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Natural disasters are increasing in frequency and severity. They cause widespread hardship and are associated with detrimental effects on mental health.
Our aim is to provide the best estimate of the effects of natural disasters on mental health through a systematic review and meta-analysis of the rates of psychological distress and psychiatric disorder after natural disasters.
This systematic review and meta-analysis is limited to studies that met predetermined quality criteria. We required included studies to make comparisons with pre-disaster or non-disaster exposed controls, and sample representative populations. Key studies were identified through a comprehensive search of PubMed, EMBASE and PsycINFO from 1980 to 3 March 2017. Random effects meta-analyses were performed for studies that reported key outcomes with appropriate statistics.
Forty-one studies were identified by the literature search, of which 27 contributed to the meta-analyses. Continuous measures of psychological distress were increased after natural disasters (combined standardised mean difference 0.63, 95% CI 0.27–0.98, P = 0.005). Psychiatric disorders were also increased (combined odds ratio 1.84, 95% CI 1.43–2.38, P < 0.001). Rates of post-traumatic stress disorder and depression were significantly increased after disasters. Findings for anxiety and alcohol misuse/dependence were not significant. High rates of heterogeneity suggest that disaster-specific factors and, to a lesser degree, methodological factors contribute to the variance between studies.
Increased rates of psychological distress and psychiatric disorders follow natural disasters. High levels of heterogeneity between studies suggest that disaster variables and post-disaster response have the potential to mitigate adverse effects.
Most of the recent advances in X-ray astronomy have resulted from satellite observations in the low energy (< 20 keV) range. The Einstein X-ray Observatory in particular has been responsible for a dramatic increase in our knowledge of the X-ray sky, in that all major classes of astronomical objects have been detected.
The binary X-ray source GX 1 + 4 was observed during a balloon flight in 1986, November. The source was in a relatively high intensity state. Time analysis of the data shows that the pulsation period was 111.8 ± 1.0 s indicating that one or more episodes of spin-down occurred between 1980 and 1986. Folded pulse profiles are very broad with an indication of a notch at the peak. Evidence has been found for a correlation between hard X-ray intensity and phase of the proposed 304 day orbital period. The time averaged intensity since 1980 is an order of magnitude lower than during the 1970’s. A survey of the post 1980 data shows that several reversals of the period derivative have occurred. Spin-up at the rates typical of the 1970’s has been followed by a dramatic spin-down episode with dP/dt>2.4 × 10−7 s/s.
To investigate relationships between mortality and circulating 25-hydroxyvitamin D (25(OH)D), 25-hydroxycholecalciferol (25(OH)D3) and 25-hydroxyergocalciferol (25(OH)D2).
Case–cohort study within the Melbourne Collaborative Cohort Study (MCCS). We measured 25(OH)D2 and 25(OH)D3 in archived dried blood spots by LC–MS/MS. Cox regression was used to estimate mortality hazard ratios (HR), with adjustment for confounders.
The MCCS included 29 206 participants, who at recruitment in 1990–1994 were aged 40–69 years, had dried blood spots collected and no history of cancer. For the present study we selected participants who died by 31 December 2007 (n 2410) and a random sample (sub-cohort, n 2996).
The HR per 25 nmol/l increment in concentration of 25(OH)D and 25(OH)D3 were 0·86 (95 % CI 0·78, 0·96; P=0·007) and 0·85 (95 % CI 0·77, 0·95; P=0·003), respectively. Of 5108 participants, sixty-three (1·2 %) had detectable 25(OH)D2; their mean 25(OH)D concentration was 11·9 (95 % CI 7·3, 16·6) nmol/l higher (P<0·001). The HR for detectable 25(OH)D2 was 1·80 (95 % CI 1·09, 2·97; P=0·023); for those with detectable 25(OH)D2, the HR per 25 nmol/l increment in 25(OH)D was 1·06 (95 % CI 0·87, 1·29; P interaction=0·02). HR were similar for participants who reported being in good, very good or excellent health four years after recruitment.
Total 25(OH)D and 25(OH)D3 concentrations were inversely associated with mortality. The finding that the inverse association for 25(OH)D was restricted to those with no detectable 25(OH)D2 requires confirmation in populations with higher exposure to ergocalciferol.
To identify predictors of increased adiposity for different measures of adiposity.
Prospective cohort study, the Melbourne Collaborative Cohort Study (MCCS), with data at baseline (1990–1994) and wave 2 (2003–2007).
Participants recruited from the community.
Australian-born participants (n 5879) aged 40 to 69 years who were not current smokers and who were free from common chronic diseases at recruitment. At baseline and at wave 2, weight and waist circumference were measured; while demographic and lifestyle variables were obtained at baseline via structured interviews.
