Many-body theory calculations of positronic-bonded molecular dianions.

The energetic stability of positron-dianion systems [A-; e+; A-] is studied via many-body theory, where A- includes H-, F-, Cl-, and the molecular anions (CN)- and (NCO)-. Specifically, the energy of the system as a function of ionic separation is determined by solving the Dyson equation for the positron in the field of the two anions using a positron-anion self-energy as constructed in Hofierka et al. [Nature 606, 688 (2022)] that accounts for correlations, including polarization, screening, and virtual-positronium formation. Calculations are performed for a positron interacting with H22-, F22-, and Cl22- and are found to be in good agreement with previous theory. In particular, we confirm the presence of two minima in the potential energy of the [H-; e+; H-] system with respect to ionic separation: a positronically bonded [H-; e+; H-] local minimum at ionic separations r ∼ 3.4 Å and a global minimum at smaller ionic separations r ≲ 1.6 Å that gives overall instability of the system with respect to dissociation into a H2 molecule and a positronium negative ion, Ps-. The first predictions are made for positronic bonding in dianions consisting of molecular anionic fragments, specifically for (CN)22- and (NCO)22-. In all cases, we find that the molecules formed by the creation of a positronic bond are stable relative to dissociation into A- and e+A- (positron bound to a single anion), with bond energies on the order of 1 eV and bond lengths on the order of several ångstroms.

Many-Body Theory Calculations of Positron Scattering and Annihilation in H_{2}, N_{2}, and CH_{4}.

The recently developed ab initio many-body theory of positron molecule binding [22J. Hofierka et al., Many-body theory of positron binding to polyatomic molecules, Nature (London) 606, 688 (2022)NATUAS0028-083610.1038/s41586-022-04703-3] is combined with the shifted pseudostates method [A. R. Swann and G. F. Gribakin, Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis, Phys. Rev. A 101, 022702 (2020)PLRAAN2469-992610.1103/PhysRevA.101.022702] to calculate positron scattering and annihilation rates on small molecules, namely H_{2}, N_{2}, and CH_{4}. The important effects of positron-molecule correlations are delineated. The method provides uniformly good results for annihilation rates on all the targets, from the simplest (H_{2}, for which only a sole previous calculation agrees with experiment), to larger targets, where high-quality calculations have not been available.

Psychometric properties of the English language version of the C-BiLLT evaluated in typically developing Canadian children.

PURPOSE: This study aimed to 1) investigate the convergent and discriminant validity, internal consistency, and test-retest reliability of the Canadian English version of the Computer-Based instrument for Low motor Language Testing (C-BiLLT-CAN), and 2) explore feasibility of the C-BiLLT assessment for children with cerebral palsy (CP) and complex communication needs in the Canadian health care context. METHODS: Eighty typically developing children between 1.5 and 8.5 years of age completed the C-BiLLT-CAN, the Peabody Picture Vocabulary Test-IV (PPVT-4), the receptive language sub-test of the New Reynell Developmental Language Scales (NRDLS), and/or the Raven's 2. Correlations between raw scores were calculated for estimates of convergent and discriminant validity. Internal consistency was calculated for all items and separately for items pertaining to vocabulary and grammar. To calculate the standard error of measurement (SEM) and intraclass correlation coefficient (ICC), 33 participants were re-tested with the C-BiLLT within three weeks. Feasibility was explored with nine participants with CP. RESULTS: C-BiLLT-CAN's convergent validity was good to excellent (Spearman's rho > 0.78) and discriminant validity was higher than hypothesized (Spearman's rho > 0.8). Internal consistency (Cronbach's alpha = 0.96), test-retest reliability (ICC > 0.9), and measurement error (SEM < 5%) were excellent. The feasibility study could not be fully completed due to the COVID-19 pandemic. Preliminary data demonstrated some technical and practical barriers for using the C-BiLLT in children with CP in Canada. CONCLUSION: The C-BiLLT-CAN showed good to excellent psychometric properties in a sample of typically developing children, indicating that it is an adequate test for measuring language comprehension in English-speaking Canadian children. Further research is needed to investigate the feasibility of the C-BiLLT-CAN in children with CP.

What are the risk factors for complications after combined injury of the pelvic ring and acetabulum?

