bluuebunny/crossref_metadata_2025_split huggingface dataset:
Desaturation of color by environment light in cataract eyes
Authors: Ikeda Mitsuo , Obama Tomoko 
Published: February 2008

AbstractThe visual perception of the cataract eyes is composed of three elements, color, brightness, and haze. The color element is related to the reduced transmittance of light at short wavelengths of crystalline lens, the brightness element to the reduced transmittance at entire region of wavelength, and the haze element to the opacity of the crystalline lens. Researchers pay attention to only the color and brightness elements when they discuss on the color perception by the cataract eyes. We will show in this article that the haze element is also related to the color perception. There exists always environment light in our living situation. Light comes to the eyes from every direction. When the light enters the cataract eye it is scattered by the opacity of the crystalline lens and overlaps on the retinal image of objects that the eye is looking at. The environment light is usually white in color, and it reduces the colorimetric purity of the objects. The color appearance of the objects desaturates. This purity change was confirmed colorimetrically by measuring colors of test patches with the cataract simulating goggles placed in front of the lens of a colorimeter. The desaturation was then confirmed psychophysically by subjects wearing the goggles, who matched two color patches with and without the goggles. The same experiment was done by a subject whose right eye was operated for the cataract and the left eye was before the operation. Desaturation of color was found, though the desaturation was not as strong as with the goggles. In another psychophysical experiment the subject did the heterochromatic brightness matching experiment by using his right eye and left eye, respectively, before and after operation. The results were interpreted that all the color patches presented were perceived as being less saturated by eyes having cataracts. The importance was pointed out that, when we do experiments on the color perception by elderly observers we should not neglect the effect of the environment light. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 142–147, 2008
Aryltellurenyl Cation [RTe(CR′2)]+ Stabilized by an N‐Heterocyclic Carbene
Authors: Beckmann Jens , Finke Pamela , Heitz Stephan , Hesse Malte 
Published: February 2008

AbstractThe reaction of the (mixed‐valent) aryltellurenyl halidesRTeTeCl2R (1), RTeTeBr2R (2) and RTeI (3, R = 2,6‐Mes2C6H3) with 1,3,4,5‐tetramethylimidazol‐2‐ylidene (CR′2) provides cationic aryltellurenyl carbene complexes of the type [RTe(CR′2)]+ A– (4, A = RTeCl2; 5, A = RTeBr2; 6, A = I). The stabilization energy and natural charge distribution of the model cation [PhTe(CR′2)]+ as well as the related σ‐donor‐stabilized cations [PhTe(PMe3)]+, [I(CR′2)]+, [I(PMe3)]+ were investigated by DFT calculations and NBO analyses.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
An Efficient Approach for the Synthesis of N‐1 Substituted Hydantoins
Authors: Kumar Vinod , Kaushik M. P. , Mazumdar Avik 
Published: February 2008

AbstractAn efficient three‐step route for the synthesis of N‐1 alkyl/aryl‐substituted hydantoins was developed from inexpensive commercially available substrates. The reaction of amines with cyanogen bromide takes place to give monoalkyl/aryl cyanamides. This on treatment with methyl bromoacetate in the presence of sodium hydride in tetrahydrofuran affords methyl N‐cyano‐N‐alkyl/arylaminoacetate, which undergoes hydrolysis and cyclization in the presence of 50 % H2SO4 to afford N‐1 substituted hydantoins in very good‐to‐excellent yields. Wide varieties of final products having primary, secondary, tertiary, and aryl substituents at the N‐1 position were successfully synthesized by this method. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Crystallographic and Theoretical Evidence of Anion–π and Hydrogen‐Bonding Interactions in a Squaramide–Nitrate Salt
Authors: Rotger Carmen , Soberats Bartomeu , Quiñonero David , Frontera Antonio , Ballester Pablo , Benet‐Buchholz Jordi , Deyà Pere M. , Costa Antoni 
Published: February 2008

