Novel MCP-Windowed EUV Light Source and Its Mass Spectrometric Application for Detecting Chlorinated Methanes.

Various vacuum ultraviolet (VUV) lamps are simple and convenient VUV light sources for mass spectrometry and other research fields. However, the strong absorption of high-energy photons by window materials limits the application of an extreme ultraviolet (EUV) light. In this study, a novel high-flux EUV light source is developed using a microchannel plate (MCP) window to transmit 73.6 nm (16.9 eV) EUV light generated via the radio frequency (RF) inductive discharge of neon. The MCP used is a 0.5 mm thick glass plate with a regular array of microtubes (12 µm i.d.). The photon fluxes of the EUV light source with the MCP window (12 mm i.d.) and an aperture (1.8 mm i.d.) are ∼1.31 × 1014 and ∼9.80 × 1012 photons s-1, respectively, while their corresponding leakage flow rates of the discharge gas are 0.062 and 0.046 cm3 atom s-1, according to the contrast experiments. The transmission efficiency of the MCP to the EUV light is 30.2%, with a 1.2% deviation. An EUV photoionization time-of-flight mass spectrometer (EUV-PI-TOFMS) is built to validate the practicality of the MCP-windowed EUV light source further. The detection sensitivities in 30 s measurements for methyl chloride (CH3Cl), methylene chloride (CH2Cl2), trichloromethane (CHCl3), and carbon tetrachloride (CCl4) in synthetic air are 4366, 4120, 5854, and 4095 counts ppbv-1, respectively. The corresponding 3σ limits of detection (LODs) are 42, 34, 24, and 15 pptv. This study develops a new feasible method for efficiently utilizing high-energy EUV light, with many application prospects in scientific research.

Colchicine efficacy comparison at varying time points in the peri-operative period for coronary artery disease: a systematic review and meta-analysis of randomized controlled trials.

Objectives: Over the years, it has been found that colchicine offers substantial benefits in secondary prevention in patients with coronary artery disease (CAD). We studied the effects of colchicine timing because there are no guidelines about when to provide it during the perioperative period for patients with CAD. Methods: Up to January 1, 2023, seven electronic literature databases were screened (including three English databases and four Chinese databases). Randomized controlled trials included only treatment with colchicine in the perioperative period of CAD. The Cochrane Evaluation Tool was used to judge the risk of bias in research. Statistical analysis was performed by Stata 16.0 software. Results: We evaluated twelve studies that found colchicine to be effective in decreasing the occurrence of major adverse cardiac events (MACEs) (p < 0.00001), but it also raised the rate of adverse events (p = 0.001). Subgroup analysis showed the same benefit in lowering the incidence of MACE with continuous administration of a total daily dose of 0.5 mg postoperatively while minimizing drug-related side effects in the patients (p = 0.03). When it comes to preventing surgical stroke occurrences, postoperative administration is more effective (p = 0.006). While the effect of simultaneous preoperative and postoperative administration was marginally greater than other periods in reducing postoperative hs-CRP levels (p = 0.02). Conclusion: Colchicine, a traditional anti-inflammatory drug, also reduces the risk of MACE by reducing inflammation after PCI. Administration at different periods had no significant effect on decreasing the occurrence of MACE, but when administered postoperatively, we advise continuous administration with a total daily dose of 0.5 mg to obtain the same benefit while minimizing the drug's side effects. Postoperative administration is the better measure to prevent postoperative stroke events. Due to the effective anti-inflammatory effect of colchicine, we recommend its use as early as possible in the perioperative period and its continued use at low doses in the postoperative period. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=316751, identifier CRD42022316751.

Insight into the crucial reason causing the difference in secondary organic aerosol yields of monocyclic aromatic hydrocarbons with different methyl substituent numbers.

The secondary organic aerosol (SOA) yield of toluene photooxidation was reported to substantially higher than that of trimethylbenzene due to the effect of the number of methyl substituents. However, the intrinsic mechanism for this disparity is not clear enough. In this study, a highly-sensitive thermal-desorption photoinduced associative ionization mass spectrometer (TD-PAI-MS) was used to real-time characterize the molecular composition and its evolution of the SOA generated from the photooxidation of toluene and 1,2,3-trimethylbenzene (1,2,3-TMB) in a smog chamber. In the new particle formation (NPF) stage, toluene generated more variety of nucleation precursors, such as benzaldehyde (MW 106) and benzoic acid (MW 122), resulting in a much higher nucleation rate and SOA number concentration. In the SOA growth/aging stage, the key SOA components of toluene were mainly dialdehydes, e.g., 2-oxopropanedial (MW 86) and 4-oxopent-2-enedial (MW 112), which played an important role in the formation of highly oxidized species (HOS) through oligomerization or cyclization reactions. In contrast, due to the presence of more methyl groups, 1,2,3-TMB was inclined to produce ketones, e.g., 2,3-butanedione (MW 86) and 3-methyl-4-oxopent-2-enal (MW 112), which would be cleaved into high-volatility low molecular compounds, e.g., acetic acid, through fragmentation. Taken together, relative to 1,2,3-TMB, the higher nucleation rate during NPF and the significant oligomerization/functionalization process during SOA growth are thought to be the major reasons resulting in the higher SOA yield of toluene. This work provides a reference for the insight into the different SOA yields of monocyclic aromatic hydrocarbons (MAHs) through further revealing the SOA formation mechanism during toluene and 1,2,3-TMB photooxidation.

