Steady Decay Research Articles

Probing energy transfer in luminescent CaMoO4:Tb3+ by steady state and decay dynamics

Polyvinylpyrrolidone functionalized CaMoO4:Tb3+ were synthesized hydrothermally. The formation of tetragonal phase CaMoO4:Tb3+ and morphology of nanoparticles are thoroughly studied with XRD, TEM and FT-IR spectroscopy. Nanophosphors show green emission of Tb3+ at 544 nm when excited at 290 nm due to MoO42− absorption. The energy transfer from the host MoO42− to the activator Tb3+ is occurred mainly through dipole-dipole interactions. The decay lifetime of MoO42− emission decreases from ∼13 to 1 μs with the increase in Tb3+ concentration indicating occurrence of energy transfer. This is further corroborated with the calculation of radiative and non-radiative decay rates. The quantum yield and CIE color chromaticity are also studied.

Single-Molecule Orientation Imaging Reveals the Nano-Architecture of Amyloid Fibrils Undergoing Growth and Decay.

Amyloid-beta (Aβ42) aggregates are characteristic Alzheimer's disease signatures, but probing how their nanoscale architectures influence their growth and decay remains challenging using current technologies. Here, we apply time-lapse single-molecule orientation-localization microscopy (SMOLM) to measure the orientations and rotational "wobble" of Nile blue (NB) molecules transiently binding to Aβ42 fibrils. We correlate fibril architectures measured by SMOLM with their growth and decay over the course of 5 to 20 min visualized by single-molecule localization microscopy (SMLM). We discover that stable Aβ42 fibrils tend to be well-ordered and signified by well-aligned NB orientations and small wobble. SMOLM also shows that increasing order and disorder are signatures of growing and decaying fibrils, respectively. We also observe SMLM-invisible fibril remodeling, including steady growth and decay patterns that conserve β-sheet organization. SMOLM reveals that increased fibril architectural heterogeneity is correlated with dynamic remodeling and that large-scale fibril remodeling tends to originate from strongly heterogeneous local regions.

Real‐Time Underwater Spectral Rendering

AbstractThe light field in an underwater environment is characterized by complex multiple scattering interactions and wavelength‐dependent attenuation, requiring significant computational resources for the simulation of underwater scenes. We present a novel approach that makes it possible to simulate multi‐spectral underwater scenes, in a physically‐based manner, in real time. Our key observation is the following: In the vertical direction, the steady decay in irradiance as a function of depth is characterized by the diffuse downwelling attenuation coefficient, which oceanographers routinely measure for different types of waters. We rely on a database of such real‐world measurements to obtain an analytical approximation to the Radiative Transfer Equation, allowing for real‐time spectral rendering with results comparable to Monte Carlo ground‐truth references, in a fraction of the time. We show results simulating underwater appearance for the different optical water types, including volumetric shadows and dynamic, spatially varying lighting near the water surface.

New insight into biodegradable macropore filler on tuning mechanical properties and bone tissue ingrowth in sparingly dissolvable bioceramic scaffolds

Structural parameters of the implants such as shape, size, and porosity of the pores have been extensively investigated to promote bone tissue repair, however, it is unknown how the pore interconnectivity affects the bone growth behaviors in the scaffolds. Herein we systematically evaluated the effect of biodegradable bioceramics as a secondary phase filler in the macroporous networks on the mechanical and osteogenic behaviors in sparingly dissolvable bioceramic scaffolds. The pure hardystonite (HT) scaffolds with ∼550 & 800 μm in pore sizes were prepared by digital light processing, and then the Sr-doped calcium silicate (SrCSi) bioceramic slurry without and with 30 % organic porogens were intruded into the HT scaffolds with 800 μm pore size and sintered at 1150 °C. It indicated that the organic porogens could endow spherical micropores in the SrCSi filler, and the invasion of the SrCSi component could not only significantly enhance the compressive strength and modulus of the HT-based scaffolds, but also induce osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). The pure HT scaffolds showed extremely slow bio-dissolution in Tris buffer after immersion for 8 weeks (∼1 % mass decay); in contrast, the SrCSi filler would readily dissolve into the aqueous medium and produced a steady mass decay (>6 % mass loss). In vivo experiments in rabbit femoral bone defect models showed that the pure HT scaffolds showed bone tissue ingrowth but the bone growth was impeded in the SrCSi-intruded scaffolds within 4 weeks; however, the group with higher porosity of SrCSi filler showed appreciable osteogenesis after 8 weeks of implantation and the whole scaffold was uniformly covered by new bone tissues after 16 weeks. These findings provide some new insights that the pore interconnectivity is not inevitable to impede bone ingrowth with the prolongation of implantation time, and such a highly biodegradable and bioactive filler intrusion strategy may be beneficial for optimizing the performances of scaffolds in bone regenerative medicine applications.

Dynamic Response of a Polyvinylidene Fluoride (PVDF) Sensor Embedded in a Metal Structure Using Ultrasonic Additive Manufacturing

This study aims to examine the dynamic response of a polyvinylidene fluoride (PVDF) piezoelectric sensor which is embedded into an aluminum coupon using ultrasonic additive manufacturing (UAM). Traditional manufacturing techniques used to attach smart materials to metals on the surface have drawbacks, including the potential of exposing the sensor to adverse environments or physical degradation during manufacture. UAM can avoid these issues by integrating solid-state metal joining with subtractive processes to enable the fabrication of smart structures. A commercial PVDF sensor is embedded in aluminum with a compression technique to provide frictional coupling between the sensor and the metallic matrix. The PVDF sensor’s frequency bandwidth and impact detection performance are evaluated by conducting cantilever and axial impact tests, as well as harmonic excitation tests with an electrodynamic shaker. Under axial loading, the embedded sensor displays high linearity with a sensitivity of 43.7 mV/N, whereas impact tests in the cantilever configuration exhibit a steady decay rate of 0.13%. Finally, bending tests show good agreement between theoretical and experimental natural frequencies with percentage errors under 6% in two different clamping positions, and correspond to the maximum voltage output obtained from the embedded PVDF sensor at resonance.

Exponential mixing of Vlasov equations under the effect of gravity and boundary

In this paper, we study exponentially fast mixing induced/enhanced by gravity and stochastic boundary in the kinetic theory of Vlasov equations. We consider the Vlasov equations with and without a vertical magnetic field inside a horizontally-periodic 3D half-space equipped with a non-isothermal diffusive reflection boundary condition of bounded continuous boundary temperature at the bottom. We construct both stationary solutions and global-in-time dynamical solutions in L∞. We prove that moments of a dynamical fluctuation around the steady solutions decay exponentially fast in L∞. As a key of this proof, we establish a uniform bound of so-called residual measures independently of the bouncing number of stochastic characteristics, by constructing a continuous stationary outgoing boundary flux which is strictly positive almost everywhere.

Properties of the Extremely Energetic GRB 221009A from Konus-WIND and SRG/ART-XC Observations

We report on Konus-WIND (KW) and Mikhail Pavlinsky Astronomical Roentgen Telescope – X-ray Concentrator (ART-XC) observations and analysis of a nearby GRB 221009A, the brightest γ-ray burst (GRB) detected by KW for >28 yr of observations. The prompt, pulsed phase of the burst emission lasts for ∼600 s and is followed by a steady power-law decay lasting for more than 25 ks. From the analysis of the KW and ART-XC light curves and the KW spectral data, we derive time-averaged spectral peak energy of the burst E p ≈ 2.6 MeV, E p at the brightest emission peak ≈ 3.0 MeV, the total 20 keV–10 MeV energy fluence of ≈0.22 erg cm−2, and the peak energy flux in the same band of ≈0.031 erg cm−2 s−1. The enormous observed fluence and peak flux imply, at redshift z = 0.151, huge values of isotropic energy release E iso ≈ 1.2 × 1055 erg (or ≳6.5 solar rest mass) and isotropic peak luminosity L iso ≈ 3.4 × 1054 erg s−1 (64 ms scale), making GRB 221009A the most energetic and one of the most luminous bursts observed since the beginning of the GRB cosmological era in 1997. The isotropic energetics of the burst fit nicely both “Amati” and “Yonetoku” hardness–intensity correlations for >300 KW long GRBs, implying that GRB 221009A is most likely a very hard, super-energetic version of a “normal” long GRB.

