Tunable multifunctional polarization conversion in bilayer chiral metamaterials.

A chiral metamaterial composed of bilayer twisted split-ring resonators is proposed and demonstrated to realize tunable, dual-directional, and multifunctional polarization conversion for terahertz waves. Simulations show that the converter can selectively achieve linear-to-linear, linear-to-right-handed circular, or linear-to-left-handed circular polarization conversion by tuning the polarization and propagating direction of the incident waves. Stokes parameters, ellipticity, and a polarization rotation angle are introduced to determine the output polarization. The circular polarization transmission coefficients and surface current distribution are employed to demonstrate the physical mechanisms of the phenomena above. The proposed converter can find potential applications in terahertz imaging and communications.

[Analysis of COL1A1 and COL1A2 gene variants in two fetuses with osteogenesis imperfecta].

OBJECTIVE: To explore the genetic basis of two fetuses with an osteogenesis imperfecta (OI) phenotype. METHODS: Two fetuses diagnosed at the Affiliated Hospital of Weifang Medical College respectively on June 11, 2021 and October 16, 2021 were selected as the study subjects. Clinical data of the fetuses were collected. Amniotic fluid samples of the fetuses and peripheral blood samples of their pedigree members were collected for the extraction of genomic DNA. Whole exome sequencing (WES) and Sanger sequencing were carried out to identify the candidate variants. Minigene splicing reporter analysis was used to validate the variant which may affect the pre-mRNA splicing. RESULTS: For fetus 1, ultrasonography at 17+6 weeks of gestation had revealed shortening of bilateral humerus and femurs by more than two weeks, in addition with multiple fractures and angular deformities of long bones. WES revealed that fetus 1 had harbored a heterozygous c.3949_3950insGGCATGT (p.N1317Rfs*114) variant in exon 49 of the COL1A1 gene (NM_000088.4). Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), it was classified as a pathogenic variant (PVS1+PS2+PM2_Supporting) for disrupting the downstream open reading frame resulting in premature translational termination, being de novo in origin, and lacking records in the population and disease databases.For fetus 2, ultrasonography at 23 weeks of gestation also revealed shortening of bilateral humerus and femurs by one and four weeks, respectively, in addition with bending of bilateral femurs, tibias and fibulas. Fetus 2 had harbored a heterozygous c.1557+3A>G variant in intron 26 of the COL1A2 gene (NM_000089.4). Minigene experiment showed that it has induced skipping of exon 26 from the COL1A2 mRNA transcript, resulting in an in-frame deletion (c.1504_1557del) of the COL1A2 mRNA transcript. The variant was inherited from its father and had been previously reported in a family with OI type 4. It was therefore classified as a pathogenic variant (PS3+PM1+PM2_Supporting+PP3+PP5). CONCLUSION: The c.3949_3950insGGCATGT (p.N1317Rfs*114) variant in the COL1A1 gene and c.1557+3A>G variant in the COL1A2 gene probably underlay the disease in the two fetuses. Above findings not only have enriched the mutational spectrum of OI, but also shed light on the correlation between its genotype and phenotype and provided a basis for genetic counseling and prenatal diagnosis for the affected pedigrees.

Sleep Disturbances and Their Association With Quality of Life in Older Psychiatric Patients During the COVID-19 Pandemic.

AIMS: The negative effect of the COVID-19 pandemic on sleep quality of clinically stable psychiatric patients is unknown. This study examined the prevalence of sleep disturbances and their association with quality of life (QOL) in clinically stable older psychiatric patients during the COVID-19 pandemic. METHODS: This multicenter, cross-sectional study involved older patients attending maintenance treatment at outpatient departments of four major psychiatric hospitals in China. Patients' socio-demographic and clinical characteristics were collected. Sleep disturbances, depressive symptoms, and QOL were assessed with the Insomnia Severity Index, the 9-item Patient Health Questionnaire, and 2 items of the World Health Organization Quality of Life-Brief version, respectively. Binary logistic regression analysis was conducted to examine the independent associations of socio-demographic and clinical variables with sleep disturbances, while the association between sleep disturbances and QOL was explored with analysis of covariance. RESULTS: A total of 941 patients were recruited. The prevalence of sleep disturbances was 57.1% (95% CI: 53.9-60.2%). Analysis of covariance revealed that QOL was significantly lower in patients with sleep disturbances compared to those without. Multivariate logistic regression analysis showed that sleep disturbances were positively and independently associated with more severe depressive symptoms (OR = 1.32, 95% CI: 1.26-1.37). Compared to patients with major depressive disorder, those with other psychiatric diagnoses had a significantly higher prevalence of sleep disturbances (OR = 1.44, 95% CI: 1.00-2.08). CONCLUSION: Sleep disturbances were common among clinically stable older psychiatric patients during the COVID-19 pandemic. Considering the negative association with QOL, this subpopulation needs regular assessment and timely treatment to reduce their sleep disturbances and improve their QOL.

