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A large-scale landslide occurred at the waste dump of Dagushan open-pit iron mine in Anshan, China. The landslide caused the collapse of 8.45 × 106 m3 of waste rock with a maximum runout distance of 150 m, resulting in the burial of 7.2 × 104 m2 of the site and destruction of numerous buildings and roads. Based on field investigations, laboratory tests, and numerical simulations, the failure characteristics of the landslide were investigated and the inducing factors as well as the failure mechanism were analyzed. According to field surveys, the landslide area was divided into the traction failure area, the main sliding area, and the accumulation area. A series of in situ and laboratory tests were performed to obtain the engineering properties of the waste material and the foundation silty clay of the waste dump. Then, a conceptual model of the landslide mechanism was constructed and the failure process was divided into four stages: foundation weakening stage, shearing and dislocation stage, sliding and shearing out stage, and tractive sliding stage. Two- and three-dimensional numerical simulations were performed to clarify the landslide evolution and related triggering mechanism combining the strength reduction method with the finite difference program FLAC3D. The results show that the saturation and weakening of foundation silty clay under the action of groundwater were the trigger factors of the landslide, which resulted in the shear failure of the weak foundation, and further triggered the mass collapse and formed the large-scale landslide. The sliding surface passed through the overlying waste materials and progressed along the weak foundation of the slope. The failure pattern obtained by numerical simulations matched closely with the observations in the field. The understanding of the landslide characteristics and mechanism may offer a reference for disaster identification and stability analysis of large-scale waste dumps around the world. [ABSTRACT FROM AUTHOR]

A landslide occurred on November 24, 2019, in weathered phyllite at the western longwall of Yabaling open pit of Anqian iron mine in Anshan City, Liaoning Province, China. The landslide was estimated to be 3.0 × 104 m3 in volume and caused severe damage to the road of transporting waste materials. This landslide was a typical jointed rock mass landslide, and the cause of the landslide was related to four factors: open-pit mining activity, the weak rock, discontinuities, and the high rainfall. According to the failure characteristics, the landslide area was divided into three parts: the tension-cracking area, the sliding-deformation area, and the colluvium area. The failure mechanism of the landslide was investigated through a back analysis combining nonlinear Hoek–Brown criterion and FLAC3D program with a parameter reduction technique. The results showed that the predicted sliding surface at the critical state matched closely the field observations. A remedial scheme of landslide stabilization including four rows of micropiles was proposed and the stabilization mechanism of the micropiles was discussed. The shear strain increment contours show that the micropiles arrested the original sliding surface and controlled the movement of the sliding mass behind them, and thereby significantly improved the stability of the landslide. This paper also presents the results obtained from the parametric analysis in order to understand the impact of strength parameters on the long-term stability of the stabilized slope. The findings improved understanding of the failure characteristics and mechanism of jointed rock mass landslides may be used for evaluating the stability of slopes and early identification for both active and inactive open-pit mines. [ABSTRACT FROM AUTHOR]

A rainfall-induced landslide occurred in the north highwall of the Fushun west open pit at 5:00 (UTC + 8) on July 26, 2016, in China. The landslide was about 3.1 × 106 m3 and caused considerable destruction of houses, roads, and railways. Field investigations, laboratory tests, and numerical analyses have been performed to explore the failure characteristics and formation mechanism of the landslide. The landslide was divided into three parts: the crack area, the sliding body area, and the accumulation area. The X-ray diffraction and scanning electron microscope techniques were used to reveal the mineral composition and microstructure of the landslide material. Then, a conceptual model of the landslide mechanism was constructed and the process of the landslide was divided into four stages: unloading and cracking stage; sliding and partial locking stage; shearing out and failure stage; and flowing and accumulating stage. A combined seepage and stability analysis was performed to explore the mechanism of the landslide by numerical simulation. The relationship of volumetric water content and hydraulic conductivity to matric suction was established to describe the hydraulic characteristics of the slope material under infiltration. The results show that the maximum matric suction in the slope decreases continually with the increase of rainfall intensity and duration, and the north highwall will not be stable after 7.2 h for 16 mm/h of rainfall. The original slope was stable and heavy rainfall triggered the landslide, and the obtained critical failure surface matched the field survey closely. The findings improved understanding of the failure mechanism and process of rainfall-induced landslides may be used for evaluating the stability of slopes and early identification for both active and inactive open-pit mines. [ABSTRACT FROM AUTHOR]

