Optimization of Covert Communication in Multi-Sensor Asymmetric Noise Systems.

This work investigates wireless covert communication in a multi-sensor asymmetric noise scenario. We adopt KL (Kullback-Leibler) divergence as the covertness constraint metric and mutual information as the transmission rate metric. To accurately approximate KL divergence and mutual information in covert communication, we employ the Taylor series expansion technique. Analytical expressions for KL divergence and mutual information in covert communication are derived, and we optimize the amplitude gain and phase angles based on these analytical expressions. Our findings underscore the importance of phase angle selection in covert communication within asymmetric noise systems. We propose an effective method for optimizing the transmission amplitude gain and phase angles in scenarios with asymmetric noise. Numerical results validate the effectiveness and superiority of our proposed method.

Worldwide scientific efforts on nursing in the field of SARS-CoV-2: a cross-sectional survey analysis.

INTRODUCTION: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been a global public health issue. This study aimed to characterize global nursing research on SARS-CoV-2. METHODOLOGY: Nursing-related publications through December 31, 2022, were identified using Scopus. The number of studies, study types, countries, institutions, journals, authors, h-index, total confirmed cases, total deaths, and the highest-cited studies were investigated. RESULTS: In total, 12,427 studies were identified. The number of studies increased rapidly, particularly between 2020 and 2021, with a 2.36-fold increase. The United States published the most studies (3,289, 26.47%), followed by the United Kingdom (1,059, 8.52%) and China (877, 7.06%). Scientific productivity significantly correlated with the total confirmed cases (r = 0.701, p = 0.024) and total deaths (r = 0.804, p = 0.005). The United States had the highest h-index (80), followed by China (59), and the United Kingdom (57). The University of Toronto published the most studies (181), followed by Harvard Medical School (165), and the University of São Paulo (107). Gravenstein S (23) was the most prolific author, followed by Mor V (22), and Rosa WE (19). The International Journal of Environmental Research and Public Health published the most papers (436), followed by PLOS ONE (219), and BMJ Open (185). CONCLUSIONS: Several countries, institutions, journals, and authors contributed greatly to SARS-CoV-2-related nursing studies. Countries with larger numbers of confirmed cases and deaths tended to publish more nursing studies. The United States, United Kingdom, and China had the highest quantity and quality of studies.

Nontargeted screening of aldehydes and ketones by chemical isotope labeling combined with ultra-high performance liquid chromatography-high resolution mass spectrometry followed by hybrid filtering of features.

Aldehydes and ketones are important carbonyl compounds that are widely present in foodstuffs, biological organisms and human living environment. However, it is still challenging to comprehensively detect and capture them using liquid chromatography - mass spectrometry. In this work, a chemical isotope labeling (CIL) coupled with ultra-high performance liquid chromatography - high resolution mass spectrometry (UHPLC-HRMS) strategy was developed for the capture and detection of this class of compounds. 2,4-Dinitrophenylhydrazine (DNPH) and isotope-labeled DNPH (DNPH-d3) were utilized to selectively label the target analytes. To address the difficulties in processing UHPLC-HRMS data, a post-acquisition data processing method called MSFilter was proposed to facilitate the screening and identification aldehydes and ketones in complex matrices. The MSFilter consists of four independent filters, namely statistical characteristic-based filtering, mass defect filtering, CIL paired peaks filtering, and diagnostic fragmentation ion filtering. These filters can be used individually or in combination to eliminate unrelated interfering MS features and efficiently detect DNPH-labeled aldehydes and ketones. The results of a mixture containing 48 model compounds showed that although all individual filtering methods could significantly reduce more than 95% of the raw MS features with acceptable recall rates above 85%, but they had relatively high false positive ratios of over 90%. In comparison, the hybrid filtering method combining four filters is able to eliminate massive interfering features (> 99.5%) with a high recall rate of 81.25% and a much lower false positive ratio of 15.22%. By implementing the hybrid filtering method in MSFilter, a total of 154 features were identified as potential signals of CCs from the original 45,961 features of real tobacco samples, of which 70 were annotated. We believe that the proposed strategy is promising to analyze the potential CCs in complex samples by UHPLC-HRMS.

