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The second Singapore Mental Health Study (SMHS) – a nationwide, cross-sectional, epidemiological survey - was initiated in 2016 with the intent of tracking the state of mental health of the general population in Singapore. The study employed the same methodology as the first survey initiated in 2010. The SMHS 2016 aimed to (i) establish the 12-month and lifetime prevalence and correlates of major depressive disorder (MDD), dysthymia, bipolar disorder, generalised anxiety disorder (GAD), obsessive compulsive disorder (OCD) and alcohol use disorder (AUD) (which included alcohol abuse and dependence) and (ii) compare the prevalence of these disorders with reference to data from the SMHS 2010.
Door-to-door household surveys were conducted with adult Singapore residents aged 18 years and above from 2016 to 2018 (n = 6126) which yielded a response rate of 69.0%. The subjects were randomly selected using a disproportionate stratified sampling method and assessed using World Health Organization Composite International Diagnostic Interview version 3.0 (WHO-CIDI 3.0). The diagnoses of lifetime and 12-month selected mental disorders including MDD, dysthymia, bipolar disorder, GAD, OCD, and AUD (alcohol abuse and alcohol dependence), were based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria.
The lifetime prevalence of at least one mood, anxiety or alcohol use disorder was 13.9% in the adult population. MDD had the highest lifetime prevalence (6.3%) followed by alcohol abuse (4.1%). The 12-month prevalence of any DSM-IV mental disorders was 6.5%. OCD had the highest 12-month prevalence (2.9%) followed by MDD (2.3%). Lifetime and 12-month prevalence of mental disorders assessed in SMHS 2016 (13.8% and 6.4%) was significantly higher than that in SMHS 2010 (12.0% and 4.4%). A significant increase was observed in the prevalence of lifetime GAD (0.9% to 1.6%) and alcohol abuse (3.1% to 4.1%). The 12-month prevalence of GAD (0.8% vs. 0.4%) and OCD (2.9% vs. 1.1%) was significantly higher in SMHS 2016 as compared to SMHS 2010.
The high prevalence of OCD and the increase across the two surveys needs to be tackled at a population level both in terms of creating awareness of the disorder and the need for early treatment. Youth emerge as a vulnerable group who are more likely to be associated with mental disorders and thus targeted interventions in this group with a focus on youth friendly and accessible care centres may lead to earlier detection and treatment of mental disorders.
To identify the common causal beliefs of mental illness in a multi-ethnic Southeast Asian community and describe the sociodemographic associations to said beliefs. The factor structure to the causal beliefs scale is explored. The causal beliefs relating to five different mental illnesses (alcohol abuse, depression, obsessive-compulsive disorder (OCD), dementia and schizophrenia) and desire for social distance are also investigated.
Data from 3006 participants from a nationwide vignette-based study on mental health literacy were analysed using factor analysis and multiple logistic regression to address the aims. Participants answered questions related to sociodemographic information, causal beliefs of mental illness and their desire for social distance towards those with mental illness.
Physical causes, psychosocial causes and personality causes were endorsed by the sample. Sociodemographic differences including ethnic, gender and age differences in causal beliefs were found in the sample. Differences in causal beliefs were shown across different mental illness vignettes though psychosocial causes was the most highly attributed cause across vignettes (endorsed by 97.9% of respondents), followed by personality causes (83.5%) and last, physical causes (37%). Physical causes were more likely to be endorsed for OCD, depression and schizophrenia. Psychosocial causes were less often endorsed for OCD. Personality causes were less endorsed for dementia but more associated with depression.
The factor structure of the causal beliefs scale is not entirely the same as that found in previous research. Further research on the causal beliefs endorsed by Southeast Asian communities should be conducted to investigate other potential causes such as biogenetic factors and spiritual/supernatural causes. Mental health awareness campaigns should address causes of mental illness as a topic. Lay beliefs in the different causes must be acknowledged and it would be beneficial for the public to be informed of the causes of some of the most common mental illnesses in order to encourage help-seeking and treatment compliance.
