Apparent Dispersion Research Articles

Multi-modality relation attention network for breast tumor classification

Automatic breast image classification plays an important role in breast cancer diagnosis, and multi-modality image fusion may improve classification performance. However, existing fusion methods ignore relevant multi-modality information in favor of improving the discriminative ability of single-modality features. To improve classification performance, this paper proposes a multi-modality relation attention network with consistent regularization for breast tumor classification using diffusion-weighted imaging (DWI) and apparent dispersion coefficient (ADC) images. Within the proposed network, a novel multi-modality relation attention module improves the discriminative ability of single-modality features by exploring the correlation information between two modalities. In addition, a module ensures the classification consistency of ADC and DWI modality, thus improving robustness to noise. Experimental results on our database demonstrate that the proposed method is effective for breast tumor classification, and outperforms existing multi-modality fusion methods. The AUC, accuracy, specificity, and sensitivity are 85.1%, 86.7%, 83.3%, and 88.9% respectively.

Malachite Green Dye Decoloration over Au/TiO2-Nanotubes Photocatalyst under Simulate Visible-Light Irradiation.

Au nanoparticles were supported on TiO2 nanotubes by a novel vapor phase impregnation approach (VPI) using gold dimethyl-acetylacetonate as a precursor. This study aimed to evaluate the capacity of these materials in the photodecoloration of malachite green dye, with the vision to correlate the chemical, structural, morphological, and optical properties with its photocatalytic performance. The photocatalysts were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectronic spectroscopy (XPS), electronic microscopy (HAADF-STEM and HRTEM), and UV–vis spectroscopy. The techniques mentioned above made it possible to detect the presence of small gold nanoparticles (around 3.1 nm), with a high apparent dispersion even at high metal loading for all analyzed systems. According to the XPS results, the Au nanoparticles remain reduced (Au°), and they have a high electronic interaction with TiO2, which eventually originates an electronic exchange between them and consequently a decrease in the band gap energy. In addition, the surface plasmonic resonance observed through UV–vis spectroscopy of the Au nanoparticles are factors that can be related to the high decoloration observed in these photocatalysts, specifically in the 15 wt% Au material, which achieves maximum photodecoloration of malachite green dye at 93%.

Study of magnetic resonance imaging based on liver imaging reporting and data system for evaluating phosphatidylinositol proteoglycan-3 expression in hepatocellular carcinoma

Objective: To clarify the diagnostic value of magnetic resonance imaging based on liver imaging reporting and data system (LI-RADS) for phosphatidylinositol proteoglycan-3 (GPC3) expression in hepatocellular carcinoma (HCC). Methods: Clinical and pathological data of 95 HCC cases with positive GPC3 expression (+) and 40 HCC cases with negative GPC3 expression (-) were retrospectively analyzed, and their MRI image features based on the 2018 version of LI-RADS were compared. Multivariate logistic regression analysis was used to determine the main predictors of GPC3 expression. Receiver operating characteristic curve was used further to determine the diagnostic efficacy of combined clinical imaging model to predict GPC3 expression. Enumeration data were compared with χ2 test or Fisher's exact test. Measurement data were compared using independent samples t-test or Mann-Whitney U-test. Results: There were statistically significant differences between HCC in GPC3 (+) and GPC3(-) group at alpha-fetoprotein (AFP) levels (χ2=31.814, P<0.000 1), and MRI features: capsular enhacement (χ2=4.108, P=0.043), halo type enhancement (χ2=4.847, P=0.028), and lesion apparent dispersion coefficient (ADC) (t=2.552, P=0.011 8). Multivariate regression analysis showed that AFP>20 μg/L (OR=9.358, P<0.000 1) and ADC≤1.404×10-3 mm2/s (OR=1.003, P=0.017) were independent predictors for GPC3 expression in HCC. The combined model and the area under the curve value for the diagnosis of GPC3(+) in HCC was 0.810, and its diagnostic sensitivity and specificity were 76.8% and 77.5%, respectively. Conclusion: AFP>20 μg/L and ADC≤1.404×10-3 mm2/s may indicate the expression of GPC3 in HCC, and the combination of the two diagnostic indicators can provide a simple and effective non-invasive diagnostic method for clinical practice.

