Toward Nonepitaxial Laser Diodes.

Thin-film organic, colloidal quantum dot, and metal halide perovskite semiconductors are all being pursued in the quest for a wavelength-tunable diode laser technology that does not require epitaxial growth on a traditional semiconductor substrate. Despite promising demonstrations of efficient light-emitting diodes and low-threshold optically pumped lasing in each case, there are still fundamental and practical barriers that must be overcome to reliably achieve injection lasing. This review outlines the historical development and recent advances of each material system on the path to a diode laser. Common challenges in resonator design, electrical injection, and heat dissipation are highlighted, as well as the different optical gain physics that make each system unique. The evidence to date suggests that continued progress for organic and colloidal quantum dot laser diodes will likely hinge on the development of new materials or indirect pumping schemes, while improvements in device architecture and film processing are most critical for perovskite lasers. In all cases, systematic progress will require methods that can quantify how close new devices get with respect to their electrical lasing thresholds. We conclude by discussing the current status of nonepitaxial laser diodes in the historical context of their epitaxial counterparts, which suggests that there is reason to be optimistic for the future.

Phase-related differences in egg production of the migratory locust regulated by differential oosorption through microRNA-34 targeting activinß.

Outbreaks of locust plagues result from the long-term accumulation of high-density egg production. The migratory locust, Locusta migratoria, displays dramatic differences in the egg-laid number with dependence on population density, while solitarious locusts lay more eggs compared to gregarious ones. However, the regulatory mechanism for the egg-laid number difference is unclear. Herein, we confirm that oosorption plays a crucial role in the regulation of egg number through the comparison of physiological and molecular biological profiles in gregarious and solitarious locusts. We find that gregarious oocytes display a 15% higher oosorption ratio than solitarious ones. Activinß (Actß) is the most highly upregulated gene in the gregarious terminal oocyte (GTO) compared to solitarious terminal oocyte (STO). Meanwhile, Actß increases sharply from the normal oocyte (N) to resorption body 1 (RB1) stage during oosorption. The knockdown of Actß significantly reduces the oosorption ratio by 13% in gregarious locusts, resulting in an increase in the egg-laid number. Based on bioinformatic prediction and experimental verification, microRNA-34 with three isoforms can target Actß. The microRNAs display higher expression levels in STO than those in GTO and contrasting expression patterns of Actß from the N to RB1 transition. Overexpression of each miR-34 isoform leads to decreased Actß levels and significantly reduces the oosorption ratio in gregarious locusts. In contrast, inhibition of the miR-34 isoforms results in increased Actß levels and eventually elevates the oosorption ratio of solitarious locusts. Our study reports an undescribed mechanism of oosorption through miRNA targeting of a TGFß ligand and provides new insights into the mechanism of density-dependent reproductive adaption in insects.

Thermal Properties of Polymer Hole-Transport Layers Influence the Efficiency Roll-off and Stability of Perovskite Light-Emitting Diodes.

While the performance of metal halide perovskite light-emitting diodes (PeLEDs) has rapidly improved in recent years, their stability remains a bottleneck to commercial realization. Here, we show that the thermal stability of polymer hole-transport layers (HTLs) used in PeLEDs represents an important factor influencing the external quantum efficiency (EQE) roll-off and device lifetime. We demonstrate a reduced EQE roll-off, a higher breakdown current density of approximately 6 A cm-2, a maximum radiance of 760 W sr-1 m-2, and a longer device lifetime for PeLEDs using polymer HTLs with high glass-transition temperatures. Furthermore, for devices driven by nanosecond electrical pulses, a record high radiance of 1.23 MW sr-1 m-2 and an EQE of approximately 1.92% at 14.6 kA cm-2 are achieved. Thermally stable polymer HTLs enable stable operation of PeLEDs that can sustain more than 11.7 million electrical pulses at 1 kA cm-2 before device failure.

Epidemiological investigation and genetic characterization of porcine astrovirus genotypes 2 and 5 in Yunnan province, China.

