The aim of this study was to determine if aging or dietary restriction (DR) alters activation-ind... more The aim of this study was to determine if aging or dietary restriction (DR) alters activation-induced cell death, which is known to regulate cell proliferation and eliminate the high number of activated cells during an immune response. Splenic T cells were isolated from young (4–6 months) and old (25–26 months) Fischer 344 rats that had free access to food, ad libitum (AL), and from dietary-restricted (DR) old (25–26 months) rats that beginning at 6 weeks of age were fed 60% (40% food-restricted) of the diet consume by the AL rats. T cells were incubated with anti-CD3 antibody, or staphylococcal enterotoxin B (primary stimulus) for 72–96 h, followed by restimulation with anti-CD3 (secondary stimulus) for 72 h. Activation-induced apoptosis was assessed by DNA fragmentation and the expression of Fas/CD95 receptor and Fas ligand (Fas-L) was measured by flow cytometry. We found that the amount of DNA fragmentation was significantly (P<0.05) higher in the stimulated and restimulated T cells from AL old rats and DR old rats compared to young rats. The increase in DNA fragmentation with age was paralleled by an increase in the proportion of the cells expressing Fas and Fas-L. However, DR had no significant effect on the age-related increase in DNA fragmentation or the expression of Fas or Fas-L. We also measured the levels of Bcl-2 and Bax protein and found that the level of Bcl-2 decreased and Bax increased with age and that DR had no effect on the age-related changes in the level of Bcl-2 or Bax protein. These results demonstrate that aging but not DR alters activation-induced apoptosis in rat T cells.
A generalized cubic equation of state proposed by one of the authors has been modified, used to c... more A generalized cubic equation of state proposed by one of the authors has been modified, used to calculate some physical and thermodynamic properties of water, and applied to the modeling and simulation of vapor power cycles. The cubic equation contains four generalized constants, which are calculated using the acentric factor and the critical compressibility factor. In this work, the constants for water have been specifically recalculated so values of all properties of interest in the calculation of thermodynamic cycles can be accurately predicted. Saturation temperature-pressure data have been used to determine the constants and several other properties (volume, enthalpy and entropy of both liquid and vapor phases, and saturation pressure), have been calculated in a wide range of pressure and temperature. Also an application of the proposed equation to a vapor cycle is shown and result compared to other methods. The equation and the proposed parameters have shown to be accurate enough for the prediction of all properties involved in processes that use water as a working fluid.
From the aerial parts of Drymaria arenarioides, two previously known compounds, atractyligenin an... more From the aerial parts of Drymaria arenarioides, two previously known compounds, atractyligenin and 2-O- β-d-glucopyranosyl atractyligenin, and two new natural substances, atractyligenin 2-O-β-d-glucopyranosyl-(1→2)-β- d-glucopyranoside and atractyligenone (2-oxo-15α-hydroxyatractyl-16,17-ene-4α-carboxylic acid) have been isolated. Their structures were established by chemical and spectroscopic techniques as well as comparison with authentic samples.
Potassium glutamate accumulates upon hyper-osmotic shock and serves as a temporary osmoprotectant... more Potassium glutamate accumulates upon hyper-osmotic shock and serves as a temporary osmoprotectant. This salt leads to transcriptional activation of sets of genes that allow the cell to achieve long-term adaptation to high osmolarity. The current experiments show that potassium glutamate also acts as an inhibitor of bulk cellular transcription. It can do so independent of the involvement of macromolecular repressors or activators by virtue of its ability to directly inhibit RNA polymerase binding to ribosomal promoters. Thus, potassium glutamate mediates a global transcription switch by acting differentially on RNA polymerase at sets of genomic promoters that differ in their built-in direct response to this salt.
ABSTRACT Three triterpene glucosides have been isolated from the methanol extract of the leaves o... more ABSTRACT Three triterpene glucosides have been isolated from the methanol extract of the leaves of Aphloia theiformis. The identities of the compounds were established by spectroscopic (1H NMR, 13C NMR, MS) and chemical methods (hydrolysis, acetylation). Two of the compounds were identified as tormentic acid ester glucoside and 23-hydroxytormentic acid ester glucoside, respectively. The structure of the third compound was established as 6β-hydroxytormentic acid ester glucoside, a new naturally occurring saponin.
