NOVI EKOLOŠKI PRIHVATLJIVI I JEFTINIJI ADITIVI ZA ISPLAKE NA BAZI VODE

This study investigates the possibility of using rice husk ash as an additive to develop an environmentally friendly and low-cost drilling fluid system. Rice husk ash was added as an additive to water-based bentonite drilling fluids at different concentrations ranging from 2 wt% to 15 wt%. The rheological and filtration properties of each developed drilling fluid were measured by using a viscometer and standard low-pressure low-temperature filter press. Subsequently, the cutting carrying index, the minimum annulus velocity required to clean the bottom of the well efficiently, the flow behaviour index and the permeability of mud cakes of the formulated systems were calculated in order to assess the performance of the systems. The results demonstrated that the rheological and properties were improved depending on the concentration of the rice husk ash introduced. With the introduction of 15 wt% concentration of rice husk ash, while apparent viscosity and yield point increased by 60% and 183%, respectively, thixotropy and plastic viscosity decreased by 29% and 63%, respectively. On the other hand, drilling fluid with 4% wt% content of rice husk ash reduced the fluid loss by 10%. Moreover, the results showed that cutting the carrying index, the minimum annulus velocity required to clean the bottom of the well efficiently and the flow behaviour index of the enhanced with the exploitation of the rice husk ash in the drilling fluid. This study showed that rice husk ash is a promising additive to use in water-based bentonite drilling fluids when properly implemented, and hence reduces the impact on the environment, and the total cost for drilling.Istražene su mogućnosti upotrebe pepela rižine ljuske kao aditiva za pripremu ekološki prihvatljivijih i jeftinijih isplaka. Pepeo rižine ljuske dodan je u bentonitnu isplaku u različitim koncentracijama u rasponu od 2 do 15% maseno. Reološka i filtracijska svojstva pripremljenih isplaka mjerena su upotrebom viskozimetra i standardne API filtar preše. Naknadno, kako bi se bolje procijenila svojstva ispitivanih isplaka određen je indeks iznošenja krhotina, minimalna brzina protjecanja isplake u prstenastome prostoru potrebna za efikasno čišćenje dna bušotine, indeks toka te propusnost isplačnoga obloga. Dobiveni rezultati upućuju na poboljšanje reoloških i ostalih svojstava ispitivanih isplaka u ovisnosti o korištenoj koncentraciji pepela rižine ljuske. Kod isplake u koju je dodano 15% maseno pepela rižine ljuske uočeno je povećanje prividne viskoznosti za 60% i naprezanja pri pokretanju za 183%, dok su tiksotropna svojstva i plastična viskoznost smanjeni za 29 % odnosno 63%. S druge strane, kod isplaka koje su pripremljene s 4% maseno pepela rižinih ljuski izmjereno je smanjenje filtracije za 10 %. Štoviše, rezultati upućuju na poboljšanje indeksa iznošenja krhotina, smanjenje minimalne vrijednosti brzine protoka u prstenastome prostoru za efikasno čišćenje dna bušotine i vrijednosti indeksa toka kod upotrebe pepela rižinih ljuski u isplaci. Ovo istraživanje jasno pokazuje da je pravilnom primjenom pepela rižinih ljuski kao aditiva u bentonitnoj isplaci moguće smanjiti utjecaj na okoliš i troškove bušenja

POBOLJŠANJE MEHANIČKIH SVOJSTAVA CEMENTNOGA KAMENA U NAFTNIM BUŠOTINAMA UPOTREBOM POLIPROPILENSKIH VLAKANA I ISPITIVANJE NOVE LABORATORIJSKE METODE ZA MJERENJE ČVRSTOĆE VEZANJA CEMENTNOGA KAMENA NA ZAŠTITNE CIJEVI

