Multiscale Supercrystal Meta-atoms

Meta-atoms are the building blocks of metamaterials, which are employed to control both generation and propagation of light as well as provide novel functionalities of localization and directivity of electromagnetic radiation. In many cases, simple dielectric or metallic resonators are employed as meta-atoms to create different types of electromagnetic metamaterials. Here, we fabricate and study supercrystal meta-atoms composed of coupled perovskite quantum dots. We reveal that these multiscale structures exhibit specific emission properties, such as spectrum splitting and polaritonic effects. We believe that such multiscale supercrystal meta-atoms will provide novel functionalities in the design of many novel types of active metamaterials and metasurfaces.

Advanced spectroscopic investigation of colour centres in LiF crystals irradiated with monochromatic hard x-rays

Nominally-pure lithium fluoride (LiF) crystals were irradiated with monochromatic hard x-rays of energy 5, 7, 9 and 12 keV at the METROLOGIE beamline of the SOLEIL synchrotron facility, in order to understand the role of the selected x-ray energy on their visible photoluminescence (PL) response, which is used for high spatial resolution 2D x-ray imaging detectors characterized by a wide dynamic range. At the energies of 7 and 12 keV the irradiations were performed at five different doses corresponding to five uniformly irradiated areas, while at 5 and 9 keV only two irradiations at two different doses were carried out. The doses were planned in a range between 4 and 1.4 × 103Gy (10.5 mJ cm-3to 3.7 J cm-3), depending on the x-ray energy. After irradiation at the energies of 7 and 12 keV, the spectrally-integrated visible PL intensity of the F2and F3+colour centres (CCs) generated in the LiF crystals, carefully measured by fluorescence microscopy under blue excitation, exhibits a linear dependence on the irradiation dose in the investigated dose range. This linear behaviour was confirmed by the optical absorption spectra of the irradiated spots, which shows a similar linear behaviour for both the F2and F3+CCs, as derived from their overlapping absorption band at around 450 nm. At the highest x-ray energy, the average concentrations of the radiation-induced F, F2and F3+CCs were also estimated. The volume distributions of F2defects in the crystals irradiated with 5 and 9 keV x-rays were reconstructed in 3D by measuring their PL signal using a confocal laser scanning microscope operating in fluorescence mode. On-going investigations are focusing on the results obtained through thisz-scanning technique to explore the potential impact of absorption effects at the excitation laser wavelength.

All-optical generation of static electric field in a single metal-semiconductor nanoantenna

Electric field is a powerful instrument in nanoscale engineering, providing wide functionalities for control in various optical and solid-state nanodevices. The development of a single optically resonant nanostructure operating with a charge-induced electrical field is challenging, but it could be extremely useful for novel nanophotonic horizons. Here, we show a resonant metal-semiconductor nanostructure with a static electric field created at the interface between its components by charge carriers generated via femtosecond laser irradiation. We study this field experimentally, probing it by second-harmonic generation signal, which, in our system, is time-dependent and has a non-quadratic signal/excitation power dependence. The developed numerical models reveal the influence of the optically induced static electric field on the second harmonic generation signal. We also show how metal work function and silicon surface defect density for different charge carrier concentrations affect the formation of this field. We estimate the value of optically-generated static electric field in this nanoantenna to achieve ≈108V/m. These findings pave the way for the creation of nanoantenna-based optical memory, programmable logic and neuromorphic devices.

Damage threshold of LiF crystal irradiated by femtosecond hard XFEL pulse sequence

Here we demonstrate the results of investigating the damage threshold of a LiF crystal after irradiating it with a sequence of coherent femtosecond pulses using the European X-ray Free Electron Laser (EuXFEL). The laser fluxes on the crystal surface varied in the range ∼ 0.015-13 kJ/cm2 per pulse when irradiated with a sequence of 1-100 pulses (tpulse ∼ 20 fs, Eph = 9 keV). Analysis of the surface of the irradiated crystal using different reading systems allowed the damage areas and the topology of the craters formed to be accurately determined. It was found that the ablation threshold decreases with increasing number of X-ray pulses, while the depth of the formed craters increases non-linearly and reaches several hundred nanometers. The obtained results have been compared with data already available in the literature for nano- and picosecond pulses from lasers in the soft X-ray/VUV and optical ranges. A failure model of lithium fluoride is developed and verified with simulation of material damage under single-pulse irradiation. The obtained damage threshold is in reasonably good agreement with the experimentally measured one.

A novel whole-head RF coil design tailored for concurrent multichannel brain stimulation and imaging at 3T

PURPOSE

Multichannel Transcranial Magnetic Stimulation (mTMS) [1] is a novel non-invasive brain stimulation technique allowing multiple sites to be stimulated simultaneously or sequentially under electronic control without movement of the coils. To enable simultaneous mTMS and MR imaging, we have designed and constructed a whole-head 28-channel receive-only RF coil at 3T.

METHODS

A helmet-shaped structure was designed considering a specific layout for a mTMS system with holes for positioning the TMS units next to the scalp. Diameter of the TMS units defined the diameter of RF loops. The placement of the preamplifiers was designed to minimize possible interactions and to allow straightforward positioning of the mTMS units around the RF coil. Interactions between TMS-MRI were analyzed for the whole-head system extending the results presented in previous publications [2]. Both SNR- and g-factors maps were obtained to compare the imaging performance of the coil with commercial head coils.

RESULTS

Sensitivity losses for the RF elements containing TMS units show a well-defined spatial pattern. Simulations indicate that the losses are predominantly caused by eddy currents on the coil wire windings. The average SNR performance of the TMSMR 28-channel coil is about 66% and 86% of the SNR of the 32/20-channel head coil respectively. The g-factor values of the TMSMR 28-channel coil are similar to the 32-channel coil and significantly better than the 20-channel coil.

CONCLUSION

We present the TMSMR 28-channel coil, a head RF coil array to be integrated with a multichannel 3-axisTMS coil system, a novel tool that will enable causal mapping of human brain function.

Laser-Activated Second Harmonic Generation in Flexible Membrane with Si Nanowires

Nonlinear silicon photonics has a high compatibility with CMOS technology and therefore is particularly attractive for various purposes and applications. Second harmonic generation (SHG) in silicon nanowires (NWs) is widely studied for its high sensitivity to structural changes, low-cost fabrication, and efficient tunability of photonic properties. In this study, we report a fabrication and SHG study of Si nanowire/siloxane flexible membranes. The proposed highly transparent flexible membranes revealed a strong nonlinear response, which was enhanced via activation by an infrared laser beam. The vertical arrays of several nanometer-thin Si NWs effectively generate the SH signal after being exposed to femtosecond infrared laser irradiation in the spectral range of 800-1020 nm. The stable enhancement of SHG induced by laser exposure can be attributed to the functional modifications of the Si NW surface, which can be used for the development of efficient nonlinear platforms based on silicon. This study delivers a valuable contribution to the advancement of optical devices based on silicon and presents novel design and fabrication methods for infrared converters.

