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Jun Ye

Publications and source records attributed to Jun Ye.

At least 19 recordsLinked to original sources
PubMed2007

Cavity-ringdown molecular spectroscopy based on an optical frequency comb at 1.45-1.65 microm.

Optical frequency comb-based cavity-ringdown spectroscopy has recently enabled high-sensitivity absorption detection of molecules over a broad spectral range. We demonstrate an improved system based on a mode-locked erbium-doped fiber laser source centered at 1.5 microm, resulting in a spectrometer that is inexpensive, simple, and robust. It provides a very large spectral bandwidth (1.45-1.65 microm) for investigation of a wide variety of molecular absorptions. Strong molecular absorptions at 1.5 mum allow for detection at sensitivities approaching the 1 part in 10(9) volume level. We provide a detailed description of our spectrometer and present measurements of the rovibrational spectra for CO, NH3, and C2H2 with an absorption sensitivity of 2 x 10(-8) cm(-1)Hz(-1/2) per detection channel.

Journal Article↗
PubMed2006

Optical atomic coherence at the 1-second time scale.

Highest-resolution laser spectroscopy has generally been limited to single trapped ion systems because of the rapid decoherence that plagues neutral atom ensembles. Precision spectroscopy of ultracold neutral atoms confined in a trapping potential now shows superior optical coherence without any deleterious effects from motional degrees of freedom, revealing optical resonance linewidths at the hertz level with a good signal-to-noise ratio. The resonance quality factor of 2.4 x 10(14) is the highest ever recovered in any form of coherent spectroscopy. The spectral resolution permits direct observation of the breaking of nuclear spin degeneracy for the 1S0 and 3P0 optical clock states of 87Sr under a small magnetic bias field. This optical approach for excitation of nuclear spin states allows an accurate measurement of the differential Landé g factor between 1S0 and 3P0. The optical atomic coherence demonstrated for collective excitation of a large number of atoms will have a strong impact on quantum measurement and precision frequency metrology.

Journal Article↗
PubMed2006

Transmembrane domains 4, 5, 7, 8, and 10 of the human reduced folate carrier are important structural or functional components of the transmembrane channel for folate substrates.

The human reduced folate carrier (hRFC) facilitates membrane transport of folates and antifolates. hRFC is characterized by 12 transmembrane domains (TMDs). To identify residues or domains involved in folate binding, we used substituted cysteine (Cys) accessibility methods (SCAM) with sodium (2-sulfonatoethyl)methanethiosulfonate (MTSES). We previously showed that residues in TMD11 of hRFC were involved in substrate binding, whereas those in TMD12 were not (Hou, Z., Stapels, S. E., Haska, C. L., and Matherly, L. H. (2005) J. Biol. Chem. 280, 36206-36213). In this study, 232 Cys-substituted mutants spanning TMDs 1-10 and conserved stretches within the TMD6-7 (residues 204-217) and TMD10-11 connecting loop domains were transiently expressed in hRFC-null HeLa cells. All Cys-substituted mutants showed moderate to high levels of expression on Western blots, and only nine mutants including R133C, I134C, A135C, Y136C, S138C, G163C, Y281C, R373C, and S313C were inactive for methotrexate transport. MTSES did not inhibit transport by any of the mutants in TMDs 1, 3, 6, and 9 or for positions 204-217. Whereas most of the mutants in TMDs 2, 4, 5, 7, 8, and 10, and in the TMD10-11 connecting loop were insensitive to MTSES, this reagent inhibited methotrexate transport (25-75%) by 26 mutants in these TMDs. For 13 of these (Y126C, S137C, V160C, S168C, W274C, S278C, V284C, V288C, A311C, T314C, Y376C, Q377C, and V380C), inhibition was prevented by leucovorin, another hRFC substrate. Combined with our previous findings, these results implicate amino acids in TMDs 4, 5, 7, 8, 10, and 11, but not in TMDs 1, 2, 3, 6, 9, or 12, as important structural or functional components of the putative hydrophilic cavity for binding of anionic folate substrates.

Amino Acid Sequence↗
PubMed2006

Synchronization of mode-locked femtosecond lasers through a fiber link.

Two mode-locked femtosecond fiber lasers, connected via a 7 km fiber link, are synchronized to an rms timing jitter of 19 fs, observed over the entire Nyquist bandwidth (half of the 93 MHz repetition frequency). This result is achieved in two steps. First, active cancellation of the fiber-transmission noise reduces timing jitter caused by path length fluctuations to a record level of 16 fs. Second, using a wide bandwidth interactivity actuator, the slave laser is synchronized to the incoming stable pulse train from the reference laser to within 10 fs. These results are confirmed by an optical cross-correlation measurement performed independently of the feedback loop operated in the microwave domain.