PURPOSE: Combined acetabular and pelvic ring injuries represent a unique subset of pelvic trauma and little is known regarding their complications and outcomes. We sought to further evaluate these injury patterns and quantify their outcomes. METHODS: A retrospective review at a single level 1 trauma center was performed on all patients with operatively treated combined ring and acetabulum injuries during a seven-year period. Main outcome measurements include all-cause complication including residual neurologic deficit, deep infection, conversion to total hip arthroplasty, deep venous thrombosis and mortality. RESULTS: Seventy operatively treated combined ring and acetabulum patients with one-year follow-up were reviewed. The overall complication rate was 44%. Hip dislocation occurred in 40% of the cohort and was significantly associated with residual neurologic deficit and all-cause complication. Angiography with embolization was not associated with an increased rate of deep infection. Open acetabular approaches had a significantly higher complication rate compared to percutaneous procedures. Delay to definitive fixation greater than 36 h trended toward but did not reach association with all complications. CONCLUSION: Combined injuries to the acetabulum and pelvic ring have high rates of complications. No individual fracture patterns were identified as risk factors, but hip dislocation was associated with an increased rate of complications. When possible, percutaneous reduction and fixation of acetabular fractures and early definitive fracture fixation lead to lower rates of complications. Use of angiography with embolization appears to be safe and does not increase the risk of infection or other complications.

Implementing the language comprehension test C-BiLLT: a qualitative description study using the COM-B model of behaviour change.

BACKGROUND: It is challenging to reliably assess the language comprehension of children with severe motor and speech impairments using traditional assessment tools. The Computer Based instrument for Low motor Language Testing (C-BiLLT) aims to reduce barriers to evidence-based assessment for this population by allowing children to access the test using non-traditional methods such as eye gaze so they can independently respond to test items. The purpose of this study is to develop a contextualized understanding of the factors that influenced clinicians' implementation of the C-BILLT in practice in the Netherlands and Norway. MATERIALS AND METHODS: A qualitative approach including semi-structured individual interviews with 15 clinicians (speech-language pathologists, neuropsychologists, and one teacher, counsellor, and vision specialist) was used. Data analysis was conducted in two rounds. First, a deductive approach including a codebook was used to code data within the COM-B components describing clinicians' capability, opportunity, and motivation for behaviour change. Then, an abductive approach applying thematic analysis was used to identify meaningful patterns within the COM-B components. RESULTS: Several meaningful barriers and facilitators were identified across the data. Clinicians used the C-BiLLT with two distinct groups of clients: (1) the population it was originally developed for, and (2) clients that could have also been assessed using a traditional language test. Clinicians working with the first group experienced more, and more complex barriers across all COM-B components, to successful C-BiLLT use than the latter. CONCLUSION: This study provides timely insights into the capability, opportunity, and motivation factors important for creating and sustaining assessment behaviour change in clinicians who used or attempted to use the C-BiLLT. Potential tailored intervention strategies aimed at improving implementation of novel assessment tools are discussed and may be helpful for others working to improve service delivery for children with complex needs.

Use of a door handle disinfection system to reduce the risks associated with microbial loads on fomites in a healthcare setting.

BACKGROUND: Pathogenic organisms, including those that are multidrug resistant, can survive for extended periods of time on surfaces. Numerous studies show that contaminated hand-touch sites, such as door handles, pose a serious risk for onward transfer to patients. AIM: To compare microbial levels on the handles of ten frequently used door locations, with and without a door handle disinfection system in place, in a busy rehabilitation unit consisting of two wards at the National Orthopaedic Hospital, Dublin. METHODS: A door handle disinfection system (Handle Hygiene®), utilizing an atomizing pump (non-aerosol), automatically delivered a pulse of disinfectant to a door handle each time the door was used. Microbial levels on the handles of frequently used door locations were monitored over a 16-week period, to compare microbial loads with and without a door handle disinfection system in place. Samples of two disinfectant types, Steri-7 (broad-spectrum disinfectant) and Dew (hypochlorous acid), were used in the study. FINDINGS: Levels of ≤2.5 cfu/cm2 were recorded on 93% of samples collected where a door handle disinfection system was in use, with 66% of samples showing no microbes recovered. Where a level of >2.5 cfu/cm2 was recorded, the door handle disinfection system reduced this to a negligible level by the time the next sample was taken, compared with several days where no system was in place. CONCLUSION: Door handle disinfection systems offer an effective solution to reducing microbial levels on frequently touched door handles, as an automated solution with minimal additional costs.

Internalization, reduced growth, and behavioral effects following exposure to micro and nano tire particles in two estuarine indicator species.

