Half-peak Bandwidth Research Articles

Objective Evaluation of Fabric Wrinkles Based on 2-D Gabor Transform

In order to establish an objective, stable and efficient wrinkle evaluation system for fabric wrinkle evaluation, a method based on 2-D Gabor transform was proposed. Among this system, the directions of Gabor filter were determined according to the range of amplitude response. Then a set of Gabor filters were obtained by selecting and optimizing the central frequency, the half peak bandwidth and the shape factor of the Gaussian surface. After Gabor transform by such filter bank, the amplitudes of different response spectrums were extracted, constructing a multi-dimensional feature vector. Finally, the feature vectors of the fabric image samples, whose wrinkle degrees were evaluated manually in advance, were extracted and used to train a support vector machine (SVM), which achieved 81.82 % evaluation accuracy on the 345 samples. The trained SVM was applied to evaluate the wrinkle degree of the fabric samples acquired in different illumination directions, and verified the stability of the proposed method to illumination environment. Compared with the existing method, the proposed method has higher classification accuracy. The comparison results indicate the Gabor amplitude feature proposed by this research has a high correlation with the fabric wrinkle grades.

Effects of Different Light Spectra on the Growth Performance and Survival of Largemouth Bass (Micropterus salmoides) Larvae in Recirculating Aquaculture Systems

The effects of light-emitting diode (LED) spectra on the survival rate and growth performance of largemouth bass in the nursery stage were explored in this study. By means of recirculating aquaculture systems, largemouth bass larvae (initial body length of 6.5 ±0.23 mm) were reared under four different light spectra: blue (half-peak bandwidth = 429 to 450 nm), green (half-peak bandwidth = 503 to 535 nm), white (320 < λ < 950), and full spectrum. After the 16-day experiment, the results showed that the survival rate was highest for the larvae in the full spectrum group (33.5% ±3.5%) and lowest for the larvae in the blue light group (11.6% ±0.7%). The final body lengths of the larvae under different light spectra was as follows: the full spectrum group had the longest average body length (12.4 ±0.3 mm), followed by the white light group and the green light group, and the larvae in the blue light group had the shortest average body length (12.1 ±0.4 mm). The dorsal and anal fins of the larvae differentiated fastest in the full spectrum group, and the caudal fins differentiated fastest in the green light group. The maximal and minimal malformation rates of the larvae occurred under white light (26.7% ±0.2%) and full spectrum light (16.7% ±0.9%), respectively. The results demonstrated that a full spectrum light environment can improve the survival of largemouth bass larvae and promote their growth and development.

Sound absorbing properties of perforated composite panels of recycled rubber, fiberboard sawdust, and high density polyethylene

Abstract Recycled natural or synthetic polymers, typically waste rubber, may find their novel usage in the production of acoustic materials for their good impedance properties. To that end, rubber granules from used tires (R), high-density fiberboard flooring sawdusts (W), and fresh HDPE pellets (P) were fully blended at a proven mass ratio of 18, 40, and 42 percent, with 5 percent MA-PE as coupling agent based on W/R/P overall weight. The mixture was mould-pressed into composite panels at 185 °C for 20 min, under a pressure of 1 MPa. Small holes of 1 mm–6 mm in diameter were subsequently drilled at three perforation rates (3%, 6%, and 9%). Sound absorption testing was conducted with an impedance tube following ISO 10534-2 standard at incident sound frequencies from 63 Hz to 6300 Hz. To imitate a Helmholtz resonating structure, distance (D) between the perforated sample and the adjuster was set as 50 mm, 100 mm, and 150 mm, creating different cavity volumes. It was found that perforated WRPC panels have both high sound absorption coefficients and broad bandwidth, especially at frequencies lower than 1000 Hz. At higher frequencies range, hole size seemingly showed no evident influences while larger perforation rates produced higher sound absorption coefficients (SAC). The SAC-frequency curves showed 2, 4, and 6 peaks as D was 50 mm, 100 mm, and 150 mm, respectively, with half-peak bandwidth decreasing as frequency increases. The above results may supply helpful guidance to design WRPC acoustic materials.

A study of determination of dynamic viscosity in liquids using radial mode piezo-resonator

ABSTRACTAn investigation on determination of viscosity based on radial mode resonance of a piezoelectric ceramic ring transducer operating at 32.5 kHz is reported. The change in its resonant frequency and in the half peak bandwidth have been measured with the disc vibrating in air, water, pure glycerine and a glycerine-water mixture. An improved configuration of coupling the transducer to the liquid medium has been used so that it has semi-infinite loading of its front face. Also, a correction in the bandwidth eliminating the mechanical loss inherent in the piezoelectric element has been made, which has improved the accuracy of viscosity determination.

