bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observation of a Cobalt as a Chemical Modifier for Lead in Electrothermal Atomic Absorption Spectrometry Using a Tungsten Furnace by Means of a Surface Analysis
Authors: Narukawa Tomohiro , Yoshimura Wataru , Uzawa Atsushi 
Published: February 2006

Abstract
The behavior and effect of cobalt as a chemical modifier for lead were studied by electrothermal atomic absorption spectrometry using a tungsten furnace. The characterization of materials formed on the tungsten surface at the charring stage was performed using of a scanning electron microscope and X-ray photoelectron spectrometer. The experimental results indicate that the effect of a cobalt modifier is related to the formation of granular cobalt crystals during a pre-heating stage. Under the coexistence of lead, however, the cobalt crystals became irregularly shaped, probably forming an intermetallic compound between cobalt and lead. By an examination using sample materials containing chloride, nitrate, and sulfate salts, it was found that a cobalt modifier is effective for suppressing the interference of chloride and nitrate. All of the sulfate salts gave negative interference; the cobalt crystal, which acted as a chemical modifier, was included inside a large crystal which originated from the sulfate at the charring stage. The thermal stability of lead is difficult to maintain with increasing sulfate salts. The cobalt modifier was applied to the determination of lead in several water samples.
Synthesis of a Fragment A Derivative of an Antibiotic, Nosiheptide
Authors: Umemura Kazuyuki , Noda Hirofumi , Yoshimura Juji , Konn Akihito , Yonezawa Yasuchika , Shin Chung-gi 
Published: February 2006

Abstract
Two 4-ethoxycarbonyl thiazolyl groups were introduced into 2- and 5-positions of 3-hydroxypyridine in 8 steps using 5-cyano-3-hydroxypyridine (2) as the starting material. The pyridine derivative obtained in the last step was converted to a fragment A derivative (21) by stepwise introduction of the 2-substituted 4-thiazolyl group into the 6-position. The total yield for the formation of 21 via 14 steps was 7.6%.
Tetrachlorocyclopentadienone O-Oxide, a Facile Oxygen-Atom-Transfer Reagent: The Disproportionation of Cycloalkyldioxyl Radicals
Authors: Dunkin Ian R , McCluskey Adam 
Published: February 2006

Abstract
Photolysis of tetrachlorodiazocyclopentadiene (1) in oxygen-saturated hydrocarbon solvents results in the transient formation of tetrachlorocyclopentadienone O-oxide (3). This rapidly decomposes, giving rise to products derived from oxidation of the hydrocarbons. Cyclopentane, cyclopentene, cycloheptane, cycloheptene, cycloheptatriene, and indene have been studied. Cycloheptatriene and indene gave only low yields of tractable products, but the others gave the corresponding ketones and secondary alcohols as the major products. Although yields varied considerably, the ketone and alcohol products were always obtained, within experimental error, in a 1 : 1 molar ratio. This observed product ratio supports the disproportionation of cycloalkyldioxyl radicals as a crucial step.
Thermodynamic Stabilities of Phenonium Ions Based on Bromide-Transfer Equilibria in the Gas Phase
Authors: Mustanir  , Mishima Masaaki , Fujio Mizue , Tsuno Yuho 
Published: February 2006

Abstract
The thermodynamic stabilities of the phenonium (ethylenebenzenium) ion and ring-substituted derivatives were determined based on the bromide-transfer equilibria in the gas phase. It has been shown that the phenonium ion is 2.4 kcal mol−1 more stable than the t-butyl cation, and that the substituent effect on its stability can be correlated with the Yukawa–Tsuno equation with a ρ value of −12.6 and an r+ of 0.62. An r+ value smaller than unity of the α-cumyl(1-methyl-1-phenylethyl) cation suggested that π-delocalization in the phenonium ion is essentially less effective than through a benzylic π-interaction. On the other hand, the ρ value of −12.6 is distinctly larger than that for the ordinary benzylic carbocation systems, but is comparable to that of the benzenium ion. In addition, it has been found that the r+ value of the phenonium ions in the gas phase is in complete agreement with that for the aryl-assisted process in the acetolysis of 2-arylethyl toluenesulfonates. This suggests that the degree of π-delocalization of the positive charge is the same in the transition state and the intermediate cation. It is concluded that an r+ value of 0.6, which is ranked at a unique position in the continuous spectrum of the resonance demand, is characteristic of the bridged structure of the phenonium ion intermediate and the transition state.
Tail-to-Tail Dimerization of Acrylonitrile Catalyzed by Low-Valent Ruthenium Complexes
Authors: Fukuoka Atsushi , Nagano Takeyuki , Furuta Shuichi , Yoshizawa Michito , Hirano Masafumi , Komiya Sanshiro 
Published: February 2006

