Sudden Release Research Articles

Modelling 3D force-free neutron star magnetospheres

ABSTRACT Magnetars exhibit a variety of transient high-energy phenomena in the form of bursts, outbursts, and giant flares. It is a common belief that these events originate in the sudden release of magnetic energy due to the rearrangement of a twisted magnetic field. We present global models of a 3D force-free (FF) non-linear twisted magnetar magnetosphere. We solve the FF equations following the Grad–Rubin approach in a compactified spherical domain. Appropriate boundary conditions are imposed at the surface of the star for the current distribution and the magnetic field. Our implementation is tested by reproducing various known analytical as well as axisymmetric numerical results. We then proceed to study general 3D models with non-axisymmetric current distributions, such as fields with localized twists that resemble hotspots at the surface of the star, and we examine characteristic quantities such as energy, helicity, and twist. Finally, we discuss implications on the available energy budget, the surface temperature, and the diffusion time-scale, which can be associated with observations.

Photomechanical Motions in Organoboron-Based Phosphorescent Molecular Crystals Driven by a Crystal-State [2 + 2] Cycloaddition Reaction.

Photoluminescent molecular crystals integrated with the ability to transform light energy into macroscopic mechanical motions are a promising choice of materials for both actuating and photonic devices. However, such dynamic photomechanical effects, based on molecular organoboron compounds as well as phosphorescent crystalline materials, are not yet known. Here we present an intriguing example of photomechanical molecular single crystals of a newly synthesized organoboron containing Lewis acid-base molecular adduct (BN1, substituted triphenylboroxine and 1,2-di(4-pyridyl)ethylene) having a capsule shape molecular geometry. The single crystals of BN1 under UV light exhibit controllable rapid bending-shape recovery, delamination, violent splitting-jumping, and expanding features. The detailed structural investigation by single-crystal X-ray diffraction and 1H NMR spectroscopy reveals that the photosalient behavior of the BN1 single crystals is driven by a crystal-to-crystal [2 + 2] cycloaddition reaction, supported by four donor-acceptor type B←N bonds. The instant photomechanical reaction in the BN1 crystals occurs under UV on account of sudden release of stress associated with the strained molecular geometry, significant solid-state molecular movements (supramolecular change), and cleavage of half intermolecular B←N linkages to result in a complete photodimerized single-crystalline product via the existence of two other intermediate photoproducts. In addition, the BN1 crystals display short-lived room temperature phosphorescence, and the photodynamic events are accompanied by the enhancement of their phosphorescence intensity to yield the photoproduct. Interestingly, the molecular crystals of the final photoproduct polymerize at ambient conditions when recrystallized from the solution forming a 2D supramolecular crystalline polymer stabilized by the retention of all B←N coordination modes.

F3‐functionalized nanoscale metal–organic frameworks for tumor‐targeting combined chemotherapy and chemodynamic therapy

AbstractNanoscale metal–organic frameworks (nMOFs) have attracted much attention as emerging porous materials as drug delivery carriers. Appropriate surface modification of them can greatly improve stability and introduce biocompatibility and cancer targeting functionality into drug delivery systems. Herein, we prepared nano‐sized MIL‐101(Fe)‐N3 and loaded anticancer drug doxorubicin (DOX) into it. The synthetic polymer layer Alkyne‐PLA‐PEG was then attached to the F3 peptide (labeled as Alkyne‐PLA‐PEG‐F3), and the surface of DOX/MIL‐101(Fe)‐N3 was covalently modified with it to obtain DOX/MIL‐101‐PLA‐PEG‐F3. Nano‐sized MIL‐101(Fe)‐N3 has high drug loading capacity and the modification of MIL‐101(Fe)‐N3 by polymer Alkyne‐PLA‐PEG not only improved the dispersion, but also avoided the sudden release of the drugs and increased the biocompatibility of nanocarriers. The F3 peptide introduced into the nanocarriers also enabled it to specifically target tumor tissues and achieved active targeted drug delivery. As a nucleolin‐mediated endocytosis drug delivery system, DOX/MIL‐101‐PLA‐PEG‐F3 can not only deliver anticancer drugs to tumors accurately, but also participate in Fenton‐like reaction to generate hydroxyl radicals (•OH) for chemodynamic therapy (CDT), thus enabling combination therapy. It holds great promise as drug candidates to reduce systemic toxicity and improve the efficacy of cancer treatment.

