A quest toward a mathematical theory of the dynamics of swarms

Bellomo, Nicola,Ha, Seung-Yeal World Scientific Publishing Company 2017 MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES Vol.27 No.4

<P>This paper addresses some preliminary steps toward the modeling and qualitative analysis of swarms viewed as living complex systems. The approach is based on the methods of kinetic theory and statistical mechanics, where interactions at the microscopic scale are nonlocal, nonlinearly additive and modeled by theoretical tools of stochastic game theory. Collective learning theory can play an important role in the modeling approach. We present a kinetic equation incorporating the Cucker-Smale flocking force and stochastic game theoretic interactions in collision operators. We also present a sufficient framework leading to the asymptotic velocity alignment and global existence of smooth solutions for the proposed kinetic model with a special kernel. Analytic results on the global existence and flocking dynamics are presented, while the last part of the paper looks ahead to research perspectives.</P>

The Role of Oliguria and the Absence of Fluid Administration and Balance Information in Illness Severity Scores

Neil J. Glassford,Rinaldo Bellomo 대한중환자의학회 2017 Acute and Critical Care Vol.32 No.2

Urinary examination has formed part of patient assessment since the earliest days of medicine. Current definitions of oliguria are essentially arbitrary, but duration and intensity of oliguria have been associated with an increased risk of mortality, and this risk is not completely attributable to the development of concomitant acute kidney injury (AKI) as defined by changes in serum creatinine concentration. The increased risk of death associated with the development of AKI itself may be modified by directly or indirectly by progressive fluid accumulation, due to reduced elimination and increased fluid administration. None of the currently extant major illness severity scoring systems or outcome prediction models use modern definitions of AKI or oliguria, or any values representative of fluid volumes variables. Even if a direct relationship with mortality is not observed, then it is possible that fluid balance or fluid volume variables mediate the relationship between illness severity and mortality in the renal and respiratory physiological domains. Fluid administration and fluid balance may then be an important, easily modifiable therapeutic target for future investigation. These relationships require exploration in large datasets before being prospectively validated in groups of critically ill patients from differing jurisdictions to improve prognostication and mortality prediction.

The Complexities of Intravenous Fluid Research: Questions of Scale, Volume, and Accumulation

Neil J Glassford,Rinaldo Bellomo 대한중환자의학회 2016 Acute and Critical Care Vol.31 No.4

Despite near ubiquity, information regarding fluids consumption at a health care systems level, and patient exposure at an individual level, is surprisingly limited in the medical literature. The epidemiology of the foundational medical intervention of intravenous fluid administration is incredibly complex, with millions of patients being exposed internationally every year. Fluid is being given for different reasons, to different targets, following different triggers, by different specialties in different countries, and any observations that can be made are thought to have limited external validity to other jurisdictions and patient groups. The independent effects of fluid administration and fluid accumulation are very hard to separate from other markers of illness severity and aspects of the process of care. Fluid accumulation can result in organ injury, even when the fluid is being given to purportedly ameliorate or prevent such injury, and if it were independently associated with mortality then would be an easily accessible and modifiable risk factor for subsequent morbidity or death. Despite their ubiquity, it is clear that we have limited understanding of the effects of the intravenous fluids we use daily in the most vulnerable of patient groups. The research agenda in this field is large and urgent.

Neutrophil Gelatinase-Associated Lipocalin Cutoff Value Selection and Acute Kidney Injury Classification System Determine Phenotype Allocation and Associated Outcomes

Albert Annemarie,Radtke Sebastian,Blume Louisa,Bellomo Rinaldo,Haase Michael,Stieger Philipp,Hinkel Ulrich Paul,Braun-Dullaeus Rüdiger C.,Albert Christian 대한진단검사의학회 2023 Annals of Laboratory Medicine Vol.43 No.6

