Vibronic structure of photosynthetic pigments probed by polarized two-dimensional electronic spectroscopy and ab initio calculations

Bacteriochlorophyll a (Bchl a) and chlorophyll a (Chl a) play important roles as light absorbers in photosynthetic antennae and participate in the initial charge-separation steps in photosynthetic reaction centers. Despite decades of study, questions remain about the interplay of electronic and vibrational states within the Q-band and its effect on the photoexcited dynamics. Here we report results of polarized two-dimensional electronic spectroscopic measurements, performed on penta-coordinated Bchl a and Chl a and their interpretation based on state-of-the-art time-dependent density functional theory calculations and vibrational mode analysis for spectral shapes. We find that the Q-band of Bchl a is comprised of two independent bands, that are assigned following the Gouterman model to Q x and Q y states with orthogonal transition dipole moments. However, we measure the angle to be ∼75°, a finding that is confirmed by ab initio calculations. The internal conversion rate constant from Q x to Q y is found to be 11 ps-1. Unlike Bchl a, the Q-band of Chl a contains three distinct peaks with different polarizations. Ab initio calculations trace these features back to a spectral overlap between two electronic transitions and their vibrational replicas. The smaller energy gap and the mixing of vibronic states result in faster internal conversion rate constants of 38-50 ps-1. We analyze the spectra of penta-coordinated Bchl a and Chl a to highlight the interplay between low-lying vibronic states and their relationship to photoinduced relaxation. Our findings shed new light on the photoexcited dynamics in photosynthetic systems where these chromophores are primary pigments.

Predicting and Controlling Entangled Two-Photon Absorption in Diatomic Molecules

The use of nonclassical states of light to probe organic molecules has received great attention due to the possibility of providing new and detailed information regarding molecular excitations. Experimental and theoretical results have been reported which show large enhancements of the nonlinear optical responses in organic materials due to possible virtual-electronic-state interactions with entangled photons. In order to predict molecular excitations with nonclassical light, more detailed investigations of the parameters involved must be carried out. In this report we investigate the details of the state-to-state parameters important in calculating the contribution of particular transitions involved in the entangled two-photon absorption process for diatomic molecules. The theoretical discussion of the entangled two-photon process is described for a set of diatomic molecules. Specifically, we provide detailed quantum chemical calculations which give accurate energies and transition moments for selection-rule allowed intermediate states important in the entangled nonlinear effect for the diatomic molecules. These results are used to estimate in a more accurate manner the nonmonotonic behavior of the entangled two-photon absorption cross-section. We also derive accurate approximations that can be used to predict the period between entanglement-induced transparencies without needing exact values of the transition dipole moments. These results suggest that with the additional parameters allotted by the entangled two-photon absorption (in comparison to the classical case), it may be possible to predict and later control the nonlinear absorption and transparency of a molecule at a constant incident photon frequency.

Modern Anesthetic Ethers Demonstrate Quantum Interactions with Entangled Photons

Despite decades of research, the mechanism of anesthetic-induced unconsciousness remains incompletely understood, with some advocating for a quantum mechanical basis. Despite associations between general anesthesia and changes in physical properties such as electron spin, there has been no empirical demonstration that general anesthetics are capable of functional quantum interactions. In this work, we studied the linear and non-linear optical properties of the halogenated ethers sevoflurane (SEVO) and isoflurane (ISO), using UV-Vis spectroscopy, time dependent-density functional theory (TD-DFT) calculations, classical two-photon spectroscopy, and entangled two-photon spectroscopy. We show that both of these halogenated ethers interact with pairs of 800 nm entangled photons while neither interact with 800 nm classical photons. By contrast, nonhalogenated diethyl ether does not interact with entangled photons. This is the first experimental evidence that halogenated anesthetics can directly undergo quantum interaction mechanisms, offering a new approach to understanding their physicochemical properties.

Enhancing Entangled Two-Photon Absorption for Picosecond Quantum Spectroscopy

Entangled two-photon absorption (ETPA) is known to create photoinduced transitions with extremely low light intensity, reducing the risk of phototoxicity compared to classical two-photon absorption. Previous works have predicted the ETPA cross-section, σ_e, to vary inversely with the product of entanglement time (T_e) and entanglement area (A_e), i.e., σ_e ∼ 1/A_eT_e. The decreasing σ_e with increasing T_e has limited ETPA to fs-scale T_e, while ETPA applications for ps-scale spectroscopy have been unexplored. However, we show that spectral-spatial coupling, which reduces A_e as the SPDC bandwidth (σ_f) decreases, plays a significant role in determining σ_e when T_e > ∼100 fs. We experimentally measured σ_e for zinc tetraphenylporphyrin at several σ_f values. For type-I ETPA, σ_e increases as σ_f decreases down to 0.1 ps^-1. For type-II SPDC, σ_e is constant for a wide range of σ_f. With a theoretical analysis of the data, the maximum type-I σ_e would occur at σ_f = 0.1 ps^-1 (T_e = 10 ps). At this maximum, σ_e is 1 order of magnitude larger than fs-scale σ_e and 3 orders of magnitude larger than previous predictions of ps-scale σ_e. By utilizing this spectral-spatial coupling, narrowband type-I ETPA provides a new opportunity to increase the efficiency of measuring nonlinear optical signals and to control photochemical reactions requiring ps temporal precision.

Entangled Photon Spectroscopy

The enhanced interest in quantum-related phenomena has provided new opportunities for chemists to push the limits of detection and analysis of chemical processes. As some have called this the second quantum revolution, a time has come to apply the rules learned from previous research in quantum phenomena toward new methods and technologies important to chemists. While there has been great interest recently in quantum information science (QIS), the quest to understand how nonclassical states of light interact with matter has been ongoing for more than two decades. Our entry into this field started around this time with the use of materials to produce nonclassical states of light. Here, the process of multiphoton absorption led to photon-number squeezed states of light, where the photon statistics are sub-Poissonian. In addition to the great interest in generating squeezed states of light, there was also interest in the formation of entangled states of light. While much of the effort is still in foundational physics, there are numerous new avenues as to how quantum entanglement can be applied to spectroscopy, imaging, and sensing. These opportunities could have a large impact on the chemical community for a broad spectrum of applications.In this Account, we discuss the use of entangled (or quantum) light for spectroscopy as well as applications in microscopy and interferometry. The potential benefits of the use of quantum light are discussed in detail. From the first experiments in porphyrin dendrimer systems by Dr. Dong-Ik Lee in our group to the measurements of the entangled two photon absorption cross sections of biological systems such as flavoproteins, the usefulness of entangled light for spectroscopy has been illustrated. These early measurements led the way to more advanced measurements of the unique characteristics of both entangled light and the entangled photon absorption cross-section, which provides new control knobs for manipulating excited states in molecules.The first reports of fluorescence-induced entangled processes were in organic chromophores where the entangled photon cross-section was measured. These results would later have widespread impact in applications such as entangled two-photon microscopy. From our design, construction and implementation of a quantum entangled photon excited microscope, important imaging capabilities were achieved at an unprecedented low excitation intensity of 10⁷ photons/s, which is 6 orders of magnitude lower than the excitation level for the classical two-photon image. New reports have also illustrated an advantage of nonclassical light in Raman imaging as well.From a standpoint of more precise measurements, the use of entangled photons in quantum interferometry may offer new opportunities for chemistry research. Experiments that combine molecular spectroscopy and quantum interferometry, by utilizing the correlations of entangled photons in a Hong-Ou-Mandel (HOM) interferometer, have been carried out. The initial experiment showed that the HOM signal is sensitive to the presence of a resonant organic sample placed in one arm of the interferometer. In addition, parameters such as the dephasing time have been obtained with the opportunity for even more advanced phenomenology in the future.

Gag-dependent enrichment of HIV-1 RNA near the uropod membrane of polarized T cells

The enrichment of HIV-1 macromolecules at the uropod of polarized T cells can significantly promote virus assembly and cell-mediated infection. Using live-cell fluorescence microscopy, we demonstrate that full-length HIV-1 RNA is enriched at the uropod membrane; furthermore, the presence of HIV-1 Gag containing a functional nucleocapsid domain is necessary for this HIV-1 RNA enrichment. The results from these studies provide novel insights into the mechanism of HIV-1 replication in polarized T cells.

A modified large sample approach in the assessment of population bioequivalence

The U.S. Food and Drug Administration (FDA) requires pharmaceutical companies to show bioequivalence between different formulations or generic companies to show bioequivalence between generic drugs and brand drugs before approval. In a recent FDA guidance on bioequivalence, new criteria were proposed for assessment of population and individual bioequivalence. In this article, computer simulation is used to compare a modified large sample (MLS) upper bound for the population bioequivalence ratio with the bootstrap upper bound recommended by the FDA. The comparison criteria are the ability to maintain the stated confidence level and the estimated power of tests based on these bounds.

