Immersion In Pure Water Research Articles

Computational insights into survival durations and prehospital interventions in accidental cold-water immersion: A comprehensive analysis of fresh and saltwater temperatures

This study examines the complex relationship between scenarios of cold-water immersion, survival durations, and prehospital interventions. It utilizes computational modeling methods to shed light on how different water temperatures affect individuals facing accidental cold-water immersion incidents. The analysis reveals significant variations in survival times based on water temperature. For example, subjects immersed in water at temperatures of 5 °C, 2 °C, and 0 °C had average survival times of 136, 113, and 100 min, respectively, under stable conditions. In flowing water at the same temperatures, survival times decreased to 119, 92, and 81 min, indicating the impact of water movement on cooling rates and survival durations. Likewise, individuals immersed in saltwater at temperatures of 5 °C, 2 °C, 0 °C, and −2 °C showed average survival times of 111, 88, 80, and 66 min, respectively, in static conditions. In flowing saltwater at the same temperatures, survival times decreased to 98, 74, 68, and 57 min, highlighting the influence of water flow on cooling rates and survival durations. A comparison between immersion in pure water and saltwater at 2 °C revealed survival times of 113 and 88 min under stable conditions and 92 and 74 min under dynamic conditions, emphasizing the role of water composition in survival outcomes. The study also challenges the notion that the demise of the Titanic's passengers and crew resulted from hypothermia, asserting instead that severe thermal shock was the primary cause. These numerical findings underscore the importance of considering water temperature, flow dynamics, and prompt medical responses in cold-water emergencies to enhance survival prospects. The study identifies water within the range of 41–43 °C as the most effective active external rewarming fluid for critical hypothermal conditions. By quantifying the impact of these variables on survival times, the study provides data-driven recommendations to improve emergency protocols and outcomes for individuals facing cold-water immersion incidents.

Ion-Cross-Linked Hybrid Photochromic Hydrogels with Enhanced Mechanical Properties and Shape Memory Behaviour.

Shape-shifting polymers usually require not only reversible stimuli-responsive ability, but also strong mechanical properties. A novel shape-shifting photochromic hydrogel system was designed and fabricated by embedding hydrophobic spiropyran (SP) into double polymeric network (DN) through micellar copolymerisation. Here, sodium alginate (Alg) and poly acrylate-co-methyl acrylate-co-spiropyran (P(SA-co-MA-co-SPMA)) were employed as the first network and the second network, respectively, to realise high mechanical strength. After being soaked in the CaCl2 solution, the carboxyl groups in the system underwent metal complexation with Ca2+ to enhance the hydrogel. Moreover, after the hydrogel was exposed to UV-light, the closed isomer of spiropyran in the hydrogel network could be converted into an open zwitterionic isomer merocyanine (MC), which was considered to interact with Ca2+ ions. Interestingly, Ca2+ and UV-light responsive programmable shape of the copolymer hydrogel could recover to its original form via immersion in pure water. Given its excellent metal ion and UV light stimuli-responsive and mechanical properties, the hydrogel has potential applications in the field of soft actuators.

Flexible, stretchable and lightweight polyurethane and graphene nanoplatelets nanocomposite for high performance EMI shielding application

