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Perfluorooctanoic acid (PFOA) and arsenic are widely distributed pollutants and can coexist in the environment. However, no study has been reported about the effects of different arsenic species on the joint toxicity of arsenic and PFOA to soil invertebrates. In this study, four arsenic species were selected, including arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA). Earthworms Eisenia fetida were exposed to soils spiked with sublethal concentrations of PFOA, different arsenic species, and their binary mixtures for 56 days. The bioaccumulation and biotransformation of pollutants, as well as eight biomarkers in organisms, were assayed. The results indicated that the coexistence of PFOA and different arsenic species in soils could enhance the bioavailability of arsenic species while reducing the bioavailability of PFOA, and inhibit the arsenic biotransformation process in earthworms. Responses of most biomarkers in joint treatments of PFOA and As(III)/As(V) showed more significant variations compared with those in single treatments, indicating higher toxicity to the earthworms. The Integrated Biomarker Response (IBR) index was used to integrate the multi-biomarker responses, and the results also exhibited enhanced toxic effects in combined treatments of inorganic arsenic and PFOA. In comparison, both the biomarker variations and IBR values were lower in joint treatments of PFOA and MMA/DMA. Then the toxic interactions in the binary mixture systems were characterized by using a combined method of IBR and Effect Addition Index. The results revealed that the toxic interactions of the PFOA/arsenic mixture in earthworms depended on the different species of arsenic. The combined exposure of PFOA with inorganic arsenic led to a synergistic interaction, while that with organic arsenic resulted in an antagonistic response. Overall, this study provides new insights into the assessment of the joint toxicity of perfluoroalkyl substances and arsenic in soil ecosystems.
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Arsénico , Arsenicales , Contaminantes Ambientales , Fluorocarburos , Oligoquetos , Contaminantes del Suelo , Animales , Arsénico/análisis , Ecosistema , Arsenicales/metabolismo , Fluorocarburos/toxicidad , Fluorocarburos/metabolismo , Ácido Cacodílico/metabolismo , Contaminantes Ambientales/metabolismo , Biomarcadores/metabolismo , Suelo , Contaminantes del Suelo/análisisRESUMEN
OBJECTIVES: To investigate the clinical phenotypes, genetic characteristics, and pathological features of children with disorders of sex development (DSD). METHODS: A retrospective analysis was conducted on epidemiological, clinical phenotype, chromosomal karyotype, gonadal pathology, and genotype data of 165 hospitalized children with DSD at Children's Hospital of Hebei Province and Tangshan Maternal and Child Health Hospital from August 2008 to December 2022. RESULTS: Among the 165 children with DSD, common presenting symptoms were short stature (62/165, 37.6%), clitoromegaly (33/165, 20.0%), cryptorchidism (28/165, 17.0%), hypospadias (24/165, 14.5%), and skin pigmentation abnormalities/exteriorized pigmented labia majora (19/165, 11.5%). Chromosomal karyotype analysis was performed on 127 cases, revealing 36 cases (28.3%) of 46,XX DSD, 34 cases (26.8%) of 46,XY DSD, and 57 cases (44.9%) of sex chromosome abnormalities. Among the sex chromosome abnormal karyotypes, the 45,X karyotype (11/57, 19%) and 45,X/other karyotype mosaicism (36/57, 63%) were more common. Sixteen children underwent histopathological biopsy of gonadal tissues, resulting in retrieval of 25 gonadal tissues. The gonadal tissue biopsies revealed 3 cases of testes, 3 cases of dysplastic testes, 6 cases of ovaries, 11 cases of ovotestes, and 1 case each of streak gonad and agenesis of gonads. Genetic testing identified pathogenic/likely pathogenic variants in 23 cases (23/36, 64%), including 12 cases of 21-hydroxylase deficiency congenital adrenal hyperplasia caused by CYP21A2 pathogenic variants. CONCLUSIONS: Short stature, clitoromegaly, cryptorchidism, hypospadias, and skin pigmentation abnormalities are common phenotypes in children with DSD. 45,X/other karyotype mosaicism and CYP21A2 compound heterozygous variants are major etiological factors in children with DSD. The most commonly observed gonadal histopathology in children with DSD includes ovotestes, ovaries, and testes/dysgenetic testes.
