Effects of foliar selenium, biochar, and pig manure on cadmium accumulation in rice grains and assessment of health risk.

Addressing cadmium (Cd) contamination in agricultural lands is crucial, given its health implications and accumulation in crops. This study used pot experiments to evaluate the impact of foliar selenium spray (Se) (0.40 mM), corn straw biochar (1%), and pig manure (1%) on the growth of rice plants, the accumulation of Cd in rice grain, and to examine their influence on health risk indices associated with Cd exposure. The treatments were designated as follows: a control group without any amendment (CK), biochar (T1), pig manure (T2), Se (T3), Se and biochar (T4), Se and pig manure (T5), and Se along with biochar and pig manure (T6). Our results indicated that the treatments affected soil pH and redox potential and improved growth and the nitrogen and phosphorus content in rice plants. The soil-plant analysis development (SPAD) meter readings of leaves during the tillering stage indicated a 5.27%-15.86% increase in treatments T2 to T6 compared to CK. The flag leaves of T2 exhibited increases of 12.06%-38.94% for electrolyte leakage and an 82.61%-91.60% decline in SOD compared to treatments T3 to T6. Treatments T1 to T6 increased protein content; however, amylose content was significantly reduced in T6. Treatment T6 recorded the lowest Cd concentration in rice grains (0.018 mg/kg), while T2 recorded the highest (0.051 mg/kg). The CK treatment group showed a grain Cd content reduction of 29.30% compared to T2. The assessment of acceptable daily intake, hazard quotient, and carcinogenic risk revealed an ascending order as follows: T6 < T3 < T5 < T4 < T1 < CK < T2. In conclusion, the application of treatment T6 demonstrates the potential to lower oxidative stress, enhance production, reduce cancer risk, and ensure the safe cultivation of rice in environments affected by Cd contamination.

Positive effect of deep diaphragmatic breathing training on gastroesophageal reflux-induced chronic cough: a clinical randomized controlled study.

BACKGROUND AND OBJECTIVE: To explore the efficacy of deep diaphragmatic breathing training (DEP) in patients with gastroesophageal reflux-induced chronic cough (GERC). METHODS: A randomized controlled study was conducted involving 60 GERC patients who were divided into the intervention group and the control group (each with 30 patients). Both groups received routine medication treatment for GERC, while the intervention group received DEP training additionally. Both groups were evaluated by cough symptom scores, Hull airway reflux questionnaire (HARQ), gastroesophageal reflux diagnostic questionnaire (GerdQ), generalized anxiety disorder scale-7 (GAD-7), patient health questionnaire-9 (PHQ-9), Pittsburgh sleep quality index (PSQI), the Leicester cough questionnaire (LCQ), as well as capsaicin cough sensitivity testing, B-ultrasound and surface electromyography (sEMG) of the diaphragmatic muscles before and after treatment. The cough resolution rate and changes of the above indictors was compared between the two groups after eight weeks of treatment. RESULTS: After eight weeks of treatment, cough symptoms improved in both groups, but the cough resolution rate in the intervention group of 94% was significantly higher than that in the control group of 77% (χ2 = 6.402, P = 0.041). The intervention group showed significant improvements to the control group in GerdQ (6.13(0.35) VS 6.57(0.77)), GAD-7 (0(0;1) VS 1(0;3)), PSQI (2(1;3) VS 4(3;6)), LCQ (17.19(1.56) VS 15.88(1.92)) and PHQ-9 (0(0;0) VS 0(0;3)) after treatment. Compared to control group, sEMG activity of the diaphragmatic muscle was significantly increased in the intervention group after treatment, measured during DEP (79.00(2.49) VS 74.65 (1.93)) and quiet breathing (72.73 (1.96) VS 67.15 (2.48)). CONCLUSION: DEP training can improve cough symptoms as an adjunctive treatment in GERC patients. TRIAL REGISTRATION: The protocol was registered in February 2, 2022 via the Chinese Clinical Trials Register ( http://www.chictr.org.cn/ ) [ChiCTR2200056246].