Unraveling the Evolution of Luminescence Center in an Eu‐Doped Orthophosphate: Beyond the Probe Limitation to Trace Activator

AbstractTo precisely tune the performance of phosphors, a proper understanding of the luminescence center is necessary. However, precisely probing into the luminescence center is still challenging. In this study, the luminescence center and the evolution are revealed in Eu3+‐doped Li4Zn(PO4)2 (LZP:Eu) depending on the activator in as low as trace amounts: Eu3+ ions evolve from the LZP lattice to hardly measurable EuPO4 impurities. By utilizing the spectroscopic probe effect of Eu3+ ion with multiscale characterizations, pressure‐induced spectral behavior, and ab initio calculations, the luminescence origin, local environment, and nanostructure evolution are fully deciphered. The contribution of the two luminescence centers during the evolution process is deeply elucidated by steady spectra and decay kinetics analysis. This study provides a broader understanding of the luminescence center from micro‐ to macro‐length, which would be beneficial for the design and modulation of luminescent materials.

Diagnosis and mechanism analysis of startup-shutdown-induced fuel cell degradation in stack-level

The durability of proton exchange membrane fuel cell stacks is a key limiting factor in transportation application due to severe conditions, where startup-shutdown and local fuel starvation most severely threaten the structure stability. In this paper, potentiostatic test at the average of 1.4 V is conducted to accelerate the carbon corrosion and structure damage in the cathode in a seven-cell commercial stack. A complete diagnosis framework based on micro-current excitation is established to systematically and in-situ evaluate the state-of-health of the cathode and the membrane, the mass transfer state, and the cell inconsistency in stack-level. Afterwards, the structure damage of cathode catalyst layer is characterized with scanning electron microscopy and energy disperse spectroscopy to provide direct evidences. In the early stage, the electrochemical surface area attenuates severely attributed to detachment and agglomeration of Pt particles, and the catalyst layer framework becomes more porous and hydrophilic, thus raising the double-layer capacitance. The weak catalyst layer structure tends to collapse starting from the lower layer close to the membrane, thereby leaving the dense lower layer and the porous upper layer in all cells. The damage mode is accurately manifested by the stepwise increase in the hydrogen transfer coefficient in the cathode that is identified in electrochemical testing. Meanwhile, the performance decay during operation exhibits typical characteristics of water flooding deterioration, as indicated by the three stages of steady voltage decay, drastic and periodic voltage fluctuation, and cell reversal. Therefore, the increase in water sensitivity and its dominant role in startup-shutdown-induced degradation are confirmed, which are also supported by the carbon-corrosion-induced ionomer agglomeration surrounding the enlarged pores in the upper layer. The enlarged pores are prone to be flooded, and the collapsed partial structure inherently limits the mass transfer. The aging process, evolution mechanisms of internal damage, and dominant factors during startup-shutdown are therefore identified and clearly revealed in stack-level.

Long-term stress monitoring and in-service durability evaluation of a large-span tunnel in squeezing rock

The long-term safety and in-service durability of tunnels in squeezing rock are the focus of tunnel management and maintenance. Previous studies mainly focused on the disaster-causing mechanism, prediction method, and control technology of large deformation during the construction of squeezing rock tunnels. So far, only few studies have concentrated on the long-term safety of in-service highway/railway tunnels in squeezing rock tunnels, resulting in unclear long-term mechanical response of tunnel structure and lack of data support for safety evaluation and durability prediction. Therefore, we conducted long-term, real-time, and continuous monitoring on the structural stress of the Lianchengshan Tunnel, which suffered severe large deformation during the construction, and performed a regression analysis on the structural stress by constructing four typical stress-time mathematical models. Subsequently, we evaluated the long-term safety and in-service durability of the tunnel structure based on a stress prediction. The results of our study show that the structural stress of the tunnel is not stabilized during the operation period but fluctuates periodically with an annual cycle. Moreover, the structural stress peak presents an increasing trend with the service life. The rheology of the surrounding rock composed of chlorite schists in Lianchengshan Tunnel is dominated by steady creep and decay creep. Despite a risk of local cracking or damage of concrete before the design service life due to excessive stress at individual positions of the secondary lining, such as the inverted arch, the safety factors of the secondary lining in the early stage (within 30 years) are higher than the threshold of 2.0. This indicates that the early safety of the tunnel structure can achieve the service requirements. The results of our study provide a reference for the long-term safety evaluation and in-service durability prediction of squeezing rock tunnels with high geo-stress.

