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https://www.readbyqxmd.com/read/27906486/the-fractional-occupation-number-weighted-density-as-a-versatile-analysis-tool-for-molecules-with-a-complicated-electronic-structure
#1
Christoph Alexander Bauer, Andreas Hansen, Stefan Grimme
The fractional occupation number weighted density (FOD) analysis is explored as a general theoretical diagnostic for complicated electronic structures. Its main feature is to provide robustly and fast the information where 'hot' (strongly correlated and chemically active) electrons are localized in a molecule. We demonstrate its usage in four different prototypical applications: (i) As a new and fast measure for the biradical character of polycyclic aromatic hydrocarbons, (ii) for the selection of active orbital spaces in multiconfigurational or complete active space self consistent field (MCSCF/CASSCF) treatments, (iii) as a possibility to consistently describe molecular energy landscapes in regions with varying biradical character as exemplified by partial double bond torsions, and (iv) as a powerful visualization method for static electron correlation effects in large biomolecules in connection with an efficient semi-empirical tight-binding molecular orbital scheme...
December 1, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27812560/orientation-order-and-rotation-mobility-of-nitroxide-biradicals-determined-by-quantitative-simulation-of-epr-spectra
#2
Alexey V Bogdanov, Andrey Kh Vorobiev
The problem of quantitative numerical simulation of electron paramagnetic resonance (EPR) spectra of biradical probes in both isotropic and aligned media was solved for the first time. The models suitable for the description of the spectra of the probes, both in the rigid limit and in the presence of rotational motions, were developed and successfully applied to model systems. The simulation of EPR spectra allows obtaining the following information about the molecular structure and dynamics: the values of orientation order parameters, the type of rotation mobility and its quantitative characteristics, and the sign and value of the spin exchange constant of the biradical...
November 16, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27771952/using-molecular-architecture-to-control-the-reactivity-of-a-triplet-vinylnitrene
#3
Sujan K Sarkar, Onyinye Osisioma, William L Karney, Manabu Abe, Anna D Gudmundsdottir
Photolysis of 3-azido-1-indenone (1) with a light-emitting diode (LED, λ= 405 nm) or mercury arc lamp (Pyrex) resulted in the formation of heterodimer 3 in excellent yield, through dimerization of triplet vinylnitrene (3)2. At ambient temperature, vinylnitrene (3)2 (λmax at 340 and 480 nm) was detected directly with laser flash photolysis of vinyl azide 1. The vinylnitrene intermediate was also characterized directly with IR and ESR spectroscopy in cryogenic matrices. The ESR spectrum of vinylnitrene (3)2 yielded a zero-field splitting parameter |D/hc| of 0...
October 22, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27747007/cell-block-samples-from-endobronchial-ultrasound-transbronchial-needle-aspiration-provide-sufficient-material-for-ancillary-testing-in-lung-cancer-a-quaternary-referral-centre-experience
#4
Emily Hopkins, David Moffat, Ian Parkinson, Peter Robinson, Hubertus Jersmann, Brendan Dougherty, Mohammed I Birader, Kate Francis, Phan Nguyen
BACKGROUND: Rapid on site examination (ROSE) is encouraged at endobronchial ultrasound transbronchial needles aspiration (EBUS-TBNA) to improve diagnostic yield. Due to new therapeutic options in lung cancer, it is not sufficient to merely distinguish between non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma (SCLC). Immunohistochemistry (IHC) distinction is now standard practice, as well as additional molecular testing where clinically indicated. We investigated the diagnostic yield of on-site smears vs...
