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Wood-decaying fungi are important study subjects for their ecological role as well as for their biotechnological applications. They break down lignin, cellulose, and hemicelluloses using enzymes that modify the chemical structure of these complex macromolecules. Due to their ability to degrade wood, these fungi can create structural damage to wooden structures and to trees, especially those with very low level of fitness. Previous studies on wood decay fungi in the Maltese Islands are limited to records and checklists described by a handful of authors. The aim of this study was to provide a comprehensive description of wood decay fungal diversity in the Maltese Islands including an updated checklist based on DNA barcoding, as well as to establish the first wood-decay fungal culture collection at the Biology Department Seed Bank of the University of Malta. Several surveys were carried out during the rainy season along wooded areas of the Maltese Islands as well as in historical gardens. Isolates were identified using macro- and micro-morphological features, dichotomous keys, as well as molecular data. Basidiomes were recorded growing on 14 different host plant species, 11 axenic cultures have been made and 9 species of wood decay fungi have been conclusively identified by DNA barcoding. The collection of the axenic isolates includes one of Aurificaria cf. euphoria, three of Ganoderma resinaceum sl., two of Laetiporus sulphureus, one of Inonotus sp., one of Inonotus rickii anamorph, one of Inocutis tamaricis, one of Stereum hirsutum, and one of Pleurotus eryngii. However, the mycelium of Coriolopsis gallica, though collected and identified, could not be isolated. [ABSTRACT FROM AUTHOR]

This study assessed presence of Trichoderma spp. in the Maltese Islands. Isolates were identified using dichotomous keys and DNA barcoding. Ten distinct isolates were obtained from different soils and other substrates, and were identified as T. virens, T. citrinoviride, T. gamsii, and, in the former T. harzianum species complex, T. breve, T. afroharzianum and T. atrobrunneum. Five out of these six fungi are reported for the first time in the Maltese Islands, and T. brevis is reported for the first time in Europe. [ABSTRACT FROM AUTHOR]

The use of additively manufactured components specifically utilizing titanium alloys has seen rapid growth particularly in aerospace applications; however, the propensity for retained porosity, high(er) roughness finish, and detrimental tensile surface residual stresses are still a limiting factor curbing its expansion to other sectors such as maritime. The main aim of this investigation is to determine the effect of a duplex treatment, consisting of shot peening (SP) and a coating deposited by physical vapor deposition (PVD), to mitigate these issues and improve the surface characteristics of this material. In this study, the additive manufactured Ti-6Al-4V material was observed to have a tensile and yield strength comparable to its wrought counterpart. It also exhibited good impact performance undergoing mixed mode fracture. It was also observed that the SP and duplex treatments resulted in a 13% and 210% increase in hardness, respectively. Whilst the untreated and SP treated samples exhibited a similar tribocorrosion behavior, the duplex-treated sample exhibited the greatest resistance to corrosion-wear observed by the lack of damage on the surface and the diminished material loss rates. On the other hand, the surface treatments did not improve the corrosion performance of the Ti-6Al-4V substrate. [ABSTRACT FROM AUTHOR]

This research studies the individual and combined effects of mechanical shot peening and the deposition of TiAlCuN coating on additively manufactured 316L stainless steel. Shot peening has been found to induce a 40% increase in surface hardness, while the combined effect of shot peening and the coating produced an approximately three-fold increase in surface hardness when compared to the as-printed coupons. Shot peening reduced the surface roughness of printed metal coupons by 50%, showing that shot peening can also serve to improve the surface finish of as-printed 316L stainless steel components. The peening process was found to induce a compressive residual stress of 589 MPa, with a maximum affected depth of approximately 200 μm. Scratch testing of the printed and coated specimens showed complete delamination failure at a normal load of 14 N, when compared to hybrid treated samples which failed at 10 N. On the other hand, from the corrosion tests, it was found that the hybrid treated samples provided the optimal results as opposed to the other variables. [ABSTRACT FROM AUTHOR]

