Short Light Research Articles

Photoadsorption of Cr(VI) on titanium dioxide modified by high-energy milling

Microcrystalline powders of rutile and anatase were milled in a high-energy planetary mill down to obtain nanosized TiO2 powders (the size of coherent scattering region (CSR) about 30 nm and 60 nm, respectively). The resulting powders were characterized by HRTEM, Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the ξ-potential of the aqueous suspensions was determined. High-energy milling made it possible to significantly increase the ability of TiO2 to remove chromium from aqueous solutions. The effectiveness of the powders for not only Cr(VI) removing but also total chromium adsorption under UV-irradiation and short wavelength visible light has been shown. This is important, since Cr(III) does not remain in the aqueous medium and cannot be oxidized back to Cr(VI) under the influence of some environmental factors. It is possible to remove more than 99.9% of total chromium and 100 % of chromium hexavalent from a 50 mg·L-1 solution of Cr(VI) using milled anatase. XPS showed that, upon the photoadsorption, Cr(VI) is reduced to Cr(III). The presence of an acetate buffer in the solution promotes the most efficient removal of chromium. This work shows a simple way to obtain a highly effective material with potential applications for the removal of high toxic hexavalent chromium from industrial wastewater. The milled anatase sample was successfully tested to remove Cr (VI) from a real wastewater sample.

Short-wavelength artificial light affects visual neural pathway development in mice

Nearly all modern life depends on artificial light; however, it does cause health problems. With certain restrictions of artificial light emitting technology, the influence of the light spectrum is inevitable. The most remarkable problem is its overload in the short wavelength component. Short wavelength artificial light has a wide range of influences from ocular development to mental problems. The visual neuronal pathway, as the primary light-sensing structure, may contain the fundamental mechanism of all light-induced abnormalities. However, how the artificial light spectrum shapes the visual neuronal pathway during development in mammals is poorly understood. We placed C57BL/6 mice in three different spectrum environments (full-spectrum white light: 400–750 nm; violet light: 400 ± 20 nm; green light: 510 ± 20 nm) beginning at eye opening, with a fixed light time of 7:00–19:00. During development, we assessed the ocular axial dimension, visual function and retinal neurons. After two weeks under short wavelength conditions, the ocular axial length (AL), anterior chamber depth (ACD) and length of lens thickness, real vitreous chamber depth and retinal thickness (LLVR) were shorter, visual acuity (VA) decreased, and retinal electrical activity was impaired. The density of S-cones in the dorsal and ventral retinas both decreased after one week under short wavelength conditions. In the ventral retina, it increased after three weeks. Retinal ganglion cell (RGC) density and axon thickness were not influenced; however, the axonal terminals in the lateral geniculate nucleus (LGN) were less clustered and sparse. Amacrine cells (ACs) were significantly more activated. Green light has few effects. The KEGG and GO enrichment analyses showed that many genes related to neural circuitry, synaptic formation and neurotransmitter function were differentially expressed in the short wavelength light group. In conclusion, exposure to short wavelength artificial light in the early stage of vision-dependent development in mice delayed the development of the visual pathway. The axon terminus structure and neurotransmitter function may be the major suffering.

Quantifying Charge Extraction and Recombination Using the Rise and Decay of the Transient Photovoltage of Perovskite Solar Cells.

The extraction of photogenerated charge carriers and the generation of a photovoltage belong to the fundamental functionalities of any solar cell. These processes happen not instantaneously but rather come with finite time constants, e.g., a time constant related to the rise of the externally measured open circuit voltage following a short light pulse. Herein, a new method to analyze transient photovoltage measurements at different bias light intensities combining rise and decay times of the photovoltage. The approach uses a linearized version of a system of two coupled differential equations that are solved analytically by determining the eigenvalues of a 2×2 matrix. By comparison between the eigenvalues and the measured rise and decay times during a transient photovoltage measurement, the rates of carrier recombination and extraction as a function of bias voltage are determined, and establish a simple link between their ratio and the efficiency losses in the perovskite solar cell.

