Revealing roles of S-layer protein (SlpA) in Clostridioides difficile pathogenicity by generating the first slpA gene deletion mutant

Clostridioides difficile infection (CDI) with high morbidity and high mortality is an urgent threat to public health, and C. difficile pathogenesis studies are eagerly required for CDI therapy. The major surface layer protein, SlpA, was supposed to play a key role in C. difficile pathogenesis; however, a lack of isogenic slpA mutants has greatly hampered analysis of SlpA functions. In this study, the whole slpA gene was successfully deleted for the first time via CRISPR-Cas9 system. Deletion of slpA in C. difficile resulted in smaller, smother-edged colonies, shorter bacterial cell size, and aggregation in suspension. For life cycle, the mutant demonstrated lower growth (changes of optical density at 600 nm, OD600) but higher cell density (colony-forming unit, CFU), decreased toxins production, and inhibited sporulation. Moreover, the mutant was more impaired in motility, more sensitive to vancomycin and Triton X-100-induced autolysis, releasing more lactate dehydrogenase. In addition, SlpA deficiency led to robust biofilm formation but weak adhesion to human host cells.IMPORTANCEClostridioides difficile infection (CDI) has been the most common hospital-acquired infection, with a high rate of antibiotic resistance and recurrence incidences, become a debilitating public health threat. It is urgently needed to study C. difficile pathogenesis for developing efficient strategies as CDI therapy. SlpA was indicated to play a key role in C. difficile pathogenesis. However, analysis of SlpA functions was hampered due to lack of isogenic slpA mutants. Surprisingly, the first slpA deletion C. difficile strain was generated in this study via CRISPR-Cas9, further negating the previous thought about slpA being essential. Results in this study will provide direct proof for roles of SlpA in C. difficile pathogenesis, which will facilitate future investigations for new targets as vaccines, new therapeutic agents, and intervention strategies in combating CDI.

Multi-scale analysis of acidophilic microbial consortium biofilm's tolerance of lithium and cobalt ions in bioleaching

Metal ions stress will inhibit the oxidation capacity of iron and sulfur of an acidophilic microbial consortium (AMC), which leads to reduced bioleaching efficiency. This work explored the impacts of Li+ and Co2+ on the composition and function of AMC biofilms with a multi-scale approach. At the reactor scale, the results indicated that the oxidative activity, the adsorption capacity, and the biofilm formation ability of AMC on pyrite surfaces decreased under 500 mM Li+ and 500 mM Co2+. At the biofilm scale, the electrochemical measurements showed that Li+ and Co2+ inhibited the charge transfer between the pyrite working electrode and the biofilm, and decreased the corrosion current density of the pyrite working electrode. At the cell scale, the content of proteins in extracellular polymers substrate (EPS) increased as the concentrations of metal ions increased. Moreover, the adsorption capacity of EPS for Li+ and Co2+ increased. At the microbial consortium scale, a BugBase phenotype analysis showed that under 500 mM Li+ and 500 mM Co2+, the antioxidant stress capacity and the content of mobile gene elements in AMC increased. The results in this work can provide useful data and theoretical support for the regulation strategy of the bioleaching of spent lithium-ion batteries to recover valuable metals.

Conductive magnetic nanowires accelerated electron transfer between C1020 carbon steel and Desulfovibrio vulgaris biofilm

Microbial biofilms are behind microbiologically influenced corrosion (MIC). Sessile cells in biofilms are many times more concentrated volumetrically than planktonic cells in the bulk fluids, thus providing locally high concentrations of chemicals. More importantly, "electroactive" sessile cells in biofilms are capable of utilizing extracellularly supplied electrons (e.g., from elemental Fe) for intracellular reduction of an oxidant such as sulfate in energy metabolism. MIC directly caused by anaerobic biofilms is classified into two main types based on their mechanisms: extracellular electron transfer MIC (EET-MIC) and metabolite MIC (M-MIC). Sulfate-reducing bacteria (SRB) are notorious for their corrosivity. They can cause EET-MIC in carbon steel, but they can also secrete biogenic H2S to corrode other metals such as Cu directly via M-MIC. This study investigated the use of conductive magnetic nanowires as electron mediators to accelerate and thus identify EET-MIC of C1020 by Desulfovibrio vulgaris. The presence of 40 ppm (w/w) nanowires in ATCC 1249 culture medium at 37 °C resulted in 45 % higher weight loss and 57 % deeper corrosion pits after 7-day incubation. Electrochemical tests using linear polarization resistance and potentiodynamic polarization supported the weight loss data trend. These findings suggest that conductive magnetic nanowires can be employed to identify EET-MIC. The use of insoluble 2 μm long nanowires proved that the extracellular section of the electron transfer process is a bottleneck in SRB MIC of carbon steel.

