51 research outputs found
Thermodynamics of the adsorption of organic cations on kaolinite : temperature dependence and calorimetry
No full textThe present work is aimed at understanding the interactions involved in the adsorption of cationic surfactants on heterogeneous surfaces. The relevance of the study derives from the environmental aspects of the adsorption of small organic molecules onto soil constituents. This thesis emphasizes the experimental aspects.In order to achieve a better understanding of the driving forces involved in the adsorption process, classical equilibrium thermodynamics is used to estimate the energetic and entropic parameters of the system.The main experimental systems were a homo-ionic kaolinite in an aqueous electrolyte solution which contained a cationic surfactant with a dodecyl tail and either a pyridinium chloride (DPC), or a trimethylammonium bromide head group (DTAB).In Chapter 2 a comprehensive study of the physico-chemical properties of the adsorbent has been carried out. Several techniques, such as X-ray diffractometry, electron microscopy, Ar/N2 adsorption calorimetry, and BET gas adsorption have been used to characterize the kaolinite surface. The collected evidence shows that our kaolinite is free of 2:1 clay contaminants. Combination of electrophoresis measurements and potentiometric titration results gives information on the properties of our representative of the group of 1:1 clay minerals. Contrary to the idea of some soil scientists, about 50% of our kaolinite surface charge stems from isomorphic substitution which is mainly exposed to the basal surfaces. These surfaces are homogeneous with respect to Ar and surfactant adsorption. The particles posses a variable charge (pH-dependent) on the edges. The edges have a more heterogeneous character. Constant hysteresis observed between back- and forward potentiometric titrations confirm the binary nature of the surface charge and the possibility of edge-plate interactions resulting in a so-called card-house packing. The ratio found for the edge/plate surface area depends on the method used, viz. 0.35 from DPC adsorption, 0.55 from potentiometric titration, 0.20 from Ar adsorption calorimetry and 0.41 from electron microscopy. The CEC measured by the silver-thiourea method amounts to 57 μmole/g whereas that determined by using the ammonium acetate method is 30 μmole/g. Potentiometric titrations show that the clay surface is not covered by any oxide coating. Over the experimental pH range of 4 to 10, neither an isoelectric point (iep), nor a zero point of charge (pzc) has been found for the entire particles. Extrapolation of the electrophoretic data suggests a pzc of about 2. The zero point of charge of the edges (epzc) is estimated from the inflection point of charge-potential curves which is located in the region of minimum electrolyte effect. Of the three cations Li +, Na +and Cs +, Cs +adsorbs most strongly, resulting in a lower electrophoretic mobility and a slightly lower epzc for Cs-kaolinite. The epzc is 6.7 for Li- and Na- kaolinite and 6.0 for Cs-kaolinite.Protons are specifically adsorbed, not only on the functional edge groups but also on the plates. Adsorption of protons on Na-kaolinite is exothermic, with the enthalpies increasing when the surface charge becomes more negative. The electrolyte effect on the proton adsorption enthalpy is very small. This suggests that the pH has a more pronounced effect on the surface potential than the indifferent electrolyte. From the fact that electrophoretic mobilities change more strongly with pH than with the electrolyte concentration we come to the same conclusion. The proton adsorption enthalpies at each pH show a qualitative similarity to that of oxides with similar pzc's.Chapter 3 deals with the properties of the adsorbate. Here the thermodynamic properties of a homologous series of surfactants are studied. The micellization enthalpies of three surfactants with C10, C12 and C14 tails and pyridinium head groups are directly measured as a function of electrolyte concentration and temperature. At a certain temperature and electrolyte concentration each surfactant has a characteristic critical micelle concentration (cmc) value, which is some 60-80, 10-20 and 5-10 mmoles per litre for C 10 - C 12 - and C 14 -pyridinium chloride, respectively. Enthalpies of micellization of the surfactants (Δ mic H m ) are temperature dependent. They change sign at a certain temperature, T trans . T trans is dependent on the chain length and to a lesser extent on the electrolyte concentration. The (extrapolated) Δ mic H m (T) curves of the three surfactants cross each other at - -12°C. The enthalpy at this temperature is attributed to the head group contribution; here the enthalpic contribution of the tail is zero.Increasing the temperature decreases the structuring of water around the tails and, consequently, the entropy rises upon association of tails, but this effect is more than compensated by the decrease in enthalpy.An attempt has been made to break down the Gibbs energy, enthalpy and entropy of micellization into their electrical, hydrophobic