Acute Exposure to Two Biocides Causes Morphological and Molecular Changes in the Gill Ciliary Epithelium of the Invasive Golden Mussel Limnoperna fortunei (Dunker, 1857).

Limnoperna fortunei, the golden mussel, is a bivalve mollusk considered an invader in South America. This species is responsible for ecological and economic damages due to its voluminous fouling capability. Chemical biocides such as MXD-100™ and sodium dichloroisocyanurate (NaDCC) are often used to control L. fortunei infestations in hydraulic systems. Thus, we proposed to investigate the effects of different periods (24, 48 and 72 h) of exposure to MXD-100™ (0.56 mg L-1) and NaDCC (1.5 mg L-1) on the gills of L. fortunei through morphological and molecular analyses. NaDCC promoted progressive morphological changes during the analyzed periods and only an upregulation of SOD and HSP70 expression during the first 24 h of exposure. MXD-100™ led to severe morphological changes from the first period of exposure, in addition to an upregulation of SOD, CAT, HSP70 and CYP expression during the first 24 h. In contrast, MXD-100™ led to a downregulation of CAT transcription between 24 and 48 h. In static conditions, NaDCC causes lethal damage after 72 h of exposure, and that exposure needs to be continuous to achieve the control of the species. Meanwhile, the MXD-100™ treatment presented several effects during the first 24 h, showing acute toxicity in a shorter period of time.

Effects of the multi-channeled oral irrigation (MCOI) unit in preventing dental plaque formation and gingivitis: A randomized controlled trial.

PURPOSE: To evaluate the efficacy of COMORAL a new multi-channeled oral irrigation (MCOI) unit with pulsating water jet, in plaque score reduction and gingivitis. METHODS: This was a single-blinded clinical randomized controlled trial (NCT05031260). Forty-two healthy subjects between 18 to 35 years old were initially recruited, and the control group (n = 20) and the intervention group (n = 17) were randomly assigned. Both groups were asked to brush their teeth one or two times a day without any supplementary oral hygiene products while the intervention group used COMORAL 3 times a day, 5 days a week. Clinical indices including gingival index (GI), plaque index (PI), bleeding on probing (BOP), pocket depth (PD), gingival recession (GR), and clinical attachment loss (CAL) were obtained at the baseline (D0), day 14 (D14), and day 28 (D28). Saliva was collected to examine the presence of periodontal pathogens. The repeated measures analysis of variance or generalized estimating equation was used to compare the interaction between groups and time points. The independent t-test or Mann-Whitney test were used for intergroup differences at each time point. RESULTS: At V0, PI, GI, BOP, and PD scores showed no differences between the two groups. At V1 and V2, these scores showed significant difference between two groups (P < 0.05) such that the intervention group showed gradual decreases while the control group showed no change. There were no differences in GR, CAL, and periodontal pathogens between the two groups. COMORAL showed improvement in reducing gingival inflammation and dental plaque formation adjuvant to routine toothbrushing in healthy adults. CLINICAL SIGNIFICANCE: The results of this study can be useful to clinicians when selecting oral hygiene devices that can help improve patients' routine oral hygiene practice and their overall oral health.

The Child Emotion Facial Expression Set: A Database for Emotion Recognition in Children.

Background: This study developed a photo and video database of 4-to-6-year-olds expressing the seven induced and posed universal emotions and a neutral expression. Children participated in photo and video sessions designed to elicit the emotions, and the resulting images were further assessed by independent judges in two rounds. Methods: In the first round, two independent judges (1 and 2), experts in the Facial Action Coding System, firstly analysed 3,668 emotions facial expressions stimuli from 132 children. Both judges reached 100% agreement regarding 1,985 stimuli (124 children), which were then selected for a second round of analysis between judges 3 and 4. Results: The result was 1,985 stimuli (51% of the photographs) were produced from 124 participants (55% girls). A Kappa index of 0.70 and an accuracy of 73% between experts were observed. Lower accuracy was found for emotional expression by 4-year-olds than 6-year-olds. Happiness, disgust and contempt had the highest agreement. After a sub-analysis evaluation of all four judges, 100% agreement was reached for 1,381 stimuli which compound the ChildEFES database with 124 participants (59% girls) and 51% induced photographs. The number of stimuli of each emotion were: 87 for neutrality, 363 for happiness, 170 for disgust, 104 for surprise, 152 for fear, 144 for sadness, 157 for anger 157, and 183 for contempt. Conclusions: The findings show that this photo and video database can facilitate research on the mechanisms involved in early childhood recognition of facial emotions in children, contributing to the understanding of facial emotion recognition deficits which characterise several neurodevelopmental and psychiatric disorders.

