Dark Fluid Research Articles

Relativistic corrections to the growth of structure in modified gravity

We present a method to introduce relativistic corrections including linear dark energy perturbations in Horndeski theory into Newtonian simulations based on the N-body gauge approach. We assume that standard matter species (cold dark matter, baryons, photons and neutrinos) are only gravitationally-coupled with the scalar field and we then use the fact that one can include modified gravity effects as an effective dark energy fluid in the total energy-momentum tensor. In order to compute the scalar field perturbations, as well as the cosmological background and metric perturbations, we use the Einstein-Boltzmann code hi_class. As an example, we study the impact of relativistic corrections on the matter power spectrum in k-essence, a subclass of Horndeski theory, including the effects of massless and massive neutrinos. For massive neutrinos with ∑ mν = 0.1 eV, the corrections due to relativistic species (photons, neutrinos and dark energy) can introduce a maximum deviation of approximately 7% to the power spectrum at k ∼ 10−3 Mpc−1 at z=0, for a scalar field with sound speed cs2∼0.013 during matter domination epoch. Our formalism makes it possible to test beyond \\lcdm models probed by upcoming large-scale structure surveys on very large scales.

Dark energylt;img alt=quot;quot; src=quot;C:UsersguptaDesktop/1 file png.(png)quot; /gt;lt;img alt=quot;quot; src=quot;http://www.physicsjournal.net/uploads/JPG_20210419_095951.jpgquot; style=quot;height:12px; width:25pxquot; /gt;gravity cosmological models in the form of wet dark fluid

The paper devotes to dynamical investigations of spatially homogeneous Bianchi type-I space-time filled with wet dark fluid, which is a candidate for dark energy in the framework of gravity. The equation of state parameter modeled on in the form of wet dark fluid for the dark energy component of the universe. Solutions to the corresponding field equations are obtained towards power and exponential volumetric law of expansion. The geometrical and physical parameters for both the models are studied in details. PACS numbers: 98.80.Es; 14.65.q; 04.60.m; 04.50.Kd.

Влияние теплового излучения на сингулярное поведение Вселенной

Cosmological models with inhomogeneous viscous fluids with a logarithmic equation of state in the Friedmann-Lemaitre-Robertson-Walker universe are considered. The influence of thermal effects caused by Hawking radiation on the visible horizon of the Universe on the change in the type of singularity of the dark Universe is investigated. It is shown that under the influence of thermal radiation, taking into account the viscosity property of a dark fluid, a qualitative change in the type of the Big Rip singularity is possible, which can lead to the absence of a singularity in the Universe at all.

