Inverse estimation of the acoustic impedance of a porous woven hose from measured transmission coefficients

A porous tube, comprised of a resin-coated woven fabric has recently been used as an effective component for use in intake systems of internal combustion engines to reduce the intake noise. For the prediction of the acoustic performance of an engine intake system with a porous woven hose, the acoustic wall impedance of the hose must be known. However, the accurate measurement of the wall impedance of a porous woven hose is not easy because of its peculiar acoustical and structural characteristics. A new measurement technique is proposed herein, that is valid over the low to mid frequency ranges. The acoustics impedance is inversely estimated from an overdetermined set of measured pressure transmission coefficients for specimens of different lengths and the reflection coefficient of end termination. The method involves only one measurement setup, and, as a result, it is very simple. A variation of the proposed method, an inverse estimation method using one of the four-pole parameters is also proposed. An error sensitivity analysis was performed to investigate the effect of measurement error on the accuracy of the final result. The measured TL for samples with arbitrary lengths and arbitrary porous frequency are in reasonably good agreement with values predicted from curve-fitted impedance data.     

Secondary Metabolites from the Stem Bark of Litsea akoensis and Their Cytotoxic Activity

Six new butanolides, litseadioxanins A and B ( 1 and 2 , resp.) bearing a 1,2‐dioxane moiety, litseatrinolides A and B ( 3 and 4 , resp.), and litseakolides D₁ and D₂ ( 5 and 6 , resp.), were isolated from the stem bark of Litsea akoensis, together with six known compounds. The structures of the new compounds were characterized by in‐depth NMR‐spectroscopic and mass‐spectrometric analyses. Butanolides 1 – 4 , and a mixture of 6 and litsenolide E₂, and litsenolide B₁ were tested against human tumor cells, including MCF‐7 (human breast adenocarcinoma), NCI‐H460 (non‐small‐cell lung cancer), and SF‐268 (glioblastoma) cell lines. Among the tested compounds, litsenolide B₁ exhibited marginal cytotoxic activity against MCF‐7, NCI‐H460, and SF‐268 cell lines in vitro.     

Identification of Five New Minor Constituents from the Whole Plant of Amischotolype hispida

Bioassay‐guided fractionation of the active AcOEt‐soluble layer from the whole plant of Amischotolype hispida resulted in the isolation of four new compounds, i.e., amisbenzoic acid ( 1 ), one butenolide derivative, amisnolide ( 2 ), one chlorin analog, amisphytin ( 3 ), one lignan, amislignol ( 4 ), and one metabolite isolated for the first time from nature, (?)‐glaberide I ( 5 ), along with 20 known compounds, 6 – 25 . Their structures were elucidated on the basis of UV, IR, 1D‐ and 2D‐NMR (¹H,¹H‐COSY, DEPT, HSQC, HMBC), as well as HR‐ESI‐MS, analyses. Among these isolates, palmitic acid ( 13 ) showed an antimycobacterial activity with an MIC value of 20.0 μg/ml against Mycobacterium tuberculosis H37Rv.     

Chemical and Cytotoxic Constituents from the Stem of Machilus zuihoensis

Five new compounds, including a novel lactone, machilactone (=rel‐(2R,3aR,6E,6aS)‐2‐heptadecyl‐3a‐methyl‐6‐octadecylidene‐6,6a‐dihydrofuro[2,3‐d][1,3]dioxol‐5(3aH)‐one; 1 ), a new sesquiterpene, 3,4‐dihydroxy‐β‐bisabolol (=rel‐(1R,2S,4R)‐1‐[(1R)‐1,5‐dimethylhex‐4‐enyl]‐1‐methylcyclohexane‐1,2,4‐triol; 2 ), a new secobutyrolactone, methyl (2E)‐2‐(1‐hydroxy‐2‐oxopropyl)eicos‐2‐enoate ( 3 ), two new butyrolactones, machicolide A ( 4 ) and machicolide B ( 5 ) (=3E,4R,5R)‐ and (3Z,4R,5R)‐4,5‐dihydro‐4‐hydroxy‐5‐methoxy‐5‐methyl‐3‐octadecylidenefuran‐2(3H)‐one, resp.) as a mixture, together with known caryophyllene oxide (=4,12,12‐trimethyl‐9‐methylene‐5‐oxatricyclo[8.2.0.0^4,6]dodecane), hexacosane, tetracosanoic acid, isomahubanolide‐23 (=(3E,4R)‐4,5‐dihydro‐4‐hydroxy‐5‐methylidene‐3‐octadecylidenefuran‐2(3H)‐one), and β‐bisabolol (=(1S)‐1‐[(1S)‐1,5‐dimethylhex‐4‐enyl]‐4‐methylcyclohex‐3‐en‐1‐ol) were isolated from the stem wood of Machilus zuihoensis. The structures of these compounds were established by spectroscopic studies. The eicos‐2‐enoate ( 3 ) and β‐bisabolol exhibited marginal cytotoxicity against NUGC and HONE‐1 cancer cell lines in vitro.     

