Modification of surface properties of polyethylene by perfluoropolyether blending

The preparation of a stabile blend from thermoplastic polymer and lubricating additive was studied with high density polyethylene (HDPE) and perfluoropolyether (PFPE). PFPE was melt blended within HDPE by injection molding. The chemical composition of the mixtures, the relative amount of PFPE on the surface, and the nature of the surface were studied by three surface sensitive methods: attenuated total reflectance infrared (ATR‐IR) spectroscopy, secondary ion mass spectroscopy (SIMS), and contact angle (CA) measurement. All the blends exhibited improved hydrophobicity. CA and SIMS gave a maximum response when about 2.0 wt % PFPE was added, whereas ATR‐IR spectroscopy gave maximum response for an addition of about 3.0 wt %. No changes in surface properties were observed when samples were reanalyzed about 1–4 months after preparation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2252–2258, 2005     

Elimination and rearrangement reactions in the electron impact ionization mass spectrometry of 2,4,5,5-tetrasubstituted 1,2,4-triazolidine-3-thiones

The electron impact mass spectra of 2,4,5,5-tetrasubstituted l,2,4-triazolidine-3-thiones exhibited, in addition to four main routes of fragmentation, a reaction leading to the formation of 5-alkyl-l,2,4-triazoline-3-thiones via an elimination of HR⁴ (R³ ≤ R⁴ are the substituents at C(5)) or via a McLafferty-type reaction from the rearranged molecular ion in the case of the 5,5-spiro derivatives. Substitution at N(2), N(4) and/or C(5) had a decisive effect on the contribution of the alternative reaction routes. Some fragments via the triazoline-thione structure were also formed.     

Local dimensions of sliced measures and stability of packing dimensions of sections of sets

Let m and n be integers with 0<m<n. We relate the absolutely continuous and singular parts of a measure μ on to certain properties of plane sections of μ. This leads us to prove, among other things, that the lower local dimension of (n−m)-plane sections of μ is typically constant provided that the Hausdorff dimension of μ is greater than m. The analogous result holds for the upper local dimension if μ has finite t-energy for some t>m. We also give a sufficient condition for stability of packing dimensions of section of sets.     

An evaluation of some sodium ion-selective glass electrodes in aqueous solution: Part I. Electrode calibration characteristics and selectivity with respect to hydrogen ions

Some properties of a series of commercial sodium ion-selective electrodes have been investigated and the results compared. In general the potential response of the electrodes was found to approach Nernstian with aging.An improved method for investigating the selectivity of ion-selective electrodes with respect to hydrogen ions is based on the mixed solution method utilizing tris buffers. The selectivity of the sodium ion electrodes with respect to hydrogen ions was also found to depend on the ratio of the primary to interfering ion activity. Some other improvements in technique are also reported.     

Interpretation of KL2,3L2,3 radiative auger thresholds in metals and semiconductors

High-resolution measurements of the KL_2,3L_2,3 radiative Auger edge in Mg and Al are reported. The theory of soft X-ray absorption thresholds by Flynn and Lipari is modified to account for the KL_2,3L_2,3 threshold energies. The calculated energies are in excellent agreement with the experimental results including previous measurements on Si.     

A Review on Recent Progress of Stingless Bee Honey and Its Hydrogel-Based Compound for Wound Care Management

Stingless bee honey has a distinctive flavor and sour taste compared to Apis mellifera honey. Currently, interest in farming stingless bees is growing among rural residents to meet the high demand for raw honey and honey-based products. Several studies on stingless bee honey have revealed various therapeutic properties for wound healing applications. These include antioxidant, antibacterial, anti-inflammatory, and moisturizing properties related to wound healing. The development of stingless bee honey for wound healing applications, such as incorporation into hydrogels, has attracted researchers worldwide. As a result, the effectiveness of stingless bee honey against wound infections can be improved in the future to optimize healing rates. This paper reviewed the physicochemical and therapeutic properties of stingless bee honey and its efficacy in treating wound infection, as well as the incorporation of stingless bee honey into hydrogels for optimized wound dressing.     

Theoretical description of low divergence Gaussian fields in self-defocusing photorefractive media

Experimental evidence is presented that shows that low intensity optical fields preserve their Gaussian transverse amplitude distribution as they propagate through self-defocusing Ce:BaTiO₃ photorefractive media. The Gaussian nature of the field is used in a theoretical treatment to derive conditions under which bright solitons are formed in photorefractive media that have a light induced refractive index that is approximately quadratic. This analysis shows that while it is not possible to produce a single bright soliton in self-defocusing media that it is possible to minimize the field’s divergence such that the change in beam radius is small (<1%) over large propagation distances (∼1 m). An imaginary light induced refractive index component is necessary to generate the low divergence fields in both self-focusing and self-defocusing media when illuminated with Gaussian fields that have a non-planar wavefront.     

Decreased oxygen saturation in asymmetrically prominent cortical veins in patients with cerebral ischemic stroke

Decreased oxygen saturation in asymmetrically prominent cortical veins (APCV) seen in ischemic stroke has been hypothesized to correlate with an increase of de-oxygenated hemoglobin. Our goal is to quantify magnetic susceptibility to define APCV by establishing a cutoff above which the deoxyhemoglobin levels are considered abnormal. A retrospective study was conducted on 26 patients with acute ischemic stroke in one cerebral hemisphere that exhibited APCV with 30 age- and sex-matched healthy controls. Quantitative susceptibility mapping (QSM) was used to calculate the magnetic susceptibility of the cortical veins. A paired t-test was used to compare the susceptibility of the cortical veins in the left and right hemispheres for healthy controls as well as in the contralateral hemisphere for stroke patients with APCV. The change in oxygen saturation in the APCV relative to the contralateral side was calculated after thresholding the susceptibility using the mean plus two standard deviations of the contralateral side for each individual. The thresholded susceptibility value of the APCVs in the stroke hemisphere was 254 ± 48 ppb which was significantly higher (p < 0.05) than that in the contralateral hemisphere (123 ± 12 ppb) and in healthy controls (125 ± 8 ppb). There was a decrease of oxygen saturation in the APCV ranging from 16% to 44% relative to the veins of the contralateral hemisphere. In conclusion, APCV seen in SWI correspond to reduced levels of oxygen saturation and these abnormal veins can be identified using a susceptibility threshold on the QSM data.     

An acoustically enhanced gold film Raman sensor on a lithium niobate substrate

The surface enhanced Raman scattering effect has shown immense potential for detecting trace amounts of explosive vapor molecules. To date, efforts to produce a commercially available, reliable SERS sensor have been impeded by an inability to separate the electromagnetic enhancement produced by the metallic nanostructure from other signal enhancing effects. Here, we show a new Raman sensor that uses surface acoustic waves (SAWs) to produce controllable surface structures on gold films deposited on LiNbO₃ substrates that modulate the Raman signal of a target compound (thiophenol) adsorbed on the films. We demonstrate that this sensor can dynamically control the Raman signal simply by changing the SAW's amplitude, allowing the Raman signal enhancement factor to be directly measured with no variation in the concentration of the target compound. The physically adsorbed molecules can be removed from the sensor without physical cleaning or damage, making it possible to reuse it for real‐time Raman detection. Copyright © 2014 John Wiley & Sons, Ltd.