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National University of Uzbekistan

UniversityTashkent, Uzbekistan

Research output, citation impact, and the most-cited recent papers from National University of Uzbekistan (Uzbekistan). Aggregated across the NobleBlocks index of 300M+ scholarly works.

Total works
15.6K
Citations
95.4K
h-index
100
i10-index
2.4K
Also known as
National University of UzbekistanOʻzbekiston Milliy UniversitetiНациональный университет Узбекистана

Top-cited papers from National University of Uzbekistan

Salt-Tolerant Plant Growth Promoting Rhizobacteria for Enhancing Crop Productivity of Saline Soils
Dilfuza Egamberdieva, Stephan Wirth, Sonoko Dorothea Bellingrath‐Kimura, Jitendra Mishra +1 more
2019· Frontiers in Microbiology561doi:10.3389/fmicb.2019.02791

, etc.) are of limited success and also adversely affect the agro-ecosystems. In this context, developing sustainable methods which increase the productivity of saline soil without harming the environment are necessary. Since long, breeding of salt-tolerant plants and development of salt-resistant crop varieties have also been tried, but these and aforesaid conventional approaches are not able to solve the problem. Salt tolerance and dependence are the characteristics of some microbes. Salt-tolerant microbes can survive in osmotic and ionic stress. Various genera of salt-tolerant plant growth promoting rhizobacteria (ST-PGPR) have been isolated from extreme alkaline, saline, and sodic soils. Many of them are also known to mitigate various biotic and abiotic stresses in plants. In the last few years, potential PGPR enhancing the productivity of plants facing salt-stress have been researched upon suggesting that ST-PGPR can be exploited for the reclamation of saline agro-ecosystems. In this review, ST-PGPR and their potential in enhancing the productivity of saline agro-ecosystems will be discussed. Apart from this, PGPR mediated mechanisms of salt tolerance in different crop plants and future research trends of using ST-PGPR for reclamation of saline soils will also be highlighted.

Shadow of rotating regular black holes
Ahmadjon Abdujabbarov, M. Jamil Amir, Bobomurat Ahmedov, Sushant G. Ghosh
2016· Physical review. D/Physical review. D.398doi:10.1103/physrevd.93.104004

We study the shadows cast by the different types of rotating regular black holes viz. Ay\'on-Beato-Garc\'{\i}a (ABG), Hayward, and Bardeen. These black holes have in addition to the total mass ($M$) and rotation parameter ($a$), different parameters as electric charge ($Q$), deviation parameter ($g$), and magnetic charge (${g}_{*}$). Interestingly, the size of the shadow is affected by these parameters in addition to the rotation parameter. We found that the radius of the shadow in each case decreases monotonically, and the distortion parameter increases when the values of these parameters increase. A comparison with the standard Kerr case is also investigated. We have also studied the influence of the plasma environment around regular black holes to discuss its shadow. The presence of the plasma affects the apparent size of the regular black hole's shadow to be increased due to two effects: (i) gravitational redshift of the photons and (ii) radial dependence of plasma density.

Global Retinoblastoma Presentation and Analysis by National Income Level
Global Retinoblastoma Study Group, Ido Didi Fabian, Abdallah Elhassan, Shehu U. Abdullahi +4 more
2020· JAMA Oncology368doi:10.1001/jamaoncol.2019.6716

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4%) were female. Most patients (n = 3685 [84.7%]) were from low- and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 [62.8%]), followed by strabismus (n = 429 [10.2%]) and proptosis (n = 309 [7.4%]). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 [95% CI, 12.94-24.80], and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 [95% CI, 4.30-7.68]). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs.

High incidence of plant growth‐stimulating bacteria associated with the rhizosphere of wheat grown on salinated soil in Uzbekistan
Dilfuza Egamberdieva, Faina Kamilova, Shamil Validov, Lazizakhon Gafurova +2 more
2007· Environmental Microbiology362doi:10.1111/j.1462-2920.2007.01424.x

Soil salinization is increasing steadily in many parts of the world and causes major problems for plant productivity. Under these stress conditions, root-associated beneficial bacteria can help improve plant growth and nutrition. In this study, salt-tolerant bacteria from the rhizosphere of Uzbek wheat with potentially beneficial traits were isolated and characterized. Eight strains which initially positively affect the growth of wheat plants in vitro were investigated in detail. All eight strains are salt tolerant and have some of the following plant growth-beneficial properties: production of auxin, HCN, lipase or protease and wheat growth promotion. Using sequencing of part of the 16S rDNA, the eight new isolates were identified as Acinetobacter (two strains), Pseudomonas aeruginosa, Staphylococcus saprophyticus, Bacillus cereus, Enterobacter hormaechei, Pantoae agglomerans and Alcaligenes faecalis. All these strains are potential human pathogens. Possible reasons for why these bacteria present in the rhizosphere and establish there are discussed.