Selenium loss during boiling processes and its bioaccessibility in different crops: Estimated daily intake.

Food crops provide a good selenium (Se) source for Se-deficient populations. This study assessed how boiling affects Se concentration, speciation, and bioaccessibility in common food crops to determine human Se intake. Boiling rice resulted in an 11.9% decrease in minimum Se content, while sorghum experienced a maximum (34.9%) reduction. Boiled vegetables showed a 21% - 40% Se loss. Cereals showed notable decreases in selenomethionine (SeMet) and selenocysteine (SeCys2), while most vegetables exhibited a significant reduction in Se-methylselenocysteine (SeMeCys). Boiling significantly reduced the Se bioaccessibility in all food crops, except cabbage and potato. Cereal crops were more efficacious in meeting the recommended daily intake (RDI) of Se compared to vegetables. Rice exceeds other crops and provides up to 39.2% of the WHO/FAO-recommended target minimum daily intake of 60 µg/day. This study provides insight into a substantial dissonance between the estimated daily intake (EDI) of Se and the bioaccessible Se in both raw and boiled crops. Consequently, revising EDI standards is imperative.

A preliminary predictive model for selenium nutritional status in residents based on three selenium biomarkers.

BACKGROUND: Selenium (Se) is an essential nutrient and an important component of many selenoproteins that possess fundamental importance to human health. Selenium deficiency and excess will cause corresponding diseases in the human body. The nutritional health of Se in the human body mainly depends on the daily dietary Se intake of the human body, which in turn depends to a certain extent on the content of Se transmitted along the food chain. This study aims to research the transport of Se through the soil-crop-human chain in regions with different Se levels, and to establish the model between the residents' dietary Se intake and the three Se biomarkers (hair, nails, and plasma), to predict the nutritional health status of Se in residents through Se biomarkers. METHOD: Carry out field and cross-sectional surveys of populations in Loujiaba Village and Longshui Village. Samples were collected from soil, crops, drinking water, residents' hair, nails, plasma, and diet. The concentration of available Se fractions was extracted from soil samples using 0.1 mol/L K2HPO4. The concentration of total Se for all samples was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and the relative standard deviation was less than 5%. In this study, hair, nails, and blood samples were collected from volunteers according to the Declaration of Helsinki and the Ethics Committee of Soochow University. The dietary nutritional structure and dietary Se intake of the population were randomly selected by 12 volunteers using the duplicate portion method. Data were described using mean ± standard deviation. We performed saliency analysis and correlation analysis (with Pearson correlation coefficient), and fitted a regression to evaluate the associations between these variables. RESULTS: The soil total Se (5201 ± 609.2 µg/kg) and available Se (307.7 ± 83.5 µg/kg) in Luojiaba Village (LJB) were significantly higher than the soil total Se (229.2 ± 32.5 µg/kg) and available Se (21.9 ± 4.0 µg/kg) in Longshui Village (LS). The residents' dietary Se intake of LJB (150.3 ± 2.2 µg/d) was within the World Health Organization (WHO) recommended intake range, while LS (16.0 ± 0.4 µg/d) was close to the range of Keshan disease occurrence, and there was a risk of insufficient Se intake. The correlation analysis found significant positive correlations between residents' dietary Se intake and the three Se biomarkers. According to the preliminary model established in this study, if the daily dietary Se intake of residents reaches the WHO recommended value of 55-400 µg, the hair, nails, and plasma of Se concentration will be 522.1-2850.5 µg/kg, 1069.0-6147.4 µg/kg, and 128.3-661.36 µg/L, respectively. CONCLUSION: Selenium is transmitted through the soil-crop-human chain, and the Se concentration that enters the human body through the food chain in high-Se areas is significantly higher than that in low-Se areas. The nutritional health status of Se in the human body depends on the daily dietary intake of the human body, and there is a significant correlation between the daily dietary Se intake of the human body and the three biomarkers of Se levels in the human body, so the three biomarkers can be used to evaluate the Se nutritional health of the human.

