Experimental Parameters Research Articles

Impingement of a liquid jet on an opposing gas jet

In contrast to the existing research on the liquid jet colliding with a physical target to produce a single type of liquid sheet or bell, we used an opposing gas jet target to generate a series of diverse shapes of axisymmetric liquid films. Specifically, we experimentally investigated the outcome of a 0.4-mm diameter water jet impinging on an opposing gas jet of 0.3 mm initial diameter. Five different axisymmetric film shapes are identified for the experimental parameters explored in this work, and the momentum flux ratio (X) of the gas jet to the water jet is the dictating factor for the exact film shape: (i) X = 0: smooth bells that share the same shape and profile model with classic water bells of a liquid jet impacting a solid target. (ii) 0 < X < 0.4: crumpled bells being lifted off from the gas nozzle by a thin layer of squeezing gas flow that is quantifiable by the lubrication model. (iii) 0.4 < X < 0.9: transient bells with mildly wrinkled surfaces that undergo periodic cycles from closure to bursting at a gas Reynolds number of ∼2400. (iv) 0.9 < X < 1.4: turbulent parachutes with curved and rough shapes. (v) X > 1.4: turbulent sheets that are flattened and atomized by the relatively strong gas stream. This work demonstrated that an opposing gas jet is a simple yet versatile approach to achieving a rich collection of phenomena by diverting the liquid jet momentum in multiple ways. This investigation aims to explore and rationale the rich phenomenology of water bells resulting from the impingement of a water jet on a gaseous jet target.

Dynamic Fabrication of Porous Polymeric Coating for Efficient Passive Daytime Radiative Cooling using In-Situ Pore-Formation Strategy

Porous polymeric material has emerged as promising choice for making passive daytime radiative cooling (PDRC) emitter. However, it is still an unmet challenge to establish a flexible method to achieve dynamic pore-formation for the purpose of studying the relationships between the porous structure and the resultant cooling performance. The current study reports a novel strategy to construct asymmetric multi-layered porous structure in situ within the matrix of pre-formed polystyrene coating. The modified procedure of inverse emulsion - breath figure method is adopted, and solvent-nonsolvent exchanging process is also involved during the pore-formation process, leading to the formation of hierarchical porous structure with rather high porosity. Geometrical features of the generated pores are effectively regulated by simple adjustment of the experimental parameters of the water ratio of the emulsion and the humidity. The relationship between the pore structure and optical & cooling properties has been established based on experimental facts. By tuning of optimal conditions, the in-situ pore-formation can endow the polymeric coating with high solar reflectance (∼85 %) and infrared emittance (∼98.4 %), resulting in passive temperature drop of 12 °C and cooling power of 91 W/m2. This study provides experimental information to get some insight into the designing principle of porous polymeric PDRC materials, and formulates unique strategy of in-situ functionalization via structural transformation upon polymeric objects or devices.

THERMODYNAMIC PROPERTIES OF TERNARY LIQUID MIXTURE OF TOCOPHEROL ACETATE WITH CHLOROFORM AND DIETHYL ETHER AT 293 K

The reported study, measured the ultrasonic velocity (u), density (ρ) and viscosity (η) of ternary liquid mixtures of α-Tocopherol acetate with chloroform and diethyl ether in the concentration range (0 to 0.1 M) at 293K. These experimental parameters can be used to calculate various thermodynamic parameters like free volume (Vf), internal pressure (πin), Vander-Wall Constant (b) and Gibbs free energy (∆G*) etc. to identify the strength of molecular interaction. The results so obtained support the formation of complex structure and molecular aggregation through intermolecular hydrogen bonding in the ternary liquid system of α -Tocopherol acetate with chloroform and diethyl ether.

