bluuebunny/crossref_metadata_2025 huggingface dataset:
Recurrent Cutaneous Melanoma of the Head and Neck
Authors: Zitsch Robert P. , Roberts Gregory D. , Smith Russell B.
Published: November 2005

INTRODUCTION

Recurrent cutaneous melanoma is generally regarded as having an extremely poor prognosis, particularly when regional lymph nodes are involved. A few reports have documented long‐term survival among those patients treated for regionally recurrent melanoma.

METHODS

This article reviews patients at our institution undergoing complete neck dissection for recurrent head and neck melanoma.

RESULTS

Twenty‐six patients with locoregionally recurrent cutaneous melanoma of the head and neck underwent complete neck dissection with or without parotidectomy. Seventeen of these procedures were for clinically evident cervical lymphadenopathy, whereas 9 of the neck dissections were done electively. Fourteen of the 17 patients with clinical adenopathy were confirmed to have cervical lymph node metastases. Two of the 9 patients who underwent elective neck dissections had pathologic lymph nodes. At 5 years, 38% of the patients with isolated neck recurrences not also having concurrent primary site recurrence were alive without disease.

CONCLUSIONS

These results provide further evidence suggesting a benefit in the form of long‐term survival or cure for patients receiving aggressive surgical treatment for resectable recurrent head and neck melanoma involving cervical lymphatics in the absence of distant metastases.
Betahistine Increases Vestibular Blood Flow
Authors: Dziadziola James K. , Laurikainen Esa L. , Rachel John D. , Quirk Wayne S.
Published: November 2005

Betahistine is used for treatment of several vestibular disorders. Despite the accepted use of this histamine‐like substance, its mechanism of action is not well understood. The purpose of this study was to assess the possibility that one of the activities of betahistine is increasing blood flow in the peripheral vestibular end organs. Using a novel surgical approach, we identified the posterior semicircular canal ampulla of guinea pigs and placed a laser Doppler probe in position to obtain blood flow measurements from the posterior semicircular canal ampulla. Blood pressure, heart rate, and vestibular blood flow were continuously recorded. Concentration‐response curves were obtained for betahistine (2.5, 5, 7.5, and 10 mg/kg) and control‐vehicle (0.15 mol/L NaCl) infusions. A separate group of subjects was pretreated with the competitive selective H3 agonist, thioperimide maleate, before betahistine treatment. Increases in vestibular blood flow and decreases in blood pressure were observed in response to betahistine infusions. Pretreatment with thioperamide maleate abolished these changes at low doses of betahistine and attenuated the responses at higher doses of betahistine. These results show that betahistine administration induces increases in vestibular blood flow. These findings support the potential use of betahistine for treatment of vestibular disorders, which may be caused by compromised circulation.
Preventing Myringotomy Closure with Topical Mitomycin C in Rats
Authors: Estrem Scott A. , Batra Pete S.
Published: November 2005

The purpose of this study was to determine whether mitomycin C could be used to prolong the patency of the myringotomy site in the absence of ventilation tubes in rats. We examined the effect of increased exposure time and repeat application of mitomycin C to the myringotomy site. Sixty animals were separated into 4 groups: group A had a single application of mitomycin C for 10 minutes; group B had a single application for 20 minutes; group C received 2 10‐minute applications separated by 1 week; and group D received 2 applications (20 and 10 minutes) separated by 1 week. Mitomycin C and bacteriostatic saline solution were applied to the right and left myringotomy sites in each rat, respectively. Experimental ears in groups A, B, C, and D remained open for a median time of 6.5, 5.5, 6.5, and 8.5 weeks, respectively. The control ears healed within 1.5 weeks. This difference was statistically significant with P < 0.001 for each group. We conclude that mitomycin C is effective in prolonging the patency of myringotomies in rat tympanic membranes. Increased exposure time or repeat application of mitomycin C did not statistically alter the patency rate.
Impact of Laryngeal Paralysis and its Treatment on the Glottic Aperture and Upper Airway Flow Characteristics during Exercise
Authors: Beaty Mark M. , Hoffman Henry T.
Published: November 2005

Patients with unilateral vocal fold paralysis occasionally report shortness of breath during exercise. This symptom may persist in some patients after medialization thyroplasty. A review of the literature revealed no study that objectively evaluated laryngeal dynamics or airway flow characteristics during exercise after medialization thyroplasty for unilateral laryngeal paralysis. This study evaluates glottic aperture size and configuration as well as upper airway flow characteristics during exercise in 16 subjects. Six patients who underwent medialization thyroplasty for unilateral vocal fold paralysis were compared with 10 healthy control subjects. During a standardized exercise protocol on an incremental ergometer (bicycle type), real‐time videolaryngoscopy was obtained and correlated in a synchronized fashion with maximum‐effort respiratory efforts at the beginning, midpoint, and end of the exercise period. Direct calculations of glottic size during various phases of the exercise period were performed from digitized images. These data were correlated with inspiratory flow data for each patient. Patients with laryngeal paralysis demonstrated smaller mean glottic areas and lower peak inspiratory flow rates than controls both at rest and during all phases of the exercise period. This study suggests that after treatment of unilateral laryngeal paralysis with medialization thyroplasty, inspiratory flow rate and glottic area are significantly less than in normal controls.
Use of Postoperative Chest X‐Ray after Elective Adult Tracheotomy
Authors: Smith Daniel K. , Grillone Gregory A. , Fuleihan Nabil
Published: November 2005

