Yujun Yang - Academia.edu (original) (raw)

Papers by Yujun Yang

Research paper thumbnail of Probing dynamic information and spatial structure of Rydberg wave packets by harmonic spectra in a few-cycle laser pulse

Physical Review A, 2015

ABSTRACT We demonstrate that the dynamic information and the spatial structure of a Rydberg wave ... more ABSTRACT We demonstrate that the dynamic information and the spatial structure of a Rydberg wave packet formed by two neighboring Rydberg states can be simultaneously probed by harmonic spectra in a few-cycle laser pulse, where the Rydberg wave packet is produced by a pump laser field. By controlling the time delay of the pump-probe laser pulses, the harmonic spectra present a periodic variation, which directly illustrates the electron oscillation between the two neighboring Rydberg states. Specifically, by taking advantage of the periodic variation of the harmonic efficiency and the dip structure in the spectrum, one can detect the spatial characteristics and the dynamic information of the initial Rydberg wave packet.

Research paper thumbnail of Isolated attosecond pulse generation via the interference of ionized multi-recollision wave-packets

Proceedings of SPIE - The International Society for Optical Engineering

We propose and theoretically demonstrate a method for generating an intense isolated attosecond p... more We propose and theoretically demonstrate a method for generating an intense isolated attosecond pulse by a few-cycle strong laser pulse. The numerical simulations show that a broadband supercontinuum spectrum can be obtained by the interference of the ionized multi-recollision wave-packets with different energies, which are produced from the laser field at different ionization instants. By controlling the peak intensity of the few-cycle laser pulse, the atom can be completely ionized in the rising edge of the few-cycle laser pulse. Therefore, the probability of ionized wave packet is large enough to ensure the continuous harmonics with high efficiency, and an intense isolated 77 as pulse can be achieved successfully. Moreover, it is shown that our scheme can modulate the duration of the isolated attosecond pulse by adjusting the initial population of the atom.

Research paper thumbnail of The dynamic process of two-electron atom irradiated by intense laser pulse using time dependent quantum Monte Carlo method

Acta Physica Sinica -Chinese Edition-

ABSTRACT Times Cited: 0

Research paper thumbnail of Effect of the carrier phase of ultra-short laser pulses on high-order harmonic generation spectra

Acta Physica Sinica -Chinese Edition-

ABSTRACT Times Cited: 3

Research paper thumbnail of Isolated attosecond pulse generation from atom radiated by a three-color laser pulse

Chinese Physics B

We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom... more We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 10 fs/800 nm Ti-sapphire laser and a two-color field consisting of 30 fs/532 nm and 30 fs/1330 nm pulses. Compared with harmonic spectrum generated by a monochromatic field, the harmonics generated from the synthesized three-color field show a supercontinuum spectrum with a bandwidth of 235 eV, ranging from the 154th to the 306th order harmonic. This phenomenon can be attributed to the fact that the ionization of atoms as well as motion of ionized electron can be effectively controlled in the three-color field. Therefore, an isolated 46-as pulse can be generated. by superposing supercontinuum from the 160th to the 210th order harmonics.

Research paper thumbnail of Investigation of atomic radiative recombination processes by the Bohmian-mechanics method

Physical Review A, 2013

The light-emission process by the recombination of an ionized electron with its parent ion is inv... more The light-emission process by the recombination of an ionized electron with its parent ion is investigated by the Bohmian trajectory scheme, and the efficiency of light emission calculated by 20 Bohmian trajectories is qualitatively identical to that obtained by numerically solving the time-dependent Schrödinger equation. It is found that the efficiency of light emission by recombination is determined by the oscillation amplitude of the Bohmian particle's Coulomb acceleration. Along with the decrease of the energy of the incident Bohmian particle, the deepening of the ion's potential well, and the increase of the product factor of the bound-state and continuum-state populations, the oscillation amplitude of the particle's Coulomb acceleration increases.

