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1.
Environ Monit Assess ; 196(4): 369, 2024 Mar 15.
Article in English | MEDLINE | ID: mdl-38489113

ABSTRACT

Protected areas are typically managed as a network of sites exposed to varying anthropogenic conditions. Managing these networks benefits from monitoring of conditions across sites to help prioritize coordinated efforts. Monitoring marine vessel activity and related underwater radiated noise impacts across a network of protected areas, like the U.S. National Marine Sanctuary system, helps managers ensure the quality of habitats used by a wide range of marine species. Here, we use underwater acoustic detections of vessels to quantify different characteristics of vessel noise at 25 locations within eight marine sanctuaries including the Hawaiian Archipelago and the U.S. east and west coasts. Vessel noise metrics, including temporal presence and sound levels, were paired with Automatic Identification System (AIS) vessel tracking data to derive a suite of robust vessel noise indicators for use across the network of marine protected areas. Network-wide comparisons revealed a spectrum of vessel noise conditions that closely matched AIS vessel traffic composition. Shifts in vessel noise were correlated with the decrease in vessel activity early in the COVID-19 pandemic, and vessel speed reduction management initiatives. Improving our understanding of vessel noise conditions in these protected areas can help direct opportunities for reducing vessel noise, such as establishing and maintaining noise-free periods, enhancing port efficiency, engaging with regional and international vessel quieting initiatives, and leveraging co-benefits of management actions for reducing ocean noise.


Subject(s)
Pandemics , Ships , Humans , Environmental Monitoring , Noise , Acoustics , Ecosystem
2.
Opt Express ; 32(5): 6848-6864, 2024 Feb 26.
Article in English | MEDLINE | ID: mdl-38439381

ABSTRACT

Two classes of higher-order, fractal spatial eigenmodes have been predicted computationally and observed experimentally in microlasers. The equatorial plane of a close-packed array of microspheres, lying on one mirror within a Fabry-Pérot resonator and immersed in the laser gain medium, acts as a refractive slit array in a plane transverse to the optical axis. Edge diffraction from the slit array generates the high spatial frequencies (>104 cm-1) required for the formation of high-order laser fractal modes, and fractal transverse modes are generated, amplified, and evolve within the active medium. With a quasi-rectangular (4-microsphere) aperture, the fundamental mode and several higher-order eigenmodes (m = 2,4,5) are observed in experiments, whereas only the m = 1,2 modes are observed experimentally for the higher-loss resonators defined by triangular (3-microsphere) apertures. The fundamental and 2nd-order modes (m = 1,2) for the 4-sphere aperture are calculated to have qualitatively similar intensity profiles and nearly degenerate resonant frequencies that differ by less than <0.1% of the free-spectral range (375 GHz) but exhibit even and odd parity, respectively. For all of the observed fractal modes, the fractal dimension (D) rises rapidly beyond the intracavity aperture array as a result of the high spatial frequencies introduced into the mode profile. Elsewhere, D varies gradually along the resonator axis and 2.2 < D < 2.5. Generating fractal laser modes in an equivalent optical waveguide is expected to allow the realization of new optical devices and imaging protocols based on the spatial frequencies and variable D values available.

