Search

CaCO3 carriers are efficiently loaded with Griseofulvin antifungal drug (25% w/w). Stabilizing coating formation prolongs the carrier degradation and payload release. The proposed system enables delivery to hair follicles and bioavailability enhancement for Gf.

One of very demanded and actively developed areas of modern biomedicine is tissue engineering, investigating synthesis and reparation of various kinds of tissues, including trauma treatment. Normally cells in tissue grow in the microenvironment provided by exttacellular matrix – a three-dimensional network of macromolecules, mostly peptides and proteins, that provide structural and biochemical support. To substitute this matrix in medical applications and promote new cells growth and repair damaged tissue, various types of artificial scaffolds are proposed. Morphology, as well as physical and chemical properties of scaffolds influence the fate of cells, including attachment, proliferation and differentiation, and strongly correlate with the type of target tissue. This review is aimed to provide a short insight in materials and technologies for synthesis of tissue engineering scaffolds, with focus on polymeric electrospun nonwoven materials and ones with conductive structures that can be potentially used to direct electrical signals to cells for the aims of electrostimulation, which was demonstrated to induce functional repairmen of certain cell types such as myocytes and neurons.

A miniature planar meander-type slow-wave structure (SWS) for a W-band traveling-wave tube is studied. Computer simulation of the SWS electrodynamic parameters is performed. A new technology for fabrication of planar microstrip SWSs with the aid of laser ablation is proposed. The S-parameters of the SWS are experimentally studied. The experimental data are in good agreement with the results of the 3D computer simulation. Output characteristics of the traveling-wave tube with a sheet electron beam and planar SWS are calculated.

Superficial fungal infections are of serious concern worldwide due to their morbidity and increasing distribution across the globe in this era of growing antimicrobial resistance. The delivery of antifungals to the target regions of the skin and sustaining the effective drug concentration are essential for successful treatment of such mycoses. Topical formulations get extra benefits here if they penetrate into the hair follicles since fungal hyphae can proliferate and produce spores in such reservoirs. We designed a novel particulate system for the encapsulation and intrafollicular delivery of griseofulvin (Gf) antifungal drug, which is water-insoluble and currently commercially available in oral dosage forms. Micron-sized calcium carbonate (vaterite) carriers containing 25 ± 3% (w/w) of Gf were prepared

Application of higher harmonics generation mode in a compact low-voltage vircator-type vacuum electronic device utilizing nonlaminar electron beams operating in millimeter band is considered and preliminary experimental results are reported. Higher harmonics generation was achieved by formation of translaminar electron layer through the choice of the optimal voltages for the control electrode and electron beam inhibition by the electrostatic field of the collector. This approach allowed for dense electron grouping in nonlaminar electron beams that provided the growth of the amplitude of the higher harmonics in the output power spectrum. In this system, the increase of the fundamental operating frequency by application of external magnetic field was experimentally demonstrated. If combined with higher harmonics generation mode, this can lead to significant increase of resulting operating frequency of the compact low-voltage system to millimeter wavelength band.

The results of fabrication and cold-test study of the slow-wave interaction structure for the V-band backward-wave oscillator with a pseudospark-sourced sheet electron beam are presented. The proposed interaction structure is comprised of a truncated sine waveguide with wideband-matched output couplers. The slow-wave structure is designed, simulated, and fabricated by CNC-micro milling. The results of characterization of the microfabricated SWS sample by the scanning electron microscopy and stylus profilometry technique are presented. Preliminary results of experimental studies of electromagnetic parameters and their comparison with the numerical simulation are presented. The electron gun providing a high-current-density pseudospark sheet electron beam is also developed.

Results of experimental study of the reflection and transmission losses in the V-band of µm-thick Si-Al films on the dielectric substrates are considered. Two sources magnetron co-sputtering deposition of Si-Al alloys was utilized to prepare a series of coatings of varied chemical composition and thus different properties. Control over films composition was provided by variation of Al magnetron power source with constant Si magnetron power source. Segregation of Si and Al atoms in Al-Si films was observed at a specific power of Al magnetron source during the deposition: Si atoms were mainly concentrated at the lower levels of the film adjacent to the substrate, while Al atoms tended to concentrate near the upper surface of the coating. Distinct electromagnetic properties of Al-Si films fabricated at the transient phase of segregation mode were observed: one side of the film demonstrated low reflection in the millimeter-band while almost full reflection was observed from the other side. Such properties of µm-thick Si-Al films upon dielectric substrates can be useful for development of millimeter-wave antenna modules technology.

