Succinonitrile-Polymer Composite Electrolytes for Li-Ion Solid-State Batteries-The Influence of Polymer Additives on Thermomechanical and Electrochemical Properties

A plastic crystalline electrolyte (PCE) consisting of 0.4 mol/L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in succinonitrile (SN) was blended with poly(ethylene oxide) (PEO), poly(vinylpyrrolidone) (PVP), poly(ethylene carbonate) (PEC), and polyacrylonitrile (PAN). The influences of the regarding polymers on thermomechanical properties of the PCE were studied systematically, utilizing differential scanning calorimetry, thermogravimetric analysis, and oscillation experiments. Depending on the chosen polymer, the melting temperature and overall crystallinity of the PCE were increased. For PCEs containing PEO and PVP, overall crystallinity was enhanced the most resulting in lamellae-like superstructures, identified by light microscopy images. Furthermore, the onset for the sublimation process of SN was shifted to higher temperatures, and the mechanical strength was increased by the presence of some polymers, with exception of PEC. Electrochemical characterization, including electrochemical impedance spectroscopy and linear sweep voltammetry, revealed ionic conductivities of 10^-4 S/cm at room temperature for PCE with PAN and extended electrochemical stability windows of ≥4.5 V vs lithiated graphite for PCE with PEO. By correlating the thermomechanical and electrochemical properties, some structure-property relationships were drawn, pointing out great potential for specific tailoring of PCEs by polymer additives. The synergistic effect of increasing both, mechanical stability and ionic conductivity, made the PCE + PAN composition especially attractive for a possible application in batteries.

Multivalent non-covalent interactions lead to strongest polymer adhesion

Multivalent interactions play a leading role in biological processes such as the inhibition of inflammation or virus internalization. The multivalent interactions show enhanced strength and better selectivity compared to monovalent interactions, but they are much less understood due to their complexity. Here, we detect molecular interactions in the range of a few piconewtons to several nanonewtons and correlate them with the formation and subsequent breaking of one or several bonds and assign these bonds. This becomes possible by performing atomic force microcopy (AFM)-based single molecule force spectroscopy of a multifunctional polymer covalently attached to an AFM cantilever tip on a substrate bound polymer layer of the multifunctional polymer. Varying the pH value and the crosslinking state of the polymer layer, we find that bonds of intermediate strength (non-covalent), like coordination bonds, give the highest multivalent bond strength, even outperforming strong (covalent) bonds. At the same time, covalent bonds enhance the polymer layer density, increasing in particular the number of non-covalent bonds. In summary, we can show that the key for the design of stable and durable polymer coatings is to provide a variety of multivalent interactions and to keep the number of non-covalent interactions at a high level.

Current State of Bone Adhesives-Necessities and Hurdles

The vision of gluing two bone fragments with biodegradable and biocompatible adhesives remains highly fascinating and attractive to orthopedic surgeons. Possibly shorter operation times, better stabilization, lower infection rates, and unnecessary removal make this approach very appealing. After 30 years of research in this field, the first adhesive systems are now appearing in scientific reports that may fulfill the comprehensive requirements of bioadhesives for bone. For a successful introduction into clinical application, special requirements of the musculoskeletal system, challenges in the production of a bone adhesive, as well as regulatory hurdles still need to be overcome. In this article, we will give an overview of existing synthetic polymers, biomimetic, and bio-based adhesive approaches, review the regulatory hurdles they face, and discuss perspectives of how bone adhesives could be efficiently introduced into clinical application, including legal regulations.

Dry eye following cataract surgery: The effect of light exposure using an in-vitro model

PURPOSE

Cataract surgery can lead to the temporary development or worsening of dry eye symptoms. Contributing factors may include corneal incisions, agents used before, during or after surgery, light from the operating microscope, disruption of ocular surface tissues and inflammatory processes. The purpose of this study was to observe the effect of light exposure on conjunctival fibroblasts in order to determine whether light has an effect on wound healing closure, assuming that operating microscopes might have an effect on the ocular surface.

METHOD

An in vitro scratch assay was performed on porcine conjunctival fibroblasts. Ten minutes of light exposure from a light microscope with a halogen bulb was performed after the scratch assay. Fibroblasts were kept in culture for 48 hours post-exposure and the wound closure rates were visualized by live/dead staining. The fibroblasts which were exposed to light were compared to those without light exposure. Cell viability was also analysed by MTT assay.

RESULTS

A Slower wound closure rate was found when fibroblasts were exposed to light compared to the non-light exposed controls. Cell viability reduced by 20% with light exposure compared to controls in p3 cells (p = 0.04; however, the trend was not observed with p4 and p5 cells (p > 0.05).

