Crest Region Research Articles

The Influence of Three‐Dimensional Topography on Turbulent Flow Structures Over Dunes in Unidirectional Flows

AbstractDunes are the most prevalent bedform present in sand‐bedded rivers and their morphology typically comprises multiple scales of three‐dimensional topography. However, our understanding of flow over dunes is predicated largely on two‐dimensional models, a condition which is rare in nature. Here, we present results of Large Eddy Simulations over a static, three‐dimensional dune field, using a two‐ and three‐ dimensional topographic realisation, to investigate the interaction between bed topography and turbulent flow structures. We show that flow over two‐dimensional bedforms increases the velocity over the stoss slope and reduces the size of the leeside separation zone as compared to 3D topography. Flow over three‐dimensional bedforms generates twice as many vortices as over two‐dimensional bedforms, and these vortices are longer, wider and taller than flow over their two‐dimensional counterparts. Turbulence is dominated by hairpin‐shaped vortices and Kelvin‐Helmholtz instabilities that interact with the bed in the brink point region of the dune crest and down the lee slope, and generate high shear stresses for long durations. These results are used to propose a new conceptual model showing the differences between flow over two‐ and three‐dimensional bedforms. The findings highlight how the size, morphology and stacking of coherent flow structures into larger flow superstructures may be critical in sediment entrainment, and may dictate the relationship between event duration and magnitude that drives sediment impulses at the bed. This will ultimately lead to an increased in the three‐dimensionality of bedform morphology.

IPSC-derived cranial neural crest-like cells can replicate dental pulp tissue with the aid of angiogenic hydrogel

The dental pulp has irreplaceable roles in maintaining healthy teeth and its regeneration is a primary aim of regenerative endodontics. This study aimed to replicate the characteristics of dental pulp tissue by using cranial neural crest (CNC)-like cells (CNCLCs); these cells were generated by modifying several steps of a previously established method for deriving NC-like cells from induced pluripotent stem cells (iPSCs). CNC is the anterior region of the neural crest in vertebrate embryos, which contains the primordium of dental pulp cells or odontoblasts. The produced CNCLCs showed approximately 2.5–12,000-fold upregulations of major CNC marker genes. Furthermore, the CNCLCs exhibited remarkable odontoblastic differentiation ability, especially when treated with a combination of the fibroblast growth factors (FGFs) FGF4 and FGF9. The FGFs induced odontoblast marker genes by 1.7–5.0-fold, as compared to bone morphogenetic protein 4 (BMP4) treatment. In a mouse subcutaneous implant model, the CNCLCs briefly fated with FGF4 + FGF9 replicated dental pulp tissue characteristics, such as harboring odontoblast-like cells, a dentin-like layer, and vast neovascularization, induced by the angiogenic self-assembling peptide hydrogel (SAPH), SLan. SLan acts as a versatile biocompatible scaffold in the canal space. This study demonstrated a successful collaboration between regenerative medicine and SAPH technology.

EP News: Basic and Translational

Pérez-Hernández et al (Circ Res 2021;128:419, PMID 33342222) investigated the subcellular domain formed by cardiac Na+ channel (Nav1.5) clusters in the crest region of the adult ventricular myocytes by using super-resolution microscopy and electron microscopy. The investigators identified an Nav1.5 subpopulation in close proximity to subjacent subsarcolemmal mitochondria that preferentially host the mitochondrial Na+/Ca2+ exchanger (NCLX). Upon tetrodotoxin exposure, mitochondria near Nav1.5 channels accumulated more Ca2+ and showed increased reactive oxygen species production.

Prediction of Total Electron Content (TEC) using Neural Network over Anomaly Crest Region Bhopal

