Influence of waxes remelting used in investment casting on their thermal properties and linear shrinkage

This paper presents the results of thermal properties and linear shrinkage of jewelry waxes utilized in investment casting. Three types of jewelry waxes were cyclically processed (by heating, holding in a molten state and cooling)in the temperature range between 25 and 90 °C for about 7 hours. The samples were tested after 5th, 10th and 15thcycle. The remelting was designed to simulate the process of waxes reusability for production of patterns. Changes in thermal properties of waxes were determined using differential scanning calorimetry (DSC) and linear shrinkage values were specified. The conducted examinations allowed to establish the way of multiple utilization of waxes in producing precise models

A concise review on microwave-assisted polycondensation reactions and curing of polycondensation polymers with focus on the effect of process conditions

During the past 15 years, increasing application of microwave heating to polycondensation reactions has been witnessed. Experiments have been carried out at laboratory scale using widely different experimental procedures. The use of microwaves has often led to significant benefits compared to conventional heating experiments in terms of multi-fold decrease in reaction times and energy consumption and production of polymers with increased molecular weight and improved mechanical properties. In other cases, microwaves do not appear to produce any significant benefits compared to conventional heating. At present, guidelines to experimentalist as to the process conditions and experimental design that should be applied are missing and experimentation seems to be based on an empirical trial-and-error approach. In view of the very different experimental protocols that have been applied and the contradictory trends that are frequently reported, we aim in this review to shed light on the role of important process parameters, such as the presence and type of solvent, the dielectric properties of the mixture and the individual phases, the use of heterogeneous catalysts, pressure, stirring, reflux conditions, temperature measurement method and microwave absorbing fillers, which all seem to determine the occurrence and magnitude of the benefits enabled by microwaves during polycondensation reactions

Manufacturing and characterization of sustainable and recyclable wood-polypropylene biocomposites:Multiprocessing-properties-structure relationships

In this study, sustainable polymeric materials with a polypropylene matrix reinforced with wood waste were developed for structural applications. The new polymer biocomposites (WPCs) were evaluated for their mechanical and structural properties regarding their susceptibility to multiple processing. As thermo-mechanical degradation processes are associated with the repeated processing of plastics, which causes changes in the properties and structure of these materials. Therefore, to determine the extent to which the composites can be used under operating conditions, the composites were examined by DMA. As a result of the study observed some effects caused by the repeated effects of shear stress and temperature on the rheological and mechanical properties of polymer composites. The first of these is related to a decrease in viscosity of WPC composites subjected to the six times processing and changes in flow conditions during extrusion and injection moulding due to the degradation of the polypropylene matrix. As the viscosity of the composites decreased, a reduction in tensile strength and other mechanical properties of the polypropylene matrix was noted. On the other hand, the second effect observed leads to the conclusion that, as the composites' processing cycles increase, the WPC composite's mechanical properties increase due to an increase in the degree of homogenization of the individual components of the WPC composition. This study aims to describe the relationship between these two primary processes and to determine the relationship between the properties and the structure of the new WPCs.</p

Relatedness decreases and reciprocity increases cooperation in Norway rats

Funding was provided by SNF-grant no. 31003A_156152 to M.T.Kin selection and reciprocity are two mechanisms underlying the evolution of cooperation, but the relative importance of kinship and reciprocity for decisions to cooperate are yet unclear for most cases of cooperation. Here, we experimentally tested the relative importance of relatedness and received cooperation for decisions to help a conspecific in wild-type Norway rats (Rattus norvegicus). Test rats provided more food to non-kin than to siblings, and they generally donated more food to previously helpful social partners than to those that had refused help. The rats thus applied reciprocal cooperation rules irrespective of relatedness, highlighting the importance of reciprocal help for cooperative interactions among both related and unrelated conspecifics.PostprintPeer reviewe

The importance of factors affecting the entry of entrepreneurial subjects to organic farming in the Czech Republic

The aim of the article is to identify the key factors influencing the entry of entrepreneurial subjects into the sphere of organic farming in the Czech Republic. Primary data for the research was obtained from a questionnaire survey carried out in 2016 through an internal communication system of the PRO BIO Association, comprising 481 operators in the field of organic farming in the Czech Republic. The research questions mainly concerned the reason for entering the sphere of organic farming, and what influenced this decision, the motivation of entrepreneurs to stay in organic farming and what could possibly be the reason for their departure from this sector of business. Another part of the research questions related to the knowledge about organic farming in the establishment of their business. a combination of factors that are important in deciding on entry into the industry and subsequent stay was found.O

What do we know about carcinoid heart disease in the present era?

Carcinoid heart disease (CHD) is a severe complication of carcinoid syndrome (CS) found primarily in patients with small intestine neuroendocrine neoplasms (SI-NENs). Patients who develop CHD have significantly worse morbidity and mortality outcomes, highlighting the importance of clinical practice recommendations for CHD screening, diagnosis, and treatment that are both consistent and practical. CHD is characterized by white plaque-like deposits on the endocardial surface of heart structures, generally affecting the right heart valves, causing tricuspid and pulmonary regurgitation and, less commonly, valve stenosis. Cardiac imaging is essential for both the diagnosis and management of CHD. Previously, imaging for CHD was mostly achieved by echocardiography, but more recently, imaging has become multimodal. N-terminal pro-B-type natriuretic peptide (NT-proBNP) and 5-hydroxyindoleacetic acid in the urine (u5-HIAA) are currently the most effective markers used in screening CS patients and evaluating CHD severity. Managing patients with CHD is challenging since both systemic malignant disease and cardiac involvement must be treated concurrently. Early diagnosis and surgical intervention when required are critical to patient prognosis, especially in those without primary tumor resection. Valve replacement surgery is the most effective treatment for patients with advanced carcinoid heart disease for alleviating cardiac symptoms and contributing to survival outcomes. To deliver effective patient treatment, multidisciplinary team collaboration is needed. This review summarizes current research findings on CHD pathogenesis, clinical and epidemiological features, useful biomarkers and imaging modalities, and treatment strategies

Coulomb excitation of 222Rn

The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electricquadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball gamma -ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10 h over bar and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) e fm2. The values of the intrinsic electric-octupole moment for the 0+ -> 3- and 2+ -> 5- transitions were found to be respectively -210 e fm3 and 2300+300-500 e fm3 while a smaller value, 1200+500-900 e fm3, was found for the 2+ -> 1- transition. In addition, four excited non-yrast states were identified in this work via gamma -gamma coincidences.Peer reviewe

The observation of vibrating pear-shapes in radon nuclei (vol 10, 2473, 2019)

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Quadrupole collectivity in Ca 42 from low-energy Coulomb excitation with AGATA

A Coulomb-excitation experiment to study electromagnetic properties of Ca42 was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in Ca42 were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in Ca42, including the diagonal E2 matrix elements of 21+ and 22+ states, were determined using the least-squares code gosia. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 01,2+ and 21,2+ states, as well as triaxiality for 01,2+ states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca42. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in Ca42