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Hiperplasia Suprarrenal Congénita , Criptorquidismo , Trastornos del Desarrollo Sexual , Hipospadias , Masculino , Humanos , Niño , Trastornos del Desarrollo Sexual/genética , Trastornos del Desarrollo Sexual/diagnóstico , Trastornos del Desarrollo Sexual/patología , Hipospadias/genética , Hipospadias/complicaciones , Criptorquidismo/complicaciones , Estudios Retrospectivos , Esteroide 21-HidroxilasaRESUMEN
This study aimed to explore the co-removal effect and mechanism of Cr(VI) and Cd(II) with an optimized synthetic material. The toxicity and accumulation characteristics of Cr(VI) and Cd(II) encountered in wastewater treatment areas present significant challenges. In this work, a rational assembly of sulfide-modified nanoscale zero-valent iron (SnZVI) was introduced into a biochar (BC), and a Cr(VI)-Cd(II) binary system adsorbent with high efficiency was synthesized. When the preparation temperature of the BC was 600 °C, the molar ratio of S/Fe was 0.3, the mass ratio of BC/SnZVI was 1, and the best adsorption capacities of BC-SnZVI for Cr(VI) and Cd(II) in the binary system were 58.87 mg/g and 32.55 mg/g, respectively. In addition, the adsorption mechanism of BC-SnZVI on the Cr(VI)-Cd(II) binary system was revealed in depth by co-removal experiments, indicating that the coexistence of Cd(II) could promote the removal of Cr(VI) by 9.20%, while the coexistence of Cr(VI) could inhibit the removal of Cd(II) by 43.47%. This work provides a new pathway for the adsorption of Cr(VI) and Cd(II) in binary systems, suggesting that BC-SnZVI shows great potential for the co-removal of Cr(VI) and Cd(II) in wastewater.
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Hierro , Contaminantes Químicos del Agua , Adsorción , Cadmio , Carbón Orgánico , Cromo , Sulfuros , Contaminantes Químicos del Agua/análisisRESUMEN
Peyronellaea arachidicola is the causal agent of peanut (Arachis hypogaea L.) web blotch. Here, we report an assembled draft genome sequence of P. arachidicola strain YY187 obtained from the symptomatic leaf of peanut in China. The genome size is 47.3 Mb, consisting of 26 contigs (N50 = 2.2 Mb) with G+C content of 56.37%. This genome will provide a valuable foundation for further research on genetics and comparative genomics of P. arachidicola.
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Arachis , Ascomicetos , Ascomicetos/genética , China , Genómica , PhomaRESUMEN
Radio-based positioning systems are typically utilized to provide high-precision position information for automatic-guided vehicles (AGVs). However, the presence of obstacles in harsh environments, as well as carried cargoes on the AGV, will degrade the localization performance, since they block the propagation of radio signals. In this paper, a distributed multi-antenna positioning system is proposed, where multiple synchronous antennas are equipped on corners of an AGV to improve the availability and accuracy of positioning. An estimator based on the Levenberg-Marquardt algorithm is introduced to solve the nonlinear pseudo-range equations. To obtain the global optimal solutions, we propose a coarse estimator that utilizes the displacement knowledge of the antennas to provide a rough initial guess. Simulation results show a better availability of our system compared with the single antenna positioning system. Decimeter accuracy can be obtained under a Gaussian measurement noise with a standard deviation of 0.2 m. The results also demonstrate that the proposed algorithm can achieve positioning accuracy close to the theoretical Cramer-Rao lower bound. Furthermore, given prior information of the yaw angle, the same level of accuracy can be obtained by the proposed algorithm without the coarse estimation step.
