Wavelength-Tunable Vortex Beam Emitter Based on Silicon Micro-Ring with PN Depletion Diode.

Herein we propose a design of a wavelength-tunable integrated vortex beam emitter based on the silicon-on-insulator platform. The emitter is implemented using a PN-depletion diode inside a microring resonator with the emitting hole grating that was used to produce a vortex beam. The resonance wavelengths can be shifted due to the refractive index change associated with the free plasma dispersion effect. Obtained numerical modeling results confirm the efficiency of the proposed approach, providing a resonance wavelength shift while maintaining the required topological charge of the emitted vortex beam. It is known that optical vortices got a lot of attention due to extensive telecommunication and biochemical applications, but also, they have revealed some beneficial use cases in sensors. Flexibility in spectral tuning demonstrated by the proposed device can significantly improve the accuracy of sensors based on fiber Bragg gratings. Moreover, we demonstrate that the proposed device can provide a displacement of the resonance by the value of the free spectral range of the ring resonator, which means the possibility to implement an ultra-fast orbital angular momentum (de)multiplexing or modulation.

Design and Modeling of a Fully Integrated Microring-Based Photonic Sensing System for Liquid Refractometry.

The design of a refractometric sensing system for liquids analysis with a sensor and the scheme for its intensity interrogation combined on a single photonic integrated circuit (PIC) is proposed. A racetrack microring resonator with a channel for the analyzed liquid formed on the top is used as a sensor, and another microring resonator with a lower Q-factor is utilized to detect the change in the resonant wavelength of the sensor. As a measurement result, the optical power at its drop port is detected in comparison with the sum of the powers at the through and drop ports. Simulations showed the possibility of registering a change in the analyte refractive index with a sensitivity of 110 nm per refractive index unit. The proposed scheme was analyzed with a broadband source, as well as a source based on an optoelectronic oscillator using an optical phase modulator. The second case showed the fundamental possibility of implementing an intensity interrogator on a PIC using an external typical single-mode laser as a source. Meanwhile, additional simulations demonstrated an increased system sensitivity compared to the conventional interrogation scheme with a broadband or tunable light source. The proposed approach provides the opportunity to increase the integration level of a sensing device, significantly reducing its cost, power consumption, and dimensions.

Effect of Chemically Modified Carbon-Coated Iron Nanoparticles on the Structure of Human Atherosclerotic Plaques Ex Vivo and on Adipose Tissue in Chronic Experiment In Vivo.

The high mortality rate caused by atherosclerosis makes it necessary to constantly search for new and better treatments. In previous reports, chemically modified carbon-coated iron nanoparticles (Fe@C NPs) have been demonstrated a high biocompatibility and promising anti-plaque properties. To further investigate these effects, the interaction of these nanoparticles with the adipose tissue of Wistar rats (in vivo) and human atherosclerotic plaques (ex vivo) was studied. For the in vivo study, cobalt-chromium (CoCr) alloy tubes, which are used for coronary stent manufacturing, were prepared with a coating of polylactic acid (PLA) which contained either modified or non-modified Fe@C NPs in a 5% by weight concentration. The tubes were implanted into an area of subcutaneous fat in Wistar rats, where changes in the histological structure and functional properties of the surrounding tissue were observed in the case of coatings modified with Fe@C NPs. For the ex vivo study, freshly explanted human atherosclerotic plaques were treated in the physiological solution with doses of modified Fe@C NPs, with mass equal to 5% or 25% relative to the plaques. This treatment resulted in the release of cholesterol-like compounds from the surface of the plaques into the solution, thus proving a pronounced destructive effect on the plaque structure. Chemically modified Fe@C NPs, when used as an anti-atherosclerosis agent, were able to activate the activity of macrophages, which could lead to the destruction of atherosclerotic plaques structures. These findings could prove the fabrication of next-generation vascular stents with built-in anti-atherosclerotic agents.

Recent Advances in Generation and Detection of Orbital Angular Momentum Optical Beams-A Review.

Herein, we have discussed three major methods which have been generally employed for the generation of optical beams with orbital angular momentum (OAM). These methods include the practice of diffractive optics elements (DOEs), metasurfaces (MSs), and photonic integrated circuits (PICs) for the production of in-plane and out-of-plane OAM. This topic has been significantly evolved as a result; these three methods have been further implemented efficiently by different novel approaches which are discussed as well. Furthermore, development in the OAM detection techniques has also been presented. We have tried our best to bring novel and up-to-date information to the readers on this interesting and widely investigated topic.