Astroviruses (AstVs) are among the most important viruses causing diarrhea in human infants and many animals, posing a threat to public health safety and a burden on the economy. Five porcine AstV (PAstV) genotypes have been identified in various countries, including China. However, the epidemiology of PAstV in Yunnan province, China, remains unknown. In this study, 489 fecal samples from pigs in all 16 prefectures/cities of Yunnan were collected between April and August of 2020 for epidemiological investigation. The total infection rate of PAstV-2 or PAstV-5 was 39.9%, with suckling piglets having the highest infection rate (62.3%). The ORF2 genes of seven PAstV-2 and 10 PAstV-5 isolates were sequenced and phylogenetically analyzed. In addition to coinfections with PAstV-2 and PAstV-5, coinfections of PAstV with other diarrhea-inducing viruses (e.g., porcine bocavirus) were also discovered. A comparison of ORF2-encoded capsid protein sequences revealed that there were multiple insertions and deletions in the seven Yunnan PAstV-2 sequences, while point mutations, but no deletions or insertions, were found in the 10 Yunnan PAstV-5 sequences, which were very similar to the reference sequences. This is the first epidemiological investigation and genetic characterization of PAstV-2 and PAstV-5 in Yunnan province, China, demonstrating the current PAstV infection situation in Yunnan.

Juvenile hormone-dependent Kazal-type serine protease inhibitor Greglin safeguards insect vitellogenesis and egg production.

In addition to preventing insect metamorphosis, juvenile hormone (JH) is known to stimulate aspects of insect reproduction. However, the molecular mechanisms of JH action in insect reproduction remain largely unknown. By reanalyzing the transcriptomic data from adults and other developmental stages of the migratory locust Locusta migratoria, we identified a gene coding for Kazal-type protease inhibitor, previously named Greglin. Greglin is specifically expressed in adult females and most abundant in the fat body and ovaries. Interestingly, Greglin is among the top 3 of highly expressed genes in adult female locusts, after 2 vitellogenin ( Vg) genes. Greglin is induced by JH and expressed at remarkably high levels in the vitellogenic stage. Knockdown of Greglin in adult female locusts results in accelerated degradation of serine protease substrate and significantly reduced levels of Greglin protein in hemolymph and ovaries. The consequent phenotypes include blocked oocyte maturation, arrested ovarian growth and shrunken follicular epithelium, as well as declines in egg number and hatchability. The data provide the first evidence, to our knowledge, that JH-dependent Greglin is involved in locust vitellogenesis and oocyte maturation likely by protecting vitellogenesis and other forms of yolk precursors from proteolysis. The result offers new insights into the regulation of JH and function of protease inhibitors in insect vitellogenesis, oocyte maturation and fecundity.-Guo, W., Wu, Z., Yang, L., Cai, Z., Zhao, L., Zhou, S. Juvenile hormone-dependent Kazal-type serine protease inhibitor Greglin safeguards insect vitellogenesis and egg production.

miRNA-200b improves hepatic fibrosis induced by CCL4 by regulating toll-like receptor 4 in mice.

To study the effect of miRNA-200b on hepatic fibrosis induced by CCl4 in mice. The C59BL/6 mice were randomly divided into three groups (normal control [NC], CCLR model [Model], and CCl 4 + miRNA-200b [miRNA]). The hepatic fibrosis was induced by CCl 4 injected subcutaneously twice per week in Model and miRNA groups. After 6 weeks building model, the mice of miRNA group were injected the miRNA-200b from caudal vein twice per week. The mice of Model and miRNA groups were continuously fed for 3 weeks. The IL-1ß, IL-6, and TNF-α concentrations of serum were measured by enzyme-linked immunosorbent assay. The hepatic tissues of difference groups were observed by hematoxylin and eosin (H&E) staining, sirius red staining, Masson staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay and measured toll-like receptor 4 (TLR4) and nuclear factor-κB (NF-κB) proteins expressions by western blot assay. The correlation between miRNA-200b and TLR4 were analyzed by dual luciferase target assay. Compared with NC group, the interleukin-1ß (IL-1ß), IL-6, and tumor necrosis factor-α (TNF-α) concentrations of Model group were significantly upregulated (P < 0.05, respectively). With miRNA-200b overexpression, the IL-1ß, IL-6, and TNF-α concentrations were significantly suppressed (P < 0.05, respectively). The pathologies were improved by H&E staining, sirius red staining, and Masson staining; meanwhile, the hepatic cell apoptosis rate was significantly suppressed (P < 0.05). The TLR4 and NF-κB protein expressions of miRNA group were significantly suppressed compared with the Model group (P < 0.05, respectively). By dual luciferase target assay, the TLR4 was a target gene of miRNA-200b. The miRNA-200b upregulation improved hepatic fibrosis induced by CCl 4 via regulation of TLR4 in vivo.