Background: We explored the extent to which neutrophil gelatinase-associated lipocalin (NGAL) cutoff value selection and the acute kidney injury (AKI) classification system determine clinical AKI-phenotype allocation and associated outcomes. Methods: Cutoff values from ROC curves of data from two independent prospective cardiac surgery study cohorts (Magdeburg and Berlin, Germany) were used to predict Kidney Disease: Improving Global Outcome (KDIGO)- or Risk, Injury, Failure, Loss of kidney function, End-stage (RIFLE)-defined AKI. Statistical methodologies (maximum Youden index, lowest distance to [0, 1] in ROC space, sensitivity≈specificity) and cutoff values from two NGAL meta-analyses were evaluated. Associated risks of adverse outcomes (acute dialysis initiation and in-hospital mortality) were compared. Results: NGAL cutoff concentrations calculated from ROC curves to predict AKI varied according to the statistical methodology and AKI classification system (10.6–159.1 and 16.85–149.3 ng/mL in the Magdeburg and Berlin cohorts, respectively). Proportions of attributed subclinical AKI ranged 2%–33.0% and 10.1%–33.1% in the Magdeburg and Berlin cohorts, respectively. The difference in calculated risk for adverse outcomes (fraction of odds ratios for AKI-phenotype group differences) varied considerably when changing the cutoff concentration within the RIFLE or KDIGO classification (up to 18.33- and 16.11-times risk difference, respectively) and was even greater when comparing cutoff methodologies between RIFLE and KDIGO classifications (up to 25.7-times risk difference). Conclusions: NGAL positivity adds prognostic information regardless of RIFLE or KDIGO classification or cutoff selection methodology. The risk of adverse events depends on the methodology of cutoff selection and AKI classification system.

Flat Foot and Postural Harmony in 6-Year-Old Caucasians: What is Their Relationship?

Teresa Paolucci,Letizia Pezzi,Alice Mannocci,Giuseppe La Torre,Rosa Grazia Bellomo,Raoul Saggini 대한재활의학회 2020 Annals of Rehabilitation Medicine Vol.44 No.4

Objective To determine whether asymptomatic flexible flat feet show specific postural assessment with respect to neutral feet in 6-year-old children. Methods In this cross-sectional observational study, 164 subjects were observed and divided into two groups: 57 with flexible flat feet and 107 with neutral feet. A non-quantitative inspection by podoscopy and baropodometry were performed to evaluate plantar support, and a clinical examination to assess postural setting. Results The prevalence of flexible flat feet was 34.8%. The differenceinthe mean centre of pressure (CoP) between the two groups was significant (p=0.028), regarding the antero-posterior direction of CoP only. There was no significant differencein the presence of postural growth disharmony between the neutral and flat-feet groups. Conclusion The flattening of the plantar archseems to be linked to a displacement of CoP Y, more posterior in flat feet than in neutral feet; on the other hand, postural harmony in 6-year-old children during growth is not influenced by flat feet.

Predictive Value of Plasma NGAL:Hepcidin-25 for Major Adverse Kidney Events After Cardiac Surgery with Cardiopulmonary Bypass: A Pilot Study

Albert Christian,Haase Michael,Albert Annemarie,Ernst Martin,Kropf Siegfried,Bellomo Rinaldo,Westphal Sabine,Braun-Dullaeus Rüdiger C.,Haase-Fielitz Anja,Elitok Saban 대한진단검사의학회 2021 Annals of Laboratory Medicine Vol.41 No.4

Background: Neutrophil gelatinase-associated lipocalin (NGAL) and hepcidin-25 are involved in catalytic iron-related kidney injury after cardiac surgery with cardiopulmonary bypass. We explored the predictive value of plasma NGAL, plasma hepcidin-25, and the plasma NGAL:hepcidin-25 ratio for major adverse kidney events (MAKE) after cardiac surgery. Methods: We compared the predictive value of plasma NGAL, hepcidin-25, and plasma NGAL:hepcidin-25 with that of serum creatinine (Cr) and urinary output and protein for primary-endpoint MAKE (acute kidney injury [AKI] stages 2 and 3, persistent AKI >48 hours, acute dialysis, and in-hospital mortality) and secondary-endpoint AKI in 100 cardiac surgery patients at intensive care unit (ICU) admission. We performed ROC curve, logistic regression, and reclassification analyses. Results: At ICU admission, plasma NGAL, plasma NGAL:hepcidin-25, plasma interleukin-6, and Cr predicted MAKE (area under the ROC curve [AUC]: 0.77, 0.79, 0.74, and 0.74, respectively) and AKI (0.73, 0.89, 0.70, and 0.69). For AKI prediction, plasma NGAL:hepcidin-25 had a higher discriminatory power than Cr (AUC difference 0.26 [95% CI 0.00–0.53]). Urinary output and protein, plasma lactate, C-reactive protein, creatine kinase myocardial band, and brain natriuretic peptide did not predict MAKE or AKI (AUC <0.70). Only plasma NGAL:hepcidin-25 correctly reclassified patients according to their MAKE and AKI status (category-free net reclassification improvement: 0.82 [95% CI 0.12–1.52], 1.03 [0.29–1.77]). After adjustment to the Cleveland risk score, plasma NGAL:hepcidin-25 ≥0.9 independently predicted MAKE (adjusted odds ratio 16.34 [95% CI 1.77–150.49], P=0.014). Conclusions: Plasma NGAL:hepcidin-25 is a promising marker for predicting postoperative MAKE.