Investigation of the roots and aerial parts of Solidago rugosa afforded the known diterpenes kola... more Investigation of the roots and aerial parts of Solidago rugosa afforded the known diterpenes kolavenol, hardwickiic acid, (−)-kaur-16-en-19-oic acid, (+)-manool, (+)-3β-hydroxymanool, manoyl oxide and ent-abietic acid. In addition, the new labdane diterpene (+)-18-tigloyloxymanool and four new ent-abietanes were obtained. The structures of all known and new compounds were elucidated by spectroscopic methods, especially high-field 1H and 13C NMR, and inverse 1H-13C-correlation techniques, as well as chemical transformations. Six diterpenes were tested against Mycobacterium tuberculosis and M. avium, but showed no significant activities with minimum inhibitory concentrations of > 100 μg ml−1
2012 19th International Conference on Telecommunications (ICT), 2012
The demand for high bit-rate service transmission is increasing for digital terrestrial broadcast... more The demand for high bit-rate service transmission is increasing for digital terrestrial broadcasting just like other transmission technologies. Multiple-input multiple-output (MIMO) transmission is one of the most promising techniques to fulfill this demand for high transmission rates. This paper introduces enhanced spatial multiplexing (eSM) scheme adopted as technical baseline for the DVB next generation handheld (DVB-NGH) system. Most technical challenges
This paper investigates the performance of time interleaving in DVB-T2 in the context of mobile r... more This paper investigates the performance of time interleaving in DVB-T2 in the context of mobile reception. By means of time interleaving it is possible to provide time diversity and improve the robustness of the transmitted information in mobile environments. DVB-T2 implements a highly flexible time interleaving that allows different trade-offs in terms of time diversity, latency and power saving. DVB-T2 also includes the possibility to particularize the transmission parameters on a service basis by means of multiple physical layer pipes. This way, it is possible to accommodate different use cases: fixed, portable and mobile, in the same frequency channel. This paper evaluates the time interleaving capabilities of DVB-T2 by means of physical layer simulations. The paper also proposes and evaluates a configuration that has been optimized for handheld reception.
A chemical study of the leaves of the southern evergreen Magnolia virginiana provided, besides th... more A chemical study of the leaves of the southern evergreen Magnolia virginiana provided, besides the known sesquiterpene lactones costunolide, parthenolide and trifloculoside, two new sesquiterpenes, costunolact-12β-ol and its acetal dimer. The molecular structure of the acetal dimer of costunolact-12β-ol was determined by single crystal X-ray diffraction. An annual study of the relative ratios of the major sesquiterpenes in leaves of M. virginiana showed < 10% of costunolide over the 12 month period. In contrast, parthenolide and costunolact-12β-ol varied markedly over the same time period with a maximum of > 90% of parthenolide in July/August and a minimum of < 20% in January. However, no lignans typical of the northern variety of M. virginiana could be detected in the annual study of the southern variety of this taxon.
Phytochemistry, Vol. 34, No. 3, pp. 737-742, 1993 Printed in Great Britain. 0031 9422/93 $6.00+0.... more Phytochemistry, Vol. 34, No. 3, pp. 737-742, 1993 Printed in Great Britain. 0031 9422/93 $6.00+0.00 i 1993 Pergamon Press Ltd SESQUITERPENES FROM BRINTONIA DISCO IDEA TIANSHENG LU, DAVID VARGAS* and NIKOLAUS H. FiSCHERf Department of ...
Weather radars are used for short term meteorological prediction all over the world. Radars in 5 ... more Weather radars are used for short term meteorological prediction all over the world. Radars in 5 GHz band can be jammed by RLAN devices (e.g. Wi-Fi routers). We introduce the background of this problem, and analyze the weakness of the current solution (DFS - dynamic frequency selection). We propose some other solutions, and introduce our channel allocation technique. We analyze it theoretically by modeling the radar operation and RLAN traffic, and we also show its high efficiency in practice, based on well-known IEEE 802.11 RTS/CTS mechanism.
