Apportioning Atmospheric Ammonia Sources across Spatial and Seasonal Scales by Their Isotopic Fingerprint.

Mitigating ammonia (NH3) emissions is a significant challenge, given its well-recognized role in the troposphere, contributing to secondary particle formation and impacting acid rain. The difficulty arises from the highly uncertain attribution of atmospheric NH3 to specific emission sources, especially when accounting for diverse environments and varying spatial and temporal scales. In this study, we established a refined δ15N fingerprint for eight emission sources, including three previously overlooked sources of potential importance. We applied this approach in a year-long case study conducted in urban and rural sites located only 40 km apart in the Shandong Peninsula, North China Plain. Our findings highlight that although atmospheric NH3 concentrations and seasonal trends exhibited similarities, their isotopic compositions revealed significant distinctions in the primary NH3 sources. In rural areas, although agriculture emerged as the dominant emission source (64.2 ± 19.5%), a previously underestimated household stove source also played a considerably greater role, particularly during cold seasons (36.5 ± 12.5%). In urban areas, industry and traffic (33.5 ± 15.6%) and, surprisingly, sewage treatment (27.7 ± 11.3%) associated with high population density were identified as the major contributors. Given the relatively short lifetime of atmospheric NH3, our findings highlight the significance of the isotope approach in offering a more comprehensive understanding of localized and seasonal influences of NH3 sources compared to emissions inventories. The refined isotopic fingerprint proves to be an effective tool in distinguishing source contributions across spatial and seasonal scales, thereby providing valuable insights for the development of emission mitigation policies aimed at addressing the increasing NH3 burden on the local atmosphere.

Transcriptomic analysis of maize uncovers putative genes involved in metabolic detoxification under four safeners treatment.

Isoxadifen-ethyl (IDF) and cyprosulfamide (CSA) can effectively protect maize from nicosulfuron (NIC) injury, while mefenpyr-diethyl (MPR) and fenchlorazole-ethyl (FCO) did not. Their chemical diversity and requirement to use them in combination with the corresponding herbicides suggest that their elicitation of gene expression are complex and whether it is associated with the safening activity remains elusive. In this study, our first objective was to determine whether or not the ability of four safeners to enhance the metabolic rate of nicosulfuron. It was found that nicosulfuron degradation in maize was accelerated by IDF and CSA, but not by FCO and MPR. Transcriptomic analysis showed that the number of genes induced by IDF and CSA were larger than that induced by FCO and MPR. Overall, 34 genes associated with detoxification were identified, including glutathione S-transferase (GST), cytochrome P450 (CYP450), UDP-glucosyltransferase (UGT), transporter and serine. Moreover, 14 detoxification genes were screened for further verification by real-time PCR in two maize inbred lines. Two maize inbred lines exhibited high expression levels of four genes (GST31, GST39, AGXT2 and ADH) after IDF treatment. GST6, GST19, MATE, SCPL18 and UF3GT were specifically up-regulated in telerant maize inbred line under IDF and IDF + NIC treatments. Seven genes, namely GST31, GST6, GST19, UF3GT, MATE, ADH and SCPL18, are induced by IDF and CSA to play a vital role in regulating the detoxification process of NIC. Accordingly, the GST activity in maize was accelerated by IDF and CSA, but not by FCO and MPR. This result is consistent with transcriptome and metabolic data.These results indicate that the mitigation of NIC damage is associated with enhanced herbicide metabolism. IDF and CSA were more effective in protecting maize from NIC injury due to their ability to enhance the detoxification of specific types of herbicides, compared to FCO and MPR. The chemical specificity of four safeners is attributed to the up-regulated genes related to the detoxification pathway.

The strong competitive role of 2n pollen in several polyploidy hybridizations in Rosa hybrida.

BACKGROUND: 2n pollen play a strong competitive role in hybridization and breeding of multiploids in Rosa hybrida. The ploidy inheritable characteristic of 'Orange Fire' × 'Old Blush' were analyzed. RESULT: The results of the cytological observations indicated that 2n pollen developed from the defeated cytoplasmic division or nuclear division in the meiosis metaphase II of PMC (pollen mother cell) in 'Old Blush'. The natural generation rate of the 2n pollen in 'Old Blush' (2x) was about 1.39 in percentage of all male gametes, whereas the tetraploids in the F1 offspring possessed a high rate, i.e., 44.00%. The temporal and spatial characteristics of 'Old Blush' pollen germination on the stigma and growth in pistil of 'Orange Fire' and 'DEE' were observed, and the results suggested that the germination rate of 2n pollen on the stigma was not superior to that of 1n pollen, but that the proportion of 2n pollen increased to 30.90 and 37.20%, respectively, while it traversed the stigma and entered into style. The callose plug in the 2n pollen tube was significantly thinner than that of 1n pollen tube. And each trait involved in our experiment probably is very important for F1 morphological phenotypes. CONCLUSION: We conclude that 2n pollen are involved in hybridization and have a competitive advantage while it traversed the stigma and entered into style. The callose plug in the 2n pollen tube was may have strongly influenced the competitive process in R. hybrida.

