Microm In Diameter Research Articles

Electromagnetic Shielding Effectiveness of Thin Film with Composite Carbon Nanotubes and Stainless Steel Fibers

Using the polymer blending method, conductive materials and waterborne polyurethane (WPU) were mixed to fabricate conductive composite films for application in electromagnetic shielding. First, nitric acid was used to purify the multi-walled carbon nanotubes (MWCNT). Second, sodium dodecyl sulfate (SDS) was utilized to disperse the carbon nanotubes, and then they were mixed with 8 microm diameter and 2 mm long stainless steel fibers (SSF) in the WPU by the polymer blending method. Finally, the thickness of 0.25 mm of conductive composite film was fabricated by means of coating. According to the ASTM D4935-99 standard, a coaxial transmission line was used to measure the electromagnetic shielding effectiveness (EMSE) of conductive composite film within the range of 50 MHz approximately 3.0 GHz. Moreover, the influence of the prior and posterior dispersion of carbon nanotubes dispersed on electromagnetic shielding was dealt with in the paper. Results demonstrated that the conductive composite film, within 50 MHz approximately 3.0 GHz, fabricated by the 15 wt% of the multi-walled carbon nanotubes and 30 wt% of the stainless steel fibers can achieve the maximum of the electromagnetic shielding effectiveness, 34.86 dB, and its shielding effect, 99.9%.

Photothermal Lens Spectoscopy in Highly Scattering Media

Photothermal lens spectrometry is a highly-sensitive technique used to measure simultaneously absorption and thermal parameters of various scatter free samples. However, recently researchers have extended the use of this technique to for measuring the absorption of light in complex samples, including highly scattering media such as biological samples, . It is commonly applied in either scattering-free samples or without a systematic study of assumed that the effects of scattering on the photothermal signals. measurements are negligible. In this work, we report the results of a pump-probe experiment in which In the present study we measured both the photothermal signal and the scattering intensity at 90o angle from samples of water solutions prepared with a mixture of absorptive gold nanoparticles (concentration 150 ppb and 2-nm diameter) and scattering latex microspheres (0.2-25 microm diameter and concentrations 1.3-50 microg/ml). The data show that the photothermal signal slowly decreases when the concentration of the latex scatterers is increased. At latex concentration 50 microg/ml, the scattered signal increases more than 2 orders of magnitude for 0.2-microm latex microspheres while the photothermal signal reduces by less than 50%. This result suggests that the signal reduction may be caused by the distortion of the excitation beam profile due to multiple scattering, inducing hence reduction of the local temperature gradient necessary for thermal lensing. In the case of Latex, we show that the photothermal lens method can be considered scattering free for turbidity values smaller than ?? (1/cm).

Nanofiber Network of Electropolymerized 3,4-(2-Benzylpropylenedioxy)thiophene on Single Carbon Fiber Microelectrode

Electropolymerization of 3,4-(2-benzylpropylene)-dioxythiophene (ProDOT-Bz) on (approximately 7 microm diameter) single carbon fiber microelectrodes (SCFMEs) in different electrolytes resulted the network of nanofiber structure. Electropolymerization performed in different electrolytes by using cyclovoltammetric technique. Surface morphology of coatings was investigated by Scanning Electron Microscopy (SEM), the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used for the characterization. A linear relationship between peak currents of films with polymerization charge, and capacitances and coating thickness were obtained. The size of nanofiber network (and pores) can be controlled by the scan rate of the cyclovoltammetric process. Electrochemical impedance spectroscopic investigation of these nanostructures has been indicated the capacitive behavior of electrode system. Electrochemical Impedance Spectroscopic characterization (Capacitance) of the PProDOTBz/SCFME consisting cell was simulated at applied potential and parameters explained by equivalent circuit modeling.