The Modified Apically Repositioned Flap Technique and Its Potential to Create Attached Gingiva in Areas with No Keratinized Tissue: A Long-Term (1 to 11 Years) Retrospective Case Series Study.

The modified apically repositioned flap (MARF) technique has been previously published as a successful method to increase the zone of attached gingiva with numerous advantages, such as simplicity, predictability, and long-term stability. However, this technique has only been used in areas with at least 0.5 mm of attached gingiva, presurgically. In the current study, the MARF technique was utilized in 21 sites (teeth) with no attached gingiva and only mucosa comprising the marginal tissue. The long-term follow-up results over the course of 1 to 11 years (average follow-up: 3.2 years) show a statistically significant increase of 3.6 ± 0.8 mm for keratinized tissue and of 2.21 ± 0.83 mm for attached gingiva, and no increases in probing depths or marginal tissue recession. These results indicate that the MARF procedure has generated keratinized tissue and attached gingiva in areas with a presurgical absence of these tissues.

Rieger Syndrome: Rehabilitation With Dental Implants.

INTRODUCTION: Axenfeld-Rieger syndrome (ARS), also known as Rieger syndrome, is a rare autosomal dominant condition defined by craniofacial, ocular, dental, periumbilical, and systemic anomalies. CASE PRESENTATION: This case report describes in detail a multidisciplinary approach to successfully restore the oral function and esthetics of a 22-year-old patient diagnosed with ARS. The patient's clinical evaluation revealed that the area corresponding with teeth #13, #12, #11, #21, #22, and #23 was occupied by four malformed and/or deciduous teeth. The four anterior teeth were extracted, and socket preservation was performed using bovine-derived porous bone mineral. Six months after extractions, two implants were placed in the location of the lateral incisors and additional bone graft was performed. Two months after the initial healing, a temporary fixed partial was delivered and 9 months after implant placement the implants were restored with a porcelain-fused-to-metal fixed partial denture. CONCLUSIONS: The use of implant-supported fixed partial dentures to restore missing teeth in patients with ARS provides biological and mechanical advantages over conventional, fixed, or removable prosthodontics. Further evaluation is needed to determine the longevity and long-term prognosis of dental implants in patients with ARS.

Dynamic magnetization on the low temperature magnetoelectric effect in multiferroic composites.

The dependence of frequency and applied magnetic field in the magnetoelectric effect (ME) of the composites 0.68Pb(Mg1/3Nb2/3)-0.32PbTiO3/CoFe2O4 (PMN-PT/CFO) and 0.68Pb(Mg1/3Nb2/3)-0.32PbTiO3/NiFe2O4 (PMN-PT/NFO) are investigated. The results for PMN-PT/CFO composite, show a hysteretic behavior for the ME coefficient, at low temperatures (5 K), for frequencies higher than 1000 Hz. Contrasting with these results, the ME coefficient for the PMN-PT/NFO shows a well-known peak-peak related with the magnetostriction coefficient. Based on energy levels of stabilization for each ferromagnetic phase, it was possible to explain the ME hysteretic distinct behavior of PMN-PT/CFO, because of the degeneracy in the energy levels, due to the spin-orbit coupling causing changes in the dynamic properties of the magnetoelastic interactions.

Peri-implant diseases and conditions: Consensus report of workgroup 4 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.

A classification for peri-implant diseases and conditions was presented. Focused questions on the characteristics of peri-implant health, peri-implant mucositis, peri-implantitis, and soft- and hard-tissue deficiencies were addressed. Peri-implant health is characterized by the absence of erythema, bleeding on probing, swelling, and suppuration. It is not possible to define a range of probing depths compatible with health; Peri-implant health can exist around implants with reduced bone support. The main clinical characteristic of peri-implant mucositis is bleeding on gentle probing. Erythema, swelling, and/or suppuration may also be present. An increase in probing depth is often observed in the presence of peri-implant mucositis due to swelling or decrease in probing resistance. There is strong evidence from animal and human experimental studies that plaque is the etiological factor for peri-implant mucositis. Peri-implantitis is a plaque-associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri-implant mucosa and subsequent progressive loss of supporting bone. Peri-implantitis sites exhibit clinical signs of inflammation, bleeding on probing, and/or suppuration, increased probing depths and/or recession of the mucosal margin in addition to radiographic bone loss. The evidence is equivocal regarding the effect of keratinized mucosa on the long-term health of the peri-implant tissue. It appears, however, that keratinized mucosa may have advantages regarding patient comfort and ease of plaque removal. Case definitions in day-to-day clinical practice and in epidemiological or disease-surveillance studies for peri-implant health, peri-implant mucositis, and peri-implantitis were introduced. The proposed case definitions should be viewed within the context that there is no generic implant and that there are numerous implant designs with different surface characteristics, surgical and loading protocols. It is recommended that the clinician obtain baseline radiographic and probing measurements following the completion of the implant-supported prosthesis.

