bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoswitching of ferroelectric liquid crystals using chiral thioindigo dopants: The development of a photochemical switch hitter
Authors: Lemieux Robert P.
Published: January 2004

By virtue of its spontaneous polarization (PS), a ferroelectric SmC* liquid crystal can be switched between two states corresponding to opposite molecular tilt orientations using an electric field, thus producing an ON–OFF light shutter between crossed polarizers. Considerable efforts have been made over the past decade to develop photonic FLC light shutters because of their potential uses in dynamic holography and optical data storage. The ON–OFF switching of a FLC light shutter can be triggered by light via a photoinversion of PS using a photochromic dopant. The spontaneous polarization is a chiral bulk property that can be left‐handed (negative) or right‐handed (positive), depending on the absolute configuration of the chiral component of the SmC* phase. In the approach described herein, the magnitude of PS is modulated via the photoisomerization of a chiral thioindigo dopant that undergoes a large increase in transverse dipole moment upon trans–cis photoisomerization. The sign of PS is photoinverted using an “ambidextrous” thioindigo dopant containing a chiral 2‐octyloxy side chain that is coupled to the thioindigo core and induces a positive PS, and a chiral 2,3‐difluorooctyloxy side chain that is decoupled from the core and induces a negative PS. In the trans form, the 2,3‐difluorooctyloxy side chain predominates and the net PS induced by the dopant is negative. However, upon trans–cis‐photoisomerization, the increase in transverse dipole moment of the 2‐octyloxy/thioindigo unit raises its induced PS over that of the decoupled 2,3‐difluorooctyloxy side chain, and thus inverts the net sign of PS induced by the dopant from negative to positive. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 3: 288–295; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10067
Selective alkane CH‐bond functionalizations utilizing oxidative single‐electron transfer and organocatalysis
Authors: Schreiner Peter R. , Fokin Andrey A.
Published: January 2004

Alkane CH‐bond functionalization methods not utilizing metal‐catalysis are discussed based on experimental and computational data, beginning with molecule‐induced homolysis (reactions of alkanes with dioxiranes). Electrophilic reactions are elaborated next with an emphasis on mechanistic details that reveal that many so‐called electrophilic CH or CC‐bond insertions can be rationalized by electron‐transfer reactions (inner sphere, H‐coupled, and outer sphere). Finally, radical functionalizations utilizing carbon‐centered (relatively stable) radicals generated under organocatalytic (phase‐transfer catalysis, PTC) conditions are presented as valuable alternatives to other radical‐chain alkane functionalizations. The remarkable chemo‐ and regioselectivities of these PTC radical reactions and the tolerance of high strain in certain aliphatic hydrocarbons make them particularly useful for laboratory‐scale halogenations, in particular, iodinations of unactivated alkane CH‐bonds. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 3: 247–257; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10070
Population growth impairment of aliphatic alcohols to Tetrahymena
Authors: Schultz T. Wayne , Seward‐Nagel Julie , Foster Karen A. , Tucker Vera A.
Published: January 2004

The toxicity of a series of 120 aliphatic alcohols was evaluated using the Tetrahymena pyriformis population growth impairment assay. For tertiary propargylic alcohols; primary, secondary, and tertiary homopropargylic alcohols; allylic alcohols; and saturated alcohols, a statistically robust structure‐activity model was developed for toxicity data [log (IGC50−1)] using the 1‐octanol/water partition coefficient (log Kow) as the lone descriptor [log (IGC50)−1 = 0.74 (log Kow) − 1.73; n = 97; r2 (adj.) = 0.933; r2 (pred.) = 0.932; s = 0.298; F = 1328; Pr > F = 0.0001]. Analysis of data for the primary propargylic alcohols yielded a separate, high‐quality log Kow‐dependent quantitative structure‐activity relationship (QSAR) [log (IGC50)−1 = 0.65 (log Kow) − 1.22; n = 10; r2 (adj.) = 0.969; r2 (pred.) = 0.964; s = 0.222; F = 254; Pr > F = 0.0001]. A comparison of the observed toxicity and that predicted by the first QSAR showed that the primary propargylic alcohols with log Kow values < 2.00 exhibited enhanced toxicity and that this increased toxicity was inversely related to hydrophobicity. In sharp contrast, analysis of the data for the secondary propargylic alcohols exhibited little relationship with log Kow (r2 = 0.339). Although the initial QSAR can be used to model the toxicity of any aliphatic alcohol for the T. pyriformis population growth impairment end point, the estimated potency would be underestimated for primary propargylic alcohols with log Kow values < 2.00. Moreover, estimates of toxic potency of secondary propargylic alcohols based on this QSAR should be viewed with limited confidence. The findings for β‐unsaturated alcohols in Tetrahymena were sharply different from that reported for fathead minnow acute mortality; this difference in toxicity is a result of a difference in the protocol used rather than in metabolism. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 1–10, 2004.
Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailability
Authors: Mkandawire Martin , Lyubun Yelena V. , Kosterin Paul V. , Dudel E. Gert
Published: January 2004