Supercritical carbon dioxide assisted synthesis of ultra-stable sulfur/carbon composite cathodes for Li– S batteries

To mitigate the shuttle effect and enhance the electrical conductivity in lithium battery cathode, the unique characteristics of supercritical CO2 solvent (SC–CO2) and the distinctive porous and layered microstructure of reduced graphene oxide (rGO) are exploited in the fabrication of a high-performance rGO/sulfur composite cathode. Exploiting SC-CO2 technology can realize highly efficient sulfur transfer and precise microstructure regulation of S/C composite cathodes for Li–S batteries. On exposure, due to the sudden pressure release process, the SC-CO2 expands the interlayers of rGO rendering plenty of storage space for small sulfur allotropes in carbon matrices which increases the active sulfur loading. Being a remarkable hydrophobic solvent, the wetting properties of SC-CO2 are excellent, ensuring sulfur dissolution and penetration deep into the voids and interlayers of rGO. This creates intimate contact of sulfur with rGO interlayers, guaranteeing precise sulfur content, uniform sulfur distribution, and strong interaction between sulfur and carbon leading to enhanced electrical conductivity and sulfur utilization efficiency. Another important feature is that the S/C composites can be prepared at room temperature, unlike other conventional techniques which require a higher temperature. Moreover, the product mixture can be separated simply by de-pressuring SC-CO2. Herein, the rGO/sulfur composite cathode prepared on a lab scale showed an initial discharge capacity of 1024 mAh/g at 0.1C rate with capacity retention of 92.2% and coulombic efficiency of 99% even after 200 charge-discharge cycles. The developed cells showed excellent performance (929 mAh/g at 1 C rate) with an ultralow decay of 0.04% per cycle even after 200 charge-discharge cycles. Through this work, we believe that the synergistic effect of SC-CO2 technology and rGO as sulfur host will open up a promising future for the synthesis of efficient S/C composite cathodes with ultra-high cycling stability.

Abstract 12919: Stress Induced Cardiomyopathy After the Covid-19 Vaccine

Introduction: The SARS-CoV-2 virus has potential to cause acute and long-term cardiac effects. The vaccines were developed to prevent severe illness, but there are concerns about vaccine related side effects. Specific to the heart there have been case reports of mRNA vaccine related cardiomyopathies, particularly myocarditis. We present a case of a patient with presumptive stress induced cardiomyopathy in the setting of recent Covid-19 mRNA vaccination. Case Presentation: A 93-year-old female with a past medical history of hypertension presented with worsening shortness of breath and bilateral lower extremity edema. She received her second dose of the Covid-19 mRNA vaccine five days prior to presentation. She had no history of heart disease, was a nonsmoker, and denied alcohol or drug use. In the ED she was noted to be fluid-overloaded, and her CT chest showed minimal coronary calcification and bilateral pleural effusions. She was admitted for heart failure exacerbation and started on IV furosemide. Her transthoracic echocardiogram showed an ejection fraction of 40-45%. The pattern of left ventricular dysfunction was consistent with stress induced cardiomyopathy with apical akinesis and basal sparing of the left ventricular wall segments. Cardiology was consulted and recommended management with diuretics and beta blocker. She had a diuresis of 5 liters during her hospitalization. At clinic follow-up, dyspnea had improved, and her peripheral edema had resolved. Repeat echocardiogram showed recovery of left ventricular ejection fraction to 61% by Simpsons biplane technique with no regional wall motion abnormalities. Further cardiac assessment to evaluate for obstructive coronary artery disease and myocarditis was discussed and offered to the patient but was declined due to her positive response to conservative management. Discussion: The precise etiology of stress induced cardiomyopathy is unknown, but it is thought to be secondary to the sudden release of stress hormones. There are isolated reports of stress induced cardiomyopathy associated with Covid-19 vaccination, but the potential mechanism is unclear. An improved understanding of the potential effects of mRNA vaccines may help guide decisions regarding future booster vaccinations.