Research paper thumbnail of Single rotational state preparation via coherent control of laser pulse

Laser Physics, 2014

We present a scheme to prepare a single rotational state with high probability from an arbitrary ... more We present a scheme to prepare a single rotational state with high probability from an arbitrary superposition state. The NO molecule is used as a computational example. By using a series of linearly and circularly polarized laser pulses and adjusting their parameters, a ground rotational state with probability of 99.982% can be obtained. Starting from the ground rotational state prepared, we can prepare any desired single rotational state with high probability and some rotational superposition states. On this basis, the molecular orientation with initial thermal distribution can be considerably enhanced and well controlled.

Research paper thumbnail of Dynamic stabilization of ionization for an atom irradiated by high-frequency laser pulses studied with the Bohmian-trajectory scheme

Physical Review A, 2013

We study the atomic ionization process in high-frequency laser pulses by the Bohmian-trajectory s... more We study the atomic ionization process in high-frequency laser pulses by the Bohmian-trajectory scheme. Combined with the analysis of the trajectories of Bohmian particles and the time-dependent potential well based on the Kramers-Henneberger transformation, we find that there are two kinds of forces that act on each Bohmian particle (BP): the classical force from the combined potential of the atomic Coulomb potential and the laser field and the quantum force. By investigating the forces acting on different BPs, we find that the quantum force plays an important role in the atomic ionization process in the laser pulse.

Research paper thumbnail of Carrier-envelope-phase effect on laser-driven bound-bound transitions in the high-frequency region

Research paper thumbnail of Influence of group-velocity-dispersion effects on the propagation of femtosecond laser pulses in air at different pressures

Physical Review A, 2014

The influence of group-velocity-dispersion (GVD) effects on the propagation of femtosecond laser ... more The influence of group-velocity-dispersion (GVD) effects on the propagation of femtosecond laser pulses in air at different pressures is investigated by numerically solving the extended nonlinear Schrödinger equation. It is observed that GVD has a great influence on the collapse distance L c of the self-focusing short laser pulses when the pressure is relatively high (e.g., 10 atm), in which case the semiempirical formula describing the collapse distance of self-focusing laser pulse [Dawes and Marburger, Phys. Rev. 179, 862 (1969)] is no longer applicable, while GVD has little influence on the self-focusing process of longer laser pulses. Through the results of numerical simulations as well as analytical analysis, we find that the initial duration of the laser pulse is the main factor that determines the GVD effect on the propagation and the increase of the pressure and pulse compression during the propagation enhance this effect. The spectral data show that GVD also influences the spectrum broadening in high-pressure cases.

Research paper thumbnail of Controlling High-order Harmonic Generation from the Stretched Diatom Molecules Subject to an Attosecond Pulse

Journal of the Korean Physical Society, 2011

ABSTRACT Times Cited: 0

Research paper thumbnail of State-selection via the quantum coherent control of laser pulse

Journal of Physics: Conference Series, 2014

ABSTRACT We propose to prepare arbitrary rotational state from the molecule at low rotational tem... more ABSTRACT We propose to prepare arbitrary rotational state from the molecule at low rotational temperature through the quantum coherent of laser pulse, thus providing a scheme to control molecules. On that basis, the molecular orientation at certain temperatures can be remarkably enhanced and well controlled.

Research paper thumbnail of Investigation of the carrier envelope phase effect for molecular ionization

Journal of Physics: Conference Series, 2014

ABSTRACT In the interaction between the matter and the intense laser pulses of which only include... more ABSTRACT In the interaction between the matter and the intense laser pulses of which only include a few optical cycles, the carrier envelope phase (CEP) of pulses will play an important role on strong field phenomena, such as the high-order harmonic generation and above threshold ionization etc. In this work, we investigated the influence of CEP on the molecular ionization.

Research paper thumbnail of The effect carrier-envelope phase on the cut-off of molecular harmonic generation

Journal of Physics: Conference Series, 2014

We investigated the high-order harmonic generation from H + 2 ion radiated by a few cycle infrare... more We investigated the high-order harmonic generation from H + 2 ion radiated by a few cycle infrared laser field. Our numerical simulations show that there exists a highly efficient plateau structure in the molecular harmonic spectrum. The carrier envelope phase effect on the cut-off of this plateau is investigated.