3.
Front Robot AI ; 10: 1292632, 2023.
Article in English | MEDLINE | ID: mdl-38035123

ABSTRACT

This article provides a comprehensive narrative review of physical task-based assessments used to evaluate the multi-grasp dexterity and functional impact of varying control systems in pediatric and adult upper-limb prostheses. Our search returned 1,442 research articles from online databases, of which 25 tests-selected for their scientific rigor, evaluation metrics, and psychometric properties-met our review criteria. We observed that despite significant advancements in the mechatronics of upper-limb prostheses, these 25 assessments are the only validated evaluation methods that have emerged since the first measure in 1948. This not only underscores the lack of a consistently updated, standardized assessment protocol for new innovations, but also reveals an unsettling trend: as technology outpaces standardized evaluation measures, developers will often support their novel devices through custom, study-specific tests. These boutique assessments can potentially introduce bias and jeopardize validity. Furthermore, our analysis revealed that current validated evaluation methods often overlook the influence of competing interests on test success. Clinical settings and research laboratories differ in their time constraints, access to specialized equipment, and testing objectives, all of which significantly influence assessment selection and consistent use. Therefore, we propose a dual testing approach to address the varied demands of these distinct environments. Additionally, we found that almost all existing task-based assessments lack an integrated mechanism for collecting patient feedback, which we assert is essential for a holistic evaluation of upper-limb prostheses. Our review underscores the pressing need for a standardized evaluation protocol capable of objectively assessing the rapidly advancing prosthetic technologies across all testing domains.

5.
Sci Rep ; 13(1): 10629, 2023 Jun 30.
Article in English | MEDLINE | ID: mdl-37391450

ABSTRACT

Modern communication and navigation systems are increasingly relying on atomic clocks. As timing precision requirements increase, demands for lower SWaP (size, weight, and power) clocks rise. However, it has been challenging to break through the general trade-off trend between the clock stability performance and SWaP. Here we demonstrate micro mercury trapped ion clock (M2TIC) prototypes integrated with novel micro-fabricated technologies to simultaneously achieve high performance and low SWaP. The M2TIC prototypes could reach the [Formula: see text]-stability level in 1 day with a SWaP of 1.1 L, 1.2 kg, and under 6 W of power. This stability level is comparable to the widely used rack-mount Microchip 5071A cesium frequency standard. These standalone prototypes survived regular commercial shipping across the North American continent to a government laboratory, where their performance was independently tested. The M2TIC sets a new reference point for SWaP and performance and opens opportunities for high-performance clocks in terrestrial and space applications.


Subject(s)
Cesium , Mercury , Communication , Government , Ions
6.
Article in English | MEDLINE | ID: mdl-37200580

ABSTRACT

Abstract: In honor of Professor Kurt Becker's pioneering contributions to microplasma physics and applications, we report the capabilities of arrays of microcavity plasmas in two emerging and disparate applications. The first of these is the generation of ultrasound radiation in the 20-240 kHz spectral range with microplasmas in either a static or jet configuration. When a 10×10 array of microplasma jets is driven by a 20-kHz sinusoidal voltage, for example, harmonics as high as m = 12 are detected and fractional harmonics are produced by controlling the spatial symmetry of the emitter array. The preferential emission of ultrasound in an inverted cone having an angle of ±45∘ with respect to the surface normal of the jet array's exit face is attributed to interference between spatially periodic, outward-propagating waves generated by the arrays. The spatial distribution of ultrasound generated by the arrays is analogous to the radiation patterns produced by Yagi-Uda phased array antennas at RF frequencies for which radiation is emitted broadside to arrays of parallel electric dipoles. Also, the nonperturbative envelope of the ultrasound harmonic spectrum resembles that for high-order harmonic generation at optical frequencies in rare gas plasmas and attests to the strong nonlinearity provided by the pulsed microplasmas in the sub-250-kHz region. Specifically, the relative intensities of the second and third harmonics exceed that for the fundamental, and a "plateau" region is observed extending from the 5th through the 8th harmonics. A strong plasma nonlinearity appears to be responsible for both the appearance of fractional harmonics and the nonperturbative nature of the acoustic harmonic spectrum. Multilayer metal-oxide optical filters designed to have peak transmission near 222 nm in the deep-UV region of the spectrum have been fabricated by microplasma-assisted atomic layer deposition. Alternating layers of ZrO2 and Al2O3, each having a thickness in the 20-50 nm range, were grown on quartz and silicon substrates by successively exposing the substrate to the Zr or Al precursor (tetrakis(dimethylamino) zirconium or trimethylaluminum, respectively) and the products of an oxygen microplasma while maintaining the substrate temperature at 300 K. Bandpass filters comprising 9 cycles of 30-nm-thick ZrO2/50-nm-thick Al2O3 film pairs transmit 80% at 235 nm but < 35% in the 250-280 nm interval. Such multilayer reflectors appear to be of significant value in several applications, including bandpass filters suppressing long wavelength (240-270 nm) radiation emitted by KrCl (222) lamps.

