Operating point control method for the Mach-Zehnder modulator in a phase-shift laser range finder.

An operating point control method is proposed for the Mach-Zehnder modulator (MZM) based on a dual-cascaded MZM structure. Unlike traditional methods with dither signals, the proposed method is advantageous because the components monitored in the control process are not masked by the spectrum noise floor and the drift direction is clearly determined at the quadrature point, thus imparting greater control stability. Additionally, the proposed control method is suitable for phase-shift laser range finders (PSLRFs). Compared with traditional methods, experimental results reveal that the proposed method increases the operating point stability of MZM from ±0.59° to ±0.36° within 2 h, resulting in better ranging stability than 17 µm in 1 min and 39 µm in 1 h in a PSLRF with a 200 MHz modulation frequency.

High-speed and high-precision measurement of biaxial in-plane displacements: tens of nanometers principle error suppression in microprobe sensors.

When the microprobe sensor is faced with the demand of high-speed biaxial displacement measurement, due to the characteristics of phase generated carrier (PGC) technology, accompanying optical intensity modulation (AOIM) and unfavorable phase modulation depth (PMD) will bring about the tens of nanometer cyclic nonlinear errors, further hindering high-speed and high-precision measurement. Herein, a light source intensity stabilization system based on semiconductor optical amplifier (SOA) feedback control is achieved to eliminate the error caused by AOIM in the presence of high-frequency and large-amplitude laser modulation. Based on this, the reasons for large nonlinear errors in biaxial measurements and the inability to ensure the stability of the accuracy of multiple measurement axes are methodically examined, and an effective nonlinear error elimination methodology based on the normalized amplitude correction of active temperature scanning is proposed. The continuity and linearity of the temperature scanning are also discussed. The performed experiments show that the above approach is capable of reducing the displacement demodulation error from the nanometer scale to the sub-nanometer scale. Further, the nonlinear error is reduced to within 0.1 nm for both measurement axes and the performance becomes consistent. The dual-axis measurement resolution of the microprobe sensor reaches 0.4 nm and the measurement speed is better than 1.2 m/s with the standard deviation of lower than 0.5 nm.

The earliest optimal timing for total-body 68Ga-fibroblast activation protein inhibitor-04 PET scans: an evidence-based single-centre study.

OBJECTIVES: To investigate the earliest optimal timing for positron emission tomography (PET) scans after 68Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) injection. METHODS: This prospective study enrolled patients who underwent 60-min dynamic 68Ga-FAPI-04 total-body PET/CT scans; the images were reconstructed at 10-min intervals (G0-10, G10-20, G20-30, G30-40, G40-50, and G50-60), and the [68Ga]Ga-FAPI-04 uptake patterns were evaluated. The standardised uptake value (SUV), liver signal-to-noise ratio (SNR), and lesion-to-background ratios (LBRs) for different time windows were calculated to evaluate image quality and lesion detectability. The period from 30 to 40 min was then split into overlapping 5-min intervals starting 1 min apart for further evaluation. G50-60 was considered the reference. RESULTS: A total of 30 patients with suspected malignant tumours were analysed. In the images reconstructed over 10-min intervals, longer acquisition times were associated with lower background uptake and better image quality. Some lesions could not be detected until G30-40. The lesion detection rate, uptake, and LBRs did not differ significantly among G30-40, G40-50, and G50-60 (all p > 0.05). The SUVmean and LBRs of primary tumours in the reconstructed images did not differ significantly among the 5-min intervals between 30 and 40 min; for metastatic and benign lesions, G34-39 and G35-40 showed significantly better SUVmean and LBR values than the other images. The G34-39 and G50-60 scans showed no significant differences in uptake, LBRs, or detection rates (all p > 0.05). CONCLUSION: The earliest optimal time to start acquisition was 34 min after injection of half-dose [68Ga]Ga-FAPI-04. CLINICAL RELEVANCE STATEMENT: This study evaluated 68Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) uptake patterns by comparing the image quality and lesion detection rate with 60-min dynamic [68Ga]Ga-FAPI-04 total-body PET/CT scans and identified the earliest optimal scan time after [68Ga]Ga-FAPI-04 injection. KEY POINTS: • A prospective single-centre study showed that the earliest optimal time point to start acquisition was 34 min after injection of half-dose [68Ga-fibroblast activation protein inhibitor-04 (68Ga]Ga-FAPI-04). • There were statistically significant differences in standardised uptake value, lesion-to-background ratios, and lesion detectability between scans before and after 34 min from the injection of [68Ga]Ga-FAPI-04, but these values did not change further from 34 to 60 min after injection. • With a reasonable acquisition time, the image quality could still meet diagnostic requirements.