On energy absorption capacity, flexural and dynamic properties of flax/epoxy composite tubes

In this study, energy absorption capacity, flexural and dynamic properties of flax fibre reinforced epoxy polymer composite (FFRP) tubes are investigated. The energy absorption capacity of the tubes is investigated under uniaxial compression. Flexural behaviour of the tubes is studied under four-point bending and the dynamic properties (i.e., natural frequency and damping characteristics) are evaluated by impact hammer vibration testing of the tube specimens. The damping characteristics of the tubes are determined by using both a logarithmic decrement curve and the half-peak bandwidth method. The influence of tube laminate thickness and specimen size on the mechanical properties of FFRP tubes is determined. Compressive testing indicates that the FFRP tube provides a specific absorbed energy of 22 J/g, which is close to the conventional metal energy absorption materials, i.e. stainless steel and aluminium tubes. Flexural study shows that the FFRP tube exhibits a brittle failure as similar to that of the FFRP composites in a flat-coupon tension. The load carrying capacity and deflection of the tube increase with an increase in the tube thickness. Impact loading test concludes that an increase in tube thickness leads to a reduction in natural frequency and damping ratio of the tubes. The FFRP tubes have sizedependent dynamic properties, i.e. an increase in tube size increased the natural frequency but reduced the damping ratio of the specimens remarkably. However, all FFRP tubes have high damping ratios, thus reducing the effect of dynamic loading on the structural response. Therefore, this study suggests that FFRP tubes could be used in several structural applications, i.e. in automotive as energy absorbers and in civil infrastructure as poles.

Effects of different colors of light on melatonin suppression and expression analysis of Aanat1 and melanopsin in the eye of a tropical damselfish

Ocular melatonin production exhibits a daily rhythm with a decrease during photophase and an increase during scotophase (nocturnal pattern) in teleost fish due to day–night changes in the activity of the rate-limiting melatonin synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT). Acute light exposure during scotophase suppresses AANAT activity and melatonin production in the eyes, suggesting that external light signals are a principal regulator of ocular melatonin synthesis. To better understand the photic regulation of ocular melatonin synthesis in teleost fish, this study sought to characterize the effect of light on ocular melatonin synthesis in the sapphire devil Chrysiptera cyanea, which shows a nocturnal pattern and light-induced inhibition of ocular melatonin production during scotophase. Exposure to three different wavelengths of light (half-peak bandwidth=435–475nm with a peak of 455nm, 495–565nm with a peak of 530nm, and 607–647nm with a peak of 627nm for the blue, green, and red LEDs) for 2h during scotophase resulted in the blue wavelength significantly decreasing ocular melatonin content within 30min after light exposure. This result clearly indicates that the effective range of visible light on ocular melatonin suppression is distributed within the wavelengths of blue light and that a blue light-sensitive opsin is involved in ocular melatonin suppression in the fish. A PCR-based cloning method revealed the expression of melanopsin, a putative blue light-sensitive nonvisual opsin, in the eyes. Furthermore, in situ hybridization using the sapphire devil Aanat1 and melanopsin RNA probes showed mRNA expressions of both genes in the inner nuclear and ganglion cell layer of the fish retina. These results suggest that melanopsin is a possible candidate photoreceptor involved in ocular melatonin suppression by an external light signal in the sapphire devil.

Effects of light during early larval development of some aquacultured teleosts: A review

Light is a key environmental factor that synchronizes all life-stages of fish, from embryo development to sexual maturation. The underwater photo-environment is complex since light characteristics (i.e. intensity, photoperiod and spectrum) depend on the absorbance properties of the water column. The aim of this paper is to review the effects of artificial lighting conditions on the performance, development and welfare of some fish larvae of commercial interest. Reviewed results show that larvae were significantly affected by light characteristics. For example, European sea bass and sole larvae achieved the best performance, and showed fastest development and lowest degree of deformity under a light/dark cycle using blue light (half-peak bandwidth = 435–500 nm), conditions which were the closest to their natural aquatic environment. However, constant light (LL) or constant darkness (DD) was shown to negatively affect normal larval development and resulted in increased malformations and poor survival in most of the studied species. Similar results have been observed in other fish larvae such as Atlantic cod, which performed better under short wavelengths (blue and green). These findings highlight the role of lighting conditions during the early development of fish larvae and should be taken into account for the optimization of rearing protocols in fish hatcheries as juvenile supply is one of the main production bottlenecks.

