[Physical and mechanical properties of hydroxyapatite plasma sprayed materials applied in implantology]. / Fizykomechaniczne wlasciwosci materialów hydroksyapatytowych natryskiwanych plazmowo stosowanych w implantologii.

BACKGROUND: The research involved the evaluation of physical and mechanical properties of hydroxyapatite (HAp) bio-ceramics sprayed on titanium substrate of the type Ti-grade 2 (CP-Ti) by means of the plasma method. An innovative method of coating is applied when using implantology for healing bone defects in the body. MATERIAL AND METHODS: Hydroxyapatite coating was prepared in order to conduct research. The powder was made using wet-chemical technology consisting in separating the solids from the solution. Next, a titanium substrate was prepared, onto which hydroxyapatite was applied with a plasma technique. RESULTS: As a result of the research it has to be noted that the properties of the obtained coating may be used for covering large surfaces of implants of any shape. CONCLUSIONS: During the research into the physical and mechanical properties of hydroxyapatite composites it has been observed that they show sufficient mechanical properties to be used in implantology. The further aim of the research will involve selecting technological parameters of spray coating in order to increase adhesion and cohesion of HAp coatings. Med Pr 2018;69(6):651-661.

Electrostatic interactions in aminoglycoside-RNA complexes.

Electrostatic interactions often play key roles in the recognition of small molecules by nucleic acids. An example is aminoglycoside antibiotics, which by binding to ribosomal RNA (rRNA) affect bacterial protein synthesis. These antibiotics remain one of the few valid treatments against hospital-acquired infections by Gram-negative bacteria. It is necessary to understand the amplitude of electrostatic interactions between aminoglycosides and their rRNA targets to introduce aminoglycoside modifications that would enhance their binding or to design new scaffolds. Here, we calculated the electrostatic energy of interactions and its per-ring contributions between aminoglycosides and their primary rRNA binding site. We applied either the methodology based on the exact potential multipole moment (EPMM) or classical molecular mechanics force field single-point partial charges with Coulomb formula. For EPMM, we first reconstructed the aspherical electron density of 12 aminoglycoside-RNA complexes from the atomic parameters deposited in the University at Buffalo Databank. The University at Buffalo Databank concept assumes transferability of electron density between atoms in chemically equivalent vicinities and allows reconstruction of the electron densities from experimental structural data. From the electron density, we then calculated the electrostatic energy of interaction using EPMM. Finally, we compared the two approaches. The calculated electrostatic interaction energies between various aminoglycosides and their binding sites correlate with experimentally obtained binding free energies. Based on the calculated energetic contributions of water molecules mediating the interactions between the antibiotic and rRNA, we suggest possible modifications that could enhance aminoglycoside binding affinity.

Metabolic Syndrome in Polish Ischemic Stroke Patients.

BACKGROUND: Metabolic syndrome (MetS) predisposes individuals to cardiovascular disease or stroke development. We aimed at evaluating the prevalence of MetS in a population of acute ischemic stroke (IS) patients from central Poland and at estimating the relationship between MetS and stroke risk. METHODS: We analyzed 672 IS patients who were consecutively admitted to stroke units. The control group was composed of 612 patients with other neurologic disorders. MetS was diagnosed if 3 of 5 factors were present (obesity, increased blood pressure, increased triglycerides, low high-density lipoprotein [HDL] cholesterol, and fasting hyperglycemia) according to the Unified Criteria for Clinical Diagnosis of the Metabolic Syndrome (2009). RESULTS: MetS was diagnosed in 61.2% of stroke patients versus 18.1% of the control group (P < .001). Multiple logistic regression showed that MetS was 1.8 times more common in women than in men (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.4-2.5). The adjusted OR (95% CI) associated with MetS was 2.44 (1.48-3.64; P < .001) for IS. Hypertension and hypertriglyceridemia were the most frequent disturbances of IS patients (87.2% and 68.2%, respectively). The analysis of the interaction between MetS and its components showed significant associations with hypertension (OR, 2.15; 95% CI, .98-4.24; P < .01), high triglyceride levels (OR, 4.35; 95% CI, 2.87-9.43; P < .0001), and low HDL cholesterol levels (OR, 5.12; 95% CI, 3.15-8.20; P < .001). CONCLUSIONS: Over 60% of Polish IS patients have MetS. The prevalence of MetS was significantly higher in women than in men. Thus, MetS may be a risk factor for IS.