3D printed biodegradable multifunctional implants for effective breast cancer treatment

By carefully controlling the dose administered and the drug release rate from drug-eluting implants, safety and efficacy of the therapeutic agent dispensed can be improved. The present work focuses on the promising advantages of 3D Bioprinting process in developing two layers’ implantable scaffolds. The two layers have different functions, in order to ensure a more effective and synergistic breast cancer therapy. First layer involves use of polymers such as Poly- ε-Caprolactone (PCL) and Chitosan (CS), and incorporation of 5-Fluorouracil (5-FU). The aim of the first layer is releasing the drug within 4 weeks, obtaining a prolonged and modified release. According to in vitro drug release tests performed, ∼32 % of 5-FU was released after one month, after an initial burst effect of 17.22 %. The sudden release of the drug into the body would quickly reach an effective therapeutic concentration, while the drug sustained release maintains an effective therapeutic concentration range during the administration time. The second layer is made exclusively from PCL as polymeric matrix, into which Gold Nanoparticles (AuNPs) were subsequently loaded, and its main purpose is to be radiation enhancement. The long biodegradation time of PCL would make the non-soluble scaffold an alternative to conventional chemotherapy, optimizing drug release to the specific needs of the patients.

POLLEN INDUCED ANAPYLAXIS THROUGH SKIN ABRASION

<h3>Introduction</h3> Anaphylaxis is an acute, potentially lethal, multisystem syndrome resulting from the sudden release of mast cell- and basophil-derived mediators into the circulation. We present an unusual case of anaphylaxis to pollen exposure through abraded skin secondary to a skateboard accident. <h3>Case Description</h3> A 19- year-old women with past medical history of mild allergic rhinitis treated with OTC antihistamines as needed had a skate board accident that led to large abrasion" road rash" on the right posterior thigh and buttocks. She notices the abrasion occurred on ground where there was a significant degree of pollen dust which contaminated her abrasion significantly. One hour later, she developed diffuse urticaria, dyspnea and wheezing. She went to emergency room and was treated with epinephrine intramuscular injection, methylprednisolone, diphenhydramine IV and albuterol. She was admitted overnight for observation with no biphasic reaction. No clear source for the anaphylaxis was immediately noted as there had been no new foods, medications, insect sting or history of exercise induced anaphylaxis. On subsequent evaluation she was found to have markedly elevated timothy grass pollen IgE (96.7 kU/L) known to be pollinating at the time. <h3>Discussion</h3> Grass pollens hypersensitivity is common allergic rhinitis trigger, however, anaphylaxis from exposure via a skin abrasion is not reported to the best of our knowledge. We would like to draw attention that grass pollen sensitization as a potential source of anaphylaxis following exposure to the blood stream via significant abraded skin.

Revealing Crustal Deformation and Strain Rate in Taiwan Using InSAR and GNSS

AbstractInterseismic deformation describes the gradual accumulation of crustal strain within the tectonic plate and along the plate boundaries before the sudden release as earthquakes. In this study, we use 5 years of high spatial and temporal geodetic measurements, including Global Navigation Satellite System and Interferometric Synthetic Aperture Radar to monitor 3‐dimension interseismic crustal deformation and horizontal strain rate in Taiwan. We find significant deformation (strain rate &gt;8 10−6 yr−1) along the plate boundary between the Philippine Sea and the Eurasian Plates in east Taiwan. The high strain rate in the southern part of the Western Foothills is distributed along a few major fault systems, which reveals the geometry of the deformation front in west Taiwan. Our results help identify active faults in southwest and north Taiwan that were not identified before. These findings can be insightful in informing future seismic hazard models.

Political spending, related voluntary disclosure, and the cost of public debt

Following the Supreme Court decision in the Citizens United v. Federal Election Commission case of 2010, which removed restrictions in relation to firms’ political spending, and building on the growing debate over whether voluntary political spending disclosure (VPSD) provides valuable information, we examine the effect of political spending on the cost of public debt and the role of VPSD on this effect. Based on a measure of VPSD that became available in 2012 and a large dataset on US firms’ actual political spending, manually extracted from different filings, we provide novel evidence that, in the post-Supreme Court decision period, political spending increases the cost of public debt. This is consistent with the uncertainty associated with political spending. Moreover, we find that the level of voluntary disclosure weakens the positive association between political spending and the cost of public debt. These results hold across multiple specifications as well as when we use a sudden release of firms’ political spending as an exogenous shock to political spending.

Spatio-temporal changes in degassing behavior at Stromboli volcano derived from two co-exposed SO2 camera stations

Improving volcanic gas monitoring techniques is central to better understanding open-vent, persistently degassing volcanoes. SO2 cameras are increasingly used in volcanic gas studies, but observations are commonly limited to one single camera alone viewing the volcanic plume from a specific viewing direction. Here, we report on high frequency (0.5 Hz) systematic measurements of the SO2 flux at Stromboli, covering a 1-year long observation period (June 2017-June 2018), obtained from two permanent SO2 cameras using the same automated algorithm, but imaging the plume from two different viewing directions. Our aim is to experimentally validate the robustness of automatic SO2 camera for volcano monitoring and to demonstrate the advantage of using two co-exposed SO2 camera stations to better capturing degassing dynamics at open-vent volcanoes. The SO2 flux time-series derived from the two SO2 camera stations exhibit good match, demonstrating the robustness of the automatic SO2 camera method. Our high-temporal resolution SO2 records resolve individual Strombolian explosions as transient, repetitive gas bursts produced by the sudden release of over pressurized gas pockets and scoriae. Calculations show that explosive degassing activity accounts for ∼10% of the total SO2 emission budget (dominated by passive degassing) during mild regular open-vent activity. We show that the temporal variations of the explosive SO2 flux go in tandem with changes in total SO2 flux and VLP seismicity, implicating some commonality in the source processes controlling passive degassing and explosive activity. We exploited the spatial resolution of SO2 camera to discriminate degassing at two distinct regions of the crater area, and to minimize biases due by the station position respect to the target plume. We find that the SO2 fluxes from southwest-central (SWCC) and northeast (NEC) crater areas oscillate coherently but those from the NEC are more sensitive to the changes in the volcanic intensity. We interpret this as due to preferential gas/magma channeling into the structurally weaker north-eastern portion of the crater terrace in response to increasing supply rate of buoyant, bubble-rich magma in the shallow plumbing system.

The morphology and stratification of giant eddy bars reflect the variation in shape of palaeoflood hydrographs: A flume study

AbstractEvidence for ungauged large freshwater palaeofloods in valley‐confined landscapes frequently includes giant flow‐eddy bars, deposited in alcoves along the floodway margins. Elevations of the bar tops commonly are used to define the minimum water level for computational flood simulations. Field study has shown that giant bar stratigraphy and sedimentology can be distinctive; identifying the alluvial signature of large palaeofloods where the morphological evidence may be less clear. However, whether the shape and stratigraphy of eddy bars provide indicators as to the nature of the floodwaves has not been considered widely. Flood hydrographs might be dam‐break surge waves, gradually varied, or steady flows, for example. Yet, if bar form and stratigraphy vary systematically with the nature of the flood wave, then bars have additional value in defining the style of unrecorded floodwaves for environmental interpretation and flood modelling purposes.An experimental water flume was used to reproduce three styles of scaled floodwave that might be associated with sudden and more protracted releases of water from upstream reservoirs. Discharge was through a channel consisting of a series of contractions and expansions. Eddy bars were deposited within the flow separation zones that formed at each flow expansion. The basic hydraulic characteristics of the floodwaves were recorded and the form of the bars and the stratigraphy were examined.The results indicate that each style of flood deposited a distinctive barform and related stratigraphy. In this manner, we demonstrate that the examination of the form and stratification of giant bars in the natural environment can provide information on the style of the palaeoflood – sudden release or protracted flow – that was responsible for the deposition of the bars. Such information assists with the identification and interpretation of the nature and source of the floodwater as well as informing attempts to model hydrograph shapes.

