A first-principles-based high fidelity, high throughput approach for the design of high entropy alloys.

Here, we present a preselected small set of ordered structures (PSSOS) method, a first principles-based high fidelity (HF), high throughput (HT) approach, for fast screening of the large composition space of high entropy alloys (HEAs) to select the most energetically stable, single-phase HEAs. Taking quinary AlCoCrFeNi HEA as an example system, we performed PSSOS calculations on the formation energies and mass densities of 8801 compositions in both FCC and BCC lattices and selected five most stable FCC and BCC HEAs for detailed analysis. The calculation results from the PSSOS approach were compared with existing experimental and first-principles data, and the good agreement was achieved. We also compared the PSSOS with the special quasi-random structures (SQS) method, and found that with a comparable accuracy, the PSSOS significantly outperforms the SQS in efficiency, making it ideal for HF, HT calculations of HEAs.

Atomistic-scale analysis of the deformation and failure of polypropylene composites reinforced by functionalized silica nanoparticles.

Interfacial adhesion between polymer matrix and reinforcing silica nanoparticles plays an important role in strengthening polypropylene (PP) composite. To improve the adhesion strength, the surface of silica nanoparticles can be modified by grafted functional molecules. Using atomistic simulations, we examined the effect of functionalization of silica nanoparticles by hexamethyldisilazane (HMDS) and octyltriethoxysilane (OTES) molecules on the deformation and failure of silica-reinforced PP composite. We found that the ultimate tensile strength (UTS) of PP composite functionalized by OTES (28 MPa) is higher than that of HMDS (25 MPa), which is in turn higher than that passivated only by hydrogen (22 MPa). To understand the underlying mechanistic origin, we calculated the adhesive energy and interfacial strength of the interphase region, and found that both the adhesive energy and interfacial strength are the highest for the silica nanoparticles functionalized by OTES molecules, while both are the lowest by hydrogen. The ultimate failure of the polymer composite is initiated by the cavitation in the interphase region with the lowest mass density, and this cavitation failure mode is common for all the examined PP composites, but the cavitation position is dependent on the tail length of the functional molecules. The present work provides interesting insights into the deformation and cavitation failure mechanisms of the silica-reinforced PP composites, and the findings can be used as useful guidelines in selecting chemical agents for surface treatment of silica nanoparticles.

Mechanical properties of pristine and defective carbon-phosphide monolayers: a density functional tight-binding study.

Using density functional tight-binding theory, we investigated the elastic properties and deformation and failure behaviors of pristine and defective carbon-phosphide (CP) monolayers subjected to uniform uniaxial tensile strain along arm-chair (AC) and zig-zag (ZZ) directions. Two variants of CP (α-CP and ß-CP) were studied and two types of carbon and phosphorous vacancies (single and double) were considered. It was found that carbon monovacancies have the lowest formation energy, while phosphorous divacancies have the highest one in both CP allotropes. A strong mechanical anisotropy for CP was found with the Young's modulus and the failure stress along ZZ direction being an order of magnitude larger than those along AC direction. In both allotropes, the Young's modulus, failure stress and strain are considerably affected by vacancies, especially along AC direction. Fracture of pristine CP monolayer occurred via the rupture of phosphorous-phosphorous bonds when CP monolayer is stretched along AC direction, while via the rupture of carbon-phosphorous bonds when stretched along ZZ direction. Defective α-CP and ß-CP monolayers both undergo a brittle-like failure initiated around the hosted vacancies at a lower critical strain. The failure strain and stress along the AC direction are affected only by phosphorous vacancies, while along the ZZ direction, they are almost equally affected by both phosphorous and carbon vacancies. These understandings may provide useful guidelines for potential applications of CP monolayers in nanoelectromechanical systems.

Effect of vacancies on the mechanical properties of phosphorene nanotubes.

