Broad-spectrum Light Research Articles

Degeneration of cortical function in the Royal College of Surgeons rat

The purpose of the current study was to determine the progress of cortical functional degeneration in the Royal College of Surgeons (RCS) rat. Cortical responses were measured with optical imaging of intrinsic signals using gratings of various spatial frequencies. Subsequently, electrophysiological recordings were also taken across cortical layers in response to a pulse of broad-spectrum light. We found significant degeneration in the cortical processing of visual information as early as 4 weeks of age. These results show that degeneration in the cortical response of the RCS rat starts before development has been properly completed.

Treatment of Hidradenitis Suppurativa with Intense Pulsed Light: A Prospective Study

Hidradenitis suppurativa is a chronic skin condition characterized by recurrent inflammation and infection of skin in intertriginous areas containing apocrine glands. Intense pulsed light uses high-energy broad-spectrum light. Current applications include hair removal and the treatment of acne vulgaris, which has a pathogenesis similar to that of hidradenitis suppurativa. The authors conducted a study to determine whether intense pulsed light is an effective treatment for hidradenitis suppurativa. Eighteen patients were randomized to treatment of one axilla, groin, or inframammary area with intense pulsed light two times per week for 4 weeks using a Harmony Laser. The contralateral side received no treatment and acted as a control. The response to treatment was assessed using a validated examination and clinical photographs, and by measuring patient satisfaction on a Likert scale. After treatment, there was a significant improvement in the mean examination score that was maintained at 12 months (p < 0.001, logistical regression analysis). The improvement was confirmed by independent assessment of clinical photographs (interrater reliability, 0.79; p < 0.001). Patients reported high levels of satisfaction with the treatment. There was no concurrent improvement on the untreated control side. This small study suggests that intense pulsed light may be an effective treatment for hidradenitis suppurativa. It could be added to treatments used for this condition, particularly for patients keen on avoiding surgery and those with groin and inframammary disease. Further studies are required to confirm the efficacy and mechanism of action of intense pulsed light in hidradenitis suppurativa.

SIRAD – Personal radiation detectors

Abstract SIRAD badge dosimeters provide a visual qualitative measurement of exposure to radiation for mid range dose exposure. This is performed using an active radiochromic dosimeter in a transparent window, combined into a badge assembly. When irradiated, the badges active window turns blue, which can be matched against the given colour chart for a qualitative assessment of the exposure received. Two peaks in the absorption spectra located at 617 nm and 567 nm were found. When analysed with a common computer desktop scanner, the optical density response of the film to radiation exposure is non-linear but reproducible. The net OD of the film was 0.21 when exposed to 50cGyand 0.31 at 200 cGy exposure when irradiated with a 6 MV x-ray energy beam and analysed using a broad spectrum light source. These values reduced when exposed with kilovoltage x-rays with an approximate 30% reducing in sensitivity at 50 kVp. The film provides an adequate measurement and visually qualitative assessment of radiation exposure for levels in the range of 0–50 cGy.

Cyclic tetrapyrrolic photosensitizers from Cladophora patentiramea (Cladophoraceae, Chlorophyta) and Turbinaria conoides (Sargassaceae, Phaeophyta) for photodynamic therapy

In screening for novel photosensitizers for photodynamic therapy, 14 seaweed samples from Port Dickson in Malaysia were collected. Methanolic extracts of these samples were prepared and evaluated for phototoxicity using a short-term cell viability assay, where promyelocytic leukemia cells, HL60 were incubated with the extracts prior to irradiation with a broad spectrum light at 9.6 J cm−2 (equivalent to 10.5 mW cm−2 for 10 min). Four of the methanolic extracts demonstrated moderate to strong phototoxicity and bioassay-guided isolation of photosensitizers was carried out on two selected seaweeds to yield a total of eight cyclic tetrapyrrolic compounds which are derivatives of chlorophyll-a and -b. Seven of these compounds showed >50% phototoxicity at 5 μg mL−1 while exhibiting minimal cytotoxicity in the dark, which is an important characteristic of an ideal photosensitizer.