Hot deformation behavior and processing map of vanadium particles reinforced AZ31 composite

The vanadium particles reinforced AZ31 matrix composite (VP/AZ31) was prepared using the powder metallurgy method. Subsequently, hot deformation behavior of VP/AZ31 composite was studied through hot compression trials. The experimental parameters were set in a temperature range of 250–400 °C and a strain rate range of 0.001–1 s−1. Based on the experimental results, a strain-compensated Arrhenius constitutive model was developed to accurately forecast the flow behavior of VP/AZ31 composite. Moreover, the thermal activation energy was calculated to be 138.605 kJ/mol and the processing map was delineated according to the dynamic material model theory. The processing map revealed that the optimal processing area existed under 363–400 °C/0.001–0.004 s−1, where the efficiency of power dissipation exceeded 23 %. Notably, the highest efficiency of power dissipation occurred at 400 °C/1 s−1, which exceeded 30 %. Under these conditions, dynamic recrystallization (DRX) was sufficiently developed, indicating the enhancement of workability. It is estimated that the instability region for VP/AZ31 composites occurred within the conditions of 250–325 °C/0.16–1 s−1, characterized by crack formation. The DRX of VP/AZ31 composite is predominantly governed through the mechanism of discontinuous DRX (DDRX).

Large Language Model-Based AI Agent for Organic Semiconductor Devices Research.

Large language models (LLMs) have attracted widespread attention recently, however, their application in specialized scientific fields still requires deep adaptation. In this work, we designed an artificial intelligence (AI) agent for organic field effect transistors (OFETs) by integrating the GPT-4 model with well-trained machine learning (ML) algorithms. It can efficiently extract the experimental parameters of OFETs from scientific literature and reshape them into a structured database, achieving precision and recall rates both exceeding 92%. Combined with well-trained ML models, this AI agent can further provide targeted guidance and suggestions for device design. With prompt engineering and human-in-loop strategies, the agent extracted sufficient information of 709 OFETs from 277 research articles across different publishers and gathered them into a standardized database containing more than 10000 device parameters. Using this database, we trained a ML model based on XGBoost for device performance judgment. Combined with the interpretation of the high-precision model, the agent has provided a feasible optimization scheme that has tripled the charge transport properties of DP-DTT OFETs. Our work is an effective practice of LLMs in the field of organic optoelectronic devices and expands the research paradigm of organic optoelectronic materials and devices. This article is protected by copyright. All rights reserved.

Eccentrically compressed behavior of UHPC columns considering the P-delta effect

Eccentric compression is a critical behavior observed in arches and columns, particularly in structures constructed with ultra-high performance concrete (UHPC). Compared to normal concrete structures, those made with UHPC exhibit distinct behaviors that need to be clearly investigated. This study comprehensively investigates UHPC columns under eccentric compression load through experimental study and theoretical analysis. Various experimental parameters, including slenderness ratio, eccentricity distance, fiber content, and stirrup ratio, were examined across 26 UHPC columns. Failure modes were evaluated using digital image correlation (DIC) methods. The load-displacement responses indicated that slender columns subjected to significant eccentricity exhibited load decreases during yielding stages, whereas short columns experienced load increases. This discrepancy in yielding stages was attributed to P-delta effects. In addition, theoretical models were developed to determine the ultimate bearing capacity of columns experiencing compression-controlled and tension-controlled failures, considering the P-delta effect caused by the different slenderness ratios. The moment magnifying coefficients for UHPC were calibrated based on theoretical analyses of the limit curvature of eccentric compression members. The proposed theoretical models agreed well with the experimental results, with an average ratio of 1.02. The second-order effect for the case of UHPC short column with a slenderness ratio of 5 can be ignored as per Eurocode 2, which is less than 10 % of the corresponding first-order effect.

Asymmetric CapMix Device Exploiting Functionalized Graphene Oxide and SPEEK Coatings for Improved Energy Harvesting From Salinity Gradients

AbstractThis work investigated the possibility of using functionalized graphene oxide and sulfonated poly(ether ether ketone) coatings on activated carbons to obtain an asymmetric device suitable for Capacitive Mixing (CapMix) application. Herein the synthesis and fabrication procedures of both materials and electrodes are reported, together with a comprehensive list of electrochemical characterization techniques. The results from the electrochemical characterization are used to design the optimal operational parameters for CapMix experiments involving the materials being studied. A homemade cell is designed and fabricated for CapMix application by polymer micromachining. Electrochemical tests are conducted to optimize the process parameters and the results of this optimization are reported, proving that both the materials and the process parameters play a key role in CapMix. The final device can generate a net power output of 12 mW m−2 by mixing simulated seawater and freshwater. This result paved the way for further application of graphene oxide in the field of renewable energy.

