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D1

, commonly abbreviated as D1, is the highest competitive level of intercollegiate athletics governed by the (NCAA) in the United States, featuring over 350 member institutions that sponsor programs in up to 24 sports for men and women. These institutions, which include many of the nation's largest public and private universities, emphasize high-profile competition, substantial athletic budgets, and opportunities for full scholarships, distinguishing D1 from the NCAA's lower divisions by allowing professional draft eligibility and revenue-generating events like bowl games and March Madness. Division I is uniquely subdivided for into the Football Bowl Subdivision (FBS), with about 130 schools eligible for postseason bowls and higher financial aid limits, and the Football Championship Subdivision (FCS), comprising around 130 others that compete in a playoff system. Over 200,000 student-athletes participate annually, benefiting from academic support services amid rigorous schedules, with recent data showing a 91% graduation success rate for entering cohorts. D1 programs serve as primary pipelines to , particularly in , , and , where standout performers often transition directly to leagues like the or NBA, though this pathway involves intense scrutiny over athlete compensation, transfer rules, and name, image, and likeness (NIL) rights, which have reshaped recruiting and eligibility since 2021. Defining characteristics include mandatory sponsorship of at least 14 sports (seven for each gender, with team sports required), extensive coverage, and multimillion-dollar facilities, fostering a commercialized environment that generates billions in revenue but also draws criticism for prioritizing athletics over academics in some cases.

Sports

Collegiate athletics

(D1) represents the highest level of intercollegiate athletics competition sanctioned by the (), encompassing over 350 member institutions as of 2025 that sponsor at least 14 sports each and provide athletic scholarships to more than 190,000 student-athletes annually. These programs emphasize competitive excellence, with participation in 24 sports for men and 26 for women, including , , and emerging like . Membership requires adherence to NCAA bylaws on financial aid, academic progress rates, and squad size minimums, distinguishing D1 from lower divisions by its scale, media exposure, and revenue generation, particularly from and men's . Football sponsorship divides D1 into two primary subdivisions: the Football Bowl Subdivision (FBS), comprising approximately 134 teams with larger budgets, stadium capacities often exceeding 30,000, and up to 85 full scholarships per team; and the Football Championship Subdivision (FCS), with about 130 teams offering up to 63 scholarships (which may be partial) and focusing on playoff rather than bowl games. FBS programs, such as those in the Big Ten or conferences, generate billions in media rights deals, while FCS emphasizes broader participation and postseason tournaments culminating in a 24-team playoff. Non-football D1 schools, numbering around 100, compete in other sports without these distinctions but must meet overall financial and competitive thresholds. Governance has evolved significantly with the 2024 House v. NCAA settlement, effective for the 2025-26 academic year, which ended traditional scholarship caps in favor of roster limits and introduced direct of up to 22% of average athletic department revenues—approximately $20.5-22 million annually per opting-in school—prioritizing and players while allowing distribution to all rostered athletes. This shift, alongside name, image, and likeness (NIL) rights established in 2021, has accelerated conference realignments, such as the PAC-12's contraction to two members by 2024 and subsequent FBS expansions, driven by lucrative TV contracts exceeding $7 billion over seven years for . Eligibility rules now permit unlimited NIL compensation via third-party collectives, though schools opting into must comply with enhanced reporting and roster caps (e.g., 105 for FBS ), aiming to amateurism's with antitrust . Academic and welfare standards include a 930 minimum (APR) for multi-year continuing eligibility and progress-toward-degree requirements, with penalties like postseason bans for noncompliance. Recent structural reforms, such as the Division I Board's 2025 elimination of redundant committees and addition of 40 student-athlete voting seats, reflect efforts to increase athlete input amid revenue-sharing mandates. These changes address lawsuits alleging exploitation, yet critics argue they favor revenue sports, potentially straining non-revenue programs like wrestling or , with over a dozen cuts reported in 2025 due to and budget pressures.