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Functional, noncoding RNA of about 200 nucleotides in length are known as long noncoding RNA (lncRNA). Advances in -omics have revolutionized the information with respect to the coding and noncoding regions of the genome. Several studies have illustrated the role of lncRNA in cell growth and cancer. Profiling and bioinformatic studies of laryngeal cancer has identified LINC-PINT as one of the lncRNA. However, the functional aspects of the deregulation have not been studied in laryngeal tumors. In this study, LINC-PINT expression in normal and tumor tissues were studied. Using a bioinformatic approach, microRNA (miRNA) targets of LINC-PINT and gene targets of the miRNA were determined. The impact of LINC-PINT on cell proliferation and chemoresistance was determined. Further through a set of silencing and re-expression studies phenotype rescue was studied. LINC-PINT expression was downregulated in laryngeal tumors. LINC-PINT targeted miR-425-5p by three sites. miR-425-5p also targeted PTCH1 a protein of the Hedgehog pathway. Downregulation of LINC-PINT was associated with increased cancer stemness and chemoresistance to cisplatin. Our results indicate a probable role of LINC-PINT in the pathology of laryngeal tumors. LINC-PINT re-expression in laryngeal tumors may be explored for reversion of cancer cell stemness and also for rescue of drug resistance phenotype.
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Carcinoma/tratamiento farmacológico , Neoplasias Laríngeas/tratamiento farmacológico , MicroARNs/genética , Receptor Patched-1/genética , ARN Largo no Codificante/genética , Carcinoma/genética , Carcinoma/patología , Ciclo Celular/genética , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular/genética , Cisplatino/farmacología , Resistencia a Antineoplásicos/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Proteínas Hedgehog/genética , Humanos , Neoplasias Laríngeas/genética , Neoplasias Laríngeas/patología , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , Transducción de Señal/efectos de los fármacosRESUMEN
China proposed the Belt and Road Initiative (BRI), an unprecedented development strategy in terms of scope and scale, to increase the connectivity with the rest of the world by infrastructure development and trade activities. Recently, more attention has been directed to the environmental implications of the international trade activities under this initiative, which contributes to the development of a green, i.e. environmentally friendly, partnership. This study examines the evolution of virtual water trade in relation to agricultural products between China and BRI countries during 2000-2016. The Logarithmic Mean Divisia Index (LMDI) method is adopted for uncovering the driving factors underlying the trade imbalance, as well as the major virtual water exports. Results reveal that China has experienced the shift from a net virtual water exporter to a net importer. At the regional level, Southeastern Asia and Southern Asia are the major net virtual water exporters to China, and Eastern Asia is the major importer. For the selected export countries, an increase in proportion of trade in relation to domestic production significantly contributes to their virtual water export, while water intensity could decrease virtual water export for most export countries. As for the driving forces behind the imbalance of virtual water trade, trade structure was an obvious positive effect, while the effects of water intensity, product structure, and trade scale shifted in favor of virtual water outflows from BRI countries to China in 2008. Massive global water loss has incurred, indicating the inefficiency of this partnership in relation to freshwater. A closer trade relationship is established between China and BRI countries, and relevant environment implications are identified. Policy implications are proposed in terms of trade structure, relationship of trade and domestic production, and international cooperation. This study provides valuable insights into the equity and sustainability of historic trade activities with respect to freshwater resources.
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Agricultura , Agua , Asia , China , Asia OrientalRESUMEN
Jamming and spoofing are the two main types of intentional interference for global navigation satellite system (GNSS) receivers. Due to the entirely different signal characteristics they have, a few techniques can deal with them simultaneously. This paper proposes a two-stage interference suppression scheme based on antenna arrays, which can detect and mitigate jamming and spoofing before the despreading of GNSS receivers. First, a subspace projection was adopted to eliminate the high-power jamming signals. The output signal is still a multi-dimensional vector so that the spatial processing technique can be used in the next stage. Then, the cyclostationarity of GNSS signals were fully excavated to reduce or even remove the noise component in the spatial correlation matrix. Thus, the signal subspace, including information of the power and the directions-of-arrival (DOAs) of the GNSS signals, can be obtained. Next, a novel cyclic correlation eigenvalue test (CCET) algorithm was proposed to detect the presence of a spoofing attack, and the cyclic music signal classification (Cyclic MUSIC) algorithm was employed to estimate the DOAs of all the navigation signals. Finally, this study employed a subspace projection again to eliminate the spoofing signals and provide a higher gain for authentic satellite signals through beamforming. All the operations were performed on the raw digital baseband signal so that they did not introduce additional computational complexity to the GNSS receiver. The simulation results show that the proposed scheme not only suppresses jamming and spoofing effectively but also maximizes the power of the authentic signals. Nonetheless, the estimated DOA of spoofing signals may be helpful for the interference source positioning in some applications.