Evaluation of Magnetic Resonance Imaging for Microsurgical Efficacy and Relapse of Rolandic Meningioma.

In this study, magnetic resonance imaging (MRI) was used to evaluate the relapse features of patients with Rolandic meningioma after the microsurgery. 53 patients with Rolandic meningioma were selected as the research objects, and they were divided into the relapse group (n = 16) and nonrelapse group (n = 37) according to whether patients had a relapse during the follow-up period. Differences in quality of life, 1H-MRS index, vascular density, and cell proliferation between the two groups were assessed as well as imaging differences between the two groups were analyzed using MRI. The results showed that the patients' quality-of-life scores in the two groups increased notably after the surgical treatment (P < 0.05). Compared with the nonrelapse group, the proportion of irregular boundary and uneven enhancement of focal tissue in the relapse group was signally increased (P < 0.05). Compared with the nonrelapse group, cell proliferation index, vascular density and imaging index, mean tumor diameter, mean transit time (MTT), time to peak (TTP), fractional anisotropy (FA), choline (Cho)/N-acetylaspartic acid (NAA), Cho/creatine (Cr), lactic acid (Lac)/Cr, and the maximum value of relative cerebral blood volume (rCBVmax) in the relapse group were obviously increased (P < 0.05). However, the apparent dispersion coefficient, NAA/Cr, and Lac/NAA values decreased greatly (P < 0.05). To sum up, the microsurgical treatment helped improve the quality of life of patients with Rolandic meningioma, and MR imaging could be used to determine the relapse of Rolandic meningioma after microsurgical treatment.

Study on the influence of various factors on dispersion during enhance natural gas recovery with CO2 sequestration in depleted gas reservoir

In CO2 enhanced gas recovery (EGR), physical dispersion occurs between CO2 and natural gas, which can pollute the produced natural gas. Therefore, accurate assessment of the dispersion process is important for the commercialization of EGR. Under reservoir conditions, the effects of gravity, impurities, and other factors on dispersion in porous media were systematically evaluated. Comparison of the apparent dispersion characteristics of sandstone and unconsolidated cores (sandpacks) revealed that the vertically upward dispersion coefficient was smaller owing to the greater permeability and homogeneity of the sandpacks. With horizontal and vertically downward displacement of CO2–CH4, gravity promotes CO2–CH4 dispersion. However, dispersion was suppressed with vertically upward displacement (opposite to the direction of gravity). Under the same experimental conditions, pure N2 exhibited greater dispersion than CO2 as a displacing fluid. Finally, CO2 was used to displace natural gas containing different impurities. The results show that the more impurities (CO2, C2H6) exist in the displaced phase, the greater the mixing degree in the displacement process and the larger the dispersion coefficient.

Global fallout Pu isotopes, 137Cs and 237Np records in the sediments of Lake Xingkai and their response to environmental changes in the catchment

Plutonium (Pu) isotopes, neptunium-237 (237Np) and cesium-137 (137Cs) in the environment have emerged as important tools for promoting geochemical studies. To elucidate their source terms, deposition process, and the geochemical behavior, as well as their response to catchment environmental changes in lacustrine environment, 239, 240Pu, 137Cs and 237Np were determined for the first time in a sediment core collected from the Lake Xingkai. The 240Pu/239Pu atom ratios (0.163–0.178) in all sediment samples corresponded well with the typical global fallout value of ∼0.18, indicating that there were no other significant radioactive source inputs. The activity concentrations of 239+240Pu, 137Cs, and 237Np were 0.010–1.030 Bq kg−1, 6.4–30.1 Bq kg−1, and (0.020–2.195) × 10−3 Bq kg−1, respectively. They presented similar vertical distribution patterns, with a typical global fallout peak (15–16 cm) corresponding to the year of 1964. On the other hand, the 237Np/239Pu atom ratios exhibited a wide range (0.207–1.306), and showed a trend of increasing values with depth, implying different geochemical behaviors of these two elements. Using the advection-dispersion equation model (ADE), the obtained apparent dispersion coefficient of 237Np (0.58 ± 0.09 cm2 yr−1) was higher than that of 239+240Pu (0.38 ± 0.07 cm2 yr−1), indicating that Np has greater mobility than Pu. The total global fallout inventories of 239+240Pu, 137Cs, and 237Np were 145, 4592, and 0.291 Bq m−2, respectively. Approximately 46% of the total global fallout was derived from riverine input, indicating that severe soil erosion occurred in the catchment of Lake Xingkai in the past decades.

