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To characterise multi-level obstruction in terms of prevalence, obstructive sleep apnoea severity and predictive factors, and to collect epidemiological data on upper airway morphology in obstructive sleep apnoea patients.
Retrospective review of 250 obstructive sleep apnoea patients.
On clinical examination, 171 patients (68.4 per cent) had multi-level obstruction, 49 (19.6 per cent) had single-level obstruction and 30 (12 per cent) showed no obstruction. Within each category of obstructive sleep apnoea severity, multi-level obstruction was more prevalent. Multi-level obstruction was associated with severe obstructive sleep apnoea (more than 30 events per hour) (p = 0.001). Obstructive sleep apnoea severity increased with the number of obstruction sites (correlation coefficient = 0.303, p < 0.001). Multi-level obstruction was more likely in younger (p = 0.042), male (p = 0.045) patients, with high body mass index (more than 30 kg/m2) (p < 0.001). Palatal (p = 0.004), tongue (p = 0.026) and lateral pharyngeal wall obstructions (p = 0.006) were associated with severe obstructive sleep apnoea.
Multi-level obstruction is more prevalent in obstructive sleep apnoea and is associated with increased severity. Obstruction at certain anatomical levels contributes more towards obstructive sleep apnoea severity.
Epidemiological studies have reported that higher education (HE) is associated with a reduced risk of incident Alzheimer's disease (AD). However, after the clinical onset of AD, patients with HE levels show more rapid cognitive decline than patients with lower education (LE) levels. Although education level and cognition have been linked, there have been few longitudinal studies investigating the relationship between education level and cortical decline in patients with AD. The aim of this study was to compare the topography of cortical atrophy longitudinally between AD patients with HE (HE-AD) and AD patients with LE (LE-AD).
We prospectively recruited 36 patients with early-stage AD and 14 normal controls. The patients were classified into two groups according to educational level, 23 HE-AD (>9 years) and 13 LE-AD (≤9 years).
As AD progressed over the 5-year longitudinal follow-ups, the HE-AD showed a significant group-by-time interaction in the right dorsolateral frontal and precuneus, and the left parahippocampal regions compared to the LE-AD.
Our study reveals that the preliminary longitudinal effect of HE accelerates cortical atrophy in AD patients over time, which underlines the importance of education level for predicting prognosis.
High quality Ga-face and N-face AlGaN/GaN based heterostructures have been grown by plasma induced molecular beam epitaxy. By using Ga-face material we are able to fabricate conventional heterojunction field effect transistors. Because the N-face material confines electrons at a different heterojunction, the resulting transistors are called inverted. The Ga-face structures use a high temperature AlN nucleation layer to establish the polarity. Structures from these materials, relying only on polarization induced interface charge effects to create the two-dimensional electron gases, are used to confirm the polarity of the material as well as test the electrical properties of the layers. The resulting sheet concentrations of the two dimensional electron gases agree very well with the piezoelectric theory for this materials system. Hall mobilities of the two-dimensional gases for the N-face structures are as high as 1150 cm2/Vs and 3440 cm2/Vs for 300 K and 77 K respectively, while the Ga–face structures yield room temperature mobilities of 1190 cm2/Vs. Both structures were then fabricated into transistors and characterized. The inverted transistors, which were fabricated from the N-face material, yielded a maximum transconductance of 130 mS/mm and a current density of 905 mA/mm. Microwave measurements gave an ft of 7 GHz and an fmax of 12 GHz for a gate length of 1 µm. The normal transistors, fabricated from the Ga-face material, produced a maximum transconductance of 247 mS/mm and a current density of 938 mA/mm. Microwave measurements gave an ft of 50 GHz and an fmax of 97 GHz for a gate length of 0.25 µm. This shows that using plasma induced molecular beam epitaxy N-face and Ga(Al)-face AlGaN/GaN heterostructures can be grown with structural and electrical properties very suitable for high power field effect transistors.