Perovskite Light-Emitting Diodes with Improved Outcoupling Using a High-Index Contrast Nanoarray.

Organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) are promising for next-generation optoelectronic devices due to their potential to achieve high color purity, efficiency, and brightness. Although the external quantum efficiency (EQE) of PeLEDs has recently surpassed 20%, various strategies are being pursued to increase EQE further and reduce the EQE gap compared to other LED technologies. A key point to further boost EQE of PeLEDs is linked to the high refractive index of the perovskite emissive layer, leading to optical losses of more than 70% of emitted photons. Here, it is demonstrated that a randomly distributed nanohole array with high-index contrast can effectively enhance outcoupling efficiency in PeLEDs. Based on a comprehensive optical analysis on the perovskite thin film and outcoupling structure, it is confirmed that the nanohole array effectively distributes light into the substrate for improved outcoupling, allowing for 1.64 times higher light extraction. As a result, highly efficient red/near-infrared PeLEDs with a peak EQE of 14.6% are demonstrated.

Inferring Drug-Related Diseases Based on Convolutional Neural Network and Gated Recurrent Unit.

Predicting novel uses for drugs using their chemical, pharmacological, and indication information contributes to minimizing costs and development periods. Most previous prediction methods focused on integrating the similarity and association information of drugs and diseases. However, they tended to construct shallow prediction models to predict drug-associated diseases, which make deeply integrating the information difficult. Further, path information between drugs and diseases is important auxiliary information for association prediction, while it is not deeply integrated. We present a deep learning-based method, CGARDP, for predicting drug-related candidate disease indications. CGARDP establishes a feature matrix by exploiting a variety of biological premises related to drugs and diseases. A novel model based on convolutional neural network (CNN) and gated recurrent unit (GRU) is constructed to learn the local and path representations for a drug-disease pair. The CNN-based framework on the left of the model learns the local representation of the drug-disease pair from their feature matrix. As the different paths have discriminative contributions to the drug-disease association prediction, we construct an attention mechanism at the path level to learn the informative paths. In the right part, a GRU-based framework learns the path representation based on path information between the drug and the disease. Cross-validation results indicate that CGARDP performs better than several state-of-the-art methods. Further, CGARDP retrieves more real drug-disease associations in the top part of the prediction result that are of concern to biologists. Case studies on five drugs demonstrate that CGARDP can discover potential drug-related disease indications.

Mixed-Halide Perovskites with Stabilized Bandgaps.

One merit of organic-inorganic hybrid perovskites is their tunable bandgap by adjusting the halide stoichiometry, an aspect critical to their application in tandem solar cells, wavelength-tunable light emitting diodes (LEDs), and lasers. However, the phase separation of mixed-halide perovskites caused by light or applied bias results in undesirable recombination at iodide-rich domains, meaning open-circuit voltage (VOC) pinning in solar cells and infrared emission in LEDs. Here, we report an approach to suppress halide redistribution by self-assembled long-chain organic ammonium capping layers at nanometer-sized grain surfaces. Using the stable mixed-halide perovskite films, we are able to fabricate efficient and wavelength-tunable perovskite LEDs from infrared to green with high external quantum efficiencies of up to 5%, as well as linearly tuned VOC from 1.05 to 1.45 V in solar cells.

Intraplate thrust orogeny of the Altai Mountains revealed by deep seismic reflection.

The Altai orogen is a typical intracontinental orogen in Central Asia that experienced far-field deformation associated with Indian-Eurasian plate convergence. This region is characterized by uplift comparable to that of the Tianshan Mountains but has a distinct strain rate. Half of the Indo-Asia strain is accommodated by the Tianshan Mountains, whereas the Altai Mountains accommodates only 10%. To elucidate how the Altai Mountains produced such a large amount of uplift with only one-fifth of the strain rate of the Tianshan Mountains, we constructed a detailed crustal image of the Altai Mountains based on a new 166.8-km deep seismic reflection profile. The prestack migration images reveal an antiform within the Erqis crust, an âˆ¼10 km Moho offset between the Altai arc and the East Junggar area, and a major south-dipping (30° dip) thrust in the lower crust beneath the Altai Mountains, which is connected to the Moho offset. The south-dipping thrust not only records the southward subduction of the Ob-Zaisan Ocean in the Paleozoic but also controlled the Altai deformation pattern in the Cenozoic with the Erqis antiform. The Erqis antiform prevented the extension of deformation to the Junggar crust. The south-dipping thrust in the lower crust of the Altai area caused extrusion of the lower crust, generating uplift at the surface, thickening of the crust, and steep (∼10 km) Moho deepening in the Altai Mountains. This process significantly widened the deformation zone of the Altai Mountains. These findings provide a new geodynamic model for describing how inherited crustal structure controls intraplate deformation without strong horizontal stress.

