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Your search keyword '"XIE, X.-J."' showing total 161 results
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161 results on '"XIE, X.-J."'

1. Response time of electron inside a molecule to light in strong-field ionization

Author

Che, J. Y., Peng, Y. G., Zhang, F. B., Xie, X. J., Xin, G. G., and Chen, Y. J.

Subjects
Physics - Atomic Physics
Abstract

We study ionization of aligned H$_2^+$ in strong elliptically-polarized laser fields numerically and analytically. The calculated offset angle in photoelectron momentum distribution is several degrees larger for the molecule than a model atom with similar ionization potential at diverse laser parameters. Using a strong-field model that considers the properties of multi-center and single-center Coulomb potentials, we are able to quantitatively reproduce this angle difference between the molecule and the atom. Further analyses based on this model show that the response time of electron to light which is encoded in the offset angle and is manifested as the time spent in tunneling ionization, is about 15 attoseconds longer for the molecule than the atom. This time difference is further enlarged when increasing the internuclear distance of the molecule., Comment: 7 pages,4 figures. arXiv admin note: substantial text overlap with arXiv:2212.09886

Published
2023

2. Discovery of Nine Super Li-rich Unevolved Stars from the LAMOST Survey

Author

Yan, T. -S., Shi, J. -R., Wang, L., Yan, H. -L., Zhou, Z. -M., Zhou, Y. -T., Fang, X. -S., Li, C. -Q., Chen, T. -Y., and Xie, X. -J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution spectroscopic survey (MRS), we report the discovery of nine super Li-rich unevolved stars with A(Li) $>$ 3.8 dex. These objects show unusually high levels of lithium abundances up to three times higher than the meteoritic value of 3.3 dex, which indicates that they must have experienced a history of lithium enrichment. It is found that seven of our program stars are fast rotators with $vsini>9$ km\,s$^{-1}$, which suggests that the accretion of circumstellar matter may be the main contributor to the lithium enhancement of these unevolved stars, however, other sources cannot be excluded., Comment: 10 pages, 3 figures

Published
2022
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3. Response time of photoemission at quantum-classic boundary

Author

Chen, C., Che, J. Y., Li, W. Y., Wang, S., Xie, X. J., Huang, J. Y., Peng, Y. G., Xin, G. G., and Chen, Y. J.

Subjects
Physics - Atomic Physics
Abstract

The response time of the electron to light in photoemission is difficult to define and measure. Tunneling ionization of atoms, a strong-laser-induced photoemission process, provides a semiclassical case for visiting the problem. Here, we show that the response time can be determined at the boundary between quantum and classic. Specifically, tunneling is instantaneous but a finite response time (about 100 attoseconds) is needed for the state of the tunneling electron to evolve into the ionized state around tunnel exit. This time can be well described with a compact expression related to some basic laser and atomic parameters. Moreover, it can be directly mapped to and easily decoded from photoelectron momentum with a simple mapping, allowing an unambiguous measurement. These results shed light on definition and measurement of the response time of photoemission., Comment: 11 pages, 8 figures. We have changed the title, reorganized this article, and replaced or deleted some of the data plots, but the main conclusions remain unchanged

Published
2021

4. Coulomb Effects on time-trajectory-resolved high-order harmonic generation

Author

Xie, X. J., Xu, R. H., Yu, S. J., Liu, X., Li, W., and Chen, Y. J.

Subjects
Physics - Atomic Physics
Abstract

We study the effect of Coulomb potential on high-order harmonic generation (HHG) numerically and analytically. We focus on the influence of Coulomb potential on emission times of HHG associated with specific electron trajectories. By using a numerical procedure based on numerical solution of time-dependent Schr\"{o}dinger equation (TDSE) in three dimensions, we extract the HHG emission times both for long and short electron trajectories. We compare TDSE predictions with those of a Coulomb-modified model arising from strong-field approximation (SFA). We show that the Coulomb effect induces earlier HHG emission times than those predicted by the general SFA model without considering the Coulomb potential. In particular, this effect influences differently on long and short electron trajectories and is more remarkable for low-energy harmonics than high ones. It also changes the HHG amplitudes for long and short electron trajectories. We validate our discussions with diverse laser parameters and forms of Coulomb potential. Our results strongly support a four-step model of HHG.

Published
2021
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5. Coulomb-induced ionization time lag after electrons tunnel out of a barrier

Author

Chen, Y. J., Xie, X. J., Chen, C., Xin, G. G., and Liu, J.

