Optimization of Deacetylation Process for Regenerated Cellulose Hollow Fiber Membranes

Cellulose acetate (CA) hollow fibers were spun from a CA+ Polyvinylpyrrolidone (PVP)/N-methyl-2-pyrrolidone (NMP)/H2O dope solution and regenerated by deacetylation. The complete deacetylation time of 0.5 h was found at a high concentration (0.2 M) NaOH ethanol (96%) solution. The reaction rate of deacetylation with 0.5 M NaOH was faster in a 50% ethanol compared to a 96 vol.% ethanol. The hydrogen bond between CA and tertiary amide group of PVP was confirmed. The deacetylation parameters of NaOH concentration, reaction time, swelling time, and solution were investigated by orthogonal experimental design (OED) method. The degree of cross-linking, the residual acetyl content, and the PVP content in the deacetylated membranes were determined by FTIR analysis. The conjoint analysis in the Statistical Product and Service Solutions (SPSS) software was used to analyze the OED results, and the importance of the deacetylation parameters was sorted as Solution > Swelling time > Reaction time > Concentration. The optimal deacetylation condition of 96 vol.% ethanol solution, swelling time 24 h, the concentration of NaOH (0.075 M), and the reaction time (2 h) were identified. The regenerated cellulose hollow fibers under the optimal deacetylation condition can be further used as precursors for preparation of hollow fiber carbon membranes

Membranes for CO2 capture - report on pilot plant tests

Although the main part of the world has now accepted the fact that the global climate change is due to human activities, we will not be able to switch gear and only go for “green energy” without fossil fuels for still many decades. One way of contributing to combat the climate change is hence to capture the CO2 from fossil fuel flue gases, and either find ways to utilize the CO2 or sequestrate it in aquifers or depleted oil fields, while we slowly develop a “green way of living”. Membranes will for sure represent one of the emerging technologies to be used for CO2 capture. Today there are a few pilot installations around the world using different types of membranes, to demonstrate and learn the best way of optimize such a capture plant – in Norway there are two of such kind; one at a cement factory in Brevik in South Norway and one at a test center at Tiller in Trondheim. At the cement plant the CO2 concentration in the flue gas can be close to 20 vol%, while at the Tiller plant there is a possibility to vary the CO2 concentration over a range of 8 – 12vol%. At the cement plant the flue gas contains quite a few unwanted components, while at Tiller the flue gas is relatively “clean”. The type of membrane installed at these two sites is hollow fiber modules where the support fiber is polysulfone (PSf) and the coated mebrane is a polyvinylamine (PVAm). The technique for applying the coating is not straight forward, and an efficient flue gas separation depends strongly on a successful coating procedure. Going from lab tests using a few cm2 up to several m2 of a commercial scale module is extremely challenging. The tests are being performed with 2 or 3 modules in parallel or series, but not yet as a complete two-stage process. Based on obtained results, a full scale process will be simulated. Preliminary results using only one stage at Tiller are already documenting an encouraging 58% CO2 in permeate from 7% CO2 in feed line. The PVAm membrane is based on facilitated transport of the CO2 through the membrane, which means that water needs to be handled in the separation process – this has again a large influence on the engineering design of the process and process operation parameters. The presentation will highlight and report some results and challenges from these two tests sites. Acknowledgement The GASSNOVA projects 229949 and 249036 are highly recognized for contributions from the CLIMIT-Demo program in the Norwegian Research Council, Air Products and Chemicals, Inc. (USA), Air Products AS (Norway), Alberta Funders (Canada), Statoil ASA, NORCEM (Heidelberg Cement), SINTEF Materials and Chemistry, DNV GL (The Netherlands)

Directional Spin Wave in Spin-Torque Oscillators Induced by Interfacial Dzyaloshinskii–Moriya Interaction

Spin torque oscillators (STOs) are currently of great interest due to its wide tunable frequencies, low energy consumption and high quality factors compared with traditional oscillators. Here, we report the characteristics of the nanocontact-(NC-)STO in the presence of interfacial Dzyaloshinskii-Moriya interaction (DMI), using micromagnetic simulations. We find that the DMI can decrease the STO frequency by around 2 GHz. More importantly, the DMI is able to break the isotropy of the spin-wave spectrum and turn the emitted microwave into directional spin-wave beams potentially facilitating the synchronization of multiple STOs