7.
J Phys Chem A ; 127(16): 3675-3683, 2023 Apr 27.
Article in English | MEDLINE | ID: mdl-37043375

ABSTRACT

Interatomic potentials for the B2Σ1/2+ states of CsAr, CsXe, and RbXe have been determined through comparisons of experimental B ← X absorption spectra for alkali vapor-rare gas mixtures with calculations of the Franck-Condon factors (FCFs) associated with free-free transitions of thermal atomic pairs. Simulations of optical transitions of alkali-rare gas atomic pairs between the thermal and vibrational continua of the X2Σ1/2+ and B2Σ1/2+ states of the molecule, responsible for the blue satellites of the Cs and Rb D2 resonance lines in a rare gas background, require the incorporation of ground-state J values above ∼400 into the FCF calculations and proper normalization of the free-particle wave functions. Absorption spectra computed on the basis of several X and B state interatomic potentials available in the literature were found to be sensitive to the height of the B2Σ1/2+ state barrier, as well as the X2Σ1/2+ state repulsive wall contour and the location of the van der Waals minimum. Other spectral simulations entailed iterative modifications to a selected B2Σ1/2+ interatomic potential, again coupled with comparison to experimental B ← X spectra. Comparisons of calculated spectra with experiment yield a CsXe B2Σ1/2+ potential, for example, exhibiting a barrier height of 76 cm-1 at 5.2 Å and yet is nearly flat at smaller values of internuclear separation (R). The latter contrasts with previous theoretical calculations of VB(R) in the vicinity of the barrier maximum. For the CsAr molecule, the B2Σ1/2+ barrier height was found to be 221 cm-1, which is within 3% of the value determined from pseudopotential calculations incorporating the spin-orbit effect. Reproducing Cs-rare gas experimental absorption spectra also requires the existence of a broad, shallow potential well lying beyond the B2Σ1/2+ barrier that, for CsAr, has a dissociation energy (De ∼ 24 cm-1) a factor of 3 larger than values predicted by theory. Similar results are obtained for the RbXe and CsXe complexes.

8.
NASN Sch Nurse ; 37(6): 303-305, 2022 Nov.
Article in English | MEDLINE | ID: mdl-35786075

ABSTRACT

Awarded by the National Board for Certification of School Nurses, the Nationally Certified School Nurse (NCSN) credential exemplifies that a school nurse has passed a "rigorous national credentialing process to validate practice competency based on professional standards." Board certification in school nursing is a formal recognition of advanced knowledge, competence, and a personal commitment to excellence in the specialty practice of school nursing on behalf of the better health and education of school-age children. Read the answers to these frequently asked questions to learn how and why school nurses should earn the NCSN credential.


Subject(s)
School Nursing , Child , Humans , Certification
9.
Public Health ; 198: 161-163, 2021 Sep.
Article in English | MEDLINE | ID: mdl-34461448

ABSTRACT

OBJECTIVE: To investigate the associations of state gubernatorial party control and 2016 county-level presidential election preference on COVID-19 case and death rates in the United States. STUDY DESIGN: This was a secondary analysis of publicly available data. METHODS: Data including county-level COVID-19 case and death counts through February 9, 2021, 2020 gubernatorial data, and county-level US Census Bureau data, Broadstreet area deprivation index, and 2016 presidential voting tallies were included. Negative binomial regression estimated the adjusted impact of each variable on COVID-19 case and death rates. RESULTS: A total of 3102 counties in the 48 continental United States plus Washington DC were included. County-level case and death rates were higher (12% and 22%, respectively) in Republican vs Democrat controlled states. Case and death rates were higher in counties voting Republican vs Democrat in 2016 and were modified by counties with median ages ≥ 50 years (54% increase in case rate and 91% increase in death rate). CONCLUSIONS: These data further support the need for prevention efforts to focus on public health while extricating guidance and prevention from political agendas.


