Co-nonsolvency effects in the thermoprecipitation of oligomeric polyacrylamides from hydro-organic solutions

Co-solutes and co-solvents influence the thermoprecipitation of stimulus-responsive polymers from aqueous solution. Taking the behavior of oligomeric poly-(N-isopropylacrylamide) prepared by chain transfer polymerization as reference, the influence of organic solvents (concentration <2 M) on the thermoprecipitation of polyacrylamides with critical solution temperatures (CST) in pure water between 30 and 75 °C is investigated using turbidity and differential scanning calorimetry. Depending on the system, both increase and decrease but also the disappearance of the CST is observed. The strength of the observed effect is related not only to the size but also the structure of the hydrophobic domain of the solvent molecule. Contrary to the effects observed upon the addition of simple salts as additives, the chemistry of the investigated polyacrylamide is of direct consequence for the effect of a given solvent. Certain parallels can hence be drawn to the behavior previously observed for additives such as anionic surfactants and alkylamines.     

Scanning force microscopy of Escherichia coli RNA polymerase.sigma54 holoenzyme complexes with DNA in buffer and in air

Scanning force microscopy (SFM) was used to visualize complexes of Escherichia coli RNA polymerase.sigma54 (RNAP.sigma54) and a 1036 base-pair linear DNA fragment containing the glnA promoter. In order to preserve the native hydration state of the protein-DNA complexes, the samples were injected directly into the SFM fluid cell and imaged in buffer. With this protocol, an apparent bending angle of 26(+/-34) degrees was determined for the specific complexes at the promoter. The bending angle of the unspecifically bound RNAP.sigma54 showed a somewhat broader distribution of 49(+/-48) degrees, indicating the existence of conformational differences as compared to the closed complex. In about two-thirds of the closed complexes, the RNA polymerase holoenzyme was located in a lateral position with respect to the DNA and the bend of the DNA was pointing away from the protein. This conformation was consistent with the finding that for the complexes at the promoter, the apparent contour length was reduced by only about 6 nm in buffer as compared to the free DNA. From these results we conclude that in the closed complex of RNAP. sigma54, the DNA was not wrapped around the polymerase, and we present a model for the trajectory of the DNA with respect to the RNA polymerase. The images acquired in buffer were compared to samples that were washed with water and then dried before imaging. Two artefacts of the washing and drying process were detected. First, extensive washing of the sample reduced the number of the specific complexes bound at the promoter (closed complex of RNAP.sigma54) from about 70% to 30%. This is likely to be a result of sliding of the RNAP.sigma54 holoenzyme along the DNA induced by the washing process. Second, the apparent DNA shortening of the contour length of RNAP.sigma54-DNA complexes at the promoter as compared to the contour length of the free DNA was 22 nm for the dried samples as opposed to only 6 nm for the undried samples imaged in buffer. This suggests an artefact of the drying process.     

冶炼烟气净化：所有步骤在一台设备内完成

介绍Kimre公司的SXF^TM半错流洗涤器的结构、优点和应用。该洗涤器采用卧式并流气液接触方式,可根据需要分隔成不同操作段,在由交织单丝构成的纤维介质上完成气体的冷却、净化和除沫。与传统立式逆流填料塔相比,该洗涤器的优点为：高度低,泵、阀门、控制器等可在地面安装,容易操作和维修;液气比范围宽;可进行多级操作,包括在一台设备内完成多个化学过程。如用于冶炼烟气净化,所有步骤可在一台设备内完成。列举了化肥厂造粒塔气体净化、磷酸厂气体除氟和硫酸厂干燥塔除沫等应用实例。     

Study of mechanical degradation of UHMWPE acetabular components due to clinical X-ray procedures

The use of multi-component femoral implants to replace the femur head and re-establish bone motion has been widespread since the 70s. Frequently these implants have spherical metallic heads made of, for example, 316-L stainless steel or Cr–Co alloys, which allow rotational motion towards a polymeric component (UHMWPE). One of the major causes of implant rejection is the generation of UHMWPE debris on the surface between the implant head and the polymeric component. The gamma ray sterilization of implants and the periodical X-ray medical control could contribute to premature degradation of the polymeric surface, resulting in increased wear and shortened lifetime of the implant. In this work we study the degradation degree of the polymeric UHMWPE component as function of the X-ray dose. The elasto-plastic deformation and recovery were carried out by means of a nanohardness tester equipment and the polymer degradation was measured using a fast Fourier transform infra-red (FT-IR) equipment. The results show the compromise among the irradiation doses, the surface oxidation and the mechanical properties of the samples.     