Botanical discrimination and classification of Mentha plants applying two-chiral column tandem GC-MS analysis of eight menthol enantiomers.

The concentration and distribution of menthol enantiomers have great significance in discriminating natural mint varieties and evaluating the origin of foodstuffs containing menthol additives. However, the chiral separation of eight chiral menthol enantiomers in Mentha plants offers an easy approach to eliminating or reducing the identification technology problem. The application of derivatized ß-cyclodextrin capillary chiral column coupled with derivatized γ-cyclodextrin capillary chiral column, and gas chromatography-mass spectrometry (GC-MS) technology, to isolate and analyze eight chiral menthol enantiomers in 23 natural Mentha plants was investigated. The results showed that the two-chiral columns tandem technology enabled the baseline separation of the eight menthol enantiomers. Four different menthol compounds were only detected in seven out of the 23 natural mint plants. (1R,3R,4S)-(-)-menthol and (1R,3S,4S)-(+)-neomenthol were detected in the seven mint plant samples, while (1S,3S,4R)-(+)-menthol and (1S,3R,4R)-(-)-neomenthol could not be detected in the seven mint plant samples. For the two enantiomer couples of (+/-)-isomenthol and (+/-)-neoisomenthol, only (+)-isomers were detected in field mint, candy mint, and peppermint. The Mentha plant samples were distinguished and identified by principal component analysis and radar chart statistical analysis based on the data of the menthol content and isomer ratio. Furthermore, the presence or absence of (1S,3S,4R)-(+)-menthol in the samples can be used as an identification factor for discriminating between synthetic menthol and natural sources of menthol.

Direct adsorption sampling and ambient mass spectrometry analysis of tobacco smoke with porous paper strips.

Chemical analysis of atmospheric aerosols by conventional analytical methods is usually required to perform complicated and time-consuming sample preparation processes. In recent decades, ambient ionization mass spectrometry (AI-MS) methods have been proven to be simple, rapid, and effective analytical tools for direct analysis of various complex samples. In this work, we applied porous paper filters for direct adsorptive sampling of tobacco smoke, and then the sampled paper filters were performed the emitters of the paper spray ionization (PSI) device. An auto-sampling device was made to control the generation and collection of tobacco smoke. Nicotine, the typical compound of tobacco smoke, was used to optimize the key conditions of auto-sampling. Moreover, different types of tobacco smoke were also compared with multivariate variable analysis, and the makers of tobacco smoke from different sources of tobacco smoke were investigated. By using this method, direct sampling and analysis of a single tobacco sample can be completed within minutes. Overall, our results show that PSI-MS is a powerful tool that integrates collection, extraction, ionization, and identification analytes in smoke.

Recyclable molecularly imprinted polymers based on Fe3O4@SiO2 and PAMAM dendrimers for the determination of myosmine in cigarettes.

A selective method for the determination of myosmine (a tobacco alkaloid) was developed using molecularly imprinted polymers (MIPs) based on Fe3O4@SiO2 and PAMAM dendrimers. Fe3O4@SiO2 with excellent magnetism and rapid separation performance was chosen as carrier for the MIPs. Moreover, the MIPs modified with PAMAM dendrimers exhibited a regular structure and abundant functional groups, which improve the efficiency of imprinting sites. The myosmine concentration was measured by HPLC with PDA detector, and the UV detection wavelength was set to 200 nm. The linear range of this assay was 13.2-400 mg/L with a correlation coefficient of 0.999, and the detection limit was 4.0 mg/L (S/N = 3). The MIPs have been used for the determination of myosmine in cigarettes, and the recovery range was 84.2-93.5%, with RSD values in the range 0.41-3.1%. In conclusion, our MIPs combine advantages of simple preparation and remarkable selectivity, which gives them excellent application prospects for the sensitive determination of trace myosmine in tobacco products.