The incidence of papillary thyroid cancer is rising, with an increase in the number of microcarcinomas being discovered. There is controversy in the literature regarding the optimal management of these tumours. This study aimed to review our institution's experience with the presentation and management of papillary thyroid microcarcinoma.
Retrospective analysis from the Sydney Head and Neck Cancer Institute, from 1987 to 2009.
A total of 228 patients were analysed. Papillary thyroid microcarcinomas were discovered incidentally in 116 (50.9 per cent) patients and non-incidentally in the remaining 112 (49.1 per cent) patients. Amongst the non-incidental group, 11.6 per cent of patients presented with lateral cervical lymph node involvement. Non-incidental microcarcinomas were significantly associated with younger age (<45 years) (p = 0.007) and larger tumours (5–10 mm) (p < 0.001). Only four patients in the incidental group suffered recurrent disease (locoregional). No patient developed distant metastatic disease or died during follow up.
Papillary thyroid microcarcinomas present both incidentally and non-incidentally, with equal prevalence. Non-incidental tumours not infrequently present with cervical lymph node disease. The patient outcome is generally excellent.
Whether autism spectrum maps onto a spectrum of brain abnormalities and whether Asperger's syndrome (ASP) is distinct from high-functioning autism (HFA) are debated. White-matter maldevelopment is associated with autism and disconnectivity theories of autism are compelling. However, it is unknown whether children with ASP and HFA have distinct white-matter abnormalities.
Voxel-based morphometry mapped white-matter volumes across the whole brain in 91 children. Thirty-six had autism spectrum disorder. A history of delay in phrase speech defined half with HFA; those without delay formed the ASP group. The rest were typically developing children, balanced for age, IQ, gender, maternal language and ethnicity. White-matter volumes in HFA and ASP were compared and each contrasted with controls.
White-matter volumes around the basal ganglia were higher in the HFA group than ASP and higher in both autism groups than controls. Compared with controls, children with HFA had less frontal and corpus callosal white matter in the left hemisphere; those with ASP had less frontal and corpus callosal white matter in the right hemisphere with more white matter in the left parietal lobe.
HFA involved mainly left hemisphere white-matter systems; ASP affected predominantly right hemisphere white-matter systems. The impact of HFA on basal ganglia white matter was greater than ASP. This implies that aetiological factors and management options for autism spectrum disorders may be distinct. History of language acquisition is a potentially valuable marker to refine our search for causes and treatments in autism spectrum.
We and others have reported that patients experiencing their first episode of psychosis already have significant structural brain abnormalities. Antipsychotics seem to reverse subcortical volume deficits after months of treatment. However, the early impact of medication on brain morphology is not known.
Forty-eight individuals in their first episode of psychosis underwent magnetic resonance imaging (MRI) brain scanning. Twenty-six were antipsychotic naive and 22 were newly treated with antipsychotic medication for a median period of 3 weeks. In each group, 80% of subjects received a diagnosis of schizophrenia. The two groups were balanced for age, sex, handedness, ethnicity, height, years of education, paternal socio-economic status (SES) and Positive and Negative Syndrome Scale (PANSS) score. Group differences in whole-brain grey matter were compared voxel by voxel, using Brain Activation and Morphological Mapping (BAMM) software. We also conducted testing of group differences with region-of-interest (ROI) measurements of the caudate nucleus.
Relative to the untreated group, those receiving antipsychotic medication for 3–4 weeks had significantly greater grey-matter volumes in the bilateral caudate and cingulate gyri, extending to the left medial frontal gyrus. ROI analysis confirmed that, in treated patients, the right and left caudate nuclei were significantly larger by 10% (p<0.039, two-tailed) and 9% (p<0.048, two-tailed) respectively.
Early striatal grey-matter enlargement may occur within the first 3–4 weeks of antipsychotic treatment. Possible reasons for putative striatal hypertrophy and its implications are discussed.