Visual Modeling: A Socialization-Based Intervention to Improve Nutritional Intake Among Nursing Home Residents

Purpose Malnutrition is a widespread, dangerous, and costly condition among institutionalized older adults and can be both a contributor to and consequence of dysphagia for individuals with cognitive impairment. However, interventions to maximize intake in individuals with dementia are limited and frequently problematic, with negative implications for independence and quality of life. The goal of this study was to examine a novel, socialization-grounded intervention based on visual modeling, utilizing the theoretical underpinnings of motor resonance and mimicry. Method To examine the impact of environment on intake, data were collected from four nursing home residents (M _age = 83.5 years, SD = 4.2; three women) with dementia. Weight of food and liquid intake was measured across 15 meals and three different mealtime conditions: the "baseline condition" in which the individual ate alone, the "watch condition" in which the individual ate in the company of a "mealtime buddy," and the "eat" condition in which the individual consumed a meal while the "mealtime buddy" did the same. Results Data visualization supported a weak functional relation between eating environment and amount of intake consumed across participants. Log response ratio estimates suggested a trend for increased weight of food consumed during the eat condition as compared to baseline and the eat condition as compared to the watch condition for some participants. Conclusions These results preliminarily support the benefit of a visual model for increased consumption in some individuals with dementia. The presence and magnitude of the effect across conditions varied based on individual-level factors, such as cognitive status, which has implications for implementation. Overall, this study provides initial proof of concept regarding the use of visual modeling as an intervention approach, laying the foundation for larger scale future studies.

The rate of use of Veterans Affairs chiropractic care: a 5-year analysis

BACKGROUND

The US Department of Veterans Affairs (VA) has initiated various approaches to provide chiropractic care to Veterans. Prior work has shown substantial increase in use of VA chiropractic care between fiscal years (FY) 2005-2016. However, the extent of the availability of these services to the Veteran population remains unclear. The purpose of this study was to analyze the rate of Veteran use of VA chiropractic services, both from on-site care at VA facilities and VA purchased care from community care providers. This study analyzed facility characteristics associated with chiropractic use by both care delivery mechanisms (on-site and in the community).

METHODS

Cross-sectional analyses of administrative data were conducted for FY 2014-2019. Data were obtained from VA's Corporate Data Warehouse. The variables extracted included number of unique Veterans receiving VA chiropractic care on-site and in the community, total Veteran population of the VA facilities, size of the VA chiropractic workforce (measured as Full-Time Equivalent, FTE), and facility characteristics (geographic region and the facility complexity). Descriptive statistics, mixed model, and multivariant models were used to analyze data.

RESULTS

Use of VA chiropractic care increased over the six-year period for both on-site and community care. National average for on-site use of the population was 1.27% in FY14 and 1.48% in FY19. Community care use was 0.29% and 1.76% for the same years. Use at individual facilities varied widely in each FY. Factors such as chiropractor FTE, geographic locations, and the complexity of the VA facility are associated with use of chiropractic services.

CONCLUSION

The VA has expanded the non-pharmacologic treatments available to Veterans by providing chiropractic services, yet chiropractic use remains low compared to other US populations. As Veterans have a high prevalence of pain and musculoskeletal conditions, continued work to assess and achieve the optimal levels of chiropractic use in this population is warranted.

Deglutologist Practices and Perceptions of the Penetration-Aspiration Scale: A Survey Study

Successful dysphagia management requires accurate, succinct diagnosis and characterization of swallowing safety impairments. However, the Penetration-Aspiration Scale (PAS) remains the only available tool developed exclusively for assessment of airway protection. To best support efforts to advance the field's understanding of swallowing safety, it is crucial to understand current clinician practice patterns, perceptions, and accuracy regarding the PAS. A 46-item survey was developed and distributed to deglutologists internationally examining: (1) Demographics; (2) Scale Practices; (3) Swallowing Safety Priorities; (4) Scale Perceptions; and (5) Accuracy. The first four sections consisted of questionnaires. In the optional fifth section, respondents were asked to score five videos of swallows collected via videofluoroscopy and previously PAS-scored by two trained raters. In total, 335 responses were analyzed. The majority of respondents self-reported PAS training (84%); 90% of untrained respondents were receptive to training. Respondents reported using the PAS "always" (40%) or "frequently" (29%), and that the PAS carries "a great deal of" weight in assessment (40%). Reported application of the PAS was heterogeneous, with the most common approach being "single worst score per unique presentation" (45%). Most respondents (64%) prioritized a parameter not captured by the PAS. Untrained respondents were significantly more confident with PAS ratings than trained respondents (X2 = 7.47; p = 0.006). Of 1460 PAS ratings provided, 364 of them were accurate (25%) when compared to ratings by trained lab members. Results of this survey reflect ubiquitous use of the PAS, unmet needs for assessment of swallowing safety, low accuracy despite generally high confidence, and heterogenous training that does not correspond to confidence. This emphasizes the need for additional training in clinical application of the PAS as well as development of novel metrics to optimize assessments of swallowing safety.