Subnuclear targeting of the RNA-binding motif protein RBM6 to splicing speckles and nascent transcripts

RNA-binding motif (RBM) proteins comprise a large family of RNA-binding proteins whose functions are poorly understood. Since some RBM proteins are candidate alternative splicing factors we examined whether one such member of the family, RBM6, exhibited a pattern of nuclear distribution and targeting consistent with this role. Using antibodies raised against mouse RBM6 to immunostain mammalian cell lines we found that the endogenous protein was both distributed diffusely in the nucleus and concentrated in a small number of nuclear foci that corresponded to splicing speckles/interchromatin granule clusters (IGCs). Tagged RBM6 was also targeted to IGCs, although it accumulated in large bodies confined to the IGC periphery. The basis of this distribution pattern was suggested by the targeting of tagged RBM6 in the giant nuclei (or germinal vesicles (GVs)) of Xenopus oocytes. In spread preparations of GV contents RBM6 was localized both to lampbrush chromosomes and to the surface of many oocyte IGCs, where it was confined to up to 50 discrete patches. Each patch of RBM6 labelling corresponded to a bead-like structure of 0.5-1 microm diameter that assembled de novo on the IGC surface. Assembly of these novel structures depended on the repetitive N-terminal region of RBM6, which acts as a multimerization domain. Without this domain, RBM6 was no longer excluded from the IGC interior but accumulated homogeneously within it. Assembly of IGC-surface structures in mammalian cell lines also depended on the oligomerization domain of RBM6. Oligomerization of RBM6 also had morphological effects on its other major target in GVs, namely the arrays of nascent transcripts visible in lampbrush chromosome transcription units. The presence of oligomerized RBM6 on many lampbrush loops caused them to appear as dense structures with a spiral morphology that appeared quite unlike normal, extended loops. This distribution pattern suggests a new role for RBM6 in the co-transcriptional packaging or processing of most nascent transcripts.

Probing Chirality of a Lipid Tubular by Confocal Raman Microscopy

The chiral phospholipids 1,2-bis-(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9 PC) can self assemble into lipid nanotubules. This hollow cylindrical supramolecular structure shows promise in a number of biotechnological applications. The mechanism of lipid tubule formation was initiated by assembling of lipid bilayer sheets from amphiphilic solution. Upon cooling, small ribbons were detached from the sheets and rolled up into helical tubules. The lipid tubules obtained were 0.6-0.8 microm in diameter and approximately 50 microm in length. Raman spectra of individual polymerized lipid tubules were measured by focused laser excitation of 532 nm leading to intense and reproducible Raman spectra. The chirality of lipid tubules was investigated by atomic force microscopy (AFM) and confocal Raman microscopy. We report the Raman mapping images revealing helical tubular profiles of C=C stretching and C[triple bond]C stretching of lipid tubules. Circular dichroism property of lipid tubules has also been probed with a 532 nm laser.

Fabrication and Chromatographic Performance of Porous-Shell Pillar-Array Columns

We report on a new approach to obtain highly homogeneous silica-monolithic columns, applying a sol-gel fabrication process inside a rectangular pillar-array column (1 mm in width, 29 microm in height and 33.75 mm in length) having a cross-sectional area comparable to that of a 200 microm diameter circular capillary. Starting from a silicon-based pillar array and working under high phase-separation-tendency conditions (low poly(ethylene glycol) (PEG)-concentration), highly regular silica-based chromatographic systems with an external porosity in the order of 66-68% were obtained. The pillars, 2.4 microm in diameter, were typically clad with a 0.5 microm shell layer of silica, thus creating a 3.4 microm total outer pillar diameter and leaving a minimal through-pore size of 2.2 microm. After mesopore creation by hydrothermal treatment and column derivatization with octyldimethylchlorosilane, the monolithic column was used for chip-based liquid-chromatographic separations of coumarin dyes. Minimal plate heights ranging between 3.9 microm (nonretaining conditions) and 6 mum (for a retention factor of 6.5) were obtained, corresponding to domain-size-reduced plate heights ranging between 0.7 and 1.2. The column permeability was in the order of 1.3 x 10(13) m(2), lower than theoretically expected, but this is probably due to obstructions induced by the sol-gel process in the supply channels.

