Chronic dysphonia secondary to gastroesophageal reflux disease (GERD): Diagnosis using simultaneous dual-probe prolonged pH monitoring

The association of chronic dysphonia with gastroesophageal reflux has been reported in the otalaryngologic literature; unfortunately, these reports are primarily anecdotal. Because of the difficulty in documenting reflux, patients are often left without a definitive diagnosis or therapy. The purpose of this paper is to report on an objective method of documenting gastroesophageal reflux disease by using ambulatory esophageal and hypopharyngeal pH monitoring. 70% of the subjects who underwent simultaneous dual-probe pH monitoring evidenced reflux in the hypopharynx in both an upright and supine position. All of the subjects had erythema of the arytenoid cartilages on indirect examination; so this appears to be of clinical diagnostic significance.     

Metastable precursor for oxygen dissociation on Si(0 0 1) 2 × 1 resolved by high lateral resolution work function measurements

The development of contact potential difference (CPD) inhomogeneities on oxide-covered silicon samples was investigated by monitoring the CPD of a clean Si(0 0 1) 2 × 1 surface during exposure to molecular oxygen with Kelvin Probe Force Microscopy. A steady fluctuation level is reached within the completion of a monolayer of oxide. Non-continuous oxygen exposure at room temperature and at lower temperatures unequivocally demonstrates the coexistence of two oxidation processes. One of these processes involves a metastable precursor to oxygen dissociation.     

The proximal probe in esophageal pH monitoring: Development of a normative database

Healthy volunteers without symptoms of either gastroesophageal reflux or laryngopharyngeal reflux and without abnormalities on laryngologic examination were recruited for esophageal pH monitoring. Thirty subjects underwent ambulatory 24-hour double-channel pH probe monitoring to establish normative data for the upper probe, which was positioned just above the upper esophageal sphincter. Data were analyzed excluding meal periods plus 2 minutes of postprandial time. The mean, standard deviation, median, and 95th percentile were calculated for various reflux parameters for the following intervals: total study duration, upright time, supine time, and postprandial time. Normal subjects display physiologic reflux above the upper esophageal sphincter (median one event, 95th percentile 6.9 events), and 80.4% of these events occur in the upright position. The reflux area index (RAI) appears to be the most useful parameter to measure laryngopharyngeal reflux severity.     

Short-Term Therapeutic Trial of Proton Pump Inhibitors in Suspected Extraesophageal Reflux

Pharyngoesophageal gastric acid reflux is thought to initiate chronic posterior laryngitis. The gold standard for measuring gastric reflux is dual-channel 24-hour pH monitoring. This is a time-consuming, inconvenient, expensive method that is not available in all areas. New therapeutic regimes that make use of proton pump inhibitors (PPIs) have proven to be therapeutically efficient for control of acid reflux. Twenty-four consecutive patients with chronic voice disorders and signs of posterior laryngitis were selected for therapy. Twenty-four hour pH monitoring was performed independently before the therapy. The trial therapy consisted of all patients receiving pantoprazole, 40 mg once daily for 6 weeks. Immediately following the therapy a statistically significant (p < 0.05) improvement was observed in all patients. This improvement was analyzed retrospectively by comparison with the results of 24-hour pH monitoring. In 71% of the patients the 24-hour pH-monitoring gave a positive result showing a high number of patients with extraesophageal reflux in our study group. Patients with positive results of pH-monitoring responded in a statistically significant manner (p < 0.05) to the pantoprazole therapy, whereas those patients without detected reflux did not. A 3-month follow-up of the patients with a positive result of the pH-monitoring confirmed the improvement. No patients reported adverse effects. A 6-week treatment with pantoprazole can be clinically justified. It helps to save time and reduce costs, allows for selection of reflux-negative patients for alternative therapy, and may prevent inadequate treatment of patients with false-negative pH monitoring. Twenty-four hour pH monitoring is still recommended for patients unresponsive to this trial therapy.     