Cyclic Tetrapyrrolic Photosensitisers from the leaves of Phaeanthus ophthalmicus

BackgroundTwenty-seven extracts from 26 plants were identified as photo-cytotoxic in the course of our bioassay guided screening program for photosensitisers from 128 extracts prepared from 64 terrestrial plants in two different collection sites in Malaysia - Royal Belum Forest Reserve in the State of Perak and Gunung Nuang in the State of Selangor. One of the photo-cytotoxic extracts from the leaves of Phaeanthus ophtalmicus was further investigated.ResultsThe ethanolic extract of the leaves from Phaeanthus ophtalmicus was able to reduce the in vitro viability of leukaemic HL60 cells to < 50% when exposed to 9.6 J/cm2 of a broad spectrum light at a concentration of 20 μg/mL. Dereplication of the photo-cytotoxic fractions from P. ophthalmicus extracts based on TLC Rf values and HPLC co-injection of reference tetrapyrrolic compounds enabled quick identification of known photosensitisers, pheophorbide-a, pheophorbide-a methyl ester, 132-hydroxypheophorbide-a methyl ester, pheophytin-a and 151-hydroxypurpurin 7-lactone dimethyl ester. In addition, compound 1 which was not previously isolated as a natural product was also identified as 7-formyl-151-hydroxypurpurin-7-lactone methyl ester using standard spectroscopic techniques.ConclusionsOur results suggest that the main photosensitisers in plants are based on the cyclic tetrapyrrole structure and photosensitisers with other structures, if present, are present in very minor amounts or are not as active as those with the cyclic tetrapyrrole structure.

Occlusive IOLs for Intractable Diplopia Demonstrate a Novel Near-Infrared Window of Transmission for SLO/OCT Imaging and Clinical Assessment

Occlusive intraocular lens (IOL) implantation is an effective therapeutic option in patients with intractable diplopia, visual confusion, and unsightly leukocoria. However, their use has been restricted by concerns that inability to visualize the retina may prevent the diagnosis of important posterior pole diseases. In this study, transmission spectra of occlusive IOLs were defined as a basis for acquiring scanning laser ophthalmoscopy/optical coherence tomography (SLO/OCT) images. Fifteen IOLs of three designs were examined: black small and large PMMA and black Lotus (Morcher GmbH, Stuttgart, Germany). Each IOL was placed between a broad-spectrum white light source and a spectroradiometer, to generate transmission spectra for each lens and determine the cutoff wavelength. Transmission in the near-infrared (NIR) range was confirmed with an 850-nm LED. A model eye was implanted with occlusive IOLs, and SLO/OCT scans were acquired with seven clinical SLO/OCT imaging systems. Occlusive IOLs demonstrated high levels of transmission of NIR light. It was determined that most SLO/OCT scanners would achieve 99% to 100% transmission at their operational wavelengths of NIR light. Furthermore, all clinical SLO/OCT imaging systems were capable of imaging fine retinal features without attenuation through occlusive IOLs in a model eye. In this study, a novel NIR window of high-level transmission was identified across the occlusive IOLs with applications to SLO/OCT imaging and NIR-based clinical assessment. The ability to acquire high-quality SLO/OCT scans to detect posterior pole disease may fundamentally change the current view on occlusive IOLs and encourage their use in patients with intractable diplopia.

Advanced method for increasing the efficiency of white light quantum dot LEDs

AbstractCovering a light‐emitting diode (LED) with quantum dots (QDs) can produce a broad spectrum of white light. However, current techniques for applying QDs to LEDs suffer from a high density of defects and a non‐uniform distribution of QDs, which, respectively, diminish the efficiency and quality of emitted light. Oak Ridge National Laboratory (ORNL) has the unique capability to thermally anneal QD structures at extremely high power densities for very short durations. This process, called pulse thermal processing (PTP), reduces the number of point defects while maintaining the size and shape of the original QD nanostructure. Therefore, the efficiency of the QD wavelength conversion layer is improved without altering the emission spectrum defined by the size distribution of the QD nanoparticles. The current research uses a thermal model to predict annealing temperatures during PTP and demonstrates up to a 300% increase in photoluminescence for QDs on passive substrates.

Derivatives of Pheophorbide‐a and Pheophorbide‐b from Photocytotoxic Piper penangense Extract

In our screening program for new photosensitizers from Malaysian biodiversity for photodynamic therapy (PDT) of cancer, MeOH extracts of ten terrestrial plants from Cameron Highlands in Pahang, Peninsular Malaysia, were tested. In a short-term 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, 20 μg/ml each of these extracts were incubated in a pro-myelocytic leukemia cell-line, HL60, with or without irradiation with 9.6 J/cm(2) of a broad spectrum light. Three samples, Labisia longistyla, Dichroa febrifuga, and Piper penangense, were photocytotoxic by having at least twofold lower cell viability when irradiated compared to the unirradiated assay. The extract of the leaves of Piper penangense, a shrub belonging to the family Piperaceae and widely distributed in the tropical and subtropical regions in the world, was subsequently subjected to bioassay-guided fractionation using standard chromatography methods. Eight derivatives of pheophorbide-a and -b were identified from the fractions that exhibited strong photocytotoxicity. By spectroscopic analysis, these compounds were identified as pheophorbide-a methyl ester (1), (R,S)-13(2) -hydroxypheophorbide-a methyl ester (2 and 3), pheophorbide-b methyl ester (4), 13(2) -hydroxypheophorbide-b methyl ester (5), 15(2) -hydroxylactone pheophorbide-a methyl ester (6), 15(2) -methoxylactone pheophorbide-a methyl ester (7), 15(2) -methoxylactone pheophorbide-b methyl ester (8).

