Linear-wavenumber swept source based on an acousto-optic device for optical coherence tomography.

Linear-wavenumber swept-source optical coherence tomography (SS-OCT) enables real-time, high-quality OCT imaging by eliminating the need for data resampling, as required in conventional SS-OCT. In this study, we introduced a high-performance linear-wavenumber swept source (k-SS) with a broad scanning range and high output power. The linear k-SS is an acousto-optic-modulator-based external-cavity laser diode analogous to the Littrow configuration. The k-SS exhibits strong linearity in the 1.3 µm region, justified by a high goodness of fit R2 value of 0.9998. Additionally, its scanning range, output power, and linewidth are 120 nm, more than 43 mW, and approximately 1.6 nm, respectively. The sweep rate is 280 Hz after the linear k compensation of the experimental equipment. We demonstrated the effectiveness of the linear k-SS by applying it to measure a sample distribution without k-domain resampling before the Fourier transform. This successful implementation indicates that the linear k-SS has practical potential for application in SS-OCT systems.

Correlation between wastewater and COVID-19 case incidence rates in major California sewersheds across three variant periods.

Monitoring for COVID-19 through wastewater has been used for adjunctive public health surveillance, with SARS-CoV-2 viral concentrations in wastewater correlating with incident cases in the same sewershed. However, the generalizability of these findings across sewersheds, laboratory methods, and time periods with changing variants and underlying population immunity has not been well described. The California Department of Public Health partnered with six wastewater treatment plants starting in January 2021 to monitor wastewater for SARS-CoV-2, with analyses performed at four laboratories. Using reported PCR-confirmed COVID-19 cases within each sewershed, the relationship between case incidence rates and wastewater concentrations collected over 14 months was evaluated using Spearman's correlation and linear regression. Strong correlations were observed when wastewater concentrations and incidence rates were averaged (10- and 7-day moving window for wastewater and cases, respectively, ρ = 0.73-0.98 for N1 gene target). Correlations remained strong across three time periods with distinct circulating variants and vaccination rates (winter 2020-2021/Alpha, summer 2021/Delta, and winter 2021-2022/Omicron). Linear regression revealed that slopes of associations varied by the dominant variant of concern, sewershed, and laboratory (ß = 0.45-1.94). These findings support wastewater surveillance as an adjunctive public health tool to monitor SARS-CoV-2 community trends.

The influence of attorney anger on juror decision making.

We investigated the interactive effect of attorney anger expression and attorney gender on juror decision-making. Jury eligible Amazon MTurk participants (N = 455) were recruited. They listened to an audio recording of a male or female prosecutor delivering a closing statement with varying levels of authenticity (authentic, inauthentic or no anger). Then, they rendered a verdict. After the verdict, participants filled out various measures: guilty verdict confidence, current feelings of anger, and perceptions of prosecutor trust and competence. We found that the prosecutor's authentic displays of anger provoked anger in the participants, which, subsequently, increased the odds of a guilty verdict and guilty verdict confidence. Moreover, authentic displays of anger improved perceptions of the prosecutor's competence, which also increased the odds of a guilty verdict. However, perceptions of the prosecutor's trustworthiness did not vary, and attorney gender did not play a moderating role. The implications of these findings are discussed.

External-cavity laser diode using acousto-optic deflector as tunable grating.

In this study, a novel, to the best of our knowledge, external-cavity laser diode (ECLD) without a diffraction grating is proposed and demonstrated. In the proposed configuration, an acousto-optic deflector (AOD) acts not only as a deflector but also as a diffraction grating. Thus, the AOD functions as a wavelength-selective device, which helps improve the overall performance of the ECLD. In fact, the proposed configuration realizes a wide range of wavelength scanning with a simple configuration, highly efficient optical feedback, and a steady optical resonator with a constant cavity length. We confirm that the wavelengths scanned with the proposed ECLD agree well with theoretical calculations. The scanning range and maximum frequency response reached approximately 60 nm and 50 kHz, respectively. Moreover, reproducible measurements of the three-dimensional thickness distribution of a thin glass plate indicates that the proposed ECLD can be used for optical coherence tomography imaging systems.