CONCLUSIONS

These results suggest that light exposure might be one of the possible contributory factors for dry eye after ophthalmic surgery. Further evaluation of light effects should be carried out with different ocular surface cells.

Adhesion and friction of the smooth attachment system of the cockroach Gromphadorhina portentosa and the influence of the application of fluid adhesives

Two different measurement techniques were applied to study the attachment of the smooth foot pads of the Madagascar hissing cockroach Gromphadorhina portentosa. The attachment of the non-manipulated adhesive organs was compared with that of manipulated ones (depletion or substitution by artificial secretions). From measurements of the friction on a centrifuge, it can be concluded that on nanorough surfaces, the insect appears to benefit from employing emulsions instead of pure oils to avoid excessive friction. Measurements performed with a nanotribometer on single attachment organs showed that, in the non-manipulated euplantulae, friction was clearly increased in the push direction, whereas the arolium of the fore tarsus showed higher friction in the pull direction. The surface of the euplantulae shows an imbricate appearance, whereupon the ledges face distally, which might contribute to the observed frictional anisotropy in the push direction. Upon depletion of the tarsal adhesion-mediating secretion or its replacement by oily fluids, in several cases, the anisotropic effect of the euplantula disappeared due to the decrease of friction forces in push-direction. In the euplantulae, adhesion was one to two orders of magnitude lower than friction. Whereas the tenacity was slightly decreased with depleted secretion, it was considerably increased after artificial application of oily liquids. In terms of adhesion, it is concluded that the semi-solid consistence of the natural adhesion-mediating secretion facilitates the detachment of the tarsus during locomotion. In terms of friction, on smooth to nanorough surfaces, the insects appear to benefit from employing emulsions instead of pure oils to avoid excessive friction forces, whereas on rougher surfaces the tarsal fluid rather functions in improving surface contact by keeping the cuticle compliable and compensating surface asperities of the substratum.

Summary: Friction and adhesion of a cockroach are analysed in an experimental approach that focuses on the function of the tarsal adhesion-mediating secretion.

Structural and tribometric characterization of biomimetically inspired synthetic "insect adhesives"

Background: Based on previous chemical analyses of insect tarsal adhesives, we prepared 12 heterogeneous synthetic emulsions mimicking the polar/non-polar principle, analysed their microscopical structure and tested their adhesive, frictional, and rheological properties. Results: The prepared emulsions varied in their consistency from solid rubber-like, over soft elastic, to fluid (watery or oily). With droplet sizes >100 nm, all the emulsions belonged to the common type of macroemulsions. The emulsions of the first generation generally showed broader droplet-size ranges compared with the second generation, especially when less defined components such as petrolatum or waxes were present in the lipophilic fraction of the first generation of emulsions. Some of the prepared emulsions showed a yield point and were Bingham fluids. Tribometric adhesion was tested via probe tack tests. Compared with the "second generation" (containing less viscous components), the "first generation" emulsions were much more adhesive (31-93 mN), a finding attributable to their highly viscous components, i.e., wax, petrolatum, gelatin and poly(vinyl alcohol). In the second generation emulsions, we attained much lower adhesivenesses, ranging between 1-18 mN. The adhesive performance was drastically reduced in the emulsions that contained albumin as the protein component or that lacked protein. Tribometric shear tests were performed at moderate normal loads. Our measured friction forces (4-93 mN in the first and 0.1-5.8 mN in the second generation emulsions) were comparatively low. Differences in shear performance were related to the chemical composition and emulsion structure. Conclusion: By varying their chemical composition, synthetic heterogeneous adhesive emulsions can be adjusted to have diverse consistencies and are able to mimic certain rheological and tribological properties of natural tarsal insect adhesives.

First protein and peptide characterization of the tarsal adhesive secretions in the desert locust, Schistocerca gregaria, and the Madagascar hissing cockroach, Gromphadorhina portentosa

Peptides and proteins have been largely neglected in the analysis of insect tarsal adhesives. After extraction of the protein fraction of the tarsal secretion of the desert locust, Schistocerca gregaria, and Madagascar hissing cockroach, Gromphadorhina portentosa, we combined Fourier transform infrared spectroscopy (FTIR), sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analyses for protein mass detection. In both these insects, SDS-PAGE analysis revealed several protein bands ranging from 8-190 kDa in both the tarsal secretion and the tibia control sample. Two (S. gregaria) and one (G. portentosa) protein bands exclusively occurred in the tarsal secretion and can be considered to belong to peptides and proteins specific to this secretion. MALDI-TOF analyses revealed 83 different proteins/peptides of 1-7 kDa in S. gregaria, and 48 of 1-11 kDa in G. portentosa. 59 (S. gregaria) and 27 (G. portentosa) proteins exclusively occurred in the tarsal secretion. In G. portentosa, a characteristic series of signal peaks occurred in the range of c. 10-12 kDa, each peak being approximately 160 Da apart. Such a pattern is indicative of proteins modified by glycosylation. Our approach demonstrates that extensive sampling involving considerable time and manpower to sample the adhesive fluid directly from the tarsi opens up a perspective for extracting peptides and proteins in sufficient quantities. This makes them accessible to the field of proteomics and thus to elucidate their possible function in the adhesive process.

