Design and simulation of digital channelized receivers in fractional Fourier domain

An approach is proposed to realize a digital channelized receiver in the fractional Fourier domain （FRFD） for signal intercept applications. The presented architecture can be considered as a generalization of that in the traditional Fourier domain. Since the linear frequency modulation （LFM） signal has a good energy concentration in the FRFD, by choosing an appropriate fractional Fourier transform （FRFT） order, the presented architecture can concentrate the broadband LFM signal into only one sub-channel and that will prevent it from crossing several sub-channels. Thus the performance of the signal detection and parameter estimation after the sub-channel output will be improved significantly. The computational complexity is reduced enormously due to the implementation of the polyphase filter bank decomposition, thus the proposed architecture can be realized as efficiently as in the Fourier domain. The related simulation results are presented to verify the validity of the theories and methods involved in this paper.

Investigation of Strain-Temperature Cross-Sensitivity of FBG Strain Sensors Embedded Onto Different Substrates

The strain-temperature cross-sensitivity problem easily occurs in the engineering strain monitoring of the self-sensing embedded with fiber Bragg grating(FBG)sensors.In this work,a theoretical investigation of the strain-temperature cross-sensitivity has been performed using the temperature reference grating method.To experimentally observe and theoretically verify the problem,the substrate materials,the preloading technique,and the FBG initial central wavelength were taken as main parameters.And a series of sensitivity coefficients calibration tests and temperature compensation tests have been designed and carried out.It was found that when the FBG sensors were embedded on different substrates,their coefficients of the temperature sensitivity were significantly changed.Besides,the larger the coefficients of thermal expansion(CTE)of substrates were,the higher the temperature sensitivity coefficients would be.On the other hand,the effect of the preloading technique and FBG initial wavelength was negligible on both the strain monitoring and temperature compensation.In the case of similar substrates,we did not observe any difference between temperature sensitivity coefficients of the temperature compensation FBG with one free end or two free ends.The curves of the force along with temperature were almost overlapped with minor differences(less than 1%)gained by FBG sensors and pressure sensors,which verified the accuracy of the temperature compensation method.We suggest that this work can provide efficient solutions to the strain-temperature cross-sensitivity for engineering strain monitoring with the self-sensing element embedded with FBG sensors.

Spirolindemers A and B,Lindenane Sesquiterpenoid Oligomers Equipped with Oxaspiro[4.5]decane from Chloranthus henryi

Spirolindemers A and B,unprecedented lindenane sesquiterpenoid dimer(1)and trimer(2)equipped with oxaspiro[4.5]decane unit,were discovered from the medicinal plant Chloranthus henryi.Their structures including absolute configurations were achieved by HRMS,NMR,ECD,X-ray diffraction analyses,and quantum chemical calculations.Biogenetically,hetero-and homo-Diels-Alder additions may dominate the formation of oxaspiro[4.5]decane and spiro[4.5]decane skeletons,respectively.Compound 1 showed anti-inflammatory activity by inhibiting the expression of iNOS and COX-2.

Sarcaglarols A-D, Lindenane-Monoterpene Heterodimers from Sarcandra glabra Based on Molecular Networks

Sarcaglarols A-D(1-4),two pairs of lindenane-monoterpene heterodimers fused by a 1,2-dioxane moiety,were discovered and isolated from the leaves of Sarcandra glabra guided by MS/MS molecular networking-based strategy.Their planar structures,absolute configurations of basic skeleton and flexible polyhydric side chain were established by analysis of HRESIMS,NMR spectroscopic data,ECD spectrum,and the X-ray diffraction study of isopropylidene derivatives.An intermolecular[2+2+2]cycloaddition may play a key role in the biosynthesis pathway of the 1,2-dioxane moiety fused lindenane-monoterpene heterodimer skeleton,which can be recognized as the biogenetic precursors of our previous reported lindenane-normonoterpene conjugates.In addition,compounds 1,3 and 4 exhibited moderate inhibitory effects of lipid accumulation in free fatty acid-exposed L02 cells.

Diverse Ring-seco Limonoids from Munronia unifoliolata and Their Biological Activities

Twenty-two new limonoids,mufolinoids A—V(1—22),including six rings A,B-seco limonoids(1—6),twelve ring A-seco limonoids(7—18),four ring-intact limonoids(19—22),together with thirteen known compounds(23—35)were isolated from Munronia unifoliolata.Their structures including absolute configurations were elucidated by combination of NMR,HR-MS,single-crystal X-ray diffraction and calculations of ECD and NMR technologies.Compounds 24,25,33,34 could be significantly reversed the multidrug resistance of MCF-7/doxorubicin(DOX)cells,and the reversal fold(RF)was much higher than that of positive drug Verapamil.Compounds 24,28,and 29 exhibited significant anti-inflammatory activity with the IC50 values in the range of 17.7—39.4μmol/L.Furthermore,compound 29 could markedly inhibit the release of IL-1βby inhibiting the initiation and assembly of NLRP3 inflammasome,which demonstrates the great potential of limonoids as an anti-inflammatory agent.

Mufolinin A,an unprecedented ring A-seco 10-ethyllimonoid from Munronia unifoliolata

Mufolinin A(1),a ring A-seco rearranged limonoid with an unprecedented ethyl at C-10 and novel 6/6/6/5 fused-ring skeleton,together with three new potential precursors(ring A-seco limonoids,2–4)were isolated from Munronia unifoliolata.Their structures and absolute configurations were confirmed by nuclear magnetic resonance(NMR),high resolution electrospray ionization mass spectroscopy(HRESIMS),X-ray crystallography,electronic circular dichroism(ECD)calculations and NMR calculations with DP4+analyses.The unprecedented ethyl group of 1 was hypothesized to be derived from methyl migration and ring reduction rearrangement of ring A-seco limonoid 4.Compounds 2 and 4 showed significant multidrug resistance(MDR)reversal activities in MCF-7/DOX cells with reversal fold(RF)values of 13.1 and 8.0,respectively.

Chlospicenes A and B,cyclopropane cracked lindenane sesquiterpenoid dimers with anti-nonalcoholic steatohepatitis activity from Chloranthus henryi

Guided by MS/MS molecular networks strategy,chlospicenes A and B(1 and 2),the first example of cyclopropane moiety cracked lindenane sesquiterpene Michael addition dimers,along with their biogenetic analogues(3 and 4),were targetedly discovered from the roots of Chloranthus henryi.Their structures including absolute configurations were characterized by NMR,ECD and X-ray diffraction analysis.The plausible biogenic pathway speculation indicated that cyclopropylcarbinyl rearrangement may dominate the key crack of cyclopropane moiety.In addition,compounds 1 and 2 showed significant anti-nonalcoholic steatohepatitis(NASH)activity in free fatty acid(FFA)-induced HepG2 cells by decreasing intracellular lipid accumulation.

Aphamines A-C,dimeric acyclic diterpene enantiomers from Aphanamixis polystachya

Aphamines A-C(1-3),three pairs of acyclic diterpene dimer enantiomers with an unprecedent ploymerization pattern,were discovered from Aphanamixis polystachya by NMR-guided isolation and chiral resolution.The elucidation of their novel carbon skeletons was achieved based on spectroscopic analysis,exciton chirality,and calculated electronic circular dichroism(ECD).Plausible Claisen rearrangement,5-exo-trig cyclization,and reduction reactions may play important roles in the polymeric biosynthesis pathway.Compounds 1 and 3 showed inhibitory effects on nitric oxide(NO)production(IC_(50):6.71-15.36 μmol/L) and reduced the expression of iNOS in LPS-induced RAW 264.7 macrophages.