Subject(s)
COVID-19 , Humans , Middle Aged , Politics , Public Health , SARS-CoV-2 , United States/epidemiology
10.
NPJ Biofilms Microbiomes ; 7(1): 48, 2021 06 02.
Article in English | MEDLINE | ID: mdl-34078901

ABSTRACT

Otitis media (OM), known as a middle ear infection, is the leading cause of antibiotic prescriptions for children. With wide-spread use of antibiotics in OM, resistance to antibiotics continues to decrease the efficacy of the treatment. Furthermore, as the presence of a middle ear biofilm has contributed to this reduced susceptibility to antimicrobials, effective interventions are necessary. A miniaturized 3D-printed microplasma jet array has been developed to inactivate Pseudomonas aeruginosa, a common bacterial strain associated with OM. The experiments demonstrate the disruption of planktonic and biofilm P. aeruginosa by long-lived molecular species generated by microplasma, as well as the synergy of combining microplasma treatment with antibiotic therapy. In addition, a middle ear phantom model was developed with an excised rat eardrum to investigate the antimicrobial effects of microplasma on bacteria located behind the eardrum, as in a patient-relevant setup. These results suggest the potential for microplasma as a new treatment paradigm for OM.


Subject(s)
Otitis Media/microbiology , Plasma Gases/administration & dosage , Pseudomonas Infections/microbiology , Pseudomonas aeruginosa/drug effects , Animals , Biomarkers , Disease Models, Animal , Microbial Sensitivity Tests/instrumentation , Microbial Sensitivity Tests/methods , Otitis Media/diagnosis , Otitis Media/drug therapy , Pseudomonas Infections/diagnosis , Pseudomonas Infections/drug therapy , Rats , Tomography, Optical Coherence
11.
Sci Rep ; 11(1): 9511, 2021 05 04.
Article in English | MEDLINE | ID: mdl-33947906

ABSTRACT

The successful completion of complex tasks like hanging a picture or laparoscopic surgery requires coordinated motion of more than two limbs. User-controlled supernumerary robotic limbs (SL) have been proposed to bypass the need for coordination with a partner in such tasks. However, neither the capability to control multiple limbs alone relative to collaborative control with partners, nor how that capability varies across different tasks, is well understood. In this work, we present an investigation of tasks requiring three-hands where the foot was used as an additional source of motor commands. We considered: (1) how does simultaneous control of three hands compare to a cooperating dyad; (2) how this relative performance was altered by the existence of constraints emanating from real or virtual physical connections (mechanical constraints) or from cognitive limits (cognitive constraints). It was found that a cooperating dyad outperformed a single user in all scenarios in terms of task score, path efficiency and motion smoothness. However, while the participants were able to reach more targets with increasing mechanical constraints/decreasing number of simultaneous goals, the relative difference in performance between a dyad and a participant performing trimanual activities decreased, suggesting further potential for SLs in this class of scenario.


Subject(s)
Hand/physiology , Psychomotor Performance/physiology , Adult , Female , Foot/physiology , Humans , Laparoscopy/methods , Robotics/methods , Task Performance and Analysis , User-Computer Interface
12.
J Cyst Fibros ; 20(6): 932-936, 2021 11.
Article in English | MEDLINE | ID: mdl-33685776