3D and Inkjet Printing by Colored Mie-Resonant Silicon Nanoparticles Produced by Laser Ablation in Liquid

Optically resonant silicon nanoparticles have emerged as a prospective platform for the structural coloration of surfaces because of their strong and spectrally selective light scattering. In this work, we developed colorful inks based on polymer mixed with monodisperse Mie-resonant silicon nanoparticles for 3D and inkjet printing. We applied a laser ablation method in a flow cell for the mass production of silicon nanoparticles in water and separated the resulting nanoparticles with different sizes by density-gradient centrifugation. Mixing the colorful nanoparticles with the polymer allows for the printing of 3D objects with various shapes and colors, which are rigid against environmental conditions.

Direct LiF imaging diagnostics on refractive X-ray focusing at the EuXFEL High Energy Density instrument

The application of fluorescent crystal media in wide-range X-ray detectors provides an opportunity to directly image the spatial distribution of ultra-intense X-ray beams including investigation of the focal spot of free-electron lasers. Here the capabilities of the micro- and nano-focusing X-ray refractive optics available at the High Energy Density instrument of the European XFEL are reported, as measured in situ by means of a LiF fluorescent detector placed into and around the beam caustic. The intensity distribution of the beam focused down to several hundred nanometers was imaged at 9 keV photon energy. A deviation from the parabolic surface in a stack of nanofocusing Be compound refractive lenses (CRLs) was found to affect the resulting intensity distribution within the beam. Comparison of experimental patterns in the far field with patterns calculated for different CRL lens imperfections allowed the overall inhomogeneity in the CRL stack to be estimated. The precise determination of the focal spot size and shape on a sub-micrometer level is essential for a number of high energy density studies requiring either a pin-size backlighting spot or extreme intensities for X-ray heating.

Insulinoma in childhood: a retrospective review of 22 patients from one referral centre

Background

Insulinomas are very rare in childhood with sparse knowledge on the clinical aspects and the presence of Multiple Endocrine Neoplasia type 1 (MEN1).

Methods

We conducted a retrospective review of patients diagnosed with insulinoma between 1995 and 2021, presenting to one referral centre in Russia. Clinical, biochemical, genetic, imaging and histological data were collected. In addition, follow-up and family data were obtained.

Results

A total of twenty-two children aged 5 to 16 years were identified. The median (range) gap between the first hypoglycaemia symptoms and diagnosis was 10 (1-46) months. Twelve children (55%) were misdiagnosed to have epilepsy and were treated with anticonvulsants before hypoglycemia was revealed. Contrast enhanced MRI and/or CT were accurate to localize the lesion in 82% (n=18). Five patients (23%) had multiple pancreatic lesions. All children underwent surgical treatment. The median (range) diameter of removed tumors was 1.5 (0.3-6) cm. Histopathological studies confirmed the presence of insulinoma in all cases. Immunohistochemical studies revealed G2 differentiation grade in 10 out of 17 cases. Two patients were diagnosed with metastatic insulinoma. One of them had metastases at the time of insulinoma diagnosis, while the other was diagnosed with liver metastases eight years after the surgery. Eight children (36%) were found to carry MEN1 mutations, inherited n=5, de novo n=1, no data, n=2. Children with MEN1 had significantly higher number of pancreatic tumors compared to sporadic cases. All of them developed additional MEN1 symptoms during the following 2-13 years. In the five patients with inherited MEN1, seven family members had hitherto undiscovered MEN1 manifestations.

Conclusions

In this large cohort of children with rare pediatric insulinomas, MEN1 syndrome and G2 tumors were frequent, as well as hitherto undiscovered MEN1 manifestations in family members. Our data emphasize the need of genetic testing in all children with insulinoma and their relatives, even in the absence of any other features, as well as the importance of a prolonged follow-up observation.

The Use of Cheilectomy with Hemispheric Reamers in Combination with Autologous Matrix-Induced Chondrogenesis in Treatment of Patients with Hallux Rigidus

Category:

Midfoot/Forefoot

Introduction/Purpose:

Hallux rigidus (HR) is a common disease that occurs, according to the literature, in 2-10% of the population. However, currently there is no single approach to the choice of a surgical method for the treatment of this disease. It is known that the most common method at early stages of HR is cheilectomy, and the first metatarsophalangeal (1st MTP) joint arthrodesis at late stages. On the other hand, autologous matrix-induced chondrogenesis (AMIC) is known to be successfully applied in the presence of the osteochondral defects in the ankle, knee and hip joints. In this regard, we proposed to use cheilectomy in combination with this technique in treatment of patients with HR.

Methods:

Cheilectomy with AMIC was performed in 35 patients with HR. The operation technique included removing of the osteophytes from the metatarsal bone head and the proximal phalanx basement, clearing of the cartilage defect, microfracturing and covering the metatarsal bone head by the collagen memebrane, then - suturing the memebrane to the periosteum by absorbable thread. 16 patients underwent cheilectomy using hemispheric reamers. The results of surgical treatment were assessed using visual analog scale (VAS) of pain, AOFAS scale and range of motion (ROM) in 1st MTP joint. Also foot X-ray and MRI before and 3, 6, 12 months after the surgery were used.

Results:

In patients who underwent cheilectomy without reamers (1st group), the median ROM before the surgery was 20o, VAS of pain - 72.5, AOFAS - 49. As for the patients who underwent cheilectomy with reamers (2nd group), the median ROM was also 20o, VAS of pain - 70, AOFAS - 52.In the 1st group, after a year of observation, the median VAS of pain decreased to 10, ROM increased to 72.5o and AOFAS - to 82.5.In the 2nd group, after 12 months the median VAS of pain decreased to 7.5, ROM increased to 77o, AOFAS - to 85.On the radiographs 12 months after the surgery, there was some narrowing of the joint space compared to the first day after the operation. However, the ROM in the 1st MTP joint, on the contrary, increased.

Conclusion:

The results showed that cheilectomy in combination with AMIC allows to relieve pain and significantly improve the quality of life of patients with HR; the results in patients who underwent cheilectomy using hemispheric reamers were better, therefore, in most cases we recommend to use these reamers. Also, this technique, unlike isolated cheilectomy or arthrodesis, can be used at any stage of HR.

AB0969 Factors influencing the result of local injection therapy with hyaluronic acid preparations in osteoarthritis of the knee joint

Background

Local injection therapy (LIT) with hyaluronic acid (HA) preparations is one of the methods of conservative treatment of the knee joint osteoarthritis (KOA). However, the factors affecting the effectiveness of such treatment require clarification.

Objectives

to study the influence of age, body mass index (BMI), stage of KOA, the presence of deformity of the knee joint and enthesitis on the results of LIT with HA preparations in KOA.