Arbuscular mycorrhizal fungi regulate the oxidative system, hormones and ionic equilibrium to trigger salt stress tolerance in Cucumis sativus L.
Abeer Hashem, Abdulaziz A. Alqarawi, Ramalingam Radhakrishnan, Al-Bandari Fahad Al-Arjani +3 more
2018· Saudi Journal of Biological Sciences313doi:10.1016/j.sjbs.2018.03.009

Arbuscular mycorrhizal fungi (AMF) association increases plant stress tolerance. This study aimed to determine the mitigation effect of AMF on the growth and metabolic changes of cucumbers under adverse impact of salt stress. Salinity reduced the water content and synthesis of pigments. However, AMF inoculation ameliorated negative effects by enhancing the biomass, synthesis of pigments, activity of antioxidant enzymes, including superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase, and the content of ascorbic acid, which might be the result of lower level lipid peroxidation and electrolyte leakage. An accumulation of phenols and proline in AMF-inoculated plants also mediated the elimination of superoxide radicals. In addition, jasmonic acid, salicylic acid and several important mineral elements (K, Ca, Mg, Zn, Fe, Mn and Cu) were enhanced with significant reductions in the uptake of deleterious ions like Na+. These results suggested that AMF can protect cucumber growth from salt stress.

Organic and inorganic nanomaterials: fabrication, properties and applications
Basmah H. Alshammari, Maha M. A. Lashin, Muhammad Adil Mahmood, Fahad S. Al‐Mubaddel +4 more
2023· RSC Advances295doi:10.1039/d3ra01421e

Nanomaterials and nanoparticles are a burgeoning field of research and a rapidly expanding technology sector in a wide variety of application domains. Nanomaterials have made exponential progress due to their numerous uses in a variety of fields, particularly the advancement of engineering technology. Nanoparticles are divided into various groups based on the size, shape, and structural morphology of their bodies. The 21st century's defining feature of nanoparticles is their application in the design and production of semiconductor devices made of metals, metal oxides, carbon allotropes, and chalcogenides. For the researchers, these materials then opened a new door to a variety of applications, including energy storage, catalysis, and biosensors, as well as devices for conversion and medicinal uses. For chemical and thermal applications, ZnO is one of the most stable n-type semiconducting materials available. It is utilised in a wide range of products, from luminous materials to batteries, supercapacitors, solar cells to biomedical photocatalysis sensors, and it may be found in a number of forms, including pellets, nanoparticles, bulk crystals, and thin films. The distinctive physiochemical characteristics of semiconducting metal oxides are particularly responsible for this. ZnO nanostructures differ depending on the synthesis conditions, growth method, growth process, and substrate type. A number of distinct growth strategies for ZnO nanostructures, including chemical, physical, and biological methods, have been recorded. These nanostructures may be synthesized very simply at very low temperatures. This review focuses on and summarizes recent achievements in fabricating semiconductor devices based on nanostructured materials as 2D materials as well as rapidly developing hybrid structures. Apart from this, challenges and promising prospects in this research field are also discussed.

Endophytic Bacteria Improve Plant Growth, Symbiotic Performance of Chickpea (Cicer arietinum L.) and Induce Suppression of Root Rot Caused by Fusarium solani under Salt Stress
Dilfuza Egamberdieva, Stephan Wirth, Vyacheslav Shurigin, Abeer Hashem +1 more
2017· Frontiers in Microbiology295doi:10.3389/fmicb.2017.01887

