SSR
Sushant Singh Rajput (21 January 1986 – 14 June 2020) was an Indian actor recognized for his transition from television to Bollywood, where he portrayed diverse roles in commercially and critically acclaimed films, including biopics and dramas.[1][2] Born in Patna, Bihar, Rajput pursued engineering at Delhi College of Engineering before entering the entertainment industry as a dancer and actor, debuting on television in the series Kis Desh Mein Hai Meraa Dil (2008) and achieving breakthrough success with Pavitra Rishta (2009–2011), for which he received multiple awards including the Indian Telly Award for Best Male Actor in a Lead Role.[1] His film career began with Kai Po Che! (2013), an adaptation of Chetan Bhagat's novel that highlighted his athletic and dramatic range, followed by roles in PK (2014), Detective Byomkesh Bakshy! (2015), and the biographical sports film M.S. Dhoni: The Untold Story (2016), which grossed over ₹2 billion worldwide and earned him praise for embodying the cricketer's persona.[1][2] Other significant works included Kedarnath (2018), a romantic drama amid religious tensions, and Chhichhore (2019), a coming-of-age story that became one of his highest-grossing films, posthumously released Dil Bechara (2020) further underscored his versatility in adapting international stories like The Fault in Our Stars.[2][1] Rajput's death, discovered in his Bandra apartment, was officially attributed to suicide by hanging, but it ignited intense public scrutiny and allegations from his family of foul play, including potential murder, financial siphoning of approximately ₹15 crore by his live-in partner Rhea Chakraborty, and systemic exclusion by Bollywood's nepotistic networks favoring insiders over self-made talents like him.[3][4] These claims, amplified by supporters questioning the Mumbai Police's initial handling and links to the earlier death of his manager Disha Salian, led to investigations by the CBI, ED, and NCB, revealing drug procurement angles but no conclusive evidence of abetment; however, mainstream coverage often minimized family assertions of investigative lapses amid institutional pressures.[3][5] In March 2025, the CBI submitted a closure report reaffirming suicide without foul play and exonerating Chakraborty of embezzlement or abetment, citing her departure from the apartment days prior and accounting for expenditures like ₹17 lakh in transactions; Rajput's family dismissed this as superficial, vowing court challenges over unresolved forensic and procedural doubts.[6][4][3]Science and Technology
Solid-State Relay
A solid-state relay (SSR) is an electronic switching device that controls high-power loads using semiconductor components, such as thyristors or MOSFETs, without mechanical contacts or moving parts. Unlike electromechanical relays, which rely on physical armature movement to open or close circuits, SSRs achieve switching through electronic means, typically triggered by a low-voltage control signal across input terminals. This design enables reliable operation in applications requiring frequent cycling or isolation between control and load circuits.[7][8] SSRs were first commercialized in 1971 by Crydom, marking a significant advancement over earlier relay technologies by eliminating wear-prone mechanical elements. The core principle of operation involves an input stage that receives a DC control voltage (often 3-32 V), which activates an optocoupler—typically an LED paired with a photodetector—to provide galvanic isolation and prevent feedback from the load to the control circuit. This isolated signal then drives the output stage, where power semiconductors conduct to switch the load: TRIACs or silicon-controlled rectifiers (SCRs) for AC loads, and MOSFETs or IGBTs for DC loads. Zero-crossing SSRs synchronize switching with the AC waveform's zero point to minimize electrical noise and stress, while random-turn-on variants enable immediate response regardless of phase.[9][10][11] SSRs are classified by load type, switching mode, and isolation method. AC-output SSRs handle alternating current up to several kilowatts, often using back-to-back SCRs or TRIACs for bidirectional conduction. DC-output SSRs, suited for unidirectional loads like motors or solenoids, employ MOSFETs in series or parallel configurations for higher efficiency at low voltages. Switching modes include zero-crossing for reduced electromagnetic interference (EMI) in inductive loads and random switching for precise phase control in dimming applications. Isolation types encompass photo-coupled (using optocouplers for high isolation up to 4 kV), transformer-coupled (for higher power isolation), and hybrid variants combining reed relays with semiconductors for enhanced performance in specific scenarios. Mounting forms range from PCB-integrated modules to DIN-rail or panel-mount units with integrated heatsinks.