First Report of Anthracnose Caused by Colletotrichum acutatum On Olive Fruits in Pakistan

Anthracnose symptoms on olive (Olea europaea) fruits cv. “Gamlick” were found in farmer orchards in Chakwal, Punjab, Pakistan (32° N and 72° E), with an average prevalence of 59%. Fruit symptoms start as thin, black, sunken lesions with a watery appearance that grow in diameter and coalesce into a large sunken soft zone. Lesions on mature fruit become noticeable in 5 to 6 days after infection, if temperatures are favorable (28°C). On the fruit lesion, orange conidial masses in dispersed or concentric circle arrangement can appear. Fragments (5 mm) were taken from the margins of fruit lesions and surface-sterilized with 70% ethanol (1 min) and 1% NaClO (2 min), cleaned with sterile purified water, blotted dry, and plated on potato dextrose agar (PDA) in Petri dishes. The petri plates were incubated at 27°C. A fungus was consistently isolated, and thirty-five isolates were characterized. Aerial mycelia from olive isolates Colonies were compact, initially white or cream white, then grey, and eventually dark grey, with conidium masses forming in the middle. Mycelium is branched, septate, and hyaline. Conidia are hyaline, aseptate, fusiform, or often cylindrical, with obtuse apices and tapering bases. Their mean size was 8.5µm in length and 3.0 µm in width. Based on morphological features, the fungus was tentatively identified as Colletotrichum acutatum (Agosteo G.E., 2010). The identification was confirmed by amplification and sequencing of a representative isolate's internal transcribed region (ITS), Beta- tubulin region (TUB2), Actin region (ACT), and Glyceraldehyde 3-phosphate dehydrogenase region (GAPDH) with the primers ITS1/ITS4 (Gardes & Bruns 1993), TUB4/TUB5 (Woudenberg et al. 2009), ACT1/ACT3 (Carbone & Kohn 1999) and GDF1/GDR1 (Guerber et al. 2003). BLAST analysis revealed 100% identity for ITS, GAPDH and ACT and 99% identity for TUB, between the sequences of the olive fruit isolate (GenBank Accessions MW647502, MZ436968, MZ714412 and MW810331, respectively) and sequences of C. acutatum reference isolates (GenBank Accessions GO613492, KF975660.1, MT274752.1 and MH547616 respectively). Phylogenetic analysis based on ITS, GAPDH and TUB regions of the olive fruit isolates and reference isolates of various Colletotrichum species using the MEGA X software program confirmed the isolate from olive was C. acutatum. The fungal isolate was deposited as a living culture in the Barani Agricultural Research Institute's fungal culture collection center (BACA.9381). Pathogenicity tests were conducted with this isolate by placing a 20 µl drop of a conidial suspension (3 × 107conidia ml−1) on five healthy olive cv. Gemlik fruits. As a control, five non-inoculated olive fruits were used. Fruits were placed at a temperature of 27°C with artificial light and a photoperiod of 12 hours. Anthracnose symptoms developed only on inoculated fruits after seven days of inoculation. The fungus was re-isolated from symptomatic fruits, and its identity was confirmed through morphological characteristics, thus verifying Koch's postulates. To the best of our knowledge, this is the first report of C. acutatum infecting olive fruits in Chakwal region of Pakistan.

Mechanical Properties Of Laser Welded Dual-Phase Steel Joints

The application of dual phase (DP) steels in the automobile industry unavoidably involves welding operation. The objective of this thesis was to study the microstructure and mechanical properties of laser welded DP steel joints. The laser welding resulted in a significant hardness increase in the FZ but the formation of a soft zone in the heat affected zone (HAZ). While the soft zone influenced the tensile properties of the joints considerably, the fatigue properties of the welds showed dependence on both the softening and the applied stress amplitudes. Fatigue crack was observed to initiate from the specimen surface and crack propagation was basically characterized by striation-like features. Post-weld heat treatment was found to eradicate the negative effect of the soft zone and improve the mechanical properties of welds. However, the heat treatment resulted in a brittle fracture mode from the dominating ductile mode of fracture of the welded joints.

Mechanical Properties Of Laser Welded Dual-Phase Steel Joints

The application of dual phase (DP) steels in the automobile industry unavoidably involves welding operation. The objective of this thesis was to study the microstructure and mechanical properties of laser welded DP steel joints. The laser welding resulted in a significant hardness increase in the FZ but the formation of a soft zone in the heat affected zone (HAZ). While the soft zone influenced the tensile properties of the joints considerably, the fatigue properties of the welds showed dependence on both the softening and the applied stress amplitudes. Fatigue crack was observed to initiate from the specimen surface and crack propagation was basically characterized by striation-like features. Post-weld heat treatment was found to eradicate the negative effect of the soft zone and improve the mechanical properties of welds. However, the heat treatment resulted in a brittle fracture mode from the dominating ductile mode of fracture of the welded joints.