Urinary Biomarkers may Complement the Cleveland Score for Prediction of Adverse Kidney Events After Cardiac Surgery: A Pilot Study

Christian Albert,Michael Haase,Annemarie Albert,Siegfried Kropf,Rinaldo Bellomo,Sabine Westphal,Mark Westerman,Rüdiger Christian Braun-Dullaeus,Anja Haase-Fielitz 대한진단검사의학회 2020 Annals of Laboratory Medicine Vol.40 No.2

Background: The ability of urinary biomarkers to complement established clinical risk prediction models for postoperative adverse kidney events is unclear. We assessed the effect of urinary biomarkers linked to suspected pathogenesis of cardiac surgery-induced acute kidney injury (AKI) on the performance of the Cleveland Score, a risk assessment model for postoperative adverse kidney events. Methods: This pilot study included 100 patients who underwent open-heart surgery. We determined improvements to the Cleveland Score when adding urinary biomarkers measured using clinical laboratory platforms (neutrophil gelatinase-associated lipocalin [NGAL], interleukin-6) and those in the preclinical stage (hepcidin-25, midkine, alpha-1 microglobulin), all sampled immediately post-surgery. The primary endpoint was major adverse kidney events (MAKE), and the secondary endpoint was AKI. We performed ROC curve analysis, assessed baseline model performance (odds ratios [OR], 95% CI), and carried out statistical reclassification analyses to assess model improvement. Results: NGAL (OR [95% CI] per 20 concentration-units wherever applicable): (1.07 [1.01–1.14]), Interleukin-6 (1.51 [1.01–2.26]), midkine (1.01 [1.00–1.02]), 1-hepcidin-25 (1.08 [1.00–1.17]), and NGAL/hepcidin-ratio (2.91 [1.30–6.49]) were independent predictors of MAKE and AKI (1.38 [1.03–1.85], 1.08 [1.01–1.15], 1.01 [1.00–1.02], 1.09 [1.01–1.18], and 3.45 [1.54–7.72]). Category-free net reclassification improvement identified interleukin-6 as a model-improving biomarker for MAKE and NGAL for AKI. However, only NGAL/hepcidin-25 improved model performance for event- and event-free patients for MAKE and AKI. Conclusions: NGAL and interleukin-6 measured immediately post cardiac surgery may complement the Cleveland Score. The com

A Stabilizing Agent, PCA/DTPA, Improves Plasma Storage Life for the Chromsystems Vitamin C Assay up to Six Months

Collie Jake TB,Hudson Elizabeth P,Deane Adam M,Bellomo Rinaldo,Greaves Ronda F 대한진단검사의학회 2021 Annals of Laboratory Medicine Vol.41 No.4

