Inflammatory bowel disease : determinants related to gut microbiota

Inflammatory bowel disease (IBD) is a chronic and idiopathic disorder that causes inflammation in the gastrointestinal tract. Overall, it can be classified into two types: ulcerative colitis (UC) and Crohn's disease (CD). The causes of IBD have been extensively studied, with heredity, lifestyle, and environmental factors being identified as possible contributors. These factors can trigger an imbalance in the bacterial flora in the colon, which is increasingly thought to play a crucial role in the development of IBD. As dysbiosis in the gut microbiota has been frequently reported in inflammatory bowel disease, it has been proposed that both UC and CD may be caused by an auto-immune response to gut bacteria in genetically susceptible individuals. However, the exact aetiology of these diseases is still largely unknown. The aim of this thesis was to investigate epidemiological aspects of surgical abdominal procedures and possible biochemical markers associated with gut microbiota, in relation to IBD. In Paper I, we investigated the association between juvenile appendicitis, treated with appendectomy or conservatively treated without surgery, and adult risk of IBD. This, nation-wide, population-based retrospective cohort study, based on Swedish national registers, included all individuals with a diagnosed appendicitis before the age of 16, during the time-period 1973-1996, and matched controls. The study population was followed until 2017 for any development of UC and CD. We found that childhood appendicitis with appendectomy was associated with lower risk of UC (aHR 0.30 95% CI 0.25-0.36) and CD (aHR 0.82 95% CI 0.68-0.97), whereas conservative treatment was associated with lower risk of adult UC (aHR 0.29 95% CI 0.12-0.69), only, compared to unexposed individuals. Our findings warrant further research of the appendix in relation to gut microbiota and IBD pathogenesis. In Paper II, we investigated the association between bariatric surgery and new onset of IBD. This population-based retrospective cohort study included Swedish individuals registered in the Scandinavian Obesity Surgery Registry who underwent primary Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) during 2007 – 2018 and matched controls. The study population was followed up until 2019 to determine the development of CD and UC. We found that individuals operated on with RYGB had an increased risk of later development of CD (HR 1.8 95% CI 1.5 - 2.2) whereas individuals who underwent SG had an increased risk of UC (HR 1.8 95% CI 1.1-3.1). The findings should encourage further studies on surgical procedures for obesity and their effect on gut microbiota and development of IBD. In Paper III, the aim was to analyse plasma concentrations of short chain fatty acids (SCFA) in relation to CD and UC and to evaluate SCFA as a potential biomarker for IBD. This cross-sectional study included 132 and 119 individuals with CD and UC respectively and 205 controls. Although we found lower plasma concentrations of succinic acid among individuals with CD and UC in comparison to controls in univariate analysis, the difference did not remain after adjusting for sex, age and dietary factors. For all other SCFA, no differences could be found between the groups. In conclusion, CD and UC were not associated with alterations in plasma SCFA concentration. In Paper IV, we aimed to assess alterations of plasma bile acid (BA) profiles in association to CD. This cross-sectional study included 88 individuals with CD and 88 controls. CD was found to be associated with lower concentrations of most secondary BA, particularly derivatives of deoxycholic acid and lithocholic acid. Moreover, plasma concentration of secondary BA among participants with active CD was lower in comparison to participants with CD in remission. We concluded that the immune dysfunction in CD may be associated with altered bile acid composition in blood plasma

Sub-wavelength Imaging with Composite Metamaterials

After reviewing the requirements, which has to be satisfied by a metamaterial based sub-wavelength imaging systems a thin films lens is reported herein. The material of the lens is a composite of spherical Ag nanoparticles embedded in SiO$_2$ host material. The image of the lens is calculated, by solving the Maxwell equations, with the Transfer Matrix method. The procedure applies Maxwell-Garnet mixing rule and high frequency effective medium theory to calculate the electromagnetic parameters of the composite material. The formula of the composite material, the optimum working frequency and the thicknesses of the layers are determined by minimizing the absolute difference of the field distribution in the source and image planes. The details of the design procedure are presented and optimized configurations obtained under different constrains are discussed. The main advantage of the composite lens is that it can eliminate the hotspots present in the images of metallic superlens

Effect of qualitative feed restriction on energy metabolism and nitrogen retention in sheep

Periodic restrictions in feed quality and quantity is an important phenomenon in regions where animal production should bridge the gap between periods of forage production separated by a dry season. Eighteen Swifter male lambs, weaned at the age of ca. three months, were used to quantify effects of feed quality restriction and realimentation on changes in energy and nitrogen metabolism. The diet consisted of grass straw (17 MJ of gross energy [GE] and 46 g crude protein [CP] per kg dry matter [DM]) on an ad libitum basis and 35 g/kg0.75/d mixed concentrates (16.5 MJ of GE and 173 g CP per kg DM). At the age of ca. 3.5 months the animals were randomly divided into six blocks, based on live weight, according to a randomized complete block design. Within each block, the animals were randomly assigned to two restricted treatments (R1 and R2) and an unrestricted control (C) treatment. Treatments R1 and R2 were subjected to feed quality restriction by withholding the concentrate for 3 and 4.5 months, respectively. A modified linear model was developed to study the effects of restriction and realimentation. The comparison between treatments was made by analyzing the data of the R1 and R2 animals as deviations from the control animal in each block. During the restriction period, restricted animals lost weight and showed negative energy (EB) and nitrogen balances (NB), whereas their intake of low quality roughage increased significantly. During the realimentation period (5 and 6 months for the R1 and R2 animal, respectively), the R1 and R2 animals grew significantly faster than the control animals. The realimented animals persisted in ingesting significantly more low quality roughage and their EB and NB were significantly greater that those of the control animals. The R2 animals needed a longer period of realimentation because of a longer period of restriction. The expression of compensatory growth was mainly related to a sustained higher grass straw (low quality roughage) intake during the realimentation periods, and a significantly greater efficiency of metabolizable energy intake. The maintenance requirement of realimented animals was significantly lower only during the initial stages of realimentation compared with the controls. It seemed as if a three months feed restriction period in weaned sheep was better than 4.5 months

