"Nanodentistry": exploring the beauty of miniature

Feynman's early vision in 1959 gave birth to the concept of nanotechnology. He saw it as an unavoidable development in the progress of science and said that there is plenty of room at the bottom. Since then, nanotechnology has been part of mainstream scientific theory with. potential medical and dental applications. Numerous theoretical predictions have been made based on the potential applications of nanotechnology in dentistry, with varying levels of optimism. While a few layers of nanotechnologic capability have become a reality for oral health in the last decade, many of these applications are still in their puerile stage .The most substantial contribution of nanotechnology to dentistry till date, is the more enhanced restoration of tooth structure with nanocomposites. The field of nanotechnology has tremendous potential, which if harnessed efficiently, can bring out significant benefits to the human society such as improved health, better use of natural resources, and reduced environmental pollution. The future holds in store an era of dentistry in which every procedure will be performed using equipments and devices based on nanotechnology. This article reviews the current status and the potential clinical applications of nanotechnology in dentistry

Fluorescence signalling of the transition metal ions: design strategy based on the choice of the fluorophore component

Transition metal ions are notorious for their fluorescence quenching abilities. In this paper, we discuss the design strategies for the development of efficientoff-on fluorescence signalling systems for the transition metal ions. It is shown that even simplefluorophore-spacer-receptor systems can display excellentoff-on fluorescence signalling towards the quenching metal ions when the fluorophore component is chosen judiciously

Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites

Experimental results on the strain hardening and multiple cracking behaviors of polyvinyl alcohol (PVA) fiber reinforced cementitious composites under bending are reported in this paper. Different hybrid combinations of PVA fibers with different lengths and volume fractions are considered to reinforce the mortar matrix. Among different hybrid combinations, the composite containing 2% thicker PVA fibers of 12 mm length and 1% thinner PVA fibers of 6 mm length and the composite containing 2% thicker PVA fibers of 24 mm length and 1% thinner PVA fibers of 6 mm length showed the best performance in terms of highest ultimate load, largest CMOD (crack mouth opening displacement) at peak load and multiple cracking behavior. The effects of four types of light weight sands on the strain hardening and multiple cracking behavior of hybrid fiber composites are also evaluated in this study. It has been observed that the ultimate load and CMOD at peak load for all light weight hybrid fiber composites are almost the same irrespective of volume fractions of light weight sand. The composites containing finer light weight sands exhibited higher ultimate load than those containing coarser light weight sands. It is also observed that the hybrid fiber composite containing normal silica sand exhibited higher ultimate load than the composites with light weight sands

Development of a Lightweight Low-Carbon Footprint Concrete Containing Recycled Waste Materials

Use of any recycled material helps to maintain a greener environment by keeping waste materials out of the landfills. Recycling practices also can decrease the environmental and economical impact of manufacturing the materials from virgin resources, which reduces the overall carbon footprint of industrial materials and processes. This study examined the use of waste materials such as crushed glass, ground tire rubber, and recycled aggregate in concrete. Compressive strength and elastic modulus were the primary parameters of interest. Results demonstrated that ground tire rubber introduced significant amounts of air into the mix and adversely affected the strength. The introduction of a defoamer was able to successfully remove part of the excess air from the mix, but the proportional strength improvements were not noted implying that air left in the defoamed mixture had undesirable characteristics. Freeze-thaw tests were next performed to understand the nature of air in the defoamed mixtures, and results demonstrated that this air is not helpful in resisting freeze-thaw resistance either. Overall, while lightweight, low-carbon footprint concrete materials seem possible from recycled materials, significant further optimization remains possible

A systematic review on materials, design, and manufacturing of swabs

From simple cleaning to metagenomic studies and now the detection of the SARS-2 virus, swabs are absorbent pads with handles that hold significant promise in several applications and properties. Furthermore, the swab is now used for a wide range of medical purposes, such as the collection of bacteria and other pathogens such as influenza and H1N1. Various designs and materials used for the tip have led to a wide range of applications. In this review, we discuss the characteristics of essential tip materials such as rayon, polyester, nylon, and polyurethane in the context of specimen collection from various substrates. Further, this article reviews swab manufacturing techniques, including injection molding and calendar roll pressing, among others. In recent years, advances in additive manufacturing technology have made it possible to produce swabs in a fast and efficient manner. Furthermore, the design for additive manufacturing (DfAM) is given for the production of swabs. We also examine how 3-D printing of bio-resin swabs has revolutionized the manufacturing process, making it autonomous, quicker, more efficient, and environmentally friendly. Additionally, a shortage of medical devices for testing the SARS-2 virus has zealously motivated the medical industry to revolutionize through additive manufacturing of swabs, thus revolutionizing the medical industry. In conclusion, the limitations of the current techniques and future directions for swabs are discussed