The goal of this work is an investigation of peculiarities of the molybdenum-copper alloys formation by magnetron sputtering to meet the requirements of low thermal expansion coefficient together with high electrical/thermal conductivity of the material for potential use in microfabrication of slow-wave structures for miniaturized millimeter-band vacuum electron devices. The study is focused on controlling the roughness and adhesion of the fabricated thin Cu-Mo alloy films. The roughness mainly determines the transmission losses at millimeter and THz frequencies, whereas the adhesion of the film is quite important for further processing, such as laser ablation.

Travelling-wave-tube (TWT) power amplifiers with planar microstrip slow wave structures (SWS) on dielectric substrates are very promising for operation at high frequencies due to their low-voltage operation, small size and relatively high output power. Recently, the interest to the planar SWSs has increased since their using can significantly decrease the complexity of microfabrication process. In our previous work, we reported successful fabrication of millimeter-band microstrip planar SWSs using the scalable and cost-effective laser ablation process with nanosecond pulse duration. However, the SWS samples fabricated by nanosecond laser ablation suffer from surface distortions and debris on the borders of the ablated zone. In order to improve the quality of resulting structures, here we propose deposition of a supplementary metallic (Al or Ti) layer on top of copper film prior to laser treatment. Such coating is aimed to prevent defects formation in the course of laser irradiation. In the proposed system, debris and distortions from Cu layer irradiation, naturally sediment on the sacrificial layer instead of sticking to the copper layer itself. Sacrificial aluminium coating can later be easily chemically removed together with sedimented debris leaving a clean underlying patterned Cu surface. In contrast, titanium layer prevents sticking of copper debris due to the higher melting temperature of Ti, thus preventing attachment of those to the surface in the first place.

We have designed D-bandplanar meander-line slow wave structure for low voltage compact traveling-wave tubes (TWTs) with sheet electron beam. The designed D-band slow wave structure was microfabricated by magnetron sputtering and picoseconds laser ablation. We further develop our approach for planar slow wave structure microfabrication based on magnetron sputtering and laser ablation processes. Transmission and reflection losses of proposed SWS were measured experimentally and evaluated numerically. The experimental results are in good agreement with the numerical ones.

Sources of millimeter and submillimeter (terahertz) band radiation are very important in modern society due to their broad application from telecommunication to non-destructive evaluation and chemical analysis. In this work, we present a review of technological approaches for fabrication of RF structures of µVEDs. Technological approaches to the microfabrication of planar slow-wave structures (SWS) on dielectric substrates operating with a sheet electron beam are considered. Such SWSs are attractive due to the simplicity of the structure, compact dimensions, low voltage operating, and wide bandwidth. We consider lithography-based technology, deep reactive ion etching, computer-numerical-control (CNC) micro- and nano-milling, electrical discharge micromachining, and technologies based on the additive manufacturing such as three-dimensional (3-D) printing, selective laser sintering, and selective laser melting. We also describe an original approach to microfabrication of planar structures based on magnetron sputtering and CNC laser ablation. Fabrication tolerance and surface roughness provided by the considered technologies are compared.

Nowadays vacuum electron devices still remain the main sources of high power coherent and broadband millimeterwave radiation. Among electron beam sources the pseudospark discharge can be distinguished as a promising pulsed plasma electron beam source. The reason is that the pseudospark discharge sourced electron beam has the ability to self-focus due to the unique discharge structure and the formation of the ion channel generated by the beam front. The ion channel enables the electron beam to propagate and eliminates the need for a guiding magnetic field. Therefore the development of compact and high-power vacuum electron devices utilizing a pseudospark discharge based hollow cathode electron gun is one of the promising trends. Here the results of the design, optimization and development of a pseudospark-based high-current-density sheet electron beam source are presented. A slow-wave structure for the backward-wave oscillator driven by a pseudospark-sourced sheet electron beam was also designed and numerically studied. Preliminary results of numerical simulations of electrodynamic characteristics of the suggested slow-wave structure are shown. We are going to use a CNC-micro milling based technological approach to microfabricate the designed slow-wave structure. The first steps of microfabrication results are also presented.