Durability of B and T cell responses against a spike protein of SARS-CoV2 elicited by mRNA vaccines

Abstract The pandemic of SARS-CoV2 had resulted in over 266 million infections and over 5.2 million deaths throughout the world as of early-December 2021. Pfizer and Moderna mRNA vaccines were approved for Emergency Use Authorization by the US FDA. Even though 8.2 billion doses of vaccine have been administered, the world continues to see wide-spread SARS-CoV2 infection. Therefore, it is important to understand the durability of anti-SARS-CoV2 immune responses. Serum and PBMC samples were collected from vaccinated volunteers (N=40, Age 22–67, median age 41, Male/Female = 14/26, Moderna/Pfizer = 37/3) over 8 months (pre-vaccination baseline: TP1, 2 weeks-, 3 months-, and 8 months-post full vaccination: TP2, TP3, and TP4, respectively). First, we found robust induction of anti-S IgG and IgA for all subjects at TP2, which was higher than those from Covid-19 patients. Follow up samples (TP3 and TP4) showed steady decay of antibody levels over 8 months post-vaccination. Next, we evaluated memory B cell response using flow cytometry. We detected S-protein specific B cells by using flag-tagged S-protein. The frequency of S-protein specific B cells varied among donors and was weakly associated with the level of serum anti-S IgG antibody. Lastly, we assessed T cell responses. PBMCs were stimulated with an overlapping 15-mer peptide mix that covers the entire S-protein. Antigen-specific activation of T cells were detected based upon IFN-γ and TNF-α production. We found induction of robust CD4 T cell response at TP2 but a clear reduction at TP3. TP4 showed equivalent levels of T cell responses as TP3. Together, we found that B and T cell responses against the spike protein of SARS-CoV2 induced by mRNA vaccines are not durable. This study was supported by funding from Shimadzu Corporation.

Bi3+ sensitized Gd2O3:Eu3+: A potential red phosphor for UV LED pumped white light emission

Bi3+ sensitized Gd2O3:Eu3+ phosphors were synthesized by hydrothermal method using polyvinylpyrrolidone as capping agent. As-prepared samples exhibit crystalline hexagonal phase Gd(OH)3. While post annealing at 900 °C, Gd(OH)3 transforms to cubic phase Gd2O3. The lattice substitution by Bi3+ in different symmetry sites, viz. C2 and S2 of Gd2O3 leads to 2 (two) prominent excitation bands related to the 1S0 → 3P1 of Bi3+. Both the excitation bands induce efficient energy transfer to the excited states of Eu3+. In both the cases, the energy transfer efficiency can reach upto ~97%. The energy transfer from the sensitizer (Bi3+) to the activator (Eu3+) occurs mainly through dipole-dipole interactions. The occurrence of energy transfer from Bi3+ to the Eu3+ is corroborated from both the steady state and decay lifetime studies. Color saturation of the red emission when excited in the wavelength range ~330–380 nm is observed ~70–85%. CIE chromaticity reveals the tunability of the color emission by changing the activator concentration.

Plasma electrolytic oxidation of magnesium by sawtooth pulse current

Mg 2 SiO 4 coatings were formed on cp-Mg by Plasma Electrolytic Oxidation (PEO) using electrical regimes based on sawtooth anodic current pulses with extended ascending or descending segments (ramps). Voltage, current and light emission signals were simultaneously acquired to derive and analyse the evolution of system current and discharge population density during PEO process, while optical emission spectroscopy was employed for identification of plasma species. Coating morphological characterisation was carried out using Scanning Electron Microscopy. Phase composition was identified by X-ray diffraction. The corrosion performance was evaluated with Electrochemical Impedance Spectroscopy at various periods of exposure to corrosive media (0.5 wt% NaCl). It was shown that the application of sawtooth pulses allowed the controlling of microdischarge characteristics and coating morphology in both pulsed unipolar and reversed current regimes. Results further demonstrate that the application of anodic sawtooth pulses with the negative ramp facilitated defect healing during coating formation leading to production of more uniform PEO coatings with lower porosity and a slower degradation rate of magnesium substrate. A steady decay in the coating resistance with immersion time provides a possibility for controlling magnesium degradation and thereby for optimisation of component lifetime in applications where predictable Mg dissolution rate is required, such as sacrificial anodic protection of metallic structures and resorbable biomedical implants. • The quality of PEO coatings is modified by sawtooth pulse current regimes with controlled positive or negative anodic ramp. • Applying sawtooth waveforms with positive ramps refined the coating morphology. • Negative ramps introduced a defect healing effect reducing coating porosity and roughness. • Corrosion resistance of refined coating was proved to be better by EIS measurement.

