High resolution PET, SPECT and projection imaging in small animals

Positron emission tomography, single photon emission computed tomography and planar projection imaging of radioactive tracers have long been in use for detecting and diagnosing disease in human subjects. More recently, advanced versions of these same technologies have begun to be used across the breadth of modern biomedical research to study non-invasively small laboratory animals in a myriad of experimental settings. In this report, we describe some of the new instruments and techniques that make these measurements possible and illustrate, with a few examples, the potential power of these methods in modern biomedical researchPublicad

Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template

[EN] The inherent properties of a single atomic carbon layer in graphene offer opportunities for the creation of catalytically active centers tailored on a molecular level on a support with high thermal stability and very high specific surface area. We demonstrate that organization of the two-dimensional system of the carbon layer into three-dimensional (3D) graphene-like catalytic materials with the connectivity of a pore network providing good accessibility to the active centers allows the preparation of catalytic materials that exploit the properties of graphene. In this study, 3D graphene-like microporous carbons, denoted as)6 beta-carbon and Y-carbon, were synthesized by nanocasting of beta (*BEA) and faujasite (FAU) zeolite templates. Structural analyses show that the materials are characterized by 3D-assembled and highly stable single-atom graphene an open porous system resembling the regular channel system of the zeolites with a specific surface area comparable to the surface area of graphene. The materials effectively catalyze the hydrogenation of alkenes, alkynes, and cycloalkenes into the corresponding alkanes and cycloalkanes. The materials facilitate catalytic intramolecular rearrangements, including the selective isomerization of double bonds and branching of linear chains, as well as stereoselective isomerization of unsaturated hydrocarbons. layers that formThis work was supported by the Grant Agency of the Czech Republic under project No. 15-12113S. The authors acknowledge the assistance provided by the Research Infrastructures NanoEnviCz (Project No. LM2015073) and Pro-NanoEnviCz (Project No. CZ.02.1.01/0.0/0.0/16_013/0001821), supported by the Ministry of Education, Youth and Sports of the Czech Republic.Sazama, P.; Pastvova, J.; Rizescu, C.; Tirsoaga, A.; Parvulescu, VI.; García Gómez, H.; Kobera, L.... (2018). Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template. ACS Catalysis. 8(3):1779-1789. https://doi.org/10.1021/acscatal.7b04086S177917898

Case-matched comparison of cardiovascular outcome in Loeys-Dietz syndrome versus Marfan syndrome

Background: Pathogenic variants in TGFBR1, TGFBR2 and SMAD3 genes cause Loeys-Dietz syndrome, and pathogenic variants in FBN1 cause Marfan syndrome. Despite their similar phenotypes, both syndromes may have different cardiovascular outcomes. Methods: Three expert centers performed a case-matched comparison of cardiovascular outcomes. The Loeys-Dietz group comprised 43 men and 40 women with a mean age of 34 +/- 18 years. Twenty-six individuals had pathogenic variants in TGFBR1, 40 in TGFBR2, and 17 in SMAD3. For case-matched comparison we used 83 age and sex-frequency matched individuals with Marfan syndrome. Results: In Loeys-Dietz compared to Marfan syndrome, a patent ductus arteriosus (p = 0.014) was more prevalent, the craniofacial score was higher (p < 0.001), the systemic score lower (p < 0.001), and mitral valve prolapse less frequent (p = 0.003). Mean survival for Loeys-Dietz and Marfan syndrome was similar (75 +/- 3 versus 73 +/- 2 years; p = 0.811). Cardiovascular outcome was comparable between Loeys-Dietz and Marfan syndrome, including mean freedom from proximal aortic surgery (53 +/- 4 versus 48 +/- 3 years; p = 0.589), distal aortic repair (72 +/- 3 versus 67 +/- 2 years; p = 0.777), mitral valve surgery (75 +/- 4 versus 65 +/- 3 years; p = 0.108), and reintervention (20 +/- 3 versus 14 +/- 2 years; p = 0.112). In Loeys-Dietz syndrome, lower age at initial presentation predicted proximal aortic surgery (HR = 0.748; p < 0.001), where receiver operating characteristic analysis identified <= 33.5 years with increased risk. In addition, increased aortic sinus diameters (HR = 6.502; p = 0.001), and higher systemic score points at least marginally (HR = 1.175; p = 0.065) related to proximal aortic surgery in Loeys-Dietz syndrome. Conclusions: Cardiovascular outcome of Loeys-Dietz syndrome was comparable to Marfan syndrome, but the severity of systemic manifestations was a predictor of proximal aortic surgery

