Tomographic reconstruction with non-linear diagonal estimators

In tomographic reconstruction, the inversion of the Radon transform in the presence of noise is numerically unstable. Reconstruction estimators are studied where the regularization is performed by a thresholding in a wavelet or wavelet packet decomposition. These estimators are efficient and their optimality can be established when the decomposition provides a near-diagonalization of the inverse Radon transform operator and a compact representation of the object to be recovered. Several new estimators are investigated in different decomposition. First numerical results already exhibit a strong metrical and perceptual improvement over current reconstruction methods. These estimators are implemented with fast non-iterative algorithms, and are expected to outperform Filtered Back-Projection and iterative procedures for PET, SPECT and X-ray CT devices

Regularization in tomographic reconstruction using thresholding estimators

In tomographic medical devices such as SPECT or PET cameras, image reconstruction is an unstable inverse problem, due to the presence of additive noise. A new family of regularization methods for reconstruction, based on a thresholding procedure in wavelet and wavelet packet decompositions, is studied. This approach is based on the fact that the decompositions provide a near-diagonalization of the inverse Radon transform and of the prior information on medical images. An optimal wavelet packet decomposition is adaptively chosen for the specific image to be restored. Corresponding algorithms have been developed for both 2-D and full 3-D reconstruction. These procedures are fast, non-iterative, flexible, and their performance outperforms Filtered Back-Projection and iterative procedures such as OS-EM

Regularization in Tomographic Reconstruction Using Thresholding Estimators

In tomographic medical devices such as single photon emission computed tomography or positron emission tomography cameras, image reconstruction is an unstable inverse problem, due to the presence of additive noise. A new family of regularization methods for reconstruction, based on a thresholding procedure in wavelet and wavelet packet (WP) decompositions, is studied. This approach is based on the fact that the decompositions provide a near-diagonalization of the inverse Radon transform and of prior information in medical images. A WP decomposition is adaptively chosen for the specific image to be restored. Corresponding algorithms have been developed for both two-dimensional and full three-dimensional reconstruction. These procedures are fast, noniterative, and flexible. Numerical results suggest that they outperform filtered back-projection and iterative procedures such as ordered-subset-expectation-maximization

Coping with global uncertainty: Perceptions of COVID-19 psychological distress, relationship quality, and dyadic coping for romantic partners across 27 countries

Following the global outbreak of COVID-19 in March 2020, individuals report psychological distress associated with the “new normal”—social distancing, financial hardships, and increased responsibilities while working from home. Given the interpersonal nature of stress and coping responses between romantic partners, based on the systemic transactional model this study posits that perceived partner dyadic coping may be an important moderator between experiences of COVID-19 psychological distress and relationship quality. To examine these associations, self-report data from 14,020 people across 27 countries were collected during the early phases of the COVID-19 pandemic (March–July, 2020). It was hypothesized that higher symptoms of psychological distress would be reported post-COVID-19 compared to pre-COVID-19 restrictions (Hypothesis 1), reports of post-COVID-19 psychological distress would be negatively associated with relationship quality (Hypothesis 2), and perceived partner DC would moderate these associations (Hypothesis 3). While hypotheses were generally supported, results also showed interesting between-country variability. Limitations and future directions are presented

Efficient management of nutrient in zaï system using biochar and compost in central north region of Burkina Faso

peer reviewedPour faire face à la dégradation des sols, les producteurs des zones arides ont développé le zaï, technique de collecte d’eau et de nutriments, pour restaurer la productivité de leurs sols. Cependant, les effets bénéfiques du zaï sont en déclin faute d’amendements de qualité, la baisse et la mauvaise des précipitations. Un dispositif en blocs randomisé comportant T0= 3125 kg compost /ha; T1 = 3125 kg biochar/ha + 62,5 kg NPK/ha et 31,25 kg d’urée/ha ; T2 = 62,5 kg NPK/ha et 31,25 kg d’urée/ha; T3 = 62,5 kg biochar-SRF/ha et 31,25 kg d’urée/ha; T4 = 62,5 kg biochar/ha + 62,5 kg NPK/ha et 31,25 kg d’urée/ha et T5 = 3125 kg compost/ha + 100 kg NPK/ha et 50 kg d’urée/ha a été mis en place au Centre-Nord du Burkina Faso, pour évaluer l’efficacité du biochar activé avec une solution de NPK (biochar-SRF) en comparaison avec les pratiques vulgarisées. Après deux campagnes d’expérimentation, les analyses chimiques montrent que les amendements ont amélioré les paramètres du sol de 2 à 285 %. Les rendements grain du sorgho ont augmenté de 10 à 85 % avec le biochar-SRF comparativement au témoin. Par conséquent, le biochar-SRF peut être vulgarisé comme une alternative durable à la fertilisation classique.Amélioration durable de la productivité des sols par l'utilisation raisonnée d'amendement organique et du biochar13. Climate actio

