Nonlinear analysis of a simple model of temperature evolution in a satellite

We analyse a simple model of the heat transfer to and from a small satellite orbiting round a solar system planet. Our approach considers the satellite isothermal, with external heat input from the environment and from internal energy dissipation, and output to the environment as black-body radiation. The resulting nonlinear ordinary differential equation for the satellite's temperature is analysed by qualitative, perturbation and numerical methods, which show that the temperature approaches a periodic pattern (attracting limit cycle). This approach can occur in two ways, according to the values of the parameters: (i) a slow decay towards the limit cycle over a time longer than the period, or (ii) a fast decay towards the limit cycle over a time shorter than the period. In the first case, an exactly soluble average equation is valid. We discuss the consequences of our model for the thermal stability of satellites.Comment: 13 pages, 4 figures (5 EPS files

Nonlinear analysis of spacecraft thermal models

We study the differential equations of lumped-parameter models of spacecraft thermal control. Firstly, we consider a satellite model consisting of two isothermal parts (nodes): an outer part that absorbs heat from the environment as radiation of various types and radiates heat as a black-body, and an inner part that just dissipates heat at a constant rate. The resulting system of two nonlinear ordinary differential equations for the satellite's temperatures is analyzed with various methods, which prove that the temperatures approach a steady state if the heat input is constant, whereas they approach a limit cycle if it varies periodically. Secondly, we generalize those methods to study a many-node thermal model of a spacecraft: this model also has a stable steady state under constant heat inputs that becomes a limit cycle if the inputs vary periodically. Finally, we propose new numerical analyses of spacecraft thermal models based on our results, to complement the analyses normally carried out with commercial software packages.Comment: 29 pages, 4 figure

Risk Factors for Graft-versus-Host Disease in Haploidentical Hematopoietic Cell Transplantation Using Post-Transplant Cyclophosphamide

Post-transplant cyclophosphamide (PTCy) has significantly increased the successful use of haploidentical donors with a relatively low incidence of graft-versus-host disease (GVHD). Given its increasing use, we sought to determine risk factors for GVHD after haploidentical hematopoietic cell transplantation (haplo-HCT) using PTCy. Data from the Center for International Blood and Marrow Transplant Research on adult patients with acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, or chronic myeloid leukemia who underwent PTCy-based haplo-HCT (2013 to 2016) were analyzed and categorized into 4 groups based on myeloablative (MA) or reduced-intensity conditioning (RIC) and bone marrow (BM) or peripheral blood (PB) graft source. In total, 646 patients were identified (MA-BM = 79, MA-PB = 183, RIC-BM = 192, RIC-PB = 192). The incidence of grade 2 to 4 acute GVHD at 6 months was highest in MA-PB (44%), followed by RIC-PB (36%), MA-BM (36%), and RIC-BM (30%) (P =.002). The incidence of chronic GVHD at 1 year was 40%, 34%, 24%, and 20%, respectively (P <.001). In multivariable analysis, there was no impact of stem cell source or conditioning regimen on grade 2 to 4 acute GVHD; however, older donor age (30 to 49 versus <29 years) was significantly associated with higher rates of grade 2 to 4 acute GVHD (hazard ratio [HR], 1.53; 95% confidence interval [CI], 1.11 to 2.12; P =.01). In contrast, PB compared to BM as a stem cell source was a significant risk factor for the development of chronic GVHD (HR, 1.70; 95% CI, 1.11 to 2.62; P =.01) in the RIC setting. There were no differences in relapse or overall survival between groups. Donor age and graft source are risk factors for acute and chronic GVHD, respectively, after PTCy-based haplo-HCT. Our results indicate that in RIC haplo-HCT, the risk of chronic GVHD is higher with PB stem cells, without any difference in relapse or overall survival

