Trait Loss in Evolution: What Cavefish Have Taught Us about Mechanisms Underlying Eye Regression.

Reduction or complete loss of traits is a common occurrence throughout evolutionary history. In spite of this, numerous questions remain about why and how trait loss has occurred. Cave animals are an excellent system in which these questions can be answered, as multiple traits, including eyes and pigmentation, have been repeatedly reduced or lost across populations of cave species. This review focuses on how the blind Mexican cavefish, Astyanax mexicanus, has been used as a model system for examining the developmental, genetic, and evolutionary mechanisms that underlie eye regression in cave animals. We focus on multiple aspects of how eye regression evolved in A. mexicanus, including the developmental and genetic pathways that contribute to eye regression, the effects of the evolution of eye regression on other traits that have also evolved in A. mexicanus, and the evolutionary forces contributing to eye regression. We also discuss what is known about the repeated evolution of eye regression, both across populations of A. mexicanus cavefish and across cave animals more generally. Finally, we offer perspectives on how cavefish can be used in the future to further elucidate mechanisms underlying trait loss using tools and resources that have recently become available.

Development of the Vicarious Resilience Scale (VRS): A measure of positive effects of working with trauma survivors.

OBJECTIVE: Attending to the potential impacts, both positive and negative, of clinical work with trauma survivors on professionals themselves is a crucial aspect of clinical training and supervision. Vicarious resilience refers to unique, positive effects that transform therapists in response to witnessing trauma survivors' resilience and recovery process. This study describes the development and exploratory factor analysis of the first instrument to assess vicarious resilience. METHOD: The Vicarious Resilience Scale (VRS) was developed and administered via electronic survey to 190 helping professionals from around the globe working with survivors of severe traumas, such as torture. RESULTS: Exploratory factor analysis yielded 7 factors: Changes in life goals and perspective, client-inspired hope, increased recognition of clients' spirituality as a therapeutic resource, increased capacity for resourcefulness, increased self-awareness and self-care practices, increased consciousness about power and privilege relative to clients' social location, and increased capacity for remaining present while listening to trauma narratives. The Cronbach's alpha reliability of the VRS was .92 and, as hypothesized, the VRS was moderately and positively correlated with posttraumatic growth and compassion satisfaction, indicating convergent validity. The VRS was not significantly correlated with compassion fatigue (CF) or burnout, indicating discriminant validity and that vicarious resilience is a unique construct that is not merely "the opposite" of CF or burnout. CONCLUSION: The VRS possesses sound psychometric properties and can be utilized in supervision and training contexts and for self-assessment by professionals working with trauma survivors to aid the recognition and cultivation of vicarious resilience. (PsycINFO Database Record

Vicarious resilience: Complexities and variations.

This article presents results from a qualitative study further exploring the concept of vicarious resilience. Thirteen therapists working with survivors of torture in 3 different locations were interviewed to better understand the complexities and variations of vicarious resilience. The analysis focuses on the therapists' perception of clients' resilience and the therapists' awareness of how this affects the therapists themselves. Four major themes emerge: change in the therapists' self-perception and their general outlook on the world, altered spirituality, modified thoughts about self-care, and new views on trauma work and connecting with clients. The results suggest that vicarious resilience can significantly influence therapists' personal lives as well as their therapeutic work. Therapists employing a strengths-based approach seem to be affected more by vicarious resilience. The results are situated within the growing body of literature that documents the positive effect of trauma work on therapists. The development of training curricula for strengthening therapists' awareness of vicarious resilience is recommended. (PsycINFO Database Record

Exploring the context of trafficking and adolescent sex industry involvement in Tijuana, Mexico: consequences for HIV risk and prevention.

Coerced and adolescent sex industry involvement are linked to serious health and social consequences, including enhanced risk of HIV infection. Using ethnographic fieldwork, including interviews with 30 female sex workers with a history of coerced or adolescent sex industry involvement, we describe contextual factors influencing vulnerability to coerced and adolescent sex industry entry and their impacts on HIV risk and prevention. Early gender-based violence and economic vulnerability perpetuated vulnerability to coercion and adolescent sex exchange, while HIV risk mitigation capacities improved with increased age, control over working conditions, and experience. Structural interventions addressing gender-based violence, economic factors, and HIV prevention among all females who exchange sex are needed.

Sex workers perspectives on strategies to reduce sexual exploitation and HIV risk: a qualitative study in Tijuana, Mexico.