An investigation of the mechanisms for strength gain or loss of geopolymer mortar after exposure to elevated temperature

When fly ash-based geopolymer mortars were exposed to a temperature of 800 °C, it was found that the strength after the exposure sometimes decreased, but at other times increased. This paper shows that ductility of the mortars has a major correlation to this strength gain/loss behaviour. Specimens prepared with two different fly ashes, with strengths ranging from 5 to 60 MPa, were investigated. Results indicate that the strength losses decrease with increasing ductility, with even strength gains at high levels of ductility. This correlation is attributed to the fact that mortars with high ductility have high capacity to accommodate thermal incompatibilities. It is believed that the two opposing processes occur in mortars: (1) further geopolymerisation and/or sintering at elevated temperatures leading to strength gain; (2) the damage to the mortar because of thermal incompatibility arising from non-uniform temperature distribution. The strength gain or loss occurs depending on the dominant process

Progressive non-infectious anterior vertebral fusion, split cord malformation and situs inversus visceralis

BACKGROUND: Progressive non-infectious anterior vertebral fusion is a unique spinal disorder with distinctive radiological features. Early radiographic findings consist of narrowing of the anterior aspect of the intervertebral disk with adjacent end plate erosions. There is a specific pattern of progression. The management needs a multi-disciplinary approach with major input from the orthopaedic surgeon. CASE REPORT: We report a 12-year-old-female with progressive anterior vertebral fusion. This occurred at three vertebral levels. In the cervical spine there was progressive fusion of the lateral masses of the Axis with C3. Secondly, at the cervico-thoracic level, a severe, progressive, anterior thoracic vertebral fusion (C7-T5) and (T6-T7) resulted in the development of a thick anterior bony ridge and massive sclerosis and thirdly; progressive anterior fusion at L5-S1. Whereas at the level of the upper lumbar spines (L1) a split cord malformation was encountered. Situs inversus visceralis was an additional malformation. The role of the CT scan in detecting the details of the vertebral malformations was important. To our knowledge, neither this malformation complex and nor the role of the CT scan in evaluating these patients, have previously been described. CONCLUSION: The constellations of the skeletal abnormalities in our patient do not resemble any previously reported conditions with progressive anterior vertebral fusion. We also emphasise the important role of computerized tomography in the investigation of these patients in order to improve our understanding of the underlying pathology, and to comprehend the various stages of the progressive fusion process. 3D-CT scan was performed to improve assessment of the spinal changes and to further evaluate the catastrophic complications if fracture of the ankylosed vertebrae does occur. We believe that prompt management cannot be accomplished, unless the nature of these bony malformations is clarified

A Randomised Trial to Compare the Safety, Tolerability and Efficacy of Three Drug Combinations for Intermittent Preventive Treatment in Children

BACKGROUND: Results from trials of intermittent preventive treatment (IPT) in infants and children have shown that IPT provides significant protection against clinical malaria. Sulfadoxine-pyrimethamine (SP) given alone or in combination with other drugs has been used for most IPT programmes. However, SP resistance is increasing in many parts of Africa. Thus, we have investigated whether SP plus AQ, SP plus piperaquine (PQ) and dihydroartemisinin (DHA) plus PQ might be equally safe and effective when used for IPT in children in an area of seasonal transmission. METHODS: During the 2007 malaria transmission season, 1008 Gambian children were individually randomized to receive SP plus amodiaquine (AQ), SP plus piperaquine (PQ) or dihydroartemisinin (DHA) plus PQ at monthly intervals on three occasions during the peak malaria transmission season. To determine the risk of side effects following drug administration, participants in each treatment group were visited at home three days after the start of each round of drug administration and a side effects questionnaire completed. To help establish whether adverse events were drug related, the same questionnaire was administered to 286 age matched control children recruited from adjacent villages. Morbidity was monitored throughout the malaria transmission season and study children were seen at the end of the malaria transmission season. RESULTS: All three treatment regimens showed good safety profiles. No severe adverse event related to IPT was reported. The most frequent adverse events reported were coughing, diarrhoea, vomiting, abdominal pain and loss of appetite. Cough was present in 15.2%, 15.4% and 18.7% of study subjects who received SP plus AQ, DHA plus PQ or SP plus PQ respectively, compared to 19.2% in a control group. The incidence of malaria in the DHA plus PQ, SP plus AQ and SP plus PQ groups were 0.10 cases per child year (95% CI: 0.05, 0.22), 0.06 (95% CI: 0.022, 0.16) and 0.06 (95% CI: 0.02, 0.15) respectively. The incidence of malaria in the control group was 0.79 cases per child year (0.58, 1.08). CONCLUSION: All the three regimens of IPT in children were safe and highly efficacious TRIAL REGISTRATION: ClinicalTrials.gov NCT00561899