A massive toppling failure occurred at the edge of the Furnas Reservoir at 12:30 (UTC-03) on 8 January 2022, in Brazil. The toppling belongs to single-block toppling with a volume of about 3.32 × 102 m3 and caused 10 deaths and 32 injuries. Field investigation, numerical analysis, and base friction tests were performed to explore the failure characteristics and mechanism of the toppling. A conceptual model of the toppling mechanism was constructed and the toppling process was divided into four stages: foundation erosion and weakening stage, crack propagation and dislocation stage, opening up and rotation stage, and disintegration and collapse stage. A series of real three-dimensional numerical simulations was performed to clarify the toppling evolution and related triggering mechanism using the finite difference program FLAC3D. Two different alternatives of triggering mechanism for the toppling were comparatively analyzed, the first with a reduction in the shear strength of the weak foundation layer believed to represent the foundation weakening mechanism, and the second with removal of the weak layer believed to represent the foundation erosion mechanism. We found that the foundation weakening of the weak layer resulted in a sliding mechanism of the block, while the foundation erosion resulted in a clear toppling mechanism of the block. The base friction test was conducted to investigate the toppling process and to verify the numerical results over a limited time span. The experimental evidence demonstrated a good agreement with the numerical results as well as those observations in the field. We concluded that the slope was in a critical state due to the foundation erosion of the weak layer, while the heavy rainfall triggered the toppling. It is emphasized that the undermining of the slope foundation and/or existed cavities induced by the foundation erosion played a vital role in the formation of the toppling. Moreover, a produced vertical crack or the propagation of an existed crack in the rear part of the slope may be signs of movements and thought of precursors of the single-block toppling. Dealing with the eroded cavities was suggested to be an effective way to prevent the toppling in the Furnas Reservoir, such as backfilling the eroded cavities with masonry rubble and/or grouting. The understanding of the toppling characteristics and mechanism may offer a reference for single-block toppling issues, such as its movement characteristics and failure mechanism, and may be used for stability analysis and disaster identification of potential failures. [ABSTRACT FROM AUTHOR]

Owing to the heavy rainfall, a landslide occurred at the Anqian Iron mine, at 18:00(UTC + 8) on November 24, 2019, in China. The landslide was about 3.0 × 104 m3 and caused damage to the road of transporting waste materials. Failure characteristics and the mechanism of this landslide were analyzed in this study. The landslide area was divided into three parts: the rear tension cracking area, the middle sliding deformation area, and the front colluvium area. A contact-free measuring technique using the new ShapeMetrix3D system was applied and 204 joints were analyzed based on equal-angle stereographic projection. Thus, a conceptual model of the mechanism of the landslide was constructed and the formation process of the landslide was divided into three stages: the first shearing and dislocation stage; the second sliding, front bulging, and rear tractive cracking stage; and the third local rock mass collapse and colluvium depositing stage. Numerical modeling was performed to discover the landslide mechanism by progressively reducing the shear strength of rock mass. The results showed that the original slope was stable, whereas heavy rainfall triggered the landslide, and the predicted failure surface matched closely the field investigations. The factor of safety obtained by real three-dimensional analyses was slightly higher than that obtained by plane problem analyses, and the difference was attributed to the three-dimensional effect of the landslide. This paper also presents the results obtained from the parametric analysis in order to understand the impact of shear strength parameters on the overall stability of the slope. [ABSTRACT FROM AUTHOR]

Piles are extensively used as a means of slope stabilization. A novel engineering technique of truncated piles that are unlike traditional piles is introduced in this paper. A simplified numerical method is proposed to analyze the stability of slopes stabilized with truncated piles based on the shear strength reduction method. The influential factors, which include pile diameter, pile spacing, depth of truncation, and existence of a weak layer, are systematically investigated from a practical point of view. The results show that an optimum ratio exists between the depth of truncation and the pile length above a slip surface, below which truncating behavior has no influence on the piled slope stability. This optimum ratio is bigger for slopes stabilized with more flexible piles and piles with larger spacing. Besides, truncated piles are more suitable for slopes with a thin weak layer than homogenous slopes. In practical engineering, the piles could be truncated reasonably while ensuring the reinforcement effect. The truncated part of piles can be filled with the surrounding soil and compacted to reduce costs by using fewer materials. [ABSTRACT FROM AUTHOR]

This paper presents a study of the failure mechanism and control measures for a seismically induced landslide along the Wanzhou-Liangping expressway in China. It is shown that the dominant cause of the slope stability problem is the original inappropriate geometry of the slope. Slope stability analyses were performed using Spencer's method incorporated with the pseudostatic method, which showed that the rock slope was unstable after the Wenchuan earthquake, and the stability of the studied area was governed mainly by the significant potential of deep sliding. Measures to stabilize unstable zones include resloping and unloading the slope, installing rock anchors and a retaining wall, improving drainage, and vegetating bare areas. The results indicate that the measures were effective in controlling the landslide. [ABSTRACT FROM AUTHOR]

