bluuebunny/crossref_metadata_2025 huggingface dataset:
Memory characteristics of Pt nanocrystals self-assembledfrom reduction of an embedded PtOx ultrathin film in metal-oxide-semiconductor structures
Authors: Tseng Jiun-Yi , Cheng Cheng-Wei , Wang Sheng-Yu , Wu Tai-Bor , Hsieh Kuang-Yeu , Liu Rich
Published: September 2004

The nonvolatile memory characteristics of metal-oxide-semiconductor structures containing Pt nanocrystals in SiO2 gate oxide were studied. The Pt nanocrystals of 2–3nm in diameter were self-assembled from reduction of an ultrathin PtOx layer embedded in the SiO2 by vacuum annealing at 425°C. A large hysteresis loop was found in the capacitance–voltage (C–V) relation indicating this significant memory effect. However, two different charge storage mechanisms were found for the Pt nanocrystals in devices with different tunnel oxide thickness. A counterclockwise C–V hysteresis was induced from substrate injection for the devices made with a thin tunnel oxide layer 2.5–5.0nm thick. Contrast, a clockwise behavior attributed to the electron transfer from charged defects in the gate oxide was found for the devices having a tunnel oxide layer 7.5nm thick. The relatively stable memory characteristics of Pt nanocrystals resulted from substrate injection were also demonstrated.
Generation of atomic hydrogen during radio-frequency nitrogenplasma-assisted gas-source molecular-beam epitaxy of III-V dilute nitrides
Authors: Fotkatzikis A. , Pinault M.-A. , Freundlich A.
Published: September 2004

The interaction of a typical gas-source molecular-beam epitaxy (GSMBE) environment with a radio-frequency (RF) nitrogen plasma source is investigated. In particular, a real-time in situ analysis of the evolution of the emission spectrum of an RF nitrogen plasma source, under high partial pressures of hydrogen (∼10−5Torr), is presented. Hydrogen, emanating from the decomposition of hydride precursors in GSMBE, results in the appearance of a sharp emission peak at the region of 656nm in the plasma spectrum, suggesting the generation of atomic hydrogen species in the nitrogen plasma cavity. The intensity of this peak is used for a qualitative evaluation of this interaction and its evolution as a function of the RF nitrogen plasma source conditions is investigated.
Anisotropic dielectric properties in epitaxial Bi3.25La0.75Ti3O12 thin films along different crystal directions
Authors: Lee Jang-Sik , Kang B. S. , Lin Y. , Li Y. , Jia Q. X.
Published: September 2004

Epitaxial (001)-oriented Bi3.25La0.75Ti3O12 (BLT) thin films were grown by pulsed-laser deposition on (001) LaAlO3 single-crystal substrates. The dielectric properties of the BLT films are highly anisotropic along different crystal directions. The dielectric constants are 358 and 160 along [100] and [11¯0], respectively. Dielectric nonlinearity is also detected along these crystal directions. On the other hand, a much smaller dielectric constant and no detectable dielectric nonlinearity in a field range of 0–200kV∕cm are observed for a film along [001] where c-axis oriented SrRuO3 is used as the bottom electrode.
Cantilever effects on electrostatic force gradient microscopy
Authors: Sacha G. M. , Sáenz J. J.
Published: September 2004

The effects of the cantilever on electrostatic force microscopy are discussed. Numerical calculations of the electrostatic potential distribution and force gradient for typical experimental geometries are presented. A simple analytical relation between the calculated force gradients with and without cantilever is found. The main effect of the cantilever is to reduce the electric field in the tip–sample gap and, as a consequence, the force gradient can be strongly reduced. This effect can be very important for dielectric films while it can be neglected for metallic samples.
Distant clock synchronization using entangled photon pairs
Authors: Valencia Alejandra , Scarcelli Giuliano , Shih Yanhua
Published: September 2004

We report a proof-of-principle experiment on distant clock synchronization. Besides the achievement of picosecond resolution at 3km distance, this experiment demonstrated a concept for high-accuracy nonlocal timing and positioning based on the quantum feature of entangled states.
The thermo-optic effect of Si nanocrystals in silicon-rich silicon oxidethin films
Authors: Seo Se-Young , Lee Jinku , Shin Jung H. , Kang Eun-Seok , Bae Byeong-Soo
Published: September 2004

The thermo-optic effect of Si nanocrystals in silicon-rich silicon oxide (SRSO) thin films at 1530nm is investigated. SRSO thin films, which consist of nanocrystal Si (nc-Si) embedded inside the SiO2 matrix, were prepared by electron-cyclotron-resonance plasma-enhanced chemical vapor deposition of SiH4 and O2 followed by a 30min anneal at 1150°C. The refractive indices of all SRSO films increased with increasing temperature, with the thermo-optic coefficient increasing from 1.0to6.6×10−5K−1 as the Si content is increased from 37to45at.%. The thermo-optic coeffecients of nc-Si, obtained by correcting for the volume fraction of nc-Si, also increased with increasing Si content from 1to2.5×10−4K−1. The results indicate that the thermo-optic effect of nc-Si is size-dependent, and that it must be taken into account when interpreting the luminescence data from SRSO films with high density of nc-Si.
Generation of polarization-entangled photon pairs in 1550nm band by a fiber-optic two-photon interferometer
Authors: Yoshizawa Akio , Tsuchida Hidemi
Published: September 2004