Dichromacy in the brown marmorated stink bug? Spectral sensitivity of the compound eyes and phototaxis of Halyomorpha halys

AbstractThe brown marmorated stink bug (Halyomorpha halys) is an invasive pest insect species, which was recently introduced from Asia to America and then to Europe. Besides causing serious damage in agriculture, this species also represents a source of intense annoyance for humans in residential areas, because large amounts of individuals can aggregate on buildings while seeking shelter before overwintering. Taking into account the need for pesticide-free pest management methods, for example light trapping, we measured the spectral sensitivity of the compound eyes of H. halys with electroretinography (ERG). In behavioural experiments, we also quantified the attraction of H. halys to 14 quasi-monochromatic light stimuli in the 368–743 nm spectral range. The dark-adapted compound eyes were mostly sensitive to the green range, but a minor sensitivity peak in the UV region was also identified. Recordings on chromatic-adapted eye preparations unequivocally revealed the presence of only a green- and a UV-sensitive photoreceptor type, with sensitivity maxima at 519 nm and 367 nm, respectively. No sign of any blue-sensitive receptor was detected, and thus only a receptor set allowing dichromatic vision was found. Based on the results of the behavioural experiments, we established that the attraction of H. halys to light is increasing with decreasing wavelength, and thus we emphasize the importance of short wavelength lights (368–455 nm) when phototactic attraction of H. halys is the aim.

Behavioural responses of cockroaches <i>Periplaneta americana</i> L. to short and long wavelength light in a wind tunnel

The behavioural responses of the American cockroach Periplaneta americana to short-wavelength and long-wavelength light were studied in a wind tunnel. Initial directional movement towards the light source was observed in response to both stimuli, but the latency in response to green light was significantly shorter. The cockroaches moving towards the UV light often returned to the less illuminated starting point, while this behaviour was not typical under green light. UV light often initiated masking, the behavior characteristic of the inactive, diurnal phase of the 24-hour cycle.

Nuclear Receptor Subfamily 2 Group E Member 3 (NR2E3): Role in Retinal Development and Disease.

NR2E3 is a nuclear hormone receptor gene required for the correct development of the retinal rod photoreceptors. Expression of NR2E3 protein in rod cell precursors suppresses cone-specific gene expression and, in concert with other transcription factors including NRL, activates the expression of rod-specific genes. Pathogenic variants involving NR2E3 cause a spectrum of retinopathies, including enhanced S-cone syndrome, Goldmann-Favre syndrome, retinitis pigmentosa, and clumped pigmentary retinal degeneration, with limited evidence of genotype-phenotype correlations. A common feature of NR2E3-related disease is an abnormally high number of cone photoreceptors that are sensitive to short wavelength light, the S-cones. This characteristic has been supported by mouse studies, which have also revealed that loss of Nr2e3 function causes photoreceptors to develop as cells that are intermediate between rods and cones. While there is currently no available cure for NR2E3-related retinopathies, there are a number of emerging therapeutic strategies under investigation, including the use of viral gene therapy and gene editing, that have shown promise for the future treatment of patients with NR2E3 variants and other inherited retinal diseases. This review provides a detailed overview of the current understanding of the role of NR2E3 in normal development and disease, and the associated clinical phenotypes, animal models, and therapeutic studies.

Emission and optical characteristics of brown carbon in size-segregated particles from three types of Chinese ships

Brown carbon (BrC) is one of the important light absorption substances that have high light absorption ability under short wavelength light. However, limit studies have focused on the BrC emission from ships. In this study, size-segregated particulate matters (PM) were collected from three different types of ships, light absorption characteristics and size distribution of methanol-soluble BrC and water-soluble BrC in PM from ship exhausts were investigated. Results showed that four-stroke low-power diesel fishing boat (4-LDF) had the highest mass concentrations of methanol-soluble organic carbon (MSOC) and water-soluble organic carbon (WSOC), followed by 2-stroke high-power heavy-fuel-oil vessel (2-HHV), and four-stroke high-power marine-diesel vessel (4-HMV). While 2-HHV had obviously higher light absorption coefficients of methanol-soluble BrC (Abs365,M) and water-soluble BrC (Abs365,W) in unit weight of PM than the other two types of ships. The tested ships presented comparable or higher absorption efficiency of BrC in water extracts (MAE365,W) compared with other BrC emission sources. Majority of BrC was concentrated in fine particles, and the particle size distributions of both Abs365,M and Abs365,W showed bimodal patterns, peaking at 0.43–0.65 µm and 4.7–5.8 µm, respectively. However, different particle size distributions were found for MAE365,M between diesel and heavy fuel oil ships. Besides, different wavelength dependence in particles with different size were also detected. Ship exhaust could be confirmed as a non-ignorable BrC emission source, and complex influencing factor could affect the light absorption characteristics of ship emissions. Particle size should also be considered when light absorption ability of BrC was evaluated.