Background: Synaptic deficits and neuronal loss are the major pathological manifestations of Alzheimer's disease. However, the link between the early synaptic loss and subsequent neurodegeneration is not entirely clear. Cell culture studies have shown that amyloid-β (Aβ) applied to axonal terminals can cause retrograde degeneration leading to the neuronal loss, but this process has not been demonstrated in live animals. Objective: To test if Aβ applied to retinal ganglion cell axonal terminals can induce axonal damage in the optic nerve and optic tract in mice. Methods: Aβ was injected into the terminal field of the optic tract, in the left lateral geniculate nucleus of wildtype C57BL/6 mice. Following the injection, monthly diffusion tensor imaging was performed. Three months after the injection, mice underwent visual evoked potential recordings, and then sacrificed for immunohistochemical examination. Results: There were no significant changes seen with diffusion tensor imaging in the optic nerve and optic tract 3 months after the Aβ injection. The myelin and axons in these regions remained intact according to immunohistochemistry. The only significant changes observed in this study were delayed transduction and reduced amplitude of visual evoked potentials, although both Aβ and its reversed form caused similar changes. Conclusion: Despite the published in vitro studies, there was no significant axonal damage in the optic nerve and optic tract after injecting Aβ onto retinal ganglion cell axonal terminals of wildtype C57BL/6 mice. [ABSTRACT FROM AUTHOR]

To reveal the deformation mechanism and evolution of potential diseases of the dumping site slope, a series of geo-mechanical model tests was conducted on the background of Yinwan Dumping site slope, Heidaigou open-pit mine. The process of dump slope elevating and groundwater infiltrating into loess basement was simulated. A method to simulate dumping site above the water-saturated loess basement was introduced. During the tests, the influence of water in loess basement was simulated by water injection from the holes on the bottom of the model. The variety of displacement of dumping site above the loess basement under filling, weak base, as well as water-saturated conditions was studied. It shows that, as dump height increased, the main deformation transformed from the shear deformation above the water-saturated loess basement to the vertical settlement above the natural loess basement, and the destruction of the model was caused directly by the continually increasing of moisture content of the loess basement. The destruction mode trailing edge attachment the silty loess and the loess (puddles edge) overall sliding interface. [ABSTRACT FROM AUTHOR]

Background: Diffusion tensor imaging (DTI) suggests the presence of white matter abnormality at the prodromal stage in human Alzheimer's disease (AD).Objective: To use a mouse model of AD to determine whether the white matter abnormality detected by in vivo DTI is associated with functional deficits and axon damage.Methods: Amyloid-β1-42 (Aβ1-42) was injected into the left lateral ventricle in mice. Two months after the injection, in vivo DTI and visual evoked potential (VEP) recordings were performed, followed by immunohistochemistry of phosphorylated neurofilament and myelin basic protein.Results: DTI of Aβ1-42-treated mice showed a significant increase of radial diffusivity in white matter including the optic nerves and tracts. The abnormality was associated with decreased amplitude and increased latency of VEP. Immunohistochemistry confirmed a significant loss of axons and myelin integrity.Conclusion: White matter damage induced by Aβ1-42 in mice can be detected non-invasively by DTI. [ABSTRACT FROM AUTHOR]

Background: Diffusion tensor imaging (DTI) suggests the presence of white matter abnormality at the prodromal stage in human Alzheimer's disease (AD). Objective: To use a mouse model of AD to determine whether the white matter abnormality detected by in vivo DTI is associated with functional deficits and axon damage. Methods: Amyloid-β1-42 (Aβ1-42) was injected into the left lateral ventricle in mice. Two months after the injection, in vivo DTI and visual evoked potential (VEP) recordings were performed, followed by immunohistochemistry of phosphorylated neurofilament and myelin basic protein. Results: DTI of Aβ1-42-treated mice showed a significant increase of radial diffusivity in white matter including the optic nerves and tracts. The abnormality was associated with decreased amplitude and increased latency of VEP. Immunohistochemistry confirmed a significant loss of axons and myelin integrity. Conclusion: White matter damage induced by Aβ1-42 in mice can be detected non-invasively by DTI. [ABSTRACT FROM AUTHOR]