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Robust and centimeter-level Real-time Kinematic (RTK)-based Global Navigation Satellite System (GNSS) positioning is of paramount importance for emerging GNSS applications, such as drones and automobile systems. However, the performance of conventional single-rover RTK degrades greatly in urban environments due to signal blockage and strong multipath. The increasing use of multiple-antenna/rover configurations for attitude determination in the above precise positioning applications, just as well, allows more information involved to improve RTK positioning performance in urban areas. This paper proposes a dual-antenna constraint RTK algorithm, which combines GNSS measurements of both antennas by making use of the geometric constraint between them. By doing this, the reception diversity between two antennas can be taken advantage of to improve the availability and geometric distribution of GNSS satellites, and what is more, the redundant measurements from a second antenna help to weaken the multipath effect on the first antenna. Particularly, an Ambiguity Dilution of Precision (ADOP)-based analysis is carried out to explore the intrinsic model strength for ambiguity resolution (AR) with different kinds of constraints. Based on the results, a Dual-Antenna with baseline VEctor Constraint algorithm (RTK) is developed. The primary advantages of the reported method include: 1) Improved availability and success rate of RTK, even if neither of the two single-antenna receivers can successfully solve the AR problem; and 2) reduced computational burden by adopting the concept of measurement projection. Simulated and real data experiments are performed to demonstrate robustness and precision of the algorithm in GNSS-challenged environments.
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As a longstanding problem, Alzheimer's disease (AD) has stymied researchers in the medical field with its increasing incidence and enormous treatment difficulty. Silymarin has always been valued by researchers for its good efficacy and safety in treating liver disease. Recent studies have shown that silymarin also has good pharmacological activity in the nervous system, especially for the treatment of AD. Silymarin can control the production of Aß by inhibiting the precursor substance of Aß (ß-amyloid precursor protein), and it can inhibit the polymerization of Aß. Silymarin can also increase the acetylcholine content in the nervous system by inhibiting cholinesterase activity. At the same time, it also has the effect of resisting oxidative stress and the inflammatory response of the nervous system. These pharmacological activities contribute to the inhibition of the onset of AD. The good efficacy of silymarin on AD and its high safety and availability give it huge potential for the treatment of AD.
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Enfermedad de Alzheimer/tratamiento farmacológico , Precursor de Proteína beta-Amiloide/antagonistas & inhibidores , Silimarina/uso terapéutico , Acetilcolina/metabolismo , Animales , Antiinflamatorios/farmacología , Inhibidores de la Colinesterasa/farmacología , Colinesterasas/metabolismo , Humanos , Estructura Molecular , Sistema Nervioso/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Silimarina/farmacologíaRESUMEN
Anatomical adaptations to high-salinity environments in mangrove leaves may be recorded in leaf water isotopes. Recent studies observed lower 18 O enrichment (ΔL ) of leaf water with respect to source water in three mangrove species relative to adjacent freshwater trees, but the factors that govern this phenomenon remain unclear. To resolve this issue, we investigated leaf traits and ΔL in 15 species of true mangrove plants, 14 species of adjacent freshwater trees, and 4 species of semi-mangrove plants at five study sites along south-eastern coast of China. Our results confirm that ΔL was generally 3-4 lower for mangrove species than for adjacent freshwater or semi-mangrove species. We hypothesized that higher leaf water content (LWC) and lower leaf stomatal density (LS) both played important roles in reducing ΔL in mangroves relative to nearby freshwater plants. Both differences acted to elongate effective leaf mixing length (L) in mangroves by about 200% and lower stomatal conductance by about 30%. Péclet models based on both LWC and LS could accurately predict ΔL . Our findings highlight the potential species-specific anatomical determinants of ΔL (or L), which has important implications for the interpretation of environmental information from metabolites produced by leaf water isotopes in palaeoclimate research.
