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CT theory and use

Rachael Al-Saadon, Christopher Sutton, Weitao Yang
Thermally activated delayed florescence (TADF) is a mechanism that increases the electroluminescence efficiency in organic light-emitting diodes by harnessing both singlet and triplet excitons. TADF is facilitated by a small energy difference between the first singlet (S1 ) and triplet (T1 ) excited states (ΔE(ST)), which is minimized by spatial separation of the donor and acceptor moieties. The resultant charge-transfer (CT) excited states are difficult to model using time-dependent density functional theory (TDDFT) because of the delocalization error present in standard density functional approximations to the exchange-correlation energy...
May 17, 2018: Journal of Chemical Theory and Computation
F van Ommen, E Bennink, A Vlassenbroek, J W Dankbaar, A M R Schilham, M A Viergever, H W A M de Jong
PURPOSE: Spectral CT using a dual layer detector offers the possibility of retrospectively introducing spectral information to conventional CT images. In theory, the dual-layer technology should not come with a dose or image quality penalty for conventional images. In this study, we evaluate the influence of a dual-layer detector (IQon Spectral CT, Philips) on the image quality of conventional CT images, by comparing these images with those of a conventional but otherwise technically comparable single-layer CT scanner (Brilliance iCT, Philips), by means of phantom experiments...
May 10, 2018: Medical Physics
Scott V Wiener, Ling Chen, Alex R Shimotake, Misun Kang, Marshall L Stoller, Sunita P Ho
Purpose/Aim: The most common kidney stone composed of calcium oxalate forms on interstitial calcium phosphate mineral known as a Randall's plaque (RP). Due to limited information about events leading to the initial deposition of nanometer size interstitial calcium phosphate pre-clusters, there continues to be a debate on the initial site of calcium phosphate deposition and factors leading to stone formation. MATERIALS AND METHODS: High-resolution X-ray micro-computed tomography (CT), and light and electron microscopy techniques were used to characterize human renal pyramids and five representative kidney stones with identifiable stems...
December 2018: Connective Tissue Research
Yongming Liu, Huan Yu, Xihui Zhang, Yong Wang, Zhentao Song, Jian Zhao, Haibin Shi, Ruibin Li, Yangyun Wang, Leshuai W Zhang
Bismuth is widely used in metallurgy, cosmetic industry, and medical diagnosis and recently, bismuth nanoparticles (NPs) (BiNP) have been made and proved to be excellent CT imaging agents. Previously, we have synthesized bovine serum albumin based BiNP for imaging purpose but we found a temporary kidney injury by BiNP. Due to the reported adverse events of bismuth on human health, we extended our studies on the mechanisms for BiNP induced nephrotoxicity. Blood biochemical analysis indicated the increase in creatinine (CREA) and blood urea nitrogen (BUN), and intraluminal cast formation with cell apoptosis/necrosis was evident in proximal convoluted tubules (PCTs) of mice...
May 6, 2018: Nanotoxicology
Cristina Rodrigues, Daniel Cabral, Leonor Mota, António Bettencourt
INTRODUCTION: We report a case of a patient with recurrent bilateral spontaneous pneumothorax presumably originating in a left bulla. METHODS: A 68 year old male, was admitted to the emergency department with shortness of breath and bilateral chest pain. He had had oesophageal cancer resection 2 years before, with a posterior mediastinal reconstruction using a gastric tube. Afterwards he had to be operated twice for hiatal hernia. RESULTS: Bilateral chest tubes were inserted, with complete resolution in 72 hours...
July 2017: Revista Portuguesa de Cirurgia Cardio-torácica e Vascular
Jan-Michael Mewes
The origin of the thermally-activated delayed fluorescence (TADF) of three organic emitters is investigated, focusing on the nature of the lowest excited states, their transition properties, as well as the role of the environment. For this purpose, the algebraic-diagrammatic construction for the polarization propagator at second order of perturbation theory [ADC(2)], time-dependent density-functional theory in the Tamm-Dancoff approximation (TDA) and unrestricted Kohn-Sham DFT in combination with the maximum-overlap method (ΔDFT) are employed...
April 27, 2018: Physical Chemistry Chemical Physics: PCCP
Martin Peter Bircher, Ursula Rothlisberger
Linear-response time-dependent density functional theory (LR-TDDFT) has become a valuable tool in the calculation of excited states of molecules of various sizes. However, standard generalised gradient approximation (GGA) and hybrid exchange-correlation (xc) functionals often fail to correctly predict charge-transfer (CT) excitations with low orbital overlap, thus limiting the scope of the method. The Coulomb-attenuation method (CAM) in the form of the CAM-B3LYP functional has been shown to reliably remedy this problem in many CT systems, making accurate predictions possible...