ABSTRACT

BACKGROUND: Retrospective studies indicate that more cystic fibrosis (CF) pulmonary exacerbations (PEx) are treated with oral (PO) than with intravenous (IV) antimicrobials despite little knowledge of the relative effects of PO treatment on lung function recovery or long-term impacts on lung disease progression. Previous studies have suggested that PO treatment may be associated with slower lung function recovery compared with IV treatment. We used longitudinal home spirometry data from the eICE study (NCT01104402) to compare PO versus IV antimicrobial treatment responses for PEx diagnosed by home spirometry and symptom assessment. METHODS: Adolescent and adult eICE participants performed home spirometry twice weekly for one year. PEx were diagnosed by a protocol-defined algorithm of change in percent predicted forced expiratory volume in 1 second (ppFEV1) and/or respiratory signs and symptoms. PO- and IV-treated PEx were grouped by initial ppFEV1 drop magnitude. Group ppFEV1 treatment responses were modeled with multivariate, repeat-measure linear regression. RESULTS: Of 87 qualifying PEx from 56 participants, 62 were PO-treated and 25 were IV-treated. The average drop from best ppFEV1 to PEx start was 11.0 [95%CI: 8.5, 13.5] with similar treatment group means (p=0.72). Participants with IV-treated PEx averaged 0.72 [0.24, 1.20] ppFEV1/day greater response than those treated with PO, who experienced minimal ppFEV1 recovery. Many PO-treated participants who had <10 ppFEV1 drop from baseline tended to worsen or show no ppFEV1 improvement. DISCUSSION: These results suggest that, in this cohort, PO antimicrobial treatment of CF PEx were less effective than IVs at improving ppFEV1 during treatment.


Subject(s)
Anti-Bacterial Agents/administration & dosage , Cystic Fibrosis/drug therapy , Cystic Fibrosis/physiopathology , Symptom Flare Up , Administration, Oral , Adolescent , Adult , Cystic Fibrosis/microbiology , Female , Forced Expiratory Volume , Humans , Male , Retrospective Studies , Spirometry
13.
Nanoscale ; 12(32): 16796-16804, 2020 Aug 28.
Article in English | MEDLINE | ID: mdl-32766620

ABSTRACT

Precision photoablation of bulk polymers or films with incoherent vacuum ultraviolet (VUV) radiation from flat, microplasma array-powered lamps has led to the realization of a photolithographic process in which an acrylic, polycarbonate, or other polymer serves as a dry photoresist. Patterning of the surface of commercial-grade, bulk polymers (or films spun onto Si substrates) such as poly-methyl methacrylate (PMMA) and acrylonitrile butadiene styrene (ABS) with 172 nm lamp intensities as low as ∼10 mW cm-2 and a fused silica contact mask yields trenches, as well as arbitrarily-complex 3D structures, with depths reproducible to ∼10 nm. For 172 nm intensities of 10 mW cm-2 at the substrate, linearized PMMA photoablation rates of ∼4 nm s-1 are measured for exposure times t≤ 70 s but a gradual decline is observed thereafter. Beyond t∼ 300 s, the polymer removal rate gradually saturates at ∼0.2 nm s-1. Intricate patterns are readily produced in bulk acrylics or 40-200 nm thick acrylic films on Si with two or more exposures and overall process times of typically 10-300 s. The photoablation process is sufficiently precise that the smallest lateral feature size fabricated reproducibly to date, ∼350 nm, appears to be limited primarily by the photomask itself. Examples of the versatility and precision of this photolithographic process include the fabrication of arrays of aluminum nanomirrors, each atop a 350 nm or 1 µm-diameter Si post, as well as optical components such as transmission gratings or Fresnel lenses photoablated into PMMA.

