Search

The coronavirus disease (COVID-19) pandemic, originating in Wuhan, China, in 2019, has spread to over 200 countries, posing a significant burden on global health systems and the global economy. The urgent need for faster and more accessible diagnostic methods has become evident, especially in regions with limited resources. Early detection can help reduce the death rate and prevent the spread of disease between people. Reverse transcription polymerase chain reaction (RT-PCR) tests have been widely used as a reliable method for detecting the presence of the virus. However, PCR testing has its drawbacks, such as being time-consuming, expensive, and putting healthcare workers at risk due to close contact with patients. In response to these challenges, medical imaging techniques like X-rays have been utilized for COVID-19 screening due to their speed, safety, and wider availability compared to traditional methods. Integrating artificial intelligence (AI) into image processing has shown promising results in accurately distinguishing between normal and diseased chest radiographs, aiding in early diagnosis and patient management. In this study, we propose a deep learning model to analyze COVID-19 chest X-rays, aiming to address the limitations of PCR testing and enhance the efficiency of diagnosis. One of the major challenges faced in this research is the low amount of available data for training the deep learning model. The lack of comprehensive and well-labeled datasets hinders the model's ability to generalize effectively and may limit its performance. Despite this limitation, we aim to achieve the best possible results using the available data. The proposed method includes a preprocessing step to improve image quality, followed by lung segmentation using UNet to eliminate irrelevant data and improve learning. Data augmentation is applied to address the class imbalance, ensuring the model's generalization capability. The core of the system is a lightweight convolutional neural network (CNN), optimized for small training datasets and low computation cost, making it suitable for resource-limited devices and real-time applications. The classification performance of the proposed model is compared with widely-used CNN models, including DenseNet, ResNet, InceptionV3, VGG16, and VGG19. The results demonstrate the superiority of the lightweight CNN model in terms of computation cost and generalization, showing great promise for its practical implementations. This research contributes to advancing the diagnosis and medical decision support system of COVID-19 through deep learning techniques, particularly in regions where PCR testing is limited or not readily accessible. By providing a faster, reliable, and cost-effective alternative to PCR testing, the proposed method can aid in mitigating the spread of the virus and improve patient outcomes. [ABSTRACT FROM AUTHOR]

The distribution of nerve veins in oral and maxillofacial region is very rich and connected with many parts of the body. Once the infection occurs behind the mouth and maxilla, the effects will be widespread. Therefore, this study aims to explore the application of light enhanced medical imaging technology based on computer diagnosis in the analysis of infection factors in oral and maxillofacial surgery to improve the ability of early diagnosis and accurate treatment. The oral and maxillofacial surgical infection was recorded by using light enhanced medical imaging. The clinical data of patients were collected and analyzed, and the images were processed by computer diagnostic technology. It was found that the relaxation factor λ was 0.5 and the number of iterations was 25 times to improve the accuracy. Studies have also shown that plasma fibrin has an advantage in predicting oral infections. This study demonstrated the potential application value of light enhanced medical imaging technology based on computer diagnosis in the analysis of infection factors in oral and maxillofacial surgery. This technique is helpful for early diagnosis and accurate treatment of oral and maxillofacial surgical infection, improving the treatment effect and quality of life of patients. Further research should also consider expanding the sample size and improving the accuracy of the analysis algorithm. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing fascination with suspended two-dimensional (2D) materials, owing to their excellent mechanical, optical, and electronic characteristics. This surge of interest stems from the remarkable properties exhibited by these materials when they are isolated in a two-dimensional counterpart. Nanofabrication technologies provide a new platform to further explore the properties of 2D materials by suspending them to reduce the influence of substrates. In recent years, many scientists have discovered the feasibility of using suspended membranes of 2D materials in various fields, including optoelectronics and photonics. This review summarizes the recent progress in the fabrication, characterization, and applications of suspended 2D materials, focusing on critical properties such as optical and electronic properties, strain engineering, and thermal properties. This area has the potential to lead to new technologies and applications in a wide range of innovative fields. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing fascination with suspended two-dimensional (2D) materials, owing to their excellent mechanical, optical, and electronic characteristics. This surge of interest stems from the remarkable properties exhibited by these materials when they are isolated in a two-dimensional counterpart. Nanofabrication technologies provide a new platform to further explore the properties of 2D materials by suspending them to reduce the influence of substrates. In recent years, many scientists have discovered the feasibility of using suspended membranes of 2D materials in various fields, including optoelectronics and photonics. This review summarizes the recent progress in the fabrication, characterization, and applications of suspended 2D materials, focusing on critical properties such as optical and electronic properties, strain engineering, and thermal properties. This area has the potential to lead to new technologies and applications in a wide range of innovative fields.