Salinity causes disturbance in symbiotic performance of plants, and increases susceptibility of plants to soil-borne pathogens. Endophytic bacteria are an essential determinant of cross-tolerance to biotic and abiotic stresses in plants. The aim of this study was to isolate non–rhizobial endophytic bacteria from the root nodules of chickpea (Cicer arietinum L.), and to assess their ability to improve plant growth and symbiotic performance, and to control root rot in chickpea under saline soil conditions. A total of forty bacterial isolates from internal root tissues of chickpea grown in salinated soil were isolated. Four bacterial isolates, namely Bacillus cereus NUU1, Achromobacter xylosoxidans NUU2, Bacillus thuringiensis NUU3 and Bacillus subtilis NUU4 colonising root tissue demonstrated plant beneficial traits and/or antagonistic activity against F. solani and thus were characterized in more detail. The strain B. subtilis NUU4 proved significant plant growth promotion capabilities, improved symbiotic performance of host plant with rhizobia, and promoted yield under saline soil as compared to untreated control plants under field conditions. A combined inoculation of chickpea with M. ciceri IC53 and B. subtilis NUU4 decreased H2O2 concentrations and increased proline contents compared to the un-inoculated plants indicating an alleviation of adverse effects of salt stress. Furthermore, the bacterial isolate was capable to reduce the infection rate of root rot in chickpea caused by F. solani. This is the first report of F. solani causing root rot of chickpea in a salinated soil of Uzbekistan. Our findings demonstrated that the endophytic Bacillus subtilis strain NUU4 provides high potentials as a stimulator for plant growth and as biological control agent of chickpea root rot under saline soil conditions. These multiple relationships could provide promising practical approaches to increase the productivity of legumes under salt stress.

Endophytic bacterium<i>Bacillus subtilis</i>(BERA 71) improves salt tolerance in chickpea plants by regulating the plant defense mechanisms
Elsayed Fathi Abd Allah, Abdulaziz A. Alqarawi, Abeer Hashem, Ramalingam Radhakrishnan +4 more
2017· Journal of Plant Interactions237doi:10.1080/17429145.2017.1414321

Plant growth-promoting endophytic bacteria can stimulate the growth, nutrient acquisition, symbiotic performance and stress tolerance of chickpea plants under saline soil conditions. The aim of this study was to investigate the stress-adaptive mechanisms of chickpea plants mediated by Bacillus subtilis (BERA 71) under saline conditions. Inoculation with BERA 71 enhanced plant biomass and the synthesis of photosynthetic pigments and reduced the levels of reactive oxygen species (ROS) and lipid peroxidation in plants under conditions of stress. Furthermore, the activities of ROS-scavenging antioxidant enzymes (superoxide dismutase, peroxidase, catalase and glutathione reductase), the levels of non-enzymatic antioxidants (ascorbic acid and glutathione) and the total phenol content were increased in stressed plants during bacterial association. The bacteria decreased sodium accumulation and enhanced the nitrogen, potassium, calcium and magnesium content in the plants. The suppression of ROS generation and of lipid peroxidation and the accumulation of proline in BERA-71-inoculated plants enhanced the membrane stability under salinity stress and non-stress conditions.

Optical properties of black holes in the presence of a plasma: The shadow
Farruh Atamurotov, Bobomurat Ahmedov, Ahmadjon Abdujabbarov
2015· Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology233doi:10.1103/physrevd.92.084005

We have studied photon motion around axially symmetric rotating Kerr black holes in the presence of a plasma with radial power-law density. It is shown that in the presence of a plasma, the observed shape and size of the shadow changes depending on the (i) plasma parameters, (ii) black hole spin, and (iii) inclination angle between the observer plane and the axis of rotation of the black hole. In order to extract the pure effect of the plasma influence on the black hole image, the particular case of the Schwarzschild black hole has also been investigated and it has been shown that the photon sphere around the spherically symmetric black hole is left unchanged under the plasma influence; however, the Schwarzschild black hole shadow size in the plasma is reduced due to the refraction of the electromagnetic radiation in the plasma environment of the black hole. The study of the energy emission from the black hole in plasma environment shows that in the presence of the plasma the maximal energy emission rate from the black hole decreases.

QUADRATIC STOCHASTIC OPERATORS AND PROCESSES: RESULTS AND OPEN PROBLEMS
Rasul Ganikhodzhaev, Farrukh Mukhamedov, U. A. Rozikov
2011· Infinite Dimensional Analysis Quantum Probability and Related Topics230doi:10.1142/s0219025711004365

The history of the quadratic stochastic operators can be traced back to the work of Bernshtein (1924). For more than 80 years, this theory has been developed and many papers were published. In recent years it has again become of interest in connection with its numerous applications in many branches of mathematics, biology and physics. But most results of the theory were published in non-English journals, full text of which are not accessible. In this paper we give all necessary definitions and a brief description of the results for three cases: (i) discrete-time dynamical systems generated by quadratic stochastic operators; (ii) continuous-time stochastic processes generated by quadratic operators; (iii) quantum quadratic stochastic operators and processes. Moreover, we discuss several open problems.