Methods

from September 2017 to June 2019, intra-articular injections of HA were performed in 160 patients with primary and posttraumatic KOA stage I-III. For the analysis, the patients were divided into groups depending on the factor studied: by age into young - 36 (22.5%), middle age - 51 (31.3%), elderly - 61 (38.7%) and old age - 12 (7.5%); by BMI: on patients with normal values - 32 (20%), preobesity - 56 (35%), I - 43 (26.9%), II - 16 (10%) and III - 13 (8.1%) degrees of obesity; by stages of KOA: I - 37 (23.1%), II - 91 (56.8%), III - 32 (20.1%); by the presence of deformity: varus deformity <10° - 83 (51.8%), >10° - 23 (14.4%), valgus deformity - 22 (13.8%), no deformity - 32 (20%); and also depending on the presence (44 (27.5%)) or absence (116 (72.5%)) of enthesites. To assess the results, the pain intensity was determined using a visual analogue scale and the knee injury and osteoarthritis outcome score before treatment, 1, 3, and 6 months after the course of LIT.

Results

1 month after the course of LIT, the best results were obtained in young patients (p=0.001), as well as stage I of KOA (p=0.0001) and normal BMI values (p=0.034), the worst in elderly patients (p=0.006), at stage III of KOA (p=0.01), varus deformity >10° (p=0.006), obesity degree 3 (p=0.015) and the presence of concomitant enthesitis (p=0.003). 3 months after the course of LIT, the previously identified differences persisted, so the best results were again revealed in young people (p=0.0001), in stage I of KOA (p=0.0001), in the absence of deformity (p=0.002) and in normal BMI values (p=0.002), while lack of improvement or deterioration in elderly patients (p=0.001), in stage III KOA (p=0.0001), varus deformity >10° (p=0.001), obesity degree 3 (p=0.022) and the presence of concomitant enthesitis (p=0.001). 6 months after the course of LIT, the improvement remained as before in young patients (p=0.0001), as well as stage I of KOA (p=0.0001), in the absence of deformity (p=0.001) and with normal BMI values (p=0.0001). Lack of improvement or deterioration of knee joint function 6 months after the course of LIT was found in the elderly (p=0.03) and old age patients (p=0.06), in stage II (p=0.045) and III of KOA (p=0.007), varus deformity >10° (p=0.015), obesity degree 2 (p=0.025) and the presence of concomitant enthesitis (p=0.02).

Conclusion

The best LIT results with HA preparations can be obtained in young patients with normal BMI values, at the initial stage of KOA, in the absence of deformity and enthesitis. The elderly age of patients, the presence of stage III KOA, varus deformity of the knee joint >10°, BMI >40 kg/m2, and the presence of enthesitis are associated with the lack of effect from intra-articular injections of HA preparations. Performing LIT with HA preparations in patients with stage II KOA and degree 2 obesity allows maintaining improvement for up to 6 months.

Disclosure of Interests

None declared

POS1110 WHAT FACTORS ARE ASSOCIATED WITH THE DEVELOPMENT OF PAIN AFTER TOTAL JOINT REPLACEMENT?

Background

Chronic postoperative pain (CPP) is one of the most common complications of total hip (HJ) and knee (CJ) arthroplasty (TA). The search for the factors that determine this pathology is an urgent scientific and practical task.

Objectives

To determine the factors associated with the development of CPP in patients who underwent TA, CJ or HJ.

Methods

The study group consisted of 124 patients with osteoarthritis of the knee or hip joint, mean age 63.6 + 9.9 years, 63% of women and 37% of men, who in 2019-2020 year done out by TA KJ or HJ. The development of CPP was assessed after 3 and 6 months. telephone survey of patients. This complication was diagnosed in the presence of moderate to severe pain (≥40 mm on a visual analogue scale, VAS), persisting for at least 3 months, causing concern in patients and / or requiring regular use of analgesics. A comparison was made between the groups of patients with CPP and the absence of CPP for a number of factors determined in the preoperative period.

Results

The incidence of CPP was 27.4%. There were no differences in the incidence of CPP in patients who underwent TA CJ and TA HJ: 28.1% and 26.9%, respectively (p = 0.88). The presence of CPP was significantly associated with such preoperative indicators as a higher body mass index (BMI), a higher intensity of pain at rest, higher values of the WOMAC pain index, WOMAC and WOMAC stiffness in general, and the severity of symptoms of neuropathic pain. (PainDetect questionnaire), signs of depression and anxiety (HADS questionnaire). The risk of developing CPP was significantly higher (p <0.05) in patients with BMI> 30 kg / m2 - odds ratio (OR) 2.755 (95% confidence interval, CI 1.053-7.206), for pain at rest ≥40 mm VAS - OR 1.349 (95% CI 0.478-3.803), Pain Detect score ≥13 - OR 3.598 (95% CI 1.048-12.36), depression score HADS ≥8 - OR 2.193 (95% CI 0.745-6.454), number of pain sources ≥ 2 - OR 6.996 (95% CI 2.358-20.756).

Conclusion

The risk of CPP after TA CJ and HJ is higher in patients with overweight, high preoperative pain, signs of neuropathic pain and depression, and in the presence of several sources of musculoskeletal pain (except for the affected joint planned for TA).

Disclosure of Interests

None declared

AB0404 DEPENDENCE OF COMPLICATIONS IN TOTAL HIP AND KNEE ARTHROPLASTY ON THE TREATMENT OF RHEUMATOID ARTHRITIS

Background

Surgical treatment of patients with rheumatoid arthritis (RA) is associated with an increased risk of complications. This is due to the presence of an inflammatory process, a variety of variants of the course of the disease, reduced physical activity, the severity of functional disorders, prolonged therapy with glucocorticoids, disease-modifying and genetically engineered biological drugs, osteoporosis, as well as the activity of the underlying disease.

Objectives

to conduct a comparative analysis of the effect of RA treatment on local complications, such as periprosthetic infection, periprosthetic fractures, wound complications, ligamentous disorders in hip and knee total arthroplasty in patients with RA.

Methods

1113 arthroplasties of large joints in patients with RA, which were performed in the period from 2002 to 2020, were analyzed. Of these, 649 total knee replacements (TKA) and 464 total hip replacements (THA) were performed.

Results

In patients with therapy of methotrexate at an average dose of 12.5 mg per week, the incidence of local complications was 7.87%. In patients receiving Leflunomide (Arava), complications were detected in 9.29% of cases. In group of patients with Sulfasalazine (SSZ) intake, local complications were detected in 7.73% of cases. The complication rate of 7.01% was determined in group of patients who received Glucocorticoids (GC) at an average dose of 7.5 mg (recalculation in Prednisone). 1.87% of complications were observed in patients with intake of genetically engineered biological drugs (bDMARD). The highest incidence of local complications was found in patients with RA who had no therapy (27.27%).

Statistical data analysis revealed a significantly higher number of complications in the group of RA patients (p<0.005). Analyzing each type of complications, significant differences were also obtained (p<0.005).