From Molecules to Behavior in Long-Term Inorganic Mercury Intoxication: Unraveling Proteomic Features in Cerebellar Neurodegeneration of Rats

Mercury is a severe environmental pollutant with neurotoxic effects, especially when exposed for long periods. Although there are several evidences regarding mercury toxicity, little is known about inorganic mercury (IHg) species and cerebellum, one of the main targets of mercury associated with the neurological symptomatology of mercurial poisoning. Besides that, the global proteomic profile assessment is a valuable tool to screen possible biomarkers and elucidate molecular targets of mercury neurotoxicity; however, the literature is still scarce. Thus, this study aimed to investigate the effects of long-term exposure to IHg in adult rats’ cerebellum and explore the modulation of the cerebellar proteome associated with biochemical and functional outcomes, providing evidence, in a translational perspective, of new mercury toxicity targets and possible biomarkers. Fifty-four adult rats were exposed to 0.375 mg/kg of HgCl₂ or distilled water for 45 days using intragastric gavage. Then, the motor functions were evaluated by rotarod and inclined plane. The cerebellum was collected to quantify mercury levels, to assess the antioxidant activity against peroxyl radicals (ACAPs), the lipid peroxidation (LPO), the proteomic profile, the cell death nature by cytotoxicity and apoptosis, and the Purkinje cells density. The IHg exposure increased mercury levels in the cerebellum, reducing ACAP and increasing LPO. The proteomic approach revealed a total 419 proteins with different statuses of regulation, associated with different biological processes, such as synaptic signaling, energy metabolism and nervous system development, e.g., all these molecular changes are associated with increased cytotoxicity and apoptosis, with a neurodegenerative pattern on Purkinje cells layer and poor motor coordination and balance. In conclusion, all these findings feature a neurodegenerative process triggered by IHg in the cerebellum that culminated into motor functions deficits, which are associated with several molecular features and may be related to the clinical outcomes of people exposed to the toxicant.     

Development and characterization of collagen/gelatin films and gels incorporated with pequi oil

Natural compounds, such as pequi oil, could be added to collagen/gelatin mixtures to improve its properties. Gels characterized by rheological analysis indicated modifications in entanglement network of the mixtures after pequi oil addition. Films processed by casting were analyzed by mechanical and thermal properties, contact angle, and scanning electron microscopy (SEM). The pequi oil addition reduced the contact angle values due to the addition of carboxyl groups found in the palmitic and oleic acid chains of pequi oil. The rough characteristic observed by SEM images was a result of a good homogenization process after oil incorporation. In addition, pequi oil addition decreased the tensile forces and elongation of the films and increased the thermal stability possibly due to lower inter‐ and intra‐molecules interactions. The results suggested a good compatibility between pequi oil and biopolymers and the potential application of this natural compound to increase the wound healing process. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46627.     

Liver is not essential for solute transport during peritoneal dialysis

Based on theoretical calculations on solute exchange capacities of various peritoneal tissues, the liver has been predicted to account for up to 43% of the permeability-surface area product (PS) of the entire peritoneal "membrane" for a small solute (sucrose) during peritoneal dialysis (PD). In these calculations, the abdominal wall and the diaphragm were found to contribute only approximately 10 to 15% of the total PS. However, evisceration has in previous studies been shown to affect the PS characteristics during PD only marginally (10 to 30%). In such evisceration experiments the liver was usually not removed, and therefore it has been suggested that an intact liver might have significantly contributed to the solute exchange under these premises. We assessed the peritoneal PS of 51Cr-EDTA (constantly infused intravenously) and the plasma-to-peritoneal clearance (ClB-->P) of 125I-human serum albumin (RISA) (given as an i.v. bolus) in Wistar rats during acute PD. In one group of rats the liver surface was sealed off using Histoacrylate glue (N = 6) and in another group a 90% hepatectomy was performed, the remaining portion of the liver, usually the right lower lobe, being sealed off by glue (N = 6). A third group was sham operated to serve as control (N = 12). The PS for 51Cr-EDTA was 0.32 +/- 0.03(+/- SE) ml. min-1 (N = 12) during control, 0.32 +/- 0.04 ml.min-1 after "sealing" of the liver surface (N = 6, P > 0.1) and 0.40 +/- 0.03 after hepatectomy (N = 6, P > 0.1), that is, remained unchanged after experimental intervention. The CIB-->P of RISA during control was 5.88 +/- 1.0 microliter.min-1 (N = 10), and was not altered after hepatectomy, 6.17 +/- 0.48 microliters.min-1 (N = 5, P > 0.1), but slightly increased after liver surface sealing (9.69 +/- 1.09 microliters.min-1, N = 5, P < 0.05). In conclusion, the present experiments indicate that the liver does not play an essential role in the overall solute exchange between the plasma and the peritoneal cavity (PC) during PD.     

Cross-layer routing metrics for mesh networks: Current status and research directions

Despite efforts to improve the current IEEE 802.11 standard to fully optimize the physical layer, the performance of wireless mesh networks still depends on the routing process for a correct selection of routes. With regard to this question, several cross-layer routing metrics have been developed to improve wireless multi-hop mesh routing. This paper sets out a new taxonomy that can be used to help understand, classify and compare the state-of-the-art situation with regard to cross-layer routing metrics for wireless mesh networks. A simulation study has been carried out to evaluate the capability of the most recent and promising cross-layer routing metrics to support multimedia applications, such as Voice over IP. The evaluation of the routing metrics has been undertaken from three main perspectives: user perception, network performance, and routing stability. The simulation results show that the impact of routing metrics is more noticeable on the network and routing stability evaluation parameters than on the user-perception parameters. Furthermore, the results show that the routing metrics, the level of stability attained, and the application performance are interdependent. Finally, there is a discussion of the direction that future research might take with regard to some open issues in the design of routing metrics for wireless mesh networks.