The ambrosanolide confertiflorin ( 2 ) from Ambrosia confertrfia provided, upon treatment with to... more The ambrosanolide confertiflorin ( 2 ) from Ambrosia confertrfia provided, upon treatment with toluenesulfonic acid, a mixture of desacetylconfertiflorin (3) and allodesacetylconfeniflorin (5). Treatment of confertiflorin with phenylselenyl chloride followed by H 2 0 2 oxidation resulted in a mixture of 8a-acetoxyambrosin (7) and the dilactone 8a-acetoxy-2,3-dehydropsilostachyin C (8). The structures of the new compounds were inferred from nmr and mass spectral data. The molecular structures of the molluscicidal lactones confertiflorin and allodesacetylconfertiflorin (5) were determined by single crystal X-ray diffraction.
^ investigation of BF,-mediated rearrangements of parthenolide [I] provided micheliolide (51 as a... more ^ investigation of BF,-mediated rearrangements of parthenolide [I] provided micheliolide (51 as a major product. Minor reaction products included 10 (14)dehydm-5a-hydroxy-tram-guaianolide (21, 9,10-dehydro-5a-hydroxy-traru-guaianolide (31, the xanthanolide 2desoxy-6-tp- dehydmampressanolide E7), and b i c y c l~6 . 2 . 0~-1 0 ( 1 4 > e n -l 2 ,~l i d e (81. Their mechanisms of formation were interpmed as rearrangements involving carbocation intermediates.
... spectral correlations with related eudesmanolides. The + Author to whom correspondance should... more ... spectral correlations with related eudesmanolides. The + Author to whom correspondance should be addressed. 1353 Copyright 0 1991 by Marcel Dekker, Inc. Page 2. 1354 VARGAS ET AL. stereochemistry at the chiral center ...
The aim of this study was to determine if aging or dietary restriction (DR) alters activation-ind... more The aim of this study was to determine if aging or dietary restriction (DR) alters activation-induced cell death, which is known to regulate cell proliferation and eliminate the high number of activated cells during an immune response. Splenic T cells were isolated from young (4–6 months) and old (25–26 months) Fischer 344 rats that had free access to food, ad libitum (AL), and from dietary-restricted (DR) old (25–26 months) rats that beginning at 6 weeks of age were fed 60% (40% food-restricted) of the diet consume by the AL rats. T cells were incubated with anti-CD3 antibody, or staphylococcal enterotoxin B (primary stimulus) for 72–96 h, followed by restimulation with anti-CD3 (secondary stimulus) for 72 h. Activation-induced apoptosis was assessed by DNA fragmentation and the expression of Fas/CD95 receptor and Fas ligand (Fas-L) was measured by flow cytometry. We found that the amount of DNA fragmentation was significantly (P<0.05) higher in the stimulated and restimulated T cells from AL old rats and DR old rats compared to young rats. The increase in DNA fragmentation with age was paralleled by an increase in the proportion of the cells expressing Fas and Fas-L. However, DR had no significant effect on the age-related increase in DNA fragmentation or the expression of Fas or Fas-L. We also measured the levels of Bcl-2 and Bax protein and found that the level of Bcl-2 decreased and Bax increased with age and that DR had no effect on the age-related changes in the level of Bcl-2 or Bax protein. These results demonstrate that aging but not DR alters activation-induced apoptosis in rat T cells.
A generalized cubic equation of state proposed by one of the authors has been modified, used to c... more A generalized cubic equation of state proposed by one of the authors has been modified, used to calculate some physical and thermodynamic properties of water, and applied to the modeling and simulation of vapor power cycles. The cubic equation contains four generalized constants, which are calculated using the acentric factor and the critical compressibility factor. In this work, the constants for water have been specifically recalculated so values of all properties of interest in the calculation of thermodynamic cycles can be accurately predicted. Saturation temperature-pressure data have been used to determine the constants and several other properties (volume, enthalpy and entropy of both liquid and vapor phases, and saturation pressure), have been calculated in a wide range of pressure and temperature. Also an application of the proposed equation to a vapor cycle is shown and result compared to other methods. The equation and the proposed parameters have shown to be accurate enough for the prediction of all properties involved in processes that use water as a working fluid.
