HAC
Human artificial chromosomes (HACs) are synthetic, non-integrating genetic constructs designed to replicate autonomously and segregate during cell division in human cells, serving as vehicles for large-scale gene delivery and expression without disrupting the host genome.[1] Developed to overcome limitations of viral vectors and plasmids, which often suffer from insertional mutagenesis risks or size constraints, HACs incorporate essential chromosomal elements such as centromeres, telomeres, and origins of replication to maintain stability over multiple generations.[2] Key achievements include the creation of functional HACs capable of expressing full-length human genes, with applications in modeling genetic diseases and potential gene therapies for conditions like hemophilia or muscular dystrophy.[3] Recent methodological advances, such as epigenetic manipulation of centromeres to minimize multimerization and enable single-copy formation, have improved efficiency and reduced instability issues that previously hindered practical use.[4][5] While promising for synthetic biology and clinical translation, HAC technology faces ongoing challenges in scalability, immune responses, and long-term epigenetic fidelity, with empirical data emphasizing the need for rigorous validation beyond in vitro models.[6]Military and Defense
Honourable Artillery Company
The Honourable Artillery Company (HAC) was incorporated by royal charter on 25 August 1537, granted by King Henry VIII for the purposes of military exercise, training, and enhancing the defence of the realm.[7] As the oldest regiment in the British Army and the second most senior unit in the Army Reserve, it has maintained continuous existence without amalgamation, a distinction shared with only a few other units such as the Foot Guards regiments.[7][8] The HAC comprises two integrated components: the Regiment, an operational Army Reserve unit, and the Company, a membership organization overseeing civil, financial, and ceremonial affairs.[7] The Regiment, based at Finsbury Barracks in London, specializes in surveillance and target acquisition (STA), intelligence, surveillance, and reconnaissance (ISR), and field artillery support, including light gun operations and close support roles.[8] Its subunits include 1 (Special Operations) Squadron, dedicated ISR squadrons, and A (1st City of London) Battery, enabling capabilities such as forward patrols for target identification and long-range fire support.[8] Historically, HAC elements fought in major conflicts, forming three infantry battalions and five artillery batteries in World War I, and four artillery regiments in World War II; post-1945 deployments began in 1995 in Bosnia, followed by commitments in Iraq and Afghanistan, with over 300 personnel involved in operations and training exercises across 15 years.[8] The Company maintains approximately 2,500 members, including around 400 active participants in the Regiment or affiliated units, and manages HAC facilities such as Armoury House while supporting a benevolent fund.[7] It oversees ceremonial detachments, including the Pikemen & Musketeers who serve as the Lord Mayor of London's bodyguard, the Light Cavalry squadron escorting the Lady Mayoress, and the Corps of Drums; these units perform in state events, such as gun salutes at the Tower of London.[7][8] Additionally, the HAC supports two Combined Cadet Force contingents and a City of London Special Constabulary unit, alongside affiliations with units in the United States and South Africa.[7]Honorary Air Commodore
An Honorary Air Commodore (HAC) is an honorary appointment within the Royal Air Force (RAF), typically associated with specific squadrons or units of the Royal Auxiliary Air Force (RAuxAF), bestowed upon prominent civilians, retired RAF officers, or members of the royal family to strengthen ties between military aviation and civilian sectors.[9][10] The role emphasizes advocacy, representation, and support for the unit without granting operational command or rank privileges equivalent to active service air commodores, who hold a one-star officer position comparable to a brigadier in the British Army.[9] The appointment originated in the interwar period with the expansion of auxiliary air units, as evidenced by Winston Churchill's designation as Honorary Air Commodore of No. 615 (County of Surrey) Squadron, RAuxAF, on September 1, 1939, shortly before the outbreak of World War II, to bolster public and political engagement with reserve forces.[11] Nearly all RAuxAF squadrons and units maintain an HAC, selected for their influence in business, community, or public life to promote recruitment, funding, and awareness of RAF activities.[9] HACs participate in an annual conference where they receive briefings on RAF strategic priorities, fostering informed civilian input into reserve force development.[9] Royal family members often hold prefixed "Royal Honorary Air Commodore" titles for regular RAF stations, distinct from unit-specific HAC roles in the RAuxAF; for instance, Catherine, Princess of Wales, was appointed Royal Honorary Air Commodore of RAF Coningsby in November 2023 and conducted her inaugural station visit on October 3, 2025, engaging with personnel and operations.[12] Similarly, Queen Camilla serves as Honorary Air Commodore for RAF Halton and RAF Leeming, roles involving ceremonial duties and morale support.[13] These appointments, announced via official RAF channels, underscore the tradition's evolution from wartime mobilization aids to modern public-military partnerships, with transitions like King Charles III assuming Royal Honorary Air Commodore of RAF Marham in August 2023 following Queen Elizabeth II's tenure.[14] Notable non-royal HACs include Veronica Pickering, appointed to No. 504 (County of Nottingham) Squadron in 2021 for her community leadership, and various high-profile figures installed as county representatives, such as the 2023 High Sheriff of Nottinghamshire from the same squadron.[10][15] The title remains a ceremonial honor, with HACs contributing to events like squadron awards and commemorations, as seen in the 2024 Clyde Trophy presentation linked to a former HAC's legacy.[16]Healthcare
Hospital-acquired condition
A hospital-acquired condition (HAC) refers to a medical condition that develops in a patient during an inpatient hospital stay and was not present on admission.[17] These conditions encompass both infectious and noninfectious complications, such as healthcare-associated infections (HAIs), procedural errors, and injuries resulting from hospital care processes.[18] HACs are tracked primarily through administrative coding data, with the Centers for Medicare & Medicaid Services (CMS) maintaining a standardized list under the Deficit Reduction Act of 2005, which identifies 14 categories reasonably preventable through evidence-based practices.[18] In the United States, HACs contribute to significant morbidity, mortality, and healthcare costs. On any given day, approximately 1 in 31 hospitalized patients has at least one HAI, a key subset of HACs, with national point prevalence surveys estimating overall HAI rates at 3.2% to 4.0% in acute care settings as of 2023.[19] [20] Broader HAC rates, including noninfectious events, have declined over time; for instance, from 2014 to 2017, national HAC rates fell by 13%, averting an estimated 350,000 incidents and saving $7.8 billion in costs.[21] However, preventable HACs still impose an annual economic burden of $28.4 billion to $45 billion in direct treatment costs, with additional indirect expenses from extended stays and readmissions.[22] Examples of CMS-designated HACs include:- Foreign object retained after surgery
- Air embolism
- Blood incompatibility
- Stage III and IV pressure ulcers
- Falls and trauma
- Catheter-associated urinary tract infections (CAUTIs)
- Central line-associated bloodstream infections (CLABSIs)
- Surgical site infections following certain procedures, such as colon surgery or abdominal hysterectomy[18] [23]