Borosilicate Glass Fiber Research Articles

Tire-derived contaminants 6PPD and 6PPD-Q: Analysis, sample handling, and reconnaissance of United States stream exposures

The environmental ubiquity of tire and road wear particles (TRWP) underscores the need to understand the occurrence, persistence, and environmental effects of tire-related chemicals in aquatic ecosystems. One such chemical is 6PPD-quinone (6PPD-Q), a transformation product of the tire antioxidant 6PPD. In urban stormwater runoff 6PPD-Q can exceed acute toxicity thresholds for several salmonid species and is being implicated in significant coho salmon losses in the Pacific Northwest. There is a critical need to understand the prevalence of 6PPD-Q across watersheds to identify habitats heavily affected by TRWPs. We conducted a reconnaissance of 6PPD and 6PPD-Q in surface waters across the United States from sites (N = 94) with varying land use (urban, agricultural, and forested) and streamflow to better understand stream exposures. A rapid, low-volume direct-inject, liquid chromatography mass spectrometry method was developed for the quantitation of 6PPD-Q and screening for 6PPD. Laboratory holding times, bottle material, headspace, and filter materials were investigated to inform best practices for 6PPD-Q sampling and analysis. Glass bottles with PTFE-lined caps minimized sorption and borosilicate glass fiber filters provided the highest recovery. 6PPD-Q was stable for at least 5 months in pure laboratory solutions and for 75 days at 5 °C with minimal headspace in the investigated surface water and stormwaters. Results also indicated samples can be frozen to extend holding times. 6PPD was not detected in any of the 526 analyzed samples and there were no detections of 6PPD-Q at agricultural or forested sites. 6PPD-Q was frequently detected in stormwater (57%, N = 90) and from urban impacted sites (45%, N = 276) with concentrations ranging from 0.002 to 0.29 μg/L. The highest concentrations, above the lethal level for coho salmon, occurred during stormwater runoff events. This highlights the importance of capturing episodic runoff events in urban areas near ecologically relevant habitat or nursery grounds for sensitive species.

Pre-analytical challenges from adsorptive losses associated with thiamine analysis

Thiamine (vitamin B1) is an essential vitamin serving in its diphosphate form as a cofactor for enzymes in the citric acid cycle and pentose-phosphate pathways. Its concentration reported in the pM and nM range in environmental and clinical analyses prompted our consideration of the components used in pre-analytical processing, including the selection of filters, filter apparatuses, and sample vials. The seemingly innocuous use of glass fiber filters, glass filter flasks, and glass vials, ubiquitous in laboratory analysis of clinical and environmental samples, led to marked thiamine losses. 19.3 nM thiamine was recovered from a 100 nM standard following storage in glass autosampler vials and only 1 nM of thiamine was obtained in the filtrate of a 100 nM thiamine stock passed through a borosilicate glass fiber filter. We further observed a significant shift towards phosphorylated derivatives of thiamine when an equimolar mixture of thiamine, thiamine monophosphate, and thiamine diphosphate was stored in glass (most notably non-silanized glass, where a reduction of 54% of the thiamine peak area was observed) versus polypropylene autosampler vials. The selective losses of thiamine could lead to errors in interpreting the distribution of phosphorylated species in samples. Further, some loss of phosphorylated thiamine derivatives selectively to amber glass vials was observed relative to other glass vials. Our results suggest the use of polymeric filters (including nylon and cellulose acetate) and storage container materials (including polycarbonate and polypropylene) for thiamine handling. Losses to cellulose nitrate and polyethersulfone filters were far less substantial than to glass fiber filters, but were still notable given the low concentrations expected in samples. Thiamine losses were negated when thiamine was stored diluted in trichloroacetic acid or as thiochrome formed in situ, both of which are common practices, but not ubiquitous, in thiamine sample preparation.