Abstract
Zero-valent ruthenium complexes, [Ru(cod)(cot)] and [Ru(cod)(benzene)], are effective catalyst precursors for the tail-to-tail dimerization of acrylonitrile. Hydrogen pressure is necessary for the catalytic reaction, and the turnover number for dimers is greatly improved in neat acrylonitrile. Under the conditions of 150 °C and 25 atm of H2 (initial pressure at room temperature), the conversion of acrylonitrile is 61% and the yield of tail-to-tail dimers is 42% (selectivity 69%) in 3 h. The turnover number for the dimers is 2060, which is much higher than those reported so far. From the results of a catalytic reaction under D2 pressure, a reaction mechanism is proposed, in which two successive insertions of acrylonitrile into dihydridoruthenium complex are involved. A fast and reversible insertion of the third acrylonitrile is responsible for the H–D exchange of acrylonitrile in the deuterium labeling experiment.
Synthetic Studies on Biscembranoids. Asymmetric Total Synthesis of the 14-Membered Diene Unit of Methyl Sarcophytoate
Authors: Yasuda Minoru , Ide Mitsuaki , Matsumoto Yuka , Nakata Masaya 
Published: February 2006

Abstract
An asymmetric total synthesis of the 14-membered diene unit, (1S,2S,4E,6E,10S,11Z,14R)-10,14-epoxy-4-isopropenyl-1,7,11-trimethyl-4,6,11-cyclotetradecatriene-1,2-diol (3), of methyl sarcophytoate (1) has been achieved. Methyl ketone, (3S,4S)-3,4-(isopropylidenedioxy)-3,7-dimethyl-6-octen-2-one (6), was enantioselectively prepared from geraniol via Sharpless asymmetric epoxidation and a regioselective epoxide-opening reaction. The aldol coupling between the lithium enolate of 6 and aldehyde, (2E,6E)-2,6-dimethyl-8-(2,2-dimethylpropanoyloxy)-2,6-octadienal (7), which was also prepared from geraniol, gave a 1 : 1 separable mixture of the adducts (17 and 18). Reduction of the carbonyl group in 17 and 18, followed by regioselective oxidation of the allylic hydroxy group, afforded α,β-unsaturated ketone, (2E,6E,10R,11R,12S)-1-(2,2-dimethylpropanoyloxy)-10-hydroxy-11,12-(isopropylidenedioxy)-3,7,11,15-tetramethyl-2,6,14-hexadecatrien-8-one (5). The intramolecular oxy-Michael addition of 5 followed by regioselective enol triflation and deoxygenation gave dihydropyran, (2E,6S,7Z,10R,11R,12S)-1-(2,2-dimethylpropanoyloxy)-6,10-epoxy-11,12-(isopropylidenedioxy)-3,7,11,15-tetramethyl-2,7,14-hexadecatriene (31). The regioselective epoxidation of 31 and a subsequent functional-group transformation gave (2E,6S,7Z,10R,11R,12S,14RS)-6,10 : 14,15-diepoxy-11,12-(isopropylidenedioxy)-3,7,11,15-tetramethyl-1-(phenylthio)-2,7-hexadecadiene (4). The 14-membered ring formation was achieved by the treatment of 4 with the n-BuLi–Bu2Mg complex to give (1Z,3S,6E,8RS,9RS,11S,12R,13R)-3,13-epoxy-9-(1-hydroxy-1-methylethyl)-11,12-(isopropylidenedioxy)-2,6,12-trimethyl-8-(phenylthio)-1,6-cyclotetradecadiene (33), which was transformed to 3 through triene construction and deacetonidation.
Syntheses and Properties of 11,11,12,12-Tetracyano-2,6-anthraquinodimethane (TANT) and Its 9,10-Dichloro Derivative as Novel Extensive Electron Acceptors
Authors: Takimiya Kazuo , Yanagimoto Tetsuya , Yamashiro Takashi , Ogura Fumio , Otsubo Tetsuo 
Published: February 2006