Research paper thumbnail of Influence of Higher-Order Kerr Effect on Femtosecond Laser Filamentation in Air at Different Pressures

Journal of Physics: Conference Series, 2014

ABSTRACT Utilizing the pressure dependent high-order kerr indices, the propagation of intense ult... more ABSTRACT Utilizing the pressure dependent high-order kerr indices, the propagation of intense ultrashort laser pulse in atmosphere at different pressures can be investigated. The results of spectroscopic investigation provide an effective way to generate supercontinuum as well as higher conversion efficiency high-order harmonic generation.

Research paper thumbnail of Prognostic Significance of Gene Expression Profiles of Metastatic Neuroblastomas Lacking MYCN Gene Amplification

JNCI Journal of the National Cancer Institute, 2006

The aggressiveness of metastatic neuroblastomas that lack MYCN gene amplifi cation varies with ag... more The aggressiveness of metastatic neuroblastomas that lack MYCN gene amplifi cation varies with agethey are least aggressive when diagnosed in patients younger than 12 months and most aggressive when diagnosed in patients older than 24 months. However, age at diagnosis is not always associated with patient survival. We examined whether molecular classifi cation of metastatic neuroblastomas without MYCN gene amplifi cation at diagnosis using gene expression profi ling could improve the prediction of risk of disease progression. Methods: We used Affymetrix microarrays to determine the gene expression profi les of 102 untreated primary neuroblastomas without MYCN gene amplifi cation obtained from children whose ages at diagnosis ranged from 0.1 to 151 months. A supervised method using diagonal linear discriminant analysis was devised to build a multigene model for predicting risk of disease progression. The accuracy of the model was evaluated using nested crossvalidations, permutation analyses, and gene expression data from 15 additional tumors obtained at disease progression. Results: An expression profi le model using 55 genes defi ned a tumor signature that distinguished two groups of patients from among those older than 12 months at diagnosis and clinically classifi ed as having high-risk disease, those with a progression-free survival (PFS) rate of 16% (95% confi dence interval [CI] = 8% to 28%), and those with a PFS rate of 79% (95% CI = 57% to 91%) ( P <.01). These tumor signatures also identifi ed two groups of patients with PFS of 15% (95% CI = 7% to 27%) and 69% (95% CI = 40% to 86%) ( P <.01) from among patients who were older than 18 months at diagnosis. The gene expression signature of untreated molecular high-risk tumors was also present in progressively growing tumors. Conclusion: Gene expression signatures of tumors obtained at diagnosis from patients with clinically indistinguishable high-risk, metastatic neuroblastomas identify subgroups with different outcomes. Accurate identifi cation of these subgroups with gene expression profi les may facilitate development, implementation, and analysis of clinical trials aimed at improving outcome. [J Natl Cancer Inst 2006;98: 1193 -203 ] Neuroblastoma is one of the most common solid tumors in infants and children. One-half of neuroblastoma patients have metastatic (clinical stage 4) disease at diagnosis, and approximately 65% of patients with metastatic disease have tumors that lack amplifi cation of the MYCN proto-oncogene ( 1 , 2 ) . All metastatic tumors with amplifi ed MYCN genes are aggressive, whereas metastatic tumors with nonamplifi ed MYCN genes have variable clinical behaviors that generally correlate with the patient's age at diagnosis . For example, among patients Affi liations of authors:

Research paper thumbnail of Natural Killer T Cells Infiltrate Neuroblastomas Expressing the Chemokine CCL2

