RH
The Rh blood group system is a genetically determined human blood group system, second in clinical importance only to the ABO system, comprising over 50 distinct antigens primarily expressed on the surface of red blood cells via proteins encoded by the RHD and RHCE genes on chromosome 1.[1][2] The system's defining feature is the Rh(D) antigen, whose presence or absence classifies individuals as Rh-positive (approximately 85% of Caucasians) or Rh-negative, a distinction critical for preventing alloimmunization during transfusions and pregnancies.[3][1] Discovered in 1940 during investigations into hemolytic transfusion reactions—initially misattributed to rhesus monkey antigens—the Rh system has since been recognized for its polymorphic complexity, with the D antigen proving the most potent immunogen capable of eliciting strong antibody responses.[4][5] Key clinical achievements include the development of antigen-matching protocols that have drastically reduced transfusion-related morbidity, as well as the introduction of anti-D immunoglobulin (RhoGAM) in the 1960s, which prevents Rh incompatibility-induced hemolytic disease of the fetus and newborn (HDFN) by neutralizing fetal Rh-positive cells in sensitized Rh-negative mothers, saving countless infant lives annually.[1][6] The system's molecular basis, involving intricate protein structures and variant alleles, underpins ongoing research into rare null phenotypes (e.g., Rh-null, lacking all Rh antigens) and their associations with hereditary stomatocytosis, a condition marked by hemolytic anemia and altered membrane integrity.[2][7] While not inherently controversial, the Rh system's historical nomenclature errors and ethnic variations in antigen prevalence (e.g., near-universal Rh-positivity in some Asian populations) highlight the need for population-specific serological data in global transfusion practices, underscoring empirical genetics over generalized assumptions.[4][8]Business and organizations
RH (retailer)
RH is a publicly traded American luxury retailer specializing in home furnishings, offering products such as furniture, lighting, textiles, décor, and outdoor items through an integrated model of physical showrooms, e-commerce, and membership programs.[9][10] Headquartered in Corte Madera, California, the company trades on the New York Stock Exchange under the ticker symbol RH and emphasizes experiential retail spaces known as "galleries," which blend retail, hospitality, and design services to create immersive environments.[11] The company originated in 1979 when Stephen Gordon founded Restoration Hardware in Eureka, California, initially operating from his home to sell high-quality reproduction hardware and fixtures sourced for restoring Victorian-era homes.[12][13] By 1980, Gordon opened the first retail store in Eureka, expanding the business through catalogs and additional locations focused on authentic period reproductions.[14] Over the next two decades, Restoration Hardware grew into a national chain retailing broader home goods, achieving public listing status in 1997 amid rapid store expansion but encountering financial strain from overexpansion and market shifts in the early 2000s.[15] Gary Friedman assumed the role of chairman and chief executive officer in 2001, steering the company through near-bankruptcy by divesting underperforming assets, streamlining operations, and pivoting toward premium, design-forward products inspired by global aesthetics and historical references.[16][17] Under Friedman's leadership, RH introduced innovative strategies including the elimination of traditional catalogs in favor of sourcebooks, the development of large-scale gallery formats exceeding 50,000 square feet to function as lifestyle destinations, and international expansion into markets like the United Kingdom and Canada.[18] The brand shortened its name to RH around 2012 to signal a shift from niche restoration items to aspirational luxury, further enhanced by ventures into hospitality with RH Guesthouses and restaurants.[15] As of fiscal year 2024, ending February 1, 2025, RH generated net revenues of $3.181 billion, a 5% increase from $3.029 billion in the prior year, with fourth-quarter revenues reaching $812 million, up 10% year-over-year.[19][20] The retailer operates approximately 82 RH Galleries, 40 RH outlet stores, one RH Guesthouse, and maintains a global supply chain with manufacturing partnerships primarily in Asia and Europe.[21] RH's business model prioritizes direct-to-consumer channels and a membership program offering perks like free design services, which accounted for a significant portion of sales, while navigating challenges such as supply chain disruptions and economic volatility through focused product curation and pricing discipline.[11]Science and technology