Measurement of the relative non-degenerate two-photon absorption cross-section for fluorescence microscopy.

In non-degenerate two-photon microscopy (ND-TPM), the required energy for fluorescence excitation occurs via absorption of two photons of different energies derived from two synchronized pulsed laser beams. ND-TPM is a promising imaging technology offering flexibility in the choice of the photon energy for each beam. However, a formalism to quantify the efficiency of two-photon absorption (TPA) under non-degenerate excitation, relative to the resonant degenerate excitation, is missing. Here, we derive this formalism and experimentally validate our prediction for a common fluorophore, fluorescein. An accurate quantification of non-degenerate TPA is important to optimize the choice of photon energies for each fluorophore.

Efficient non-degenerate two-photon excitation for fluorescence microscopy.

Non-degenerate two-photon excitation (ND-TPE) has been explored in two-photon excitation microscopy. However, a systematic study of the efficiency of ND-TPE to guide the selection of fluorophore excitation wavelengths is missing. We measured the relative non-degenerate two-photon absorption cross-section (ND-TPACS) of several commonly used fluorophores (two fluorescent proteins and three small-molecule dyes) and generated 2-dimensional ND-TPACS spectra. We observed that the shape of a ND-TPACS spectrum follows that of the corresponding degenerate two-photon absorption cross-section (D-TPACS) spectrum, but is higher in magnitude. We found that the observed enhancements are higher than theoretical predictions.

Construction of a thermo-sensitive pRI857 vector for efficient DNA capturing in Escherichia coli.

OBJECTIVES: To establish a positive cloning system with a zero background for high-throughput DNA cloning purpose. RESULTS: The cloning vector, pRI857, and the genomic-library construction vector, pRI857-BAC, were constructed based on the mechanism of expression of the thermo-sensitive cI857 repressor gene that can stringently repress the PR promoter and kanamycin resistance gene (PR-kan R ) at 30 °C, but have no effect on PR-kan R gene at 37 °C or at higher temperatures. When the pRI857 vectors were transformed into E. coli with or without a target foreign DNA fragment inserted at the BfrBI site of the cI857 gene, only colonies with the foreign DNA fragment survive. We extended this method to construct a pRI857-BAC vector for genomic library cloning which displays an efficiency of ~107 cfu per µg of genomic DNA, with no empty vectors detected. CONCLUSIONS: Cloning by indirect activation of resistance marker gene represents a novel DNA-capturing system, which can be widely applied for high-throughput DNA cloning.

Non-degenerate 2-photon excitation in scattering medium for fluorescence microscopy.

Non-degenerate 2-photon excitation (ND-2PE) of a fluorophore with two laser beams of different photon energies offers an independent degree of freedom in tuning of the photon flux for each beam. This feature takes advantage of the infrared wavelengths used in degenerate 3-photon excitation (D-3PE) microscopy to achieve increased penetration depths, while preserving a relatively high 2-photon excitation cross section in comparison to that of D-3PE. Here, using spatially and temporally aligned Ti:Sapphire laser and optical parametric oscillator beams operating at near infrared (NIR) and short-wavelength infrared (SWIR) optical frequencies, we employ ND-2PE and provide a practical demonstration that a constant fluorophore emission intensity is achievable deeper into a scattering medium using ND-2PE as compared to the commonly used degenerate 2-photon excitation (D-2PE).

Observation of second-harmonic generation in silicon nitride waveguides through bulk nonlinearities.

We present experimental results on the observation of a bulk second-order nonlinear susceptibility, derived from both free-space and integrated measurements, in silicon nitride. Phase-matching is achieved through dispersion engineering of the waveguide cross-section, independently revealing multiple components of the nonlinear susceptibility, namely χ(2) yyy = 0.14 ± 0.08 pm/V and χ(2) xxy = 0.30 ± 0.18 pm/V. Additionally, we show how the second-harmonic signal may be tuned through the application of bias voltages across silicon nitride. The material properties measured here are anticipated to allow for the realization of new nanophotonic devices in CMOS-compatible silicon nitride waveguides, adding to their viability for telecommunication, data communication, and optical signal processing applications.