[The role of vitamin D in the pathogenesis and course of multiple sclerosis]. / Wplyw witaminy D na patogeneze i przebieg stwardnienia rozsianego.

Multiple sclerosis (MS) is a progressive, inflammatory demyelinating disease of the central nervous system, with an unknown aetiology. The pathogenesis of MS is mainly related with the autoimmune process, environmental factors and genetic predispositions. In recentyears, hypovitaminosis D has been considered as an independent factor increasing the risk of multiple sclerosis. Hypovitaminosis D is defined as a condition in which the concentration of 25(OH)D in serum is lower than 75 nmol/l (30 ng/ml). Numerous studies have documented the relation between the occurrence of MS, its course and activity, and vitamin D concentration dependent on sunlight and dietary intake. Conclusions from research on the effectiveness of supplementation have also been presented. They indicate the necessity of using higher doses of calcitriol. Most authors consider a preventive dose of 4000 IU daily as safe and well-tolerated by people living in low-insolation latitudes. It has been pointed out that vitamin D supplementation is indicated and effective only in cases of actual deficiency. The low risk and low cost of vitamin D supplementation, as well as patients' positive attitude towards it, makes it a promising strategy for decreasing the incidence and alleviating the signs and symptoms of multiple sclerosis.

Sunitinib: from charge-density studies to interaction with proteins.

Protein kinases are targets for the treatment of a number of diseases. Sunitinib malate is a type I inhibitor of tyrosine kinases and was approved as a drug in 2006. This contribution constitutes the first comprehensive analysis of the crystal structures of sunitinib malate and of complexes of sunitinib with a series of protein kinases. The high-resolution single-crystal X-ray measurement and aspherical atom databank approach served as a basis for reconstruction of the charge-density distribution of sunitinib and its protein complexes. Hirshfeld surface and topological analyses revealed a similar interaction pattern in the sunitinib malate crystal structure to that in the protein binding pockets. Sunitinib forms nine preserved bond paths corresponding to hydrogen bonds and also to the C-H···O and C-H···π contacts common to the VEGRF2, CDK2, G2, KIT and IT kinases. In general, sunitinib interacts with the studied proteins with a similar electrostatic interaction energy and can adjust its conformation to fit the binding pocket in such a way as to enhance the electrostatic interactions, e.g. hydrogen bonds in ligand-kinase complexes. Such behaviour may be responsible for the broad spectrum of action of sunitinib as a kinase inhibitor.

Treat-to-target in systemic lupus erythematosus: recommendations from an international task force.

The principle of treating-to-target has been successfully applied to many diseases outside rheumatology and more recently to rheumatoid arthritis. Identifying appropriate therapeutic targets and pursuing these systematically has led to improved care for patients with these diseases and useful guidance for healthcare providers and administrators. Thus, an initiative to evaluate possible therapeutic targets and develop treat-to-target guidance was believed to be highly appropriate in the management of systemic lupus erythematosus (SLE) patients as well. Specialists in rheumatology, nephrology, dermatology, internal medicine and clinical immunology, and a patient representative, contributed to this initiative. The majority convened on three occasions in 2012-2013. Twelve topics of critical importance were identified and a systematic literature review was performed. The results were condensed and reformulated as recommendations, discussed, modified and voted upon. The finalised bullet points were analysed for degree of agreement among the task force. The Oxford Centre level of evidence (LoE, corresponding to the research questions) and grade of recommendation (GoR) were determined for each recommendation. The 12 systematic literature searches and their summaries led to 11 recommendations. Prominent features of these recommendations are targeting remission, preventing damage and improving quality of life. LoE and GoR of the recommendations were variable but agreement was >0.9 in each case. An extensive research agenda was identified, and four overarching principles were also agreed upon. Treat-to-target-in-SLE (T2T/SLE) recommendations were developed by a large task force of multispecialty experts and a patient representative. It is anticipated that 'treating-to-target' can and will be applicable to the care of patients with SLE.

