Secondary Electron Emission Induced by Electron Bombardment of Polycrystalline Metallic Targets

The aim of the present paper is the analysis of the backward secondary electron emission phenomenon, under electron bombardment, on the basis of experimental and theoretical results. Among the theoretical models, we will mention the phenomenological models, those which use a Monte-Carlo type simulation method, and those based on the numerically solved Boltzmann transport equation. To correlate experimental and theoretical results on all the data characterizing this phenomenon, it is necessary to use an appropriate description for the excitation process of the internal secondary electrons; it also needs a complete description of the transport process for the excited electrons, which incorporates the elastic and inelastic interactions, as well as the energy and angular distribution of the incident primary beam. From this, it follows that it will be necessary, either to use a direct Monte-Carlo simulation method, or, in the case of the transport model, to carry out a preliminary treatment of the primary electron dispersion; this treatment is also based upon a Boltzmann equation resolution. The results of such an analysis will be useful in electron microscopy and in quantitative Auger spectroscopy

Transport Models for Backscattering and Transmission of Low Energy ( \u3c 3 Kilovolts) Electrons from Solids

This paper deals with the backscattering and the transmission of electrons with energy \u3c 3 keV through thin self supporting films, or on bulk metals. We present the main theoretical models used in such problems, and we analyse mainly the models based on the Boltzmann transport equation, similar to those developed in our laboratory. For any model shown here, we try to give the precise domain in which they give reliable results as well as the limitations connected to the simplifying assumptions. In the case of the most sophisticated model, we give original results for copper. The models are presented in a comparative form, and when it is possible we compare our results with the experimental ones. The theoretical models were applied to Al and Cu. We give, for bulk metals, the values of the backscattering yield, and the energy distributions of backscattered electrons. In the case of thin self supporting films, we studied mainly the backscattering and transmission coefficients, as well as the energy distributions of transmitted and backscattered electrons

Bathymetric segmentation of multispectral SPOT images

This paper addresses the analysis of multispectral SPOT images in order to update nautical charts and to control nautical data. We have developed a segmentation approach based on two Markovian modeling steps. The first one is based on Markov chain (1D) modeling, whereas the second step involves a hierarchical process, Markovian in scale. Each of them includes the unsupervised estimation of the parameters. The model parameters are automatically calibrated whereas the noise parameters are estimated in the context of generalized distribution mixtures. An adaptive bathymetric inversion model is then derived in order to recover the water depth near the coasts. This bathymetric estimation has been validated on real data, for which control points are available that correspond to bathymetric measures supplied by previous hydrographic campaigns.Cet article présente la segmentation des images multispectrales SPOT pour la mise à jour des cartes marines et le contrôle d'informations nautiques. La segmentation des images multispectrales est réalisée en deux étapes grâce à une première modélisation par chaîne de Markov, puis une seconde par champ de Markov hiérarchique. Elle inclut l'estimation automatique des paramètres du modèle ainsi que l'identification des paramètres du bruit dans le contexte de l'estimation de mélange de lois généralisé. Un modèle d'inversion bathymétrique adaptatif est ensuite proposé et validé sur des images réelles, pour lesquelles on dispose de points de contrôle correspondant à des mesures bathymétriques réalisées in situ dans le cadre de campagnes hydrographiques

Recreational Diving Impacts on Coral Reefs and the Adoption of Environmentally Responsible Practices within the SCUBA Diving Industry

Recreational diving on coral reefs is an activity that has experienced rapidly growing levels of popularity and participation. Despite providing economic activity for many developing coastal communities, the potential role of dive impacts in contributing to coral reef damage is a concern at heavily dived locations. Management measures to address this issue increasingly include the introduction of programmes designed to encourage environmentally responsible practices within the dive industry. We examined diver behaviour at several important coral reef dive locations within the Philippines and assessed how diver characteristics and dive operator compliance with an environmentally responsible diving programme, known as the Green Fins approach, affected reef contacts. The role of dive supervision was assessed by recording dive guide interventions underwater, and how this was affected by dive group size. Of the 100 recreational divers followed, 88 % made contact with the reef at least once per dive, with a mean (±SE) contact rate of 0.12 ± 0.01 per min. We found evidence that the ability of dive guides to intervene and correct diver behaviour in the event of a reef contact decreases with larger diver group sizes. Divers from operators with high levels of compliance with the Green Fins programme exhibited significantly lower reef contact rates than those from dive operators with low levels of compliance. The successful implementation of environmentally responsible diving programmes, which focus on influencing dive industry operations, can contribute to the management of human impacts on coral reefs

Long-Term Impact of Cyclosporin Reduction with MMF Treatment in Chronic Allograft Dysfunction: REFERENECE Study 3-Year Follow Up