Surgeons have been creating tracheotomies since at least 124 ad, when first reported by Asclepiades (Price HC, Postma DS. Ear Nose Throat J 1983;62:44–59). Intraoperative and postoperative complications specifically associated with this procedure have been well established. The incidence of pneumothorax ranges from 0% to 17%, depending on the age group studied. To evaluate this complication, it is generally accepted that a postoperative chest film should routinely be obtained after a tracheotomy in adult patients. In adult nonemergent tracheotomies, the routine use of a postoperative chest film has a low yield for detecting a pneumothorax in patients without clinical findings of pneumothorax. To evaluate the use of postoperative chest x‐ray in adult tracheotomy patients, a retrospective review of tracheotomies performed at the Boston Medical Center from January 1994 to June 1996 was undertaken. Data examined consisted of age, sex, surgical indication, urgency, operating service, intraoperative and postoperative complications, difficulty of procedure, anesthetic technique, findings on postoperative chest film, signs and symptoms of pneumothorax, and specific treatment of pneumothorax if present. In total, 250 patients were identified. The main indication for tracheostomy in this study was ventilator dependence, accounting for 77% of the procedures. A complication rate of 11.6% was encountered, with no deaths. Postoperative hemorrhage was the most common complication (3.6%). Pneumothorax was documented by chest x‐ray in 3 (1.2%) patients, 1 of whom had bilateral pneumothoraces. The most common symptom of a pneumothorax was tachycardia, with 8.8% of the patients exhibiting at least 1 episode. Of the 3 cases of pneumothorax in this study, only 1 was clinically relevant and required treatment. Furthermore, the clinical signs and symptoms in this patient clearly supported the diagnosis of pneumothorax before a postoperative chest film was obtained. Thus postoperative chest radiographs did not change the treatment or outcome of any of the patients undergoing a tracheotomy. This suggests that postoperative chest x‐ray after adult tracheotomy is not required in routine cases. Chest radiographs should be obtained after emergent procedures, after difficult procedures, or in patients exhibiting signs or symptoms of pneumothorax.
Health Impact of Head and Neck Cancer
Authors: Terrell Jeffrey E. , Nanavati Kinjal , Esclamado Ramon M. , Bradford Carol R. , Wolf Gregory T.
Published: November 2005

A multidimensional Head and Neck Quality of Life (HNQOL) instrument and a general health status measure were administered to 397 patients with head and neck cancer. Scores for the 4 domains of the HNQOL (communication, eating, pain, and emotional well‐being) were calculated. Patient demographics, comorbidities, clinical characteristics, treatment data, disability status, and a global “overall bother” score were assessed. When compared with the US population aged 55 to 64 years, the group had significantly worse scores in the 8 health domains of the SF‐36. Patients' overall bother scores from the head and neck cancer treatment correlated best with the HNQOL emotion domain (r = 0.71) and the HNQOL pain domain (r = 0.63), and least with the patients' perception of their response to treatment (r = 0.39). Pain, eating, emotion, physical component summary score, age, and an interaction term between eating and emotion were significant predictors for overall bother. Of the 217 patients who were working before the diagnosis of cancer, 74 (34.1%) reported that they had become disabled. Patients who had more than 1 type of treatment were 5.9 times more likely to report themselves as disabled (odds ratio [OR] = 5.94, P < 0.01), even after adjusting for age, emotion score, and physical component summary score, which were other factors that predicted disability.
Reflux in Infants with Laryngomalacia: Results of 24‐Hour Double‐Probe pH Monitoring
Authors: Matthews Brian L. , Little John P. , McGuirt William F. , Koufman James A.
Published: November 2005

Laryngomalacia is the most common cause of stridor in children. Previous studies using barium esophagrams or single‐probe esophageal pH testing have indicated that 68% to 80% of infants with laryngomalacia have reflux. A recent study in a large series of pediatric patients has shown that these 2 testing modalities are relatively insensitive in detecting reflux when compared with 24‐hour double‐probe pH testing. This study was undertaken to determine the incidence and frequency of reflux in children with laryngomalacia by use of 24‐hour double‐probe pH monitoring. Twenty‐four children with endoscopically diagnosed laryngomalacia underwent 24‐hour double‐probe pH testing. The distal probe was placed in the lower esophagus, and the proximal probe was placed just above the cricopharyngeus immediately posterior to the larynx. All 24 (100%) children had pharyngeal acid exposure as judged by the proximal pH probe. These children had a mean of 15.21 episodes of reflux to the level of the pharynx during the 24‐hour study period. In contrast, only 16 (66%) children had abnormal acid exposure as measured by the distal esophageal probe. These results indicate that essentially all children with laryngomalacia have reflux of gastric acid to the pharyngeal level. Multiple authors have documented the detrimental effects of acid and the accompanying pepsin in the larynx and tracheobronchial tree. Persistent laryngeal edema is an almost universal finding in patients with reflux to the pharyngeal level and is a common finding in children with laryngomalacia. In some patients with laryngomalacia, reflux may be the primary cause of their airway compromise, whereas in others it may be a significant cofactor exacerbating a preexisting neurologic or anatomic abnormality.
Food Pollution
Authors: Trevino Richard J.
Published: November 2005