Unsupervised domain adaptive (UDA) person re-identification (re-ID) aims to generalize the model trained on a labeled source domain to an unlabeled target domain. Recently, the methods based on pseudo labels have achieved great success in the field of UDA person re-ID. However, pseudo label noise is still a problem to be solved. In this paper, we propose a novel framework to refine pseudo labels for UDA person re-ID. Firstly, in order to learn more discriminative features for better clustering, we propose a No-Reference Light Enhancement network (NRLE-Net) and a novel feature extraction model called Trans-Encoder. The NRLE-Net can reduce the inter-domain and intra-domain person image style differences caused by light condition changes simultaneously, which is helpful to improve the performance of the pre-trained model in target domain and reduce the noise of initial pseudo labels. The feature extraction model Trans-Encoder is designed based on Transformer. Compared with traditional Convolutional Neural Networks (CNN), the features extracted by Trans-Encoder are more robust to domain shift. On this base, the confidence of feature clustering can be improved. Secondly, to further reduce the noise of clustering pseudo labels, we design two noise refinement strategies. One is noise correction based on neighborhood consistency and the other is noise restraint based on label confidence. Through these two strategies, our model can be effectively optimized with the noise pseudo labels. Experimental results on Market-1501, DukeMTMC-reID and MSMT17 datasets demonstrate the effectiveness of our proposed UDA person re-ID framework.

The applicability of heterogeneous catalysis is often marred by a requirement for large energy inputs to achieve optimal reaction temperatures. Removing the need for thermal input by utilising photocatalysts offers an alternate pathway towards achieving sufficient energy input, but it is severely limited by the current low efficiencies of solar energy conversion. Recent findings have suggested that utilising solar energy to supplement heterogeneous reaction systems can enhance performance, although integrating light within a thermal-catalytic system is not necessarily straightforward nor beneficial. Herein, we offer a perspective on the complexities of using light when promoting three systems of heterogeneous catalysis; (i) enhancing catalyst activity via a plasmonic effect, (ii) promoting reaction systems based on semiconducting catalyst materials, and (iii) activating intermediary species. Engaging light to boost the activity and/or selectivity of a heterogeneous catalytic reaction is not necessarily straightforward whereby a raft of complexities can be introduced. The complexities have the potential to negate any positive effects imposed by the light and, in some cases, can be to the detriment of catalyst performance. [ABSTRACT FROM AUTHOR]

In this work, soft polydimethylsiloxane (PDMS) screen protectors with microlens arrays (MLAs) are fabricated through a feasible high‐throughput approach. Based on the lateral size scaling effect during discontinuous dewetting, desired SU‐8 convex MLAs with simultaneously controlled focal length (f) and numerical aperture (NA) are produced on a single substrate. A replication technique is employed to prepare PDMS MLAs with the same structure as that of the SU‐8 MLAs. The contact angle and other optical parameters of the MLAs can be tuned over a wide range based on the number of sliding times and lateral size. When the diameter of the MLAs decreases from 100 to 10 µm, the curvature changes from 0.07 to 0.17 for the single‐layer MLAs and from 0.15 to 0.31 for the three‐layer MLAs. The enhancement effect of MLAs on the light from wide‐angle organic light‐emitting diode (OLED) packaging modules is investigated. It is found that PDMS films containing MLAs can increase the brightness of an OLED by 14.13%. The fabricated PDMS concave MLAs can serve as flexible screen protectors to shield OLEDs from damage while enhancing the brightness to improve the energy efficiency. [ABSTRACT FROM AUTHOR]

Erect Au nanocones with high adhesion to substrates are obtained by simply drawing from Au nano-films through Au-Si eutectic welding. Nanocones with diameters ranging from about 5 to 150 nm and length ranging from about 60 to 600 nm can be observed on both Au and Si substrate surfaces. Nano-scale Au-Si eutectics formed at the rough Au–silicon film interface under annealing at 450 °C and the subsequent cooling process facilitate the formation of nano-bonding points and draw Au nanocones from Au nano-film by mechanical separation. Erect Au nanocones adhered to Au or Si substrates shows higher light enhancement than itself, observed by FDTD simulation. This method provides new strategy for the fabrication of SERS detectors, solar cells et al. with high stability.