Baseline peripheral refractive error and changes in axial refraction during one year in a young adult population

PURPOSE

To determine whether the initial characteristics of individual patterns of peripheral refraction relate to subsequent changes in refraction over a one-year period.

METHODS

54 myopic and emmetropic subjects (mean age: 24.9±5.1 years; median 24 years) with normal vision were recruited and underwent conventional non-cycloplegic subjective refraction. Peripheral refraction was also measured at 5° intervals over the central 60° of horizontal visual field, together with axial length. After one year, measurements of subjective refraction and axial length were repeated on the 43 subjects who were still available for examination.

RESULTS

In agreement with earlier studies, higher myopes tended to show greater relative peripheral hyperopia. There was, however, considerable inter-subject variation in the pattern of relative peripheral refractive error (RPRE) at any level of axial refraction. Across the group, mean one-year changes in axial refraction and axial length did not differ significantly from zero. There was no correlation between changes in these parameters for individual subjects and any characteristic of their RPRE.

CONCLUSION

No evidence was found to support the hypothesis that the pattern of RPRE is predictive of subsequent refractive change in this age group.

Accommodation response to Chinese and Latin characters in Chinese-illiterate young adults

BACKGROUND

Differences in accommodation when reading Chinese, as compared to Latin, characters have been suggested to have a role in the higher prevalence of myopia in some Asian countries. Yeo and colleagues (Optom Vis Sci 2013; 90: 156-163) found that, in Chinese-literate children, accommodation was marginally more accurate (by less than 0.05 D), when reading Chinese text. This was attributed to the additional cognitive demand associated with interpreting the more complex Chinese symbols. The present study compared responses to single Chinese and Latin characters, while controlling for cognitive demand.

METHODS

The monocular accommodative response was measured in Chinese-illiterate adults (10 emmetropes, mean spherical equivalent: -0.07 ± 0.42 D, age: 29.9 ± 4.2 years; 11 myopes, mean spherical equivalent: -4.28 ± 2.84 D, age: 31.7 ± 4.6 years) with an open-field autorefractor. Four Chinese and three Latin characters (approximately 1.15 degrees subtense) were individually presented on a display screen one metre away from the subject, while their vergence was varied over the range zero to 5.00 D using spectacle trial lenses. The slope and the accommodative error index (AEI) were calculated from the accommodative stimulus/response curves (ASRC).

RESULTS

No statistically significant differences were found between refractive groups or among characters within the same refractive group in ARSC slopes (Latin: 0.87 ± 0.14 for myopes versus 0.81 ± 0.12 for emmetropes; Chinese: 0.84 ± 0.12 for myopes versus 0.85 ± 0.12 for emmetropes). No significant differences were found between characters in accommodative error index either (Latin, 0.78 ± 0.42 D for myopes versus 1.15 ± 0.72 D for emmetropes; Chinese, 0.74 ± 0.37 D for myopes versus 1.17 ± 0.83 D for emmetropes). However, accommodative error indices and accommodative errors were significantly higher for emmetropes.

CONCLUSION

Under controlled cognitive demand, Chinese and Latin characters elicited similar responses in both individual refractive groups. This study fails to support the hypothesis that development of myopia in some Asian populations is associated with larger lags of accommodation when reading or viewing Chinese characters.

Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

Nature often serves as a model system for developing new adhesives. In aqueous environments, mussel-inspired adhesives are promising candidates. Understanding the mechanism of the extraordinarily strong adhesive bonds of the catechol group will likely aid in the development of adhesives. With this aim, we study the adhesion of catechol-based adhesives to metal oxides on the molecular level using atomic force microscopy (AFM). The comparison of single catechols (dopamine) with multiple catechols on hyperbranched polyglycerols (hPG) at various pH and dwell times allowed us to further increase our understanding. In particular, we were able to elucidate how to achieve strong bonds of different valency. It was concluded that hyperbranched polyglycerols with added catechol end groups are promising candidates for durable surface coatings.

