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CDR

Carbon Dioxide Removal (CDR) encompasses anthropogenic techniques that actively extract (CO₂) from the atmosphere and store it durably in geological formations, soils, , or oceans to offset persistent and support net-zero or negative emissions goals. These methods include engineered systems such as (DAC) with geological storage and bioenergy with (BECCS), as well as enhanced natural processes like , , and enhanced rock weathering. Achieving climate stabilization below 2°C in integrated assessment models typically requires deploying CDR at scales of 5–10 s of CO₂ removed annually by mid-century, far exceeding current levels where technological approaches capture less than 0.01 GtCO₂ per year and contribute around 2 GtCO₂ but often lack additionality or permanence. High costs—such as hundreds of dollars per ton for DAC—energy-intensive operations, and resource demands like land for BECCS or minerals for pose scalability barriers, compounded by unproven deployment at levels despite pilot successes. A central controversy surrounds CDR's potential , where anticipation of future removals incentivizes delayed and higher interim emissions, risking overshoot of carbon budgets if technologies underperform; empirical analyses indicate this effect could minimize emissions reductions before mid-century under optimistic CDR assumptions. Additional risks include ecological side effects, such as from large-scale plantations or ocean disruptions from marine CDR, underscoring the need for emissions cuts as the primary strategy absent robust empirical validation of CDR's causal efficacy at required volumes.

Military

Commander

Commander (abbreviated CDR) is a commissioned officer primarily used in forces, equivalent to the O-5 in the United States . Holders of this rank exercise command authority over personnel, units, or vessels, with responsibilities including operational leadership, tactical decision-making, and administrative oversight. The term derives from the Latin mandare, meaning "to commit" or "entrust," reflecting the role of delegating authority and control. In the United States Navy, the rank of was formalized in the early as the service evolved from post-Revolutionary War traditions, where senior lieutenants commanding smaller warships were designated "lieutenant commanding." By 1838, the rank was distinct, with commanders typically leading destroyers, frigates, or shore-based squadrons today, while also serving as department heads on aircraft carriers or executive officers in larger commands. consists of three half-inch gold stripes on sleeves or shoulder boards with two silver stars over a silver spread . Promotion to commander requires approximately 16-18 years of service, competitive selection boards, and demonstrated performance in prior roles like . Equivalents exist across armed forces: in the US , , and Marine Corps, it aligns with (O-5), who commands s of 300-1,000 personnel or equivalent aviation units. In the US Coast Guard, mirrors the and insignia, often overseeing cutters or sector operations. Internationally, the Royal 's , established by the 18th century, holds similar standing above and below , commanding frigates or as principal warfare officers. While "" functions as a title in land armies (e.g., , regardless of ), the formal CDR designation remains naval-centric.

Engineering

Critical design review

The Critical Design Review (CDR) is a formal, multi-disciplined technical review conducted in projects, particularly in , , and complex development, to determine if the system's detailed design is mature enough to proceed to fabrication, integration, and testing phases. It evaluates whether the design, as documented in product specifications for each , meets allocated functional and performance requirements while identifying and mitigating remaining risks. In U.S. government acquisition processes, the CDR typically follows the Preliminary Design Review (PDR) and precedes system verification activities, serving as a gate to baseline the detailed "build-to" or "code-to" documentation. During the CDR, an independent review board assesses the completeness of engineering analyses, such as failure modes, effects, and criticality analysis (FMECA), thermal and structural simulations, and interface verifications, ensuring no critical design gaps remain. Key success criteria include confirmation that hardware and software specifications are detailed enough to achieve system performance without major redesigns, that production and test plans are feasible, and that affordability goals align with the design baseline. The review often involves scrutiny of trade studies, risk assessments, and verification plans, with outputs establishing the initial product baseline and authorizing resource allocation for manufacturing. For NASA projects, the CDR verifies that manufacturing and test procedures will produce a system meeting mission requirements with acceptable risk, drawing from lessons in prior missions where incomplete CDRs led to costly rework. Failure to rigorously apply CDR criteria can result in downstream issues, such as failures or budget overruns, as evidenced in programs where immaturity at this stage propagated unaddressed risks into production. Standards from organizations like the Department of Defense emphasize tailoring CDR depth to program complexity, with lower-tier reviews for subsystems feeding into system-level evaluations. In practice, effective CDRs incorporate peer-reviewed data and empirical modeling to validate causal links between design choices and performance outcomes, prioritizing verifiable evidence over assumptions.