Micromanipulation of Live Microdissected Tissues with a Low-Cost Integrated Robotic Platform.

The small amount of human tissue available for testing is a paramount challenge in cancer drug development, cancer disease models, and personalized oncology. Technologies that combine the microscale manipulation of tissues with fluid handling offer the exciting possibility of miniaturizing and automating drug evaluation workflows. This approach minimizes animal testing and enables inexpensive, more efficient testing of samples with high clinical biomimicry using scarce materials. We have developed an inexpensive platform based on an off-the-shelf robot that can manipulate microdissected tissues (µDTs) into user-programmed positions without using intricate microfluidic designs nor any other accessories such as a microscope or a pneumatic controller. The robot integrates complex functions such as vision and fluid actuation by incorporating simple items including a USB camera and a rotary pump. Through the robot's camera, the platform software optically recognizes randomly-seeded µDTs on the surface of a petri dish and positions a mechanical arm above the µDTs. Then, a custom rotary pump actuated by one of the robot's motors generates enough microfluidic lift to hydrodynamically pick and place µDTs with a pipette at a safe distance from the substrate without requiring a proximity sensor. The platform's simple, integrated construction is cost-effective and compact, allowing placement inside a tissue culture hood for sterile workflows. The platform enables users to select µDTs based on their size, place them in user-programmed arrays, such as multi-well plates, and control various robot motion parameters. As a case application, we use the robotic system to conduct semi-automated drug testing of mouse and human µDTs in 384-well plates. Our user-friendly platform promises to democratize microscale tissue research to clinical and biological laboratories worldwide.

Angiotensin 1-7 increases cardiac tolerance to ischemia/reperfusion and mitigates adverse remodeling of the heart-The signaling mechanism.

BACKGROUND: The high mortality rate of patients with acute myocardial infarction (AMI) remains the most pressing issue of modern cardiology. Over the past 10 years, there has been no significant reduction in mortality among patients with AMI. It is quite obvious that there is an urgent need to develop fundamentally new drugs for the treatment of AMI. Angiotensin 1-7 has some promise in this regard. OBJECTIVE: The objective of this article is analysis of published data on the cardioprotective properties of angiotensin 1-7. METHODS: PubMed, Scopus, Science Direct, and Google Scholar were used to search articles for this study. RESULTS: Angiotensin 1-7 increases cardiac tolerance to ischemia/reperfusion and mitigates adverse remodeling of the heart. Angiotensin 1-7 can prevent not only ischemic but also reperfusion cardiac injury. The activation of the Mas receptor plays a key role in these effects of angiotensin 1-7. Angiotensin 1-7 alleviates Ca2+ overload of cardiomyocytes and reactive oxygen species production in ischemia/reperfusion (I/R) of the myocardium. It is possible that both effects are involved in angiotensin 1-7-triggered cardiac tolerance to I/R. Furthermore, angiotensin 1-7 inhibits apoptosis of cardiomyocytes and stimulates autophagy of cells. There is also indirect evidence suggesting that angiotensin 1-7 inhibits ferroptosis in cardiomyocytes. Moreover, angiotensin 1-7 possesses anti-inflammatory properties, possibly achieved through NF-kB activity inhibition. Phosphoinositide 3-kinase, Akt, and NO synthase are involved in the infarct-reducing effect of angiotensin 1-7. However, the specific end-effector of the cardioprotective impact of angiotensin 1-7 remains unknown. CONCLUSION: The molecular nature of the end-effector of the infarct-limiting effect of angiotensin 1-7 has not been elucidated. Perhaps, this end-effector is the sarcolemmal KATP channel or the mitochondrial KATP channel.

Insights into ascending aortic aneurysm: Interactions between biomechanical properties of the aortic wall and tissue biomarkers.