At present there are no objective, biological markers that can be used to reliably identify individuals with post-traumatic stress disorder (PTSD). This study assessed the diagnostic potential of structural magnetic resonance imaging (sMRI) for identifying trauma-exposed individuals with and without PTSD.
sMRI scans were acquired from 50 survivors of the Sichuan earthquake of 2008 who had developed PTSD, 50 survivors who had not developed PTSD and 40 healthy controls who had not been exposed to the earthquake. Support vector machine (SVM), a multivariate pattern recognition technique, was used to develop an algorithm that distinguished between the three groups at an individual level. The accuracy of the algorithm and its statistical significance were estimated using leave-one-out cross-validation and permutation testing.
When survivors with PTSD were compared against healthy controls, both grey and white matter allowed discrimination with an accuracy of 91% (p < 0.001). When survivors without PTSD were compared against healthy controls, the two groups could be discriminated with accuracies of 76% (p < 0.001) and 85% (p < 0.001) based on grey and white matter, respectively. Finally, when survivors with and without PTSD were compared directly, grey matter allowed discrimination with an accuracy of 67% (p < 0.001); in contrast the two groups could not be distinguished based on white matter.
These results reveal patterns of neuroanatomical alterations that could be used to inform the identification of trauma survivors with and without PTSD at the individual level, and provide preliminary support to the development of SVM as a clinically useful diagnostic aid.
Group-level results suggest that relative to healthy controls (HCs), ultra-high-risk (UHR) and first-episode psychosis (FEP) subjects show alterations in neuroanatomy, neurofunction and cognition that may be mediated genetically. It is unclear, however, whether these groups can be differentiated at single-subject level, for instance using the machine learning analysis support vector machine (SVM). Here, we used a multimodal approach to examine the ability of structural magnetic resonance imaging (sMRI), functional MRI (fMRI), diffusion tensor neuroimaging (DTI), genetic and cognitive data to differentiate between UHR, FEP and HC subjects at the single-subject level using SVM.
Three age- and gender-matched SVM paired comparison groups were created comprising 19, 19 and 15 subject pairs for FEP versus HC, UHR versus HC and FEP versus UHR, respectively. Genetic, sMRI, DTI, fMRI and cognitive data were obtained for each participant and the ability of each to discriminate subjects at the individual level in conjunction with SVM was tested.
Successful classification accuracies (p < 0.05) comprised FEP versus HC (genotype, 67.86%; DTI, 65.79%; fMRI, 65.79% and 68.42%; cognitive data, 73.69%), UHR versus HC (sMRI, 68.42%; DTI, 65.79%), and FEP versus UHR (sMRI, 76.67%; fMRI, 73.33%; cognitive data, 66.67%).
The results suggest that FEP subjects are identifiable at the individual level using a range of biological and cognitive measures. Comparatively, only sMRI and DTI allowed discrimination of UHR from HC subjects. For the first time FEP and UHR subjects have been shown to be directly differentiable at the single-subject level using cognitive, sMRI and fMRI data. Preliminarily, the results support clinical development of SVM to help inform identification of FEP and UHR subjects, though future work is needed to provide enhanced levels of accuracy.
Nanoscale superlattice-like (SLL) dielectric was employed to reduce the power consumption of the Phase-change random access memory (PCRAM) cells. In this study, we have simulated and found that the cells with the SLL dielectric have a higher peak temperature compared to that of the cells with the SiO2 dielectric after constant pulse activation, due to the interface scattering mechanism. Scaling of the SLL dielectric has resulted in higher peak temperatures, which can be even higher after material/structural modifications. Furthermore, the SLL dielectric has good material properties that enable the cells to have high endurance. This shows the effectiveness of the SLL dielectric for advanced memory applications.
We investigated the electrical characteristics of the MOSCAP structures with W/WNx/poly Si1−xGex gates stack using C-V and I-V. The low frequency C-V measurements demonstrated that the flat band voltage of the W/WNx /poly Si0.4Ge0.6 stack was lower than that of W/ WNx /poly Si0.2Ge0.8 stack by 0.3V, and showed less gate-poly-depletion-effect than that of W/ WNx /poly- Si0.2Ge0.8 gates due to the increase of dopant activation rate with the increase of Ge content in the poly Si1−xGex films. As Ge content in poly Si1−xGex increased, the leakage current level increased a little due to the increase of direct tunneling and QBD became higher due to the lower boron penetration.