Effect of light spectrum and photoperiod on the growth, development and survival of European sea bass ( Dicentrarchuslabrax) larvae

This study investigates how the characteristics (spectrum and photoperiod) of artificial light affect European sea bass eggs and larvae from − 1 to 40 days post-hatching. Fertilised eggs and larvae were reared under five different light treatments: 12L:12D red light (LDR; half-peak bandwidth = 641–718 nm), 12L:12D blue light (LDB; half-peak bandwidth = 435–500 nm), 12L:12D broad-spectrum white light (LDW; 367 < λ < 1057 nm), 24L:0D broad-spectrum white light (LL) and 0L:24D (DD). The results showed that total length at day post-hatching 40 was significantly larger in larvae reared under LDB (15.4 ± 0.6 mm) and LL (15.2 ± 0.6 mm) than in larvae reared under LDR (11.7 ± 0.7 mm). Overall wet weight was highest under LDB (21.6 ± 2.02 mgr) and lowest in LDR larvae (13.6 ± 1.48 mgr). Yolk sac and oil globule absorption occurred more slowly in LDR and DD larvae, while LDB larvae developed their fin, teeth and swim bladder significantly earlier than the rest of the groups. DD larvae were unable to capture food and mortality was 100% by day post-hatching 18, while LDR larvae did not feed on rotifers, but fed on Artemia from day post-hatching 16 onwards. The best survival was obtained with the LL treatment, although significantly more problems with swim bladder development and lower jaw malformations were also identified in this group. In summary, these results highlight the key role of the light spectrum and photoperiod for European sea bass larvae, the best performance being achieved under the light conditions that best approached those of their natural aquatic environment (LDB). These findings should be considered when designing rearing protocols for larvae in aquaculture.

Spectral Sensitivity of Circadian, Neuroendocrine and Neurobehavioral Effects of Light

The mammalian eye detects light for a range of behavioral and physiological responses separate and apart from sight. In humans, ocular light exposure resets the endogenous circadian pacemaker, suppresses synthesis of the pineal hormone melatonin, enhances morning cortisol production, increases heart rate and core body temperature, induces pupillary constriction, and improves subjective and objective measures of alertness. Several lines of evidence suggest that these responses are mediated primarily via a novel photoreception system with short-wavelength sensitivity (λmax 460–480 nm) different from that used for sight. In order to compare the relative contribution of the novel photoreceptor system with the three-cone visual photopic system for multiple non-visual effects of light, we compared the responses following exposure to an equal photon density (2.8×1013 photons/cm2/s) either 460 nm (n=8) or 555 nm (n=8) monochromatic light (10 nm half-peak bandwidth) at night on circadian phase resetting, melatonin suppression and subjective and objective correlates of alertness. As compared to 555 nm exposure, 460 nm light caused twice the phase shift in the circadian melatonin rhythm, double the amount of melatonin suppression, and significantly reduced auditory reaction time and lapses of attention. Exposure to 460 nm light also preferentially suppressed delta-theta (0.5–5.5 Hz) activity and elevated high alpha power (9.5–10.5 Hz) in the waking electroencephalogram (EEG) recordings, indicating a more alert state. The short-wavelength sensitivity to the non-visual effects of light indicates that the photopic visual system is not the primary photoreceptor system mediating these responses to light, and is consistent with predominant input from the novel melanopsin-containing photosensitive retinal ganglion cells. These data also suggest that short-wavelength light may be an effective therapy for resetting the circadian system in Circadian Rhythm Sleep Disorders and could be used as a direct fatigue countermeasure in a range of clinical and occupational settings. Translation of these basic findings into real-world applications is beginning to occur but the challenge to architects and lighting designers is to provide lighting that optimizes both the visual and non-visual effects of light simultaneously and safely.

Spectral characterization of yeast cells with an epitaxy-based UV-Vis optical sensor

The optical spectra of yeast cells in phosphate buffer saline (PBS) were analyzed with an optical UV-vis sensor based on a shallow p(+)n junction realized in a low doped n-type epitaxial silicon layer grown on a strongly doped n(+) substrate. The presence of the n/n(+) interface allows a significantly enhanced sensitivity, due to an increased collection of carriers photogenerated both by short and large wavelengths in the range 250...800 nm. In our experiments the optical absorption of yeast cells was investigated in the wavelength range 250...500 nm as a function of the cells concentration in PBS in the range of 6 x 10(6)-2 x 10(8) cells/ml. The main absorption peaks were found at 310, 350, 400 and 427 nm, respectively. A significant red shift of the wide absorption band at 427 nm has been observed when increasing cell concentration. This red shift behaviour was nonlinear, with saturation observed for yeast concentrations larger than 5 x 10(7) cells/ml. The half-peak bandwidth of this peak also showed a most significant nonlinear variation. These findings suggest that monitoring the parameters of the absorption band at 427 nm versus cells concentration could be used, e.g. using a dedicated integrated spectrometric microsystem, for fast quantitative measurements of yeast cell concentrations in various bio-samples, with possible applications in the food industry.