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Hojas de la Planta/anatomía & histología , Plantas Tolerantes a la Sal/anatomía & histología , China , Isótopos de Oxígeno/metabolismo , Hojas de la Planta/metabolismo , Estomas de Plantas/anatomía & histología , Estomas de Plantas/metabolismo , Transpiración de Plantas , Plantas Tolerantes a la Sal/metabolismo , Agua/metabolismo , HumedalesRESUMEN
Endophytes are barely untapped as vital sources in the medicine. They are microorganisms which mostly exist in plants. As they are exploited, it is accepted that endophytes can produce active metabolites that possess same function as their hosts such as taxol, podophyllotoxin, hypericin, and azadirachtin. These metabolites have been promising potential usefulness in safety and human health concerns. We are supposed to adopt measures to raise production for the low yield of metabolites. This paper summarizes the latest advances in various bioprocess optimization strategies. These techniques can overcome the limitations associated with rare pharmaceutical metabolite-producing endophytic fungi. These strategies include strain improvement, genome shuffling, medium optimization, fermentation conditions optimization, addition of specific factor, addition of solid sorbent, and co-culturing. It will enable endophytes to produce high and sustainable production of rare pharmaceutical metabolites.
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Endófitos/química , Plantas/microbiología , Antracenos , Barajamiento de ADN , Fermentación , Microbiología Industrial , Limoninas/química , Limoninas/uso terapéutico , Metaboloma , Paclitaxel/química , Paclitaxel/uso terapéutico , Perileno/análogos & derivados , Perileno/química , Perileno/uso terapéutico , Podofilotoxina/química , Podofilotoxina/uso terapéuticoRESUMEN
Vehicles driving in urban canyons are always confronted with a degraded Global Navigation Satellite System (GNSS) signal environment. The surrounding obstacles may cause signal reflections or blockages, which lead to large multipath noises and intermittent GNSS reception. Under these circumstances, it is not feasible to use conventional real-time kinematic (RTK) algorithms to maintain high-precision performance for positioning. In order to meet the special requirements of safety-critical applications under non-ideal observation conditions, a novel tightly coupled RTK/Inertial Navigation System (INS) algorithm is proposed in this paper, which can provide accurate and reliable positioning results continuously. Our integrated RTK/INS algorithm has three features. Firstly, INS measurements are used to help search for integer ambiguities in the position domain. INS solutions can provide a more accurate initial location and a more efficient search region. Secondly, the criterion for determining whether a candidate position is the correct solution is only related to the fractional value of the carrier-phase measurement. Thus, the new algorithm is immune to cycle slips as well as large pseudorange noises. Thirdly, our algorithm can provide more accurate ranging information than the pseudorange, even though it may not necessarily be fixed successfully, because it selects the weighted ambiguity solution as the result rather than the candidate point with maximum probability. The proposed algorithm is demonstrated on both simulated and real datasets. Compared with single epoch RTK and conventional tightly coupled RTK/INS integrations that search integer ambiguities in the ambiguity domain, our method attains better accuracy and stability in a simulated environment. Moreover, the real experimental results are presented to validate the performance of the new integrated navigation algorithm.
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Traditional attitude determination using global navigation satellite system (GNSS) carrier phases is mostly applied on geodetic-grade receivers with sufficient baseline length. However, for some special applications such as mobile communication base station smart antenna attitude determination, only low-cost receivers with ultra-short baselines can be employed, and the environments are more challenging. When solving the ambiguity resolution (AR) problem with low-cost receivers, it is hard for the traditional methods in ambiguity domain to estimate float ambiguities accurately due to the large code pseudorange noises; thus, such systems fail to determine the correct ambiguities. Aiming at improving the AR success rate for ultra-short baselines attitude determination with low-cost receivers, we provide an objective function named Mean Square Residual (MSR) based on the geometrical relationship among the position spherical search space, the fractional carrier phases, and the possible ambiguities. The method can be calculated without code pseudoranges, and thus, can provide a higher AR success rate when using low-cost receivers. The corresponding analysis and acceptance test method are discussed in this contribution, and further, as an extension for more complicated urban dynamic applications, a GNSS/Inertial Navigation System (INS) integrated system is introduced. Several experiments have been conducted to verify performance.