Electrical and optical measurements were performed on p-type GaAs implanted with 1013 Er ions/cm2 at an energy of 1 MeV. The samples were annealed at 650, 750, 850, or 900 °C for 15 seconds using the rapid thermal annealing technique. Although annealing at 650 °C was insufficient to recover measureable electrical conductivity in the implanted region, Er3+ 4f-4f emissions were still observed. Annealing at 750 TC produced a large concentration of hole traps at EV + 360 meV, and the most intense Er-related emissions at 1.54 μm. The two higher annealing temperatures returned the implanted region to the conductivity of the substrate but resulted in weak Er-related emissions. Two distinct Er-related centers were found, and they are believed to be the cause of the intense and weak emissions, an Er-interstitial and Er substituting for Ga, respectively.
A systematic photoluminescence study of erbium and oxygen co-implantation into GaAs and AlxGal1−xAs with × = 0.1, 0.2, 0.3, and 0.4 was carried out. The addition of oxygen greatly enhanced the Er emission intensity from AlxGal1−xAs:Er while the O and Er co-doping into GaAs rather made the Er emission intensity decrease from that of the GaAs:Er. The Er emission intensity from AlxGal1−xAs:(Er+O) generally increases with increasing Al mole fraction and O dose up to 1 × 10 15/cm2, but it does not depend much on the substrate conductivity.
High quality Ga-face and N-face AlGaN/GaN based heterostructures have been grown by plasma induced molecular beam epitaxy. By using Ga-face material we are able to fabricate conventional heterojunction field effect transistors. Because the N-face material confines electrons at a different heterojunction, the resulting transistors are called inverted. The Ga-face structures use a high temperature AIN nucleation layer to establish the polarity. Structures from these materials, relying only on polarization induced interface charge effects to create the two-dimensional electron gases, are used to confirm the polarity of the material as well as test the electrical properties of the layers. The resulting sheet concentrations of the two dimensional electron gases agree very well with the piezoelectric theory for this materials system. Hall mobilities of the two-dimensional gases for the N-face structures are as high as 1150 cm2/Vs and 3440 cm2/Vs for 300 K and 77 K respectively, while the Ga-face structures yield room temperature mobilities of 1190 cm2/Vs. Both structures were then fabricated into transistors and characterized. The inverted transistors, which were fabricated from the N-face material, yielded a maximum transconductance of 130 mS/mm and a current density of 905 mA/mm. Microwave measurements gave an ft of 7 GHz and an fmax of 12 GHz for a gate length of 1 μm. The normal transistors, fabricated from the Ga-face material, produced a maximum transconductance of 247 mS/mm and a current density of 938 mA/mm. Microwave measurements gave an ft of 50 GHz and an fmax of 97 GHz for a gate length of 0.25 μm. This shows that using plasma induced molecular beam epitaxy N-face and Ga(A1)-face AlGaN/GaN heterostructures can be grown with structural and electrical properties very suitable for high power field effect transistors.