Field Emission from Few-Layer Graphene Nanosheets Produced by Liquid Phase Exfoliation of Graphite

Graphene nanosheets have been synthesized from commercial expandable graphite by heating in a microwave oven and dispersing in ethanol by ultrasonication. Scanning and transmission electron microscopy and electron energy-loss spectroscopy and atomic force microscope showed that the nanosheets were about 2 nm in thickness and 10 microm in diameter. The field emission of the graphene sheets has been investigated. An emission current density of 1 mA/cm2 has been achieved at an electric field of 3.7 V/microm with a turn-on field of 1.7 V/microm at 0.01 mA/cm2. The annealing of the samples at 400 degrees C in vacuum greatly improved the field emission performance.

Wider Pore Superficially Porous Particles for Peptide Separations by HPLC

Fused-core superficially porous particles have recently created considerable interest for high-performance liquid chromatography separations because of their unusual high column efficiency and much lower back pressure when compared to sub-2-microm particles. With superficially porous particles, larger solutes can move rapidly in and out of a thin porous shell, resulting in reduced band broadening at higher mobile phase velocities for greater separation speeds. The original silica fused-core particles were 2.7 microm in diameter with a 0.5-microm thick shell of 90 A pores designed for the fast separation of small molecules with molecular weights of less than approximately 5000. This manuscript describes new fused-core particles with similar physical characteristics except with a porous shell of 160 A pores designed specifically for rapidly separating peptides (and some small proteins) with molecular weights up to approximately 15,000 Daltons. Because of the larger pore size, restricted diffusion of these larger molecules is not seen since ready access to the entire porous shell is featured. Data are given to define sample loading qualities for columns of these new particles. Column stability studies indicate that these particles bonded with a sterically protected C(18) stationary phase can be used at low pH and higher temperatures with excellent results. The wider-pore particles of this study are shown to be particularly useful with a mass spectrometer detector for the rapid gradient separation of peptides using both volatile trifluoroacetic acid and formic acid containing mobile phases. Examples are provided for the separation of complex peptide mixtures to illustrate the capabilities for columns of these new wider-pore, fused-core particles.

Wavefront aberration measurements and corrections through thick tissue using fluorescent microsphere reference beacons

We present a new method to directly measure and correct the aberrations introduced when imaging through thick biological tissue. A Shack-Hartmann wavefront sensor is used to directly measure the wavefront error induced by a Drosophila embryo. The wavefront measurements are taken by seeding the embryo with fluorescent microspheres used as “artificial guide-stars.” The wavefront error is corrected in ten millisecond steps by applying the inverse to the wavefront error on a micro-electro-mechanical deformable mirror in the image path of the microscope. The results show that this new approach is capable of improving the Strehl ratio by 2 times on average and as high as 10 times when imaging through 100 μm of tissue. The results also show that the isoplanatic half-width is approximately 19 μm resulting in a corrected field of view 38 μm in diameter around the guide-star.

Studies on morphology and aristolochic acid analogue constituents of Asarum campaniflorum and a comparison with two official species of Asari Radix et Rhizoma

Dried whole herbs or roots and rhizomes of Asarum campaniflorum have been sold under the trade name Xixin and used as folk remedies in its producing areas for a long time. In order to avoid the misuse of A. campaniflorum as official species of Xixin (Asari radix et rhizoma), a comparative study based on the morphological and phytochemical analysis of the aerial and underground parts was carried out. The usual morphological methods and a microscopic imaging system were used. The results show that A. campaniflorum could be easily distinguished from two official species (Asarum sieboldii and A. heterotropoides var. mandshuricum) by the diameter of thicker roots (1.3-2.7 mm), distinct large parenchymatous cells in phloem of roots, and the size of oil cells in upper leaf epidermises [(40)80-140(174) microm in diameter, where numbers in parentheses are for rare cases], etc. Nine aristolochic acid analogues (AAAs) were identified and estimated by high-performance liquid chromatography-diode array detection (HPLC-DAD). The aerial and underground parts of A. campaniflorum contained 3-4 AAAs, i.e., aristololactam-II-N-beta-D-glucoside (AL-II-Glc), aristololactam I (AL-I), aristololactam II (AL-II), and aristolochic acid I (AA-I), while only AL-I was detected in underground parts of A. sieboldii and no AAAs were detected in underground parts of A. heterotropoides var. mandshuricum. The respective contents (in mg/g) in aerial and underground parts of A. campaniflorum, were as follows: AL-I, 0.06-0.12, 0.05-0.10; AL-II, 0.03-0.04, 0.01-0.03; AA-I, 0.01-0.02, 0.0-0.0. These data suggest A. campaniflorum has a high risk of causing aristolochic acid nephropathy. All these discoveries can contribute to not only the better understanding of this new resource species, but also the safe use of the crude drug Xixin.

