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Specific Gravity: The ratio of the density of a material to the density of some standard material, such as water or air, at a specified temperature.

Aggregates for Concrete and Asphaltic Mixes

JoVE 10419

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA

Concrete and asphalt are by far the most common construction materials used today. Concrete is a composite material consisting of cement, water, air, coarse aggregate, and fine aggregates. Fine aggregates are typically sands and coarse aggregates are natural or crushed rocks. Chemical admixtures to modify certain specific properties are also commonly used (i.e., superplasticizers to make the concrete fluid during casting). Asphaltic mixes consist primarily of asphalts, coarse aggregates, and fine aggregates, in addition to a number of emulsifiers and other additives used to improve viscosity during placement. In both concrete and asphaltic mixes, aggregates make up a very significant portion of the mix volume, as economy requires that the amount of cement and asphalt be minimized. Two types of aggregates are commonly recognized: coarse aggregates, defined as particles larger than about 4.75mm (rocks), and fine aggregates, consisting of smaller particles (sands). Other important characteristics of aggregates are that they be rigid, durable, and chemically inert with respect to the concrete mortar or asphalt. Aggregates are intended to be fillers, but they are not intended to play a key rol

 Structural Engineering

Preparation of Giant Vesicles Encapsulating Microspheres by Centrifugation of a Water-in-oil Emulsion

1Department of Mathematical and Physical Sciences, Faculty of Science, Japan Women's University, 2Department of Bioorganization Research, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 3Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 4Research Center for Complex Systems Biology, The University of Tokyo

JoVE 55282


Efficiency of Liquid-liquid Extraction

JoVE 10426

Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA

Liquid-liquid extraction (LLE) is a separation technique used instead of distillation when either: (a) the relative volatilities of the compounds to be separated are very similar; (b) one or more of the mixture components are temperature sensitive even near ambient conditions; (c) the distillation would require a very low pressure or a very high distillate/feed ratio.1The driving force for mass transfer is the difference in solubility of one material (the solute) in two other immiscible or partially miscible streams (the feed and the solvent). The feed and solvent streams are mixed and then separated, allowing the solute to transfer from the feed to the solvent. Normally, this process is repeated in successive stages using counter-current flow. The solute-rich solvent is called the extract as it leaves, and the solute-depleted feed is the raffinate. When there is a reasonable density difference between the feed and solvent streams, extraction can be accomplished using a vertical column, although in other cases a series of mixing and settling tanks may be used.

Diagnosis of Ecto- and Endoparasites in Laboratory Rats and Mice

1Research Animal Diagnostic Services, Charles River, 2Research Models and Services, Charles River, 3Department of Comparative Medicine, University of Washington

JoVE 2767

 Immunology and Infection

Tests on Fresh Concrete

JoVE 10420

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA

Concrete is one of the most common construction materials and consists of two phases: the mortar phase, comprised of concrete, water and air, and the aggregate phase, comprised of coarse and fine aggregates. There are two key considerations when designing a concrete mix. First, the concrete must be workable and easy to cast in the forms in its fresh condition, even when the forms are packed with steel reinforcement. In this condition, it is the rheology of concrete that is important. Second, the mix must produce a hardened concrete of specified strength at 28 days (or similar specified time) that is durable and provides good serviceability. In this laboratory exercise, a method of concrete mixture proportioning, named the trial batch method, will be explored. The concrete produced will be used in conducting typical tests to determine the principal characteristics of fresh concrete, including slump, flowability, air content, and density. The trial batch method is a simple, empirical approach to mixture design. The objectives of this experiment are fourfold: (1) to use the trial batch mix method to determine optimum proportions of aggregates, cement, an

 Structural Engineering

Kinetics of Addition Polymerization to Polydimethylsiloxane

JoVE 10369

Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA

Polymers are molecules consisting of many repeating monomer units that are chemically bonded into long chains. They exhibit a broad range of physical properties, which are affected by their chemical structure, molecular weight and degree of polymerization. The polymer industry manufactures thousands of raw materials used in a broad variety of commercial products.1,2 The goal of this video is to perform an addition polymerization reaction and then evaluate the resulting product to understand how viscosity can be used to determine polymer molecular weight. Additionally, this experiment will investigate how molecular weight can be related to monomer conversion.

 Chemical Engineering

Hydraulic Jumps

JoVE 10405

Source: Alexander S Rattner and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA

When liquid flows along an open channel at high velocity, the flow can become unstable, and slight disturbances can cause the liquid upper surface to transition abruptly to a higher level (Fig. 1a). This sharp increase in the liquid level is called a hydraulic jump. The increase in the liquid level causes a reduction in the average flow velocity. As a result, potentially destructive fluid kinetic energy is dissipated as heat. Hydraulic jumps are purposely engineered into large water works, such as dam spillways, to prevent damage and reduce erosion that could be caused by fast moving streams. Hydraulic jumps also occur naturally in rivers and streams, and can be observed in household conditions, such as the radial outflow of water from a faucet onto a sink (Fig. 1b). In this project, an open-channel flow experimental facility will be constructed. A sluice gate will be installed, which is a vertical gate that can be raised or lowered to control the discharge rate of water from an upstream reservoir to a downstream spillway. The flow rate required to produce hydraulic jumps at the gate outlet will be measured. These findings will b

 Mechanical Engineering

Rapid and Low-cost Prototyping of Medical Devices Using 3D Printed Molds for Liquid Injection Molding

1Department of Bioengineering & Therapeutic Sciences, University of California, San Francisco, 2Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, San Francisco, 3Keck School of Medicine, University of Southern California

JoVE 51745


Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

1Institute for Critical Technology and Applied Science, Virginia Tech, 2Macromolecules and Interfaces Institute, Virginia Tech, 3Institute for Food Safety and Health, Illinois Institute of Technology- Moffett Campus, 4Wood, Cellulose, and Paper Research Department, University of Guadalajara, 5Department of Sustainable Biomaterials, Virginia Tech, 6Sustainable Nanotechnology Interdisciplinary Graduate Education Program, Virginia Tech

JoVE 51257


Use of Rabbit Eyes in Pharmacokinetic Studies of Intraocular Drugs

1Department of Ophthalmology, Seoul National University Bundang Hospital, 2Department of Ophthalmology, College of Medicine, Seoul National University, 3Department of Ophthalmology, Hanyang University Hospital, 4Department of Ophthalmology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, 5Department of Clinical Pharmacology, Seoul National University Hospital, 6Department of Clinical Pharmacology, Seoul National University Bundang Hospital

JoVE 53878


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