Searching for Two-Neutrino and Neutrinoless Double Beta Decay of

^{134}Xe is a candidate isotope for neutrinoless double beta decay (0νßß) search. In addition, the two-neutrino case (2νßß) allowed by the standard model of particle physics has not yet been observed. With the 656-kg natural xenon in the fiducial volume of the PandaX-4T detector, which contains 10.4% of ^{134}Xe, and its initial 94.9-day exposure, we have established the most stringent constraints on 2νßß and 0νßß of ^{134}Xe half-lives, with limits of 2.8×10^{22} yr and 3.0×10^{23} yr at 90% confidence level, respectively. The 2νßß (0νßß) limit surpasses the previously reported best result by a factor of 32 (2.7), highlighting the potential of large monolithic natural xenon detectors for double beta decay searches.

Miltiradiene Production by Cytoplasmic Metabolic Engineering in Nicotiana benthamiana.

Plant natural products are important sources of innovative drugs, but the extraction and isolation of medicinal natural products from plants is challenging as these compounds have complex structures that are difficult to synthesize chemically. Therefore, utilizing heterologous expression systems to produce medicinal natural products in plants is a novel, environmentally friendly, and sustainable method. In this study, Nicotiana benthamiana was used as the plant platform to successfully produce miltiradiene, the key intermediate of tanshinones, which are the bioactive constituents of the Chinese medicinal plant Salvia miltiorrhiza. The yield of miltiradiene was increased through cytoplasmic engineering strategies combined with the enhancement of isoprenoid precursors. Additionally, we discovered that overexpressing SmHMGR alone accelerated apoptosis in tobacco leaves. Due to the richer membrane systems and cofactors in tobacco compared to yeast, tobacco is more conducive to the expression of plant enzymes. Therefore, this study lays the foundation for dissecting the tanshinone biosynthetic pathway in tobacco, which is essential for subsequent research. Additionally, it highlights the potential of N. benthamiana as an alternative platform for the production of natural products in plants.

Search for Dark-Matter-Nucleon Interactions with a Dark Mediator in PandaX-4T.

We report results of a search for dark-matter-nucleon interactions via a dark mediator using optimized low-energy data from the PandaX-4T liquid xenon experiment. With the ionization-signal-only data and utilizing the Migdal effect, we set the most stringent limits on the cross section for dark matter masses ranging from 30 MeV/c^{2} to 2 GeV/c^{2}. Under the assumption that the dark mediator is a dark photon that decays into scalar dark matter pairs in the early Universe, we rule out significant parameter space of such thermal relic dark-matter model.

Search for Light Dark Matter from the Atmosphere in PandaX-4T.

We report a search for light dark matter produced through the cascading decay of η mesons, which are created as a result of inelastic collisions between cosmic rays and Earth's atmosphere. We introduce a new and general framework, publicly accessible, designed to address boosted dark matter specifically, with which a full and dedicated simulation including both elastic and quasielastic processes of Earth attenuation effect on the dark matter particles arriving at the detector is performed. In the PandaX-4T commissioning data of 0.63 tonne·year exposure, no significant excess over background is observed. The first constraints on the interaction between light dark matter generated in the atmosphere and nucleus through a light scalar mediator are obtained. The lowest excluded cross section is set at 5.9×10^{-37} cm^{2} for a dark matter mass of 0.1 MeV/c^{2} and mediator mass of 300 MeV/c^{2}. The lowest upper limit of η to the dark matter decay branching ratio is 1.6×10^{-7}.

Chemical Constituents of Euphorbia stracheyi Boiss (Euphorbiaceae).

