Hydrodynamic lift of vesicles and red blood cells in flow — from Fåhræus & Lindqvist to microfluidic cell sorting

Hydrodynamic lift forces acting on cells and particles in fluid flow receive ongoing attention from medicine, mathematics, physics and engineering. The early findings of Fåhræus & Lindqvist on the viscosity change of blood with the diameter of capillaries motivated extensive studies both experimentally and theoretically to illuminate the underlying physics. We review this historical development that led to the discovery of the inertial and non-inertial lift forces and elucidate the origins of these forces that are still not entirely clear. Exploiting microfluidic techniques induced a tremendous amount of new insights especially into the more complex interactions between the flow field and deformable objects like vesicles or red blood cells. We trace the way from the investigation of single cell dynamics to the recent developments of microfluidic techniques for particle and cell sorting using hydrodynamic forces. Such continuous and label-free on-chip cell sorting devices promise to revolutionize medical analyses for personalized point-of-care diagnosis. We present the state-of-the-art of different hydrodynamic lift-based techniques and discuss their advantages and limitations.     

Development and validation of a rapid HPLC method for the determination of five banned fat-soluble colorants in spices using a narrow-bore monolithic column

This work reports a fast and simple liquid chromatographic method for the simultaneous determination of five banned fat-soluble synthetic colorants, namely Sudan I-IV and Para-Red, in spice samples. The analytes were successfully separated isocratically in less than 5 min on the new narrow bore monolithic column, FastGradient^® Chromolith (50 mm × 2.0 mm i.d.) using a mobile phase of 0.1% (v/v) HCOOH/acetonitrile (35/65%, v/v) at a flow rate of 1.5 mL min⁻¹. All colorants were detected at 506 nm. The main parameters (mobile phase composition, flow rate, injection volume) affecting the separation were studied. The proposed method was thoroughly validated in terms of linearity, LODs, precision and accuracy. The method was applied to the determination of the studied azo-dyes in various spices (paprika, chilli and mixed spice powders) after ultrasound-assisted extraction. Satisfactory recoveries, ranging from 92% to 109% were obtained.     

甲酚红褪色分光光度法测定芬布芬的研究及其应用

在pH9.00的tris-HCl缓冲溶液中,甲酚红与芬布芬反应形成离子缔合物,使甲酚红溶液褪色.实验结果表明:最大褪色波长位于569.0nm,芬布芬浓度在0.05086～10.17μg/mL范围内遵循比尔定律,回归方程为ΔA=0.1702c+0.0107(c=μg/mL),相关系数为r=0.9996,表观摩尔吸光系数为4.537×104 L·mol-1·cm-1.据此建立了测定药物制剂和生物样品中芬布芬含量的褪色分光光度法,样品测定平均回收率为97.97%～101.6%.     

Insight into Amyloid Formation Using Congo Red as the Electrochemical Probe

The amyloid‐β (Aβ) aggregation pathway is an important target for the discovery of drugs that can prevent or delay the onset of Alzheimer’s disease (AD). The electrochemistry of Congo Red (CR) represents a particularly promising tool for screening of Aβ‐binding therapeutics in a rapid and cost‐effective format. The results of the differential pulse voltammetry (DPV) measurements were confirmed using simultaneous UV‐vis analysis of the same incubated Aβ samples. The early changes in the electrochemical signals were attributed to the interaction of the Aβ oligomers with CR. The electrochemical approach, in principle, allowed monitoring small molecule‐Aβ interactions on the time scale of aggregation.     

UV/Vis光谱法研究红子色素的稳定性

本文报导了从红子提取，分离天然色素及酸碱和温度等对该色素稳定性的影响。     

Bestimmung von Arsen in Blei und Bleilegierungen

Zusammenfassung Es wird ein Verfahren zur Bestimmung von g/g- bis mg/g-Gehalten Arsen in Blei und Bleilegierungen beschrieben. Das Arsen wird dazu mit NaBH₄ als AsH₃ aus der Probenlösung ausgetrieben und atomabsorptions-spektrometrisch in einer geheizten Quarzküvette bestimmt. Durch geeignete Arbeitsbedingungen werden Störungen durch die Matrix ausgeschaltet. Für den gesamten Arbeitsbereich beträgt die relative Standardabweichung etwa 3% (N=12); die Nachweisgrenze (3 -Grenze) wurde zu 0,1 g/g As ermittelt.

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Determination of arsenic in lead and lead alloys

Summary A method is described for the determination of g/g to mg/g concentrations of As in lead and lead alloys. For that purpose arsenic is blown out from the sample solutions as AsH₃ by use of NaBH₄ and determined by AAS in a heated quartz cuvette. Using suitable conditions disturbances caused by the matrix are eliminated. The relative standard deviation over the whole working range is about 3% (N=12); the detection limit (3 ) was found to be 0.1 g/g As.

     

Application de la Spectroscopie Infra Rouge à L'étude du Comportement Thermique de la Cellulose Partie I.

In this work, we describe and evaluate the use of the Fourier transform infra red (FTIR) spectroscopy in DRIFT mode (diffuse reflectance infra red Fourier transform) in an environmental device to follow the functional evolution of cellulose during thermal treatments. The potentialities (and difficulties) of the technic are given. This revised version was published online in July 2006 with corrections to the Cover Date.     

Energy transfers between Sm and Eu in YPO4, LaP5O14 and LaP3O9 phosphates. Potential quantum cutters for red emitting phosphors

This work concerns the studies of energy transfers between Sm³⁺ and Eu³⁺ ions in some phosphates as new luminescent materials emitting in the orange-red color. The choose of ions is based on the possibility of quantum cutting process and the matrices are selected according to the 5d bands position of Sm³⁺ ion. The Sm³⁺ and Eu³⁺ doped YPO₄, LaP₅O₁₄ and LaP₃O₉ are synthesized and spectroscopic studies in ultraviolet and vacuum ultraviolet ranges have been achieved.     

A DLM/FD/IB Method for Simulating Cell/Cell and Cell/Particle Interaction in Microchannels

A spring model is used to simulate the skeleton structure of the red blood cell （RBC） membrane and to study the red blood cell （RBC） rheology in Poiseuille flow with an immersed boundary method. The lateral migration properties of many cells in Poiseuille flow have been investigated. The authors also combine the above methodology with a distributed Lagrange multiplier/fictitious domain method to simulate the interaction of cells and neutrally buoyant particles in a microchannel for studying the margination of particles.