The atmospheric electric current, "air-earth current", flows between the low ionosphere and Earth's surface. The source of this current is the potential difference between the global equalizing layer ...called the ionosphere and the ground surface. According to Wilson's concept of the Earth's Global Electric Circuit, in the areas of so-called fair weather, based on current measurements at the Earth's surface, it is possible to conclude the global electrical processes in the ionosphere and higher layers. The theoretical basis for this inference is the law of continuity of electric current or the principle of conservation of electric charge. We present the results of simulations of the distribution of electric field lines for sensors with different geometries placed in a uniform electric field, representing the atmospheric electric field. The sensors are metal surfaces on which electric charges are induced or deposited. In the external measuring circuit to which the sensor is connected, an electric current A will flow, related to the air-earth current density A/m
, but their relationship may be challenging to interpret. We analyze the impact of sensor geometry on the possibility of interpreting the atmospheric electric conduction and atmospheric displacement current based on the current measured in the external circuit. This present method can be used for the geometric construction of new sensors at the stage of determining the electrical characteristics of the sensor (e.g., effective collecting area). It can support the comprehensive design of a measurement system at the interface between an atmosphere, sensor, and electronic equipment.
PURPOSE OF REVIEWWe review diffusion tensor imaging (DTI) studies that investigate white matter abnormalities in patients with chronic schizophrenia, first episode schizophrenia, and those who are at ...genetic risk for developing schizophrenia. Additionally, we include studies that combine DTI and functional MRI (fMRI) to investigate brain connectivity abnormalities.
RECENT FINDINGSSchizophrenia is a complex mental disorder with a peak age of onset in early adulthood. Abnormalities in white matter tracts, which connect brain regions into functional networks, are most likely relevant for understanding structural and functional brain abnormalities in schizophrenia. Dysconnectivity between brain regions, in fact, is thought to underlie cognitive abnormalities in schizophrenia but little is known about how alterations at the functional level relate to abnormalities in anatomical connectivity. DTI has become one of the most popular tools in brain research to address such questions. Here we review white matter abnormalities using DTI with the aim of understanding dysconnectivity of brain regions and their implications in schizophrenia.
SUMMARYAdvances in DTI and in combining DTI with fMRI provide new insight into anatomical and functional connections in the brain, and for studying dysconnectivity in schizophrenia.
A series of coordination polymers (CPs), some of them featuring an unusual architecture, have been constructed by treatment of RSCH 2 CCCH 2 SR (R = C 6 H 11 L1 , t -Bu L2 ) with CuX (X = Cl, Br, I) ...and CuX 2 . The outcome of the reaction of L1 with CuI depends on the metal-to-ligand ratio. Treatment of CuI with L1 in a 2 : 1 ratio affords the luminescent 2D CP Cu 4 I 4 (μ- L1 ) 2 n (CP1), whose grid-shaped network is built upon Cu 4 (μ 3 -I) 4 cubane-like clusters as secondary building units (SBUs), interconnected via bridging L1 ligands. The use of a 1 : 1 ratio gives a material, whose particularity is the coexistence of two topological isomers within the unit cell. The first one, {Cu(μ 2 -I) 2 Cu}(μ- L1 ) 2 n (CP2), consists of 1D ribbons. The second isomer having a 0D topology, {Cu(μ 2 -I) 2 Cu}(μ- L1 ) 2 D1, is built upon discrete molecular complexes, whose dinuclear Cu(μ 2 -I) 2 Cu rhomboid-shaped core is spanned by two bridging L1 ligands. Mixing CuBr with L1 in MeCN solution leads to an isostructural material incorporating both 0D {Cu(μ 2 -Br) 2 Cu}(μ- L1 ) 2 complex D2 along with the 1D isomer {Cu(μ 2 -Br) 2 Cu}(μ- L1 ) 2 n (CP3). However, only the 1D CP {Cu(μ 2 -Cl) 2 Cu}(μ- L1 ) 2 n (CP4) results from complexation of L1 with CuCl. A stoichiometry-dependence is also noticed upon treatment of CuI with L2 . Conducting the reaction in a 2 : 1 ratio yields the luminescent 