Search results for "Zen"

Exploring the validity of the long term data record V4 database for land surface monitoring

2015

The last (and final) version of the Long Term Data Record (LTDR) — Version 4 — has been released recently by NASA. This database includes daily information for all AVHRR (Advanced Very High Resolution Radiometer) channels, as well as ancillary data, since July 1981 up to present. This database is the longest available record of remotely sensed data useful for land surface monitoring, since it allows the estimation of vegetation indices at daily resolution, as well as the daily estimation of land surface temperature (LST). Here, we analyze the fitness of this database for land surface monitoring. To that end, we first estimated NDVI (Normalized Difference Vegetation Index), LST, as well as e…

From attraction to repulsion : anion–π interactions between bromide and fluorinated phenyl groups

2011

Anion–π interactions in crystals of fluorobenzyl ammonium salts depend on the degree of fluorination at the aromatics.

Determination of non-ionic and anionic surfactants in industrial products by separation on a weak ion-exchanger, derivatization and liquid chromatogr…

2013

Abstract A method for the determination of priority surfactants, including fatty alcohol ethoxylates (FAE), alkylether sulfates (AES) and linear alkylbenzene sulfonates (LAS) is described. The samples were diluted with 50% methanol at pH 4 prior to solid-phase extraction on a weak anionic exchanger (WAX). The AES and LAS surfactant classes were retained, whereas the non-ionic components, including most FAE oligomers were eluted. After washing the WAX cartridge to remove cations, the remaining hydrophobic FAE oligomers were eluted using hot 80% methanol at pH 4 (at ca. 50 °C). These two eluates were combined to constitute the non-ionic fraction. Then, AES and LAS were eluted using 80% MeOH w…

Anionic-anionic asymmetric tandem reactions: one-pot synthesis of optically pure fluorinated indolines from 2-p-tolylsulfinyl alkylbenzenes.

2008

Rearrangement of the carbon skeleton in the intramolecular photoadduct of anthracene and benzene rings

2003

Abstract The effectivity of optical switching between anthracene derivatives 3a,b and their intramolecular photocycloadducts 4a,b is impaired by traces of acid. The systematic treatment of 4a,b with an increasing excess of formic acid revealed that—apart from the normal enolether cleavage 4a,b → 6a,b → 7a,b —a cleavage with rearrangement of the carbon skeleton can occur: 5b → 6b′ . The driving force is a stability enhancement of the involved carbenium ions 5b → 5b′ . A further increased excess of formic acid leads finally to a competitive ether cleavage in the tetrahydrofuran ring 5b → 8 .

Density functional theory studies of OH-modified open-ended single-wall zigzag carbon nanotubes (SWCNTs)

2010

Abstract Functionalized carbon nanotubes (CNTs) are often formed as result of oxidation and cleaning of raw product grown on metal catalyst. Structure and energy of ideal and OH-modified single-wall nanotubes (SWCNTs) of different length (2.8, 7.0 and 13.5 A) were obtained at the DFT-B3LYP level. From one to nine OH groups were added at the end of the nanotube and a nonadditive dependence of attachment energy on the number of substituents was observed. The energetics of SWCNT end substitution with OH groups was supported by high level MP2 and CCSD(T) determination of reaction energy: R – H + 1 / 2 O 2 → R – OH + Δ E for methane, benzene and anthracene. In addition, a vibrational analysis of…

Intramolecular photocycloaddition of anthracene and benzene ring systems

2002

Abstract The anthracenes 3a – c , substituted in the 9-position with 3,5-dialkoxybenzyloxymethyl groups exhibit, in diluted solutions, intramolecular [4π+4π] photocycloaddition reactions to the polycyclic compounds 4a – c . The quantitative processes are completely reversible by heating, unless acid-catalyzed cleavages lead to thermally stable mono- and diketones: 4a – c → 5a – c → 6 .

4-dimethylamino-3′,4′-dimethoxychalcone downregulates iNOS expression and exerts anti-inflammatory effects

2001

Abstract Reactive oxygen and nitrogen species contribute to the pathophysiology of inflammatory conditions. We have studied the effects of a novel superoxide scavenger, 4-dimethylamino-3′,4′-dimethoxychalcone (CH11) in macrophages and in vivo. CH11 has been shown to inhibit the chemiluminescence induced by zymosan in mouse peritoneal macrophages and the cytotoxic effects of superoxide. In the same cells, the modulation by superoxide of nitric oxide (NO) production in response to zymosan was investigated. CH11 was more effective than the membrane-permeable scavenger Tiron for inhibition of inducible nitric oxide synthase (iNOS) protein expression and nitrite production. We have shown that CH…

Melatonin protects human red blood cells from oxidative hemolysis: new insights into the radical-scavenging activity.

1999

Antioxidant activity of melatonin in human erythrocytes, exposed to oxidative stress by cumene hydroperoxide (cumOOH), was investigated. CumOOH at 300 microM progressively oxidized a 1% suspension of red blood cells (RBCs), leading to 100% hemolysis in 180 min. Malondialdehyde and protein carbonyls in the membrane showed a progressive increase, as a result of the oxidative damage to membrane lipids and proteins, reaching peak values after 30 and 40 min, respectively. The membrane antioxidant vitamin E and the cytosolic reduced glutathione (GSH) were totally depleted in 20 min. As a consequence of the irreversible oxidative damage to hemoglobin (Hb), hemin accumulated into the RBC membrane d…

Autentiskuma konstruēšana: “Bēniņi” un to reprezentācija. Sociālantropoloģisks skats uz latvijas televīzijas raidījumu “Province”

2015

Šajā darbā apkopotais etnogrāfiskais materiāls apskata to, kā caur “citādā” veidošanu, zināmu marģinalizāciju, kā arī reprezentatīvu līdzekļu izmantošanu, tiek radīts stāstījums par “autentisku” dzīvi ārpus pilsētas - dzīvi provincē, laukos. Atražojot publiskajā diskursā izmantotās aktualitātes, apstrādājot tās subjektīvā veidā un pieslēdzot žurnālistikas kultūras autoritāti, tiek radīts patērējams kultūras produkts, kas reprezentē raidījuma veidotāju redzējumu par dzīvi ārpus pilsētas.