Peri-implant health, peri-implant mucositis, and peri-implantitis: Case definitions and diagnostic considerations.

The objective of this review is to identify case definitions and clinical criteria of peri-implant healthy tissues, peri-implant mucositis, and peri-implantitis. The case definitions were constructed based on a review of the evidence applicable for diagnostic considerations. In summary, the diagnostic definition of peri-implant health is based on the following criteria: 1) absence of peri-implant signs of soft tissue inflammation (redness, swelling, profuse bleeding on probing), and 2) the absence of further additional bone loss following initial healing. The diagnostic definition of peri-implant mucositis is based on following criteria: 1) presence of peri-implant signs of inflammation (redness, swelling, line or drop of bleeding within 30 seconds following probing), combined with 2) no additional bone loss following initial healing. The clinical definition of peri-implantitis is based on following criteria: 1) presence of peri-implant signs of inflammation, 2) radiographic evidence of bone loss following initial healing, and 3) increasing probing depth as compared to probing depth values collected after placement of the prosthetic reconstruction. In the absence of previous radiographs, radiographic bone level ≥3 mm in combination with BOP and probing depths ≥6 mm is indicative of peri-implantitis.

Peri-implant health, peri-implant mucositis, and peri-implantitis: Case definitions and diagnostic considerations.

The objective of this review is to identify case definitions and clinical criteria of peri-implant healthy tissues, peri-implant mucositis, and peri-implantitis. The case definitions were constructed based on a review of the evidence applicable for diagnostic considerations. In summary, the diagnostic definition of peri-implant health is based on the following criteria: 1) absence of peri-implant signs of soft tissue inflammation (redness, swelling, profuse bleeding on probing), and 2) the absence of further additional bone loss following initial healing. The diagnostic definition of peri-implant mucositis is based on following criteria: 1) presence of peri-implant signs of inflammation (redness, swelling, line or drop of bleeding within 30 seconds following probing), combined with 2) no additional bone loss following initial healing. The clinical definition of peri-implantitis is based on following criteria: 1) presence of peri-implant signs of inflammation, 2) radiographic evidence of bone loss following initial healing, and 3) increasing probing depth as compared to probing depth values collected after placement of the prosthetic reconstruction. In the absence of previous radiographs, radiographic bone level ≥3 mm in combination with BOP and probing depths ≥6 mm is indicative of peri-implantitis.

Peri-implant diseases and conditions: Consensus report of workgroup 4 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.

A classification for peri-implant diseases and conditions was presented. Focused questions on the characteristics of peri-implant health, peri-implant mucositis, peri-implantitis, and soft- and hard-tissue deficiencies were addressed. Peri-implant health is characterized by the absence of erythema, bleeding on probing, swelling, and suppuration. It is not possible to define a range of probing depths compatible with health; Peri-implant health can exist around implants with reduced bone support. The main clinical characteristic of peri-implant mucositis is bleeding on gentle probing. Erythema, swelling, and/or suppuration may also be present. An increase in probing depth is often observed in the presence of peri-implant mucositis due to swelling or decrease in probing resistance. There is strong evidence from animal and human experimental studies that plaque is the etiological factor for peri-implant mucositis. Peri-implantitis is a plaque-associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri-implant mucosa and subsequent progressive loss of supporting bone. Peri-implantitis sites exhibit clinical signs of inflammation, bleeding on probing, and/or suppuration, increased probing depths and/or recession of the mucosal margin in addition to radiographic bone loss. The evidence is equivocal regarding the effect of keratinized mucosa on the long-term health of the peri-implant tissue. It appears, however, that keratinized mucosa may have advantages regarding patient comfort and ease of plaque removal. Case definitions in day-to-day clinical practice and in epidemiological or disease-surveillance studies for peri-implant health, peri-implant mucositis, and peri-implantitis were introduced. The proposed case definitions should be viewed within the context that there is no generic implant and that there are numerous implant designs with different surface characteristics, surgical and loading protocols. It is recommended that the clinician obtain baseline radiographic and probing measurements following the completion of the implant-supported prosthesis.