Surface roughness influence on extracellular electron microbiologically influenced corrosion of C1018 carbon steel by Desulfovibrio ferrophilus IS5 biofilm

Carbon steel microbiologically influenced corrosion (MIC) by sulfate reducing bacteria (SRB) is known to occur via extracellular electron transfer (EET). A higher biofilm sessile cell count leads to more electrons being harvested for sulfate reduction by SRB in energy production. Metal surface roughness can impact the severity of MIC by SRB because of varied biofilm attachment. C1018 carbon steel coupons (1.2 cm2 top working surface) polished to 36 grit (4.06 μm roughness which is relatively rough) and 600 grit (0.13 μm) were incubated in enriched artificial seawater inoculated with highly corrosive Desulfovibrio ferrophilus IS5 at 28 ℃ for 7 d and 30 d. It was found that after 7 d of SRB incubation, 36 grit coupons had a 11% higher sessile cell count at (2.0 ± 0.17) × 108 cells/cm2, 52% higher weight loss at 22.4 ± 5.9 mg/cm2 (1.48 ± 0.39 mm/a uniform corrosion rate), and 18% higher maximum pit depth at 53 μm compared with 600 grit coupons. However, after 30 d, the differences diminished. Electrochemical tests with transient information supported the weight loss data trends. This work suggests that a rougher surface facilitates initial biofilm establishment but provides no long-term advantage for increased biofilm growth.

[Salivary carcinoma showing thymus-like differentiation: clinicopathological analysis of 7 cases]

Objective: To analyze the clinicopathological features of salivary carcinoma showing thymus-like differentiation(CASTLE). Methods: Cases diagnosed with salivary CASTLE from January 2020 to December 2023 were collected and selected from the Department of Oral Pathology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine. A total of 7 cases of salivary CASTLE were identified. All the cases originated from parotid. There were 3 males and 4 females. The patients' age range was 11-70 years.The clinical, microscopic, immunohistochemical and prognostic features of these cases were analyzed. Results: The duration of disease ranged from 1 month to 1 year, and 1 patient had facial numbness and 1 with swelling sensation occasionally. Radiographically, 4 cases showed malignant signs. Microscopically, 4 cases involved in parotid gland, and all the tumors had different degrees of lymphoid tissue background. The tumor cells arranged in nests, 5 cases with lymphoepithelial carcinoma-like and 2 cases with squamous cell carcinoma morphology. The tumor cells expressed CD5 and CD117 proteins diffusely in lymphoepithelial carcinoma-like cases. However, the tumor cells expressed CD5 diffusely and CD117 focally in cases with squamous cell carcinoma morphology. All the cases had no Epstein-Barr virus infection. Among the 6 patients with follow-up information, all of them underwent postoperative radiotherapy, and none of them had local recurrence and lymph node metastasis. Conclusions: Salivary CASTLE is a rare tumor, it should be distinguished from lymphoepithelial carcinoma and squamous cell carcinoma. The patients often have better prognosis and CD5 protein expression has a valuable role in the differential diagnosis.