Development of millimeter and submillimeter-band (THz-band) vacuum electronic devices put forward special requirements to the properties of structural materials for microfabrication of such basic electronic components as slow-wave structures. One of the promising composite materials for vacuum microelectronic devices is molybdenum-copper alloys. This composite combines high thermal and electrical conductivity of copper and low thermal expansion of molybdenum. The influence of the composition of molybdenum-copper alloy on the electrodynamics parameters (S-parameters) of the slow-wave structure was revealed with the help of numerical simulation. Two sources magnetron co-sputtering can be utilized for Mo-Cu alloys deposition with the resulting composition of the alloy controlled by varying the power of the magnetron sources, working gas pressure and the substrate temperature.

Metamaterials recently attracted a wide interest in many areas of scientific research. Particularly, application of metamaterials is very promising in vacuum electronics devices of mm and sub-THz range. Dielectric substrate with metamaterials coating was used in several devices such as travelling wave tubes and backward wave oscillators. Use of metamaterials can be quite attractive if electrical properties of those can be controlled, for example, through the variation of basic materials properties. Here Si-A1 alloy is suggested as the base material for metamaterial formation. Two source magnetron co-sputtering deposition of Si-A1 alloys was utilized to obtain series of coatings with different chemical composition and thus different resistivity. Control of composition was provided by varying the power of Al magnetron source while power of Si source was constant. Three series of samples were deposited at different substrate temperatures. A sharp decrease in surface resistivity is observed while the Al content in the film changes smoothly. This result is explained by the segregation of Si and Al atoms due to Al diffusion during film deposition process.

For miniaturized vacuum-tube electron devices at millimeter and submillimeter (THz) bands, the possibility of low-voltage operation is of primary importance. Planar slow-wave structures (SWS) on dielectric substrates are favorable for the low-voltage operation. In this paper, we discuss design, fabrication and cold test of millimeter-wave planar SWSs. We consider the microstrip meander-line SWSs, which are designed for operation in traveling-wave tube power amplifiers with sheet electron beam.

Design and preliminary numerical simulations of D-band planar microstrip meander-line slow wave structure for lowvoltage tubes with sheet electron beam were carried out. An original approach based on magnetron sputtering and laser ablation methods was utilized for microstrip meander-line slow wave structure microfarication. An application of nanosecond and picosecond laser ablation for microfabrication of D-band (110-170 GHz) planar microstrip meander-line slow wave structure was considered. We have verified our original approach for planar slow wave structures microfabrication by using different CNC precision laser machines operating with different values of laser pulse duration (100 ns, 8 ns, 4 ns and 10 ps). Samples of slow wave structures were fabricated and characterized by scanning electron microscopy and profilometry methods. It was shown that each considered CNC precision laser machine allows fabricating D-band microstrip meander-line slow wave structure with required dimensions, but picosecond laser ablation has such advantages as the absence of ablation products (droplets, and etc.) on the slow wave structure surface. As the next step, we are going to study S-parameters of microfabricated D-band microstrip meander-line slow wave structure samples experimentally by using vector network analyzer with D-band frequency converters.

We consider the results of dielectric properties study in millimeter band of thin-films based on silicon nitride compositions. Silicon nitride thin-film coatings were deposited on a substrate by DC magnetron sputtering. As a substrate for silicon nitride thin-film coatings a quartz plate were utilized. The ratio of argon and nitrogen in the working gas mixture was chosen as the variable parameter to control the composition of the deposited thin-film coating. Several samples of silicon nitride thin-film coatings with about 1 um thickness were fabricated. Radiophysical and dielectric properties of the fabricated SiN-type thin-film coatings were studied in millimeter wave frequency band of 50-70 GHz (V-band) with help of free space measurement method. The obtained results have shown that by controlling the resistive thin-film coating composition one can only slightly vary the radiophysical and dielectric properties of coating in millimeter-band.