A coordinate-independent characterization of a black hole shadow
Ahmadjon Abdujabbarov, Luciano Rezzolla, Bobomurat Ahmedov
2015· Monthly Notices of the Royal Astronomical Society228doi:10.1093/mnras/stv2079

A large international effort is under way to assess the presence of a shadow in the radio emission from the compact source at the centre of our Galaxy, Sagittarius A * (Sgr A * ). If detected, this shadow would provide the first direct evidence of the existence of black holes and that Sgr A * is a supermassive black hole. In addition, the shape of the shadow could be used to learn about extreme gravity near the event horizon and to determine which theory of gravity better describes the observations. The mathematical description of the shadow has so far used a number of simplifying assumptions that are unlikely to be met by the real observational data. We here provide a general formalism to describe the shadow as an arbitrary polar curve expressed in terms of a Legendre expansion. Our formalism does not presume any knowledge of the properties of the shadow, e.g. the location of its centre, and offers a number of routes to characterize the distortions of the curve with respect to reference circles. These distortions can be implemented in a coordinate-independent manner by different teams analysing the same data. We show that the new formalism provides an accurate and robust description of noisy observational data, with smaller error variances when compared to previous approaches for the measurement of the distortion.

A future prospects and current scenario of aluminium metal matrix composites characteristics
Bharat Singh, Indradeep Kumar, Kuldeep K. Saxena, Kahtan A. Mohammed +3 more
2023· Alexandria Engineering Journal216doi:10.1016/j.aej.2023.06.028

This paper provides a synergistic review of the current scenario and future prospects of aluminum metal matrix composites (AMMCs). AMMCs are advanced materials that have garnered significant attention in recent years due to their unique characteristics, including high strength, low density, and excellent wear resistance. This review covers various aspects of AMMCs, including processing techniques, mechanical and physical properties, microstructural features, and applications. The review begins with an overview of different processing techniques for AMMCs, including stir casting, powder metallurgy, and infiltration methods. It then discusses the mechanical and physical properties of AMMCs, such as tensile strength, hardness, and thermal conductivity, and how these properties are influenced by various factors such as reinforcement type, size, and volume fraction. Furthermore, the microstructural features of AMMCs, including the distribution of reinforcements, are discussed in detail. The review also highlights the potential applications of AMMCs in various industries such as aerospace, automotive, and electronics. Finally, the review concludes by discussing the current scenario and future prospects of AMMCs. It highlights the challenges that need to be addressed to enhance the performance of AMMCs and the potential areas of research that could lead to the development of advanced AMMCs with superior properties. Overall, this review provides a comprehensive overview of the current status and future prospects of AMMCs and highlights the importance of continued research and development in this field.

Coordination between<i>Bradyrhizobium</i>and<i>Pseudomonas</i>alleviates salt stress in soybean through altering root system architecture
Dilfuza Egamberdieva, Stephan Wirth, Dilfuza Jabborova, Leena Räsänen +1 more
2017· Journal of Plant Interactions187doi:10.1080/17429145.2017.1294212

It is a well accepted strategy to improve plant salt tolerance through inoculation with beneficial microorganisms. However, its underlying mechanisms still remain unclear. In the present study, hydroponic experiments were conducted to evaluate the effects of Bradyrhizobium japonicum USDA 110 with salt-tolerant Pseudomonas putida TSAU1 on growth, protein content, nitrogen, and phosphorus uptake as well as root system architecture of soybean (Glycine max L.) under salt stress. The results indicated that the combined inoculation with USDA 110 and TSAU1 significantly improved plant growth, nitrogen and phosphorus contents, and contents of soluble leaf proteins under salt stress compared to the inoculation with the symbiont alone or compared to un-inoculated ones. The root architectural traits, like root length, surface area, project area, and root volume; as well as nodulation traits were also significantly increased by co-inoculation with USDA 110 and TSAU1. The plant-growth promoting rhizobacteria (PGPR) P. putida strain TSAU1 could improve the symbiotic interaction between the salt-stressed soybean and B. japonicum USDA 110. In conclusion, inoculation with B. japonicum and salt-tolerant P. putida synergistically improved soybean salt tolerance through altering root system architecture facilitating nitrogen and phosphorus acquisition, and nodule formation.

