Receptor-based detection of microplastics and nanoplastics: Current and future

Plastic pollution is an emerging environmental concern, gaining significant attention worldwide. They are classified into microplastics (MP; defined from 1 μm to 5 mm) and smaller nanoplastics (NP; <1 μm). NPs may pose higher ecological risks than MPs. Various microscopic and spectroscopic techniques have been used to detect MPs, and the same methods have occasionally been used for NPs. However, they are not based on receptors, which provide high specificity in most biosensing applications. Receptor-based micro/nanoplastics (MNP) detection can provide high specificity, distinguishing MNPs from the environmental samples and, more importantly, identifying the plastic types. It can also offer a low limit of detection (LOD) required for environmental screening. Such receptors are expected to detect NPs specifically at the molecular level. This review categorizes the receptors into cells, proteins, peptides, fluorescent dyes, polymers, and micro/nanostructures. Detection techniques used with these receptors are also summarized and categorized. There is plenty of room for future research to test for broader classes of environmental samples and many plastic types, to lower the LOD, and to apply the current techniques for NPs. Portable and handheld MNP detection should also be demonstrated for field use since the current demonstrations primarily utilized laboratory instruments. Detection on microfluidic platforms will also be crucial in miniaturizing and automating the assay and, eventually, collecting an extensive database to support machine learning-based classification of MNP types.

satmut_utils: a simulation and variant calling package for multiplexed assays of variant effect

The impact of millions of individual genetic variants on molecular phenotypes in coding sequences remains unknown. Multiplexed assays of variant effect (MAVEs) are scalable methods to annotate relevant variants, but existing software lacks standardization, requires cumbersome configuration, and does not scale to large targets. We present satmut_utils as a flexible solution for simulation and variant quantification. We then benchmark MAVE software using simulated and real MAVE data. We finally determine mRNA abundance for thousands of cystathionine beta-synthase variants using two experimental methods. The satmut_utils package enables high-performance analysis of MAVEs and reveals the capability of variants to alter mRNA abundance.

Aptamer-Based Magnetic Nanoprobe for Quantitative Measurement of Chloramphenicol in Milk through Portable Reader

Background

We described here an aptamer-based magnetic nanoprobe for measuring the amount of chloramphenicol (CAP) in milk.

Methods

The nanoprobe presented in this method consists of a magnetic nanoparticle conjugated to a specific CAP aptamer. If the target is detected in the sample, the nanoprobe binds to it, and the aptamer forms a G-quadruplex structure. This structure mimics the peroxidase activity in the presence of the hemin cofactor. If tetramethylbenzidine is added to the sample containing the nanoprobe, a blue color light is observed. After adding a stop reagent solution, the color produced is measured by a microplate reader and a portable meter.

Results

This study proves a 99% positive linear relationship between the microplate reader's results and the portable meter results.

Conclusion

Conjugation of the aptamer to magnetic nanoparticles and applying magnetic separation operations change the nanoprobe performance by 11% for both mentioned devices.

Activity patterns of Asiatic black bear (Ursus thibetanus) in the moist temperate forests of Machiara National Park, Azad Jammu and Kashmir, Pakistan

The Asiatic black bear (Ursus thibetanus) is an environmental indicator species whose activity patterns may be highly impacted by habitat changes. We monitored the monthly and daily activity patterns of black bears in the moist temperate forests of Machiara National Park. We used infrared camera traps and local ecological knowledge for data collection from April 2019 to April 2021. Camera traps recorded 109 [inside forest = 107, outside forest (near crop fields and human settlements) = 2] independent registrations (IR) in 5541 (692.63 ± 36.72, mean ± SD) camera days. We found (i) spring and autumn to be the lowest activity seasons for black bears inside the forest. (ii) The highest activity was recorded in summer, with a peak in August followed closely by July. (iii) The activity level sharply declined after August and halted from December to March, indicative of the bears' hibernation period. Local knowledge revealed that (i) bears remained active from May to November and hibernated the rest of the period. (ii) Bear activity was at its peak inside the forest in summer and outside the forest in autumn when bears sought to raid the widely cultivated maize crop (Zea mays) planted along forest edges. This increased activity outside of the forest is likely driven by decreased food availability inside the forest area and maize crop being a preferred anthropogenic food type for bears. Based on the daily activity pattern, bears exhibited cathemeral behavior (i.e., active throughout the day) with maximum overlap between camera trap and local ecological knowledge data. Human activity may be impacting the daily activity patterns of bears via disturbance and interference. The data collected in this study can help mitigate conflicts between humans and black bears and consequently assist in future conservation of black bears in the area.