The Value of DTI Parameters in Predicting Postoperative Spinal Cord Function Fluctuations in Patients with High Cervical Disc Tumors.

Objective To explore the characteristics of magnetic resonance diffusion tensor imaging (DTI) parameters in patients with high cervical spinal myeloma and the evaluation of postoperative spinal cord function. Methods In recent years, 42 patients with high cervical spine myeloma were selected as the observation group, and 42 healthy volunteers were selected as the control group during the same period. The apparent dispersion coefficient (ADC), the fractional anisotropy (FA), the number of fiber bundles (FT), and the fiber bundle ratio (FTR) were compared between the two groups. The correlation between the ADC, FA, FT, FTR, and the International Standard for Neurological Classification of Spinal Cord Injury (ISNCSCI) score in the observation group were analyzed. Spinal cord function was evaluated using the Japanese Orthopaedic Association Score (JOA). Logistic regression model was used to analyze the factors affecting the recovery of spinal cord function after surgery. The receiver operating characteristic curve (ROC) was used to analyze the value of ADC, FA, FT, FTR1, and FTR2 in predicting the recovery of spinal cord function. Results The ADCs of the lesion layer and lower layer of the observation group were higher than the middle and lower layers of the control group, the FA and FT were lower than the middle and lower layers of the control group, and FTR1 and FTR2 were lower than those of the control group (P < 0.05). The ADC of the lesion layer in the observation group was negatively correlated with ISNCSCI score, and the FA, FT, FTR1, FTR2, and ISNCSCI scores were positively correlated (P < 0.05). Three months after the operation, JOA was used to evaluate the spinal cord function, which was excellent in 23 cases and poor in 19 cases. Logistic regression model analysis showed that after the ISNCSCI score was controlled, the increase in ADC and the decrease in FA, FT, FTR1, and FTR2 of the lesion layer were independent risk factors for poor postoperative body function recovery (P < 0.05). ROC analysis showed that the combination of ADC, FA, FT, FTR1, and FTR2 of the lesion layer predicted the AUC of spinal cord functional recovery was 0.941, which was better than the single prediction (P < 0.05). Conclusion The abnormal DTI parameter values of patients with high cervical spinal myeloma can better reflect the lack of spinal cord function, and they can effectively predict the recovery of the patient's body function after surgery, providing a reference for clinical diagnosis and treatment.

A new experimental method for comparing solvents in steam-solvent coinjection for bitumen recovery under controlled thermodynamic conditions

Solvent-aided steam-assisted gravity drainage (SA-SAGD) involves the interplay between phase behavior and fluid flow near the edge of a steam chamber, which affects the mixing of solvent with bitumen. The mixing of solvent with bitumen (i.e., dispersion) results in dilution of the bitumen and can improve the energy efficiency of SAGD. However, it is often difficult to analyze this complex interplay through large-scale steam injection experiments because of the transient chamber-edge thermodynamic conditions.This paper presents an experimental program that compares the bitumen gravity drainage with steam injection (SAGD) and solvent-steam co-injection (SA-SAGD) under controlled thermodynamic conditions. In addition to SAGD as the base case, two sets of SA-SAGD were performed with 20 mol% C4 and 10 mol% C8 in the coinjected vapor at 3500 kPa. The experiments used a sand-pack of 3-inch diameter and 15-inch length, which was placed in a 25-L cylindrical pressure vessel. The sand-pack was surrounded by one-inch annular space, into which the vapor phase was injected under controlled pressure, temperature, and composition. Oil production and temperature profiles inside and outside the sand-pack were recorded for all experiments. Excavated samples from the sand-pack were analyzed after the experiments.The total recovery factors for SAGD, C4-SAGD, and C8-SAGD were 78%, 84%, and 89%, respectively. The recovery factors at 1 h for SAGD, C4-SAGD, and C8-SAGD were 71%, 80%, and 85%, respectively. The peak oil rate was 9.8 cm3/min with SAGD, 14.6 cm3/min with C4-SAGD, and 31.3 cm3/min with C8-SAGD. The SA-SAGD cases resulted in markedly better results than the SAGD case, and C8-SAGD yielded more rapid oil drainage than C4-SAGD.The SAGD experimental data were history-matched using a numerical simulation model. Based on the calibrated numerical model, the SA-SAGD experimental data were history-matched by adjusting the dispersion coefficient to model the mixing between the solvent and bitumen. The apparent dispersion coefficients for C4 and C8 in bitumen were determined to be 0.012 m2/day and 0.093 m2/day, respectively. The experimental program verified in this research offers a way to systematically compare different solvents for SA-SAGD with their quantifiable dispersion coefficients under given chamber conditions.

