An experiment to detect gut monopoles

Recent advances in the development of Grand Unification Theories have led to several interesting predictions. One of these states that Grand Unification Monopoles (GUMs) exist as solutions in may nonabelian gauge theories. Another consequence of Unification is the possibility of baryon decay. The efficiency of the water tank detector in registering a Rubakov type decay will vary with both the interaction length and the GUM's velocity, expressed in terms of beta ( 0.01). The efficiency decreases at large values of because of the limited resolving time of the detector (approx. 50 ns). At lower values of Beta the time between interactions is such that the criterion of 4 events in 2 mu s can no longer be satisfied. The Rubakov experiment has now been in operation for almost 2 years with an estimated live time of 80%. During this time no candidate events have been observed leading to an estimated upper limit on the flux of 7.82 x 0.00001 m(-2) d(-1) Sr(-1). The ionization loss detection system has only recently come on line and as yet no results are available from this experiment

Thickness dependence of spin-orbit torques generated by WTe2

We study current-induced torques in WTe2/permalloy bilayers as a function of WTe2 thickness. We measure the torques using both second-harmonic Hall and spin-torque ferromagnetic resonance measurements for samples with WTe2 thicknesses that span from 16 nm down to a single monolayer. We confirm the existence of an out-of-plane antidamping torque, and show directly that the sign of this torque component is reversed across a monolayer step in the WTe2. The magnitude of the out-of-plane antidamping torque depends only weakly on WTe2 thickness, such that even a single-monolayer WTe2 device provides a strong torque that is comparable to much thicker samples. In contrast, the out-of-plane field-like torque has a significant dependence on the WTe2 thickness. We demonstrate that this field-like component originates predominantly from the Oersted field, thereby correcting a previous inference drawn by our group based on a more limited set of samples.Comment: 8 pages, 8 figure

In reply to: Questioning the ethics of ethicists

Hamor questions ‘the ethics of the ethicists’ without addressing the substantive points made in our paper.1 While our empirical findings were that physicians and members of the public consider that some gifts are appropriate, we go further and explore the implications of those findings.2 Just as a public survey finding support for capital punishment would not be sufficient to convince us that it was right, we argue that pharmaceutical industry largesse should not be accepted simply because it enjoys popular or professional support. Data are important, but are not the only consideration. Values, including the independence of clinical decision making and the primacy of patient welfare, should also be considered. These are accepted ethical commitments within the profession. For these reasons, we question pharmaceutical marketing and the use of ‘gifts’ to influence doctors' prescribing. There is concern in the literature about the potential for this strategy to bias doctors' judgments. The giving of ‘gifts’ to doctors has the intended outcome that doctors prescribe from loyalty to the ‘gift’ giver rather than prescribing on the basis of evidence of drug efficacy and safety. Even a small gift like ‘post-it’ notes can have this effect. Hamor, however, appears to argue that acceptance of gifts from industry is not morally problematic without addressing the primary concern that this may undermine the independence of clinical decision making and potentially put patients at risk

Spin-orbit torques in NbSe2_2/Permalloy bilayers

We present measurements of current-induced spin-orbit torques generated by NbSe$_2$, a fully-metallic transition-metal dichalcogenide material, made using the spin-torque ferromagnetic resonance (ST-FMR) technique with NbSe$_{2}$/Permalloy bilayers. In addition to the out-of-plane Oersted torque expected from current flow in the metallic NbSe$_{2}$ layer, we also observe an in-plane antidamping torque with torque conductivity $\sigma_{S} \approx 10^{3} (\hbar / 2e)$($\Omega$m)$^{-1}$ and indications of a weak field-like contribution to the out-of-plane torque oriented opposite to the Oersted torque. Furthermore, in some samples we also measure an in-plane field-like torque with the form $\hat{m} \times \hat{z}$, where $\hat{m}$ is the Permalloy magnetization direction and $\hat{z}$ is perpendicular to the sample plane. The size of this component varies strongly between samples and is not correlated with the NbSe$_{2}$ thickness. A torque of this form is not allowed by the bulk symmetries of NbSe$_{2}$, but is consistent with symmetry breaking by a uniaxial strain that might result during device fabrication.Comment: 14 pages, 3 figure

Do temperature changes cause eczema flares? An English cohort study.

