Effect of mechanical and thermochemical tool steel substrate pre-treatment on diamond-like carbon (DLC) coating durability

Diamond-like carbon (DLC) coatings are becoming well established across many industrial sectors including aerospace, automotive, oil and gas, and cold-forming tools. While DLC coatings exhibit good mechanical properties and a low coefficient of friction, the coating–substrate systems may suffer from insufficient wear resistance. This paper describes the effect of mechanical and thermochemical tool steel substrate pre-treatment on DLC coating durability. We have investigated two tool steel substrates, Sverker 21 (AISI D2) and an advanced powder metallurgy alloyed steel Vanadis 8. Initially, the substrates were heat treated in a vacuum furnace and gas quenched resulting in hardness of 59 ± 1 and 64 ± 1 Hardness Rockwell C (HRC) respectively. Subsequently, the samples were subjected to mechanical turning and burnishing with 130 N and 160 N forces, using diamond composite tools with a ceramic bonding phase. Afterwards, a plasma-assisted vacuum nitriding process in a physical vapour deposition (PVD) coating chamber, as a pre-treatment for subsequent DLC coating deposition, was carried out. Coated samples were subjected to a series of ball-on-disc wear tests against Al2O3 and Si3N4 counterparts. X-ray diffraction, instrumented indentation and scanning electron microscopy were employed to examine the mechanical and chemical properties of the wear scars. Selected variable factors, including the type of steel, the burnishing force and the type of counterbody material, were analysed in order to correlate them with the durability of DLC coating deposited on a pre-treated steel substrate. The effect of sequential processes used as pre-treatment on DLC coating durability was demonstrated. The wear resistance was over 180 (Sverker 21 substrate) and 10 (Vanadis 8 substrate) times greater against the Al2O3 counterbody for samples subjected to the following treatment: turning + burnishing with 160 N force + vacuum nitriding + DLC coating, comparing with the sample after grinding. The results are discussed in light of improving the cold-forming tools' tribological performance

Worldwide diversity of endophytic fungi and insects associated with dormant tree twigs

International trade in plants and climate change are two of the main factors causing damaging tree pests (i.e. fungi and insects) to spread into new areas. To mitigate these risks, a large-scale assessment of tree-associated fungi and insects is needed. We present records of endophytic fungi and insects in twigs of 17 angiosperm and gymnosperm genera, from 51 locations in 32 countries worldwide. Endophytic fungi were characterized by high-throughput sequencing of 352 samples from 145 tree species in 28 countries. Insects were reared from 227 samples of 109 tree species in 18 countries and sorted into taxonomic orders and feeding guilds. Herbivorous insects were grouped into morphospecies and were identified using molecular and morphological approaches. This dataset reveals the diversity of tree-associated taxa, as it contains 12,721 fungal Amplicon Sequence Variants and 208 herbivorous insect morphospecies, sampled across broad geographic and climatic gradients and for many tree species. This dataset will facilitate applied and fundamental studies on the distribution of fungal endophytes and insects in trees

Some indices of reactivity of organism in a chronic trichinellosis

Sixty four patients who had passed the acute phase of trichinellosis 3, 4, 5 and 8 months and 1, 2 and 4 years earlier, have been examined with respect to their clinical condition, persistence of possible subjective complaints which could be associated with the acute phase passed, leucocytosis, absolute number of acidophilic granulocytes in blood, indices of immunological response, both humoral (IgG, IgA and IgM) and cellular (percentage of T and B lymphocytes in blood), serotonine level in blood, monoaminooxidase activity in blood serum and passive hemaglutination reaction with trichinellosis antigen. It has been found that the frequency of occurrence and intensity of subjective complaints decreases with time. Changes in humoral and cellular reactivity, and long-lasting persistence of antibodies against the trichinellosis antigen, determined with passive hemaglutination method, have been also observed in particular patients

Occurrence and clinical picture of parasitoses in patients of the Clinic of Infectious Diseases, Medical Academy in Bialystok in 1975-1986

Within 12 years among 21.024 patients hospitalized in the Clinic of Infectious Diseases of the Medical Academy parasitoses were recognized in 485, i.e. 2.3%. The numbers testify to the importance of the problem of parasitoses in that region of Poland. The most frequent parasitoses of the Białystok region are at present giardiasis and taeniasis, most of all in inhabitants of towns, and within the last years also diseases introduced from the tropics - amebiasis, malaria and intestinal trematodosis

Influence of hybrid lluidized-bed apparatus design on its hydrodynamic characteristics

