Interactions of brain, blood, and CSF: a novel mathematical model of cerebral edema

Background Previous models of intracranial pressure (ICP) dynamics have not included flow of cerebral interstitial fluid (ISF) and changes in resistance to its flow when brain swelling occurs. We sought to develop a mathematical model that incorporates resistance to the bulk flow of cerebral ISF to better simulate the physiological changes that occur in pathologies in which brain swelling predominates and to assess the model’s ability to depict changes in cerebral physiology associated with cerebral edema. Methods We developed a lumped parameter model which includes a representation of cerebral ISF flow within brain tissue and its interactions with CSF flow and cerebral blood flow (CBF). The model is based on an electrical analog circuit with four intracranial compartments: the (1) subarachnoid space, (2) brain, (3) ventricles, (4) cerebral vasculature and the extracranial spinal thecal sac. We determined changes in pressure and volume within cerebral compartments at steady-state and simulated physiological perturbations including rapid injection of fluid into the intracranial space, hyperventilation, and hypoventilation. We simulated changes in resistance to flow or absorption of CSF and cerebral ISF to model hydrocephalus, cerebral edema, and to simulate disruption of the blood–brain barrier (BBB). Results The model accurately replicates well-accepted features of intracranial physiology including the exponential-like pressure–volume curve with rapid fluid injection, increased ICP pulse pressure with rising ICP, hydrocephalus resulting from increased resistance to CSF outflow, and changes associated with hyperventilation and hypoventilation. Importantly, modeling cerebral edema with increased resistance to cerebral ISF flow mimics key features of brain swelling including elevated ICP, increased brain volume, markedly reduced ventricular volume, and a contracted subarachnoid space. Similarly, a decreased resistance to flow of fluid across the BBB leads to an exponential-like rise in ICP and ventricular collapse. Conclusions The model accurately depicts the complex interactions that occur between pressure, volume, and resistances to flow in the different intracranial compartments under specific pathophysiological conditions. In modelling resistance to bulk flow of cerebral ISF, it may serve as a platform for improved modelling of cerebral edema and blood–brain barrier disruption that occur following brain injury.

Multimodal Freezing System for Cryogenic 3D Printing

Cryogenic 3D Printing (Cryo-3DP) creates 3D objects by deposition-then-freezing of aqueous solutions of various materials layer-by-layer. The process generally takes place at the temperature ranging from -20 °C to -25°C. At the beginning of the process, cryo-3DP demands a high cooling rate to reduce the work envelope’s temperature rapidly. After the work envelope reaches the working temperature (-20 to -25°C), lower cooling rates are enough. The proposed multimodal freezing system uses two modes of cooling. Rapid injection of the CO2 gas in the chamber is suitable for achieving high cooling rates (0.5 °Cs-1) initially and Vapor Compression Refrigeration (VCR) for sustained heat removal from the system (0.5 °Cmin-1). The results show that the proposed multimodal system performs faster than the conventional system.

Development and Application of Rapid Injection Molds Using Aluminum-Filled Epoxy Resins for Metal Injection Molding

Metal injection molding (MIM) is a near net-shape manufacturing process combing conventional plastic injection molding and powder metallurgy. Two kinds of injections molds for MIM were developed using conventional mold steel and aluminum (Al)-filled epoxy resins in this study. The characteristics of the mold made by rapid tooling technology (RTT) were evaluated and compared to that fabricated conventional machining method through MIM process. It was found that the service life of the injection mold fabricated by Al-filled epoxy resins is about 1300 molding cycles. The saving in manufacturing cost of an injection mold made by Al-filled epoxy resins is about 30.4% compared to that fabricated conventional mold steel. The saving in manufacturing time of an injection mold made by RT technology is about 30.3% compared to that fabricated conventional machining method.

Injectable poly(γ-glutamic acid)-based biodegradable hydrogels with tunable gelation rate and mechanical strength

Polypeptide-based hydrogels have potential applications in polymer therapeutics and regenerative medicine. However, designing reliable polypeptide-based hydrogels with a rapid injection time and controllable stiffness for clinical applications remains a challenge....

