Some words used across various scientific disciplines. Click on a word to see the definition.
Hydrogen is the most abundant element in the universe, and the third most abundant on Earth (after oxygen and silicon).
Fossils contain isotopes of elements that accumulated in the organisms when they were alive.
In classical physics, the accuracy of measurements has always been limited by the measuring instruments used, and no instrument is perfect.
Even greater specificity is provided by specialized transmembrane proteins which act as active and passive transporters for a huge diversity of molecules.
In rare cases, such long-distance dispersal can lead to adaptive radiation, the rapid evolution of an ancestral species into new species that fill many ecological niches.
But midway between two adjacent nodes, the string vibrates with the largest amplitude.
How advanced were Alhazen’s inventions and theories?
Hydrophobic interactions between sickle-cell hemoglobin proteins lead to their aggregation into a fiber.
When the wire carries a strong current, the alignments of the iron filings show that the magnetic field induced by the current forms concentric circles around the wire.
Some of the alpha particles were deflected from their original direction through very large angles.
Assistive listening devices serve to amplify a specific small range of frequencies for people who have only partial hearing loss in that range.
One useful application of superconductivity is superconducting magnets.
Because a linkage map is based strictly on recombination frequencies, it gives only an approximate picture of a chromosome.
The Very Large Array, located near Socorro, New Mexico, consists of 27 radio antennas, each 25 meters in diameter.
Under some conditions, prokaryotes can increase the availability of nutrients that plants require for growth, such as nitrogen, phosphorus, and potassium.
When a bat is held at its end, its length is greatest with respect to the rotation axis, so its moment of inertia is greatest.
Alpha particles can usually be stopped by a piece of paper, beta particles can penetrate a few millimeters of aluminum, and gamma rays can penetrate several centimeters of lead.
An additional advantage of fusion reactors is that few radioactive by-products are formed.
Filled with confidence that his calculations could be useful in determining chemical structures, Karplus published a paper that included what has become known as the Karplus equation.
During calibration at the crash-test site, engineers calibrate the sensors in the heads of crash-test dummies by removing the heads and dropping them from a known height.
Sweat alone has been used to power a radio for two days, demonstrating the capability of a new skin patch.
But to understand what a chemical catalyst or a biological enzyme actually does, think of it as a helper particle.
In music, the mixture of harmonics that produces the characteristic sound of an instrument is referred to as the spectrum of the sound.
Once a capacitor is charged, the battery or other source of potential difference that charged it can be removed from the circuit.
The structure and biochemical functions of the leaves of C4 plants are an evolutionary adaptation to hot, dry climates.
When two sex cells fuse, the outcome may depend not just on the compatibility of the genes stowed in their nuclei, but on the behaviour of another group of organelles in cells, known as mitochondria.
DNA strands are an attractive option as components of nanoscale structures because of the way they lock or “zip” together when the sequence of bases in a pair of strands complement each other.
A diagram of the basic components of a spectrometer is shown in Figure 18.
The fuel itself was obtained by distilling oil – heating it up to a specific temperature and waiting for the kerosene fraction to boil and condense.
This charge configuration is called an electric dipole.
The mammalian kidney’s ability to conserve water is a key terrestrial adaptation.
Thus, the coil and the shaft are kept in continuous rotational motion.
People who choose alternative medicine over conventional treatment for their cancer are more likely to die from the disease.
Generators use induction to convert mechanical energy into electrical energy.
The measuring stick can serve as the y-axis of our coordinate system.
The graph of decreasing temperature versus time of a hot object is called its cooling curve.
Most animals exhibit cycles in reproductive activity, often related to changing seasons.
These ramp experiments provided data that matched the predictions Galileo made in his hypothesis.
Both 12C and 13C are stable isotopes, meaning that their nuclei do not have a tendency to lose subatomic particles, a process called decay.
When John receives the message, he uses his private key to decode it
Because unlike poles attract, we can deduce that the geographic North Pole of Earth corresponds to the magnetic south pole and the geographic South Pole of Earth corresponds to the magnetic north pole.