Food can influence the human body in many ways, both positively and negatively. Several key elements of contemporary food cultivation and production are presented, along with their potential consequences to our health. The history of food cultivation and consumption is contrasted between early hunter‐gatherer societies and modern day societies. Natural nutrient‐rich foods produced from the soil in early societies have been replaced with artificial supplements and treated with pesticides and herbicides to control plant disease. The evolution of pesticides is chronicled from the synthesis of DDT in 1870 to present day. Several commonly used chemicals are described along with their documented side effects. A number of methods of pest control from ancient to modern day are offered as alternatives to polluting chemicals. Integrated pest management is proposed as a promising, economically feasible method of pest management, reducing pollution and risk to wildlife and human health.
‘THE GRANT IS WHAT I EAT’: THE POLITICS OF SOCIAL SECURITY AND DISABILITY IN THE POST-APARTHEID SOUTH AFRICAN STATE
Authors: MACGREGOR HAYLEY
Published: November 2005

In South Africa, disability grant allocation has been under review and tensions are evident in government rhetoric stressing welfare provision on the one hand, and encouraging ‘rationalization’ on the other. This ambiguity is traced down to the level of grant negotiations between doctors and ‘clients’ in a psychiatry clinic in Khayelitsha. Here ‘having nerves’ embodies the distress associated with harsh circumstances and is deemed by supplicants as sufficient to secure a grant. The paper illustrates how national discourses influence the presentation and experience of suffering and the way in which doctors mediate diagnoses. The implications of local understandings of ‘health citizenship’ for expectations of the post-apartheid state are explored.
Models of hydrothermal circulation within 106 Ma seafloor: Constraints on the vigor of fluid circulation and crustal properties, below the Madeira Abyssal Plain
Authors: Fisher A. T. , Von Herzen R. P.
Published: November 2005

Heat flow measurements colocated with seismic data across 106 Ma seafloor of the Madeira Abyssal Plain (MAP) reveal variations in seafloor heat flow of ±10–20% that are positively correlated with basement relief buried below thick sediments. Conductive finite element models of sediments and upper basement using reasonable thermal properties are capable of generating the observed positive correlation between basement relief and seafloor heat flow, but with variability of just ±4–8%. Conductive simulations using a high Nusselt number (Nu) proxy for vigorous local convection suggest that Nu = 2–10 within the upper 600–100 m of basement, respectively, is sufficient to achieve a reasonable match to observations. These Nu values are much lower than those inferred on younger ridge flanks where greater thermal homogeneity is achieved in upper basement. Fully coupled simulations suggest that permeability below the MAP is on the order of 10−12–10−10 m2 within the upper 300–600 m of basement. This permeability range is broadly consistent with values determined by single‐hole experiments and from modeling studies at other (mostly younger) sites. We infer that the reduction in basement permeability with age that is thought to occur within younger seafloor may slow considerably within older seafloor, helping hydrothermal convection to continue as plates age.
Dielectric properties of relaxor ferroelectric films
Authors: Wu Zhongqing , Duan Wenhui , Wu Jian , Gu Bing-Lin , Zhang Xiao-Wen
Published: November 2005

Dielectric properties of the relaxor films are theoretically investigated with the Monte Carlo simulation. We find that the size effect on the dielectric susceptibility of films is neglectable while the influence of the surface layer of the film is overlooked. On the contrary, while the surface layer is explicitly considered, we observe a systematic increase of Tm (the temperature at which the dielectric susceptibility reaches the maximum) and a systematic decrease of the maximum dielectric susceptibility as the film thickness decreases. An additional broadening of the transition region around Tm and the frequency dispersion of the dielectric susceptibility above Tm are also observed. The mechanism responsible for these phenomena is presented.
Two-dimensional cross-spectral correlation analysis and its application to time-resolved Fourier transform emission spectra of transient radicals
Authors: McNavage William , Dai Hai-Lung
Published: November 2005

A spectral analysis method, based on the generalized two-dimensional (2D) vibrational spectra correlation analysis, is developed for deciphering the correlation among the spectral peaks of two different spectra. This 2D cross-spectral correlation (2DCSC) analysis is aimed at revealing the vibrational features associated with a common species in two spectra, each obtained from a system containing multiple species with at least one common species. The cross-spectral correlation is based on the premise that the spectral features of the same species should have the same time and frequency responses toward similar perturbations. The effectiveness of the cross-spectral correlation analysis is first illustrated with model systems, with spectral peaks decaying linearly or exponentially with time, before being applied to analyzing time-resolved emission spectra obtained, by a Fourier transform IR spectrometer, for samples consisting of the vibrationally excited transient cyanooxomethyl radical (OCCN). 2DCSC among the three different sets of time-resolved spectra collected following the photodissociation of three different precursor molecules of OCCN, respectively, allows the identification of the CN and CO stretching modes of this radical.
Ab initio calculation of the NH(Σ−3)−NH(Σ−3) interaction potentials in the quintet, triplet, and singlet states
Authors: Dhont Guillaume S. F. , van Lenthe Joop H. , Groenenboom Gerrit C. , van der Avoird Ad
Published: November 2005