Journal of Experimental Medicine, 2004

CD1d-restricted Valpha24-Jalpha18-invariant natural killer T cells (iNKTs) are potentially import... more CD1d-restricted Valpha24-Jalpha18-invariant natural killer T cells (iNKTs) are potentially important in tumor immunity. However, little is known about their localization to tumors. We analyzed 98 untreated primary neuroblastomas from patients with metastatic disease (stage 4) for tumor-infiltrating iNKTs using TaqMan((R)) reverse transcription polymerase chain reaction and immunofluorescent microscopy. 52 tumors (53%) contained iNKTs, and oligonucleotide microarray analysis of the iNKT(+) and iNKT(-) tumors revealed that the former expressed higher levels of CCL2/MCP-1, CXCL12/SDF-1, CCL5/RANTES, and CCL21/SLC. Eight tested neuroblastoma cell lines secreted a range of CCL2 (0-21.6 ng/ml), little CXCL12 (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/=0.1 ng/ml), and no detectable CCL5 or CCL21. CCR2, the receptor for CCL2, was more frequently expressed by iNKT compared with natural killer and T cells from blood (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). Supernatants of neuroblastoma cell lines that produced CCL2 induced in vitro migration of iNKTs from blood of patients and normal adults; this was abrogated by an anti-CCL2 monoclonal antibody. CCL2 expression by tumors was found to inversely correlate with MYCN proto-oncogene amplification and expression (r = 0.5, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), and MYCN-high/CCL2-low expression accurately predicted the absence of iNKTs (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). In summary, iNKTs migrate toward neuroblastoma cells in a CCL2-dependent manner, preferentially infiltrating MYCN nonamplified tumors that express CCL2.

Research paper thumbnail of Clinical characteristics and predictive factors of myasthenic crisis after thymectomy

Journal of Clinical Neuroscience, 2011

The aims of this study were to assess the clinical characteristics of myasthenic crisis after thy... more The aims of this study were to assess the clinical characteristics of myasthenic crisis after thymectomy (MCAT) and to identify predictors affecting the occurrence of MCAT. Of 66 patients with myasthenia gravis (MG), MCAT occurred in 20 patients (30.3%). The median time interval from thymectomy to MCAT was 3.4 months. MCAT occurred in 65.0% of patients within the first 6 months of a thymectomy, and 35.0% after 6 months. A second MCAT occurred in nine (45.0%) patients who survived the first MCAT, and in seven (50.0%) of 14 patients with a history of a preoperative myasthenic crisis before thymectomy (MCBT). A history of MCBT, and clinical factors reflecting perioperative clinical severity at thymectomy, including preoperative Osserman's grade, bulbar symptoms, use of immunosuppressants, pulmonary function, and postoperative delayed ventilator weaning, were significantly correlated with the occurrence of MCAT on univariate analysis. However, a history of MCBT was the only independent factor affecting the occurrence of MCAT on multivariate logistic regression analysis (odds ratio, 17.9; 95% confidence interval, 4.019-79.873; p < 0.001). Thus, the occurrence of MCAT may be correlated only with a history of MCBT rather than with factors reflecting perioperative clinical severity. MG patients with a history of MCBT are more susceptible to MCAT, particularly within the first 6 months of thymectomy.

Research paper thumbnail of Luminescent properties and thermal stability of BaMgAl10O17:Eu2+ synthesized by sol–gel route

Journal of Alloys and Compounds, 2008

BaMgAl 10 O 17 :Eu 2+ (BAM) phosphor particles were prepared by sol-gel processes. The effect of ... more BaMgAl 10 O 17 :Eu 2+ (BAM) phosphor particles were prepared by sol-gel processes. The effect of the firing temperature and the Eu 2+ concentration on the distribution of Eu 2+ among different sites was firstly investigated through the changes of excitation spectra with changing firing temperature and Eu 2+ concentration. The mechanism underlying was elucidated. The stability of BAM could be improved by increasing the firing temperature and Eu 2+ concentration.

Research paper thumbnail of Carrier Envelope Phase Effect of a Long Duration Pulse in the Low Frequency Region

Chinese Physics Letters, 2014

ABSTRACT Using the characteristic of small energy difference between two high Rydberg states, we ... more ABSTRACT Using the characteristic of small energy difference between two high Rydberg states, we theoretically investigate the carrier envelope phase (CEP) effect in a bound-bound transition of an atom in a low-frequency long laser pulse with tens of optical cycles. Particularly, we first prepare a Rydberg state of a hydrogen-like atom by a laser field with the resonant frequency between this state and the ground state. Then by using a low-frequency long laser pulse interacting with this Rydberg atom, we calculate the population of another Rydberg state nearby this Rydberg state at the end of the laser pulse and find that the population changes dramatically with the CEP of the low-frequency pulse. This CEP effect is attributed to the interference between the positive-frequency and negative-frequency components in one-photon transition. These results may provide a method to measure the CEP value of a long laser pulse with low frequency.