Energy Injection Driven by Precessing Jets in Gamma-Ray Burst Afterglows

Abstract Jet precession is considered to universally exist in different-scale astronomical phenomena, including gamma-ray bursts (GRBs). For the long-lived GRB central engine, the relativistic precessing jets will periodically inject kinetic energy into the external shocks, then significantly modulate the shapes of the light curves (LCs) in GRB afterglows. In this paper, we adopt the standard external shock model to investigate the effects of jet precession on GRB X-ray afterglows in cases with different parameters, i.e., the steady or time-dependent jet powers, precession periods, precession angles, and viewing angles. In the case where the jet powers are in steady or slow decay and the jet can sweep across the line of sight, shallow decay (or plateau) segments should appear; otherwise, a giant bump will emerge in the GRB afterglow LCs. We show that jet precession is a new plausible mechanism of the energy injection in GRBs. Moreover, some observed X-ray transients without GRB associations might be powered by the precessing jets.

Excitation and activator concentration induced color tuning and white light generation from Bi3+ sensitized Y2O3:Eu3+: Energy transfer studies

Hydrothermally synthesized Bi3+ sensitized Y2O3:Eu3+ phosphors were characterized using X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The substitution of Bi3+ in the different symmetry sites of Y3+ lattice in Y2O3 i.e., C2 and S6 induces two different excitation (1S0 → 3P1) and emission (3P1 → 1S0) bands of Bi3+. These two excitation bands of Bi3+ efficiently transfer the energy to the excited states of Eu3+ in Y2O3:Eu3+. The occurrence of energy transfer from Bi3+ to Eu3+ ions is carefully investigated using the steady state and decay lifetime measurements. The energy transfer efficiency reaches up to 93% and 99% for S6 and C2 related excitations, respectively. The energy transfer occurs mainly through dipole-dipole interactions. The appropriate selection of excitation wavelength and careful choose of Eu3+ concentration in Y2O3 can provide the multicolor emission as well as white light emission. The maximum quantum yield of 24% was observed from Bi3+ (1 at%) sensitized Y2O3:Eu3+ (2 at%).

An Analysis of Agriculture Sector of Inclusive Growth in India

Agriculture remains the dominant supporter of the Indian populace. The thriving industry and service sectors depend on the agricultural sector for their development. The inter-linkage among the three sectors could not be undermined at any cost. It is the massive absorbent of the labor force even though the disguised unemployment exists in varied magnitude. The share of agriculture to the GDP has come down from 57.7% in 1950-51 to 32.2% in 1990-91 at the time of liberalization, 24.6% in 2000-2001, 15.7% in 2009-2010 then 17%. In the post-independence era, stagnant production, low productivity, traditional technology, and poor rural infrastructure were the major challenges for the Government. India is principally an agricultural country. The agriculture sector estimates 18.0% of the GDP and employs 52% of the total workforce. There is a continuous steady decay in its presence towards the GDP, and the agriculture sector is losing its shine and anchor position in the Indian economy. The problems with which the Indian agricultural scenario is charged in present times are many. Still, this in no way undermines the interest of the sector and the role it can play in the holistic and inclusive growth of the country. Agriculture is fundamental for the sustenance of an economy, as is food for a human being.

VVER-1000/V446 spent fuel pool risk assessment and support through portable mitigating equipment

The Spent Fuel Pool (SFP) accident at the Fukushima Daiichi unit 4 demonstrated the need for identifying and analyzing possible accident sequences and subsequent application of severe accident mitigating systems in LWR (Light Water Reactor) SFPs. In this study, Level 1 Probabilistic Safety Assessment (PSA) is applied to evaluate the Fuel Damage Frequency (FDF) in SFP of Bushehr Nuclear Power Plant unit-1 (BNPP-1). This paper specifically focuses on assessing the SFP risk using Portable Mitigating Equipment (PME) including a reliable robust Portable Diesel Generator (PDG), a Portable Diesel Pump (PDP), and an SFP-spray system proposed to maintain steady decay heat removal. PME is the recommended equipment proposed by IAEA -following the Fukushima disaster- to mitigate accident consequences. In this study, the fault/event trees have been applied to conduct PSA using the SAPHIRE code. The results indicate that the most dominant Initiating Events (IEs) in the reference plant are the Loss of Offsite Power (LOOP) and Loss of Service Water (LOSW), both simultaneously affecting the reactor core and the SFP. There is a significant decrease in calculated FDF – after implementing PDG and PDP- in respect of the reference plant from 3.086E to 6 to 2.166E−7 in the normal storage mode. Heavy load drop, which is a low probability/high consequence IE, becomes crucially important in cases where PME is employed as it directly leads to fuel damage. It is expected that the analyses set forth here would provide efficient guidelines and insights into the strengths and weaknesses inherent in the design and operation of SFP in VVER-1000/V-446 nuclear power plant.