Network Analysis of Depression, Anxiety, Posttraumatic Stress Symptoms, Insomnia, Pain, and Fatigue in Clinically Stable Older Patients With Psychiatric Disorders During the COVID-19 Outbreak.

OBJECTIVES: The Coronavirus Disease 2019 (COVID-19) pandemic has profound negative effects on the mental health of clinically stable older patients with psychiatric disorders. This study examined the influential nodes of psychiatric problems and their associations in this population using network analysis. METHODS: Clinically stable older patients with psychiatric disorders were consecutively recruited from four major psychiatric hospitals in China from May 22 to July 15, 2020. Depressive and anxiety syndromes (depression and anxiety hereafter), insomnia, posttraumatic stress symptoms (PTSS), pain, and fatigue were measured using the Patient Health Questionnaire, General Anxiety Disorder, Insomnia Severity Index, Posttraumatic Stress Disorder Checklist - Civilian Version, and Numeric Rating Scales for pain and fatigue, respectively. RESULTS: A total of 1063 participants were included. The network analysis revealed that depression was the most influential node followed by anxiety as indicated by the centrality index of strength. In contrast, the edge connecting depression and anxiety was the strongest edge, followed by the edge connecting depression and insomnia, and the edge connecting depression and fatigue as indicated by edge-weights. The network structure was invariant by gender based on the network structure invariance test (M = .14, P = .20) and global strength invariance tests (S = .08, P = .30). CONCLUSIONS: Attention should be paid to depression and its associations with anxiety, insomnia, and fatigue in the screening and treatment of mental health problems in clinically stable older psychiatric patients affected by the COVID-19 pandemic.

Prevalence of Suicidality and its Association with Quality of Life in Older Patients with Clinically Stable Psychiatric Disorders in China During the COVID-19 Pandemic.

AIMS: The pattern of suicidality in older patients with psychiatric disorders during the COVID-19 pandemic is not clear. This study examined the prevalence of suicidality and its association with quality of life (QOL) among older clinically stable patients with psychiatric disorders during the COVID-19 pandemic. METHODS: A multicenter, cross-sectional study was conducted from May 22 to July 15, 2020, among four major tertiary psychiatric hospitals in China. Suicidality was assessed by asking 3 standardized questions. Depressive symptoms, pain, and QOL were assessed with the 9-item Patient Health Questionnaire (PHQ-9), the numeric pain rating scale (NPRS), and the World Health Organization Quality of Life Questionnaire-brief version, respectively. RESULTS: A total of 1063 clinically stable patients participated and completed the assessment. The prevalence of suicidality was 11.8% (95% CI: 9.9%-13.7%) during the COVID-19 pandemic. Multiple logistic regression analysis revealed that poor treatment adherence (P = .009, OR = 1.86, 95% CI: 1.17-2.96) and perceived illness worsening during the COVID-19 outbreak (P = .02, OR = 2.07, 95% CI: 1.15-3.73), being diagnosed with major depressive disorder (P < .001, OR = 2.79, 95% CI: 1.68-4.64), PHQ-9 total score (P < .001, OR = 1.20, 95% CI: 1.15-1.24) and NPRS total score (P = .002, OR = 1.17, 95% CI: 1.06-1.29) were associated with higher risk of suicidality. After controlling for covariates, older psychiatric patients with suicidality had lower QOL compared to those without (F(1, 1063) =16.5, P<.001). CONCLUSIONS: Suicidality was common in older patients with clinically stable psychiatric disorders during the COVID-19 pandemic. Considering its negative impact on QOL and personal suffering, routine screening and preventive suicide measures should be implemented for older psychiatric patients.

Lattice-induced strong coupling in symmetric and asymmetric split-ring metamaterial arrays.