The Incidence and Effect of Different Organ Metastasis on the Prognosis of NSCLC.

OBJECTIVE: The aim of this study was to explore the effect of different organ metastasis on the prognosis of non-small cell lung cancer (NSCLC). METHODS: Patients with distant metastatic NSCLC were selected from Surveillance, Epidemiology, and End Results database during 2016 to 2019. The incidence of different organ metastasis and their association with clinicopathological factors were explored. Overall survival (OS) and lung cancer-specific survival (LCSS) for metastatic NSCLC were calculated, and multivariate Cox regression analysis was performed with a nomogram for OS being constructed based on Cox regression. RESULTS: Total 26,210 patients with distant metastatic NSCLC were included in this study. Around 48.9% of the metastatic NSCLC were multiple-organ metastasis and bone was the most commonly involved organ (44.4%). For patients with single-organ metastasis, the prognosis for lung or distant lymph nodes (LNs) metastasis was better than others (with median OS of 15 and 16 months for lung and distant LNs metastasis, respectively), and liver metastasis resulted in the worst prognosis with median OS of 8 months. A nomogram was constructed to visualize Cox regression model, along with the receiver operating characteristic (ROC) curve demonstrated good discrimination for the predictive model with 1- and 2-year area under the curve of ROC of 0.687 and 0.702, respectively. CONCLUSION: The prognosis of NSCLC patients with distant metastasis was poor. Liver metastasis results in the worst prognosis among the single-organ metastasis. The nomogram developed based on the Cox regression model has provided a useful tool to estimate the probability of OS of the metastatic NSCLC.

Differential Sampling of AC Waveforms Based on a Commercial Digital-to-Analog Converter for Reference.

This paper introduces an innovative differential sampling technique for calibrating AC waveforms, leveraging a commercially available 16-bit digital-to-analog converter (DAC) as the reference standard. The novelty of this approach lies in its enhanced stability over traditional direct sampling methods, especially as the frequency of the AC waveform increases. Notably, this technique provides a cost-effective sampler alternative to the differential sampling methods that rely on a programmable Josephson voltage standard (PJVS). A critical aspect of this methodology is the precise measurement of the DAC's output voltage, for which a static measurement strategy is adopted to utilize the exceptional linearity and transfer accuracy of the Keysight 3458A (Santa Rosa, CA, USA) in its standard DCV mode. The differential sampling method has demonstrated good accuracy, achieving a near 1 µV/V agreement with a pulse-driven AC Josephson voltage standard (ACJVS) across a 40 Hz to 200 Hz frequency range. The method attained an expanded uncertainty (k = 2) of 1 part in 106 while measuring a 0.707107 VRMS sine wave at 50 Hz, showcasing its efficacy in precise AC waveform calibration.

Citric Acid Promotes Immune Function by Modulating the Intestinal Barrier.

Amidst increasing concern about antibiotic resistance resulting from the overuse of antibiotics, there is a growing interest in exploring alternative agents. One such agent is citric acid, an organic compound commonly used for various applications. Our research findings indicate that the inclusion of citric acid can have several beneficial effects on the tight junctions found in the mouse intestine. Firstly, the study suggests that citric acid may contribute to weight gain by stimulating the growth of intestinal epithelial cells (IE-6). Citric acid enhances the small intestinal villus-crypt ratio in mice, thereby promoting intestinal structural morphology. Additionally, citric acid has been found to increase the population of beneficial intestinal microorganisms, including Bifidobacterium and Lactobacillus. It also promotes the expression of important protein genes such as occludin, ZO-1, and claudin-1, which play crucial roles in maintaining the integrity of the tight junction barrier in the intestines. Furthermore, in infected IEC-6 cells with H9N2 avian influenza virus, citric acid augmented the expression of genes closely associated with the influenza virus infection. Moreover, it reduces the inflammatory response caused by the viral infection and thwarted influenza virus replication. These findings suggest that citric acid fortifies the intestinal tight junction barrier, inhibits the replication of influenza viruses targeting the intestinal tract, and boosts intestinal immune function.