Single-Step Fabrication of Highly Tunable Blazed Gratings Using Triangular-Shaped Femtosecond Laser Pulses.

Blazed gratings are periodic surface structures of great interest for applications such as friction control, light trapping, and spectrometry. While different laser processing methods have been explored to produce these elements, they have not yet surpassed conventional surface manufacturing techniques, often based on lithography processes or mechanical ruling. This work introduces a new approach based on the combination of ultrashort pulses and triangular beam shaping, which enables the generation of asymmetrical grooves in a single step. The main advantage of this strategy is that by simply changing the laser processing direction we can induce a significant modification in the ratio of asymmetry between the sidewall angles of the machined channels. The paper includes a comprehensive study, which has been supported by statistical tools, of the effect of this and other experimental parameters on the morphology of grooves machined on stainless steel. As a result, we achieved a wide range of geometries, with asymmetry ratios spanning from 1 to 5 and channel depths between 3 and 15 µm. Furthermore, we demonstrate the validity of the approach through the successful manufacture of blazed gratings of various slopes. The results reflect the versatility and cost-efficiency of the proposed fabrication strategy, and thus its potential to streamline the production of sawtooth gratings and other devices that are based on asymmetrical features.

A novel organoselenium-based Schiff base for selective separation of copper and zinc from food samples using ultrasonic-assisted solidified floating organic drop microextraction strategy

Herein, we document the development of a novel organoselenium-based Schiff base, 2-((4-((2-hydroxy-4-nitrobenzylidene)amino)phenyl)selanyl)-N-phenylacetamide (HOASe), to selectively separate zinc and copper from food samples. To the best of our knowledge, OSe compound has never been used in microextraction procedures before, until today. HOASe was synthesized from aniline by a simple four-step procedure. The structure of HOASe was elucidated by various spectroscopic techniques (e.g., IR, MS, 1H- and 13C NMR). After that, HOASe was used to extract Cu2+ and Zn2+ by ultrasonic-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic drop (UA-DLLME-SFOD) combined with flame atomic absorption spectrometry. Important experimental parameters including amount of the extraction solvent, initial pH, amount of HOASe, ultrasonication time, centrifugation, and salt addition, were studied and optimized to offer quantitative separation of the analytes. The detection limits and the linear ranges for Cu2+ and Zn2+ were 1.9, 8.0 – 400.0, and 2.4, 6 – 150 μg L-1, respectively. The method's greenness and applicability were assessed using the Analytical GREEnness metric methodology and the Blue Applicability Grade Index, respectively. Finaly, this approach was used for quantification of Cu2+ and Zn2+ in food samples and, therefore, can be further developed for food safety and quality control programs.

Aerosol trace element solubility determined using ultrapure water batch leaching: an intercomparison study of four different leaching protocols

Abstract. Solubility of aerosol trace elements, which determines their bioavailability and reactivity, is operationally defined and strongly depends on the leaching protocol used. Ultrapure water batch leaching is one of the most widely used leaching protocols, while the specific leaching protocols used in different labs can still differ in agitation methods, contact time, and filter pore size. It is yet unclear to which extent the difference in these experimental parameters would affect the aerosol trace element solubility reported. This work examined the effects of agitation methods, filter pore size, and contact time on the solubility of nine aerosol trace elements and found that the difference in agitation methods (shaking vs. sonication), filter pore size (0.22 vs. 0.45 µm), and contact time (1 vs. 2 h) only led to small and sometimes insignificant difference in the reported solubility. We further compared aerosol trace element solubility determined using four ultrapure water leaching protocols, which are adopted by four different labs and vary in agitation methods, filter pore size, and/or contact time, and observed good agreement in the reported solubility. Therefore, our work suggests that although ultrapure water batch leaching protocols used by different labs vary in specific experimental parameters, the determined aerosol trace element solubility is comparable. We recommend that ultrapure water batch leaching be one of the reference leaching schemes and emphasize that additional consensus in the community on agitation methods, contact time, and filter pore size is needed to formulate a standard operating procedure for ultrapure water batch leaching.

