Optimization of multi-grating volume holographic spectrum splitters for photovoltaic applications.

Recent research has shown that using multiple diverse-bandgap photovoltaic (PV) cells in conjunction with a spectrum splitting optical system can significantly improve PV power generation efficiency. Although volume Bragg gratings (VBGs) can serve as effective spectrum splitters, the inherent dispersion of a VBG can be detrimental given a broad-spectrum input. The performance of a single holographic spectrum splitter element can be improved by utilizing multiple single volume gratings, each operating in a slightly different spectral band. However, care must be taken to avoid inter-grating coupling effects that limit the ultimate performance. This work explores broadband two-grating holographic optical elements (HOEs) in multiplexed (single element) and sandwiched-grating arrangements. Particle swarm optimization is used to tailor these systems to the solar spectrum, taking into account both efficiency and dispersion. Both multiplexed and sandwiched two-grating systems exhibit performance improvements over single-grating solutions, especially when reduced dispersion is required. Under a ±2° constraint on output angular spread from wavelength dispersion, sandwiched-, multiplexed-, and single-grating systems exhibit power conversion efficiencies of 82.1%, 80.9%, and 77.5%, respectively, compared to an ideal bandpass spectrum splitter. Dispersion performance can be further improved by employing more than two VBGs in the spectrum splitter, but efficiency is compromised by additional cross-coupling effects. Multiplexed-grating systems are especially susceptible to these effects, but have the advantage of utilizing only a single HOE.

Channel density and efficiency optimization of spectral beam combining systems based on volume Bragg gratings in sequential and multiplexed arrangements.

Spectral-beam-combining (SBC) systems utilizing multiple volume Bragg gratings must be carefully analyzed to maximize channel density and efficiency, and thus output radiance. This analysis grows increasingly difficult as the number of channels in the system increases, and heuristic optimization techniques are useful tools for exploring the limits of these systems. We explore three classes of multigrating SBC systems: cascaded, where each grating adds a new channel to the system in sequence; sandwiched, where several individual gratings are placed together and all channels enter the system at the same facet; and multiplexed, where all of the gratings occupy the same holographic optical element (HOE). Loss mechanisms differ among these three basic classes, and our optimization algorithm shows that the highest channel density for a given minimum efficiency and fixed operating bandwidth is achieved for a cascaded grating system. The multiplexed grating system exhibits the lowest channel density under the same constraints but has the distinct advantage of being realized by a single HOE. For a particular application, one must weigh channel density and efficiency versus system complexity when choosing among these basic classes of SBC systems. Additionally, one may need to consider the effects of finite-width input beams. As input beam radius is reduced, angular clipping effects begin to dominate over spectral interference and crosstalk effects, limiting all three classes of SBC systems in a similar manner.

Spectral interference in multiplexed volume Bragg gratings: theoretical calculations and experimental verification.

Multiplexed volume Bragg gratings can be applied to many types of broad- and narrowband spectral systems. However, there are often deleterious side effects to combining several gratings into a single holographic optical element, including loss of efficiency in diffracted waves of interest and the introduction of spurious waves. Design of these spectral systems requires analysis methods that are flexible and efficient and that take these side effects into account. We present a matrix-based algorithm for determining diffraction efficiencies of significant coupled waves in these multiplexed grating Holographic optical elements (HOEs). Several carefully constructed experiments with spectrally multiplexed gratings in dichromated gelatin verify our conclusions.

Development of an instrument to measure patient perception of the quality of nursing care.

Although patient satisfaction has been given considerable attention in health care, analysis of the conceptual and measurement limitations of existing measures indicates that a more elemental approach to obtaining patients' perspectives is warranted. In this investigation we developed and evaluated the psychometric properties of an instrument designed to measure patients' perceptions of the degree to which their needs were met while hospitalized. This 15-item instrument, Patient Perception of Hospital Experience with Nursing (PPHEN), based on Swanson-Kauffman's framework of caring, is internally consistent and represents a single construct best described as feeling cared for. The relationship of PPHEN to other measures demonstrates concurrent validity; moreover, the scale is responsive to differences in care provided, as shown by differences in means for different hospitals. PPHEN offers a brief, theoretically oriented, internally consistent, and valid patient self-report measure of nursing care. It does not require patients to compare their expectations of care with the care received but only to evaluate whether their needs were met. It promises to be useful to clinical and health services researchers.

Employee response to major organizational redesign.

A number of health care organizations are currently undergoing major organizational redesign. Despite these efforts, little is known about how these changes are affecting the employees participating in the redesign process. In response to this, a study was undertaken to determine the perceived impact of organizational redesign on nursing staff at 2 acute care hospitals that were undergoing major organizational change. Data were collected through semi-structured focus group interviews conducted on all 3 shifts (days, evenings, and nights). Findings suggest the early redesign period is highly turbulent and difficult for staff. Nurses expressed concern over changes in roles and responsibilities, disruption in work group relationships, loss of resource availability, reduction in quality of care, and alterations in physical and psychological state.