Mitigation of Desulfovibrio ferrophilus IS5 degradation of X80 carbon steel mechanical properties using a green biocide

Most microbiologically influenced corrosion (MIC) studies focus on the threat of pinhole leaks caused by MIC pitting. However, microbes can also lead to structural failures. Tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide mitigated the microbial degradation of mechanical properties of X80 steel pipeline by Desulfovibrio ferrophilus (IS5 strain), a very corrosive sulfate reducing bacterium. It was found that 100 ppm (w/w) THPS added to the enriched artificial seawater (EASW) culture medium before incubation resulted in 2.8-log reduction in sessile cell count after a 7-d incubation at 28 °C under anaerobic conditions, leading to 94% uniform corrosion rate reduction (from 1.3 to 0.07 mm/a), and 84% pitting corrosion rate reduction (from 0.70 to 0.11 mm/a). The X80 dogbone coupon incubated with 100 ppm THPS for 7 d suffered 3% loss in ultimate tensile strain and 0% loss in ultimate tensile strength compared with the abiotic control in EASW. In comparison, the no-treatment X80 dogbone coupon suffered losses of 13% in ultimate tensile strain and 6% in ultimate tensile stress, demonstrating very good THPS efficacy.

Filamentous marine Gram-positive Nocardiopsis dassonvillei biofilm as biocathode and its electron transfer mechanism

This study investigated electrochemical characteristics of Gram-positive, Nocardiopsis dassonvillei B17 facultative bacterium in bioelectrochemical systems. The results demonstrated that anodic and cathodic reaction rates were catalyzed by this bacterium, especially by utilization of aluminium alloy as a substrate. Cyclic voltammogram results depicted an increase of peak current and surface area through biofilm development, confirming its importance on catalysis of redox reactions. Phenazine derivatives were detected and their electron mediating behavior was evaluated exogenously. A symmetrical redox peak in the range of -59 to -159 mV/SHE was observed in cyclic voltammogram of bacterial solution supplemented with 12 μM phenazine, a result consistent with cyclic voltammogram of a 5-d biofilm, confirming its importance as an electron mediator in extracellular electron transfer. Furthermore, the dependency of bacterial catalysis and polarization potential were studied. These results suggested that B17 biofilm behaved as a biocathode and transferred electrons to bacterial cells through a mechanism associated with electron mediators.

Mitigation of galvanized steel biocorrosion by Pseudomonas aeruginosa biofilm using a biocide enhanced by trehalase

Pseudomonas aeruginosa is a facultative bacterium that is pathogenic. It is ubiquitous in the environment including air handling systems. It causes microbiologically influenced corrosion (MIC) aerobically and anaerobically. In this work, P. aeruginosa was grown as a nitrate reducing bacterium (NRB) in Luria-Bertani medium with KNO3 at 37 °C. Trehalase, an enzyme which plays a crucial role in biofilm formation was found to enhance the treatment of P. aeruginosa biofilm and its MIC against galvanized steel by tetrakis-hydroxymethyl phosphonium sulfate (THPS) green biocide. After a 7-d incubation, 30 ppm (w/w) trehalase reduced sessile cell count by 0.8-log, and it also reduced galvanized steel weight loss by 14%, compared to 2.3-log and 39%, respectively for the 30 ppm THPS treatment. The combination of 30 ppm THPS + 30 ppm trehalase reduced sessile cell count further by 0.1-log and weight loss by 13% compared to using THPS alone. Electrochemical corrosion measurements supported weight loss results. The injection of 20 ppm riboflavin into a 3-d P. aeruginosa broth failed to accelerate the corrosion rate, suggesting that nitrate reducing P. aeruginosa MIC of galvanized steel did not belong to extracellular electron transfer-MIC, because Zn was hydrolyzed after the microbe damaged the passive film.

Tests of Light-Lepton Universality in Angular Asymmetries of B^{0}→D^{*-}ℓν Decays

We present the first comprehensive tests of the universality of the light leptons in the angular distributions of semileptonic B^{0}-meson decays to charged spin-1 charmed mesons. We measure five angular-asymmetry observables as functions of the decay recoil that are sensitive to lepton-universality-violating contributions. We use events where one neutral B is fully reconstructed in ϒ(4S)→BB[over ¯] decays in data corresponding to 189  fb^{-1} integrated luminosity from electron-positron collisions collected with the Belle II detector. We find no significant deviation from the standard model expectations.

