Materials In Particulate Form Research Articles

Aluminum doped CuS nanocrystals for efficient antibacterial activity via photothermal and photodynamic pathways

The overuse of antibiotics has led to the emergence of drug-resistant bacteria, presenting a significant risk to public health and human well-being. A novel antibacterial material with safe and effective antibacterial properties is a viable strategy to address these issues. In this work, Al ions doped CuS particles (CuS@Al) with a flower-like nanostructure were synthesized through a simple hydrothermal method, exhibiting good photothermal and photodynamic antibacterial properties. The morphological, microstructural and crystallinity of CuS@Al were evaluated by SEM, EDS, TEM, FTIR, XRD and XPS analyses. The introduction of Al ions significantly enhanced the photothermal effects of CuS@Al, and the temperature increased from 50.7 ℃ (CuS) to 58.1 ℃ (CuS-6) under irradiation (808 nm, 2.0 W·cm−2, 10 min). The resulting CuS@Al exhibited a good photothermal conversion efficiency, effective release of reactive oxygen species (ROS), and remarkable photothermal antibacterial activity. Both E. coli and S. aureus were completely inactivated by CuS@Al (0.5 mg/mL) under photodynamic conditions. The synthesis of CuS@Al provides a strategy for creating highly effective antibacterial materials in particulate form.

Quantification of soot deposit on a resistive sensor: Proposal of an experimental calibration protocol

During a fire in an industrial facility, the main consequences concerning aerosol are the production of large amount of soot and potential resuspension of hazardous material in particulate form. Soot deposition quantification on walls in a room during a fire is essential for the prediction of aerosol quantities that can be transported in the ventilation ducts and clog high efficiency particulate air filters.For this purpose, accumulative resistive sensors, initially developed for monitoring Diesel Particulate Filters (DPF), have been used to quantify soot particles that are deposited on its sensing side. After validation of the fabrication process via electrical measurements, the sensor response has been studied under different polarization voltages and an experimental protocol for soot quantification has been qualified.Thanks to those protocols, it was first demonstrated that the polarization voltage has no influence on the deposition velocity. Then, the resistive sensor was calibrated at polarization voltages of 10 V and 0.1 V. For 0.1 V, results are less repeatable and do not allow to propose a correlation between conductance and deposited mass. Better repeatability was found for a polarization voltage of 10 V allowing to propose and develop a calibration procedure aiming to correlate sensor conductance and deposited mass of aerosol.Indeed, it was proved that the sensor has a blind zone, in terms of conductance, for mass deposit ranging from 0 to 230 mg/m2. A linear calibration curve with a good sensitivity of 2.49 μS mg-1.m2 was obtained for deposited mass between 230 and 1630 mg/m2.

Particulate Composites with Wastes from Treated Wood and Tire Rubber

The segment of wood preservation is responsible for considerable waste generation, typically consisting of products not approved by quality control or post-consumer. Another type of waste to be considered is tire rubber, which accumulate due to deficiencies in logistics and fiscalization. Although it has been classified as intractable, tire rubber enables to add properties in products that promote the use of materials in particulate form. This study aimed producing and characterization of particulate composites containing CCB-treated Pinus sp. with addition of tire rubber, and castor oil-based polyurethane resin. Properties of particleboards were obtained according to Brazilian Code NBR 14810:2006. The results were compared by statistical analysis. It was observed that addition of tire rubber waste resulted in higher densities, and rubber proportion of 50% showed greater internal bond. In some cases, strength in bending of panels was in accordance with standards requirements and commercial products destined for acoustic conditioning, enabling different applications.

Materials in particulate form for tissue engineering. 2. Applications in bone

Materials in particulate form have been the subjects of intensive research in view of their use as drug delivery systems. While within this application there are still issues to be addressed, these systems are now being regarded as having a great potential for tissue engineering applications. Bone repair is a very demanding task, due to the specific characteristics of skeletal tissues, and the design of scaffolds for bone tissue engineering presents several difficulties. Materials in particulate form are now seen as a means of achieving higher control over parameters such as porosity, pore size, surface area and the mechanical properties of the scaffold. These materials also have the potential to incorporate biologically active molecules for release and to serve as carriers for cells. It is believed that the combination of these features would create a more efficient approach towards regeneration. This review focuses on the application of materials in particulate form for bone tissue engineering. A brief overview of bone biology and the healing process is also provided in order to place the application in its broader context. An original compilation of molecules with a documented role in bone tissue biology is listed, as they have the potential to be used in bone tissue engineering strategies. To sum up this review, examples of works addressing the above aspects are presented.

Materials in particulate form for tissue engineering. 1. Basic concepts

For biomedical applications, materials small in size are growing in importance. In an era where 'nano' is the new trend, micro- and nano-materials are in the forefront of developments. Materials in the particulate form aim to designate systems with a reduced size, such as micro- and nanoparticles. These systems can be produced starting from a diversity of materials, of which polymers are the most used. Similarly, a multitude of methods are used to produce particulate systems, and both materials and methods are critically reviewed here. Among the varied applications that materials in the particulate form can have, drug delivery systems are probably the most prominent, as these have been in the forefront of interest for biomedical applications. The basic concepts pertaining to drug delivery are summarized, and the role of polymers as drug delivery systems conclude this review.

