Nighttime Applications of Germicidal UV Light to Suppress Cercospora Leaf Spot in Table Beet.

Cercospora leaf spot (CLS), caused by the hemibiotrophic fungus Cercospora beticola, is a destructive disease affecting table beet. Multiple applications of fungicides are needed to reduce epidemic progress to maintain foliar health and enable mechanized harvest. The sustainability of CLS control is threatened by the rapid development of fungicide resistance, the need to grow commercially acceptable yet CLS-susceptible cultivars, and the inability to manipulate agronomic conditions to mitigate disease risk. Nighttime applications of germicidal UV light (UV-C) have recently been used to suppress several plant diseases, notably those caused by ectoparasitic biotrophs such as powdery mildews. We evaluated the efficacy of nighttime applications of UV-C for suppression of CLS in table beet. In vitro lethality of UV-C to germinating conidia increased with increasing dose, with complete suppression at 1,000 J/m2. Greenhouse-grown table beet tolerated relatively high doses of UV-C without lethal effects despite some bronzing on the leaf blade. A UV-C dose >1,500 J/m2 resulted in phytotoxicity severities greater than 50%. UV-C exposure to ≤750 J/m2 resulted in negligible phytotoxicity. Older (6-week-old) greenhouse-grown plants were more susceptible to UV-C damage than younger (2- and 4-week-old) plants. Suppression of CLS by UV-C was greater when applied within 6 days of C. beticola inoculation than if delayed until 13 days after infection in greenhouse-grown plants. In field trials, there were significant linear relationships between UV-C dose and CLS control and phytotoxicity severity, and a significant negative linear relationship between phytotoxicity and CLS severity at the final assessment. Significant differences between UV-C doses on the severity of CLS and phytotoxicity indicated an efficacious dose near 800 J/m2. Collectively, these findings illustrate significant and substantial suppression by nighttime applications of UV-C for CLS control on table beet, with potential for incorporation in both conventional and organic table beet broadacre production systems.

Melanin bias in pulse oximetry explained by light source spectral bandwidth.

BACKGROUND: Pulse oximetry uses noninvasive optical measurements of light transmission from each of two sources through vascularised living tissue over the cardiac cycle (SpO2). From those measurements, the relative amount of oxygenated haemoglobin (SaO2) in circulating blood can be deduced. Recent reports have shown that, compared with SaO2 measurements from blood samples, SpO2 measurements are biased erroneously high for patients with dark skin. METHODS: We developed a new method, spectrally resolved photoplethysmography (srPPG), to examine how spectral bandwidth affects the transmission of polychromatic light through the fingertip across the cardiac cycle. We measured and recorded the spectral transmission through the fingertip as the O2 concentration in inspired air was reduced. We applied digital spectral filters of two different bandwidths, narrow or broad, to the same srPPG recordings to determine whether SpO2 readings systematically varied for the two bandwidths. The srPPG method also allowed us to measure the fractional amount of melanin in the optical path. The effect of melanin content on the ratio of SpO2 readings for narrow and broad spectral bandwidths was analysed. RESULTS: We hypothesised, based upon the Beer-Lambert law, and then showed experimentally, that the light emission spectra of light-emitting diode light sources, as used in commercial pulse oximeters, result in erroneously high SpO2 measurements for patients having greater melanin concentrations in their skin than those of the subject pool used for instrument calibration. CONCLUSIONS: To eliminate melanin bias, pulse oximeters should use much narrower spectral bandwidths than those used in current models.

Evaluation of a Novel Ambient Light Survey Question in the Cancer Prevention Study-3.