Microbially mediated metal corrosion

A wide diversity of microorganisms, typically growing as biofilms, has been implicated in corrosion, a multi-trillion dollar a year problem. Aerobic microorganisms establish conditions that promote metal corrosion, but most corrosion has been attributed to anaerobes. Microbially produced organic acids, sulfide and extracellular hydrogenases can accelerate metallic iron (Fe0) oxidation coupled to hydrogen (H2) production, as can respiratory anaerobes consuming H2 as an electron donor. Some bacteria and archaea directly accept electrons from Fe0 to support anaerobic respiration, often with c-type cytochromes as the apparent outer-surface electrical contact with the metal. Functional genetic studies are beginning to define corrosion mechanisms more rigorously. Omics studies are revealing which microorganisms are associated with corrosion, but new strategies for recovering corrosive microorganisms in culture are required to evaluate corrosive capabilities and mechanisms. Interdisciplinary studies of the interactions among microorganisms and between microorganisms and metals in corrosive biofilms show promise for developing new technologies to detect and prevent corrosion. In this Review, we explore the role of microorganisms in metal corrosion and discuss potential ways to mitigate it.

Precise Measurement of the D_{s}^{+} Lifetime at Belle II

We measure the lifetime of the D_{s}^{+} meson using a data sample of 207  fb^{-1} collected by the Belle II experiment running at the SuperKEKB asymmetric-energy e^{+}e^{-} collider. The lifetime is determined by fitting the decay-time distribution of a sample of 116×10^{3} D_{s}^{+}→ϕπ^{+} decays. Our result is τ_{D_{s}^{+}}=(499.5±1.7±0.9)  fs, where the first uncertainty is statistical and the second is systematic. This result is significantly more precise than previous measurements.

High Dose Hyperfractionated Thoracic Radiotherapy vs. Standard Dose for Limited Stage Small-Cell Lung Cancer: A Multicenter, Open-Label Randomized, Phase 3 Trial

PURPOSE/OBJECTIVE(S)

Limited stage small-cell lung cancer (LS-SCLC) is associated with poor prognosis. We aimed to assess the efficacy and safety of high-dose, hyperfractionated thoracic radiotherapy of 54 Gy in 30 fractions compared with standard dose (45 Gy in 30 fractions) as a first-line treatment for LS-SCLC.

MATERIALS/METHODS

The study was an open-label, randomized, phase 3 trial, done at 16 public hospitals in China. Key inclusion criteria were patients aged 18-70 years, with previously histologically or cytologically confirmed LS-SCLC, previously untreated or received 1-2 courses of intravenous cisplatin (75 mg/m²of body-surface area, on day 1 or divided into two days of each cycle) or carboplatin (area under the curve of 5 mg/mL per min, day 1 of each cycle)and intravenous etoposide (100 mg/m²of body-surface area, on days 1-3 of each cycle), and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.Eligible patients were randomly assigned (1:1) to receive volumetric-modulated arc radiotherapy (VMAT) of 45 Gy in 30 fractions or the simultaneous integrated boost VMAT (SIB-VMAT) of 54 Gy in 30 fractions to the primary lung tumor and lymph node metastases starting 0-42 days after the first chemotherapy course. Both groups of patients received thoracic radiotherapy twice per day and 10 fractions per week. Prophylactic cranial radiation (PCI, 25 Gy in 10 fractions) was implemented to patients with responsive disease. The primary endpoint was overall survival. Safety was analyzed in the as-treated population.

RESULTS

Between June 30, 2017, and April 6, 2021, 224 eligible patients were enrolled and randomly assigned to 54 Gy (n = 108) or 45 Gy (n = 116). Median follow-up for the primary analysis was 45 months (IQR 41-48). Median overall survival was significantly improved in the 54 Gy group (62.4 months) compared with the 45 Gy group (43.1 months; p = 0.001). Median progression-free survival was significantly improved in the 54 Gy group (30.5 months) compared with the 45 Gy group (16.7 months; p = 0.044). The most common grade 3-4 adverse events were neutropenia (30 [28%] of 108 patients in the 54 Gy group vs 27 [23%] of 116 patients in the 45 Gy group), neutropenic infections (6 [6%] vs 2 [2%]), thrombocytopenia (13 [12%] vs 12 [10%]), anemia (6 [6%] vs 4 [3%]), and esophagitis (1 [1%] vs 3 [3%]). Treatment-related serious adverse events occurred in 9 [8%] patients in the 54 Gy group and 16 [14%] patients in the 45 Gy group. There were one treatment-related deaths in 54 Gy group (myocardial infarction).