Radio Wave Generation Using Dark and Bright Soliton

In this study we propose a new system for radio wave using a soliton pulse within a micro waveguide and nano-waveguide. The system consists of two micro ring resonators and a nano ring resonator that can be integrated into a single system. The input soliton power, coupling coefficients, and ring radii, are used to control the short-wave and millimeter-wave output signals being generated and filtered in a single system. The large bandwidth signal is generated using a soliton pulse within a Kerr-type nonlinear medium. The signals with broad bandwidth or wavelength can then be generated. Results obtained have shown the potential of using this system for a broad light spectra generation.

Low intensity light stimulates nitrite-dependent nitric oxide synthesis but not oxygen consumption by cytochrome c oxidase: Implications for phototherapy

Cytochrome c oxidase (Cco) has been reported to be a receptor for some of the beneficial effects of low intensity visible and near-infrared light on cells and tissues. Here, we have explored the role of low intensity light in affecting a newly described function of Cco, its ability to catalyze nitrite–dependent nitric oxide (NO) synthesis (Cco/NO). Using a new assay for Cco/NO we have found that both yeast and mouse brain mitochondrial Cco produce NO over a wide range of oxygen concentrations and that the rate of NO synthesis increases as the oxygen concentration decreases, becoming optimal under hypoxic conditions. Low intensity broad-spectrum light increases Cco/NO activity in an intensity-dependent fashion but has no effect on oxygen consumption by Cco. By using a series of bandpass filters and light emitting devices (LEDs) we have determined that maximal stimulation of Cco/NO activity is achieved by exposure to light whose central wavelength is 590 ± 14 nm. This wavelength of light stimulates Cco/NO synthesis at physiological nitrite concentrations. These findings raise the interesting possibility that low intensity light exerts a beneficial effect on cells and tissues by increasing NO synthesis catalyzed by Cco and offer a new explanation for the increase in NO bioavailability experienced by tissue exposed to light.

Achieving accurate radiochromic optical-CT imaging when using a polychromatic light source

Optical-CT performed with a broad spectrum light source can lead to inaccurate reconstructed attenuation coefficients (and hence dose) due to 'spectral warping' as the beam passes through the dosimeter. Some wavelengths will be attenuated more strongly than others depending on the absorption spectrum of the radiochromic dosimeter. A simulation was run to characterize the error introduced by the spectrum warping phenomena. Simulations of a typical dosimeter and delivered dose (6cm diameter, 2 Gy irradiation) showed reconstructed attenuation coefficients can be in error by >12% when compared to those obtained from a monochromatic scan. A method to correct for these errors is presented and preliminary data suggests that with the correction, polychromatic imaging can yield imaging results equal in accuracy to those of monochromatic imaging. The advantage is that polychromatic imaging may be less sensitive to prominent schlerring artefacts that are often observed in telecentric optical-CT scanning systems with tight bandwidth filters applied.

Quantifying and mapping the spatial distribution of fluence inside a pulsed light treatment chamber and various liquid substrates

Pulsed light (PL) is a technology that uses short, high-energy pulses of UV-rich broad spectrum light to inactivate a range of pathogenic and spoilage microorganisms in foods and on food contact surfaces. Microbial inactivation is directly related to the energy dose (fluence) received by the target microbes. Since fluence decays away from the lamp source due to light absorption and scattering phenomena, it is necessary to accurately quantify the fluence received locally within a substrate in order to design uniform antimicrobial PL treatments. The main objective of this work was to quantify and map the spatial distribution of both total and UV fluence both in air and in liquid substrates with different optical properties. Butterfield’s phosphate buffer (BPB), trypticase soy broth (TSB), and apple juice (clarified apple cider) were used as substrates and Listeria innocua was used as the challenge microorganism. A pyroelectric head, and a UV–VIS–NIR spectrophotometer connected to a 1000 μm optical fiber, were used to measure the fluence in air and the three liquid substrates. Fluence was measured at incremental distances from the lamp, along the x-, y- and z-axes. As expected, fluence decreased with increasing distance from the lamp, in all three directions. A 3-parameter Gaussian model described well the spatial distribution of fluence, both in air and in the liquid substrates. Overall, this study emphasizes the fact that substrate–light interactions affect the spatial distribution of fluence within a substrate, and these non-uniformities need to be taken into account when developing commercial applications of PL.