Particulate Matter Air Pollution and Atherosclerosis

Particulate matter (PM) air pollution less than 2.5 microm in diameter (PM(2.5)), which is now an all-pervading element of modern-day society, is associated with heightened cardiovascular morbidity and mortality. Not only can short-term PM(2.5) exposure trigger acute cardiovascular events, but longer-term exposure over years augments cardiovascular risk to an even greater extent. One biological mechanism capable of explaining this observation is that chronic exposure may promote the progression and vulnerability of atherosclerotic plaques. Indeed, recent epidemiologic studies have demonstrated an association between ambient PM(2.5) exposure and the presence or extent of atherosclerosis in humans. Several animal experiments have provided corroborating evidence that chronic exposures in fact do enhance the progression and perhaps vulnerability of atherosclerotic lesions. Due to the billions of people continually exposed to PM(2.5), the long-term pro-atherosclerotic effects of this ubiquitous air pollutant are likely to be of enormous and growing global public health importance.

Histoplasmosis: cytodiagnosis and review of literature with special emphasis on differential diagnosis on cytomorphology

Human infection with Histoplasma capsulatum runs the gamut from asymptomatic to disseminated disease. In immunocompromised patients, a tiny inoculum can lead to widespread disseminated infection. Early diagnosis and initiation of treatment is therefore important. To review the cases of histoplasmosis diagnosed on fine needle aspiration cytology (FNAC) and to discuss the clinical presentation, associated inflammatory response, load of organisms and differential diagnosis on cytomorphology in these cases. Retrospective review of seven cases of histoplasmosis at a tertiary-care centre during the period from 1998 to 2009 was performed. Clinical presentation along with cytomorphological features were studied and discussed in detail. The mean age of patients was 48.6 years and six out of seven were male. History of immunodeficiency (HIV) was available in five cases. Six patients presented with peripheral and/or abdominal lymphadenopathy. One patient had nodular shadows in both lungs and two also had skin lesions. On cytological smears, a variable load of uniform round to oval, about 2-4 microm in diameter, budding yeasts were seen intracellularly (within histiocytes) as well as extracellularly. In one case (HIV positive), these organisms were also seen within neutrophil polymorphonuclear leucocytes. In two cases, an inflammatory response in the form of epithelioid cell granulomas along with multinucleated giant cells was seen. FNAC is a reliable tool to recognize infection with H. capsulatum in tissues. This infection can cause a variable inflammatory response, which should be considered while reporting on such cases.

Short vertical tube furnace for the fabrication of doped glass microsphere lasers

We report on the design of an electric tube furnace that can be used for the fabrication of doped glass microsphere lasers. The tube furnace has a short hot zone of length 133 mm and is based on a quartz tube design. Doped laser glass particles, specifically Er:Yb phosphate glass (IOG-2), of approximately 1 microm diameter are blown into the furnace using a 60 ml syringe and microspheres ranging in size from 10 to 400 microm are collected at the output of the tube furnace in a Petri dish. The furnace operates at a wall temperature of approximately 900 degrees C and is capable of making microspheres from glasses with glass transition temperatures of at least 375 degrees C. High quality (Q approximately 10(5)) whispering gallery modes have been excited within the microspheres by optically pumping at 978 nm via a tapered optical fiber.

Magnet polepiece design for uniform magnetic force on superparamagnetic beads.