A framework for the biophysical screening of antibody mutations targeting solvent-accessible hydrophobic and electrostatic patches for enhanced viscosity profiles

The formulation of high-concentration monoclonal antibody (mAb) solutions in low dose volumes for autoinjector devices poses challenges in manufacturability and patient administration due to elevated solution viscosity. Often many therapeutically potent mAbs are discovered, but their commercial development is stalled by unfavourable developability challenges. In this work, we present a systematic experimental framework for the computational screening of molecular descriptors to guide the design of 24 mutants with modified viscosity profiles accompanied by experimental evaluation. Our experimental observations using a model anti-IL8 mAb and eight engineered mutant variants reveal that viscosity reduction is influenced by the location of hydrophobic interactions, while targeting positively charged patches significantly increases viscosity in comparison to wild-type anti-IL-8 mAb. We conclude that most predicted in silico physicochemical properties exhibit poor correlation with measured experimental parameters for antibodies with suboptimal developability characteristics, emphasizing the need for comprehensive case-by-case evaluation of mAbs. This framework combining molecular design and triage via computational predictions with experimental evaluation aids the agile and rational design of mAbs with tailored solution viscosities, ensuring improved manufacturability and patient convenience in self-administration scenarios.

Measurement of the double-layer capacitance of Pt(111) in acidic conditions near the potential of zero charge

Quantifying the charge density stored at the Pt(111)/aqueous interface using the double-layer capacitance close to the potential of zero charge (Cdl,PZC) at 0.30 VNHE is of critical importance to elucidating the structure of the electrical double layer (EDL) in the absence of any competing adsorption processes. Marked discrepancies in the values of Cdl for this interface exist in the literature, which we show are likely attributable to the measurement technique used. To directly observe the predicted Gouy-Chapman capacitance minimum at the PZC in the double-layer window between 0.40-0.55 VRHE, anomalously low electrolyte concentrations (0.1 mM HClO4) are needed. The measurement of accurate values of Cdl,PZC is made highly non-trivial by the extremely large solution resistances (∼80-100 kΩ) measured in this required dilute electrolyte as well as the non-negligible deviations from ideal capacitive behaviour (i.e., constant phase element behaviour) displayed even by this well-ordered model electrochemical system. We provide here a comparison between using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and alternating current-cyclic voltammetry (AC-CV) in determining Cdl,PZC for the Pt(111)/HClO4 interface, for different concentrations of the electrolyte. In particular, even when using optimized experimental parameters, we show that the estimated values of Cdl,PZC at 0.1 mM HClO4 still display a marked discrepancy depending on the technique used, ranging from 27-41 μF cm−2. At higher HClO4 concentrations, the discrepancies are much less pronounced. Importantly, however, the measured deviation from Gouy-Chapman theory, as quantified by the Parsons-Zobel plot slope, remains consistent across these techniques, implying that the EDL structure of the Pt(111)/aqueous interface continues to prove anomalous and enigmatic.

