Publications by authors named "Congcong Huang"

26 Publications

  • Page 1 of 1

Capillary Forces between Concave Gripper and Spherical Particle for Micro-Objects Gripping.

Micromachines (Basel) 2021 Mar 8;12(3). Epub 2021 Mar 8.

State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150080, China.

The capillary action between two solid surfaces has drawn significant attention in micro-objects manipulation. The axisymmetric capillary bridges and capillary forces between a spherical concave gripper and a spherical particle are investigated in the present study. A numerical procedure based on a shooting method, which consists of double iterative loops, was employed to obtain the capillary bridge profile and bring the capillary force subject to a constant volume condition. Capillary bridge rupture was characterized using the parameters of the neck radius, pressure difference, half-filling angle, and capillary force. The effects of various parameters, such as the contact angle of the spherical concave gripper, the radius ratio, and the liquid bridge volume on the dimensionless capillary force, are discussed. The results show that the radius ratio has a significant influence on the dimensionless capillary force for the dimensionless liquid bridge volumes of 0.01, 0.05, and 0.1 when the radius ratio value is smaller than 10. The effectiveness of the theorical approach was verified using simulation model and experiments.
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http://dx.doi.org/10.3390/mi12030285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8001796PMC
March 2021

Diastereoselective and Stereodivergent Synthesis of 2-Cinnamylpyrrolines Enabled by Photoredox-Catalyzed Iminoalkenylation of Alkenes.

Angew Chem Int Ed Engl 2021 Apr 10;60(17):9672-9679. Epub 2021 Mar 10.

State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.

A photoredox-catalyzed iminoalkenylation of γ-alkenyl O-acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)- and (Z)-cinnamylpyrrolines are accessible depending on the reaction solvent. In dichloromethane, (E)-cinnamylpyrrolines are produced through a photoredox-mediated single-electron-transfer process. In tetrahydrofuran, (Z)-cinnamylpyrrolines are generated by photocatalytic contra-thermodynamic E-to-Z isomerization of (E)-cinnamylpyrrolines though an energy-transfer pathway. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated.
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http://dx.doi.org/10.1002/anie.202016941DOI Listing
April 2021

Postoperative analgesic effects of the quadratus lumborum block III and transversalis fascia plane block in paediatric patients with developmental dysplasia of the hip undergoing open reduction surgeries: a double-blinded randomised controlled trial.

BMJ Open 2021 02 4;11(2):e038992. Epub 2021 Feb 4.

Department of Pain Management, Jinan Central Hospital Affiliated to Shandong University, Jinan, Shandong, China

Objective: To evaluate the analgesic effectiveness of two novel regional nerve blocks in paediatric patients with developmental dysplasia of the hip (DDH) after open reduction surgeries.

Design: Prospective, double-blinded, randomised controlled trial.

Setting: 2 tertiary teaching hospitals in China between August 2017 and July 2018.

Participants: 110 paediatric patients aged 2-10 years with DDH undergoing open reduction surgeries were recruited, 95 were randomised and 90 were included in the final analysis.

Interventions: Random assignment to quadratus lumborum block III (QLB III) group, transversalis fascia plane block (TFPB) group and the control (no region nerve block) group.

Primary And Secondary Outcome Measures: The primary outcome was the Face, Legs, Activity, Cry and Consolability (FLACC) Scale Scores. Secondary outcomes included perioperative opioid consumption, the time until first press of nurse-controlled analgesia/patient-controlled analgesia (NCA/PCA) pump and the total counts number of pressing, length of postanaesthesia care unit (PACU) stay, length of hospital stay, parental satisfaction with pain management and adverse events.

Results: Mean FLACC Scores were significantly lower in QLB III group and TFPB group while in the PACU and for 48 hours postoperatively, compared with control group (p<0.0001, p<0.0001, respectively). No differences were found for FLACC Scores between QLB III group and TFPB group, neither at rest (p=0.0402) nor while posture changing (p=0.0306). TFPB prolonged the first-time request for NCA/PCA analgesia, and decreased the total number of pressing counts, compared with QLB III (22.5 (16.2 to 28.7) vs 11.7 (6.6 to 16.8), p<0.0001; 2.4 (1.3 to 3.6) vs 3.8 (2.8 to 4.8), p=0.0111, respectively). No patient experienced any adverse events.

