Fast localized wavefront correction using area-mapped phase-shift interferometry

We propose an innovative method for localized wavefront correction based on area-mapped phase-shift (AMPS) interferometry. In this Letter, we present the theory and then experimentally compare it with a previously demonstrated method based on spot-optimized phase-stepping (SOPS) interferometry. We found that AMPS outperforms SOPS interferometry in terms of speed by threefold, although in noisy environments the improvements may be larger. AMPS yielded similar point-spread functions (PSF) as SOPS for moderate system-induced aberrations, but yielded a slightly less ideal PSF for larger aberrations. The method described in this Letter may prove crucial for applications where the phase-stepping solution does not have sufficient speed.     

Wavelet compression of three-dimensional time-lapse biological image data.

The use of multifocal-plane, time-lapse recordings of living specimens has allowed investigators to visualize dynamic events both within ensembles of cells and individual cells. Recordings of such four-dimensional (4D) data from digital optical sectioning microscopy produce very large data sets. We describe a wavelet-based data compression algorithm that capitalizes on the inherent redunancies within multidimensional data to achieve higher compression levels than can be obtained from single images. The algorithm will permit remote users to roam through large 4D data sets using communication channels of modest bandwidth at high speed. This will allow animation to be used as a powerful aid to visualizing dynamic changes in three-dimensional structures.     

Targeting choroid plexus epithelia and ventricular ependyma for drug delivery to the central nervous system

Background  

Because the choroid plexus (CP) is uniquely suited to control the composition of cerebrospinal fluid (CSF), there may be therapeutic benefits to increasing the levels of biologically active proteins in CSF to modulate central nervous system (CNS) functions. To this end, we sought to identify peptides capable of ligand-mediated targeting to CP epithelial cells reasoning that they could be exploited to deliver drugs, biotherapeutics and genes to the CNS.     

Quantification of collagen organization and extracellular matrix factors within the healing ligament

Ligament healing of a grade III injury (i.e., a complete tear) involves a multifaceted chain of events that forms a neoligament, which is more scar-like in character than the native tissue. The remodeling process may last months or even years with the injured ligament never fully recovering pre-injury mechanical properties. With tissue engineering and regenerative medicine, understanding the normal healing process in ligament and quantifying it provide a basis to create and assess innovative treatments. Ligament fibroblasts produce a number of extracellular matrix (ECM) components, including collagen types I and III, decorin and fibromodulin. Using a combination of advanced histology, molecular biology, and nonlinear optical imaging approaches, the early ECM events during ligament healing have been better characterized and defined. First, the dynamic changes in ECM factors after injury are shown. Second, the factors associated with creeping substitution are identified. Finally, a method to quantify collagen organization is developed and used. Each ECM factor described herein as well as the temporal quantification of fiber organization helps elucidate the complexity of ligament healing.     

Non-invasive quantification of brain tumor-induced astrogliosis

Background  

CNS injury including stroke, infection, and tumor growth lead to astrogliosis, a process that involves upregulation of glial fibrillary acidic protein (GFAP) in astrocytes. However, the kinetics of astrogliosis that is related to these insults (i.e. tumor) is largely unknown.     

The onset of coulomb explosions in polyatomic molecules

With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd.     

Uniform molecular analysis using femtosecond laser mass spectrometry

The potential of femtosecond laser time-of-flight mass spectrometry (FLMS) for uniform quantitative analysis of molecules has been investigated. Various samples of molecular gases and vapours have been studied, using ultra-fast ( approximately 50 fs) laser pulses with very high intensity (up to 1.6 x 10(16) Wcm(-2)) for non-resonant multiphoton ionisation/tunnel ionisation. Some of these molecules have high ionisation potentials, requiring up to ten photons for non-resonant ionisation. The relative sensitivity factors (RSF) have been determined as a function of the laser intensity and it has been demonstrated that for molecules with very different masses and ionisation potentials, uniform ionisation has been achieved at the highest laser intensities. Quantitative laser mass spectrometry of molecules is therefore a distinct possibility. Copyright 1999 John Wiley & Sons, Ltd.     

Tools for visualizing multidimensional images from living specimens

Over the last 50 years modern cell biology has been driven by the development of powerful imaging techniques. In particular, new developments in light microscopy that provide the potential to image the dynamics of biological events have had significant impact. Optical sectioning techniques allow three-dimensional information to be obtained from living specimens noninvasively. When used with multimodal fluorescence microscopy, advanced optical sectioning techniques provide multidimensional image data that can reveal information not only about the changing cytoarchitecture of a cell but also about its physiology. These additional dimensions of information, although providing powerful tools, also pose significant visualization challenges to the investigator. Particularly in the current postgenomic era there is a greater need than ever for the development of effective tools for image visualization and management. In this review we discuss the visualization challenges presented by multidimensional imaging and describe three open-source software programs being developed to help address these challenges: ImageJ, the Open Microscopy Environment, and VisBio.