Assessing cross-laboratory performance for quantifying coliphage using EPA Method 1642.

AIMS: Widespread adoption of the new U.S. Environmental Protection Agency (USEPA) Method 1642 for enumeration of coliphage in recreational water requires demonstration that laboratories consistently meet internal method performance goals and yield results that are consistent across laboratories. METHODS AND RESULTS: Here we assess the performance of six laboratories processing a series of blind wastewater- and coliphage-spiked samples along with laboratory blanks. All laboratories met the method-defined recovery requirements when performance was averaged across samples, with the few failures on individual samples mostly occurring for less-experienced laboratories on the initial samples processed. Failures that occurred on later samples were generally attributed to easily correctable activities. Failure rates were higher for somatic vs. F+ coliphage, attributable to the more stringent performance criteria associated with somatic coliphage. There was no difference in failure rate between samples prepared in a marine water matrix compared to that in phosphate-buffered saline. CONCLUSIONS: Variation among laboratories was similar to that previously reported for enterococci, the current bacterial indicator used for evaluating beach water quality for public health protection. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings suggest that laboratory performance is not an inhibitor to the adoption of coliphage as a new indicator for assessing recreational health risk.

Rapid optical tomographic vibrometry using a swept multi-gigahertz comb.

We propose a rapid tomographic vibrometer technique using an optical comb to measure internal vibrations, transient phenomena, and tomographic distributions in biological tissue and microelectromechanical system devices at high frequencies. This method allows phase-sensitive tomographic measurement in the depth direction at a multi-MHz scan rate using a frequency-modulated broadband electrooptic multi-GHz supercontinuum comb. The frequency spacing was swept instantaneously in time and axisymmetrically about the center wavelength via a dual-drive Mach-Zehnder modulator driven by a variable radio frequency signal. This unique sweeping method permits direct measurement of fringe-free interferometric amplitude and phase with arbitrarily changeable measurement range and scan rate. Therefore, a compressive measurement can be made in only the depth region where the vibration exists, reducing the number of measurement points. In a proof-of-principle experiment, the interferometric amplitude and phase were investigated for in-phase and quadrature phase-shifted interferograms obtained by a polarization demodulator. Tomographic transient displacement measurements were performed using a 0.12 mm thick glass film and piezo-electric transducer oscillating at 10-100 kHz with scan rates in the range 1-20 MHz. The depth resolution and precision of the vibrometer were estimated to be approximately 25 µm and 1.0 nm, respectively.

Measurement of phase refractive index directly from phase distributions detected with a spectrally resolved interferometer.

A phase refractive index is measured directly from an unwrapped spectral phase distribution whose 2π ambiguity is determined by fitting the spectral phase distribution with functions based on Cauchy's equation. The phase refractive index of a quartz glass with 20 µm thickness is measured exactly from three spectral phase distributions detected in two different configurations of a spectrally resolved interferometer. Since there is a high possibility that the 2π ambiguity cannot be correctly determined when there is a large difference between a function of the real refractive index and Cauchy's equation, characteristics of the fitting are examined.

Characterisation of the static offset in the travelling wave in the cochlear basal turn.

In mammals, audition is triggered by travelling waves that are evoked by acoustic stimuli in the cochlear partition, a structure containing sensory hair cells and a basilar membrane. When the cochlea is stimulated by a pure tone of low frequency, a static offset occurs in the vibration in the apical turn. In the high-frequency region at the cochlear base, multi-tone stimuli induce a quadratic distortion product in the vibrations that suggests the presence of an offset. However, vibrations below 100 Hz, including a static offset, have not been directly measured there. We therefore constructed an interferometer for detecting motion at low frequencies including 0 Hz. We applied the interferometer to record vibrations from the cochlear base of guinea pigs in response to pure tones. When the animals were exposed to sound at an intensity of 70 dB or higher, we recorded a static offset of the sinusoidally vibrating cochlear partition by more than 1 nm towards the scala vestibuli. The offset's magnitude grew monotonically as the stimuli intensified. When stimulus frequency was varied, the response peaked around the best frequency, the frequency that maximised the vibration amplitude at threshold sound pressure. These characteristics are consistent with those found in the low-frequency region and are therefore likely common across the cochlea. The offset diminished markedly when the somatic motility of mechanosensitive outer hair cells, the force-generating machinery that amplifies the sinusoidal vibrations, was pharmacologically blocked. Therefore, the partition offset appears to be linked to the electromotile contraction of outer hair cells.