Acoustic Analysis in Asthmatics and the Influence of Inhaled Corticosteroid Therapy

The impact of sustained inhaled corticosteroid (ICS) therapy on the larynx and pharynx was assessed using a prospective, cross-sectional, and investigator-blinded study conducted at the University Hospital Aintree, Liverpool, UK. Forty-six adults recruited from two local general practices and from general ENT clinics at our University hospital were investigated for the study. Patients were allocated to three groups according to ICS use. Laryngeal effects were measured by correlating the results of a vocal performance questionnaire, a respiratory symptom questionnaire, and measurements obtained by computerized speech analysis. Sustained vowels and connected speech were analyzed in normal and asthmatic subjects. Acoustic analysis was correlated with cellular markers of inflammation after biopsy. Regular ICS users had significantly more pharyngeal inflammation and throat discomfort (P < 0.0001). Vocal performance was also worse in this group (P < 0.0001). They were more likely to have hoarseness, weakness of voice, aphonia, sore throat, throat irritation, and cough (P < 0.0001). All these variables were directly related to one another (P < 0.0001). Multiple linear regression analysis showed that jitter was a good objective measure of hoarseness (P < 0.05). Regular ICS users were significantly more likely to have abnormal jitter, shimmer, and closed-phase quotient scores (P < 0.0001). There was no difference between the groups in the observed parameters of inflammation (P > 0.01). A higher pharyngitis score did not correlate with any of the histological markers of inflammation (P > 0.01). Local side effects are more common in asthmatics that use ICS regularly. Measures of laryngeal function are significantly worse in regular ICS users. However, histological markers and oropharyngeal redness are not reliable measures of inflammation.     

Monolithic fused 1 × 4 couplers with high uniformity

A new method for the fabrication of high uniformity monolithic 1 × 4 singlemode fused coupler is described together with details of its performance in terms of coupling ratio, spectral response and uniformity. The fabricated device exhibits ultra-broadband performance with a port-to-port uniformity of 0.4 dB. The reliability of such couplers is also evaluated and found to have good stability. Moreover, by controlling the process parameters it is possible to control the power remaining in the through put port of the device, which can be used for dedicated non-intrusive network health monitoring.     

Acoustic Analysis Findings in Objective Laryngopharyngeal Reflux Patients

OBJECTIVE: The aim of this study was to identify the effects of objective laryngopharyngeal reflux (LPR) on the acoustic parameters of patients by comparing their voice samples with that of control subjects. STUDY DESIGN: Prospective study in two tertiary reference hospitals. METHODS: 48 consecutive patients with symptoms related to LPR and 64 control subjects were included in the study. Suspected LPR patients underwent a 24-hour ambulatory pH monitoring, and 25 (52%) of them were shown to have objective LPR. Acoustical evaluation results of objective LPR patients were compared with that of symptomatic LPR patients and control subjects. RESULTS: All frequency perturbation values obtained from objective and symptomatic LPR patients were higher than the control subjects (P<0.01). Mean fundamental frequency, amplitude perturbation measures, and noise-to-harmonics ratio were not significantly different between groups. CONCLUSION: LPR patients have significantly different frequency perturbation values than control subjects.     

Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO–P2O5–Na2O–SrO–ZnO system

The bioactive glass-ceramics in the CaO–P₂O₅–Na₂O–SrO–ZnO system were synthesized by the sol–gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca₂P₂O₇ and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP₂O₆ was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca₄P₆O₁₉ was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.     

GaN/AlN quantum dot photodetectors at 1.3–1.5 μm

We have demonstrated GaN/AlN quantum dots (QD) photodetectors, relying on intraband absorption and in-plane carrier transport in the wetting layer. The devices operate at room temperature in the wavelength range 1.3–1.5 μm. Samples with 20 periods of Si-doped GaN QD layers, separated by 3 nm-thick AlN barriers, have been grown by plasma-assisted molecular-beam epitaxy on an AlN buffer on a c-sapphire substrate. Self-organized dots are formed by the deposition of 5 monolayers of GaN under nitrogen-rich conditions. The dot height is 1.2±0.6 to 1.3±0.6 nm and the dot density is in the range 10¹¹–10¹² cm⁻². Two ohmic contacts were deposited on the sample surface and annealed in order to contact the buried QD layers. The dots exhibit TM polarized absorption linked to the s–p_z transition. The photocurrent at 300 K is slightly blue-shifted with respect to the s–p_z intraband absorption. The responsivity increases exponentially with temperature and reaches a record value of 10 mA/W at 300 K for detectors with interdigitated contacts.     

Simulations of germanium epitaxial growth on the silicon (1 0 0) surface incorporating intermixing

We present kinetic lattice Monte Carlo simulations of Ge deposition onto a reconstructed Si (1 0 0) surface. We account for the exchange of Ge with Si atoms in the substrate, considering two different exchange mechanisms: a dimer exchange mechanism whereby Ge–Ge dimers on the surface become intermixed with substrate Si atoms, and the exchange of Ge atoms below the surface to relieve misfit strain. We examine how Si–Ge exchange affects the interface between the materials when the growth simulations are done at different temperatures.     

Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T = 25 °C

Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T = 25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H⁺]-glass electrode) in NaCl, NaNO₃ and mixed NaNO₃ + Na₂SO₄ ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be simply described by two protonation constants in all the acidic pH range. The dependence on ionic strength of protonation constants in NaCl aqueous solution was modelled by Specific ion Interaction Theory (SIT). The ion pair formation between protonated chitosan and Cl⁻, NO₃⁻ and SO₄²⁻ was also considered, and the relative formation constants are reported.Solubility investigations were performed in NaCl aqueous solutions in a wide range of ionic strength (0.1 < I/mol L^− 1 < 3.0), with the aim to determine the activity coefficients of neutral species and the Setschenow coefficient of chitosan 310 kDa.     

SiGe (Ge-dot) heterojunction phototransistors for efficient light detection at 1.3–1.55 μm

The aim of this work is to develop a Si/SiGe HBT-type phototransistor with several Ge dot layers incorporated in the collector, in order to obtain improved light detectivity at 1.3–1.55 μm. The MBE grown HBT detectors are of n–p–n type and based on a multilayer structure containing 10 Ge-dot layers (8 ML in each layer, separated by 60 nm Si spacer) in the base-collector junction. The transistors were processed for normal incidence or with waveguide geometry where the light is coupled through the edge of the sample. The measured breakdown voltage, BV_ceo, was about 6 V. Compared to a p–i–n reference photodiode with the same dot layer structure, photoconductivity measurements show that the responsivity is improved by a factor of 60 for normal incidence at 1.3 μm. When the light is coupled through the edge of the device, the detectivity is even further enhanced. The measured photo-responsivity is more than 100 and 5 mA/W at 1.3 and 1.55 μm, respectively.     

Misfit driven azimuthal orientation of NaCl domains on Ag(1 0 0)

We investigated the growth of thin NaCl films on Ag(1 0 0) by spot-profile-analysis low energy electron diffraction (SPA-LEED), varying extensively the growth temperature (200–500 K) and the film thickness (0.5–14 ML). The incommensurate growth of NaCl on Ag(1 0 0) yields (1 0 0)-terminated epitaxial NaCl domains, which are preferentially oriented with their [0 1 0] axis parallel to that of the substrate. At 300 K, the NaCl domains exhibit an azimuthal mosaicity by 14° around this orientation and the NaCl unit cell is laterally contracted in the first layers by 0.9% with respect to the bulk. At higher growth temperatures, the azimuthal mosaic distribution sharpens and additional distinct orientations appear, presumably due to a higher-order commensurability. The evolution of the azimuthal mosaic distribution with increasing temperature can be ascribed to both the NaCl thermal expansion and higher diffusion rates of NaCl on Ag(1 0 0). The best epitaxy, i.e. that with the highest selectivity of a specific azimuthal domain orientation, is achieved by growing NaCl films at low deposition rate (0.1 ML min⁻¹) on the Ag(1 0 0) substrate at constant high temperature (450–500 K). The observations made here can probably be applied more generally to other heterogeneous interfaces and, in particular, be used to improve the quality of thin insulating films.     

A direct measurement of theZ0 invisible width by single photon counting

The OPAL detector at LEP is used to measure the branching ratio of theZ ⁰ into invisible particles by measuring the cross section of single photon events ine ⁺ e ^– collisions at centre-of-mass energies near theZ ⁰ resonance. In a data sample of 5.3 pb^–1, we observe 73 events with single photons depositing more than 1.5 GeV in the electromagnetic calorimeter, with an expected background of 8±2 events not associated with invisibleZ ⁰ decay. With this data we determine theZ ⁰ invisible width to be 0.50±0.07±0.03 GeV, where the first error is statistical and the second systematic. This corresponds to 3.0±0.4±0.2 light neutrino generations in the Standard Model.     

Ab initio study of the chemical states of water on Cr2O3(0 0 0 1): From the isolated molecule to saturation coverage

The reactivity of the (0 0 0 1)-Cr–Cr₂O₃ surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H₂O/nm² to 14.1H₂O/nm², corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr₂O₃ surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H₂O/nm²), 5 (9.4H₂O/nm²) and 6 (14.1H₂O/nm²). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H₂O/nm², the Cr–O_s (surface oxygen) acid–base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H₂O/nm², molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H₂O/nm², 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are –Cr(OH)₂ and –Cr(OH)₃– like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr (t_2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the –Cr(OH)₃-like, –Cr(OH)₂ and anhydrous surfaces may be stabilized depending on (T, P) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation.     