Aberrant expression of SPAG6 and NM23 predicts poor prognosis of human osteosarcoma.

Objective: To investigate the expression and clinical significance of sperm-associated antigen 6 and NM23 proteins in human osteosarcoma. Methods: The specimens of conventional osteosarcoma with follow-up from 42 Chinese patients were analyzed in this study, and 12 cases of osteochondroma were considered controls. The expression of SPAG6 and NM23 was inspected using immunohistochemical staining, qRT-PCR, and Western blotting methods. Results: The positive expression rate of SPAG6 protein (71.43%) in 42 cases of osteosarcoma tissue was significantly higher than that (33.33%) in 12 cases of osteochondroma tissues (p < 0.05), while the positive rate of NM23 protein (35.71%) in osteosarcoma tissue was lower than that (58.33%) in osteochondroma tissue (p < 0.05). The mRNA and protein levels of SPAG6 were significantly higher than those of the adjacent normal tissues, while the expression of NM23 was lower in osteosarcoma tissues than that in the controls (p < 0.05 for all). There was a positive relationship between the expression of SPAG6 and pathological grade, metastasis, and Enneking stage (p < 0.05 for all). The overall survival rate of osteosarcoma patients with SPAG6 positive expression was significantly lower than that with SPAG6 negative expression. The relationship between the expression of NM23 and pathological grade, metastasis, and Enneking stage was negative (p < 0.05 for all). The overall survival rate of the osteosarcoma patients with NM23 positive expression was higher than that of the patients with NM23 negative expression (p < 0.05). Conclusion: Overexpression of SPAG6 and low expression of NM23 are negatively related to pathological grade, metastasis, and Enneking stage and prognosis of osteosarcoma patients. This suggested that SPAG6 and NM23 should be considered candidate prognostic biomarkers for patients with osteosarcoma.

Determination and Difference Analysis of Phenolic Compounds in Smokers' Saliva and Mainstream Smoke.

To study the differences in phenolic compounds between tobacco smokers' saliva and mainstream smoke, a method was developed for the analysis of 12 phenolic compounds in saliva and mainstream smoke based on ultrahigh-performance liquid chromatography with fluorescence detection (UPLC-FLD). The contents and distributions of phenolic compounds in tobacco smokers' saliva and mainstream smoke were compared. The results were as follows: (1) Phenolic compounds were quantitatively analyzed by the internal standard method using 4-fluorophenol as an internal standard. For smokers' saliva samples, the limits of quantification (LOQs) ranged from 2.2 to 19.1 µg/L, and the recoveries were from 80.2% to 119.2% at the three spiked levels. For mainstream smoke samples, the LOQs ranged from 0.03 to 0.26 µg/cig, and the recoveries ranged from 84.9% to 107.0% at the three spiked levels. (2) The contents of phenolic compounds from 14 cigarettes in mainstream smoke and smokers' saliva were determined. In mainstream smoking, the main phenolic compounds were hydroquinone, catechol, phenol, meta- and para-Cresol, and o-methylhydroquinone. In smokers' saliva, the main phenolic compounds were phenol and meta- and para-Cresol and the contents of phenolic compounds in smokers' saliva from different cigarettes were significantly different. (3) The content distribution patterns of phenolic compounds in smokers' saliva differed from those in mainstream smoke. The predominant phenolic compound in mainstream smoke was dihydroxybenzene, while monophenols predominated in smokers' saliva. (4) The contents of phenolic compounds from five kinds of cigarettes were analyzed in the saliva of different smokers using principal component analysis, which indicated that cigarettes with different sensory effects were clearly distinguished by differences in the contents of phenolic compounds in saliva.

Components and Persistent Free Radicals in the Volatiles during Pyrolysis of Lignocellulose Biomass.