April 16, 2018: Journal of Chemical Theory and Computation
Ali Amidi, S M Hadi Hosseini, Alexander Leemans, Shelli R Kesler, Mads Agerbæk, Lisa M Wu, Robert Zachariae
Background: Cisplatin-based chemotherapy may have neurotoxic effects within the central nervous system. The aims of this study were 1) to longitudinally investigate the impact of cisplatin-based chemotherapy on whole-brain networks in testicular cancer patients undergoing treatment and 2) to explore whether possible changes are related to decline in cognitive functioning. Methods: Sixty-four newly orchiectomized TC patients underwent structural magnetic resonance imaging (T1-weighted and diffusion-weighted imaging) and cognitive testing at baseline prior to further treatment and again at a six-month follow-up...
December 1, 2017: Journal of the National Cancer Institute
Yuezhi Mao, Qinghui Ge, Paul Richard Horn, Martin Head-Gordon
Charge-transfer (CT) is an important binding force in the formation of intermolecular complexes, and there have been a variety of theoretical models proposed to quantify this effect. These approaches, which typically rely on a definition of a "CT-free" state based on a partition of the system, sometimes yield significantly different results for a given intermolecular complex. Two widely used definitions of the "CT-free" state, the absolutely localized molecular orbitals (ALMO) method (where only on-fragment orbital mixings are permitted) and the constrained density functional theory (CDFT) approach (where fragment electron populations are fixed), are carefully examined in this work...
April 3, 2018: Journal of Chemical Theory and Computation
Stuart A J Thomson, Jens Niklas, Kristy L Mardis, Christopher Mallares, Ifor D W Samuel, Oleg G Poluektov
Organic solar cells are a promising renewable energy technology, offering the advantages of mechanical flexibility and solution processability. An understanding of the electronic excited states and charge separation pathways in these systems is crucial if efficiencies are to be further improved. Here we use light induced electron paramagnetic resonance (LEPR) spectroscopy and density functional theory calculations (DFT) to study the electronic excited states, charge transfer (CT) dynamics and triplet exciton formation pathways in blends of the small molecule donors (DTS(FBTTh2 )2 , DTS(F2 BTTh2 )2 , DTS(PTTh2 )2 , DTG(FBTTh2 )2 and DTG(F2 BTTh2 )2 ) with the fullerene derivative PC61 BM...
October 19, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
William F Paolo, Rhonaldo Silaban, Long Nguyen, Susan Wojcik, William Grant
OBJECTIVE: Computerized tomography (CT) is often employed to diagnose or rule out certain suspected abdominal pathologies. The aim of this study is to compare emergency physicians' estimated post-test disease probabilities to the probabilities obtained for similar diagnostic tests as reported in the literature. METHODS: Physicians were asked to estimate pre and posttest probabilities before and after CT scan results in patients with nontraumatic abdominal and pelvic pain...
February 27, 2018: American Journal of Emergency Medicine
R J Charlton, R M Fogarty, S Bogatko, T J Zuehlsdorff, N D M Hine, M Heeney, A P Horsfield, P D Haynes
An ab initio study of the effects of implicit and explicit hosts on the excited state properties of pentacene and its nitrogen-based derivatives has been performed using ground state density functional theory (DFT), time-dependent DFT, and ΔSCF. We observe a significant solvatochromic redshift in the excitation energy of the lowest singlet state (S1 ) of pentacene from inclusion in a p-terphenyl host compared to vacuum; for an explicit host consisting of six nearest neighbour p-terphenyls, we obtain a redshift of 65 meV while a conductor-like polarisable continuum model (CPCM) yields a 78 meV redshift...
March 14, 2018: Journal of Chemical Physics
Blaine G McCarthy, Ryan M Pearson, Chern-Hooi Lim, Steven M Sartor, Niels H Damrauer, Garret M Miyake
Through the study of structure-property relationships using a combination of experimental and computational analyses, a number of phenoxazine derivatives have been developed as visible light absorbing, organic photoredox catalysts (PCs) with excited state reduction potentials rivaling those of highly reducing transition metal PCs. Time-dependent density functional theory (TD-DFT) computational modeling of the photoexcitation of N-aryl and core modified phenoxazines guided the design of PCs with absorption profiles in the visible regime...