Background: It remains difficult to understand the association between the local mechanical properties of ascending thoracic aorta aneurysm (asTAA), its tissue, and its cellular and molecular changes. The purpose of our study was to investigate the relationship between biomechanical properties, histopathological findings, and tissue biomarkers of asTAA. Methods: Intraoperative asTAA samples from 30 patients were studied. All samples were examined histologically and underwent a tensile test. We determined the tensile strength (σв, MPa), the strain (ε, mm/mm˟%), and the area under the strength-strain curve (S) along with the concentrations of tissue matrix metalloproteinases (MMP-1 et al.) and their inhibitors, their interleukins (IL) -6 -10, and their tumor necrosis factor (TNF) -α. Results: It was found that 43.3 % of asTAA patients had atherosclerosis, 3.3 % had aortitis, and 53.3 % of patients had connective tissue dysplasia. Differences in the studied parameters between these subgroups were not found. Age correlated with ε (r = -0.49) and S (r = -0.54). ε was also associated with media fibrosis degree (r = -0.5), collagen/elastin ratio (r = -0.61), and IL-10 (r = 0.52). IL-10 correlated with collagen/elastin ratio (r = -0.58), TNF-α (r = 0.77), and MMP-1 (r = 0.71). Conclusion: Tissue IL-10 has a protective effect on the elastic structures of the aortic wall and is positively associated with the activity of MMP-1 and pro-inflammatory cytokines. IL-6 is associated with media fibrosis degree, and negatively affects strength-strain parameters of asTAA samples.

Microdissected tumor cuboids: a microscale cancer model that retains a complex tumor microenvironment.

Present cancer disease models - typically based on cell cultures and animal models that lack the human tumor microenvironment (TME) - are extremely poor predictors of human disease outcomes. Microscale cancer models that combine the micromanipulation of tissues and fluids offer the exciting possibility of miniaturizing the drug testing workflow, enabling inexpensive, more efficient tests of high clinical biomimicry that maximize the use of scarce human tissue and minimize animal testing. Critically, these microscale models allow for precisely addressing the impact of the structural features of the heterogeneous TME to properly target and understand the contributions of these unique zones to therapeutic response. We have recently developed a precision slicing method that yields large numbers of cuboidal micro-tissues ("cuboids", ∼ (400 µm) 3 ) from a single tumor biopsy. Here we evaluate cuboids from syngeneic mouse tumor models and human tumors, which contain native immune cells, as models for drug and immunotherapy evaluation. We characterize relevant TME parameters, such as their cellular architecture (immune cells and vasculature), cytokine secretion, proteomics profiles, and their response to drug panels in multi-well arrays. Despite the cutting procedure and the time spent in culture (up to 7 days), the cuboids display strong functional responses such as cytokine and drug responses. Overall, our results suggest that cuboids make an excellent model for applications that require the TME, such as immunotherapy drug evaluations, including for clinical trials and personalized oncology approaches.

Macrophages of the Cardiorenal Axis and Myocardial Infarction.

The aim of our study was to compare the features of macrophage (mf) composition of the kidneys in patients with fatal myocardial infarction (MI) and in patients without cardiovascular diseases (CVD). We used kidney fragments taken during autopsy. Macrophage infiltration was assessed by immunohistochemistry: antibodies CD68 were used as a common mf marker, CD80-M1 type mf marker, CD163, CD206, and stabilin-1-M2 type. Macrophage composition of the kidneys in patients with fatal MI was characterized by the predominance of CD163+ cells among studied cells, and the control group was characterized by the predominance of CD163+, CD206+, and CD68+. In patients with MI, biphasic response from kidney cells was characterized for CD80+ and CD206+: their number decreased by the long-term period of MI; other cells did not show any dynamics. The exact number of CD80+ cells in kidneys of individuals without CVD was slightly higher than in patients with MI, and the number of CD206+-strikingly predominant. Subsequent analysis of CD80+ and CD206+ cells in a larger sample, as well as comparison of data with results obtained from survivors of MI, may bring us closer to understanding whether the influence on these cells can serve as a new target in personalized therapy in postinfarction complications.

Old wine into new wineskins? "Legacy data" in research on Roman Period East Germanic iron smelting.

This paper discusses the use of "legacy data" in research on Roman Period iron smelting in the territory of the Przeworsk Culture in Magna Germania. The dataset includes results of 240 analyses of smelting slag and iron ores chemistry. A majority of these analyses were conducted in the 1950s-1980s. The quality of these data is far below present-day standards. Only major elements were reported, analytical methods were often not specified (although optical emission spectroscopy and wet chemical analyses can be assumed in such cases) and information on detection limits, precision and accuracy of the results is missing. In spite of this, a Principal Component Analysis-Agglomerative Hierarchical Clustering treatment successfully isolated observations from the three main iron smelting regions of the Przeworsk Culture (the Holy Cross Mountains, Masovia and Silesia). These results to a degree confirm a theory proposed in the 1960s by J. Piaskowski, according to whom it was possible to distinguish iron produced in the Holy Cross Mountains from the iron produced elsewhere in the territory of what is now Poland on the basis of metal characteristics. These findings will pave the way to the ongoing research project on the Przeworsk Culture metallurgy. It is also argued that, apart from a search for new methods in iron provenance studies, more attention should be paid to results of earlier analyses and to a compilation of legacy databases. The other result is an open and flexible Agglomerative Hierarchical Clustering R code to examine discrimination between production areas and to propose artefact provenance patterns in a convenient interactive way using the R development environment.

