Multiphoton Resonance Meets Tunneling Ionization: High-Efficient Photoexcitation in Strong-Field-Dressed Ions.

Tunneling ionization, a fascinating quantum phenomenon, has played the key role in the development of attosecond physics. Upon absorption of a few tens of photons, tunneling ionization creates ions in different excited states and even enables the formation of population inversion between ionic states. However, the underlying physics is still being debated. Here, we demonstrate a significant enhancement in the efficiency of multiphoton excitation when ionization of neutral molecules and resonant excitation of ions coexist in strong laser fields. It facilitates the dramatic increase in population inversion and lasing radiation in N_{2}^{+} around 1000 nm pump wavelength. Utilizing the ionization-coupling theory, we discover that the synergistic interplay between tunneling ionization and multiphoton excitation enables the ionic coherence to be maximized by phase locking of the periodically created ionic dipoles and consistently maintain an optimal phase for the follow-up photoexcitation. This Letter provides new insights into the photoexcitation mechanism of ions in strong laser fields and opens up a route for optimizing ionic lasing radiations.

Design of a Double-Photoelectrode Sensing System with a Metal-Organic Framework-Based Antenna-like Strategy for Highly Sensitive Detection of PD-L1.

Currently, the construction of heterojunctions as a method to enhance photoelectrochemical (PEC) activity has shown prospective applications in the analytical field. Restricted by carrier separation at the interface, developing a heterojunction sensing platform with high sensitivity remains challenging. Here, a double-photoelectrode PEC sensing platform was fabricated based on an antenna-like strategy by integrating MIL-68(In)-NH2, a p-type metal-organic framework (MOF) photocatalyst, as a photocathode with the type-II heterojunction of CdSe/MgIn2S4 as a photoanode synchronously. According to the ligand-to-metal charge transition (LMCT), the photo-generated carriers of MIL-68(In)-NH2 transferred from the organic ligand to the metal cluster, which provides an efficient antenna-like transfer path for the charge at the heterojunction interface. In addition, the sufficient Fermi energy difference between the double photoelectrode provides the continuous internal driving force required for rapid carrier separation at the anode detection interface, significantly improving the photoelectric conversion efficiency. Hence, compared with the traditional heterojunction single electrode, the photocurrent response of the double-photoelectrode PEC sensing platform developed using the antenna-like strategy is 2.5 times stronger. Based on this strategy, we constructed a PEC biosensor for the detection of programed death-ligand 1 (PD-L1). The elaborated PD-L1 biosensor exhibited sensitive and precise detection capability with a detection range of 1 × 10-5 to 1 × 103 ng/mL and a lower detection limit of 3.26 × 10-6 ng/mL and demonstrated the feasibility of serum sample detection, providing a novel and viable approach for the unmet clinical need of PD-L1 quantification. More importantly, the charge separation mechanism at the heterojunction interface proposed in this study provides new creative inspiration for designing sensors with high-sensitivity PEC performance.

Destructive interference in N2+ lasing.

We report an unexpected experimental observation in rotation-resolved N2+ lasing that the R-branch lasing intensity from a single rotational state in the vicinity of 391 nm can be greatly stronger than the P-branch lasing intensity summing over the total rotational states at suitable pressures. According to a combined measurement of the dependence of the rotation-resolved lasing intensity on the pump-probe delay and the rotation-resolved polarization, we speculate that the destructive interference can be induced for the spectrally-indistinguishable P-branch lasing due to the propagation effect while the R-branch lasing is little affected due to its discrete spectral property, after precluding the role of rotational coherence. These findings shed light on the air-lasing physics, and provide a feasible route to manipulate air lasing intensity.

Background-free single-beam coherent Raman spectroscopy assisted by air lasing.

We develop a background-free single-beam coherent Raman scattering technique enabling the high-sensitivity detection of greenhouse gases. In this scheme, Raman coherence prepared by a femtosecond laser is interrogated by self-generated narrowband air lasing, thus allowing single-beam measurements without complex pulse shaping. The unique temporal and spectral characteristics of air lasing are beneficial for improving the signal-to-noise ratio and spectral resolution of Raman signals. With this method, SF6 gas present at a concentration of 0.38% was detected in an SF6-air mixture. This technique provides a simple and promising route for remote detection due to the low divergence of Raman signals and the availability of high-energy pump lasers, which may broaden the potential applications of air lasing.

Blastocyst euploidy rates in low-prognosis patients according to the POSEIDON criteria: a retrospective analysis of 3016 embryos.