The incessant growth of technology has extensively increased the usage of electronics and telecommunication devices, leading to critical electromagnetic (EM) pollution and affecting the performance of intensely sensitive electronic devices. Herein, graphene nanoplatelets (GNP) were synthesized from the microwave intercalation method, followed by water-bath sonication. The different dosing of synthesized GNP (2, 4, 6, and 8 weight%) is further encapsulated in polyurethane (PU) matrix via solution casting technique to obtain enhanced electromagnetic interference (EMI) shielding performance. It was found that the 6 weight % of GNP (GNP6) having a density of 0.74 g/cc shows excellent stretching mechanical properties (> 400%), mechanical strength (1.4 times PU), electrical conductivity (2.75 S/m) and microwave properties. The maximum EMI shielding efficiency (SE) of 40.9 dB and 70.5 dB is noticed for GNP6 at 1 mm and 2 mm thickness, respectively. The SE is also measured for GNP6 2 mm thick sample after mechanically bending for 500 cycles and observed average variation <3 dB. The EMI SE is measured after placing the GNP6 inside the waveguide at different bending radii varying from 3 to 9 mm, and 75 dB of SE is observed for a bending radius of 3 mm. The fabricated GNP6 nanocomposite can show stable EMI shielding performance even after immersion in pure water, followed by sonication treatment for 2 hours and confirming the capability of the nanocomposite to handle the complex environment. The EMI shielding mechanism for GNP/PU is extensively explained concerning the microstructure and microwave properties. The computational analysis is done by simulating the GNP6 in the CST microwave studio tool over the broad frequency range (1-18 GHz). Thus, the highly stretchable, flexible, and lightweight GNP6 is a favourable nanocomposite providing a high EMI shielding value for next-generation electronic packaging of flexible electronic devices and coating of conformal devices used in aerospace industries.

The Effect of Dielectric Barrier Discharge Plasma Gas and Plasma-Activated Water on the Physicochemical Changes in Button Mushrooms (Agaricus bisporus).

Button mushrooms (Agaricus bisporus) are highly popular worldwide due to their rich nutritional value and health benefits. However, the rapid water loss rate and browning restrict their economic value. The atmospheric cold plasma (ACP) generated by the plasma equipment used by dielectric barrier discharge preservation technology is widely used for food preservation since it is cost-efficient and environmentally friendly, generating no chemical residues. This study established four treatment groups, namely the direct ACP treatment group (DBD), plasma-activated water immersion group (PAW), pure water immersion group (PW), and control group (control), to explore the effect that ACP preservation technology has on button mushrooms. The results indicated that ACP treatment decreased the pH of pure water from 5.90 ± 0.03 to 5.16 ± 0.03, while significantly increasing the temperature (p &lt; 0.05). During the storage period, the browning index (BI) and E value were the lowest in the PAW group, which exhibited the best hardness and sensory properties. Neither the pH nor water activity changed significantly during the storage period in any of the groups. The polyphenol oxidase (PPO) activity in the button mushroom decreased significantly compared with the control after plasma-activated water treatment. In summary, plasma-activated water significantly reduced the BI and E value of button mushrooms, inhibited PPO activity, and yielded the most stable sensory properties for the optimal preservation of button mushrooms.

Effect of marine environment on the mechanical properties degradation and long-term creep failure of CFRP

The carbon fiber reinforced plastics (CFRP) has broad application prospect in the marine field, but its significate long-term performance and failure mechanism are still unclear. In this paper, the mechanical property degradation and creep failure mechanism of CFRP in marine environment were investigated by the molecular dynamics (MD) method. Based on the CFRP molecular model established in dry, pure water and salt immersion environment, the effect of service conditions on it in marine environment was explored. The results show that the marine environment can lead to a significant decrease in the mechanical properties of CFRP only in the vertical fiber direction, and the degradation extent increases with the increase of temperature. The effects of pure water immersion and salt immersion environment on its mechanical properties are basically the same. High stress level, hygrothermal environment and high temperature salt immersion environment will accelerate the creep failure of CFRP. Later, the creep failure mechanism of CFRP is analyzed from microstructure and microscopic energy. Microstructure analysis shows that water molecules could accelerate the movement of epoxy fragments and lead to CFRP failure. Microscopic energy analysis shows that the conversion process of strain energy and the decline of interface performance are the important reasons for creep failure. The finds of this paper introduce a new method to study the long-term performance of CFRP and can provide reference for the engineering application of CFRP in marine environment.