Polarization-entangled photon pairs in a band around 1550nm are generated by use of a fiber-optic two-photon interferometer having two periodically poled lithium niobate waveguides. Coincidence measurements are adopted for feedback control, in order to suppress phase drifts in the state of entanglement. Two-photon interference with a visibility of ∼1 (after subtraction of accidental coincidences) is observed over an hour. The visibility including accidental coincidences is ∼0.77.
Epitaxial BiFeO3 thin films on Si
Authors: Wang J. , Zheng H. , Ma Z. , Prasertchoung S. , Wuttig M. , Droopad R. , Yu J. , Eisenbeiser K. , Ramesh R.
Published: September 2004

BiFeO 3 was studied as an alternative environmentally clean ferro/piezoelectric material. 200-nm-thick BiFeO3 films were grown on Si substrates with SrTiO3 as a template layer and SrRuO3 as bottom electrode. X-ray and transmission electron microscopy studies confirmed the epitaxial growth of the films. The spontaneous polarization of the films was ∼45μC∕cm2. Retention measurement up to several days showed no decay of polarization. A piezoelectric coefficient (d33) of ∼60pm∕V was observed, which is promising for applications in micro-electro-mechanical systems and actuators.
Formation of silicon-on-diamond by direct bonding of plasma-synthesized diamond-like carbon to silicon
Authors: Zhu Ming , Chu Paul K , Shi Xuejie , Wong Man , Liu Weili , Lin Chenglu
Published: September 2004

We propose to replace the buried SiO2 layer in silicon-on-insulator with a plasma synthesized diamond-like-carbon (DLC) thin film to mitigate the self-heating effects. The DLC films synthesized on silicon by a plasma immersion ion implantation & deposition process exhibit outstanding surface topography, and excellent insulating properties are maintained up to an annealing temperature of 900°C. Hence, the degree of graphitization in our DLC materials is insignificant during thin-film transistor processing and even in most annealing steps in conventional complementary metal oxide silicon processing. Using Si∕DLC direct bonding and the hydrogen-induced layer transfer method, a silicon-on-diamond structure has been fabricated. Cross-sectional high-resolution transmission electron microscopy reveals that the bonded interface is abrupt and the top Si layer exhibits nearly perfect single crystalline quality. A model is postulated to describe the reactions occurring at the interface during the annealing steps in Si-DLC wafer bonding.
Dual-frequency liquid crystal gels with submillisecond response time
Authors: Fan Yun-Hsing , Ren Hongwen , Liang Xiao , Lin Yi-Hsin , Wu Shin-Tson
Published: September 2004

Two types of gels using dual-frequency liquid crystal are demonstrated. The one using a homogeneous cell shows anisotropic scattering behavior while the other prepared using a cell without polyimide alignment layers exhibits isotropic scattering properties. Both liquid crystal gels are highly transparent in the voltage-off state. Light scattering occurs when a high frequency voltage is applied. The isotropic gel exhibits a high contrast ratio and submillisecond response time. Potential applications of these gels for switchable polarizer, telecom optical switch, and reflective displays are emphasized.
Micropatterned epitaxial (Pb,La)(Zr,Ti)O3 thin films on Nb-doped SrTiO3 substrates by a chemical solution deposition processwith resist molds
Authors: Aoki Tsuyoshi , Kuwabara Makoto , Kondo Masao , Tsukada Mineharu , Kurihara Kazuaki , Kamehara Nobuo
Published: September 2004

Arrays of lead lanthanum zirconate titanate pillars were fabricated on niobium-doped (001) strontium titanate substrates using a chemical solution deposition method with resist molds. Periodic arrays of submicron ferroelectric pillars with high crystallinity are required to produce high-quality tunable photonic-crystal devices. The relationship between the crystallinity and width of the pillars was investigated. The highest crystallinity was obtained at a width of 0.67μm. All the pillars exhibited ferroelectric strain. Since this width is in the order of that of optical wavelengths, this process and the periodic structures produced have potential applications in fabricating two-dimensional tunable photonic crystals.
Scanning near–field photoluminescence mapping of (110) InAs-GaAs self-assembled quantum dots
Authors: Hadjipanayi M. , Maciel A. C. , Ryan J. F. , Wasserman D. , Lyon S. A.
Published: September 2004

We report low-temperature near-field optical measurements of single InAs quantum dots formed by self-assembled growth on (110) GaAs substrates. We have measured the distribution of dots by photoluminescence mapping and obtain a value ∼2×108cm−2, two orders of magnitude smaller than typical densities obtained in (100) growth. The appearance of additional lines in the spectrum at high excitation energies is consistent with the formation of biexciton and charged exciton states. These results establish the feasibility of quantum dot-based optical devices based on (110) GaAs quantum structures.
Phase separation and magnetic properties of Nd60Fe30Al10 thin films
Authors: Bracchi A. , Samwer K. , Niermann T. , Seibt M. , Schneider S.
Published: September 2004