Broadband near-infrared emission in barium gallo-germanate glasses co-doped with bismuth, chromium and erbium ions

This work presents barium gallo-germanate glasses co-doped with Bi+/Er3+ and Cr3+/Er3+ ions for NIR luminescence. The addition of Al2O3 content in the glass matrix made it possible to obtain luminescence corresponding to the 3P1→3P0 transition of Bi+ ions. Co-doping with the Bi+/Er3+ system resulted in a broad luminescence spectrum of 1.0-1.6 µm and Cr3+/Er3+ co-doping in selected glass matrix resulted in luminescence in 0.9-1.6 µm band. However, the luminescence of the Cr3+ ions is much lower than that of Er3+ ions. Full Text: PDF References T. Suzuki, G.S. Murugan, and Y. Ohishi, 'Optical properties of transparent Li2O-Ga2O3-SiO2 glass-ceramics embedding Ni-doped nanocrystals', Appl. Phys. Lett., 86(13), 131903 (2005). CrossRef N.V. Golubev et al., 'Pre-crystallization heat treatment and infrared luminescence enhancement in Ni2+-doped transparent glass-ceramics', J. Non-Cryst. Solids, 515, 42 (2019) CrossRef Z. Xu, W. Feng, T. Chen, X. Liu, and J. Qiu, 'Tuning optical properties in PbSe quantum dot-doped borosilicate glass fiber by modulation of network topology', Opt. Laser Technol., 158, 108910 (2023). CrossRef M.A. Hughes, T. Suzuki, and Y. Ohishi, 'Spectroscopy of bismuth-doped lead-aluminum-germanate glass and yttrium-aluminum-silicate glass', J. Non-Cryst. Solids, 356(44), 2302 (2010). CrossRef J. Song, Z. Zhou, B. Zhong, M. Zhang, J. Huang, and L. Han, 'Ultra-broadband near-infrared Cr3+-doped multi-phase glass-ceramics realized by the selective enrichment strategy for near-infrared spectroscopy applications', J. Alloys Compd., 968, 172126 (2023). CrossRef M.A.U. Martines, M.R. Davolos, M.J. Júnior, D.F. de Souza, and L.A.O. Nunes, 'Cr3+ and Cr4+ luminescence in glass ceramic silica', J. Lumin., 128(11), 1787 (2008). CrossRef S. Zhou, H. Dong, H. Zeng, J. Hao, J. Chen, and J. Qiu, 'Infrared luminescence and amplification properties of Bi-doped GeO2−Ga2O3−Al2O3 glasses', J. Appl. Phys., 103(10), 103532 (2008). CrossRef T. Suzuki and Y. Ohishi, 'Ultrabroadband near-infrared emission from Bi-doped Li2O-Al2O3-SiO2 glass', Appl. Phys. Lett., 88(19), 191912 (2006). CrossRef T. Minh Hau et al., 'Super broadband near-infrared emission and energy transfer in Bi-Er co-doped lanthanum aluminosilicate glasses', Opt. Mater., 35(3), 487 (2013). CrossRef H.K. Dan et al., 'Effects of Y3+on the enhancement NIR emission of Bi+-Er3+ co-doped in transparent silicate glass-ceramics for Erbium-doped fiber amplifier (EDFA)', J. Lumin., 219, 116942 (2020). CrossRef E.M. Dianov, 'Bismuth-doped optical fibers: a challenging active medium for near-IR lasers and optical amplifiers', Light Sci. Appl., 1(5) (2012). CrossRef L. Wang, L. Tan, Y. Yue, M. Peng, and J. Qiu, 'Efficient Enhancement of Bismuth NIR Luminescence by Aluminum and Its Mechanism in Bismuth‐Doped Germanate Laser Glass', J. Am. Ceram. Soc., 99(6), 2071 (2016). CrossRef Z. Jiang et al., 'Effects of Al2O3 composition on the near-infrared emission in Bi-doped and Yb-Bi-codoped silicate glasses for broadband optical amplification', J. Non-Cryst. Solids, 383, 196 (2014). CrossRef

Cotton-wool-like borosilicate glass fibers for tissue regeneration: Preparation, characterization and in vitro bioactivity

Borosilicate (60SiO2-20CaO-16B2O3-4P2O5) glass fibers (BSGF) were fabricated by electrospinning in combination with sol-gel processing. BSGF were calcined at 600, 700 and 800 °C to remove the polymeric binder and optimize the formation of the inorganic phase. HCA (hydroxycarbonate apatite) was formed on BSGF within 24h of immersion in simulated body fluid (SBF), which was confirmed by XRD and FTIR analyses. In vitro cytotoxicity was measured with mouse osteoblast and fibroblast cell lines. WST-8 assay and fluorescence images confirmed the non-cytotoxic nature of the BSGF which did not induce any adverse effect on the cell activity.