The valence subband structures, density-of-states, and optical gain of (0001) wurtzite (WZ) InxGa1-xN/GaN quantum wells (QWs) are studied using a numerical approach without analytical approximations. We used the effective-mass parameters of GaN and InN derived using the Empirical Pseudopotential Method. By varying the well width and mole fraction of In in the well material, the effects of quantum confinement and compressive strain are studied. A narrower well width and a higher In mole fraction in the well lead to TE enhancement and TM suppression of the optical gain. From the relationship between the optical gain and the radiative current density, we obtain the transparent current density for a single QW to be 200 A/cm2. Further, we analyze the InxGa1-xN/GaN/AlGaN separate confinement heterostructure multiple-QW laser structure. It is shown that a suitable combination of well width and number of QWs should be selected in optimizing the threshold current density in such MQW lasers
Self-aligned arrays of long multi-walled carbon nanotubes (MWCNT) were grown by chemical vapor deposition (CVD) from a gas mixture of C2H4-H2-Ar-H2O at 750°C. A catalytically active alumina surfaces coated with a thin layer of iron and supported by a Si/SiO2 substrate were prepared using pulsed laser deposition method. Combinatorial approach has been used for optimization of catalytic properties of the multilayered system Si/SiO2/Al2O3/Fe. Sixteen different combinations of catalytic surfaces having thicknesses of Fe (0, 1, 2, and 3 nm), alumina (0, 10, 20 and 30 nm) per sample were deposited on two Si/SiO2 substrates with silica thickness 150 and 500 nm. To study the effect of alumina phase on efficiency of catalytic surfaces two substrate temperatures 200 and 700°C were used to produce amorphous and γ-alumina phases correspondingly. This approach allowed the optimal structure of catalytic surface to be determined from 64 different substrates on 4 samples in a single MWCNT growth experiment, for a given set of processing conditions. It was found that most efficient growth of MWCNT arrays on amorphous alumina occurred at Fe nanolayer thickness of 2 nm while catalyst having γ-alumina layer has tendency to be more efficient at higher thickness of Fe. Catalytic substrate containing amorphous alumina has less sensitivity to thickness of iron while γ-alumina based catalyst has significant variation in catalytic activity with change of iron content.
We report the use of nickel-platinum silicide (NiPtSi) as a source/drain (S/D) material for strain engineering in P-MOSFETs to improve drive current performance. The material and electrical characteristics of NiPtSi with various Pt concentrations was investigated and compared with those of NiSi. Ni0.95Pt0.05Si was selected for device integration. A 0.18 μm gate length P-MOSFET achieved a 22% gain in IDsat when Ni0.95Pt0.05Si S/D is employed instead of NiSi S/D. The enhancement is attributed to strain modification effects related to the nickel-platinum silicidation process.
Highly aligned multi-walled carbon nanotube (MWCNT) arrays were synthesized on Si wafers. Water vapor was used to enhance the catalyst performance, which enabled continuous growth of MWCNT arrays for up to 3 hours. Various types of Fe patterning on a Si substrate with a multilayered structure were tested. MWCNT arrays up to 4 mm long were grown by Chemical Vapor Deposition (CVD). Environmental scanning electron microscopy was used to characterize the MWCNT morphology and showed that the nanotubes typically reveal a 20 nm outer diameter and 8 nm inner diameter. To investigate applications, a nanotube tower 1 mm × 1 mm × 4 mm in size was grown and peeled off the Si wafer. Each tower contains millions of individual nanotubes with 20–30 nm diameters. Electrochemical actuation of one MWCNT tower was demonstrated in a 2M NaCl solution. The MWCNT tower actuator operated up to 10 Hz without significantly decreasing strain. Only 1-2 volts was needed to obtain 0.2% strain. The aligned nanotube morphology of the tower is the reason for the high strain in the axial direction, which is an improvement compared to previously tested entangled buckypaper actuators. Cyclic voltammetry (CV) was performed to analyze the redox behavior of the nanotube tower used as an electrode. The CV response showed a sigmodal shape in a 6 mM K3(CN)6 ferrocyanide solution. This behavior provides ideal characteristics for biosensor development and application. Also, the measured electrical volume resistivity of the material was in the range of 0.1 ohm · cm. The overall improvement in the electrochemical actuation and electrical conductivity was much greater than previous nanocomposites obtained by dispersing powdered nanotubes into polymers. The demonstrated good properties suggest nanotube array towers can be considered a novel intelligent material.
To define the clinical and audiological features of normal-hearing tinnitus patients with spontaneous otoacoustic emissions, and to evaluate the role of spontaneous otoacoustic emissions in tinnitus generation.
Materials and methods:
Thirty-two patients with spontaneous otoacoustic emissions were compared with 29 patients without spontaneous otoacoustic emissions, regarding clinical and audiological aspects.
The mean age of the study group subjects was significantly lower, and they experienced the kindling effect less frequently than the control group. The mean tinnitus handicap inventory score of the study group was considerably higher than that of the controls, although the difference was not statistically significant. The study group had significantly quieter tinnitus, and higher transient evoked and distortion product otoacoustic emission responses, compared with the control group.