From the aerial parts of Drymaria arenarioides, two previously known compounds, atractyligenin an... more From the aerial parts of Drymaria arenarioides, two previously known compounds, atractyligenin and 2-O- β-d-glucopyranosyl atractyligenin, and two new natural substances, atractyligenin 2-O-β-d-glucopyranosyl-(1→2)-β- d-glucopyranoside and atractyligenone (2-oxo-15α-hydroxyatractyl-16,17-ene-4α-carboxylic acid) have been isolated. Their structures were established by chemical and spectroscopic techniques as well as comparison with authentic samples.
Potassium glutamate accumulates upon hyper-osmotic shock and serves as a temporary osmoprotectant... more Potassium glutamate accumulates upon hyper-osmotic shock and serves as a temporary osmoprotectant. This salt leads to transcriptional activation of sets of genes that allow the cell to achieve long-term adaptation to high osmolarity. The current experiments show that potassium glutamate also acts as an inhibitor of bulk cellular transcription. It can do so independent of the involvement of macromolecular repressors or activators by virtue of its ability to directly inhibit RNA polymerase binding to ribosomal promoters. Thus, potassium glutamate mediates a global transcription switch by acting differentially on RNA polymerase at sets of genomic promoters that differ in their built-in direct response to this salt.
ABSTRACT Three triterpene glucosides have been isolated from the methanol extract of the leaves o... more ABSTRACT Three triterpene glucosides have been isolated from the methanol extract of the leaves of Aphloia theiformis. The identities of the compounds were established by spectroscopic (1H NMR, 13C NMR, MS) and chemical methods (hydrolysis, acetylation). Two of the compounds were identified as tormentic acid ester glucoside and 23-hydroxytormentic acid ester glucoside, respectively. The structure of the third compound was established as 6β-hydroxytormentic acid ester glucoside, a new naturally occurring saponin.
Investigation of the roots and aerial parts of Solidago rugosa afforded the known diterpenes kola... more Investigation of the roots and aerial parts of Solidago rugosa afforded the known diterpenes kolavenol, hardwickiic acid, (−)-kaur-16-en-19-oic acid, (+)-manool, (+)-3β-hydroxymanool, manoyl oxide and ent-abietic acid. In addition, the new labdane diterpene (+)-18-tigloyloxymanool and four new ent-abietanes were obtained. The structures of all known and new compounds were elucidated by spectroscopic methods, especially high-field 1H and 13C NMR, and inverse 1H-13C-correlation techniques, as well as chemical transformations. Six diterpenes were tested against Mycobacterium tuberculosis and M. avium, but showed no significant activities with minimum inhibitory concentrations of > 100 μg ml−1
2012 19th International Conference on Telecommunications (ICT), 2012
The demand for high bit-rate service transmission is increasing for digital terrestrial broadcast... more The demand for high bit-rate service transmission is increasing for digital terrestrial broadcasting just like other transmission technologies. Multiple-input multiple-output (MIMO) transmission is one of the most promising techniques to fulfill this demand for high transmission rates. This paper introduces enhanced spatial multiplexing (eSM) scheme adopted as technical baseline for the DVB next generation handheld (DVB-NGH) system. Most technical challenges
This paper investigates the performance of time interleaving in DVB-T2 in the context of mobile r... more This paper investigates the performance of time interleaving in DVB-T2 in the context of mobile reception. By means of time interleaving it is possible to provide time diversity and improve the robustness of the transmitted information in mobile environments. DVB-T2 implements a highly flexible time interleaving that allows different trade-offs in terms of time diversity, latency and power saving. DVB-T2 also includes the possibility to particularize the transmission parameters on a service basis by means of multiple physical layer pipes. This way, it is possible to accommodate different use cases: fixed, portable and mobile, in the same frequency channel. This paper evaluates the time interleaving capabilities of DVB-T2 by means of physical layer simulations. The paper also proposes and evaluates a configuration that has been optimized for handheld reception.