Flexible and conductive core-sheath fiber using multifunctional merocyanine as a smart electrolyte for a high-performance fibrous visible light sensor

Flexible conductive fibers have attracted significant attention in the wearable electronics field because of light weight, small size, and easy shape morphing. To date, there are few reports on multifunctional flexible conductive fibers. Finding a facile and effective solution for large-scale production of flexible conductive fibers is still a challenge. In this work, a flexible core-sheath fiber with excellent electrical conductivity (24.71 Ω·m) and visible light sensing is fabricated, which contains a merocyanine diol (MC(OH)2)/CrCl3·6H2O/ethanol aqueous solution core layer and a silicon rubber outer layer. The synthesized MC(OH)2 is an intelligent molecular switch with a visible light response that can reversibly convert from open-form MC(OH)2 to closed-form spiropyran diol (SP(OH)2) after short visible light irradiation. In the reverse process, the transition from SP(OH)2 to MC(OH)2 can occur gradually in the dark. This can be used to sense visible light in addition to electrical conductivity. The reversible change in the electrical resistance of the MC(OH)2/CrCl3·6H2O/ethanol aqueous solution reaches 15.59%. This fiber shows excellent electrical conductivity, good flexibility, a sensitive visible light response, good photochromism, a simple structure, low cost, easy preparation, and suitability for industrial large-scale production, offering promise for applications in the fields of flexible and wearable electronics.

A Compact Polarization MMI Combiner Using Silicon Slot-Waveguide Structures.

The study of designing a compact transverse electric (TE)/transverse magnetic (TM) polarization multimode interference (MMI) combiner based on silicon slot-waveguide technology is proposed for solving the high demands for high-speed ability alongside more energy power and minimizing the environmental impact of power consumption, achieving a balance between high-speed performance and energy efficiency has become an important consideration in an optical communication system. The MMI coupler has a significant difference in light coupling (beat-length) for TM and TE at 1550 nm wavelength. By controlling the light propagation mechanism inside the MMI coupler, a lower order of mode can be obtained which can lead to a shorter device. The polarization combiner was solved using the full-vectorial beam propagation method (FV-BPM), and the main geometrical parameters were analyzed using Matlab codes. Results show that after a short light propagation of 16.15 μm, the device can function as TM or TE combiner polarization with an excellent extinction ratio of 10.94 dB for TE mode and 13.08 dB for TM mode with low insertion losses of 0.76 dB (TE) and 0.56 dB (TM) and the combiner function well over the C-band spectrum. The polarization combiner also has a robust MMI coupler length tolerance of 400 nm. These attributes make it a good candidate for using this proposed device in photonic integrated circuits for improving power ability at the transmitter system.

The dependence of light extraction improvement on optimized surface microstructure for AlGaN-based UVC-LEDs considering TM-polarized emission

In order to improve the light extraction of AlGaN-based short wavelength ultraviolet light emitting diodes (DUC-LEDs), a type of microstructure with high aspect ratio is introduced and optimized on the AlN substrate surface. And, particle swarm optimization (PSO) algorithm is used to inverse design of the surface microstructure to maximize the light extraction efficiency (LEE). Considering that the propagation characteristics of TM-polarized light are different from that of TE-polarized light, the optical field distribution and LEE is analyzed for the UVC-LEDs with different TE-polarized component when the optimized surface microstructure is applied. Furthermore, the preparation process tolerance of the high aspect ratio structure is discussed by calculating the LED's LEE when the structural deviation occurs or morphology changes. Simulation results show that, by using the optimized surface microstructure based on parabola cone array, the LEDs' LEE is increased from 4.4% to 8.7% and from 0.4% to 3.7% for TE-polarized and TM-polarized emission, respectively. In addition, it is demonstrated that the light extraction improvement by the surface microstructure has a good tolerance to the structural deviation and morphology. The results are significant for improving light extraction and realizing high efficient short wavelength AlGaN-based UVC-LEDs by designing surface microstructures.