Conclusion

The risk of local complications was 3 or more times higher in group of patients with RA without any treatment. So, arthroplasties of large joints in patients with RA without treatment are often accompanied by a high risk of intra- and postoperative complications.

Disclosure of Interests

None declared

AB0970 What is the effect of intra-articular injections of glucocorticoids in real clinical practice?

Background

Intra-articular injections of glucocorticoids (IAI GC) are widely used in the complex therapy of rheumatic diseases (RD). However, there are relatively few modern data on their efficacy and safety in real clinical practice.

Objectives

To evaluate the effectiveness of IAI HA in RD in clinical practice.

Methods

The study group consisted of 290 patients with RD, mainly osteoarthritis (OA) and rheumatoid arthritis (RA) (69.0% of women, age 55.6 ± 12.6 years), who underwent IAI GC in the knee joint. The indications for IAI were determined by the attending physicians. The control consisted of 112 patients with OA (71.4% of women, age 59.3 ± 14.6 years), who underwent a course of IAI of hyaluronic acid (HA). The result of treatment was assessed after 2 weeks, 1 and 3 months. according to a telephone survey.

Results

After 2 weeks, 1 month. and 3 months. after IAI GC, the severity of pain during movement decreased (numerical rating scale, NRS 0-10, Me [25%; 75%]) from 6.0 [4.0; 8.0] to 1.0 [0; 2.0], 2.0 [1.0; 4.0] and 2.5 [1.0; 4.0], respectively (p <0.001). After 3 months. the number of patients with no / mild pain (<4 according to the NRS) was 63.8%, with a complete / almost complete absence of pain (≤1 by the NRS) - 30.3%. The effect of HSI HA was higher in RA than in OA: the dynamics of pain after 3 months. -4.0 [-2.0; -6.0] and -2.0 [-1.0; -5.0], p = 0.003. In OA, the effect of HAI HA and HA did not differ: the dynamics of pain after 3 months. was -2.0 [-1.0; -5.0] and -3.0 [-1.0; -5.0] p = 0.869. There were no serious adverse reactions in IAI.

Conclusion

IAI GC are an effective and fairly safe method of short-term treatment of synovitis in RD.

Disclosure of Interests

None declared

POS1109 GENETIC MARKERS PREDICT THE DEVELOPMENT OF POSTOPERATIVE PAIN

Background

Postoperative pain (POP) is a serious complication that affects the outcome of total arthroplasty (TA) of the knee (CJ) and hip (HJ) joints in patients with osteoarthritis (OA). The search for the genetic characteristics of POP is an urgent direction in the study of this problem.

Objectives

To determine the relationship between the polymorphisms of the KCNS1, COMT, and OPRM1 genes and the development of postoperative pain in patients with osteoarthritis of the knee joint and hip joint who underwent total arthroplasty.

Methods

The study group consisted of 95 patients with knee osteoarthritis and / or hip joint osteoarthritis (64.6% of women; mean age - 65.4 ± 9.0 years) who underwent TA CJ (47.8%) or TA HJ (52.2 %). The presence of POP was determined when it persisted or appeared after 3 and 6 months. After surgery, pain in the area of the operated joint ≥40 mm by 100 mm visual analogue scale. All patients underwent genotyping of KCNS1 (rs734784), COMT (rs6269, rs4633), and OPRM1 (rs1799971) gene polymorphisms by real-time polymerase chain reaction using original sequence-specific primers and probes labeled with various fluorescent labels. Registration and interpretation of the obtained results were carried out on a DT-96 amplifier (DNA-Technology LLC, Russia).

Results

POP was observed in 32.6% of patients who underwent TA CJ or TA HJ. The incidence of POP after TA CJ and TA HJ was 30.2% and 34.0%, respectively (p = 0.882). There were no differences in the frequencies of genotypes of the studied genes (p>0.05). The presence of the homozygous GG genotype of the KCNS1 gene polymorphism (rs734784) was associated with the presence of POP in accordance with the recessive genetic model (GG vs AA + AG; odds ratio (OR) - 3.96 [95% confidence interval (CI): 1, 51; 10.37]; p = 0.005). The presence in the genotype of the mutant allele T (TT + CT) of the COMT polymorphism (rs4633) reduced the risk of developing POP compared with the carriage of the CC genotype (OR = 0.32 [95% CI: 0.12; 0.83]; p = 0, 02) according to the dominant genetic model. There was no statistically significant correlation between the development of POP and the carriage of various genotypes and alleles of the COMT (rs6269) and OPRM1 (rs1799971) genes.

Conclusion

There is a statistically significant association between the polymorphism of the KCNS1 (rs734784) and COMT (rs4633) genes and the development of chronic POP in patients who underwent TA CJ and TA HJ. Further studies of the genetic predisposition to POP are required using more clinical material.

Disclosure of Interests

None declared

Femtosecond Laser-Assisted Formation of Hybrid Nanoparticles from Bi-Layer Gold–Silicon Films for Microscale White-Light Source

It is very natural to use silicon as a primary material for microelectronics. However, silicon application in nanophotonics is limited due to the indirect gap of its energy band structure. To improve the silicon emission properties, it can be combined with a plasmonic part. The resulting metal–dielectric (hybrid) nanostructures have shown their excellence compared to simple metallic dielectric nanostructures. Still, in many cases, the fabrication of such structures is time consuming and quite difficult. Here, for the first time, we demonstrate a single-step and lithography-free laser-induced dewetting of bi-layer nanoscale-thickness gold–silicon films supported by a glass substrate to produce hybrid nanoparticles. For obtaining hybrid nanoparticles, we study nonlinear photoluminescence by mapping their optical response and morphology by scanning electron microscopy. This method can be used for the fabrication of arrays of hybrid nanoparticles providing white-light photoluminescence with a good control of their microscopic sizes and position. The developed approach can be useful for a wide range of photonic applications including the all-optical data processing and storage where miniaturization down to micro- and nanoscale together with an efficiency increase is of high demand.

Opto-thermally controlled beam steering in nonlinear all-dielectric metastructures

Reconfigurable metasurfaces have recently gained a lot of attention in applications such as adaptive meta-lenses, hyperspectral imaging and optical modulation. This kind of metastructure can be obtained by an external control signal, enabling us to dynamically manipulate the electromagnetic radiation. Here, we theoretically propose an AlGaAs device to control the second harmonic generation (SHG) emission at nanoscale upon optimized optical heating. The asymmetric shape of the used meta-atom is selected to guarantee a predominant second harmonic (SH) emission towards the normal direction. The proposed structure is concurrently excited by a pump beam at a fundamental wavelength of 1540 nm and by a continuous wave (CW) control signal above the semiconductor band gap. The optical tuning is achieved by a selective optimization of meta-atoms SH phase, which is modulated by the control signal intensity. We numerically demonstrate that the heating induced in the meta-atoms by the CW pump can be used to dynamically tune the device properties. In particular, we theoretically demonstrate a SH beam steering of 8° with respect to the vertical axis for an optimized device with average temperature increase even below 90° C.

