Global, regional, and national burden of intestinal obstruction from 1990 to 2019: an analysis from the Global Burden of Disease Study 2019.

BACKGROUND: Intestinal obstruction (IO) is a common surgical acute abdominal condition that places a significant burden on modern health systems. Unfortunately, the global burden and trends of IO remain unknown. Therefore, this study aimed to comprehensively assess its long-term trends and epidemiological features, which will help policymakers to formulate appropriate health policies. METHODS: We conducted an ecological study using data from the Global Burden of Disease Study (GBD) 2019. Data on IO were analyzed by sex, age, year, sociodemographic index (SDI), and location according to GBD 2019. In addition, joinpoint regression analysis was used to assess temporal trends. Age-period-cohort analysis (APC Analysis) was conducted to evaluate age, period, and birth cohort effects on IO incidence and mortality risk. RESULTS: Globally, the prevalent and incident cases increased by 56.91% and 86.67% from 1990 to 2019, respectively. Joinpoint regression analysis showed that age-standardized incidence rate (ASIR) and age-standardized prevalence rate (ASPR) increased, but age-standardized mortality rate (ASMR) and age-standardized disability-adjusted life year (DALY) rate decreased over the past three decades. The age effect demonstrated that older people have a higher risk of morbidity and mortality. The period effect of incidence and mortality showed an upward trend from 1990 to 2019. Cohort effect revealed that the incidence and death risk peaked in the earlier-born cohort and was lower in the more recent-born cohort. Notably, we found that the burden of IO was higher in males than in females throughout the study period. There are huge disparities in IO burden among countries. CONCLUSION: Globally, the reported incidence and prevalence of IO increased from 1990 to 2019. The burden of IO differed markedly by age, sex, country, and region. Middle-aged and elderly people over 50 years old were at high risk. Given the ageing population, the burden of IO will be a major public health challenge. Thus, there is a strong necessity to strengthen prevention and early intervention in the at-risk population.

Knowledge and willingness toward SARS-CoV-2 rapid antigen testing among older adults in China: a nationwide cross-sectional study.

BACKGROUND AND AIMS: The end of the zero-COVID-19 policy placed a large number of older adults in China at increased risk of COVID-19 infection. SARS-CoV-2 rapid antigen testing (RAT) is a promising tool for scaling up testing and ensuring that patient management and public health measures can be implemented without delay. We aimed to understand the knowledge and willingness of RAT, and its correlates among older adults in China. METHODS: A nationwide cross-sectional survey on knowledge and willingness about RAT among older adults in China was conducted between January 14 and 28, 2023, shortly after the end of the zero-COVID-19 policy. An online questionnaire was used to collect information on sociodemographic characteristics, health characteristics, sources to access RAT information, and attitudes toward COVID-19 and its RAT. Logistic regression was used to assess correlates of knowledge of RAT and willingness to take RAT among older adults. RESULTS: A total of 1030 older adults (494 women and 536 men, mean age 68.7 ± 7.0 years) were recruited. 49.4% of the participants had a high level of RAT knowledge. After adjusting for sociodemographic characteristics, chronic diseases (0.70, 0.49-0.99), learning RAT from new media (5.46, 3.48-8.68) and traditional media (3.35, 2.13-5.34), and perceiving RAT as convenient (4.03, 2.80-5.85) were associated with levels of RAT knowledge. 53.3% of the participants were willing to take RAT. After adjusting for sociodemographic characteristics, learning RAT from new media (8.46, 5.26-14.0) and traditional media (1.63, 1.04-2.55), perceiving RAT as convenient (2.97, 2.10-4.22), and worrying about (re)infection with COVID-19 (2.12, 1.55-2.92) were associated with willingness to take RAT. CONCLUSION: The levels of RAT knowledge and willingness to take RAT among older adults in China may hinder the scale-up of RAT. Health education about RAT should be strengthened among older adults. Special efforts should be made to integrate traditional and new media to promote RAT among older adults, specifically, for virus susceptibility and the convenience of RAT. Given the reopening of society, our study could inform our response to future novel infectious diseases and aid in the timely scale-up of RAT.

Polycephalums A and B, New Anticoagulant Constituents Isolated from Clinopodium polycephalum.

Two previously undescribed compounds (1 and 2) were isolated from Clinopodium polycephalum, a medicinal plant distributed in southwestern and eastern China. Their structures were elucidated using MS analyses and extensive 2D-homo and heteronuclear NMR data interpretations. Both compounds 1 and 2 could significantly shorten APTT and PT, and their procoagulant effect was comparable to that of positive drugs. At the same time, compound 2 had certain antioxidant activity (IC50 value of 2.25±0.05 µM in ABTS assay).

