sentence-transformers/squad huggingface dataset:
Passage: On the other hand, classical (analog) television transmissions are usually horizontally polarized, because in urban areas buildings can reflect the electromagnetic waves and create ghost images due to multipath propagation. Using horizontal polarization, ghosting is reduced because the amount of reflection of electromagnetic waves in the p polarization (horizontal polarization off the side of a building) is generally less than s (vertical, in this case) polarization. Vertically polarized analog television has nevertheless been used in some rural areas. In digital terrestrial television such reflections are less problematic, due to robustness of binary transmissions and error correction.

Question: What is another name for classical television transmissions?

Question: Buildings can create ghost images because of what?

Question: When is ghosting reduced?

Question: What cause less problems in digital terrestrial television?
Passage: Current circulating in one antenna generally induces a voltage across the feedpoint of nearby antennas or antenna elements. The mathematics presented below are useful in analyzing the electrical behaviour of antenna arrays, where the properties of the individual array elements (such as half wave dipoles) are already known. If those elements were widely separated and driven in a certain amplitude and phase, then each would act independently as that element is known to. However, because of the mutual interaction between their electric and magnetic fields due to proximity, the currents in each element are not simply a function of the applied voltage (according to its driving point impedance), but depend on the currents in the other nearby elements. Note that this now is a near field phenomenon which could not be properly accounted for using the Friis transmission equation for instance.

Question: Where are the indiviual array elements known?

Question: What induces a feedpoint to antennas nearby?

Question: What are the mathmatic useful towards?

Question: What cause mutual interactions between the elements electric and magnetic fields?
Passage: This is a consequence of Lorentz reciprocity. For an antenna element not connected to anything (open circuited) one can write . But for an element which is short circuited, a current is generated across that short but no voltage is allowed, so the corresponding . This is the case, for instance, with the so-called parasitic elements of a Yagi-Uda antenna where the solid rod can be viewed as a dipole antenna shorted across its feedpoint. Parasitic elements are unpowered elements that absorb and reradiate RF energy according to the induced current calculated using such a system of equations.

Question: a antenna element not connected to anything is circuited how?

Question: When is the element not allowed voltage?

Question: What element absorbs and reradiate RF-energy?

Question: What antenna can the solid rod be viewed as a dipole antenna?

Question: Where can this solid rod be viewed?
Passage: The difference in the above factors for the case of θ=0 is the reason that most broadcasting (transmissions intended for the public) uses vertical polarization. For receivers near the ground, horizontally polarized transmissions suffer cancellation. For best reception the receiving antennas for these signals are likewise vertically polarized. In some applications where the receiving antenna must work in any position, as in mobile phones, the base station antennas use mixed polarization, such as linear polarization at an angle (with both vertical and horizontal components) or circular polarization.

Question: What type of programmin relies on vertical polarization?

Question: If you were to position your receiver closer to the ground what might be a negative of this placement?

Question: What is one use that would require an antenna to receive signals in various ways at once?

Question: If you were to develop a signal to be used with mobile phones what would be an effective antenna type?

Question: What would the antenna you are using take advantage of to allow it to work in multiple locations?
Passage: Loop antennas consist of a loop or coil of wire. Loops with circumference of a wavelength or larger act similarly to dipole antennas. However loops small in comparison to a wavelength act differently. They interact with the magnetic field of the radio wave instead of the electric field as other antennas do, and so are relatively insensitive to nearby electrical noise. However they have low radiation resistance, and so are inefficient for transmitting. They are used as receiving antennas at low frequencies, and also as direction finding antennas.

Question: What type of antenna can be formed by a circular segment of wire?

Question: What is a loop antenna compared with to determine its beahvior?

Question: If you needed to place an antenna somewhere with a large amount of interference, which type would be best?

Question: Why would this type be good for receiving but not transmtting?

Question: What else would be an effective application of this antenna type?
Passage: It is a fundamental property of antennas that the electrical characteristics of an antenna described in the next section, such as gain, radiation pattern, impedance, bandwidth, resonant frequency and polarization, are the same whether the antenna is transmitting or receiving. For example, the "receiving pattern" (sensitivity as a function of direction) of an antenna when used for reception is identical to the radiation pattern of the antenna when it is driven and functions as a radiator. This is a consequence of the reciprocity theorem of electromagnetics. Therefore, in discussions of antenna properties no distinction is usually made between receiving and transmitting terminology, and the antenna can be viewed as either transmitting or receiving, whichever is more convenient.

Question: Are essential properties of an antenna changed based on what fungtion they are performing

Question: What proposition explains the equivalency of the recieving pattern of an antenna?