Drosophila photoreceptor systems converge in arousal neurons and confer light responsive robustness.

Lateral ventral neurons (LNvs) in the fly circadian neural circuit mediate behaviors other than clock resetting, including light-activated acute arousal. Converging sensory inputs often confer functional redundancy. The LNvs have three distinct light input pathways: (1) cell autonomously expressed cryptochrome (CRY), (2) rhodopsin 7 (Rh7), and (3) synaptic inputs from the eyes and other external photoreceptors that express opsins and CRY. We explored the relative photoelectrical and behavioral input contributions of these three photoreceptor systems to determine their functional impact in flies. Patch-clamp electrophysiology measuring light evoked firing frequency (FF) was performed on large LNvs (l-LNvs) in response to UV (365 nm), violet (405 nm), blue (450 nm), or red (635 nm) LED light stimulation, testing controls versus mutants that lack photoreceptor inputs gl60j, cry-null, rh7-null, and double mutant gl60j-cry-null flies. For UV, violet, and blue short wavelength light inputs, all photoreceptor mutants show significantly attenuated action potential FF responses measured in the l-LNv. In contrast, red light FF responses are only significantly attenuated in double mutant gl60j-cry-null flies. We used a light-pulse arousal assay to compare behavioral responses to UV, violet, blue and red light of control and light input mutants, measuring the awakening arousal response of flies during subjective nighttime at two different intensities to capture potential threshold differences (10 and 400 μW/cm2). The light arousal behavioral results are similar to the electrophysiological results, showing significant attenuation of behavioral light responses for mutants compared to control. These results show that the different LNv convergent photoreceptor systems are integrated and together confer functional redundancy for light evoked behavioral arousal.

Sequential absorption of two photons creates a bistable form of RubyACR responsible for its strong desensitization

Channelrhodopsins with red-shifted absorption, rare in nature, are highly desired for optogenetics because light of longer wavelengths more deeply penetrates biological tissue. RubyACRs (Anion ChannelRhodopsins), a group of four closely related anion-conducting channelrhodopsins from thraustochytrid protists, are the most red-shifted channelrhodopsins known with absorption maxima up to 610nm. Their photocurrents are large, as is typical of blue- and green-absorbing ACRs, but they rapidly decrease during continuous illumination (desensitization) and extremely slowly recover in the dark. Here, we show that long-lasting desensitization of RubyACRs results from photochemistry not observed in any previously studied channelrhodopsins. Absorption of a second photon by a photocycle intermediate with maximal absorption at 640nm (P640) renders RubyACR bistable (i.e., very slowly interconvertible between two spectrally distinct forms). The photocycle of this bistable form involves long-lived nonconducting states (Llong and Mlong), formation of which is the reason for long-lasting desensitization of RubyACR photocurrents. Both Llong and Mlong are photoactive and convert to the initial unphotolyzed state upon blue or ultraviolet (UV) illumination, respectively. We show that desensitization of RubyACRs can be reduced or even eliminated by using ns laser flashes, trains of short light pulses instead of continuous illumination to avoid formation of Llong and Mlong, or by application of pulses of blue light between pulses of red light to photoconvert Llong to the initial unphotolyzed state.