Nano titanium oxide (nano-TiO2): A review of synthesis methods, properties, and applications
Chou‐Yi Hsu, Zaid H. Mahmoud, Sherzod Abdullaev, Farah K. Ali +4 more
2024· Case Studies in Chemical and Environmental Engineering177doi:10.1016/j.cscee.2024.100626

Nanoparticles have revolutioned materials secience and manufacturing industry thanks to their ultrafine scale. Nano-scale titanium oxide (nano-TiO2) are key elements of a wide variety of sectors of advanced materials, devices, and systems in view of their versatility and extraordinary characetristics, mainly optical, electrical and catalytic properties. Thnaks to aforementioned features, they found a key position in different industries such as colors and pigments, photocatalysts, photovoltaic solar cells, adsorbents, cosmetics, electric and electronic devices. Nano-SiO2 application gives rise to a wide range of properties and performance, which severely depends on particle size, particle size distribution, and agglomeration in the bulk of host materials or systems. When they are used as surface coating additive or even functionalized, nano- TiO2 takes more roles, which are state-of-the-art depending on synthesis method. Therefore, review of synthesis, properties, surface- and bulk-functionalization/modification (respectively with function groups and doping) methods in achieving high-performance nano- TiO2 seems essential. In this review, background information and developments from pure Titanium Oxide to chemically modified Titanium Oxide -based materials as photocatalysts were discussed in detail, Photocatalytic activity of Titanium oxide-based materials in nitrogen group pollutant decomposition. It also Titanium Oxide Nanoparticles as a Vehicle for Chemotherapeutics and Other Applications of Titanium Oxide Nanoparticles in Medicine and also an overview of the synthesis methods and factors affecting their properties in different synthesis methods have been reviewed.

Shadow of the rotating black hole with quintessential energy in the presence of plasma
Ahmadjon Abdujabbarov, Bobir Toshmatov, Zdeněk Stuchlík, Bobomurat Ahmedov
2016· International Journal of Modern Physics D158doi:10.1142/s0218271817500511

We study the shadow of the rotating black hole with quintessential energy (i) in vacuum, (ii) in the presence of plasma with radial power-law density. For the vacuum case, the quintessential field parameter of the rotating black hole significantly changes the shape of the shadow. With increasing quintessential field parameter, the radius of the shadow also increases. With the increase of the radius of the shadow of the rotating black hole, the quintessential field parameter causes decrease of the distortion of the shadow shape: in the presence of the quintessential field parameter, the shadow of the fast rotating black hole becomes too close to the circle. We assume the distant observer of the black hole shadow to be located near the so-called static radius where the gravitational attraction of the black hole is just balanced by the cosmic repulsion. The shape and size of the shadow of quintessential rotating black hole surrounded by plasma depends on (i) plasma parameters, (ii) black hole spin and (iii) quintessential field parameter. With the increase of the plasma refraction index, the apparent radius of the shadow increases. However, for the large values of the quintessential field parameter, the change of the black hole shadow shape due to the presence of plasma is not significant, i.e. the effect of the quintessential field parameter dominates over the plasma effect.

Leukemia Blood Cell Image Classification Using Convolutional Neural Network
T. T. P. Thanh, Caleb Vununu, Sukhrob Atoev, Suk‐Hwan Lee +1 more
2018· International Journal of Computer Theory and Engineering153doi:10.7763/ijcte.2018.v10.1198

Acute myeloid leukemia is a type of malignant blood cell cancer that can affect both children and adults.There are 60,140 people were expected to be diagnosed with Leukemia in 2016, according to the Leukemia and Lymphoma Society.In order to get the most effective treatment, the patient needs early diagnosis.Therefore we need to have a support system of early diagnosis to guide treatment for patients with acute leukemia as soon as possible.In this paper, the authors propose a Convolutional Neural Network (CNN) based method to distinguish normal and abnormal blood cell images.The proposed method achieves an accuracy up to 96.6% with the dataset including 1188 blood cell images.