Flexible, stretchable, waterproof (IPX7) electro-thermal films based on graphite nanoplatelets & polyurethane nanocomposites for wearable heaters

Electrothermal materials have been widely used due to controllable heat energy in our life. With the development of wearable technology, a flexible, safe and waterproof heater with the good ability to endure repeated bending is required in future. In this paper, we have developed a novel wearable heater based on flexible, stretchable graphite nanoplates and polyurethane (GNP/PU) nanocomposite films. Firstly, the GNP/PU thin films with a thickness of 30–200 μm were fabricated in mass production by the method of gap-coating, which can be bent 180° repeatedly, or even knotted for their excellent flexibility, and has a maximum elongation up to 387.8%, due to the homogenous distribution of GNP in PU matrix. By the control on the amount of GNP and the thickness of the film, the minimum resistivity and square resistance of the GNP/PU films can be 80 mΩ·cm and 4 Ω/□, respectively. Through a further flexible structure designing and waterproof electronic packaging process, the fabricated wearable heaters are able to withstand 100,000 180-degrees bending with the resistance changes of only 3.24%, and have a IPX7 waterproof ability to work continuously for 120 min under 1.30 m water. Interestingly, as-prepared bare GNP/PU films have a good resistence to water and salt erosion, with the light 2.1%, 2.4% and 3.1% increasing in electrical resistance, and without obvious change in heating performance, even after the immersion in pure water, 0.5% and 5% salt water and dried completely. Furthermore, the wearable heaters can generate heat uniformly under the safe voltage of 5–24 V to achieve rapid heating and cooling rate of 25 °C/min and 13 °C/min, respectively. Lastly, a heating full-body vest mode of as-prepared wearable heaters was fabricated, which can work well with hand raising, bending and walking. The results showed that as-prepared wearable heaters were very suitable for wearable electronics, due to the excellent flexibility and stretchability of GNP/PU films and their special packaging structure, which provides a new choice for wearable heating products.

Influence of CO2–water–rock interactions on the fracture properties of sandstone from the Triassic Xujiahe Formation, Sichuan Basin

Carbon dioxide (CO2) storage in deep saline aquifers has been lauded as one of the most effective techniques to mitigate greenhouse effects globally. Nevertheless, despite many investigations, clarifying the influence of CO2–water–rock interactions on the fracture characteristics of sandstone remains a challenge. In this work, the fracture properties of sandstone collected from the Triassic Xujiahe Formation are systematically studied in tests simulating CO2 sequestration. The results indicate that the water–rock interactions occur in a system of sandstone and CO2 solution. Due to the interactions, the porosity of sandstone specimens slightly increases from 8.24 to 8.45% when immersed in CO2 solution and from 8.20 to 8.40% in pure water after 28 days. In addition, the parameters of fracture toughness, tensile strength, uniaxial compressive strength and elastic modulus are reduced by 24.12%, 27.16%, 31.78% and 33.21% after immersion in pure water, while they are reduced by 24.05%, 29.72%, 30.75% and 25.79% after immersion in CO2 solution, respectively. These results suggest that the mechanical properties of the Xujiahe sandstone deteriorate after soaking. The results also show that the critical fracture energy of sandstone specimens after immersion in the CO2 solution is 10.4% lower than that in pure water and 24.1% lower than that under natural drying conditions. These research results have great significance for understanding the dissolution processes during CO2 sequestration and their influence on the fracture properties of sandstone, which may be theoretically instructive for CO2 storage in the Xujiahe Formation in the Sichuan Basin.

Effects of water absorption on the mechanical properties of GFRPs

This study reports on the effects of water absorption on the anisotropic mechanical response of an epoxy resin reinforced with E-glass fibres. Composite specimens were conditioned by immersion in pure water at 50 °C for different time durations, up to full saturation. Water-saturation resulted in reduction of stiffness and strength, in the range of strain rate 0.001–700s−1. Experiments on re-dried specimens after water saturation showed a limited recoverability of the original mechanical properties. Water absorption increased the sensitivity of the mechanical response of the GFRPs to the applied strain rate. Finite element simulations of the response of a unit cell of the unidirectional composite were performed to understand the role of the hygroscopic stresses induced by water absorption, and it was found that this is negligible due to the active mechanisms of viscoelastic relaxation.

Use of ozone and detergent for removal of pesticides and improving storage quality of tomato.