Research paper thumbnail of Probing dynamic information and spatial structure of Rydberg wave packets by harmonic spectra in a few-cycle laser pulse

Physical Review A, 2015

ABSTRACT We demonstrate that the dynamic information and the spatial structure of a Rydberg wave ... more ABSTRACT We demonstrate that the dynamic information and the spatial structure of a Rydberg wave packet formed by two neighboring Rydberg states can be simultaneously probed by harmonic spectra in a few-cycle laser pulse, where the Rydberg wave packet is produced by a pump laser field. By controlling the time delay of the pump-probe laser pulses, the harmonic spectra present a periodic variation, which directly illustrates the electron oscillation between the two neighboring Rydberg states. Specifically, by taking advantage of the periodic variation of the harmonic efficiency and the dip structure in the spectrum, one can detect the spatial characteristics and the dynamic information of the initial Rydberg wave packet.

Research paper thumbnail of Isolated attosecond pulse generation via the interference of ionized multi-recollision wave-packets

Proceedings of SPIE - The International Society for Optical Engineering

We propose and theoretically demonstrate a method for generating an intense isolated attosecond p... more We propose and theoretically demonstrate a method for generating an intense isolated attosecond pulse by a few-cycle strong laser pulse. The numerical simulations show that a broadband supercontinuum spectrum can be obtained by the interference of the ionized multi-recollision wave-packets with different energies, which are produced from the laser field at different ionization instants. By controlling the peak intensity of the few-cycle laser pulse, the atom can be completely ionized in the rising edge of the few-cycle laser pulse. Therefore, the probability of ionized wave packet is large enough to ensure the continuous harmonics with high efficiency, and an intense isolated 77 as pulse can be achieved successfully. Moreover, it is shown that our scheme can modulate the duration of the isolated attosecond pulse by adjusting the initial population of the atom.

Research paper thumbnail of The dynamic process of two-electron atom irradiated by intense laser pulse using time dependent quantum Monte Carlo method

Acta Physica Sinica -Chinese Edition-

ABSTRACT Times Cited: 0

Research paper thumbnail of Effect of the carrier phase of ultra-short laser pulses on high-order harmonic generation spectra

Acta Physica Sinica -Chinese Edition-

ABSTRACT Times Cited: 3

Research paper thumbnail of Isolated attosecond pulse generation from atom radiated by a three-color laser pulse

Chinese Physics B

We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom... more We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 10 fs/800 nm Ti-sapphire laser and a two-color field consisting of 30 fs/532 nm and 30 fs/1330 nm pulses. Compared with harmonic spectrum generated by a monochromatic field, the harmonics generated from the synthesized three-color field show a supercontinuum spectrum with a bandwidth of 235 eV, ranging from the 154th to the 306th order harmonic. This phenomenon can be attributed to the fact that the ionization of atoms as well as motion of ionized electron can be effectively controlled in the three-color field. Therefore, an isolated 46-as pulse can be generated. by superposing supercontinuum from the 160th to the 210th order harmonics.

Research paper thumbnail of Investigation of atomic radiative recombination processes by the Bohmian-mechanics method

Physical Review A, 2013

The light-emission process by the recombination of an ionized electron with its parent ion is inv... more The light-emission process by the recombination of an ionized electron with its parent ion is investigated by the Bohmian trajectory scheme, and the efficiency of light emission calculated by 20 Bohmian trajectories is qualitatively identical to that obtained by numerically solving the time-dependent Schrödinger equation. It is found that the efficiency of light emission by recombination is determined by the oscillation amplitude of the Bohmian particle's Coulomb acceleration. Along with the decrease of the energy of the incident Bohmian particle, the deepening of the ion's potential well, and the increase of the product factor of the bound-state and continuum-state populations, the oscillation amplitude of the particle's Coulomb acceleration increases.