Motorsports

The (D1GP), subtitled Professional Drift, is a series specializing in drifting competitions using modified production rear-wheel-drive vehicles. Drifting in this context involves a controlled side-slip of the rear wheels or all tires, with the steering wheels pointed in the opposite direction of the turn to maintain vehicle control beyond standard cornering limits. The series emphasizes judged over lap times, prioritizing visual appeal, precision, and execution in both and formats. Vehicles must retain their original chassis and body shell, though extensive modifications to engines, suspensions, and tires are permitted to achieve high angles and sustained slides. Launched in 2000 as the All Japan Professional Drift Championship by San-Ei , the publisher of Option magazine, D1GP formalized drifting as a discipline following informal touge () racing origins in during the 1970s and 1980s. Key figures Daijiro Inada, founder of Option, and drifter collaborated to organize the series starting around 1999, building on amateur events to create a structured championship. Early seasons featured domestic rounds at circuits like and Ebisu, with the series gaining international exposure through media coverage and a 2003 U.S. event at Irwindale Speedway, won by Katsushi Ueo in a AE86. Expansion to continued briefly, including a 2005 win by Vaughn Gittin Jr., but returned focus to after 2007 amid logistical challenges. Competition structure divides into Tanso (solo runs) and Tsuiso (tandem battles). In Tanso, drivers perform two judged laps on a defined course, with scores from the D1 Original Scoring System (DOSS)—employing like entry speed, drift angle, transition speed, and smoothness—determining advancement; spins or clipping deduct points, and engine sound factors into overall impression. Tsuiso advances top qualifiers into head-to-head pursuits, where drivers alternate as lead (setting the line) and chase (mirroring closely), judged out of 10 points per run on criteria including gap maintenance, matching angle, speed, and stability; the higher combined score from two runs wins the matchup in a knockout tournament. Annual series typically include 8-10 rounds at Japanese venues, with separate championships for overall, Tanso, and Tsuiso titles; as of 2025, it marks the 25th season, starting at Okuibuki Motorpark. Prominent drivers include Masato Kawabata, who secured the 2013 overall and Tanso championships driving a Toyota 86 for Team Toyo Tires Drift, and veterans like Manabu Orido, known for high-power builds exceeding 1,000 horsepower in vehicles such as Nissan Silvia S15s or Toyota Chasers. The series has influenced global drifting by establishing objective metrics like DOSS, reducing judging subjectivity in solo phases, though tandem remains reliant on human evaluation for "coolness" and execution. Despite criticisms of event predictability in the late 2010s, innovations in car technology—such as turbocharged engines in chassis like the Subaru BRZ or Chevrolet Corvette—and circuit adaptations have sustained domestic appeal. D1GP operates under strict safety rules, including FIA-compliant head restraint systems for licensed drivers.

Military designations

World War I aircraft

In the Imperial German aviation designation system administered by the Idflieg during , the "D" class signified single-seat armed biplane fighters or scouts, evolving by 1918 to include monoplanes and other configurations for single-seat fighters; the Roman numeral "I" denoted the first such model from a specific manufacturer. This system facilitated rapid identification amid wartime production, with designations prefixed by the producer's name (e.g., ). D.I aircraft represented early efforts to counter Allied aerial dominance, emphasizing speed, climb rate, and armament synchronization, though many suffered from structural or engine limitations inherent to the era's . The , entering service in January 1917, featured a streamlined , sesquiplane for reduced , and twin 7.92 mm machine guns synchronized to fire through the arc. Powered by a 160 inline engine, it achieved a maximum speed of approximately 170 km/h at sea level and a service ceiling of 5,000 m, outperforming contemporaries like the in dives due to its mass distribution. Deployed to Jagdstaffeln squadrons, around 50 units contributed to the German resurgence in air superiority during the "" period on the Western Front, though vulnerability to prompted quick replacement by the refined D.II variant after brief frontline use. The (factory J 9), a with revolutionary all-metal construction for enhanced durability, first flew in September 1917 and reached by mid-1918. Equipped with a 185 hp inline engine and dual synchronized machine guns, it offered superior structural integrity over fabric-covered rivals but suffered from poor visibility, high landing speeds, and corrosion issues in the humid Jasta environment. Only 41 examples were completed before , with limited combat deployment yielding inconclusive results against foes like the ; its design foreshadowed interwar all-metal fighters despite wartime teething problems. Siemens-Schuckert's D.I, rushed into production in as a near-exact copy of the captured French sesquiplane, utilized a 110 hp Siemens-Halske Sh.I geared and single forward-firing . Its top speed reached 155 km/h, but chronic engine overheating, vibration from the geared reduction, and inferior climb rate rendered it obsolete by mid-1917, with fewer than 20 operational units seeing minimal front-line success before redesigns like the D.IV addressed flaws. The type underscored the risks of derivative engineering without iterative testing under combat stresses. The , engineered by in 1918, pioneered a strutless with aluminum stressed-skin and wings, powered by D.IIIa or higher-output variants up to 185 , aiming for 200 km/h speeds and exceptional maneuverability. Only prototypes were tested, revealing balance issues and production complexity too advanced for wartime scaling, though its load-bearing skin construction influenced by reducing drag and weight compared to wired s. None entered squadron service, limited by the ceasefire.