Nighttime light exposure may increase cancer risk by disrupting the circadian system. However, there is no well-established survey method for measuring ambient light. In the Cancer Prevention Study-3, 732 men and women answered a light survey based on seven environments. The light environment in the past year was assessed twice, one year apart, and four one-week diaries were collected between the annual surveys. A total of 170 participants wore a meter to measure photopic illuminance and circadian stimulus (CS). Illuminance and CS values were estimated for lighting environments from measured values and evaluated with a cross validation approach. The kappas for self-reported light environment comparing the two annual surveys were 0.61 on workdays and 0.49 on non-workdays. Kappas comparing the annual survey to weekly diaries were 0.71 and 0.57 for work and non-workdays, respectively. Agreement was highest for reporting of darkness (95.3%), non-residential light (86.5%), and household light (75.6%) on workdays. Measured illuminance and CS identified three peaks of light (darkness, indoor lighting, and outdoor daytime light). Estimated illuminance and CS were correlated with the measured values overall (r = 0.77 and r = 0.67, respectively) but were less correlated within each light environment (r = 0.23-0.43). The survey has good validity to assess ambient light for studies of human health.

The circadian stimulus-oscillator model: Improvements to Kronauer's model of the human circadian pacemaker.

Modeling how patterns of light and dark affect circadian phase is important clinically and organizationally (e.g., the military) because circadian disruption can compromise health and performance. Limit-cycle oscillator models in various forms have been used to characterize phase changes to a limited set of light interventions. We approached the analysis of the van der Pol oscillator-based model proposed by Kronauer and colleagues in 1999 and 2000 (Kronauer99) using a well-established framework from experimental psychology whereby the stimulus (S) acts on the organism (O) to produce a response (R). Within that framework, using four independent data sets utilizing calibrated personal light measurements, we conducted a serial analysis of the factors in the Kronauer99 model that could affect prediction accuracy characterized by changes in dim-light melatonin onset. Prediction uncertainty was slightly greater than 1 h for the new data sets using the original Kronauer99 model. The revised model described here reduced prediction uncertainty for these same data sets by roughly half.

Corrigendum: Modeling Circadian Phototransduction: Quantitative Predictions of Psychophysical Data.

[This corrects the article DOI: 10.3389/fnins.2021.615322.].

UV-Transmitting Plastics Reduce Powdery Mildew in Strawberry Tunnel Production.

Strawberry powdery mildew, caused by Podosphaera aphanis, can be particularly destructive in glasshouse and plastic tunnel production systems, which generally are constructed of materials that block ultraviolet (UV) solar radiation (about 280 to 400 nm). We compared epidemic progress in replicated plots in open fields and under tunnels constructed of polyethylene, which blocks nearly all solar UV-B, and two formulations of ethylene tetrafluoroethylene (ETFE), one of which contained a UV blocker and another that transmitted nearly 90% of solar UV-B. Disease severity under all plastics was higher than in open-field plots, indicating a generally more favorable environment in containment structures. However, the foliar severity of powdery mildew within the tunnels was inversely related to their UV transmissibility. Among the tunnels tested, incidence of fruit infection was highest under polyethylene and lowest under UV-transmitting ETFE. These effects probably transcend crop, and the blocking of solar UV transmission by glass and certain plastics probably contributes to the widely observed favorability of greenhouse and high-tunnel growing systems for powdery mildew.

Spatial sensitivity of human circadian response: Melatonin suppression from on-axis and off-axis light exposures.

A better understanding of the spatial sensitivity of the human circadian system to photic stimulation can provide practical solutions for optimized circadian light exposures. Two psychophysical experiments, involving 25 adult participants in Experiment 1 (mean age = 34.0 years [SD 15.5]; 13 females) and 15 adult participants in Experiment 2 (mean age = 43.0 years [SD 12.6]; 12 females), were designed to investigate whether varying only the spatial distribution of luminous stimuli in the environment while maintaining a constant spectrally weighted irradiance at the eye could influence nocturnal melatonin suppression. Two spatial distributions were employed, one where the luminous stimulus was presented On-axis (along the line of sight) and one where two luminous stimuli were both presented Off-axis (laterally displaced at center by 14°). Two narrowband LED light sources, blue (λmax  = 451 nm) for first experiment and green (λmax  = 522 nm) for second experiment, were used in both the On-axis and the Off-axis spatial distributions. The blue luminous stimulus targeting the fovea and parafovea (On-axis) was about three times more effective for suppressing melatonin than the photometrically and spectrally matched stimulus targeting the more peripheral retina (Off-axis). The green luminous stimulus targeting the fovea and parafovea (On-axis) was about two times more effective for suppressing melatonin than the photometrically and spectrally matched stimulus targeting the more peripheral retina (Off-axis).

