Observing viral morphology is essential in virology, for which transmission electron microscopy (TEM) is the most widely used technique because it allows direct visualization at the nanometer scale. Currently, advanced TEM techniques such as cryogenic TEM and electron tomography are being rapidly developed for constructing precise three-dimensional images of viruses and small proteins1,2,3,4,5, which require expensive TEM equipment and advanced expertise. Thus, methods for simple, rapid, and clear observations using traditional TEM are needed worldwide.
Pta Observation Essay Examplesl
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Generally, negative staining methods using heavy metals are required for traditional TEM observations6,7,8,9; the procedure is illustrated in Fig. 1. Initially, virions are adsorbed on a carbon support film (Fig. 1a). A small drop of staining reagent containing heavy metals is dropped onto the film (Fig. 1b). After removing excess solution, the sample is dried, leading to coating of the virions by heavy metals (Fig. 1c). Finally, reverse-contrast images are generated via enhanced electron scattering from the heavy elements coating the virions (Fig. 1d,e).
Without using staining reagents, it is difficult to obtain sufficient contrast between the virions and carbon support, resulting in unclear observations of virus morphology because the fragments of virions dispersed on the carbon support film are smaller than the thickness of the film. Therefore, viruses must be coated with heavy metals that have high electron-scattering constants.
Furthermore, an AFM image obtained from image area C on the TEM grid (Fig. 3g and Supplementary Fig. S5) after TEM observation revealed head and tails. The observed length (230 and 225 nm) of the T4 body (head and tail together) was close to that expected for a T4 phage (Fig. 3a). However, the observed height of the head (47 nm) (Supplementary Fig. S5) was less than its thickness (78 nm in Fig. 3a), indicating that the head shrank under TEM vacuum conditions.
Negative staining has been widely used to observe the morphologies of viruses6, other biological particles, lipid vesicles, micelles, liposomes, and polymer particles30. Our results indicate that Preyssler-type phosphotungstates are good negative staining reagents for virus observations. Furthermore, tungsten forms a variety of metal oxide clusters known as polyoxotungstate in an aqueous solution, depending on the other elements present and pH12. Polyoxotungstates are promising tools for developing negative staining reagents for TEM observations.
This research was supported by A-STEP of the Japan Science and Technology Agency (JST), Furukawa Foundation, Catalysis Research Center of Hokkaido University, Japan Society for the Promotion of Science (JSPS KAKENHI Grant Number 21H02028), Mitsubishi Chemical Corporation, International Network on Polyoxometalate at Hiroshima University, and JSPS Core-to-Core program. We would like to thank Mr. Matsuda at Shimadzu Corporation and Ms. M. Onishi for the AFM observations and drawing the phage images, respectively. We would like to thank Editage (www.editage.com) for English Language editing.
M.S. and T.N. managed this research. K.S., T.S., and M.S. prepared and characterized staining reagents. K.S., K.K., and M.S. performed TEM and SEM observations. Y.K. and T.N. produced and purified all viruses. All authors reviewed this manuscript.
Rethinking Schools produced an award-winning special report in the aftermath of 9/11 called War, Terrorism and Our Classrooms. The contents continue to offer a rich repository of writing prompts and teaching strategies. For example, an essay by the late naturalist Steven Jay Gould explained a theory he called "the Great Asymmetry," in which "every spectacular incident of evil will be balanced by 10,000 acts of kindness, too often unnoted and invisible as the 'ordinary' efforts of a vast majority." Students might respond to his essay by drawing their own version of what Gould called a "web of bustling goodness," or writing stories that document examples of human compassion in their communities.
Clinic observation is strongly recommended fo the NMC Physical Therapist Assistant Program for admission. This is your opportunity to weigh your interest in the field and to learn more about the physical therapy profession. Therapists or assistants within the clinic who are providing you the opportunity for this experience will need to verify your participation in writing by signing an observation form. Twenty hours (20) are recommended to meet the minimum admission criteria. It is YOUR responsibility to arrange this observation. You may fulfill the hours at more than one facility.
