(n.) The anterior or superior part of an animal, containing the brain, or chief ganglia of the nervous system, the mouth, and in the higher animals, the chief sensory organs; poll; cephalon.
(n.) The uppermost, foremost, or most important part of an inanimate object; such a part as may be considered to resemble the head of an animal; often, also, the larger, thicker, or heavier part or extremity, in distinction from the smaller or thinner part, or from the point or edge; as, the head of a cane, a nail, a spear, an ax, a mast, a sail, a ship; that which covers and closes the top or the end of a hollow vessel; as, the head of a cask or a steam boiler.
(n.) The place where the head should go; as, the head of a bed, of a grave, etc.; the head of a carriage, that is, the hood which covers the head.
(n.) The most prominent or important member of any organized body; the chief; the leader; as, the head of a college, a school, a church, a state, and the like.
(n.) The place or honor, or of command; the most important or foremost position; the front; as, the head of the table; the head of a column of soldiers.
(n.) Each one among many; an individual; -- often used in a plural sense; as, a thousand head of cattle.
(n.) The seat of the intellect; the brain; the understanding; the mental faculties; as, a good head, that is, a good mind; it never entered his head, it did not occur to him; of his own head, of his own thought or will.
(n.) The source, fountain, spring, or beginning, as of a stream or river; as, the head of the Nile; hence, the altitude of the source, or the height of the surface, as of water, above a given place, as above an orifice at which it issues, and the pressure resulting from the height or from motion; sometimes also, the quantity in reserve; as, a mill or reservoir has a good head of water, or ten feet head; also, that part of a gulf or bay most remote from the outlet or the sea.
(n.) A headland; a promontory; as, Gay Head.
(n.) A separate part, or topic, of a discourse; a theme to be expanded; a subdivision; as, the heads of a sermon.
(n.) Culminating point or crisis; hence, strength; force; height.
(n.) Power; armed force.
(n.) A headdress; a covering of the head; as, a laced head; a head of hair.
(n.) An ear of wheat, barley, or of one of the other small cereals.
(n.) A dense cluster of flowers, as in clover, daisies, thistles; a capitulum.
(n.) A dense, compact mass of leaves, as in a cabbage or a lettuce plant.
(n.) The antlers of a deer.
(n.) A rounded mass of foam which rises on a pot of beer or other effervescing liquor.
(n.) Tiles laid at the eaves of a house.
(a.) Principal; chief; leading; first; as, the head master of a school; the head man of a tribe; a head chorister; a head cook.
(v. t.) To be at the head of; to put one's self at the head of; to lead; to direct; to act as leader to; as, to head an army, an expedition, or a riot.
(v. t.) To form a head to; to fit or furnish with a head; as, to head a nail.
(v. t.) To behead; to decapitate.
(v. t.) To cut off the top of; to lop off; as, to head trees.
(v. t.) To go in front of; to get in the front of, so as to hinder or stop; to oppose; hence, to check or restrain; as, to head a drove of cattle; to head a person; the wind heads a ship.
(v. t.) To set on the head; as, to head a cask.
(v. i.) To originate; to spring; to have its source, as a river.
(v. i.) To go or point in a certain direction; to tend; as, how does the ship head?
(v. i.) To form a head; as, this kind of cabbage heads early.
Example Sentences:
(1) This study was undertaken to determine whether the survival of Hispanic patients with squamous cell carcinoma of the head and neck was different from that of Anglo-American patients.
(2) An association of cyclophosphamide, fluorouracil and methotrexate already employed with success against solid tumours in other sites was used in the treatment of 62 patients with advanced tumours of the head and neck.
(3) Head-injured patients had a low thyroxine (T4), low triiodothyronine (T3), and high reverse T3.
(4) Currently, photodynamic therapy is under FDA-approved clinical investigational trials in the treatment of tumors of the skin, bronchus, esophagus, bladder, head and neck, and of gynecologic and ocular tumors.
(5) A triphasic pattern was evident for the neck moments including a small phase which represented a seating of the headform on the nodding blocks of the uppermost ATD neck segment, and two larger phases of opposite polarity which represented the motion of the head relative to the trunk during the first 350 ms after impact.
(6) Businesses fleeing Brexit will head to New York not EU, warns LSE chief Read more Amid attempts by Frankfurt, Paris and Dublin to catch possible fallout from London, Sir Jon Cunliffe said it was highly unlikely that any EU centre could replicate the services offered by the UK’s financial services industry.
(7) By means of computed tomography (CT) values related to bone density and mass were assessed in the femoral head, neck, trochanter, shaft, and condyles.
(8) A substance with a chromatographic mobility of Rf = 0.8 on TLC plates having an intact phosphorylcholine head group was also formed but has not yet been identified.
(9) Lin Homer's CV Lin Homer left local for national government in 2005, giving up a £170,000 post as chief executive of Birmingham city council after just three years in post, to head the Immigration Service.
(10) The skull films and CT scans of 1383 patients with acute head injury transferred to a regional neurosurgical unit were reviewed.