Journal Article↗
PubMed2006

Tapered semiconductor amplifiers for optical frequency combs in the near infrared.

A tapered semiconductor amplifier is injection seeded by a femtosecond optical frequency comb at 780 nm from a mode-locked Ti:sapphire laser. Energy gains of more than 17 dB(12 dB) are obtained for 1 mW(20 mW) of average input power when the input pulses are stretched into the picosecond range. A spectral window of supercontinuum light generated in a photonic fiber has also been amplified. Interferometric measurements show sub-Hertz linewidths for a heterodyne beat between the input and amplified comb components, yielding no detectable phase-noise degradation under amplification. These amplifiers can be used to boost the infrared power in f-to-2f interferometers used to determine the carrier-to-envelope offset frequency, with clear advantages for stabilization of octave-spanning femtosecond lasers and other supercontinuum light sources.

Journal Article↗
PubMed2006

Recombined DNA vaccines encoding calreticulin linked to HPV6bE7 enhance immune response and inhibit angiogenic activity in B16 melanoma mouse model expressing HPV 6bE7 antigen.

Calreticulin (CRT) has been reported to have an effect of upregulating MHC class I presentation as well as inhibiting angiogenesis in vitro and in vivo. Combination of dual mechanisms of enhanced immunogenicity of human papillomavirus (HPV) 6bE7 antigen and antiangiogenesis may be introduced in the strategy of vaccines against condyloma acuminatum (CA) resulting from HPV infection. Therefore, we constructed DNA vaccines by employing different lengths of CRT chimerically linked to a model antigen HPV6bE7 and investigated the immunological and antiangiogenic effects of these vaccines in a B16 melanoma model that express HPV6bE7 antigen. Our results showed that vaccination with CRT180/HPV6bE7 or CRT120/HPV6bE7 enhanced the presence of CD8(+) T cells and TCRgammadelta T cells in vivo, increased the specific lysis activity against E7-expressing cells and secretion levels of IL-2 and IFN-gamma by activating T cells in vitro significantly. Moreover, recombined CRT180 or CRT120 with HPV6bE7 vaccines could elicit a more efficient E7-specific immune response than HPV6bE7 alone. The similarity of immunological enhancement of CRT180/HPV6bE7 and CRT120/HPV6bE7 implies that the immunologically active region mainly exist in fragment 1-120 aa. Furthermore, CRT180/HPV6bE7 and CRT180 displayed remarkable superiority over CRT120/HPV6bE7 in vivo angiogenesis assay, suggesting that the antiangiogenic activity of CRT resides in a domain between aa 120 and 180. Vaccination with CRT180/HPV6bE7 generated the best protective effect of delaying tumor formation and reduction of tumor size in tumor growth inhibition experiment among all DNA constructs. Therefore, CRT180/HPV6bE7 vaccine may enhance the immunological response to HPV6bE7 and inhibit angiogenesis. This construct may be useful in preventing HPV-associated dermatosis and may be developed as a promising strategy to control CA.

Animals↗
PubMed2006

High resolution atomic coherent control via spectral phase manipulation of an optical frequency comb.

We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.

Journal Article↗
PubMed2006

Cold molecule spectroscopy for constraining the evolution of the fine structure constant.

We report precise measurements of ground-state, Lambda-doublet microwave transitions in the hydroxyl radical molecule (OH). Utilizing slow, cold molecules produced by a Stark decelerator we have improved over the precision of the previous best measurement 25-fold for the F'=2-->F=2 transition, yielding (1 667 358 996 +/- 4)Hz, and by tenfold for the F'=1-->F=1 transition, yielding (1 665 401 803 +/-12)Hz. Comparing these laboratory frequencies to those from OH megamasers in interstellar space will allow a sensitivity of 1 ppm for Delta(alpha/alpha) over approximately 10(10) yr.

Journal Article↗
PubMed2006

Broadband cavity ringdown spectroscopy for sensitive and rapid molecular detection.

We demonstrate highly efficient cavity ringdown spectroscopy in which a broad-bandwidth optical frequency comb is coherently coupled to a high-finesse optical cavity that acts as the sample chamber. 125,000 optical comb components, each coupled into a specific longitudinal cavity mode, undergo ringdown decays when the cavity input is shut off. Sensitive intracavity absorption information is simultaneously available across 100 nanometers in the visible and near-infrared spectral regions. Real-time, quantitative measurements were made of the trace presence, the transition strengths and linewidths, and the population redistributions due to collisions and the temperature changes for molecules such as C2H2, O2, H2O, and NH3.

Acetylene↗
PubMed2006

Systematic study of the 87Srclock transition in an optical lattice.