15.
Opt Express ; 28(9): 14072-14084, 2020 Apr 27.
Article in English | MEDLINE | ID: mdl-32403869

ABSTRACT

Optical amplification by the stimulated emission of Cs(6p2P3/2)-Ar atomic pairs, observed in pump-probe experiments over a ∼290 GHz-wide spectral region lying to the red of the Cs D2 line (852.1 nm), has been realized by photoexciting thermalized, ground state Cs-Ar atoms in the 834-849 nm wavelength interval. When the gain medium is pumped at the peak of the CsAr B2Σ1/2+←X2Σ1/2+ transition at 836.7 nm, maximum gain occurs between 852.2 nm and 852.3 nm and >28% of the energy stored in the upper laser level is extracted with 8 ns (FWHM) probe pulses in a single pass. From the measured rate of saturation of the extracted pulse energy with increasing probe intensity, the product of γ0L and Esat, the saturation pulse energy, is measured directly to be 400 ± 20 µJ and the lower limit for the saturation intensity (Isat) of this amplifier is estimated to be 10 kW-cm-2 at 852.2 nm. Circularly polarizing the optical pump beam increases the optical-to-optical conversion efficiency by 20%, and the storage lifetime of the upper laser level is observed from temporally-resolved gain spectra to be 5 ± 1 ns. Pump excitation spectra also reveal a significant contribution from Ar-Cs-Ar (3-body) photoassociation and suprathermal Ar atoms generated by the dissociation of the CsAr B2Σ1/2+ complex. Multipass-amplifier geometries with broad-bandwidth probe signals are expected to yield upper state energy extraction efficiencies above 50%. This alkali-rare gas amplifier demonstrates the efficiencies available with the storage of energy in, and optical extraction from, excited atomic collision pairs.

16.
J Clin Virol ; 127: 104374, 2020 06.
Article in English | MEDLINE | ID: mdl-32361322

ABSTRACT

INTRODUCTION: There is limited data on the analytical performance of commercial nucleic acid tests (NATs) for laboratory confirmation of COVID-19 infection. METHODS: Nasopharyngeal, combined nose and throat swabs, nasopharyngeal aspirates and sputum was collected from persons with suspected SARS-CoV-2 infection, serial dilutions of SARS-CoV-2 viral cultures and synthetic positive controls (gBlocks, Integrated DNA Technologies) were tested using i) AusDiagnostics assay (AusDiagnostics Pty Ltd); ii) in-house developed assays targeting the E and RdRp genes; iii) multiplex PCR assay targeting endemic respiratory viruses. Discrepant SARS-CoV-2 results were resolved by testing the N, ORF1b, ORF1ab and M genes. RESULTS: Of 52 clinical samples collected from 50 persons tested, respiratory viruses were detected in 22 samples (42 %), including SARS CoV-2 (n = 5), rhinovirus (n = 7), enterovirus (n = 5), influenza B (n = 4), hMPV (n = 5), influenza A (n = 2), PIV-2 (n = 1), RSV (n = 2), CoV-NL63 (n = 1) and CoV-229E (n = 1). SARS-CoV-2 was detected in four additional samples by the AusDiagnostics assay. Using the in-house assays as the "gold standard", the sensitivity, specificity, positive and negative predictive values of the AusDiagnostics assay was 100 %, 92.16 %, 55.56 % and 100 % respectively. The Ct values of the real-time in-house-developed PCR assay targeting the E gene was significantly lower than the corresponding RdRp gene assay when applied to clinical samples, viral culture and positive controls (mean 21.75 vs 28.1, p = 0.0031). CONCLUSIONS: The AusDiagnostics assay is not specific for the detection SARS-CoV-2. Any positive results should be confirmed using another NAT or sequencing. The case definition used to investigate persons with suspected COVID-19 infection is not specific.


Subject(s)
Betacoronavirus/isolation & purification , Coronavirus Infections/diagnosis , Molecular Diagnostic Techniques/methods , Nasopharynx/virology , Pneumonia, Viral/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , COVID-19 , Child , Child, Preschool , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Pandemics , SARS-CoV-2 , Sensitivity and Specificity , Young Adult
17.
Sci Adv ; 6(3): eaay4508, 2020 01.
Article in English | MEDLINE | ID: mdl-32010770

ABSTRACT

Monolithic strong magnetic induction at the mtesla to tesla level provides essential functionalities to physical, chemical, and medical systems. Current design options are constrained by existing capabilities in three-dimensional (3D) structure construction, current handling, and magnetic material integration. We report here geometric transformation of large-area and relatively thick (~100 to 250 nm) 2D nanomembranes into multiturn 3D air-core microtubes by a vapor-phase self-rolled-up membrane (S-RuM) nanotechnology, combined with postrolling integration of ferrofluid magnetic materials by capillary force. Hundreds of S-RuM power inductors on sapphire are designed and tested, with maximum operating frequency exceeding 500 MHz. An inductance of 1.24 µH at 10 kHz has been achieved for a single microtube inductor, with corresponding areal and volumetric inductance densities of 3 µH/mm2 and 23 µH/mm3, respectively. The simulated intensity of the magnetic induction reaches tens of mtesla in fabricated devices at 10 MHz.

