All articles starting with P
28,818 articles
Periodic coupled cluster CCSD(T) for solids
Periodic coupled cluster CCSD(T) for solids extends the coupled cluster method with singles, doubles, and perturbative triples, molecular chemistry's "gold standard," to bulk crystals, molecular crystals, and adsorption on surfaces.
Periodic fever-immunodeficiency-thrombocytopenia syndrome
Periodic fever-immunodeficiency-thrombocytopenia syndrome (PFITS), also called lazy leukocyte syndrome, is an autosomal recessive WDR1-related autoinflammatory immunodeficiency with recurrent infections, neutropenia, and thrombocytopenia.
Periodic function
A periodic function, also called a periodic signal or periodic wave, repeats its values at regular intervals, like sine and cosine, which repeat every 2π radians.
Periodic law
The periodic law is the rule of chemistry that the properties of the elements recur periodically when ordered by atomic number, as the modern periodic table shows.
Periodic limb movement disorder
Periodic limb movement disorder (PLMD): a diagnosis-of-exclusion sleep disorder with PLMI >15/h (adults), NREM-clustered leg movements, distinguished from RLS; 2024 AASM favors alpha-2-delta ligands over dopamine agonists.
Periodic potential
A periodic potential is a potential energy function repeating at fixed spatial intervals, the standard quantum-mechanical model of an electron in a crystal, leading to energy bands and band gaps.
Periodic table
The periodic table is a tabular arrangement of the chemical elements in order of increasing atomic number, first published by Dmitri Mendeleev in 1869 to predict undiscovered elements.
Periodic trends
Periodic trends, also known as chemical periodicity, are the regular patterns in atomic size, ionization energy, electron affinity, and electronegativity across the rows and columns of the periodic table.
Periodical cicadas
Periodical cicadas (Magicicada) are North American insects with 13- or 17-year underground nymph stages, synchronized brood emergences, predator satiation, seven species, and the 2024 Brood XIX/XIII co-emergence.
Periodically poled lithium niobate
Periodically poled lithium niobate (PPLN) is lithium niobate with periodically inverted ferroelectric domains, enabling efficient quasi-phase-matched frequency conversion via electric-field poling since the early 1990s.
Periodisation of the Indus Valley Civilisation
The periodisation of the Indus Valley Civilisation is the scholarly chronology dividing the Harappan civilization into Early, Mature, and Late phases, spanning roughly 3500–1300 BC.
Periodization
Periodization is the division of history into named periods such as ancient, medieval, and modern, a scheme first used by Georg Hornius (1666) and spread by Cellarius (1696), and criticized as Eurocentric and artificial.
Periodogram
The periodogram is a nonparametric estimator of a signal's power spectral density, computed from the squared magnitude of its Fourier transform; Arthur Schuster introduced it in 1898.
Periodontal abscess
Periodontal abscess: acute localized pus in the gingival wall of a periodontal pocket, mainly gram-negative anaerobic flora (Porphyromonas gingivalis 50-100%), treated by drainage and debridement rather than antibiotics.
Periodontal debridement
Periodontal debridement is a nonsurgical dental procedure that removes plaque and calculus from tooth root surfaces and periodontal pockets without deliberately removing cementum, replacing classical scaling and root planing.
Periodontal disease
Periodontal (gum) disease, including gingivitis and periodontitis, is inflammation and infection of gum and bone tissues supporting teeth, caused by plaque biofilm; over 1 billion severe cases worldwide, smoking the leading risk factor.
Periodontal disease in animals
Periodontal disease in animals is plaque-driven inflammation and destruction of the tissues anchoring the teeth, affecting up to 80% of dogs and 70% of cats by age 2.
Periodontal Dressings
Periodontal dressings (periodontal packs) are protective materials applied over periodontal surgical wounds. Types include zinc oxide eugenol, noneugenol (Coe-Pak, Peripac), and collagen or cyanoacrylate dressings; routine use after flap surgery is no longer indicated.
Periodontal Ehlers-Danlos syndrome
Periodontal Ehlers-Danlos syndrome (pEDS, formerly EDS type VIII) is an ultra-rare autosomal dominant connective tissue disorder caused by gain-of-function variants in C1R or C1S, causing severe childhood periodontitis, lack of attached gingiva, pretibial plaques, and premature tooth loss.
Periodontal index
A periodontal index is a standardized clinical scoring method grading periodontal disease severity, notably Russell's Periodontal Index of 1956 and the WHO's Community Periodontal Index of Treatment Needs.
Periodontal probing
Periodontal probing is a dental diagnostic method in which a calibrated, millimeter-marked probe measures probing depth at six sites per tooth, usually with bleeding on probing recorded.
Periodontal Prosthesis
Periodontal prosthesis: restorative or replacement dental devices used as adjunctive therapy for periodontal disease (MeSH D010515, 1966). Covers fixed, removable, implant-supported splinting and reconstruction with defined occlusal objectives.
Periodontal Splints
Periodontal splints join mobile periodontally compromised teeth to stabilize them, improving comfort and function. EFP stage IV guidelines endorse temporary and long-term splinting; survival ranges from about 65% at 5 years to 80% at 10 years, with frequent repairs.
Periodontics
Periodontics (periodontology) is the dental specialty for prevention, diagnosis, and treatment of diseases of tooth-supporting tissues; periodontists train 3 extra years, treat periodontitis with scaling, surgery, and implants.
Periodontosis
Periodontosis (ICD-11 DA0C.2; 歯周症) is rapid alveolar bone loss around multiple permanent teeth in otherwise healthy adolescents; formerly a degenerative-disease label, now grouped with aggressive periodontitis.
Perioperative Care
Perioperative care (MeSH D019990) is coordinated patient care before, during, and immediately after surgery, spanning preoperative, intraoperative, and postoperative phases, guided by programs such as ERAS, NICE NG180, and AORN guidelines.
Perioperative monitoring in veterinary anesthesia
Perioperative monitoring in veterinary anesthesia is the observation of anesthetized animals' cardiovascular, respiratory, and metabolic function, including anesthetic depth and analgesia, guided by the ACVAA 2025 minimum standards.
Perioperative Nursing
Perioperative nursing, also called surgical or operating room nursing, is the nursing specialty caring for surgical patients before, during, and after surgery across preoperative, intraoperative, and postoperative phases, with roles such as scrub nurse, circulating nurse, and RN first assistant.
Perioperative tachyarrhythmia
Perioperative tachyarrhythmia is a rapid heart rhythm, above 100 beats per minute, arising during or after surgery and anesthesia; atrial fibrillation accounts for about 90% of cases.
Perioral dermatitis
Perioral dermatitis, also called periorificial dermatitis (POD), is a chronic acneiform rash around the mouth, nose, or eyes, mainly in women 20–45, strongly linked to topical corticosteroids and treated with zero therapy and tetracyclines.