With ultracold 87Srconfined in a magic wavelength optical lattice, we present the most precise study (2.8 Hz statistical uncertainty) to date of the 1S0-3P0 optical clock transition with a detailed analysis of systematic shifts (19 Hz uncertainty) in the absolute frequency measurement of 429 228 004 229 869 Hz. The high resolution permits an investigation of the optical lattice motional sideband structure. The local oscillator for this optical atomic clock is a stable diode laser with its hertz-level linewidth characterized by an octave-spanning femtosecond frequency comb.

Journal Article↗
PubMed2006

Increased endocytic activity in monocyte-derived dendritic cells in patients with psoriasis vulgaris.

BACKGROUND & OBJECTIVE: The understanding of the pathogenesis of psoriasis vulgaris has focused on T cell mediated immune disorder for many years. Recent studies provide evidence that dendritic cells may be of major importance as regulatory cells driving the psoriasis tissue reaction, and they are one of the therapeutic targets. In order to further characterize the role of dendritic cells in psoriasis, this study was designed to assess the differentiation of dendritic cells from monocytes (MoDC), the expression of phagocytosis related receptors by MoDC, their endocytic activity for fluorescent beads and lucifer yellow as well as their superoxide generation in patients with psoriasis. METHODS: Twenty eight patients with psoriasis vulgaris and 12 healthy controls were included in the study. MoDC were obtained by culturing monocytes with granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin-4 (IL-4) for 5 days. Cell surface expression of CD1a, CD14, CD40, CD80, CD83, CD86, HLA-DR, mannose receptor (MR) and Fcg receptors by MoDC and their endocytosis of dextran and lucifer yellow were analyzed by flow cytometry. Zymosan ingestion was measured to access the phagocytosis of MoDC. RESULTS: Differentiation of monocytes to dendritic cells was upregulated in patients manifested as significantly increased expression of CD40, CD80, CD86 and HLA-DR compared with that in healthy controls (P<0.01). Expression of MR and Fcg receptor II (CD32) by MoDC was significantly increased in patients with psoriasis as well (P<0.01). Endocytosis of dextran but not lucifer yellow in patients was significantly higher than controls (P<0.01), and significantly enhanced phagocytosis by increasing zymosan ingestion was also observed (P<0.01) in patients. Taken together, endocytic and phagocytic activity of MoDC in psoriasis was increased than normal persons. INTERPRETATION & CONCLUSION: Enhanced activity of dendritic cells binding and capturing foreign antigens for subsequent antigen presentation and the initiation of immune responses in psoriasis may contribute to the pathogenesis of the disease. The upregulated expression of MR and the enhanced endocytic activity of DC might be an explanation for the absence of skin infection observed in psoriasis.

Adolescent↗
PubMed2005

Mode-locked fiber laser frequency-controlled with an intracavity electro-optic modulator.

We demonstrate a mode-locked, erbium-doped fiber laser with its repetition frequency synchronized to a second fiber laser via an intracavity electro-optic modulator (EOM). With servo control from the EOM (bandwidth approximately 230 kHz) and a slower speed intracavity piezoelectric transducer (resonance at approximately 20 kHz), we demonstrate stabilization of the repetition frequency with an in-loop rms timing jitter of 10 fs, integrated over a bandwidth from 1 Hz to 100 kHz. This represents what is to our knowledge the first time an EOM has been introduced inside a mode-locked laser cavity for fast servo action and the lowest timing jitter reported for a mode-locked fiber laser.

Journal Article↗
PubMed2005

Direct frequency comb measurements of absolute optical frequencies and population transfer dynamics.

A phase-stabilized femtosecond laser comb is directly used for high-resolution spectroscopy and absolute optical frequency measurements of one- and two-photon transitions in laser-cooled 87Rb atoms. Absolute atomic transition frequencies, such as the 5S1/2 F=2-->7S1/2 F"=2 two-photon resonance measured at 788,794 768,921 (44) kHz, are determined without a priori knowledge about their values. Detailed dynamics of population transfer driven by a sequence of pulses are uncovered and taken into account for the measurement of the 5P states via resonantly enhanced two-photon transitions.

Journal Article↗
PubMed2005

Multicenter clinical study on Fuzhenghuayu capsule against liver fibrosis due to chronic hepatitis B.