Light interaction with multilayer arbitrary anisotropic structure: an explicit analytical solution and application for subwavelength imaging

A systematic analytical approach to simulate the propagation of electromagnetic plane waves in multilayer anisotropic structures, where the layers can have arbitrary oriented optical axis, is presented. The explicit expressions for the vector polarizations of electric and magnetic fields inside a randomly oriented anisotropic medium are derived. The developed algorithm operates with analytic 4×4 matrices to calculate the transmission and reflection coefficients. This algorithm is suitable to investigate the near-field/far-field electromagnetic wave interaction at any angle of incidence for numerous intriguing applications. The procedure is applied to design anisotropic single and multilayer lenses for subwavelength imaging

Phosphosulfonic acid, an efficient solid acid catalyst for the one-pot preparation of 14-aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxo-octahydro-xanthenes under solvent-free conditions

An expeditious procedure for the synthesis of 14- aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxo-octahydro-xanthenes through one-pot pseudo three component condensation of β-naphthol or dimedone with various aryl aldehydes is described. This greener protocol is catalyzed by phosphosulfonic acid, and proceeds efficiently in the absence of any organic solvent under optimized, mild, green and environmentally benign reaction conditions in high yields within 20-55 minutes

Polyvinyl Sulfuric Acid: A Novel Solid Acid Catalyst for Preparation of Symmetrical Ethers and Theoretical Calculation

In this paper, polyvinyl sulfuric acid as a novel solid acid was easily prepared by simple mixing of polyvinyl alcohol with chlorosulfonic acid at room temperature. The facile procedure for conversion of benzylic alcohols to the corresponding symmetrical ethers in the presence of this solid acid under solvent free conditions was investigated. Results showed that the solid acid was an appropriate catalytic agent for this condensation reaction. It also showed its ability to produce the products in short reaction times while having high isolated yields.Also theoretical calculation by DFT method with B3LYP using 6-31G** basis sets was done. Based on the calculation, Transition state is a primary carbocation that the positive charge is dispersed by the benzene ring. The dipole moment of transition state is 0.2226D and the total energy of produced carbonation is more than symmetrical ether and alcohol, as the results the produced carbocation via SN1 is an appropriate transition state

SCATTERING OF LIGHT BY PLASMONIC AND DIELECTRIC NANOPARTICLES & ITS APPLICATION IN SUBWAVELENGTH IMAGING

Ph.DDOCTOR OF PHILOSOPH

Dual-Wavelength Spectral Correction Method for Simultaneous Determination of V(IV) and V(V)

Abstract: Simultaneous determination of V(IV) and V(V) was performed when the calibration matrix was obtained using beta-corrected spectral data. The method is based on the reaction between V(IV) and V(V) and 4-(2-pyridylazo)-resorcinol (PAR) as a ligand at pH 6. Using β-correction technique true absorbance of chelate produced can be calculated because the quantity of absorbance, which has related to the fraction of reagent that reacted with metal ion and has been subtracted when reagent applied as reference by this correction has compensated. The parameters controlling behavior of the system were investigated and optimum conditions selected. Calibration model was constructed based on absorption spectra in the 540-600 nm range for 25 different mixtures of V(IV) and V(V) in the concentration ranges of 0.10-4.00 µgmL −1 of V(IV) and 0.10-5.00 µgmL −1 of V(V). Applying this method to the analysis of mixtures of V(IV) and V(V) in waste water and soil samples with total relative standard error of less than 4.3% validated the proposed method

Experimental Study of Fatigue Durability in Bending Effect on Welded Joints in Steel Profiles

Ships are always prone to fatigue through high periodic loads, usually caused by waves and changing load conditions. So, fatigue is an important factor in design. One of the reasons for fatigue in welding parts is variable bending loads. In this paper, a specimen of low-carbon steel T-Bar profiles is used, along with plates of the same type of steel that have been welded by the manual electrode welding process. To determine the distribution of static and dynamic forces created by welding, the specimens were subjected to bending (three-point loading) and tensile tests, and finally fatigue tests. The T-Bar Steel profile has more tolerance for fatigue loads than welded. The load T-Bar profile has not failed until the two million cycles, while the welding specimen has failed in about 3×105 cycles. Finally, strong penetrating welds should be used if a stronger welding joint is required