(11) Both Ken Whisenhunt and Lovie Smith were fired as head coaches after the 2012 season.
(12) Thirteen patients had had a posterior dislocation with an associated fracture of the femoral head located either caudad or cephalad to the fovea centralis (Pipkin Type-I or Type-II injury), one had had a posterior dislocation with associated fractures of the femoral head and neck (Pipkin Type III), two had had a posterior dislocation with associated fractures of the femoral head and the acetabular rim (Pipkin Type IV), and three had had a fracture-dislocation that we could not categorize according to the Pipkin classification.
(13) Eight cases of calcification following anterior dislocation of the head of the radius are described.
(14) Younge, a former head of US cable network the Travel Channel, succeeded Peter Salmon in the role last year.
(15) Martin Wheatley will remain head of the Conduct Business Unit and become the future chief executive of the FCA.
(16) It happens to anyone and everyone and this has been an 11-year battle.” Emergency services were called to the oval about 6.30pm to treat Luke for head injuries, but were unable to revive him.
(17) This study reviewed 148 patients who had received radiation for head and neck cancer.
(18) In this study, a technique is described by which large obturators can be retained with an acrylic resin head plate.
(19) The authors describe a new technique for evaluating traumatic conditions to the elbow: the radial head-capitellum view.
(20) Nick Robins, head of the Climate Change Centre at HSBC, said: "If you think about low-carbon energy only in terms of carbon, then things look tough [in terms of not using coal].
Quadruplex
Definition:
(a.) Fourfold; folded or doubled twice.
Example Sentences:
(1) However, at a 50-fold higher strand concentration, the single-stranded oligomer is gradually converted into the quadruplex.
(2) We propose a model in which duplex or hairpin forms of G-DNA are folding intermediates in the formation of either 1-, 2-, or 4-stranded quadruplex structures.
(3) There has been much recent interest in the self-association of short deoxyguanosine-rich motifs within single-stranded DNAs to generate monovalent cation modulated four-stranded helical segments called G-quadruplexes stabilized by hydrogen-bonded G-tetrad alignments.
(4) Thus the number of T residues surrounding the dG cluster might control the rigidity of the quadruplex structure.
(5) Equilibrium ultracentrifugation studies confirm that these quadruplexes are composed of two strands of d(G3T4G3).
(6) The only precedent known (to us) for a cation-specific stabilization is that seen in the quadruplex structure formed by poly I.
(7) The quadruplex, [d(TTGGGGTT)]4, is resistant to denaturation in 7 M urea, in which the Watson-Crick type d(TTGGGGTT).d(AACCCCAA) duplex dissociates.
(8) We observe well-resolved proton NMR spectra corresponding to a G-quadruplex monomer conformation predominant at 50 mM K cation concentration and a G-quadruplex dimer conformation predominant at 300 mM K cation concentration.
(9) Our results indicate that specific differences in ionic interactions can result in a switch in telomeric DNAs between intramolecular hairpin-like or quadruplex-containing species and intermolecular quadruplex structures, all of which involve G.G base pairing interactions.
(10) The possible biological function of quadruplexes is discussed.
(11) The DNA oligonucleotide d(CGCG3GCG) can form either a Watson-Crick (WC) hairpin or a parallel-stranded quadruplex structure containing six G-quartet base pair assemblies.
(12) We find that these molecules fold to form a symmetrical bimolecular and an intramolecular quadruplex, respectively.
(13) An increase in ionic strength stabilizes the single-stranded structure, so it seems to inhibit the formation of the quadruplex.
(14) Experiments on ethidium bromide binding to the oligonucleotides have shown that the oligomer anti(A-T) exists, at a low ionic strength, as a four stranded complex ("quadruplex") contains two antiparallel helices, d(A).d(T), which have a parallel orientation and are bound to one another owing to the formation of additional hydrogen bonds between nucleic acid bases.
(15) The quadruplex is stable in the presence of 40 mM K+ at micromolar DNA concentration and can be kinetically trapped as a metastable form when prepared at millimolar DNA concentration and then diluted into buffer containing 40 mM Na+.
(16) Cations stabilize the quadruplex in the order K+ greater than Ca2+ greater than Na+ greater than Mg2+ greater than Li+ and K+ greater than Rb+ greater than Cs+, indicating that K+ has an optimum ionic radius for complex formation and that ionic charge affects the extent of ion-induced stabilization.
(17) Comparison with the corresponding CD spectral characteristics suggests that the electrophoretic intensity enhancement of the intermolecular G-quadruplex band is correlated to the intensity enhancement of of the positive CD maximum at 265 nm.
(18) Similar but less dramatic enhancement of the intermolecular quadruplex band is also observed in T4.
(19) Since K+ and NH4+ are known to stabilize a parallel-stranded quadruplex structure of poly[r(I)4], we infer that the multistranded structure is a quadruplex.
(20) UV thermal denaturation curves show a single concentration-dependent transition and provide data for quantitating the thermodynamics of quadruplex formation.