A Compact UV-LED-Induced Fluorescence With Short Metal Capillary and Low Light Leakage: Application to Noninvasive Glucose Detection

Laser-induced fluorescence (LIF) is one of the most sensitive techniques for detection. As for the LIF with UV excitation, replacing UV laser with UV LED (i.e., UV LED-IF) has advantages of long life time and low cost. However, for LED-IF, the background signal (noise) would be much higher, due to the poor beam quality of LED. Here, an axial-excitation UV LED-IF with short metal capillary (MC) and black sealing (i.e., MC-LED-IF) was proposed for noninvasive detection of human saliva glucose (HSG). The SNR was improved 3.1-fold by employing the black sealing, due to the effective suppression of the background signal, which mainly results from light leakage. Moreover, the transmission loss of UV LED light in MC and saliva-filled MC was investigated, and an optimal MC length of only 4 cm was obtained. By using the MC-LED-IF, a detection limit of concentration (DLC) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4 \mu \text{M}$ </tex-math></inline-formula> was realized for detecting HSG via conventional 3-(4-hydroxyphenyl)-propionic acid (HPPA) reagent with good selectivity and reliability. The MC-LED-IF features low cost and compact ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11\times 4\times $ </tex-math></inline-formula> 4 cm), which is suitable for personal use.

Tetra-Dentate Cycloaddition Catalysts for Rapid Photopolymerization Reactions

[4 + 4] and [2 + 2] cycloadditions are unique reactions since they form and deform cycloadducts under irradiation due to their inherent reversible nature. Whereas promising for the field of recycling, these reactions usually suffer from two major shortcomings: long reaction durations (hours) and the requirement of high-intensity light (∼100 W/cm2), typically at a short wavelength (<330 nm). We demonstrate several tetra-dentate catalysts that can overcome these fundamental limitations. Among them is a tin complex that enables 76% conversion within only 2 min of irradiation at 395 nm, much faster than the known ruthenium-based catalyst, under irradiation with light intensity two orders of magnitude lower than that reported in the literature. Due to the short photopolymerization time, low intensity (27 mW/cm2), and long UV light (395 nm), this unique complex opens new avenues for recycling three-dimensional printing products based on photopolymerization of cycloaddition reactions.

Effectiveness Use of Tiktok Social Media @DitjenPajakRI Deployment Information Taxation

Public Relations Directorate General Tax (DGT) has role alone as extension worker tax. For increase awareness about information taxation to society. DJP Public Relations Using TikTok for educate public about taxation, mandatory tax Even though the TikTok @DitjenPajakRI had popular, however No Can last long because complicated TikTok algorithm. So, using TikTok requires a communication strategy special. Objective from study This is For describe the Directorate General of Public Relations communication strategy tax using the social media TikTok. Study This use method qualitative descriptive and interview as well as technique Documentation data collection. Research results This show that DGT Public Relations implemented the strategy communicate with appropriate with download and use content form short Language light and atypical.

PhiReX 2.0: A Programmable and Red Light-Regulated CRISPR-dCas9 System for the Activation of Endogenous Genes in Saccharomyces cerevisiae.

Metabolic engineering approaches do not exclusively require fine-tuning of heterologous genes but oftentimes also modulation or even induction of host gene expression, e.g., in order to rewire metabolic fluxes. Here, we introduce the programmable red light switch PhiReX 2.0, which can rewire metabolic fluxes by targeting endogenous promoter sequences through single-guide RNAs (sgRNAs) and activate gene expression in Saccharomyces cerevisiae upon red light stimulation. The split transcription factor is built from the plant-derived optical dimer PhyB and PIF3, which is fused to a DNA-binding domain based on the catalytically dead Cas9 protein (dCas9) and a transactivation domain. This design combines at least two major advantages: first, the sgRNAs, guiding dCas9 to the promoter of interest, can be exchanged in an efficient and straightforward Golden Gate-based cloning approach, which allows for rational or randomized combination of up to four sgRNAs in a single expression array. Second, target gene expression can be rapidly upregulated by short red light pulses in a light dose-dependent manner and returned to the native expression level by applying far-red light without interfering with the cell culture. Using the native yeast gene CYC1 as an example, we demonstrated that PhiReX 2.0 can upregulate CYC1 gene expression by up to 6-fold in a light intensity-dependent and reversible manner using a single sgRNA.