We present the ab initio potential-energy surfaces of the NH–NH complex that correlate with two NH molecules in their Σ−3 electronic ground state. Three distinct potential-energy surfaces, split by exchange interactions, correspond to the coupling of the SA=1 and SB=1 electronic spins of the monomers to dimer states with S=0, 1, and 2. Exploratory calculations on the quintet (S=2), triplet (S=1), and singlet (S=0) states and their exchange splittings were performed with the valence bond self-consistent-field method that explicitly accounts for the nonorthogonality of the orbitals on different monomers. The potential surface of the quintet state, which can be described by a single Slater determinant reference function, was calculated at the coupled cluster level with single and double excitations and noniterative treatment of the triples. The triplet and singlet states require multiconfiguration reference wave functions and the exchange splittings between the three potential surfaces were calculated with the complete active space self-consistent-field method supplemented with perturbative configuration interaction calculations of second and third orders. Full potential-energy surfaces were computed as a function of the four intermolecular Jacobi coordinates, with an aug-cc-pVTZ basis on the N and H atoms and bond functions at the midpoint of the intermolecular vector R. An analytical representation of these potentials was given by expanding their dependence on the molecular orientations in coupled spherical harmonics, and representing the dependence of the expansion coefficients on the intermolecular distance R by the reproducing kernel Hilbert space method. The quintet surface has a van der Waals minimum of depth De=675cm−1 at Re=6.6a0 for a linear geometry with the two NH electric dipoles aligned. The singlet and triplet surfaces show similar, slightly deeper, van der Waals wells, but when R is decreased the weakly bound NH dimer with S=0 and S=1 converts into the chemically bound N2H2 diimide (also called diazene) molecule with only a small energy barrier to overcome.
Effect of the wall on the velocity autocorrelation function and long-time tail of Brownian motion in a viscous compressible fluid
Authors: Felderhof B. U.
Published: November 2005

Brownian motion of a particle situated near a wall bounding the fluid in which it is immersed is affected by the wall. Specifically, it is assumed that a viscous compressible fluid fills a half space bounded by a plane wall, and that the fluid flow satisfies stick boundary conditions at the wall. The fluctuation-dissipation theorem shows that the velocity autocorrelation function of the Brownian particle can be calculated from the frequency-dependent admittance valid locally. The admittance can be found from the linearized Navier-Stokes equations. The t−3∕2 long-time tail of the velocity relaxation function, valid in bulk fluid, is obliterated by the wall and replaced by a t−5∕2 long-time tail of positive amplitude for motions parallel to the wall and by a t−5∕2 long-time tail of negative amplitude for motions perpendicular to the wall. In both cases the amplitude of the t−5∕2 long-time tail turns out to be independent of fluid compressibility and bulk viscosity.
Harmonic fields on the extended projective disk and a problem in optics
Authors: Otway Thomas H.
Published: November 2005

The Hodge equations for 1-forms are studied on Beltrami’s projective disk model for hyperbolic space. Ideal points lying beyond projective infinity arise naturally in both the geometric and analytic arguments. An existence theorem for weakly harmonic 1-fields, changing type on the unit circle, is derived under Dirichlet conditions imposed on the noncharacteristic portion of the boundary. A similar system arises in the analysis of wave motion near a caustic. A class of elliptic-hyperbolic boundary-value problems is formulated for those equations as well. For both classes of boundary-value problems, an arbitrarily small lower-order perturbation of the equations is shown to yield solutions which are strong in the sense of Friedrichs.
A new insight on the structural changes of linear quadrupole liquids
Authors: Cortada María , Calero Sofia , Lago Santiago
Published: November 2005

Molecular-dynamics simulations for linear quadrupole liquids are presented. The study is carried out for two different molecular lengths at constant density and a number of temperatures and quadrupole moments. All the simulated thermodynamic states correspond to the condensed phases and some of them show typical features of a solid structure. Furthermore, a change on the preferred intermolecular orientation in the liquid phase is observed from a shifted parallel molecular arrangement to a perpendicular orientation as the quadrupole raises. This change depends on the quadrupole moment as well as on the molecular length and is put in relation with the solid structure of different “diatomic” molecules such as nitrogen, ethane, and acetylene. The appearance of a plastic solid phase at low quadrupole moment and density is also justified. A thoroughly discussion about the availability of classical perturbation theories for this kind of systems is presented.
Asymptotic trends in thermodynamic perturbation theory
Authors: Elliott J. Richard , Gray Neil H.
Published: November 2005

The development of transferable force fields for n-alkanes has enabled molecular-dynamics simulation of the reference (A0) and perturbation (A1,A2) terms in thermodynamic perturbation theory (TPT) over a broad range of chain length. The implied equations of state yield 9.1% average error in vapor pressure and 4.7% error in liquid density for compounds ranging from propane to triacontane. Further simulations extend to nC80, but there are no experimental data to which comparisons can be made. With reliable TPT terms from molecular simulation, it is possible to analyze the trends with respect to molecular weight. Each TPT contribution is shown to approach an asymptote in the long chain limit. The asymptotes and the approaches to them are quantitatively characterized. A0 and A1 approach their asymptotes at relatively short chain lengths (nC30). A2, on the other hand, approaches its asymptote slowly (nC80). Simulation-based TPT terms also permit unambiguous interpretation of the number of coarse-grained segments relative to the number of carbons in the chain. Previous attempts have relied on characterizations that included the repulsive and attractive contributions simultaneously in a manner susceptible to a cancellation of errors. In this work, the reference fluid alone provides the characterization and the result is shown to be consistent with expectations for the A1 term. The conclusion is that the number of carbons per segment approaches roughly 10 in the long chain limit, much larger than previously reported. A small adjustment to the chain contribution from Wertheim’s [J. Stat. Phys. 42, 477 (1986)] TPT1 model is sufficient to provide quantitative accuracy for A0.
Stress relaxation in the GaN∕AlN multilayers grown on a mesh-patterned Si(111) substrate
Authors: Chen C.-H. , Yeh C.-M. , Hwang J. , Tsai T.-L. , Chiang C.-H. , Chang C.-S. , Chen T.-P.
Published: November 2005