Persistent free radicals (PFRs) may cause negative impacts to human health and the environment because of the induced reactive oxygen species. We expect that PFRs could be generated in the condensable volatiles formed during lignocellulose biomass pyrolysis. Elucidating the structural origin and the formation mechanism of PFRs is important for an in-depth understanding of air pollutants from the pyrolysis or combustion of lignocellulose biomass. This work selected rice straw and pine sawdust to represent agricultural and forest biomass residues. The pyrolysis mechanism, volatile components, and PFR generation were discussed based on the analysis of thermogravimetry-Fourier transform infrared spectroscopy-mass spectrometry (MS), pyrolysis-gas chromatography/MS, and electron spin resonance (ESR). Levoglucosan, furans, and 2-methoxyphenols were the main pyrolytic compounds for cellulose (CL), hemicellulose (HC), and lignin (LG), respectively. Obvious ESR signals were detected in the condensable volatiles of LG, while no ESR signals were detected for those of CL and HC. Higher ESR signals were detected in lignocellulose with a higher content of LG. Therefore, LG was the main structural basis to generate PFRs in lignocellulose condensable volatiles, mostly attributed to the methoxyphenol components. This study provides useful information regarding the generation mechanisms of and the structures related to PFRs, which is essential to understand the risks of lignocellulose pyrolytic volatiles.

Formation of persistent free radicals in biochar derived from rice straw based on a detailed analysis of pyrolysis kinetics.

The presence of persistent free radicals (PFR) in biochars may greatly broaden the application of biochars in pollution control, but may also cause negative impacts to the environment. Understanding the structural basis and the formation mechanisms of PFR is essential for a targeted biochar production and application. This study used rice straw (RS), a ubiquitous agricultural waste, to investigate the generation processes of PFR in relation to RS pyrolysis kinetics. Based on a detailed thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis, the activation energy was calculated by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods. This work combined pyrolysis kinetics analysis and solid particle characterization. Our results showed that lignin started to pyrolyze at a lower temperature than cellulose and hemicellulose. Lignin was the main factor for PFR generation. Chemical bond breaking contributed only slightly to PFR formation. The reconfiguration of the carbonaceous structures may be a more important contributor to PFR formation, while the cross-linking between different compositions and the interactions between the chemical compositions and inorganic minerals may play a significant role for PFR generation and stabilization in RS. This study provides useful theoretical basis to understand the thermal pyrolysis process of RS and the manipulation of biochar properties.

Antiviral and Cytotoxic Isocoumarin Derivatives from an Endophytic Fungus Aspergillus oryzae.

Oryzaeins A-D (1-4), four new isocoumarin derivatives, along with five known ones (5-9) were isolated from solid cultures of an endophytic fungus Aspergillus oryzae. Their structures were elucidated by detailed spectroscopic analysis and by comparison with reported data of related derivatives. Among them, compounds 1 and 2 represent the first examples of isocoumarins possessing an unusual 2-oxopropyl group and a rare 3-hydroxypropyl group. Compounds 1 and 2 displayed moderate anti-tobacco mosaic virus activities with inhibition rates of 28.4% and 30.6%, respectively, at the concentration of 20 µM. The new compounds showed moderate inhibitory activities against several human tumor cell lines with IC50 values in the range of 2.8-8.8 µM. Supporting information available online at http://www.thieme-connect.de/products.

Two new benzolactones from the leaves of Nicotiana tabacum and their anti-tobacco mosaic virus activities.

Two new benzolactones, 5-methyl-6-prenyl-isobenzofuran-1(3H)-one (1), 5-hydroxymethyl-6-prenyl-isobenzofuran-1(3H)-one (2), together with four known phenolic compounds (3-6), were isolated from the leaves of Nicotiana tabacum. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1-6 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that compounds 1-6 exhibited high anti-TMV activities with inhibition rates in the range of 16.9-26.2%, respectively.

Anti-TMV activity flavones from the leaves of Yunnan local air cured tobacco.