and chemical constituents. Using the mass action model, Gibbs energies of micellization are estimated. In the presence of 0.1 M NaCl, the thermodynamic parameters of micellization of the surfactants expressed per CH 2 group are very close to the corresponding parameters of transporting a methyl group from water to a hydrophobic phase. According to our calculations, hydrophobic bonding contributes most to the micellization Gibbs energy. The electrical contribution is rather small and unfavourable. The constant chemical contribution is also unfavourable and can perhaps be attributed to a decrease in hydration forces of the solvent around the head group.The enthalpy of adsorption may be derived from adsorption isotherms determined at different temperatures or may be directly measured by using a microcalorimetric technique. The former method is discussed in Chapters 4 and 5, the latter in Chapter 6.More specifically, in Chapter 4 the adsorption of DPC and DTAB on Nakaolinite is studied as a function of electrolyte concentration and pH at two temperatures. Adsorption isotherms have steep initial slopes reflecting the high affinity of the adsorptives for the surface. For both surfactants and at both temperatures, all isotherms, if measured at different salt concentrations, exhibit a common intersection point (cip) roughly around the iep. Below the cip adsorption is reduced by electrolyte addition; beyond it electrolyte promotes adsorption. Below the cip adsorption is to a large extent electrostatically driven; addition of salt reduces the attraction. However, beyond the cip association of adsorbed surfactant molecules takes place, which occurs despite the repulsion between the head groups; now electrolyte reduces this repulsion and hence promotes adsorption. The pyridinium head group shows a slightly higher affinity for the kaolinite surface than the trimethylammonium head group.On kaolinite, adsorption of both surfactants takes place mainly on the plates. With increasing pH the (total) adsorption increases, but not so much that all adsorption sites on the edges become covered. On the plates adsorbed protons are, at least partly, exchanged against the surfactant molecules, as the pH is increased. A bilayer adsorption model has been developed on the basis of the Frumkin-Fowler-Guggenheim isotherm equation fits the adsorption data well.Chapter 5 compares the temperature dependence of the adsorption of organic cations on Na-kaolinite with that on AgI. The former adsorbent is hydrophilic, the latter hydrophobic. On AgI the adsorption of tetrabutylammonium nitrate (TBAN) proceeds up to a monolayer, whereas on the hydrophilic kaolinite the adsorption of DPC and DTAB continues up to a bilayer. On AgI the adsorption of TBAN exhibits a maximum as a function of temperature. For amphiphilic molecules on kaolinite, the enthalpies of the formation of the first layer show hardly any temperature dependence, whereas those of the formation of the second layer again pass through a maximum as a function of temperature. The adsorption of surfactant molecules increases the hydrophobicity of kaolinite, hence, around the region of completion of the first layer, the surface becomes hydrophobic. Adsorption enthalpies on AgI and on the hydrophobic kaolinite show the same trend as those for the micellization of the surfactants used. This indicates that all these processes are determined by the same mechanism, viz. hydrophobic bonding.Chapter 6 discusses the micro calorimetric measurements of the enthalpies of adsorption of DPC on Na-kaolinite at different salt levels and temperatures. Adsorption enthalpies are temperature dependent; they are positive at low temperatures, reduce to zero at about 24°C and turn to negative at T>24°C. A break in the plots of the cumulative adsorption enthalpy as a function of adsorbed amount is detected under most experimental conditions. This break, the iep and the cip of the adsorption isotherms at different electrolyte concentrations are all identical within experimental error. Below and above the break, the adsorption enthalpies are fairly constant, suggesting that the surface is homogeneous. This is in accordance with the earlier conclusion thatadsorption takes place mainly on the basal surfaces. The change of the slope of the ΔH(Γ) curves upon completion of the first layer shows again the different adsorption mechanism for the first and second layer. This part of the study confirms that among the different contributions to the enthalpy the hydrophobic part is the most important for the second layer formation. However, for the first layer the head group affinity for the surface dominates.Comparison of the isosteric adsorption enthalpy and the directly measured heat of adsorption leads to the next two conclusions: (a) For the formation of the first layer the isosteric heat of adsorption deviates somewhat from that measured by calorimetry. (b) For the formation of the second layer, good agreement has been found between the two. Both values are rather close to the enthalpy of micelle formation. Probably an important reason for the discrepancy found for the first layer is the variation of the concentrations of the other adsorbed cations at the interface as a consequence of a temperature change. Since the formation of the second layer starts when the charge of the kaolinite is compensated, the concentration of these ions at the interface is of minor importance. Therefore, beyond the iep a complete agreement between the two techniques is found.With regard to the adsorption mechanism our results can be summarized as follows:- Adsorption of cationic surfactants on charged clay surfaces takes place with a Gibbs energy of few tens of kJ/mole, implying a physical adsorption.