A chemical study of the leaves of the southern evergreen Magnolia virginiana provided, besides th... more A chemical study of the leaves of the southern evergreen Magnolia virginiana provided, besides the known sesquiterpene lactones costunolide, parthenolide and trifloculoside, two new sesquiterpenes, costunolact-12β-ol and its acetal dimer. The molecular structure of the acetal dimer of costunolact-12β-ol was determined by single crystal X-ray diffraction. An annual study of the relative ratios of the major sesquiterpenes in leaves of M. virginiana showed < 10% of costunolide over the 12 month period. In contrast, parthenolide and costunolact-12β-ol varied markedly over the same time period with a maximum of > 90% of parthenolide in July/August and a minimum of < 20% in January. However, no lignans typical of the northern variety of M. virginiana could be detected in the annual study of the southern variety of this taxon.
Phytochemistry, Vol. 34, No. 3, pp. 737-742, 1993 Printed in Great Britain. 0031 9422/93 $6.00+0.... more Phytochemistry, Vol. 34, No. 3, pp. 737-742, 1993 Printed in Great Britain. 0031 9422/93 $6.00+0.00 i 1993 Pergamon Press Ltd SESQUITERPENES FROM BRINTONIA DISCO IDEA TIANSHENG LU, DAVID VARGAS* and NIKOLAUS H. FiSCHERf Department of ...
Weather radars are used for short term meteorological prediction all over the world. Radars in 5 ... more Weather radars are used for short term meteorological prediction all over the world. Radars in 5 GHz band can be jammed by RLAN devices (e.g. Wi-Fi routers). We introduce the background of this problem, and analyze the weakness of the current solution (DFS - dynamic frequency selection). We propose some other solutions, and introduce our channel allocation technique. We analyze it theoretically by modeling the radar operation and RLAN traffic, and we also show its high efficiency in practice, based on well-known IEEE 802.11 RTS/CTS mechanism.
The ambrosanolide confertiflorin ( 2 ) from Ambrosia confertrfia provided, upon treatment with to... more The ambrosanolide confertiflorin ( 2 ) from Ambrosia confertrfia provided, upon treatment with toluenesulfonic acid, a mixture of desacetylconfertiflorin (3) and allodesacetylconfeniflorin (5). Treatment of confertiflorin with phenylselenyl chloride followed by H 2 0 2 oxidation resulted in a mixture of 8a-acetoxyambrosin (7) and the dilactone 8a-acetoxy-2,3-dehydropsilostachyin C (8). The structures of the new compounds were inferred from nmr and mass spectral data. The molecular structures of the molluscicidal lactones confertiflorin and allodesacetylconfertiflorin (5) were determined by single crystal X-ray diffraction.
^ investigation of BF,-mediated rearrangements of parthenolide [I] provided micheliolide (51 as a... more ^ investigation of BF,-mediated rearrangements of parthenolide [I] provided micheliolide (51 as a major product. Minor reaction products included 10 (14)dehydm-5a-hydroxy-tram-guaianolide (21, 9,10-dehydro-5a-hydroxy-traru-guaianolide (31, the xanthanolide 2desoxy-6-tp- dehydmampressanolide E7), and b i c y c l~6 . 2 . 0~-1 0 ( 1 4 > e n -l 2 ,~l i d e (81. Their mechanisms of formation were interpmed as rearrangements involving carbocation intermediates.
... spectral correlations with related eudesmanolides. The + Author to whom correspondance should... more ... spectral correlations with related eudesmanolides. The + Author to whom correspondance should be addressed. 1353 Copyright 0 1991 by Marcel Dekker, Inc. Page 2. 1354 VARGAS ET AL. stereochemistry at the chiral center ...
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Papers by David Vargas