Vernalization attenuates dehydration tolerance in winter-annual Arabidopsis.

In winter-annual plants, exposure to cold temperatures induces cold tolerance and accelerates flowering in the following spring. However, little is known about plant adaptations to dehydration stress after winter. Here, we found that dehydration tolerance is reduced in winter-annual Arabidopsis (Arabidopsis thaliana) after vernalization. Winter-annual Arabidopsis plants with functional FRIGIDA (FRI) exhibited high dehydration tolerance, with small stomatal apertures and hypersensitivity to exogenous abscisic acid. Dehydration tolerance and FLOWERING LOCUS C (FLC) transcript levels gradually decreased with prolonged cold exposure in FRI plants. FLC directly bound to the promoter of OPEN STOMATA1 (OST1) and activated OST1 expression. Loss of FLC function resulted in decreased dehydration tolerance and reduced OST1 transcript levels. FLC and OST1 act in the same dehydration stress pathway, with OST1 acting downstream of FLC. Our study provides insights into the mechanisms by which FRI modulates dehydration tolerance through the FLC-OST1 module. Our results suggest that winter-annual Arabidopsis integrates dehydration tolerance and flowering time to adapt to environmental changes from winter to spring.

An artificial intelligence-driven image quality assessment system for whole-body [18F]FDG PET/CT.

PURPOSE: Image quality control is a prerequisite for applying PET/CT. This study aimed to develop an artificial intelligence-driven real-time and accurate whole-body [18F]FDG PET/CT image quality assessment system. METHODS: This study included 173 patients (age, 59 ± 12 years; 66.3% males) with whole-body [18F]FDG PET/CT imaging. Images of ten patients were used as an educational set. Images of the rest 163 patients were reconstructed to 952 images by simulating several scanning times and randomly split into training (60%, 98 patients, 578 images), validation (20%, 33 patients, 192 images), and test (20%, 32 patients,182 images) sets. Two experienced physicians (R1 and R2) independently assessed the image quality of thorax, abdomen, and pelvis region twice (R1a and b; R2a and b), 1 month apart, using a 5-point Likert scale. Objective image quality metrics were extracted from the mediastinal blood pool, three liver levels, and the bilateral gluteus maximus. The developed convolutional neural networks for image quality assessment (IQA-CNNs) generated the subjective quality scores and objective image metrics. The IQA-CNNs and physicians' performances were compared for localization accuracy, score agreement, and process time. RESULTS: The physicians demonstrated good inter- and intra-rater subjective assessment agreement, with kappa coefficients (R1a vs. R2a, R1a vs. R1b, R2a vs. R2b, and R1a vs. R2b) of 0.78, 0.77, 0.76, and 0.80. The IQA-CNNs and R1 or R2 agreed in the subjective assessments, with kappa coefficients of 0.79 and 0.78. IQA-CNNs and R1 or R2 also agreed in their objective image quality assessment (ICC > 0.60). The IQA-CNNs evaluation speed was 200 times faster than the manual assessment. CONCLUSION: An automated system for rapid assessment of [18F]FDG PET/CT image quality was developed, showing comparable performance to senior physicians. The system generates a comprehensive and detailed image quality assessment report, including subjective visual scores and objective image metrics for various anatomical regions.

Enhanced Sum Frequency Generation for Monolayers on Au Relative to Silica: Local Field Factors and SPR Effect.

Using metals as signal magnified substrates, surface plasmon-enhanced sum frequency generation (SFG) vibrational spectroscopy is a promising technique to probe weak molecular-level signals at surfaces and interfaces. In this study, the vibrational signals of the n-alkane monolayer on the gold (Au) and silica substrates are investigated using the broadband femtosecond SFG. The enhancement factors are discovered to be up to ∼1076 and ∼31 for the methyl symmetric and asymmetric stretching (ss and as) modes of the monolayer, respectively. By systematically analyzing the second-order nonlinear susceptibility tensor components (χijks), the Fresnel coefficients (Fijks), and the surface plasmon resonance (SPR) effect, we find that the interplay between Fijk and χijk terms and the SPR effect dominate the SFG signal enhancement. Our study reveals that the relative contributions of different influencing factors (i.e., Fresnel coefficients and SPR) to the SFG signal enhancement provide an approach to interpreting enhanced SFG vibrational signals detected from probe molecules on distinct substrates and may finally guide the design of the experimental methodology to improve the detection sensitivity and signal-to-noise ratio.