Plasmonic enhanced two-photon absorption in silicon photodetectors for optical correlators in the near-infrared.

A high-density array of plasmonic coaxial nanoantennas is used to enhance the two-photon absorption (TPA) process in a conventional silicon photodetector from a mode-locked 76 MHz Ti:sapphire laser over a spectral range from 1340 to 1550 nm. This enhanced TPA was used to generate an interferometric autocorrelation trace of a 150 fs laser pulse. Unlike second-harmonic generation, this technique does not require phase matching or a bulky crystal and can be used on a low-cost integrated silicon platform over a wide range of near-IR wavelengths compatible with modern commercial tunable femtosecond sources.

Yki stability and activity are regulated by Ca2+-calpains axis in Drosophila.

Yorkie (Yki) is a key effector of the Hippo pathway that activates the expression of targets by associating with the transcription factor Scalloped. Various upstream signals, such as cell polarity and mechanical cues, control transcriptional programs by regulating Yki activity. Searching for Yki regulatory factors has far-reaching significance for studying the Hippo pathway in animal development and human diseases. In this study, we identify Calpain-A (CalpA) and Calpain-B (CalpB), two calcium (Ca2+)-dependent modulatory proteases of the calpain family, as critical regulators of Yki in Drosophila that interact with Yki, respectively. Ca2+ induces Yki cleavage in a CalpA/CalpB-dependent manner, and the protease activity of CalpA/CalpB is pivotal for the cleavage. Furthermore, overexpression of CalpA or CalpB in Drosophila partially restores the large wing phenotype caused by Yki overexpression, and F98 of Yki is an important cleavage site by the Ca2+-calpains axis. Our study uncovers a unique mechanism whereby the Ca2+-calpain axis modulates Yki activity through protein cleavage.

Adaptability and Germination Characteristics of Volunteer Wheat in China's Main Wheat-Producing Areas.

Volunteer wheat commonly occurs and spreads rapidly in the main wheat-producing areas of China, seriously impacting cultivated wheat production. Limited information is currently available regarding the adaptability and germination traits of volunteer wheat. Therefore, this study's aim was to evaluate the effects of environmental conditions on the germination and emergence of volunteer wheat seeds through laboratory experiments. The results showed that the germination percentages and viability of volunteer wheat were significantly higher than those of cultivated wheat at a low temperature of 5 °C, and they were lower than those of cultivated wheat at high temperatures of above 30 °C. Compared to cultivated wheat, volunteer wheat was able to tolerate higher salinity and lower osmotic potential, especially long-dormancy volunteer wheat. The secondary germination ability of volunteer wheat was higher than that of cultivated wheat after water immersion. Furthermore, volunteer wheat could not emerge normally when the seeding depth was greater than 8 cm, and the emergence ability of the volunteer wheat was weaker than that of the cultivated wheats when the seeding depth was 4-8 cm, which indicates that the deep tillage of cultivated land could effectively prevent the spread of volunteer wheat. This study revealed differences in the germination characteristics of volunteer wheat and cultivated wheat under the influence of different environmental factors, which provides a basis for future studies concerning the control of volunteer wheat.

Electronic Metamaterials with Tunable Second-order Optical Nonlinearities.

The ability to engineer metamaterials with tunable nonlinear optical properties is crucial for nonlinear optics. Traditionally, metals have been employed to enhance nonlinear optical interactions through field localization. Here, inspired by the electronic properties of materials, we introduce and demonstrate experimentally an asymmetric metal-semiconductor-metal (MSM) metamaterial that exhibits a large and electronically tunable effective second-order optical susceptibility (χ(2)). The induced χ(2) originates from the interaction between the third-order optical susceptibility of the semiconductor (χ(3)) with the engineered internal electric field resulting from the two metals possessing dissimilar work function at its interfaces. We demonstrate a five times larger second-harmonic intensity from the MSM metamaterial, compared to contributions from its constituents with electrically tunable nonlinear coefficient ranging from 2.8 to 15.6 pm/V. Spatial patterning of one of the metals on the semiconductor demonstrates tunable nonlinear diffraction, paving the way for all-optical spatial signal processing with space-invariant and -variant nonlinear impulse response.