The carotid web: Current research status and imaging features.

The carotid web is commonly found in the carotid bulb or the beginning of the internal carotid artery. It presents as a thin layer of proliferative intimal tissue originating from the arterial wall and extending into the vessel lumen. A large body of research has proven that the carotid web is a risk factor for ischemic stroke. This review summarizes the current research status of the carotid web and focuses on its imaging presentation.

Experimental and Theoretical Study on Electron Momentum Spectroscopy of SF6: Distorted-Wave and Vibrational Motion.

The vibrational and distorted-wave effects are usually invoked to explain the measured electron momentum profiles for molecular orbitals. The vibrational effect can be accounted for quantitatively by a harmonic analytical quantum mechanical approach within the plane-wave impulse approximation (PWIA). On the other hand, quantitative calculation considering the distorted-wave effect was available only recently by a multicenter-three-distorted-wave (MCTDW) method (Phys. Rev. A2022, 105, 042805). Here, we report a joint experimental and theoretical investigation on electron momentum spectroscopy of SF6. The experiments were performed using a high-sensitivity (e, 2e) spectrometer employing non-coplanar symmetric geometry with incident electron energy equal to 1200 eV + binding energy. The experimental electron momentum profiles are compared with theoretical calculations by the MCTDW method at equilibrium geometry and by the PWIA method both at equilibrium geometry and considering vibrational motions. For all the measured orbitals, large discrepancies were observed between the experiments and the PWIA calculations at equilibrium geometry. For the highest occupied molecular orbital 1t1g, the vibrational effect can partly explain the high intensity of the experimental momentum profile at low momenta. For the other orbitals, the influence of the vibrational effect is negligible. On the other hand, the MCTDW calculations improve the agreement with the experiments for all the observed orbitals, indicating that the distorted-wave effect plays an important role in reproducing the measured momentum profiles of SF6.

A Study on Cough Sensitivity and Airway Inflammation in Patients with Sinobronchial Syndrome.

Objective: This study aimed to clarify the characteristics of cough-reflex sensitivity and airway inflammation in patients with sinobronchial syndrome (SBS). Methods: 39 patients with SBS, 53 patients with upper airway cough syndrome (UACS) induced by rhinitis, 33 patients with chronic sinusitis without cough, and 39 healthy controls (HCs) were enrolled between January 2013 and December 2018. All participants underwent a capsaicin cough-sensitivity test and cytology of induced sputum. The concentration of calcitonin-gene-related peptide (CGPR), histamine, prostaglandin (PG) E2, and eosinophil cationic protein (ECP) in induced sputum were measured using enzyme-linked immunosorbent assays (ELISAs). Results: The lowest concentration of capsaicin solution that induced ≥5 coughs (C5) was decreased markedly in patients with UACS induced by rhinitis compared with SBS patients (1.95 ± 2.92 vs. 31.2 ± 58.6 mol/L, P < 0.001), indicating higher cough-reflex sensitivity among UACS patients induced by rhinitis. However, there was no difference of these threshold between SBS patients and patients with sinusitis without cough and HCs. The percentage of neutrophils in sputum was increased remarkably in patients with SBS compared with HCs (40.0 ± 48.5% vs. 5.5 ± 9.0%, P < 0.001). A higher concentration of CGPR, histamine, and PGE2 was observed in induced sputum from patients with UACS induced by rhinitis than that in controls, and the ECP level was increased significantly in UACS induced by rhinitis compared with that in the other three groups. Conclusions: Cough-reflex sensitivity and airway inflammation in patients with SBS were different in patients with UACS induced by rhinitis. Thus, the mechanism of cough in those two patient populations might differ. Our study is registered in the Chinese Clinical Trials Register (https://www.chictr.org.cn/) as ChiCTR-TRC-00000152.

Cough hypersensitivity in patients with metabolic syndrome: a clinical finding and its possible mechanisms.