For decades, the default approach has been to assume a “stationary” climate — one in which the odds of extremes have remained unchanged.
This highlights the link between environmental degradation and health.
Forestry experts have cautioned that Ghana’s natural forests may run the risk of being depleted in the next 10 to 20 years.
The relationship between the incident pressure and the electric signal is microphone sensitivity, an important parameter in microphone design.
Sites like El Gigante that allow detailed analysis of maize over time, especially stretching back more than 4,000 years, are quite rare.
The system has the capability to detect planet-size bodies on the outer fringes of our solar system.
The next step is to adapt this device to test for and identify environmental contaminants.
In force diagrams, all forces are drawn as if they act at that point, no matter where the force is applied.
Thanks to new spatial models that were used to evaluate the movement of the whales, we could differentiate behaviors and gauge the speed of the whales during their reproductive and migratory periods.
For small insects, diffusion through the tracheae brings in enough O2 and removes enough CO2 to support cellular respiration.
Volunteers also were given directional coordinates within a predetermined segment of the Appalachian Trail and instructed to set up their camera within 100 meters of that location.
Women like Henrietta Swan Leavitt, Williamina Fleming, and Annie Jump Cannon made some of the most important discoveries in astronomy in the early 20th century.
Following initial migration to Australia, Aboriginal groups lived in “discrete geographical regions” until the arrival of Europeans.
A circular eddy in the bay region may prevent its larvae from moving out into the Kuroshio Current and being dispersed northward up to Taiwan.
A major impediment to research has been the lack of accessible and reliable information on spills, wastewater disposal and the composition of fracturing fluids.
The distribution of the intensity of the different wavelengths varies with temperature.
Activated carbon can be spread on the surface of a contaminated sediment or soil, without physical disturbance, and left in place to mix into the sediment surface.
Knowledge of archaeal biological diversity and their role in evolution has rapidly expanded in the past decade.
While climate change may be beneficial in this way to monarchs, there are also potential drawbacks.
Pan-STARRS also has given us an unprecedented view of the dynamic and transient nature of astronomical phenomena.
Airflow through a wheel or wheel well can have an important impact on the overall aerodynamic performance of a car and therefore an important impact on its efficiency and range.
Interpreting the positions and intensities of the peaks on the resulting graph can give insights into the electronic structure of the diamond.
The clues to answer this question lie in our ability to learn from Earth’s deep past—the crucible of our present world—embedded in the fossil record.
Such 3-D reconstructions encode important information for astronomers about how massive stars actually explode.
Current restoration plans also include enhancement of oyster density using hatchery seed and the addition of new hard substrate where needed.
The value of this is that it forces us to think differently about the history of human-environmental interactions in North America.
To calculate this figure, some 30 different mathematical equations are in use based on the known methane outputs of specific livestock types, the type of food they are fed and their numbers.
For an object in equilibrium, the frictional force must point in the direction that results in a net force of zero.
The detailed analysis of the surface characteristics of this area of Mars provides avenues for other study, such as the formation of the planet’s regolith, or the crushed-up soil created through erosion and meteor impacts.
To estimate the energy released in a typical fission process, note that the binding energy per nucleon is about 7.6 MeV for heavy nuclei and about 8.5 MeV for nuclei of intermediate mass.
Such a stage in the evolution of the turtle shell had long been predicted by embryological research on present-day turtles but had never been observed in fossils.
Thomas Young’s 1803 experiment provided crucial evidence for the wave nature of light.
Extracting DNA from Phragmites leaves, the ecologist determined how many distinct clones were in each patch and how closely related they were.
Consumers could potentially download a free smartphone app that would run in the background, monitoring appropriate frequencies and sending the data to a central processing facility.
They examined the feasibility of creating a radio transmitter strong enough for it to be detectable across such immense distances.
The photon theory of light explains features of the photoelectric effect that cannot be understood using classical concepts.
Satellite ground operators use the feedback from a device called a magnetometer, which senses the direction of Earth’s magnetic field, to decide which torque coil to activate.