[12][13][14] Key advantages of SSRs include extended operational life exceeding 10 million cycles due to the absence of mechanical degradation, rapid switching speeds under 10 ms, and silent, spark-free operation that avoids contact arcing and bounce. They exhibit high resistance to vibration and shock, making them ideal for harsh industrial environments, and provide inherent electrical isolation to protect control systems. However, SSRs generate significant heat from on-state voltage drops (typically 1-2 V for AC types), necessitating heatsinks or fans for ratings above 10 A to prevent thermal runaway, which can limit maximum load current to 100 A without cooling. Other drawbacks encompass higher upfront costs compared to electromechanical relays, potential failure in a shorted state (requiring fuses for protection), sensitivity to overvoltage transients, and off-state leakage currents up to 10 mA that may not fully isolate sensitive loads.[15][16][13] Common applications leverage SSRs' reliability for precise power control, including temperature regulation in HVAC systems and plastic extrusion machinery, lighting dimmers, electric vehicle battery chargers, and medical devices like infusion pumps where silent operation and long-term stability are critical. In industrial automation, they interface PLCs with high-power actuators, offering MTBF ratings over 10^9 hours under rated conditions. Selection requires derating for ambient temperature—e.g., halving current capacity above 40°C—and incorporating overcurrent protection to mitigate failure modes.[8][17][13]Server-Side Rendering
Server-side rendering (SSR) is a web development technique in which a server dynamically generates complete HTML markup for a requested page from data and templates, then delivers this fully rendered HTML to the client's browser for immediate display.[18][19] This process contrasts with client-side rendering (CSR), where the server sends minimal HTML along with JavaScript bundles that execute in the browser to build the page dynamically.[20] In SSR, the server handles rendering logic—often using templating engines or component frameworks—fetches necessary data (e.g., from databases or APIs), embeds it into the HTML, and may include hydration scripts to enable client-side interactivity post-load.[21] SSR originated as the dominant paradigm in early dynamic web development, predating widespread client-side JavaScript execution. Server programming languages such as PHP (released in 1995), Java servlets, Python with frameworks like Django, and Ruby on Rails (launched in 2004) enabled template-based HTML generation on the server for each request, supporting the shift from static HTML pages of the 1990s to data-driven sites.[22][23] The rise of AJAX around 2005 and single-page applications (SPAs) in the late 2000s favored CSR for richer interactivity, but SSR resurged in the 2010s amid concerns over CSR's limitations in search engine optimization (SEO) and initial load times, particularly with React's introduction of server rendering capabilities in 2013 and frameworks like Next.js in 2016.[24][23] By 2025, SSR remains integral to hybrid rendering strategies, balancing server efficiency with client responsiveness.[25] Key advantages of SSR include improved SEO, as search engine crawlers receive fully populated HTML without needing to execute JavaScript, facilitating better indexing of dynamic content.[20] It also enhances perceived performance through faster time-to-first-byte and initial paint, benefiting users on slow connections or devices with limited JavaScript capabilities, and supports accessibility by providing semantic HTML upfront for screen readers.[21][20] Drawbacks encompass increased server computational demands per request, potentially raising latency and costs under high traffic, as rendering occurs anew for each user rather than leveraging cached client-side state.[26] Additionally, SSR setups introduce complexity in code sharing between server and client environments, hydration mismatches, and debugging distributed logic.[27] Popular modern frameworks for implementing SSR include Next.js for React-based applications, which automates routing, data fetching, and static generation alongside dynamic rendering; Nuxt.js for Vue.js; SvelteKit for Svelte; Remix for full-stack React; and Astro for lightweight, content-focused sites with partial hydration.[25][28] These tools, often built atop Node.js, support hybrid modes combining SSR with static site generation (SSG) and CSR for optimized performance, as evidenced by their adoption in production environments for e-commerce, blogs, and data-heavy applications by 2025.[29][25]Secondary Surveillance Radar