Computing

CAR and CDR

In the Lisp family of programming languages, and are primitive functions that operate on cons cells, the foundational for representing pairs and linked lists. A cons cell comprises two slots: the CAR slot, which holds an arbitrary Lisp object such as an or another cons cell, and the CDR slot, which typically points to the next cons cell in a list or holds another object. The function returns the contents of the first slot, while the function returns the contents of the second slot. The terms derive from macros on the computer, the hardware used for early implementations in the late 1950s. CAR expands to "Contents of the Address [Register] part," referring to the register's address field (bits 0-8 and 9-35 on the 704), and CDR to "Contents of the Decrement [Register] part," referring to the decrement field (bits 36-63). These macros were defined to extract portions of a machine word treated as a pair of pointers, influencing 's design by John McCarthy and Steve Russell around 1958-1960. Lisp retained the names despite their hardware-specific origins, embedding them as core primitives rather than abstracting them away. Cons cells enable recursive list construction via the function, which creates a new cons cell with the provided object in the CAR slot and the existing structure in the CDR slot; for instance, (cons 'a '(b c)) yields (a b c). List access patterns rely on these primitives: CAR retrieves the head element, and CDR the tail, allowing traversal as (car lst) for the first item and (cdr lst) for the remainder. This structure supports Lisp's , where code and data share the same form, but exposes implementation details unlike higher-level abstractions in other languages. Lisp dialects compose and into shorthand functions for deeper access, such as CADR (CAR of CDR, equivalent to the second element) or CDDR (CDR of CDR, skipping the first two elements), with up to four levels standardized (e.g., CADADR, CDADAR). These are generated programmatically in implementations but named conventionally; for example, defines 14 such functions. While some dialects provide mnemonic aliases like first for CAR and for CDR to aid readability, CAR and CDR remain the low-level, efficient operations directly mapping to machine instructions in early systems, preserving Lisp's emphasis on symbolic computation over hardware abstraction.

Call detail record

A call detail record (CDR) is a data record generated by telephone exchanges, switching centers, or other that captures about a communication event, such as a voice call, , or data session, without including the actual content of the communication. These records are produced in real-time or near-real-time by network elements during call setup, processing, and teardown. CDRs form the basis for subscriber billing in , with formats often standardized for , such as those outlined in ETSI TS 132 250, which defines charging data records that encompass traditional CDRs. Typical fields in a CDR include the calling party number, called party number, call start , call duration, call type (e.g., voice, , or GPRS data), originating and terminating network identifiers, and routing information such as ID or group. Additional fields may cover chargeable units, service types, or diagnostic codes for failed attempts, with exact contents varying by equipment vendor and regulatory requirements. For instance, in IP-based systems like those using , CDRs might incorporate details or quality metrics. Telecommunications operators primarily use CDRs for accurate billing and revenue assurance, aggregating usage data to generate invoices based on tariffs for call duration, destination, and time of day. They also enable fraud detection by identifying anomalies, such as unusual call volumes, international patterns, or rapid successive attempts indicative of schemes like international revenue share fraud. Network optimization relies on CDR analysis for traffic engineering, coverage assessment, and performance monitoring, while law enforcement accesses them under legal warrants for investigations, as CDRs provide location approximations via cell tower data without revealing conversation contents. Privacy implications arise from CDR retention, as can reveal behavioral patterns like social networks or movement histories; regulations such as the EU's or U.S. govern access and storage durations, typically 6-12 months for operators. Unlike call content, which requires higher legal thresholds for , CDRs' nature has sparked debates on , with empirical studies showing they enable probabilistic tracking accurate to within 100-500 meters in urban areas. Operators must balance utility for fraud prevention—where on CDRs detects up to 90% of anomalies in systems—with minimization to mitigate risks of misuse.