- Surfactants adsorb primarily on the basal surfaces of kaolinite which possesses a negative charge. Whether the adsorption also takes place on the edges is uncertain. On the plates first a monolayer is formed, then a bilayer. For the former, electrolytes act as competitors, for the latter, where hydrophobic bonding is the driving force, as promoters.- Formation of the second layer is similar to micellization. The enthalpies of both processes have the same trend as a function of temperature. They are close to each other and their transition temperature agrees within a few degrees.- The nature of the head group does not play a dominating role in micelle formation or in adsorption.The adsorption of amphiphiles is sensitive to parameters such as the nature of the surface charge, electrolyte concentration, pH, and temperature. Therefore, in different climates one must expect different adsorption capacities of soils and hence, different rates of water pollution. For example, in natural systems consisting mainly of particles with a permanent charge, the adsorption capacity is probably much higher than in those systems which contain relatively large amounts of particles with variable charge. Hence, from this point of view, tropical soils may be more prone to pollution caused by the transport of organic compounds to ground water.The adsorption of amphiphiles is not limited to charge compensation. Therefore the value of the CEC may underestimate the adsorption capacity of soils.As the hydrophobic character of the charged particles changes with the amount adsorbed, there may be a large effect of soil pollution on the permeability of soils.The overall conclusion is that the present study not only contributes to our knowledge about adsorption forces but may also be helpful in understanding and predicting processes which occur in natural systems
تعيين اثربخشي سيستم تهويه در يک سالن تشريح با استفاده از روش استاندارد ISO 16000-8
No full textBackground and Objectives: Dissection laboratories should have effective ventilation always. This study aimed to determine the effectiveness of the ventilation system in a dissection labratory.
Materials and Methods: Based on ISO 16000-8 using tracer gas decay method, the effectiveness of a ventilation system operating at 4 different modes including 1)exhaust system is “on”, 2) supply system is “on”, 3) both systems are “on”, and 4 both systems are “off” in a dissection lab was evaluated. Tracer gas (SF6) was injected into dissection lab and air sampling was conducted in five zones of the lab. The air samples were then transferred to the laboratory and their concentration was determined. Finally, the Local mean age (LMA) and Room mean age of air (RMA) and the rate of local and general exhaust ventilation were calculated. Ethical issues relatet to human bodies was considered in the research protochol.
Results: Two-way analysis of variances showed that while the LMA and the local rate of ventilation at different ventilating modes had no significant, the effect of ventilating mode on the RMA and general ventilation rate, was significant (P <0.001). One-way ANOVA test showed that the exhaust system had the greatest effect on RMA and general ventilation rate of the room.
Conclusion: According to the results, the ventilation is more effective when the supply and exhaust systems are “on” together considering the toxicity of formaldehyde, in addition to the general exhaust ventilation, the implementation of a local exhaust ventilation system for each mortuary desk is recommended.
How to cite this article: Jafari MJ, Mehrian M, Rezazadeh-Azari M, Khodakarim S. Determining the Effectiveness of the Ventilation System in an Anatomy Lab using ISO 16000-8.Irtiqa Imini Pishgiri Masdumiyat (Safety Promotion and Injury Prevention). 2018; 6(3):113-122.
سابقه و هدف: سالنهاي تشريح ازجمله مکانهايي هستند که بايد همواره از تهويه مؤثري برخوردار باشند. هدف از اين مطالعه تعيين اثربخشي سيستم تهويه يک سالن تشريح با استفاده از روش استاندارد 8-16000 ISO بود.
روش بررسي: در مطالعه حاضر ضمن حفظ شأن و احترام اجساد انساني موجود در يک سالن تشريح در طول مدت پژوهش، اثربخشي سيستم تهويه يک سالن تشريح در چهار حالت متفاوت شامل: مکنده روشن، دمنده روشن، هر دو سيستم روشن و هر دو سيستم خاموش، بر پايه استاندارد 8-16000 ISO، به روش نرخ کاهش گاز ردياب (SF6) مورد ارزيابي قرار گرفت. گاز ردياب در سالن، تزريق و سپس نمونهبرداري در پنج نقطه انجام و در آزمايشگاه تعيين مقدار شد. سپس ميانگين عمر موضعي هوا و ميانگين عمر هواي سالن و همچنين نرخ تهويه موضعي و کلي هواي سالن تعيين گرديد.