The band gap energies of zinc-blende InNxAs1-x alloy as a function
of its nitrogen composition have been calculated using the density
functional theory. The results agree well with those obtained from
experimental results. The minimum band gap energy of InNxAs1-x
alloy obtained is 70 meV at its N composition of 0.45. The band gap bowing
coefficient of InNxAs1-x alloy is obtained from the curve fitting
of the simulated band gap energy versus the nitrogen composition, x. The
band gap bowing coefficient of zinc-blende InNxAs1-x alloy is
found to be 2.072 ± 0.236 eV. The energy band gap for InN is also
correctly predicted from this calculation.
Diffusion tensor imaging (DTI) can be used to investigate cerebral structural connectivity in never-medicated individuals with first-episode schizophrenia.
Subjects with first-episode schizophrenia according to DSM-IV-R who had never been exposed to antipsychotic medication (n=25) and healthy controls (n=26) were recruited. Groups were matched for age, gender, best parental socio-economic status and ethnicity. All subjects underwent DTI and structural magnetic resonance imaging (MRI) scans. Voxel-based analysis was performed to investigate brain regions where fractional anisotropy (FA) values differed significantly between groups. A confirmatory region-of-interest (ROI) analysis of FA scores was performed in which regions were placed blind to group membership.
In patients, FA values significantly lower than those in healthy controls were located in the left fronto-occipital fasciculus, left inferior longitudinal fasciculus, white matter adjacent to right precuneus, splenium of corpus callosum, right posterior limb of internal capsule, white matter adjacent to right substantia nigra, and left cerebral peduncle. ROI analysis of the corpus callosum confirmed that the patient group had significantly lower mean FA values than the controls in the splenium but not in the genu. The intra-class correlation coefficient (ICC) for independent ROI measurements was 0.90 (genu) and 0.90 (splenium). There were no regions where FA values were significantly higher in the patients than in the healthy controls.
Widespread structural dysconnectivity, including the subcortical region, is already present in neuroleptic-naive patients in their first episode of illness.
Schottky barrier height (ÖB) engineering of NiGe/n-Ge(001) diodes was achieved through germanidation induced dopant segregation on As implanted-Ge substrates. was reduced from 0.55 eV to 0.16 eV with increasing As dose on n-Ge(001) while on p-Ge(001), the diodes exhibited increasing ÖB.
Zinc oxide (ZnO) quantum dots (QDs) embedded films were fabricated on silicon substrates by metal organic chemical vapor deposition at 350°C. The QDs can be obtained in a matrix of amorphous ZnO films by introducing a large amount of precursors. The size of the QDs ranged from 3 to 12 nm, which was estimated by high-resolution transmission electron microscopy. The photoluminescence measured at 80 K showed that the emission of QDs embedded film ranged from 3.0 to 3.6 eV. The broad near-band-edge emission is due to the quantum confinement effect of the QDs. The quantum confinement effect of the QDs disappears after the post-growth annealing due to the ripening of QDs.
The optical absorption spectra of intersubband transitions in In0.3Ga0.7As/GaAs multiple quantum dots (MQDs) grown by molecular beam epitaxy were investigated. By varying the number of In0.3Ga0.7As monolayers deposited, a series of samples with varying dot sizes ranging from 10 – 50 monolayers were obtained. The quantum dots grown with size less than 15 monolayers or more than 50 monolayers did not yield any observable measurements of intersubband transition. This suggests that there exist a critical upper and lower limit of In0.3Ga0.7As quantum dots for infrared detectors. A wavelength range of 8.60 – 13.70 μm is achieved for structures grown with the above monolayers range. The theoretical line-shape of the intersubband transition absorption was compared to the experimental measurements. From the lineshape, it was deduced that bound-to-continuum transtition is present in thick quantum dots and bound-to-bound transition is present in thinly grown quantum dots.