Multiple Exciton Collection in a Sensitized Photovoltaic System

Multiple exciton generation, the creation of two electron-hole pairs from one high-energy photon, is well established in bulk semiconductors, but assessments of the efficiency of this effect remain controversial in quantum-confined systems like semiconductor nanocrystals. We used a photoelectrochemical system composed of PbS nanocrystals chemically bound to TiO(2) single crystals to demonstrate the collection of photocurrents with quantum yields greater than one electron per photon. The strong electronic coupling and favorable energy level alignment between PbS nanocrystals and bulk TiO(2) facilitate extraction of multiple excitons more quickly than they recombine, as well as collection of hot electrons from higher quantum dot excited states. Our results have implications for increasing the efficiency of photovoltaic devices by avoiding losses resulting from the thermalization of photogenerated carriers.

Novel storage and tunable light source generated by a soliton pulse in a micro ring resonator system

We propose a novel system of a dense wavelength division operation using the nonlinear micro ring resonators system that can be used to generate the broad output light spectra, whereas the significant increasing in channel capacity is obtained. A system consists of two micro and a nano ring resonators incorporating an add/drop filter that can be integrated into a single system. The large bandwidth signal is generated by using a soliton pulse propagating within a Kerr type nonlinear medium. The obtained results have shown the potential of using such a system for broadband light source generation, amplification, storage and regeneration, whereas the amplified signals can be stored within a nano-waveguide, which is allowed to form the regeneration of the broad light spectra after amplification. The advantage is that the specific wavelength of the broadband source, for instance, 1.50 μm can provide the super dense wavelength division multiplexing channels, whereas the increasing in channel capacity of 10,000 times is achieved.

Full-field optical coherence tomography by achromatic phase shifting with a rotatinghalf-wave plate

An achromatic phase shifter with a rotating half-wave plate (HWP) and a full-field opticalcoherence tomography (FF-OCT) system based on it are presented. The novelconfiguration of this phase shifter in the FF-OCT system can achromaticallyprovide a phase shift of eight times the rotation angle of the HWP. The theoreticalcalculation of the phase shift and numerical analysis of the phase shift error,as well as the amplitude ratio, are conducted by means of Jones matrices. Theactual phase shift has also been measured to confirm the validity of the ‘8θ phase shift—HWProtation angle θ’ relation. The coherent image of a mirror has been obtained by using the Hariharanalgorithm to verify the phase shifter’s feasibility. Using traditional phase shiftingalgorithms, en-face images of a coin have been measured at different depths to illustrate thetomographic capability of this FF-OCT system. In comparison with other current systems,our design has several advantages, and high-resolution high-speed FF-OCT imaging can beenvisioned. The phase shifter can be used for common path setups and is verysuitable for implementing the phase shifting of a broad-spectrum light source.

Super DWDM light source generation for personnel health data and security camera

We propose a novel system of a dense wavelength division operation using the nonlinear micro ring resonators system that can be used to generate the broad output light spectra, whereas the significant increasing in channel capacity is obtained. A system consists of two micro and a nano ring resonators incorporating an add/drop filter that can be integrated into a single system. The large bandwidth signal is generated by using a soliton pulse propagating within a Kerr type nonlinear medium. The obtained results have shown the potential of using such system for broad band light source generation, amplification, storage and regeneration, whereas the amplified signals can be stored within a nano-waveguide, which is allowed to form the regeneration of the broad light spectra after amplification. The advantage is that the specific wavelength of the broadband source, for instance, 1.50μm can provide the super dense wavelength division multiplexing channels, whereas the increasing in channel capacity of 200 times is achieved. The use of super dense wavelength division multiplexing for large population monitoring and closed circuit television for security using the personnel wavelength carrier and networking is described and discussed in details.