Salivary exRNA biomarkers to detect gingivitis and monitor disease regression.

AIM: This study tests the hypothesis that salivary extracellular RNA (exRNA) biomarkers can be developed for gingivitis detection and monitoring disease regression. MATERIALS AND METHODS: Salivary exRNA biomarker candidates were developed from a total of 100 gingivitis and non-gingivitis individuals using Affymetrix's expression microarrays. The top 10 differentially expressed exRNAs were tested in a clinical cohort to determine whether the discovered salivary exRNA markers for gingivitis were associated with clinical gingivitis and disease regression. For this purpose, unstimulated saliva was collected from 30 randomly selected gingivitis subjects, the gingival and plaque indexes scores were taken at baseline, 3 and 6 weeks and salivary exRNAs were assayed by means of reverse transcription quantitative polymerase chain reaction. RESULTS: Eight salivary exRNA biomarkers developed for gingivitis were statistically significantly changed over time, consistent with disease regression. A panel of four salivary exRNAs [SPRR1A, lnc-TET3-2:1, FAM25A, CRCT1] can detect gingivitis with a clinical performance of 0.91 area under the curve, with 71% sensitivity and 100% specificity. CONCLUSIONS: The clinical values of the developed salivary exRNA biomarkers are associated with gingivitis regression. They offer strong potential to be advanced for definitive validation and clinical laboratory development test.

Genomewide Association Study Identifies Cxcl Family Members as Partial Mediators of LPS-Induced Periodontitis.

Periodontitis (PD) is characterized by bacterial infection and inflammation of tooth-supporting structures and can lead to tooth loss. PD affects ∼47% of the US population over age 30 years and has a heritability of about 50%. Although the host immunoinflammatory response and genetic background play a role, little is known of the underlying genetic factors. We examined natural genetic variation in lipopolysaccharide (LPS)-induced PD across a panel of inbred mouse strains, the hybrid mouse diversity panel (HMDP). We observed a strain-dependent sixfold difference in LPS-induced bone loss across the HMDP with a heritability of 53%. We performed a genomewide association study (GWAS) using FAST-LMM, which corrects for population structure, and identified loci significantly associated with PD. We examined candidate genes at a locus on chromosome 5, which suggested a relationship between LPS-induced bone loss and, together with expression data, identified Cxcl family members as associated with PD. We observed an increase in Cxcl10 protein, as well as immune cells and pro-inflammatory cytokines in C57BL/6J (high bone loss strain) but not in A/J (low bone loss strain) after LPS injections. Genetic deletion of CXCR3 (Cxcl9 and10 receptor) demonstrated a ∼50% reduction in bone loss and reduced osteoclasts after LPS injections. Furthermore, WT mice treated with AMG-487 (a CXCR3 antagonist) showed a ∼45% reduction in bone loss and decreased osteoclasts after LPS injections. We conclude that CXCR3 is a strong candidate for modulating the host response in individuals susceptible to PD. © 2018 American Society for Bone and Mineral Research.

Early intervention of peri-implantitis and periodontitis using a mouse model.

BACKGROUND: Peri-implantitis is an inflammatory response to bacterial biofilm resulting in bone loss and can ultimately lead to implant failure. Because of the lack of predictable treatments available, a thorough understanding of peri-implantitis's pathogenesis is essential. The objective of this study is to evaluate and compare the response of acute induced peri-implantitis and periodontitis lesions after insult removal. METHODS: Implants were placed in one-month-old C57BL/6J male mice eight weeks post extraction of their left maxillary molars. Once osseointegrated, ligatures were placed around the implants and contralateral second molars of the experimental groups. Controls did not receive ligatures. After one week, half of the ligatures were removed, creating the ligature-retained and ligature-removed groups. Mice were sacrificed at two time points, 5 and 14 days, from ligature removal. The specimens were analyzed via micro-computed tomography and histology. RESULTS: By 5 and 14 days after ligature removal, the periodontitis group experienced significant bone gain, whereas the peri-implantitis group did not. Histologically, all implant groups exhibited higher levels of cellular infiltrate than any of the tooth groups. Osteoclast numbers increased in peri-implantitis and periodontitis ligature-retained groups and decreased following insult removal. Collagen was overall more disorganized in peri-implantitis than periodontitis for all groups. Peri-implantitis experimental groups revealed greater matrix metalloproteinase-8 and NF-kB levels than periodontitis. CONCLUSIONS: Implants respond slower and less favorably to insult removal than teeth. Future research is needed to characterize detailed peri-implantitis disease pathophysiology.