The efficiencies of two conventional domestic procedures (immersion in pure water and detergent solution at 0.25 and 1%) and two treatments using ozone (immersion in water with bubbling O3 and immersion in ozonated water, both at 1 and 3 mg L-1) were evaluated for the removal of residues of the fungicides azoxystrobin, chlorothalonil and difenoconazole in tomatoes. The fungicides were sprayed on the fruits at the recommended concentration for the crop. The residues in the tomatoes and in the washing solutions were determined by extraction with low-temperature partition techniques and analysis by gas chromatography. More concentrated solutions were more effective in removing pesticide residues. The water bubbled with ozone at 3 mg L-1 was the most efficient treatment for the removal of fungicides, reaching a reduction of 70-90% of the residues. However, the treatments with the lowest concentration of ozone had lower loss of fruit mass during storage.

Application of non-destructive integrated CT-XRD method to investigate alteration of cementitious materials subjected to high temperature and pure water

In order to analyze the alteration mechanism after the exposure to various maximum temperatures and immersion in pure water, non-destructive integrated CT-XRD method (the CT-XRD) was applied. Firstly, the verification of the CT-XRD was carried out to compare with conventional powder X-ray diffraction. It revealed that the CT-XRD could evaluate the crystals properly with a given limitation for low energy band. Besides, the CT-XRD indicated the advantage that can detect the presence of crystals which cannot be detected after grinding in preparing the powder sample for the conventional powder XRD. Then, the carbonated cement paste that was heated at 200, 400, 600, and 800 °C followed by immersion in pure water was evaluated by the CT-XRD. The results suggest that sample heated at 400 °C showed the resistance of leaching at most. In addition, rehydration of clinker minerals generated due to heating at 800 °C could be identified although the hydration product was easily dissolved into water.

Ag release from sputtered Ag/a:C nanocomposite films after immersion in pure water and NaCl solution

Diamond-like carbon (DLC) coatings doped with Ag nanoparticles are promising materials for several application, as, for example, a biomaterial. In addition to their numerous properties, when doped with silver, DLCs can acquire antibacterial properties. In this study, Ag/a:C films were deposited by unbalanced magnetron sputtering. The dimension and distribution of silver nanoparticles in the carbon matrix were characterized before and after immersion in different liquid environments, ultra-pure water and NaCl (0.9%). Inductively coupled plasma-optical emission spectroscopy was used to quantify the Ag ions released from the film. Based on the aspect of Ag nanoparticles on the films surface, suggested by atomic force microscopy analysis, scanning electron microscopy was performed to access the dimension and the distribution of the nanoparticles at the surface and, then, to calculate the mass of Ag in the film, before and after exposure to both liquids. Agglomeration and coalescence of the nanoparticles in the film surface were studied and information about the segregation from the bulk to the surface was achieved, also confirmed by X-ray photoelectron spectroscopy analysis.

Effect of Si-Addition in Stainless Steel on Surface Oxidation in High Temperature Water Environments

