Rapid Lipid Content Screening in Neochloris oleoabundans Utilizing Carbon-Based Dielectrophoresis

In this study, we carried out a heterogeneous cytoplasmic lipid content screening of Neochloris oleoabundans microalgae by dielectrophoresis (DEP), using castellated glassy carbon microelectrodes in a PDMS microchannel. For this purpose, microalgae were cultured in nitrogen-replete (N+) and nitrogen-deplete (N−) suspensions to promote low and high cytoplasmic lipid production in cells, respectively. Experiments were carried out over a wide frequency window (100 kHz–30 MHz) at a fixed amplitude of 7 VPP. The results showed a statistically significant difference between the dielectrophoretic behavior of N+ and N− cells at low frequencies (100–800 kHz), whereas a weak response was observed for mid- and high frequencies (1–30 MHz). Additionally, a finite element analysis using a 3D model was conducted to determine the dielectrophoretic trapping zones across the electrode gaps. These results suggest that low-cost glassy carbon is a reliable material for microalgae classification—between low and high cytoplasmic lipid content—through DEP, providing a fast and straightforward mechanism.

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Biomass and lipid induction strategies in microalgae for biofuel production and other applications

Microbial Cell Factories ◽

10.1186/s12934-019-1228-4 ◽

2019 ◽

Vol 18 (1) ◽

Cited By ~ 35

Author(s):

Hossein Alishah Aratboni ◽

Nahid Rafiei ◽

Raul Garcia-Granados ◽

Abbas Alemzadeh ◽

José Rubén Morones-Ramírez

Keyword(s):

Lipid Content ◽

Large Scale ◽

Fossil Fuels ◽

Low Cost ◽

Lipid Production ◽

Arable Land ◽

Economic Cost ◽

Biofuel Production ◽

Scale Production ◽

Microalgae Biomass

Abstract The use of fossil fuels has been strongly related to critical problems currently affecting society, such as: global warming, global greenhouse effects and pollution. These problems have affected the homeostasis of living organisms worldwide at an alarming rate. Due to this, it is imperative to look for alternatives to the use of fossil fuels and one of the relevant substitutes are biofuels. There are different types of biofuels (categories and generations) that have been previously explored, but recently, the use of microalgae has been strongly considered for the production of biofuels since they present a series of advantages over other biofuel production sources: (a) they don’t need arable land to grow and therefore do not compete with food crops (like biofuels produced from corn, sugar cane and other plants) and; (b) they exhibit rapid biomass production containing high oil contents, at least 15 to 20 times higher than land based oleaginous crops. Hence, these unicellular photosynthetic microorganisms have received great attention from researches to use them in the large-scale production of biofuels. However, one disadvantage of using microalgae is the high economic cost due to the low-yields of lipid content in the microalgae biomass. Thus, development of different methods to enhance microalgae biomass, as well as lipid content in the microalgae cells, would lead to the development of a sustainable low-cost process to produce biofuels. Within the last 10 years, many studies have reported different methods and strategies to induce lipid production to obtain higher lipid accumulation in the biomass of microalgae cells; however, there is not a comprehensive review in the literature that highlights, compares and discusses these strategies. Here, we review these strategies which include modulating light intensity in cultures, controlling and varying CO2 levels and temperature, inducing nutrient starvation in the culture, the implementation of stress by incorporating heavy metal or inducing a high salinity condition, and the use of metabolic and genetic engineering techniques coupled with nanotechnology.

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Predicting stroke severity with a 3-min recording from the Muse portable EEG system for rapid diagnosis of stroke

Scientific Reports ◽

10.1038/s41598-020-75379-w ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Cassandra M. Wilkinson ◽

Jennifer I. Burrell ◽

Jonathan W. P. Kuziek ◽

Sibi Thirunavukkarasu ◽

Brian H. Buck ◽

...

Keyword(s):

Ischemic Stroke ◽

Low Cost ◽

Minor Stroke ◽

Stroke Severity ◽

Stroke Patients ◽

Low Frequencies ◽

Severe Stroke ◽

High Frequencies ◽

Detection Tool ◽

Record Data

Abstract In this study, we demonstrated the use of low-cost portable electroencephalography (EEG) as a method for prehospital stroke diagnosis. We used a portable EEG system to record data from 25 participants, 16 had acute ischemic stroke events, and compared the results to age-matched controls that included stroke mimics. Delta/alpha ratio (DAR), (delta + theta)/(alpha + beta) ratio (DBATR) and pairwise-derived Brain Symmetry Index (pdBSI) were investigated, as well as head movement using the on-board accelerometer and gyroscope. We then used machine learning to distinguish between different subgroups. DAR and DBATR increased in ischemic stroke patients with increasing stroke severity (p = 0.0021, partial η2 = 0.293; p = 0.01, partial η2 = 0.234). Also, pdBSI decreased in low frequencies and increased in high frequencies in patients who had a stroke (p = 0.036, partial η2 = 0.177). Using classification trees, we were able to distinguish moderate to severe stroke patients and from minor stroke and controls, with a 63% sensitivity, 86% specificity and accuracy of 76%. There are significant differences in DAR, DBATR, and pdBSI between patients with ischemic stroke when compared to controls, and these effects scale with severity. We have shown the utility of a low-cost portable EEG system to aid in patient triage and diagnosis as an early detection tool.