Synthetic rubber emissions from automobile tires are common in aquatic ecosystems. To assess potential impacts on exposed organisms, early life stages of the estuarine indicator species Inland Silverside (Menidia beryllina) and mysid shrimp (Americamysis bahia) were exposed to three tire particle (TP) concentrations at micro and nano size fractions (0.0038, 0.0378 and 3.778 mg/L in mass concentrations for micro size particles), and separately to leachate, across a 5-25 PSU salinity gradient. Following exposure, M. beryllina and A. bahia had significantly altered swimming behaviors, such as increased freezing, changes in positioning, and total distance moved, which could lead to an increased risk of predation and foraging challenges in the wild. Growth for both A. bahia and M. beryllina was reduced in a concentration-dependent manner when exposed to micro-TP, whereas M. beryllina also demonstrated reduced growth when exposed to nano-TP (except lowest concentration). TP internalization was dependent on the exposure salinity in both taxa. The presence of adverse effects in M. beryllina and A. bahia indicate that even at current environmental levels of tire-related pollution, which are expected to continue to increase, aquatic ecosystems may be experiencing negative impacts.

Rapid Isothermal Amplification and Portable Detection System for SARS-CoV-2.

The COVID-19 pandemic provides an urgent example where a gap exists between availability of state-of-the-art diagnostics and current needs. As assay details and primer sequences become widely known, many laboratories could perform diagnostic tests using methods such as RT-PCR or isothermal RT-LAMP amplification. A key advantage of RT-LAMP based approaches compared to RT-PCR is that RT-LAMP is known to be robust in detecting targets from unprocessed samples. In addition, RT-LAMP assays are performed at a constant temperature enabling speed, simplicity, and point-of-use testing. Here, we provide the details of an RT-LAMP isothermal assay for the detection of SARS-CoV-2 virus with performance comparable to currently approved tests using RT-PCR. We characterize the assay by introducing swabs in virus spiked synthetic nasal fluids, moving the swab to viral transport medium (VTM), and using a volume of that VTM for performing the amplification without an RNA extraction kit. The assay has a Limit-of-Detection (LOD) of 50 RNA copies/µL in the VTM solution within 20 minutes, and LOD of 5000 RNA copies/µL in the nasal solution. Additionally, we show the utility of this assay for real-time point-of-use testing by demonstrating detection of SARS-CoV-2 virus in less than 40 minutes using an additively manufactured cartridge and a smartphone-based reader. Finally, we explore the speed and cost advantages by comparing the required resources and workflows with RT-PCR. This work could accelerate the development and availability of SARS-CoV-2 diagnostics by proving alternatives to conventional laboratory benchtop tests.

Hands-free smartphone-based diagnostics for simultaneous detection of Zika, Chikungunya, and Dengue at point-of-care.

Infectious diseases remain the world's top contributors to death and disability, and, with recent outbreaks of Zika virus infections there has been an urgency for simple, sensitive and easily translatable point-of-care tests. Here we demonstrate a novel point-of-care platform to diagnose infectious diseases from whole blood samples. A microfluidic platform performs minimal sample processing in a user-friendly diagnostics card followed by real-time reverse-transcription loop-mediated isothermal amplification (RT-LAMP) on the same card with pre-dried primers specific to viral targets. Our point-of-care platform uses a commercial smartphone to acquire real-time images of the amplification reaction and displays a visual read-out of the assay. We apply this system to detect closely related Zika, Dengue (types 1 and 3) and Chikungunya virus infections from whole blood on the same pre-printed chip with high specificity and clinically relevant sensitivity. Limit of detection of 1.56e5 PFU/mL of Zika virus from whole blood was achieved through our platform. With the ability to quantitate the target nucleic acid, this platform can also perform point-of-care patient surveillance for pathogen load or select biomarkers in whole blood.

Recent Advances in Biosensing With Photonic Crystal Surfaces: A Review.

Photonic crystal surfaces that are designed to function as wavelength-selective optical resonators have become a widely adopted platform for label-free biosensing, and for enhancement of the output of photon-emitting tags used throughout life science research and in vitro diagnostics. While some applications, such as analysis of drug-protein interactions, require extremely high resolution and the ability to accurately correct for measurement artifacts, others require sensitivity that is high enough for detection of disease biomarkers in serum with concentrations less than 1 pg/ml. As the analysis of cells becomes increasingly important for studying the behavior of stem cells, cancer cells, and biofilms under a variety of conditions, approaches that enable high resolution imaging of live cells without cytotoxic stains or photobleachable fluorescent dyes are providing new tools to biologists who seek to observe individual cells over extended time periods. This paper will review several recent advances in photonic crystal biosensor detection instrumentation and device structures that are being applied towards direct detection of small molecules in the context of high throughput drug screening, photonic crystal fluorescence enhancement as utilized for high sensitivity multiplexed cancer biomarker detection, and label-free high resolution imaging of cells and individual nanoparticles as a new tool for life science research and single-molecule diagnostics.