Daily supplementation of a multiple micronutrient powder improves folate but not thiamine, riboflavin, or vitamin B12 status among young Laotian children: a randomized controlled trial

PURPOSE

To assess the effects of intervention with a daily multiple micronutrient powder (MNP) on thiamine, riboflavin, folate, and B₁₂ status among young Laotian children.

METHODS

Children (n = 1704) aged 6-23 mo, participating in a double-blind placebo-controlled randomized trial were individually randomized to receive daily either MNP (containing 0.5 mg of thiamine, 0.5 mg riboflavin, 150 μg folic acid, and 0.9 μg vitamin B₁₂ along with 11 other micronutrients) or placebo and followed for ~ 36 weeks. In a randomly selected sub-sample of 260 children, erythrocyte thiamine diphosphate (eThDP), plasma folate and B₁₂ concentrations, and erythrocyte glutathione reductase activation coefficient (EGRac; riboflavin biomarker) were assessed at baseline and endline.

RESULTS

There was no treatment effect on endline eThDP concentrations (110.6 ± 8.9 nmol/L in MNP vs. 109.4 ± 8.9 nmol/L in placebo group; p = 0.924), EGRac (1.46 ± 0.3 vs. 1.49 ± 0.3; p = 0.184) and B₁₂ concentrations (523.3 ± 24.6 pmol/L vs. 515.9 ± 24.8 pmol/L; p = 0.678). Likewise, the prevalence of thiamine, riboflavin, and B₁₂ deficiencies did not differ significantly between the two groups. However, endline folate concentration was significantly higher in the MNP compared to the placebo group (28.2 ± 0.8 nmol/L vs 19.9 ± 0.8 nmol/L, respectively; p < 0.001), and correspondingly, the prevalence of folate deficiency was significantly lower in the MNP group (1.6% vs 17.4%; p = 0.015).

CONCLUSIONS

Compared to a placebo, daily MNP for 9 months increased only folate but not thiamine, riboflavin, or B₁₂ status in young Laotian children.

TRIAL REGISTRATION

The trial was registered at www.

CLINICALTRIALS

gov (NCT02428647) on April 29 2015.

An Integrated Infant and Young Child Feeding and Micronutrient Powder Intervention Does Not Affect Anemia, Iron Status, or Vitamin A Status among Children Aged 12-23 Months in Eastern Uganda

BACKGROUND

Micronutrient powders (MNP) can reduce iron deficiency and anemia in children.

OBJECTIVE

We evaluated the impact of an integrated infant and young child feeding (IYCF)-MNP intervention on anemia and micronutrient status among children aged 12-23 mo in Eastern Uganda. The intervention focused on MNP distribution, IYCF education, and caregiver behavior change.

METHODS

Population-based cross-sectional surveys representative of children aged 12-23 mo in Amuria (intervention) and Soroti (nonintervention) districts were collected in June/July 2015 at baseline (n = 1260) and 12 mo after implementation at endline in 2016 (n = 1490). From pooled capillary blood, we assessed hemoglobin, malaria, ferritin, retinol binding protein (RBP), C-reactive protein, and ɑ1-acid glycoprotein. Ferritin and RBP were regression-adjusted to correct for inflammation. Caregivers reported sociodemographic characteristics and MNP knowledge and practices. Linear regression estimated the difference-in-difference (DiD) effect of MNP on hemoglobin, ferritin, and RBP, and logistic regression estimated DiD effect of MNP on anemia (hemoglobin <11.0 g/dL), iron deficiency (ferritin <12.0 µg/L), iron deficiency anemia (hemoglobin <11.0 g/dL and ferritin <12.0 µg/L), and vitamin A deficiency (VAD; RBP equivalent to <0.70 µmol/L retinol: <0.79 µmol/L at baseline and RBP <0.67 µmol/L at endline).

