EXPERIMENTAL STUDY ON OIL WELL CEMENT RESISTANCE TOWARDS HYDROCHCLORIC ACID ATTACK

Hydrochloric acid (HCI) and Hydrofluoric acid (HF) are used in acidizing treatment to stimulate oil and gas production. It is proven that these acids had successfully increased the oil well production worldwide. However, on the other hand, it has been observed that several oil wells, after submitted to acidizing operations, exhibited zonal intercommunication problems. This is attributed to the occurrence of reactions between the hardened cement slurry in the annulus and the acid. The indication of cement deterioration is the motivation of an extensive experimental program to study the involved mechanisms. The objectives of this study are to investigate the effect of curing temperature and pressure towards the compressive strength and acid resistance towards Class G oilwell cement. Various concentration of HCI solution is exposed to cement cube samples under different curing condition for the analysis of samples of hardened cement slurries (2-inch cement cube), aiming the verification of changes in chemical compositions due to acid attack. Also, the tests are conducted on the analysis of the acid solutions, aiming the identification and quantification of the elements liberated from the cement into the acid solutions. The techniques of X-ray fluorescence (XRF) , Scanning Electron Microscopy (SEM) and equipment compressive strength tester are to be used for this purpose. Based on the results, the depth of the acid attack and the influence of the acid solution composition and of the cement chemical composition on the degree of acid attack are to be evaluated. In previous study, it is observed that HCI will react with calcium oxide forming calcium chloride and water. The higher the curing temperature and pressure, the stronger the compressive strength of the sample of cement slurries, leading to the stronger acid attack resistance. This study will enable a better comprehension of the process of acid attack on cement, and consequently a reduction of this problem in the field will be obtained

EXPERIMENTAL STUDY ON OIL WELL CEMENT RESISTANCE TOWARDS HYDROCHCLORIC ACID ATTACK

Hydrochloric acid (HCI) and Hydrofluoric acid (HF) are used in acidizing treatment to stimulate oil and gas production. It is proven that these acids had successfully increased the oil well production worldwide. However, on the other hand, it has been observed that several oil wells, after submitted to acidizing operations, exhibited zonal intercommunication problems. This is attributed to the occurrence of reactions between the hardened cement slurry in the annulus and the acid. The indication of cement deterioration is the motivation of an extensive experimental program to study the involved mechanisms. The objectives of this study are to investigate the effect of curing temperature and pressure towards the compressive strength and acid resistance towards Class G oilwell cement. Various concentration of HCI solution is exposed to cement cube samples under different curing condition for the analysis of samples of hardened cement slurries (2-inch cement cube), aiming the verification of changes in chemical compositions due to acid attack. Also, the tests are conducted on the analysis of the acid solutions, aiming the identification and quantification of the elements liberated from the cement into the acid solutions. The techniques of X-ray fluorescence (XRF) , Scanning Electron Microscopy (SEM) and equipment compressive strength tester are to be used for this purpose. Based on the results, the depth of the acid attack and the influence of the acid solution composition and of the cement chemical composition on the degree of acid attack are to be evaluated. In previous study, it is observed that HCI will react with calcium oxide forming calcium chloride and water. The higher the curing temperature and pressure, the stronger the compressive strength of the sample of cement slurries, leading to the stronger acid attack resistance. This study will enable a better comprehension of the process of acid attack on cement, and consequently a reduction of this problem in the field will be obtained

Phylogeographic analysis suggests a recent population Bottleneck in the rare Red Sea Tridacna squamosina

Giant clams are an important ecological component of coral reefs in the Red Sea, as they enhance the reef’s productivity and provide habitat that can increase diversity. Three species of giant clams, namely Tridacna maxima, T. squamosa, and T. squamosina have been described within the Red Sea. However, due to its scarcity, information about the distribution and ecology of T. squamosina in the Saudi Arabian Red Sea is still lacking. This study used DNA barcoding to confirm the identity of the rare T. squamosina in the Farasan Banks. Six mtCOI fragments (500 bp) of T. squamosina were successfully amplified using the SQUA-primers for the first time. We used our data along with 18 reference sequences (16S) from the online database to assess the genetic diversity and population structure of T. squamosina. Low genetic diversity among the T. squamosina populations inferred from the 16S sequences implies a recent bottleneck for this species, which is supported by their historically higher diversity based on the coalescent-based estimator. Given the small population abundance and limited genetic variation of T. squamosina, it may warrant immediate local protections such as biobanking and fertility preservation programs as well as effective integrated coastal zone management plans.info:eu-repo/semantics/publishedVersio

Abundance, placement and sexual identity of the epizoic barnacle Chelonibia testudinaria relative to the size and species of host turtles in Mabul Island, Malaysia