Characterization of biodegradable core–clad borosilicate glass fibers with round and rectangular cross‐section

AbstractHere, we report on core–clad bioactive borosilicate fibers, that we have prepared both with round and rectangular cross‐section profile. The exposed approach, which relies on the stacking and drawing of glass slabs, demonstrates our ability to develop bioactive‐based glass fibers with tailored cross‐section profiles. Tens‐of‐meters‐long fibers were successfully drawn, although suffering from elevated losses in the case of the rectangular ones. The response of the fibers in simulated body fluid was studied for both geometries. We found that a round cladding can act as protective layer, tempering effects of the corrosion. We also noticed that rectangular fibers are more prone to degradation, the enhanced corrosion beginning from their sharp corners as they accumulated residual tensile stress during drawing. To the best of our knowledge, this is the first report on the effect of residual tensile stresses from surface tension deformations applied to the corrosion of rectangular fibers. As geometry plays a critical role on the biodegradation behavior of the fiberglass, we believe the enclosed results could lead to the design of fiber devices with tailored cross‐section profile in order to tune their rate of degradation on solely based geometrical effects.

Tuning optical properties in PbSe quantum dot-doped borosilicate glass fiber by modulation of network topology

Borosilicate glasses doped with PbSe quantum dots (QDs) were prepared by traditional melt-quenching followed by thermal treatment. By introducing a metal fluoride (NaF) network modifier that reduces the number of bridge oxygen bonds, the mobility of Pb2+ and Se2- ions is enhanced during thermal treatment, thereby promoting the precipitation of PbSe QDs. With increasing the thermal treatment temperature or NaF concentration, the absorption peak and emission peak undergo a red shift, which is accompanied by an increase and then decrease of the photoluminescence (PL) intensity, and a gradual increase of the PL lifetime. This evolution in spectral properties is associated with the growth in number and size of PbSe QDs. Furthermore, PbSe QD-doped glass fibers were prepared by a direct drawing method, and the addition of 4 mol % NaF results in an enhancement by 13.5 times in the PL intensity as compared with the fiber fabricated from the glass melt without NaF. Our method could be used to regulate the ultra-wideband near infrared PL of QD-doped glasses, which could find potential applications in ultra-wideband fiber amplifiers.

Investigating the Effect of Drawing Process Parameters on Borosilicate Glass Fiber Thickness

Borosilicate glasses have many usage areas due to high thermal and chemical resistance with a very low thermal expansion coefficient. The number of waste borosilicate glasses is increasing in direct proportion to their usage areas. Creating new usage areas by recycling these glasses will provide cost savings. In this paper, the fiber drawing method is used to recycle borosilicate glass. The aim of this article is to investigate the effect of winding speed and temperature of drawing process on fiber thickness. The fiber drawing process was performed at specific temperatures (1100 °C, 1200 °C, and 1300 °C) and at specific winding speeds (50 rpm, 175 rpm, and 300 rpm). In this context, the thermal behavior of borosilicate glasses was determined by DSC and TGA analysis. The structural, elemental, and chemical corrosion resistance properties of borosilicate glass fibers were examined by SEM, XPS, and corrosion test, respectively. The results show that the fiber thickness increased with the increase in the amount of material fed in the crucible, while it decreased with the increase of fiber drawing speed and time.