Euphorbia stracheyi Boiss was used for hemostasis, analgesia, and muscular regeneration in traditional Chinese medicine. To study the chemical constituents of E. stracheyi, the ethyl acetate part of the methanol extract of the whole plant was separated by silica gel, sephadex LH-20 column chromatography, and semi-preparative HPLC. The isolation led to the characterization of a new lathyrane type diterpenoid, euphostrachenol A (1), as well as eleven known compounds (2-11), including a lathyrane, three ingenane-type and two abietane-type diterpenoids, two ionones, and two flavonoids. The structures of these compounds were established using 1D- and 2D-NMR experiments, mass spectrometry, and X-ray crystallographic experiments. The MTT method was used to determine the cytotoxic activity of five cancer cell lines (Leukemia HL-60, lung cancer A-549, liver cancer SMMC-7721, breast cancer MCF-7, and colon cancer SW480) on the isolated compounds. However, only compound 4 showed moderate cytotoxicity against these cell lines, with IC50 values ranging from 10.28 to 29.70 µM, while the others were inactive. Our chemical investigation also confirmed the absence of jatrophane-type diterpenoids in the species, which may be related to its special habitat.

Search for Light Dark Matter with Ionization Signals in the PandaX-4T Experiment.

We report the search results of light dark matter through its interactions with shell electrons and nuclei, using the commissioning data from the PandaX-4T liquid xenon detector. Low energy events are selected to have an ionization-only signal between 60 to 200 photoelectrons, corresponding to a mean nuclear recoil energy from 0.77 to 2.54 keV and electronic recoil energy from 0.07 to 0.23 keV. With an effective exposure of 0.55 tonne·year, we set the most stringent limits within a mass range from 40 MeV/c^{2} to 10 GeV/c^{2} for pointlike dark matter-electron interaction, 100 MeV/c^{2} to 10 GeV/c^{2} for dark matter-electron interaction via a light mediator, and 3.2 to 4 GeV/c^{2} for dark matter-nucleon spin-independent interaction. For DM interaction with electrons, our limits are closing in on the parameter space predicted by the freeze-in and freeze-out mechanisms in the early Universe.

Search for Solar

A search for interactions from solar ^{8}B neutrinos elastically scattering off xenon nuclei using PandaX-4T commissioning data is reported. The energy threshold of this search is further lowered compared with the previous search for dark matter, with various techniques utilized to suppress the background that emerges from data with the lowered threshold. A blind analysis is performed on the data with an effective exposure of 0.48 tonne year, and no significant excess of events is observed. Among the results obtained using the neutrino-nucleus coherent scattering, our results give the best constraint on the solar ^{8}B neutrino flux. We further provide a more stringent limit on the cross section between dark matter and nucleon in the mass range from 3 to 9 GeV/c^{2}.

First Search for the Absorption of Fermionic Dark Matter with the PandaX-4T Experiment.

Compared with the signature of dark matter elastic scattering off nuclei, the absorption of fermionic dark matter by nuclei opens up a new searching channel for light dark matter with a characteristic monoenergetic signal. In this Letter, we explore the 95.0-day data from the PandaX-4T commissioning run and report the first dedicated searching results of the fermionic dark matter absorption signal through a neutral current process. No significant signal was found, and the lowest limit on the dark matter-nucleon interaction cross section is set to be 1.5×10^{-50} cm^{2} for a fermionic dark matter mass of 40 MeV/c^{2} with 90% confidence level.

Search for Light Fermionic Dark Matter Absorption on Electrons in PandaX-4T.

We report a search on sub-MeV fermionic dark matter absorbed by electrons with an outgoing active neutrino using the 0.63 tonne year exposure collected by the PandaX-4T liquid xenon experiment. No significant signals are observed over the expected background. The data are interpreted into limits to the effective couplings between such dark matter and the electron. For axial-vector or vector interactions, our sensitivity is competitive in comparison to existing astrophysical bounds on the decay of such a dark matter candidate into photon final states. In particular, we present the first direct detection limits for a vector (axial-vector) interaction which are the strongest in the mass range from 35 to 55 (25 to 45) keV/c^{2} in comparison to other astrophysical and cosmological constraints.

Mesh plug erosion into the small intestine after inguinal hernia repair: A case report.