Participants who reported any recreational physical activity at baseline had lower weight and smaller waist circumference at wave 2 than those who did not, particularly for younger participants and for vigorous physical activity. Walking for leisure was not associated, and greater physical activity at work was associated, with greater adiposity measures at wave 2. A diet low in carbohydrates and fibre, but high in fat and protein, predicted greater weight and waist circumference at wave 2. Participants were less likely to have elevated weight or waist circumference at wave 2 if they consumed low to moderate amounts of alcohol.
Our findings indicate that promoting vigorous physical activity, encouraging a diet high in carbohydrate and fibre but low in fat and protein, and limiting alcohol intake could be promising approaches for preventing obesity in middle-aged adults. Similar interventions should successfully address the management of both weight and waist circumference, as they were predicted by similar factors.
In the fourth part of this paper devoted to the problem of the thermal self-focusing of an electromagnetic wave in an underdense plasma, we examine the spatial nonlinear development of the instability, assuming that a stationary state of the type described earlier has been established. Our treatment considers the interaction of the pump wave with the Stokes side-band waves and the density perturbation corresponding to the most unstable linear mode. We show that the system of equations describing their interaction possesses three invariants. These invariants are used to reduce the problem to a single differential equation for the axial behaviour of the amplitude of the density perturbation. The form of the invariants differs according as the inclination of the beam to the magnetic field is above or below the critical value defined earlier. Above the critical orientation, the amplitude of the density perturbation can be expressed algebraically in terms of the amplitudes of the pump and side-band waves. We show that this case is integrable in terms of the Jacobean elliptic function dn and we use the results to find the saturation level. Below the critical orientation, the response of the plasma becomes non-local, above a certain threshold power. The algebraic relation is then replaced by a differential equation which results in a significantly more complicated differential equation for the amplitude of the density perturbation. A particular solution of this equation is found for a special choice of initial conditions and from this the saturation level is found. The results of these calculations are applied to the problem of ionospheric modification by microwave transmissions from the proposed solar power satellite systems.
We investigate the low-frequency azimuthal oscillations on a non-neutral magnetized electron column of very low density. A perturbation analysis of the slow mode of the rigid rotator equilibrium is developed to illustrate the nature of large-amplitude fundamental-mode oscillations. The results of this theoretical analysis show two important characteristics: firstly, as the perturbation amplitude is increased the wave form ceases to be purely sinusoidal and shows period doubling. Secondly, above a certain threshold, all harmonics of the wave grow and the wave breaks. The results of the former are compared with a simple electron beam experiment and are found to be in good qualitative agreement.
We consider two non-parallel beams, each of width a, that interact in a plasma and excite a wave that travels across their region of intersection. We determine the dependence of the amplitude of the excited wave on a for the limiting cases of large and small values of the ratio of the initial beam intensities.
In the second part of this paper devoted to the problem of the thermal self-focusing of an electromagnetic wave in an underdense plasma, we extend the linear theory of part 1 to include the effect of collisional energy transfer from the electrons to the ions. The eigenvalue problem which gives the spectrum of the wave modes that occur in a beam of finite width is formulated and solved for the case of a square beam profile. From the resulting dispersion relation, we derive the unstable wavenumber band and the maximum spatial growth rate. An approximate solution of the dispersion relation is obtained for the case of a thin beam which illustrates how the stabilizing influence of energy transfer to the ions affects the unstable spectrum. In addition, some numerical solutions of the dispersion relation are presented for the cases of ionospheric modification by a power satellite microwave beam and by an ionospheric HF heater.
In the third part of this paper devoted to the problem of the thermal self-focusing of an electromagnetic wave in an underdense plasma, we extend the lineary theory of part 1 to include the effect of ambient drift motion perpendicular to the plane of the axis of the beam and the magnetic field. We show that the amplitude of the density perturbation satisfies a third-order hyperbolic equation, when this effect is included, and we apply Riemann's method to obtain its solution in integral form. This solution shows that a state of stationary self-focusing is established within the beam after a time equal to the transit time for a perturbation to drift across it. The form of the axial growth in the stationary state is derived from an asymptotic evaluation of the integral representation for large axial distances. It is found that the axial growth increases across the beam starting from zero at the edge through which plasma enters the beam and reaching its maximum attainable value at or before the opposite edge, depending on the magnitude of the drift velocity. The maximum growth decreases as the drift velocity increases and only occurs at the rates deduced in parts 1 and 2 when the beam width is several times larger than the scale length which describes the decay of a density perturbation within the beam due to the combined effect of drift longitudinal ambipolar diffusion, recombination and the stabilizing influence of perturbations to the electrical conductivity. The factor by which the amplitude of a convected density perturbation is reduced relative to the value it would have in the absence of drift motion is evaluated and the results are applied to the case of ionospheric modification by a transmission from the proposed solar power satellite systems.
In the fifth part of this paper devoted to the problem of the thermal self-focusing of an electromagnetic wave in an underdense plasma, we extend the nonlinear theory of part 4 to include the effect of cubic nonlinearities. These terms describe the stabilizing influence of perturbations to the electrical conductivity. We assume that a stationary state of the type described earlier has been established and consider the spatial nonlinear interaction of the pump wave with the Stokes side-band waves and the density perturbation corresponding to the most unstable linear mode. We show that the system of єquations describing their interaction possesses three invariants. These invariants are used to reduce the problem to quadratures and an implicit solution is obtained in terms of incomplete elliptic integrals of the first and third kinds. From this solution we derive explicit expressions for the saturation level and the nonlinear growth length. The results are applied to the problem of ionospheric modification by microwave transmissions from the proposed solar power satellite systems.
A new approach to the problem of the radiation emitted from a localized external current source embedded in a magnetoplasma is described. It is argued that the calculation of the fields in the radiation zone can be substantially simplified by adopting at the outset a suitable parametrization of the dispersion surface. We illustrate the approach by calculating the far fields using the full expression for the dielectric tensor of a warm magnetized electron gas. In this case one can take the angle of rotation about the external magnetic field and the square of the refractive index as the curvilinear co-ordinates of the dispersion surface. The form of the surfaces of constant phase and the amplitudes of the emitted waves are described for each topologically different region of parameter space and their structures are related to the shapes of the refractive index surfaces. Attention is also drawn to the existence of locally cylindrical waves that can produce beams which are highly collimated in the direction of the external magnetic field.
The equilibrium statistical mechanics of electrostatic ion wave turbulence is studied within the framework of a continuum ion flow with adiabatic electrons. Attention is drawn to the fact that the wave field consists in general of two components, namely ion-acoustic and ion vortex modes. It is shown that the latter can significantly affect the equilibria on accoant of their ability both to emit and to scatter ion sound. Exact equilibria for the vortex—acoustic wave field are given in terms of a canonical distribution and the correlation functions are expressed in terms of a generating functional. A nonlinear transformation of the wave field, which removes the vortex-acoustic interaction energy to lowest order in the strength of the coupling, while preserving the phase space volume element, is then introduced. This enables the Feynman-Hibbs variational principle to be used to obtain an approximate generating functional based on a ‘trial’ energy functional, which is a quadratic in the new variables. Detailed calculations are carried out for the case in which the dominant coupling is an indirect interaction of the vortex modes mediated by the sound field. An equation for the spectrum of the vortex modes is obtained for this case, which is shown to possess a simple exact solution. This solution shows that the spectrum of fluctuations changes considerably as the total energy increases. At low levels of excitation the solution reduces to equipartition of energy. At higher levels the indirect interaction becomes significant and the formation of a condensed vortex state is possible when the mean energy exceeds the electron thermal energy. It is suggested that condensed vortex states could occur in the plasma sheet of the earth's magnetosphere and it is shown that the predicted ratio of the mean ion energy to the mean electron energy is consistent with the trend of observed values.
The present series of papers is concerned with the problem of the thermal selffocusing of an electromagnetic wave in an underdense plasma which is examined within the context of ionospheric modification by high-power radio waves. We formulate this problem as a coherent four-wave interaction between a pump wave, Stokes side-band waves and a thermally driven density perturbation. Our treatment assumes that the heating of the electrons in the interference pattern of the pump and side-band waves is in equilibrium with longitudinal heat conduction and energy transfer to the ions and, in addition, that the density perturbation is subject to decay on account of longitudinal ambipolar diffusion, ambient plasma drift motion, recombination and the stabilizing influence of perturbations to the electrical conductivity.
The effect of a magnetic field on the diffusion of a cylindrical column of ionization, having an initial electron density much greater than that of the ambient weakly ionized plasma in which it is embedded, is examined for the case in which the electron gyro-frequency is much greater than the electron neutral collision frequency Ve. The nonlinear diffusion equations are solved by means of a perturbation expansion based on their exact solution for the case Ve = 0. This approach leads to a singular perturbation problem, and shows that, when the column is not closely aligned with the field the distribution of plasma differs appreciably from that obtained from an ordinary anisotropic diffusion equation.
Bulk ZnO grown by the hydrothermal technique was investigated using electron paramagnetic resonance (EPR), photoluminescence (PL), and infrared absorption (FTIR) techniques. Isolated subsitutional lithium is the dominant acceptor and could be detected using EPR or PL. A large concentration of neutral Li+-OH− centers were observed using FTIR data. EPR spectra assigned to Mn, Co, Ni, Fe, and Group III (Al, Ga) donors were also observed. Photoinduced changes in the charge states of the different deep and shallow centers were produced using 325 nm light, and the stability of these changes were monitored with EPR during pulsed thermal anneals. The charge-state changes for some defects were persistent and remained up to 300 K. These impurities, when present in device structures, may act as stable charge trapping sites.