Head-to-head intra-individual comparison of total-body 2-[18F]FDG PET/CT and digital PET/CT in patients with malignant tumor: how sensitive could it be?

OBJECTIVES: To comparatively evaluate the lesion-detecting ability of 2-[18F]FDG total-body PET/CT (TB PET/CT) and conventional digital PET/CT. METHODS: This study enrolled 67 patients (median age, 65 years; 24 female and 43 male patients) who underwent a TB PET/CT scan and a conventional digital PET/CT scan after a single 2-[18F]FDG injection (3.7 MBq/kg). Raw PET data for TB PET/CT were acquired over the course of 5 min, and images were reconstructed using data from the first 1, 2, 3, and 4 min and the entire 5 min (G1, G2, G3, G4, and G5, respectively). The conventional digital PET/CT scan acquired in 2-3 min per bed (G0). Two nuclear medicine physicians independently assessed subjective image quality using a 5-point Likert scale and recorded the number of 2-[18F]FDG-avid lesions. RESULTS: A total of 241 lesions (69 primary lesions; 32 liver, lung, and peritoneum metastases; and 140 regional lymph nodes) among 67 patients with various types of cancer were analyzed. The subjective image quality score and SNR (signal-to-noise ratio) increased gradually from G1 to G5, and these values were significantly higher than the values at G0 (all p < 0.05). Compared to conventional PET/CT, G4 and G5 of TB PET/CT detected an additional 15 lesions (2 primary lesions; 5 liver, lung, and peritoneum lesions; and 8 lymph node metastases). CONCLUSION: TB PET/CT was more sensitive than conventional whole-body PET/CT in detecting small (4.3 mm, maximum standardized uptake value (SUVmax) of 1.0) or low-uptake (tumor-to-liver ratio of 1.6, SUVmax of 4.1) lesions. CLINICAL RELEVANCE STATEMENT: This study explored the gain of the image quality and lesion detectability of TB PET/CT, compared to conventional PET/CT, and recommended the appropriate acquisition time for TB PET/CT in clinical practice with an ordinary 2-[18F] FDG dose. KEY POINTS: • TB PET/CT increases the effective sensitivity to approximately 40 times that of conventional PET scanners. • The subjective image quality score and signal-to-noise ratio of TB PET/CT from G1 to G5 were better than those of conventional PET/CT. • 2-[18F]FDG TB PET/CT with a 4-min acquisition time at a regular tracer dose detected an additional 15 lesions compared to conventional PET/CT.

Carbon capture technology exploitation for vanadium tailings and assessment of CO2 sequestration potential.

In recent years, the global warming trend is still increasing due to CO2 emissions from various sources, such as electricity, heat production, industry, and transportation. In the vanadium industry, the vanadium bearing shale is of low grade, and the extraction of the required elemental vanadium produces large quantities of vanadium tailings (VTs). Both the roasting pretreatment of vanadium shale during vanadium extraction and the high-temperature calcination process for the preparation of vanadium products generate large amounts of CO2 gas. Therefore, it is particularly important to find an effective and environmentally friendly method for the treatment of vanadium tailings and CO2 generated by the vanadium industry. In this study, a potential method for the indirect carbonation of low calcium VTs under atmospheric pressure conditions was investigated. The carbonation reaction was investigated for different ammonia addition factors and different introduced CO2 concentrations and temperatures. The carbonation experiments showed that under the conditions of coefficient of ammonia addition of 1.4, reaction time of 60 min and reaction temperature of 60 °C, the utilization rate of calcium in VTs reached 97.9% and the CO2 uptake of VTs at 0.073 g-CO2/g, indicating that the carbonation of vanadium with low-calcium VTs was effective. The carbonation product was analyzed and measured using TG, XRD, and SEM-EDS, and it was discovered to be CaCO3, confirming the feasibility of carbonation reaction with vanadium tailings. Furthermore, the characterization of the carbonation product confirmed the mechanism and safety of the carbonation reaction, laying the groundwork for future applications.

