scholarly journals Direct Measurement of Sedimentation Coefficient Distributions in Multimodal Nanoparticle Mixtures

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1027
Author(s):  
Claudia Simone Plüisch ◽  
Rouven Stuckert ◽  
Alexander Wittemann
Keyword(s):  
Sedimentation Coefficient ◽  
Practical Implementation ◽  
Particle Sizing ◽  
Physical Separation ◽  
Coefficient Distribution ◽  
Multimodal Distributions ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment ◽  
Actual Shape

Differential centrifugal sedimentation (DCS) is based on physical separation of nanoparticles in a centrifugal field prior to their analysis. It is suitable for resolving particle populations, which only slightly differ in size or density. Agglomeration presents a common problem in many natural and engineered processes. Reliable data on the agglomeration state are also crucial for hazard and risk assessment of nanomaterials and for grouping and read-across of nanoforms. Agglomeration results in polydisperse mixtures of nanoparticle clusters with multimodal distributions in size, density, and shape. These key parameters affect the sedimentation coefficient, which is the actual physical quantity measured in DCS, although the method is better known for particle sizing. The conversion into a particle size distribution is, however, based on the assumption of spherical shapes. The latter disregards the influence of the actual shape on the sedimentation rate. Sizes obtained in this way refer to equivalent diameters of spheres that sediment at the same velocity. This problem can be circumvented by focusing on the sedimentation coefficient distribution of complex nanoparticle mixtures. Knowledge of the latter is essential to implement and optimize preparative centrifugal routines, enabling precise and efficient sorting of complex nanoparticle mixtures. The determination of sedimentation coefficient distributions by DCS is demonstrated based on supracolloidal assemblies, which are often referred to as “colloidal molecules”. The DCS results are compared with sedimentation coefficients obtained from hydrodynamic bead-shell modeling. Furthermore, the practical implementation of the analytical findings into preparative centrifugal separations is explored.

Nonproteolyzed Form of DNA-Polymerase ε from T-Cell Spontaneous Lymphoma of Sprague-Dawley Inbred Rat: Isolation and Characterization

1998 ◽  
Vol 63 (5) ◽  
pp. 723-731 ◽  
Author(s):  
Gabriel Birkuš ◽  
Pavel Kramata ◽  
Ivan Votruba ◽  
Berta Otová ◽  
Miroslav Otmar ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
Sedimentation Coefficient ◽  
Isolation Procedure ◽  
Sprague Dawley ◽  
Nucleotide Analogs ◽  
Isolation And Characterization ◽  
Inbred Rats ◽  
Catalyzed Reactions ◽  
Inbred Rat

Using a simple isolation procedure and selective assay for the determination of enzyme activity the nonproteolyzed and proteolyzed form of DNA-polymerase ε (pol ε and pol ε*) from the lymphoma of Sprague-Dawley inbred rats were purified. Nonproteolyzed pol ε is composed of two subunits (240 000 and 50 000) with sedimentation coefficient 10.5 S, while the subunit composition of pol ε* was 145 000 and 73 000. Estimated Km values for dATP and dGTP as well as Ki values for acyclic nucleotide analogs (PMEApp, HPMPApp and PMEDAPpp) in pol ε and pol ε* catalyzed reactions have shown that a proteolysis probably does not affect pol ε binding site for dNTPs. Both enzymes (pol ε and pol ε*) possess 3'-5'-exonuclease activity with different Km for 3'-OH end of template poly dA-oligo dT18 (1.6 μmol/l and 0.36 μmol/l, respectively).

scholarly journals Definitions and Concepts for Quantitative Rockfall Hazard and Risk Analysis

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 158
Author(s):  
Didier Hantz ◽  
Jordi Corominas ◽  
Giovanni B. Crosta ◽  
Michel Jaboyedoff
Keyword(s):  
Risk Assessment ◽  
At Risk ◽  
Failure Probability ◽  
Rockfall Hazard ◽  
Process Failure ◽  
Failure Propagation ◽  
Element At Risk ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment ◽  
Definition Of

There is an increasing need for quantitative rockfall hazard and risk assessment that requires a precise definition of the terms and concepts used for this particular type of landslide. This paper suggests using terms that appear to be the most logic and explicit as possible and describes methods to derive some of the main hazards and risk descriptors. The terms and concepts presented concern the rockfall process (failure, propagation, fragmentation, modelling) and the hazard and risk descriptors, distinguishing the cases of localized and diffuse hazards. For a localized hazard, the failure probability of the considered rock compartment in a given period of time has to be assessed, and the probability for a given element at risk to be impacted with a given energy must be derived combining the failure probability, the reach probability, and the exposure of the element. For a diffuse hazard that is characterized by a failure frequency, the number of rockfalls reaching the element at risk per unit of time and with a given energy (passage frequency) can be derived. This frequency is relevant for risk assessment when the element at risk can be damaged several times. If it is not replaced, the probability that it is impacted by at least one rockfall is more relevant.