Research paper thumbnail of Single rotational state preparation via coherent control of laser pulse

Laser Physics, 2014

We present a scheme to prepare a single rotational state with high probability from an arbitrary ... more We present a scheme to prepare a single rotational state with high probability from an arbitrary superposition state. The NO molecule is used as a computational example. By using a series of linearly and circularly polarized laser pulses and adjusting their parameters, a ground rotational state with probability of 99.982% can be obtained. Starting from the ground rotational state prepared, we can prepare any desired single rotational state with high probability and some rotational superposition states. On this basis, the molecular orientation with initial thermal distribution can be considerably enhanced and well controlled.

Research paper thumbnail of Dynamic stabilization of ionization for an atom irradiated by high-frequency laser pulses studied with the Bohmian-trajectory scheme

Physical Review A, 2013

We study the atomic ionization process in high-frequency laser pulses by the Bohmian-trajectory s... more We study the atomic ionization process in high-frequency laser pulses by the Bohmian-trajectory scheme. Combined with the analysis of the trajectories of Bohmian particles and the time-dependent potential well based on the Kramers-Henneberger transformation, we find that there are two kinds of forces that act on each Bohmian particle (BP): the classical force from the combined potential of the atomic Coulomb potential and the laser field and the quantum force. By investigating the forces acting on different BPs, we find that the quantum force plays an important role in the atomic ionization process in the laser pulse.

Research paper thumbnail of Carrier-envelope-phase effect on laser-driven bound-bound transitions in the high-frequency region

Research paper thumbnail of Influence of group-velocity-dispersion effects on the propagation of femtosecond laser pulses in air at different pressures

Physical Review A, 2014

The influence of group-velocity-dispersion (GVD) effects on the propagation of femtosecond laser ... more The influence of group-velocity-dispersion (GVD) effects on the propagation of femtosecond laser pulses in air at different pressures is investigated by numerically solving the extended nonlinear Schrödinger equation. It is observed that GVD has a great influence on the collapse distance L c of the self-focusing short laser pulses when the pressure is relatively high (e.g., 10 atm), in which case the semiempirical formula describing the collapse distance of self-focusing laser pulse [Dawes and Marburger, Phys. Rev. 179, 862 (1969)] is no longer applicable, while GVD has little influence on the self-focusing process of longer laser pulses. Through the results of numerical simulations as well as analytical analysis, we find that the initial duration of the laser pulse is the main factor that determines the GVD effect on the propagation and the increase of the pressure and pulse compression during the propagation enhance this effect. The spectral data show that GVD also influences the spectrum broadening in high-pressure cases.

Research paper thumbnail of Controlling High-order Harmonic Generation from the Stretched Diatom Molecules Subject to an Attosecond Pulse

Journal of the Korean Physical Society, 2011

ABSTRACT Times Cited: 0

Research paper thumbnail of State-selection via the quantum coherent control of laser pulse

Journal of Physics: Conference Series, 2014

ABSTRACT We propose to prepare arbitrary rotational state from the molecule at low rotational tem... more ABSTRACT We propose to prepare arbitrary rotational state from the molecule at low rotational temperature through the quantum coherent of laser pulse, thus providing a scheme to control molecules. On that basis, the molecular orientation at certain temperatures can be remarkably enhanced and well controlled.

Research paper thumbnail of Investigation of the carrier envelope phase effect for molecular ionization

Journal of Physics: Conference Series, 2014

ABSTRACT In the interaction between the matter and the intense laser pulses of which only include... more ABSTRACT In the interaction between the matter and the intense laser pulses of which only include a few optical cycles, the carrier envelope phase (CEP) of pulses will play an important role on strong field phenomena, such as the high-order harmonic generation and above threshold ionization etc. In this work, we investigated the influence of CEP on the molecular ionization.

Research paper thumbnail of The effect carrier-envelope phase on the cut-off of molecular harmonic generation

Journal of Physics: Conference Series, 2014

We investigated the high-order harmonic generation from H + 2 ion radiated by a few cycle infrare... more We investigated the high-order harmonic generation from H + 2 ion radiated by a few cycle infrared laser field. Our numerical simulations show that there exists a highly efficient plateau structure in the molecular harmonic spectrum. The carrier envelope phase effect on the cut-off of this plateau is investigated.