Hydronephrosis in a Dog Related to Ovariosalpingohysterectomy

Background: Hydronephrosis is the dilation of the pelvis and renal calyxes due to post-renal obstruction. The obstruction is often associated with extraluminal masses, blood clots and ureter ligation in castration procedures. Ureter ligation is reported as a malpractice. The renal function is reestablished if ligation is rapidly undone, but not for obstructions longer than four weeks. Often, clinical signs are results from months to years after the castration, when nephrectomy is the best therapeutic option. This paper aims to report a case of asymptomatic unilateral hydronephrosis in a 10-year-old dog caused by chronic ureter occlusion with Nylon 3.0 suture during an elective procedure.Case: A 10-year-old female pinscher dog, spayed 3 years ago was admitted at the Surgery Department of the Veterinary Hospital of the Federal University of Jataí (HV-UFJ). The animal was taken for periodontal treatment. In the physical and laboratory examination (complete blood count, hepatic and renal biochemical tests) no significant and noteworthy alterations were found. Ultrasonographic examination showed no changes in the topography and echotexture of the left kidney, however the right kidney was not visualized, with an anechoic structure suggestive of advanced and severe hydronephrosis. Therefore, exploratory laparotomy was proposed to identify the observed structure, with the periodontal treatment considered for a later time. So, a retroumbilical incision was made, followed by linea alba and the removal of simple isolated suture remaining from previous surgical procedure. In the cavity, the viscera were isolated and the left kidney was identified, observing preserved anatomy. On the other hand, the right kidney had altered topography and morphology, being exposed after release of adhesions in adjacent structures. The right renal artery and vein were dissected and a double ligature was made. Then, the right ureter was dissected, observing marked dilatation in the proximal portion and the presence of local ligation with Nylon 3.0. Right ureterectomy and right nephrectomy were performed. After nephrectomy, the capsule was ruptured, observing dark fluid in it and absence of tissue compatible with renal parenchyma. The material was preserved in 10% formaldehyde and sent for histopathological examination. Histopathology revealed risk of rupture of the renal capsule due to the advance of renal degeneration and complete absence of parenchyma. However, contrary to the severity of the histopathological, surgical and ultrasonographic findings, the patient did not present clinical signs at the time of diagnosis.Discussion: In the intraoperative evaluation, the cause of the hydronephrosis was verified to be in fact the ligation of the ureter, which may have been accidental or due to the malpractice of the veterinarian surgeon. Other possible causes such as adhesions and granulomas were ruled out because the Nylon 3.0 suture was found in the proximal portion of the right ureter. It is believed that the patient may have presented clinical signs of hydronephrosis that may have been confused by the tutors as postoperative complications, changes that if identified and performed in time, could have avoided the occurrence or worsening of hydronephrosis and subsequent nephrectomy. Clinically, the bitch did not show clinical signs presented in the literature as consistent with hydronephrosis such as polyuria, polydipsia, abdominalgia, external fistula and anorexia. Therefore, it is believed that this case is one of the first reports of the occurrence of severe hydronephrosis without typical clinical manifestations of hydronephrosis. This fact raises a warning about the thorough monitoring in the postoperative period by owners and veterinarians, in addition to highlighting concerns regarding the occurrence of medical malpractice versus surgical accidents. Keywords: castration, malpractice, nephrectomy, nylon.

Time-dependent diffusive interactions between dark matter and dark energy in the context of k-essence cosmology

We investigated the scenario of time-dependent diffusive interaction between dark matter and dark energy and showed that such a model can be accommodated within the observations of luminosity distance-redshift data in Supernova Ia (SN Ia) observations. We obtain constraints on different relevant parameters of this model from the observational data. We consider a homogeneous scalar field ϕ(t) driven by a k-essence Lagrangian of the form L = V(ϕ)F(X) with constant potential V(ϕ) = V, to describe the dynamics of dark energy in this model. Using the temporal behaviour of the FRW scale factor, the equation of state and total energy density of the dark fluid, extracted from the analysis of SN Ia (JLA) data, we have obtained the time-dependence of the k-essence scalar field and also reconstructed the form of the function F(X) in the k-essence Lagrangian.

Testing lambert [formula omitted] equation of state with observational hubble parameter data

In this paper, we investigate the possibility that the Universe is driven by a single dark fluid described by a Lambert W equation of state parameter, weff, which is essentially dependent on two parameters ϑ1 and ϑ2 which need to be fixed from observations. We obtain the constraints on these parameters using the latest 51 data points of H(z) measurements, spanning the redshift range 0.07≤z≤2.36. The present study shows that the Universe is indeed undergoing an accelerated expansion phase following the decelerated one at the transition redshift, zt=0.77±0.03 (1σ) and is well consistent with the recent observations. We also find that at low redshifts, weff evolves only in the quintessence regime (−1<weff<−13) within 1σ confidence level. Its present value is found to be −0.96±0.02 (1σ). The fact that the present value of weff is very close to the Cosmological Constant Λ implies that our proposed equation of state parameter might serve as a unification of dark matter and dark energy. Furthermore, we compare the evolution of H(z) for the model under consideration with that of the ΛCDM model. Finally, we observe that for the best-fit case, the differences between the two models are negligible at z∼0.67.

Testing dissipative dark matter in causal thermodynamics

In this paper we study the consistency of a cosmological model representing a universe filled with a one-component dissipative dark matter fluid, in the framework of the causal Israel–Stewart theory, where a general expression arising from perturbation analysis for the relaxation time [Formula: see text] is used. This model is described by an exact analytic solution recently found in [N. Cruz, E. González and G. Palma, Gen. Relat. Gravit. 52, 62 (2020), which depends on several model parameters as well as integration constants, allowing the use of Type Ia Supernovae and Observational Hubble data to perform by an astringent observational tests. The constraint regions found for the parameters of the solution allow the existence of an accelerated expansion of the universe at late times, after the domination era of the viscous pressure, which holds without the need of including a cosmological constant. Nevertheless, the fitted parameter values lead to drawbacks as a very large non-adiabatic contribution to the speed of sound, and some inconsistencies, not totally conclusive, with the description of the dissipative dark matter as a fluid, which is nevertheless a common feature of these kind of models.