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(1) Background: Application of echinacoside has become increasingly important for its significant biological activities. However, there are many disadvantages in existing synthesis methods such as contaminating the environment, harsh reaction conditions and so on. Therefore, it is urgent to invent a novel alternative method that can increase the yield of echinacoside. (2) Methods: In this study, we isolated and purified an endophyte from the leaves of Ligustrum lucidum Ait. Then, we improved the yield of echinacoside by optimizing the fermentation condition with an endophytic fungus. Penicillium sp. H1 was isolated from Ligustrum lucidum Ait. In addition, response surface methodology was used to optimize the fermentation condition. (3) Results: The results indicate that the maximal yield of echinacoside (37.16 mg/L) was obtained when inoculation rate, temperature and days were 13.98%, 27.85 °C and 26.06 days, respectively. The yield of echinacoside was 150.47 times higher under the optimal conditions than under the control conditions. The results indicate that the yield of echinacoside could be improved with endophytic fermentation by optimizing the fermentation condition. We provide an alternative method for echinacoside production by endophytic fermentation in this paper. It may have a profound effect on the application of echinacoside.
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Endófitos/aislamiento & purificación , Fermentación , Glicósidos/biosíntesis , Ligustrum/microbiología , Penicillium/aislamiento & purificación , Penicillium/metabolismo , Análisis de Varianza , Cromatografía Líquida de Alta Presión , Glicósidos/químicaRESUMEN
Traditional Chinese Medicine (TCM) has been widely used in China and is regarded as the most important therapeutic. Polygonatum sibiricum (PS), a natural plant used in traditional Chinese medicine, has various functions associated with a number of its components. There are many compositions in PS including polysaccharides, steroids, anthraquinone, alkaloids, cardiac glycosides, lignin, vitamins, various acids, and so on. Of these, polysaccharides play a significant role in PS-based therapeutics. This article summarizes Polygonatum sibiricum polysaccharides (PSP) have many pharmacological applications and biological activities, such as their antioxidant activity, anti-aging activity, an anti-fatigue effect, immunity enhancement effect, antibacterial effect, anti-inflammatory effect, hypolipidemic and antiatherosclerotic effects, anti-osteoporosis effect, liver protection, treatment of diabetes mellitus (DM), anti-cancer effect, and may help prevent Alzheimer's disease, and so on. This review summarized the extraction method, purification method, compositions, pharmacological applications, biological activities, biosynthesis, and prospects of PSP, providing a basis for further study of PS and PSP.
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Medicamentos Herbarios Chinos/química , Medicamentos Herbarios Chinos/farmacología , Polygonatum/química , Polisacáridos/química , Polisacáridos/farmacología , Animales , Antibacterianos/química , Antibacterianos/farmacología , Antioxidantes/química , Antioxidantes/farmacología , Medicamentos Herbarios Chinos/uso terapéutico , Humanos , Factores Inmunológicos/química , Factores Inmunológicos/farmacología , Medicina Tradicional China , Ratones , Fitoquímicos/química , Fitoquímicos/farmacología , Polisacáridos/biosíntesis , Polisacáridos/uso terapéuticoRESUMEN
A supramolecular polycatenane stabilized by outer surface interactions between cucurbit[6]uril (Q[6] or CB[6]) cations and [CdCl4 ]2- is reported. The arrangement of the poly-interlocked supramolecular framework is evidently constructed by a favorable combination of weak non-covalent interactions such as hydrophobic effects, hydrogen bonding, ion-dipole interactions, and C-Hâ â â Cl interactions in the solid state. Further study suggests that such 3D poly-interlocked species could be rapidly precipitated from the mixture solution in high yield owing to electrostatic interaction of the [CdCl4 ]2- anion with the electropositive outer surface of Q[6] host. This work thus demonstrates a simple, low-cost, and efficient non-covalent approach for the construction of a infinite 3D interlocked structure in water besides through coordination or covalent bonds.