In the present work neural network has been developed for the prediction of Vertical Total Electron Content (VTEC) over Bhopal (23.2°N, 77.4°E & MLAT 14.2°N), an equatorial anomaly crest region. The study is based on the VTEC data recorded by a multi-frequency multi-constellation GNSS receiver installed at Bhopal during May 2016 to August 2017. Neural Network (NN) consists of artificial neurons that are used to learn data patterns adjusting weights between input, hidden and output layers by computational modelling. In order to obtain the optimal number of neurons in the hidden layer, the performance of four systems of neural network have been tested. Out of which, the fourth neural network has been used to predict VTEC with 7 input neurons in the present study. The number of hidden layer neurons is a factor that affects the performance of the trained networks. The input layer of the network includes the year, day of the year, hour of the day, geographic latitude, geographic longitude, SSN and IRI NmF2. We have compared the TEC obtained from the neural network prediction (NN TEC), GPS derived TEC (GPS TEC) and TEC from IRI-2016 model (IRI TEC) and analysis has been made. We observed that the Root Mean Square Error (RMSE) decreases with increase in the number of hidden layer neurons. The RMSE comes out to be lowest (1.96 TECU), when the number of hidden layer neurons are 41.The TEC predicted from the NN model and estimated from GPS receiver have same trend at 01:00 and 07:00 UT. The modelled NN TEC values are in good agreement with GPS TEC values for all seasons and 0.99 correlation coefficient was calculated for summer months, but IRI TEC always underestimates GPS TEC in all seasons. The NN model excellently predicted the TEC values of August 2017 by putting the credentials of August 2016 and only 0.55–32.16% relative errors were estimated between them whereas it reaches up to 93.86% with IRI TEC. Thus, the result shows that the proposed NN model can predict the diurnal and seasonal GPS TEC more accurate than IRI over anomaly crest region Bhopal. However, the inclusion of IRI-NmF2 as input layer neuron increases the network performance.

Responses of the Ionosphere and Neutral Winds in the Mesosphere and Lower Thermosphere in the Asian‐Australian Sector to the 2019 Southern Hemisphere Sudden Stratospheric Warming

AbstractIn this study, the neutral winds from meteor radars and the total electron content (TEC) from Beidou Geostationary (GEO) satellites were utilized to study the responses of the mesosphere and lower thermosphere and the ionosphere in the Asian‐Australian sector to the recent Sudden Stratospheric Warming (SSW) occurred in the Antarctic polar region during September 2019. It was demonstrated that the ionospheric TEC increased significantly, especially around the equatorial ionization anomaly (EIA) region during this SSW. A pronounced semidiurnal signature in the deviation TEC was observed near the EIA crest region, which was more significant in the southern hemisphere. Meanwhile, the enhancement period of the amplitudes of solar and lunar semidiurnal tides in winds in the mesosphere was coincided with that in TEC. The solar semidiurnal amplitudes increased from about 18 to 35 m/s in the zonal wind and from 15 to 25 m/s in the meridional wind at Mengcheng (33.4°N, 116.5°E, MLAT 27.4°N), and from about 15–38 m/s in the zonal wind at Kunming (25.6°N, 103.6°E, MLAT 19.3°N). The lunar semidiurnal amplitudes increased from 2 to 6 m/s in the zonal wind and from about 3–9 m/s in the meridional wind at Mengcheng, and from about 3–7 m/s in the meridional wind at Kunming, respectively. These indicated that the semidiurnal signature in TEC during the 2019 southern hemisphere SSW could be associated with the SSW induced by the atmospheric semidiurnal tide variations in the mesosphere.

Rogue wave generation in wind-driven water wave turbulence through multiscale phase-amplitude coupling, phase synchronization, and self-focusing by curved crests

Rogue wave events (RWEs), localized high amplitude extreme events, uncertainly emerge in various nonlinear waves. For RWE generation, modulation instability leading to amplitude soliton formation for one-dimensional (1D) systems; and the additional wave directional property and the ratio of nonlinearity to spectrum bandwidth on the modulation instability for two-dimensional (2D) systems, are the accepted mechanisms. However, those studies have mainly focused on RWEs in weakly disordered wave states dominated by a single scale, but to a much lesser extent on wave turbulence with multiscale excitations. Wind-driven water surface wave turbulence widely occurs in nature. Unraveling RWE generation in wind-driven water surface wave turbulence is an important issue. Here, using multidimensional empirical mode decomposition, we experimentally investigate the dynamics of decomposed multiscale spatiotemporal waveforms of wind-driven water wave turbulence in the 2 + 1D space. We demonstrate how the cascaded amplitude modulation of the faster (higher frequency) modes by the phases of the slower modes, the phase synchronization of the largest peaks in the bursts of fast modes emerging in the crest regions of the medium modes, and self-focusing by the curved crests of the three fastest modes lead to RWE generation.

Refining medium resolution fractional cover for arid Australia to detect vegetation dynamics and wind erosion susceptibility on longitudinal dunes

Medium resolution satellite-derived fractional cover estimates of bare soil (fBS), photosynthetic vegetation (fPV), and non-photosynthetic vegetation (fNPV) provide a powerful means to study arid ecosystem dynamics. This paper employed remote sensing estimates of fPV and fNPV from five case study sites from Australia's vegetated dunefields to observe (a) vegetation growth response to rainfall ‘pulses’ and subsequent transition to non-photosynthetic dormancy or senescence; (b) multiple time scales of antecedent climatic influence on vegetation cover; (c) the susceptibility of dunes to wind-blown sand drift during periods of low cover; and (d) the implications of image resolution choice when ground cover is heterogeneous.A spectral unmixing model for Australia's arid zone (termed ‘AZN’) was first developed by generating endmembers from a dataset of 1405 field surveys; Landsat time series estimates of fPV and fNPV were subject to a Seasonal-Trend decomposition by Loess (STL); Time series components were correlated with rainfall (P) and aridity at various accumulation periods; Fire maps were used to compare the climatic response of unburnt and burnt vegetation; Landform maps were used to isolate dune vegetation cover from the adjacent interdunes; and Landsat estimates of erodible area were compared with Sentinel-2 and WorlView-3 data.The new AZN model yielded Root Mean Square Error (RMSE) estimates of 14.5% (fBS), 6.5% (fPV) and 15.8% (fNPV) during cross validation. The AZN model also compared favourably to an existing continental-scale model when evaluated with independent reference data. Rainfall pulse responses of dune vegetation were detected initially as fPV, and 3–9 months later as a peak in fNPV. Components of fPV responded to P accumulated over 3–9-months (intra-annual), and 12–15-months (trend). The long-term build-up of fNPV, if left unburnt, was influenced by rainfall patterns over the preceding 45–114 months. Fires reduced both the depth and strength of antecedent rainfall's influence on vegetation, and vegetation was often more sensitive to P than to aridity. Erodibility (total cover <14%) and partial erodibility (cover <35%) were more common at the driest sites but did not universally match aridity levels, due to fires and differing vegetation. The targeting of dune crest regions highlighted their enhanced susceptibility to sand drift (in most cases), and, given their occurrence on relatively narrow ridges (~30 m), the importance of estimating cover at Landsat resolutions or better (e.g. Sentinel-2).

Characterization of ionospheric irregularities over Vietnam and adjacent region for the 2008-2018 period

This paper presents the variations of the rate of change of Total Electron Content (TEC) index (ROTI), characterizing the occurrence of ionospheric plasma irregularities over Vietnam and neighboring countries in the Southeast Asian region using the continuous GPS data during the 2008-2018 period. The results showed that the occurrence of strong ROTI in all stations is maximum in equinox months March/April and September/October and depends on solar activity. The ROTI is weak during periods of low solar activity and strong during periods of high solar activity. There is an asymmetry between the two equinoxes. During maximum and declining phases of 2014-2016, occurrence rates in March equinox are larger than in September equinox, but during the descending period of 2010-2011, the occurrence rates in September equinox at almost all stations are larger than in March equinox. The correlation coefficients between the monthly occurrence rate of irregularities and the F10.7 solar index at the stations in the equatorward EIA crest region are higher than at those in the magnetic equatorial and the poleward EIA crest regions. The irregularity occurrence is high in the pre-midnight sector, maximum between 2000 LT to 2200 LT. The maximum irregularity occurrence is located around 4-5° degrees in latitude equator-ward away from the anomaly crests.

Frequency‐Dependent Modulation of Whistler‐Mode Waves by Density Irregularities During the Recovery Phase of a Geomagnetic Storm

AbstractDensity irregularities near the plasmapause are commonly observed and play an important role in whistler‐mode wave excitation and propagation. In this study, we report a frequency‐dependent modulation event of whistler‐mode waves by background density irregularities during a geomagnetic storm. Higher‐frequency whistler waves (near , where is the equatorial electron cyclotron frequency) are trapped in the density trough regions due to the small refractive index near the parallel direction, while lower‐frequency whistler waves (below ) are trapped in the density crest regions due to the refractive index maximum along the parallel direction. In addition to the modulation, we also find that, quantitatively, the wave amplitude of the higher‐ (lower‐) frequency whistler‐mode waves is anti‐correlated (correlated) with the relative plasma density variation. Our study suggests the importance of density irregularity dynamics in controlling whistler‐mode wave intensity, and thus radiation belt dynamics.