300 × 300 μ m 2 crack-free GaN∕AlN multilayers of 2μm in thickness have been successfully grown on the Si(111) substrate patterned with the SixNy mesh by metal-organic chemical-vapor deposition. The in-plane stress exhibits a U-shape distribution across the “window” region, supported by the Raman shift of the GaN E2(TO) mode. This indicates a stress relaxation abruptly occurring near the edge of the window region due to the freestanding surface (11¯01) or (112¯2). The in-plane stress is almost relaxed at the corner of the window region due to three freestanding surfaces (11¯01), (112¯2), and (101¯1). The maximum in-plane stress is located near the surface of the multilayers at the center of the window region, supported by the Raman measurements and the failure observations. The role of the SixNy mesh in the stress relaxation is discussed.
Gallium nitride surface quantum wells
Authors: Muth J. F. , Zhang X. , Cai A. , Fothergill D. , Roberts J. C. , Rajagopal P. , Cook J. W. , Piner E. L. , Linthicum K. J.
Published: November 2005

Surface quantum-well emission has been observed from GaN-capped AlGaN∕GaN heterostructures grown by metalorganic chemical vapor deposition. The GaN cap, which forms the surface quantum well, is confined on one side by the vacuum level and on the other side by the AlGaN barrier layer. Photoluminescence at room temperature and cathodoluminescence studies show a strong emission peak corresponding to the lowest bound state of the surface quantum well and a correlation was made to the shift in surface quantum-well emission energy and the thickness of the GaN capping layer, which was varied from ∼15to40Å. The efficient surface quantum-well emission is indicative of low surface recombination velocities even without any surface passivation.
Second-harmonic generation in hydrogenated amorphous-Si1−xNx doubly resonant microcavities with periodic dielectric mirrors
Authors: Lettieri S. , Gesuele F. , Maddalena P. , Liscidini M. , Andreani L. C. , Ricciardi C. , Ballarini V. , Giorgis F.
Published: November 2005

We report on the realization of microcavities made of hydrogenated amorphous-Si1−xNx multilayers, with dual-wavelength periodic dielectric mirrors in order to obtain first and second order stop bands. Optical second-harmonic generation with simultaneous resonance for the pump and harmonic waves is demonstrated at finite values of the angle of incidence. The results are in good agreement with a theoretical calculation of the harmonic generation process based on a nonlinear polarization localized at the interfaces between different amorphous layers.
Deep levels and low-frequency noise in AlGaAs∕GaAs heterostructures
Authors: Khlil Rachid , El Hdiy Abdelillah , Jin Yong
Published: November 2005

The low-frequency noise is studied in different AlGaAs∕GaAs heterostructures under electric biases as a function of the temperature. The heterostructures differ in the two-dimensional electron-gas density and the mobility. In addition to the thermal noise, different contributions are found and characterized (1∕f and generation-recombination noises). The presence of the generation-recombination noise is linked to defects in the interface between the channel and electrical contacts. Thermal activation energy values are deduced from Arrhenius plots and related to AsGa antisite defects and DX centers. The 1∕f noise is also characterized and its origin is identified as being the carrier mobility fluctuation dominated by lattice phonons.
Photoconductivity of AlN films on SiC
Authors: Choi Jongwoo , Chang Jane P.
Published: November 2005

The band gap and deep donor levels of bulk 6H-SiC are studied by photoconductivity and optical absorption measurements. The absorption spectrum displays two nitrogen-induced bands: one near 2 eV and another partially overlapped with the fundamental absorption of 6H-SiC at 3 eV. The low-temperature photoconductivity data reveal that the 2 eV band is due to a localized electron transition, whereas the higher-energy band involves a delocalized-electron transition from a deep center to the conduction band of the host. We also used the photoconductivity technique to estimate the band offset at the AlN∕6H-SiC interface. The measured conduction and valence band offsets are 1.9 and 1.3 eV, respectively, agreeing well with our previously reported results from x-ray photoelectron spectroscopy measurements and density functional theory calculations.
SQUID magnetometer operating at 37 K based on nanobridges in epitaxial MgB2 thin films
Authors: Mijatovic D. , Brinkman A. , Veldhuis D. , Hilgenkamp H. , Rogalla H. , Rijnders G. , Blank D. H. A. , Pogrebnyakov A. V. , Redwing J. M. , Xu S. Y. , Li Q. , Xi X. X.
Published: November 2005