Spatial distribution and migration of 239+240Pu in Chinese soils

The migration of radionuclides is a critical threat to the soil and groundwater environment. This study investigates highly radiological toxic 239+240Pu in 647 surface soils and 66 soil cores in China. First, the spatial distributions of 239+240Pu activities and 240Pu/239Pu ratios are presented in Chinese surface soils. Second, four different types of vertical distribution of 239+240Pu, namely 45.4%, 40.9%, 9.1% and 4.5% of Chinese soil cores proportions are integrated using statistical analysis. Furthermore, different soil types are accompanied by different 239+240Pu vertical distributions, which relate closely to the 239+240Pu migration. Finally, based on the Convection Dispersion Equation (CDE) model, the present work find that the apparent convection velocities of 239+240Pu are ranging from 0.00032 ± 0.00031 cm a−1 to 0.473 ± 0.083 cm a−1. As shown by the four typical vertical activity distribution of 239+240Pu in soil cores, the deepened activity maximum value position of 239+240Pu implies a fast migration rate or apparent convection velocity. This study, for the first time, suggests a significant linear correlation (R2 = 0.847) between the depth of 239+240Pu maximum value (cm) and the apparent convection velocity (v, cm a−1). We hypothesize that v usually does not exceed 0.5 cm a−1 in the CDE model. A significant linear correlation is also identified between apparent dispersion coefficient (D, cm2 a−1) and v2 in Chinese soil cores from the CDE model. It will provide an important reference for harmful heavy metal migration research in the future.

Bias in apparent dispersion measure due to de-magnification of plasma lensing on background radio sources

ABSTRACT The effect of ionized gas on the propagation of radio signals is known as plasma lensing. Unlike gravitational lensing, plasma lensing causes both magnification and strong de-magnification effects to background sources. We study the cross-section of plasma lensing for two density profiles, the Gaussian and power-law models. In general, the cross-section increases with the density gradient. Radio sources can be used to measure the free electron density along the line of sight. However, plasma lensing de-magnification causes an underestimate of the electron density. Such a bias increases with the electron density, and can be up to $\sim 15{{\ {\rm per \ cent}}}$ in the high density region. There is a large probability that high density clumps will be missed due to this bias. The magnification of plasma lensing can also change the luminosity function of the background sources. The number density of sources on both the high- and low-luminosity ends can be overestimated due to this biasing effect.

High turn-over rates at the upper range limit and elevational source-sink dynamics in a widespread songbird

The formation of an upper distributional range limit for species breeding along mountain slopes is often based on environmental gradients resulting in changing demographic rates towards high elevations. However, we still lack an empirical understanding of how the interplay of demographic parameters forms the upper range limit in highly mobile species. Here, we study apparent survival and within-study area dispersal over a 700 m elevational gradient in barn swallows (Hirundo rustica) by using 15 years of capture-mark-recapture data. Annual apparent survival of adult breeding birds decreased while breeding dispersal probability of adult females, but not males increased towards the upper range limit. Individuals at high elevations dispersed to farms situated at elevations lower than would be expected by random dispersal. These results suggest higher turn-over rates of breeding individuals at high elevations, an elevational increase in immigration and thus, within-population source-sink dynamics between low and high elevations. The formation of the upper range limit therefore is based on preference for low-elevation breeding sites and immigration to high elevations. Thus, shifts of the upper range limit are not only affected by changes in the quality of high-elevation habitats but also by factors affecting the number of immigrants produced at low elevations.