Density functional study of the adsorption of aspirin on the hydroxylated (0 0 1) -quartz surface

In this study the adsorption geometry of aspirin molecule on a hydroxylated (0 0 1) α-quartz surface has been investigated using DFT calculations. The optimized adsorption geometry indicates that both, adsorbed molecule and substrate are strongly deformed. Strong hydrogen bonding between aspirin and surface hydroxyls, leads to the breaking of the original hydroxyl–hydroxyl hydrogen bonds (Hydrogenbridges) on the surface. In this case new hydrogen bonds on the hydroxylated (0 0 1) α-quartz surface appear which significantly differ from those at the clean surface. The 1.11 eV adsorption energy reveals that the interaction of aspirin with α-quartz is an exothermic chemical interaction.     

Mid-infrared spectroscopic studies and lasing in GaAs–AlGaAs quantum cascade devices

Complementary intersubband and interband optical measurements have been employed in order to study GaAs–AlGaAs quantum cascade light-emitting diode and laser structures. Using these techniques, we have measured the redistribution of electrons throughout the bridging regions and upper states in the active regions of the diode device with increasing bias. The high quality of the sample gives very narrow line widths in the optical spectra, permitting the resolution of transitions involving closely spaced energy levels. This has allowed the direct observation of level alignment at the onset of current flow through the device. In addition, stimulated emission at λ=9.7 μm has been observed from a GaAs–AlGaAs laser structure under pulsed operation. A threshold current density of 6.5 kA/cm² and peak power 300 mW are measured at 10 K and lasing operation is observed up to 200 K.     

Density-functional study of the CO chemisorption on bimetallic Pd–Sn(1 1 0) surfaces

We study the ordered PdSn c(2 × 2), (2 × 1), and PdSn₂ (3 × 1) overlayers deposited on Pd(1 1 0) by using first-principles density-functional calculations. It appears that the two PdSn structures are almost degenerate in the energy. Pd–Sn surfaces we consider do not display the marked buckling with Sn atoms displaced towards vacuum that is common for Pt–Sn surfaces. Low-coverage CO chemisorption at these overlayers and on analogous surface structures on Pd₃Sn is considered. It is shown that inclusion of an empirical correction to the CO adsorption energy changes the stable adsorption site from the long-bridge to the top one in most cases. The adsorption energy decreases with the number of Sn atoms in the vicinity of the adsorption site, and this property correlates well with the position of the centre of gravity of the local Pd d-electron band, and also with the variation of the local density of d-electron states at the Fermi level. The centre-of-gravity value is used to assess the core-level shifts for Pd atoms in various geometries. Most of the calculated data compare rather well with the recent measurements on Pd–Sn overlayers at Pd(1 1 0) as well as with other data on related bimetallic systems.     

Search for pentaquarks decaying to Ξπ in deep inelastic scattering at HERA

A search for pentaquarks decaying to Ξ⁻π⁻ (Ξ⁻π⁺) and corresponding antiparticles has been performed with the ZEUS detector at HERA. The data sample consists of deep inelastic ep scattering events at centre-of-mass energies of 300 and 318 GeV, and corresponds to 121 pb⁻¹ of integrated luminosity. A clear signal for Ξ⁰(1530)→Ξ⁻π⁺ was observed. However, no signal for any new baryonic state was observed at higher masses in either the Ξ⁻π⁻ or Ξ⁻π⁺ channels. The searches in the antiparticle channels were also negative. Upper limits on the ratio of a possible () signal to the Ξ⁰(1530) signal were set in the mass range 1650–2350 MeV.     

InGaN/GaN MQD p–n junction photodiodes

The p–n junction photodiodes with InGaN/GaN MQD have been prepared by metal-organic chemical vapor deposition (MOCVD) growth; we achieved nanoscale InGaN self-assembled QDs in the well layers of the active region. The RT PL spectrum peak position for the fabricated InGaN/GaN MQD p–n Junction PDs is located at 464.6 nm and FWHM is 24.2 nm. After finishing device process, it was fond that the turn on voltage in forward bias and the break down voltage in reverse bias are about 3 and −13.5 V, respectively. Furthermore, with 1, 2, and 3 V applied bias, the maximum responsivity of the fabricated MQD p–n junction PD was observed at 350 nm, and the minimum of spectral response was measured at 465 nm. It was also found that the responsivity was nearly a constant from 390 to 440 nm. It seems to suggest that the spectral response in the range of 390–440 nm is due to the effect of the InGaN dots-in a-well active layers.