变系数mKdV方程的对称群分类

利用古典无穷小算法,等价性变换技巧和有限维抽象李代数的分类理论给出了变系数mKdV方程的对称群分类。证明了在一维和二维可解李代数情况下不变的方程分别为4个和6个。并进一步证明了不存在容许有三维及更高维李代数下不变的方程。     

Instrument development of the Confidence in Home Care Services Questionnaire for use with elders and caregivers of Mexican descent

Mexican American elders use home care services less than non-Hispanic white elders, and a larger study is testing whether lack of confidence in home care services, measured by the Community Service Attitude Inventory, is a factor. In order to further develop the questionnaire for use with Mexican American elders and caregivers, qualitative interviews were conducted with Mexican American elders (n = 5), Mexican American caregivers (n = 5), and home care providers (n = 5). Content analysis of interviews supported 2 dimensions: confidence and fear/worry. The research team developed 29 items from the dimensions. Testing of the items (n = 15) suggested content validity and two additional items. The revised questionnaire was translated and tested for language equivalence in Spanish and English, assisted by a local community advisory council (n = 9). Through collaboration, bicultural/bilingual teams and community partners refined 1 instrument that can be used to measure one of many barriers to equity in health care services with vulnerable populations. Thematic findings may be incorporated into nurses' interventions as they offer home care services to families.     

Test for qualitative interaction in equivalence trials when the number of centres is large

We propose a generalized testing procedure to test for qualitative interaction in equivalence trails when the number of centres is large. The proposed testing procedure allows for an adaptable definition of qualitative interaction that can take into account the total number of centres. A tuning parameter k (k > or = 0) is introduced to quantify qualitative interaction. The testing procedure is proposed for equivalence trials with symmetric or asymmetric margins. In addition to the test procedure, we also provide explicit formulae for the power calculation. The proposed test is relatively easy to implement using any statistical software. Examples for detecting qualitative interaction are given to illustrate the method.     

Low-dose oral contraceptives: health consequences of discontinuation

Presently, the lowest effective estrogen dose available as a combination oral contraceptive (OC) in the United States is 20 μg of ethinyl estradiol (EE) with different progestins. Twenty micrograms of EE coupled with levonorgestrel results in fewer side effects and cycle control comparable with higher-dose pills. Differences between therapeutically equivalent and brand-name, low-dose oral contraceptives, with respect to the bioavailability of hormones, may interfere with contraceptive efficacy and increase breakthrough bleeding. One of the most common reasons why women discontinue OCs is increased breakthrough bleeding. Because after OC discontinuation most women switch to a less-effective method, or no method, of contraception, an increase in breakthrough bleeding could ultimately result in an increase in unintended pregnancy. Thus, substituting a therapeutically equivalent for a brand-name low-dose oral contraceptive may have significant clinical and economic effects on individual and public health.     

Arm–trunk coordination in the absence of proprioception

During trunk-assisted reaching to targets placed within arms length, the influence of trunk motion on the hand trajectory is compensated for by changes in the arm configuration. The role of proprioception in this compensation was investigated by analyzing the movements of 2 deafferented and 12 healthy subjects. Subjects reached to remembered targets (placed ~80° ipsilateral or ~45° contralateral to the sagittal midline) with an active forward movement of the trunk produced by hip flexion. In 40% of randomly selected trials, trunk motion was mechanically blocked. No visual feedback was provided during the experiment. The hand trajectory and velocity profiles of healthy subjects remained invariant whether or not the trunk was blocked. The invariance was achieved by changes in arm interjoint coordination that, for reaches toward the ipsilateral target, started as early as 50 ms after the perturbation. Both deafferented subjects exhibited considerable, though incomplete, compensation for the effects of the perturbation. Compensation was more successful for reaches to the ipsilateral target. Both deafferented subjects showed invariance between conditions (unobstructed or blocked trunk motion) in their hand paths to the ipsilateral target, and one did to the contralateral target. For the other deafferented subject, hand paths in the two types of trials began to deviate after about 50% into the movement, because of excessive elbow extension. In movements to the ipsilateral target, when deafferented subjects compensated successfully, the changes in arm joint angles were initiated as early as 50 ms after the trunk perturbation, similar to healthy subjects. Although the deafferented subjects showed less than ideal compensatory control, they compensated to a remarkably large extent given their complete loss of proprioception. The presence of partial compensation in the absence of vision and proprioception points to the likelihood that not only proprioception but also vestibulospinal pathways help mediate this compensation.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Evaluation of Latent Models Assessing Physical Fitness and the Healthy Eating Index in Community Studies: Time-, Sex-, and Diabetes-Status Invariance

Accurate measurement requires assessment of measurement equivalence/invariance (ME/I) to demonstrate that the tests/measurements perform equally well and measure the same underlying constructs across groups and over time. Using structural equation modeling, the measurement properties (stability and responsiveness) of intervention measures used in a study of metabolic syndrome (MetS) treatment in primary care offices, were assessed. The primary study (N = 293; mean age = 59 years) had achieved 19% reversal of MetS overall; yet neither diet quality nor aerobic capacity were correlated with declines in cardiovascular disease risk. Factor analytic methods were used to develop measurement models and factorial invariance were tested across three time points (baseline, 3-month, 12-month), sex (male/female), and diabetes status for the Canadian Healthy Eating Index (2005 HEI-C) and several fitness measures combined (percentile VO₂ max from submaximal exercise, treadmill speed, curl-ups, push-ups). The model fit for the original HEI-C was poor and could account for the lack of associations in the primary study. A reduced HEI-C and a 4-item fitness model demonstrated excellent model fit and measurement equivalence across time, sex, and diabetes status. Increased use of factor analytic methods increases measurement precision, controls error, and improves ability to link interventions to expected clinical outcomes.     

The acquisition of stimulus equivalence in individuals with fragile X syndrome

Background Few studies have employed stimulus equivalence procedures to teach individuals with intellectual disabilities (IDs) new skills. To date, no studies of stimulus equivalence have been conducted in individuals with fragile X syndrome (FXS), the most common known cause of inherited ID. Method Five adolescents with FXS were taught basic math and geography skills by using a computerized stimulus equivalence training programme administered over 2 days in 2‐h sessions. Results Four of the five participants learned the math relations, with one participant demonstrating stimulus equivalence at post‐test. Three of the five participants learned the geography relations, with all three of these participants demonstrating stimulus equivalence at post‐test. Conclusions These data indicate that computerized stimulus equivalence procedures, conducted in time‐limited sessions, may help individuals with FXS learn new skills. Hypotheses concerning the failure of some participants to learn the training relations and to demonstrate stimulus equivalence at post‐test are discussed.     

Critical review of the international assessments of health-related quality of life

This paper reviews the international adaptation and use of generic health quality of life measures over the last several years, including the Nottingham Health Profile (NHP) the Sickness Impact Profile (SIP), the Medical Outcomes Short-Form 36 (MOS SF-36), the EuroQol, and Dartmouth COOP Charts. International work with disease or condition specific HRQL measures is exemplified with the European Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (QLQ), and the Spitzer Quality of Life (QL) Index. Progress towards cross national measurement equivalence in HRQL measures reported in the literature has been uneven. Results show that the development of language-adapted versions of HRQL measures to date have mostly concerned translation issues, within the context of independently conducted studies. Substantially less focus has been placed on psychometric equivalence across language versions necessary for coordinated international studies, such as multi-national clinical trials. However, this picture is rapidly changing with recent projects underway to develop and refine new or existing HRQL measures. Overall, the lack of prominent differences found between countries in ranking of health states in major HRQL measures supports the feasibility of developing internationally applicable HRQL instruments. Recommendations are made for additional data needed to better ascertain the degree of measurement equivalence developed in the various versions of each instrument reviewed.Preparation of this document was supported by a grant from the Burroughs Wellcome Foundation and by the Bowman Gray School of Medicine.