September 2016: Journal of Thoracic Disease
https://www.readbyqxmd.com/read/27730235/double-quantum-coherence-esr-spectroscopy-and-quantum-chemical-calculations-on-a-bdpa-biradical
#5
Haleh Hashemi Haeri, Philipp Spindler, Jörn Plackmeyer, Thomas Prisner
Carbon-centered radicals are interesting alternatives to otherwise commonly used nitroxide spin labels for dipolar spectroscopy techniques because of their narrow ESR linewidth. Herein, we present a novel BDPA biradical, where two BDPA (α,α,γ,γ-bisdiphenylene-β-phenylallyl) radicals are covalently tethered by a saturated biphenyl acetylene linker. The inter-spin distance between the two spin carrier fragments was measured using double quantum coherence (DQC) ESR methodology. The DQC experiment revealed a mean distance of only 1...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27722408/role-of-a-singlet-diradical-character-in-carbon-nanomaterials-a-novel-hot-spot-for-efficient-nonlinear-optical-materials
#6
Shabbir Muhammad, Masayoshi Nakano, Abdullah G Al-Sehemi, Yasutaka Kitagawa, Ahmad Irfan, Aijaz R Chaudhry, Ryohei Kishi, Soichi Ito, Kyohei Yoneda, Kotaro Fukuda
Carbon atoms have the potential to produce a variety of fascinating all-carbon structures with amazing electronic and mechanical properties. Over the last few decades, several efforts have been made using experimental and computational techniques to functionalize graphene, carbon nanotubes and fullerenes for potential use in modern hi-tech electronic, medicinal, optical and nonlinear optical (NLO) applications. Since photons replaced electrons as a carrier of information, the field of NLO material design has drawn immense interest in contemporary materials science...
September 30, 2016: Nanoscale
https://www.readbyqxmd.com/read/27722293/triplet-state-formation-and-quenching-dynamics-of-2-mercaptobenzothiazole-in-solution
#7
Daisuke Koyama, Andrew J Orr-Ewing
The photochemical dynamics of the thione 2-mercaptobenzothiazole (MBT) initiated by absorption of 330 nm ultraviolet light are investigated by ultrafast transient absorption spectroscopy. The lowest energy triplet state (T1) has mixed (3)ππ*/(3)nπ* character and is populated with a quantum yield of 0.58 ± 0.01 from the photo-excited (1)ππ* S2 state in methanol solution via rapid internal conversion to the (1)nπ* S1 state (with time constant τ1 < 150 fs). The spectroscopic evidence points to a mechanism involving intersystem crossing from S1 to the (3)nπ*/(3)ππ* T2 state (τ2 = 400 ± 100 fs) and internal conversion to T1 (with time constant for growth τ3 = 6...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27670569/malignancy-rate-number-needed-to-treat-and-positive-predictive-value-for-breast-mri
#8
John S Kennedy, Patrick A Robbins
Breast MRI is being used more frequently for advanced screening for breast cancer. Patients may be at increased risk, or are symptomatic, with nonsuspicious mammograms. There is little data regarding the likelihood of a recommendation for biopsy, or for detecting a malignancy, in this population. We intended to determine the malignancy rate, number needed to treat, and positive predictive value for patients receiving adjunctive MRI at our institution. A retrospective review of all breast MRIs from 2008 to 2010 was done...
September 2016: American Surgeon
https://www.readbyqxmd.com/read/27661775/diagnostic-performance-of-diffusion-tensor-imaging-parameters-in-breast-cancer-and-correlation-with-the-prognostic-factors
#9
Can Onaygil, Handan Kaya, Mustafa Umit Ugurlu, Erkin Aribal
PURPOSE: To evaluate the diagnostic performances of the diffusion tensor imaging (DTI) parameters in the diagnosis of breast cancer and to investigate the variations in DTI parameters according to the breast cancer biomarkers. MATERIALS AND METHODS: At 3.0 Tesla (T), DTI was performed in 85 patients with 92 enhancing breast lesions. λ1 , λ2 , λ3 , mean diffusivity (MD), radial diffusivity (RD), fractional anisotropy (FA), relative anisotropy (RA), and geodesic anisotropy (GA) were studied and compared with diffusion-weighted imaging-derived apparent diffusion coefficient...
September 23, 2016: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/27661756/competition-between-meta-effect-photochemical-reactions-of-selected-benzophenone-compounds-having-two-different-substituents-at-meta-positions
#10
Jiani Ma, Huai Li, Xiting Zhang, Wen-Jian Tang, Mingde Li, David Lee Phillips
Recent studies conducted on some "meta effect" photochemical reactions focused on aromatic carbonyls having a substitution on one meta position of the benzophenone (BP) and anthraquinone parent compound. In this paper, two different substitutions were introduced with one at each meta position of the BP parent compound to investigate possible competition between different types of meta effect photochemistry observed in acidic solutions containing water. The photochemical pathways of 3-hydroxymethyl-3'-fluorobenzophenone (1) and 3-fluoro-3'-methylbenzophenone (2) were explored in several solvents, including acidic water-containing solutions, using time-resolved spectroscopic experiments and density functional theory computations...