The toxicity of arsenic (As) species to Lemna gibba L. and the influence of PO on As bioavailability and uptake were tested in batch culture. L. gibba were exposed to six test concentrations of NaHAsO4 · 7H2O and NaAsO3, with 0, 0.0136, 13.6, and 40 mg L−1 KH2PO4. In batch culture As toxicity to L. gibba did not relate linearly to As concentration. The growth rate, related to frond number as recommended by OECD and ISO/DIN, was significantly inhibited in fronds exposed to 20–50 μg L−1 As(III) compared with fronds exposed to As(V). The growth rate was stimulated when plants were exposed to 50–250 μg L−1 of both As(III) and As(V). After exposure to 300–800 μg L−1 growth inhibition was significantly higher for As(III) than for As(V), whereas above 800 μg L−1 As(V) was inhibited the most. The bioaccumulation of As(III) and As(V) was significantly higher for P‐deficient cultures (0.98 ± 0.08 and 1.02 ± 0.19 g kg−1, respectively for 0.0136 mg L−1 PO) than for P‐sufficient cultures (243 and 343 mg kg−1 for 40 mg L−1, respectively). Plants exposed to As(V) had uptake and accumulation values slightly higher than did plants exposed to As(III). No significant differences in bioaccumulation were found between plants exposed to a concentration of As(III) >1 mg L−1 and those exposed to As(V) at the same concentration. This indicates a direct relationship to P content in the culture. Toxicity may result from the uptake of As(V) instead of PO as a result of ion competition during uptake because of close thermodynamic properties, which may change the interaction among components in the media. The toxicity pattern is interpreted as a manifestation of changing speciation in the batch culture and of the oxidation of As(III) to As(V) in an oxygen‐rich environment. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 26–34, 2004.
Mercury concentrations in migratory waterfowl harvested from Southern Nevada Wildlife Management Areas, USA
Authors: Gerstenberger Shawn L.
Published: January 2004

Mercury concentrations were determined in 14 species of migratory waterfowl harvested from Southern Nevada Wildlife Management areas during the 2001–2002 hunting season. Common mergansers (2.61 ± 0.87 ppm liver; 0.22 ± 0.04 ppm muscle), northern shovelers (3.51 ± 3.8 ppm liver; 0.16 ± 0.03 ppm muscle), and bufflehead (2.63 ± 0.24 ppm liver; 0.91 ppm muscle) had the highest concentrations of mercury in the liver and muscle of the species harvested. The relationships between muscle and liver concentrations were also examined. These data indicate that liver tissue can be used with reasonable confidence (r >.80 for most species) to predict mercury concentrations in muscle, the most commonly consumed portion of waterfowl. The mercury concentrations reported here are some of the highest reported in the scientific literature, and they identify certain species, such as the northern shoveler and common merganser, that have accumulated unusually high concentrations of mercury. Evidence for the use of these three species as possible bioindicators for mercury is also presented. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 35–44, 2004.
Evaluation of flushing of a high‐selenium backwater channel in the Colorado River
Authors: Hamilton Steven J. , Holley Kathy M. , Buhl Kevin J. , Bullard Fern A. , Weston L. Ken , McDonald Susan F.
Published: January 2004

Concern has been raised that selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The objective of the study was to determine if operation of a water control structure (opened in December 1996) that allowed the Colorado River to flow through a channel area at Walter Walker State Wildlife Area (WWSWA) would reduce selenium and other inorganic elements in water, sediment, aquatic invertebrates, and forage fish. Endangered Colorado pikeminnow were collected and muscle plug samples taken for selenium analysis. Selenium concentrations in filtered water were 21.0 μg/L in 1995, 23.5 μg/L in 1996, 2.1 μg/L in 1997, and 2.1 μg/L in 1998. Selenium concentrations in sediment cores and sediment traps were 8.5 μg/g in 1995, 8.2 μg/g in 1996, 4.8 μg/g in 1997, and 1.1 μg/g in 1998. Selenium concentrations in aquatic invertebrates were 27.4 μg/g in 1996, 15.5 μg/g in 1997, and 4.9 μg/g in 1998. Selenium concentrations in forage fish were 27.2 μg/g in 1996, 20.2 μg/g in 1997, and 8.6 μg/g in 1998. Selenium concentrations in muscle plugs of Colorado pikeminnow were 9.8 μg/g in 1995, 9.5 μg/g in 1996, 9.0 μg/g in 1997, and 10.3 μg/g in 1998. Although selenium concentrations in water, sediment, aquatic invertebrates, and forage fish decreased substantially after operation of the water control structure, a corresponding change in Colorado pikeminnow did not seem to occur. Selenium concentrations in muscle plugs decreased with increasing fish total length and weight, did not change between repeat sampling in the same year or recapture in subsequent years, and seemed to be most closely associated with the mean monthly river flow for the March–July period. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 51–81, 2004.
Extraction of cyanobacterial endotoxin
Authors: Papageorgiou John , Linke Thomas A. , Kapralos Con , Nicholson Brenton C. , Steffensen Dennis A.
Published: January 2004