Social Interaction, Stochastic Volatility, and Momentum

This paper incorporates information uncertainty and social interaction among investors into a random utility framework and develops an evolutionary equilibrium model of asset pricing and investor choice dynamics. We show that strong social interaction can lead to endogenous switching between two persistent regimes for the mean choice and return volatility, which can simultaneously generate time-series momentum and volatility clustering in asset returns. By using StockTwits post volume as a proxy for social interaction, we provide empirical evidence for the model predictions for various equity indices

Mammalian PER2 Regulates AKT Activation and DNA Damage Response

PER2 is a key mammalian circadian clock protein. It also has a tumor suppressive function. Down regulation of PER2 in the cultured cancer cells accelerates cell proliferation, while overexpression of PER2 inhibits cell growth and induces apoptosis. The Per2 mutant mice have a cancer prone phenotype and an altered DNA damage response. Here we report that PER2 regulates AKT activity. Cells with down-regulated PER2 expression have prolonged high levels of AKT T308 phosphorylation after growth factor stimulation or DNA damage. PER2 down-regulation delays DNA damage induced Chk2 activation and overrides DNA damage induced apoptosis and cell cycle arrest

Femtosecond laser-heating effect on the magnetization dynamics in perpendicularly magnetized Ta/CoFeB/MgO film

We have studied the effect of ultrafast laser-heating on the magnetization dynamics of perpendicularly magnetized CoFeB film by means of the time-resolved magneto-optical Kerr rotation effect. The effective perpendicular magnetic anisotropy field HK is significantly decreased with enhancing the pump laser-fluence in a moderate range of 5-12 mJ cm-2. The Gilbert damping, however, is found to be independent of the pump fluence. These findings provide a new method of separately manipulating the Gilbert damping and perpendicular magnetic anisotropy

Enhanced magnetoresistance in NiFe/GaAs/Fe hybrid magnon valve

The magnon valve (MV), which consists of a one spacer layer sandwiched between two ferromagnetic layers, is a potential spintronic device. The operation principle of the magnon valve depends on magnon current propagating between the two magnetic layers. More specifically, the magnon current is induced in one ferromagnetic layer and then injects magnons into the other ferromagnetic layer through the spacer layer. During this process, the magnetization of the injected ferromagnetic layer is changed, leading to the different relative magnetic orientations of the two magnetic layers. Here, we investigated the electromagnetic property of the NiFe/GaAs/Fe magnon valve assisted by microwaves with various frequencies. We find that the magnetoresistance (MR) of the magnon valve increases up to 40% when applying an external 3.4GHz microwave. The increase in the magnetoresistance results from the magnon current propagating between the two ferromagnetic layers. The magnons induced by the external microwave share the same phase, and thus the magnon current can penetrate into a 70 μm thick GaAs by coherent propagation

Investigation into the Influence of Physician for Treatment Based on Syndrome Differentiation

Background. The characteristics of treatment based on syndrome differentiation (TBSD) cause great challenges to evaluate the effectiveness of the clinical methods. Objectives. This paper aims to evaluate the influence of physician to personalized medicine in the process of TBSD. Methods. We performed a randomized, triple-blind trial involving patients of primary insomnia treated by 3 physicians individually and independently. The patients (n=30) were randomly assigned to receive treatments by the 3 physicians for every visit. However, they always received the treatment, respectively, prescribed by the physician at the first visit. The primary outcome was evaluated, respectively, by the Pittsburgh Sleep Quality Index (PSQI) and the TCM symptoms measuring scale. The clinical practices of the physicians were recorded at every visit including diagnostic information, syndrome differentiation, treating principles, and prescriptions. Results. All patients in the 3 groups (30 patients) showed significant improvements (>66%) according to the PSQI and TCM symptoms measuring scale. Conclusion. The results indicate that although with comparable effectiveness, there exist significant differences in syndrome differentiation, the treating principles, and the prescriptions of the approaches used by the 3 physicians. This means that the physician should be considered as an important factor for individualized medicine and the related TCM clinical research

Transient enhancement of magnetization damping in CoFeB film via pulsed laser excitation

Laser-induced spin dynamics of in-plane magnetized CoFeB films has been studied by using time-resolved magneto-optical Kerr effect measurements. While the effective demagnetization field shows little dependence on the pump laser fluence, the intrinsic damping constant has been found to be increased from 0.008 to 0.076 with the increase in the pump fluence from 2 mJ/cm2 to 20 mJ/cm2. This sharp enhancement has been shown to be transient and ascribed to the heating effect induced by the pump laser excitation, as the damping constant is almost unchanged when the pump-probe measurements are performed at a fixed pump fluence of 5 mJ/cm2 after irradiation by high power pump pulses