2D CP Cu 4 I 4 (μ- L2 ) 2 n (CP5), whereas mixing equimolar amounts of the reactants produces 2D CP {Cu(μ 2 -I) 2 Cu}(μ- L2 ) 2 n (CP6). Structurally similar 2D CPs {Cu(μ 2 -X) 2 Cu}(μ- L2 ) 2 n (CP8 and CP9) result from complexation of L2 on CuBr or CuCl, respectively. Treatment of L2 with an excess of CuBr or CuBr 2 in refluxing acetonitrile led to the transfer of Br to the acetylenic triple bond, generating an olefinic halogenated dithioether ligand Bu L3 that coordinates to CuBr to generate a 1D network {Cu(μ 2 -Br) 2 Cu}(CH 3 CN)(μ- L3 ) n (CP9). Using different conditions (propionitrile at 293 K), the reaction of L2 and excess CuBr led to the formation of a 2D network {Cu(μ 2 -Br) 2 Cu}(μ- L2 )(μ- L3 ) n (CP10) incorporating both L2 and L3 in an alternating manner as assembling ligands. An isostructural chloro-analogue 2D {Cu(μ 2 -Cl) 2 Cu}(μ- L2 )(μ- L4 ) n (CP11) was obtained using CuCl or CuCl 2 . The crystallographic work is completed by thermal analyses and investigation of the luminescence properties of CP1 and CP5 at 77 and 298 K.
Functional neurological disorder (FND) is a condition at the intersection of neurology and psychiatry. Individuals with FND exhibit corticolimbic abnormalities, yet little is known about the role of ...white matter tracts in the pathophysiology of FND. This study characterized between-group differences in microstructural integrity, and correlated fiber bundle integrity with symptom severity, physical disability, and illness duration.
A diffusion tensor imaging (DTI) study was performed in 32 patients with mixed FND compared to 36 healthy controls. Diffusion-weighted magnetic resonance images were collected along with patient-reported symptom severity, physical disability (Short Form Health Survey-36), and illness duration data. Weighted-degree and link-level graph theory and probabilistic tractography analyses characterized fractional anisotropy (FA) values across cortico-subcortical connections. Results were corrected for multiple comparisons.
Compared to controls, FND patients showed reduced FA in the stria terminalis/fornix, medial forebrain bundle, extreme capsule, uncinate fasciculus, cingulum bundle, corpus callosum, and striatal-postcentral gyrus projections. Except for the stria terminalis/fornix, these differences remained significant adjusting for depression and anxiety. In within-group analyses, physical disability inversely correlated with stria terminalis/fornix and medial forebrain bundle FA values; illness duration negatively correlated with stria terminalis/fornix white matter integrity. A FND symptom severity composite score did not correlate with FA in patients.
In this first DTI study of mixed FND, microstructural differences were observed in limbic and associative tracts implicated in salience, defensive behaviors, and emotion regulation. These findings advance our understanding of neurocircuit pathways in the pathophysiology of FND.
We have developed a novel method to describe human white matter anatomy using an approach that is both intuitive and simple to use, and which automatically extracts white matter tracts from diffusion ...MRI volumes. Further, our method simplifies the quantification and statistical analysis of white matter tracts on large diffusion MRI databases. This work reflects the careful syntactical definition of major white matter fiber tracts in the human brain based on a neuroanatomist’s expert knowledge. The framework is based on a novel query language with a near-to-English textual syntax. This query language makes it possible to construct a dictionary of anatomical definitions that describe white matter tracts. The definitions include adjacent gray and white matter regions, and rules for spatial relations. This novel method makes it possible to automatically label white matter anatomy across subjects. After describing this method, we provide an example of its implementation where we encode anatomical knowledge in human white matter for ten association and 15 projection tracts per hemisphere, along with seven commissural tracts. Importantly, this novel method is comparable in accuracy to manual labeling. Finally, we present results applying this method to create a white matter atlas from 77 healthy subjects, and we use this atlas in a small proof-of-concept study to detect changes in association tracts that characterize schizophrenia.