Bianchi Type- I Bulk Viscosity with a DE Cosmological Model

The finding article presents Bianchi type- I universe in the presence of bulk viscous and DE fluid nature of a cosmological model. The solutions of field equations were obtained by assuming hybrid expansion law. The physical significance of the obtained findings illustrates the dominance of bulk viscosity in early and dominance of dark energy fluid emergences in late. This leads to indicate the presence of bulk viscosity nature more effective in early time rather than late times, and also, it shows the dominance of dark energy in late times which grants the current observational result of the universe. Certain physical and geometrical properties of the model are also discussed.

Torsion of pediatric indirect inguinal hernia sac: A rare case

Torsion of the hernia sac is a rare condition that presents as an acute scrotum. There are 11 cases reported in the English literature at the best of our knowledge, this case is the 12th case. We report a case, a 2.5 -year-old boy, who presented to the emergency room with tender right sided scrotal swelling. Ultra-sonography revealed intra-scrotal extra-testicular cystic lesion with normal right testis and epididimys. At surgery, a necrotic cyst with dark altered fluid was identified extending into the scrotum, it was connected to the peritoneal cavity, not connected to the testis or the epididymis, and it was twisted.

Cosmology of Tsallis holographic scalar field models in Chern–Simons modified gravity and optimization of model parameters through χ 2 minimization

Abstract The present study reports reconstruction schemes for tachyon, k-essence and dilaton scalar field model of Dark Energy (DE) through Tsallis holographic dark fluid under the framework of Chern–Simons modified gravity. Reproducing the conservation equation for a coupled model with interaction term Q = 3 H b 2 ρ m $Q=3H{b}^{2}{\rho }_{m}$ we have reconstructed the different scalar fields and the corresponding potentials. In the case of tachyon, ΛCDM fixed point is attained under this cosmological settings. Considering k-essence in this interacting situation, we have derived some constraints on the interaction term as well as Tsallis holographic dark energy parameter. Reconstructing dilaton scalar field, we have studied the behavior of scalar field and potential. In all those cases, the reconstructed Equation of State (EoS) parameters have been plotted and when computed for current universe z = 0 are found to be consistent with various observational data including Planck + WP + BAO. The only exception is a particular case of reconstructed k-essence model where phantom behavior is apparent, but its numerical value is deviated from the bounce set by the observations. Expressions for different constraints have been obtained and evolutionary behavior of reconstructed scalar fields and potentials for the various cases have been pictorially presented. Finally, we have developed a functional relationship between Hubble parameter and redshift and optimized the parameter values through χ 2 minimization using the observed Hubble parameter values from Hai Yu et al. 2018 ApJ 856 3.

Kantowski–Sachs universe with dark energy fluid and massive scalar field

This study is mainly concerned with a spatially homogeneous and anisotropic Kantowski–Sachs cosmological model with anisotropic dark energy fluid and massive scalar field. We solve the field equations using (i) the shear scalar proportionality to the expansion scalar and (ii) a mathematical condition that is a consequence of the power law between the scalar field and the average scale factor of the universe, and the corresponding dark energy model is presented. The cosmological parameters of the model are computed and discussed, as well as the relevance of its dynamical aspects to the recent scenario of the accelerated expansion of the universe.