The emission from bias voltage driven In0.06Al0.08Ga0.86As/Al0.3Ga0.7As edge-emitting diode lasers with cavity lengths of 0.6 and 0.9 mm was measured at 290 K using a high resolution Fourier-transform infrared spectrometer. The light-current (L-I) characteristic curves showed that a threshold current of ∼ 0.5 and 0.8 A was needed to reach the stimulated emission in laser diodes with cavity lengths of 0.6 and 0.9 mm, respectively. The laser diode longitudinal modes were observed in the stimulated emission spectrum for each of the devices. These spectra enabled us to calculate the refractive index, total loss, and gain of the active region. On the other hand, the cavity length was determined by utilizing the interferogram spectrum, longitudinal modes spacing, and direct measurements of the laser dimensions. A good agreement between the cavity length values obtained from the three methods was achieved.
The periodic silane burst technique was employed during metalorganic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111). Periodic silicon delta doping during growth of both the AlN and GaN layers led to growth of GaN films with decreased tensile stresses and decreased threading dislocation densities, as well as films with improved quality as indicated by x-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. The possible mechanism of the reduction of tensile stress and the dislocation density is discussed in the paper.
In order to understand how N2 plasma conditions impact on the incorporation of nitrogen species into a thin SiO2 (1.4 nm), tuning of some pulsed RF (pRF) Decoupled Plasma Nitridation (DPN) process parameters was performed: duty cycle (DC) or on-time per period, frequency (f), process time (t) and some cross-combinations (DC*f, DC*t, DC*f*t). The N2 plasma and the SiOx Ny film were characterized using Langmuir probe analysis (LP) and Delay to Reoxidation (D2R) techniques, respectively. Correlations are established between ion density and electron temperature and the resultant nitrogen concentration and parasitic physical thickness increase. The LP results indicate that while DC impacts the ion density and energy, the frequency has no impact to first order. This is consistent with the physical characteristics of the film. From the combination of DC*f*t, the importance of the off-time portion of the pulse was revealed. With the help of a modified pulsed RF DPN generator, allowing a decrease of the frequency down to 2 kHz, a 5% improvement of the drive current for pMOS transistors was obtained.
Intersubband transitions (ISTs) in GaN/AlxGa1-xN multiple quantum wells (MQWs) were investigated using an optical absorption technique. Several samples were grown by either Molecular Beam Epitaxy (MBE) or Metal-Organic Chemical Vapor Deposition (MOCVD) and were investigated using both normal incident and waveguide configurations. The waveguides were fabricated by dicing each sample into 2 mm wide by 5 mm long pieces with two facets polished at 45 degrees with respect to the surface such that light propagates across the sample's width. Preliminary results indicate that ISTs are observable in Si-doped and undoped GaN/AlxGa1-xN MQWs. The source of these charge carriers in the undoped samples are explained as being due to the spontaneous polarization effect which exists at the GaN/AlxGa1-xN interfaces where the GaN surface has Ga-polarity. Scanning Electron Microscopy indicates that a sample containing what appeared to be a large number of cracks and or hexagonal voids lacked the presence of ISTs.
Using temperature-dependent photoluminescence (PL), we report a detailed study on the optical transitions in AlyInxGa1−x−yN (0.01≤ × ≤ 0.023, 0.07 ≤ y ≤ 0.14) of variable thickness (20 – 100 nm) grown on GaN by metalorganic chemical vapor deposition (MOCVD). At 100 K, highest electron mobility has been obtained for samples with 40 nm thick AlInGaN epilayer and this is due to the contribution from the two-dimensional electron gas (2DEG) in the confined two dimensional potential well. In literature, such 2DEG phenomenon is not discussed for AlInGaN quaternary alloys. In our samples, we have clearly observed such effects from low-temperature PL spectroscopy for AlInGaN epilayer of thickness ≥ 40 nm. The PL peaks observed due to the interband transitions from 2DEG sub-bands to the valence band are in the range 3.55 – 3.68 eV for the sample with an epilayer thickness of 100 nm. Due to the composition pulling effect in this alloy, there is a higher incorporation of Al towards the surface for thicker AlInGaN epilayer, which generates a stronger piezoelectric field and a deeper triangular potential for electron confinement. This is evident from the observation of higher intensity ratio for 2DEG transition compared to band-edge transitions, I2DEG/IBE in sample with thicker AlInGaN epilayer at higher temperature. The intensity ratio, I2DEG/IBE however decreases subsequently for all the samples with further increase in temperature due to thermal excitation.