Outage Performance Analysis of Improper Gaussian Signaling for Two-User Downlink NOMA Systems with Imperfect Successive Interference Cancellation.

The improper Gaussian signaling (IGS) technique can improve the achievable rate of an interference-limited network by fully exploiting the second-order statistics of complex signaling. This paper addresses the outage performance analysis of a two-user downlink non-orthogonal multiple access (NOMA) system using the IGS technique in the presence of imperfect successive interference cancellation (SIC). The strong channel user (SU) adopts the IGS, while the weak channel user (WU) adopts the traditional proper Gaussian signaling (PGS). Considering a practical scenario where the transmitter has obtained the statistics of the channel coefficients instead of the instantaneous channel state information (CSI), the expressions of the achievable rates of both users under residual interference due to imperfect SIC are derived, together with their outage probabilities, subject to predetermined target rates and channel statistics. Given a fixed transmit power of the WU, both the transmit power and the degree of impropriety of the SU are optimized to minimize the outage probability subject to the outage constraint of the WU. Numerical results are provided to assess the benefits of the proposed IGS-based downlink NOMA system, which are consistent with the analysis.

High-performance one-dimensional MOSFET array photodetectors in the 0.8-µm standard CMOS process.

This paper reports a series of novel photodetectors based on one-dimensional array of metal-oxide-semiconductor field-effect transistors (MOSFETs), which were fabricated using the standard 0.8-µm complementary metal oxide semiconductor (CMOS) process. Normally, the metal fingers of MOSFET must be manufactured above active region in standard CMOS process, causing MOSFET insensitive to light. The proposed photodetectors use the metal fingers of MOSFETs in a one-dimensional array to form periodical slit structures, which make the transmittance of incident light higher, due to the surface plasmons (SPs) resonance effect. The number of parallel MOSFETs in one-dimensional array is 3, 5, 7, 9 and 11. The experimental results show that all responsivities (Rv) are greater than 103 A/W within visible and near-infrared spectra under room temperature and a maximum value of 1.40 × 105 A/W is achieved, which is at least one order of magnitude larger than those of published photodetectors. Furthermore, a minimum noise equivalent power (NEP) of 5.86 fW/Hz0.5 at 30 Hz and a maximum detectivity (D*) of 2.21 × 1013 Jones are obtained. The photodetectors still have good signal-to-noise ratio when the bandwidth is 1 GHz. At the same time, the optical scanning imaging was completed by utilizing the photodetectors. This combination of high Rv, excellent NEP, high speed and broad spectrum range photodetectors will be widely used in imaging systems.

High-responsivity photodetector using a grating-gate MOSFET in the 0.8-µm standard CMOS process.

This letter reports a novel photodetector based on a metal-oxide-semiconductor field-effect transistor with a grating-gate structure, which was fabricated by employing the standard 0.8-µm complementary metal-oxide-semiconductor process. The use of a periodical slit structure allows the channel to be generated and exposed on the shallow surface, which makes the transmission and absorption of incident light more efficient, due to the surface plasmon resonance effect. The experimental results show that a responsivity (Rv) greater than 100 A/W was achieved within visible and near-infrared spectra under room temperature. Furthermore, a minimum noise equivalent power of 8.2 fW/Hz0.5 at 15 Hz and a maximum detectivity (D*) of 1.7 × 1012 Jones were obtained. It is believed that the photodetector will be widely used in communication or imaging systems.

Association between Predicted Effects of TP53 Missense Variants on Protein Conformation and Their Phenotypic Presentation as Li-Fraumeni Syndrome or Hereditary Breast Cancer.

Rare germline pathogenic TP53 missense variants often predispose to a wide spectrum of tumors characterized by Li-Fraumeni syndrome (LFS) but a subset of variants is also seen in families with exclusively hereditary breast cancer (HBC) outcomes. We have developed a logistic regression model with the aim of predicting LFS and HBC outcomes, based on the predicted effects of individual TP53 variants on aspects of protein conformation. A total of 48 missense variants either unique for LFS (n = 24) or exclusively reported in HBC (n = 24) were included. LFS-variants were over-represented in residues tending to be buried in the core of the tertiary structure of TP53 (p = 0.0014). The favored logistic regression model describes disease outcome in terms of explanatory variables related to the surface or buried status of residues as well as their propensity to contribute to protein compactness or protein-protein interactions. Reduced, internally validated models discriminated well between LFS and HBC (C-statistic = 0.78-0.84; equivalent to the area under the ROC (receiver operating characteristic) curve), had a low risk for over-fitting and were well calibrated in relation to the known outcome risk. In conclusion, this study presents a phenotypic prediction model of LFS and HBC risk for germline TP53 missense variants, in an attempt to provide a complementary tool for future decision making and clinical handling.