Abstract
The title compound (TANT) and its 9,10-dichloro derivative (TANT-Cl) have been prepared as higher homologues in an extended electron-acceptor series of TCNQ and TNAP. On the basis of cyclic voltammetry, the accepting ability of TANT is nearly comparable to those of TCNQ and TNAP, and that of TANT-Cl is further enhanced by the chloro substitutuent groups. In addition, TANT and TANT-Cl show an effective reduction of on-site coulombic repulsion, due to their extensive anthraquinone quinonoid system. They thus behave as superior electron acceptors for forming electrically conductive charge-transfer complexes with various electron donors, mostly of the TTT type.
Generation of Radical Species from Cyclohexane-1,2-dione and the Reaction with Olefins: Preparation of 4,5-Dihydro-7(6H)-benzofuranone Derivatives
Authors: Miura Masanori , Arai Noriyoshi , Narasaka Koichi 
Published: February 2006

Abstract
Oxidation of cyclohexane-1,2-dione with ammonium hexanitratocerate(IV) (CAN) generates 2,3-dioxocyclohexyl radical, which reacts with electron-rich olefins to afford the corresponding addition products. The adducts thus generated are converted to 4,5-dihydro-7(6H)-benzofuranone by acid treatment. In addition to cyclohexane-1,2-dione, radical species are also generated from cyclopentane-1,2-dione and cycloheptane-1,2-dione.
Norbornadiene-Fused Heterocycles: Synthesis and Bromination Reaction of 5,8-Dihydro-5,8-methanoquinoxaline Derivatives
Authors: Kobayashi Tomoshige , Miki Kiyomi 
Published: February 2006

Abstract
A norbornadiene-fused pyrazine was prepared by the condensation reaction of bicyclo[2.2.1]hept-5-ene-2,3-dione with ethylenediamine followed by oxidation. Treatments of the norbornadiene-fused pyrazine and its benzo derivative with bromine in carbon tetrachloride or in dioxane afforded trans-adducts as major products, accompanied by the formations of cis-adducts and dibromo derivatives derived from Wagner–Meerwein type skeletal rearrangement, while bromination of a fused dicyanopyrazine in carbon tetrachloride gave only a trans-adduct. In contrast, a fused pyrazine with an electron-donating N-oxide group gave a 7,9-dibromo derivative as the main component. The possibility of the intervention of a 2H-pyrazinium ion for the formation of the skeletally rearranged products is discussed together with the results of ab-initio (3-21G*) calculations.
Selective PdZn Alloy Formation in the Reduction of Pd/ZnO Catalysts
Authors: Iwasa Nobuhiro , Ogawa Noriaki , Masuda Satoshi , Takezawa Nobutsune 
Published: February 2006

Abstract
Temperature programmed reduction (TPR) experiments were carried out over Pd/ZnO with different Pd loadings. Combined results with an X-ray diffraction method and X-ray photoelectron spectroscopy showed that a Pd–Zn alloy with a structure of PdZn was selectively produced in the course of TPR of Pd/ZnO. It was suggested that hydrogen retained in Pd spilled over to ZnO. The ZnO was reduced to metallic Zn, being converted to PdZn. The molar amounts of the ZnO reduced were practically the same as the those of Pd loaded. Hence, all the Pd loaded was completely transformed to the PdZn alloys upon reduction.
Thermal and Rheological Properties of Physical Gels Formed from Benzylidene-d-sorbitol Derivatives
Authors: Watase Mineo , Itagaki Hideyuki 
Published: February 2006

