measurement ofq ls and its dependence on target density and deuterium concentration was performed in H/D (protium/deuterium) mixtures. Charge coupled devices (CCDs) were employed to detect the muonic hydrogen X rays. The presented preliminary results were obtained by determining the relative Kagr-yields of both isotopes.

Abstract: In this article we report the results of an experiment performed in 1993 at PSI. The goal was to determine the absolute rate of nuclear muon capture by3He. In the experiment we used a new technique recently developed at Gatchina. As a preliminary result from this experiment we obtainedlambdac=(1496±3(stat)-3(syst)) s–1.

Abstract: Muon transfer from the ground state of muonic deuterium to a helium atom proceeds mainly via the formation of a muonic molecule in an excited state. A large number of decay X rays (sim 6.8 keV) from these (dµHe)* molecules were observed for the4He as well as for the3He case. The time distributions of these X rays allow the determination of the ground state transfer rate. The simultaneous employment of Ge/Si-detectors and CCDs for the same target conditions allows the determination of the branching ratio of radiative to nonradiative decay for the first time.

Abstract: The triton energy spectrum of the muon capture reaction µ3Herarrt+ngrµ where µ3He is the ground state of muonic3He, has been measured by means of a high-pressure ionization chamber in order to investigate a possible heavyv admixture into the µ flavor with high sensitivity. The upper limit of the µ-heavy vi mixing matrix element squared was obtained to be midUµimid2les10–3 for heavy neutrino masses in the range of 25les E0Vles75 MeV.

Complementary to the investigations of the most efficient dt cycle, also the other muon-induced fusion cycles in mixtures of hydrogen isotopes have been studied. The results of these dedicated experiments provide rich information about muon-induced few-body reactions and contribute significantly to a better overall understanding of µCF. A summary of the recent progress will be presented. Special emphasis will be put on two characteristic examples, namely a new experimental approach to study the muonic cascade in H-D mixtures and the systematic study of hyperfine effects in muon-induced reactions.