Psychological factors at work and musculoskeletal disorders: a one year prospective study.

The etiology of musculoskeletal disorders is complex, with physical and psychosocial working conditions playing an important role. This study aimed to determine the relationship between psychosocial work conditions, such as psychological job demands, decision latitude, social support and job insecurity and musculoskeletal complains (MSCs) and (repetitive strain injuries (RSIs) in a 1-year prospective study. The job content questionnaire, the Nordic musculoskeletal questionnaire and provocation tests were used to study 725 employees aged 20-70 years. Pain in the lower back (58 % of subjects), neck (57 %), wrists/hands (47 %) and upper back (44 %) was most frequent. The carpal tunnel syndrome (CTS) (33.6 %), rotator cuff tendinitis (15.4 %), Guyon's canal syndrome (13.4 %), lateral epicondylitis (7.6 %), medial epicondylitis (5.3 %), tendinitis of forearm-wrist extensors (7.8 %) and tendinitis of forearm-wrist flexors (7.3 %) were the most frequent RSIs. Logistic analysis showed that increased psychological job demands statistically significantly increased the probability of lateral and medial epicondylitis, and increased control (decision latitude) statistically significantly decreased the risk of CTS. There was no relationship between job insecurity, social support and the studied RSIs. Psychosocial factors at work predict prevalence of MSCs and RSIs, irrespectively of demographic factors, e.g., age or gender, and organizational and physical factors.

Influence of Surface Preparation on the Microstructure and Mechanical Properties of Cold-Sprayed Nickel Coatings on Al 7075 Alloy.

This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation had a significant effect on coating adhesion and microstructure. The coating deposited at the highest gas temperature revealed a dense microstructure, showing very good adhesion of the impacting powder particles to the substrate and good bonding between deposited layers. The Ni grains with different shapes (elongated, equiaxed) and sizes of a few dozen to several hundred nanometres were present in the splats. An increase in temperature caused significant growth in coating thickness as a result of the powder grains' higher velocity. Moreover, higher gas temperature resulted in the enhancement of micro- and nanohardness, elastic modulus, and adhesion. The adhesive bond strength of Ni coatings in the tested temperature ranges from 500 °C to 800 °C increased with the increase in the surface roughness of the substrate. For the Al 7075 coarse grit-blasted (CG) substrate with the highest roughness, the adhesion reached the highest value of 44.6 MPa when the working gas was at a temperature of 800 °C. There were no distinct dependencies of surface roughness and thickness on the mechanical properties of the cold-sprayed nickel coating.

Synergistic Effect of Precursor and Interface Engineering Enables High Efficiencies in FAPbI3 Perovskite Solar Cells.

Formamidinium lead iodide (FAPbI3)-based perovskite solar cells have gained immense popularity over the last few years within the perovskite research community due to their incredible opto-electronic properties and the record power conversion efficiencies (PCEs) achieved by the solar cells. However, FAPbI3 is vulnerable to phase transitions even at room temperature, which cause structural instability and eventual device failure during operation. We performed post-treatment of the FAPbI3 surface with octyl ammonium iodide (OAI) in order to stabilize the active phase and preserve the crystal structure of FAPbI3. The formation of a 2D perovskite at the interface depends on the stoichiometry of the precursor. By optimizing the precursor stoichiometry and the concentration of OAI, we observe a synergistic effect, which results in improved power conversion efficiencies, reaching the best values of 22% on a glass substrate. Using physical and detailed optical analysis, we verify the presence of the 2D layer on the top of the 3D surface of the perovskite film.

Crystal structure of a putative isochorismatase hydrolase from Oleispira antarctica.