Conclusions: We suggested that both ultrasound-guided QLB III and TFPB should be considered as an option for perioperative analgesia in children with DDH undergoing open reduction surgeries. TFPB was superior to the QLB III because it prolonged the first-time request for NCA/PCA analgesia and decreased the total counts number of pressing.

Trial Registration Number: NCT03189966/2017.
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http://dx.doi.org/10.1136/bmjopen-2020-038992DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7925863PMC
February 2021

CPK5 Phosphorylates the Chitin Receptor LYK5 to Regulate Plant Innate Immunity.

Front Plant Sci 2020 11;11:702. Epub 2020 Jun 11.

State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China.

Chitin, a major component of the fungal cell wall, triggers plant innate immunity in a receptor complex including two major lysin motif receptor-like kinases, AtLYK5, and AtCERK1. Although AtLYK5 has been proposed to be a major chitin-binding receptor, the pseudokinase domain of AtLYK5 is required to mediate chitin-triggered immune responses in plants. In this study, 48 AtLYK5-interacting proteins were identified using immunoprecipitation and mass spectrometry assay. Among them, CALCIUM-DEPENDENT PROTEIN KINASE 5 (AtCPK5) is a protein kinase interacting with both AtLYK5 and AtCERK1. Chitin-induced immune responses are inhibited in both and mutant plants. AtLYK5 and AtLYK4 but not AtCERK1 are phosphorylated by AtCPK5 and AtCPK6 . Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and kinase assay identified that Ser-323 and Ser-542 of AtLYK5 are important phosphorylation residues by AtCPK5. Transgenic expressing either AtLYK5-S323A or AtLYK5-S542A in the mutant only partially rescue the defects in chitin-triggered MPK3/MPK6 phosphorylation. Overexpression of AtCPK5 could increase AtCERK1 protein level after chitin treatment. These data proposed a model in which AtCPK5 directly phosphorylates AtLYK5 and regulates chitin-induced defense responses in .
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http://dx.doi.org/10.3389/fpls.2020.00702DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7300259PMC
June 2020

UrbanMotion: Visual Analysis of Metropolitan-Scale Sparse Trajectories.

IEEE Trans Vis Comput Graph 2020 May 4;PP. Epub 2020 May 4.

Visualizing massive scale human movement in cities plays an important role in solving many of the problems that modern cities face (e.g., traffic optimization, business site configuration). In this work, we study a big mobile location dataset that covers millions of city residents, but is temporally sparse on the trajectory of individual user. Mapping sparse trajectories to illustrate population movement poses several challenges from both analysis and visualization perspectives. In the literature, there are a few techniques designed for sparse trajectory visualization; yet they do not consider trajectories collected from mobile apps that possess long-tailed sparsity with record intervals as long as hours. This work introduces UrbanMotion, a visual analytics system that extends the original wind map design by supporting map-matched local movements, multi-directional population flows, and population distributions. Effective methods are proposed to extract and aggregate population movements from dense parts of the trajectories leveraging their long-tailed sparsity. Both characteristic and anomalous patterns are discovered and visualized. We conducted three case studies, one comparative experiment, and collected expert feedback in the application domains of commuting analysis, event detection, and business site configuration. The result demonstrates significance and effectiveness of our system in completing key analytics tasks for urban users.
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http://dx.doi.org/10.1109/TVCG.2020.2992200DOI Listing
May 2020

A Highly Efficient Dimeric Manganese-Catalyzed Selective Hydroarylation of Internal Alkynes.

Angew Chem Int Ed Engl 2020 Jul 25;59(31):12789-12794. Epub 2020 May 25.

State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.

We have developed a general and site-predictable manganese-catalyzed hydroarylation of internal alkynes in the presence of water, under an air atmosphere without the involvement of ligand. The unique catalytic feature of this reaction is highlighted by comparison with other widely used transition metal catalysts including palladium, rhodium, nickel, or copper. The simple operation, high efficiency and excellent functional group compatibility make this protocol practical for more than 90 structurally diverse internal alkynes, overcoming the influence of both electronic and steric effect of alkynes. Its exclusive regio- and chemoselectivity originates from the unique reactivity of the manganese-based catalyst towards an inherent double controlled strategy of sterically hindered propargyl alcohols without the installing of external directing groups. Its synthetic robustness and practicality have been illustrated by the concise synthesis of bervastatin, a hypolipidemic drug, and late-stage modification of complex alkynes with precise regioselectivity.
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http://dx.doi.org/10.1002/anie.202004950DOI Listing
July 2020

Natural variation at OsCERK1 regulates arbuscular mycorrhizal symbiosis in rice.