The intrinsic link between surface plasmon modes (eigenmodes) and lattice modes in subwavelength periodic structures is investigated based on the split-ring metamaterial structure. The paper shows that the strong coupling between the eigenmodes and the lattice modes can be achieved by appropriately adjusting the period of the metamaterial structure, and the emergence of new, to the best of our knowledge, modes at low frequencies is observed, resulting in a lower spectral loss of a single hybrid resonance and an increase in its Q factor up to 110. In addition, an asymmetric double-split-ring structure is proposed, and the Fano resonance is excited, giving rise to a spectral line with three resonance valleys. The coupled harmonic-oscillator model is used to interpret the underlying coupling mechanism in lattice-induced transparent systems, which agrees well with our simulation results. This strong-coupling scheme between the lattice and the mixed modes of the metamaterial unit provides a new avenue to modulate lattice-induced transparency, high-Q resonance, and strong-field confinement, which may find applications in the design of ultrasensitive sensors, slow-light devices, as well as multiple frequency absorbers and other fields.

Involvement of endoplasmic reticulum stress-activated PERK-eIF2α-ATF4 signaling pathway in T-2 toxin-induced apoptosis of porcine renal epithelial cells.

T-2 toxin is a highly toxic trichothecene that can induce toxic effects in a variety of organs and tissues, but the pathogenesis of its nephrotoxicity has not been elucidated. In this study, we assessed the involvement of protein kinase RNA-like ER kinase (PERK)-mediated endoplasmic reticulum (ER) stress and apoptosis in PK-15 cells cultured at different concentrations of T-2 toxin. Cell viability, antioxidant capacity, intracellular calcium (Ca2+) content, apoptotic rate, levels of ER stress, and apoptosis-related proteins were studied. T-2 toxin inhibited cell proliferation; increased the apoptosis rate; and was accompanied by increased cleaved caspase-3 expression, altered intracellular oxidative stress marker levels, and intracellular Ca2+ overloading. The ER stress inhibitor 4-phenylbutyrate (4-PBA) and PERK selective inhibitor GSK2606414 prevented the decrease of cell activity and apoptosis caused by T-2 toxin. The altered expression of glucose regulatory protein 78 (GRP78), C/EBP homologous protein (CHOP), and caspase-12 proved that ER stress was involved in cell injury triggered by T-2 toxin. T-2 toxin activated the phosphorylation of PERK and the alpha subunit of eukaryotic initiation factor 2 (eIF2α) and upregulated the activating transcription factor 4 (ATF4), thereby triggering ER stress via the GRP78/PERK/CHOP signaling pathway. This study provides a new perspective for understanding the nephrotoxicity of T-2 toxin.

Optically controlled ultrafast terahertz switching in wafer scale PtSe2 thin films.

In this study, we have reported a newly ultrafast optically modulated terahertz (THz) switch based on the transition metal dichalcogenide (TMD) material platinum diselenide (${{\rm PtSe}_2}$) with different thicknesses. The high-quality ${{\rm PtSe}_2}$ thin films with centimeter scale are fabricated on sapphire substrate by the chemical vapor deposition method. The optical pump and THz probe (OPTP) spectroscopy reveals that the THz response of the thin films is as fast as ${\sim} 2.0 \; {\rm ps}$ after photoexcitation of a 780 nm pulse. Interestingly, we found that the THz response time of the ${{\rm PtSe}_2}$ semimetal phase is faster than that of the semiconducting phase. In addition, the THz response time becomes faster when increasing the film thickness for the semimetal phase ${{\rm PtSe}_2}$, while for the semiconducting phase, the response time becomes slower with film thickness. Moreover, degenerate optical pump and optical probe spectroscopy (OPOP) demonstrated that the ultrafast photoinduced negative absorption (photoinduced bleaching) occurs after photoexcitation of 780 nm, and the subsequent recovery consists of two relaxation processes: the fast component with more than 85% of weight has a lifetime of ${\sim}{1.5}\;{\rm ps}$ for semiconducting-phase films and less than 1 ps for the semimetal phase, similar to the response time obtained from OPTP measurement. The slow component with less than 15% of weight has a lifetime of a few hundred picoseconds. The subpicosecond response time observed in both OPTP and OPOP is ascribed to the carrier trapping by defect states, and the slow relaxation process appearing in OPOP arises from the defect state relevant relaxation that is insensitive to the THz photoconductivity due to the frozen carrier mobility in defect states. Our experimental results demonstrate a new application of TMD materials such as ${{\rm PtSe}_2}$ in THz technology, for instance, the design and fabrication of THz modulators and THz switches.

Sub-pixel position estimation algorithm based on Gaussian fitting and sampling theorem interpolation for wafer alignment.

