Consistent Gravitationally-Coupled Spin-2 Field Theory

Inspired by the translational gauge structure of teleparallel gravity, the theory for a fundamental massless spin-2 field is constructed. Accordingly, instead of being represented by a symmetric second-rank tensor, the fundamental spin-2 field is assumed to be represented by a spacetime (world) vector field assuming values in the Lie algebra of the translation group. The flat-space theory naturally emerges in the Fierz formalism and is found to be equivalent to the usual metric-based theory. However, the gravitationally coupled theory, with gravitation itself described by teleparallel gravity, is shown not to present the consistency problems of the spin-2 theory constructed on the basis of general relativity.Comment: 16 pages, no figures. V2: Presentation changes, including addition of a new sub-section, aiming at clarifying the text; version accepted for publication in Class. Quantum Grav

Absence of Magnetism in Hcp Iron-Nickel at 11 K

Synchrotron Mössbauer spectroscopy (SMS) was performed on an hcp-phase alloy of composition Fe92Ni8 at a pressure of 21 GPa and a temperature of 11 K. Density functional theoretical calculations predict antiferromagnetism in both hcp Fe and hcp Fe-Ni. For hcp Fe, these calculations predict no hyperfine magnetic field, consistent with previous experiments. For hcp Fe-Ni, however, substantial hyperfine magnetic fields are predicted, but these were not observed in the SMS spectra. Two possible explanations are suggested. First, small but significant errors in the generalized gradient approximation density functional may lead to an erroneous prediction of magnetic order or of erroneous hyperfine magnetic fields in antiferromagnetic hcp Fe-Ni. Alternately, quantum fluctuations with periods much shorter than the lifetime of the nuclear excited state would prohibit the detection of moments by SMS

Menstrual phase influences cerebrovascular responsiveness in females but may not affect sex differences

Background and aims: Sex differences in the rate and occurrence of cerebrovascular diseases (e.g., stroke) indicate a role for female sex hormones (i.e., oestrogen and progesterone) in cerebrovascular function and regulation. However, it remains unclear how cerebrovascular function differs between the sexes, and between distinct phases of the menstrual cycle. This study aimed to compare cerebrovascular-CO(2) responsiveness in 1) females during the early follicular (EF), ovulatory (O) and mid-luteal (ML) phases of their menstrual cycle; and 2) males compared to females during phases of lower oestrogen (EF) and higher oestrogen (O). Methods: Eleven females (25 ± 5 years) complete experimental sessions in the EF (n = 11), O (n = 9) and ML (n = 11) phases of the menstrual cycle. Nine males (22 ± 3 years) completed two experimental sessions, approximately 2 weeks apart for comparison to females. Middle and posterior cerebral artery velocity (MCAv, PCAv) was measured at rest, during two stages of hypercapnia (2% and 5% CO(2) inhalation) and hypocapnia (voluntary hyperventilation to an end-tidal CO(2) of 30 and 24 mmHg). The linear slope of the cerebral blood velocity response to changes in end-tidal CO(2) was calculated to measure cerebrovascular-CO(2) responsiveness.. Results: In females, MCAv-CO(2) responsiveness to hypocapnia was lower during EF (−.78 ± .45 cm/s/mmHg) when compared to the O phase (−1.17 ± .52 cm/s/mmHg; p < .05) and the ML phase (−1.30 ± .82; p < .05). MCAv-CO(2) responsiveness to hypercapnia and hypo-to-hypercapnia, and PCAv-CO(2) responsiveness across the CO(2) range were similar between menstrual phases (p ≥ .20). MCAv-CO(2) responsiveness to hypo-to hypercapnia was greater in females compared to males (3.12 ± .91 cm/s/mmHg vs. 2.31 ± .46 cm/s/mmHg; p = .03), irrespective of menstrual phase (EF or O). Conclusion: Females during O and ML phases have an enhanced vasoconstrictive capacity of the MCA compared to the EF phase. Additionally, biological sex differences can influence cerebrovascular-CO(2) responsiveness, dependent on the insonated vessel

Infant feeding bottle design, growth and behaviour: results from a randomised trial