Performance characteristic of the NIH atlas small animal PET scanner

[Abstract] AMI International Conference 2003, September 21 - 27, Madrid, Spain: "High Resolution Molecular Imaging: from Basic Science to Clinical Applications"The Advanced Technology Laboratory Animal Scanner (ATLAS) is a small animal positron emission tomography (PET) scanner with depth-of-interaction (DOI) capability designed to image animals the size of mice and rats. We report performance measurements and show animal studies that suggest that ATLAS offers advantages over systems without DOI capabilityPublicad

Numerical investigations of forced laminar and turbulent wall jets over a heated surface

The effect of high amplitude forcing on laminar and turbulent wall jets over a heated flat plate is analyzed. Highly accurate Direct Numerical Simulations (DNS) are used in the laminar case to investigate the dominant transport mechanisms. When forcing is applied, the skin friction is reduced markedly and the wall heat transfer is increased, in contrast to the prediction of the Reynolds analogy, which states proportionality between both quantities. Detailed examination of the unsteady flow field showed that the concepts of eddy viscosity and eddy thermal diffusivity can be applied to analyze unsteady laminar flows and to explain the effect of highly unsteady phenomena. For the investigation of the turbulent wall jet, a new Flow Simulation Methodology (FSM) is employed in the limit of unsteady BANS (Reynolds averaged Navier-Stokes) simulations. With this novel approach, the simulation of large, coherent structures in the turbulent flow field very closely parallels the laminar simulations. Following the idea of Large Eddy Simulation (LES), the large coherent motion is computed directly, while the effect of the small scale, random motion is modelled. In FSM, a state-of-the-art two-equation turbulence model is used. Forcing the turbulent wall jet results in a reduction of the skin friction and an increase in wall heat transfer. The mechanisms responsible for these mean flow changes show a remarkable similarity to the mechanisms found in the laminar case. This is confirmed by close examination of the large coherent motion and its effect on the turbulent mean flow. Using this approach, several questions regarding the character of the turbulent wall jet could be answered

Phosphate-free ornithine lipid contents in Desulfovibrio spp. respond to growth temperature

Eight sulfate-reducing Desulfovibrio strains isolated from intertidal sediments of the North Sea were investigated for their intact polar lipid (IPL) composition. They contained two types of IPLs, phospholipids and aminolipids. The dominating phospholipids were phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and, in lower concentration, diphosphatidylglycerol (DPG). Aminolipids formed a significant IPL fraction in all strains and high resolution tandem mass spectrometry assigned them as phosphate-free ornithine lipids (OLs). In intertidal flat sediments microorganisms may face strong temperature changes on varying timescales and it is crucial for the microbes to maintain constant membrane fluidity, e.g. by modification of their membrane lipid composition. We therefore investigated whether or not these strains employ the same strategies for adjusting their membrane composition to growth temperature and, in particular, how OLs are modified. In all strains the relative OL content was found to be higher at higher growth temperature, in most cases at the expense of PE content and less often PG content. The fatty acid (FA) side chains of the main PE and PG species were similar, i.e. both were dominated by C17 or C18, whereas C15 FAs were additionally found as major OL side chains. The temperature-related side chain variation was similar for all IPLs: unsaturated FA content was lower at higher temperature. The corresponding FA patterns after hydrolysis revealed elevated branched FA content and anteiso/iso ratio at higher growth temperature. As the temperature-related changes in the IPL side chains were similar for all strains, we conclude that side chain modification plays a major role in the maintenance of membrane fluidity at higher temperature and that alternative roles of OLs in the membrane adaptation of Desulfovibrio spp. other than melting point adjustment are possible