New Phytol 2020 02 3;225(4):1762-1776. Epub 2019 Oct 3.

State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.

The symbiotic interaction between arbuscular mycorrhizal fungi (AMF) and land plants is essential for efficient nutrient acquisition and utilisation. Our understanding of key processes controlling the AMF colonisation in rice is still limited. Dongxiang wild rice (DY) exhibited a stronger colonisation with Rhizophagus irregularis than the rice cultivar Zhongzao 35 (ZZ35). Chromosome segment substitution lines were constructed and the OsCERK1 gene from DY was mapped. Transgenic plants in the japonica rice Zhonghua 11 (ZZ11) were constructed to compare root colonisation by AMF. Chromosome single-segment substitution lines containing OsCERK1 showed higher phosphorus content and grain yield relative to ZZ35. Four amino acids substitutions were identified among the OsCERK1 haplotypes of DY, ZZ35 and ZH11 and two of these were in the second lysine-motif domain, which is essential for the differences of AMF colonisation level among rice varieties. Heterologous expression of OsCERK1 in ZH11 significantly enhanced AMF colonisation and increased resistance against the pathogenic fungi Magnaporthe oryzae. Notably, the OsCERK1 haplotype was absent from 4660 cultivated rice varieties. We conclude that OsCERK1 is a key gene affecting the symbiotic interaction with AMF and OsCERK1 has the biotechnological potential to increase rice phosphorus acquisition and utilisation efficiency for sustainable agriculture.
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http://dx.doi.org/10.1111/nph.16158DOI Listing
February 2020

Swirling swimmer.

Authors:
Congcong Huang

Nat Nanotechnol 2019 07;14(7):638

Nature Nanotechnology, .

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http://dx.doi.org/10.1038/s41565-019-0509-8DOI Listing
July 2019

Visual Analysis of Collective Anomalies Using Faceted High-Order Correlation Graphs.

IEEE Trans Vis Comput Graph 2020 Jul 24;26(7):2517-2534. Epub 2018 Dec 24.

Successfully detecting, analyzing, and reasoning about collective anomalies is important for many real-life application domains (e.g., intrusion detection, fraud analysis, software security). The primary challenges to achieving this goal include the overwhelming number of low-risk events and their multimodal relationships, the diversity of collective anomalies by various data and anomaly types, and the difficulty in incorporating the domain knowledge of experts. In this paper, we propose the novel concept of the faceted High-Order Correlation Graph (HOCG). Compared with previous, low-order correlation graphs, HOCG achieves better user interactivity, computational scalability, and domain generality through synthesizing heterogeneous types of objects, their anomalies, and the multimodal relationships, all in a single graph. We design elaborate visual metaphors, interaction models, and the coordinated multiple view based interface to allow users to fully unleash the visual analytics power of the HOCG. We conduct case studies for three application domains and collect feedback from domain experts who apply our method to these scenarios. The results demonstrate the effectiveness of the HOCG in the overview of point anomalies, the detection of collective anomalies, and the reasoning process of root cause analyses.
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http://dx.doi.org/10.1109/TVCG.2018.2889470DOI Listing
July 2020

An enzyme-free and resettable platform for the construction of advanced molecular logic devices based on magnetic beads and DNA.

Nanoscale 2016 Aug;8(34):15681-8

Department of Chemistry, Taizhou University, Jiaojiang, 318000, China.