Abstract
The thermal and rheological properties of gels formed from 2,4-(mono)-O-benzylidene-d-sorbitol (MBS), 1,3 : 2,4-di-O-benzylidene-d-sorbitol (DBS), and 1,3 : 2,4 : 5,6-tri-O-benzylidene-d-sorbitol (TBS) in ethylene glycol (EG) and from DBS in glycerol (GL) were investigated. In all the gels studied, the values of the enthalpy of melting for the gel obtained from the Eldridge–Ferry plot agreed well with those obtained from the peak area of the DSC curves. This agreement has not been demonstrated clearly for biopolymeric systems thus far but can now be successfully shown by first using small molecule systems. In conclusion, the transitions of the gel formation and gel melting proceed via a second order or higher order process. The experimental results show that the ease by which formation and stabilization of gels takes place for the sorbitol derivatives in EG is in the following order: DBS &gt; TBS &gt; MBS. Accordingly, the main reason for the stabilization of sorbitol gels in alcoholic solvents is concluded to be not simply due to hydrogen bonding or hydrophobic interactions among benzylidene groups but rather it is due to a delicate balance of chemical structure that facilitates the formation of crystals. In particular, the symmetric structure of a DBS molecule, which has a rigid and chiral ten-member ring symmetrically connected with two benzylidene groups in equatorial positions, is considered to be the most crucial reason to form most stable gels studied in this work.
Adsorption Behavior of Methyl Orange on the Monolayer and Langmuir–Blodgett Films of Octadecylamine
Authors: Takahashi Masashi , Kobayashi Koichi , Takaoka Kyo , Tajima Kazuo 
Published: February 2006

Abstract
The monolayer properties of octadecylamine (ODA) on both distilled water and aqueous Methyl Orange (MO) solution were studied from the measurements of surface pressure–area (π–A) isotherms. From the π–A isotherms at various pHs, hydroxide ions, and MO anions in the subphase were confirmed to interact competitively with the ODA monolayer. Furthermore, Langmuir–Blodgett (LB) film of ODA was fabricated from the surface of an alkaline subphase, and the adsorption characteristics of the ODA LB film were investigated by using MO as an adsorbate. As a result, the ODA LB film exhibited specific adsorbability for the MO anion, similar to that of the LB film of long-chain quaternary alkylammonium salt, but the adsorption rate of the MO on the ODA LB film was slower than that on the LB film of long-chain quaternary alkylammonium salt. In addition, adsorbability of the ODA LB film showed pH dependence.
Antioxidative Dopant for Thermal-Resisting Polypyrrole and Its Mechanism
Authors: Takeoka Shinji , Hara Tomitaro , Fukushima Kazuaki , Yamamoto Kimihisa , Tsuchida Eishun 
Published: February 2006

Abstract
In order to improve the thermal stability of the electric conductivity of polypyrrole (PPy), a series of aromatic sulfonate derivatives having acid-type substitute groups, such as –COOH, –OH, and –SO3H, were used as dopants. The PPy doped with these dopants showed excellent thermal stability of their electric conductivity, even at 150 °C in air. Especially, 2-hydroxy-5-sulfobenzoic acid, having one –COOH and one –OH, provided the highest thermal stability; the doped PPy maintained 95% of its initial conductivity, even after heating for 8 h at 150 °C in air. Furthermore, the PPy showed 20-times higher stability against long-term heating at 125 °C for 1000 h in comparison with PPy doped with p-methylbenzenesulfonic acid, which is conventionally used to provide high thermal stability. The thermal-stabilization mechanism has suggested that dopants having acidic substituents should suppress proton dissociation from the N-position of the PPy main chain and keep the π-conjugation structure by supplying a proton from the acidic groups. Such a proton supplement was confirmed by the IR spectroscopy of deuterized PPy.
Preparation of α,ω-Diols of Long Carbon Chains and Their Use in Polyurethane Synthesis
Authors: Osakada Kohtaro , Takenaka Yasumasa , Yamaguchi Isao , Yamamoto Takakazu 
Published: February 2006

Abstract
NaH promoted coupling reaction of HO(CH2)12O–TBDMS (1, TBDMS=SiMe2(t-Bu)) and Br(CH2)12O–TBDMS (2) followed by deprotection of the organosilyl groups affords HO(CH2)12O(CH2)12OH (5). 1,12-Dodecanediol reacts with an excess amount of 2 in the presence of NaH to give TBDMS–O(CH2)12O(CH2)12O(CH2)12O–TBDMS (6) which is turned into HO(CH2)12O(CH2)12O(CH2)12OH (7) by removal of the protecting groups. Similar 1 : 2 condensation of hydroquinone with 2 and with Br(CH2)6O–TBDMS (3) leads to formation of the corresponding α,ω-diols, HO(CH2)12OC6H4O(CH2)12OH (9) and HO(CH2)6OC6H4O(CH2)6OH (11), respectively. The four new long α,ω-diols are isolated and characterized by means of IR and NMR spectroscopy as well as elemental analyses. Polyaddition reactions of 5, 7, 9, and 11 to 1,3-bis(isocyanatomethyl)benzene and 1,1′-methylenebis[4-isocyanatobenzene] give the corresponding poly(urethane)s in high yields. The obtained polymers, which were characterized by IR and NMR spectroscopy, have molecular weights over 20000 as determined from gel permeation chromatography using polystyrene standards.
Alkene and Alkyne Complexes of Zirconocene. Their Preparation, Structure, and Novel Transformations
Authors: Negishi Ei-ichi , Takahashi Tamotsu 
Published: February 2006

