Efficient rate-power allocation for OFDM in a realistic fading environment

The implementation of practical adaptive resource allocation scheme remains a key criterion to be satisfied for realising spectrally efficient multitone wireless communications. The ever-increasing demand for spectrally efficient broadband wireless transmission technologies has spurred intensive research leading towards the implementation of adaptive OFDM and adaptive MIMO systems. Efforts in this direction have been frustrated however by the lack of a clear and accurate description of the fading behaviour typically encountered in the broadband wireless transmission environment. This has been partially been overcome by the use of mathematical modelling which captures certain large-scale characteristics of the channel and facilitates theoretical research. The “average” channel parameters gleaned from these processes is typically then used to inform the design and configuration of wireless networking equipment after the broad application of generous safety margins. The resulting solu�tion is therefore quite robust to certain transient channel quality degradation yet the generous safety tolerances render it unable to exploit other transient transmission quality improvements We seek to overcome the problems associated with this ap�proach by applying a theoretically sound novel adaptive resource allocation framework to actual broadband wireless channel development data. The allocation framework is derived from the optimal OFDM allocation scheme for a known channel [1]: the channel development data is obtained from actual measurement of a broadband wireless mobile environment [2]. Prediction tech�niques are employed to overcome the time lag between channel assessment and symbol transmission. We present the details of the predictive resource allocation scheme used and include a broad characterisation of the transmission environment in terms of the time-varying fading processes observed. We provide some results of the application of this scheme as typical performance levels that may be achieved in an actual transmission environment

Diterpene Glycosides from the Seeds of <i>Pharbitis nil</i>

Six new ent-kaurane diterpene glycosides, pharbosides A−F (1−6), and a new ent-gibbane diterpene glycoside, pharboside G (7), together with three known ent-kaurane diterpenoids, 7β,16β,17-trihydroxy-ent-kauran-6α,19-olide (8), 6β,7β,16α,17-tetrahydroxy-ent-kauranoic acid (9), and 6β,7β,16β,17-tetrahydroxy-ent-kauranoic acid (10), were isolated from an ethanolic extract of the seeds of Pharbitis nil. The structures of the new compounds were determined by spectroscopic methods including 1D and 2D NMR analysis. The absolute configurations of the compounds were clarified by CD spectroscopic studies. Full NMR data assignments of the three known compounds (8−10) are reported. The isolated compounds were evaluated for their cytotoxic activities against four human cancer cell lines

Lignans from the Tuber-barks of Colocasia antiquorum var. esculenta and Their Antimelanogenic Activity

Colocasia antiquorum var. esculenta, a variant of C. antiquorum, commonly known as “Imperial Taro”, is an edible vegetable in many tropical and subtropical regions of the world. This study with the aim of evaluating the potential of C. antiquorum var. esculenta as a functional food with a depigmenting effect resulted in the identification of a new sesquilignan, named colocasinol A (1), and a new acyclic phenylpropane lignanamide, named cis-grossamide K (2), together with 10 known compounds (3−12). The identification and structural elucidation of these compounds were based on 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data analysis as well as high-resolution fast atom bombardment mass spectrometry (FABMS) and electron impact mass spectrometry (EIMS). Quantitation of the melanin contents and cell viability in murine melanocyte melan-a cells was used to assess the antimelanogenic activities of the isolated compounds. Among them, cis-grossamide K (2), isoamericanol A (3), americanol A (4), 2-hydroxy-3,2′-dimethoxy-4′-(2,3-epoxy-1-hydroxypropyl)-5-(3-hydroxy-1-propenyl)biphenyl (5), and (−)-pinoresinol (6) showed inhibitory effects on melanin production. Compounds 2, 5, and 6 exerted a particularly strong antimelanogenic activity on the cells without high cell toxicity (IC50 = 54.24, 53.49, and 56.26 μM, and LD50 = 163.60, 110.23, and >500 μM, respectively)

Tirucallane Triterpenoids from <i>Cornus walteri</i>

Twelve new tirucallane triterpenoids, named cornusalterins A−L (1−12), and two known tirucallane triterpenoids, deoxyflindissone (13) and (−)-leucophyllone (14), were isolated from a MeOH extract of stems and stem bark of Cornus walteri. The structures of the new compounds were determined by spectroscopic methods, including 1D and 2D NMR analyses. Compounds 12 and 13, possessing a tetrahydrofuran ring in the side chain, exhibited significant cytotoxic activity against the A549, SK-OV-3, SK-MEL-2, and XF498 cell lines

Antiskin Aging Effects of Indole Alkaloid <i>N</i>‑Glycoside from Ginkgo Fruit (<i>Ginkgo biloba</i> fruit) on TNF-α-Exposed Human Dermal Fibroblasts

