15 research outputs found

    State-to-State Mode Specificity: Energy Sequestration and Flow Gated by Transition State

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    Energy flow and sequestration at the state-to-state level are investigated for a prototypical four-atom reaction, H<sub>2</sub> + OH → H + H<sub>2</sub>O, using a transition-state wave packet (TSWP) method. The product state distribution is found to depend strongly on the reactant vibrational excitation, indicating mode specificity at the state-to-state level. From a local-mode perspective, it is shown that the vibrational excitation of the H<sub>2</sub>O product derives from two different sources, one attributable to the energy flow along the reaction coordinate into the newly formed OH bond and the other due to the sequestration of the vibrational energy in the OH spectator moiety during the reaction. The analysis provided a unified interpretation of some seemingly contradicting experimental observations. It is further shown that the transfer of vibrational energy from the OH reactant to H<sub>2</sub>O product is gated by the transition state, accomplished coherently by multiple TSWPs with the corresponding OH vibrational excitation

    Theoretical Study of FH<sub>2</sub><sup>–</sup> Electron Photodetachment Spectra on New Ab Initio Potential Energy Surfaces

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    The FH<sub>2</sub><sup>–</sup> anion has a stable structure that resembles a configuration in the vicinity of the transition state for neutral reaction F + H<sub>2</sub> → HF + H. Electron photodetachment spectra of the FH<sub>2</sub><sup>–</sup> anion reveal the neutral reaction dynamics in the critical transition-state region. Accurate quantum dynamics simulations of the photodetachment spectra using highly accurate new ab initio potential energy surfaces for both anionic and neutral FH<sub>2</sub> are performed and compared with all available experimental results. The results provide reliable interpretations for the experimental observations of FH<sub>2</sub><sup>–</sup> photoelectron detachment and reveal a detailed picture of the molecular dynamics around the transition state of the F + H<sub>2</sub> reaction. The latest high-resolution photoelectron detachment spectra [Kim et al. <i>Science</i>, <b>2015</b>, 349, 510–513] confirm the high accuracy of our new potential energy surface for describing the resonance-enhanced reactivity of the neutral F + H<sub>2</sub> reaction

    Data_Sheet_1_Term breech presentation vaginal births in Tibet: A retrospective analysis of 451 cases.ZIP

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    BackgroundIn high altitude areas, like Tibet, most fetuses in breech presentation at term are delivered vaginally owing to a variety of reasons, but this has not been published.ObjectiveThis study aimed to provide references and evidence for the delivery of breach presentation term fetuses in high altitude areas, through comparing and analyzing the data of full-term singleton fetuses with breech or cephalic presentation in Naqu People’s Hospital, Tibet.Study designWe retrospectively analyzed the clinical data of 451 breech presentation fetuses mentioned above over a period of 5  years (2016–2020). A total of 526 cephalic presentation fetuses’ data within 3  months (1 June to 1 September 2020) of the same period were collected too. Statistics were compared and assembled on fetal mortality, Apgar scores, and severe neonatal complications for both planned cesarean section (CS) and vaginal delivery. In addition, we also analyzed the types of breech presentation, the second stage of labor, and damage to the maternal perineum during vaginal delivery.ResultsAmong the 451 cases of breech presentation fetuses, 22 cases (4.9%) elected for CS and 429 cases (95.1%) elected for vaginal delivery. Of the women who chose vaginal trial labor, 17 cases underwent emergency CSs. The perinatal and neonatal mortality rate was 4.2% in the planned vaginal delivery group and the incidence of severe neonatal complications was 11.7% in the transvaginal group, no deaths were detected in the CS group. Among the 526 cephalic control groups with planned vaginal delivery, the perinatal and neonatal mortality was 1.5% (p = 0.012), and the incidence of severe neonatal complications was 1.9%. Among vaginal breech deliveries, most of them were complete breech presentation (61.17%). Among the 364 cases, the proportion of intact perinea was 45.1%, and first degree lacerations accounted for 40.7%.ConclusionIn the Tibetan Plateau region, vaginal delivery was less safe than cephalic presentation fetuses for full-term breech presentation fetuses delivered in the lithotomy position. However, if dystocia or fetal distress can be identified in time and then encouraged to convert to cesarean, its safety will be greatly improved.</p

    Molecular Conformations and Dynamics on Surfaces of Gold Nanoparticles Probed with Multiple-Mode Multiple-Dimensional Infrared Spectroscopy