Superconducting quantum interference devices (SQUIDs) and magnetometers are fabricated from nanoconstrictions in epitaxial MgB2 films. The nanobridges are contained within single-crystalline grains, resulting in clean transport, a large critical current density of 5×107A∕cm2 at 4.2 K, and stable SQUID voltage modulation up to 38.8 K. The magnetometer is realized with an inductively coupled pickup loop, giving rise to a field sensitivity of 1pTHz−1∕2 down to 1 Hz. The device properties are governed by the two-band superconducting nature of MgB2, posing, however, no problems to a successful development of boride magnetic field sensing devices. The MgB2 zero-temperature London penetration depth is measured to be 62 nm, close to theoretical predictions.
Spontaneous formation of ordered nanocrystal arrays in films evaporated onto nanopore array substrates
Authors: Pavenayotin Niravun , Stewart M. D. , Valles James M. , Yin Aijun , Xu J. M.
Published: November 2005

We have investigated the structure of films thermally evaporated onto anodic aluminum oxide substrates that are patterned with a hexagonal array of 34 and 80 nm diameter holes spaced by 100 nm. Over a range of film thicknesses, Pb and Sn films spontaneously self-assemble into an array of nanocrystals in registry with the underlying hole lattice. The development of the arrays with thickness indicates that surface energies drive coalescing grains to move over the holes. Materials that wet the substrate (Pd, Ge) or whose grains do not coalesce at the substrate temperature (Au) do not form arrays. Potential applications are discussed.
Out-of-plane dispersion and homogenization in photonic crystal slabs
Authors: Jian Zhongping , Mittleman Daniel M.
Published: November 2005

We report a measurement of out-of-plane dispersion in two-dimensional photonic crystal slabs. Using terahertz time-domain spectroscopy, we obtain the complex transmission coefficient over a broad spectrum, ranging from the long wavelength (homogeneous) limit up to beyond the first few guided resonances. Despite the absence of a band gap, the out-of-plane dispersion is significant and in addition exhibits a complicated spectral dependence. Calculations of the effective refractive index which assume translational invariance in the direction perpendicular to the slab are in only approximate agreement with the measured homogeneous effective index and dispersion. In contrast, numerical simulations which accurately account for the finite slab thickness give much more accurate predictions.
Response of barramundi, Lates calcarifer, populations in the Fly River, Papua New Guinea to mining, fishing and climate-related perturbation
Authors: Milton David , Yarrao Markson , Fry Gary , Tenakanai Charles
Published: November 2005

Migrating barramundi (Perciformes : Centropomidae) spawners support a valuable artisanal fishery on the coast of south-western Papua New Guinea. This fishery declined dramatically during the 1990s shortly after the large Ok Tedi copper mine began in the headwaters of the large Fly River nearby. In order to understand the factors causing the decline, populations were sampled quarterly with gill-nets at over 20 sites throughout the Fly River from 1987 to 2001. Barramundi were most abundant in the middle and upper reaches of the Fly River. No evidence was found that output from the large Ok Tedi mine was negatively impacting on barramundi catch rates. However, the commercial fishery in the middle Fly River was found to have a negative impact on the weight of barramundi in monitoring catches in that region. Additionally, catch rates of juvenile barramundi (1 year olds) in the Fly River were negatively correlated with the amount of rainfall on the breeding grounds during the previous monsoon. This suggests that the reduced catch rates in the coastal commercial fishery in the late 1980s and early 1990s may have been affected by both the riverine commercial fishery and the El Niño (ENSO) that occurred at that time.
Geology - benthos relationships on a temperate rocky bank, eastern Bass Strait, Australia
Authors: Beaman Robin J. , Daniell James J. , Harris Peter T.
Published: November 2005

To better understand the possible relationships between the geology of the seabed and the associated biological communities, a multibeam sonar survey over New Zealand Star Bank in the eastern Bass Strait was conducted. A hierarchical method of benthic habitat mapping was applied to the secondary biotope and biological facies levels at the site (<10 km) scale. Four secondary biotopes and four biological facies have been defined on the basis of geomorphology revealed by the bathymetry model and the results of statistical analysis of the sediment and underwater video transect data over the bank. The major differences that control the distribution of biological communities in the New Zealand Star Bank area appear to be related to variations in substrate. (1) Hard-ground features related to high-relief granite outcrops are associated with diverse and abundant sessile and motile fauna. These faunal communities may be biologically modified to patchy barrens habitat by grazing urchins. (2) Unconsolidated sediment on a flat seabed is associated with sparse small sponges on the inner shelf. On the middle shelf and seaward of bank, the flat and muddy seabed supports a community dominated by infauna. (3) Unconsolidated sediment on a low-relief seabed is associated with an increase in the density and sizes of sponges concentrated on any low-relief feature raised above the surrounding flat seabed.
Comparison of arsenic and trace metal contents of discharges from adjacent coal and gold mines, Reefton, New Zealand
Authors: Hewlett L. , Craw D. , Black A.
Published: November 2005