RESEARCH QUESTION: Do embryo euploidy rates differ in the four groups of women with low prognosis as stratified by the POSEIDON criteria? DESIGN: This was a retrospective cohort study of low-prognosis patients who met the POSEIDON criteria and underwent preimplantation genetic testing for aneuploidies (PGT-A) from January 2013 to June 2020 at the Center for Reproductive Medicine, Shandong University, China. A total of 3016 blastocysts from 1269 PGT-A cycles were included in the study. The primary outcome was the euploidy rate of the blastocysts. For each group, regression analyses were performed to quantitatively describe the relationship between maternal age and embryo euploidy rate. RESULTS: The euploidy rate of embryos in women with poor ovarian response (POR) was 39.1% in total. There were 727, 1052, 275 and 962 blastocysts in groups 1, 2, 3 and 4, respectively, with corresponding embryo euploidy rates of 57.2%, 34.9%, 52.4% and 26.2% (P < 0.001). Within each group, the euploidy rate decreased with age, especially in women aged 35 years or older (i.e. groups 2 and 4). CONCLUSIONS: Euploidy rates were more favourable in groups 1 and 3, of a young age, re-emphasizing that oocyte quality is the primary factor determining embryo euploidy rate. The study's findings demonstrated the reasonability of categorizing women with POR by the POSEIDON criteria depending on female age and ovarian reserve biomarkers. These results also provide information for women with POR in different subgroups so they can receive proper counselling on the possible prognosis.

The low fetal fraction at the first trimester is associated with adverse pregnancy outcomes in IVF singleton pregnancies with single embryo transfer from frozen cycles.

PURPOSE: To study the associations between fetal fraction at the first trimester and subsequent adverse pregnancy outcomes (APOs) in IVF singleton pregnancies with single embryo transfer from frozen cycles. METHODS: This is a single-center retrospective cohort study on IVF singleton pregnancies with single embryo transfer from frozen cycles. A total of 8457 women were collected between March 2015 and September 2018 from the Center for Reproductive Medicine, Shandong University, China. Participants underwent cell-free DNA (cfDNA) sequencing at 11-13 weeks' gestation. Multivariable logistic regressions were performed with the risk of APOs based on various predictor variables. RESULTS: A total of 8457 women were included in the analysis of which 1563 (18.48%) women developed one or more APOs. The hypertensive disorders of pregnancy (HDP) (N = 515), gestational diabetes mellitus (GDM) (N = 684), preterm birth (PTB) (N = 567), and low birth weight (LBW) (N = 306) groups had lower fetal fraction compared with the no pregnancy complication (NPC) group (all p values < 0.05). Based on the multivariable logistic regression results, the optimal cutoff values of fetal fraction were 9.30%, 12.54%, 9.10%, 12.65%, and 13.83% for at least one APO, HDP, GDM, PTB, and LBW, respectively. After adjustment for potential maternal confounders, women in the low fetal fraction (LFF) group had a higher risk for the APOs compared with high fetal fraction (HFF) group. CONCLUSIONS: The fetal fraction in HDP, GDM, PTB, and LBW groups were lower than NPC group in IVF singleton pregnancies with single embryo transfer from frozen cycles in China.

Mechanism and control of rotational coherence in femtosecond laser-driven N2.

We investigate the formation of rotational coherence of N2+ resonantly interacting with an intense femtosecond laser field by numerical simulations based on a strong-field ionization-coupling model described with the density matrix formalism. The created N2+ system is unique in many aspects: the variable total population within the pump duration due to the intensity-dependent ionization injection, the readily accessible resonance owing to the effect of Stark shift, and the involvement of a few dozen of quantum states. By regarding the N2+ system as an open and non-stationary Λ-type cascaded multi-level system, we quantitatively studied the dependence of rotational coherence in different electronic-vibrational states of N2+ on the alignment angle θ and the pumping intensity. Our simulation results indicate that the quantum coherence between the neighbouring rotational states of J, J+2 in the vibrational state ν=0, 1 of the ground state of N2+ can be changed from a negative to a positive. The significant contribution of rotational coherence to inducing an extra gain or absorption of N2+ air lasing is further verified by solving the Maxwell's propagating equation. The finding provides crucial clues on how to manipulate N2+ lasing by controlling the rotational coherence and paves the way to studying strong-field quantum optics effects such as lasing without inversion and electromagnetically induced transparency in molecular ionic systems.

Enhanced resonant vibrational Raman scattering of N2+ induced by self-seeding ionic lasers created in polarization-modulated intense laser fields.

We report on an experimental investigation of the five vibrational Raman lines at 358 nm, 388 nm, 391 nm, 428 nm, and 471 nm of N2+ resonantly driven by the self-seeding ionic lasers generated by a polarization-modulated (PM) or alternatively a linearly polarized (LP) femtosecond laser. It was found that the spectral intensities of several Raman lines can be dramatically enhanced by exploiting the PM laser pulses in comparison to the LP laser pulses. The evaluated Raman conversion efficiency reaches ∼10-2 for some lasing lines at suitable pressures. Moreover, the role of interplay between the seed amplification and the resonant vibrational Raman scattering processes in inducing the gain of N2+ lasing is characterized for the first time. The developed vibrational Raman spectroscopy with intense ultrafast lasers provides an additional approach to interrogate the products in a femtosecond filament, and it therefore can be a powerful tool for identifying chemical species at remote distances in the atmosphere.