In this paper, we consider a short review of existing technologies of flexible antenna fabrication and propose our original approach for flexible antenna fabrication. Review of existing technologies of flexible antenna fabrication includes photolithography, screen printing, pad printing, gravure printing, inkjet printing, micro-dispensing, micro-jetting, and aerosol-jet technology. Advantages and disadvantages of each mentioned above technologies were noted. In the second part of this study, we consider our original technology for antenna fabrication on flexible substrates utilizing magnetron sputtering and laser ablation methods. Samples of flexible antennas are formed on a flexible dielectric substrate in a technology process comprising following basic stages: 1) deposition a conductive coating onto the dielectric substrate with help of magnetron sputtering, 2) formation the pattern of the antenna structure on the conductive coating by laser ablation. In the final stage, the substrate is divided into individual samples of specific sizes. A number of test flexible antennas fabricated by our original approach are shown.

Slow-wave structure (SWS) is a core part of a traveling-wave-tube (TWT) amplifier. In this letter, the planar microstrip meander SWS on a dielectric substrate at $V$ -band (50–70 GHz) is studied. The basic electromagnetic parameters of the SWS are calculated. The SWS circuits are designed and fabricated, and good transmission characteristics are measured. The SWS developed is characterized by a wide bandwidth and a relatively-large slow-wave factor, and is suitable for a low-voltage TWT with the sheet electron beam.

Ongoing active development of modern radio frequency electronic devices operating in the millimeter (V) band, such as fifth-generation wireless communications, demands new materials to control electromagnetic interference, compatibility, and reliability of such systems. This work investigates feasibility absorptive non-reflective thin coatings deposition on dielectric substrates using simultaneous magnetron co-deposition. For this, electromagnetic waves propagation in the millimeter band through in micrometer-thick Al–Si films of varied composition was studied. The co-deposition process was controlled by the ratio of sputtered atoms fluxes. Graded segregation was observed under certain parameters of the co-deposition process, resulting in a depth gradient of an aluminum content, as confirmed by the secondary ion mass spectrometry study. A qualitative model was proposed involving aluminum-induced silicon recrystallization happening in the course of a known aluminum interlayer exchange process. The observed Al–Si segregation effect in micrometer-thick films allows for preparation of the non-reflective and absorptive material for operation in the V-band with reflection losses more than 10 dB and transmission losses around 5 dB in the bandwidth of up to 20 GHz.

In this paper, we deal with the study of flexible antennas for ISM range fabricated by our original approach based on magnetron sputtering and laser ablation. We used polyimide film with a thickness of 100 |xm as a flexible dielectric substrate. As a conductive layer we used oxygen free copper and nickel. We used a known sketch for the antenna with a coplanar feeding structure that has already numerically verified, fabricated by the inkjet printing technology and experimentally studied. We have fabricated several flexible antenna samples with coplanar feeding structure using our original approach. Results of scanning electron microscopy and optical microscopy studies of fabricated flexible antennas were considered. Antennas measurements were carried out with the help of an experimental setup based on the vector network analyzer. The experimental measurements were preceded by 1-port type calibration procedure in 0.3-3 GHz band on coaxial ends of cables using automated electronic calibration module. A comparison of obtained experimental results with the already known results from several scientific papers was considered. Fabricated antennas demonstrate reflection loss not worse than 16 dB throughout full ISM band (2.4-2.5 GHz). Obtained experimental results are in good agreement with the numerical ones and other published experimental studies.

We consider further development of our original technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS). The technology is based on magnetron sputtering and laser ablation methods. V-band (50-75 GHz) and W-band (75-110 GHz) SWSs are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed SWSs are studied by numerical simulation and cold-test measurement. We have also carried out preparations and preliminary technological steps for the microfabrication of D-band (110-170 GHz) planar microstrip slow-wave structures.

