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The mathematical methods that have been used to analyze the statistical properties of boson fields, and in particular the coherence of photons in quantum optics, have their counterparts for Fermi fields. The coherent states, the displacement operators, the P-representation, and the other operator expansions all possess surprisingly close fermionic analogues. These methods for describing the statistical properties of fermions are based upon a practical calculus of anti-commuting variables. They are used to calculate correlation functions and counting distributions for general systems of fermions.

Older Americans are now working longer than pre-1980s trends would have predicted. Given concerns about the traditional sources of retirement income (Social Security, employer pensions, and prior savings), older Americans may have to rely more on earnings. This article suggests that many are already doing so by moving to bridge jobs after leaving their career employment.

The "do-it-yourself" approach to retirement planning-with individuals managing a large portion of their retirement finances-is now common among older Americans. This change in the retirement environment, combined with a significant and persistent cyclical downturn, may have long-lasting effects and suggests that the concept of retirement in the United States will continue to evolve.

BACKGROUND: Gout is a common cause of inflammatory arthritis in the United States, and its prevalence has increased in recent decades, especially among older adults. Older adults with gout are of particular interest because they tend to experience higher rates of tophi, an advanced stage of gout, than do younger patients.OBJECTIVE: For older adults with gout to (1) assess health care utilization and costs from a third-party payer perspective; (2) evaluate health care costs related to tophi; and (3) explore the relationship between elevated serum uric acid (UA) level, an indicator of disease control, and health care utilization.METHODS: Data were extracted from the Integrated Healthcare Information Services (IHCIS) claims database (1999)(2000)(2001)(2002)(2003)(2004)(2005), which includes approximately 40 private health plans in the United States for approximately 13 million beneficiaries, about 4% of whom are aged 65 years or older. Patients were included in the study if they: (1) had 2 diagnoses of gout (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code of 274.xx) on separate medical claims or 1 gout diagnosis plus at least 1 gout-related pharmacy claim (i.e., allopurinol, probenecid, colchicines, or sulfinpyrazone); (2) were at least 65 years old at the first diagnosis date (study index date); and (3) had 1 year of continuous eligibility both before and after the study index date. A comparison sample of elderly members without gout was selected using a 1:1 match to gout patients based on age, gender, and geographic region. Individuals in the comparison group also had 1 year of continuous eligibility both before and after the study index date, defined as the same index date as the respective matched gout patient. Patients with possible tophi were identified from at least 1 medical claim with an ICD-9-CM code 274.8x (274.81=gouty tophi of the ear; 274.82 = gouty tophi of other sites except ear; 274.89 = gout with other specified manifestations) during the 12-month study period following the study index date. Additionally, a subgroup of gout patients with at least 1 serum UA measure was selected. Patients were divided into 3 groups according to their serum UA level on the earliest test date (serum UA index date): low (< 6 mg per dL), moderate-high (6-8.99 mg per dL), and very high (≥ 9 mg per dL). Health care utilization was categorized into inpatient services, outpatient services, emergency room services, other medical services, and use of prescription drugs. Medical services were classified by the place of service indicated in the claim. Medical services costs and pharmacy costs were defined as the amount paid to the provider plus member cost share (e.g., deductible, copayment). Two types of costs were assessed in the analysis: total all-cause health care costs and gout-related costs, defined as costs associated with a claim with a primary or secondary diagnosis of gout (ICD-9-CM code 274.xx). Differences in total all-cause health care costs were calculate...

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