Abstract
Dialkylzirconocenes in situ generated such as Cp2Zr(n-Bu)2, Cp2ZrEt2, and Cp2Zr(t-Bu)(i-Bu) are thermolyzed to afford zirconocene-alkene complexes. In the cases of Cp2Zr(n-Bu)2 and Cp2Zr(t-Bu)(i-Bu), Cp2Zr-alkene complexes generated from them tend to act as a “Cp2Zr” equivalent, since the initially generated alkene is often replaced by another π-bond containing compound. In the presence of alkynes, for example, alkyne complexes may be generated. On the other hand, Cp2Zr(ethylene) tends to serve as an intermediate since the ethylene moiety is often incorporated in the final organic products. Ring expansion and contraction, ligand substitution, transmetallation, migratory insertion, stereoisomerization, regioisomerization, oxidative addition involving these Cp2Zr-alkene and Cp2Zr-alkyne complexes as well as their structures are reviewed.
Studies on Polyketide Metabolites of a Symbiotic Dinoflagellate, Symbiodinium sp.: A New C30 Marine Alkaloid, Zooxanthellamine, a Plausible Precursor for Zoanthid Alkaloids
Authors: Nakamura Hideshi , Kawase Yuko , Maruyama Kyoko , Murai Akio 
Published: February 2006

Abstract
In studies on the biogenesis of vasocontrictive macrolides, zooxanthellatoxins isolated from a symbiotic dinoflagellate Symbiodinium sp., we have investigated metabolites of the dinoflagellate cultured under different conditions. Four new compounds were isolated from 70% EtOH extract of the cells cultured in f/2 medium. Two betaines (zooxanthellabetaine-A and -B) were obtained from a neutral fraction of n-BuOH soluble portion and the structure of zooxanthellabetaine-A was determined as 4-(4-hydroxybenzoyloxy)-3-(trimethylammonio)butyrate. The EtOAc soluble portion afforded a new C-30 alkaloid, zooxanthellamine, and a new ceramide, symbioramide-C16. The structural similarity of zooxanthellamine to zoanthid alkaloids, zoanthamines, suggested an algal origin of these zoanthamines. Zooxanthellamine might be derived biogenetically from a polyketide chain presumably started from a glycine unit, like other marine toxins such as zooxanthellatoxin and palytoxin.
Adsorption of Metal Ions to Surface-Template Resins Prepared with Amphiphilic Styrene Monomers Bearing Amino Carboxylic Acid
Authors: Koide Yoshifumi , Tsujimoto Keigo , Shosenji Hideto , Maeda Mizuo , Takagi Makoto 
Published: February 2006

Abstract
Monomer-type functional surfactants, 2-(p-vinylbenzylamino)alkanoic acid (RnNAc) and N,N-dialkyl derivatives (RRnNAc), have been used as both a ligand and an emulsifier for the preparation of surface-template resins. The surfactants adsorbed at the toluene–water interface and emulsified divinylbenzene–styrene in a Cu2+ or Zn2+ solution. Emulsion polymerization using a K2S2O8 initiator (80 °C) or by irradiation with γ-rays gave fine particles of 200—800 nm in diameter. Metal-imprinted resins prepared with RnNAc and RRnNAc showed a high adsorptive capacity for the metal ion (surface-template effect). Cu-imprinted resins prepared with R8NAc were 2.69-times as effective for Cu2+ in competitive sorption from a Cu2+–Zn2+ mixture and Zn-imprinted resins were 1.84-times as effective for Zn2+, compared with unimprinted resins. Because of the great emulsifying power, metal-imprinted resins prepared with R8NAc showed the most metal-selective adsorption and the largest capacity among resins prepared with RnNAc and RRnNAc.
Crystal Structure and Physical Properties of M = Rb and Tl Salts of (BEDT-TTF)2MM′(SCN)4 [M′ = Co, Zn]
Authors: Mori Hatsumi , Tanaka Shoji , Mori Takehiko , Kobayashi Akiko , Kobayashi Hayao 
Published: February 2006