April 18, 2018: Journal of the American Chemical Society
Mikhail A Filatov, Safakath Karuthedath, Pavel M Polestshuk, Susan Callaghan, Keith J Flanagan, Maxime Telitchko, Thomas Wiesner, Frédéric Laquai, Mathias O Senge
A family of heavy atom-free BODIPY-anthracene dyads (BADs) exhibiting triplet excited state formation from charge-transfer states is reported. Four types of BODIPY scaffolds, different in the alkyl substitution pattern, and four anthracene derivatives have been used to access BADs. Fluorescence and intersystem crossing (ISC) in these dyads depend on donor-acceptor couplings and can be accurately controlled by substitution or media polarity. Under conditions that do not allow charge transfer (CT), the dyads exhibit fluorescence with high quantum yields...
March 28, 2018: Physical Chemistry Chemical Physics: PCCP
Qinghe Wu, Donglin Zhao, Matthew B Goldey, Alexander S Filatov, Valerii Sharapov, Yamil J Colón, Zhengxu Cai, Wei Chen, Juan de Pablo, Giulia Galli, Luping Yu
Two types of electron acceptors were synthesized by coupling two kinds of electron-rich cores with four equivalent perylene diimides (PDIs) at the α-position. With fully aromatic cores, TPB and TPSe have π-orbitals spread continuously over the whole aromatic conjugated backbone, unlike TPC and TPSi, which contain isolated PDI units due to the use of a tetrahedron carbon or silicon linker. Density functional theory calculations of the projected density of states showed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for TPB are localized in separate regions of space...
March 28, 2018: ACS Applied Materials & Interfaces
Yinsheng Li, John W Garrett, Ke Li, Yijing Wu, Kevin Johnson, Sebastian Schafer, Charles Strother, Guang-Hong Chen
Time-resolved C-arm cone-beam CT (CBCT) angiography (TR-CBCTA) images can be generated from a series of CBCT acquisitions that satisfy data sufficiency condition in analytical image reconstruction theory. In this work, a new technique was developed to generate TR-CBCTA images from a single short-scan CBCT data acquisition with contrast media injection. The reconstruction technique enabling this application is a previously developed image reconstruction technique, synchronized multi-artifact reduction with tomographic reconstruction (SMART-RECON)...
March 22, 2018: Physics in Medicine and Biology
Arun K Pal, Thomas J Duignan, Jochen Autschbach
Linear polarizabilities (α) and second hyperpolarizabilities (γ) of unsubstituted azobenzenes and 'push-pull' azobenzene derivatives are investigated using Kohn-Sham theory (KST) and coupled-cluster (CC) approaches. Various standard exchange-correlation functionals as well as a non-empirically 'tuned' long-range corrected (LC) functional with range-separated exchange are used in the KST calculations. When compared to correlated ab initio calculations and measurements, the tuned functional gives accurate low-energy excitation energies, especially for charge transfer (CT) transitions, and performs well for α...
March 7, 2018: Physical Chemistry Chemical Physics: PCCP
Ebenezer Owusu-Addo, Andre M N Renzaho, Ben J Smith
Cash transfer programs (CTs) have been rigorously evaluated since their inception in the 1990s. However, to date, there has been no study critically examining the utility of the methodological approaches used to evaluate CTs. This article reviews the approaches used to evaluate CTs in sub-Saharan Africa (SSA) to provide recommendations for improving future CTs evaluations. We conducted searches for CTs evaluation studies in SSA in the peer-reviewed and grey literature using electronic databases, hand searching of selected journals, organisational websites, Google Scholar and Scirus Internet search engines...
February 14, 2018: Evaluation and Program Planning
Puzi Wang, Rongli Xie, Zhifeng Zhao, Jiajun Ren, Jian Fei
RATIONALE: Autoimmune pancreatitis is a form of chronic pancreatitis, characterized by diffused enlargement of the pancreas and irregular narrowing of the main pancreatic duct. The theory that portal hypertension is associated with autoimmune pancreatitis has not been emphasized. In addition, only a few studies report that the gastrointestinal tract hemorrhage caused by portal hypertension is associated with autoimmune pancreatitis. PATIENT CONCERNS: The patient was a 61-year-old male with pancreas occupying lesion detected in a physical examination...
February 2018: Medicine (Baltimore)
S A Pervukhin, A M Ageenko, M N Lebedeva, R I Golikov
Lumbar epidural anesthesia is a commonly used anaesthetic technique for trauma and orthopedic surgery of the lower extremities. One of the rare complications of epidural anesthesia is pneumocephalia. The article describes a case of pneumocephalia after epidural anesthesia performed for anesthetic management of the hip replacement surgery. Eight hours after the epidural anesthesia the patient had depression of consciousness progressing to coma. Computed tomog- raphy of the brain detected pneumocephalia. Symptomatic treatment provided a regression of neurological deficit...
September 2017: Anesteziologiia i Reanimatologiia
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