Research paper thumbnail of Influence of Higher-Order Kerr Effect on Femtosecond Laser Filamentation in Air at Different Pressures

Journal of Physics: Conference Series, 2014

ABSTRACT Utilizing the pressure dependent high-order kerr indices, the propagation of intense ult... more ABSTRACT Utilizing the pressure dependent high-order kerr indices, the propagation of intense ultrashort laser pulse in atmosphere at different pressures can be investigated. The results of spectroscopic investigation provide an effective way to generate supercontinuum as well as higher conversion efficiency high-order harmonic generation.

Research paper thumbnail of Prognostic Significance of Gene Expression Profiles of Metastatic Neuroblastomas Lacking MYCN Gene Amplification

JNCI Journal of the National Cancer Institute, 2006

The aggressiveness of metastatic neuroblastomas that lack MYCN gene amplifi cation varies with ag... more The aggressiveness of metastatic neuroblastomas that lack MYCN gene amplifi cation varies with agethey are least aggressive when diagnosed in patients younger than 12 months and most aggressive when diagnosed in patients older than 24 months. However, age at diagnosis is not always associated with patient survival. We examined whether molecular classifi cation of metastatic neuroblastomas without MYCN gene amplifi cation at diagnosis using gene expression profi ling could improve the prediction of risk of disease progression. Methods: We used Affymetrix microarrays to determine the gene expression profi les of 102 untreated primary neuroblastomas without MYCN gene amplifi cation obtained from children whose ages at diagnosis ranged from 0.1 to 151 months. A supervised method using diagonal linear discriminant analysis was devised to build a multigene model for predicting risk of disease progression. The accuracy of the model was evaluated using nested crossvalidations, permutation analyses, and gene expression data from 15 additional tumors obtained at disease progression. Results: An expression profi le model using 55 genes defi ned a tumor signature that distinguished two groups of patients from among those older than 12 months at diagnosis and clinically classifi ed as having high-risk disease, those with a progression-free survival (PFS) rate of 16% (95% confi dence interval [CI] = 8% to 28%), and those with a PFS rate of 79% (95% CI = 57% to 91%) ( P <.01). These tumor signatures also identifi ed two groups of patients with PFS of 15% (95% CI = 7% to 27%) and 69% (95% CI = 40% to 86%) ( P <.01) from among patients who were older than 18 months at diagnosis. The gene expression signature of untreated molecular high-risk tumors was also present in progressively growing tumors. Conclusion: Gene expression signatures of tumors obtained at diagnosis from patients with clinically indistinguishable high-risk, metastatic neuroblastomas identify subgroups with different outcomes. Accurate identifi cation of these subgroups with gene expression profi les may facilitate development, implementation, and analysis of clinical trials aimed at improving outcome. [J Natl Cancer Inst 2006;98: 1193 -203 ] Neuroblastoma is one of the most common solid tumors in infants and children. One-half of neuroblastoma patients have metastatic (clinical stage 4) disease at diagnosis, and approximately 65% of patients with metastatic disease have tumors that lack amplifi cation of the MYCN proto-oncogene ( 1 , 2 ) . All metastatic tumors with amplifi ed MYCN genes are aggressive, whereas metastatic tumors with nonamplifi ed MYCN genes have variable clinical behaviors that generally correlate with the patient's age at diagnosis . For example, among patients Affi liations of authors:

Research paper thumbnail of Natural Killer T Cells Infiltrate Neuroblastomas Expressing the Chemokine CCL2