Evaluation of Synthetic CT Image Generated Using a Neural Network for MR-Only Radiotherapy

The MR-only radiotherapy workflow has been an active topic because of the increasing use of Magnetic Resonance (MR) image in the identification and delineation of tumors, while a fast generation of synthetic Computer Tomography (sCT) image from MR image is still one of the key challenges. This study aims to develop a neural network to generate the sCT and evaluate its performance in terms of both CT number difference and dosimetry accuracy. A generative adversarial network (GAN) is designed to translate MRI to sCT. For the generation of sCT, we use a "U-net” shaped encoder-decoder network with some image translation-specific modifications. Then a discriminator network is designed to distinguish between synthetic and real CT images. We enrolled 30 patients with brain tumors who have undergone external beam radiotherapy acquiring both CT and MRI for their simulation. 24 pairs of 2D T1-weighted turbo dark fluid MR images and rigidly registered CT are used to train the GAN, and the remaining 6 pairs are used to access the translation through the metric of mean absolute error. Furthermore, the dose distribution of the clinical VMAT treatment plan on sCT is calculated and compared with those on real CT using gamma analysis. On average, 5 and 10 seconds are needed to generate one sCT on GPU and CPU respectively. The mean absolute error between synthetic and real CT is 52±15 HU over six testing patients. For dose distribution on sCT and CT, the average gamma pass rates using the 3%,3mm and 2%,2mm criteria are above 97 and 92%, respectively. The GAN model is able to generate synthetic CT based on a single MRI sequence within seconds, and no significant radiotherapy dose difference is found between sCT-based and real CT-based plans.

A fake interacting dark energy detection?

ABSTRACT Models involving an interaction between the dark matter and the dark energy sectors have been proposed to alleviate the long-standing Hubble constant tension. In this paper, we analyse whether the constraints and potential hints obtained for these interacting models remain unchanged when using simulated Planck data. Interestingly, our simulations indicate that a dangerous fake detection for a non-zero interaction among the dark matter and the dark energy fluids could arise when dealing with current cosmic microwave background (CMB) Planck measurements alone. The very same hypothesis is tested against future CMB observations, finding that only cosmic variance limited polarization experiments, such as PICO or PRISM, could be able to break the existing parameter degeneracies and provide reliable cosmological constraints. This paper underlines the extreme importance of confronting the results arising from data analyses with those obtained with simulations when extracting cosmological limits within exotic cosmological scenarios.

UNEXPECTED EFFUSION: BILOTHORAX IN PATIENT WITH METASTATIC BREAST CANCER

SESSION TITLE: Fellows Disorders of the Pleura Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: October 18-21, 2020 INTRODUCTION: Bilothorax is a rare cause of pleural effusion. It is thought to be caused by translocation of bilious fluid through a diaphragmatic defect, whether passive, congenital or iatrogenic [1,2]. It is often described as a rapidly-accumulating, right-sided pleural effusion occurring after instrumentation near to or on the biliary tree. Patients are at high risk of developing empyema and can present with signs of infection. We describe a case of a slowly-accumulating right-sided bilothorax in a patient without signs of infection. CASE PRESENTATION: A 39 y/o lady with history of triple-negative breast cancer, metastasized to the brain and spine, was referred to our clinic for dyspnea on exertion for 1 month. She had been treated with multiple lines of chemotherapy & proton beam radiation to her metastases. A staging PET/CT scan 3 months prior revealed a liver lesion that was suspicious for metastases. A CT-guided percutaneous liver biopsy was recommended. An abdominal scan incidentally caught segmental pulmonary emboli (PE), for which a chest CT was performed. Due to a post-procedural complication of hepatic sub-capsular hematoma, the patient was not anti-coagulated & had IVC filter placement instead. Her chest imaging at this time was revealing of minimal, trace bilateral effusions. She presented 1 month later for staging scans. Chest imaging at this time was significant for a trace right-sided pleural effusion. The patient did not have any respiratory symptoms. When she was seen by her oncologist for follow-up one month thereafter, she reported feeling dyspnea on exertion. At this point, a CT chest confirmed a small-to-moderate right pleural effusion. She had no fevers, cough, or constitutional symptoms except chronic fatigue and weakness which preceded her dyspnea. In our clinic, we appreciated a moderate-sized right pleural effusion on ultrasound. Given the insidious nature of her dyspnea, we postulated that her effusion was likely malignant. We performed thoracentesis for both diagnostic and therapeutic purposes. A total of 1.1L of dark green fluid was drained. Fluid studies returned with a pleural fluid to serum bilirubin ratio greater than one, confirming bilothorax. Cytology of the effusion was negative for cancer cells. Repeated chest imaging at 1 and 2 months post-thoracentesis did not reveal re-accumulation of pleural fluid, and patient’s dyspnea did not return. DISCUSSION: We describe a case of a slowly accumulating bilothorax after percutaneous CT-guided liver biopsy. Fortunately, our patient did not develop an empyema from this effusion. CONCLUSIONS: A high suspicion for bilothorax should be maintained when patients develop a novel pleural effusion within the days to months following an abdominal procedure in close proximity to the biliary tree. Prompt diagnosis and drainage lends to both symptomatic relief & prevention of further complications of infection in the pleural space. Reference #1: Jenkinson MRJ, Campbell W, Taylor MA. Bilothorax as a rare sign of intra-abdominal bile leak in a patient without peritonitis. Ann R Coll Surg Engl. 2013;95(7):e12-e13. doi:10.1308/003588413X13629960047678 Reference #2: Basu S, Bhadani S, Shukla VK. A dangerous pleural effusion. Ann R Coll Surg Engl. 2010;92(5):W53-W54. doi:10.1308/147870810X12699662980637 DISCLOSURES: No relevant relationships by Saamia Hossain, source=Web Response No relevant relationships by Robert Lee, source=Web Response