Cell-free expression of natively folded hydrophobins.

Hydrophobins are a family of cysteine-rich proteins unique to filamentous fungi. The proteins are produced in a soluble form but self-assemble into organised amphipathic layers at hydrophilic:hydrophobic interfaces. These layers contribute to transitions between wet and dry environments, spore dispersal and attachment to surfaces for growth and infection. Hydrophobins are characterised by four disulphide bonds that are critical to their structure and function. Thus, obtaining correctly folded, soluble and functional hydrophobins directly from bacterial recombinant expression is challenging and in most cases, initial denaturation from inclusion bodies followed by oxidative refolding are required to obtain folded proteins. Here, we report the use of cell-free expression with E. coli cell lysate to directly obtain natively folded hydrophobins. All six of the hydrophobins tested could be expressed after optimisation of redox conditions. For some hydrophobins, the inclusion of the disulfide isomerase DsbC further enhanced expression levels. We are able to achieve a yield of up to 1 mg of natively folded hydrophobin per mL of reaction. This has allowed the confirmation of the correct folding of hydrophobins with the use of 15N-cysteine and 15N-1H nuclear magnetic resonance experiments within 24 h of starting from plasmid stocks.

Signal correction by detection of scanning position in a white-light interferometer for exact surface profile measurement.

In order to perform an exact surface profile measurement with a white-light scanning interferometer (WLSI), an actual optical path difference (OPD) changing with time is detected with an additional interferometer in which the light source of the WLSI and an optical band-pass filter are used. This interferometer is simply equipped in the WLSI and does not negatively influence the WLSI. The real OPD is easily calculated from an interference signal with the same signal processing as that in the WLSI. The interference signal of the WLSI is corrected with the real OPD values or the real scanning position values. The corrected interference signal with a constant sampling interval is obtained with an interpolation method. With this correction method, a surface profile with a step shape of 3-µm height is measured accurately with an error less than 2 nm.

Exact surface profile measurement without subtracting dispersion phase through Fourier transform in a white-light scanning interferometer.

A new signal processing is proposed in which the dispersion phase is not subtracted from the detected spectral phase distribution. The linear and bias components in the spectral phase distribution are used to calculate the complex-valued interference signal (CVIS). The simulations verify that the dispersion phase generates an inclination in the measured surface profile along one direction in which the magnitude of the dispersion phase changes linearly. The simulations also show that the position of zero phase nearest the position of amplitude maximum in the CVIS almost does not change due to the bias component, although the random phase noise contained in the interference signal changes the slope of the linear component. Measured surface profiles show that the new signal processing achieves highly accurate measurement by the CVIS.

The unique ion permeability profile of cochlear fibrocytes and its contribution to establishing their positive resting membrane potential.