[A multicenter study of the birth condition of preterm infants and the causes of preterm birth in Henan Province, China].

OBJECTIVE: To investigate the birth condition of preterm infants and the causes of preterm birth in Henan Province, China, and to provide a basis for the prevention and treatment of preterm birth. METHODS: An epidemiological investigation was conducted for live-birth preterm infants who were born in 53 hospitals in 17 cities of Henan Province from January 1, 2019 to December 31, 2019 to investigate the incidence rate of preterm birth, the distribution of gestational age and birth weight, the use of antenatal glucocorticoids, and the causes of preterm birth. RESULTS: The incidence rate of preterm birth was 5.84% (12 406/212 438) in the 53 hospitals. The proportions of preterm infants with gestational ages of < 28 weeks, 28 - < 32 weeks, 32 - < 34 weeks, and 34 - < 37 weeks were 1.58% (196/12 406), 11.46% (1 422/12 406), 15.18% (1 883/12 406), and 71.78% (8 905/12 406) respectively. The proportions of preterm infants with birth weights of < 1 000 g, 1 000- < 1 500 g, 1 500- < 2 500 g, 2 500- < 4 000 g, and ≥ 4 000 g were 1.95% (240/12 313), 8.54% (1 051/12 313), 49.53% (6 099/12 313), 39.59% (4 875/12 313), and 0.39% (48/12 313) respectively. The infants born by natural labor accounted for 28.76% (3 568/12 406), and those born by cesarean section accounted for 70.38% (8 731/12 406). The rate of use of antenatal glucocorticoids was 52.52% (6 293/11 983) for preterm infants and 68.69% (2 319/3 376) for the preterm infants with a gestational age of < 34 weeks. Iatrogenic preterm labor was the leading cause of preterm birth[40.06% (4 915/12 270)], followed by spontaneous preterm birth[30.16% (3 701/12 270)] and preterm birth due to premature rupture of membranes[29.78% (3 654/12 270)]. The top three causes of iatrogenic preterm birth were hypertensive disorders of pregnancy[47.12% (2 316/4 915)], fetal intrauterine distress[22.85% (1 123/4 915)], and placenta previa/placental abruption[18.07% (888/4 915)]. CONCLUSIONS: There is a relatively low incidence rate of preterm birth in Henan Province, and late preterm infants account for a relatively high proportion. Iatrogenic preterm birth is the main cause of preterm birth in Henan Province, and hypertensive disorders of pregnancy and fetal intrauterine distress are the main causes of iatrogenic preterm birth.

Three-Dimensional Graphene Field-Effect Transistors as High-Performance Photodetectors.

Graphene is an ideal material for high-performance photodetectors because of its superior electronic and optical properties. However, graphene's weak optical absorption limits the photoresponsivity of conventional photodetectors based on planar (two-dimensional or 2D) back-gated graphene field-effect transistors (GFETs). Here, we report a self-rolled-up method to turn 2D buried-gate GFETs into three-dimensional (3D) tubular GFETs. Because the optical field inside the tubular resonant microcavity is enhanced and the light-graphene interaction area is increased, the photoresponsivity of the resulting 3D GFETs is significantly improved. The 3D GFET photodetectors demonstrated room-temperature photodetection at ultraviolet, visible, mid-infrared, and terahertz (THz) regions, with both ultraviolet and visible photoresponsivities of more than 1 A W-1 and photoresponsivity of 0.232 A W-1 at 3.11 THz. The electrical bandwidth of these devices exceeds 1 MHz. This combination of high photoresponsivity, a broad spectral range, and high speed will lead to new opportunities for 3D graphene optoelectronic devices and systems.

[Risk factors for poor prognosis of neonatal bacterial meningitis].