Lewis Superacidic Tellurenyl Cation-Induced Electrophilic Activation of an Inert Carborane

The aryltellurenyl cation [2-(tBuNCH)C6 H4 Te]+ , a Lewis super acid, and the weakly coordinating carborane anion [CB11 H12 ]- , an extremely weak Brønsted acid (pKa =131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C6 H4 Te][CB11 H12 ], in which the Brønsted acidity (pKa 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude. The electrophilic activation of B-H bonds in the carborane moiety gives rise to a proton transfer from boron to nitrogen at slightly elevated temperatures, as rationalized by the isolation of a mixture of the zwitterionic isomers 12- and 7-[2-(tBuN{H}CH)C6 H4 Te(CB11 H11 )] in ratios ranging from 62 : 38 to 80 : 20.

AB0585 COMPARISON OF THE EFFECTIVENESS OF HYALURONIC ACID PREPARATIONS WITH DIFFERENT MOLECULAR WEIGHTS AND IN COMBINATION WITH CHONDROITIN SULFATE DEPENDING ON THE STAGE OF OSTEOARTHRITIS OF THE KNEE JOINT

Background:

intra-articular (IA) injections of hyaluronic acid (HA) preparations are one of conservative treatment of the knee osteoarthritis (OA). However, the results of this treatment are inconsistent.

Objectives:

to evaluate the effectiveness of HA preparations with different molecular weights and in combination with chondroitin sulfate (HS) for IA injections in the treatment of patients with stage I-III knee OA.

Methods:

IA HA injections were performed 160 patients with primary and post-traumatic knee OA of the I-III stages at the department of rheumoorthopaedic and rehabilitation, V. A. Nasonova Research Institute of Rheumatology for the period from September 2017 to June 2019. Patients were divided into 4 groups. Group 1 consisted of 80 patients treated with low molecular weight (LMW) HA, group 2 - 20 patients treated with medium molecular weight (MMW) HA, group 3 - 30 patients treated with high molecular weight (HMW) HA, and group 4 - 30 patients who were intraarticular introduced HA with HS. The course of IA injections was 2 for LMW, HMW, and HA with HS, and 3 for MMW HA. Injections were performed with an interval of 1 week. To evaluate the results of treatment, we studied the intensity of pain according to VAS and the total score of KOOS before treatment and on follow-up examinations 1, 3 and 6 months after the course of IA HA injections.

Results:

the maximum reduction in pain with IA HA injections at stage I of knee OA occurred by 3 months after the course of treatment. Moreover, improvement was detected by 1 month in 84.3% of cases, and remained until the end of the study in 71.1% of patients. All HA preparations used in stage I of knee OA were effective. At stage II of the knee OA after 3 months after the course of IA HA, different efficiencies of HA preparations were revealed. So, in the groups of LMW, MMW and HA with HS, the improvement persisted up to 3 months, and in the group of HMW HA - up to 1 month. After 3 months, the best results were shown by HA with HS, by 6 months the results were comparable. IA HA injections at the II stage of knee OA led to good and excellent results 1 month after the course of treatment in 53.9% of cases, but by the end of the study, improvement remained in only 30.8% of patients. In the case of the use of HA in stage III of the knee OA, the effectiveness of the studied drugs was comparable, and the maximum improvement was achieved by 1 month. The positive effect of IA HA injections in patients with stage III of the knee OA one month after the course of treatment was obtained in 40.6% of cases, by 3 months it decreased to 18.8%, and by 6 months - to 15.7% of patients.

Conclusion:

IA injections of HA at stage I of the knee OA is a highly effective method of conservative treatment, which allows to relieve pain and improve the condition of the knee joint for a period of 6 months or more. The use of HA preparations at stage II of the knee OA allows reducing pain up to 3 months with IA injections of LMW and MMW HA, as well as HA with HS. HMW HA helps reduce pain intensity for a period of 1 month. The use of HA preparations in stage III of the knee OA leads to a short-term relief of symptoms of OA.

Disclosure of Interests:

None declared.

POS0098 THE INFLUENCE OF THE ACTIVITY OF RHEUMATOID ARTHRITIS TO INFECTIOUS AND WOUND COMPLICATIONS AFTER TOTAL HIP AND KNEE ARTHROPLASTY

Background:

Surgical treatment of patients with rheumatoid arthritis (RA) is associated with an increased risk of complications. This is due to the presence of inflammation, many variants of the disease, reduced physical activity, severity of functional disorders, prolonged therapy with glucocorticoids, disease-modifying antirheumatic drugs (DMARDs) and biological DMARDs, osteoporosis, as well as activity of the underlying disease.

Objectives:

to conduct a comparative analysis of the influence of RA activity levels on infectious complications (periprosthetic infection) and wound complications (poor healing, divergence, necrosis of the wound edges) after hip and knee arthroplasty in RA patients.

Methods:

1113 arthroplasties were analyzed in patients with RA, which were performed between 2002 and 2019. Of these, 649 total knee arthroplasties and 464 total hip arthroplasties were performed.

Results:

Infectious complications after total hip and knee arthroplasty did not occur at 0 grade of disease activity (remission). At the I grade of activity, periprosthetic infections were detected with a frequency of 0.31%, at the II grade – 0.89%, and at the III level in 3.06% of cases.

Complications from the operative wound occurred in 0.91% of cases with I grade of activity, at II grade with a frequency of 5.68%, and at III – 6.98%. There were no cases of complications from the wound in patients with remission of RA.

Statistical analysis of the obtained data revealed a significantly higher number of complications in the group of RA patients (p<0.005). During analyzing each type of complication, significant differences were also obtained (p<0.005).

Conclusion:

Risk of periprosthetic infection and complications from the wound is several times higher in patients with a high grade of RA activity. This means that performing arthroplasty, as well as other operations, in patients with high RA activity correlates to a high risk of complications.

Disclosure of Interests:

None declared

AB0714 COMPARISON OF THE EFFECT OF SUBACROMIAL ADMINISTRATION OF HYALURONIC ACID AND PLATELET RICH PLASMA IN CASES OF DAMAGE TO THE TENDONS OF THE ROTATORS OF THE SHOULDER IN INDIVIDUALS OF DIFFERENT AGE GROUPS

Background:

Everyone has had shoulder pain at least once in their life. From 70 to 80% of chronic pain in the shoulder joint is associated with subacromial impingement syndrome. The use of non-steroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids does not always meet the needs of patients and have a number of adverse reactions. Local administration of PRP and HA preparations is widely used for chronic shoulder pain. However, the question of the effectiveness of these drugs in patients of different ages has been insufficiently studied.

Objectives:

To compare the efficacy of GLA and PRP in patients with chronic shoulder pain by age.