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Mangroves in China are severely affected by the rapid invasion of the non-native species Spartina alterniflora Although many studies have addressed the possible impacts of S. alterniflora on the performance of mangrove seedlings, how excessive nitrogen (N) input due to eutrophication affects the interactions between mangrove species and S. alterniflora remains unknown. Here, we report the results from a mesocosm experiment using seedlings of the native mangrove species Kandelia obovata and the exotic S. alterniflora grown in monoculture and mixed culture under no nitrogen addition and nitrogen (N) addition treatments for 18 months. Without N addition, the presence of S. alterniflora inhibited the growth of K. obovata seedlings. Excessive N addition significantly increased the growth rate of K. obovata in both cultures. However, the positive and significantly increasing relative interaction intensity index under excessive N input suggested that the invasion of S. alterniflora could favour the growth of K. obovata under eutrophication conditions. Our results imply that excessive N input in southeastern China can increase the competitive ability of mangrove seedlings against invasive S. alterniflora.
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Nitrógeno , Poaceae/crecimiento & desarrollo , Rhizophoraceae/crecimiento & desarrollo , China , Especies Introducidas , Nitrógeno/farmacología , Poaceae/efectos de los fármacos , Rhizophoraceae/efectos de los fármacos , Agua de Mar/química , Plantones/efectos de los fármacos , Plantones/crecimiento & desarrollo , HumedalesRESUMEN
It is well known that multipath effect remains a dominant error source that affects the positioning accuracy of Global Navigation Satellite System (GNSS) receivers. Significant efforts have been made by researchers and receiver manufacturers to mitigate multipath error in the past decades. Recently, a multipath mitigation technique using dual-polarization antennas has become a research hotspot for it provides another degree of freedom to distinguish the line-of-sight (LOS) signal from the LOS and multipath composite signal without extensively increasing the complexity of the receiver. Numbers of multipath mitigation techniques using dual-polarization antennas have been proposed and all of them report performance improvement over the single-polarization methods. However, due to the unpredictability of multipath, multipath mitigation techniques based on dual-polarization are not always effective while few studies discuss the condition under which the multipath mitigation using a dual-polarization antenna can outperform that using a single-polarization antenna, which is a fundamental question for dual-polarization multipath mitigation (DPMM) and the design of multipath mitigation algorithms. In this paper we analyze the characteristics of the signal received by a dual-polarization antenna and use the maximum likelihood estimation (MLE) to assess the theoretical performance of DPMM in different received signal cases. Based on the assessment we answer this fundamental question and find the dual-polarization antenna's capability in mitigating short delay multipath-the most challenging one among all types of multipath for the majority of the multipath mitigation techniques. Considering these effective conditions, we propose a dual-polarization sequential iterative maximum likelihood estimation (DP-SIMLE) algorithm for DPMM. The simulation results verify our theory and show superior performance of the proposed DP-SIMLE algorithm over the traditional one using only an RHCP antenna.
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Along with the rapid development of the Global Navigation Satellite System (GNSS), satellite navigation signals have become more diversified, complex, and agile in adapting to increasing market demands. Various techniques have been developed for processing multiple navigation signals to achieve better performance in terms of accuracy, sensitivity, and robustness. This paper focuses on a technique for processing two signals with separate but adjacent center frequencies, such as B1I and B1C signals in the BeiDou global system. The two signals may differ in modulation scheme, power, and initial phase relation and can be processed independently by user receivers; however, the propagation delays of the two signals from a satellite are nearly identical as they are modulated on adjacent frequencies, share the same reference clock, and undergo nearly identical propagation paths to the receiver, resulting in strong coherence between the two signals. Joint processing of these signals can achieve optimal measurement performance due to the increased Gabor bandwidth and power. In this paper, we propose a universal scheme of asymmetric dual-band tracking (ASYM-DBT) to take advantage of the strong coherence, the increased Gabor bandwidth, and power of the two signals in achieving much-reduced thermal noise and more accurate ranging results when compared with the traditional single-band algorithm.