Human skin aging has internal and external factors, both of which are characterized by TNF-α overproduction. Therefore, we aimed to identify a natural product that suppresses the damage that occurs in cutaneous dermal fibroblasts exposed to TNF-α. The protective effects of the indole alkaloid N-glycoside, ginkgoside B dimethyl ester (GBDE), isolated from ginkgo fruit (Ginkgo biloba fruit) were evaluated in TNF-α stimulated human dermal fibroblasts (HDFs). GBDE inhibited TNF-α-induced MMP-1 expression to 2.2 ± 0.1-fold (p < 0.01) and reversed the decrease in collagen levels to 0.4 ± 0.00-fold (p < 0.01) at 50 μM. The effect of GBDE was due to the suppression of the phospolylaton of MAPKs (ERK, 0.47 ± 0.05; JNK, 1.21 ± 0.07; p38, 0.77 ± 0.07-folds, p p < 0.001) compared to the TNF-α group. GBDE also reduced the expression of COX-2 to 2.06 ± 0.12-fold (p < 0.001) and increased the expression of HO-1 to 10.64 ± 0.2-fold (p < 0.001). In addition, GBDE inhibited the expression of the pro-inflammatory cytokines (IL-8, 2.2 ± 0.0; IL-1β, 1.6 ± 0.0; IL-6, 2.0 ± 0.10-folds, p < 0.05). These results provide experimental evidence that GBDE can protect against skin damage, including aging

Biphenyls from <i>Berberis koreana</i>

Three new biphenyls, berbekorin A (1), 2′-hydroxy-3,4,5-trimethoxybiphenyl (2), and 4,5-dihydroxy-3-methoxybiphenyl (3), together with 11 known biphenyls (4−14), were isolated from the n-hexane-soluble fraction of the MeOH extract of the trunk of Berberis koreana. The structures of 1−3 were determined by spectroscopic methods, including 1D and 2D NMR analysis. Compound 1 exhibited cytotoxic activity against the SK-MEL-2 skin melanoma cell line, in particular. Moreover, compounds 2, 5, 6, and 14 inhibited NO production in LPS-activated BV-2 cells, a microglial cell line

Data_Sheet_1_Efomycins K and L From a Termite-Associated Streptomyces sp. M56 and Their Putative Biosynthetic Origin.PDF

Two new elaiophylin derivatives, efomycins K (1) and L (2), and five known elaiophylin derivatives (3–7) were isolated from the termite-associated Streptomyces sp. M56. The structures were determined by 1D and 2D NMR and HR-ESIMS analyses and comparative CD spectroscopy. The putative gene cluster responsible for the production of the elaiophylin and efomycin derivatives was identified based on significant homology to related clusters. Phylogenetic analysis of gene cluster domains was used to provide a biosynthetic rational for these new derivatives and to demonstrate how a single biosynthetic pathway can produce diverse structures.</p

Data_Sheet_1_Potential Antimicrobial Activity of Galloyl-Flavonoid Glycosides From Woodfordia uniflora Against Methicillin-Resistant Staphylococcus aureus.PDF

Antibiotic-resistant infections are a growing problem; to combat multi-drug resistant bacterial infections, antibiotics with novel mechanisms of action are needed. Identification of potent bioactive natural products is an attractive avenue for developing novel therapeutic strategies against bacterial infections. As part of our ongoing research to explore bioactive natural products from diverse resources, we investigated the antimicrobial compounds from Woodfordia uniflora, a flowering shrub unique to the Dhofar region of Oman. The plant has been used as a remedy for skin infections in Oman. However, to date, no study has examined the antimicrobial compounds in W. uniflora. Phytochemical analysis of the methanolic extract of W. uniflora leaves in combination with LC/MS-based analysis allowed us to isolate and identify four flavonoid-type analogs (1–4), procyanidin B3-3-O-gallate (1), rhamnetin 3-O-(6″-galloyl)-β-D-glucopyranoside (2), rhamnetin 3-O-α-L-rhamnopyranoside (3), and quercetin 3-O-(6″-galloyl)-β-D-glucopyranoside (4). The isolates have a novel mechanism of action; the compounds inhibit biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA) and synergize with methicillin. Our metabolite analysis revealed that this synergizing activity by compounds was achieved by remodeling metabolism including central carbon metabolism and glutamine biosynthesis that resulted in abnormal cell formation and reduction in biofilm formation of MRSA. Taken together, these findings provide experimental evidence that rhamnetin 3-O-(6″-galloyl)-β-D-glucopyranoside (2) and quercetin 3-O-(6″-galloyl)-β-D-glucopyranoside (4) can be considered as potential therapeutic agents for the treatment of methicillin-resistant S. aureus-associated diseases.</p

Macrocyclic Trichothecene Mycotoxins from a Deadly Poisonous Mushroom, <i>Podostroma cornu-damae</i>

Three new macrocyclic trichothecenes (1–3) and five known related compounds (4–8) were isolated from the MeOH extract of a plate culture of the fungus Podostroma cornu-damae, a deadly poisonous mushroom. Miophytocen D (1) is a rearranged macrocyclic type D trichothecene, featuring a bicyclo-[6.5]­dodecahydrocyclopenta­[b]­chromene scaffold, and the structures of new compounds (1–3) were delineated by the combination of 1D and 2D NMR spectroscopic experiments and HRESIMS, modified Mosher’s esterification, and quantum chemical ECD calculations. The isolated compounds (1–8) were evaluated for cytotoxicity against four human breast cancer cell lines (Bt549, HCC70, MDA-MB-231, and MDA-MB-468). Compounds 4, 6, and 8 exhibited significant cytotoxic effects against the breast cancer cell lines, with IC50 values in the range of 0.02–80 nM, which is stronger than doxorubicin, the positive control, and a structure–activity relationship was suggested