BACKGROUND: Mesh plug (MP) erosion into the intra-abdominal organs is a rare but serious long-term complication after inguinal hernia repair (IHR), and may lead to aggravation of symptoms if not treated promptly. It is difficult to diagnose MP erosion as there are no obvious specific clinical manifestations, and surgery is often needed for confirmation. In recent years, with the increased understanding of postoperative complications, MP eroding into the intra-abdominal organs has been a cause for concern among surgeons. CASE SUMMARY: A 50-year-old man was referred to the Department of General Surgery with the complaint of abdominal pain in the right lower quadrant for 2 d. He had a surgical history of right open IHR and partial thyroidectomy performed 20 years and 15 years ago, respectively. Computed tomography revealed a circinate high-density image with short segmental thickening of the ileum stuck to the abdominal wall, and no evidence of recurrent inguinal hernia. Laparoscopic abdominal exploration confirmed adhesion of the middle segmental portion of the ileal loop to the right inguinal abdominal wall; the rest of the small intestine was normal. Further exploration revealed migration of the polypropylene MP into the intraperitoneal cavity and formation of granulation tissue around the plug, which eroded the ileum. Partial resection of the ileum, including the MP and end-to-side anastomosis with an anastomat, was performed. CONCLUSION: Surgeons should aim to improve their ability to predict patients at high risk for MP erosion after IHR.

Search for Cosmic-Ray Boosted Sub-GeV Dark Matter at the PandaX-II Experiment.

We report a novel search for the cosmic-ray boosted dark matter using the 100 tonne·day full dataset of the PandaX-II detector located at the China Jinping Underground Laboratory. With the extra energy gained from the cosmic rays, sub-GeV dark matter particles can produce visible recoil signals in the detector. The diurnal modulations in rate and energy spectrum are utilized to further enhance the signal sensitivity. Our result excludes the dark matter-nucleon elastic scattering cross section between 10^{-31} and 10^{-28} cm^{2} for dark matter masses from 0.1 MeV/c^{2} to 0.1 GeV/c^{2}, with a large parameter space previously unexplored by experimental collaborations.

Determination of Double Beta Decay Half-Life of 136Xe with the PandaX-4T Natural Xenon Detector.

Precise measurement of two-neutrino double beta decay (DBD) half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay. We report the measurement of DBD half-life of 136Xe using the PandaX-4T dual-phase Time Projection Chamber (TPC) with 3.7-tonne natural xenon and the first 94.9-day physics data release. The background model in the fiducial volume is well constrained in situ by events in the outer active region. With a 136Xe exposure of 15.5 kg-year, we establish the half-life as 2.27 ± 0.03(stat.) ± 0.10(syst.) × 1021 years. This is the first DBD half-life measurement with natural xenon and demonstrates the physics capability of a large-scale liquid xenon TPC in the field of rare event searches.

Search for Light Dark Matter-Electron Scattering in the PandaX-II Experiment.

We report constraints on light dark matter through its interactions with shell electrons in the PandaX-II liquid xenon detector with a total 46.9 tonnes/day exposure. To effectively search for these very low energy electron recoils, ionization-only signals are selected from the data. 1821 candidates are identified within an ionization signal range between 50 and 75 photoelectrons, corresponding to a mean electronic recoil energy from 0.08 to 0.15 keV. The 90% C.L. exclusion limit on the scattering cross section between the dark matter and electron is calculated with systematic uncertainties properly taken into account. Under the assumption of point interaction, we provide the world's most stringent limit within the dark matter mass range from 15 to 30 MeV/c^{2}, with the corresponding cross section from 2.5×10^{-37} to 3.1×10^{-38} cm^{2}.

Multiple well-differentiated retroperitoneal liposarcomas with different patterns of appearance on computed tomography: A case report.

BACKGROUND: Primary retroperitoneal liposarcoma (PRPLS) is a rare soft tissue tumor with nonspecific clinical symptoms; it has different computed tomography (CT) image features according to pathological types. Some patients with a single tumor have been previously reported in the literature. We present an exceptional case of a PRPLS patient with multiple large tumors exhibiting different patterns of appearance on CT and confirmed as atypical lipomatous tumor/well-differentiated liposarcoma by postoperative pathology. CASE SUMMARY: A 64-year-old man presented with abdominal distension for 1 year. The patient was diagnosed with PRPLS based on physical examination, laparotomy, ultrasonography, CT scan, and surgery. Both of the tumors were completely resected through surgery and confirmed as atypical lipomatous tumor/well-differentiated liposarcoma by postoperative pathology. The postoperative course was uneventful without recurrence or metastasis, as demonstrated by abdominal-pelvic CT during an 18 mo follow-up. CONCLUSION: Multiple large Well-differentiated liposarcomas with different patterns of appearance on CT image can occur simultaneously in the same patient, to which more attention should be paid to make an effective differential diagnosis.