Ligature-induced peri-implantitis and periodontitis in mice.

AIM: Peri-implantitis (PI), inflammation around dental implants, shares characteristics with periodontitis (PD). However, PI is more difficult to control and treat, and detailed pathophysiology is unclear. We aimed to compare PI and PD progression utilizing a murine model. MATERIALS AND METHODS: Four-week-old male C57BL/6J mice had their left maxillary molars extracted. Implants were placed in healed extraction sockets and osseointegrated. Ligatures were tied around the implants and second molars. Controls did not receive ligatures. Mice were sacrificed 1 week, 1 and 3 months (n ≥ 5/group/time point) post-ligature placement. Bone loss analysis was performed. Histology was performed for: haematoxylin and eosin (H&E), tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-8 (MMP-8), nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), toluidine blue and calcein. RESULTS: PI showed statistically greater bone loss compared to PD at 1 and 3 months. At 3 months, 20% of implants in PI exfoliated; no natural teeth exfoliated in PD. H&E revealed that alveolar bone surrounding implants in PI appeared less dense compared to PD. PI presented with increased osteoclasts, MMP-8 and NF-κB, compared to PD. CONCLUSION: PI exhibited greater tissue and bone destruction compared to PD. Future studies will characterize the pathophysiological differences between the two conditions.

The Modified Apically Repositioned Flap Technique: A Long-Term (4 to 16 Years) Retrospective Study.

Attached gingiva is desirable for the maintenance of gingival health. Although many methods are used to increase the zone of attached gingiva, the modified apically repositioned flap (MARF) technique has the advantages of simplicity and predictability. The short-term follow-up of the MARF technique demonstrated an increase in keratinized tissue and attached gingiva. This study evaluated long-term results of the MARF technique as used to increase the apicocoronal dimensions of keratinized tissue and attached gingiva in 28 sites (25 patients; average follow-up of 9 years). There was a statistically significant increase in keratinized tissue and attached gingiva with no increase in probing depths or gingival recession. These results suggest that the MARF procedure predictably generates keratinized tissue and attached gingiva with long-term stability.

Comparing the Healing Potential of Late-Stage Periodontitis and Peri-Implantitis.

Peri-implantitis is defined as an inflammatory disease affecting the tissues around osseointegrated functioning implants. Unfortunately, detailed peri-implantitis pathogenesis is not well understood and current treatments lack predictability. Compare the healing potential of late-stage ligature-induced periodontitis and peri-implantitis after ligature removal. Four-week-old C57BL/6J male mice had their left maxillary molars extracted. After 8 weeks, implants were placed in healed sockets and allowed to osseointegrate. Mice were separated into control (no ligature) and experimental (ligature) groups. In the experimental group, ligatures were placed around the implant and the contralateral second molar. Four weeks later, the ligature group was randomly divided into ligature-retained and ligature-removed groups. Mice were sacrificed at 2 time points: 1 and 2 weeks after ligature removal. The samples were analyzed by microcomputed tomography (micro-CT) and histology. Ligature-induced significant bone loss in peri-implantitis and periodontitis were compared with respective controls. At the 2-week time point, bone formation was observed in the ligature-removed groups compared with respective controls; however, more bone was regained in periodontitis ligature-removed compared with the peri-implantitis ligature-removed group. Histologically, the peri-implantitis ligature-retained group had higher inflammatory levels and a higher number of osteoclasts compared with the periodontitis ligature-retained group. Moreover, in the peri-implantitis ligature-retained group, collagen appeared less organized compared with the periodontitis ligature-retained group at both time points; although collagen tended to reorganize following ligature removal in both conditions. Peri-implantitis does not respond to treatment as well as periodontitis. Future work includes understanding peri-implantitis pathogenesis and developing predictable treatment protocols.

Hybrid Geoid Model: Theory and Application in Brazil.