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Rapid Lipid Content Screening in Neochloris Oleoabundans by Carbon-Based Dielectrophoresis

Engineering Proceedings ◽

10.3390/micromachines2021-09605 ◽

2021 ◽

Vol 4 (1) ◽

pp. 41

Author(s):

Cynthia M. Galicia-Medina ◽

Matías Vázquez-Piñón ◽

Sergio Camacho-León ◽

Gibran S. Alemán-Nava ◽

Roberto C. Gallo-Villanueva ◽

...

Keyword(s):

Lipid Content ◽

Lipid Production ◽

Biofuel Production ◽

Neochloris Oleoabundans ◽

Atmospheric Concentration ◽

Machine Material ◽

Fixation Rate ◽

Screening Process ◽

High Lipid

The use of microalgae as a biomass source for biofuel production has drawn the attention of many scientists due to several associated environmental advantages over conventional terrestrial crops, including microalgae growing using wastewaters and a higher CO2 fixation rate, contributing to the reduction of atmospheric concentration. Consequently, a reliable cytoplasmic lipid screening process in microalgae is a valuable asset for harvesting optimization in mass production processes. In this study, the heterogeneous cytoplasmic lipid content of Neochloris oleoabundans was dielectrophoretically assorted in a microfluidic device using castellated carbon microelectrodes. The experiments carried out over a wide frequency window (100 kHz to 30 MHz) at a fixed amplitude of 7 VPP showed a significant contrast between the dielectrophoretic behavior of high lipid content and low lipid content cells at the low frequency range (100–800 kHz). A weak response for the mid and high frequency ranges (1–30 MHz) was also identified for high and low lipid content samples, allowing one to establish an electrokinetic footprint of the studied strain. These results suggest that the development of a reliable screening process for harvesting optimization is possible through a fast and straightforward mechanism, such as dielectrophoresis, which is a low-cost and easy-to-machine material that employs glassy carbon. The experimental setup in this study involved in vitro culturing of nitrogen-replete (N+) and nitrogen-deplete (N-) cell suspensions to promote low and high lipid production in cells, respectively. Cell populations were monitored using spectrophotometry, and the resulting lipid development among cells was quantified by Nile red fluorescence.

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High Frequency Performance of Piezoelectric Diaphragms for Impedance-Based SHM Applications

Engineering Proceedings ◽

10.3390/ecsa-7-08185 ◽

2020 ◽

Vol 2 (1) ◽

pp. 16

Author(s):

Guilherme Rezende ◽

Fabricio Baptista

Keyword(s):

High Frequency ◽

Structural Damage ◽

Low Cost ◽

Low Frequency ◽

Experimental Tests ◽

Piezoelectric Transducers ◽

Low Frequencies ◽

High Frequencies ◽

Electromechanical Impedance ◽

Damage Indices

Piezoelectric transducers are used in a wide variety of applications, including damage detection in structural health monitoring (SHM) applications. Among the various methods for detecting structural damage, the electromechanical impedance (EMI) method is one of the most investigated in recent years. In this method, the transducer is typically excited with low frequency signals up to 500 kHz. However, recent studies have indicated the use of higher frequencies, usually above 1 MHz, for the detection of some types of damage and the monitoring of some structures’ characteristics that are not possible at low frequencies. Therefore, this study investigates the performance of low-cost piezoelectric diaphragms excited with high frequency signals for SHM applications based on the EMI method. Piezoelectric diaphragms have recently been reported in the literature as alternative transducers for the EMI method and, therefore, investigating the performance of these transducers at high frequencies is a relevant subject. Experimental tests were carried out with piezoelectric diaphragms attached to two aluminum bars, obtaining the impedance signatures from diaphragms excited with low and high frequency signals. The analysis was performed using the real part of the impedance signatures and two basic damage indices, one based on the Euclidean norm and the other on the correlation coefficient. The experimental results indicate that piezoelectric diaphragms are usable for the detection of structural damage at high frequencies, although the sensitivity decreases.