Other military applications

The was a developed in the as an support vehicle. Originating from the NC1 prototype, it resulted from the French Army's 1926 plan to produce a dedicated tank, with production commencing in and totaling approximately 160 units by 1935. The design featured a cast hull and turret, armed primarily with a 47 mm SA 34 gun and coaxial machine gun, while its armor provided relatively strong protection for the era, with the hull alone weighing about 11 metric tons. Despite its advancements, the suffered from mechanical limitations, including low speed, poor mobility, and chassis constraints that hindered upgrades, rendering it obsolete by the late 1930s. Units were deployed with battalions, some reassigned to North African garrisons by for colonial defense, where they saw limited combat during the early stages of before being outclassed by more modern armored threats. In modern contexts, the Kornet-D1 represents a airborne anti-tank system, a self-propelled variant of the designed for deployment. Introduced for final firing tests around 2022, it mounts eight on an air-droppable to enhance rapid anti-armor capabilities in airborne operations. This system underscores evolving designations for specialized carriers, though its operational deployment remains limited as of recent assessments.

Transportation

Rail vehicles

The designation D1 in rail vehicles refers to multiple classes of locomotives and multiple units employed by various railway operators worldwide, often denoting specific design or power classifications within national or regional systems. In the , D1 (Д1) denotes a series of four-car diesel multiple units manufactured by the Hungarian company Ganz-MÁVAG from the to the , primarily for regional services on railways; these units featured diesel-mechanical and were later remanufactured for operators such as Moldovan Railways. British Railways assigned the numbers D1 through D10 to the initial batch of ten Sulzer Type 4 diesel-electric locomotives, constructed between and 1960 at Works for heavy express passenger duties on routes including the ; these 2,700 horsepower machines utilized a 12-cylinder Sulzer engine and hydraulic transmission, with D1 (later 44001) entering service in 1959. The South Eastern & Chatham Railway's D1 class consisted of 4-4-0 express passenger steam locomotives rebuilt by Richard Maunsell starting in 1921 from earlier D class engines, incorporating superheaters, larger boilers, and piston valves for improved performance on southeastern English routes; eleven such rebuilds were completed by 1925, supplemented by new builds. In , the D1 class designates low-floor vehicles based on the Combino modular design, deployed since 2002 for urban tram operations in , featuring articulated bi-directional configurations with asynchronous motors for high-capacity inner-city service.

Road infrastructure

In the , the D1 motorway serves as the principal east-west highway, linking through and to the border at Petrovice. Its total planned length upon completion will measure 377 km. Construction of the final 10 km segment between Říkovice and began in recent years, with full operational status anticipated by the end of 2025, marking the completion of the route. Modernization efforts, including widening to six lanes in high-traffic areas near , have progressed ahead of schedule, with sections fully reopened as of April 2025 to enhance capacity and safety. In , the D1 motorway constitutes the country's longest and most heavily trafficked road, spanning from eastward through , , , and toward and the Ukrainian border as part of the Trans-European Transport Network's Corridor V. Approximately km of the planned 517 km corridor were operational as of recent assessments, with ongoing builds incorporating tunnels, bridges, and interchanges. A €125 million EU-funded project in targeted the 13.5 km Hubová-Ivachnová section in central , replacing the existing I/18 class I road to alleviate congestion and improve regional connectivity. Development has proceeded since 1972, featuring elements like the 2 km twin-tube tunnel in northern sections managed by firms such as .

Other transportation uses

In , the D1 nautical licence, enacted through Legislative Decree 46/2024 and effective from October 2024, authorizes operators aged 16 and older to conduct daytime navigation exclusively within 6 s of the coast using motor pleasure craft 10 in length with engines limited to 115 horsepower, or (jet skis) 1 nautical mile offshore. This qualification addresses demand for accessible entry-level certification for minors, differing from the standard entro le 6 miglia patent by imposing stricter power, distance, and temporal constraints to prioritize safety for novice users. Obtaining the D1 requires enrollment in an accredited nautical training program, comprising theoretical modules on rules, protocols, and vessel handling; mandatory practical sea trials demonstrating basic maneuvering; and successful completion of a 20-question multiple-choice with a passing of 75% correct answers, administered either at the school or a Motorizzazione Civile office upon presentation of course certification. No prior boating experience is mandated beyond the course, though applicants must provide medical fitness certification and identification; the licence remains valid indefinitely post-issuance, subject to renewal only if lost or expired equivalents are involved. This framework aligns with European recreational boating directives while tailoring restrictions to mitigate risks associated with youthful operators, as evidenced by the exclusion of night operations and extended capabilities reserved for higher certifications like D2.