Methods:

The study group included 100 patients, 46% women and 54% men, aged 51.5 ± 15.1, with chronic shoulder pain (≥3 months) caused by damage to the tendons of the muscles of the shoulder rotators. Patients <45 years old accounted for 34%, patients ≥45 years old - 66%. All patients were randomly divided into 2 groups. Patients in group 1 received 2 consecutive subacromial injections of GLK, groups 2 - 3 consecutive subacromial injections of PRP. Pain dynamics were assessed using a 100-mm visual analogue scale (VAS), functional impairments according to ASS (American Shoulder and Elbow Surgeons Assessment) and CS (Constant Score), and a decrease in the need for NSAID use after 6 months. after the course of treatment.

Results:

The dynamics of pain and functional disorders in the treatment of GLC and PRP did not differ. The pain decreased from 57.6 ± 17.8 to 30.2 ± 26.3 and 56.0 ± 14.6 to 31.8 ± 26.3 (p = 0.768), ASS from 54.7 ± 15.1 to 77.3 ± 22.5 and 54.8 ± 13.8 to 74.6 ± 22.4 (p = 0.552), CS from 47.8 ± 16.9 to 65.6 ± 19.3 and 59.2 ± 14.4 to 66.9 ± 17.4 (p = 0.245). In general, with the treatment of GLA and PRP, the dynamics of pain and functional disorders was significantly better in patients <45 years old than in patients ≥45 years old. So, pain according to VAS after 6 months. was 22.4 ± 26.3 and 35.5 ± 26.2 (p = 0.022), ASS 83.3 ± 20.9 and 72.1 ± 22.6 (p = 0.017), CS 76.2 ± 16, 1 and 63.2 ± 18.2 (p = 0.001). There was no need to take NSAIDs in 82.4% and 65.2% of patients (p = 0.103). No serious adverse reactions have been reported with the treatment of GLC and PRP.

Conclusion:

The efficacy of GLA and PRP in chronic shoulder pain caused by damage to the tendons of the muscles of the rotator of the shoulder does not differ. The clinical response to both drugs was significantly higher in those under 45 years of age.

Disclosure of Interests:

None declared

Micron-scale phenomena observed in a turbulent laser-produced plasma

Turbulence is ubiquitous in the universe and in fluid dynamics. It influences a wide range of high energy density systems, from inertial confinement fusion to astrophysical-object evolution. Understanding this phenomenon is crucial, however, due to limitations in experimental and numerical methods in plasma systems, a complete description of the turbulent spectrum is still lacking. Here, we present the measurement of a turbulent spectrum down to micron scale in a laser-plasma experiment. We use an experimental platform, which couples a high power optical laser, an x-ray free-electron laser and a lithium fluoride crystal, to study the dynamics of a plasma flow with micrometric resolution (~1μm) over a large field of view (>1 mm²). After the evolution of a Rayleigh–Taylor unstable system, we obtain spectra, which are overall consistent with existing turbulent theory, but present unexpected features. This work paves the way towards a better understanding of numerous systems, as it allows the direct comparison of experimental results, theory and numerical simulations.

Turbulence effects explored use macroscale systems in general. Here the authors generate a turbulent plasma using laser irradiation of a solid target and study the dynamics of the plasma flow at the micron-scale by using scattering of an XFEL beam.

Black Au-Decorated TiO2 Produced via Laser Ablation in Liquid

The rational combination of plasmonic and all-dielectric concepts within hybrid nanomaterials provides a promising route toward devices with ultimate performance and extended modalities. Spectral matching of plasmonic and Mie-type resonances for such nanostructures can only be achieved for their dissimilar characteristic sizes, thus making the resulting hybrid nanostructure geometry complex for practical realization and large-scale replication. Here, we produced amorphous TiO₂ nanospheres decorated and doped with Au nanoclusters via single-step nanosecond-laser irradiation of commercially available TiO₂ nanopowders dispersed in aqueous HAuCl₄. Fabricated hybrids demonstrate remarkable light-absorbing properties (averaged value ≈96%) in the visible and near-IR spectral range mediated by bandgap reduction of the laser-processed amorphous TiO₂ as well as plasmon resonances of the decorating Au nanoclusters. The findings are supported by optical spectroscopy, electron energy loss spectroscopy, transmission electron microscopy, and electromagnetic modeling. Light-absorbing and plasmonic properties of the produced hybrids were implemented to demonstrate catalytically passive SERS biosensor for identification of analytes at trace concentrations and solar steam generator that permitted to increase water evaporation rate by 2.5 times compared with that of pure water under identical 1 sun irradiation conditions.

Core growth of detonation nanodiamonds under high-pressure annealing

The present paper reports the results of a study of the X-ray and Raman spectra of detonation nanodiamonds after high-pressure high-temperature (HPHT) annealing at different temperatures.

Molecular Aggregation in Immune System Activation Studied by Dynamic Light Scattering

Determination of the concentration and size of the circulating immune complexes in the blood is an essential part of diagnostics of immune diseases. In this work, we suggest using the dynamic light scattering method to determine the sizes of circulating immune complexes in blood serum. By the dynamic light scattering spectrometer, we found that for healthy and sick donors, the size and concentration of circulating immune complexes differed significantly. The dynamics of formation of these complexes were also examined in this work. It was shown that the formation of immune complexes in the blood of healthy donors is faster than the same reactions in the blood serum of donors with diseases. The results can be used in the diagnostics of the immune status and detection of chronic inflammation. We can recommend the dynamic light scattering method for implementation in biomedical diagnostics.

AB0900 FREQUENCY OF LOCAL COMPLICATIONS AFTER TOTAL HIP ARTHROPLASTY IN PATIENTS WITH RHEUMATIC DISEASES

Background:

Surgical treatment of patients with rheumatic diseases (RD) is associated with an increased risk of complications. It is caused by presence of an inflammatory process, osteoporosis, reduced physical activity, severity of functional impairment, long-term glucocorticoid therapy, biological and disease-modifying antirheumatic drugs. All this provides elongated wound healing period, the development of infectious complications and increased risk of periprosthetic fractures.

Objectives:

To study a frequency of local complications of total hip arthroplasty (THA) in patients with inflammatory RD and osteoarthritis (OA).

Methods:

We analyzed 1591 THA, which were performed to RD patients between 2000 and 2019 years.

Results:

We performed 882 arthroplasties in patients with inflammatory RD, which consisted of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), juvenile rheumatoid arthritis (JRA), ankylosing spondylitis (AS), systemic scleroderma (SSD), and also 709 operations in OA patients.

Local complications after THA were 120 (7.54%), of these 83 (9.41%) in patients with inflammatory RD and 37 (5.22%) in OA patients.

We revealed a significantly greater number of complications in patients with inflammatory RD (p<0.005).