Uterirle distension media for outpatient hysteroscopy

Background Hysteroscopy done in an outpatient setting is the 'gold standard' method for evaluating the uterine cavity. Media used to distend the uterine cavity include gas as carbon dioxide and liquid as saline that can be used at room temperature or warmed to body temperature. Both media offer advantages as well as disadvantages. Objectives The objective of this review is to compare the effectiveness, tolerability, and safety of gas (carbon dioxide) and liquid (normal saline) used for uterine distension during outpatient hysteroscopy. Search methods We searched the Cochrane Gynaecology and Fertility (CGF) Group Specialised Register, CENTRAL, MEDLINE, Embase and PsycINFO on 28 April 2021. We checked references of relevant trials and contacted study authors and experts in the field to identify additional studies. CINAHL records and ongoing trials from the trial registries were included in the CENTRAL search. Selection criteria We included randomised controlled trials (RCTs) comparing saline with carbon dioxide, as well as RCTs comparing saline at different temperatures, for uterine distension in outpatient hysteroscopy done for any indication. Data collection and analysis We used standard methodological procedures recommended by Cochrane. Primary review outcomes were patient tolerability and adverse events or complications related to the distending medium. Secondary outcomes were quality of the hysteroscopic view and duration of the procedure. Main results We included 12 RCTs (1946 women). The quality of evidence ranged from very low to moderate: the main limitations were risk of bias due to absence of blinding due to the nature of the procedure, imprecision, and inconsistency. Saline versus carbon dioxide Analysis ruled out a clinically relevant difference in pain scores during the procedure between saline and carbon dioxide, but the quality of evidence was low (standardised mean difference (SMD) ‐0.07, 95% confidence interval (CI) ‐0.17 to 0.02; 9 RCTs, N = 1705; I² = 86%). This translates to differences of 0.39 cm (lower) and 0.05 cm (higher) on a 10‐cm visual analogue scale (VAS). Evidence was insufficient to show differences between groups in the proportion of procedures abandoned due to intense pain (Peto odds ratio (OR) 0.48, 95% CI 0.09 to 2.42; 1 RCT, N = 189; very low‐quality evidence). We are uncertain whether saline decreases the need for analgesia compared to carbon dioxide (Peto OR 0.34, 95% CI 0.12 to 0.99; 1 RCT, N = 189; very low‐quality evidence). Saline compared to carbon dioxide is probably associated with fewer vasovagal reaction events (Peto OR 0.53, 95% CI 0.32 to 0.86; 6 RCTs, N = 1076; I² = 0%; moderate‐quality evidence) and fewer shoulder‐tip pain events (Peto OR 0.28, 95% CI 0.14 to 0.54; 4 RCTs, N = 623; I² = 0%, moderate‐quality evidence). Evidence suggests that if 10% of women undergoing outpatient hysteroscopy experience a vasovagal reaction event with the use of carbon dioxide, this rate would be between 3% and 9% with the use of saline. Similarly, if the rate of shoulder‐tip pain with carbon dioxide is 9%, it would be between 1% and 5% with saline. We are uncertain whether saline is similar to carbon dioxide in terms of endometrial bleeding (Peto OR 0.83, 95% CI 0.25 to 2.75; 2 RCTs, N = 349; I² = 0%; very low‐quality evidence). Infection was not reported by any study in this comparison. Saline may result in fewer procedures with an unsatisfactory hysteroscopic view than carbon dioxide (Peto OR 0.51, 95% CI 0.32 to 0.82; 5 RCTs, N = 1082; I² = 67%; low‐quality evidence). The duration of the procedure was shorter with saline in three of the four studies that reported this outcome, and duration was similar in both arms in the fourth study. Warm saline versus room temperature saline Use of warm saline for uterine distension during office hysteroscopy may reduce pain scores when compared with room temperature saline (mean difference (MD) ‐1.14, 95% CI ‐1.55 to ‐0.73; 3 RCTs, N = 241; I² = 77%; low‐quality evidence). Evidence is insufficient to show differences between groups in either the proportion of procedures abandoned due to intense pain (Peto OR 0.97, 95% CI 0.06 to 15.87; 1 RCT, N = 77; very low‐quality evidence) or the need for analgesia (Peto OR 1.00, 95% CI 0.14 to 7.32; 1 RCT, N = 100; very low‐quality evidence). Analysis ruled out a clinically relevant difference in duration of the procedure between warm and room temperature saline, but the quality of evidence is low (MD 13.17 seconds, 95% CI ‐12.96 to 39.29; 2 RCTs, N = 141; I² = 21%). No cases of infection were reported in either group (1 RCT, N = 100). No other adverse events and no information on quality of the hysteroscopic view were reported by any study in this comparison. Authors' conclusions Evidence was insufficient to show differences between different distension media used for uterine distension in outpatient hysteroscopy in terms of patient tolerability, operator satisfaction, or duration of the procedure. However, saline was superior to carbon dioxide in producing fewer adverse events (shoulder‐tip pain and vasovagal reaction).Karim S Abdallah, Moustafa A. Gadalla, Maria C Breijer, Ben Willem J Mo

A renewable lignin-derived bio-oil for boosting the oxidation stability of biodiesel

The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing its oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil to biodiesel has led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol

A Personalized Prediction Model for Outcomes after Allogeneic Hematopoietic Cell Transplant in Patients with Myelodysplastic Syndromes

Allogeneic hematopoietic stem cell transplantation (HCT) remains the only potentially curative option for myelodysplastic syndromes (MDS). Mortality after HCT is high, with deaths related to relapse or transplant-related complications. Thus, identifying patients who may or may not benefit from HCT is clinically important. We identified 1514 patients with MDS enrolled in the Center for International Blood and Marrow Transplant Research Registry and had their peripheral blood samples sequenced for the presence of 129 commonly mutated genes in myeloid malignancies. A random survival forest algorithm was used to build the model, and the accuracy of the proposed model was assessed by concordance index. The median age of the entire cohort was 59 years. The most commonly mutated genes were ASXL1(20%), TP53 (19%), DNMT3A (15%), and TET2 (12%). The algorithm identified the following variables prior to HCT that impacted overall survival: age, TP53 mutations, absolute neutrophils count, cytogenetics per International Prognostic Scoring System-Revised, Karnofsky performance status, conditioning regimen, donor age, WBC count, hemoglobin, diagnosis of therapy-related MDS, peripheral blast percentage, mutations in RAS pathway, JAK2 mutation, number of mutations/sample, ZRSR2, and CUX1 mutations. Different variables impacted the risk of relapse post-transplant. The new model can provide survival probability at different time points that are specific (personalized) for a given patient based on the clinical and mutational variables that are listed above. The outcomes' probability at different time points may aid physicians and patients in their decision regarding HCT. (C) 2020 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved