scholarly journals Comparison of Different Procedures for Separating Microplastics from Sediments

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2854
Author(s):  
Veronica Nava ◽  
Barbara Leoni

The separation of microplastics from environmental matrices is still challenging, especially for sediments where microplastics can accumulate affecting benthic organisms. Many authors have adopted different procedures, but their effectiveness has been rarely compared. The present study aims to compare the recovery rate of three different methodologies for the separation of dense microplastics from fine sediments and provide insights about contamination processes occurring in microplastic separation techniques. The protocols tested are a density separation method with NaCl and NaI, a density separation with NaI followed by a centrifugation step, and a digestion method with 10%KOH (m/v). The recovery yields of two high-density polymers of three different dimensional classes were tested. The highest recovery rate was reported for the first protocol. However, this method proved to be expensive, and unsatisfactory results were found when using merely NaCl. The digestion method was the one that was proven to be simple, reproducible, and affordable. The contamination tests highlighted as multiple filtration steps can increase the number of fibers deriving from airborne contamination. Since a unified approach for microplastic separation from sediments is still not selected, this study is of paramount importance as it provides data about the reliability of different methods widely adopted.

Author(s):  
Ram Ben-Shalom

This chapter examines the genres and motives behind Jewish chronology during the Middle Ages. Jewish historiography focused on correlating Jewish chronology, general chronology, and Christian chronology. This was a similar approach to Christian writers. The chapter shows that this correlation of Jewish chronology with Christian and general chronology was one of the many components of medieval Jewish–Christian discourse. On the one hand, this suggests that Jews had a unified approach to history, in which they saw themselves as full participants. On the other, the timing and meaning of historical events were part of the religious polemic with Christianity. Religious polemic and apocalypticism were important reasons why Jewish scholars in Spain and southern France engaged in historiography. Other motives included the moral lessons that could be found in history and intellectual curiosity.


2010 ◽  
Vol 22 (1) ◽  
pp. 360
Author(s):  
M. I. Cueto ◽  
F. Pereyra-Bonnet ◽  
P. Silvestre ◽  
A. E. Gibbons

The aim of the study was to assess possible variations in superovulatory yields due to different FSH treatments at 2 times of the year. Superovulation and embryo recovery were performed during the breeding (n = 63) andnonbreeding (n = 46) seasons in Merino ewes located at 41°S latitude. Animals were kept under the same conditions, housed outdoors in a sheltered and covered pen, and were fed a liveweight maintenance ration. All animals received 60-mg medroxyprogesterone acetate intravaginal sponges (Progespon®, Syntex, Buenos Aires, Argentina) for 14 days. Ewes were then randomly assigned to 2 different superovulatory treatments: classic (n = 74) and one shot (n = 35) in both seasons. Classic superovulatory treatment consisted of 7 decreasing doses (2 × 48 mg, 2 × 24 mg, 2 × 20 mg, and1 × 16 mg NIH-FSH-P1)ofFSH (Folltropin®-V, Bioniche, Belleville, Ontario, Canada), administered twice daily from 48 h before to 24 h after pessary removal. A dose of eCG (300 IU; Novormon®, Syntex) was administered at progestagen removal. One shot superovulatory treatment consisted of a single dose of FSH (70 mg NIH-FSH-P1) plus 300 UI of eCG injected at pessary withdrawal. Embryo donors were inseminated by laparoscopy with frozen-thawed semen (100 × 106 spz) 12 h after the onset of estrus. Surgical embryo recovery was done on Day 7 after sponge withdrawal and embryos were graded for quality according to morphology (Grade 1 = excellent or good; Grade 2 = fair; Grade 3 = poor; and Grade 4 = dead or degenerated; IETS 1998). A 2 × 2 factorial ANOVA was used to test the main effects (season and superovulatory treatment) and interactions. There were no significant differences in the proportion of responding ewes (>3 corpora lutea), ovulation rate, and recovered Grades 1 to 2 embryos between the breeding and nonbreeding season (Table 1; P > 0.05). However, number of recovered ova/embryos and ova/embryo recovery rate were higher during the breeding season compared with the nonbreeding season, whereas the percentage of nonfertilized ova was lower in the breeding season than in the nonbreeding season (P < 0.05). Analysis of data comparing superovulatory treatments showed that the proportion of responding ewes, ovulation rate, recovered embryos, and recovered Grades 1 to 2 embryos were lower for the one shot treatment than for the classic treatment (P < 0.05). Embryo recovery rate and nonfertilization rate did not differ between treatments (P > 0.05). It was concluded that there was an increase in the number of total recovered ova/embryos during the breeding season compared with the nonbreeding season, although the number of recovered good-quality embryos was not affected. The use of multiple FSH injections produced a higher number of total recovered and viable embryos in Merino sheep than the one shot superovulatory treatment. Table 1.Embryo yields in ewes submitted to superovulation


Author(s):  
Arash Mohtat ◽  
József Kövecses

When interacting with a virtual object (VO) through a haptic device, it is crucial to feedback a contact force to the human operator (HO) that displays the VO physical properties with high fidelity. The core challenge, here, is to expand the renderable range of these properties, including larger stiffness and smaller inertia, at the available sampling rate. To address this challenge, a framework entitled high-fidelity contact rendering (HFCR) has been developed in this paper. The framework consists of three main strategies: an energy-based rendering of the contact force, smooth transition (ST) between contact modes, and remaining leak dissipation (LD). The essence of these strategies is to make the VO emulate its continuous-time counterpart. This is achieved via physically meaningful modifications in the constitutive relations to suppress artificial energy leaks. The strategies are first developed for the one-dimensional (1D) canonical VO; then, generalization to the multivariable case is discussed. Renderability has been analyzed exploring different stability criteria within a unified approach. This leads to stability charts and identification of renderable range of properties in the presence and absence of the HO. The framework has been validated through simulation and various experiments. Results verify its promising aspects for various scenarios including sustained contact and sudden collision events with or without the HO.


2020 ◽  
Vol 81 (4) ◽  
pp. 834-844
Author(s):  
Olga Konechnaya ◽  
Sabine Lüchtrath ◽  
Larissa Dsikowitzky ◽  
Jan Schwarzbauer

Abstract Microplastic particles have been recognized as global hazardous pollutants in the last few decades pointing to the importance of analyzing and monitoring microplastics, especially in soils and sediments. This study focused on a multi-step approach for microplastic analysis combining grain size fractionation, density separation and identification by μ-FTIR-spectroscopy. Eight widely used polymers (polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polystyrol (PS), polyethylenterephthalate (PET), polymethylmethacrylate (PMMA), polyurethane (PU) and polyamide (PA)) were fractionated into four groups of grain sizes (0.1–5 mm). Thereafter, sea sand was spiked with these particles to test a ZnCl2-based density separation for the polymer types and the various grain sizes. The obtained recovery rates were close to 100% showing that ZnCl2-based density separation is suitable to separate the polymer particles from a sandy matrix. This approach was extended on three further environmental matrices and recovery rates for two of them (sandy-silty and fine-grained sediment) also provided reliable values (94–106%). Lastly, the developed multi-step approach was verified by analyzing an environmental sample (sediment from river Tiranë, Albania) characterized by smaller grain size and moderate organic matter content. Identification of two polymer types in different grain size classes verified the suitability of the developed approach for microplastic analyses on particulate matter such as soils and sediments.


1985 ◽  
Vol 10 (3) ◽  
pp. 211-221
Author(s):  
Gottfried E. Noether

The paper presents a unified approach to some of the more popular nonparametric methods in current use. The approach provides the reader with new insights by exhibiting relationships to relevant population parameters, such as location and scale parameters for the one- and two-sample problems and regression parameters for bivariate data. For each parameter, a set of so-called elementary estimates is defined. The elementary estimates are then used to determine point estimates, confidence intervals, and test statistics for testing relevant nonparametric hypotheses. Among the tests discussed are the sign test, the Wilcoxon one- and two-sample tests, and Kendall’s test of independence.


Our Nature ◽  
2013 ◽  
Vol 10 (1) ◽  
pp. 199-205
Author(s):  
R. Sirmour ◽  
M.L. Naik ◽  
M.P. Goutam

Water bodies contain a large number of microorganisms, like bacteria, algae, protozoa etc. Algae are the one of the very important group of the organisms. Diatoms are the well known water planktons belonging to family Bacillariophyceae (Hendy, 1980). Diatom flora of koria was observed by using acid digestion method. The present account is based on the collection of about 5 water samples from different place of koria. 18 species from 11 genera were identified from these collection sites; the genera include Achnanthes, Amphora, Cymbella, Eunotia, Fragilaria, Gomphonema, Hantizschia, Navicula, Nitzschia, Stauroneis and Synedra.DOI: http://dx.doi.org/10.3126/on.v10i1.7782


2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
S. C. Shongwe ◽  
J.-C. Malela-Majika ◽  
E. M. Rapoo

The one-sided and two-sided Shewhart w-of-w standard and improved runs-rules monitoring schemes to monitor the mean of normally distributed observations from independent and identically distributed (iid) samples are investigated from an overall performance perspective, i.e., the expected weighted run-length (EWRL), for every possible positive integer value of w. The main objective of this work is to use the Markov chain methodology to formulate a theoretical unified approach of designing and evaluating Shewhart w-of-w standard and improved runs-rules for one-sided and two-sided X- schemes in both the zero-state and steady-state modes. Consequently, the main findings of this paper are as follows: (i) the zero-state and steady-state ARL and initial probability vectors of some of the one-sided and two-sided Shewhart w-of-w standard and improved runs-rules schemes are theoretically similar in design; however, their empirical performances are different and (ii) unlike previous studies that use ARL only, we base our recommendations using the zero-state and steady-state EWRL metrics and we observe that the steady-state improved runs-rules schemes tend to yield better performance than the other considered competing schemes, separately, for one-sided and two-sided schemes. Finally, the zero-state and steady-state unified approach run-length equations derived here can easily be used to evaluate other monitoring schemes based on a variety of parametric and nonparametric distributions.


1996 ◽  
Vol 118 (1) ◽  
pp. 187-192 ◽  
Author(s):  
Miomir Vukobratovic´ ◽  
Radoslav Stojic´

In this paper, the problem of simultaneous stabilization of both the robot motion and interaction force in Cartesian space, based on the unified approach to contact task problem in robotics [1], is considered. This control task is solved under the conditions set on environment dynamics which are less restrictive than those in [1] where some particular environment properties are required to ensure overall system stability. Furthermore, the one-to-one correspondence between closed-loop motion and force dynamic equations is obtained and unique control law ensuring system stability and preset either motion or force transient response is proposed.


2010 ◽  
Vol 35 (2) ◽  
pp. 43-47
Author(s):  
Susan Smith ◽  
Debbie Sturmfels

New Zealand currently operates separate doors and different entry pathways for people wishing to adopt, foster or offer permanent care for a child. This presentation outlines the work now underway to develop a unified application, preparation, assessment, training and support system for applicants wishing to care for a child, whether by adoption, guardianship or as a transitional (foster) caregiver. Placing the child at the centre, One Door uses a framework comprised of six core attributes for parenting a child not born to you; safety; attachment; resilience; identity; integrity; and support. A challenge for the One Door design team will be the application of the model to the family/whänau caregiver whose entry into the care system is, in the main, through necessity not desire.


Foods ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2118
Author(s):  
Rizky Prihandari ◽  
Weeraya Karnpanit ◽  
Suwapat Kittibunchakul ◽  
Varongsiri Kemsawasd

Currently, research on the accumulation of microplastics (MPs) in the marine food web is being highlighted. An accurate and reliable digestion method to extract and isolate MPs from complex food matrices has seldom been validated. This study aimed to compare the efficacy of MP isolation among enzymatic-, oxidative-, and the combination of two digestion methods on red seaweed, Gracilaria fisheri. The dried seaweed sample was digested using three different methods under various conditions using enzymes (cellulase and protease), 30% H2O2, and a combination of enzymes and 30% H2O2. The method possessing the best digestion efficiency and polymer recovery rate of MPs was selected, and its effect on spiked plastic polymer integrity was analyzed by Raman spectroscopy. As a result, the enzymatic method rendered moderate digestion efficiency (59.3–63.7%) and high polymer recovery rate (94.7–98.9%). The oxidative method using 30% H2O2 showed high digestion efficiency (93.0–96.3%) and high polymer recovery rate (>98%). The combination method was the most effective method in terms of digestion efficiency, polymer recovery rate, and expenditure of digestion time. The method also showed no chemical changes in the spiked plastic polymers (PE, PP, PS, PVC, and PET) after the digestion process. All the spiked plastic polymers were identifiable using Raman spectroscopy.


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