Near-Infrared Light-Activated Ruthenium Complex-based Photocage for Cancer Phototherapy.

Conventional photocages only respond to short wavelength light, which is a significant obstacle to developing efficient phototherapy in vivo. The development of photocages activated by near-infrared (NIR) light at wavelengths from 700 to 950 nm is important for in vivo studies but remains challenging. Herein, we describe the synthesis of a photocage based on a ruthenium (Ru) complex with NIR light-triggered photocleavage reaction. The commercial anticancer drug, tetrahydrocurcumin (THC), was coordinated to the Ru(II) center to create the Ru-based photocage that is readily responsive to NIR light at 760 nm. The photocage inherited the anticancer properties of THC. As a proof-of-concept, we further engineered a self-assembled photocage-based nanoparticle system with amphiphilic block copolymers. Upon exposure to NIR light at 760 nm, the Ru complex-based photocages were released from the polymeric nanoparticles and efficiently inhibited tumor proliferation in vivo.

A Near‐Infrared Light‐Activated Photocage Based on a Ruthenium Complex for Cancer Phototherapy

AbstractConventional photocages only respond to short wavelength light, which is a significant obstacle to developing efficient phototherapy in vivo. The development of photocages activated by near‐infrared (NIR) light at wavelengths from 700 to 950 nm is important for in vivo studies but remains challenging. Herein, we describe the synthesis of a photocage based on a ruthenium (Ru) complex with NIR light‐triggered photocleavage reaction. The commercial anticancer drug, tetrahydrocurcumin (THC), was coordinated to the RuII center to create the Ru‐based photocage that is readily responsive to NIR light at 760 nm. The photocage inherited the anticancer properties of THC. As a proof‐of‐concept, we further engineered a self‐assembled photocage‐based nanoparticle system with amphiphilic block copolymers. Upon exposure to NIR light at 760 nm, the Ru complex‐based photocages were released from the polymeric nanoparticles and efficiently inhibited tumor proliferation in vivo.

Visible to Mid-Infrared Photodetector Based on Black Phosphorous-MoS2 Van Der Waals Heterojunction

Van der Waals heterostructures of black phosphorous(BP) and Molybdenum Disulfide(MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is designed and evaluated for photodetection application from visible to mid-infrared wavelength up to 4.5 μm. The device possesses a low dark current less than 0.1 μA for short wavelength light. For visible and near infrared radiation, the contribution of heat and photo energy to current enhancement is analyzed. Dark current drift by joule heat and laser heat absorbed is observed in short waveband. The difference in response speed is believed to be a result of the competition of BP and MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> photocurrent. Gate tunable response time and on-off ratio makes the device versatile in potential application. For mid infrared radiation, BP-MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> heterojunction with a dedicated thickness tailoring of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> exhibits similar negative response as an intrinsic BP. The normalized detectivity is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D}^*$</tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2.02 \times {10}^8\ Jones$</tex-math></inline-formula> for the 4.5 μm mid-infrared radiation. Elaborate reduction of the noise is conducted to get the time resolvable photo-response. A low bias is necessary for a time resolved photocurrent, reducing the flicker noise to an acceptable level.

Light-induced dynamic microcavities created in a resonant medium by collision of non-harmonic rectangular 1-fs light pulses

Recently, interest in extremely short unipolar electromagnetic pulses with non-harmonic shape (e.g. rectangular or triangular) is rising. Such pulses do not contain a carrier frequency and have an ultra-wide spectrum. Compared to conventional harmonic multicycle pulses, they are faster and more efficient in controlling the properties of quantum systems, which allows, in the future, for faster data transmission and processing. With coherent interaction of extremely short light pulses with a medium, formation and ultrafast control of population difference gratings and polarization structures are possible when the pulses both overlap and do not overlap in the medium. In this work, based on the numerical solution of Maxwell–Bloch equations, we demonstrate possible creation of a dynamic “microcavity” as a burst of population difference, arising from the collision of rectangular unipolar 1-femtosecond pulses of self-induced transparency in a two-level resonant medium. Potential to control the microcavities parameters (changing the depth, turning it on, erasing it, etc.) is demonstrated.