Using density functional tight-binding method, we studied the mechanical properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nanotubes (PNTs) with monovacancies and divacancies subjected to uniaxial tensile strain. We found that divacancies in AC PNTs and monovacancies in ZZ PNTs possess the lowest vacancy formation energy, which decreases with the tube diameter in AC PNTs and increases in ZZ PNTs. The Young's modulus is reduced, while the radial and thickness Poisson's ratios are increased by hosted vacancies. In defective AC PNTs, deformation involves fracture of the intra-pucker bonds and formation of the new inter-pucker bonds at a critical strain, and the most stretched bonds around the vacancy rupture first, triggering a sequence of the structural transformations terminated by the ultimate failure. The critical strain of AC PNTs is reduced significantly by hosted vacancies, whereas their effect on the critical stress is relatively weaker. Defective ZZ PNTs fail in a brittle-like manner once the most stretched bonds around a vacancy rupture, and vacancies are able to significantly reduce the failure strain but only moderately reduce the failure stress of ZZ PNTs. The understandings revealed here on the mechanical properties and the deformation and failure mechanisms of PNTs provide useful guidelines for their design and fabrication as building blocks in nanodevices.

Mechanical properties and failure behavior of phosphorene with grain boundaries.

Using the density-functional tight-binding method, we studied the effect of grain boundaries on the mechanical properties and failure behavior of phosphorene. We found that the high-angle tilt boundaries with a higher density of (5∣7) defect pairs (oriented along the armchair direction) are stronger than the low-angle tilt boundaries with a lower defect density, and similarly the high-angle boundaries with a higher density of (4∣8) defect pairs (oriented along the zigzag direction) are stronger than the low-angle boundaries with a lower defect density. The failure is due to the rupture of the most pre-strained bonds in the heptagons of the (5∣7) defect pair or octagons of the (4∣8) pairs. The high-angle grain boundaries are better at accommodating the pre-strained bonds in heptagon and octagon defects, leading to a higher failure stress and strain. The results cannot be described by a Griffith-type fracture mechanics criterion, since this does not take into account the bond pre-stretching. Interestingly, these anomalous mechanical and failure characteristics of tilt grain boundaries in phosphorene are also shared by graphene and hexagonal boron nitride, signifying that they may be universal for 2D materials. The findings revealed here may be useful in tuning the mechanical properties of phosphorene via defect engineering for specific applications.

Mechanical properties of phosphorene nanotubes: a density functional tight-binding study.

Using the density functional tight-binding method, we studied the elastic properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nanotubes (PNTs) under uniaxial tensile strain. We found that the deformation and failure of PNTs are very much anisotropic. For ZZ PNTs, three deformation phases are recognized: the primary linear elastic phase-which is associated with interactions between neighboring puckers, succeeded by the bond rotation phase-where the puckered configuration of phosphorene is smoothed via bond rotation, and lastly the bond elongation phase-where the P-P bonds are directly stretched up to the maximally allowed limit and failure is initiated by the rupture of the most stretched bonds. For AC PNTs, the applied strain stretches the bonds up to the maximally allowed limit, causing their ultimate failure. For both AC and ZZ PNTs, their failure strain and failure stress are sensitive- while the Young's modulus, flexural rigidity, radial Poisson's ratio and thickness Poisson's ratio are relatively insensitive-to the tube diameter. More specifically, for AC PNTs, the failure strain decreases from 0.40 to 0.25 and the failure stress increases from 13 GPa to 21 GPa when the tube diameter increases from 13.3 Å to 32.8 Å; while for ZZ PNTs, the failure strain decreases from 0.66 to 0.55 and the failure stress increases from 4 GPa to 9 GPa when the tube diameter increases from 13.2 Å to 31.1 Å. The Young's modulus, flexural rigidity, radial and thickness Poisson ratios are 114.2 GPa, 0.019 eV · nm(2), 0.47 and 0.11 for AC PNTs, and 49.2 GPa, 0.071 eV · nm(2), 0.07 and 0.21 for ZZ PNTs, respectively. The present findings provide valuable references for the design and application of PNTs as device elements.

The structure and elastic properties of phosphorene edges.