Self-scheduling and staff incentives: meeting patient care needs in a neonatal intensive care unit.

Nursing staff and leadership in a resource-intensive NICU identified an innovative process for covering the unit's scheduling needs. Early concerns about the feasibility of achieving self-scheduling with a large staff were unwarranted. The use of a unit-based committee and the support of the nurse manager allowed us to develop a process that met the needs of the staff members and maintained the staffing standards of the unit. Contributing to the success of the self-scheduling is a mechanism for recognizing and rewarding staff members who adjust their work schedules to meet the needs of the unit. Satisfaction among staff members with self-scheduling is high, and new employees cite the opportunity for self-scheduling as a contributing factor in their decisions to work in the NICU.

Nurse-sensitive outcomes of advanced practice.

Advanced practice nurses (APNs) in the USA are registered nurses who hold masters or doctoral degrees in a specialized area of nursing. They provide advanced clinical care to clients, manage health care systems and influence health care decision-making through expert clinical reasoning and research and theory-based action. APN impact on health care outcomes is supported by studies using physician-focused indicators, although a few studies have identified several that are sensitive to or reflective of advanced practice nursing. A modified Delphi survey was conducted during May 1997-December 1998 to determine the outcome indicators APNs recommend for use in measuring their effect on care delivery outcomes. A convenience sample of 66 APNs attending a statewide outcomes conference identified 27 potential outcome indicators. These indicators were included in a mailed survey sent to APNs working in Tennessee. Respondents were asked to rate each indicator for validity, sensitivity, feasibility, utility and cost. In the second round of the survey, they were asked whether or not they agreed with the rank ordering of indicators, which was determined by the means calculated from responses in the first round. The 10 highest ranked indicators were satisfaction with care delivery, symptom resolution/reduction, perception of being well cared for, compliance/adherence with treatment plan, knowledge of patients and families, trust of care provider, collaboration among care providers, frequency and type of procedures ordered and quality of life. APNs identified both direct and indirect measures of effect on care delivery outcomes. Some of these are currently used as indicators of advanced practice, but many are not. Additional research is needed to determine whether the indicators proposed are valid and sensitive to advanced practice care by nurses.

Relationship of organizational culture and readiness for change to employee commitment to the organization.

OBJECTIVES: A study was undertaken to determine the relationships among organizational culture, organizational commitment, and organizational readiness in a sample of employees participating in a hospital-wide redesign process. METHODS: Employees of an organization undergoing patient-focused redesign were surveyed after a 6-month period of preparation and before the initiation of the new care delivery model. RESULTS: Organizational readiness, a variable rarely described in organizational change literature, was the strongest predictor of employee commitment to the organization. Constructive culture also was predictive, but less so than readiness for change. CONCLUSIONS: Additional research is needed to clarify how an organization's history and culture of change contribute to employee willingness to work for the goals of the organization. Findings suggest that when change is seen as a positive characteristic of the environment, employees are more likely to commit to the work of the institution.

Managed-care research, Part 2: Researching the domain.

A review of research pertaining to managed care suggests that little information is known about the impact of the components of managed care on care delivery outcomes. Characteristics of managed-care systems rarely are considered, resulting in uncertainty and confusion about which of the domain components of managed care have contributed to the outcomes seen. In part 1 (JONA November 1999) of this two-part series, we described how the shift to managed care has affected healthcare organizations and healthcare providers. We also identified several research questions relevant to the five domain components of managed care. In this article, we review the research literature concerning managed care and identify where research deficiencies exist within the domain.

Managed-care research, Part 1: Defining the domain.

New research opportunities are arising in response to the changes associated with care delivery provided in managed-care environments. A review of the managed-care literature suggests five characteristics that are associated with the care delivery models currently in place. Each of these components needs investigation to determine which of them contribute to cost reductions and care delivery outcomes seen.

Concept analysis of outcomes for advanced practice nursing.

The importance of accurately measuring health care outcomes is mentioned frequently in the literature. To do so, a common understanding of what constitutes a care delivery outcome is needed. In this article, a concept analysis of outcomes is provided, with identification of potential outcomes relevant to advanced practice.

Teaching video effect on renal transplant patient outcomes.

A study was undertaken to test the effect of a teaching video on renal transplant recipient outcomes. A quasi-experimental, pretest/posttest design was used. Fifty-nine adults undergoing renal transplantation were studied. Subjects were randomly assigned to either an experimental group, which received discharge preparatory teaching with the use of a teaching video, or to a control group, which received standard teaching. Subjects in the experimental group had significantly greater improvements in knowledge scores postteaching. No other differences were seen. Findings suggest the use of a teaching video can be a useful adjunct to educational programs designed for renal transplant patients and their families.

