Spin-orbit coupling (SOC) is central to many physical phenomena, including fine structures of atomic spectra and topological phases in ultracold atoms. Whereas, in general, SOC is fixed in a system, laser-atom interaction provides a means to create and control synthetic SOC in ultracold atoms 1 . Despite significant experimental progress in this area 2-8 , two-dimensional (2D) synthetic SOC, which is crucial for exploring two-and threedimensional topological phases, is lacking. Here, we report the experimental realization of 2D SOC in ultracold 40 K Fermi gases using three lasers, each of which dresses one atomic hyperfine spin state. Through spin-injection radiofrequency (rf) spectroscopy 4 , we probe the spin-resolved energy dispersions of the dressed atoms, and observe a highly controllable Dirac point created by the 2D SOC. These results constitute a step towards the realization of new topological states of matter.There have been many theoretical proposals for creating multi-dimensional SOC in ultracold atoms 9-14 , so as to access novel macroscopic quantum phenomena and quantum topological states [15][16][17][18][19][20][21][22][23][24] . Whereas these proposals have not been realized in laboratories, physicists have also just begun to explore topological phenomena in optical lattices [25][26][27][28] . Here, we use the Raman scheme to produce a highly controllable 2D synthetic SOC for an ultracold Fermi gas of 40 K. Such SOC allows us to create and manipulate a single stable Dirac point on a 2D plane, which is detected by spin-injection rf spectroscopy 4 .We apply three far-detuned lasers propagating on the x-y plane to couple three ground hyperfine spin states, within the 4 2 S 1/2 ground electronic manifold, |1 = |F = 9/2, m F = 3/2 , |2 = |F = 9/2, m F = 1/2 and |3 = |F = 7/2, m F = 1/2 , where (F, m F ) are the quantum numbers for hyperfine spin states as shown in Fig. 1a, to the electronically excited states. Unlike the tripod scheme, where a single excited state is considered [9][10][11][15][16][17][18] , in the 40 K used here the excited states include a fine-structure doublet 4 2 P 1/2 (D 1 line) and 4 2 P 3/2 (D 2 line) with a finestructure splitting of ∼3.4 nm. Each of two D-line components also has hyperfine structures. After adiabatically eliminating excited states, the ring scheme proposed in ref. 12 is realized for three cyclically coupled states, with a generalization to arbitrary laser configurations. The Hamiltonian is written as( 1) where p denotes the momentum of atoms, k i (|k i | = 2π/λ i ) and ω i are the wavevectors and frequencies of the three lasers, Ω i are the Rabi frequencies, i, j are the indices for the three ground hyperfine spin and the excited states respectively, ε i and E j are the ground and excited state energies, n is the total number of the excited states and M ij is the matrix element of the dipole transition. Different from refs 9,10,15, each hyperfine ground spin state here is dressed by only one laser field, regardless of the excited states it is coupled to. A gau...

The recent experimental realization of synthetic spin-orbit coupling (SOC) opens a new avenue for exploring novel quantum states with ultracold atoms. However, in experiments for generating twodimensional SOC (e.g., Rashba type), a perpendicular Zeeman field, which opens a band gap at the Dirac point and induces many topological phenomena, is still lacking. Here we theoretically propose and experimentally realize a simple scheme for generating two-dimension SOC and a perpendicular Zeeman field simultaneously in ultracold Fermi gases by tuning the polarization of three Raman lasers that couple three hyperfine ground states of atoms. The resulting band gap opening at the Dirac point is probed using spin injection radio-frequency spectroscopy. Our observation may pave the way for exploring topological transport and topological superfluids with exotic Majorana and Weyl fermion excitations in ultracold atoms. Spin-orbit coupling (SOC), the intrinsic interaction between a particle spin and its motion, plays a key role in many important phenomena, ranging from anomalous Hall effects [1] to topological insulators and superconductors [2][3][4]. Although SOC is ubiquitous in nature, the experimental control and observation of SOC induced effects are quite difficult. In this context, the recent experimental realization of synthetic SOC for cold atoms [5][6][7][8][9][10][11][12] provides a completely new and tunable platform for exploring SOC related physics. Early experiments only realized the 1D SOC (i.e., an equal sum of Rashba and Dresselhaus coupling, ∝ k x σ y ) using two counterpropagating Raman lasers [5][6][7][8][9][10][11][12]. Many theoretical proposals have explored the generation of 2D SOC (i.e., ∝ αk x σ y + βk y σ x ) [13][14][15][16][17][18][19][20] as well as their interesting physical properties in Bose and Fermi gases [21][22][23][24][25][26]. Recently, 2D SOC was also experimentally realized in ultracold 40 K Fermi gases [27] using three Raman lasers and the associated stable Dirac point on a 2D momentum plane was observed [27].The experimental generation of SOC is usually accompanied with a Zeeman field, which breaks various symmetries of the underlying system and induces interesting quantum phenomena. The accompanied Zeeman field can be in-plane (e.g., V σ y for SOC ∝ k x σ y ) or perpendicular (e.g., V σ z for SOC ∝ αk x σ y + βk y σ x ). The in-plane Zeeman field, while preserves the Dirac point, makes the band dispersion asymmetric, leading to new quantum states such as Fulde-Ferrell superfluids [28][29][30][31]. In contrast, the perpendicular Zeeman field can open a topological band gap at the Dirac point of the SOC, leading to many interesting topological transport [1] and superfluid phenomena, such as the long-sought Majorana [32,33] and Weyl [24,34,35] fermions. In cold atom experiments, although both in-plane and perpendicular Zeeman fields have been realized with 1D SOC, only inplane Zeeman field was realized with 2D SOC [27]. A perpendicular Zeeman field with 2D SOC is still lacked but highly...