Globally, female sex workers are a population at greatly elevated risk of HIV infection, and the reasons for and context of sex industry involvement have key implications for HIV risk and prevention. Evidence suggests that experiences of sexual exploitation (i.e., forced/coerced sex exchange) contribute to health-related harms. However, public health interventions that address HIV vulnerability and sexual exploitation are lacking. Therefore, the objective of this study was to elicit recommendations for interventions to prevent sexual exploitation and reduce HIV risk from current female sex workers with a history of sexual exploitation or youth sex work. From 2010-2011, we conducted in-depth interviews with sex workers (n = 31) in Tijuana, Mexico who reported having previously experienced sexual exploitation or youth sex work. Participants recommended that interventions aim to (1) reduce susceptibility to sexual exploitation by providing social support and peer-based education; (2) mitigate harms by improving access to HIV prevention resources and psychological support, and reducing gender-based violence; and (3) provide opportunities to exit the sex industry via vocational supports and improved access to effective drug treatment. Structural interventions incorporating these strategies are recommended to reduce susceptibility to sexual exploitation and enhance capacities to prevent HIV infection among marginalized women and girls in Mexico and across international settings.

Calibration of spatial light modulators suffering from spatially varying phase response.

We present a method for converting the desired phase values of a hologram to the correct pixel addressing values of a spatial light modulator (SLM), taking into account detailed spatial variations in the phase response of the SLM. In addition to thickness variations in the liquid crystal layer of the SLM, we also show that these variations in phase response can be caused by a non-uniform electric drive scheme in the SLM or by local heating caused by the incident laser beam. We demonstrate that the use of a global look-up table (LUT), even in combination with a spatially varying scale factor, generally does not yield sufficiently accurate conversion for applications requiring highly controllable output fields, such as holographic optical trapping (HOT). We therefore propose a method where the pixel addressing values are given by a three-dimensional polynomial, with two of the variables being the (x, y)-positions of the pixels, and the third their desired phase values. The coefficients of the polynomial are determined by measuring the phase response in 8 × 8 sub-sections of the SLM surface; the degree of the polynomial is optimized so that the polynomial expression nearly replicates the measurement in the measurement points, while still showing a good interpolation behavior in between. The polynomial evaluation increases the total computation time for hologram generation by only a few percent. Compared to conventional phase conversion methods, for an SLM with varying phase response, we found that the proposed method increases the control of the trap intensities in HOT, and efficiently prevents the appearance of strong unwanted 0th order diffraction that commonly occurs in SLM systems.

Reducing the effect of pixel crosstalk in phase only spatial light modulators.

A method for compensating for pixel crosstalk in liquid crystal based spatial light modulators is presented. By modifying a commonly used hologram generating algorithm to account for pixel crosstalk, the intensity errors in obtained diffraction spot intensities are significantly reduced. We also introduce a novel method for characterizing the pixel crosstalk in phase-only spatial light modulators, providing input for the hologram generating algorithm. The methods are experimentally evaluated and an improvement of the spot uniformity by more than 100% is demonstrated for an SLM with large pixel crosstalk.

Unconventional structure-assisted optical manipulation of high-index nanowires in liquid crystals.

Stable optical trapping and manipulation of high-index particles in low-index host media is often impossible due to the dominance of scattering forces over gradient forces. Here we explore optical manipulation in liquid crystalline structured hosts and show that robust optical manipulation of high-index particles, such as GaN nanowires, is enabled by laser-induced distortions in long-range molecular alignment, via coupling of translational and rotational motions due to helicoidal molecular arrangement, or due to elastic repulsive interactions with confining substrates. Anisotropy of the viscoelastic liquid crystal medium and particle shape give rise to a number of robust unconventional trapping capabilities, which we use to characterize defect structures and study rheological properties of various thermotropic liquid crystals.

Minimizing intensity fluctuations in dynamic holographic optical tweezers by restricted phase change.

We present a method for reducing intensity fluctuations that typically occur when a spatial light modulator is updated between consecutive computer generated holograms. The method is applicable to most iterative hologram generating algorithms and minimizes the average phase difference between consecutive holograms. Applications with high stability requirements, such as optical force measurement with holographic optical tweezers, should benefit from this improvement.

Psychological classification as a communication and management tool in obese patients undergoing bariatric surgery.