Association of Ang-2, vWF, and EVLWI with risk of mortality in sepsis patients with concomitant ARDS: A retrospective study.

BACKGROUND/PURPOSE: This study aimed to determine the potential effects of angiopoietin-2 (Ang-2), von Willebrand factor (vWF), and extravascular lung water index (EVLWI) on the risk of mortality in sepsis patients with concomitant acute respiratory distress syndrome (ARDS). METHODS: This retrospective study recruited 41 sepsis patients with concomitant ARDS from January 2015 to June 2018. Data of Ang-2 and vWF levels, EVLWI, and sequential organ failure assessment scores were collected at 0, 24, and 48 h after admission to the hospital. RESULTS: The length of intensive care unit stay (P = 0.041) and Acute Physiology and Chronic Health Evaluation-2 (APACHE II) score (P = 0.003) were associated with the risk of mortality. Furthermore, increased Ang-2 levels and EVLWI at 24 h and 48 h were associated with an increased risk of mortality. Moreover, the APACHE II score at hospital admission significantly predicted the risk of mortality (area under the curve [AUC], 0.834; 95% confidence interval [CI], 0.665-0.983). Finally, the models containing a combination of Ang-2 level and EVLWI at 24 h (AUC, 0.908; 95% CI, 0.774-0.996) and Ang-2 level and EVLWI at 48 h (AUC, 0.981; 95% CI, 0.817-1.000) had high diagnostic values for predicting risk of mortality. CONCLUSION: The study findings indicate that Ang-2 levels and EVLWI at 24 h and 48 h after admission are significantly associated with the risk of mortality.

[Identification of a novel splicing variant of IDS gene in a pedigree affected with type II glycosaminoglycan product storage disease].

OBJECTIVE: To analyze variant of IDS gene in a pedigree affected with mucopolysaccharidosis type II (MPS II). METHODS: The proband was subjected to next generation sequencing and Sanger sequencing to identify potential variants. Suspected variant was analyzed by its co-segregation with the disease in the pedigree. Its impact on mRNA splicing was analyzed by using reverse transcription PCR (RT-PCR). RESULTS: A hemizygous IVS1-3T>G variant was found in the IDS gene in the proband. RT-PCR results revealed two abnormal cDNA fragments of 600 bp and 300 bp. The 600 bp fragment had inserted 216 nucleotides at the 3' end of intron 1, while the 300 bp fragment had lost 109 nucleotides at the 5' end of exon 2, which resulted in two truncated proteins comprising 38 and 92 amino acids, respectively, instead of the normal product (550 amino acids). The proband and his mother were respectively hemizygous and heterozygous for the variant. The same variant was not found among 100 normal controls. CONCLUSION: The IVS1-3T>G variant of the IDS gene probably underlies the MPS II in this pedigree by causing reduction or elimination of the IDS protein.

[Identification of a novel variant of COL4A5 gene in a pedigree affected with Alport syndrome].

OBJECTIVE: To explore the genetic basis for a pedigree affected with Alport syndrome. METHODS: Next generation sequencing and Sanger sequencing was carried out to detect potential variant of the COL4A5 gene among members from the pedigree and 100 unrelated healthy controls. RESULTS: A novel missense c.3293G>T (p.Gly1098Val) variant was found in the COL4A5 gene among 6 affected members but not the unaffected members of the pedigree or the 100 healthy controls. According to the American College of Medical Genetics and Genomics standards and guidelines, the c.3293G>T variant was classified as pathogenic (PP1-strong+PM1+PM2+PP3+PP4). CONCLUSION: By destructing the Gly-X-Y structure of its protein product, the c.3293G>T variant of the COL4A5 gene probably underlies the Alport syndrome in this pedigree. Above finding has enriched the spectrum of COL4A5 variants.

[Application of droplet digital PCR for non-invasive prenatal diagnosis of single gene disease in two families].

OBJECTIVE: To assess the value of droplet digital PCR (ddPCR) for non-invasive prenatal diagnosis of single gene disease in two families. METHODS: Paternal mutation in cell-free DNA derived from the maternal blood and amniotic fluid DNA was detected by ddPCR. Suspected mutation in the amniotic fluid DNA was verified with Sanger sequencing. RESULTS: The result of ddPCR and Sanger sequencing indicated that the fetuses have carried pathogenic mutations from the paternal side in both families. CONCLUSION: Droplet digital PCR can accurately detect paternal mutation carried by the fetus, and it is sensitive and reliable for analyzing trace samples. This method may be applied for the diagnosis of single gene diseases caused by paternal mutation using peripheral blood sample derived from the mother.