Content disarm and reconstruction

Content Disarm and Reconstruction (CDR) is a cybersecurity technology that neutralizes file-borne threats by deconstructing incoming files, eliminating potentially malicious elements such as executable , macros, embedded objects, scripts, and hyperlinks, and then rebuilding a sanitized version using only verified safe components. This proactive method assumes all active content in files poses a , enabling against both known and zero-day exploits without dependence on signature-based detection or behavioral analysis. The CDR process begins with file decomposition, where the input—typically office documents (e.g., , Excel, PowerPoint), PDFs, or images—is parsed into atomic elements like text streams, , vector shapes, and . Threat-prone components are discarded or neutralized based on file-type-specific whitelists that define allowable structures, such as permitting only static text and images while excluding in PDFs or VBA macros in files. Reconstruction follows, assembling a new file compliant with the original format's benign specifications, preserving core content integrity for usability while ensuring no exploitable code remains. This end-to-end occurs in or near-real-time, often within security gateways, with processing times under one second for standard files. CDR excels in defending against advanced threats embedded in weaponized documents, including ransomware delivery via attachments, vectors exploiting vulnerabilities like CVE-2017-11882 in or CVE-2021-40444 in MSHTML, and supply-chain attacks via tainted files. By treating files as untrusted by default, it integrates with zero-trust architectures, complementing sandboxing and antivirus but surpassing them in handling polymorphic or obfuscated payloads that evade detection. Deployment occurs in email security platforms, secure file transfer protocols (e.g., ), web portals, and endpoint protection, scanning inbound and outbound traffic to prevent lateral movement in networks. Limitations include potential minor alterations to file or functionality, such as flattened layouts in complex spreadsheets or removed interactive elements, though these are minimized through precise algorithms. Not all file types are equally supported; binaries (.exe) or archives may require hybrid approaches, as full disarm could render them non-functional. Efficacy relies on up-to-date whitelists, with vendors like and reporting near-100% threat neutralization rates in controlled tests against exploit kits. While no formal NIST standard governs specifically, it aligns with NIST SP 800-53 controls for media sanitization (e.g., SC-8) and risk-based file handling in the Cybersecurity Framework.

Electronics and media

Clock and data recovery

Clock and data recovery (CDR) is a fundamental process in high-speed communication systems, where a extracts an embedded from an incoming lacking a dedicated timing reference, enabling precise data retiming and sampling to minimize bit errors. This technique is critical for maintaining in environments prone to , , and distortion, such as long-distance transmission lines or optical fibers, by regenerating a clean clock aligned to data transitions. In (NRZ) encoding, prevalent in protocols, data edges provide the primary timing cues, as the signal lacks a at the . The core operation of CDR relies on a (PLL) architecture, comprising a that compares recovered clock edges against incoming data transitions, a low-pass loop filter to suppress high-frequency , and a (VCO) whose frequency is adjusted via feedback to achieve alignment. detectors vary by type: linear detectors like the Hogge provide low- performance with a of approximately 0.5 but require higher , while binary detectors such as the offer higher for faster locking at the cost of increased from sampling errors. Loop , often tuned to 1-10 MHz, trades off attenuation against tracking speed and tolerance for frequency offsets up to ±500 ppm. CDR architectures span analog PLLs for multi-gigabit rates, leveraging continuous-time components for low , and all-digital implementations that enhance scalability in processes for integration with . Alternative approaches include delay-locked loops (DLLs) for reduced accumulation over multiple stages and methods that use multiple phases from a fixed clock to detect data without a VCO, though they demand higher power. In optical and media applications, CDRs support standards like /SDH at 622.08 Mbps or up to 1.25 Gbps, often incorporating frequency acquisition via training sequences to initialize locking before phase fine-tuning. Challenges in CDR design include managing low transition densities in data patterns, which prolong locking and risk anomalous behaviors like or sidelocking, and optimizing for variable conditions such as Doppler shifts in media. Performance is evaluated via eye diagrams assessing margins and bit-error rates, with modern devices like the ADN2855 employing external loop filters for customizable damping. These circuits underpin in PCIe, USB, Ethernet, and high-speed video interfaces, ensuring reliable across media transmission.

Compact disc recordable

The Compact Disc Recordable (CD-R) is a write-once optical disc format designed for storing digital data, audio, or video, with a standard capacity of approximately 650 megabytes (74 minutes of audio) on a 12-centimeter disc. Unlike pressed compact discs, which use physical pits molded into the substrate, CD-R media employs a photosensitive organic dye layer that permanently alters under laser exposure to encode data as non-reflective regions mimicking those pits. This allows compatibility with standard CD readers, though early drives required specific support for variable reflectivity. Development of CD-R stemmed from the original standard co-created by and in 1980, with the recordable variant conceptualized in 1988 to enable for archiving and duplication. The format was formalized in Part II standard in 1990, specifying the dye-based recording mechanism and ensuring interoperability with existing CD playback systems. Initial commercial CD-R drives emerged in 1992 for professional applications, such as and mastering, but high costs—often exceeding $10,000—limited adoption until consumer models dropped below $1,000 in 1995, spurring widespread use for data backup and music burning. In operation, a CD-R uses a high-power (typically 4-8 mW) to heat the layer, causing it to darken or and reduce reflectivity in targeted spiral tracks, while a lower-power reading (around 0.5 mW) detects these changes as during playback. The disc's structure includes a base, the recording layer, a metallic reflector (usually or silver alloy), and a protective . Recording speeds evolved from 1x (150 KB/s) to high-speed variants up to 48x via standards like ECMA-394, which define write strategies for types supporting 16x to 48x rates, though faster speeds increase error risks without advanced error correction. relies on the ATIP (Absolute Time In Pregroove) track for addressing and the for logical organization, enabling cross-platform readability. CD-R discs exhibit high archival stability when stored properly—away from heat, humidity, and UV light—with dye degradation typically occurring over decades rather than years, outperforming magnetic tapes in longevity for . However, once-written discs cannot be erased or overwritten, distinguishing them from rewritable formats introduced later in 1996. Adoption peaked in the late and early for personal computing and music production, before declining with the rise of flash and streaming, though CD-R remains relevant for specialized archiving due to its low cost per gigabyte in bulk and resistance to magnetic interference.

