Spin-orbit coupling (SOC), the interaction between the spin and momentum of a quantum particle, is crucial for many important condensed matter phenomena. The recent experimental realization of SOC in neutral bosonic cold atoms provides a new and ideal platform for investigating spin-orbit coupled quantum many-body physics. In this Letter, we derive a generic Gross-Pitaevskii equation as the starting point for the study of many-body dynamics in spin-orbit coupled Bose-Einstein condensates. We show that different laser setups for realizing the same SOC may lead to different mean-field dynamics. Various ground state phases (stripe, phase separation, etc.) of the condensate are found in different parameter regions. A new oscillation period induced by the SOC, similar to the Zitterbewegung oscillation, is found in the center-of-mass motion of the condensate.

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Spin-orbit-coupled Bose-Einstein condensates (BECs) provide a powerful tool to investigate interesting gauge field-related phenomena. Here we study the ground state properties of such a system and show that it can be mapped to the well-known Dicke model in quantum optics, which describes the interactions between an ensemble of atoms and an optical field. A central prediction of the Dicke model is a quantum phase transition between a superradiant phase and a normal phase. We detect this transition in a spin-orbit-coupled BEC by measuring various physical quantities across the phase transition. These quantities include the spin polarization, the relative occupation of the nearly degenerate single-particle states, the quantity analogous to the photon field occupation and the period of a collective oscillation (quadrupole mode). The applicability of the Dicke model to spin-orbit-coupled BECs may lead to interesting applications in quantum optics and quantum information science.

Bike sharing is a new form of transport and is becoming increasingly popular in cities around the world. This study aims to quantitatively estimate the environmental benefits of bike sharing. Using big data techniques, we estimate the impacts of bike sharing on energy use and carbon dioxide (CO2) and nitrogen oxide (NOX) emissions in Shanghai from a spatiotemporal perspective. In 2016, bike sharing in Shanghai saved 8,358 tonnes of petrol and decreased CO2 and NOX emissions by 25,240 and 64 tonnes, respectively. From a spatial perspective, environmental benefits are much higher in more developed districts in Shanghai where population density is usually higher. From a temporal perspective, there are obvious morning and evening peaks of the environmental benefits of bike sharing, and evening peaks are higher than morning peaks. Bike sharing has great potential to reduce energy consumption and emissions based on its rapid development.

The realization of artificial gauge fields and spin-orbit coupling for ultra-cold quantum gases promises new insight into paradigm solid state systems. Here we experimentally probe the dispersion relation of a spin-orbit coupled Bose-Einstein condensate loaded into a translating optical lattice by observing its dynamical stability, and develop an effective band structure that provides a theoretical understanding of the locations of the band edges. This system presents exciting new opportunities for engineering condensed-matter analogs using the flexible toolbox of ultra-cold quantum gases.PACS numbers: 03.75. Kk, 03.75.Mn, 03.75.Lm Spin-orbit coupling -the interaction between a particle's spin and its mechanical motion -plays a prominent role in condensed matter physics [1]. Even though the spin-orbit interaction is usually relatively weak, it can be important for bands close to the Fermi level [2]. The combination of spin-orbit coupling with a periodic potential resulted in the prediction and discovery of topological insulators [3,4]. Such spin-orbit coupled lattice systems, with the addition of strongly correlated manybody effects, can exhibit novel phases [5]. These systems have transformed our understanding and classification of insulators and have become a significant focus of recent research [6,7]. They afford the possibility of studying new phase transitions and realizing exotic spin models [8].Simulating model Hamiltonians relevant to condensed matter physics has developed into a major area of research for experiments with dilute gas Bose-Einstein condensates and degenerate Fermi gases [9,10]. Quantum gases in optical lattices are nearly disorder free and often exhibit long coherence times [9,10]. Additionally, quantum gases allow the modification of the interparticle interactions, e.g. by tuning the two-body scattering length [11] or engineering long range dipolar interactions [12], creating great flexibility for implementing model Hamiltonians. While many electronic condensedmatter systems naturally exhibit a band structure due the periodicity of an underlying crystal lattice, in ultracold quantum gases band structures can be engineered by loading the system into an optical lattice. Both an optical lattice potential [13] and spin-orbit coupling [14] can strongly modify the single-particle dispersion relation of a quantum gas, resulting in novel band structures.In this letter we perform a detailed study of a BoseEinstein condensate (BEC) with spin-orbit coupling [14][15][16][17][18] loaded into a shallow, translating one-dimensional optical lattice. We find that the system exhibits a number of dynamical instabilities induced by the periodic dispersion relation of the lattice [19]. The instabilities are marked by an initial exponential growth of excitations in the BEC, and are most significant in the vicinity of a band gap. We characterize the strengths of the instabilities by the loss rate of condensate atoms and find that a dynamical instability is present for lattice velocities exceeding a critical...

T cells engineered with chimeric antigen receptor (CAR) have been successfully applied to treat advanced refractory B cell malignancy. However, many challenges remain in extending its application toward the treatment of solid tumors. The immunosuppressive nature of tumor microenvironment is considered one of the key factors limiting CAR-T efficacy. One negative regulator of Tcell activity is lymphocyte activation gene-3 (LAG-3). We successfully generated LAG-3 knockout Tand CAR-T cells with high efficiency using CRISPR-Cas9 mediated gene editing and found that the viability and immune phenotype were not dramatically changed during in vitro culture. LAG-3 knockout CAR-T cells displayed robust antigen-specific antitumor activity in cell culture and in murine xenograft model, which is comparable to standard CAR-T cells. Our study demonstrates an efficient approach to silence immune checkpoint in CAR-T cells via gene editing.

A negative effective mass can be realized in quantum systems by engineering the dispersion relation. A powerful method is provided by spin-orbit coupling, which is currently at the center of intense research efforts. Here we measure an expanding spin-orbit coupled Bose-Einstein condensate whose dispersion features a region of negative effective mass. We observe a range of dynamical phenomena, including the breaking of parity and of Galilean covariance, dynamical instabilities, and self-trapping. The experimental findings are reproduced by a single-band Gross-Pitaevskii simulation, demonstrating that the emerging features -shockwaves, soliton trains, self-trapping, etc.-originate from a modified dispersion. Our work also sheds new light on related phenomena in optical lattices, where the underlying periodic structure often complicates their interpretation.

Mitochondria undergo frequent morphological changes through fission and fusion. Mutations in core members of the mitochondrial fission/fusion machinery are responsible for severe neurodegenerative diseases. However, the mitochondrial fission/fusion mechanisms are poorly understood. We found that the loss of a mitochondrial protein encoding gene, mitoguardin (miga), leads to mitochondrial defects and neurodegeneration in fly eyes. Mammals express two orthologs of miga: Miga1 and Miga2. Both MIGA1 and MIGA2 form homotypic and heterotypic complexes on the outer membrane of the mitochondria. Loss of MIGA results in fragmented mitochondria, whereas overexpression of MIGA leads to clustering and fusion of mitochondria in both fly and mammalian cells. MIGA proteins function downstream of mitofusin and interact with MitoPLD to stabilize MitoPLD and facilitate MitoPLD dimer formation. Therefore, we propose that MIGA proteins promote mitochondrial fusion by regulating mitochondrial phospholipid metabolism via MitoPLD.