Interaction Between an EMSTID and an EPB in the EIA Crest Region Over China

AbstractFew observations investigated the interaction between an electrical medium‐scale traveling ionospheric disturbance (EMSTID) and an equatorial plasma bubble (EPB). This paper presents another interaction between a southwestward propagating EMSTID and an eastward drifting EPB in the equatorial ionization anomaly (EIA) crest region of China. When the EMSTID and the EPB touched each other, several depletions of the EMSTID (EPB) showed the eastward (westward) velocity disturbances of the EPB (EMSTID) depletions. Besides, phase elongations of the EPB depletions contrarotated as the EMSTID propagated southwestward. However, of important finding is that the interaction of the EMSTID and the EPB could have polarized one depletion of the postmidnight EPB that should have become a fossilized bubble. Inside that polarized EPB depletion were meter‐scale irregularities that caused activated radar echoes and enhanced ranged spread F (RSF). The interaction occurred in descending ionosphere and the lower density regions got filled up with an enhanced density plasma. We propose that the EMSTID and the EPB could have electrically coupled with each other, causing an enhanced polarization electric field (PEF) that polarized that EPB depletion; the E × B gradient drift instability (Kelley, 1989) could have caused the meter‐scale irregularities when that enhanced PEF was imposed on that reactivated EPB depletion surrounded by that enhanced density plasma. This study provides observational evidence that how an electrical couple of EMSTID and EPB events can activate a postmidnight EPB depletion that should become a fossilized structure.

The Role of Storm‐Time Electrodynamics in the Dawn and Dusk Sectors Across Equatorial and Low‐Latitude Ionosphere During December 19–21, 2015

AbstractWe present the distinct responses of the nighttime ionosphere due to an intense and long lasting geomagnetic storm of December 19–21, 2015 using a chain of ionosondes from magnetic equator to anomaly crest region over India. The observations exhibited unique features throughout the night including dawn and dusk sectors. The results showed twin episodes of pre‐reversal enhancement (PRE) in dusk sector associated with oscillatory vertical plasma drift due to shielding electric field that produced briefly post‐sunset equatorial spread F (ESF) irregularities. Accordingly, relative dominance of interplanetary magnetic field (IMF) and auroral electrojet (AE) related electric field fluctuations in vertical and zonal drifts at different times are investigated throughout the night. Also the application of wavelet/wavelet coherence analysis on interplanetary and geomagnetic conditions and ionospheric data showed distinct relationships. The results showed that vertical drift is in phase with interplanetary electric fields (IEFy) with period of ∼30 min at ∼18:30 IST (13:00 UT) that drives first PRE whereas ∼60 min period in AE which is in phase with vertical drifts drives second PRE at ∼20:30 IST (15:00 UT). However, other short term periods in vertical drifts are in phase with IEFy and AE at other times suggesting that both are contributing to the drift variations. The simultaneous upliftment of F layer at all stations producing fresh ESF irregularities in the dawn sector is attributed to the unique electrodynamical response of the Indian low latitude stations to the eastward disturbance dynamo electric fields (DDEFs). These results are also in concomitant with satellite observations and thermospheric ionospheric electrodynamics general circulation model (TIE‐GCM) drifts.

Bone depth and thickness of different infrazygomatic crest miniscrew insertion paths between the first and second maxillary molars for distal tooth movement: A 3-dimensional assessment

This research aimed to measure the bone depth and thickness of different insertion paths for safe placement of infrazygomatic crest miniscrews between the first (U6) and second maxillary molars (U7) by 3-dimensional (3D) reconstruction and to explore their clinical significance. Cone-beam computed tomography data from 36 adult orthodontic patients were obtained to generate 3D models (n=72) of the infrazygomatic crest region. For each model, the bone depth and thickness of 27 different insertion paths were measured in the region between U6 and U7. The relationship between bone depth and thickness was statistically analyzed. The clinical risk for each insertion path was assessed according to the impacts of bone depth and thickness on insertion failure. Maximum bone depth (median, 7.41mm; mean, 8.42mm) was present at 13mm insertion sites with a gingival tipping angle of 50° and a distal tipping angle of 30°. Maximum bone thickness (median, 3.73mm; mean, 4.00mm) was present at 17mm insertion site with a gingival tipping angle of 70° and a distal tipping angle of 30°. There was a significant negative correlation between bone depth and bone thickness (rs=-0.569, P<0.001). Failure rates were significantly different among different insertion paths (P<0.001). Because the bone depth and thickness may affect the safe insertion of infrazygomatic crest miniscrews in the region between U6 and U7 and they are negatively related, a safe insertion protocol design for distal tooth movement should take both into consideration.