October 11, 2016: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27622201/the-value-of-constant-sharpness-as-a-diagnostic-sign-in-mr-mammography
#11
REVIEW
Clemens G Kaiser, Pascal Baltzer, Anna K Kaiser, Julia Krammer, Michael Uder, Werner A Kaiser, Matthias Dietzel
PURPOSE: To examine "constant lesion sharpness" as a morphological diagnostic sign in the differential diagnosis between benign and malignant lesions. MATERIAL AND METHODS: This prospective study had institutional review board approval and was HIPAA compliant. In total 1014 consecutive patients were examined (mean age 55 years ± 13 years) and evaluated in our University hospital towards the morphological shape of the lesion borders. The "Constant sharpness Sign" was defined as a lesion remaining continuously sharp for the duration of the dynamic scan...
2016: European Journal of Radiology Open
https://www.readbyqxmd.com/read/27610475/contrast-enhanced-dual-energy-spectral-mammogram-an-emerging-addendum-in-breast-imaging
#12
Kalpana D Kariyappa, Francis Gnanaprakasam, Subhapradha Anand, Murali Krishnaswami, Madan Ramachandran
OBJECTIVE: To assess the role of contrast-enhanced dual-energy spectral mammogram (CEDM) as a problem-solving tool in equivocal cases. METHODS: 44 consenting females with equivocal findings on full-field digital mammogram underwent CEDM. All the images were interpreted by two radiologists independently. Confidence of presence was plotted on a three-point Likert scale and probability of cancer was assigned on Breast Imaging Reporting and Data System scoring. Histopathology was taken as the gold standard...
November 2016: British Journal of Radiology
https://www.readbyqxmd.com/read/27586736/a-task-based-analytical-framework-for-ultrasonic-beamformer-comparison
#13
Nghia Q Nguyen, Richard W Prager, Michael F Insana
A task-based approach is employed to develop an analytical framework for ultrasound beamformer design and evaluation. In this approach, a Bayesian ideal-observer provides an idealized starting point and a way to measure information loss in practical beamformer designs. Different approximations of this ideal strategy are shown to lead to popular beamformers in the literature, including the matched filter, minimum variance (MV), and Wiener filter (WF) beamformers. Analysis of the approximations indicates that the WF beamformer should outperform the MV approach, especially in low echo signal-to-noise conditions...
August 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27585658/can-positron-emission-mammography-help-to-identify-clinically-significant-breast-cancer-in-women-with-suspicious-calcifications-on-mammography
#14
Almir G V Bitencourt, Eduardo N P Lima, Bruna R C Macedo, Jorge L F A Conrado, Elvira F Marques, Rubens Chojniak
OBJECTIVE: To evaluate the diagnostic accuracy of positron emission mammography (PEM) for identifying malignant lesions in patients with suspicious microcalcifications detected on mammography. METHODS: A prospective, single-centre study that evaluated 40 patients with suspicious calcifications at mammography and indication for percutaneous or surgical biopsy, with mean age of 56.4 years (range: 28-81 years). Patients who agreed to participate in the study underwent PEM with 18F-fluorodeoxyglucose before the final histological evaluation...
September 2, 2016: European Radiology
https://www.readbyqxmd.com/read/27578999/bilateral-desmoid-tumor-of-the-breast-case-seriesand-literature-review
#15
Phanchaporn Wongmaneerung, Areewan Somwangprasert, Kirati Watcharachan, Chagkrit Ditsatham
BACKGROUND: Desmoid tumor of the breast is very rare and locally aggressive but has no distant metastasis. Bilateral lesions are extremely rare, found in only 4% of patients. Two cases of bilateral desmoid tumor of the breast are reported. The clinical presentation, diagnosis, imaging, treatment, and follow-up outcomes of recurrence as well as a brief literature review are provided. CASE REPORTS: Case 1 is a 31-year-old woman who presented with nipple retraction...