Medicine

Clinical dementia rating

The (CDR) is a clinician-administered, informant-based instrument designed to stage the severity of , particularly in and related disorders, through evaluation of cognitive and functional impairments across multiple domains. It employs a format where a trained rater assesses the patient and a knowledgeable , such as a family member, to rate performance levels. The scale yields both a global score reflecting overall severity and a sum-of-boxes (CDR-SB) score that aggregates domain ratings for finer granularity in tracking progression. Originally developed in 1982 by Hughes, Berg, Danziger, and colleagues at , the was created to provide a standardized method for classifying stages in research cohorts, addressing inconsistencies in prior clinical judgments. Early validation occurred within clinics, where it demonstrated utility in distinguishing normal cognition from and progressive phases. Subsequent adaptations, such as the CDR-SB introduced for enhanced sensitivity to change, have been integrated into longitudinal studies like the Neuroimaging Initiative. Assessment involves rating six domains: , , and problem-solving, affairs, and hobbies, and . Each domain is scored on a 5-point ordinal scale: 0 (no impairment), 0.5 (questionable impairment), 1 (mild), 2 (moderate), or 3 (severe), with weighted heavily in deriving the global score via predefined algorithms that prioritize impairments in daily functioning over isolated cognitive deficits. For instance, a global CDR of 0 indicates no , 0.5 suggests very mild or questionable , 1 denotes mild , 2 moderate, and 3 severe. The CDR-SB, ranging from 0 to 18, sums these ratings and correlates strongly with neuropathological burden in autopsy-confirmed cases. Reliability studies report high inter-rater agreement, with intraclass correlation coefficients exceeding 0.80 in multicenter trials, supporting its use across diverse clinical settings. Validity is evidenced by strong associations with neuroimaging biomarkers, neuropsychological tests, and functional outcomes, positioning the CDR as a gold standard for dementia staging despite limitations in cultural adaptations or non-Alzheimer's etiologies. In practice, it facilitates trial eligibility, progression monitoring, and prognostic estimates, with a change from CDR 0.5 to 1 often signaling transition to clinically manifest dementia.

Environmental science

Carbon dioxide removal

Carbon dioxide removal (CDR) encompasses technologies, practices, and approaches that extract CO₂ from the atmosphere and store it durably in geological, terrestrial, or oceanic reservoirs to counteract emissions. Unlike , which prevents CO₂ release, CDR addresses legacy atmospheric accumulations, with global models indicating a need for 7–9 billion tonnes of annual removal by mid-century to align with targets limiting warming to 1.5–2°C. Deployment remains limited, with current removals under 0.1 GtCO₂/year, constrained by high costs, energy demands, and environmental trade-offs. CDR methods divide into biological (leveraging ecosystems like forests and soils) and engineered (using chemical or physical processes) categories, each with varying scalability and permanence. Biological approaches, such as and , enhance natural carbon sinks but face limits from land competition and reversal risks like fires or decay. Engineered methods include (DAC), which uses chemical sorbents to bind dilute atmospheric CO₂ (0.04% concentration), followed by energy-intensive release and storage; costs range from $94–$600 per tonne as of 2024, with projections for reductions via modular designs but thermodynamic barriers persisting due to low CO₂ . Bioenergy with carbon capture and storage (BECCS) combines biomass combustion for energy with CO₂ capture (typically 90% efficiency) and geological sequestration, yielding negative emissions if biomass regrowth sequesters more CO₂ than emitted during production. Feasibility hinges on sustainable biomass sourcing; large-scale deployment could remove 3–5 GtCO₂/year but requires vast land (up to 25% of global arable area for 5 Gt), risking food security and biodiversity loss, with only pilot projects operational as of 2024. Enhanced rock weathering accelerates natural silicate mineral dissolution to form bicarbonates, potentially removing 0.5–4 GtCO₂/year via cropland application of crushed basalt, though field studies show rates 10–100 times slower than lab models due to soil hydrology limits. Ocean-based CDR, such as alkalinity enhancement via dissolving minerals like , boosts seawater's CO₂ capacity and counters acidification, with theoretical potential exceeding 1 GtCO₂/year at scale. However, risks include trace metal , altered gradients disrupting webs, and uncertain long-term verification, prompting calls for precautionary governance amid nascent trials. Economic analyses project CDR costs falling with innovation but emphasize that overreliance delays emissions cuts, as no method achieves gigatonne-scale deployment without infrastructure investments exceeding trillions annually. Monitoring permanence remains critical, as reversals (e.g., from droughts or leaks) could undermine net benefits, underscoring CDR's role as a supplement, not substitute, for decarbonization.