Observation is an act or instance of noticing or perceiving[1] and the acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data via the use of scientific instruments. The term may also refer to any data collected during the scientific activity. Observations can be qualitative, that is, only the absence or presence of a property is noted, or quantitative if a numerical value is attached to the observed phenomenon by counting or measuring.
Observations play a role in the second and fifth steps of the scientific method. However, the need for reproducibility requires that observations by different observers can be comparable. Human sense impressions are subjective and qualitative, making them difficult to record or compare. The use of measurement was developed to allow recording and comparison of observations made at different times and places, by different people. The measurement consists of using observation to compare the phenomenon being observed to a standard unit. The standard unit can be an artifact, process, or definition which can be duplicated or shared by all observers. In measurement, the number of standard units which is equal to the observation is counted. Measurement reduces an observation to a number that can be recorded, and two observations which result in the same number are equal within the resolution of the process.
Human senses are limited and subject to errors in perception, such as optical illusions. Scientific instruments were developed to aid human abilities of observation, such as weighing scales, clocks, telescopes, microscopes, thermometers, cameras, and tape recorders, and also translate into perceptible form events that are unobservable by the senses, such as indicator dyes, voltmeters, spectrometers, infrared cameras, oscilloscopes, interferometers, Geiger counters, and radio receivers.
One problem encountered throughout scientific fields is that the observation may affect the process being observed, resulting in a different outcome than if the process was unobserved. This is called the observer effect. For example, it is not normally possible to check the air pressure in an automobile tire without letting out some of the air, thereby changing the pressure. However, in most fields of science, it is possible to reduce the effects of observation to insignificance by using better instruments.
In some specific fields of science, the results of observation differ depending on factors that are not important in everyday observation. These are usually illustrated with apparent "paradoxes" in which an event appears different when observed from two different points of view, seeming to violate "common sense".
The human senses do not function like a video camcorder, impartially recording all observations.[5] Human perception occurs by a complex, unconscious process of abstraction, in which certain details of the incoming sense data are noticed and remembered, and the rest is forgotten. What is kept and what is thrown away depends on an internal model or representation of the world, called by psychologists a schema, that is built up over our entire lives. The data is fitted into this schema. Later when events are remembered, memory gaps may even be filled by "plausible" data the mind makes up to fit the model; this is called reconstructive memory. How much attention the various perceived data are given depends on an internal value system, which judges how important it is to the individual. Thus two people can view the same event and come away with entirely different perceptions of it, even disagreeing about simple facts. This is why eyewitness testimony is notoriously unreliable.[citation needed]
Human observations are biased toward confirming the observer's conscious and unconscious expectations and view of the world; we "see what we expect to see".[6] In psychology, this is called confirmation bias.[6] Since the object of scientific research is the discovery of new phenomena, this bias can and has caused new discoveries to be overlooked; one example is the discovery of x-rays. It can also result in erroneous scientific support for widely held cultural myths, on the other hand, as in the scientific racism that supported ideas of racial superiority in the early 20th century.[7] Correct scientific technique emphasizes careful recording of observations, separating experimental observations from the conclusions drawn from them, and techniques such as blind or double blind experiments, to minimize observational bias.
Modern scientific instruments can extensively process "observations" before they are presented to the human senses, and particularly with computerized instruments, there is sometimes a question as to where in the data processing chain "observing" ends and "drawing conclusions" begins. This has recently become an issue with digitally enhanced images published as experimental data in papers in scientific journals. The images are enhanced to bring out features that the researcher wants to emphasize, but this also has the effect of supporting the researcher's conclusions. This is a form of bias that is difficult to quantify. Some scientific journals have begun to set detailed standards for what types of image processing are allowed in research results. Computerized instruments often keep a copy of the "raw data" from sensors before processing, which is the ultimate defense against processing bias, and similarly, scientific standards require preservation of the original unenhanced "raw" versions of images used as research data.[citation needed] 2ff7e9595c
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