In this letter we report results of the investigation of Nd60Fe30Al10 thin films prepared by electron-beam evaporation and studied by analytical transmission electron microscopy, x-ray diffraction, and magnetometry. Structural and magnetic characterizations show the existence of an amorphous matrix, which embeds a second glassy phase. The observed microstructure confirms the tendency of the Nd60Fe30Al10 system to show phase separation and to form an intrinsic composite as previously reported for slow-cooled bulk samples of the same composition. The magnetic properties of the thin films prepared with high cooling rate are discussed, taking into account magnetic pinning effects of the main magnetic phase.
Room temperature nanofabrication of atomically registeredheteromolecular organosilicon nanostructures using multistepfeedback controlled lithography
Authors: Basu R. , Guisinger N. P. , Greene M. E. , Hersam M. C.
Published: September 2004

Ultrahigh vacuum scanning tunneling microscopy is employed for the nanofabrication and characterization of atomically registered heteromolecular organosilicon nanostructures at room temperature. In the first fabrication step, feedback controlled lithography (FCL) is used to pattern individual 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) free radical molecules at opposite ends of the same dimer row on the Si(100)-2×1:H surface. In atomic registration with the first pattern, FCL is subsequently applied for the removal of a single hydrogen atom. The resulting dangling bond templates the spontaneous growth of a styrene chain that is oriented along the underlying dimer row. The styrene chain growth is bounded by the originally patterned TEMPO molecules, thus resulting in a heteromolecular organosilicon nanostructure. The demonstration of multistep FCL suggests that this approach can be widely used for fundamental studies and fabricating prototype devices that require atomically registered organic molecules mounted on silicon surfaces.
Identification of a major locus for age-related cortical cataract on chromosome 6p12-q12 in the Beaver Dam Eye Study
Authors: Iyengar Sudha K. , Klein Barbara E. K. , Klein Ronald , Jun Gyungah , Schick James H. , Millard Christopher , Liptak Rachel , Russo Karlie , Lee Kristine E. , Elston Robert C.
Published: September 2004

Age-related cataracts are one of the leading causes of visual impairment and blindness among the elderly worldwide. Among age-related cataracts, cortical opacities rank as the second most common type; however, little is known about their molecular pathogenesis or genetics. To identify susceptibility loci for cortical cataracts, we genotyped a subset of families (102 families;n= 224 sib pairs) from the Beaver Dam Eye Study and performed a model-free genome-wide linkage analysis for markers linked to a quantitative measure of cortical opacity. We obtained evidence for linkage at marker D1S1622 on chromosome 1p35 (P< 0.0002) and at marker D6S1053 on 6q12 (P< 0.00008) in the initial scan. Five additional regions on 1q31, 2p24, 2q11, 4q28, and 15q13 that are suggestive of linkage (P≤ 0.01 or logarithm of the likelihood ratio ≥ 1.18) were observed. The region on chromosomes 6p12-q12 was selected for fine mapping, and the intermarker distance was reduced to 3 cM by adding 11 markers in the interval between D6S1017 and D6S1021. After fine mapping, significant evidence of linkage remained on chromosome 6p12-q12 at D6S1053 (P< 0.00005). The current genome scan for age-related cortical cataracts may lead to identification of novel genes, because few regions identified in the current scan have previously been implicated in congenital or age-related cataracts.
Restoration of an absent G
1
arrest and protection from apoptosis in embryonic stem cells after ionizing radiation
Authors: Hong Yiling , Stambrook Peter J.
Published: September 2004

Response to DNA damage and cell-cycle regulation differ markedly between embryonic stem (ES) cells and somatic cells. ES cells require exquisitely sensitive mechanisms to maintain genomic integrity and do so, in part, by suppressing spontaneous mutation. Spontaneous mutation frequency in somatic cells is ≈10
-4
compared with 10
-6
for ES cells. ES cells also lack a G
1
checkpoint and are hypersensitive to IR and other DNA-damaging agents. These characteristics facilitate apoptosis and the removal of cells with a mutational burden from the population, thereby keeping the population free of damaged cells. Here, we identify signaling pathways that are compromised and lead to a natural absence of aG
1
arrest in ES cells after DNA damage. The affected pathways are those mediated by p53 and p21 and by ATM, Chk2, Cdc25A, and Cdk2. In ES cells, Chk2 kinase is not intranuclear as in somatic cells but is sequestered at centrosomes and is unavailable to phosphorylate Cdc25A phosphatase and cause its degradation. Although ectopic expression of Chk2 does not rescue the p53/p21 pathway, its expression is sufficient to allow it to phosphorylate Cdc25A, activate downstream targets, restore a G
1
arrest, and protect the cell from apoptosis.
Regulatory potential and control ofFoxp3expression in newborn CD4+T cells
Authors: Dujardin Helene C. , Burlen-Defranoux Odile , Boucontet Laurent , Vieira Paulo , Cumano Ana , Bandeira Antonio
Published: September 2004