Clinical predictors of shunt response in the diagnosis and treatment of idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis.

BACKGROUND: Positive shunt response (SR) remains the gold standard for diagnosing idiopathic normal pressure hydrocephalus (iNPH). However, multiple pathologies mimic iNPH symptoms, making it difficult to select patients who will respond to shunt surgery. Although presenting features, extended lumbar drainage (ELD), infusion test (IT), intracranial pressure monitoring (ICPM), and tap test (TT) have been used to predict SR, uncertainty remains over which diagnostic test to choose. OBJECTIVE: To conduct a systematic review and meta-analysis to identify clinical predictors of shunt responsiveness, evaluate their diagnostic effectiveness, and recommend the most effective diagnostic tests. METHODS: Embase, MEDLINE, Scopus, PubMed, Google Scholar, and JSTOR were searched for original studies investigating clinical predictors of SR in iNPH patients. Included studies were assessed using the QUADAS-2 tool, and eligible studies were evaluated using univariate and bivariate meta-analyses. RESULTS: Thirty-five studies were included. Nine studies discussed the diagnostic use of presenting clinical features, 8 studies ELD, 8 studies IT, 11 studies ICPM, and 6 studies TT. A meta-analysis of 21 eligible studies was conducted for TT, ELD, IT, and ICPM. ICPM yielded the highest diagnostic effectiveness, with diagnostic odds ratio (DOR) = 50.9 and area under curve (AUC) = 0.836. ELD yielded DOR = 27.70 and AUC = 0.753, IT had DOR = 5.70 and AUC = 0.729, and TT scored DOR = 3.86 and AUC = 0.711. CONCLUSION: Intraparenchymal ICPM is statistically the most effective diagnostic test, followed by ELD, IT, and lastly TT. Due to the higher accessibility of TT and IT, they are recommended to be used first line, using a timed-up-and-go improvement ≥ 5.6 s or a Rout cut-off range between 13 and 16 mmHg, respectively. Patients who test negative should ideally be followed up with ICPM, using mean ICP wave amplitude [Formula: see text] 4 mmHg, or 1- to 4-day ELD with an MMSE cut-off improvement [Formula: see text] 3. Future research must use standardized methodologies for each diagnostic test and uniform criteria for SR to allow better comparison.

Relative light sensitivities of four retinal hemi-fields for suppressing the synthesis of melatonin at night.

The magnitude of the stimulus to the biological clock will depend upon the distribution of circadian phototransduction circuits across the retinae and the spatial distribution of luminous stimuli in the environment. The present study compared nocturnal melatonin suppression for light exposures to the superior, inferior, nasal, and temporal retina in one eye independent of shading from the brow and the nose. The stimulus was a 40° diameter luminous disc, half of which was blue light (LED, λpeak = 470 nm) and the other amber light (LED, λpeak = 590 nm). Experimentally, the orientation of the bipartite disc was rotated to each of the four cardinal points of the visual field. A full, 40° blue disc was also employed by replacing the amber half-disc with another blue half-disc. The blue full- and half-discs always produced 100 photopic lx at the cornea. As hypothesized, nocturnal melatonin suppression was statistically greatest when the blue half-disc was delivered to the nasal hemi-field (35%); the other three hemi-fields were equally affected by the blue half-disc (≈20%). Melatonin suppression for the full-disc was 24%, which was not statistically different than the average suppression for the four hemi-fields of 27%.

Modeling Circadian Phototransduction: Quantitative Predictions of Psychophysical Data.