PURPOSE: To investigate the changes of cough sensitivity in patients with metabolic syndrome and its possible mechanisms. METHOD: A total of 29 metabolic syndrome (MetS) patients with OSAHS (group-1), 22 MetS patients without OSAHS (group-2), and 25 healthy controls (group-3) were included. All participants underwent a routine physical examination and completed the gastroesophageal reflux disease questionnaire (GerdQ), and the inflammatory mediator profile were determined. The cough threshold for capsaicin, induced sputum cell count and cell classification, and inflammatory mediators in induced sputum supernatants were compared. The correlation between capsaicin cough sensitivity and various indicators in the MetS population was analyzed. RESULTS: The minimum concentration of inhaled capsaicin needed to induce ≥ 5 coughs (C5) was significantly different among three groups (H = 14.393, P = 0.001) and lower for group-1 and group-2 than it for group-3 (P = 0.002, P = 0.005). The percentage of neutrophils in induced sputum and the concentrations of calcitonin gene-related peptide (CGRP), substance P (SP), and interleukin 8 (IL-8) in the sputum supernatant of group-1 and group-2 were significantly higher than those of group-3. Besides, the pepsin concentrations were significantly different among the 3 groups (F = 129.362, P < 0.001), which significantly was highest in group-1 (P < 0.001) and lowest in group-3 (P < 0.001). Triglycerides, AHI, pepsin concentration and BMI were risk factors of increased capsaicin cough sensitivity. CONCLUSION: Increased capsaicin cough sensitivity in MetS patients is closely related to sleep apnea and gastroesophageal reflux. For patients in MetS patients without OSAHS, gastroesophageal reflux is an important factor for increased capsaicin cough sensitivity. Airway inflammation, especially airway neurogenic inflammation, may also play a role in the pathogenesis of increased capsaicin cough sensitivity. Trial registration The protocol was registered in the Chinese Clinical Trials Register ( http://www.chictr.org.cn/ ) (ChiCTR1800014768). Written informed consent was obtained from all participants before enrollment.

Dynamic Behavior of Single-Atom Catalysts in Electrocatalysis: Identification of Cu-N3 as an Active Site for the Oxygen Reduction Reaction.

Atomically dispersed M-N-C (M refers to transition metals) materials represent the most promising catalyst alternatives to the precious metal Pt for the electrochemical reduction of oxygen (ORR), yet the genuine active sites in M-N-C remain elusive. Here, we develop a two-step approach to fabricate Cu-N-C single-atom catalysts with a uniform and well-defined Cu2+-N4 structure that exhibits comparable activity and superior durability in comparison to Pt/C. By combining operando X-ray absorption spectroscopy with theoretical calculations, we unambiguously identify the dynamic evolution of Cu-N4 to Cu-N3 and further to HO-Cu-N2 under ORR working conditions, which concurrently occurs with reduction of Cu2+ to Cu+ and is driven by the applied potential. The increase in the Cu+/Cu2+ ratio with the reduced potential indicates that the low-coordinated Cu+-N3 is the real active site, which is further supported by DFT calculations showing the lower free energy in each elemental step of the ORR on Cu+-N3 than on Cu2+-N4. These findings provide a new understanding of the dynamic electrochemistry on M-N-C catalysts and may guide the design of more efficient low-cost catalysts.

Is the Symptom of Cough in Chronic Obstructive Pulmonary Disease Important?

Chronic obstructive pulmonary disease (COPD) is a common disease and a significant burden worldwide. The clinical symptoms of this disease include progressive dyspnea, cough, expectoration, and wheezing, among others. At present, the primary focus has been on reducing the frequency of acute exacerbations and improving lung function and dyspnea symptoms, and limited attention has been paid to cough and expectoration symptoms, which may be associated with a decrease in lung function, more acute exacerbations, and hospitalizations. Therefore, this outcomes in patients with COPD.

Should computed tomography and bronchoscopy be routine examinations for chronic cough?