CONCLUSION

Compared with standard thoracic radiotherapy dose of 45 Gy, the high dose of 54 Gy improved overall survival and progression-free survival without increasing toxicities in patients with LS-SCLC, supporting twice-daily hyperfractionated thoracic radiotherapy of 54 Gy with concurrent chemotherapy is an alternative treatment option for LS-SCLC. This study is complete and registered with ClinicalTrials.gov, NCT03214003.

Search for a τ^{+}τ^{-} Resonance in e^{+}e^{-}→μ^{+}μ^{-}τ^{+}τ^{-} Events with the Belle II Experiment

We report the first search for a nonstandard-model resonance decaying into τ pairs in e^{+}e^{-}→μ^{+}μ^{-}τ^{+}τ^{-} events in the 3.6-10  GeV/c^{2} mass range. We use a 62.8  fb^{-1} sample of e^{+}e^{-} collisions collected at a center-of-mass energy of 10.58 GeV by the Belle II experiment at the SuperKEKB collider. The analysis probes three different models predicting a spin-1 particle coupling only to the heavier lepton families, a Higgs-like spin-0 particle that couples preferentially to charged leptons (leptophilic scalar), and an axionlike particle, respectively. We observe no evidence for a signal and set exclusion limits at 90% confidence level on the product of cross section and branching fraction into τ pairs, ranging from 0.7 to 24 fb, and on the couplings of these processes. We obtain world-leading constraints on the couplings for the leptophilic scalar model for masses above 6.5  GeV/c^{2} and for the axionlike particle model over the entire mass range.

Measurement of CP Violation in B^{0}→K_{S}^{0}π^{0} Decays at Belle II

We report a measurement of the CP-violating parameters C and S in B^{0}→K_{S}^{0}π^{0} decays at Belle II using a sample of 387×10^{6}  BB[over ¯] events recorded in e^{+}e^{-} collisions at a center-of-mass energy corresponding to the ϒ(4S) resonance. These parameters are determined by fitting the proper decay-time distribution of a sample of 415 signal events. We obtain C=-0.04_{-0.15}^{+0.14}±0.05 and S=0.75_{-0.23}^{+0.20}±0.04, where the first uncertainties are statistical and the second are systematic.

[Analysis of clinicopathological characteristics of IgG4-related sialadenitis]

Objective: To analyze the clinicopathological characteristics of IgG4-related sialadenitis (IgG4-RS). Methods: A total of 40 cases diagnosed with IgG4-RS were collected from the Department of Oral Pathology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from January 2019 to December 2022. Among them, there were 26 males and 14 females. The age range was 29-77 years old [(59.4±11.8) years old], with 23 patients being older than 60 years. The lesion site, imaging manifestations, histopathological features, serological test and treatment information of patients were collected. The expression of IgG4 and IgG proteins was detected by immunohistochemistry. Results: Submandibular region swelling was the most common initial symptom of IgG4-RS (38/40, 95.0%). All the patients having serum IgG4 levels> 1.35 g/L. Serum IgG4 levels were significantly increased in patients aged>60 years (Z=-2.45, P=0.014) and those involving multiple glands (Z=-2.04, P=0.042). Thirty six cases received major salivary gland biopsy, and all the cases showed dense lymphocyte and plasma cell infiltration. Lymphoid follicle, storiform fibrosis and obliterative phlebitis were seen in 88.9% (32/36), 63.9% (23/36), 30.6% (11/36) of the cases, respectively. Twenty one cases received labial salivary gland biopsy, 66.7% (14/21) showed lymphocyte and plasma cell infiltration, 19.0% (4/21) had lymphoid follicle structures, and 33.3% (7/21) showed no obvious histological abnormalities. No signs of fibrosis or obliterative phlebitis were observed in all labial salivary gland biopsies. And 95.0% (38/40) of cases had IgG4 positive plasma cell>10/HPF, 82.5% (33/40) of cases had IgG4/IgG positive plasma cell ratio>40%. All the patients had a decrease in serum IgG4 levels after glucocorticoid treatment, but only 21.4% (6/28) of cases had reduced to normal levels (≤1.35 g/L), and there were still significant fluctuations in serum IgG4 levels thereafter. Conclusions: IgG4-RS has a predilection for middle-aged and elderly male patients, and serum IgG4 levels are significantly related to the patient's age and whether multiple glands are involved. Labial salivary gland biopsy cannot replace submandibular gland for histopathological evaluation. It is a common phenomenon that serum IgG4 levels cannot restored to normal levels after glucocorticoid treatment. This study provides certain assistance for clinical and pathological diagnosis of IgG4-RS. This study is beneficial for further understanding IgG4-RS and improving the clinical and pathological diagnosis of the disease.