Abstract: Diffusion tensor imaging (DTI) is achieved by collecting a series of diffusion-weighted images (DWIs). Signal averaging of multiple repetitions can be performed in the k-space (k-avg) or in the image space (m-avg) to improve the image quality. Alternatively, one can treat each acquisition as an independent image and use all of the data to reconstruct the DTI without doing any signal averaging (no-avg). To compare these three approaches, in this study, in vivo DTI data were collected from five normal mice. Noisy data with signal-to-noise ratios (SNR) that varied between five and 30 (before averaging) were then simulated. The DTI indices, including relative anisotropy (RA), trace of diffusion tensor (TR), axial diffusivity (λ║), and radial diffusivity (λ⊥), derived from the k-avg, m-avg, and no-avg, were then compared in the corpus callosum white matter, cortex gray matter, and the ventricles. We found that k-avg and m-avg enhanced the SNR of DWI with no significant differences. However, k-avg produced lower RA in the white matter and higher RA in the gray matter, compared to the m-avg and no-avg, regardless of SNR. The latter two produced similar DTI quantifications. We concluded that k-avg is less preferred for DTI brain imaging. [Copyright &y& Elsevier]

Abstract: Keyhole diffusion tensor imaging (keyhole DTI) was previously proposed in cardiac imaging to reconstruct DTI maps from the reduced phase-encoding images. To evaluate the feasibility of keyhole DTI in brain imaging, keyhole and zero-padding DTI algorithms were employed on in vivo mouse brain. The reduced phase-encoding portion, also termed as the sharing rate, was varied from 50% to 90% of the full k-space. Our data showed that zero-padding DTI resulted in decreased fractional anisotropy (FA) and decreased mean apparent diffusion coefficient (mean ADC) in white matter (WM) regions. Keyhole DTI showed a better edge preservation on mean ADC maps but not on FA maps as compared to the zero-padding DTI. When increasing the sharing rate in keyhole approach, an underestimation of FA and an over- or underestimation of mean ADC were measured in WM depending on the selected reference image. The inconsistency of keyhole DTI may add a challenge for the wide use of this modality. However, with a carefully selected directive diffusion-weighted image to serve as the reference image in the keyhole approach, this study demonstrated that one may obtain DTI indices of reduced-encoding images with high consistency to those derived with full k-space DTI. [ABSTRACT FROM AUTHOR]

Abstract: The changes of directional diffusivities derived from diffusion tensor imaging (DTI), i.e. decreased axial diffusivity (λ ||) and increased radial diffusivity (λ ⊥), have shown significant correlation with axonal and myelin damage, respectively. However, after formalin fixation, reduced sensitivity of λ || in detecting axonal damage in tissue has raised the concern of applying DTI ex vivo. In order to distinguish whether death or the fixation process diminishes the sensitivity of DTI in detecting lesions, in vivo, pre-fixed postmortem, and fixed postmortem DTI were conducted on mouse optic nerves 3 and 14 days after transient retinal ischemia. Our data showed that, from in vivo to pre-fixed postmortem, λ || and λ ⊥ decreased by 50 to 70% in both healthy and injured optic nerves (3 and 14 day injury). From pre-fixed postmortem to fixed postmortem, λ || and λ ⊥ decreased by 40 to 50% in normal and 3-day injured optic nerves, but only by 15 to 25% in 14-day injured optic nerves. Consequently, for the 14-day injured optic nerves, the differences between healthy and injured nerves were not preserved after fixation: the 40% decreased λ|| and 200% increased λ⊥ in injured nerves as compared to the normal nerves were measured in vivo and pre-fixed postmortem, but after the fixation process, 300% increased λ⊥ and insignificant changes in λ|| were found in injured nerves as compared to the normal nerves. This study clarified that fixation process, but not death, could change the sensitivity of DTI in detecting injury. [Copyright &y& Elsevier]

Abstract: Wallerian degeneration plays a significant role in many central nervous system (CNS) diseases. Tracking the progression of Wallerian degeneration may provide better understanding of the evolution of many CNS diseases. In this study, a 28-day longitudinal in vivo DTI of optic nerve (ON) and optic tract (OT) was conducted to evaluate the temporal and spatial evolution of Wallerian degeneration resulting from the transient retinal ischemia. At 3–28 days after ischemia, ipsilateral ON and contralateral OT showed significant reduction in axial diffusivity (32–40% and 21–29% respectively) suggestive of axonal damage. Both ON and OT showed significant increase in radial diffusivity, 200–290% and 58–65% respectively, at 9–28 days suggestive of myelin damage. Immunohistochemistry of phosphorylated neurofilament (pNF) and myelin basic protein (MBP) was performed to assess axonal and myelin integrities validating the DTI findings. Both DTI and immunohistochemistry detected that transient retinal ischemia caused more severe damage to ON than to OT. The current results suggest that axial and radial diffusivities are capable of reflecting the severity of axonal and myelin damage in mice as assessed using immunohistochemistry. [Copyright &y& Elsevier]