Omówiono sposób obliczania granicznych prędkości napowietrzania hybrydowych aparatów fluidyzacyjnych zależny od ich właściwości hydrodynamicznych. Wartości graniczne odnoszą się istnienia złoża fluidalnego i braku porywania pęcherzy gazowych do strefy opadania, a zależą od konstrukcji aparatu. Zaproponowano korzystną i prostą modyfikację aparatu z wewnętrzną cyrkulacją cieczy, która zwiększa intensywność napowietrzania, (lepsze natlenienie fazy ciekłej). Wykazano, że zastosowanie dodatkowej strefy odgazowania cieczy powoduje inny sposób obliczania górnej granicznej wartości prędkości gazu.A method for calculation of critical aeration velocities for hybrid fluidized-bed apparatuses is discussed from the point of view of their hydrodynamic properties. The critical values refer to the fluidized bed and to the lack of entrainment of gas bubbles into a down-comer. They depend on the apparatus design. An advantageous and simple modification of the apparatus with the liquid internal circulation is proposed. The circulation increases the aeration intensity resulting in better oxygenation of liquid phase. It is demonstrated that the use of additional liquid degassing zone leads to a different method of calculation of upper critical gas velocity

Conditions for the application of hybrid fluidized-bed bioreactors

Przedstawiono analityczny sposób wyznaczania podstawowych parametrów hydrodynamicznych i granicznych wartości współczynnika recyrkulacji w hybrydowym bioreaktorze fluidyzacyjnym z wewnętrzną cyrkulacją cieczy. Wartość współczynnika recyrkulacji wynika z hydrodynamiki aparatu i nie może być wymuszana zewnętrznie np. przez pompę. Przedstawiona metoda ma charakter ogólny, ponieważ nie jest związana z konkretnym procesem mikrobiologicznym. Można ją zastosować do dowolnego procesu aerobowego, jeżeli dane są wartości współczynników wydajności WBA i WBT lub WTA.The paper presents an analytical method for the determination of basic hydrodynamic parameters and limit values of recirculation ratio in a hybrid fluidized-bed airlift bioreactor with the internal circulation of liquid phase. The values of recirculation ratio in such bioreactors are related to hydrodynamic conditions. Therefore, they cannot be imposed by using an external pump. The presented method may be treated as general one because it is not tied up with particular microbiological process. It may by used for any aerobic process with given values of yield coefficients WKA and wRT or WTA

A Simple Analytical Method for Determining Basic Hydrodynamic Characteristics of Hybrid Fluidized-Bed Air-Lift Apparatae

A simple analytical method for determination of basic hydrodynamic characteristics of hybrid fluidized-bed air-lift devices was presented. These devices consist of two parts: a two-phase air-lift part and a two-phase liquid-solid fluidized-bed part. Forced circulation of fluid in the air-lift part is used for fluidization of solid particles in the fluidized-bed part. According to the opinion given in the literature, if such apparatus is used for aerobic microbiological processes, its advantage is lower shear forces acting on the biofilm immobilized on fine-grained material compared with shear forces in three-phase fluidized-bed bioreactors. Another advantage is higher biomass concentration due to its immobilization on fine particles, compared with two-phase airlift bioreactors. A method of calculating gas hold-up in the air-lift part, and gas and liquid velocities in all zones of the analyzed apparatus is presented

The influence of pre-exposition with zinc on the toxic effects of cadmium action at rats