Enhancing the Performance of the Photonic Integrated Sensing System by Applying Frequency Interrogation.

Lab-on-a-chip systems are currently one of the most promising areas in the development of ultra-compact sensor systems, used primarily for gas and liquid analysis to determine the concentration of impurities. Integrated photonics is an ideal basis for designing "lab-on-a-chip" systems, advantageous for its compactness, energy efficiency, and low cost in mass production. This paper presents a solution for "lab-on-a-chip" device realization, consisting of a sensor and an interrogator based on a silicon-on-insulator (SOI) integrated photonics platform. The sensor function is performed by an all-pass microring resonator (MRR), installed as a notch filter in the feedback circuit of an optoelectronic oscillator based on an electro-optic phase modulator. This structure realizes the frequency interrogation of the sensor with high accuracy and speed using a conventional single-mode laser source. The system sensitivity for the considered gases is 13,000 GHz/RIU. The results show that the use of frequency interrogation makes it possible to increase the intrinsic LoD by five orders. The proposed solution opens an opportunity for fully integrated implementation of a photonic "laboratory-on-a-chip" unit.

Micro-Ring Resonator-Based Tunable Vortex Beam Emitter.

Light beams bearing orbital angular momentum (OAM) are used in various scientific and engineering applications, such as microscopy, laser material processing, and optical tweezers. Precise topological charge control is crucial for efficiently using vortex beams in different fields, such as information encoding in optical communications and sensor systems. This work presents a novel method for optimizing an emitting micro-ring resonator (MRR) for emitting vortex beams with variable orders of OAM. The MRR consists of a ring waveguide with periodic structures side-coupled to a bus waveguide. The resonator is tunable due to the phase change material Sb2Se3 deposited on the ring. This material can change from amorphous to crystalline while changing its refractive index. In the amorphous phase, it is 3.285 + 0i, while in the transition to the crystalline phase, it reaches 4.050 + 0i at emission wavelength 1550 nm. We used this property to control the vortex beam topological charge. In our study, we optimized the distance between the bus waveguide and the ring waveguide, the bending angle, and the width of the bus waveguide. The optimality criterion was chosen to maximize the flux density of the radiated energy emitted by the resonator. The numerical simulation results proved our method. The proposed approach can be used to optimize optical beam emitters carrying OAM for various applications.

Analyzing Russian Media Policy on Promoting Vaccination and Other COVID-19 Risk Mitigation Measures.

The coronavirus disease 2019 (COVID-19) pandemic has resulted in many tangible and intangible losses. To manage the risk of the pandemic and to mitigate its further spread, governments of many countries applied various pandemic risk mitigation measures. Media campaigns played a particularly large role during the pandemic, too. In addition, social media grew in importance because of the spread of technologies and as a result of the increased attention to information about COVID-19. Media information strongly influenced both the public perception of COVID-19 risk and decision-making processes and choices, which people made regarding risk reduction measures during the pandemic. Moreover, media information has had a major impact on the effectiveness and efficiency of various countries' risk management actions. Therefore, the purpose of this article is to investigate the influence of the Russian media on the population's perception of risk, and to address the question about which linguistic and psychological methods they used to shape different media discourses about the COVID-19 pandemic. Thus, we analyzed media discourses as a part of the case study of COVID-19 risk management in the Russian Federation. The theoretical basis of the study includes mass communication theories. The methodological basis consists of linguo-cognitive analysis of empirical materials for specific political-philosophical, linguistic-publicistic, and sociopsychological functioning.

Characteristics of the Cardiosplenic Axis in Patients with Fatal Myocardial Infarction.