Thymectomy at day 3 after birth leads to autoimmune disease in some genetic backgrounds. Disease is thought to be caused by the lack/paucity of regulatory T cells. We show that 3-day-old mice already contain a significant compartment ofFoxp3-expressing CD25+CD4+splenocytes. Whereas, in adult spleen, the subsets of regulatory T cells (CD25+and/or CD103+) express high amounts ofFoxp3mRNA, in 3-day-old mice, both thymic and splenic CD25+CD4+T cell subsets express lower amounts ofFoxp3mRNA, and CD103+cells are barely detected. In adult day 3-thymectomized mice, the CD25+CD4+T cell subset is overrepresented (most of the cells being CD103+) and expresses high amounts ofFoxp3mRNA, independent of the development of autoimmune gastritis. These cells control inflammatory bowel disease and the homeostatic expansion of lymphocytes. This study demonstrates that the peripheral immune system of newborn mice is endowed of a remarkable regulatory potential, which develops considerably in the absence of thymic supply.
Measuring single-molecule nucleic acid dynamics in solution by two-color filtered ratiometric fluorescence correlation spectroscopy
Authors: Li Haitao , Ren Xiaojun , Ying Liming , Balasubramanian Shankar , Klenerman David
Published: September 2004

This work presents a general method for determining single-molecule intramolecular dynamics in biomolecules by using a reporter fluorophore, whose fluorescence is quenched or partially quenched as a result of intramolecular motion, and a remote observer fluorophore. These fluorophores were excited independently with two different lasers, and the ratio of the two fluorophores' fluorescence was calculated. The time-varying ratio was then filtered to reduce contributions from molecules outside the overlapped laser volume and then correlated. The rates of opening and closing of a DNA hairpin were measured by using both fluorescence correlation spectroscopy and this method for comparison. We found at 50 pM, where molecules were studied one by one as they diffused through the probe volume, we obtained accurate opening and closing rates and could also measure dynamic heterogeneity. To demonstrate applicability to a more complex biological molecule we then probed intramolecular motions in the dimer of a human telomerase RNA fragment (hTR
380-444
), in the presence of an excess of monomer. The motion was found to occur on the time scale of 180-750 μs and slowed with increasing magnesium ion concentration. Blocking experiments using complementary oligonucleotides suggested that the motion involves substantial changes in dimer tertiary structure. This method appears to be a general method for selectively studying intramolecular motion in large biomolecules or complexes.
Systematic investigation of protein phase behavior with a microfluidic formulator
Authors: Hansen Carl L. , Sommer Morten O. A. , Quake Stephen R.
Published: September 2004

We demonstrated a microfluidic device for rapidly generating complex mixtures of 32 stock reagents in a 5-nl reactor. This “formulation chip” is fully automated and allows thousands of experiments to be performed in a single day with minimal reagent consumption. It was applied to systematically study the phase behavior of the protein xylanase over a large and complex chemical space. For each chemical formulation that demonstrated a pronounced effect on solubility, the protein phase behavior was completely mapped in the chip, generating a set of empirical phase diagrams. This
ab initio
phase information was used to devise a rational crystallization screen that resulted in 72-fold improvement in successful crystallization hits compared with conventional sparse matrix screens. This formulations tool allows a physics-based approach to protein crystallization that may prove useful in structural genomics efforts.
Distinct ontogenic and regional expressions of newly identified Cajal-Retzius cell-specific genes during neocorticogenesis
Authors: Yamazaki Hiroshi , Sekiguchi Mariko , Takamatsu Masako , Tanabe Yasuto , Nakanishi Shigetada
Published: September 2004

Cajal-Retzius (CR) cells are early-generated transient neurons and are important in the regulation of cortical neuronal migration and cortical laminar formation. Molecular entities characterizing the CR cell identity, however, remain largely elusive. We purified mouse cortical CR cells expressing GFP to homogeneity by fluorescence-activated cell sorting and examined a genomewide expression profile of cortical CR cells at embryonic and postnatal periods. We identified 49 genes that exceeded hybridization signals by >10-fold in CR cells compared with non-CR cells at embryonic day 13.5, postnatal day 2, or both. Among these CR cell-specific genes, 25 genes, including the CR cell marker genes such as the
reelin
and
calretinin
genes, are selectively and highly expressed in both embryonic and postnatal CR cells. These genes, which encode generic properties of CR cell specificity, are eminently characterized as modulatory composites of voltage-dependent calcium channels and sets of functionally related cellular components involved in cell migration, adhesion, and neurite extension. Five genes are highly expressed in CR cells at the early embryonic period and are rapidly down-regulated thereafter. Furthermore, some of these genes have been shown to mark two distinctly different focal regions corresponding to the CR cell origins. At the late prenatal and postnatal periods, 19 genes are selectively up-regulated in CR cells. These genes include functional molecules implicated in synaptic transmission and modulation. CR cells thus strikingly change their cellular phenotypes during cortical development and play a pivotal role in both corticogenesis and cortical circuit maturation.
Spatial memory, recognition memory, and the hippocampus
Authors: Broadbent Nicola J. , Squire Larry R. , Clark Robert E.
Published: September 2004

There is wide agreement that spatial memory is dependent on the integrity of the hippocampus, but the importance of the hippocampus for nonspatial tasks, including tasks of object recognition memory is not as clear. We examined the relationship between hippocampal lesion size and both spatial memory and object recognition memory in rats. Spatial memory was impaired after bilateral dorsal hippocampal lesions that encompassed 30-50% total volume, and as lesion size increased from 50% to ≈100% of total hippocampal volume, performance was similarly impaired. In contrast, object recognition was intact after dorsal hippocampal lesions that damaged 50-75% of total hippocampal volume and was impaired only after larger lesions that encompassed 75-100% of hippocampal volume. Last, ventral hippocampal lesions that encompassed ≈50% of total hippocampal volume impaired spatial memory but did not affect object recognition memory. These findings show that the hippocampus is important for both spatial memory and recognition memory. However, spatial memory performance requires more hippocampal tissue than does recognition memory.
Hormesis at the National Toxicology Program (NTP): Evidence of Hormetic Dose Responses in NTP Dose-Range Studies
Authors: Calabrese Edward J. , Baldwin Linda A.
Published: September 2004

