Dispersion-strengthened chromium alloy

Finely divided powder mixture produced by vapor deposition of CR on small ThO2 particles was hot pressed or pressure bonded. Resulting alloy has lower ductile-to-brittle transition temperature than pure chromium, and high strength and oxidation resistance at elevated temperatures, both in as-rolled condition and after annealing

Evaluation of in-situ shrinkage and expansion properties of polymer composite materials for adhesive anchor systems by a novel approach based on digital image correlation

The curing reaction of thermosetting resins is associated with chemical shrinkage which is overlapped with thermal expansion as a result of the exothermal enthalpy. Final material properties of the polymer are determined by this critical process. For adhesive anchor systems the overall shrinkage behavior of the material is very important for the ultimate bond behavior between adhesive and the borehole wall. An approach for the insitu measurement of 3-dimensional shrinkage and thermal expansion with digital image correlation (DIC) is presented, overcoming the common limitation of DIC to solids. Two polymer-based anchor systems (filled epoxy, vinylester) were investigated and models were developed, showing good agreement with experimental results. Additionally, measurements with differential scanning calorimetry (DSC) provided supporting information about the curing reaction. The vinylester system showed higher shrinkage but much faster reaction compared to the investigated epoxy

Random walks of molecular motors arising from diffusional encounters with immobilized filaments

Movements of molecular motors on cytoskeletal filaments are described by directed walks on a line. Detachment from this line is allowed to occur with a small probability. Motion in the surrounding fluid is described by symmetric random walks. Effects of detachment and reattachment are calculated by an analytical solution of the master equation in two and three dimensions. Results are obtained for the fraction of bound motors, their average velocity and displacement. The diffusion coefficient parallel to the filament becomes anomalously large since detachment and subsequent reattachment, in the presence of directed motion of the bound motors, leads to a broadening of the density distribution. The occurrence of protofilaments on a microtubule is modeled by internal states of the binding sites. After a transient time all protofilaments become equally populated.Comment: 20 pages Phys Rev E format + 11 figure

Simple Wriggling is Hard unless You Are a Fat Hippo

We prove that it is NP-hard to decide whether two points in a polygonal domain with holes can be connected by a wire. This implies that finding any approximation to the shortest path for a long snake amidst polygonal obstacles is NP-hard. On the positive side, we show that snake's problem is "length-tractable": if the snake is "fat", i.e., its length/width ratio is small, the shortest path can be computed in polynomial time.Comment: A shorter version is to be presented at FUN 201

Development of a chromium-thoria alloy

Low temperature ductility and high temperature strength of pure chromium and chromium-thoria alloy prepared from vapor deposited powder

ORGANIZATIONAL FACTOR AS BASIC ELEMENTS OF THE ESTONIAN YOUTH WORKERS´ PROFESSIONAL GROWTH

The issue of the Estonian youth workers´ professionality has been relevant for many years. Organizational factors are important in the youth worker´s professional growth. Youth worker is a promoter of non-formal education. Research explained the issues related to the youth workers professional growth, including organizational factors. The theoretical framework of the research created Ruohotie, Tamm concepts of professional growth and Hackman, Oldham job satisfaction characteristics. The purpose of this research was brought to the light youth work specialists´ opinions about the organizational factors of the professional growth. For qualitative data collection semi-structed interviews were conducted with 35 Estonian youth work specialists in 2016-2018. The results showed that in eight key-topics important opinions were received. Most attention should be given further to the beginner youth workers´ support for efficient and faster adaptation with work. Mostly were explained interviewees high satisfaction with team and colleagues. Interviews revealed a different commitment to work, which depends of the employee´s professional awareness and involvement in initiatives, that could have resulted from different education, professional training or personal characteristics. The quality of the feedback is important for the employee's professional growth. Individualisation of the work may create a threat to versatility. For further clarification: youth workers´ professional identity.

PERSONALITY FACTORS AS BASIC ELEMENTS OF THE ESTONIAN YOUTH WORKERS´PROFESSIONAL GROWTH

The article dealt with one aspect of the professional growth basic elements. The issue of the Estonian Youth Centers youth workers´ professionality has been relevant for many years, as employees often exchange. Expectations for youth work as a promotion of non-formal education are high. There is no research that explained the issues related to the youth workers professional growth, including personal factors. The theoretical framework of the research created Ruohotie, Tamm, Clarke and Hollingsworth concepts of professional growth. The purpose of this research was brought to the light youth work specialists´ opinions about the personal factors of the professional growth. For qualitative data collection semi-structed interviews were conducted with 35 Estonian youth work specialists in 2016-2018. The results showed that in eight key-topics important opinions were received. Most attention should be given further to the youth workers´ internal motivation, treatment and professional identity. Mostly were explained the high expectations to the youth work generally. Interviews revealed a different commitment to everyday work, that could have resulted from their different education and professional training or attitudes towards education. The needs for further clarification are: occupational and organizational elements of youth workers professional growth.

ESTONIAN YOUTH WORK EXPERTS PROFESSIONAL GROWTH: CASES STUDY

Estonian youth work (YW) has been in development almost 30 years. In the last more than 15 years the same trends have been observed in the studies in terms of professional development: the shortage of employees with professional education and workers high mobility. At the same time, the progressive decisions and regulations made in Estonia, on the field of European YW are exemplary. Thus, the prerequisites for professional YW were created and experts in the field have also developed.The aim of research was to give an overview of the stories of becoming as experts. Semi-structured interviews were compiled in 2019. Special focus was on the professional growth in the content of life story. The study revealed both – randomness entry into YW, but various supporting external aspects (active school life, supportive community, camps). However, the most important were the personal factors - motivation, consistency, entrepreneurship, courage, YW studies, participation in (foreign) projects, mission. Professional knowledge and skills supported mostly the development from a novice specialist into an advanced employee and expert. Commitment, autonomy were the main work-load impact factors. The desire to work with young people has brought some retired youth workers back to YW. Horizontal career was limited but usual.

Cellulose / Dry, hydrophobic microfibrillated cellulose powder obtained in a simple procedure using alkyl ketene dimer

In order to produce dry and hydrophobic microfibrillated cellulose (MFC) in a simple procedure, its modification with alkyl ketene dimer (AKD) was performed. For this purpose, MFC was solvent-exchanged to ethyl acetate and mixed with AKD dissolved in the same solvent. Curing at 130 \ub0C for 20 h under the catalysis of 1-methylimidazole yielded a dry powder. Scanning electron microscopy of the powder indicated loss in nanofibrillar structure due to aggregation, but discrete microfibrillar structures were still present. Water contact angle measurements of films produced from modified and unmodified MFC showed high hydrophobicity after AKD treatment, which persisted even after extraction with THF for 8 h. The hydrophobized MFC was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance and X-ray analysis. In summary, strong indications for the presence of AKD on the surface of MFC before and after extraction with solvent were found, but only a very small amount of covalent \u3b2-ketoester linkages between the modification agent and cellulose was revealed