Modeling scanning probe microscope lateral dynamics using the probe-surface interaction signal

In this paper, a novel scanning probe microscope (SPM) modeling technique is presented. The novelty of this technique is that it exploits the SPM's probe-surface interaction measurement capabilities [e.g., the topography signal in atomic force microscopy (AFM)] to determine the SPM's lateral positioning dynamics. SPM operation speed is limited due to mechanical vibrations induced by movement of the SPM nanopositioner. In order to facilitate high-speed SPM operation, the dynamics of the SPM can be modeled and used to design feedforward and feedback controllers that reduce nanopositioner vibrations. The proposed technique seeks to develop a transfer function model of the SPM dynamics using only the SPM probe-surface interaction signal obtained while scanning a calibration sample. The technique is presented in the context of an AFM example, errors associated with the method are analyzed, and the method is experimentally verified using a commercial AFM. Experimental modeling results show that the method is capable of modeling the dynamics of SPM systems.

Iterative image-based modeling and control for higher scanning probe microscope performance

In this article, we develop an image-based approach to model and control the dynamics of scanning probe microscopes (SPMs) during high-speed operations. SPMs are key enabling tools in the experimental investigation and manipulation of nano- and subnanoscale phenomena; however, the speed at which the SPM probe can be positioned over the sample surface is limited due to adverse dynamic effects. It is noted that SPM speed can be increased using model-based control techniques. Modeling the SPM dynamics is, however, challenging because currently available sensing methods do not measure the SPM tip directly. Additionally, the resolution of currently available sensing methods is limited by noise at higher bandwidth. Our main contribution is an iterative image-based modeling method which overcomes these modeling difficulties (caused by sensing limitations). The method is applied to model an experimental scanning tunneling microscope (STM) system and to achieve high-speed imaging. Specifically, we model the STM up to a frequency of 2000 Hz (corresponds to approximately 23 of the resonance frequency of our system) and achieve approximately 1.2% error in 1 nm square images at that same frequency.

The structure of the ultraspiracle ligand-binding domain reveals a nuclear receptor locked in an inactive conformation

Ultraspiracle (USP) is the invertebrate homologue of the mammalian retinoid X receptor (RXR). RXR plays a uniquely important role in differentiation, development, and homeostasis through its ability to serve as a heterodimeric partner to many other nuclear receptors. RXR is able to influence the activity of its partner receptors through the action of the ligand 9-cis retinoic acid. In contrast to RXR, USP has no known high-affinity ligand and is thought to be a silent component in the heterodimeric complex with partner receptors such as the ecdysone receptor. Here we report the 2.4-A crystal structure of the USP ligand-binding domain. The structure shows that a conserved sequence motif found in dipteran and lepidopteran USPs, but not in mammalian RXRs, serves to lock USP in an inactive conformation. It also shows that USP has a large hydrophobic cavity, implying that there is almost certainly a natural ligand for USP. This cavity is larger than that seen previously for most other nuclear receptors. Intriguingly, this cavity has partial occupancy by a bound lipid, which is likely to resemble the natural ligand for USP.

Individual foods and food group patterns of the oldest old

This study compares the dietary patterns of centenarians (n = 85) with sexagenarians (n = 76) and octogenarians (n = 83). A Daily Diet Diary was developed to code the responses of the 24-hour dietary recalls. Centenarians and octogenarians consumed a more varied (P < 0.05) diet, with higher (P < 0.01) consumption frequencies of milk and grains, and fewer (P < 0.01) skipped breakfasts than sexagenarians. However, centenarians also consumed high fat foods (P < 0.01), such as whole milk and biscuits, and coffee (P < 0.5) more frequently than the two younger cohorts. Several of the variations found in the food patterns among the three age groups may reflect cohort differences, rather than true antecedents for longevity.

The influence of rural/urban residence on health in the oldest-old

Differences between rural (n = 18) and urban (n = 66) centenarians are examined across the following variables: physical health, activities of daily living, mental health, and life satisfaction. Results demonstrate higher levels of morale in rural residents and higher levels of functional health as exhibited by urban elders. Qualitative data support trends of increased degrees of independence among the rural participants. The absence of robust differences in rural and urban centenarians is discussed in terms of a leveling-off effect.

Age-related changes in the neurologic examination of healthy sexagenarians, octogenarians, and centenarians

Although numerous studies have focused on age-related changes in the nervous system, few have systematically assessed global neurologic examination changes, and even fewer have included the most elderly population, ie, the centenarians. To perform such a study, we developed a quantitative assessment that includes the major components of a standard bedside neurologic evaluation, with special emphasis on cognitive function. First, we demonstrated that the quantitated examination could correctly classify healthy controls and patients with stroke or dementia based on discriminant analysis. This examination was then applied to healthy community-dwelling elderly ranging from 60 to 108 years of age. Significant age-related neurobehavioral changes were apparent across even these most "successfully" aged groups. Analysis of the full pattern of cognitive and neurologic findings provided the most accurate assessment. Pathologic reflexes, reportedly associated with normal aging, occurred infrequently in this healthy geriatric population, suggesting that age-related changes in the neurologic examination may be more accurately interpreted when assessed in conjunction with cognitive status. This quantitative examination may be useful in future population-based studies of neurologic function in the aged.