A series of multiple logic circuits based on magnetic beads and DNA are constructed to perform resettable nonarithmetic functions, including a digital comparator, 4-to-2 encoder and 2-to-3 decoder, 2-to-1 encoder and 1-to-2 decoder. The signal reporter is composed of a G-quadruplex/NMM complex and a AuNP-surface immobilized molecular beacon. It is the first time that the designed DNA-based nonarithmetic nanodevices can share the same DNA platform with a reset function, which has great potential application in information processing at the molecular level. Another novel feature of the designed system is that the developed nanodevices are operated on a simple DNA/magnetic bead platform and share a constant threshold setpoint without the assistance of any negative logic conversion. The reset function is realized by heating the output system and the magnetic separation of the computing modules. Due to the biocompatibility and design flexibility of DNA, these investigations may provide a new route towards the development of resettable advanced logic circuits in biological and biomedical fields.
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http://dx.doi.org/10.1039/c6nr04762aDOI Listing
August 2016

Pediatric preoperative risk factors to predict postoperative ICU admission and death from a multicenter retrospective study.

Paediatr Anaesth 2016 Jun;26(6):637-43

Department of Anesthesiology, Critical Care and Pain Medicine, The 2nd Affiliated Hospital & Yuying Children's Hospital of WenZhou Medical University, Wenzhou, China.

Background: Although some studies have investigated the potential predictors of perioperative mortality, there are few specifically for pediatrics.

Objective: The aim of the retrospective study was to analyze potential preoperative risk factors and to develop a pediatric preoperative risk prediction score (PRPS), and to predict postoperative ICU admission and the incidence of perioperative death in pediatric patients.

Methods: Patients who postoperatively admitted to ICU or died (occurred within 30 days after the surgery) from 263 607 pediatric surgical patients with age from 1 day to 14 years old in eight centers in China from October 2010 to September 2013 were retrospectively analyzed. About 5500 non-ICU admission and death patients were randomly selected from those 263 607 patients as controls for analysis comparison. Independent risk factors and a risk model were derived from these analyses, and were further assessed with the likelihood ratio test and the area under the receiver operating characteristic (ROC) curve.

Results: There were 1812 ICU admission or death patients but 187 patients' records are incomplete. There were 487 patients with incomplete records among 5500 controls. Collectively, data from 6626 patients were enrolled in final analyses. With multiple logistic regression analysis, age, ASA physical status, SpO2 , prematurity, and unfasted status were found to be independent predictors for critical patients. The AUC value of 0.905 indicated excellent predictive performance between critical and noncritical predictors.

Conclusions: Our study revealed that age, ASA physical status, SpO2 , prematurity, and unfasted status are risk factors to predict postoperative ICU admission and death in pediatric patients.
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http://dx.doi.org/10.1111/pan.12905DOI Listing
June 2016

Reconfigurable and resettable arithmetic logic units based on magnetic beads and DNA.

Nanoscale 2015 Dec 25;7(48):20749-56. Epub 2015 Nov 25.

College of Sciences, Northeastern University, Shenyang, 110819, China.

Based on the characteristics of magnetic beads and DNA, a simple and universal platform was developed for the integration of multiple logic gates to achieve resettable half adder and half subtractor functions. The signal reporter was composed of a split G-quadruplex DNAzyme and AuNP-surface immobilized molecular beacon molecule. The novel feature of the designed system is that the inputs (split G-quadruplexes) can interact with hairpin-modified Au NPs linked to magnetic particles. Another novel feature is that the logic operations can be reset by heating the output system and by using the magnetic separation of the computing modules. Moreover, the developed half adder and half subtractor are realized on a simple DNA/magnetic bead platform in an enzyme-free system and share a constant threshold setpoint. Due to the diversity and design flexibility of DNA, these investigations may provide a new method for the development of resettable DNA-based arithmetic operations.
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http://dx.doi.org/10.1039/c5nr06733bDOI Listing
December 2015

Anomalous Behavior of the Homogeneous Ice Nucleation Rate in "No-Man's Land".

J Phys Chem Lett 2015 Jul 2;6(14):2826-2832. Epub 2015 Jul 2.

SUNCAT Ctr Interface Sci & Catalysis, SLAC National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, California 94025, United States ; Department of Physics, AlbaNova University Center, Stockholm University , S-106 91 Stockholm, Sweden ; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, California 94025, United States.