SEL1L-HRD1 endoplasmic reticulum-associated degradation controls STING-mediated innate immunity by limiting the size of the activable STING pool.

Stimulator of interferon genes (STING) orchestrates the production of proinflammatory cytokines in response to cytosolic double-stranded DNA; however, the pathophysiological significance and molecular mechanism underlying the folding and maturation of nascent STING protein at the endoplasmic reticulum (ER) remain unknown. Here we report that the SEL1L-HRD1 protein complex-the most conserved branch of ER-associated degradation (ERAD)-is a negative regulator of the STING innate immunity by ubiquitinating and targeting nascent STING protein for proteasomal degradation in the basal state. SEL1L or HRD1 deficiency in macrophages specifically amplifies STING signalling and immunity against viral infection and tumour growth. Mechanistically, nascent STING protein is a bona fide substrate of SEL1L-HRD1 in the basal state, uncoupled from ER stress or its sensor inositol-requiring enzyme 1α. Hence, our study not only establishes a key role of SEL1L-HRD1 ERAD in innate immunity by limiting the size of the activable STING pool, but identifies a regulatory mechanism and therapeutic approach to targeting STING.

A novel mechanism for macrophage pyroptosis in rheumatoid arthritis induced by Pol ß deficiency.

Rheumatoid arthritis (RA) is a chronic and inflammatory autoimmune disease. Macrophage pyroptosis, a proinflammatory form of cell death, is critically important in RA; however, the detailed mechanism underlying pyroptosis induction is not yet well understood. Here, we report that DNA polymerase ß (Pol ß), a key enzyme in base excision repair, plays a pivotal role in RA pathogenesis. Our data shows that Pol ß expression is significantly decreased in peripheral blood mononuclear cells (PBMCs) from active RA patients and collagen-induced arthritis (CIA) mice, and Pol ß deficiency increases the incidence of RA, macrophage infiltration, and bone destruction in CIA mouse models. In vitro, experiments showed that Pol ß deficiency exacerbated macrophage pyroptosis induced by LPS plus ATP, while overexpression of Pol ß inhibited macrophage pyroptosis. Further characterization revealed that Pol ß knockout resulted in DNA damage accumulation and cytosolic dsDNA leakage, which activated the cGAS-STING-NF-κB signaling pathway and upregulated the expression of NLRP3, IL-1 ß, and IL-18. In conclusion, our findings clarify the influence of Pol ß on the development of RA and provide a detailed explanation for the STING-NF-κB pathway to induce macrophage pyroptosis.

Nanosecond-Pulsed Perovskite Light-Emitting Diodes at High Current Density.

While metal-halide perovskite light-emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, their slow operation speed and response time limit their application scope. Here, high-speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2 ns are reported with a maximum radiance of approximately 480 kW sr-1  m-2 at 8.3 kA cm-2 , and an external quantum efficiency (EQE) of 1% at approximately 10 kA cm-2 , through improved device configuration designs and material considerations. Enabled by the fast operation of PeLEDs, the temporal response provides access to transient charge carrier dynamics under electrical excitation, revealing several new electroluminescence quenching pathways. Finally, integrated distributed feedback (DFB) gratings are explored, which facilitate more directional light emission with a maximum radiance of approximately 1200 kW sr-1  m-2 at 8.5 kA cm-2 , a more than two-fold enhancement to forward radiation output.

Small molecule screening identified cepharanthine as an inhibitor of porcine reproductive and respiratory syndrome virus infection in vitro by suppressing integrins/ILK/RACK1/PKCα/NF-κB signalling axis.