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    Knowledge about molecular conformations and nuclear and electronic motions on surfaces of metal nanomaterials is critical for many applications but extremely difficult to obtain. We demonstrate that valuable information of this sort can be determined using multiple-mode multiple-dimensional vibrational spectroscopy. A model compound, 4-mercaptophenol, on the surface of 3.5 nm gold nanoparticles demonstrates the method. Its 3D molecular conformations and vibrational dynamics on the particle surfaces were determined with the method. The experimental results imply that on the particle surfaces, the ligand molecules cannot form energy-optimized hydrogen bonds because of the surface geometry constraint. The conclusion is supported with experiments on the ligand molecules in the crystalline phase and in a dilute solution. Our experiments also showed that the effect of the particle surface nonadiabatic electron/vibration coupling does not play a significant role in the vibrational relaxation of high-frequency modes (>1000 cm<sup>–1</sup>) about 3 Å away from the surface. Simple theoretical calculations support this observation. The method holds promise as a general tool for the studies of molecular structures and dynamics on the surfaces of nanomaterials. The capability of resolving 3D molecular conformations on nanomaterials surfaces is expected to be helpful for understanding specific intermolecular interactions and conformation-selective reactions (e.g., chirality selectivity) on the surfaces of these materials

    Study on the Thermoelectric Properties of n‑Type Polycrystalline SnSe by CeCl<sub>3</sub> Doping

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    SnSe is a promising medium-temperature thermoelectric material due to its extremely low thermal conductivity and tunable electronic transport properties. In this work, n-type SnSe0.95 polycrystals doped with CeCl3 are synthesized by a melting method combined with a spark plasma sintering (SPS) process. The samples have highly textured structures and anisotropic thermoelectric properties. CeCl3 doping has a favorable effect on the electronic transport above 473 K, which may benefit from the excitation of the introduced impurity energy level. Moreover, the thermal conductivity is significantly reduced due to the phonon scattering by point defects. Finally, a peak ZT value of 1.17 is obtained at 773 K in SnSe0.95–0.5 mol % CeCl3, which paves the way for improving the thermoelectric performance of n-type SnSe via rare-earth halide doping

    Isotope-Dependent Rotational States Distributions Enhanced by Dynamic Resonance States: A Comparison Study of the F + HD → HF(<i>v</i><sub>HF</sub> = 2) + D and F + H<sub>2</sub> → HF(<i>v</i><sub>HF</sub> = 2) + H Reaction

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    An interesting trimodal structure in the HF (<i>v</i>′ = 2) rotational distribution produced by the F + HD (<i>v</i> = 0, <i>j</i> = 0) reaction, but monomodal structure in the HF (<i>v</i>′ = 2) rotational distribution produced by the F + H<sub>2</sub> (<i>v</i> = 0, <i>j</i> = 0) reaction, were observed using a high-resolution crossed molecular beam apparatus. The rotational states of product HF (<i>v</i>′ = 2) are much hotter in the F + HD reaction. It is uncovered that the observations are due to the dominant role of the dynamical resonance states in these two isotopic reactions. The angular potential well in the region of the resonance state of the F + HD reaction is much deeper and supports wave function with high angular kinetic energy, which in turn comes from different H tunneling processes in the F + HD and F + H<sub>2</sub> reaction

    The Clinical Significance of DC-SIGN and DC-SIGNR, which Are Novel Markers Expressed in Human Colon Cancer