Medical diagnostics with mobile devices: Comparison of intrinsic and extrinsic sensing.

We review the recent development of mobile detection instruments used for medical diagnostics, and consider the relative advantages of approaches that utilize the internal sensing capabilities of commercially available mobile communication devices (such as smartphones and tablet computers) compared to those that utilize a custom external sensor module. In this review, we focus specifically upon mobile medical diagnostic platforms that are being developed to serve the need in global health, personalized medicine, and point-of-care diagnostics.

Performance monitoring of mycobacterium tuberculosis dried culture spots for use with the GeneXpert system within a national program in South Africa.

The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instruments as being "fit for purpose" for the South African National implementation program. We investigated and compared the performance of the DCSs for verification across different bulk batches, testing the settings and cadre of staff, and the Xpert MTB/RIF assay version. Four bulk batches (V005 to V008) were used to prepare (i) 619 DCS panels for laboratory testing on G3 or G4 cartridges by a technologist, (ii) 13 DCS panels (batch V005) used for clinic verification on G3 cartridges by a nurse or lay counselor, and (iii) 20 DCS panels (batch V005) used for the verification of 10 GeneXpert 16 module instruments in mobile vehicles on the G3 cartridge performed by a scientist. The stabilities of the DCSs over 6 months at 4°C, room temperature, and 37°C were investigated. The mean cycle threshold (CT) and standard deviation (SD) for probe A were calculated. The proportions of variability in the CT values across bulk batches, assay versions, and settings and cadre of staff were determined using regression analysis. Overall, the DCSs demonstrated SDs of 3.3 (n = 660) for the G3 cartridges and 3.8 (n = 1,888) for the G4 cartridges, with an overall error rate of 1.5% and false rifampin resistance rate of 0.1%. The proportions of variability (R(2)) in the CT values explained by batch were 14%, by setting and cadre of staff, 5.6%, and by assay version, 4.2%. The most stable temperature in a period of up to 6 months was 37°C (SD, 2.7). The DCS is a robust product suitable for storage, transport, and use at room temperature for the verification of the GeneXpert instrument, and the testing can be performed by non-laboratory-trained personnel in nonlaboratory settings.

Bidirectional scatter measurements of a guided-mode resonant filter photonic crystal structure.

This work investigates the Bidirectional Scatter Distribution Function (BSDF) at incident angles other than normal and at 544-nm wavelength of a Guided Mode Resonance Filter (GMRF) Photonic Crystal (PC) structure designed for normally incident light at 532 nm. Strong out-coupling of PC diffraction orders into both the transmitted and reflected hemispheres was observed specifically at a 25.7° incidence angle, which we attribute to this incident angle/wavelength pair being a good match to the ( ± 1, 0) PC grating mode. BSDF measurements at incident angles of 15° and 35° also displayed some out-coupled diffraction, though much lower in magnitude, and are also attributed to being a weaker match to the ( ± 1, 0) PC grating mode. Three-dimensional finite-difference time-domain Maxwell's equation simulations demonstrate that since this GMRF was designed for complete destructive interference of the transmitted light upon normal incidence, stronger out-coupling of the diffraction is expected for modal solutions as the angle of incidence increases.

Dried culture spots for Xpert MTB/RIF external quality assessment: results of a phase 1 pilot study in South Africa.

Implementation of Xpert MTB/RIF requires quality assessment. A pilot program using dried culture spots (DCSs) of inactivated Mycobacterium tuberculosis is described. Of 274 DCS results received, 2.19% generated errors; the remainder yielded 100% correct Mycobacterium tuberculosis detection. The probe A cycle threshold (C(T)) variability of three DCS batches was ≤ 3.47. The study of longer-term DCS stability is ongoing.

Multicolor fluorescence enhancement from a photonics crystal surface.

A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ∼3×5 in.(2) surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ=632.8 nm laser (cyanine-5) and a dye excited by a λ=532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays.

Label-free prehybridization DNA microarray imaging using photonic crystals for quantitative spot quality analysis.