Identifiability of spatiotemporal tissue perfusion models

Objective. Standard models for perfusion quantification in DCE-MRI produce a bias by treating voxels as isolated systems. Spatiotemporal models can remove this bias, but it is unknown whether they are fundamentally identifiable. The aim of this study is to investigate this question in silico using one-dimensional toy systems with a one-compartment blood flow model and a two-compartment perfusion model. Approach. For each of the two models, identifiability is explored theoretically and in-silico for three systems. Concentrations over space and time are simulated by forward propagation. Different levels of noise and temporal undersampling are added to investigate sensitivity to measurement error. Model parameters are fitted using a standard gradient descent algorithm, applied iteratively with a stepwise increasing time window. Model fitting is repeated with different initial values to probe uniqueness of the solution. Reconstruction accuracy is quantified for each parameter by comparison to the ground truth. Main results. Theoretical analysis shows that flows and volume fractions are only identifiable up to a constant, and that this degeneracy can be removed by proper choice of parameters. Simulations show that in all cases, the tissue concentrations can be reconstructed accurately. The one-compartment model shows accurate reconstruction of blood velocities and arterial input functions, independent of the initial values and robust to measurement error. The two-compartmental perfusion model was not fully identifiable, showing good reconstruction of arterial velocities and input functions, but multiple valid solutions for the perfusion parameters and venous velocities, and a strong sensitivity to measurement error in these parameters. Significance. These results support the use of one-compartment spatiotemporal flow models, but two-compartment perfusion models were not sufficiently identifiable. Future studies should investigate whether this degeneracy is resolved in more realistic 2D and 3D systems, by adding physically justified constraints, or by optimizing experimental parameters such as injection duration or temporal resolution.

β-Aminopropionitrile Induces Distinct Pathologies in the Ascending and Descending Thoracic Aortic Regions of Mice.

β-aminopropionitrile (BAPN) is a pharmacological inhibitor of LOX (lysyl oxidase) and LOXLs (LOX-like proteins). Administration of BAPN promotes aortopathies, although there is a paucity of data on experimental conditions to generate pathology. The objective of this study was to define experimental parameters and determine whether equivalent or variable aortopathies were generated throughout the aortic tree during BAPN administration in mice. BAPN was administered in drinking water for a period ranging from 1 to 12 weeks. The impacts of BAPN were first assessed with regard to BAPN dose, and mouse strain, age, and sex. BAPN-induced aortic pathological characterization was conducted using histology and immunostaining. To investigate the mechanistic basis of regional heterogeneity, the ascending and descending thoracic aortas were harvested after 1 week of BAPN administration before the appearance of overt pathology. BAPN-induced aortic rupture predominantly occurred or originated in the descending thoracic aorta in young C57BL/6J or N mice. No apparent differences were found between male and female mice. For mice surviving 12 weeks of BAPN administration, profound dilatation was consistently observed in the ascending region, while there were more heterogeneous changes in the descending thoracic region. Pathological features were distinct between the ascending and descending thoracic regions. Aortic pathology in the ascending region was characterized by luminal dilatation and elastic fiber disruption throughout the media. The descending thoracic region frequently had dissections with false lumen formation, collagen deposition, and remodeling of the wall surrounding the false lumen. Cells surrounding the false lumen were predominantly positive for α-SMA (α-smooth muscle actin). One week of BAPN administration compromised contractile properties in both regions equivalently, and RNA sequencing did not show obvious differences between the 2 aortic regions in smooth muscle cell markers, cell proliferation markers, and extracellular components. BAPN-induced pathologies show distinct, heterogeneous features within and between ascending and descending aortic regions in mice.

Extractive Mass Transfer of Zr(IV) into a Hydrophobic Ionic Liquid Medium Containing Diglycolamide Extractant: Solvent Extraction and Spectroscopic Analysis.

Solvent extraction of Zr(IV) in ionic liquid (IL) medium is less known and Zr(IV) - IL chemistry indeed needs exploration to realize the coordination approach of Zr(IV) in IL phase. In view of this, in the present work, a strongly hydrophobic imidazolium based IL: 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mim][NTf2]) as the medium containing a diglycolamide (DGA) extractant: N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) was opted to understand the extraction behavior of Zr(IV) from nitric acid medium. Different experimental parameters such as the concentration of initial nitric acid, initial feed metal concentration, equilibration time and ligand concentration were tuned to unravel the extraction efficiency of the proposed IL phase towards Zr(IV). The extraction scenario was completely dependent on the hydrophobicity of IL diluent and increasing extraction trend with an increase in feed acidity along with the coordination of two TODGA molecules ensured Zr(IV) - complex formation in a neutral solvation mechanistic pathway. The extraction trend of Zr(IV) was compared with molecular diluent (n-dodecane (n-DD)) containing TODGA and a phase modifier: N,N-dihexyloctanamide (DHOA). The coordination aspect of Zr(IV) with ligand in IL phase was ascertained spectroscopically to validate Zr(IV) loading in IL phase. Thermodynamics of Zr(IV) extraction revealed the nature of the extraction process and the complex formation.