OBJECTIVE: To investigate the risk factors for poor prognosis of neonatal bacterial meningitis. METHODS: A retrospective analysis was performed for the clinical data of 152 children with neonatal bacterial meningitis. According to their prognosis, they were divided into a good prognosis group with 122 children and a poor prognosis group with 30 children. The two groups were compared in terms of general status, initial symptoms, and laboratory findings, and the risk factors for poor prognosis were analyzed. RESULTS: Compared with the good prognosis group, the poor prognosis group had a significantly higher proportion of children with a very low birth weight, a peripheral blood white blood cell count (WBC) of <5×109/L or >20×109/L, a C-reactive protein level of >50 mg/L, a cerebrospinal fluid (CSF) WBC of >500×106/L, a CSF glucose level of <1 mmol/L, or a CSF protein level of >2 g/L, as well as significantly higher positive rates of blood culture and/or CSF culture, Gram-positive bacteria, and Streptococcus agalactiae (P<0.05). The multivariate logistic regression analysis showed that a CSF glucose level of <1 mmol/L and a CSF protein level of >2 g/L were independent risk factors for poor prognosis of neonatal bacterial meningitis. CONCLUSIONS: A CSF glucose level of <1 mmol/L and a CSF protein level of >2 g/L are risk factors for poor prognosis of neonatal bacterial meningitis.

Photophysical/Chemistry Properties of Distyryl-BODIPY Derivatives: An Experimental and Density Functional Theoretical Study.

Singlet oxygen is the key element for photodynamic therapy. In this paper, six novel distyryl-BODIPY compounds were synthesized and investigated in detail to fully evaluate their photophysical/chemistry characteristics. Specially, the singlet oxygen (1O2) quantum yield of compounds 2 and 4 each bearing two bromine atoms in their skeleton revealed the position effect of heavy atom for 1O2 production. The 1O2 quantum yield of 4, which was brominated at 2/6 position of BODIPY skeleton, was much higher than that of compound 2, brominated at styryl group with a long distance toward BODIPY core. Importantly, theoretical calculations were carried out to elaborate the essential reason for the difference of 2 and 4 by investigating intersystem crossing rate.

Pathogenesis of Abnormal Hepatic Lipid Metabolism Induced by Chronic Intermittent Hypoxia in Rats and the Therapeutic Effect of N-Acetylcysteine.

BACKGROUND The pathogenesis of chronic intermittent hypoxia (CIH)-induced abnormal hepatic lipid metabolism in rats remains unclear. Here, we investigated the therapeutic effect of N-acetylcysteine (NAC) on abnormal hepatic lipid metabolism. MATERIAL AND METHODS Rats were subjected to hypoxia and NAC treatment, and evaluated in terms of hepatic lipid metabolism, hepatocyte ultrastructure, oxidative stress in hepatocytes, expression of nuclear factor-kappa B (NF-κB) and inflammatory cytokines (IL-1ß, IL-6, and TNFα), serum lipoprotein lipase (LPL) levels, and blood lipids (triglycerides and cholesterol). RESULTS Compared to the normoxic control group, animals in the hypoxic model group showed significant body weight gain; abnormal hepatic lipid metabolism; lipid vacuolization; accumulation of lipid droplets; abundant autophagosomes and lysosomes; significant increases in oxidative stress, inflammation level, and blood lipid levels; and significantly reduced LPL levels. Compared to control animals, rats in the treatment group exhibited normal body weight gain, improved lipid metabolism, fewer lipid droplets, alleviated ultrastructural injuries, decreased oxidative stress and inflammation level, as well as elevated LPL and reduced blood lipid levels. CONCLUSIONS The harmful effects of CIH on rat liver are possibly associated with the reactive oxygen species (ROS)/NF-κB signaling pathway. NAC is capable of attenuating lipid metabolism alterations and abnormal body weight gain in the CIH rat model, via a possible mechanism related to inhibition of ROS/NF-κB signaling.

[A comparison study of diagnostic value between the old and revised guidelines in patients with idiopathic pulmonary fibrosis].

OBJECTIVE: To compare the strengths and limitations of the old and revised guidelines for the diagnosis in patients with idiopathic pulmonary fibrosis(IPF). METHODS: Patients who were admitted and diagnosed as interstitial lung diseases (ILDs) in our hospital from 2009 to 2014 were enrolled in our study.Eachpatient was reevaluated respectively according to the old and revised guidelines of IPF. RESULTS: A total of 553 cases were initially reviewed, among whom 355 cases were excluded for pulmonary fibrosis secondary to definite underlying diseases, 28 excluded due to high resolution computed tomography(HRCT) not done, 26 excluded because serum immunology examination was not available.The remaining 144 cases were finally enrolled in this study including 92 males and 52 females with median age 21-92 (68 ± 11) years old. Twenty five patients (17.4%, 25/144) met the diagnostic criteria of IPF by the old guideline.While by the revised guideline, 53 patients (36.8%, 53/144) were diagnosed as classical IPF, 29 patients(20.1%, 29/144) as probable cases, another 69 non-IPF patients accounting for 43.1% (62/144). The result revealed that there's a significant difference between the two guidelines in the diagnosis of IPF. CONCLUSIONS: The revised guideline favors an early diagnosis of IPF and simplifies the diagnostic process.However the possibility of over diagnosis or missed diagnosis by the revised guideline does exist.On the other hand, despite of the delayed diagnosis by the old guideline, it may reduce the misdiagnosis of IPF in some circumstance.