A revised computational model of circadian phototransduction is presented. The first step was to characterize the spectral sensitivity of the retinal circuit using suppression of the synthesis of melatonin by the pineal gland at night as the outcome measure. From the spectral sensitivity, circadian light was defined. Circadian light, thereby rectifies any spectral power distribution into a single, instantaneous photometric quantity. The second step was to characterize the circuit's response characteristic to different amounts of circadian light from threshold to saturation. By doing so a more complete instantaneous photometric quantity representing the circadian stimulus was defined in terms of both the spectral sensitivity and the response magnitude characteristic of the circadian phototransduction circuit. To validate the model of the circadian phototransduction circuit, it was necessary to augment the model to account for different durations of the circadian stimulus and distribution of the circadian stimulus across the retina. Two simple modifications to the model accounted for the duration and distribution of continuous light exposure during the early biological night. A companion paper (https://www.frontiersin.org/articles/10.3389/fnins.2020.615305/full) provides a neurophysiological foundation for the model parameters.

Use of Ultraviolet Light to Suppress Powdery Mildew in Strawberry Fruit Production Fields.

We designed and deployed an apparatus to apply UV light for suppression of powdery mildew in open field production of strawberry. The unit was evaluated in a commercial production field for one season, and for two additional seasons in open field research plots at the University of Florida Gulf Coast Research and Education Center. The apparatus contained two 180-cm-long hemicylindrical arrays of twenty 55-W low-pressure discharge UV-C lamps (operated at 30 W; peak wavelength = 254 nm) backed by polished aluminum reflectors covering two adjacent beds of the strawberry planting. The lamp arrays were suspended within a steel carriage that was tractor-drawn through the planting at 2.3, 4.6, and 5.6 km h-1. Nighttime applications of UV-C at doses ranging from 65 to 170 J⋅m-2 either once or twice weekly provided suppression of foliar and fruit disease that was consistently equal to or better than that provided by a commercial calendar-based fungicide spray program.

Long-Term, All-Day Exposure to Circadian-Effective Light Improves Sleep, Mood, and Behavior in Persons with Dementia.

BACKGROUND: Persons with Alzheimer's disease and related dementias (ADRD) frequently experience sleep-wake (circadian) cycle disturbances that lead them to remain awake at night, causing stress and fatigue for families and caregivers. Light therapy shows promise as a nonpharmacological treatment for regulating sleep in this population. OBJECTIVE: We investigated the long-term impact of a circadian-effective lighting intervention on sleep, mood, and behavior problems in persons with ADRD. METHODS: This 25-week clinical trial administered an all-day lighting intervention to 47 patients with ADRD in 9 senior-care facilities, employing wrist-worn actigraphy measures and standardized measures of sleep quality, mood, and behavior. RESULTS: The intervention significantly improved Pittsburgh Sleep Quality Index scores, from an estimated mean±SEM of 11.89±0.53 at baseline to 5.36±0.63 at the end of the intervention. Additional improvements were noted for sleep efficiency data from actigraph measurements. The intervention significantly reduced Cornell Scale for Depression in Dementia scores (mean±SEM of 11.36±0.74 at baseline and 4.18±0.88 at the end of the intervention) and Cohen-Mansfield Agitation Inventory scores (mean±SEM of 47.10±1.98 at baseline and 35.33±2.23 at the end of the intervention). CONCLUSION: A regular circadian-effective daytime lighting intervention can improve sleep at night and reduce depression and agitation in patients with dementia living in controlled environments. More importantly, the positive effects of the tailored lighting intervention on these outcomes appear to be cumulative over time.

Predictions of melatonin suppression during the early biological night and their implications for residential light exposures prior to sleeping.

The magnitude of nocturnal melatonin suppression depends upon the spectrum, amount, and duration of light exposure. The functional relationship between melatonin suppression and the light spectrum and amount have been previously described. Only one duration-dependent parameter was needed to extend this functional relationship to predict nocturnal melatonin suppression during the early biological night from a variety of published studies. Those predictions suggest that ambient lighting commonly found in North American homes will not suppress melatonin for durations up to 3 h, whereas extended use of self-luminous displays in the home prior to sleep can.

Declines in Wavelength Discrimination and Shifts in Unique Hue with Hypoxia.