Embedded micro-probe fiber optic interferometer with low nonlinearity against light intensity disturbance.

A novel low-nonlinearity Michelson microprobe fiber interferometer against light intensity disturbance for high-precision embedded displacement measurements is introduced. To analyze the influence of light intensity disturbance on the microprobe and measurement accuracy of the integrated fiber interferometer, an equivalent model of micro-probe sensing with the tilted target is established. The proposed PGC demodulation and nonlinearity correction method with simple principle helps avoid DC component varying with light intensity. The experiments show that residual displacement errors of the micro-probe fiber interferometer are reduced from 4.36 nm to 0.46 nm, thus allowing embedded displacement detection with sub-nanometer accuracy under low frequency light intensity disturbance.

Phenological optimization of late reproductive phase for raising wheat yield potential in irrigated mega-environments.

Increasing grain number through fine-tuning duration of the late reproductive phase (LRP; terminal spikelet to anthesis) without altering anthesis time has been proposed as a genetic strategy to increase yield potential (YP) of wheat. Here we conducted a modelling analysis to evaluate the potential of fine-tuning LRP in raising YP in irrigated mega-environments. Using the known optimal anthesis and sowing date of current elite benchmark genotypes, we applied a gene-based phenology model for long-term simulations of phenological stages and yield-related variables of all potential germplasm with the same duration to anthesis as the benchmark genotypes. These diverse genotypes had the same duration to anthesis but varying LRP duration. Lengthening LRP increased YP and harvest index by increasing grain number to some extent and an excessively long LRP reduced YP due to reduced time for canopy construction for high biomass production of pre-anthesis phase. The current elite genotypes could have their LRP extended for higher YP in most sites. Genotypes with a ratio of the duration of LRP to pre-anthesis phase of about 0.42 ensured high yields (≥95% of YP) with their optimal sowing and anthesis dates. Optimization of intermediate growth stages could be further evaluated in breeding programmes to improve YP.

Ultrafast 30-s total-body PET/CT scan: a preliminary study.

PURPOSE: The aim of this study is to explore the diagnostic value of the images obtained in ultrafast 30-s acquisition time by the total-body PET/CT (18F-FDG injection dose of about 3.7 MBq/kg), and to evaluate whether they can meet the requirements of clinical diagnosis or not. METHODS: This retrospective study explored the clinical value of ultrafast 30-s 18F-FDG total-body PET/CT in 88 oncology patients, using the post-surgical pathological diagnosis as the reference standard. The data were acquired over 300 s and reconstructed using all 300-s data (G300) and only the initial 30 s (G30). Two readers independently assessed all images qualitatively and quantitatively. The diagnostic performance was compared between G300 and G30. RESULTS: The G300 average qualitative score was higher than G30 (P < 0.001). G300 and G30 also differed quantitatively in the liver and mediastinum SUVmax, SD, and SNR (all P < 0.001), but had similar sensitivities (89.09% vs. 86.36%, P = 0.250). The G300 group had higher accuracy (79.73%) and a larger area under the curve (0.709) than G30 (77.70% and 0.695, respectively; all P > 0.05). CONCLUSION: The 30-s total-body PET/CT could meet clinical diagnostic requirements for malignant tumors in patients intolerant to prolonged horizontal positioning.

Short-time total-body dynamic PET imaging performance in quantifying the kinetic metrics of 18F-FDG in healthy volunteers.