Girl with left-sided hip pain and fever.

A previously healthy 13-year-old girl presented to the pediatric emergency department (PED) with 5 days of progressively worsening left-sided hip pain and 4 days of fever. Although she was able to bear weight on the left leg, she walked with a limp. There was no preceding trauma or illness. In the PED, she was febrile to 39.5°C and tachycardic with other vital signs appropriate for her age. On examination, she had full range of motion of the left hip with significant tenderness only to palpation over the left iliac crest and left gluteal region. Examination was otherwise unremarkable with no overlying skin changes, warmth, edema, or breaks in the skin. Initial laboratory studies revealed abnormalities, including pancytopenia (WBC 2.5 k/uL, hemoglobin 11.5 g/dL, and platelets 32 k/uL), elevated inflammatory markers (C-reactive protein 12.6 mg/dL and erythrocyte sedimentation rate 31 mm/hour), and elevated liver enzymes (alanine aminotransferase 153 U/L and aspartate aminotransferase 221 U/L). The working diagnosis at this point was acute osteomyelitis of the iliac bone. Magnetic resonance imaging (MRI) of the pelvis was performed with and without contrast and revealed abnormal signal intensity and contrast enhancement of the left iliacus and gluteal musculature surrounding the left iliac wing without evidence of abscess (Figure 1). In addition, diffusely increased T2 signal and slightly decreased T1 signal intensity was noted throughout all visible osseous structures (Figure 2). Hours after initial presentation, blood culture resulted positive for methicillin-sensitive staph aureus (MSSA). This patient's MRI findings were consistent with myositis. Given her MSSA bacteremia and imaging finding consistent with soft-tissue infection, the most likely diagnosis is pyomyositis without abscess formation. Acute bacterial myositis can be caused by contiguous spread from a soft-tissue infection, penetrating trauma, or hematogenous spread. When the source is hematogenous, it is referred to as pyomyositis and is often associated with abscess formation. MSSA is the most common pathogen in these cases.1 Although primary pyomyositis is rare in temperate climates, its incidence outside of tropical climates has been increasing in recent years. Risk factors include immunodeficiency (eg, HIV), diabetes mellitus, malignancy, and local muscle trauma. MRI is the imaging modality of choice, and treatment includes drainage of the abscess with pathogen identification when possible, followed by targeted antibiotic therapy.2 This patient's abnormal bone marrow enhancement on MRI and significant cytopenia initially raised suspicion for a malignant process such as leukemic infiltration of the bone marrow. However, given that the patient's cytopenia resolved with antibiotic treatment, bone marrow abnormalities were likely secondary to infection. The patient completed a 3-week course of cephalexin and made a full recovery.

Computed tomography assessment of maxillary bone density for orthodontic mini-implant placement with respect to vertical growth patterns.

To quantitatively measure and report bone density of maxilla in the interradicular (alveolar and basal bone) and infrazygomatic crest (IZC) region in various growth patterns among Dravidian individuals. This was a retrospective spiral computed tomography (CT) study. The study was conducted at the Department of Orthodontics, Saveetha Dental College and Hospital, Tamil Nadu, India. Sixty CT scans (24 men, 36 women; mean age = 25.3 years and 23.8 years, respectively) divided equally into three groups based on vertical facial proportions were included. Bone density measurements in Hounsfield units (HU) were performed using Philips and RadiAnt DICOM viewers. Buccal cortical, palatal cortical and cancellous bone regions were analysed in a Philips DICOM viewer and IZC region was analysed in a RadiAnt DICOM viewer. Statistical analysis with one-way ANOVA and post-hoc Tukey HSD test was done. The hypodivergent group had a significantly higher bone density at the buccal cortex in posterior region (P < 0.05) when compared to the normodivergent and hyperdivergent groups. Buccal basal bone was denser than buccal alveolar bone (P < 0.05) in all three groups. In the IZC region, hypodivergent groups had significantly higher density values when compared to the normodivergent and hyperdivergent groups (P < 0.05). The present study concluded that cancellous bone density in the interradicular regions was greatest in the anterior sites and was not influenced by growth pattern. Hypodivergent groups tend to have higher density in the posterior regions (buccal and palatal cortical bone) and at the IZC region compared to normodivergent and hyperdivergent groups.