We present an analysis of ice nucleation kinetics from near-ambient pressure water as temperature decreases below the homogeneous limit by cooling micrometer-sized droplets (microdroplets) evaporatively at 10-10 K/s and probing the structure ultrafast using femtosecond pulses from the Linac Coherent Light Source (LCLS) free-electron X-ray laser. Below 232 K, we observed a slower nucleation rate increase with decreasing temperature than anticipated from previous measurements, which we suggest is due to the rapid decrease in water's diffusivity. This is consistent with earlier findings that microdroplets do not crystallize at <227 K, but vitrify at cooling rates of 10-10 K/s. We also hypothesize that the slower increase in the nucleation rate is connected with the proposed "fragile-to-strong" transition anomaly in water.
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http://dx.doi.org/10.1021/acs.jpclett.5b01164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4507474PMC
July 2015

Long-range ion-water and ion-ion interactions in aqueous solutions.

Phys Chem Chem Phys 2015 Apr 28;17(13):8427-30. Epub 2015 Jan 28.

Department of Chemistry, Stanford University, Stanford, California 94305, USA.

Using small-angle X-ray scattering (SAXS), we obtained direct experimental evidence on the structure of hydrated polyatomic anions, with hydration effects starkly different from those of cations (J. Chem. Phys., 2011, 134, 064513). We propose that the size and charge density of the naked ions do not sufficiently account for the differences in the SAXS curves. For cations, the ion-ion contribution gives a prominent first-order diffraction peak, whereas for anions, the low-Q enhancement in the SAXS curves indicates density inhomogeneities as a result of ion-water interactions.
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http://dx.doi.org/10.1039/c4cp04759aDOI Listing
April 2015

Synthesis of phosphorus-doped graphene and its wide potential window in aqueous supercapacitors.

Chemistry 2015 Jan 7;21(1):80-5. Epub 2014 Nov 7.

Nanomaterials Centre, School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia 4072, Queensland (Australia).

Phosphorus-doped (P-doped) graphene with the P doping level of 1.30 at % was synthesized by annealing the mixture of graphene and phosphoric acid. The presence of P was confirmed by elemental mapping and X-ray photoelectron spectroscopy, while the morphology of P-doped graphene was revealed by using scanning electron microscopy and transmission electron microscopy. To investigate the effect of P doping, the electrochemical properties of P-doped graphene were tested as a supercapacitor electrode in an aqueous electrolyte of 1 M H2 SO4. The results showed that doping of P in graphene exhibited significant improvement in terms of specific capacitance and cycling stability, compared with undoped graphene electrode. More interestingly, the P-doped graphene electrode can survive at a wide voltage window of 1.7 V with only 3 % performance degradation after 5000 cycles at a current density of 5 A g(-1), providing a high energy density of 11.64 Wh kg(-1) and a high power density of 831 W kg(-1).
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http://dx.doi.org/10.1002/chem.201404779DOI Listing
January 2015

[Effect of single-dose dexmedetomidine on recovery profiles after sevoflurane anesthesia with spontaneous respiration in pediatric patients undergoing cleft lip and palate repair].

Zhonghua Yi Xue Za Zhi 2014 May;94(19):1466-9

Department of Anesthesiology, Second Affiliated Hospital, Wenzhou Medical University, Wenzhou 325027, China. Email:

Objective: To explore the effect of single-dose dexmedetomidine on recovery period after sevoflurane anesthesia with spontaneous respiration in pediatric patients undergoing cleft lip and palate repair.

Methods: A total of 60 American Society of Anesthesiologists (ASA) I-II pediatric patients undergoing cleft lip and palate repair from October to December 2013 were randomly divided into groups D and C (n = 30 each) . Dexmedetomidine 0.5 µg/kg (group D) or an equal volume of normal saline (group C) was ad ministered intravenously over a period of 10 min at 30 min before the end of surgery. Anesthesia was induced and maintained with sevoflurane under spontaneous ventilation. Heart rate, mean arterial pressure (MAP), hemoglobin oxygen saturation (SpO2), respiratory rate, tidal volume (VT) and pressure of end-tidal carbon dioxide (PETCO2) were recorded at the time before induction (T0), 30 min before the end of surgery (T1) , 20 min before the end of surgery (T2), 15 min before the end of surgery (T3), 10 min before the end of surgery (T4), the end of surgery (T5), extubation (T6), 5 min after transferal into post-anesthesia care unit (PACU) (T7) , 1 h after surgery (T8) , extubation time, length of PACU stay, fentanyl consumption and adverse events were all recorded. The incidence and severity of coughing and emergence agitation were assessed.