Myocardial ischemia triggers neurohumoral activation of the cardiosplenic axis. In rodents, adverse outcomes occur upon prolonged entrance of mononuclear cells from the spleen into myocardial tissue. The purpose of this study is to assess the features of spleen structure in patients with fatal myocardial infarction (MI), the dynamics of macrophage infiltration of the spleen and its relationship with cardiac macrophage infiltration and unfavorable outcomes. Using immunohistochemistry techniques, we analyzed the macrophage infiltration of the spleen and myocardium sections collected from patients (n = 30) with fatal MI. The spleen of the patients was decreased and showed a predominance of red pulp with a high concentration of CD68+ and stabilin-1+ cells. The white pulp contained many medium and small follicles and a lower concentration of CD68+ and stabilin-1+ cells, which was comparable to that in the infarct area of the myocardium. The concentration of CD68+ and stabilin-1+ cells increased in the myocardium in the late period of MI, but did not show any dynamics in the spleen. A high number of CD68+ cells in the red pulp and reduced concentration of stabilin-1+ cells in the white pulp were associated with unfavorable post-infarction outcomes. These fundamental findings could be a basis for the development of new personalized therapeutic and diagnostic approaches for the treatment of MI and its complications.

Minimally Invasive Resection of a Gangliocytic Paraganglioma of the Cauda Equina: A Case Report and Review of Literature.

Gangliocytic paraganglioma (GP) is considered a rare neuroendocrine tumor (NET) most often located in the distal half of the duodenum. Insufficient reports describe tumors of this histological type located in the distal parts of the spinal canal, the conus medullaris and cauda equina. To date, nine cases of GP of the cauda equina and one case of GP of conus medullaris have been described. After analyzing all available treatment reports of GP, a study described it as a tumor with an extremely good prognosis in cases of total tumor removal. Here, we present a case of a female patient with a GP at the level of the L4 vertebra treated at Burdenko Neurosurgical Center using a minimally invasive approach through a tubular retractor. The tumor was removed en bloc through an intralaminar opening, and the patient was discharged two days after surgery with total regression of symptoms.

Mid-Term to Long-Term Outcomes After Total Cervical Disk Arthroplasty Compared With Anterior Diskectomy and Fusion: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

STUDY DESIGN: This study was a meta-analysis of published randomized controlled trials (RCTs). OBJECTIVE: We investigated the mid-term to long-term outcomes of cervical disk arthroplasty (CDA) versus anterior cervical diskectomy and fusion (ACDF) for the surgical treatment of symptomatic cervical disk degenerative disease. SUMMARY OF BACKGROUND DATA: ACDF has been widely performed for the surgical treatment of symptomatic cervical disk degenerative disease. However, the loss of motion at the operated level has been hypothesized to accelerate adjacent-level disk degeneration. CDA was designed to preserve motion segments and decrease the risk/rate of adjacent segment degeneration. However, it is still uncertain whether mid-term to long-term outcomes after CDA is more effective and safer than those observed after ACDF. METHODS: Two independent reviewers conducted a search of PubMed, Embase, and the Cochrane Library databases for RCTs with a minimum of 48 months of follow-up. For dichotomous variables, the risk ratio and 95% confidence intervals were calculated. For continuous variables, the standardized mean difference and 95% confidence intervals were calculated. RESULTS: Eleven RCTs, finally, were included. The rate of neurological success in the CDA group was not significantly different from that in the ACDF group. The pooled results show that patients who underwent CDA had a significantly greater improvement in Neck Disability Index (NDI) and Short Form 36 Health Survey physical component (SF-36 HSPC) than did those who underwent ACDF. No significant difference was found when comparing the neck and arm pain scores between the CDA and ACDF groups. The overall rate of secondary surgical procedures was significantly lower in patients who underwent CDA than in those who underwent ACDF. We observed similar overall rates of adverse events and adjacent segment degeneration when comparing the CDA group with the ACDF group. CONCLUSIONS: This meta-analysis provides evidence suggesting that CDA was superior to ACDF in terms of NDI score, SF-36 HSPC score, and low rate of secondary surgical procedures. Furthermore, no significant differences existed between the CDA group and the ACDF group in the neck pain visual analog scale score, arm pain visual analog scale score, the rate of neurological success, adjacent segment degeneration, and adverse events. LEVEL OF EVIDENCE: Level 1.

A systematic review and meta-analysis comparing open versus endoscopic in situ decompression for the treatment of cubital tunnel syndrome.