RESULTS

In Amuria, 96% of children had ever consumed MNP versus <1% of children in Soroti. Fifty-four percent of caregivers reported organoleptic changes when MNP were added to foods cooked with soda ash. Adjusting for age, sex, malaria, recent morbidity, and household-level factors, the intervention was associated with -0.83 g/dL lower hemoglobin (95% CI, -1.36, -0.30 g/dL; P = 0.003) but not with anemia, ferritin, iron deficiency, iron deficiency anemia, RBP, or VAD.

CONCLUSIONS

Despite high program fidelity, the intervention was associated with reduced hemoglobin concentrations but not with change in anemia or micronutrient status among children aged 12-23 mo in Eastern Uganda. Contextual factors, such as cooking with soda ash, might explain the lack of effectiveness.

Co-delivery of Doxorubicin and D-α-Tocopherol Polyethylene Glycol 1000 Succinate by Magnetic Nanoparticles

BACKGROUND

Although conventional chemotherapy is the most common method for cancer treatment, it has several side effects such as neuropathy, alopecia and cardiotoxicity. Since the drugs are given to body systemically, normal cells are also affected, just like cancer cells. However, in recent years, targeted drug delivery has been developed to overcome these drawbacks.

OBJECTIVE

The aim of this study was targeted co-delivery of doxorubicin (Dox) which is an anticancer agent and D-α-Tocopherol polyethylene glycol 1000 succinate (vitamin E TPGS or simply TPGS) to breast cancer cells. For this purpose, Magnetic Nanoparticles (MNPs) were synthesized and coated with Oleic Acid (OA). Coated nanoparticles were encapsulated in Poly Lactic-co-Glycolic Acid (PLGA) and TPGS polymers and loaded with Dox. The Nanoparticles (NPs) were characterized by Fourier Transform Infrared (FTIR) spectroscopy, zetapotential analysis, Dynamic Light Scattering (DLS) analysis, Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscope (SEM) analysis.

RESULTS

The results showed that NPs were spherical, superparamagnetic and in the desired range for use in drug targeting. The targetability of NPs was confirmed. Moreover, TPGS and Dox loading was shown by TGA and FTIR analyses. NPs were internalized by cells and the cytotoxic effect of drug loaded NPs on sensitive (MCF-7) and drug-resistant (MCF-7/Dox) cells were examined. It was seen that the presence of TPGS increased cytotoxicity significantly. TPGS also enhanced drug loading efficiency, release rate, cellular internalization. In MCF- 7/Dox cells, the drug resistance seems to be decreased when Dox is loaded onto TPGS containing NPs.

CONCLUSION

This magnetic PLGA nanoparticle system is important for new generation targeted chemotherapy and could be used for breast cancer treatment after in vivo tests.

Linked Mutations at Adjacent Nucleotides Have Shaped Human Population Differentiation and Protein Evolution

Despite the fundamental importance of single nucleotide polymorphisms (SNPs) to human evolution, there are still large gaps in our understanding of the forces that shape their distribution across the genome. SNPs have been shown to not be distributed evenly, with directly adjacent SNPs found unusually frequently. Why this is the case is unclear. We illustrate how neighboring SNPs that cannot be explained by a single mutation event (that we term here sequential dinucleotide mutations [SDMs]) are driven by distinct processes to SNPs and multinucleotide polymorphisms (MNPs). By studying variation across populations, including a novel cohort of 1,358 Scottish genomes, we show that, SDMs are over twice as common as MNPs and like SNPs display distinct mutational spectra across populations. These biases are not only different to those observed among SNPs and MNPs but are also more divergent between human population groups. We show that the changes that make up SDMs are not independent and identify a distinct mutational profile, CA → CG → TG, that is observed an order of magnitude more often than expected from background SNP rates and the numbers of other SDMs involving the gain and deamination of CpG sites. Intriguingly particular pathways through the amino acid code appear to have been favored relative to that expected from intergenic SDM rates and the occurrences of coding SNPs, and in particular those that lead to the creation of single codon amino acids. We finally present evidence that epistatic selection has potentially disfavored sequential nonsynonymous changes in the human genome.