Statistics of GPS TEC at the northern EIA crest region of the Indian subcontinent during the solar cycle 24 (2013-2018): comparison with IRI-2016 and IRI-2012 models

Statistics of GPS TEC at the northern EIA crest region of the Indian subcontinent during the solar cycle 24 (2013-2018): comparison with IRI-2016 and IRI-2012 models

SPH Open Boundary Simulation of Free-Surface Flow Over Ogee-crested Spillway

This study was conducted to compare water surface profiles with standard ogee-crested spillways. Different methods were used, such as (experimental models, numerical models, and design nomographs for the United States Army Corps of Engineers, USACE). In accordance with the USACE specifications, three different models were constructed from rigid foam and then installed in a testing flume. The water surface profile has been recorded for these models with different design heads. For modeling the experimental model configurations, a numerical model based on the smoothed particle hydrodynamics (SPH) technique was used and is developed to simulate the water surface profile of the flow over the ogee-crested spillway. A 2D SPHysics open-source software has been used in this study, using the SPH formulation to model fluid flow, developing the SPH boundary procedure to handle open-boundary simulations, and modifying the open-source SPHysics code for this purpose. The maximum absolute difference between the measured and computed results of the water surface profile for all head ratios of (H/Hd), does not exceed 4.63% at the crest region, the numerical results for the water surface profile showed good agreement with the physical model results. The results obtained experimentally and numerically by SPH are compared with the CFD results in order to be more reassuring from the results. Additional comparisons were made using interpolated data from USACE, Waterways Experiment Station (WES), and design nomographs. The SPH technique is considered very promising and effective for free surface flow applications.

Equatorial F-region irregularities at different seasons in Africa

Trans-ionospheric signals such as the Global Positioning System (GPS) signals propagating through irregular ionospheric plasma structures may experience phase variation and amplitude fades causing degradation in system performance. This paper investigates the latitudinal structure of equatorial F-region irregularities (EFI) in the African region at different seasons using a GPS-based proxy index (rate of change of TEC index (ROTI)). The results obtained indicate the dependence of EFI on local time, season and latitude. Its occurrence time ranges between 19:00 and 0:00LT depending on the season. Its appearance is earlier in equinoxes, particularly in March equinox, and late in June solstice. Further, its occurrence lies generally within ±22° magnetic latitudes for all seasons. The probability of occurrence, which is observed to be generally higher in equinoxes than solstices, is almost comparable across the entire latitudes where it was observed in equinoxes while the observations in solstices indicate a dip around the magnetic equator. Furthermore, the average seasonal value of ROTI indicates a clear latitudinal dependence; with appearance within ±(0°-12°) magnetic latitude in solstices while it extends up to 18° in equinoxes, particularly in the south. While the hemispheric asymmetry in the average seasonal values is favored by the hemispheric asymmetry of latitudinal TEC profile, the TEC gradient could help delineate the latitude of its peak occurrence. In addition, severe irregularities are mostly observed in equinoxes than in solstices across all latitudes of occurrence and are most pronounced around the crest region mainly in the south. Conversely, moderate irregularities are typically observed in solstices and are most frequent around the magnetic equator and the poleward edge of equatorial ionization anomaly (EIA) region in the northern hemisphere.