Abstract: In this study, axial (λ ||) and radial (λ ⊥) diffusivities derived from diffusion tensor imaging (DTI) were used to evaluate white matter injury in brains of mice affected by experimental autoimmune encephalomyelitis (EAE). Sixteen female C57BL/6 mice were immunized with amino acids 35–55 of myelin oligodendrocyte glycoprotein (MOG35–55). Three months after immunization, optic nerve and tract were severely affected with 19% and 18% decrease in λ || respectively, suggesting the presence of axonal injury. In addition, a 156% and 86% increase in λ ⊥ was observed in optic nerve and tract respectively, suggestive of myelin injury. After in vivo DTI, mice were perfusion fixed and immunohistochemistry for the identification of myelin basic protein (MBP) and phosphorylated neurofilament (pNF) was performed to verify the presence of axonal and myelin injury. The present study demonstrated that the visual pathway is selectively affected in MOG35–55 induced murine EAE and these injuries are non-invasively detectable using λ || and λ ⊥. [Copyright &y& Elsevier]

Abstract: Decreased axial (λ ||) and increased radial (λ ⊥) diffusivity have been shown to reflect axonal and myelin injury respectively. In the present study, evolving white matter injury within the optic nerves of mice with retinal ischemia was examined by in vivo and ex vivo measurements of λ || and λ ⊥. The results show that at 3 days after retinal ischemia, a 33% decrease in vivo and a 38% decrease ex vivo in λ || without change in λ ⊥ was observed in the injured optic nerve compared to the control, suggestive of axonal damage without myelin injury. At 14 days, both in vivo and ex vivo measured λ ⊥ increased significantly to 220–240% of the control level in the injured optic nerve suggestive of myelin damage. In contrast, the axonal injury that was clearly detected in vivo as a significantly decreased λ || (33% decrease) was not as clearly detected by ex vivo λ || (17% decrease). The current findings suggest that ex vivo λ ⊥ is comparable to in vivo λ ⊥ in detecting myelin injury. However, the structural changes resulting from axonal damage causing the decreased in vivo λ || may not be preserved ex vivo in the fixed tissues. Despite the accurate depiction of the pathology using λ || and λ ⊥ in vivo, the use of ex vivo λ || to extrapolate the status of axonal injury in vivo would require further investigation. [Copyright &y& Elsevier]

Abstract: The inner product of the major eigenvectors of adjacent pixels, known as the directional correlation (DC), has been used previously as a quantitative index to investigate directional similarity in white matter (WM) tracts. A high degree of directional similarity (i.e., high DC) among pixels within individual WM tracts was observed. Based on this observation, a region growing algorithm was employed to propagate an area from a seed point as a function of the DC threshold (DCt) to manually identify WM tracts in two-dimensional (2D) slices from diffusion tensor imaging (DTI). In the present study, an improved unsupervised DC based region growing (DCRG) method was implemented to reduce the operator-dependent variance and to improve the ease of use of the technique. By employing improved method, a multi-slice DTI data set of an in vivo mouse brain was used to identify the external capsule, visual pathway, and corpus callosum. The resultant WM tracts are computer rendered in three-dimensional (3D) images with anatomical images as structural references. In addition, three sets of ex vivo mouse brain data were used to examine the effects of different slice thickness and the signal-to-noise ratio (SNR) to the outcome of DCRG. [Copyright &y& Elsevier]

Abstract: Using magnetic resonance diffusion tensor imaging (DTI), the present study investigates changes in both gray and white matter in the APPsw transgenic mouse (Tg2576), a model of β-amyloid plaque deposition associated with Alzheimer''s disease (AD). DTI analyses were performed in cross-sectional groups of transgene-positive and -negative mice at 8, 12, 16, and 18 months of age to assess the magnitude of water diffusion in gray matter (i.e., Tr(D)) and changes in diffusion in white matter that may be indicative of axonal degeneration (i.e., reduced water diffusion parallel to axonal tracts, λ‖) and myelin degradation (i.e., increased water diffusion perpendicular to axonal tracts, λ⊥). No appreciable changes in gray or white matter were observed between the APPsw and the age-matched control mice at 8 months of age. Reduced Tr(D) and λ‖ were observed in gray and white matter, respectively, for the APPsw mice at ages greater than 8 months, which coincides with the time period when appreciable amyloid plaque accumulation was confirmed by ex vivo histopathological studies. The decreases in λ‖ suggest the presence of axonal injury in multiple white matter tracts of APPsw mice. Unlike λ‖, λ⊥was unaltered between control and APPsw mice in most white matter tracts. However, in the corpus collosum (CC), λ⊥ increased at 16 and 18 months of age, suggesting the possibility of myelin damage in the CC at these later ages. This work demonstrates the potential for DTI as a noninvasive modality to detect evolving pathology associated with changes in tissue water diffusion properties in brain tissues. [Copyright &y& Elsevier]