The use of elemental metallic powders and in situ alloying in additive manufacturing (AM) is of industrial relevance as it offers the required flexibility to tailor the batch powder composition. This solution has been applied to the AM manufacturing of nickel-titanium (NiTi) shape memory alloy components. In this work, we show that laser powder bed fusion (LPBF) can be used to create a Ni55.7Ti44.3 alloyed component, but that the chemical composition of the build has a large heterogeneity. To solve this problem three different annealing heat treatments were designed, and the resulting porosity, microstructural homogeneity, and phase formation was investigated. The heat treatments were found to improve the alloy's chemical and phase homogeneity, but the brittle NiTi2 phase was found to be stabilized by the 0.54 wt.% of oxygen present in all fabricated samples. As a consequence, a Ni2Ti4O phase was formed and was confirmed by transmission electron microscopy (TEM) observation. This study showed that pore formation in in situ alloyed NiTi can be controlled via heat treatment. Moreover, we have shown that the two-step heat treatment is a promising method to homogenise the chemical and phase composition of in situ alloyed NiTi powder fabricated by LPBF. [ABSTRACT FROM AUTHOR]

This study investigated seed germination in five indigenous species of plants in the Maltese Islands, predominantly occurring in coastal garrigue habitats but also inland, namely Drimia maritima, Periploca angustifolia, Asparagus aphyllus, Myrtus communis, and Pancratium maritimum. Different germination protocols were tested for one or more populations, namely: four different temperature regimes - constant 15, 20 and 25°C as well as alternating 23.5/15°C; three different photoperiods, 12/12, 16/8 and 0/24 light/dark. The best germination results for each species are provided and additional notes on the species and germination behaviour are also given. [ABSTRACT FROM AUTHOR]

Chemical composition of different organs and cytotoxic potential of essential oils (EO) of Tuscan Juniperus oxycedrus, was studied in human breast adenocarcinoma (MCF7), human chronic myeloge- nous erythroleukemia (K562) and a human neuroblastoma cell line derived from a highly malignant tumor (SH- SY5Y) cells. GC-MS analyses confirmed the prevalence of monoterpene hydrocarbons (MHs) class in all studied organs with α-pinene as the main compound. The relative abundance of this constituent ranged from 35.3 % in seed EO to exceed 50 % in the mixture (1:1) of leaf and fruit EO. Other MH compounds present in high amounts were myrcene (25.7 % and 10.9 % in seeds and fruits EOs, respectively) and limonene (11.9 % and 7.4 % in leaf and mixture EOs, respectively). Germacrene D, a sesquiterpene hydrocarbon, was the most abundant constituent of fruit EO (30.8 %). Leaf EO showed to be very active on MCF7 (IC50, 19.1 ppm) and K562 (IC50, 35.1ppm) un- derlining the time- and dose-depend way of action. The human neuroblastoma cell line (SH-SY5Y) were almost exclusively sensitive to the fruit EO (IC50, 30.8 ppm). [ABSTRACT FROM AUTHOR]

In this work, we investigated the chromosome number and genome size of two Mediterranean Amaranthaceae species, namely Atriplex mollis from southern Tunisia and A. lanfrancoi (formerly Cremnophyton lanfrancoi) from Malta. The two species were found to be diploid (2n = 18) for all examined populations. This result is different from that previously reported for Cremnophyton lanfrancoi Brullo and Pavone (2n = 20). Genome size showed that both species have a close mean amount with 2C = 3.41 and 3.51 pg, respectively. Two groups were distinguished with regard to genome size (P < 0.01). It should, however, be noted that the majority of populations, with the exception of those from Djerba and Chbika, may be intermediate between the two basic groups. Moreover, the difference does not appear to depend on geographical distribution and environmental aspects. It would rather depend on chromosome rearrangements. The morphological similarities, the monophyly of Atriplex including A. lanfrancoi, previously ranked in genus Cremnophyton, sharing the same chromosome number and the same genome size, support the placement of Cremnophyton within the genus Atriplex. [ABSTRACT FROM AUTHOR]