Eukaryotic cells exhibit negative resting membrane potential (RMP) owing to the high K(+) permeability of the plasma membrane and the asymmetric [K(+)] between the extracellular and intracellular compartments. However, cochlear fibrocytes, which comprise the basolateral surface of a multilayer epithelial-like tissue, exhibit a RMP of +5 to +12 mV in vivo. This positive RMP is critical for the formation of an endocochlear potential (EP) of +80 mV in a K(+)-rich extracellular fluid, endolymph. The epithelial-like tissue bathes fibrocytes in a regular extracellular fluid, perilymph, and apically faces the endolymph. The EP, which is essential for hearing, represents the potential difference across the tissue. Using in vivo electrophysiological approaches, we describe a potential mechanism underlying the unusual RMP of guinea pig fibrocytes. The RMP was +9.0 ± 3.7 mV when fibrocytes were exposed to an artificial control perilymph (n = 28 cochleae). Perilymphatic perfusion of a solution containing low [Na(+)] (1 mM) markedly hyperpolarized the RMP to -31.1 ± 11.2 mV (n = 10; p < 0.0001 versus the control, Tukey-Kramer test after one-way ANOVA). Accordingly, the EP decreased. Little change in RMP was observed when the cells were treated with a high [K(+)] of 30 mM (+10.4 ± 2.3 mV; n = 7; p = 0.942 versus the control). During the infusion of a low [Cl(-)] solution (2.4 mM), the RMP moderately hyperpolarized to -0.9 ± 3.4 mV (n = 5; p < 0.01 versus the control), although the membranes, if governed by Cl(-) permeability, should be depolarized. These observations imply that the fibrocyte membranes are more permeable to Na(+) than K(+) and Cl(-), and this unique profile and [Na(+)] gradient across the membranes contribute to the positive RMP.

Multifrequency swept common-path en-face OCT for wide-field measurement of interior surface vibrations in thick biological tissues.

Microvibrations that occur in bio-tissues are considered to play pivotal roles in organ function; however techniques for their measurement have remained underdeveloped. To address this issue, in the present study we have developed a novel optical coherence tomography (OCT) method that utilizes multifrequency swept interferometry. The OCT volume data can be acquired by sweeping the multifrequency modes produced by combining a tunable Fabry-Perot filter and an 840 nm super-luminescent diode with a bandwidth of 160 nm. The system employing the wide-field heterodyne method does not require mechanical scanning probes, which are usually incorporated in conventional Doppler OCTs and heterodyne-type interferometers. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. Indeed, our OCT achieved the axial resolution of ~2.5 µm when scanning the surface of a glass plate. Moreover, when examining a mechanically resonant multilayered bio-tissue in full-field configuration, we captured 22 nm vibrations of its internal surfaces at 1 kHz by reconstructing temporal phase variations. This so-called "multifrequency swept common-path en-face OCT" can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research.

Profile measurement of glass sheet using multiple wavelength backpropagation interferometry.

Multiple-wavelength backpropagation interferometry based on a spectral interferometer is proposed for measuring thin glass sheets with nanometer accuracy. The multiwavelength backpropagation method introduced to the spectral interferometer eliminates time-encoded wavelength sweeping and mechanical scanning, which enables high-speed profile measurements. The applicability of the proposed method is experimentally demonstrated through cross-sectional profile and vibrating surface displacement measurements of a glass sheet.

SARS-CoV-2 genetic material is removed during municipal wastewater treatment and is undetectable after advanced treatment.

The aim of this study was to establish whether SARS-CoV-2 genetic material is detectable after municipal wastewater treatment and to verify its expected removal from purified water that is reclaimed for potable reuse. Viral loads of SARS-CoV-2 (N1 and N2 genes) were monitored in raw influent wastewater (sewage) entering a water reclamation facility and in subsequent advanced treatment. Despite the large viral RNA load in raw sewage during peak COVID-19 outbreaks, substantial amounts of SARS-CoV-2 genetic material were removed during the conventional wastewater treatment process. Further, SARS-CoV-2 genetic material was undetectable after advanced purification. This confirms that potable reuse is resilient against high viral loads which are expected results given the advanced degree of wastewater and water treatment. Findings from this study may enhance public perception of the safety of potable water reuse; however, it should also be noted that studies to date worldwide indicate no evidence of SARS-CoV-2 transmission via water, and the CDC does not consider fecal waste or wastewaters as a source of exposure.

Relationship between coliphage and Enterococcus at southern California beaches and implications for beach water quality management.