Secondary Surveillance Radar (SSR) is an active radar surveillance system employed in aviation to interrogate aircraft transponders, eliciting responses that convey identity, altitude, and other data for air traffic control purposes. Unlike primary surveillance radar, which detects passive echoes from an aircraft's surface, SSR depends on cooperative transponders aboard aircraft to transmit modulated replies, enabling precise identification and reducing susceptibility to ground clutter or weather interference.[30] The system operates via a ground-based interrogator that transmits pulsed signals at 1030 MHz to prompt responses from aircraft transponders, which reply at 1090 MHz with encoded information derived from onboard sensors. Interrogations occur in specific formats, including selective addressing in advanced modes to minimize interference, with typical ranges extending 200-250 nautical miles depending on altitude and equipment. This cooperative mechanism supports en-route and terminal surveillance, integrating with systems like TCAS for collision avoidance by providing bearing, range, and altitude relative to nearby aircraft.[31][32] SSR originated from military Identification Friend or Foe (IFF) systems developed during World War II, with early active IFF variants like Mk I entering service around 1940 using aircraft receivers to retransmit signals. Post-war adaptations for civil aviation led to standardization efforts by the International Civil Aviation Organization (ICAO), building on IFF Mark X principles discussed at ICAO's 5th Communications Division meeting in Montreal in 1954. By the early 1960s, ICAO promoted SSR for global air traffic management, as detailed in instructional materials emphasizing its role in enhancing control over primary radar limitations.[33][34] SSR employs multiple interrogation modes standardized by ICAO and implemented by authorities like the FAA. Mode A delivers a 4-digit identity code (up to 4096 possibilities) for aircraft squawk assignment, while Mode C appends pressure altitude data in 100-foot increments for vertical separation. Mode S, introduced for selective interrogation to address Mode A/C overload in dense airspace, uses 24-bit addressing for unique aircraft identification, supports data link communications, and facilitates enhanced surveillance like ADS-B integration, operating on the same 1030/1090 MHz frequencies.[35][36]Simple Sequence Repeat
Simple sequence repeats (SSRs), also known as microsatellites, are tandemly repeated DNA sequences consisting of short motifs typically 1–6 nucleotides in length, repeated multiple times in a contiguous manner.[37] [38] These repeats occur at thousands of loci across eukaryotic and prokaryotic genomes, often comprising a small but functionally significant portion of the total DNA, such as approximately 0.03% in maize.[39] [40] SSRs exhibit high polymorphism primarily due to variations in the number of repeat units, arising from replication slippage, unequal crossing-over, or defects in DNA mismatch repair, which confer a mutation rate orders of magnitude higher than non-repetitive DNA regions.[41] [42] This leads to multiple alleles per locus—often exceeding ten—and codominant inheritance, enabling precise genotyping via polymerase chain reaction (PCR) amplification of flanking regions.[43] [44] While predominantly located in non-coding genomic regions, SSRs can influence gene expression, chromatin structure, or protein function when expanded or positioned near regulatory elements.[45] [46] In genetics and molecular biology, SSRs serve as versatile markers for applications including genetic mapping, quantitative trait locus (QTL) identification, population structure analysis, kinship determination, and biodiversity assessment across species from plants to pathogens.[47] [48] [49] Their abundance, reproducibility, and hypervariability facilitate high-throughput genotyping, such as in maize breeding for trait association or bacterial strain differentiation via antigenic variation.[50] [51] Recent genome-wide analyses, enabled by sequencing technologies, have expanded SSR discovery for marker development, as seen in potato where they underpin breeding for disease resistance and yield.[52][49]Historical and Political Entities
Soviet Socialist Republic