Being used as the internal components of pressurized water reactor (PWR), austenitic stainless steels (SSs) are susceptible to irradiation-assisted stress corrosion cracking (IASCC) that is a critical issue for the long term safe operation. Radiation induced segregation (RIS) at grain boundaries in austenitic SSs, such as the depletion of Cr and enrichment of Ni and Si, is thought to contribute to IASCC. Studying the oxidation behavior of the model alloys simulating grain boundary RIS in high temperature water could provide evidence for the effect of RIS on IASCC. In this study, the model alloys 9Cr-25Ni-1.5Mo-5Si and 9Cr-25Ni-1.5Mo-3Si were used to simulate the depletion of Cr and enrichment of Ni and Si at grain boundaries of irradiated 316L SS. The oxide film properties of 316L SS and model alloys in of high temperature water environments were investigated. After the immersion in high-temperature water environments, the surface morphologies of the oxide films formed on the immersed specimens were examined using JEOL JSM-7500F field emission scanning electron microscope (FESEM). The oxide films were analyzed using INVIA laser Raman spectrometer with laser wavelength of 514.5 nm. The compositions of oxide particles were analyzed by the energy-dispersive spectrometry (EDS) attached to the FESEM. Fig.1 shows the SEM morphologies of the 316L SS, 9Cr-25Ni-1.5Mo-3Si and 9Cr-25Ni-1.5Mo-5Si alloy surfaces after immersion in pure water at 290 oC (pH at 290 oC of about 5.6) for 120h. The surfaces of all the test specimens were covered with polyhedral particles of different sizes. Larger size outer layer oxides are formed on 9Cr-25Ni-1.5Mo-3Si and 9Cr-25Ni-1.5Mo-5Si specimen surface. On the surface of 316L SS, there were only sparsely distributed large-size particles. Si addition in the alloy matrix favors the formation of the oxide layer in this environment. Fig. 2 shows the SEM morphologies of 316L SS, 9Cr-25Ni-1.5Mo-5Si and 9Cr-25Ni-1.5Mo-3Si alloys surfaces after the immersion in high temperature water of pH 9.5 (pH adjusted with monoethanolamine) at 290 oC for 24h, 48h and 120h. Compact and homogeneous oxide particles were formed on the surfaces of 316L SS and model alloys. The size of the oxide particles on model alloys was smaller than that on 316L SS. The oxide particle size of 9Cr-25Ni-1.5Mo-5Si and 9Cr-25Ni-1.5Mo-3Si was similar. The morphologies of particles became more stereoscopic with increasing immersion time. The outer layer oxide particles formed on the 316L SS and model alloys decreased with increasing solution pH value. The pH value has a significant influence on the oxidation of 316L SS and model alloys. These results show that the effect of Si in the alloy on oxide film properties is strongly dependent on the water chemistry. Si in the alloy facilitated the formation of large-sized outer layer in 290 oC water of pH 5.6, which refined the outer layer oxide particles in 290 oC water of pH 9.5. High solubility of Si-bearing oxide in high temperature water can modify the oxide film on the surface. These results show that Si in the alloy would play a role in IASCC through the modification of oxide film. Figure 1

Effects of Hydrogen on Corrosion Products Formed on Iron in Chloride Solutions

The effects of charged-hydrogen on the properties of the surface films formed on iron after 21 h immersion in pure water and 10-4 to 0.5 mol/L NaCl solutions at 25 °C are investigated by open circuit potential (OCP) measurements, optical microscope, Raman spectroscopy and X-ray diffraction (XRD). Hydrogen-charging favors the formation of with dark film with yellow corrosion sites on iron. After immersion in 10-4 mol/L NaCl solution, the non-charged iron is partly covered by surface film, while the hydrogen-charged iron is fully covered by surface film. After immersion in 0.5 mol/L NaCl solution, the surface of the non-charged iron is partly dark and partly covered with yellow rusts, and the surface of the hydrogen-charged iron has a larger area covered with yellow rusts than that on the non-charged iron. OCP values for hydrogen-charged iron in pure water, 10-3 and 10-4 mol/L NaCl solutions are lower than those for non-charged iron. In 0.5 mol/L NaCl solution, the OCP difference between non-charged iron and hydrogen-charged iron is at first large and gradually becomes smaller with increasing immersion time. Raman spectra and XRD patterns show the presence of magnetite in the film on hydrogen-charged iron after immersion in 10-4 mol/L NaCl solution. In solutions with a high chloride concentration, hydrogen in iron can promote the formation of high valence iron oxide layer by precipitation.

The Effects of Hydrogen on Corrosion Products Formed on Iron in Chloride Solutions

