272 research outputs found
Is depression a disconnection syndrome? Meta-analysis of diffusion tensor imaging studies in patients with MDD
No full textBackground: Many studies using diffusion tensor imaging (DTI) have demonstrated impaired white matter integrity in patients with major depressive disorder (MDD), with significant results found in diverse brain regions. We sought to identify whether there are consistent changes of regional white matter integrity in patients with MDD, as shown by decreased fractional anisotropy in DTI. Method: A systematic search strategy was used to identify relevant whole brain voxel-based DTI studies of patients with MDD in relation to comparison groups. Relevant databases were searched for studies published between January 1994 and February 2011 using combinations of the terms "DTI" or "diffusion tensor;" "whole brain" or "voxel-based;" and "depress*." Using the studies that met our inclusion criteria, we performed a meta-analysis of the coordinates of decreased fractional anisotropy using the activation likelihood estimation (ALE) method, which detects 3-dimensional conjunctions of coordinates from multiple studies, weighted by sample size. We then used DTIquery software for fibre tracking to locate the fascicles involved in each region. Results: We included 11 studies with a combined sample of 231 patients with MDD and 261 comparison participants, providing 50 coordinates of decreased fractional anisotropy. Our meta-analysis identified 4 consistent locations of decreased fractional anisotropy in patients with MDD: white matter in the right frontal lobe, right fusiform gyrus, left frontal lobe and right occipital lobe. Fibre tracking showed that the main fascicles involved were the right inferior longitudinal fasciculus, right inferior fronto-occipital fasciculus, right posterior thalamic radiation and interhemispheric fibres running through the genu and body of the corpus callosum. Limitations: The number of studies included was relatively small, and the DTI data acquisition and analysis techniques were heterogeneous. The ALE method cannot handle studies with no significant group differences. Conclusion: Voxel-based analysis of DTI studies of patients with MDD consistently identified decreased fractional anisotropy in the white matter fascicles connecting the prefrontal cortex within cortical (frontal, temporal and occipital lobes) and subcortical areas (amygdala and hippocampus). This is strong evidence for the involvement of these neural circuits in the pathology of MDD
Inter-source seismic interferometry by multidimensional deconvolution (MDD) for borehole sources
No full textSeismic interferometry (SI) is usually implemented by crosscorrelation (CC) to retrieve the impulse response between pairs of receiver positions. An alternative approach by multidimensional deconvolution (MDD) has been developed and shown in various studies the potential to suppress artifacts due to irregular source distribution and intrinsic loss. Following previous theories on SI by MDD, we extend it to retrieve the impulse response between pairs of source positions by invoking source and receiver reciprocity. We verify the theory using a simple two-layered model and show that the retrieved response by MDD is more accurate than that by CC, and furthermore, it is free of free-surface multiples. We discuss the necessary pre-processing required for this method. This inter-source SI approach creates a virtual acquisition geometry with both borehole sources and receivers without the need to deploy receivers in the borehole, which might be of interest to applications such as seismic while drilling (SWD).Geoscience & EngineeringCivil Engineering and Geoscience
Full-field MDD for body-wave reflections from passive transient-sources under severely limited and irregular illumination conditions
No full textSeismic interferometry (SI) presents a set of inexpensive and noninvasive methods that can be applied to any array at the surface to retrieve virtual body-wave reflection responses from earthquake recordings. Conventional SI by cross-correlation requires recordings of wavefields in lossless media generated by a smooth continuous distribution of passive sources with isotropic source radiation patterns and similar power spectra. These conditions are unlikely to be met in the lithosphere: earthquakes are distributed sparsely and generated by complex mechanisms. The resulting anisotropy in the illumination of the receiver array causes the retrieved virtual-source radiation patterns to be irregular, leading to artifacts which can obscure the desired body-wave reflections. SI by multidimensional deconvolution (MDD) can inherently correct for anisotropic illumination of the array and does not rely on the medium being lossless. We propose an alternative formulation of MDD for two-way wavefields: full-field MDD. Different from previous MDD methods for passive two-way wavefield recordings, full-field MDD uses multiples in the passive data to construct the reflection response without free-surface interaction. Therefore, this MDD method profits from additional wavenumbers provided by scattering to compensate for sparse earthquake distributions. Besides, this method does not require wavefield decomposition, which is sensitive to velocity variations at the receiver level. We compare the reflection retrieval by full-field MDD and cross-correlation for a limited passive source distribution in a lithospheric model with a discontinuous Moho at a depth of 50 km. We simulate earthquakes generated by dipole sources along a listric fault-system with power spectra varying within bandwidth 0.2-2.6 Hz. The reflection response retrieved by full-field MDD shows a continuous high-resolution Moho reflection, while cross-correlation yields a very low resolution response obscured by artifacts
Material Driven Design (MDD): A Method to Design for Material Experiences
No full textMaterials research constantly offers novel materials as better alternatives to convention. Functional aptness is taken for granted at the first commercial launch of a new material. Nevertheless, this alone may not be enough for its commercial success and widespread use. The ‘material’ should also elicit meaningful user experiences in and beyond its utilitarian assessment. This requires qualifying the material not only for what it is, but also for what it does, what it expresses to us, what it elicits from us, and what it makes us do. In search of a proper application through such an understanding, material scientists and industries have reached out to designers to guide the development of materials by experiential goals. However, how to design for experiences with and for a material at hand has been poorly addressed to date. In this article, we propose a method, Material Driven Design (MDD), to facilitate designing for material experiences. After explaining the theoretical foundation of the method, an illustrative case is presented—where ‘coffee waste’ is the subject of a design effort to conceive a new product concept. Finally, possible research directions are addressed to bring new insights to the effective application of the MDD method to diverse projects.Design EngineeringIndustrial Design Engineerin
Multiple Path Switching Device Utilizing Size-Controlled Nano-Schottky Wrap Gates for MDD-Based Logic Circuits
No full textA novel simple and compact multiple-path-switching device for multiple-valued decision diagram (MDD) is proposed and investigated theoretically in order to realize highperformance nanowire-network-based logic circuits with advanced functionality. The device is designed on multi-semiconductor-nanowire branches having a couple of size-controlled nanometer-scale Schottky wrap gates (WPGs). The device selects an exit branch for messenger electrons according to gate voltage as a multiple-valued input variable. The pathswitching function is realized by multiple assign of gate threshold voltages and applying complementary gate voltages to the two WPGs. Theoretical investigation based on threedimensional potential simulation confirms that clear current path switching takes place in the proposed device
Double Sided Moral Hazard and Share Contracts in agriculture
No full textThis paper develops a double-sided moral hazard model of share contract in agriculture, with imperfect quality measurement by the agent and the principal, who contribute to the final good quality in terms of production effort and marketing effort respectively. Using this model, we analyse the implications of the share contract for quantity and quality, often ignored in previous analysis. With the help of a simulation exercise, we prove that the outcome-conditioned share generally weakens the agent´s incentive to make effort in quality input. This finding could explain the contractual evidence in some differentiated markets such as the wine market, where bottle-price conditioned contracts are rarely used.share-contract, double moral-hazard, quality, Farm Management,
Post-typhoon prevalence of post-traumatic stress disorder, major depressive disorder, panic disorder, and generalized anxiety disorder in a Vietnamese sample
No full textIn 2006, typhoon Xangsane disrupted a multiagency health needs study of 4,982 individuals in Vietnam. Following this disaster, 798 of the original participants were reinterviewed to determine prevalence and risk factors associated with posttraumatic stress disorder (PTSD), major depressive disorder (MDD), panic disorder (PD), and generalized anxiety disorder (GAD). Posttyphoon prevalences were PTSD 2.6%, MDD 5.9%, PD 9.3%, and GAD 2.2%. Of those meeting criteria for a disorder, 70% reported only one disorder, 15% had two, 14% had three, and 1% met criteria for all four disorders. Risk factors for posttyphoon psychopathology differed among disorders, but generally were related to high typhoon exposure, prior trauma exposure, and in contrast to Western populations, higher age, but not gender