Impact of Two Forms of Daily Preventive Zinc or Therapeutic Zinc Supplementation for Diarrhea on Hair Cortisol Concentrations Among Rural Laotian Children: A Randomized Controlled Trial

Zinc supplementation has been shown to reduce the morbidity burden among young children, and may reduce chronic stress. Hair cortisol has been promoted as an indicator of chronic stress. We assessed the impact of different strategies for delivering supplementary zinc on hair cortisol concentrations (HCC) in young Laotian children and examined risk factors associated with HCC. In a randomized double-blind controlled trial (NCT02428647), children aged 6⁻23 mo were randomized to one of four intervention groups and followed for ~36 weeks: daily preventive zinc (PZ) tablets (7 mg/day), daily multiple micronutrient powder (MNP) sachets (containing 10 mg zinc and 14 other micronutrients), therapeutic zinc (TZ) supplements for diarrhea treatment (20 mg/day for 10 days) or daily placebo powder. HCC of 512 children was assessed at baseline and endline. ANCOVA and linear regression models were used to assess group differences in HCC and to examine the risk factors associated with HCC, respectively. At enrollment, mean HCC was 28.8 ± 43.9 pg/mg. In models adjusted for age at enrollment, health district, and baseline HCC there was no overall effect of the interventions on endline HCC and change in HCC. When controlling for additional predetermined covariates, there was a marginally significant effect on change in HCC (p = 0.075) with a slightly lower reduction of HCC in TZ compared to PZ (mean change (95% CI): -4.6 (-7.0; -2.3) vs. -9.4 (-11.7; -7.0) pg/mg; p = 0.053). At baseline, consumption of iron rich foods was negatively associated with HCC, whereas AGP (α1-acid glycoprotein) levels, elevated AGP and C-reactive protein and high soluble transferrin receptor were positively associated with HCC. In young Laotian children, MNP, PZ and TZ had no impact on HCC. The marginal difference in change in HCC between the PZ and TZ groups was too small to be considered of health significance.

Coverage and Consumption of Micronutrient Powders, Fortified Staples, and Iodized Salt Among Children Aged 6 to 23 Months in Selected Neighborhoods of Nairobi County, Kenya

BACKGROUND

Intake of micronutrient-rich foods among children aged 6 to 23 months in Nairobi is low.

OBJECTIVE

This study aimed to assess existing coverage and utilization of micronutrient powders (MNPs), fortified staples, and iodized salt among children aged 6 to 23 months prior to implementation of an MNP program.

METHODS

A cross-sectional survey among caregivers of children aged 6 to 23 months (n = 618) was implemented in 7 neighborhoods within Nairobi County, representing the implementation area of the new MNP program.

RESULTS

Results for MNP coverage and utilization showed 28.5% of all caregivers were aware of MNP, 18.5% had ever received MNP for their child, and 10.8% had fed MNP to their child in the previous 7 days. Effective coverage (ie, the child had been given the MNP at least 3 times in the previous 7 days) was 5.8%. Effective coverage of infants and young children with poor feeding practices was significantly lower as compared to those with non-poor feeding practices (coverage ratio, 0.34; confidence interval, 0.12-0.70). Most households purchased iodized salt (96.9%), fortified oil (61.0%), and fortified maize flour (93.9%). An estimated 23.9% of vitamin A requirements of children (6-23 months) were provided from fortified oil and 50.7% of iron from fortified maize flour. Most households consumed processed milk (81%).

CONCLUSION

Coverage of MNPs in the surveyed neighborhoods was low. Coverage of fortified salt, oil, and maize flour was high and provided significant amount of micronutrients to children. Processed milk has potential as a vehicle for food fortification.

The effect of lipids, a lipid-rich ready-to-use therapeutic food, or a phytase on iron absorption from maize-based meals fortified with micronutrient powders