Test of Light-Lepton Universality in the Rates of Inclusive Semileptonic B-Meson Decays at Belle II

We present the first measurement of the ratio of branching fractions of inclusive semileptonic B-meson decays, R(X_{e/μ})=B(B→Xeν)/B(B→Xμν), a precision test of electron-muon universality, using data corresponding to 189  fb^{-1} from electron-positron collisions collected with the Belle II detector. In events where the partner B meson is fully reconstructed, we use fits to the lepton momentum spectra above 1.3  GeV/c to obtain R(X_{e/μ})=1.007±0.009(stat)±0.019(syst), which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation.

Electrochemical Assessment of Mitigation of Desulfovibrio ferrophilus IS5 Corrosion against N80 Carbon Steel and 26Cr3Mo Steel Using a Green Biocide Enhanced by a Nature-Mimicking Biofilm-Dispersing Peptide

MIC (microbiologically influenced corrosion) is problematic in many industries, especially in the oil and gas industry. In this work, N80 carbon steel for pipelines was tested with 26Cr3Mo chromium pipeline steel for comparison in SRB (sulfate-reducing bacterium) MIC mitigation using a THPS (tetrakis hydroxymethyl phosphonium sulfate)-based commercial biocide (Biotreat 5475 with 75-80% THPS by mass). Peptide A, a nature-mimicking synthetic cyclic peptide (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with biofilm dispersal ability was used as a biocide enhancer. Metal coupons covered with 3-d old Desulfovibrio ferrophilus IS5 biofilms were immersed in different biocide solutions. After 1-h treatment, 200 ppm Biotreat 5475, 200 ppm Biotreat 5475 + 200 nM (360 ppb) Peptide A, and 400 ppm Biotreat 5475 achieved 0.5-log, 1.7-log and 1.9-log reductions in sessile cell count on N80, and 0.7-log, 1.7-log, and 1.8-log on 26Cr3Mo, respectively. The addition of 200 nM Peptide A cut the THPS biocide dosage by nearly half. Biocide injection tests in electrochemical glass cells after 1 h exhibited 15%, 70%, and 72% corrosion inhibition efficiency (based on corrosion current density) on N80, and 27%, 79%, 75% on 26Cr3Mo, respectively. Linear polarization resistance and electrochemical impedance spectrometry results also indicated antimicrobial efficacies.

First Measurement of the Michel Parameter ξ^{'} in the τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} Decay at Belle

We report the first measurement of the Michel parameter ξ^{'} in the τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} decay with a new method proposed just recently. The measurement is based on the reconstruction of the τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} events with subsequent muon decay in flight in the Belle central drift chamber. The analyzed data sample of 988  fb^{-1} collected by the Belle detector corresponds to approximately 912×10^{6} τ^{+}τ^{-} pairs. We measure ξ^{'}=0.22±0.94(stat)±0.42(syst), which is in agreement with the standard model prediction of ξ^{'}=1. Statistical uncertainty dominates in this study, being a limiting factor, while systematic uncertainty is well under control. Our analysis proved the practicability of this promising method and its prospects for further precise measurement in future experiments.