The National Toxicology Program (NTP) dose-ranging studies typically employ five dosages and a concurrent control and are conducted for 2- and 13-week exposure periods. Because five doses are employed it suggested the possibilities of the occurrence of sub-NOAEL doses in many of these bioassays and of evaluating the occurrence of hormesis within the NTP bioassay. As a result, 59 environmentally relevant agents in the NTP toxicity database were assessed for their capacity to affect hormetic dose responses for growth as measured by change in weight gain. Hormetic effects were observed with 51 (88%) of the 58 agents evaluated. When considered by species, hormetic effects were observed in 48% (98/205) of bioassays involving mice and 14% (29/204) of bioassays involving rats. Hormetic effects were seen in a comparable fashion between males and females of both mice (i.e., 47 male and 51 female) and rats (13 male and 16 female rats). These observations represent a new finding within the NTP bioassay database that have potential implications for issues relating to study design and endpoint measured, as well as underlying biological mechanisms that affect efficiency of nutrient utilization under conditions of low-level toxicant exposure.
Biphasic Response of Ciprofloxacin in Human Fibroblast Cell Cultures
Authors: Hincal Filiz , Gürbay Aylin , Favier Alain
Published: September 2004

To investigate the possibility of the involvement of an oxidative stress induction in the mechanism of the cytotoxic effect of quinolone antibiotics, we examined the viability of human fibroblast cells exposed to ciprofloxacin (CPFX), and measured the levels of lipid peroxidation (LP), glutathione (GSH), and the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX). The data showed that the effect of CPFX on the viability of cells, as determined by neutral red uptake assay, was time-dependent, and the dose-response relation was biphasic. Cytotoxicity was not observed in the concentration range 5–150 mg/l CPFX when the cells were incubated for 24 h. In contrast, lower concentrations (5 and 12.5 mg/l) of CPFX increased the cell growth in all incubation periods tested. Marked decreases in the viability of fibroblasts were observed at concentrations 50 and 75 mg/l, and ⩾50 mg/l, following 48 and 72 h exposure, respectively ( p < 0.05). However, when the cells were exposed to >75 mg/l CPFX for 48 h, no cytotoxicity was observed. By exposing fibroblast cultures to 75 mg/l CPFX for 48 h, an induction of LP enhancement and a marked decrease in intracellular GSH were observed. Vitamin E pretreatment of the cells lowered the level of LP, increased the total GSH content, and provided significant protection against CPFX-induced cytotoxicity. The biphasic effect of CPFX possibly resulted from the complex dose-dependent relationships between reactive oxygen species (ROS), cell proliferation, and cell viability. It was previously reported, in fact, for several cell models that ROS exert a biphasic effect on cell growth. Furthermore, cultured fibroblasts release their own free radicals, and the inhibition of endogenous ROS inhibits the fibroblast cell proliferation, whereas the effect of exogenous ROS is biphasic.
Mathematical Modeling of Allelopathy. III. A Model for Curve-Fitting Allelochemical Dose Responses
Authors: Liu De Li , An Min , Johnson Ian R. , Lovett John V.
Published: September 2004

Bioassay techniques are often used to study the effects of allelochemicals on plant processes, and it is generally observed that the processes are stimulated at low allelochemical concentrations and inhibited as the concentrations increase. A simple empirical model is presented to analyze this type of response. The stimulation-inhibition properties of allelochemical-dose responses can be described by the parameters in the model. The indices, p% reductions, are calculated to assess the allelochemical effects. The model is compared with experimental data for the response of lettuce seedling growth to Centaurepensin, the olfactory response of weevil larvae to α-terpineol, and the responses of annual ryegrass ( Lolium multiflorum Lam.), creeping red fescue ( Festuca rubra L., cv. Ensylva), Kentucky bluegrass ( Poa pratensis L., cv. Kenblue), perennial ryegrass ( L. perenne L., cv. Manhattan), and Rebel tall fescue ( F. arundinacea Schreb) seedling growth to leachates of Rebel and Kentucky 31 tall fescue. The results show that the model gives a good description to observations and can be used to fit a wide range of dose responses. Assessments of the effects of leachates of Rebel and Kentucky 31 tall fescue clearly differentiate the properties of the allelopathic sources and the relative sensitivities of indicators such as the length of root and leaf.
Mechanistic Basis for Nonlinear Dose-Response Relationships for Low-Dose Radiation-Induced Stochastic Effects
Authors: Scott Bobby R. , Walker Dale M. , Tesfaigzi Yohannes , Schöllnberger Helmut , Walker Vernon
Published: September 2004