Four new flavones, tobaflavones E-H (1-4), together with two known flavones (5 and 6), were isolated from the leaves of Dali Tiandeng tobacco (a variety of Yunnan local air cured tobacco). Their structures were elucidated by spectroscopic methods, including extensive 1D- and 2D NMR techniques. Compound 2 is the first naturally occurring flavone bearing a (4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)methyl moiety. These compounds were also evaluated for their anti-tobacco mosaic virus (anti-TMV) activity. The results revealed that compounds 1 and 2 exhibited high anti-TMV activity with inhibition rate of 35.3% and 39.6%, respectively. The rates are higher than those of positive control. The other compounds also showed potential anti-TMV activity with inhibition rates in the range of 18.7-28.4%, respectively.

Direct detection of DNA below ppb level based on thionin-functionalized layered MoS2 electrochemical sensors.

A layered MoS2-thionin composite was prepared by sonicating their mixture in an ionic liquid and gradient centrifugation. Because DNA is rarely present in single-stranded form, either naturally or after PCR amplification, the composite was used for fabrication of a double-stranded DNA (dsDNA) electrochemical biosensor due to stable electrochemical response, intercalation, and electrostatic interaction of thionin with DNA. The linear range over dsDNA concentration from 0.09 ng mL(-1) to 1.9 ng mL(-1) is obtained, and moreover, it is suitable for the detection of single-stranded DNA (ssDNA). The biosensor has been applied to the detection of circulating DNA from healthy human serum, and satisfactory results have been obtained. The constructed DNA electrochemical biosensor shows potential application in the fields of bioanalysis and clinic diagnosis. Furthermore, this work proposes a new method to construct electrochemical biosensors based on MoS2 sheets.

Bitriazolyl acyclonucleosides synthesized via Huisgen reaction using internal alkynes show antiviral activity against tobacco mosaic virus.

A family of novel bitriazolyl acyclonucleosides were synthesized using a simple and convenient one-step synthetic procedure via the Huisgen reaction by addition of NaN(3) onto triazole nucleosides bearing internal alkynyl groups introduced at the 5-position of the triazole ring. Some of the compounds exhibited interesting antiviral activity against tobacco mosaic virus, demonstrating the importance of the bitriazolyl motif for the observed antiviral activity.

[Separation and identification of 5 glycosidic flavor precursors in tobacco by ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry].

A qualitative method for the identification of 5 main glycosidic flavor precursors in tobacco was developed by using ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI MS/MS) and gas chromatography-mass spectrometry (GC-MS). The glycosidic flavor precursors in tobacco were extracted with methanol, cleaned up with an XAD-2 column. The aglycones were later released by enzyme-mediated hydrolysis under the condition of pH 5. The 5 volatile aglycone moieties were identified by GC-MS standard spectra library. The precursor ions of glycosides were determined by using electrospray ionization mass spectrometry in negative ion mode, then the 5 glycosidic flavor precursors were identified by using product ion scan (MS2) finally, using UPLC-ESI MS/MS, separation and identification of 5 glycosidic flavor precursors were accomplished on an RP-C,8 column in the multiple reaction monitoring (MRM) mode by using methanol and acetic acid-ammonium acetate aqueous solution as eluent. This work lays a foundation for the analysis of glycosidic flavor precursors without the standards by using liquid chromatography-mass spectrometry.

Arylethynyltriazole acyclonucleosides inhibit hepatitis C virus replication.

Novel acyclic triazole nucleosides with various ethynyl moieties appended on the triazole nucleobase were synthesized efficiently using a convenient one-step Sonogashira reaction in aqueous solution and under microwave irradiation. One of the compounds, 1f, inhibited HCV subgenomic replication with a 50% effective concentration (EC(50)) of 22 microg/ml and did not inhibit proliferation of the host cell at a concentration of 50 microg/ml. A preliminary SAR study suggests that the appended phenyl ring as well as the rigid triple bond linker contributes importantly to the anti-HCV activity.