Real-time emission characteristics, health risks, and olfactory effects of VOCs released from soil disturbance during the remediation of an abandoned chemical pesticide industrial site.

Volatile organic compounds (VOCs) released along with soil disturbance during the remediation of abandoned industrial sites have attracted great attention due to their possible toxicity and odour. However, the real-time emission characteristics of these VOCs and their subsequent effects on health and olfaction are less understood. In this study, the gaseous VOCs released from soil disturbance by excavators and drilling rigs at an abandoned chemical pesticide plant were monitored online with a laboratory-built single photoionization time-of-flight mass spectrometer (SPI-TOFMS). Twelve main VOCs with total mean concentrations ranging from 2350 to 3410 µg m-3 were observed, with dichloromethane (DCM) having a significant contribution. The total concentrations of the remaining 11 VOCs increased substantially during soil disturbance, with the total mean concentrations increasing from 18.65-39.05 to 37.95-297.94 µg m-3 and those of peak concentrations increasing from 28.46-58.97 to 88.38-839.13 µg m-3. This increase in VOC concentrations during soil disturbance leads to an enhanced heath risk for on-site workers. The distinctive difference between the mean and peak concentrations of VOCs indicates the importance of using mean and peak concentrations, respectively, for risk and olfactory evaluation due to the rapid response of the human nose to odours. As a result, the cumulative noncarcinogenic risk at the relatively high pollutant plot was higher than the occupational safety limit, while the total carcinogenic risks at all monitored scenarios exceeded the acceptable limit. Among the VOCs investigated, DCM and trichloroethylene (TCE) were determined to be crucial pollutants for both noncarcinogenic and carcinogenic risks of VOCs. With regard to olfactory effects, organic sulphides, including dimethyl disulphide (DMDS), dimethyl sulphide (DMS), and dimethyl trisulphide (DMTS) were identified as dominant odour contributors (78.28-92.11%) during soil disturbance.

A Simple High-Flux Switchable VUV Lamp Based on an Electrodeless Fluorescent Lamp for SPI/PAI Mass Spectrometry.

Single-photon ionization (SPI) is a unique soft ionization technique for organic analysis. A convenient high-flux vacuum ultraviolet (VUV) light source is a key precondition for wide application of SPI techniques. In this study, we present a novel VUV lamp by simply modifying an ordinary electrodeless fluorescent lamp. By replacing the glass bulb with a stainless steel bulb and introducing 5% Kr/He (v/v) as the excitation gas, an excellent VUV photon flux over 4.0 × 1014 photons s-1 was obtained. Due to its rapid glow characteristics, the VUV lamp can be switched on and off instantly as required by detection, ensuring the stability and service life of the lamp. To demonstrate the performance of the new lamp, the switchable VUV lamp was coupled with an SPI-mass spectrometer, which could be changed to photoinduced associative ionization (PAI) mode by doping gaseous CH2Cl2 to initiate an associative ionization reaction. Two types of volatile organic compounds sensitive to SPI and PAI, typically benzene series and oxygenated organics, respectively, were selected as samples. The instrument exhibited a high detection sensitivity for the tested compounds. With a measurement time of 11 s, the 3σ limits of detection ranged from 0.33 to 0.75 pptv in SPI mode and from 0.03 to 0.12 pptv in PAI mode. This study provides an extremely simple method to assemble a VUV lamp with many merits, e.g., portability, robustness, durability, low cost, and high flux. The VUV lamp may contribute to the development of SPI-related highly sensitive detection technologies.

Direct detection of acetonitrile at the pptv level with photoinduced associative ionization time-of-flight mass spectrometry.