Kadm (Cd) jest srebrzystobiałym metalem należącym do grupy metali ciężkichgęstość ponad 5g/cm3 i jest zaliczany do rodziny cynkowców. Posiada masę atomową 112,4, ciężar właściwy 8,65 i jego temperatura topnienia wynosi321°C [1, 2]. W przyrodzie kadm występuje w rudach cynkowych i ołowiowych w postaci siarczanów i węglanów [115]. W temperaturze 300°C kadm może przechodzi w stan gazowy [110, 118]. Światowa produkcja kadmu wynosi około 17000 ton na rok, a globalna emisja tego metalu do atmosfery ok. 7000 ton rocznie [118]. Dopuszczalne stężenie kadmu w atmosferze wynosi 0,01 g/m3, natomiast w litosferze średnie stężenie kadmu wynosi 0,15 do 0,2 ppm [3, 110]. W Polsce stężenie kadmu w wodzie pitnej wynosi 1÷4 g/dm3 przy dopuszczalnym maksymalnym stężeniu wynoszącym 5 g/dm3 [3, 114, 117]. Kadm występuje także w poprodukcyjnych zawiesinach przemysłowych [112]. Głównymi źródłami kadmu w środowisku jest przemysł, gdzie używa się go do produkcji akumulatorów, wyrobu stopów z miedzią stosowanych w elektronice, w reaktorach jądrowych gdzie służy on jako regulator ilości neutronów powstałych z rozszczepienia uranu [109, 111, 113, 118]. Poza tym kadm używany jest jako stabilizator w produkcji tworzyw sztucznych i pigmentów a chlorek kadmowy stosowany jest jako pestycyd w rolnictwie. Kadm używany jest też do produkcji błon filmowych i do barwienia tkanin.Main source of cadmium in the environment is the industry, where it is used for production of batteries, alloys with copper applied in electronics, in nuclear reactors where it is used serves as a regulator of quantity of formed neutrons from dissociating of uranium [109, 111, 113, 118]. Cadmium is also used as stabiliser in the production of artificial materials and pigments and cadmic chloride is applied as pesticide in agriculture. Cadmium is also used for production of movie films and for dying of fabrics. Cadmium also occurs in post production industrial suspensions [112]. WHO has placed cadmium in the first place of ranking of toxic metals due to its exceptional toxic proprieties [1, 5, 6]. Total quantity of cadmium accumulated in kidneys of 50 year old inhabitant of Europe and America is estimated to 15÷50 mg/kg [7]. The highest danger of cadmium intoxication is for people engaged in production and processing of this metal and smokers of tobacco. After smoking 20 cigarettes daily absorption of cadmium is 3.6 to 6.0 g per day, while estimate absorption at people not subjected professionally and nonsmoking is about 2,4 g per day [3, 4]. In addition cadmium is absorbed by lungs In 10÷50% of received dose [4, 6]. The aim of work was to examine the influence of the single dose of zinc on the metabolism of nucleic acids and proteins at adult rats subjected to cadmium during uterus development. Tritium labelled thymidine was used in order to asses DNA transformations, tritium labelled uridine was used in order to asses RNA transformations and tritium labelled glycine was used in order to asses transformations of proteins in tissues of descendant rats which were subjected to cadmium and zinc in the cycle of uterus development (prenatal).Experiments were carried out on female rats, their new-born progeny and 6÷7 week old male progeny. Conducted experiments allow to formulate two principal conclusions: ? Single dose of zinc given before prenatal risk of rats on cadmium prevents toxic effects of cadmium mainly on transformation of DNA, and also (though in smaller degree) RNA and proteins in organisms of mammals. investigations confirm the protective influence of zinc against toxic action of cadmium at mammals

Wpływ metali ciężkich na wzrost Escherichia coli izolowanych z wód pochodzących ze składowiska odpadów komunalnych

The aim of this study was to assess the sensitivity of Escherichia coli isolates originating from a municipal waste landfill to the selected heavy metals. The analyses were conducted using environmental strains, isolated from surface water – a stream flowing along the landfill and from leachate and the observations were compared to the reaction of a reference strain EC ATCC 25922. The growth rate of bacterial cultures was evaluated in the liquid medium supplemented with 0.02; 0.1 and 0.5 mg dm–3 of heavy metal salts: chromium, zinc, cadmium, copper, lead and mercury. The bacterial growth was examined turbidimetrically every 24 hours for 5 days. The performed study showed differences between the examined isolates in their response to the addition of the heavy metals in the liquid medium. Additionally, varied intensity of the heavy metals’ effect on bacterial growth was observed, with the weakest growth inhibition being recorded in the case of lead, while chromium and mercury causing the greatest growth inhibition of bacterial strains.Celem pracy była ocena wrażliwości izolatów Escherichia coli, pochodzących ze składowiska odpadów komunalnych na działanie wybranych metali ciężkich. Badaniu poddano izolaty środowiskowe, pochodzące z wody powierzchniowej – strumienia płynącego wzdłuż składowiska oraz z odcieków, a także szczep wzorcowy EC ATCC 25922. Ocenie poddano tempo wzrostu kultur bakteryjnych w podłożu płynnym z dodatkiem 0,02; 0,1 oraz 0,5 mg dm–3 soli metali ciężkich: chromu, cynku, kadmu, miedzi, ołowiu i rtęci. The Effect of Heavy Metals on the Growth of Waterborne Escherichia coli... 183 Wzrost bakterii badano turbidymetrycznie w odstępach 24-godzinnych przez okres 5 dni. Na podstawie przeprowadzonych badań stwierdzono różnice pomiędzy badanymi izolatami w ich reakcji na obecność badanych metali ciężkich w podłożu. Zaobserwowano także różną intensywność działania metali, przy czym najsłabsze zahamowanie wzrostu bakterii stwierdzono w przypadku ołowiu, natomiast najsilniejszy efekt hamujący miały chrom i rtęć