Reliability‐based design of transmission and anchorage lengths in prestressed concrete elements

AbstractThis work proposes new reliability‐based formulations for the design of transmission and anchorage lengths in prestressed reinforced concrete, starting from the equations discussed and proposed by fib TG2.5 “Bond and Material Models.” To this end, an extensive experimental dataset with more than 900 results was collected from the scientific literature. Then, two deterministic models were proposed, one for the transmission and one for the anchorage length. For each, model uncertainty was evaluated, and then a probabilistic calibration of their distributions was carried out, separating the cases when sudden or gradual prestress release was applied. Then, probabilistic models were developed for transmission and anchorage length evaluation, depending on the prestress release method: from them, it was possible to evaluate suitable coefficients to target varying reliability indexes. Particularly, two design situations were considered, for transverse stresses verification at the Serviceability Limit State (SLS) and shear and anchorage verification at the Ultimate Limit State (ULS). Lastly, the reliability of current deterministic models was verified.

Thermal energy storage for increased waste heat recovery at a silicon production plant in Norway

• Case study of a heat recovery system in a Norwegian silicon production plant. • Novel field of application for Ruths steam accumulator. • Combined approach of techno-economic optimization and dynamic system simulation. • Thermal storage increases annual electricity production by up to 500 MW h. • Public funds required to achieve desirable payback periods. The production of silicon is an energy-intensive process, which requires high temperatures. Sudden release of high-temperature gas to the exhaust system is an inevitable part of silicon furnace operation and causes strong fluctuations in the waste heat recovery system. This makes waste heat recovery challenging and leads to frequent throttling of the produced steam reducing the efficiency of the system. To avoid this throttling and thus increase system efficiency, retrofitting a thermal energy storage to the existing waste heat recovery system is analyzed for a silicon production plant in Norway. A steam accumulator installed in parallel to existing bypasses, which does not interfere with the existing waste heat recovery system, is found to be ideally suited for the case. The analysis is carried out using real plant data, which is used to calibrate a dynamic simulation model modelled in the Modelica language. Design parameters of the steam accumulator are identified based on economic optimizations and their performance is verified with the dynamic simulation model. The simulation results shows that the simplifications in the economic optimizations are acceptable and that storage sizes of less than 10 m 3 can lead to annual profits of around 23 k€. Investment costs excluding transport and on-site installation are around 120 k€, yielding payback times from three to six years, depending on public funds. Including transport and on-site installation increases the payback times to about seven to ten years. The integration of a storage of this size was deemed realistic by the plant operators. The results will therefore be used for the creation of a business case with a more detailed cost analysis.

Push-and-release tests of a steel building with hybrid base isolation

Experimental testing of a two-storey 5875 square meters steel braced-frame structure resting on a reinforced concrete slab isolated from the foundations through a hybrid system (28 high-damping rubber bearings and 36 low-friction sliding bearings) is presented. The building incorporates a push-and-release device to evaluate its actual global dynamic response up to displacement amplitudes induced by extreme seismic events, allowing test repetitions during its service life. The testing set up and the experimental campaign, consisting of quasi-static push tests (slow loading and unloading) and push-and-release dynamic tests (slow loading and subsequent sudden release), are described. The experimental results have peculiarities related to the building (structural typology and size, foundation geometry on a steep slope, presence of the push-and-release device for future additional tests), the magnitude of the maximum horizontal displacement never achieved before (285 mm and 227 mm in the quasi-static and dynamic tests, respectively), the global and local monitored parameters (horizontal and vertical displacements, strains, accelerations, in addition to environmental conditions) providing a comprehensive insight into the behaviour of the hybrid isolation system and superstructure.

Study on release and occurrence of typical metals in corrosion products of drinking water distribution systems under stagnation conditions.