STUDY ON BISPHENOL F, A BISPHENOL A ANALOGUE, AT A DAIRY COMPANY: HEALTH HAZARD AND RISK ASSESSMENT

2021 ◽  
pp. 112334
Author(s):  
Serena Santonicola ◽  
Stefania Albrizio ◽  
Maria Carmela Ferrante ◽  
Mercogliano Raffaelina
Keyword(s):  
Risk Assessment ◽  
Bisphenol A ◽  
Health Hazard ◽  
Bisphenol F ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment

Aquatic hazard and risk assessment of two selected substances produced in high volumes in the Slovak Republic

Chemosphere ◽  
1997 ◽  
Vol 34 (1) ◽  
pp. 179-190 ◽  
Author(s):  
Martin Murín ◽  
Juraj Gavora ◽  
Iveta Drastichová ◽  
Elena Dušková ◽  
Torben Madsen ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Slovak Republic ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment

Enzymes and Their Forms Used in Detection of Organophosphorus Compounds

2021 ◽  
pp. 22-41
Keyword(s):  
Organophosphorus Compounds ◽  
Degradation Products ◽  
Rapid Development ◽  
Hydrolytic Enzymes ◽  
Immobilized Enzymes ◽  
Amino Acid Sequences ◽  
Practical Implementation ◽  
Scientific Results ◽  
Physical And Chemical

Еnzymes are able to effectively interact with various organophosphorus compounds (OPC), entering into (bio)chemical reactions with them. Changes in the initial activity of enzymes as a result of their inhibition by OPC, the formation of OPC degradation products under the action of hydrolytic enzymes, etc. can be determined using different physical and chemical methods and used in bioanalytic systems to determine the concentrations of OPC. The purpose of the review is to analyze the main scientific results achieved over the past 10 years in the development of analytical systems based on enzymes intended for the determination of OPC. It is shown in the article, that the requirements for the sensitivity of biosensors are based on the norms of the content of the analyzed substances detected in/at the objects of mandatory control. The cholinesterases compose a basis for the development of the largest number of ultra-sensitive biosensors, although other enzymes can be successfully used as a biosensitive element. The most technologically advanced solution that is close to the practical implementation seems to be bioanalytical systems using immobilized enzymes. Improving the detection limits of the OPC can be achieved by using nanoobjects together with modern methods of signal transducers, for example, with nanomechanical detectors and signal converters. This combination of technical solutions ensures the sensitivity of the OPC analysis up to pg/l. At present, «reagentless» systems have received significant development, which have become the basis for the production of a large number of commercially available strips for the express determination of OPC. Modern demands stimulate the rapid development of portable and, especially, wearable biosensors that can be attached to various surfaces, including a clothing. The progress in the development of affine amino acid sequences, in the future, will allow the creation of enzyme biosensors on any surface.

New Methodology for the Determination of the Vertical Center of Gravity of In-Service Semisubmersibles: Proposal and Numerical Assessment

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Ivan N. Porciuncula ◽  
Claudio A. Rodríguez ◽  
Paulo T. T. Esperança
Keyword(s):  
Accurate Determination ◽  
Center Of Gravity ◽  
Practical Implementation ◽  
Numerical Assessment ◽  
Neutral Equilibrium ◽  
Inclination Angles ◽  
Numerical Tools ◽  
The Stability ◽  
Metacentric Height

Along its lifetime, an offshore unit is subjected to several equipment interventions. These modifications may include large conversions in loco that usually are not adequately documented. Hence, the accurate determination of the platform's center of gravity (KG) is not possible. For vessels with low metacentric height (GM), such as semisubmersibles, Classification Societies penalize the platform's KG, inhibiting the installation of new equipment until an accurate measurement of KG is provided, i.e., until an updated inclining test is performed. For an operating semisubmersible, the execution of this type of test is not an alternative because it implies in removing the vessel from its in-service location to sheltered waters. Relatively recently, some methods have been proposed for the estimation of KG for in-service vessels. However, as all of the methods depend on accurate measurements of inclination angles and, eventually, on numerical tools for the simulation of vessel dynamics onboard, they are not straightforward for practical implementation. The objective of the paper is to present a practical methodology for the experimental determination of KG, without the need of accurate measurements of inclinations and/or complex numerical simulations, but based on actual operations that can be performed onboard. Indeed, the proposed methodology relies on the search, identification, and execution of a neutral equilibrium condition where, for instance, KG = KM. The method is exemplified using actual data of a typical semisubmersible. The paper also numerically explores and discusses the stability of the platform under various conditions with unstable initial GM, as well as the effect of mooring and risers.

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