Why was Galileo unable to conclude that light had a finite speed?
Solid objects are not considered to be fluids because they cannot flow and therefore have a definite shape.
Over the past million years, atmospheric carbon dioxide has been generally low and fluctuated predictably within a window of 200 to 300 ppm.
For a spherical mirror, the focal length is equal to half the radius of curvature of the mirror.
Because white light can be dispersed into its elementary colors, it is reasonable to suppose that elementary colors can be combined to form white light.
Scientific journals can now mandate that authors make their metadata available in a searchable and standardized format, just as they have long done for genetic sequence data.
What fraction of a radioactive sample has decayed after two half-lives have elapsed?
The fossil bone is a fragment from a long bone of a large mammal—most likely either a mammoth or mastodon, or less likely a giant sloth.
Because of friction and other problems, the actual efficiency of a heat engine will be lower than the calculated efficiency.
A star forms when a giant clump of gas pulls together under its own gravity, growing denser and hotter until nuclear fusion ignites.
The potential difference between the terminals of a battery is fixed, so batteries always generate a direct current.
The geometric earthworks of southwestern Amazonia have intrigued researchers, the media and the general public.
The graph shows the electric field strength at different distances from the center of the charged conducting sphere of a Van de Graaff generator.
Let us assume that the mass moves on a frictionless horizontal surface.
Although many different species interbreed in the wild, their hybrid offspring often cannot reproduce successfully.
In an experiment to test a hypothesis, you must change one variable at a time to determine what influences the phenomenon you are observing.
The image produced by a converging lens is real and inverted when the object is outside the focal point and virtual and upright when the object is inside the focal point.
The 27 antennas at the Very Large Array in New Mexico are used together to provide improved resolution for observing distant radio sources.
For example, proportional mortality of the kelp perch (Brachyistius frenatus) rose as its density increased.
If friction is disregarded, the input torque will equal the output torque.
A computer motherboard is a multilayered collection of integrated circuits containing millions of transistors and other circuit elements.
As they pass through one another, the waves interact to form an interference pattern of light and dark bands.
The visible light that our eyes can detect occupies an intermediate range of wavelengths.
The flow of a fluid becomes irregular, or turbulent, above a certain velocity or under conditions that can cause abrupt changes in velocity, such as where there are obstacles or sharp turns in a river.
Indigenous groups have always hunted peccaries, but with the continued advance of agricultural frontiers, cattle ranches, new roads and large-scale development projects throughout the region, this species is now threatened with extinction.
Australian researchers have tested the hypothesis that sea urchins are a biotic factor limiting seaweed distribution.
In particular, is there a linear (straight-line) relationship between brain volume and time?
This localized response produces lesions and protects other parts of an infected leaf.
For example, humans maintain a fairly constant body temperature of about 37°C (98.6°F).
It’s fair for researchers to look at complex hand use among primates and ask if it was a precursor to the manual dexterity that gave rise to modern humans.
The industrial manufacture of methanol and ethanol is big business, with methanol ranking among the top 30 chemicals produced commercially in the US.
The point of mapping the human genome is not just to know how genes interact in general, but to be able to apply that mapping to individuals.
In a ferro-magnetic material, large domains of magnetic dipoles are aligned in the same direction.
One identified a complex sugar between cells—in what’s known as the extracellular matrix—that is nearly five times larger in the naked mole rat than in cancer-prone animals.
The maximum absorbance corresponds to the highest concentration of the coloured product in solution.
To measure the specific heat capacity of a substance, it is necessary to measure mass, temperature change, and energy transferred as heat.
The other principal energy transfer mechanism is electromagnetic radiation.
Micro technology deals with the fabrication of structures in the length scale between 0.1 and 1000 μm and can be considered as an important enabler for micro systems such as miniaturized sensors.
Humpback whales have distinctive tail markings that scientists use to track individuals as they migrate long distances.
Competition with elimination reactions can be minimized if primary halogenoalkanes are used.
Although the physical world is very complex, physicists often use models to explain the most fundamental features of various phenomena.
