ABSTRACT
Much of the long controversy concerning the workings of electric batteries revolved around the concept of the contact potential (especially between different types of metals), originated by Alessandro Volta in the late eighteenth century. Although Volta's original theory of batteries has been thoroughly rejected and most discussions in today's electrochemistry hardly ever mention the contact potential, the concept has made repeated comebacks through the years, and has by no means completely disappeared. In this paper, I describe four salient foci of its revivals: dry piles, thermocouples, quadrant electrometers, and vacuum phenomena. I also show how the contact potential has maintained its presence in some cogent modern scientific literature. Why has the death of the Voltaic contact potential been such an untidy affair? I suggest that this is because the concept has displayed significant meaning and utility in various experimental and theoretical contexts, but has never been successfully given a simple, unified account. Considering that situation, I also suggest that it would make sense to preserve and develop it as a multifarious concept.
ABSTRACT
This article describes the theory of the formation of the vacuum phenomenon (VP), the detection of the VP, the different medical causes, the different locations of the presentation of the VP, and the differential diagnoses. In the human body, the cavitation effect is recognized on radiological studies; it is called the VP. The mechanism responsible for the formation of the VP is as follows: if an enclosed tissue space is allowed to expand as a rebound phenomenon after an external impact, the volume within the enclosed space will increase. In the setting of expanding volume, the pressure within the space will decrease. The solubility of the gas in the enclosed space will decrease as the pressure of the space decreases. Decreased solubility allows a gas to leave a solution. Clinically, the pathologies associated with the VP have been reported to mainly include the normal joint motion, degeneration of the intervertebral discs or joints, and trauma. The frequent use of CT for trauma patients and the high spatial resolution of CT images might produce the greatest number of chances to detect the VP in trauma patients. The VP is observed at locations that experience a traumatic impact; thus, an analysis of the VP may be useful for elucidating the mechanism of an injury. When the VP is located in the abdomen, it is important to include perforation of the digestive tract in the differential diagnosis. The presence of the VP in trauma patients does not itself influence the final outcome.
Subject(s)
Gases , Joint Diseases/diagnostic imaging , Tomography, X-Ray Computed , Vacuum , Diagnosis, Differential , HumansABSTRACT
El fenómeno de vacío es una alteración conocida en las articulaciones osteoartríticas. En ocasiones puede verse gas en las bursas adyacentes a las articulaciones debido a la existencia de una comunicación con la articulación. Presentamos un caso de fenómeno de vacío en la bursa iliopsoas en asociación a una cadera osteoartrítica sobre la base de una displasia acetabular en una mujer de 48 años que acudió a nuestra consulta con sospecha inicial de absceso de iliopsoas.
Vacuum phenomena is a well-known alteration in osteoarthritis. It´s possible to see gas in bursas around osteoarthritic joints due to comunication between them. We describe an unusual case of vacuum phenomena arising within an enlarged iliopsoas bursa in association with mildly osteoarthritic and dysplastic hip in a 48-year-old woman who underwent radiologic study in our institution with an initial suspiction of iliopsoas abscess.