Metal contaminants in corrosion products of drinking water distribution systems (DWDS) can be released into potable water under specific conditions, thereby polluting drinking water and posing a health risk. Under stagnation conditions, the release characteristics, occurring forms, and environmental risks of ten metals were determined in loose and tubercle scale solids of an unlined cast iron pipe with a long service history, before and after immersion. Most Al, As, Cr, Fe, and V in corrosion scales existed in the residual fraction, with the released concentration and pollution risk being low. Since more than 59% of Ca in pipe scales existed in the exchangeable fraction, Ca release was high. Although the Pb and Cd content of corrosion solids was low, a high proportion of Pb and Cd was present in non-residual fractions with high mobility. Sudden severe Pb or Cd pollution events in DWDS could result in high pollution and environmental risk levels. The total content and released amount of Mn and Zn in corrosion scales were both high. Therefore, while special attention should be paid to Mn and Zn, Pb and Cd also present a high risk in pipe scales, despite their low concentrations. During stagnation immersion, metal release from powdered pipe scales occurred via the processes of mass release, re-adsorption into scales, and slow release until equilibrium was reached. The levels of metal re-adsorption into scales were much higher than the concentrations dissolved into bulk water. However, the amount of metal re-adsorption into tubercle scale blocks was less. Importantly, these findings highlight that during DWDS operation, the sudden release of metal pollutants caused by pipe scale breakage should be avoided.

Polylactic acid/silk fibroin composite hollow fibers as excellent controlled drug release systems

AbstractPolylactic acid (PLA) and silk fibroin (SF) have been widely used in biomedical applications because of their excellent biocompatibility and degradability. In this study, PLA and SF were used as raw materials to prepare hollow fibers with a skin‐core structure by wet spinning technology. Scanning electron microscopy observations revealed that the structure of hollow fibers became increasingly uniform with increasing silk fibroin mass fraction. Tensile test results showed that with the increase of silk fibroin content, the elastic modulus of hollow fibers decreased and their tensile properties improved. The results of hollow fibers degradation experiments revealed that increasing the content of silk fibroin can effectively shorten the degradation time of hollow fibers. Ultraviolet spectrophotometry was used to measure the absorbance of tetracycline hydrochloride in phosphate buffer saline and calculate its release rate in hollow fibers with different silk fibroin contents, the result is HFs‐9 &gt; HFs‐7 &gt; HFs‐0 &gt; HFs‐5 &gt; HFs‐3. The PLA/SF controlled drug release system has precise controlled release of the drug, realizes the separation of the drug from the controlled release system, and solves the problem of sudden drug release. In addition, the controlled release system is non‐toxic, degradable, and has excellent mechanical properties.

An insect larvae inspired MXene-based jumping actuator with controllable motion powered by light

Many creatures in nature can carry objects to precisely jump, however, this is difficult to achieve in untethered artificial soft robots. Here, by mimicking the latching mechanism of the insect larva jumping, an untethered MXene-based soft actuator with adjustable jumping motion controlled by light is designed. The actuator prepared by the large size MXene nanosheets and polymer has an original closed rolled structure with an adhesive coating serving as a latch, which perfectly simulates the formed loop of the insect larva before jumping. Under light, due to the storage and sudden release of light-driven elastic energy caused by the latch, the actuator produces jumping motion. More importantly, by regulating irradiation angle to locally irradiate the actuator, it can generate elastic forces in different directions, realizing different jumping motions including high jump and long jump. Moreover, the actuator’s ability to carry a load for high jump under light is also demonstrated.

Real World Management of Anaphylaxis Versus the National Institute for Health and Clinical Excellence (NICE) Guidelines.