INTRODUCTION: Hypoxia can be a problem for warfighters, compromising visual and cognitive performance. One area of study has been hypoxia-induced decrements in color vision.METHODS: The present study examined how hypoxia affected the perception of wavelengths associated with unique green and with unique yellow as well as discriminability by the blue vs. yellow (b-y) and the red vs. green (r-g) spectrally opponent color channels while breathing O2 levels found at sea level and at 5500 m. Measurements of wavelengths producing unique green (minimizing response by the b-y channel) and unique yellow (minimizing response by the r-g channel) preceded measurements of wavelength discriminability near those unique hues.RESULTS: Relative to sea level, unique yellow shifted to shorter wavelengths (0.54 nm) and unique green shifted to longer wavelengths (2.3 nm) under hypoxia. In terms of an equal psychophysical scale, both unique hues shifted by similar magnitudes. Wavelength discriminability of both color channels was compromised by statistically reliable amounts of 16-17% under hypoxia.DISCUSSION: These results were consistent with previous studies and the inference that postreceptor, M-cone neurons were differentially compromised by hypoxia. However, these measurable changes in color vision due to hypoxia were not perceived by the subjects.Bierman A, LaPlumm T, Rea MS. Declines in wavelength discrimination and shifts in unique hue with hypoxia. Aerosp Med Hum Perform. 2020; 91(5):394-402.

Modeling Circadian Phototransduction: Retinal Neurophysiology and Neuroanatomy.

The retina is a complex, but well-organized neural structure that converts optical radiation into neural signals that convey photic information to a wide variety of brain structures. The present paper is concerned with the neural circuits underlying phototransduction for the central pacemaker of the human circadian system. The proposed neural framework adheres to orthodox retinal neuroanatomy and neurophysiology. Several postulated mechanisms are also offered to account for the high threshold and for the subadditive response to polychromatic light exhibited by the human circadian phototransduction circuit. A companion paper, modeling circadian phototransduction: Quantitative predictions of psychophysical data, provides a computational model for predicting psychophysical data associated with nocturnal melatonin suppression while staying within the constraints of the neurophysiology and neuroanatomy offered here.

Effects of a Tailored Lighting Intervention on Sleep Quality, Rest-Activity, Mood, and Behavior in Older Adults With Alzheimer Disease and Related Dementias: A Randomized Clinical Trial.

STUDY OBJECTIVES: We investigated the effectiveness of a lighting intervention tailored to maximally affect the circadian system as a nonpharmacological therapy for treating problems with sleep, mood, and behavior in persons with Alzheimer disease and related dementias (ADRD). METHODS: This 14-week randomized, placebo-controlled, crossover design clinical trial administered an all-day active or control lighting intervention to 46 patients with ADRD in 8 long-term care facilities for two 4-week periods (separated by a 4-week washout). The study employed wrist-worn actigraphy measures and standardized measures of sleep quality, mood, and behavior. RESULTS: The active intervention significantly improved Pittsburgh Sleep Quality Index scores compared to the active baseline and control intervention (mean ± SEM: 6.67 ± 0.48 after active intervention, 10.30 ± 0.40 at active baseline, 8.41 ± 0.47 after control intervention). The active intervention also resulted in significantly greater active versus control differences in intradaily variability. As for secondary outcomes, the active intervention resulted in significant improvements in Cornell Scale for Depression in Dementia scores (mean ± SEM: 10.30 ± 1.02 at baseline, 7.05 ± 0.67 after active intervention) and significantly greater active versus control differences in Cohen-Mansfield Agitation Inventory scores (mean ± SEM: -5.51 ± 1.03 for the active intervention, -1.50 ± 1.24 for the control intervention). CONCLUSIONS: A lighting intervention tailored to maximally entrain the circadian system can improve sleep, mood, and behavior in patients with dementia living in controlled environments. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov, title: Methodology Issues in a Tailored Light Treatment for Persons With Dementia, URL: https://clinicaltrials.gov/ct2/show/NCT01816152, identifier: NCT01816152.