Specific Adsorption Rate Research Articles

The Non Thermal Effect of Weak Intensity Millimeter Waves on Physicochemical Properties of Water and Water Solutions

The comparative study of the effects of 5.8mW/cm2 Millimeter Waves (MMW) and near Infrared (IR) irradiation on thermal properties, specific adsorption rate (SAR), specific electrical conductivity (SEC) and hydrogen peroxide (H2O2) content of distilled water (DW), and physiological solutions (PS) was performed. The thermal effect of MMW irradiation appeared only after the first minute of irradiation, while the IR heating started from the first minute of irradiation. The heat fusion of frozen MMW-treated DW and PS was significantly less than sham and IR-treated DW and PS. MMW irradiation had time-dependent elevation effect on water SEC and SAR, which was accompanied by the increase of H2O2 formation in it. We suggest that the MMW-induced vibration of water dipole molecules caused the non thermal changes of physicochemical properties of DW and PS, which promote the formation of H2O2 in water.

Equilibrium and kinetics of 5-aminosalicylic acid adsorption by halloysite

This paper investigates equilibrium, kinetics and thermodynamic aspects of the adsorption of 5-amino salicylic acid [5-ASA], an anti-inflammatory agent, onto halloysite, a mesoporous polymorph of kaolin appearing as hollow nanotubes with diameters typically smaller than 100 nm and lengths ranging from 500 nm to over 1 μm. Kinetic and equilibrium studies were performed in aqueous medium at different temperatures and drug concentrations. The amounts of 5-ASA retained by the clay was evaluated by UV spectroscopy. Mathematical treatment of the data was performed following Valenzuela et al. [C. Valenzuela-Calahorro, A. Navarrete-Guijosa, M. Stitou, E. Cuerda-Correa, Colloids Surf. A: Physicochem. Eng. Aspects 224 (2003) 135–147], and thermodynamic parameters were then calculated by using the Eyring equation. The overall adsorption process of 5-ASA onto halloysite was explained as the result of two separate processes. Initial rapid adsorption of 5-ASA (specific adsorption rates between 10.0 and 12.3 s −1) on the external halloysite surface (ΔH = 7.59 kJ/g) was followed by slow adsorption (specific adsorption rates between 0.2 and 0.4 s −1) of the drug inside the phyllosilicate pores (ΔH = 42.28 kJ/g). Adsorption experiments showed that promising delivery systems may be designed by supporting 5-ASA onto halloysite.

Gd-doped iron-oxide nanoparticles for tumour therapy via magnetic field hyperthermia

Gd-doped iron oxide nanoparticles were developed for use in tumour therapy via magnetic fluid hyperthermia (MFH). The nanoparticle composition was Gd0.02Fe2.98O4 as determined by ICP-AES. TEM image analysis showed the primary particles to be about 13 nm in diameter. The specific power adsorption rate (SAR) determined with a field strength of 246 Oe and 52 kHz was 36 W per gram of Fe. This value is about 4 times higher than the reported SAR values for Fe3O4. The heating rate for the nanoparticles in vivo and the potential for tumour therapy were determined in a mouse model. The mouse models treated with doped iron oxide displayed much slower tumour growth, the tumour doubled its mass after 7 days post-treatment compared to 4 days for those models treated with standard iron oxide or saline solution.

The number of genes changing expression after chronic exposure to Code Division Multiple Access or Frequency DMA radiofrequency radiation does not exceed the false‐positive rate

Experiments with cultured C3H 10T 1/2 cells were performed to determine if exposure to cell phone radiofrequency (RF) radiations induce changes in gene expression. Following a 24 h exposure of 5 W/kg specific adsorption rate, RNA was extracted from the exposed and sham control cells for microarray analysis on Affymetrix U74Av2 Genechips. Cells exposed to 0.68 Gy of X-rays with a 4-h recovery were used as positive controls. The number of gene expression changes induced by RF radiation was not greater than the number of false positives expected based on a sham versus sham comparison. In contrast, the X-irradiated samples showed higher numbers of probe sets changing expression level than in the sham versus sham comparison.