To simplify our efforts in acquiring toxicological information on endotoxins produced by cyanobacteria, a method development study was undertaken to identify relatively hazard‐free and efficient procedures for their extraction. One article sourced and two novel methods were evaluated for their ability to extract lipopolysaccharides (LPSs) or endotoxins from cyanobacteria. The Limulus polyphemus amoebocyte lysate (LAL) assay was employed to compare the performance of a novel method utilizing a 1‐butanol–water (HBW) solvent system to that of Westphal's (1965) phenol–water system (HPW) for the extraction of endotoxin from various cyanobacteria. The traditional HPW method extracted from 3‐ to 12‐fold more endotoxin from six different cyanobacterial blooms and culture materials than did the novel HBW method. In direct contrast, the novel HBW method extracted ninefold more endotoxin from a non–microcystin producing Microcystis aeruginosa culture as compared to the HPW method. A solvent system utilizing N,N′‐dimethylformamide–water (HDW) was compared to both the HPW and HBW methods for the extraction of endotoxin from natural samples of Anabaena circinalis, Microcystis flos‐aquae, and a 1:1 mixture of Microcystis aeruginosa/Microcystisflos‐aquae. The LAL activities of these extracts showed that the novel HDW method extracted two‐ and threefold more endotoxin from the Anabaena sample that did the HBW and HPW methods, respectively. The HDW method also extracted approximately 1.5‐fold more endotoxin from the Microcystis flos‐aquae sample as compared to both the HBW and HPW methods. On the other hand, the HBW method extracted 2‐ and 14‐fold more endotoxin from the Microcystis flos‐aquae/Microcystis aeruginosa mixture than did the HPW and HDW methods, respectively. Results of this study demonstrate that significant disparities exist between the physicochemical properties of the cell wall constituents not only of different cyanobacterial species but also of different strains of the same cyanobacterial species, as showing by the varying effectiveness of the solvent systems investigated. Therefore, a sole method cannot be regarded as universal and superior for the extraction of endotoxins from cyanobacteria. Nevertheless, the ability of the novel HBW and HDW methods to utilize easily handled organic solvents that are less hazardous than phenol render them attractive alternatives to the standard HPW method. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 82–87, 2004.
Metallothionein induction in aquatic oligochaete tubifex tubifex exposed to herbicide isoproturon
Authors: Mosleh Y. Y. , Paris‐Palacios S. , Arnoult F. , Couderchet M. , Biagianti‐Risbourg S. , Vernet G.
Published: January 2004

Metallothioneins (MTs) are low‐molecular‐weight proteins mainly involved in metal ion detoxification. Recently it has been demonstrated that MTs participate in several cellular functions such as regulation of growth and antioxidative defenses. Moreover, pesticides can induce their synthesis. The aim of the current work was to determine the effects of isoproturon, either pure or formulated as Matin® (suspension containing an isoproturon concentration of 500 g · L−1), on the metallothionein and total protein contents of the aquatic worm Tubifex tubifex. MT levels in exposed worms increased significantly after 7 and 15 days of exposure to a concentration of the herbicide of 50 mg · L−1. Isoproturon reduced the metal (Cu, Zn, and Cd) content of metallothioneins, and it also increased the total protein content of the worms. These results suggest that MT induction may not be considered a specific biomarker of metal exposure but that it can be used as a nonspecific biomarker of the effect of isoproturon effect in aquatic worms. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 88–93, 2004.
Safety of Topical Minoxidil Solution: A One-Year, Prospective, Observational Study
Authors: Shapiro Jerry
Published: January 2004

Background:

Topical minoxidil solution (TMS) is widely used for androgenetic alopecia (AGA), and this is the first report of a large safety trial.

Objectives:

The aim of the study was to evaluate the safety profile of TMS by comparing hospitalization and death rates among subjects using TMS with controls. Cardiovascular safety and pregnancy outcomes were evaluated, and usage patterns were described.

Methods:

All subjects were followed at baseline, 3, 6, 9, and 12 months. Usage patterns, pregnancy status, overnight hospital stays, and cardiovascular risk factors were evaluated. Subjects rated effectiveness of TMS in the treatment of AGA. Statistical analyses were conducted to determine if TMS was associated with an increased risk of death or hospitalization.

Results:

TMS is a safe and effective treatment for AGA. There were no increases in cardiovascular events and no apparent increased risk for adverse pregnancy outcomes.

Conclusions:

This large, prospective study demonstrated the overall safety of TMS in the treatment of AGA.
Regulation of Plasma Substance P and Skin Mast Cells by Odorants
Authors: Hosoi Junichi , Tanida Masahiro , Tsuchiya Toru
Published: January 2004

Background:

Mast cells stimulate inflammation and itch sensation in the skin by releasing various mediators when they are activated. Stress exacerbates some skin diseases. We have reported that inhalation of certain odorants modulates immune reactions in the skin.

Objective:

The possible usage of odorants in the regulation of skin inflammation and itch sensation was to be examined.

Methods:

Female volunteers were subjected to interview stress with or without odorant inhalation. Mice were immobilized while inhaling odorants. Toluidene blue-stained sections were analyzed for activated mast cells. Plasma substance P level was determined by enzyme-linked immunoassay.

Results:

Interview stress induced plasma substance P only in volunteers who did not inhale odorants containing 2% 1,3-dimethoxy-5-methyl benzene (DMMB). Immobilization stress induced mast cell activation in mice and the activation was blocked by exposure to DMMB.

Conclusions:

Stress causes mast cell activation via an increase in substance P. The effect of stress is suppressed by inhalation of DMMB.
Axillary Granular Parakeratosis
Authors: English Joseph C. , Derdeyn Amalie S. , Wilson Wendy M. , Patterson James W.
Published: January 2004

Background:

Granular parakeratosis is a hyperkeratotic eruption of unknown etiology that occurs in the axilla and other intertriginous areas. The histologic features are unique for the retention of keratohyalin granules in the stratum corneum.

Objective:

The aim of the article is to review the clinical manifestations and treatment of granular parakeratosis.

Methods:

A case report and literature review are presented.

Results:

Twenty-six cases of granular parakeratosis now have been reported and reviewed.

