Identifying trade-offs and co-benefits of climate policies in China to align policies with SDGs and achieve the 2 °C goal

The Paris Agreement set long-term global climate goals to pursue stabilization of the global mean temperature increase at below 2 °C (the so-called 2 °C goal). Individual countries submitted their own short-term targets, mostly for the year 2030. Meanwhile, the UN's sustainable development goals (SDGs) were designed to help set multiple societal goals with respect to socioeconomic development, the environment, and other issues. Climate policies can lead to intended or unintended consequences in various sectors, but these types of side effects rarely have been studied in China, where climate policies will play an important role in global greenhouse gas emissions and sustainable development is a major goal. This study identified the extent to which climate policies in line with the 2 °C goal could have multi-sectoral consequences in China. Carbon constraints in China in the 2Deg scenario are set to align with the global 2 °C target based on the emissions per capita convergence principle. Carbon policies for NDC pledges as well as policies in China regarding renewables, air pollution control, and land management were also simulated. The results show that energy security and air quality have co-benefits related to climate policies, whereas food security and land resources experienced negative side effects (trade-offs). Near-term climate actions were shown to help reduce these trade-offs in the mid-term. A policy package that included food and land subsidies also helped achieve climate targets while avoiding the adverse side effects caused by the mitigation policies. The findings should help policymakers in China develop win–win policies that do not negatively affect some sectors, which could potentially enhance their ability to take climate actions to realize the global 2 °C goal within the context of sustainable development

Interpreting The Unresolved Intensity Of Cosmologically Redshifted Line Radiation

Intensity mapping experiments survey the spectrum of diffuse line radiation rather than detect individual objects at high signal-to-noise ratio. Spectral maps of unresolved atomic and molecular line radiation contain three-dimensional information about the density and environments of emitting gas and efficiently probe cosmological volumes out to high redshift. Intensity mapping survey volumes also contain all other sources of radiation at the frequencies of interest. Continuum foregrounds are typically approximately 10(sup 2)-10(Sup 3) times brighter than the cosmological signal. The instrumental response to bright foregrounds will produce new spectral degrees of freedom that are not known in advance, nor necessarily spectrally smooth. The intrinsic spectra of fore-grounds may also not be well known in advance. We describe a general class of quadratic estimators to analyze data from single-dish intensity mapping experiments and determine contaminated spectral modes from the data themselves. The key attribute of foregrounds is not that they are spectrally smooth, but instead that they have fewer bright spectral degrees of freedom than the cosmological signal. Spurious correlations between the signal and foregrounds produce additional bias. Compensation for signal attenuation must estimate and correct this bias. A successful intensity mapping experiment will control instrumental systematics that spread variance into new modes, and it must observe a large enough volume that contaminant modes can be determined independently from the signal on scales of interest

Lack of clustering in low-redshift 21-cm intensity maps cross-correlated with 2dF galaxy densities

We report results from 21-cm intensity maps acquired from the Parkes radio telescope and cross-correlated with galaxy maps from the 2dF galaxy survey. The data span the redshift range $0.057<z<0.098$ and cover approximately 1,300 square degrees over two long fields. Cross correlation is detected at a significance of $5.18\sigma$. The amplitude of the cross-power spectrum is low relative to the expected dark matter power spectrum, assuming a neutral hydrogen (HI) bias and mass density equal to measurements from the ALFALFA survey. The decrement is pronounced and statistically significant at small scales. At $k\sim1.5$ $h \mathrm{Mpc^{-1}}$, the cross power spectrum is more than a factor of 6 lower than expected, with a significance of $14.8\,\sigma$. This decrement indicates either a lack of clustering of neutral hydrogen (HI), a small correlation coefficient between optical galaxies and HI, or some combination of the two. Separating 2dF into red and blue galaxies, we find that red galaxies are much more weakly correlated with HI on $k\sim1.5$ $h \mathrm{Mpc^{-1}}$ scales, suggesting that HI is more associated with blue star-forming galaxies and tends to avoid red galaxies.Comment: 12 pages, 3 figures; fixed typo in meta-data title and paper author

Anisotropic normal-state properties of the MgB2 superconductor

Based on the experimentally found existence of two gaps in MgB2 (one gap associated to the boron sigma-states and the other to the boron pi-states), the different contributions to the transport properties, electrical conductivity and Hall coefficient, were studied using the full potential-linearized augmented plane wave method and the generalized gradient approximation. MgB2 doping was analyzed in the rigid band approximation. This permitted the study of the partial substitution of magnesium for aluminium (Mg1-xAlxB2) as well as other substitutions such as AB2 (A=Be, Zr, Nb and Ta). The sigma-bands (boron sigma-states), which are associated to the large superconducting gap, are very anisotropic at EF, while the pi-bands have very little anisotropic character. In (Mg1-xAlxB2) Tc diminishes with Al content, the other compounds are not superconductors. In this work it was found that with electron doping, such as Al substitution, the sigma-band conductivity decreases and the corresponding bands become less anisotropic. sigma-band contribution for BeB2 and ScB2 at EF is very small and the anisotropy is much lower. For Zr, Nb and Ta there are no sigma-bands at EF. These results give a connection between superconductivity and the character of the sigma-band; band conductivity and band anisotropy. This gives a plausible explanation for the diminution of Tc with different doping of MgB2