The main objective of this study is to enhance the poor performance of oil well cement in terms of mechanical properties by using pure polypropylene fibers. Polypropylene fibers were added in increasing concentrations from 0 to 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% by weight of cement (BWOC). Rheological parameters, density, fluid loss, permeability, porosity, compressive strength, tensile strength, and flexural strength were all tested. A new method for measuring the tensile strength of cement samples in the presence of a casing is also evaluated in this research. In addition, the interfacial bonding shear strength, which represents the strength of cement adhesion to the casing, was measured using a new laboratory procedure. The influence of adding polypropylene fibers on rheology, density, and fluid loss can be ignored, according to the results of the experiments. The permeability and porosity of cement samples increased as the proportion of polypropylene fibers increased, according to the findings. Further, an increase in polypropylene fibers concentration up to 0.3% BWOC led to improving the mechanical properties at different curing times. The bonding strength of the casing cement interface improved with increasing polypropylene fibers concentration up to 0.5% BWOC.Glavni je cilj ovoga istraživanja poboljšati učinkovitost cementnoga kamena u naftnim bušotinama u pogledu mehaničkih svojstava korištenjem čistih polipropilenskih vlakana. U istraživanju su polipropilenska vlakna dodavana u koncentracijama od 0 do 0,1 %, 0,3 %, 0,5 %, 0,7 % i 0,9 % masenoga udjela cementa (engl. by weight of cement, BWOC). Ispitana su reološka svojstva, gustoća, gubitak fluida, propusnost, poroznost, tlačna čvrstoća, vlačna čvrstoća i čvrstoća na savijanje. U ovome je istraživanju također ispitivana i nova metoda za mjerenje vlačne čvrstoće uzoraka cementnoga kamena u kombinaciji sa zaštitnim cijevima. Osim toga, novim laboratorijskim postupkom izmjerena je posmična čvrstoća međufaznoga vezanja, koja predstavlja snagu adhezije između cementnoga kamena i zaštitnih cijevi. Na temelju provedenoga istraživanja moguće je zaključiti da je utjecaj polipropilenskih vlakana na reološka svojstva, gustoću i svojstvo gubitak fluida zanemariv. Rezultati upućuju na to da se povećanjem udjela polipropilenskih vlakana povećava propusnost i poroznost uzoraka cementnoga kamena. Nadalje, povećanje koncentracije polipropilenskih vlakana do 0,3 % masenoga udjela cementa dovelo je do poboljšanja mehaničkih svojstava u različitim vremenima očvršćivanja. Čvrstoća vezivanja cementnoga kamena duž zaštitnih cijevi poboljšana je povećanjem koncentracije polipropilenskih vlakana do 0,5 % masenoga udjela cementa

A long-lasting controversy : Western democracy promotion in Jordan

Since the end of the cold war and, in particular, the Al Qaeda attacks of 11 September 2001 in the United States, Western governments have in their rhetoric stressed democratization in the Middle East and North Africa (MENA) region as a key policy goal. 1 The EU, the US and other Western countries have developed and extended their democracy promotion activities in the region, in particular democracy assistance to civil society, independent media, the judiciary, parliament and political parties. 2 Such assistance has at times been complemented with public criticism of perceived non-democratic behaviour and political conditionalities, i.e. making democratic reform a precondition for granting favours such as trade deals and development assistance.peer-reviewe

Seroprevalence of SARS-CoV-2 (COVID-19) among Healthcare Workers in Saudi Arabia: Comparing Case and Control Hospitals