Background: Ready-to-use-therapeutic foods (RUTFs) high in lipid, protein, and iron are used to treat malnutrition. Lipids increase gastric residence time, which could increase iron absorption, particularly from poorly soluble iron compounds and in combination with phytase.Objectives: The objectives were to 1) assess the effect on iron absorption of a lipid emulsion given 20 min before or together with an iron-fortified maize meal and 2) assess iron absorption from a micronutrient powder (MNP) given with a nutrient-dense RUTF and/or a microbial phytase.Design: A total of 41 women participated in 3 studies. They consumed a maize meal fortified with isotopically labeled ferrous sulfate (FeSO₄; study 1) or ferric pyrophosphate (FePP; study 2). In studies 1 and 2, a lipid emulsion was given with or 20 min before the meal. In study 3, with the use of a 2 × 2 factorial design, subjects consumed a maize meal fortified with an MNP containing labeled FeSO₄ (MNP) given with an RUTF (MNP+RUTF), with a phytase (MNP+phytase), or both (MNP+RUTF+phytase). Iron absorption was assessed by isotope incorporation in erythrocytes 14 d after the test meals.Results: The lipid emulsion given either before or with the meal significantly increased iron absorption from FePP by 2.55-fold (95% CI: 1.48-, 4.37-fold; P = 0.001) but not from FeSO₄ There was a trend to increase iron absorption with the MNP+RUTF meal, which did not reach significance (1.21-fold; 95% CI: 0.92-, 1.61-fold; P = 0.060). The addition of phytase to MNP and MNP+RUTF significantly increased iron absorption by 1.85-fold (95% CI: 1.49-, 2.29-fold; P < 0.001), with no interaction between phytase and RUTF.Conclusions: In iron-fortified maize-based meals, the addition of lipids more than doubles iron absorption from FePP. Our results suggest the possibility of an enhancing effect on iron absorption of lipid-rich RUTFs, but more research is needed to determine this. This trial was registered at clinicaltrials.gov as NCT01991626.

Flow analysis of individual blood extracellular vesicles in acute coronary syndrome

A diverse population of small extracellular vesicles (EVs) that are released by various cells has been characterized predominantly in bulk, a procedure whereby the individual characteristics of EVs are lost. Here, we used a new nanotechnology-based flow cytometric analysis to characterize the antigenic composition of individual EVs in patients with acute coronary syndrome (ACS). Plasma EVs were captured with 15-nm magnetic nanoparticles coupled to antibodies against CD31 (predominantly an endothelial marker), CD41a (a marker for platelets), and CD63 or MHC class I (common EV markers). The total amounts of EVs were higher in the ACS patients than in the controls, predominantly due to the contribution of patients with acute myocardial infarction. For all captured fractions, the differences in the EV amounts were restricted to CD41a+ EVs. The increase in the numbers of EVs in the ACS patients, predominantly of platelet origin, probably reflects platelet activation and may indicate disease progression.

Complementary approaches for the evaluation of biocompatibility of 90Y-labeled superparamagnetic citric acid (Fe,Er)3O4 coated nanoparticles

Magnetic nanoparticles (MNPs) are of immense interest for diagnostic and therapeutic applications in medicine. Design and development of new iron oxide-based MNPs for such applications is of rather limited breadth without reliable and sensitive methods to determine their levels in body tissues. Commonly used methods, such as ICP, are quite problematic, due to the inability to decipher the origin of the detected iron, i.e. whether it originates from the MNPs or endogenous from tissues and bodily fluids. One of the approaches to overcome this problem and to increase reliability of tracing MNPs is to partially substitute iron ions in the MNPs with Er. Here, we report on the development of citric acid coated (Fe,Er)₃O₄ nanoparticles and characterization of their physico-chemical and biological properties by utilization of various complementary approaches. The synthesized MNPs had a narrow (6-7nm) size distribution, as consistently seen in atomic pair distribution function, transmission electron microscopy, and DC magnetization measurements. The particles were found to be superparamagnetic, with a pronounced maximum in measured zero-field cooled magnetization at around 90K. Reduction in saturation magnetization due to incorporation of 1.7% Er³⁺ into the Fe₃O₄ matrix was clearly observed. From the biological standpoint, citric acid coated (Fe,Er)₃O₄ NPs were found to induce low toxicity both in human cell fibroblasts and in zebrafish (Danio rerio) embryos. Biodistribution pattern of the MNPs after intravenous administration in healthy Wistar rats was followed by the radiotracer method, revealing that ⁹⁰Y-labeled MNPs were predominantly found in liver (75.33% ID), followed by lungs (16.70% ID) and spleen (2.83% ID). Quantitative agreement with these observations was obtained by ICP-MS elemental analysis using Er as the detected tracer. Based on the favorable physical, chemical and biological characteristics, citric acid coated (Fe,Er)₃O₄ MNPs could be further considered for the potential application as a diagnostic and/or therapeutic agent. This work also demonstrates that combined application of these techniques is a promising tool for studies of pharmacokinetics of the new MNPs in complex biological systems.