Dark Matter Search Results from the PandaX-4T Commissioning Run.

We report the first dark matter search results using the commissioning data from PandaX-4T. Using a time projection chamber with 3.7 tonne of liquid xenon target and an exposure of 0.63 tonne·year, 1058 candidate events are identified within an approximate nuclear recoil energy window between 5 and 100 keV. No significant excess over background is observed. Our data set a stringent limit to the dark matter-nucleon spin-independent interactions, with a lowest excluded cross section (90% C.L.) of 3.8×10^{-47} cm^{2} at a dark matter mass of 40 GeV/c^{2}.

Constraining Dark Matter Models with a Light Mediator at the PandaX-II Experiment.

We search for nuclear recoil signals of dark matter models with a light mediator in PandaX-II, a direct detection experiment in the China Jinping underground laboratory. Using data collected in 2016 and 2017 runs, corresponding to a total exposure of 54 ton day, we set upper limits on the zero-momentum dark matter-nucleon cross section. These limits have a strong dependence on the mediator mass when it is comparable to or below the typical momentum transfer. We apply our results to constrain self-interacting dark matter models with a light mediator mixing with standard model particles, and set strong limits on the model parameter space for the dark matter mass ranging from 5 GeV to 10 TeV.

Limits on Axion Couplings from the First 80 Days of Data of the PandaX-II Experiment.

We report new searches for solar axions and galactic axionlike dark matter particles, using the first low-background data from the PandaX-II experiment at China Jinping Underground Laboratory, corresponding to a total exposure of about 2.7×10^{4} kg day. No solar axion or galactic axionlike dark matter particle candidate has been identified. The upper limit on the axion-electron coupling (g_{Ae}) from the solar flux is found to be about 4.35×10^{-12} in the mass range from 10^{-5} to 1 keV/c^{2} with 90% confidence level, similar to the recent LUX result. We also report a new best limit from the ^{57}Fe deexcitation. On the other hand, the upper limit from the galactic axions is on the order of 10^{-13} in the mass range from 1 to 10 keV/c^{2} with 90% confidence level, slightly improved compared with the LUX.

Dark Matter Results from 54-Ton-Day Exposure of PandaX-II Experiment.

We report a new search for weakly interacting massive particles (WIMPs) using the combined low background data sets acquired in 2016 and 2017 from the PandaX-II experiment in China. The latest data set contains a new exposure of 77.1 live days, with the background reduced to a level of 0.8×10^{-3} evt/kg/day, improved by a factor of 2.5 in comparison to the previous run in 2016. No excess events are found above the expected background. With a total exposure of 5.4×10^{4} kg day, the most stringent upper limit on the spin-independent WIMP-nucleon cross section is set for a WIMP with mass larger than 100 GeV/c^{2}, with the lowest 90% C.L. exclusion at 8.6×10^{-47} cm^{2} at 40 GeV/c^{2}.

Spin-Dependent Weakly-Interacting-Massive-Particle-Nucleon Cross Section Limits from First Data of PandaX-II Experiment.

New constraints are presented on the spin-dependent weakly-interacting-massive-particle–- (WIMP-)nucleon interaction from the PandaX-II experiment, using a data set corresponding to a total exposure of 3.3×10^{4} kg day. Assuming a standard axial-vector spin-dependent WIMP interaction with ^{129}Xe and ^{131}Xe nuclei, the most stringent upper limits on WIMP-neutron cross sections for WIMPs with masses above 10 GeV/c^{2} are set in all dark matter direct detection experiments. The minimum upper limit of 4.1×10^{-41} cm^{2} at 90% confidence level is obtained for a WIMP mass of 40 GeV/c^{2}. This represents more than a factor of 2 improvement on the best available limits at this and higher masses. These improved cross-section limits provide more stringent constraints on the effective WIMP-proton and WIMP-neutron couplings.