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Agricultural biowaste, rice bran, as carbon source to enhance biomass and lipid production: analysis with various growth rate models

Water Science & Technology ◽

10.2166/wst.2020.342 ◽

2020 ◽

Vol 82 (6) ◽

pp. 1120-1130

Author(s):

H. J. Choi

Keyword(s):

Growth Rate ◽

Carbon Source ◽

Rice Bran ◽

Lipid Content ◽

Mass Culture ◽

Low Cost ◽

Lipid Production ◽

Substrate Inhibition ◽

Good Alternative ◽

High Lipid

Abstract As a byproduct of agriculture, rice bran can be a good alternative carbon source to mass-produce microalgae and increase lipid content. The purpose of this study was to investigate the effects of rice bran extract (RBE) on the mass culture and oil content of microalgae. Various parameters were applied to the growth rate model to explain the dynamics of substrate inhibition and growth of microalgae. The rice bran contains 46.1% of carbohydrates, in which is 38.3% glucose, and is very suitable as a carbon source for microalgae growth. The culture with RBE had a four times higher biomass production than microalgae cultured on Jaworski's medium (JM) with a small amount of 1 g/L. In addition, for RBE, the lipid content was three times higher and saturated fatty acid was 3% lower than were those of JM. According to the above results, when Chlorella vulgaris is cultured using RBE, a high amount of biomass and high lipid content can be obtained with a small amount of RBE. RBE is a discarded waste and has a high content of glucose, so it can be replaced by an organic carbon source to increase microbial biomass growth and lipid content at low cost.

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The effect of audio–visual expectancies on stereoacuity

Seeing and Perceiving ◽

10.1163/187847612x647919 ◽

2012 ◽

Vol 25 (0) ◽

pp. 160

Author(s):

Marina Zannoli ◽

Pascal Mamassian

Keyword(s):

Visual System ◽

Sound Source ◽

Binocular Disparity ◽

Frequency Content ◽

High Pitch ◽

Low Frequencies ◽

High Frequencies ◽

Depth Difference ◽

Significant Difference ◽

Do So

Because of greater attenuation of high frequencies, a distant sound carries more low frequencies. As the distance between the listener and a sound source increases, the sound is therefore perceived as having a lower pitch. In the present study, we investigated whether there pre-exists a relationship between depth, as it is perceived by the visual system, and pitch. To do so, we measured stereoacuity (the smallest detectable depth difference that can be seen from binocular disparity). Two lines were presented sequentially at a different depth. Each line was presented along with a beep that lasted as long as the presentation of the line. The two beeps could either have the same pitch or a different pitch associated with the two depths. When the pitch was different, the high pitch could either be associated with the near (congruent with the hypothesis) or the far (incongruent) line. Five participants were asked to determine which line was nearer and instructed not to pay attention to the sound. Results showed no significant difference between the congruent and incongruent sound conditions. However, sensitivity was much better in the two different-pitch conditions compared to the same-pitch condition. In addition, we found no difference between the same-pitch condition and a control condition in which no sound was presented. To conclude, our results suggest that a difference in pitch can improve stereacuity, independent of the frequency content of the sound.

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Glassy Carbon Electrocorticography Electrodes on Ultra-Thin and Finger-Like Polyimide Substrate: Performance Evaluation Based on Different Electrode Diameters

Materials ◽

10.3390/ma11122486 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2486 ◽

Cited By ~ 8

Author(s):

Maria Vomero ◽

Elena Zucchini ◽

Emanuela Delfino ◽

Calogero Gueli ◽

Norma Mondragon ◽

...

Keyword(s):

Glassy Carbon ◽

Photoelectron Spectroscopy ◽

Implantable Devices ◽

Signal Source ◽

Electrode Diameter ◽

Low Frequencies ◽

High Frequencies ◽

X Ray ◽

Polyimide Substrate

Glassy carbon (GC) has high potential to serve as a biomaterial in neural applications because it is biocompatible, electrochemically inert and can be incorporated in polyimide-based implantable devices. Miniaturization and applicability of GC is, however, thought to be partially limited by its electrical conductivity. For this study, ultra-conformable polyimide-based electrocorticography (ECoG) devices with different-diameter GC electrodes were fabricated and tested in vitro and in rat models. For achieving conformability to the rat brain, polyimide was patterned in a finger-like shape and its thickness was set to 8 µm. To investigate different electrode sizes, each ECoG device was assigned electrodes with diameters of 50, 100, 200 and 300 µm. They were electrochemically characterized and subjected to 10 million biphasic pulses—for achieving a steady-state—and to X-ray photoelectron spectroscopy, for examining their elemental composition. The electrodes were then implanted epidurally to evaluate the ability of each diameter to detect neural activity. Results show that their performance at low frequencies (up to 300 Hz) depends on the distance from the signal source rather than on the electrode diameter, while at high frequencies (above 200 Hz) small electrodes have higher background noises than large ones, unless they are coated with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS).