Positive bias in particulate matter emissions data due to sulfur dioxide adsorption and oxidation on glass fiber filters

ABSTRACT Recent particulate matter emisssion tests at an ArcelorMittal sintering line in Vitoria, Brazil have indicated a change in particulate matter emissions that was not consistent with the steady and proper operation of the combined electrostatic precipitator and pulse jet fabric filter control system. ArcelorMittal Brazil, ERM Brasil, and Air Control Techniques, P.C. have evaulated the use of borosilicate glass fiber filters in the U.S. EPA Method 5 sampling train as a possible reason for the anomolous change. The scope of this study included (1) possible adsorption and oxidation of SO2 on borosilicate glass and quartz filter media, and (2) the possible loss of fibers from borosilicaate glass and quartz filter media at normal sampling train vacuums and temperatures. Air Control Techniques, P.C. conducted a series of laboratory tests replicating gas stream conditions using both borosilicate and quartz circular and thimble filters. The laboratory tests confirmed the formation of sulfate artifacts due to sulfur dioxide adsorption on the borosilicate filters. These tests also confirmed that neither the borosilicate glass-fiber filters or the quartz filter lost significant filter weight during sampling at normal Method 5 sampling train vacuum levels and filter temperatures. Tests conducted by ERM Brasil, SA on the ArcelorMittal sintering process stack using both quartz and borosilicate glass fibers also indicated significant adsorption and oxidation of sulfur dioxide on the borosilicate filters. These laboratory and field tests confirmed the positive bias associated with glass fiber filters in SO2 environments reported as early as 1970. The authors recommend that only quartz fiber filter be used for particulate matter testing in SO2-containing gas streams. Furthermore, EPA Method 5 Section 7.1.1 should be revised to explicitly approve the use of quartz fiber filters. Implications: Filterable particulate matter emission tests using EPA Method 5 in sulfur dioxide laden gas streams have had a large positive bias due to outdated sampling practices. Our manuscript provides bias quantification data from both laboratory tests and tests on a sintering process stack. We recommend that (1) particulate matter emission tests conducted in SO2-containing gas streams be conducted using only quartz filter and (2) The U.S. EPA change the definition of filter media to be used in EPA Method 5 and other particulate matter test methods based on Method 5 specifically allow the use of quartz filters.

Surface modification and fabrication of white‐light‐emitting Tm3+/CdS quantum dots co‐doped glass fibers

AbstractDue to the widely tunable band gap and broadband excitation, CdS quantum dots (QDs) show great promise for yellow‐light luminescence center in white‐light‐emitting devices. The light intensity of the CdS QD‐doped glass was enhanced by doping the Tm3+ ions due to the higher absorption rate. The influence of Tm3+ ions on the surface structure of CdS QDs was enormous according to the first‐principles calculations. Doping Tm3+ ions change the surface state of CdS QDs, which will fix the QDs emission peaks and enhance the luminescence of CdS QDs at a lower heat‐treatment temperature. White‐light emission was obtained by tuning the relative concentration between Tm3+/CdS QDs. However, there is a fundamental challenge to fabricate QD‐doped glass fibers by rod‐in‐tube method since uncontrollable QDs crystallization is hard to avoid. Herein, a white‐light‐emitting borosilicate glass fiber was fabricated by the “melt‐in‐tube” method using a special designed Tm3+/CdS QDs co‐doped borosilicate glass with low‐melting temperature as fiber core. After heat treatment, ideal white‐light emission was observed from the fiber under excitation at single wavelength (359 nm). This finding indicates that Tm3+/CdS QDs co‐doped glass fiber with white‐light‐emitting devices has potential application as gain medium of white‐light‐emitting sources and fiber lasers.

Filtration via Conventional Glass Fiber Filters in 15N2 Tracer Assays Fails to Capture All Nitrogen-Fixing Prokaryotes

Biological dinitrogen fixation (BNF) represents a major input of reduced nitrogen (N) to the oceans. Accurate direct measurements of BNF rates are crucial for reliably determining the biogeochemical significance of diazotrophy at local and global scales. Traditionally, borosilicate glass fiber filters (GF/F, Whatman) with a nominal pore size of 0.7 µm are used to collect suspended particles by filtration after incubations with added 15N2 tracer. We carried out BNF experiments in the Baltic Sea, Danish coastal waters, and the Pacific Ocean comparing the retentive characteristics of precombusted GF/F filters with newer Advantec glass fiber filters which have a smaller nominal pore size of 0.3 µm. Where BNF was detected, rates were nearly always higher, and sometimes even exclusively detectable, when using Advantec filters. In the majority of samples across tested habitats, significantly more cells were lost to GF/F filtrate (average = 51 %, range = 10 – 70 % of cells) than to Advantec filtrate (average = 40 %, range = 10 – 54 %). Using Illumina sequencing of nitrogenase (nifH) gene amplicons, we show that diazotroph communities can markedly differ between bulk water and filtrates from GF/F and Advantec filtrations, suggesting that different diazotrophs can pass through the filter types. In order to reduce the potential underestimations of BNF due to filtration loss of diazotrophs, we recommend using Advantec filters or alternatively silver membranes with 0.2 µm pore size, especially in waters expected to be inhabited by relatively small, unicellular diazotrophs.