يافتهها: نتايج آزمون آناليز واريانس دوطرفه نشان داد که ميانگين عمر موضعي هوا و نرخ تهويه محلي در محلها و حالات مختلف سيستم تهويه تفاوت معنيداري (0.390=p-value و 0.220=p-value ) نداشتند. همچنين اثر حالت سيستم تهويه بر ميانگين عمر هواي سالن و نرخ تهويه سالن معنيدار بود (P<0.001). آزمون آناليز واريانس يکطرفه نشان داد که سيستم مکنده بيشترين اثر را بر ميانگين عمر هوا و نرخ تهويه سالن داشت.
نتيجهگيري: بر اساس نتايج حاصله سيستم تهويه در هنگاميکه هم دمنده و هم مکنده روشن باشند اثربخشتر بود. با توجه به سميت فرمالدئيد، علاوه بر تهويه عمومي استفاده از تهويه موضعي استاندارد نيز براي ميزهاي تشريح قوياً توصيه ميشود.
How to cite this article:
Jafari MJ, Mehrian M, Rezazadeh-Azari M, Khodakarim S. Determining the Effectiveness of the Ventilation System in an Anatomy Lab using ISO 16000-8. J Saf Promot Inj Prev. 2018; 6(3):113-22.
 
COVID-19 2022 update: transition of the pandemic to the endemic phase
No full textCOVID-19, which is caused by the SARS-CoV-2, has ravaged the world for the past 2 years. Here, we review the current state of research into the disease with focus on its history, human genetics and genomics and the transition from the pandemic to the endemic phase. We are particularly concerned by the lack of solid information from the initial phases of the pandemic that highlighted the necessity for better preparation to face similar future threats. On the other hand, we are gratified by the progress into human genetic susceptibility investigations and we believe now is the time to explore the transition from the pandemic to the endemic phase. The latter will require worldwide vigilance and cooperation, especially in emerging countries. In the transition to the endemic phase, vaccination rates have lagged and developed countries should assist, as warranted, in bolstering vaccination rates worldwide. We also discuss the current status of vaccines and the outlook for COVID-19
COVID-19 update: the first 6 months of the pandemic
No full textThe COVID-19 pandemic is sweeping the world and will feature prominently in all our lives for months and most likely for years to come. We review here the current state 6 months into the declared pandemic. Specifically, we examine the role of the pathogen, the host and the environment along with the possible role of diabetes. We also firmly believe that the pandemic has shown an extraordinary light on national and international politicians whom we should hold to account as performance has been uneven. We also call explicitly on competent leadership of international organizations, specifically the WHO, UN and EU, informed by science. Finally, we also condense successful strategies for dealing with the current COVID-19 pandemic in democratic countries into a developing pandemic playbook and chart a way forward into the future. This is useful in the current COVID-19 pandemic and, we hope, in a very distant future again when another pandemic might arise
COVID-19 one year into the pandemic: from genetics and genomics to therapy, vaccination, and policy
No full textCOVID-19 has engulfed the world and it will accompany us all for some time to come. Here, we review the current state at the milestone of 1 year into the pandemic, as declared by the WHO (World Health Organization). We review several aspects of the on-going pandemic, focusing first on two major topics: viral variants and the human genetic susceptibility to disease severity. We then consider recent and exciting new developments in therapeutics, such as monoclonal antibodies, and in prevention strategies, such as vaccines. We also briefly discuss how advances in basic science and in biotechnology, under the threat of a worldwide emergency, have accelerated to an unprecedented degree of the transition from the laboratory to clinical applications. While every day we acquire more and more tools to deal with the on-going pandemic, we are aware that the path will be arduous and it will require all of us being community-minded. In this respect, we lament past delays in timely full investigations, and we call for bypassing local politics in the interest of humankind on all continents
Convected Stress/Strain Measures in the Physical Frame
No full textAn oblique, Cartesian coordinate system arises from the geometry affiliated with a QR decomposition
of the deformation gradient F, wherein Q is an orthogonal matrix and R is an uppertriangular
matrix. We analyzed the deformation of a cube into a parallelepiped, whose convected
coordinates are oblique. Components for the metric tensor and its dual evaluated in this convected
coordinate system are established for any state of deformation. Strains and strain rates are defined
and quantified in terms of these metrics and their rates. Quotient laws are constructed that govern
how vector and tensor fields map between the convected coordinate system and the rectangular
Cartesian coordinate systems, where boundary value problems are typically solved.