Conclusion:

Inflammatory RD (RA, SLE, JRA, AS, SSD) patients have local complications after THA (9.41%) 1.8 times more often than OA patients (5.22%). It shows that the operative treatment of patients with RD requires a special approach, management and careful treatment of the bone and surrounding tissues during surgery.

Disclosure of Interests:

None declared

Tunable Mie Resonances of Tin-based Iodide Perovskite Islandlike Films with Enhanced Infrared Photoluminescence

The ability of light manipulation at a sub-wavelength scale of metal halide perovskite-based nanostructures through nanophotonic design were employed for advanced optical and optoelectronic applications. While these nanostructures could be efficiently tuned in the visible spectral range, their operation at infrared wavelengths is still challenging. Herein, we illustrate that islandlike films of lead-free CH₃NH₃SnI₃ can generate strong and tunable Mie-type resonances in the near-infrared spectral range. Two critical factors contribute to the Mie resonance properties-the microscale geometry is crucial for the initiation of Mie resonances in the particles, while the concentration of free holes formed via the oxidation of Sn²⁺ to Sn⁴⁺ modulates the spectral position of Mie resonances. Moreover, coupling the Mie resonances to the photoluminescence peak wavelength results in the enhancement of the photoluminescence intensity. This study offers a platform for the implementation of optically resonant perovskite nanostructures as tunable light emitters for infrared photonics and optoelectronics.

Soft X-ray diffraction patterns measured by a LiF detector with sub-micrometre resolution and an ultimate dynamic range

The unique diagnostic possibilities of X-ray diffraction, small X-ray scattering and phase-contrast imaging techniques applied with high-intensity coherent X-ray synchrotron and X-ray free-electron laser radiation can only be fully realized if a sufficient dynamic range and/or spatial resolution of the detector is available. In this work, it is demonstrated that the use of lithium fluoride (LiF) as a photoluminescence (PL) imaging detector allows measuring of an X-ray diffraction image with a dynamic range of ∼10⁷ within the sub-micrometre spatial resolution. At the PETRA III facility, the diffraction pattern created behind a circular aperture with a diameter of 5 µm irradiated by a beam with a photon energy of 500 eV was recorded on a LiF crystal. In the diffraction pattern, the accumulated dose was varied from 1.7 × 10⁵ J cm^-3 in the central maximum to 2 × 10^-2 J cm^-3 in the 16th maximum of diffraction fringes. The period of the last fringe was measured with 0.8 µm width. The PL response of the LiF crystal being used as a detector on the irradiation dose of 500 eV photons was evaluated. For the particular model of laser-scanning confocal microscope Carl Zeiss LSM700, used for the readout of the PL signal, the calibration dependencies on the intensity of photopumping (excitation) radiation (λ = 488 nm) and the gain have been obtained.

Optical cooling of lead halide perovskite nanoparticles enhanced by Mie resonances

Halide perovskites are a family of semiconductor materials demonstrating prospective properties for optical cooling owing to efficient luminescence at room temperature and strong electron-phonon interaction. Moreover, perovskite based nanophotonic designs would allow for efficient optical cooling at the nanoscale. Here, we propose a novel strategy for the enhancement of optical cooling at the nanoscale based on optical resonance engineering in halide perovskite nanoparticles. Namely, the photoluminescence up-conversion efficiency in a nanoparticle is optimized via excitation of Mie-resonances both at emission and absorption wavelengths. The optimized theoretical photo-induced temperature decrease achieved for a hybrid halide perovskite (CH3NH3PbI3) 530 nm nanoparticle on a glass substrate is more than 100 K under CW illumination at wavelength 980 nm and moderate intensities (∼7 × 106 W cm-2). The optimized regime originates from simultaneous excitation of a magnetic quadrupole and a magnetic octupole at pump and emission wavelengths, respectively. The combination of a thermally sensitive photoluminescence signal and simplicity in the fabrication of a halide perovskite nanocavity will pave the way for implementation of nanoscale optical coolers for advanced applications.

Si1-xGex nanoantennas with a tailored Raman response and light-to-heat conversion for advanced sensing applications

Active light-emitting all-dielectric nanoantennas recently have demonstrated great potential as highly efficient nanoscale light sources owing to their strong luminescent and Raman responses. However, their large-scale fabrication faces a number of problems related to productivity limits of existing lithography techniques. Thus, high-throughput fabrication strategies allowing in a facile way to tailor of the nanoantenna emission and thermal properties in the process of their fabrication are highly desirable for various applications. Here, we propose a cost-effective approach to large-scale fabrication of Si1-xGex alloyed Mie nanoresonators possessing an enhanced inherent Raman response which can be simply tailored via tuning the Ge concentration. Moreover, by tailoring the relative Ge composition one can gradually change a complex refractive index of the produced Si1-xGex alloy, which affects the ratio between radiative and nonradiative losses in Si1-xGex nanoantennas, which is crucial for optimization of their optical heating efficiency. Composition-tunable Si1-xGex nanoantennas with an optimized size, light-to-heat conversion and Raman response are implemented for non-invasive sensing of 4-aminothiophenol molecules with a temperature feedback modality and high subwavelength spatial resolution. The results are important for advanced multichannel optical sensing, providing information on analyte's composition, analyte-nanoantenna temperature response and spatial position.

Characterization of high spatial resolution lithium fluoride X-ray detectors

The response of lithium fluoride (LiF) crystal detectors to monochromatic X-rays is measured in the multi-kilo-electron-volt range. This response, as a function of the X-ray dose, is independent of photon energy with no saturation level found. The response, as a function of the incident energy flux, is found to increase for photons of lower energy due to the differing attenuation lengths of X-ray photons within the crystal. Small differences are seen between different confocal microscopes used to scan the data, suggesting the need for absolute calibration. The spatial resolution of the LiF is also measured (1.19-1.36 μm) and is found to be independent of incident photon energy. Finally, a photometric study is performed in order to assess the feasibility of using these detectors at current X-ray free electron laser and laser facilities worldwide.

Resonant silicon nanoparticles with controllable crystalline states and nonlinear optical responses

High-throughput laser printing of resonant silicon nanoparticles has emerged as a novel tool for the fabrication of deeply subwavelength objects with various functionalities. The applications of resonant silicon nanoparticles crucially depend on their crystalline state. However, the ways to control the crystalline structure during laser printing remain unstudied. Here we demonstrate, both experimentally and theoretically, how the crystalline structure of silicon nanoparticles fabricated by a laser printing technique can be varied from almost amorphous to a polycrystalline state. In particular, we propose a method of crystalline structure control via changing the distance between the irradiated silicon film and the receiving substrate. This study allows the most optimal conditions for second harmonic generation to be revealed. We believe that the proposed method opens the door to fully controllable laser printing of functional nanoparticles and nanostructures.

