4,404 research outputs found
Vaccine Myths: Setting the Record Straight
Despite their standing as one of the most remarkable public health achievements, vaccines have been surrounded by dangerous myths since the development of the smallpox vaccine in the 18th century. In recent decades, with the publication of a fraudulent article linking vaccines to autism, the involvement of celebrities in the debate, and the rise of the internet and social media as sources for information for patients, these myths have become more widespread. This paper reviews four common vaccine myths: vaccines cause autism, vaccines are not safe, too many vaccines are given too soon, and the influenza vaccine is not necessary. For each of these myths, we review the origin and spread of misinformation. The authors then present the scientific evidence against each myth. Extensive research has found no link between vaccines, and particularly the MMR vaccine or the preservative thimerosal, and autism. The U.S. and world health agencies have effective mechanisms in place to review and monitor vaccine safety. These systems have worked to detect and evaluate even rare vaccine adverse events. The recommended vaccine schedule is safe for infants’ immune systems. The flu vaccine is an essential tool in the fight against the seasonal influenza deaths.
A consequence of these myths is that parents are choosing to delay or refuse recommended vaccines for themselves and their children. This has resulted in outbreaks of measles, pertussis, H. influenza type b, varicella, and pneumococcal disease in the United States. Unvaccinated and undervaccinated children risk contracting the disease themselves, and pose a risk to their community as herd immunity decreases. It is important to explore and refute the myths leading to decreased vaccination rates, so health care providers and parents can make educated decisions to protect children and ensure public health
A diluvial land:Earth histories in the early modern Low Countries, 1550-1830
In the seventeenth and eighteenth centuries, scholars and naturalists reimagined the history of the earth—crafting new chronologies, amassing new evidence, and resituating humans within the history of nature. This dissertation looks to the early modern Low Countries to argue that new ideas about Earth’s past drew on two principal sources: the material evidence of the landscape and the textual evidence of the Bible and other ancient cosmologies. Before 1600, commentators in Flanders and Holland looked to the Rhine delta and the North Sea to explain the formation of these lowlands. By the mid-seventeenth century however, the coastal plain was increasingly envisioned as a diluvial land, shaped by Noah’s flood and other deluges. By the late eighteenth century, the story had changed again, as fossils became the key markers of epochs in earth history. In six chapters, this dissertation charts the rise and gradual decline of the biblical narrative between 1600 and 1800. It explores the interplay between scholarly debate and local conceptions of the landscape, delving into hydrological, antiquarian, and natural historical discourses about the geography of the Northern and the Southern Netherlands.This dissertation ties transnational debates about biblical interpretation and natural philosophy to more local histories, situated in the particular environments of the Low Countries. It thus shows how even the most global of all learned debates—about the formation of the earth—was rooted in local circumstances
Fatigue of intermittently stimulated quadriceps during imposed cyclical lower leg movements
During prolonged experiments the influence of knee angular velocity, and stimulation parameters (interpulse interval (IPI), duty cycle (DC), number of pulses per cycle (NP)) on fatigue-induced torque\ud
decline of paralyzed human quadriceps was studied. Identification of torque-angle and -angular velocity was also performed. The overall loss of maximum torque (MT) and torque-time integral ('lTI) per cycle during sustained intermittent stimulation during isokinetic movement had a typical exponential decay reaching asymptotic values. Larger knee velocities resulted in a significantly faster and relative larger decay of MT and TTI. The rate and relative magnitude of fatigue during concentric contractions are in direct relation\ud
to NP. The results may be valuable in the design of optimal control systems for FES which pursue minimization of muscle fatigue
Repulsive force support system feasibility study
A new concept in magnetic levitation and control is introduced for levitation above a plane. A set of five vertical solenoid magnets mounted flush below the plane supports and controls the model in five degrees of freedom. The compact system of levitation coils is contained in a space 2.4 m (96 in) diameter by 1 m (40 in) deep with the top of the levitation system 0.9 m (36 in) below the center line of the suspended model. The levitated model has a permanent magnet core held in position by the five parallel superconductive solenoids symmetrically located in a circle. The control and positioning system continuously corrects for model position in five dimensions using computer current pulses superimposed on the levitation coil base currents. The conceptual designs include: superconductive and Nd-Fe-B permanent magnet model cores and levitation solenoids of either superconductive, cryoresistive, or room temperature windings
Recent advances in the formation of phase inversion membranes made from amorphous or semi-crystalline polymers
Structural characteristics in membranes formed by diffusion induced phase separation processes are discussed. Established theories on membrane formation from ternary systems can be extended to describe the effects of high or low molecular weight additives. A mechanism for the formation of nodular structures in the top layer of ultrafiltration membranes is presented. In the last part structures arising from polymer crystallization during immersion precipitation are discussed
Magnetic suspension and balance system advanced study
An improved compact design for a superconducting magnetic suspension and balance system for an 8 ft. x 8 ft. transonic wind tunnel is developed. The original design of an MSBS in NASA Cr-3802 utilized 14 external superconductive coils and a superconductive solenoid in the airplane test model suspended in a wind tunnel. The improvements are in the following areas: test model solenoid options, dynamic force limits on the model, magnet cooling options, structure and cryogenic designs, power supply specifications, and cost and performance evaluations. The improvements are: MSBS cost reduction of 28%, weight; reduction of 43%, magnet system ampere-meter reduction of 38%, helium liquifier capacity reduction by 33%, magnet system stored energy reduction by 55%, AC loss to liquid helium reduced by 76%, system power supply reduced by 68%, test coil pole strength increased by 19%, wing magnetization increased by 40%, and control frequency limit increased by 200% from 10 Hz to 30 Hz. The improvements are due to: magnetic holmium coil forms in the test model, better rare earth permanent magnets in the wings, fiberglass-epoxy structure replacing stainless steel, better coil configuration, and new saddle roll coil design
Magnetic suspension and balance system study
A compact design for a superconducting magnetic suspension and balance system is developed for a 8 ft. x 8 ft. transonic wind tunnel. The main features of the design are: a compact superconducting solenoid in the suspended airplane model; permanent magnet wings; one common liquid helium dewar for all superconducting coils; efficient new race track coils for roll torques; use of established 11 kA cryostable AC conductor; acceptable AC losses during 10 Hz control even with all steel structure; and a 560 liter/hour helium liquefier. Considerable design simplicity, reduced magnet weights, and reduced heat leak results from using one common dewar which eliminates most heavy steel structure between coils and the suspended model. Operational availability is thought to approach 100% for such magnet systems. The weight and cost of the magnet system is approximately one-third that of previous less compact designs
Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification
Although many aspects of microchannel emulsification have been covered in literature, one major uncharted area is the effect of viscosity of both phases on droplet size in the stable droplet generation regime. It is expected that for droplet formation to take place, the inflow of the continuous phase should be sufficiently fast compared to the outflow of the liquid that is forming the droplet. The ratio of the viscosities was therefore varied by using a range of continuous and dispersed phases, both experimentally and computationally. At high viscosity ratio (eta (d)/eta (c)), the droplet size is constant; the inflow of the continuous phase is fast compared to the outflow of the dispersed phase. At lower ratios, the droplet diameter increases, until a viscosity ratio is reached at which droplet formation is no longer possible (the minimal ratio). This was confirmed and elucidated through CFD simulations. The limiting value is shown to be a function of the microchannel design, and this should be adapted to the viscosity of the two fluids that need to be emulsified
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