18.
Adv Mater ; 32(18): e1905508, 2020 May.
Article in English | MEDLINE | ID: mdl-31854023

ABSTRACT

Microplasmas are low-temperature plasmas that feature microscale dimensions and a unique high-energy-density and a nonequilibrium reactive environment, which makes them promising for the fabrication of advanced nanomaterials and devices for diverse applications. Here, recent microplasma applications are examined, spanning from high-throughput, printing-technology-compatible synthesis of nanocrystalline particles of common materials types, to water purification and optoelectronic devices. Microplasmas combined with gaseous and/or liquid media at low temperatures and atmospheric pressure open new ways to form advanced functional materials and devices. Specific examples include gas-phase, substrate-free, plasma-liquid, and surface-supported synthesis of metallic, semiconducting, metal oxide, and carbon-based nanomaterials. Representative applications of microplasmas of particular importance to materials science and technology include light sources for multipurpose, efficient VUV/UV light sources for photochemical materials processing and spectroscopic materials analysis, surface disinfection, water purification, active electromagnetic devices based on artificial microplasma optical materials, and other devices and systems including the plasma transistor. The current limitations and future opportunities for microplasma applications in materials related fields are highlighted.

19.
J Opt Soc Am A Opt Image Sci Vis ; 36(5): 898-909, 2019 May 01.
Article in English | MEDLINE | ID: mdl-31045019

ABSTRACT

Representing the reflection and transmission of light by multilayer dielectric structures in terms of Markov chains provides an intuitive, precise, and computationally efficient framework for calculating the dispersive properties (group delay, group delay dispersion, and higher order phase derivatives) of ultrafast laser mirrors and other broadband optical components. The theoretical basis for the Markov-Airy formalism is described, and its ability to precisely determine the dispersive characteristics of multilayer dielectric structures is demonstrated here. Exact expressions for the three lowest order phase derivatives for a dielectric mirror and waveguide are derived, and Markov-Airy-based numerical simulations of specific mirror designs are compared with results obtained with the conventional transition matrix formalism.

20.
Article in English | MEDLINE | ID: mdl-30374407

ABSTRACT

Biofilms exist and thrive within drinking water distribution networks, and can present human health concerns. Exposure of simulated drinking water biofilms, grown from groundwater, to a 9 × 9 array of microchannel plasma jets has the effect of severely eroding the biofilm and deactivating the organisms they harbor. In-situ measurements of biofilm structure and thickness with an optical coherence tomography (OCT) system show the biofilm thickness to fall from 122 ± 17 µm to 55 ± 13 µm after 15 min. of exposure of the biofilm to the microplasma column array, when the plasmas are dissipating a power density of 58 W/cm2. All biofilms investigated vanish with 20 min. of exposure. Confocal laser scanning microscopy (CLSM) demonstrates that the number of living cells in the biofilms declines by more than 93% with 15 min. of biofilm exposure to the plasma arrays. Concentrations of several oxygen-bearing species, generated by the plasma array, were found to be 0.4-21 nM/s for the hydroxyl radical (OH), 85-396 nM/s for the 1O2 excited molecule, 98-280 µM for H2O2, and 24-42 µM for O3 when the power density delivered to the array was varied between 3.6 W/cm2 and 79 W/cm2. The data presented here demonstrate the potential of microplasma arrays as a tool for controlling, through non-thermal disruption and removal, mixed-species biofilms prevalent in commercial and residential water systems.

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