Synthesis, XRD/HSA-interactions, synthon, TD-DFT/optical analysis, docking and antibacterial evaluation of two (±)-Isoflavonoid derivatives

A high-yield synthesis of the new racemic (±)-2-(1-bromoethyl)-7‑methoxy-3-(4-methoxyphenyl)-4H-chromen-4-one was achieved in two steps by O- and 2-C-methylation 7,4′-dihydroxy-2-methylisoflavone, followed by radical bromination of the allylic methylene moiety using N-bromosuccinimide. XRD-crystallography, NMR, UV–vis CHN-EA, and FT-IR were all used to establish the identity and structure of the target ligand. Both the XRD, Hirshfeld surface area (HSA) and the DFT structural optimization validated the (±)‑bromo-chromen-4-one structural formula. XRD analysis reveals two types of synthons due to the presence of multiple short interactions, including CMe-H.....Br/Cph-H.....O and H…πCC. There is a high harmony between the experimental XRD-structural parameters and their DFT counterparts; additionally, the optical characteristics were derived by comparing the experimental UV–Vis result to the TD-DFT/B3LYP and TD-DFT/CAM-B3LYP ones. The compounds capacity to bind to DNA was assessed via the molecular docking technique with the use of 1BNA. The antibacterial activity of the produced (±)‑bromo-chroman-4-one and (±)-the non bromo‑chroman-4-one derivatives was evaluated against eight bacterial strains.

Mathematical Modeling of The Estimate of Methane Gas Generation, of The Organic Fraction Of Msw From The Agreste Alagoano Sanitary Landfill, From Standard Data And Experimental Data

Objective: The objective of this study is to carry out mathematical modeling in the generation of methane gas, through two mathematical models, using standard data and data obtained in the laboratory. Theoretical framework: The emission of methane gas, generated by the decomposition of solid waste in landfills, is one of the serious problems of air pollution and one way to minimize the impacts of methane on the environment is through its use to generate energy. To this end, there are ways to estimate the generation of CH4 during the useful life of the landfill. Method: For modeling, the computer programs of LandGEM and the Intergovernmental Panel on Climate Change (IPCC) were used to carry out the theoretical estimate of CH4 production during the useful life of the Agreste Alagoano landfill in two scenarios: one with standard program values for the local climate region and another with information obtained from experimental data from research by Santana (2022). Results and Discussion: When standard input data was adopted, the LandGEM model presented a 38% higher value in CH4 production compared to the IPCC model. When considering input data obtained experimentally, the IPCC showed CH4 generation 32.66% higher than the LandGEM, this was possible due to the COD value that was high as a result of the L0 of the organic fraction, exceeding the theoretical value of 0.15 to the experimental value of 0.27 in the new scenario. Implications of the research: Determining parameters for modeling methane gas generation will help in managing landfill waste and its energy recovery potential, in addition to the application of mathematical models for estimating biogas production potential as tools essential for both energy and environmental studies. Originality/value: This research presents as originality the determination of experimental parameters applied to the mathematical modeling of methane gas generation in landfills in the rural region, since studies on modeling in landfills with the climatic conditions of the rural region of Brazil are not common in the literature.

