Beyond fall risk assessment: A case-control study in an Urban Medical Center.

AIMS AND OBJECTIVES: To examine the characteristics of patients that fell and compare them with patients that did not fall and to seek differences between the two groups that might help better predict falls in future patients. BACKGROUND: It has been estimated that between 700,000 and one million inpatient falls occur yearly in hospitals in the United States, which results in an increase in healthcare costs of over $19 billion dollars per year. DESIGN: This was a case-control study employing a retrospective analysis of inpatient electronic health records. It includes records from 160 patients who experienced a fall after the implementation of the Johns Hopkins Fall Risk Assessment Tool, and 160 records of patient with similar fall risk scores that did not fall. METHODS: All fall and nonfall patient data for the database were obtained by one research team member, while systematic random selection of nonfall patient records was performed by three research team members as described below. Each patient was assigned a unique study code number which was entered into the research database. The final sample size was 302 patients. RESULTS: Patients who did not receive lorazepam within 12 hr of the fall risk assessment were less likely to fall than patients who did receive lorazepam. A statistical relationship was also found between toileting at the time of the fall and age. CONCLUSIONS: Better stratification of patient populations combined with astute nursing awareness may result in a further reduction in falls. RELEVANCE TO CLINICAL PRACTICE: The results indicate that the nursing assessment with respect to falls is critical to identifying fall-prone individuals who may score as a low-to-moderate fall risk. In addition, the administration of lorazepam should cue the nurse that fall precautions be implemented regardless of scored risk.

Transient absorption imaging of hemes with 2-color, independently tunable visible-wavelength ultrafast source.

Pump probe microscopy is a time-resolved multiphoton imaging technique capable of generating contrast between non-fluorescent pigments based on differences in excited-state lifetimes. Here we describe a fiber-based ultrafast system designed for imaging heme proteins with an independently-tunable pulse pair in the visible-wavelength regime. Starting with a 1060 nm fiber amplifier (1.3 W at 63 MHz, 140 fs pulses), visible pulses were produced in the vicinity of 488 nm and 532 nm by doubling the output of a short photonic crystal fiber with a pair of periodically-poled lithium niobate crystals, providing 5-20 mW power in each beam. This was sufficient for acquiring transient absorption images from unstained cryosectioned tissue.

Superresolved multiphoton microscopy with spatial frequency-modulated imaging.

Superresolved far-field microscopy has emerged as a powerful tool for investigating the structure of objects with resolution well below the diffraction limit of light. Nearly all superresolution imaging techniques reported to date rely on real energy states of fluorescent molecules to circumvent the diffraction limit, preventing superresolved imaging with contrast mechanisms that occur via virtual energy states, including harmonic generation (HG). We report a superresolution technique based on spatial frequency-modulated imaging (SPIFI) that permits superresolved nonlinear microscopy with any contrast mechanism and with single-pixel detection. We show multimodal superresolved images with two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) from biological and inorganic media. Multiphoton SPIFI (MP-SPIFI) provides spatial resolution up to 2η below the diffraction limit, where η is the highest power of the nonlinear intensity response. MP-SPIFI can be used to provide enhanced resolution in optically thin media and may provide a solution for superresolved imaging deep in scattering media.

General theoretical treatment of spectral modulation light-labeling spectroscopy.

We theoretically derive the analytic relationship between experimental parameters and the measured incident (or illumination) optical power spectrum for a new form of spectroscopy, entitled light labeling spectroscopy. The light labeling signals are shown to arise from the interference between fields diffracted from a grating with time varying ruling density. A Gaussian model is used to illustrate the bounds of the method for recovering power spectra without artificial spectral apodization. Finally, several example systems are tabulated to give numerical insight into the possible system performances across a range of wavelength regions.

Third harmonic generation microscopy of a mouse retina.