Conclusion:

Granular parakeratosis occurs predominantly in middle age women and most frequently in the axilla. A number of treatments have been applied to the 26 cases reported to date, without consistent responses. No evidence-based therapy can be suggested at present.
Human herpesvirus 6 infection arrests cord blood mononuclear cells in G2 phase of the cell cycle
Authors: De Bolle Leen , Hatse Sigrid , Verbeken Erik , De Clercq Erik , Naesens Lieve
Published: January 2004

We here report that after infection with human herpesvirus 6A, human cord blood mononuclear cells accumulate in G2/M phase of the cell cycle. Experiments with foscarnet or ultraviolet (UV)‐irradiated virus stocks pointed at an (immediate‐)early, newly formed viral protein to be responsible for the arrest. At the molecular level, p53, cyclin B1, cyclin A and tyrosine15‐phosphorylated cdk1 accumulated after HHV‐6A infection, indicating an arrest in G2. However, no change was observed in the levels of downstream effectors of p53 in establishing a G2 arrest, i.e. p21 and 14‐3‐3σ. We thus conclude that the HHV‐6A‐induced G2 arrest occurs independently of p53 accumulation.
Purification, characterization, cDNA cloning, and expression of a xyloglucan endoglucanase from Geotrichum sp. M1281
Authors: Yaoi Katsuro , Mitsuishi Yasushi
Published: January 2004

A novel xyloglucan‐specific endo‐β‐1,4‐glucanase (XEG), xyloglucanase, with a molecular mass of 80 kDa and a pI of 4.8, was isolated from the fungus Geotrichum sp. M128. It was found to be an endoglucanase active toward xyloglucan and not active toward carboxymethylcellulose, Avicel, or barley 1,3‐1,4‐β‐glucan. Analysis of the precise substrate specificity using various xyloglucan oligosaccharide structures revealed that XEG has at least four subsites (−2 to +2) and specifically recognizes xylose branching at the +1 and +2 sites. The full‐length cDNA encoding XEG was cloned and sequenced. It consists of a 2436‐bp open reading frame encoding a 776‐amino acid protein. From its deduced amino acid sequence, XEG can be classified as a family 74 glycosyl hydrolase. The cDNA encoding XEG was then expressed in Escherichia coli, and enzymatically active recombinant XEG was obtained.
Antiviral activity of caspase inhibitors: effect on picornaviral 2A proteinase
Authors: Deszcz Luiza , Seipelt Joachim , Vassilieva Elena , Roetzer Andreas , Kuechler Ernst
Published: January 2004

Peptide‐based fluoromethyl ketones have been considered for many years to be highly specific caspase inhibitors distinctly blocking the progress of apoptosis in a variety of systems. Here we demonstrate that these compounds can significantly reduce rhinovirus multiplication in cell culture. In their methylated forms they block eIF4GI cleavage in vivo and in vitro and inhibit the activity of picornaviral 2A proteinases.
Mitochondrial permeability transition induced by reactive oxygen species is independent of cholesterol‐regulated membrane fluidity
Authors: Colell Anna , Garcı́a-Ruiz Carmen , Mari Montserrat , Fernández-Checa José C
Published: January 2004

Cholesterol enrichment of rat liver mitochondria (CHM) impairs atractyloside‐induced mitochondrial permeability transition (MPT) due to decreased membrane fluidity. In this study we addressed the effect of cholesterol enrichment on MPT induced by reactive oxygen species (ROS). Superoxide anion generated by xanthine plus xanthine oxidase triggered mitochondrial swelling and cytochrome c release in CHM, which was prevented by butylated hydroxytoluene, an anti‐voltage‐dependent anion channel antibody, or cyclosporin A. Furthermore, hydrogen peroxide generated by the combination of ganglioside GD3 and mitochondrial GSH depletion elicited mitochondrial swelling and release of cytochrome c, Smac/Diablo and apoptosis‐inducing factor in control mitochondria and CHM. Thus, ROS induce MPT and apoptosome activation regardless of decreased mitochondrial membrane dynamics due to cholesterol enrichment.
I Wanna Be Your Man: Suzi Quatro's musical androgyny
Authors: AUSLANDER PHILIP
Published: January 2004

As a woman who performs rock music in an unabashedly ‘masculine’ fashion, Suzi Quatro is often criticised for trying to be ‘one of the boys’. Through close examinations of Quatro's performance strategies, including her repertoire, physical performance and vocal presence, I hope to show that Quatro's performances of gender and sexual identity on sound recordings and video belie such an uncomplicated characterisation. Focusing particularly on Quatro's ability to construct multiple subject positions that are ambiguous or mutually contradictory with respect to gender and sexuality, I shall argue that the role of female cock-rocker, as she performs it, is a paradoxical one that destabilises the gender codings from which it is constructed and celebrates the polymorphousness and performativity of identity.
The music industry, technology and utopia – an exchange between Marcus Breen and Eamonn Forde
Authors: BREEN MARCUS
Published: January 2004

A new struggle has emerged within popular music. This struggle is about technology and access to music through computer-mediated technology. Somewhat typical of the state of cultural things being more complex in their multiple articulations, this struggle runs in tandem with the historical struggle by youth for ‘their music’ against that of previous generations. The multiple characteristics of the struggle over cultural production, ownership and circulation represents a change from earlier days when pop music was articulated to youth culture and social movements, offering relatively direct relationships from one to another. (For example, ‘The Sixties’ became the shorthand reference for these cultural formations.) That relationship still exists, albeit in a self-conscious historical sense that requires continuous examination as it changes with the new generations of youth and the available technologies.
Drag, camp and gender subversion in the music and videos of Annie Lennox
Authors: RODGER GILLIAN
Published: January 2004