Isochorismatase-like hydrolases (IHL) constitute a large family of enzymes divided into five structural families (by SCOP). IHLs are crucial for siderophore-mediated ferric iron acquisition by cells. Knowledge of the structural characteristics of these molecules will enhance the understanding of the molecular basis of iron transport, and perhaps resolve which of the mechanisms previously proposed in the literature is the correct one. We determined the crystal structure of the apo-form of a putative isochorismatase hydrolase OaIHL (PDB code: 3LQY) from the antarctic γ-proteobacterium Oleispira antarctica, and did comparative sequential and structural analysis of its closest homologs. The characteristic features of all analyzed structures were identified and discussed. We also docked isochorismate to the determined crystal structure by in silico methods, to highlight the interactions of the active center with the substrate. The putative isochorismate hydrolase OaIHL from O. antarctica possesses the typical catalytic triad for IHL proteins. Its active center resembles those IHLs with a D-K-C catalytic triad, rather than those variants with a D-K-X triad. OaIHL shares some structural and sequential features with other members of the IHL superfamily. In silico docking results showed that despite small differences in active site composition, isochorismate binds to in the structure of OaIHL in a similar mode to its binding in phenazine biosynthesis protein PhzD (PDB code 1NF8).

Analysis of conditions and organization of work of notebook computer users.

AIM: The aim of this study was to evaluate working conditions with a notebook computer (notebook) as a potential cause of musculoskeletal disorders. MATERIAL AND METHODS: The study had 2 stages. The first one was a questionnaire survey among 300 notebook users. The next stage was an expert analysis of 53 randomly selected workstations. The questionnaire survey included questions about the participants, their working conditions, work organization and also duration of work with a notebook. RESULTS AND CONCLUSIONS: The results of the research showed that most examined operators used a notebook as a basic working tool. The most important irregularities included an unadjustable working surface, unadjustable height of the seat pan and backrest, unadjustable height and distance between the armrests and no additional ergonomic devices (external keyboard, docking station, notebook stand or footstool).

The Effect of the Substrate on the Microstructure and Tribological Properties of Cold Sprayed (Cr3C2-25(Ni20Cr))-(Ni-graphite) Cermet Coatings.

In this work, the effect of the substrate, Al 7075 alloy and 1H18NT9 stainless steel, on the microstructure and tribological properties of cold sprayed (Cr3C2-25(Ni20Cr))-(Ni-graphite) coatings was investigated. Both coatings were dense and did not reveal any discontinuities at the interfaces. They had similar Cr3C2 and graphite contents. Their microstructures showed a variety of grain sizes of the matrix phase between the inner part of the splat, showing large ones, and their boundaries, where elongated and nanostructured grains were formed during the deposition process. The coating deposited on the steel substrate revealed a slightly higher hardness and lower abrasive wear with the Al2O3 loose abrasive particles. The force required to destroy the durability of the coating-steel substrate system in the three-point bending test was higher than those of the other ones. The cermet deposit cold sprayed on steel and examined at 25 °C under 10 N revealed the best wear resistance and the lowest friction coefficient.

[The role of psychosocial work factors in the development of musculoskeletal disorders in workers]. / Rola psychospolecznych czynników pracy w powstawaniu zaburzen miesniowo-szkieletowych u pracowników.

The aim of the study was to determine the role of psychosocial work factors in the development of musculoskeletal disorders in workers. It should be stressed that over a decade these disorders have been the subject of studies because of complaints reported not only by workers performing heavy physical work or working in awkward, forced body posture. It has also been acknowledged that stress at work caused by various psychosocial work factors can significantly influence their development. One of the models, most popular nowadays, was used in the study. It takes into account various risk factors in the etiology of cervical spine disorders. Based on this model it was shown that certain psychosocial and cultural variables (e.g., work demands and control, individual variables, individual values, work group's culture) may constitute occupational stressors and, when combined with physical load factors, may lead to stress and musculoskeletal disorders. It was also indicated that such psychosocial work factors as excessive work demands (quantitative or qualitative), inadequate control at work or lack of social support are the most frequent sources of work-related stress. The article presents the results of some prospective studies in which the role of these factors in the development of musculoskeletal disorders has been considered. Apart from work properties (factors), the role of other psychological variables was shown; these include: work involvement, perfectionism, negative affectivity or work style, which in numerous studies turned out to be important risk factors in the development of musculoskeletal disorders. Finally, potential mechanisms underlying the relationships between psychosocial factors and musculoskeletal disorders were indicated. However, it was stressed that the majority of them still require to be confirmed in future descriptive or experimental studies.