This work describes a new diffusion MR framework for imaging and modeling of microstructure that we call q-space trajectory imaging (QTI). The QTI framework consists of two parts: encoding and ...modeling. First we propose q-space trajectory encoding, which uses time-varying gradients to probe a trajectory in q-space, in contrast to traditional pulsed field gradient sequences that attempt to probe a point in q-space. Then we propose a microstructure model, the diffusion tensor distribution (DTD) model, which takes advantage of additional information provided by QTI to estimate a distributional model over diffusion tensors. We show that the QTI framework enables microstructure modeling that is not possible with the traditional pulsed gradient encoding as introduced by Stejskal and Tanner. In our analysis of QTI, we find that the well-known scalar b-value naturally extends to a tensor-valued entity, i.e., a diffusion measurement tensor, which we call the b-tensor. We show that b-tensors of rank 2 or 3 enable estimation of the mean and covariance of the DTD model in terms of a second order tensor (the diffusion tensor) and a fourth order tensor. The QTI framework has been designed to improve discrimination of the sizes, shapes, and orientations of diffusion microenvironments within tissue. We derive rotationally invariant scalar quantities describing intuitive microstructural features including size, shape, and orientation coherence measures. To demonstrate the feasibility of QTI on a clinical scanner, we performed a small pilot study comparing a group of five healthy controls with five patients with schizophrenia. The parameter maps derived from QTI were compared between the groups, and 9 out of the 14 parameters investigated showed differences between groups. The ability to measure and model the distribution of diffusion tensors, rather than a quantity that has already been averaged within a voxel, has the potential to provide a powerful paradigm for the study of complex tissue architecture.
•We have described a new diffusion MR framework for imaging of microstructure that we call q-space trajectory imaging.•Performing diffusion encoding with a wide range of q-space trajectories is feasible on a clinical system.•The cumulant expansion of the MR signal yields the mean diffusion tensor and a fourth-order covariance tensor.•QTI can disentangle variation in size from variation in shape and direction.•QTI does not require macroscopic anisotropy and could be useful not only in white matter but also in gray matter.
Abstract In a previous study we have demonstrated, using a novel diffusion MRI analysis called free-water imaging, that the early stages of schizophrenia are more likely associated with a ...neuroinflammatory response and less so with a white matter deterioration or a demyelination process. What is not known is how neuroinflammation and white matter deterioration change along the progression of the disorder. In this study we apply the free-water measures on a population of 29 chronic schizophrenia subjects and compare them with 25 matching controls. Our aim was to compare the extent of free-water imaging abnormalities in chronic subjects with the ones previously obtained for subjects at their first psychotic episode. We find that chronic subjects showed a limited extent of abnormal increase in the volume of the extracellular space, suggesting a less extensive neuroinflammatory response relative to patients at the onset of schizophrenia. At the same time, the chronic schizophrenia subjects had greater extent of reduced fractional anisotropy compared to the previous study, suggesting increased white matter deterioration along the progression of the disease. Our findings substantiate the role of neuroinflammation in the earlier stages of the disorder, and the effect of neurodegeneration that is worsening in the chronic phase.
•Few studies were performed to expose the effect of oral contraceptives (OCs) on the brain.•In women using OCs, changes in brain gray and white matter were reported.•Standardized MRI acquisitions and ...postprocessing allow comparisons of findings across studies.•Referential study design according to follicular and luteal phase, active and inactive OCs phase.•Applying clinical imaging to animals to understand the effects of OCs on the brain.