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    <div><p>Background</p><p>Colon cancer has always been diagnosed at a late stage, which is associated with poor prognosis. The currently used serum tumor markers CEA and CA19-9 display low sensitivity and specificity and may not have diagnostic value in early stage colon cancer. Thus, there is an urgent need to identify novel serum biomarkers for use in the early detection of colon cancer.</p><p>Methods</p><p>In this study, the expression of DC-SIGN and DC-SIGNR in serum was detected by enzyme-linked immunosorbent assay (ELISA). DC-SIGN and DC-SIGNR expression was detected in cancer tissues by immunohistochemistry (IHC).</p><p>Results</p><p>The level of sDC-SIGN was lower in patients than in the healthy controls, while the level of sDC-SIGNR in patients was higher than in the healthy controls. Both sDC-SIGN and sDC-SIGNR had diagnostic significances for cancer patients, and the combined diagnosis of these two markers was higher than both of them alone. Furthermore, there were significant differences between both sDC-SIGN and sDC-SIGNR in stage I/II patients and the healthy controls. Moreover, high sDC-SIGN level was accompanied with the long survival time. Additionally, DC-SIGNR was negative in the cancer foci and matched normal colon tissues but was weakly positive between the cancer foci. DC-SIGN staining was faint in matched normal colon tissues, strong in the tumor stroma and the invasive margin of colon cancer tissues, and negatively correlated with the sDC-SIGN level in serum from the same patient. Interestingly, the percent survival of patients with a DC-SIGN mean density of>0.001219 (the upper 95% confidence interval of matched normal colon tissues) was higher than for all other patients.</p><p>Conclusion</p><p>DC-SIGN and DC-SIGNR are blood-based molecular markers that can potentially be used for the diagnosis of early stage patients. Moreover, expression of DC-SIGN in serum and cancer tissues may affect the survival time for colon cancer patients.</p></div

    The early diagnostic values of sDC-SIGN and sDC-SIGNR in stage I/II colon cancer patients.

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    <p><b>A–B</b>: Both sDC-SIGN and sDC-SIGNR levels from early colon cancer patients. Stage I/II patients were significantly different from healthy people, P<0.01. sDC-SIGN is lower than in the healthy control, while sDC-SIGNR is higher. <b>C–D</b>: In the stage I/II patients, sDC-SIGN and sDC-SIGNR had a significant diagnostic value (P<0.01). The cut-off concentrations of DC-SIGN and DC-SIGNR were less than 2.211 µg/ml and more than 189.3 ng/ml, respectively. The corresponding sensitivity and specificity of the two molecules were 81.33% and 55.56%, 48.65% and 92.50%, respectively. <b>E–F</b>: The AUC of CEA and CA19-9 in early cancer were 0.6904 and 0.6917. At the above clinical decisive level, the sensitivity of both CEA (18.64) and CA19-9 (10.00) were very low, while, the specificity of both CEA (92.33) and CA19-9 (94.55) was high. <b>G</b>: The comparison between the ROC curves of four markers, DC-SIGN, DC-SIGNR, CEA and CA19-9. There were significant differences between the AUCs of sDC-SIGN and both sDC-SIGNR and CA19-9. According to the cut-off values for sDC-SIGN and sDC-SIGNR obtained from the ROC curves, CEA and CA19-9 from the clinical decisive level, the sensitivity (diagnostic values) of both sDC-SIGN (81%) and sDC-SIGNR (49%) were higher than CEA (19%) and CA19-9 (10%).</p

    The levels and diagnostic values of sDC-SIGN and sDC-SIGNR in colon cancer patients.

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    <p><b>A–B</b>: There was statistical significance in the sDC-SIGN and sDC-SIGNR level between healthy controls and colon cancer patients, P<0.001. The sDC-SIGN level (A) was lower in colon cancer patients than healthy controls; however, the sDC-SIGNR level (B) was higher in colon cancer patients than healthy controls. <b>C</b>: The level of sDC-SIGN in serum was significantly correlated with that of sDC-SIGNR in the same patient, P<0.001, r = 0.8137. <b>D–E</b>: According to the analysis of Youden index, the cut-off concentrations for sDC-SIGN and sDC-SIGNR are less than 2.226 µg/ml and more than 227.2 ng/ml, respectively, and the corresponding Sensitivity and Specificity of sDC-SIGN and sDC-SIGNR are 87.56%, 55.56% and 61.90%, 97.50%, respectively. Additionally, the Area under the curve (AUC) for sDC-SIGN is 0.7538, while the AUC of sDC-SIGNR is 0.8031. <b>F–G</b>: The AUC of CEA and CA19-9 in patients were 0.7477 and 0.6126, respectively. Based on the clinical decisive levels (0–5 ug/l for CEA, 0–27 U/ml for CA19-9), the cut-off values of CEA and CA19-9 were obtained. And the corresponding sensitivity and specificity of CEA and CA19-9 were 29.22 and 92.38, 14.67 and 94.55, respectively. <b>H</b>: The combined diagnosis of these two markers, sDC-SIGN and sDC-SIGNR, was analyzed through the binary logistic regression and ROC curve. The AUC of sDC-SIGN/sDC-SIGNR was 0.9885, the specificity and sensitivity were 94.8% and 98.7%, respectively.</p
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