AbstractSynthetic anionic receptors are fundamental to the understanding of the mechanism of recognition phenomena, which is the basis of many fundamental biological processes. Recognition studies and X‐ray crystallography techniques provide accurate information on the structure of the molecular complexes and the nature of the interactions involved. Here, we present the first example of a squaramide–nitrate salt. X‐ray crystallography and theoretical studies show the important roles of anion–π and hydrogen‐bonding interactions in the crystal packing of this compound in relation to those found in the free squaramide solid structure.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthetic Strategies for Oseltamivir Phosphate
Authors: Shibasaki Masakatsu , Kanai Motomu 
Published: February 2008

AbstractWe review here the synthetic strategies for oseltamivir phosphate, an important orally active anti‐influenza drug. The Roche synthesis utilized naturally occurring shikimic acid as a starting material. Introduction of the 1‐ethylpropyloxy (“3‐pentyloxy”) functionality by regioselective reduction of the acetal and iterative ring‐opening reactions with azide to introduce nitrogen functionalities were the key steps. Corey and Fukuyama's syntheses utilized catalytic asymmetricDiels–Alder reactions as the starting points, whereas Shibasaki and Kanai's synthesis began with an asymmetric aziridine‐opening reaction with TMSN3 catalyzed by a polymetallic gadolinium complex. These three syntheses demonstrate the power of asymmetric catalysis in pharmaceutical synthesis. Although Kann's synthesis required resolution to provide an enantiomerically pure intermediate, the properties of chiral iron–diene complexes were elegantly utilized. Yao and Fang's syntheses started from abundant natural chiral sources: L‐serine and D‐xylose, respectively. Specifically, Fang's study identified new analogues of oseltamivir with higher potency against several neuraminidases, including oseltamivir‐resistant mutants. Despite the relatively small molecular size, oseltamivir synthesis highlights an important frontier in organic synthesis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Interactive manipulation of blood cells using a lens‐integrated liquid crystal display based optoelectronic tweezers system
Authors: Hwang Hyundoo , Choi Yong‐Je , Choi Wonjae , Kim Se‐Hwan , Jang Jin , Park Je‐Kyun 
Published: February 2008

AbstractThis paper reports a lens‐integrated liquid crystal display (LCD)‐based optoelectronic tweezers (OET) system for interactive manipulation of polystyrene microspheres and blood cells by optically induced dielectrophoretic force. When a dynamic image pattern is projected into a specific area of a photoconductive layer in an OET, virtual electrodes are generated by spatially resolved illumination of the photoconductive layer, resulting in dielectrophoresis of microparticles suspended in the liquid layer under nonuniform electric field. In this study, the simple‐structured OET system has been easily constructed with an OET device, an LCD and a condenser lens integrated in a conventional microscope. By using a condenser lens, both stronger dielectrophoretic forces and higher virtual electrode resolution than previously reported lens‐less LCD‐based OET platform are obtained. The effects of blurred LCD image and liquid chamber height on the performances of optoelectronic particle manipulation are investigated by measuring the bead velocities according to their sizes. An interactive control program for OET‐based microparticle manipulation is also developed by Flash language. The integrated system is successfully applied to the parallel and interactive manipulation of red and white blood cells. Due to its simple structures, cheap manufacturing costs, and high performances, this new LCD‐based OET platform may be a widely usable integrated system for optoelectronic manipulation of microparticles including living cells.
Cationic surfactants for micellar electrokinetic chromatography: 1. Characterization of selectivity using the linear solvation energy relationships model
Authors: Schnee Vincent P. , Palmer Christopher P. 
Published: February 2008

AbstractMEKC and the linear solvation energy relationship (LSER) model have been applied to two series of cationic surfactants. The synthetic flexibility of the quaternary ammonium group is exploited to generate the two series, one consisting of linear substitutions and the other incorporating the ammonium into ring structures of varying size. The effects of the head group structure on the CMC, aggregation number, and electrophoretic properties of the surfactants were determined. These surfactants were also characterized with the LSER model, which allowed the contributions of five chemical factors to the interactions between solutes and the micelles to be evaluated. Trends were observed in the cohesivity and polarity of the linear surfactant series, with both increasing with the size of the head group. No trends in the LSER parameters were observed in the cyclic series, but the LSER results do show that the surfactants with cyclic head groups provide a significantly different solvation environment from the linear series. Additional trends were observed in the aggregation behavior and chromatographic properties of the surfactants. These included changes in the CMCs, aggregation numbers, EOF, and electrophoretic mobility of the micelles that correlate to changes in head group size.
Characterization of a cationic phosphonium surfactant for micellar electrokinetic chromatography: Using the linear solvation energy relationships model
Authors: Schnee Vincent P. , Palmer Christopher P. 
Published: February 2008