Ultra Rapid and Highly Sensitive Disperser-less Liquid-liquid Microextraction of Organophosphate Pesticides Prior to Gas Chromatography with Mass Spectrometry Detection

Background: Organophosphates (OPPs) are toxic chemicals that can cause serious health problems through poisoning water and food. Objectives: A very simple and fast disperser-less liquid microextraction strategy before chromatographic detection was designed for the analysis of organophosphates in various water solutions. Methods: A 60 µL aliquot of chloroform, as extraction solvent (without using disperser), was introduced into the sample solution by rapid injection, and the sedimented organic phase was analyzed to assay some organophosphates. Results: Analytical characteristics, including limits of detection (0.0003 - 0.001 µg.L-1), linear dynamic ranges (0.001 - 100 µg.L-1), relative standard deviations (2.5 - 10), enrichment factors (up to 238), and extraction recoveries (84% - 108%), indicated the high efficacy of the developed method for analyzing the target analytes. Conclusions: The proposed procedure was effectively used for the analysis of the OPPs in real tap water, river water, and fruit juice samples. In the present study, the examined analytes were in the range of 0.07 - 1.56 µg.L-1.

Are single-lumen 5Fr and triple-lumen 6Fr PICCs suitable for hemodynamic assessment by trans-pulmonary thermodilution? A pilot study

Background Single-lumen 4Fr or double-lumen 5Fr power injectable peripherally inserted central catheters (PICCs) are not accurate for trans-pulmonary thermodilution (TPTD), since they overestimate cardiac index and other TPTD-derived parameters when compared with centrally inserted central catheters (CICCs) because of the smaller size of their lumen. We hypothesize that PICCs with larger lumen size may be reliable for the cardiac index assessment using the TPTD. Methods This is a single-centre, prospective method–comparison study that included adult patients admitted in ICU who required a calibrated Pulse Contour hemodynamic monitoring system (VolumeView/EV1000™) for circulatory shock and had both PICC and CICC in place. We compared TPTD measurements via single-lumen 5Fr or triple-lumen 6Fr polyurethane power injectable PICCs with triple-lumen 7Fr CICC (reference standard). To rule out biases related to manual injection, measurements were repeated using an automated rapid injection system. We performed Bland–Altman analysis accounting for multiple observations per patient. Results A total of 320 measurements were performed in 15 patients. During the manual phase, the cardiac index measured with either single-lumen 5Fr or triple-lumen 6Fr PICCs were comparable with cardiac index measured with triple-lumen 7Fr CICC (3.2 ± 1.04 vs. 3.2 ± 1.06 L/min/m2, bias 2.2% and 3.3 ± 0.8 vs. 3.0 ± 0.7 L/min/m2, bias 8.5%, respectively). During the automated phase, triple-lumen 6Fr PICC slightly overestimated the cardiac index when compared to triple-lumen 7Fr CICC (CI 3.4 ± 0.7 vs. 3.0 ± 0.7 L/min/m2, bias 12.5%; p = 0.012). For both single-lumen 5Fr and triple-lumen 6Fr PICCs, percentage error vs. triple-lumen 7Fr CICC was below 20% (14.7% and 19% during the manual phase and 14.4% and 13.8% during the automated phase, respectively). Similar results were observed for TPTD-derived parameters. Conclusions During hemodynamic monitoring with TPTD, both single-lumen 5Fr PICCs and triple-lumen 6Fr PICCs can be used for cold fluid bolus injection as an alternative to CICC (ClinicalTrials.gov NCT04241926).

Relativistic electron acceleration at Saturn and Jupiter by global scale electric fields

<p>Electrons in Saturn's radiation belts are distributed along discrete energy bands, a feature often attributed to the energisation of charged particles following their rapid injection towards a planet's inner magnetosphere. However, the mechanism that could deliver electrons deep into Saturn's radiation belts remains elusive, as for instance, the efficiency of magnetospheric interchange injections drops rapidly for electrons above 100 keV and at low L-shells. Using Cassini measurements and simulations we demonstrate that the banding derives from slow radial plasma flows associated to a persistent convection pattern in Saturn's magnetosphere (noon to midnight electric field), making the need for rapid injections obsolete. This transport mode impacts electron acceleration throughout most the planet's radiation belts and at quasi and fully relativistic energies, suggesting that this global scale electric field is ultimately responsible for the bulk of the highest energy electrons near the planet. We also present evidence from Galileo and Juno that the influence of Jupiter's inner magnetospheric convection pattern on its radiation belts is fundamentally similar to Saturn's but affects its higher energy ultra-relativistic electrons. The comparison of the two radiation belts indicates there is an energy range above which there is a transition from interchange to global scale electric field driven electron acceleration. This transiroty energy range can be scaled by the two planets' magnetic moment and strength of corotation, allowing us to study these two systems in complement.</p>