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Cu,Zn-superoxide dismutase (SOD), Se-dependent glutathione peroxidase (GSH-Px), catalase (CAT), and glutathione (GSH) play an important role in attenuating free radical-induced oxidative damage. The purpose of this research was to determine (1) whether sulfur dioxide (SO(2)) increases levels of lipid peroxidation and alters intracellular redox status in multiple organs of mice, and (2) whether SO(2) is a systemic toxic agent. The effect of SO(2) on levels of thiobarbituric acid-reactive substances (TBARS) and GSH and activities of SOD, GSH-Px, and CAT were investigated in nine organs (brain, lung, heart, liver, stomach, intestine, spleen, kidney, and testis) of Kunming albino mice of both sexes. SO(2) at 20 ppm (56 mg/m(3)) was administrated to the animals of SO(2) groups in an exposure chamber for 6 h/day for 7 days while control groups were exposed to filtered air in the same condition. Results show that SO(2) inhalation decreased significantly activities of SOD and GSH-Px in all organs tested in all SO(2) groups, with respect to their corresponding control groups; CAT activities in all organs tested of both sexual mice were significantly unaltered, except CAT activities in livers were significantly lowered by SO(2); SO(2) exposure decreased significantly GSH contents and significantly increased TBARS levels of all organs tested, in comparison with their respective control groups. These results lead to two conclusions: (1) SO(2) is a systemic oxidative damage agent. It results in a significant increase in the lipid peroxidation process in all organs tested of mice of both sexes, which is accompanied by changes of antioxidant status in these organs. (2) SO(2) may cause toxicological damage to multiple organs of animals, and it is suggested that the oxidative damage produced by SO(2) inhalation may influence or promote the progression or occurrence of some disease states of various organs, not only to respiratory system. Further work is required to understand the toxicological role of SO(2) on multiple or even all organs in mammals.

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The DNA-damaging effects of sulfur dioxide (SO2) derivatives (a mixture of sodium sulfite and sodium bisulfite, 3:1 M/M) in the cells of various organs (brain, lung, heart, liver, stomach, spleen, thymus, bone marrow and kidney) of male mice were studied using the single cell gel electrophoresis technique (SCGE). Three groups of six mice each received an i.p. dose of SO2 derivatives (125, 250 or 500 mg/kg body wt) daily for 7 days. A control group of six mice received 200 microl of normal saline i.p. daily for 7 days. Our results show that SO2 derivatives caused significant increases in olive tail moment (OTM) in cells from all organs tested in a dose-dependent manner. These results show that SO2 derivatives can cause DNA damage to multiple organs of mice and that SO2 derivatives are systemic DNA-damaging agents, not only to the respiratory system. It is suggested that SO2 derivative exposure has a potential risk to DNA in multiple organs of mammals and might be related to carcinogenesis or other diseases related to DNA damage. Further work is required to understand the toxicological role of SO2 and its derivatives on multiple or even all organs in humans and animals. Recent research results have shown that SO2 and its derivatives can also induce an increase in the frequencies of chromosomal aberrations, sister chromatid exchanges and micronuclei in mammalian cells and cause oxidative damage in multiple organs of male and female mice. Taken together, these results suggest that SO2 and its derivatives are systemic toxic agents. However, further studies need to be performed before a definitive conclusion can be drawn.

BackgroundOver the last decade, coverage of maternal and newborn health indicators used for global monitoring and reporting have increased substantially but reductions in maternal and neonatal mortality have remained slow. This has led to an increased recognition and concern that these standard globally agreed upon measures of antenatal care (ANC), skilled birth attendance (SBA) and postnatal care (PNC) only capture the level of contacts with the health system and provide little indication of actual content of services received by mothers and their newborns. Over this period, large household surveys have captured measures of maternal and newborn care mainly through questions assessing contacts during the antenatal, delivery and postnatal periods along with some measures of content of care. This study aims to describe the gap between contact and content –as a proxy for quality– of maternal and newborn health services by assessing level of co–coverage of ANC and PNC interventions.MethodsWe used Demographic and Health Surveys (DHS) data from 20 countries between 2010 and 2015. We analysed the proportion of women with at least 1 and 4+ antenatal care visit, who received 8 interventions. We also assessed the percentage of newborns delivered with a skilled birth attendant who received 7 interventions. We ran random effect logistic regression to assess factors associated with receiving all interventions during the antenatal and postnatal period.ResultsWhile on average 51% of women in the analysis received four ANC visits with at least one visit from a skilled health provider, only 5% of them received all 8 ANC interventions. Similarly, during the postnatal period though two–thirds (65%) of births were attended by a skilled birth attendant, only 3% of newborns received all 7 PNC interventions. The odds of receiving all ANC and PNC interventions were higher for women with higher education and higher wealth status.ConclusionThe gap between coverage and content as a proxy of quality of antenatal and postnatal care is excessively large in all countries. In order to accelerate maternal and newborn survival and achieve Sustainable Development Goals, increased efforts are needed to improve both the coverage and quality of maternal and newborn health interventions.

We investigate experimentally and theoretically radio-frequency spectroscopy and pairing of a spin-orbit-coupled Fermi gas of 40 K atoms near a Feshbach resonance at B0 = 202.2 G. Experimentally, the integrated spectroscopy is measured, showing characteristic blue and red shifts in the atomic and molecular responses, respectively, with increasing spin-orbit coupling. Theoretically, a smooth transition from atomic to molecular responses in the momentum-resolved spectroscopy is predicted, with a clear signature of anisotropic pairing at and below resonance. Our many-body prediction agrees qualitatively well with the observed spectroscopy near the Feshbach resonance.