Levels of nitrites and nitrates in water must be monitored, and levels are controlled by legislation.
Magnets are also used in meters, motors, and loudspeakers.
Although the carbon cycle is a natural means of recycling carbon, man-made CO 2 emissions from the combustion of fossil fuels and as a waste product from the cement industry contribute to global warming.
The average velocity of an object can be positive or negative, depending on the sign of the displacement.
A neutron and a proton have approximately the same mass and, relative to these, the electron has a negligible mass.
The net force is the vector sum of all forces acting on an object.
The property is particularly noticeable for beryllium, which is resistant to reaction with water and acids because of the presence of the protective oxide covering.
This is particularly striking since this is neither a positive result (evidence of learning) nor a null result (no learning) but a negative one.
This kind of estimate is called an order-of-magnitude calculation, which means determining the power of 10 that is closest to the actual numerical value of the quantity.
The distinction between contact forces and field forces is useful when dealing with forces that we observe at the macroscopic level.
The trematodes produce offspring that leave the snails and eventually infect migratory sea birds.
Because the purpose of a simple machine is to change the direction or magnitude of an input force, a useful way of characterizing a simple machine is to compare how large the output force is relative to the input force.
To analyze what other parameters affect the force the bird experiences, the researchers created a simplified model from a 3-D printed cone on a flexible rubber “neck”.
The researchers looked at the principle of niche partitioning, which states that two species in the same niche, or ecological distribution of resources, cannot co-exist.
This protection is called passive immunity because the antibodies in the recipient (in this case, the fetus) are produced by another individual (the mother).
Percy Spencer developed and patented the first microwave oven after noticing that a magnetron was emitting heat-generating microwaves during an experiment with radar in 1945.
The broken filament means that there is a gap in the conducting pathway used to make up the circuit.
Using the periodic table is a quick way of spotting isoelectronic relationships.
The new South Pole Telescope is currently completing its pioneering millimeter-wave survey of a huge swath of sky covering 2,500 square degrees.
The light is brightest when its plane of polarization is parallel to the transmission axis.
Describe the positioning of lenses in compound microscopes and refracting telescopes.
We should avoid building up a large positive or negative charge on any one atom.
A meterstick that includes millimeters, for example, will give a more precise result than a meterstick whose smallest unit of measure is a centimeter.
The results could “drastically change predictions of the fate of coral-reef ecosystems globally over the next 100 years of climate change”.
Hence, there is a probability that the electron will actually be found outside the potential well.
Dark matter in this mass range can be probed by direct detection and by the Large Hadron Collider (LHC).
Although the Downs process is the major manufacturing process for sodium, the Cl2 produced represents a minor contribution to the global supply.
Heat is produced and this raises the temperature and opposes the external change.
Most of our estimates for future carbon dioxide levels and climate do not fully take into consideration the various feedbacks involving forests, so current projections likely underestimate the magnitude of carbon dioxide flux to the atmosphere.
Sound travels well underwater, meaning that noise produced by a reef can propagate several kilometres out to sea.
Experimental observations show that the magnitude of the force of friction is approximately proportional to the magnitude of the normal force that a surface exerts on an object.
By using GC-MS and GC-MS/MS techniques, it is possible to unambiguously identify and quantify a drug.
A vector is a physical quantity that has both direction and magnitude.
Gases, on the other hand, are compressible and can have densities over a wide range of values.
It forms deliquescent, white crystals which rapidly absorb water to give an oily liquid.
For a heat engine, the efficiency is the ratio of work done by the engine to the energy added to the system as heat during one cycle.
The authors also demonstrate how the presence and various refinements of the head-joint complex may help elucidate the evolutionary relationships among the Stomiidae.
The ability of lianas to rapidly invade open areas and young forests may dramatically reduce tropical tree regeneration.
It is relatively easy to lift someone if you are both standing in a swimming pool.
Giving up both freedom and light for safety and a reliable food source, the crab’s ultimate goal is successful reproduction.
A striking example of structural resonance occurred in 1940, when the Tacoma Narrows bridge, in Washington, was set in motion by the wind.
