Влияние предыонизации на микроканальную структуру искрового разряда в воздухе в промежутке острие-плоскость

The initial phase of a spark discharge in the gap between the pin (cathode) and a plane 1.5 mm long in atmospheric pressure air under conditions of preliminary photoionization by an auxiliary discharge was investigated by the method of shadow photography. In the absence of preionization, the discharge from the first nanoseconds after breakdown is an aggregate of a large number of micron-diameter channels. It was found that the electron concentration resulting from preionization, estimated at 108  109 cm-3, increases the degree of uniformity of the discharge channel in the near-cathode region; however, in the near-anode region, the channel remains microstructured. Within the framework of the mechanism of microstructure formation due to the instability of the ionization wave front, a criterion for the formation of a uniform discharge is obtained and an explanation of the results obtained is presented.

In-Situ Depth Measurement of Laser Micromachining

Precision laser micromachining plays an important role in the biomedical, electronics, and material processing industries. During laser drilling, precision depth detection with micrometer-level resolution is required, particularly with blind-hole or heterogeneous structures. We present an optical detection system utilizing an optical confocal structure, experimentally confirmed to achieve a >95% accuracy for micron-diameter holes that are tens-of-microns deep. This system can be easily integrated into commercial laser micromachining processes, and can be employed in laser drilling and three-dimensional active-feedback laser printing.

Specificfeatures of evolution of dense atomized superheated water plumes and peculiarities of its diagnostics

Experimental study of evolution of plumes of atomized metastable superheated water during its discharge through convergent-divergent nozzles is conducted. Dispersion characteristics of dense plumes in micron and submicron droplet diameter ranges are obtained. Theoretical and prediction analyses of different coagulation mechanisms in the considered two-phase flow are performed. The negligible effect of Brown-type coagulation is shown. It is also demonstrated that turbulent coagulation can change the fraction of micron-diameter droplets within 9%. In addition, for the first time, an “inertial” mechanism of coagulation is considered for the studied plumes under the conditions of plume baking in a cocurrent flow or in the ambient air. It can lead to a considerable decrease in the submicron-droplet mass fraction, which is observed in experiments even at a small distance from the nozzle cut. The predicted data are compared with experimental ones obtained at theexperimental setup.

Short- and Long-Range Microparticle Transport on Permalloy Disk Arrays in Time-Varying Magnetic Fields

We investigate maneuvering superparamagnetic microparticles, or beads, in a remotely-controlled, automated way across arrays of few-micron-diameter permalloy disks. This technique is potentially useful for applying tunable forces to or for sorting biological structures that can be attached to magnetic beads, for example nucleic acids, proteins, or cells. The particle manipulation method being investigated relies on a combination of stray fields emanating from permalloy disks as well as time-varying externally applied magnetic fields. Unlike previous work, we closely examine particle motion during a capture, rotate, and controlled repulsion mechanism for particle transport. We measure particle velocities during short-range motion—the controlled repulsion of a bead from one disk toward another—and compare this motion to a simulation based on stray fields from disk edges. We also observe the phase-slipping and phase-locked motion of particles engaging in long-range transport in this manipulation scheme.

Microscopy and chemical analyses reveal flavone-based woolly fibres extrude from micron-sized holes in glandular trichomes of Dionysia tapetodes

Background Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic “woolly” farina. This contrasts with some related Primula which instead form a fine powder. Farina is formed by specialized cellular factories, a type of glandular trichome, but the precise composition of the fibres and how it exits the cell is poorly understood. Here, using a combination of cell biology (electron and light microscopy) and analytical chemical techniques, we present the principal chemical components of the wool and its mechanism of exit from the glandular trichome. Results We show the woolly farina consists of micron-diameter fibres formed from a mixture of flavone and substituted flavone derivatives. This contrasts with the powdery farina, consisting almost entirely of flavone. The woolly farina in D. tapetodes is extruded through specific sites at the surface of the trichome’s glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle and forming a tight seal between the fibre and hole. The data is consistent with formation and thread elongation occurring from within the cell. Conclusions Our results suggest the composition of the D. tapetodes farina dictates its formation as wool rather than powder, consistent with a model of thread integrity relying on intermolecular H-bonding. Glandular trichomes produce multiple wool fibres by concentrating and maintaining their extrusion at specific sites at the cell cortex of the head cell. As the wool is extensive across the plant, there may be associated selection pressures attributed to living at high altitudes.

Development of a nanoscale electroless plating procedure for bismuth and its application in template-assisted nanotube fabrication

We outline the development of a remarkably stable electroless bismuth plating bath. Its nanofabrication potential is showcased by coating ion-track etched polymer membranes, enabling the synthesis of sub-micron diameter bismuth tubes.

Increasing ionic conductivity within thermoplastics via commercial additives results in a dramatic decrease in fiber diameter from melt electrospinning

Role of conductivity and viscosity in determining jet size and fiber diameter in melt electrospinning is explored by new data and application of theory. Increasing conductivity via an additive leads to a large fraction of sub-micron diameter fibers.

Objective Evaluation of the Longevity of A Calcium Hydroxylapatite-Based Filler (Radiesse®)

Background: Calcium hydroxylapatite (CaHA) based soft-tissue filler (Radiesse® , Merz) is categorised as a biodegradable collagen-stimulating implant. It is comprised of a suspension of 25-45 micron diameter microspheres of CaHA(30%) in a carboxymethylcellulose (CMC) gel carrier (70%) and is one of the most well researched soft-tissue fillers. However, great discrepancies exist in the literature regarding the duration of clinical effect with the implant, ranging from only 6 to 24 months.

Quantitative and qualitative measurement of carbon compounds in dust emitted in the work environment for electrical insulators production factory: القياس الكمي والنوعي لمركبات الكربون في الغبار المنبعث في بيئة العمل لمصنع إنتاج العوازل الكهربائية

A quantitative and qualitative determination of the pollutants emitted within the work environment, including dust and its components of organic and inorganic carbon was conducted in one of the factories of electrical insulators production. A dust sampler and 5 micron diameter filters were used and prepared for analysis in the carbon analyzer of organic and inorganic components. The result of the analysis shows the dust emissions concentrations of organic carbon (OC) in the mechanical lathing unit for cutting Phenolic Carbon Insulators (PCI) is (244.0 µg.m-3) and the lowest inorganic emissions (59.0 µg.m-3). The emission of manual filings from inorganic carbon dust is the highest concentration (916.0 µg.m-3) and the lowest organic carbon is (4.0 µg. m-3). The highest level for total inorganic carbon (TIC) in the manual unit fillings is (440.0 mg.m-3. .8hr-1) and the lowest TIC concentration is (2.8 mg.m-3. .8hr-1) in the mechanical lathing unit for phenolic carbon. While the highest level for OC in the mechanical lathing unit is (117.0 mg.m-3. .8hr-1) and the lowest OC concentration is (2.0 mg.m-3..8hr-1) in manual and pressing units. All concentrations of the dust and their components of organic and inorganic carbon are out of standards limitation of the International Standards Units (ISU). Exposure to these emissions during an actual working time of 8 hours a day requires commitments to individual and group safety measures to maintain workers safety.

Super stable giant tubes with densely packed multilayer ultrathick membranes self-assembled from amphiphilic polyamide

This work reports on the preparation of giant tubes with millimeter-scale length, micron diameter and ultrathick walls above 250 nm, from the aqueous self-assembly of a novel amphiphilic polyamide.