BACKGROUND: Psychological evaluations are used to ascertain patient suitability for bariatric surgery and to challenge their ability to comply with therapy. The modern paradigm of obesity includes a neurobiologic component working in parallel with the limbic system of appetite and reward. To achieve the goals of surgery, an evaluation of the psychological fitness of the patient is often included in the clinical pathway. We present a psychological classification system with the goal of integrating the psychological factors into patient treatment. METHODS: All patients (Roux-en-Y gastric bypass, n = 1814; laparoscopic adjustable gastric banding, n = 589) were evaluated using psychological testing/interview and assigned to groups 1-4 before surgery. The group 1 patients (n = 788; 32.8%) did not necessitate intervention, group 2 (n = 1110; 46.2%) were requested to attend the support group, groups 3A (n = 394; 16.4%) and 3B (n = 111; 4.6%) required intervention to continue to surgery, and group 4 patients were not recommended for surgery. The main outcome measures, including complication, readmission, and reoperation rates, were analyzed for differences among the psychological groups. RESULTS: After comparing the outcome measures between each classification, no significant differences were found in the major complication rates, readmissions, reoperations, or length of stay among the groups. Groups 3A and 3B were able to achieve similar rates of success, despite their psychosocial impairment at the initial evaluation. CONCLUSION: The assignment of a psychological classification can facilitate bariatric team recognition of the unique psychological factors that affect the success of surgery. Assessing the patient's psychological composition and addressing potential psychosocial barriers before surgery can increase the positive long-term outcomes and reduce the incidence of complications after bariatric surgery.

Grid-free 3D multiple spot generation with an efficient single-plane FFT-based algorithm.

Algorithms based on the fast Fourier transform (FFT) for the design of spot-generating computer generated holograms (CGHs) typically only make use of a few sample positions in the propagated field. We have developed a new design method that much better utilizes the information-carrying capacity of the sampled propagated field. In this way design tasks which are difficult to accomplish with conventional FFT-based design methods, such as spot positioning at non-sample positions and/or spot positioning in 3D, are solved as easily as any standard design task using a conventional method. The new design method is based on a projection optimization, similar to that in the commonly used Gerchberg-Saxton algorithm, and the vastly improved design freedom comes at virtually no extra computational cost compared to the conventional design. Several different design tasks were demonstrated experimentally with a liquid crystal spatial light modulator, showing highly accurate creation of the desired field distributions.

Segmented assimilation theory and the life model: an integrated approach to understanding immigrants and their children.

The life model offers social workers a promising framework to use in assisting immigrant families. However, the complexities of adaptation to a new country may make it difficult for social workers to operate from a purely ecological approach. The authors use segmented assimilation theory to better account for the specificities of the immigrant experience. They argue that by adding concepts from segmented assimilation theory to the life model, social workers can better understand the environmental stressors that increase the vulnerabilities of immigrants to the potentially harsh experience of adapting to a new country. With these concepts, social workers who work with immigrant families will be better positioned to achieve their central goal: enhancing person and environment fit.

Automated focusing of nuclei for time lapse experiments on single cells using holographic optical tweezers.

Experiments on single cells are currently gaining more and more interest. Single cell studies often concerns the spatio-temporal distribution of fluorescent proteins inside living cells, visualized using fluorescence microscopy. In order to extract quantitative information from such experiments it is necessary to image the sample with high spatial and temporal resolution while keeping the photobleaching to a minimum. The analysis of the spatial distribution of proteins often requires stacks of images at each time point, which exposes the sample to unnecessary amounts of excitation light. In this paper we show how holographic optical tweezers combined with image analysis can be used to optimize the axial position of trapped cells in an array in order to bring the nuclei into a single imaging plane, thus eliminating the need for stacks of images and consequently reducing photobleaching. This allows more images to be collected, as well as increasing the time span and/or the time resolution in time lapse studies of single cells.

Fast beam steering with a ferroelectric-liquid-crystal optical phased array.

We demonstrate fast, efficient beam steering using a single 1x32 analog ferroelectric liquid crystal (FLC) spatial light modulator. A high-tilt FLC material with 82 degrees optic-axis switching provides, in a reflective-mode device with a passive quarter-wave retarder between a half-wave FLC layer and a mirror, 91% of full 0-2pi phase modulation. Electronic drive based on applied charge gives 200 micros response-time analog modulation.

Improved beam steering accuracy of a single beam with a 1D phase-only spatial light modulator.

The limited number of pixels and their quantized phase modulation values limit the positioning accuracy when a phase-only one dimensional spatial light modulator (SLM) is used for beam steering. Applying the straightforward recipe for finding the optimal setting of the SLM pixels, based on individually optimizing the field contribution from each pixel to the field in the steering position, the inaccuracy can be a significant fraction of the diffraction limited spot size. This is especially true in the vicinity of certain steering angles where precise positioning is particularly difficult. However, by including in the optimization of the SLM setting an extra degree of freedom, we show that the steering accuracy can be drastically improved by a factor proportional to the number of pixels in the SLM. The extra degree of freedom is a global phase offset of all the SLM pixels which takes on a different value for each steering angle. Beam steering experiments were performed with the SLM being set both according to the conventional and the new recipe, and the results were in very good agreement with the theoretical predictions.