AbstractA phosphonium surfactant is introduced as a pseudostationary phase for MEKC and its performance and selectivity are compared to that of an analogous ammonium surfactant. The linear solvation energy relationship model has been applied to the two cationic surfactants, allowing the contributions of five chemical factors to the interactions between solutes and the micelles to be evaluated. Differences in the pseudophases cohesivity and acid/base interactions were observed. Despite the significant differences observed in the solvation parameter results the two phases have remarkably similar electrophoretic properties, with the anodic EOF produced by the dynamic coating and the electrophoretic mobility of the two surfactants being statistically equal.
Probabilistic impedance of foundation: Impact of the seismic design on uncertain soils
Authors: Cottereau Régis , Clouteau Didier , Soize Christian 
Published: February 2008

AbstractIn the linear seismic design of buildings, the (deterministic) substructure method is a customary and efficient approach. However, the existence of spatial variability in the parameters of the mechanical model of the soil, as well as parametric errors, calls for the use of probabilistic approaches in order to provide a reliable design of the structure. The construction of probabilistic models of the soil impedance matrix provides a natural path to such approaches within the context of the substructure method. Two main techniques are described in this paper: a parametric one, typically using the stochastic finite element method, and a nonparametric one, which was introduced more recently. The latter is explored more specifically, and the possibilities it offers in terms of seismic design are presented. In particular, it is shown that it allows for the estimation of quantiles of the quantities of interest, rather than confidence intervals, which lead to highly conservative design. Copyright © 2008 John Wiley & Sons, Ltd.
The morphological distinctiveness of Homo sapiens and its recognition in the fossil record: Clarifying the problem
Authors: Tattersall Ian , Schwartz Jeffrey H. 
Published: February 2008

AbstractSpecies are historically differentiated entities that, osteologically, may be differentiated to inconveniently varying extents. Living Homo sapiens is a distinctive morphological entity that is easily distinguished in both cranial and postcranial morphology from all other living hominoids and from the vast majority of its fossil relatives. In this contribution, we offer several apparent cranial apomorphies of the living species, while recognizing that it is reasonable to expect some degree of overlap in the ranges of variation of individual characters among closely related species such as those within the genus Homo. No one aspect of morphological detail may be considered totally diagnostic within very close‐knit groups of this sort or, conversely, be regarded as blurring the identities of their components. Overlap in morphological detail may even be expected in cases where striking Gestalt differences exist between closely related species due to major developmental reorganization. As a result, while the morphological and, by extension, historical distinction between such highly differentiated species pairs as Homo neanderthalensis and Homo sapiens is effectively unequivocal, in a nod to the intrinsic untidiness of biology the hominid fossil record does offer some instances that are much more difficult to interpret. In such cases, most, but not all, of the cranial apomorphies of living Homo sapiens, are present in individual fossil specimens or apparent populations. This is true, for example, of a set of variably dated and archeologically associated, as well as mostly incomplete, South African fossils (for example, Border Cave, Boskop, Fish Hoek, and most Klasies River Mouth specimens). These specimens very closely resemble living Homo sapiens in preserved overall cranial structure, but most conspicuously lack bipartite brows and fully developed human chin configurations. Whatever resolutions hominid systematists may reach in such cases, it is clear that to resort reflexively to such pernicious if convenient devices as “archaic Homo sapiens” only obscures any potential signals of systematic diversity in what is increasingly evidently a highly complex late Pleistocene hominid record.
Speculations about the selective basis for modern human craniofacial form
Authors: Lieberman Daniel E. 
Published: February 2008