Photoionization mass spectrometry (PI-MS) has become a versatile tool in the real-time analysis of volatile organic compounds (VOCs) from the atmosphere or exhaled breath. However, some key species, e.g., acetonitrile, are hard to measure due to their higher ionization energies than photon energy. In this study, the direct and sensitive detection of gaseous acetonitrile based on a photoinduced associative ionization (PAI) reaction was investigated with a laboratory-built PAI time-of-flight mass spectrometer (PAI-TOFMS). By doping CH2Cl2 in the photoionization ion source, the mass signal of acetonitrile that cannot be effectively obtained by photoionization appeared with an extremely high intensity through the PAI reaction between acetonitrile, CH2Cl2, and residual H2O in the system. Though the moisture in the sample gas has an evident impact on the detection efficiency of acetonitrile, with a relative signal intensity decreasing from 100% under dry conditions to 60% at saturated relative humidity, excellent detection sensitivity was still obtained for gaseous acetonitrile in different matrixes. The sensitivity calibration experiment showed that the detection sensitivities of acetonitrile in N2 buffer gas, exhaled gas, and outdoor air were 682.4 ± 5.2, 17.0 ± 0.7, and 23.9 ± 0.2 counts pptv-1, respectively, with an analysis time of 10 s. The corresponding 3σ LODs reached 0.22, 8.82, and 6.28 pptv, which are equivalent to 0.40, 16.0, and 11.4 ng m-3. The performance of the PAI-TOFMS was first demonstrated by analyzing exhaled acetonitrile from healthy non-smokers and smokers and continuous monitoring of acetonitrile in outdoor air. In summary, this study provides a new and highly sensitive method for the real-time detection of acetonitrile through mass spectrometry.

An ultrasensitive SPI/PAI ion source based on a high-flux VUV lamp and its applications for the online mass spectrometric detection of sub-pptv sulfur ethers.

Single-photon ionization mass spectrometry (SPI-MS) is an attractive analytical technique for the online detection of volatile organic compounds; however, the low photon flux of the vacuum ultraviolet (VUV) lamp commonly used in the SPI ion source and the corresponding low detection sensitivity remain a constraint to its wide field applications. In this study, a new VUV lamp-based SPI ion source was developed. By increasing the discharging volume and optimizing the configuration of the lens and ionizer, the photon flux of the VUV lamp and the sensitivity of the ion source were significantly improved. The VUV lamp output was 2.8 × 1015 photons s-1, which was focused into the small ionization zone, and the ion intensity of gaseous benzene under SPI achieved 1.7 × 104 counts per second per pptv (cps pptv-1). This ion source can also function in photoinduced associative ionization (PAI) mode by introducing gaseous CH2Cl2 to initiate an associative ionization reaction. Because of the high efficiency of the ion source, the amount of doped CH2Cl2 needed for PAI was greatly reduced (∼2.5% of that used in previous experiments). PAI exhibited an outstanding protonation effect on monosulfur ethers (CnH2n+1S). The signal intensities of the protonated molecular ions (MH+) were 46-128 times higher than those of the molecular ions (M+) produced by SPI. Since monosulfur ethers generally have lower SPI cross-sections than polysulfur ethers (CnH2n+1S2 or CnH2n+1S3), the PAI and SPI modes were selected for the online measurement of a series of mono- and polysulfur ethers, respectively. The obtained detection sensitivity of the mono- and polysulfur ethers reached 476.5 ± 1.72-2835.1 ± 99.5 and 47.9 ± 0.4-105.1 ± 2.3 counts pptv-1, respectively, in 10 s of sampling time. The corresponding 3σ limits of detection (LODs) were 0.12-0.71 and 0.06-0.14 pptv, respectively. This study provides advances in the development of a high-flux VUV lamp and a highly efficient SPI/PAI ion source, as well as an ultrasensitive analytical method for detecting sulfur ethers.

Neuroimaging of situational urgency and incontinence provoked by personal urgency cues.

INTRODUCTION: Situational triggers for urinary urgency and incontinence (UUI) such as "latchkey incontinence" and running water are often reported clinically, but no current clinical tools exist to directly address symptoms of UUI provoked by environmental stimuli. Previously we have shown that urgency and leakage can be reproduced during urodynamic studies with exposure to personal urgency-related images. Here we investigate the neural signatures associated with such situational triggers to inform potential therapies for reducing reactivity to these personal urgency-related cues among women with situational UUI. METHOD: We recruited 23 women with situational UUI who took photographs of their personal "urgency trigger" and "safe" situations and were exposed to them in a magnetic resonance imaging (MRI) scanner. We identified brain areas that were more active during urgency versus safe image exposure. RESULTS: We found that, during urgency image exposure, main components of the attention network and decision-related processes, the middle and medial frontal gyri, were more active (p < 0.01). In addition, areas well known to be involved in the continence mechanism, such as the cingulate and parahippocampal areas, were also more active during urgency image exposure. CONCLUSION: Exposure to personal situational urgency images activated different areas of the brain compared with safe environments, highlighting the complex brain mechanisms that provoke real-world urgency. Using brain and behavioral-based therapies which target the attentional areas identified here and extinguish cue reactivity might reduce symptom burden in this subset of UUI sufferers.