Results: Compared to T0, MAP and heart rate at T1 to T5 all decreased in two groups (P < 0.05). MAP and heart rate at T6 both increased in two groups and group C was higher than group D (P < 0.05). No inter-group differences existed in SpO2, respiratory rate, VT or PETCO2. The incidence of coughing and emergence agitation (30% and 13.3%), fentanyl consumption of group D (0.8 ± 2.1 µg) were all significantly lower than that of group C [(66.7% vs 56.7%) and (4.9 ± 6.50) µg, P < 0.05]. Length of PACU stay in group D was shorter than that in group C [(15 ± 6) vs (23 ± 19) min, P < 0.05]. No inter-group difference existed in extubation time or adverse events.

Conclusion: A single intravenous dose of dexmedetomidine is effective in reducing emergence agitation and coughing, shortening length of PACU stay and improving the quality of recovery period after sevoflurane anesthesia in pediatric patients undergoing cleft lip and palate repair.
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May 2014

Wide electrochemical window of supercapacitors from coffee bean-derived phosphorus-rich carbons.

ChemSusChem 2013 Dec 12;6(12):2330-9. Epub 2013 Sep 12.

Northeastern University of China, College of Science, Department of Chemistry, No.11, Lane 3, Wen Hua Road, 110819 Shenyang (P.R. China); The University of Queensland, ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnology, Corner College and Cooper Roads, St Lucia, 4072 QLD (Australia).

Phosphorus-rich carbons (PCs) were prepared by phosphoric acid activation of waste coffee grounds in different impregnation ratios. PCs were characterized by nitrogen and carbon dioxide adsorption and X-ray photoelectron spectroscopy. The results indicate that the activation step not only creates a porous structure, but also introduces various phosphorus and oxygen functional groups to the surface of carbons. As evidenced by cyclic voltammetry, galvanostatic charge/discharge, and wide potential window tests, a supercapacitor constructed from PC-2 (impregnation ratio of 2), with the highest phosphorus content, can operate very stably in 1 M H2 SO4 at 1.5 V with only 18 % degradation after 10 000 cycles at a current density of 5 A g(-1) . Due to the wide electrochemical window, a supercapacitor assembled with PC-2 has a high energy density of 15 Wh kg(-1) at a power density of 75 W kg(-1) . The possibility of widening the potential window above the theoretical potential for the decomposition of water is attributed to reversible electrochemical hydrogen storage in narrow micropores and the positive effect of phosphorus-rich functional groups, particularly the polyphosphates on the carbon surface.
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http://dx.doi.org/10.1002/cssc.201300457DOI Listing
December 2013

Solvation structures of protons and hydroxide ions in water.

J Chem Phys 2013 Apr;138(15):154506

Department of Chemistry, Stanford University, Stanford, California 94305, USA.

X-ray Raman spectroscopy (XRS) combined with small-angle x-ray scattering (SAXS) were used to study aqueous solutions of HCl and NaOH. Hydrated structures of H(+) and OH(-) are not simple mirror images of each other. While both ions have been shown to strengthen local hydrogen bonds in the hydration shell as indicated by XRS, SAXS suggests that H(+) and OH(-) have qualitatively different long-range effects. The SAXS structure factor of HCl (aq) closely resembles that of pure water, while NaOH (aq) behaves similar to NaF (aq). We propose that protons only locally enhance hydrogen bonds while hydroxide ions induce tetrahedrality in the overall hydrogen bond network of water.
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http://dx.doi.org/10.1063/1.4801512DOI Listing
April 2013

Benchmark oxygen-oxygen pair-distribution function of ambient water from x-ray diffraction measurements with a wide Q-range.

J Chem Phys 2013 Feb;138(7):074506

Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100, USA.