AbstractThe last few decades have seen an explosion of knowledge about the time and place of origin of our species, Homo sapiens. New fossils, more sites, better dates, modern and fossil DNA, and scores of analyses have mostly disproved the multiregional model of human evolution. By and large, the evidence generally supports some version of the out‐of‐Africa model, according to which humans first evolved in Africa at least 200,000 years ago and then migrated to other parts of the world. Remaining debates about human origins primarily address if and how much hybridization occurred between modern humans and taxa of archaic Homo such as H. neanderthalensis.
One‐Pot Four‐Component Synthesis of Tetrasubstituted Pyrroles
Authors: Kassaee M. Z. , Masrouri Hassan , Movahedi Farnaz , Partovi Tayyebeh 
Published: February 2008

AbstractA convenient one‐pot four‐component synthesis of tetrasubstituted pyrroles was carried out through the reaction of butane‐2,3‐dione with α‐aminophosphorous ylides, obtained in situ from the 1 : 1 : 1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylate, and ammonium acetate.
A Biomimetic Synthesis of Sacculatane Diterpenoids
Authors: Grinco Marina , Kulciţki Veaceslav , Ungur Nicon , Vlad Pavel F. , Gavagnin Margherita , Castelluccio Francesco , Cimino Guido 
Published: February 2008

AbstractThe biomimetic synthesis of sacculatane‐type epimeric compounds 14a and 14b is reported. The key synthetic step is the low‐temperature superacidic cyclization of (all‐E)‐ω‐acetoxygeranylgeraniol 12 obtained in nine steps from geranyllinalool (13). The 19‐acetoxysacculata‐7,17‐dien‐11‐ol (14a) could be an important and convenient starting compound for the synthesis of other sacculatane diterpenoids.
Copper‐Free Sonogashira Coupling of Acid Chlorides with Terminal Alkynes in the Presence of a Reusable Palladium Catalyst: An Improved Synthesis of 3‐Iodochromenones (=3‐Iodo‐4H‐1‐benzopyran‐4‐ones)
Authors: Likhar Pravin R. , Subhas M. S. , Roy Moumita , Roy Sarabindu , Kantam M. Lakshmi 
Published: February 2008

AbstractPd/C is used as an efficient catalyst for the copper‐free Sonogashira coupling of acid chlorides and terminal alkynes to afford ynones in high yields (Tables 1 and 3). Cyclization of (2‐methoxyaryl)‐substituted ynones induced by I2/ammonium cerium(IV) nitrate (CAN) at room temperature gave 3‐iodochromenones (=3‐iodo‐4H‐1‐benzopyran‐4‐ones) in excellent yield (Table 4).
New Approaches to the Synthesis of 4‐(2‐Aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones and 3‐Ureidoindoles and a Study of Their Interconversion
Authors: Klásek Antonín , Lyčka Antonín , Holčapek Michal , Hoza Ignác 
Published: February 2008

Abstract3‐Alkyl/aryl‐3‐ureido‐1H,3H‐quinoline‐2,4‐diones (2) and 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones (3) react in boiling concentrated HCl to give 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones (6). The same compounds were prepared by the same procedure from 2‐alkyl/aryl‐3‐ureido‐1H‐indoles (4), which were obtained from the reaction of 3‐alkyl/aryl‐3‐aminoquinoline‐2,4(1H,3H)‐diones (1) with 1,3‐diphenylurea or by the transformation of 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones (3) and 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones (6) in boiling AcOH. The latter were converted into 1,3‐bis[2‐(2‐oxo‐2,3‐dihydro‐1H‐imidazol‐4‐yl)phenyl]ureas (5) by treatment with triphosgene. All compounds were characterized by 1H‐ and 13C‐NMR and IR spectroscopy, as well as atmospheric pressure chemical‐ionisation mass spectra.
Stereoselective Total Synthesis of Natural (S)‐Bakuchiol and Its Enantiomer
Authors: Du Xiao‐Long , Chen Hong‐Li , Feng Hui‐Jin , Li Yuan‐Chao 
Published: February 2008