Determination of the ellipsoidal height by Global Navigation Satellite Systems (GNSS) is becoming better known and used for purposes of leveling with the aid of geoid models. However, the disadvantage of this method is the quality of the geoid models, which degrade heights and limit the application of the method. In order to provide better quality in transforming height using GNSS leveling, this research aims to develop a hybridization methodology of gravimetric geoid models EGM08, MAPGEO2015 and GEOIDSP2014 for the State of São Paulo, providing more consistent models with GNSS technology. Radial Basis Function (RBF) neural networks were used to obtain the corrector surface, based on differences between geoid model undulations and the undulations obtained by GNSS tracking in benchmarks. The experiments showed that the most suitable interpolation for correction modeling is the linear RBF. Checkpoints indicate that the geoid hybrid models feature root mean square deviation ± 0.107, ± 0.104 and ± 0.098 m, respectively. The results shows an improvement of 30 to 40% in consistencies compared with the gravimetric geoids, providing users with better quality in transformation of geometric to orthometric heights.

Hybrid Geoid Model: Theory and Application in Brazil

Determination of the ellipsoidal height by Global Navigation Satellite Systems (GNSS) is becoming better known and used for purposes of leveling with the aid of geoid models. However, the disadvantage of this method is the quality of the geoid models, which degrade heights and limit the application of the method. In order to provide better quality in transforming height using GNSS leveling, this research aims to develop a hybridization methodology of gravimetric geoid models EGM08, MAPGEO2015 and GEOIDSP2014 for the State of São Paulo, providing more consistent models with GNSS technology. Radial Basis Function (RBF) neural networks were used to obtain the corrector surface, based on differences between geoid model undulations and the undulations obtained by GNSS tracking in benchmarks. The experiments showed that the most suitable interpolation for correction modeling is the linear RBF. Checkpoints indicate that the geoid hybrid models feature root mean square deviation ± 0.107, ± 0.104 and ± 0.098 m, respectively. The results shows an improvement of 30 to 40% in consistencies compared with the gravimetric geoids, providing users with better quality in transformation of geometric to orthometric heights.

Numerical Simulations to Assess ART and MART Performance for Ionospheric Tomography of Chapman Profiles

ABSTRACT The incomplete geometrical coverage of the Global Navigation Satellite System (GNSS) makes the ionospheric tomographic system an ill-conditioned problem for ionospheric imaging. In order to detect the principal limitations of the ill-conditioned tomographic solutions, numerical simulations of the ionosphere are under constant investigation. In this paper, we show an investigation of the accuracy of Algebraic Reconstruction Technique (ART) and Multiplicative ART (MART) for performing tomographic reconstruction of Chapman profiles using a simulated optimum scenario of GNSS signals tracked by ground-based receivers. Chapman functions were used to represent the ionospheric morphology and a set of analyses was conducted to assess ART and MART performance for estimating the Total Electron Content (TEC) and parameters that describes the Chapman function. The results showed that MART performed better in the reconstruction of the electron density peak and ART gave a better representation for estimating TEC and the shape of the ionosphere. Since we used an optimum scenario of the GNSS signals, the analyses indicate the intrinsic problems that may occur with ART and MART to recover valuable information for many applications of Telecommunication, Spatial Geodesy and Space Weather.

Numerical Simulations to Assess ART and MART Performance for Ionospheric Tomography of Chapman Profiles.

The incomplete geometrical coverage of the Global Navigation Satellite System (GNSS) makes the ionospheric tomographic system an ill-conditioned problem for ionospheric imaging. In order to detect the principal limitations of the ill-conditioned tomographic solutions, numerical simulations of the ionosphere are under constant investigation. In this paper, we show an investigation of the accuracy of Algebraic Reconstruction Technique (ART) and Multiplicative ART (MART) for performing tomographic reconstruction of Chapman profiles using a simulated optimum scenario of GNSS signals tracked by ground-based receivers. Chapman functions were used to represent the ionospheric morphology and a set of analyses was conducted to assess ART and MART performance for estimating the Total Electron Content (TEC) and parameters that describes the Chapman function. The results showed that MART performed better in the reconstruction of the electron density peak and ART gave a better representation for estimating TEC and the shape of the ionosphere. Since we used an optimum scenario of the GNSS signals, the analyses indicate the intrinsic problems that may occur with ART and MART to recover valuable information for many applications of Telecommunication, Spatial Geodesy and Space Weather.