The germanosilicidation of Ni on strained (001) Si0.8Ge0.2, particularly Ge segregation, grain boundary grooving, and surface morphology, during rapid thermal annealing (RTA) was studied. High-resolution cross-sectional transmission electron microscopy (HRXTEM) suggested that Ge-rich Si1−zGez segregation takes place preferentially at the germanosilicide/Si1−xGex interface, more specifically at the triple junctions between two adjacent NiSi1−uGeu grains and the underlying epi Si1−xGex, and it is accompanied with thermal grooving process. The segregation process accelerates the thermal grooving of NiSi1−uGeu grain boundaries at the interface. The segregation-accelerated grain boundary grooving has significant effect on the surface morphology of NiSi1−uGeu films in Ni-SiGe system.
AlN self-assembled quantum dots (QDs) with high density of ∼ 4.4 × 1010/cm2 on Si(111) substrates have been grown by low-pressure chemical vapor deposition under a very low V/III ratio of 350. We found that using AlN-QD/AlN buffer two-inch GaN epilayers without cracks were grown, indicating the underlying quantum dots play a crucial role in relaxing the stain of GaN epilayer. The quality and morphology were investigated by atom force microscopy, transmission electron microscopy, X-ray diffraction and optical microscope.
In this paper, deep level defects in high quality continuous GaN films grown over a cracked Si-doped GaN template has been studied using digital deep level transient spectroscopy (DLTS) and transmission electron microscopy (TEM). From TEM observation, it is found that the density of pure screw dislocations have been effectively suppressed while pure edge dislocations remained in substantial quantity. From DLTS measurement, trap levels at Ec -ET ∼ 0.11-0.12 eV, 0.24-0.27 eV, 0.60-0.63 eV were detected in the high quality GaN layer. DLTS measurement was also carried out on the underlying cracked Si-doped GaN template after the top high quality continuous GaN film was removed by plasma etching. An additional defect level at Ec-Et ∼ 0.37 eV was detected which we attributed to defect decoration at screw dislocation. Both the trap levels Ec-ET ∼ 0.24–0.27 eV, 0.60-0.63 eV are believed to originate from mixed screw/edge dislocation based on observation of the logarithmic capture behavior. Trap level at Ec -ET ∼ 0.24-0.27eV, however, experiences a more drastic increase in transient capacitance (i.e. in trap concentration) compared to that of Ec -ET ∼ 0.60-0.63 eV after plasma etching, illustrating that the latter is related to a higher proportion of edge dislocation. The 0.11-0.12 eV trap level, which exhibits an exponential capture kinetic, is believed to be related to nitrogen vacancies. This high quality continuous GaN layer can be used as a template to grow any device structure and the underneath cracked Si-doped GaN layer may help to release stress for the top continuous GaN layer. This can bring about a cracked free epilayer for subsequent device fabrication.
A NiSi silicide process employing a Ni(Ti) alloy has been investigated. It was experimentally demonstrated that a small amount of Ti in Ni could overcome the reaction-inhibiting effect of an interfacial oxide layer on Si. Ti in the deposited Nil film reacts with the interfacial oxide, yielding an altered oxide layer, which acts as a Ni-permeable diffusion membrane during silicidation. Good diode characteristics were obtained from p+/n silicided Ni(Ti)-diodes with an initial interfacial oxide. It is believed that the ability to form silicide effectively in the presence of a native oxide will greatly relieve constraints on processing conditions and significantly enhance manufacturing yield.