In this article I examine Lennox's earliest performance strategies, and her reasons for employing them, as well as some of the reactions to her adoption of transvestism as a sartorial style. I discuss three videos from Lennox's 1988 LP Savage, which, in my view, marked a radical shift in her approach to depicting gender through performance. I argue that Lennox may be more productively viewed by keeping in mind performance ideals of music hall and other popular musical theatre styles of the late nineteenth and early twentieth centuries. Finally I discuss Lennox's challenge to late twentieth-century gender construction using Judith Butler's theories of the performative nature of gender and of the subversive reiteration of gender, outlined in her books Gender Trouble and Bodies that Matter, and suggesting ways in which Lennox's performance embodies these theories, while extending them to include a broader range of sexualities.
PICKING CLUMPY ORDERS ON A CAROUSEL
Authors: Wan Yat-wah , Wolff Ronald W.
Published: January 2004

Carousels are rotatable closed-loop storage systems for small items,
where items are stored in bins along the loop. An order at a carousel
consists of (say) n different items stored there. We analyze
two problems: (1) minimizing the total time to fill an order (travel
time) and (2) order delays as they arrive, are filled, and depart. We
define clumpy orders and the nearest-end-point heuristic
(NEPH) for picking them. We determine conditions for NEPH to be optimal
for problem (1), and under a weak stochastic assumption, we derive the
distribution of travel time. We compare NEPH with the nearest-item
heuristic. Under Poisson arrivals and assumptions much weaker than in
the literature, we show that problem (2) may be modeled as an
M/G/1 queue.
STABILITY CONDITIONS FOR GATED
M/G/∞ QUEUES
Authors: Pinotsi Dimitra , Zazanis Michael A.
Published: January 2004

The question of stability for the
M/G/∞ queue with gated service is
investigated using a Foster–Lyapunov drift criterion. The
necessary and sufficient condition for positive recurrence is shown to
be the finiteness of the first moment of the service time distribution,
thus weakening the stability condition given in Browne et al.
[3].
STOCHASTIC DIFFERENTIAL EQUATION FOR TCP WINDOW SIZE: ANALYSIS AND EXPERIMENTAL VALIDATION
Authors: Budhiraja A. , Hernández-Campos F. , Kulkarni V. G. , Smith F. D.
Published: January 2004

In this paper we develop a stochastic differential equation to describe the dynamic evolution of the congestion window size of a single TCP session over a network. The model takes into account recovery from packet losses with both fast recovery and time-outs, boundary behavior at zero and maximum window size, and slow-start after time-outs. We solve the differential equation to derive the distribution of the window size in steady state. We compare the model predictions with the output from the NS simulator.
A model of high-frequency oscillatory potentials in retinal
ganglion cells
Authors: KENYON GARRETT T. , MOORE BARTLETT , JEFFS JANELLE , DENNING KATE S. , STEPHENS GREG J. , TRAVIS BRYAN J. , GEORGE JOHN S. , THEILER JAMES , MARSHAK DAVID W.
Published: January 2004

High-frequency oscillatory potentials (HFOPs) have been recorded from
ganglion cells in cat, rabbit, frog, and mudpuppy retina and in
electroretinograms (ERGs) from humans and other primates. However, the
origin of HFOPs is unknown. Based on patterns of tracer coupling, we
hypothesized that HFOPs could be generated, in part, by negative
feedback from axon-bearing amacrine cells excited via
electrical synapses with neighboring ganglion cells. Computer
simulations were used to determine whether such axon-mediated feedback
was consistent with the experimentally observed properties of HFOPs.
(1) Periodic signals are typically absent from ganglion cell PSTHs, in
part because the phases of retinal HFOPs vary randomly over time and
are only weakly stimulus locked. In the retinal model, this phase
variability resulted from the nonlinear properties of axon-mediated
feedback in combination with synaptic noise. (2) HFOPs increase as a
function of stimulus size up to several times the receptive-field
center diameter. In the model, axon-mediated feedback pooled signals
over a large retinal area, producing HFOPs that were similarly size
dependent. (3) HFOPs are stimulus specific. In the model, gap junctions
between neighboring neurons caused contiguous regions to become phase
locked, but did not synchronize separate regions. Model-generated HFOPs
were consistent with the receptive-field center dynamics and spatial
organization of cat alpha cells. HFOPs did not depend qualitatively on
the exact value of any model parameter or on the numerical precision of
the integration method. We conclude that HFOPs could be mediated, in
part, by circuitry consistent with known retinal anatomy.
Chromatic detection and discrimination in the periphery: A
postreceptoral loss of color sensitivity
Authors: NEWTON JESSICA R. , ESKEW RHEA T.
Published: January 2004

The peripheral visual field is marked by a deterioration in color
sensitivity, sometimes attributed to the random wiring of midget
bipolar cells to cone photoreceptors in the peripheral retina (Mullen, 1991; Mullen &
Kingdom, 1996). Using psychophysical methods, we explored
differences in the sensitivity of peripheral color mechanisms with
detection and discrimination of 2-deg spots at 18-deg eccentricity, and
find evidence for a postreceptoral locus for the observed loss in
sensitivity. As shown before, observers' sensitivity to green was
lower than to red in the periphery, although the magnitude of this
effect differed across observers. These results suggest that the
asymmetry in peripheral sensitivity occurs at a postreceptoral site,
possibly a cortical one. In addition, noise masking was used to
determine the cone inputs to the peripheral color mechanisms. The
masked detection contours indicate that the red and green mechanisms in
the periphery respond to the linear difference of approximately equally
weighted L- and M-cone contrasts, just as they do in the fovea. Thus,
if the midget retinal ganglion system is responsible for red/green
color perception in the fovea, it is likely to be responsible at 18-deg
eccentricity as well.
Visual resolution with epi-retinal electrical stimulation estimated
from activation profiles in cat visual cortex
Authors: WILMS MARCUS , EGER MARCUS , SCHANZE THOMAS , ECKHORN[dagger] REINHARD
Published: January 2004

