Optical Imaging Approaches to Monitor Static and Dynamic Cell‐on‐Chip Platforms: A Tutorial Review

Miniaturized laboratories on chip platforms play an important role in handling life sciences studies. The platforms may contain static or dynamic biological cells. Examples are a fixed medium of an organ‐on‐a‐chip and individual cells moving in a microfluidic channel, respectively. Due to feasibility of control or investigation and ethical implications of live targets, both static and dynamic cell‐on‐chip platforms promise various applications in biology. To extract necessary information from the experiments, the demand for direct monitoring is rapidly increasing. Among different microscopy methods, optical imaging is a straightforward choice. Considering light interaction with biological agents, imaging signals may be generated as a result of scattering or emission effects from a sample. Thus, optical imaging techniques could be categorized into scattering‐based and emission‐based techniques. In this review, various optical imaging approaches used in monitoring static and dynamic platforms are introduced along with their optical systems, advantages, challenges, and applications. This review may help biologists to find a suitable imaging technique for different cell‐on‐chip studies and might also be useful for the people who are going to develop optical imaging systems in life sciences studies.     

Implementation of design of experiments approach for the micronization of a drug with a high brittle–ductile transition particle diameter

Objective: To optimize air-jet milling conditions of ibuprofen (IBU) using design of experiment (DoE) method, and to test the generalizability of the optimized conditions for the processing of another non-steroidal anti-inflammatory drug (NSAID).

Methods: Bulk IBU was micronized using an Aljet mill according to a circumscribed central composite (CCC) design with grinding and pushing nozzle pressures (GrindP, PushP) varying from 20 to 110?psi. Output variables included yield and particle diameters at the 50th and 90th percentile (D₅₀, D₉₀). Following data analysis, the optimized conditions were identified and tested to produce IBU particles with a minimum size and an acceptable yield. Finally, indomethacin (IND) was milled using the optimized conditions as well as the control.

Results: CCC design included eight successful runs for milling IBU from the ten total runs due to powder “blowback” from the feed hopper. DoE analysis allowed the optimization of the GrindP and PushP at 75 and 65?psi. In subsequent validation experiments using the optimized conditions, the experimental D₅₀ and D₉₀ values (1.9 and 3.6?μm) corresponded closely with the DoE modeling predicted values. Additionally, the optimized conditions were superior over the control conditions for the micronization of IND where smaller D₅₀ and D₉₀ values (1.2 and 2.7?μm vs. 1.8 and 4.4?μm) were produced.

Conclusion: The optimization of a single-step air-jet milling of IBU using the DoE approach elucidated the optimal milling conditions, which were used to micronize IND using the optimized milling conditions.     

A new newsvendor policy model for dual-sourcing supply chains by considering disruption risk and special order

Newsvendor model is one of the most important issues in inventory models. In this paper, we investigate a newsvendor model without lead time, which have difference between distributer and wholesale/retailer. At the end of day, the residual products of newsvendor sold to a secondary market at a unit salvage value. Also, the amount of orders that cannot be met, should be paid the penalty for each unit. In addition, in each one of channels, the percent of these orders cannot be met by the distributer. Then, the newsvendor provides the difference between the amount that ordered to distributor and the amount that met in the occurrence of interruptions risk as a special order from the manufacturer, more expensive than the price of distributor. The limitations of the study are the procurement budget that used for special order. Finally, the model is applied in a real case as a numerical example to determine order amount that maximize profit and is solved by Maple 15. The Kuhn–Tucker method was used to illustrate the optimal points that have necessary condition. Also, the hessian matrix was used to illustrate the optimal points that have sufficient condition for optimization. Consequently, the considered points are global optimum. The main factor in the disruption risk that effect on the ordering amount and profit, are including the probability of appearing of disruption \((p_i)\) and a percent of ordering amount which are met in the case of appearing of disruption \((y_i)\). Therefore, the analysis of sensitivity has been done on two parameters of \(p_i\) and \(y_i\) by using contour curves. According to result of solved problem, the change of disruption appearance reduced. Finally, the proposed method besides being simple is so exact which is sensible in the solved problems.     

Drought Occurrence Probability Analysis Using Multivariate Standardized Drought Index and Copula Function Under Climate Change

This study aims to investigate the effect of climate change on the probability of drought occurrence in central Iran. To this end, a new drought index called Multivariate Standardized Drought Index (MSDI) was developed, which is composed of the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Soil Moisture Index (SSI). The required data included precipitation, temperature (from CRU TS), and soil moisture (from the ESA CCA SM product) on a monthly time scale for the 1980–2016 period. Moreover, future climate data were downloaded from CMIP6 models under the latest SSPs-RCPs emission scenarios (SSP1-2.6 and SSP5-8.5) for the 2020–2056 period. Based on the normalized root mean square error (NRMSE), Cramer-von mises statistic (S_n), and Nash Sutcliffe (NS) evaluation criteria, the Galambos and Clayton functions were selected to derive copula-based joint distribution functions in both periods. The results showed that more severe and longer droughts will occur in the future compared to the historical period and in particular under the SSP5-8.5 scenario. From the derived joint return period, a drought event with defined severity or duration will happen in a shorter return period as compared with the historical period. In other words, the joint return period indicated a higher probability of drought occurrence in the future period. Moreover, the joint return period analysis revealed that the return period of mild droughts will remain the same, while it will decrease for extreme droughts in the future.