Low Loading of CoRe/TiO2 for Efficient Hydrodeoxygenation of Levulinic Acid to γ-Valerolactone

CoRe bimetallic catalysts with low loading were designed for hydrodeoxygenation of levulinic acid to γ-valerolactone. Results show that the 1 wt % Co0.5Re0.5/TiO2 catalyst achieved the highest yield of γ-valerolactone (>99%) at 220 °C, 3 h, a 1,4-dioxane solvent and Co/levulinic acid molar ratio of 1:1760, with a turnover frequency (TOF) of 1328 h–1. The catalyst can be reused four times with only slight activity loss. The catalyst was characterized with various physicochemical measurements, and its adsorption styles with H2 and levulinic acid were calculated by density functional theory. The results reveal that four main factors are related to its excellent catalytic performance. First, the Re oxides synergize with Co by spillover of the dissociated H atoms, which increases the apparent dispersion of Co and promotes the reaction. Second, the low loading of 1 wt % allowed the metal nanoparticles to be well dispersed with a very fine size of ca. 1.24 nm, which may expose more active sites to the substrate and result in a higher catalytic efficiency. Third, CoRe formed an amorphous alloy with the formula Co-ReO1.6, which showed a synergistic effect during the reaction. Finally, the TiO2 support was nonporous and hydrophilic, which would be beneficial for the mass diffusion of the reaction components to be adsorbed/desorbed onto the vicinity of the metallic active sites and lead to a high TOF in the hydrodeoxygenation process.

On the cosmic distance duality relation and strong gravitational lens power law density profile

Many new strong gravitational lensing (SGL) systems have been discovered in the last two decades with the advent of powerful new space and ground-based telescopes. The effect of the lens mass model (usually the power-law mass model) on cosmological parameters constraints has been performed recently in literature. In this paper, by using SGL systems and Supernovae type Ia observations, we explore if the power-law mass density profile (ρ ∝ r-γ) is consistent with the cosmic distance duality relation (CDDR), DL (1+z)-2/DA = η(z) = 1, by considering different lens mass intervals. It has been obtained that the verification of the CDDR validity is significantly dependent on lens mass interval considered: the sub-sample with σap ≥ 300 km/s (where σap is the lens apparent stellar velocity dispersion) is in full agreement with the CDDR validity, the sub-sample with intermediate σap values (200 ≤ σap < 300) km/s is marginally consistent with η = 1 and, finally, the sub-sample with low σap values (σap < 200 km/s) ruled out the CDDR validity with high statistical confidence. Therefore, if one takes the CDDR as guarantee, our results suggest that using a single density profile is not suitable to describe lens with low σap values and it is only an approximate description to lenses with intermediate mass interval.

Apparent survival and dispersal in a recovered Osprey population: effects of age, sex and social status

Apparent survival and dispersal in a recovered Osprey population: effects of age, sex and social status

Variable-order optimal implicit finite-difference schemes for explicit time-marching solutions to wave equations

The time-space-domain finite-difference method (FDM) is widely used in forward modeling of wave equations. Conventional explicit FDMs (EFDMs) (with high order in space and the second order in time) would result in apparent temporal and spatial dispersion for high frequencies and large time steps. Moreover, the saturation effect of Taylor expansion seriously restricts the improvement of bandwidth coverage and efficiency of EFDMs. We have developed a variable-order optimization scheme of the implicit FDM (IFDM) to improve the computational efficiency and numerical accuracy of forward modeling. Then, we applied time-dispersion transforms (TDTs) to filter out the temporal dispersion generated by the second-order temporal approximations. Our method greatly alleviates the saturation effect of the high-order spatial finite-difference (FD) operators. Dispersion analysis indicates that the optimized coefficients of the IFDM based on the Remez algorithm can achieve the widest bandwidth (close to the Nyquist wavenumber), which corresponds to the shortest length of the spatial FD operator under a given error threshold. Our method has great potential to approach the highest spectral accuracy but with minimal increase in computational cost. Numerical experiments indicate that the combination of the variable-order optimization of IFDM and TDTs can significantly reduce numerical dispersion. Compared with traditional methods, our scheme is more advantageous for numerical simulation of large-scale geologic models because it has the least amount of calculation burden under the same accuracy requirements.