Four recent x-ray diffraction measurements of ambient liquid water are reviewed here. Each of these measurements represents a significant development of the x-ray diffraction technique applied to the study of liquid water. Sources of uncertainty from statistical noise, Q-range, Compton scattering, and self-scattering are discussed. The oxygen-hydrogen contribution to the measured x-ray scattering pattern was subtracted using literature data to yield an experimental determination, with error bars, of the oxygen-oxygen pair-distribution function, g(OO)(r), which essentially describes the distribution of molecular centers. The extended Q-range and low statistical noise of these measurements has significantly reduced truncation effects and related errors in the g(OO)(r) functions obtained. From these measurements and error analysis, the position and height of the nearest neighbor maximum in g(OO)(r) were found to be 2.80(1) Å and 2.57(5) respectively. Numerical data for the coherent differential x-ray scattering cross-section I(X)(Q), the oxygen-oxygen structure factor S(OO)(Q), and the derived g(OO)(r) are provided as benchmarks for calibrating force-fields for water.
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http://dx.doi.org/10.1063/1.4790861DOI Listing
February 2013

Microscopic probing of the size dependence in hydrophobic solvation.

J Chem Phys 2012 Feb;136(7):074507

Stanford Synchrotron Radiation Lightsource, P. O. Box 20450, Stanford, California 94309, USA.

We report small angle x-ray scattering data demonstrating the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in hydrophobic solvation. By increasing the side chain length of amphiphilic tetraalkyl-ammonium (C(n)H(2n+1))(4)N(+) (R(4)N(+)) cations in aqueous solution we observe diffraction peaks indicating association between cations at a solute size between 4.4 and 5 Å, which show temperature dependence dominated by hydrophobic attraction. Using O K-edge x-ray absorption we show that small solutes affect hydrogen bonding in water similar to a temperature decrease, while large solutes affect water similar to a temperature increase. Molecular dynamics simulations support, and provide further insight into, the origin of the experimental observations.
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http://dx.doi.org/10.1063/1.3684893DOI Listing
February 2012

X-ray Raman scattering provides evidence for interfacial acetonitrile-water dipole interactions in aqueous solutions.

J Chem Phys 2011 Oct;135(16):164509

Stanford Synchrotron Radiation Lightsource, P.O.B. 20450, Stanford, California 94309, USA.

Aqueous solutions of acetonitrile (MeCN) have been studied with oxygen K-edge x-ray Raman scattering (XRS) which is found to be sensitive to the interaction between water and MeCN. The changes in the XRS spectra can be attributed to water directly interacting with MeCN and are reproduced by density functional theory calculations on small clusters of water and MeCN. The dominant structural arrangement features dipole interaction instead of H-bonds between the two species as revealed by the XRS spectra combined with spectrum calculations. Small-angle x-ray scattering shows the largest heterogeneity for a MeCN to water ratio of 0.4 in agreement with earlier small-angle neutron scattering data.
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http://dx.doi.org/10.1063/1.3655468DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3298555PMC
October 2011

Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water.

Phys Chem Chem Phys 2011 Nov 19;13(44):19997-20007. Epub 2011 Oct 19.

Stanford Synchrotron Radiation Lightsource, Stanford, CA 94309, USA.

We have developed wide-angle X-ray diffraction measurements with high energy-resolution and accuracy to study water structure at three different temperatures (7, 25 and 66 °C) under normal pressure. Using a spherically curved Ge crystal an energy resolution better than 15 eV has been achieved which eliminates influence from Compton scattering. The high quality of the data allows for a reliable Fourier transform of the experimental data resolving shell structure out to ~12 Å, i.e. 5 hydration shells. Large-scale molecular dynamics (MD) simulations using the TIP4P/2005 force-field reproduce excellently the experimental shell-structure in the range 4-12 Å although less agreement is seen for the first peak in the intermolecular pair-correlation function (PCF). The Shiratani-Sasai Local Structure Index [J. Chem. Phys. 104, 7671 (1996)] identifies a tetrahedral minority giving the intermediate-range oscillations in the O-O PCF and a disordered majority providing a more featureless background in this range. The current study supports the proposal that the structure of liquid water, even at high temperatures, can be described in terms of a two-state fluctuation model involving local structures related to the high-density and low-density forms of liquid water postulated in the liquid-liquid phase transition hypothesis.
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http://dx.doi.org/10.1039/c1cp22804hDOI Listing
November 2011

The surface phase diagram of Li/Cu(001) explored by helium atom scattering.

J Phys Condens Matter 2011 Sep 21;23(35):355001. Epub 2011 Jul 21.

Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK.