We investigated the edge atomic structures and elastic properties of defect-free phosphorene nanoribbons (PNRs). Density functional tight binding simulations were used to optimize two main edge configurations: armchair (AC) and zigzag (ZZ). It was found that the energy relaxation of PNRs leads to the noticeable changes in edge atomic configurations. The effective width of the edge region, which includes all the atoms involved in the edge relaxation, was found to contain approximately three atomic rows near the edge for both AC and ZZ PNRs. We further extracted the edge stress and modulus for the ZZ and AC edges. Both the AC and ZZ edge stresses of PNRs are positive, indicating tensile stress at the edges. In addition, both the AC and ZZ edge moduli are positive. However, the edge elastic modulus and edge stress of ZZ PNRs are about three times larger than those of AC PNRs. Furthermore, we showed that the tensile edge stresses along ZZ and AC edges are able to cause distortion in freestanding phosphorene nanoribbons. Our results highlight the importance of accounting for edge stresses in the design and fabrication of PNRs.

Molecular dynamics simulations on the frictional behavior of a perfluoropolyether film sandwiched between diamond-like-carbon coatings.

We perform molecular dynamics simulations to investigate the nanoscale frictional behavior of a perfluoropolyether (PFPE) film sandwiched between two diamond-like-carbon (DLC) coatings. We show that the PFPE films behave like a solid and can perform either a motion-station movement or a continuous motion with fluctuating velocities. The former movement is caused by the alternating stick and slip at the two individual interfaces, while the latter is due to the dynamic sliding motions simultaneously occurring at both interfaces. We reveal that these motion characteristics are governed by the competition between the two interfacial adhesion energies, which are strongly affected by the thermal vibrations and interface roughness fluctuations. We also find that the Amonton's law modified by incorporating the adhesion effect can be used to describe the mean friction traction vs normal pressure relation, but large fluctuations are present at low contact pressures. The magnitude of atomic level friction forces at the interface is found to be highly nonuniform. The directions of atomic level friction forces can even be opposite. With increasing the normal pressure, the nonuniformity of atomic level friction forces decreases first and then increases again. This change can be explained by the concurrent effects from the large difference in material stiffness and the changes in surface roughness under normal pressure. The present work reveals interesting insights into the sliding mechanisms in sandwiched structures and provides useful guidelines for the design of nanoscale lubricant systems.

[Histological structure of a tumor as a criterion of primary multiplicity in bilateral cancer of mammary glands]. / Gistologicheskoe stroenie opukholi kak kriterii pervichnoi mnozhestvennosti pri bilateral'nom rake molochnykh zhelez.

Comparative estimation of histological structure of contralateral tumors in 104 patients with primary and in 54--with metastatic mammarial gland cancer (MGC) was performed. Revealing of various histological types of tumoral nodes--of a one component infiltrating ductal cancer (IDC) in one mammarial gland and a one-component infiltrating lobular cancer (IPC)--in another one, combination of special form of the MGC with IDC and/or IPC, combination of cancer in situ with invasive form of the MGC constitutes the criterion of primarily-multiple affection. In differentiated diagnosis of primary and metastatic tumor this criterion is highly specific (92.9%), but has low prognostic value (37.5%). That's why in 73% of women-patients it is necessary to analyze the clinical examination data in addition to establish the diagnosis of primary bilateral MGC.

[Criteria of primary multiple bilateral tumors of mammary gland, their clinical significance in diagnosis of primary and metastatic tumors]. / Kriterii pervichnoi mnozhestvennosti bilateral'nykh opukholei molochnoi zhelezy, ikh klinicheskaia znachimost' v diagnostike pervichnykh i metastaticheskikh novoobrazovanii.

Clinical data and results of morphological investigation of the mammarial gland (MG) tumor in 158 women with bilateral affection are summarized. For diagnosis of primary bilateral MG tumors it is possible to use following criterions: absence of remote metastasizing and local recurrency of cancer, spread of the first metachronous or both synchronous tumors no more than of T1-2N0-1M0 stage, presence of nodular form of the MG cancer, localization of tumoral nodes in external hemispheres contralateral MG. In diagnosis of metastatic bilateral tumors may be used criteria, owing acceptable prognostical validity of negative result, presence of remote metastasizing (PVNR 95.2%), spread of the first metachronous or both synchronous tumors of T3-4N0-3M0-1 stage (PVNR 93.6%); infiltrating form of the bilateral MG cancer (PVNR 95.2%); revealing of tumor in contralateral MG during 2 years (PVNR 84.4%); much lower degree of differentiation of the second tumor (PVNR 77.4%).