Morphological adjustment determines the properties of cationically polymerized epoxy resins

Method of integrating a crystalline polyester into an epoxy resin determines morphology and by this mechanical properties.

Formation and structure of copper(II) oxalate layers on carboxy-terminated self-assembled monolayers

Copper(II) oxalate was grown on carboxy-terminated self-assembled monolayers using a step-by-step approach by dipping the surfaces alternately in ethanolic solutions of copper(II) acetate and oxalic acid with intermediate thorough rinsing steps. The deposition was monitored by reflection absorption infrared spectroscopy (RAIRS), a quartz microbalance with dissipation measurement (QCM-D), scanning electron microscopy (SEM), and helium ion microscopy (HIM). Amounts of material corresponding to a coverage of 75% of a monolayer are deposited in each dipping step in copper(II) acetate solution while deposition of oxalic acid produces a viscoelastic layer that is partially removed by rinsing. This points toward initial aggregation but acid not bound to Cu(2+) ions as oxalate ions is removed by the rinsing steps. RAIRS further indicates that the material grows as copper(II) oxalate ribbons similar to the crystal structure but with ribbons oriented roughly parallel to the surface. SEM and HIM give evidence of the formation of needle-shaped structures which are a possible explanation for the viscoelastic behavior of the layer.

The timing of surgery for undescended testis - a retrospective multicenter analysis

BACKGROUND

n Germany, it is recommended that the surgical treatment of an undescended testis should be carried out between the ages of 6 months and 1 year to lower the risks of subfertility and testicular carcinoma. Although this recommendation has appeared in the German guidelines from 2007 onward, orchidopexy is still frequently performed at later ages.

METHOD

We retrospectively analyzed data from seven pediatric surgical services in the German state of Baden-Württemberg on all boys who underwent orchidopexy from 2009 to 2012. We classified the timing of surgery as Age Group I (before the first birthday), Age Group II (between the first and second birthdays), and Age Group III (after the second birthday). We determined whether preoperative hormonal treatment was given and distinguished primary from secondary undescended testis.

RESULTS

Among 2213 boys who underwent orchidopexy, 1850 had primary and 363 had secondary undescended testis. Of those with primary undescended testis, the percentages of boys who underwent surgery in Age Groups I, II, and III were (respectively, with 95% confidence intervals): 18.7% (17-20.6%), 24.4% (22.5-26.5%), and 57% (54.6-59.2%). A small percentage of boys in each group also received preoperative hormonal treatment. From 2009 to 2012, there was a secular trend favoring earlier orchidopexy. In 2012, 28 boys (14.2% [9.7-20.0%]) had orchidopexy in outpatient pediatric surgery practices before their first birthday, while 68 did on hospital inpatient services (40.7% [33.2-48.6%]).

CONCLUSION

Most of the patients studied had surgery at a later age than recommended. Adherence to the guidelines in this respect is nonetheless relatively good in Germany compared to other countries, as studies from abroad have yielded findings that are just as bad or worse.

Effects of Exposure to Welding Fume on Lung Function: Results from the German WELDOX Study

The association between exposure to welding fume and chronic obstructive pulmonary disease (COPD) has been insufficiently clarified. In this study we assessed the influence of exposure to welding fume on lung function parameters. We investigated forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC, and expiratory flow rates in 219 welders. We measured current exposure to respirable particles and estimated a worker's lifetime exposure considering welding techniques, working conditions and protective measures at current and former workplaces. Multiple regression models were applied to estimate the influence of exposure to welding fume, age, and smoking on lung function. We additionally investigated the duration of working as a welder and the predominant welding technique. The findings were that age- and smoking-adjusted lung function parameters showed no decline with increasing duration, current exposure level, and lifetime exposure to welding fume. However, 15% of the welders had FEV1/FVC below the lower limit of normal, but we could not substantiate the presence of an association with the measures of exposure. Adverse effects of cigarette smoking were confirmed. In conclusion, the study did not support the notion of a possible detrimental effect of exposure to welding fume on lung function in welders.

Analysis of higher-order aberrations in a large clinical population

PURPOSE

To use a large wave-front database of a clinical population to investigate relationships between refractions and higher-order aberrations and between aberrations of right and left eyes.

METHODS

Third- and fourth-order aberration coefficients and higher-order root-mean-squared aberrations (HO RMS), scaled to a pupil size of 4.5-mm diameter, were analyzed in a population of approximately 24,000 patients from Carl Zeiss Vision's European wave-front database. Correlations were determined between the aberrations and the variables of refraction, near addition, and cylinder.