Organizations

Council for Development and Reconstruction

The Council for Development and Reconstruction (CDR) is an autonomous Lebanese public institution established by Decree No. 5 on January 31, 1977, amid the (1975–1990), with the mandate to plan, finance, and execute national reconstruction and development initiatives. Initially focused on addressing war-induced infrastructure devastation, the CDR was granted broad financial and administrative powers, including the ability to borrow internationally and manage donor funds, reporting directly to the and rather than line ministries. The CDR's responsibilities encompass overseeing major projects, such as roads, bridges, systems, grids, and facilities, often through international tenders and partnerships with donors like the and . By 2024, it managed a including over $1.2 billion in outstanding loans for redevelopment, with ongoing initiatives like the Roads and Employment Project aimed at enhancing connectivity and job creation. Leadership is vested in a —currently Mohammad Ali Kabbani—who directs operations from the headquarters in Beirut's Riad El Solh area, supported by technical committees for , feasibility studies, and project supervision. Despite its central role in post-war recovery, the CDR has faced challenges including delays from Lebanon's political instability, economic crises since 2019, and the 2020 Beirut port explosion, which necessitated additional reconstruction funding channeled through the entity. Its processes, detailed on its official portal, emphasize competitive bidding for , though execution has been hampered by fiscal constraints and sectarian dynamics inherent to Lebanon's system. The institution continues to prioritize infrastructure resilience, with recent activities including environmental impact assessments and urban development plans aligned with national recovery frameworks.

Commission on Dietetic Registration

The Commission on Dietetic Registration (CDR) serves as the credentialing agency for dietetics practitioners in the United States, administering examinations, maintaining professional registries, and enforcing recertification standards for credentials such as Registered Dietitian Nutritionist (RDN) and Nutrition and Dietetics Technician, Registered (NDTR). Established in 1969 as an administratively autonomous entity under the American Dietetic Association (now the Academy of Nutrition and Dietetics), CDR initially grandfathered 19,457 practitioners into its registry upon inception. Its core functions encompass credentialing through rigorous eligibility verification and national examinations—delivered via Pearson VUE testing centers—along with oversight of continuing professional education (CPE) requirements, which CDR pioneered for RDNs in 1969 and extended to NDTRs in 1986. To obtain the RDN credential (interchangeable with , with "RDN" adopted to highlight nutritional expertise), candidates must complete an accredited didactic in dietetics, fulfill supervised practice hours via an accredited coordinated or , and pass CDR's registration , which assesses competencies in areas like care, clinical interventions, and foodservice . The exam pass rates vary by type but generally exceed 80% for first-time test-takers from accredited pathways as of recent data. NDTR certification follows a similar but requires an associate's from an accredited dietetic technician and a distinct focused on supportive roles in care. CDR also offers advanced board certifications in specialties such as renal , oncology , and sports dietetics, requiring additional exams and CPE portfolio submissions beyond core recertification. Recertification mandates 75 CPE credits every five years for RDNs and 50 for NDTRs, emphasizing updates to ensure competency amid evolving nutritional science. CDR enforces credential use guidelines, prohibiting misuse of designations like or RDN by non-registrants, and provides verification services for licensure in states requiring such credentials—currently 45 states for RDNs. While CDR's standards align with bodies like ACEND, critics have noted potential conflicts from the Academy's historical influences on broader dietetics guidelines, though CDR's operational limits direct overlap in decisions. The organization maintains a strategic focus on practice-area and of registry , supporting over 100,000 active credential holders as of the latest reports.