Science and technology

Biochemistry and medicine

The dopamine D1 receptor, encoded by the DRD1 gene on chromosome 5q35.2, is the most abundant subtype of dopamine receptors in the central nervous system and belongs to the D1-like family (D1 and D5). It functions as a Gs/olf-coupled G protein-coupled receptor (GPCR), primarily activating adenylyl cyclase to elevate intracellular cyclic AMP (cAMP) levels, which modulates downstream signaling pathways including protein kinase A activation and gene transcription via CREB. High densities of D1 receptors are found in the striatum, nucleus accumbens, prefrontal cortex, and hippocampus, where they regulate neuronal excitability, synaptic plasticity, and processes such as reward processing, motivation, voluntary movement, and cognition. Dysregulation of D1 receptor signaling contributes to disorders including Parkinson's disease, schizophrenia, attention-deficit/hyperactivity disorder (ADHD), and addiction; for instance, D1 agonists like fenoldopam have been explored for hypertension, while selective modulators target motor symptoms in Parkinson's without inducing dyskinesia associated with non-selective dopamine therapies. Structural studies, including cryo-electron microscopy of D1-Gs complexes, have revealed ligand-binding pockets and biased agonism mechanisms that favor certain signaling pathways, informing drug design for neurodegenerative conditions as of 2021. Cyclin D1, a member of the D-type cyclin family encoded by CCND1 on chromosome 11q13, serves as a regulatory subunit for cyclin-dependent kinases CDK4 and CDK6, forming active complexes that phosphorylate the retinoblastoma protein (Rb) to release E2F transcription factors and drive G1-phase progression to S-phase in the cell cycle. Overexpression of cyclin D1, often due to gene amplification or chromosomal translocations (e.g., t(11;14) in mantle cell lymphoma), is implicated in oncogenesis across multiple cancers including breast, colorectal, and esophageal carcinomas, where it promotes uncontrolled proliferation and resistance to CDK4/6 inhibitors like palbociclib. In normal physiology, cyclin D1 levels oscillate with mitogenic signals such as growth factors, ensuring timely cell cycle entry; therapeutic targeting via selective CDK4/6 inhibitors has shown efficacy in hormone receptor-positive breast cancer, with FDA approvals dating to 2015 and ongoing trials expanding to other solid tumors as of 2023. Protectin D1 (PD1), a specialized pro-resolving mediator derived from the (DHA) via enzymatic oxidation, exhibits potent anti-inflammatory and neuroprotective effects by limiting infiltration, promoting , and inhibiting pro-inflammatory production in tissues like the and . In medical contexts, PD1 has been studied for its role in resolving neuroinflammation in conditions such as , , and , with preclinical data from 2000s onward demonstrating reduced infarct size and preserved neuronal function in animal models through GPR32 and ALX/FPR2 receptor activation. Clinical relevance includes potential adjunctive therapies for dry eye disease and age-related , though human trials remain limited as of 2022, emphasizing its causal role in shifting inflammation from initiation to resolution phases.

Computing and electronics

Cloudflare D1 is a serverless service supporting , enabling developers to create and query directly within Workers without managing infrastructure. Launched in open beta in 2022, it scales automatically across Cloudflare's global network and supports features like read replication for low-latency access in multiple regions, with pricing based on storage and operations rather than database count. Tesla's D1 chip is a custom-designed system-on-a-chip for training, integral to the company's architecture aimed at accelerating autonomous vehicle data processing. Each D1 chip delivers 362 teraflops of BF16 performance and incorporates high-bandwidth memory, with tiles interconnected via a network to form exaflop-scale clusters; production began scaling in 2021 for internal workloads. The Allwinner D1 is a 64-bit system-on-chip featuring a XuanTie C906 CPU core clocked at 1 GHz, integrated graphics, and interfaces for multimedia and networking, targeted at embedded and maker applications. Released in 2021, it powers single-board computers like the Sipeed Lichee RV, supporting distributions and serving as an open-source alternative to ARM-based platforms with 512 MB to 1 GB DDR3 RAM options. The Wemos D1 Mini is a compact development board based on the Wi-Fi , offering compatibility with 11 digital I/O pins, one analog input, and scripting support for projects. Introduced around 2015, it operates at 3.3V with built-in USB-to-serial conversion and has been widely adopted for its low cost and small form factor in prototyping wireless sensors and controllers.