Historic gold and coal mines in the same catchment near Reefton, New Zealand allow comparison of environmental effects of the different mines in the same climate and topography. Gold mine discharge waters (neutral pH) deposit hydrated iron oxide (HFO) abundantly at mine entrances, whereas coal mine discharge waters (low pH) precipitate HFO tens to hundreds of metres downstream as pH rises. Waters leaving historic mines have up to 59 mg L−1 dissolved arsenic, and HFO at gold mines has up to 20 wt% arsenic. Coal mine discharge waters have low dissolved arsenic (typically near 0.01 mg L−1) and HFO has <0.2 wt% arsenic. Minor dissolved Cu, Cr, Ni, and Zn are being leached from background host rocks by acid solutions during sulfide oxidation, and attenuated by HFO downstream of both gold and coal mines. A net flux of 30 mg s−1 arsenic is leaving the catchment, and nearly all of this arsenic flux is from the gold mining area, but >90% of that flux is from background sources. The present study demonstrates that elevated trace metal concentrations around mines in a wet climate are principally from non-anthropogenic sources and are readily attenuated by natural processes.
Telomere length and heredity: Indications of paternal inheritance
Authors: Nordfjäll Katarina , Larefalk Åsa , Lindgren Petter , Holmberg Dan , Roos Göran
Published: October 2005

Cellular telomere length is linked to replicative life span. Telomere repeats are lost in peripheral blood cellsin vivoby age, and women show less telomere attrition than men. Previous reports have indicated that telomere length and chromosome-specific telomere-length patterns partly are inherited. The mode of heredity has not been clarified, but a link to the X chromosome was recently suggested. We analyzed peripheral mononuclear cells from 49 unrelated families for telomere length using a real-time PCR method. Short-term cultured Epstein–Barr virus-transformed lymphoblasts from the same individuals (n= 130) were analyzed for ability to maintain telomere length and possible gender-linked inheritance. A statistically significant association between telomere lengths comparing father–son (P= 0.011,n= 20) and father–daughter (P= 0.005,n= 22) pairs was found. However, no correlation was observed between mother–daughter (P= 0.463,n= 23) or mother–son (P= 0.577,n= 18). The father–offspring correlation was highly significant (P< 0.0001), in contrast to mother–offspring (P= 0.361). Epstein–Barr virus cultures demonstrated in most cases telomere preservation inversely related to initial mononuclear cell telomere length with short telomeres displaying the most pronounced elongation. Telomere length is inherited, and evidence for a father-to-offspring heritage of this trait was obtained, whereasin vitrotelomere length maintenance was found to be dependent on the initial telomere length.
The ETV6-NTRK3 chimeric tyrosine kinase suppresses TGF-β signaling by inactivating the TGF-β type II receptor
Authors: Jin Wook , Kim Byung-Chul , Tognon Cristina , Lee Ho-Jae , Patel Sejal , Lannon Chris L. , Maris John M. , Triche Timothy J. , Sorensen Poul H. B. , Kim Seong-Jin
Published: October 2005

An emerging theme in cancer biology is that although some malignancies occur through the sequential acquisition of different genetic alterations, certain dominantly acting oncoproteins such as those associated with chromosomal translocations have multiple functions and do not require additional mutations for cell transformation. The ETV6-NTRK3 (EN) chimeric tyrosine kinase, a potent oncoprotein expressed in tumors derived from multiple cell lineages, functions as a constitutively active protein tyrosine kinase. Here, we show that EN suppresses TGF-β signaling by directly binding to the type II TGF-β receptor, thereby preventing it from interacting with the type I TGF-β receptor. This activity requires a functional EN protein tyrosine kinase, and type II TGF-β receptor appears to be a direct target of EN. Our findings provide evidence for a previously undescribed mechanism by which oncogenic tyrosine kinases can block TGF-β tumor suppressor activity.
An IL-7-dependent rebound in thymic T cell output contributes to the bone loss induced by estrogen deficiency
Authors: Ryan Michaela Robbie , Shepherd Rebecca , Leavey Jennifer K. , Gao Yuhao , Grassi Francesco , Schnell Frederick J. , Qian Wei-Ping , Kersh Gilbert J. , Weitzmann M. Neale , Pacifici Roberto
Published: November 2005

The bone wasting induced by estrogen deficiency is, in part, a consequence of increased T cell production of the osteoclastogenic cytokine TNF-α. This phenomenon is due to an expansion of T cells, but the responsible mechanism is unknown. We now show that ovariectomy (ovx) disregulates T lymphopoiesis and induces bone loss by stimulating, through a rise in IL-7 levels, both thymic-dependent differentiation of bone marrow-derived progenitors and thymic-independent, peripheral expansion of mature T cells. Attesting to the relevance of the thymic effects, thymectomy decreases by ≈50% the bone loss and the stimulation of T lymphopoiesis induced by ovx. In contrast,in vivoattenuation of the elevated IL-7 completely prevents the stimulation of T lymphopoiesis and the bone loss that follow ovx. Thus, the disruption of both T cell and bone homeostasis induced by ovx is mediated by IL-7 and due to both the thymic and extrathymic mechanisms. We conclude that IL-7 is a pivotal upstream target through which estrogen regulates hematopoietic and immune functions that are critical for bone homeostasis.
An improved reverse genetics system for influenza A virus generation and its implications for vaccine production
Authors: Neumann Gabriele , Fujii Ken , Kino Yoichiro , Kawaoka Yoshihiro
Published: November 2005