[Acquired musculoskeletal dysfunction syndromes in workers in the light of epidemiological studies]. / Nabyte zespoly dysfunkcji ukladu miesniowo-szkieletowego u pracowników w swietle badan epidemiologicznych.

Acquired musculoskeletal dysfunction syndromes (overload syndromes) that cause limitation of the system efficiency belong nowadays to the most serious problems in the medical care of workers. The etiology of overload syndromes is multifactorial, which means that occupational factors constitute only one of many causes fostering the development of those disorders. Occupational factors which increase the risk of musculoskeletal disorders include physical factors related to the work environment or the way the work is performed, such as body posture, value of exerted forces, movement repetitiveness, load handling, mechanical vibration or microclimate as well as psychosocial factors, such as quantitative and qualitative overload, lack of control, lack of social support or work insecurity. The consequence of musculoskeletal overload syndromes is the progressing reduction of its efficiency causing limitation or even loss of work ability, which results in premature exclusion from social and occupational activities. This article presents etiological factors of musculoskeletal complains and overload syndromes and their prevalence in workers.

Job strain, overtime, life style, and cardiovascular risk in managers and physical workers.

The purpose of the study was to determine the relation between overtime, job strain and life style, and cardiovascular risk (CVR) in 97 managers and 98 physical workers. CVR was measured with the Framingham method. Information about job strain, overtime, life style and extra-occupational activities was obtained with a self-administered questionnaire. The results showed that both groups had a similar, medium-level job stress. Being a manager and having extra-occupational activities (self-education) were significantly related with CVR (p = .000, p = .035, respectively), whereas other factors that were analysed (i.e., physical work and overtime) were not. The managers were older than the physical workers; that may be why the factor of being a manager was significantly related to CVR. The extra-occupational activities connected with improving workers' skills may play an important role in the development of workers' overload and an increase in CVR.

Effect of Mo and Ta on the Mechanical and Superelastic Properties of Ti-Nb Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering.

The effect of ternary alloying elements (Mo and Ta) on the mechanical and superelastic properties of binary Ti-14Nb alloy fabricated by the mechanical alloying and spark plasma sintering was investigated. The materials were prepared in two ways: (i) by substituting Nb in base Ti-14Nb alloy by 2 at.% of the ternary addition, giving the following compositions: Ti-8Nb-2Mo and Ti-12Nb-2Ta and (ii) by adding 2 at.% of the ternary element to the base alloy. The microstructures of the materials consisted of the equiaxed ß-grains and fine precipitations of TiC. The substitution of Nb by both Mo and Ta did not significantly affect the mechanical properties of the base Ti-14Nb alloy, however, their addition resulted in a decrease of yield strength and increase of plasticity. This was associated with the occurrence of the {332} <113> twinning that was found during the in-situ observations. The elevated concentration of interstitial elements (oxygen and carbon) lead to the occurrence of stress-induced martensitic transformation and twinning mechanisms at lower concentration of ß-stabilizers in comparison to the conventionally fabricated materials. The substitution of Nb by Mo, and Ta caused the slight improvement of the superelastic properties of the base Ti-14Nb alloy, whereas their addition deteriorated the superelasticity.

Influence of Laser Treatment on the Corrosion Resistance of Cr3C2-25(Ni20Cr) Cermet Coating.