The linear nonthreshold (LNT) model plays a central role in low-dose radiation risk assessment for humans. With the LNT model, any radiation exposure is assumed to increase one's risk of cancer. Based on the LNT model, others have predicted tens of thousands of deaths related to environmental exposure to radioactive material from nuclear accidents ( e.g., Chernobyl) and fallout from nuclear weapons testing. Here, we introduce a mechanism-based model for low-dose, radiation-induced, stochastic effects (genomic instability, apoptosis, mutations, neoplastic transformation) that leads to a LNT relationship between the risk for neoplastic transformation and dose only in special cases. It is shown that nonlinear dose-response relationships for risk of stochastic effects (problematic nonlethal mutations, neoplastic transformation) should be expected based on known biological mechanisms. Further, for low-dose, low-dose rate, low-LET radiation, large thresholds may exist for cancer induction. We summarize previously published data demonstrating large thresholds for cancer induction. We also provide evidence for low-dose-radiation-induced, protection (assumed via apoptosis) from neoplastic transformation. We speculate based on work of others ( Chung 2002 ) that such protection may also be induced to operate on existing cancer cells and may be amplified by apoptosis-inducing agents such as dietary isothiocyanates.
Diagnosis and Management of Post‐Traumatic Vertigo
Authors: Marzo Sam J. , Leonetti John P. , Raffin Michael J. , Letarte Peter
Published: September 2004

Objectives/Hypothesis: Patients with post‐traumatic vertigo can be difficult to treat secondary to the chronicity of their symptoms. Patients can have peripheral, central, and combined vestibular deficits. Furthermore, no comprehensive guidelines exist for returning these patients to work. The objectives of the study were to discuss diagnosis, management techniques, and guidelines for returning these patients to work.

Study Design: Retrospective analysis of a tertiary referral neurotology and balance clinic.

Methods: Between July 1997 and July 2003, 2390 patients with chief complaints of vertigo and/or dizziness were analyzed. Of these, 16 patients met the requirements for inclusion in the study, including head trauma and/or concussion and residual vertigo. Their inpatient and outpatient charts, imaging studies, audiograms, vestibular tests, and physical therapy evaluations were reviewed. All patients had at least 6 months of follow‐up.

Results: There were 5 women and 11 men, with an average age of 42 years. Five patients had symptoms consistent with traumatic perilymphatic fistulas, and two patients had symptoms consistent with post‐traumatic Meniere's syndrome. Surgical therapy was not beneficial in relieving dysequilibrium. Balance testing results did not predict return‐to‐work status. Eleven patients were not allowed to return to work in any capacity, two patients were allowed to return to work with limited duties, and three patients were allowed to return to work with no restrictions.

Conclusion: Post‐traumatic vertigo can result in chronic symptoms. Balance testing did not predict the ability of patients to return to work. Surgical intervention might not control patient symptoms. Many patients were unable to return to work.
Wegener's Granulomatosis Presenting as Unilateral Parotid Enlargement
Authors: Chegar Burke E. , Kelley Richard T.
Published: September 2004

Objective: Major salivary gland enlargement is a rare presenting symptom of Wegener's granulomatosis. The unrecognized occurrence of this entity can delay diagnosis, leading to increased morbidity from disease progression. This report discusses the clinical features and diagnostic testing of salivary gland enlargement secondary to Wegener's granulomatosis to differentiate it from other, more common, salivary gland diseases.

Study Design: A case report of a single subject with unilateral parotid gland enlargement secondary to Wegener's granulomatosis.

Methods: A review of the clinical course, diagnostic studies, and histopathology related to the presenting disease.

Results: A 54‐year‐old male was evaluated for a 6‐week history of progressive right parotid enlargement and pain unresponsive to antimicrobial therapy. Computed tomography scans showed diffuse, unilateral parotid swelling without enhancement and without a mass lesion or sialolith. Multiple open biopsies from the gland were necessary to demonstrate the presence of necrotizing granulomatous inflammation with vasculitis. Elevated antineutrophil cytoplasmic autoantibody, cytoplasmic pattern (c‐ANCA) titers confirmed Wegener's granulomatosis. Hemoptysis and acute renal failure requiring hemodialysis developed shortly after diagnosis but eventually resolved after the initiation of corticosteroids and cyclophosphamide.

Conclusions: Unilateral parotid enlargement is a rare presentation of Wegener's granulomatosis. A high level of clinical suspicion should prompt biopsy and testing of c‐ANCA when initial studies or empirical treatment fails to lead to a proper diagnosis. Early treatment may prevent the development of other serious systemic complications such as renal failure.
Role of Intrathyroidal Calcifications Detected on Ultrasound as a Marker of Malignancy
Authors: Seiberling Kristin A. , Dutra Jose C. , Grant Tom , Bajramovic Sanija
Published: September 2004

Objectives: Clinically palpable thyroid nodules are present in between 4% and 7% of the population, with only a small percentage of those harboring malignancy. Thus, it is important to find a cost‐effective way to determine which nodules are more likely to be malignant. The purpose of this study was to evaluate the use of intrathyroidal calcifications detected on ultrasound as a risk factor for malignancy.

Study Design: Retrospective chart review.

Methods: One hundred fifty‐nine patients with thyroid disease were included in this study. Patients were selected from a thyroid ultrasound (TUS) database. Charts were then reviewed, and only those patients who had a preoperative TUS and underwent surgery for tissue diagnosis were included.