S2981 Emphysematous Gastritis: An Uncommon Cause of Acute Abdomen

INTRODUCTION: Emphysematous gastritis (EG) is defined as air within the gastric wall leading to inflammation and systemic compromise. It is often caused by gas-forming microorganisms. Malignancy, bowel obstruction, excessive steroid use, chemotherapy, nonsteroidal anti-inflammatory drugs, and perforated ulcers can all lead to EG. We report the case of a male who presented with peritonitis and septic shock in the setting of intramural air in the stomach. CASE DESCRIPTION/METHODS: An 83-year-old male with history of congestive heart failure, diabetes mellitus, hypertension, and hyperlipidemia presented with diffuse abdominal pain for 2 days. On presentation, the patient was tachycardic, tachypneic, and hypotensive. Initial Laboratory values are shown in table 1. Examination revealed a rigid abdomen with guarding and rebound tenderness. He was started on IV norepinephrine to maintain blood pressure. NG tube was placed which produced 1.5 L of dark fluid. CT angiogram of abdomen illustrated intraperitoneal free air and evidence of pneumatosis within the fundus and posterior wall of the body of the stomach (figure 1a, 1b, 1c). An emergent exploratory laparotomy was performed with wedge resection of the fundus. During the procedure, copious amounts of purulent material was noted which was cultured, revealing Candida glabrata. Postoperatively, the patient was transferred to the intensive care unit for further management. He remained hypotensive despite fluid resuscitation requiring vasopressors. Patient was started on fluconazole and piperacillin-tazobactam as antimicrobial therapy. His condition improved and was successfully extubated, and transferred to the surgical floors. He was later discharged to a nursing facility in stable condition. DISCUSSION: EG often presents with systemic compromise. The diagnosis requires a CT scan. Although a serious illness, conservative management is usually first attempted before considering surgical intervention. Vasopressors and fluid resuscitation are sometimes required to stabilize the patient hemodynamically. Appropriate antimicrobial therapy should be initiated with coverage of anaerobic organisms, gram negative organisms as well as candida species. If patients develop complications, such as peritonitis or fail conservative management, surgical intervention is warranted. Although rare, ED personnel should consider this condition in differentials of acute abdomen as prompt diagnosis and management can be lifesaving.Table 1.: Illustrating laboratory values on presentationFigure 1.: Figure 1a (coronal), 1b (sagittal) and 1c (axial): abdominal CT scan illustrating pneumatosis seen within the fundal portions and posterior wall of the body of the stomach (red arrows) with gastric distention.