Sea turtles are partners in commensal relationships with a variety of epibionts, including barnacles. The acorn barnacle Chelonibia testudinaria is one species commonly found associated with sea turtles and other marine fauna throughout temperate to tropical waters including the Indo-Pacific. We conducted a study to assess the occurrence of this barnacle, relative to host life stage and species in a mixed foraging population of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles ( juvenile, sub-adult, adults (female and male)) in Mabul Island, Sabah, Malaysia (Celebes Sea). Expecting similar relative abundance by life stage, we found instead a significant effect between the combined dependent variables (abundance and size of barnacles) and the life stages of sea turtles in Mabul after controlling for the covariates of size and species of sea turtles (F(8, 428) = 5.77, P < 0.001, Pillai = 0.19). Among green turtles with barnacles, though adult males had larger barnacles compared with the female turtles, the mean barnacle abundance on adult females (43.4 individuals ± 5.19 SD) was higher than all other life stages. Most of the barnacles (85.6%; N = 1931) were found on the plastron of the sea turtles. The highest number of barnacle reacquisition was found among the juvenile turtles. In assessing the complemental males of the barnacles, we found they were consistently attached to the shells of the larger of the hermaphrodites from each region of the host’s body despite average shell-size differences with each region

The small giant clam, Tridacna maxima exhibits minimal population genetic structure in the Red sea and genetic differentiation from the Gulf of Aden

The Red Sea serves as a natural laboratory to investigate mechanisms of genetic differentiation and population dynamics of reef organisms due to its high species endemism. Giant clams, important yet understudied coral reef engineering species, are ideal candidates for such study in this region. This paper presents the first population genetics study of giant clams covering the entire East coast of the Red Sea. Our study aimed to investigate the population structure of the small giant clam, Tridacna maxima, based on 501-bp fragment of the cytochrome c oxidase I gene from 194 individuals (126 new sequences from this study plus 68 sequences from GenBank), collected from 14 locations in the Red Sea and Gulf of Aden (RSGA). For the genetic analysis, each sampling site was treated as a population. T. maxima showed high genetic diversity, with high gene flow in almost all sampling sites. The insignificant global #ST-value of 0.02 (p > 0.05) suggests the presence of one large, panmictic population across a wide range of temperature and salinity gradients in the RSGA. Despite this, the population in Djibouti was genetically differentiated from the other 11 populations in the Red Sea, suggesting a connectivity break between the Red Sea and the Gulf of Aden. These results could be explained by the oceanographic features facilitating wide larval transport inside the Red Sea, and creating a dispersal barrier to the Gulf of Aden. Besides larval dispersal by currents, apparent successful establishment following dispersal is probably facilitated by the mode and time of reproduction as well as the ability of T. maxima to achieve high fitness in the highly variable environmental conditions of the Red Sea.King Abdullah University of Science & Technology: BAS/1/1071-01-01info:eu-repo/semantics/publishedVersio

Optimization of metabolite extraction protocols for untargeted metabolite profiling of mycoparasitic Scytalidium parasiticum using LC-TOF-MS

Basal stem rot disease of oil palm caused by Ganoderma boninense is one of the most devastating diseases in oil palm plantation resulting in low yield, loss of palm stands and shorter replanting cycle. To-date, there is no effective treatment for Ganoderma infected palms. Control measures, either chemical or cultural approaches, show varying degrees of effectiveness. The application of biological control agents which is environmental-friendly could be an attractive solution to overcome the problem. Earlier, we had isolated a mycoparasite, Scytalidium parasiticum, from the basidiomata of Ganoderma boninense. In vitro assay and nursery experiment showed that this fungus could suppress Ganoderma infection and reduce disease severity. However, metabolites which might contribute to the antagonistic or mycoparasitic effect remain unknown. In the current study, optimization of fungal sample processing, extraction, and analytical procedures were conducted to obtain metabolites from the maize substrate colonized by mycoparasitic ascomycetous Scytalidium parasiticum. This technique capable of producing sexual spores in sac-like organs. Untargeted metabolomics profiling was carried out by using Liquid Chromatography Time of Flight Mass Spectrometry (LC-ToF-MS). We found that S. parasiticum in both liquid- and solid-state cultivation gave higher metabolite when extracted with 60% methanol with 1% formic acid in combination with homogenisation methods such as ultrasonication and grinding. The findings from this study are useful for optimisation of metabolite extraction from other fungi-Ganoderma-plant interactions

Genetic diversity of natural and restored api-api putih (Avicennia alba) populations in the west coast of Peninsular Malaysia

