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Exploration of the impact of synthetic material landscapes featuring tunable geometrical properties on physical processes is a research direction that is currently of great interest because of the outstanding phenomena that are continually being uncovered. Twistronics and the properties of wave excitations in moiré lattices are salient examples. Moiré patterns bridge the gap between aperiodic structures and perfect crystals, thus opening the door to the exploration of effects accompanying the transition from commensurate to incommensurate phases. Moiré patterns have revealed profound effects in graphene-based systems1–5, they are used to manipulate ultracold atoms6,7 and to create gauge potentials8, and are observed in colloidal clusters9. Recently, it was shown that photonic moiré lattices enable observation of the two-dimensional localization-to-delocalization transition of light in purely linear systems10,11. Here, we employ moiré lattices optically induced in photorefractive nonlinear media12–14 to elucidate the formation of optical solitons under different geometrical conditions controlled by the twisting angle between the constitutive sublattices. We observe the formation of solitons in lattices that smoothly transition from fully periodic geometries to aperiodic ones, with threshold properties that are a pristine direct manifestation of flat-band physics11.Moiré lattices optically induced in photorefractive nonlinear media are used to explain the formation of optical solitons under different geometrical conditions controlled by the twisting angle between the constitutive sublattices.

Generalization of Fractional Schrödinger equation (FSE) into optics is fundamentally important, since optics usually provides a fertile ground where FSE-related phenomena can be effectively observed. Beam propagation management is a topic of considerable interest in the field of optics. Here, we put forward a simple scheme for the realization of propagation management of light beams by introducing a double-barrier potential into the FSE. Transmission, partial transmission/reflection, and total reflection of light fields can be controlled by varying the potential depth. Oblique input beams with arbitrary distributions obey the same propagation dynamics. Some unique properties, including strong self-healing ability, high capacity of resisting disturbance, beam reshaping, and Goos-Hänchen-like shift are revealed. Theoretical analysis results are qualitatively in agreements with the numerical findings. This work opens up new possibilities for beam management and can be generalized into other fields involving fractional effects.

Moiré lattices consist of two superimposed identical periodic structures with a relative rotation angle. Moiré lattices have several applications in everyday life, including artistic design, the textile industry, architecture, image processing, metrology and interferometry. For scientific studies, they have been produced using coupled graphene–hexagonal boron nitride monolayers 1 , 2 , graphene–graphene layers 3 , 4 and graphene quasicrystals on a silicon carbide surface 5 . The recent surge of interest in moiré lattices arises from the possibility of exploring many salient physical phenomena in such systems; examples include commensurable–incommensurable transitions and topological defects 2 , the emergence of insulating states owing to band flattening 3 , 6 , unconventional superconductivity 4 controlled by the rotation angle 7 , 8 , the quantum Hall effect 9 , the realization of non-Abelian gauge potentials 10 and the appearance of quasicrystals at special rotation angles 11 . A fundamental question that remains unexplored concerns the evolution of waves in the potentials defined by moiré lattices. Here we experimentally create two-dimensional photonic moiré lattices, which—unlike their material counterparts—have readily controllable parameters and symmetry, allowing us to explore transitions between structures with fundamentally different geometries (periodic, general aperiodic and quasicrystal). We observe localization of light in deterministic linear lattices that is based on flat-band physics 6 , in contrast to previous schemes based on light diffusion in optical quasicrystals 12 , where disorder is required 13 for the onset of Anderson localization 14 (that is, wave localization in random media). Using commensurable and incommensurable moiré patterns, we experimentally demonstrate the two-dimensional localization–delocalization transition of light. Moiré lattices may feature an almost arbitrary geometry that is consistent with the crystallographic symmetry groups of the sublattices, and therefore afford a powerful tool for controlling the properties of light patterns and exploring the physics of periodic–aperiodic phase transitions and two-dimensional wavepacket phenomena relevant to several areas of science, including optics, acoustics, condensed matter and atomic physics. A superposition of tunable photonic lattices is used to create optical moiré patterns and demonstrate the resulting localization of light waves through a mechanism based on flat-band physics.