To examine whether endoscopic in situ decompression (EISD) or open in situ decompression (OISD) would have superior outcomes with lower morbidity in patients with idiopathic cubital tunnel syndrome, we reviewed all studies compared both surgical techniques with regard to postoperative outcomes and complication profile in a systematic review design with meta-analysis. Two independent reviewers conducted a PRISMA-compliant search of PubMed, EMBASE, and the Cochrane Library databases for relevant studies about clinical comparisons of OISD and EISD in cubital tunnel syndrome. We performed all meta-analyses with the Review Manager 5.3 software. For dichotomous variables, the risk ratio (RR) and 95% confidence intervals (CIs) were calculated. For continuous variables, the mean difference (MD) and 95% CIs were calculated. The level of significance was set as p < 0.05. Finally, 8 articles with 582 patients finally were included in this meta-analysis. Pooled analysis showed that the difference in Bishop score, visual analogue scale score reduction, postoperative satisfaction, postoperative hematoma rate and secondary surgical procedures were not statistically significant between the EISD group and the OISD group (p > 0.05). However, pooled results showed that patients who underwent EISD had a greater improvement in the scar tenderness/elbow pain than did those who underwent OISD with statistical significance (p < 0.0001). This meta-analysis demonstrated that EISD and OISD for surgical treating cubital tunnel syndrome had equivalent efficacy regarding postoperative clinical recovery, whereas the incidences of adverse events of EISD were also same as those with the OISD technique.

Osmium isotope analysis as an innovative tool for provenancing ancient iron: A systematic approach.

The innovation of iron production is often considered one of the greatest technological advances in human history. A reliable provenancing method for iron is instrumental for the reconstruction of economic, social and geo-political aspects of iron production and use in antiquity. Although the potential of osmium isotopes analysis for this purpose has been previously suggested, here we present for the first time the results of osmium isotope analysis of ores, bloom and metal obtained from a set of systematic, bloomery iron-smelting experiments, utilizing selected ores from the Southern Levant. The results show that the 187Os/188Os ratio is preserved from ore to metal, with no isotopic fractionation. In addition, enrichment/depletion of osmium content was observed in the transition from ore to metal and from ore to slag. This observation has potential significance for our ability to differentiate between the various processes and sheds light on the suitability of various production remains for this method, which emerges as a robust and promising tool for the provenancing of archaeological ferrous metals.

Supporting data and methods for the characterization of iron oxide nanoparticles conjugated with pH-(low)-insertion peptide, testing their cytotoxicity and analyses of biodistribution in SCID mice bearing MDA-MB231 tumor.

The method of Fe3O4 magnetic nanoparticle synthesis by co-precipitation, modification by 3-aminopropylsilane and conjugation with pH-(low)-insertion peptide (pHLIP) is reported. The characterization of nanoparticles by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, elemental and thermogravimetric analyses as well as dynamic light scattering and z-potential measurements is provided. The effect of nanoparticles on the viability of mouse and human peripheral blood mononuclear cells is tested by flow cytometry. The experimental details of nanoparticle administration to tumor-bearing mice, magnetic resonance imaging scanning as well as subsequent tumor sample collection and their processing for transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy, histological and immunohistochemical analyses are described. Biodistribution of the nanoparticles in mice and blood serum analysis data for experimental animals are given. The data are useful for an experiment workflow design and for the development of theranostic systems based on magnetic nanoparticles.

Microvascular Anastomosis Training in Neurosurgery: A Review.

Cerebrovascular diseases are among the most widespread diseases in the world, which largely determine the structure of morbidity and mortality rates. Microvascular anastomosis techniques are important for revascularization surgeries on brachiocephalic and carotid arteries and complex cerebral aneurysms and even during resection of brain tumors that obstruct major cerebral arteries. Training in microvascular surgery became even more difficult with less case exposure and growth of the use of endovascular techniques. In this text we will briefly discuss the history of microvascular surgery, review current literature on simulation models with the emphasis on their merits and shortcomings, and describe the views and opinions on the future of the microvascular training in neurosurgery. In "dry" microsurgical training, various models created from artificial materials that simulate biological tissues are used. The next stage in training more experienced surgeons is to work with nonliving tissue models. Microvascular training using live models is considered to be the most relevant due to presence of the blood flow. Training on laboratory animals has high indicators of face and constructive validity. One of the future directions in the development of microsurgical techniques is the use of robotic systems. Robotic systems may play a role in teaching future generations of microsurgeons. Modern technologies allow access to highly accurate learning environments that are extremely similar to real environment. Additionally, assessment of microsurgical skills should become a fundamental part of the current evaluation of competence within a microneurosurgical training program. Such an assessment tool could be utilized to ensure a constant level of surgical competence within the recertification process. It is important that this evaluation be based on validated models.