Light Therapy for Seasonal Affective Disorder with Blue Narrow-Band Light-Emitting Diodes (LEDs)

While light has proven an effective treatment for Seasonal Affective Disorder (SAD), an optimal wavelength combination has not been determined. Short wavelength light (blue) has demonstrated potency as a stimulus for acute melatonin suppression and circadian phase shifting. This study tested the efficacy of short wavelength light therapy for SAD. Blue light emitting diode (LED) units produced 468 nm light at 607 microW/cm2 (27 nm half-peak bandwidth); dim red LED units provided 654 nm at 34 microW/cm2 (21 nm half-peak bandwidth). Patients with major depression with a seasonal pattern, a score of > or =20 on the Structured Interview Guide for the Hamilton Depression Rating Scale-SAD version (SIGH-SAD) and normal sleeping patterns (routine bedtimes between 10:00 pm and midnight) received 45 minutes of morning light treatment daily for 3 weeks. Twenty-four patients completed treatment following random assignment of condition (blue vs. red light). The SIGH-SAD was administered weekly. Mixed-effects analyses of covariance determined that the short wavelength light treatment decreased SIGH-SAD scores significantly more than the dimmer red light condition (F = 6.45, p = .019 for average over the post-treatment times). Narrow bandwidth blue light at 607 microW/cm2 outperforms dimmer red light in reversing symptoms of major depression with a seasonal pattern.

A New Type of Bacteriophytochrome Acts in Tandem with a Classical Bacteriophytochrome to Control the Antennae Synthesis in Rhodopseudomonas palustris

Phytochromes are chromoproteins found in plants and bacteria that switch between two photointerconvertible forms via the photoisomerization of their chromophore. These two forms, Pr and Pfr, absorb red and far-red light, respectively. We have characterized the biophysical and biochemical properties of two bacteriophytochromes, RpBphP2 and RpBphP3, from the photosynthetic bacterium Rhodopseudomonas palustris. Their genes are contiguous and localized near the pucBAd genes encoding the polypeptides of the light harvesting complexes LH4, whose synthesis depends on the light intensity. At variance with all (bacterio)phytochromes studied so far, the light-induced isomerization of the chromophore of RpBphP3 converts the Pr form to a form absorbing at shorter wavelength around 645 nm, designated as Pnr for near red. The quantum yield for the transformation of Pr into Pnr is about 6-fold smaller than for the reverse reaction. Both RpBphP2 and RpBphP3 autophosphorylate in their dark-adapted Pr forms and transfer their phosphate to a common response regulator Rpa3017. Under semiaerobic conditions, LH4 complexes replace specifically the LH2 complexes in wild-type cells illuminated by wavelengths comprised between 680 and 730 nm. In contrast, mutants deleted in each of these two bacteriophytochromes display no variation in the composition of their light harvesting complexes whatever the light intensity. From both the peculiar properties of these bacteriophytochromes and the phenotypes of their deletion mutants, we propose that they operate in tandem to control the synthesis of LH4 complexes by measuring the relative intensities of 645 and 710 nm lights.

Influence of light intensity, spectrum and orientation on sea bass plasma and ocular melatonin.

Melatonin is involved in the transduction of light information and the photoperiodic control of many important physiological functions in fish. Although artificial photoperiods have been used to improve fish growth and manipulate reproduction, there is little information about the characteristics of light 'quality'. In this paper we describe the effects of a light pulse in the middle of the dark phase on plasma and ocular melatonin in European sea bass. We first determined the light intensity necessary to elicit a melatonin response using white light of varying intensities (0.6-600 mu W/cm(2), experiment 1). Secondly, we tested the effect of the light spectrum on melatonin production using three differently coloured lights (half-peak bandwidth=434-477, 498-575 and 610-687 nm for the blue, green and red lamp, respectively, experiment 2) and, finally, we determined the effect of light orientation (downwards directed versus upwards directed, experiment 3). The results show that the minimum light intensity needed to inhibit or stimulate melatonin levels in both plasma and the eye was 6.0 mu W/cm(2). A linear correlation was found between the logarithm of light intensity and the relative inhibition. In addition, the blue wavelength was more effective in decreasing melatonin levels in the former and increasing the levels in the latter. Nevertheless, red light at sufficient intensity proved effective at significantly suppressing circulating melatonin. Downwards light had a greater effect than upward-directed illumination in suppressing plasma melatonin. In conclusion, the results point to the importance of giving proper consideration to the characteristics of light, to adequately control melatonin production and its related physiological processes.