Healthcare workers (HCWs) stand at the frontline for fighting coronavirus disease 2019 (COVID-19) pandemic. This puts them at higher risk of acquiring the infection than other individuals in the community. Defining immunity status among health care workers is therefore of interest since it helps to mitigate the exposure risk. This study was conducted between May 20th and 30th, 2020. Eighty-five hospitals across Kingdom of Saudi Arabia were divided into 2 groups: COVID-19 referral hospitals are those to which RT-PCR-confirmed COVID-19 patients were admitted or referred for management (Case-hospitals). COVID-19 nonaffected hospitals where no COVID-19 patients had been admitted or managed and no HCW outbreak (Control hospitals). Next, seroprevalence of severe acute respiratory syndrome coronavirus 2 among HCWs was evaluated; there were 12,621 HCWs from the 85 hospitals. There were 61 case-hospitals with 9379 (74.3%) observations, and 24 control-hospitals with 3242 (25.7%) observations. The overall positivity rate by the immunoassay was 299 (2.36%) with a significant difference between the case-hospital (2.9%) and the control-group (0.8%) (P value <0.001). There was a wide variation in the positivity rate between regions and/or cities in Saudi Arabia, ranging from 0% to 6.31%. Of the serology positive samples, 100 samples were further tested using the SAS2pp neutralization assay; 92 (92%) samples showed neutralization activity. The seropositivity rate in Kingdom of Saudi Arabia is low and varies across different regions with higher positivity in case-hospitals than control-hospitals. The lack of neutralizing antibodies (NAb) in 8% of the tested samples could mean that assay is a more sensitive assay or that neutralization assay has a lower detection limits; or possibly that some samples had cross-reaction to spike protein of other coronaviruses in the assay, but these were not specific to neutralize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

3D-based strain analysis and cardiotoxicity detection in cancer patients received chemotherapy

Abstract Background Chemotherapy-induced cardiotoxicity has become a prevalent complication. Regular monitoring of patients who received chemotherapy using 3D strain parameters may aid in early detection of myocardial damage and its prevention. The purpose of this study was to evaluate the effectiveness of three-dimensional speckle tracking imaging (3D-STI) in diagnosing and predicting the likelihood of cardiotoxicity. This was achieved by conducting a systematic review of original research articles. Objectives To evaluate the role of 3D speckle tracking echocardiography in early detection of cardiotoxicity. Methods Relevant case control studies published prior to December 2022 were extracted to assess cardiotoxicity by 3D STE in patients after chemotherapy. Results A total of 1991 chemotherapy treated patients and control patients were included in the present review via pooling 22 studies. Conclusions 3D speckle tracking echocardiography has the utility of non-invasive and objective evaluation of changes in left ventricular function in cancer patients undergoing chemotherapy. ROSPERO registration No Study ID, CRD42023383790 on PROSPERO: International prospective register of systematic reviews

ISPITIVANJE MOGUĆNOSTI KORIŠTENJA ČEŠERA KAO EKOLOŠKI PRIHVATLJIVIH ADITIVA U ISPLAKAMA NA BAZI VODE

This study is investigating the possibility of using pinecones as additive materials to develop a water-based drilling mud. Pinecones are environmentally friendly agricultural wastes and have no practical applications. Therefore, this study is of great importance in that it highlights the investment of these natural waste materials in practical fields. The study focused on the effectiveness of pinecone powder in a water-based drilling mud. To this end, an experimental study on five types of pinecones (Austrian pinecones, Black Hills Spruce, Sitka Spruce, Norway Spruce, and White pinecones) was performed and tested to determine their ability to reduce filter loss and also the effect of those eco-friendly materials on the rheological properties and density of the mud. In the study, 26 samples of water-based mud mixed with the different types of pinecones at different concentrations based on the weight of mud sample (1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%) were used to perform the experiments. The results of the study showed that pinecones have a great ability to reduce filter loss, particularly Norway Spruce cones, which, based on this study, are considered the superior type with a concentration of 3 wt%.Ovo istraživanje obuhvaća ispitivanje mogućnosti upotrebe češera kao aditiva u isplakama na bazi vode. Češeri su ekološki poljoprivredni otpad i kao takav nemaju praktičnu primjenu. Stoga ovo istraživanje ima veliku ulogu u isticanju potrebe investiranja u upotrebu prirodnoga otpada u praktične svrhe. Fokus je ovoga istraživanja na poboljšanju reoloških svojstava i gustoće isplake na bazi vode dodavanjem praškastoga materijala dobivenoga mljevenjem češera. Također, primjena navedenoga praha kao aditiva za sprečavanje gubitka cirkulacije smanjuje zagađenje okoliša te znatno smanjuje troškove isplake na bazi vode. U ovome su radu provedena ispitivanja pet tipova češera (austrijski šišar, smreka Black Hills, sitkanska smreka, norveška smreka i bijeli bor) i njihove sposobnosti smanjenja gubitka fluida, kao i utjecaj toga ekološki prihvatljivoga materijala na reološka svojstva i gustoću isplake. Ispitivanje je provedeno na 26 uzoraka isplake na bazi vode koje su sadržavale različite tipove češera dodane pri različitim koncentracijama (težinski udio 1 %, 2 %, 3 %, 4 % i 5 %). Rezultati istraživanja pokazuju da češeri imaju znatnu sposobnost sprečavanja gubitka fluida, posebice češeri norveške smreke, koji su se tijekom ovoga istraživanja, u usporedbi s ostalim češerima, pokazali kao najučinkovitiji, i to pri koncentraciji 3 % težinskoga udjela