Mechanisms of electron-phonon coupling unraveled in momentum and time: The case of soft phonons in TiSe2

The complex coupling between charge carriers and phonons is responsible for diverse phenomena in condensed matter. We apply ultrafast electron diffuse scattering to unravel electron-phonon coupling phenomena in 1T-TiSe2 in both momentum and time. We are able to distinguish effects due to the real part of the many-body bare electronic susceptibility, R[χ0(q)], from those due to the electron-phonon coupling vertex, gq, by following the response of semimetallic (normal-phase) 1T-TiSe2 to the selective photo-doping of carriers into the electron pocket at the Fermi level. Quasi-impulsive and wave vector–specific renormalization of soft zone-boundary phonon frequencies (stiffening) is observed, followed by wave vector–independent electron-phonon equilibration. These results unravel the underlying mechanisms driving the phonon softening that is associated with the charge density wave transition at lower temperatures.

Properties Evaluation of the Welded Joints Made by Disk Laser

The process of laser welding of sheets of HSLA (high-strength low-alloy steel), DP600 (dual-phase steel) and TRIP steels was investigated. A weld was successfully made in a double-sided hot-dip galvanized sheet with a thickness of 0.78–0.81 mm using a laser power of 2 kW per pass without any pretreatment of the weld zone. Microstructure studies revealed the presence of martensitic and ferritic phases in the weld zone, which could be associated with a high rate of its cooling. This made it possible to obtain good strength of the weld, while maintaining sufficient ductility. A relationship between the microstructural features and mechanical properties of welds made in the investigated steels has been established. The highest hardness was found in the alloying region of steels due to the formation of martensite. The hardness test results showed a very narrow soft zone in the heat affected zone (HAZ) adjacent to the weld interface, which does not affect the tensile strength of the weld. The ultimate tensile strength of welds for HSLA steel was 340–450 MPa, for DP600 steel: 580–670 MPa, for TRIP steel: ~700 MPa, respectively, exceeding the strength of base steels.

Influence of Welding Parameters and Filler Material on the Mechanical Properties of HSLA Steel S960MC Welded Joints

This article provides an overview of the influence of welding parameters and filler material on changes in the heat-affected zone (HAZ) of thermo-mechanically controlled processed (TMCP) steel welded joints. The research focused on evaluating the effect of heat input and cooling rate on the width of the soft zone, which significantly affects the mechanical properties of welded joints. The negative effect of the soft zone is more pronounced as the thickness of the material decreases. Therefore, the object of this research was a 3-mm-thick sheet of S960MC steel welded by gas metal arc welding (GMAW) and metal-cored arc welding (MCAW) technology. Variable welding parameters were reflected in different heat input and cooling rate values, which led to a change in the properties of the HAZ and thus the mechanical properties of the welded joints. The changes in the HAZ were analyzed by microscopic analysis and mechanical testing. The measured results showed a significant effect of heat input on the cooling rate, which considerably affected the width of the soft zone in the HAZ and thus the overall mechanical properties of the welded joints.

Research on the Re-Deformation Characteristics of Hot Stamping of Boron Steel Parts with Tailored Properties

Traditional hot-stamping products have super-high strength, but their plasticity is usually low and their integrated mechanical properties are not excellent. Functionally graded property structures, a relatively novel configuration with a higher material utilization rate, have increasingly captured the attention of researchers. Hot stamping parts with tailored properties display the characteristics of local high strength and high plasticity, which can make up for the limitations of conventional hot stamping and optimize the crash safety performance of vehicles. This new idea provides a means of personalized control in the hot-stamping process. In this paper, a new strategy of local induction heating and press hardening was used for the hot stamping of boron steel parts with tailored properties, of which the microstructure from the hard zone to the soft zone shows a gradient distribution consisting of a martensite phase, multiphase and initial phase, with the hardness ranging from 550 HV to 180 HV. The re-deformation characteristics of hot stamping parts with tailored properties have been studied through the uniaxial tensile test, in cooperation with digital image correlation (DIC) and electron backscattered diffraction (EBSD) techniques. The experiments show that there are easily observable strain distribution characteristics in the re-deformation of hot stamping parts with tailored properties. In the process of tensile deformation, the initial phase zone takes the role of deformation and energy absorption, with the maximum strain before necking reaching 0.32. The local misorientation of this zone was high, and a large number of low angle grain boundaries were formed, while the proportion of small angle grain boundaries increased from 13.5% to 63.3%, and the average grain size decreased from 8.15 μm to 3.43 μm. Meanwhile, the martensite zone takes on the role of anti-collision protection, with a maximum strain of only 0.006, and its local misorientation is mostly unchanged. The re-deformation experimental results show that the hot stamping of boron steel parts with tailored properties meets the functional requirements of a hard zone for anti-collision and a soft zone for energy absorption, suitable for automobile safety parts.