AIM: To study the efficacy and safety of Fuzhenghuayu capsule (FZHY capsule, a capsule for strengthening body resistance to remove blood stasis) against liver fibrosis due to chronic hepatitis B. METHODS: Multicenter, randomized, double blinded and parallel control experiment was conducted in patients (aged from 18 to 65 years) with liver fibrosis due to chronic hepatitis B. Hepatic histologic changes and HBV markers were examined at wk 0 and 24 during treatment. Serologic parameters (HA, LM, P-III-P, IV-C) were determined and B ultrasound examination of the spleen and liver was performed at wk 0, 12 and 24. Liver function (liver function and serologic parameters for liver fibrosis) was observed at wk 0, 6, 12, 18 and 24. Blood and urine routine test, renal function and ECG were examined before and after treatment. RESULTS: There was no significant difference between experimental group (110 cases) and control group (106 cases) in demographic features, vital signs, course of illness, history for drug anaphylaxis and previous therapy, liver function, serologic parameters for liver fibrosis, liver histologic examination (99 cases in experimental group, 96 cases in control group), HBV markers, and renal function. According to the criteria for liver fibrosis staging, mean score of fibrotic stage(s) in experimental group after treatment (1.80) decreased significantly compared to the previous treatment (2.33, P<0.05), but there was no significant difference in mean score of fibrotic stage(s) (2.11 and 2.14 respectively). There was a significant difference in reverse rate between experimental group (52%) and control group (23.3%) in liver biopsy. With marked effect on decreasing the mean value of inflammatory activity and score of inflammation (P<0.05), Fuzhenghuayu capsule had rather good effects on inhibiting inflammatory activity and was superior to that of Heluoshugan capsule. Compared to that of pretreatment, there was a significant decrease in HA, LM, P-III-P and IV-C content in experimental group after 12 and 24 wk of treatment. The difference in HA, LM, P-III-P and IV-C content between 12 and 24 wk of treatment and pretreatment in experimental group was significantly greater than that in control group (P<0.01-0.05). The effect, defined as two of four parameters lowering more than 30% of the baseline, was 72.7% in experimental group and 27.4% in control group (P<0.01). Obvious improvement in serum Alb, ALT, AST and GGT was seen in two groups. Compared to that of control group, marked improvement in GGT and Alb was seen in experimental group (P<0.05). The effective rate of improvement in serum ALT was 72.7% in experimental group and 59.4% in control group. No significant difference was seen in blood and urine routine and ECG before and after treatment. There was also no significant difference in stable rate in ALT and serologic parameters for liver fibrosis between experimental group and control group after 12 wk of withdrawal. CONCLUSION: Fuzhenghuayu capsule has good therapeutic effects on alleviating liver fibrosis due to chronic hepatitis B without any adverse effect and is superior to that of Heluoshugan capsule.

Adolescent↗
PubMed2005

Phase-coherent frequency combs in the vacuum ultraviolet via high-harmonic generation inside a femtosecond enhancement cavity.

We demonstrate the generation of phase-coherent frequency combs in the vacuum utraviolet spectral region. The output from a mode-locked laser is stabilized to a femtosecond enhancement cavity with a gas jet at the intracavity focus. The resulting high-peak power of the intracavity pulse enables efficient high-harmonic generation by utilizing the full repetition rate of the laser. Optical-heterodyne-based measurements reveal that the coherent frequency comb structure of the original laser is fully preserved in the high-harmonic generation process. These results open the door for precision frequency metrology at extreme ultraviolet wavelengths and permit the efficient generation of phase-coherent high-order harmonics using only a standard laser oscillator without active amplification of single pulses.

Journal Article↗
PubMed2005

Remote transfer of a high-stability and ultralow-jitter timing signal.

Transfer of a high-stability and ultralow-jitter timing signal through a fiber network via a mode-locked fiber laser is demonstrated. With active cancellation of the fiber-transmission noise, the fractional instability for transfer of a radio-frequency signal through a 6.9- (4.5-) km round-trip installed (laboratory-based) fiber network is below 9(7) x 10(-15) tau(-1/2) for an averaging time tau > or = 1 s, limited by the noise floor of the frequency-counting system. The noise cancellation reduces the rms timing jitter, integrated over a bandwidth from 1 Hz to 100 kHz, to 37 (20) fs for the installed (laboratory-based) fiber network, representing what is to our knowledge the lowest reported jitter for transfer of a timing signal over kilometer-scale distances using an installed (laboratory-based) optical-fiber network.

Journal Article↗
PubMed2005

High-accuracy optical clock via three-level coherence in neutral bosonic 88Sr.

An optical atomic clock scheme is proposed that utilizes two lasers to establish coherent coupling between the 5s2 1S0 ground state of 88Sr and the first excited state, 5s5p 3P0. The coupling is mediated by the broad 5s5p 1P1 state, exploiting the phenomenon of electromagnetically induced transparency. The effective linewidth of the clock transition can be chosen at will by adjusting the laser intensity. By trapping the 88Sr atoms in an optical lattice, long interaction times with the two lasers are ensured; Doppler and recoil effects are eliminated. Based on a careful analysis of systematic errors, a clock accuracy of better than 2 x 10(-17) is expected.

Journal Article↗