Results: Of the 159 patients, 66 (41.5%) were diagnosed with cancer. Of those with malignancy, 52 (78.8%) had calcifications noted on TUS. Ninety‐three of the patients were diagnosed with benign pathology. Of those 93 patients, 36 (38.7%) had TUS findings consistent with calcifications, whereas 57 (61.3%) did not. Statistical analysis using a chi‐square test showed a strong association between cancer status and calcification, with P < .001. In our study, calcifications on TUS had a sensitivity of 78.8% and a specificity of 61.3%, with an odds ratio of 5.88.

Conclusion: The presence of calcifications detected on TUS should alert the physician for the possibility of malignancy, and further work‐up should be pursued. This information may be used to improve the sensitivity of other diagnostic tests such as fine needle aspiration biopsies. Given the relatively low sensitivity and specificity of the test, its use alone as a marker of malignancy is limited, but it may be used in combination with other known risk factors and tests to decide on the most appropriate treatment plan.
Malignant Odontogenic Tumors: A 22‐Year Experience
Authors: Goldenberg David , Sciubba James , Koch Wayne , Tufano Ralph P.
Published: September 2004

Objectives/Hypothesis: Malignant odontogenic tumors are exceedingly rare and arise from odontogenic epithelial residues and odontogenic cysts in the jaw bones. Odontogenic malignancies have various origins. Some develop directly from the remnants of odontogenic epithelium left after completion of dental development; others may result from malignant transformation of a benign odontogenic cyst or ameloblastoma. These lesions are usually locally aggressive with radical surgery being the primary mode of treatment. Because of their rarity, much of the existing information about malignant odontogenic tumors with regard to their origin, clinicopathological features, biological behavior, and therapeutics is derived from case reports or small series. The study represents one of the largest series of malignant odontogenic tumors compiled in a single institution.

Study Design: Retrospective 22‐year review from an Academic Medical Center.

Methods: Twenty cases of reported malignant odontogenic tumors were diagnosed in the authors' institution between 1981 and 2002. All pathological slides were reviewed to reconfirm diagnosis. Malignancy was confirmed based on the following criteria: histological findings of infiltrative growth, atypical cytological features, and focal necrosis or clear evidence of distant metastatic spread. Patient age, race, sex, treatment and outcome were recorded on chart review.

Results: Of the twenty reported cases, only nine were actually found to be malignant tumors on re‐evaluation. These consisted of four cases of malignant ameloblastomas, two cases of ameloblastic carcinoma, one case of malignant Pindborg tumor (calcifying epithelial odontogenic tumor), one case of odontogenic ghost cell carcinoma, and one case of squamous cell carcinoma arising in an odontogenic keratocyst. The racial demographics were six Caucasian patients, one African American patient, and two Asian patients; seven men and two women represented the gender distribution. Tumors of six cases were located in the mandible, and of three cases, in the maxilla. All cases were treated with radical surgical excision. Two patients died of their disease, three patients were alive and free of disease, and four patients were lost to follow‐up.

Conclusion: Malignant odontogenic tumors are rare. They require a multidisciplinary team to determine proper treatment. Long‐term surveillance is mandatory and is accomplished by routine physical examinations, along with serial radiographic imaging.
Quality and Safety in a Complex World: Why Systems Science Matters to Otolaryngologists
Authors: Roberson David W. , Kentala Erna , Healy Gerald B.
Published: September 2004

Almost all modern medical care is delivered in the setting of many overlapping systems. Each system may consist of multiple providers and in most cases electronic and mechanical components. Even “simple” outpatient care is delivered by teams of providers, administrators, and devices. Critically ill inpatients are cared for in extraordinarily complex systems with hundreds of human and non‐human elements. The science of complex systems has exploded in recent decades, and there is a large body of knowledge about how such systems function effectively or ineffectively. Many principles of systems science are simple to understand and apply, but few Otolaryngologists are well educated about them. A basic knowledge of systems science will greatly improve the Otolaryngologist's ability to function in complex health care systems and to provide the best care for his or her patients.
Stress as a Trigger of Attacks in Menière's Disease. A Case‐Crossover Study
Authors: Söderman Anne‐Charlotte Hessén , Möller Jette , Bagger‐Sjöbäck Dan , Bergenius Johan , Hallqvist Johan
Published: September 2004

Background: Menière's disease is defined as the presence of recurrent, spontaneous episodic vertigo, hearing loss (HL), aural fullness, and tinnitus. The occurrence of attacks is unpredictable. The etiology is still unknown, but the disease has a pathologic correlate in hydropic distension of the endolymphatic system. Earlier studies have shown increased incidence of stress on the same day as vertigo attacks, but it has not been determined whether stress occurring on the day of the vertiginous episode came before or after the onset of the vertigo.

Methods: A case‐crossover study including 46 patients with active Menière's disease.

Main Outcome Measure: Relative risks with 95% confidence intervals (CI).

Findings: During the study period, 153 Menière's attacks were reported. Twenty‐four (52%) of the 46 patients reported attacks. Twelve of the 153 (8%) attacks occurred within 3 hours after exposure to emotional stress. The relative risk of having an attack was 5.10 (95% CI 2.37–10.98) during 3 hours after being exposed to emotional stress. Twenty‐nine percent of the patients with attacks had at least one attack after exposure to emotional stress. For mental stress, the relative risk was 4.16 (95% CI 1.46–11.83) and the hazard period 1 hour, but only five attacks were exposed. No excess risk was found after physical stress.