Wafer alignment is the core technique of lithographic tools. Image-processing-based wafer alignment techniques are commonly used in lithographic tools. An alignment algorithm is used to analyze the alignment mark image for obtaining the mark position. The accuracy and speed of the alignment algorithm are very important for guaranteeing the overlay and throughput of lithographic tools. The most commonly used algorithm in image-processing-based alignment techniques is the self-correlation method. This method has a high accuracy, but the calculation is complex, and the calculation speed is slow. In this paper, we propose a sub-pixel position estimation algorithm based on Gaussian fitting and sampling theorem interpolation. The algorithm first reconstructs the alignment signal by sampling theorem interpolation and then obtains the sub-pixel position of the mark by Gaussian fitting. The accuracy and robustness of the algorithm are verified by testing the simulated marks and experimentally captured marks. The repeat accuracy can reach 1/100 pixels, which is in the same level with the self-correlation method. The calculation speed is highly improved compared with the self-correlation method, which needs only about 1/3 of even short calculation time.

Novel Hybrid Peptide Cathelicidin 2 (1-13)-Thymopentin (TP5) and Its Derived Peptides with Effective Antibacterial, Antibiofilm, and Anti-Adhesion Activities.

The increasing numbers of infections caused by multidrug-resistant (MDR) pathogens highlight the urgent need for new alternatives to conventional antibiotics. Antimicrobial peptides have the potential to be promising alternatives to antibiotics because of their effective bactericidal activity and highly selective toxicity. The present study was conducted to investigate the antibacterial, antibiofilm, and anti-adhesion activities of different CTP peptides (CTP: the original hybrid peptide cathelicidin 2 (1-13)-thymopentin (TP5); CTP-NH2: C-terminal amidated derivative of cathelicidin 2 (1-13)-TP5; CTPQ: glutamine added at the C-terminus of cathelicidin 2 (1-13)-TP5) by determining the minimal inhibitory concentrations (MICs), minimal bactericidal concentrations (MBCs), propidium iodide uptake, and analysis by scanning electron microscopy, transmission electron microscopy, and confocal laser scanning microscopy). The results showed that CTPs had broad-spectrum antibacterial activity against different gram-positive and gram-negative bacteria, with MICs against the tested strains varying from 2 to 64 µg/mL. CTPs at the MBC (2 × MIC 64 µg/mL) showed strong bactericidal effects on a standard methicillin-resistant Staphylococcus aureus strain ATCC 43300 after co-incubation for 6 h through disruption of the bacterial membrane. In addition, CTPs at 2 × MIC also displayed effective inhibition activity of several S. aureus strains with a 40-90% decrease in biofilm formation by killing the bacteria embedded in the biofilms. CTPs had low cytotoxicity on the intestinal porcine epithelial cell line (IPEC-J2) and could significantly decrease the rate of adhesion of S. aureus ATCC 43300 on IPEC-J2 cells. The current study proved that CTPs have effective antibacterial, antibiofilm, and anti-adhesion activities. Overall, this study contributes to our understanding of the possible antibacterial and antibiofilm mechanisms of CTPs, which might be an effective anti-MDR drug candidate.

Prevalence and correlates of fatigue and its association with quality of life among clinically stable older psychiatric patients during the COVID-19 outbreak: a cross-sectional study.

BACKGROUND: The pattern of fatigue in older psychiatric patients during the COVID-19 outbreak was unknown. This study examined the prevalence of fatigue and its association with overall quality of life (overall QOL) in clinically stable older patients with psychiatric disorders during the COVID-19 outbreak. METHODS: This was a multicenter, cross-sectional study. Fatigue, depressive symptoms, pain, insomnia symptoms, and overall QOL were assessed with standardized instruments. RESULTS: A total of 1063 patients were recruited. The prevalence of fatigue was 47.1% (95%CI: 44.1-50.1%). An analysis of covariance revealed that overall QOL was significantly lower in patients with fatigue compared to those without (P = 0.011). A multiple logistic regression analysis revealed that more severe depressive symptoms (OR = 1.15, P < 0.001), insomnia symptoms (OR = 1.08, P < 0.001) and pain (OR = 1.43, P < 0.001) were significantly associated with fatigue. CONCLUSIONS: Fatigue is common among clinically stable older patients with psychiatric disorders during the COVID-19 outbreak. Considering its negative impact on overall QOL, regular assessment of fatigue and appropriate treatment warrant attention in this subpopulation.

Eightfold optical encoder with high-density grating.