2016: International Medical Case Reports Journal
https://www.readbyqxmd.com/read/27573478/a-biradical-balancing-act-redox-amphoterism-in-a-diindenoanthracene-derivative-results-from-quinoidal-acceptor-and-aromatic-donor-motifs
#16
Gabriel E Rudebusch, Guzmán L Espejo, José L Zafra, Miriam Peña-Alvarez, Sarah N Spisak, Kotaro Fukuda, Zheng Wei, Masayoshi Nakano, Marina A Petrukhina, Juan Casado, Michael M Haley
The reduced and oxidized states of an open-shell diindeno[b,i]anthracene (DIAn) derivative have been investigated by experimental and theoretical techniques. As a result of moderate biradical character and the ability of cyclopenta-fused scaffolds to stabilize both positive and negative charges, DIAn exhibits rich redox chemistry with four observable and isolable charged states. Structural and electronic properties of the DIAn system are brought to light by UV-vis-NIR and Raman spectroelectrochemical measurements...
September 28, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27559371/biradical-vs-singlet-oxygen-photogeneration-in-suprofen-cholesterol-systems
#17
Fabrizio Palumbo, Francisco Bosca, Isabel Maria Morera, Inmaculada Andreu, Miguel A Miranda
Cholesterol (Ch) is an important lipidic building block and a target for oxidative degradation, which can be induced via free radicals or singlet oxygen ((1)O2). Suprofen (SP) is a nonsteroidal anti-inflammatory drug that contains the 2-benzoylthiophene (BZT) chromophore and has a π,π* lowest triplet excited state. In the present work, dyads (S)- and (R)-SP-α-Ch (1 and 2), as well as (S)-SP-β-Ch (3) have been prepared from β- or α-Ch and SP to investigate the possible competition between photogeneration of biradicals and (1)O2, the key mechanistic steps in Ch photooxidation...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27548566/intramolecular-photocycloaddition-reactions-of-arylcyclopropane-tethered-1-cyanonaphthalenes
#18
Hajime Maeda, Shoji Matsuda, Kazuhiko Mizuno
Intramolecular photocycloaddition reactions of 1-cyanonaphthalenes bearing an arylcyclopropane containing side chain were investigated. Photoreactions of members of this family in which the arylcyclopropane moiety is bonded at the 2-position of the 1-cyanonaphthalene ring produce head-to-head and head-to-tail 1,2-[3+2] photocycloadducts. On the other hand, substances in this family containing an arylcyclopropane side chain linked to the 4-position of the cyanoarene ring undergo photoreactions to form [4+3] photocycloadducts along with novel nine-membered ring products, which are produced by photochemically induced 10π conrotatory ring opening of the initially formed intramolecular [3+2] cycloadducts...
September 16, 2016: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27539406/mechanism-investigation-of-hs-radical-and-cs-losses-from-positively-charged-biradicals-of-diphenyl-sulfides-by-apci-mass-spectrometry
#19
Xiaoji Cao, Chenlu Wang, Weimin Mo
RATIONALE: Aryl thioethers are potentially useful precursors for constructing various biologically active sulfur-containing heterocycles. The detailed relationship between the losses of HS radical and CS with the spin multiplicity of positively charged diphenyl sulfide biradicals derived from 3-iodophenyl phenyl sulfides has not been obtained by tandem mass spectrometry combined with theoretical calculations. METHODS: Collision-induced dissociation mass spectrometry experiments were carried out using an ion trap mass spectrometer with APCI in positive mode...
August 2016: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/27524177/biradical-character-in-the-ground-state-of-mn-si12-a-dft-and-caspt2-study
#20
Vaida Arcisauskaite, Domagoj Fijan, Mariano Spivak, Coen de Graaf, John E McGrady
Both density functional theory and multi-configurational ab initio (CASPT2) calculations are used to explore the potential energy surface of the hexagonal prismatic cluster [Mn@Si12](+). Unlike isoelectronic Cr@Si12, the ground state is a biradical, with triplet and open-shell singlet states lying very close in energy. The results are discussed in the context of recent experimental studies using infra-red multiple photon dissociation spectroscopy and X-ray MCD spectroscopy.
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
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