Question: Can the antenna serve more than one fungtion at a time?

Question: What is one electrical trait of an antenna?
Passage: The flowering plants (angiosperms), also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants, with about 350,000 species. Like gymnosperms, angiosperms are seed-producing plants; they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, and the production of fruits that contain the seeds. Etymologically, angiosperm means a plant that produces seeds within an enclosure, in other words, a fruiting plant. The term "angiosperm" comes from the Greek composite word (angeion-, "case" or "casing", and sperma, "seed") meaning "enclosed seeds", after the enclosed condition of the seeds.

Question: What are the most diverse group of land plants?

Question: How many species of flowering plants are there about?

Question: What does an angiosperm produce its seeds within?

Question: What do angiosperms have in common with gymnosperms?

Question: What is the Greek word for "case" or "casing"?
Passage: Fossilized spores suggest that higher plants (embryophytes) have lived on land for at least 475 million years. Early land plants reproduced sexually with flagellated, swimming sperm, like the green algae from which they evolved. An adaptation to terrestrialization was the development of upright meiosporangia for dispersal by spores to new habitats. This feature is lacking in the descendants of their nearest algal relatives, the Charophycean green algae. A later terrestrial adaptation took place with retention of the delicate, avascular sexual stage, the gametophyte, within the tissues of the vascular sporophyte. This occurred by spore germination within sporangia rather than spore release, as in non-seed plants. A current example of how this might have happened can be seen in the precocious spore germination in Selaginella, the spike-moss. The result for the ancestors of angiosperms was enclosing them in a case, the seed. The first seed bearing plants, like the ginkgo, and conifers (such as pines and firs), did not produce flowers. The pollen grains (males) of Ginkgo and cycads produce a pair of flagellated, mobile sperm cells that "swim" down the developing pollen tube to the female and her eggs.

Question: How long have higher plants lived on land?

Question: How did early plants reproduce sexually?

Question: Upright meisporangia allowed what to be dispersed to new habitats?

Question: What are the nearest algal relatives existing today?

Question: What is the common name for Selaginella?
Passage: The apparently sudden appearance of nearly modern flowers in the fossil record initially posed such a problem for the theory of evolution that it was called an "abominable mystery" by Charles Darwin. However, the fossil record has considerably grown since the time of Darwin, and recently discovered angiosperm fossils such as Archaefructus, along with further discoveries of fossil gymnosperms, suggest how angiosperm characteristics may have been acquired in a series of steps. Several groups of extinct gymnosperms, in particular seed ferns, have been proposed as the ancestors of flowering plants, but there is no continuous fossil evidence showing exactly how flowers evolved. Some older fossils, such as the upper Triassic Sanmiguelia, have been suggested. Based on current evidence, some propose that the ancestors of the angiosperms diverged from an unknown group of gymnosperms in the Triassic period (245–202 million years ago). Fossil angiosperm-like pollen from the Middle Triassic (247.2–242.0 Ma) suggests an older date for their origin. A close relationship between angiosperms and gnetophytes, proposed on the basis of morphological evidence, has more recently been disputed on the basis of molecular evidence that suggest gnetophytes are instead more closely related to other gymnosperms.[citation needed]

Question: What did Charles Darwin call the sudden appearance of nearly modern flowers in the fossil record?

Question: What type of fossil is the recently discovered Archaefructus?

Question: What fossil evidence is lacking when it comes to flowers?

Question: From what period does fossilized pollen suggest an older date for angiosperm origin?

Question: What relationship proposed on the basis of morphological evidence has recently been disputed?
Passage: The evolution of seed plants and later angiosperms appears to be the result of two distinct rounds of whole genome duplication events. These occurred at 319 million years ago and 192 million years ago. Another possible whole genome duplication event at 160 million years ago perhaps created the ancestral line that led to all modern flowering plants. That event was studied by sequencing the genome of an ancient flowering plant, Amborella trichopoda, and directly addresses Darwin's "abominable mystery."

Question: How many distinct rounds of genome duplication events are suspected in the evolution of seed plants?

Question: When did the first whole genome duplication event occur?

Question: What type of event perhaps created the line which led to modern flowering plants?

Question: How are duplication events studied?

Question: Who coined the term "abominable mystery"?
Passage: The earliest known macrofossil confidently identified as an angiosperm, Archaefructus liaoningensis, is dated to about 125 million years BP (the Cretaceous period), whereas pollen considered to be of angiosperm origin takes the fossil record back to about 130 million years BP. However, one study has suggested that the early-middle Jurassic plant Schmeissneria, traditionally considered a type of ginkgo, may be the earliest known angiosperm, or at least a close relative. In addition, circumstantial chemical evidence has been found for the existence of angiosperms as early as 250 million years ago. Oleanane, a secondary metabolite produced by many flowering plants, has been found in Permian deposits of that age together with fossils of gigantopterids. Gigantopterids are a group of extinct seed plants that share many morphological traits with flowering plants, although they are not known to have been flowering plants themselves.