Porcine Reproductive and Respiratory Syndrome (PRRS) is a devastating disease among the most notorious threats to the swine industry worldwide and is characterized by respiratory distress and reproductive failure. Highly evolving porcine reproductive and respiratory syndrome virus (PRRSV) strains with complicated genetic diversity make the current vaccination strategy far from cost-effective and thus urge identification of potent lead candidates to provide prevention and treatment approaches. From an in vitro small molecule screening with the TargetMol Natural Compound Library comprising 623 small molecules, cytopathic effect (CPE) observations and RT-qPCR analysis of viral ORF7 gene expression identified cepharanthine (CEP) to be one of the most protent inhibitors of PRRSV infection in Marc-145 cells. When compared with tilmicosin, which is one of the most commonly used antibiotics in swine industry to inhibit infections, CEP more prominently inhibited PRRSV infection represented by both RNA and protein levels, further reduced the TCID50 by 5.6 times, and thus more remarkably protected Marc-145 cells against PRRSV infection. Mechanistically, western blot analyses of the Marc-145 cells and the porcine alveolar macrophages (PAMs) with or without CEP treatment and PRRSV infection at various time points revealed that CEP can inhibit the expression of integrins ß1 and ß3, integrin-linked kinase (ILK), RACK1 and PKCα, leading to NF-κB suppression and consequent alleviation of PRRSV infection. Collectively, our small molecule screening identified cepharanthine as an inhibitor of PRRSV infection in vitro by suppressing Integrins/ILK/RACK1/PKCα/NF-κB signalling axis, which may enlighten the deeper understanding of the molecular pathogenesis of PRRSV infection and more importantly, suggested CEP as a potential promising drug for PRRS control in veterinary clinics.

Thermal Management Enables Bright and Stable Perovskite Light-Emitting Diodes.

The performance of lead-halide perovskite light-emitting diodes (LEDs) has increased rapidly in recent years. However, most reports feature devices operated at relatively small current densities (<500 mA cm-2 ) with moderate radiance (<400 W sr-1 m-2 ). Here, Joule heating and inefficient thermal dissipation are shown to be major obstacles toward high radiance and long lifetime. Several thermal management strategies are proposed in this work, such as doping charge-transport layers, optimizing device geometry, and attaching heat spreaders and sinks. Combining these strategies, high-performance perovskite LEDs are demonstrated with maximum radiance of 2555 W sr-1 m-2 , peak external quantum efficiency (EQE) of 17%, considerably reduced EQE roll-off (EQE > 10% to current densities as high as 2000 mA cm-2 ), and tenfold increase in operational lifetime (when driven at 100 mA cm-2 ). Furthermore, with proper thermal management, a maximum current density of 2.5 kA cm-2 and an EQE of ≈1% at 1 kA cm-2 are shown using electrical pulses, which represents an important milestone toward electrically driven perovskite lasers.

Convolutional Neural Network and Bidirectional Long Short-Term Memory-Based Method for Predicting Drug-Disease Associations.

Identifying novel indications for approved drugs can accelerate drug development and reduce research costs. Most previous studies used shallow models for prioritizing the potential drug-related diseases and failed to deeply integrate the paths between drugs and diseases which may contain additional association information. A deep-learning-based method for predicting drug-disease associations by integrating useful information is needed. We proposed a novel method based on a convolutional neural network (CNN) and bidirectional long short-term memory (BiLSTM)-CBPred-for predicting drug-related diseases. Our method deeply integrates similarities and associations between drugs and diseases, and paths among drug-disease pairs. The CNN-based framework focuses on learning the original representation of a drug-disease pair from their similarities and associations. As the drug-disease association possibility also depends on the multiple paths between them, the BiLSTM-based framework mainly learns the path representation of the drug-disease pair. In addition, considering that different paths have discriminate contributions to the association prediction, an attention mechanism at path level is constructed. Our method, CBPred, showed better performance and retrieved more real associations in the front of the results, which is more important for biologists. Case studies further confirmed that CBPred can discover potential drug-disease associations.

Predicting miRNA-Disease Associations by Incorporating Projections in Low-Dimensional Space and Local Topological Information.