Blinds with receptor degeneration can perceive localized phosphenes
in response to focal electrical epi-retinal stimuli. To avoid extensive
basic stimulation tests in human patients, we developed techniques for
estimating visual spatial resolution in anesthetized cats. Electrical
epi-retinal and visual stimulation was combined with multiple-site
retinal and cortical microelectrode recordings of local field
potentials (LFPs) from visual areas 17 and 18. Classical visual
receptive fields were characterized for retinal and cortical recording
sites using multifocal visual stimulation combined with
stimulus–response cross-correlation. We estimated visual spatial
resolution from the size of the cortical activation profiles in
response to single focal stimuli. For comparison, we determined
activation profiles in response to visual stimuli at the same retinal
location. Activation profiles were single peaked or multipeaked. In
multipeaked profiles, the peak locations coincided with discontinuities
in cortical retinotopy. Location and width of cortical activation
profiles were distinct for retinal stimulation sites. On average, the
activation profiles had a size of 1.28 ± 0.03 mm cortex.
Projected to visual space this corresponds to a spatial resolution of
1.49 deg ± 0.04 deg visual angle. Best resolutions were 0.5 deg
at low and medium stimulation currents corresponding to a visus of
1/30. Higher stimulation currents caused lower spatial, but higher
temporal resolution (up to 70 stimuli/s). In analogy to the
receptive-field concept in visual space, we defined and characterized
electrical receptive fields. As our estimates of visual resolutions are
conservative, we assume that a visual prosthesis will induce phosphenes
at least at this resolution. This would enable visuomotor coordinations
and object recognition in many indoor and outdoor situations of daily
life.
Speaking My Mind: Just Another Hand-Me-Down? From Hand to Mouth:
The Origins of Language, by Michael C. Corballis. 2002. Princeton, NJ:
Princeton University Press. 272 pp., $27.95.
Authors: Hellige Joseph B.
Published: January 2004

In From Hand to Mouth: The Origins of Language Michael
Corballis provides an engaging, highly readable and provocative account
of the evolution of human language. The primary thesis of his book is
that language evolved from manual and facial gestures rather than from
animal vocalizations, as is often assumed. While this point of view has
been expressed by others during the last few centuries (for example,
Condillac in 1747), it has never been argued more forcefully and with
as much supporting scholarly evidence. (I suspect that it has also
never been argued with greater use of hand/mouth adages,
clichés and puns.) Among the more provocative ideas is the
suggestion that human speech, like writing, was a cultural invention
subsequent to gestural language rather than the evolutionary essence of
language.
Olfaction and the Brain. Olfaction, Taste, and Cognition.
C. Rouby, B. Schaal, D. Doubois, R. Gervais, and A. Holley (Eds.). 2002.
Cambridge, UK: Cambridge University Press. 462 pp., $95.00.
Authors: Doty Richard L.
Published: January 2004

This 27-chapter volume arose from a symposium held in Lyon, France,
in June of 1999, that sought to integrate information from academic
scientific studies of olfaction, largely psychological in nature, with
knowledge derived from the perfume industry. It is dedicated to the
French perfumer Edmond Roudnitska, known for creating such classic
fragrances as “Femme” (1944, Rochas), “Diorama”
(1948, Dior), L'Eau” (1951, Hermès),
“Diorissimo” (1956, Dior), “Eau Savage” (1966,
Dior), and “Diorella” (1972, Dior), and addresses such
topics as odor classification, odor memory, odor conditioning, and the
plasticity of chemosensation.
Predictors of postconcussion symptom complex in community dwelling
male veterans
Authors: LUIS CHERYL A. , VANDERPLOEG RODNEY D. , CURTISS GLENN
Published: January 2004

The presence of a persistent postconcussion symptom complex (PPCSC)
was examined in a non-referred sample of male veterans with a history
of mild head injury and a comparison group without a history of head
injury. Hierarchical logistic regression procedures were used to
determine possible predictors of PPCSC using variables supported by
previous research (i.e., preexisting psychiatric difficulties,
demographic and social support variables, and history of an accidental
injurious event). Although PPCSC was common in all groups (23% of the
total sample), a significantly greater proportion of individuals in the
mild head injury with loss of consciousness group (37.2%) had PPCSC
compared with three other groups (head injury without loss of
consciousness = 26.1%; motor vehicle accident without head injury =
23%; and control = 17.3%). However, the most salient predictors of
PPCSC were early life psychiatric difficulties such as anxiety or
depression, limited social support, lower intelligence, and
interactions among these variables. The predictive value of loss of
consciousness was significant, but low (1.4% of unique variance). The
findings provide support for the premise that PPCSC is mediated in part
by individual resilience, preexisting psychological status, and
psychosocial support. (JINS, 2003, 9,
1001–1015.)
Learning in children and sleep disordered breathing: Findings of
the Tucson Children's Assessment of Sleep Apnea (TuCASA)
Prospective Cohort Study
Authors: KAEMINGK KRIS L. , PASVOGEL ALICE E. , GOODWIN JAMES L. , MULVANEY SHELAGH A. , MARTINEZ FERNANDA , ENRIGHT PAUL L. , ROSEN GERALD M. , MORGAN WAYNE J. , FREGOSI RALPH F. , QUAN STUART F.
Published: January 2004