Here we report construction of a simple electromagnet with novel polepieces which apply a spatially uniform force to superparamagnetic beads in an optical microscope. The wedge-shaped gap was designed to keep partial differential B(x)/ partial differential y constant and B large enough to saturate the bead. We achieved fields of 300-600 mT and constant gradients of 67 T/m over a sample space of 0.5x4 mm(2) in the focal plane of the microscope and 0.05 mm along the microscope optic axis. Within this space the maximum force on a 2.8 microm diameter Dynabead was 12 pN with a spatial variation of approximately 10%. Use of the magnet in a biophysical experiment is illustrated by showing that gliding microtubules propelled by the molecular motor kinesin can be stopped by the force of an attached magnetic bead.

Hospital admissions for respiratory conditions in children and outdoor air pollution in Southwest Milan, Italy

To evaluate whether a relationship exists in hospital admissions for respiratory conditions in children with outdoor pollution in the Southwest Milan, Italy. Daily count of hospital admissions for asthma, upper or lower respiratory diseases (LRD) occurred among children aged < or =14 years at the San Paolo Hospital during 2007-2008 was recorded. Pollutants included the particular matter of <10 microm diameter, ozone, carbon monoxide (CO) and nitrogen dioxide (NO(2)), reported on the same day of admission and 1 up to 5 days before admission. The moving weekly average (MWA) was also considered. Total respiratory admissions were associated with the same day level of CO (30.6% increase per 1 mg/m(3) increase, 95% confidence interval, 3.9-69.9%) and with the MWA of NO(2) (9.0% increase per 10 microg/m(3) increase, 1.2-16.8%). The effect of CO was stronger on upper respiratory diseases (URD) (lag 0, 21.3% increase, 6.4-38.3%). The effect of NO(2) was stronger on LRD (MWA, 5.3% increase, 0.9-10.2%). Multipollutant models confirmed the role of CO on URD and that of NO(2) on LRD. Carbon monoxide and nitrogen dioxide may be associated with emergency hospital admissions for respiratory conditions among children in Southwest Milan.

Tracking Giant Folds in a Monolayer

The collapse dynamics of giant folds in a catanionic monolayer at the air-water interface are examined. A monolayer of dioctadecyldimethylammonium bromide (DODAB) and sodium dodecyl sulfate (SDS) in a 1:1 ratio is the system of study that previously was found to fold upon compression in a Langmuir trough. Carboxylate-coated polystyrene beads (1 microm diameter) are deposited and bound to the monolayer. Displacement of the beads is measured with epifluorescence microscopy and particle image velocimetry, yielding a measurement of the velocity of the monolayer around the fold. Reversibility is confirmed by measuring the amount of monolayer material entering and leaving the fold. Material near folds are found to have a maximum relative velocity on the order of 0.1 mm/s, and fold depths are found to be on the order of 1 mm. The folds exhibit regular unfolding behavior, which can be explained qualitatively by a simple mechanical model.

High-power vertical-cavity surface-emitting laser with an optimized p-contact diameter

A 980 nm bottom-emitting vertical-cavity surface-emitting laser (VCSEL) with a p-contact diameter is reported to achieve high power and good beam quality. A numerical simulation is conducted on the current spreading in a VCSEL with oxidation between the active region and the p-type distributed Bragg reflector. It is found that, for a particular oxide aperture diameter, somewhat homogeneous current distribution can be achieved for a VCSEL with an optimized p-contact diameter. The far-field divergence angle from a 600 microm diameter VCSEL is suppressed from 30 degrees to 15 degrees, and no strong sidelobe is observed in the far-field pattern by using the optimized p-contact diameter. There is a slight rise in threshold and optical output power that is due to the p-contact optimization. By improving the device packaging method, the maximum optical output power of the device is 2.01 W.