Aerodynamic Analysis Of A Vertically Landing Lifting Body

The vertical landing lifting body (VLLB) is a new concept for reusable launch vehicles, which launches vertically, but re-enters the atmosphere at a high angle of attack (alpha) for its entire flight. The VLLB remains at high angles of attack through all Mach numbers under aerodynamic control until shortly before touchdown. One of the important risk areas for the VLLB concept concerns flight below Mach 2 at high angles of attack where the flow is dominated by separated, highly vortical behavior. The purpose of this study is to investigate the aerodynamic characteristics and control effectiveness of the high-alpha flow of the Hot Eagle Vertically Landing Lifting Body geometry. Several test cases were performed utilizing Detached Eddy Simulations (DES) to both analyze and control the flow over Hot Eagle geometry at different flow conditions. According to results of the time-dependent DES computations, the flow is symmetric and steady at both subsonic and transonic Mach numbers for both 45 and 60 degrees angle of attack. As the angle of attack or the Mach number increases, the vortices get stronger; but the flow remains steady and symmetric. This is probably because of the blunt nature of the nose and its cross-section. Symmetric and asymmetric blowing were performed to control the flow structure around the body. Different blowing rates have been investigated, and the vehicle is found to be controllable with reasonable amounts of blowing.This research was supported by Universal Space Lines LLC, monitored by Mike Talbot and Mike Mahoney. Funding for the work came from AFRL under the sponsorship of Jess Sponable. The authors would also like to thank to Dr. Dave McDaniel for his help in creating the grid for asymmetric blowing. The results of this study were presented at an AIAA conference

Experimental Evaluation of Depth-of-Interaction Correction in a Small-Animal Positron Emission Tomography Scanner

Human and small-animal positron emission tomography (PET) scanners with cylindrical geometry and conventional detectors exhibit a progressive reduction in radial spatial resolution with increasing radial distance from the geometric axis of the scanner. This “depth-of-interaction” (DOI) effect is sufficiently deleterious that many laboratories have devised novel schemes to reduce the magnitude of this effect and thereby yield PET images of greater quantitative accuracy. Here we examine experimentally the effects of a particular DOI correction method (dual-scintillator phoswich detectors with pulse shape discrimination) implemented in a small-animal PET scanner by comparing the same phantom and same mouse images with and without DOI correction. The results suggest that even this relatively coarse, two-level estimate of radial gamma ray interaction position significantly reduces the DOI parallax error. This study also confirms two less appreciated advantages of DOI correction: a reduction in radial distortion and radial source displacement as a source is moved toward the edge of the field of view and a resolution improvement detectable in the central field of view likely owing to improved spatial sampling

High Resolution Simulation of Full Aircraft Control at Flight Reynolds Numbers

This paper documents interim results of a three year project to develop a computational method for accurately determining static and dynamic stability and control characteristics of fighter and transport aircraft with various store configurations, as well as the aircraft response to pilot input. In this second year of the project computational data is gathered for a rigid F-16C with no control surface movement in forced motion that approximates flight test maneuvers. Computational maneuvers designed to efficiently gather three axes of motion data to build a comprehensive reduced order model are also developed. The data is then post- processed to determine the resulting static and dynamic stability characteristics. The main benefits of this effort are: 1) early discovery of complex aerodynamic phenomena that are typically only present in dynamic flight maneuvers and therefore not discovered until flight test, and 2) rapid generation of an accurate aerodynamic database to support aircraft and weapon certification by reducing required flight test hours and complementing current stability and control testing