Video and recording formats

D1, also known as 4:2:2 , is a professional recording format that stores signals in an uncompressed manner on 19 mm wide cassettes. Developed by and standardized through SMPTE engineering committees, it was introduced in as the first , broadcast-quality tape system, adhering to CCIR 601 for sampling and at 4:2:2 ratios with 10-bit depth per component. The format's high data rate—approximately 177 Mbps for video alone—ensured minimal generational loss compared to analog predecessors like , making it suitable for mastering and in television broadcasting. Cassettes, such as the D1L-94 model, typically offered up to 94 minutes of recording time at standard definition resolutions (720×480 for or 720×576 for PAL), with longitudinal audio tracks supporting four channels of uncompressed PCM audio at 48 kHz sampling and 16- or 20-bit depth. The large cassette size accommodated the format's demands, which exceeded 200 Mbps including audio and , requiring robust error correction via Reed-Solomon coding to maintain signal integrity during playback. D1 recorders, like Sony's DVR-10, operated at 90 mm/s tape speed, enabling and editing capabilities that facilitated nonlinear workflows in professional environments. Adopted widely in the late and by broadcasters for its fidelity in handling effects-heavy content and multi-generation , D1 saw peak use in high-end facilities but declined with the rise of compressed formats like Digital Betacam (1993) and D5 (1995), which offered similar quality at lower storage costs. Despite in active by the early , D1 remains relevant for archival preservation, as its uncompressed nature preserves original signal quality better than lossy alternatives, with institutions transferring masters to digital files to mitigate tape degradation over time. Note that "D1" in surveillance contexts refers merely to a (equivalent to full at 704×480), unrelated to this tape format's technical implementation.

Business and finance

Investment entities

is a New York City-based firm founded in July 2018 by Daniel Sundheim, a former at . The firm manages approximately $24.5 billion in assets as of October 2025 and employs long/short equity strategies across global public and private markets, with a focus on fundamental research-driven investments in sectors including , healthcare, and consumer goods. Since inception, its public market portfolio has generated a net return of 109 percent, while private investments have returned 122 percent net of fees, though annual performance has varied, with 2023 and 2024 marked by challenges leading to strategic adjustments such as team restructuring. In October 2025, D1 Capital announced plans to raise over $1 billion for its inaugural dedicated private equity fund, expanding beyond its traditional hedge fund model into more illiquid assets amid improving private market liquidity and technology sector rebounds. The firm's public equity holdings, as disclosed in SEC filings, include 33 positions managed by Sundheim, with notable investments such as a participation in Ramp's $500 million Series E-2 round in July 2025, valuing the fintech at $22.5 billion. Through September 2025, D1's equity portfolio achieved a year-to-date gain of nearly 24 percent, outperforming broader markets during periods of volatility. Other entities bearing the D1 designation in finance include Decision 1 Financial, a smaller advisory firm emphasizing low-risk and for individual clients, though it lacks the scale and institutional focus of D1 Capital. D1 Capital's operations are registered with the U.S. Securities and Exchange Commission as an investment adviser, subjecting it to regulatory oversight on portfolio management and disclosures.

Cultural and miscellaneous uses

Slang and informal references

In American slang, particularly among youth and sports enthusiasts, "D1" commonly abbreviates "Division 1," referring to the top tier of National Collegiate Athletic Association (NCAA) athletics, characterized by the most competitive programs, largest budgets, and highest-profile athletes as of the 2024–2025 season. This usage extends metaphorically to denote elite performance, extreme dedication, or superior quality in non-athletic contexts, such as describing a highly skilled individual or an impressive achievement. For instance, on platforms like TikTok, "D1" praises something as outstanding, drawing from the prestige of Division I's 352 institutions competing in 24 sports. The term also appears in phrases like "D1 hater," which informally signifies a highly proficient or relentless , paralleling the intensity of I competition. In texting and online chats, "D1" can alternatively mean "Day 1," indicating from the outset of a , , or , though this overlaps with connotations in casual discourse. Emerging variants, such as "D1 crashout," describe an intensified loss of composure or reckless outburst, amplified for emphasis in Gen Z vernacular on . These informal references reflect the term's from structured to broader hyperbolic expression, with usage surging in digital by mid-2025.

Entertainment and media

D1 Entertainment operates as a music label featuring artists and WillTheRapper, with distribution handled by under . D1 Media Productions provides services for , , and content, primarily in and , including programming aired on Media Network. In music, D1 refers to an artist known for releases such as the album D1:V3 (2008), featuring tracks like "Ongie Bongie" and "Joy," available via . Separate from this, Diversity of One (D1) is a rock band based in , active in local performances. D1 Film functions as a focused on projects, operating from a platform in the . D1 Entertainment and Media Private Limited, incorporated on July 14, 2023, in , , engages in entertainment activities under classification U90009 for cultural and artistic services.