The influence of the laser treatment on the corrosion resistance of the Cr3C2-25(Ni20Cr) cermet coating on the Al7075 (EN, AW-7075) substrate (Cr3C2-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold sprayed (CS) method. The tested coatings were irradiated with a laser spot speed of 600 mm/min, 800 mm/min, and 1000 mm/min. The mechanical properties of the Cr3C2-25(Ni20Cr)/Al7075 were characterized by microhardness (HV) measurements. The surface and microstructure of the specimens were observed by ascanning electron microscope (SEM) and other assistive techniques. The corrosion test of materials wascarried out by using the electrochemical method in the acidic chloride solution. Cermet coatings perfectly protect the Al7075 substrate against contact with an aggressive corrosion environment. The laser remelting process of the Cr3C2-25(Ni20Cr) layer caused the homogenization of the structure cermet coatings. The irradiation with the laser beam eliminates microcracks and pores on the Cr3C2-25(Ni20Cr) surface. However, the best effect of improving the anti-corrosion properties of cermet coating was obtained for the lowest laser spot speed (i.e., 600 mm/min). It was found that the corrosion rate of the Cr3C2-25(Ni20Cr) cermet coating was reduced by more than two times compared to the highest speed of the laser spot.

Optimization of Mechanical Properties of Cr3C2-Ni20Cr/Graphite Cold Sprayed Coatings.

This study analyzed the mechanical properties of cold-sprayed Cr3C2-25(Ni20Cr) blended with Ni-graphite as a solid lubricant deposited on 7075 aluminum alloy substrate. To optimize the coating properties, different sets of parameters (graphite content in feedstock, process gas composition, spraying distance, and traverse gun speed) were tested in the frame of the Taguchi experiment. The cold-sprayed coatings were evaluated for their chromium carbide and graphite content, hardness, and coefficient of friction. Analysis of the microstructure of the deposited coatings revealed that graphite as a soft and brittle component fills all voids in the coating and its quantity depends on its content in the feedstock. The experimental results show that the composition of the process gas has the greatest impact on the Cr3C2 content in the coating and the proportion of graphite in the sprayed blend directly affects its hardness. In the case of the coefficient of friction, the most significant parameters were the graphite content in the sprayed blend, the spraying distance, and process gas composition. The conducted verification experiment with the optimum parameter values allowed a coating with the highest hardness and the lowest coefficient of friction to be obtained.

Experimental and Numerical Investigations of Titanium Deposition for Cold Spray Additive Manufacturing as a Function of Standoff Distance.

In this research, the cold spray process as an additive manufacturing method was applied to deposit thick titanium coatings onto 7075 aluminium alloy. An analysis of changes in the microstructure and mechanical properties of the coatings depending on the standoff distance was carried out to obtain the maximum deposition efficiency. The process parameters were selected in such a way as to ensure the spraying of irregular titanium powder at the highest velocity and temperature and changing the standoff distance from 20 to 100 mm. Experimental studies demonstrated that the standoff distance had a significant effect on the microstructure of the coatings and their adhesion. Moreover, its rise significantly increased the deposition efficiency. The standoff distance also significantly affected the coating microstructure and their adhesion to the substrate, but did not cause any changes in their phase composition. The standoff distance also influenced the coating porosity, which first decreased to a minimum level of 0.2% and then increased significantly to 9.8%. At the same time, the hardness of the coatings increased by 30%. Numerical simulations confirmed the results of the tests.

The Ag-Li system's experimental and ab initio thermodynamic dataset.

The Ag-Li system was analysed using first-principles calculations 10.1016/j.jallcom.2019.152811 [1]. The method included using density functional theory to optimize the crystal structure of the phases constituting the binary phase diagram by relaxing atomic positions, volume, and shape. The optimized structures were subsequently used to calculate thermodynamic properties at different temperatures; by determining the zero-point energy, the vibrational internal energy, and the entropy, the heat capacity at constant volume was obtained as well as the phases' stability limits. Furthermore, optimized structures were used to calculate the XRD patterns and to compare them with experimental data. All the referred data are now accessible to researchers and industrials demanding to work with binary and higher-order systems that include Ag and Li, for example, for energy storage. Binaries should be well assessed prior to higher-order phase diagrams and in that resides additional usefulness to this data.