Adding multiple micronutrient powders to a homestead food production programme yields marginally significant benefit on anaemia reduction among young children in Nepal

Anaemia affects 46% of preschool-aged children in Nepal. A cluster-randomised study was conducted in rural Nepal to test whether providing micronutrient powders (MNP) in addition to enhanced homestead food production (EHFP) programme, consisting of home gardens, poultry and nutrition education, could lead to a higher reduction in anaemia compared with providing only EHFP. This sub-study enrolled 335 children aged 6-9 months into one of three groups: (1) EHFP + MNP; (2) EHFP; or (3) control. The EHFP + MNP group received 60 sachets of MNP for flexible consumption at the start and 6 months later for a total supplementation period of 11 months. The MNP contained 15 micronutrients including iron (10 mg encapsulated ferrous fumarate). Haemoglobin and anthropometry were measured at baseline and post-MNP supplementation. Mean ± SE haemoglobin concentration increased significantly in all groups, with a slightly higher but non-significant increase in the EHFP + MNP and EHFP compared with control (difference-in-differences: 4.1 g L(-1) for EHFP + MNP vs. control; 3.6 g L(-1) for EHFP vs. control; 0.5 g L(-1) for EHFP + MNP vs. EHFP). Anaemia decreased at a slightly higher magnitude in the EHFP + MNP [51.5 percentage points (PP)] than the EHFP (48.6 PP) and control (39.6 PP), with adjusted odds ratios (95% CI) at post-supplementation of 0.52 (0.25-1.12) for EHFP + MNP and 0.69 (0.35-1.36) for EHFP, compared with control. There was no impact on child growth. Combining EHFP and MNP programmes yielded a marginally significant reduction in anaemia among children.

Adsorptive removal of phenolic compounds using cellulose acetate phthalate-alumina nanoparticle mixed matrix membrane

Mixed matrix membranes (MMMs) were prepared using alumina nanoparticles and cellulose acetate phthalate (CAP) by varying concentration of nanoparticles in the range of 10 to 25wt%. The membranes were characterized by scanning electron micrograph, porosity, permeability, molecular weight cut off, contact angle, surface zeta potential, mechanical strength. Addition of nanoparticles increased the porosity, permeability of the membrane up to 20wt% of alumina. pH at point of zero charge of the membrane was 5.4. Zeta potential of the membrane became more negative up to 20wt% of nanoparticles. Adsorption of phenolic derivatives, catechol, paranitrophenol, phenol, orthochloro phenol, metanitrophenol, by MMMs were investigated. Variation of rejection and permeate flux profiles were studied for different solutes as a function of various operating conditions, namely, solution pH, solute concentration in feed and transmembrane pressure drop. Difference in rejection of phenolic derivatives is consequence of interplay of surface charge and adsorption by alumina. Adsorption isotherm was fitted for different solutes and effects of pH were investigated. Catechol showed the maximum rejection 91% at solution pH 9. Addition of electrolyte reduced the rejection of solutes. Transmembrane pressure drop has insignificant effects on solute rejection. Competitive adsorption reduced the rejection of individual solute.

Magnetic nanoparticle mediated transfection of neural stem cell suspension cultures is enhanced by applied oscillating magnetic fields

Safe genetic modification of neural stem cell (NSC) transplant populations is a key goal for regenerative neurology. We describe a technically simple and safe method to increase transfection in NSCs propagated in the neurosphere (suspension culture) model, using magnetic nanoparticles deployed with applied oscillating magnetic fields ('magnetofection technology'). We show that transfection efficiency was enhanced over two-fold by oscillating magnetic fields (frequency=4 Hz). The protocols had no effect on cell viability, cell number, stem cell marker expression and differentiation profiles of 'magnetofected' cultures, highlighting the safety of the technique. As far as we are aware, this is the first successful application of magnetofection technology to suspension cultures of neural cells. The procedures described offer a means to augment the therapeutic potential of NSCs propagated as neurospheres - a culture model of high clinical translational relevance - by safe genetic manipulation, with further potential for incorporation into 'magneto-multifection' (repeat transfection) protocols.

FROM THE CLINICAL EDITOR

This team of investigators describe a simple and safe method to increase transfection in neural stem cells using magnetic nanoparticles deployed with oscillating magnetic fields, demonstrating a greater than two-fold transfection efficiency increase by applying low frequency magnetic oscillation.