[Novel mutations of XPC gene detected in a family affected with xeroderma pigmentosum group C].

OBJECTIVE: To detect mutations of the XPC (XPC complex subunit, DNA damage recognition and repair factor) gene in a family affected with xeroderma pigmentosum group C (XP-C). METHODS: The patient was subjected to next-generation sequencing and Sanger sequencing. Suspected mutations were validated by Sanger sequencing. Effect of splicing mutation was confirmed by reverse transcription-PCR (RT-PCR). RESULTS: Compound heterozygous mutations of c.2098G to T and c.2034-7_2040del were found in the XPC gene in the proband. Among these, c.2098G to T (p.G700X) is a nonsense mutation resulting in a truncated XPC protein. C.2034-7_2040del involves the -1 position, which may alter the splice donor site of the intron 11 of XPC and result in a truncated XPC protein with loss of amino acids from 940 to 679 positions. The two mutations were not detected among 100 unrelated healthy controls. CONCLUSION: Mutations of c.2098 G to T and c.2034-7_2040del of the XPC gene may lead to abnormal XPC expression and reduction or elimination of normal XPC functions, which may underlie the disease in this family.

[A novel mutation of GLI3 gene underlying synpolydactyly in a family].

OBJECTIVE: To detect mutation of GLI3 gene in a family affected with autosomal dominant synpolydactyly. METHODS: Genomic DNA was extracted from peripheral blood samples from members of the family and 100 unrelated healthy controls. Potential mutation was screened by next-generation sequencing and confirmed by Sanger sequencing. RESULTS: A heterozygous frameshift mutation c.480dupC was identified in the GLI3 gene among all patients from the family. The same mutation was not found in unaffected family members and the 100 healthy controls. CONCLUSION: The c.480dupC of the GLI3 gene probably underlies the synpolydactyly in this family.

Population Redistribution Among Multiple Electronic States of Molecular Nitrogen Ions in Strong Laser Fields.

We carry out a combined theoretical and experimental investigation on the population distributions in the ground and excited states of tunnel-ionized nitrogen molecules at various driver wavelengths in the near- and midinfrared range. Our results reveal that efficient couplings (i.e., population exchanges) between the ground N_{2}^{+}(X^{2}Σ_{g}^{+}) state and the excited N_{2}^{+}(A^{2}Π_{u}) and N_{2}^{+}(B^{2}Σ_{u}^{+}) states occur in strong laser fields. The couplings result in a population inversion between the N_{2}^{+}(X^{2}Σ_{g}^{+}) and N_{2}^{+}(B^{2}Σ_{u}^{+}) states at wavelengths near 800 nm, which is verified by our experimental observation of the amplification of a seed at ∼391 nm. The result provides insight into the mechanism of free-space nitrogen ion lasers generated in remote air with strong femtosecond laser pulses.

Time-resolved shadowgraphs of transient plasma induced by spatiotemporally focused femtosecond laser pulses in fused silica glass.

We report on experimental observations of formation and evolution of transient plasma produced in fused silica glass with spatiotemporally focused (STF) femtosecond laser pulses using a pump-probe shadow imaging technique. Surprisingly, the observation shows that the track of the plasma is significantly curved, which is attributed to an asymmetric density distribution of the transient plasma produced in the focal volume caused by the pulse front tilt of the STF laser field.

Generation of an air laser at extended distances by femtosecond laser filamentation with telescope optics.

We present the generation of self-induced-white-light-seeded lasing action of nitrogen molecules in air by a Ti:sapphire femtosecond laser (800 nm, 5.5 mJ) and demonstrate that such lasing action is strongly influenced by external focusing conditions. It is found that the self-seeded lasing signal of N(2)(+) at ~391 nm decreases dramatically by orders of magnitude and ultimately disappears when the focal length of an external lens increases from 0.5 m to 1 m. By using a telescope, it is shown that such limitation can be overcome and the 391 nm lasing can be controlled to occur at remotely designated distance, providing a possibility for practical applications in standoff spectroscopy.

Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses.

We experimentally demonstrate ultrafast dynamic of generation of the 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the C(3)Π(u) and B(3)Π(g) states of N(2) for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.

Interferometric characterization of pulse front tilt of spatiotemporally focused femtosecond laser pulses.

We report on an experimental measurement of the pulse front tilt (PFT) of spatiotemporally focused femtosecond laser pulses in the focal plane in both air and bulk transparent materials, which is achieved by examination of the interference pattern between the spatiotemporally focused pulse and a conventional focused reference pulse as a function of time delay between the two pulses. Our simulation results agree well with the experimental observations.