The effect of patient-focused redesign on midlevel nurse managers' role responsibilities and work environment.

OBJECTIVE: The authors determine the effect of patient-focused redesign on midlevel nurse managers' role responsibilities and perceptions of work environment. BACKGROUND: Patient-focused redesign models have been initiated in a number of hospitals over the past 10 years. Few studies of the impact of these models on nurse leaders' roles and work responsibilities have been conducted. METHODS: Nine midlevel nurse managers were interviewed about their redesigned leadership roles and the challenges they experienced in implementing patient-focused redesign. RESULTS: Several themes emerged from the data. These themes focused on role change, ambiguity, position power, and environmental uncertainty and turbulence. Each of the nurse managers described feelings of frustration, disconnectedness, and inadequacy and spoke of how difficult it was to be the central figure in the eye of the storm. They noted that previously successful administrative strategies were not producing the same effect as in the past. CONCLUSION: This study provides beginning information about the magnitude of the impact of organizational redesign on midlevel nurse managers. Midlevel managers in this study struggled to keep up with the demands of the change and their own recognition of the importance of remaining committed to the uncertain goals of the institution. They were frustrated by their perceived inability to fix the situation and to meet the multiple needs of the staff. Nonetheless, they supported senior executives and attempted reasonable solutions to the problem.

Impact of home health care on health care costs and hospitalization frequency in patients with heart failure.

This study was undertaken to investigate the costs of delivering home health care services to patients with heart failure and the impact of these services on hospitalization frequency. Results suggest that referring patients with heart failure to home health care is costly and does not necessarily reduce hospitalization frequency.

Grants management skills keep funded projects on target.

An often neglected but equally relevant aspect of program development and nursing research is the management of funded projects from the time an idea is generated to the final submission of project report. When effective grants management skills are used to oversee the development of a program proposal and the oversight of the funded project, the likelihood for successful outcome is increased. In this article several steps have been described in the grants management process that can be used to assure that projects are developed and proceed according to plan.

Longitudinal health endangering behavior risk among resilient and nonresilient early adolescents.

PURPOSE: To explore the relative likelihood of engaging in new health-endangering behaviors among a group of resilient early adolescents compared to a sample of nonresilient peers and a sample of normal, low-risk peers in a nonclinical, school-based setting. METHODS: Resilient adolescents and their peer groups were identified by way of a multiple linear regression equation in which age, family structure (single or step-parent family), gender, self-injurious behaviors, and emotional risk were used to predict propensity to initiate risky health behaviors. The resilient sample consisted of those adolescents who were predicted to be above the standardized mean, yet actually scored below it. The nonresilient population included those who were predicted to and actually scored above the standardized mean. The normal, low-risk population consists of adolescents who were predicted to and scored below the standardized mean. The mean age for all populations was 13.78 years. All students completed a Health Behavior Questionnaire and the Rosenberg Self-Esteem Inventory. RESULTS: Odds ratios with 95% confidence intervals revealed that in the year following identification as resilient, nonresilient, or normal, the resilient adolescents were less likely than the nonresilient adolescents to initiate a variety of risky behaviors. At the same time, the resilient adolescents were more likely than their normal, not at-risk peers to have initiated those same risky behaviors. The resilient adolescents have modestly higher mean self-esteem than the nonresilient peers (t = 2.47, p < 0.05) but lower self-esteem than their normal, not at-risk peers (t = 3.66, p < 0.01). CONCLUSIONS: Determination of resilience status by way of multiple linear regression yielded identifiable groups which conformed to expected elevated risk of initiating new risky behaviors relative to normal, not at-risk peers but lowered risk relative to nonresilient peers. Differences were most notable with reference to new reports of substance use. The lower rate of initiating new risky behaviors among resilient relative to nonresilient peers is seen as a reflection of behavioral competence in an adverse context. However, the elevated rate of initiating new risky behaviors among resilient relative to normal, not at-risk peers is seen as a reflection of the continuing, negative impact of that adverse context.

Impact of a nurse practitioner on the cost of managing inpatients with heart failure.

We examined the impact on hospital costs of having a nurse practitioner manage uncomplicated patients hospitalized for decompensated heart failure. This strategy was associated with a significant decrease in total hospital costs ($6,659+/-5,843 vs $5,211+/-4,137 [p < 0.03]), a trend toward decreased length of stay (4.0+/-3.0 vs 3.4+/-2.4 days [p = 0.13]), and no significant change in the 30-day readmission rate (13% of patients vs 16% of patients [p = NS]).