Faraday rotation measures of northern-hemisphere pulsars using CHIME/Pulsar

Using commissioning data from the first year of operation of the Canadian Hydrogen Intensity Mapping Experiment's (CHIME) Pulsar backend system, we conduct a systematic analysis of the Faraday Rotation Measure (RM) of the northern hemisphere pulsars detected by CHIME. We present 55 new RMs as well as obtain improved RM uncertainties for 25 further pulsars. CHIME's low observing frequency and wide bandwidth between 400-800 MHz contribute to the precision of our measurements, whereas the high cadence observation provide extremely high signal-to-noise co-added data. Our results represent a significant increase of the pulsar RM census, particularly regarding the northern hemisphere. These new RMs are for sources that are located in the Galactic plane out to 10 kpc, as well as off the plane to a scale height of ~16 kpc. This improved knowledge of the Faraday sky will contribute to future Galactic large-scale magnetic structure and ionosphere modelling.Comment: 13 pages, 7 figures, accepted by MNRA

Determination of z~0.8 neutral hydrogen fluctuations using the 21 cm intensity mapping auto-correlation

The large-scale distribution of neutral hydrogen in the Universe will be luminous through its 21 cm emission. Here, for the first time, we use the auto-power spectrum of 21 cm intensity fluctuations to constrain neutral hydrogen fluctuations at z~0.8. Our data were acquired with the Green Bank Telescope and span the redshift range 0.6 < z < 1 over two fields totalling ~41 deg. sq. and 190 h of radio integration time. The dominant synchrotron foregrounds exceed the signal by ~10^3, but have fewer degrees of freedom and can be removed efficiently. Even in the presence of residual foregrounds, the auto-power can still be interpreted as an upper bound on the 21 cm signal. Our previous measurements of the cross-correlation of 21 cm intensity and the WiggleZ galaxy survey provide a lower bound. Through a Bayesian treatment of signal and foregrounds, we can combine both fields in auto- and cross-power into a measurement of Omega_HI b_HI = [0.62^{+0.23}_{-0.15}] * 10^{-3} at 68% confidence with 9% systematic calibration uncertainty, where Omega_HI is the neutral hydrogen (HI) fraction and b_HI is the HI bias parameter. We describe observational challenges with the present data set and plans to overcome them.Comment: 5 pages, 3 figures. v2 as published; MNRASL (2013

Anisotropic resistivity and Hall effect in MgB2 single crystals

We report resistivity and the Hall effect measurements in the normal and superconducting states of MgB2 single crystal. The resistivity has been found to be anisotropic with slightly temperature dependent resistivity ratio of about 3.5. The Hall constant, with a magnetic field parallel to the Mg and B sheets is negative in contrast to the hole-like Hall response with a field directed along the c-axis indicating presence of both types of charge carriers and, thus, multi-band electronic structure of MgB2. The Hall effect in the mixed state shows no sign change anomaly reproducing the Hall effect behavior in clean limit type-II superconductors.Comment: Minor changed content, 11 pages including 3 figure

Elastic and total reaction cross sections of oxygen isotopes in Glauber theory

We systematically calculate the total reaction cross sections of oxygen isotopes, $^{15-24}$O, on a $^{12}$C target at high energies using the Glauber theory. The oxygen isotopes are described with Slater determinants generated from a phenomenological mean-field potential. The agreement between theory and experiment is generally good, but a sharp increase of the reaction cross sections from ^{21}O to ^{23}O remains unresolved. To examine the sensitivity of the diffraction pattern of elastic scattering to the nuclear surface, we study the differential elastic-scattering cross sections of proton-^{20,21,23}O at the incident energy of 300 MeV by calculating the full Glauber amplitude.Comment: 9 pages, 8 figure

Crystal growth and characterization of MgB2: Relation between structure and superconducting properties

We discuss the important aspects of synthesis and crystal growth of MgB2 under high pressure (P) and temperature (T) in Mg-B-N system, including the optimisation of P-T conditions for reproducible crystal growth, the role of liquid phases in this process, the temperature dependence of crystal size and the effect of growing instabilities on single crystals morphology. Extensive experiments have been carried out on single crystals with slightly different lattice constants and defects concentration, which revealed and possible effects of Mg-deficiency and lattice strain on the superconducting properties of MgB2 (Tc, Jc, residual resistivity ratio, anisotropy etc.).Comment: 29 pages, 9 figures, 1 table, Proc.of International Workshop on Superconductivity in Magnesium Diboride and Related Materials "BOROMAG", 17-19 June 2002, Genoa, Italy (submitted to Supercond.Sci and Technol.