We also derived a set of thermodynamically admissible stress-strain pairs that are quantified in
terms of physical components from a convected stress and velocity gradient, with elastic models
being presented. This model supports two modes of deformation: elongation and shear, which is
distinguished by the pure- and simple-shear responses.
Then, we start out in an oblique convected coordinate system and finish up in an orthonormal
coordinate system. This reversing process results in working with convected tensor fields that are
evaluated in a rectangular Cartesian, coordinate system at the current time, which are ‘physical’ by
construction. We also compared the classical approach with our proposed approach
On Nonlocal Lagrangian-based Models and Applications to Material Failure
No full textThrough this study, we present a discrete nonlocal Lagrangian approach called ”tridynamics” which is designed at a length scale of interest to characterize the response of the body. As a basic unit to describe the interaction, instead of two particles required to define a bond in conventional discrete frameworks, we introduce three particles at the vertices of a triangular surface. The main idea is to understand the dynamics of a deformable body via a macro potential corresponding to a coupled interaction of rigid particles in the reduced dimension. Because the continuum limit is not taken, the framework automatically relaxes the requirement of differentiability of field variables. The discrete Lagrangian based approach is illustrated to derive equivalent Euler–Bernoulli beam model based upon the corresponding potential function. We also present a set of physical quantities that explain the deformation of Timoshenko beam and Mindlin plate, which help to derive the potential energy.
Although the construction of potential functions for basic elements such as beam and plate might be possible, it is challenging to create it in the generic case. For example, the behavior of carbon nanotube or a graphene sheet is very dependent upon molecular structure. Therefore a derivative-free balance law pertaining to a higher scale of interest has been developed based on the molecular level information, which might be useful in a continuum or discrete setting. Derived using a probabilistic projection technique, the law exploits certain microstructural information in a weakly unique manner. The projection generalizes the notion of directional derivative and, depending on the application, may be interpreted as a discrete Cauchy–Born map with the structure of the classical deformation gradient emerging in the infinitesimal limit. As an illustration, we use the Tersoff–Brenner potential and obtain a discrete macroscopic model for studying the deformation of a singlewalled carbon nanotube (SWCNT). The macroscopic (or continuum) model shows the effect of chirality – a molecular phenomenon – in its deformation profile. We also demonstrate the deformation of a fractured SWCNT, which is a first-of-its-kind simulation, and predict crack branching phenomena in agreement with molecular dynamics simulations. As another example, we have included simulation results for fractured SWCNT bundle with a view to establishing our claim regarding the efficacy of the proposed method.
The discrete Cauchy-Born rule with the principle of virtual work done are employed to formulate a generalized model with the hope to unify local and nonlocal continuum frameworks. We also found a compact mapping matrix which converts surface-based forces (stresses) to the nonlocal body-based forces. The transformation matrix allows reconstructing continuum models at a lower length scale in a discrete setting. Despite the conventional mapping of the microscopic bond from the undeformed configuration, the consistent derivation requires a transformation on the Average Deviation of Lattice (ADL) vector in the region of influence. The new conversion proffers flexibility to the framework for the analysis of nonuniform distribution of particles in the field. To see the credibility of the model, fracture evolution in SCB specimen made of Polymethyl methacrylate (PMMA) is simulated, and the results are compared with experiments
A Framework for Modeling Large Deformations and Stress Wave Mechanics in Soft Biological Tissue
No full textAn oblique, Cartesian, coordinate system arises from the geometry affiliated with a Gram-Schmidt (QR) factorization of the deformation gradient F, wherein Q is a proper orthogonal matrix and R is an upper-triangular matrix.
First, a cube deforms into a parallelepiped whose edges are oblique and serve as the base vectors for a convected coordinate system. Components for the metric tensor, its dual, and their rates, evaluated in this convected coordinate system, are established for any state of deformation. Strains and strain rates are defined and quantified in terms of these metrics and their rates. Quotient laws and their affiliated Jacobians are constructed that govern how vector and tensor fields transform between this oblique coordinate system, where constitutive equations are ideally cast, and the reference, rectangular, Cartesian, coordinate system described in terms of Lagrangian variables, where boundary value problems are solved.