Objectives Anaphylaxis is an acute, life-threatening immediate allergic reaction caused by the sudden systemic release of mediators from mast cells. This study aims to assess the current practice of emergency management of children and adults diagnosed with anaphylaxis at the Royal Hospital, Muscat, Oman, in line with the National Institute for Health and Clinical Excellence (NICE) guidelines. MethodsThis is an observational retrospective study of all anaphylaxis cases seen at the emergency department (ED) from January 2013 to January 2018 and compared with the management of anaphylaxis in the ED as per the NICE guidelines. Inclusion criteria were all patients, children (age 16 and below), and adults diagnosed with anaphylaxis based on the World Allergy Organization (WAO) criteria. Exclusion criteria are all cases labeled as anaphylaxis that did not match the WAO criteria for anaphylaxis.ResultsOf 100 patients with a preliminary diagnosis of anaphylaxis, 49 patients (49%) were true-anaphylaxis cases based on the WAO definition 16 were children (age 16 years and below), and 33 were adults ( age 16 years and above). The other 51 patients (51%) with misdiagnosed anaphylaxis were later diagnosed with spontaneous urticaria, septic shock, vocal cord dysfunction, severe asthma, and anxiety attack. All 49 patients with true-anaphylaxis appropriately received adrenaline intramuscularly at the ED. All 16 children were admitted, seen by an allergist, and received an adrenaline auto-injector when indicated. Only 5 of the 33 adults were admitted and seen by an allergist, and 4 of those required an adrenaline auto-injector upon discharge. The remaining 28 adults were discharged from the ED, and only 3 of these were referred to the allergist. None received an adrenaline auto-injector upon discharge from the ED, and no mention in the ED notes on patient education regarding allergen avoidance.ConclusionThird of the patients who presented to ED were children (<16 years), and two third were adults. Insect venom was the main reason for anaphylaxis in both age groups. There was an underutilization of adrenaline auto-injector prescriptions for adult patients. This could be very well improved by disseminating policies and guidelines to adult physicians.

Numerical study on the shock evolution and the spontaneous ignition of high-pressure hydrogen during its sudden release into the tubes with different angles

High-pressure hydrogen storage is one of the best choices of hydrogen storage at present and in the future. However, the spontaneous ignition of high-pressure hydrogen release blocks its wide application. This paper further studies the shock evolution, temperature accumulation and spontaneous ignition inside the tubes with different angles by employing LES, RNG and EDC models, 10-step like opening process of burst disk and detailed hydrogen/air combustion mechanism. Four tubes with different angles (60, 90, 120 and 150°) are employed based on the previous experimental result. It is found that the smaller the angle of the tube, the greater the maximum pressure and temperature of the first shock reflection zone. And the maximum pressure and temperature of the second shock reflection zone is the highest inside the 90° angle tube. This is due to two shock reflection mechanisms inside the tubes: in acute angle tube, only the reflected hemispherical shock hits the inner wall of the tube corner, however, for non-acute tubes, both the reflected hemispherical shock and reflected normal shock hit the inner wall of the tube corner. In addition, it requires a longer time and a further distance to initiate the spontaneous ignition inside the tubes with larger angle. And the flame induced by the spontaneous ignition could move upstream steadily inside the 60° angle tube and the flame length increases with the release time to a maximum value of 21.44 mm.

Development of pH-sensitive biomaterial-based nanocomposite for highly controlled drug release

Combining non-toxic biomaterials to obtain high effective hybrids is a promising approach in medicine and drug delivery. This study aims to combine the biomaterial with different swelling behavior to attain high controlled release. Hydroxyapatite (HA) nanoparticles do not possess swelling properties and are stable in different pH solutions. HA was used to prevent the unwanted sudden release in acidic media by modifying the swelling properties of chitosan-based hydrogels (CTS). CTS being soluble in acidic pHs causes drug release as it dissolves, resulting in burst release behavior. The experiments confirmed that the introduction of HA remarkably reduced the swelling ratio, which independent of the pH led to a decrease in the release amount (approximately 38–73%) and prevented the burst release. The metronidazole-loaded CTS/MMt/HA1 with low content HA showed a high sustained pH-responsive release. However, the metronidazole-loaded CTS/MMt/HA2 with high content of HA didn't show sustained release. Indeed, the release rate was sustained by modifying the HA content. The kinetic investigations indicated the release mechanisms were changed from dissolution in CTS/MMt to diffusion in CTS/MMt/HA by introducing HA, which is compatible with the swelling ratio reduction. As well as CTS/MMt, HA grafted samples showed high encapsulation efficiency (>96%) and pH-sensitive properties. The biocompatibility of Metronidazole-loaded nanocomposites was confirmed by the cytotoxicity tests on the human nasopharyngeal carcinoma L929 cells.