We examined the relationship between nocturnal respiratory
disturbance and learning and compared learning in children with and
without nocturnal respiratory disturbance. Subjects were 149
participants in a prospective cohort study examining sleep in children
ages 6–12: The Tucson Children's Assessment of Sleep Apnea
study (TuCASA). Sleep was assessed via home polysomnography.
Intelligence, learning and memory, and academic achievement were
assessed. Parents rated attention. Group comparisons were used to test
the hypothesis that the group with an apnea/hypopnea index (AHI) of
5 or more (n = 77) would have weaker performance than the
group with AHI less than 5 (n = 72). The group with AHI of 5
or more had weaker learning and memory though differences between
groups decreased when arousals were taken into account. There was a
greater percentage of Stage 1 sleep in the AHI 5 or more group, and
Stage 1 percentage was negatively related to learning and memory in the
sample (n = 149). There were negative relationships between
AHI and immediate recall, Full Scale IQ, Performance IQ, and math
achievement. Hypoxemia was associated with lower Performance IQ. Thus,
findings suggest that nocturnal respiratory disturbance is associated
with decreased learning in otherwise healthy children, that sleep
fragmentation adversely impacts learning and memory, and that hypoxemia
adversely influences nonverbal skills. (JINS, 2003,
9, 1016–1026.)
Subcortical functions in cognition: Toward a consensus
Authors: CROSSON BRUCE , HAALAND KATHLEEN Y.
Published: January 2004

Behavioral neurologists and neuropsychologists have debated the role
of the thalamus and basal ganglia in cognition and behavior for more
than a century (e.g., Bucy, 1942; Marie, 1906; Penfield &
Roberts, 1959; Wernicke, 1874). However,
over these 100-plus years, there is little consensus regarding whether or
how these structures contribute to cognition. Fortunately, recent research
findings are rapidly changing this state of affairs. It is now obvious
we will not understand how the brain controls complex activities until
we understand the contribution of these deep brain structures. In
healthy and brain-damaged individuals, application of methodologies
such as semantic priming, event related potentials, and functional
neuroimaging to the question of subcortical functions is beginning to
resolve this conundrum. This symposium demonstrates the utility of
combining these different approaches. It features empirical work from
six laboratories that have engaged in systematic inquiries regarding
the role of the thalamus and basal ganglia in cognition. This body of
work represents both new directions and convergence of recent findings
in the quest to integrate our understanding of this complex issue.
Neural hybrid model of semantic object memory: Implications from
event-related timing using fMRI
Authors: KRAUT MICHAEL A. , CALHOUN VINCE , PITCOCK JEFFERY A. , CUSICK CATHERINE , HART JOHN
Published: January 2004

Previous studies by our group have demonstrated fMRI signal changes
and synchronized gamma rhythm EEG oscillations between thalamus and
cortical regions as subjects recall objects from visually presented
features. Here, we extend this work by estimating the time course of
fMRI signal changes in the cortical and subcortical regions found to
exhibit evidence for task-related activation. Our results indicate that
there are separate loci of signal changes in the thalamus (dorsomedial
and pulvinar) that exhibit notable differences in times of onset, peak
and return to baseline of signal changes. The signal changes in the
pulvinar demonstrate the slowest transients of all the cortical and
subcortical regions we examined. Evaluation of cortical regions
demonstrated salient differences as well, with the signal changes in
Brodmann area 6 (BA6) rising, peaking, and returning to baseline
earlier than those detected in other regions. We conclude that BA6
mediates early designation or refinement of search criteria, and that
the pulvinar may be involved in the binding of feature stimuli for an
integrated object memory. (JINS, 2003, 9,
1031–1040.)
The basal ganglia and semantic engagement: Potential insights from semantic priming in individuals with subcortical vascular lesions, Parkinson's disease, and cortical lesions
Authors: COPLAND DAVID
Published: January 2004

The impact of basal ganglia dysfunction on semantic processing was investigated by comparing the performance of individuals with nonthalamic subcortical (NS) vascular lesions, Parkinson's disease (PD), cortical lesions, and matched controls on a semantic priming task. Unequibiased lexical ambiguity primes were used in auditory prime-target pairs comprising 4 critical conditions; dominant related (e.g.,bank–money), subordinate related (e.g.,bank–river), dominant unrelated (e.g.,foot–money) and subordinate unrelated (e.g.,bat–river). Participants made speeded lexical decisions (word/nonword) on targets using a go–no-go response. When a short prime–target interstimulus interval (ISI) of 200 ms was employed, all groups demonstrated priming for dominant and subordinate conditions, indicating nonselective meaning facilitation and intact automatic lexical processing. Differences emerged at the long ISI (1250 ms), where control and cortical lesion participants evidenced selective facilitation of the dominant meaning, whereas NS and PD groups demonstrated a protracted period of nonselective meaning facilitation. This finding suggests a circumscribed deficit in the selective attentional engagement of the semantic network on the basis of meaning frequency, possibly implicating a disturbance of frontal–subcortical systems influencing inhibitory semantic mechanisms. (JINS, 2003,9, 1041–1052.)
A Quantitative Nanodiffraction System for Ultrahigh Vacuum Scanning
Transmission Electron Microscopy
Authors: Hembree Gary G. , Koch Christoph , Spence John C.H.
Published: January 2004