Association of flying time with hearing loss in military pilots

Background: Military pilots are exposed to harmful noise levels, and the two possible effects of this are hearing loss and tinnitus. Objective: This study was conducted to determine the prevalence of noise-induced hearing loss among Saudi military pilots and to determine its association with total flight hours and aircraft type (i.e., fixed and rotary wing). Materials and Methods: This cross-sectional study was conducted at the Armed Forces Aeromedical Centre, Dhahran, Saudi Arabia, between November 2015 and October 2016. A total of 150 Saudi military pilots were interviewed using a structured questionnaire. Pure-tone audiometry was used to measure hearing thresholds. Hearing threshold levels were compared between age groups and aircraft category. The association between total flying hours and the development of noise-induced hearing loss was analyzed. Results: The overall prevalence of noise-induced hearing loss in the military pilots was 18.4%, with a higher prevalence among fixed-wing pilots (42%) as compared with rotary-wing pilots (23%). Pilots with ≥2000 flying hours had a significantly higher hearing threshold compared with those in other categories. Age was a statistically significant risk factor. Conclusions: This study found that active pilots of both fixed- and rotary-wing aircrafts are at a high risk of noise-induced hearing loss; however, fixed-wing pilots with ≥2000 flying hours are at a higher risk. These findings support recommendations requiring instructions on the proper use of hearing protection devices to avoid noise-induced hearing loss

Comparative Analysis of the Impact of Urolithins on the Composition of the Gut Microbiota in Normal-Diet Fed Rats

The gut microbiota consists of a community of microorganisms that inhabit the large intestine. These microbes play important roles in maintaining gut barrier integrity, inflammation, lipid and carbohydrate metabolism, immunity, and protection against pathogens. However, recent studies have shown that dysfunction in the gut microbiota composition can lead to the development of several diseases. Urolithin A has recently been approved as a functional food ingredient. In this study, we examined the potentials of urolithin A (Uro-A) and B (Uro-B) in improving metabolic functions and their impact on gut microbiota composition under a metabolically unchallenged state in normal rats. Male Wistar rats (n = 18) were randomly segregated into three groups, with Group 1 serving as the control group. Groups 2 and 3 were administered with 2.5 mg/kg Uro-A and Uro-B, respectively, for four weeks. Our results showed that both Uro-A and B improved liver and kidney functions without affecting body weight. Metagenomic analysis revealed that both Uro-A and B induced the growth of Akkermansia. However, Uro-A decreased species diversity and microbial richness and negatively impacted the composition of pathogenic microbes in normal rats. Taken together, this study showed the differential impacts of Uro-A and B on the gut microbiota composition in normal rats and would thus serve as a guide in the choice of these metabolites as a functional food ingredient or prebiotic