Relative humidity
Relative humidity (RH) is defined as the ratio of the partial pressure of water vapor in air to the saturation vapor pressure of water at the same temperature, expressed as a percentage.[22] This measure indicates the air's capacity to hold additional water vapor before reaching saturation, where condensation begins.[23] Unlike absolute humidity, which quantifies the mass of water vapor per unit volume regardless of temperature, RH is temperature-dependent: as temperature rises at constant absolute humidity, RH decreases because warmer air can hold more vapor.[24] The standard formula for RH is RH = (e / e_s) × 100, where e is the actual vapor pressure and e_s is the saturation vapor pressure at the given temperature.[25] Saturation vapor pressure e_s can be approximated using the Clausius-Clapeyron equation or empirical formulas like the Magnus-Tetens approximation: e_s ≈ 6.1078 × 10^{(7.5T)/(T+237.3)} hPa, with T in °C.[26] In practice, RH is often derived from measurements of dry-bulb temperature (ambient air) and wet-bulb temperature (cooled by evaporation), using psychrometric charts or equations such as those in ASHRAE standards, where the wet-bulb depression informs vapor pressure.[27] RH is measured using hygrometers, instruments that detect water vapor content through physical or chemical changes. Common types include psychrometers, which compare dry- and wet-bulb thermometers to calculate RH via evaporation-induced cooling; capacitive sensors, where a polymer dielectric changes capacitance with absorbed moisture; and chilled-mirror dew point hygrometers, which measure the temperature at which dew forms for precise vapor pressure determination.[28] These devices achieve accuracies of ±1-2% RH in controlled conditions, though calibration against traceable standards like NIST is essential for reliability in scientific applications.[29] In meteorology, RH influences cloud formation, precipitation, and visibility: values near 100% signal imminent dew, fog, or condensation nuclei for clouds, while low RH promotes clear skies and desiccation.[30] The National Weather Service reports RH to forecast heat stress indices like the heat index, which adjusts apparent temperature upward in high-RH environments (e.g., 80°F at 100% RH feels like 87°F).[30] Empirically, RH below 40% correlates with reduced convective activity, as insufficient moisture limits uplift for thunderstorms.[31] For human physiology, optimal indoor RH ranges from 30-50% to balance evaporative cooling and mucosal health; levels above 60% hinder sweat evaporation, elevating perceived temperature and heat illness risk, as seen in studies where 70% RH at 30°C showed no thermal comfort gain but increased physiological strain.[32] Conversely, RH below 30% dries skin and airways, exacerbating respiratory irritation, though high RH (>60%) fosters mold growth above 75%, triggering allergens.[33] These effects underscore RH's causal role in comfort via thermodynamics: high RH suppresses latent heat loss, while low RH accelerates it.[34]Rhodium (notation note)
In chemical notation, Rh is the internationally recognized symbol for rhodium, a chemical element classified as a transition metal in the periodic table.[35] This two-letter abbreviation follows the IUPAC standards for elemental symbols, derived directly from the element's name to ensure concise representation in formulas, equations, and scientific literature.[36] Rhodium has atomic number 45 and standard atomic weight of 102.90550(24).[37] Discovered in 1803 by English chemist William Hyde Wollaston while refining platinum ore, the element's name—and thus its symbol—stems from the Ancient Greek rhodon ("rose"), alluding to the rose-red hue of its salts in aqueous solution.[38] Wollaston isolated it as a distinct metal from crude platinum residues, noting its chemical inertness and high melting point of 1,964 °C.[39] The Rh notation distinguishes rhodium in contexts like catalysis (e.g., RhCl(PPh₃)₃ for Wilkinson's catalyst) and alloys, where its rarity—one of the scarcest non-radioactive elements, with annual global production around 30 metric tons as of 2023—underscores its value in industrial applications such as automotive catalytic converters.[40] Unlike abbreviations in other fields (e.g., RH for relative humidity), the capitalized Rh adheres to periodic table conventions, with isotopes denoted as ^{A}Rh (e.g., ^{103}Rh, the sole stable isotope comprising 100% of natural rhodium).[41]Medicine and biology