This study aims to deepen the analysis of seed germination ecology and salinity tolerance of Sarcopoterium spinosum (Rosaceae). Germination tests were conducted to evaluate the effect of the fruit's spongy tissue and the intraspecific variability in seed germination among eight populations of the species on responses to light and total darkness, constant and alternating temperatures, salt stress and germination recovery. The effect of the presence of the spongy tissue varied among populations, with significant results for seed germination. For all populations, optimum germination temperatures were observed in the range of 10–20°C, indicating that S. spinosum and its germination in the field might occur preferably in the period between autumn and early spring. The high water availability due to rainfall during this period could be a considerable advantage for the seed germination of this species. Seeds of S. spinosum showed the ability to germinate in up to 250 mM NaCl in the substrate, and their ability to recover after salt exposure may be interpreted as adaptation to the coastal habitats in which they generally grow. These results give this species a halo‐tolerant character. Great inter‐population variability is detected in this study in several aspects, which indicated that the Mediterranean populations of S. spinosum differ considerably and are adapted to their local conditions. This study provides new information about S. spinosum seed ecology, which could help to preserve and apply effective conservation measures for this species, which in several areas of its distribution range is endangered. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to compare the degradation resistance of nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys used as a base material for partial dentures in contact with saliva. Methods: Wiron® 99 and Wironit Extra-Hard® were selected as representative casting alloys for Ni-Cr and Co-Cr alloys, respectively. The alloys were tested in contact with deionized water, artificial saliva and acidified artificial saliva. Material characterization was performed by X-ray diffractometry (XRD) and microhardness and nanohardness testing. The corrosion properties of the materials were then analyzed using open circuit potential analysis and potentiodynamic analysis. Alloy leaching in solution was assessed by inductively coupled plasma mass spectrometry techniques. Results: Co-Cr alloy was more stable than the Ni-Cr alloy in all solutions tested. Leaching of nickel and corrosion attack was higher in Ni-Cr alloy in artificial saliva compared with the acidified saliva. The corrosion resistance of the Co-Cr alloy was seen to be superior to that of the Ni-Cr alloy, with the former exhibiting a lower corrosion current in all test solutions. Microstructural topographical changes were observed for Ni-Cr alloy in contact with artificial saliva. The Ni-Cr alloy exhibited microstructural changes and lower corrosion resistance in artificial saliva. The acidic changes did not enhance the alloy degradation. Conclusions: Ni-Cr alloys are unstable in solution and leach nickel. Co-Cr alloys should be preferred for clinical use. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) methods are generally used to produce an early sample or near net-shape elements based on three-dimensional geometrical modules. To date, publications on AM of metal implants have mainly focused on knee and hip replacements or bone scaffolds for tissue engineering. The direct fabrication of metallic implants can be achieved by methods, such as Selective Laser Melting (SLM) or Electron Beam Melting (EBM). This work compares the SLM and EBM methods used in the fabrication of titanium bone implants by analyzing the microstructure, mechanical properties and cytotoxicity. The SLM process was conducted in an environmental chamber using 0.4-0.6 vol % of oxygen to enhance the mechanical properties of a Ti-6Al-4V alloy. SLM processed material had high anisotropy of mechanical properties and superior UTS (1246-1421 MPa) when compared to the EBM (972-976 MPa) and the wrought material (933-942 MPa). The microstructure and phase composition depended on the used fabrication method. The AM methods caused the formation of long epitaxial grains of the prior β phase. The equilibrium phases (α + β) and non-equilibrium ά martensite was obtained after EBM and SLM, respectively. Although it was found that the heat transfer that occurs during the layer by layer generation of the component caused aluminum content deviations, neither methods generated any cytotoxic effects. Furthermore, in contrast to SLM, the EBM fabricated material met the ASTMF136 standard for surgical implant applications. [ABSTRACT FROM AUTHOR]

High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. this thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. this hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising® treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. the objective of this paper is to analyze the biocompatibility of a Kolsterised® Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised® material relative to the original untreated alloy, and other materials. this work has been performed on 3 fronts including: material characterization, "in-vitro" corrosion testing, and biological testing conforming to BS eN ISo 10993-18:2009--Biological evaluation of medical devices. Using these techniques, the Kolsterised® cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. the Kolsterised® samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties. [ABSTRACT FROM AUTHOR]

The corrosion properties of S-phase surface layers formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C) has been investigated. The corrosion behaviour of the S-phase layers in Ringer's solutions was evaluated using potentiodynamic and immersion corrosion tests. The corrosion damage was evaluated using microscopy, hardness testing, inductive coupled plasma mass spectroscopy and X-ray diffraction. The experimental results have demonstrated that low-temperature nitriding, carburising and carbonitriding can improve the localised corrosion resistance of both industrial and medical grade austenitic stainless steels as long as the threshold sensitisation temperature is not reached. Carburising at 500°C has proved to be the best hardening treatment with the least effect on the corrosion resistance of the parent alloy. [ABSTRACT FROM AUTHOR]

S-phase surface layers were formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C). The presence of the S-phase was confirmed by microscopy, hardness testing, depth-profile analysis of chemical composition and X-ray Diffraction. Attachment and proliferation of mouse osteoblast MC3T3-E1 cells were tested on S-phase and untreated controls and the results demonstrated that all the S-phase layers formed were biocompatible under the conditions used. Cells adhered equally well to all samples but proliferation was enhanced on the treated materials. [ABSTRACT FROM AUTHOR]