Subjects
Physics - Atomic Physics
Abstract

After electrons tunnel out of a laser-Coulomb-formed barrier, %formed by the strong laser field and the atomic Coulomb potential, the movement of the tunneling electron can be affected by the Coulomb tail. We show that this Coulomb effect induces a large time difference (longer than a hundred attoseconds) between the exiting time at which the electron exits the barrier and the ionization time at which the electron is free. This large time difference has important influences on strong-field processes such as above-threshold ionization and high-harmonic generation, with remarkably changing time-frequency properties of electron trajectories. Some semi-quantitative evaluations on these influences are addressed, which provide new insight into strong-field physics and give important suggestions on attosecond measurements., Comment: 5 pages, 4 figures

Published
2019

29. The experience of growing old in chronic mental health patients.

Author

Lai, Daniel W. L., Chan, K. C., Xie, X. J., and Daoust, G. D.

Subjects
ADAPTABILITY (Personality), AUTONOMY (Psychology), HEALTH behavior, HEALTH status indicators, INTERPERSONAL relations, INTERVIEWING, MENTAL illness, MOTIVATION (Psychology), OCCUPATIONS, SPIRITUALITY, TIME management, QUALITATIVE research, AFFINITY groups, FAMILY relations, LIFESTYLES, INDEPENDENT living, PATIENTS' attitudes, DESCRIPTIVE statistics, ACTIVE aging, ATTITUDES toward aging
Abstract

Objectives: Research evidence has demonstrated disparities and barriers associated with mental illness, which creates challenges for individuals with mental illness to maintain physical, mental, and social health as they age. The aim of this study was to examine the meaning of aging from the perspective of individuals with mental illness and explore their motivations and challenges to adopting healthy aging lifestyles and practices. Method: Using a qualitative narrative inquiry approach, interviews were conducted with 61 aging patients with mental illness aged 40 and older in community and institutional settings in Hong Kong. Results: Participants discussed the meaning of healthy aging in terms of meaningful occupation and use of time, and independence and autonomy. Motivating factors included a desire to avoid 'burdening' other people, to 'give back' to society, and gain back 'lost time'. These were connected to strategies for healthy aging, including social relationships and activities, spirituality, and healthy lifestyles. Challenges to adopting healthy aging practices included physical health difficulties and medication side effects, lack of purpose and boredom associated with daily routines and use of time, and conflicts and loss affecting family and peer relationships. Conclusion: Social and health services should be tailored to support aging individuals with mental illness and their families, addressing motivations and barriers to adopting healthy lifestyles. Promoting healthy aging practices to enable individuals with mental illness to achieve healthy aging is important for preparing for the aging of this population. [ABSTRACT FROM AUTHOR]

Published
2020
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30. Association of major adverse cardiovascular events and cardiac troponin-I levels following percutaneous coronary intervention: a three-year follow-up study at a single center.

Author

HUANG, Z.-S., ZHENG, Z.-D., ZHANG, J.-W., TANG, L.-L., ZHOU, L.-L., LI, S.-H., XIE, X.-J., DONG, R.-M., ZHU, J.-M., and LIU, J.-L.

Abstract

OBJECTIVE: Major adverse cardiovascular events occurrences of patients with different cardiac troponin-I (cTnI) levels following percutaneous coronary intervention (PCI) remained controversial. The prognostic relevance and risk factors of PCI-related myocardial infarction (MI) were not very clear as well. PATIENTS AND METHODS: Our study included 249 coronary artery disease patients without preoperative cTnI elevation who successfully accepted PCI from 2013 to 2014. A three-year follow-up was conducted for each patient. The patients were divided into PCI-related MI group and non-PCI-related MI group. Risk factors of PCI-related MI were first explored. The occurrence of MACE was recorded. The prognostic relevance between PCI-related MI (PMI) group and non-PCI-related MI group, as well as different postoperative cTnI levels, were compared. RESULTS: Low-density lipoprotein cholesterol (LDL-C), age, Gensini Score, total stent length, and intra-operative complication were found positively correlated with PCI-related MI occurrence, while hemoglobin and prior PCI history were negatively correlated. After 3-year follow-up, the Kaplan-Meier survival curve showed MACE occurrence was significantly increased in PCI-related MI group. Comparing to patients with normal postoperative cTnI, MACE occurrence was increased in patients with a 10xupper limit of normal (ULN)≤cTnI<70xULN and cTnI≥ 70xULN, while there was no difference in patients with 1xULN≤cTnI<5xULN and 5xULN≤cTnI< 10xULN. Cox proportional hazard regression analysis revealed PMI, NT-proBNP, and left ventricular ejection function (LVEF)<50% were positively correlated with MACE occurrence, while maximum inflation pressure and apoA-I were negatively correlated. CONCLUSIONS: Prognosis of PCI-related MI was poor, as well as in patients with postoperative cTnI≥10xULN. Among the risk factors of PMI, LDL-C, age, Gensini Score, total stent length, and intra-operative complication were positively correlated with PCI-related MI occurrence, while hemoglobin and prior PCI history were negatively correlated. [ABSTRACT FROM AUTHOR]

Published
2020

32. Direct Optical Carbon Dioxide Sensing Based on a Polymeric Film Doped with a Selective Molecular Tweezer-Type Ionophore

Author

Xie X. J., Pawlak M., Tercier-Waeber M. L., and Bakker E.