BACKGROUND: It is unclear if ambient temperature changes affect eczema. It is also unclear if people with worse disease are more susceptible to weather-related flares, or specific types of emollient offer protection. Substantiating these links may help inform action plans and patients self-management. OBJECTIVE: To investigate the effect of short-term temperature variations on eczema symptoms in children. METHODS: Data from a UK cohort of 519 children (6 months-12 years) with at least mild eczema, participating in a randomised trial comparing four types of emollients on eczema symptoms, were combined with observed temperature data from the Hadley Centre's Integrated Surface Database.Hot & cold weeks were defined by average regional temperature >75th or <25th percentile, January 2018-February 2020. Eczema flares were defined as ≥3 point change in patient-oriented eczema measure (POEM). Random effects logistic regression models were used to estimate the odds ratios of flares in hot & cold weeks (reference group: temperate weeks). The likelihood ratio test assessed for evidence of effect modification by disease severity and emollient type. RESULTS: The baseline mean age was 4.9 years (SD 3.2) and POEM score was 9.2 (SD 5.5), indicating moderate eczema. 90% of participants lived within 20 km of their nearest weather station. From the 519 participants there were 6,796 consecutively paired POEMs and 1,082 flares.Seasonal variation in POEM scores was observed, suggesting symptoms worsening with colder weather in winter and improving with warmer weather in summer. Odds ratios of flares were: 1.15 (p = 0.136, 95%CI 0.96-1.39) in cold weeks, 0.85 (p = 0.045, 95%CI 0.72-1.00) in hot weeks. Likelihood ratio test showed no evidence of this differing by disease severity (p = 0.53) or emollient type used (p = 0.55). CONCLUSIONS: Our findings are consistent with previous studies demonstrating either improvements in eczema symptoms or reduced flares in hot weather. Worse disease and different emollient types did not increase susceptibility or provide protection against temperature changes. Further work should investigate the role of sunlight, humidity, air pollution and other environmental factors

Observation of the nonlinear Hall effect under time reversal symmetric conditions

The electrical Hall effect is the production of a transverse voltage under an out-of-plane magnetic field. Historically, studies of the Hall effect have led to major breakthroughs including the discoveries of Berry curvature and the topological Chern invariants. In magnets, the internal magnetization allows Hall conductivity in the absence of external magnetic field. This anomalous Hall effect (AHE) has become an important tool to study quantum magnets. In nonmagnetic materials without external magnetic fields, the electrical Hall effect is rarely explored because of the constraint by time-reversal symmetry. However, strictly speaking, only the Hall effect in the linear response regime, i.e., the Hall voltage linearly proportional to the external electric field, identically vanishes due to time-reversal symmetry. The Hall effect in the nonlinear response regime, on the other hand, may not be subject to such symmetry constraints. Here, we report the observation of the nonlinear Hall effect (NLHE) in the electrical transport of the nonmagnetic 2D quantum material, bilayer WTe2. Specifically, flowing an electrical current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of magnetic field. The NLHE exhibits unusual properties sharply distinct from the AHE in metals: The NLHE shows a quadratic I-V characteristic; It strongly dominates the nonlinear longitudinal response, leading to a Hall angle of about 90 degree. We further show that the NLHE directly measures the "dipole moment" of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new Hall effect and provide a powerful methodology to detect Berry curvature in a wide range of nonmagnetic quantum materials in an energy-resolved way

Switching magnetization with a Weyl semimetal

Energy-efficient magnetization manipulation is a prerequisite for competitive spintronic devices. The Weyl semimetal WTe2 can act as a spin current source that enables magnetization switching of an adjacent ferromagnet at low power consumption and additionally induces chiral magnetism.</p

DNA replication: archaeal oriGINS

GINS is an essential eukaryotic DNA replication factor that is found in a simplified form in Archaea. A new study in this issue of BMC Biology reveals the first structure of the archaeal GINS complex. The structure reveals the anticipated similarity to the previously determined eukaryotic complex but also has some intriguing differences in the relative disposition of subunit domains