PURPOSE: To demonstrate lipid-specific imaging of the retina through the use of third harmonic generation (THG), a multiphoton microscopic technique in which tissue contrast is generated from optical inhomogeneities. METHODS: A custom fiber laser and multiphoton microscope was constructed and optimized for simultaneous two-photon autofluorescence (TPAF) and THG retinal imaging. Imaging was performed using fixed-frozen sections of mouse eyes without the use of exogenous fluorescent dyes. In parallel experiments, a fluorescent nuclear stain was used to verify the location of the retinal cell nuclei. RESULTS: Simultaneous THG and TPAF images revealed all retinal layers with subcellular resolution. In BALB/c strains, the THG signal stems from the lipidic organelles of the cellular and nuclear membranes. In the C57BL/6 strain, the THG signal from the RPE cells originates from the pigmented granules. CONCLUSIONS: THG microscopy can be used to image structures of the mouse retina using contrast inherent to the tissue and without the use of a fluorescent dye or exogenously expressed recombinant protein.

Nonlinear fiber amplifier with tunable transform limited pulse duration from a few 100 to sub-100-fs at watt-level powers.

We report a fiber amplifier system with an output transform limited pulse duration that is broadly tunable from 400 to 60 fs. We produce <100 fs pulses with >200 kW of peak power by compensating a significant amount of third-order dispersion. The spectral noise characteristics are also investigated to insure highly stable supercontinuum generation.

Three-photon excitation source at 1250 nm generated in a dual zero dispersion wavelength nonlinear fiber.

We demonstrate 1250 nm pulses generated in dual-zero dispersion photonic crystal fiber capable of three-photon excitation fluorescence microscopy. The total power conversion efficiency from the 28 fs seed pulse centered at 1075 nm to pulses at 1250 nm, including coupling losses from the nonlinear fiber, is 35%, with up to 67% power conversion efficiency of the fiber coupled light. Frequency-resolved optical gating measurements characterize 1250 nm pulses at 0.6 nJ and 2 nJ, illustrating the change in nonlinear spectral phase accumulation with pulse energy even for nonlinear fiber lengths < 50 mm. The 0.6 nJ pulse has a 26 fs duration and is the shortest nonlinear fiber derived 1250 nm pulse yet reported (to the best of our knowledge). The short pulse durations and energies make these pulses a viable route to producing light at 1250 nm for multiphoton microscopy, which we we demonstrate here, via a three-photon excitation fluorescence microscope.

Overcoming temporal polarization instabilities from the latent birefringence in all-normal dispersion, wave-breaking-extended nonlinear fiber supercontinuum generation.

The intrinsic weak birefringence in all-normal dispersion highly nonlinear fiber, particularly ultra-high-numerical-aperture fiber, generates supercontinuum with long term polarization instabilities, even for seed pulses launched along the perceived slow axis of the fiber. Highly co/anti-correlated fluctuations in energy between regions of power spectral density mask the extent of the spectral noise in total integrated power measurements. The instability exhibits a seed pulse power threshold above which the output polarization state of the supercontinuum seeds from noise. Eliminating this instability through the utilization of nonlinear fiber with a large designed birefringence, encourages the exploration of compression schemes and seed sources. Here, we include an analysis of the difficulties for seeding supercontinuum with the highly attractive ANDi-type lasers. Lastly, we introduce an intuitive approach for understanding supercontinuum development and evolution. By modifying the traditional characteristic dispersion and nonlinear lengths to track pulse properties within the nonlinear fiber, we find simple, descriptive handles for supercontinuum evolution.

Improved beam characteristics of solid-target soft x-ray laser amplifiers by injection seeding with high harmonic pulses.

Injection seeding of solid-target soft x-ray laser amplifiers with high harmonic pulses is shown to dramatically improve the far-field laser beam profile and reduce the beam divergence. Measurements and two-dimensional simulations for a 13.9 nm nickel-like Ag amplifier show that the amplified beam divergence depends strongly on the seed and can therefore be controlled by selecting the divergence of the seed. The near-field beam size of both the seeded and unseeded lasers is shown to be determined by the size of the gain region and the divergence of the amplified beams.