Chronic cough is a common symptom of many diseases. Guidelines on cough from different countries recommend chest X-ray as the first-line examination. However, as compared to computerized tomography (CT), chest X-ray is insensitive in the diagnosis of many diseases. We speculate that CT is more helpful in excluding the causes of long-term cough, such as bronchial tumors and pulmonary interstitial diseases, which prevents patients from receiving unnecessary examinations and diagnostic treatments for chronic cough. In addition, a single chest CT is safe and affordable in some regions. Therefore, chest CT may be recommended as a first-line examination for patients with chronic cough. In addition, although bronchoscopy is employed as a further examination for chronic cough, it plays an important role in the diagnosis of chronic cough, especially in rare bronchial diseases such as amyloidosis and foreign body inhalation. Induced sputum cytology was not accepted as a necessary examination for chronic cough, but it becomes a first-line examination until physicians recognize that non-asthmatic eosinophilic bronchitis is a common cause of chronic cough. Therefore, we speculate that the roles of chest CT and bronchoscopy in the identification of causes of chronic cough are increasingly important; in some regions, or for patients suspicious for uncommon causes of chronic cough, CT and bronchoscopy are recommended as first-line examinations.

Highly Sensitive Fluorescence-Linked Immunosorbent Assay for the Determination of Human IgG in Serum Using Quantum Dot Nanobeads and Magnetic Fe3O4 Nanospheres.

The aim of this study is to establish a new method with high sensitivity, accuracy, and stability for the determination of human IgG and then expand it to analyze severe acute respiratory syndrome corona virus 2 (SARS-CoV-2)-specific IgM and IgG, which is of great significance for the screening and diagnosis of COVID-19. In this study, the magnetic Fe3O4 nanospheres coupled with mouse antihuman IgG (Ab1IgG) were used as an immune capture probe (Fe3O4@Ab1IgG) to capture and separate the target, and rabbit antihuman IgG (Ab2IgG) coupled with highly luminescent quantum dot nanobeads (QBs) as a fluorescence detection probe (QBs@Ab2IgG) was used to realize high sensitivity detection. After the formation of a sandwich immunocomplex, the fluorescence intensity of the precipitate after magnetic separation was measured at the excitation wavelength of 370 nm. Under optimal conditions, a wide linear range varying from 0.005 to 40 ng·mL-1 was obtained for the detection of human IgG with a lower limit of detection at 4 pg·mL-1 (S/N = 3). The recoveries of intra- and interassays were 90.0-101.9 and 96.0-106.6%, respectively, and the relative standard deviations were 6.3-10.2 and 2.6-10.5%, respectively. Furthermore, the proposed method was successfully demonstrated to detect human IgG in serum samples, and the detection results were not statistically different (P > 0.05) from commercial enzyme-linked immunosorbent assay kits. This method is sensitive, fast, and accurate, which could be expanded to detect the specific IgM and IgG antibodies against SARS-CoV-2.

Electron Momentum Spectroscopy Study on the Valence Electronic Structure of Dimethyl Sulfide Considering Vibrational Effects.

We report an electron momentum spectroscopy study on the valence electronic structure of dimethyl sulfide. The binding energy and electron momentum profiles are measured using a high-sensitivity (e, 2e) apparatus employing a symmetric non-coplanar geometry at an incident energy of 1200 eV plus binding energy. The measurements are compared with the theoretical calculations by density functional theory performed both at equilibrium molecular geometry and by considering vibrational effects through a harmonic analytical quantum mechanical approach. The results demonstrate a significant influence of nuclear vibrational motions on the momentum profiles for valence orbitals of dimethyl sulfide, especially for 5b2, 1a2, and 4b2. A detailed analysis shows that the observed vibrational effects come mainly from vibrational normal modes breaking the mirror symmetry of (CH3)2S with respect to a plane perpendicular to the O-S-O plane.

Sensitivity and specificity of combination of Hull airway reflux questionnaire and gastroesophageal reflux disease questionnaire in identifying patients with gastroesophageal reflux-induced chronic cough.