The effects of charged hydrogen on the properties of the surface films formed on iron in pure water and 10-4 to 0.5 mol/L NaCl solutions at 25°Cwere investigated by open circuit potential (OCP) measurements, optical microscope, scanning electron microscope and X-ray diffraction (XRD). After 21h immersion in pure water, the surface of non-charged iron did not significantly and showed only local corrosion sites, while the surface of hydrogen-charged iron was covered with dark film with many yellow corrosion sites on it. After 21h immersion in 10-4 mol/L NaCl solution, the non-charged iron was partly covered by surface film, while the hydrogen-charged iron was fully covered by surface film, as shown in Fig. 1. After 21h immersion in 0.5 mol/L NaCl solution, the surface of the non-charged iron was partly dark and partly covered with yellow rusts, and the surface of the hydrogen-charged iron had a larger area covered with more yellow rusts than that on the non-charged iron, as shown in Fig. 2. Results of OCP monitoring showed that OCP values for hydrogen-charged iron in pure water, 10-3 and 10-4 mol/L NaCl solutions were lower than those for non-charged iron, as partly shown in Fig. 3a. In 0.5 mol/L NaCl solution, the OCP differences between non-charged iron and hydrogen-charged iron was at first big but gradually became smaller with increasing immersion time, as shown in Fig. 3b. Raman spectra showed the presence of magnetite in the film on hydrogen-charged iron after immersion in 10-4 mol/L NaCl solution, as shown in Fig. 4a, which was supported by XRD results. Yellow rust and the XRD peak for hematite in the films on non-charged and hydrogen iron specimens (Fig. 4) indicated that the mechanism for the effect of hydrogen on the corrosion products of iron in dilute NaCl solutions could be different from that in concentrated NaCl solutions. In solutions with a high chloride concentration, hydrogen in iron might be able to promote the formation of high valence iron oxide, while in many other cases it was found that the formation of magnetite was promoted by hydrogen in iron. Figure 1

Corrosion of Al alloys in repeated wet-dry cycle tests with NaCl solution and pure water at 323 K

Corrosion of Al alloys was examined by repeated wet-dry cycle tests with 5.5 M NaCl solution and pure water at 323 K and compared with immersion test corrosion. All Al alloy specimens after the immersion tests for 7 days in the NaCl solution showed preferential dissolution of the aluminum matrix around Si phases and Al3Fe intermetallic compounds, and in pure water showed formation of thick amorphous hydroxide films. The corrosion rate in pure water was higher than that in the NaCl solution. In the repeated wet-dry cycle test with NaCl solutions, a 0.02-ml droplet of 5.5 M NaCl solutions was initially dripped on specimens at 323 K and left for 690 s to allow the dry up of the droplet, resulting in solid NaCl precipitation. Then, the dissolution and precipitation of NaCl were repeated 150 times by dripping 0.02-ml pure water at 690-s intervals. At the edge of the droplet, pits with 20–100-μm diameter had formed after the 150 cycles, while, at the central areas, the corrosion behavior was similar to that observed in the NaCl immersion test. In similar cycle tests with pure water, dripping of water droplet was also repeated 150 times. Here, needle-like crystalline hydroxides formed at the edge of the droplet, while thick hydroxide films formed at the central areas, like in the pure water immersion test.

Comparative Investigation on the Friction and Wear Behaviors of Carbon Fabric–Reinforced Phenolic Composites under Seawater Lubrication

Carbon fabric–reinforced phenolic composites were prepared by dip-coating and hot press-molding techniques. The interlaminar shear strength (ILSS) of phenolic composites was determined by a three-point bending test on a universal material testing machine and their friction and wear behaviors under dry friction, pure water, and seawater lubrication were investigated comparatively using a block-on-ring test rig. Experimental results showed that carbon fabric–reinforced phenolic composite with 30 wt% resin had the best ILSS and tribological properties, and the ILSS of phenolic composites decreased with increasing content of resin. When experiencing immersion in pure water and seawater for 24 h, the ILSS of phenolic composites decreased greatly, and this decrease was in particular more obvious after immersion in pure water. In addition, compared to dry sliding condition, phenolic composites exhibited much better tribological properties under seawater lubrication but worse tribological properties under pure water lubrication. The differences in the tribological behaviors of phenolic composites were determined by two competitive effects of aqueous medium, including cooling, lubricating and washing effect, and plasticization effect. Moreover, the wear mechanisms of phenolic composites under dry friction and lubrication with aqueous media were adhesive wear and slight abrasive wear, respectively.