A novel grating interferometer configuration with eightfold optical subdivision to achieve ultrahigh resolution using a special symmetrical prism is proposed. The optical subdivision is enhanced by four times compared to traditional linear optical encoders. In this work, we take advantage of a high linear density grating of 1780 lines/mm, which is combined with an eightfold optical subdivision configuration. As a result, a high resolution of 68.6 pm is achieved. The apparatus adopts a symmetrical measurement configuration to reduce the error arising from environmental fluctuations. The verification experiments involve high optical subdivision, long- and short-range displacement measurement, and stability, with all results compared to those obtained with a commercial interferometer. The excellent agreement of the results demonstrates the effectiveness of our proposed system.

Generation of individually modulated femtosecond pulse string by multilayer volume holographic gratings.

A scheme to generate individually modulated femtosecond pulse string by multilayer volume holographic grating (MVHG) is proposed. Based on Kogelnik's coupled-wave theory and matrix optics, temporal and spectral expressions of diffracted field are given when a femtosecond pulse is diffracted by a MVHG. It is shown that the number of diffracted sub-pulses in the pulse string equals to the number of grating layers of the MVHG, peak intensity and duration of each diffracted sub-pulse depend on thickness of the corresponding grating layer, whereas pulse interval between adjacent sub-pulses is related to thickness of the corresponding buffer layer. Thus by modulating parameters of the MVHG, individually modulated femtosecond pulse string can be acquired. Based on Bragg selectivity of the volume grating and phase shift provided by the buffer layers, we give an explanation on these phenomena. The result is useful to design MVHG-based devices employed in optical communications, pulse shaping and processing.

Periodical energy oscillation and pulse splitting in sinusoidal volume holographic grating.

This paper presents dynamical diffraction properties of a femtosecond pulse in a sinusoidal volume holographic grating (VHG). By the modified coupled-wave equations of Kogelnik, we show that the diffraction of a femtosecond pulse on the VHG gives rise to periodical energy oscillation and pulse splitting. In the initial stage of diffraction, one diffracted pulse and one transmitted pulse emerge, and energy of the transmitted pulse periodically transfers to the diffracted pulse and vice versa. In the latter stage, both the diffracted and transmitted pulses split into two spatially separated pulses. One pair of transmitted and diffracted pulses propagates in the same direction and forms the output diffracted dual pulses of the VHG, and the other pair of pulses forms the output transmitted dual pulses. The pulse interval between each pair of dual pulses is in linearly proportional to the refractive index modulation and grating thickness. By the interference effect and group velocity difference we give explanations on the periodical energy oscillation and pulse splitting respectively.

Forced rotation of nanograting in glass by pulse-front tilted femtosecond laser direct writing.

Femtosecond pulse laser with tilted intensity front demonstrates the capability of rotating the writing of nanograting in glass in 3D space. Other than the light polarization, this phenomenon is also associated with the quill-writing effect, which depends on the correlation between the sample movement and the pulse front tilt. This is because a pondermotive force, perpendicular to the tilted intensity plane, can push the excited electron plasma forward towards the pulse front. This behavior further tilts the electrical field plane and eventually result in a forced rotation of nanograting in 3D space.

Smoking, smoking cessation and tobacco control in rural China: a qualitative study in Shandong Province.

BACKGROUND: Smoking prevalence is high in China and even higher among rural residents. The aims of this study were: 1) to gain insights into the motivations of tobacco use and barriers to smoking cessation among rural village residents; 2) to understand the current tobacco control measures in the rural villages and barriers encountered or perceived for implementation. METHODS: Qualitative semi-structured face-to-face interviews and focus group discussions were conducted of 59 rural villagers including 37 village residents, 10 village leaders and 12 village doctors in three counties in Shandong Province, China. RESULTS: Smoking initiation was most often out of curiosity when seeing others smoke, but pressure from cigarette sharing and gifting custom was the major barrier to smoking cessation. The most important reason for quitting successfully was a detrimental health problem. Although many attempted to quit at the advice of other family members, relapses were common and few were able to quit completely and for long-term unless accompanied by significant health issues. Although doctor's advice to quit is effective, many doctors do not offer advice to all patients. There is a lack of true understanding of the harm of smoking and second-hand smoking among the villagers and a lack of access to and knowledge of effective smoking cessation tools among both smokers and village doctors. Tobacco control activities at villages were rare and infrequent. CONCLUSIONS: This study highlighted the need to develop tobacco control measures that reflect the unique culture in rural China. Smoking cessation measures are not likely to achieve large scale effect unless the prevailing cigarette sharing and gifting custom is drastically changed. More educations of the hazards of smoking and second-hand smoking to village residents and educations of effective smoking cessation treatment to both village residents and healthcare providers are needed.