Interpretation: Being exposed to emotional stress increases the risk of getting an attack of Menière's disease during the next hour, and the hazard period is possibly extended up to 3 hours.
Reduction of Salivary Flow With Botulinum Toxin: Extended Report on 33 Patients with Drooling, Salivary Fistulas, and Sialadenitis
Authors: Ellies Maik , Gottstein Ulrike , Rohrbach‐Volland Saskia , Arglebe Christian , Laskawi Rainer
Published: September 2004

Objectives/Hypothesis: The aim of the study was the evaluation of the clinical data of 33 patients who had had drooling attributable to various diseases, salivary fistulas, and sialadenitis and had been treated with injection of botulinum toxin type A (Botox). A controlled follow‐up study documenting efficiency, possible side effects, and duration of the effect of treatment was also performed.

Study Design: Retrospective clinical evaluation.

Methods: Thirty‐three patients with drooling attributable to head and neck carcinoma, neurodegenerative diseases, stroke, or idiopathic hypersalivation or with salivary fistula or chronic sialadenitis received injections of 20 to 65 U botulinum toxin type A into salivary glands under sonographic control. The entire salivary flow rate and the output per minute of the salivary analytes thiocyanate, total protein, α‐amylase, acid phosphatase, kallikrein, and immunoglobulin A were measured at various times before and after injection. The patients were examined with regard to severity of their symptoms, including sonographic control investigation of their cephalic salivary glands.

Results: Twenty‐six patients (79% of all patients) reported a distinct improvement of their symptoms after toxin injection. Seven patients noted a return of high salivation rates and requested a second injection after 4 to 7 months. Duration of toxin effect varied widely among individuals. In general, salivary flow rates and thiocyanate output dropped sharply within 1 week after injection and had increased again after a period of 12 to 16 weeks. Conversely, amylase outputs increased during this period, whereas the outputs of the other analytes remained roughly constant. Sonography did not reveal any major changes in salivary gland parenchyma, and side effects were not noted.

Conclusion: Reduction of salivary flow in patients with drooling, salivary fistulas, or chronic sialadenitis by local injection of botulinum toxin type A into the salivary glands proved to be a dependable therapy for these disorders, as shown in the present extended report on 33 patients. Side effects were not observed. The effect of toxin application lasted for approximately 3 months. Based on their results, the authors recommend botulinum toxin injection as the therapy of choice in patients with the problem of drooling.
A new retropubic suspension operation technique for transvaginal Burch operation, using newly developed equipment
Authors: Çapar Metin
Published: September 2004

Background.  Genuine stress urinary incontinence is a very common pathologic condition among women. In order to operate this, different techniques have been introduced. Here, a new technique is described for the operation of genuine stress urinary incontinence with newly developed equipment. The present technique offers more advantages than previous techniques introduced by different authors. With this technique, the duration of operation and of the recovery period are both shorter than with previous techniques. All patients had symptoms and signs of stress urinary loss. We performed multichannel cystometry preoperatively to all patients.

Method.  A special valve is used with reflector having 97% reflection capacity for transvaginal burch operation technique. Twenty five women (n = 25) having genuine stress urinary incontinence were taken under transvaginal Burch bladder neck suspension operation with fixation of suspension sutures to the Cooper (iliopectineal) ligament.

Results.  Following urodynamic workup 6 months after the surgery, one out of the 25 patients (4%) was diagnosed to have genuine stress incontinence, while one patient (4%) were diagnosed as having urinary stress incontinence and detrussor instability. One patient was found to be wet postoperatively due to only detrussor instability (4%). There were no significant differences pre‐ and postoperatively regarding capacity, residual volume, pressure rise on filling or standing, or maximal voiding pressure or peak flow rate.
Is stress urinary incontinence a familial condition?
Authors: Ertunc Devrim , Tok Ekrem C. , Pata Ozlem , Dilek Umut , Ozdemir Gulay , Dilek Saffet
Published: September 2004

Background.  Stress urinary incontinence (SUI) is a common problem of multifactorial origin. Some authors have claimed that it has a familial predisposition. This study was undertaken to investigate the prevalence of SUI among first‐degree relatives of 154 women who had been operated on for this disorder and of 100 women without SUI.

Methods.  This report is concerned with a questionnaire‐based, case‐control study. A total of 154 women who had undergone operations for SUI and 100 women who denied having SUI were included. A comparison was made of 413 first‐degree relatives of incontinent women and 372 first‐degree relatives of continent women according to the demographic characteristics, obstetric and gynecologic history and risk factors for SUI. The prevalence of SUI was investigated among the relatives. Furthermore, the characteristics of the women who had SUI operation were compared according to the continence state of their families.

Results.  The prevalence of SUI was 71.4% among mothers and 24.6% among sisters of operated women compared with 40.3% among mothers and 11.6% among sisters of continent women (p < 0.05). Furthermore, the age at which symptoms began was significantly lower in the members of the ‘incontinent families’ (p < 0.001).

Conclusions.  The relatives of incontinent women displayed a higher prevalence of SUI than the relatives of continent women. Although this condition has a multifactorial origin, the familial aggregation of SUI and the appearance of symptoms at younger ages in women with a family history of SUI suggest that heredity may play a significant role.