Of all the long-lived particles available as probes of condensed
matter, and of all the signals available on a modern electron
microscope, electron nanodiffraction patterns provide the strongest
signal from the smallest volume. The technique is therefore perfectly
suited to nanostructural investigations in inorganic chemistry and
materials science. The Vacuum Generators HB501S, an ultrahigh vacuum
(UHV) variant of the HB501 scanning transmission electron microscope
(STEM), with side-entry double-tilt stage, specimen preparation and
analysis chamber, three postspecimen lenses, and cold field-emission
tip with integral magnetic gun lens, has therefore been modified to
optimize nanodiffraction and quantitative convergent beam electron
diffraction (QCBED) performance. A one-micrometer grain-size phosphor
screen lying on a fiber-optic faceplate atop the instrument is
fiber-optically coupled to a 2048 × 2048 charge-coupled device
(CCD), 16-bit camera. This arrangement promises to provide much greater
sensitivity, larger dynamic range, and a better modulation transfer
function (MTF) than conventional single crystal scintillator (YAG) CCD
systems, with noticeable absence of cross talk between pixels. The
design of the nanodiffraction detector system is discussed, the gain of
the detector is measured, the spherical aberration constant of the
objective lens is measured by the Ronchigram method, and preliminary
results from the modified instrument are shown.
A Combination Method of Charge Density Measurement in Hard
Materials Using Accurate, Quantitative Electron and X-ray Diffraction:
The α-Al2O3 Case
Authors: Streltsov Victor A. , Nakashima Philip N.H. , Johnson Andrew W.S.
Published: January 2004

Current X-ray diffraction techniques intended for “ideally
imperfect” specimens provide structure factors only on a relative
scale and ever-present multiple scattering in strong low-angle Bragg
reflections is difficult to correct. Multiple scattering is implicit in
the quantitative convergent beam electron diffraction (QCBED) method,
which provides absolutely scaled structure factors. Conventional single
crystal X-ray diffraction has proved adequate in softer materials where
crystal perfection is limited. In hard materials, the highly perfect
nature of the crystals is often a difficulty, due to the inadequacy of
the conventional corrections for multiple scattering (extinction
corrections). The present study on α-Al2O3
exploits the complementarity of synchrotron X-ray measurements for weak
and medium intensities and QCBED measurement of the strong low-angle
reflections. Two-dimensional near zone axis QCBED data from different
crystals at various accelerating voltages, thicknesses, and
orientations have been matched using Bloch-wave and multislice methods.
The reproducibility of QCBED data is better than 0.5%. The low-angle
strong QCBED structure factors were combined with middle and high-angle
extinction-free data from synchrotron X-ray diffraction measurements.
Static deformation charge density maps for
α-Al2O3 have been calculated from a multipole
expansion model refined using the combined QCBED and X-ray data.
Introduction: A Special Issue on Electron Diffraction
Authors: Spence John C.H.
Published: January 2004

This special issue of Microscopy and Microanalysis explores
quantitative electron diffraction from nonbiological materials. Jim
Turner and I have put many hours of work into bringing it together, and
we thank the authors for their fine contributions. The articles cover a
wide range of materials and techniques, from convergent-beam electron
diffraction (CBED) to the new Kohler SAD mode, as well as the use of
direct methods, the study of diffuse elastic scattering from defects,
strain measurement, and multiwavelength methods. We were sorry that we
could not obtain recent work using the precession electron diffraction
camera by our deadline, but readers should be aware of that promising
method also.
Scanning Electron Microscopy and X-Ray Microanalysis.
J. Goldstein, D. Newbury, D. Joy, C, Lyman, P. Echlin, E. Lifshin,
L. Sawyer, and J. Michael. Kluwer Academic, Plenum Publishers, New York;
2003, 688 pages (Hardback, $75.00) ISBN 0-306-47292-9
Authors: Burany Sandy
Published: January 2004

It is a pleasure to review the third edition of Scanning Electron
Microscopy and X-Ray Microanalysis. The 15 chapter book can be
divided into three sections: (1) scanning electron microscopy, (2)
X-ray microanalysis, and (3) specimen preparation.
Besser als ..., schlechter als ...
Authors: Dickhäuser Oliver , Galfe Eva
Published: January 2004

Zusammenfassung. Soziale, dimensionale und temporale Vergleichsprozesse stellen vermittelnde Mechanismen zwischen erbrachter Leistung und dem Fähigkeitsselbstkonzept (FSK) dar. Die vorliegende Arbeit überprüft den Zusammenhang zwischen Vergleichsprozessen und dem mathematischen FSK im Grundschulalter. Dabei wird berücksichtigt, ob die Leistung den Erwartungen der Schüler/-innen widerspricht. 379 Dritt- und Viertklässler wurden am Tag vor einer Mathematikarbeit zu ihrer Notenerwartung und zu ihrem mathematischen FSK befragt. Nach der Rückgabe der benoteten Arbeit machten die Schüler Angaben zu den Vergleichsprozessen sowie erneut zum FSK. Wie erwartet zeigte sich, dass Vergleiche mit besseren Mitschülern (soziale Aufwärtsvergleiche) negative Auswirkungen auf das FSK haben, soziale Abwärtsvergleiche dagegen positive. Trotz der negativen Konsequenzen sozialer Aufwärtsvergleiche werden diese gegenüber Abwärtsvergleichen bevorzugt, insbesondere, wenn die Leistung schlechter als erwartet ausfiel. Dimensionale und temporale Vergleiche haben den Befunden zufolge keine Effekte auf das FSK.