Borosilicate Glass Fiber-Optic Biosensor for the Detection of Escherichia coli.

Polyclonal antibodies against Escherichia coli and fluorescent, secondary, antibodies were immobilized on borosilicate glass fibers pre-treated with 3-glycidyloxypropyl trimethoxysilane (GPS). Light with an average wavelength of 627nm, emitted by a diode placed at one end of the glass fiber, was detected by an ultrasensitive photodiode with peak sensitivity at 640nm. Changes in fluorescence, caused by binding of E. coli to the antibodies, changed the net refractive index of the glass fiber and thus the internal reflection of light. These evanescent changes in photon energy were recorded by an ultrasensitive photodiode. Signals were amplified and changes in voltage recorded with a digital multimeter. A linear increase in voltage readings was recorded over 2h when 3.0×107 CFU/ml and 2.77×109 CFU/ml E. coli were adhered to the antibodies. Voltage readings were recorded with E. coli cell numbers from 2×103 CFU/ml to 2×106 CFU/ml, but readings remained unchanged for 2h, indicating that the limit of detection is 3.0×107 CFU/ml. This simple technology may be used to develop a low-cost, portable, fiber-optic biosensor to detect E. coli in infections and may have applications in the medical field. Research is in progress to optimize the sensitivity of the fiber-optic biosensor and determine its specificity.

Influence of thin glass films coherence on the Schottky and Rebinder effects in sensors

On the basis of the experimental study common property of three vitreous systems (SiO2, alumina borosilicate glass fiber and GeSe2), which are two- or multilevel group of atoms presence capable of changing their electronic configuration in these systems under the influence of external influences has been established. The change in the structure of film glassy systems is accompanied by changes in the work electron function (Schottky effect). It was found that the strength of alumina borosilicate glass fibers was due to coherent domains that form a kind of surface film “cover”. A sharp decrease in the strength of glass fibers from 400 to ∼250 kg/mm2 (Rebinder effect) was established in a water-containing medium and heat treatment.

Three-dimensional imaging of electrospun fiber mats using confocal laser scanning microscopy and digital image analysis

Confocal laser scanning microscopy with fluorescent markers and index matching has been used to collect three-dimensional (3D) digitized images of electrospun fiber mats and of a borosilicate glass fiber material. By embedding the fluorescent dye in either the material component (fibers) or pore space component (the index-matching fluid), acquisitions of both positive and negative images of the porous fibrous materials are demonstrated. Image analysis techniques are then applied to the 3D reconstructions of the fibrous materials to extract important morphological characteristics such as porosity, specific surface area, distributions of fiber diameter and of pore diameter, and fiber orientation distribution; the results are compared with other experimental measurements where available. The topology of the pore space is quantified for an electrospun mat for the first time using the Euler-Poincare characteristic. Finally, a method is presented for subdividing the pore space into a network of cavities and the gates that interconnect them, by which the network structure of the pore space in these electrospun mats is determined.