Semiconductor nanowires are the building blocks of future nanoelectronic devices. The study of the interaction between nanowires and visible light reveals resonances that promise light absorption/scattering engineering for photonic applications. We carried out experimental measurements through the micro-Raman spectroscopy of different group IV nanowires, both homogeneous Si nanowires and axially heterostructured SiGe/Si nanowires. These experimental measurements show an enhancement of the Raman signal in the vicinity of the heterojunction of SiGe/Si nanowires. The results are analysed in terms of the electromagnetic modelling of the light/nanowire interaction using finite element methods. The presence of axial heterostructures is shown to produce electromagnetic resonances, and the results are understood as a consequence of a finite change in the relative permittivity of the material at the SiGe/Si heterojunction. This effect opens a path to controlling interactions between light and matter at the nanoscale with direct applications in photonic nanodevices. [ABSTRACT FROM AUTHOR]

We present systematic predictions for light enhancement in optical nanowires with nanoscale air holes in the core through numerical modeling. We show that the light intensity within such holes is strongly dependent on the hole size and refractive index of the host material and that light enhancement becomes significant only when the hole size is less than a critical value: 70 nm for silica and F2 nanowires and 50 nm for a As2S3 nanowire. High index As2S3 nanowires exhibit nearly eight times higher average mode intensity than silica glass for hole sizes of less than 10 nm. Such intensity enhancements open up new device opportunities; for example, filling nanoscale holes within silicon nanowires with silicon nanocrystals enables 30% enhancement of the nonlinear coefficient.

The performances of GaN-based vertical light emitting diodes with surface texture of GaN cones were studied. The cones were fabricated by inductively coupled plasma reactive ion etching with Cr mask, which can enhance the light intensity by about 95 % at injection current of 350 mA. Angle and wavelength-resolved far-field spectra were measured, and the maximum light enhancement lies at about ±15°-50° respect to normal direction. This is because of the successive reflection of light by the sidewall of cones, which can be concluded from the far-field pattern that the Fabry-Perot like resonance of patterned LED disappears compared to the original device. The polarization property of patterned LED was also analyzed, which can explain the increasing of enhancement ratio with injection current. [ABSTRACT FROM AUTHOR]

We have numerically demonstrated the significant impacts on the resonance mode characteristics of subwavelength grating structures due to tapered sidewall profile and high aspect ratio, which is normally obtained due to the practical CMOS-compatible fabrication and etching processes. Our simulation results have revealed that the tapered sidewall profile with high aspect ratio plays important roles on the resonance mode behavior of subwavelength grating photonic devices. The coupling mechanism between the guided mode resonance and the grating cavity is also emphasized. Our numerical studies can be utilized for a series of integrated photonic devices applications, such as compact optical filter, photonic amplifier, and lasers, while considering realistic subwavelength grating structures due to current nanoelectronics fabrication process. [ABSTRACT FROM PUBLISHER]

The basidiomycetous yeast, Xanthophyllomyces dendrorhous, is one of the very few organisms which can be used for biological production of the carotenoid astaxanthin. crtE cDNA has been cloned from this fungus for engineering of the terpenoid pathway. The function of its gene product as a geranylgeranyl pyrophosphate synthase was established. X. dendrorhous was transformed with the crtE cDNA to divert metabolite flow from the sterol pathway towards carotenoid biosynthesis. Transformants were obtained with increased levels of geranylgeranyl pyrophosphate synthase leading to higher carotenoid levels including astaxanthin. Physiological conditions for maximum carotenoid synthesis for wild type and the CrtE transformant were dim light and extra air supply of the shaking culture. These conditions and the transformation with crtE had additive effects and resulted in an 8-fold higher astaxanthin formation as compared to the initial wild type culture without illumination and extra air supply yielding 451 μg/g dry wt within 4 days of growth. [ABSTRACT FROM AUTHOR]

We present systematic predictions for light enhancement in optical nanowires with nanoscale air holes in the core through numerical modeling. We show that the light intensity within such holes is strongly dependent on the hole size and refractive index of the host material and that light enhancement becomes significant only when the hole size is less than a critical value: 70 nm for silica and F2 nanowires and 50 nm for a \As2\S3 nanowire. High index \As2\S3 nanowires exhibit nearly eight times higher average mode intensity than silica glass for hole sizes of less than 10 nm. Such intensity enhancements open up new device opportunities; for example, filling nanoscale holes within silicon nanowires with silicon nanocrystals enables 30% enhancement of the nonlinear coefficient. [ABSTRACT FROM PUBLISHER]

In this review, an overview of the subwavelength confinement of light with plasmonics is presented. Among the varieties of state-of-the-art technologies on this intensively-studied topic, we focus on the surface plasmon-assisted light enhancement via the single metallic aperture. Based on a systematic overview of the physical principles of light enhancement in subwavelength-sized metallic apertures, we investigate various types of apertures and discuss their characteristics. [ABSTRACT FROM AUTHOR]