Evaluation of damping and elastic properties of composites and composite structures by the resonance technique

This paper describes the resonance technique for determining the stiffness and damping properties of a composite or composite structure. Pultruded GRP composites and optical fibre cables (multi-component structures) were investigated. The resonance frequencies (natural frequencies) of a material, or a system, are a function of its elastic properties, dimensions and mass. This concept is used to determine the stiffness of a vibrated material by the resonance technique, which applies only very low stresses through the application of acoustic energy. This makes it applicable to measure the stiffness of multi-element cables. The damping properties, in terms of Q−1 (internal friction) were determined by both a free exponential decay curve and half-peak bandwidth methods. The influence of specimen length and measurement set-up was investigated. The applicability and accuracy of the resonance technique for a composite structure were discussed. The measured elasticity of optical cables was found to be in good agreement with the derived theoretical value.

Theta-frequency resonance in hippocampal CA1 neurons in vitro demonstrated by sinusoidal current injection.

Sinusoidal currents of various frequencies were injected into hippocampal CA1 neurons in vitro, and the membrane potential responses were analyzed by cross power spectral analysis. Sinusoidal currents induced a maximal (resonant) response at a theta frequency (3-10 Hz) in slightly depolarized neurons. As predicted by linear systems theory, the resonant frequency was about the same as the natural (spontaneous) oscillation frequency. However, in some cases, the resonant frequency was higher than the spontaneous oscillation frequency, or resonance was found in the absence of spontaneous oscillations. The sharpness of the resonance (Q), measured by the peak frequency divided by the half-peak power bandwidth, increased from a mean of 0.44 at rest to 0.83 during a mean depolarization of 6.5 mV. The phase of the driven oscillations changed most rapidly near the resonant frequency, and it shifted about 90 degrees over the half-peak bandwidth of 8.4 Hz. Similar results were found using a sinusoidal function of slowly changing frequency as the input. Sinusoidal currents of peak-to-peak intensity of >100 pA may evoke nonlinear responses characterized by second and higher harmonics. The theta-frequency resonance in hippocampal neurons in vitro suggests that the same voltage-dependent phenomenon may be important in enhancing a theta-frequency response when hippocampal neurons are driven by medial septal or other inputs in vivo.

EFFECTS OF LIGHT ON T‐CELLS IN HIV‐INFECTED SUBJECTS ARE NOT DEPENDENT ON HISTORY OF SEASONAL AFFECTIVE DISORDER

In order to evaluate the effect of light on helper- and suppressor-T-cell counts in HIV-infected individuals, with and without a history of seasonal affective disorder (SAD), we treated 35 subjects with 45 min of light therapy in the morning, in a crossover design involving two 2 week treatment conditions: visible white light (half-peak band width, 530-620 nm; 10,000 lux) and visible red light (half-peak band width, 615-685 nm; 175 lux). We found small but significant differences between the two treatment conditions, with higher CD4 and CD8 levels during the white, as compared with the red, condition. There were no differences between baseline and treatment conditions. Both light treatment conditions were associated with significant mood improvements in the SAD, but not the non-SAD, subjects. There was no evidence that the higher cell counts seen under the bright light conditions were mediated by the effects of light on mood or on plasma cortisol levels. While the size of the light effect on T-cells renders questionable the potential therapeutic value of this treatment modality for HIV, the finding is of theoretical interest and is reassuring for those HIV-infected individuals who require light treatment for other reasons.

Spectral sensitivity of the blood-retinal barrier at the pigment epithelium for blue light in the 400–500 nm range

To specify the spectral sensitivity of the retinal pigment epithelium (RPE) for blue light damage, pigmented rabbits were exposed to light of 408, 418, 439, 455, 485, and 500 nm (half-peak bandwidth approximately 12 nm). The range of radiant exposure was 15-275 J cm-2 (1.7-19 mW cm-2 for 0.5-5 h). Vitreous fluorophotometry was used to functionally evaluate the blood-retinal barrier at the RPE in vivo, and electron microscopy to visualize RPE ultrastructure in vitro. A significant increase in permeability of the blood-retinal barrier was seen only after exposure to light of 418 nm. Radiant exposure at threshold for permeability increase was 18 J cm-2. Electron microscopy of the RPE demonstrated dispersion and clumping of melanin granules. The results suggest that the RPE is most sensitive to light in the range 412-425 nm, possibly due to damage-mediating chromophores such as cytochrome c oxidase and lipofuscin.