Implications of dispersion in connecting capillaries for separation systems involving post-column flow splitting

It is common practice in liquid chromatography to split the flow of the effluent exiting the analytical column into two or more parts, either to enable parallel detection (e.g., coupling the separation to two destructive detectors such as light scattering and mass spectrometry (MS)), or to accommodate flow rate limitations of a detector (e.g., electrospray ionization mass spectrometry). In these instances the user must make choices about split ratio and dimensions of connecting tubing that is used between the split point and the detector, however these details are frequently not mentioned in the literature, and rarely justified. In our own work we often split the effluent following the second dimension (2D) column in two-dimensional liquid chromatography systems coupled to MS detection, and we have frequently observed post 2D column peak broadening that is larger than we would expect to result from dispersion in the MS ionization source itself. For the present paper we describe a series of experiments aimed at understanding the impact of the split ratio and post-split connecting tubing dimensions on dispersion of peaks exiting an analytical column. We start with the simple idea – based on the principle of conservation of mass – that analyte peaks entering the split point are split into two parts such that the analyte mass (and thus peak volume) entering and exiting the split point is conserved, and directly related to the ratio of flow rates entering and exiting the split point. Measurements of peak width and variance after the split point show that this simple view of the splitting process – along with estimates of additional dispersion in the post-split tubing - is sufficient to predict peak variances at the detector with accuracy that is sufficient to guide experimental work (median error of about 10% over a wide range of conditions). We feel it is most impactful to recognize that flow splitting impacts apparent post-column dispersion not because anything unexpected happens in the splitting process, but because the split dramatically reduces the volume of the analyte peak, which then is more susceptible to dispersion in connecting tubing that would not cause significant dispersion under conditions where splitting is not implemented. These results will provide practitioners with a solid basis on which rational decisions about split ratios and dimensions of post-split tubing can be made.

Source, Spatial Distribution and Migration of &lt;sup&gt;239+240&lt;/sup&gt;Pu in Chinese Soils

The source, spatial distribution, typical vertical distribution and migration of 239+240 Pu in Chinese 647 surface soils and 66 soil cores are investigated in this study. To provide a complete spatial distribution of 239+240 Pu in Chinese surface soil, an overall pattern of and mechanism for 239+240 Pu migration in Chinese core soil, we summarize and analyze the 239+240 Pu surface and vertical distributions in literature. Comprehensive statistical analysis suggests four typical distributions in Chinese soil cores. It is found that the 239+240 Pu vertical distribution is closely related to the soil type and the 239+240 Pu migration. The result indicates that global fallout is the major source of 239+240 Pu in Chinese soils, with the average 240 Pu/ 239 Pu atom ratios around 0.18. Abnormally low 240 Pu/ 239 Pu ratios are detected in Jiuquan region and northern Xinjiang province in Northwest China, which can be attributed to nuclear weapons tests. To further investigate the migration behaviors of 239+240 Pu in soil cores in China, we apply the Convection Dispersion Equation (CDE) model and find that 239+240 Pu apparent convection velocities ranges from 0.00032±0.00031 cm/a to 0.473±0.083 cm/a. As shown in four typical vertical 239+240 Pu activity distribution soil cores, the deepened 239+240 Pu activity maximum value position implies a fast 239+240 Pu migration rate or apparent convection velocity. This study for the first time suggests a significant linear correlation ( R 2 =0.847) between depth of 239+240 Pu maximum value (cm) and apparent convection velocity (v, cm/a), and we speculate that v usually does not exceed 0.5 cm/a. A significant linear correlation is also identified between apparent dispersion coefficient (D, cm 2 /a) and v 2 in Chinese soil cores.

Estimation of shallow subsurface S-wave velocity structure in urban area based on inversion of apparent dispersion curve

AbstractDue to its efficiency, convenience, non-destructive nature and strong anti-interference capability, the microtremor survey method (MSM) has found wide applications in urban geological surveys. The spatial autocorrelation method is diffusely applied to extract the dispersion curves from microtremor signals, which needs to satisfy the assumption that the energy of the fundamental Rayleigh wave is dominant. However, for layered media containing a layer with a significant low- or high-velocity contrast, this assumption is distinctly incorrect for certain frequency ranges. We present a processing methodology comprising the extraction and inversion of the apparent dispersion curves based on extended spatial autocorrelation method and fast simulated-annealing algorithm. We analyse synthetic microtremor signals for three selected geological models, and then compare the S-wave velocity structures estimated from their inversions with the actual models. Subsequently, a filed data example is given to detect the shallow stratigraphic structures in Guangzhou city, China, in which the new MSM was used. The estimated two-dimensional S-wave velocity model provided an accurate description of the thickness and depth of the strata in the study area, based on a priori information. Moreover, the S-wave velocity structures estimated from the MSM and the results from the drilling match very well, indicating that MSM is a reliable geophysical technique in urban geological surveys. Combined with available borehole information, MSM can be a very robust and effective method for detecting the shallow three-dimensional velocity structures in an urban area.