The Soviet Socialist Republics (SSRs) formed the constituent entities of the Union of Soviet Socialist Republics (USSR), a centralized Marxist-Leninist state established on December 30, 1922, and dissolved on December 25, 1991. These republics were designed as nominally sovereign units within a federal structure, each purportedly representing a distinct national or ethnic group under socialist governance, but subjected to uniform ideological control from the Communist Party of the Soviet Union (CPSU). The SSR model aimed to integrate diverse territories acquired through revolution and conquest into a single proletarian dictatorship, prioritizing class struggle over ethnic self-determination.[53][54] The origins of the SSRs trace to the Bolshevik seizure of power in the October Revolution of November 7, 1917 (Old Style), which overthrew the Russian Provisional Government and initiated the establishment of soviet power structures. The Russian Soviet Federative Socialist Republic (RSFSR), the largest and dominant SSR, was formally constituted on July 10, 1918, with the adoption of its first constitution by the 5th All-Russian Congress of Soviets, marking the world's initial constitutionally defined socialist republic. During the Russian Civil War (1917–1922), additional SSRs emerged in territories where Bolshevik forces prevailed, including the Ukrainian Soviet Socialist Republic (declared December 1917, formalized 1919) and Byelorussian Soviet Socialist Republic (1919). The Transcaucasian Soviet Federative Socialist Republic followed in 1922, enabling the unification treaty signed on December 30, 1922, by representatives of these four republics to create the USSR.[55][53][54] Expansion continued through the 1920s and 1940s as the Soviet regime delimited internal borders and annexed external territories. Central Asian SSRs—Uzbek (1924), Turkmen (1924), Tajik (1929), Kazakh (1936), and Kyrgyz (1936)—were carved from the RSFSR to formalize ethnic divisions while enforcing collectivization and industrialization policies that caused widespread famine and demographic losses, such as the 1932–1933 Holodomor in Ukraine, which killed an estimated 3.5–5 million. In 1936, the Transcaucasian SFSR split into separate Armenian, Azerbaijani, and Georgian SSRs. Post-1939 invasions added the Estonian, Latvian, Lithuanian, and Moldavian SSRs in 1940. By the USSR's peak, 15 SSRs comprised the union, covering 22.4 million square kilometers and over 100 ethnic groups.[53][56]| Republic | Admission Year | Notes |
|---|---|---|
| Russian SFSR | 1918 (foundational) | Largest by area and population; core of USSR. |
| Ukrainian SSR | 1919 | Formed amid civil war; site of major collectivization famines. |
| Byelorussian SSR | 1919 | Incorporated Polish territories post-1939. |
| Transcaucasian SFSR | 1922 | Dissolved 1936 into Armenia, Azerbaijan, Georgia SSRs. |
| Uzbek SSR | 1924 | From Turkestan ASSR. |
| Turkmen SSR | 1924 | From Turkmen ASSR. |
| Tajik SSR | 1929 | Initially Tajik ASSR within Uzbek SSR. |
| Kazakh SSR | 1936 | Upgraded from ASSR. |
| Kyrgyz SSR | 1936 | Upgraded from ASSR. |
| Armenian SSR | 1936 | From Transcaucasian SFSR. |
| Azerbaijani SSR | 1936 | From Transcaucasian SFSR. |
| Georgian SSR | 1936 | From Transcaucasian SFSR. |
| Estonian SSR | 1940 | Annexed post-Molotov-Ribbentrop Pact. |
| Latvian SSR | 1940 | Annexed post-Molotov-Ribbentrop Pact. |
| Lithuanian SSR | 1940 | Annexed post-Molotov-Ribbentrop Pact. |
| Moldavian SSR | 1940 | Formed from annexed Romanian Bessarabia. |
Businesses and Products
SSR Mining
SSR Mining Inc. is a Denver, Colorado-headquartered precious metals producer focused primarily on gold, with additional output of silver, copper, lead, and zinc. The company operates mines across the United States, Canada, Argentina, and Türkiye, emphasizing low-cost, open-pit and underground extraction methods such as heap leaching and flotation processing. As of the second quarter of 2025, SSR Mining reported trailing twelve-month revenue of $1.3 billion, net income attributable to common shareholders of $164.97 million, and a cash balance of $412.1 million.[60] [61] Originally incorporated in 1946 as Silver Standard Resources Inc., the company shifted from a silver-centric focus to diversified precious metals production, culminating in a name change to SSR Mining Inc. effective August 1, 2017, to better align with its growing gold portfolio.[62] This rebranding followed acquisitions and developments that expanded operations beyond silver streaming, including the 2021 merger with Alacer Gold Corp., which added the Çöpler mine. SSR Mining's strategy prioritizes organic growth through exploration and free cash flow generation while maintaining a strong balance sheet for stakeholder value.[63] The company's active operations include the Marigold open-pit gold mine in Nevada, United States, which produced significant gold dore bars via heap leaching; the Seabee Gold Operation, an underground mine in Saskatchewan, Canada, restarted in June 2025 after a temporary suspension; the Puna Operations in Jujuy Province, Argentina, yielding silver, lead, and zinc concentrates; and the Cripple Creek & Victor (CC&V) mine in Colorado, United States, focused on gold recovery. The Çöpler mine in Erzincan Province, Türkiye, a key gold asset using pressure oxidation and heap leaching, has been suspended since February 13, 2024, following a major slip on its heap leach pad that resulted in nine fatalities and extensive remediation efforts costing approximately $272.9 million in 2024.