The Impact of Modifiable Preoral Factors on Swallowing and Nutritional Outcomes in Healthy Adults: A Scoping Review

PURPOSE

Swallowing has previously been characterized as consisting of four phases; however, it has become apparent that these four phases are not truly discrete and may be influenced by factors occurring prior to bolus entrance into the oral cavity (i.e., preoral factors). Still, the relationship between these factors and swallowing remains poorly understood. The aim of this review was to synthesize and characterize the literature pertaining to the influence of preoral factors on swallowing and nutritional outcomes in healthy individuals.

METHOD

We performed a scoping review, searching the databases of PubMed, CINAHL, Cochrane, and Scopus. Search terms included those related to swallowing, experience of preoral factors, and exclusionary terminology to reduce animal and pediatric literature. Our initial search revealed 5,560 unique articles, of which 153 met our inclusionary criteria and were accepted into the review.

RESULTS

Of the accepted articles, 78% were focused exclusively on nutritional outcomes, 17% were focused on both swallowing and nutritional outcomes, and 5% were focused on solely swallowing outcomes. Of the preoral factors examined, 99% were exteroceptive in nature (17% olfactory, 44% visual, 21% auditory, 7% tactile, 11% other), while 1% were proprioceptive in nature.

CONCLUSIONS

This review supports the influence of preoral factors on swallowing and nutritional outcomes. However, there is a large emphasis on the visual modality and on nutritional outcomes. Nearly none of the literature found in this review directly measured swallowing safety, efficiency, or physiology. Future work will benefit from a larger focus on proprioceptive preoral factors as they relate to swallowing outcomes.

Use of deep learning to segment bolus during videofluoroscopic swallow studies

Anatomical segmentations generated using artificial intelligence (AI) have the potential to significantly improve video fluoroscopic swallow study (VFS) analysis. AI segments allow for various metrics to be determined without additional time constraints streamlining and creating new opportunities for analysis. While the opportunity is vast, it is important to understand the challenges and limitations of the underlying AI task. This work evaluates a bolus segmentation network. The first swallow of thin or liquid bolus from 80 unique patients were manually contoured from bolus first seen in the oral cavity to end of swallow motion. The data was split into a 75/25 training and validation set and a 4-fold cross validation was done. A U-Net architecture along with variations were tested with the dice coefficient as the loss function and overall performance metric. The average validation set resulted in a dice coefficient of 0.67. Additional analysis to characterize the variability of images and performance on sub intervals was conducted indicating high variability among the processes required for training the network. It was found that bolus in the oral cavity consistently degrades performance due to misclassification of teeth and unimportant residue. The dice coefficients dependence on structure size can have substantial effects on the reported value. This work shows the efficacy of bolus segmentation and identifies key areas that are detriments to the performance of the network.

Dysphagia in Parkinson Disease: Part I - Pathophysiology and Diagnostic Practices

Purpose of Review

Dysphagia affects the majority of individuals with Parkinson disease (PD) and is not typically diagnosed until later in disease progression. This review will cover the current understanding of PD pathophysiology, and provides an overview of dysphagia in PD including diagnostic practices, gaps in knowledge, and future directions.

Recent Findings

Many non-motor and other motor signs of PD appear in the prodrome prior to the manifestation of hall- mark signs and diagnosis. While dysphagia often presents already in the prodrome, it is not routinely addressed in standard neurology examinations.

Summary

Dysphagia in PD can result in compromised efficiency and safety of swallowing, which significantly contributes to malnutrition and dehydration, decrease quality of life, and increase mortality. The heterogeneous clinical presentation of PD complicates diagnostic procedures which often leads to delayed treatment. Research has advanced our knowledge of mechanisms underlying PD, but dysphagia is still largely understudied, especially in the prodromal stage.

Confidence intervals on the ratio of expected mean squares (theta 1 + d theta 2)/theta 3

The variance component ratio delta = (theta 1 + d theta 2)/theta 3 is of interest in many fields of application. This paper proposes and compares two methods for constructing confidence intervals on delta. The better method is compared with a method proposed by Graybill and Wang (1979, Journal of the American Statistical Association 74, 368-374) for the special problem of constructing an interval on sigma 2E/(sigma 2A + sigma 2B + sigma 2E) in a two-fold nested design. An example concerning a heritability study is provided.