We address the nonlinear dynamics of binary Bose-Einstein condensates with mutually symmetric spinor components trapped in an optical lattice. The interaction between the repulsive Lee–Huang–Yang nonlinearity and the intercomponent attraction as well as Bragg scattering of an optical lattice results in formation of multi-peaked quantum droplets. Even- and odd-symmetric droplets can bifurcate from Bloch modes of the corresponding periodic systems. Linear stability analysis corroborated by direct evolution simulations reveals that even-symmetric droplets with different norms and different number of peaks can evolve stably at the same chemical potential, i.e., multi-stable droplets are possible in the present scheme. Besides the droplets in the semi-infinite gap, the properties of droplets in the first finite bandgap are also discussed. Both even- and odd-symmetric droplets are stable in almost their whole existence domains. We reveal that optical lattice plays an important role for the stabilization of droplets, in sharp contrast to the nonlinear system without a lattice modulation. We, thus, furnish a paradigmatic example of multi-stable quantum droplets held in optical lattices.

We predict a novel family of off-center localized nonlinear modes in a rotating optical system. The whispering-gallery-like solitons bifurcate out from the symmetric fundamental solitons through a symmetry breaking. They can appear as localized spots, nearly flat-top beams and crescent-like patterns extending over the entire range of polar angles. At critical rotation frequency, asymmetric solitons transform into vortex solitons, whose topological charge gradually increases with the growth of the propagation constant. Asymmetric solitons rotate around the origin persistently during propagation and preserve their shape over arbitrary distance in almost the whole existence domain. Thus, we put forward the first example of stable asymmetric intermediate states in optical systems that bridge the symmetric fundamental solitons and the symmetric vortex solitons with different topological charges, through the variance of the propagation constant and rotation frequency.

We introduce a composite optical lattice created by two mutually rotated square patterns and allowing observation of continuous transformation between incommensurate and completely periodic structures upon variation of the rotation angle θ. Such lattices acquire periodicity only for rotation angles cos θ =  a / c , sin θ =  b / c , set by Pythagorean triples of natural numbers ( a , b , c ). While linear eigenmodes supported by lattices associated with Pythagorean triples are always extended, composite patterns generated for intermediate rotation angles allow observation of the localization-delocalization transition of eigenmodes upon modification of the relative strength of two sublattices forming the composite pattern. Sharp delocalization of supported modes for certain θ values can be used for visualization of Pythagorean triples. The effects predicted here are general and also take place in composite structures generated by two rotated hexagonal lattices.

BackgroundThis study aimed to compare the long-term survival of patients undergoing minimally invasive gastrectomy and those undergoing open gastrectomy for gastric adenocarcinoma (GA) in the United States and China.MethodsData on patients with GA who underwent gastrectomy without neoadjuvant therapy were retrieved from prospectively maintained databases at Memorial Sloan Kettering Cancer Center (MSKCC) and Fujian Medical University Union Hospital (FMUUH). Using propensity score-matching (PSM), equally sized cohorts of patients with similar clinical and pathologic characteristics who underwent minimally invasive versus open gastrectomy were selected. The primary end point of the study was 5-year overall survival (OS).ResultsThe study identified 479 patients who underwent gastrectomy at MSKCC between 2000 and 2012 and 2935 patients who underwent gastrectomy at FMUUH between 2006 and 2014. Of the total 3432 patients, 1355 underwent minimally invasive gastrectomy, and 2059 underwent open gastrectomy. All the patients had at least 5 years of potential follow-up evaluation. Before PSM, most patient characteristics differed significantly between the patients undergoing the two types of surgery. After PSM, each cohort included 889 matched patients, and the actual 5-year OS did not differ significantly between the two cohorts, with an OS rate of 54% after minimally invasive gastrectomy and 50.4% after open gastrectomy (p = 0.205). Subgroup analysis confirmed that survival was similar between surgical cohorts among the patients for each stage of GA and for those undergoing distal versus total/proximal gastrectomy. In the multivariable analysis, surgical approach was not an independent prognostic factor.ConclusionsAfter PSM of U.S. and Chinese patients with GA undergoing gastrectomy, long-term survival did not differ significantly between the patients undergoing minimally invasive gastrectomy and those undergoing open gastrectomy.