Question: When is the earliest known macrofossil identified as an angiosperm dated?

Question: What is the earliest known angiosperm?

Question: What pushes the age of angiosperm 5 million years further back?

Question: How long ago has circumstantial evidence has been found for the existence of angiosperms?

Question: What group of now extinct seed plants had many of the traits of what are now flowering plants?
Passage: The great angiosperm radiation, when a great diversity of angiosperms appears in the fossil record, occurred in the mid-Cretaceous (approximately 100 million years ago). However, a study in 2007 estimated that the division of the five most recent (the genus Ceratophyllum, the family Chloranthaceae, the eudicots, the magnoliids, and the monocots) of the eight main groups occurred around 140 million years ago. By the late Cretaceous, angiosperms appear to have dominated environments formerly occupied by ferns and cycadophytes, but large canopy-forming trees replaced conifers as the dominant trees only close to the end of the Cretaceous 66 million years ago or even later, at the beginning of the Tertiary. The radiation of herbaceous angiosperms occurred much later. Yet, many fossil plants recognizable as belonging to modern families (including beech, oak, maple, and magnolia) had already appeared by the late Cretaceous.

Question: When does a great diversity of angiosperms appear in the fossil record?

Question: What is the appearance of a large amount of angiosperms in the fossil record known as?

Question: When did the division of the eight main groups of angiosperms occur?

Question: What were the angiosperms up to by the late Cretaceous?

Question: Beech and maple had already appeared by what period?
Passage: Island genetics provides one proposed explanation for the sudden, fully developed appearance of flowering plants. Island genetics is believed to be a common source of speciation in general, especially when it comes to radical adaptations that seem to have required inferior transitional forms. Flowering plants may have evolved in an isolated setting like an island or island chain, where the plants bearing them were able to develop a highly specialized relationship with some specific animal (a wasp, for example). Such a relationship, with a hypothetical wasp carrying pollen from one plant to another much the way fig wasps do today, could result in the development of a high degree of specialization in both the plant(s) and their partners. Note that the wasp example is not incidental; bees, which, it is postulated, evolved specifically due to mutualistic plant relationships, are descended from wasps.

Question: What is one proposed explanation for the instant appearance of flowering plants?

Question: What is island genetics thought to be a default source of?

Question: What did radical adaptations seem to have required?

Question: How did an isolated setting like an island help flowering plants evolve?

Question: What are bees descended from?
Passage: Animals are also involved in the distribution of seeds. Fruit, which is formed by the enlargement of flower parts, is frequently a seed-dispersal tool that attracts animals to eat or otherwise disturb it, incidentally scattering the seeds it contains (see frugivory). Although many such mutualistic relationships remain too fragile to survive competition and to spread widely, flowering proved to be an unusually effective means of reproduction, spreading (whatever its origin) to become the dominant form of land plant life.

Question: What are animals also a part of?

Question: What did the enlargement of flower parts evolve to form?

Question: What does a plant get out of forming fruit?

Question: What are many mutualistic relationships, thus failing to survive competition?

Question: What turned out to be unusually effective for plants to reproduce?
Passage: Flower ontogeny uses a combination of genes normally responsible for forming new shoots. The most primitive flowers probably had a variable number of flower parts, often separate from (but in contact with) each other. The flowers tended to grow in a spiral pattern, to be bisexual (in plants, this means both male and female parts on the same flower), and to be dominated by the ovary (female part). As flowers evolved, some variations developed parts fused together, with a much more specific number and design, and with either specific sexes per flower or plant or at least "ovary-inferior".

Question: What uses a combination of genes to form new shoots?

Question: What were plant parts like in their primitive days?

Question: How did flowers become bixsexual?

Question: What did some plant parts do as they evolved?

Question: What is a term for a plant with a specific sex per flower?
Passage: Flower evolution continues to the present day; modern flowers have been so profoundly influenced by humans that some of them cannot be pollinated in nature. Many modern domesticated flower species were formerly simple weeds, which sprouted only when the ground was disturbed. Some of them tended to grow with human crops, perhaps already having symbiotic companion plant relationships with them, and the prettiest did not get plucked because of their beauty, developing a dependence upon and special adaptation to human affection.

Question: How long has flower evolution occurred?

