Transport behavior of humic acid-modified nano-hydroxyapatite in saturated packed column: effects of Cu, ionic strength, and ionic composition

The surfaces of nano-hydroxyapatite (nHAP) used for contaminated soil and groundwater remediation may be modified to render nHAP highly mobile in the subsurface. Humic acid (HA) is widely used to modify and stabilize colloid suspensions. In this work, column experiments were conducted to determine the effects of contaminant (e.g., Cu) concentration, ionic strength (IS), and ion composition (IC) on the transport behavior of HA-modified nHAP in saturated packed columns. IS and nature of the cation had strong effects on the deposition of nHAP, and the effect was greater for divalent than for monovalent cations. Divalent cations have a greater capacity to screen the surface charge of nHAP, and Ca(2+) bridges the HA-modified nHAP colloidal particles, which causes greater deposition. Moreover, Cu(2+) had a greater effect on the transport behavior than Ca(2+) due to their strong exchange with Ca(2+) of nHAP and its surface complexation with nHAP. The relative travel distance L(T), of the injected HA-modified nHAP colloids, ranges from less than one to several meters at varying Cu concentrations, ISs, and ICs in saturated packed columns. The results are crucial to evaluate the efficacy of nHAP on the remediation of contaminated soil and groundwater environments.     

Aspect-ratio dependent oscillatory thermocapillary convection in the floating half zone

The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection.The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio,and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several mil...     

Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.     

Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Bioassay directed identification of natural aryl hydrocarbon-receptor agonists in marmalade

Citrus fruit and citrus fruit products, like grapefruit, lemon and marmalade were shown to contain aryl hydrocarbon receptor (AhR) agonists, as detected with the DR CALUX bioassay. This is of interest regarding the role of the Ah-receptor pathway in the adverse effects of dioxins, PCBs and other aromatic hydrocarbons. So far it is unclear which compounds in citrus fruit are responsible for the AhR-mediated activity and whether regular exposure to these compounds can cause effects comparable to, e.g. dioxins. The present study aimed at developing a method for identifying unknown Ah-receptor agonists in citrus products based on bioassay directed analysis, using marmalade as a first target. Following extraction with hexane and purification on an aluminium oxide-column, the extract was fractionated by HPLC using a C-18 semi-preparative column. Fractions were extracted, solvent-exchanged into dimethylsulfoxide and subsequently tested with DR CALUX. Extracts were shown to contain primarily coumarins, furocoumarins (FCs) and polymethoxyflavones (PMFs). Identification of fractions most active in the bioassay via LC/MS revealed that bergapten (an FC) is the most important Ah-receptor agonist in marmalade. The approach and method developed resulted in the successful identification of the bioactive component. However, potential pitfalls of the procedure will be discussed.