     

Comparison of pH-dependent sonodisruption of re-assembled casein micelles by 35 and 130 kHz ultrasounds

Sonodisruption behavior of re-assembled casein micelles was compared at two ultrasound frequencies (35 and 130 kHz) by turbidity measurement and laser-diffraction based particle size analysis. Sonochemical ultrasound (130 kHz) was more effective than power ultrasound (35 kHz) in micelle disruption. This was attributed to the higher strain rates generated upon implosion of cavities, as well as the liberation of more free radicals to the surrounding medium. The higher the pH of solution, the more effective was the ultrasonic disruption due to a looser expanded assembly of particles at higher pH values. Sonochemical ultrasound decreased the consistency coefficient of casein solutions and increased their flow index except at a pH value of 6.35, while power ultrasound did not affect the flow behavior of solutions across the whole pH range.     

Compression and impact testing of two-layer composite pyramidal-core sandwich panels

Quasi-static uniform compression tests and low-velocity concentrated impact tests were conducted to reveal the failure mechanisms and energy absorption capacity of two-layer carbon fiber composite sandwich panels with pyramidal truss cores. Three different volume-fraction cores (i.e., with different relative densities) were fabricated: 1.25%, 1.81%, and 2.27%. Two-layer sandwich panels with identical volume-fraction cores (either 1.25% or 2.27%), and also stepwise graded panels consisting of one light and one heavy core, were investigated under uniform quasi-static compression. Under quasi-static compression, load peaks were identified with complete failure of individual truss layers due to strut buckling or strut crushing, and specific energy absorption was estimated for different core configurations. In the impact test, the damage resulting from low-velocity concentrated impact was investigated. Our results show that compared with glass fiber woven textile truss cores, two-layer carbon fiber composite pyramidal truss cores have comparable specific energy absorptions, and thus could be used in the development of novel light-weight multifunctional structures.     

Hydrothermal synthesis of Pt/MWCNTs nanocomposite electrocatalysts for proton exchange membrane fuel cell systems

A hydrothermal method for preparation of size-controlled Pt nanoparticles dispersed highly on multiwalled carbon nanotubes (Pt/MWCNTs) has been studied to optimize the effective parameters (temperature, time, pH and stirring rate) using Taguchi method. The synthesized Pt/MWCNTs nanocomposite samples were characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray fluorescence (XRF) analyses to identify mean Pt nanoparticles size and Pt content. The analysis of the primary experimental data and demonstration of the main effect trend of each parameter showed that a reaction temperature of about 140 °C, a reaction period of 5 h, a slightly basic reaction pH (∼9) and a stirring rate of 500 rpm are the optimum process conditions which give a low mean Pt nanoparticles size (2.8 nm) and a high Pt content (19.4 wt.%) simultaneously. Cyclic voltammetry (CV) analysis showed that under optimum conditions the synthesized sample gives a specific surface area of 99 m² g⁻¹. Obtaining the polarization curves for the two fabricated membrane electrode assemblies (MEAs) using the optimized catalyst and a commercial Pt/C catalyst (10 wt.%, Aldrich) with Pt loading of 0.4 mg cm⁻² demonstrated that the catalyst prepared under optimum conditions shows a considerably better performance.     

Isotropic-kinematic cyclic hardening characteristics of plate steels

Cyclic hardening of metals is considered as one of the most important features that affects extremely the hysteresis behavior of steel structures. One approach to study this characteristic is dividing it into two components, including isotropic hardening and kinematic hardening, and defining any of these components for any type of metals by calibrated data obtained from experiments. However, the lack of these calibrated data on metals, restricts this approach. Therefore, in this paper the isotropic and kinematic characteristics of five different steel grades from 100 to 485 MPa, under various strain ranges between ±1 and ±7% were proposed. Afterwards, four of these five grades were validated in order to find the appropriate combination of data for any of them, and to compare the result of this approach with those obtained from a well-known hardening model, Ramberg-Osgood. The results showed the high accuracy of the isotropic-kinematic hardening model in comparison to the Ramberg-Osgood method.     

ZnO nanoparticles induced effects on nanomechanical behavior and cell viability of chitosan films

The aim of this paper is to develop novel chitosan–zinc oxide nanocomposite films for biomedical applications. The films were fabricated with 1, 5, 10 and 15% w/w of zinc oxide (ZnO) nanoparticles (NPs) incorporated with chitosan (CS) using a simple method. The prepared nanocomposite films were characterized using atomic force microscopy, Raman and X-ray diffraction studies. In addition, nano and micro mechanical properties were measured. It was found that the microhardness, nanohardness and its corresponding elastic modulus increased with the increase of ZnO NP percentage in the CS films. However, the ductility of films decreased as the percentage of ZnO NPs increased. Cell attachment and cytotoxicity of the prepared films at days two and five were evaluated in vitro using osteoblasts (OBs). It was observed that OB viability decreased in films with higher than 5% ZnO NPs. This result suggests that although ZnO NPs can improve the mechanical properties of pure CS films, only a low percentage of ZnO NPs can be applied for biomedical and bioengineering applications because of the cytotoxicity effects of these particles.