Measurements of indoor 222RN activity in dwellings and workplaces of Curitiba (Brazil)

Abstract The present work describes the results of systematic measurements of radon ( 222 Rn) in residential environments and workplaces in the Metropolitan Region of Curitiba (Parana State, Brazil) during the period 2004–2012. For radon in air activity measurements, polycarbonate Track Etch Detectors CR-39, mounted in diffusion chambers protected by borosilicate glass fiber filters, were used. After being exposed in air, the CR-39 detectors were submitted to a chemical etching in a 6.25 M NaOH solution at 70 °C for 14 h. The alpha particle tracks were identified and manually counted with an optical microscope, and with the results of previously performed calibrations, the indoor activity concentration of 222 Rn was calculated. The calibration of CR-39 and the alpha particle tracks chemical development procedures were performed in collaboration the National Institute of Radiological Sciences (NIRS, Japan). The major part of indoor 222 Rn concentration in residences was found to be below 100 Bq/m 3 . In the case of working places, all measurements of 222 Rn concentrations were below 100 Bq/m 3 . These values are considered within the limits set by international regulatory agencies, such as the US EPA and ICRP, which adopt up to 148 and 300 Bq/m 3 as upper values for the reference levels for radon gas activity in dwellings, respectively. The latest value of 300 Bq/m 3 for radon activity in air is proposed by ICRP considering the upper value for the individual dose reference level for radon exposure of 10 mSv/yr.

Composition and Integrity of PAHs, Nitro-PAHs, Hopanes, and Steranes in Diesel Exhaust Particulate Matter

Diesel exhaust particulate matter contains many semivolatile organic compounds (SVOCs) of environmental and health significance. This study investigates the composition, emission rates, and integrity of 25 SVOCs, including polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and diesel biomarkers hopanes and steranes. Diesel engine particulate matter (PM), generated using an engine test bench, three engine conditions, and ultra-low sulfur diesel (ULSD), was collected on borosilicate glass fiber filters. Under high engine load, the PM emission rate was 0.102 g/kWh, and emission rate of ΣPAHs (10 compounds), ΣNPAHs (6 compounds), Σhopanes (2 compounds), and Σsteranes (2 compounds) were 2.52, 0.351, 0.02 ~ 2 and 1μg/kWh, respectively. Storage losses were evaluated for three cases: conditioning filters in clean air at 25 °C and 33% relative humidity (RH) for 24 h; storing filter samples (without extraction) wrapped in aluminum foil at 4 °C for up to one month; and storing filter extracts in glass vials capped with Teflon crimp seals at 4 °C for up to six months. After conditioning filters for 24 h, 30% of the more volatile PAHs were lost, but lower volatility NPAHs, hopanes and steranes showed negligible changes. Storing wrapped filters and extracts at 4 °C for up to one month did not lead to significant losses, but storing extracts for five months led to significant losses of PAHs and NPAHs; hopanes and steranes demonstrated greater integrity. These results suggest that even relatively brief filter conditioning periods, needed for gravimetric measurements of PM mass, and extended storage of filter extracts can lead to underestimates of SVOC concentrations. Thus, SVOC sampling and analysis protocols should utilize stringent criteria and performance checks to identify and limit possible biases occurring during filter and extract processing.

Primary isolation of Geotrichum klebahnii polygalacturonase by capturing with glass fiber microfilters

This study reports the use of borosilicate glass fiber microfilters (GFMs) for capturing and concentrating Geotrichum klebahnii polygalacturonase (GkPG) from the culture media through a simple coupled filtration–sorption process. GFM was characterized by scanning electron microscopy and intrusion mercury porosimetry. Adsorption of GkPG was almost instantaneous with maximum effectiveness at pH 3.0. Using the parameters of Langmuir model and a material balance, a filter bed consisting of a stack of GFM was designed for recovering GkPG from a certain volume of culture media. After adsorption and washing, the enzyme was efficiently eluted with a buffer solution at pH 5.0 containing 0.5M NaCl. The filter bed was reused in several sorption cycles and enzyme recovery could be also done without prior cell removal with the benefits of using microfiltration for enzyme cell separation in a single step. Under the process conditions employed, GkPG recovery was about 80% with a concentration factor of about 4-fold.