Photodynamic therapy with methyl aminolevulinate for primary nodular basal cell carcinoma: results of two randomized studies

Data suggest that photodynamic therapy using topical methyl aminolevulinate (MAL PDT) may be a noninvasive alternative to excisional surgery for nodular basal cell carcinoma (BCC). In the studies described here, we investigated the histologic response, tolerability, and cosmetic outcome with MAL PDT for primary nodular BCC (<or= 5 mm in depth). Two multicenter, randomized, double-blind studies with similar design and procedures were conducted. After surface debridement and minor tumor debulking, MAL cream 160 mg/g (66 patients with 75 lesions) or placebo cream (65 patients with 75 lesions) was applied for 3 h, followed by illumination with broad-spectrum red light (75 J/cm(2), 570-670 nm). This was repeated 7 days later. Lesions with a partial response (>or= 50% reduction in greatest diameter) at 3 months were re-treated (21%). Treatment sites were excised at 3 months (clinical nonresponders) or 6 months (clinical responders) after the last treatment. Histologically verified lesion complete response rates were higher with MAL PDT than with placebo [73% (55/75) vs. 27% (20/75)]. Treatment was most effective for facial lesions (89% complete response). Cosmetic outcome was good or excellent in 98% of evaluable, completely responding lesions treated with MAL PDT. Although longer follow-up studies are required, these promising data indicate the potential of topical MAL PDT as a noninvasive treatment alternative for nodular BCC.

A novel storage and tunable light source generated by a soliton pulse in a micro ring resonator system for super dense wavelength division multiplexing use

AbstractWe propose a novel system of a dense wavelength division operation using the nonlinear microring resonators system that can be used to generate the broad output light spectra, whereas the significant increase in channel capacity is obtained. A system consists of two micro and a nanoring resonators incorporating an add/drop filter that can be integrated into a single system. The large bandwidth signal is generated by using a soliton pulse propagating within a Kerr type nonlinear medium. The obtained results have shown the potential of using such system for broad band light source generation, amplification, storage, and regeneration, whereas the amplified signals can be stored within a nanowaveguide, which is allowed to form the regeneration of the broad light spectra after amplification. The advantage is that the specific wavelength of the broadband source, for instance, 1.50 μm can provide the super dense wavelength division multiplexing channels, whereas the increase in channel capacity of 1000 times is achieved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2948–2952, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24807

Overview of the FTU results

Spontaneous increases in plasma density, up to ∼1.6 times the Greenwald value, are observed in FTU with lithized walls. These plasmas are characterized by profile peaking up to the highest obtained densities. The transport analysis of these discharges shows a 20% enhancement of the energy confinement time, with respect to the ITER97 L-mode scaling, correlated with a threshold in the peaking factor. It has been found that 0.4 MW of ECRH power, coupled at q = 2 surface, are sufficient to avoid disruptions in 0.5 MA discharges. Direct heating of magnetic islands produced by MHD modes determines current quench delay or avoidance. Supra-thermal electrons generated by 0.5 MW of lower hybrid power are sufficient to trigger precursors of the electron-fishbone instability. Evidence of spatial redistribution of fast electrons, on the ∼100 µs typical mode timescale, is shown by the fast electrons bremsstrahlung diagnostic. From the presence of new magnetic island induced accumulation points in the continuous spectrum of the shear Alfvén wave spectrum, the existence of new magnetic island induced Alfvén eigenmodes (MiAE) is suggested. Due to the frequency dependence on the magnetic island size, the feasibility of utilizing MiAE continuum effects as a novel magnetic island diagnostic is also discussed. Langmuir probes have been used on FTU to identify hypervelocity (10 km s−1), micrometre size, dust grains. The Thomson scattering diagnostic was also used to characterize the dust grains, present in the FTU vacuum chamber, following a disruption. Analysis of the broad emitted light spectrum was carried out and a model taking into account the particle vaporization is compared with the data. A new oblique ECE diagnostic has been installed and the first results, both in the presence of lower hybrid or electron cyclotron waves, are being compared with code predictions. A time-of-flight refractometer at 60 GHz, which could be a good candidate for the ITER density feedback control system, has also been tested.

High‐Throughput Near‐Infrared Reflectance Spectroscopy for Predicting Quantitative and Qualitative Composition Phenotypes of Individual Maize Kernels

ABSTRACTNear‐infrared reflectance (NIR) spectroscopy can be used for fast and reliable prediction of organic compounds in complex biological samples. We used a recently developed NIR spectroscopy instrument to predict starch, protein, oil, and weight of individual maize (Zea mays) seeds. The starch, protein, and oil calibrations have reliability equal or better to bulk grain NIR analyzers. We also show that the instrument can differentiate quantitative and qualitative seed composition mutants from normal siblings without a specific calibration for the constituent affected. The analyzer does not require a specific kernel orientation to predict composition or to differentiate mutants. The instrument collects a seed weight and a spectrum in 4–6 sec and can collect NIR data alone at a 20‐fold faster rate. The spectra are acquired while the kernel falls through a glass tube illuminated with broad spectrum light. These results show significant improvements over prior single‐kernel NIR systems, making this instrument a practical tool to collect quantitative seed phenotypes at high throughput. This technology has multiple applications for studying the genetic and physiological influences on seed traits.