BACKGROUND: Whether the design of an anti-vacuum infant feeding bottle influences infant milk intake, growth or behavior is unknown, and was the subject of this randomized trial. METHODS: SUBJECTS: 63 (36 male) healthy, exclusively formula-fed term infants. INTERVENTION: Randomisation to use Bottle A (n = 31), one-way air valve: Philips Avent) versus Bottle B (n = 32), internal venting system: Dr Browns). 74 breast-fed reference infants were recruited, with randomisation (n = 24) to bottle A (n = 11) or B (n = 13) if bottle-feeding was subsequently introduced. Randomisation: stratified by gender and parity; computer-based telephone randomisation by independent clinical trials unit. SETTING: Infant home. PRIMARY OUTCOME MEASURE: infant weight gain to 4 weeks. SECONDARY OUTCOMES: (i) milk intake (ii) infant behaviour measured at 2 weeks (validated 3-day diary); (iii) risk of infection; (iv) continuation of breastfeeding following introduction of mixed feeding. RESULTS: Number analysed for primary outcome: Bottle A n = 29, Bottle B n = 25. PRIMARY OUTCOME: There was no significant difference in weight gain between randomised groups (0-4 weeks Bottle A 0.74 (SD 1.2) SDS versus bottle B 0.51 (0.39), mean difference 0.23 (95% CI -0.31 to 0.77). SECONDARY OUTCOMES: Infants using bottle A had significantly less reported fussing (mean 46 versus 74 minutes/day, p < 0.05) than those using bottle B. There was no significant difference in any other outcome measure. Breast-fed reference group: There were no significant differences in primary or secondary outcomes between breast-fed and formula fed infants. The likelyhood of breastfeeding at 3 months was not significantly different in infants subsequently randomised to bottle A or B. CONCLUSION: Bottle design may have short-term effects on infant behaviour which merit further investigation. No significant effects were seen on milk intake or growth; confidence in these findings is limited by the small sample size and this needs confirmation in a larger study. TRIAL REGISTRATION: Clinical Trials.gov NCT00325208

Observation of huge thermal spin currents in magnetic multilayers

Thermal spin pumping constitutes a novel mechanism for generation of spin currents; however their weak intensity constitutes a major roadblock for its usefulness. We report a phenomenon that produces a huge spin current in the central region of a multilayer system, resulting in a giant spin Seebeck effect in a structure formed by repetition of ferromagnet/metal bilayers. The result is a consequence of the interconversion of magnon and electron spin currents at the multiple interfaces. This work opens the possibility to design thin film heterostructures that may boost the application of thermal spin currents in spintronics

Thermoelectric performance of spin Seebeck effect in Fe3O4/Pt-based thin film heterostructures

All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license.-- et al.We report a systematic study on the thermoelectric performance of spin Seebeck devices based on Fe3O4/Pt junction systems. We explore two types of device geometries: a spin Hall thermopile and spin Seebeck multilayer structures. The spin Hall thermopile increases the sensitivity of the spin Seebeck effect, while the increase in the sample internal resistance has a detrimental effect on the output power. We found that the spin Seebeck multilayers can overcome this limitation since the multilayers exhibit the enhancement of the thermoelectric voltage and the reduction of the internal resistance simultaneously, therefore resulting in significant power enhancement. This result demonstrates that the multilayer structures are useful for improving the thermoelectric performance of the spin Seebeck effect.This work was supported by the Spanish Ministry of Science (through Project Nos. PRI-PIBJP-2011-0794 and MAT2011-27553-C02, including FEDER funding), the Aragón Regional Government (Project No. E26), Thermo-spintronic Marie-Curie CIG (Grant Agreement No. 304043), JST-PRESTO “Phase Interfaces for Highly Ecient Energy Utilization” from JST, Japan, Grant in-Aid for Scientific Research on Innovative Areas “Nano-Spin Conversion Science” (Grant No. 26103005), Grant-in-Aid for Challenging Exploratory Research (Grant No. 26600067), Grant-inAid for Scientific Research (A) (Grant No. 15H02012) from MEXT, Japan, NEC Corporation, and The Noguchi Institute.Peer Reviewe

Experiments with a Malkus-Lorenz water wheel: Chaos and Synchronization

We describe a simple experimental implementation of the Malkus-Lorenz water wheel. We demonstrate that both chaotic and periodic behavior is found as wheel parameters are changed in agreement with predictions from the Lorenz model. We furthermore show that when the measured angular velocity of our water wheel is used as an input signal to a computer model implementing the Lorenz equations, high quality chaos synchronization of the model and the water wheel is achieved. This indicates that the Lorenz equations provide a good description of the water wheel dynamics.Comment: 12 pages, 7 figures. The following article has been accepted by the American Journal of Physics. After it is published, it will be found at http://scitation.aip.org/ajp

Limits to Interstellar C_4 and C_5 Towards zeta Ophiuchi

We have made a sensitive search for the origin bands in the known electronic transitions of the linear carbon chains C_4 and C_5 at 3789 and 5109 A towards zeta Oph (A_V <= 1). The incentive was a recent detection of C_3 in this interstellar cloud with a column density of 1.6 x 10^12 cm^-2 plus the availability of laboratory gas phase spectra of C_4 and C_5. Further, some models of diffuse interstellar clouds predict that the abundance of these latter species should be within an order of magnitude of C_3. Despite achieving S/N of 2300 to 2600 per pixel at a resolution of ~110,000, the searches were negative, leading to 3 sigma upper limits to the column density of N(C_5) = 2 x 10^11 cm^-2 and N(C_4) = 4 x 10^12-13 cm^-2 where these values rely on theoretically calculated oscillator strengths. The implication of these limits are discussed on the choice of molecules for study in future attempts to identify the carriers of the stronger diffuse interstellar bands.Comment: 12 pages, 3 figure