Aggressive squamous cell carcinoma of the cranium of a dog

BackgroundThe authors report a case of keratinized squamous cell carcinoma (SCC) in a 14-year-old dog with extensive cranial bone invasion. To our knowledge, this is the first description of such a case of cranial keratinized SCC with aggressive generalized osteolysis described in a dog.Case presentationThe 14-year-old dog was referred for radiological examination with suspicion of head trauma with clinical signs of head deformation, exophthalmos and nasal discharge. The skull radiographs showed a large osteolytic defect of the frontal bone and parietal bone in the region of the external sagittal crest. Findings from the skull CT scan included generalized osteolysis in the region of parietal bone, frontal bones, maxilla on the right side and the nasal bone including the dorsal nasal concha. In the area of bone loss, new soft tissue formation with multifocal foci of mineralization was visible. The ultrasound examination revealed hypoechogenic changes with hyperechoic foci consistent with mineralization and poor vascularization. The brain and ocular structures were without visible changes. Fine needle aspiration cytology (FNAC) was performed, and squamous cell carcinoma was suspected. After 3 months, the re-presented to the clinic. The dog became progressively listless, his appetite was decreased, and he became acutely blind. Follow-up skull CT scan revealed significant osteolysis, which affected a significant aspect of the cranium. All bone defects had been replaced by new 3.5 cm-thick soft tissue formations with multifocal small 1–2 mm areas of mineralization. There was no evidence of metastasis. Histological examination confirmed the suspicion of squamous cell carcinoma.ConclusionsThis paper is the first report of cranial SCC in a dog causing extensive bone osteolysis. The lesions in this dog originated from the frontal and parietal bones including frontal sinuses.There are variants of tumors that arise from squamous epithelium or resemble SCC in the skull. These examples include adenosquamous carcinoma and proliferating trichilemmal tumours. In addition, there is possible malignant transformation caused by papilloma viruses. In the veterinary literature, there is only one similar description of adenosquamous carcinoma in a cat with similar clinical manifestations. It is justified to suspect a process of neoplastic epithelial origin in all cases of aggressive and extensive skull bone lysis. This issue should be subject to further investigation.

The Interface Zone of Explosively Welded Titanium/Steel after Short-Term Heat Treatment

This work presents a detailed description of a bonding zone of explosively welded Ti/steel clads subjected to stress relief annealing, applied in order to improve the plasticity of the final product. The typical joint formed by the welding process possesses a characteristic wavy interface with melted regions observed mainly at the crest regions of waves. The interface of Ti/steel clads before and after annealing was previously investigated mostly in respect to the melted regions. Here, a sharp interface between the waves was analyzed in detail. The obtained results indicate that the microstructure of a transition zone of that area is different along the width. After the heat treatment at 600 °C for 1.5 hours, titanium carbide (TiC) together with α-Fe phase forms at the interface in local areas of relatively wide interlayer (~ 1 µm), while for most of the sharp interface, a much thinner zone up to about 400 nm, formed by four sublayers containing intermetallic phase and carbides, is present. This confirms that carbon diffusion induced by applied heat treatment significantly influences the final microstructure of the Ti/steel interface zone. Side bending tests confirmed high plasticity of welds after applied heat treatment; however, the microhardness measurements indicated that the strengthening of the steel in the vicinity of the interface had not been removed completely.

Evidence for the Significant Differences in Response Times of Equatorial Ionization Anomaly Crest Corresponding to Plasma Fountains During Daytime and Post‐Sunset Hours

AbstractBased on 10 years' (2010–2019) of vertical total electron content (VTEC) data from Ahmedabad (23.0°N, 72.6°E, dip angle 35.2°) and campaign based OI 630.0 nm airglow intensity measurements from Mt. Abu (24.6°N, 72.7°E, dip angle 38.0°), it is shown that plasma density over the equatorial ionization anomaly (EIA) crest region increases in varying degrees during post‐sunset hours (2000–2100 LT) in magnetically quiet periods. The post‐sunset peak in VTEC precedes the corresponding peak in airglow intensity. By comparing post‐sunset VTEC enhancements with ionosonde observations from Tirunelveli (8.7°N, 77.7°E, dip angle 1.7°), it is shown that pre‐reversal enhancement (PRE) of the zonal electric field causes these enhancements over the EIA crest region. These observations are supported by TEC measurements by GAGAN (GPS Aided Geo Augmented navigation), the Indian Satellite‐based Augmentation System (SBAS). Comparison of average VTEC variations with global empirical model drifts reveals that the post‐sunset enhancements in VTEC occurs ∼1.7 h after the PRE and are significant only during December solstice and equinoctial months in high solar activity years similar to seasonal variations in PRE amplitudes. This time delay (response time of EIA crest) is almost half compared to the average response time (3–4 h) associated with the daytime fountain. Based on the latitudinal gradient in SBAS‐TEC, it is proposed that the PRE drives plasma from 5°N to 10°N magnetic latitudes to the EIA crest region leading to shorter response time. These results show the important role of the PRE in conditioning the EIA crest region.