Technical variability during DNA capture probe printing remains an important obstacle to obtaining high quality data from microarray experiments. While methods that use fluorescent labels for visualizing printed arrays prior to hybridization have been presented, the ability to measure spot density using label-free techniques would provide valuable information on spot quality without altering standard microarray protocols. In this study, we present the use of a photonic crystal biosensor surface and a high resolution label-free imaging detection instrument to generate prehybridization images of spotted oligonucleotide microarrays. Spot intensity, size, level of saturation, and local background intensity were measured from these images. This information was used for the automated identification of missed spots (due to mechanical failure or sample depletion) as well as the assignment of a score that reflected the quality of each printed feature. Missed spots were identified with >95% sensitivity. Furthermore, filtering based on spot quality scores increased pairwise correlation of posthybridization spot intensity between replicate arrays, demonstrating that label-free spot quality scores captured the variability in the microarray data. This imaging modality can be applied for the quality control of printed cDNA, oligonucleotide, and protein microarrays.

Virtual grand rounds: a new educational approach in social work that benefits long-term care providers and patients in rural Idaho.

INTRODUCTION: Nationwide, rural USA is experiencing a shortage of social workers. In rural Idaho, three state-wide non-profit organizations worked together to develop Virtual Grand Rounds (VGRs), a new approach to delivering continuing education to social workers and residential care coordinators, in order to promote their retention in the workforce. This study examined participant satisfaction and the potential for the delivery system to be replicated in other states. METHODS: Between July 2002 and December 2006, 740 person-hours (359 attendees x 2.06 hours) of continuing education were delivered to resident care coordinators and social workers in 9 sessions of VGRs. In total, 287 evaluation forms (79% return rate) were collected on the quality of the presentation, the presenter's expertise and delivery, the relevance and value of the presentation to the attendee, and the quality of the technology. The questionnaire consisted of 10 questions that aimed to measure participant satisfaction level, using a five-point Likert scale with a comments section. RESULTS: Programs and presenters received positive scores. Participants approved of the delivery method and the overall satisfaction rating was 4.1. As to whether the information presented would lead to changes in practice, participants responded positively with a score of 3.25. CONCLUSION: The Telehealth Idaho program contributed to a thorough training for new healthcare employees and for those in rural Idaho unable to attend the annual conference for essential training. Initial successes led to an expansion of the program to include other facility staff, and other topics which provided a new training system and infrastructure. This represents one unique contribution to addressing the rural social workers shortage.

Growth and survival of northern leopard frog (Rana pipiens) tadpoles exposed to two common pesticides.

Aquatic pollution is an important factor implicated in global amphibian declines. Often amphibians are exposed to sublethal levels of agrochemicals continuously throughout their larval period either because of application regimes or persistence of the chemicals in the larvae's environment. Although most studies have examined the effects of one-time or short-term exposure to contaminants on amphibian larvae, few have investigated the implications of continuous exposure over a substantial interval during larval development. We examined the effects of continuous exposure to environmentally relevant concentrations of two common pesticides--endosulfan (0.2, 1, and 5 microg/L) and mancozeb (16, 80, and 400 microg/L)--on the growth and survival of leopard frog tadpoles. The concentrations used are comparable to those estimated to be found in waterbodies near agricultural fields. The exposure period was seven weeks. Mortality was recorded daily, and length was measured photographically once before and twice during the exposure period. Both chemicals greatly reduced survival at these concentrations. Hazard ratios were significantly positive for all treatments. Growth rates of tadpoles exposed to endosulfan were not significantly reduced, but exposure to all three levels of mancozeb resulted in reduced growth rates. These results underscore the importance of further investigation into the effects of endosulfan and mancozeb on environmental and wildlife health.

Species differences in the identification of acoustic stimuli by birds.

The perceptual organization of auditory stimuli can reveal a great deal about how the brain naturally groups events. The current study uses identification techniques to investigate the abilities of two species of birds in identifying zebra finch song as well as synthetically generated speech stimuli. Budgerigars (Melopsittacus undulatus) and zebra finches (Taeniopygia guttata) were trained to differentially peck keys in response to the presentation of various complex stimuli. Although there were no clear differences in performance during the training paradigm between the two species, budgerigars were far more adept at learning to identify both sets of complex stimuli than were zebra finches, requiring far less trials to reach criterion. The non-singing but vocally plastic budgerigars vastly outperformed zebra finches at identifying both zebra finch song and synthetically designed human speech despite known similarities in auditory sensitivities between the two species and seemingly equivalent learning capacity. The flexibility that budgerigars seem to have at identifying various stimuli is highlighted by their enhanced performance in these tasks. These results are discussed in the context of what is known about both general and specialized processes which may contribute to any differences or similarities in performance.