Actin and serum response factor transduce physical cues from the microenvironment to regulate epidermal stem cell fate decisions

Epidermal homeostasis depends on a balance between stem cell renewal and differentiation and is regulated by extrinsic signals from the extracellular matrix (ECM). A powerful approach to analysing the pathways involved is to engineer single-cell microenvironments in which individual variables are precisely and quantitatively controlled. Here, we employ micropatterned surfaces to identify the signalling pathways by which restricted ECM contact triggers human epidermal stem cells to initiate terminal differentiation. On small (20 microm diameter) circular islands, keratinocytes remained rounded, and differentiated at higher frequency than cells that could spread on large (50 microm diameter) islands. Differentiation did not depend on ECM composition or density. Rather, the actin cytoskeleton mediated shape-induced differentiation by regulating serum response factor (SRF) transcriptional activity. Knockdown of SRF or its co-factor MAL inhibited differentiation, whereas overexpression of MAL stimulated SRF activity and involucrin expression. SRF target genes FOS and JUNB were also required for differentiation: c-Fos mediated serum responsiveness, whereas JunB was regulated by actin and MAL. Our findings demonstrate how biophysical cues are transduced into transcriptional responses that determine epidermal cell fate.

Depth of tissue ablation and residual thermal damage caused by a pixilated 2,940 nm laser in a swine skin model

The purpose of this study was to assess the effects of fluence, pulse stacking, and multiple passes on the depth of injury caused by a fractionated Er:YAG laser in an in vivo farm pig model. DESIGN/MATERIAL/METHODS: A fractionated 2,940 nm Er:YAG laser (Pixel, Alma Lasers, Caesarea, Israel) was applied to the flank skin of a Yorkshire cross pig. The 11 mmx11 mm handpiece was comprised of either 49 or 81 microbeams (200 microm diameter), depending on the tip configuration. There were six different parameter sets divided according to total energy per pulse (150, 285, and 500 mJ) and tip type (81 or 49 microbeams per 11 mmx11 mm macrospot). Each of these six groups was subdivided according to number of stacked pulses (1, 3, and 6) and number of passes (1, 3, and 6). This resulted in a total of 36 treatment parameters. With the 49 microbeam configuration, a single pulse resulted in partial epidermal ablation at 150 mJ, complete epidermal ablation at 285 mJ and partial dermal ablation at 500 mJ to a depth of 90 microm. Stacking the pulses resulted in a significant increase in ablation with each fluence with the maximal depth of ablation measured at 140 microm after six stacked pulses at 500 mJ. Increasing the number of passes did not result in a significant increase in ablative depth, but did create a larger surface area of ablation. Residual thermal damage (RTD) was minimal and remained between 10 and 20 microm. The fractionated Er:YAG laser exhibited some of the same tissue interactions as its fully ablative counterparts. An increase in fluence resulted in an increase in ablative depth with minimal RTD. Additionally, RTD was unaffected by pulse stacking or by additional passes. Differences were that pulse stacking appeared to yield a more rapid decrease in ablation efficiency and additional passes did not seem to increase the depth of ablation.

High-energy flat-top beams for laser launching using a Gaussian mirror

Converting a Gaussian to a flat-top beam is useful for many applications including laser-launched thin-foil flyer plates. A flat-top beam is needed to maintain a constant launch velocity across the flyer; otherwise, the flyer can disintegrate in flight. Here we discuss and demonstrate the use of a variable reflectivity mirror (VRM) with a Gaussian reflectivity profile with an additional hard aperture and compare it to a refractive beam shaper. An ideal VRM would generate a flat-top beam with 37% efficiency. Readily available high-power Gaussian or super-Gaussian mirrors create an approximate flat-top profile, but there is a trade-off between flatness and efficiency. We show that a super-Gaussian mirror can, in principle, convert an input Gaussian beam with 30% efficiency to a flat-top beam with 3% (maximum-to-minimum) variation. With a Gaussian mirror and a high-energy pulsed Nd:YAG laser having relatively poor beam quality, we generate flat-top beams with 25% conversion efficiency having 6% variation (standard deviation sigma=4.2%). The beams are used to launch 400 microm diameter, 25 microm thick Al flyer plates, whose flight was monitored by a high-speed displacement interferometer. The plates flew across a 300 microm gap at 1.3 km/s. The distribution of arrival times at the witness plate was 5 ns, as determined by the rise time of the impact emission. Compared to a total flight time of 260 ns, the velocity spread of different parts of the flyer plate was 2%.