[63] [64] [65] Expert analysis of the Çöpler incident, released January 15, 2025, attributed the failure to a "deeply-rooted flaw" in third-party engineered design, specifically overestimated shear strength in the pad's liner system based on flawed test data, rather than operational errors by SSR Mining. The company has since removed 86% of the collapsed material by late 2024 and anticipates potential restart in 2026, pending regulatory approvals and further stabilization. This event temporarily reduced production but highlighted SSR Mining's diversified portfolio, with other sites compensating through increased output, such as Seabee's resumption contributing to a 15% rise in gold-equivalent ounces to 120,000 in the second quarter of 2025.[66] [67] [68]Other Commercial Entities and Products
The Chevrolet SSR (Super Sport Roadster) was a retro-styled retractable hardtop convertible pickup truck produced by General Motors under the Chevrolet brand from 2003 to 2006.[69] Unveiled as a concept in 2000 at the Detroit Auto Show, it featured a 5.3-liter V8 engine initially producing 300 horsepower, paired with a four-speed automatic transmission, and later upgrades in 2005 and 2006 models included a more powerful 6.0-liter V8 option with 390 horsepower and a heavier-duty chassis.[70][71] Production totaled around 24,000 units, with the final vehicle assembled on March 17, 2006, due to modest sales despite its unique design blending hot rod aesthetics with modern utility.[72] SSR Motorsports, established in 2002 by William and Jeff Li as a father-son venture on the U.S. West Coast, imports and distributes powersports vehicles including pit bikes, dirt bikes, scooters, ATVs, side-by-sides, mopeds, and electric vehicles, with a focus on affordable off-road options.[73][74] The company initially specialized in small-displacement pit bikes for youth and amateur riders, expanding to larger motorcycles and serving as the worldwide distributor for Benelli products, emphasizing engineering for recreational and entry-level performance.[75] SSR Wheels, a Japanese manufacturer based in Osaka, produces lightweight, high-strength alloy wheels for motorsport racing and aftermarket automotive applications.[76] Founded in 1971 under the Speedstar brand, it pioneered three-piece wheel designs like the MK1 and maintains a lineup including forged models such as the GTX series, prioritizing precision engineering for durability and reduced weight in performance vehicles.[77][78] SSR Health LLC specializes in analytics and data on U.S. prescription brand drug pricing, offering a proprietary database tracking net prices for approximately 1,000 branded medications based on disclosed product-level sales and rebate estimates.[79] Founded to address gaps in healthcare pricing transparency, its tools are used by investors and analysts for sub-sector weighting in pharmaceutical research, with subscriptions providing access to historical archives and updates on gross-to-net price dynamics.[80][81]Transportation and Infrastructure
Railway Systems
The Sub-Surface Railway (SSR) of the London Underground encompasses the Metropolitan, District, Circle, and Hammersmith & City lines, which utilize cut-and-cover tunnels constructed just below street level, distinguishing them from the deep-level bored tube lines. These lines feature larger tunnel diameters, allowing for wider carriages akin to those on British mainline railways, and together they form approximately 40% of the Underground network by route length.[82][83] The SSR originated with the Metropolitan Railway, the world's first underground passenger railway, which opened on 10 January 1863 between Paddington (Bishop's Road) and Farringdon Street to alleviate surface congestion from steam-powered mainline services. The District line followed in 1868, extending westward and eastward, while the Circle line emerged in 1884 through joint operations between the Metropolitan and District railways, creating a loop around central London. The Hammersmith & City line, initially part of the Metropolitan network, traces its roots to 1864 services between Hammersmith and the City of London. Early operations relied on steam locomotives in smoke-filled tunnels, transitioning to electric traction by the early 1900s, which enabled denser services but highlighted persistent capacity constraints due to shared tracks and outdated signalling.[84][85][86] In response to overcrowding and inefficiency, Transport for London initiated the Four Lines Modernisation programme in the 2000s, a £5.4 billion initiative to overhaul rolling stock, power supply, track, and signalling across the SSR. This included deploying 192 air-conditioned S-stock trains with walk-through interiors, introduced progressively from 2010, to replace older A- and C-stock vehicles and boost capacity by up to 65%. The signalling upgrade, employing Communications-Based Train Control (CBTC) supplied by Thales and later integrated by Hitachi Rail, aims for automatic train operation, reduced headways, and interoperability, though it has encountered delays and technical challenges, including interfacing with legacy systems. By July 2025, key phases such as the Neasden Depot area had been completed, enabling more frequent services and paving the way for full network capacity increases.[82][87][88][89]Aviation and Radar Applications
