A New Concept for Interpretation of the Viscoelastic Behavior of Aqueous Sodium Carboxymethyl Cellulose Systems.

Viscoelastic behaviors of aqueous systems of commercially available sodium carboxymethyl cellulose (NaCMC) samples with the degrees of substitution (DS) of approximately 0.68 and 1.3, and the weight-average molar masses (Mw) higher than 200 kg mol-1 dissolved in pure water and aqueous sodium chloride solutions were investigated over a wide concentration (c) range of NaCMC samples. The dependencies of the specific viscosity (ηsp), the average relaxation time (τw), and the reciprocal of the steady-state compliance (Je-1) on c were discussed. The relationships ηsp ∝ c3, τw ∝ c2, and Je-1 ∝ c, characteristic of the rod particle suspensions, were clearly observed in a range lower than the c where the critical gel behavior was observed. Thus, a new concept based on the rheology of rod particle suspensions was employed to interpret the viscoelastic behaviors obtained in the c range. In this context, NaCMC polymer molecules are assumed to behave as extended rod particles with length (L) and diameter (d), including effective electrostatic repulsive distances, due to the dissociation of Na+ in aqueous systems. Thus, the number density of polymer molecules is given to be ν = c/Mw, and viscoelastic parameters such as ηsp, τw, and Je-1 are calculated using the theoretical model for rod particle suspensions proposed by Doi and Edwards. This concept reasonably described not only the viscoelastic data obtained in this study but also those from other groups using NaCMC samples with different DS and Mw values.

Rigid Rod-like Viscoelastic Behaviors of Methyl Cellulose Samples with a Wide Range of Molar Masses Dissolved in Aqueous Solutions.

The viscoelastic behaviors of aqueous solutions of commercially available methyl cellulose (MC) samples with a degree of substitution of 1.8 and a wide range of weight average molar masses (Mw) were investigated over a wide concentration (c) range at some temperatures from -10 to 25 °C. The viscoelastic parameters useful to discuss the structure and dynamics of MC-forming particles in aqueous solutions were precisely determined, such as the zero-shear viscosity (η0), the steady-state compliance (Je), the average relaxation time (τw), and the activation energy (E*) of τw. Because previously obtained scattering and intrinsic viscosity ([η]) data revealed that the MC samples possess a rigid rod-like structure in dilute aqueous solutions over the entire Mw range examined, the viscoelastic data obtained in this study were discussed in detail based on the concept of rigid rod particle suspension rheology. The obtained Je-1 was proportional to the number density of sample molecules (ν = cNAMw-1, where NA means the Avogadro's constant) over the ν range examined irrespective of Mw. The reduced relaxation time (4NAτw(3νJe [η]ηmMw)-1), where ηm means the medium viscosity, was proportional to (νL3)2, L; the average particle length depending on Mw for each sample was determined in a previous study; and the reduced specific viscosity (ηspNAL3(Mw [η])-1), where ηsp means the specific viscosity, was proportional to (νL3)3 in a range of νL3 < 3 × 102. These findings were typical characteristics of the rigid rod suspension rheology. Therefore, the MC samples behave as entangling rigid rod particles in the νL3 range from rheological points of view. A stepwise increase in E* was clearly observed in a c range higher than the [η]-1 value irrespective of Mw. This observation proposes that contact or entanglement formation between particles formed by MC molecules results in an increase in E*.

Fabrications of boron-containing apatite ceramics via ultrasonic spray-pyrolysis route and their responses to immunocytes.

Immunotherapy without side effects has been expected as a novel medical treatment for cancer. However, drugs such as cytokines typically used for immunotherapy are very expensive. Therefore, we propose the concept of immunoceramics that affect the immune system. Previous studies have shown that polymers including the phenylboronic acid group activate lymphocytes. This activation may be due to interaction between the sugar chains in cells and the OH group in B(OH)3 formed via dissociation of the BO2 group. In the present study, boron-containing apatite (BAp; Ca9.5+0.5x{(PO4)6-x(BO3)x}{(BO2)1-xOx} (0 ≤ x ≤ 1)) was successfully fabricated via the ultrasonic spray-pyrolysis (USSP) route. We examined the material properties of the BAp ceramics with an aim to application as immunoceramics and the responses of immune cells to the BAp ceramics. The crystalline phases of the BAp ceramics included the apatite phase and infrared (IR) absorption of BO2 and BO3 groups was detected in the BAp ceramics. The cellular response of immune cells derived from mice spleens to dense BAp ceramics was examined next. The proportion of helper T cells and killer T cells on BAp (x = 0.4) ceramics increased compared to that on hydroxyapatite (Ca10(PO4)6(OH)2; HAp) ceramics and on a control. These results indicate that BAp (x = 0.4) ceramics fabricated via the USSP route can be expected to act as immunoceramics that can affect the immune system.

Reduction of light source noise from optical intrinsic signals of mouse neocortex by using independent component analysis.

Because the optical intrinsic signal (OIS) of the brain is very weak, noise reduction is essential. Independent component analysis (ICA) is widely used for noise reduction. However, the applicability of ICA to the reduction of light source (LS) noise has not been discussed in detail. In addition, determining the proper number of independent components (ICs) for decomposition is very important to a reasonable classification of the ICs. In this study, we considered the applicability of ICA to LS noise reduction by modeling the impact of LS noise on OIS data. We propose a method for determining the number of ICs that uses the power spectral density of LS noise. To evaluate its usefulness, the method was applied to real OIS data of a mouse's cerebral cortex.