Both axon and myelin degeneration have significant impact on the long-term disability of patients with white matter disorder. However, the clinical manifestations of the neurological dysfunction caused by white matter disorders are not sufficient to determine the origin of neurological deficits. A noninvasive biological marker capable of detecting and differentiating axon and myelin degeneration would be a significant addition to currently available tools. Directional diffusivities derived from diffusion tensor imaging (DTI) have been previously proposed by this group as potential biological markers to detect and differentiate axon and myelin degeneration. To further test the hypothesis that axial (λ&z.dfnc;) and radial (λ⊥) diffusivities reflect axon and myelin pathologies, respectively, the optic nerve was examined serially using DTI in a mouse model of retinal ischemia. A significant decrease of λ&z.dfnc;, the putative DTI axonal marker, was observed 3 days after ischemia without concurrently detectable changes in λ⊥, the putative myelin marker. This result is consistent with histological findings of significant axonal degeneration with no detectable demyelination at 3 days after ischemia. The elevation of λ⊥ observed 5 days after ischemia is consistent with histological findings of myelin degeneration at this time. These results support the hypothesis that λ&z.dfnc; and λ⊥ hold promise as specific markers of axonal and myelin injury, respectively, and, further, that the coexistence of axonal and myelin degeneration does not confound this utility. [Copyright &y& Elsevier]

Myelin loss and axonal damage are both observed in white matter injuries. Each may have significant impact on the long-term disability of patients. Currently, there does not exist a noninvasive biological marker that enables differentiation between myelin and axonal injury. We describe herein the use of magnetic resonance diffusion tensor imaging (DTI) to quantify the effect of dysmyelination on water directional diffusivities in brains of shiverer mice in vivo. The principal diffusion eigenvalues of eight axonal fiber tracts that can be identified with certainty on DTI maps were measured. The water diffusivity perpendicular to axonal fiber tracts, λ⊥, was significantly higher in shiverer mice compared with age-matched controls, reflecting the lack of myelin and the increased freedom of cross-fiber diffusion in white matter. The water diffusivity parallel to axonal fiber tracts, λ∥, was not different, which is consistent with the presence of intact axons. It is clear that dysmyelination alone does not impact λ∥. The presence of intact axons in the setting of incomplete myelination was confirmed by electron microscopy. Although further validation is still needed, our finding suggests that changes in λ⊥ and λ∥ may potentially be used to differentiate myelin loss versus axonal injury. [Copyright &y& Elsevier]

We simulated hydraulic fracturing in different lithologic rocks in the horizontal drilling by using the true physical model experiment and large rock specimens, carried out the real-time dynamic monitoring with adding tracer and then did post-fracturing cutting and so on. Based on this monitoring results, we compared and assessed the factors affecting expansion in shale, shell limestone, and tight sandstone and the fracture expansion in these rocks. In shale, the reformed reservoir volume is the highest, fracture network is formed in the process of fracturing. In tight sandstone, the fracture surface boundaries are curved, and the fracture surface area accounts for 25–50% of the entire specimen. In shell limestone, the complexity of the fracture morphology is between shale and tight sandstone, but no fracture network is developed. Brittleness controls the fracture surface area. In highly brittle rocks, the fracture surface area is high. Fracture toughness mainly affects the initiation and propagation of cracks. A fracture network is formed only if bedding planes are present and are more weaker than their corresponding matrix. The horizontal in situ deviatoric stress affects the crack propagation direction, and different lithologies have different horizontal in situ deviatoric stress thresholds. Low fluid injection rate facilitates the formation of complex cracks, whereas high fluid injection rate favors the development of fractures. Fluid injection weakly controls the complexity of hydraulic fracturing in low-brittleness rocks, whereas low-viscosity fracturing fluids favor the formation of complex cracks owing to easy enter microcracks and micro-pore. Displacement has a greater impact on high brittle rocks than low brittle rocks. [ABSTRACT FROM AUTHOR]

In view of the advantages of 1.6‐μm laser, it has important applications in the fields of laser radar, industry, military, and optical communication. This paper mainly focuses on 1.6‐μm Er: YAG solid‐state‐laser for Laser Radar. The references about pulsed 1.6‐μm single‐longitudinal‐mode laser, continuous wave 1.6‐μm Er: YAG single‐longitudinal‐mode seed laser, and pulsed 1.6‐μm Er: YAG Q‐switched amplifier are collected and analyzed. The development status is introduced, the main problems are identified, and the future development direction is clarified. Maybe, this can provide a reference for other scholars. [ABSTRACT FROM AUTHOR]