The generation of vaccines for highly pathogenic avian influenza viruses, including those of the H5N1 subtype, relies on reverse genetics, which allows the production of influenza viruses from cloned cDNA. In the future, reverse genetics will likely be the method of choice for the generation of conventional influenza vaccine strains because gene reassortment by more traditional methods is cumbersome. Established systems for the artificial generation of influenza A viruses require transfection of cells with the eight to 12 plasmids that provide the eight influenza viral RNAs as well as the polymerase and nucleoproteins of the virus. However, cell lines appropriate for human vaccine production (e.g., Vero cells) cannot be transfected with high efficiencies. To overcome these problems, we established a reverse genetics system in which the eight RNA polymerase I transcription cassettes for viral RNA synthesis are combined on one plasmid. Similarly, two cassettes encoding the hemagglutinin and neuraminidase segments and six cassettes encoding the remaining proteins were combined. We also combined three RNA polymerase II transcription cassettes for the expression of the polymerase subunits. By combining these cassettes, we reduced the number of plasmids required for virus generation significantly and produced influenza A virus in Vero cells with higher efficiency than with the traditional 12 plasmid system. This new system is thus suitable for influenza virus vaccine production and may be applicable to other reverse genetics systems that rely on the introduction of several plasmids into eukaryotic cells.
Protein folding by distributed computing and the denatured state ensemble
Authors: Marianayagam Neelan J. , Fawzi Nicolas L. , Head-Gordon Teresa
Published: November 2005

The distributed computing (DC) paradigm in conjunction with the folding@home (FH) client server has been used to study the folding kinetics of small peptides and proteins, giving excellent agreement with experimentally measured folding rates, although pathways sampled in these simulations are not always consistent with the folding mechanism. In this study, we use a coarse-grain model of protein L, whose two-state kinetics have been characterized in detail by using long-time equilibrium simulations, to rigorously test a FH protocol using ≈10,000 short-time, uncoupled folding simulations starting from an extended state of the protein. We show that the FH results give non-Poisson distributions and early folding events that are unphysical, whereas longer folding events experience a correct barrier to folding but are not representative of the equilibrium folding ensemble. Using short-time, uncoupled folding simulations started from an equilibrated denatured state ensemble (DSE), we also do not get agreement with the equilibrium two-state kinetics because of overrepresented folding events arising from higher energy subpopulations in the DSE. The DC approach using uncoupled short trajectories can make contact with traditionally measured experimental rates and folding mechanism when starting from an equilibrated DSE, when the simulation time is long enough to sample the lowest energy states of the unfolded basin and the simulated free-energy surface is correct. However, the DC paradigm, together with faster time-resolved and single-molecule experiments, can also reveal the breakdown in the two-state approximation due to observation of folding events from higher energy subpopulations in the DSE.
Protein synthesis required for long-term memory is induced by PKC activation on days before associative learning
Authors: Alkon Daniel L. , Epstein Herman , Kuzirian Alan , Bennett M. Catherine , Nelson Thomas J.
Published: October 2005

Protein synthesis has long been known to be required for associative learning to consolidate into long-term memory. Here we demonstrate that PKC isozyme activation on days before training can induce the synthesis of proteins necessary and sufficient for subsequent long-term memory consolidation. Bryostatin (Bryo), a macrolide lactone with efficacy in subnanomolar concentrations and a potential therapeutic for Alzheimer's disease, is a potent activator of PKC, some of whose isozymes undergo prolonged activation after associative learning. Under normal conditions, two training events with paired visual and vestibular stimuli cause short-term memory of the molluscHermissendathat lasts ≈7 min. However, after 4-h exposures to Bryo (0.25 ng/ml) on two preceding days, the same two training events produced long-term conditioning that lasted >1 week and that was not blocked by anisomycin (1 μg/ml). Anisomycin, however, eliminated long-term memory lasting at least 1 week after nine training events. Both the nine training events alone and two Bryo exposures plus two training event regimens caused comparably increased levels of the PKC α-isozyme substrate calexcitin in identified type B neurons and enhanced PKC activity in the membrane fractions. Furthermore, Bryo increased overall protein synthesis in cultured mammalian neurons by up to 60% for >3 days. The specific PKC antagonist Ro-32-0432 blocked much of this Bryo-induced protein synthesis as well as the Bryo-induced enhancement of the behavioral conditioning. Thus, Bryo-induced PKC activation produces those proteins necessary and sufficient for long-term memory on days in advance of the training events themselves.
Economic benefits of biodiversity exceed costs of conservation at an African rainforest reserve
Authors: Naidoo Robin , Adamowicz Wiktor L.
Published: November 2005

Economic research on biodiversity conservation has focused on the costs of conservation reserves and the benefits of intact ecosystems; however, no study has simultaneously considered the costs and benefits of species diversity, a fundamental component of biodiversity. We quantified the costs and benefits of avian biodiversity at a rainforest reserve in Uganda through a combination of economic surveys of tourists, spatial land-use analyses, and species-area relationships. Our results show that revising entrance fees and redistributing ecotourism revenues would protect 114 of 143 forest bird species (80%) under current market conditions. This total would increase to 131 species (≈90%) if entrance fees were optimized to capture the tourist's willingness to pay for forest visits and the chance of seeing increased numbers of bird species. In contrast, the cost of purchasing agricultural land for ecological rehabilitation of the avian habitat would be economically prohibitive. These results suggest that local biodiversity markets could play a positive role in tropical conservation strategies if the appropriate institutions for redistribution can be developed.