We use helium atom scattering to investigate the structures formed by Li adsorption onto Cu(001) in the 0-2 ML regime. Submonolayer growth at 180 K proceeds through a sequence of ordered overlayers, including a c(2 × 2) structure at 0.5 ML and a series of 'ladder' superlattices around 0.6 ML. Beyond 1 ML, incommensurate, three-dimensional Li islands develop. A quantum close-coupled scattering analysis is performed to study the empirical He-surface potential of the structurally heterogeneous ladder structures. Good agreement with the measured distribution of diffracted intensity is obtained by describing the He-ladder interaction potential as the summation of only six one-dimensional Fourier components. The fitted potential indicates a remarkably flat surface that is punctuated by substantial, striped protrusions in the electron density. The result is consistent with the formation of one-dimensional Li wires, indicating an inhomogeneous metallization process.
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http://dx.doi.org/10.1088/0953-8984/23/35/355001DOI Listing
September 2011

Increased fraction of low-density structures in aqueous solutions of fluoride.

J Chem Phys 2011 Jun;134(22):224507

Department of Chemistry, Stanford University, Stanford, California 94305, USA.

X-ray absorption spectroscopy (XAS) and small angle x-ray scattering (SAXS) were utilized to study the effect of fluoride (F(-)) anion in aqueous solutions. XAS spectra show that F(-) increases the number of strong H-bonds, likely between F(-) and water in the first hydration shell. SAXS data show a low-Q scattering intensity increase similar to the effect of a temperature decrease, suggesting an enhanced anomalous scattering behavior in F(-) solutions. Quantitative analysis revealed that fluoride solutions have larger correlation lengths than chloride solutions with the same cations but shorter compared to pure water. This is interpreted as an increased fraction of tetrahedral low-density structures in the solutions due to the presence of the F(-) ions, which act as nucleation centers replacing water in the H-bonding network and forming stronger H-bonds, but the presence of the cations restricts the extension of strong H-bonds.
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http://dx.doi.org/10.1063/1.3597606DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3188619PMC
June 2011

The structure of water in the hydration shell of cations from x-ray Raman and small angle x-ray scattering measurements.

J Chem Phys 2011 Feb;134(6):064513

Department of Chemistry, Stanford University, Stanford, California 94305, USA.

X-ray Raman scattering (XRS) spectroscopy and small angle x-ray scattering (SAXS) are used to study water in aqueous solutions of NaCl, MgCl(2), and AlCl(3) with the particular aim to provide information about the structure of the hydration shells of the cations. The XRS spectra show that Na(+) weakens the hydrogen bonds of water molecules in its vicinity, similar to the effect of increased temperature and pressure. Mg(2+) and Al(3+), on the other hand, cause the formation of short and strong hydrogen bonds between the surrounding water molecules. The SAXS data show that Mg(2+) and Al(3+) form tightly bound hydration shells that give a large density contrast in the scattering data. From the form factors extracted from the SAXS data, we found that Mg(2+) and Al(3+) have, respectively, an equivalent of one and one and a half stable hydration shells that appear as a density contrast. In addition, we estimated that the density of water in the hydration shells of Mg(2+) and Al(3+) is, respectively, ∼61% and ∼71% higher than in bulk water.
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http://dx.doi.org/10.1063/1.3533958DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3188634PMC
February 2011

Increasing correlation length in bulk supercooled H2O, D2O, and NaCl solution determined from small angle x-ray scattering.

J Chem Phys 2010 Oct;133(13):134504

Stanford Synchrotron Radiation Lightsource, P.O. Box 20450, Stanford, California 94309, USA.

Using small angle x-ray scattering, we find that the correlation length of bulk liquid water shows a steep increase as temperature decreases at subzero temperatures (supercooling) and that it can, similar to the thermodynamic response functions, be fitted to a power law. This indicates that the anomalous properties of water are attributable to fluctuations between low- and high-density regions with rapidly growing average size upon supercooling. The substitution of H(2)O with D(2)O, as well as the addition of NaCl salt, leads to substantial changes of the power law behavior of the correlation length. Our results are consistent with the proposed existence of a liquid-liquid critical point in the deeply supercooled region but do not exclude a singularity-free model.
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http://dx.doi.org/10.1063/1.3495974DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2966487PMC
October 2010