The commonly used Chromsystems vitamin C (ascorbate) assay (Munich, Germany) has a sample storage life of five days at –20°C. Stabilizing agents have been successfully used to increase longevity; however, their suitability with this commercial assay is unclear. We investigated the compatibility of a stabilizing agent, perchloric acid/diethylenetriaminepentaacetic acid (PCA/DTPA), with the Chromsystems assay. Plasma was stored at –80°C, with or without PCA/DTPA. Storage up to six months was assessed through baseline and repeat analyses, stability was assessed by comparing paired non-stabilized and PCA/DTPA-stabilized plasma, and performance was assessed using allowable performance specifications of an external quality assurance program. Ascorbate concentration was significantly lower in non-stabilized plasma than in paired PCA/DTPA-stabilized plasma, with a proportional difference of 11% (P=0.01). All storage analysis results were within the allowable performance specifications. Storage at –80°C prevented plasma ascorbate oxidation; however, substantial oxidation occurred during sample processing. In conclusion, PCA/DTPA significantly reduces ascorbate oxidation, and PCA/DTPA-stabilized ascorbate plasma is compatible with the Chromsystems assay and stable for up to six months, when stored at –80°C.

Environmental test campaign of a 6U CubeSat Test Platform equipped with an ambipolar plasma thruster

Stesina, Fabrizio,Corpino, Sabrina,Borras, Eduard Bosch,Amo, Jose Gonzalez Del,Pavarin, Daniele,Bellomo, Nicolas,Trezzolani, Fabio Techno-Press 2022 Advances in aircraft and spacecraft science Vol.9 No.3

The increasing interest in CubeSat platforms ant their capability of enlarging the frontier of possible missions impose technology improvements. Miniaturized electrical propulsion (EP) systems enable new mission for multi-unit CubeSats (6U+). While electric propulsion systems have achieved important level of knowledge at equipment level, the investigation of the mutual impact between EP system and CubeSat technology at system level can provide a decisive improvement for both the technologies. The interaction between CubeSat and EP system should be assessed in terms of electromagnetic emissions (both radiated and conducted), thermal gradients, high electrical power management, surface chemical deposition, and quick and reliable data exchanges. This paper shows how a versatile CubeSat Test Platform (CTP), together with standardized procedures and specialized facilities enable the acquisition fundamental and unprecedented information. Measurements can be taken both by specific ground support equipment placed inside the vacuum facility and by dedicated sensors and subsystems installed on the CTP, providing a completely new set of data never obtained before. CTP is constituted of a 6U primary structure hosting the EP system, representative CubeSat avionics and batteries. For the first test campaign, CTP hosts the ambipolar plasma propulsion system, called Regulus and developed by T4I. After the integration and the functional test in laboratory environment, CTP + Regulus performed a Test campaign in relevant environment in the vacuum chamber at CISAS, University of Padua. This paper is focused on the test campaign description and the main results achieved at different power levels for different duration of the firings.

Environmental test campaign of a 6U CubeSat Test Platform equipped with an ambipolar plasma thruster

Stesina, Fabrizio,Corpino, Sabrina,Borras, Eduard Bosch,Amo, Jose Gonzalez Del,Pavarin, Daniele,Bellomo, Nicolas,Trezzolani, Fabio Techno-Press 2022 Advances in aircraft and spacecraft science Vol.9 No.3

The increasing interest in CubeSat platforms ant their capability of enlarging the frontier of possible missions impose technology improvements. Miniaturized electrical propulsion (EP) systems enable new mission for multi-unit CubeSats (6U+). While electric propulsion systems have achieved important level of knowledge at equipment level, the investigation of the mutual impact between EP system and CubeSat technology at system level can provide a decisive improvement for both the technologies. The interaction between CubeSat and EP system should be assessed in terms of electromagnetic emissions (both radiated and conducted), thermal gradients, high electrical power management, surface chemical deposition, and quick and reliable data exchanges. This paper shows how a versatile CubeSat Test Platform (CTP), together with standardized procedures and specialized facilities enable the acquisition fundamental and unprecedented information. Measurements can be taken both by specific ground support equipment placed inside the vacuum facility and by dedicated sensors and subsystems installed on the CTP, providing a completely new set of data never obtained before. CTP is constituted of a 6U primary structure hosting the EP system, representative CubeSat avionics and batteries. For the first test campaign, CTP hosts the ambipolar plasma propulsion system, called Regulus and developed by T4I. After the integration and the functional test in laboratory environment, CTP + Regulus performed a Test campaign in relevant environment in the vacuum chamber at CISAS, University of Padua. This paper is focused on the test campaign description and the main results achieved at different power levels for different duration of the firings.