Mental health and social support among public safety personnel
No full textSocial support may be a protective factor for the mental health of public safety personnel (PSP), who are frequently exposed to potentially psychologically traumatic events and report substantial post-traumatic stress disorder (PTSD) and major depressive disorder (MDD) symptoms. Research examining perceived social support and its association with PTSD and MDD in different PSP categories (e.g. firefighters, paramedics) is limited. This article is to examine differences in perceived social support across PSP and determine whether perceived social support is associated with differences in rates of MDD and PTSD.Peer reviewedoccupational health; post-traumatic stress disorder; public safety personnel; social support
Passive seismic interferometry by multidimensional deconvolution
No full textWe introduce seismic interferometry of passive data by multidimensional deconvolution (MDD) as an alternative to the crosscorrelation method. Interferometry by MDD has the potential to correct for the effects of source irregularity, assuming the first arrival can be separated from the full response. MDD applications can range from reservoir imaging using microseismicity to crustal imaging with teleseismic data.GeotechnologyCivil Engineering and Geoscience
Co-expression network analysis of peripheral blood transcriptome identifies dysregulated protein processing in endoplasmic reticulum and immune response in recurrent MDD in older adults
No full text© 2018 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license:
http://creativecommons.org/licenses/by-nc-nd/4.0/ which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. This author accepted manuscript is made available following 12 month embargo from date of publication (October 2018) in accordance with the publisher’s archiving policyThe molecular factors involved in the pathophysiology of major depressive disorder (MDD) remain poorly understood. One approach to examine the molecular basis of MDD is co-expression network analysis, which facilitates the examination of complex interactions between expression levels of individual genes and how they influence biological pathways affected in MDD. Here, we applied an unsupervised gene-network based approach to a prospective experimental design using microarray genome-wide gene expression from the peripheral whole blood of older adults. We utilised the Sydney Memory and Ageing Study (sMAS, N = 521) and the Older Australian Twins Study (OATS, N = 186) as discovery and replication cohorts, respectively. We constructed networks using Weighted Gene Co-expression Network Analysis (WGCNA), and correlated identified modules with four subtypes of depression: single episode, current, recurrent, and lifetime MDD. Four modules of highly co-expressed genes were associated with recurrent MDD (N = 27) in our discovery cohort (FDR<0.2), with no significant findings for a single episode, current or lifetime MDD. Functional characterisation of these modules revealed a complex interplay between dysregulated protein processing in the endoplasmic reticulum (ER), and innate and adaptive immune response signalling, with possible involvement of pathogen-related pathways. We were underpowered to replicate findings at the network level in an independent cohort (OATS), however; we found a significant overlap for 9 individual genes with similar co-expression and dysregulation patterns associated with recurrent MDD in both cohorts. Overall, our findings support other reports on dysregulated immune response and protein processing in the ER in MDD and provide novel insights into the pathophysiology of depression.This work was supported by funding from the National Health and Medical Research Council (NHMRC; ID 1060524 to BTB, SCW, SR, JT) of Australia. The Sydney Memory and Ageing Study (sMAS) was supported by a National Health and Medical Research Council (NHMRC)/Australian Research Council Strategic Award (ID 401162), NHMRC Program Grants (ID 350833 and 568969) and a Project Grant (ID 1045325). The Older Australian Twins Study (OATS) was funded by an NHMRC/ARC Strategic Award Grant of the Ageing Well, Ageing Productively Program (ID 401162) and NHMRC Project Grant (ID 1045325 and 1085606). SCW is supported by the Matthew Flinders Fellowship, Flinders University, Australia
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