Search for the Lepton Flavor Violating Decays B^{+}→K^{+}τ^{±}ℓ^{∓} (ℓ=e, μ) at Belle

We present a search for the lepton flavor violating decays B^{+}→K^{+}τ^{±}ℓ^{∓}, with ℓ=(e,μ), using the full data sample of 772×10^{6}  BB[over ¯] pairs recorded by the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode. We find no evidence for B^{±}→K^{±}τℓ decays and set upper limits on their branching fractions at the 90% confidence level in the (1-3)×10^{-5} range. The obtained limits are the world's best results.

Search for an Invisible Z^{'} in a Final State with Two Muons and Missing Energy at Belle II

The L_{μ}-L_{τ} extension of the standard model predicts the existence of a lepton-flavor-universality-violating Z^{'} boson that couples only to the heavier lepton families. We search for such a Z^{'} through its invisible decay in the process e^{+}e^{-}→μ^{+}μ^{-}Z^{'}. We use a sample of electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019-2020, corresponding to an integrated luminosity of 79.7  fb^{-1}. We find no excess over the expected standard-model background. We set 90%-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from 3×10^{-3} at low Z^{'} masses to 1 at Z^{'} masses of 8  GeV/c^{2}.

Copper recovery from printed circuit boards leaching solution with bioelectricity generation using microbial fuel cell

Recovery of valuable metals via leaching printed circuit boards (PCBs) has gained moment recently. This work studied the Microbial fuel cell (MFC) performances for recovery of Cu from a Cu²⁺ solution by examining key operating parameters. A dual-chamber MFC with 6 cm × 6 cm × 7 cm dimensions was constructed. Both anode and cathode electrodes were made of a carbon cloth sheet. The anodic and cathodic chambers were separated by a Nafion membrane. The highest Cu recovery efficiency was 99.7% after 240 h batch mode operation, yielding 102 mW/m² MFC power density output using 1 g/L Cu²⁺ solution as the catholyte (initial pH 3) and an anolyte containing 1 g/L sodium acetate inoculated with a sludge from a wastewater treatment plant's anaerobic pond, with 2 cm distance between the electrodes made of polyacrylonitrile polymer. The highest open circuit voltage, current density (based on cross-section cathode area) and power density with an external load of 1 kΩ was 555 mV, 347 mA/m² and 193 mW/m², respectively. Additionally, recovery of Cu in the leachate of PCBs using sulfuric acid leaching after 48 h was performed and the highest Cu recovery was 50% in 48 h.

First Measurement of the B^{+}→π^{+}π^{0}π^{0} Branching Fraction and CP Asymmetry

We study B^{+}→π^{+}π^{0}π^{0} using 711  fb^{-1} of data collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We measure an inclusive branching fraction of (19.0±1.5±1.4)×10^{-6} and an inclusive CP asymmetry of (9.2±6.8±0.7)%, where the first uncertainties are statistical and the second are systematic, and a B^{+}→ρ(770)^{+}π^{0} branching fraction of (11.2±1.1±0.9_{-1.6}^{+0.8})×10^{-6}, where the third uncertainty is due to possible interference with B^{+}→ρ(1450)^{+}π^{0}. We present the first observation of a structure around 1  GeV/c^{2} in the π^{0}π^{0} mass spectrum, with a significance of 6.4σ, and measure a branching fraction to be (6.9±0.9±0.6)×10^{-6}. We also report a measurement of local CP asymmetry in this structure.

Search for Lepton-Flavor-Violating τ Decays to a Lepton and an Invisible Boson at Belle II

We search for lepton-flavor-violating τ^{-}→e^{-}α and τ^{-}→μ^{-}α decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8  fb^{-1}, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ^{-}→e^{-}ν[over ¯]_{e}ν_{τ} and τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ^{-}→e^{-}α)/B(τ^{-}→e^{-}ν[over ¯]_{e}ν_{τ}) in the range (1.1-9.7)×10^{-3} and on B(τ^{-}→μ^{-}α)/B(τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ}) in the range (0.7-12.2)×10^{-3} for α masses between 0 and 1.6  GeV/c^{2}. These results provide the most stringent bounds on invisible boson production from τ decays.