RESULTS

Most aberration coefficients were significantly dependent upon these variables, but the proportion of aberrations that could be explained by these factors was less than 2% except for spherical aberration (12%), horizontal coma (9%), and HO RMS (7%). Near addition was the major contributor for horizontal coma (8.5% out of 9.5%) and spherical equivalent was the major contributor for spherical aberration (7.7% out of 11.6%). Interocular correlations were highly significant for all aberration coefficients, varying between 0.16 and 0.81. Anisometropia was a variable of significance for three aberrations (vertical coma, secondary astigmatism, and tetrafoil), but little importance can be placed on this finding because of the small proportion of aberrations that can be explained by refraction (all <1.0%).

CONCLUSIONS

Most third- and fourth-order aberration coefficients were significantly dependent upon spherical equivalent, near addition, and cylinder, but only horizontal coma (9%) and spherical aberration (12%) showed dependencies greater than 2%. Interocular correlations were highly significant for all aberration coefficients, but anisometropia had little influence on aberration coefficients.

Synthesis of polymer/inorganic nanocomposite films using highly porous inorganic scaffolds

Polymeric/inorganic nanocomposite films have been fabricated through a combination of flame-spray-pyrolysis (FSP) made inorganic scaffold and surface initiated polymerization of cyanoacrylate. The highly porous structure of pristine SnO(2) films allows the uptake of cyanoacrylate and the polymerization is surface initiated by the water adsorbed onto the SnO(2) surface. Scanning electron microscopy study reveals a nonlinear increase in the composite particle size and the film thickness with polymerization time. The structural change is rather homogeneous throughout the whole layer. The composite is formed mainly by an increase of the particle size and not by just filling the existing pores. High-resolution transmission electron microscopy imaging shows SnO(2) nanoparticles embedded in the polymeric matrix, constituting the nanocomposite material. Thermogravimetric analysis indicates that the porosity of the nanocomposite films decreases from 98% to 75%, resulting in a significant enhancement of the hardness of the films. DC conductivity measurements conducted in situ on the nanocomposite layer suggest a gradual increase in the layer resistance, pointing to a loss of connectivity between the SnO(2) primary particles as the polymerization proceeds.

Synthesis of stable AuAg bimetallic nanoparticles encapsulated by diblock copolymer micelles

We present a facile method for the preparation of bimetallic AuAg nanoparticles (NPs) with controlled size and composition rendering them ideally suitable for optical and catalytic applications. In analogy to methods for the generation of monometallic Au and Ag NPs, AuAg NPs were prepared inside polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block-copolymer micelles formed in toluene, by loading the P4VP cores of the micelles first with AgNO(3) and then with HAuCl(4). In contrast to the reverse sequence of loading, homogenously bimetallic AuAg particle arrays were achieved after reduction carried out in solution with hydrazine monohydrate as the reducing agent. TEM reveals that stable and spherical NPs can be prepared well separated from one another and with a narrow size distribution with diameters of ∼3 nm. The bimetallic NP composition was confirmed by energy-dispersive X-ray spectroscopy (EDX) of single NPs. The atomic ratio of Ag and Au contained in single particles is in good agreement with the relative concentrations of both metals used in the synthesis which was confirmed by atomic absorption spectroscopy. The atomic ratio Au : Ag was systematically varied between 3 : 1 and 1 : 3. For all ratios UV-vis spectra showed a single plasmon band. Its wavelength varied from 430 for Au : Ag = 1 : 3 to 515 nm for Au : Ag = 3 : 1, showing a linear dependence on the relative amount of gold within the range of plasmon wavelengths from monometallic gold (538 nm) to silver (415 nm).

Specifying peripheral aberrations in visual science

PURPOSE

Investigations of foveal aberrations assume circular pupils. However, the pupil becomes increasingly elliptical with increase in visual field eccentricity. We address this and other issues concerning peripheral aberration specification.

METHODS

One approach uses an elliptical pupil similar to the actual pupil shape, stretched along its minor axis to become a circle so that Zernike circular aberration polynomials may be used. Another approach uses a circular pupil whose diameter matches either the larger or smaller dimension of the elliptical pupil. Pictorial presentation of aberrations, influence of wavelength on aberrations, sign differences between aberrations for fellow eyes, and referencing position to either the visual field or the retina are considered.

RESULTS

Examples show differences between the two approaches. Each has its advantages and disadvantages, but there are ways to compensate for most disadvantages. Two representations of data are pupil aberration maps at each position in the visual field and maps showing the variation in individual aberration coefficients across the field.

CONCLUSIONS

Based on simplicity of use, adequacy of approximation, possible departures of off-axis pupils from ellipticity, and ease of understanding by clinicians, the circular pupil approach is preferable to the stretched elliptical approach for studies involving field angles up to 30 deg.