A large tract of mangrove forest in Malaysia has been lost due to increased anthropogenic activities. Restorative practices of mangrove forest have been adopted nationwide to re-establish ecosystem services in combating coastal erosion. However, genetic considerations in local mangrove restoration practices are still far lacking despite the vast literature on their genetic diversity. To understand whether the restored mangroves can impact the genetic diversity distribution among natural populations, we used eight microsatellite markers to assess the genetic diversity of the Api-api putih (Avicennia alba) between the natural and restored populations along the west coast of Peninsular Malaysia. We found no difference in terms of genetic diversity between these populations. Two genetic clusters were detected among A. alba along the west coast based on Bayesian clustering and discriminant analysis of principal components (DAPC). The southwest monsoon current circulation that coincides the timing of seed dispersal of A. alba may explain such pattern of genetic differentiation. Despite the minimal genetic structure, our results suggest that seed sourcing from either population is viable for the local mangrove restoration programs in the future

Singapore industrial relations : an analysis of the collective bargaining issues of the metal industries

This research report has been organised into two main parts. Starting off the first part is a brief historical account of Singapore's development since its independence. A brief history of the Singapore Labour Movement and a background of the Industrial Relations Scene should follow. A performance review of the Metal Industries as compared to the Manufacturing Sector will be done.BUSINES

In situ observation on two ‘elusive’ rhodaliid siphonophores (Cnidaria; Hydrozoa; Siphonophora) from the Red Sea, including a potential new species within the genus Archangelopsis

Rhodaliids, a specific family of siphonophores inhabiting the benthic zone, have remained enigmatic due to their rarity and elusive nature. These unique organisms, primarily found in open ocean habitats, exhibit distinctive features and are characterized by complex structures. During the Red Sea Decade Expedition, two rhodaliid specimens were collected at the sea bed at water depths of 438 and 495 meters. Regardless of challenges in specimen preservation, detailed morphological analysis revealed unique characteristics. Genetic analysis, employing the 16S rRNA marker, revealed one specimen closely related to Thermopalia taraxaca , while the taxonomic traits of this specimen suggested the identification of Archangelopsis jagoa . While most of the morphological features of the second specimen were also very similar to A. jagoa , some differences in coloration suggest the discovery of either an unusual colour variant or a potential new species within this genus. Notably, this study reports the first sequencing of A. jagoa . This species demonstrated a capacity to thrive in low-oxygen environments, challenging conventional assumptions about their habitat requirements. Despite difficulties in specimen handling and genetic analysis limitations due to a lack of comprehensive data, this research sheds light on the elusive world of benthic rhodaliids

Identification of hub genes in digestive system of mandarin fish (Siniperca chuatsi) fed with artificial diet by weighted gene co-expression network analysis

Mandarin fish (Siniperca chuatsi) is a carnivorous freshwater fish and an economically important species. The digestive system (liver, stomach, intestine, pyloric caecum, esophagus, and gallbladder) is an important site for studying fish domestication. In our previous study, we found that mandarin fish undergoes adaptive changes in histological morphology and gene expression levels of the digestive system when subjected to artificial diet domestication. However, we are not clear which hub genes are highly associated with domestication. In this study, we performed WGCNA on the transcriptomes of 17 tissues and 9 developmental stages and combined differentially expressed genes analysis in the digestive system to identify the hub genes that may play important functions in the adaptation of mandarin fish to bait conversion. A total of 31,657 genes in 26 samples were classified into 23 color modules via WGCNA. The modules midnightblue, darkred, lightyellow, and darkgreen highly associated with the liver, stomach, esophagus, and gallbladder were extracted, respectively. Tan module was highly related to both intestine and pyloric caecum. The hub genes in liver were cp, vtgc, c1in, c9, lect2, and klkb1. The hub genes in stomach were ghrl, atp4a, gjb3, muc5ac, duox2, and chia2. The hub genes in esophagus were mybpc1, myl2, and tpm3. The hub genes in gallbladder were dyst, npy2r, slc13a1, and slc39a4. The hub genes in the intestine and pyloric caecum were slc15a1, cdhr5, btn3a1, anpep, slc34a2, cdhr2, and ace2. Through pathway analysis, modules highly related to the digestive system were mainly enriched in digestion and absorption, metabolism, and immune-related pathways. After domestication, the hub genes vtgc and lect2 were significantly upregulated in the liver. Chia2 was significantly downregulated in the stomach. Slc15a1, anpep, and slc34a2 were significantly upregulated in the intestine. This study identified the hub genes that may play an important role in the adaptation of the digestive system to artificial diet, which provided novel evidence and ideas for further research on the domestication of mandarin fish from molecular level.Key National and Special Project of Blue Granary Science and Technology Innovation 202008967002, China Scholarship Council 5101229170829, Training plan for applied talents integrating industry and education - Collage of Future Technology 2020YFD0900400,info:eu-repo/semantics/publishedVersio