BACKGROUND: There is a need to find a simple, non-invasive and effective diagnostic tool for diagnosing gastroesophageal reflux-induced chronic cough (GERC) in clinic. This study aimed to evaluate the predictive diagnostic value of Hull airway reflux questionnaire (HARQ) and its combination with gastroesophageal reflux disease questionnaire (GerdQ) for GERC. METHODS: Chronic cough patients were enrolled and the diagnosis of GERC was established according to the chronic cough diagnosis and treatment process. The diagnostic value of HARQ and GerdQ alone or the combination of HARQ and GerdQ was analyzed. RESULTS: A total of 402 patients with chronic cough were eventually enrolled, including 166 GERC patients. When the HARQ score was used to predict the diagnosis of GERC, the area under the ROC curve was 0.796. The sensitivity and specificity were 77.19% and 77.06%, respectively. When the GerdQ was used to predict the diagnosis of GERC, the area under the ROC curve was 0.763. The sensitivity and specificity were 70.18% and 76.15%, respectively. When HARQ combined with GerdQ were used to predict the diagnosis of GERC, the area under the ROC curve was 0.848. The sensitivity and specificity were 77.19% and 79.82%, respectively. CONCLUSIONS: HARQ used to evaluate the cough hypersensitivity has a certain predictive diagnostic value for GERC. The diagnosis of GERC should be considered when the HARQ score is ≥24. The predictive diagnostic value of the combination of HARQ and GerdQ is significantly higher, which makes the diagnosis of GERC simpler, quicker and more effective.

Development of an electron momentum spectrometer for time-resolved experiments employing nanosecond pulsed electron beam.

The low count rate of (e, 2e) electron momentum spectroscopy (EMS) has long been a major limitation of its application to the investigation of molecular dynamics. Here we report a new EMS apparatus developed for time-resolved experiments in the nanosecond time scale, in which a double toroidal energy analyzer is utilized to improve the sensitivity of the spectrometer and a nanosecond pulsed electron gun with a repetition rate of 10 kHz is used to obtain an average beam current up to nA. Meanwhile, a picosecond ultraviolet laser with a repetition rate of 5 kHz is introduced to pump the sample target. The time zero is determined by photoionizing the target using a pump laser and monitoring the change of the electron beam current with time delay between the laser pulse and electron pulse, which is influenced by the plasma induced by the photoionization. The performance of the spectrometer is demonstrated by the EMS measurement on argon using a pulsed electron beam, illustrating the potential abilities of the apparatus for investigating the molecular dynamics in excited states when employing the pump-probe scheme.

MXene-Based Electrode with Enhanced Pseudocapacitance and Volumetric Capacity for Power-Type and Ultra-Long Life Lithium Storage.

Powerful yet thinner lithium-ion batteries (LIBs) are eagerly desired to meet the practical demands of electric vehicles and portable electronic devices. However, the use of soft carbon materials in current electrode design to improve the electrode conductivity and stability does not afford high volumetric capacity due to their low density and capacity for lithium storage. Herein, we report a strategy leveraging the MXene with superior conductivity and density to soft carbon as matrix and additive material for comprehensively enhancing the power capability, lifespan, and volumetric capacity of conversion-type anode. A kinetics favorable 2D nanohybrid with high conductivity, compact density, accumulated pseudocapacitance, and diffusion-controlled behavior is fabricated by coupling Ti3C2 MXene with high-density molybdenum carbide for fast lithium storage over 300 cycles with high capacities. By replacing the carbonaceous conductive agent with Ti3C2 MXene, the electrodes with better conductivity and dramatically reduced thickens could be further manufactured to achieve 37-40% improvement in capacity retention and ultra-long life of 5500 cycles with extremely slow capacity loss of 0.002% per cycle at high current rates. Ultrahigh volumetric capacity of 2460 mAh cm-3 could be attained by such MXene-based electrodes, highlighting the great promise of MXene in the development of high-performance LIBs.

Magnetic immunoassay using CdSe/ZnS quantum dots as fluorescent probes to detect the level of DNA methyltransferase 1 in human serum sample.