Predicting the potential microRNA (miRNA) candidates associated with a disease helps in exploring the mechanisms of disease development. Most recent approaches have utilized heterogeneous information about miRNAs and diseases, including miRNA similarities, disease similarities, and miRNA-disease associations. However, these methods do not utilize the projections of miRNAs and diseases in a low-dimensional space. Thus, it is necessary to develop a method that can utilize the effective information in the low-dimensional space to predict potential disease-related miRNA candidates. We proposed a method based on non-negative matrix factorization, named DMAPred, to predict potential miRNA-disease associations. DMAPred exploits the similarities and associations of diseases and miRNAs, and it integrates local topological information of the miRNA network. The likelihood that a miRNA is associated with a disease also depends on their projections in low-dimensional space. Therefore, we project miRNAs and diseases into low-dimensional feature space to yield their low-dimensional and dense feature representations. Moreover, the sparse characteristic of miRNA-disease associations was introduced to make our predictive model more credible. DMAPred achieved superior performance for 15 well-characterized diseases with AUCs (area under the receiver operating characteristic curve) ranging from 0.860 to 0.973 and AUPRs (area under the precision-recall curve) ranging from 0.118 to 0.761. In addition, case studies on breast, prostatic, and lung neoplasms demonstrated the ability of DMAPred to discover potential disease-related miRNAs.

Structural and functional differentiation of a fat body-like tissue adhering to testis follicles facilitates spermatogenesis in locusts.

The fat body is distributed throughout the body of insects, playing the essential role in intermediary metabolism and nutrient storage. However, the function of differentiation of fat bodies adhering to different tissues remains largely unknown. Here, we identified a fat body-like tissue (FLT) surrounding testis follicles and described its features at morphological, cellular and molecular levels. The FLT is morphologically distinguished with the abdominal fat body (FB) and dominated by diploid cells instead of polyploid cells. The transcriptomic analysis demonstrated that the FLT and FB have dramatically different gene expression profiles. Moreover, genes in the cell cycle pathway, which include both DNA replication- and cell division-related genes, were successively active during development of the FLT, suggesting that FLT cells possibly undergo a mitotic cycle rather than an endocycle. Deprivation of the FLT resulted in distortion of the testis follicles, disappearance of sperm bundles, reduction of total sperm number and increase of dead sperm, indicating a critical role of the FLT in the spermatogenesis in testis follicles. The special functional differentiation of the two similar tissues suggested that FLT-FB cells are able to establish a promising system to study mitotic-to-endocycle transition.

Improved Outcoupling Efficiency and Stability of Perovskite Light-Emitting Diodes using Thin Emitting Layers.

Hybrid organic-inorganic perovskite semiconductors have shown potential to develop into a new generation of light-emitting diode (LED) technology. Herein, an important design principle for perovskite LEDs is elucidated regarding optimal perovskite thickness. Adopting a thin perovskite layer in the range of 35-40 nm is shown to be critical for both device efficiency and stability improvements. Maximum external quantum efficiencies (EQEs) of 17.6% for Cs0.2 FA0.8 PbI2.8 Br0.2 , 14.3% for CH3 NH3 PbI3 (MAPbI3 ), 10.1% for formamidinium lead iodide (FAPbI3 ), and 11.3% for formamidinium lead bromide (FAPbBr3 )-based LEDs are demonstrated with optimized perovskite layer thickness. Optical simulations show that the improved EQEs source from improved light outcoupling. Furthermore, elevated device temperature caused by Joule heating is shown as an important factor contributing to device degradation, and that thin perovskite emitting layers maintain lower junction temperature during operation and thus demonstrate increased stability.

Lateral Variation of Crustal Lg Attenuation in Eastern North America.

We perform Q Lg tomography for the northeastern part of North America. Vertical broadband seismograms of 473 crustal earthquakes recorded by 302 stations are processed to extract the Lg amplitude spectra. Tomographic inversions are independently conducted at 58 discrete frequencies distributed evenly in log space between 0.1 and 20.0 Hz. This relatively large dataset with good ray coverage allows us to image lateral variation of the crustal attenuation over the region. Obtained Q Lg maps at broadband and individual frequencies provide new insights into the crustal attenuation of the region and its relationship to geological structures and past tectonic activity in the area. The Q Lg shows more uniform values over the older, colder, and drier Canadian Shield, in contrast to higher variations in the younger margins. Results confirm the correlation of large-scale variations with crustal geological features in the area. Existence of low-velocity anomalies, thick sediments, volcanic rocks, and thin oceanic crust are potential sources of observed anomalies. The mean Q values are inversely correlated with average heat flow/generation for main geological provinces.