Experimental and numerical studies of an electrodynamic structure assembled according to photonic crystals’ principles placed inside a X-band rectangular waveguide are considered. Such structures are promising for microwave electronics (vircators, FELs, and etc.). Efficient excitation of high-order (and, hence, high-frequency) electromagnetic modes is one the most valuable features of dispersion characteristics of photonic crystal-like structures. The proposed electrodynamic structure is a 2D array of thin metal pins. Transmission and reflection characteristics of the proposed structure were measured experimentally and evaluated numerically in K, Ka and Q bands. The experimental results are in good agreement with the numerical ones.

We have propose an original approach for fabrication of flexible antennas for biomedical-related applications. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a flexible substrate (polyimide film). Then laser ablation is utilized to remove excess copper thus forming an antenna pattern on the metal layer. ISM band flexible design with microstrip feeding structure was chosen for testing this technique. Results of numerical simulation are presented. A number of test flexible antennas were fabricated by our original approach. Similar flexible antennas were also fabricated via photolithography process. A comparison of the experimental results of return loss (S11) measurements of antennas with different fabrication approach was carried out. The obtained experimental data is in a good agreement with the numerical modeling results. Proposed technology has significant advantages in cost, speed, and flexibility over photolithography processes commonly utilized for such applications.

Encapsulation of various nanoparticles in nanofibers has become one of the most interesting topics in the field of electrospinning and SERS. Literature review shows that several main approaches can be distinguished for the preparation of electrospun nanofibers with embedded metal nanostructures. However, there is no information about the comparison of various methods of metal nanoparticles introduction into nanofiber-based SERS-platforms. Three main approaches were used here for preparation of SERS-platforms based on electrospun nanofibers with embedded silver nanoparticles: synthesis of metal nanostructures inside fibers prepared with incorporated precursor, metal nanostructures synthesis via their nucleation in prepared nanofibers and sorption of metal nanostructures onto ready-made nanofibers. SERS-platforms based on polyacrylonitrile nanofibers containing various concentrations of Ag nanoparticles were obtained using techniques described above and tested.

A traveling wave tube amplifier (TWTa) operating in V-band (62–65 GHz) was designed considering a planar slow wave structure (SWS). Particle in cell simulations were performed to calculate the gain and the output power of the TWT. The simulated TWT showed a maximum gain of 36 dB at 64 GHz and an output power of 16 W. The planar SWS was then fabricated with a laser machining technique. S parameters measurements of the SWS showed excellent matching and low losses in the operating frequency band.

Here we report on experimental and numerical investigations of an electrodynamic structure assembled according to photonic crystals' principles placed inside a X-band rectangular waveguide which is promising for microwave electronics. The features of dispersion characteristics of photonic crystals can be used for efficient excitation of high-order (and, hence, high-frequency) electromagnetic modes. In this work, the electrodynamic structure is a2D array of thin metal pins. Transmission and reflection of proposed system were measured experimentally and evaluated numerically. The experimental results are in good agreement with the numerical ones.

The elaboration of biocompatible and biodegradable carriers for photosensitizer targeted delivery is one of the most promising approaches in a modern photodynamic therapy (PDT). This approach is aimed at reducing sides effects connected with incidental toxicity in healthy tissue whilst also enhancing drug accumulation in the tumour area. In the present work, Photosens-loaded calcium carbonate (CaCO3) submicron particles in vaterite modification are proposed as a novel platform for anticancer PDT. Fast penetration of the carriers (0.9±0.2μm in diameter) containing 0.12% (w/w) of the photosensitizer into NIH3T3/EGFP cells is demonstrated. The captured particles provide the dye localization inside the cell increasing its local concentration, compared with "free" Photosens solution which is uniformly distributed throughout the cell. The effect of photosensitizer encapsulation into vaterite submicron particles on cell viability under laser irradiation (670nm, 19mW/cm(2), 10min) is discussed in the work. As determined by a viability assay, the encapsulation renders Photosens more phototoxic. By this means, CaCO3 carriers allow improvement of the photosensitizer effectiveness supposing, therefore, the reduction of therapeutic dose. Summation of these effects with the simplicity, upscalability and cheapness of fabrication, biocompatibility and high payload ability of the vaterite particles hold out the prospect of a novel PDT platform.