Coliphage have been suggested as an alternative to fecal indicator bacteria for assessing recreational beach water quality, but it is unclear how frequently and at what types of beaches coliphage produces a different management outcome. Here we conducted side-by-side sampling of male-specific and somatic coliphage by the new EPA dead-end hollow fiber ultrafiltration (D-HFUF-SAL) method and Enterococcus at southern California beaches over two years. When samples were combined for all beach sites, somatic and male-specific coliphage both correlated with Enterococcus. When examined categorically, Enterococcus would have resulted in approximately two times the number of health advisories as somatic coliphage and four times that of male-specific coliphage,using recently proposed thresholds of 60 PFU/100 mL for somatic and 30 PFU/100 mL for male-specific coliphage. Overall, only 12% of total exceedances would have been for coliphage alone. Somatic coliphage exceedances that occurred in the absence of an Enterococcus exceedance were limited to a single site during south swell events, when this beach is known to be affected by nearby minimally treated sewage. Thus, somatic coliphage provided additional valuable health protection information, but may be more appropriate as a supplement to FIB measurements rather than as replacement because: (a) EPA-approved PCR methods for Enterococcus allow a more rapid response, (b) coliphage is more challenging owing to its greater sampling volume and laboratory time requirements, and (c) Enterococcus' long data history has yielded predictive management models that would need to be recreated for coliphage.

Multi-gigahertz frequency comb-based interferometry using frequency-variable supercontinuum generated by optical pulse synthesizer.

A multi-gigahertz frequency comb (MGFC)-based interferometer was developed for profilometry and tomography using a frequency variable supercontinuum (SC). The comparatively flattened and broadened SC light source with variable multi-gigahertz interval frequency was developed using an optical pulse synthesizer and highly nonlinear dispersion flattened fiber. The generated SC provided a stable interference output with a full width half maximum of 19 µm during interval frequency sweeping of over 400 MHz. We experimentally confirmed that the interference signal exhibited an envelope-only waveform without fringes, which enabled the drastic reduction of the sampling points resulting in high speed measurement. A full-field 3-D image with 320 × 256 × 300 pixels was acquired with a measurement time of only 10 seconds. It was demonstrated that the MGFC-based interferometer with the novel SC light source has the potential for application in a high speed full-field 3-D metrology.

Utilization of frequency information in a linear wavenumber-scanning interferometer for profile measurement of a thin film.

The positions of the front and rear surfaces of a silicon dioxide film with 4 µm thickness is measured with a novel and simple method in which both amplitude and phase of a sinusoidal wave signal corresponding to one optical path difference of a reflecting surface is utilized in a linear wavenumber-scanning interferometer. For this utilization, the scanning width and the position of the reference mirror are adjusted exactly to distinguish the two sinusoidal waves corresponding to the two surfaces of the film. The scanning width of the wavenumber and wavelength of the light source are 0.326×10(-3) nm(-1) and 140 nm, respectively.

Phase-shifting laser diode interferometer using pulse modulation.

A phase-shifting laser diode interferometer that uses direct pulse modulation is proposed and demonstrated. We found that a laser beam with a wide range of wavelength variation at constant optical power could be generated when a pulsed current was injected into the laser diode. We constructed a highly accurate interferometer by using a pair of interferometers. Several experiments, such as observations of temporal interference signals and spatial interferograms, measurement of a concave mirror, and duplicate measurements, confirmed the characteristics of pulse modulation and demonstrated the effectiveness of our technique.

Geographic distribution of prejudice toward African Americans: Applying the two-dimensional model.

Using the two-dimensional model of prejudice as a theoretical framework, we examined the geographic distribution of prejudice toward African Americans in the United States (N = 10,522). We found the East South Central, West South Central, and South Atlantic regions were associated with modern racism, principled conservatism characterized the Mountain region, aversive racism was prevalent in the East North Central region, and finally, low in prejudice was found in the Pacific, West North Central, Mid Atlantic, and New England regions. Additional analyses on political conservatism, social conservatism, and egalitarianism generally supported the distinctions between prejudice types made by the two-dimensional model. We believe mapping regional prejudice may have implications for testing theoretical differences between distinct types of prejudice as well as for implementing prejudice reduction strategies.