• Correlation between MEMRI and DTI was found in P301L tau mice. • Axonal transport deficits in tauopathy were correlated with the loss of myelin. • Myelin loss may contribute to the axonal degeneration in tauopathy. Diffusion Tensor Imaging (DTI) and Manganese Enhanced MRI (MEMRI) are noninvasive tools to characterize neural fiber microstructure and axonal transport. A combination of both may provide novel insights into the progress of neurodegeneration. To investigate the relationship of DTI and MEMRI in white matter of tauopathy, twelve optic nerves of 11-month-old p301L tau mice were imaged and finished with postmortem immunohistochemistry. MEMRI was used to quantify Mn2+ accumulation rates in the optic nerve (ON, termed ONAR) and the Superior Colliculus (SC, termed SCAR), the primary terminal site of ON in mice. We found that both ONAR and SCAR revealed a significant linear correlation with mean diffusion (mD) and radial diffusion (rD) but not with other DTI quantities. Immunohistochemistry findings showed that ONAR, mD, and rD are significantly correlated with the myelin content (Myelin Basic Protein, p < 0.05) but not with the axonal density (SMI-31), tubulin density, or tau aggregates (AT8 staining). In summary, slower axonal transport appeared to have less myelinated axons and thinner remaining axons, associated with reduced rD and mD of in vivo DTI. A combination of in vivo MEMRI and DTI can provide critical information to delineate the progress of white matter deficits in neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Visual deficits are commonly seen in patients with Alzheimer's disease (AD), but postmortem histology has not found substantial damage in visual cortex regions, leading to the hypothesis that the visual pathway, from eye to the brain, may be damaged in AD. Diffusion tensor imaging (DTI) has been used to characterize white matter abnormalities. However, there is a lack of data examining the optic nerves and tracts in patients with AD. In this study, we used DTI to analyze the visual pathway in healthy controls, patients with mild cognitive impairment (MCI) and AD using scans provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI). We found significant increases in the total diffusivity and radial diffusivity and reductions in fractional anisotropy in optic nerves among AD patients. Similar but less extensive changes in these metrics were seen in MCI patients as compared to controls. The differences in DTI metrics between groups mirrored changes in the splenium of the corpus callosum, which has commonly been shown to exhibit white matter damage during AD and MCI. Our findings indicate that white matter damage extends to the visual system, and may help explain the visual deficits experienced by AD patients. [ABSTRACT FROM AUTHOR]

Visual deficits are commonly seen in patients with Alzheimer's disease (AD), but postmortem histology has not found substantial damage in visual cortex regions, leading to the hypothesis that the visual pathway, from eye to the brain, may be damaged in AD. Diffusion tensor imaging (DTI) has been used to characterize white matter abnormalities. However, there is a lack of data examining the optic nerves and tracts in patients with AD. In this study, we used DTI to analyze the visual pathway in healthy controls, patients with mild cognitive impairment (MCI) and AD using scans provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI). We found significant increases in the total diffusivity and radial diffusivity and reductions in fractional anisotropy in optic nerves among AD patients. Similar but less extensive changes in these metrics were seen in MCI patients as compared to controls. The differences in DTI metrics between groups mirrored changes in the splenium of the corpus callosum, which has commonly been shown to exhibit white matter damage during AD and MCI. Our findings indicate that white matter damage extends to the visual system, and may help explain the visual deficits experienced by AD patients. [ABSTRACT FROM AUTHOR]

With the rapid demand for underwater optical communication (UOC), studies of UOC degradation by oceanic turbulence have attached increasing attention worldwide and become a research hot-spot in recent years. Previous studies used a simplified and inaccurate oceanic turbulence spectrum, in which the eddy diffusivity ratio between temperature and salinity is assumed to be unity and the outer scale of turbulence is assumed to be infinite. However, both assumptions are not true in most of the actual marine environments. In this paper, based on the Rytov theory in weak turbulence, we derive analytical expressions of "the aperture-averaged scintillation index" (SI) for both plane and spherical waves, which can clearly demonstrate how SI is influenced by several key factors in UOC. Then, typical fade statistics of the UOC system in weak turbulence is discussed including the probability of fade, the expected number of fades per time, the mean fade time, signal-to-noise ratio and bit error rate. Our results show that spherical wave is preferable in the UOC system in weak turbulence compared to plane wave, and the aperture-averaged effect has a significant impact on UOC system's performance. Our results can be used to determine those key parameters for designing the UOC system over reasonable ranges. [ABSTRACT FROM AUTHOR]