Effective autogenous full-penetration welding of 4 mm thick AISI 316LTi austenitic stainless steel bars was achieved using a CO2 laser. The welding process parameters required to obtain an optimal and repeatable procedure giving the best quality welds were identified. The use of side jet of gas suppressing plasma formation was investigated, and it was discovered that there are optimal conditions that result in increased power transmission and improved repeatability. Tests were carried out on the final welds in the as-welded state and in the annealed state. These included microstructural and X-ray diffraction (XRD) analysis as well as potentiodynamic and salt spray corrosion tests. Microstructural analysis showed that solidification occurred in primary ferrite solidification (FA) mode. Application of a heat treatment to the welded samples dissolved the ferrite, but resulted in carbide precipitation diminishing resistance to pitting, and the corrosion tests carried out demonstrated that the corrosion-resistant properties of the material were not compromised by the welding process, and that a post-process heat treatment was unnecessary. [ABSTRACT FROM AUTHOR]

The author reflects on the scientific knowledge of S-phase in the industrial processes developed and modified in 25 years. He cites the ongoing debate on the true structure of S-phase and the rationale behind the growing interest of attending seminars in the field of S-phase surface engineering. He mentions the lack of agreement among several authors on the structure of S-phase and its name. An overview of the history of S-phase and its industrial processes and applications are offered.

Plants are an important source of several clinically useful anti-cancer agents. A volatile extract was obtained from Ricinus communis L. (Euphorbiaceae) leaves by standard hydrodistillation and subsequent extraction of the cohobated water in chloroform. GC-MS identified three monoterpenoids: 1,8-cineole, camphor and α-pinene, and a sesquiterpenoid: β-caryophyllene, as the main constituents. The leaf extract is cytotoxic to several human tumour cell lines in a dose-dependent fashion, with IC50 values ranging between 10-40 µg mL-1. Apoptosis was shown to be induced in SK-MEL-28 human melanoma cells at a concentration of 20 µg mL-1, as identified by means of morphological examination, nuclear staining and flow cytometric analysis of DNA content. Translocation of phosphatidyl serine to the cell membrane's external surface and loss of mitochondrial membrane potential were also detected. This study provides further insight into the potential use of mixtures of terpenoids as they occur in nature, as inducers of apoptosis in cancer cells. [ABSTRACT FROM AUTHOR]

In this work, the quality of coatings prepared by plasma electrolytic oxidation (PEO) on an AZ31 magnesium alloy were evaluated. This was done by studying the effects of the chemical composition of phosphate-based process electrolytes in combination with different applied current densities on coating thickness, porosity, micro-cracking and corrosion resistance in 0.1 M NaCl. Both processing parameters were studied in four different levels. Mid-term corrosion resistance in 0.1 M NaCl was examined by electrochemical impedance spectroscopy and based on this, corrosion mechanisms were hypothesized. Results of performed experiments showed that the chosen processing parameters and electrolyte composition significantly influenced the morphology and corrosion performance of the prepared PEO coatings. The PEO coating prepared in an electrolyte with 12 g/L Na3PO4·12H2O and using an applied current density 0.05 A/cm2 reached the highest value of polarization resistance. This was more than 11 times higher when compared to the uncoated counterpart. [ABSTRACT FROM AUTHOR]

Tribocorrosion damage is a cause for the premature failure of hip implants made of cobalt-based alloys. Low-temperature carburising can be a plausible solution towards mitigating the tribocorrosion damage of articulating components. This diffusion treatment introduces a supersaturated carbon solid solution, termed S-phase, which hardens the CoCrMo alloy without detriment to the corrosion resistance. This work investigates and compares the tribocorrosion behaviour of untreated and carburised ASTM F1537 CoCrMo alloys tested in Ringer's solution using a reciprocating sliding configuration against a polycrystalline alumina counterface under different electrochemical conditions. The research shows that whereas the carburised alloy suffered a slightly higher wear loss under a cathodic potential, it was able to reduce the material losses considerably when tested under both open circuit and anodic potential conditions. Under anodic conditions material losses by corrosion due to wear dominated. The better tribocorrosion resistance of the carburised layer was attributed to the better qualities of the passive film for the carburised sample coupled with an increased load support. [ABSTRACT FROM AUTHOR]