Calcineurin inhibitor (CNI) toxicity contributes to chronic allograft nephropathy (CAN). In the 2-year, randomized, study, we showed that 50% cyclosporin (CsA) reduction in combination with mycophenolate mofetil (MMF) treatment improves kidney function without increasing the risk for graft rejection/loss. To investigate the long-term effect of this regimen, we conducted a follow up study in 70 kidney transplant patients until 5 years after REFERENCE initiation. The improvement of kidney function was confirmed in the MMF group but not in the control group (CsA group). Four graft losses occurred, 2 in each group (graft survival in the MMF group 95.8% and 90.9% in control group). One death occurred in the control group. There was no statistically significant difference in the occurrence of serious adverse events or acute graft rejections. A limitation is the weak proportion of patient still remaining within the control group. On the other hand, REFERENCE focuses on the CsA regimen while opinions about the tacrolimus ones are still debated. In conclusion, CsA reduction in the presence of MMF treatment seems to maintain kidney function and is well tolerated in the long term

Alternatives to immediate release tacrolimus in solid organ transplant recipients: When the gold standard is in short supply

Given the current climate of drug shortages in the United States, this review summarizes available comparative literature on the use of alternative immunosuppressive agents in adult solid organ transplant recipients including kidney, pancreas, liver, lung, and heart, when immediate‐release tacrolimus (IR‐TAC) is not available. Alternative options explored include extended‐release tacrolimus (ER‐TAC) formulations, cyclosporine, belatacept, mammalian target of rapamycin inhibitors, and novel uses of induction therapy for maintenance immunosuppression. Of available alternatives, only ER‐TAC formulations are of non‐inferior efficacy compared to IR‐TAC when used de novo or after conversion in stable kidney transplant recipients (KTRs). All other alternatives were associated with higher rates of biopsy‐proven rejection, but improved tolerance from classic adverse effects of IR‐TAC including nephrotoxicity and development of diabetes. While most alternative therapies are approved in KTRs, access via third‐party payors is an obstacle in non‐KTRs. In the setting of IR‐TAC shortage, alternate therapeutic options may be plausible depending on the organ population and individual patient situation to ensure appropriate, effective immunosuppression for each patient.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156148/2/ctr13903.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156148/1/ctr13903_am.pd

Conversion from calcineurin inhibitor to belatacept-based maintenance immunosuppression in renal transplant recipients:A randomized phase 3b Trial

Significance Statement This randomized trial demonstrates the safety and efficacy of conversion from calcineurin inhibitor (CNI)? to belatacept-based maintenance immunosuppression in renal transplant recipients 6?60 months post-transplant. Patients converted to belatacept showed sustained improvement in renal function associated with an acceptable safety profile consistent with prior experience and a smaller treatment difference in acute rejection postconversion compared with that observed in earlier studies in de novo renal allograft recipients. These results favor the use of belatacept as an alternative to continued long-term CNI-based maintenance immunosuppression, which is particularly relevant for CNI-intolerant patients, including those who experience nephrotoxicity. These data help inform clinical practice guidelines regarding the conversion of such patients to an alternative immunosuppressive drug regimen.Background Calcineurin inhibitors (CNIs) are standard of care after kidney transplantation, but they are associated with nephrotoxicity and reduced long-term graft survival. Belatacept, a selective T cell costimulation blocker, is approved for the prophylaxis of kidney transplant rejection. This phase 3 trial evaluated the efficacy and safety of conversion from CNI-based to belatacept-based maintenance immunosuppression in kidney transplant recipients.Methods Stable adult kidney transplant recipients 6?60 months post-transplantation under CNI-based immunosuppression were randomized (1:1) to switch to belatacept or continue treatment with their established CNI. The primary end point was the percentage of patients surviving with a functioning graft at 24 months.Results Overall, 446 renal transplant recipients were randomized to belatacept conversion (n=223) or CNI continuation (n=223). The 24-month rates of survival with graft function were 98% and 97% in the belatacept and CNI groups, respectively (adjusted difference, 0.8; 95.1% CI, ?2.1 to 3.7). In the belatacept conversion versus CNI continuation groups, 8% versus 4% of patients experienced biopsy-proven acute rejection (BPAR), respectively, and 1% versus 7% developed de novo donor-specific antibodies (dnDSAs), respectively. The 24-month eGFR was higher with belatacept (55.5 versus 48.5 ml/min per 1.73 m(2) with CNI). Both groups had similar rates of serious adverse events, infections, and discontinuations, with no unexpected adverse events. One patient in the belatacept group had post-transplant lymphoproliferative disorder.Conclusions Switching stable renal transplant recipients from CNI-based to belatacept-based immunosuppression was associated with a similar rate of death or graft loss, improved renal function, and a numerically higher BPAR rate but a lower incidence of dnDSA. Clinical Trial registry name and registration number: A Study in Maintenance Kidney Transplant Recipients Following Conversion to Nulojix? (Belatacept)-Based, NCT01820572Nephrolog