The logotropic dark fluid: Observational and thermodynamic constraints

We have considered a spatially flat, homogeneous and isotropic FLRW universe filled with a single fluid, known as logotropic dark fluid (LDF), whose pressure evolves through a logarithmic equation-of-state. We use the recent Pantheon SNIa and cosmic chronometer datasets to constrain the parameters of this model, the present fraction of DM [Formula: see text] and the Hubble constant [Formula: see text]. We find that the mean values of these parameters are [Formula: see text] and [Formula: see text] at the [Formula: see text] CL. We also find that the LDF model shows a smooth transition from the deceleration phase to acceleration phase of the universe in the recent past. We note that the redshift of this transition [Formula: see text] ([Formula: see text] error) and is well consistent with the present observations. Interestingly, we find that the universe will settle down to a [Formula: see text]CDM model in future and there will not be any future singularity in the LDF model. Furthermore, we notice that there is no significant difference between the LDF and [Formula: see text]CDM models at the present epoch, but the difference (at the percent level) between these models is found as the redshift increases. We have also studied the generalized second law of thermodynamics at the dynamical apparent horizon for the LDF model with the Bekenstein and Viaggiu entropies.

Unified dark fluid and cosmic transit models in Brans–Dicke theory

Some dark energy cosmological models are constructed in the framework of a generalised Brans-Dicke theory which contains a self interacting potential and a dynamical coupling parameter. The dark sector of the universe is considered through a unified linear equation of state. The parameters of the unified dark fluid have been constrained from some physical basis. Since the universe is believed to have undergone a transition from an early deceleration to a late time acceleration, the deceleration parameter should have a signature flipping behaviour at the transition redshift. We have used a hybrid scale factor to simulate the dynamical behaviour of the deceleration parameter. Basing upon the observational constraints on the transition redshift, we have constructed four different transitioning dark energy models. The constructed models are confronted with observational data. For all the models, the behaviour of the dynamical scalar field, Brans-Dicke parameter, Self interacting potential are investigated. Also, on the basis of the generalised Brans-Dicke theory, we have estimated the time variation of the Newtonian gravitational constant.

A new model for dark matter fluid sphere

We develop a new model for a spherically symmetric dark matter fluid sphere containing two regions: (i) Isotropic inner region with constant density and (ii) Anisotropic outer region. We solve the system of field equation by assuming a particular density profile along with a linear equation of state. The obtained solutions are well-behaved and physically acceptable which represent equilibrium and stable matter configuration by satisfying the Tolman–Oppenheimer–Volkoff (TOV) equation and causality condition, condition on adiabatic index, Harrison–Zeldovich–Novikov criterion, respectively. We consider the compact star EXO 1785-248 (Mass [Formula: see text] and radius R[Formula: see text]8.8 km) to analyze our solutions by graphical demonstrations.

Dietary Abomasal Impaction In Weaned Egyptian Calves

Abomasal disorders can lead to severe and potentially life-threatening conditions for the affected calves. In this study, the dietary abomasal impaction was investigated in 12 weaned buffalo and cow calves aged 6-12 months admitted to the Veterinary Teaching Hospital, Faculty of Veterinary Medicine, Zagazig University, Egypt, five apparently healthy cow calves were also included as controls. The diagnosis was based upon case history, general clinical examination with special reference to the gastrointestinal system, and the abomasal measurements including length, width, and depth that taken for all cases under ultrasonographic guidance. Non-significant differences were found for the measured physical parameters in the clinical cases versus controls. Right ventral abdominal distension was reported in all cases, evacuation of dark greenish ruminal fluid using the stomach tube was reported also and to a lesser extent the oral feed regurgitation. Significant differences were found in all the abomasal dimensions in cases when compared to control (P<0.0001). Also, the ultrasonographic examination revealed the extension of the abomasum beyond its limits. The abdominal ultrasound as a quick, feasible and non-invasive tool showed relative accuracy in the diagnosis of abomasal impaction in weaned calves.

Scalar field unification of interacting viscous dark fluid from a geometrical scalar–tensor theory of gravity

We investigate, in the framework of a recently introduced new class of invariant geometrical scalar-tensor theory of gravity, the possibility that a viscous dark fluid can be described in a unified manner by a single scalar field. Thus we developed a model in which both the metric tensor and the scalar field have geometrical origin. The scalar field is characterized by a non-canonical kinetic term and the scalar viscosity of the dark fluid appears as soon the kinetic energy of the scalar field is no longer canonical. The scalar viscosity is considered as a function of the Hubble and the deceleration parameters. To illustrate the formalism we have considered two cases: a constant and a thermodynamic equation of state parameters. In the both cases we obtain analytic representations for the scalar field and their respective potentials. We delimit free parameters by comparing with some Planck 2018 results.