Planothidium marganaiensis sp. nov. (Bacillariophyta), a new cavum-bearing species from a karst spring in south-western Sardinia (Italy)

Planothidium marganaiensis sp. nov. is described from periphytic samples collected at the karst spring San Giovanni at Domusnovas, Sardinia (Italy). Light and scanning electron microscope observations revealed that the taxon shares similarities with species within the Planothidium frequentissimum sensu lato, such as P. naradoense and P. victori. Planothidium marganaiensis seems to be morphologically closely related to P. frequentissimum but stands out for its smaller valves, lower striae density, subrostrate to slightly protracted apices, and areolation pattern of the striae in the rapheless valve (four to five areolae per stria). Planothidium marganaiensis was found in slightly alkaline waters presenting medium hardness and mineralization and phosphorus enrichment.

The effectivity of used-oil as quenching medium of 42-CrMo4 steel for automotive materials

The research aims to investigate the effect of the cooling medium on the hardness characteristic and microstructure of the 42CrMo4 steel due to hardening treatment at a temperature of 830°C and holding time of 30 minutes. Various oil such as SAE-10W40, SAE-20W50, SAE-40, and used oil was used in the cooling medium. The changes in product size, hardness, and microstructure have been carefully assessed. The results indicated that the viscosity of the coolant medium strongly influenced the cooling rate of the cooling medium, hardness, and microstructure. SAE-10W40 oil and SAE-20W50 oil only needed 2 hours to return within room temperatures before quenching, whereas SAE-40 oil and used oil took 3 hours. The sample size did not change after hardening-quenching. However, there was a residual carbon layer on the sample surfaces. Quenching caused the changes of microstructure from pearlite and ferrite to ultrafine double phase, consisting of martensite and austenite, which were unable to transform during rapid cooling. The highest hardness value was achieved by the treated product, which was quenched in SAE-10W40, which had 54.59 HRC. The high hardness was attributed to the content of 95% martensite. However, used-oil caused in similar hardness as SAE-20W50.

Assessment of the Usefulness of the Twin-Screw Press in Terms of the Pressing Efficiency and Antioxidant Properties of Apple Juice

The paper presents the possibility of applying a twin-screw press for juice extraction from apples with different textural properties. The research was carried out with six different varieties; namely, Granny Smith, Modi, Ligol, Lobo, Boscop and Szampion. During the experiment, the following properties were measured: texture properties, pressing yield and polyphenolic content; and ascorbic acid content and antioxidant activity both in raw apples and apple juice. Based on the analysis, three hardness levels of apples can be distinguished, impacting the course of juice pressing in a twin-screw press (low hardness below 30 N, medium hardness 30–50 N and high hardness 50 N). The study showed that only high hardness apples are suitable for pressing on a twin-screw press. The mechanism by which texture properties influence the juice pressing process in the studied press was explained. It was further demonstrated that the hardness of apples has a positive impact on the degree of extraction of polyphenols and ascorbic acid into apple juice. This is caused by the different fracture patterns of tissues with different mechanical properties. High hardness apples (Granny Smith and Modi) were characterized by a considerably greater degree of bioactive substance extraction into juice than medium hardness apples.

Ductile-brittle transition temperature shift controlled by grain boundary decohesion and thermally activated energy in Ni-Cr steels

Temper embrittlement induced by segregation of metalloid solutes to grain boundary (GB) was evaluated by a shift of the ductile-brittle transition temperature (DBTT). DBTT was found to be linearly correlated with the amount of metalloid on the GB (Xgb) for both dynamic and static displacement rates (dδ/dt) in high and medium hardness steels. Recent first-principles calculations have determined the GB embrittling potency (Δep) of segregated Sb, Sn and P. In both high and medium hardness steels, the slope (α) of DBTT vs. Xgb was found to be linearly dependent on Δep regardless of the segregated solutes. In high hardness steels, the slope is independent of dδ/dt, while in medium hardness steels the α is dependent on dδ/dt. An Arrhenius plot of dδ/dt vs. the reciprocal DBTT was used to drive the thermal activation energy (Eact), which represents a barrier to plasticity. It was found that Eact correlates to a reduction in the GB fracture surface energy. The Eact depends strongly on GB decohesion in high hardness steels but only weakly depends on it in medium hardness steels.

Modern carbonate formation in low-mineralized flowing waters

Continental carbonate formation in low-mineralized flowing waters of temperate latitude is rare phenomenon. Taking this into account a study was conducted of crustate and stalactite-like authigenic calcite aggregates formed in the thalwegs of the ravines of the Volga Upland. According to chemical and isotopic analysis, modern carbonates are formed from poorly mineralized, meteoric waters of medium hardness, hydrocarbonate-magnesium-calcium hydrochemical type. It has been established that newly formed carbonate aggregates are characterized by the predominance of lightweight carbon and oxygen in the crystal structure. The osmotic hypothesis of the formation of lime-calcite aggregates is proposed.

Sellaphora gologonica sp. nov. (Bacillariophyta, Sellaphoraceae), a new diatom species from a Mediterranean karst spring (Sardinia, Italy)

A new epilithic Sellaphora (Bacillariophyceae) species from a karst spring of Sardinia is described based on light and scanning electron microscopic observations. Sellaphora gologonica sp. nov. shares similarities with small-celled Sellaphora previously described from Europe and particularly with S. atomoides, S. hafnearae and S. seminulum. Sellaphora gologonica seems to be related to S. seminulum based on the striae patterns and valve ultrastructure, as well as the sinuous raphe system. The main differences between S. gologonica and S. seminulum lies in its valve shape (small, elliptic to oval), not presenting capitated nor protracted apices, as in the later taxon. Sellaphora gologonica was discovered in freshwater habitats with slightly alkaline and oligotrophic waters presenting medium hardness and mineralization, at the smaller water emergence of karst spring system Su Gologone (Sardinia).

An Experimental Low-Cost Ultrasonic Phacoemulsifier—A Prototype Test

The structure and the features of a low-cost ultrasonic phacoemulsification prototype device are described in this paper. The phacoemulsifier was designed to comply with the techniques of modern cataract surgery. The functionality and reliability of the device were confirmed through in vitro experiments and animal studies. The device was designed to minimize surgical trauma: Reduced heat dissipation was achieved by specific power modulation, while the original design of aspiration control assured a reduced surge effect. In order to assess the suitability of the device, phacoemulsification was performed on rabbit eyes with nuclei of medium hardness. Their recovery was closely observed and only mild inflammation caused by surgical trauma was noticed. The device performed well in terms of reliability, ergonomics, and controllability throughout the experiments.