PURPOSE: To investigate the performance of short-time dynamic imaging in quantifying kinetic metrics of 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG). METHODS: Dynamic total-body positron emission tomography (PET) imaging was performed in 11 healthy volunteers for 75 min. The data were divided into 30-, 45- and 75-min groups. Nonlinear regression (NLR) generated constant rates (k1 to k3) and NLR-based Ki in various organs. The Patlak method calculated parametric Ki images to generate Patlak-based Ki values. Paired samples t-test or the Wilcoxon signed-rank test compared the kinetic metrics between the groups, depending on data normality. Deming regression and Bland-Altman analysis assessed the correlation and agreement between NLR- and Patlak-based Ki. A two-sided P < 0.05 was considered statistically significant. RESULTS: The 45- and 75-min groups were similar in NLR-based kinetic metrics. The relative difference ranges were as follows: k1, from 3.4% (P = 0.627) in the spleen to 57.9% (P = 0.130) in the white matter; k2, from 6.0% (P = 0.904) in the spleen to 60.7% (P = 0.235) in the left ventricle (LV) myocardium; k3, from 45.6% (P = 0.302) in the LV myocardium to 96.3% (P = 0.478) in the liver; Ki, from 14.0% (P = 0.488) in the liver to 77.8% (P = 0.067) in the kidney. Patlak-based Ki values were also similar between these groups in all organs, except the grey matter (9.6%, P = 0.029) and cerebellum (14.4%, P = 0.002). However, significant differences in kinetic metrics were found between the 30-min and 75-min groups in most organs both in NLR- and Patlak-based analyses. The NLR- and Patlak-based Ki values significantly correlated, with no bias in any of the organs. CONCLUSION: Dynamic imaging using a high-sensitivity total-body PET scanner for a shorter time of 45 min could achieve relevant kinetic metrics of 18F-FDG as done by long-time imaging.

Investigating ultra-low-dose total-body [18F]-FDG PET/CT in colorectal cancer: initial experience.

PURPOSE: This study was to evaluate the effects of an ultra-low dose of [18F]-FDG on the image quality of total-body PET/CT and its lesion detectability in colorectal cancer (CRC). METHODS: Sixty-two CRC patients who underwent total-body PET/CT (uEXPLORER, United Imaging Healthcare, Shanghai, China) with an ultra-low dose (0.37 MBq/kg) of [18F]-FDG were enrolled in this retrospective study. The PET images were reconstructed with the entire 15-min dataset first and then split into 13-, 8-, 5-, 4-, 3-, 2-, and 1-min duration groups to simulate fast scanning images. For simplicity, the images reconstructed with the data from 15 to 1 min were referred to as G15, G13, and so on until G1. Subjective image quality was assessed with 5-point Likert scales. The objective image quality parameters included the SUVmax, SUVmean, and signal-to-noise ratio (SNR) of the liver and blood pool and the SUVmax and tumor-to-background ratio (TBR) of the lesions. G15 served as the control to evaluate lesion detectability. RESULTS: A total of 62 patients (43 men, 19 women; age 41-88, mean ± SD 64.0 ± 10.9 years) with 64 CRC primary tumor lesions and 10 low-grade intraepithelial neoplasia (LGIN) lesions were enrolled in this study. The subjective scores were highest for G15 (4.5 ± 0.5) and then decreased from G13 (4.3 ± 0.4) to G8 (3.7 ± 0.5). The liver SNR increased with the extension of acquisition time from G8 (17.2 ± 2.8) to G13 (20.6 ± 3.4) and G15 (21.9 ± 3.4). The liver SNR of G8 was not significantly different from that of G13 (p = 0.15) and was significantly different from that of G15 (p = 0.001). All 64 CRC lesions could be identified in all image groups, even on G1. One of ten LGINs was missed on G1, G2, and G3, and one LGIN was missed on G1, G2, G3, and G4. G15 served as the control, and 100% (48/48) lymph nodes could be found on G13 and G8 compared to 93.8% (45/48) lymph nodes on G5 and G4, 85.4% (41/48) lymph nodes on G3, 81.3% (39/48) lymph nodes on G2, and 77.1% (37/48) lymph nodes on G1. For liver metastases, there were no missed liver lesions on G13 and G8 and 3, 4, 6, 7, and 9 missed liver lesions on G5, G4, G3, G2, and G1, respectively. For other areas of metastasis, including the lung, peritoneum, and ovaries, there were no missed lesions in any group. CONCLUSIONS: Total-body PET/CT with an ultra-low dose of [18F]-FDG can maintain satisfactory image quality and lesion detectability in CRC.

Homodyne laser vibrometer modified by an LCVR for measurement at the nanometer level.