The chlorination process of crosslinked aromatic polyamide reverse osmosis membrane: New insights from the study of self-made membrane

The development of chlorine-resistant membranes requires good understanding of membrane chlorination process. However, researches involving membrane chlorination processes are often influenced by experimental materials, especially the commercial crosslinked aromatic polyamide RO membranes, the preparation or modification technology and composition of which are not fully disclosed. In this work, the changes in membrane chemical structure and composition during the chlorination process were systematically studied by the use of self-made crosslinked aromatic polyamide RO membranes to avoid these influences. The effects of different chlorination conditions and pure water immersion time were analyzed. For the first time, the reversibility of the chlorination process was investigated. The ATR-FTIR and XPS results indicated that chlorination involves a multi-step process. The IR bands which characterize the amide groups (1540 and 1608cm−1) gradually disappear, followed by the appearance of the bands which characterize the chlorination of aromatic ring (780 and 811cm−1). The increase rates of the chlorine content are different at different stages. The changes in chemical structure and composition of self-made membrane were compared with those of two representative commercial membranes (RE2521 and BW30). Furthermore, the consequential effects of these changes on surface hydrophilicity, charge, permselectivity performance, and morphology of self-made membrane were discussed.

The nature and stability of the Au(110)/electrochemical interface produced by flame annealing

It is shown using reflection anisotropy spectroscopy (RAS) that following flame annealing and immersion in pure water, the Au(110) surface adopts a (1×1) structure and that this structure is preserved in a 0.1 M H2SO4 environment. The surface transforms to the (1×2) reconstruction following the application of a potential of 0.0 V versus SCE (a saturated calomel electrode). This surface is unstable and the RAS profile changes over periods of 15 min and 1 h in a manner which suggests that changes are occurring in the structure and distribution of steps. Over longer periods the RAS transforms towards a profile attributed to a surface associated with the specific adsorption of anions.

A novel ultrafiltration (UF) membrane with controllable selectivity for protein separation

A novel ultrafiltration (UF) membrane with controllable selectivity for protein separation was obtained by altering the structure of the thick sieving layer on the membrane surface and subsurface. Poly(vinyl pyrrolidone) (PVP) was first cross-linked on/in the poly(vinylidene fluoride) (PVDF) hollow fiber microfiltration (MF) membrane to attract more sulfobetaine (SB) monomer adjacent to membrane for subsequent grafting polymerization and the formed thick sulfobetaine polymer (PSB) layer on the membrane surface and subsurface acted as the sieving layer with environment sensitivity. After immersed in 20mmol/L NaCl solution at 60°C, the novel UF membrane with the sieving layer of 4.8μm showed high permeate capacity with a water flux of 590L/m2h and a good selective behavior with MWCO of 95–110kDa. The protein mixture (BSA and Lys) could be separated through the novel UF membrane efficiently by isoelectric focusing of one component with a larger size (BSA). By means of the simple immersion in pure water, the membrane permeated most of proteins and the degree of flux decline reduced obviously. After swelled in NaCl solution again, the membrane restored the selectivity and the protein separation efficiency. Such novel smart UF membrane is an attractive candidate for the batch separation of protein mixtures, expanding the membrane application in the fields of agro-food, biomedicine and other bio-filtration.

Correlation between surface composition and luminescence of nanocrystalline silicon particles dispersed in pure water

The stability of the luminescene of nanocrystalline silicon (nc-Si) particles passivated with a number of different elements, including hydrogen, carbon, and oxygen, has been investigated in pure water. Each sample emitted red light with a peak wavelength in the range of 740–800nm. The intensity of red luminescence decreased after a short period of time when the hydrogen- and/or carbon-passivated samples were immersed in pure water. Further, the peak wavelength concomitantly shifted toward a shorter wavelength. These effects were attributed to the generation of defects (Pb centers), the reduction in particle size due to the desorption of hydrogen and/or carbon atoms, and the replacement of the Si–H and/or Si–C bonds, respectively, with Si-O bonds on the surface of nc-Si particles. On the other hand, the oxygen-passivated samples showed stable luminescence in addition to a slight blueshift of the peak wavelength upon immersion in pure water for 400h. This stability was attributed to the development of stable surface conditions. These results are a strong indication that the stability of luminescence in pure water can be remarkably improved by oxygen passivation on the surface of nc-Si particles.