[Determination of Trace Germanium in Plant Samples by Dry Ashing-Atomic Fluorescence Spectrometry].

To reduce the limit of detection (LOD) and allow the accurate determination of Ge, a dry ashing method was performed to enrich the Ge in plant samples. A method for the determination.of trace Ge in plant samples by HG-AFS was established. Study of the effect of temperature on the ashing of plant samples showed that no volatile loss of Ge occurred even at 900 °C. Additional experiments indicated that a 4 h burning process at 600 °C would be sufficient to fully ash the plant samples. Various digestion methods (involving nitric acid, hydrofluoric acid, and sulfuric acid digestion methods) for ashed samples were investigated. High-temperature ashing with large sample weights was used, which could reduce the reagent doses and the method's LOD effectively and simultaneously, the precision of the method was improved. The method's LOD was 0.27 ng · g(-1), and the relative standard deviation was 3.99%-6.81%. Verified with national biological reference materials (grade I), the proposed method was accurate and reliable.

Identification and characterization of a pab gene cluster responsible for the 4-aminobenzoate degradation pathway, including its involvement in the formation of a γ-glutamylated intermediate in Paraburkholderia terrae strain KU-15.

Paraburkholderia terrae strain KU-15 grows on 2- and 4-nitrobenzoate and 2- and 4-aminobenzoate (ABA) as the sole nitrogen and carbon sources. The genes responsible for the potential degradation of 2- and 4-nitrobenzoate and 2-ABA have been predicted from its genome sequence. In this study, we identified the pab operon in P. terrae strain KU-15. This operon is responsible for the 4-ABA degradation pathway, which involves the formation of a γ-glutamylated intermediate. Reverse transcription-polymerase chain reaction revealed that the pab operon was induced by 4-ABA. Herein, studying the deletion of pabA and pabB1 in strain KU-15 and the examining of Escherichia coli expressing the pab operon revealed the involvement of the operon in 4-ABA degradation. The first step of the degradation pathway is the formation of a γ-glutamylated intermediate, whereby 4-ABA is converted to γ-glutamyl-4-carboxyanilide (γ-GCA). Subsequently, γ-GCA is oxidized to protocatechuate. Overexpression of various genes in E. coli and purification of recombinant proteins permitted the functional characterization of relevant pathway proteins: PabA is a γ-GCA synthetase, PabB1-B3 functions in a multicomponent dioxygenase system responsible for γ-GCA dioxygenation, and PabC is a γ-GCA hydrolase that reverses the formation of γ-GCA by PabA.

Non-covalent interactions between rice protein and three polyphenols and potential application in emulsions.

Rice protein (RP) and polyphenols are often used in functional foods. This study investigated the non-covalent interactions between RP and three polyphenols (curcumin, CUR; quercetin, QUE; resveratrol, RES) and used the complexes as emulsifiers to create emulsions. Three polyphenols interacted with RP to varying extents, with QUE showing the greatest binding affinity and inducing the greatest alterations in its secondary structure. Molecular docking analysis elucidated the driving forces between them including hydrophobic interactions, hydrogen bonding, and van der Waals forces. Combination with QUE or RES induced structural changes of RP, increasing particle size of complexes. The synergistic effect of polyphenols and protein also enhanced radical scavenging capacity of complexes. Compared to pure protein, all complexes successfully created emulsions with smaller particle size (378-395 nm vs. 470 nm), higher absolute potential (37.43-38.26 mV vs. 35.62 mV), and greater lipid oxidation stability by altering protein conformation.

Impact of rGO modified with FAS on corrosion protection performance of inorganic phosphate bonded coating.