The dynamics of granular materials - towards grasping the fundamentals

The manufacture of a wide range of materials in particulate form currently has to rely upon a design basis that is not at all strong theoretically. The most developed methods exist in the design of storage vessels for particles but many weaknesses remain. In those areas of processing concerned with the development of product properties, the knowledge of the dynamics of granular motion is more rudimentary. However, we are now in a position where progress of a fundamental character elucidating the mechanisms operating in engineering systems can now be undertaken. This is illustrated by recent studies aimed at understanding how the axial motion of particles occurs in mixers which the particles are stirred mechanically by blades. Representation is possible in terms of an axial diffusion coefficient, for instance. A more physical approach reveals a cellular structure to the flow with transfers between cells limiting behaviour. The axial limits of these cells correspond to the plane of rotation of ploughshare blades or of the mechanical supports for long flat blades.

Performance of radar absorbing materials by waveguide measurements for X- and Ku-band frequencies

In this work, samples consisting of an elastomeric matrix containing different kinds of active materials in particulate form were prepared for reflectivity measurements. The materials individually used in weight contents of 80% in polychloroprene matrix were: carbonyl-iron (CI) and doped ferrite powders. The microwave reflectivity levels were determined from the magnetic and dielectric properties of the elastomeric composites obtained from scattering data, by fitting the samples in a waveguide, for measurements in the frequency range from 8 to 16 GHz. Better microwave absorption for X-band was obtained for CI while doped ferrite absorbed at higher frequencies (Ku-band).

Aging effect on the reflectivity measurements of polychloroprene matrices containing carbon black and carbonyl-iron powder

The effect of aging, arising from salt spray exposure, on the microwave reflectivity was studied for polychloroprene (CR) matrices, containing different kinds of active material in particulate form. The materials used as microwave absorbers in different contents were carbon black (CB) and carbonyl-iron powder (CIP). The microwave reflectivities were determined for the frequency range of 8–16 GHz. The formation of a superficial layer of iron oxide on CIP:CR composites was responsible for a reduction and change of microwave absorption towards a higher frequency. The reflectivity curves of CB:CR composites did not display any significant difference before and after the exposure.

The effect of surface properties of EVAL membranes on the inflammatory response

The purpose of this study was to examine the relationship between tissue response and the membrane surface structure. A series of ethylene vinyl alcohol (EVAL) membranes provide an ideal system for a study of the relative contributions to biocompatibility derived from the surface morphology. This is different from other reports using different kinds of polymers, which may thus result in considerable variation since polymer implants are both chemically and physically heterogeneous. This study demonstrated that the tissue response to three different membrane structures were quite different. Flat and dense EVAL surfaces induced a mild foreign body reaction indicating that EVAL copolymer does not provide a stimulus for a continued inflammatory response. The inflammatory response was strong using a porous surface and a surface with a particulate morphology. In addition, particulate surfaces provoked a more intense inflammatory response than porous surfaces, indicating that a material in particulate form, suitable for phagocytosis, may provoke a different degree of inflammatory response than the same material in a nonphagocytosable form. Therefore, although a material may be considered to be biocompatible, however, its surface properties may alter the observed tissue reaction and inflammatory response. Consequently, the surface properties should be suitably selected according to the purpose for which the material is to be used.

Propellant Losses Because of Particulate Emission in a Pulsed Plasma Thruster

Abstract : Propellant inefficiency material in particulate form is characterized in a laboratory pulsed plasma thruster (PPT) operating at 1 Hz with a 204 discharge energy (20 W). Exhaust deposits are collected and analyzed using a combination of a scanning electron microscope with energy dispersive x-ray analysis and microscopic imaging. Teflon(trademark) particulates are observed with characteristic dianietens ranging from over 100 micrometers down to less than 1 micrometer.

Cellular immune responses to orthopaedic implant materials following cemented total joint replacement.

In vitro cellular immune responses to metallic and polymeric implant materials in particulate form were measured preoperatively in 185 patients. The patients were candidates for either primary total joint replacement (n = 65) or revision arthroplasty (n = 120). Proliferative cellular responses to polymethylmethacrylate particles in patients with osteoarthritis at revision surgery for aseptic loosening were significantly higher than the responses of patients with osteoarthritis at either primary surgery or surgical revision for mechanical failure of the prosthesis or sepsis. The responses to particles of cobalt-chromium alloy at revision surgery were also higher than the responses at primary surgery. The responses were reevaluated in 32 patients after a minimum of 10 months following surgery to correlate individual changes in the biological responses with clinical progress. Reevaluation at early follow-up of patients who had undergone primary surgery revealed significantly elevated proliferative responses and in vitro cytokine production in response to polymethylmethacrylate and cobalt-chromium alloy particles compared with their preoperative responses. In contrast, the response at follow-up to polymethylmethacrylate was significantly reduced in patients who had undergone revision surgery, and this reduction corresponded with a marked improvement in pain, joint motion, and function following revision surgery. These data suggest that specific cellular responses to polymethylmethacrylate or cobalt-chromium alloy particles, or both, may be associated with loose or painful prostheses.

Enhanced magnetic moment of monocomponent toner particles by surface coating

Because of advantages in machine simplicity and consistent image quality, dry monocomponent toners will play an increasingly important role as consumables for nonimpact electrostatic and magnetic imaging systems. Most currently available monocomponent toners have the ferromagnetic component, generally magnetite, present as uniformly dispersed particles in a matrix of thermoplastic resin. It is shown that, by incorporating the ferromagnetic material as a surface coating, the same magnetic moment can be obtained at given field strength with a reduced proportion of ferromagnetic material. With the ferromagnetic material in particulate form, the enhancement in magnetic moment over the case of a uniform distribution is relatively modest. For example, if magnetite particles are incorporated in a thin, dense outer shell, a toner particle with 40 wt-pct magnetite develops the same magnetic moment for applied fields up to 500 oersteds as a toner particle with 60 wt-pct magnetite uniformly distributed. A higher degree of magnetic moment enhancement requires applying a continuous outer shell of ferromagnetic material.