Intrinsic strength of sodium borosilicate glass fibers by using a two-point bending technique

Flaws existing on glass surface can be divided into two types, extrinsic and intrinsic. Although the extrinsic flaws are generated during processing and using, the intrinsic flaws are regarded as structural defects which result from thermal fluctuation. It is known that the extrinsic flaws determine glass strength, but effects of the intrinsic flaws on the glass strength are still unclear. Since it is considered that the averaged bond-strength and the intrinsic flaw would affect the intrinsic strength, the intrinsic strength of glass surely depends on the glass composition. In this study, the intrinsic failure strain of the glass fibers with the compositions of 20Na2O-40xB2O3-(80-40x)SiO2 (mol%, x = 0, 0.5, 1.0, 1.5) were measured by using a two-point bending technique. The failure strength was estimated from the failure strain and Young's modulus of glass. It is elucidated that two-point bending strength of glass fiber decreases with increasing B2O3 content in glass. The effects of the glass composition on the intrinsic strength are discussed in terms of elastic and inelastic deformation behaviors prior to fracture.

SLC24A5 Encodes a trans-Golgi Network Protein with Potassium-dependent Sodium-Calcium Exchange Activity That Regulates Human Epidermal Melanogenesis

A non-synonymous single nucleotide polymorphism in the human SLC24A5 gene is associated with natural human skin color variation. Multiple sequence alignments predict that this gene encodes a member of the potassium-dependent sodium-calcium exchanger family denoted NCKX5. In cultured human epidermal melanocytes we show using affinity-purified antisera that native human NCKX5 runs as a triplet of approximately 43 kDa on SDS-PAGE and is partially localized to the trans-Golgi network. Removal of the NCKX5 protein through small interfering RNA-mediated knockdown disrupts melanogenesis in human and murine melanocytes, causing a significant reduction in melanin pigment production. Using a heterologous expression system, we confirm for the first time that NCKX5 possesses the predicted exchanger activity. Site-directed mutagenesis of NCKX5 and NCKX2 in this system reveals that the non-synonymous single nucleotide polymorphism in SLC24A5 alters a residue that is important for NCKX5 and NCKX2 activity. We suggest that NCKX5 directly regulates human epidermal melanogenesis and natural skin color through its intracellular potassium-dependent exchanger activity.

Influence of fiber orientation on global mechanical behavior and mesoscale strain localization in a short glass-fiber-reinforced epoxy polymer composite during tensile deformation investigated using digital image correlation

Advanced polymer composites are used in various fields such as light-weight automobile, aerospace and bio-implant engineering owing to their extraordinary mechanical properties. The various fields of application and the complex microstructures of such materials require better understanding of their micromechanical behavior under external loads. In this work, the tensile testing is coupled with the novel technique of surface displacement mapping via digital image correlation (DIC) is utilized for resolving the mechanical behavior and spatial distribution of the plastic microstrains in an epoxy resin reinforced with 35 wt% short borosilicate glass fibers. The DIC method works by correlating the digital images of surface patterns before and after straining. The material exhibited a pronounced mechanical anisotropy at both macro and mesoscale, which depends on the alignment of the fibers relative to the external load. The underlying microstructure of the material explained formation of strain gradients during evolution of full-field strain fields. The levels of localized strain are higher than the global failure strain of the material. Also, scanning electron microscopy (SEM) on the fracture surfaces revealed the multiple failure mechanisms of the material as a function of the fiber orientation.

Do Vitreous Fibers Break in the Lung?

In order to determine whether breakage of long vitreous fibers in the lung could be responsible for removing significant numbers of these fibers, an intratracheal instillation study was done with a preparation consisting of mostly long fibers of two different types. Following instillation of both fibers, laboratory rats were sacrificed at 6 times up to 14 days. The NK (conventional borosilicate glass) fiber preparation had about 20% short fibers (length ≤ 15 μm) initially, and fibers recovered from the lungs remained at that proportion for the entire 14 days. But the HT (a new rock or stone wool) fiber preparation, which had about 5% short fibers initially, jumped to about 50% short fibers at 2 days and remained at that proportion for the rest of the study. The appearance of many short HT fibers where there were few initially is conclusive evidence that these long fibers break, and it explains their rapid removal from the lung. Since the HT fibers dissolve rapidly at acid pH, but slowly at the near neutral pH of the extracellular lung fluid, it is likely that acid attack by phagocytic cells is causing the long fibers to dissolve and break. The long NK fibers dissolve rapidly at neutral pH but slowly at acid pH and thus appear to clear by more or less uniform dissolution without apparent breakage. The long fibers of these two kinds are removed rapidly at about the same rate, but by a different mechanism.