In this paper, inorganic phosphate bonded coatings (IPBCs) via embedding reduced graphene oxide (rGO) modified with heptadecafluoro-1,1,2,2-tetradecyl trimethoxysilane (FAS) were prepared through sol-gel method. Aim of this paper is to research the corrosion resistance of IPBCs with the addition of rGO modified with FAS. Firstly, the Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman) and surface morphology of GO and rGO modified with and without FAS were characterized. Results indicated that the hydrophobic -CF2- and -CF3 groups were successfully introduced into GO and rGO after modification. And IPBCs with rGO-FAS exhibited higher hydrophobicity and corrosion resistance than IPBCs with the addition of GO or GO-FAS. That is because the hydrophobicity and the introduction of low surface energy material is conducive to overcoming the interaction of rGO itself, thus rGO can be better utilized and played, which resulting the excellent corrosion performance of IPBC@rGO-FAS.

Plastic takeaway food containers may cause human intestinal damage in routine life usage: Microplastics formation and cytotoxic effect.

The microplastics and organic additives formed in routine use of plastic takeaway food containers may pose significant health risks. Thus, we collected plastic containers made of polystyrene, polypropylene, polyethylene terephthalate, polylactic acid and simulated two thermal usages, including hot water (I) and microwave treatments (M). Nile Red fluorescence staining was developed to improve accurate counting of microplastics with the aid of TEM and DLS analysis. The quantity of MPs released from thermal treatments was determined ranging from 285.7 thousand items/cm2 to 681.5 thousand items/cm2 in containers loaded with hot water with the following order: IPS>IPP>IPET>IPLA, while microwave treatment showed lower values ranging from 171.9 thousand items/cm2 to 301.6 thousand items/cm2. In vitro toxicity test using human intestinal epithelial Caco-2 cells indicated decrease of cell viability in raw leachate, resuspended MPs and supernatants, which might further lead to cell membrane rupture, ROS production, and decreased mitochondrial membrane potential. Moreover, the leachate inhibited the expression of key genes in the electron transport chain (ETC) process, disrupted energy metabolism. For the first time, we isolate the actually released microplastics and organic substances for in vitro toxicity testing, and demonstrate their potential impacts to human intestine. SYNOPSIS: Plastic take-out containers may release microplastics and organic substances during daily usage, both of which can cause individual and combined cytotoxic effects on human colon adenocarcinoma cells Caco-2.

Characteristics and effects of global sloping land urbanization from 2000 to 2020.

Cities usually expand on flat land. However, in recent decades, the increasing scarcity of available flat land has compelled many cities to expand to sloping land (sloping land urbanization, SLU), and the understanding for global SLU is still unclear. This study, based on the currently available high-precision global Digital Elevation Model (FABDEM) and global land cover dataset (GlobeLand30), investigated the characteristics and impacts of SLU in 26,402 urban residential areas worldwide from 2000 to 2020. Results show that the total area of SLU globally is 16,383 km2, accounting for 9.54 % of the overall urban expansion. This phenomenon is widespread globally and relatively concentrated in a few countries, with 42.78 %, 24.35 %, and 21.83 % of the area coming from cultivated land, forest, and grassland respectively. Global SLU has accommodated 34.78 million urban population, and indirectly protected 8922 km2 of flat cultivated land, while causing a net loss of 4373 km2 of green ecological land. Deliberately balancing the dual effects of SLU is crucial for advancing sustainable global urbanization.

Favipiravir biotransformation by a side-stream partial nitritation sludge: Transformation mechanisms, pathways and toxicity evaluation.

Information on biotransformation of antivirals in the side-stream partial nitritation (PN) process was limited. In this study, a side-stream PN sludge was adopted to investigate favipiravir biotransformation under controlled ammonium and pH levels. Results showed that free nitrous acid (FNA) was an important factor that inhibited ammonia oxidation and the cometabolic biodegradation of favipiravir induced by ammonia oxidizing bacteria (AOB). The removal efficiency of favipiravir reached 12.6% and 35.0% within 6 days at the average FNA concentrations of 0.07 and 0.02 mg-N L-1, respectively. AOB-induced cometabolism was the sole contributing mechanism to favipiravir removal, excluding AOB-induced metabolism and heterotrophic bacteria-induced biodegradation. The growth of Escherichia coli was inhibited by favipiravir, while the AOB-induced cometabolism facilitated the alleviation of the antimicrobial activities with the formed transformation products. The biotransformation pathways were proposed based on the roughly identified structures of transformation products, which mainly involved hydroxylation, nitration, dehydrogenation and covalent bond breaking under enzymatic conditions. The findings would provide insights on enriching AOB abundance and enhancing AOB-induced cometabolism under FNA stress when targeting higher removal of antivirals during the side-stream wastewater treatment processes.