Journal of Experimental Medicine, 2004

CD1d-restricted Valpha24-Jalpha18-invariant natural killer T cells (iNKTs) are potentially import... more CD1d-restricted Valpha24-Jalpha18-invariant natural killer T cells (iNKTs) are potentially important in tumor immunity. However, little is known about their localization to tumors. We analyzed 98 untreated primary neuroblastomas from patients with metastatic disease (stage 4) for tumor-infiltrating iNKTs using TaqMan((R)) reverse transcription polymerase chain reaction and immunofluorescent microscopy. 52 tumors (53%) contained iNKTs, and oligonucleotide microarray analysis of the iNKT(+) and iNKT(-) tumors revealed that the former expressed higher levels of CCL2/MCP-1, CXCL12/SDF-1, CCL5/RANTES, and CCL21/SLC. Eight tested neuroblastoma cell lines secreted a range of CCL2 (0-21.6 ng/ml), little CXCL12 (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/=0.1 ng/ml), and no detectable CCL5 or CCL21. CCR2, the receptor for CCL2, was more frequently expressed by iNKT compared with natural killer and T cells from blood (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). Supernatants of neuroblastoma cell lines that produced CCL2 induced in vitro migration of iNKTs from blood of patients and normal adults; this was abrogated by an anti-CCL2 monoclonal antibody. CCL2 expression by tumors was found to inversely correlate with MYCN proto-oncogene amplification and expression (r = 0.5, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), and MYCN-high/CCL2-low expression accurately predicted the absence of iNKTs (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). In summary, iNKTs migrate toward neuroblastoma cells in a CCL2-dependent manner, preferentially infiltrating MYCN nonamplified tumors that express CCL2.

Research paper thumbnail of Clinical characteristics and predictive factors of myasthenic crisis after thymectomy

Journal of Clinical Neuroscience, 2011

The aims of this study were to assess the clinical characteristics of myasthenic crisis after thy... more The aims of this study were to assess the clinical characteristics of myasthenic crisis after thymectomy (MCAT) and to identify predictors affecting the occurrence of MCAT. Of 66 patients with myasthenia gravis (MG), MCAT occurred in 20 patients (30.3%). The median time interval from thymectomy to MCAT was 3.4 months. MCAT occurred in 65.0% of patients within the first 6 months of a thymectomy, and 35.0% after 6 months. A second MCAT occurred in nine (45.0%) patients who survived the first MCAT, and in seven (50.0%) of 14 patients with a history of a preoperative myasthenic crisis before thymectomy (MCBT). A history of MCBT, and clinical factors reflecting perioperative clinical severity at thymectomy, including preoperative Osserman's grade, bulbar symptoms, use of immunosuppressants, pulmonary function, and postoperative delayed ventilator weaning, were significantly correlated with the occurrence of MCAT on univariate analysis. However, a history of MCBT was the only independent factor affecting the occurrence of MCAT on multivariate logistic regression analysis (odds ratio, 17.9; 95% confidence interval, 4.019-79.873; p < 0.001). Thus, the occurrence of MCAT may be correlated only with a history of MCBT rather than with factors reflecting perioperative clinical severity. MG patients with a history of MCBT are more susceptible to MCAT, particularly within the first 6 months of thymectomy.

Research paper thumbnail of Luminescent properties and thermal stability of BaMgAl10O17:Eu2+ synthesized by sol–gel route

Journal of Alloys and Compounds, 2008

BaMgAl 10 O 17 :Eu 2+ (BAM) phosphor particles were prepared by sol-gel processes. The effect of ... more BaMgAl 10 O 17 :Eu 2+ (BAM) phosphor particles were prepared by sol-gel processes. The effect of the firing temperature and the Eu 2+ concentration on the distribution of Eu 2+ among different sites was firstly investigated through the changes of excitation spectra with changing firing temperature and Eu 2+ concentration. The mechanism underlying was elucidated. The stability of BAM could be improved by increasing the firing temperature and Eu 2+ concentration.

Research paper thumbnail of Carrier Envelope Phase Effect of a Long Duration Pulse in the Low Frequency Region

Chinese Physics Letters, 2014

ABSTRACT Using the characteristic of small energy difference between two high Rydberg states, we ... more ABSTRACT Using the characteristic of small energy difference between two high Rydberg states, we theoretically investigate the carrier envelope phase (CEP) effect in a bound-bound transition of an atom in a low-frequency long laser pulse with tens of optical cycles. Particularly, we first prepare a Rydberg state of a hydrogen-like atom by a laser field with the resonant frequency between this state and the ground state. Then by using a low-frequency long laser pulse interacting with this Rydberg atom, we calculate the population of another Rydberg state nearby this Rydberg state at the end of the laser pulse and find that the population changes dramatically with the CEP of the low-frequency pulse. This CEP effect is attributed to the interference between the positive-frequency and negative-frequency components in one-photon transition. These results may provide a method to measure the CEP value of a long laser pulse with low frequency.