Secondary Surveillance Radar (SSR) is a cooperative surveillance system employed in aviation to enhance air traffic control by interrogating aircraft transponders for identification, altitude, and other data, supplementing primary radar's range and bearing measurements. The ground-based interrogator transmits pulses at 1030 MHz, prompting aircraft transponders to reply at 1090 MHz with encoded information, enabling precise tracking even in cluttered environments.[90][30] In aviation operations, SSR facilitates safer separation of aircraft by providing controllers with real-time identity codes and pressure altitude readings, critical for en-route and terminal airspace management. Mode A delivers a 4-digit octal identity code (up to 4096 possibilities), while Mode C reports altitude in 100-foot increments, allowing automated conflict detection and reducing pilot workload through systems like Traffic Collision Avoidance System (TCAS). Mode S, introduced to address Mode A/C limitations such as synchronous garble and limited capacity, uses a unique 24-bit aircraft address for selective interrogation, minimizing interference and enabling data link communications for enhanced situational awareness.[30][91] SSR's radar applications extend to integration with multilateration systems and automatic dependent surveillance, where transponder replies contribute to wide-area surveillance beyond line-of-sight limitations of ground radars. Deployed since the 1960s in civil aviation—exemplified by early systems at Heathrow Airport—SSR has evolved under ICAO Annex 10 standards to support global interoperability, with Mode S mandated in high-density European airspace by 2005 to handle projected traffic growth. This evolution mitigates deficiencies like reply overload in dense traffic, where primary radar alone fails to distinguish aircraft identities, thereby improving overall radar surveillance reliability.[92][93]Geography and Locations
Named Places and Regions
The Soviet Socialist Republics (SSRs) represented the foundational named geographical regions of the Union of Soviet Socialist Republics (USSR), comprising 15 distinct territories that collectively spanned Eurasia from the Baltic Sea to the Pacific Ocean. Established through the 1922 Treaty on the Creation of the USSR and expanded over subsequent decades, these republics were delineated by administrative borders often aligned with ethnic majorities, though internal ethnic diversity was common. Their geographical extent covered approximately 22.4 million square kilometers, encompassing diverse biomes from Arctic tundra to Central Asian steppes.[94][95] The republics included:- Russian Soviet Federative Socialist Republic (RSFSR): The largest by area, dominating the northern and eastern expanse of the USSR, including Siberia and the Russian Far East.
- Ukrainian Soviet Socialist Republic: Situated in Eastern Europe, bordering the Black Sea and encompassing fertile steppe lands.
- Byelorussian Soviet Socialist Republic: Located in Eastern Europe, featuring marshy plains and forests between the RSFSR and Ukrainian SSR.
- Uzbek Soviet Socialist Republic: In Central Asia, centered around the Fergana Valley and Aral Sea basin.
- Kazakh Soviet Socialist Republic: Vast steppe and semi-desert regions in Central Asia, extending from the Caspian Sea to the Altai Mountains.
- Georgian Soviet Socialist Republic: In the South Caucasus, including the Black Sea coast and Greater Caucasus range.
- Azerbaijan Soviet Socialist Republic: South Caucasus territory with Caspian Sea access and mountainous terrain.
- Lithuanian Soviet Socialist Republic: Baltic coastal region with plains and lagoons.
- Moldavian Soviet Socialist Republic: Eastern European area between the Ukrainian SSR and Romania, along the Dniester River.
- Latvian Soviet Socialist Republic: Baltic state with Gulf of Riga shoreline and interior forests.
- Kirghiz Soviet Socialist Republic: Central Asian highland republic in the Tian Shan mountains.
- Tajik Soviet Socialist Republic: Mountainous Central Asian region bordering Afghanistan and China.
- Armenian Soviet Socialist Republic: South Caucasus enclave with Lake Sevan and volcanic highlands.
- Turkmen Soviet Socialist Republic: Central Asian desert expanse, including the Kara Kum and Caspian coast.
- Estonian Soviet Socialist Republic: Northernmost Baltic republic, featuring islands and boreal forests.