The existence of periodic nonlinear error restricts the performance of the homodyne laser vibrometer in sub-fringe amplitude vibration measurement. A homodyne laser vibrometer with nanoscale-amplitude detectability by using a liquid crystal variable retarder (LCVR) is proposed. The LCVR introduces an extra variation of optical path difference larger than the laser wavelength to acquire a full ellipse so that the nonlinearity correction parameters could be pre-extracted. The experiments showed that the nonlinear error could be well suppressed with the correction process based on the pre-extracted parameters, and the detectable minimum amplitude is less than 1 nm. In addition, measurement of vibration with the reflectivity of measured targets down to 0.048% was achieved with an automatic-gain-control module.

Analysis of light coupling in AlxGa1-xAs waveguide arrays.

Light propagation in arrays of AlxGa1-xAs waveguides is studied. The power coupling constant between two adjacent waveguides is precisely measured as waveguide material and structure is varied. Aluminum concentration contrast between waveguide core/cladding layers and waveguide width/height produce an asymmetric effective refractive index between linearly polarized modes, which in turn causes a polarization dependence of the coupling constants. Experimental measurement results agree well with an analytical model. The sensitivity of coupling constant to the waveguide parameters is analyzed. Through a careful geometric design, comparable coupling constants can be achieved in three waveguide arrays with different structure. Similar formation processes of discrete spatial optical solitons are observed respectively, confirming that the parameterization in the discrete nonlinear Schrödinger equation characterizes waveguide arrays.

Using a gene-based phenology model to identify optimal flowering periods of spring wheat in irrigated mega-environments.

To maximize the grain yield of spring wheat, flowering needs to coincide with the optimal flowering period (OFP) by minimizing frost and heat stress on reproductive development. This global study conducted a comprehensive modelling analysis of genotype, environment, and management to identify the OFPs for sites in irrigated mega-environments of spring wheat where the crop matures during a period of increasing temperatures. We used a gene-based phenology model to conduct long-term simulation analysis with parameterized genotypes to identify OFPs and optimal sowing dates for sites in irrigated mega-environments, considering the impacts of frost and heat stress on yield. The validation results showed that the gene-based model accurately predicted wheat heading dates across global wheat environments. The long-term simulations indicated that frost and heat stress significantly advanced or delayed OFPs and shrank the durations of OFPs in irrigated mega-environments when compared with OFPs where the model excluded frost and heat stress impacts. The simulation results (incorporating frost and heat penalties on yield) also showed that earlier flowering generally resulted in higher yields, and early sowing dates and/or early flowering genotypes were suggested to achieve early flowering. These results provided an interpretation of the regulation of wheat flowering to the OFP by the selection of sowing date and cultivar to achieve higher yields in irrigated mega-environments.

Kinetic metrics of 18F-FDG in normal human organs identified by systematic dynamic total-body positron emission tomography.

PURPOSE: To investigate the kinetic metrics of 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) in normal organs by using dynamic total-body (TB) positron emission tomography (PET). METHODS: Dynamic TB-PET was performed for nine healthy volunteers. Time-to-activity curves (TACs) were obtained by drawing regions of interest in the organs. A two-tissue compartment model was fitted for each tissue TAC. Constant rates, including k1, k2, and k3, and the metabolic rate of FDG (MRFDG) were obtained. The parameter statistics, including the average, standard deviation, coefficient of variance, and inter-site and inter-individual variances, were compared. RESULTS: Constant rates and MRFDG varied significantly among organs and subjects, but not among sides or sub-regions within an organ. The mean k1 and k2 ranged from 0.0158 min-1 in the right lower lung to 1.1883 min-1 in the anterior wall of the left ventricle (LV) myocardium and from 0.1116 min-1 in the left parietal white matter to 4.6272 min-1 in the left thyroid, respectively. The k3 was lowest in the right upper area of the liver and highest in the septal wall of the LV myocardium. Mean MRFDG ranged from 23.1696 µmol/100 g/min in the parietal cortex to 0.5945 µmol/100 g/min in the lung. Four groups of organs with similar kinetic characteristics were identified: (1) the cerebral white matter, lung, liver, muscle, bone, and bone marrow; (2) cerebral and cerebellar cortex; (3) LV myocardium and thyroid; and (4) pancreas, spleen, and kidney. CONCLUSION: The kinetic rates and MRFDG significantly differed among organs. The kinetic metrics of FDG parameters in normal organs can serve as a reference for future dynamic PET imaging and research.