APOE-\u03b54-related differences in left thalamic microstructure in cognitively healthy adults

APOE-ε4 is a main genetic risk factor for developing late onset Alzheimer’s disease (LOAD) and is thought to interact adversely with other risk factors on the brain. However, evidence regarding the impact of APOE-ε4 on grey matter structure in asymptomatic individuals remains mixed. Much attention has been devoted to characterising APOE-ε4-related changes in the hippocampus, but LOAD pathology is known to spread through the whole of the Papez circuit including the limbic thalamus. Here, we tested the impact of APOE-ε4 and two other risk factors, a family history of dementia and obesity, on grey matter macro- and microstructure across the whole brain in 165 asymptomatic individuals (38–71 years). Microstructural properties of apparent neurite density and dispersion, free water, myelin and cell metabolism were assessed with Neurite Orientation Density and Dispersion (NODDI) and quantitative magnetization transfer (qMT) imaging. APOE-ε4 carriers relative to non-carriers had a lower macromolecular proton fraction (MPF) in the left thalamus. No risk effects were present for cortical thickness, subcortical volume, or NODDI indices. Reduced thalamic MPF may reflect inflammation-related tissue swelling and/or myelin loss in APOE-ε4. Future prospective studies should investigate the sensitivity and specificity of qMT-based MPF as a non-invasive biomarker for LOAD risk.

Strong Gene Flow Undermines Local Adaptations in a Host Parasite System.

Simple SummaryThe co-evolution of hosts and parasites depends on their ability to adapt to each other’s defense and counter-defense mechanisms. The strength of selection on those mechanisms may vary among populations, resulting in a geographical mosaic of co-evolution. The boreo-montane paper wasp Polistes biglumis and its parasite Polistes atrimandibularis exemplify this type of co-evolutionary system. Here, we used genetic markers to examine the genetic population structures of these wasps in the western Alps. We found that both host and parasite populations displayed similar levels of genetic variation. In the host species, populations located near to each other were genetically similar; in both the host and the parasite species populations farther apart were significantly different. Thus, apparent dispersal barriers (i.e., high mountains) did not seem to restrict gene flow across populations as expected. Furthermore, there were no major differences in gene flow between the two species, perhaps because P. atrimandibularis parasitizes both alpine and lowland host species and annually migrates between alpine and lowland populations. The presence of strong gene flow in a system where local populations experience variable levels of selection pressure challenges the classical hypothesis that restricted gene flow is required for local adaptations to evolve.The co-evolutionary pathways followed by hosts and parasites strongly depend on the adaptive potential of antagonists and its underlying genetic architecture. Geographically structured populations of interacting species often experience local differences in the strength of reciprocal selection pressures, which can result in a geographic mosaic of co-evolution. One example of such a system is the boreo-montane social wasp Polistes biglumis and its social parasite Polistes atrimandibularis, which have evolved local defense and counter-defense mechanisms to match their antagonist. In this work, we study spatial genetic structure of P. biglumis and P. atrimandibularis populations at local and regional scales in the Alps, by using nuclear markers (DNA microsatellites, AFLP) and mitochondrial sequences. Both the host and the parasite populations harbored similar amounts of genetic variation. Host populations were not genetically structured at the local scale, but geographic regions were significantly differentiated from each other in both the host and the parasite in all markers. The net dispersal inferred from genetic differentiation was similar in the host and the parasite, which may be due to the annual migration pattern of the parasites between alpine and lowland populations. Thus, the apparent dispersal barriers (i.e., high mountains) do not restrict gene flow as expected and there are no important gene flow differences between the species, which contradict the hypothesis that restricted gene flow is required for local adaptations to evolve.