[Breast cancer in women with prior malignant tumors]. / Rak molochnii zhelezy u zhenshchin, ranee bolevshikh drugimi zlokachestvennymi novobrazovaniiami.

Indices have been studied for a relative risk of development of subsequent metachronic breast cancer (BC) in 15627 sick female subjects presenting with different localizations of primary malignant tumours. The risk for development of BC in those women presenting with cancer of chief localizations exceeds the populational morbidity probability up to 30-fold. It is the female patients having cancer of the other mammary gland, endometrium, thyroid gland, lung, and skin who demonstrated the highest risk for development of BC. Such a polyneoplasia was recorded in 150 female subjects out of the 191 ones (78.6%). The risk for BC development in those female patients with cancer of the ovaries, cervical cancer, stomach, and melanosis cutis appeared to be insignificant. Metachronic BC in cancer patients depending on the site of the primary tumour can be a sequel of different pathogenetic mechanisms, of which hormonal-and-metabolic disturbances are the chief ones together with the genetical factor, and exposure to prior methods of antitumour chemoradiation therapy as well.

[The primary-multiple malignant tumors inpatients with mammary gland cancer]. / Pervichno-mnozhestvennye zlokachestvennye opukholi u bol'nykh rakov molochnoi zhelezy.

Of 5073 patients with mammarial gland cancer (MGC) observed during 20 years of follow-up in 409 (8.1%) polyneoplasia was revealed. In 21 (5.1%) of 409 patients three polyorganic primary tumors and more were revealed. In 108 (26.4%) of them the primarily-multiple tumors were synchronous, in 301 (73.6%)--metachronous. Most frequently MGC occurred in conjunction with tumors of genital and digestive systems, which have the highest frequency in population. In the other organs polyneoplasia was revealed significantly rarely.

[The incidence of bilateral multiple primary breast cancer among the female inhabitants of Crimea]. / Chastota bilateral'nogo pervichno-mnozhestvennogo raka molochnoi zhelezy sredi zhitel'nits Kryma.

A method is proposed for calculation of PMSO frequency depending on succession of origination of polyneoplasias. The incidence rate of synchronous bilateral breast cancer (BC) was calculated in reference to all primary BC patients and came to 0.75%. The incidence rate of metachronous bilateral BC was calculated depending on the number of those BC patients having been registered every year of observation and it was found to be 5.4%. The total frequency of bilateral BC in a 20-year follow-up in the Crimean region appeared to be 6.15%. The incidence of metachronous bilateral BC was noted to be dependent on the length of follow-up: 1.27 percent and 4.14 percent in the 3- to 10- and 11- to 20-year periods respectively. The risk for the development of bilateral BC is conditioned by the time having elapsed since detection of the first tumor and increases after 10 and 18 years.

[The frequency of detection of and criteria for primary multiple malignant tumors in patients with mammary gland cancer]. / Chastota vyiavleniia i kriterii pervichnoi mnozhestvennosti zlokachestvennykh opukholei u bol'nykh rakom molochnoi zhelezy.

The method of calculation of the primarily-multiple malignant tumors (PMMT) frequency depending on their occurrence succession was supposed. The frequency of synchronous PMMT calculated in relation to total quantity of patients with mammarial gland cancer (MGC) was 1.5%. The frequency of metachronous PMMT was calculated basing on the MGC patients quantity in every year of observation. The summary frequency of metachronous PMMT for last 20 years of observation of 11512 MGC patients was 16.2%, the total PMMT frequency-17.7%, approximating to the true frequency at the end of life in all the MGC patients. The differences of metachronous PMMT revealing were established, witnessing the existence of at least two heterogenic groups of patients, in one of which the influence of some etiological factors with the determined term of the cancerogenic effect realization, causing the PMMT occurrence frequency rising were established.

[Results of esophageal cancer surgical treatment in multiple primary neoplasms]. / Khirurgicheskoe lechenie pishchevoda pri pervichno-mnozhestvennykh opukholiakh.