Acute detection of optical tissue changes in real-time during pulsed field ablation (PFA)

Abstract Background It has been established in previous animal and human studies that it is possible to assess lesion formation in real-time using optical means during the application of radiofrequency (RF) energy in cardiac ablation procedures. The optical interrogation was accomplished using a novel catheter and instrument system whereby the catheter has embedded optical fibers that transmit and receive light from the instrument. Purpose The aim of this study was to see if there are similar indications of lesion formation, detected by the same optical means, during the application of pulsed field ablation (PFA) energy to cause lesions through electroporation. Methods A series of 3 anesthetized pigs underwent PFA in the right atrium. An 8-electrode circular catheter was placed high in the right atrium, near the superior vena cava, to simulate pulmonary vein isolation as part of an AF ablation procedure. The optical catheter was placed adjacent to the circular catheter between stimulation electrode pairs. A bolus of adenosine was administered to create a window of asystole to avoid stimulation on the T-wave. Bipolar PFA was delivered immediately post drug infusion and the optical signature from the catheter was recorded and displayed in real-time. Electrograms were recorded and the mapping of the lesion was performed with the optical catheter at the following time intervals post PFA delivery: 0 min, 15 min, 1 hour, and 3 hours. Necropsy and histology followed the procedure. Results The optical signal is distinctly higher in intensity during the PFA pulse train. The optical signal showed an immediate significant decrease and a slow but steady decay over the mapping interval. Electrogram reduction accompanied PFA application and also showed a marked reduction over the mapping interval. The optical signal amplitudes were markedly lower when on the lesion compared to healthy non-ablated myocardium as predicted. Conclusions Preliminary results indicate that optical mapping detects immediate tissue changes during PFA at these energy levels and hence could be is a viable method of evaluating lesion formation during and after PFA energy application. The optical signal indicates that cell damage occurs immediately at these energy levels and continues to progress slowly in lesions made by PFA energy compared to those made by RF energy. The findings also suggest that optical mapping can identify acute lesions made with PFA energy in real-time implying that optical mapping could evolve as a PFA gap detector. Funding Acknowledgement Type of funding source: None

Sonallah Ibrahim and Miriam Naoum’sZaat

AbstractThis article explores the television adaptation of Sonallah Ibrahim’s novel Zaat, arguing that the series provides us with an interesting representation of the various ways in which national projects in Egypt are gendered. It adds to feminist debates around nationalism, capitalism, and gender. In particular, the focus on the intimate in Zaat reveals how political projects are depicted in the domestic sphere through the lens of women’s work. The article explores two themes: one, the increasing financial pressure and its effects on constructs of masculinity and femininity, and two, the steady decay of infrastructure and social services and how it renders middle-class life an impossibility. The article argues that by focusing on the intimate, Ibrahim’s novel and the TV adaptation both reveal the various forms of work women perform and make use of women’s work to critique or celebrate national projects.

Propagation of distinct Love-wave pulses from regional to teleseismic distances in continental and oceanic environments

SUMMARYSurface waves are usually dispersive with long wave trains and steady decay of amplitude with distance. However, if the group velocity is nearly constant for a span of periods a strong pulse is produced that retains its amplitude for large distances. This situation arises for the fundamental mode of Love waves in the period band 40–500 s for crust and mantle structures with a positive gradient of S wave speed in the uppermost mantle. Such a distinct Love-wave pulse with limited dispersion observed at teleseismic distance is termed the G wave in honour of Gutenberg. The long-period G-wave pulse caused by large earthquakes carries a large amount of energy to substantial distances, with significant effects across the globe, for example event triggering. A similar G-type Love-wave pulse with a much shorter-period of 10–20 s is generated for crustal structures without thick sediment. Such pulses produce anomalously large ground displacement at near-regional distances with, for example an overestimate of surface wave magnitude. We investigate the generation and propagation mechanism of the G-type Love-wave pulses in the crust and upper-mantle with the analysis of observed strong motion records from the Mw 6.2 2016 Central Tottori earthquake and the Mw 9.0 2011 Off Tohoku earthquake in Japan, in conjunction with 3-D finite-difference simulation of seismic wave propagation and analysis of dispersion curves.