Normal-hearing tinnitus patients with spontaneous otoacoustic emissions have different clinical and audiological characteristics, compared with those without spontaneous otoacoustic emissions. Appropriate evaluation and treatment should be considered at an early stage in these patients.
We aimed to evaluate a practical, computerised database for collection of patient-reported and clinical outcome data, introduced as a means of characterising our patient population and assessing the effect of our interventions.
A prospectively updated, computerised database was used to detail each patient's coded and structured diagnosis and clinical findings. Response to treatment was recorded using the Sino-Nasal Outcome Test 22 and changes in graded clinical examination findings.
Data for 770 patients were prospectively entered into the database. Patients were grouped diagnostically as follows: rhinitis (20.4 per cent), chronic rhinosinusitis (12.2 per cent), chronic rhinosinusitis with polyps (24.7 per cent), anatomical anomaly (22.7 per cent), epistaxis (3.4 per cent) and ‘other’ (18.4 per cent). Following initial medical intervention, the greatest improvement in the Sino-Nasal Outcome Test 22 score was seen in the chronic rhinosinusitis with polyps group (−11.3), followed by the rhinitis group (−6.1) and the chronic rhinosinusitis group (−5.4).
The tested rhinology database provides a simple, effective and practical tool for integrating the recording of clinical and patient-reported outcome measures during the out-patient visit. It enables characterisation of the patient population, and accurately monitors and records treatment responses.
Trypanosoma cruzi is the protozoan agent of Chagas disease, and the most important parasitic disease in Latin America. Protozoa of the genus Leishmania are global agents of visceral and cutaneous leishmaniasis, fatal and disfiguring diseases. In the 1970s multilocus enzyme electrophoresis demonstrated that T. cruzi is a heterogeneous complex. Six zymodemes were described, corresponding with currently recognized lineages, TcI and TcIIa-e – now defined by multiple genetic markers. Molecular epidemiology has substantially resolved the phylogeography and ecological niches of the T. cruzi lineages. Genetic hybridization has fundamentally influenced T. cruzi evolution and epidemiology of Chagas disease. Genetic exchange of T. cruzi in vitro involves fusion of diploids and genome erosion, producing aneuploid hybrids. Transgenic fluorescent clones are new tools to elucidate molecular genetics and phenotypic variation. We speculate that pericardial sequestration plays a role in pathogenesis. Multilocus sequence typing, microsatellites and, ultimately, comparative genomics are improving understanding of T. cruzi population genetics. Similarly, in Leishmania, genetic groups have been defined, including epidemiologically important hybrids; genetic exchange can occur in the sand fly vector. We describe the profound impact of this parallel research on genetic diversity of T. cruzi and Leishmania, in the context of epidemiology, taxonomy and disease control.
This study used a prospective design and the technique of structural modelling to examine the complex interrelations between psychological factors, immune status and complications after major surgery.
Twenty-nine women scheduled for elective cholecystectomy were studied prospectively. Information regarding medical history, health practices, life stressors, and coping strategies was obtained two weeks prior to admission. At this initial meeting, as well as three days after surgery, and at one month follow-up immunological tests were performed and the level of psychological distress was assessed. The study additionally included measures of post-operative complications, and infections and negative effect during follow-up.
Pre-operative immune status emerged as a key variable exerting strong effects on subsequent immune function and, thereby producing significant, indirect effects on every recovery variable. Pre-operative distress was directly linked to increased mood disturbance at follow-up. Moreover, distress significantly influenced immune function both before and after surgery, which mediated a significant impact on most recovery variables. Active coping behaviour directly increased the risk of a complicated recovery.
The study demonstrated that distress-induced changes in immune functioning have clinical relevance. Overall, the present findings suggest that recovery from surgery is facilitated in patients with a well-functioning immune system, a low-level of pre-operative distress and a passive coping disposition.
We address two points. First, one must explain how different, rare mutations ultimately lead to common psychopathological conditions. The developmental instability model offers one solution. Second, Keller & Miller (K&M) perhaps miss the major processes other than variation fueled by rare deleterious mutations that account for interesting genetic variation in psychopathology, particularly when single alleles have non-negligible effects: Red Queen processes.