Biomaterials cross-linked graphene oxide composite aerogel with a macro-nanoporous network structure for efficient Cr (VI) removal.

Chitosan (CS) is an attractive bio-adsorbent in pollutant removal due to its environment-friendly properties and abundant adsorption sites. However, the weak mechanical properties and strong dissolubility in acidic conditions of CS hinder its wide application. Herein, a facile method was proposed to fabricate polydopamine (PDA) and CS cross-linked graphene oxide (GO) (GO/CS/PDA) composite aerogel for Cr (VI) removal. GO was cross-linked with CS, forming a reinforced and three-dimensional macroporous structure; the introduced PDA was simultaneously cross-linked with CS and GO, providing more abundant nanopores and active sites for Cr(VI) removal. Based on the batch experiment results, GO/CS/PDA exhibited an optimized mass ratio (1:20:2) of GO, CS, and PDA for the most effective Cr(VI) adsorption; the adsorption removal rate of Cr(VI) was pH dependent, with the highest removal rate at pH = 3.0. The pseudo-second-order kinetic and Freundlich models were more suitable for fitting the adsorption kinetics and adsorption isotherms, respectively, and the maximum adsorption capacity for GO/CS/PDA was 312.05 mg/g at 298 K. Thermodynamics parameters indicated that the adsorption was a spontaneous and exothermic process. The excellent mechanical integrity and reusable adsorption performance of GO/CS/PDA promise the adsorbent with satisfactory reusability.

Efficient oxygen reduction electrocatalyst based on edge-nitrogen-rich graphene nanoplatelets: toward a large-scale synthesis.

The large-scale synthesis of nitrogen doped graphene (N-graphene) with high oxygen reduction reaction (ORR) performance has received a lot of attention recently. In this work, we have developed a facile and economical procedure for mass production of edge-nitrogen-rich graphene nanoplatelets (ENR-GNPs) by a combined process of ball milling of graphite powder (GP) in the presence of melamine and subsequent heat treatment. It is found that the ball milling process can not only crack and exfoliate pristine GP into edge-expanded nanoplatelets but also mechanically activate GP to generate appropriate locations for N-doping. Analysis results indicate that the doped N atoms mainly locate on the edge of the graphitic matrix, which contains ca. 3.1 at.% nitrogen content and can be well-dispersed in aqueous to form multilayer nanoplatelets. The as-prepared ENR-GNPs electrocatalyst exhibits highly electrocatalytic activity for ORR due to the synergetic effects of edge-N-doping and nanosized platelets. Besides, the stability and methanol tolerance of ENR-GNPs are superior to that of the commercial Pt/C catalyst, which makes the nanoplatelets a promising candidate for fuel cell cathode catalysts. The present approach opens up the possibility for simple and mass production of N-graphene based electrocatalysts in practice.

Catalyst-free synthesis of crumpled boron and nitrogen co-doped graphite layers with tunable bond structure for oxygen reduction reaction.

Two-dimensional materials based on ternary system of B, C and N are useful ranging from electric devices to catalysis. The bonding arrangement within these BCN nanosheets largely determines their electronic structure and thus chemical and (or) physical properties, yet it remains a challenge to manipulate their bond structures in a convenient and controlled manner. Recently, we developed a synthetic protocol for the synthesis of crumpled BCN nanosheets with tunable B and N bond structure using urea, boric acid and polyethylene glycol (PEG) as precursors. By carefully selecting the synthesis condition, we can tune the structure of BCN sheets from s-BCN with B and N bond together to h-BCN with B and N homogenously dispersed in BCN sheets. Detailed experiments suggest that the final bond structure of B and N in graphene depends on the preferentially doped N structure in BCN nanosheets. When N substituted the in-plane carbon atom with all its electrons configured into the π electron system of graphene, it facilitates the formation of h-BCN with B and N in separated state. On the contrary, when nitrogen substituted the edge-plane carbon with the nitrogen dopant surrounded with the lone electron pairs, it benefits for the formation of B-N structure. Specially, the compound riched with h-BCN shows excellent ORR performance in alkaline solution due to the synergistic effect between B and N, while s-BCN dominant BCN shows graphite-like activity for ORR, suggesting the intrinsic properties differences of BCN nanosheets with different dopants bond arrangement.

Identifying the active site in nitrogen-doped graphene for the VO2+/VO2(+) redox reaction.

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.