Synthesis and Cytotoxic Evaluation of Some 4‐Anilinofuro[2,3‐b]quinoline Derivatives

Some 4‐anilinofuro[2,3‐b]quinoline derivatives were synthesized from dictamnine, a natural alkaloid, and evaluated for their cytotoxicity in the NCI's full panel of 60 human cancer cell lines derived from nine cancer cell types, including leukemia, non‐small‐cell lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer, and breast cancer. 1‐[4‐(Furo[2,3‐b]quinolin‐4‐ylamino)phenyl]ethanone ( 5 ) (mean GI₅₀=0.025 μM ), bearing an 4‐acetylanilino substituent at C(4) of furo[2,3‐b]quinoline, was more active than its 3‐acetylanilino counterpart 7 (mean GI₅₀=5.27 μM ), and both clinically used anticancer drugs, N‐[4‐(acridin‐9‐ylamino)‐3‐methoxyphenyl]methanesulfonamide (m‐AMSA; mean GI₅₀=0.44 μM ) and daunomycin (mean GI₅₀=0.044 μM ). Compound 5 was capable of inhibiting all types of cancer cells tested with a mean GI₅₀ of less than 0.04 μM in each case except for the non‐small‐cell lung cancer (average GI₅₀=1.75 μM ). Although non‐small‐cell lung cancer is resistant to compound 5 , the sensitivity within this type of cancer cells varies: HOP‐62 (GI₅₀<0.01 μM ), NCI‐H460 (GI₅₀=0.01 μM ), and NCI‐H522 (GI₅₀<0.01 μM ) are very sensitive, while HOP‐92 (GI₅₀ = 12.4 μM ) is resistant. Among these non‐small‐cell lung cancers, NCI‐H522 was found to be very sensitive to 5, 8a , and 8b with a GI₅₀ values of <0.01, 0.074, and <0.01 μM , respectively.     

Secondary Metabolites from the Endophytic Fungus Xylaria cubensis

Seven new metabolites, including three sesquiterpenoids, 10‐hydroxythujopsene ( 1 ), akotriol ( 2 ), and xylaritriol ( 3 ), one diterpenoid, cubentriol ( 4 ), one aliphatic derivative, akoenic acid ( 5 ), one alkaloid, akodionine ( 6 ), and one isocoumarin, akolitserin ( 7 ), together with seven known compounds, 8 – 14 , were isolated from the AcOEt‐soluble fraction of the fermentation broth of the endophytic fungus Xylaria cubensis, derived from the leaves of Litsea akoensis Hayata (Lauraceae). Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR experiments, and by HR‐ESI‐MS mass spectrometry. Among the isolates, (?)‐(R)‐7‐hydroxymellein showed IL‐6 inhibitory activity with an IC₅₀ value of 9.41 μM .     

Prediction of intake noise of an automotive engine in run-up condition

It is very important to predict the radiated noise from the engine intake system for the effective noise control and virtual prototyping of in-cavity and outdoor noise of a vehicle. To this end, one should precisely measure the in-duct acoustic source parameters of the intake system, viz., source strength and source impedance. Usually, the noise radiation characteristics need to be expressed as a function of engine speed. In this study, acoustic source parameters of an engine intake system under engine run-up condition were measured by using the direct method. Direct method employed two external loudspeakers, turned on simultaneously, and three microphones for the separation of upstream and downstream wave components. It was noted that the frequency spectra of source impedance hardly changes with the increase of engine speed. Utilizing this fact, source strength under the engine run-up condition was calculated by assuming invariant source impedance. Predicted insertion loss and radiated sound pressure level using the measured source parameters were compared with those of measured data and predicted data using several idealized source models, which have been adopted for the calculations. A reasonably good agreement was observed between measured sound spectra at the intake orifice and predicted one using the measured source data. It was shown that the source data obtained by the present method yielded a far better prediction accuracy than those by the idealized source models.     

Chemical Constituents from the Root Wood of Zanthoxylum Integrifoliolum

Two new phenylpropanoids, integrifoliolin ( 1 ) and integrifoliodiol ( 2 ), together with 23 known compounds, have been isolated from the root wood of Zanthoxylum integrifoliolum. The structures of these compounds were determined by means of spectral analyses. The reported anti‐HIV constituents of decarine and γ‐fagarine were also isolated from the root wood of this plant.     

Flavones and Cytotoxic Constituents from the Stem Bark of Muntingia Calabura

Two new flavones, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone and 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, together with thirteen known compounds have been isolated from the stem bark of Muntingia calabura. The structures of two new compounds were determined through spectral analyses. Among the isolates, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone, 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, and 3‐hydroxy‐1‐(3,5‐dimethoxy‐4‐hydroxyphenyl)propan‐1‐one exhibited effective cytotoxicities (ED₅₀ values = 3.56, 3.71, and 3.27 μg/mL, respectively) against the P‐388 cell line in vitro.