Abstract

A novel optical method for the determination of CO2 concentration in aqueous and gaseous samples of plasticized PVC film is presented. The detection principle makes use of a direct molecular recognition of the carbonate ion by a molecular tweezer type ionophore which has previously been demonstrated to exhibit excellent carbonate selectivity. The carbonate ion is extracted together with hydrogen ions into a polymeric film that contains the anion exchanger tridodecylmethylammonium chloride a lipophilic electrically charged and highly basic pH indicator which is used for the readout in absorbance mode in addition to the lipophilic carbonate ionophore. According to known bulk optode principles such an optical sensor responds to the product of the carbonate ion activity and the square of hydrogen ion activity. This quantity is thermodynamically linked to the activity of carbon dioxide. This allows one to realize a direct carbon dioxide sensor that does not make use of the traditional Severinghaus sensing principle of measuring a pH change upon CO2 equilibration across a membrane. A selectivity analysis shows that common ions such as chloride are sufficiently suppressed for direct PCO2 measurements in freshwater samples at pH 8. Chloride interference however is too severe for direct seawater measurements at the same pH. This may be overcome by placing a gas permeable membrane over the optode sensing film. This is conceptually confirmed by establishing that the sensor is equally useful for gas phase PCO2 measurements. As expected humid air samples are required for proper sensor functioning as dry CO2 gas will not cause any signal change. The sensor showed acceptable response times and good reproducibility under both conditions.

Published
2012
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34. Dissecting the Role of PCDH7, an Oncogenic Cell Surface Receptor, in Non–Small Cell Lung Cancer

Author

Zhou, X., primary, Updegraff, B.L., additional, Guo, Y., additional, Peyton, M., additional, Girard, L., additional, Larsen, J.E., additional, Xie, X.-J., additional, Zhou, Y., additional, Hwang, T.H., additional, Xie, Y., additional, Rodriguez-Canales, J., additional, Villalobos, P., additional, Behrens, C., additional, Wistuba, I.I., additional, Minna, J.D., additional, and O’Donnell, K.A., additional

Published
2017
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36. A validated tumorgraft model reveals activity of dovitinib against renal cell carcinoma

Author

Sivanand, Sharanya, Peña-Llopis, Samuel, Zhao, Hong, Kucejova, Blanka, Spence, Patrick, Pavia-Jimenez, Andrea, Yamasaki, Toshinari, McBride, David J., Gillen, Jessica, Wolff, Nicholas C., Morlock, Lorraine, Lotan, Yair, Raj, Ganesh V., Sagalowsky, Arthur, Margulis, Vitaly, Cadeddu, Jeffrey A., Ross, Mark T., Bentley, David R., Kabbani, Wareef, Xie, Xian-Jin, Kapur, Payal, Williams, Noelle S., Brugarolas, James, and Xie, X.-J.

Subjects
Adult, Male, Medizin, Gene mutation, Pharmacology, Quinolones, Article, Mice, Renal cell carcinoma, medicine, Carcinoma, Animals, Humans, Carcinoma, Renal Cell, Aged, Aged, 80 and over, business.industry, Sunitinib, General Medicine, Middle Aged, medicine.disease, Xenograft Model Antitumor Assays, Temsirolimus, Kidney Neoplasms, Drug development, Sirolimus, Cancer research, Benzimidazoles, Female, Erlotinib, business, medicine.drug
Abstract

Most anticancer drugs entering clinical trials fail to achieve approval from the US FDA. Drug development is hampered by the lack of preclinical models with therapeutic predictive value. Herein, we report the development and validation of a tumorgraft model of renal cell carcinoma (RCC) and its application to the evaluation of an experimental drug. Tumor samples from 94 patients were implanted in the kidney of mice without additives or disaggregation. Tumors from 35 patients formed tumorgrafts, and 16 stable lines were established. Samples from metastatic sites engrafted at high frequency, and stable engraftment of primary tumors in mice correlated with decreased patient survival suggesting that tumor growth in mice may reveal the acquisition by the tumor of an ability to thrive at distant sites and metastasize. Tumorgrafts retained the histology, gene expression, DNA copy number alterations, and over 90% of the protein-coding gene mutations of the corresponding tumors. As determined by the induction of hypercalcemia in tumorgraft-bearing mice, tumorgrafts were able to act on the host causing paraneoplastic syndromes. In studies simulating drug exposures in patients, RCC tumorgraft growth was inhibited by sunitinib and sirolimus (into which temsirolimus is converted in humans), but not by erlotinib, which was used as a control. Dovitinib, a drug in clinical development, showed greater activity than sunitinib and sirolimus. The routine incorporation of models recapitulating the molecular genetics and drug sensitivities of human tumors into preclinical programs has the potential to improve oncology drug development.

Published
2012

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