Estudio del comportamiento a cortante de vigas de hormigón reforzado con fibras

This study presents a series of tests for characterizing the structural behaviour of fibre reinforced concrete beams subjected to shear loading. The experimental program involves three types of fibres; two steel fibres and a polypropylene fibre. As a reference, plain concrete and conventionally reinforced concrete specimens have also been tested. The ultimate shear capacity of the beams is calculated and these values compared with those predicted by existing formulations. The study confirms that the toughness and shear crack resistance of the material is greatly enhanced by the fibres. However, the incorporation of 1% of fibres yielded lower shear strength than conventionally reinforced beams with the same amount of steel in the form of transversal stirrups. Existing design methods seem sufficiently robust to estimate the maximum shear load, even when using material properties (toughness, tensile strength) extrapolated from code formulae.Este trabajo presenta una serie de ensayos para caracterizar el comportamiento estructural de vigas realizadas con hormigón reforzado con fibras sometidas a cortante. El programa de ensayos incluía tres tipos de fibras, dos de acero y una de polipropileno. Asimismo, se realizó una serie de ensayos con una viga confeccionada con hormigón armado convencional. La resistencia a cortante de las vigas es comparada con los valores que la formulación existente predice. El estudio confirma que la tenacidad y la resistencia a cortante son incrementadas tras la adición de fibras al hormigón. Sin embargo, la incorporación de un 1% en volumen de fibras conduce a valores de resistencia última a cortante inferiores a los obtenidos con vigas de hormigón convencional con la misma cantidad de acero dispuesta en forma de cercos de cortante. Los actuales métodos de cálculo parecen lo suficientemente precisos para evaluar la carga de cortante último, incluso cuando los parámetros mecánicos utilizados en las fórmulas (tenacidad, resistencia a tracción) son deducidos a partir de la formulación propuesta en la normativa

Hybrid fiber reinforcement and crack formation in cementitious composite materials

The use of different types of fibers simultaneously for reinforcing cementitious matrices is motivated by the concept of a multi-scale nature of the crack propagation process. Fibers with different geometrical and mechanical properties are used to bridge cracks of different sizes from the micro- to the macroscale. In this study, the performance of different fiber reinforced cementitious composites is assessed in terms of their tensile stress-crack opening behavior. The results obtained from this investigation allow a direct quantitative comparison of the behavior obtained from the different fiber reinforcement systems. The research described in this paper shows that the multi-scale conception of cracking and the use of hybrid fiber reinforcements do not necessarily result in an improved tensile behavior of the composite. Particular material design requirements may nevertheless justify the use of hybrid fiber reinforcements.Fundação para a Ciência e a Tecnologia (FCT) - SFRH / BD / 36515 / 200

Patterns oF organoPHosPHorous Poisoning attenDing a teacHing HosPital

The objective of this was to study the pattern of patients of organophosphorous (OP) poisoning attending Kathmandu Medical College Teaching Hospital (KMCTH). This is a retrospective study of OP poisoning from hospital records were analyzed meticulously and data extracted. Data col-lected were: patient’s demographics, motive for poisoning, type of OP poison, arrival time, time since ingestion, patient’s vitals, predisposing factors, serum cholinesterase levels, treatment given, duration of hospital stay and mortality. A total of 47 patients of OP poisoning attended KMCTH from Aug 2003 to July 2005. 22(46.8%) cases were male and 25(53.2%) were female. The maximum number of patients were between the age of 20-40 (33-70.2%). Married patients outnumbered the unmarried (35/74.5% vs 12/25.5%). The most common motive for poisoning was suicidal, 41 cases (87.2%). Metacid (methyl-parathion) was the most commonly used OP compounds in 32 (68%) patients. Interpersonal marital relationship seemed to be the commonest predisposing factor, 23 cases (48.9%).The commonest time of presentation was between 6 pm-12 midnight. 7(57.4%) cases presented within 2 hours of ingestion of the poison. Serum cholinesterase level measured after full atropinisation was >50% of normal level in 17 cases (36.2%). 10 cases (21.3%) required respiratory support. Intermediate syndrome (IMS) was observed in 3 cases. Overall mortality occurred in 3 cases (6.4%). This study highlights the problem of OP poisoning in our region. Establishment of strict policies against the sale and availability of insecticides and pesticides which are freely avail-able in the market is an effective way to control OP poisoning. Key Words: Organophosphate poisoning (OPP), OP compounds, insecticides, pesticides

Effect of the displacement rate and inclination angle in steel fiber pullout tests

This paper summarizes the results obtained in an experimental campaign on the effect of the displacement pullout rate and the inclination angle of the steel fiber pullout tests. For that purpose, specimens were obtained from a self-compacting concrete with a compressive strength of 86 MPa. In the experimental program, hooked-end steel fibers of 0.75 mm diameter and 60 mm length were used. Tests were executed with both hooked-end fibers, and smooth fibers obtained from the former by cutting the hooked end. For both type of fibers, their embedment length into concrete was 20 mm, and the influence of fiber inclination angle toward the load direction was investigated by adopting values of 0∘, 30∘ and 60∘. The tests were performed at displacement rates of 0.01, 0.1 and 1 mm/s. The results have shown that the peak pullout load increased with the inclination angle, in particular for the smooth series. Furthermore, higher displacement rates led to a higher energy absorption capacity for the pullout of the smooth fibers, while the energy absorption remained almost stable for hooked-end fibers.project BIA2015-68678-C2-1-R. M. Tarifa appreciates the financial support from the Department of Applied Mechanics and Project Engineering, UCLM (2018), and from the Programa propio de I+D+i de la Universidad Politécnica de Madrid para realizar estancias de investigación internacional igual o superior a un mes (2019), to do two stays at the University of Minho, Guimarães, Portugal. E. Poveda acknowledges the funding from the International Campus of Excellence CYTEMA and the University of Castilla-La Mancha, throughout Ayudas para estancias en universidades y centros de investigación en el extranjero en 2019 en el ámbito del plan propio de investigación susceptibles de cofinanciación por el Fondo Europeo de Desarrollo Regional (FEDER), Programa 010100021 to fund her stays in the University of Minho during 2018 and 2019, respectively. The authors thank the support of the Department of Civil Engineering and the Laboratory of the Structural Division (LEST), University of Minh