Then, we derived two sets of thermodynamically admissible stress-strain pairs. They are quantified in terms of physical components extracted from a convected stress and a convected velocity gradient, with elastic models being presented for both sets. The first model supports two modes of deformation: elongation and shear. The second model supports three modes of deformation: dilatation, squeeze and shear. These models are distinguished by their pure-and simple-shear responses. They contain the coupling effects of Lord Kelvin [1], Poisson [2] and Poynting [3].
The Eulerian formulation, consists of a lower-triangular stretch postmultiplied by a different rotation tensor is studied. The corresponding stretch tensors is denoted as the Eulerian Laplace stretches. Kinematics (with physical interpretations) and work conjugate stress measures are analyzed. The Eulerian formulation, which may be advantageous for modeling isotropic solids and fluids with no physically identifiable reference configuration, does not seem to have been used elsewhere in a continuum mechanical setting.
As the application of our work, we introduced a dodecahedron to model an alveolus. Its geometric properties are derived in detail with regard to its three geometric features: 1D septal chords, 2D septal membranes, and the 3D alveolar sac. The kinematics are derived for us to model a deforming dodecahedron, including the shape functions needed for interpolating each geometry. Constitutive models are derived that are suitable for describing the thermomechanical response for the structural constituents of an alveolus: its septal chords, its permeable membranes, and its volume. Numerical methods are advanced for solving first- and second-order ordinary differential equations (ODEs) and spatial integrations along a bar, across a pentagon, and throughout a tetrahedron using Gaussian quadrature schemes designed for each geometry. A variational formulation is used to create our structural modeling of an alveolus. Constitutive equations suitable for modeling biological tissues are derived from thermodynamics using the theory of implicit elasticity, presented in an appendix
COVID-19 annual update: a narrative review
No full textThree and a half years after the pandemic outbreak, now that WHO has formally declared that the emergency is over, COVID-19 is still a significant global issue. Here, we focus on recent developments in genetic and genomic research on COVID-19, and we give an outlook on state-of-the-art therapeutical approaches, as the pandemic is gradually transitioning to an endemic situation. The sequencing and characterization of rare alleles in different populations has made it possible to identify numerous genes that affect either susceptibility to COVID-19 or the severity of the disease. These findings provide a beginning to new avenues and pan-ethnic therapeutic approaches, as well as to potential genetic screening protocols. The causative virus, SARS-CoV-2, is still in the spotlight, but novel threatening virus could appear anywhere at any time. Therefore, continued vigilance and further research is warranted. We also note emphatically that to prevent future pandemics and other world-wide health crises, it is imperative to capitalize on what we have learnt from COVID-19: specifically, regarding its origins, the world's response, and insufficient preparedness. This requires unprecedented international collaboration and timely data sharing for the coordination of effective response and the rapid implementation of containment measures
Computed Tomography Findings of Pulmonary Mycobacterium simiae Infection
No full textNontuberculous mycobacterial (NTM) pulmonary infections can be quite similar to tuberculosis, both clinically and radiologically. However, the treatment protocol is not similar. Mycobacterium simiae is a rare cause of NTM pulmonary infection. Herein, we aimed to evaluate and compare the computed tomography (CT) scan findings of M. simiae infection in lungs. For this reason, thirty-four patients (n=34) with M. simiae lung infection were retrospectively evaluated. Diagnosis was confirmed by American Thoracic Society (ATS) guidelines and CT scans were reviewed in both lung and mediastinal windows. The average age of patients was 63±14.54 years and 52.9% were male. The majority of patients had cough (91.2%) and sputum production (76.5%). Clinically, 41.2% of patients had previous history of TB (14/34), 38.2% had cardiac diseases (13/34), and 35.3% had diabetes mellitus (12/34). The most common CT findings in our study were nodular lesions (100%) and bronchiectasis (85.29%). Regarding the severity, grade I bronchiectasis was the most prevalent. Other prominent findings were tree-in-bud sign (88.2%), consolidation (52.94%), and lobar fibrosis and volume loss (67.6%). There was no significant zonal distribution of findings. In conclusion, nodular lesions and bronchiectasis are the most frequent features in CT scan of M. simiae pulmonary infection
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