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Squirt-flow seismic dispersion models: a comparison

Geophysical Journal International ◽

10.1093/gji/ggaa274 ◽

2020 ◽

Vol 222 (3) ◽

pp. 2068-2082 ◽

Cited By ~ 1

Author(s):

Yongyang Sun ◽

José M Carcione ◽

Boris Gurevich

Keyword(s):

Aspect Ratio ◽

Pore Space ◽

Crack Density ◽

Fluid Pressure ◽

Porous Rocks ◽

Dispersion Models ◽

Pore Characteristics ◽

Low Frequencies ◽

High Frequencies ◽

Significant Difference

SUMMARY The anelastic properties of porous rocks depend on the pore characteristics, specifically, the pore aspect ratio and the pore fraction (related to the soft porosity). At high frequencies, there is no fluid pressure communication throughout the pore space and the rock becomes stiffer than at low frequencies, where the pore pressure is fully equilibrated. This causes a significant difference between the moduli at low and high frequencies, which is known as seismic dispersion and is commonly explained by the squirt-flow mechanism. In this paper, we consider and contrast three squirt-flow dispersion models: the modified Mavko–Jizba model, valid for a porous medium with arbitrary shapes of the pores and cracks, and two other models, based on idealized geometries of spheres and ellipsoids: the EIAS (equivalent inclusion-average stress) and CPEM (cracks and pores effective medium) models. We first perform analytical comparisons and then compute several numerical examples to demonstrate similarities and differences between the models. The analytical comparison shows that when the stiff pores are spherical and the crack density is small, the theoretical predictions of the three models are very close to each other. However, when the stiff pores are spheroids with an aspect ratio smaller than 1 (say, between 0.2 and 1), the predictions of inclusion based models are not valid at frequencies of ultrasonic measurements on rock samples. In contrast, the predictions of the modified Mavko–Jizba model are valid at ultrasonic frequencies of about 106 Hz, which is a typical frequency of laboratory measurements on core samples. We also introduce Zener-based bulk and shear dispersion indices, which are proportional to the difference between the high- and low-frequency stiffness moduli, and are a measure of the degree of anelasticity, closely related to the quality factors by view of the Kramers–Kronig relations. The results show that the three models yield similar moduli dispersion with very small differences when the crack density is relatively high. The indices versus crack density can be viewed as a template to obtain the crack properties from low- and high-frequency velocity measurements.

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Non-enzymatic determination of purine nucleotides using a carbon dot modified glassy carbon electrode

Analytical Methods ◽

10.1039/c9ay00718k ◽

2019 ◽

Vol 11 (30) ◽

pp. 3866-3873 ◽

Cited By ~ 1

Author(s):

R. Karthikeyan ◽

D. James Nelson ◽

S. Abraham John

Keyword(s):

Glassy Carbon ◽

Low Cost ◽

Phosphate Buffer Solution ◽

Purine Nucleotides ◽

Buffer Solution ◽

Solution Ph ◽

Carbon Dot ◽

Enzymatic Determination ◽

Sensitive Determination

Selective and sensitive determination of one of the purine nucleotides, inosine (INO) using a low cost carbon dot (CD) modified glassy carbon (GC) electrode in 0.2 M phosphate buffer solution (pH 7.2) was demonstrated in this paper.

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Quantification and Classification of Diclofenac Sodium Content in Dispersed Commercially Available Tablets by Attenuated Total Reflection Infrared Spectroscopy and Multivariate Data Analysis

Pharmaceuticals ◽

10.3390/ph14050440 ◽

2021 ◽

Vol 14 (5) ◽

pp. 440

Author(s):

Eirini Siozou ◽

Vasilios Sakkas ◽

Nikolaos Kourkoumelis

Keyword(s):

Infrared Spectroscopy ◽

Low Cost ◽

Diclofenac Sodium ◽

Reference Method ◽

Sodium Content ◽

Attenuated Total Reflection ◽

Accuracy And Precision ◽

Significant Difference ◽

Ft Ir

A new methodology, based on Fourier transform infrared spectroscopy equipped with an attenuated total reflectance accessory (ATR FT-IR), was developed for the determination of diclofenac sodium (DS) in dispersed commercially available tablets using chemometric tools such as partial least squares (PLS) coupled with discriminant analysis (PLS-DA). The results of PLS-DA depicted a perfect classification of the tablets into three different groups based on their DS concentrations, while the developed model with PLS had a sufficiently low root mean square error (RMSE) for the prediction of the samples’ concentration (~5%) and therefore can be practically used for any tablet with an unknown concentration of DS. Comparison with ultraviolet/visible (UV/Vis) spectrophotometry as the reference method revealed no significant difference between the two methods. The proposed methodology exhibited satisfactory results in terms of both accuracy and precision while being rapid, simple and of low cost.

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