Abstract
Crystal structure analyses, band calculations, and electrical resistivity and magnetic susceptibility measurements have been carried out for new θ-type BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene; abbreviated as ET] salts, θ-(BEDT-TTF)2TlCo(SCN)4 and θ-(BEDT-TTF)2TlZn(SCN)4 [abbreviated as θ-TlCo and θ-TlZn], as well as crystal structure analyses of θ-(BEDT-TTF)2RbM′(SCN)4 [M′ = Co, Zn; abbreviated as θ-RbM′]. θ-TlCo and θ-RbM′ [M′ = Co, Zn] are isostructural to the previously reported θ-CsM′, and the metal-insulator transition temperature increases from 20 K (θ-CsM′ [M′ = Co, Zn]), 190 K (θ-RbM′) to 250 K (θ-TlCo) with decreasing the unit cell volume, namely, the inverse chemical pressure effect. A structural investigation for θ-RbM′ [M′ = Co, Zn] indicates a lattice a modulation at the metal-insulator transition temperature (190 K). For the other salt, θ-TlZn, a semiconductor–semiconductor transition has been observed at 165 K, where the behavior of the magnetic susceptibility, following the two-dimensional Heisenberg model, changes from J = −30 K to −57 K under a slow cooling condition.
EPR Studies at High-Pressures. V. Spin-Exchange Reactions of Nitroxide Radicals with Cobalt and Nickel Complexes
Authors: Sueishi Yoshimi , Inoue Hajime , Oka Tetsuhito , Tsukube Hiroshi , Yamamoto Shunzo 
Published: February 2006

Abstract
The rate constants kex for the spin exchange of nitroxides with various kinds of cobalt(II) and nickel(II) complexes were determined from the EPR line-broadening of nitroxides. The rate constants estimated were in the range of 108—109 M−1 s−1 and this reaction was found to be diffusion-controlled. In order to distinguish cases of strong and weak spin exchange, we examined the pressure dependence of the spin exchange between nitroxide and the complexes. It was found that the ligand in the first coordination sphere of the complexes plays an important role for the efficiency of spin exchange. The presence of the coordinated halide ion provides strong exchange, regardless of any screening of the complex’s internal atoms by organic molecules. From the pressure dependence of kex, the J2fs values (the exchange integral J and the steric factor fs) for the spin exchange of nitroxides with cobalt and nickel complexes were estimated to be about 1020 s−2. Based on the results, the steric hindrance for the reaction of spin exchange is discussed.
Luminous Characteristics and 89Y-Static NMR in Red Phosphor, Eu-Doped Y2O3
Authors: Harazono Toshie , Yokota Etsuzo , Uchida Hiroshi , Watanabe Tokuko 
Published: February 2006

Abstract
Luminous properties of a red phosphor, Eu–Y2O3 (Eu-doped Y2O3) have been studied by 89Y (nuclear spin 1/2)-static NMR. Pure Y2O3 showed an anisotropic pattern with the peak centered at 299 ppm assigned to the Y atom in the site, where none of the 12 nearest neighbouring Y atoms are substituted by an Eu atom. The signal became broader with increasing doped Eu content. Additionally, a shoulder peak assigned to the Y atom in the site where one of the 12 nearest neighbouring Y atoms was replaced by one Eu atom appeared around 100—110 ppm in the samples with more than 1 mol/% Eu content.
The spin–spin relaxation of the centered signal was mainly dominated by the dipole–dipole interaction mechanism between the 89Y nucleus and the paramagnetic electrons of Eu3+ with 4f6 electron configuration which substituted at the second nearest and further neighbouring Y. In conclusion, the line-broadening of 89Y signal at constant Eu content was correlated with the Eu distribution on the basis of the facts that the phosphor sample with higher brightness showed broader linewidth and the intensity of the ESR signal corresponding to the lattice defects has no relation to the brightness.