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Heat Treatment By Rajan And Sharma Pdf Free _HOT_ 161

Heat treatment industries require various quenching media to improve the properties of the materials to be quenched. Petroleum based mineral (PBM) oil, a non-biodegradable oil, is popular amongst others quenchants in heat treatment processes. Recently, biodegradable oils mostly in their raw, unblended and unbleached forms have been employed for quenching of various engineering materials. Therefore, the present study examined the effects of some selected bio-quenchants in blended raw (BR) and blended bleached (BB) forms on the mechanical properties and microstructure of solution heat treated aluminum (Al)-alloy. Edible vegetable oil (70% by volume) was blended with 30% by volume of jatropha oil to form the bio-quenchant oils. Another set of bio-quenchants were formed by bleaching the raw oils before mixing so as to reduce the oxidation level and contaminations in the oil. The Al-alloy is solution heat treated at 500 C and soaked for 15 min in an electric muffle furnace before quenching in the various established bio-quenchants. Results showed that samples treated in blended raw melon (BRM) oil have higher tensile strength of 151.76 N/mm2 while samples quenched in blended bleached melon (BBM) oil have higher hardness value of 61.00 HRC. In accordance to the results obtained the bio-quenchants were found to be effective replacement to the PBM oil.

heat treatment by rajan and sharma pdf free 161


There have been various investigations on the use of vegetable oils as quenchants as reported in references [21, 22]. One of the studies involved the use of shea nut oil, palm kernel oil, and control sample (engine oil, SAE 20W-50) on 6061 aluminum material [22]. Tensile strength results showed that when the materials are quenched in shea nut oil and palm kernel oil at solutionizing temperature of 530 C, the highest values obtainable are 88.0 and 90.1 N/mm2, respectively, with the yield strength values of 66.72 and 64.94 N/mm2, respectively obtained. Highest impact energy value of 65 J was obtained in sample quenched in palm kernel oil while the ultimate tensile strength for the control sample is 83.8 N/mm2 and yield strength is 64.44 N/mm2. Odusote et al. [3] evaluated the effects of vegetable oils such as groundnut, melon, palm kernel, shea butter, and palm oil as quenchants on the properties of pure commercial aluminum heat treated at different temperatures of 200, 250, 300, and 350 C. The results indicated that the bio-quenching oil that provided the highest ductility is shea butter oil at 200 C while groundnut oil gives the best result at 350 C. Meanwhile, the highest hardness values were obtained from sample quenched in melon oil. Durowoju et al. [21] investigated the impact of severity and hardness using eco-friendly quenchants such as groundnut, shea butter, jatropha, melon, mineral, and palm oil as quenchants on heat treatment of AISI 4137 medium carbon steel. It was reported that melon oil and palm oil gave the highest hardness values of 657 and 649 HVN, respectively. To achieve an effective solution heat treatment of aluminum alloy, vegetable oil has been considered as alternative bio-quenchant to petroleum based mineral (PBM) oil, water, and water-based liquid. This is due to the increasing interest in tackling environmental challenges because vegetable oils are biodegradable, safe, offer great performance, cost effectiveness, and high productive advantages.

However, the increase in tensile strength of all the quenched samples was largely influenced by the heat treatment temperature and quench behavior [21, 22, 27]. Percentage elongation of the cast Al-alloy was 2.96%, which was less than the elongation for petroleum based mineral oil of 3.30%. The percentage elongation obtained using BRM oil, BRP, oil and BBG oil as bio-quenchant were much higher than other bio-quenchants with their values been 3.40, 3.70, and 3.76%, respectively, as shown in Fig. 3. The increase in percentage elongation offered by all the bio-quenchants might be as a result of total saturated acid (palmitic and stearic) present in the oil. BRG oil and BBM oil offered the quenched samples the lowest elongation value of 3.19 and 3.16%, respectively, which was due to the high percentage of linoleic acid value; however, bio-quenchant oils with higher percentage of linoleic acid gave lower elongation value. Also the increase in percentage elongation was influenced by the presence of palmitic, stearic, and linoleic acid. The tensile strength of the samples using the formulated bio-quenchants decreases in the following order: BR Melon oil > PBM oil > BR Palm oil > BB Melon oil > BB Groundnut oil > BR Groundnut oil > As-cast > BB Palm oil, while the percentage elongation decreases in the order: BB Groundnut oil > BR Palm oil > BR Melon oil > BB Palm oil > PBM oil > BB Melon oil > BR Groundnut oil > As-cast. In general, tensile strength and percentage elongation of samples quenched in formulated bio-quenchant oils were influenced by their respective cooling rate, thus, leading to overall increase in percentage elongation which makes the material to be more ductile and less brittle as against the as-cast material and this is in agreement with the work of Rajan et al. [28].

Ovarian cancer (OC) is the most lethal gynecologic malignancy worldwide. One of the main challenges in the management of OC is the late clinical presentation of disease that results in poor survival. Conventional tissue biopsy methods and serological biomarkers such as CA-125 have limited clinical applications. Liquid biopsy is a novel sampling method that analyzes distinctive tumour components released into the peripheral circulation, including circulating tumour DNA (ctDNA), circulating tumour cells (CTCs), cell-free RNA (cfRNA), tumour-educated platelets (TEPs) and exosomes. Increasing evidence suggests that liquid biopsy could enhance the clinical management of OC by improving early diagnosis, predicting prognosis, detecting recurrence, and monitoring response to treatment. Capturing the unique tumour genetic landscape can also guide treatment decisions and the selection of appropriate targeted therapies. Key advantages of liquid biopsy include its non-invasive nature and feasibility, which allow for serial sampling and longitudinal monitoring of dynamic tumour changes over time. In this review, we outline the evidence for the clinical utility of each liquid biopsy component and review the advantages and current limitations of applying liquid biopsy in managing ovarian cancer. We also highlight future directions considering the current challenges and explore areas where more studies are warranted to elucidate its emerging clinical potential.

Ovarian cancer has also been classified into two subtypes with distinct molecular profiles and clinical courses (Fig. 1). Type I tumours are low-grade, more indolent, and less aggressive tumours that are characterized by mutations in mitogen-activated protein kinase (MAPK) regulator pathways (e.g. KRAS or BRAF) [4]. In contrast, Type II tumours such as high-grade serous ovarian cancer (HGSOC) are aggressive and have high genetic instability. These are associated with high mutation rates in TP53, somatic and germline BRCA1/2 and other homologous recombination genes [5]. Identifying the unique tumour mutational profile can guide treatment decisions and the selection of appropriate targeted therapy. For example, polyadenosine diphosphate (ADP)-ribose polymerase inhibitor (PARPi) treatment confers a significant progression-free survival (PFS) benefit in patients with a germline or somatic BRCA1/2 mutation by causing an accumulation of double-stranded DNA breaks and cell death [6,7,8].

In the last decade, liquid biopsies that measure various tumour components, including circulating tumour DNA (ctDNA), cell-free RNA (cfRNA), circulating tumour cells (CTCs), tumour educated platelets (TEPs) and exosomes, have become recognized as a method for molecular screening and earlier diagnosis of ovarian cancer (Fig. 2). Compared to traditional tissue biopsies, liquid biopsy is minimally invasive and serial blood samples can be collected over time to monitor cancer progression in real-time. This review discusses the advantages and current limitations of liquid biopsy in the management of ovarian cancer. It will also explore different components and techniques of liquid biopsy, and its utility in ovarian cancer diagnosis, prognosis, and clinical monitoring of treatment response or recurrence. 350c69d7ab


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