We report the results of the design, simulation, fabrication, and cold-test measurements of millimeter-band 2D planar microstrip slow-wave structures (SWSs) on dielectric substrates. Such structures have a high slow-wave factor, which allows for low-voltage operation and reduction in the size and weight of the device. A low-cost and flexible fabrication technology based on magnetron sputtering and subsequent laser ablation has been developed and is reported in the paper. Microstrip meander-line SWS circuits at V-, W-, and D-bands have been fabricated and characterized. The fabrication of ring-bar planar SWSs by the photolithographic method is also discussed. Experimental measurement of S-parameters of the fabricated structures reveals good transmission properties. Return loss (S11) does not exceed −10 dB and attenuation is about 2 dB/cm in the V-band, 10 dB/cm in the W-band, and 8.5 dB/cm in the D-band.

Results of experimental studies on Si-W coatings fabrication by magnetron co-sputtering from two sources for electrodynamic structures in millimeter and submillimeter range of electromagnetic waves are presented. Control over sheet resistivity of the resulting coatings by varying the power of a magnetron with a tungsten target is demonstrated. Dependence of complex permittivity of Si-W coatings upon dielectric substrates on chemical composition in the frequency range of 50-70 GHz is studied.

A novel technology for microfabrication of millimeter-band planar microstrip slow-wave structures is considered. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a dielectric substrate. Then laser ablation is utilized to cut a slow wave structure from the copper layer. V-band (50–70 GHz) and W-band (75–110 GHz) meander-line slow wave structures are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed slow wave structures are studied by numerical simulation. Cold-test measurement are also carried out for microfabricated meander-line slow wave structures. The experimental results are in good agreement with the numerical ones. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications. The future work will be aimed to expansion of the proposed technology to manufacturing of higher-frequency E-band (110–170 GHz) planar slow wave structures.

We have proposed and developed an original approach for fabrication flexible antennas for biomedical application. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a flexible (polyimide) substrate. Then laser ablation is utilized to cut an antenna structure from the copper layer. For testing our approach we have chosen a number of examples of flexible antenna scheme with microstrip feeding structure working in ISM bands. A number of test flexible antennas were fabricated. Return loss (S11) of fabricated antennas were measured experimentally and calculated numerically. The obtained experimental results are in good agreement with the numerical ones. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications.

Folded waveguide (FW) is a promising type of slow-wave structure (SWS) for millimeter-wave traveling-wave tubes. Results of development of several millimeter-band FW SWSs are presented. SWS circuits at Q- and V -band are fabricated by CNC-machining. Cold electromagnetic parameters of the SWS characteristics are simulated and reasonable agreement with the results of measurements is observed. Small-signal and large-signal gain is calculated.

A novel technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS) is proposed. The technology is based on magnetron sputtering and laser ablation methods. V-band (50–70 GHz) and W-band (75–110 GHz) meander-line SWSs are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed SWSs are studied by numerical simulation and cold-test measurement. Small-signal and large-signal gain is calculated.

Microfabricated vacuum-tube millimeter- and THz-band sources are of great interest for numerous applications such as communications, radar, sensors, imaging, etc. Recently, miniaturized sheet-beam traveling-wave tubes for operation at sub-THz and THz bands have attracted a considerable interest. In this paper, we present the results of modeling and development of slow-wave structures (SWS) for medium power (10-100 W) traveling-wave tubes (TWT) amplifiers in near-THz frequency band. Different types of SWSs are considered, such as double-vane SWS for TWT with a sheet electron beam, folded-waveguide SWS, and novel planar SWSs on dielectric substrates.

A novel technology for microfabrication of millimeter and THz band planar microstrip slow-wave structures (SWS) is proposed. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a quartz substrate. Then laser ablation is utilized to fabricate a slow wave structure from the copper layer. V-band (50–70 GHz) meander-line SWSs were fabricated and characterized by scanning electron and optical microscopy. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications. The future work will be aimed to expansion of the proposed technology to manufacturing of higher-frequency W-band (75–110 GHz) and E-band (110–170 GHz) planar SWSs.