Single-Step Laser Plasmonic Coloration of Metal Films

Utilization of structural colors produced by nanosized optical antennas is expected to revolutionize the current display technologies based on an inkjet or a pigmentation-based color printing. Meanwhile, the versatile color-mapping strategy combining the fast single-step single-substrate fabrication cycle with low-cost scalable operation is still missing. We propose lithography-free pure optical approach based on a direct local ablative reshaping of the gold film with nanojoule (nJ)-energy femtosecond laser pulses. Plasmon-color printing at a resolution up to 2.5 × 10⁴ dots per inch satisfying the current visualization demands and data storage capacity is achieved. By controlling only the applied pulse energy, wide gamut of colors in scattering regime was reproduced via tuning the size of the printed nanovoids, which have a polarization- and shape-dependent localized plasmon-mediated scattering. Additionally, brightness of a single pixel was gradually adjusted via varying of the spacing between the printed nanovoids. The presented experimental demonstration opens a new direction toward plasmon-color printing for various applications where durability is required: low-cost cryptography, security tagging, and ultracompact optical data storage.

The degree of cartilage degradation assessed by serum biomarker levels changes after arthroscopic knee synovectomy in rheumatoid arthritis patients

PURPOSE

In order to test the validity of the selected surgical technique as a way to manage persistent synovitis of the knee joint, as well as to slow down the cartilage and bone destruction, we studied the dynamics of biomarkers of inflammatory conditions, and bone and cartilage destruction after total arthroscopic synovectomy (TAS) of the knee joint.

METHODS

The sampling comprised 124 RA patients (158 knees) who had undergone the TAS procedure between 2003 and 2015. Before surgery the rheumatoid factor (IgM), C-reactive protein (CRP), erythrocyte sedimentation rate test was completed for all patients. Blood serum samples were collected (prior to surgery, and three, six and 12 months after surgery) and frozen at -70°С. The content of CRP, Matrix metalloproteinase-3 (MMP-3), Cartilage Oligomeric Matrix Protein, as well as cross-linked Ctelopeptides of types I and II were measured in blood serum by means of polarization fluoroimmunoassay with the use of a standard set of reagents.

RESULTS

The average duration of the disease in the studied group was 8.7 ± 6.6 years. Concentration of the inflammation markers showed that only MMP-3 displayed statistical significance.

CONCLUSIONS

The obtained results can be used as basis in assessing the efficiency and effectiveness of this method of treatment of persistent knee joint synovitis associated with the RA.

Resonant silicon nanoparticles for enhancement of light absorption and photoluminescence from hybrid perovskite films and metasurfaces

Recently, hybrid halide perovskites have emerged as one of the most promising types of materials for thin-film photovoltaic and light-emitting devices because of their low-cost and potential for high efficiency. Further boosting their performance without detrimentally increasing the complexity of the architecture is critically important for commercialization. Despite a number of plasmonic nanoparticle based designs having been proposed for solar cell improvement, inherent optical losses of the nanoparticles reduce photoluminescence from perovskites. Here we use low-loss high-refractive-index dielectric (silicon) nanoparticles for improving the optical properties of organo-metallic perovskite (MAPbI₃) films and metasurfaces to achieve strong enhancement of photoluminescence as well as useful light absorption. As a result, we observed experimentally a 50% enhancement of photoluminescence intensity from a perovskite layer with silicon nanoparticles and 200% enhancement for a nanoimprinted metasurface with silicon nanoparticles on top. Strong increase in light absorption is also demonstrated and described by theoretical calculations. Since both silicon nanoparticle fabrication/deposition and metasurface nanoimprinting techniques are low-cost, we believe that the developed all-dielectric approach paves the way to novel scalable and highly effective designs of perovskite based metadevices.

Ion pinhole imaging diagnostics on fast ion source in femtosecond laser plasma of cluster targets

The spatial configuration of the ion source generated under femtosecond laser interaction with clusters is investigated. While intense laser pulses (36 fs, 60 mJ, intensity of 4 × 10¹⁷ W/cm²) propagated in CO₂ cluster (~0.22 μm in diameter) media, the shape of the obtained plasma ion source was registered for the first time by means of pinhole imaging method. The remarkable decrease in fast ion yield in the vicinity of the assumed best laser focus near the gas cluster jet axis is observed. Such observed anisotropy of the ion source is suggested to originate from the influence of the laser prepulse destroying clusters in advance to the arrival of the main pulse. The assumption is confirmed by optical shadowgraphy images of the plasma channel and is important for further development of an efficient laser-plasma-based fast ion source. Following the observed geometry of the ion source, the laser intensity limit allowing to accelerate ions to ~100 keV energy range was estimated.

Laser printing of resonant plasmonic nanovoids

Hollow reduced-symmetry resonant plasmonic nanostructures possess pronounced tunable optical resonances in the UV-vis-IR range, being a promising platform for advanced nanophotonic devices. However, the present fabrication approaches require several consecutive technological steps to produce such nanostructures, making their large-scale fabrication rather time-consuming and expensive. Here, we report on direct single-step fabrication of large-scale arrays of hollow parabolic- and cone-shaped nanovoids in silver and gold thin films, using single-pulse femtosecond nanoablation at high repetition rates. The lateral and vertical size of such nanovoids was found to be laser energy-tunable. Resonant light scattering from individual nanovoids was observed in the visible spectral range, using dark-field confocal microspectroscopy, with the size-dependent resonant peak positions. These colored geometric resonances in far-field scattering were related to excitation and interference of transverse surface plasmon modes in nanovoid shells. Plasmon-mediated electromagnetic field enhancement near the nanovoids was evaluated via finite-difference time-domain calculations for their model shapes simulated by three-dimensional molecular dynamics, and experimentally verified by means of photoluminescence microscopy and Raman spectroscopy.

The Complex Admixture History and Recent Southern Origins of Siberian Populations

Although Siberia was inhabited by modern humans at an early stage, there is still debate over whether it remained habitable during the extreme cold of the Last Glacial Maximum or whether it was subsequently repopulated by peoples with recent shared ancestry. Previous studies of the genetic history of Siberian populations were hampered by the extensive admixture that appears to have taken place among these populations, because commonly used methods assume a tree-like population history and at most single admixture events. Here we analyze geogenetic maps and use other approaches to distinguish the effects of shared ancestry from prehistoric migrations and contact, and develop a new method based on the covariance of ancestry components, to investigate the potentially complex admixture history. We furthermore adapt a previously devised method of admixture dating for use with multiple events of gene flow, and apply these methods to whole-genome genotype data from over 500 individuals belonging to 20 different Siberian ethnolinguistic groups. The results of these analyses indicate that there have been multiple layers of admixture detectable in most of the Siberian populations, with considerable differences in the admixture histories of individual populations. Furthermore, most of the populations of Siberia included here, even those settled far to the north, appear to have a southern origin, with the northward expansions of different populations possibly being driven partly by the advent of pastoralism, especially reindeer domestication. These newly developed methods to analyze multiple admixture events should aid in the investigation of similarly complex population histories elsewhere.