Available are the results of surgical treatment of 11 patients with cancer of the esophagus revealed metachronously through 6 months--3 years after treatment of oro-pharyngeolaryngeal cancer (5 patients) and diagnosed synchronously with cancer of the stomach (3 patients), the lung (2 patients) and leiomyoma of the esophagus (1 patient). Radical operations on the esophagus were performed in all the patients, in synchronous tumors they were one-stage surgical intervention. Postoperative complications such as pneumonia were observed in the majority of patients, who previously underwent radiation or combined treatment for laryngeal cancer, as well as in all patients, who were operated on the esophagus and the lung in one stage. The necessity of active bronchial sanation in pre- and postoperative period of patients after treatment of laryngeal cancer and advisability of two-stage surgical treatment of synchronous tumors of the esophagus and the lung, the operation for lung cancer being performed at the second stage of treatment, are stressed in conclusion. In synchronous involvement of the esophagus and the stomach one-stage intervention on these organs is the most advisable.

[The characteristics of the intestinal Escherichia microflora in patients with acute intestinal infections]. / Kharakteristika ésherikhioznoi mikroflory kishechnika bol'nykh ostrymi kishechnymi infektsiiami.

The content of enterobacteria in fecal samples obtained from 1,146 patients with acute enteric infections was studied. In the first days of the disease about 70% of the patients were found to have abundant and highly diversified intestinal microflora with Escherichia contamination of feces constituting 10(6)-10(7) microbial cells/g in children and 10(7)-10(8) microbial cells/g in adults. The number of patients excreting Escherichia and pathogenic enterobacteria increased from 8.8% (children under 6 months) to 28.6% (adults), the number of patients excreting Escherichia and opportunistic enterobacteria decreased from 69.1% (children under 6 months) to 36.8%. In 75% of cases the reverse relationship between the number of Escherichia and opportunistic enterobacteria was registered, the latter numbering two and more genera in 50% of cases. The serological picture of Escherichia was poorer when they were isolated simultaneously with shigellae (83 O-groups) than in those cases when Escherichia alone were isolated (108 O-groups), or when Escherichia were isolated simultaneously with opportunistic enterobacteria (119 O-groups).

[The hemagglutinating activity of bacteria in the genus Klebsiella and the morphofunctional characteristics of their fimbriae]. / Gemaggliutiniruiushchaia aktivnost' bakterii roda Klebsiella i morfofunktsional'nye osobennosti ikh fimbrii.

The hemagglutinating activity of 77 Klebsiella strains from the international collection, grown in a culture medium prepared on the basis of soy-bean flour enzymatic hydrolysate, was studied. These strains could be divided into four groups according to their capacity for synthesizing different types of hemagglutinins on their surface: 2 strains carried mannose-sensitive hemagglutinins, 18 strains had mannose-resistant K-type hemagglutinins, 48 strains exhibited the signs indicating the presence of both mannose-sensitive and mannose-resistant hemagglutinins, and 9 strains showed no hemagglutinating activity. The hemagglutinating activity of strains K-74, K-79, K-80, K-81 and K-82 was characterized. Of the reference strains under study, 22 strains were found to have mannose-resistant hemagglutinating activity with respect to fresh chick red blood cells. The occurrence of hemagglutinins in Klebsiella was shown to depend on the temperature of cultivation and the consistency of the culture medium. The formation of large-sized capsules in Klebsiella grown in the Werfel-Fergusson medium with a considerable content of saccharose was shown to cause the absorption of their fimbrial structures by the capsular substance and, as a consequence, the suppression of their hemagglutinating activity.

[Fucosylation of serum proteins in stomach cancer]. / Fukozilirovanie belkov syvorotki krovi pri rake zheludka.

Content of fucose and of fucosylated protein fractions was studied in blood serum of healthy donors as well as in blood serum of patients with chronic gastritis and with stomach cancer. Concentration of fucose was increased in blood serum under conditions of the tumor generalization. At the same time, content of fucosylated albumin was elevated within early steps of stomach cancer, while the content of fucosylated globulins was decreased. Estimation of albumin-bound fucose might be used in diagnosis of stomach cancer.