When one end of a conductor is more pointed than the other, excess charge tends to accumulate at the sharper end, resulting in a larger charge per unit area.
We wanted to conduct a robust study by looking at both the historical record and field experiments.
This phenomenon is important but its discussion is beyond the scope of this book.
Or it could be possible that these other species get some benefit from the fruit, and so there wouldn’t be strong selection for this particular mutation.
The ability of a conductor to store energy in the form of electrically separated charges is measured by the capacitance of the conductor.
And a modern description usually includes a DNA sequence generated from the animal’s tissue.
A signal was sent to the orbiter to fire the thrusters a final time in order to push the spacecraft into orbit around the planet.
One way to simplify the concept of motion is to consider only the kinds of motion that take place in one direction.
A field experiment that simulated a similar range of CO2 exposures, but included future CO2 concentrations up to 500 parts per million (ppm) confirmed the herbarium results.
Soon after the dinosaur extinctions 60 million years ago, the ancestors of leaf-cutter ants swapped a hunter-gatherer lifestyle for this bucolic existence on small-scale subsistence farms.
With three structures rising like sails over its span, it is the longest of its type in the world at 1.7 miles (2.7 km).
The high spatial, temporal, and spectral resolution of IRIS was crucial to the discovery.
Sounds in the middle of the spectrum of frequencies can be heard more easily (at lower intensities) than those at lower and higher frequencies.
The official standard kilogram mass is a platinum-iridium cylinder kept in a sealed container at the International Bureau of Weights and Measures at Sèvres, France.
As the applied force increases, the force of static friction also increases; if the applied force decreases, the force of static friction also decreases.
Connections to the external circuit are made by stationary graphite strips, called brushes, that make continuous contact with the slip rings.
The hope is that we can apply our knowledge of how P. blytheae adapted to environmental changes millions of years ago to predict the sustainability of snow leopard populations in existence today.
The normal laboratory synthesis of an oxirane is by the reaction of an alkene with a peracid such as perbenzoic acid.
In fact, every function involving the nervous system is initiated by electrical activity.
The technical information gathered will help in making informed treatment decisions.
Silver recognized that the technologies used to study giant supernova remnants and other X-ray-emitting celestial objects, could also be used to examine cells chemically.
Kaufman tested the hypothesis that the amount of contrast between the coat color of a mouse and the color of its surroundings would affect the rate of nighttime predation by owls.
The theory of fields was developed as a tool to explain how objects could exert force on each other without touching.
If not for the shafts of transient sunlight provided by leaf trembling, the lower leaves would be too shaded to photosynthesize sufficiently.
These bones in turn transmit the vibrations to the inner ear, which contains a snail-shaped tube about 2 cm long called the cochlea.
From the vascular cylinder, the xylem sap is transported long distances by bulk flow to the veins that branch throughout each leaf.
For example, speeds are typically expressed in units of meters per second (m/s).
This new model of the atom is consistent with Heisenberg’s uncertainty principle, which states that we cannot know the electron’s location with complete certainty.
A uniform, or evenly spaced, pattern of dispersion may result from direct interactions between individuals in the population.
When scientists do research, they must communicate the results of their experiments with each other and agree on a system of units for their measurements.
Applied fertilizers make up for the loss of usable nitrogen from agricultural ecosystems.
This does not diminish the utility of Mendelian genetics, however, because the basic principles of segregation and independent assortment apply even to more complex patterns of inheritance.
To be certain he was observing differences due to weight, he kept all other variables the same.
Variations in those features reflected differences in the animals’ diets.
You can verify some of these values by carefully measuring the slope of the curve.
Yet calculating the vertical lifting capacity of a small bird or insect is no simple matter.
Make sure there is plenty of water in the heating vessel, and do not leave the hot plate unattended.
Astronomers have created the first realistic virtual universe using a computer simulation.
What your eyes recognize as “white” light is actually light that can be separated into six elementary colors of the visible spectrum: red, orange, yellow, green, blue, and violet.
The human population may also be limited by the capacity of the environment to absorb its wastes.