Studies on the interaction of palmatine hydrochloride with bovine hemoglobin.

The interaction between bovine hemoglobin (BHb) and palmatine hydrochloride (PMT) was investigated at different temperatures using multispectroscopy, as well as the effect of common metal ions (Ca(2+) , Mg(2+) , Zn(2+) , Cu(2+) , Fe(2+) , Fe(3+) , Co(2+) , Ni(2+) ) on the BHb-PMT system. Results showed that the quenching mechanism of PMT on BHb was a static process. The electrostatic force played an important role in the conjugation reaction between BHb and PMT. The order of magnitude of the binding constants (Ka ) was 10(4) , and the number of binding sites (n) in the binary system was ~ 1. The binding distance (r) was ~ 2.44 nm and the primary binding for PMT was located at ß-37 tryptophan in the hydrophobic cavity of BHb. In addition, the Hill's coefficients were ~ 1. Synchronous and circular dichroism spectra revealed that the microenvironment and the conformation of BHb were changed during the binding reaction.

Chiral separation of racemic naproxen by high-performance liquid chromatography with beta-CD/SiO2 as the chiral stationary phase.

A novel derivative beta-cyclodextrin (beta-CD) bonded silica gel (beta-CD/SiO2) was prepared via carbodiimide activation and used as a chiral stationary phase (CSP). The beta-CD/SiO2 CSP was characterized by X-ray photoelectron spectroscopy and FTIR spectroscopy to prove the successful immobilization of beta-CD onto the surface of the silica gel. The thermal behavior of the CSP was studied by differential scanning calorimetry and then used for the chiral separation of racemic naproxen using HPLC. Several factors affecting the separation efficiency of naproxen enantiomers were investigated systematically. The following parameters were selected: methanol-0.01 M phosphate buffer solution (85 + 15, v/v, pH 3.5) was the mobile phase, the flow rate was 1.0 mL/min, and the column temperature was 35 degrees C. Under optimal conditions, the racemic naproxen was efficiently separated with a resolution factor (R(S)) of 1.70 and a separation factor (alpha) of 1.25. This method was successfully used for the enantiomeric separation and purity assessment of naproxen in commercial naproxen sustained release tablets.

Terahertz Biosensor Engineering Based on Quasi-BIC Metasurface with Ultrasensitive Detection.

Terahertz (THz) sensors have attracted great attention in the biological field due to their nondestructive and contact-free biochemical samples. Recently, the concept of a quasi-bound state in the continuum (QBIC) has gained significant attention in designing biosensors with ultrahigh sensitivity. QBIC-based metasurfaces (MSs) achieve excellent performance in various applications, including sensing, optical switching, and laser, providing a reliable platform for biomaterial sensors with terahertz radiation. In this study, a structure-engineered THz MS consisting of a "double C" array has been designed, in which an asymmetry parameter α is introduced into the structure by changing the length of one subunit; the Q-factor of the QBIC device can be optimized by engineering the asymmetry parameter α. Theoretical calculation with coupling equations can well reproduce the THz transmission spectra of the designed THz QBIC MS obtained from the numerical simulation. Experimentally, we adopt an MS with α = 0.44 for testing arginine molecules. The experimental results show that different concentrations of arginine molecules lead to significant transmission changes near QBIC resonant frequencies, and the amplitude change is shown to be 16 times higher than that of the classical dipole resonance. The direct limit of detection for arginine molecules on the QBIC MS reaches 0.36 ng/mL. This work provides a new way to realize rapid, accurate, and nondestructive sensing of trace molecules and has potential application in biomaterial detection.

Femtosecond pulse shaping by modulating the refractive index modulation of volume holographic grating.

Based on the modified Kogelnik's coupled-wave theory, time- and frequency-domain diffractions of a femtosecond pulse from transmitted volume holographic gratings (VHGs) are theoretically studied. Results show that when the refractive index modulation of the VHG changes in a certain range, the number of temporal diffracted pulse will evolve from one to two, then to three, and this pulse number evolution is periodic. This particular phenomenon can be explained by diffraction intensity spectrum and the overmodulation effect of refractive index modulation of transmitted VHG. Moreover, we find centers of all temporal diffracted pulses translate along the negative time axis, and the translation is irrelevant to the refractive index modulations. We will use time delay of volume grating to give a reasonable explanation.