BACKGROUND: DNA methyltransferase 1 (DNMT1), a dominant enzyme responsible for the transfer of a methyl group from the universal methyl donor to the 5-position of cytosine residues in DNA, is essential for mammalian development and closely related to cancer and a variety of age-related chronic diseases. DNMT1 has become a useful biomarker in early disease diagnosis and a potential therapeutic target in cancer therapy and drug development. However, till now, most of the studies on DNA methyltransferase (MTase) detection have focused on the prokaryote MTase and its activity. METHODS: A magnetic fluorescence-linked immunosorbent assay (FLISA) using CdSe/ZnS quantum dots as fluorescent probes was proposed for the rapid and sensitive detection of the DNMT1 level in this study. Key factors that affect the precision and accuracy of the determination of DNMT1 were optimized. RESULTS: Under the optimal conditions, the limit of detection was 0.1 ng/mL, the linear range was 0.1-1,500 ng/mL, the recovery was 91.67%-106.50%, and the relative standard deviations of intra- and inter-assays were respectively 5.45%-11.29% and 7.03%-11.25%. The cross-reactivity rates with DNA methyltransferases 3a and 3b were only 4.0% and 9.4%, respectively. Furthermore, FLISA was successfully used to detect the levels of DNMT1 in human serum samples, and compared with commercial enzyme-linked immunosorbent assay (ELISA) kits. The results revealed that there was a good correlation between FLISA and commercial ELISA kits (correlation coefficient r=0.866, p=0.001). The linear scope of FLISA was broader than ELISA, and the measurement time was much shorter than ELISA kits. CONCLUSION: These indicated that the proposed FLISA method was sensitive and high throughput and can quickly screen the level of DNMT1 in serum samples.

Electron Momentum Spectroscopy Investigation of Molecular Conformations of Ethanol Considering Vibrational Effects.

The interpretation of experimental electron momentum distributions (EMDs) of ethanol, one of the simplest molecules having conformers, has confused researchers for years. High-level calculations of Dyson orbital EMDs by thermally averaging the gauche and trans conformers as well as molecular dynamical simulations failed to quantitatively reproduce the experiments for some of the outer valence orbitals. In this work, the valence shell electron binding energy spectrum and EMDs of ethanol are revisited by the high-sensitivity electron momentum spectrometer employing symmetric noncoplanar geometry at an incident energy of 1200 eV plus binding energy, together with a detailed analysis of the influence of vibrational motions on the EMDs for the two conformers employing a harmonic analytical quantum mechanical (HAQM) approach by taking into account all of the vibrational modes. The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively, indicating that the vibrational effect plays a significant role in reproducing the experimental results, not only through the low-frequency OH and CH3 torsion modes but also through other high-frequency ones. Rational explanation of experimental momentum profiles provides solid evidence that the trans conformer is slightly more stable than the gauche conformer, in accordance with thermodynamic predictions and other experiments. The case of ethanol demonstrates the significance of considering vibrational effects when performing a conformational study on flexible molecules using electron momentum spectroscopy.

Imaging molecular geometry with electron momentum spectroscopy.

Electron momentum spectroscopy is a unique tool for imaging orbital-specific electron density of molecule in momentum space. However, the molecular geometry information is usually veiled due to the single-centered character of momentum space wavefunction of molecular orbital (MO). Here we demonstrate the retrieval of interatomic distances from the multicenter interference effect revealed in the ratios of electron momentum profiles between two MOs with symmetric and anti-symmetric characters. A very sensitive dependence of the oscillation period on interatomic distance is observed, which is used to determine F-F distance in CF4 and O-O distance in CO2 with sub-Ångström precision. Thus, using one spectrometer, and in one measurement, the electron density distributions of MOs and the molecular geometry information can be obtained simultaneously. Our approach provides a new robust tool for imaging molecules with high precision and has potential to apply to ultrafast imaging of molecular dynamics if combined with ultrashort electron pulses in the future.