Background Laparoscopic resection of gastric gastrointestinal stromal tumors (GISTs) appears technically feasible and associated with favorable outcomes. Tumor size plays an important role in surgical approach, with laparotomy tending to be used to treat larger tumors. This study evaluated the technical feasibility, safety, and oncologic efficacy of laparoscopic surgery for GISTs ≥5 cm in diameter. Methods One hundred forty patients who underwent resection of primary gastric GIST at our institution from January 2007 to December 2012 were identified. Twenty-three patients with tumor larger than 5 cm in diameter treated by laparoscopic resection and were randomly matched (1:1) by tumor size (±1 cm) to patients with open resection. Clinical and pathologic variables and surgical outcomes for each surgical type were identified and compared. Results There were no significant differences in clinicopathologic characteristics between the two groups. Laparoscopic group was superior to open group in operation time, blood loss, time to ground activities, time to first flatus, times to liquid diet, and postoperative stay ( P  < 0.05). Number of transfusions and time to semi-liquid diet, however, did not differ between groups. There was no operative mortality, and the postoperative complications were similar. Fifteen patients in the laparoscopic group and 17 patients in the open group received adjuvant treatment with imatinib. Recurrence or metastasis occurred in eight cases (three in the laparoscopic group and five in the open group). No significant difference in long-term disease-free survival was found between the two groups ( P  > 0.05). Conclusion When performed by experienced surgeons, laparoscopic resection for gastric GISTs larger than 5 cm is a safe and effective minimally invasive surgery.

The existence of thresholdless vortex solitons trapped at the core of disclination lattices that realize higher-order topological insulators is reported. The study demonstrates the interplay between nonlinearity and higher-order topology in these systems, as the vortex state in the disclination lattice bifurcates from its linear topological counterpart, while the position of its propagation constant within the bandgap and localization can be controlled by its power. It is shown that vortex solitons are characterized by strong field confinement at the disclination core due to their topological nature, leading to enhanced stability. Simultaneously, the global discrete rotational symmetry of the disclination lattice imposes restrictions on the maximal possible topological charge of such vortex solitons. The results illustrate the strong stabilizing action that topologically nontrivial structures may exert on excited soliton states, opening new prospects for soliton-related applications.

Background Laparoscopy-assisted gastrectomy (LAG) has been indicated to be safe, feasible, and oncologically efficacious for the treatment of early gastric cancer by both retrospective and prospective studies. Although some reports have demonstrated that LAG was also a safe and technically feasible procedure for advanced gastric cancer (AGC), its oncologic outcomes have not yet been confirmed in a multicenter, large-scale study. The aim of this study was to evaluate the oncologic outcomes of LAG for AGC on a multicenter basis in China. Methods Data of 1,184 consecutive patients with locally AGC who underwent LAG with curative intent between February 2003 and December 2009 were collected from the Chinese Laparoscopic Gastrointestinal Surgery Study group database and retrospectively analyzed. Survival rates were estimated by the Kaplan–Meier method. Risk factors for recurrence and survival were evaluated by Cox regression models. Results Postoperatively, 121 patients (10.2 %) experienced complications, and 1 patient died (0.1 %). Median follow-up was 12 months. Recurrence was observed in 185 patients (16.7 %), including hematogenous (31 patients), peritoneal (52), locoregional (25), distant lymph node (LN) (8), mixed (63), and uncertain (6) recurrences. The cumulative 3-year overall survival and disease-free survival rates were 75.3 and 69.0 %, respectively. The 3-year overall survival and disease-free survival rates were 89.7 and 88.9 % for stage I tumors, 85.0 and 77.0 % for stage II, 60.5 and 59.3 % for stage III. Independent risk factors for recurrence were tumor size > 40 mm, intraoperative blood transfusion, and advanced tumor stage. For survival, age > 65 years, tumor size > 40 mm, and advanced tumor stage were independent risk factors. Conclusions In addition to being safe and technically feasible, LAG for locally AGC could also yield acceptable short-term oncologic outcomes.