Worldwide over 150 million women use oral contraceptives (OCs), which are the most prescribed form of contraception in both the United States and in European countries. Sex hormones, such as estradiol and progesterone, are important endogenous hormones known for shaping the brain across the life span. Synthetic hormones, which are present in OCs, interfere with the natural hormonal balance by reducing the endogenous hormone levels. Little is known how this affects the brain, especially during the most vulnerable times of brain maturation. Here, we review studies that investigate differences in brain gray and white matter in women using OCs in comparison to naturally cycling women. We focus on two neuroimaging methods used to quantify structural gray and white matter changes, namely structural MRI and diffusion MRI. Finally, we discuss the potential of these imaging techniques to advance knowledge about the effects of OCs on the brain and wellbeing in women.
The thioether-functionalized 2-azabutadiene (iPrS)2C=C(H)-N=CPh2 L ligates to CdI2 and HgI2 to form the chelate compounds CdI2{(iPrS)2C=C(H)-N=CPh2 (1) and HgI2(iPrS)2C=C(H)-N=CPh2 (2). Their crystal ...structures were solved via X-ray diffraction. Both crystallize in the non-centrosymmetric space groups: monoclinic P21 (1) and orthorhombic P212121 (2), respectively. The closed-shell d10 metal centers are four-coordinated (two iodides and S and N coordinating atoms from the ligand L) in both complexes. The geometrical indexes τ indicate that a highly distorted trigonal pyramidal is adopted for 1 and a seesaw geometry for 2. The comparative nature of metal–ligand bonds is discussed on the basis of metric parameters and of QT-AIM (quantum theory of atoms in molecules) calculations. L was also treated with CuI to obtain the dinuclear species LCu(μ2-I2)CuL (3), in which the two Cu(I) centers are linked by a short metal–metal bond. The geometric and electronic properties of 3 are compared with those of 1 and 2.
The 1D coordination polymer (CP) (Me2S)3{Cu2(μ-I)2} n (1) is formed when CuI reacts with SMe2 in n-heptane, whereas in acetonitrile (MeCN), the reaction forms exclusively the 2D CP (Me2S)3{Cu4(μ-I)4} ...n (2) containing “flower-basket” Cu4I4 units. The reaction product of CuI with MeSEt is also solvent-dependent, where the 1D polymer (MeSEt)2{Cu4(μ3-I)2(μ2-I)2}(MeCN)2 n (3) containing “stepped-cubane” Cu4I4 units is isolated in MeCN. In contrast, the reaction in n-heptane affords the 1D CP (MeSEt)3{Cu4(μ3-I)4} n (4) containing “closed-cubane” Cu4I4 clusters. The reaction of MeSPr with CuI provides the structurally related 1D CP (MeSPr)3{Cu4(μ3-I)4} n (5), for which the X-ray structure has been determined at 115, 155, 195, 235, and 275 K, addressing the evolution of the metric parameters. Similarly to 4 and the previously reported CP (Et2S)3{Cu4(μ3-I)4} n (Inorg. Chem. 2010, 49, 5834), the 1D chain is built upon closed cubanes Cu4(μ3-I)4 as secondary building units (SBUs) interconnected via μ-MeSPr ligands. The 0D tetranuclear clusters (L)4{Cu4(μ3-I)4} L = EtSPr (6), Pr2S (7) respectively result from the reaction of CuI with EtSPr and n-Pr2S. With i-Pr2S, the octanuclear cluster (i-Pr2S)6{Cu8(μ3-I)3}(μ4-I)2} (8) is formed. An X-ray study has also been performed at five different temperatures for the 2D polymer (Cu3Br3)(MeSEt)3 n (9) formed from the reaction between CuBr and MeSEt in heptane. The unprecedented framework of 9 consists of layers with alternating Cu(μ2-Br)2Cu rhomboids, which are connected through two μ-MeSEt ligands to tetranuclear open-cubane Cu4Br4 SBUs. MeSPr forms with CuBr in heptane the 1D CP (Cu3Br3)(MeSPr)3 n (10), which is converted to a 2D metal–organic framework (Cu5Br5)(μ2-MeSPr)3 n (11) incorporating pentanuclear (Cu5(μ4-Br)(μ2-Br) SBUs when recrystallized in MeCN. The thermal stability and photophysical properties of these materials are also reported.
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