We consider a zero-order diffraction metallic grating having two subwavelength rectangular slits per period. The electromagnetic behavior of this system is studied theoretically in the resonance spectral domain of the cavities. We show that, by choosing judicious opto-geometrical parameters, we can perform the selective excitation of one or the other category of cavities with a very appreciable quality factor, illustrating then a switch effect. The results open the way to the quantitative light addressing on passive metallic micro/nano-structures. In particular, for transmitting gratings, we can force light to cross each subwavelength channel doublet through a determined aperture, reconsidering in some extent the Young's slits experiment. [ABSTRACT FROM PUBLISHER]

Abstract: The stereodifferentiation of the baker''s yeast reduction of β-ketoesters is improved by exposing this reaction to 300–400nm UV light and via a new method entitled ‘two-substrate application’. Both routes are accomplished by selectively interfering with those oxidoreductases that compete for the same substrate. While the irradiation enhances the enantioselectivity of the baker''s yeast upon reducing the substrate 3-oxo-n-valeric ethylester inhibits it the conversion of ethyl acetoacetate, whereas other homologues are not influenced. Corresponding in vitro reductions with the baker''s yeast enzymes alcohol dehydrogenase I (ADH I), l-lactate dehydrogenase (l-LDH), and β-ketoacylreductase are light-resistant, whereby the l-LDH reacts in the presence of β-nicotinamide adenine dinucleotide (NADH). The catalytic activity of pre-irradiated ADH I is reduced because the light changes the conformation of the isolated enzyme according to CD spectroscopy. The natural enzyme cofactor NADH protects the ADH I in the in vitro reduction experiment from the near UV light by absorbing it for conducting its own photochemistry. In the baker''s yeast reduction of ethyl acetoacetate, apparently four oxidoreductases compete for this substrate. [Copyright &y& Elsevier]

We have proposed novel photoresponsive green- and blue-emitting organic electroluminescent (EL) devices combining organic EL diodes with titanyl phthalocyanine as a photoconductive layer. By irradiating red and near-infrared (IR) lights to these devices, green and blue emissions were generated, respectively, well below the turn-on voltage. The results indicate that the devices act as an optical switch and up-converter. The EL response time using a laser pulse was about 300 μs. Above the turn-on voltage, enhancement of the EL intensities was observed with the light irradiation with the ratio of up to 104. [Copyright &y& Elsevier]

A pulse generator is described, which enhances the analyzing light emitted from a xenon lamp as used in kinetic photospectrometry experiments. The lamp current is increased to 600 A for a duration of 3 ms; the current is constant within ±0.2% during a time interval of 2 ms. Because of instabilities of the lamp arc during pulsing, the use of the enhanced light source is limited to measuring times up to 500 μs. The enhancement in light intensity depends on the wavelength and amounts to more than 400-fold in the UV-region. [Copyright &y& Elsevier]

Erect Au nanocones with high adhesion to substrates are obtained by simply drawing from Au nano-films through Au-Si eutectic welding. Nanocones with diameters ranging from about 5 to 150 nm and length ranging from about 60 to 600 nm can be observed on both Au and Si substrate surfaces. Nano-scale Au-Si eutectics formed at the rough Au–silicon film interface under annealing at 450 °C and the subsequent cooling process facilitate the formation of nano-bonding points and draw Au nanocones from Au nano-film by mechanical separation. Erect Au nanocones adhered to Au or Si substrates shows higher light enhancement than itself, observed by FDTD simulation. This method provides new strategy for the fabrication of SERS detectors, solar cells et al. with high stability. [ABSTRACT FROM AUTHOR]

Non-enzymatic electrochemical platforms sensitive towards glucose presence have attracted a worldwide attention during last decades. We report on influence of solar light onto response of gold-titanium heterostructures prepared via controllable approach. The material based on Au nanoparticles orderly distributed over the structured titanium foil was obtained by electrochemical anodization followed by chemical etching, magnetron sputtering of gold and finally thermal treatment in the continuous regime. It is proven that the applied synthesis route leads to the enhanced visible light absorption boosting material photoactivity. Fabricated electrode immersed in the glucose containing solution and exposed to the solar light exhibits superior increase of oxidation current comparing to pristine substrate before thermal annealing. Photosensor is characterized by broad linear response up to 40 mM of glucose, limit of detection of 0.2 and 0.1 mM and sensitivity of 3.08 and 0.92 μA/cm2 in NaOH and PBS, respectively. It is concluded that the electrode exhibits enhanced performance taking advantage from plasmon resonance effect and the presence of thin titania passive film. Moreover, obtained material is stable under prolonged illumination and was verified in the presence of blood serum sample. Overall, presented results suggest that the impact of solar light should be taken into account during works on sensing devices. [ABSTRACT FROM AUTHOR]