Question: What heritage do many modern domesticated flower species have?

Question: Humans have effected some flowers so much they can no longer do what in nature?

Question: Why did weeds grow with human crops?

Question: What feature helped flowers not get plucked?
Passage: The exact relationship between these eight groups is not yet clear, although there is agreement that the first three groups to diverge from the ancestral angiosperm were Amborellales, Nymphaeales, and Austrobaileyales. The term basal angiosperms refers to these three groups. Among the rest, the relationship between the three broadest of these groups (magnoliids, monocots, and eudicots) remains unclear. Some analyses make the magnoliids the first to diverge, others the monocots. Ceratophyllum seems to group with the eudicots rather than with the monocots.

Question: What three groups were the first to diverge from angiosperm?

Question: What term refers to the first three groups to diverge from angiosperm?

Question: How clear is the relationship between the broadest of the three non-basal angiosperm groups?

Question: What group do some analyses seem to indicate diverged first?
Passage: The botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon (bottle, vessel) and σπέρμα, (seed), was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked. The term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any approach to its modern scope became possible only after 1827, when Robert Brown established the existence of truly naked ovules in the Cycadeae and Coniferae, and applied to them the name Gymnosperms.[citation needed] From that time onward, as long as these Gymnosperms were, as was usual, reckoned as dicotyledonous flowering plants, the term Angiosperm was used antithetically by botanical writers, with varying scope, as a group-name for other dicotyledonous plants.

Question: What term did Paul Hermann come up with in 1690?

Question: What did Hermann use the term angiosperm a primary division of in the plant kingdom?

Question: Who restricted the application of the angiosperm term?

Question: What did Robert Brown establish the existence of in Cycadeae and Coniferae?

Question: What is the group-name angiosperm has been used for by botanical writers?
Passage: In most taxonomies, the flowering plants are treated as a coherent group. The most popular descriptive name has been Angiospermae (Angiosperms), with Anthophyta ("flowering plants") a second choice. These names are not linked to any rank. The Wettstein system and the Engler system use the name Angiospermae, at the assigned rank of subdivision. The Reveal system treated flowering plants as subdivision Magnoliophytina (Frohne & U. Jensen ex Reveal, Phytologia 79: 70 1996), but later split it to Magnoliopsida, Liliopsida, and Rosopsida. The Takhtajan system and Cronquist system treat this group at the rank of division, leading to the name Magnoliophyta (from the family name Magnoliaceae). The Dahlgren system and Thorne system (1992) treat this group at the rank of class, leading to the name Magnoliopsida. The APG system of 1998, and the later 2003 and 2009 revisions, treat the flowering plants as a clade called angiosperms without a formal botanical name. However, a formal classification was published alongside the 2009 revision in which the flowering plants form the Subclass Magnoliidae.

Question: In taxonomies, what type of group are flowering plants treated?

Question: What does anthophyta mean?

Question: What do the Wettstein and Engler systems use at the assigned rank of subdivision?

Question: How does the APG system of 1998, with its 2003 and 2009 revisions, treat flowering plants?

Question: What formal subclass classification were flowering plants given in 2009?
Passage: The internal classification of this group has undergone considerable revision. The Cronquist system, proposed by Arthur Cronquist in 1968 and published in its full form in 1981, is still widely used but is no longer believed to accurately reflect phylogeny. A consensus about how the flowering plants should be arranged has recently begun to emerge through the work of the Angiosperm Phylogeny Group (APG), which published an influential reclassification of the angiosperms in 1998. Updates incorporating more recent research were published as APG II in 2003 and as APG III in 2009.

Question: What consensus is the AGP trying to reach?

Question: What internal component has undergone considerable revision?

Question: What system did Arthur Cronquist put forth in 1968, but not publish in full form until 1981?

Question: Who published an influential reclassification of the angiosperms in 1998?
Passage: Recent studies, as by the APG, show that the monocots form a monophyletic group (clade) but that the dicots do not (they are paraphyletic). Nevertheless, the majority of dicot species do form a monophyletic group, called the eudicots or tricolpates. Of the remaining dicot species, most belong to a third major clade known as the magnoliids, containing about 9,000 species. The rest include a paraphyletic grouping of primitive species known collectively as the basal angiosperms, plus the families Ceratophyllaceae and Chloranthaceae.

Question: What type of groups do monocots form, based on a recent APG studies?

Question: Eudicots or tricolpates are part of a monophyletic group formed by what species?

Question: What third major clade can many dicot species be found in?

Question: How many species dicot species are magnoliids?

Question: Basal angiosperms are what type of grouping of primitive species?