Abstract White matter abnormalities, revealed by Diffusion Tensor Imaging (DTI), are observed in patients with Alzheimer's Disease (AD), representing neural network deficits that underlie gradual cognitive decline in patients. However, how DTI changes related to the development of Amyloid beta (Aβ) and tau pathology, two key hallmarks of AD, remain elusive. We hypothesized that tauopathy induced by Aβ could initiate an axonal degeneration, leading to DTI-detectable white matter abnormalities. We utilized the visual system of the transgenic p301L tau mice as a model system. Aβ was injected in Lateral Geniculate Nucleus (LGN), where the Retinal Ganglion Cell (RGC) axons terminate. Longitudinal DTI was conducted to detect changes in the optic tract (OT) and optic nerve (ON), containing the distal and proximal segments of RGC axons, respectively. Our results showed DTI changes in OT (significant 13.2% reduction in axial diffusion, AxD vs. vehicle controls) followed by significant alterations in ON AxD and fractional anisotropy, FA. Histology data revealed loss of synapses, RGC axons and cell bodies resulting from the Aβ injection. We further tested whether microtubule-stabilizing compound Epothilone D (EpoD) could ameliorate the damage. EpoD co-treatment with Aβ was sufficient to prevent Aβ-induced axon and cell loss. Using an acute injection paradigm, our data suggest that EpoD may mediate its protective effect by blocking localized, acute Aβ-induced tau phosphorylation. This study demonstrates white matter disruption resulting from localized Aβ, the importance of tau pathology induction to changes in white matter connectivity, and the use of EpoD as a potential therapeutic avenue to prevent the axon loss in AD. Highlights • Aβ injection into the Lateral Geniculate Nucleus of p301L mice precipitated degeneration of Retinal Ganglion Cells. • Degeneration induced by Aβ was detectable by Diffusion Tensor Imaging early in OT and later in ON, confirmed by histology. • Treating mice with microtubule stabilizer EpoD ameliorated Aβ-induced tauopathy, axonal damage, and neuronal loss. [ABSTRACT FROM AUTHOR]

Purpose: Diffusion tensor imaging (DTI) is commonly used to evaluate white matter integrity in multiple sclerosis (MS), but the relationship between DTI measures and functional changes during disease remains ambiguous. Using a mouse model of MS, we tested the hypothesis that DTI measures would correlate to the visual evoked potential (VEPs) dynamically at different disease stages. Methods: In vivo DTI, gadolinium-enhanced T1WI (Gd-T1WI) and VEPs were performed in 5 control and 25 mice after 2-12 weeks of experimental autoimmune encephalomyelitis (EAE). DTI indices, including fractional anisotropy (FA), axial and radial diffusivities (AD and RD), and Gd-T1WI enhancement, were measured in the optic nerve and tract (ON and OT), which were compared with measured VEPs. Results: Gd-T1WI showed a 3- to 4-fold enhancement over controls beginning after 2 weeks of EAE. Across the time course, we found progressive reductions in FA and increases in RD with increases in VEP latency and reductions in amplitude. Significant correlations between DTI (FA and RD) and VEP evolved; in control/early asymptomatic EAE mice, both FA and RD were highly correlated with VEP latency (but not amplitude), while in late EAE, both DTI indices were highly correlated with VEP amplitude (but not latency). Conclusion: DTI measures FA and RD are associated to VEP latency in early stages of EAE but associated to VEP amplitude in later stages, suggesting that the patterns of DTI related to the functional decline may depend on the stage of disease progression. [ABSTRACT FROM AUTHOR]

Abstract: Myelin damage, as seen in multiple sclerosis (MS) and other demyelinating diseases, impairs axonal conduction and can also be associated with axonal degeneration. Accurate assessments of these conditions may be highly beneficial in evaluating and selecting therapeutic strategies for patient management. Recently, an analytical approach examining diffusion tensor imaging (DTI) derived parameters has been proposed to assess the extent of axonal damage, demyelination, or both. The current study uses the well-characterized cuprizone model of experimental demyelination and remyelination of corpus callosum in mouse brain to evaluate the ability of DTI parameters to detect the progression of myelin degeneration and regeneration. Our results demonstrate that the extent of increased radial diffusivity reflects the severity of demyelination in corpus callosum of mouse brain affected by cuprizone treatment. Subsequently, radial diffusivity decreases with the progression of remyelination. Furthermore, radial diffusivity changes were specific to the time course of changes in myelin integrity as distinct from axonal injury, which was detected by βAPP immunostaining and shown to be most extensive prior to demyelination. Radial diffusivity offers a specific assessment of demyelination and remyelination, as distinct from acute axonal damage. [Copyright &y& Elsevier]