Rh factor
The Rh factor, also known as the Rhesus factor, refers to the presence or absence of a specific protein, the D antigen, on the surface of red blood cells. Individuals expressing this antigen are classified as Rh-positive, while those lacking it are Rh-negative.[4] [3] The factor was identified in 1940 by Karl Landsteiner and Alexander S. Wiener through experiments involving antibodies produced in rabbits immunized with red blood cells from rhesus monkeys, which cross-reacted with human cells bearing the antigen; the name derives from this primate source, though the antigen itself is human-specific.[4] [42] Genetically, the Rh factor is determined by alleles at the RHD gene locus on chromosome 1, inherited independently of ABO blood group genes. The Rh-positive phenotype is dominant, requiring only one functional RHD allele, whereas Rh-negative status results from inheriting two non-functional (null) alleles, often due to a large deletion in the RHD gene.[4] [43] Parental genotypes influence offspring outcomes: two Rh-positive parents can produce an Rh-negative child if both are heterozygous carriers of the null allele, with a 25% probability per pregnancy under Mendelian inheritance.[44][3] Prevalence of Rh-negative status varies significantly by population, reflecting genetic ancestry: approximately 15-16% of individuals of European descent are Rh-negative, compared to 1-3% in Asian populations and 5-8% in African populations, with a global average of about 15% Rh-negative.[45][46] In the United States, roughly 85% of the population is Rh-positive, with type O-positive being the most common overall blood type at 37-38%.[47] Clinically, Rh factor mismatches pose risks in transfusions and pregnancy. Rh-negative recipients can develop anti-D antibodies upon exposure to Rh-positive blood, leading to hemolytic transfusion reactions in future exposures; thus, Rh-negative individuals receive only Rh-compatible blood to prevent sensitization.[4] In obstetrics, an Rh-negative mother carrying an Rh-positive fetus risks alloimmunization if fetal blood enters her circulation, typically during delivery or miscarriage, prompting IgG anti-D production that crosses the placenta in subsequent pregnancies and destroys fetal Rh-positive red cells, causing hemolytic disease of the fetus and newborn (HDFN).[48][49] HDFN manifests as fetal anemia, hydrops fetalis, or neonatal jaundice, with historical mortality rates exceeding 50% before interventions; incidence has dropped dramatically since the 1960s due to Rho(D) immune globulin prophylaxis, administered at 28 weeks gestation and postpartum to unsensitized Rh-negative mothers, preventing antibody formation in over 99% of cases.[48][49] Rh incompatibility accounts for the majority of severe HDFN cases, though ABO mismatches contribute mildly; ethnic variations influence risk, with higher HDFN rates in populations with greater Rh polymorphism.[48][50]Places and geography
RH postcode area
The RH postcode area, also known as the Redhill postcode area, is a postal region defined by Royal Mail for mail delivery in the United Kingdom, primarily encompassing eastern Surrey and north-western West Sussex in England.[51] It includes urban centers such as Redhill, Reigate, Dorking, Horley, Crawley, Horsham, Burgess Hill, Haywards Heath, and East Grinstead, along with surrounding rural localities.[52] The area extends slightly into the London Borough of Croydon (for RH8 Kenley) and covers diverse terrain from the North Downs to the edges of the Weald.[53] This postcode area consists of 19 districts (RH1–RH19), each associated with specific post towns and managed through the Redhill Delivery Office.[54] The districts are distributed as follows:| Postcode district | Post town | Primary coverage examples |
|---|---|---|
| RH1 | Redhill | Redhill, Merstham |
| RH2 | Reigate | Reigate, Brockham |
| RH3 | Betchworth | Betchworth, Buckland |
| RH4 | Dorking | Dorking town center |
| RH5 | Dorking | Beare Green, Newdigate |
| RH6 | Horley | Horley, Gatwick Airport vicinity |
| RH7 | Lingfield | Lingfield, Dormansland |
| RH8 | Kenley | Kenley (Croydon borough) |
| RH9 | Godstone | Godstone, Oxted fringes |
| RH10 | Crawley | Crawley north |
| RH11 | Crawley | Crawley south, Ifield |
| RH12 | Horsham | Horsham town, Broadbridge Heath |
| RH13 | Horsham | Southwater, Rudgwick |
| RH14 | Billingshurst | Billingshurst, Wisborough Green |
| RH15 | Burgess Hill | Burgess Hill |
| RH16 | Haywards Heath | Haywards Heath |
| RH17 | Haywards Heath | Lindfield, Ardingly |
| RH18 | Forest Row | Forest Row, Coleman's Hatch |
| RH19 | East Grinstead | East Grinstead, Imberhorne |