COORDINATION DYNAMICS OF THE COMPLEMENTARY NATURE.

Niels Bohr's maxim contraria sunt complementa indicated his strong suspicion that the complementarity interpretation of quantum mechanics might someday be expanded into a generalized principle. It now appears that such a principle has been found in metastability which appears at the scale of living things. Metastability has been proposed as a principle of brain~behavior, and is captured in the extended or 'broken-symmetry' version of the HKB model of coordination dynamics. The metastable regime of coordination dynamics reconciles the tendency of specialized brain regions to express autonomy (segregation) and their simultaneous tendency to work together as a synergetic whole (integration). There is growing evidence from recent studies in the brain and behavioral sciences that the complementary nature of integrating and segregating tendencies is essential to the way human brain~minds work.

Vicarious resilience: a new concept in work with those who survive trauma.

This study explores the formulation of a new concept: vicarious resilience. It addresses the question of how psychotherapists who work with survivors of political violence or kidnapping are affected by their clients'stories of resilience. It focuses on the psychotherapists' interpretations of their clients' stories, and how they make sense of the impact that these stories have had on their lives. In semistructured interviews, 12 psychotherapists who work with victims of political violence and kidnapping were interviewed about their perceptions of their clients' overcoming of adversity. A phenomenological analysis of the transcripts was used to describe the themes that speak about the effects of witnessing how clients cope constructively with adversity. These themes are discussed to advance the concept of vicarious resilience and how it can contribute to sustaining and empowering trauma therapists.

Diffractive optical elements designed for highly precise far-field generation in the presence of artifacts typical for pixelated spatial light modulators.

Diffractive optical elements (DOEs) realized by spatial light modulators (SLMs) often have features that distinguish them from most conventional, static DOEs: strong coupling between phase and amplitude modulation, a modulation versus steering parameter characteristic that may not be precisely known (and may vary with, e.g., temperature), and deadspace effects and interpixel cross talk. For an optimal function of the DOE, e.g. as a multiple-beam splitter, the DOE design must account for these artifacts. We present an iterative design method in which the optimal setting of each SLM pixel is carefully chosen by considering the SLM artifacts and the design targets. For instance, the deadspace-interpixel effects are modeled by dividing the pixel to be optimized, and its nearest neighbors, into a number of subareas, each with its unique response and far-field contribution. Besides the customary intensity control, the design targets can also include phase control of the optical field in one or more of the beams in the beam splitter. We show how this can be used to cancel a strong unwanted zeroth-order beam, which results from using a slightly incorrect modulation characteristic for the SLM, by purposely sending a beam in the same direction but with the opposite phase. All the designs have been implemented on the 256 x 256 central pixels of a reflective liquid crystal on silicon SLM with a selected input polarization state and a direction of transmission axis of the output polarizer such that for the available different pixel settings a phase modulation of ~2pi rad could be obtained, accompanied by an intensity modulation depth as high as >95%.

Three-level phase modulator based on orthoconic antiferroelectric liquid crystals.

Surface-stabilized orthoconic antiferroelectric liquid crystals (OAFLCs) have a director tilt of theta = 45 degrees and are, with no field applied, negatively uniaxial with the optic axis perpendicular to the cell substrates. We demonstrate that OAFLCs can be utilized to achieve lossless phase modulation with three almost equidistant phase levels. This turns out to be true also for polymer-stabilized OAFLCs, where the polymer network increases the switching speed of the device without affecting the phase modulation appreciably.

Diffraction-based determination of the phase modulation for general spatial light modulators.

We describe a characterization method based on diffraction for obtaining the phase response of spatial light modulators (SLMs), which in general exhibit both amplitude and phase modulation. Compared with the conventional interferometer-based approach, the method is characterized by a simple setup that enables in situ measurements, allows for substantial mechanical vibration, and permits the use of a light source with a fairly low temporal coherence. The phase determination is possible even for a SLM with a full amplitude modulation depth, i.e., even if there are nulls in the amplitude transmission characteristic of the SLM. The method successfully determines phase modulation values in the full 2pi rad range with high accuracy. The experimental work includes comparisons with interferometer measurements as well as a SLM characterization with a light-emitting diode (LED).