Retention of Progesterone by an Activated Carbon: Study of the Adsorption Kinetics

The process by which progesterone in an ethanol solution is retained by Merck granular activated carbon involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (θ) of the adsorbing surface and (1−θ). Over the temperature range 10–40°C, the specific adsorption rate varies from 5.8·10−5 to 1.3·10−4 s−1. The thermodynamic activation functions for the process are ΔH*=41.6 kJ/mol and ΔS*=−0.20 kJ/K· mol. The rate of the adsorption-desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent.

Application of a Single Model to Study the Adsorption Kinetics of Prednisolone on Six Carbonaceous Materials

The knowledge of the adsorption processes of nonelectrolytes from liquid solution on solid materials involves the study of their kinetic and equilibrium aspects as well as the understanding of their thermodynamic functions. However, in most published papers adsorption isotherms are analyzed by using the Giles classification and other proposed equations which are either empirical or based on kinetic or thermodynamic criteria. Our opinion is that both the kinetic and the equilibrium studies must be complementary and that, in general, equations describing the adsorption isotherms come from the kinetic laws governing the different partial processes which determine the global process. These kinetic laws may be derived from single models. In this paper a single model is proposed, which makes it possible to establish a kinetic law satisfactorily fitting a great number of C (concentration) vs t (time) isotherms. This model has been applied to study the adsorption process of prednisolone by six carbonaceous materials from ethanol solution, the specific adsorption rate, and the activation thermodynamic functions being calculated. The results obtained have also been used to analyze the influence of the intraparticle diffusion on the kinetics of the process.

A coupled adsorption–aggregation model of the POC/ [formula omitted] ratio of marine particles

Thorium has been frequently used as a tracer of particulate carbon removal from the ocean surface mixed layers. Although coagulation is known to be important in the process, models used to interpret measurements have been limited to simple descriptions of coagulation. We present results from a coupled adsorption–aggregation model for 234 Th scavenging. The aggregation component models the particle size spectrum from colloidal particles to particles of about 100 μm in size and incorporates details of the physical mechanisms that bring particles together. We make comparisons between an adsorption model that has a constant mass specific adsorption rate and one that is purely transport limited, the former of which is shown to be unphysical for larger particles. The combined model reproduces the observed inverse dependence of POC/ 234 Th on particle size. Comparison with observational results is made by simulating a series of filtrations using the model results. The filtered values are determined by the maximum of the particle distribution within the relevant size range, and consequently affect the comparison between observed values and model output. This stresses the importance of the particle size spectrum in the scavenging process and suggests that measurements using more particle size classes should be made to accurately determine kinetic rates.

Effect of functional magnetic particles on radiofrequency capacitive heating.

Magnetic particles (magnetite) were used to make radio frequency (RF) capacitive hyperthermia effective to a specific site. In an agar phantom experiment, a magnetite‐containing agar piece was buried in a large agar phantom and heated by an 8 MHz‐RF capacitive heating device. The magnetite‐containing agar piece was heated more than the magnetite‐free agar phantom, and the specific adsorption rate in the phantom was increased 1.5 times by the magnetite particles. The temperature distribution in the large agar phantom showed that the highest temperature was obtained at the center of the magnetite‐containing piece. The rate of temperature increase was approximately proportional to the magnetite concentration to the power 0.8. This method was applied to an in vivo experiment using a pig. Magnetite was prepared as a colloidal material dispersed in a carboxymethylcellulose solution (CMC‐Mag) and intramuscularly injected in the pig femur. As a result of 8 MHz‐RF heating, the temperature at the CMC‐Mag‐injected point increased to over 43°C after 7 min, while the temperature at a point without magnetite was under 40°C at the same time. The specific adsorption rate in the magnetite‐containing tissue was twice that of the magnetite‐ free tissue. In addition, the time required to reach a temperature of over 43°C was only 7 min, while it was over 15 min in the case without the CMC‐Mag.