Clarifying the Concept of Critical Thinking in Nursing

Nursing must chart a course between the pedagogical extremes of process versus content-focused courses. No one would deny the fact that nurses must have a solid knowledge base in addition to demonstrating an ability to think critically. Reason favors a "both-and" rather than an "either-or" approach to this issue. Justifiably, nurses have jumped on the bandwagon of critical thinking. Once on the bandwagon, however, the elusive butterfly of critical thinking has been difficult to net. It is time to inform the driver that a new course for nursing must be charted. So far, the reported nursing research has focused on critical thinking conceptualized as a score on a broad, objective test. The important first step of establishing a clear concept that defines critical thinking in nursing has not been accomplished. Finding out what the expert nurse does with knowledge will help us to articulate a conception of critical thinking that can then be used as a springboard for various teaching strategies. If educators are persuaded that "students can and should think their way through the content of their courses, can and should gain some grasp of the logic of what they study, can and should develop explicit intellectual standards, then they can find many ways to move instruction in this direction" (Barnes, 1992, p. 22).

Physical health measurement of the older adult: new instrumentation

The Georgia Centenarian Study examines the biologic, psychologic, and social factors contributing to life satisfaction and successful aging in late adulthood. Three age groups are included, 60 through 69 years, 80 through 89 years, and 100+ years. While the overall theoretical model includes multiple variables, physical health is viewed as critical to successful aging. This article presents an overview of physical health measurement for older persons. Some existing measures of physical health are included in the test battery for the Georgia Centenarian Study; however, the investigators determined the need for the inclusion of a new instrument. This article describes existing measures as well as the rationale and process of development of a new instrument.

Survivors of the century

Stereotypical views of the elderly hold that very old persons are less adaptable to change and less comfortable handling crisis situations. Over the last five years, we have had the privilege of meeting 96 people aged 100 years or older as part of the National Institute of Mental Health (NIMH) funded, Georgia Centenarian Study (R01 MH 43435-05). We have encountered optimistic, wise individuals very engaged in living. Our research team continues to be amazed at the quality of life and the individual differences amongst centenarians.

The undergraduate student as research assistant: promoting scientific inquiry

As nurse scientists, we must find a way to excite our undergraduate students about research so that they will value it and include it as an integral part of their practice. The ambience surrounding scientific inquiry cannot be captured from readings and classroom activities alone, but must be modelled by enthusiastic faculty who are actively involved in research. Two exemplary cases involving the use of undergraduate students as integral members of faculty-directed research teams are described.

The Georgia Centenarian Study

This paper presents the theoretical rationale, hypotheses, models, and methods and procedure of the Georgia Centenarian Study, an interdisciplinary study of the oldest-old.

Religiosity and adaptation in the oldest-old

Previous research has yielded mixed results with respect to the relationship between religiosity and adaptation in older adults. Most studies show that religiosity is stable over the life span, but that religiosity may or may not be related to such factors as physical and mental health, life satisfaction, and coping. This study adds to earlier investigations by including centenarians among the sample. The preliminary results of this research project support earlier findings that religiosity does not change significantly as one ages, although there is a trend in the results that suggests otherwise. The results also indicate a significant relationship between religiosity and physical health but no significant relationship between religiosity and mental health and life satisfaction. Religiosity and coping are strongly related, and there is the suggestion that religious coping mechanisms might be more important in the oldest-old.

Personality, life events and coping in the oldest-old

This paper compares older adults in their sixties, eighties, and 100s on personality, experience of life events, and coping. A secondary goal was to test a structural model of adaptation. Participants (165) filled out a personality inventory, life-event lists, and coping and mental health measures. Results revealed differences in personality: centenarians scored higher on dominance, suspiciousness, and imagination. While centenarians scored lower on active behavioral coping than other age groups, they used cognitive strategies when coping with health and family events. Results from the structural equation model indicated that extraversion and anxiety predicted morale and mental health.

The influences of cognitive resources on adaptation and old age

In the Georgia Centenarian Study, cognitive resources were estimated by fluid and crystallized intelligence, acquisition and retrieval of new information, retrieval of familiar information, and problem-solving ability in community-dwelling and nondemented adults ranging from sixty to one hundred plus years of age. Five clusters of results were found: 1) cognitive performances were lower for the older cohorts; 2) when cognitive activities were dependent on everyday experiences, no age-related problem-solving decline was found; 3) physical health and mental health can significantly influence cognitive performances; 4) cognitive and personality factors can combine to account for a larger amount of adaptation variance than can be accounted for by either of the factors alone; and 5) individuals with a high level of intelligence and affect sustain their instrumental activities of daily living. Cognitive resources were an important contributor to successful adaptation for the oldest-old.

Nutritional patterns of centenarians

This study compares the dietary patterns of centenarians (n = 24) with elderly adults in their sixties (n = 54) and eighties (n = 47). Compared to the younger cohorts, centenarians consumed breakfast more regularly, avoided weight loss diets and large fluctuations in body weight, consumed slightly more vegetables, and relied on their doctor and family more than on the news media for nutrition information. On the other hand, centenarians were less likely to consume diets low in fat and to comply with nutritional guidelines designed to reduce the risk of chronic disease. Elderly black men consumed diets higher in sweets and fat compared to black women and white men and women. Nearly three times as many blacks expressed the desire to eat more nutritiously. High nutrition risks, particularly in blacks, were associated with lower physical and mental health and impaired activities of daily living.

Relationship Between a Preceptorship Experience and Role Socialization of Graduate Nurses

The purpose of this quasi-experimental study was to determine the effect of preceptorship on the socialization of the baccalaureate graduate nurse into roles of professional nurses. Two groups, one having a preceptorship experience in the final quarter of their baccalaureate program (n = 33) and one having the traditional course (n = 33), participated in the study. Both groups completed Schwerian's Six-Dimension Scale of Nursing Performance on three testing occasions: prior to the course, immediately following the course, and the six months after graduation. There was a significant interaction effect between group and time. The preceptor group at the 6-month follow-up scored significantly higher on four of the six subscales as well as on the overall socialization instrument.