PVDF membranes for membrane distillation prepared by VIPS – A combined study of artificial water channel effectiveness and membrane performance prediction

Background A combined VIPS-NIPS technique was used to investigate the potential of self-supporting flat-sheet polyvinylidene fluoride (PVDF) membranes containing amphiphilic I-quartet Artificial Water Channels (AWC) for Direct Contact Membrane Distillation (DCMD). The AWC are formed in situ by self-assembly of HC6 molecules upon contact with water during membrane formation. Methods A Design of Experiment (DoE) was used to investigate the influence of various experimental parameters and their interactions on membrane performance, namely polymer and AWC concentrations in the dope solution, relative humidity and duration of the VIPS treatment. Pure water permeability (PWP), Liquid Entry Pressure (LEP) and DCMD flux were used to characterize membrane performance. A Response Surface Methodology (RSM) was used to evaluate the DoE results and a second order model was fitted. Based on the model predictions several multiple response-optimized (MRO) membranes were prepared. Results The performance improvement of the MRO membranes was 7.0 times for PWP (M-T4) and 3.3 times for MD flux (M-T3) over the average performance of the DoE membranes, while maintaining LEP of 1.9 bar and Salt rejection of 99.9%. In addition, hybrid PVDF/HC6 MRO membranes improved PWP by 3.2 times and MD flux by 1.6 times over pure PVDF MRO membranes. Conclusions DoE in conjunction with RSM enabled the prediction of membrane PWP, LEP and MD flux performance by varying the levels of the experimental parameters within predefined limits. The HC6 additive improves PWP and MD flux without loss of LEP or selectivity. HC6 promotes the formation of porous skin and asymmetric cross-sections with finger-like structures. Probably by affecting diffusion during phase separation due to its amphiphilic properties.

Not All Arms of IgM Are Equal: Following Hinge-Directed Cleavage by Online Native SEC-Orbitrap-Based CDMS.

Immunoglobulins M (IgM) are key natural antibodies produced initially in humoral immune response. Due to their large molecular weights and extensive glycosylation loads, IgMs represent a challenging target for conventional mass analysis. Charge detection mass spectrometry (CDMS) may provide a unique approach to tackle heterogeneous IgM assemblies, although this technique can be quite laborious and technically challenging. Here, we describe the use of online size exclusion chromatography (SEC) to automate buffer exchange and sample introduction, and demonstrate its adaptability with Orbitrap-based CDMS. We discuss optimal experimental parameters for online SEC-CDMS experiments, including ion activation, choice of column, and resolution. Using this approach, CDMS histograms containing hundreds of individual ion signals can be obtained in as little as 5 min from single injections of <1 μg of sample. To demonstrate the unique utility of online SEC-CDMS, we performed real-time kinetic monitoring of pentameric IgM digestion by the protease IgMBRAZOR, which cleaves specifically in the hinge region of IgM. Several digestion intermediates corresponding to processive losses of F(ab')2 subunits could be mass-resolved and identified by SEC-CDMS. Interestingly, we find that for the J-chain linked IgM pentamer, cleavage of one of the F(ab')2 subunits is much slower than the other four F(ab')2 subunits, which we attribute to the symmetry-breaking interactions of the J-chain within the pentameric IgM structure. The online SEC-CDMS methodologies described here open new avenues into the higher throughput automated analysis of heterogeneous, high-mass protein assemblies by CDMS.

Investigation of flashover occurrence criterion based on thermal equilibrium theory

Flashover is the rapid transition to a state of total surface involvement in a fire of combustible material within an enclosure fire, which is the most serious and fatal event in building fires. Although previous studies have provided quantitative and qualitative standards for flashover, the criteria of flashover were normally based on the independent measurement of experimental parameters and phenomena rather than the underlying physical reasons, resulting in a lack of mutual relationships between these criteria and the inability to reflect physical mechanisms. Moreover, the flashover criteria vary for different compartment fire fuels, which directly affects the calculation of compartment fire theory. This work was performed to provide a unified principle on the criteria of flashover based on the thermal equilibrium theory. The critical conditions for flashover are quantitatively developed by establishing a partial differential equation for the energy generation rate and energy loss rate with respect to the temperature inside the compartment. Moreover, based on the partial differential equation, inequalities were established for the relationship between the temperature of the hot gas and the heat flux of the floor at the onset of flashover, which was validated by the compartment experiment data. It was found that due to differences in emissivity and net heat transfer rate, at the onset of flashover, the hot gas temperature and the radiation heat flux at the floor were different for different fuels, and a high hot gas temperature does not necessarily indicate a high radiation heat flux at the floor.