Acceleration of adiabatic quantum dynamics in electromagnetic fields
Shumpei Masuda, Katsuhiro Nakamura
2011· Physical Review A151doi:10.1103/physreva.84.043434

We show a method to accelerate quantum adiabatic dynamics of wave functions under electromagnetic field (EMF) by developing the preceding theory [Masuda and Nakamura, Proc. R. Soc. London Ser. A 466, 1135 (2010)]. Treating the orbital dynamics of a charged particle in EMF, we derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states in any desired short time. The scheme is consolidated by describing a way to overcome possible singularities in both the additional phase and driving potential due to nodes proper to wave functions under EMF. As explicit examples, we exhibit the fast forward of adiabatic squeezing and transport of excited Landau states with nonzero angular momentum, obtaining the result consistent with the transitionless quantum driving applied to the orbital dynamics in EMF.

Over 17% efficiency all-small-molecule organic solar cells based on an organic molecular donor employing a 2D side chain symmetry breaking strategy
Zhiya Li, Xunchang Wang, Nan Zheng, Aziz Saparbaev +4 more
2022· Energy & Environmental Science145doi:10.1039/d2ee02107b

The 2D asymmetric side chain strategy via modification with different halogens can optimize the morphology, improve the molecular interaction and control the photophysical properties, promoting an outstanding PCE of 17.0% in binary ASM-OSCs.

The Influence of Densely Organized Maltose Shells on the Biological Properties of Poly(propylene imine) Dendrimers: New Effects Dependent on Hydrogen Bonding
Barbara Klajnert‐Maculewicz, Dietmar Appelhans, Hartmut Komber, Nina Morgner +4 more
2008· Chemistry - A European Journal139doi:10.1002/chem.200800342

Maltose-modified poly(propylene imine) (PPI) dendrimers were synthesized by reductive amination of unmodified second- to fifth-generation PPI dendrimers in the presence of excess maltose. The dendrimers were characterized by using (1)H NMR, (13)C NMR, and IR spectroscopies; laser-induced liquid beam ionization/desorption mass spectrometry; dynamic light scattering analyses; and polyelectrolyte titration. Their scaffolds have enhanced molecular rigidity and their outer spheres, at which two maltose units are bonded to the former primary amino groups on the surface, have hydrogen-bond-forming properties. Furthermore, the structural features reveal the presence of a dense shell. Experiments involving encapsulation (1-anilinonaphthalene-8-sulfonic acid) and biological properties (hemolysis and interactions with human serum albumin (HSA) and prion peptide 185-208) were performed to compare the modified with the unmodified dendrimers. These experiments gave the following results: 1) The modified dendrimers entrapped a low-molecular-weight fluorescent dye by means of a dendritic box effect, in contrast to the interfacial uptake characteristic of the unmodified PPI dendrimers. 2) Both low- and high-generation dendrimers containing maltose units showed markedly reduced toxicity. 3) The desirable features of bio-interactions depended on the generation of the dendrimer; they were retained after maltose substitution, but were now mainly governed by nonspecific hydrogen-bonding interactions involving the maltose units. The modified dendrimers interacted with HSA as strongly as the parent compounds and appeared to have potential use as antiprion agents. These improvements will initiate the development of the next platform of glycodendrimers in which apparently contrary properties can be combined, and this will enable, for example, therapeutic products such as more efficient and less toxic antiamyloid agents to be synthesized.

Black hole mimicker hiding in the shadow: Optical properties of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi></mml:math> metric
Askar B. Abdikamalov, Ahmadjon Abdujabbarov, Dimitry Ayzenberg, Daniele Malafarina +2 more
2019· Physical review. D/Physical review. D.139doi:10.1103/physrevd.100.024014

Can the observation of the ``shadow'' allow us to distinguish a black hole from a more exotic compact object? We study the motion of photons in a class of vacuum static axially symmetric space-times that is continuously linked to the Schwarzschild metric through the value of one parameter that can be interpreted as a measure of the deformation of the source. We investigate the lensing effect and shadow produced by the source with the aim of comparing the expected image with the shadow of a Schwarzschild black hole. In the context of astrophysical black holes, we found that it may not be possible to distinguish an exotic source with small deformation parameter from a black hole. However, as the deformation increases, noticeable effects arise. Therefore, the future more precise measurement of the shadow of astrophysical black hole candidates would in principle allow one to put constraints on the deviation of the object from spherical symmetry.