AbstractA practical stereoselective synthesis of (S)‐bakuchiol (1) and its enantiomer is reported. The important intermediate, (R)‐configured β‐siloxy aldehyde 5, was obtained in three steps from the easily available material geraniol (2) via the key step of Yamamoto's rearrangement of epoxy silyl ethers. (S)‐Bakuchiol (1) and its enantiomer, (R)‐bakuchiol (17), were finally obtained in different synthetic sequences with overall yields of 51% (ten steps) and 40% (nine steps) from geraniol (2), respectively.
Vitamin C suppresses proliferation of the human melanoma cell SK‐MEL‐2 through the inhibition of cyclooxygenase‐2 (COX‐2) expression and the modulation of insulin‐like growth factor II (IGF‐II) production
Authors: Lee Seung Koo , Kang Jae Seung , Jung Da Jung , Hur Dae Young , Kim Jee Eun , Hahm Eunsil , Bae Seyeon , Kim Hyung Woo , Kim Daejin , Cho Byung Joo , Cho Daeho , Shin Dong Hoon , Hwang Young‐Il , Lee Wang Jae 
Published: February 2008

AbstractVitamin C plays a crucial role in the suppression of proliferation of several types of cancer. Over‐expression of cyclooxygenase (COX)‐2 and type I insulin‐like growth factor (IGF) receptor are important for proliferation and protection from apoptosis in malignancies. However, its specific mechanisms, especially the interaction between COX‐2 expression and IGF‐I axis mediated by vitamin C, remain yet to be clarified. Therefore, we investigated the effects of vitamin C on the proliferation of melanoma cells via the modulation of COX‐2 expression and IGF‐I axis. As a result, we found that 1.0 mM vitamin C inhibits the proliferation of SK‐MEL‐2 without induction of apoptosis. At that moment, IGF‐II production was decreased, followed by the inhibition of COX‐2 activity. IGF‐IR expression was also down‐regulated by vitamin C treatment. It coincided with the result from the inhibition of COX‐2 by NS‐398 and COX‐2 siRNA. In addition, the decreased IGF‐IR expression by vitamin C was restored by the treatment of recombinant prostaglandin E2. Finally, we determined whether the signal pathway would be involved in vitamin C‐induced IGF‐II and IGF‐IR down‐regulation. When the cells were exposed to SB203580, a specific inhibitor of p38 MAPK, COX‐2 expression was dramatically recovered. In addition, phosphorylated p38 MAPK was increased after vitamin C treatment. Taken together, vitamin C suppresses proliferation of the human melanoma cell line SK‐MEL2 via the down‐regulation of IGF‐II production and IGF‐IR expression, which is followed by the activation of p38 MAPK and the inhibition of COX‐2 expression. J. Cell. Physiol. 216: 180–188, 2008. © 2008 Wiley‐Liss, Inc.
Roles of insulin and transferrin in neural progenitor survival and proliferation
Authors: Erickson Rebecca I. , Paucar Andres A. , Jackson Robert L. , Visnyei Koppany , Kornblum Harley 
Published: February 2008

AbstractMultipotent neural progenitor cells or neural stem cells (NSC) can be propagated in vitro from a variety of sources and have great potential for neural repair. Although it is well known that NSC divide in response to basic fibroblast growth factor (FGF‐2) and epidermal growth factor (EGF), cofactors necessary for survival and maintenance of a multipotent potential are still a matter of debate. In the current study, we examined the requirements for NSC proliferation and survival in vitro using the neurosphere culture system. Apotransferrin (TF), along with EGF and FGF‐2, was sufficient for the formation of primary neurospheres derived from embryonic rat cortices. The addition of low concentrations of insulin or insulin‐like growth factor‐1 (IGF‐1) enhanced neurosphere size and number and was necessary for continued passaging. Both insulin and IGF‐1 acted at low concentrations, suggesting that their effects were mediated by their cognate receptors, both of which were expressed by neurosphere cultures. Sphere‐forming progenitors survived for long periods in culture without EGF or FGF‐2 when either insulin or IGF‐1 was added to the media. Cell cycle analysis determined that surviving progenitors were relatively quiescent during the period without mitogens. Upon the reintroduction of EGF and FGF‐2, surviving progenitors gave rise to new spheres that produced largely glial‐restricted progeny compared with sister cultures. These data indicate that the neurogenic potential of NSC may be intimately linked to a continuous exposure to mitogens. © 2008 Wiley‐Liss, Inc.